Note: Descriptions are shown in the official language in which they were submitted.
CA 02329806 2004-10-O1
P'ROGESS FAR 1NCR~eSING BULK O~ FORESH~RTE~IEp i:l~t~pUS
V11FB
FIELD OF TFIE iNV'EhITI~N
The present invention is related to processes and apparatuses for
making strong; soft, absorbent fibrous webs. More particularly, the
present invention is concerned with foreshortened fibrous webs.
BACKGROUND OF THE INVENTION
Fibrous strmctures, such as paper webs, are produced by a variety
of processes. For example, paper webs may be produced according to
commonly-assigned U. S. Patents: 5,556,509, issued Sept. 1 T, 1996 to
Trokhan et al.; 5,580,423, issued Dec. 3, 1996 to Ampuls.ki et al.;
5,609,725,issued Mar 11, 1997 to Phan; 5,629,052, issued May 13, 199P
to Trokhan et al.; 5,637,194, issued June 10, 1987 to Arnpulski et al.;
and 5,674,663, issued Oct 7, 1997 to McFarland et at. Paper webs may
also be made using through-air drying processes as described in commonly-
assigned U.S. Patents 4,514,345, issued April 30, 1985 to Johnson et al.;
4,528,239, issued July 9 to Trokhan, 1985; 4,529,480, issued July 16,
1985 to Trokhan; 4,637,859, issued January 2D, 1987 to Trokhan; and
5, 334,289, issued August 2, 1994 to Trokhan et al.
WO 93111301 A, commonly assigned to The Procter 8~ Gamble
Company, discloses a ceilulosic fibrous structure, particularly consumer
products such as toilet tissue, facial tissue or a paper tow~I, having a
CA 02329806 2004-10-O1
2
pluPality ~ of pro~uberat'~~s extending outwardly from each face of the
cellulosic fibrous structure. The prptubsrsnces may extend bilaterally
outwardly from the plane of the cellulosic fibrous structure in both
directions. The bilaterally extending protuberances increase the caliper
and texture of the cansurner product embodied in the cellulosic fibrous
structure. The protuberances may be induced by mechanical embossing
or by fluid embossing. This application also discloses a fluid embossing
process for making such celiulosie fibrous structures.
U.S. Patent No. 5,7Q2,571 discloses tissue sheets, such as are
useful for facial ar bath tissue, which are embossed with a fine scale
embossing pattern to (ntxease bulk with a minimal loss in strength. The
fine scale embossing pattern contains at least about 15 discrete
intermeshing embossing elements per square centimeter and can enable
the tissue manufacturer to produce premium quality tissue having
adequate softness, bulk " and strength from conventional tissue
basesheets without layering or throughdrying equipment.
G8 1,220,070 discloses a device for the continuous manufacture of
patterned paper. The device comprises a movable machine-ruvire means,
means fog distributing liquid stock onto said machine-wire means at
uniform thickness, first dewatering means for removing the bulk of the
moisture in the liquid stock distributed on said wire means so as to form a
continuous wet-web of uniform thickness, patterning belt means having
perforations and movable at the same speed as said machine-wire
means, means for ejecting water under pressure through said
perforations onto ~5aid wet web, at water pressure equalising means
disposed below said water-ejecting means and above the lower run of
said patterning belt means, second dewatering means for removing
ejected water alter said ejected water has passed through the
perforations, the wet-web and the machine wire means, and means for
heating the wet-web to produce dry patterned paper_ The patterned
paper thus dried, may be subjected further to a mechanical cocking
CA 02329806 2004-10-O1
3
treatment to make the paper shrinkable by alkyiamine. The patterned
paper according to that Specification may also be laminated with nan-
pattemed paper by superimposing the patterned paper on the wet-web
and rolling them together under pressure.
Foreshortening of a fibrous web$ may be used to increase the
web's caliper, absorbency and softness. Foreshortening refers to
reduction in length of a dry web, resulting from application of energy to
the web. Typically, during foreshortening, rearrangement of the fibers in
the web occurs, accompanied by at least partial disruption of fiber-to-fiber
bonds. As a result ot~ foreshortening, micro folds, commonly called
°crepe' are formed in the web.
It has been discovered that -the increase in caliper, .or bulk, of the
foreshortened web may further be achieved by relaxing, at least partially, the
crepe in the web. It has been further found that the crepe can be relaxed in
pre-
selected portions of the web such that the rest of the web, not affected by
the
crepe relaxation, retains the quality of the foreshortened web.
Accordingly, it is a subject of an aspect of the present invention to
provide a novel process for increasing bulk of the foreshortened web by
relaxing the web's crepe in the selected portions of the web. It is another
object of an aspect of the present invention to provide an apparatus for
increasing bulk of the foreshortened web by relaxing the web's crepe in the
selected portions of the web.
SUMMARY OF THE INVENT10N
The present invention provides a process and an apparatus for
increasing caliper/bulk of a foreshortened fibrous web by causing selected
micro-regions, or portions, of the foreshortened web to relax crepe therein,
thereby expanding outwardly from the general plan of the web. The process
comprises the steps of providing a foreshortened web comprising crepe and
having a general plane; and adding moisture to the web or to at least the
web's
selected portions, thereby causing relaxation of the crepe in the selected
portions and their expansion outwardly from the ge!~eral plane of the web,
while
CA 02329806 2004-10-O1
3a
retaining the crepe in the rest of the web. The preferred apparatus comprises
two mutually opposite surfaces designed to receive and restrain the
foreshortened web therebetween, at least one of the surfaces having a
plurality of fluid-permeable expansion conduits therethrough; a means for
moistening the web or at least its selected portions corresponding to the
expansion conduits when the foreshortened web is disposed between the two
surfaces; and a means for creating a temperature differential between the two
surfaces such that when the web is restrained between the surfaces, the
temperature differential is sufficient to cause the moisture added to the web
to
move through the web in the direction from one surface toward the other,
thereby relaxing crepe in the selected portions of the web and causing the
selected portions to expand through the expansion conduits.
In one aspect, the invention provides a process for increasing bulk of a
foreshortened web, the process comprising the steps of:
(a) providing a foreshortened web comprising crepe and having a
general plane, the web being in contact with a working surface;
(b) adding moisture to at least selected portions of the foreshortened
web, thereby causing relaxation of the crepe in the selected
portions of the web and expansion of the selected portions of the
web outwardly from the general plane of the web; and
(c) retaining the crepe in the rest of the web by means of one of
friction, mechanical engagement and adhesive engagement with
the working surface.
In a further aspect, the invention provides an apparatus for increasing
bulk of a foreshortened web, the apparatus comprising a working surface
designed to receive thereon a foreshortened web comprising crepe, the
working surface having a plurality of fluid-permeable expansion conduits
therethrough, a means for adding moisture to at least selected portions of the
foreshortened web, and a means for retaining the crepe in the rest of the web.
A first step of the process of the present invention comprises providing
a foreshortened, and preferably fibrous, web. The term "foreshortened" web
refers to a web which has been reduced in length, i. e., substantially
proportionally contracted along its length, in a machine direction. The first
step of providing a fibrous web may be preceded by the steps of forming such
CA 02329806 2004-10-O1
3b
a web and then foreshortening the web. The fibrous web suitable for the
present invention may be made by any papermaking process known in the
art, including, but not limited to, a conventional process and a through-air
drying process. The present invention also contemplates the use of the web
that has been rewetted prior to being foreshortened. The foreshortened web
is generally characterized by a plurality of micro-folds running across the
web's length, which is known in the art as "crepe." Foreshortening may be
accomplished by any method known in the art, for example, by creping, by
transferring the web from the first press surface to a slower-moving transfer
fabric, or by the combination thereof.
