U.S. patent application number 10/795935 was filed with the patent office on 2004-09-02 for low friction fibers, methods for their preparation and articles made therefrom.
Invention is credited to Gunn, Robert T..
Application Number | 20040170829 10/795935 |
Document ID | / |
Family ID | 25466896 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040170829 |
Kind Code |
A1 |
Gunn, Robert T. |
September 2, 2004 |
Low friction fibers, methods for their preparation and articles
made therefrom
Abstract
The invention relates to fibers having a low coefficient of
friction formed from a combination of at least two or more
materials, such as a base polymer, such as polyethylene, and
ultra-high molecular weight silicone, wherein one of the materials
has a low coefficient of friction
Inventors: |
Gunn, Robert T.; (New York,
NY) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG
745 FIFTH AVENUE- 10TH FL.
NEW YORK
NY
10151
US
|
Family ID: |
25466896 |
Appl. No.: |
10/795935 |
Filed: |
March 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10795935 |
Mar 8, 2004 |
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09935305 |
Aug 22, 2001 |
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Current U.S.
Class: |
428/364 |
Current CPC
Class: |
D01F 1/10 20130101; Y10T
428/2913 20150115; Y10T 428/2933 20150115 |
Class at
Publication: |
428/364 |
International
Class: |
D02G 003/00 |
Claims
What is claimed is:
1. A low friction fiber comprising: a polymeric component; and a
low friction component, wherein the polymeric component is combined
with the low friction component, thereby imparting onto the fiber a
low coefficient of friction characteristic which is of a
non-temporary nature.
2. The low friction fiber according to claim 1, wherein the
polymeric component is selected from the group consisting of
polyester, nylon, acrylics, polyethylene, polyurethane and plastic
copolymers.
3. The low friction fiber according to claim 1, wherein the low
friction component is selected from the group consisting of
fluorocarbon polymers, boron, molybdenum sulfide, ultrahigh
molecular weight silicone, siloxane, fluoroesters, fluorinated
ethylene propylene copolymers, perfluoroelastomers, polychloro,
trifluoroethylene homo- and copolymers, silicone/silane modified
polymers, graphite, fluorinated high molecular weight polyolefins
or cyclic organic compounds, non-modified polyolefins,
fluoropolymers and homopolymers and copolymers thereof.
4. The low friction fiber according to claim 1, wherein the
concentration of the polymeric component is about 30 wt % and the
concentration of the low friction component is about 70 wt %.
5. The low friction fiber according to claim 1, wherein the
coefficient of friction of the fiber is from about 0.22 to about
0.005
6. The low friction fiber according to claim 1, wherein the
coefficient of friction of the fiber is from about 0.15 to about
0.01.
7. The low friction fiber according to claim 1, wherein the
coefficient of friction of the fiber is from about 0.01 to about
0.005.
8. The low friction fiber according to claim 1, wherein the low
friction component is a fluoroester.
9. An article comprised of a low friction fiber comprising: a
polymeric component; and a low friction component, wherein the
polymeric component is combined with the low friction component,
thereby imparting onto the fiber a low coefficient of friction
characteristic which is of a non-temporary nature.
10. A low friction fiber comprising: a polymeric component; and a
low friction component, wherein the concentration of the polymeric
component is about 30 wt % of the fiber and the concentration of
the low friction component is about 70 wt % of the fiber, and
wherein the polymeric component is combined with the low friction
component, thereby imparting onto the fiber a low coefficient of
friction characteristic which is of a non-temporary nature.
11. The low friction fiber of claim 1, having a denier of from
about 0.5 to about 1500.
12. The low friction fiber of claim 8, having a denier of from
about 0.5 to about 1500.
13. A low friction fiber comprising: a polymeric component; and a
low friction component, wherein the low friction component is
fluorinated, and wherein the polymeric component is combined with
the low friction component, thereby imparting onto the fiber a low
coefficient of friction characteristic which is of a non-temporary
nature.
14. The low friction fiber of claim 1, which further comprises
flame retardants, antimicrobials, and anti-static agents.
15. A method of imparting a low coefficient of friction
characteristic onto a fiber comprising the steps of: a) combining a
polymeric component and a low friction component; and b) forming a
fiber from the combination of the polymeric component and the low
friction component.
16. The method of claim 15, wherein the polymeric component is
selected from the group consisting of polyester, nylon, acrylics,
polyethylene, polyurethane and other plastic copolymers.
17. The method of claim 15, wherein the low friction component is
selected from the group consisting of fluorocarbon polymers, boron,
molybdenum sulfide, ultrahigh molecular weight silicone, siloxane,
fluoroesters, fluorinated ethylene propylene copolymers,
perfluoroelastomers, polychloro, trifluoroethylene homo- and
copolymers, silicone/silane modified polymers, graphite,
fluorinated high molecular weight polyolefins or cyclic organic
compounds, non-modified polyolefins, fluoropolymers and
homopolymers and copolymers thereof.
18. A method of reducing the coefficient of friction in an article
which comprises incorporating a low friction fiber according to
claim 1 into the article.
19. The article of claim 9, wherein the article comprises
apparel.
20. The method of claim 18, wherein the article comprises
apparel.
21. The article of claim 9, wherein the article comprises
footwear.
22. The method of claim 18, wherein the article comprises
footwear.
23. The article of claim 9, wherein the article is selected from
the group consisting of mattresses, upholstery, bedding, bedsheets,
sheets, pillows, pillow cases, mattress and pads.
24. The method of claim 18, wherein the article is selected from
the group consisting of mattresses, upholstery, bedding, bedsheets,
sheets, pillows, pillow cases, mattress and pads.
25. The article of claim 9, wherein the low friction fibers can be
incorporated overall or in specific areas of the article.
