U.S. patent application number 10/762718 was filed with the patent office on 2004-10-07 for fluoropolymer yarn blends.
Invention is credited to Tokarsky, Edward William, Vinod, Yashavant Vinayak.
Application Number | 20040194444 10/762718 |
Document ID | / |
Family ID | 33310724 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040194444 |
Kind Code |
A1 |
Vinod, Yashavant Vinayak ;
et al. |
October 7, 2004 |
Fluoropolymer yarn blends
Abstract
The present invention relates to yarn blends of fluoropolymer
yarn and yarn of polyester, polyamide, or acrylic fiber, the latter
when dyed providing color to the yarn blend even with the
fluoropolymer yarn being undyed. When the polyester, polyamide, or
acrylic fiber yarn is stronger than the fluoropolymer yarn, the
yarn of such fiber strengthens the yarn blend.
Inventors: |
Vinod, Yashavant Vinayak;
(Hockessin, DE) ; Tokarsky, Edward William;
(Newark, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
33310724 |
Appl. No.: |
10/762718 |
Filed: |
January 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60460509 |
Apr 4, 2003 |
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Current U.S.
Class: |
57/243 |
Current CPC
Class: |
D02G 3/38 20130101; D10B
2321/042 20130101; D02G 3/46 20130101 |
Class at
Publication: |
057/243 |
International
Class: |
D02G 003/02 |
Claims
What is claimed is:
1. Yarn blend of at least first and second yarns, said first yarn
comprising fluoropolymer fiber and said second yarn comprising at
least one dyed or dyeable fiber comprising polyester, polyamide, or
acrylic.
2. The yarn blend of claim 1 wherein said yarns are co-mingled.
3. The yarn blend of claim 2 wherein said first yarn is undyed and
said second yarn is dyed, the co-mingling of said yarns to form
said yarn blend giving said yarn blend the appearance of the color
of said second yarn.
4. The yarn blend of claim 1 wherein said first and second yarns
are twisted together.
5. The yarn blend of claim 4 wherein multiple ends of said yarn
blend are corded together.
6. Sewing thread comprising multiple ends of said yarn blend of
claim 1.
7. Yarn blend of claim 1 wherein the elongation and tenacity of
said second yarn is such that the overall tenacity of said yarn
blend is at least 1 gpd greater than the first yarn by itself.
8. The yarn blend of claim 7 wherein the tenacity of said first
yarn is at least 2 gpd and the tenacity of said second yarn is at
least 5.9 gpd, the elongation of said second yarn having an
elongation which is greater than the elongation of said first
yarn.
9. The yarn blend of claim 8 wherein the elongation of said second
yarn is less than 10% above the elongation of said first yarn.
10. The yarn blend of claim 1 wherein said first yarn is
ethylene/tetrafluoroethylene copolymer having a tenacity of at
least 2 gpd.
11. The yarn blend of claim 10 wherein said tenacity of said first
yarn is at least 2.5 gpd.
12. The yarn blend of claim 1 comprising a greater number of first
yarns than second yarns.
13. The yarn blend of claim 1 having a greater number of second
yarns than first yarns.
14. The yarn blend of claim 1 wherein the tenacity of said second
yarn is at least 6.5 gpd.
15. The yarn blend of claim 1 wherein said first and second yarns
are selected from the group consisting of continuous filament yarn
and staple fiber yarn.
16. The yarn blend of claim 1 containing at least two said second
yarns, one of said second yarns being acrylic staple fiber and
another of said second yarns being selected from the group
consisting of polyester and polyamide.
17. The yarn blend of claim 1 comprising a core and a sheath, said
second yarn being present in said core and said first yarn being
present in said sheath.
18. The yarn of claim 6 additionally containing binder.
19. The yarn of claim 1 wherein said second yarns are polyester or
polyamide.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention.
[0002] This invention relates to blends of fluoropolymer yarn with
other yarns.
[0003] 2. Description of Related Art.
[0004] U.S. Patent Publication 2002/0079610 A1 discloses the melt
spinning of fluoropolymer yarn at a high temperature above the
melting point of the fluoropolymer to produce high tenacity yarns
at high rates of production relative to prior fluoropolymer yarns
and processes. The addition of colorant to the fluoropolymer prior
to yarn formation is disclosed, i.e., the pigment is added to the
copolymer prior to melt spinning so that the melt spun yarn has the
color of the pigment, depending on the pigment concentration. The
reason the colorant (pigment) is added to the fluoropolymer prior
to melt spinning is that the chemical inertness of the
fluoropolymer yarn makes it virtually undyeable by conventional
textile fiber dyeing processes and dyes after spinning. Dyeing has
the advantage over pigment coloring by offering greater versatility
in enabling the conversion of an undyed yarn to a wide range of
colors. Fluoropolymer yarn has not provided this versatility. Thus,
without pigment coloring, the fluoropolymer exhibits a natural
color, which ranges from white to milky white (translucent), to
transparent. Another problem with fluoropolymer yarns is that they
do not have the strength of common high tenacity synthetic textile
fiber yarns, i.e., polyester and polyamide, usually greater than
5.9 gpd (g/den). As disclosed in Example 9 of the above-identified
Patent Publication, PFA polymer
(tetrafluoroethylene/perfluoro(propyl vinyl ether) copolymer is
melt spun at different rates to produce yarn having a
tenacity/elongation of 0.94-1.10 gpd/68-80% elongation and 1.41
gpd/25% elongation, revealing the usual situation of elongation
decreasing as tenacity increases. The highest tenacity yarn
prepared in the Patent Publication is disclosed in Example 26,
wherein the ethylene/tetrafluoroethylene copolymer yarn has a
tenacity of 2.44 gpd and elongation of 18.8%.
