Note: Descriptions are shown in the official language in which they were submitted.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-1-
Wrapper For Smoking Material Rods
Field of the invention
The present invention relates to a wrapper for a smoking material rod and also
to a method
of making a smoking material rod wrapper.
Background
Wrappers for smoking articles in which the wrapper is formed as a single sheet
are well
known. For example EP-A-0 407 022 discloses a wrapper for smoking articles in
which
/0 the wrapper comprises a single paper sheet formed from two or more discrete
webs, the
webs being combined while at least one of the webs is still in the wet stage
of formation
before drying. Further, EP-A-0 475 580 discloses a wrapper for smoking
articles, the
wrapper comprising a single paper sheet having two or more plies, each ply
being formed
from a paper stock and wherein the paper stocks are applied to each other
while at least
one of the stocks is unformed. In both EP-A-0 407 022 and EP-A-0 475 580 one
of the
plies may contain carbon.
Flavourant materials such as menthol have been applied to smoking articles to
modify the
smoke and taste characteristics thereof. Flavourant materials have been added
to smoking
articles by various methods, for example, by spraying a flavourant-containing
solution onto
tobacco or by applying flavourant material to the cigarette paper. However,
due to the
volatile or semi-volatile nature of many flavourant materials a significant
amount of the
flavourant material is lost through evaporation during the manufacture and
storage of the
smoking articles. Further, during smoking, more flavourant material is
volatilised by the
smoke in the initial puffs, resulting in uneven provision of the flavourant
material to the
smoker.
In order to prevent loss or premature volatilisation of the flavourant
material various
substances have been utilised to encapsulate the flavourant material. A number
of
flavourant encapsulation techniques involve encapsulation of a flavourant
material within a
polysaccharide coating. For example, EP-A-0 490 559 discloses a filament
comprising a
core of flavourant material and polysaccharide binder with a coextensive
alginate sheath
coating. It is, however, difficult to insert such a filament into a cigarette
using conventional
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-2-
high speed machinery. The control of flavour delivery to the smoker at
specific stages
during smoking is also not easily achieved using such filaments due to a
necessity for
precise positioning of the flavourant material in a cigarette.
A further encapsulation technique for smoking article involves
microencapsulation of a
flavourant material, and incorporation of the microcapsules into a tobacco
blend.
Disadvantages of such a technique include the difficulty in attaining an even
distribution of
microcapsules in the smoking article if desired, or alternatively, the
difficulty in precisely
positioning the microcapsules in a specific location in a smoking article.
WO 2005/082180 discloses smoking articles comprising a rod of smokable
material, a
wrapper about the rod of smokable material and a web material comprising an
adsorbent
material and a flavourant, the web material being positioned between the rod
of smokable
material and the wrapper and preferably being adhered to the wrapper using an
adhesive.
The adsorbent material may be carbon. In WO 2005/082180 a filler material such
as
calcium carbonate and a burn additive such as citrate are preferably used. The
presence of
such filler and burn additive are often desirable to control sparking problems
associated
with the use of the carbon-containing web.
Summary of the invention
According to the present invention there is provided a smoking material rod
wrapper
which comprises a single sheet comprising two or more plies, wherein a first
ply
comprises fibrous material, and a said second ply comprises adsorbent
material,
fibrous material and flavourant.
Applicant has found that a single sheet comprising at least two plies, wherein
one of the
plies contains adsorbent material and flavourant, can be formed in which the
flavourant is
stabilised by the adsorbent material such that the flavourant is not released
prior to
smoking of a smoking material rod enwrapped in such sheet, and in which the
presence of
filler and burn additive may not be required in order to control sparking
problems.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-3-
Further, since the single sheet can be produced having a thickness similar to
that of
conventional cigarette papers, it can be used in conventional cigarette
manufacturing
machinery for producing smoking articles.
A still further advantage of forming a wrapper for a smoking material rod
(e.g. a cigarette)
as a single sheet is that it can be formed remote from the smoking material
rod making
machine. For example, it can be formed and then transported to the smoking
material rod
manufacturer, as for a conventional cigarette paper. This is advantageous as
it reduces the
complexity of the manufacturing machinery required by the smoking material rod
/0 manufacturer since the smoking material rod manufacturer does not require
machinery to
manufacture the sheet itself. As such, the invention can allow the smoking rod
manufacturer to produce improved smoking rods without requiring any
modification or
replacement of their existing machinery.
