U.S. patent application number 10/334513 was filed with the patent office on 2004-07-01 for grooved-shape monofilaments and the fabrics made thereof.
Invention is credited to Billings, Alan L., Luo, Shuiyuan.
Application Number | 20040127129 10/334513 |
Document ID | / |
Family ID | 32655083 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127129 |
Kind Code |
A1 |
Luo, Shuiyuan ; et
al. |
July 1, 2004 |
Grooved-shape monofilaments and the fabrics made thereof
Abstract
A monofilament with longitudinally oriented grooves and fabrics
made thereof having reduced air permeability, wherein the reduced
permeability is achieved without using additional coatings or
stuffer yarns. Bicomponent monofilaments made from these grooved
monofilaments using solution or wire coating have improved coating
adhesion and may also include a conductive coating.
Inventors: |
Luo, Shuiyuan; (Syracuse,
NY) ; Billings, Alan L.; (Clifton Park, NY) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG
745 FIFTH AVENUE- 10TH FL.
NEW YORK
NY
10151
US
|
Family ID: |
32655083 |
Appl. No.: |
10/334513 |
Filed: |
December 31, 2002 |
Current U.S.
Class: |
442/362 ;
428/373; 442/199 |
Current CPC
Class: |
Y10T 442/3146 20150401;
D02G 3/447 20130101; Y10T 442/637 20150401; D02G 3/22 20130101;
Y10T 442/638 20150401; Y10T 428/2936 20150115; B32B 2255/02
20130101; Y10T 428/2929 20150115; D21F 1/0027 20130101; Y10T
442/611 20150401; D21F 7/083 20130101; D01D 5/253 20130101; D21F
7/08 20130101 |
Class at
Publication: |
442/362 ;
428/373; 442/199 |
International
Class: |
D03D 015/00 |
Claims
We claim:
1. A fabric comprising a plurality of uncoated functional
monofilaments having a grooved-shaped cross-section and having
reduced air permeability compared with a fabric not having said
monofilaments.
2. The fabric of claim 1 wherein a surface of each respective
monofilament has a plurality of grooves formed thereon.
3. The fabric of claim 2 wherein each groove is C-shaped.
4. The fabric of claim 2 wherein each groove has an open angle less
than 180 degrees.
5. The fabric of claim 1 wherein the fabric is a forming, press,
dryer, TAD, pulp forming, sludge filter, chemiwasher, or engineered
fabric.
6. A monofilament having a plurality of longitudinal grooves formed
in its surface.
7. The monofilament of claim 6 wherein each groove is C-shaped.
8. The monofilament of claim 6 wherein each groove has an open
angle less than 180 degrees.
9. The monofilament of claim 6 wherein coating adhesion is
improved.
10. The monofilament of claim 6 wherein the grooved monofilament is
made of a material selected from the group consisting essentially
of polyester, polyamide, poly(phenylene sulfide),
polyetheretherketone, poly(aryl ether ketone), polyethylene, and
polypropylene.
11. A fabric comprising a plurality of grooved-shaped functional
monofilaments and having improved adhesion to coatings compared
with a fabric not having said grooved-shaped monofilaments.
12. The fabric of claim 11 wherein said fabric has improved
adhesion to lamination substrates mechanically interlocked by way
of a flow of thermoplastic material.
13. The fabric of claim 11 wherein the improved adhesion is
achieved due to mechanical interlock regardless of the coating
chemistry.
14. The fabric of claim 11 wherein the improved adhesion is
achieved by an interlocking mechanism between the coating and the
yarns in the fabric.
15. The fabric of claim 11 wherein the fabric is a forming, press,
dryer, TAD, or engineered fabric.
16. A bicomponent monofilament made from a coated grooved-shaped
monofilament.
17. The bicomponent monofilament of claim 16 having improved
delamination resistance compared with a bicomponent monofilament
not made from a coated grooved-shaped monofilament.
18. The bicomponent monofilament of claim 16 wherein the
bicomponent monofilament is made using solution coating.
19. The bicomponent monofilament of claim 16 wherein the
bicomponent monofilament is made using wire coating.
20. The bicomponent monofilament of claim 16 wherein said
bicomponent monofilament has a conductive coating.
21. A die used for extruding groove-shaped monofilaments and having
a capillary cross section with a plurality of projections oriented
towards an interior of the capillary, wherein an angle centering at
the origin of a respective projection and facing into said interior
is over 250 degrees, and the open angle defined as the angle
centering at the origin of a C and facing its outlet is much less
than 180 degrees.