BRIEF SUMMARY OF THE INVENTION
[0005] One aspect of the present invention solves the problem of
providing color to fluoropolymer which has no added color, i.e., it
is neither pigmented nor dyed, the latter because the fluoropolymer
is undyeable by conventional textile fiber dyes and dyeing
processes. The embodiment solving this problem can be described as
a yarn blend of at least first and second yarns, said first yarn
comprising fluoropolymer fiber and said second yarn comprising at
least one dyed or dyeable fiber comprising polyester, polyamide, or
acrylic. Although the first and second yarns can be combined into
the yarn blend by twisting together, the preferred method of
combining the yarns is by co-mingling by an air jet blending
process. The second yarn can be undyed at the time of combining
with the first yarn, followed by subjecting the yarn blend to
dyeing, which colors only the second yarn. Alternatively, the
second yarn can be dyed prior to combining with the first yarn. In
either embodiment, the yarn blend has the appearance of the color
of the second yarn, with the color being the most uniform when the
combining of the yarns is by co-mingling. The weather resistance
(chemical stability, dampness, sunlight, high and low temperature
exposure) of the fluoropolymer yarn component of the yarn blend
makes it especially useful in outdoor applications. A particularly
preferred application is sewing thread comprising multiple ends of
the yarn blend to achieve the breaking strength desired. Sewing
threads are available in a wide variety of colors to match the
variety of colored fabrics that are available. The sewing thread of
the present invention has the versatility of being dyeable in these
wide variety of colors, by virtue of the dyeability of the
polyester, polyamide, and/or acrylic fiber making up the second
yarn. A preferred sewing thread of the present invention includes a
binder. Binders for the second yarn do not normally adhere to
fluoropolymer, because of the well-known non-stick property of
fluoropolymers. Surprisingly, application of the binder to the yarn
blend serves to bind both the fluoropolymer and the second yarn
together, so that the resultant bound sewing thread can provide the
most trouble-free (snag free) sewing by using conventional
industrial sewing equipment.
[0006] Another aspect of the present invention solves the problem
of the tenacity of the fluoropolymer yarn by itself having less
than desired tenacity for certain applications. This problem is
solved by the yarn blend of first and second yarns described above
wherein the elongation and tenacity of said second yarn is such
that the overall tenacity of said yarn blend is at least 1 gpd
greater than the first yarn by itself. Polyester and polyamide
yarns typically have high elongation, such that the second yarn
merely being stronger than the first yarn does not give a stronger
yarn blend if the second yarn merely elongates under the tension
applied to the yarn blend while the elongation of the first yarn is
exceeded, resulting in breakage of the first yarn. Thus, it is
preferred that the elongation of the second yarn should be no
greater than the elongation of the first yarn. This is difficult to
achieve, however, because high tenacity second yarns have high
elongation, e.g., greater than 20, while high tenacity first yarns
typically have lower elongations, e.g., less than 15%.
Surprisingly, it has been discovered that even though the second
yarn has a higher elongation than the first yarn, the second yarn
can still increase the tenacity of the yarn blend. Preferably, the
elongation of the second yarn is less than 10% above that of the
first yarn, i.e., if the first yarn has an elongation of 10%, the
elongation of the second yarn should be less than 20%.
[0007] It is preferred that the fluoropolymer yarn is as strong as
possible, so that in outdoor utility as the strength of the second
yarn diminishes from weathering, the first yarn component of the
yarn blend provides sufficient residual strength required for the
particular application. Thus, it is preferred that the first yarn
in the yarn blend has a tenacity of at least 2 gpd and the tenacity
of said second yarn is at least 5.9 gpd, with the second yarn
having an elongation as described in the preceding paragraph.
Typically the tenacity of the first yarn will not exceed 5 gpd.
[0008] Surprisingly, it has been found that the presence of the
fluoropolymer yarn in the yarn blend increases the weatherability
of the second yarn, such that the higher tenacity of the yarn blend
arising from the presence of the second yarn when it is polyester
or polyamide is surprisingly high in view of the deterioration of
the tenacity of the second yarn when exposed by itself to the same
weathering.