Preferably, the foreshortened web is disposed on a working surface.
The preferred working surface has a plurality of fluid-permeable expansion
conduits therethrough. One preferred working surface is formed by a belt
comprising a (preferably resinous) framework joined to a fluid-permeable
reinforcing structure and protruding outwardly from the reinforcing structure,
thereby forming the network area. The framework may comprise an
essentially continuous and macroscopically monoplanar network area, in
which case the plurality of expansion conduits preferably comprises a
plurality
of discrete orifices, or holes, which are dispersed throughout and
encompassed by the continuous network area of the working surface.
Alternatively or additionally, the work surface may comprise a plurality of
discrete areas formed by discrete protrusions extending from the reinforcing
structure, in which case an essentially continuous expansion conduit
encompasses the plurality of discrete protrusions.
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4
Preferably, the expansion conduits and/or protrusions are arranged in a
pre-selected pattern, and more preferably, the pattern of the arrangement of
the
expansion conduits andlor protrusions is non-random and repeating. If the
patterned working surface comprises discrete areas formed by the individual
protrusions, the work surface's discrete areas may have the discrete expansion
conduits therethrough, analogous to the discrete expansion conduits in the
continuous work surface. The working surtace may comprise a surface of a
fluid-permeable platen or - in a preferred continuous process - a fluid-
permeable endless belt or band capable of traveling in a machine direction.
The steps of disposing the foreshortened web on the working surface and
moistening the web may be performed either sequentially or simultaneously. If
the dry foreshortened web is being first disposed on the working surface, the
moisture can subsequently be added to the web disposed on the working
surface. Various means may be used for moistening the foreshortened web,
such as, for example, spraying the web with water or penetrating the web by
steam under pressure. A plurality of jets discharging water onto the selected
portions of the web according to a pre-determined pattern may also be used.
Preferably, the web, or its selected portions, is/are moistened to have a
moisture
content from about 95% to about 25%, i. e., the web's preferred fiber-
consistency is from about 5% to about 75%. More preferably, the moisture
content of the selected portions of the web, after they have been moistened,
is
from 85% to 35%, i. e., the web's more preferred fiber-consistency is from
about
15% to about 65%.
The moisture may be added primarily to the selected portions of the
foreshortened web, i. e., those portions which correspond to the expansion
conduits of the working surface, and which are not in direct and immediate
contact with the working surface. The moisture is added to the selected
portions
of the web preferably after or simultaneously with the step of disposing the
web
on the working surface. The moisture added to the web may comprise such
CA 02329806 2004-10-O1
functional papermaking additives as softeners and debonders, including, but
not
limited to, lotions, perfumes, anti-microbial agents, wet-strength resin, etc.
Under the influence of the moisture added, the web's selected portions
relax the crepe therein and consequently expand outwardly from the general
plane of the web, thus increasing bulk of the web. At the same time, the rest
of
the web, comprising surface-contacting portions which are in direct and
immediate contact with the working surface, retains the crepe therein. The
resulting web structure comprises, therefore, at least two distinct regions: a
region formed by the web's previously foreshortened portion which has retained
the crepe therein, and a region comprising the crepe-relaxed portion having
increased (relative to the previously foreshortened portion) caliper. Each of
the
regions may be substantially continuous, or may comprise a plurality of
discrete
micro-regions, or a combination thereof. Preferably, the crepe-relaxed portion
comprises a plurality of discrete domes outwardly extending from the plane
formed by the foreshortened portions of the web. The domes may extend from
one side of the web, or from both opposite sides of the web.
One way of retaining crepe in the surface-contacting portions of the
foreshortened web comprises adhering the surface-contacting portions to the
working surface such as to prevent lateral movement of the surface-contacting
portions relative to the working surface with, which they are in contact. To
accomplish this, the working surface can be treated with an adhesive material,
such as, for example, creping adhesive. Alternatively or additionally, the
working surface can comprise asperities thereon, preventing the lateral
movement of the surface-contacting portions. Other means of creating a
sufficient friction between the working surface and the surface-contacting
portions of the foreshortened web may be employed to prevent the lateral
movement of the surface-contacting portions relative to the working surtace.
In the preferred embodiment gf the process and the apparatus, a pressing
surface, opposite to and facing the working surface, is provided. The pressing
surface is a surface adapted to impress the foreshortened web against the
CA 02329806 2004-10-O1
6
working surface. The foreshortened web is constrained, or impressed, between
the working and pressing surfaces to the extent necessary to prevent (or
contain
if desired) expansion of those portions of the web which do not correspond to
the expansion conduits. Those portions (defined herein as "surface-contacting
portions") retain the crepe therein, while the selected portions of the web
are
free to expand through the expansion conduits.
The pressing surface may comprise an essentially flat area, or it may have
projected areas. The projected areas may comprise continuous network area,
or discrete areas, or a combination thereof. Pressing surface may also have
expansion conduits therethrough, similar to those of the working surface. The
expansion conduits of the pressing surface can correspond to the expansion
conduits of the working surface. In the latter instance, the moisture (water
and/or steam) can be delivered to and removed from the web using
corresponding expansion conduits of the pressing and working surtaces. The
latter embodiment provides an additional benefit of allowing the selected
portions expand in both opposite directions - through the expansion conduits
of
the working surface and through the expansion conduits of the pressing
surface.
In another embodiment, the pressing surface's conduits do not correspond to
the working surface's conduits. In this instance some of the selected portions
of
the web can expand only through the pressing surface's conduits; while the
other selected portions can expand only through the working surface's
conduits.
The last two embodiments of the process and the apparatus allow one to create
structured patterned webs.
Preferably, the working surface is associated with a supporting surface
such that the working surface having the web thereon is juxtaposed between the
pressing surface (contacting the web) and the supporting surface. In the
preferred embodiment of the apparatus and the process of the present
invention, a temperature differential of at least 50°F is created
between the
pressing surface and the supporting surface. Preferably, but not necessarily,
the pressing surface has a relatively higher temperature, and the supporting
CA 02329806 2004-10-O1
7
surface has a relatively lower temperature. The preferred temperature
differential is at least 50°F, and the more preferred temperature
differential is at
least 100°F. A preferred temperature of the "cold" surface is less than
212°F.
The temperature differential drives the moisture added to the web through the
web's selected portions thereby relaxing the crepe in the selected portions
and
causing the selected portions to expand through the expansion conduits. To
accumulate the moisture driven through the web, a fluid-permeable fabric is
juxtaposed between the "cold" (preferably working) surface and the "hot"
(preferably supporting) surface. The fabric should have a void volume
sufficient
to accumulate the moisture condensing thereinto. This process or any other
process known in the art may be used to dry the web.
