Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to new and improved nonwoven
fabrics and methods for manufacturing the same.
Backqround of the Invention
A. Prior Art
~onwoven fabrics have been known for some time. Nonwoven
fabrics have been made from synthetic fibers such as the
polyester and polypropylene fibers. Generally, these
fabrics are produced by forming a web of fibers and
applying an adhesive binder to the web to hold the fibers
together and provide strength. In some instances (i.e.,
the spunbonding technique), synthetic polymers are
extruded into filaments and directly formed into webs
which selfbond to produce the final fabric. In other
instances, the fibrous web is fluid rearranged and then
resin binder is added to form a useful, coherent nonwoven
fabric. See, for instance, Kalwaites, U.S. Patent-Nos.
2,862,251, 3,033,721, 3,193,436 and 3,769,659 and
Griswold, U.S. Patent Nos. 3,081,515 and 3,025,585. Still
other nonwoven fabrics are made by forming a web of
~0 synthetic fibers and txeating it with high-pressure jets
to entangle the ~ibers and produce a strong fabric that
does not require the addition of binder to be
self-supporting and useful for many purposes. Such a
technique is described by Evans in U.S. Patent No. ;
3,485,706 and Canadian Patent No. 791,925.
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The prior art polyester fiber nonwoven fabrics suffer from
one or more of the following problems: Adhesively bonded
webs of textile polyester fibers require relatively large
amounts of adhesive binder for most end uses to provide
the fabric with adequate strength. The large amount of
binder increases cost and can detract from the desirable
textile-like properties of the fiber itself. The
spunbonded type of product is expensive, and being of
continuous extruded filaments, also has some limitations
on its unctional properties and its textile-like nature.
For instance, spunbonded fabrics can be stiff and boardy
in the higher weight range of products. The highly
entangled fabrics of Evans have excellent fabric
properties, but the Evans process requires a substantial
capital investment and it uses large amounts of power.
This invention provides a process and fabric product that
eliminate many of the above-mentioned problems.
B. Objects Of The Invention
~t is an object of the invention to provide a relatively
economical process for producing strong, durable nonwoven
fabrics having reduced binder content.
It is another object of the invention to provide a process~
for producing strong, durable nonwoven fabrics from
polyester and/or polyolefin fibers.
It is a further object of the invention to provide strong,
durable polyester and/or polyolefin nonwoven fabrics.
Still another object of the invention is to provide an
economical process for producing strong, durable polyester ;~
and/or polyolefin nonwoven fabrics having reduced binder ~;
content.
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These and other objects of the invention will be apparent
from the following description of the invention.
Summary Of The Invention
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The invention provides a strong, durable nonwoven fabric
comprising a layer of polyester and/or polyolefin fibers
disposed in a regular repeating pattern of lightly
entangled fiber regions of higher area density than the
average area density of the layer, and interconnecting
fibers extending between said regions and being randomly
lightly entangled with each other in said regions, and an
adhesive binder material distributed in said layer. These
fabrics are produced by a process which includes the steps
of lightly entangling a layer of polyester and/or
polyolefin fibers, followed by applying adhesive bonding
material to the lightly entangled layer.
Description Of The Invention
The nonwoven fabric of the invention comprises a layer of
polyester and/or polyolefin fibers, with the fibers being
disposed in a regular repeating pattern of lightly
entangled fiber regi~ns of higher area density than the
average area density of the layer. The fiber layer has
interconnecting fibers which extend between the said
lightly e~tangled fiber regions. The interconnecting
fibers are randomly entangled with each other in the
regions. The fabric also contains an effective amount,
for instance, from about ~-1/2 per cent to about 30 per
cent by weight of the fabric, plus binder, o an adhesive
binder material. The adhesive binder material can be
distributed in the fabric in a spaced, intermittent
pattern of binder sites, or it can be uniformly
distributed throughout the fabric.
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The nonwoven fabric of the invention is made by forming a
layer of overlapping, intersecting polyester and/or
polyolefin fibers. The fibrous layer is supported on an
apertured patterned member having apertures arranged in a
pattern. Liquid streams are jetted at the layer to
randomly and lightly entangle the layer in a pattern of
high-density regions interconnected by fibers extending
between regions. An adhesive binder material is then
applied to the layer of lightly entangled fibers.
The fibrous web can be formed in any convenient known
manner, as by air-laying or carding. The web is then
lightly entangled by passing the fibrous web under
essentially columnar liquid streams while the web is
supported on a foraminous forming or patterning member.
Apparatus such as the general type disclosed by Evans in
U.S. Patent No. 3,485,706 can be employed to carry out the
entangling. It is an important Eeature oE the invention
that the fiber layer is lightly entangled. For instance,
it is preferred that the lightly entangled fibrous layer
have a structural measure of fiber entanglement oE less
than 0.1. (The test procedure for measuring the
structural measure of fiber entanglement is set forth
below.)