22. The die of claim 21 wherein a diameter of the capillary is
approximately three times the size of the monofilaments to be
produced.
23. The die of claim 21 wherein the ratio of length to diameter of
the capillary is approximately 3:1.
24. The die of claim 21 wherein the monofilaments to be produced
are made of PET.
25. The die of claim 21 wherein the monofilaments are extruded
according to a melt spinning process.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to industrial fabrics. More
specifically, the present invention relates to using yarns with
longitudinally oriented grooves to reduce fabric permeability
without the need of an additional coating or stuffer yarns. These
yarns can also be bicomponent yarns with improved coating
adhesion.
[0003] 2. Description of the Prior Art
[0004] During the papermaking process, a cellulosic fibrous web is
formed by depositing a fibrous slurry, that is, an aqueous
dispersion of cellulose fibers, onto a moving forming fabric in the
forming section of a paper machine. A large amount of water is
drained from the slurry through the forming fabric, leaving the
cellulosic fibrous web on the surface of the forming fabric.
[0005] The newly formed cellulosic fibrous web proceeds from the
forming section to a press section, which includes a series of
press nips. The cellulosic fibrous web passes through the press
nips supported by a press fabric, or, as is often the case, between
two such press fabrics. In the press nips, the cellulosic fibrous
web is subjected to compressive forces which squeeze water
therefrom, and which adhere the cellulosic fibers in the web to one
another to turn the cellulosic fibrous web into a paper sheet. The
water is accepted by the press fabric or fabrics and, ideally, does
not return to the paper sheet.
[0006] The paper sheet finally proceeds to a dryer section, which
includes at least one series of rotatable dryer drums or cylinders,
which are internally heated by steam. The newly formed paper sheet
is directed in a serpentine path sequentially around each in the
series of drums by a dryer fabric, which holds the paper sheet
closely against the surfaces of the drums. The heated drums reduce
the water content of the paper sheet to a desirable level through
evaporation.
[0007] It should be appreciated that the forming, press and dryer
fabrics all take the form of endless loops on the paper machine and
function in the manner of conveyors. It should further be
appreciated that paper manufacture is a continuous process which
proceeds at considerable speeds. That is to say, the fibrous slurry
is continuously deposited onto the forming fabric in the forming
section, while a newly manufactured paper sheet is continuously
wound onto rolls after it exits from the dryer section.
[0008] Contemporary papermaking fabrics are produced in a wide
variety of styles designed to meet the requirements of the paper
machines on which they are installed for the paper grades being
manufactured. Generally, they comprise a<woven base fabric. The
base fabrics may be woven from monofilament, plied monofilament,
multifilament or plied multifilament yarns, and may be
single-layered, multi-layered or laminated. The yarns are typically
extruded from any one of the synthetic polymeric resins, such as
polyamide and polyester resins, used for this purpose by those of
ordinary skill in the paper machine clothing arts.
[0009] The woven base fabrics themselves take many different forms.
For example, they may be woven endless, or flat woven and
subsequently rendered into endless form with a woven seam.
Alternatively, they may be produced by a process commonly known as
modified endless weaving, wherein the widthwise edges of the base
fabric are provided with seaming loops using the machine-direction
(MD) yarns thereof. In this process, the MD yarns weave
continuously back-and-forth between the widthwise edges of the
fabric, at each edge turning back and forming a seaming loop. A
base fabric produced in this fashion is placed into endless form
during installation on a paper machine, and for this reason is
referred to as an on-machine-seamable fabric. To place such a
fabric into endless form, the two widthwise edges are brought
together, the seaming loops at the two edges are interdigitated
with one another, and a seaming pin or pintle is directed through
the passage formed by the interdigitated seaming loops.
[0010] Further, the woven base fabrics may be laminated by placing
at least one base fabric within the endless loop formed by another,
and by needling a staple fiber batt through these base fabrics to
join them to one another. One or more of these woven base fabrics
may be of the on-machine-seamable type. This is now a well known
laminated press fabric with a multiple base support structure.
[0011] In any event, the woven base fabrics are in the form of
endless loops, or are seamable into such forms, having a specific
length, measured longitudinally therearound, and a specific width,
measured transversely thereacross.
[0012] Turning now to the yarns used heretofore, particularly for
dryer fabrics, monofilament yarns have typically been extruded with
a simple circular cross-section. More recently, monofilaments with
shaped cross-section have been produced. These shaped monofilaments
have been used in woven fabrics to modify the fabric surface
texture or density, or in particular, to control the fabric air
permeability. In this connection, for example, U.S. Pat. No.