In one preferred embodiment, the pressing surface comprises a surface of
a sintered layer capable of retaining sufficient volume of moisture. The
preferred sintered layer comprises metal woven belt capable of containing a
sufficient volume of moisture therein and to release the moisture under the
influence of the temperature differential. The metal is preferred for its
superior
heat-transfer properties. When the web and the working surface .are impressed
between the pressing and supporting surfaces, the moisture contained in the
sintered layer moves into and through the web and towards the supporting
surface. The crepe in the surface-contacting portions of the web, which are
sufficiently contained between the pressing surface and the working surface,
is
not affected (or affected to a lower degree, if desired) by the water driven
through the web from the pressing surface towards the supporting surface. The
web's selected areas, which corresporid to the expansion conduits of the
working surface and/or the pressing surface, are not sufficiently contained
between the pressing surface and the working surface, due to the existence of
the expansion conduits in both or one of the surfaces. Therefore, the selected
portions are not prevented from expanding through the expansion conduits (or
prevented to a significantly lower degree relative to the surface-contacting
portions). The expanded selected portions of the web form "domes" of a
CA 02329806 2004-10-O1
finished product, thereby increasing the bulk or overall caliper of the
finished
web.
In one of the embodiments of the preferred continuous process of the
present invention, each of the pressing surface and the working surface is
formed by an endless belt or band traveling in the machine direction. An
endless condensation belt (fabric) traveling in the machine direction and
capable of receiving a sufficient amount of the condensed moisture is disposed
between the supporting surface and the working surface. The moisture which is
driven through the selected portions of the web and through the expansion
conduits of the working surface condenses into the fabric disposed between the
working surface and the supporting surface. A means for collecting and
recycling the moisture, well known in the art, may be used in the process of
the
present invention.
The portions which are impressed between the working surface and the
pressing surface may be further densified, if desired. The selected portions
of
the web corresponding to the expansion conduits are not densified, or
densified
(if desired) to a lesser degree than the impressed portions are. In the latter
instance, a pressure differential may be controlled, on the one hand - by the
distance between the pressing surface and the corresponding working surface,
and on the other hand - by the distance between the pressing surface and a
surface restricting the expansion of the selected portions.
In the pressing surface comprising projected areas, some of the projected
areas may be registered (either in a knob-to-knob pattern, or in a nested
pattern, or in a pattern comprising a combination thereof) with the working
surface when the web is impressed between the pressing surface and the
working surface. The embodiment of the apparatus is contemplated, in which
only some of the projected areas of the pressing surface have corresponding
projected areas of the working surface. Thus, some of the selected portions of
the web may be partially restrained, in -the direction perpendicular to the
working
surface, to a lesser degree relative to the portions impressed between the
CA 02329806 2004-10-O1
9
working surface and the pressing surface, Consequently, it is believed that
the
selected portions of the web may comprise in the latter instance sub-portions
which are relatively unconstrained in the direction perpendicular to the
working
surface, and sub-portions which are relatively constrained and may be
partially
impressed (and therefore possibly densified) by the pressing surtace's
projected
areas corresponding to the expansion conduits of the working surface. Such an
arrangement of the working surface and the pressing surface may beneficially
produce a web having at least three differential micro-regions: first micro-
regions formed by the portions constrained in the direction perpendicular to
the
working surface and thus substantially retaining the crepe therein; second
micro-regions formed by the sub-portions partially-constrained in the
direction
perpendicular to the working surtace and thus having crepe partially relaxed,
the
second micro-regions partially expanding in the direction perpendicular to the
working surface; and the third micro-regions formed by the sub-portions
relatively unconstrained in the direction perpendicular to the working
surface,
having crepe substantially relaxed therein, the third micro-regions expending
in
the direction perpendicular to the working surface.
The expansion of the selected areas may be assisted by deflecting, under
pressure, the moistened selected portions of the web through the expansion
conduits. Vacuum or differential pressure can be used as a means for
deflecting the selected portions through the expansion conduits. The means for
deflecting may also comprise steam or water moving, preferably under pressure,
through the selected portions and through the expansion conduits. A
combination of steam and water as means for deflecting is also contemplated in
the present invention. The pressing surface's projected areas corresponding to
the expansion conduits of the working surface can also comprise the means for
deflecting the selected portions of the web. In one exemplary embodiment, the
projected areas of the pressing surface correspond to the expansion conduits
of
the working surface and are. in contact with the selected portions of the web.
When the web is constrained between the pressing surface and the working
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0
surface, the projected areas of the pressing surface push the selected
portions
of the web through the expansion conduits of the working surface, thereby
facilitating the expansion of the selected portions.
"Angled" expansion of the selected portions is also contemplated by the
present invention. In this instance, the selected portions of the web are
caused
to expand to form an "angled" position relative to the plane of the belt, i.
e., the
axes of at least some of the domes formed by the selected portions and the
working surface form acute angles therebetween. The working surface may
comprise a plurality of protuberances, at least some of which are angled
relative
to the working surface, i. e., the axes of the protuberances and the working
surface form acute angles therebetween. Than, the selected portions of the
web, while expanding through the expansion conduits, will take the "angled"
position relative to the working surface, and the final web product will have
the
"angled" continuous domes, i. e., the continuous domes cross-sectional axes of
which form acute angles with the general plan of the web.
The web having the crepe relaxed in the selected portions may be re-
foreshortened by, for example, adhering the crepe-relaxed and expanded
selected portions of the web to the creping surface and then creping therefrom
with a doctor blade.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic and simplified side elevational view of the apparatus of
the
present invention, showing a web disposed on a working surface.
FIG. 2 is a view similar to one shown in FIG. 1, and showing the web being
impressed between the working surface and a pressing surface.
FIG. 3 is a schematic and simplified side elevational view of another
embodiment of the apparatus of the present invention, having a pressing
surface comprising extending projected areas.
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FIG. 4 is a schematic and simplified side elevational view of still another
embodiment of the apparatus of the present invention, having a pressing
surface comprising extending projected areas and expansion conduits.
FIG. 5 is a schematic and simplified side elevational view of another
embodiment of the apparatus of the present invention, showing the
pressing surface comprising a sintered layer.
F1G. 5A is a schematic and simplified side elevational view of still another
embodiment of the apparatus comprising two mutually opposite surfaces
having corresponding expansion conduits therethrough.
FIG. 6 is a schematic plan view of one embodiment of the working surface
comprising a plurality of discrete conduits, taken along lines 6-6 of FIG.
1.
FIG. 7 is a schematic plan view of another embodiment of the working surface
comprising a continuous conduit, taken along fines 7-7 of FIG. 3.
FIG. 8 is a schematic and simplified side elevational view of another
embodiment of the apparatus of the present invention, showing both the
pressing surface and the working surface having the expansion conduits
therethrough, the expansion conduits of the working surface partially
corresponding to the expansion conduits of the pressing surface.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process and an apparatus for
increasing bulk of a foreshortened web by causing selected portions of the
foreshortened web to relax crepe, thereby expanding outwardly from one or both
opposite sides of the web.
A first step of the process of the present invention comprises providing a
foreshortened, and preferably fibrous, web. As used herein the term "fibrous
web" or simply "web" designates a macroscopically planar substrate comprising
cellulosic fibers, synthetic fi4ers, or any combination thereof. The first
step of
providing a web 60 may be preceded by the steps of forming such a web and
CA 02329806 2004-10-O1
12
then foreshortening the web. One skilled in the art will readily recognize
that
forming the web 60 may include the steps of providing a plurality of
papermaking fibers. Suitable fibers comprising the web 60 may include
recycled, or secondary, papermaking fibers, as well as virgin papermaking
fibers. Such fibers may comprise hardwood fibers, softwood fibers, and non-
wood fibers.
In a typical continuous papermaking process, the plurality of fibers are
preferably suspended in a liquid carrier. More preferably, the plurality of
fibers
comprises an aqueous dispersion. An equipment for preparing the aqueous
dispersion of fibers is well-known in the art and is therefore not illustrated
herein. The aqueous dispersion of fibers may be provided to a headbox or
headboxes. The headbox(es) and the equipment for preparing the aqueous
dispersion of fibers are typically of the type disclosed in U.S. Patent No.