26. The method of claim 18, wherein the low friction fibers can be
incorporated overall or in specific areas of the article.
27. The article of claims 9, wherein the low friction fibers can be
incorporated in a single layer or in multilayers.
28. The method of claim 18, wherein the low friction fibers can be
incorporated in a single layer or in multilayers.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to fibers having a low
coefficient of friction. More particularly, the invention provides
fibers formed from a combination of at least two or more materials,
such as a base polymer, such as polyethylene, and ultra-high
molecular weight silicone, wherein one of the materials has a low
coefficient of friction. Further, the invention is directed to a
method and process for manufacturing the fibers and articles made
therefrom.
[0002] Documents cited in the following text are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0003] Low-friction fibers, and products made therefrom, possess
commercially desirable properties. Not only do such materials have
beneficial wear characteristics for apparel, because of improved
sliding properties when in contact with the skin, they also achieve
higher performance through reduced frictional loss. Low-friction
fibers traditionally are produced by a number of methods. Such
methods include, for example, applying an external lubricant to a
finished product, coating the material with a low-friction polymer
layer, or adding inactive agents, such as spheroidal beads, during
the formulation of the material. Other methods include forming
multi-layer materials wherein one side has a low-friction
surface.
[0004] In the patent literature; there are various methods of
forming low-friction materials. For example, U.S. Pat. No.
4,138,524 relates to a method of forming an article with an
integral protective surface having a low coefficient of friction.
Low friction is achieved by inserting chemically inactive
spheroidal beads into a bonding material, wherein the density
differential allows the beads to migrate to form a low-friction
layer.
[0005] U.S. Pat. No. 4,996,094 relates to a thermoplastic stretch
wrap films with one cling layer and one slip layer. The cling
portion is made of low density polymers and the slip portion is
made of coextruded high density polyethylene resin.
[0006] U.S. Pat. No. 4,996,094 relates to a stretch wrap film
having one surface with cling properties and the other with
non-cling properties, one noncling property being a slip property
exhibited when the noncling surface is in contact with a like
surface of itself with relative motion therebetween having the
improvement which is comprised of positioning at least one region
between the cling and noncling surfaces of the film, said region
being of a material selected to provide barrier properties
sufficient to maintain the cling and noncling properties of the
cling and noncling surfaces. A high number average molecular weight
cling additive is used to reduce additive migration and
transfer.
[0007] U.S. Pat. No. 5,750,620 relates to a polymeric composition
including a blend of at least two different polymers selected from
the group consisting of polystyrene, polycarbonate, polyetherimide,
polyolefin, polysulphone, polyethersulphone, polyacetal, nylon,
polyester, polyphenylene sulphide, polyphenylene oxide and
polyetheretherketone and at least one elastomer having a tensile
modulus less than about 50,000 p.s.i. Alternatively or
additionally, the elastomer may be functionalized to graft with at
least one of the polymers. The present invention also provides a
method of making a tribological wear system by melt-mixing the
polymeric composition to improve the wear resistance of a polymeric
composite whose surface bears against another surface, thereby
causing friction and wear of the polymeric composite.
[0008] U.S. Pat. No. 6,093,482 relates to a carbon-carbon composite
for friction products comprises an outer friction part and a load
bearing structure part supporting the friction part. The friction
part contains a mixture of carbon fibers, pitch powder and graphite
powder, whereas the structure part is comprised of a pack of
alternating layers of the mixture and layers of one member selected
from the group consisting of carbon fabrics, carbon-based prepregs
and carbon-based, segmented prepregs. The carbon-carbon composite
is formed by way of alternatingly piling up layers of a mixture of
carbon fibers, pitch powder and graphite powder and layers of one
member selected from the group consisting of carbon fabrics,
carbon-based prepregs and carbon-based, segmented prepregs one
above the other to provide a preform, heating and pressing the
preform within a mold to obtain a green body, carbonizing the green
body to prepare a carbonized body, impregnating the carbonized body
with pitch powder and recarbonizing the impregnated body, and
subjecting the impregnated and recarbonized body to chemical vapor
infiltration with hydrocarbon gas.
[0009] U.S. Pat. No. 4,371,445 relates to a tribological system
with plastic/plastic pairings, especially sliding bearings, in
which plastics--optionally supported by lubricants--carry out
motions in sliding friction relative to one another and at least
one of the main sliding partners and/or auxiliary partner is a
plastic, containing polar, cyclic compounds, in which the cyclic
part of the molecule on at least one side is coupled directly to an
atom of Group V (especially nitrogen) or of Group VI (especially
oxygen and/or sulfur) of the Periodic System of the elements, or in
which the rings contain the atoms mentioned. Excellent sliding
conditions are obtained when the polar synthetic materials,
containing the cyclic compound(s), either are monovalent, cyclic
chain polymers or chain polymers in the form of polyheterocycles
("semi-ladder polymers") or chain polymers in the form of
monovalent polyheterocycles or fully cyclic chain polymers ("ladder
polymers") or homopolymers or copolymers or polymer mixtures within
the above groups or of these groups or with other molecules or
polymers and either both main polymers are polar and contain
different cyclic compounds, while the auxiliary sliding partner
however is nonpolar, or that both main sliding partners are
nonpolar, while the auxiliary sliding partner however is polar and
contains cyclic compounds.
[0010] U.S. Pat. No. 4,626,365 relates to a composition for sliding
parts, comprising 0.1 to 50 vol % in total of at least one selected
from the group (A) consisting of FEP, PFA, ETFE, PVDF, PCTFE and
EPE; 0.1 to 35 vol % of compound metal oxide; and the balance PTFE,
the total content of components other than PTFE ranging between 0.2
and 70 vol %. Such composition may further contain at least one of
metal oxide, metallic lubricant, metal sulfide, metal fluoride,
carbonic solid lubricant, fibrous material, ceramics.
