Note: Descriptions are shown in the official language in which they were submitted.
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BANDED PAPERS, SMOKING ARTICLES AND METHODS
10
FIELD OF THE DISCLOSURE
This disclosure relates generally to a smoking article and, more particularly,
a banded
wrapper for use in cigarette manufacturing, related materials, processes, and
methods. Anti-
wrinkling agents, specially formulated oxidized starch material, smoking
articles and wrappers
which exhibit a low ignition propensity and/or low self-extinguishment
characteristics, and
patterns for banded regions are disclosed.
BACKGROUND
As part of efforts to reduce the incidence of accidental fires resulting from
untended
smoking articles, various jurisdictions have imposed, are imposing, and may
impose in the
future limitations on the burning characteristics of smoking articles. One
measure of the
tendency of a smoking article to cause ignition of an underlying substrate is
the ignition
propensity value. To satisfy those increasingly common governmental
requirements, the
ignition propensity value for a smoking article should preferably be no
greater than about 25%.
More preferably, the ignition propensity value should be no greater than about
20%; and even
more preferably no greater than about 10%. Accordingly, efforts meet such
limits are
undertaken by various manufacturers of smoking articles.
Reduced ignition propensity values typically are associated with a tendency
for the
smoking article to self-extinguish during smoldering between puffs. Generally
speaking,
consumers do not like to re-light a cigarette during their smoking experience.
A measure of the
tendency for a smoking article to self-extinguish during free burn has been
developed and is
known as the self-extinguishment value. The self-extinguishment value has been
found to be a
useful indicia to evaluate the likelihood of consumer satisfaction for a
smoking article where
various techniques for ignition propensity reduction have been employed. The
average self-
extinguishment average value for a smoking article should preferably be no
greater than about
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80% and/or the self-extinguishment at 0 value should be no greater than about
50%, and more
preferably no greater than about 25%.
IGNITION PROPENSITY
Ignition propensity is a standard test conducted as set forth in ASTM E 2187-
04,
"Standard Test Method for Measuring the Ignition Strength of Smoking
articles".
Ignition propensity measures the
probability that a smoking article, when smoldering and placed on a substrate,
will generate
sufficient heat to maintain smoldering of the tobacco rod. Low values for
ignition propensity are
io desirable as such values correlate with a reduced likelihood that a
smoldering smoking article,
when inadvertently left unattended upon a substrate, will cause combustion in
the substrate.
SELF-EXTINGUISHMENT
Self-extinguishment herein is a reference to smoldering characteristics of a
smoking
article under free burn conditions. To evaluate self-extinguishment, a
laboratory test is
conducted at a temperature of 23 C t 3 C and relative humidity of 55% t 5%,
both of which
should be monitored by a recording hygrothermograph. Exhaust hood(s) remove
combustion
products formed during testing. Prior to testing, smoking articles to be
tested are conditioned at
55% t 5% relative humidity and 23 c t 3 C for 24 hours. Just prior to testing,
the smoking
articles are placed in glass beakers to assure free air access.
Self-extinguishment testing takes place within an enclosure or test box. A
single port
smoking machine or an electric lighter is used to ignite the smoking articles
for the test. During
testing, an apparatus or "angle holder" holds the smoking articles to be
tested by holding an end
at angles of 0 (horizontal), 45 , and/or 90 (vertical). Preferably, twenty
(20) smoking articles
are tested at each of the 0 , 45 , and 90 positions. If more than one
apparatus is used, the
apparatuses are preferably positioned such that the smoking articles face away
from each other
to avoid cross interference. If a smoking article goes out before the front
line of the smoldering
coal reaches the tipping paper, the outcome is scored as "self-
extinguishment"; on the other
hand, if the smoking article continues smoldering until the front line of the
smoldering coal
reaches the tipping paper, then the outcome is scored as "non-extinguishment".
Thus, for
example, an self-extinguishment value of 95% indicates that 95% of the smoking
articles tested
exhibited self-extinguishment under free burn conditions; while an self-
extinguishment value of
20% indicates that only 20% of the smoking articles tested exhibited self-
extinguishment under
such free burn conditions.
The self-extinguishment value may be referred to in terms of "self-
extinguishment at 00
value", "self-extinguishment at 45 value", or "self-extinguishment at 90
value", each of which
refers to the value of self-extinguishment at the specified tested angle. In
addition, the self-
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extinguishment value may be referred to in terms of "self-extinguishment
average value", which
refers to an average of the three angular positions: namely, an average of (i)
the "self-
extinguishment at 0 value", (ii) the "self-extinguishment at 45 value", and
(iii) the "self-
extinguishment at 90 value". A reference to "self-extinguishment value" or
"self-extinguishment
value" does not distinguish between self-extinguishment at 0 , self-
extinguishment at 45 , self-
extinguishment at 90 , or self-extinguishment average values and may refer to
any one of them.
In execution of multi-pass printing operations, the operator will typically
establish a press
at the very beginning to print registration marks. Accordingly, in
understanding the description
herein of "first pass", "second pass", "third pass" and so forth, it should be
understood that
typically such passes will be preceded with a pass (or print station) for
establishing registration
marks on the paper, which marks are used to maintain desired registration from
pass to pass
(print-station to print-station)
SUMMARY
Embodiments herein disclosed include banded papers and smoking articles
constructed
= from such papers, wherein the add-on material comprises an aqueous starch
solution (or
system) that includes an anti-wrinkling agent as disclosed herein, such that
the following are
achievable:
countermeasure against tendency of the aqueous solution to create wrinkles and
creases in the paper;
countermeasure against tendency of the aqueous solution to cause the paper to
shrink
transversely during printing operations so that print-registration can be more
precisely
maintained from print-station to print-station, especially in the transverse
dimension of the
paper;
with the aforementioned countermeasures, printing of intricate patterns on
base web
with aqueous add-on systems at commercially viable printing speeds becomes
possible;
possibility of single pass, gravure-printed banded paper with an aqueous
solution when
coupled with sufficient drying capabilities;
more precise multi-pass printing of banded paper with an aqueous solution; and
improved stability of the solution, including a longer operational shelf-life,
which reduces
costs and waste during printing operations.
In addition there are teachings herein of embodiments that include banded
papers and
smoking articles constructed from such papers, wherein the add-on material
comprises an
aqueous, preferably starch solution that includes a chalk content sufficient
to abate the
tendency of the banded paper to cause self-extinguishments and to enhance
appearance of the
product to a consumer. Further teachings include embodiments which include
features and
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provision for maintaining capability to machine vision inspect the banded
paper during printing
operations, despite the presence of the chalk content in the add-on material.
Furthermore, there are teachings herein of embodiments that include banded
papers
and smoking articles constructed from such papers, wherein the bands are
established
according to patters which help abate the statistical occurrences of self-
extinguishments while
maintaining desired ignition propensity performance.
In accordance with one aspect of this disclosure, a wrapper paper for a
smoking article
may have a base web to which add-on material is applied in a pattern using an
aqueous starch
solution that includes an anti-wrinkling agent. The wrapper paper may include
regions of add-
io on material that include starch at about 1.5g/m2 and 1,2 propylene
glycol in the range of about
0.36 g/m2 to about 0.90g/m2. As desired, the add-on material may also include
chalk or calcium
carbonate in the range of about 0.64g/m2 to about 1.2g/m2.
In accordance with another aspect of this disclosure, a smoking article may
include
tobacco and a wrapper paper where the wrapper paper includes a pattern of add-
on material
applied as an aqueous starch solution containing an anti-wrinkling agent.
Another aspect of this disclosure involves a method of making or preparing a
patterned
wrapper paper by establishing a supply of an aqueous starch solution
incorporating an anti-
wrinkling agent to a printing station through which a base web is passed so
that the pattern can
be applied using the aqueous starch solution.
Further aspects of this disclosure involve, without limitation, patterns for
the add-on
material, characteristics of the constituents of the add-on material. Further,
the disclosure
relates to resulting features of the smoking article including without
limitation ignition propensity
and self-extinction characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
Many objects and advantages of the present disclosure will be apparent to
those skilled
in the art when this specification is read in conjunction with the
accompanying drawings,
wherein like reference numerals are applied to like elements and wherein:
FIG. 1 is a schematic perspective view of a smoking article according to this
disclosure;
FIG. 2 is a schematic view of a wrapper paper according to this disclosure;
FIG. 3 is an enlarged partial cross-sectional view taken along the line 3-3 of
FIG. 2;
FIG. 4 is a mosaic of photomicrographs taken of actual wrapper with two layers
of add-
on material; FIGs. 4A-4G join one another at the indicated match lines;
FIG. 5 is a schematic view of wrapper according to another embodiment of this
disclosure;
FIG. 6 is an enlarged partial cross-sectional view taken along the line 6-6 of
FIG. 5;
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FIG. 7 is a schematic view of wrapper according to a further embodiment of
this
disclosure;
FIG. 8 is a schematic view of wrapper according to yet another embodiment of
this
disclosure;
5 FIG. 9 is an enlarged schematic cross-sectional view taken along the
line 9-9 of FIG. 2;
FIG. 10 is a schematic cross-sectional view, similar to FIG. 9, of a multi-
layer band
construction;
FIG. 11 is a schematic view of a wrapper having longitudinally extending
banded
regions;
FIG. 12 illustrates a plan view of a wrapper for making a tobacco rod with
helical,
longitudinal, banded regions;
FIG. 13 is a perspective view of still another embodiment of a smoking article
according
to this disclosure;
FIG. 14 is an enlarged cross-sectional view of the smoking article positioned
on a
substrate and illustrating airflow to a smoldering coal;
FIG. 15 is an enlarged cross-sectional view of the smoking article removed
from the
substrate and illustrating airflow to a smoldering coal;
FIG. 16 is a perspective view of a smoking article in accordance with another
embodiment;
FIG. 17 is an enlarged plan view of an unwrapped portion of wrapper used in
the
construction of the smoking article of FIG. 16;
FIG. 18 is an enlarged plan view of a wrapper for the smoking article
illustrating another
quadrilateral pattern;
FIG. 19 is an enlarged plan view of a wrapper for the smoking article,
illustrating a
further quadrilateral pattern;
FIG. 20 is an enlarged plan view of a wrapper for the smoking article,
illustrating a still
another quadrilateral pattern;
FIG. 21 is an enlarged plan view of a wrapper for the smoking article,
illustrating a
triangular pattern;
FIG. 22 is a side view of the smoking article using the wrapper of FIG. 18
with the
smoking article on a substrate and oriented so that a first side portion of
the smoking article
contacts a substrate;
FIG. 23 is a side view of the smoking using the wrapper of FIG. 18 with the
smoking
article on a substrate and oriented so that a second side portion of the
smoking article contacts
the substrate;
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FIG. 24 is a side view of the smoking article using the wrapper of FIG. 18
with the
smoking article on the substrate and oriented so that a third side portion of
the smoking article
contacts the substrate;
FIG. 25 is a cross-sectional view of the smoking article taken along line 25-
25 of FIG. 22;
FIG. 26 is a cross-sectional view of the smoking article taken along line 26-
26 of FIG. 22;
FIG. 27 is a cross-sectional view of the smoking article taken along line 27-
27 of FIG. 22;
FIG. 28 is an embodiment with axially slit banded regions;
FIG. 29 is a partial cross sectional view taken along the line 29-29 of FIG.
28;
FIG 30 is an embodiment with two axial slits in the banded regions;
FIG. 31 is a partial cross-sectional view taken along the line 31-31 of FIG.
30;
FIG 32 is an embodiment with an axially slit banded region;
FIG. 33 is a partial cross-sectional view taken along the line 33-33 of FIG.
32;
FIG. 34 is a side elevation view of another embodiment of a smoking article
according to
this disclosure;
FIG. 35 is an enlarged partial cross-sectional view taken along the line 35-35
of FIG. 34;
FIG. 36 is a side elevation view of a further embodiment of a smoking article
according
to this disclosure;
FIG. 37 is an enlarged partial cross-sectional view taken along line 37-37 of
FIG. 36;
FIG. 38 is an enlarged partial cross-sectional view of an alternative
embodiment, similar
zo to FIG. 31;
FIG. 39 is a perspective view of another embodiment of a smoking article
according to
this disclosure;
FIG. 40 is a partial plan view of the wrapper of another embodiment;
FIG. 41 is a perspective view of a further embodiment of a smoking article
according to
this disclosure;
FIG. 42 is a side elevation view of a still another embodiment of a smoking
article
according to this disclosure;
FIG. 43 is a side elevation view of a yet still another embodiment of a
smoking article
according to this disclosure;
FIG. 44 illustrates an embodiment of a smoking article comprising helical
longitudinally
banded regions and a helical angle i3 of about arctangent (2 I/C), where I is
the length of the
tobacco rod and C is the circumference of the smoking article as described
herein;
FIG. 45 illustrates an embodiment of a smoking article comprising helical
longitudinally
banded regions and a helical angle 13 of about arctangent (4 I/C) as described
herein;
FIG. 46 illustrates an embodiment of a smoking article comprising helical
longitudinally
banded regions and a helical angle 13 of about arctangent (//C) as described
herein;
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FIG. 47 illustrates a plan view of a wrapper for making a tobacco rod with
longitudinally
banded regions;
FIG. 48 illustrates an embodiment of a smoking article comprising
longitudinally banded
regions parallel to a longitudinal axis of the smoking article as described
herein;
FIG. 49 is a perspective view of a smoking article according to this
disclosure;
FIG. 50 is a schematic view of a wrapper having a crenellated banded region;
FIG. 51 is a schematic view of a wrapper having another embodiment of a
crenellated
banded region;
FIG 52 is a schematic view of a wrapper having a further embodiment of a
crenellated
banded region;
FIG. 53 is a schematic view of a wrapper having a yet another embodiment of a
crenellated banded region;
FIG. 54 is a schematic view of a wrapper having a still further embodiment of
a
crenellated banded region;
FIG. 55 is a schematic view of a wrapper having another embodiment of a
crenellated
banded region;
FIG. 56 is a schematic view of a wrapper having another embodiment of a
crenellated
banded region;
FIG. 57 is a schematic view of a wrapper having a another embodiment of a
crenellated
zo banded region;
FIG. 58 is a cross-sectional view of a smoking article comprising another
embodiment of
longitudinally banded regions as described herein;
FIG. 59 is a schematic view of a gravure printing process suitable for
producing
embodiments of print banded wrapper as disclosed herein; and
FIG. 60 is a collection of photographs showing the effect of anti-wrinkling
agents on
wrapper paper.
BACKGROUND DEFINITIONS
Referring to FIG 1, this disclosure concerns a smoking article 120, such as a
cigarette,
3o which preferably comprises a tobacco rod 122 and a filter 132 attached
to the tobacco rod 122
with tipping paper 132. Preferably, the tobacco rod 122 comprises a column of
shredded
tobacco ("cut filler") and a wrapper 123 disposed about the column of tobacco,
which wrapper
123 is constructed in accordance with teachings which follow. The tobacco rod
122 has a
lightable or lit end 124 and a tipped end 130 (which in the case of non-
filtered cigarettes, is
referenced as the mouth end 130 of the cigarette 120). Cut filler tobacco is
an industry-
standard designation. Further, the tobacco rod 122 typically has a generally
circular cross
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section, although other oval cross section and other shapes are within the
scope of this
disclosure. The wrapper is sealed along a longitudinal seam to form the
tobacco rod 122.
The tobacco rod has a nominal length measured from the edge 131 of the tipping
paper
to the free end of the tobacco rod along a longitudinal axis of smoking
article. By way of
example, that nominal length may lie in the range of about 60mm to about
100mm.
The "wrapper" paper 123 (see FIG. 2) typically includes a "base web" 140 that
may be
made from flax, wood pulp, cellulose fiber, or the like, and may have a
plurality of banded
regions 126 applied to one or both sides. Preferably, the banded region 126 is
applied to the
inside of the wrapper 123 in the sense of how the wrapper 123 surrounds a
column of tobacco
io in the tobacco rod 122.
In the manufacture of base web suited for the construction of the various
embodiments
of print banded paper disclosed herein, such manufacture usually will include
the production of
a roll of base web of several feet across (usually about 1m (3 feet) across or
in transverse
dimension), which is then slit into bobbins. Printing operations are
preferably conducted on the
rolls, but could be conducted after slitting. Preferably, the bobbins
themselves will have a
transverse dimension equivalent to the width needed to make tobacco rods 122
or an integral
number of such widths (e.g., 1, 2, or 4 of such widths). The bobbins are
adapted for use with
typical cigarette making machines. The wrapper preferably has a dimension in
cross-direction
that takes into account the nominal circumference of the tobacco rod and an
overlapping seam.
As a result, when the wrapper is slit, the smoking article formed therefrom
always has a
longitudinal seam with an exact overlap.
For purposes of this disclosure, "longitudinal" refers to the direction along
the length of a
tobacco rod (e.g., along the axis 134 in FIG. 1), or along the length of a
base web 140 (e.g.,
arrow 142 in FIG. 2) used in the preparation of wrapper that, in turn, may be
used to fabricate a
tobacco rod.
For purposes of this disclosure, "transverse" refers to the direction
circumferentially
around a tobacco rod 122 (see FIG. 1), or transversely of a base web 140
(e.g., arrow 144 in
FIG. 2) used in the preparation of wrapper that, in turn, may be used to
fabricate a tobacco rod.
For purposes of this disclosure, a "banded region" or "zone" is an area 126
(see FIG. 2)
on an underlying base web 140 to which an add-on material has been applied.
The banded
region typically exhibits a two-dimensional pattern or array on the base web
140. More
specifically, the pattern or array may comprise repeating units in the
longitudinal direction 142 of
the base web 140, repeating units in the transverse direction 144 of the base
web 123, and or
units which repeat in both the transverse 144 and longitudinal 142 directions
of the base web
140. The regions 126 of add-on material are applied to the wrapper 123 to
obtain satisfactory or
improved Ignition Propensity characteristics and may also obtain improved self-
extinguishment
characteristics.
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The regions 126 of add-on material are spaced along the base web 140 such that
at
least one region of add-on material 126 is positioned between the first and
second ends 128,
130 of the tobacco rod 122 in each finished smoking article, but more
preferably at least two
regions of addOon material appear on the tobacco rod 122. The region 126 of
add-on material
preferably extends in the circumferential direction at one or more spaced
locations along the
axis 134, extending around the tobacco rod 122 of the smoking article 120.
While the region
126 of add-on material is depicted in this disclosure as being substantially
continuous in its
circumferential direction, other configurations for the add-on material are
within the spirit and
scope of this disclosure.
