U.S. patent application number 11/906268 was filed with the patent office on 2008-03-27 for non-woven through air dryer and transfer fabrics for tissue making.
Invention is credited to Andrew Peter Bakken, Mark Alan Burazin, Jeffrey Dean Lindsay.
Application Number | 20080073047 11/906268 |
Document ID | / |
Family ID | 32593815 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080073047 |
Kind Code |
A1 |
Bakken; Andrew Peter ; et
al. |
March 27, 2008 |
Non-woven through air dryer and transfer fabrics for tissue
making
Abstract
One embodiment of the present invention is an endless non-woven
tissue making fabric having a three-dimensional texture suitable
for use as a fabric for producing three-dimensional fibrous webs.
The endless non-woven tissue making fabric comprises a plurality of
substantially parallel adjoining sections of non-woven material.
Each section of non-woven material has a width substantially less
than the width of the non-woven tissue making fabric. Each section
of non-woven material may be joined to at least one other adjoining
section of non-woven material. The non-woven tissue making fabric
has a machine direction, a cross-machine direction, a tissue
contacting surface and a tissue machine contacting surface. The
tissue contacting surface comprises solid matter at a plurality of
heights such that the tissue contacting surface of the non-woven
tissue making fabric has an Overall Surface Depth of at least 0.2
mm in regions of solid matter on the tissue contacting surface.
Inventors: |
Bakken; Andrew Peter;
(Appleton, WI) ; Burazin; Mark Alan; (Oshkosh,
WI) ; Lindsay; Jeffrey Dean; (Appleton, WI) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.;Catherine E. Wolf
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Family ID: |
32593815 |
Appl. No.: |
11/906268 |
Filed: |
October 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11051340 |
Feb 4, 2005 |
7294238 |
|
|
11906268 |
Oct 1, 2007 |
|
|
|
10325565 |
Dec 19, 2002 |
6878238 |
|
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11051340 |
Feb 4, 2005 |
|
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Current U.S.
Class: |
162/116 |
Current CPC
Class: |
Y10S 162/903 20130101;
D21F 11/006 20130101; D21F 11/145 20130101; Y10S 162/90 20130101;
Y10T 428/192 20150115; Y10T 428/24479 20150115; Y10T 428/24612
20150115; Y10T 428/2495 20150115; D21F 1/0054 20130101; Y10S
162/904 20130101; D21F 11/14 20130101 |
Class at
Publication: |
162/116 |
International
Class: |
D21H 27/02 20060101
D21H027/02 |
Claims
1. A method of making an endless non-woven tissue making fabric
having a three-dimensional texture suitable for use as a fabric for
producing three-dimensional fibrous webs comprising: a. providing
an endless non-woven tissue making fabric having a tissue
contacting surface and a tissue machine contacting surface; b.
passing heated air through a molding device; c. passing the endless
non-woven tissue making fabric over a surface of the molding
device, wherein the surface of the molding device includes a
textured molding surface; and, d. conforming at least a portion of
the endless non-woven tissue making fabric to the textured molding
surface of the molding device, thereby forming a three-dimensional
texture on the endless non-woven tissue making fabric.
2. The method of claim 1, wherein the molding device further
comprises a suction roll.
3. The method of claim 2, wherein the suction roll provides a zone
of vacuum.
4. The method of claim 1, further comprising providing a cooling
device to cool the endless non-woven tissue making fabric.
5. The method of claim 1, wherein the molding device comprises
raised molding elements.
6. The method of claim 1, wherein the molding device comprises
molding elements having a shape selected from the group consisting
of: sine wave-shaped; triangle-shaped; square wave-shaped;
irregular-shaped; and, any combination thereof.
7. The method of claim 1, wherein the heated air is provided by an
air knife.
8. The method of claim 1, wherein the molding device comprises
porous molding elements.
9. The method of claim 8, wherein the molding elements are
comprised of material selected from the group consisting of:
sintered metal; finely drilled metal; finely drilled plastic;
sintered ceramic; ceramic foam; and, any combination thereof.
10. The method of claim 1, further comprising contacting the tissue
contacting surface of the endless non-woven tissue making fabric
with the surface of the molding device.
11. The method of claim 10, wherein at least a portion of the
tissue contacting surface of the endless non-woven tissue making
fabric conforms with the surface of the molding device.
12. The method of claim 1, further comprising contacting the tissue
machine contacting surface of the endless non-woven tissue making
fabric with the surface of the molding device.
13. The method of claim 1, wherein the three-dimensional texture
comprises a repeating pattern.
14. The method of claim 13, wherein the repeating pattern includes
a series of raised elements and depressed elements defining a
repeating unit cell.
15. The method of claim 14, wherein the repeating unit cell of the
repeating pattern includes a width of about 3 mm or greater in the
cross-machine direction of the endless non-woven tissue making
fabric.
16. The method of claim 14, wherein the repeating unit cell of the
repeating pattern includes a length of about 3 mm or greater in the
machine direction of the endless non-woven tissue making
fabric.
17. The method of claim 14, wherein the repeating unit cell of the
repeating pattern includes a percentage value in the machine
direction length of the endless non-woven making fabric of about 1%
or greater.
18. The method of claim 1, wherein the tissue contacting surface of
the endless non-woven tissue making fabric is differently textured
than the tissue machine contacting surface of the endless non-woven
tissue making fabric.
19. The method of claim 1, wherein the tissue contacting surface of
the endless non-woven tissue making fabric is substantially
textured the same as the tissue machine contacting surface of the
endless non-woven tissue making fabric.
20. The method of claim 15, wherein the endless non-woven tissue
making fabric comprises multi-component binder materials.
21. The method of claim 20, wherein the multi-component binder
material includes at least a first portion and a second portion,
wherein the first portion has a lower melting point that the second
portion.
22. The method of claim 20, wherein the multi-component binder
material is selected from the group consisting of: bi-component
concentric sheath-core; bi-component asymmetric sheath-core;
bi-component side-by-side; and, any combination thereof.
23. The method of claim 1, wherein the endless non-woven tissue
making fabric is formed on a carrier fabric.
24. The method of claim 23, wherein the endless non-woven tissue
making fabric is attached to the carrier fabric.
25. The method of claim 20, wherein the endless non-woven tissue
making fabric is comprised of fibers or filaments selected from the
group consisting of: spunbond fibers; melt blown fibers; and,
combinations thereof.
26. The method of claim 1, further comprising providing a gas
pervious roll having a surface wherein a nip is formed between the
surface of the gas pervious roll and the surface of the molding
device.
27. The method of claim 26, wherein the surface of the gas pervious
roll includes molding elements.
28. The method of claim 27, wherein the surface of the gas pervious
roll including the molding elements is a textured sleeve.
29. The method of claim 27, wherein the molding elements of the gas
pervious roll are raised elements.
30. The method of claim 29, wherein the surface of the gas pervious
roll including the raised elements is a textured sleeve.
31. The method of claim 27, wherein the molding elements of the gas
pervious roll mesh with raised molding elements of the molding
device.
32. The method of claim 1, wherein the tissue contacting surface of
the endless non-woven tissue making fabric includes a
three-dimensional texture and the tissue machine contacting surface
of the endless non-woven tissue making fabric includes a
three-dimensional texture.
33. The method of claim 27, wherein the tissue contacting surface
of the endless non-woven tissue making fabric includes a
three-dimensional texture and the tissue machine contacting surface
of the endless non-woven tissue making fabric includes a
three-dimensional texture.
34. The method of claim 1, wherein the non-woven tissue making
fabric does not comprise a woven element.
Description
[0001] This application is a continuation of application Ser. No.
11/051,340 filed Feb. 4, 2005, which application is a divisional of
application Ser. No. 10/325,565, now U.S. Pat. No. 6,878,238, filed
on Dec. 19, 2002. The entirety of application Ser. Nos. 11/051,340
and 10/325,565 are hereby incorporated by reference.
BACKGROUND
[0002] Fabrics used as through air drying and transfer fabrics in a
tissue making process are typically woven endless fabrics
manufactured using a tubular weaving technique or seaming a flat
woven fabric into an endless structure. In either method of
manufacturing, the weaving process is an expensive, complex,
labor-intensive process. Developing new weaving patterns and
materials that deliver the desired characteristics of the fabric
and the tissue product can require a large investment of time and
money. Additionally, there are physical constraints on the patterns
and height differentials that may be woven on a loom, and there are
further constraints on the runnability of fabrics so
manufactured.
[0003] The use of substrates other than woven fabrics in the
formation or drying of paper is known to a limited degree, such as
non-fibrous monoplanar films and membranes used in the production
of tissue. In tissue making, these structures typically offer flat,
planar, non-fibrous regions for imprinting a web during a
compression step in order to provide a network of densified regions
surrounding undensified regions, with the densified regions
providing strength and the undensified regions providing softness
and absorbency. Such structures and processes lack the contoured,
non-planar three-dimensionality that may be useful in producing
textured and noncompressively dried materials and lack the
intrinsic porosity and other properties found in fibrous materials.
Such processes also result in a sheet with regions of high density
and regions of low density, which is not suitable for some
products. Further, substantially planar films are inherently
limited in their ability to impart three-dimensional structures to
a sheet.
[0004] Therefore, there is a need for improved tissue making
fabrics capable of overcoming one or more of the limitations of
previously known materials.
SUMMARY
[0005] The present invention is a non-woven tissue making fabric
comprising a plurality of substantially parallel adjoining sections
of non-woven material having a width less than the width of the
non-woven tissue making fabric, the sections being joined together
to form a non-woven tissue making fabric of sufficient strength and
permeability to be suitable for use as a through-drying fabric, a
forming fabric, an imprinting fabric, a transfer fabric, a carrier
fabric, an impulse drying fabric, a pressing fabric or press felt,
a drying fabric, a capillary dewatering belt, or other fabrics of
use in tissue making or in the manufacture of other bulky fibrous
webs such as airlaid webs, coform, nonwoven webs, and the like
(such uses are encompassed in the general term "non-woven tissue
making fabric," unless otherwise specified). The plurality of
sections of nonwoven material may comprise a single fabric strip
that is repeatedly wrapped in a substantially spiral manner to form
parallel adjacent sections that can abut one another or overlap one
another in successive turns to form a continuous loop of non-woven
tissue making fabric having a width substantially greater than the
width of the fabric strip of non-woven material. When a single
fabric strip wrapped in a spiral manner is bonded to itself in
regions of overlap for adjacent sections of the strip, the
non-woven tissue making fabric is said to have a spirally
continuous seam. In such a non-woven tissue making fabric, wherein
each fabric strip of non-woven material has a first edge and an
opposing second edge, the fabric strip of non-woven material is
spirally wound in a plurality of contiguous turns such that the
first edge in a turn of the fabric strip extends beyond the second
edge of an adjacent turn of the fabric strip, forming a spirally
continuous seam with adjacent turns of the fabric strip. In another
embodiment, the first edge of the fabric strip in a turn may abut
the second edge of the fabric strip in an adjacent turn.
[0006] A seam formed between the adjacent sides of parallel fabric
strips or adjacent sections of a single spirally wound fabric strip
may represent a region with higher basis weight or thickness when
the non-woven materials of the adjacent fabric strips overlap.
However, non-woven fabric strips may be used that have a tapered
basis weight profile or thickness profile in the cross-direction,
with lower basis weight or thickness at or adjacent the first
and/or second opposing edges. In this manner, two overlapping
adjacent edges of adjacent fabric strips may result in a more
uniform non-woven tissue making fabric because the region of
overlap may have a less pronounced increase in thickness or basis
weight, and may even yield a substantially uniform thickness or
basis weight profile in the cross-direction of the non-woven tissue
making fabric when the profiles of the individual fabric strips are
suitably tailored.
[0007] In another embodiment, the plurality of sections of
non-woven material may comprise a plurality of fabric strips that
abut or overlap adjacent fabric strips. Seams may be formed by
bonding adjacent fabric strips in regions of overlap or in regions
where adjacent, non-overlapping fabric strips abut about their
first and second opposing end edges, yielding a non-woven tissue
making fabric that is said to have discontinuous seams. In yet
another embodiment, the non-woven tissue making fabric may have
regions where fabric strips abut one another and regions where the
fabric strips overlap. For example, lower layers of fabric strips
may overlap to provide good bond strength, while one or more upper
layers of fabric strips may abut to provide a more uniform
surface.
[0008] In still another embodiment, the non-woven tissue making
fabric comprises a single fabric strip having at least one section
substantially as wide as the non-woven tissue making fabric itself,
and further comprising at least one other section having a width
less than the non-woven tissue making fabric. Such a non-woven
tissue making fabric may be made by spiral winding a fabric strip
of non-woven material of a first width to form a multiply spiral
wound structure, and then trimming the structure to a second width
less than the first width. (Typically, this would be done in the
machine direction.) In this case, some sections of the trimmed
structure may have a width substantially less than the width of the
non-woven tissue making fabric.
[0009] In another embodiment, the non-woven tissue making fabric
comprises a least one fabric strip of non-woven material wound upon
itself to form at least one region in the non-woven tissue making
fabric having two superimposed plies of the non-woven material
bonded together, one above the other. Such a non-woven tissue
making fabric may have a substantially heterogeneous basis weight
distribution, with high basis weight regions coinciding with
regions of self-overlap of the wound fabric strip of non-woven
material, where two or more plies are superimposed. Such a
non-woven tissue making fabric may be bonded together such that a
nonlinear (discontinuous) seam region exists for improved fabric
strength.
[0010] A single non-woven tissue making fabric may comprise more
than one type of seam. For example, a spirally wound non-woven
fabric strip may be joined with a plurality of non-spirally wound
non-woven fabric strips, either in a plurality of separately formed
layers or in more complex structures in which various fabric strips
pass over or under each other.
[0011] The present invention is also a method of making a non-woven
tissue making fabric. In one embodiment, a fabric strip of
non-woven material having a first edge and an opposing second edge
is provided. The fabric strip is spirally wound in a plurality of
turns such that the first edge in a turn of the fabric strip
extends beyond the second edge of an adjacent turn of the fabric
strip. A spirally continuous seam is formed with adjacent turns of
the fabric strip. In another embodiment, the first edge of the
fabric strip in a turn may abut the second edge of the fabric strip
in an adjacent turn.
[0012] In another embodiment, a plurality of fabric strips of one
or more non-woven fabrics are aligned to be substantially parallel
with each other but offset such that adjacent fabric strips either
abut (adjoin without an overlapping rejoin) or overlap but not
completely, and the adjoining strips are then bonded together to
form a non-woven tissue making fabric. For embodiments of a
non-woven tissue making fabric having a substantially
three-dimensional tissue contacting surface (generally understood
to be the web-contacting surface), the non-woven fabric strip may
have been previously treated to have a three-dimensional surface
structure, or the non-woven tissue making fabric may have been
further treated to impart increased three-dimensional texture.
[0013] In another embodiment, a fabric strip of non-woven material
is folded upon itself in a flattened helical pattern and bonded to
form a non-woven tissue making fabric such that a tissue contacting
surface of the non-woven tissue making fabric comprises
substantially parallel abutting and/or overlapping sections of the
non-woven material aligned with an axis at a first angle, and the
inner layer (in some embodiments, the tissue machine contacting
surface of the non-woven tissue making fabric opposite the tissue
contacting surface of the non-woven tissue making fabric) comprises
substantially parallel abutting or overlapping sections of the
non-woven material aligned with an axis at a second angle, the
first axis being a mirror image of the second axis reflected about
the machine direction axis of the non-woven tissue making
fabric.