[0011] U.S. Pat. No. 4,812,367 relates to a material for a
low-maintenance sliding surface bearing comprises a metallic
backing and on said backing a bearing layer comprising PVDF and an
additive for improving the friction and sliding properties. To meet
more stringent requirements regarding hygiene, the bearing layer is
free of lead and contains 0.5 to 3% by weight of a non-toxic metal
oxide power and 10 to 40% by weight of glass microspheres.
[0012] U.S. Pat. No. 4,847,135 relates to a composite material for
sliding surface bearings, a rough metallic surface is provided with
a polymeric matrix, which forms a friction contact or sliding layer
over the rough base surface. To increase the wear resistance, the
matrix contains zinc sulfide and/or barium sulfate in a particle
size from 0.1 to 1.0 .mu.m and an average particle size of 0.3
.mu.m.
[0013] U.S. Pat. No. 5,527,594 relates to optical tape comprising a
substrate having a center line average roughness on one side of
0.005 to 0.5 .mu.m and a tensile strength (F.sub.5) in the
longitudinal direction of not less than 8 kg/mm.sup.2, and an
optical recording layer formed on the other side of said
substrate.
[0014] U.S. Pat. No. 5,171,622 relates to a lacquer coating is
applied to a laminated metal composite forming a sliding element
such as a plane bearing and has particles of solid lubricants
incorporated therein to form islets of greater thicknesses than the
surrounding film and which serve as lubricant-trapping surface
formations. The particles may be of polytetrafluoroethylene,
fluorinated graphite or molybdenum disulfide and the lacquer is
preferably an epoxy resin-based lacquer.
[0015] U.S. Pat. No. 5,763,011 relates to a urethane-resin based
coating for reducing friction includes a urethane paint and a first
powder. The coating is to be applied to a shaped article which is
to be subjected to a heat treatment at a certain temperature after
the application of the coating to the shaped article. The first
powder has a melting point lower than the certain temperature and a
solubility parameter which is smaller than or larger than that of
the urethane paint by at least 0.5. The coating optionally further
includes a second powder which has a melting point higher than the
certain temperature. The coating provides the shaped article with
low friction, irrespective of the coating film's thickness
[0016] U.S. Pat. No. 5,866,647 relates to a polymeric based
composite bearing is injected molded of a thermoplastic material
reinforced with a high strength fiber and reinforcing beads.
Typically, the high strength fiber is selected from the group
consisting of aromatic polyamide fiber, high strength/high purity
glass fiber, carbon fiber, boron fiber, and metallic fibers. The
reinforcing spheres are selected from the group consisting of glass
beads, boron nitride beads, silicon carbide beads and silicon
nitride beads. The thermoplastic matrix material may consist of
polyamide, polyacetal, polyphenylene sulfide, polyester and
polyimide. Preferably, the composite bearing comprises between
about 5 to about 35 percent weight of the high strength fiber,
between about 5 to about 15 percent weight percent of the
reinforcing spheres, and between about 50 to about 90 weight
percent of the thermoplastic matrix material. The bearing may be
injection molded by blending the composite material, heating the
composite material to a temperature above its melting temperature,
injecting the composite material into a mold cavity, and demolding
the bearing after the temperature of the bearing drops
substantially below the melting temperature.
[0017] U.S. Pat. No. 3,781,205 relates to a composite bearing
comprising a backing member to which there is secured a
dimensionally stable bearing surface layer comprising a solid
lubricant selected from the group consisting of the sulfides,
selenides, and tellurides of molybdenum, tungsten, and titanium,
lead diiodine, boron nitride, carbon, graphite, and
polytetrafluoroethylene and fibers of a material characterized by a
heat distortion temperature exceeding that of
polytetrafluoroethylene and selected from the class consisting of
aromatic polyamides, carbon, graphite, aromatic polysulfones,
aromatic polyimides and aromatic polyester-imides.
[0018] U.S. Pat. No. 4,104,176 relates to a porous
lubricant-impregnated bearing comprising a matrix of closely
packed, discrete particles, such as glass microspheres, bonded
together with a bonding material that is different from the
particles, such as a cured organic bonding material, and that only
partially fills the interstices between the particles; and a
migratable lubricant dispersed in the unfilled interstices.
[0019] U.S. Pat. No. 5,080,969 relates to a composite friction
material for brakes comprising a main friction material containing
thermosetting resin as a binder, and a layer of high friction
material with a higher friction coefficient than said main friction
material for exhibiting a high braking power on initial
application, which high friction layer is provided on the surface
of said main friction material and contains a phenol resin of not
more than 5 wt. %.
[0020] U.S. Pat. No. 4,201,777 relates to a unitary carbonaceous
body consists of turbostratic carbon formed with a superficial
graphitized portion in situ, preferably by passing a high-amperage
electric current through this portion.
[0021] U.S. Pat. No. 3,980,570 relates to a sliding member having
anti-frictional and anti-static properties for a tape or film
cassette of an audio- or video-tape recorder or a movie projector,
comprising a thermoplastic resin containing 5 to 90% by weight of
carbon fiber, said member having less than 10.sup.8 ohms of surface
resistance and also having a coefficient of dynamic friction of
less than 0.2.
[0022] U.S. Pat. No. 5,082,512 relates to seizure resistance of
boronized sliding material improved by surface microstructure,
i.e., co-existence of the Fe.sub.2B phase and Fe.sub.3B phase.
