U.S. patent application number 13/078514 was filed with the patent office on 2011-07-21 for forming fabric with extended surface.
This patent application is currently assigned to Voith Patent GmbH. Invention is credited to Lippi A. Fernandes, John Jeffery, Antony Morton, Justin Payne, Martin Ringer.
Application Number | 20110174456 13/078514 |
Document ID | / |
Family ID | 38596411 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110174456 |
Kind Code |
A1 |
Fernandes; Lippi A. ; et
al. |
July 21, 2011 |
FORMING FABRIC WITH EXTENDED SURFACE
Abstract
A method of forming a structured fibrous web including the steps
of supplying a fiber slurry to a nip, the nip being formed by a
structured fabric and a forming fabric; dewatering the fiber slurry
through the forming fabric to create a web; retaining the web with
the structured fabric through at least one dewatering process, the
forming fabric including a woven fabric having a paper side and a
roll side, the paper side having a paper side surface and said roll
side having a roll side surface; and providing a polymer material
deposit extending above the paper side surface, the polymer
material deposit having at least one of a random pattern, a random
motif, a pseudo-random pattern, a pseudo-random motif, a
predetermined pattern and a predetermined motif.
Inventors: |
Fernandes; Lippi A.;
(Overijssel, NL) ; Ringer; Martin; (Lancashire,
GB) ; Morton; Antony; (Yorkshire, GB) ;
Jeffery; John; (Lancashire, GB) ; Payne; Justin;
(Lancashire, GB) |
Assignee: |
Voith Patent GmbH
|
Family ID: |
38596411 |
Appl. No.: |
13/078514 |
Filed: |
April 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12353367 |
Jan 14, 2009 |
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13078514 |
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PCT/EP2007/057142 |
Jul 12, 2007 |
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12353367 |
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Current U.S.
Class: |
162/203 |
Current CPC
Class: |
D21F 11/14 20130101;
D21F 11/145 20130101; D21F 1/0027 20130101; Y10T 442/20 20150401;
D21F 11/006 20130101; Y10T 442/172 20150401 |
Class at
Publication: |
162/203 |
International
Class: |
D21F 11/00 20060101
D21F011/00 |
Claims
1. A method of forming a structured fibrous web, said method
comprising the steps of: supplying a fiber slurry to a nip, said
nip being formed by a structured fabric and a forming fabric;
dewatering said fiber slurry through said forming fabric to create
a web; retaining the web with said structured fabric through at
least one dewatering process, said forming fabric including a woven
fabric having a paper side and a roll side, said paper side having
a paper side surface and said roll side having a roll side surface;
and providing a polymer material deposit extending above said paper
side surface, said polymer material deposit having at least one of
a random pattern, a random motif, a pseudo-random pattern, a
pseudo-random motif, a predetermined pattern and a predetermined
motif.
2. The method according to claim 1, wherein said polymer material
deposit is at least one of an RTY-type material, an RTV-type heat
curable material, an acrylic, an epoxy resin, a silicone, a
polyurethane, a hydrosol, a polyolefin, UV curable, a natural
rubber, a synthetic rubber, nanopolymers, carbon fullerenes,
dendrimers, polymers loaded with carbon, polymers loaded with
metals, electrically conducting polymers, semi-conductors, liquid
crystal polymers, hot melts, polymers that are sensitive to
pressure, polymers that are sensitive to light, polymers that are
sensitive to temperature, reactive polymers and living
polymers.
3. The method according to claim 2, wherein said structured fabric
has peaks and valleys, said structured fabric further comprising a
plurality of yarns woven together and having a mesh count and a
weave pattern, said weave pattern including said valleys being from
approximately 0.07 mm to approximately 0.60 mm deep and said mesh
count being between 95.times.120 and 26.times.20 per square inch,
the method further comprising the step of substantially collecting
fibers of said fiber slurry in a plurality of said valleys of said
structured fabric.
4. The method according to claim 3, further comprising the step of
dewatering said fiber slurry through said forming fabric and not
through said structured fabric.
5. The method according to claim 4, wherein said step of collecting
said fibers of said fiber slurry further includes the step of
forming a structured web.
6. The method according to claim 5, wherein said structured web has
a pillow thickness and a pillow basis weight formed in said valleys
and a top surface thickness and a top surface basis weight formed
on said peaks, said pillow thickness being one of equal to and
greater than said top surface thickness and said pillow basis
weight being one of equal to and greater than said top surface
basis weight.
7. The method according to claim 6, further comprising the steps of
removing said forming fabric from said structured web and
contacting said structured web with a dewatering fabric and
removing moisture from said structured web through said dewatering
fabric.
8. The method according to claim 7, further comprising the steps
of: applying pressure against a contact area of said fibrous web
with a portion of a permeable belt, said contact area being at
least approximately 10% of an area of said portion; and moving a
fluid through an open area of said permeable belt and through said
fibrous web, said open area being at least approximately 25% of
said portion, said permeable belt having a tension of at least
approximately 30 KN/m during said step of applying pressure and
said step of moving said fluid.
9. The method according to claim 8, further comprising the steps
of: applying pressure against a contact area of said fibrous web
with a portion of a permeable belt, said contact area being at
least approximately 25% of an area of said portion; and moving a
fluid through an open area of said permeable belt and through said
fibrous web, said open area being at least approximately 25% of
said portion, said permeable belt having a tension of at least
approximately 30 KN/m during said step of applying pressure and
said step of moving said fluid.
10. The method according to claim 9, wherein during said steps of
applying pressure and moving fluid, said structured fibrous web is
positioned between said structured fabric and said dewatering
fabric, said permeable belt contacting said structured fabric and
said dewatering fabric contacting a surface of a roll, said
pressure being applied through said structured fabric to said
fibrous web and said fluid moving first through said fibrous web
and second through said dewatering fabric.
11. The method according to claim 10, wherein said tension is
greater than approximately 60 KN/m.
12. The method according to claim 11, wherein said step of applying
pressure and said step of moving said fluid occur for a dwell time
sufficient to produce a fibrous web solids level in a range between
approximately 25% to approximately 55%.
13. The method according to claim 12, wherein said dwell time is
one of equal to and greater than approximately 40 ms.
14. The method according to claim 13, wherein said dwell time is
one of equal to and greater than approximately 50 ms.
15. A method of forming a structured fibrous web, said method
comprising the steps of: supplying a fiber slurry to a nip, said
nip being formed by a structured fabric and a forming fabric, said
structured fabric having peaks and valleys and including a
plurality of yarns woven together, said structured fabric having a
mesh count and a weave pattern, said weave pattern including said
valleys being from approximately 0.07 mm to approximately 0.60 mm
deep and said mesh count being between 95.times.120 and 26.times.20
per square inch; dewatering said fiber slurry through said forming
fabric to create a web; retaining the web with said structured
fabric through at least one dewatering process, said forming fabric
including a woven fabric having a paper side and a roll side, said
paper side having a paper side surface and said roll side having a
roll side surface; and providing a polymer material deposit
extending above said paper side surface, said polymer material
deposit having at least one of a random pattern, a random motif, a
pseudo-random pattern, a pseudo-random motif, a predetermined
pattern and a predetermined motif.