[0014] In forming the non-woven tissue making fabrics of the
present invention, a hierarchy of components may be defined
employing the terms "ply," "layer," and "stratum." The non-woven
tissue making fabric may comprise one or more distinct non-woven
plies substantially as wide as the non-woven tissue making fabric
itself, including at least one ply comprising a plurality of
sections of non-woven material bonded together wherein neighboring
sections abut or overlap to form one or more layers (e.g., when two
neighboring sections overlap, the region of overlap has two layers;
whereas abutting, non-overlapping parallel sections of non-woven
fabric would form a single layer). In turn, each section or layer
of non-woven material may itself comprise a plurality of
joined-together strata (e.g., a unitary web formed by laying
meltblown fibers onto a spunbond web would have two strata within
the unitary web). In some embodiments, "section" and "strip" may be
synonymous, while in some other embodiments hereafter described, a
single fabric strip may form multiple sections, or a section may
comprise multiple fabric strips joined together. A single fabric
strip may also comprise multiple strata, which need not be
completely coextensive, such that the edges of one stratum are not
directly aligned with the edges of the adjacent stratum. The width
of a ply, layer, stratum, strip, and/or section may have a width of
less than the finished non-woven tissue making fabric, about the
same width of the finished non-woven tissue making fabric, or have
a width greater than the finished non-woven tissue making
fabric.
[0015] The term "web" may refer to a ply, layer, or stratum in the
above-mentioned hierarchy, depending on the context.
[0016] In some embodiments, a fabric strip of non-woven material
may be spiral wound to form a section of non-woven material having
a first width and regions having two layers of the fabric strips of
non-woven material. The section may then be further spiral wound to
form a ply having a second width greater than the first width. The
resulting ply may then be joined to other non-woven plies or
reinforcement plies to form a non-woven fabric strip, or the ply
may be used as a non-woven tissue making fabric per se, and further
provided with additional treatments as needed (e.g., edge
reinforcement, perforations, three-dimensional molding, chemical
finishing, foam bonding, point bonding, heat treatments, curing of
adhesive components, electron beam treatments, corona discharge
treatment, generation of electrets, needling, hydroneedling,
hydroentangling, or treatment with surfactants, web lubricants,
silicone agents, etc.).
[0017] Joining any of these elements--plies, layers, or strata--to
one another may be accomplished by any means known in the art. In
addition to thermal bonding and its known variants involving the
application of heat and pressure (e.g., point bonding, etc.), many
other known methods may be used to join two materials together
(e.g., joining superposed portions of two fabric strips in a region
where one fabric strip abuts an adjacent fabric strip) or for
joining one material to an underlying material. For example,
hydroentangling or hydroneedling with jets of water may entangle
fibers in one material with those of an adjoining material to
attach the material. Illustrative methods are disclosed in U.S.
Pat. No. 3,485,706, issued to Evans in 1969; U.S. Pat. No.
3,494,821, issued to Evans in 1970; U.S. Pat. No. 4,808,467, issued
on Feb. 28, 1989 to Suskind et al.; and, U.S. Pat. No. 6,200,669,
issued on Mar. 13, 2001 to Marmon et al., all of which are herein
incorporated by reference to the extent that they are
non-contradictory herewith.
[0018] Coaperturing of two superposed webs of material (e.g.,
sections of non-woven material) may also be done, particularly
coaperturing with heated pins that induce a degree of fusion of
thermoplastic material in the webs of material in the vicinity of
the aperture. Exemplary methods for coaperturing and equipment
therefor are disclosed in U.S. Pat. No. 5,986,167, issued on Nov.
16, 1999 to Arteman et al. and U.S. Pat. No. 4,886,632, issued on
Dec. 12, 1989 to Van Iten et al., both of which are herein
incorporated by reference to the extent that they are
non-contradictory herewith. Related methods also include
perf-embossing, crimping of two or more webs of material, and
embossing in general.
[0019] Joining these elements may also be achieved by the
application of adhesive between the webs of material, such as a hot
melt adhesive or adhesive meltblown, or binder material such as
binder fibers added between adjoining webs of material followed by
sufficient heating to fuse the binder material and join the webs of
material, or other adhesives known in the art. Equipment and
methods for adhesively joining two webs of material are taught in
U.S. Pat. No. 5,871,613, issued on Feb. 16, 1999 to Bost et al.;
U.S. Pat. No. 5,882,573, issued on Mar. 16, 1999 to Kwok et al.;
and, U.S. Pat. No. 5,904,298, issued on May 18, 1999 to Kwok et
al., all of which are herein incorporated by reference to the
extent that they are non-contradictory herewith. Hot melt or
thermosetting adhesive applied by spray nozzles (including
meltblowing methods) may be applied with such technologies.
Photocurable adhesives may also be used, such as photocuring
cyanoacrylates and acrylics described by P. J. Courtney, "Shedding
New Light on Adhesives," Adhesives Age, February 2001, or the
photocuring systems described in commonly owned U.S. patent
application Ser. No. 09/705,684, "Improved Deflection Members for
Tissue Production," filed on Nov. 3, 2000 by Lindsay et al., herein
incorporated by reference to the extent that it is
non-contradictory herewith.
[0020] Ultrasonic welding may be applied to join webs of material
using rotary horns, ultrasonically activated pressing plates, or
other devices. Equipment and methods useful for ultrasonic welding
of nonwoven webs are disclosed in U.S. Pat. No. 3,993,532, issued
on Nov. 23, 1976 to McDonald et al.; U.S. Pat. No. 4,659,614,
issued on Apr. 21, 1987 to Vitale; and, U.S. Pat. No. 5,096,532,
issued on Mar. 17, 1992 to Neuwirth et al.
[0021] Other techniques may be applied, including, without
limitation, application of electron beams to fuse adjacent fibers
or to activate an adhesive; photocuring of resins contacting the
fabric strips; through-air bonding; sewing of webs of material;
application of rivets, staples, snaps, grommets, or other
mechanical fasteners; hook-and-loop attachment means; or,
mechanical needling of the web of material. Methods and equipment
for joining nonwoven webs of material with mechanical needling are
disclosed in U.S. Pat. No. 5,713,399, issued on Feb. 3, 1998 to
Collette et al.; U.S. Pat. No. 3,729,785, issued on May 1, 1973 to
Sommer; U.S. Pat. No. 3,890,681, issued on Jun. 24, 1975 to Fekete
et al.; U.S. Pat. No. 4,962,576, issued on Oct. 16, 1990 to
Minichshofer et al.; and, U.S. Pat. No. 5,511,294, issued on Apr.
30, 1996 to Fehrer, as well as EP 1 063 349 A2, published on Dec.
27, 2000 in the name of Paquin, all of which are herein
incorporated by reference to the extent that they are
non-contradictory herewith. Needling (such as pin seaming) and
aperturing, as well as other systems, have the potential to induce
favorable changes in physical properties of the web of material
such as increased permeability or improved fluid intake of the
non-woven tissue making fabric.
[0022] When a hotmelt adhesive is used, the equipment for
processing the hotmelt adhesive and supplying a stream of hotmelt
adhesive to the printing systems of the present invention may be
any known hotmelt or adhesive processing devices. For example, the
ProFlex.RTM. applicators of Hot Melt Technologies, Inc. (Rochester,
Mich.), the "S" Series Adhesive Supply Units of ITW Dynatec,
Hendersonville, Tenn., as well as the DynaMelt "M" Series Adhesive
Supply Units, the Melt-on-Demand Hopper, and the Hotmelt Adhesive
Feeder, all of ITW Dynatec are all exemplary systems which may be
used.
[0023] Binder materials may also be applied to one or more webs of
material or portions thereof in the form of liquid resins,
slurries, colloidal suspensions, or solutions that become rigid or
crosslinked upon application of energy (e.g., microwave energy,
heat, ultraviolet radiation, electron beam radiation, and the
like). For example, Stypol XP44-AB12-51B of Freeman Chemical Corp.,
a diluted version of the Freeman 44-7010 binder, is a
microwave-sensitive binder that was used by Buckley et al. in U.S.
Pat. No. 6,001,300, issued on Dec. 14, 1999, previously
incorporated by reference. Various types of thermosetting binders
are known to the art such as polyvinyl acetate, vinyl acetate,
ethylene-vinyl chloride, styrene butadiene, polyvinyl alcohol,
polyethers, and the like. A heat-activated adhesive film is
disclosed in EP 1 063 349 A2, published on Dec. 27, 2000 in the
name of Paquin, wherein it is herein incorporated by reference to
the extent that it is not contradictory herewith.
[0024] As used herein, the term "non-woven" indicates that the
material in question was produced without weaving techniques.
Weaving processes produce a structure of individual strands which
are interwoven generally in an identifiable repeating manner.
Non-woven materials may be formed by a variety of processes such as
meltblowing, spunbonding, and staple fiber carding. The term
"non-woven" frequently refers to fibrous materials, but may also
refer to non-fibrous material or webs that comprise non-fibrous
materials, such as photocured resin elements or polymeric foams.
However, in some embodiments, the non-woven materials of the
present invention may be predominantly fibrous, or may be
substantially free of non-fibrous protrusions on the
paper-contacting side of the web. For example, the non-woven tissue
making fabric of the present invention may comprise about 50 weight
% or more fibrous non-woven materials, specifically about 70 weight
% or more, more specifically about 80 weight % or more, more
specifically still about 90 weight % or more, and most specifically
about 95 weight % or more fibrous non-woven materials. In another
embodiment, the non-woven tissue making fabrics may be
substantially free of photocured polymeric resins, or substantially
free of polymeric foams. Further, the non-woven tissue making
fabrics of the present invention may be substantially free of
elevated non-thermoplastic resinous elements on the tissue
contacting surface of the non-woven tissue making fabric.
[0025] The non-woven tissue making fabric may be reinforced with
added fabric strips of material where needed, including layers of
scrim, tow, woven materials, cured resins, and fabric strips of
nonwoven material in any direction (e.g., lying in the
cross-directional or machine directional or any direction
therebetween).
[0026] The materials used may also vary with position in the
non-woven tissue making fabric to obtain desirable material or
mechanical properties. For example, the non-woven material may be
polyester in most locations of the non-woven tissue making fabric,
supplemented with polyphenylsulfide, polyether ether ketone, or a
polyaramid at the side edges of the non-woven tissue making fabric
to better resist hydrolysis, withstand elevated temperatures in a
drying hood, or resist other mechanical or thermal challenges
exacerbated at the side edges.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic of a papermaking apparatus.
[0028] FIGS. 2A, 2B, and 2C depict cross-sections of an embryonic
web on a non-woven tissue making fabric.
[0029] FIG. 3 is a schematic view of a method for manufacturing a
non-woven tissue making fabric of one embodiment of the present
invention.
[0030] FIG. 4 is a schematic view of a molding section in a process
for making a non-woven tissue making fabric according to one
embodiment of the present invention.
[0031] FIG. 5 is a schematic view of a rotating molding section in
a process for making a non-woven tissue making fabric according to
one embodiment of the present invention.
[0032] FIG. 6 is a schematic view of a rotating molding section in
a process for making a two-ply non-woven tissue making fabric
according to one embodiment of the present invention.
[0033] FIG. 7 is a schematic of a top view of a portion of a
non-woven tissue making fabric according to the present invention
having a plurality of fabric strips.
[0034] FIGS. 8A and 8B are schematic views of embodiments of
non-woven tissue making fabrics according to the present invention
comprising a fabric strip that is wound in a plurality of turns at
an acute angle to the machine direction.
[0035] FIG. 9 is a schematic view of a non-woven tissue making
fabric of another embodiment of the present invention.
[0036] FIG. 10 is a schematic view of a non-woven tissue making
fabric of another embodiment of the present invention.
[0037] FIG. 11 is a schematic view of a non-woven tissue making
fabric of another embodiment of the present invention.
[0038] FIG. 12 is a schematic view of a non-woven tissue making
fabric having discrete parallel fabric strips of non-woven
material.
[0039] FIG. 13 is a cross-sectional view of the non-woven tissue
making fabric of FIG. 12, taken as indicated by line 13-13 in FIG.
12.
[0040] FIG. 14 is a photograph of a three-dimensional drilled metal
plate used to mold a section of a non-woven tissue making fabric
according to the present invention.
[0041] FIG. 15 is a screen shot showing a topographic height map of
a portion of the first metal plate and a characteristic profile
extracted from the height map.
[0042] FIG. 16 is a screen shot showing a topographic height map of
the first metal plate and a characteristic profile extracted from
the height map.
[0043] FIG. 17 is a photograph of a two-ply non-woven tissue making
fabric molded against the three-dimensional plate of FIG. 14.
[0044] FIG. 18 is a screen shot showing a topographic height map of
a portion of the non-woven tissue making fabric of FIG. 17.
DETAILED DESCRIPTION
[0045] Referring to FIG. 1, a process of carrying out using the
present invention will be described in greater detail. The process
shown depicts an uncreped through dried process, but it will be
recognized that any known papermaking method or tissue making
method can be used in conjunction with the non-woven tissue making
fabrics of the present invention. Related uncreped through air
dried tissue processes are described in U.S. Pat. No. 5,656,132
issued on Aug. 12, 1997 to Farrington et al. and in U.S. Pat. No.
6,017,417 issued on Jan. 25, 2000 to Wendt et al. Both patents are
herein incorporated by reference to the extent they are not
contradictory herewith. Exemplary methods for the production of
creped tissue and other paper products are disclosed in U.S. Pat.
No. 5,855,739, issued on Jan. 5, 1999 to Ampulski et al.; U.S. Pat.
No. 5,897,745, issued on Apr. 27, 1999 to Ampulski et al.; U.S.
Pat. No. 5,893,965, issued on Apr. 13, 1999 to Trokhan et al.; U.S.
Pat. No. 5,972,813 issued on Oct. 26, 1999 to Polat et al.; U.S.
Pat. No. 5,503,715, issued on Apr. 2, 1996 to Trokhan et al.; U.S.
Pat. No. 5,935,381, issued on Aug. 10, 1999 to Trokhan et al.; U.S.
Pat. No. 4,529,480, issued on Jul. 16, 1985 to Trokhan; U.S. Pat.
No. 4,514,345, issued on Apr. 30, 1985 to Johnson et al.; U.S. Pat.
No. 4,528,239, issued on Jul. 9, 1985 to Trokhan; U.S. Pat. No.
5,098,522, issued on Mar. 24, 1992 to Smurkoski et al.; U.S. Pat.
No. 5,260,171, issued on Nov. 9, 1993 to Smurkoski et al.; U.S.
Pat. No. 5,275,700, issued on Jan. 4, 1994 to Trokhan; U.S. Pat.
No. 5,328,565, issued on Jul. 12, 1994 to Rasch et al.; U.S. Pat.
No. 5,334,289, issued on Aug. 2, 1994 to Trokhan et al.; U.S. Pat.
No. 5,431,786, issued on Jul. 11, 1995 to Rasch et al.; U.S. Pat.
No. 5,496,624, issued on Mar. 5, 1996 to Stelljes, Jr. et al.; U.S.
Pat. No. 5,500,277, issued on Mar. 19, 1996 to Trokhan et al.; U.S.
Pat. No. 5,514,523, issued on May 7, 1996 to Trokhan et al.; U.S.
Pat. No. 5,554,467, issued on Sep. 10, 1996, to Trokhan et al.;
U.S. Pat. No. 5,566,724, issued on Oct. 22, 1996 to Trokhan et al.;
U.S. Pat. No. 5,624,790, issued on Apr. 29, 1997 to Trokhan et al.;
U.S. Pat. No. 6,010,598, issued on Jan. 4, 2000 to Boutilier et
al.; and, U.S. Pat. No. 5,628,876, issued on May 13, 1997 to Ayers
et al., the specification and claims of which are incorporated
herein by reference to the extent that they are not contradictory
herewith.