[0023] U.S. Pat. No. 5,093,388 relates to a high friction brake
shoe formulation having a high static friction coefficient in shear
of about 1.5 and low adhesion to materials having microscopic pores
therein in contact with said brake shoe formulation which comprises
a mixture of about 75 phr of neoprene W rubber and about 25 phr of
neoprene WHV rubber; a first curing system comprising about 1 phr
of a fatty acid, about 5 phr of ZnO, and about 1-3 phr of MgO; and
a second curing system comprising about 1.25 phr of sulfur and
about 0.6 phr of a sulfur accelerator; together with about 50 phr
of a reinforcing agent of N555 or N650 carbon black.
[0024] U.S. Pat. No. 5,508,109 relates to a fiber blend for use in
friction materials. The fiber contains a blend of a highly
fibrillated fiber, such as a fibrillated polyacrylonitrile fiber
and a fiber with a high carbon content, such as an oxidized carbon
fiber precursor.
[0025] U.S. Pat. No. 5,811,042 relates to a composite friction or
gasketting material is disclosed having a combination of thermoset
or thermo-plastic matrix resin, fiber reinforcing material, and
aramid particles. The composite material exhibits improved wear
resistance when compared with materials having no aramid
particles.
[0026] U.S. Pat. No. 5,889,080 relates to a method for making a dry
blend for use in the preparation of a friction material, a dry
blend per se and dry friction materials is disclosed wherein the
components thereof include a) fibrillated, organic, synthetic
polymer, b) organic, synthetic polymer staple and c) organic,
synthetic soluble polymer particles.
[0027] It would be desirable to combine two or more components,
wherein one of the components is a polymeric component and the
other is a low friction component, to form a fiber imparted with a
low coefficient of friction characteristic of a non-temporary
nature.
OBJECTS AND SUMMARY OF THE INVENTION
[0028] An object of the present invention is to provide a novel
fiber having low coefficient of friction characteristics. It is a
further object of the present invention to provide a fiber wherein
the low coefficient of friction characteristics are permanent. It
is yet another object of the present invention to provide articles
possessing low coefficients of friction including apparel,
bandages, bedding, footwear and accessories.
[0029] In accordance with the present invention, a low friction
fiber is provided comprising a polymeric component and a low
friction component, wherein the polymeric component is combined
with the low friction component, thereby imparting onto the fiber a
low coefficient of friction characteristic which is of a
non-temporary nature.
[0030] Further, and in accordance with the present invention,
methods and/or processes of forming a low friction fiber is
provided including precompounding; utilizing low friction
particles; coating; and extrusion.
[0031] Still further, and in accordance with the present invention,
there is provided a method of reducing the coefficient of friction
in an article which comprises incorporating a low friction fiber
comprising a polymeric component and a low friction component,
wherein the polymeric component is combined with the low friction
component, thereby imparting onto the fiber a low coefficient of
friction characteristic which is of a non-temporary nature, into an
article
[0032] It is apparent that the fibers of the present invention, and
the articles made therefrom, have the advantages of, for example,
low coefficients of friction, shock absorption, thermal stability,
soil repellency, water repellency, oil repellency, acid repellency,
low cost and ease of manufacturing into articles. Another advantage
of the fibers of the present invention, and the articles made
therefrom, is the avoidance or minimization of the development of
irritations, blisters and calluses.
[0033] In this disclosure, "comprises", "comprising", and the like
can have the meaning ascribed to them in U.S. Patent Law and can
mean "includes", "including", and the like. These and other objects
and embodiments of the invention are provided in, or are obvious
from, the following detailed description.
DETAILED DESCRIPTION
[0034] The present invention provides a low-friction fiber, its
methods and process for making it, and articles made therefrom. The
fiber is comprised of at least one polymeric component and at least
one low friction component, wherein the low friction component,
when combined with the polymeric component, imparts a low
coefficient of friction characteristic onto the fiber. The present
invention also provides for a method of reducing the coefficient of
friction of a fiber comprising the steps of combining a polymeric
component and a low friction component; and forming a fiber from
the combination of the polymeric component and the low friction
component. It will be understood that the low coefficient
characteristic is of a non-temporary nature, such as a permanent or
lasting nature. An example of a low friction component is ultra
high molecular weight silicone, which is environmentally friendly
and degrades into sand.
[0035] The fiber of the present invention achieves a low
coefficient of friction through the use of at least one polymeric
component and at least one low friction component. Such a polymeric
component may include, but is not limited to, polyester, nylon,
acrylics, aramids, polyethylene, polyurethaene and plastic
copolymers. The concentration of the polymeric component is
typically comprises 30% by weight of the total fiber; preferably
from about 70-97% by weight of the total fiber most preferably from
about 80-95% by weight of the total fiber. Suppliers of the
polymeric component include, for example, DuPont, Nilestar, Wellman
and Foss. One of ordinary skill in the art would understand in
light of the present disclosure that more than one polymeric
component may be used, such as, for example, a blend of two, three
or four different polymeric components may be used.
[0036] Examples of the low friction component includes, but is not
limited to, fluorocarbon polymers (e.g., polytetrafluroethylene
(PTFE), polymers of chlorotrifluoroethylene, fluorinated
ethylenepropylene polymers, polyvinylidene fluoride,
hexafluoropropylene, etc.) boron, molybdenum sulfide, ultrahigh
molecular weight silicone, siloxane, fluoroesters (e.g.,
FLUOROPLENE.RTM.), fluorinated ethylene propylene copolymers (FEP),
perfluoroelastomers (e.g., Viton.TM., etc.), polychloro,
trifluoroethylene homo- and copolymers (e.g., Aclar.TM., etc.),
silicone/silane modified polymers, graphite, fluorinated high
molecular weight polyolefins or cyclic organic compounds,
non-modified polyolefins, or other fluoropolymers (e.g.,
HALAR.TM.). The concentration of the low friction component
typically comprises about 70% by weight of the total fiber;
preferably from about 5.0 to about 30% by weight of the total
fiber; most preferably from about 3.0 to about 20% by weight of the
total fiber, even more preferably from about 0.2 to about 1.0% by
weight. Suppliers of the low friction component include, for
example, DuPont, Dow Corning, Ausimont and General Electric.
