U.S. patent application number 14/104136 was filed with the patent office on 2014-06-19 for cut resistant articles.
This patent application is currently assigned to E I Du Pont De Nemours And Company. The applicant listed for this patent is E I Du Pont De Nemours And Company. Invention is credited to XUN MA, LARRY JOHN PRICKETT.
Application Number | 20140165251 14/104136 |
Document ID | / |
Family ID | 49950028 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140165251 |
Kind Code |
A1 |
PRICKETT; LARRY JOHN ; et
al. |
June 19, 2014 |
Cut Resistant Articles
Abstract
A cut resistant article comprising a glove, sleeve, or apron
comprising a knit fabric having yarns of fibers having essentially
a round cross section and comprising linear polyethylene having a
weight average molecular weight of at least 1 million, the yarns
having a tensile modulus equal to 500 grams per denier (455 grams
per dtex) or less and a yarn elongation at break of 4 percent or
greater, the fabric further having a basis weight of 857 grams per
square meter or less and having a mass index of 6000 or less.
Inventors: |
PRICKETT; LARRY JOHN;
(Chesterfield, VA) ; MA; XUN; (Midlothian,
VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I Du Pont De Nemours And Company |
Wilmington |
DE |
US |
|
|
Assignee: |
E I Du Pont De Nemours And
Company
Wilmington
DE
|
Family ID: |
49950028 |
Appl. No.: |
14/104136 |
Filed: |
December 12, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61737340 |
Dec 14, 2012 |
|
|
|
Current U.S.
Class: |
2/2.5 |
Current CPC
Class: |
D02G 3/442 20130101;
D04B 1/28 20130101; D10B 2321/0211 20130101; D10B 2403/0114
20130101; F41H 1/02 20130101 |
Class at
Publication: |
2/2.5 |
International
Class: |
F41H 1/02 20060101
F41H001/02 |
Claims
1. A cut resistant article comprising a glove, sleeve, or apron
comprising a knit fabric having yarns of fibers having essentially
a round cross section and comprising linear polyethylene having a
weight average molecular weight of at least 1 million, the yarns
having a tensile modulus equal to 500 grams per denier (455 grams
per dtex) or less and a yarn elongation at break of 4 percent or
greater, the fabric further having a basis weight of 857 grams per
square meter or less and having a mass index of 6000 or less.
2. The cut resistant article of claim 1 having a mass index of 2000
to 6000.
3. The cut resistant article of claim 2 having a mass index of 3000
to 5000.
4. The cut resistant article of claim 1 wherein the fiber has a
yarn tensile modulus of 400 grams per denier (275 grams per dtex)
or less.
5. The cut resistant article of claim 1 wherein the fiber has a
yarn tensile modulus of 100 grams per denier (91 grams per dtex) or
greater.
6. The cut resistant article of claim 1 wherein the fiber has a
yarn elongation at break of 4 to 15 percent.
7. The cut resistant article of claim 1 further comprising a
polymeric coating for gripping objects.
8. The cut resistant article of claim 7 wherein the polymeric
coating is positioned in discrete areas on the article.
9. The cut resistant article of claim 1 wherein the knit is 7 gauge
or higher.
10. The cut resistant article of claim 9 wherein the knit is 10
gauge or higher.
11. The cut resistant article of claim 10 wherein the knit is 13
gauge or higher.
12. The cut resistant article of claim 11 wherein the knit is 15
gauge or higher.
13. The cut resistant article of claim 12 wherein the knit is 18
gauge or higher.
14. The cut resistant article of claim 9 wherein the knit is 24
gauge or lower.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to cut resistant articles, which
include such items as gloves, sleeves, or aprons, and methods of
making the same.