16. A method of forming a structured fibrous web, said method
comprising the steps of: supplying a fiber slurry to a nip, said
nip being formed by a structured fabric and a forming fabric, said
structured fabric having peaks and valleys; dewatering said fiber
slurry through said forming fabric to create a web to form a
structured web having a pillow thickness formed in said valleys and
a top surface thickness formed on said peaks, said pillow thickness
being one of equal to and greater than said top surface thickness;
retaining the web with said structured fabric through at least one
dewatering process, said forming fabric including a woven fabric
having a paper side and a roll side, said paper side having a paper
side surface and said roll side having a roll side surface; and
providing a polymer material deposit extending above said paper
side surface, said polymer material deposit having at least one of
a random pattern, a random motif, a pseudo-random pattern, a
pseudo-random motif, a predetermined pattern and a predetermined
motif.
17. The method according to claim 16, said structured web having a
pillow basis weight formed in said valleys and a top surface basis
weight formed on said peaks, said pillow basis weight being one of
equal to and greater than said top surface basis weight.
18. The method according to claim 17, further comprising the steps
of removing said forming fabric from said structured fabric and
contacting said structured web with a dewatering fabric and
removing moisture from said structured web through said dewatering
fabric.
19. The method according to claim 18, further comprising the steps
of: applying pressure against a contact area of said fibrous web
with a portion of a permeable belt, said contact area being at
least approximately 10% of an area of said portion; and moving a
fluid through an open area of said permeable belt through said
fibrous web, said open area being at least approximately 25% of
said portion, said permeable belt having a tension of at least
approximately 30 KN/m during said step of applying pressure and
said step of moving said fluid.
20. The method according to claim 19, said contact area being at
least 25% of said area of said portion.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a division of U.S. patent application Ser. No.
12/353,367, entitled "FORMING FABRIC WITH EXTENDED SURFACE", filed
Jan. 14, 2009, which is incorporated herein by reference. U.S.
patent application Ser. No. 12/353,367 is a continuation of PCT
application No. PCT/EP2007/057142, entitled "FORMING FABRIC WITH
EXTENDED SURFACE", filed Jul. 12, 2007, which claims priority to
U.S. patent application Ser. No. 11/486,783, entitled "FORMING
FABRIC WITH EXTENDED SURFACE", filed Jul. 14, 2006, each of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a fabric used in
papermaking. More specifically, the present invention relates to
forming fabrics used in the forming section of a papermaking
machine, and more specifically, to a forming fabric for use in
tissue making. The present invention further relates to a method of
making a fibrous web, and more specifically, to a method of making
a tissue web.
[0004] 2. Description of the Related Art
[0005] In the art of papermaking, multiple steps occur from the
introduction of a pulp slurry to the output of a finished paper
product. The initial introduction of the slurry is at the portion
of a papermaking machine known as the wet end. Here, the slurry, or
fiber suspension, is initially dewatered when the slurry is
introduced onto a moving forming fabric in the forming section of
the papermaking machine. Varying amounts of water are removed from
the slurry through the forming fabric, resulting in the formation
of a fibrous web on the surface of the forming fabric.
[0006] Forming fabrics address not only the dewatering of the
slurry, but also the sheet formation and, therefore, the sheet
quality resulting from the formation of the fibrous web. More
specifically, the forming fabric must simultaneously control the
rate of drainage while preventing fiber and other solid components
contained in the slurry from passing through the fabric with the
water. The role of the forming fabric also includes conveyance of
the fibrous web to the press section of the papermaking
machine.
[0007] Additionally, if drainage of water from the slurry occurs
too rapidly or too slowly, the quality of the fibrous web and the
overall machine production efficiency are reduced. Controlling
drainage by way of fabric void volume is one of the fabric design
criteria.
[0008] Forming fabrics have been produced to meet the needs and
requirements of the various papermaking machines for the various
paper grades being manufactured. As the need arises to increase
production speed of the papermaking machines and the quality of the
paper being produced, the need for improved paper machine clothing
allowing for increased production rates and improved quality
results.
[0009] In tissue making, it is known to add texture or patterns to
the fibrous web during manufacturing. In WO 02/088464 it is known
to pattern paper for use in a tissue for beverage infusion, for
example, a tea bag. Here, a screen, or forming fabric, is used for
producing paper by a wet-laying technique. The screen has a base
material woven in a mesh-like structure, for example, with
synthetic monofilaments. Drainage blockage of the base material is
accomplished by applying a synthetic resin to block apertures of
the base fabric mesh. The pattern or letters are formed by laying
down a polymer that provides complete or partial blockage of
discrete apertures. In this manner, the polymer does not affect the
surface properties of the woven fabric as the polymer fills
discrete apertures of the fabric mesh. A pattern is formed when the
water of the fibrous suspension drains through regions of the
fabric that are not blocked. The result is a paper product with
higher fiber concentration corresponding to unblocked areas as
compared to blocked areas. In this manner, a pattern is formed
where there is lower fiber concentration. This results in a
weakness of the fibrous web in the areas of lower fiber
concentration.
[0010] While printed forming fabrics can be used on conventional
tissue machines, there is no advantage to using them on
conventional tissue machines were the sheet is 100% pressed and the
bulk is too low to produce micro-embossed and macro-embossed sheets
in the machine and a converting line to emboss the sheet is needed.
The printed forming fabric can be used on through air drying
machines (TAD) where the bulk and sheet absorbency is 50 to 100%
higher than on conventional machines. On this kind of machine, the
sheet is formed on a twin wire and is vacuum dewatered to a dryness
between 22% and 26%. Only at this high consistency, the sheet is
transferred to a structured fabric where it is wet molded by a
vacuum box (wet shaping box), which suctions the fibers into the
valleys of the structured fabric. By suctioning an already formed
sheet, with over 20% consistency, the fibers are stretched into the
valleys, thus the sheet caliper is reduced and only a small portion
of the fibers remain protected within the structure of the fabric,
these being the fibers which will be remain unpressed for quality.
Thus, on TAD machines, there is a need to run a negative draw
between the forming section and the TAD section. Generally, TAD
machines run at 20% lower speed on the TAD section to brush the
fibers into the valleys of the fabric. In this manner, all the
macro embossing (drawings) coming from the printed forming fabric
will be destroyed by the speed difference between the forming
section and the TAD section. Accordingly, on TAD machines the macro
and micro-embossing has to be done with the structured fabric in
the TAD section and not in the forming section. By doing this micro
and macro embossing in the machine it would be possible to avoid
doing it in the converting line, thus compacting the sheet and
loosing quality.
[0011] What is needed in the art is a fabric that forms a web
having texture and more uniform fiber concentrations for improved
marking and overall performance.