3,994,771, issued to Morgan and Rich on November 30, 1976. The
preparation of the aqueous dispersion of the papermaking fibers and
exemplary characteristics of such an aqueous dispersion are described in
greater detail in U.S. Patent 4,529,480. The fibrous web suitable for the
present invention may be made by any papermaking process known in the
art, including, but not limited to, a conventional process and a through-air
drying process. The present invention also contemplates the use of the web
60 that has been rewetted. Rewetting of a previously-manufactured dry web
may be used for creating three-dimensional web structures by, for example,
embossing the rewetted web and than drying the embossed web.
As used herein, the term "foreshortened" web refers to a web which
has been substantially proportionally contracted along its length, i. e., in a
machine direction. In the papermaking, the machine direction, or MD,
indicates that direction which is parallel to and has the same direction as
the
flow of the web through a papermaking equipment. The cross-machine
direction, or CD, is perpendicular to the machine direction and parallel to
the
general plane of the web.
CA 02329806 2004-10-O1
13
The foreshortened web is generally characterized by a plurality of
micro-folds running across the web's length. Such micro-folds are typically
known in the art as "crepe." Foreshortening may be accomplished by any
method known in the art, for example, by creping, by transferring the web
from the first press surface to a slower moving transfer fabric, or by the
combination thereof. As used herein, the web which has been foreshortened
has crepe therein, regardless of the method of foreshortening.
Creping is usually performed with a creping doctor blade juxtaposed with
the creping surface having the web adhered thereto. Creping may be
accomplished according to commonly assigned U. S. Patent 4,919,756,
issued on April 24, 1992 to Sawdai. A conventional creping blade is
positioned against the creping surface so as to create an impact angle
between the blade and the creping surface, wherein the impact angle ranges
from about 70 degrees to about 90 degrees. A creping adhesive may be
applied directly to the creping surface. Creping adhesives comprising
polyvinyl alcohol, animal-based protein glues, or mixtures thereof, well known
in the art, may be utilized. The commonly-assigned U.S. Patent 3,926,716
issued to Bates on Dec. 16, 1975 teaches a polyvinyl alcohol creping
adhesive. The U.S. Patent 4,501,640 issued to Soerens on Feb. 26, 1985;
U.S. Patent 5,187,219 issued to Furman, Jr. on Feb. 16, 1993; U.S. Patent
5,494,554 issued to Edwards et al. on Feb. 27, 1996 describe various types of
creping adhesives. Optionally, various plasticizers may be used in
conjunction with the creping adhesive. For example, the plasticizer
commercially sold as CREPETROLTM R 6390 is available from Hercules
Incorporated of Wilmington, DE.
Foreshortening comprises a process commonly described as a
"microcontraction." Microcontraction includes transferring the web from one
moving surface (typically a foraminous member or a papermaking belt) to
another, a slower-moving surface (typically a transfer belt). U. S. Patent
CA 02329806 2004-10-O1
t4
4,440,597 describes in detail a "wet - microcontraction". Briefly,
wet-microconstriction involves transferring the web having a
low fiber - consistency from a first member ( such as
a foraminous member) to a second member (such as a loop of open-weave
fabric) moving slower than the first member. According to U.S. Patent
4;440,97, the preferred consistency of the web prior to the transfer is from
about 10% to about 30% fibers by weight; and the most preferred consistency is
from about 10% to about 15%.
The next step in the process of the present invention may comprise
providing a working surface 20 designed to receive the foreshortened fibrous
web 60. FIGs. 1-7 show various embodiments of the working surface 20.
Regardless of the embodiment, the preferred working surface 20 has a plurality
of fluid-permeable micro-regions, or expansion conduits, 25 therefhrough. As
used herein, the term "fluid-pervious" refers to the capability of the
expansion
conduits 25 to have a fluid, such as liquid (water) or gas (air or steam),
transmitted through the conduits 25 without significant obstruction. The
conduits 25 are termed "expansion conduits" because they provide void areas
through which selected portions of the web can expand outwardly, as will be
explained in greater detail below. The preferred expansion conduits 25
comprise
unobstructed orifices, or holes, through the working surface 20. Preferably,
the
expansion conduits 25 are arranged in a pre-selected pattern, and more
preferably, the pattern of their arrangement is non-random and repeating
throughout the working surface.
One preferred working surface 20 is formed by a belt comprising a
framework 21 joined to a reinforcing structure 23, as shown in FJGs. 1-3.
Preferably, the framework 21 is resinous. The framework 21 protrudes outwardly
from the reinforcing structure 23, thereby forming the network area 22, as
best
CA 02329806 2004-10-O1
shown in FIGs. 1 and 6. This type of belt is described in several commonly-
assigned U.S. Patents referred to above.
In the embodiment shown in FIGs. 1, 6, and 2, the network 22 is essentially
continuous and macroscopically monoplanar, and the plurality of fluid-
permeable conduits 25 comprises a plurality of discrete orifices, or holes,
which
are dispersed throughout and encompassed by the essentially continuous
network 22. As used herein, the term "essentially continuous" indicates that
interruptions in absolute geometrical continuity, while are not preferred, may
be
tolerable -- as long as these interruptions do not adversely affect the
performance of the framework 21 and network 22. It should also be carefully
noted that embodiments (not shown) are possible in which interruptions in the
absolute continuity of the framework 21 (and thus network 22) are intended as
part of the overall design of the working surface 20.
Preferably, the conduits 25 are arranged in a pre-selected pattern
throughout the network 22, and more preferably, the pattern of the arrangement
of the conduits 25 is non-random and repeating, such as, for example, a
continuously-reticulated pattern, best shown in F1G. 6. The belt having a
continuous network 22 and discrete fluid-permeable expansion conduits 25 is
primarily disclosed in the commonly assigned U.S. Patents 4,528,239 issued
Jul. 9, 1985 to Trokhan; 4,529,480 issued Jul. 16, 1985 to Trokhan; 4,637,859
issued Jan. 20, 1987 to Trokhan; 5,098,522 issued Mar. 24, 1992 to Trokhan
et al.; 5,275,700 issued Jan. 4, 1994 to Trokhan; 5,334,289 issued Aug. 2,
1994 to Trokhan; and 5,364,504 issued Nov. 15, 1985 to Smurkoski et al.
The patterned working surtace 20 may comprise discrete areas,
alternatively or in addition to the continuous network 22. FIGs. 3 and 7 show
the working surface 20 comprising a plurality of discrete areas formed by
discrete protrusions 27 outwardly extending from the reinforcing structure 23
and separated from one another by an area of essentially continuous expansion
conduits 25. The discrete areas formed by the individual protrusions may have
CA 02329806 2004-10-O1
16
the discrete expansion conduits therethrough, similar to the discrete
expansion
conduits described above in the context of the continuous working area. The
belt having the framework 21 comprising the discrete protrusions is primarily
disclosed in the commonly assigned U:S. Patent 4,245,025 issued Sep. 14,
1993 to Trokhan et al. and U.S. Patent 5,527,428 issued June 18, 1996 to
Trokhan et al.~Also, the papermaking belt having the discrete protuberances
raised above the plane of the fabric may be made according to the
European Patent application 95105513.6, Publication No. 0 677 612 A2, filed
12.04.95, inventor Wendt et al.