DETAILED DESCRIPTION OF THE INVENTION
[0009] To first describe the yarns making up the yarn blend of the
present invention, examples of fluoropolymer from which the first
yarn can be made include the following: (A) non-melt-fabricable
polytetrafluoroethylene, including modified
polytetrafluoroethylene, i.e., wherein a small amount of comonomer
is copolymerized with the tetrafluoroethylene and (B)
melt-fabricable fluoropolymers, including homopolymers other than
polytetrafluoroethylene (PTFE), such as polyvinylidene fluoride
(PVDF), and perfluorinated copolymers, such as copolymers of
tetrafluoroethylene (TFE) prepared with comonomers including
perfluoroolefins and perfluoro(alkyl vinyl ethers)(PAVE), wherein
the alkyl group contains 1 to 6 carbon atoms and the PAVE can be
more than one PAVE, or blends of such polymers. The term
"copolymer", for purposes of this invention, is intended to
encompass polymers comprising two or more comonomers in a single
polymer. A representative perfluoroolefin is hexafluoropropylene.
Representative perfluoro(alkyl vinyl ethers) are perfluoro(methyl
vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and
perfluoro(propyl vinyl ether) (PPVE). Preferred highly fluorinated
polymers are the copolymers prepared from tetrafluoroethylene and
one or more perfluoro(alkyl vinyl ethers) and the copolymers
prepared from tetrafluoroethylene and hexafluoropropylene. Most
preferred copolymers are TFE with 1-20 mol % of a perfluoroolefin
comonomer, preferably 3-10 mol % hexafluoropropylene or 3-10 mol %
hexafluoropropylene and 0.2-2 mol % PEVE or PPVE, commonly known as
FEP, and copolymers of TFE with 0.5-10 mol % perfluoro(alkyl vinyl
ether), including 0.5-3 mol % PPVE or PEVE, commonly known as PFA,
or such copolymers which contain both PMVE and one or more of PEVE
and PPVE, commonly known as MFA. The fluoropolymers (B) described
above preferably exhibit a melt flow rate (MFR) of 1 to about 50
g/10 minutes as determined at 372.degree. C. according to ASTM
D2116, D3307, D1238, or corresponding tests available for other
highly fluorinated thermoplastic polymers. Polyvinylidene fluoride
preferably has a melt viscosity of 1 to 4.times.10.sup.3
Pa.multidot.s measured in accordance with ASTM D 3222.
[0010] In addition to the fluorinated thermoplastic
tetrafluoroethylene copolymers (B) described above, such
fluorinated thermoplastic (melt-fabricable) polymers as
ethylene/tetrafluoroethylene copolymers (ETFE) and
ethylene/chlorotrifluoroethylene (ECTFE) can also be used in the
present invention, with ETFE being preferred. Such ETFE is a
copolymer of ethylene and tetrafluoroethylene, preferably
containing minor proportions of one or more additional monomers to
improve the copolymer properties, such as stress crack resistance.
U.S. Pat. No. 3,624,250 discloses such polymers. The molar ratio of
E (ethylene) to TFE (tetrafluoroethylene) is from about 40:60 to
about 60:40, preferably about 45:55 to about 55:45. The copolymer
also preferably contains about 0.1 to about 10 mole % of at least
one copolymerizable vinyl monomer that provides a side chain
containing at least 2 carbon atoms. Perfluoroalkyl ethylene is such
a vinyl monomer, perfluorobutyl ethylene being a preferred monomer.
The polymer has a melting point of from about 250.degree. C. to
about 270.degree. C., preferably about 255.degree. C. to about
270.degree. C. Melting point is determined according to the
procedure of ASTM 3159. In accordance with this ASTM procedure, the
melting point is the peak of the endotherm obtained from the
thermal analyzer. Preferably, the ETFE used in the present
invention has a melt flow rate (MFR) of less than 45 g/10 min using
a 5 kg load in accordance with ASTM D 3159, wherein the melt
temperature of 297.degree. C. is specified. More preferably, the
MFR of the ETFE is no more than 35 g/10 min and is at least 15 g/10
min, preferably at least 20 g/10 min. As the MFR increases from 35
g/10 min, resulting from reduced molecular weight of the polymer,
the advantage of higher in melt spin rate becomes counterbalanced
by reduced strength (tenacity) of the yarn from the reduced
molecular weight polymer, such that upon reaching an MFR of 45 g/10
min, the decrease in tenacity outweighs the increase in production
rate. As the MFR decreases from 20 g/10 min, the difficulty in
extruding the more viscous polymer increases, leading to
uneconomical melt spin rates, until an MFR of 15 g/10 min is
reached, below which the polymer is barely melt spinnable through
the small extrusion orifices required for yarn.
