Claim for Priority and Cross-Reference to Related Applications
[0001] This non-provisional application is based upon
U.S. Provisional Patent Application Serial No. 60/808,863, of the same title, filed May 26, 2006. The priority of
U.S. Provisional Patent Application Serial No. 60/808,863 is hereby claimed and the disclosure thereof is incorporated into this application
by reference. This application is also based, in part, on United States Patent Application
No.
11/451,111 (United States Patent Application Publication No.
US 2006-0289134), entitled "Method of Making Fabric-Creped Sheet for Dispensers", filed June 12,
2006 Attorney Docket No. 20079; GP-05-10), the priority of which is also claimed and
the disclosure thereof incorporated into this application by reference.
Technical Field
[0002] 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
[0003] 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 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.
[0004] 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.
[0005] 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 et al. and
4,637, 859 to Trokhan. With respect to the use of fabrics used to impart texture to 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.
[0006] United States Patent No.
5,503,715 to Trokhan et al. 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.
[0007] Throughdried (TAD), creped products are disclosed in the following patents: United
States Patent No.
3,994,771 to Morgan, Jr. et al.; 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%.
[0008] 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.
[0009] 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
[0010] 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.
[0011] 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 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.
[0012] 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.
[0013] The invention is better understood by reference to
Figures 1 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 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.
[0014] 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.
[0015] 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).
[0016] Further details and attributes of the inventive products and process for making them
are discussed below.
Brief Description of the Drawings
[0017] 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;
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;
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;
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;
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.
[0018] 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
[0019] 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.
[0020] 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, 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. The sheet has a specific bulk
of greater than 5.5 ((mils/8 plies)/(Ib/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.
[0021] 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.
[0022] 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 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.
[0023] 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.
[0024] 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)/(lb/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 ((mils/8plies)/(lb/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)/(lb/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 ((mils/8plies)/(lb/ream)) (at least 0.08 (mm/8plies)/(gsm)) up to about
10 ((mils/8plies)/(lb/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)).
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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 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)/(lb/ream)) (greater than 0.039 (mm/8plies)/(gsm)),
such as a bulk of greater than 2.5 ((mils/8plies)/(lb/ream)) (greater than 0.039 (mm/8plies)/(gsm))
up to about 3 ((mils/8plies)/(lb/ream)) (to about 0.047 (mm/8plies)/(gsm). In some
cases having a bulk of at least 2.75 ((mils/8plies)/(lb/ream)) (at least 0.043 (mm/8plies)/(gsm))
is desirable.
[0030] 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 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.
[0031] 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
-1 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
-1 to about 500 meter
-1; typically a CD repeat frequency of from about 150 meter
-1 to about 300 meter
-1; such as a CD repeat frequency of from about 175 meter
-1 to about 250 meter
-1.
[0032] In still another aspect of the invention, there is provided an absorbent cellulosic
sheet having variable local basis weight comprising a papermaking fiber 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.
[0033] 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.
[0034] 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 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.
[0035] 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.
[0036] The present invention also includes methods of producing absorbent sheet.
[0037] There is provided in still other aspects of the invention a method of making a belt-creped
absorbent cellulosic sheet comprising: (a) compactively 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.
[0038] 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
f) 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.
[0039] A still further aspect of the invention is a method of making fabric-creped absorbent
cellulosic sheet comprising: a) compactively 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) 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.
[0040] 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 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 Gain/% 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.
[0041] The foregoing and further features of the invention are further illustrated in the
discussion which follows.
[0042] Terminology used herein is given its ordinary meaning consistent with the exemplary
definitions set forth immediately below; mg refers to milligrams and m
2 refers to square meters and so forth.
[0043] 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 (m
2/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.
[0044] 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.
[0045] Unless otherwise specified, "basis weight", BWT, bwt and so forth refers to the weight
of a 3000 square-foot (279 m
2) ream of product. Likewise, "ream" means 3000 square-foot ream (279 m
2) 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%.
[0046] 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
kraft 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.
[0047] 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 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%.
[0048] 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.
[0049] "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.
[0050] Fpm refers to feet per minute (data is also sometimes expressed in meters per minute
(m/min); while fps refers to feet per second.
[0051] MD means machine direction and CD means cross-machine direction.
[0052] 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.
[0053] Nip width means the MD length over which the nip surfaces are in contact.
[0054] "Predominantly" means more than 50% of the specified component, by weight unless
otherwise indicated.
[0055] 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.
[0056] 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-II-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.
[0057] Characteristic local basis weights and differences therebetween are calculated by
measuring the local basis weight at 2 or more representative low 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 ft
2 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 ft
2 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.
[0058] 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
41.5° 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 231°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 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.
[0059] 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.