SUMMARY OF THE INVENTION
[0012] The present invention provides a fabric used in papermaking,
and more particularly, a forming fabric for manufacturing a web for
tissue in an advanced dewatering system. In an embodiment, the
fabric is a forming fabric having a polymeric deposit. The fabric
may be any known forming fabric, for example, single or
multi-layer.
[0013] Additionally, the present invention provides a forming
fabric that produces a structured sheet in the Advanced Dewatering
System (ADS, also known as Advanced Tissue Molding System, or
ATMOS) machine, which produces the same quality, bulk and water
absorbency as TAD machines and does the micro-embossing with the
structured fabric and the macro-embossing with the special
developed forming fabric. Since the produced sheet is already wet
structured in the machine, there is no need to further emboss the
sheet going through an expensive converting line to press the micro
and macro structures into the sheet. By pressing the structure into
the dry sheet on a converting line, the sheet is compacted, thus
the quality, bulk, volume and absorbency capacity are reduced. In
ATMOS, the speed of the paper stays approximately the same during
fabric transfer.
[0014] On an ADS, the sheet is formed and dewatered between the
structured fabric and a forming fabric, and the sheet is further
dewatered between the structured fabric and a dewatering fabric.
The sheet is dewatered through the dewatering fabric (opposite to
structured fabric) and the dewatering is done by an air flow and a
mechanical pressure field. The mechanical pressure field is
generated by a permeable belt. The direction of the air flow is
from the permeable belt to the dewatering fabric. This sandwich of
fabrics forms an extended pressure nip over a vacuum roll. The max
peak pressure is approximately 40 times lower than a conventional
press and there is air flow through the nip. The sheet is protected
and further carried by the structured fabric to the Yankee dryer
and is further dried by Yankee/Hood and dry creped. Accordingly, a
structured sheet like a TAD product is produced with the same
premium quality, but without using the expensive TAD machine. There
is 40% less capital investment, less machine equipment, less civil
work, simplified building, easier operation, less maintenance and
35% less total consumable cost (energy, clothing, chemicals).
[0015] Another advantage of this solution is that the sheet is
formed over a structured fabric, starting with very low
consistency, between about 0.15% to 0.35%, and the same structured
fabric carries the fibers, protected within its structure, from the
headbox to the transfer to the Yankee dryer. Against the Yankee
dryer, only the fibers at the knuckle area of the structured fabric
will be pressed, and the protected fibers, within the body of the
structured fabric, remain unpressed for quality. The valleys of the
structured fabric are filled with the maximum amount of fibers
because this will be the mass of unpressed fibers which will give
the final premium paper quality.
[0016] Since the produced sheet is already structured, there is no
need to further emboss the sheet going through an expensive
converting line to press the micro and macro structures into the
sheet. By pressing the structure into the dry sheet in a converting
line, the sheet is compacted, thus, the quality, bulk, volume and
absorbency capacity is reduced.
[0017] Still further, the fabric is, for example, made from, but
are not limited to mono filament yarns, synthetic or polyester mono
filament yarns, twisted mono filament yarns, twisted synthetic or
twisted polyester or twisted polyamide mono filament yarns, twisted
multi-filament yarns, twisted synthetic or twisted polyester
multi-filament yarns, core and sheath, non-plastic materials,
co-polymer materials, and others. Various yarn profiles can be
employed including, for example, yarns having a circular cross
sectional shape with one or more diameters or other cross sectional
shapes, for example, non-round cross sectional shapes such as oval,
or a polygonal cross sectional shapes, for example diamond, square,
pentagonal, hexagonal, septagonal, octagonal, and so forth, or any
other shape that the yarns may be fabricated.
[0018] Materials used to make the base fabric can be from, for
example, polyethylenepterathalate (PET), polyamides (PA),
polyethylene naphthalate (PEN), polybutylene tere-phthalate (PBT)
and polyetheretherketone (PEEK). Likewise, the fabric can be made
from one or more materials.
[0019] The polymeric material to be deposited is at least one of a
silicone and a polyurethane. By way of example, the silicone can be
any RTY-type, two-component heat curable material. Other possible
polymeric materials, selectable based on the application, include,
but are not limited to, acrylics, epoxy resins, silicones,
polyurethanes--such as thermoplastic, thermoset, and two component
polyurethanes, hydrosols, polyolefins--such as ABS, PS, PC, PET,
PPS, PEEK, PA, EVA, PE, HDPE, LDPE, LLDPE, PP, PTFE, and PVC, UV
curables, rubbers--both natural and synthetic,
nanopolymers/technology, carbon fullerenes, dendrimers, polymers
loaded with carbon or metals, electrically conducting polymers and
semi-conductors, liquid crystal polymers, hot melts, polymers that
are sensitive to pressure, light and temperature, reactive polymers
and living polymers. When cured, the polymeric material has a shore
A hardness of approximately 3 to approximately 80, depending on the
material used and the predetermined application.
[0020] The polymer material added to the fabric can be deposited in
a random pattern, a pseudo-random pattern, a predetermined pattern,
or any combination of the three to form a pattern or motif on the
final tissue paper.
[0021] In an embodiment, the polymeric material is delivered to the
fabric either through a screen or from a bank of small bore tubes
(needle application) set at a predetermined distance above the
fabric. When the screen method is used, the polymeric material is
delivered through the screen by a blade that is in contact with the
inside face of the screen. In this manner the print height is
determined by the thickness of the screen wall.
[0022] For the screen application, to control the flow of the
polymeric material into the fabric, the viscosity of the polymeric
material is less than 40,000 centipoises cP. For small bore needle
applications, the viscosity of the polymeric material is less than
50,000 centipoises cP. The viscosity of the polymeric material is
selected to control the amount of penetration of the polymeric
material into the fabric. For the present invention, penetration is
between about 10% and about 100%. The amount of penetration into
the fabric is a function of the fabric and the use of the fabric.
For general applications, the penetration is, for example,
approximately 40%-60%. When a fine mesh fabric is used, the
penetration can be, for example, up to 100%.
