Note: Descriptions are shown in the official language in which they were submitted.
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FABRIC CREPED ABSORBENT SHEET WITH VARIABLE
LOCAL BASIS WEIGHT
Technical Field
This application relates generally to absorbent sheet for paper towel and
tissue. Typical products have variable local basis weight with (i) elongated
densified regions oriented along the machine direction of the product having
relatively low basis weight and (ii) fiber-enriched regions of relatively high
basis
weight between the densified regions.
Background
Methods of making paper tissue, towel, and the like are well known,
including various features such as Yankee drying, throughdrying, fabric
creping,
dry creping, wet creping and so forth. Conventional wet pressing (CWP)
processes have certain advantages over conventional through-air drying (TAD)
processes including: (1) lower energy costs associated with the mechanical
removal of water rather than transpiration drying with hot air; and (2) higher
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production speeds which are more readily achieved with processes which utilize
wet pressing to form a web. On the other hand, through-air drying processes
have
become the method of choice for new capital investment, particularly for the
production of soft, bulky, premium quality towel products.
Fabric creping has been employed in connection with papermaking
processes which include mechanical or compactive dewatering of the paper web
as a means to influence product properties. See, United States Patent Nos.
4,689,119 and 4,551,199 of Weldon; 4,849,054 of Klowak; and 6,287,426 of
Edwards et al. Operation of fabric creping processes has been hampered by the
difficulty of effectively transferring a web of high or intermediate
consistency to a
dryer. Further patents relating to fabric creping include the following:
4,834,838;
4,482,429 as well as 4,445,638. Note also, United States Patent No. 6,350,349
to
Hermans et al. which discloses wet transfer of a web from a rotating transfer
surface to a fabric.
In connection with papermaking processes, fabric molding has also been
employed as a means to provide texture and bulk. In this respect, there is
seen in
United States Patent No. 6,610,173 to Lindsey et al. a method for imprinting a
paper web during a wet pressing event which results in asymmetrical
protrusions
corresponding to the deflection conduits of a deflection member. The '173
patent
reports that a differential velocity transfer during a pressing event serves
to
improve the molding and imprinting of a web with a deflection member. The
tissue webs produced are reported as having particular sets of physical and
geometrical properties, such as a pattern densified network and a repeating
pattern
of protrusions having asymmetrical structures. With respect to wet-molding of
a
web using textured fabrics, see also, the following United States Patents:
6,017,417 and 5,672,248 both to Wendt et al.; 5,508,818 to Hermans etal. and
4,637, 859 to Trokhan. With respect to the use of fabrics used to impart
texture to
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a mostly dry sheet, see United States Patent No. 6,585,855 to Drew et al., as
well
as United States Publication No. US 2003/0000664.
United States Patent No. 5,503,715 to Trokhan etal. discloses a cellulosic
fibrous structure having multiple regions distinguished from one another by
basis
weight. The structure is reported as having an essentially continuous high
basis
weight network, and discrete regions of low basis weight which circumscribe
discrete regions of intermediate basis weight. The cellulosic fibers forming
the
low basis weight regions may be radially oriented relative to the centers of
the
regions. The paper may be formed by using a forming belt having zones with
different flow resistances. The basis weight of a region of the paper is
generally
inversely proportional to the flow resistance of the zone of the forming belt,
upon
which such region was formed. The zones of different flow resistances provide
for
selectively draining a liquid carrier having suspended cellulosic fibers
through the
different zones of the forming belt. A similar structure is reported in United
States
Patent No. 5,935,381 also to Trokhan et al. where the features are achieved by
using different fiber types.
Throughdried (TAD), creped products are disclosed in the following
patents: United States Patent No. 3,994,771 to Morgan, Jr. etal.; United
States
Patent No. 4,102,737 to Morton; and United States Patent No. 4,529,480 to
Trokhan. The processes described in these patents comprise, very generally,
forming a web on a foraminous support, thermally pre-drying the web, applying
the web to a Yankee dryer with a nip defined, in part, by an impression
fabric, and
creping the product from the Yankee dryer. A relatively uniformly permeable
web
is typically required, making it difficult to employ recycle furnish at levels
which
may be desired. Transfer to the Yankee typically takes place at web
consistencies
of from about 60% to about 70%.
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As noted in the above, throughdried products tend to exhibit enhanced
bulk and softness; however, thermal dewatering with hot air tends to be energy
intensive and requires a relatively uniformly permeable substrate. Thus, wet-
press
operations wherein the webs are mechanically dewatered are preferable from an
energy perspective and are more readily applied to furnishes containing
recycle
fiber which tends to form webs with less uniform permeability than virgin
fiber.
A Yankee dryer can be more effectively employed because a web is transferred
thereto at consistencies of 30% or so which enables the web to be firmly
adhered
for drying.
Despite the many advances in the art, improvements in absorbent sheet
qualities such as bulk, softness and tensile strength generally involve
compromising one property in order to gain advantage in another. Moreover,
existing premium products generally use limited amounts of recycle fiber or
none
at all, despite the fact that use of recycle fiber is beneficial to the
environment and
is much less expensive as compared with virgin Kraft fiber.
Summary of Invention
The present invention provides absorbent paper sheet products of variable
local basis weight which may be made by compactively dewatering a furnish and
wet-creping the resulting web into a fabric chosen such that the absorbent
sheet is
provided with a plurality of elongated, machine-direction oriented densified
regions of relatively low basis weight and a plurality of fiber-enriched
regions of
relatively high local basis weight which occupy most of the area of the sheet.
The products are produced in a variety of forms suitable for paper tissue or
paper towel and have remarkable absorbency over a wide range of basis weights
exhibiting, for example, Porofil void volumes of over 7g/g even at high basis
weights. With respect to tissue products, the sheet of the invention has
surprising
softness at high tensile, offering a combination of properties particularly
sought in
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the industry. With respect to towel products, the absorbent sheet of the
invention
makes it possible to employ large amounts of recycle fiber without abandoning
softness or absorbency requirements; again, a significant advance over
existing
art.
In another aspect of the invention, papermachine efficiency is enhanced by
providing a sheet to the Yankee exhibiting greater Caliper Gain/Reel Crepe
ratios
which make lesser demands on wet-end speed ¨ a production bottleneck for many
papermachines.
The invention is better understood by reference to Figures I and 2.
Figure 1 is a photomicrograph of an absorbent sheet 10 of the invention and
Figure 2 is a cross-section showing the structure of the sheet along the
machine
direction. In Figures 1 and 2, it is seen in particular that inventive sheet
10
includes a plurality of cross machine direction (CD) extending, fiber-enriched
pileated or crested regions 12 of relatively high local basis weight
interconnected
by a plurality of elongated densified regions 14 having relatively low local
basis
weight which are generally oriented along the machine direction (MD) of the
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sheet. The elongated densified regions extend in the MD the length 18 and they
extend in the CD a length 20. The elongated densified regions are
characterized
by a MD/CD aspect ratio i.e. distance 18 divided by distance 20 of at least
1.5.
The profile of the density and basis weight variation is further appreciated
by
reference to Figure 2 which is an enlarged photomicrograph of a section of the
sheet taken along line X-S#1 of Figure 1. In Figure 2 it is also seen that the
pileated regions 12 include a large concentration of fiber having a fiber
orientation
bias toward the cross-machine direction (CD) as evidenced by the cut fiber
ends
seen in the photograph. This fiber orientation bias is further seen in the
high CD
stretch and tensile strengths discussed hereinafter. It is further seen in
Figure 2
that the elongated densified regions 14 include highly compressed fiber 16
which
also has fiber bias in the cross direction as evidenced by cut fiber ends.
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Fiber orientation bias is likewise illustrated in Figure 1 wherein it is seen
that the fiber-enriched, pileated regions 12 are bordered at lateral
extremities by
CD aligned elongated densified regions 14 and that regions 12 generally extend
in
the CD direction between aligned densified regions, being linked thereto by CD-
extending fibers. See also, Figures 16-18.
Among the notable features of the invention is elevated absorbency as
evidenced by Figure 3, for example, which shows that the inventive absorbent
sheet exhibits very high void volumes even at high basis weights. In Figure 3,
it
is seen that products having Porofil void volumes of 7 grams/gram and greater
are readily produced in accordance with the invention at basis weights of 12
lbs/ream (19.5 gsm) and at basis weights of 24 lbs/ream (39.1 gsm) and more.
This level of absorbency over a wide range is remarkable, especially for a
compactively dewatered, wet-creped product (prior art wet-creped products
typically have void volumes of less than 5 grams/gram).
Further details and attributes of the inventive products and process for
making them are discussed below.
Brief Description of the Drawings
The invention is described in detail below with reference to the various
Figures, wherein like numerals designate similar parts. In the Figures:
Figure 1 is a plan view of an absorbent cellulosic sheet of the invention;
Figure 2 is an enlarged photomicrograph along line X-S#1 of Figure 1
showing the microstructure of the inventive sheet;
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Figure 3 is a plot showing Porofil void volume in grams/gm of various
products including those of the present invention;
Figure 4 is a schematic view illustrating fabric creping as practiced in
connection with the present invention;
Figure 5 is a schematic diagram of a paper machine which may be used to
manufacture products of the present invention;
Figure 6 is a schematic view of another paper machine which may be used
to manufacture products of the present invention;
Figure 7 is a gray scale topographical photomicrograph of a multi-layer
fabric which is used as a creping fabric to make the products of the present
invention;
Figure 8 is a color topographical representation of the creping fabric
shown in Figure 7;
Figure 9 is a schematic view illustrating a fabric creping nip utilizing the
fabric of Figures 7 and 8;
Figure 10 is an enlarged schematic view of a portion of the creping nip
illustrated in Figure 9;
Figure 11 is yet another enlarged schematic view of the creping nip of
Figures 9 and 10;
Figure 12 is still yet another enlarged schematic view of the creping nip of
Figures 9, 10 and 11;
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Figure 13 is a schematic representation of the creping fabric pattern of
Figures 7 and 8 as well as being a schematic representation of the patterned
product made using that fabric;
Figure 14 is a schematic representation of the creping fabric pattern of
Figures 7 and 8 aligned with a sheet produced utilizing that fabric wherein it
is
seen that the MD knuckles correspond to the densified regions in the fabric;
Figure 15 is a photomicrograph similar to Figure 2 showing the structure
of the pileated regions of the sheet after the sheet has been drawn in the
machine
direction;
Figure ,16 is a photograph of absorbent cellulosic sheet of the invention
similar to Figure 1;
Figure 17 is a photomicrograph taken along line X-S#2 shown in Figure
16 wherein it is seen that the fiber-enriched, pileated regions of the sheet
have not
been densified by the knuckle;
Figure 18 is an enlarged view showing an MD knuckle impression on a
sheet of the present invention;
Figure 19 is an X-ray negative through a sheet of the invention at
prolonged exposure, 6kV;
Figure 20 is another X-ray negative through a sheet of the invention at
prolonged exposure, 6kV;
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Figure 21A through Figure 21D are photomicrographs of various sheets
of the invention at different calipers and at the same crepe ratios;
Figure 22 and Figure 23 are photomicrographs showing the cross-section
of absorbent sheet of the invention along the machine direction;
Figure 24 is a cross-sectional view of an absorbent sheet produced by a
CWP process;
Figure 25 is a calibration curve for a beta particle attenuation basis weight
profiler;
Figure 26 is a schematic diagram showing the locations of local basis
weight measurements on a sheet of the invention;
Figure 27 is a bar graph comparing panel paired-comparison softness of
sheet creped with a fabric of the class shown in Figures 7 and 8 versus
softness of
absorbent sheet creped with a single layer fabric;
Figure 28 is a plot of panel paired comparison softness versus GM tensile
of a sheet creped with a fabric of the class shown in Figure 7 and 8 and
absorbent
sheet creped with a single layer fabric;
Figure 29 is a plot of caliper versus suction for absorbent sheet made with
single layer fabrics and absorbent sheet made with a multi-layer fabric of the
class
shown in Figures 7 and 8;
Figure 30A through 30F are photomicrographs of fabric creped sheets;
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Figure 31 is a bar graph illustrating panel paired-comparison softness of
various products of the present invention;
Figure 32 is a schematic diagram of yet another paper machine useful for
practicing the present invention;
Figure 33 is a plot of caliper versus CD wet tensile strength for various
fabric creped sheets;
Figure 34 is a plot of stiffness versus CD wet tensile for various fabric
creped sheets which are particularly useful for automatic touchless
dispensers;
Figure 35 is a plot of base sheet caliper versus fabric crepe; and
Figures 36-38 are photomicrographs showing the effect of combined reel
crepe and fabric crepe on an absorbent sheet.
In connection with photomicrographs, magnifications reported herein are
approximate except when presented as part of a scanning electron micrograph
where an absolute scale is shown.
Detailed Description
The invention is described below with reference to numerous
embodiments. Such discussion is for purposes of illustration only.
Modifications
to particular examples within the spirit and scope of the present invention,
set
forth in the appended claims, will be readily apparent to one of skill in the
art.
There is provided in a first aspect of the invention an absorbent cellulosic
sheet having variable local basis weight comprising a papermaking-fiber
reticulum provided with (i) a plurality of cross-machine direction (CD)
extending,
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fiber-enriched pileated regions of relatively high local basis weight
interconnected by (ii)
a plurality of elongated densified regions of compressed papermaking fibers,
the
elongated densified regions having relatively low local basis weight and being
generally
oriented along the machine direction (MD) of the sheet. The elongated
densified regions
are further characterized by an MD/CD aspect ratio of at least 1.5, and may be
identical.
The sheet has a specific bulk of greater than 5.5 ((mils/8 plies)/(1b/ream)) (
greater than
0.085 (mm/8plies/gsm) and has a void volume of 9 grams/gram or greater when it
has a
basis weight of 23 lb/ream (37.5 gsm) or less or has a void volume of 7
grams/gram or
greater when it has a basis weight of greater than 23 lbs/ream (37.5 gsm).
Typically, the
MD/CD aspect ratios of the densified regions are greater than 5 or greater
than 6;
generally between about 6 and 10. In most cases the fiber-enriched, pileated
regions
have fiber orientation bias toward the CD of the sheet and the densified
regions of
relatively low basis weight extend in the machine direction and also have
'fiber
orientation bias along the CD of the sheet.
In one preferred embodiment, the fiber-enriched pileated regions are bordered
at
lateral extremities by a laterally-spaced pair of CD-aligned densified
regions; and the
fiber-enriched regions are at least partially-bordered intermediate the
lateral extremities
thereof at longitudinal portions by a longitudinally-spaced, CD-staggered pair
of
densified regions. For many sheet products, the sheet has a basis weight of
from 8 lbs
per 3000 square- foot ream (13 gsm.) to 35 lbs per 3000 square-foot ream (57.0
gsm) and
a void volume of 7 grams/gram or greater. A sheet may have a void volume of
equal to
or greater than 7 grams/gram and perhaps up to 15 grams/gram. A suitable void
volume
of equal to or greater than 8 grams/gram and up to 12 grams/gram is seen in
Figure 3.
The present invention provides products of relatively high Porofil void
volume, even at high basis weights. For example, in some cases the sheet has a
basis weight of from 20 lbs per 3000 square foot ream (32.5 gsm) to 35 lbs per
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3000 square-foot ream (57.0 gsm) and a void volume of 7 grams/gram or more
and perhaps up to 15 grams/gram. Suitably, the void volume is equal to or
greater
than 8 or 9 grams/gram and up to 12 grams/gram.
Salient features of the invention likewise include high CD stretch and the
ability to employ recycle furnish in premium products. A CD stretch of from 5%
to 10% is typical. At least 5%, at least 7% or at least 8% is preferred in
some
cases. The papermaking fiber may be 50% by weight fiber of recycle fiber or
more. At least 10%, 25%, 35% or 45% is used depending upon availability and
suitability for the product.