[0060] 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). 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.
[0061] 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.
[0062] 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.
[0063] "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:

[0064] Fabric crepe can also be expressed as a percentage calculated as:

[0065] 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%.
[0066] 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%.
[0067] The fabric crepe/reel crepe ratio is calculated by dividing the fabric crepe by the
reel crepe.
[0068] 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.
[0069] 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:

[0070] 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%.
[0071] PLI or pli 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. 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.
[0072] 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).
[0073] Velocity delta means a difference in linear speed.
[0074] 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 the 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, 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 ½
second contact) the lower corner of the specimen on #4 filter paper (Whatman 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:

wherein
"W1" is the dry weight of the specimen, in grams; and
"W2" is the wet weight of the specimen, in grams.
[0075] 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.
[0076] 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.
[0077] 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 Creping Adhesive Modifier and Process for Producing Paper Products"
(Attorney Docket No. 2394). The disclosures of the '316 patent and the'255 application
are incorporated herein by reference. 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.
[0078] 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 disclosure of which is incorporated herein
by reference.
[0079] 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.
[0080] 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/m
2 with 32 mg/m
2 of PVOH (Celvol 523)/ 11.3 mg/m
2 of PAE (Hercules 1145) and 10.5 mg/m
2 of modifier (Hercules 4609VF). A preferred coating for a peeling process may be applied
at a rate of 20 mg/m
2 with 14.52 mg/m
2 of PVOH (Celvol 523)/ 5.10 mg/m
2 of PAE (Hercules 1145) and 0.38 mg/m
2 of modifier (Hercules 4609VF).
[0081] 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 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 all of which are incorporated herein by reference in their entirety. One forming
fabric particularly useful with the present invention is Voith Fabrics Forming Fabric
2164 made by Voith Fabrics Corporation, Shreveport, LA.
[0082] 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 disclosures of which are incorporated herein by reference. 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.
[0083] 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, opacifiers, 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.
[0084] 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 Coscia et al. and
3,556,933 to Williams et al., both of which are incorporated herein by reference in their entirety. Resins of this
type are commercially available under the trade name of PAREZ 631 NC 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 Kymene 557LX and Kymene 557H by Hercules Incorporated
of Wilmington, Delaware and Amres® 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 each of which is incorporated herein by reference in its entirety. 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), herein incorporated by reference in its entirety. A reasonably comprehensive list
of wet strength resins is described by
Westfelt in Cellulose Chemistry and Technology Volume 13, p. 813, 1979, which is also incorporated herein by reference.
[0085] 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.
[0086] The temporary wet strength resin may be any one of a variety of watersoluble 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).
[0087] 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.
[0088] 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.
[0089] 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 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, J.Am. Oil Chemist's Soc., Vol. 55 (1978), pp. 118-121; and
Trivedi et al., J. Am. Oil Chemist's Soc., June 1981, pp. 754-756, incorporated by reference in their entirety, 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.
[0090] Quasoft 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.
[0091] 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.
[0092] Biodegradable softeners can be utilized. Representative biodegradable cationic softeners/debonders
are disclosed in United States Patent Nos.
5,312,522;
5,415,737;
5,262,007;
5,264,082; and
5,223,096, all of which are incorporated herein by reference in their entirety. 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.
[0093] In some embodiments, a particularly preferred debonder composition includes a quaternary
amine component as well as a nonionic surfactant.
[0094] 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 Vector 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.
[0095] Suitable creping or textured fabrics include single layer or multi-layer, or composite
preferably open meshed structures. Fabric construction
per 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 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 yarns. An especially preferred fabric is a WO13 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.
[0096] 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.
[0097] 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.
[0098] A preferred mode of making the inventive products involves compactively dewatering
a papermaking furnish having an apparently random distribution of 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.
[0099] 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.
[0100] A papermachine suitable for making the product of the invention may have various
configurations as is seen in
Figures 5 and
6 discussed below.
[0101] 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 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.
[0102] 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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] 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 provided with a Fabric Crepe typically in an amount of from about
10 to about 100% in the machine direction.
[0108] 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.
[0109] Creping nip
64 generally extends over a fabric creping nip distance or width of anywhere from about
1/8" to about 2", typically ½" 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
44 thus will encounter anywhere from about 4 to 64 weft filaments in the nip.
[0110] 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 (PLI) (suitably 3.6-17.9 kg, preferably 7.1-12.5 kg per linear cm
(plcm)).
[0111] 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.
[0112] 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.
[0113] 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 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.
[0114] 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.
[0115] In a particularly preferred embodiment, the nip width at 100 pli (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 using the Deshpande method, assuming
a 1" (2.54 cm) thick sleeve. A 2" (5.08 cm) thick sleeve is likewise suitable.
