U.S. patent application number 11/526350 was filed with the patent office on 2010-04-01 for process for making uniform high strength yarns and fibrous sheets.
Invention is credited to Brian D. Arvidson, Thomas Y-T. Tam, Chok B. Tan.
Application Number | 20100078851 11/526350 |
Document ID | / |
Family ID | 39230866 |
Filed Date | 2010-04-01 |
United States Patent
Application |
20100078851 |
Kind Code |
A1 |
Tam; Thomas Y-T. ; et
al. |
April 1, 2010 |
PROCESS FOR MAKING UNIFORM HIGH STRENGTH YARNS AND FIBROUS
SHEETS
Abstract
Methods for preparation of high strength yarns having superior
yarn-to-yarn uniformity of denier, tenacity and tensile modulus and
uniform unidirectional fibrous sheets. Ballistic composites
prepared from these yarns and fibrous sheets have improved
uniformity of ballistic resistance. The drawn yarns, fibrous sheets
and articles made therefrom are more uniform than the prior art and
are useful in applications requiring impact absorption and
ballistic resistance, such as body armor, helmets, breast plates,
helicopter seats, spall shields; composite sports equipment such as
kayaks, canoes, bicycles and boats; and in fishing line, sails,
ropes, sutures and fabrics.
Inventors: |
Tam; Thomas Y-T.; (Richmond,
VA) ; Tan; Chok B.; (Richmond, VA) ; Arvidson;
Brian D.; (Chester, VA) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.;PATENT SERVICES
101 COLUMBIA ROAD, P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Family ID: |
39230866 |
Appl. No.: |
11/526350 |
Filed: |
September 25, 2006 |
Current U.S.
Class: |
264/210.8 ;
156/244.11 |
Current CPC
Class: |
B29K 2223/00 20130101;
B65H 2701/31 20130101; B32B 5/28 20130101; B65H 2701/38 20130101;
B65H 49/32 20130101; B29K 2023/00 20130101; F41H 1/02 20130101;
B29K 2023/0683 20130101; B65H 59/04 20130101; B29C 70/20 20130101;
D02J 1/22 20130101; F41H 5/0485 20130101; D04H 3/04 20130101 |
Class at
Publication: |
264/210.8 ;
156/244.11 |
International
Class: |
D02J 1/22 20060101
D02J001/22; D01D 5/12 20060101 D01D005/12; B32B 37/00 20060101
B32B037/00 |
Claims
1. A process for simultaneously drawing multiple ultra-high
molecular weight poly(alpha-olefin) (UHMWPO) yarns comprising the
steps of: a) forming a plurality of substantially identical
gel-spun multi-filament feed yarns comprising an UHMWPO having an
intrinsic viscosity measured in decalin at 135.degree. C. from 5
dl/g to 45 dl/g, said feed yarns having a tenacity of from 5 g/d to
65 g/d (0.43 GPa to 5.56 GPa) as measured by ASTM D2256-02, a
denier of from 100 to 20,000, and the filaments of said yarns being
of from 0.5 to 100 denier/filament (0.055 to 11.1 tex/filament); b)
winding up said plurality of feed yarns without imparting twist to
the yarns; c) unrolling the plurality of feed yarns without
imparting twist to the yarns, wherein the unrolling torque is
substantially the same for each yarn; d) passing the plurality of
feed yarns simultaneously and continuously into, through, and out
of an oven, wherein one or more zones are present along the yarn
path, said zones having zone temperatures in the range of about
100.degree. C. to about 165.degree. C., and wherein the exiting
speed of the yarns from the oven is greater than the entrance speed
of the yarns into the oven, said yarns being drawn in the oven; e)
cooling the drawn yarns under tension; and f) winding up a
plurality of the drawn yarns without imparting twist thereto.
2. The process of claim 1, wherein said UHMWPO is polyethylene.
3. The process of claim 1, wherein said feed yarns are wound up in
a form selected from the group consisting of tube packages and a
beam.
4. The process of claim 3, wherein said feed yarns are wound up
with tails.
5. The process of claim 3, wherein said feed yarns are wound up
with uniform yarn length.
6. The process of claim 1 wherein the plurality of feed yarns is
passed into said oven under substantially uniform and constant
tension.
7. The process of claim 1, wherein the plurality of drawn yarns are
passed out of said oven under substantially uniform tension.
8. The process of claim 1, wherein the drawn yarns are wound up in
a form selected from the group consisting of tube packages and
beams.
9. The process of claim 1, wherein the drawn yarns are wound up
with uniform yarn length.
10. The process of claim 1, wherein the drawn packages are wound at
substantially the same tension.
11. The process of claim 1, wherein the drawn yarns are comprised
of filaments having a denier/filament of from 0.1 to 20.
12. The process of claim 1, wherein the drawn yarns are comprised
of filaments having a denier/filament of from 0.1 to 2.
13. The process of claim 1, wherein from 2 to 1000 feed yarns are
drawn simultaneously.
14. The process of claim 1, wherein from 20 to 500 feed yarns are
drawn simultaneously.
15. A process for forming a unidirectional fibrous sheet comprising
the steps of: a) selecting a plurality of wound-up multi-filament
untwisted high strength yarns from the group consisting of UHMWPO
drawn by the process of claim 1, poly(p-phenylene
tererephthalamide), poly(p-phenylene-2,6-benzobisoxazole),
poly{2,6-diimidazo[4,5-b4'5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}
and their blends and mixtures; b) unrolling the plurality of high
strength yarns without imparting twist to the yarns, wherein the
unrolling torque is substantially the same for each yarn; c)
spreading the yarns side-by-side into their constituent filaments
to form a unidirectional sheet-like array of substantially parallel
filaments; d) applying a bonding material to the filaments; and e)
consolidating the array of filaments and bonding material into a
unitary unidirectional fibrous sheet.