A still further advantage of single sheet comprising at least two plies,
wherein one of the
plies contains carbon and flavourant wrapper, is that, when used to enwrap a
smoking
material rod it potentially enables certain smoke constituents generated by
the smoking
material rod during use to be reduced.
The use of a wrapper according to the present invention enables issues with
regard to
ashing characteristics and sparking to be avoided or reduced.
Although the sheet may comprise more than two plies, the sheet may be a double
ply sheet,
i.e. has only two plies.
The fibrous material present in the first and/or second ply is preferably a
fibrous cellulosic
material. More preferably, the fibrous cellulosic material is in the form of a
paper material.
The fibrous material may, for example, be present in the second ply in an
amount of up to
40 gsm. The fibrous material may, for example, be present in the second ply in
an amount
of up to 20 gsm. The total amount of fibrous material in the sheet may be at
least 17 gsm.
The total amount of fibrous material in the wrapper may be up to 60 gsm.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-4-
The flavourant may be selected from the following compound types: menthol
(natural
and/or synthetic), alcohols, esters, ketones, lactones, essential oils,
aldehydes and
heterocyclic compounds. A number of other flavourants may be suitable. One
flavourant
is menthol.
The single sheet may comprise one or more burn additive. Examples of suitable
burn
additives include citrates such as sodium citrate and potassium citrate,
acetates and
phosphate compounds. The one or more burn additive may comprise sodium citrate
or
potassium citrate. The one or more burn additive may be tri-potassium citrate.
The one or
90 more burn additive may be present in the first and/or second ply. The one
or more burn
additive may, for example, be present in an amount of at least 0.5% by weight
based on the
weight of the sheet. The one or more burn additive may, for example, be
present in an
amount of up to 1% by weight based on the weight of the sheet. The one or more
burn
additive may be present in an amount of from 0.5 to I % by weight based on the
weight of
the sheet.
The one or more adsorbent material present in the second ply may be selected
from one or
more of the following: zeolite, sepiolite, clay, activated alumina, mineral,
resin, and carbon.
The adsorbent material may be carbon. The adsorbent particularly may be
activated
carbon. Any form of activated carbon may be used. Activity of carbon is
measured in per
cent carbon tetrachloride (CTC), a measurement well known in the art. The
activated
carbon may have an activity level (CTC) of from 60 to 130, and preferably from
80-120,
and may suitably be approximately 100. The one or more adsorbent may, for
example, be
in granular, powder or particulate form. The adsorbent material may, for
example, be
present in the second ply in an amount of up to 40 gsm.
Put another way, the second ply may be a carbon paper.
The total amount of adsorbent material in the sheet may, for example, be up to
40 gsm.
The first and/or second ply may comprise one or more filler material. A non-
exhaustive
list of suitable filler materials includes calcium carbonate titanium dioxide,
magnesium
oxide, calcium sulphate, clays and kaolins. The one or more filler material
may comprise
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
5-
calcium carbonate. The one or more filler material may, for example, be
present in the
second ply in an amount of up to 25 gsm. The one or more filler material may,
for
example, be present in the first ply in an amount of up to 15 gsm. The total
amount of
filler material in said sheet may, for example, be at least 8 gsm. The total
amount of filler
material in the wrapper may, for example, be up to 40 gsm.
The wrapper may have a thickness of at least 45 m. The wrapper may have a
thickness of
up to 250 m.
/0 The second ply extends over at least a part of one surface of the first
ply. In embodiments
of the present invention, the second ply extends over the whole of one surface
of the first
ply. It is to be understood that, in the situation where more than two plies
are present in
the single sheet, the second ply may be separated from the first ply by one or
more
additional plies.
In embodiments of the present invention, the second ply comprises one or more
diluent.
The one or more flavourant may be added to the adsorbent material prior to
forming the
second ply. For example, the flavourant may be added to the adsorbent material
by
spraying.
Alternatively, the one or more flavourant may be added to the second ply after
formation
of that ply. A further alternative is wherein the one or more flavourant is
added to said
second ply after formation of the wrapper.