Another aspect of the invention is directed to tissue base sheet exhibiting
softness, elevated bulk and high strength. Thus, the inventive absorbent sheet
may be in the form of a tissue base sheet wherein the fiber is predominantly
hardwood fiber and the sheet has a bulk of at least 6
((mils/8plies)/(1b/ream)),
(0.093 (mm/8plies)/(gsm)) or in the form of a tissue base sheet wherein the
fiber is
predominantly hardwood fiber and the sheet has a bulk of at least 6.5
amils/8plies)/(1b/ream)) (at least 0.1 (mm/8plies)/(gsm)). Typically, the
sheet has
a bulk of equal to or greater than 6.5 and up to about 8
((mils/8plies)/(1b/ream))
(greater than 0.1 up to about 0.125 (mm/8plies)/(gsm)) and is incorporated
into a
two-ply tissue product. The invention sheet is likewise provided in the form
of a
tissue base sheet wherein the fiber is predominantly hardwood fiber and the
sheet
has a normalized GM tensile strength of greater than 21 ((g/3")/(lbs/ream))
(greater than 1.69 (g/cm)/(gsm)) and a bulk of at least 5
amils/8plies)/(1b/ream))
(at least 0.08 (mm/8plies)/(gsm)) up to about 10 ((mils/8plies)/(1b/ream)) (to
about 0.15 (mm/8plies)/(gsm)). Typically, the tissue sheet has a normalized GM
tensile of greater than 21 ((g/3")/(lbs/ream)) (greater than 1.69
(g/cm)/(gsm)) and
up to about 30 ((g/3")/(lbs/ream)) (or 2.42 (g/cm)/(gsm)).
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The base sheet may have a normalized GM tensile of 25
((g/3")/(lbs/ream)) (of 2 (g/cm)/(gsm)) or greater and be incorporated into a
two-
ply tissue product.
Alternatively, the inventive products are produced in the form of a towel
base sheet incorporating mechanical pulp and wherein at least 40% by weight of
the papermaking fiber is softwood fiber or in the form of a towel base sheet
wherein at least 40% by weight of the papermaking fiber is softwood fiber and
at
least 20% by weight of the papermaking fiber is recycle fiber. At least 30%,
at
least 40% or at least 50% of the papermaking fiber may be recycle fiber. As
much
as 75% or 100% of the fiber may be recycle fiber in some cases.
A typical towel base sheet for two-ply toweling has a basis weight in the
range of from 12 to 22 lbs per 3000 square-foot ream and an 8-sheet caliper of
greater than 90 mils, up to about 120 mils (from 19.5 to 35.8 gsm and an 8-
sheet
caliper of greater than 2.3 mm, up to about 3.1 mm). Base sheet may be
converted
into a towel with a CD stretch of at least about 6%. Typically, a CD stretch
in the
range of from 6% to 10% is provided, sometimes a CD stretch of at least 7% is
preferred.
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The present invention is likewise suitable for manufacturing towel base
sheet for use in automatic towel dispensers. Thus, the product is provided in
the
form of a towel base sheet wherein at least 40% by weight of the papermaking
fiber is softwood fiber and at least 20% by weight of the papermaking fiber is
recycle fiber, and wherein the MD bending length of the base sheet is from
about
3.5 cm to about 5 cm. An MD bending length of the base sheet in the range of
from about 3.75 cm to about 4.5 cm is typical.
Such sheets may include at least 30% recycle fiber, at least 40% recycle
fiber. In some cases, at least 50% by weight of the fiber is recycle fiber. As
much
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as 75% or 100% by weight recycle fiber may be employed. Typically, the base
sheet has a bulk of greater than 2.5 ((mils/8plies)/(1b/ream)) (greater than
0.039
(mm/8plies)/(gsm)), such as a bulk of greater than 2.5
((mils/8plies)/(1b/ream))
(greater than 0.039 (mm/8plies)/(gsm)) up to about 3 ((mils/8plies)/(1b/ream))
(to
about 0.047 (mm/8plies)/(gsm). In some cases having a bulk of at least 2.75
((mils/8plies)/(1b/ream)) (at least 0.043 (mm/8plies)/(gsm)) is desirable.
A further aspect of the invention is an absorbent cellulosic sheet having
variable local basis weight comprising a patterned papermaking-fiber reticulum
provided with: (a) a plurality of generally machine direction (MD) oriented
elongated densified regions of compressed papermaking fibers having a
relatively
low local basis weight as well as leading and trailing edges, the densified
regions
being arranged in a repeating pattern of a plurality of generally parallel
linear
arrays which are longitudinally staggered with respect to each other such that
a
plurality of intervening linear arrays are disposed between a pair of CD-
aligned
densified regions; and (b) a plurality of fiber-enriched, pileated regions
having a
relatively high local basis weight interspersed between and connected with the
densified regions, the pileated regions having crests extending generally in
the
cross-machine direction of the sheet; wherein the generally parallel,
longitudinal
arrays of densified regions are positioned and configured such that a fiber-
enriched region between a pair of CD-aligned densified regions extends in the
CD
unobstructed by leading or trailing edges of densified regions of at least one
intervening linear array. Typically, the generally parallel, longitudinal
arrays of
densified regions are positioned and configured such that a fiber-enriched
region
between a pair of CD-aligned densified regions extends in the CD unobstructed
by
leading or trailing edges of densified regions of at least two intervening
linear
arrays. So also, the generally parallel, longitudinal arrays of densified
regions are
positioned and configured such that a fiber-enriched region between a pair of
CD-
aligned densified regions is at least partially truncated in the MD and at
least
partially bordered in the MD by the leading or trailing edges of densified
regions
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of at least one intervening linear array of the sheet at an MD position
intermediate
an MD position of the leading and trailing edges of the CD-aligned densified
regions. More preferably, the generally parallel, longitudinal arrays of
densified
regions are positioned and configured such that a fiber-enriched region
between a
pair of CD-aligned densified regions is at least partially truncated in the MD
and
at least partially bordered in the MD by the leading or trailing edges of
densified
regions of at least two intervening linear arrays of the sheet at an MD
position
intermediate an MD position of the leading and trailing edges of the CD-
aligned
densified regions. It is seen from the various Figures that the leading and
trailing
MD edges of the fiber-enriched pileated regions are generally inwardly concave
such that a central MD span of the fiber-enriched regions is less than an MD
span
at the lateral extremities of the fiber-enriched areas. Further, the elongated
densified regions occupy from about 5% to about 30% of the area of the sheet;
more typically, the elongated densified regions occupy from about 5% to about
25% of the area of the sheet or the elongated densified regions occupy from
about
7.5% to about 20% of the area of the sheet. The fiber-enriched, pileated
regions
typically occupy from about 95% to about 50% of the area of the sheet, such as
from about 90% to about 60% of the area of the sheet.
While any suitable repeating pattern may be employed, the linear arrays of
densified regions have an MD repeat frequency of from about 50 meter-1 to
about
200 meter-1, such as an MD repeat frequency of from about 75 meter-1 to about
175 meter-1 or an MD repeat frequency of from about 90 meter'' to about 150
meter-1. The densified regions of the linear arrays of the sheet have a CD
repeat
frequency of from about 100 meter-Ito about 500 meter-1; typically a CD repeat
frequency of from about 150 metefl to about 300 meter-1; such as a CD repeat
frequency of from about 175 meter' to about 250 meter-1.
In still another aspect of the invention, there is provided an absorbent
cellulosic sheet having variable local basis weight comprising a papermaking
fiber
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reticulum provided with: (a) a plurality of elongated densified regions of
compressed papermaking fiber, the densified regions being oriented generally
along the machine direction (MD) of the sheet and having a relatively low
local
basis weight as well as leading and trailing edges at their longitudinal
extremities;
and (b) a plurality of fiber-enriched, pileated regions connected with the
plurality
of elongated densified regions, the pileated regions having (i) a relatively
high
local basis weight and (ii) a plurality of cross-machine direction (CD)
extending
crests having concamerated CD profiles with respect to the leading and
trailing
edges of the plurality of elongated densified regions.
Many embodiments of the invention include an absorbent cellulosic sheet
having variable local basis weight comprising a papermaking-fiber reticulum
provided with (i) a plurality of cross-machine direction (CD) extending, fiber-
enriched pileated regions of relatively high local basis weight having fiber
bias
along the CD of the sheet adjacent (ii) a plurality of densified regions of
compressed papermaking fibers, the densified regions having relatively low
local
basis weight and being disposed between pileated regions.
In another aspect of the invention, there is provided an absorbent cellulosic
sheet having variable local basis weight comprising (i) a plurality of cross-
machine direction (CD) extending fiber-enriched regions of relatively high
local
basis weight and (ii) a plurality of low basis weight regions interspersed
with the
high basis weight regions, wherein representative areas within the relatively
high
basis weight regions exhibit a characteristic local basis weight at least 25%
higher
than a characteristic local basis weight of representative areas within the
low basis
weight regions. In other cases, the characteristic local basis weight of
representative areas within the relatively high basis weight regions is at
least 35%
higher than the characteristic local basis weight of representative areas
within the
low basis weight regions; while in still others, the characteristic local
basis weight
of representative areas within the relatively high basis weight regions is at
least
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50% higher than the characteristic local basis weight of representative areas
within the low basis weight regions. In some embodiments, the characteristic
local basis weight of representative areas within the relatively high basis
weight
regions is at least 75% higher than the characteristic low basis weight of
representative areas within the local basis weight regions or at least 100%
higher
than the characteristic local basis weight of the low basis weight regions.
The
characteristic local basis weight of representative areas within the
relatively high
basis weight regions may be at least 150% higher than the characteristic local
basis weight of representative areas within the low basis weight regions;
generally, the characteristic local basis weight of representative areas
within the
relatively high basis weight regions is from 25% to 200% higher than the
characteristic local basis weight of representative areas within the low basis
weight regions.
In another embodiment, there is made an absorbent cellulosic sheet having
variable local basis weight comprising (i) a plurality of cross-machine
direction
(CD) extending fiber-enriched regions of relatively high local basis weight
and (ii)
a plurality of elongated low basis weight regions generally oriented in the
machine
direction (MD), wherein the regions of relatively high local basis weight
extend in
the CD generally a distance of from about 0.25 to about 3 times a distance
that the
elongated relatively low basis weight regions extend in the MD. This feature
is
seen in Figures 19, 20. Typically, the fiber-enriched regions are pileated
regions
having a plurality of macrofolds. So also, the elongated low basis weight
regions
have an MD/CD aspect ratio of greater than 2 or 3, usually between about 2 and
10 such as between 2 and 6.
The present invention also includes methods of producing absorbent sheet.
There is provided in still other aspects of the invention a method of
making a belt-creped absorbent cellulosic sheet comprising: (a) compactively
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dewatering a papermaking furnish to form a nascent web having an apparently
random distribution of papermaking fiber orientation; (b) applying the
dewatered
web having the apparently random distribution of fiber orientation to a
translating
transfer surface moving at a first speed; (c) belt-creping the web from the
transfer
surface at a consistency of from about 30% to about 60% utilizing a patterned
creping belt, the creping step occurring under pressure in a belt creping nip
defined between the transfer surface and the creping belt wherein the belt is
traveling at a second speed slower than the speed of said transfer surface.
The
belt pattern, nip parameters, velocity delta and web consistency are selected
such
that the web is creped from the transfer surface and redistributed on the
creping
belt to form a web with a reticulum having a plurality of interconnected
regions of
different local basis weights including at least (i) a plurality of fiber-
enriched
pileated regions of high local basis weight, interconnected by way of (ii) a
plurality of elongated densified regions of compressed papermaking fiber. The
elongated densified regions have relatively low local basis weight and are
generally oriented along the machine direction (MD) of the sheet. The
elongated
densified regions are further characterized by an MD/CD aspect ratio of at
least
1.5; and the process further includes (d) drying the web. Preferably, the
creping
belt is a fabric. The process may yet further include applying suction to the
creped web while it is disposed in the creping fabric. Most preferably, the
creping
belt is a woven creping fabric with prominent MD warp knuckles which project
into the creping nip to a greater extent than weft knuckles of the fabric and
the
creping fabric is a multilayer fabric. The pileated regions include drawable
macrofolds which may be expanded by drawing the web along the MD of the
sheet. In some embodiments the pileated regions include drawable macrofolds
and nested therein drawable microfolds and the process further includes the
step
of drawing the microfolds of the pileated regions by application of suction.
In a
typical process, the pileated regions include a plurality of overlapping
crests
inclined with respect to the MD of the sheet.
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An additional aspect of the invention is a method of making a fabric-
creped absorbent cellulosic sheet with improved dispensing characteristics
comprising: a) compactively dewatering a papermaking furnish to form a nascent
web; b) applying the dewatered web to a translating transfer surface moving at
a
first speed; c) fabric-creping the web from the transfer surface at a
consistency of
from about 30% to about 60% utilizing a patterned creping fabric, the creping
step
occurring under pressure in a fabric creping nip defined between the transfer
surface and the creping fabric wherein the fabric is traveling at a second
speed
slower than the speed of said transfer surface. The fabric pattern, nip
parameters,
velocity delta and web consistency are selected such that the web is creped
from
the transfer surface and transferred to the creping fabric. The process also
includes d) adhering the web to a drying cylinder with a resinous adhesive
coating
composition; e) drying the web on the drying cylinder; and 0 peeling the web
from the drying cylinder; wherein the furnish, creping fabric and creping
adhesive
are selected and the velocity delta, nip parameters and web consistency,
caliper
and basis weight are controlled such that the MD bending length of the dried
web
is at least about 3.5 cm and the web has a papermaking-fiber reticulum
provided
with (i) a plurality of cross-machine direction (CD) extending, fiber-enriched
pileated regions of relatively high local basis weight interconnected by (ii)
a
plurality of elongated densified regions of compressed papermaking fibers. The
elongated densified regions have relatively low local basis weight and are
generally oriented along the machine direction (MD) of the sheet; the
elongated
densified regions are further characterized by an MD/CD aspect ratio of at
least
1.5. The MD bending length of the dried web is from about 3.5 cm to about 5 cm
in many cases, such as from about 3.75 cm to about 4.5 cm. The process may be
operated at a fabric crepe of from about 2% to about 20% and is operated at a
fabric crepe of from about 3% to about 10% in a typical embodiment.
A still further aspect of the invention is a method of making fabric-creped
absorbent cellulosic sheet comprising: a) compactively dewatering a
papermaking
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furnish to form a nascent web having an apparently random distribution of
papermaking fiber orientation; b) applying the dewatered web having the
apparently random distribution of fiber orientation to a translating transfer
surface
moving at a first speed; c) fabric-creping the web from the transfer surface
at a
consistency of from about 30% to about 60%, the creping step occurring under
pressure in a fabric creping nip defined between the transfer surface and the
creping fabric wherein the fabric is traveling at a second speed slower than
the
speed of said transfer surface. The fabric pattern, nip parameters, velocity
delta
and web consistency are selected such that the web is creped from the transfer
surface and redistributed on the creping fabric to form a web with a drawable
reticulum having a plurality of interconnected regions of different local
basis
weights including at least (i) a plurality of fiber-enriched regions of high
local
basis weight, interconnected by way of (ii) a plurality of elongated densified
regions of compressed papermaking fibers, the elongated densified regions
having
relatively low local basis weight and being generally oriented along the
machine
direction (MD) of the sheet. The elongated densified regions are further
characterized by an MD/CD aspect ratio of at least 1.5. The process further
includes d) drying the web; and thereafter e) drawing the web along its MD,
wherein the drawable reticulum of the web is characterized in that it
comprises a
cohesive fiber matrix which exhibits elevated void volume upon drawing.
Suitably, the at least partially dried web is drawn along its MD at least
about 10%
after fabric-creping or the web is drawn in the machine direction at least
about
15% after fabric-creping. The web may be drawn in its MD at least about 30%
after fabric-creping; at least about 45% after fabric-creping; and the web may
be
drawn in its MD up to about 75% or more after fabric-creping, provided that a
sufficient amount of fabric crepe has been applied.