It is noted for sake of convention that, in describing dimensions of various
embodiments
herein, that band or zone "width" extends in a longitudinal direction 134 (see
FIG. 1) of the
tobacco rod 122, whereas a dimension in the circumferential direction will be
expressed as
"circumferential" or "transverse" or "in cross-direction."
Where the banded region 126 extends transversely of the base web 140 (or
circumferentially around a tobacco rod), the "width" of the banded region 126
is measured in the
longitudinal direction 142 from the leading edge 146 to the trailing edge 148
and is preferably
lies in the range of from about 5mm to about 9mm (from the leading edge 146 to
the trailing
edge 148), more preferably from about 5.5mm to about 7.5mm, and even more
preferably from
about 6mm to about 7mm. Further, banded regions may have a 27mm "phase" (i.e.,
the
zo
spacing from the leading edge 146 of one banded region 126 to the leading
edge 145 of the
next adjacent banded region 126). Preferably, the banded regions of add-on
material reduce
permeability of the wrapper to the range of from about 0 to about 12 CORESTA,
more
preferably the range of from about 0 to about 10 CORESTA.
For purposes of this disclosure, "band spacing" refers to the distance between
the
trailing edge148 of one banded region 126 and the leading edge 146 of an
adjacent banded
region 126 on the base web 140 from which a wrapper is fashioned.
As used herein, the phrase "leading edge" refers to the edge 146 (see FIG. 1)
of a
banded region 126 that is closest to an approaching coal during smoldering of
a smoking article
120 whose wrapper 123 contains the banded region 126, while the phrase
"trailing edge" refers
to the edge 148 of a banded region 126 that is farthest from an approaching
coal during
smoldering of a smoking article 120 whose wrapper 123 contains the banded
region126. In
crenellated embodiments, the overall width "W" of the banded region is
measured from the
farthest forward extent of the leading edge to the farthest trailing extent of
the trailing edge, as is
illustrated in FIG. 6 with the width 'W".
As used herein, the term "crenellated" refers to a pattern of multiple,
spaced,
geometrically shaped spaces removed from an otherwise substantially continuous
solid banded
region 126. A crenellated pattern or band can also be described as notched or
appearing
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similar to a pulse wave. As used herein, "crenels" refer to openings, or
valleys, in a crenellated
edge, while "merlons" refer to raised portions, or plateaus of a crenellated
edge, between
crenels. The term "undulating" as used herein includes a crenellate edge as
well as broader
geometric shapes that exhibit a increasing and decreasing width
characteristics.
5 For purposes of this disclosure, "layer" refers to a quantity of add-
on material applied to
a base web from which a wrapper is fabricated. A banded region 126 may be
fashioned from
one or more layers 150, 152 (see FIG.3) that may be superimposed on one
another. Each
banded region 126 may be formed by applying one or more "layers" 150, 152 of
an aqueous
film-forming composition to the base web 140 of the wrapper to reduce the
permeability of the
io paper in the corresponding banded region. Alternatively, a cellulose
material may also be used
to form the banded regions.
Where a film-forming composition is used, that "film-forming composition"
preferably
may include water and a high concentration of an occluding agent, e.g., 14% to
about 50% by
weight. The film-forming compound can include one or more occluding agents
such as starch,
alginate, cellulose or gum and may also include calcium carbonate as a filler.
Further, the film-
forming composition preferably includes an anti-wrinkling agent. Where starch
is the film-
forming compound, a concentration of about 14% to about 26% may be
particularly
advantageous, and a concentration of about 16% is presently most preferred.
An "anti-wrinkling agent" is a material which inhibits transverse shrinkage of
the base
web 140 (see FIG. 2) during printing or other conversion operations. A
suitable anti-wrinkling
agent may be selected from the group consisting of 1,2 propylene glycol,
propylene glycol,
glycerin, and starch plasticizing agents.
The film-forming composition may be applied to the base web of the wrapper 140
using
conversion technologies such as gravure printing, digital printing, coating or
spraying using a
template, or any other suitable technique. If desired, the banded regions 126
of add-on material
can be formed by printing multiple, successive layers, e.g., two or more
successive layers
registered or aligned with one another. Given the tolerances in gravure
printing equipment, for
example, adjacent layers are considered to be in registry where their
respective overlying edges
are within about 0.4mm of one another when measured in either the longitudinal
or transverse
direction of the base web 140. Furthermore, when layers are used to form the
banded regions
of add-on material, the material in adjacent layers may be the same or
different. For example,
one layer may be starch while the next layer may be starch and calcium
carbonate.
When discussing application rates for add-on material applied using gravure
printing
techniques, often use values with "X" as a suffix to refer to a volumetric
application rate. The
table below sets out the volumetric equivalents for "X" in terms of billion
cubic microns, or
"BCM":
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Volume BCM Volume BCM Volume
BCM
0.5X 3.4 2.5X 10.7 4.5X 19.9
1.0X 4.6 3.0X 12.3 5.0X 22.4
1.5X 6.8 3.5X 13.6 5.5X 24.7
2.0X 10 4.0X 17.8 6.0X 27.8
When the phrase "weight ratio" is used herein with respect to the starch
component of a
starch solution, the "weight ratio" is the ratio of the weight of the
additional material compared to
the weight of starch used to prepare the starch solution. Moreover, for
purposes of this
disclosure, references to an "X% starch solution" refer to an aqueous starch
solution in which
the starch weight is X% of the solution weight (e.g., weight of starch divided
by the sum of
starch weight and aqueous component weight).
The wrapper includes a base web which typically is permeable to air.
Permeability of
wrapper is typically identified in CORESTA units. A CORESTA unit measures
paper
permeability in terms of volumetric flow rate (i.e., cm3/sec) per unit area
(i.e., cm2) per unit
pressure drop (i.e., cm of water). The base web of conventional wrapper also
has well-known
basis weights, measured in grams per square meter (g/m2). The permeability and
basis weight
for the base web of typical smoking article papers commonly used in the
industry are set out in
the table below:
Permeability, CORESTA units Basis Weight/(g/m2)
24 25
33 25
46 25
60 26
For purposes of this description, the base web of a preferred wrapper has a
permeability
of at least about 20 CORESTA units. Most preferably, the wrapper has a
permeability greater
than about 30 CORESTA, such as common base webs having nominal permeabilities
of about
33 and about 46 CORESTA with a basis weight of about 25g/m2. For some
applications, the
base web may have a permeability of greater than about 60 CORESTA, or greater
than about
80 CORESTA, or even higher permeability values.
SCHEMATIC vs ACTUAL DEPICTIONS
Depictions of cross sections taken through a banded paper, such as FIG. 3, are
believed
to be useful schematic representations of a paper web having banded regions
fashioned from
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one or more layered applications, and of the application processes by which
such banded
papers are fabricated. However, such schematic representations do not
accurately depict the
reality of the cross-section base web structures, or the reality of the cross-
section of base web
structures to which one or more layers of add-on material have been applied,
or the reality of
the cross-section of those layers of add-on material in the final banded paper
product.
More particularly, FIG. 4 is a mosaic of photomicrographs taken of a cross-
section of a
banded wrapper of the type discussed above and elsewhere in this disclosure.
The
photomicrographs of FIG. 4 cover an actual length of wrapper measuring about
2.1mm in
length, to which add-on material has been applied in two layers; one layer
containing starch and
calcium carbonate, and one layer having starch but no calcium carbonate. Match
lines are
applied to the different sheets of the FIG. 4 mosaic so that the relationship
between different
portions of FIG. 4 are readily apparent.
The individual photomicrographs of FIG. 4 enlarge the actual paper sample 2500
times.
Procedurally, actual banded paper was cut into sections several millimeters
long and embedded
into SpurrTM epoxy. The embedded paper was then cut into 51.1m (micrometers)
thick cross
sections using a Leica Ultracut UCT Ultramicrotome equipped with a glass
knife. The sample
was mounted on a carbon adhesive disk attached to an aluminum stub, and
sputter coated with
15nm (nanometers) of Au-Pd using a Cressington 208HR Sputter Coater operating
in argon.
The sample was imaged in adjacent overlapping portions using an FEI XL30
Environmental
Scanning Electron Microscope (ESEM) operating at 15kV in Hi-Vac mode.
FIGs. 4A, 4B depict a portion of the base web 140 which is free of any add-on
material.
The base web 140 includes a multiplicity of randomly dispersed, light areas
(e.g., 160) which
represent calcium carbonate particles incorporated into the base web during
paper formation.
The base web 140 also includes a multiplicity of darker shapes 162 some of
which are
elongated, others of being rounded, which are cuts through fibers used in the
paper making
process. The base web 140 has a pair of surfaces 161, 163, that can be
characterized as
having random roughness at this level of magnification, and having both
calcium carbonate
particles and fibers randomly distributed along the surface regions. The base
web 140 itself
exhibits a thickness which, at best, may also be characterized as random, but
having some
n statistically average or nominal value.
When the first portion or layer of add-on material 164 is applied (see FIG.
4C), the add-
on material shows on the surface of the base web 140 due principally to the
presence of chalk
(or calcium carbonate) in the material. In the sample which has been magnified
in FIG. 4, the
second portion or layer of add-on material 166 is applied (see FIG. 4C) on the
surface of the
base web 140 and is positioned on the firs layer 164. The second layer 166
begins at about the
location 168 (FIG. 4C). While it appears that the second layer 166 is not
aligned so as to start
at the same location as the first layer 164, the tolerances involved in
application techniques
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13
such as printing effectively do not allow the layers to be controlled within a
tolerance of any less
than about 0.3mm. From the scale of magnification shown on the images of the
FIG. 4 mosaic,
the distance between the beginning of the first layer and the beginning of the
second layer is
about 0.12mm; a distance well within the minimum tolerance noted above.
Examining the first layer as it extends across FIGs. 4C-4G, several
observations can be
made about the first layer 164 containing starch and calcium carbonate:
(i) the layer 164 is not continuous in the direction of the base web 140;
(ii) the layer 164 does not have uniform thickness;
(iii) the layer 164 has non-uniform thickness;
(iv) the layer 164 does not have a smooth surface; and
(v) the actual thickness of the first layer 164 can be greater than the
actual thickness
of the second layer 166, even though the second layer is usually thicker than
the first layer.
A similar examination of the second layer 166, which does not include starch,
as that
layer extends across FIGs. 4C-4G permits several similar observations:
(I) the second layer 166 is not continuous in the direction of the base web
140;
(ii) the second layer 166 does not have a uniform thickness;
(iii) the second layer 166 has a non-uniform thickness;
(iv) the second layer 166 tends to have a smooth surface, but the base web
(paper)
has areas; e.g., 170 (FIG. 4D), 172, 174 (FIG. 4E), and 176 (FIG. 4F), which
are devoid of the
zo add-on material constituting the second layer 166.
Differences such as those discussed above demonstrate that the schematic
descriptions
of paper with one or more layers of add-on material are at significant
variance with the real
world results of applying one or more layers of add-on material to a base web
140. Accordingly,
while the schematic representations of add-on layers fairly show the process
application rates,
as might be used as a guide to etch application zones of a gravure print
cylinder or the like,
those schematic representations do accurately represent the structure of the
finished wrapper
prepared by applying one or more layers of add-on material to a base web.
AN ILLUSTRATIVE EMBODIMENT ¨ SOLID BAND PATTERN
Referring now to FIG. 10, in a presently preferred embodiment of multi-layered
application of add-on material to construct a solid band configuration from a
multi-application of
add-on material and having a band width in the range of approximately 6 to 7
mm. A first layer
210 of the band may be applied at a rate of 4X and may comprise an aqueous
solution
containing approximately 16% starch, 60% chalk or calcium carbonate, and 60%
1,2 propylene
glycol. The second layer 212 may be applied as a smaller rate of 3.5X and may
comprise the
same solution as the first layer. The third layer 214 may be applied at an
even lower rate of 3X
and may comprise an aqueous solution containing 16% starch, and 60% 1,2
propylene glycol.
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In this formulation, the 60% value for starch and propylene glycol means that
the weight of
those components is included at 60% of the weight of the starch in the aqueous
solution. After
the various layers have dried, the resulting base web has regions of add-on
material in which
starch is present at about 1.5g/m2, 1,2 propylene glycol is present in the
range of about 0.36 to
about 0.90g/m2, and calcium carbonate is present in the range of about 0.64 to
about 1.2g/m2.
With inclusion of the propylene glycol in this embodiment as described, one
may achieve
the associated advantages summarized above (in the Summary) and detailed
further in the
description which follows.
With inclusion of the chalk in this embodiment as described, one may abate the
io
tendency of the banded paper cigarettes to self-extinguish, enhance appearance
of the product
to a consumer and achieve these and other associated advantages summarized
above (in the
Summary) and detailed further in the description which follows.
Likewise, with application of a third layer 214 using a composition of little
or no chalk
content, machine vision inspection of banded paper during printing operations
is made possible
and practicable, despite the presence of the chalk content in the add-on
material of first and
second layers 210 and212. This feature contribute to these and other
associated advantages
as summarized above (in the Summary) and detailed further in the description
which follows.
It is also to be appreciated that with the solid band construction as
described in
reference to FIG. 10 one achieves a wrapper which is capable of contributing a
desirable
ignition propensity performance, including in many applications, an ignition
propensity
performance of at or about zero (0).
DIFFICULTIES ENCOUNTERED WITHAPPLYING AQUEOUS, PREFERABLY STARCH, ADD-
ON SOLUTIONS
There are advantages with the concept of using aqueous starch solutions as add-
on
material for making banded wrapper to control ignition propensity
characteristics of smoking
articles manufactured using such banded wrapper. However, the application of
aqueous starch
solutions to a base web creates difficulties. For example, aqueous starch
solutions have a
tendency to penetrate the irregular, rough, and porous surface of the base web
140, and a
tendency to cause transverse shrinking of the base web in the vicinity of the
banded regions.
As to the last point, it has been observed that when applying an aqueous
starch solution to a
base web about 92cm (36 inch) in transverse dimension, the web may shrink
about from 1.3cm
(0.50 inch) to 1.9cm (0.75 inch) or more upon drying. This degree of shrinking
would frustrate
maintaining proper registration through printing and other conversion
operations.
Since shrinkage is localized to the banded regions, the transverse width of
the base web
in the space between adjacent banded regions is greater than the transverse
width of the base
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web in the banded regions. That disparity in transverse width gives rise to
transverse waviness
in the base web in those spaces between banded regions.
Such waviness in the wrapper adversely affects both the subsequent handling of
the
wrapper and the manufacture of smoking articles from the wrapper. For example,
when
5 wrapper with waviness is wound on a spool, or slit and wound on bobbins,
the winding process
flattens the waviness causing creases in the wrapper. When the creased wrapper
is used to
manufacture smoking articles, those creases in the wrapper are carried into
the smoking articles
resulting in visually unacceptable smoking articles.
10 ANTI-WRINKLING AGENT
Surprisingly, applicants have discovered that the inclusion of an anti-
wrinkling agent
(preferably, such a propylene glycol) in an aqueous starch solution used to
make banded
wrapper in a manner consistent with the teaching herein can reduce transverse
shrinkage to
operationally manageable levels, alleviate pronounced wrinkling and
essentially eliminate
15 creasing problems that first presented themselves. Inclusion of an anti-
wrinkling agent has
been found to have additional benefits, too. For example, when an anti-
wrinkling agent is
incorporated into the aqueous starch solution, the anti-wrinkling agent
functions as a plasticizer
so that the starch is more elastic during the drying process and in the
finished paper. Cracking
and flaking at banded regions was alleviated. In addition, the presence of the
anti-wrinkling
agent appears to cause the starch solution to reside more on the surface of
the base web with
less penetration into that material, and thus enhance film formation.
Shrinkage of the wrapper
in the vicinity of banded regions formed from an aqueous starch solution that
includes an anti-
wrinkling agent has been observed to be in the range of about 1.6mm to 3.2mm
(0.0625 inch to
0.125 inch) for a 92cm (36 inch) wide base web; a range which does not result
in creasing nor
excessive waviness. Further, inclusion of an anti-wrinkling agent in the
aqueous starch solution
has been found to make possible the application of add-on material to be
applied to the base
web in a single application, printing pass, or the like, provided that
sufficient drying capability is
established with such practices. Moreover, the inclusion of an anti-wrinkling
agent in the
aqueous starch solution to be applied in patterns exhibiting more intricacy
than solid band
regions, because print registration can be more precisely maintained from
print station to print
station. In addition, the pot life of the aqueous starch solution is
materially improved by the
inclusion of an anti-wrinkling agent as disclosed herein.
The foregoing advantages will be better understood by those skilled in the art
from the
following teachings. Referring now to FIG. 2, the regions 126 of add-on
material determine and
regulate the ignition propensity and self-extinguishment characteristics of
the smoking article.
Those regions 126 of add-on material are applied to a base web 140 (see FIG.
2) of the
wrapper 123 and then formed into a tobacco rod in conventional cigarette
making equipment.
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Nominal permeability of the base web 140 may be in the range of about 25 to
about 100
CORESTA. Currently, the preferred nominal permeability of the base web lies in
the range of
about 33 to about 65 CORESTA, with the most preferred nominal permeabilities
being about 33
and about 60. The base web 140 has a longitudinal direction 142 extending
along the length of
the wrapper 123 and a transverse direction 144 extending transversely across
of the wrapper
123 so as to be generally perpendicular or transverse to the longitudinal
direction 142.
Those regions 126 of add-on material may be applied to the base web 140
preferably by
a printing technique. While one or more printing technique (selected from the
group consisting
of direct printing, offset printing, inkjet printing, gravure printing, and
the like) may be used to
io apply the region 126, preferably a gravure printing process will be
used. Gravure printing
provides ample control over deposition rates, deposition patterns, and the
like, and is suitable
for high-speed printing on the base web 140. For purposes of this disclosure,
"high-speed"
printing refers to printing processes where the base web 140 advances through
the printing
process at a linear speed greater than about 1.5m/s (300 feet/min). For
cigarette manufacturing
purposes, base web printing speeds greater than 2.3m/s (450 feet/min). are
preferred, and
speeds greater than 2.5m/s (500 feet/min) or more are even more preferred. In
this regard, the
rates of deposition for add-on material, as well as the quality of the pattern
of deposited add-on
material, can vary considerably when wrapper prepared by high-speed printing
processes is
compared with wrapper prepared by low-speed printing processes. Higher-speed
printing
operations can achieve both desirable ignition propensity values (performance)
and desired
self-extinguishment values (performance).