A typical apparatus for carrying out the process of the
invention employs rows of orifices through which liquid
(usually water) is jetted under pressure in the form of
essentially columnar jetsO A suitable apparatus has up to
20-25 rows of orifices, with the orifices being spaced
such that there are about 30 to 50 orifices per linear
inch. The orifices are preferably circular, with
diameters of from 0.005 to 0.007 inch. The travelling
fibrous web can be positioned about 1 to 2 inches below
the orifises.
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Using the above-described typical apparatus, representa-
tive conditions include a liquid pressure of about 200 to ;
700 psi and a web speed of up to 100 yards per minute, for
a fibrous web weighing about 1/2 to 2-1/2 ounces per
square yard. Routine experimentation that is well within
the ordinary skill in the art will suffice to determine
the desired conditions for particular cases.
After the fibrous web has been lightly entangled, it is
bonded employing known procedures. For instance, the~
lightly entangled web may be passed through a print~
bonding station which employs a set of counterrotating
rolls. The upper (back-up) roll is adjustable, and the~
lower (applicator) roll is engraved with a predetermined
pattern to be printed. The lower roll is partially
immersed in a bath of binder solution or suspension. As
the roll rotates, it picks up binder, and a doctor blade
wipes the roll clean except for the binder contained in
the engraved pattern. As the web passes through the nip
between the rolls, the binder is printed on the web from
the engraved pattern. This procedure is well known in the
art. U.S. patents which disclose such print bonding~ of ;
nonwoven fibrous webs include Nos. 2,705,498, 2,705,687,~
2,705,688, 2,880,111, and 3,009,822. I~ desired the web
may also be overall saturation bonded. ;;~
The adhesive binder employed can be any of the aqueous~
latex binders that are conventionally employed as binders~
for nonwoven fabrics. Such binders include acrylics,~
ethylene-vinyl acetate copolymers, SBR latex rubbers, and
the like.
After the binder has been applied, the printed web is
dried in the usual fashion, as by passing the web over a
series of drying cans.
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The binder is employed in an effective amount, that is
that amount which will result in a fabric having
sufficient strength and cohesiveness for the intended
end-use application~ The exact amount of binder employed
depends, in part, upon factors such as nature of fiber,
weight of fibrous layer, nature of binder, and the like.
Usually, an effective amount will be found within the
range of from about 5 to about 30 weight per cent, based
upon weight of fibers plus binder.
.
The fibers used to produce the products of the invention
are polyester or polyolefin, such as polypropylene or high
density polyethylene, fibers. The fibers may have a
denier of from 1 or less up to 15 or more and they may be
in the form of short fibers such as 1/~ inch in length up
to as long as continuous filament fibers. Preferably,
fibers in the range of 3/4 to 2 inches in length are used.
The weight of -the fiber layer used to produce the fabrics
of the present invention may vary from 100 grains per
square yard to a few thousand grains per square yard.
The invention will be further illustrated in greater
detail by the following specific examples
Example 1
A web of 1~75 denier 1.5 inch polyester fibers weighing
537 grains per square yard is formed using an air-laying
machine sold by the Rando Machine Corporation of
Rochester, New York under the registered trademark Rando
Webber. The web is placed on a woven belt. The belt is
woven with 22 warp filaments per inch and 24 filling
filamen~s. The belt has 528 openings per square inch.
The web and belt are passed under 16 manifolds. Each
manifold contains 2 rows of 12 orifices per inch running in
the transverse direction of the web. Each orifice is
rectangular, with
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an opening of about 0.012 inch by 0.014 inch. Water is
jetted through the orifices onto the web at a pressure of
about 250 pounds per square inch to lightly entangle the
fibers into a pattern of high density regions. The
lightly entangled web is passed through a pair of print
rolls~ The top roll is a flannel-covered, rubber back-up
roll, and the bottom roll is an engraved roll. The
engraved roll is engraved with 6 wavy lines per inch
running parallel to the axis of the roll. (See Fig. l of
U.SO Patent No, 3,009,822)-. Each line has a width of
about 0.024 inch. The roll rotates in a pan of binder
material and picks up-the binder material and places it on
the web. The binder material has the following
composition: a self-cross-linking vinyl acrylic
terpolymer sold by the National Starch Company as NS2853;
water, and water soluble hydrophylic surfactant sold by
At:Las Chemicals as Tween 20*. Approximately 125 grains per
square yard of binder is applied. The fabric is dried at
a temperature of 270F. for 1 minuté to remove excess
water and cure the binder. The fabric contains lightly
entangled fiber areas of higher density. The higher
density areas are interconnected by fibers extending
between the areas. The binder material runs transverse of
the fabric and bonds the fibers together. The strength of
the resultant fabric is tested using an Instron Tensile -
Tester in accordance with ASTM Method No. D-1117. The
fabric has a strip tenacity in the machine direction of
1.19 pounds per inch per 100 grains and a strip tenacity
in the cross direction of 0.89 pound per inch per 100
grains.
