U.S. patent application number 14/748864 was filed with the patent office on 2015-10-15 for process for spinning uhmwpe, uhmwpe multifilament yarns produced thereof and their use.
The applicant listed for this patent is DSM IP ASSETS B.V.. Invention is credited to Roelof MARISSEN, Joseph Arnold Paul Maria SIMMELINK.
Application Number | 20150292116 14/748864 |
Document ID | / |
Family ID | 39522450 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150292116 |
Kind Code |
A1 |
SIMMELINK; Joseph Arnold Paul Maria
; et al. |
October 15, 2015 |
PROCESS FOR SPINNING UHMWPE, UHMWPE MULTIFILAMENT YARNS PRODUCED
THEREOF AND THEIR USE
Abstract
Gel-spinning processes for producing a high tensile strength
ultra high molecular weight polyethylene (UHMWPE) multifilament
yarn comprising ultra-low dtex filaments, include applying a draw
ratio DR.sub.fluid to fluid filaments obtained by spinning a
solution of UHMWPE through a spinneret and into an air gap, is at
least 450, wherein DR.sub.fluid=DR.sub.sp.times.DR.sub.ag, the
DR.sub.sp and DR.sub.ag being the draw ratios in the spinholes and
in the air gap, respectively; and provided that DR.sub.ag is at
least 30. The UHMWPE multifilament yarns produced thereof were
characterized by a tensile strength of at least 3.5 GPa and
contained filaments having a dtex of at most 0.5. The invention
further relates to products comprising said yarns, e.g. fabrics,
medical devices and composite and ballistic articles.
Inventors: |
SIMMELINK; Joseph Arnold Paul
Maria; (Dilsen-Stokkem, BE) ; MARISSEN; Roelof;
(Born, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DSM IP ASSETS B.V. |
Heerlen |
|
NL |
|
|
Family ID: |
39522450 |
Appl. No.: |
14/748864 |
Filed: |
June 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13889204 |
May 7, 2013 |
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14748864 |
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12747968 |
Jun 14, 2010 |
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PCT/EP2008/010748 |
Dec 17, 2008 |
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13889204 |
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Current U.S.
Class: |
428/36.3 ;
264/13; 428/364; 442/1 |
Current CPC
Class: |
D10B 2505/00 20130101;
D01F 6/04 20130101; Y10T 428/2915 20150115; D10B 2509/00 20130101;
Y10T 442/69 20150401; Y10T 428/2913 20150115; D10B 2321/0211
20130101; B29C 48/05 20190201; D01D 5/06 20130101 |
International
Class: |
D01F 6/04 20060101
D01F006/04; B29C 47/00 20060101 B29C047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2007 |
EP |
07024437 |
Claims
1. An ultra high molecular weight polyethylene (UHMWPE)
multifilament yarn, wherein the UHMWPE has an intrinsic viscosity
as measured on solution in decalin at 135.degree. C. of at least 3
dl/g and at most 40 dl/g, and the yarn has a tensile strength of
3.5-5.5 GPa and comprises filaments of 0.06-0.5 dtex.
2. The yarn according to claim 1, wherein the yarn has a tensile
strength of 4.0-5.5 GPa.
3. The yarn according to claim 1, wherein the yarn has a tensile
modulus of at least 100 GPa.
4. The yarn according to claim 1, wherein the yarn has a tensile
modulus of at least 130 GPa.
5. The yarn according to claim 1, wherein the yarn comprises
filaments of 0.09 -0.45 dtex.
6. The yarn according to claim 1, wherein the yarn comprises
filaments of 0.09-0.3 dtex.
7. The yarn according to claim 1, wherein the UHMWPE has an
intrinsic viscosity of at least 5 dl/g.
8. The yarn according to claim 1, wherein the UHMWPE is a linear
polyethylene containing up to 5 mol-% of one or more comonomers,
such as alkenes like propylene, butene, pentene, 4-methylpentene or
octene, and less than 3 wt-% of customary additives, such as
anti-oxidants, thermal stabilizers, colorants, flow promoters,
etc.
9. The yarn according to claim 1, wherein the the UHMWPE contains
0.2-20 per 1000 carbon atoms of C1-C4 alkyl groups as side
chains.
10. The yarn according to claim 1, wherein the yarn comprises
residual spinning solvent in an amount of below 800 ppm.
11. The yarn according to claim 1, wherein the yarn comprises
residual spinning solvent in an amount of below 300 ppm.
12. The yarn according to claim 1, wherein the yarn comprises
residual spinning solvent in an amount of below 100 ppm.
13. A semi-finished or end-use article containing the yarn
according to claim 1.
14. The semi-finished or end-use article according to claim 13,
selected from the group consisting of ropes, fishing lines, fishing
nets, ground nets, cargo nets, cargo curtains, kite lines, dental
floss, tennis racquet strings, canvas, webbings, battery
separators, capacitors, pressure vessels, hoses, automotive
equipment, power transmission belts, building construction
materials, cut and stab resistant articles, incision resistant and
abrasion resistant articles, protective gloves, skis, helmets,
kayaks, canoes, bicycles, boat hulls and spars, speaker cones, high
performance electrical insulation, and radomes.
15. A medical device containing the yarn according to claim 1.
16. The medical device according to claim 15, selected from the
group consisting of a surgical repair product, a suture, a medical
cable, a vascular graft, a mesh, and an implantable valve.
17. A composite article containing at least one monolayer that
comprises the UHMWPE yarn according to claim 1.