[0116] 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.
[0117] 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.
[0118] 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
1a-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, 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
-1. 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 meter
-1.
[0119] 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.
[0120] The product thus has the attributes shown and described above in connection with
Figures 1 and
2.
[0121] 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.
[0122] 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.
[0123] 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.
[0124] 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 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.
[0125] 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.
[0126] 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.
[0127] 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.
[0128] 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 (41 gsm) 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.
[0129] 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 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 invention
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
[0130] In order to quantify local basis weight variation, a beta particle attenuation technique
was employed.
[0131] 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 (β
+) 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 (β
-) and an antineutrino. Promethium

undergoes negative beta decay.
[0132] 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 penetrating or being backscattered
after partial energy loss and ultimately exiting the solid at a wide range of angles.
[0134] 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
ft
2 ream (16.8 gsm). Results appear in Table 1 and presented graphically in Figure 25.
Table 1 - Calibration
| Counts |
Weight lbs/3000 ft2 |
Weight (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 |
[0135] 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 |
[0136] 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 somewhat higher than expected, perhaps due to the presence of folds
in the sample occurring during fabric or reel crepe.
[0137] 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.
[0138] 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.
[0139] Details as to various tissue products are summarized in Tables
3, 4 and
5. The 44M fabric is a single layer fabric while the WO13 fabric is the multilayer fabric
discussed in connection with
Figures 7 and following.
Table 3 - Comparison of Base Sheet and Finished Product Properties
| Fabric |
2005 |
2006 |
| 44M (MD) |
WO13 (MD) |
| Fiber |
75% euc |
60% euc |
| Forming |
Blended |
Bl. 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)
| Fabric |
2005 |
2006 |
| 44M |
WO13 |
| 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 |
Table 5 - Comparison of Finished Products and TAD Product
| Fabric |
2005 |
2006 |
TAD Commercial |
| 44M |
WO13 |
| 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 WO13
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 |
WO13 |
| % 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) |
| GM Tensile g/3" (g/cm) |
330 (43.3) |
444 (58.3) |
| MD Stretch (%) |
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 ((mm/8plies)/(gsm)) |
4.85 (0.075) |
6.90 (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/cm) |
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 mils/8 plies/lb/R ((mm/8plies)/(gsm)) |
4.91 (0.077) |
5.78 (0.090) |
[0140] 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.
[0141] 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.
[0142] 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.
Table 9 - Recycled Content Furnish Trial (Finished Product Test Data)
| Identification |
TAD |
Single layer Creping Fabric |
Cell 1 |
Cell 2 |
Cell 2A |
Cell 3 |
Cell 4 |
Product Targets |
| Furnish (Softwood / Secondary) |
100/0 |
80/20 |
75/25 |
50/50 |
50/50 |
25/75 |
0/100 |
Target |
Minimum |
Maximum |
| FC/RC |
NA |
20/0 |
20/0 |
20/0 |
23/0 |
23/0 |
26/0 |
|
|
|
| Parameter |
|
|
|
|
|
|
|
|
|
|
| Basis Weight Ibs/rm (gsm) |
22.6 (36.8) |
21.3 (34.7) |
21.2 (34.5) |
21.4 (34.8) |
20.8 (33.8) |
21.5 (35.0) |
21.3 (34.7) |
21.0 (34.2) |
20.0 (32.5) |
22.0 (35.8) |
| Caliper miis/8 sheets (mm/8 sheets) |
67 (1.70) |
68 (1.73) |
68 (1.73) |
64 (1.63) |
63 (1.60) |
67 (1.70) |
63 (1.60) |
70 (1.78) |
62 (1.57) |
78 (1.98) |
| Dry MD Tensile g/3" (g/cm) |
2,810 (369) |
2,868 (376) |
2,734 (359) |
2,916 (383) |
2,574 (338) |
3,179 (417) |
3,057 (401) |
2,800 (367) |
2,000 (262) |