16. The method of claim 15, wherein the high strength yarns are
unrolled at substantially the same tension.
17. The method of claim 15, wherein the high strength yarns are
unrolled from packages on one or more unrolling creels, each
unrolling creel having from 10 to 1000 package positions and the
unidirectional fibrous sheet is formed from 10 to 2000 yarns.
18. An article comprising a unidirectional fibrous sheet prepared
by the method of claim 15.
19. An article comprising at least two unidirectional sheets as
described in claim 18 assembled together surface-to-surface,
wherein the direction of the filaments in a sheet is at an angle to
the direction of the filaments in adjacent sheets.
20. The article of claim 19, wherein at least two unidirectional
sheets are bonded together at their surfaces.
21. The process of claim 1 wherein the unrolling torque is from
about 0.6 lb-in (0.07 N-m) to about 1.2 lb-in (0.14 N-m).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to methods for preparing high
strength yarns having superior yarn-to-yarn uniformity of denier,
tenacity and tensile modulus and to methods for preparing uniform
unidirectional fibrous sheets. Ballistic composites prepared from
these yarns and fibrous sheets have improved uniformity of
ballistic resistance.
[0003] The yarns and fibrous sheets are useful in applications
requiring impact absorption, penetration resistance and ballistic
resistance, such as Hi body armor, helmets, breast plates,
helicopter seats, spall shields; composite sports equipment such as
kayaks, canoes, bicycles and boats; and in fishing line, sails,
ropes, sutures and fabrics.
[0004] 2. Description of the Related Art
[0005] High strength yarns for the purposes of the invention are
yarns having tensile strengths determined by ASTM D2256-02 of at
least 17 g/d.
[0006] Examples of such yarns are aramids such as KEVLAR.RTM.
brand, polybenzazoles (PBO) such as ZYLON.RTM. brand,
poly{2,6-diimidazo[4,5-b4'5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}
such as M5.RTM. brand, ultra-high molecular weight
poly(alpha-olefins) (UHMWPO), and their blends and mixtures.
Ultra-high molecular weight polyolefins include polyethylene,
polypropylene, poly(butene-1), poly(4-methyl-pentene-1), their
copolymers, adducts, blends and mixtures.
[0007] High strength yarns are employed in impact resistant and
ballistic resistant articles in the form of woven fabrics and also
as cross-plied unidirectional sheets. Woven fabrics are preferably
produced from yarns that have a small degree of twist, preferably
less than about 2.5 turns/inch (0.98 turns/cm), or else are
entangled as described in U.S. Pat. No. 5,773,370. Cross-plied
unidirectional sheets are preferably produced from yarns that have
been spread into thin layers as described in U.S. Pat. No.
4,916,000. The disclosure of U.S. Pat. No. 4,916,000 is hereby
incorporated by reference to the extent not incompatible
herewith.
[0008] Multi-filament high strength polyethylene yarns are
commercially produced from ultra-high molecular weight polyethylene
(UHMWPE) by Honeywell International Inc. Gel-spun UHMWPO fibers are
prepared by spinning a solution of a UHMWPO into solution
filaments, cooling the solution filaments to a gel state, then
removing some or all of the spinning solvent. One or more of the
solution filaments, the gel filaments and the solid filaments are
drawn to a highly oriented state. The gel-spinning process
discourages the formation of folded chain lamellae and favors
formation of extended chain structures that more efficiently
transmit tensile loads.
[0009] U.S. Pat. Nos. 4,551,296, 4,663,101, 6,448,659 and 6,969,533
and U.S. application Ser. No. 11/393,218 describe drawing all three
of the solution filaments, the gel filaments and the solid
filaments. A process for drawing high molecular weight polyethylene
yarns is described in U.S. Pat. No. 5,741,451. Yet more recent
drawing processes are described in co-pending U.S. application Ser.
No. 11/206,838 and in United States Publication 20050093200. An
oven useful for drawing polyethylene fibers is described in United
States Patent Publication 20040040176. The disclosures of U.S. Pat.
Nos. 4,551,296, 4,663,101, 5,741,451, 6,448,659, and 6,969,533,
U.S. application Ser. Nos. 11/206,838 and 11/393,218 and United
States Publications 20040040176 and 20050093200 are hereby
incorporated by reference to the extent not incompatible
herewith.
[0010] Each of these references represented an advance in the state
of the art, however none suggests the process of this invention,
and none satisfies all of the needs met by this invention.
SUMMARY OF THE INVENTION
[0011] In one embodiment the invention is a process for
simultaneously drawing a plurality of substantially identical
UHMWPO yarns in a manner that preserves their yarn-to-yarn
uniformity and carries this uniformity forward into the drawn yarn.
Specifically, this embodiment comprises a process for
simultaneously drawing a plurality of UHMWPO yarns comprising the
steps of: [0012] a) forming a plurality of substantially identical
UHMWPO multi-filament feed yarns comprising a UHMWPO having an
intrinsic viscosity measured in decalin at 135.degree. C. of from 5
dl/g to 45 dl/g, said feed yarns having a tenacity of from 5 g/d to
65 g/d (0.43 GPa to 5.56 GPa) as measured by ASTM D2256-02, a
denier of from 100 to 20,000, and the filaments of said yarns being
of from 0.5 to 100 denier/filament (0.055 to 11.1 tex/filament);
[0013] b) winding up said feed yarns without imparting twist to the
yarns [0014] c) unrolling the plurality of feed yarns without
imparting twist to the yarns; wherein the unrolling torque is
substantially the same for each yarn; [0015] d) passing the
plurality of unrolled feed yarns simultaneously and continuously
into, through, and out of an oven wherein one or more zones are
present along the yarn path, said zones having temperatures in the
range of about 100.degree. C. to about 165.degree. C., and wherein
the exiting speed of the yarns from said oven is greater than the
entrance speed of the yarns into the oven, said yarns being drawn
in the oven; [0016] e) cooling the drawn yarns under tension; and
[0017] f) winding up a plurality of the drawn yarns without
imparting twist thereto.