18. A multifilament ultrahigh molecular weight polyethylene
(UHMWPE) yarn having a tensile strength of 3.5-5.5 GPa and
comprising filaments of 0.06-0.5 dtex which is obtained by a
gel-spinning process comprising the steps of: a) preparing a
solution of an UHMWPE in a solvent; b) spinning through a spinneret
and into an air gap the solution of step a) to form fluid
filaments, the spinneret containing multiple spinholes and wherein
each spinhole comprises at least one zone with a gradual decrease
in diameter and wherein the downstream diameter of the spinhole
from which the solution is issued in the air gap is between 0.1 and
1.5 mm; c) drawing the fluid filaments with a fluid draw ratio
DR.sub.fluid=DR.sub.sp.times.DR.sub.ag, wherein DR.sub.sp and
DR.sub.ag are the draw ratios in the spinholes and in the air gap,
respectively, wherein the fluid filaments are drawn with a fluid
draw ratio DR.sub.fluid of 450-1200, provided that DR.sub.ag is at
least 50, and with an overall draw ratio DR.sub.overall of
12000-50000, wherein
DR.sub.overall=DR.sub.fluid.times.DR.sub.gel.times.DR.sub.solid
where DR.sub.fluid is the fluid draw ratio of the fluid filaments,
DR.sub.gel is a draw ratio of the gel filaments and DR.sub.solid is
a draw ratio of the solid filaments; d) cooling the fluid filaments
to form solvent-containing gel filaments; and e) removing at least
partly the remaining solvent from the gel filaments to form solid
filaments, before, during or after drawing the solid filaments with
a draw ratio DR.sub.solid of at least 4 and thereby obtain a UHMWPE
yarn having a tensile strength of 3.5-5.5 GPa comprised of UHMWPE
filaments of 0.06-0.5 dtex.
19. The yarn according to claim 18, wherein the yarn has a tensile
strength of 4.0-5.5 GPa.
20. The yarn according to claim 18, wherein the yarn has a tensile
modulus of at least 100 GPa.
21. The yarn according to claim 18, wherein the yarn comprises
filaments of 0.09-0.45 dtex.
22. The yarn according to claim 21, wherein the filaments are
0.09-0.3 dtex.
Description
[0001] This application is a divisional of commonly owned copending
U.S. application Ser. No. 13/889,204, filed May 7, 2013, which is a
divisional of Ser. No. 12/747,968, filed Jun. 14, 2010 (now
abandoned), which is the national phase application under 35 USC
.sctn.371 of PCT/EP2008/010748, filed Dec. 17, 2008 which
designated the US and claims benefit of European Application
07024437.1, filed Dec. 17, 2007, the entire contents of each of
which are hereby incorporated by reference.
[0002] The invention relates to a gel-spinning process for
producing a high tensile strength ultra high molecular weight
polyethylene (UHMWPE) multifilament yarn comprising ultra-low dtex
filaments and to a UHMWPE multifilament yarn produced thereof. The
invention further relates to products comprising said yarns.
[0003] A gel-spinning process for producing UHMWPE multifilament
yarns having a high tensile strength is known for example from EP
1,699,954. The process disclosed therein comprises the steps of:
[0004] a) Preparing a solution of an UHMWPE in a solvent; [0005] b)
Spinning through a spinneret and into an air gap the solution of
step a) to form fluid filaments, the spinneret containing multiple
spinholes and wherein each spinhole comprises at least one zone
with a gradual decrease in diameter and wherein the downstream
diameter of the spinhole from which the solution is issued in the
air gap is between 0.1 and 1.5 mm; [0006] c) Drawing the fluid
filaments with a fluid draw ratio
DR.sub.fluid=DR.sub.sp.times.DR.sub.ag, wherein DR.sub.sp and
DR.sub.ag are the draw ratios in the spinholes and in the air gap,
respectively; and [0007] d) Cooling the fluid filaments to form
solvent-containing gel filaments; and [0008] e) Removing at least
partly the remaining solvent from the gel filaments to form solid
filaments, before, during or after drawing the solid filaments with
a draw ratio DR.sub.solid of at least 4.
[0009] The UHMWPE multifilament yarns produced thereof presented
tensile strengths as high as 5 GPa, however, the yarns contained
relatively thick filaments in the range of 1 dtex.
[0010] A gel-spinning process wherein relatively high tensile
strength UHMWPE multifilament yarns are produced, containing
however thinner filaments thereof, is known for example from the
Chinese Patent No. 1,400,342, hereafter CN 1,400,342. Said
publication discloses both a melt and a gel spinning process. With
reference to the gel spinning process, a solution of between 4 and
15 wt-% of an UHMWPE with molecular weight between 1.times.10.sup.6
and 6.times.10.sup.6 g/mol is spun through a spinneret with
spinholes of a diameter in the range of 0.6-1 mm to form fluid
filaments. The fluid filaments are drawn with draw ratios of
maximum 35 according to its Example 1. The maximum total draw ratio
achieved for a gel spun filament was about 390. According to the
referred publication, for a highly concentrated UHMWPE solution,
i.e. around 15 wt-%, a low fluid draw ratio should be applied to
prevent filament breakage and for a dilute UHMWPE solution, i.e.
around 4 wt-%, the fluid draw ratio can be increased the maximum
achieved being about 35, i.e. according to Example 1 using a 7 wt-%
concentrated UHMWPE solution. According to CN 1,400,342 by
stretching further above the disclosed limits, it is not possible
to obtain UHMWPE filaments with a structure having an "appropriate
degree of macromolecular entanglements". Lacking the appropriate
degree of entanglements, the obtained filaments are difficult to
draw further this also explaining the low overall draw ratio
achieved therein. UHMWPE multifilament yarns were obtained having
tensile strengths as high as 4.3 GPa, and containing filaments
having a dtex of not smaller than 0.55 (0.5 den).