3,600 (472) |
| Dry CD Tensile g/3" (g/cm) |
2,074 (272) |
1,785 (234) |
1,927 (253) |
1,973 (259) |
1,791 (235) |
1,993 (262) |
2,095 (275) |
1,950 (256) |
1,350 (177) |
2,550 (335) |
| MD/CD Ratio |
1.4 |
1.6 |
1.4 |
1.5 |
1.4 |
1.6 |
1.5 |
1.5 |
0.8 |
2.2 |
| Total Tensile g/3" (g/cm) |
4,884 (642) |
4,653 (611) |
4,661 (612) |
4,889 (642) |
4,365 (573) |
5,172 (679) |
5,152 (676) |
4,750 (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 |
- |
- |
- |
| Identification |
TAD |
Single Layer Fabric |
Cell 1 |
Cell 2 |
Cell 2A |
Cell 3 |
Cell 4 |
Product Targets |
| Target |
Min |
Max |
| Wet MD Tensile (Finch) g/3" {g/cm} |
754 {99.0} |
802 {105} |
694 {91.1} |
799 {112} |
697 {91.5} |
854 {112} |
989 {130} |
- |
- |
- |
| Wet CD Tensile (Finch) g/3" {g/cm} |
485 {63.6} |
543 {71.3} |
467 {61.3} |
481 {63.1} |
429 {56.3} |
513 {67.3} |
583 {76.5} |
425 {55.8} |
300 {39.4} |
800 {105} |
| CD Wet/Dry Ratio (%) |
23 |
30 |
24 |
24 |
24 |
26 |
28 |
22 |
- |
- |
| WAR (seconds) |
5 |
9 |
4 |
6 |
5 |
6 |
8 |
5 |
0 |
15 |
| MacBeth 3100 Brightness (%) UV Ex. |
79.4 |
78.7 |
82.9 |
83.4 |
83.4 |
83.7 |
83.9 |
78 |
76 |
- |
| MacBeth 3100 Opacity (%) |
62 |
58 |
59 |
61 |
60 |
61 |
63 |
- |
- |
- |
| SAT Capacity (g/m^2) |
192 |
205 |
201 |
172 |
172 |
165 |
181 |
- |
- |
- |
| GM Break Modulus (g/%Stretch) |
232 |
209 |
183 |
199 |
166 |
194 |
189 |
- |
- |
- |
| Roll Diameter inches (cm) |
9.09 (23.09) |
9.11 (23.14) |
7.09 (18.01) |
7.06 (17.93) |
6.82 (17.32) |
6.98 (17.73) |
6.82 (17.32) |
7.00 (17.78) |
6.75 (17.15) |
7.25 (18.42) |
| Roll Compression (%) |
1.6 |
0.4 |
2.3 |
2.1 |
2.4 |
2.0 |
2.1 |
2.0 |
0 |
4.0 |
| 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 |
- |
- |
- |
[0143] 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.
[0144] 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; the disclosures of which are incorporated herein by reference. In this connection,
the base sheet is suitably produced on a paper machine of the class shown in
Figure 32.
[0145] 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.
[0146] 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.
[0147] 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
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.
[0148] 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 m/min-1830 m/min), to the creping
fabric.
[0149] 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.
[0150] 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.
[0151] 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.
[0152] 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.
[0153] 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.
[0154] Creping nip
64 generally extends over a fabric creping nip distance or width of anywhere from about
1/8" to about 2", typically ½" 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.
[0155] 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)).
[0156] 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.
[0157] 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. This aspect of the process
is important, particularly when it is desired to use a high velocity drying hood.
[0158] 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/m
2 of sheet. Build-up is controlled as hereinafter described.
[0159] 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.
[0160] 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.
[0161] Utilizing the above procedures a series of "peeled" towel products were prepared
utilizing the WO13 fabric. Process parameters and product attributes are in Tables
10, 11 and
12, below.
Table 10 - Single-Ply Towel Sheet
| Roll ID |
11429 |
11418 |
11441 |
11405 |
11137 |
| NSWK |
100% |
50% |
100% |
50% |
|
| Recycled Fiber |
|
50% |
|
50% |
100% |
| %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 (#/T) |
9 |
6 |
9 |
3 |
0 |
| PVOH (#/T) |
0.75 |
0.75 |
0.75 |
0.75 |
0.45 |
| PAE (#/T) |
0.25 |
0.25 |
0.25 |
0.25 |
0.15 |
| Modifier (#/T) |
0.25 |
0.25 |
0.25 |
0.25 |
0.15 |
| 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) |
| 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) |
| Caliper mils/8 sheets (mm/8 sheets) |
41 (1.04) |
44 (1.12) |
44 (1.12) |
45 (1.14) |
44 (1.12) |
| Dry MD Tensile g/3" (g/cm) |
4861 (638) |
5517 (724) |
6392 (839) |
6147 (807) |
7792 (1022) |
| 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) |
| MD Stretch (%) |
6.9 |
6.6 |
7.2 |
6.2 |
6.4 |
| 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 |
| 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 |
| MacBeth 3100 B* UV Included |
6.2 |
3.5 |
6.2 |
3.3 |
1.1 |
| MacBeth 3100 Brightness (%) UV Included |
80.6 |
83.5 |
80.3 |
84.3 |
87.1 |
| GM Break Modulus |
691 |
817 |
831 |
858 |
1033 |