Another method of making fabric-creped absorbent cellulosic sheet of the
invention includes: a) compactively dewatering a papermaking furnish to form a
nascent web having an apparently random distribution of papermaking fiber
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orientation; b) applying the dewatered web having the apparently random
distribution of fiber orientation to a translating transfer surface moving at
a first
speed; c) fabric-creping the web from the transfer surface at a consistency of
from
about 30% to about 60%, the creping step occurring under pressure in a fabric
creping nip defined between the transfer surface and the creping fabric
wherein
the fabric is traveling at a second speed slower than the speed of said
transfer
surface; d) applying the web to a Yankee dryer; e) creping the web from the
Yankee dryer; and f) winding the web on a reel; the fabric pattern, nip
parameters,
velocity delta and web consistency and composition being selected such that:
i)
the web is creped from the transfer surface and redistributed on the creping
fabric
to form a web with local basis weight variation including at least (A) a
plurality of
fiber-enriched regions of relatively high local basis weight; (B) a plurality
of
elongated regions having relatively low local basis weight and being generally
oriented along the machine direction (MD) of the sheet; and ii) the process
exhibits a Caliper Gaird% Reel Crepe ratio of at least 1.5. Typically, the
process
exhibits a Caliper Gain/% Reel Crepe ratio of at least 2; such as a Caliper
Gain/%
Reel Crepe ratio of at least 2.5 or 3. Usually, the process exhibits a Caliper
Gain/% Reel Crepe ratio of from about 1.5 to about 5 and is operated at a
Fabric
Crepe/Reel Crepe ratio of from about 1 to about 20. The process may be
operated
at a Fabric Crepe/Reel Crepe ratio of from about 2 to about 10, such as at a
Fabric
Crepe/Reel Crepe ratio of from about 2.5 to about 5.
The foregoing and further features of the invention are further illustrated in
the discussion which follows.
Terminology used herein is given its ordinary meaning consistent with the
exemplary definitions set forth immediately below; mg refers to milligrams and
m2 refers to square meters and so forth.
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The creping adhesive "add-on" rate is calculated by dividing the rate of
application of adhesive (mg/min) by surface area of the drying cylinder
passing
under a spray applicator boom (m2/min). The resinous adhesive composition most
preferably consists essentially of a polyvinyl alcohol resin and a polyamide-
epichlorohydrin resin wherein the weight ratio of polyvinyl alcohol resin to
polyamide-epichlorohydrin resin is from about 2 to about 4. The creping
adhesive
may also include modifier sufficient to maintain good transfer between the
creping fabric and the Yankee cylinder; generally less than 5% by weight
modifier
and more preferably less than about 2% by weight modifier, for peeled
products.
For blade creped products, 15%-25% modifier or more may be used.
Throughout this specification and claims, when we refer to a nascent web
having an apparently random distribution of fiber orientation (or use like
terminology), we are referring to the distribution of fiber orientation that
results
when known forming techniques are used for depositing a furnish on the forming
fabric. When examined microscopically, the fibers give the appearance of being
randomly oriented even though, depending on the jet to wire speed, there may
be a
significant bias toward machine direction orientation making the machine
direction tensile strength of the web exceed the cross-direction tensile
strength.
Unless otherwise specified, "basis weight", BWT, bwt and so forth refers
to the weight of a 3000 square-foot (279 m2) ream of product. Likewise, "ream"
means 3000 square-foot ream (279 m2) unless otherwise specified, for example
in
grams per square meter (gsm). Consistency refers to % solids of a nascent web,
for example, calculated on a bone dry basis. "Air dry" means including
residual
moisture, by convention up to about 10% moisture for pulp and up to about 6%
for paper. A nascent web having 50% water and 50% bone dry pulp has a
consistency of 50%.
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The term "cellulosic", "cellulosic sheet" and the like is meant to include
any product incorporating papermaking fiber having cellulose as a major
constituent. "Papermaking fibers" include virgin pulps or recycle (secondary)
cellulosic fibers or fiber mixes comprising cellulosic fibers. Fibers suitable
for
making the webs of this invention include: nonwood fibers, such as cotton
fibers
or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto grass, straw,
jute
hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and wood
fibers
such as those obtained from deciduous and coniferous trees, including softwood
fibers, such as northern and southern softwood lcraft fibers; hardwood fibers,
such
as eucalyptus, maple, birch, aspen, or the like. Papermaking fibers can be
liberated from their source material by any one of a number of chemical
pulping
processes familiar to one experienced in the art including sulfate, sulfite,
polysulfide, soda pulping, etc. The pulp can be bleached if desired by
chemical
means including the use of chlorine, chlorine dioxide, oxygen, alkaline
peroxide
and so forth. The products of the present invention may comprise a blend of
conventional fibers (whether derived from virgin pulp or recycle sources) and
high coarseness lignin-rich tubular fibers, mechanical pulps such as bleached
chemical thermomechanical pulp (BCTMP). "Furnishes" and like terminology
refers to aqueous compositions including papermaking fibers, optionally wet
strength resins, debonders and the like for making paper products. Recycle
fiber
is typically more than 50% by weight hardwood fiber and may be 75%-80% or
more hardwood fiber.
As used herein, the term compactively dewatering the web or furnish
refers to mechanical dewatering by wet pressing on a dewatering felt, for
example,
in some embodiments by use of mechanical pressure applied continuously over
the web surface as in a nip between a press roll and a press shoe wherein the
web
is in contact with a papermaking felt. The terminology "compactively
dewatering" is used to distinguish from processes wherein the initial
dewatering
of the web is carried out largely by thermal means as is the case, for
example, in
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United States Patent No. 4,529,480 to Trokhan and United States Patent No.
5,607,551 to Farrington et al.. Compactively dewatering a web thus refers, for
example, to removing water from a nascent web having a consistency of less
than
30% or so by application of pressure thereto and/or increasing the consistency
of
the web by about 15% or more by application of pressure thereto; that is,
increasing the consistency, for example, from 30% to 45%.
Creping fabric and like terminology refers to a fabric or belt which bears a
pattern suitable for practicing the process of the present invention and
preferably
is permeable enough such that the web may be dried while it is held in the
creping
fabric. In cases where the web is transferred to another fabric or surface
(other
than the creping fabric) for drying, the creping fabric may have lower
permeability.
"Fabric side" and like terminology refers to the side of the web which is in
contact with the creping fabric. "Dryer side" or "Yankee side" is the side of
the
web in contact with the drying cylinder, typically opposite the fabric side of
the
web.
Fpm refers to feet per minute (data is also sometimes expressed in meters
per minute (m/min); while fps refers to feet per second.
MD means machine direction and CD means cross-machine direction.
Nip parameters include, without limitation, nip pressure, nip width,
backing roll hardness, creping roll hardness, fabric approach angle, fabric
takeaway angle, uniformity, nip penetration and velocity delta between
surfaces of
the nip.
Nip width means the MD length over which the nip surfaces are in contact.
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"Predominantly" means more than 50% of the specified component, by
weight unless otherwise indicated.
A translating transfer surface refers to the surface from which the web is
creped into the creping fabric. The translating transfer surface may be the
surface
of a rotating drum as described hereafter, or may be the surface of a
continuous
smooth moving belt or another moving fabric which may have surface texture and
so forth. The translating transfer surface needs to support the web and
facilitate
the high solids creping as will be appreciated from the discussion which
follows.
Calipers and or bulk reported herein may be measured at 8 or 16 sheet
calipers as specified. The sheets are stacked and the caliper measurement
taken
about the central portion of the stack. Preferably, the test samples are
conditioned
in an atmosphere of 23 1.0 C (73.4 1.8 F) at 50% relative humidity for
at
least about 2 hours and then measured with a Thwing-Albert Model 89-11-JR or
Progage Electronic Thickness Tester with 2-in (50.8-mm) diameter anvils, 539
10 grams dead weight load, and 0.231 in./sec (5.87 mm/sec) descent rate. For
finished product testing, each sheet of product to be tested must have the
same
number of plies as the product is sold. For testing in general, eight sheets
are
selected and stacked together. For napkin testing, napkins are unfolded prior
to
stacking. For base sheet testing off of winders, each sheet to be tested must
have
the same number of plies as produced off the winder. For base sheet testing
off of
the papermachine reel, single plies must be used. Sheets are stacked together
aligned in the MD. On custom embossed or printed product, try to avoid taking
measurements in these areas if at all possible. Bulk may also be expressed in
units
of volume/weight by dividing caliper by basis weight.
Characteristic local basis weights and differences therebetween are
calculated by measuring the local basis weight at 2 or more representative low
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basis weight areas within the low basis weight regions and comparing the
average
basis weight to the average basis weight at two or more representative areas
within the relatively high local basis weight regions. For example, if the
representative areas within low basis weight regions have an average basis
weight
of 15 lbs/3000 ft2 ream (24.4 gsm) and the average measured local basis weight
for the representative areas within the relatively high local basis regions is
20
lbs/3000 ft2 ream (32.5 gsm), the representative areas within high local basis
weight regions have a characteristic basis weight of ((20-15)/15) X 100% or
33%
higher than the representative areas within low basis weight regions.
Preferably,
the local basis weight is measured using a beta particle attenuation technique
as
described herein.
MD bending length (cm) is determined in accordance with ASTM test
method D 1388-96, cantilever option. Reported bending lengths refer to MD
bending lengths unless a CD bending length is expressly specified. The MD
bending length test was performed with a Cantilever Bending Tester available
from Research Dimensions, 1720 Oakridge Road, Neenah, Wisconsin, 54956
which is substantially the apparatus shown in the ASTM test method, item 6.
The
instrument is placed on a level stable surface, horizontal position being
confirmed
by a built-in leveling bubble. The bend angle indicator is set at 41.50 below
the
level of the sample table. This is accomplished by setting the knife edge
appropriately. The sample is cut with a one inch (2.54 cm) JD strip cutter
available from Thwing-Albert Instrument Company, 14 Collins Avenue, W.
Berlin, NJ 08091. Six (6) samples are cut 1 inch x 8 inch (2.54 cm x 20.32 cm)
machine direction specimens. Samples are conditioned at 23 C 1 C (73.4 F
1.8 F) at 50% relative humidity for at least two hours. For machine direction
specimens the longer dimension is parallel to the machine direction. The
specimens should be flat, free of wrinkles, bends or tears. The Yankee side of
the
specimens is also labeled. The specimen is placed on the horizontal platform
of
the tester aligning the edge of the specimen with the right hand edge. The
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movable slide is placed on the specimen, being careful not to change its
initial
position. The right edge of the sample and the movable slide should be set at
the
right edge of the horizontal platform. The movable slide is displaced to the
right in
a smooth, slow manner at approximately 5 inch/minute (12.7 cm/minute) until
the
specimen touches the knife edge. The overhang length is recorded to the
nearest
0.1 cm. This is done by reading the left edge of the movable slide. Three
specimens are preferably run with the Yankee side up and three specimens are
preferably run with the Yankee side down on the horizontal platform. The MD
bending length is reported as the average overhang length in centimeters
divided
by two to account for bending axis location.
Water absorbency rate or WAR, is measured in seconds and is the time it
takes for a sample to absorb a 0.1 gram droplet of water disposed on its
surface by
way of an automated syringe. The test specimens are preferably conditioned at
23 C 1 C (73.4 1.8 F) at 50 % relative humidity for 2 hours. For each
sample, 4 3x3 inch (7.62 x 7.62 cm) test specimens are prepared. Each specimen
is placed in a sample holder such that a high intensity lamp is directed
toward the
specimen. 0.1 ml of water is deposited on the specimen surface and a stop
watch
is started. When the water is absorbed, as indicated by lack of further
reflection of
light from the drop, the stopwatch is stopped and the time recorded to the
nearest
0.1 seconds. The procedure is repeated for each specimen and the results
averaged
for the sample. WAR is measured in accordance with TAPPI method T-432 cm-
99.
Dry tensile strengths (MD and CD), stretch, ratios thereof, modulus, break
modulus, stress and strain are measured with a standard Instron test device or
other suitable elongation tensile tester which may be configured in various
ways,
typically using 3 or 1 inch (7.62 or 2.54 cm) wide strips of tissue or towel,
conditioned in an atmosphere of 23 1 C (73.4 1 F) at 50% relative
humidity
for 2 hours. The tensile test is run at a crosshead speed of 2 in/min (5.1
cm/min).
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Break modulus is expressed in grams/3 inches/ %strain ((grams/cm)! %strain). %
strain is dimensionless and need not be specified. Unless otherwise indicated,
values are break values. GM refers to the square root of the product of the MD
and CD values for a particular product.
Tensile ratios are simply ratios of the values determined by way of the
foregoing methods. Unless otherwise specified, a tensile property is a dry
sheet
property.
The wet tensile of the tissue of the present invention is measured using a
three-inch (7.62 cm) wide strip of tissue that is folded into a loop, clamped
in a
special fixture termed a Finch Cup, then immersed in a water. The Finch Cup,
which is available from the Thwing-Albert Instrument Company of Philadelphia,
Pa., is mounted onto a tensile tester equipped with a 2.0 pound (0.907 kg)
load
cell with the flange of the Finch Cup clamped by the tester's lower jaw and
the
ends of tissue loop clamped into the upper jaw of the tensile tester. The
sample is
immersed in water that has been adjusted to a pH of 7.0+- 0.1 and the tensile
is
tested after a 5 second immersion time. The results are expressed in g/3"
(g/cm),
dividing by two to account for the loop as appropriate.
"Fabric crepe ratio" is an expression of the speed differential between the
creping fabric and the forming wire and typically calculated as the ratio of
the web
speed immediately before fabric creping and the web speed immediately
following fabric creping, the forming wire and transfer surface being
typically, but
not necessarily, operated at the same speed:
Fabric crepe ratio = transfer cylinder speed +. creping fabric speed
Fabric crepe can also be expressed as a percentage calculated as:
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Fabric crepe = [Fabric crepe ratio ¨ 1] x 100
A web creped from a transfer cylinder with a surface speed of 750 fpm
(228.8 m/min) to a fabric with a velocity of 500 fpm (152.5 m/min) has a
fabric
crepe ratio of 1.5 and a fabric crepe of 50%.
For reel crepe, the reel crepe ratio is typically calculated as the Yankee
speed divided by reel speed. To express reel crepe as a percentage, 1 is
subtracted
from the reel crepe ratio and the result multiplied by 100%.
The fabric crepe/reel crepe ratio is calculated by dividing the fabric crepe
by the reel crepe.
The Caliper Gain/% Reel Crepe ratio is calculated by dividing the
observed caliper gain in mils/8 sheets (mm/8 sheets) by the % reel crepe. To
this
end, the gain in caliper is determined by comparison with like operating
conditions with no reel crepe. See Table 13, below.
The line or overall crepe ratio is calculated as the ratio of the forming wire
speed to the reel speed and a % total crepe is:
Line Crepe = [Line Crepe Ratio ¨1]x 100
A process with a forming wire speed of 2000 fpm (610 m/min) and a reel
speed of 1000 fpm (305 m/min) has a line or total crepe ratio of 2 and a total
crepe
of 100%.
PLI or ph i means pounds force per linear inch (kg force per linear
centimeter (plcm)). The process employed is distinguished from other
processes,
in part, because fabric creping is carried out under pressure in a creping
nip.
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Typically, rush transfers are carried out using suction to assist in detaching
the
web from the donor fabric and thereafter attaching it to the receiving or
receptor
fabric. In contrast, suction is not required in a fabric creping step, so
accordingly
when we refer to fabric creping as being "under pressure" we are referring to
loading of the receptor fabric against the transfer surface although suction
assist
can be employed at the expense of further complication of the system so long
as
the amount of suction is not sufficient to undesirably interfere with
rearrangement
or redistribution of the fiber. =
Pusey and Jones (P&J) hardness (indentation) is measured in accordance
with ASTM D 531, and refers to the indentation number (standard specimen and
conditions).
Velocity delta means a difference in linear speed.