Remarkably, it has been found that a base web may be converted (printed) to
include
bands in accordance with the embodiment described with reference to FIG. 10 at
5m/s
(1000 feet per minute), with acceptable paper appearance (i.e., without
quality defects ) and
without elevated or unacceptable statistical occurrences of creases or
wrinkles.
One object of this description is to provide wrappers 123 (see FIG. 2)
produced at
commercial-scale high-speed which, when formed into a tobacco rod, exhibit
ignition propensity
values no greater than 25% and self-extinguishment values no greater than 50%.
Accordingly,
deposit rates and characteristics of the resulting printed regions are
important features of high-
speed printing here. While those ignition propensity and self-extinguishment
values are
considered to be adequate at this time, even more preferred is an ignition
propensity value for
the resulting smoking article no greater than about 15%; and the most
preferred ignition
propensity value for the resulting smoking article is no greater than about
10%. Lower self-
extinguishment values are also desired.
In this connection, a more preferred self-
extinguishment value is less than about 25%; while the most preferred self-
extinguishment
value is less than about 10%.
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The materials used for the regions of add-on material can be important in the
ignition
propensity and self-extinguishment performance of a smoking article
manufactured using the
wrapper discussed herein. In one embodiment, the regions of add-on material
may be printed
with a starch solution that includes an anti-wrinkling agent. While an aqueous
starch solution is
presently preferred as the aqueous component is readily dried, use of a non-
aqueous starch
solution is also within the spirit and scope of this disclosure. In another
embodiment, the
regions of add-on material may be printed with a solution comprising a mixture
of calcium
carbonate (or chalk) particles, starch, and an anti-wrinkling agent. As with
the starch and anti-
wrinkling agent solution, the solution comprising a mixture of calcium
carbonate (or chalk)
.10 particles, starch, and an anti-wrinkling agent preferably is applied as
an aqueous solution, but a
non-aqueous solution also falls within the spirit and scope of this
disclosure.
This disclosure contemplates that various anti-wrinkling agents are suitable
to attain the
desired characteristics described herein. In particular, the anti-wrinkling
agent is selected from
the group consisting of glycerin, propylene glycol, and 1,2 propylene glycol.
Glycerin is a
preferred member of the anti-wrinkling agent group. Presently, however, 1,2
propylene glycol is
the most preferred member of the anti-wrinkling agent group.
Generally speaking, this disclosure contemplates that either (i) an anti-
wrinkling agent or
(ii) a combination of anti-wrinkling agent and calcium carbonate will be added
to a nominal
aqueous starch solution to obtain the add-on solution to be used for printing.
For the nominal
aqueous starch solutions used in this description, the starch may comprise
from about 10% to
about 28%, by weight, of the nominal solution. Preferably, the starch may
comprise from about
14% to about 26%, by weight of the nominal solution. Most preferably, starch
may comprise
about 16%, by weight, of the nominal solution.
An anti-wrinkling agent is preferably added to the nominal starch solution,
with
the weight of the anti-wrinkling agent being in the range of about 10% to
about 120% of the
weight of the starch in the nominal starch solution. When the anti-wrinkling
agent is 1,2
propylene glycol, the weight of the anti-wrinkling agent is more preferably in
the range of about
40% to about 120% of the weight of the starch in the nominal starch solution;
even more
preferably in the range of about 40% to about 80%; and most preferably in the
range of about
55% to about 65%. Where the anti-wrinkling agent is glycerin, the weight of
the anti-wrinkling
agent is more preferably in the range of about 10% to about 45% of the weight
of the starch in
the nominal starch solution; even more preferably in the range of about 20% to
about 40%; and
most preferably about 20% to about 30%. Where glycerin is used as the anti-
wrinkling agent at
about 40 to about 45%, the glycerin appears to adversely affect the drying
quality of the add-on
solution.
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EXAMPLES
The following illustrative, non-limiting examples are intended to provide
further
explanation. The results provided in Tables I and II compare the initial
viscosity and time
stability of a printing solution without an anti-wrinkling agent additive and
to the initial viscosity
and time stability of a printing solution with an anti-wrinkling agent
additive. The observations
recorded in Table I (for 1,2 propylene glycol) and Table II (for glycerin)
show that a printing
solution containing an anti-wrinkling agent such as 1,2 propylene glycol or
glycerin is less
viscous initially and more stable in that it has a lower viscosity for a much
longer period of time.
Table I
Viscosity of 24% starch solution
Viscosity of 24% starch
+ 80% CaCO3 + 100% 1,2
solution + 80% CaC031
propylene glycol2
Day 1 65mPa.s (cP, centipoise) 50mPa.s
Day 2 71mPa.s 51mPa.s
Day 3 77mPa.s 50mPa.s
Day 4 88mPa.s
Day 6 52mPa.s
Day 7 147mPa.s 58mPa.s
Day 8 61mPa-s
Day 9 66mPa-s
Day 10 225mPa's 70mPa.s
Day 16 114mPa.s
1CaCO3 added to a solution of 24% dry starch in water; ratio by weight of
added CaCO3
to dry starch present in the solution is 0.8:1Ø
2CaCO3 added to a solution of 24% dry starch in water; ratio by weight of
added
1,2 propylene glycol to added CaCO3 to dry starch present in the solution is
1.0:0.8:1Ø
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Table ll
Viscosity of 20% starch solution Viscosity of 20% starch solution
+ CaC031 + CaCO3 + glycerin2
Day 1 51mPa.s (cP, centipoise) 41mPa.s
Day 2 50mPai -
Day 5 66mPa.s 52mPa.s
Day 6 78mPa.s -
Day 7 102mPa.s
Day 8 - 55mPa.s
Day 12 - 62mPa.s
Day 14 - 72mPa-s
1 CaCO3 added to a solution of 20% dry starch in water; ratio by weight of
added CaCO3
to dry starch present in the solution is 1: 1.
2 CaCO3 and glycerin added to a solution of 20% dry starch in water; the ratio
by weight
of added glycerin to added CaCO3 to dry starch present in the solution is 1 :
5: 5.
The foregoing Tables demonstrate that the useful shelf-life of the printing
solution using
an anti-wrinkling agent, as measured by its viscosity, essentially doubles the
shelf-life of a
io printing solution without the anti-wrinkling agent. The addition of an
anti-wrinkling agent in the
material applied to the add-on regions thus improves rheological properties of
the printing
solution used to form the regions of add-on material.
When the add-on material is applied with a printing technique, viscosity of
the applied
material is important. Where the viscosity of the applied material increases
over time, the add-
on material has a finite shelf life, or pot life, after which the material
loses its usefulness. As
Table I demonstrates, with the addition of an anti-wrinkling agent to the
applied material
formulation, the initial viscosity of add-on material can be reduced by about
20%. Moreover, the
shelf life, or pot life, of the add-on material increases by a factor of at
least two or more
compared to material not having an anti-wrinkling agent.
The results provided in Tables Ill and IV indicate that addition of an anti-
wrinkling agent
to the printing solution reduces free-burn self-extinguishment without
unacceptably affecting
ignition propensity performance (i.e., while maintaining an acceptable
ignition propensity levels).
For purposes of the information presented in Table Ill, batches of 40
cigarettes were tested to
obtain the ignition propensity performance, while batches of 20 cigarettes
were tested at each
angular position to obtain the self-extinguishment performance.
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Table Ill
Print solution with 22% Starch + 100% 1,2 propylene Glycol' + CaCO3
(SE is self-extinguishment)
width ignition propensity SE
CaCO3 % SE (00) SE (45 ) SE(90 )
/mm 1%
(average)
7 0 40 85 100 75
7 0 35 90 100 75
6 0 75 , 100 100 92
6 5 0 60 100 53
7 0 10 80 100 63
7 0 10 75 95 60
6 5 25 85 100 70
6 10 5 40 50 32
7 7.5 5 60 90 51
80 7 5 0 65 85 50
6 25 0 45 50 32
5
11,2 propylene glycol added to a solution of 22% dry starch in water; 1,2
propylene
glycol added to the starch solution with the ratio of 1,2 propylene glycol to
dry starch being
1.0:1.0; and CaCO3 being added to the starch solution in the weight percentage
stated,
measured relative to the weight of dry starch used in the solution.
n:i
From Table III, certain conclusions can be drawn. For example, the ignition
propensity
stayed well under the 25% target value for 7mm bands. In addition the ignition
propensity
stayed well under the 25% target value when CaCO3 weight was less than 80% of
the starch
weight. Further, the average self-extinguishment values was less than or equal
to 70% when
15 CaCO3 weight was greater than 40% of the starch weight; and self-
extinguishment at 00 was
less than or equal to 25 when CaCO3 weight was greater than 40% of the starch
weight.
For purposes of the information presented in Table IV, smaller groups of
cigarettes were
tested, namely groups of five. The cigarettes tested for the results in Table
IV were prepared
with two hand-brushed bands using the add-on material solution as indicated in
Table IV.
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21
Table IV
self-
ignition
Solution extinguishment
propensity
(at 0 )
20% starch solution 0 out of 5 3 out of 5
20% starch solution + glycerin'
0 out of 5 1 out of 5
Weight ratio of glycerin to dry starch = 1 : 5
Glycerin added to a solution of 20% dry starch in water; ratio by weight of
added
glycerin to dry starch present in the solution is 1 : 5.
For both solutions containing an anti-wrinkling agent, all of the cigarettes
self-
extinguished before the coal reached the filter line in the ignition
propensity test. However, in
the self-extinguishment test (at 0 ), for the solution without an anti-
wrinkling agent, 60% of the
cigarettes self-extinguished before the filter line, whereas for the solution
containing an anti-
io wrinkling agent, only 20% of the cigarettes self-extinguished before the
filter line. The self-
extinguishment thus remains below a common target of 25%. The ignition
propensity
performance was excellent, with the resulting value of 0% being well below
target values of
10%, 15%, or 25% often used. Thus, the addition or inclusion of an anti-
wrinkling agent in the
regions of add-on material reduces free-burn self-extinguishment (self-
extinguishment) without
adversely affecting ignition propensity (ignition propensity) performance.
Inclusion of an anti-wrinkling agent in the add-on material also enhances
characteristics
of the resulting banded wrapper. More particularly, an anti-wrinkling agent
has been found to
increase flexibility of add-on material when dried on the wrapper (L e., it
acts as a plasticizer).
As a result, bands of add-on material are less prone to separate from the base
web during
handling and use than bands on wrapper where an anti-wrinkling agent is not
used in the
formulation. Furthermore, as noted above, incorporation of an anti-wrinkling
agent in the add-on
material gives rise to improved self-extinguishment performance in a smoking
article fabricated
from wrapper having bands of add-on material including an anti-wrinkling agent
¨ but without
degradation of ignition propensity performance.
While the operation of the anti-wrinkling agent in the starch solution is not
fully
understood, it appears that the anti-wrinkling agent also functions as a
plasticizer in the starch
solution. A starch solution without an anti-wrinkling agent capable of also
functioning as a
plasticizer tends to infiltrate the top surface of the paper structure.
Moreover, without the agent,
a starch solution tends shrink or contract when it dries. That shrinkage
and/or contraction
causes the underlying web to also shrink or contract, i.e., in the area
underlying the banded
region. By way of example, observations have shown that the width of a 92cm
(36 inch) wide
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22
paper web may shrink by as much as about 1.3cm to 1.9cm (0.5 inch to about
0.75 inch) in the
banded region; that is, by about 1% to about 2%. Such shrinkage may create
difficulties, such
as in maintaining proper registration among multiple print stations when using
multipass
printing, among others.
Since the underlying web, between banded regions, does not experience the
shrinkage,
the region between the banded regions exhibits waviness, where the waves
extend in the
longitudinal direction of the underlying web and the undulations of the waves
occur in the cross-
web or transverse direction of the underlying web. After the underlying web is
slit longitudinally
into portions sized to manufacture cigarettes, each of those longitudinal
portions of the paper
io
web is wound tightly on a corresponding bobbin. Accordingly, the undulations
described above
sometimes result in creases in the unbanded regions where the paper folds on
itself to adjust to
the width reduction caused by shrinkage in the banded regions. Such creases in
the wrapper
are generally unacceptable for tobacco rod production. The effect of that
shrinkage can be
easily seen in FIGs. 60A, 60B, 60C. Those figures are optical microscope
images of the
wrinkled region between print banded regions where a single application of
film-forming material
is applied at 5.5X. The film-forming material used contained 22% starch and
40% chalk or
calcium carbonate.
Thus, the shrinkage of the banded regions appears to be a cause of wrinkling
in the
unbanded, or unprinted, area of the wrapper. Again, the mechanisms are not
fully understood,
zo
but the addition of an anti-wrinkling agent to the starch solution appears to
cause the printed
layer or banded region to be more flexible. That flexibility may result from
the printed starch
layer being more elastic. That flexibility may also result from the printed
layer having reduced
infiltration into the paper structure such that the printed layer lies more on
the surface of the
paper web. Regardless of whether those mechanisms, a combination of those
mechanisms, or
some other mechanism is active, observations indicate that, when the wrapper
flexes, the
enhanced elasticity of the layer or banded region reduces the likelihood that
the layer or banded
region will separate from the wrapper. Moreover, the elasticity of the layer
or banded region
appears to allow the layer or banded region to dimensionally conform to the
underlying paper as
the applied solution dries; hence shrinkage in the banded region is reduced
and,
simultaneously, wrinkling and/or puckering between the banded regions is also
reduced.
Accordingly, incorporating the anti-wrinkling agent in the starch solution
counteracts the
wrinkling described above.
The effect of adding an anti-wrinkling agent to a film-forming material may be
easily seen
in FIGs. 600, 60E, 60F, 60G, 60H, 601, which are photographs taken through an
optical
microscope of the region between print banded regions under the same
conditions as
FIGs. 60A-G.
In FIGs. 60D-60F, glycerin was used as an anti-wrinkling agent. The film-
forming material was applied at 5.5X, and contained 22% starch, 40% chalk, and
20% glycerin.
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23
In FIGs. 60G-601, 1,2 propylene glycol was used as an anti-wrinkling agent. In
these figures,
the film-forming material was applied at 5X, and container 22% starch, 40%
chalk, and 100%
propylene glycol. FIG. 60 demonstrates the surprising impact on print banded
paper obtained
by adding an anti-wrinkling agent to the film-forming material.
A further advantage of the anti-wrinkling agent herein disclosed concerns the
film-
forming attributes of the solution. More particularly, inclusion of the anti-
wrinkling agent in the
add-on material seems to enhance the film-forming characteristic of the add-on
material with
respect to the surface of the base web to which the add-on material is
applied. That improved
film-forming characteristic is believed to enhance the ignition propensity
performance of banded
io
wrappers constructed from the add-on material. Moreover, the film-forming
characteristic
enhances the desired occlusive effect of the layer sufficiently such that it
may be possible to
reduce the number of multi-pass applications that may have been needed with
solutions not
having the anti-wrinkling agent. With the anti-wrinkling agent, single pass
operation may be
possible with addition of adequate drying capability.
Some further advantage has been observed when 1,2 propylene glycol is used as
the
anti-wrinkling agent. Specifically, 1,2 propylene glycol can be effectively
used where the ratio of
1,2 propylene glycol weight to starch weight in the solution is about 100%. By
contrast, glycerin
can be effectively used when the ratio of glycerin weight to starch weight in
the solution is less
than 40% because at that ratio the drying time for the starch-and-starch-
plasticizer solution
becomes unacceptable. That difference in drying time may result from the
difference in boiling
point for glycerin (290 C) and the boiling point for 1,2 propylene glycol
(187.3 C); a difference of
about 100 degs C. For 1,2 propylene glycol, the boiling point is closer to the
boiling point of an
aqueous solvent than is the boiling point of glycerin.
With the addition of an anti-wrinkling agent to the starch solution,
permeability of the
banded region is improved, i.e., the permeability is more uniform and is lower
than permeability
for a band that does not use plasticizer. This phenomenon is significant
because it permits the
required quantity of starch solution to be applied or printed in a single
printing step. Those
skilled in the art will appreciate that, in the past, multiple printing steps
were typically needed to
effect the necessary permeability reduction in the banded regions. Of course,
it may still be
desirable, for other reasons, to continue use of multilayer printing
operations.
CALCIUM CARBONATE
Calcium carbonate, or chalk, is preferably added to the nominal starch
solution in
addition to the anti-wrinkling agent, the weight of chalk may lie in the range
of 0 to about 100%
of the weight of starch in the nominal solution; preferably in the range of
about 40% to about
100%; and most preferably in the range of about 40% to about 80%, with a
preferred target level
of approximately 60%. Chalk may be added to the nominal starch solution to
adjust the
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reflectance of the resulting add-on material so as to be comparable to the
reflectance of the
uncoated base web material. With such reflectance, banded regions constructed
from the add-
on material are less visible to the casual observer.
The CaCO3-to-starch ratio may also be a significant factor in determining
ignition
propensity and self-extinguishment performance of a smoking article fashioned
from the
wrapper of this disclosure, when prepared by high-speed printing. The CaCO3-to-
starch ratio is
determined as the ratio, by weight, of calcium carbonate to starch for the
region of add-on
material. More specifically, a CaCO3-to-starch ratio of less than about 0.8 is
preferred to obtain
desired ignition propensity performance together with improved self-
extinguishment (at 00)
performance less than about 25%. CaCO3 is included in the make-up of the
embodiment
described with reference to FIG. 10 to enhance its self-extinguishment
performance, among the
other reasons set forth herein.
From the foregoing description and the attached drawings, those skilled in the
art will
understand that a method of manufacturing a banded wrapper for smoking
articles has been
described. In that process, banded regions 126 (see FIG. 2) of add-on material
are established
as spaced locations on one surface of the base web 123. Spacing of those
banded regions 126
may be selected so as to be substantially greater than the width of those
banded regions 126 in
the longitudinal direction 142 of the base web 140. The width of the banded
regions 126 may
be selected to lie in the range of about 5mm to about 10mm (millimeters); and
the spacing
between those banded regions 126 (that spacing being measured as the distance
from the
trailing edge of one banded region to the leading edge of the next adjacent
banded region) may
be in the range of about 12mm to about 40mm.
PREFERRED STARCH COMPOSITIONS AND THEIR PREPARATION
Banded regions of this disclosure preferably comprise an aqueous solution
containing
starch, chalk or CaCO3, and an anti-wrinkling agent. While many types of
starch are
contemplated, tapioca starch is presently preferred for the starch component
of the layers 210,
212, 214 (FIG. 10). A suitable commercially available starch is FLO-MAX8
available from
National Starch & Chemical Co.