Control Example 1
:
For comparison purposes, a part of the air-layed polyester ~ -
fiber web used in Example 1 is not lightly entangled, but
binder is applied to the air-layed web and then cured
* Registered Trademar~
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using conditions analogous to those described in Example
1. Also, ano~her portion of the air-layed polyester fiber
web is lightly entangled as described in Example lr and is~
then dried to remove water. No adhesive binder is
applied. Both of these comparative samples are tested for
tenacity by the same method described in Example 1. The~
fabric which is only adhesively bonded and not lightly~
entangled has a strip tenacity in the machine direction of
0.505 pound per inch per lO0 grains, and a strip tenacity ;~
in the cross direction of 0.209 pound per inch per 100~
grains. The fabric which was lightly entangled but not
adhesively bonded had a strip tenacity in the machine ~
direction of 0.476 pound per inch per 100 grains, and a
strip tenacity in the cross direction of 0.358 pound per
inch per 100 grains.
Example 2
By procedures analogous to those described above in
Example 1 and Control Example 1, polypropylene fibers were~
formed into a web using the "Rando Webber" air-laying
machine, and were then subjected to light entangIement~
plus print bonding with NS2853 (Run 1), light entanglement
only (Run 2), and print bonding only with NS2853 (Run 3).
The resulting nonwoven fabrics were tested for grab
tensile strength (ASTM D - 1117 ) and specific grab tensile
(ASTM D-1117 ) in the machine and cross directions. The~
results are displayed in Table I~
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Table I
Specific Grab
Weight, Grab Tensile, Tensile,
S Run No. Grains ~ pounds/inch lbs/in/gr/yd2
M/D C/D M/D C/D
1 597 11.1 ~.7 1.86 1.46
2 432 0.6 0.5 0.15 0.12
3 588 2.6 1.6 0.44 0.27
Control Exampl_ 2
By a procedure analogous to that described in Example 1
and Control Example 1, rayon fibers were formed into a web
using the "Rando Webber" air-laying machine, and then
subjecting to light entanglement plus print bonding with
NS2853 (Run 1), light entanglement only (Run 2), and print
bonding only (Run 3). The resulting nonwoven fabrics were
tested for strip tenacity (ASTM D-1117) in the machine and
cross direction. The results are displayed in Table II:
Table II
Weight, Strip Tenacity,
~5 Run No.Grains/y~d2lbs/in~100 g ains/~d2
M/D C/D
1 697 0.94 0.53
2 514 0.84 0.51
3 676 1.03 0.67
Unlike the case with polyester and polypropylene fibers,
when rayon fibers are lightly entangled plus print bonded,
the strengths are not greater than the sum of the
strengths o~tained by entangling and printing alone. In
fact, printing without entangling actually gave higher
strengths than printing plus light entangling.
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Example 3
A web of 1-1/2 denier 1-3/4 inch polyester fibers weighing
about 375 grains per square yard is formed by a "Rando
Webber". The web is placed on a 16X14 woven belt. The
web and belt are passed under four strips, each containing
50 orifices per inch running in the cross direction. Each
orifice is circular with a diameter of 0.005 inch. Water
at a temperature of 14CF. is jetted through the ori~ices
at a pressure of 500 psi to lightly entangle the fibers
into a pattern of high density regions. The speed of the
belt and web under the orifices is 4~ feet per minute.
The lightly entangled web is dried by passing it over a ~
series of steam cans. ~ -
Portions of the lightly entangled web are saturation
bonded by padding with varying proportions of a self-
cross-linking vinyl acrylic terpolymer latex sold by
National Starch Company as NS2853. The samples with
binder are dried at 300F. The unbonded and bonded webs
are tested for specific grab tenacity and strip tenacity.
The results are set forth below in Table III.
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Control Example 3
Using the same polyester fiber described in Example 3, a ~ ~
"Rosebud" web is produced Rando Webber-laid web using the ~ ;
process of Kalwaites, U.S. Patent Nos. 2,862,251, and ~ ~ -
3,033,721. The water pressure employed is 200 psi. The~
web product weighs about 400 grains per square yard. The
web is dried, and then portions of it are saturation
bonded with varying proportions of the binder described in
Example 3, and then dried at 300F. The unbonded and
bonded webs are tested or specific grab tenacity and
strip tenacity. The results are displayed in Table III.