The void volume and /or void volume ratio as referred to hereafter, are
determined by saturating a sheet with a nonpolar POROFIL liquid and
measuring the amount of liquid absorbed. The volume of liquid absorbed is
equivalent to the void volume within the sheet structure. The % weight
increase
(PWI) is expressed as grams of liquid absorbed per gram of fiber in the sheet
structure times 100, as noted hereinafter. More specifically, for each single-
ply
sheet sample to be tested, select 8 sheets and cut out a 1 inch by 1 inch
square (1
inch in the machine direction and 1 inch in the cross-machine direction) (2.54
cm
by 2.54 cm square (2.54 cm in the machine direction and 2.54 cm in the cross-
machine direction). For multi-ply product samples, each ply is measured as a
separate entity. Multiple samples should be separated into individual single
plies
and 8 sheets from each ply position used for testing. Weigh and record the dry
weight of each test specimen to the nearest 0.0001 gram. Place thd specimen in
a
dish containing POROFIL liquid having a specific gravity of about 1.93 grams
per cubic centimeter, available from Coulter Electronics Ltd., Northwell
Drive,
CA 02652814 2014-11-20
Luton, Beds, England; Part No. 9902458.) After 10 seconds, grasp the specimen
at the very edge (1-2 millimeters in) of one corner with tweezers and remove
from
the liquid. Hold the specimen with that corner uppermost and allow excess
liquid
to drip for 30 seconds. Lightly dab (less than 1/2 second contact) the lower
corner
of the specimen on #4 filter paper (WhatmanCD Lt., Maidstone, England) in
order
to remove any excess of the last partial drop. Immediately weigh the specimen,
within 10 seconds, recording the weight to the nearest 0.0001 gram. The PWI
for
each specimen, expressed as grams of POROFIL liquid per gram of fiber, is
calculated as follows:
PWI = [(W)-Wi)/Wil X 100
wherein
"WI" is the dry weight of the specimen, in grams; and
"W2" is the wet weight of the specimen, in grams.
The PWI for all eight individual specimens is determined as described
above and the average of the eight specimens is the PWI for the sample.
The void volume ratio is calculated by dividing the PWI by 1.9 (density of
fluid) to express the ratio as a percentage, whereas the void volume (gms/gm)
is
simply the weight increase ratio; that is, PWI divided by 100.
The creping adhesive used to secure the web to the Yankee drying cylinder
is preferably a hygroscopic, re-wettable, substantially non-crosslinking
adhesive.
Examples of preferred adhesives are those which include poly(vinyl alcohol) of
the general class described in United States Patent No. 4,528,316 to Soerens
et al.
Other suitable adhesives are disclosed in co-pending United States Provisional
Patent Application Serial No. 60/372,255, filed April 12, 2002, entitled
"Improved
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Creping Adhesive Modifier and Process for Producing Paper Products" (Attorney
Docket No. 2394). Suitable adhesives are optionally provided with modifiers
and
so forth. It is preferred to use crosslinker and/or modifier sparingly or not
at all in
the adhesive.
Creping adhesives may comprise a thermosetting or non-thermosetting
resin, a film-forming semi-crystalline polymer and optionally an inorganic
cross-
linking agent as well as modifiers. Optionally, the creping adhesive of the
present
invention may also include other components, including, but not limited to,
hydrocarbons oils, surfactants, or plasticizers. Further details as to creping
adhesives useful in connection with the present invention are found in
copending
Provisional Application No. 60/779,614, filed March 6, 2006 (Attorney Docket
No. 20140; GP-06-1).
The creping adhesive may be applied as a single composition or may be
applied in its component parts. More particularly, the polyamide resin may be
applied separately from the polyvinyl alcohol (PVOH) and the modifier.
When using a creping blade, a normal coating package is suitably applied
at a total coating rate (add-on as calculated above) of 54 mg/m2 with 32 mg/m2
of
PVOH (CelvolTm 523)/ 11.3 mg/m2 of PAE (Hercules 1145) and 10.5 mg/m2 of
modifier (Hercules 4609VF). A preferred coating for a peeling process may be
applied at a rate of 20 mg/m2 with 14.52 mg/m2 of PVOH (CelvolTM 523)/ 5.10
mg/m2 of PAE (Hercules 1145) and 0.38 mg/m2 of modifier (Hercules 4609VF).
In connection with the present invention, an absorbent paper web is made
by dispersing papermaking fibers into aqueous furnish (slurry) and depositing
the
aqueous furnish onto the forming wire of a papermaking machine. Any suitable
forming scheme might be used. For example, an extensive but non-exhaustive
list
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in addition to Fourdrinier formers includes a crescent former, a C-wrap twin
wire
former, an S-wrap twin wire former, or a suction breast roll former. The
forming
fabric can be any suitable foraminous member including single layer fabrics,
double layer fabrics, triple layer fabrics, photopolymer fabrics, and the
like. Non-
exhaustive background art in the forming fabric area includes United States
Patent
Nos. 4,157,276; 4,605,585; 4,161,195; 3,545,705; 3,549,742; 3,858,623;
4,041,989; 4,071,050; 4,112,982; 4,149,571; 4,182,381; 4,184,519; 4,314,589;
4,359,069; 4,376,455; 4,379,735; 4,453,573; 4,564,052; 4,592,395; 4,611,639;
4,640,741; 4,709,732; 4,759,391; 4,759,976; 4,942,077; 4,967,085; 4,998,568;
5,016,678; 5,054,525; 5,066,532; 5,098,519; 5,103,874; 5,114,777; 5,167,261;
5,199,261; 5,199,467; 5,211,815; 5,219,004; 5,245,025; 5,277,761; 5,328,565;
and 5,379,808. One forming fabric particularly useful with the present
invention
is Voith Fabrics Forming Fabric 2164 made by Voith Fabrics Corporation,
Shreveport, LA.
Foam-forming of the aqueous furnish on a forming wire or fabric may be
employed as a means for controlling the permeability or void volume of the
sheet
upon fabric-creping. Foam-forming techniques are disclosed in United States
Patent No. 4,543,156 and Canadian Patent No. 2,053,505. The foamed fiber
furnish is made up from an aqueous slurry of fibers mixed with a foamed liquid
carrier just prior to its introduction to the headbox. The pulp slurry
supplied to the
system has a consistency in the range of from about 0.5 to about 7 weight %
fibers, preferably in the range of from about 2.5 to about 4.5 weight %. The
pulp
slurry is added to a foamed liquid comprising water, air and surfactant
containing
50 to 80% air by volume forming a foamed fiber furnish having a consistency in
the range of from about 0.1 to about 3 weight % fiber by simple mixing from
natural turbulence and mixing inherent in the process elements. The addition
of
the pulp as a low consistency slurry results in excess foamed liquid recovered
from the forming wires. The excess foamed liquid is discharged from the system
and may be used elsewhere or treated for recovery of surfactant therefrom.
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The furnish may contain chemical additives to alter the physical properties
of the paper produced. These chemistries are well understood by the skilled
artisan and may be used in any known combination. Such additives may be
surface modifiers, softeners, debonders, strength aids, latexes, pacifiers,
optical
brighteners, dyes, pigments, sizing agents, barrier chemicals, retention aids,
insolubilizers, organic or inorganic crosslinkers, or combinations thereof;
said
chemicals optionally comprising polyols, starches, PPG esters, PEG esters,
phospholipids, surfactants, polyamines, HMCP (Hydrophobically Modified
Cationic Polymers), HMAP (Hydrophobically Modified Anionic Polymers) or the
like.
The pulp can be mixed with strength adjusting agents such as wet strength
agents, dry strength agents and debonders/softeners and so forth. Suitable wet
strength agents are known to the skilled artisan. A comprehensive but non-
exhaustive list of useful strength aids include urea-formaldehyde resins,
melamine
formaldehyde resins, glyoxylated polyacrylamide resins, polyamide-
epichlorohydrin resins and the like. Thermosetting polyacrylamides are
produced
by reacting acrylamide with diallyl dimethyl ammonium chloride (DADMAC) to
produce a cationic polyacrylamide copolymer which is ultimately reacted with
glyoxal to produce a cationic cross-linking wet strength resin, glyoxylated
polyacrylamide. These materials are generally described in United States
Patent
Nos. 3,556,932 to Coseia et al. and 3,556,933 to Williams et al.. Resins of
this
type are commercially available under the trade name of PAREZ 631NC by Bayer
Corporation. Different mole ratios of acrylamide/-DADMAC/glyoxal can be used
to produce cross-linking resins, which are useful as wet strength agents.
Furthermore, other dialdehydes can be substituted for glyoxal to produce
thermosetting wet strength characteristics. Of particular utility are the
polyamide-
epichlorohydrin wet strength resins, an example of which is sold under the
trade
names KymeneTM 557LX and KymeneTM 557H by Hercules Incorporated of
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Wilmington, Delaware and Amres0 from Georgia-Pacific Resins, Inc. These
resins and the process for making the resins are described in United States
Patent
No. 3,700,623 and United States Patent No. 3,772,076. An extensive description
of polymeric-epihalohydrin resins is given in Chapter 2: Alkaline-Curing
Polymeric Amine-Epichlorohydrin by Espy in Wet Strength Resins and Their
Application (L. Chan, Editor, 1994). A reasonably comprehensive list of wet
strength resins is described by Westfelt in Cellulose Chemistry and Technology
Volume 13, p. 813, 1979.
Suitable temporary wet strength agents may likewise be included,
particularly in applications where disposable towel, or more typically, tissue
with
permanent wet strength resin is to be avoided. A comprehensive but non-
exhaustive list of useful temporary wet strength agents includes aliphatic and
aromatic aldehydes including glyoxal, malonic dialdehyde, succinic dialdehyde,
glutaraldehyde and dialdehyde starches, as well as substituted or reacted
starches,
disaccharides, polysaccharides, chitosan, or other reacted polymeric reaction
products of monomers or polymers having aldehyde groups, and optionally,
nitrogen groups. Representative nitrogen containing polymers, which can
suitably
be reacted with the aldehyde containing monomers or polymers, includes vinyl-
amides, acrylamides and related nitrogen containing polymers. These polymers
impart a positive charge to the aldehyde containing reaction product. In
addition,
other commercially available temporary wet strength agents, such as, PAREZ
745,
manufactured by Bayer can be used, along with those disclosed, for example in
United States Patent No. 4,605,702.
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The temporary wet strength resin may be any one of a variety of water-
soluble organic polymers comprising aldehydic units and cationic units used to
increase dry and wet tensile strength of a paper product. Such resins are
described
in United States Patent Nos. 4,675,394; 5,240,562; 5,138,002; 5,085,736;
4,981,557; 5,008,344; 4,603,176; 4,983,748; 4,866,151; 4,804,769 and
5,217,576.
Modified starches sold under the trademarks CO-BOND 1000 and CO-BOND
1000 Plus, by National Starch and Chemical Company of Bridgewater, N.J. may
be used. Prior to use, the cationic aldehydic water soluble polymer can be
prepared by preheating an aqueous slurry of approximately 5% solids maintained
at a temperature of approximately 240 degrees Fahrenheit (116 degrees Celsius)
and a pH of about 2.7 for approximately 3.5 minutes. Finally, the slurry can
be
quenched and diluted by adding water to produce a mixture of approximately
1.0% solids at less than about 130 degrees Fahrenheit (116 degrees Celsius).
Other temporary wet strength agents, also available from National Starch
and Chemical Company are sold under the trademarks CO-BOND 1600 and
CO-BOND 2300. These starches are supplied as aqueous colloidal dispersions
and do not require preheating prior to use.
Suitable dry strength agents include starch, guar gum, polyacrylamides,
carboxymethyl cellulose and the like. Of particular utility is carboxymethyl
cellulose, an example of which is sold under the trade name Hercules CMC, by
Hercules Incorporated of Wilmington, Delaware. According to one embodiment,
the pulp may contain from about 0 to about 15 lb/ton (from about 0 to about
7.5
kg/mton) of dry strength agent. According to another embodiment, the pulp may
contain from about 1 to about 5 lbs/ton (from about 0.5 to about 2.5 kg/mton)
of
dry strength agent.
Suitable debonders are likewise known to the skilled artisan. Debonders
or softeners may also be incorporated into the pulp or sprayed upon the web
after
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its formation. The present invention may also be used with softener materials
including but not limited to the class of amido amine salts derived from
partially
acid neutralized amines. Such materials are disclosed in United States Patent
No.
4,720,383. Evans, Chemistry and Industry, 5 July 1969, pp. 893-903; Egan, lAm.
Oil Chemist's Soc., Vol. 55 (1978), pp. 118-121; and Trivedi et al., lAm.Oil
Chemist's Soc., June 1981, pp. 754-756, indicate that softeners are often
available
commercially only as complex mixtures rather than as single compounds. While
the following discussion will focus on the predominant species, it should be
understood that commercially available mixtures would generally be used in
practice.
QUASOFTO 202-JR is a suitable softener material, which may be derived
by alkylating a condensation product of oleic acid and diethylenetriamine.
Synthesis conditions using a deficiency of alkylation agent (e.g., diethyl
sulfate)
and only one alkylating step, followed by pH adjustment to protonate the non-
ethylated species, result in a mixture consisting of cationic ethylated and
cationic
non-ethylated species. A minor proportion (e.g., about 10%) of the resulting
amido amine cyclize to imidazoline compounds. Since only the imidazoline
portions of these materials are quaternary ammonium compounds, the
compositions as a whole are pH-sensitive. Therefore, in the practice of the
present invention with this class of chemicals, the pH in the head box should
be
approximately 6 to 8, more preferably 6 to 7 and most preferably 6.5 to 7.
Quaternary ammonium compounds, such as dialkyl dimethyl quaternary
ammonium salts are also suitable particularly when the alkyl groups contain
from
about 10 to 24 carbon atoms. These compounds have the advantage of being
relatively insensitive to pH.
Biodegradable softeners can be utilized. Representative biodegradable
cationic softeners/debonders are disclosed in United States Patent Nos.
5,312,522;
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5,415,737; 5,262,007; 5,264,082; and 5,223,096. The compounds are
biodegradable diesters of quaternary ammonia compounds, quaternized amine-
esters, and biodegradable vegetable oil based esters functional with
quaternary
ammonium chloride and diester dierucyldimethyl ammonium chloride and are
representative biodegradable softeners.
In some embodiments, a particularly preferred debonder composition
includes a quaternary amine component as well as a nonionic surfactant.
The nascent web may be compactively dewatered on a papermaking felt.
Any suitable felt may be used. For example, felts can have double-layer base
weaves, triple-layer base weaves, or laminated base weaves. Preferred felts
are
those having the laminated base weave design. A wet-press-felt which may be
particularly useful with the present invention is VectorTM 3 made by Voith
Fabric.
Background art in the press felt area includes United States Patent Nos.
5,657,797;
5,368,696; 4,973,512; 5,023,132; 5,225,269; 5,182,164; 5,372,876; and
5,618,612. A differential pressing felt as is disclosed in United States
Patent No.
4,533,437 to Curran et al. may likewise be utilized.
Suitable creping or textured fabrics include single layer or multi-layer, or
composite preferably open meshed structures. Fabric constructionper se is of
less
importance than the topography of the creping surface in the creping nip as
discussed in more detail below. Long MD knuckles with slightly lowered CD
knuckles are greatly preferred for many products. Fabrics may have at least
one
of the following characteristics: (1) on the side of the creping fabric that
is in
contact with the wet web (the "top" side), the number of machine direction
(MD)
strands per inch (mesh) is from 10 to 200 (strands per cm (mesh) is from 3 to
18)
and the number of cross-direction (CD) strands per inch (count) is also from
10 to
200 (strands per cm (count) is from 3 to 18); (2) The strand diameter is
typically
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smaller than 0.050 inch (0.13 cm); (3) on the top side, the distance between
the
highest point of the MD knuckles and the highest point on the CD knuckles is
from about 0.001 to about 0.02 or 0.03 inch (from about 0.0025 to about 0.05
or
0.08 cm); (4) In between these two levels there can be knuckles formed either
by
MD or CD strands that give the topography a three dimensional hill/valley
appearance which is imparted to the sheet; (5) The fabric may be oriented in
any
suitable way so as to achieve the desired effect on processing and on
properties in
the product; the long warp knuckles may be on the top side to increase MD
ridges
in the product, or the long shute knuckles may be on the top side if more CD
ridges are desired to influence creping characteristics as the web is
transferred
from the transfer cylinder to the creping fabric; and (6) the fabric may be
made to
show certain geometric patterns that are pleasing to the eye, which is
typically
repeated between every two to 50 warp yams. An especially preferred fabric is
a
W013 Albany International multilayer fabric. Such fabrics are formed from
monofilament polymeric fibers having diameters typically ranging from about
0.25 mm to about 1 mm. A particularly preferred fabric is shown in Figure 7
and
following.