For example, the flavourant may be added to the second ply using a flavour
applicator
means, for instance as a stream or streams of flavourant. Suitably, the
plurality of streams
of flavourant is applied to the second ply in a line or in an array. When
applied in an array,
the array may comprise two lines of streams of flavourant, one of the lines
being offset
from the streams of flavourant in an adjacent line. Suitably, the flavourant
is applied to the
surface of the second ply as I to 30 streams of flavourant, and preferably as
4 to 18 streams
of flavourant.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-6-
If the flavourant is solid at room temperature, it is heated to maintain the
flavourant in the
molten liquid state during application to the adsorbent or to the second ply,
and may be
heated to a temperature of 40 to 45 C.
The wrapper may be formed by any suitable method provided that the resultant
wrapper
comprises a single sheet. As used herein the term "single sheet" refers to a
sheet in which
the plies thereof are integral in the sense that the plies are not merely
placed adjacent to
one another or adhered to one another using such as adhesive (i.e. as in the
case of WO
2005/082180).
>0
In embodiments of the present invention, the wrapper is formed by combining
the two or
more plies to form the single sheet while at least one of the plies is in the
wet stage of
formation prior to drying. For example, when the wrapper is a double ply
sheet, the plies
may be combined while one of the plies is in the wet stage of formation prior
to drying, or
while both of the plies are in the wet stage of formation prior to drying.
Accordingly, the present invention also provides a method of preparing a
wrapper
according to the invention, which method comprises combining said plies while
at least
one of said plies is still in the wet stage of formation prior to drying.
An apparatus suitable for use in preparing the wrapper may, for example, be a
multi-wire
paper making machine such as a double wire paper making machine. Such machines
are
known in the art of paper making.
After combining the plies the formed sheet is typically dried.
The present invention further provides a smoking article as defined in the
claims.
In embodiments of the smoking article the second ply of the wrapper is located
on the
smoking material rod side of said wrapper since this will be more
aesthetically pleasing to
the majority of smokers. That is, the second ply, which contains the adsorbent
material,
will be located between the first ply and the smoking material rod such that
the second ply
will not be visible to the smoker. This allows the adsorbent material to be
relatively
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-7-
proximate to the flow of smoke through the smoking article, thereby allowing
greater
interaction with constituents of the smoke than would be the case if the
second ply were an
outer ply. Thus, the removal of vapour phase constituents is enhanced. This
also allows
the outward appearance of the plug wrap not to be affected, or to be affected
less, by the
content of the second ply. This is particularly useful in the case where the
adsorbent
material in the second ply is carbon.
The smoking material may be a tobacco-containing smoking material or a non-
tobacco-
containing smoking material. The smoking material may be a tobacco-containing
material,
or a tobacco material. Suitably, the tobacco material comprises one or more of
stem,
lamina and tobacco dust. An example, of a tobacco material is one containing
one or more
of the following tobacco types: Virginia or flue-cured tobacco, Burley
tobacco, Oriental
tobacco, reconstituted tobacco and stem. The smoking material may comprise a
blend of
tobacco material.
In embodiments of the present invention the smoking article comprises a filter
element
located at one end of the rod of smoking material.
The filter element may be a multiple filter comprising multiple sections such
as, for
example, a dual or triple filter. Suitable filters are well known to those
skilled in the art. A
filter element may contain one or more adsorbent material for the reduction of
vapour
phase constituents of smoke. Such filters known in the art include Dalmation
filters in
which particulate adsorbent material is interspersed in fibrous filter
material, for example
fibrous cellulosic material, and cavity filters in which a cavity portion of
the multi-segment
filter contains one or more adsorbent material. When the second ply is
positioned near to
the mouth end of the smoking article, it has been found that the flavourant is
released from
the second ply during smoking of the smoking article without being adsorbed by
the
adsorbent material of the filter and without adversely affecting the ability
of the adsorbent
in the filter to reduce vapour phase constituents of the smoke.
The one or more adsorbent material, when present in the filter of the smoking
article, may
be one or more of the following: zeolite, sepiolite, clay, activated alumina,
mineral, resin, or
carbon, particularly activated carbon.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
8-
In embodiments of the smoking article of the present invention the smoking
article
comprises a filter element comprising a filter rod and the filter rod
comprises one or more
adsorbent material. The filter rod may comprise a cellulose acetate mouth end
section and
a Dalmatian rod section, containing the adsorbent material, located at the
smoking material
rod end of the filter element. Alternatively, the filter rod may be a cavity
filter comprising
two end sections and a central cavity containing said adsorbent material.