[0046] In FIG. 1, a twin wire former 8 having a papermaking headbox
10 injects or deposits a stream 11 of an aqueous suspension of
papermaking fibers onto a plurality of forming fabrics, such as the
outer forming fabric 12 and the inner forming fabric 13, thereby
forming a wet tissue web 15. The forming process of the present
invention may be any conventional forming process known in the
papermaking industry. Such formation processes include, but are not
limited to, Fourdriniers, roof formers such as suction breast roll
formers, and gap formers such as twin wire formers and crescent
formers.
[0047] The wet tissue web 15 forms on the inner forming fabric 13
as the inner forming fabric 13 revolves about a forming roll 14.
The inner forming fabric 13 serves to support and carry the
newly-formed wet tissue web 15 downstream in the process as the wet
tissue web 15 is partially dewatered to a consistency of about 10
percent based on the dry weight of the fibers. Additional
dewatering of the wet tissue web 15 may be carried out by known
paper making techniques, such as vacuum suction boxes, while the
inner forming fabric 13 supports the wet tissue web 15. The wet
tissue web 15 may be additionally dewatered to a consistency of at
least about 20%, more specifically between about 20% to about 40%,
and more specifically about 20% to about 30%. The wet tissue web 15
is then transferred from the inner forming fabric 13 to a transfer
fabric 17 traveling preferably at a slower speed than the inner
forming fabric 13 in order to impart increased MD stretch into the
wet tissue web 15.
[0048] The wet tissue web 15 is then transferred from the transfer
fabric 17 to a throughdrying fabric 19 whereby the wet tissue web
15 may be macroscopically rearranged to conform to the surface of
the throughdrying fabric 19 with the aid of a vacuum transfer roll
20 or a vacuum transfer shoe like the vacuum shoe 18. If desired,
the throughdrying fabric 19 can be run at a speed slower than the
speed of the transfer fabric 17 to further enhance MD stretch of
the resulting absorbent tissue product 27. The transfer may be
carried out with vacuum assistance to ensure conformation of the
wet tissue web 15 to the topography of the throughdrying fabric
19.
[0049] While supported by the throughdrying fabric 19, the wet
tissue web 15 is dried to a final consistency of about 94 percent
or greater by a throughdryer 21 and is thereafter transferred to a
carrier fabric 22. Alternatively, the drying process can be any
noncompressive drying method that tends to preserve the bulk of the
wet tissue web 15.
[0050] The dried tissue web 23 is transported to a reel 24 using a
carrier fabric 22 and an optional carrier fabric 25. An optional
pressurized turning roll 26 can be used to facilitate transfer of
the dried tissue web 23 from the carrier fabric 22 to the carrier
fabric 25. If desired, the dried tissue web 23 may additionally be
embossed to produce a pattern on the absorbent tissue product 27
produced using the throughdrying fabric 19 and a subsequent
embossing stage.
[0051] Once the wet tissue web 15 has been non-compressively dried,
thereby forming the dried tissue web 23, it is possible to crepe
the dried tissue web 23 by transferring the dried tissue web 23 to
a Yankee dryer prior to reeling, or using alternative
foreshortening methods such as microcreping as disclosed in U.S.
Pat. No. 4,919,877 issued on Apr. 24, 1990 to Parsons et al.
[0052] In an alternative embodiment not shown, the wet tissue web
15 may be transferred directly from the inner forming fabric 13 to
the throughdrying fabric 19 and the transfer fabric 17 eliminated.
The throughdrying fabric 19 may be traveling at a speed less than
the inner forming fabric 13 such that the wet tissue web 15 is rush
transferred, or, in the alternative, the throughdrying fabric 19
may be traveling at substantially the same speed as the inner
forming fabric 13. If the throughdrying fabric 19 is traveling at a
slower speed than the speed of the inner forming fabric 13, an
uncreped absorbent tissue product 27 is produced. Additional
foreshortening after the drying stage may be employed to improve
the MD stretch of the absorbent tissue product 27. Methods of
foreshortening the absorbent tissue product 27 include, by way of
illustration and without limitation, conventional Yankee dryer
creping, microcreping, or any other method known in the art.
[0053] Differential velocity transfer from one fabric to another
can follow the principles taught in any one of the following
patents, each of which is herein incorporated by reference to the
extent it is not contradictory herewith: U.S. Pat. No. 5,667,636,
issued on Sep. 16, 1997 to Engel et al.; U.S. Pat. No. 5,830,321,
issued on Nov. 3, 1998 to Lindsay et al.; U.S. Pat. No. 4,440,597,
issued on Apr. 3, 1984 to Wells et al.; U.S. Pat. No. 4,551,199,
issued on Nov. 5, 1985 to Weldon; and, U.S. Pat. No. 4,849,054,
issued on Jul. 18, 1989 to Klowak.
[0054] In yet another alternative embodiment of the present
invention, the inner forming fabric 13, the transfer fabric 17, and
the throughdrying fabric 19 can all be traveling at substantially
the same speed. Foreshortening may be employed to improve MD
stretch of the absorbent tissue product 27. Such methods include,
by way of illustration without limitation, conventional Yankee
dryer creping or microcreping.
[0055] Any known papermaking or tissue manufacturing method may be
used to create a web 23 using the non-woven tissue making fabrics
30 of the present invention. Though the non-woven tissue making
fabrics 30 of the present invention are especially useful as
transfer and through drying fabrics and can be used with any known
tissue making process that employs throughdrying, the non-woven
tissue making fabrics 30 of the present invention can also be used
in the formation of wet tissue webs 15 as forming fabrics, carrier
fabrics, drying fabrics, imprinting fabrics, and the like in any
known papermaking or tissue making process. Such methods can
include variations comprising any one or more of the following
steps in any feasible combination: [0056] wet tissue web formation
in a wet end in the form of a classical Fourdrinier, a gap former,
a twin-wire former, a crescent former, or any other known former
comprising any known headbox, including a stratified headbox for
bringing layers of two or more furnishes together into a single
tissue web, or a plurality of headboxes for forming a multi-layered
tissue web, using known wires and fabrics or the non-woven tissue
making fabrics 30 of the present invention; [0057] wet tissue web
formation or wet tissue web dewatering by foam-based processes,
such as processes wherein the fibers are entrained or suspended in
a foam prior to dewatering, or wherein foam is applied to an
embryonic wet tissue web prior to dewatering or drying, including
the methods disclosed in U.S. Pat. No. 5,178,729, issued on Jan.
12, 1993 to Janda, and U.S. Pat. No. 6,103,060, issued on Aug. 15,
2000 to Munerelle et al., both of which are herein incorporated by
reference to the extent they are not contradictory herewith; [0058]
differential basis weight formation by draining a slurry through a
forming fabric having high and low permeability regions, including
the non-woven tissue making fabrics 30 of the present invention or
any known forming fabric; [0059] rush transfer of a wet tissue web
from a first fabric to a second fabric moving at a slower velocity
than the first fabric, wherein the first fabric can be a forming
fabric, a transfer fabric, or a throughdrying fabric, and wherein
the second fabric can be a transfer fabric, a throughdrying fabric,
a second throughdrying fabric, or a carrier fabric disposed after a
throughdrying fabric (one exemplary rush transfer process is
disclosed in U.S. Pat. No. 4,440,597, issued on Apr. 3, 1984 to
Wells et al., herein incorporated by reference to the extent that
it is non-contradictory herewith), wherein the aforementioned
fabrics can be selected from any suitable fabrics known in the art
or the non-woven tissue making fabrics 30 of the present invention;
[0060] application of differential air pressure across the wet
tissue web to mold it into one or more of the fabrics on which the
wet tissue web rests, such as using a high vacuum pressure in a
vacuum transfer roll or transfer shoe to mold a wet tissue web into
a throughdrying fabric as it is transferred from a forming fabric
or intermediate carrier fabric, wherein the carrier fabric,
throughdrying fabric, or other fabrics can be selected from the
non-woven tissue making fabrics 30 of the present invention or
other fabrics known in the art; [0061] use of an air press or other
gaseous dewatering methods to increase the dryness of a tissue web
and/or to impart molding to the tissue web, as disclosed in U.S.
Pat. No. 6,096,169, issued on Aug. 1, 2000 to Hermans et al.; U.S.
Pat. No. 6,197,154, issued on Mar. 6, 2001 to Chen et al.; and,
U.S. Pat. No. 6,143,135, issued on Nov. 7, 2000 to Hada et al., all
of which are herein incorporated by reference to the extent they
are not contradictory herewith; [0062] drying the wet tissue web by
any compressive or noncompressive drying process, such as
throughdrying, drum drying, infrared drying, microwave drying, wet
pressing, impulse drying (e.g., the methods disclosed in U.S. Pat.
No. 5,353,521, issued on Oct. 11, 1994 to Orloff and U.S. Pat. No.
5,598,642, issued on Feb. 4, 1997 to Orloff et al.), high intensity
nip dewatering, displacement dewatering (see J. D. Lindsay,
"Displacement Dewatering To Maintain Bulk," Paperi Ja Puu, vol. 74,
No. 3, 1992, pp. 232-242), capillary dewatering (see any of U.S.
Pat. Nos. 5,598,643; 5,701,682; and 5,699,626, all of which issued
to Chuang et al.), steam drying, etc. [0063] printing, coating,
spraying, or otherwise transferring a chemical agent or compound on
one or more sides of the wet tissue web uniformly or
heterogeneously, as in a pattern, wherein any known agent or
compound useful for a web-based product can be used (e.g., a
softness agent such as a quaternary ammonium compound, a silicone
agent, an emollient, a skin-wellness agent such as aloe vera
extract, an antimicrobial agent such as citric acid, an
odor-control agent, a pH control agent, a sizing agent; a
polysaccharide derivative, a wet strength agent, a dye, a
fragrance, and the like), including the methods of U.S. Pat. No.
5,871,763, issued on Feb. 16, 1999 to Luu et al.; U.S. Pat. No.
5,716,692, issued on Feb. 10, 1998 to Warner et al.; U.S. Pat. No.
5,573,637, issued on Nov. 12, 1996 to Ampulski et al.; U.S. Pat.
No. 5,607,980, issued on Mar. 4, 1997 to McAtee et al.; U.S. Pat.
No. 5,614,293, issued on Mar. 25, 1997 to Krzysik et al.; U.S. Pat.
No. 5,643,588, issued on Jul. 1, 1997 to Roe et al.; U.S. Pat. No.
5,650,218, issued on Jul. 22, 1997 to Krzysik et al.; U.S. Pat. No.
5,990,377, issued on Nov. 23, 1999 to Chen et al.; and, U.S. Pat.
No. 5,227,242, issued on Jul. 13, 1993 to Walter et al., each of
which is herein incorporated by reference to the extent they are
not contradictory herewith; [0064] imprinting the wet tissue web on
a Yankee dryer or other solid surface, wherein the wet tissue web
resides on a fabric that can have deflection conduits (openings)
and elevated regions (including the fabrics of the present
invention), and the fabric is pressed against a surface such as the
surface of a Yankee dryer to transfer the wet tissue web from the
fabric to the surface of the Yankee dryer, thereby imparting
densification to portions of the wet tissue web that were in
contact with the elevated regions of the fabric, whereafter the
selectively densified dried tissue web can be creped from or
otherwise removed from the surface of the Yankee dryer; [0065]
creping the dried tissue web from a drum dryer, optionally after
application of a strength agent such as latex to one or more sides
of the tissue web, as exemplified by the methods disclosed in U.S.
Pat. No. 3,879,257, issued on Apr. 22, 1975 to Gentile et al.; U.S.
Pat. No. 5,885,418, issued on Mar. 23, 1999 to Anderson et al.;
U.S. Pat. No. 6,149,768, issued on Nov. 21, 2000 to Hepford, all of
which are herein incorporated by reference to the extent they are
not contradictory herewith; [0066] creping with serrated crepe
blades (e.g., see U.S. Pat. No. 5,885,416, issued on Mar. 23, 1999
to Marinack et al.) or any other known creping or foreshortening
method; and, [0067] converting the tissue web with known operations
such as calendering, embossing, slitting, printing, forming a
multiply structure having two, three, four, or more plies, putting
on a roll or in a box or adapting for other dispensing means,
packaging in any known form, and the like.
[0068] The present invention resides in a process for making tissue
wherein the fibrous tissue web, prior to complete drying,
transferred onto a non-woven tissue making fabric 30 comprising at
least one layer of a porous synthetic polymeric, ceramic, or
metallic non-woven material 31 in contact with the wet tissue web
15. An embodiment of such a non-woven tissue making fabric 30 is
shown in FIGS. 2A and 2B, showing a cross-section of a porous
non-woven tissue making fabric 30 with an embryonic wet tissue web
15 superposed thereon, such as a tissue web in the process of being
through-air dried on the three-dimensional non-woven tissue making
fabric 30 as depicted. As shown in FIG. 2A, the tissue making
fabric 30 comprises a ply of non-woven material 31. In FIG. 2B, the
non-woven tissue making fabric 30 comprises a first ply of
non-woven material 31a joined to an underlying second ply of
non-woven material 31b. Alternatively, the second ply 31b may be
replaced with a woven layer (not shown). Alternatively, the first
ply of non-woven material 31a may be replaced with a
three-dimensional woven layer which may comprise the tissue
contacting surface of the resulting tissue making fabric 30.
[0069] In other embodiments of the present invention (not shown),
the tissue making fabric 30 may comprise a ply of non-woven
material 31 and a ply of woven material. The non-woven tissue
making fabric 30 may comprise a first ply of woven material joined
to an underlying second ply of non-woven material 31b.
[0070] In FIG. 2C, a lower non-woven ply 31b has been provided with
elevated non-woven photocured deflection elements 33 defining an
upper layer 31a of non-woven material. The deflection elements 33
have openings 37 therebetween (deflection conduits) into which the
wet tissue web 15 may be deflected in the presence of an air
pressure differential or by pressing operations to create a
three-dimensional effect in the wet tissue web 15. The deflection
elements 33, as shown are asymmetrical, have a three-dimensional
topography (as opposed to flat or macroscopically monoplanar
deflection elements), according to the teachings in commonly owned
U.S. patent application Ser. No. 09/705,684, previously
incorporated by reference, but symmetrical deflection elements may
also be used. The deflection elements 33 may be part of a
continuous network or may be isolated islands of photocured resin.
The deflection elements 33 need not be impervious, but may comprise
a plurality of pores through which gas can flow. For example, the
deflection elements 33 may comprise an open-celled foam or other
porous material. The deflection elements 33 need not be photocured,
but may be cured by free radical polymerization, thermosetting,
electron beam curing, ultrasonic curing, and other methods known in
the art.
[0071] Regarding FIG. 2C, the three-dimensional features of the
non-woven tissue making fabric 30, in general may comprise
non-fibrous polymeric protrusions or an elevated polymeric network,
created by applying a layer of photocurable resin to a ply of
non-woven material 31b, then selectively photocuring portions of
the resin by application of actinic or other radiation through a
mask to create a pattern or network of cured resin, followed by
removal of uncured resin, to create a photocured layer attached to
an underlying layer or ply of material. Exemplary methods for such
processes are disclosed in U.S. Pat. No. 6,420,100, issued on Jul.
16, 2002 to Trokhan et al. and U.S. Pat. No. 5,817,377, issued on
Oct. 6, 1998 to Trokhan et al., both of which are herein
incorporated by reference to the extent that they are
non-contradictory herewith, as well as U.S. Pat. No. 4,514,345,
issued on Apr. 30, 1985 to Johnson et al. and U.S. Pat. No.
5,334,289, issued on Aug. 2, 1994 to Trokhan et al., both of which
were previously incorporated by reference. Further improvements in
these methods have been disclosed by Lindsay et al. in commonly
owned U.S. patent application Ser. No. 09/705,684, herein
incorporated by reference to the extent that it is
non-contradictory herewith.