[0018] In another embodiment, the invention is a process for
forming a unidirectional fibrous sheet comprising the steps of:
[0019] a) selecting a plurality of wound-up multi-filament
untwisted high strength yarns selected from the group consisting of
UHMPO drawn as described above, poly(p-phenylene
tererephthalamide), poly(p-phenylene-2,6-benzobisoxazole),
poly{2,6-diimidazo[4,5-b4'5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}
and their blends and mixtures; [0020] b) unrolling the plurality of
high strength yarns without imparting twist to the yarns, wherein
the unrolling torque is substantially the same for each yarn;
[0021] c) spreading the yarns side-by-side into their constituent
filaments to form a unidirectional sheet-like array of
substantially parallel filaments; [0022] d) applying a bonding
material to the filaments; and [0023] e) consolidating the array of
filaments and bonding material into a unitary unidirectional
fibrous sheet.
[0024] The invention includes the fibrous sheet articles prepared
by the above method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIGS. 1 and 2 schematically illustrate alternative modes of
carrying out the drawing method of the invention. FIG. 1 depicts
the use of restraining rolls 40 and drawing rolls 60 external to a
drawing oven 50, whereas FIG. 2 depicts the use of drawing rolls
both internal 80 and external 60 to a drawing oven 90.
DETAILED DESCRIPTION OF THE INVENTION
[0026] For purposes of the invention, a fiber is an elongate body
the length dimension of which is much greater than the transverse
dimensions of width and thickness. Accordingly, the term fiber
includes filament, ribbon, strip and the like having regular or
irregular cross-section. A yarn is a continuous strand comprised of
many fibers or filaments. A yarn package is a yarn wound onto a
core.
[0027] Many different types of yarn packages are known and used in
the fiber industry. The "Dictionary of Fiber and Textile
Technology", KoSa Communications and Public Affairs, Charlotte.
N.C., 1999, describes package types known as a "cheese", a "cone",
a "hosiery cone", a "warp-wind package", a "pineapple package" and
a "tube". A "tube" or "tube package" is a cylindrical build-up of
yarn wound on a cylindrical core.
[0028] In many kinds of fiber operations, it is customary to unwind
yarn from a stationary package by pulling the yarn off the end of
the package in a direction essentially parallel to the package
axis. This mode of unwinding produces a twist in the yarn.
Alternatively, a yarn may be unwound from a package by rotating the
package about its axis and withdrawing the yarn end in a direction
essentially perpendicular to the axis of the package. As used
herein, this mode of unwinding is termed "unrolling". For purposes
of the invention, if the yarn is unrolled from a package, the
unrolling torque is the product of the tension in the unrolling
yarn times the outside diameter of the package core. A creel is a
framework, typically metal, designed to hold yarn packages so that
a plurality of yarn ends may be unwound simultaneously without
tangling. The process of the invention may be practiced with a
creel designed to unwind yarn packages by unrolling.
[0029] A beam is a horizontal cylinder, typically metal, on which a
large number of yarns are wound up in preparation for further
processing. The process of the invention may also be practiced by
unwinding yarns from a beam by unrolling. For purposes of the
invention, if the yarn is unrolled from a beam, the unrolling
torque is the product of the tension in the unrolling yarn times
the outside diameter of the beam.
[0030] In one embodiment, the invention is a process for
simultaneously drawing multiple UHMWPO yarns comprising the steps
of: [0031] a) forming a plurality of substantially identical UHMWPO
multi-filament feed yarns comprising a UHMWPO having an intrinsic
viscosity measured in decalin at 135.degree. C. from 5 dl/g to 45
dl/g, said feed yarns having a tenacity of from 5 g/d to 65 g/d
(0.43 to 5.56 GPa) as measured by ASTM D2256-02, a denier of from
100 to 20,000, and the filaments of said yarns being of from 0.5 to
100 denier/filament (0.055 to 11.1 tex/filament); [0032] b) winding
up said plurality of feed yarns without imparting twist to the
yarns; [0033] c) unrolling the plurality of feed yarns without
imparting twist to the yarns, wherein the unrolling torque is
substantially the same for each yarn; [0034] d) passing the
plurality of unrolled feed yarns simultaneously and continuously
into, through, and out of an oven, wherein one or more zones are
present along the yarn path, said zones having zone temperatures in
range of from about 100.degree. C. to about 165.degree. C., and
wherein the exiting speed of the yarns from the oven is greater
than the entrance speed of the yarns into the oven, said yarns
being drawn in the oven; [0035] e) cooling the so-drawn yarns under
tension; and [0036] f) winding up a plurality of the drawn yarns
without imparting twist thereto.
[0037] The UHMWPO used in the process of the invention is
preferably selected from the group consisting of polyethylene,
polypropylene, poly(butene-1), poly(4-methyl-pentene-1), their
copolymers and adducts. More preferably, the UHMWPO is a
polyethylene with less than one pendent side group per 100 carbon
atoms, still more preferably less than one side group per 300
carbon atoms, yet more preferably less than one side group per 500
carbon atoms, and most preferably less than side group per 1000
carbon atoms. Side groups may include but are not limited to 01-010
alkyl groups, vinyl terminated alkyl groups, norbornene, halogen
atoms, carbonyl, hydroxyl, epoxide and carboxyl. The UHMWPO may
contain small amounts, generally less than 5 wt. %, preferably less
than 3 wt. % of additives such as anti-oxidants, thermal
stabilizers, colorants, flow promoters, solvents, etc.