Unexpectedly, it has been found that certain characteristics of the starch
material give
rise to predetermined patterns that yield very low Ignition Propensity values
when the patterned
base paper is formed into smoking articles. Even more surprising has been the
realization that
within the standard specifications for some well-known starch materials, batch-
to-batch
variations in material properties can affect the Ignition Propensity of the
resulting smoking
articles. By way of example, the specifications of an oxidized tapioca starch
commercially
offered by National Starch & Chemical Co. as Flo-Max 8 indicate a pH in a 1%
solution lying in
the range of 4.5 to 6.5, with particles having molecular weights in excess of
10,000.
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Surprisingly, when a predetermined pattern was applied to a base web with a
batch of
Flo-Max 8 having a pH in the range of about 6 to about 6.5, ignition
propensity has been found
to be much improved when compared to other batches of Flo-Max 8 for which the
pH was less
than about 6 but still within the manufacturer's specifications.
5
Various balances or trade-offs need to be made in selection of starch
parameters for use
in applying films to wrapper. For example, while high molecular weight starch
may give rise to
effective permeability reduction, such high molecular weight starches must be
used in low
concentrations, resulting in a solution having a very high water content. But
high-water-content
films are much more difficult to effectively dry on porous wrapper. Moreover,
it has been found
10
that surface tension of the starch solution affects the retention of small
bubbles of air; low
surface tension allows smaller bubbles to remain in the solution, whereas high
surface tension
causes bubbles to agglomerate and separate out of the solution giving a more
uniform and
consistent material for application to the wrapper.
Although not fully understood, the preferred pH range of the oxidized starch
is believed
15
to reflect a lower degree, or less complete, oxidation of the starch polymer
chains giving more,
longer polymer chains than the more acidic (i.e., lower pH) starches.
Furthermore, longer polymer chains yield a solution having a higher viscosity.
Higher
viscosity for the starch solution translates to better control when applied to
a wrapper in a
printing process.
20
Based on these understandings, it has been found that marked improvement in
the
ignition propensity of patterned wrapper results for starch solutions having
particular, and
improved, characteristics. Those characteristics for an aqueous solution
including oxidized
starch include a pH in the range of about 6 to about 6.5; a surface tension of
at least about
6.5.10-2N/m (65 dynes/centimeter); a room temperature viscosity of no greater
than about
25
50mPa.s (50 centipoises); and a particle size distribution in the range of
about 4pm (microns) to
about 40pm for dry particles, with about 90% also being in the range of about
10pm to about
100pm when wet. Furthermore, the particles preferably have a molecular weight
such that the
solution can have starch concentrations in the range of about 14% to about
24%. Preferably,
the starch comprises an oxidized tapioca starch.
The aqueous starch solutions used for application to the base web or wrapper
are
typically prepared by making a starch/water mixture by first mixing the
desired weight of dry
starch powder with the desired weight of room temperature water (i.e., at
about 15 C to about
25 C) to obtain a starch/water mixture having the reselected concentration.
For example, to
prepare a starch/water solution with a reselected concentration of 20%, 20
parts by weight of
starch are mixed with 80 parts by weight of water. The starch/water solution
is then heated to
an elevated sub-boiling temperature in the range of about 90 C to about 95 C;
i.e., below the
boiling temperature. The starch/water solution is held at the elevated
temperature for about 20
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to about 30 minutes for thermal soaking. Then, the starch/water solution is
cooled to room
temperature. That cooling step can occur by passively, such as by naturally
occurring heat
transfer processes; or the cooling step can be active (or forced) such as by
immersion in a
cooling bath or by use of a conventional mechanical cooling system. Throughout
the mixing
step, the heating step, the thermal soaking step, and the cooling step, the
starch/water mixture
is stirred. The stirring can be continuous or substantially continuous. If
additional constituents,
such as calcium carbonate, are to be incorporated into the starch/water
solution, those
constituents should be added after the starch/water solution returns to room
temperature
following the thermal soaking step.
io
Aqueous starch solutions having the characteristics specified above and
prepared in the
manner described above can be applied to a base web using any of a multitude
of printing
techniques including, by way of example and without limitation, the group
consisting of gravure
printing, offset printing, inkjet printing, spraying, and die printing. Other
printing processes may
also be suitable and are intended to lie within the teachings of this
specification. Preferably,
however, gravure printing may be used to apply the starch solution to a base
web to obtain a
patterned wrapper.
Surprisingly, it has been found that the CaCO3/starch ratio is a significant
factor in
determining ignition propensity and self-extinguishment performance of a
smoking article
fashioned from the wrapper of this disclosure prepared by high-speed printing.
The
CaCO3/starch ratio is determined as the ratio, by weight, of calcium carbonate
to starch for the
region 126 of add-on material, i.e., for both layers. More specifically,
iCaCO3/starch ratio of at
least about 35% is preferred to obtain ignition propensity and self-
extinguishment(0 )
performance less than about 25%. Even more preferred is a CaCO3/starch ratio
of at least
about 45% to obtain ignition propensity and self-extinguishment(0 )
performance less than
about 20%.
If desired, the layer 150 printed on the base web 140 (see FIG. 3) may be the
starch
layer, and the layer 152 may be the layer comprising a mixture of starch and
calcium carbonate.
A presently preferred arrangement, however, places the mixture of starch and
calcium
carbonate in the first layer 150 and applies only starch in the other layer
152.
It has been observed that (i) the optical reflectance of the base web 140 and
(ii) the
optical reflectance of the mixture of starch and calcium carbonate are quite
similar. In fact,
those two reflectances are sufficiently similar that optical inspection
equipment can have
operational difficulty. On the other hand, (i) the optical reflectance of the
base web 40 and (ii)
the optical reflectance of a layer comprising starch have been observed to be
substantially
different.
The different reflectance characteristics of the layers 150, 152 are
advantageously used
to enhance the optical inspection characteristics of the wrapper of this
disclosure. With the
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27
starch layer deposited on top of the starch-calcium-carbonate layer, optical
inspection of the
wrapper is materially enhanced. More particularly, as the base web 140
advances from a
supply bobbin through the gravure printing apparatus to the take-up bobbin ,
the web 140 may
also pass through an inspection station. In the inspection station, a light
source is focused on
the moving web 140. A light beam emanating from the light source reflects from
the surface of
the moving base web 140 such that the reflected light is collected by a
sensor. As each region
126 of add-on material moves through the inspection station, the region 126
interrupts the light
beam and modulates the quantity of light reflected to the sensor. Because the
reflectance of the
starch layer is different from the reflectance of the base web 140, the sensor
can be constructed
to sense the presence or absence of a region 126. When coupled with an input
related to the
speed of the base web through the inspection station, an even more
sophisticated sensor can
determine the width of the region 126 in the longitudinal direction of the
base web 140, as well
as longitudinal spacing between adjacent regions, for quality control and
manufacturing
consistency. In connection with the inspection of banded regions, please also
see
US 5 966 218 and US 6 198537.
Surprisingly, as calcium carbonate levels are increased in the banded regions
126
exposed to the optical inspection, or machine vision, systems, those systems
have been
observed to become less reliable. That reduced reliability appears to result
from increased
reflectivity of the surface of the banded regions 126. Such increased
reflectivity overwhelms, or
"blinds", the inspection systems, a phenomenon perhaps resulting because the
reflectance of
banded regions 126 with high calcium carbonate levels is comparable to, and
may be
substantially equivalent to, the reflectance of the base web itself. That
reflectance parity seems
to result when the calcium carbonate level in the surface region of the banded
regions 126 is
greater than about 80% of the starch level in the surface region of the banded
regions 126.
That reflectance parity problem can be alleviated by establishing an structure
for the
banded regions 126 in which the surface region has a reflectance which is
sufficiently different
from the reflectance of the base web that the inspection systems consistently
identify the
reflectance variation to identify parameters related to the banded regions
126, including by way
of example presence of the reflectance variation (beginning or end of banded
region 126),
absence of the reflectance variation (a missing banded region 126, or a
misplaced banded
region 126), and longitudinal extent of a banded region 126 or spacing between
banded regions
126 (e.g., how long a particular reflectance continues for a sensed velocity
or speed of the base
web through the inspection station). One way of establishing a desired
structure for the banded
regions 126 is to provide the increased calcium carbonate layer in a position
more remote from
the inspection system than the layer having essentially starch. Stated
differently, by
superposing the starch layer on the calcium-carbonate-containing layer,
efficacy of optical
inspection systems will not be impeded, but will continue to be effective.
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Such an arrangement of layers in the banded region 126 provides another
surprising
and beneficial attribute for the wrapper. When the first layer of the banded
region 126 applied to
the base web contains both calcium carbonate and starch, the presence of the
banded region
126 is less evident when observed or examined from the side of the base web
opposite to the
side on which the banded region 126 is applied, i.e., the side opposite from
the side where
machine vision operates. In fact, as the calcium carbonate levels approach
high levels which
are the subject of this disclosure, presence or existence of the banded region
126 becomes less
visible to a consumer, and may actually become substantially invisible to an
ordinary consumer.
Such visual masking is important because consumers of smoking articles are
io accustomed to products in which the wrapper exhibits a uniform,
homogeneous appearance.
The preferred arrangement for the layers 150, 152 (see FIG 3) yields a further
significant
advantage to a smoking article manufactured using the wrapper of this
disclosure.
Similarly, many types of calcium carbonate particles are contemplated as
falling within
the spirit and scope of this disclosure. Presently, however, calcium carbonate
available from
Solvay Chemicals, Inc., as SOCAL 31 is a suitable commercially available
calcium carbonate.
SOCAL 31 is an ultrafine, precipitated form of calcium carbonate having an
average particle
size of about 70nm (nanometers). Larger particles of calcium carbonate have
been observed to
not function as well in this application when compared to the ultrafine,
precipitated form of
calcium carbonate, due at least in part to the tendency of larger particles to
precipitate from
solution more quickly and due at least in part to the need for greater
quantities to attain the
beneficial characteristics discussed herein.
The materials used for the regions of add-on material can be important in the
ignition
propensity and self-extinguishment performance of a smoking article
manufactured using the
wrapper discussed herein. In one embodiment, the regions of add-on material
may be printed
with a starch solution that includes an anti-wrinkling agent. While an aqueous
starch solution is
presently preferred as the aqueous component is readily dried, use of a non-
aqueous starch
solution is also within the spirit and scope of this disclosure. In another
embodiment, the
regions of add-on material may be printed with a solution comprising a mixture
of calcium
carbonate (or chalk) particles, starch, and an anti-wrinkling agent. As with
the starch and anti-
wrinkling agent solution, the solution comprising a mixture of calcium
carbonate (or chalk)
particles, starch, and an anti-wrinkling agent preferably is applied as an
aqueous solution, but a
non-aqueous solution also falls within the spirit and scope of this
disclosure.
Generally speaking, this disclosure contemplates that either (i) an anti-
wrinkling agent or
(ii) a combination of anti-wrinkling agent and calcium carbonate will be added
to a nominal
aqueous starch solution to obtain the add-on solution to be used for printing.
As discussed in more detail above, incorporation of an anti-wrinkling agent in
the
starch solution permits the aqueous starch solution to be applied in a single
printing step or
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layer to the underlying paper web. While an anti-wrinkling agent may also be
used in a
multilayer construction for a banded region applied in multiple printing steps
or passes, the
benefits of the anti-wrinkling agent flow from its use in the first layer
applied to the base web.
From the discussion above, it will now be apparent to those skilled in the art
that many
different patterns for the banded regions of wrapper fall within the spirit
and scope of this
disclosure. For example, a pattern comprising a plurality of solid
transversely extending bands
has been described (see FIG. 2). Solid bands may be either transversely
extending,
longitudinally extending 220 (see FIG. 11), or helical 222 (see FIG. 12). The
description as
being solid meaning, for purposes of this disclosure, that the regions of add-
on material are
io applied in a single step.
The foregoing discussion also makes clear that the regions of add-on material
may, if
desired, be applied in two or more successive steps or applications. Gravure
printing
techniques, as well as other printing techniques, are well-suited to such
successive steps, or
multiple applications.
IMPROVED SELF-WEXTINGUISHMENT PERFORMANCE WHILE MAUNTAINING IGNITION
PROPENSITY PERFORMANCE
As noted above, it is desirable to achieve ignition propensity performance
that meets
and exceeds governmental requirements. Such is achievable with a solid band
configuration
such as that described with reference to FIG. 10. Moreover, as also previously
noted, that
desired ignition propensity performance often adversely impacts the self-
extinguishment
performance of the smoking article. Stated differently, while the ignition
propensity performance
may meet or exceed the governmental requirements, that ignition propensity
performance is
typically associated with a smoking article that will self extinguish when
hand held by a smoker,
a self-extinguishment of 100%. Since smokers ordinarily prefer not to need to
relight a smoking
article, improvement of self-extinguishment performance while maintaining
ignition propensity
performance constitutes a highly desirable feature for improved wrappers.
Applicants have
discovered arrangements of the banded regions on wrapper that provide such
improved self-
extinguishment performance while maintaining the ignition propensity
performance. For
example, the inclusion of chalk content in the embodiment described with
reference to FIG. 10
contributes enhancement of self-extinguishment performance amongst other
attributes.
In addition to or in lieu of applying chalk to improve self-extinguishment
performance,
certain band configurations and patterns disclosed herein are useful in
constructing smoking
articles having both improved self-extinguishment performance and desired
ignition propensity
performance. For example, a slit band configuration such as shown in FIG. 5
and others is
capable of better sustaining smoldering during free burns, yet when placed
adjacent a
substrate, does not sustain smoldering.
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Referring to Table V, wrapper A comprises a slit band arrangement, having
three
regions of about 2mm each, for a total width of 6mm for the printed banded
region with add-on
rates in the various regions ranging from about 3.5x to about 5.5x. An add-on
rate of 5.5x
results in about 8g/m2 to about 9g/m2 of add-on material on a dry weight
basis, where the
5 wrapper has a nominal basis weight of about 26.5g/m2. Lower add-on rates
would be expected
to provide proportionally adjusted values for the weight of the add-on
material, measured on a
dry weight basis. The widths of the banded regions are typically measured in
the longitudinal
direction, and have a 27mm phase (i.e., the spacing from the leading edge of a
banded region
to the leading edge of the next or subsequent banded region).
Table V
Banded Region Total Banded Base
Web
Wrapper
Configuration Region Width
Permeability
A 2-2-2 6mm 33 CORESTA
2.5-2-2.5 7mm 33 CORESTA
2.5-2-2.5 7mm 60 CORESTA
3-2-3 8mm 60 CORESTA
In Table V, the "banded region configuration" is a shorthand description of
the width of
portions of the band, viewed in the direction which the coal advances in a
burning tobacco rod.
Thus, the 2.5-2-2.5 configuration (see FIG. 5) of the banded region 126 means
that the first
portion or zone 202 (see FIG. 6) of the total banded region width is 2.5mm,
the second portion
or zone 203 of the total banded region width is 2mm (and may be a space), and
the third portion
or zone 204 of the total banded region width is 2.5mm. Here, the first portion
202 would be
encountered first by the advancing coal of a burning tobacco rod, the second
portion 203 would
be encountered next by the advancing coal, and the third portion 204 would be
encountered last
by the advancing coal.
Table VI ¨ Details of Wrapper A
Zone 1 Zone 2 Zone 3
Width 2mm 2mm 2mm
Layers of Add-on Material 1 1 1
Add-on Rate Per Layer 5x 3.5-4x 5x
Total Add-on Material 5x 3.5-4x 5x
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Table VII ¨ Details of Wrapper B
Zone 1 Zone 2 Zone 3
Width 2.5mm 2mm 2.5mm
Layers of Add-on Material 1 1 1
Add-on Rate Per Layer 5x 3.5-4x 5x
Total Add-on Material 5x 3.5-4x 5x
Table VIII ¨ Details of Wrapper C
Zone 1 Zone 2 Zone 3
Width 2.5mm 2mm 2.5mm
Layers of Add-on Material 1 1 1
Add-on Rate Per Layer 5x 3.5-4x 5x
Total Add-on Material 5x 3.5-4x 5x
Table IX ¨ Details of Wrapper D
Zone 1 Zone 2 Zone 3
Width 3mm 2mm 3mm
Layers of Add-on Material 1 1 1
Add-on Rate Per Layer 5x 3.5-4x 5x
Total Add-on Material 5x 3.5-4x 5x
Tables VI-IX show that the multizone banded region 126 (see FIG. 5) may be
fashioned
in a single pass printing operation with the application rates indicated in
those tables. In each of
wrappers A through D, the add-on material preferably included an aqueous
solution containing
io
starch, chalk or calcium carbonate, and 1,2 propylene glycol. A presently
preferred mixture for
that aqueous solution includes starch, chalk, and 1,2 propylene glycol in a
weight ratio of about
100 (for starch), to about 40 to about 80 (for chalk), to about 100 (for 1,2
propylene glycol), in
weight percent. The starch alone may be in the range of about 20% to about 24%
in the
aqueous solution.
Some changes in the relative proportions of constituents of the add-on
material may
change when the aqueous solution is applied to a base web and dried. For
example,
observations indicate that when 1,2 propylene glycol is used as the anti-
wrinkling agent, about
50% to about 60% of the propylene glycol added to the solution remains in the
add-on material
when it has dried on the paper web. Some weight loss may also occur in other
anti-wrinkling
agents during the drying process. However, such weight loss has not been
observed with
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respect to the starch and calcium carbonate constituents of the add-on
material during the
drying process.
The region 126 of add-on material may be substantially continuous transverse
of the
paper web, as shown (see FIG. 2), or may have one or more longitudinally
extending
separations so as to define a C-shaped region when formed into a wrapper for a
tobacco rod
(see FIG. 7), or may have several arcuately-shaped portions 127' (see FIG. 8)
generally
symmetrically positioned around the tobacco rod when viewed in cross section
transverse to the
longitudinal axis 134 of the tobacco rod 122.
In addition, the region 126 of add-on material on the wrapper 123 may be
divided into
two or more substantially ring-shaped portions (see FIG. 5) that are spaced
from one another
along the axis 142 by a distance, w, that typically does not exceed the width
of the rings 126,
when measured in a direction generally parallel to the axis 134 of the tobacco
rod 122. Such a
spacing feature provides a "slit" in the band structure.
It is also within the contemplation of this disclosure that the region 126 on
the wrapper
123 may comprise a plurality of patches 127 (see FIG. 8) disposed
circumferentially around the
tobacco rod 122, with patches 127' of an adjacent region 126 being
circumferentially displaced
from patches of other adjacent regions 126. In addition, the patches 127, 127'
may be arranged
according to a predetermined pattern such as taught in U.S. Patent Application
Serial No.