| Sheet Width inches (cm) |
7.9 (20.1) |
7.9 (20.1) |
7.9 (20.1) |
7.9 (20.1) |
7.9 (20.1) |
| Roll Diameter inches (cm) |
7.8 (19.8) |
7.9 (20.1) |
8.0 (20.3) |
7.9 (20.1) |
8.1 (20.6) |
| Roll Compression (%) |
1.3 |
1.3 |
1.2 |
1.1 |
1.1 |
| AVE Bending Length (cm) |
3.7 |
3.9 |
4.0 |
4.1 |
4.7 |
Table 12 - Single-Ply Towel Sheet
| Roll ID |
Base sheet |
Base sheet |
Base sheet |
| 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 |
| WSR (#/T) |
13 |
13 |
11 |
| CMC (#/T) |
2 |
1 |
1 |
| Parez 631 (#/T) |
0 |
0 |
0 |
| PVOH (#/T) |
0.45 |
0.75 |
0.75 |
| PAE (#/T) |
0.15 |
0.25 |
0.25 |
| Modifier (#/T) |
0.15 |
0.25 |
0.25 |
| Yankee Speed fpm (m/min) |
1599 (488) |
1749 (533) |
1749 (533) |
| 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) |
| Tensile MD g/3" (g/cm) |
6543 (859) |
5973(784) |
6191 (813) |
| Stretch MD % |
6 |
7 |
7 |
| Tensile CD g/3" (g/cm) |
3787 (497) |
3963 (520) |
3779 (496) |
| Stretch CD % |
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 |
| Tensile Total Dry g/3 in (g/cm) |
10331 (1356) |
9936 (1304) |
9970 (1308) |
| Tensile Wet/Dry CD |
29% |
30% |
27% |
| Ovrhang Dwn-MD cms |
9.8 |
7.6 |
8.0 |
| Bending Len MD Yank Do cm |
4.9 |
3.8 |
4.0 |
| 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 |
[0162] 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.
[0163] 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
[0164] 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
[0165] 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
ft
2 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.
[0166] 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.
[0167] The results of these experiments are shown in
Figure 35. These data show that, at 0% reel crepe the caliper generated using the WO13 fabric
can be matched or exceeded by several single layer fabrics.
[0168] 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.
[0169] 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 WO13 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.
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 |
WO13 |
| FC/RC (%) |
30/0 |
40/0 |
30/0 |
40/0 |
30/0 |
25/0 |
| Line Crepe (%) |
30 |
40 |
30 |
40 |
30 |
25 |
| Caliper mils/8 sheets |
92.4 |
94.1 |
91.5 |
80.9 |
79.7 |
83.3 |
| (mm/8 sheets) |
(2.34) |
(2.39) |
(2.32) |
(2.05) |
(2.02) |
(2.12) |
| 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 mils/8 sheets |
95.2 |
96.0 |
96.5 |
93.6 |
97.3 |
103.2 |
| (mm/8 sheets) |
(2.42) |
(2.44) |
(2.45) |
(2.38) |
(2.47) |
(2.62) |
| Caliper Gain/% Reel Crepe Ratio |
0.6 |
1.0 |
1.0 |
1.1 |
1.2 |
2.8 |
[0170] With the WO13 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 WO13 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).
[0171] 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 a 44 M fabric
57% line crepe was required for a final caliper of 94. The multilayer WO13 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 WO13 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 m/min).
[0172] 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.
[0173] 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.
[0174] 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 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 creped products of the present invention and the disclosures of these
applications are incorporated herein by reference.
[0175] While the invention has been described in detail, modifications within the spirit
and scope of the invention will be readily apparent to those of skill in the art.
In view of the foregoing discussion, relevant knowledge in the art and references
including co-pending applications discussed above in connection with the Background
and Detailed Description, the disclosures of which are all incorporated herein by
reference, further description is deemed unnecessary.
[0176] Further special embodiments of the invention are disclosed in the following:
- 1. 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 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 being further characterized by an MD/CD aspect ratio of at least 1.5, wherein
the sheet has a specific bulk of greater than 5.5 ((mils/8 plies)/(lb/ream)) ( greater
than 0.085 (mm/8plies/gsm) and (iii) has a void volume of 9 grams/gram or greater
when it has a basis weight of 23 Ib/ream (37.5 gsm) or less or (iv) has a void volume
of 7 grams/gram or greater when it has a basis weight of greater than 23 Ibs/ream
(37.5 gsm).
- 2. The absorbent cellulosic sheet according to Embodiment 1, wherein the MD/CD aspect
ratios of the densified regions are greater than 5.
- 3. The absorbent cellulosic sheet according to Embodiment 1, wherein the MD/CD aspect
ratios of the densified regions are greater than 6.