[0072] The topography of the non-woven tissue making fabric 30 in
FIG. 2C illustrates a feature that is possible in many of the
embodiments of the present invention, namely, that the surface of
the non-woven tissue making fabric 30 need not be monoplanar, but
can have a complex topography with raised and depressed elements at
a variety of heights (e.g., raised elements at two or more heights
relative to the plane of an underlying layer). The wet tissue web
15 through-dried on such a non-woven tissue making fabric 30 may
have a complex topography as well, with an Overall Surface Depth of
about 0.2 mm or greater, more specifically about 0.3 mm or greater,
and most specifically about 0.4 mm or greater. "Overall Surface
Depth." described more fully hereafter, is a measure of the
topography of a surface, indicative of a characteristic height
different between elevated and depressed portions of the surface of
the non-woven tissue making fabric 30. The Overall Surface Depth of
non-apertured portions of the non-woven tissue making fabric 30 may
likewise be about 0.2 mm or greater, more specifically about 0.3 mm
or greater, and most specifically about 0.4 mm or greater. In some
embodiments, even greater ranges are possible, such as about 0.5 mm
or greater (e.g., from about 0.5 mm to about 3 mm or from about 0.5
mm to about 2 mm), more specifically about 0.8 mm or greater, and
most specifically about 1.5 mm or greater. The thickness of the
non-woven tissue making fabric 30 may be about 1 mm or greater,
more specifically about 3 mm or greater, most specifically about 6
mm or greater, and may be about 10 mm or less, about 7 mm or less,
or about 5 mm or less.
[0073] It is understood that in the structures shown in FIGS. 2A,
2B, and 2C, the tissue machine contacting surface 50 may have a
topography substantially independent of the topography of the
tissue contacting surface 51. The non-woven tissue making fabric 30
may have a relatively uniform basis weight; low density, high
caliper regions; high density, low caliper regions; high basis
weight regions alternating with low basis weight regions; and/or,
combinations thereof.
[0074] When the non-woven tissue making fabric 30 comprises more
than one layer, as it does in FIGS. 2B and 2C, each layer of
non-woven material 31a and 31b in the non-woven tissue making
fabric 30 (or the entire non-woven material 31 as depicted in FIG.
2A) may independently be in the form of fibrous mats or webs of
material, such as bonded carded webs, airlaid webs, scrim, needled
webs, extruded net-works, and the like, or foams, which may be open
cell or reticulated foams, as well as extruded foams, including
extruded polyurethane foams. Suitable polymers may comprise
polyester, polyurethane, vinyl, acrylic, polycarbonates, nylon,
polyamides (e.g., nylon 6, nylon 66, etc.), polyethylene,
polypropylene, polybutylene terephthalate (PBT), polyphenylsulfide
(PPS), Nomex.RTM. or Kevlar.RTM. (both manufactured by DuPont),
syndiotactic polystyrene, polyacrylonitrile, phenolic resins,
polyvinyl chloride, polymethacrylates, polymethacrylic acids,
polyether ether ketone (PEEK), and the like, as well as copolymers
and homopolymers thereof. Useful polymers may also include liquid
crystal polymers (e.g., polyesters) and other high-temperature
polymers and specialty polymers, such as those available from
Ticona Corp. (Summit, N.J.), including Vectra.TM.; Celanex.RTM. or
Vandar.RTM. thermoplastic polyester; Riteflex.RTM. thermoplastic
polyester elastomer; long fiber reinforced thermoplastics such as
Compel.RTM., Celstran.RTM., and Fiberod.RTM. products; Topas.RTM.
cyclic-olefin copolymer; Duracon.RTM., Celcon.RTM., and
Hostaform.RTM. acetal copolymers; Fortron.RTM. polyphenylene
sulfide; and, Duranex.TM. thermoplastic polyester (PBT). For
fibrous mats of material, the non-woven materials 31 may be either
the synthetic polymers mentioned above or optionally a bulky
ceramic material such as fiberglass or fibrous ceramic materials
commonly used as filters or insulating material, including alumina
or silicate structures produced by Thermal Ceramics, Inc. of
Augusta, Ga., in the form of wet laid or air laid fiber mats, or
may comprise composite fibers with mineral and synthetic
components, or carbon fibers.
[0075] The non-woven material 31 may be stable to temperatures at
or above about 110.degree. C., specifically at or above about
130.degree. C., more specifically at or above about 150.degree. C.,
more specifically at or above about 170.degree. C., and most
specifically at or above about 190.degree. C., in order to ensure a
suitable life-time under intense drying conditions. Commercial
polymeric fibers known for temperature resistance include
polyesters; aramids, such as Nomex.RTM. fibers, manufactured by
DuPont, Inc.; polyphenylsulfide; polyether ether ketone, PEEK such
as having a glass transition temperature of 142.degree. C. or
288.degree. F.; and, the like. For durability at elevated
temperatures, the glass transition temperature may be at or above
about 60.degree. C., such as about 80.degree. C. or greater,
specifically about 100.degree. C. or greater, more specifically
about 110.degree. C. or greater, and most specifically about
120.degree. C. or greater. Typically, the non-woven material 31 is
sufficiently gas permeable throughout the breadth of the substrate
such that no roughly circular region about 2.5 mm in diameter or
greater, specifically about 1.5 mm in diameter or greater, more
specifically about 0.9 mm in diameter or greater, and most
specifically about 0.5 mm in diameter or greater will be
substantially blocked from air flow under conditions of
differential air pressure across the substrate with a pressure
differential of about 0.1 psi or greater at a temperature of about
25.degree. C.
[0076] The non-woven material 31 depicted in FIG. 2A (or the plies
of non-woven materials 31a and 31b depicted in FIGS. 2B and 2C,
hereafter generally understood to be comprised by reference to the
non-woven material 31) may be reinforced by additional plies of
non-woven material, scrim material, woven webs, polymeric or
metallic filaments, and the like. Such reinforcing elements may be
away from the paper-contacting side of the non-woven tissue making
fabric, or do not form elevated regions that could affect the
topography of the tissue web produced thereon.
[0077] In some embodiments, the non-woven tissue making fabric 30
is free of woven components, or, more specifically, does not have a
ply or layer of woven polymeric filaments. In another embodiment,
the non-woven tissue making fabric 30 consists essentially of
non-woven materials 31 and means for binding the non-woven
materials 31 one to another. In other embodiments of the present
invention, the non-woven tissue making fabric 30 may comprise woven
components and/or photocured elements. The woven components and/or
photocured elements may comprise the tissue contacting surface 51
and/or the tissue machine contacting surface 50 and/or any portion
therebetween of the non-woven tissue making fabric 30.
[0078] The non-woven material 31 may be intrinsically gas permeable
to permit drying and molding of the wet tissue web 15 onto the
non-woven tissue making fabric 30 by air flow through the wet
tissue web 15 and the non-woven tissue making fabric 30. The
permeability and/or porosity of a non-woven tissue making fabric 30
may be increased, if desired, by any method known in the art. For
example, the non-woven material 31 may be provided with numerous
holes or apertures (not shown), or selected regions of the
non-woven tissue making fabric 30 may be thinned to decrease the
resistance to air flow offered by the non-woven material 31. Such
treatments can be applied before, after, or simultaneously with
bonding of adjacent fabric strips 34 of the non-woven material 31.
Specific operations for increasing the permeability of the
non-woven material 31 and/or the non-woven tissue making fabric 30
include hot-pin aperturing, perf-embossing, cutting, drilling,
debonding, needling, laser drilling, laser ablation,
hydroentangling or general impact with high velocity jets or
droplets of water or other liquids to rearrange fibers in the
non-woven material 31, mechanical abrasion, peening the non-woven
material 31 or impacting it with particles that pierce the
non-woven material 31 or cause the non-woven material 31 to be
relatively more open, and the like. Such non-woven material 31
and/or the non-woven tissue making fabric 30 may be manufactured
such that the non-woven tissue making fabric 30 results in a more
uniform drying rate and/or profile. In addition, the non-woven
material 31 and/or the non-woven tissue making fabric 30 may be
manufactured such that the non-woven tissue making fabric 30
provides more uniform air permeability characteristics.
[0079] Obviously, holes and apertures of various sizes may be
provided in the layer of the non-woven material 31, but if they are
used, the air pressure differential during transfer and through
drying should be low enough to prevent excessive puncturing of the
wet tissue web 15 over the apertures.
[0080] As used herein, the "Air Permeability" of the non-woven
tissue making fabric 30 or the non-woven material 31 may be
measured with the FX 3300 Air Permeability device manufactured by
Textest AG (Zurich, Switzerland), set to a pressure of 125 Pa with
the normal 7-cm diameter opening (38 square centimeters area),
which gives readings of Air Permeability in cubic feet per minute
(CFM) that are comparable to well-known Frazier Air Permeability
measurements. The Air Permeability value for the non-woven tissue
making fabric 30 or for the non-woven material 31 thereof (or any
non-woven ply of the non-woven tissue making fabric 30) may be
about 30 CFM or greater, such as any of the following values (about
or greater): 50 CFM, 70 CFM, 100 CFM, 150 CFM, 200 CFM, 250 CFM,
300 CFM, 350 CFM, 400 CFM, 450 CFM, 500 CFM, 550 CFM, 600 CFM, 650
CFM, 700 CFM, 750 CFM, 800 CFM, 900 CFM, 1000 CFM, and 1100 CFM.
Exemplary ranges include from about 200 CFM to about 1400 CFM, from
about 300 CFM to about 1200 CFM, and from about 100 CFM to about
800 CFM. For some applications, low Air Permeability may be
desirable. Thus, the Air Permeability of the non-woven tissue
making fabric 30 may be about 500 CFM or less, about 400 CFM or
less, about 300 CFM or less, or about 200 CFM or less, such as from
about 30 CFM to about 150 CFM, and from about 0 CFM to about 50
CFM. Substantially water impervious or substantially air impervious
non-woven tissue making fabrics 30 (or both air and liquid
impervious fabrics) are within the scope of the present invention
when no through-flow of fluid is needed.
[0081] The structure of the non-woven material 31 of the present
invention may provide for a faster throughdrying rate at a given
Air Permeability. Non-woven tissue making fabrics 30 may provide a
more uniform basis weight network of small diameter fibers, more
numerous, smaller orifices, and a higher fiber support tissue
contacting surface 51. There more numerous, smaller orifices are
anticipated to result in more numerous drying fronts in the wet
tissue web 15 during throughdrying. The higher fiber support tissue
contacting surface 51 is anticipated to result in fewer pinholes in
the wet tissue web 15 during molding and throughdrying. The
combination of more numerous drying fronts and fewer pinholes in
the wet tissue web 15 during throughdrying is anticipated to result
in a faster throughdrying rate at a given air permeability, or
require less air permeability than conventional woven fabrics for a
given throughdrying rate.
[0082] The non-woven material 31 may have sufficient resilience to
maintain a three-dimensional structure under vacuum or pneumatic
pressure levels typical of through drying or impingement drying.
However, the non-woven material 31 may also have a degree of
compressibility to permit deformation during mechanical loading or
shear such that highly elevated elements on the surface of the
non-woven material 31 or the resulting non-woven tissue making
fabric 30 may deform without causing damage to the wet tissue web
15 during contact with another surface, as occurs during typical
web transfer events, pressing events, watermarking, or transfer to
a can dryer. While non-compressive drying may be valuable in some
applications, compressive drying and pressing is also within the
scope of the present invention. Further, even in non-compressive
drying, it is recognized that somewhat compressive events may occur
prior to drying or during normal wet handling operations which may
have the effect of pressing or shearing a wet tissue web 15. During
such operations, a wet tissue web 15 on a highly contoured
substrate with high surface depth might suffer damage as only a
small fraction of the wet tissue web 15 at the most elevated points
might be required to bear the load, shear stress, or friction of
the operation. Compressible deflection elements 33 may also help
alleviate stress in the wet tissue web 15 during treatment by
differential air pressure as stressed regions of the non-woven
tissue making fabric 30 deform and distribute the stress to broader
regions of the non-woven tissue making fabric 30.
[0083] Low Pressure Compressive Compliance of a non-woven material
31 may be measured by compressing a substantially planar sample of
the non-woven material 31 having a basis weight above 50 gsm with a
weighted platen of 3-inches in diameter to impart mechanical loads
of 0.05 psi and then 0.2 psi, measuring the thickness of the sample
while under such compressive loads. Subtracting the ratio of
thickness at 0.2 psi to thickness at 0.05 psi from 1 yields the Low
Pressure Compressive Compliance, or Low Pressure Compressive
Compliance=1-(thickness at 0.2 psi/thickness at 0.05 psi). The Low
Pressure Compressive Compliance should be about 0.05 or greater,
specifically about 0.1 or greater, more specifically about 0.2 or
greater, still more specifically about 0.3 or greater, and most
specifically between about 0.2 and about 0.5.
[0084] High Pressure Compressive Compliance is measured using a
pressure range of 0.2 and 2.0 psi in making the determination of
compliance, otherwise performed as for Low Pressure Compressive
Compliance. In other words, High Pressure Compressive
Compliance=1-(thickness at 2.0 psi/thickness at 0.2 psi). The High
Pressure Compressive Compliance should be about 0.05 or greater,
specifically about 0.15 or greater, more specifically about 0.25 or
greater, still more specifically about 0.35 or greater, and most
specifically between about 0.1 and about 0.5.
[0085] A non-woven material 31 potentially suitable for the present
invention is the polyurethane foam applied to a papermaking fabric
as disclosed in U.S. Pat. No. 5,512,319, issued on Apr. 30, 1996 to
Cook et al., herein incorporated by reference to the extent that it
is non-contradictory herewith. Also of relevance to the present
invention are the related papermaking fabrics by Voith Fabircs
(Appleton, Wis.), sold under the trade names "SPECTRA" and
"Olympus." The SPECTRA fabrics incorporate a polyurethane membrane
on an underlying woven papermaking fabric or batt. Alternatively,
related fabrics may consist entirely of extruded material. The
sales literature on these composite fabrics shows the network to be
largely planar with holes or apertures imparted by the extrusion
process. However, the manufacturing process could be modified to
create a more contoured, three-dimensional surface of varying
height more suitable for the non-woven tissue making fabrics 30 of
the present invention.
[0086] Also of potential use is the "Ribbed Spectra" design
comprising two polyurethane regions of differing height. Such
engineered fabrics have the potential to allow a wide range of
three-dimensional structures to be achieved in a papermaking
fabric. These fabrics are sold for use in pressing and forming, but
for the present invention could be adapted for through drying. The
technology may be limited to producing several discrete planar
regions which differ in height. More three-dimensional or textured
variations of the SPECTRA structures may be obtained by regulating
the amount of resin applied to various regions of the composite
fabric to yield a heterogeneous basis weight distribution to
provide regions of varying height. Another method is carving or
further shaping an existing composite fabric before or after
hardening of the resin. For example, the structures can be modified
by pressing against another textured surface before full hardening,
or by selective abrasion, sanding, laser drilling, or other forms
of mechanical removal of portions of the structure before or after
hardening.