In order to provide additional bulk, a wet web is creped into a textured
fabric and expanded within the textured fabric by suction, for example.
If a Fourdrinier former or other gap former is used, the nascent web may
be conditioned with suction boxes and a steam shroud until it reaches a solids
content suitable for transferring to a dewatering felt. The nascent web may be
transferred with suction assistance to the felt. In a crescent former, use of
suction
assist is unnecessary as the nascent web is formed between the forming fabric
and
the felt.
A preferred mode of making the inventive products involves compactively
dewatering a papermaking furnish having an apparently random distribution of
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fiber orientation and fabric creping the web so as to redistribute the furnish
in
order to achieve the desired properties. Salient features of a typical
apparatus 40
for producing the inventive products are shown in Figure 4. Apparatus 40
includes a papermaking felt 42, a suction roll 46, a press shoe 50, and a
backing
roll 52. There is further provided a creping roll 62, a creping fabric 60, as
well as
an optional suction box 66.
In operation, felt 42 conveys a nascent web 44 around a suction roll 46
into a press nip 48. In press nip 48 the web is compactively dewatered and
transferred to a backing roll 52 (sometimes referred to as a transfer roll
hereinafter) where the web is conveyed to the creping fabric. In a creping nip
64
web 44 is transferred into fabric 60 as discussed in more detail hereinafter.
The
creping nip is defined between backing roll 52 and creping fabric 60 which is
pressed against roll 52 by creping roll 62 which may be a soft covered roll as
is
also discussed hereinafter. After the web is transferred into fabric 60 a
suction
box 66 may be used to apply suction to the sheet in order to draw out
microfolds if
so desired.
A papermachine suitable for making the product of the invention may have
various configurations as is seen in Figures 5 and 6 discussed below.
There is shown in Figure 5 a papermachine 110 for use in connection with
the present invention. Papermachine 110 is a three fabric loop machine having
a
forming section 112 generally referred to in the art as a crescent former.
Forming
section 112 includes a forming wire 122 supported by a plurality of rolls such
as
rolls 132, 135. The forming section also includes a forming roll 138 which
supports papermaking felt 42 such that web 44 is formed directly on felt 42.
Felt
run 114 extends to a shoe press section 116 wherein the moist web is deposited
on
a backing roll 52 and wet-pressed concurrently with the transfer. Thereafter
web
44 is creped onto fabric 60 in fabric crepe nip 64 before being deposited on
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Yankee dryer 120 in another press nip 182 using a creping adhesive as noted
above. The system includes a suction turning roll 46, in some embodiments;
however, the three loop system may be configured in a variety of ways wherein
a
turning roll is not necessary. This feature is particularly important in
connection
with the rebuild of a papermachine inasmuch as the expense of relocating
associated equipment i.e. pulping or fiber processing equipment and/or the
large
and expensive drying equipment such as the Yankee dryer or plurality of can
dryers would make a rebuild prohibitively expensive unless the improvements
could be configured to be compatible with the existing facility.
Referring to Figure 6, there is shown schematically a paper machine 210
which may be used to practice the present invention. Paper machine 210
includes
a forming section 212, a press section 40, a crepe roll 62, as well as a can
dryer
section 218. Forming section 212 includes: a head box 220, a forming fabric or
wire 222, which is supported on a plurality of rolls to provide a forming
table 212.
There is thus provided forming roll 224, support rolls 226, 228 as well as a
transfer roll 230.
Press section 40 includes a papermaking felt 42 supported on rollers 234,
236, 238, 240 and shoe press roll 242. Shoe press roll 242 includes a shoe 244
for
pressing the web against transfer drum or roll 52. Transfer roll or drum 52
may be
heated if so desired. In one preferred embodiment, the temperature is
controlled
so as to maintain a moisture profile in the web so a sided sheet is prepared,
having
a local variation in basis weight which does not extend to the surface of the
web in
contact with cylinder 52. Typically, steam is used to heat cylinder 52 as is
noted
in United States Patent No. 6,379,496 of Edwards et al. Roll 52 includes a
transfer surface 248 upon which the web is deposited during manufacture. Crepe
roll 62 supports, in part, a creping fabric 60 which is also supported on a
plurality
of rolls 252, 254 and 256.
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Dryer section 218 also includes a plurality of can dryers 258, 260, 262,
264, 266, 268, and 270 as shown in the diagram, wherein cans 266, 268 and 270
are in a first tier and cans 258, 260, 262 and 264 are in a second tier. Cans
266,
268 and 270 directly contact the web, whereas cans in the other tier contact
the
fabric. In this two tier arrangement where the web is separated from cans 260
and
262 by the fabric, it is sometimes advantageous to provide impingement air
dryers
at 260 and 262, which may be drilled cans, such that air flow is indicated
schematically at 261 and 263.
There is further provided a reel section 272 which includes a guide roll
274 and a take up reel 276 shown schematically in the diagram.
Paper machine 210 is operated such that the web travels in the machine
direction indicated by arrows 278, 282, 284, 286 and 288 as is seen in Figure
6.
A papermaking furnish at low consistency, less than 5%, is deposited on fabric
or
wire 222 to form a web 44 on table 212 as is shown in the diagram. Web 44 is
conveyed in the machine direction to press section 40 and transferred onto a
press
felt 42. In this connection, the web is typically dewatered to a consistency
of
between about 10 and 15% on wire 222 before being transferred to the felt. So
also, roll 234 may be a suction roll to assist in transfer to the felt 42. On
felt 42,
web 44 is dewatered to a consistency typically of from about 20 to about 25%
prior to entering a press nip indicated at 290. At nip 290 the web is pressed
onto
cylinder 52 by way of shoe press roll 242. In this connection, the shoe 244
exerts
pressure where upon the web is transferred to surface 248 of roll 52 at a
consistency of from about 40 to 50% on the transfer roll. Transfer roll 52
translates in the machine direction indicated by 284 at a first speed.
Fabric 60 travels in the direction indicated by arrow 286 and picks up web
44 in the creping nip indicated at 64. Fabric 60 is traveling at second speed
slower than the first speed of the transfer surface 248 of roll 52. Thus, the
web is
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provided with a Fabric Crepe typically in an amount of from about 10 to about
100% in the machine direction.
The creping fabric defines a creping nip over the distance in which creping
fabric 60 is adapted to contact surface 248 of roll 52; that is, applies
significant
pressure to the web against the transfer cylinder. To this end, creping roll
62 may
be provided with a soft deformable surface which will increase the width of
the
creping nip and increase the fabric creping angle between the fabric and the
sheet
at the point of contact or a shoe press roll or similar device could be used
as roll
52 or 62 to increase effective contact with the web in high impact fabric
creping
nip 64 where web 44 is transferred to fabric 60 and advanced in the machine-
direction. By using different equipment at the creping nip, it is possible to
adjust
the fabric creping angle or the takeaway angle from the creping nip. A cover
on
roll 62 having a Pusey and Jones hardness of from about 25 to about 90 may be
used. Thus, it is possible to influence the nature and amount of
redistribution of
fiber, delamination/debonding which may occur at fabric creping nip 64 by
adjusting these nip parameters. In some embodiments it may by desirable to
restructure the z-direction interfiber characteristics while in other cases it
may be
desired to influence properties only in the plane of the web. The creping nip
parameters can influence the distribution of fiber in the web in a variety of
directions, including inducing changes in the z-direction as well as the MD
and
= CD. In any case, the transfer from the transfer cylinder to the creping
fabric is
high impact in that the fabric is traveling slower than the web and a
significant
velocity change occurs. Typically, the web is creped anywhere from 5-60% and
even higher during transfer from the transfer cylinder to the fabric.
Creping nip 64 generally extends over a fabric creping nip distance or
width of anywhere from about 1/8" to about 2", typically Y2" to 2" (from about
0.3
to about 5.1 cm, typically 1.3 to 5.1 cm). For a creping fabric with 32 CD
strands
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=
per inch (12.5 CD strands per centimeter), web 44 thus will encounter anywhere
from about 4 to 64 weft filaments in the nip.
The nip pressure in nip 64, that is, the loading between creping roll 62 and
transfer roll 52 is suitably 20-100, preferably 40-70 pounds (suitably 9-45,
preferably 18-32 kg) per linear inch (PL) (suitably 3.6-17.9 kg, preferably
7.1-
12.5 kg per linear cm (plcm)).
Following the Fabric Crepe, web 44 is retained in fabric 60 and fed to
dryer section 218. In dryer section 218 the web is dried to a consistency of
from
about 92 to 98% before being wound up on reel 276. Note that there is provided
in the drying section a plurality of heated drying rolls 266, 268 and 270
which are
in direct contact with the web on fabric 60. The drying cans or rolls 266,
268, and
270 are steam heated to an elevated temperature operative to dry the web.
Rolls
258, 260, 262 and 264 are likewise heated although these rolls contact the
fabric
directly and not the web directly. Optionally provided is a suction box 66
which
can be used to expand the web within the fabric to increase caliper as noted
above.
In some embodiments of the invention, it is desirable to eliminate open
draws in the process, such as the open draw between the creping and drying
fabric
. and reel 276. This is readily accomplished by extending the creping
fabric to the
reel drum and transferring the web directly from the fabric to the reel as is
disclosed generally in United States Patent No. 5,593,545 to Rugowski et al.
A preferred creping fabric 60 is shown in Figures 7 and 8. Figure 7 is a
gray scale topographical photo image of creping fabric 60, while Figure 8 is
an
enhanced two-dimensional topographical color image of the creping fabric shown
in Figure 7. Fabric 60 is mounted in the apparatus of Figures 4, 5, or 6 such
that
its MD knuckles 300, 302, 304, 306, 308, 310, and so forth, extend along the
machine direction of the paper machine. It will be appreciated from Figures 7
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and 8 that fabric 60 is a multi-layer fabric having creping pockets 320, 322,
324,
and so forth, between the MD knuckles of the fabric. There is also provided a
plurality of CD knuckles 330, 332, 334 and so forth, which may be preferably
recessed slightly with respect to the MD knuckles of the creping fabric. The
CD
knuckles may be recessed with respect to the MD knuckles a distance of from
about 0.1 mm to about 0.3 mm. This geometry creates a unique distribution of
fiber when the web is wet creped from a transfer roll as will be appreciated
from
Figure 9 and following. Without intending to be bound by theory, it is
believed
the structure illustrated, with relatively large recessed "pockets" and
limited
knuckle length and height in the CD redistributes the fiber upon high impact
creping to produce sheet which is especially suitable for recycle furnish and
provides surprising caliper.
In Figures 9 through 12 there is shown schematically a creping nip 64
wherein a web 44 is transferred from a transfer or backing roll 52 into
creping
fabric 60. Fabric 60 has a plurality of warp filaments such as filaments 350
as
well as a plurality of weft filaments as will be appreciated from the Figures
discussed above. The weft filaments are arranged in a first level 352 as well
as a
second level 354 as shown in the diagrams. The various filaments or strands
may
be of any suitable dimensions, typically a weft strand would have a diameter
of
0.50 mm while a warp strand would be somewhat smaller, perhaps 0.35 mm. The
warp filaments extend around both levels of weft filaments such that the
elongated
knuckles such as knuckle 300 contacts the web as it is disposed on transfer
roll 52
as shown in the various diagrams. The warp strands also may have smaller
knuckles distal to the creping surface if so desired.
In a particularly preferred embodiment, the nip width at 100 ph i (17.9
plcm) is approximately 34.8 mm when used in connection with the crepe roll
cover having a 45 P&J hardness. The nip penetration is calculated as 0.49 mm
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using the Deshpande method, assuming a 1"(2.54 cm) thick sleeve. A 2" (5.08
cm) thick sleeve is likewise suitable.
A suitable fabric for use in connection with the present invention is a WO-
13 fabric available from Albany International. This fabric provides MD
knuckles
having a MD length of about 1.7 mm as shown in Figure 11.
Without intending to be bound by any theory, it is believed that creping
from transfer roll 52 and redistribution of the papermaking fiber into the
pockets
of the creping fabric occurs as shown in Figures 9 through 12. That is to say
the
trailing edge of the knuckles contacts the web first where upon the web
buckles
from the backing roll into the relatively deep creping pockets of the fabric
away
from the backing roll. Note particularly Figure 12. The creping process with
this
fabric produces a unique product of the invention which is described in
connection
with Figures 13 and 14.
There is illustrated schematically (and photographically) in Figures 13 and
14 a pattern with a plurality of repeating linear arrays 1, 2, 3, 4, 5, 6, 7,
8 of
compressed densified regions 14 which are oriented in the machine direction.
These regions form a repeating pattern 375 corresponding to the MD knuckles of
fabric 60. For purposes of convenience, pattern 375 is presented schematically
in
Figure 13 and the lower part of Figure 14 as warp arrays 1-8 and weft bars la-
8a;
the top of Figure 14 is a photomicrograph of a sheet produced with this
pattern.
Pattern 375 thus includes a plurality of generally machine direction (MD)
oriented
elongated densified regions 14 of compressed papermaking fibers having a
relatively low local basis weight as well as leading and trailing edges 380,
382, the
densified regions being arranged in a repeating pattern of a plurality of
generally
parallel linear arrays 1-8 which are longitudinally staggered with respect to
each
other such that a plurality of intervening linear arrays are disposed between
a pair
of CD-aligned densified regions 384, 386. There is a plurality of fiber-
enriched,
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pileated regions 12 having a relatively high local basis weight interspersed
between and connected with the densified regions, the pileated regions having
crests extending laterally in the CD. The generally parallel, longitudinal
arrays of
densified regions 14 are positioned and configured such that a fiber-enriched
region 12 between a pair of CD-aligned densified regions extends in the CD
unobstructed by leading or trailing edges 380, 382 of densified regions of at
least
one intervening linear array thereof. As shown, the generally parallel,
longitudinal arrays of densified regions are positioned and configured such
that a
fiber-enriched region 12 between a pair of CD-aligned densified regions 14
extends in the CD unobstructed by leading or trailing edges of densified
regions of
at least two intervening linear arrays. So also, a fiber-enriched region 12
between
a pair of CD-aligned densified regions 384, 386 is at least partially
truncated and
at least partially bordered in the MD by the leading or trailing edges of
densified
regions of at least one or two intervening linear arrays of the sheet at MD
position
388 intermediate MD positions 380, 390 of the leading and trailing edges of
the
CD-aligned densified regions. The leading and trailing MD edges 392, 394 of
the
fiber-enriched pileated regions are generally inwardly concave such that a
central
MD span 396 of the fiber-enriched regions is less than an MD span 398 at the
lateral extremities of the fiber-enriched areas. The elongated densified
regions
occupy from about 5% to about 30% of the area of the sheet and are estimated
as
corresponding to the MD knuckle area of the fabric employed. The pileated
regions occupy from about 95% to about 50% of the area of the sheet and are
estimated by the recessed areas of the fabric. In the embodiment shown in
Figures 13 and 14 the distance 400 between CD-aligned densified regions is
4.41
mm, such that the linear arrays of densified regions have an MD repeat
frequency
of about 225 meter-I. The densified elements of the arrays are spaced a
distance
402 of about 8.8 mm, thus having an MD repeat frequency of about 110 meteel.
47
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The fiber-enriched regions have a concamerated structure, wherein the
crests of the pileated regions are arched around the leading and trailing
edges of
the densified regions as is seen particularly at the top of Figure 14.
The product thus has the attributes shown and described above in
connection with Figures 1 and 2.
Further aspects of the invention are appreciated by reference to Figures 15
through 30. Figure 15 is a photomicrograph of a web similar to that shown in
Figure 2 wherein the web has been pulled in the machine direction. Here it is
seen that the pileated region 12 has been expanded to a much greater degree of
void volume, enhancing the absorbency of the sheet.
Figure 16 is a photomicrograph of a base sheet similar to that shown in
Figure 1 indicating the cross section shown in Figure 17. Figure 17 is a cross
section of a pileated, fiber-enriched region where it is seen that the
macrofolds
have not been densified by the knuckle. In Figure 17 it is seen that the sheet
is
extremely "sided". If it is desired to reduce this sidedness, the web can be
transferred to another surface during drying so that the fabric side of the
web
(prior to transfer) contacts drying cans thereafter.