- 4. The absorbent cellulosic sheet according to Embodiment 1, wherein the MD/CD aspect
ratios of the densified regions are between about 6 and 10.
- 5. The absorbent cellulosic sheet according to Embodiment 1, wherein the fiber-enriched
pileated regions have fiber orientation bias along the CD of the sheet.
- 6. The absorbent cellulosic sheet according to Embodiment 1, wherein the densified
regions of relatively low basis weight extending in the machine direction have fiber
orientation bias along the CD of the sheet.
- 7. The absorbent cellulosic sheet according to Embodiment 1, wherein the elongated
densified regions are substantially identical.
- 8. The absorbent cellulosic sheet according to Embodiment 1, wherein the fiber-enriched
pileated regions are bordered at lateral extremities by a laterally-spaced pair of
CD-aligned densified regions.
- 9. The absorbent cellulosic sheet according to Embodiment 8, wherein the fiber-enriched
regions are at least partially bordered at intermediate lateral extremities thereof
at longitudinal portions by a longitudinally-spaced, CD-staggered pair of densified
regions.
- 10. The absorbent cellulosic sheet according to Embodiment 1, wherein the sheet has
a basis weight of greater than 23 Ibs per 3000 square-foot ream (37.5 gsm) up to about
35 Ibs per 3000 square-foot ream (57 gsm).
- 11. The absorbent cellulosic sheet according to Embodiment 10, wherein the sheet has
a void volume of 8 grams/gram or more.
- 12. The absorbent cellulosic sheet according to Embodiment 10, wherein the sheet has
a void volume of equal to or greater than 9 grams/gram and up to 12 grams/gram.
- 13. The absorbent cellulosic sheet according to Embodiment 1, having a CD stretch
of greater than 5%, up to about 10%.
- 14. The absorbent cellulosic sheet according to Embodiment 1, having a CD stretch
of greater than 6%.
- 15. The absorbent cellulosic sheet according to Embodiment 1, having a CD stretch
of greater than 7%.
- 16. The absorbent cellulosic sheet according to Embodiment 1, having a CD stretch
of greater than 8%.
- 17. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is at least about 10% by weight recycle fiber.
- 18. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is at least about 25% by weight recycle fiber.
- 19. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is at least about 35% by weight recycle fiber.
- 20. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is at least about 45% by weight recycle fiber.
- 21. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is 50% or more by weight recycle fiber.
- 22. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is 75% or more by weight recycle fiber.
- 23. The absorbent cellulosic sheet according to Embodiment 1, wherein the papermaking
fiber is 100% by weight recycle fiber.
- 24. The absorbent cellulosic sheet according to Embodiment 1, in the form of a tissue
base sheet wherein the fiber is predominantly hardwood fiber and the sheet has a specific
bulk of at least 6 ((mils/8plies)/(Ib/ream)) (at least 0.09 (mm/8 plies)/gsm).
- 25. The tissue base sheet according to Embodiment 24, 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 ((mils/8plies)/(Ib/ream)) (at least 0.1 (mm/8 plies)/gsm).
- 26. The tissue base sheet according to Embodiment 24, wherein the sheet has a bulk
of equal to or greater than 6 and up to about 8 ((mils/8plies)/(Ib/ream)) (at least
0.09 up to 0.125 (mm/8 plies)/gsm).
- 27. The tissue base sheet according to Embodiment 24, incorporated into a two-ply
tissue product.
- 28. The tissue base sheet according to Embodiment 1, wherein the sheet has a specific
bulk of at least 6 ((mils/8 plies)/(Ib/ream)) (at least 0.09 (mm/8 plies)/gsm).
- 29. The tissue base sheet according to Embodiment 1, wherein the sheet has a specific
bulk of at least 6.5 ((mils/8 plies/lbream)) (at least 0.1 (mm/8 plies)/gsm).
- 30. The absorbent sheet according to Embodiment 1, 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")/(Ibs/ream)) (greater than 1.7 (g/cm)/gsm)
and a bulk up to about 10 ((mils/8plies)/(Ib/ream)) (to about 0.16 (mm/8 plies)/gsm).
- 31. The tissue base sheet according to Embodiment 30, wherein the sheet has a normalized
GM tensile of greater than 21 ((g/3")/(Ibs/ream)) (greater than 1.7 (g/cm)/gsm) and
up to about 30 ((g/3")/(Ibs/ream)) (to about 2.4 (g/cm)/gsm).
- 32. The tissue base sheet according to Embodiment 31, wherein the base sheet has a
normalized GM tensile of 25 ((g/3")/(lbs/ream)) (of 2 (g/cm)/gsm) or greater.
- 33. The base sheet according to Embodiment 30, incorporated into a two-ply tissue
product.