[0038] Preferably, the UHMWPO feed yarns are formed by one of the
processes described in U.S. Pat. Nos. 4,551,296, 4,663,101,
6,448,659 and 6,969,533 and U.S. application Ser. No. 11/393,218.
Preferably, the feed yarns have a denier of from 100 to 20,000 and
are comprised of filaments of from 0.5 to 100 denier/filament. More
preferably, the feed yarns have a denier of from 100 to 5,000 and
are comprised of filaments of from 2 to 25 denier/filament.
[0039] Preferably, the plurality of feed yarns is wound up as a
plurality of individual yarn packages or on one or more beams.
Preferably, feed yarn packages are tube packages. Preferably, the
plurality of feed packages or beams have uniform lengths of yarn
and uniform dimensions. Preferably, the feed yarns are wound with
the first several meters or so of yarn outside of the area where
the remaining yarn is wound so as to create a "tail" that permits
tying several yarn packages in series and unwinding continuously
without need to stop a drawing operation to tie in yarns.
[0040] Preferably, from 2 to 1000 feed yarns are drawn
simultaneously. More preferably, from 20 to 500 feed yarns are
drawn simultaneously. Preferably, each beam has from 10 to 1000
yarns. Preferably, each unrolling creel has from 10 to 1000 package
positions.
[0041] The unrolling torque for yarns on a beam is the same for all
yarns. The unrolling torque for yarns on a creel can be set the
same for each yarn by individual adjustment of slip clutches on
each position of the creel. Preferably, the creel has a mechanism
by which the same unrolling torque can be set simultaneously for
all yarn packages and the torque is constant throughout the
unwinding. A simple example of such a mechanism consists of leather
straps attached to the creel structure at one end and wrapped
around pulleys that are part of each package holder. The other ends
of the leather straps are each attached by springs to the same
moveable frame. The frame is free to slide within the creel
structure. The frame position within the creel structure is set so
as to stretch the springs. The springs tighten the straps causing
friction of the straps on the pulleys, and simultaneously setting
the unwind torque of each package holder. The mechanism is
initially calibrated so the unrolling torque is substantially the
same for each package. Preferably, the unrolling torque is from
about 0.6 lb-in (0.07 N-m) to about 1.2 lb-in (0.14 N-m). Other
mechanisms that can provide the same unwinding torque for each yarn
package are also suitable, such as a magnetic slip clutch at each
creel position such as described in U.S. Pat. No. 6,129,193 hereby
incorporated by reference to the extent not incompatible
herewith.
[0042] Preferably, the plurality of feed yarns is passed into the
oven under substantially uniform and substantially constant
tension. Substantially uniform tension means the standard deviation
of yarn tension, yarn-to-yarn, is preferably less than 25% and more
preferably, less than 10% of the mean tension. Substantially
constant tension means that the standard deviation of the time
variation of tension over 10 revolutions of a feed roll is
preferably less than 25% and more preferably less than 10% of the
mean tension.
[0043] The unrolling tension in yarns leaving a creel may be
regulated by adjusting the electric power to magnetic slip clutches
such as described in U.S. Pat. No. 6,129,193 in proportion to the
outside diameter of the yarn packages as they unroll.
Alternatively, the tension in the yarns as they pass from feed
packages or beams may be regulated to be substantially uniform and
substantially constant by having each yarn pass through a tension
controller such as described in U.S. Pat. No. 6,457,666 B1 hereby
incorporated by reference to the extent not incompatible
herewith.
[0044] Preferably, the plurality of drawn yarns are wound up as
yarn packages. Alternatively, the plurality of drawn yarns may be
wound up on a beam.
[0045] Preferably, the plurality of drawn yarns is each passed out
of the oven under substantially uniform tension. Preferably, the
drawn packages are each wound at substantially uniform tension.
[0046] Preferably, the drawn packages or beams have uniform lengths
of yarn and uniform dimensions. Preferably, the drawn yarns are
wound with the first several meters or so of yarn outside of the
area where the remaining yarn is wound so as to create a
"tail".
[0047] Preferably, the drawn yarns are comprised of filaments
having a denier/filament of from 0.1 to 20. More preferably, the
drawn yarns are comprised of filaments having a denier/filament of
from 0.1 to 10. Yet more preferably, the drawn yarns are comprised
of filaments having a denier/filament of from 0.1 to 5. Still more
preferably, the drawn yarns are comprised of filaments having a
denier/filament of from 0.1 to 2. Most preferably, the drawn yarns
are comprised of filaments having a denier/filament of from 0.1 to
1.