12/153,783 (published as US 2008-0295854 on December 4, 2008).
The regions of add-on material are preferably applied in a single layer 210
(see FIG. 9).
It should be noted that the representation of the base web cross section in
FIG. 9 is schematic.
As discussed above, the actual cross section of a base web is a slice through
the myriad of
fibers which form the base web. In the case of cigarette wrapper, that
thickness may be on the
order of about 30 microns (i.e., 30 x 10.8 meters or 30pm). Actual thickness
of the add-on
material s 2pm, and the add-on material tends to infiltrate and conform to the
surface presented
by the fibers of the base web. As a result, material build-up in the regions
of add-on material
can be schematically shown as boxes (as in FIGs. 3, 6, and 9), but actually
are nearly
imperceptible to the unaided eye. To that end, it will be appreciated that, if
multiple layers are
used to form the regions of add-on material, the resulting structure is nearly
impossible to
resolve into the individual layers. That resolution into individual, or
separate, layers is further
complicated when aqueous solutions are applied because subsequent layers tend
to re-wet the
previous layer and allow components such as chalk to settle through the
material of the prior
layer.
The application rate of the material in the preferred single layer (see FIG.
9) may be in
the range of about 4X to about 6X. For these purposes, the "X" has been
described above.
Where the base web has a nominal CORESTA value of about 33, a presently
preferred
application rate of about 5X is believed to be appropriate. Where the base web
has a nominal
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33
CORESTA value of about 60, a presently preferred application rate of about
5.5X is believed to
be appropriate.
Although the regions of add-on material are preferably applied in a single
pass,
application, or layer, this description also contemplates application of the
add-on material in
multiple applications steps, or layers (see FIG. 10). In this embodiment,
after a first layer 210 is
applied to the surface of the base web 123 at a first gravure printing station
and dried, a second
layer 212 (see FIG. 10) of add-on material may be applied to the wrapper, for
example at a
second printing station. If desired, a third or subsequent layer 214 can be
applied at further
printing stations. The second layer 212 may be arranged so as to be superposed
on, and
o substantially co-extensive with, the first layer 210. Alternatively, the
second layer 212 may
cover only one or more portions of the first layer 210. The relative
application rate of the layers
need not be the same, and preferably is different. For example, one layer may
be at least about
1.5 times to about 3 times the thickness of the other layer.
For example, the smoking article 120 (see FIG. 13) may include one or more
banded
regions 250 that are axially spaced from one another along the axis of the
smoking article 120.
Each banded region 250 may include add-on material applied such that at least
one
longitudinally extending gap 252 exists between end portions 254 of the banded
region 250.
The embodiment of FIG. 13 show a single gap 252 in each of the banded regions
250; however,
two or more gaps 252 may be provided around the circumference of the smoking
article 120.
Where more than one gap 252 is provided, the gaps are preferably generally
parallel to one
another and preferably are also substantially equally spaced from one another
around the
circumference of the smoking article 120. An embodiment of the smoking article
having a pair
of substantially diametrically opposed areas of add-on material may be seen in
FIG. 15. As
shown, the circumferential extent of the areas of add-on material 250, 250'
may be substantially
the same as the circumferential extent of the spaces or gaps 252 between those
areas of add-
on material 250, 250'.
With the foregoing arrangement, when the smoking article 120 exists in free-
burn
condition (see FIG. 15), the regions of add-on material 250, 250' obstruct
airflow to the burning
coal of the tobacco rod 122 by virtue of their reduced permeability. On the
other hand, with the
smoking article held in a substantially horizontal position, the bottom gap
252 of the wrapper
123 freely permits air to enter the side of the tobacco rod 122 to support
combustion of the coal.
A vastly different situation occurs when the smoking article 120 is placed on
a substrate 260
(see FIG. 14). Under these conditions, the substrate 260 blocks the flow of
air upwardly to the
bottom portion or bottom gap 252 of the tobacco rod 122. The regions of add-on
material 250,
250' and the substrate 260 cooperate to define much smaller areas 258, 259
through which air
can be drawn through the base web 140 of the wrapper. More specifically, the
vertical area 258
between the bottom of the region 250 and the substrate 260 and the vertical
area 258 between
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34
the bottom of the region 250' and the substrate 260 present a substantial
reduction in the area
through which air can pass to reach the smoldering coal of the tobacco rod
122. As a result of
deprivation of oxygen in the air, the smoldering coal of the smoking article
120 self-extinguishes
when the burn line reaches opposed regions of add-on material positioned as
depicted in FIG.
14. The condition of substantially reduced area for air to support burning of
the coal also exists
for rotational positions of the tobacco rod 122 between that position
illustrated in FIG. 14 and
other positions of the smoking article when rotated about its longitudinal
axis.
However, when the smoking article 120 is placed on the substrate 260 such that
one of
the add-on regions 250, 250' contacts the substrate 260, the add-on regions
still may sufficiently
io
restrict the area through which air can pass to and through the base web 140,
and there is a
lesser degree of material cooperation between the substrate 260 and the add-on
regions to
effect a reduction in that area, in comparison to what occurs at the snuffer
region 262. For
purposes of this description, a snuffer region 262 is an area on the tobacco
rod 122 which is
operable to cause extinguishment of the burning coal when placed on a
substrate 260.
In the foregoing example, the reduction in ignition propensity value is also
associated
with a reduction in self-extinguishment value, and improved free-burn quality
of a smoking
article 120 having a wrapper with regions of add-on material such as those of
FIG. 13. It will
also be appreciated by those skilled in the art that the self-extinguishment
improvement of FIG
15 occurs with the smoking article in a horizontal position (i.e., 0 ).
Similar self-extinguishment
improvements are also observed at other self-extinguishment evaluation
positions of 45 and
90 . Where the smoking article 120 happens to be placed on a substrate 260 at
one of three
specific orientations, the orientations being spaced (off-set) 45 apart from
each other around
the axis of the smoking article, the self-extinguishing characteristics and
desirable ignition
propensity are also achieved. Naturally, the discussion proceeded in this
manner for the sake
of brevity. It will be readily understood that a pattern according to this
description can extinguish
the smoking article, regardless of which side portion rests against a
substrate 260 and without a
need for applying film-forming compound to the paper to such an extent that a
desirable free-
burn quality in the smoking article is lost or such that carbon monoxide
levels in the mainstream
smoke become elevated. This may be understood by recognizing that opposing
regions of film-
forming compound need not appear at locations exactly 90 from the side
portion in contact with
the substrate 260. Those regions may be centered at a location that is closer
to or farther from
the side portion in contact with the substrate 260, for example, between about
60 and 120
from the side portion in contact with the substrate 260.
Additionally, for a particular chosen pattern, the ability to extinguish the
smoking article
may depend more on providing minimum lengthwise extent of add-on material
(e.g., a film-
forming compound), rather than a particular weight per area of film-forming
compound at
longitudinal locations. The length of a rectangular region, for example, may
be no less than
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about 5.5mm for a particular design, base web, and film-forming compound used.
The amount
of film-forming compound used may be increased to improve ignition propensity
performance,
usually without losing a free-burn quality and self-extinguishment
performance, and if desired, a
burn accelerator may be applied to the paper to support even higher add-on
levels.
5
Previously, it was thought that a permeability ratio of 3:1 between the base
web and
regions of add-on material was insufficient to extinguish the smoking article
because there is an
insufficient reduction in the permeability of the paper at the longitudinal
position of the snuffer
region. However, that permeability ratio, over a portion of the circumference
of the smoking
article, may be sufficient to extinguish the smoking article when there is an
underlying substrate
10
260 and when the add-on material is located at sides of the smoking article
120 not in contact
with the substrate 260.
Another embodiment of a smoking article which makes use of the interaction
between
longitudinal spaces between opposed regions of add-on material and a substrate
is shown in
FIG. 16. Here, a series of longitudinally spaced snuffer regions are spaced
along the axis 134
15
of the smoking article 120. Each pair of areas of add-on material in a snuffer
region may be
referred to as patches for quick reference.
With reference to FIG. 17, the paper wrapper 123 further comprises pairs of
add-on
material zones at spaced locations along the tobacco rod 122 in FIG. 16 (such
as the opposing
pair of zones 270d, 272d).
20
Each pair of rectangular zones (for example, 270a and 272a--the latter not
being visible
in FIG. 16) define a circumferential region 274 (for example, the region
274a). The "width" of
the banded region 274a is measured from a leading edge 146 of the region 274a
(it being
closest to an approaching coal) to the trailing edge 148 (it being most remote
from an
approaching coal). Preferably the width of the regions, e.g., 274a, lies in
the range of about
25
5.5mm to about 12mm, more preferably, about 7mm to about 10mm, and most
preferably about
8mm to about 9mm. Moreover, at each circumferential region, such as region
274a, the zones
270a and 272a are circumferentially spaced apart such that they are disposed
in mutually
opposing relation along opposite sides of the wrapper 123 when formed on a
tobacco rod 122.
Preferably each zone 270a, 272a extends circumferentially (i.e., in cross-
measure relative to the
30
paper web) in the range of about 5 to about 9 mm in cross-measure, more
preferably, about
6mm to about 7mm in cross-measure.
It is further noted that the area 276 of base web 140 between adjacent regions
274a,
274b and the areas between opposing zones within each zone (such as between
the opposing
zones 270b, 272b of the zone 274b) are preferably essentially free of add-on
material
35 comprising the zones (e.g., zones 270b, 272b).
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The longitudinal distance between adjacent regions (such as between zones
274a, 274b
is referenced as band spacing 276, which is preferably about 4 to about 12 mm,
and more
preferably about 6mm to about 8mm.
Preferably, the respective opposing zones 270, 272 of each region 274 are
offset from
those of a preceding row or region to a degree (in accordance with teachings
which follow) and
a sufficient number of regions 274 are established along a given tobacco rod
(by selection of
band-region width and width of band-region spacing) such that, when the
smoking article is
placed up on a substrate, at least one location 101 exists along the tobacco
rod 122 where the
respective pair of regions 270 are oriented substantially alongside the
tobacco rod 122, such as
the opposing pair of zones 250, 250' in FIG. 14. It is at or about this
location on the tobacco rod
122 where self-extinguishment is most likely to occur. The location along the
tobacco rod 122
where this orientation most closely occurs is hereinafter referenced as the
"oriented snuffer
region."
Because the smoking article 120 might be laid upon a substrate differently
from the
position shown in FIG. 16 and/or because its pattern of zones may differ, it
is to be realized that
the oriented snuffer zone may occur at different longitudinal positions along
the tobacco rod 122
for different rotational positions of the tobacco rod 122. The pattern of
zones and the band
spacing 276 may be selected such that more than one oriented snuffer zone may
occur along
the tobacco rod 122.
Preferably, each zone 270, 272 and 272' includes sufficient add-on material to
reduce
the permeability of the wrapper at each zone to about 0 to about 12 CORESTA,
more preferably
about 7 CORESTA or less.
For purposes of this description, a pattern of add-on material is applied to
the wrapper
123 to obtain improved ignition propensity characteristics and also to obtain
improved self-
extinguishment characteristics.
As presently understood, the staggered zones of add-on material according to
this
description permit a smoking article 120 (see FIG. 16) to be designed with an
advantageous
combination of desired low ignition propensity values and desired low self-
extinguishment
values. The patterns of low permeability regions of add-on material provide
areas of film-
forming compound along the length of the tobacco rod 122 that can cooperate
with a substrate
to extinguish the lit smoking article 120 when it is placed on that substrate,
yet these areas of
add-on material (such as a film-forming compound) cause the smoking article
120 to self-
extinguish at statistically fewer occurrences when the smoking article 120 is
held by a smoker in
a free-burn condition. Thus, the smoking article 120 can exhibit a reduced
ignition proclivity
while retaining a desirable free-burn quality or low self-extinguishment value
by applying a
pattern of film-forming compound to the base web according to this
description.
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To achieve desirable ignition propensity and self-extinguishment
characteristics of the
smoking article, a pattern 300 (see FIG. 17) is applied to the base web 123 of
the wrapper,
preferably while the base web 123 is in an unfolded condition, such as shown
in FIG. 17, or
when the base web comprises a roll of cigarette paper that has yet to be slit
into bobbins. An
object of this description is to provide wrappers which, when formed into a
tobacco rod 122,
exhibit ignition propensity values no greater than 25 and self-extinguishment
values no greater
than 50. Even more preferred, is an ignition propensity value for the
resulting smoking article no
greater than about 15; and the most preferred ignition propensity value for
the resulting smoking
article is no greater than about 10. Lower self-extinguishment values are also
desired. In this
io connection, a more preferred self-extinguishment value is less than
about 25; while the most
preferred self-extinguishment value is less than about 10.
Referring specifically to FIG. 17, the transverse dimensions of the wrapper
123 are
selected based on the diameter of the finished smoking article (about 7 to
about 10 mm) and
allowing for overlapping material at a longitudinal seam of about 1 to about 2
mm. For example,
is allowing for 1 mm overlapping seams, the wrapper-paper cross-web
dimension may be about
27 mm for a smoking article having a circumference of about 25.6 mm.
Preferably, the pattern 300 is applied to the base web 140 such that a
plurality of
circumferentially extending regions 274a, 274b, 274c, 274d (defined by broken
lines in FIG. 17)
are disposed at spaced locations along the tobacco rod 122 (see arrow 142, in
FIG. 17). The
20 add-on material can be applied to one or to both sides of the base web.
Preferably, three to six,
and most preferably four to six or more, of the regions 274 occur in the
nominal length of the
tobacco rod 122. Each of the circumferential regions 274a, 274b, 274c, 274d
has a longitudinal
pitch along the tobacco rod 122 (i.e., length measured along the tobacco rod
from the beginning
of one region to the beginning of the adjacent region) which is less than the
nominal length of
25 the tobacco rod 122. By selecting the longitudinal pitch length at about
25% of the nominal
length, four regions will be provided on each tobacco rod 122.
Within each circumferential region, e.g., 274a, at least two zones, e.g.,
270a, 272a, of
add-on material are provided. Note that the zones of add-on material in all of
the figures are
identified with stippling to aid identification of them; however, in a smoking
article 120 or
30 wrapper 123 for such a smoking article, these zones of add-on material
may, or may not, be
visually identifiable. Each of these zones is preferably spaced
circumferentially such that the
zones will be opposed to one another in the finished tobacco rod 122.
Moreover, for each triplet
of zones, e.g., 274a, 274b, 274c, the zones 270b, 272b of the second region
274b preferably
are circumferentially offset from the zones 270a, 272a of the first region.
Furthermore, the
35 zones 270c, 272c of the third region 274c preferably are
circumferentially offset from the zones
270b, 272b of the second region 274b, and even further offset
circumferentially form the zones
270a, 272a of the first region 274a.
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As depicted in FIG. 17, the add-on zones of each region in this embodiment are
laterally
offset in a circumferential direction from the add-on zones of an adjacent
region by a distance
that is a function of the transverse dimension of the add-on zones. Each zone
has a width
measured along the tobacco rod 122 and a transverse cross-measure dimension in
the
circumferential sense of direction of the tobacco rod 122. For this
embodiment, the zone width
is less than the longitudinal pitch of the associated region. As seen in FIG.
17, the longitudinal
pitch length may be greater than the corresponding zone width of the
corresponding region.
The add-on zones of successive regions along the tobacco rod 122 are
preferably offset from
the add-on zones of the adjacent regions, thereby defining a pattern 300 of
regions which cover
portions of the base web along lines inclined relative to the edge of the base
web. Furthermore,
the pattern of add-on zones may repeat itself at least partially along the
length of the base web.
In the illustrated embodiment (FIG. 17), each zone is placed on the wrapper
123 so that
the zone is centered upon one of three paths 270, 272, and 272', which paths
are represented
by corresponding broken lines 270, 272 and 272'. Thus, for example, path 270
passes through
the corresponding geometric features of six zones 270a, 270b, 270c, 270d,
270e, 270f. Each
zone is spaced from the other zones, but the zones could, alternatively,
contact one another.
The paths 270, 272 and 270' are parallel to each other and oriented at an
acute angle relative
to the side edge of the wrapper 123. It is to be realized that zones 272' are
preferably the same
as zones 272 and result from progression through the pattern 300 shown in FIG.
17 where, as
zones 270 disappear along one edge, zones 270' appear along the opposite edge.
Each pair of
cross-web aligned zones, e.g., zones 270a, 272a, or zones 270b, 272b, may
cover up to about
33% of the total surface area of the corresponding region 274a, 274b. For
rectangular zones,
each zone is preferably in the range of about 8mm to about 10mm in the
longitudinal direction or
width, and about 5mm to about 7mm in the circumferential cross-measure
direction.
Longitudinal spacing 276 between the zones preferably lies in the range of 4mm
to about
12mm, and more preferably in the range of about 6mm to about 8mm. The
circumferential
spacing of the zones of add-on material is preferably in the range of about
3mm to about 20mm,
more preferably in the range of about 5mm to about 8mm, and most preferably in
the range of
about 5.5mm to about 7.0mm.
When wrapper 123 is formed about tobacco to make a tobacco rod 122, zones of
add-on
material at any longitudinal location are preferably spaced about 180 from
each other.
Moreover, the ratio of the area occupied by zones of add-on material to the
total area, the total
area being the sum of (i) the corresponding region 274d and (ii) the annular
area between
adjacent regions on one side (that ratio here being defined as the "zone area
ratio") is
substantially less than one. Preferably, that zone area ratio lies in the
range of less than about
20% to less than about 50%, and more preferably in the range of less than
about 20% to less
than about 35%. More particularly, in some embodiments the zone area ratio for
zone-occupied
CA 02690199 2015-08-18
39
area to total area may be less than 30%, and even less that 25%. Generally
speaking, it is
desirable to keep the zone area coverage ratio low because high values (L e.,
closer to 1) are
believed to increase carbon monoxide concentration in mainstream smoke where
low
permeability (i.e., low CORESTA) wrapper is used for the tobacco rod.
When the wrapper 123 is formed to make the tobacco rod 122, the paths 270,
272, 272'
describe a first helical path 272/272' (zones 272 and 272' in FIG. 17 combine
to form a helical
path 272/272') and a second helical path 270 (comprising helically aligned
zones 270) both of
which extend lengthwise, around axis 134, and over the length of the tobacco
rod 122, as
illustrated in FIGS. 16-17. The helical paths 272/272' and 270 (as seen from
FIG. 17) have a
helix angle 0 and do not intersect one another. Preferably, both helical paths
may follow one of
a counterclockwise and clockwise rotation about the tobacco rod 122. As
illustrated, both paths
270, 272' follow a clockwise path, starting at the filter end of the tobacco
rod 122, when viewed
from the lit end and looking towards the filter end.