Figure 18 is a magnified photomicrograph showing a knuckle impression
of a MD knuckle of the creping fabric wherein it is seen that the fiber of the
compressed, MD region, has a CD orientation bias and that the fiber-enriched,
pileated regions, have a concamerated structure around the MD extending
compressed region.
The local basis weight variation of the sheet is seen in Figures 19 and 20.
Figures 19 and 20 are X-ray negative images of the absorbent sheet of the
invention wherein the light portions represent high basis weight regions and
the
48
CA 02652814 2008-11-18
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PCT/US2007/011967
darker portions represent relatively lower basis weight regions. These images
were made by placing sheet samples on plates and exposing the specimens to a
6kV X-ray source for 1 hour. Figure 19 is an X-ray image made without suction,
while Figure 20 was made with suction applied to the sheet.
In both Figures 19 and 20 it is seen that there are a plurality of dark, MD
extending regions of relative low basis weight corresponding to the MD
knuckles
of the fabric of Figure 7. Lighter and whiter portions show the fiber-enriched
regions of relatively high basis weight. These regions extend in the CD, along
the
folds seen in Figure 18, for example.
Figures 19 and 20 confirm the local basis weight variation seen in the
SEMs and other photomicrographs, especially the relatively orthogonal
relationship between the low basis weight regions and the high basis weight
regions.
Note that Figure 19, with the suction "off" shows a slightly stronger basis
weight variation (more prominent light areas) than Figure 20 suction "on"
consistent with Figures 22 and 23, discussed below.
Further product options are seen in Figures 21A through 21D. Figures
21A and B respectively are photomicrographs of the fabric side and Yankee side
of a 25 pound basis weight (41gsm) sheet at a fabric creped ratio of 1.3.
Figures
21C and 21D are photomicrographs of another 25 pound basis weight sheet
produced at a fabric creped ratio of 1.3. Where suction is indicated on the
legends
of the Figures, that is, Figures 21C, 21D the sheet was suction drawn after
fabric
creping.
Figures 22 and 23 show the affect of suction when making the inventive
sheet. Figure 22 is a photomicrograph along the MD of a cellulosic sheet
49
CA 02652814 2008-11-18
WO 2007/139726
PCT/US2007/011967
produced in accordance with the present invention, Yankee side up produced
with
no suction. Figure 23 is a photomicrograph of a cellulosic sheet made in
accordance with the ifivention wherein suction box 66 was turned on. It will
be
appreciated from these Figures that suction enhances the bulk (and absorbency)
of
the sheet. In Figure 22 it is seen that there are micro-folds embedded within
the
macro-folds of the sheet. In Figure 23, the micro-folds are no longer evident.
For
purposes of comparison there is shown in Figure 24 a corresponding cross-
sectional view along the machine direction of a CWP base sheet. Here it is
seen
that the fiber is relatively dense and does not exhibit the enhanced and
uniform
bulk of products of the invention.
Beta Particle Attenuation Analysis
In order to quantify local basis weight variation, a beta particle attenuation
technique was employed.
Beta particles are produced when an unstable nucleus with either too many
protons or neutrons spontaneously decays to yield a more stable element. This
process can produce either positive or negative particles. When a radioactive
element with too many protons undergoes beta decay a proton is converted into
a
neutron, emitting a positively charged beta particle or positron (p.) and a
neutrino. Conversely, a radioactive element with too may neutrons undergoes
beta decay by converting a neutron to a proton, emitting a negatively charged
beta
particle or negatron (jr) and an antineutrino. Promethium ( 1=`6", Pm )
undergoes
negative beta decay.
Beta gauging is based on the process of counting the number of beta
particles that penetrate the specimen and impinge upon a detector positioned
opposite the source over some period of time. The trajectories of beta
particles
deviate wildly as they interact with matter; some coming to rest within it,
others
CA 02652814 2008-11-18
WO 2007/139726
PCT/US2007/011967
penetrating or being backscattered after partial energy loss and ultimately
exiting
the solid at a wide range of angles.
Anderson, D. W. (1984). Absorption of Ionizing Radiation, Baltimore,
University Park Press, (pp. 69) states that at intermediate transmission
values the
transmission can be calculated as follows:
i=ioe-fic" = ioe-fl w
where: /0 is the intensity incident on the material
is the effective beta mass absorption coefficient in cm2/g
t is the thickness in cm
p is the density in g/cm3
w is the basis weight in g/ cm2
An off-line profiler fitted with an AT-100 radioisotope gauge (Adaptive
Technologies, Inc., Fredrick, MD) containing 1800 microcuries of Promethium
was calibrated using a polycarbonate collimator having an aperture of
approximately 18 mils (0.46 mm) diameter. Calibration was carried out by
placing the collimator atop the beta particle source and measuring counts for
20
seconds. The operation is repeated with 0, 1, 2, 3, 4,5, 6, 7, 8 layers of
polyethylene terephthalate film having a basis weight of 10.33 lbs/3000 ft2
ream
(16.8 gsm). Results appear in Table 1 and presented graphically in Figure 25.
51
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PCT/US2007/011967
Table 1 - Calibration
Weight Weight
Counts lbs/3000 ft2 (gsm)
165.3 0 0
114.4 10.33 16.81
80.9 20.68 33.65
62.3 30.97 50.40
43.3 41.3 67.21
33 51.63 84.02
26.2 61.93 100.78
17.1 72.28 117.62
15.2 82.61 134.43
11 92.9 151.17
The calibrated apparatus was then used to measure local basis weight on a
sample of absorbent sheet having generally the structure shown in Figure 18.
Basis weight measurements were taken generally at positions 1-9 indicated
schematically in Figure 26. Results appear in Table 2.
Table 2 - Local Basis Weight Variation
Position Count Calculated Basis Weight Calculated Basis Weight (gsm)
1 60 32.38 52.70
2 73.8 25.24 41.08
3 76.6 23.96 38.99
4 71.2 26.48 = 43.09
5 66.3 28.94 47.09
6 37.5 48.59 79.08
7 55.8 34.89 56.77
8 60.4 32.16 52.33
9 59.9 32.44 52.79
It is appreciated from the foregoing that the local basis weight at position 6
(fiber-enriched region) is much higher, by 50% or so than position 2, a low
basis
weight region. Local basis weight at position 1 between folds was consistently
relatively low; however, local basis weights at positions 4 and 7 were
sometimes
52
CA 02652814 2008-11-18
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PCT/US2007/011967
somewhat higher than expected, perhaps due to the presence of folds in the
sample
occurring during fabric or reel crepe.
The inventive products and process for making them are extremely useful
in connection with a wide variety of products. For example, there is shown in
Figure 27 a comparison of panel softness for various two-ply bathroom tissue
products.
The 2005 product was made with a single layer fabric, while the 2006
product was made with a multi-layer fabric of the invention. Note that the
products made with a multi-layer fabric exhibited much enhanced softness at a
given tensile. This data is also shown in Figure 28.
Details as to various tissue products are summarized in Tables 3, 4 and 5.
The 44M fabric is a single layer fabric while the W013 fabric is the
multilayer
fabric discussed in connection with Figures 7 and following.
25
53
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PCT/US2007/011967
Table 3 - Comparison of Base Sheet and Finished Product Properties
2005 2006
Fabric
44M (MD) W013 (MD)
Fiber 75% euc 60% euc
Forming Blended BI. and Lay.
Softener 1152,2# 1152,4#
Fabric Crepe 25 to 35 17 to 32
Suction 12 to 22 23
BS Caliper Suction Off 63 90
BS Caliper Suction Max 79 115
FP BW 27 to 29 32
FP Caliper 133 to 146 180 to 200
FP GMT 500 to 580 460 to 760
FP Softness 18.8 to 19.4 19.4 to 20.2
Table 4 - Comparison of Properties (2-ply)
2005 2006
Fabric
44M W013
BS Caliper Suction Off 63 90
BS Caliper Suction Max 79 115
FP BW 27 to 29 32
FP Caliper 133 to 146 180 to 200
FP Softness 18.8 to 19.4 19.4 to 20.2
54
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WO 2007/139726 PCT/US2007/011967
Table 5 - Comparison of Finished Products and TAD Product
2005 2006 TAD
Fabric
44M W013 Commercial
FP GMT 600 600' 600
FP Softness 18.9 20.1 20.2
FP Caliper 145 171 151
Sheet Count 200 200 200
Roll Diameter 4.70 4.90 4.75
Roll Firmness _ 17.7 9.3 17.6
Table 6 - Comparison of Base Sheet and Finished Product Results
for 44M/MD and W013 Fabrics
Cell ID: Base sheet P2150 11031/11032
Product Type QNBT Ultra QNBT Ultra
Furnish 75/25 Euc/Mar 60/40 euc/Mar
eTAD Fabric/Side Up 44M/MD W013
% Fabric Crepe/% Reel Crepe 25/2 31.5/8.5%
Suction 20 23.1
Basis Weight lbs/ream (gsm) 16.42(26.72) 17.60 (28.64)
Caliper (mils/8 sheets) (mm/8 sheets) 79.7 (2.02) 121.4 (3.08)
MD Tensile (g/3") (g/cm) 474 (62.2) 569 (74.7)
CD Tensile (g/3") (g/cm) 231 (30.3) 347 (45.5)
.,
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WO 2007/139726 PCT/US2007/011967
Table 6 (cont'd) - Comparison of Base Sheet and Finished Product Results
for 44M/MD and W013 Fabrics
Cell ID: Base sheet P2150 11031/11032
GM Tensile g/3" (g/cm) 330 (43.3) 444 (58.3)
MD Stretch CYO 28.8 51.5
CD Stretch (%) 7.9 9.6
CD Wet Tensile - Finch g/3" (g/cm) 27 (3.5) 0 (0)
GM Break Modulus (g/%) 21.9 20.0
Base sheet Bulk in mils/8 plies/lb/R 4.85 6.90
((mm/8plies)/(gsm)) (0.075) (0.11)
emboss pattern HVS9 high elements double hearts
rubber backup roll 55 Shore A 90 P&J
sheet count 176 198
Basis Weight lbs/ream (gsm) 30.6 (49.8) 29.5 (48.0)
Caliper mils/8sheets (mm/8sheets) 150.2 (3.81) 170.8 (4.34)
MD Dry Tensile g/3" (g/em) 478 (62.7) 695 (91.2)
CD Dry Tensile g/3" (g/cm) 297 (39.0) 451 (59.2)
Geometric Mean Tensile g/3" (g/cm) 376 (49.3) 559 (73.4)
MD Stretch (%) 12.0 28.7
CD Stretch (%) 7.2 9.1
Perforation Tensile g/3" (g/cm) 258 (33.9) 393 (51.6)
CD Wet Tensile g/3" (g/cm) 42.2 (5.54) 10 (1.31)
GM Break Modulus (g/%) 40.5 35.0
Friction (GMMMD) 0.546 0.586
Roll Diameter inches (cm) 4.67 (11.9) 4.91(12.5)
Roll Compression (%) 23.7 93
Sensory Softness 19.61 20.2
finished product Bulk in 4.91 5.78
mils/8 plies/lb/R amm/8plies)/(gsm)) (0.077) (0.090)
56
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It is appreciated from Tables 3 through 5 that the process and products of
the invention made with the multilayer fabric provide much more caliper at a
given basis weight as well as enhanced softness.
Table 6 above likewise shows that tissue products of the invention, those
made with the WO-13 fabric, exhibit much more softness with even much higher
tensile, a very surprising result given the conventional wisdom that softness
decreases rapidly with increasing tensile.
The present invention also provides a unique combination of properties for
making single ply towel and makes it possible to use elevated amounts of
recycled
fiber without negatively affecting product performance or hand feel. In this
connection furnish blends containing recycle fiber were evaluated. Results are
summarized in Tables 7, 8 and 9.
57
Table 7 - Process Data
0
t.,
=
Yankee Sm Yank Reel
Cal. =
ID Fabric
-4
fpm (m/min) fpm (m/min)
fpm (m/min) fpm (m/min) .
,...,
-4
Cell 1 W013 1,545 (471.2)
1,855 (565.8) 1,544 (470.9) 1,505 (459.0)
c,
Cell 2 W013 1,545(471.2)
1,855(565.8) 1,544(470.9) 1,505(459.0)
Cell 2A W013 , 1,545 (471.2) 1,901 (579.8)
1,545 (471.2) 1,505 (459.0)
Cell 3 W013 1,545 (471.2)
1,901 (579.8) 1,545 (471.2) 1,505 (459.0)
Cell 4 W013 1,545 (471.2)
1,947 (593.8) 1,545 (471.2) 1,505 (459.0)
0
Table 7 - Cont'd .
I,
,,,
u-,
I,
co
CHEMICAL ADD.
FURNISH H
Suction
Fabric Crp. Reel Crp. Calender . Refining
Parez WSR
ID
(%) (%) psi (bar) (hp) lbs./ton23
(lbs./ton) ins. Hg Recycle Douglas Fir 0"
.
co
(cm Hg)
(kg/mton) (kg/mton)
H '
,__,
,
Cell 1 20 , 0 23(1.9) 23(58) None 6(3)
12(6) 25 75 H
CO
Cell 2 20 0 20 (1.4) 23(58) None 1 (0.5)
10 (5) 50 50
Cell 2A 23 0 26(1.8) 23(58) None ,
3(1.5) 10(5) 50 50
Cell 3 23 0 17 (1.2) 23(58) None 0(0)
10(5) 75 25
Cell 4 26 0 21(1.4) 23(58) None 0 (0)
10 (5) 100 0
.;
n
,-i
cp
t.,
=
=
-4
=
58
.
c,
-4
Table 8- BASE SHEET DATA
0
t.,
BW Unc. Cal.
Cal. Cal. MD DRY "
'
MDS
-4
ID lbs./ream mils/8 ply
mils/8 ply 8/3¶
(%)
.
,...,
{gsm} {mm/8 ply) {mm/8 ply)
{g/cm}
-4
t.,
c,
21.3 (20.6/22) 78.0 (72/84)
2,750 (2300/3200)
SofPull Targets (mins/max)
23.0 (18/28)
{34.7 (33.5/35.8) (1.98 (1.83/2.13)) {361
(302/420))
Cell 1 21.1 (34.3) 95 (2.41) 77
(1.96) , 24.4 2,468 (324)
Cell 2 21.2 (34.5) 84 (2.13)
78 {1.98) 24.1 2,669 {350}
Cell 2A 20.6 (33.5) 95 (2.41)
76 {1.93) 25,5 2,254 {296}
Cell 3 21.4 (34.8) 88 (2.23)
79 (2.00) 26.2 2,867 {376} 0
Cell 4 21.4 (34.8) 88 (2.23)
76 {1.93} 27.6 2,787 {366} .
I,
,,,
u-,
I,
Table 8 - Cont'd
co
H
1,,D\)
.