[0048] Two modes of carrying out this embodiment of the invention
are illustrated schematically in FIGS. 1 and 2. FIG. 1 illustrates
use of restraining rolls 40 and drawing rolls 60 external to a
drawing oven 50. A plurality of UHMWPO feed yarns that had been
wound on tube packages 10 without twist being imparted to the yarns
are placed on one or more multiple position creels 20. The creel
positions had been adjusted to provide the same unrolling torque to
each package. One creel 20 and four yarn packages 10 are
illustrated for simplicity but are not intended to be limiting. The
plurality of feed yarns are unrolled from the packages at the same
unwinding torque or at the same unwinding tension without imparting
twist to the yarns and passed through a comb guide 30 that brings
the feed yarns into side-by-side alignment. The side-by-side array
of feed yarns 100 is passed over and under a set of large diameter
(restraining) rolls 40 that set the speed and temperature with
which the feed yarns are passed into an oven 50. The rolls 40 may
possess an internal heat source and be temperature regulated. The
number of rolls 40 necessary to restrain the yarn and regulate its
speed into the oven will vary depending on the diameter, material,
surface finish and operating temperature of the rolls and the
strength, denier and frictional characteristics of the yarns. Three
restraining rolls 40 are illustrated for convenience but the
illustration is not intended to be limiting. The oven may have one
or more temperature zones. Blowers and heaters (not illustrated)
may provide hot gas circulation in the oven. The drawn yarns 200
are passed out of the oven 50 over and under a set of large
diameter (drawing) rolls 60 that set the speed of the drawn yarns
and the extent of draw in the oven 50. The illustration of three
rolls is for convenience and is not intended to be limiting. The
drawn yarns are wound up on tube packages 70 without imparting
twist to the yarns.
[0049] FIG. 2 illustrates a second mode of carrying out this
embodiment of the invention. As in the first mode, the packages of
feed yarns 10 wound up without imparting twist thereto are placed
on one or more creels 20 and unrolled at the same torque for each
yarn. The yarns are passed through a in comb guide 30 that brings
the feed yarns into side-by-side parallel alignment. The
side-by-side array of feed yarns 100 is passed into an oven 90. The
oven 90 may have one or more temperature zones. Blowers and heaters
(not illustrated) may provide hot gas circulation in the oven 90.
Within the oven, the yarns are passed over and under a series of
driven rolls 80, each roll 80 operating (rotating) at a higher
speed than the one before. Eleven internal driven rolls are
illustrated for convenience but the illustration is not intended to
be limiting. The yarns are thereby stretched as they pass
successively over each driven roll 80. The drawn yarns 200 are
passed out of the oven 90 over and under a set of large diameter
rolls 60 that set the final speed of the drawn yarns and cool them
under tension. The drawn yarns are wound up on tube packages 70
without imparting twist to the drawn yarns.
[0050] In other modes of carrying out this embodiment of the
invention, the creel 20 and the tube packages 10 can be replaced by
one or more beams on which the feed yarns have been wound without
imparting twist thereto. Similarly, the drawn yarns 200 may be
wound up on one or more beams instead of on tube packages 70. These
modes of carrying out the invention are not illustrated but will be
readily understood by one of ordinary skill in the art.
[0051] The simultaneously drawn yarns produced by this process of
the invention are more uniform in denier, tenacity and tensile
modulus than a similar number of drawn yarns produced using a prior
art process.
[0052] In another embodiment, the invention is a process for
forming a unidirectional fibrous sheet comprising the steps of:
[0053] a) selecting a plurality of wound-up multi-filament
untwisted high strength yarns selected from the group selected from
the group consisting of UHMPO drawn as described above,
poly(p-phenylene tererephthalamide),
poly(p-phenylene-2,6-benzobisoxazole), poly
{2,6-diimidazo[4,5-b4'5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}
and their blends and mixtures; [0054] b) unrolling the plurality of
high strength yarns without imparting twist to the yarns, wherein
the unrolling torque is substantially the same for each yarn;
[0055] c) spreading the yarns side-by-side into their constituent
filaments to form a unidirectional sheet-like array of parallel
filaments; [0056] d) applying a bonding material to the filaments;
and [0057] e) consolidating the array of filaments and bonding
material into a unitary unidirectional fibrous sheet.
[0058] High strength yarns for the purposes of the invention are
yarns having tensile strengths determined by ASTM D2256-02 at least
17 g/d. Examples of such yarns are aramids such as KEVLAR.RTM.
brand, polybenzazoles (PBO) such as ZYLON.RTM. brand,
poly{2,6-diimidazo[4,5-b4'5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}
such as M5.RTM. brand, ultra-high molecular weight
poly(alpha-olefins) (UHMWPO), and their blends and mixtures.
Ultra-high molecular weight polyolefins include polyethylene,
polypropylene, poly(butene-1), poly(4-methyl-pentene-1), their
copolymers, adducts, blends and mixtures. The method of the
invention is applicable to the foregoing examples of high strength
yarns but is not restricted to this list.
[0059] Preferably, the high strength yarns are unrolled at
substantially the same tension. Preferably, the yarns are spread
and the unidirectional sheet is formed as described in U.S. Pat.
No. 4,916,000 heretofore incorporated by reference to the extent
not incompatible herewith. Preferably, the unidirectional fibrous
sheet of this invention has a ratio of sheet thickness to
equivalent filament diameter of 12.8 or less.
[0060] Preferably, the drawn yarns are unrolled from one or more
unrolling creels. Preferably, each unrolling creel has from 10 to
1000 package positions and the unidirectional fibrous sheet is
formed from 10 to 2000 yarns. Alternatively, the drawn yarns may be
unrolled from one or more beams, each beam holding 50 to 1000
yarns.
[0061] The invention includes a unidirectional fibrous sheet
article prepared by the method of the invention. The fibrous sheet
may be comprised of more than one high strength yarn having a
random or patterned arrangement. In a further embodiment, the
invention is an article comprising at least two unidirectional
fibrous sheets prepared by the method of the invention bonded
together surface-to-surface, wherein the direction of the filaments
in a sheet are at angle to the direction of filaments in adjacent
sheets.
[0062] Assemblies prepared from the unidirectional fibrous sheets
of this invention have improved uniformity of ballistic resistance
because of the greater physical property uniformity of the yarns of
which they are constructed and the greater uniformity of the
tension in the yarns as the unidirectional sheets are formed.