[0037] The low friction component may exist in the form of, but not
limited to pelletized spheroidal beads, fibers or powders. A
preferred low friction component includes ultrahigh molecular
weight silicone, such as SILOXINE.RTM. manufactured by Dow
Chemical. Other preferred low friction components include
FLUOROPLENE.RTM. manufactured by Peach State Labs, and
FIBERFILL.RTM. manufactured by DuPont as a TEFLON.RTM.-coated
staple product.
[0038] The preferred low friction component FLUOROPLENE.RTM. is a
fluorocarbon ester and may be compounded or master batched into,
inter alia, chip additives or directly fed via injection ports on
an extruder. One advantage of using FLUOROPLENE.RTM. is that it
adds hydrophobic and oleophobic properties to extruded polymers.
Another advantage is that FLUOROPLENE.RTM. has a thermal
decomposition temperature range of from about 220.degree. C. to
280.degree. C. A still further advantage of using
FLUOROPLENE.RTM.is that it is biodegradable.
[0039] One of ordinary skill in the art would understand that more
than one low friction component may be used, such as, for example,
a blend of two, three or four different low friction materials. It
is to be understood that the present invention has a broad spectrum
of utility, for example, the present invention can be used for, but
not limited to, apparel, apparel accessories, bedding, bandages,
bed sheets, footwear, footwear accessories, hospital gear,
domestics, mattresses and upholstery.
[0040] It is further envisioned that other materials may be blended
with other components such as, for example, flame retardants,
antimicrobials, and anti-static agent that impart improved physical
properties such as, for example, high-temperature resistance,
increased melt temperature, increased workability, efficient
thermal characteristics, and deformation-resistance.
[0041] The fibers of the present invention, which are made from one
or more low coefficient of friction materials, are more cost
effective than standard low coefficient of friction filaments and
staple. This is because only a percentage of the invention's fibers
contain low coefficient of friction material, while many of the
standard low coefficient of friction filaments, such as
TEFLON.RTM., and staple completely comprise low coefficient of
friction materials. Since low coefficient of friction material is a
premium product and the fibers of the invention contain less such
material than the standard low coefficient of friction filaments
and staple, the fibers of the invention are relatively cheaper than
the standard low coefficient of friction filaments and staple.
[0042] There are several methods by which the polymeric and low
friction components can be combined. One such method involves
precompounding the polymeric component with the low friction
material wherein the precompounded polymeric component melts and
becomes bonded with the low friction material. Another such method
involves utilizing low friction particles such as TEFLON.RTM. beads
that are blended with the polymeric component. A further method is
coating the low friction component permanently onto the surface of
the polymeric component. A still further method includes extrusion
whereby the low friction component is extruded into the polymeric
component. Another method includes spray coating or mechanical
dipping. Still another method includes sheath and core.
[0043] Once the polymeric and low friction components are combined,
the fiber in accordance with the present invention may be made
according to several known methods. Such methods include, for
example, extrusion; sheath and core; and slicing fibers that are
formed in a thin film. The fibers may be formed into mono- or
multifibers or into staple fibers, with a denier of from about 0.5
to about 1500. Further, once the fibers are formed, they may be
made into articles by spinning, weaving, stitch non-weaving,
spun-bond and/or melt-blown. The fibers are imparted with a
coefficient of friction of about 0.22 to about 0.005; preferably
from about 0.15 to about 0.01; most preferably from about 0.01 to
about 0.005.
EXAMPLES
[0044] The following examples are set forth to illustrate examples
of embodiments in accordance with the invention, it is by no way
limiting nor do these examples impose a limitation on the present
invention.
Example 1
Methods of Combining Polymeric and Low Friction Components
[0045] A) Blending:
[0046] Blending normally refers to the ambient temperature mixing
of all or some of the ingredients of the pre-compounded or
post-compounded formulation ingredients. Blending usually, but not
always, involves materials of similar physical size. In special
cases, blending refers to the intensive paddle mixing of powders
and sprayed liquids.
[0047] In the manufacture of articles using the present invention,
either or both of pre-compounding blending or post-compounding
blending may be used. Pre-compounding blending is the process used
to mix some or all of the formulation components prior to melt
compounding and is typically conducted at ambient or reduced
temperatures. The need and/or desirability for pre-compounding
blending depends upon a number factors. Among these are:
[0048] a) The specific type of melt compounding or extrusion
equipment to be used in the process;
[0049] b) The capability of the feed equipment, for the melt
processing of the formulation, to handle liquids, powders, pellets,
and other types of physical forms;
[0050] c) Specific appearance and/or performance attributes desired
in the finished fiber;
[0051] d) The relative economic impact on production of
pre-compounding blending, in-line compounding/extrusion and
post-compounding blending.
[0052] Post-compounding blending is the process of non-melt mixing
of the compounded, pelletized or granulated formulation. This type
of blending is often used to combine two or more compounded batches
of material to achieve a larger finished batch having more uniform
properties. Post-compounding blending may also be used to add one
or more additives to the pelletized material prior to extrusion.
For example, a non-pigmented batch of the low friction formulation
may be compounded and extruded. After pelletization, the
non-pigmented pellets may be post-compounded blended with
appropriate pelletized additives (color, UV absorber, antioxidant,
flame retardant, plasticizer or impact modifier, etc.). This
technique results in a uniform, pelletized batch of material ready
for extrusion. It is often used when the additives have
questionable thermal stability or specific visual, or performance
attributes are required in the fiber.
[0053] Equipment typically used in pre-compounding blending
includes, but is not limited to:
[0054] 1. Henshel, ribbon and other similar mixers, designed for
the blending of powders;
[0055] 2. Barrel, drum, barrel or cement and similar types of
mixers designed for mixing pellets;
[0056] 3. Specialized mixers designed to coat powders and/or
pellets with liquids;
[0057] 4. Ball Mills and similar types of mixers designed to grind
and mix either simultaneously or sequentially.
[0058] 5. Littleford mixers and similar designed paddle mixers
designed for blending powders, granules, pellets and friable
particulates.
[0059] Equipment typically used in post-compounding blending
includes, but is not limited to:
[0060] 1. Any of those used for pre-compounding blending;
[0061] 2. Silo and other similar blenders designed for homogenizing
large volumes of compacted or densified particulates;
[0062] 3. Fluidized bed and other similar mixers designed to use
high velocity gaseous streams to homogenize materials and/or remove
or segregate materials having different bulk densities.
[0063] B. Compounding
[0064] Compounding is the melt mixing or homogenization of one or
more of the major components of the fiber component materials. The
compounding equipment may consist of any one or more of the
following:
[0065] i. Single or twin screw extruders, in which the appropriate
ingredients are added to the rear end of the extruder. The
combination of:
[0066] a. Heat, from the barrel and/or extruder screw(s),
[0067] b. Shear heat, due to mixing of the ingredients,
[0068] c. Frictional/compressive heat, generated by rubbing of the
materials against the interior extruder barrel and compression
between the barrel wall and extruder screw,
[0069] cause a reduction of viscosity of the total mass. In some
cases, additional materials may be added at other locations along
the barrel between the initial entry port of the raw materials and
the exit die.
[0070] ii. Continuous mixers, in which one or more screws, or screw
elements, continuously transport, compress and shear the materials
to reduce their viscosity and improve the homogeneity of the mass.
Continuous mixers may also contain disks or taper rotors and/or
barrels. The continuous mixer may exit the molten mass through a
die or other discharge port.
[0071] iii. Batch mixers, in which the ingredients are added to a
chamber that contains blades, paddles or rotors. The chamber is
then closed and the revolving devices within it begin to rotate.
The combination of shear heat generated by these devices and
external heat supplied from the heated walls of the mixer, reduce
the viscosity and increase homogenization of the contained
materials. When the compounding is complete, the chamber opens in a
manner to allow its fluxed contents to drop onto, or into another
device to define the size and shape of the molten mass. The mass
may be shaped into pellets, slabs, rods or other convenient shapes
by this secondary device.
[0072] C) Coating:
[0073] Practice of the present invention may include coating of one
or more of the starting raw materials, as described above, and/or
coating of the pre-spun extrudate and/or coating of the finished
fiber. The coating processes may include:
[0074] i. Coextrusion, in which the coating is extruded on one or
more sides of the base fiber, or in a manner to completely surround
the outer surface of the base fiber. Coextrusion also includes the
extrusion of the fiber through a die immediately followed by
intimate contact with the coating material as the coating liquid
emerges from another portion of the same die or another die
adjacent to, or surrounding the primary fiber die.
[0075] ii. Physical dipping, where the base fiber is dipped into,
or pulled through a container which contains a liquid form of the
coating. The liquid form of the coating includes coating solutions,
emulsions, dispersions, gels or suspensions.
[0076] iii. Spraying, where the coating, either particulate or
liquid, impinges upon the fiber surface in an environment designed
to cause adhesion to, entanglement with, or encapsulation of the
base fiber.
[0077] iv. Plasma or vapor deposition, where the fiber passes
through an environment in which an electric discharge, and/or
radiation cause the coating molecules or atoms, also in the
environment, to adhere and/or chemically bond to the base fiber.
The bonding process may be accompanied by chemical reaction among
the coating molecules or atoms.
[0078] v. Surface molecular polymerization, a process in which one
or more types of reactive molecules and/or atoms are introduced
into a chamber containing the fibers. Such reactive species
polymerize and/or chemically react with the fiber surface. External
energy sources may or may not be required. An example of surface
molecular polymerization in the present invention is the
introduction of parylene into a chamber containing polyester and/or
other fibers. The resulting parylene coated fibers have a lower COF
and are more chemically inert than their non-coated precursors.
[0079] It is understood that in any of the above examples,
catalysts and/or co-reactants may also be used. The present
invention also includes the coating of the finished fiber after its
inclusion into a woven or non-woven fabric.
[0080] D. Extrusion
[0081] In extrusion, either a:
[0082] i. Pre-compounded blend,
[0083] ii. Compounded blend, or
[0084] iii. Post-compounded blend,
[0085] as described above, of the base polymeric component(s) and
the low friction component(s), where said low friction component(s)
may also consist of a:
[0086] iv. Pre-compounded blend,
[0087] v. Compounded blend, or
[0088] vi. Post-compounded blend,
[0089] are melted, or subjected to a sufficient reduction in their
viscosities, such that they can be pushed or pumped through the
extruder cylinder or chamber and through one or more dies. The
die(s) may have one or more nozzles and may be stationary or
rotating. The extruder may have a single screw, two or more screws
or one or more rotating or stationary disks to facilitate the
viscosity reduction of the polymeric materials, melting or
softening of any additional materials in the feed stream and
pumping the mass to the die(s). In addition to typical extruders,
devices know as continuous mixers may also be used in this
operation. Typically, the extrudate will consist of fibers in which
the low friction component congregates on the exterior fiber
surface and the base polymer occupies the interior of the fiber. In
cases where the fiber is coextruded, the base fiber component exits
from the extruder die and is immediately encapsulated by, or
adhered to, the low friction component, which emerges from another
die, concentric or adjacent to, the base fiber die.
[0090] Typically, fibers have diameters from less than 0.004 mm
(0.00015") to 0.2 mm (0.008"). Fibers may be produced in many
forms: continuous single fibers (monofiber), short fibers (staple
or chopped), untwisted bundles of continuous fibers (tow), twisted
bundles of continuous fibers (yarn), etc.
Example 2
Methods of Forming Fiber
[0091] A. Spinning:
[0092] Spinning is the process by which a molten, viscous mass is
extruded, drawn or pulled to form a fiber. The drawing may include
twisting the fiber into yarn or thread. There are three forms of
spinning commonly used, and a fourth specialty process occasionally
used for specialty fiber production:
[0093] 1. Melt Spinning in which the polymer is melted and pumped
through a spinneret with numerous holes (one to thousands). The
molten fibers are cooled, solidified, and collected on a take-up
wheel. Stretching of the fibers in both the molten and solid states
provides for machine direction orientation of the polymer chains
along the fiber axis. Polymers such as PET, polyamides (nylon),
polyolefins, and polyvinylidene chloride are produced this way.
Melt spun fibers are readily amenable to the low friction fiber
production and are the preferred materials, considering
cost/performance attributes.
[0094] 2. Wet Spinning is used for fiber forming materials that
have been dissolved in a solvent or suspended in an emulsion. The
dissolved polymer is extruded and pumped through spinnerets whose
exit points are below the surface of a liquid chemical. As the
extruded fibers emerge from the spinneret, the liquid chemicals
cause the dissolved fiber to precipitate out of solution and form
solid fibers. Wet spun low friction fibers can also be produced. In
practice of the present invention, it is preferable to coat the wet
spun fiber after fibrillation, rather than to simultaneously wet
spin a liquid dispersion or emulsion of the base fiber polymer and
the low friction component.
[0095] 3. Dry spinning is also used to form polymeric fibers from
solution. The polymer is dissolved in a volatile solvent and the
solution is pumped through a spinneret. As the fibers exit the
spinneret, air is used to evaporate the solvent. The fibers
solidify and can be collected on a take-up wheel. Stretching the
fibers provides for machine direction orientation of the polymer
chains along the fiber axis. In practicing the present invention,
dry spun fibers are preferably coated with the low friction
component rather than dry spinning a dispersion or emulsion of the
base fiber polymer and low friction component.
[0096] 4. Gel Spinning, specialty process, is used to produce high
strength and other specialty fibers. The base polymer is in a gel
state, not in solution during extrusion. The high polymer
concentration per unit volume of gel results in high polymer
entanglement during extrusion. The resulting fibers have very high
tensile strength in the machine direction due to shear alignment
and orientation. In the practice of the present invention, gel spun
fibers are preferably coated with the low friction component after
fibrillation, rather than gel spinning a viscous gel blend of the
base fiber polymer and low friction component.
[0097] An example of the manufacture of the low coefficient of
friction fiber of the present invention is given below:
[0098] The low COF component may consist of an ultra-high molecular
weight polysiloxane. This material may be pre-compounded, using one
or more of the types of compounding equipment described above, or
similar compounding devices, with the base fiber polymer and/or a
polymeric binder which is compatible with the base fiber material.
The pre-compounded blend is pelletized or shaped into some other
physical form, that will be readily handled in other equipment to
be used in the process. It is understood that other low COF
materials may be used in place of, or in addition to, polysiloxane.
Such other low COF materials may include, but are not limited to,
FLUOROPLENE.TM., fluorinated ethylene propylene copolymers (FEP),
particulate polytetrafluoroethylene (PTFE), perfluoroelastomers
(ex. Viton, etc.), polychloro, trifluoroethylene homo- and
copolymers (ex Aclar, etc.).
[0099] The pelletized, low COF blend and pellets of the base
polymer are introduced into an extruder, as described above.
Additional materials, such as pigment masterbatches, UV absorber
and/or antioxidant master batches, monomeric and/or polymeric
plasticizers or impact modifiers may also be added to the
extruder.
[0100] The extruder die consists of one or more spinnerets. A
spinneret is a die with one or more (1000+) small holes. Melt
spinning is the preferred method of manufacture for polymeric
fibers. The molten polymer is pumped through the spinneret. The
molten fibers are cooled, solidified, and collected on a take-up
wheel.
[0101] Stretching of the fibers in both the molten and solid states
provides for machine direction orientation of the polymer chains
along the fiber axis. Polymers such as polyethylene terephthalate
(PET), polypropylene (PP) and nylon (PA) 6,6 are examples of melt
spun fibers.
[0102] B. Fiber Geometry and Construction
[0103] For each of the spinning techniques, described above, a
variety of fiber shapes may be produced. Finished fiber shape may
be determined by: 1) shape of the spinneret holes through which the
fiber passes; 2) composition of the fiber material; 3) shrinkage of
the fiber components affects finished fiber shape; 4) inclusion of
blowing agents in the composition may also affect finished fiber
shape; 5) spinning technique employed.
[0104] Among the above spinning techniques, melt spinning allows
the greatest control of fiber geometry and shape. Wet, dry and gel
spinning, offer less precise control of finished fiber shape due to
the presence of solvents that must be removed during and after the
spinning process.
[0105] Low COF fibers may be produced using each of the above
spinning processes. Bipolar, triangular, oval, rectangular and
several other shapes may be produced. For gel, wet and dry
spinning, coating of the finished fiber by the low friction
component(s) is preferred. Such coatings may be applied to any of
the possible fiber shapes. Depending upon finished fiber geometry,
such coated fibers may have lower or higher coefficients of
friction (COF) than typical circular fibers. Shaped low friction
fibers allow the possibility of less surface area contact between
the low friction surface and external surfaces. Rectangular shaped
low friction fibers may have higher COF's than circular ones due to
greater surface area contact with external surfaces.
[0106] The effective COF of low friction fibers is also affected by
the modulus or stiffness of the base fiber. Stiffer or higher
modulus base fibers usually have lower COF's than softer or low
modulus base fibers. This is due to the greater compressibility of
lower modulus fibers. Such compression of the fiber surface
increases the area of contact between the low friction surface and
external surfaces.
[0107] Low friction fibers of the present invention may have a
sheath/core construction in which the sheath is usually the low
friction component and the core is the base polymeric component.
The economic advantage of this type of construction is that the low
friction component is often the more costly component. As the
sheath, surrounding the core, a thin layer of the low friction
component is required to perform its intended function.
Additionally, the sheath, located on the outside of the core,
presents a low COF surface to the outside world. Gauge of the low
friction sheath layer may be increased, if required, to further
enhance specific fiber properties and/or performance attributes. It
should be noted that, if required, the low friction component may
be produced as the core, with the higher friction component as the
sheath. This type of structure is useful for those applications
that require an initial high COF surface that is abraded over time
to yield a low COF fiber surface.
[0108] A skilled artisan would readily understand that with any
fiber geometry, the low friction component may be affixed to only a
portion of the base fiber surface. Both coating and coextrusion
processes are capable of achieving such constructions.
Constructions having the low friction component on only a portion
of the fiber surface offer advantages in selected types of fiber
applications:
[0109] a) Side-by Side Structures: Shrinkage of the low friction
component is usually less than that of the base fiber, due to the
greater crystallinity achieved by the base fiber during spinning.
Side-by-side fibers of this type will have a natural tendency to
curl, resulting in an increase in their bulk volume. This increase
in volume, with no change in weight, results in a fiber having
enhanced softness. The curled fibers have a greater tendency to
entangle resulting in increased resistance to fiber separation in
woven and non-woven fabrics. Such curled fibers, having a large
volume compared to their weight, may also be useful in thermal and
acoustical insulation applications.
[0110] b) Spun Bonded Structures: With the low friction component
on only a portion of the base fiber surface, fabrics which are spun
bonded, yield improved softness ("hand") and increased resistance
to fiber separation. These are due to the increase in structure
volume, as described above, and enhanced bonding between fibers due
to the ability of the base fiber polymer to melt bond to bond to
itself. This ability is generally increased since the low friction
component usually contains fluoropolymer or siloxane entities,
which have high softening temperatures, and are amorphous, having
no sharply defined melting point. During the spin bonding process,
the low friction component generates less frictional heat and
experiences less viscosity decrease than the base fiber polymer.
This yields more interfiber bonding between the base fiber polymer
segments with itself. The net result is a spun bonded structure
having a lower bulk density, greater "softness" and stronger
interfiber bonds.
[0111] C. Continuous & Staple Fibers
[0112] Continuous fibers are those consisting of long, unbroken
lengths of fiber. Fiber produced using the technology of the
present invention may be of the continuous fiber variety.
Continuous fiber is often cut into shorter lengths called staple.
Staple fibers are easier to work with than continuous fibers due to
their shorter lengths. The present invention can be utilized in
both continuous and staple forms. Typically, staple fiber is used
in blends with other fibers. Their short lengths simplifies the
fiber blending process. Blending of fibers is done to enhance the
performance of the resulting garment. Low COF staple blend more
readily than typical staple fibers due to their low COF surfaces.
Such surfaces reduce surface-to-surface friction and permit the
formation of homogeneous blends more rapidly than conventional
fibers.
[0113] Fibers are often aligned and twisted together to form thread
or yarn. Fibers of the present invention are usually easier to
twist with other fibers due to their low COF surfaces. Thread and
yarn made with fibers of the present invention are often easier to
use than conventional thread and yarn. The low COF components of
such threads and yarns often reduce the drag forces encountered in
sewing. The thread having low COF components pulls through fabric
more easily than threads that don't contain such low COF
components. This is a major benefit to those who have difficulty
sewing because of problems pulling the thread through the fabric.
Knitting with yarn that contains low COF fibers is similarly
improved.
Example 3
Articles
[0114] A) In one embodiment, low friction socks or hosiery can be
produced incorporating low friction fibers of the invention overall
or in specific areas, for example, high contact areas such as in
the heel area.
[0115] B) In another embodiment, apparel, such as clothing, gloves,
shirts, and hospital gear, can have low friction fibers of the
invention overall or in specific areas. Further, the low friction
fiber may be incorporated in either a single layer or in
multilayers.
[0116] C) The low friction fibers can also be used in bandages and
wraps which support torn and sore muscles, ligaments and joints and
as linings for casts. The low friction fibers can be incorporated
overall or in specific areas. Further, the low friction fiber may
be incorporated in a single layer or in multilayers.
[0117] D) The low friction fibers can be incorporated into
footwear, footwear inserts, and accessories, that will help avoid
blisters and callouses by reducing friction. The low friction
fibers can be incorporated overall or in specific areas. Further,
the low friction fiber may be incorporated in a single layer or in
multilayers.
[0118] E) The low friction fibers can be incorporated into
mattresses, upholstery, bedding, bedsheets, sheets, pillows, pillow
cases, mattress pads, for domestic, medical or commercial use. The
low friction fibers can be incorporated overall or in specific
areas. Further, the low friction fiber may be incorporated in a
single layer or in multilayers.
[0119] F) The low friction fibers can be incorporated into sporting
apparel, sporting equipment and accessories. The low friction
fibers can be incorporated overall or in specific areas. Further,
the low friction fiber may be incorporated in a single layer or in
multilayers.
[0120] It is also understood that the invention is not limited to
the detailed description of the invention, which may be modified
without departure from the accompany claims.
* * * * *