[0003] 2. Description of Related Art
[0004] Articles of apparel such as gloves, sleeves, and aprons made
from fabrics containing ultra-high-molecular-weight (UHMW)
polyethylene fibers having high yarn tenacities and tensile moduli
can have excellent cut performance and command a premium price in
the marketplace. However, it is believed the high fiber tensile
modulus of the fiber translates into stiffer fabric which is
undesirable, since this can mean the articles of apparel using such
fabrics are less comfortable. Since workers are less likely to wear
uncomfortable protective apparel, any improvement in the comfort of
such cut resistant articles is desired.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention relates to a cut resistant article
comprising a glove, sleeve, or apron comprising a knit fabric
having yarns of fibers having essentially a round cross section and
comprising linear polyethylene having a weight average molecular
weight of at least 1 million, the yarns having a tensile modulus
equal to 500 grams per denier (455 grams per dtex) or less and a
yarn elongation at break of 4 percent or greater, the fabric
further having a basis weight of 857 grams per square meter or less
and having a mass index of 6000 or less. In some embodiments the
article is provided with a polymeric coating for gripping
objects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a graph illustrating knit fabric mass index.
[0007] FIG. 2 is a representation of a substantially solid polymer
fiber having essentially a round cross section with a nominal
aspect ratio of 1.
DETAILED DESCRIPTION OF THE INVENTION
[0008] This invention relates to a cut resistant article comprising
a glove, sleeve, or apron comprising a knit fabric having yarns of
fibers having essentially a round cross section and comprising
linear polyethylene having a weight average molecular weight of at
least 1 million, the yarns having a tensile modulus equal to 500
grams per denier (455 grams per dtex) or less and a yarn elongation
at break of 4 percent or greater, the fabric further having a basis
weight of 857 grams per square meter or less and having a mass
index of 6000 or less.
[0009] The "mass index" as used herein relates to knit fabrics and
is the product of the fabric basis weight, in grams per square
meter, times the knit fabric gauge. The knit gauge is the number of
wales per inch (or defined in SI units the number of wales per 2.53
cm) in the fabric. The gauge of a knitting machine is the number of
knitting needles per inch (or defined in SI units the number of
wales per 2.53 cm) in the machine.
[0010] Further, it has been found that knit fabrics having a mass
index of 6000 or less made with yarns comprising high molecular
weight polyethylene fibers having a low tensile modulus and a round
cross section provide cut resistant articles having improved
comfort. Personal comfort is almost always cited as a desirable
feature of protective apparel, in that apparel that is less
comfortable is more likely to not be worn, resulting in more
injuries to workers.
[0011] Surprisingly, it has been found that the cut resistance of
low tensile modulus yarns is not sacrificed even if the lower
tensile modulus is achieved by reducing the tensile strength of the
high molecular weight polymer yarns. Instead, the inventors believe
the presence of higher molecular weight polyethylene is a more
important factor with regards to cut resistance of yarns and
fabrics, and apparel made from those yarns and fabrics. In
particular, the fabrics made with the low modulus yarns claimed
herein can have cut resistance essentially equivalent to fabrics
made with typical high strength (>30 grams per denier (27 grams
per dtex)) and high modulus (>500 grams per denier (455 grams
per dtex)) polyethylene fibers.
[0012] The knit fabrics in the cut resistant article have a mass
index of 6000 or less; in some embodiments a mass index of 2000 to
6000 is desired. In some other embodiments, a mass index of 3000 to
5000 is desired. FIG. 1 illustrates an area 1 between line 2, which
represents the upper bound mass index of 6000, and line 3, which
represents one preferred lower bound mass index of 2000. Lines 2
and 3 have endpoints at knit gauges of 7 and 24 and basis weights
of about 290 and 860 grams per square meter indicating what is
believed to be the more practical ranges for gloves, sleeves, and
aprons used by workers. Knit gauges lower than 7 and basis weights
higher than about 860 grams per square are believed to provide
gloves and other items that are too stiff, while knit gauges higher
than 24 and lower than about 290 grams per square may not provide
adequate cut protection. FIG. 1 also illustrates a preferred mass
index embodiment that is the area within the points designated by
the letters A-B-C-D. This area represents fabrics having a mass
index of 2000 to 6000 and a knit gauge of from 13 to 18.
[0013] The knit fabric utilizes yarns, and in some embodiments the
fabric has a basis weight of 3 to 25.3 oz/yd.sup.2 (100 to 857
g/m.sup.2), preferably 4 to 21 oz/yd.sup.2 (136 to 712 g/m.sup.2),
with the fabrics at the higher end of the basis weight range
providing more cut protection.