[0023] The height of the polymeric material above the surface of
the paper side of the fabric is variable depending on the method of
application and the desires of the application. For example, when
screening the polymeric material onto the fabric, the polymer
material has a height above the surface of the fabric of about 0.01
mm to about 1.0 mm, for example, about 0.05 mm. When used for
embossing type applications, for example, through air drying (TAD),
the height above the surface of the fabric is about 0.1 mm to about
2.0 mm, for example, about 0.1 mm to about 1.0 mm, or about 0.05
mm. For small bore needle applications, the height of the polymeric
material can be up to 3 mm. Permeability range of the fabric with
the applied pattern/design is approximately 50 cfm to approximately
1200 cfm, for example, in the range of approximately 200 cfm to
approximately 900 cfm, or approximately 300 cfm to approximately
800 cfm. It is also understood that there are no limitations to the
paper grades or former types where the present invention can be
applied.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0025] FIG. 1 is a cross-sectional schematic diagram illustrating
the formation of a structured web using an embodiment of a method
of the present invention;
[0026] FIG. 2 is a cross-sectional view of a portion of a
structured web of a prior art method;
[0027] FIG. 3 is a cross-sectional view of a portion of the
structured web of an embodiment of the present invention as made on
the machine of FIG. 1;
[0028] FIG. 4 illustrates the web portion of FIG. 2 having
subsequently gone through a press drying operation;
[0029] FIG. 5 illustrates a portion of the fiber web of the present
invention of FIG. 3 having subsequently gone through a press drying
operation;
[0030] FIG. 6 illustrates a resulting fiber web of the forming
section of the present invention;
[0031] FIG. 7 illustrates the resulting fiber web of the forming
section of a prior art method;
[0032] FIG. 8 illustrates the moisture removal of the fiber web of
the present invention;
[0033] FIG. 9 illustrates the moisture removal of the fiber web of
a prior art structured web;
[0034] FIG. 10 illustrates the pressing points on a fiber web of
the present invention;
[0035] FIG. 11 illustrates pressing points of prior art structured
web;
[0036] FIG. 12 illustrates a schematical cross-sectional view of an
embodiment of a papermaking machine of the present invention;
[0037] FIG. 13 illustrates a schematical cross-sectional view of
another embodiment of a papermaking machine of the present
invention;
[0038] FIG. 14 illustrates a schematical cross-sectional view of
another embodiment of a papermaking machine of the present
invention;
[0039] FIG. 15 illustrates a schematical cross-sectional view of
another embodiment of a papermaking machine of the present
invention;
[0040] FIG. 16 illustrates a schematical cross-sectional view of
another embodiment of a papermaking machine of the present
invention;
[0041] FIG. 17 illustrates a schematical cross-sectional view of
another embodiment of a papermaking machine of the present
invention; and
[0042] FIG. 18 illustrates a schematical cross-sectional view of
another embodiment of a papermaking machine of the present
invention;
[0043] FIG. 19 is a perspective view of a forming fabric with an
extended surface according to the present invention;
[0044] FIG. 20 is a top view of a forming fabric with an extended
surface according to the present invention; and
[0045] FIG. 21 is a cross-section along A-A of the forming fabric
of FIG. 20.
[0046] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0047] Referring now to the drawings, and more particularly to FIG.
1, there is shown fibrous web machine 20 including headbox 22 that
discharges fibrous slurry 24 between forming fabric 26 and
structured fabric 28. Rollers 30 and 32 direct fabric 26 in such a
manner that tension is applied against slurry 24 and structured
fabric 28. Structured fabric 28 is supported by forming roll 34
which rotates with a surface speed that matches the speed of
structured fabric 28 and forming fabric 26. Structured fabric 28
has peaks 28a and valleys 28b, which give a corresponding structure
to web 38 formed thereon. Structured fabric 28 travels in direction
W and, as moisture M is driven from fibrous slurry 24, structured
fibrous web 38 takes form. Moisture M that leaves slurry 24 travels
through forming fabric 26 and is collected in save-all 36. Fibers
in fibrous slurry 24 collect predominately in valleys 28b as web 38
takes form.
[0048] Structured fabric 28 includes warp and weft yarns interwoven
on a textile loom. Structured fabric 28 may be woven flat or in an
endless form. The final mesh count of structured fabric 28 lies
between 95.times.120 and 26.times.20. For the manufacture of toilet
tissue, for example, the mesh count may be 51.times.36 or higher
or, for example, 58.times.44 or higher. For the manufacturer of
paper towels, for example, the mesh count may be 42.times.31 or
lower, or, for example, 36.times.30 or lower. Structured fabric 28
may have a repeated pattern of 4 shed and above repeats or, for
example, 5 shed or greater repeats. The warp yarns of structured
fabric 28 have diameters of between 0.12 mm and 0.70 mm, and weft
yarns have diameters of between 0.15 mm and 0.60 mm. The pocket
depth, which is the offset between peak 28a and valley 28b, is
between approximately 0.07 mm and 0.60 mm. Yarns utilized in
structured fabric 28 may be of any cross-sectional shape, for
example, round, oval or flat. The yarns of structured fabric 28 can
be made of thermoplastic or thermoset polymeric materials of any
color. The surface of structured fabric 28 can be treated to
provide a desired surface energy, thermal resistance, abrasion
resistance and/or hydrolysis resistance. A printed design, such as
a screen printed design, of polymeric material can be applied to
structured fabric 28 to enhance its ability to impart an aesthetic
pattern into web 38 or to enhance the quality of web 38. Such a
design may be in the form of an elastomeric cast structure similar
to the Spectra.RTM. membrane described in another patent
application. Structured fabric 28 has a top surface plane contact
area at peak 28a of 10% or higher, for example, 20% or higher, or
30% depending upon the particular product being made. The contact
area on structured web 28 at peak 28a can be increased by abrading
the top surface of structured fabric 28 or an elastomeric cast
structure can be formed thereon having a flat top surface. The top
surface may also be hot calendered to increase the flatness.
[0049] Forming roll 34 is preferably solid. Moisture travels
through forming fiber 26, but not through structured fabric 28.
This advantageously forms structured fibrous web 38 into a more
bulky or absorbent web than the prior art.
[0050] Prior art methods of moisture removal remove moisture
through a structured fabric by way of negative pressure. It results
in a cross-sectional view as seen in FIG. 2. Prior art structured
web 40 has pocket depth D which corresponds to the dimensional
difference between a valley and a peak, the valley occurring at the
point where measurement C occurs and the peak occurring at the
point where measurement A is taken. Top surface thickness A is
formed in the prior art method. Sidewall dimension B and pillow
thickness C of the prior art result from moisture drawn through a
structured fabric. Dimension B is less than dimension A and
dimension C is less than dimension B in the prior art
structure.
[0051] In contrast, structured web 38, as illustrated in FIGS. 3
and 5, have, for discussion purposes, pocket depth D that is
similar to the prior art. However, sidewall thickness B' and pillow
thickness C' exceed the comparable dimensions of web 40. This
advantageously results from the forming of structural web 38 on
structured fabric 28 at low consistency and the removal of moisture
in an opposite direction from the prior art. This results in
thicker pillow dimension C'. Even after fiber web 38 goes through a
drying press operation, as illustrated in FIG. 5, dimension C' is
substantially greater than A'p. Advantageously, the fiber web
resulting from the present invention has a higher basis weight in
the pillow areas as compared to prior art. Also, the fiber to fiber
bonds are not broken as they can be in impression operations, which
expand the web into the valleys.
[0052] According to prior art, an already formed web is vacuum
transferred into a structured fabric. The sheet must then expand to
fill the contour of the structured fabric. In doing so, fibers must
move apart. Thus, the basis weight is lower in these pillow areas
and, therefore, the thickness is less than the sheet at point
A.
[0053] Now, referring to FIGS. 6 to 11, the process will be
explained by simplified schematic drawings.
[0054] As shown in FIG. 6, fibrous slurry 24 is formed into web 38
with a structure inherent in the shape of structured fabric 28.