CD DRY Total MD/CD WET CD
WAR co
,
ID GMTH
g/3" {g/cm} g/3" {g/cm} Ratio
g/3" {g/cm} (secs) H
I
H
CO
=
1,900 (1450/2550) 450 (min 325) 5.0
SofPull Targets (mins/max) 286 4650 1.42,,
{249 (190/335){59 (min 43) (max 15)
Cell 1 1,908 {250} 2,170
4,376 {574} 1.3 445 (58) 4
Cell 2 1,924 (253) 2,266
4,593 {603} 1.4 , 426 (56) 6 .o
Cell 2A 1,761 {231} 1,992
4,015 {527} 1.3 385 (51) 5 n
,-i
Cell 3 1,793 {235} 2,267
4,660 {612} 1.6 462 {61} 5
cp
t.,
Cell 4 1,974 {259} 2,346
4,761 {625} 1.4 505 {66} 5 =
=
-4
=
59
.
c,
-4
Table 9 - Recycled Content Furnish Trial (Finished Product Test Data)
0
w
Single
'
=
-4
Identification TAD layer Cell 1 Cell 2 Cell 2A Cell 3 Cell
4 Product Targets (44
Creping
-4
w
Fabric
c,
Furnish (Softwood /
100/0 80/20 75/25 50/50 50/50 25/75 0/100 Target Minimum Maximum
Secondary)
FC/RC NA
20/0 20/0 20/0 23/0 23/0 26/0
Parameter
Basis Weight lbs/rm 22.6 21.3 21.2 ' 21.4 20.8
21.5 21.3 21.0 20.0 22.0 n
(gsm) (36.8) (34.7) (34.5) (34.8) (33.8) (35.0) (34.7)
(34.2) (32.5) (35.8)
0
Caliper mils/8 sheets 67 68 68 64 63 67 63
70 62 78 "
0,
(mm/8 sheets) (1.70) (1.73) (1.73) (1.63)
(1.60) (1.70) (1.60) (1.78) (1.57) (1.98)
I.,
0
Dry MD Tensile g/3" 2,810 2,868 2,734 2,916
2,574 3,179 3,057 2,800 2,000 3,600 H
FP
(Wm) (369) (376) (359) (383) (338) (417) (401) (367)
(262) (472) "
0
0
Dry CD Tensile g/3" 2,074 1,785 1,927 1,973
1,791 1,993 2,095 1,950 1,350 2,550 0
i
(Wan) (272) (234) (253) (259) (235) (262) (275) (256)
(177) (335) H
H
I
MD/CD Ratio 1.4 1.6 1.4 1.5 1.4 1.6 1.5
1.5 0.8 2.2 H
CO
Total Tensile g/3" 4,884 4,653 4,661 4,889 4,365
5,172 5,152 4,750 _
(Wm) (642) (611) , (612) (642) (573)
(679) (676) (623) --
MD Stretch (%) 23.2 23.1 21.5 21.0 23.0 23.2
24.8 22 18 26
CD Stretch (%) 4.7 5.0 7.4 7.0 7.3 7.3 7.3
-- MM.
.o
n
,-i
cp
w
=
=
-4
=
60
.
.
c.,
-4
=
Table 9 (cont'd) - Recycled Content Furnish Trial (Finished Product Test Data)
0
t.,
=
Single Cell
Product Targets =
-4
Identification TAD Layer Cell 1 Cell 2 2A Cell 3 Cell 4
.
,...,
Target Min Max
Fabric
-4
W
Wet MID Tensile 754 802 694 799 697 854 989
---
-
(Finch) g/3" {g/cm} {99.0} (105) (91.1) (112) (91.5)
(112) (1301 .....
Wet CD Tensile 485 543 467 481 429 513 583 425
300 800
(Finch) g/3" {g/cm} {63.6} (71.3) {61.3) {63.1}
{56.3} (67.3) {76.5} {55.8} {39.4} {105}
CD Wet/Dry Ratio
23 30 24 24 24 26 28 22 -- --
(0/0)
0
WAR (seconds) 5 9 4 6 5 6 8 5
0 15 .
I,
MacBeth 3100
u-,
Brightness (%) UV 79.4 78.7 82.9 83.4 83.4 83.7
83.9 78 76 -- I,
co
H
Ex.
MacBeth 3100 =
1)
62 58 59 61 60 61 63 - -- --
.
co
Opacity CYO
I
H
SAT Capacity192 205 201 172 172 165 181 --- --H
I
--
H
(g/m A 2)
co
GM Break Modulus
232 209 183 199 166 194 189 --- - -
(g/%Stretch)
Roll Diameter inches 9.09 9.11 7.09 7.06 6.82 6.98
6.82 7.00 6.75 7.25
(cm)
(23.09) (23.14) (18.01) (17.93) (17.32) (17.73) (17.32) (17.78)
(17.15) (18.42)
Roll Compression (%) 1.6 0.4 2.3 2.1 2.4 2.0 2.1 2.0
0 4.0 .o
n
Hand Panel --- 4.59 4.54 4.12 4.39 3.87 3.43
-- - --
Hand Panel Sig. Diff. _ --- A A B, C A, B C D
- - -- cp
w
=
=
-4
=
61
.
c,
-4
CA 02652814 2014-11-20
The dramatic increase in caliper is seen in Figure 29 which illustrates that
the base sheets produced with the multi-layer fabric exhibited elevated
caliper
with respect to base sheets produced with single layer creping fabrics. The
surprising bulk is readily apparent when comparing the products to TAD
products
or products made with a singe layer fabric. In Figures 30A through 30F there
are
shown various base sheets. Figures 30A and 30D are respectively,
photomicrographs of a Yankee side and a fabric side of a base sheet produced
with a single layer fabric produced in accordance with the process described
above in connection with Figure 5. Figures 30B and 30E are photomicrographs
of the Yankee side and fabric side of a base sheet produced with a double
layer
creping fabric in accordance with the invention utilizing the process
described
generally in connection with Figure 5 above. Figures 30C and 30F are
photomicrographs of the Yankee side and fabric side of a base sheet prepared
by a
conventional TAD process. It is appreciated from the photomicrographs of
Figures 30B and 30E that the base sheet of the invention produced with a
double
layer fabric produces a higher loft than the other material, shown in Figures
30A,
D, C and F. This observation is consistent with Figure 31 which shows the
relative softness of the products of Figures 30A and Figure 30D (single layer
fabric) and other products made with increasing levels of recycled fiber in
accordance with the invention. It is seen from Figure 31 that it is possible
to
produce towel base sheet with equivalent softness while using up to 50%
recycled
fiber. This is a significant advance in as much as towel can be produced
without
utilizing expensive virgin Douglas fir furnish, for example.
The products and process of the present invention are thus likewise
suitable for use in connection with touchless automated towel dispensers of
the
class described in co-pending United States Provisional Application Nos.
60/779,614, filed March 6, 2006 and United States Provisional Patent
Application
No. 60/693,699, filed June 24, 2005. In this connection, the base sheet is
suitably
produced on a paper machine of the class shown in Figure 32.
62
CA 02652814 2014-11-20
Figure 32 is a schematic diagram of a papermachine 410 having a
conventional twin wire forming section 412, a felt run 414, a shoe press
section
416 a creping fabric 60 and a Yankee dryer 420 suitable for practicing the
present
invention. Forming section 412 includes a pair of forming fabrics 422, 424
supported by a plurality of rolls 426, 428, 430, 432, 434, 436 and a forming
roll
438. A headbox 440 provides papermaking furnish issuing therefrom as a jet in
the machine direction to a nip 442 between forming roll 438 and roll 426 and
the
fabrics. The furnish forms a nascent web 444 which is dewatered on the fabrics
with the assistance of suction, for example, by way of suction box 446.
The nascent web is advanced to a papermaking felt 42 which is supported
by a plurality of rolls 450, 452, 454, 455 and the felt is in contact with a
shoe
press roll 456. The web is of low consistency as it is transferred to the
felt.
Transfer may be assisted by suction, for example roll 450 may be a suction
roll if
so desired or a pickup or suction shoe as is known in the art. As the web
reaches
the shoe press roll it may have a consistency of 10-25%, preferably 20 to 25%
or
so as it enters nip 458 between shoe press roll 456 and transfer roll 52.
Transfer
roll 52 may be a heated roll if so desired. It has been found that increasing
steam
pressure to roll 52 helps lengthen the time between required stripping of
excess
adhesive from the cylinder of Yankee dryer 420. Suitable steam pressure may be
about 95 psig or so, bearing in mind that roll 52 is a crowned roll and roll
62 has a
negative crown to match such that the contact area between the rolls is
influenced
by the pressure in roll 52. Thus, care must be exercised to maintain matching
contact between rolls 52, 62 when elevated pressure is employed.
Instead of a shoe press roll, roll 456 could be a conventional suction
pressure roll. If a shoe press is employed, it is desirable and preferred that
roll
63
CA 02652814 2008-11-18
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PCT/US2007/011967
454 is a suction roll effective to remove water from the felt prior to the
felt
entering the shoe press nip since water from the furnish will be pressed into
the
felt in the shoe press nip. In any case, using a suction roll at 454 is
typically
desirable to ensure the web remains in contact with the felt during the
direction
change as one of skill in the art will appreciate from the diagram.
Web 444 is wet-pressed on the felt in nip 458 with the assistance of
pressure shoe 50. The web is thus compactively dewatered at 458, typically by
increasing the consistency by 15 or more points at this stage of the process.
The
configuration shown at 458 is generally termed a shoe press; in connection
with
the present invention, cylinder 52 is operative as a transfer cylinder which
operates to convey web 444 at high speed, typically 1000 fpm-6000 fpm (305
In/min-1830 m/min), to the creping fabric.
Cylinder 52 has a smooth surface 464 which may be provided with
adhesive (the same as the creping adhesive used on the Yankee cylinder) and/or
release agents if needed. Web 444 is adhered to transfer surface 464 of
cylinder
52 which is rotating at a high angular velocity as the web continues to
advance in
the machine-direction indicated by arrows 466. On the cylinder, web 444 has a
generally random apparent distribution of fiber orientation.
Direction 466 is referred to as the machine-direction (MD) of the web as
well as that of papermachine 410; whereas the cross-machine-direction (CD) is
the direction in the plane of the web perpendicular to the MD.
Web 444 enters nip 458 typically at consistencies of 10-25% or so and is
dewatered and dried to consistencies of from about 25 to about 70 by the time
it is
transferred to creping fabric 60 as shown in the diagram.
64
CA 02652814 2008-11-18
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Fabric 60 is supported on a plurality of rolls 468, 472 and a press nip roll
474 and forms a fabric crepe nip 64 with transfer cylinder 52 as shown.
The creping fabric defines a creping nip over the distance in which creping
fabric 60 is adapted to contact roll 52; that is, applies significant pressure
to the
web against the transfer cylinder. To this end, creping roll 62 may be
provided
with a soft deformable surface which will increase the width of the creping
nip
and increase the fabric creping angle between the fabric and the sheet and the
point of contact or a shoe press roll could be used as roll 62 to increase
effective
contact with the web in high impact fabric creping nip 64 where web 444 is
transferred to fabric 60 and advanced in the machine-direction.
Creping nip 64 generally extends over a fabric creping nip distance or
width of anywhere from about 1/8" to about 2", typically 'A" to 2"(from about
0.3
to about 5.1 cm, typically 1.3 to 5.1 cm). For a creping fabric with 32 CD
strands
per inch (12.5 CD strands per centimeter), web 444 thus will encounter
anywhere
from about 4 to 64 weft filaments in the nip.
The nip pressure in nip 64, that is, the loading between creping roll 62 and
transfer roll 52 is suitably 20-200 (9-91 kg), preferably 40-70pounds (18-32
kg)
per linear inch (PLI) (suitably 3.6-36 kg, preferably 7-13 kg per linear cm
(plcm)).
After fabric creping, the web continues to advance along MD 466 where it
is wet-pressed onto Yankee cylinder 480 in transfer nip 482. Optionally,
suction
is applied to the web by way of a suction box 66.
Transfer at nip 482 occurs at a web consistency of generally from about 25
to about 70%. At these consistencies, it is difficult to adhere the web to
surface
484 of cylinder 480 firmly enough to remove the web from the fabric
thoroughly.
CA 02652814 2008-11-18
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PCT/US2007/011967
This aspect of the process is important, particularly when it is desired to
use a high
velocity drying hood.
The use of particular adhesives cooperate with a moderately moist web
(25-70% consistency) to adhere it to the Yankee sufficiently to allow for high
velocity operation of the system and high jet velocity impingement air drying
and
subsequent peeling of the web from the Yankee. In this connection, a
poly(vinyl
alcohol)/polyamide adhesive composition as noted above is applied at 486 as
needed, preferably at a rate of less than about 40mg/m2 of sheet. Build-up is
controlled as hereinafter described.
The web is dried on Yankee cylinder 480 which is a heated cylinder and
by high jet velocity impingement air in Yankee hood 488. Hood 488 is capable
of
variable temperature. During operation, temperature may be monitored at wet-
end
A of the Hood and dry end B of the hood using an infra-red detector or any
other
suitable means if so desired. As the cylinder rotates, web 444 is peeled from
the
cylinder at 489 and wound on a take-up reel 490. Reel 490 may be operated 5-30
fpm or 1.5-9.1 m/min (preferably 10-20 fpm; 3-6 m/min) faster than the Yankee
cylinder at steady-state when the line speed is 2100 fpm (640.5 m/min), for
example. A creping doctor C is normally used and a cleaning doctor D mounted
for intermittent engagement is used to control build up. When adhesive build-
up
is being stripped from Yankee cylinder 480 the web is typically segregated
from
the product on reel 490, preferably being fed to a broke chute at 500 for
recycle to
the production process.
Instead of being peeled from cylinder 480 at 489 during steady-state
operation as shown, the web may be creped from dryer cylinder 480 using a
creping doctor such as creping doctor C, if so desired.
66
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Utilizing the above procedures a series of "peeled" towel products were
prepared utilizing the W013 fabric. Process parameters and product attributes
are
in Tables 10, 11 and 12, below.
=
67
Table 10 - Single-Ply Towel Sheet
0
w
=
=
-4
Roll ID 11429 11418 11441 11405
11137 .
,
,...,
NSWK 100% 50% 100% 50%
-4
w
Recycled Fiber 50% 50%
100% c,
%Fabric Crepe 5% 5% 5% 5%
5%
Suction inches Hg (cm Hg) 23(58) 23(58) 23 (58) 23 (58)
23 (58)
WSR (#/T) 12 12 12 12
12
CMC (#/T) 3 1 2 1
, 1
Parez 631 (NT) 9 6 9 3
0 n
PVOH (#/T) 0.75 0.75 0.75 0.75
0.45
0
PAE (#/T) 0.25 0.25 0.25 0.25
0.15 "
0,
u-,
Modifier (#/T) 0.25 0.25 0.25 0.25
0.15 "
co
H
Yankee Speed fpm (m/min) 1599 (488) 1768 (539) 1599 (488)
1598 (487) 1598 (487)
Reel Speed fpm (m/min) 1609 (491) 1781 (543) 1609 (491)
1612 (492) 1605 (490) "
0
0
Basis Weight lbs/rm (gsm) 18.4 (29.9) 18.8 (30.6) 21.1
(34.3) 21.0 (34.2) 20.3 (33.0) co
i
H
Caliper mils/8 sheets (mm/8 sheets) 41 (1.04) 44 (1.12) 44
(1.12) 45 (1.14) 44 (1.12) "
,
H
Dry MD Tensile g/3" (g/cm) 4861 (638) 5517 (724) 6392 (839)
6147 (807) 7792 (1022) co
Dry CD Tensile g/3" (g/cm) 3333 (437) 3983 (523) 3743 (491)
3707 (487) 4359 (572)
GMT g/3" (g/cm) 4025 (528) 4688 (615) 4891 (642) 4773
(626) 5828 (764)
.o
n
,-i
cp
w
=
=
-4
=
68
.
c,
-4
=
Table 10 (Cont'd) - Single-Ply Towel Sheet
0
w
=
=
-4
Roll ID 11429 11418 11441 11405
11137 .
(44
MD Stretch (%) 6.9 6.6 7.2 6.2
6.4 -4
w
c.,
CD Stretch (%) 5.0 5.0 4.8 5.0
4.9
Wet MD Cured Tensile g/3" (Finch) 1441 1447 1644 1571
2791
{g/cm} {189} (190) (216) {207}
{366)
Wet CD Cured Tensile g/3" (Finch) 1074 1073 1029 1064
1257
{g/cm} (141) (141) {135) (140)
(165)
WAR (seconds) (TAPPI) 33 32 20 20
39 n
MacBeth 3100 L* UV Included 95.3 95.2 95.2 95.4
95.4
MacBeth 3100 A* UV Included -0.8 -0.4 -0.8 -0.3
0.0 "
u-,
MacBeth 3100 B* UV Included 6.2 3.5 6.2 3.3
1.1 "
CO
H
MacBeth 3100 Brightness (%) UV Included 80.6 83.5 80.3 84.3
87.1
GM Break Modulus 691 817 831 858
1033 I,
Sheet Width inches (cm) 7.9 (20.1) 7.9
(20.1) 7.9 (20.1) 7.9 (20.1) 7.9 (20.1) co
,
H
Roll Diameter inches (cm) 7.8 (19.8) 7.9 (20.1) 8.0
(20.3) 7.9 (20.1) 8.1 (20.6) H
,
H
Roll Compression (%) 1.3 1.3 1.2 1.1
1.1 co
AVE Bending Length (cm) 3.7 3.9 4.0 4.1
4.7
.o
n
,-i
cp
= w
=
=
-4
=
69 .
c.,
-4
Table 11 - Single-Ply Towel
o
t.,
=
=
-4
89460 89460 89460 89460 89460
.