[0014] By "yarn" is meant an assemblage of fibers or filaments
spun, combined, or twisted together to form a continuous strand. As
used herein, a yarn generally refers to what is known in the art as
the simplest strand of textile material suitable for such
operations as weaving and knitting. The yarn can be in the form of
a continuous multifilament yarn formed with or without twist. The
yarn can be in the form of a spun staple yarn made from staple
fibers with more or less twist. When twist is present in a singles
yarn, it is all in the same direction. Preferably, the yarn is a
continuous multifilament yarn.
[0015] The term "yarn" also embraces "ply yarn" and "plied yarn",
which refers to two or more individual yarns twisted or plied
together. It is understood the ply yarn can be made from two or
more of the same type of staple or continuous filament singles
yarns, or the ply yarn can be made from at least one of the singles
yarn made from staple fibers and at least one continuous filament
yarn. Ply yarns generally contain individual yarns having the same
twist direction, plied together in the opposite twist direction to
provide a "balanced" ply yarn. Preferably, plied yarns comprise two
or more continuous multifilament yarns.
[0016] The term "yarn" also embraces a "covered yarn", which refers
to a yarn having a sheath-core structure. Covered yarns are also
known as "wrap-covered yarns" and/or "air-covered yarns". The
sheath-core structure generally has one or more center core yarns
of one type of fiber with a covering sheath made from one or more
differing types of fiber. The center core can be can be made from
one or more yarns with little or no twist. The outer sheath can be
can be made from a wrap of staple fibers, as in a DREF process, or
the outer sheath can be one or more yarns that serve as wrapper
yarns that are mechanically wrapped or positioned around the core
with "S" and/or "Z" twist. Any of these wrapper yarns can be made
from staple fibers or continuous filament. Air-covered sheath-core
yarns use air jets to wrap the yarns around the core, normally
using continuous filament yarns as both the core and the
wrapping.
[0017] In some embodiments, the yarn comprises a composite
structure made from two or more individual yarns and contains a
center core structure and outer sheath structure. At least one of
these yarns comprises low modulus high molecular weight
polyethylene fiber used in the center core structure with organic,
inorganic and/or elastomeric fibers. In some preferred composite
structures, the sheath structure contains organic fibers.
[0018] One example of the sheath/core yarn has a first core strand
of a cut-resistant, continuous-filament, polymer fiber, such as an
aramid fiber or a polyester fiber. The yarn also has a second core
strand of a cut-resistant, continuous-filament, high molecular
weight polyethylene fiber as described herein. The core strands are
wrapped with first and second wraps of continuous filament nylon
yarns, with the turns of each wrap substantially touching the
previous turn, one to the next, to cover the core and/or preceding
wrap. In some embodiments it is not critical that the turns of each
wrap substantially touch the previous turn or entirely cover the
core and/or preceding wrap. Alternatively, the core can be wrapped
with other yarns such as polyester yarns. In another alternate
embodiment, the core strand can include glass filament(s) or metal
filament(s).
[0019] Still another example of the sheath/core yarn has a single
core strand of a cut-resistant, continuous-filament, high molecular
weight polyethylene fiber as described herein. The core strand is
wrapped with first and second wraps of continuous filament nylon
yarns, with the turns of each wrap substantially touching the
previous turn, one to the next, to cover the core and preceding
wrap.
[0020] Another example of the sheath/core yarn has a first core
strand of elastomeric yarn under tension to impart stretch-recovery
properties. The yarn can also have a second core strand of a
cut-resistant, continuous-filament, high molecular weight
polyethylene fiber as described herein. The core strands are
wrapped with first and second wraps of continuous filament nylon
yarns or polyester yarns as previously described.