Forming fabric 26 is porous and allows moisture to escape during
forming. Further, water is removed as shown in FIG. 8, through
dewatering fabric 82. The removal of moisture through fabric 82
does not cause a compression of pillow areas C' in the forming web,
since pillow areas C' reside in the structure of structured fabric
28.
[0055] Prior art web 40, shown in FIG. 7, is formed with a
conventional forming fabric, as between two conventional forming
fabrics in a twin wire former, and is characterized by a flat
uniform surface. It is this fiber web that is given a
three-dimensional structure by a wet shaping stage, which results
in the fiber web shown in FIG. 2. A conventional tissue machine
that employs a conventional press fabric will have a contact area
approaching 100%. Normal contact area of the structured fiber, as
in the present invention or on a TAD machine is typically much
lower than that of a conventional machine. It is in the range of
15% to 35%, depending on the particular pattern of the product
being made.
[0056] In FIGS. 9 and 11 a prior art web structure is shown where
moisture is drawn through structured fabric 33 causing the web, as
shown in FIG. 7, to be shaped and causing pillow area C to have a
low basis weight as the fibers in the web are drawn into the
structure. The shaping can be done by performing pressure or
underpressure to web 40 forcing web 40 to follow the structure of
structured fabric 33. This additionally causes fiber tearing as
they are moved into pillow area C. Subsequent pressing at Yankee
dryer 52, as shown in FIG. 11, further reduces the basis weight in
area C. In contrast, water is drawn through dewatering fabric 82 in
the present invention, as shown in FIG. 8, preserving pillow areas
C'. Pillow areas C' of FIG. 10, are unpressed zones, which are
supported on structured fabric 28, while pressed against Yankee 52.
Pressed zone A' is the area through which most of the pressure
applied is transferred. Pillow area C' has a higher basis weight
than that of the illustrated prior art structures.
[0057] The increased mass ratio of the present invention,
particularly the higher basis weight in the pillow areas, carries
more water than the compressed areas, resulting in at least two
positive aspects of the present invention over the prior art, as
illustrated in FIGS. 10 and 11. First, it allows for a good
transfer of the web to Yankee surface 52 since the web has a
relatively lower basis weight in the portion that comes in contact
with Yankee surface 52 at a lower overall sheet solid content than
had been previously attainable because of the lower mass of fibers
that comes in contact with Yankee dryer 52. The lower basis weight
means that less water is carried to the contact points with Yankee
dryer 52. The compressed areas are dryer than the pillow areas,
thereby allowing an overall transfer of the web to another surface,
such as Yankee dryer 52, with a lower overall web solids content.
Secondly, the construct allows for the use of higher temperatures
in Yankee hood 54 without scorching or burning of the pillow areas,
which occurs in the prior art pillow areas. Yankee hood 54
temperatures are often greater than 350.degree. C. and may, for
example, be greater than 450.degree. C. or even greater than
550.degree. C. As a result, the present invention can operate at
lower average pre-Yankee press solids than the prior art, making
more full use of the capacity of the Yankee Hood drying system. The
present invention allows the solids content of web 38 prior to the
Yankee dryer to run at less than 40%, for example, less than 35%
and even as low as 25%.
[0058] Due to the formation of the web 38 with structured fabric 28
the pockets of fabric 28 are fully filled with fibers. Therefore,
at Yankee surface 52 web 38 has a much higher contact area, up to
approx. 100%, as compared to the prior art because web 38 on the
side contacting Yankee surface 52 is almost flat. At the same time
pillow areas C' of web 38 maintain unpressed, because they are
protected by the valleys of structured fabric 28 (FIG. 10). Good
results in drying efficiency were obtained only pressing 25% of the
web.
[0059] As can be seen in FIG. 11, the contact area of prior art web
40 to Yankee surface 52 is much lower as compared to the one of web
38 manufactured according to the present invention. The lower
contact area of prior art web 40 results from the shaping of web 40
that now follows the structure of structured fabric 33. Due to less
contact area of prior art web 40 to Yankee surface 52, the drying
efficiency is less.
[0060] Now, referring to FIG. 12, there is shown an embodiment of
the process where structured fiber web 38 is formed. Structured
fabric 28 carries three dimensional structured web 38 to advanced
dewatering system 50, past suction box 67 and then to Yankee roll
52 where the web is transferred to Yankee roll 52 and hood section
54 for additional drying and creping before winding up on a reel
(not shown). Shoe press 56 is placed adjacent to structured fabric
28, holding it in a position proximate to Yankee roll 52.
Structured web 38 comes into contact with Yankee roll 52 and
transfers to a surface thereof, for further drying and subsequent
creping. Vacuum box 58 is placed adjacent to structured fabric 28
to achieve a solids level of 15-25% on a nominal 20 gsm web running
at -0.2 to -0.8 bar vacuum, for example, with an operating level of
-0.4 to -0.6 bar. Web 38, which is carried by structured fabric 28,
contacts dewatering fabric 82 and proceeds toward vacuum roll 60.
Vacuum roll 60 operates at a vacuum level of -0.2 to -0.8 bar, for
example, with an operating level of at least -0.4 bar. Hot air hood
62 is optionally fit over vacuum roll 60 to improve dewatering. If,
for example, a commercial Yankee drying cylinder with 44 mm steel
thickness and a conventional hood with an air blowing speed of 145
m/s is used, production speeds of 1400 m/min or more for towel
paper and 1700 m/min or more for toilet paper are used.
[0061] Optionally, a steam box can be installed instead of hood 62
supplying steam to web 38. The steam box may have a sectionalized
design to influence the moisture re-dryness cross profile of web
38. The length of the vacuum zone inside vacuum roll 60 can be from
200 mm to 2,500 mm, for example, 300 mm to 1,200 mm, or a length of
between 400 mm to 800 mm. The solids level of web 38 leaving
suction roll 60 is 25% to 55% depending on installed options.
Vacuum box 67 and hot air supply 65 can be used to increase web 38
solids after vacuum roll 60 and prior to Yankee roll 52. Wire
turning roll 69 can also be a suction roll with a hot air supply
hood. Roll 56 includes a shoe press with a shoe width of 80 mm or
more, for example, 120 mm or more, with a maximum peak pressure of
less than 2.5 MPa. To create an even longer nip to facilitate the
transfer of web 38 to Yankee 52, web 38 carried on structured
fabric 28 can be brought into contact with the surface of Yankee
roll 52 prior to the press nip associated with shoe press 56.
Further, the contact can be maintained after structured fabric 28
travels beyond press 56.
[0062] Dewatering fabric 82 may have a permeable woven base fabric
connected to a batt layer. The base fabric includes machine
direction yarns and cross-directional yarns. The machine direction
yarn is a 3 ply multifilament twisted yarn. The cross-direction
yarn is a monofilament yarn. The machine direction yarn can also be
a monofilament yarn and the construction can be of a typical
multilayer design. In either case, the base fabric is needled with
a fine batt fiber having a weight of less than or equal to 700 gsm,
for example, less than or equal to 150 gsm, or less than or equal
to 135 gsm. The batt fiber encapsulates the base structure giving
it sufficient stability. The needling process can be such that
straight through channels are created. The sheet contacting surface
is heated to improve its surface smoothness. The cross-sectional
area of the machine direction yarns is larger than the
cross-sectional area of the cross-direction yarns. The machine
direction yarn is a multifilament yarn that may include thousands
of fibers. The base fabric is connected to a batt layer by a
needling process that results in straight through drainage
channels.