The zones of the pattern 300 may be formed by applying one or more layers of
an
aqueous film-forming composition to the base web of the wrapper to reduce the
permeability of
the paper in those zones. Incorporation of an anti-wrinkling agent into the
film-forming
composition permits the pattern to be applied in two passes if desired or a
single layer if
additional drying capacity is established. Alternatively, a cellulosic
material may also be used to
form the zones. Where a film-forming composition is used, that film-forming
composition
preferably may include water and a high concentration of an occluding agent,
e.g., 20% to about
50% by weight. The film-forming compound can include one or more occluding
agents such as
starch, alginate, cellulose or gum and may also include calcium carbonate as a
filler. Where
starch is the film-forming compound, a concentration of about 24% may be
advantageous. The
film-forming composition may be applied to the base web of the wrapper 123
using gravure
printing, digital printing, coating or spraying using a template, or any other
suitable technique.
For example, the film-forming compounds and methods for applying film-forming
compounds
described in US Publication No. 2007-0102017,
may be chosen for applying a pattern to the base web of the
wrapper. If desired, the zones of add-on material can be formed by printing
multiple, successive
layers, e.g., two or more successive layers registered or aligned with one
another. Furthermore,
when layers are used to form the zones of add-on material, the material in
layers may be the
same of different. For example, one layer may be starch while the next layer
may be starch and
calcium carbonate (or vice versa).
The presently preferred embodiment for the pattern 300 of zones of add-on
material is
illustrated in FIG. 18. Like the embodiment of FIG. 17, the zones of add-on
material in FIG. 18
are quadrilateral, specifically, generally rectangular. Preferably, at least
two zones, e.g., 280a,
280b, of add-on material are applied in each region 274a, 274b, 274c, 274d so
as to be
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circumferentially spaced in the finished smoking article. The circumferential
dimension of each
zone 280a, 280b is preferably selected to be less than about 50% of the cross-
measure of the
base web 123 when unwrapped, and most preferably about 25% of the cross-
measure of that
base web 123 or of the circumference of the tobacco rod 122. The
circumferential dimension of
5
each zone 280a, 280b, when added to the circumferential spacing of between the
zones 280a,
280b, preferably is about 50% of the circumferential cross-measure of the base
web 123.
The longitudinal length of the zones 280a, 280b plus the longitudinal spacing
276
between the zones 280a, 280b, and zones 282a, 282b, (i.e., the longitudinal
pitch length) is
preferably selected so that three or four regions 274a, 274b, 274c, 274d will
occur in the
io
nominal length of the tobacco rod 122 of the smoking article and such that add-
on zones of
adjacent regions are spaced from one another longitudinally. Preferably, the
longitudinal
expanse or "width" of the zones, e.g., 280a, 280b (i.e., the zone width or
region width as
previously defined) lies in the range of about 8 to about 10 mm. The
circumferential offset, x,
between (i) the zones 282a, 282b of the region 274b and (ii) the zones 280a,
280b of the region
15
274a preferably lies in the range of about 10% to about 35% of the total,
unwrapped cross-
measure of the base web 123. More preferably, the circumferential offset, x,
lies in the range of
about 12% to about 35% of the total, unwrapped cross-measure of the base web
123. Most
preferably, the circumferential offset, x, is about half the circumferential
dimension or cross-
measure of the add-on zone 280a, 280b. The zones of add-on material in other
regions, 274c,
20
274d, are likewise further offset circumferentially by the same offset, x,
with respect to each
other. It will be noted that, for example, in region 274d one of the zones
286a, 286c of add-on
material gets split between the two edge portions of the base web 123 when the
base web is in
an unwrapped condition.
The pattern 300 applied in regions 274a-274d preferably repeats along the
length of the
25
base web 123. Clearly, if the circumferential offset, x, is less than 12.5% of
the cross-directional
width of the base web, more than four regions will define a complete cycle or
phase length for
the pattern 300. Conversely, if the circumferential offset, x, is greater than
12.5%, less than four
regions will define a complete cycle length for the pattern 300 (as in the
case of the FIG. 17
pattern).
30 A
further embodiment of the pattern 300 (see FIG. 19) uses quadrilateral zones
290a,
290b of add-on material, namely substantially parallelogram-shaped zones.
While the zones
290a, 292a are arranged so as to be in general helical alignment with one
another when the
wrapper is formed into a tobacco rod 122, the configuration of the
parallelogram shapes 290,
292, 294, 296 may be selected as desired. For example, the mirror images of
the shapes
35
(mirrored about the longitudinal direction) could be used, even though the
general helical
impression might be lost. Likewise, the skewness of the parallelogram zones
may be changed
as may be desired. Generally, however, the circumferential dimensions,
circumferential spacing
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41
or offset, longitudinal dimensions, and longitudinal spacing or offset of the
zones 290, 292, 294,
296 and the regions 31a-31d in this embodiment may be selected as described in
other
embodiments.
Still another embodiment of the pattern 300 (see FIG. 20) uses quadrilateral
zones 310,
312, 314, 316 of add-on material, namely substantially trapezoidal zones. Here
again, the
generally trapezoidal zones 310a, 312a may be arranged so as to be in general
helical
alignment with one another when the wrapper is combined into a tobacco rod
122. In addition,
the actual shape of the trapezoidal zones 310, 312, 314, 316 may be selected
as desired. For
example, the skewness of the trapezoidal zones, and the proportions of the
trapezoidal zones
io may be changed as may be desired. Generally, however, the
circumferential dimensions,
circumferential spacing or offset, longitudinal dimensions, and longitudinal
spacing or offset of
the zones 310, 312, 314, 316 and the regions 274a-274d in this embodiment may
be selected
as described in other embodiments. It is preferred that the leading edge 146
be the longer of
the two parallel edges of the zones 310.
Yet another embodiment of the pattern 300 (see FIG.21) uses generally
triangular zones
320, 322, 324, 326 of add-on material. The generally triangular zones 320a,
320b of region
274a may be constructed and arranged so as to touch the corresponding
generally triangular
zones 322a, 322b of the next adjacent region 274b. If the ignition propensity
and self-
extinguishment characteristics desired require it, the generally triangular
zones 320a, 320b of
the first region 274a may be longitudinally spaced from the triangular zones
322a, 322b of the
adjacent region 274b. Depending on the characteristics required for the
smoking article design,
it is also contemplated that the generally triangular regions may be oriented
so that the burning
coal of a smoldering smoking article encounters the triangular apex and
gradually increasing
cross-directional dimension of the generally triangular zones (i.e., from
right-to-left in FIG. 21),
or such that the burning coal of a smoldering smoking article encounters the
base of the
triangular zones and an abrupt increase in the lower permeability zones (L e.,
from left-to-right in
FIG 21). Circumferential spacing of the triangular zones 320, 322, 324, 326
and the size of
those triangular zones may be determined in accordance with the preferred
ranges set out
elsewhere in this description. Moreover, the triangular zones may be isosceles
triangles as
depicted, or equilateral triangles, or right triangles, or any other desired
triangular shape that
may be desired. Generally, however, the circumferential dimensions,
circumferential spacing or
offset, longitudinal dimensions, and longitudinal spacing or offset of the
zones 320, 322, 324,
326 and the regions 274a-274d in this embodiment may be selected as described
in other
embodiments. Preferably, the triangular forms of the zones 320 are oriented so
that a leading
edge 146 (closest to an approaching coal) is established.
The operation of these embodiments for the wrapper pattern 300 is best
understood by
consideration of FIGs. 22-24. These figures illustrate three different
positions of the smoking
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42
article 120 resting on the substrate 260 and are illustrative of the
cooperation which occurs
between the zones of low permeability add-on material and the substrate 260.
One position
(see FIG. 22) illustrates a side view of the smoking article 120 according to
this description.
Rotation of the smoking article through a 45 angle about its longitudinal
axis (clockwise from
the left end of FIG. 22) results in an elevation similar to that shown in FIG.
23. Similarly, further
rotation of the smoking article 120 through another 45 angle (also clockwise
from the left end of
FIG. 22) results in an elevation to that illustrated in FIG. 24. In each of
FIGs. 22-24 it can be
seen that at least one pair of zones of add-on material are positioned on the
sides of the
smoking article at a location along the length of the tobacco rod 122, e.g.,
zones 332, 332' of
FIG. 22, zones 324, 324' of FIG. 23, and zones 326, 326' of FIG. 24. At those
locations where
the zones 332, 332' of add-on material are positioned substantially on the
sides of the smoking
article 120 (FIG. 26), the zones 332, 332' are substantially upright or
generally perpendicular to
the surface of the substrate 260. That orientation of the zones 332, 332' is
best illustrated in
FIG. 27, where the opposed zones 332, 332' are located on corresponding
opposed sides of the
smoking article 120 when viewed in cross section, substantially symmetrically
positioned
relative to a diameter of the tobacco rod 122, which diameter is substantially
parallel to the
surface of the substrate 260.
Orientation of the zones of add-on material at other longitudinal locations
along the
smoking article 20 are shown in FIGs. 25 and 26. In FIG. 25, the zones 330,
330' of add-on
material are positioned such that one zone 330 touches the substrate 260. The
zones 334, 334'
of the smoking article 120 in FIG. 22 would also be positioned as in FIG. 25,
when viewed from
the right end of FIG. 22. In FIG. 26, one zone 336' contacts the substrate
260, but the other
opposed zone 336 is located at the top of the smoking article 120. From
consideration of
FIGs.22-24, it will be appreciated that regardless of the angular position of
a smoking article 120
having the pattern of zones of add-on material described, at least one pair of
opposed zones of
add-on material are positioned as shown in FIG 25, or FIG. 27, or a rotated
position between
those positions. This position has been referred to above as the oriented
snuffer region.
Accordingly it is seen that the spirally rotated position of the opposed zones
of add-on
material creates a situation where, regardless of which side portion of the
wrapper is placed
against the substrate 260, there will always be at least one longitudinal
location having film-
forming compound at side portions not in contact with the substrate 98 yet
having a sufficient
add-on amount and geometry that the zones can cooperate with the substrate 260
to self-
extinguish the smoking article when the burn line reaches that longitudinal
location. This fact
results in improved ignition propensity performance of the smoking article and
permits a
smoking article to be designed with an ignition propensity value no greater
than 25%.
Nevertheless, in the absence of a substrate 260, the smoking article does not
self-extinguish yet
maintains a free-burn, such as when the smoking article is held by a smoker.
This fact results in
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43
improved self-extinguishment performance of the smoking article and permits a
smoking article
to be designed with an self-extinguishment value no greater than 50%, that
self-extinguishment
value may be the self-extinguishment average value, self-extinguishment values
at 00 may be
much lower that the self-extinguishment average value and may be less than
25%.
In the embodiments described above, the smoking article has a generally
circular cross
section. Therefore, it is possible for any side portion of the smoking article
to rest against the
substrate 260. However, a pattern as taught herein can be such that the burn
characteristics
described above (ignition propensity values no greater than 25% and self-
extinguishment values
no greater than 50%) in relation to FIGs 14 and 15 can be realized, regardless
of which side
io
portion of the smoking article happens to rest against the substrate 260.
Preferably, the pattern
is selected so that when the base web is wrapped around a tobacco rod 122,
zones of film-
forming compound appear at opposing sides not in contact with the substrate
260 at one or
more (preferably at least two) longitudinal locations along the tobacco rod
122.
If desired, the zones of add-on material may also comprise other geometric
shapes other
than quadrilaterals including, for example, ovals, other polygons, or the
like. Furthermore, the
helix angle 0 described above may be increased while keeping the dimensions of
zones the
same as in the illustrated embodiments. That change can place the zones in an
overlapping
pattern (or at least place zones in close proximity to one another).
Alternatively, a stepped
helical pattern may be formed by increasing the cross-directional dimension of
the zones or
zo
patches while the helix angle is the same as in FIG. 17 and/or a zone of equal
size to that
shown in FIG. 17 may be placed between each patch and along paths 270, 272,
272" (so that
there are 12, instead of 6 patches along a path 270).
SLIT BANDEDD REGIONS
Other patterns for the regions of add-on material are also, of course, within
the scope of
this disclosure. Moreover, the inclusion of an anti-wrinkling agent in the
aqueous solutions used
to form the banded regions allows intricate patterns to be effected.
For example, in another embodiment, the banded region can comprise first,
second and
third zones of add-on material, which may be applied by any of the methods
disclosed herein,
wherein the second zone includes perforations which preferably are filled with
an occluding
material which melts or is evaporated when the burning coal approaches the
banded region to
thereby provide the second zone with increased permeability.
Thus, a wrapper of a smoking article is disclosed comprising a base web and at
least
one transverse banded region with first, second and third zones. The first and
third zones
comprise add-on material, which reduces permeability of the wrapper. The first
and third zones
each have a width such that if either of said first or third zone were applied
separately to
wrappers of smoking articles, the smoking articles would exhibit statistically
significant
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44
occurrences of total burn through and statistically few or no occurrences of
self-extinguishment
under free burn conditions (e.g., after testing a batch of 20 to 50
cigarettes). The sum of the
widths of the first and third zones is such that if the zones were applied to
wrappers of smoking
articles as a single continuous band (without a slit or other discontinuity),
the smoking articles
would exhibit statistically few or no occurrences of total burn through and
statistically significant
occurrences of self-extinguishment under free burn conditions. The first and
third zones are
separated by the second zone. The wrapper has greater permeability along the
second zone
than along the first and third zones. The second zone has a width less than
either width of the
first and third zones (which can have equal or unequal widths), so that lit
smoking articles
io comprising the first, second and third zones exhibit statistically
reduced occurrences of self-
extinguishment under free burn conditions, as compared to smoking articles
comprising
wrappers whereon the first and third zones are applied as a single continuous
band, while
maintaining statistically few or no occurrences of total burn through.
Preferably, the first and
third zones are of uniform add-on material across the first and third zones.
Optionally, the
second zone may have a width essentially equal to the first and third zones.
Total weight of add-on material for the banded region preferably lies in the
range of
0.5 grams per square meter to 15 grams per square meter (g/m2). Conventional
cigarette paper
is permeable, with the permeability commonly designated in CORESTA, which
measures paper
permeability in terms of volumetric flow rate (i.e., cm3/sec) per unit area
(i.e., cm2) per unit
pressure drop (i.e., cm of water). Permeability of the cigarette paper
normally exceeds 20
CORESTA and preferably, the cigarette paper has a permeability of about 33 to
about 60
CORESTA and a basis weight of about 22g/m2 to 30g/m2. However, permeability
through the
banded regions and the underlying cigarette paper preferably lies in the range
of 0 to 15
CORESTA. The reduction in permeability preferably restricts air flow needed to
support
combustion of the cigarette coal in the vicinity of the banded region.
The first and third zones preferably have a greater basis weight in grams per
square
meter than the intermediate second zone; for example, the basis weight in
grams per square
meter of the first and third zones may be at least twice the basis weight in
grams per square
meter of the second zone. The second zone may comprise a gap. As used herein,
the term
"gap" refers to a discrete area of a banded region, between the first and
third zones, lacking any
permeability reducing add-on material (i.e., containing no layers of
permeability reducing add-on
material). In order to aid combustion in the second zone, the wrapper may
comprise iron oxide
at the location of the second zone. The second zone preferably has a greater
permeability than
the first and third zones.
The at least one transverse banded region preferably comprises a first printed
layer
contacting the base web and a second printed layer, preferably having an equal
or greater basis
weight in grams per square meter than the first printed layer, on the first
printed layer. However,
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the second and/or subsequent layers may be less in basis weight than the first
layer. For
example, the basis weight in grams per square meter of the second printed
layer may be at
least twice the basis weight in grams per square meter of the first printed
layer. In an
embodiment, the second zone may comprise a single printed layer and the first
and third zones
5
may each comprise at least two printed layers (more preferably three or more
layers).
Alternatively, the first and third zones may each comprise at least three or
four printed layers,
and the second zone may comprise only one or two or no printed layers.
Non-banded areas of the base web preferably do not comprise permeability
reducing
add-on material. As described below with reference to FIG. 30, the transverse
banded region
o
may comprise greater than three zones. For example, the transverse banded
region may
comprise, for example, five zones, with the second and fourth zones separating
the first, third
and fifth zones and the wrapper having greater permeability along the second
and fourth zones
than along the first, third and fifth zones.
Also provided is a wrapper of a smoking article comprising a base web and a
transverse
15
banded region of add-on material. The transverse banded region is designed to
cause
extinguishment of smoking articles comprising the transverse banded region
when left upon a
substrate. The wrapper further comprises a more permeable, intermediate zone
along the
transverse banded region such that the occurrences of self-extinguishments of
smoking articles
comprising the wrapper is statistically reduced over those without the
intermediate zone.
20
In a further embodiment, a wrapper of a smoking article comprises a base web
and at
least one transverse banded region comprising first, second and third zones on
the base web.
The at least one transverse banded region can be free of fillers and
optionally at least one of the
zones is formed at least in part from an add-on material which includes a
filler. The add-on
material is preferably uniform across the first and third zones. The first and
third zones are
25
outward of the second zone, and the overall wrapper structure at the second
zone has a greater
permeability compared to the overall wrapper structure at the first and third
zones.
Additionally provided is a wrapper of a smoking article comprising a base web
and at
least one transverse banded region comprising first, second and third zones on
the base web.
The first and third zones are outward of the second zone, the second zone has
a greater
30
permeability compared to the first and third zones, and the second zone and
the first and third
zones comprise add-on material.
Moreover, provided is a method of making a banded wrapper of a smoking article
comprising supplying a base web and forming at least one transverse banded
region comprising
first, second and third zones on the base web. The first and third zones are
outward of the
35
second zone, the second zone has a greater permeability compared to the first
and third zones,
and at least the first and third zones are formed from an add-on material free
of fillers.
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Optionally at least one of the zones is formed at least in part from an add-on
material which
includes a filler. The add-on material is preferably uniform across the first
and third zones.
Furthermore, provided is a method of making a banded wrapper of a smoking
article
comprising supplying a base web and forming at least one transverse banded
region comprising
first, second and third zones on the base web. The first and third zones are
outward of the
second zone, the second zone has a greater permeability compared to the first
and third zones,
and the second zone and the first and third zones are formed from an add-on
material.
Optionally at least one of the zones is formed at least in part from an add-on
material which
includes a filler. The add-on material is preferably uniform across the first
and third zones.
FIGs. 28-33 illustrate smoking articles comprising slit banded paper as
described herein.