[0021] In some embodiments, the yarn comprises an intimate blend of
the high molecular weight polyethylene staple fibers with other
fibers. By intimate blend it is meant the various different types
of staple fibers are distributed homogeneously in the staple yarn
bundle. For reliable processing, in some embodiments the maximum
amount of polyethylene staple fibers used in the intimate blend are
60 weight percent or less; in some embodiments, the preferred
amount of polyethylene staple fibers is 50 weight percent or less
in the intimate blend. The staple fibers used in some embodiments
can have a length of 2 to 20 centimeters. The staple fibers can be
spun into yarns using short-staple or cotton-based yarn systems,
long-staple or woolen-based yarn systems, or stretch-broken yarn
systems. In some embodiments the staple fiber cut length is
preferably 3.5 to 6 centimeters, especially for staple to be used
in cotton based spinning systems. In some other embodiments the
staple fiber cut length is preferably 3.5 to 16 centimeters,
especially for staple to be used in long staple or woolen based
spinning systems.
[0022] For purposes herein, the term "fiber" is defined as a
relatively flexible, macroscopically homogeneous body having a high
ratio of length to the width of the cross-sectional area
perpendicular to that length. Also, such fibers preferably are
generally solid polymers having a generally solid cross section for
adequate strength in textile uses; that is, the fibers do not have
a large quantity of objectionable voids or are essentially
void-free. In many embodiments, the cut resistant article includes
fibers having a filament linear density of from 0.5 to 3.5 denier
(0.55 to 3.9 dtex). In some preferred embodiments, the fiber has a
filament linear density of from 0.8 to 2.5 denier (0.88 to 2.75
dtex). The shape of the high molecular weight polyethylene fiber
cross section is round or essentially round as represented in FIG.
2. Further, the fibers have an essentially round cross section;
that is, the cross section is essentially solid circular in shape,
unlike a hollow fiber that has a circular shape but also an central
annular void. Since the shape of the fiber cross section is round
or essentially round, it necessarily has a nominal cross sectional
aspect ratio (the maximum width divided by the minimum width
measured for a particular cross section, generally measured in
perpendicular directions) of 1 or essentially 1.
[0023] The high molecular weight polyethylene fiber has a yarn
tensile modulus equal to 500 grams per denier (455 grams per dtex)
or less. In some embodiments, the fiber has a yarn tensile modulus
of 100 grams per denier (91 grams per dtex) to 500 grams per denier
(455 grams per dtex). In some preferred embodiments the fiber has a
maximum yarn tensile modulus is 400 grams per denier (364 grams per
dtex) or less. In some preferred embodiments the fiber has a yarn
tensile modulus of 100 grams per denier (91 grams per dtex) to 350
grams per denier (318 grams per dtex). In some other preferred
embodiments, the fiber has a yarn tensile modulus of from 200 grams
per denier (grams per dtex) to 400 grams per denier (364 grams per
dtex).
[0024] The high molecular weight polyethylene fiber has a yarn
tensile elongation at break of 4 percent or greater. In some
embodiments, the fiber has a yarn elongation at break of 4 to 15
percent.
[0025] For high cut resistance, the fiber is made of linear
polyethylene polymer having a weight average molecular weight of 1
million or greater. Polyethylene is made from polymers or
copolymers of ethylene with at least 50 mole percent ethylene on
the basis of 100 mole percent polymer. The ultra-high molecular
weight polyethylene polymer can have an intrinsic viscosity
measured in decalin at 135 C of 10 dl/g or greater. In some
preferred embodiments the polyethylene has a weight average
molecular weight of 2 million or greater, and in some other
preferred embodiments the polyethylene has a weight average
molecular weight of 2 million or greater. In some embodiments the
average molecular weight of the polyethylene is 1.0 million to 3.5
million. In some other embodiments the average molecular weight of
the polyethylene is 3.5 million to 6.0 million.
[0026] Since polyethylene polymer having a weight average molecular
weight of 1 million or greater creates melts of very high
viscosity, direct spinning of fibers from such melts is not
practical. Instead, the high molecular weight polyethylene fiber is
made by processes that spin fibers from a solution of polyethylene
in a solvent, and then remove essentially all or the vast majority
of the solvent from the spun fibers.