[0011] A further gel-spinning process for obtaining UHMWPE
multifilament yarns comprising filaments having however an
ultra-low dtex is known from the Japanese Patent Publication No.
2000/226721, hereafter JP 2000/226721. The gel-spinning process
disclosed therein used even smaller diameters for the spinholes of
the spinneret, in the range of 0.3-0.5 mm. The extruded fluid
filaments were drawn up to a draw ratio of 50 and again after
becoming solid filaments to a total draw ratio of about 200. The
obtained UHMWPE filaments had a dtex as low as 0.121. However, the
tensile strength of the multifilament yarn comprising these
filaments was rather low, i.e. not higher than 3.2 GPa. A further
drawback of the process is reduced productivity, because the amount
of UHMWPE solution spun through the spinholes is limited by their
very small diameter.
[0012] Therefore, it is not by any means trivial for anyone skilled
in the art to obtain UHMWPE multifilament yarns comprising
ultra-low dtex filaments and having a high tensile strength
thereof. Yet even more, it is difficult to design a process of
making thereof, having a good productivity.
[0013] It is the object of the invention to provide gel spun UHMWPE
multifilament yarns having a high tensile strength and comprising
ultra-low dtex filaments, combination that is not met by any of the
existent gel spun UHMWPE multifilament yarns and for a process for
the preparation thereof. A further object of the invention is to
provide such a process that has good productivity.
[0014] The proposed object was achieved with a gel spun process
characterized in that the fluid filaments are drawn with a fluid
draw ratio DR.sub.fluid of at least 450, provided that DR.sub.ag is
at least 30.
[0015] Surprisingly, it was found that with the process of the
invention, novel UHMWPE multifilament yarns were obtained having a
tensile strength of at least 3.5 GPa and comprising filaments with
a dtex of no more than 0.5; a combination which to inventors'
knowledge was never achieved hitherto and which in itself was
unexpected.
[0016] It was also surprisingly found that in the process of the
invention, the amount of spin breaks occurring when spinning
ultra-low dtex UHMWPE filaments due to tearing of said filaments at
the spinneret was reduced. The low amount of spin breaks positively
contributing to the productivity of the process.
[0017] The UHMWPE solution is preferably prepared with a
concentration of between 1 and 20 wt-%, more preferably of between
2 and 15 wt-%, even more preferably of between 3 and 10 wt-%, most
preferably of between 4 and 8 wt-%, with a lower concentration
being preferred the higher the molar mass of the UHMWPE is.
[0018] The UHMWPE has preferably an intrinsic viscosity (IV), as
measured on solution in decalin at 135.degree. C., of at least 3
dl/g, preferably at least 5 dl/g, more preferably at least 7 dl/g,
even more preferably at least 9 dl/g, most preferably at least 11
dl/g. Preferably, the IV is at most 40 dl/g, more preferably at
most 30 dl/g, even more preferably at most 25 dl/g, yet even more
preferably at most 20 dl/g, most preferably at most 15 dl/g.
[0019] The UHMWPE may be any UHMWPE suitable for gel spinning
processes. Preferably, the UHMWPE is a linear polyethylene with
less than one branch per 100 carbon atoms, and preferably less than
one branch per 300 carbon atoms. By branch, also known as side
chain is herein understood a branch of the main UHMWPE chain, said
branch preferably containing between 1 and 10 carbon atoms, more
preferably between 1 and 8, even more preferably between 1 and 6.
The linear polyethylene may further contain up to 5 mol % of one or
more comonomers, such as alkenes like propylene, butene, pentene,
4-methylpentene or octene and also preferably less than 5 wt-%,
more preferably less than 3 wt-% of customary additives, such as
anti-oxidants, thermal stabilizers, colorants, flow promoters,
etc.
[0020] In a preferred embodiment, the UHMWPE contains at least 0.2,
more preferably at least 0.3 per 1000 carbon atoms, of C1-C4 alkyl
groups as side chains. The amount of alkyl groups is preferably at
most 20, more preferably at most 10, even more preferably at most
5, yet even more preferably at most 3, most preferably at most 1.5
per 1000 carbon atoms. The alkyl groups are preferably methyl or
ethyl groups, more preferably methyl groups. The UHMWPE can be a
single polymer grade, but also a mixture of two or more different
polyethylene grades, e.g. differing in IV or molar mass
distribution, and/or type and number of comonomers or side
groups.
[0021] To prepare the UHMWPE solution, any technique known in the
art and any of the known solvents suitable for gel spinning the
UHMWPE may be used. Suitable examples of solvents include aliphatic
and alicyclic hydrocarbons, e.g. octane, nonane, decane and
paraffins, including isomers thereof; petroleum fractions; mineral
oil; kerosene; aromatic hydrocarbons, e.g. toluene, xylene, and
naphthalene, including hydrogenated derivatives thereof, e.g.
decalin and tetralin; halogenated hydrocarbons, e.g.
monochlorobenzene; and cycloalkanes or cycloalkenes, e.g. careen,
fluorine, camphene, menthane, dipentene, naphthalene,
acenaphtalene, methylcyclopentandien, tricyclodecane,
1,2,4,5-tetramethyl-1,4-cyclohexadiene, fluorenone, naphtindane,
tetramethyl-p-benzodiquinone, ethylfuorene, fluoranthene and
naphthenone. Also combinations of the above-enumerated solvents may
be used for gel spinning of UHMWPE, the combination of solvents
being also referred to for simplicity as solvent. In a preferred
embodiment, the solvent of choice is not volatile at room
temperature, e.g. paraffin oil. It was also found that the process
of the invention is especially advantageous for relatively volatile
solvents at room temperature, as for example decalin, tetralin and
kerosene grades. In the most preferred embodiment the solvent of
choice is decalin.