Specifically, FIG. 28 illustrates a smoking article having two banded regions
126, each
comprising first and third zones of add-on material 400, 402 separated by a
second zone 404,
which may be in the form of a gap or may be in the form of a zone of reduced
add-on material.
The first and third zones of add-on material 400, 402 may each be, for
example, about 2-5 mm
wide, and the second zone 404 may be, for example, about 1-2 mm wide. More
specifically, the
first and third zones of add-on material 400, 402 may each be, for example,
about 3 mm wide,
and the second zone 404 may be, for example, about 1.5 or 2 mm wide. The first
and third
zones of add-on material 400, 402 preferably comprise multiple layers of add-
on material, such
as, for example, two, three or four layers of add-on material. The add-on
material is preferably
uniform across the first and third zones 400, 402.
FIG. 30 illustrates a smoking article having two banded regions 126, each
comprising
first, third and fifth zones of add-on material 410, 412, 414 separated by
second and fourth
zones 416, 418, which may be in the form of gaps (see FIG. 31) or in the form
of reduced levels
of add-on material (see FIG. 38). The first, third and fifth zones of add-on
material 410, 412,
414 may each be, for example, about 2mm to 3mm wide, and the second and fourth
zones 416,
418 may each be, for example, about 1mm to 2mm wide. More preferably, the
first, third and
fifth zones of add-on material 410, 412, 414 may each be, for example, about
2mm wide, and
the second and fourth zones 416, 418 may each be, for example, about 1mm wide
or less. The
first, third and fifth zones of add-on material 410, 412, 414 preferably
comprise multiple layers of
add-on material, such as, for example, two, three or four layers of add-on
material. The add-on
material is preferably uniform across the first, third and fifth zones 410,
412, 414.
FIG. 32 illustrates a smoking article having two banded regions 126, each
comprising
first and third zones of add-on material 420, 422 separated by a second zone
424 of less add-
on material. The first and third zones of add-on material 420, 422 may each
be, for example,
about 2mm to 3mm wide, and the second zone of less add-on material 424 may be,
for
example, about 1mm to 2mm wide. More preferably, the first and third zones of
add-on material
420, 422 may each be, for example, about 3mm wide, and the second zone of less
add-on
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material 424 may be, for example, about 2mm wide or less. The first and third
zones of add-on
material 420, 422 preferably comprise multiple layers of add-on material, such
as, for example,
two, three or four layers of add-on material, while the second zone of less
add-on material 424
may comprise, for example, one or two layers of add-on material. The add-on
material is
preferably uniform across the first and third zones 420, 422. Although second
zones 424 are
operative at a lmm width, the embodiment performs better at a 1.2mm width or
greater.
Referring to FIGs. 28-33, slit banded paper facilitates use of wrappers of
lower
permeability for a given level of CO than prior designs of banded paper. For
example, it was
found that a tobacco rod comprising paper having a permeability of 33 CORESTA
and a CO
113 (FTC) delivery of 11mg would produce 15mg of CO (FTC) if previous
versions of bands were
applied without further change. In order to counteract his increase, the
permeability of the
wrapper would have to be raised to about 46 CORESTA. Such changes create a
multitude of
consequence in cigarette design, such as, for example, impacting puff count,
possibly lessening
machineability of the paper, and the like. In contrast, the slit banded paper
having a
permeability of 33 CORESTA provided 12mg CO (FTC). Thus, the slit banded
technology
described herein facilitates application of bands with a lesser impact on CO
levels (FTC).
Referring to FIGs. 34-37, further embodiments may include banded regions
wherein the
zones extend longitudinally instead of circumferentially. More specifically,
FIG. 34 corresponds
to banded region configuration of FIG. 30 with the zones extending
longitudinally instead of
circumferentially, and FIG. 36 corresponds to banded region configuration of
FIG. 32 with the
zones extending longitudinally instead of circumferentially.
In a preferred embodiment, the first layer of each banded region is preferably
formed
using an aqueous occlusive composition, which extends completely across the
banded region.
The successive layer (or layers) of each banded region may be formed by using
the same
aqueous film-forming composition or different aqueous compositions. For
example, multiple
layers may all comprise layers containing exclusively starch or multiple
layers may comprise
one or more layers containing exclusively starch and one or more layers
containing calcium
carbonate (in any order). During gravure printing, the occlusive composition
is preferably
heated to a temperature where its viscosity lies within the range of
viscosities suitable for
gravure printing. When the heated occlusive composition is applied, the
occlusive composition
is cooled or quenched and may be gelatinized. Thus, a portion of the free
water in the occlusive
composition becomes bound and unavailable to soak or migrate into underlying
fibers of the
base web. That binding of free water inhibits formation of waviness, cockling,
and/or wrinkling
in the base web. Successive layers of the banded regions preferably have
increased thickness
relative to the first layer. The banded regions provide a reduction in
permeability to the
underlying base web, which preferably restricts air flow needed to support
combustion of the
cigarette coal in the vicinity of the banded region.
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The occlusive composition used in the occlusive composition may be selected
from the
group consisting of starch, alginate, carrageenan, guar gum, pectin, and
mixtures thereof.
Preferably, the occlusive composition comprises starch, more preferably
oxidized starch, such
as, for example, tapioca starch, more specifically oxidized tapioca starch.
In these
embodiments, the occlusive composition preferably does not contain fillers,
such as, for
example, calcium carbonate, which would increase the burn rate through the
banded region. In
a preferred embodiment, the occlusive composition used for printing comprises
water and about
20% to about 50%, by weight, of the occlusive composition. At higher
concentrations of the
occlusive composition in the composition, the composition may experience
gelatinization when
o its temperature is rapidly reduced. Thus, the binding of free water into
the printed banded
region may occur.
At room temperature (about 23 C), the high-solids-content occlusive
composition has a
viscosity exceeding about 200mPa=s (centipoises (cP)) and is unsuitable for
gravure printing;
however, at a temperature in the range of about 40 to about 90 C, the
viscosity of the occlusive
composition is decreased sufficiently for use as a gravure printing
composition. For gravure
printing, the upper limit of suitable viscosity is about 200mPa.s. Most
preferably, the occlusive
composition has a viscosity of about 100mPas at a temperature in the range of
40 C to 90 C
so that the composition can be quenched on contact with the paper after
gravure printing at that
temperature. The viscosity of the composition at room temperature is also
important. The high
viscosity at room temperature is needed so that the occlusive composition gels
at room
temperature.
Preferably, the banded regions are applied to the wrapper using a successive
gravure
printing process. Gravure printing operations are capable of precise registry
of successive
printing operations. Accordingly, gravure printing can be used to effectively
print not only the
first layer of the banded regions, but also the optional successive layers.
EXAMPLES
The following examples are intended to be non-limiting and merely
illustrative.
Cigarettes with five different wrappers (i.e., wrappers with five different
banded region
configurations), were tested for ignition propensity ("ignition propensity")
and self-
extinguishment at 0 (horizontal). The base web of each of the wrappers had a
permeability of
33 CORESTA and basis weight of 25g/m2.
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Table X
IP is ignition propensity, SE is self-extinguishment
Total
Banded
Banded IP IP IP IP
Wrapper Region SE @ 00
Region Run 1 Run 2 Run 3 average.
Configuration*
Width
A control 6mm 0% 0% 0% 0% 95%
3-1-3 7mm 0% 2.5% 0% 0.8% 60%
3-2-3 8mm 0% 0% 5% 1.7% 25%
2-2-2 6mm 2.5% 0% 0% 0.8% 45%
2-1-2-1-2 8mm 2.5% .2.5% 2.5% 2.5% 20%
* Numbers refer to zone widths in mm (see Tables XI-XV below)
Referring to Table X, wrapper A was a control, comprising a continuous, solid
6 mm
printed banded region, having an add-on rate of 5.5X. As used herein, an add-
on rate of 5.5X
results in 8 g/m2 to 9g/m2 of add-on material on a dry weight basis, and a
basis weight of
26.5g/m2 for 6mm banded regions with a 27mm phase (i.e., the spacing from the
leading edge
of a banded region to the leading edge of the next banded region) applied to a
base web with a
basis weight of 25g/m2.
Table XI ¨ Details of Wrapper B
Zone 1 Zone 2 Zone 3
Width 3mm 1mm 3mm
Layers of Add-on Material 2 1 2
Add-on Rate Per Layer 1.5x/4x 1.5x/0 1.5x/4x
Total Add-on Material 5.5x 1.5x 5.5x
Table XII ¨ Details of Wrapper C
Zone 1 Zone 2 Zone 3
Width 3mm 2mm 3mm
Layers of Add-on Material 2 1 2
Add-on Rate Per Layer 1.5x/4x 1.5x/0 1.5x/4x
Total Add-on Material 5.5x 1.5x 5.5x
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Table XIII ¨ Details of Wrapper D
Zone 1 Zone 2 Zone 3
Width 2mm 2mm 2mm
Layers of Add-on Material 2 2 2
Add-on Rate Per Layer 1.5x/4x 1.5x/2x 1.5x/4x
Total Add-on Material 5.5x 3.5x 5.5x
Table XIV ¨ Details of Wrapper E
Zone 1 Zone 2 Zone 3 Zone 4 Zone 5
Width 2mm 1mm 2mm 1mm 2mm
Layers of Add-on Material 2 1 2 1 2
Add-on Rate Per Layer 1.5x/4x 1.5x/0 1.5x/4x 1.5x/0
1.5x/4x
Total Add-on Material 5.5x 1.5x 5.5x 1.5x 5.5x
5 As compared to control wrapper A, wrappers B-E exhibited the desired
reduction in self-
extinguishment while maintaining ignition propensity (i.e., without
significantly increasing ignition
propensity). In particular, wrapper B exhibited an improvement over control
wrapper A, as
evidenced by the decrease in self-extinguishment average from 95 to 60%.
Further, comparing
wrappers B and D, it can be seen that by increasing the width of the second
zone from 1mm to
10
2mm, the self-extinguishment average decreased from 60% to 25% (while
approximately
maintaining the ignition propensity value). Thus, the width of the second zone
is preferably
greater than 1mm, preferably about 1.5mm or about 2mm. While good results were
also shown
by wrapper c, which exhibited an self-extinguishment average of 45%, the best
results were
shown by wrapper E, which exhibited an self-extinguishment average of 20%.
15 It should be noted that wrapper E, having a banded region comprising
first, second,
third, fourth and fifth zones and which showed the best results, had 1 mm
second and fourth
zones of greater permeability. In contrast, wrapper B, having a banded region
comprising just
first, second and third zones, with a lmm second zone of a greater
permeability, did not perform
as well. Thus, wrappers having banded regions comprising just first, second
and third zones
20
preferably have wider zones of greater permeability (i.e., about 1.5mm or
about 2mm) than the
zones of greater permeability of wrappers having banded regions comprising
first, second, third,
fourth and fifth zones.
Moreover, a method of making a banded wrapper of a smoking article may
comprise
supplying a base web and forming at least one transverse banded region
comprising first,
25
second and third zones on the base web. The first and third zones are outward
of the second
zone, the second zone has a greater permeability compared to the first and
third zones, and at
least the first and third zones are formed from an add-on material free of
fillers. Optionally at
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least one of the zones is formed at least in part from an add-on material
which includes a filler.
The add-on material is preferably uniform across the first and third zones.
Furthermore, a method of making a banded wrapper of a smoking article may
comprise
supplying a base web and forming at least one transverse banded region
comprising first,
second and third zones on the base web. The first and third zones are outward
of the second
zone, the second zone has a greater permeability compared to the first and
third zones, and the
second zone and the first and third zones are formed from an add-on material.
Optionally at
least one of the zones is formed at least in part from an add-on material
which includes a filler.
The add-on material is preferably uniform across the first and third zones.
In a preferred embodiment, the first layer of each banded region is preferably
formed
using an aqueous occlusive composition, which extends completely across the
banded region.
The successive layer (or layers) of each banded region may be formed by using
the same
aqueous film-forming composition or different aqueous compositions. For
example, multiple
layers may all comprise layers containing exclusively starch or multiple
layers may comprise
one or more layers containing exclusively starch and one or more layers
containing calcium
carbonate (in any order). During gravure printing, the occlusive composition
is preferably
heated to a temperature where its viscosity lies within the range of
viscosities suitable for
gravure printing. When the heated occlusive composition is applied, the
occlusive composition
is cooled or quenched and may be gelatinized. Thus, a portion of the free
water in the occlusive
composition becomes bound and unavailable to soak or migrate into underlying
fibers of the
base web. That binding of free water inhibits formation of waviness, cockling,
and/or wrinkling
in the base web. Successive layers of the banded regions preferably have
increased thickness
relative to the first layer. The banded regions provide a reduction in
permeability to the
underlying base web, which preferably restricts air flow needed to support
combustion of the
cigarette coal in the vicinity of the banded region. In embodiments which
include a layer of
add-on material that includes calcium carbonate, that layer is preferably
applied as an upper
layer for a banded region intended for the outside of the wrapper or adjacent
the wrapper for a
banded region or the inside of the wrapper so as to maximize its favorable
effect on appearance
of the smoking article.
The occlusive composition of the banded regions may be selected from the group
consisting of starch, alginate, carrageenan, guar gum, pectin, and mixtures
thereof. Preferably,
the occlusive composition comprises starch, more preferably oxidized starch,
such as, for
example, tapioca starch, more specifically oxidized tapioca starch. In
embodiments, the
occlusive composition preferably does not contain fillers, such as, for
example, calcium
carbonate, which would increase the burn rate through the banded region. In a
preferred
embodiment, the occlusive composition used for printing comprises water and
about 20% to
about 50%, by weight, of the occlusive composition. At higher concentrations
of the occlusive
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composition in the composition, the composition may experience gelatinization
when its
temperature is rapidly reduced. Thus, the binding of free water into the
printed banded region
may occur.
At room temperature (about 23 C), the high-solids-content occlusive
composition has a
viscosity exceeding about 200mPa.s (centipoises (cP)) and is unsuitable for
gravure printing;
however, at a temperature in the range of about 40 C to about 90 C, the
viscosity of the
occlusive composition is decreased sufficiently for use as a gravure printing
composition. For
gravure printing, the upper limit of suitable viscosity is about 200mPa-s.
Most preferably, the
occlusive composition has a viscosity of about 100mPa's at a temperature in
the range of 40 C
io to 90 C so that the composition can be quenched on contact with the
paper after gravure
printing at that temperature. Such an occlusive composition may comprise 24%
by weight
starch. Alternatively, the occlusive composition may comprise 20% by weight
starch, which has
a viscosity of about 10mPa.s to 40mPa-s at room temperature, and low viscosity
at higher
temperatures. The viscosity of the composition at room temperature is also
important. The high
viscosity at room temperature is needed so that the occlusive composition gels
at room
tern perature.
FIG. 39 is a perspective view of a smoking article 120 having banded regions
with
angulated slits 450. FIG. 40 is an exemplary representation of angulated slits
on an unfolded
wrapper 140. FIG. 41 is a perspective view of a smoking article 120 having
banded regions 126
with one or optionally two longitudinal slits 460 that terminate short of the
leading edge 146 and
the trailing edge 148 of the banded region 126.
FIG. 42 is a side view of a smoking article comprising banded paper with
banded regions
having angulated slits as depicted in FIG. 39. In contrast to FIG 39, however,
the angulated
slits 450 are inclined in the opposite direction to the slits of FIG. 39.
Another embodiment contemplates the use of circumferential slits in both the
circumferential and longitudinal directions (see FIG. 43). The resulting
pattern of add-on
material resembles spaced-apart regions 126 having a plurality of patches 460
therein.
In other embodiments, the longitudinally banded regions 470 are helically
wound about
the length of the smoking article 120 (see FIGs. 44-46). These helical
arrangements are well-
suited for generally circular cigarettes. When the smoking article 120
experiences free burn
conditions, the opposed helically wound longitudinally banded regions only
obstruct airflow to
the burning coal of the tobacco rod by virtue of their reduced permeability.
However, the
unobstructed portions of the wrapper permit the smoking article to have
consistent, and
favorable, conditions to support combustion in the advancing coal of the
smoking article. On the
other hand, a vastly different situation occurs when the smoking article is
placed on a substrate.
The substrate blocks flow of air upwardly to the bottom portion of the tobacco
rod. The opposed
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53
helically wound longitudinally banded regions and the substrate cooperate to
define much
smaller areas through which air can be delivered to the base web as previously
discussed.
FIG. 44 illustrates a smoking article 120 including helical longitudinally
banded regions
470 that preferably extend the length of the wrapper. It should be understood
that the
circumferential width of these helical bands 470 is preferably selected so
that the helical bands
470 cover no more than about 33% of the surface area of the wrapper 123
surrounding the
tobacco rod. The helical angle p (see FIG. 12) of the helical longitudinally
banded regions 470
is equal to arctangent (21/c), where I is the length of the tobacco rod and c
is the circumference
of the smoking article. With the starting position of the helical
longitudinally banded regions 470
to as shown in FIG. 44, the smoking article 120 has one location along its
length where the helical
longitudinally banded regions 470 are in opposing relationship on a diameter
of the smoking
article which is parallel to a substrate when the smoking article 120 is
placed on the substrate
during testing.
Preferably the helical angle p of the helical longitudinally banded regions is
selected
such that at least one location along the tobacco rod exhibits the
configuration shown in FIG.
12, regardless of the rotational position of the smoking article about its
longitudinal axis. More
preferably, the helical angle 13 is selected to lie between about arctangent
(21/c) and about
arctangent (I/c) such that at least two locations along the tobacco rod
exhibit the FIG. 12
arrangement, regardless of rotational position of the smoking article about
its longitudinal axis.
zo If desired, the helical angle p can be selected with even smaller values
than arctangent (tic) so
that even more occurrences of the FIG. 12 condition occur throughout the
length of the tobacco
rod.
Such embodiments preferably assure that, independently of the angular position
of the
smoking article upon the substrate, the smoking article will have at least one
location, and
preferably two, three, four, or more locations, along its length where the
helical longitudinally
banded regions are positioned such that, in cross-section, the banded regions
are substantially
symmetrically disposed at the ends of a major dimension of the cross-section
positioned parallel
to an underlying substrate, the cross-sectional view being similar to FIG. 12.
Preferably, the
longitudinally banded regions cover 25% or less of the surface area of the
smoking article
and/or are less than or equal to about 6 mm wide in the circumferential
direction. Preferably,
each longitudinally banded region includes sufficient add-on material to
reduce the permeability
of the wrapper at each longitudinally banded region to about 0.0 to about 12
CORESTA, more
preferably about 7 CORESTA or less.