[0027] It has been found that surprisingly good cut resistance is
found in fibers made from polyethylene polymer having a weight
average molecular weight of 1 million or greater, even if the
tenacity of these fibers is not considered exceptionally high. In
some embodiments, the cut resistant article includes fiber that has
a yarn tenacity of less than 25 grams per denier (22.7 grams per
dtex) and in some embodiments the fiber has a yarn tenacity of less
than 22 grams per denier (20 grams per dtex). Further, in some
embodiments, the fiber has a yarn tenacity of less than 18 grams
per denier (16 grams per dtex).
[0028] The knit fabric comprising linear polyethylene fibers is
meant to include a structure producible by interlocking a series of
loops of one or more yarns by means of needles or wires, such as
warp knits (e.g., tricot, milanese, or raschel) and weft knits
(e.g., circular or flat). The knitted fabric uses any appropriate
knit pattern and conventional knitting machines. Knitted fabrics
can be made on a range of different gauge knitting machines. As
used herein, the unit of measure "gauge" used in the mass index is
the number of wales per inch (or in SI units the number of wales
per 2.53 cm) in a knitted fabric. A wale is the column of loops
lying lengthwise in the knitted fabric.
[0029] The knitted fabric can be made by hand, mechanical, or
modern electronic flat machines (Stoll, Shima-Seiki, Protti, etc.).
Some knitting machines are said to be of a certain gauge, which
means the knitting machine has that number of needles per inch (or
per 2.53 cm) needed to achieve that gauge knitted fabric.
[0030] Gauge is a measure of the fineness of the knitted fabric and
a lower numerical gauge fabric is a thicker fabric and a higher
numerical gauge represents a thinner fabric. In some embodiments,
the knit is 7 gauge or higher. In some embodiments the knit is 10
gauge or higher; in other embodiments the knit is 13 gauge or
higher. In some specialized applications requiring very thin
fabrics the knit is 18 gauge or higher. In some articles, the gauge
for the knit is 24 gauge or lower. In some preferred embodiments,
the knit is 10 to 18 gauge, with the most preferred embodiments
being 13 to18 gauge knit or higher.
[0031] A wide variety of flat-bed and circular knitting machines
can be employed. For example, Shima-Seiki knitting machines can be
used to make the knitted fabrics. If desired, multiple ends or
yarns can be supplied to the knitting machine. For example, two of
any of the yarns previously described herein can be knitted
two-ends-in, i.e., both yarns or ends are concurrently knitted by a
common needle to directly produce a cut-resistant protective glove.
Such machines can produce plated (also called plaited) fabrics and
gloves where one of the yarns is distributed primarily to one side
of the fabric or glove and the other yarn is distributed primarily
on the opposite side of the fabric or glove. In so doing, a glove
having distinct inner and outer sides can be produced. The
tightness of the knit can be adjusted to meet any specific need.
Very effective cut resistance has been found in, for example,
single jersey knit, interwoven knit, mesh knit and terry knit
patterns.
[0032] The cut resistant articles in the form of gloves, aprons,
and sleeves can be directly knit on a knitting machine or parts of
these articles can be knit separately and then attached together,
typically by sewing. If articles are made by sewing parts together
on a sewing machine, woven fabrics can also be combined with the
knit fabric in the articles. The cut resistant article can further
comprise a polymeric coating for gripping objects. In some
instances the polymeric coating can be positioned in discrete areas
on the article, such as beads of coating on the palm and/or fingers
of a cut resistant glove.
[0033] The high molecular weight polyethylene fiber is preferably
made by spinning a solution of polyethylene in a solvent, and then
removing essentially all or the vast majority of the solvent from
the fiber. The spinning process for forming filaments of such
ultra-high molecular weight polyethylene or extended chain
polyethylene fibers can include the principles taught, for example,
in U.S. Pat. No. 4,457,985.
[0034] Generally after spinning, in typical gel-spun fiber
processes the fiber tensile properties are then increased by hot
drawing the fiber at temperatures in excess of 125 C. The
temperatures used during hot drawing are referred to herein as
being "hot-draw" temperatures. This hot drawing can be achieved in
one or multiple stages with each stage having a specified
temperature and draw ratio. As used herein, draw ratio refers to
the ratio of the speed of the fiber exiting the draw stage to the
speed of the fiber entering the draw stage. If multiple stages are
used, the total draw is calculated by multiplying the individual
draws ratios from each stage together.