- 34. The cellulosic absorbent sheet according to Embodiment 1, 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.
- 35. The cellulosic absorbent sheet according to Embodiment 1, 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.
- 36. The towel base sheet according to Embodiment 35, wherein at least 30% of the papermaking
fiber is recycle fiber.
- 37. The towel base sheet according to Embodiment 35, wherein at least 40% of the papermaking
fiber is recycle fiber.
- 38. The towel base sheet according to Embodiment 35, wherein at least 50% by weight
of the papermaking fiber is recycle fiber.
- 39. The towel base sheet according to Embodiment 35, wherein at least 75% by weight
of the papermaking fiber is recycle fiber.
- 40. The towel base sheet according to Embodiment 35, wherein 100% by weight of the
papermaking fiber is recycle fiber.
- 41. The towel base sheet according to Embodiment 35, wherein the base sheet has a
basis weight in the range of from 12 to 22 Ibs per 3000 square-foot ream (from 19.5
and 35.8 gsm) and an 8-sheet caliper of greater than 90 mils (2.29 mm), up to about
120 mils (3.05 mm).
- 42. The towel base sheet according to Embodiment 35, converted into a towel with a
CD stretch of at least about 6%.
- 43. The towel according to Embodiment 42, having a CD stretch in the range of from
6% to 10%.
- 44. The towel according to Embodiment 43, having a CD stretch of at least 7%.
- 45. 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 thereof.
- 46. The absorbent cellulosic sheet according to Embodiment 45, 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
two intervening linear arrays.
- 47. The absorbent cellulosic sheet according to Embodiment 45, 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 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 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.
- 48. The absorbent cellulosic sheet according to Embodiment 45, 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 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.
- 49. The absorbent cellulosic sheet according to Embodiment 45, wherein 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.
- 50. The absorbent cellulosic sheet according to Embodiment 45, wherein the elongated
densified regions occupy from about 5% to about 30% of the area of the sheet.
- 51. The absorbent cellulosic sheet according to Embodiment 45, wherein the elongated
densified regions occupy from about 5% to about 25% of the area of the sheet.
- 52. The absorbent cellulosic sheet according to Embodiment 45, wherein the elongated
densified regions occupy from about 7.5% to about 20% of the area of the sheet.
- 53. The absorbent cellulosic sheet according to Embodiment 45, wherein the fiber-enriched
pileated regions occupy from about 95% to about 50% of the area of the sheet.
- 54. The absorbent cellulosic sheet according to Embodiment 45, wherein the fiber-enriched
pileated regions occupy from about 90% to about 60% of the area of the sheet.
- 55. The absorbent sheet according to Embodiment 45, wherein the linear arrays of densified
regions have an MD repeat frequency of from about 50 meter-1 to about 200 meter-1.
- 56. The absorbent sheet according to Embodiment 55, wherein the linear arrays of densified
regions have an MD repeat frequency of from about 75 meter-1 to about 175 meter-1.
- 57. The absorbent sheet according to Embodiment 55, wherein the linear arrays of densified
regions have an MD repeat frequency of from about 90 meter-1 to about 125 meter-1.
- 58. The absorbent sheet according to Embodiment 45, wherein the densified regions
of the linear arrays thereof have a CD repeat frequency of from about 100 meter-1 to about 500 meter-1.
- 59. The absorbent sheet according to Embodiment 45, wherein the densified regions
of the linear arrays thereof have a CD repeat frequency of from about 150 meter-1 to about 300 meter-1.
- 60. The absorbent sheet according to Embodiment 45, wherein the densified regions
of the linear arrays thereof have a CD repeat frequency of from about 175 meter-1 to about 250 meter-1.
- 61. An absorbent cellulosic sheet having variable local basis weight comprising a
papermaking-fiber reticulum provided with:
- (a) a plurality of elongated densified regions of compressed papermaking fibers, 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.
- 62. 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 toward 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, wherein the sheet
has a specific bulk of greater than 5.5 ((mils/8 plies)/(Ib/ream)) ( greater than
0.085 (mm/8plies/gsm) and (iii) 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 (iv) has a void volume of
7 grams/gram or greater when it has a basis weight of greater than 23 Ibs/ream (37.5
gsm).
- 63. 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, wherein the sheet has a specific bulk of greater than 5.5
((mils/8 plies)/(Ib/ream)) ( greater than 0.085 (mm/8plies/gsm) and (iii) has a void
volume of 9 grams/gram or greater when it has a basis weight of 23 Ib/ream (37.5 gsm)
or less or (iv) has a void volume of 7 grams/gram or greater when it has a basis weight
of greater than 23 Ibs/ream (37.5 gsm).