[0022] According to the invention, the UHMWPE solution is formed
into fluid filaments by spinning said solution through a spinneret
containing multiple spinholes. As used herein, the term "fluid
filament" refers to a fluid-like filament containing a solution of
UHMWPE in the solvent used to prepare said UHMWPE solution, said
fluid filament being obtained by extruding the UHMWPE solution
through the spinneret, the concentration of the UHMWPE in the
extruded fluid filaments being the same or about the same with the
concentration of the UHMWPE solution before extrusion. By spinneret
containing multiple spinholes is herein understood a spinneret
containing preferably at least 5 spinholes, more preferably at
least 10, even more preferably at least 25, yet even more
preferably at least 50, most preferably at least 100. Preferably
the spinneret contains at most 3000, more preferably at most 1000,
most preferably at most 500 spinholes.
[0023] Preferably, the spinning temperature is between 150.degree.
C. and 250.degree. C., more preferably it is chosen below the
boiling point of the spinning solvent. If for example decaline is
used as spinning solvent the spinning temperature is preferably at
most 180.degree. C., more preferably at most 175.degree. C., most
preferably at most 170.degree. C. and preferably at least
115.degree. C., more preferably at least 120.degree. C., most
preferably at least 125.degree. C. In case of paraffin, the
spinning temperature is preferably below 200.degree. C., more
preferably between 130.degree. C. and 195.degree. C.
[0024] Preferably, the spinning speed is at least 1 m/min, more
preferably at least 3 m/min, even more preferably at least 5 m/min,
yet even more preferably at least 7 m/min, most preferably at least
9 m/min. Preferably, the spinning speed is at most 20 m/min, more
preferably at most 18 m/min, even more preferably at most 16 m/min,
yet even more preferably at most 14 m/min, most preferably at most
12 m/min. It was surprisingly observed that a relatively higher
spinning speed and drawing rate can be used to form and draw the
UHMWPE filaments of the invention in comparison with known
processes of producing ultra-low dtex UHMWPE filaments. This
resulted in an improved production output and a decreased
production time, therefore, making the process of the invention
more attractive economically. By spinning speed is herein
understood the velocity in meters per min (m/min) of the extruded
fluid filaments exiting the spinneret. By drawing rate is herein
understood the drawing ratio divided by the time needed to achieve
said drawing ratio.
[0025] According to the invention, each spinhole has a geometry
comprising at least one zone, also called contraction zone, which
is a zone with a gradual decrease in diameter. Preferably the
gradual decrease in diameter has a cone angle of at least
10.degree., more preferably at least 15.degree., more preferably of
at least 30.degree., even more preferably at least 45.degree..
Preferably, the cone angle is at most 75.degree., more preferably
at most 70.degree., even more preferably at most 65.degree.. With
cone angle is herein meant the maximum angle between the tangents
to opposite wall surfaces of the contraction zone. For example, for
a conical or tapered contraction zone, the cone angle between the
tangents is constant, whereas for a so-called trumpet type of
contraction zone the cone angle between the tangents will decrease
with decreasing diameter. In case of a wineglass type of
contraction zone the angle between the tangents passes through a
maximum value. Because of the presence of said gradual decrease, a
draw ratio DR.sub.sp is achieved in the spinhole. DR.sub.sp is the
ratio of the solution flow speed at the initial cross-section and
at the final cross-section of the contraction zone, which is
equivalent to the ratio of the respective cross-sectional areas.
For example, in case of a contraction zone having the shape of a
frustum of a circular cone, DR.sub.sp is the ratio between the
square of the diameters of the initial and final cross-sections of
the contraction zone.
[0026] The diameter of the spinhole is herein meant to be the
effective diameter, i.e. for non-circular or irregularly shaped
spinholes, the largest distance between the outer boundaries of the
spinhole.
[0027] Preferably, the initial and final cross-sectional areas, or
the respective diameters thereof of the contraction zone, are
chosen to yield a DR.sub.sp of at least 5, more preferably at least
10, even more preferably at least 15, yet even more preferably at
least 20, yet even more preferably at least 25, yet even more
preferably at least 30, yet even more preferably at least 35, most
preferably at least 40.
[0028] Preferably, the spinhole further comprises upstream and/or
downstream of a contraction zone, a zone of constant diameter equal
with the diameter of the thereby correspondent cross-section of the
contraction zone, the constant diameter zone having a ratio
length/diameter of preferably at most 50, more preferably at most
30, even more preferably at most 20, most preferably at most 10.
More preferably its ratio length/diameter is at least 2, even more
preferably at least 4, most preferably at least 5.
[0029] Preferably, the downstream diameter of the spinhole from
which the solution is issued in the air gap is between 0.1 and 1.5
mm, more preferably between 0.1 and 1.2 mm, more preferably between
0.1 and 0.9 mm, even more preferably between 0.1 and 0.8 mm, yet
even more preferably between 0.1 and 0.7 mm, yet even more
preferably between 0.1 and 0.5 mm, yet even more preferably between
0.1 and 0.45 mm, most preferably between 0.2 and 0.45 mm.