5,361,808 (Bowen) discloses using finned or T-shaped monofilaments
as weft, or stuffer, yarns to reduce air permeability. As another
example, U.S. Pat. No. 5,998,310 (Bowen) shows a tri-lobal stuffer
used to reduce permeability. "Y" and "X" and "T" shaped
monofilaments are also described. Fabric stability at
permeabilities of 200 CFM or greater using the shaped
cross-machine-direction yarns is maintained. None of the prior art
however, uses shaped yarns as functional yarns which reduce air
permeability without using a coating and without using stuffer
yarns. Nor does any of the prior art used shaped monofilaments for
improved coating adhesion and for producing bicomponent
monofilaments.
SUMMARY OF THE INVENTION
[0013] The present invention uses shaped functional yarns to reduce
air permeability without the need to use a coating or stuffer
yarns. The shaped monofilaments are also used for improved coating
adhesion and for producing bicomponent monofilaments. More
specifically, groove-shaped monofilaments and the fabrics made
thereof are disclosed herein. When the fabrics are coated or
laminated, the adhesion strength, tear-resistance and other
properties are improved through an interlocking mechanism
regardless of the particular coating chemistry. Bicomponent
monofilaments made from these grooved monofilaments using solution
or wire coating have improved delamination resistance and may also
include a conductive coating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a cross-sectional view of the grooved monofilament
according to the present invention;
[0015] FIG. 2 is a typical design for a die used to make the
grooved monofilament in FIG. 1;
[0016] FIG. 3 shows a typical "tensile stress" vs. "strain" plot
for the grooved monofilaments;
[0017] FIGS. 4(b) and 4(d) are optical photomicrographs of the
sheet surfaces of sample fabrics with grooved monofilaments;
and
[0018] FIGS. 4(a) and 4(c) are the sheet surfaces of typical prior
art fabrics with circular monofilaments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] A preferred embodiment of the present invention will be
described in the context of a papermaking dryer fabric. However, it
should be noted that the invention is applicable to the fabrics
used in other sections of a paper machine, as well as to those used
in other industrial settings where surface smoothness and
planarity, and controlled permeabilities to water and air are of
importance. Some examples of other fabric types to which the
invention is applicable include papermaker's forming and press
fabrics, through-air-drying (TAD) fabrics and pulp forming fabrics.
Another example is of fabrics used in related-to-papermaking
processes such as sludge filters and chemiwashers. Yet another
example of a fabric type to which the invention is applicable is
engineered fabrics, such as fabrics used in making non-woven
textiles in the wetlaid, drylaid, meltblown and/or spunbonding
processes.
[0020] Fabric constructions include woven, spiral wound, knitted,
extruded mesh, spiral-link, spiral coil, and other nonwoven
fabrics. These fabrics may comprise monofilament, plied
monofilament, multifilament or plied multifilament yarns, and may
be single-layered, multi-layered or laminated. The yarns are
typically extruded from any one of the synthetic polymeric resins,
such as polyamide and polyester resins, used for this purpose by
those of ordinary skill in the industrial fabric arts.
[0021] A preferred embodiment of the grooved functional
monofilament 1 of the present invention is illustrated in FIG. 1
(cross-sectional view) The monofilaments 1 are incorporated in a
fabric as functional yarns as compared to stuffer yarns. The
surface 2 of the monofilament 1 has a plurality of grooves 3
running along the length thereof. The grooves 3 may be provided
during the extrusion of the monofilament 1. Each groove 3 has a
C-shaped cross-section. The "open angle", which is defined as the
angle centering at the origin of the "C" and facing its outlet, is
much less than 180 degrees.
[0022] It is an important characteristic that the grooves 3 have a
"C"-shape but not a "U"-shape cross-section. In the preferred
embodiment, the grooved monofilament 1 is made of a particularly
tough and strong polymer such as polyester (PET), or alternatively,
polyamide (PA). However, the grooved monofilament 1 can consist of
another filament/fiber forming thermoplastic polymer material such
as poly(phenylene sulfide) (PPS), polyetheretherketone (PEEK),
poly(aryletherketone) (PEK), polyethylene (PE) or polypropylene
(PP). Groove-shaped PET monofilaments are typically made through
melt spinning using a die (sometimes referred to as a "spinneret"),
and the die design is an important factor in shape extrusion. One
typical die 4 is shown in FIG. 2. Note that the cross-section of
the capillary 5 is roughly circular with five projections 6 into
the interior area of the capillary 5. The projections 6 have a
circular shape. The inlet angle 7, which is defined as the angle
centering at the origin of the projection circular shape and facing
into the interior area of the capillary 5, is over 250 degree. The
diameter of the capillary 5 is about three times the size of the
monofilaments to be produced. The ratio of length to diameter of
the capillary 5 is about 3:1. Table 1 shows an example of the
processing conditions for making the PET grooved monofilaments
using this die 4. Note that processing conditions depend on the
particular fiber-forming material used.