EXAMPLES
Comparative Example 1
[0063] A plurality of essentially identical UHMWPO feed yarns were
prepared by the process described in U.S. Pat. No. 4,551,296. The
yarns were comprised of a linear polyethylene having an intrinsic
viscosity measured in decalin at 135.degree. C. of about 12 dl/g.
The 240 filament yarns were wound up as packages on cylindrical
tubes of 3.988 inch (10.13 cm) outside diameter without twist being
imparted to the yarns. The average denier, tenacity and initial
tensile modulus (modulus of elasticity) of these feed yarn packages
are shown in Table I below together with the standard deviations,
and coefficients of variations of those characteristics. Tensile
properties of the yarns were measured by ASTM D-2256-02
[0064] Feed yarn packages were placed on two 48-position creels and
96 yarns were simultaneously unrolled without imparting twist to
the yarns. No measures were taken to insure that the unrolling
torque was the same for each yarn. Unrolling torque varied from
about 0.6 lb-in (0.07 N-m) to about 1.8 lb-in (0.2 N-m)
package-to-package. Moment-to-moment yarn tension was measured and
recorded for a single feed roll by means of a load cell and a chart
recorder. Instantaneous yarn tension averaged about 150 g.+-.67%
over a period of 12 revolutions of the feed roll.
[0065] The 96 yarns were aligned side-by-side, passed over and
under a set of driven rolls and passed into, through and out of a
forced convection oven maintained at a temperature of 150.degree.
C. to a second set of driven rolls as illustrated schematically in
FIG. 1. The second set of driven rolls operated at a speed greater
than the first set of rolls and served to draw the yarns in the
oven. The drawn yarns were cooled under tension and wound up as
individual tube packages without twist being imparted to the yarns.
This process was repeated with new sets of 96 yarns until the
entire group of feed yarns was drawn. The average denier, tenacity
and initial tensile modulus of these drawn yarn packages are shown
in Table I below together with the standard deviations, and
coefficients of variation (C.O.V.) of those characteristics.
Example 1
[0066] A plurality of essentially identical UHMWPO feed yarn
packages was prepared by the process described in U.S. Pat. No.
4,551,296. The yarns were comprised of a polyethylene having an
intrinsic viscosity measured in decalin at 135.degree. C. of 12 to
14 dl/g. The 240 filament yarns were wound up as packages on
cylindrical tubes of 3.988 inch (10.13 cm) outside diameter without
twist being imparted to the yarns. The average denier, tenacity and
initial tensile modulus (modulus of elasticity) of these feed yarn
packages as measured by ASTM D2256-02 are shown in Table I below
together with the standard deviations, and coefficients of
variations of those characteristics.
[0067] Feed yarn packages were placed on two 50-position creels and
100 yarns were simultaneously unrolled without imparting twist to
the yarns. The substantially uniform and substantially constant
unrolling torque for each yarn was set at about 0.88 lb-in (0.098
N-m). Yarn tension averaged about 100 g.+-.25% over 12 revolutions
of a feed roll. The 100 feed yarns were aligned side-by-side in
parallel, passed over and under a set of driven rolls and passed
into, through and out of a forced convection air oven maintained at
a temperature of 150.degree. C. to a second set of driven rolls as
illustrated schematically in FIG. 1. The second set of driven rolls
operated at a speed greater than the first set of rolls and served
to draw the yarns in the oven. The drawn yarns were cooled under
tension and wound up as individual tube packages without twist
being imparted to the yarns. This process was repeated with new
sets of 100 yarns until the entire group of feed yarns was drawn.
The average denier, tenacity and initial tensile modulus of these
drawn yarn packages are shown in Table I below together with the
standard deviations, and coefficients of variation of these
characteristics.
TABLE-US-00001 TABLE I EXAMPLE Comparative 1 Example 1 Feed Yarn
Drawn Yarn Feed Yarn Drawn Yarn Denier (Tex) 2415 (268) 1300 (144)
2402 (267) 1325 (147) Std. Dev. (Tex) 21.8 (2.42) 28.8 (3.2) 58.6
(6.5) 20.4 (2.27) C.O.V., % 0.90 2.21 2.44 1.54 Tenacity, g/d (GPa)
30.9 (2.64) 34.7 (2.97) 31.4 (2.69) 37.5 (3.21) Std. Dev., g/d
(GPa) 1.3 (0.11) 1.25 (0.11) 1.1 (0.094) 0.86 (0.074) C.O.V., % 4.2
3.6 3.5 2.3 Modulus, g/d (GPa) 915 (78.3) 1147 (98.1) 888 (76.0)
1245 (106) Std. Dev., g/d (GPa) 36.4 (3.11) 47.2 (4.03) 18.5 (1.58)
21.7 (1.86) C.O.V., % 4.0 4.1 2.1 1.7
[0068] It will be seen that when yarn unrolling torque was not the
same for each feed yarn, as in Comparative Example 1, the denier
variation was greater in the drawn yarns than in the feed yarns. In
contrast, when the unrolling torque was set to be substantially
identical for each feed yarn, the denier was more uniform in the
drawn yarns than in the feed yarns., and more uniform in the yarns
drawn by the method of the invention than in the yarns drawn by the
method of the Comparative Example. Similarly, the tensile
properties of the yarns drawn by the method of the invention were
more uniform compared to the feed yarns and more uniform than yarns
drawn by the method of the Comparative Example.