[0030] The fluid filaments formed by spinning the UHMWPE solution
through the spinneret are extruded into an air gap, and then into a
cooling zone from where they are picked-up on a first driven
roller. The fluid filaments are stretched in the air gap with a
drawing ratio DR.sub.ag of at least 30 by choosing an angular speed
of the first driven roller such that said roller's surface velocity
exceeds the flow rate of the UHMWPE solution issued form the
spinneret. The draw ratio in the air gap, DR.sub.ag, is preferably
at least 40, more preferably at least 50, even more preferably at
least 60, most preferably at least 80.
[0031] According to the invention, the fluid filaments are
stretched with a total fluid draw ratio
DR.sub.fluid=DR.sub.sp.times.DR.sub.ag of at least 450, preferably
at least 475, more preferably at least 500, even more preferably at
least 550, yet even more preferably at least 600, yet even more
preferably at least 650, yet even more preferably at least 700,
most preferably at least 800. It was surprisingly found that it was
possible to subject the fluid UHMWPE filaments in the process of
the invention to a higher DR.sub.fluid than it was possible
hitherto in processes producing ultra-low dtex filaments, while
keeping the occurrence of breakages at the same level. Moreover, by
increasing the DR.sub.fluid filaments with even lower dtex could
have been obtained. A high DR.sub.fluid proved also beneficial for
the tensile strength of the filaments.
[0032] It was found that using a too high total fluid draw ratio
led to an increase in filament breakage. Hence, in a preferred
embodiment, fluid filaments are stretched with a total fluid draw
ratio DR.sub.fluid=DR.sub.sp.times.DR.sub.ag of at the most 1200,
preferably the at the most 1000, more preferably at the most 900,
such as at the most 800.
[0033] In a preferred embodiment, DR.sub.sp is between 5 and 20,
more preferably between 5 and 15, whereas the DR.sub.ag is
increased to yield a DR.sub.fluid value of at least 450. It was
found that these are the optimum values for said drawing ratios for
achieving the advantages of the process of the invention.
[0034] The length of the air gap is preferably at least 1 mm, more
preferably at least 3 mm, even more preferably at least 5 mm, yet
even more preferably at least 10 mm, yet even more preferably at
least 15 mm, yet even more preferably at least 25 mm, yet even more
preferably at least 35 mm, yet even more preferably at least 25 mm,
yet even more preferably at least 45 mm, most preferably at least
55 mm. The length of the air gap is preferably at most 200 mm, more
preferably at most 175 mm, even more preferably at most 150 mm, yet
even more preferably at most 125 mm, yet even more preferably at
most 105 mm, yet even more preferably at most 95 mm, most
preferably at most 75 mm.
[0035] Cooling, also known as quenching, the fluid filaments after
exiting the air-gap to form solvent-containing gel filaments, may
be performed by any method known in the art as for example in a gas
flow and/or in a liquid cooling bath. Preferably, the temperature
to which the fluid filaments are cooled is at most 80.degree. C.,
more preferably at most 60.degree. C., most preferably at most
40.degree. C., preferably at least 1.degree. C., more preferably at
least 5.degree. C., even more preferably at least 10.degree. C.,
most preferably at least 15.degree. C.
[0036] By air-gap is meant the length travelled by the fluid
filaments before the fluid filaments are converted into
solvent-containing gel filaments if gas cooling is applied or the
distance between the face of the spinneret and the surface of the
cooling liquid in the liquid cooling bath.
[0037] As used herein, the term "gel filament" refers to a filament
which upon cooling develops a continuous UHMWPE network swollen
with the spinning solvent. An indication of the conversion of the
fluid filament into the gel filament and the formation of the
continuous UHMWPE network may be the change in filament's
transparency upon cooling from a translucent UHMWPE filament to a
substantially opaque filament, i.e. the gel filament.
[0038] In the process of the invention, the gel filaments are
subjected to a solvent removal step to form solid filaments,
before, during or after drawing the solid filaments. The amount of
residual spinning solvent, hereafter residual solvent, left in the
solid filaments after the removal step may vary within large
limits, preferably the residual solvent being in a weight percent
of at most 15% of the initial amount of solvent in the UHMWPE
solution, more preferably in a weight percent of at most 10%, most
preferably in a weight percent of at most 5%. The amount of
residual spinning solvent left in the solid filaments after the
removal step may also be described relative to the total weight of
the yarn including UHMWPE and solvent. In this case, the residual
solvent is preferably at most 15 wt-% of the total weight of yarn,
more preferably at most 10 wt-% of the total weight of yarn, and
most preferably at most 5 wt-% of the total weight of yarn. The
solvent removal process may be performed by known methods, for
example by evaporation when a relatively volatile spinning solvent,
e.g. decaline, is used to prepare the UHMWPE solution or by using
an extraction liquid, e.g. when paraffin is used, or by a
combination of both methods. Suitable extraction liquids are
liquids that do not cause significant changes in the structure of
the UHMWPE gel fibres and preferably those the spinning solvent can
be separated thereof for recycling.
[0039] Drawing the solid filaments may be performed in accordance
with any technique known in the art and in at least one drawing
step with a draw ratio DR.sub.solid of at least 4. More preferably,
DR.sub.solid is at least 7, even more preferably at least 10, yet
even more preferably at least 15, yet even more preferably at least
20, yet even more preferably at least 30, most preferably at least
40. To reduce the risk of filament breakage, the draw ratio
DR.sub.solid is preferably at the most 150, preferably at the most
100, more preferably at most 75, such as for example at most 50.