[0087] Several general methods may be applied to create
three-dimensional non-woven tissue making fabrics 30 such as those
of FIGS. 2A-2C. Photocuring of resins on a substrate has been
previously discussed. In other embodiments, if a layer of the
non-woven material 31 is attached to an woven underlying porous
member 32 (not shown), the three-dimensional shaping of the layer
(or layers) of non-woven material 31 may be carried out before or
after attachment to the woven underlying porous member 32. In
particular, the layer of non-woven material 31 may be given a
three-dimensional structure by establishment of a heterogeneous
basis weight distribution during forming or by post-processing
which adds or removes material from the non-woven material 31 at
desired locations. When additional material is added to a layer of
non-woven material 31, such as a relatively uniform or planar
layer, to thereby create a three-dimensional surface, the added
material may be of a composition or nature other than that used to
create the layer of non-woven material 31. Such composite
three-dimensional non-woven tissue making fabrics 30 are within the
scope of the present invention. For example, such a composite may
comprise a first layer of a synthetic fibrous mat of non-woven
material 31 in contact with an woven base fabric underlying porous
member 32, with a second layer of non-woven material 31 such as a
polyurethane foam or reticulated foam added to the exposed surface
of selected regions of said first layer of non-woven material 31.
The resulting composite non-woven tissue making fabric 30 may have
heterogeneous basis weight, density, and/or chemical
composition.
[0088] In another embodiment, a three-dimensional topography may be
imparted to an upper ply by adding material heterogeneously between
the upper ply and a neighboring lower ply (not shown) of the
non-woven material 31. For example, beads of adhesive, pieces of
foam, or cut pieces of non-woven material interposed between two
neighboring plies of the non-woven material 31 may impart a
three-dimensional structure to the upper ply.
[0089] There are several methods of producing fibers or filaments
that may be used in the non-woven material 31 of the non-woven
tissue making fabric 30 of the present invention; however, two
commonly used processes are known as spunbonding and meltblowing
and the resulting non-woven webs are known as spunbond and
meltblown webs, respectively. As used herein, polymeric fibers and
filaments are referred to generically as polymeric strands. In the
context of non-woven webs, the terms "filaments" refers to
continuous strands of material while the term "polymeric fibers"
refers to cut or discontinuous strands having a definite
length.
[0090] Generally described, the process for making spunbond
non-woven webs includes extruding thermoplastic material through a
spinneret and drawing the extruded material into filaments with a
stream of high-velocity air to form a random web on a collecting
surface. Such a method is referred to as meltspinning. Spunbond
processes are generally defined in numerous patents including, for
example, U.S. Pat. No. 3,692,618, issued on Sep. 19, 1972 to
Dorschner, et al.; U.S. Pat. No. 4,340,563, issued on Jul. 20, 1982
to Appel, et al.; U.S. Pat. No. 3,338,992, issued on Aug. 29, 1967
to Kinney; U.S. Pat. No. 3,341,394, issued on Sep. 12, 1967 to
Kinney; U.S. Pat. No. 3,502,538, issued on Mar. 24, 1970 to Levy;
U.S. Pat. No. 3,502,763, issued on Mar. 24, 1970 to Hartmann; U.S.
Pat. No. 3,542,615, issued on Nov. 24, 1970 to Dobo, et al.; and,
Canadian Patent No. 803,714, issued on Jan. 14, 1969 to Harmon.
[0091] On the other hand, meltblown non-woven webs are made by
extruding a thermoplastic material through one or more dies,
blowing a high-velocity stream of air past the extrusion dies to
generate an air-conveyed melt-blown fiber curtain and depositing
the curtain of fibers onto a collecting surface to form a random
non-woven web. Meltblowing processes are generally described
innumerous publications including, for example, an article titled
"Superfine Thermoplastic Fibers" by Wendt in Industrial and
Engineering Chemistry, Vol. 48, No. 8, (1956), at pp. 1342-1346,
which describes work done at the Naval Research Laboratories in
Washington, D.C.; Naval Research Laboratory Report 111437, dated
Apr. 15, 1954; U.S. Pat. No. 4,041,203, issued on Aug. 9, 1977 to
Brock et al.; U.S. Pat. No. 3,715,251, issued on Feb. 6, 1973 to
Prentice; U.S. Pat. No. 3,704,198, issued on Nov. 28, 1972 to
Prentice; U.S. Pat. No. 3,676,242, issued on Jul. 11, 1972 to
Prentice; and, U.S. Pat. No. 3,595,245, issued on Jul. 27, 1971 to
Buntin et al. as well as British Specification No. 1,217,892,
published on Dec. 31, 1970.
[0092] Spunbond and meltblown non-woven webs are usually
distinguished by the diameters and the molecular orientation of the
filaments or fibers which form the webs. The diameter of spunbond
and meltblown filaments or fibers is the average cross-sectional
dimension. Spunbond filaments or fibers typically have average
diameters of about 6 microns or greater and often have average
diameters in the range of about 15 to about 40 microns. Meltblown
fibers typically have average diameters of about 15 microns or less
and more specifically about 6 microns or less. However, because
larger meltblown fibers, having diameters of about 6 microns or
greater may also be produced, molecular orientation may be used to
distinguish spunbond and meltblown filaments and fibers of similar
diameters.
[0093] In the present invention, the average diameters of the
filaments or fibers may be about 20 microns or greater, more
specifically about 50 microns or greater, more specifically about
100 microns or greater, and most specifically about 300 microns or
greater. The average diameters of the filaments or fibers may range
from about 6 to about 700 microns, more specifically about 20 to
about 500 microns, more specifically about 30 to about 300 microns,
more specifically about 50 to about 200 microns, and most
specifically about 100 microns.
[0094] For a given fiber or filament size and polymer, the
molecular orientation of a spunbond fiber or filament is typically
greater than the molecular orientation of a meltblown fiber.
Relative molecular orientation of polymeric fibers or filaments can
be determined by measuring the tensile strength and birefringence
of fibers or filaments having the same diameter. Tensile strength
of fibers and filaments is a measure of the stress required to
stretch the fiber or filament until the fiber or filament breaks.
Birefringence numbers are calculated according to the method
described in the spring 1991 issue of INDA Journal of Nonwovens
Research, (Vol. 3, No. 2, p. 27). The tensile strength and
birefringence numbers of polymeric fibers and filaments vary
depending on the particular polymer and other factors; however, for
a given fiber or filament size and polymer, the tensile strength of
a spunbond fiber or filament is typically greater than the tensile
strength of a melt-blown fiber and the birefringence number of a
spun-bond fiber or filament is typically greater than the
birefringence number of a meltblown fiber.
[0095] If desired, the non-woven material 31 may comprise one or
more plies of a laminate material, such as
spunbonded/meltblown/spunbonded (SMS) laminate or a
spunbond/meltblown (SM) laminate. An SMS laminate may be made by
sequentially depositing onto a moving forming belt first a spunbond
web layer, then a meltblown web layer and last another spunbond
layer and then bonding the laminate in a manner described below.
Alternatively, the web layers may be made individually, collected
in rolls, and combined in a separate bonding step. SMS materials
are described in U.S. Pat. No. 4,041,203, issued on Aug. 9, 1977 to
Brock et al.; U.S. Pat. No. 5,464,688, issued on Nov. 7, 1995 to
Timmons, et al.; U.S. Pat. No. 4,374,888, issued on Feb. 22, 1983
to Bornslaeger; U.S. Pat. No. 5,169,706, issued on Dec. 8, 1992 to
Collier, et al.; and, U.S. Pat. No. 4,766,029, issued on Aug. 23,
1988 to Brock et al., all of which are herein incorporated by
reference to the extent that they are non-contradictory herewith.
For some non-woven tissue making fabrics 30 of the present
invention, the laminates should be made having higher melting point
polymers than those of conventional SMS materials, such as
polyphenylsulfide or other high-temperature polymers.
[0096] In an effort to produce non-woven webs for use as non-woven
materials 31 having desirable combinations of physical properties,
multi-component or bi-component non-woven webs have been developed.
Methods for making bi-component non-woven webs are well-known and
are disclosed in patents such as Reissue No. 30,955 of U.S. Pat.
No. 4,068,036, issued on Jan. 10, 1978 to Stanistreet; U.S. Pat.
No. 3,423,266, issued on Jan. 21, 1969 to Davies et al.; and, U.S.
Pat. No. 3,595,731, issued on Jul. 27, 1971 to Davies et al. A
bi-component non-woven web may be made from polymeric fibers or
filaments including first and second polymeric components which
remain distinct. As used herein, filaments mean continuous strands
of material and fibers mean cut or discontinuous strands having a
definite length. The first and second components of multi-component
filaments are arranged in substantially distinct zones across the
cross-section of the filaments and extend continuously along the
length of the filaments. Typically, one component exhibits
different properties than the other so that the filaments exhibit
properties of the two components. For example, one component may be
polypropylene which is relatively strong and the other component
maybe polyethylene which is relatively soft. The end result is a
strong yet soft non-woven web. Bi-component structures may be
selected depending on the needs of the layer of non-woven material
31 of the non-woven tissue making fabric 31 under consideration.
Concentric sheath-core cross-section filaments may be useful for
good strength properties, for example, while asymmertrical
sheath-core cross-section filaments or side-by-side cross-section
filaments can result in high-bulk non-wovens.
[0097] U.S. Pat. No. 3,423,266, issued on Jan. 21, 1969 to Davies
et al. and U.S. Pat. No. 3,595,731, issued on Jul. 27, 1971 to
Davies et al. disclose methods for melt spinning bi-component
filaments to form non-woven polymeric webs suitable for use as
non-woven material 31. The non-woven webs may be formed by cutting
the meltspun filaments into staple fibers and then forming a bonded
carded web or by laying the continuous bi-component filaments onto
a forming surface and thereafter bonding the non-woven web. To
increase the bulk of the bi-component non-woven webs, the
bi-component fibers or filaments are often crimped. As disclosed in
U.S. Pat. No. 3,595,731 and U.S. Pat. No. 3,423,266 (discussed
above), the bi-component filaments maybe mechanically crimped and
the resultant fibers formed into a non-woven web or, if the
appropriate polymers are used, a latent helical crimp, produced in
bi-component fibers or filaments may be activated by heat treatment
of the formed non-woven web. The heat treatment is used to activate
the helical crimp in the fibers or filaments after the fibers or
filaments have been formed into a non-woven web.
[0098] While many applications of the present invention may include
polymers capable of withstanding elevated temperatures, lower
temperature applications such as wet pressing fabrics and in some
cases, forming fabrics may also be contemplated. For such
applications, polymers with lower melting points or glass
transition temperatures (T.sub.G) can be useful. And in some
applications, improved processing of the non-woven material is
possible at lower T.sub.G. For example, the non-woven material may
comprise a polymer or polymer blend having a T.sub.G of about
60.degree. C. or less, specifically about 50.degree. C. or less,
more specifically about 45.degree. C. or less, and most
specifically about 40.degree. C. or less.
[0099] The non-woven tissue making fabric 30 may be further
provided with wear-resistance elements (not shown) on the tissue
machine surface (opposing the tissue contacting surface) that may
be extruded polymeric beads, threads, bumps, berms, strips, and the
like. Raised elements may also be added to improve traction with
roll handling equipment. Similar elements may also be added to the
tissue contacting surface and/or interior of the non-woven tissue
making fabric 30.
[0100] FIG. 3 shows a schematic view of a method for manufacturing
a non-woven tissue making fabric 30. One embodiment of the method
uses an apparatus 40 comprising a first roll 42 and a second roll
44, which are parallel to each other and which may be rotated in
the direction indicated by the arrows. A carrier fabric 41 loops
around the two rolls 42 and 44, providing a moving surface onto
which a fabric strip 34 of the non-woven material 31 may be
disposed as it is unwound from a stock roll 46. The fabric strip 34
travels with the carrier fabric 41 to pass around the first roll 42
and the second roll 44 in a continuous spiral.
[0101] The carrier fabric 41 may be a textured, woven fabric such
as a sculpted through-drying fabric disclosed in U.S. Pat. No.
6,017,417, issued on Jan. 25, 2000 to Wendt et al., previously
incorporated by reference, or other fabrics or textured belts known
in the art. In other embodiments of the present invention, a flat
woven or non-woven carrier fabric 41 may be incorporated into
tissue making fabric 30.
[0102] The process depicted in FIG. 3 is at an early stage in the
formation of the non-woven tissue making fabric 30. The initial
placement of the fabric strip 34 on the carrier fabric 41 forms the
leading edge 58 of the spirally wound fabric strip 34 in the
non-woven tissue making fabric 30. The non-woven material 31 on the
carrier fabric 41 immediately behind the leading edge 58 is part of
a first fabric turn 60a on the carrier fabric 41. The fabric strip
34, having made a complete revolution around the carrier fabric 41,
is shown in the beginnings of a second fabric turn 60b which
slightly overlaps the first fabric turn 60a. The overlapping
region, once bonded (binding means are not shown), forms a seam
48.
[0103] As the fabric strip 34 is disposed on the carrier fabric 41,
the fabric strip 34 may be held in place by the presence of a light
adhesive, pneumatic pressure (e.g., spaced apart vacuum boxes),
electrostatic charge, mechanical restraint, elevated temperature,
or other means.
[0104] According to embodiments wherein the carrier fabric 41 may
be porous and textured, the texture may be applied to the non-woven
material 31 through a combination of elevated temperature and/or
mechanical force to mold the non-woven material 31 against the
carrier fabric 41. According to embodiments of the present
invention wherein the carrier fabric 41 may be textured, the
texture may be applied to the non-woven material 31 through a
combination of elevated temperature and mechanical force to mold
the non-woven material 31 against the carrier fabric 41. The
mechanical force may be a nip, such as a soft thick nip for a
textured carrier fabric, or web tension around a curved surface.
Elevated temperature may be provided by passing hot air through the
wet tissue web 15 and the carrier fabric. Impingement and/or
radiant heating may be used, even if the web of material 31 is
impermeable.
[0105] In alternative embodiments of the present invention, the
carrier fabric 41 may be replaced with a draw between the first
roll 42 and the stock roll 46. The fabric strip 34 may then be
bonded to the first fabric turn 60a. The binding step may occur on
the first roll 42 to form the non-woven tissue making fabric 30.
Tension may be applied between the first roll 42 and the stock roll
46, thereby providing a mechanical force to hold the fabric strip
34 during binding. The first roll 42 may be replaced with a vacuum
transfer roll or other device that may increase the holding force
during binding of the fabric strip 34 to the first fabric turn
60a.
[0106] As the fabric strip 34 is held in contact to the first
fabric turn 60a on the first roll 42, the fabric strip 34 may be
held in place by the presence of a light adhesive, pneumatic
pressure (e.g., spaced apart vacuum boxes), electrostatic charge,
mechanical restraint, elevated temperature, or other means.
[0107] The first roll 42 and the second roll 44 are separated by a
distance D, such that the resulting endless non-woven tissue making
fabric 30 is of the desired length, being measured in the machine
direction 52 about the endless-loop of the non-woven tissue making
fabric 30. (Also shown are the cross-direction 53 and the
z-direction 55.) The width of the non-woven fabric strip 34 of the
non-woven material 31 may be varied to reflect desired seam
strength, ease of handling during manufacture, and trim waste
values.
[0108] The non-woven fabric strip 34 of the non-woven material 31
may have a width ranging between about 1 inch and about 600 inches;
between about 1 inch and about 300 inches; between about 2 inches
and about 100 inches; between about 2 inches and about 50 inches;
and, between about 3 inches and about 20 inches, or may have a
width of about 12 inches or less, or a width of about 6 inches or
less. In some embodiments of the present invention, the non-woven
fabric strip 34 of the non-woven material 31 may have a width
ranging between about 30 to about 100 inches. The fabric strip 34
of the non-woven material 31 has a first edge 36 and an opposing
second edge 38. The fabric strip 34 is spirally wound onto the
first and second rolls 42 and 44, respectively, in a plurality of
revolutions of the stock roll 46. The resulting non-woven tissue
making fabric 30 may have a continuous spiral seam 48 that passes
around the endless loop comprising the non-woven tissue making
fabric 30 a plurality of times. As will be seen, other seam
configurations are possible, including multiple discrete seams in
the machine direction, cross-direction, or other direction.