Example 2
[0069] A plurality of feed yarns are prepared under the same
conditions as described in Example 1 and having essentially the
same properties as described in Example 1. The feed yarns are wound
up without twist as tube packages of uniform length. Feed yarn
packages are placed on two multiple position creels and a plurality
of yarns are simultaneously unrolled without imparting twist to the
yarns. Each yarn is passed through a tension controller as
described in U.S. Pat. No. 6,457,666 such that the yarns leaving
the tension controllers are under substantially uniform and
substantially constant tension. The plurality of feed yarns are
aligned side-by-side, passed over and under a set of driven rolls
and passed into, through and out of a forced convection air oven
under essentially uniform tension and drawn as described in Example
1. The drawn yarns are cooled under substantially uniform tension
and are rewound without twist.
[0070] It is expected that the drawn yarns will be improved in
uniformity of denier and tensile properties as compared to their
feed yarns and as compared to the drawn yarns of Comparative
Example 1.
Comparative Example 2
[0071] A plurality of tube packages of 240 filament polyethylene
drawn yarns were prepared and wound up by the method of Comparative
Example 1. The denier, tensile properties and uniformity of the
drawn yarns were essentially identical to those shown in the second
column of Table 1. The drawn yarn packages were placed on multiple
position creels, unrolled and aligned side-by-side. No measures
were taken to insure that the unrolling torque was the same for
each yarn. Unrolling torque varied from about 0.6 lb-in (0.07 N-m)
to about 1.8 lb-in (0.2 N-m) package-to-package. Yarn tension
averaged about 150 g.+-.67% over a period of 12 revolutions of a
feed roll. The yarns were spread into their constituent filaments
to form a unidirectional sheet-like array as described in U.S. Pat.
No. 4,916,000. A bonding material was applied to the filaments and
the array of filaments and bonding material was consolidated and
rolled up as a unidirectional fibrous sheet of indefinite length.
Two such rolls of unidirectional fibrous sheets were cross-plied
and consolidated under heat and pressure as described in U.S. Pat.
No. 5,173,138 hereby incorporated by reference to the extent not
incompatible herewith.
[0072] Ballistic targets were formed each consisting of 37 layers
of the cross-plied material described above stacked together
surface-to-surface to an average areal density of 1.0276
lbs/ft.sup.2 (5.022 Kg/m.sup.2). The targets were fired at using a
0.22 caliber (5.588 mm), 17 grain (1.102 g) fragment simulating
projectile and the V50 velocities for these targets measured by
MIL-STD 662F. The Specific Energy Absorption (SEA) of the targets
were calculated at the V50 velocities from the following
relationship:
SEA, J-m.sup.2/Kg=1/2 m(V50).sup.2/A.D.
[0073] Where: m is the mass of the projectile in Kg [0074] V50 is
the V50 velocity in m/sec [0075] A.D. is the target area density in
Kg/m.sup.2
[0076] The average results for 45 such targets are shown in Table
II below.
Comparative Example 3
[0077] A plurality of tube packages of 240 filament polyethylene
drawn yarns were prepared and wound up by the method of Comparative
Example 1. The denier, tensile properties and uniformity of the
drawn yarns were essentially identical to those shown in the second
column of Table 1. The drawn yarn packages were placed on multiple
position creels, unrolled at substantially uniform torque and
aligned side-by-side. The substantially uniform and substantially
constant unrolling torque for each yarn was set at about 0.88 lb-in
(0.098 N-m). Yarn tension averaged about 100 g.+-.25% over 12
revolutions of a feed roll. The yarns were spread into their
constituent filaments to form a unidirectional sheet-like array as
described in U.S. Pat. No. 4,916,000. A bonding material was
applied to the filaments and the array of filaments and bonding
material was consolidated and rolled up as a unidirectional fibrous
sheet of indefinite length. Two such rolls of unidirectional
fibrous sheets were cross-plied and consolidated under heat and
pressure as described in U.S. Pat. No. 5,173,138.
[0078] Ballistic targets were formed each consisting of 37 layers
of the cross-plied material described above stacked together
surface-to-surface to an average areal density of 1.0245
lbs/ft.sup.2 (5.007 Kg/m.sup.2). The targets were fired at using a
0.22 caliber (5.588 mm), 17 grain (1.102 g) fragment simulating
projectile and the V50 velocities for these targets measured by
MIL-STD 662F. The Specific Energy Absorption for the targets was
calculated at the V50 velocity by the same relationship as given
above. The average results for 11 such targets are shown in Table
II below.
TABLE-US-00002 TABLE II Comparative Example 2 Comparative Example 3
ft/sec m/sec ft/sec m/sec V50 1682 512.7 1670 509.0 Std. Dev. Of
V50 34.6 10.5 22.1 6.7 J-m.sup.2/Kg J-m.sup.2/Kg SEA 28.8 28.8 Std.
Dev. Of SEA 1.18 0.82
[0079] The targets made using the cross-plied unidirectional sheets
made with yarns unrolled at constant torque (Comparative Example 3)
had slightly lower average V50 than for the targets made in
Comparative Example 2, but were also of slightly lower average
areal density. The average Specific Energy Absorption of both sets
of targets were identical. The principal difference was that the
ballistic properties of the targets made with the cross-plied
unidirectional sheets using yarns unrolled at constant torque were
much more uniform than those of the comparative example in both the
V50 velocity and the SEA as measured by the standard deviations of
those properties.
Example 3
[0080] A plurality of tube packages of 240 filament polyethylene
drawn yarns are prepared and wound up by the method of Example 1.
The denier, tensile properties and uniformity of the drawn yarns
are essentially identical to those shown in the fourth column of
Table 1. The drawn yarn packages are placed on multiple position
creels, unrolled at substantially uniform torque and aligned
side-by-side. The substantially uniform and substantially constant
unrolling torque for each yarn is set at about 1.0 lb-in (0.11
N-m). The yarns are spread into their constituent filaments to form
a unidirectional sheet-like array as described in U.S. Pat. No.