[0011] Also suitable for the practice of this invention are blends
of the highly fluorinated thermoplastic polymers including blends
of TFE copolymers.
[0012] The fluoropolymers (A) can be formed into yarn by known
processes, including spinning of the fluoropolymer into the yarn or
forming sheets or strands of the fluoropolymer, followed by cutting
filaments therefrom. The fluoropolymers (B) can be melt spun into
yarn preferably by the process disclosed in U.S. Patent Publication
2002/0079610 A1. The ETFE copolymer yarns can have a tenacity of at
least 2 gpd and preferably at least 2.5 gpd. A preferred process to
make a yarn having a tenacity of at least 3 gpd is described in the
Examples hereinafter. Typically, the fluoropolymer yarn used to
make yarn blends of the present invention will have an elongation
of 8 to 25% and preferably from 8 to 15% to provide the higher
tenacities.
[0013] Yarn deniers disclosed herein are determined in accordance
with the procedure of ASTM D 1577 and the tensile properties
(elongation to break (elongation) and tenacity) are determined in
accordance with the procedures disclosed in ASTM 2256.
[0014] Yarns of polyester, polyamide, acrylic polymer are
commercially available and can be used as second yarns to make yarn
blends of the present invention. Such yarns and processes for
making them and processes for dyeing them are disclosed in
Kirk-Othmer, Encyclopedia of Chemical Technology, 4.sup.th Ed,
(1994) in Vol. 10, pp. 559-565 and 576-581 (acrylics) and pp.
662-667, 670-677 (polyesters), and in Vol.19, pp. 519-522, 528,
530-539, and 543-544 (polyamides). Polyester and polyamide yarns
are made by melt spinning, while polyacrylic yarns are typically
made by wet or dry spinning. The polyesters, polyamides, and
acrylic polymers used to make the yarns can be homopolymers or
copolymers and have sufficiently high molecular weight to provide
the tenacity desired for the yarn blend of the present invention.
Suitable homo- and/or copolymers which may be used include for
example, poly(ethylene terephthalate), poly(propylene
terephthalate), poly[ethylene terephthalate/(5-sodium
sulfo)isophthalate]. Polyhexamethylene adipamide, polyhexamethylene
adipamide containing sulfo or amino groups receptive to cationic or
dark acid dyes respectively and the like and mixtures thereof.
Examples of acrylic polymers include: acrylonitrile homopolymer and
copolymers, including the modacrylics, i.e., acrylonitrile
copolymers containing 35 to 85 wt % acrylonitrile units.
[0015] The tenacity of the second yarn will depend on the polymer
from which it is made and the degree of draw to increase tenacity
once the yarn is formed. The tenacity will also depend on whether
the second yarn is continuous filament or staple fiber. For a given
polymer, the continuous filament yarn has a higher tenacity than a
staple fiber yarn. To solve the problem of providing a colored
yarn, which contains uncolored fluoropolymer yarn, the tenacity of
the second yarn is less important. Thus, acrylic polymer yarn,
which is only available as staple fiber yarn and has a tenacity of
2 to 3 gpd, can be used. Polyester staple fiber yarns generally
exhibit tenacities of 2.4 to 7 gpd, and polyamide staple fiber
yarns exhibit tenacities of 2.9 to 7.2 gpd. At the higher tenacity
levels however, even for the acrylic polymer yarn, the staple fiber
yarn can provide a yarn blend with the fluoropolymer yarn that
exhibits a greater tenacity than the fluoropolymer yarn by itself.
The same is true for continuous filament polyester and polyamide
yarns in general, which exhibit a tenacity of at least 3.5 gpd. To
provide a yarn blend having a greater tenacity than the
fluoropolymer yarn component, however, the use of high tenacity
polyester and polyamide yarn as second yarns is preferred. Such
yarns exhibit tenacities of at least 5.9 gpd, and preferably at
least 6.5 gpd. Generally the tenacity of the polyester and
polyamide yarns will not exceed 9 gpd.
[0016] Typically, the second yarn will have an elongation of 15 to
30%. Preferably, the elongation of the second yarn is less than 8%
above that of the first yarn, more preferably less than 5% above
that of the first yarn, and most preferably less than 2% above that
of the first yarn. These differences in elongations apply to each
of the first and second yarns described herein. It is also
preferred that the first yarn in the yarn blend has a tenacity of
at least at least 2.5 gpd and more preferably at least 3 gpd. It is
also preferred that the tenacity of the second yarn be at least 2
gpd greater than the tenacity of the first yarn.