The working surface 20 may comprise a fluid-permeable platen, or -- in a
preferred continuous process - a fluid-permeable endless belt or band 28, as
schematically shown in FIG. 5. The endless belt or band 28 is designed to
continuously travel in the machine direction. Fluid-permeability of the band
28
may be achieved by perforating (preferably, according to a pre-determined
pattern) the band 28 throughout its thickness or by other conventional means --
to provide expansion conduits 25. Preferably, the band 28 is juxtaposed with a
fluid-permeable fabric 50 (FIGs. 4 and 5). The fabric 50 should preferably
have
a sufficient amount of void volume to be able to receive moisture driven into
the
fabric 50 from the web 60, as will be explained in greater detail below. The
fabric 50 can be woven or non-woven. One preferred fabric comprises Spiral
Weave, Duraflex Belt made by Albany International, Engineered Fabrics of
Portland, TN.
The next two steps in ~ the process of the present invention comprise
disposing the foreshortened web 60 on the working surface 20 and moistening
the web 60. These steps may be performed sequentially or simultaneously. If
the dry foreshortened web 60 is being first disposed on the working surface
20,
the moisture can subsequently be added to the web 60 associated with the
working surface 20. If the foreshortened web 60 is being first moistened and
then disposed on the working surface 20, wet transfer may be used in the
process of the present invention for the step of depositing the web 60 on the
CA 02329806 2004-10-O1
17
working surface 20. As one skilled in the art will recognize, wet transfer
comprises transferring the wet web from one carrier (a foraminous member or a
belt) to another carrier using vacuum or differential pressure.
Various means may be used for moistening the foreshortened web 60. For
example, the foreshortened web 60 can be sprayed with water or moistened by
steam. Preferably, the web 60 is moistened to have a moisture content from
about 95% to about 25%. More preferably, the moisture content of the web 60,
after it has been moistened, is from about 80% to about 40%.
According to the present invention, the entire web 60 can be moistened to
have the necessary moisture content. Alternatively, moisture may be added
primarily to selected portions 62 of the web 60. As used herein, the "selected
portions» 62 of the web 60 are those portions which correspond to the
expansion
conduits 25 of the working surface 20 when the web is disposed on the working
surface 20. Preferably, the selected portions 62 are not in direct and
immediate
contact with the working surface 20, due to the existence of the expansion
conduits 25. In the instance when the moisture is added primarily to the
selected portions 62 of the web 60, it is preferred that the step of
moistening the
foreshortened web 60 be performed after or simultaneously with the step of
disposing the web 60 on the working surface 20.
The moisture added to the web 60 may comprise various functional
papermaking additives, such as softeners and debonders. Examples include,
but are not limited to: nonionic surfactant described in U.S. Patent
5,527,560,
issued June 18, 1996 to Fereshtehkhou et al.; a softening composition
comprising quaternary ammonium compound, polysiloxane compound, and
binder materials described in commonly-assigned U.S. Patent 5,573,753, issued
November 12, 1996 to Ampulski et al.; a water-soluble polyhydroxy compound
described in commonly-assigned U.S. Patent 5,624,532, issued April 29, 1997
to Phan et al.; a debonder described in Canadian Patent 2,118,529, issued
February 2, 1996 to Edwards et al.; softening agent described in U.S. Patent
5,716,498, issued February 10, 1998 to Jenny et al.; a cationic nitrogenous
CA 02329806 2004-10-O1
18
softener/debonder described in U.S. Patent 5,695,607, issued December 9,
1997 to Awofeso et al.; softenersldebonders described in U.S. Patent
5,552,020, issued September 3, 1996 to Schroeder et al.; a cationic silicone
described in U.S. Patent 5,591,306, issued January 7, 1997 to Kaun et al.; and
others. Other functional additives, such as lotions, emulsions, perfumes, anti-
microbial and anti-bacterial agents, and wet-strength resin may also be
included
into the moisture.
According to the present invention, the moisture added to the web 60 or to
the web's selected portions 62 relaxes the crepe in the selected portions 62.
Consequently, the selected portions 62 expand outwardly from the general
plane of the web 60, thus increasing bulk of the web 60. Preferably, the
selected portions 62 expand through the expansion conduits 25 of the working
surface 20. At the same time, in accordance with the present invention, the
rest
of the web 60 retains the crepe therein. As used herein, the rest of the web
which retains the crepe is defined as comprising "surface-contacting portions"
61 of the web 60, for the surface-contacting portions 61 are in direct and
immediate contact with the working surface 20, in contrast with the selected
portions 62 corresponding to the expansion conduits 25.
In the embodiment in which the moisture is added only to the web's
selected portion 62, the surface-contacting portions 61 retain the crepe
primarily
by virtue of not being moistened. Additionally, the working surtace 20 may be
treated to enhance friction between the working surface 20 and the surface-
contacting portions 61, which friction should preferably be sufficient to
prevent
the surface-contacting portions 61 from laterally moving relative to the
working
surface 20. The friction between the working surtace 20 and the surface-
contacting portions 61 may be enhanced by, for example, providing the working
surface 20 with asperities thereon, designed to mechanically engage the
surtace-contacting portions .61 such as to prevent or restrict their lateral
movement. Alternatively or additionally, the working surface can be treated
with
a suitable adhesive, to temporarily adhere the surface-contacting portions 61
to
CA 02329806 2004-10-O1
1J
the working surface 20. Neither the asperities nor the adhesive treatment are
illustrated in the drawings, for one skilled in the art will easily visualize
both
embodiments. Other means of creating a sufficient friction between the working
surface 20 and the surface-contacting portions 61 of the web 60 may be
employed in the apparatus of the present invention to prevent the lateral
movement of the surface-contacting portions 61 relative to the working surface
20.
After the crepe has relaxed in the selected portions 62 under the influence
of moisture, while the rest of the web 60 retains the crepe, the web 60
comprises at least two distinct regions: a region formed by the web's
previously
foreshortened portion which has retained the crepe therein (i. e., comprising
the
surface-contacting portions 61 ), and a region formed by the crepe-relaxed
portions (i. e., comprising the selected portions 62) extending outwardly from
the
general plane of the web 60 and thereby preferably having increased caliper,
relative to the surface-contacting portions 67. Each of the regions may be
substantially continuous, or comprising a plurality of discrete micro-regions,
or a
combination thereof, depending on the design of the working surtace 20, as has
been discussed above. Preferably, in the final product the crepe-relaxed
selected portions 62 comprise a plurality of discrete domes outwardly
extending
from the plane formed by the foreshortened portions of the web 60. The domes
may extend from one side of the web 20 (FIGS. 2-5), or from both opposite
sides
of the web 20 (FIGs. 5A and 8).
Optionally, the moistened selected portions 62 of the web 60 may be
subjected to deflection into the expansion conduits 25 of the working surface
20
to facilitate expansion of the selected portions 62 of the web 60 through the
expansion conduits 25 of the working surface 20. A variety of deflecting means
may be used in the process and the apparatus 10 of the present invention. One
skilled in the art will recognize that vacuum pressure or pressure
differential
may be used as deflecting means. The deflecting means may also comprise
steam or water moving, preferably under pressure, through the selected
portions
CA 02329806 2004-10-O1
62 and through the expansion conduits 25 of the working surface 20. A
combination of steam and water as deflecting means is also contemplated by
the present invention.