[0063] In another embodiment of dewatering fabric 82 there is
included a fabric layer, at least two batt layers, an
anti-rewetting layer and an adhesive. The base fabric is
substantially similar to the previous description. At least one of
the batt layers includes a low melt bi-compound fiber to supplement
fiber to fiber bonding upon heating. On one side of the base
fabric, there is attached an anti-rewetting layer, which may be
attached to the base fabric by an adhesive, a melting process or
needling wherein the material contained in the anti-rewetting layer
is connected to the base fabric layer and a batt layer. The
anti-rewetting layer is made of an elastomeric material, thereby
forming an elastomeric membrane, which has openings therethrough.
The batt layers are needled to hold dewatering fabric 82 together.
This advantageously leaves the batt layers with many needled holes
therethrough. The anti-rewetting layer is porous having water
channels or straight through pores therethrough.
[0064] In another embodiment of dewatering fabric 82, there is a
construct substantially similar to that previously discussed with
the addition of a hydrophobic layer to at least one side of
de-watering fabric 82. The hydrophobic layer does not absorb water,
but it does direct water through pores therein.
[0065] In another embodiment of dewatering fabric 82, the base
fabric has attached thereto a lattice grid made of a polymer, such
as polyurethane, that is put on top of the base fabric. The grid
may be put on the base fabric by utilizing various known
procedures, such as, for example, an extrusion technique or a
screen-printing technique. The lattice grid may be put on the base
fabric with an angular orientation relative to the machine
direction yarns and the cross direction yarns. Although this
orientation is such that no part of the lattice is aligned with the
machine direction yarns, other orientations can also be utilized.
The lattice can have a uniform grid pattern, which can be
discontinuous in part. Further, the material between the
interconnections of the lattice structure may take a circuitous
path rather than being substantially straight. The lattice grid is
made of a synthetic, such as a polymer or a polyurethane, which
attaches itself to the base fabric by its natural adhesion
properties.
[0066] In another embodiment of dewatering fabric 82, there is
included a permeable base fabric having machine direction yarns and
cross-direction yarns that are adhered to a grid. The grid is made
of a composite material the may be the same as that discussed
relative to a previous embodiment of dewatering fabric 82. The grid
includes machine direction yarns with a composite material formed
therearound. The grid is a composite structure formed of composite
material and machine direction yarns. The machine direction yarns
may be pre-coated with a composite before being placed in rows that
are substantially parallel in a mold that is used to reheat the
composite material causing it to re-flow into a pattern. Additional
composite material may be put into the mold as well. The grid
structure, also known as a composite layer, is then connected to
the base fabric by one of many techniques including laminating the
grid to the permeable fabric, melting the composite coated yarn as
it is held in position against the permeable fabric or by
re-melting the grid onto the base fabric. Additionally, an adhesive
may be utilized to attach the grid to permeable fabric.
[0067] The batt fiber may include two layers, an upper and a lower
layer. The batt fiber is needled into the base fabric and the
composite layer, thereby forming dewatering fabric 82 having at
least one outer batt layer surface. Batt material is porous by its
nature, additionally the needling process not only connects the
layers together, it also creates numerous small porous cavities
extending into or completely through the structure of dewatering
fabric 82.
[0068] Dewatering fabric 82 has an air permeability of from
approximately 5 to approximately 100 cubic feet/minute, for
example, 19 cubic feet/minute or higher or 35 cubic feet/minute or
higher. Mean pore diameters in dewatering fabric 82 are from
approximately 5 to approximately 75 microns, for example, 25
microns or higher or, 35 microns or higher. The hydrophobic layers
can be made from a synthetic polymeric material, a wool or a
polyamide, for example, nylon 6. The anti-rewet layer and the
composite layer may be made of a thin elastomeric permeable
membrane made from a synthetic polymeric material or a polyamide
that is laminated to the base fabric.
[0069] The batt fiber layers are made from fibers ranging from 0.5
d-tex to 22 d-tex and may contain a low melt bi-compound fiber to
supplement fiber to fiber bonding in each of the layers upon
heating. The bonding may result from the use of a low temperature
meltable fiber, particles and/or resin. The dewatering fabric can
be less than 2.0 millimeters, for example, less than 1.50
millimeters, less than 1.25 millimeters or less than 1.0 millimeter
thick. Embodiments of dewatering fabric 82 are also described in
the PCT/EP2004/053688 and PCT/EP2005/050198 which are herewith
incorporated by reference.
[0070] Now, referring to FIG. 13, there is shown another embodiment
of the present invention which is substantially similar to the
embodiment illustrated in FIG. 12 except that instead of hot air
hood 62 there is belt press 64. Belt press 64 includes permeable
belt 66 capable of applying pressure to the non-sheet contacting
side of structured fabric 28 that carries web 38 around suction
roll 60. Fabric 66 of belt press 64 is also known as an extended
nip press belt or a link fabric, which can run at 60 KN/m fabric
tension with a pressing length that is longer than the suction zone
of roll 60. Embodiments of fabric 66 and the required operation
concillation are also described in PCT/EP2004/053688 and
PCT/EP2005/050198 which are herewith incorporated by reference. The
above mentioned references are also fully applicable for dewatering
fabrics 82 and press fabrics 66 d described in the further
embodiments. While pressure is applied to structured fabric 28, the
high fiber density pillow areas in web 38 are protected from that
pressure as they are contained within the body of structured fabric
28, as they are in the Yankee nip. Belt 66 is a specially designed
Extended Nip Press Belt 66, made of, for example reinforced
polyurethane and/or a spiral link fabric. Belt 66 is permeable
thereby allowing air to flow therethrough to enhance the moisture
removing capability of belt press 64. Moisture is drawn from web 38
through dewatering fabric 82 and into vacuum roll 60.
[0071] Belt 66 provides a low level of pressing in the range of
50-300 KPa, for example, greater than 100 KPa. This allows a
suction roll with a 1.2 meter diameter to have a fabric tension of
greater than 30 KN/m, for example, greater than 60 KN/m. The
pressing length of permeable belt 66 against fabric 28, which is
indirectly supported by vacuum roll 60, is at least as long as a
suction zone in roll 60. Although the contact portion of belt 66
can be shorter than the suction zone.