[0035] To achieve the desired low modulus high molecular weight
polyethylene fiber, it has been found the fibers are preferably hot
drawn in only one hot draw stage, and that the fibers are exposed
to a draw ratio in the stage of preferably no more than 6, and more
preferably a draw ratio of no more than 4. However, the fibers can
be drawn in more than one stage. In that instance, the total draw
is preferably no more than 6, and more preferably no more than 4.
Typical hot draw temperatures used in the hot drawing step are from
135 to 150 C, preferably greater than 140 C.
[0036] This process differs from other processes that seek to
attain fibers having their highest possible tenacity and which are
drawn in as many as four different successive stages with
increasing temperature (close to melting temperature of the fiber)
and high draw ratios totaling 10 or greater.
[0037] Further, it has been found that after drawing, it is
preferred to relax the fiber in a least one subsequent draw stage,
wherein the amount of draw ratio is about 1.0 or less, preferably 1
or less, and most preferably less than one. If the relaxation is
done in multiple stages, then the total draw is about 1.0 or less,
preferably 1 or less, and most preferably less than one.
[0038] The temperatures used in the relaxation step are referred to
herein as being "relaxation" temperatures. The relaxation
temperature is chosen such that it is either within +/-5 degrees C.
of the hot-draw temperature or it is higher than the hot-draw
temperature. Typical temperatures used in the relaxation step are
about 140 to 160 C. In some preferred embodiments the relaxation
temperature is greater than the hot draw temperature. In some
preferred embodiments the relaxation temperature is greater than
145 C.
[0039] While this combination of spinning and drawing techniques
are known to provide the desired fiber, it is understood that the
fiber can be made by any other spinning and drawing techniques as
long as that fiber meets the claimed requirements.
Test Methods
[0040] Cut Resistance. The method used is the "Standard Test Method
for Measuring Cut Resistance of Materials Used in Protective
Clothing", ASTM Standard F 1790-97. In performance of the test, a
cutting edge, under specified force, is drawn one time across a
sample mounted on a mandrel. At several different forces, the
distance drawn from initial contact to cut through is recorded and
a graph is constructed of force as a function of distance to cut
through. From the graph, the force is determined for cut through at
a distance of 25 millimeters and is normalized to validate the
consistency of the blade supply. The normalized force is reported
as the cut resistance force.
[0041] The cutting edge is a stainless steel knife blade having a
sharp edge 70 millimeters long. The blade supply is calibrated by
using a load of 400 g on a neoprene calibration material at the
beginning and end of the test. A new cutting edge is used for each
cut test.
[0042] The sample is a square piece of fabric cut 75.times.75
millimeters on the bias at 45 degrees from the warp and fills
directions.
[0043] The mandrel is a rounded electrically conductive bar with a
radius of 38 millimeters and the sample is mounted thereto using
double-face tape. The cutting edge is drawn across the fabric on
the mandrel at a right angle with the longitudinal axis of the
mandrel. Cut through is recorded when the cutting edge makes
electrical contact with the mandrel.
[0044] Tensile Properties. Tensile modulus, tenacity, and
elongation-at-break are all determined for the polyethylene yarns
by following the procedure disclosed in ASTM D7269 "Standard Test
Methods for Tensile Testing for Aramid Yarns", substituting the
polyethylene yarns for the aramid yarns.
EXAMPLE 1
[0045] A polyethylene fiber was made in the following manner. An
oil jacketed double helical mixer is charged with 6 wt % UHMWPE
powder (GUR 4120, Ticona), 0.6 wt % of antioxidants
(tri(2,4-di-(tert)-butylphenyle)phosphate (Irgafos 168, Ciba) and
tetrakis-(methylene-(3,5-di-(tert)-butyl-4-hydrocinnamate))methane
(Irganox 1010, Ciba), and 94.4 wt % mineral oil (Hydrobrite 1000,
Sonneborn). The mixture is heated to 170 C with agitation at 60 rpm
under nitrogen until UHMWPE is fully dissolved to make a spin
dope.