[0109] As the fabric strip 34 is wound around the carrier fabric
41, overlapping sections (turns, in this case) of the fabric strip
34 may be lightly tacked together with adhesive or other means
until subsequent bonding and optional molding steps occur. In one
embodiment, the tacked-together embryonic non-woven tissue making
fabric 30 is subjected to thermal bonding with heated air, infrared
radiation, a heated nip, or other means, followed by optional
molding. In another embodiment, molding and bonding take place
simultaneously. For example, the embryonic non-woven tissue making
fabric 30 may be passed through a heated nip between opposing
intermeshing textured rolls to thermally bond and mold the
embryonic non-woven tissue making fabric 30 into a macroscopic
three-dimensional texture suitable for through-air drying or other
operations. Bonding can be done after the embryonic non-woven
tissue making fabric 30 is removed from the carrier fabric 41, or
while it remains thereon.
[0110] Successive turns of the fabric strip 34 of the non-woven
material 31 are disposed relative to one another in an overlapping
manner as illustrated hereafter, for example, in FIG. 8a, and are
bonded to one another along a spirally continuous seam 48 thereby
producing a non-woven tissue making fabric 30. It is understood
that the bonding of the spiral seam 48 (or any other seam of the
present invention) may be accomplished by any known method in the
art. Such methods may include refastenable and non-refastenable
methods. (See the discussion above). When the desired number of
turns of the fabric strip 34 of the non-woven material 31 has been
made to produce the desired width (W) of the non-woven tissue
making fabric 30 as measured in the cross-machine direction of the
nonwoven tissue making fabric 30, the spiral winding is concluded.
The non-woven tissue making fabric 30 may have a W ranging between
about 12 inches and about 500 inches; between about 50 inches and
about 300 inches; between about 100 inches and about 250 inches;
between about 120 inches and about 250 inches; and, about 200
inches.
[0111] According to one embodiment of the present invention, the
fabric strip 34 of the non-woven material 31 is spirally wound in a
plurality of contiguous turns such that the first edge 36 of the
fabric strip 34 of the non-woven material 31 in one turn extends
beyond the second edge 38 of the fabric strip 34 of the non-woven
material 31 of an adjacent (the previous) turn of the fabric strip
34 of the non-woven material 31. The over-lapping of the first edge
36 of the fabric strip 34 of the non-woven material 31 over the
second edge 38 of the fabric strip 34 of the non-woven material 31
on a previous turn creates a spirally continuous seam 48 and an
endless non-woven tissue making fabric 30.
[0112] Upon completion of the spiral winding, the lateral edges of
the non-woven tissue making fabric 30 may not be parallel to the
machine direction 52 of the non-woven tissue making fabric 30. Such
lateral edges will need to be trimmed to produce the first and
second side edges 54 and 56 of the non-woven tissue making fabric
30 thereby establishing the non-woven tissue making fabric 30
having the desired width. The non-woven tissue making fabric 30
includes a machine direction 52, and a cross-machine direction
53.
[0113] In one embodiment, the strength of the non-woven tissue
making fabric 30 or fabric seams may be increased by adding a scrim
layer (not shown), such as a scrim layer sandwiched between two or
more plies of the non-woven material 31 or the non-woven tissue
making fabric 30. The scrim layer may be a rectangular grid, a
hexagonal network, or any other network providing good tensile
strength in at least one in-plane direction. The scrim layer may be
formed of one or more materials such as a synthetic polymer,
fiberglass, metal wires, a perforated film or foil, and the like.
Examples of scrim layers as a reinforcement for a nonwoven fabric
or film are disclosed in the following patents: U.S. Pat. No.
4,363,684, issued on Dec. 14, 1982 to Hay; U.S. Pat. No. 4,731,276,
issued on Mar. 15, 1988 to Manning et al.; U.S. Pat. No. 3,597,299,
to Thomas et al.; and, U.S. Pat. No. 5,139,841, issued on Aug. 18,
1992 to Makoui et al., all of which are herein incorporated by
reference to the extent that they are non-contradictory herewith.
The scrim could be a highly open rectilinear grid of a polymeric
material. Further examples of scrim suitable for reinforcing the
non-woven tissue making fabric 30 of the present invention are
disclosed in U.S. Pat. No. 4,522,863, issued on Jun. 11, 1985 to
Keck et al.; U.S. Pat. No. 4,737,393, issued on Apr. 12, 1988 to
Linkous; and, U.S. Pat. No. 5,038,775, issued on Aug. 13, 1991 to
Maruscak et al., all of which are herein incorporated by reference
to the extent that they are non-contradictory herewith. Production
methods may also comprise the use of rotating nozzles to produce
rectilinear threads of polymer. It is understood that scrim may
also be used to add texture to the non-woven tissue making fabric
30. Scrim may also be added to the non-woven tissue making fabric
30 to provide or enhance wear resistance of the non-woven tissue
making fabric 30. Scrim may be added to the tissue contacting
surface 51, the tissue machine contacting surface 50, and/or the
interior of the non-woven tissue making fabric 30.
[0114] Seams 48 may be reinforced with adhesive, sewn thread,
ultrasonic welding, extra layers of material, an added scrim layer,
and any other means known in the art. The nonwoven tissue making
fabric 30 of the present invention may have a machine direction
seam strength of about 100 pli (pounds per linear inch) or more,
meaning that an in-plane machine direction tensile force of at
least about 200 pounds per linear inch can be applied to a seam 48
(or to any portion of the non-woven tissue making fabric 30, if
there is no seam 48 in the machine direction) without causing
failure. More specifically, the non-woven tissue making fabric 30
may have a seam strength and/or belt strength of about 150 pli or
greater, more specifically still about 200 pli or greater, more
specifically still about 250 pli or greater, and most specifically
about 350 pli or greater. Typical fabric tensions encountered by
the non-woven tissue making fabric 30 during operation may be from
about 2 pli to about 90 pli, specifically from about 5 pli to about
60 pli, more specifically from about 5 pli to about 25 pli, and
most specifically from about 5 pli to about 15 pli, though
operation outside these limits is not necessarily outside the scope
of the present invention.
[0115] While high seam strengths are sometimes desirable, they are
not necessary for all applications. Further, a spirally continuous
seam 48 or other seams 48 of the present invention generally need
not withstand the full machine direction tension normally present
during use of the non-woven tissue making fabric 30, because the
seams 48 in many embodiments of the present invention are not
aligned with the cross-direction, as is often the case in
conventional tissue machine fabrics, but rather at an angle to the
cross-direction and may even be substantially aligned with the
machine direction. Thus, the requirements for seam strength may be
substantially mitigated due to the favorable geometry achieved in
many embodiments of the non-woven tissue making fabric 30 of the
present invention. In many such embodiments, good results may be
obtained with seams 48 constructed to withstand forces normal to
the seam 48 from about 2 to about 30 pli, more specifically from
about 8 to about 25 pli, and most specifically from about 10 to
about 20 pli.
[0116] Any known method may be used to control the position of a
fabric strip 34 as it is laid down to form a non-woven tissue
making fabric 30 according to the present invention. Illustrative
tools for this purpose are disclosed in U.S. Pat. No. 4,962,576,
issued on Oct. 16, 1990 to Minichshofer et al., herein incorporated
by reference to the extent that it is non-contradictory herewith,
which treats a system for joining a nonwoven fabric to a woven
carrier. Such a system may be adapted such that a nonwoven web is
joined to a nonwoven carrier for the purposes of the present
invention. Minichshofer et al. employs a web guide in cooperative
association with a needling system. Many other systems may be used
in the present invention, such as image analysis systems or other
optical systems coupled with standard web guide devices to track
and control the location of the fabric strips 34, coupled with
mechanical actuators to ensure the fabric strip 34 is placed
correctly as the non-woven tissue making fabric 30 is formed. In
another embodiment of the present invention, the first roll 42 and
the second roll 44 are substantially parallel. Tension may be
applied on the fabric strip 34 between the first and second rolls
42 and 44. The first and second rolls 42 and 44 may rotate at the
same speed. With the application of a worm gear coupled to the
rolls 42 and/or 44, the unwinding of the fabric strip 34 from the
stock roll 46 at a set angle to the machine direction 52 may be
affected.
[0117] The non-woven tissue making fabric 30 of the present
invention or the non-woven materials 31 used therefor may be
provided with texture by any known method. For example, portions of
an upper ply, layer, or stratum (in some cases, forming the tissue
contacting surface 51 or adjacent the tissue contacting surface 51
of the non-woven tissue making fabric 30) of the non-woven material
31 (or the non-woven tissue making fabric 30) may be selectively
removed to impart texture, using any known removal method such as
cutting, stamping, laser cutting, laser ablation, drilling, and the
like. Portions of the tissue contacting surface 51 of the non-woven
tissue making fabric 30 may also be selectively densified to create
texture using any known method such as embossing, stamping,
ultrasonic welding, thermal welding, hot pin aperturing, thermal
molding, and the like. Further, additional material can be
selectively added to regions of an otherwise planar non-woven
tissue making fabric 30 to impart elevated regions for an overall
three-dimensional topography. Such added material may comprise
non-woven material 31 such as that used for one or more plies of
the non-woven tissue making fabric 30, or other permeable material
such as a polymeric foam, or even regions of substantially
impermeable material. The added material may be attached by
adhesives, thermal welding, ultrasonic welding, needling, or any
other method known in the art. In a related embodiment, the added
material may be applied to the non-woven tissue making fabric 30 by
extruding the material on to the surface or by a printing
technique, such as a hot melt or non-pressure-sensitive adhesive
applied via ink jet printing, flexographic printing, and the
like.
[0118] In one embodiment, an array of spaced apart pins is
controlled by computer or other means such that selected pins
strike the non-woven tissue making fabric 30 to densify it or
aperture the non-woven tissue making fabric 30 in a pattern. The
pins may apply digitally controlled patterns to the non-woven
tissue making fabric 30 in a manner similar to the generation of
printed patterns using dot matrix printers, with the dots of the
dot matrix printer being analogous to the pins in the pin
array.
[0119] Thermoplastic non-woven material 31 may be provided with
texture by molding methods, in which the non-woven material 31 (or
the non-woven tissue making fabric 30) is elevated in temperature
as the non-woven material 31 is constrained to take a
three-dimensional shape by methods such as pressing the non-woven
material 31 between molding plates, applying an air pressure
differential to the non-woven material 31 as the non-woven material
31 rests on a three-dimensional surface such as the textured
through-drying fabrics disclosed in U.S. Pat. No. 6,017,417, issued
on Jan. 25, 2000 to Wendt et al., previously incorporated by
reference; the textured fabrics disclosed in commonly owned U.S.
patent application Ser. No. 09/705,684 by Lindsay et al.; the
fabrics disclosed in U.S. Pat. No. 5,167,771, issued on Dec. 1,
1992 to Sayers et al.; or, the fabrics disclosed in U.S. Pat. No.
4,740,409, issued on Apr. 26, 1988 to Lefkowitz, all of which are
herein incorporated by reference to the extent that they are
non-contradictory herewith.
[0120] In addition, texture may be provided to the thermoplastic
non-woven material 31 by placing the non-woven material 31 (or the
non-woven tissue making fabric 30) under tension, such as wrapping
the non-woven material 31 (or the non-woven tissue making fabric
30) about a roll (such as a first roll 42, a second roll 44. or a
stock roll 46). Heat may or may not be used in addition to the
tension.
[0121] The three-dimensional texture of the non-woven tissue making
fabric 30 may comprise a repeating pattern, such as any pattern
known in woven papermaking fabrics, photocured fabrics such as the
previously discussed imprinting fabrics, or other fabrics, with
exemplary repeating patterns including series of raised and
depressed elements defining a repeating unit cell, the unit cell
having a width of about any of the following values or greater: 3
millimeters (mm), 1 centimeter (cm), 5 cm, 10 cm, 20 cm, or
substantially the cross-machine direction width of the non-woven
tissue making fabric 30. The width of the unit cell may also be
adapted to the finished width of the non-woven tissue making fabric
30. The length of the unit cell may be about any of the following
values or greater: 3 millimeters (mm), 1 centimeter (cm), 5 cm, 10
cm, 20 cm, or about a percentage value of the machine direction
length of the non-woven tissue making fabric 30 selected from 1%,
5%, 10%, 20%, 30%, 50%, or 100%. The length of the unit cell may
also be adapted to the finished length of the non-woven tissue
making fabric 30. It is understood that wherein the length of the
unit cell is greater than the length of the non-woven tissue making
fabric 30, and/or the tissue making fabric length is not an integer
multiple of the unit cell length, there may be a discontinuity in
the repeating pattern. In one embodiment, the unit cell is as great
as or greater than either the machine direction length or the
cross-direction width or both of the non-woven tissue making fabric
30.
[0122] FIG. 4 depicts a molding section 59 in a process for making
a non-woven tissue making fabric 30, which is one embodiment for
joining two superposed layers 39a and 39b of non-woven material 31
together to form the non-woven tissue making fabric 30, and for
imparting texture to the non-woven tissue making fabric 30. Texture
may be imparted by molding the non-woven tissue making fabric 30
(most particularly the layer 39b of the non-woven material 31
adjacent the carrier fabric 41) against the underlying carrier
fabric 41, which may be a textured fabric with significant
three-dimensional topography. An air knife 62 above the non-woven
tissue making fabric 30 delivers heated air at an elevated pressure
(stagnation pressure greater than atmospheric pressure) as the
layers 39a and 39b of the non-woven material 31 and carrier fabric
41 travel in the machine direction 52. The heated air is pulled
through the non-woven tissue making fabric 30 and the carrier
fabric 41 with the optional assistance of a vacuum box 64 beneath
the carrier fabric 41. The air knife 62 may deliver air heated to a
sufficient temperature to soften thermoplastic material in one or
both of the layers 39a and 39b of the non-woven material 31,
permitting the layers 39a and 39b (most particularly the layer 39b)
to conform better to the carrier fabric 41 and to assume its shape
to a degree.
[0123] The non-woven tissue making fabric 30 has two surfaces, a
"tissue machine contacting surface" 50 (the surface generally
intended for contacting a tissue making machine during the tissue
making process), and a "tissue contacting surface" 51 (the surface
generally intended for contacting the tissue web during the tissue
making process). In the embodiment shown in FIG. 4, the tissue
contacting surface 51 of the non-woven tissue making fabric 30 is
substantially more textured (more highly molded) than the tissue
machine contacting surface 50, though in other embodiments, both
the tissue contacting and tissue machine contacting surfaces 50 and
51, respectively, could have a similar degree of texture, or the
tissue machine contacting surface 50 could be more highly textured.
It is understood that the tissue machine contacting surface 50 may
comprise the same or different pattern or texture than the tissue
contacting surface 51 of the non-woven tissue making fabric 30.
[0124] The presence of sheath-core binder materials in non-woven
materials 31 useful in the non-woven tissue making fabrics 30 may
be helpful in molding, for the fusion of the sheath at elevated
temperature followed by cooling of the non-woven material 31
results in fusion of the thermoplastic material of the sheath to
better lock the molded structure in place. Likewise, a first
portion of fibers in the non-woven material 31 may be thermoplastic
with a lower melting point than a second portion of fibers in the
non-woven material 31, such that the first portion of fibers may
more easily melt and fuse the second portion of fibers together in
the molded shape.