The filter element may alternatively comprise a filter plug of homogeneous
filtration
/0 material, a plug wrap overwrapping the filter plug, circumferentially
spaced grooves
extending longitudinally of the filter plug, and a ventilating tipping paper
interconnecting
the filter element to a tobacco rod, a number of grooves being open on the
side of the
tobacco rod and extending continuously only over a part of the length of the
filter element,
and hence not up to the mouth end of the filter element, which grooves are
axially aligned
with respect to the filter axis, in to which axially extending grooves
ventilating air enters via
overlying ventilating tipping paper, and any mouth extending groove not being
ventilated.
The filter element may, for example, be attached to the smoking material rod
by means of a
tipping paper. The tipping paper may enwrap the whole of the filter element
and extend
part of the way along the smoking material rod. Alternatively, the tipping
paper may be a
narrow strip of material which extends over only a part, for example a small
part, of the
length of the filter element and smoking material rod.
By practice of the present invention there may be provided one or more of the
following:
- a wrapper in which flavourant is incorporated and stabilised therein such
that the
flavourant is not released prior to smoking of a smoking material rod
enwrapped in such
wrapper;
a wrapper in which the addition of filler material such as chalk and/or the
addition
of burn additive such as citrate to the adsorbent-containing ply in order to
control sparking
issues may be avoided, or reduced;
a wrapper which may be used in forming a smoking article and which enables a
reduction in the vapour phase constituents and tar, generated during smoking
of the
smoking article, delivered to the mouth of the smoker.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-9-
a wrapper that can be produced having a thickness similar to that of
conventional
cigarette papers, such that the wrapper can be used in conventional smoking
article (e.g.
cigarette) manufacturing machinery for producing smoking articles and thereby
avoid the
cost of additional machinery;
- a wrapper that can be produced remote from the smoking article making
machine,
this being advantageous as it reduces the complexity of the manufacturing
machinery
required by the smoking article manufacturer because the smoking article
manufacturer
does not require machinery to manufacture the sheet itself; and
a wrapper in which the inclusion of filler material and/or burn additive,
often
/0 required in order to control sparking problems associated with the use of
carbon in
smoking article wrappers, may be avoided.
Brief description of the drawings
Embodiments of the present invention will now be described, by way of example,
with
reference to the accompanying drawings, in which:
Figure 1 shows a cross-section longitudinally through a smoking article
including a wrapper
according to the invention;
Figure 2 shows two plies used to make the wrapper of the smoking article of
Figure 1;
Figure 3 shows a cross-section through the smoking article of Figure 1 along
line x-x; and
Figure 4 shows a flow chart of a process of making the 2-ply wrapper of Figure
2.
Detailed description
Figure 1 shows a smoking article I in longitudinal cross-section. The smoking
article 1
comprises a rod 2 of smokable material enwrapped by a wrapper 4. The filter 3
is
positioned at a mouth end of the smoking article 1. The filter 3 is enwrapped
by a plug
wrap 5. The filter 3 is attached to the rod of smokable material 2 by a
tipping paper 6. The
wrapper 4 is a single sheet of paper made by pressing two plies of paper
together, as is
described below. The thickness of the wrapper 4 is similar to that of
conventional cigarette
papers.
The plug wrap 5 extends for the entire length of the filter 3 in the
longitudinal axis of the
smoking article 1. The plug wrap 5 thus enwraps all of the radial surface of
the filter 3.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
- 10-
The wrapper 4 extends for the entire length of the smokable rod 2 in the
longitudinal axis
of the smoking article 1. The wrapper 4 thus enwraps all of the radial surface
of the
smokable rod 2.
The wrapper 4 and the plug wrap 5 meet at the boundary of the filter 3 and the
smokable
rod 2. The wrapper 4 and the plug wrap 5 do not overlap one another. The
wrapper 4 and
the plug wrap 5 are at least partially enwrapped by the tipping paper 6. The
tipping paper 6
may extend over the whole length of the filter 3 and a part of the length of
the smokable
/0 rod 2. Alternatively, the tipping paper 6 may extend over only a part of
the filter 3 and a
part of the length of the smokable rod 2.
The plug wrap 5 may be omitted. In this case, the tipping paper 6 extends over
the whole
length of the filter 3 and a part of the length of the smokable rod 2 and thus
also serves the
function of the wrap plug 5.