4,916,000. A bonding material is applied to the filaments and the
array of filaments and bonding material is consolidated and rolled
up as a unidirectional fibrous sheet of indefinite length. Two such
rolls of unidirectional fibrous sheets are cross-plied and
consolidated under heat and pressure as described in U.S. Pat. No.
5,173,138.
[0081] Ballistic targets are formed each consisting of 37 layers of
the cross-plied material described above stacked together
surface-to-surface to an average areal density of about 1.0
lbs/ft.sup.2 (4.887 Kg/m.sup.2). The targets are fired at using a
0.22 caliber (5.588 mm), 17 grain (1.102 g) fragment simulating
projectile and the V50 velocities for these targets measured by
MIL-STD 662F. It is believed that the V50 velocity, the SEA and the
uniformity of those properties will be superior to those measured
in Comparative Examples 2 or 3.
Example 4
[0082] A plurality of tube packages of 1140 denier (1270 decitex),
768 filament KEVLAR.RTM. 49 brand high strength poly(p-phenylene
tererephthalamide) aramid yarns are selected. The yarns have a
tenacity of 23.6 g/d (20.8 cN/dtex) as measured by ASTM D2256=02.
The yarn packages are placed on multiple position creels, unrolled
at substantially uniform torque and aligned side-by-side. The
substantially uniform and substantially constant unrolling torque
for each yarn is set at about 1.0 lb-in (0.11 N-m). The yarns are
spread into their constituent filaments to form a unidirectional
sheet-like array as described in U.S. Pat. No. 4,916,000. A bonding
material is applied to the filaments and the array of filaments and
bonding material is consolidated and rolled up as a unidirectional
fibrous sheet of indefinite length. Two such rolls of
unidirectional fibrous sheets are cross-plied and consolidated
under heat and pressure as described in U.S. Pat. No.
5,173,138.
[0083] Ballistic targets are formed of the cross-plied material
described above stacked together surface-to-surface to an average
areal density of about 1.0 lbs/ft.sup.2 (4.887 Kg/m.sup.2). The
targets are fired at using a 0.22 caliber (5.588 mm), 17 grain
(1.102 g) fragment simulating projectile and the V50 velocities for
these targets measured by MIL-STD 662F. It is believed that the V50
velocity, the SEA and the uniformity of those properties will be
superior in comparison to targets where the fibrous sheets are not
formed from yarns unrolled at substantially constant and
substantially uniform torque.
Example 5
[0084] A plurality of tube packages of 1300 denier (1170 decitex),
688 filament ZYLON.RTM. brand AS high strength
poly(p-phenylene-2,6-benzobisoxazole) (PBO) yarns are selected. The
yarns have a tenacity of 42 g/d (37 cN/dtex). The yarn packages are
placed on multiple position creels, unrolled at substantially
uniform torque and aligned side-by-side. The substantially uniform
and substantially constant unrolling torque for each yarn is set at
about 1.0 lb-in (0.11 N-m) measured at the outside diameter of the
w package cores. The yarns are spread into their constituent
filaments to form a unidirectional sheet-like array as described in
U.S. Pat. No. 4,916,000. A bonding material is applied to the
filaments and the array of filaments and bonding material is
consolidated and rolled up as a unidirectional fibrous sheet of
indefinite length. Two such rolls of unidirectional fibrous sheets
are cross-plied and consolidated under heat and pressure as
described in U.S. Pat. No. 5,173,138.
[0085] Ballistic targets are formed of the cross-plied material
described above stacked together surface-to-surface to an average
areal density of about 1.0 lbs/ft.sup.2 (4.887 Kg/m.sup.2). The
targets are fired at using a 0.22 caliber (5.588 mm), 17 grain
(1.102 g) fragment simulating projectile and the V50 velocities for
these targets measured by MIL-STD 662F. It is believed that the V50
velocity, the SEA and the uniformity of those properties will be
superior in comparison to targets where the fibrous sheets are not
formed from yarns unrolled at substantially constant and
substantially uniform torque.
Example 6
[0086] A plurality of tube packages of high strength
poly{2,6-diimidazo[4,5-b4'5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}
(M5.RTM. brand) yarns are selected. The yarns have a tenacity of 42
g/d (37 cN/dtex). The yarn packages are placed on multiple position
creels, unrolled at substantially uniform torque and aligned
side-by-side. The substantially uniform and substantially constant
unrolling torque for each yarn is set at about 1.0 lb-in (0.11 N-m)
measured at the outside diameter of the package cores. The yarns
are spread into their constituent filaments to form a
unidirectional sheet-like array as described in U.S. Pat. No.
4,916,000. A bonding material is applied to the filaments and the
array of filaments and bonding material is consolidated and rolled
up as a unidirectional fibrous sheet of indefinite length. Two such
rolls of unidirectional fibrous sheets are cross-plied and
consolidated under heat and pressure as described in U.S. Pat. No.
5,173,138.
[0087] Ballistic targets are formed of the cross-plied material
described above stacked together surface-to-surface to an average
areal density of about 1.0 lbs/ft.sup.2 (4.887 Kg/m.sup.2) The
targets are fired at using a 0.22 caliber (5.588 mm), 17 grain
(1.102 g) fragment simulating projectile and the V50 H) velocities
for these targets measured by MIL-STD 662F. It is believed that the
V50 velocity, the SEA and the uniformity of those properties will
be superior in comparison to targets where the fibrous sheets are
not formed from yarns unrolled at substantially constant and
substantially uniform torque.
[0088] Having thus described the invention in rather full detail,
it will be understood that such detail need not be strictly adhered
to but that further changes and modifications may suggest
themselves to one skilled in the art, all falling within the scope
of the invention as defined by the subjoined claims.
* * * * *