- 64. The absorbent cellulosic sheet according to Embodiment 63, wherein 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.
- 65. The absorbent cellulosic sheet according to Embodiment 63, wherein the characteristic
local basis weight of representative areas within the relatively high basis weight
regions is at least 50% higher than the characteristic local basis weight of representative
areas within the low basis weight regions.
- 66. The absorbent cellulosic sheet according to Embodiment 63, wherein the characteristic
local basis weight of representative areas within the relatively high basis weight
regions is at least 75% higher than the characteristic local basis weight of representative
areas within the low basis weight regions.
- 67. The absorbent cellulosic sheet according to Embodiment 63, wherein the characteristic
local basis weight of representative areas within the relatively high basis weight
regions is at least 100% higher than the characteristic local basis weight of representative
areas within the low basis weight regions.
- 68. The absorbent cellulosic sheet according to Embodiment 63, wherein the characteristic
local basis weight of representative areas within the relatively high basis weight
regions is at least 150% higher than the characteristic local basis weight of representative
areas within the low basis weight regions.
- 69. The absorbent cellulosic sheet according to Embodiment 63, wherein 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.
- 70. A method of making a belt-creped absorbent cellulosic sheet comprising:
(a) compactively 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;
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
being 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 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 being further
characterized by an MD/CD aspect ratio of at least 1.5 and
(d) drying the web , wherein the sheet has a specific bulk of greater than 5.5 ((mils/8
plies)/(Ib/ream))( greater than 0.085 (mm/8plies/gsm) and (iii) has a void volume
of 9 grams/gram or greater when it has a basis weight of 23 Ib/ream (37.5 gsm) or
less or (iv) has a void volume of 7 grams/gram or greater when it has a basis weight
of greater than 23 Ibs/ream (37.5 gsm).
- 71. The method according to Embodiment 70, wherein the creping belt is a fabric.
- 72. The method according to Embodiment 70, further comprising applying suction to
the creped web while it is disposed in the creping fabric.
- 73. The method according to Embodiment 70, wherein 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.
- 74. The method according to Embodiment 73, wherein the creping fabric is a multilayer
fabric.
- 75. The method according to Embodiment 70, wherein the pileated regions include drawable
macrofolds.
- 76. The method according to Embodiment 75, further including the step of drawing the
macrofolds by drawing the web along the MD of the sheet.
- 77. The method according to Embodiment 70, wherein the pileated regions include drawable
macrofolds and nested therein drawable microfolds.
- 78. The method according to Embodiment 77, further comprising the step of drawing
the microfolds of the pileated regions by application of suction.
- 79. The method according to Embodiment 70, wherein the pileated regions include a
plurality of overlapping crests inclined with respect to the MD of the sheet.
- 80. 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 being selected such that the web is creped from the transfer surface and
transferred to the creping fabric;
- d) adhering the web to a drying cylinder with a resinous adhesive coating composition;
- e) drying the web on the drying cylinder; and
- f) 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 having relatively low
local basis weight and being generally oriented along the machine direction (MD) of
the sheet, the elongated densified regions being further characterized by an MD/CD
aspect ratio of at least 1.5.
- 81. The method according to Embodiment 80, wherein the MD bending length of the dried
web is from about 3.5 cm to about 5 cm.
- 82. The method according to Embodiment 80, wherein the MD bending length of the dried
web is from about 3.75 cm to about 4.5 cm.
- 83. The method according to Embodiment 80, operated at a fabric crepe of from about
2% to about 20%.
- 84. The method according to Embodiment 80, operated at a fabric crepe of from about
3% to about 10%.
- 85. A method of making fabric-creped absorbent cellulosic sheet comprising:
- a) compactively 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) 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 Gain/% Reel Crepe ratio of at least 1.5.
- 86. The process according to Embodiment 85, wherein the process exhibits a Caliper
Gain/% Reel Crepe ratio of at least 2.
- 87. The process according to Embodiment 85, wherein the process exhibits a Caliper
Gain/% Reel Crepe ratio of at least 2.5.
- 88. The process according to Embodiment 85, wherein the process exhibits a Caliper
Gain/% Reel Crepe ratio of at least 3.
- 89. The process according to Embodiment 85, wherein the process exhibits a Caliper
Gain/% Reel Crepe ratio of from about 1.5 to about 5.
- 90. The process according to Embodiment 85, operated at a Fabric Crepe/Reel Crepe
ratio of from about 1 to about 20.
- 91. The process according to Embodiment 85, operated at a Fabric Crepe/Reel Crepe
ratio of from about 2 to about 10.
- 92. The process according to Embodiment 85, operated at a Fabric Crepe/Reel Crepe
ratio of from about 2.5 to about 5.