The filter 3 may alternatively comprise a filter plug of homogeneous
filtration material, a
plug wrap overwrapping the filter plug, circumferentially spaced grooves
extending
longitudinally of the filter plug, and a ventilating tipping paper
interconnecting the filter
element to a tobacco rod, a number of grooves being open on the side of the
tobacco rod
and extending continuously only over a part of the length of the filter
element, and hence
not up to the mouth end of the filter element, which grooves are axially
aligned with
respect to the filter axis, in to which axially extending grooves ventilating
air enters via
overlying ventilating tipping paper, and any mouth extending groove not being
ventilated.
Figure 2 shows two plies which constitute the wrapper 4 of the smoking article
1. The first
ply 10 is comprised of fibrous material. The second ply 11 is comprised of
adsorbent
material, fibrous material and flavourant. In this embodiment, the adsorbent
material is
carbon. The fibrous material is a fibrous cellulosic material, such as paper.
The flavourant
may for instance be a menthol flavourant. The two plies 10, 11 are integral in
the sense
that they are not merely placed adjacent to one another or adhered to one
another using
such as an adhesive, but are formed as a single sheet. The sheets may be said
to be adhered
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-11-
together by the fibre bonding inherent in the papermaking process. The wrapper
4 is
formed using a double-wire process, as described below.
Figure 3 shows a transverse cross-section through the smoking article I of
Figure 1 along
line x-x of Figure 1. This shows the 2-ply wrapper 4 as shown in Figure 1
enwrapping the
smokable rod 2. The second ply 11 is the interior ply, adjacent the smokable
rod 2. The
first ply 10 is the external ply. The outer surface of the first ply 10
corresponds to the
exterior surface I of the wrapper 4.
90 The smokable rod 2 comprises a smoking material. The smoking material is a
tobacco-
containing smoking material or a non-tobacco-containing smoking material. The
smoking
material may be a tobacco-containing material, or a tobacco material.
Suitably, the tobacco
material comprises one or more of stem, lamina and tobacco dust. An example,
of a
tobacco material is one containing one or more of the following tobacco types:
Virginia or
flue-cured tobacco, Burley tobacco, Oriental tobacco, reconstituted tobacco
and stem. The
smoking material may comprise a blend of tobacco material.
Upon smoking, the smoking article I is ignited at the end furthest from the
filter 3. Smoke
is drawn along the smokable rod 2 to the smoker. As smoke passes along the
smoking
article 1, the flavourant is released from the second ply 11 of the wrapper 4
as the
temperature becomes sufficient to cause flavourant to be released from the
carbon. If the
second ply 11 of the wrapper 4 is evenly distributed with flavourant, the
flavour experience
may be relatively even.
The filter 3 may be a multiple filter comprising multiple sections such as,
for example, a
dual or triple filter. Suitable filters are well known to those skilled in the
art. The filter 3
may include adsorbent material, for instance activated carbon, for the
reduction of vapour
phase constituents of smoke. Suitable filters include Dalmatian filters in
which particulate
adsorbent material is interspersed in fibrous filter material, for example
fibrous cellulosic
material, and cavity filters in which a cavity portion of the multi-segment
filter contains one
or more adsorbent material, for instance activated carbon. When the second ply
is
positioned near to the mouth end of the smoking article, it has been found
that the
flavourant is released from the second ply during smoking of the smoking
article without
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-12-
being adsorbed by the adsorbent material of the filter and without adversely
affecting the
ability of the adsorbent in the filter to reduce vapour phase constituents of
the smoke.
Figure 4 is a flow chart illustrating a method making the 2-ply wrapper 4.
At step S1, the first ply 10 and the second ply 11 are made separately. The
first and second
plies 10,11 have different compositions. The plies 10, 11 may be of different
thicknesses.
The first ply 10 comprises fibrous material and filler.
The fibrous material is a fibrous cellulosic material. Particularly, the
fibrous cellulosic
material is a paper material.
The filler may be calcium carbonate (chalk), titanium dioxide, magnesium
oxide, calcium
sulphate, clays or a kaolin. Advantageously the filler is calcium carbonate.
The one or
more filler material may, for example, be present in the second ply in an
amount of up to
gsm. The one or more filler material may, for example, be present in the first
ply in an
amount of up to 15 gsm. The total amount of filler material in said sheet may,
for example,
be at least 8 gsm. The total amount of filler material in the wrapper may, for
example, be
20 up to 40 gsm.
The second ply 11 comprises adsorbent material, fibrous material, and
flavourant.