[0046] The spinning dope is then pumped through an 180-hole
spinneret and each hole of the spinneret has 1 mm diameter and 6/1
L/D. The throughput is 16 g/min and the spin stretch was 13. The
extruded thread line is quenched by a water bath located at a
distance of 1 inch below the spinning die. The gel filament yarns
are wound up onto a 41/8 inch diameter perforated plastic core.
[0047] The bobbin of gel fiber yarns is immersed in hexane to
extract the mineral oil. This step is repeated several times until
mineral oil is fully extracted from the fiber. During the
extraction, the semi-extracted fiber yarns are unwound from the
bobbin to prevent filaments sticking to each other. The fully
extracted fiber yarns are dried in the air at room temperature
overnight.
[0048] The dried yarn is then drawn in multiple steps using single
zone pilot fiber convection oven from Litzler. The effective heated
length per pass is 2.08 meters. The dry gel yarn is drawn three
times at oven temperature of 125.degree. C., 135.degree. C., and
143.degree. C. with draw ratio of 4, 2 and 1.5 respectively. The
yarn feeding speed is 2.5 m/min. The loosely wound yarn is then
relaxed on the bobbin at 142.degree. C. for couple of hours. The
yarns are 400 denier (364 dtex) having round filaments with a
nominal aspect ratio of 1 and a tenacity of less than 20
grams/denier and modulus less than 350 grams/denier.
EXAMPLE 2
[0049] Five polyethylene continuous 400 denier (364 dtex)
multifilament yarns are obtained. Representative yarn properties
are shown in Table 2. Yarn 1 is the yarn obtained from Example 1.
Comparative Yarns A, B, & C are representative of commercially
available high tenacity and high modulus, solution-spun, high
molecular weight polyethylene yarns. Comparative Yarn D is
representative of low tenacity and low modulus, melt-spun, low
molecular weight polyethylene yarns.
TABLE-US-00001 TABLE 2 Yarn Polymer Tensile Modulus, Yarn Linear
Filament Linear Molecular Yarn g/dtex Density, density, Weight
Samples (g/denier) dtex (denier) dtex (denier) (millions) 1 <318
440 2.4 >1.0 (<350) (400) (2.2) A >900 440 2.2 >1.0
(>1000) (400) (2.0) B >900 440 3.9 >1.0 (>1000) (400)
(3.5) C >900 440 1.1 >1.0 (>1000) (400) (1.0) D <360
440 1.3 <0.5 (<400) (400) (1.2)
[0050] Knit fabric samples are made from each of the five filament
yarns. In particular, to facilitate acceptable knitting, two ends
of all yarns are plied and are twisted with 1.5 turns per inch
(tpi) using a Saurer Allma twisting machine. A Shima Seiki 13-gauge
glove knitting machine is used to produce knit fabric material
about two meters long, which is enough fabric to provide samples
for subsequent cut testing and other evaluations. Glove samples are
also knit from each ply twisted yarn for comparative comfort
evaluation.
[0051] The fabrics are subjected to ASTM Standard F 1790-97
"Standard Test Method for Measuring Cut Resistance of Materials
Used in Protective Clothing". The relative cut test results are
shown in Table 3, with a "+" in this column indicating good cut
resistance and with a "-" indicating less cut resistance. As shown
in the table, the fabrics made with higher molecular weight polymer
have better cut resistance.
TABLE-US-00002 TABLE 3 Fabric Per- Yarn Areal Polymer ceived
Composition Density, Molecular Cut Glove Fab- (1.5 Turns g/sq.
meter Mass Weight Resis- Fabric ric per Inch) (oz/sq. yd.) Index
(millions) tance Comfort 1 2 Ends of 325 4225 >1.0 + + Yarn 1
(9.6) A 2 Ends of 329 4277 >1.0 + - Yarn A (9.7) B 2 Ends of 325
4225 >1.0 + - Yarn B (9.6) C 2 Ends of 329 4277 >1.0 + - Yarn
C (9.7) D 2 Ends of 349 4537 <0.5 - + Yarn D (10.3)
[0052] In addition, the glove fabrics are evaluated in Table 3 for
their perceived relative flexibility and comfort, with a "+" in
this column indicating good relative flexibility and comfort and a
"-" indicating less relative flexibility comfort. Glove Fabric 1
has a subjectively more comfortable and flexible "hand" than Glove
Fabrics A, B, or C, and has comfort equivalent to Glove Fabric D.