More preferably, the drawing of solid filaments is performed in at
least two steps, even more preferably in at least three steps.
Preferably, each drawing step is carried out at a different
temperature that is preferably chosen to achieve the desired
drawing ratio without the occurrence of filament breakage. If the
drawing of solid filaments is performed in more than one step,
DR.sub.solid is calculated by multiplying the draw ratios achieved
for each individual solid drawing step. Drawing the solid filaments
is preferably carried out at a temperature of between 110 and
170.degree. C., more preferably of between 120 and 160.degree. C.,
most preferably of between 130 and 155.degree. C. The temperature
may also have an increasing profile preferably between 120 and
155.degree. C.
[0040] In a preferred embodiment, after cooling the gel filaments
in a liquid cooling bath, said filaments were introduced in an oven
set at a temperature of preferably between 110 and 145.degree. C.,
more preferably between 130 and 140.degree. C., where the solvent
was removed by evaporation while drawing the filaments with a draw
ratio of at least 2, more preferably at least 4, most preferably at
least 6 such that solid filaments exit the oven. In this step, the
draw ratio is preferably less than 50, more preferably less than
40, yet more preferably less than 30, such as less than 15. The
solid filaments are then preferably drawn in a second step in a
second oven set at a temperature of preferably between 140 and
165.degree. C., more preferably between 150 and 155.degree. C. with
a draw ratio of at least 6, more preferably at least 10, most
preferably at least 15. In the second step the draw ratio is
preferably less than 50, more preferably less than 40, yet more
preferably less than 30, such as less than 20.
[0041] Optionally, the process of the invention may also comprise a
step of removing the residual spinning solvent from the gel-spun
UHMWPE filaments of the invention, preferably, said step being
subsequent to the solid stretching step. In a preferred embodiment,
the residual spinning solvent left in the gel-spun UHMWPE filaments
of the invention is removed by placing said filaments in a vacuumed
oven at a temperature of preferably at most 148.degree. C., more
preferably of at most 145.degree. C., most preferably of at most
135.degree. C. Preferably, the oven is kept at a temperature of at
least 50.degree. C., more preferably at least 70.degree. C., most
preferably at least 90.degree. C. More preferably, the removal of
the residual spinning solvent is carried out while keeping the
filaments taut, i.e. the filaments are prevented from
slackening.
[0042] Preferably, the gel-spun UHMWPE multifilament yarns of the
invention at the end of the solvent removal step comprise spinning
solvent in an amount of below 800 ppm. More preferably said amount
of the spinning solvent is below 600 ppm, even more preferably
below 300 ppm, most preferably below 100 ppm. It was also
surprisingly found that it was possible to apply a higher overall
draw ratio (DR.sub.overall) to the ultra-low dtex UHMWPE filaments
of the invention without the occurrence of breakages, as compared
to the DR.sub.overall previously reported in the state of the art.
By DR.sub.overall is herein understood the multiplication of the
draw ratios applied at different stages in the process of the
invention, i.e. the draw ratios applied to fluid, gel and solid
filaments. Accordingly,
DR.sub.overall=DR.sub.fluid.times.DR.sub.gel.times.DR.sub.solid.
[0043] Preferably, the DR.sub.overall is at least 9000, more
preferably at least 12000, even more preferably at least 15.000,
yet even more preferably at least 18.000, yet even more preferably
at least 20.000, yet even more preferably at least 25.000, most
preferably at least 30.000. In one embodiment, the DR.sub.overall
is at most 60.000, preferably at most 50.000, more preferably at
most 40.000, such as for example at most 35.000.
[0044] The advantage of applying such high DR.sub.overall in the
process of the invention is that UHMWPE multifilament yarns are
obtained having an even higher tensile strength. An additional
advantage is that the dtex of the filaments comprising said yarn is
further lowered.
[0045] The invention further relates to an UHMWPE multifilament
yarns having a tensile strength of at least 3.5 GPa and comprising
filaments having a dtex of at most 0.5 and.
[0046] By filament is herein understood an elongated body, i.e. a
body having a length much greater than its transverse dimensions,
of regular or irregular cross-sections and having continuous and/or
discontinuous lengths. A yarn as used herein includes a plurality
of filaments. The yarn according to the invention may be a twisted
or a braided yarn. In the context of the present invention a yarn
is understood to be a gel-spun yarn.
[0047] Preferably, the filaments comprising the UHMWPE yarns of the
invention have a dtex of at most 0.45, more preferably of at most
0.4, even more preferably of at most 0.35, yet even more preferably
of at most 0.3, yet even more preferably of at most 0.25, yet even
more preferably of at most 0.2, yet even more preferably of at most
0.15, most preferably of at most 0.1. Preferably, the UHMWPE
filaments have a dtex of at least 0.01, more preferably of at least
0.03, even more preferably of at least 0.06, most preferably of at
least 0.09. The dtex of said filaments can be reached with the
process of the invention by choosing a higher DR.sub.fluid and/or
DR.sub.solid.
[0048] The tensile strength of the UHMWPE yarns of the invention is
preferably at least 3.7 GPa, more preferably at least 4.0 GPa, even
more preferably at least 4.3 GPa, yet even more preferably at least
4.5 GPa, yet even more preferably at least 5.0 GPa, yet even more
preferably at least 5.5 GPa, most preferably at least 6 GPa.
Tensile strengths within the disclosed ranges can be obtained by
e.g. increasing DR.sub.overall.
[0049] Preferably the tensile modulus of the UHMWPE yarns of the
invention is at least 100 GPa, more preferably at least 130 GPa,
even more preferably at least 160 GPa, most preferably at least 190
GPa.