[0125] The molding section 59 may be installed in the apparatus 40
of FIG. 3, and may comprise an air knife of approximately the same
width as the fabric strip 34, adapted to move in the
cross-direction 53 to bond successive turns of the fabric strip 34
of non-woven material 31 to the underlying fabric strip 34 of the
non-woven material 31 from the previous turn. The air knife may be
of a width less than about the width of the fabric strip 34, a
width about the same as the width of the fabric strip 34, or
greater than the width of the fabric strip 34. The air knife may be
of a width less than about the width of the finished non-woven
tissue making fabric 30, a width about the same as the width of the
finished non-woven tissue making fabric 30, or greater than the
width of the finished non-woven tissue making fabric 30. In some
embodiments of the present invention, the width of the fabric strip
34 may be the width of the finished non-woven tissue making fabric
30 or the width of the apparatus on which the non-woven tissue
making fabric 30 is manufactured on.
[0126] Other principles for molding a web against a molding
substrate are disclosed by Chen et al. in commonly owned
application U.S. patent application Ser. No. 09/680,719, filed on
Oct. 6, 2000 by Chen et al., herein incorporated by reference to
the extent that it is non-contradictory herewith.
[0127] In another embodiment, the non-woven tissue making fabric 30
is not separated from the carrier fabric 41, but remains in contact
with and preferably is bonded to the carrier fabric 41, such that
the carrier fabric 41 becomes an integral part of the non-woven
tissue making fabric 30, serving, for example, as a strength layer,
wear-resistant layer, and/or texture layer in one or both of the
tissue contacting surface 51 and the tissue machine contacting
surface 50 of the non-woven tissue making fabric 30.
[0128] In another embodiment (not shown), the carrier fabric 41 may
be used to receive nonwoven fibers as they are produced in a
meltblown, spunbond, or other process, such that the non-woven
material 31 is formed directly on a three-dimensional carrier
fabric 41 to directly impart a three-dimensional structure to the
non-woven material 31.
[0129] FIG. 5 depicts another embodiment of a molding section in
which a two-ply non-woven tissue making fabric 30 passes over a
rotating molding device 92 provided with raised molding elements 94
on the surface. The molding elements 94 as depicted are porous,
comprising a material such as sintered metal, sintered ceramic,
ceramic foam, or a finely drilled metal or plastic, allowing heated
air to pass from an air knife 62 or other source, through the
non-woven tissue making fabric 30 and into the rotating molding
device 92 and to a vacuum source 96. Heated air from the air knife
62 allows thermoplastic material in at least one of the plies of
non-woven material 31a and 31b to be thermally molded to conform at
least in part to the surface of the rotating molding device 92. The
molding elements 94 may be any shape, such as sine waves, triangles
(as shown), square waves, irregular shapes, or other shapes. The
rotating molding device 92 may be constructed as a suction roll to
allow a narrow zone of vacuum to be applied to a fixed region as
the roll rotates. The surface of the non-woven tissue making fabric
30 becomes substantially textured after contact with the rotating
molding device 92, which may also be heated. The surface of the
rotating device 92 may comprise discrete elements and/or may
comprise a continuous shell. It is understood that the surface or
shell of the rotating molding device 92 comprises a negative image
of the desired shape or pattern of the tissue contacting surface 51
of the resulting non-woven tissue making fabric 30. In addition,
the negative image on the surface of the rotating molding device 92
of the desired shape or pattern for the tissue contacting surface
51 of the non-woven tissue making fabric 30 may be adapted to vary
the depth or intensity of the pattern on the tissue contacting
surface 51 of the non-woven tissue making fabric 30. The pattern
may be a continuous curvilinear, discrete elements, or a
combination of both types.
[0130] It is understood that when a 2-ply non-woven tissue making
fabric 30 is discussed herein, that such discussion may be applied
to non-woven tissue making fabrics 30 comprising 2 or more plies.
The non-woven tissue making fabric 30 may comprise about 1 ply or
more. In other embodiments, the non-woven tissue making fabric 30
may comprise between about 1 ply and about 25 plies, more
specifically between about 1 ply and about 10 plies.
[0131] FIG. 6 depicts yet another embodiment of a molding section
in which a two-ply non-woven tissue making fabric 30 passes over a
rotating molding device 92 provided with raised molding elements 94
on the surface, similar to that shown in FIG. 5, but wherein the
air is supplied from a pressurized source 98 connected to a
rotating gas-pervious roll 100 through which the pressurized gas
passes into a nip 102 between the rotating gas-pervious roll 100
and the counter-rotating molding device 92. Both the rotating
gas-pervious roll 100 and the counter-rotating molding device 92
may be constructed as a suction roll to allow a narrow zone of
vacuum to be applied to a fixed region as the gas-pervious roll 100
rotates. In the nip 102, heated air passes through the non-woven
tissue making fabric 30 and mechanical pressure further conforms
the non-woven tissue making fabric 30 to the shape of the rotating
molding device 92 to improve the degree of texture imparted to the
non-woven tissue making fabric 30. A one-sided texture is shown,
but both sides of the non-woven tissue making fabric 30 may become
molded. Enhanced two-sided molding may be achieved by using a
textured rotating gas-pervious roll 100 with a texture that may be
essentially a mirror image of the texture of the rotating molding
device 92 to permit intermeshing of the textured surfaces of the
rotating molding device 92 and the gas-pervious roll 100 in the nip
102. In an alternate embodiment, a gas pervious roll 100 may be
fitted with a suitably textured surface to impart a texture to the
tissue machine contacting surface 51 which is substantially
independent of the texture on the tissue contacting surface 50 of
the non-woven tissue making fabric 30.
[0132] FIG. 7 depicts a top view of a portion of a non-woven tissue
making fabric 30 according to the present invention. A plurality of
fabric strips 34a-34e, are shown, substantially aligned with the
machine direction 52 of the non-woven tissue making fabric 30. Each
of the fabric strips 34b 34e overlaps a portion of the adjacent
fabric strips 34a 34d, respectively, defining regions of overlap
that are bonded to form seams 48a-48d. Each fabric strip 34a-34e
has a first edge 36a-36e, respectively, and a second edge 38a-38e,
respectively. The non-woven tissue making fabric 30 itself has a
first side edge 54 and a second side edge 56. The seams 48a-48d may
be spirally continuous, or may comprise a plurality of
substantially parallel, discrete seams 48 formed by joining a
plurality of discrete fabric strips 34 (which may be discrete
continuous loops).
[0133] The width "O" of the overlap region is a fraction of the
fabric strip width "S". The degree of overlap of the fabric strip
34 is the ratio O/S, which may vary from about 0 (abutting fabric
strips 34 or sections of non-woven material 31) to about 1
(multiple plies of non-woven material 31 that are coextensive, at
least in one dimension), or any value in between. For example, the
degree of overlap may range from about 0 to any integral multiple
of about 0.02 less than or equal to about 1.0 (e.g., from about 0
to about 0.64), or may range from any multiple of about 0.02 less
than or equal to about 0.98 to a maximum value of about 1 (e.g.,
from about 0.64 to about 1), or may cover any subset of such ranges
such as from about 0.06 to about 0.7, or from about 0.1 to about
0.5, or from about 0.1 to about 0.48. For example, the degree of
overlap may be about 1 or less than about 1. In another embodiment,
the degree of overlap may be about 0.66. In yet another embodiment
of the present invention, the degree of overlap may be about
0.90.
[0134] FIGS. 8A and 8B depict alternate embodiments in which a
fabric strip 34 is wound in a plurality of turns to form a
non-woven tissue making fabric 30, but wherein the fabric strip 34
is aligned at an acute angle substantially away from the machine
direction 52 of the non-woven tissue making fabric 30. In the
embodiment shown in FIG. 8A, a fabric strip 34 having a width is
folded back upon itself repeatedly in what may be termed a
"flattened helix." The first and second side edges 54 and 56 of the
non-woven tissue making fabric 30 coincide with the folds of the
fabric strip 34. A first section of the fabric strip 34a has a
longitudinal axis at a first angle 86 relative to the machine
direction 52 and reverses upon itself at a first fold 37a,
continuing in a second section of the fabric strip 34b with its
longitudinal axis at a second angle 88 relative to the machine
direction 52, which then reverses upon itself at a second fold 37b,
and so forth. The first edge 36b of the second section of the
fabric strip 34b resides beneath the first section of the fabric
strip 34a. The first edge 36c of the third section of the fabric
strip 34c abuts the second edge 38a of the first section of the
fabric strip 34b, and so forth. (In an alternate embodiment (not
shown), the first edge 36c of the third section of the fabric strip
34c overlaps the second edge 38a of the first section of the fabric
strip 34b, and so forth.)
[0135] The flattened helix structure of the non-woven tissue making
fabric 30 provides a ply having two layers throughout the non-woven
tissue making fabric 30. The abutting edges 36 and 38 of adjacent
sections of the fabric strip 34 in a given layer define a spirally
continuous seam 48 having a flattened helical form, with two sets
of parallel regions at a first angle 86 and a second angle 88,
respectively. (Other embodiments lacking the flattened helical
structure may have seams 48 that are substantially parallel
throughout the non-woven tissue making fabric 30, including seams
48 substantially aligned with or at an acute angle to the machine
direction 52, or may also have a plurality of seams 48 aligned with
a plurality of angles.)
[0136] The overlapping layers of the non-woven tissue making fabric
30 formed from the fabric strips 34 may be bonded together
throughout the non-woven tissue making fabric 30 or primarily along
the seam 48. Reinforcing layers may be added, as desired.
[0137] In general, a single fabric strip 34 may provide more than
one parallel section 34a and 34c, as can occur when a fabric strip
34 is folded back upon itself as shown in FIG. 8A or when a fabric
strip 34 has a complex shape such as a zig-zags shape, as discussed
hereafter in connection with FIG. 11. If a fabric strip 34 has a
simple linear shape (e.g., an elongated rectangle), then the fabric
strips 34 and sections of the fabric strips 34 are synonymous,
otherwise a section such as the first section of the fabric strip
34a may be a subset of a fabric strip 34.
[0138] FIG. 8B depicts a non-woven tissue making fabric 30 similar
to that of FIG. 8A but with reinforcing strips 90a and 90b added
along the first and second side edges 54 and 56 of the non-woven
tissue making fabric 30, between the two overlapping plies at the
internal portion of the folds 37a and 37b, etc. The reinforcing
strips 90a and 90b may be non-woven material, ropes, metal wires,
fiberglass-reinforced bands, a polymeric film, and the like, and
may be joined by adhesive means, thermal bonding, ultrasonic
bonding, or any other known means.
[0139] FIG. 9 depicts a non-woven tissue making fabric 30
comprising a plurality of discrete fabric strips 34 having a strip
width "S". The fabric strips 34a-34e (the 5 exemplary fabric strips
34 are numbered) lie at an acute angle 86 to the machine direction
52 of the non-woven tissue making fabric 30. Further, each fabric
strip 34a-34e overlaps about 50% of the "S" width of each
neighboring fabric strip 34a-34e (the degree of overlap in this
example would be about 0.5), such that the non-woven tissue making
fabric 30 has a basis weight equal to approximately twice the basis
weight of an individual fabric strip 34a-34e.
[0140] The non-woven tissue making fabric 30 has a tissue machine
contacting surface 50 and a tissue contacting surface 51, which in
the embodiment shown, may have substantially the same topography,
unless the individual fabric strips 34 have a two-sided texture
(wherein one side is more textured than the other side). The fabric
strips 34 need not all be comprised of the same non-woven material
31, but may be taken from a plurality of non-woven materials 31.
For example, the fabric strips 34 may alternate between a first and
second non-woven material 31. Additional material (not shown) may
be added at the first and second side edges 54 and 56 to further
reinforce the non-woven tissue making fabric 30.
[0141] In other embodiments (not shown), the discrete fabric strips
34 may have a variety of widths, such as fabric strips 34 selected
from two or more widths "S". In another embodiment (not shown), the
width of the fabric strips 34 varies with position, such as where
the fabric strips 34 have sinusoidal edges that periodically
increase and decrease the width of the fabric strip 34.
[0142] FIG. 10 shows a non-woven tissue making fabric 30 having a
plurality of fabric strips 34 that are interwoven to form an
interwoven non-woven tissue making fabric 30. The piece of the
non-woven tissue making fabric 30 shown has interwoven fabric
strips 34 comprising a first group 35 of parallel strips 34a-34e
aligned in a first direction 87 at an acute angle 88 with the
machine direction 52, and a second group 35' of parallel fabric
strips 34a'-34e' aligned in a second direction 85 at an acute angle
86 with the machine direction 52, and interwoven such that any
fabric strip 34 successively passes over and under other fabric
strips 34 in the non-woven tissue making fabric 30. While the
interwoven arrangement of fabric strips 34 may provide an
interlocking structure, the fabric strips 34 may be bonded together
in regions where one fabric strip 34 is above or below another
fabric strip 34, or along the first and second edges 36 and 38 of
adjoining parallel fabric strips 34, or both, to increase the
mechanical stability and durability of the non-woven tissue making
fabric 30.
[0143] FIG. 11 depicts another interlocking non-woven tissue making
fabric 30 comprising interlocking fabric strips 34, wherein at
least one fabric strip 34 is a non-straight strip comprising at
least two portions 45 and 45' wherein the first portion 45 is
aligned with a first direction 85 at an acute angle 86 with the
machine direction 52, and the second portion 45' is aligned with a
second direction 87 at an acute angle 88 with the machine direction
52. Within a transition region 49, the first portion 45 is joined
with the second portion 45'. The transition region 49 may be a
simple elbow as depicted, or may be curved or any other suitable
shape. The first and second portions 45 and 45' need not be linear
but may be sinusoidal or have other shapes while extending
substantially in the first and second directions 85 and 87,
respectively. As depicted, three non-straight fabric strips 34a-34c
are shown, each with linear first and second portions 45 and 45'.
The non-straight fabric strips 34a-34c are interwoven such that the
fabric strips 34 successively pass over and under each other in the
non-woven tissue making fabric 30. While the interwoven arrangement
of fabric strips 34 may provide an interlocking structure, the
fabric strips 34 may further be bonded together in regions where
one fabric strip 34 is above or below another fabric strip 34, or
along the first and second edges 36 and 38 of adjoining parallel
portions 45 and 45', or both, to increase the mechanical stability
and durability of the non-woven tissue making fabric 30.
[0144] More complex weave patterns may be contemplated other than
the simple ones shown in FIGS. 10 and 11.
[0145] FIG. 12, which is a variation of the embodiment shown in
FIG. 7, depicts a portion of another embodiment of a non-woven
tissue making fabric 30 according to the present invention, formed
into an endless loop, in which discrete parallel fabric strips 34
of non-woven material 31 have first ends 80 and second ends 82 that
are joined together to form a traverse fabric seam 84, while the
first and second edges 36 and 38 of the fabric strips 34 are joined
(shown here as overlapping) to form a longitudinal seam 48. Shown
are five fabric strips 34a-34e, each with respective first ends
80a-80e and second ends 82a-82e that are brought together to form
the fabric seam 84 comprising staggered portions of the fabric seam
84a-84e. The first and second ends 80a-80e and 82a-82e,
respectively, maybe fastened in a longitudinally overlapping or
abutting fashion (an abutting fashion is depicted) and bonded
together by any means known in the art as discussed herein to form
the fabric seam 84 as were discussed in the formation of the seam
48. The fabric seam 84 may be in a straight line or may be in a
staggered line, as shown, in the cross-machine direction.
[0146] The first and second ends 80 and 82 of the fabric strips 34
are shown to be straight cross-directional cuts, but this need not
be the case in other embodiments. The first and second ends 80 and
82 may be cut at any angle or multiple angles to the cross
direction 53 and may be nonlinear, such as cuts having dovetail,
curvilinear, or triangular characteristics.