[0072] Permeable belt 66 has a pattern of holes therethrough, which
may, for example, be drilled, laser cut, etched formed or woven
therein. Permeable belt 66 may be monoplanar without grooves. In
one embodiment, the surface of belt 66 has grooves and is placed in
contact with fabric 28 along a portion of the travel of permeable
belt 66 in belt press 64. Each groove connects with a set of the
holes to allow the passage and distribution of air in belt 66. Air
is distributed along the grooves, which constitutes an open area
adjacent to contact areas, where the surface of belt 66 applies
pressure against web 38. Air enters permeable belt 66 through the
holes and then migrates along the grooves, passing through fabric
28, web 38 and fabric 82. The diameter of the holes may be larger
than the width of the grooves. The grooves may have a cross-section
contour that is generally rectangular, triangular, trapezoidal,
semi-circular or semi-elliptical. The combination of permeable belt
66 associated with vacuum roll 60 is a combination that has been
shown to increase sheet solids by at least 15%.
[0073] An example of another structure of belt 66 is that of a thin
spiral link fabric, which can be a reinforcing structure within
belt 66 or the spiral link fabric will itself serve as belt 66.
Within fabric 28 there is a three dimensional structure that is
reflected in web 38. Web 38 has thicker pillow areas, which are
protected during pressing as they are within the body of structured
fabric 28. As such the pressing imparted by belt press assembly 64
upon web 38 does not negatively impact web quality, while it
increases the dewatering rate of vacuum roll 60.
[0074] Referring now to FIG. 14, which is similar to the embodiment
shown in FIG. 13, including hot air hood 68 placed inside of belt
press 64 to enhance the dewatering capability of belt press 64 in
conjunction with vacuum roll 60.
[0075] Referring now to FIG. 15, there is shown another embodiment
of the present invention, which is similar to the embodiment shown
in FIG. 13, but including boost dryer 70, which encounters
structured fabric 28. Web 38 is subjected to a hot surface of boost
driver 70. Structure web 38 rides around boost driver 70 with
another woven fabric 72 riding on top of structured fabric 28. On
top of woven fabric 72 is thermally conductive fabric 74, which is
in contact with both woven fabric 72 and cooling jacket 76 that
applies cooling and pressure to all fabrics and web 38. Here again,
the higher fiber density pillow areas in web 38 are protected from
the pressure as they are contained within the body of structured
fabric 28. As such, the pressing process does not negatively impact
web quality. The drying rate of boost dryer 70 is greater than 400
kg/hrm2, for example, greater than 500 kg/hrm2. The concept of
boost dryer 70 is to provide sufficient pressure to hold web 38
against the hot surface of the dryer thus preventing blistering.
Steam that is formed at the knuckle points of fabric 28 passes
through fabric 28 and is condensed on fabric 72. Fabric 72 is
cooled by fabric 74 that is in contact with the cooling jacket,
which reduces its temperature to well below that of the steam. Thus
the steam is condensed to avoid a pressure build up to thereby
avoid blistering of web 38. The condensed water is captured in
woven fabric 72, which is dewatered by dewatering device 75. It has
been shown that depending on the size of boost dryer 70, the need
for vacuum roll 60 can be eliminated. Further, depending upon the
size of boost dryer 70, web 38 may be creped on the surface of
boost dryer 70, thereby eliminating the need for Yankee dryer
52.
[0076] Referring now to FIG. 16, there is shown another embodiment
of the present invention similar to the invention disclosed in FIG.
13, but with an addition of air press 78 which is a four roll
cluster press that is used with high temperature air and is
referred to as an HPTAD for additional web drying prior to the
transfer of web 38 to Yankee 52. Four roll cluster press 78
includes a main roll and a vented roll and two cap rolls. The
purpose of this cluster press is to provide a sealed chamber that
is capable of being pressurized. The pressure chamber contains high
temperature air, for example, 150.degree. C. or higher, and is at a
significantly higher pressure than conventional TAD technology, for
example, greater than 1.5 psi resulting in a much higher drying
rate than a conventional TAD. The high pressure hot air passes
through an optional air dispersion fabric, through web 38 and
fabric 28 into a vent roll. The air dispersion fabric may prevent
web 38 from following one of the four cap rolls. The air dispersion
fabric is very open, having a permeability that equals or exceeds
that of fabric 28. The drying rate of the HPTAD depends on the
solids content of web 38 as it enters the HPTAD. The drying rate
may be at least 500 kg/hr/m2, which is a rate of at least twice
that of conventional TAD machines.
[0077] Advantages of the HPTAD process are in the areas of improved
sheet dewatering without a significant loss in sheet quality,
compactness in size and energy efficiency. Additionally, it enables
higher pre-Yankee solids, which increase the speed potential of the
present invention. Further, the compact size of the HPTAD allows
for easy retrofit to an existing machine. The compact size of the
HPTAD and the fact that it is a closed system means that it can be
easily insulated and optimized as a unit to increase energy
efficiency.
[0078] Referring now to FIG. 17, there is shown another embodiment
of the present invention. This is similar to FIGS. 13 and 16 except
for the addition of two-pass HPTAD 80. In this case, two vented
rolls are used to double the dwell time of structured web 38
relative to the design shown in FIG. 16. An optional coarse mesh
fabric may be used as in the previous embodiment. Hot pressurized
air passes through web 38 carried on fabric 28 and onto the two
vent rolls. It has been shown that, depending on the configuration
and size of the HPTAD, more than one HPTAD can be placed in series,
which can eliminate the need for roll 60.
[0079] Referring now to FIG. 18, conventional Twin Wire Former 90
may be used to replace the Crescent Former shown in previous
examples. The forming roll can be either a solid or open roll. If
an open roll is used, care must be taken to prevent significant
dewatering through the structured fabric to avoid losing basis
weight in the pillow areas. Outer forming fabric 93 can be either a
standard forming fabric or one such as that disclosed in U.S. Pat.
No. 6,237,644. Inner forming fabric 91 must be structured fabric 91
that is much coarser than the outer forming fabric. Vacuum box 92
may be needed to ensure that the web stays with structured wire 91
and does not go with outer wire 90. Web 38 is transferred to
structured fabric 28 using a vacuum device. The transfer can be a
stationary vacuum shoe or vacuum assisted rotating pick-up roll 94.
Second structured fabric 28 is at least the same coarseness and may
be courser than first structured fabric 91. The process from this
point is the same as one of the previously discussed processes. The
registration of the web from the first structured fabric to the
second structured fabric is not perfect, as such some pillows will
lose some basis weight during the expansion process, thereby losing
some of the benefit of the present invention. However, this process
option allows for running a differential speed transfer, which has
been shown to improve some sheet properties. Any of the
arrangements for removing water discussed above may be used with
the Twin Wire Former arrangement and a conventional TAD.
[0080] The fiber distribution of web 38 in the present invention is
opposite that of the prior art, which is a result of removing
moisture through the forming fabric and not through the structured
fabric. The low density pillow areas are of relatively higher basis
weight than the surrounding compressed zones, which is opposite of
conventional TAD paper. This allows a high percentage of the fibers
to remain uncompressed during the process. The sheet absorbency
capacity, as measured by the basket method, for a nominal 20 gsm
web is equal to or greater than 12 grams water per gram of fiber
and often exceeds 15 grams of water per gram fiber. The sheet bulk
is equal to or greater than 10 cm3/gm, for example, greater than 13
cm3/gm. The sheet bulk of toilet tissue is expected to be equal to
or greater than 13 cm3/gm before calendering.