This is believed to be due to the use of lower modulus yarns in
Glove Fabric 1 and Glove Fabric D. Therefore Glove Fabric 1 is
superior to the Comparative Fabrics in that it has both good cut
resistance and good perceived comfort.
EXAMPLE 3
[0053] The general process of Example 1 is repeated, using suitable
spinnerets and spinning conditions to create 200 and 1000-denier
linear density polyethylene yarns of round cross section filaments
having individual filament linear densities ranging from 1.1 to 3.9
dtex per filament (1.0 to 3.5 denier per filament). The properties
of these yarns are shown in Table 4.
TABLE-US-00003 TABLE 4 Yarn Tensile Modulus Yarn Linear Filament
Yarn grams/dtex density Linear density Samples (grams/denier) dtex
(denier) dtex (denier) 3-1 <450 220 2.2 (<500) (200) (2.0)
3-2 <450 1100 2.2 (<500) (1000) (2.0)
EXAMPLE 4
[0054] Fabrics are made from the yarn samples of Example 3 were
then prepared for knitting fabric samples. In particular, to
facilitate acceptable knitting, one end of 200-denier Yarn 3-1 is
twisted with 1.5 turns per inch (tpi) using a Saurer Allma twisting
machine to make ply twisted 200-denier yarn designated Yarn 4-1.
Then three ends of the 200-denier Yarn 3-1 are plied and twisted
with 1.5 turns per inch (tpi) using a Saurer Allma twisting machine
to make ply twisted 600-denier yarn designated 4-2. Then two ends
of 1000-denier Yarn 3-2 are twisted with 1.5 turns per inch (tpi)
using a Saurer Allma twisting machine to make ply twisted
2000-denier Yarn 4-3. Finally, three ends of the 1000-denier Yarn
3-2 are plied and twisted with 1.5 turns per inch (tpi) using a
Saurer Allma twisting machine for make 3000-denier ply twisted Yarn
4-4. The resulting four single and ply twisted yarns ranged in
linear density from 200 to 3000-denierShima Seiki glove knitting
machines are used to make 18, 15, 10, & 7 gauge knit fabric
sleeves from the Yarns 4-1, 4-2, 4-3, & 4-4, respectively, for
cut testing and gloves for comparative comfort evaluation. The
fabrics/gloves were in turn designated 4-1, 4-2, 4-3, &
4-4.
[0055] Properties of the fabrics/gloves are shown in Table 5. All
of the fabric samples have good cut resistance, equivalent to high
modulus, high tenacity polyethylene yarns. This is represented with
a "=" in in this column of Table 5. Further, all of the glove
samples had improved perceived relative flexibility and comfort
when compared to gloves made from to high modulus, high tenacity
polyethylene yarns. This is represented with a "+" in this column
in Table 5. In addition, the higher knit gauge polyethylene gloves
have more flexibility and comfort when compared to lower knit gauge
gloves.
TABLE-US-00004 TABLE 5 Fabric Per- Yarn Areal ceived Composition
Density Cut Glove Fabric/ (1.5 Turns Knit g/sq. meter Mass Resis-
Fabric Gloves per Inch) Gauge (oz/sq yd) Index tance Comfort 4-1
Yarn 4-1 18 170 3060 = + (1 End of (5) Yarn 3-1) 4-2 Yarn 4-2 15
271 4065 = + (3 Ends of (8) Yarn 3-1) 4-3 Yarn 4-3 10 423 4230 = +
(2 Ends of (12.5) Yarn 3-2) 4-4 Yarn 4-4 7 644 4508 = + (3 Ends of
(19) Yarn 3-2)
* * * * *