When the angle p approaches 0, the banded regions 126 become longitudinal
stripes
480 (see FIG. 48) positioned generally parallel to the axis of the smoking
article 120.
A wrapper for a smoking article may also comprises a base web 140 (see FIG.
49)
having a nominal permeability and a plurality of banded regions 126 with
sufficient add-on
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material such that the wrapper has a permeability at the banded region less
than the nominal
permeability of the base web. A leading edge 500 of each banded region 126 may
be
crenellated. Optionally, a trailing edge 502 of the banded region may also be
crenellated.
While various arrangements of the crenellated regions may occur to those
skilled in the
art, several such arrangements are illustrated in the appended figures. For
example (see
FIG. 50), the banded region 12 may have a leading edge 500 in which the
crenels 504 are
disposed between merlons 506. In this embodiment, the merlons 506 have a
dimension in the
transverse direction of the base web 140 which is substantially the same as
the dimension in
the transverse direction of the crenels 504. As depicted, the merlons 506 and
associated
crenels 504 may be generally rectangular. If desired, however, the merlons 506
and crenels
504 may have other geometric shapes including, without limitation,
quadrilaterals, trapezoids,
triangles, hexagons, and other regular or irregular geometric configurations.
The distance
between the top of a merlon 506 and the bottom of an adjacent crenel 504 may
lie in the range
of about 2mm to about 5mm, and preferably may be about 3mm. At the trailing
edge of the
banded region 126, a similarly crenellated arrangement may also be provided.
Turning to FIG. 51, the proportions of the merlons 524 and the crenels 526 of
the leading
edge 520 are different from the arrangement of FIG. 50. In FIG. 51 the merlons
524 may have
a cross-web dimension of about half the cross-web dimension of the associated
crenel 526.
Nevertheless, an integral number of pairs of merlons 524 and crenels 526
corresponds to the
nominal circumference of smoking article, as discussed above. The height of
the merlons 524,
or depth of the crenels 526 preferably lies in the same range of values as
discussed in
connection with FIG. 59. At the trailing edge of the embodiment of FIG. 51,
the cross-web
dimensions of the trailing edge merlons 530 and the trailing edge crenels 528
are different from
the cross-web dimensions of the leading edge merlons and the leading edge
crenels.
Turning to FIG. 52, the leading edge of the banded region 126 may have
substantially
the same characteristics discussed above in connection with FIG. 50. However,
the trailing
edge 540 may have merlons 542 having cross-web dimensions substantially
greater than the
cross-web dimensions of the opposed crenels 504 of the leading edge, while the
cross-web
dimensions of the trailing edge crenels 544 are substantially less than the
cross-web
dimensions of the corresponding opposed merlons 506 of the leading edge.
FIG. 53 illustrates yet another embodiment of the crenellated banded regions
in
accordance with this disclosure. In this embodiment, the leading edge 500 may
have the
characteristics described above in connection with FIG. 50. In this
embodiment, however, the
trailing edge 550 of the crenellated banded region 126 may be straight.
While the foregoing embodiments depict crenellated edges have a traditional
notched
shape, the crenellated band 126 of FIG. 54 has a different shape for the
crenellated edges 560.
More particularly, the crenellated edge 560 has merlons 506 that are
substantially triangular
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separated by substantially triangular crenels 504. If desired, the trailing
edge 562 of the band
may be straight. Preferably, however, the trailing edge 562 of the band 126
may also have the
triangular crenellation configuration described above in connection with the
leading edge 80.
Similar to the crenellated band of FIG. 54, the crenellated band 126 of FIG.
55 has a
5 crenellated edge 80 having merlons that are substantially triangular,
separated by, and defining,
substantially triangular crenels. While, the trailing edge 562 of the band may
be straight, in FIG.
55, the trailing edge 562 of the band also has the same triangular
crenellation configuration as
the leading edge 560. As further illustrated in FIG. 55, the band may be
divided into two band
portions 564, 56' that are spaced from one another by a "slit" 566. The slit
81 typically does not
io exceed the widths of the individual band portions as measured in a
direction generally parallel to
the axis of a smoking article having the bands. The spacing feature provides a
"slit" 566 (or
discontinuity) in the band structure where there is a lesser amount of or no
add-on material.
FIG. 56 shows crenellated bands similar to that of FIG. 55, but with the band
divided into
three band portions 564, 564', 564" that are spaced from one another along the
axis of a
15 smoking article by a pair of slits 566, 568.
In an embodiment shown in FIG. 57, the band 126 has a different shape for the
crenellated edges 560. In particular, the leading edge that is crenated (i.e.,
cut into rounded
scallops). The scallops 505 (i.e., circle segments or angular projections) can
have variable or
uniform widths and/or lengths. The trailing edge 562 of the band can be
straight, crenellated (in
20 accordance with any of FIGs. 49-56), or crenated. It is contemplated
that the crenated band of
FIG. 57 can further include a "slit" in the band structure, as illustrated in
FIGs. 55-56. In
addition, while not illustrated, a band structure can comprise a crenulated
(i.e., having an
irregularly wavy or serrate outline) leading and/or trailing edge, the band
optionally featuring one
or more "slits".
25 The geometry of the smoking article 120 may also be designed to aid in
achieving a
preferred orientation for purposes of ignition propensity reduction. For
example, the opposed
longitudinally banded regions 600 (see FIG. 58) may be located at the edges of
the major axis
of a substantially elliptical smoking article 120A, where the major axis of
the substantially
elliptical smoking article 120A naturally rests in a position substantially
parallel to the substrate
3o 260 on which the smoking article is placed.
Such a smoking article 120A is also known as an oval smoking article. The base
web
for wrapper used in such an oval smoking article preferably has applied to it
longitudinally
banded regions of a film-forming compound (the constituents of which may be
the same as
discussed elsewhere in this description). Those longitudinally banded regions
may be two
35 parallel, longitudinal stripes extending longitudinally along side
portions of the smoking article.
Stated differently, the stripes may be provided on the base web so that, when
the paper is
wrapped around the tobacco rod, the stripes are spaced about degrees apart
from one another.
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A smoking article 120 may include longitudinally extending banded regions (or
stripes) that
preferably extend the length of the wrapper or tobacco rod. Preferably, the
banded regions are
mutually opposed along opposing sides of the smoking article.
Due to the nature of an ellipse, it can be appreciated that regardless of how
an oval
smoking article is placed on the substrate 260, the smoking article 120A will
eventually rest in
one of two stable positions, with either the upper or lower side resting
against the substrate.
Therefore, even if longitudinally banded regions of add-on material are formed
only along the
side portions of the generally elliptical article where there is a maximum
curvature, film-forming
compound will always be present on those side portions of the smoking article
120A that do not
io contact the substrate 260. Moreover, cooperation between those
longitudinally banded regions
and the substrate 260 in the stable positions appears to function to restrict
airflow into the
tobacco rod and leads to self-extinction and a low ignition propensity value,
regardless of how
the smoking article 120 is initially placed on the substrate 230.
The predetermined pattern of add-on material is typically applied to a base
web having a
permeability lying in the range of about 20 to about 80 CORESTA units. When
dry, the add-on
material often forms a film on the base web that is effective to locally
reduce permeability to
values lying in the range of 0 to about 12 CORESTA units, more preferably, 0
to about 10
CORESTA units. In some applications, the add-on material is applied as an
aqueous solution
including starch.
PRINTING PROCESSES
Preferably, the banded region is applied to the wrapper using a gravure
printing process.
Gravure printing operations are capable of precise registry of successive
printing operations.
Accordingly, gravure printing can be used to effectively print not only the
first layer of the
banded regions, but also the optional successive layers.
In a successive gravure printing process, preferably after the first layer is
applied to the
base web it is allowed to dry thereon using suitable arrangements, prior to
being advanced to a
second gravure printing station where a second layer is applied to the first
layer using
conventional successive-pass gravure printing equipment. Preferably, the
second layer is
coextensive with the first layer in both width and length; however, the second
layer may have a
different basis weight in grams per square meter than the first layer. The
occlusive composition
of the second layer gels on the cooler first layer ¨ and free water does not
migrate or become
absorbed by the paper. Preferably, the second layer is allowed to dry using
suitable
arrangements prior to being advanced to successive gravure printing station(s)
where
successive layer(s) are applied. Preferably, the successive layer(s) are
coextensive with the
previous layer(s) in both width and length (i.e., the layers do not have a
stepped appearance);
however, the successive layer(s) may have different basis weight in grams per
square meter
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than the previous layer(s) or may comprise different add-on compositions.
Preferably,
successive layer(s) are preferably allowed to dry after the printing of each
successive layer in
accordance with well-known gravure printing techniques and conventional
gravure printing
systems.
The gravure printing process can be used immediately following paper
manufacture, i.e.,
at a printing station at a location near the end of the paper making machine.
Alternatively, the
gravure printing process can be used in connection with reels carrying the
wrapper onto which
the banded regions are to be printed. For example, a reel of wrapper having a
selected
permeability and a selected basis weight is mounted so that the wrapper can be
unspooled from
the reel as a continuous base web.
The base web advances or passes through a first gravure printing station where
the first
layer of each banded region is printed on the paper. The printing process may
be applied to the
felt side or the wire side of the paper, or both. Next, the wrapper passes
through a second
gravure printing station where a second layer of each banded region is printed
on the
corresponding first layer. Additional layers are applied in a similar manner
as described.
Finally, the wrapper with the printed banded regions is wound up on a
collection reel. The
collection reel is then cut into bobbins. The bobbins are then used during
manufacture of the
desired smoking article in conventional tobacco rod making machines.
The apparatus at each of the gravure printing stations is essentially the same
in its
material aspects. Accordingly, it will suffice to describe one of the gravure
printing stations in
detail, it being understood that the other gravure printing stations have
common features, unless
otherwise noted. A single pass technique can be used to make the banded paper
instead of a
multi-pass technique.
At the first gravure printing station, the apparatus includes a gravure
cylinder or roller
generally mounted for rotation around a horizontal axis. The generally
cylindrical surface of the
roller is patterned (i.e., with dots, lines, cells, etc.) in a suitable
process to define a negative of
the first layer of banded regions. Conventional engraving (etching), chemical
engraving,
electronic engraving, and photo etching can be used to pattern the surface of
the gravure
cylinder. The circumference of the roller is determined such that it is an
integral multiple of the
sum of the nominal distance between banded regions plus the banded region
width. Thus, for
each revolution of the roller, that integral number of first layers of the
banded regions is printed
on the wrapper.
With gravure printing, while each layer of add-on material may be applied
uniformly,
each layer of add-on material need not be applied uniformly. For example, a
layer of add-on
material may be applied such that discrete portions of the layer have
differing basis weights
than other areas of the layer. This may be accomplished, for example, by
printing a discrete
portion of the layer having a differing basis weight than other areas of the
layer in a separate
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printing stage using add-on material having a differing basis weight.
Alternatively, a layer of add-
on material may be applied such that discrete portions of the layer have
differing depths than
other areas of the layer. This may be accomplished, for example, by patterning
the gravure
cylinder or roller so as to provide a discrete portion of the layer having a
differing depth than
other areas of the layer.
The multiple zones, for example, first, second and third zones, of the banded
regions
described herein may be applied in a single printing stage or multiple
printing stages. When
applied in multiple printing stages, each zone which contains add-on material
may be applied in
a separate printing stage. For example, for a banded region containing first,
second and third
zones, wherein only the first and third zones contain add-on material, the
first zone may be
applied in a first printing stage and the third zone may be applied in a
second printing stage.
Alternatively, when applied in a single printing stage, the zones containing
add-on material are
applied using an appropriately patterned gravure cylinder or roller. For
example, for a banded
region containing first, second and third zones, wherein only the first and
third zones contain
add-on material, the gravure cylinder or roller is patterned so as to apply
add-on material only in
the first and third zones.
An impression cylinder is mounted for counter-rotation on an axis parallel to
the axis of
the roller. In some applications, the impression cylinder includes a
nonmetallic resilient surface.
The impression cylinder is positioned between the roller and a backing roller,
which is also
mounted for rotation on an axis parallel to the axis of the roller and which
counter-rotates
relative to the impression cylinder. One of the functions provided by the
backing roller is
stiffening the central portions of the impression cylinder so that the uniform
printing pressure is
attained between the roller and the impression cylinder. The gravure cylinder
or roller and the
impression cylinder cooperate to define a nip through which the base web
advances during the
printing process. That nip is sized to pinch the base web as it moves between
the gravure
cylinder and the impression cylinder. The nip pressure on the base web ensures
the correct
transfer of the composition from the cylinder to the paper.
A reservoir contains the occlusive composition discussed above for forming
banded
regions on the wrapper. The reservoir communicates with a suitable pump which
is capable of
handling the viscous occlusive composition. The occlusive composition may then
flow to a
suitable heat exchanger where the temperature of the occlusive composition is
elevated so that
it lies in the range of about 400 to about 90 c so that the viscosity of the
occlusive composition is
adjusted to a level that is suitable for gravure printing. As discussed above,
viscosity for
gravure printing usually needs to be less than about 200mPa=s (cP).
Preferably, the
temperature of the occlusive composition is selected so that the viscosity is
less than about
100mPa.s. For example, the occlusive composition may have a viscosity of about
1 OmPa.s to
40mPas at room temperature.
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While a separate heat exchanger is disclosed, it may be desirable to provide
thermal
conditioning of the occlusive composition in the reservoir itself. For
example, heating elements
and stirring apparatus may be included in the reservoir to maintain the
elevated temperature for
the occlusive composition. Placement of the thermal conditioning in the
reservoir has the
advantage of making pump selection and operating requirements simpler since
the pump need
not handle the occlusive composition at the higher viscosity associated with
lower temperatures
because the occlusive composition would already be heated and, therefore, at
the lower
viscosity. Whether thermal conditioning occurs in the reservoir or in a
separate heat exchanger,
it is important that the thermal conditioning step occur at a temperature
selected to avoid
o
scorching the occlusive composition. Scorching can cause discoloration of the
occlusive
composition, and can affect the occlusive characteristics of the composition.
Thus, scorching is
to be avoided while the occlusive composition is subjected to thermal
conditioning.
Regardless of where the thermal conditioning step occurs, the heated occlusive
composition is delivered to a suitable applicator that spreads the occlusive
composition along
the length of the gravure cylinder. That spreading step may be effected by
pouring or spraying
the occlusive composition onto the gravure cylinder, or simply by delivering
the liquid occlusive
composition to a bath of occlusive composition that collects at the bottom of
the gravure
cylinder, between the gravure cylinder and a collector. The cylinder may be
heated to prevent
premature cooling of the composition.
Generally, the collector extends vertically around the gravure roller to a
height sufficient
to collect the bath, but to a height well below the top of the gravure
cylinder. When the bath
reaches the top of the collector, occlusive composition can flow through a
drain at the bottom of
the apparatus back into the reservoir. Thus, the occlusive composition
circulates through the
printing station and can be maintained at suitable printing viscosity by the
thermal conditioning
apparatus discussed above.
As the gravure cylinder rotates through the applicator and/or the bath, the
occlusive
composition adheres to the surface of the gravure cylinder, including in the
impressions
provided therein to define the banded regions. Further rotation of the gravure
cylinder toward
the nip moves the cylinder surface past a suitable doctor blade. The doctor
blade extends along
the length of the gravure cylinder and is positioned so that is wipes the
surface of the gravure
cylinder. In this way, those portions of the gravure cylinder that define the
nominal spacing
between adjacent banded regions is essentially wiped clean of the occlusive
composition, while
engraved portions of the gravure cylinder that define the banded regions
themselves advance
toward the nip full of the occlusive composition.
As the wrapper and the surface of the gravure cylinder move through the nip,
the
occlusive composition is transferred to the surface of the wrapper. The linear
speed or velocity
of the wrapper matches the tangential surface speed of both the gravure
cylinder and the
CA 02690199 2015-08-18
impression cylinder as the wrapper passes through the nip. In that way,
slippage and/or
smearing of the occlusive composition on the wrapper are avoided.
The thickness of the multilayer banded regions preferably is less than about
20% of the
thickness of the base web, and may be less than 5% of the thickness of the
base web. The
5 thickness of the first layer of the banded region applied in the first
gravure printing station,
preferably is less than 4% of the base web thickness, and may be less than 1%
of the base web
thickness. Thus, it is seen that the thickness of the first layer is small in
relation to the thickness
of the underlying base web.
FIG. 59 is a schematic view of a multiple stage printing apparatus. With
reference to the
so above-description for multiple stage printing, FIG. 59 illustrates a
reel 600, first gravure printing
station 602, second gravure printing station 604, third gravure printing
station 606, collection
reel 608, rollers 610, impression cylinder 612, backing roller 614, nips 616,
reservoir 618, pump
620, heat exchanger 622, applicator 624, bath 626, collector 627, drain 628,
doctor blade 630,
adjustment cylinders 632, and idler roller 634. In FIG. 59, features of the
first gravure printing
15 station 602 contain reference numerals with the suffix "a",
corresponding febtures of the second
gravure printing station 604 contain the same reference numeral with the
suffix "b", and
corresponding features of the third gravure printing station 606 contain the
same reference
numeral with the suffix "c".
As an alternative to printing, the banded regions may comprise a slurry of
highly refined
20 fibrous cellulose (e.g., fibers, fibrils, microfibrils, or combinations
thereof) or other add-on
material applied using various spray or coating techniques, including
application techniques that
utilize a moving orifice applicator at the forming section of a paper-making
machine as
described in US 5 997 691 and US 6 596 125.
25 When the word "about" is used in this specification in connection
with a numerical value,
it is intended that the associated numerical value include a tolerance of t10%
around the stated
numerical value. Moreover, when reference is made to percentages in this
specification, it is
intended that those percentages are based on weight, i.e., weight percentages.
The terms and phases used herein are not to be interpreted with mathematical
or geometric
30 precision, rather geometric terminology is to be interpreted as meaning
approximating or similar
to the geometric terms and concepts. Terms such as "generally" and
"substantially" are
intended to encompass both precise meanings of the associated terms and
concepts as well as
to provide reasonable latitude that is consistent with form, function, andtor
meaning.
It will now be apparent to those skilled in the art that this specification
describes a new,
35 useful, and nonobvious smoking article. It will also be apparent to
those skilled in the art that
numerous modifications, variations, substitutes, and equivalents exist for
various aspects of the
smoking article that have been described in the detailed description above.
Accordingly, it is
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61
expressly intended that all such modifications, variations, substitutions, and
equivalents that fall
within the scope
of the invention, as defined by the appended claims, be embraced
thereby.