[0017] The first yarn of the present invention can be monofilament
or multifilament. When the yarn is a monofilament, it will
generally have a diameter of 50 to 1000 micrometers. When the yarn
is multifilament, the individual filaments will generally have a
diameter of 8 to 30 micrometers, and the yarn will generally have a
denier of 30 to 5000, preferably 100-1000 and contain 20 to 200
filaments. In the case of the multifilament yarn, the individual
filaments will preferably each be 2 to 50 den, preferably 5 to 40
den/filament, and most preferably 10-30 den/filament, with 20-30
den/filament being preferred for highest breaking strength without
undue stiffness. The second yarn will preferably be a multifilament
yarn that can be characterized by the same parameters
characterizing the multifilament first yarn earlier in this
paragraph. The first and second yarns can also be made of staple
fiber rather than continuous filament to enhance appearance, and
the yarn blend of the present invention can be a mixture of
continuous filament and staple fiber yarns. In the case of staple
fiber first and/or second yarns used in the yarn blend of the
present invention, the staple fibers will generally have a denier
of 1-10, preferably 1 to 5 den/fiber (or filament from which the
fiber is made).
[0018] The first and second yarns can be blended by conventional
textile fiber processes, such as twisting, and pairs of twisted
blend yarns can be further twisted together e.g., in the opposite
twist direction to form cords. The yarns can be as spun, i.e., flat
yarn, or textured by conventional processes to increase the bulk of
the yarn. Dyeing of the second yarn either before or after forming
the yarn blend will impart the second yarn color to the color of
the yarn blend, to twisted pairs of the yarn blend and to cord of
the yarn blend, even though the first yarn is undyed.
[0019] A preferred process for blending the first and second yarns
together is co-mingling such as described in "Air-Jet Texturing
& Mingling", published by Loughborough University (1989) as a
collection of papers presented at an international conference at
the University in September 1989, which includes the paper
presented by A. Demic, "Intermingling/lnterlacing: A Broad Survey
(pp.41-60). Intermingling is described as subjecting a loose bundle
of flat or textured yarn to turbulent cold air-jet impingement
(mingling jet) at an angle to the path of the yarn to open up
sections of the filaments, while in the vicinity of the opened up
section of the filaments, the filaments become intertwined and
intermingled with each other to form compact sections. Co-mingling
is described as carrying out the intermingling process on two
yarns, whereby the intertwining and intermingling involves
filaments of both yarns. The resultant co-mingled yarn is a
coherent yarn, i.e., the two yarns are united into a single yarn
(blend), and the resultant yarn blend is in the form of interlaced
sections periodically alternating with open sections. This
description and method of preparation applies to the co-mingled
yarn blend of the present invention. The co-mingled yarn blend of
the present invention resembles the yarn blend depicted as
"Blending" in Fig. 5 on p. 59 of the Demic paper. The air jets used
for co-mingling and the conditions for carrying out the co-mingling
process are well known, such as described in the Demic paper and
disclosed as intermingling in U.S. Pat. No. 4,025,595. When the
yarn fed to the co-mingling jet is textured, the texturing can
include different types of texturing such as air-jet texturing,
false twist texturing, and hot-fluid texturing. The co-mingled yarn
blends of the present invention preferably have 3 to 50
entanglements per meter (determined as disclosed in col. 3 of U.S.
Pat. No. 4,025,595) to achieve the coherence desired for textile
processing. The entanglements along the length of the blended yarn
are knots, the knots sometimes being called nips or nodes, and
these entanglements provide integrity to the blended yarn. Even
when the first yarn is monofilament or staple fiber, the second
yarn filaments will interlace with the monofilament or staple fiber
yarn to provide a blended yarn having integrity. The same is true
when one or both of the yarns are staple fiber yarns. In a
preferred yarn blend, both the first and second yarns are
multifilament yarns, which provides the highest tenacities for the
yarn blend and also the most uniform color appearance of the yarn
blend, this being the dyed color of the second yarn.
[0020] Another preferred yarn blend of the present invention is the
yarn blend comprising a core and a sheath, with the second yarn
being present in the core and the first yarn being present in the
sheath. This yarn blend can be made by wrapping the first yarn
around the second yarn, but is preferably made by co-mingling,
wherein the first yarn is overfed to the co-mingling jet relative
to the feed of the second yarn to the jet, tending to cause
filaments of the first yarn to wrap around the second yarn while
the filaments of each yarn become interlaced together by the
co-mingling process. The over feed of the first yarn is achieved by
feeding the first yarn to the co-mingling jet at a faster rate than
the windup of the yarn blend downstream from the jet. This
construction of the yarn blend of the present invention has the
advantage of better utilization of the greater strength of the
second yarn to increase the strength of the yarn blend over the
strength of the first yarn. The nature of the sheath yarn, i.e.,
the first yarn, in this construction is not a complete covering of
the core yarn, i.e., the second yarn, whereby the dyed color of the
second yarn nevertheless provides coloration of the yarn blend. The
first yarn contributes to the yarn blend color by picking up the
color of the second yarn, some by reflectance and some by light
transmission so that the second yarn color is visible through the
thickness of the filaments of the first yarn.