One preferred embodiment of the apparatus 10 comprises a pressing
surface 30. The pressing surface 30 is a surface designed to constrain, or
impress, the web 60 against the working surface 20. The pressing surface 30 is
opposite to the working surface 20 anal preferably substantially parallel to
the
working surface 20. Although the drawings show the pressing surface 30 and
the working surface 20 as substantially planar surfaces, it should be
appreciated
that both the pressing and working surfaces 30, 20 can be curved, or have
other
non-planar configuration, as long as they are capable of receiving and
constraining the web 60 therebetween.
FIGs. 1-8 show several exemplary embodiments of the pressing surface
30. In FIGs. 1 and 2, the pressing surface 30 comprises an essentially flat
and
unpatterned area. In FIGs. 3 and 4, the pressing surface 30 comprises
projected areas 31, preferably having a pre-determined pattern. The projected
areas 31 may comprise a substantially continuous or - alternatively - discrete
area, as has been explained above in the context of the network 22 of the
working surface 20. The combination of continuous areas and discrete areas of
the pressing surface 30 is also contemplated in the present invention. FIGs. 3
and 4 show that at least some of the projected areas 31 of the pressing
surface
correspond to the expansion conduits 25 of the working surface 20. In these
two embodiments, the deflecting means comprises the projected areas 31 of the
pressing surface 30, corresponding to the expansion conduits 25 of the working
surface 20. The projected areas 31 facilitate the expansion of the selected
portions 62 through the conduits 25.
As shown in FIGs. 4 and 8, the pressing surface 30, whether flat or having
the projected areas 31, may comprise expansion conduits 35, similar to those
of
the working surface 20. FIG. 4 shows the expansion conduits 35 which
correspond to the projected areas 31, and FIG. 8 shows the conduits 35 which
CA 02329806 2004-10-O1
21
do not correspond to the projected areas 31. In both instances, however, when
the web 60 is constrained between the pressing surface 30 and the working
surface 20, at least some of the expansion conduits 35 of the pressing surface
30 correspond to the expansion conduits 25 of the working surface 20, as
shown in FIGS. 4 and 8. Of course an embodiment is possible in which none of
the expansion conduits 35 of the pressing surface 30 correspond to the
expansion conduits 25 of the working surface 20 (not shown).
FIG. 5 shows an embodiment of the pressing surface 30 comprising a
surface of a sintered layer 40 capable of retaining sufficient volume of
moisture.
The sintered layer 40 is one preferred means for moistening the web 60. The
sintered layer 40 can be made from any suitable material. One preferred
material for the sintered layer 40 is sintered stainless steel having pores of
about 40 micro-meter (gym) in diameter, made by Mott Corporation, 84 Spring
Lane Farmington, CT 06032-3159. Preferably, the sintered layer 40 is capable
of retaining a moisture therein in the amount sufficient to moisten the web 60
to
the required consistency/moisture content as defined herein.
The apparatus 10 of the present invention preferably further comprises a
supporting surtace 24. The supporting surface 24, shown in FIGs. 4, 5, and 8
is
a surface designed such that the working surface 20 is capable of being
interposed between the supporting surface 24 and the pressing surtace 30, the
working surface 20 facing the pressing surface 30. Preferably, the supporting
surface 24 does not directly contact the working surface 20. That is, as shown
in FIGs. 4 and 5, there is a distance D between the working surface 20 and the
supporting surface 24. Preferably, the supporting surface 24 is associated
with
the working surface 20 through the fabric 50, as shown in FIGs. 4 and 5. In
the
embodiment of the apparatus 10 and the process of the present invention,
comprising the supporting surface 24, the process step of constraining the
foreshortened web 60 between the working surface 20 and the pressing surface
30 comprises impressing the working surface 20 with the associated web 60
thereon between the pressing surface 30 and the supporting surface 24.
CA 02329806 2004-10-O1
22
In one preferred embodiment of the process of the present invention,
schematically illustrated in FIG. 5, the dry foreshortened web 60 is first
disposed
on the working surface 20 by any conventional means. Then, the foreshortened
web 60 disposed on the working surface 20 is contacted by the working surface
20 such that the web 60 is constrained between the pressing surface 30 and the
pressing surface 30 comprising the sintered layer 40. When the web 60 is thus
contacted by the sintered layer 40, the web 60 starts receiving moisture from
the
sintered layer 40 at one of the web's sides. A pressure may be applied to
facilitate moistening of the web 60 by the sintered layer 40.
In accordance with the preferred embodiment of the present invention, a
temperature differential is created between the pressing surtace 30 and the
working surface 20. The temperature differential should be sufficient to cause
the moisture added to at least the selected portions 62 of the web 60 to move
through the selected portions 62 in the direction from one of the surfaces 30,
20
to the other 20, 30. Preferably, the temperature differential between the
pressing surface 30 and the working surface 20 is provided by heating the
pressing surface 30 to a temperature T1, and maintaining the supporting
surface 24 at a temperature T2 sufficiently lower than T1. Thus, the
temperature differential between the pressing surface 30 and the working
surface 20 is preferably provided by creating the temperature differential
between the pressing surface 30 and the supporting surface 24. fn the
drawings, the preferred arrangement is illustrated, in which the web's side
which
contacts the pressing surface 30 is first moistened, and the moisture is
driven
under the temperature differential from the pressing surface 30 to the working
surface 20, and further through the expansion conduits 25 of the working
surface 20 into the fabric 50. However, one skilled in the art should
appreciate
that the direction of the movement of the moisture through the web 60 could be
reversed, provided the temperature of the working surface 20 is sufficiently
greater relative to the temperature of the pressing surface 30. It should also
be
appreciated that, as used herein, the terms "pressing surface" .and "working
CA 02329806 2004-10-O1
23
surface" are relative terms, and the expansion conduits may be provided in
both
or either one of the pressing surface 30 and the working surface 20.
Consequently, the selected portions 62 of the web 60 can expand through the
conduits of both or either one of the pressing surface 30 and working surface
20.
In the preferred embodiment, the pressing surface 30 is heated to have the
temperature T1 higher than the temperature T2 of the supporting surface 24. In
FIG. 4, the temperature differential DT between the pressing surface 20 and
the
supporting surface 24 causes the moisture contained in the sintered layer 40
move into and through the web 60 and towards the supporting surface 24.
Because the surface-contacting portions 61 of the web 60 are sufficiently
constrained between the pressing surface 30 and the working surface 20, the
crepe in the surface-contacting portions 61 is not affected (or, if desired,
affected to a lower degree) by the moisture driven through the web 60 from the
pressing surface 30 towards the supporting surface 20. However, due to the
existence of the expansion conduits 25 in the working surface 20, the selected
areas 62; which correspond to the expansion conduits 25, are not constrained
or constrained, if at all, only at one side associated with the pressing
surface 30,
as FIG. 5 shows. Therefore, the selected portions 62 are relatively free to
expand towards the supporting surface 24. The preferred temperature
differential 0T between the pressing surface 30 and the supporting surface 24
is
at least 50°F, and the more preferred temperature differential ~T is at
least
100°F. The temperature T2 of the "cool" surface (i. e., the supporting
surface 24 .
in FIGs. 4, 5, and 8) is preferably less than 212°F.