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Table III
Binder Specific Grab
Content, Tenacity,
5Per Cent lbs/in/gr/yd2
Example 3 Control Example 3
M/D C/D M/D C/D
0 1.62 1.11 0.12 0.11
2-1/2 2.73 2.36 1.96 1.26
3.23 2.55 2.05 1.75
3.61 3.06 2.97 2.99
3.01 2.41 3.48 3.30
3.37 2.31 2.91 2.8g
Strip Tenacity,
lbs/in/100 grains/yd2
Example 3 Control Example 3
M/D C/'D M/D C/D
0 0.38 0.17 0.03 0.02
2-1/2 1.03 0.55 0.33 0.22
1.13 0.78 0.57 0.51
1.57 0.96 1.10 1.00
2.31 0.91 1.~8 1.56
2.00 0.84 1.54 1.51;
On visual examination of the above-described samples, the;~
sample of Example 3 containing 2-1/2 per cent binder is
strong enough to be handled, and could be used as an
interlining in clothing manufacture. The Control Example
3 containing 2-1/2 per cent binder is just barely strong ;~
enough to be handled, has very poor abrasion resista~nce
and surface fiber tie-down, and appears to lack sufficient
integrity to have any significant commercial use. It is
probable that the Control Example lacks sufficient
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integrity to have significant commercial use until the 10
per cent binder level is attained; but at 10 per cent
binder, stiffness imparted by the binder begins to be a
factor which limits potential commercial uses.
Structural Measure Of Fiber Entanglement
The unbonded samples of Example 3 and Control Example 3
are evaluated for "S", the Structural Measure of Fiber
Entanglement. The results are as follows:
Example 3 - 0.0564
Control Example 3 - 0.0190
The procedure for determining this value is the
following:
Structurally, the extent of fiber interentanglement is
related to the concentration o~ fibers in the inter-
entangled area (C) and the density of the interentangled
mass (d). The product of these two factors provides a
measure of the frictional engagement and interaction of
the fibers in the interentangled area serving to lock the
fibers in place in the fabric to thereby permit maximum
utilization of fiber strength ~hen the fabric is subjected
to stress. Also influencing maximum utilization of fiber
strength is the cooperation-under-stress exhibited by the
group of fibers which extends between any two entangled
areas, which cooperation is inversely related to the
average-f~ee-length-~actor of the individual fibers in the
group (F). The structural measure of entanglement and
cooperation (S) is defined by the following equation;
S C
F
S is, in turn, related to the per cent of fiber strength
converted to fabric strength. The relationship is
appro~imated by the following empirical equation:
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S = 0.0593 ~ 0.00362 (% conversion) + 0.000543
(% conversion)2
The fiber concentration factor (C) is the ratio of the
length of fiber actually in the entangled area to the
length which would be there if there were no patterning
and/or entanglement of the fibers, i.e., if the fibers of ;~
the fabric were uniformly distributed in the plane of the
fabric. Since there is a direct relation between fiber
length and fiber weight, the fiber concentration factor
(C) may also be described as the ratio of the weight per
unit area of the entangled portion (W ) to the
weight per unit area of the entire fabric (W
i~e.:
C = Wl
W2
Wl and W2 are determined from the fabric
sample by direct measurement. For Wl t an average
of ten values is used and each value is determined by
cutting the entangled mass or representative portion
thereof from the fabric with a suitable die. The area of
the mass then corresponds to the area of the die. All ten
specimens are weighed at one time on a suitable ;
microbalance.
The density (d) of the entangled mass can be measured by
calculating the volumes of the cut-out specimens mentioned
above. To do this, the specimens are mounted axially on
broaches and are photographed at 20X to provide a cross~
sectional view. The cross-sec~ion thus photographed may
be irregular in shape. If so, the shape is approximated
with rectangles and/or triangles. The shapes are then
measured and, using the appropriate geometric formulas,
the corresponding volumes are calculated. The total
weight of the ten specimens is then divided by the sum of
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the ten volumes to give the average density (d) in
grams/cu.centimeter of the entangled area. The average-
free-length-factor (F) of the fibers in the group
extending between any two entangled areas is estimated by
direct observation (under a microscope) of the fibers in
the group and comparison to a set of standards.
In practice, it is observed that structures made from
straight (i.e., non-crimped or -curled) fibers do not have
ratings of one (corresponding to no curvature). Instead,
there is always some free length and an appropriate class
rating which may be used for structures made from straight
fibers is F = 1.4. Similarly, it is observed that the
rating for samples made from conventional staple fibers or
low crimp continuous filaments ranges from 1.8 to 2.5.
For such ~ibers, an average class rating of F = 2.1 may be
used. For highly crimped fibers, the actual measured
values of F should be used. The formula for S recognizes
that the free-length-factor is inversely related to
strength conversion, i.e., the greater the free-length-
factor, the more chance for poor fiber cooperation and the
greater the reduction in weight per unit area of the
sample when stressed until a break occurs.