[0021] One criterion for combining the first and second yarns into
yarn blends of the present invention is the denier desired for the
yarn blend. Such denier is achieved by selection of the denier of
the first and second yarns and by the number of each such yarns in
the yarn blend. The yarn blend can consist of an equal number of
first and second yarns. Alternatively, the number of first yarns
can exceed the number of the second yarn or vice versa. A preferred
yarn blend has two first yarns and one second yarn, and another
preferred blend has two second yarns and one first yarn. The first
mentioned preferred yarn blend maximizes the fluoropolymer yarn
content for maximum residual outdoor weathering strength. The
second-mentioned preferred yarn maximizes initial yarn blend
strength and color uniformity. These objectives can also be
achieved by the relative denier of the first and second yarns. For
example, a higher denier second yarn tends towards maximizing color
uniformity and high initial yarn blend strength when only one
second yarn is present, depending the denier difference between
first and second yarns. In the case of co-mingled yarn blends of
the present invention, when one or both of the first and second
yarns are staple fiber yarns, a plurality of staple fiber yarns is
preferably used so as to increase the opportunity for intermingling
between yarns and between staple fibers in each yarn.
[0022] The second yarn can be dyed by conventional textile fiber
dyeing processes and using conventional textile fiber dyes,
depending on whether the second yarn is made of polyester,
polyamide, or acrylic fiber. Further description of such dyeing
processes and dyes and modifying the polymer making up the yarn is
disclosed in Kirk-Othmer referred to above. The second yarn can be
dyed before after combination into the yarn bend. Dyeing of the
yarn blend leaves the first yarn undyed.
[0023] A preferred yarn blend contains at least two second yarns,
one of which is acrylic staple fiber and the other of which is
either polyester or polyamide or both. Such yarn blend is
especially useful in applications exposed to the weather, wherein
the dye fastness of the acrylic fiber maintains color for the yarn
blend, while the fluoropolymer yarn provides long-term
strength.
EXAMPLES
[0024] The yarn used in the Examples is Tefzel.RTM. ETFE
fluoropolymer which is a terpolymer of ethylene,
tetrafluoroethylene, and less than 5 mole % perfluoroalkyl ethylene
termonomer, having a melting temperature (peak) of 258.degree. C.
and melt flow rate of 29.6 g/10 min, both as determined in
accordance with ASTM 3159, using a 5 kg weight for the MFR
determination.
[0025] The lubricant used to coat the yarn after melt spinning is
as follows: 88.9 wt % Clariant Afilan.RTM. PP polyol polyester, 5
wt % Uniqema.RTM. G-1144 polyol ethoxylated capped ester oil
emulsifier, 0.67 wt % Cytek Aerosol.RTM. OT di-octyl sulfosuccinate
wetting agent (75 wt % aqueous solution), 5 wt % Cognis Emersol 871
fatty acid surfactant, 0.26 wt % Uniroyal Naugard.RTM. PHR
phosphite antioxidant, 0.67 wt % sodium hydroxide (45 wt % aqueous
solution) stabilizer for the fatty acid, and 0.04 wt % Dow Corning
polydimethylsiloxane (process aid--minimizes deposits of the
lubricant on the hot rolls).
[0026] The fluoropolymer and the lubricant have surface tensions of
25 dynes/cm and 23.5 dynes/cm respectively, at ambient
temperature.
[0027] The melt spinning of the fluoropolymer is carried out using
an equipment arrangement as shown in FIG. 9 of U.S. Patent
Publication 2002/0079610 A1, except that the kiss roll 112 and the
guides 111 are not present, and the lubricant is applied using an
applicator guide positioned beneath the annealer 110, upstream from
the change in direction guide. The application guide is similar to
a Luro-Jet.RTM. applicator guide, having a V-shaped slot which
brings the array of extruded filaments together within the slot and
which includes an applicator at the base of the V-shape, which, in
turn, includes an orifice through which the lubricant is pumped
(metered) onto the yarn as it passes across the applicator.
[0028] The extruder is a 1.5 inch (3.8 cm) diameter Hastelloy C-276
single screw extruder connected to a gear pump, which in turn is
connected through an adapter to the spinneret assembly which
includes a screen pack to filter the molten polymer. The spinneret
assembly is the assembly 70 of FIG. 8 of the U.S. Patent
Publication and includes a transfer line and spinneret faceplate
depicted as elements 78 and 75, respectively, in FIG. 8. The
spinneret faceplate has 30 holes arranged in a circle having a
two-inch (5.1 cm) diameter, each hole (extrusion die orifice) has a
diameter of 30 mils and a length of 90 mils. The annealer is that
of Example 12 and FIGS. 10A and 10B of the U.S. Patent
Publication.
[0029] Operating temperatures are as follows:
[0030] Extruder: 250.degree. C., 265.degree. C., 270.degree. C. at
extruder zones--Feed, #1 and #2 respectively
[0031] Transfer line: 317.degree. C.