1TABLE I Processing Conditions for Preparing Grooved PET
Monofilaments. Draw & Extruder Die Spin Pump Melt & Quench
Relax Throughput Resin Single Screw As Shown Size: 10 cc Melt:
550-555.degree. F. Draw 5 .times. 5.28 Crystar Screw Size: 1.5" In
Speed: 3 rpm Quench: 144.degree. F. @ 375.degree. F. lbs./hr from
Screw Design: D- Relax 0.12 Dupont S. Barrier, 3D, @ 400.degree. F.
.95 IV High Work
[0023] Tensile properties of the grooved PET monofilaments,
prepared under the conditions in Table 1, were characterized using
an Instron machine, with a crosshead speed of 10 inches per minute,
and gage length of 10 inches. FIG. 3 shows a typical "tensile
stress" vs. "strain" plot for these grooved PET monofilaments, and
their tensile properties are detailed in Table 2.
2TABLE 2 Physical and Mechanical Properties of the PET Grooved
Monofilaments. Shrinkage Denier Break @ Loop (gm/ Diameter Tenacity
Elong. 200.degree. C. Strength 9000 m) (mm) (GPD) (%) (%) (GPD)
1669 0.55 3.64 25.0 11.0 2.87
[0024] The tensile properties of the grooved PET monofilaments
indicated in Table 2 are comparable to those of PET monofilaments
having other types of shapes. Further, by varying the processing
conditions for making the grooved monofilaments, their physical and
mechanical properties can be optimized for different
applications.
[0025] A sample fabric was produced, being made partially of the
grooved monofilaments and was woven using a monoplane weave,
forcing the CD yarn (the grooved filaments) to the sheet side.
Measurements taken from the sample fabric and from a typical prior
art fabric having conventional circular monofilaments show that the
weavability of the sample fabric was the same as the prior art
fabric. FIGS. 4(b) and 4(d) are the optical photomicrographs of the
sheet surfaces of the sample fabrics with the grooved monofilaments
on top. FIGS. 4(a) and 4(c) are the surfaces of prior art fabrics
with circular monofilaments on top. The symmetric surface of the
fabric with grooved monofilaments on top was found to "look" and
"feel" better than that of the fabric with circular monofilaments
on top. Further, the sample fabric with grooved monofilaments on
top exhibited considerably lower air permeability, e.g., 60 CFM,
compared to a permeability of 103 CFM for the same style fabric
with circular monofilaments on top. Advantageously, this reduced
permeability is achieved without using a coating and without using
stuffer yarns.
3TABLE 3 Air Permeability Testing. filling loom H/S cal. filament
weave (mm) loc. tension Perm. (in.) grooved 960 0.40 TMB 650 60
.061 circular 960 0.40 TMB 650 103 .059
[0026] In addition to demonstrating reduced permeability, fabrics
woven partially or completely with the grooved monofilaments
exhibit improved adhesion to coatings, and to laminate substrates
which would be mechanically coupled together by way of, for
example, a flow of thermoplastic material from a thermoplastic
laminate substrate which is heated. For example, the laminate
substrate may comprise bicomponent yarns which upon heating causes
the melting of a portion of such yarns which flows into the grooves
and which upon setting mechanically secures the laminate substrate
to the grooved monofilaments. Tear resistance is also improved.
These improvements are achieved through the mechanism of mechanical
interlocking and surface roughening. Moreover, these improvements
are effected regardless of the coating chemistry since it includes
a mechanical interlock rather than solely a chemical bonding of the
coating to the monofilament. Yet a further advantage is provided in
that bicomponent monofilaments can be made from these grooved
monofilaments using solution or wire coating. Compared to typical
prior art sheath-core monofilaments, it is believed that the
bicomponent monofilaments will have much better
delamination-resistance because of mechanical interlock. One
specific application of this type, for example, is the creation of
conductive monofilaments made by coating the grooved core
monofilaments with a conductive coating.
[0027] Modifications to the above would be obvious to those of
ordinary skill in the art, but would not bring the invention so
modified beyond the scope of the present invention. The claims to
follow should be construed to cover such situations.
* * * * *