Roll ID Target
Max Min ,...,
11443 11414 11437 11396 11137
-4
t1J
I
C1
NSWK 100% 50% 100% 50%
Recycled Fiber 50% 50%
100%
_
Parez 631 (#/T) 9 6 9 3
0
PV0I1 (#/T) _ 0.75 0.75 0.75 0.75
0.45
PAE (4/T) 0.25 0.25 0.25 0.25
0.15
Modifier (#/T) 0.25 0.25 0.25 0.25
0.15
Basis Weight lbs/rm 18.4 18.4 21.1 20.9
20.0 20.8 22.0 19.6 .
(gsm) (29.9) (29.9) (34.3) (34.0) , (32.5)
(33.8) (35.8) (19.6) I,
_
u-,
Caliper mils/8 sheets 48 52 49 53
47 50 55 45 I,
co
H
(mm/8 sheets) (1.22) (1.32) (1.24) (1.35)
(1.19) (1.27) (1.40) (1.14)
Dry MD Tensile g/3" 5050 5374 6470 6345
7814 6500 8000 5000 "
(g/cm) (663) (705) (849) (833) (1026)
(853) (1050) (656) co,
H
Dry CD Tensile g/3" 3678 3928 3869 3817
4314 4000 5000 3000 '7
H
(g/cm) (483) (515) (508) (501) (566) (525)
(656) (394) co
MD Stretch (%) 7.0 7.5 7.2 7.4
7.0 6 8 4
CD Stretch (%) 4.9 5.2 4.8 5.2
4.9
.o
n
,-i
cp
w
=
=
-4
=
70
.
c,
-4
Table 11 (Cont'd) - Single-Ply Towel
0
w
=
=
-4
Roll ID 11443 11414 11437 11396 11137 Target
Max Min
(44
MD Stretch (%) 7.0 7.5 7.2 7.4 7,0 6
8 4 -4
w
c,
CD Stretch (%) 4.9 5.2 4.8 5.2 4.9
Wet MD Cured Tensile g/3" (Finch) 1711 1557 1888 1851 2258
{g/cm} {225} (204} {248} {243} {296}
Wet CD Cured Tensile g/3" (Finch) 1105 1086 1005 1163 1115
900 1250 625
{g/cm} {145} {142} {132} {153} {146} {118} {164} {82}
WAR (seconds) (TAPPI) 43 29 26 23 34 18
35 1 n
MacBeth 3100 L* UV Included 95.1 95.1 95.0 95.2 95.5
.
0
MacBeth 3100 A* UV Included -0.9 -0.4 -0.8 -0.4 -0.3
"
0,
u-,
MacBeth 3100 B* UV Included 6.2 , 3.6 6.1 3.3 1.4
"
CO
H
MacBeth 3100 Brightness (%) UV 80 83 80 84 87
I.,
Included
0
0
GM Break Modulus 737 734 853 793 991
ID
H
Roll Diameter inches 7.9 8.0 8.0 8.1 8.0 8.0
7.8 8.2 H
i
H
(cm) (20.1) (20.3) (20.3) (20.6) (20.3) (20.3)
(19.8) (20.8) 0
AVE Bending Length - MD (cm) 4.0 4.0 4.2 4.1 4.8 4.5
5.3 3.7
.o
n
,-i
cp
w
=
=
-4
=
71
.
.
c,
-4
=
0
t.,
=
Table 12 - Single-Ply Towel Sheet
=
-4
,...,
Base sheet Base sheet Base sheet
-4
w
Roll ID
c,
11171 9691 9806
NSWK 100% 100% 100%
Fabric Prolux W13 36G 44G
%Fabric Crepe 5% 5% 5%
Refining (amps) 48 43 44
Suction (Hg) 23 19 23
n
WSR (#/T) 13 13 11
.
I,
CMC (#/T) 2 1 1
I.,
co
Parez 631 (#/T) 0 0 0
H
FP
PVOH (#/T) 0.45 0.75 0.75
"
PAE (#/T) 0.15 0.25 0.25
.
co
i
Modifier (#/T) 0.15 0.25 0.25
"
H
i
Yankee Speed fpm (m/min) 1599 (488) 1749 (533) 1749 (533)
H
CO
Reel Speed fpm (m/min) 1606 (490) 1760 (537) 1760 (537)
Yankee Steam psi (bar) 45(3.1) 45(3.1) 45 (3.1)
Moisture% 2.5 4.0 2.6
Caliper mils/8 sht (mm/8 sheets) 60.2 (1.53) 50.4 (1.28) 51.7
(1.31)
Basis Weight lb/3000 ft^2 (gsm) 20.9 (34.0) 20.6 (33.5)
20.8 (33.8) .o
n
Tensile MD g/3" (g/cm) 6543 (859) 5973 (784) 6191 (813)
Stretch 1VID % 6 7 7
cp
w
Tensile CD g/3" (g/cm) 3787 (497) 3963 (520) 3779 (496)
=
=
-4
=
72
.
c,
-4
0
Table 12 (Cont'd) - Single-Ply Towel Sheet
(44
Base sheet Base sheet Base sheet
Roll ID 5
11171 9691 9806
Stretch CD A 4.4 4.1 4.3
Wet Tens Finch Cured-CD g/3" (g/cm) 1097 (144) 1199 (157) 1002 (132)
Tensile GM g/3" (g/cm) 4976 (653) 4864 (638) 4836 (634)
Water Abs Rate 0.1 mL sec 20 22 20
Break Modulus GM gms/% 973 913 894
Tensile Dry Ratio 1.7 1.5 1.6
0
Tensile Total Dry g/3 in (g/cm) 10331 (1356) 9936 (1304) 9970 (1308)
co
Tensile Wet/Dry CD 29% 30% 27%
Ovrhang Dwn-MD cms 9.8 7.6 8.0
0
Bending Len MD Yank Do cm 4.9 3.8 4.0
0
Bending Len MD Yank Up cm 5.0 4.8 9.0
Ovrhang Yankee Up-MD cms 9.9 9.6 4.5
AVE Bending Length - MD (cm) 4.9 4.3 4.2
=
=73
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PCT/US2007/011967
Note, that here again, the present invention makes it possible to employ
elevated levels of recycled fiber in the towel without compromising product
quality. Also, a reduced add-on rate of Yankee coatings was preferred when
running 100% recycled fiber. The addition of recycled fiber also made it
possible
to reduce the use of dry strength resin.
In Figures 33 and 34, it is seen that the high MD bending length product
produced on the apparatus of Figure 32 exhibited relatively high levels of CD
wet
tensile strength and surprisingly elevated levels of caliper.
Reel Crepe Response
The multilayer fabric illustrated and described in connection with Figures
7 and 8 is capable of providing much enhanced reel crepe response with many
products. This feature allows production flexibility and more efficient
papermachine operation since more caliper can be achieved at a given line
crepe
and/or wet-end speed (a production bottleneck on many machines) can be more
fully utilized as will be appreciated from the discussion which follows.
Reel Crepe Examples
Towel base sheets were made from a furnish consisting of 100% Southern
Softwood Kraft pulp. The base sheets were all made to the same targeted basis
weight (15 lbs/3000 n2 ream; 24.4 gsm), tensile strength (1400 g/3 inches
geometric mean tensile; 184 g/cm geometric mean tensile), and tensile ratio
(1.0).
The base sheets were creped using several fabrics. For the single layer
fabrics,
sheets were creped using both sides of the fabric. The notation "MD" or "CD"
in
the fabric designation indicates whether the fabric's machine direction or
cross
direction knuckles were contacting the base sheet. The purpose of the
experiment
was to determine the level of fabric crepe beyond which no increases in base
sheet
caliper would be realized.
74
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For each fabric, base sheets were made to the targets mentioned above at a
selected level of fabric crepe, with no reel crepe. The fabric crepe was then
increased, in increments of five percent and refining and jet/wire ratio
adjusted as
needed to again obtain the targeted sheet parameters. This process was
repeated
until an increase in fabric crepe did not result in an increase in base sheet
caliper,
or until practical operating limitations were reached.
The results of these experiments are shown in Figure 35. These data show
that, at 0% reel crepe the caliper generated using the W013 fabric can be
matched
or exceeded by several single layer fabrics.
For several of the fabrics, trials were also run in which reel crepe, in
addition to fabric crepe, was used to reach a desired caliper level of
approximately
95 mils/8 sheets (2.41 mm/8 sheets). The results of these trials are shown in
Table
13. The designations "FC" and "RC" stand for the levels of fabric crepe and
reel
crepe, respectively, used to produce the base sheets.
The trial results show that, for the single layer fabrics (the "M" and "G"
fabrics), gains in caliper with the addition of reel crepe were all about one
mil/8
sheets of caliper for each percent of reel crepe employed. However, the gain
in
caliper with the addition of reel crepe seen for the W013 fabric was
dramatically
higher; a Caliper Gain/%Reel Crepe ratio of 3 is readily achieved. In other
words,
instead of a 1 point caliper gain with 1 point of reel crepe, 3 points of
caliper gain
are achieved per point of reel crepe employed in the process when using the
fabric
with the long MD knuckles.
75
CA 02652814 2008-11-18
WO 2007/139726 PCT/US2007/011967
Table 13 - Impact of Reel Crepe on Base Sheet Caliper
All Caliper Values Normalized to 15 lbs/ream (24.4 gsm) Basis Weight
Fabric 44G CD
36G CD 36G MD 44M MD 36M MD W013
FC/RC (%) 30/0 40/0 30/0 40/0 30/0 25/0
Line Crepe
30 40 30 40 30 25
(A)
Caliper
92.4 94.1 91.5 80.9 79.7 83.3
mils/8 sheets
(mm/8
(2.34) (2.39) (2.32) (2.05) (2.02) (2.12)
sheets)
FC/RC (%) 30/5 40/2 30/5 40/12 30/15 25/7
Line Crepe
36.5 42.8 36.5 56.8 49.5 33.75
(%)
Caliper
95.2 96.0 96.5 93.6 97.3 103.2
mils/8 sheets
(mm/8
(2.42) (2.44) (2.45) (2.38) (2.47) (2.62)
sheets)
Caliper
Gain/% Reel 0.6 1.0 1.0 1.1 1.2 2.8
Crepe Ratio
With the W013 fabric, fabric crepe can be reduced 3 times as fast as reel
crepe and still maintain caliper. For example, if a process is operating
achieving
100 caliper with the W013 fabric at 1.35 total crepe ratio (30% fabric crepe
and
4% reel crepe for a 35% overall crepe) and it is desired to increase tensile
capability while maintaining caliper, one could do the following: reduce
fabric
crepe to 21% (tensiles will likely rise) and then increase reel crepe at 7%
for an
overall ratio of 1.295 or 29.5% overall crepe; thus generating both more
tensile
and maintaining caliper (less crepe, and much less fabric crepe which is
believed
more destructive to tensile than reel crepe).
Besides better caliper and tensile control, a papermachine can be made
much more productive. For example, on a 15 lb (24.5 gsm) towel base sheet
using
76
CA 02652814 2008-11-18
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a 44 M fabric 57% line crepe was required for a final caliper of 94. The
multilayer
W013 fabric produced a caliper of 103 at about 34% line crepe. Using these
approximate values, a paper machine with a 6000 fpm (1830 m/min) wet-end
speed limit would have a speed limit of 3825 fpm (1167 m/min) at the reel to
meet
a 94 caliper target for the base sheet with the 44M fabric. However, use of
the
W013 fabric can yield nearly 10 points of caliper which should make it
possible to
speed up the reel to 4475 (6000/1.34 versus 6000/1.57) fpm (1365 tn/min).
Further, the multilayer fabric with the long MD knuckles makes it possible
to reduce basis weight and maintain caliper and tensiles. Less fabric crepe
calls
for less refining to meet tensiles even at a given line crepe (again assuming
reel
crepe is much less destructive of tensile than fabric crepe). As the product
weight
goes down, fabric crepe can be reduced 3 percentage points for every
percentage
increase in reel crepe thereby making it easier to maintain caliper and retain
tensile.
The reel crepe effects of Table 13 are confirmed in the photomicrographs
of Figures 36-38 which are taken along the MD (60 micron thick samples) of
fabric-creped sheet. Figure 36 depicts a web with 25% fabric crepe and no reel
crepe. Figure 37 depicts a web made with 25% reel crepe and 7% fabric crepe
where it is seen the crepe is dramatically more prominent then in Figure 36.
Figure 38 depicts a web with 35% fabric crepe and no reel crepe. The web of
Figure 37 appears to have significantly more crepe than that of Figure 38
despite
having been made with about the same line crepe.
In many cases, the fabric creping techniques revealed in the
following co-pending applications will be especially suitable for making
products:
United States Patent Application Serial No. 11/678,669, entitled "Method of
Controlling Adhesive Build-Up on a Yankee Dryer" (Attorney Docket No. 20140;
GP-06-1); United States Patent Application Serial No. 11/451,112 (Publication
77
CA 02652814 2008-11-18
WO 2007/139726
PCT/US2007/011967
No. US 2006-0289133), filed June 12, 2006, entitled "Fabric-Creped Sheet for
Dispensers" (Attorney Docket No. 20195; GP-06-12); United States Patent
Application Serial No. 11/451,111, filed June 12, 2006 (Publication No. US
2006-
0289134), entitled "Method of Making Fabric-creped Sheet for Dispensers"
(Attorney Docket No. 20079; GP-05-10); United States Patent Application Serial
No. 11/402,609 (Publication No. US 2006-0237154), filed April 12, 2006,
entitled
"Multi-Ply Paper Towel With Absorbent Core" (Attorney Docket No. 12601; GP-
04-11); United States Patent Application Serial No. 11/151,761, filed June 14,
2005 (Publication No. US 2005/0279471), entitled "High Solids Fabric-crepe
Process for Producing Absorbent Sheet with In-Fabric Drying" (Attorney Docket
12633; GP-03-35); United States Patent Application Serial No. 11/108,458,
filed
April 18, 2005 (Publication No. US 2005-0241787), entitled "Fabric-Crepe and
In
Fabric Drying Process for Producing Absorbent Sheet" (Attorney Docket
12611P1; GP-03-33-1); United States Patent Application Serial No. 11/108,375,
filed April 18, 2005 (Publication No. US 2005-0217814), entitled "Fabric-
Crepe/Draw Process for Producing Absorbent Sheet" (Attorney Docket No.
12389P1; GP-02-12-1); United States Patent Application Serial No. 11/104,014,
filed April 12, 2005 (Publication No. US 2005-0241786), entitled "Wet-Pressed
Tissue and Towel Products With Elevated CD Stretch and Low Tensile Ratios
Made With a High Solids Fabric-Crepe Process" (Attorney Docket 12636; GP-04-
5); United States Patent Application Serial No. 10/679,862 (Publication No. US
2004-0238135), filed October 6, 2003, entitled "Fabric-crepe Process for
Making
Absorbent Sheet" (Attorney Docket. 12389; GP-02-12); United States Provisional
Patent Application Serial No. 60/903,789, filed February 27, 2007, entitled
"Fabric Crepe Process With Prolonged Production Cycle" (Attorney Docket =
20216; GP-06-16); and United States Provisional Patent Application Serial No.
60/808,863, filed May 26, 2006, entitled "Fabric-creped Absorbent Sheet with
Variable Local Basis Weight" (Attorney Docket No. 20179; GP-06-11). The
applications referred to immediately above are particularly relevant to the
selection of machinery, materials, processing conditions and so forth as to
fabric
78
CA 02652814 2014-11-20
creped products of the present invention.
79