[0032] Spinneret faceplate: 350.degree. C.,
[0033] Annealer: 204.degree. C., 210.degree. C., and 158.degree. C.
at the #1, #2, and #3 positions, respectively.
[0034] The fluoropolymer throughput (fluoropolymer exiting the
spinneret) is set by the gear pump to be the maximum, i.e., just
short of causing melt fracture in the extruded filaments, this
maximum being 50.5 g/min (6.7 lb/hr). The resultant yarn solidifies
at a distance from the spinneret that is greater than 50.times.the
diameter of the extrusion orifice. The lubricant described above is
applied to the yarn just below the annealer and the feed rolls are
at a temperature of approximately 180.degree. C. and surface speed
of 309 m/min. The draw rolls are heated at 150.degree. C. and
rotate at a surface speed of 1240 m/min to provide a draw ratio of
4.01. The yarn is wound onto a bobbin using a Leesona winder. The
resultant yarn has the following properties: tenacity-3.45 gpd,
elongation 7.7%, tensile modulus-55 gpd. When the draw ratio is
decreased to 3.69 by reducing the surface speed of the draw rolls
to 1140 m/min, the following yarn properties are obtained:
tenacity-3.14 gpd, elongation-9.4%, modulus 51 gpd. The yarn denier
increases from 374 to 407.
[0035] The coefficients of variation of the denier of the yarns is
less than 2%. Coefficient of variation is the standard deviation
divided by the mean weight of 5 consecutive ten meter lengths of
the yarn (X 100).
Example 1
[0036] The fluoropolymer yarn used in this Example is the yarn
prepared generally by the process described above, except that the
draw ratio is decreased slightly to obtain a higher elongation yarn
having a lower tenacity. The yarn is 400 den, contains 13 filaments
and has a tenacity of 2.9 gpd and elongation of 14.3%. The other
yarn used in this Example is polyester yarn. One such yarn has 100
filaments, is 633 den after drawing (original denier 640) and has a
tenacity of 7.89 gpd and elongation of 24% (PET Yarn A). PET Yarn A
is dyed white and is obtained from the DuPont Company, Wilmington,
Del.). Another of such yarn has 108 filaments, is 885 denier after
drawing and dyeing (original denier is 840), and has a tenacity of
7.49 gpd and elongation of 20% (PET Yarn B). PET Yarn B is an Akra
Company yarn obtained from the United Yarn Co., Wayne, N.J., and is
dyed a blue color.
[0037] A yarn blend of the one end of the ETFE copolymer yarn and
one end of PET Yarn A is made by air jet blending (co-mingling) as
follows: A FOO entanglement machine is used. The machine uses an
air interlace jet IMS type 3-2 obtained from the International
Machinary Sales (IMS) inc., Winston-Salem, N.C. The fluoropolymer
yarn is overfed through the jet at a yarn tension of 5 grams, the
PET Yarn A is supplied through the jet at a yarn tension of 20
grams, the air pressure applied to co-mingle these yarns is 40 psi
and the wind-up speed is 250 ypm. The resultant co-mingled yarn
blend is a sheath/core yarn blend wherein the fluoropolymer yarn
predominates at the surface of the yarn blend and has a denier of
1070, tenacity of 4.45 gpd and elongation of 21.83%.
[0038] Another yarn blend is made by the same air jet co-mingling
process, using the same ETFE copolymer yarn and PET Yarn B, one end
of each yarn, to obtain a co-mingled sheath/core yarn blend having
a denier of 1326, tenacity of 5.5 gpd, and elongation of 21.5%, and
exhibiting a uniform blue color.
[0039] Another yarn blend is made by the same air jet co-mingling
process, using the two ends of the same ETFE copolymer yarn and one
end of PET Yarn B, with both ETFE yarns being fed through the jet
at the same tension, 5 g, and the PET Yarn tension being 20 g, to
obtain a co-mingled yarn having a denier of 1728, tenacity of 3.93
gpd and elongation of 16.24%. The yarn blend of ETFE with PET Yarn
A is white, and the yarn blend of ETFE with PET Yarn B is blue due
to the use of a blue colored PET Yarn B.
[0040] Similar results are obtained when the PET yarns are replaced
by polyamide or acrylic yarns.
Example 2
[0041] Sewing thread of yarn is made of the co-mingled yarn
prepared in Example 1 using one end of the ETFE copolymer yarn and
one end of PET Yarn B by (a) applying a twist to the yarn blend of
one twist/cm, (b) plying three ends of such yarn together at a
twist of one/cm but in the opposite direction from the twist in the
yarn, and (c) heat setting the resultant thread at 140-150.degree.
C. under tension. The resultant sewing thread has a denier of 3978.
A binder or finish can then be applied to the thread if desired.