[0050] The advantages of the UHMWPE yarns of the invention when
compared with known UHMWPE yarns containing an equal number of
UHMWPE filaments stem from its lower transversal dimensions and
improved mechanical properties or combination of mechanical
properties as for example tensile strength and/or elastic
modulus.
[0051] It was surprisingly found that the UHMWPE yarns of the
invention have advantages when used in semi-finished and end-use
articles. Said articles, in particular fabrics, containing the
UHMWPE yarns of the invention surprisingly show an increased
acoustic absorption. Without being bound by any theory, the
inventors believe that the ultra-low dtex filaments forming said
yarns create an effective structure of air micro-channels which
allows for an optimum air permeability required to absorb sound
energy. A further advantage stemming from the presence of the air
micro-channels is that said articles further present an increased
thermal insulation.
[0052] The invention therefore further relates to various
semi-finished and end-use articles containing the UHMWPE yarns of
the invention.
[0053] In particular the invention relates to a fabric comprising
the yarns of the invention. The fabric may be of any known
construction manufactured from yarns, e.g. woven, knitted,
non-woven, e.g. felt and the like.
[0054] The invention also relates to medical devices, containing
the UHMWPE yarn of the invention. Especially for medical
applications where thin cables yet having a high tensile strength
are desired, the UHMWPE yarn of the invention proved particularly
advantageous. Preferably, the medical devices contain the UHMWPE
yarn of the invention, said yarn comprising filaments having a
residual solvent content in an amount of below 800 ppm, more
preferably said amount being below 600 ppm, even more preferably
below 300 ppm, most preferably below 100 ppm.
[0055] The invention relates more in particular to a surgical
repair product and even more in particular to a suture and to a
medical cable comprising the UHMWPE yarns of the invention. It was
found that the suture and the medical cable of the invention posses
very good knot strength. It was also found that these devices
possess an increased retention of their mechanical properties. Also
their flexibility was improved imparting said suture and cable
thereof with increased handling properties.
[0056] The invention further relates to a vascular graft comprising
the UHMWPE yarns of the invention. Such vascular grafts are used
for example to replace, bypass or reinforce diseased or damaged
sections of a vein or artery. It was found that the vascular grafts
of the invention in addition to their excellent tensile strengths
possess good oxygen permeability, tissue ingrowth characteristics
as well as ease of handling. Preferably, the vascular grafts of the
invention are made of knitted or woven continuous UHMWPE yarns of
the invention.
[0057] The invention further relates to a medical device in the
form of a mesh comprising the UHMWPE yarns of the invention. The
advantage of such a mesh is that it can be produced thinner than
known meshes. Preferably the mesh of the invention is knitted by a
process which interlinks each UHMWPE yarn junction and which
provides for elasticity in both directions. This construction
permits the mesh to be cut into any desired shape or size without
unraveling and furthermore, the bi-directional elastic property
allows adaptation to various stresses encountered in the body.
[0058] Another type of medical device, which advantageously may
comprise the yarn according to the invention, is implantable
valves, such as heart valves. Examples of manufacturing and
structures of such valves are for example described in EP
08014686.3 incorporated herein by reference.
[0059] The invention also relates to a rope containing the UHMWPE
yarn of the invention. Preferably, at least 50% from the total
weight of the fibres used to manufacture the rope consists of the
UHMWPE yarns according to the invention. More preferably the rope
contains at least 75 wt-% UHMWPE yarns of the invention, even more
preferably at least 90 wt-%, most preferably the rope contains 100
wt-% UHMWPE yarns of the invention. The remaining weight percentage
of the yarns in the rope according to the invention, may contain
yarns comprising filaments made of other materials suitable for
making filaments as for example metal, nylon, polyester, aramid,
other types of polyolef in and the like, or combinations thereof.
The advantage of the rope of the invention is that it provides the
same tensile strength as a known rope for less weight.
[0060] The invention also relates to composite articles containing
the UHMWPE yarn according to the invention.
[0061] In a preferred embodiment, the composite article contains at
least one monolayer comprising the UHMWPE yarns of the invention.
The term monolayer refers to a layer of yarns or strands containing
yarns in one plane. The monolayer is preferably a unidirectional
monolayer, i.e. a monolayer comprising unidirectionally oriented
yarns, i.e. yarns in one plane that are essentially oriented in
parallel. The advantage of using the yarns of the invention to
obtain such a monolayer is that monolayers thinner than known
monolayers comprising regular UHMWPE yarns can be obtained.
[0062] In a further preferred embodiment, the composite article is
a multi-layered composite article containing a plurality of
unidirectional monolayers the direction of the fibres in each
monolayer preferably being rotated with a certain angle with
respect to the direction of the fibres in an adjacent monolayer.
Preferably, the angle is at least 30.degree., more preferably at
least 45.degree., even more preferably at least 75.degree., most
preferably the angle is about 90.degree..
[0063] Composite articles and in particular multi-layered composite
articles proved very useful in ballistic applications, e.g. body
armor, helmets, hard and flexible shield panels, panels for inserts
or vehicle armouring and the like. Therefore, the invention also
relates to ballistic-resistant articles as the ones enumerated
hereinabove containing the UHMWPE yarns of the invention.
[0064] In a preferred embodiment of the invention, the composite
article is essentially free of matrix material, such as adhesive or
resin, to bond the UHMWPE yarn together. In this embodiment, the
yarn is bonded by pressing yarn and/or layers under sufficient
temperature and time to for bonding to take place. Such bonding may
involve at least partial melting of the UHMWPE fibres.