[0147] FIG. 13 depicts a cross-sectional profile of the non-woven
tissue making fabric 30 taken along line 13-13 in FIG. 12. Shown
are the fabric strips 34a-34e, depicted with tapered thickness
profiles such that the overlapping regions in the vicinity of the
seams 48a-48d have a thickness not significantly greater than in
non-overlapping regions, such that the overall non-woven tissue
making fabric 30 has a relatively uniform thickness along most of
the cross-sectional profile.
Test Methods
"Overall Surface Depth"
[0148] A three-dimensional tissue making fabric or tissue web may
have significant variation in surface elevation due to its
structure. As used herein, this elevation difference is expressed
as the "Overall Surface Depth." The non-woven tissue making fabrics
and tissue webs of the present invention may possess
three-dimensionality and may have an Overall Surface Depth of about
0.1 millimeter (mm) or greater, more specifically about 0.3 mm or
greater, still more specifically about 0.4 mm or greater, still
more specifically about 0.5 mm or greater, and still more
specifically from about 0.4 mm to about 0.8 mm.
[0149] A suitable method for measurement of Overall Surface Depth
is moire interferometry, which permits accurate measurement without
deformation of the surface. For reference to the materials of the
present invention, surface topography should be measured using a
computer-controlled white-light field-shifted moire interferometer
with about a 38 mm field of view. The principles of a useful
implementation of such a system are described in Bieman et al. (L.
Bieman, K. Harding, and A. Boehnlein, "Absolute Measurement Using
Field-Shifted Moire," SPIE Optical Conference Proceedings, Vol.
1614, pp. 259-264, 1991). A suitable commercial instrument for
moire interferometry is the CADEYES.RTM. interferometer produced by
Medar, Inc. (Farmington Hills, Mich.), constructed for a nominal
35-mm field of view, but with an actual 38-mm field-of-view (a
field of view within the range of 37 to 39.5 mm is adequate). The
CADEYES.RTM. system uses white light which is projected through a
grid to project fine black lines onto the sample surface. The
sample surface is viewed through a similar grid, creating moire
fringes that are viewed by a CCD camera. Suitable lenses and a
stepper motor adjust the optical configuration for field shifting
(a technique described below). A video processor sends captured
fringe images to a PC computer for processing, allowing details of
surface height to be back-calculated from the fringe patterns
viewed by the video camera.
[0150] In the CADEYES moire interferometry system, each pixel in
the CCD video image is said to belong to a moire fringe that is
associated with a particular height range. The method of
field-shifting, as described by Bieman et al. (L. Bieman, K.
Harding, and A. Boehnlein, "Absolute Measurement Using
Field-Shifted Moire," SPIE Optical Conference Proceedings, Vol.
1614, pp. 259-264, 1991) and as originally patented by Boehnlein
(U.S. Pat. No. 5,069,548, issued on Dec. 3, 1991, the disclosure of
which is herein incorporated by reference to the extent that it is
non-contradictory herewith), is used to identify the fringe number
for each point in the video image (indicating which fringe a point
belongs to). The fringe number is needed to determine the absolute
height at the measurement point relative to a reference plane. A
field-shifting technique (sometimes termed phase-shifting in the
art) is also used for sub-fringe analysis (accurate determination
of the height of the measurement point within the height range
occupied by its fringe). These field-shifting methods coupled with
a camera-based interferometry approach allows accurate and rapid
absolute height measurement, permitting measurement to be made in
spite of possible height discontinuities in the surface. The
technique allows absolute height of each of the roughly 250,000
discrete points (pixels) on the sample surface to be obtained, if
suitable optics, video hardware, data acquisition equipment, and
software are used that incorporates the principles of moire
interferometry with field-shifting. Each point measured has a
resolution of approximately 1.5 microns in its height
measurement.
[0151] The computerized interferometer system is used to acquire
topographical data and then to generate a grayscale image of the
topographical data, said image to be hereinafter called "the height
map." The height map is displayed on a computer monitor, typically
in 256 shades of gray and is quantitatively based on the
topographical data obtained for the sample being measured. The
resulting height map for the 38-mm square measurement area should
contain approximately 250,000 data points corresponding to
approximately 500 pixels in both the horizontal and vertical
directions of the displayed height map. The pixel dimensions of the
height map are based on a 512.times.512 CCD camera which provides
images of moire patterns on the sample which can be analyzed by
computer software. Each pixel in the height map represents a height
measurement at the corresponding x- and y-location on the sample.
In the recommended system, each pixel has a width of approximately
70 microns, i.e. represents a region on the sample surface about 70
microns long in both orthogonal in-plane directions). This level of
resolution prevents single fibers projecting above the surface from
having a significant effect on the surface height measurement. The
z-direction height measurement should have a nominal accuracy of
less than 2 microns and a z-direction range of at least 1.5 mm.
[0152] The moire interferometer system, once installed and factory
calibrated to provide the accuracy and z-direction range stated
above, can provide accurate topographical data for materials such
as paper towels. (The accuracy of factory calibration may be
confirmed by performing measurements on surfaces with known
dimensions.) Tests are performed in a room under Tappi conditions
(73.degree. F., 50% relative humidity). The sample must be placed
flat on a surface lying aligned or nearly aligned with the
measurement plane of the instrument and should be at such a height
that both the lowest and highest regions of interest are within the
measurement region of the instrument.
[0153] Once properly placed, data acquisition is initiated using
CADEYES.RTM. PC software and a height map of 250,000 data points is
acquired and displayed, typically within 30 seconds from the time
data acquisition was initiated. (Using the CADEYES.RTM. system, the
"contrast threshold level" for noise rejection is set to 1,
providing some noise rejection without excessive rejection of data
points.) Data reduction and display are achieved using CADEYES.RTM.
software for PCs, which incorporates a customizable interface based
on Microsoft Visual Basic Professional for Windows (version 3.0),
running under Windows 3.1. The Visual Basic interface allows users
to add custom analysis tools.
[0154] The height map of the topographical data can then be used by
those skilled in the art to measure the typical peak to valley
depth of a surface. A simple method of doing this is to extract
two-dimensional height profiles from lines drawn on the
topographical height map which pass through the highest and lowest
areas of unit cells when there are repeating structures. These
height profiles may then be analyzed for the peak to valley
distance, if the profiles are taken from a sheet or portion of the
sheet that was lying relatively flat when measured. To eliminate
the effect of occasional optical noise and possible outliers, the
highest 10% and the lowest 10% of the profile should be excluded,
and the height range of the remaining points is taken as the
surface depth. Technically, the procedure requires calculating the
variable which we term "P10," defined at the height difference
between the 10% and 90% material lines, with the concept of
material lines being well known in the art, as explained by L.
Mummery, in Surface Texture Analysis: The Handbook, Hommelwerke
GmbH, M hlhausen, Germany, 1990. In this approach, the surface is
viewed as a transition from air to material. For a given profile,
taken from a flat-lying sheet, the greatest height at which the
surface begins--the height of the highest peak--is the elevation of
the "0% reference line" or the "0% material line," meaning that 0%
of the length of the horizontal line at that height is occupied by
material. Along the horizontal line passing through the lowest
point of the profile, 100% of the line is occupied by material,
making that line the "100% material line." In between the 0% and
100% material lines (between the maximum and minimum points of the
profile), the fraction of horizontal line length occupied by
material will increase monotonically as the line elevation is
decreased. The material ratio curve gives the relationship between
material fraction along a horizontal line passing through the
profile and the height of the line. The material ratio curve is
also the cumulative height distribution of a profile. (A more
accurate term might be "material fraction curve.")
[0155] Once the material ratio curve is established, the curve is
used to define a characteristic peak height of the profile. The P10
"typical peak-to-valley height" parameter is defined as the
difference between the heights of the 10% material line and the 90%
material line. One advantage of this parameter is that outliers or
unusual excursions from the typical profile structure have little
impact on the P10 height. The units of P10 are mm. The Overall
Surface Depth of a material is reported as the P10 surface depth
value for profile lines encompassing the height extremes of the
typical unit cell of that surface.
[0156] Overall Surface Depth measurements in tissue should exclude
large-scale structures such as pleats or folds which do not reflect
the three-dimensional nature of the original basesheet itself. It
is recognized that sheet topography may be reduced by calendering
and other operations which affect the entire basesheet. Overall
Surface Depth measurement can be appropriately performed on a
calendered basesheet.
[0157] Overall Surface Depth may be measured across sections of a
fabric or paper web that are free of apertures, such that the
profiles being considered pass exclusively over solid matter along
the upper surface of the fabric or paper web.
EXAMPLES
Example 1
[0158] In order to further illustrate the non-woven tissue making
fabrics of the present invention, a laminated two-layer non-woven
tissue making fabric was produced with a three-dimensional
topography. The nonwoven base fabric comprised a spunbond web made
from bi-component fibers with a concentric sheath-core structure.
The sheath material comprised Crystar.RTM. 5029 Polyethylene
Terephthalate (PET) polyester resin (The DuPont Company, Old
Hickory, Tenn., USA). The core material comprised HiPERTUF.RTM.
92004 Polyethylene Naphthalate (PEN) polyester resin (M&G
Polymers USA LLC, Houston, Tex., USA). The sheath to core ratio was
about 1:1 by weight. A bicomponent spunbond pilot line shown was
used with a forming head having 88 holes per inch of face width,
the holes having a diameter of 1.35 mm holes. The polymer was
pre-dried overnight in polymer dryers at about 320.degree. F., then
extruded at a pack temperature of about 600.degree. F. at a pack
pressure of about 980 psig for the core and about 770 psig for the
sheath, with a polymer flow rate of about 4 grams per hold per
minute. The spin line length was about 50 inches. The quench air
was provided at about 4.5 psig and a temperature of about
155.degree. F. The fiber draw unit operated at ambient temperature
and a pressure of about 4 psig. The forming height (height above
the forming wire) was about 12.5 inches. The forming wire speed was
about 65 fpm. Bonding was achieved with a hot air knife operating
at pressure of about 2.5 psig and a temperature of about
300.degree. F. at about 2 inches above the forming wire.
[0159] The resulting non-woven fabric had a fiber diameter of about
33 microns, a basis weight of about 100 grams per square meter
(gsm), and air permeability of about 630 cubic feet per minute
(CFM), and a maximum extensional stiffness of about 96 pli.
[0160] For molding of the nonwoven fabric into a three-dimensional
fabric, two porous, three-dimensional metal plates were prepared
from 2-mm thick aluminum discs 139 mm in diameter. First and second
three-dimensional plates were prepared from two aluminum disc by
machine-controlled drilling to selectively remove material as
specified by a CAD drawing. A sinusoidal pattern was created for
plates. In the first plate, the channels were specified to be about
0.035 inches (0.889 mm) deep with six channels per inch in the
cross-direction. A photograph of the resulting molding plate is
shown in FIG. 14, showing the sinusoidal channels (depressed
regions), with spaced apart holes providing passageways for gas
flow. The holes are 0.030-inch diameter holes spaced at 12 per
inch. The machined pattern and the holes were restricted to a
circular region about 98 mm in diameter centered in a slightly
larger circular plate about 100 mm in diameter. A second metal
plate was also machined with a similar geometry but with 0.015-inch
(0.38 mm) deep channels specified, spaced at 14 per inch. The
photograph in FIG. 14 has dimensions of about 33 mm by about 44
mm.
[0161] FIG. 15 is a screen shot from software used with the CADEYES
moire interferometry tool showing height map of a portion of the
first metal plate, taken with the 38-mm field of view CADEYES
system. The higher regions appear lighter in color than the lower
regions. The holes to permit air flow appear as spots of optical
noise in the height map. A profile is displayed on the right hand
side of the figure which corresponds to the height measurements
along a line (not shown) selected in the vertical direction (top to
bottom) of the height map; the line did not pass through any of the
regions corresponding to holes on the plate. The peak-to-valley
height from the CADEYES measurement is about 0.84 mm, slightly less
than the specified value.
[0162] FIG. 16 is another screen shot showing a topographical
height map of a portion of the second three-dimensional plate also
showing a profile line extracted from the a line along the height
map (indicated on the height map as a light line terminated with
circles) the topography of the channels. Optical noise occurs in
several regions, not just over holes, possibly due to the shiny
nature of the metal surface that posed difficulties for surface
topography measurements in some regions.
[0163] One or more plies of the non-woven web cut into a disc with
a diameter of 140 mm could be molded against the three-dimensional
plate by holding the disc against the three-dimensional plate with
an opposing flat backing plate, the backing plate having holes
drilled with the same size and spacing as in the three-dimensional
plate. Metal rings with an outer diameter of 139 mm and an inner
diameter of about 101 mm and joined with adjustable screws formed a
holder for the three-dimensional plate, a non-woven disc, and the
flat backing plate. Heated air from a hot air gun was applied
through a tube about 100 mm in diameter with an air velocity of
about 1 m/s. The tube terminated with the flat backing plate held
in place by the assembly of rings. Hot air passed through the
backing plate, into the non-woven web, and then out through the
holes of the three-dimensional plate. Inlet air temperature was
controlled by adjusting the power setting on the heated air gun,
with air temperature being measured after the air gun and prior to
the backing plate by a thermocouple. The inlet air temperature was
initially measured at 450.degree. F., then was gradually increased
over a period of 25 minutes to a peak temperature of 525.degree.
F., and the peak temperature was maintained for 10 minutes. Another
thermocouple measured the air temperature after passing through the
metal plates and the non-woven laminated. By the time that the
inlet air temperature has reached about 525.degree. F. the outlet
air temperature has reached between about 200.degree. F. and about
250.degree. F. However, after ten minutes, the outlet air
temperature had climbed gradually to about 275.degree. F. The hot
air gun was then turned off and room-temperature air was passed
through the system to cool off the plates and the non-woven
laminate.
[0164] Two plies of the non-woven material were superimposed and
heated as described above while being pressed lightly between the
flat backing plate and the first three-dimensional plate, resulting
in a bonded and molded two-ply laminate having three-dimensional
surface and a relatively flat surface. The Air Permeability of the
molded two-ply fabric was about 289 CFM (the mean of three samples,
with a standard deviation of 45 CFM).
[0165] FIG. 17 is a photograph of the two-ply non-woven tissue
making fabric molded against the first three-dimensional plate.
FIG. 18 is a height map of a portion of the non-woven tissue making
fabric, showing a characteristic peak-to-valley height of about
0.57 mm, somewhat less than the peak-to-valley height of the metal
plate.
Prophetic Example
[0166] A non-woven tissue making fabric may be made from non-woven
materials comprising elastomeric components or mechanically
configured to be stretchable in the cross-direction, such as
neck-bonded nonwoven laminates, such that the non-woven tissue
making fabric is extensible in the cross-direction. In one
embodiment, the non-woven tissue making fabric is elastically
stretchable in the cross-direction but relatively non-stretchable
(no more than is customary for conventional woven papermaking
fabrics) in the machine direction. A cross-direction stretchable
non-woven tissue making fabric may be stretched as embryonic tissue
web is formed thereon or prior to placing an embryonic tissue web
thereon. The cross-direction-stretched non-woven tissue making
fabric may then be relaxed to create cross-directional
foreshortening in the tissue web. Contraction of the tissue web may
be done as the non-woven tissue making fabric passes over a vacuum
box or during through drying, such that differential air pressure
helps hold the tissue web in contact with the non-woven tissue
making fabric to prevent buckling or separation of the tissue web
during contraction. The cross-directional foreshortening of the
tissue web in this manner may impart high levels of
cross-directional stretch (e.g., equal, to or greater than about
9%, about 12%, or about 15%) in the tissue web, and may impart
interesting and useful texture to the tissue web.
[0167] It will be appreciated that the foregoing examples and
description, given for purposes of illustration, are not to be
construed as limiting the scope of the present invention, which is
defined by the following claims and all equivalents thereto.
* * * * *