The fibrous material is a fibrous cellulosic material. Particularly, the
fibrous cellulosic
25 material is a paper material. The fibrous material is present in the second
ply 11 in an
amount of up to 40 gsm. The fibrous material is present in first second ply 11
in an
amount of up to 20 gsm.
The adsorbent material may be carbon, or it may be another suitable adsorbent.
The
adsorbent material may be activated carbon. Any form of activated carbon may
be used.
The activated carbon may have an activity level (CTC) of from 60 to 130,
advantageously
between 80 and 120, and advantageously approximately 100. The adsorbent
material
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
- 13-
advantageously is in powder or particulate form, or may be in granular form.
The
adsorbent material is present in the second ply in an amount of up to 40 gsm.
The flavourant may be any of the following: menthol (natural and/or
synthetic), alcohols,
esters, ketones, lactones, essential oils, aldehydes and heterocyclic
compounds. A different,
suitable flavourant may be may used instead. The flavourant is added to the
adsorbent
material prior to forming the second ply. The flavourant may be added to the
second ply
11, after the inclusion of the adsorbent material, by spraying. For example,
the flavourant
may be added to the second ply using a flavour applicator means, for instance
as a stream
/0 or streams of flavourant. Suitably, the plurality of streams of flavourant
is applied to the
second ply in a line or in an array. When applied in an array, the array may
comprise two
lines of streams of flavourant, one of the lines being offset from the streams
of flavourant
in an adjacent line. Suitably, the flavourant is applied to the surface of the
second ply as I
to 30 streams of flavourant, and preferably as 4 to 18 streams of flavourant.
If the
flavourant is solid at room temperature, it is heated to maintain the
flavourant in the
molten liquid state during application to the second ply 11, and may be heated
to a
temperature of 40 to 45 C.
Alternatively, the flavourant can be added to the second ply 11 after
formation of the two-
ply paper.
In some embodiments, the second ply also comprises filler. The filler may be
calcium
carbonate (chalk), titanium dioxide, magnesium oxide, calcium sulphate, clays
or a kaolin.
Advantageously the filler is calcium carbonate. The filler material is present
in the second
ply in an amount of up to 25 gsm.
As well as considering the first and second plies 10, 11 separately, it can be
useful to
consider the materials and physical characteristics of the resulting paper
when determining
what compositions to give to the plies 10, 11.
The two-ply sheet has a thickness of at least 45 m. The two-ply sheet has a
thickness of
up to 250 m.
CA 02718794 2010-09-17
WO 2009/109427 PCT/EP2009/050951
-14-
The total amount of filler material in the sheet is at least 8 gsm. The total
amount of filler
material in the sheet is up to 40 gsm.
The total amount of fibrous material in the sheet is at least 17 gsm. The
total amount of
fibrous material in the sheet is up to 60 gsm.
At step S2, the first and second plies 10, 11 are pressed together so as to
form a single
sheet of paper using a double-wire paper making machine. Double-wire paper
making
machines are well known in the art so this step will not be described in
detail. The result is
/0 a sheet of paper comprising a wet web having the first and second plies 10,
11. The wet
web is flat with no creping.
At step S3, the wet web is dried using a series of drying drums to form a
sheet of paper.
At step S4, the sheet of paper is size-pressed to add a burn additive, in this
example a
citrate. Examples of suitable burn additives include citrates such as sodium
citrate and
potassium citrate, acetates and phosphate compounds. The one or more burn
additive may
comprise sodium citrate or potassium citrate. Tri-potassium citrate has
certain advantages
as a burn additive in the case of a two ply wrapper paper. The burn additive
is present in
an amount of at least 0.5% by weight based on the weight of the paper sheet.
The burn
additive is present in an amount of up to I % by weight based on the weight of
the paper
sheet. Although in this embodiment step 4 is included, the addition of burn
additive such
as citrate to the second ply 11 may be omitted. Indeed, the use of two-ply
wrapper paper
reduces the need for the use of burn additives. As such, burn additives can be
avoided
using the present invention. Alternatively, if they are used, the amount of
burn additive
can be less than would be conventional to achieve a given burning
characteristic.
At step S5, the sheet is again dried, using a series of drying drums. At step
S6, the dried
sheet is rolled onto a bobbin, for storage and/or transportation.
The dried sheet is then used as a wrapper for smoking articles, e.g.
cigarettes, made using a
conventional cigarette manufacturing machine. The difference between the
resulting
cigarettes and conventional cigarettes is the composition of the wrapper.