FIG. 5A shows an embodiment in which the selected portions 62 are
relatively unconstrained at both sides of the web 60, for in FIG. 5A the
expansion conduits 25 of the working surface 20 correspond to the expansion
conduits 35 of the pressirig surface 30. 1t should also be understood that
while
FIG. 5A shows the embodiment in which the same selected portion 62 expands
CA 02329806 2004-10-O1
24
outwardly at both mutually opposite sides of the portion 62, the embodiment is
possible (and may even be preferred) in which some of the selected portions 62
expand outwardly at one side of the web 60, while the other selected portions
62
expand at the other (opposite) side of the web 60. An embodiment is also
possible in which the selected portions 62 partially expand outwardly at both
mutually opposite sides of the web 60, as shown in FIG. 8, i. e., only part of
the
selected portions) 62 expands at both sides of the web 60. In FIG. 8, the
conduits 35 of the pressing surface 30 partially correspond to the conduits 25
of
the working surface 20.
Preferably, the selected portions 62 are free to expand through the
expansion conduits 25 and 35. It is believed that the moisture moving through
the selected portions 62 and through the expansion conduits 25 in the
direction
towards the supporting surface 24 facilitates expansion of the selected
portions
62 through the expansion conduits 25, thereby relaxing the crepe in the
selected
portions 62 of the web 60. As the moistened selected portions 62 of the web 60
expand through the expansion conduits 25 and/or 35, the caliper of the
selected
portions 60 increases, thereby increasing the overall bulk of the web 60. In
the
finished web product (not shown), the selected portions 62 have a pattern
which
in plan view is essentially similar to the pattern of the working surface 20
including the expansion conduits 25 and/or 35. The preferred continuous and
still foreshortened area comprising the surface-contacting portions 61
provides
strength, while the discrete domes comprising crepe-relaxed selected portions
62 generate bulk, and thus are believed to improve softness and absorbency of
the final web product. Additional densification of the surface-contacting
portions
61 may provide further improvement of the finished web product's strength.
While not preferred, the steam moving under pressure through the web's
selected portions 62 may be used in the present invention even without the use
of the pressing surface 30 and the supporting surface 24, and without the
assistance of the temperature differential ~T between the pressing surface 30
and the supporting surface 24. One skilled in the art may easily visualize an
CA 02329806 2004-10-O1
embodiment (not shown) in which steam is forced to penetrate under pressure
the selected portions 62 arid move through the expansion conduits 25, thereby
causing the crepe in the selected portions 62 to relax and the selected
portions
62 to expand. In the latter embodiment, the steam preferably condenses into
the fabric 50 and is recycled.
FIGs. 4 and 5 show preferred embodiments of the apparatus 10 of the
present invention, comprising two opposite members: a pressing member 36
having the pressing surface 30, and a supporting member 26, having the
supporting surface 24. In the preferred continuous process of the present
invention, each of the pressing member 36 and the supporting member 26
comprises an endless belt or band traveling in the machine direction. In FIG.
5,
the pressing member 36 comprises the sintered layer 40; and the supporting
member 26 is associated with the moisture-receiving fabric 50, also comprising
an endless belt. Preferably, the moisture which is driven through the selected
portions 62 of the web 60 through the expansion conduits 25 of the working
surface 20 condenses into the fabric 50 disposed between the working surface
20 and the supporting surface 24. Preferably, a means for collecting and
recycling the moisture, well known in the art, is used in the process of the
present invention.
As shown in FIGs. 2-5, the selected portions 62 of the web 60 correspond
to the expansion conduits 25 of the working surface 20, and the surface-
contacting portions 61 of the web 60 correspond to and are in contact with the
working surface 20. In FIGs. 2-5, the surface-contacting portions 61 are
constrained between the working surface 20 and the pressing surface 30. As
has been explained above, the pressure should be sufficient to effectively
constrain the portions 61 in the direction perpendicular to the working
surface
20 so as to retain the crepe existing in the surface-contacting portions 61.
However, if desired, the pressure may be applied in excess of that which is
necessary to retain the crepe in the surface-contacting portions 61. In the
latter
instance, the surface-contacting portions 61 may be densified, while the
CA 02329806 2004-10-O1
26
selected portions 62, corresponding to the expansion conduits 25, are not
densified, or - if desired - densified to a lesser degree than the surface-
contacting portions 61 are. By densifying the foreshortened surface-contacting
portions 61, one might achieve further improvement in the web's strength. One
skilled in the art will appreciate that the degree of relative densification
of the
surface-contacting portions 61 and the selected portions 62 may depend upon
the applied pressure and a relative geometry of the working surface 20 and the
pressing surface 30. tf desired, the selected portions 62 of the web 60.may
also
be constrained in the direction perpendicular to the working surface 20. For
example, the selected portions 62 may be impressed between the pressing
surface 30 and the fabric 50, as shown in F1G. 4. In the latter instance, both
the
surface-contacting portions 61 and the selected portions 62 of the web 60 may
be densified, but to a different degree. The pressure differential between the
pressure applied to the surface-contacting portions 61 and the pressure
applied
to the selected portions 62 may be controlled, on the one hand -- by the
distance between the pressing surface 30 and the corresponding working
surface 20, and on the other hand - by the distance between the pressing
surface 30 and a surface restricting the expansion of the portions 62, i. e.,
the
surface of the reinforcing structure 23 in F1G. 3, or the surface of the
fabric 50
in FIG. 4.
FIGs. 3 and 4 show two exemplary embodiments of the working surface 20
superimposed with the pressing surface 30. In FIG. 3, the pressing surface 30
comprises the projected areas 31. Some of the projected areas 31, i. e., the
projected areas designated as 31b, correspond to (or registered with) the
working surface 20. Other projected areas 31, i. e.., the projected areas
designated as 31 a, correspond to (or registered with) the expansion conduits
25
of the working surface 20. While the embodiment of the working surface 20
shown in FIGs. 3 and 7 comprises discrete protuberances 27 encompassed by
the continuous expansion conduit 25, it is to be understood that the projected
areas of both the working surface 20 and the pressing surface 30 may (and
CA 02329806 2004-10-O1
27
preferably do) comprise the continuous network 22 described therein above and
best shown in F1G. 6. (One skilled in the art will appreciate that the
schematic
side elevational view shown in FIG. 3 is equally applicable to the network 22
comprising both the continuous pattern shown in F1G. 6, and the discrete
pattern shown in FIG. 7.)
It should be carefully noted that in FIG. 3, some of the projected areas 31,
i. e., the projected areas 31 a, of the pressing surface 30 have no
corresponding
protuberances 27 of the working surface 20, hence no corresponding working
surface 20. Still, the selected portions 62 of the web 60 may be partially
restrained between the projected areas 31 a and the reinforcing structure 23.
The selected portions 62 are constrained to a lesser degree relative to the
selected portions 61. Because the projected areas 31 a correspond . to the
expansion conduits 25 of the working surface 20, under the temperature
differential 0T the moisture travels from the projected areas 31 a through the
web 60, as has been described above. In the embodiment shown in F'IG. 3, the
pressure caused by the projected areas 31a partially impressing the selected
portions 62 against the reinforcing structure 23 is less than the pressure
caused
by the projected areas 31b impressing the surface-contacting portions .61
against the working surface 20. Therefore, it is believed that in the
embodiment
schematically shown in FIG. 3 the selected portions 62 comprise sub-portions
62a which are relatively unrestrained in the direction perpendicular to the
working surface 20, and sub-portions 62b which are restrained and may be
partially impressed by the projected areas 31 a corresponding to the expansion
conduits 25 of the working surface 20. Without wishing to be limited by
theory,
Applicants believe that this principal arrangement of the working surface 20
and
the pressing surface 30 may beneficially produce a web having at least three
differential micro-regions: a first micro-region formed by the surface-
contacting
portions 61 constrained in the direction perpendicular to the working surface
20
and thus substantially retaining crepe therein; a second micro-region formed
by
the sub-portions 62b partially-constrained and partially expanding in the
CA 02329806 2004-10-O1
28
direction perpendicular to the working surface 20 and thus having the crepe
partially relaxed therein; and a third micro-region formed by the sub-portions
62a relatively unconstrained in the direction perpendicular to the working
surface 20 and having crepe substantially relaxed therein, the sub-portions
62a of the third micro-region expending in the direction perpendicular to the
working surface 20.