[0065] It was also observed that the UHMWPE yarns of the invention
showing the above mentioned unique combination of properties are
suitable for use in other applications like for example, fishing
lines and fishing nets, ground nets, cargo nets and curtains, kite
lines, dental floss, tennis racquet strings, canvas (e.g. tent
canvas), webbings, battery separators, capacitors, pressure
vessels, hoses, automotive equipment, power transmission belts,
building construction materials, cut and stab resistant and
incision resistant and abrasion resistant articles, protective
gloves, composite sports equipment such as skis, helmets, kayaks,
canoes, bicycles and boat hulls and spars, speaker cones, high
performance electrical insulation, radomes, and the like.
Therefore, the invention also relates to the applications
enumerated above containing the UHMWPE yarns of the invention.
[0066] The invention will be further explained by the following
examples and comparative experiment.
Methods:
[0067] IV: the Intrinsic Viscosity is determined according to
method PTC-179 (Hercules Inc. Rev. Apr. 29, 1982) at 135.degree. C.
in decalin, the dissolution time being 16 hours, with DBPC as
anti-oxidant in an amount of 2 g/l solution, by extrapolating the
viscosity as measured at different concentrations to zero
concentration; [0068] Dtex: filament's dtex was measured by
weighing 100 meters of filament. The dtex of the filament was
calculated by dividing the weight in milligrams to 10;
Tensile Properties:
[0068] [0069] tensile strength (or strength) and tensile modulus
(or modulus) are defined and determined at room temperature, i.e.,
about 20.degree. C., on multifilament yarns as specified in ASTM
D885M, using a nominal gauge length of the fibre of 500 mm, a
crosshead speed of 50%/min and Instron 2714 clamps, of type "Fibre
Grip D5618C". On the basis of the measured stress-strain curve the
modulus is determined as the gradient between 0.3 and 1% strain.
For calculation of the modulus and strength, the tensile forces
measured are divided by the titre, as determined by weighing 10
metres of yarns; values in GPa are calculated assuming a density of
0.97 g/cm.sup.3. [0070] Side chains: the number of side chains in a
UHMWPE sample is determined by FTIR on a 2 mm thick compression
moulded film, by quantifying the absorption at 1375 cm using a
calibration curve based on NMR measurements (as in e.g. EP 02691
51);
COMPARATIVE EXAMPLE
[0071] A 9 wt-% solution in decalin of a UHMWPE homopolymer was
made, the UHMWPE having less than 1 side group per 1000 per carbon
atoms and an IV of 15.2 dl/g.
[0072] A 25 mm twin screw extruder was used that was equipped with
a gear-pump. The UHMWPE solution was spun at a temperature of
180.degree. C. through a spinplate having 64 spinholes into a
nitrogen atmosphere with a rate of 1.5 g/min per hole.
[0073] The spinholes had an initial cylindrical channel with a of 3
mm diameter and length/diameter of 20, followed by a conical
contraction zone with a cone angle of 60.degree. that ended into a
cylindrical channel with a diameter of 1 mm and length/diameter of
10. Accordingly, DR.sub.sp=9 (3.sup.2/1.sup.2).
[0074] The fluid filaments entered a water bath kept at about
30.degree. C. and with a water flow of about 70 liters/hour
perpendicular to the filaments entering the bath. The fluid
filaments were taken-up at such rate that a draw ratio DR.sub.ag of
about 42 was applied to the fluid filaments in the air-gap of 27
mm. The total fluid draw ratio DR.sub.fluid was about 378. The gel
filaments were subjected to a draw ratio DR.sub.gel of 1.1 and the
solvent was removed thereafter to form solid filaments having a
solvent content of about 1 wt-% of the initial amount of solvent in
the UHMWPE solution.
[0075] Subsequently, the gel filaments entered an oven at
135.degree. C. wherein solvent evaporation took place and were
stretched therein with a draw ratio DR.sub.solid 1 of 4. The solid
filaments entered subsequently in a second oven being stretched
with a draw ratio DR.sub.solid 2 of 5 in at a temperature of
153.degree. C.
[0076] The total draw ratio
DR.sub.overall(=DR.sub.fluid.times.DR.sub.gel.times.DR.sub.solid
1.times.DR.sub.solid 2) amounted 7560. The above detailed process
parameters together with the properties of the obtained yarn are
summarized in Table 1.
EXAMPLE 1-7
[0077] The Comparative Experiment was repeated with the variations
as presented in Table 1. The non reported parameters were kept at
the same values as those reported in the Comparative
Experiment.
TABLE-US-00001 TABLE 1 UHMWPE solution conc. Strength Modulus n [%]
DR.sub.ag DR.sub.fluid DR.sub.solid 1 DR.sub.solid 2 DR.sub.overall
[GPa] [GPa] dtex Comp.Exp. 9 42 378 4 5 7560 1.84 37.5 3.19 Ex 1 5
50.2 452 4 5 9944 4.6 137.9 0.26 Ex 2 5 62.7 565 5 6 18645 4.6
159.5 0.22 Ex 3 7 62.7 565 4 5.5 13673 4.2 119.1 0.4 Ex 4 7 62.7
565 4 6 14916 4.1 130 0.32 Ex 5 9 83.6 753 4 8 26505 4.5 133.9 0.39
Ex 6 5 83.6 753 4 6.5 21535 5.2 190.7 0.14 Ex 7 5 62.7 565 4 10
24860 5.3 188.4 0.11
* * * * *