The resultant sewing thread is a balanced, corded construction
having a uniform denier and exhibiting excellent stitch loop
formation, without any propensity to knot or snarl.
Example 3
[0042] One end of 400 denier Kynar.RTM. 710 (PVDF yarn) and one end
of 885 denier PET Yarn B are air-jet co-mingled together as
described in Example 1 using the overfeed condition for the PVDF
yarn, resulting in a blue colored yarn blend of 1290 denier,
tenacity of 5.56 gpd, and elongation of 20.0%. The Kynar.RTM. 710
PVDF continuous filament yarn by itself has a tenacity of 3.1 gpd
and 39.1% elongation.
Example 4
[0043] One end of 885 denier PET Yarn B and one end of 20s/2 ply
(512 denier) dark blue acrylic staple yarn and 1 one end of 400
denier ETFE yarn are air-jet co-mingled as described in Example 3,
with the ETFE and acrylic yarns both being overfed at the same
tension, resulting in a tonal blue colored yarn blend of 1885
denier, tenacity of 3.97 gpd, and elongation of 20.5%. The 512
denier acrylic staple fiber is obtained through Pharr Yarns Inc.,
and has a tenacity of 1.7 gpd and elongation of 38.34%.
Example 5
[0044] One end of 840 denier (840-140-400T), white high tenacity
nylon from the DuPont Co. and one end of 400 denier ETFE are
air-jet co-mingled as described in Example 3, resulting in a white
yarn blend of 1263 denier, tenacity of 6.15 gpd, and elongation of
25.5%. The 840 denier nylon filament yarn has a tenacity of 9.30
gpd, and elongation of 25.5%.
Example 6
[0045] This Example describes the embodiment wherein the yarn blend
contains binder for the second yarn, examples of such binder being
polyurethane- or silicone- based polymer. These binders do not
adhere to fluoropolymer but do serve to bind the composite yarn.
The general procedure for applying binder (bonding agent) to yarn
is to form a liquid medium containing the binder and apply it to
the yarn by conventional methods such as by using a kiss roll,
padding of the binder medium onto the yarn or applying the medium
to the yarn by dip or spray, followed by heat setting and wind-up
on a final package.
[0046] By way of example, commingled yarn is composed of one end of
400 denier, 13 dpf ETFE yarn and one end of 220 denier, 3.25 dpf
polyester yarn. The single yarn is characterized by 9S twist (9
turns/in (tpi), 9 turns/2.54 cm), i.e., 9 turns in the "S"
direction. Two of these yarns are plied together, the plying being
characterized by 7Z (7 tpi, 7 turns/2.54 cm), i.e., 7 turns in the
"Z" direction. The binder is aqueous-based polyurethane available
as NuBond.RTM. UVRH (Synthetic Thread, Bethlehem, Pa.) and is
applied by a kiss roll to the plied yarn having a total measured
denier of 1450, heat set and wound up on a final package. The
resultant bound yarn performs better in industrial sewing by
enabling the sewing to be carried out continuously for a much
longer time than when the same yarn is used but without the binder.
Thus, the use of the binder leads to fewer yarn breaks or yarn
entanglement, which are the typical causes for machine shutdown.
This improved sewing performance is similar to the sewing
performance for the polyester yarn used by itself together with the
same binder. The binder effect on the polyester yarn by itself is
similar to the effect of the binder on the composition
EFTE/polyester yarn. Similar improved sewing performance is
obtained for a blend of the same yarns plied together to produce a
composite yarn of 2572 measured denier to which the polyurethane
binder is applied and heat set.
Example 7
[0047] This Example is directed to the embodiment wherein the
second yarn weathers better when associated with the fluoropolymer
yarn as a composite yarn, i.e., the strength deterioration of the
second yarn is less in the yarn blend than when weathered as a yarn
by itself, whereby the tensile strength of the yarn blend is higher
than expected. This effect is obtained when the second yarn is
polyester or polyamide. The yarns in this Example are those
described in Example 6.
[0048] Accelerated weathering performance is determined in
accordance with SAE J1960 using a xenon arc accelerated weathering
apparatus available from the Atlas Company, Chicago, Ill. Tenacity
and elongation of yarns are determined before and after exposure to
450 kilojoules energy (equivalent to more than four months outdoor
exposure in Florida facing south at 45.degree.). This exposure is
enough to cause a 34% decrease in elongation of ETFE yarn by itself
and a 63% decrease in elongation of the polyester yarn by itself.
In contrast, the decrease in elongation of the composite ETFE
yarn/polyester yarn is only 37%, which is about the same as for the
ETFE yarn by itself and which decrease is much less than the
polyester yarn by itself. In addition, after the exposure, the
tenacity (gpd) of the ETFE yarn by itself is almost unaffected,
while the polyester yan by itself retains only 43% of its original
tenacity. In contrast, the composite yarn retains 91% of its
original tenacity.
* * * * *