In FIG. 4, showing another exemplary embodiment of the apparatus 10
of the present invention, the projected areas 31 of the pressing surface 30
are
registered with the conduits 25 of the working surface 20 such that when the
web 60 is constrained between the pressing surface 30 and the working
surface 20, the projected areas 31 facilitate deflection of the selected
portions
62 into the expansion conduits 25 of the working surface 20. In FIG. 4, the
projected areas 31 of the pressing surface 30 correspond to the expansion
conduits 25 of the working surface 20 and are in contact with the selected
portions 62 of the web 60. When the web 60 is impressed, the projected
areas 31 push, by contact, the selected portions 62 into the conduits 25,
thereby causing the selected portions 62 to expand, as shown in FIG. 4.
While FIGs. 2-5 show the selected portions 62 of the web 60
expending substantially perpendicular to the working surface 20 and to the
general plane of the web 60, "angled" expansion of the selected portions 62 is
also contemplated by the present invention. Two commonly assigned U.S.
Patent Nos. 5,948,210 and 5,900,122 are both entitled "Cellulosic Web,
Method and Apparatus for Making the Same Using Papermaking Belt Having
Angled Cross-Sectional Structure, and Method of Making the Belt". The
former patent discloses a papermaking belt comprising a confiinuous resinous
framework joined to a reinforcing structure and having a plurality of discrete
conduits therein, at least some of the conduits having an "angled" position
relative to the plane of the belt, i. e., the axes of the conduits and the
surface
of the belt form acute angles therebetween. The latter patent discloses a belt
having a plurality of
CA 02329806 2004-10-O1
29
of resinous protuberances joined to the reinforcing structure, and a
continuous
conduit, at least some of the protuberances being angled relative to the
surface of the belt, i. e., the axes of the protuberances and the surface of
the
belt form acute angles therebetween. These embodiments are not illustrated
herein, for in view of the two commonly-assigned patents cited herein above
one skilled in the art will be able to easily visualize the "angled" expansion
of
the selected portions 62 of the web 60.
The web 60, after having been subjected to the process of the present
invention, may be re-foreshortened, if desired. As used herein, the term "re-
foreshortening" refers to the process of foreshortening the web which has
already been at least partially foreshortened. For example, the web 60,
comprising the previously-foreshortened portions 61 and the expanded
selected portions 62, may be adhered to a creping surface and then creped
therefrom with a creping blade.
By way of illustration, and not by way of limitation, the following
examples are presented. A conventionally-made, creped paper web, having
basis weight of about 11 pounds per 3000 square feet, and the caliper of 6.0
mil, was crepe-relaxed according to the present invention and then tested.
The following TABLE illustrates results of the testing.
TABLE
ResultingChange in
Test Pressure Fiber-ConsistencyCaliper Caliper
psi % (mils) %)
Base N/A about 95 6.0 N/A
I 55 20 8.9 +48.3
II 55 about 95 5.3 -13.2
III 55 20 8.2 +36.6
IV ~ 55 about 95 5.2 -15.4
For comparison, a base sample of the dry web having caliper of 6.0 mils,
which was not subjected to the process of the present invention, is shown in
the first line of the Table.
CA 02329806 2004-10-O1
Tests I and II were conducted using the apparatus 10 of the present
invention, principally illustrated in FIG. 5. More specifically, this
apparatus 10
comprises the working surface 20 formed by the surface of a 6"x6" platen 28
having a plurality of expansion conduits 25 therein, and the pressing surface
30
formed by the surface of the sintered layer 40. The conduits 25 are
distributed
throughout the working surface 20 in a staggered pattern such that the platen
28
has 40% open area (i. e., conduits 25 comprise 40% of the entire platen's
surface). The platen 28 is made of a perforated metal, 14 gauge AL. Each of
the conduits 25 is an aperture having 0.12.5" diameter. The sintered layer 40
is
formed by a
6"x10"x0.078" Sintered Stainless Steel, having 40~m pore size, made by Mott
Corporation and referred to herein above. The platen .28 is adjacent to the
condensation fabric 50 formed by 6"x6" portion of the Spiral Weave, Duraflex
Belt, made by Albany International, Inc:, which was referenced herein above.
Tests ILI and IV were conducted using the apparatus 10, schematically
shown in FIG. 5A. This apparatus 10 comprises two mutually opposite 6"x6"
platens 28, described in the previous paragraph. The platens 28 are interposed
such that their respective conduits 25 and 35 correspond, as shown in FIG. 5A.
The sintered Layer 40 and the fabric 50 are identical to those described in
the
previous paragraph.
tn all tests I-IV, a press (not shown) was used to cause the pressing
member 36 and the supporting member 26 to move towards each other and to
iimpress the working surface 20 with the associated web 60 therebetween. The
press used is Carver Laboratory Press, Model "C," made by Carver, inc., of
Indiana (1569 Morris street, Wabash, IN 46992-0544). The press is equipped
with 6"x6" Electric Heating Platens, Catalog No. 27 01, available from Carver,
Inc. In all I-IV tests, the web 60 was interposed between the working surface
20.
and the pressing surface 30,, the web 60 was at least partially moistened and
impressed between the pressing and working surfaces 30, 20 at pressure of 55
CA 02329806 2004-10-O1
31
psi (cylinder pressure) for 7 minutes. Then, the caliper of the selected
portions
of the dried web 60 (having fiber-consistency of about 95%) was measured.
In Test I, the entire sample of the web 60 was moistened to have fiber-
consistency of about 20%. As TABLE shows, the caliper of the web 60
increased to 8.9 mils, i. e., by more than 48% relative to the base sample's
caliper of 6.0 mils. For comparison, in Test Il, a dry (about 95% fiber-
consistency) sample of the web 60 was impressed under the same pressure; the
resulting caliper was only 5.3 mils.
In Test III, only the selected portions 62, corresponding to the expansion
conduits 25 and 35 were moistened to have fiber-consistency of about 20%.
The resulting caliper of the selected portions 62 was 8.2 mils, i. e.,
increased by
more than 36%, relative to the base sample's caliper of 6.0 mil. In Test IV,
the
dry (about 95% fiber-consistency) sample of the web, after having been
impressed at the pressure of 55 psi, had 5.2 mils caliper.
Caliper of the selected portions 62 of web 60 was measured as the
thickness of the "preconditioned" selected portions 62 when subjected 'to a
compressive load of 15 gram per square centimeter (g/cm2), or 95 gram per
square inch (glint), with a presser foot having diameter of 2 inches (5.08
cm).
The term "preconditioned" means a web subjected to a temperature of (23~1
)°C;
and a relative humidity of (50~2)% for 24 hours, according to a TAPPI Method #
T4020M-88. The caliper was measured with a Thwing-Albert model 89-11
thickness tester made by Thwing-Albert Co. of Philadelphia, PA.