[0081] With the basket method of measuring absorbency, five (5)
grams of paper are placed into a basket. The basket containing the
paper is then weighted and introduced into a small vessel of water
at 20.degree. C. for 60 seconds. After 60 seconds of soak time, the
basket is removed from the water and allowed to drain for 60
seconds and then weighted again. The weight difference is then
divided by the paper weight to yield the grams of water held per
gram of fibers being absorbed and held in the paper.
[0082] Web 38 is formed from fibrous slurry 24 that headbox 22
discharges between forming fabric 26 and structured fabric 28. Roll
34 rotates and supports fabrics 26 and 28 as web 38 forms. Moisture
M flows through fabric 26 and is captured in save all 36. It is the
removal of moisture in this manner that serves to allow pillow
areas of web 38 to retain a greater basis weight and, therefore,
thickness than if the moisture were to be removed through
structured fabric 28. Sufficient moisture is removed from web 38 to
allow fabric 26 to be removed from web 38 to allow web 38 to
proceed to a drying stage. Web 38 retains the pattern of structured
fabric 28 and any zonal permeability effects from fabric 26 that
may be present.
[0083] The present invention can be further modified within the
spirit and scope of this disclosure. This application is,
therefore, intended to cover any variations, uses, or adaptations
of the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
[0084] FIGS. 19-22 show forming fabric 26. A series of warp yarns
122 and weft yarns 124 are woven in a predetermined weave pattern.
The yarn materials include, but are not limited to mono filament
yarns, synthetic or polyester mono filament yarns, twisted mono
filament yarns, twisted synthetic or twisted polyester or twisted
polyamide mono filament yarns, twisted multi-filament yarns,
twisted synthetic or twisted polyester multi-filament yarns, and
others. Various yarn profiles can be employed, including, but not
limited to, yarns having a circular cross sectional shape with one
or more diameters, or other cross sectional shapes, for example,
non-round cross sectional shapes such as oval, or a polygonal cross
sectional shapes, for example, diamond, square, pentagonal,
hexagonal, septagonal, octagonal, and so forth, or any other shape
that the yarns may be fabricated into.
[0085] Materials used to make the base fabric can be from, but are
not limited to, polyethylenepterathalate (PET), polyamides (PA),
polyethylene naphthalate (PEN), polybutylene terephthalate (PBT)
and polyetheretherketone (PEEK). Likewise, the fabric can be made
from one or more materials.
[0086] What results is forming fabric 26 having a paper side and a
wear side. On the paper side of forming fabric 26, a polymer is
applied that forms polymeric lattice 126. The polymeric material to
be deposited may be at least one of a silicone and a polyurethane.
By way of example, the silicone can be any RTV-type two-component
heat curable material. Other possible polymeric materials,
selectable based on the application, include, but are not limited
to, acrylics, epoxy resins, silicones, polyurethanes--such as
thermoplastic, thermoset, and two component polyurethanes,
hydrosols, polyolefins--such as ABS, PS, PC, PET, PPS, PEEK, PA,
EVA, PE, HDPE, LDPE, LLDPE, PP, PTFE, and PVC, UV curables,
rubbers--both natural and synthetic, nanopolymers/technology,
carbon fullerenes, dendrimers, polymers loaded with carbon or
metals, electrically conducting polymers and semi-conductors,
liquid crystal polymers, hot melts, polymers that are sensitive to
pressure, light and temperature, reactive polymers and living
polymers.
[0087] The polymer material added to fabric 26 can be deposited in
a random pattern, a pseudo-random pattern, a predetermined pattern,
or any combination of the three to form a pattern or motif on the
final tissue paper. In an embodiment, the polymeric material is
delivered to the fabric either through a screen or from a bank of
small bore tubes (needle application) set at the predetermined
distance above the fabric 26. When the screen method is used, the
polymeric material is delivered through the screen by a blade that
is in contact with the inside face of the screen. In this manner
the polymer height L above fabric surface 128 is determined by the
thickness of the screen wall. For the screen application, to
control the flow of the polymeric material into the fabric, the
viscosity of the polymeric material is less than 40,000 centipoises
cP. For small bore needle applications, the viscosity of the
polymeric material is less than 50,000 centipoises cP. The
viscosity of the polymeric material is selected to control the
amount of penetration of the polymeric material into fabric 26. For
the present invention, penetration is between about 10% and about
100%. The amount of penetration into the fabric is a function of
the fabric and the use of the fabric. For general applications, the
penetration may be approximately 40%-60%. When a fine mesh fabric
is used, the penetration can be up to 100%.
[0088] Height of the polymeric material L above surface 128 of the
paper side of forming fabric 26 is variable depending on the method
of application and the desires of the application. For example,
when screening the polymeric material onto fabric 26, the polymer
material has height L above surface 128 of fabric 26 of about 0.01
mm to about 1.0 mm, for example, about 0.05 mm. When used for
embossing type applications, for example, through air drying (TAD),
height L above the surface of the fabric is about 0.1 mm to about
2.0 mm, for example, about 0.1 mm to about 1.0 mm, or about 0.05
mm. For small bore needle applications, height L of the polymeric
material can be up to 3 mm. Polymeric lattice 126 of an embodiment
extends above surface 128 of forming fabric 26 by approximately 0.1
mm.
[0089] The polymer material added to fabric 26 can be deposited in
a random pattern, a pseudo-random pattern, a predetermined pattern,
or any combination of the three to form a pattern or motif on the
final tissue paper. That is, rather than a lattice as depicted, the
deposition can form a pattern such as a logo, or other
non-continuous pattern. Width and length of polymeric lattice 126
can vary, but can range from approximately 0.1 mm to approximately
2 mm, for example, 0.5 mm to 1.0 mm, or 0.75 mm to 1.0 mm.
[0090] When cured, the polymeric material has a shore A hardness of
approximately 3 to approximately 80, depending on the material used
and the predetermined application. Permeability range of the fabric
26 with the applied pattern/design is approximately 50 cfm to
approximately 1200 cfm, for example, in the range of approximately
200 cfm to approximately 900 cfm, or approximately 300 cfm to
approximately 800 cfm.
[0091] While the present invention has been particularly shown and
described with reference to the foregoing preferred embodiments,
those skilled in the art will understand that many variations may
be made therein without departing from the spirit and scope of the
invention as defined in the following claims. This description of
the present invention should be understood to include all novel and
non-obvious combinations of elements described herein, and claims
may be presented in this or a later application to any novel and
non-obvious combination of these elements. The foregoing
embodiments are illustrative, and no single feature or element is
essential to all possible combinations that may be claimed in this
or a later application. Where the claims recite "a" or "a first"
element or the equivalent thereof, such claims should be understood
to include incorporation of one or more such elements, neither
requiring nor excluding two or more such elements.
[0092] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *