U.S. patent application number 10/668491 was filed with the patent office on 2005-02-10 for surface-modified plexifilamentary structures, and compositions therefor.
Invention is credited to Dee, Gregory T., Rodriguez-Parada, Jose Manuel, Weinberg, Mark Gary.
Application Number | 20050029695 10/668491 |
Document ID | / |
Family ID | 32043231 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050029695 |
Kind Code |
A1 |
Weinberg, Mark Gary ; et
al. |
February 10, 2005 |
Surface-modified plexifilamentary structures, and compositions
therefor
Abstract
The present invention is concerned with flash-spinning a
surface-modified structure such as a plexifilimentary yarn or a
microcellular foam.
Inventors: |
Weinberg, Mark Gary;
(Wilmington, DE) ; Dee, Gregory T.; (Wilmington,
DE) ; Rodriguez-Parada, Jose Manuel; (Hockessin,
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: |
32043231 |
Appl. No.: |
10/668491 |
Filed: |
September 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60413315 |
Sep 25, 2002 |
|
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Current U.S.
Class: |
264/51 ; 264/205;
521/50 |
Current CPC
Class: |
C08L 67/02 20130101;
C08L 67/02 20130101; Y10T 428/2978 20150115; C08L 23/0892 20130101;
D01D 5/11 20130101; Y10T 428/2915 20150115; C08L 23/0884 20130101;
D01F 6/46 20130101; D01F 6/92 20130101; Y10T 428/2913 20150115;
Y10T 428/2973 20150115; C08L 23/0892 20130101; C08L 23/0884
20130101; C08L 2666/18 20130101; C08L 2666/06 20130101; C08L
2666/18 20130101; D04H 1/724 20130101 |
Class at
Publication: |
264/051 ;
521/050; 264/205 |
International
Class: |
D01F 006/00 |
Claims
What is claimed is:
1. A process for flash spinning comprising (a) forming a spin
mixture that comprises a spin agent and a polymer mixture, (b)
pressurizing the spin mixture to a first pressure that is greater
than the autogenous pressure thereof, and (c) extruding the spin
mixture through an aperture into a region at a pressure that is
less than the autogenous pressure of the spin mixture, and at a
temperature such that the spin agent vaporizes upon exposure to the
region, to form a flash-spun structure; wherein the polymer mixture
comprises 0 to 95% by weight of a first polymer and 5 to 100% by
weight of a second polymer; wherein the first polymer is selected
from the group consisting of polyolefins, copolymers thereof with
ethylenically unsaturated monomers, polyesters, and mixtures
thereof; and wherein the second polymer is selected from the group
consisting of polyolefins, copolymers thereof with ethylenically
unsaturated monomers, polyesters, and mixtures thereof, and the
second polymer comprises 1 to 25 mol % of pendant functional
groups.
2. The process of claim 1 further comprising subjecting the
pressurized spin mixture to a second pressure that is less than the
first pressure but is greater than the autogenous pressure of the
spin mixture prior to extruding the mixture into the region.
3. The process of claim 1 or claim 2 wherein forming the flash spun
structure comprises forming a plexifilamentary yarn.
4. The process of claim 1 or claim 2 wherein forming the flash spun
structure comprises forming a microcellular foam.
5. The process of claim 1 or claim 2 wherein the polymer mixture
comprises 70 to 95 percent by weight of the first polymer and 30 to
5 percent by weight of the second polymer.
6. The process of claim 1 or claim 2 wherein the first polymer is
polyethylene terephthalate.
7. The process of claim 1 or claim 2 wherein the first polymer is
polyethylene.
8. The process of claim 1 or claim 2 wherein the second polymer is
polyethylene terephthalate.
9. The process of claim 1 or claim 2 wherein the second polymer is
polyethylene.
10. The process of claim 1 or claim 2 wherein the pendant group is
a fluoro-olefin radical.
11. The process of claim 8 wherein the second polymer is
polyethylene terephthalate grafted with fluoro-olefin radical.
12. The process of claim 9 wherein the second polymer is
polyethylene grafted with fluoro-olefin radical.
13. The process of claim 1 or claim 2 wherein the pendant group is
oxyethylene trimer.
14. The process of claim 8 wherein the second polymer is
polyethylene terephthalate grafted with oxyethylene trimer.
15. The process of claim 9 wherein the second polymer is
polyethylene grafted oxyethylene trimer.
16. The process of claim 1 or claim 2 wherein the pendant group is
a perfluorovinyl ether.
17. The process of claim 8 wherein the second polymer is
polyethylene terephthalate grafted with perfluorovinyl ether.
18. The process of claim 9 wherein the second polymer is
polyethylene grafted perfluorovinyl ether.
19. The process of claim 1 or claim 2 wherein the pendant group is
a vinyl silane.
20. The process of claim 8 wherein the second polymer is
polyethylene terephthalate grafted with vinyl silane.
21. The process of claim 9 wherein the second polymer is
polyethylene grafted vinyl silane.
22. The process of claim 1 or claim 2 further comprising adjusting
the first pressure to an amount that is greater than the cloud
point pressure of any individual polymer in the spin mixture.
23. The process of claim 1 or claim 2 further comprising heating
the flash-spun structure thereby formed to a temperature of at
least 100.degree. C.
24. The process of claim 3 further comprising heating the
plexifilimentary yarn thereby formed to a temperature of at least
100.degree. C.
25. A process for flash spinning comprising (a) forming a spin
mixture that comprises a spin agent selected from the group
consisting of aliphatic hydrocarbons, fluorocarbons, halogenated
hydrocarbons, and hydrofluorocarbons, and a polymer mixture, (b)
pressurizing the spin mixture to a first pressure that is greater
than the autogenous pressure thereof, (c) subjecting the
pressurized spin mixture to a second pressure that is less than the
first pressure but is greater than the autogenous pressure of the
spin mixture, and (d) extruding the spin mixture through an
aperture into a region at a third pressure that is less than the
autogenous pressure of the spin mixture, and at a temperature such
that the spin agent vaporizes upon exposure to the region, to form
a flash-spun structure; wherein the polymer mixture comprises 70 to
95 percent by weight of a first polymer and 5 to 30 percent by
weight of a second polymer; wherein the first polymer is
polyethylene or polyethylene terephthalate; and wherein the second
polymer is polyethylene or polyethylene terephthalate, and the
second polymer comprises 5 to 15 mol % of pendant fluorocarbon
radicals or oxyethylene radicals.
26. The process of claim 25 wherein the second polymer is grafted
with 5 to 15 mol % fluorocarbon radicals.
27. The process of claim 25 wherein the second polymer is grafted
with 5 to 15 mol % oxyethylene radicals.
28. The process of claim 25 further comprising heating the
flash-spun structure thereby formed to a temperature of at least
100.degree. C.
29. A spin mixture comprising a spin agent and a polymer mixture
comprising 0 to 95% by weight of polyethylene or polyethylene
terephthalate and 5 to 100% by weight of a functional polymer the
functional polymer being polyethylene or polyethylene terephthalate
having 1 to 25 mol % of pendant functional groups selected from the
group consisting of fluorocarbon radicals and oxyethylene
radicals.
30. A spin mixture comprising a spin agent and a polymer mixture,
wherein the polymer mixture comprises 0 to 95% by weight of a first
polymer and 5 to 100% by weight of a second polymer; wherein the
first polymer is selected from the group consisting of polyolefins,
copolymers thereof with ethylenically unsaturated monomers,
polyesters, and mixtures thereof; and wherein the second polymer is
selected from the group consisting of polyolefins, copolymers
thereof with ethylenically unsaturated monomers, polyesters, and
mixtures thereof, and the second polymer comprises 1 to 25 mol % of
pendant functional groups.
31. The spin mixture of claim 30 wherein the spin agent is selected
from the group consisting of aliphatic hydrocarbons, fluorocarbons,
halogenated hydrocarbons, and hydrofluorocarbons
32. The spin mixture of claim 30 wherein the polymer mixture
comprises 70 to 95 percent by weight of the first polymer and 30 to
5 percent by weight of the second polymer.
33. The spin mixture of claim 30 wherein the first polymer is
polyethylene terephthalate.
34. The spin mixture of claim 30 wherein the first polymer is
polyethylene.
35. The spin mixture of claim 30 wherein the second polymer is
polyethylene terephthalate.
36. The spin mixture of claim 30 wherein the second polymer is
polyethylene.
37. The spin mixture of claim 30 wherein the pendant group is a
fluoro-olefin radical.
38. The spin mixture of claim 30 wherein the second polymer is
grafted with fluoro-olefin radical.
39. The spin mixture of claim 30 wherein the pendant group is
oxyethylene trimer.
40. The spin mixture of claim 30 wherein the second polymer is
grafted with oxyethylene trimer.
41. The spin mixture of claim 30 wherein the pendant group is a
perfluorovinyl ether.
42. The spin mixture of claim 30 wherein the second polymer is
grafted with perfluorovinyl ether.
43. The spin mixture of claim 30 wherein the pendant group is a
vinyl silane.
44. The spin mixture of claim 30 wherein the second polymer is
grafted with vinyl silane.
45. The spin mixture of claim 30 wherein the second polymer
comprises 5 to 15 mol % of pendant functional groups.
46. The spin mixture of claim 30 formed as a plexifilamentary
yarn.
47. The spin mixture of claim 30 formed as a microcellular
foam.
48. The spin mixture of claim 30 formed as a non-woven fabric.
49. The plexifilimentary yarn of claim 46 formed as a non-woven
fabric.
Description
FIELD OF THE INVENTION
[0001] The present invention is concerned with flash-spinning a
surface-modified structure such as a plexifilimentary yarn or a
microcellular foam.
BACKGROUND OF THE INVENTION
[0002] As described in Kirk-Othmer Encyclopedia of Chemical
Technology, Fourth Edition, volume 17, pages 353-355, the, term
"plexifilamentary yarn" refers to a yarn or strand characterized by
a morphology substantially consisting of a three-dimensional
integral network of thin, ribbon-like, film-fibril elements of
random length that have a mean film thickness of less than about 4
microns and a median fibril width of less than 25 microns, and that
are generally coextensively aligned with the longitudinal axis of
the yarn. In plexifilamentary yarns, the film-fibril elements
intermittently unite and separate at irregular intervals in various
places throughout the length, width and thickness of the yarn
thereby forming the three-dimensional network.
[0003] A plexifilimentary yarn is produced by flash-spinning of
polyethylene or other polymers. Flash spinning is well-known in the
art as a process for preparing plexifilimentary yarns and the
non-woven fabrics made therefrom, as well as microcellular foams.
Whether a plexifilimentary yarn or a microcellular foam is obtained
depends upon the particulars of the spinning process, as described
below. In flash-spinning, a polymer, usually polyethylene, is
dispersed in a non-solvent, known as a spin agent. The dispersion
so formed is then subject to elevated temperature and pressure to
form a homogeneous solution, and the solution is then fed to an
orifice at lower pressure. At the orifice, the highly pressurized
solvent phase separates and rapidly vaporizes, leaving behind a
unique three dimensional structure which may be a plexifilimentary
yarn or a microcellular foam.
[0004] The morphology of, and means for preparing, a
plexifilimentary yarn and a microcellular foam are described in
detail in U.S. Pat. No. 3,081,519, which is incorporated in its
entirety as a part hereof. The use of plexifilimentary yarns in the
formation of non-woven fabrics is described in U.S. Pat. No.
3,169,899 and U.S. Pat. No. 3,442,740. Plexifilamentary yarns have
found widespread commercial value primarily in the form of
flash-spun high density polyethylene non-woven fabrics, most
notably Tyvek.RTM. non-woven fabric, which is manufactured by the
DuPont Company.
[0005] There have been numerous reports in the art of efforts
directed at achieving one or another modification of the properties
of flash-spun polyethylene by employing other polymers, either
alone or in combination with polyethylene. For example, U.S. Pat.
No. 6,004,672 discloses flash-spinning of blends of polyethylene
and polypropylene. In another example, U.S. Pat. No. 6,136,911
discloses flash-spinning of blends of partially fluorinated
copolymers such as polyvinylidene fluoride or
ethylene/tetrafluoroethylene with 12-30% by weight of
polyethylene.
[0006] In another approach to achieving modified properties in
flash spun polyethylene, GB 891,944 discloses radiation induced
grafting of so-called organic modifiers on to the surface of
plexifilimentary yarns and non-woven fabrics produced therefrom.
Suitable organic modifiers include ethylenically unsaturated
monomers, including fully and partially fluorinated monomers. Also
included are unsaturated and saturated polymers. In U.S. Pat. No.
6,096,421, a maleic anhydride grafted polyethylene was used as a
modifier for ethylene/vinyl alcohol copolymer.
SUMMARY OF THE INVENTION
[0007] The present invention provides a surface-modified
plexifilimentary structure, such as a plexifilimentary yarn, a
microcellular foam or a non-woven fabric, and compositions and
processes useful in preparing such structures. A useful composition
contains a polymer having 1 to 25 mol % of pendant functional
groups.
[0008] The present invention further provides a process for forming
a spin mixture containing a spin agent and a polymer mixture by
combining 0 to 95% by weight of a first polymer and 5 to 100% by
weight of a second polymer, pressurizing the spin mixture to a
pressure above the autogenous pressure thereof, and extruding the
mixture through an aperture into a region at a pressure which is
below the autogenous pressure of the spin mixture at a temperature
such that the spin agent vaporizes upon exposure thereto; the first
polymer being selected from the group consisting of polyolefins,
copolymers thereof with ethylenically unsaturated monomers,
polyesters, and mixtures thereof; and the second polymer being
selected from the group consisting of polyolefins, copolymers
thereof with ethylenically unsaturated monomers, polyesters, and
mixtures thereof; the second polymer further containing 1 to 25 mol
% of pendant functional groups.
[0009] Further provided by the present invention is a mixture
comprising a spin agent selected from the group consisting of
aliphatic hydrocarbons, fluorocarbons, halogenated hydrocarbons,
and hydrofluorocarbons, and a polymer mixture containing 0 to 95%
by weight of polyethylene or polyethylene terephthalate and 5 to
100% by weight of a functional polymer, the functional polymer
being polyethylene or polyethylene terephthalate having 1 to 25 mol
% of pendant functional groups selected from the group consisting
of fluorocarbon radicals and oxyethylene radicals.
BRIEF DESCRIPTION OF THE DRAWING
[0010] FIG. 1 is a side elevation view of a flash spinning
apparatus.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The present invention provides a method for introducing
non-fugitive surface modifications to flash spun structures, most
particularly flash-spun polyethylene. It is particularly surprising
that the flash-spun plexifilimentary yarns produced in certain
embodiments of the present invention exhibit surface concentrations
of the surface modifying species of approximately 10-fold higher
than the bulk concentration thereof. The method of the present
invention is widely applicable for modifying the surface of
flash-spun plexifilimentary yarns to provide a vast array of
possible functionality thereto.
[0012] In one embodiment, a reduced surface tension is provided in
a flash-spun structure having a high concentration of fluorine
resident upon the surface. In another embodiment, improved adhesion
is provided in a flash-spun structure having high oxygen
concentration on the surface. Numerous other embodiments are also
envisioned. These include flash-spun structures having biologically
active surfaces. For example, the second polymer may be provided
with a pendant group comprising a vitamin, a pharmaceutical or a
nutrient. In further embodiments, the second polymer may be
provided with a pendant group comprising acid-dyeable dye-sites. In
a still further embodiment, the second polymer may be provided with
a pendant group comprising a herbicide, a fungicide or an
antibiotic. In yet a further embodiment the second polymer is
provided with an epoxide functionality or other functionality which
will react with amino groups to immobilize a protein on the
surface. In every case, the functionality provided to the surface
is built into the polymer structure itself by the attached pendant
group, and is non-fugitive.
[0013] For the purposes of this invention the term "functional
group" and related terms such as "functionality" refer to a
chemical group which provides some function to the surface of the
flash-spun structure which would not be provided in the absence of
the functional group--that is, by the polymer backbone having no or
merely a chemically similar pendant group. It is a particularly
surprising aspect of this invention that having the desired
functionality in the pendant group provides for excellent
processibility and highly concentrated localization of the desired
functionality on the surface of the flash-spun structure. The term
"functional polymer" refers to the second polymer of the
invention--a polymer possessing a pendant group provided with some
specific functionality according to the present invention.
[0014] The flash spun structures provided according to the process
of this invention may be either plexifilimentary yarns or
microcellular foams.
[0015] In the present invention, a mixture is formed by combining
about 0 to 95%, preferably about 70 to 95%, most preferably about
75 to 90% by weight of a first polymer, and about 5 to 100%,
preferably about 5 to 30%, most preferably about 10-25%, by weight
of a second polymer. Under most circumstances the second polymer
will be more costly than the first polymer so that it will
generally be desirable to employ the least amount of the second
polymer consistent with achieving the desired surface effect. In
this invention, the desired effect is often realized when the
second polymer is present in the range of about 5-30%, preferably
about 10-25%, by weight.
[0016] One of the surprising benefits of this invention when the
second polymer represents about 5-30%, preferably about 10-25%, by
weight of the total weight of polymer, is the surprisingly high
percentage of the surface modifying agent which is resident upon
the surface, as indicated by the very high ratio of surface to bulk
concentration of the surface modifying agent. This highly desirable
result may not be achieved if the second polymer represents all or
nearly all of the spinning composition employed. Thus, while the
invention is operable at or near 100% of the second polymer, the
maximum benefit provided by the invention may not be realized at
that level of second polymer.
[0017] The first polymer may be an addition polymer or a
condensation polymer. Among addition polymers, the
polyhydrocarbons, particularly linear polyethylene and
polypropylene, are preferred. Other types of polyethylene,
including low density polyethylene and linear low density
polyethylene are also included. Other addition polymers that could
be used include polymethylpentene, copolymers with ethylenically
unsaturated comonomers such as acrylates and acrylic acids
including methacrylic acid, methyl acrylate, methylmethacrylate,
ethylene vinyl acetate and polyacrylonitrile. Condensation polymers
suitable for the practice of the present invention include
polyamides, polyesters, polyacetals, polyurethanes and
polycarbonates. Suitable polyesters include, but are not limited
to, polyethylene terephthalate (2GT polyester), polypropylene
terephthalate (3GT polyester), polybutylene terephthalate (4GT
polyester), polybutylene napthalate, polyethylene napthalate, and
recycled 2GT and 4GT polyesters. Preferred polymers include
polyolefins such as polyethylene, polypropylene and their
copolymers and polyesters. Preferred for use as the first polymer
of the invention are polyethylene and polyethylene terephthalate,
with high density polyethylene being most preferred.
[0018] Depending upon the particular properties desired, it may be
found advantageous to incorporate into the spinning composition
minor amounts of other polymers such as but not limited to branched
polyethylene, polypropylene, polybutene, polyisobutylene,
polybutadiene, polyvinyl chloride, or cellulose acetate.
[0019] Polyolefins suitable for use as the first polymer in the
present invention are characterized by a melt index of about 0.3-30
g/10 minutes according to ASTM D-1238E, with a melt index of about
0.5 to 10 preferred. Polyesters suitable for use as the first
polymer in the present invention are characterized by an intrinsic
viscosity of about 0.5 to 2.5, preferably about 1.0 to 1.7, as
determined in a 0.5% solids solution in a 1:1 mixture of phenol and
tetrachloroethane at 20.degree. C.
[0020] The second polymer may be one or more of a polyolefin, a
copolymer thereof with ethylenically unsaturated monomer(s) and a
polyester, and contains about 1 to 25 mol %, preferably about 5 to
15 mol %, of pendant functional groups. The desired functional
group should be susceptible to modification to provide a locus for
attachment to the hydrocarbon backbone of the second polymer, and
the functional group should not undergo degradation, cross-linking
or other undesirable reaction during the flash-spinning operation.
The percentage of pendant groups which can be incorporated into the
second polymer will vary considerably with the particular pendant
group. Thus, when ethylenically unsaturated fluoroolefins are
grafted onto a polyethylene polymer (as described below), as many
as about 25 mol % of the methylene groups may serve as a grafting
site. However, with other species, such as maleic anhydride, fewer
of the methylene groups, such as about 4 mol %, may serve as a
grafting site.
[0021] Preferred pendant groups are fluorinated olefin radicals and
oxyethylene trimer. It will be appreciated that the oxyethylene
will be associated with improvements in adhesion while the
fluorinated olefin radicals will be associated with decreased
surface wettability. In a further preferred embodiment, the
backbone chain from which the functional groups are pendant is
polyethylene.
[0022] In a preferred embodiment, the spin mixture of the invention
is a mixture comprising a spin agent selected from the group
consisting of aliphatic hydrocarbons, fluorocarbons, halogenated
hydrocarbons, and hydrofluorocarbons, and a polymer mixture
comprising about 0 to 95% by weight of polyethylene or polyethylene
terephthalate, and about 5 to 100% by weight of a functional
polymer, the functional polymer being polyethylene or polyethylene
terephthalate and containing about 1 to 25 mol % of pendant
functional groups selected from the group consisting of
fluorocarbon radicals and oxyethylene radicals.
[0023] One method for preparing the functionalized polymer suitable
for the practice of the present invention is by free-radical
grafting. Suitable graft copolymers can be formed by free radical
attack on polymers having abstractable hydrogens along the
backbone. Particularly suitable are polymers having at least about
50 mol % of methylene units in the polymer backbone. Most olefinic
polymers are suitable. Preferred are polyethylene, polypropylene,
and their copolymers, as well as copolymers of ethylene with
acrylates, methacrylates and vinyl acetate, and terpolymers
thereof. Polyethylene is the most preferred.
[0024] The free-radical grafting reaction is conveniently performed
in a solvent such as chlorobenzene, dichlorobenzene,
trichlorobenzene or dimethyl acetamide at a temperature in the
range of from about room temperature (.about.25.degree. C.) to
250.degree. C., depending on the solubility of the polymer and the
decomposition temperature of the initiator. The most preferred
range is between about 80.degree. C. and 130.degree. C. An inert
atmosphere is necessary to avoid reaction of the free radicals with
oxygen. Nitrogen and argon are suitable atmospheres. Preferably,
the source of free radicals is a free-radical initiator, suitable
examples including inorganic peroxides and organic peroxides and
azo compounds. Organic peroxides are preferred; tert-butyl peroxide
and dicumyl peroxide are most preferred. The amount of initiator
used is between about 1 and 20 wt % of the polymer, preferably from
about 5 to 10 wt %.
[0025] A suitable polymer, having a weight average molecular weight
in the range of about 3,500 to 1,000,000 Daltons, preferably about
8,000 to 250,000 Daltons, is combined in a suitable solvent with a
suitable initiator, and one or more grafting monomers. Preferred
grafting monomers are non-homopolymerizable monomers, that is, the
grafting monomers do not appreciably polymerize in the presence of
free radicals, although some lower oligomerization might occur. The
second polymer may thus be a grafted polymer that is grafted with
about 1 to 25 mol %, preferably about 5 to 15 mol %, pendant
functional groups, the pendant functional groups being
chain-grafted to the main chain of the second polymer.
[0026] Monomers suitable for grafting to form the second polymer
include fluoroolefins, oxyethylenes, disubstituted ethylenes such
as maleic anhydride, and vinyl silanes. Preferred monomers include
perfluoroalkyl olefins such as tetrafluoroethylene,
hexafluropropylene, or perfluoroalkyl ethylenes; perfluorinated
vinyl ethers such as perfluoro methyl, ethyl, or propyl vinyl
ether. Particularly preferred are substituted perfluorovinyl ethers
having the formula
CF.sub.2.dbd.CF--O--[CF.sub.2CF(R.sub.f)O].sub.n--CF.sub.2CF.sub.2--Q
[0027] wherein R.sub.f is F or a fluoroalkyl radical having 1 to 6
carbons, n=0 to 2, and Q may be --SO.sub.2X or --Y wherein X
represents F or --O.sup.-M.sup.+ where M.sup.+ is hydrogen or
alkali metal, and Y represents --CH.sub.2OH, --CN, --CONH.sub.2, or
COO.sup.-M.sup.+ wherein M.sup.+ is hydrogen or alkali metal. It
may be found convenient to first graft a nonionic monomer and then
hydrolyze after grafting to the ionic forms.
[0028] Also suitable are disubstituted ethylenes such as maleic
anhydride and its esters; vinyl silanes containing alkyl, alkoxy,
phenyl, halo (especially chloro), and hydrogen substituents or any
combination of these; and terminal olefins containing more than 4
carbon atoms including olefins containing any functional group that
does not interfere with the grafting reaction, such as halogen,
ether, carboxylic acid and ester.
[0029] Another method for preparing functionalized polymers
suitable for the practice of this invention involves
transesterification of acrylic polymers, preferably copolymers of
ethylene with acrylic or methacrylic ester monomers, most
preferably ethylene-methyl acrylate and ethylene-methyl
methacrylate copolymers, containing from about 2 to 30 weight %
acrylic monomer. In this method the polymer is reacted with an
alcohol to introduce functional side groups in the polymer,
according to the reaction 1
[0030] The transesterification reaction is conveniently performed
in a solvent such as trichlorobenzene in a temperature range from
about 100 to 250.degree. C. The most preferred range is between
about 180 and 220.degree. C. An inert gas sweep conveniently
carries away the low boiling alcohol byproduct. Nitrogen and argon
are suitable inert gases. Typical transesterification catalysts
such as Lewis acids are suitable for the reaction. Preferred
catalysts include titanium(IV) n-butoxide. The alcohol used for
this transformation depends on the functionality wanted on the
polymer. For example, fluorinated alcohols will impart hydrophobic
and oleophobic properties, while alcohols containing polar groups
will give hydrophilic polymers. Suitable alcohols include most high
boiling alcohols. Preferred alcohols include 2-perfluoroalkylethyl
alcohols, 1-perfluoroalkylmethyl alcohols, 2-ethoxyethanol,
di(ethylene glycol) monoethyl and monomethyl ethers, and
tri(ethylene glycol) monoethyl and monomethyl ethers.
[0031] Of course, the second polymer can be formed simply by
copolymerization of a suitably functionalized olefin monomer with
an olefin such as ethylene, propylene, and/or other olefins.
[0032] Although this invention is directed primarily to
modification of the surface of flash spun yarns in order to alter
the wettability and adhesion properties thereof, numerous other
functionalities can be incorporated in the pendant group of the
second polymer, thereby imparting other, novel, properties to the
flash spun product. Included among these are acid-dye receptor
sites; incorporation of fluorosulfonyl fluoride groups which, after
flash spinning, can be readily hydrolyzed according to methods
known in the art to provide ion exchange or super acid catalyst
sites; incorporation of quaternary ammonium functional groups to
provide biocide functionality; and incorporation of amine,
carboxylic acid, epoxy or tosyl functional groups to immobilize
proteins on the surface of the yarn.
[0033] The second polymer is combined in a suitable spin agent with
the first polymer, a flash spinnable polymer, to form a spin
mixture having a second polymer concentration of about 5-30% by
weight of the total spin composition, preferably about 10 to 25% by
weight.
[0034] The first and second polymers may be combined prior to
incorporation into the spin agent to form a blend by various means
known in the art, including both melt blending and so-called dry
blending or tumbling. However, it is generally satisfactory to
combine the first and second polymers in the step in which the two
are mixed with the spin agent to form the spin mixture. In a
typical embodiment, the spin mixture contains about 5-30% solids,
the precise amount being determined by such considerations as the
molecular weight of the polymer, the choice of spin agents, and the
particular spinning conditions.
[0035] Suitable spin agents include aromatic hydrocarbons such as
benzene and toluene; aliphatic hydrocarbons such as butane,
pentane, octane, and their isomers and homologues; alicyclic
hydrocarbons such as cyclohexane; unsaturated hydrocarbons;
halogenated hydrocarbons such as trichlorofluoromethane, methylene
chloride, carbon tetrachloride, chloroform, ethyl chloride, and
methyl chloride; alcohols; esters; ethers; ketones; nitrites;
amides; fluorocarbons; hydrofluorocarbons;
hydrochlorofluorocarbons; inert gases such as sulfur dioxide and
carbon dioxide; carbon disulfide; nitromethane; water; and mixtures
of the above liquids. Preferred spin agents for use with
polyolefins are aliphatic hydrocarbons and fluorocarbons. Preferred
spin agents for polyesters are halogenated hydrocarbons and
hydrofluorocarbons. Co-spin agents can also be used in conjunction
with these primary spin agents to improve electostatic charging
and/or to reduce solvent power.
[0036] Examples of other suitable spin agents are set forth in U.S.
Pat. Nos. 3,081,519 and 3,227,784, including those having
characteristics such as: (a) the spin agent should have a boiling
point at least 25.degree. C. and preferably at least 60.degree. C.
below the melting point of the polymer used; (b) the spin agent
should be substantially unreactive with the polymer during mixing
and extrusion; (c) the spin agent should be a solvent for the
polymer under the conditions of temperature, concentration and
pressure used in the process; (d) the spin agent should dissolve
less than 1% of high polymeric material at or below its boiling
point; and (e) the spin agent should form a solution which will
undergo rapid vaporization upon extrusion, forming a nongel polymer
phase (i.e., a polymer phase containing insufficient residual
liquid to plasticize the structure).
[0037] Common additives, such as antioxidants, UV stabilizers,
dyes, pigments, and other similar materials can be added to the
spin composition prior to extrusion.
[0038] The spin mixtures utilized in this invention may be formed
and flash-spun by any convenient technique taught in the art. In
one embodiment, the polymer mixture may be mechanically dispersed
in a mixture of carbon dioxide and water at a temperature of at
least 130.degree. C., as more particularly described in U.S. Pat.
No. 5,192,468. In another embodiment, plexfiilmentary material is
produced by first continuously supplying under pressure, into a
dissolution zone, synthetic crystallizable organic polymer of
filament forming molecular weight and an inert solvent for the
polymer, the concentration of polymer being 2 to 20% by weight of
the solution. The polymer is dissolved in the zone, and a polymer
solution is produced having a temperature of at least the solvent
critical temperature minus 45.degree. C. and a pressure above the
two-liquid-phase pressure for the solution. Thereafter the solution
is forwarded through a transfer zone while maintaining a heat
balance at substantially the same level as in the dissolution
chamber. A constant pressure above the two-liquid-phase pressure is
maintained in the transfer zone by control means such that the
total supply of polymer and solvent to the dissolution zone is
varied inversely in relation to the pressure in the transfer zone,
as more particularly described in U.S. Pat. No. 3,227,794. In still
another embodiment, flash spinning may be accomplished by a process
of entraining a web in a gaseous stream flowing in a generally
horizontal path toward one location on a baffle, directing and
oscillating said web and said stream from said one location in a
plurality of downward radial directions in a substantially vertical
plane through ambient gas toward a collecting means,
electrostatically charging the web, and collecting said web on said
collecting means as a fibrous sheet, converging said stream below
said baffle in said downward radial directions within a shield
presenting substantially equal flow impedances in said radial
directions for a distance of from 30 to 60 percent of the distance
from said one location to said collecting means thereby maintaining
the stream entrained web substantially as formed by said baffle and
preventing premature mixing with said ambient gas, as more
particularly described in U.S. Pat. No. 3,851,023. Each of the
above mentioned patents is incorporated as a part hereof.
[0039] As discussed below, the morphology of the fiber strands
obtained by flash spinning of blended polymers is greatly
influenced by the spin agent in which the polymers are combined,
the concentration of the polymers in the spin solution, and the
spin conditions, such as temperature and pressure.
[0040] Flash spinning a single polymer may be accomplished by
forming a dispersion of the polymer in a spin agent which is a
non-solvent at ambient pressure and temperature but which
dispersion forms a solution with the application of sufficient heat
and pressure. The pressure is subsequently decreased and the
solution becomes cloudy as separation occurs into a polymer-rich
phase and a solvent-rich phase. The pressure at which the
separation occurs is referred to as the "cloud point pressure". The
cloud point pressure, which is directly dependent on the choice of
the polymer and solvent, the total polymer concentration, and the
temperature, can be anywhere between the autogenous pressure of the
solvent (i.e., the solvent vapor pressure at a given temperature)
and about 50 MPa. The cloud point of a single polymer solution may
be readily ascertained visually, and is a handy visual reference
for determining optimum conditions for flash spinning.
[0041] In this invention, it is desirable that both the first and
second polymers hereof be soluble in a common solvent at elevated
temperature and pressure. However, the first and second polymers
are sometimes not mutually soluble to any significant degree, i.e.
they are incompatible, resulting in phase separation even when each
polymer separately dissolves in the common solvent. Therefore, such
combinations always exist as a dispersion of one polymer solution
in another. Any resulting solution will be cloudy under most
processing conditions of interest. Therefore, there is no "true"
cloud point pressure for these blends in a common solvent.
[0042] In this invention, the cloud point of each individual
component is separately determined. The spin composition formed as
a polymer blend is mixed at a pressure higher than the cloud point
pressure of the component with the higher individual cloud point
pressure, thereby resulting in a two-phase mixture, one rich in the
first polymer and one rich in the second polymer. That is to say,
the spin mixture is two-phase at the first pressure. Then, the spin
mixture is subjected to a second pressure that is lower than the
first pressure but is still higher than the autogenous pressure of
the mixture, and at the second pressure the solution phase
separates into a three-phase system, two polymer-rich phases and a
solvent rich phase. It is possible to introduce the spin mixture
into the flash-spinning nozzle directly from the first pressure
state and thereby spin a plexifilimentary yarn. However, it is
preferred to introduce a second intermediate pressure stage, still
well above ambient pressure, at which a new solvent-rich phase
develops, and to introduce the spin mixture into the flash-spinning
nozzle from the second intermediate pressure stage.
[0043] A mixture of more than two polymers may also be flash-spun
in this invention. In such a case, the spin mixture will include
however many polymer-rich phases as there are polymers. There will
be practical limits to how many incompatible phases can be
processed, and there will be practical limits to how many polymers
are soluble in a common solvent. But there are no fundamental
limitations to the number of polymers that can be combined
according to the process of the invention. For the purposes of
clarity, the description herein is directed to a binary mixture,
but the methods herein described are equally applicable to mixtures
of more than two polymers.
[0044] The optimum spin pressure will dictated primarily by the
spin agent chosen, the polymer concentration, the temperature, and
the specific process parameters and apparatus geometry. It has been
found that optimum flash spinning pressure for the polymer blend of
this invention is usually closer to that associated with the
polymer that is present at the higher concentration in the blend,
hereinafter referred to as "the major component." The pressure
range is preferably between the autogenous pressure of the spin
mixture and 15 MPa. The most preferred spin pressure range to
produce well-fibrillated plexifilaments lies between the cloud
point pressure of the major polymeric component, and 3 MPa lower
than the cloud point pressure of the major component.
[0045] In this invention, a suitable temperature range for flash
spinning is 150 to 300.degree. C., with the optimum temperature for
a lower melting and/or more soluble polymer typically being lower
than that for a higher melting and/or less soluble polymer. The
most preferred spin temperature range to produce well-fibrillated
plexifilaments is between the critical temperature of the spin
agent and 40.degree. C. below the critical temperature of the spin
agent. The critical temperature is that temperature above which a
gas cannot be liquefied by pressure alone.
[0046] To obtain plexifilaments, the total polymer concentration in
the spin composition is kept relatively low, e.g., less than about
35% by weight, preferably less than about 30% by weight. The
concentration also needs to be greater than about 5% by weight in
order to avoid the formation of discontinuous fibers. As indicated,
the spin temperatures and pressures are generally kept high to
provide rapid flashing of the solvent. Microcellular foam fibers,
on the other hand, are usually prepared at relatively high total
polymer concentrations, between about 35 and 70% by weight. In
addition, lower spin temperatures and pressures are used compared
to those used to obtain plexifilaments.
[0047] In a further embodiment of the process of the invention, it
has been found that when a plexifilimentary yarn produced by the
process hereof is subject to elevated temperature, the surface
enrichment effect of the present invention is further enhanced, as
seen in the specific embodiments described below. The duration and
temperature will depend upon the specific compositions involved. On
the laboratory scale, heating to a temperature in the range of
about 100-150.degree. C. for a period of 15 seconds to a minute has
been found to be satisfactory.
[0048] The advantageous effects of this invention are demonstrated
by a series of examples, as described below. The embodiments of the
invention on which the examples are based are illustrative only,
and do not limit the scope of the invention. The significance of
the examples is better understood by comparing the results obtained
from these embodiments of the invention with the results obtained
from certain formulations that are designed to serve as controlled
experiments since they do not possess the distinguishing features
of this invention.
EXAMPLES
[0049] The flash spinning apparatus employed herein is described in
detail in U.S. Pat. No. 5,147,586. The apparatus, shown in FIG. 1,
consists of two high-pressure cylindrical chambers (1), each
equipped with a piston (2) which is adapted to apply pressure to
the contents of the chamber. The cylinders have an inside diameter
of 1.0 inch (2.54 cm) and each has an internal capacity of 50 cubic
centimeters. The cylinders are connected to each other at one end
through a {fraction (3/32)} inch (0.23 cm) diameter channel (3) and
a mixing chamber (4) containing a series of fine mesh screens that
act as a static mixer. Mixing is accomplished by forcing the
contents of the vessel back and forth between the two cylinders
through the static mixer. The pistons are driven by high-pressure
water supplied by a hydraulic system (5). A spinneret assembly with
a quick-acting means for opening the orifice (6) is attached to the
channel through a tee (7). The spinneret assembly consists of a
lead hole (8) of 0.25 inch (0.63 cm) diameter and about 2.0 inch
(5.08 cm) length, and a spinneret orifice (9) with a length and a
diameter each measuring 30 mils (0.762 mm).
[0050] In the examples, the polymer was charged into one cylinder.
In the case of the blends, both polymers were added simultaneously
as either pellets or powder to make a "salt and pepper"-type blend.
In all cases, 0.1 wt % (based-on-solvent) Weston.RTM. W619F
antioxidant (General Electric Specialty Chemicals) was also added.
The spin agent was added by a high pressure screw-type generator
(High Pressure Equipment Co.), calibrated to give 0.7 cc/turn.
High-pressure water was used to drive the pistons to generate a
mixing pressure of between 2000 and 4000 psig (13.8-27.6 MPa).
[0051] The polymer and spin agent were then heated to mixing
temperature, as measured by a type J thermocouple (10, Technical
Industrial Products Inc. of Cherry Hill, N.J.) and held at that
temperature for a specified period of time during which the pistons
were used to alternately establish a differential pressure of about
1500 psi (10.3 MPa) or higher between the two cylinders. This
action repeatedly forced the polymer and spin agent through the
mixing channel from one cylinder to the other to provide mixing and
to effect formation of a spin mixture. The spin mixture temperature
was then raised to the final spin temperature, and held there for a
time sufficient to equilibrate the temperature, usually 5 minutes,
during which time mixing was continued. The time at temperature was
kept as short as possible to minimize thermal degradation of the
polymer or the spin agent.
[0052] The pressure of the spin mixture was reduced to the desired
spinning pressure just prior to spinning. This was accomplished by
opening a valve between the spin cell and a much larger tank of
high-pressure water ("the accumulator") held at the desired
spinning pressure. The spinneret orifice was opened as soon as
possible (usually about one to two seconds, except that Example 6
was held for 1 minute before opening the orifice) after the opening
of the valve between the spin cell and the accumulator. When a
non-flammable spin agent was employed, the flash-spun product was
collected in a stainless steel open mesh screen basket. When
flammable spin agents were used, the flash spun product was
collected in a nitrogen-purged stainless steel enclosure. The
pressure just before the spinneret was measured with a pressure
transducer (11, Dynisco Inc. of Norwood, Mass.) and recorded during
spinning. It is referred to as "the spin pressure". The spin
pressure was recorded using a computer and was usually about 150
psi (1 MPa) below the accumulator set point. The temperature
measured just before the spinneret (10) was also recorded during
spinning and was referred to as "the spin temperature".
[0053] The resultant flash-spun yarns were analyzed for fluorine
with two techniques. Surface analysis, to a depth of 5-10
nanometers was obtained via ESCA using a Physical Electronics Inc.
Model 5600 LS with a 450 exit angle. The detection limit was ca.
0.5-1 atom percent. Ion chromatography employing a DIONEX 500
Series unit. was used to get quantitative measurements of the total
fluorine content in the yarn.
[0054] In the following examples, the functional polymer was
blended with either Alathon.RTM. 7026T high density polyethylene
obtained from Lyondell Inc, an isotactic polypropylene obtained
from Montell Inc, or Crystar.RTM. 5067 polyethylene terephthalate
obtained from DuPont. Gel permeation chromatography (GPC) was
employed to determine molecular weight distributions of the
polymers produced. Differential Scanning Calorimetry (DSC) was
performed to determine melting point according to ASTM
D-3417-83.
Example 1
[0055] 50 grams of low density polyethylene (LDPE) (Aldrich cat
#42,779-9) and 500 mL chlorobenzene (Aldrich) were placed under
nitrogen into a 1.0 liter three-neck round bottomed flask equipped
with condenser, addition funnel, magnetic stirring, and
thermocouple. The mixture was heated to 125.degree. C. and, after
the polyethylene dissolved, 10 grams of (perfluoroalkyl)ethylene
(Zonyl.RTM. BN from E.I. DuPont de Nemours and Co. of Wilmington,
Del.), which has the formula H.sub.2C.dbd.CH--(CF.sub.- 2).sub.nF,
wherein n is mostly 6, 8, 10, and 12, were added. A solution
containing 2 grams of t-butyl peroxide (Aldrich) in 20 mL of
chlorobenzene was then added drop-wise over a 60 minute period. The
reaction mixture was stirred at 125.degree. C. for a total of 8
hours. After cooling the mixture to about 60.degree. C. it was
poured into an excess of methanol. The precipitated polymer was
filtered off, washed with methanol, and then dried under vacuum at
75.degree. C. overnight. 58.8 grams of a white polymer were
obtained.
[0056] Elemental analysis of a sample indicated that the material
contained 11.2 weight % of fluorine. GPC in trichlorobenzene at
135.degree. C. gave Mn=6600 and Mw=34100. DSC of the polymer at
20.degree. C./min showed a melting transition at 95.degree. C.
Example 2
[0057] The same procedure described in Example 1 was used except
that 50 grams of Zonyl.RTM. BN were used. After isolation and
drying under vacuum, 97 grams of polymer were obtained. Elemental
analysis of this sample indicated that the material contained 34.3
weight % of fluorine. GPC in trichlorobenzene at 135.degree. C.
showed a bimodal MW distribution with Mn=2800 and Mw=44200. DSC of
the polymer at 20.degree. C./min showed a melting transition at
94.degree. C.
Examples 3-9 and Comparative Examples 1 and 2
[0058] Preparation of Plexifilamentary Yarns.
[0059] The polymers of Examples 0.1 and 2 were each blended with
Alathon.RTM. 7026 in Freon-11 (F-11) and flash spun according to
the procedures hereinabove described to form plexifilimentary
yarns. Results are shown in Table 1.
1TABLE 1 Plexifilamentary Yarns Comprised of Zonyl .RTM. BN-Graft
Low Density Polyethylene Graft Surface Polymer Polymer in Bulk
concentration in spin total Spin Spin Concentration of F Graft
agent polymer Temp. Pressure of F in Fiber in Fiber Example Polymer
(wt. %) (wt. %) (.degree. C.) (psi) (wt- %) (wt- %) Comparative
None 12 0 191 975 -- 0 Example 1 Comparative None 12 0 185 925
0.0097 0.932 Example 2 Example 3 Example 2 12 10 190 950 0.26 7.1
Example 4 Example 2 12 10 185 925 2.9 28.1 Example 5 Example 2 12
20 190 950 6 48.7 Example 6 Example 2 12 20 190 975 6 48.9 Example
7 Example 2 12 20 192 900 5.1 44.6 Example 8 Example 1 12 10 191
925 0.82 13 Example 9 Example 1 12 20 190 1000 1.9 29.7
Examples 10-13 and Comparative Example 3
[0060] Preparation of Plexifilamentary Yarns.
[0061] The polymers of Examples 1 and 2 were blended in with
Alathon.RTM. 7026T, but the spin agent was changed to
pentane/cyclopentane (60/40 wt./wt.). Plexifilamentary yarns were
then spun according to the procedures hereinabove described.
Results are shown in Table 2.
2TABLE 2 Plexifilamentary Yarns Comprised of Zonyl .RTM. BN-Graft
Low Density Polyethylene and Prepared from Alternative Spin Agent
Graft Polymer in Bulk Surface Polymer in total Spin Spin
Concentration concentration Graft spin agent polymer Temp. Pressure
of F in Fiber of F in Fiber Example Polymer (wt. %) (wt. %)
(.degree. C.) (psi) (wt- %) (wt- %) Comparative None 18 0 190 1000
0.059 0 Example 3 Example 10 Example 1 18 10 190 1000 0.45 9.72
Example 11 Example 1 18 20 190 1000 1.7 25.7 Example 12 Example 2
18 10 190 1025 2.4 40.4 Example 13 Example 2 18 20 190 1000 4.9
50.6
Example 14
[0062] 20 grams of Alathon.RTM. 7026T and 200 mL chlorobenzene
(Aldrich) were placed under nitrogen in a 500 mL three-neck round
bottomed flask equipped with condenser, addition funnel, magnetic
stirring, and thermocouple. The mixture was heated to 125.degree.
C., and after the polyethylene dissolved, 5 grams of Zonyl.RTM. BN
were added. A solution containing 1 gram of t-butyl peroxide
(Aldrich) in 20 mL of chlorobenzene was then added drop-wise over a
60 minute period. The reaction mixture was stirred at 125.degree.
C. for a total of 4 hours. After cooling the mixture to about
60.degree. C. it was poured into an excess of methanol. The
precipitated polymer was filtered off, washed with methanol, and
then dried under vacuum at 60.degree. C. overnight. The polymer was
further purified by dissolving it in hot toluene and
reprecipitating in methanol. After filtering and drying, 22.6 grams
of polymer were obtained.
[0063] The fluorine content of this sample was determined to be 11%
by ion chromatography. GPC in trichlorobenzene at 135.degree. C.
gave Mn=33,000 and Mw 248,000. DSC of the polymer at 20.degree.
C./min showed a melting transition at 131.degree. C.
Example 15
[0064] The same procedure described in Example 14 was used except
that 20 grams of Zonyl.RTM. BN were used. After isolation and
drying under vacuum, 29.3 grams of polymer were obtained. The
fluorine content of this sample was determined to be 21% by ion
chromatography. GPC in trichlorobenzene at 135.degree. C. showed a
bimodal MW distribution Mn=17,800 and Mw=112,000. DSC of the
polymer at 20.degree. C./min showed a melting transition at
131.degree. C.
Examples 16-21
[0065] Preparation of Plexifilamentary Yarns.
[0066] The polymers of Examples 14 and 15 were blended with
Alathon.RTM. 7026T in F-11. The blends were flash spun according to
the procedures indicated above. Results are shown in Table 3.
3TABLE 3 Plexifilamentary Yarns Comprised of Zonyl .RTM. BN-Graft
High Density Polyethylene Graft Polymer Bulk Surface Polymer in in
total Spin Spin Concentration concentration of Graft spin agent
polymer Temp. Pressure of F in Fiber F in Fiber Example Polymer
(wt. %) (wt. %) (.degree. C.) (psi) (wt- %) (wt- %) Example Example
12 10 191 950 2.1 27.9 16 15 Example Example 12 20 191 925 3.9 37.3
17 15 Example Example 12 20 191 950 3.9 33.1 18 15 Example Example
12 20 190 1150 3.5 24.3 19 15 Example Example 12 10 190 875 0.89
7.4 20 14 Example Example 12 20 190 900 2 11.9 21 14
Example 22
[0067] A 10 gallon stainless steel reactor was charged with 9 L of
chlorobenzene, 1 Kg of polyethylene (Aldrich cat #42,779-9), and
300 g of Zonyl.RTM. BN. After purging the reactor with nitrogen, it
was stirred and heated to 125.degree. C. After one hour at this
temperature 500 mL of a peroxide solution (0.1 g of t-butyl
peroxide/mL) in chlorobenzene were pumped into the reactor at a
rate of 10 mL/min. Once the peroxide addition was completed, the
reactor contents were further stirred at the same temperature for
an additional 4 hours. The reactor was cooled to room temperature
and discharged. The reaction mixture was warmed to 60.degree. C.
and poured slowly into 12 gallons of methanol to precipitate the
polymer. The white polymer obtained was filtered off, washed three
times with 4 L of fresh methanol, and dried under vacuum at
60.degree. C. 1.2 Kg of polymer were obtained.
[0068] Elemental analysis of a sample indicated that the material
contained 15.0 weight % of fluorine. GPC in trichlorobenzene at
135.degree. C. gave Mn=4,700 and Mw=30,200. DSC of the polymer at
20.degree. C./min showed a melting transition at 95.degree. C.
[0069] A second batch was prepared following the same procedure
described above. Elemental analysis of this second batch indicated
that the material contained 16.7 weight % of fluorine. GPC in
trichlorobenzene at 135.degree. C. gave Mn=5,400 and Mw=36,200. DSC
of the polymer at 20.degree. C./min showed a melting transition at
95.degree. C.
Examples 23-24
[0070] Preparation of Plexifilamentary Yarns.
[0071] The polymers of Example 22 were blended at the 20 wt. %
level with Alathon.RTM. 7026T in F-11. The blends were flash spun
according to the procedures hereinabove described. Results are
shown in Table 4.
4TABLE 4 Plexifilamentary Yarns Comprised of Zonyl .RTM. BN-Graft
Polyethylene Prepared in Large Scale Graft Polymer Polymer Bulk
Surface in spin in total Spin Spin Concentration concentration of F
Graft agent polymer Temp. Pressure of F in Fiber in Fiber Example
Polymer (wt. %) (wt. %) (.degree. C.) (psi) (wt- %) (wt- %) Example
Example 22, 12 20 190 900 2.4 22.3 23 first batch Example Example
22, 12 20 190 925 2.6 22.9 24 second batch
Example 25
[0072] 10 grams of an ethylene/methyl acrylate copolymer containing
20 weight % methylacrylate (E/20MA from E.I. DuPont de Nemours and
Co. of Wilmington, Del.), 10 grams of 2-perfluorooctylethanol (a
distillation fraction from Zonyl.RTM. BA made by E.I. DuPont de
Nemours and Co. of Wilmington, Del.), and 50 mL
1,2,4-trichlorobenzene (Aldrich) were placed into a 250 mL
three-neck round bottomed flask equipped with condenser, magnetic
stirring, thermocouple, and under nitrogen atmosphere. The mixture
was heated to 80.degree. C. and when the polymer started to
dissolve, 25.0 .mu.L of titanium (IV) butoxide (Aldrich) were
added. The mixture was heated to 190.degree. C. and stirred at this
temperature for 6 hours under a slow nitrogen flow. After cooling
the mixture to about 70.degree. C., it was poured into excess
methanol. The precipitated polymer was filtered off, washed with
methanol, and then dried under vacuum at 60.degree. C. overnight.
The polymer was further purified by dissolving it in hot toluene,
filtering the solution through a fritted glass funnel, and
reprecipitating into methanol. After filtering and drying under
vacuum, 14.5 grams of polymer were obtained. Analysis by NMR
showed:
[0073] .sup.1H NMR (in tetrachloroethane at 120.degree. C.,
.quadrature. in ppm): 4.33 (t, --CH.sub.2O--), 3.62 and 3.60 (s,
CH.sub.3O--), 2.44 (t of t, --CH.sub.2--CF.sub.2--), 2.31 (m,
--CH--), 1.65 to 1.05 (backbone --CH.sub.2--).
[0074] .sup.19F NMR (in tetrachloroethane at 120.degree. C.,
.quadrature. in ppm): -80.76 (CF.sub.3--), -112.34 (--CF.sub.2--),
-121.00 (three --CF.sub.2--), -121.98 (--CF.sub.2--), -122.90
(--CF.sub.2--), -125.33 (--CF.sub.2--
[0075] NMR indicates a 64.3% conversion of methyl acrylate groups
to 2-perfluorooctylethyl acrylate giving a copolymer containing
approximately 92.5% ethylene, 4.8% 2-perfluorooctylethyl acrylate,
and 2.7% methyl acrylate repeat units. GPC in trichlorobenzene at
135.degree. C. gave Mn=19,500 and Mw=91,700. DSC of the polymer at
20.degree. C./min showed a melting transition at 85.degree. C.
Examples 26-28
[0076] Preparation of Plexifilamentary Yarns.
[0077] The polymer described in Example 25 was blended with
Alathon.RTM. 7026T in F-11. The blends were flash spun according to
the procedures hereinabove. Results are shown in Table 5.
5TABLE 5 Plexifilamentary Yarns Comprised of Graft Ethylene/Methyl
Acrylate Copolymer Graft Polymer Polymer in Bulk Surface in spin
total Spin Spin Concentration concentration agent polymer Temp.
Pressure of F in Fiber of F in Fiber Example (wt. %) (wt. %)
(.degree. C.) (psi) (wt- %) (wt- %) Example 12 10 189 950 2.3 21.2
26 Example 12 20 187 950 3.8 32.1 27 Example 12 30 190 950 6.8 34.5
28
Example 29
[0078] The same procedure described in Example 25 above was
followed except that 16 grams of 2-perfluorooctylethanol and 50.0
.mu.L of titanium (IV) butoxide were used. After isolation and
drying under vacuum, 17.5 grams of polymer were obtained.
[0079] NMR spectra of this sample were identical to those of
Example 25 except in the relative intensity of the signals.
According to the .sup.1H spectrum, the copolymer contained
approximately 93.0% ethylene, 5.8% 2-perfluorooctylethyl acrylate,
and 1.2% methyl acrylate repeat units. Elemental analysis of this
sample gave 56.05% C, 7.81% H, and 30.72% F which agrees with the
NMR results. GPC in trichlorobenzene at 135.degree. C. gave
Mn=19,600 and Mw=82,500. DSC of the polymer at 20.degree. C./min
showed a melting transition at 85.degree. C.
Examples 30-32 and Comparative Example 4
[0080] Preparation of Plexifilamentary Yarns.
[0081] The polymer of Example 29 was blended with Alathon.RTM.
7026T in F-11. The blends were flash spun according to the
procedures indicated above. Results are shown in Table 6.
6TABLE 6 Plexifilamentary Yarns Comprised of Graft Ethylene/Methyl
Acrylate with Higher Fluorine Content Measure Total Fraction F in
Polymer of Graft Spin Spin Fiber Graft Content Polymer Temperature
Pressure Atom Wt. % F Example Polymer (wt. %) (wt. %) (.degree. C.)
(psi) (wt. %) ESCA Comparative None 12 0 187 950 BDL 0.00 Example 4
Example 30 Example 12 10 192 950 2.4 17.5 29 Example 31 Example 12
20 189 975 5.3 34.8 29 Example 32 Example 12 30 190 950 7.1 36.9
29
Examples 33-36 and Comparative Example 5
[0082] Heat Treatment Effect on Surface Fluorine.
[0083] The plexifilamentary yarn from Example 30 was placed between
two glass slides. This assemblage was subsequently put on a 5
mm-thick stainless steel plate in intimate contact with a heated
"hot plate." The temperature of the hot plate was controlled by a
thermocouple placed within the stainless-steel plate. The
assemblage was lightly pressed for 30 seconds so as to not deform
the sample. The percentage of fluorine on the surface of the thus
heat-treated specimen was determined by ESCA. A single,
non-heat-treated control specimen was measured twice by ESCA to
establish the error in the measurement. Results are shown in Table
7.
7TABLE 7 Heat Treatment Effect on Surface Fluorine Heat Treatment
Temperature % F on Example (.degree. C.) surface Comp Ex. 5-1 None
12 Comp Ex. 5-2 None 16 33 100 21 34 110 23 35 120 29 36 130 30
Examples 37-41 and Comparative Example 6
[0084] Surface Fluorine Effect of Contact Angle Measurements.
[0085] The plexifilamentary yarn from Examples 3, 4, 5, 8, and 9
were individually attached by double-sided tape to glass slides.
These slides were placed in turn on the stage of a goniometer. A
small drop of a 30/70 (vol/vol) water/ethanol solution was placed
on the yarns. The advancing contact angles of these drops were then
measured in three places on the yarn and results were averaged.
Results are shown in Table 8.
8TABLE 8 Surface Fluorine Effect on Contact Angle Measurements
Surface fluorine Advancing content contact angle Example Yarn
Source (atom %) (degrees) Comparative Comparative 0.6 0 Example 6
Example 2 Example 37 Example 3 4.6 0 Example 38 Example 8 8.7 0
Example 39 Example 4 20 91 Example 40 Example 9 21 106 Example 41
Example 5 38 115
Example 42
[0086] The polymer of Example 15 using F-11 as the spin agent was
flash spun according to the procedures indicated above, but without
combining it with another flash-spinnable polymer. That is, it was
flash spun neat. Results are shown in Table 9.
9TABLE 9 Spinning of Neat Zonyl .RTM. BN-Graft High Density
Polyethylene Polymer Bulk Surface in spin Spin Spin Concentration
concentration agent Temp. Pressure of F in Fiber of F in Fiber (wt.
%) (.degree. C.) (psi) (wt- %) (wt- %) 12 187 1030 19 39.7
Examples 43-44
[0087] The polymer of Example 29 was blended at the 20 wt. % level
with an isotactic polypropylene with melt flow rate of 1.43,
Mn=93,000; Mw=447,000, and molecular weight distribution of 4.77
obtained from Montell Inc. (Example 43) and with Crystar.RTM. 5067
polyethylene terephthalate (DuPont) (Example 44). Results are shown
in Table 10. Replicates of the surface fluorine measurements are
given to show the measurement error.
10TABLE 10 Plexifilamentary Yarns Comprised of Graft
Ethylene/Methyl Acrylate and Isotactic Polypropylene or
Polyethylene Terephthalate Graft Polymer Polymer Bulk Surface in
spin in total Spin Spin Concentration concentration Spin agent
polymer Temp. Pressure of F in Fiber of F in Fiber Example agent
(wt. %) (wt. %) (.degree. C.) (psi) (wt- %) (wt- %) Example pentane
10 20 194 800 4.3 44.8/35.5/39.4 43 Example methylene 25 20 249
2230 4.3 40.1/40.0/40.1 44 chloride
Example 45
[0088] 10 grams of an ethylene/methyl acrylate copolymer containing
27 weight % methylacrylate, 10 grams of diethylene glycol methyl
ether (Aldrich), and 50 mL 1,2,4-trichlorobenzene (Aldrich) were
placed into a 250 mL three-neck round bottomed flask equipped with
condenser, magnetic stirring, thermocouple, and under nitrogen
atmosphere. The mixture was heated to 80.degree. C. and when the
polymer started to dissolve, 50.0 .mu.L of titanium (IV) butoxide
(Aldrich) was added. The mixture was heated to 190.degree. C. and
stirred at this temperature for 6 hours under a slow nitrogen flow.
After cooling the mixture to about 90.degree. C., it was diluted
with 70 mL of toluene, and then it was poured into excess methanol.
The precipitated polymer was filtered off, washed with methanol,
and dried under vacuum at 60.degree. C. overnight. The polymer was
further purified by dissolving it in hot toluene, filtering the
solution through a fritted glass funnel, and reprecipitating into
methanol. After filtering and drying under vacuum, 12.2 grams of
polymer were obtained. Analysis by NMR showed:
[0089] .sup.1H NMR (in tetrachloroethane at 120.degree. C.,
.quadrature. in ppm) 4.18 (t, --CH.sub.2OOC--), 3.64, 3.59 and 3.49
(t, --CH.sub.2O--), 3.32 (s, CH.sub.3O--), 2.31 (m, --CH--), 1.0 to
1.7 (backbone --CH.sub.2--).
[0090] NMR indicates a 94% conversion of methyl acrylate
groups.
[0091] GPC in trichlorobenzene at 135.degree. C. gave Mn=26,300 and
Mw=94,700. DSC of the polymer at 20.degree. C./min showed a broad
melting transition at 69.degree. C.
Examples 46-47 and Comparative Example 7
[0092] The polymer of Example 45 was blended with Alathon.RTM.
7026T at increasing concentrations in F-11, and the resultant spin
mixtures were flash spun according to the procedure hereinabove
described. Results are shown in Table 11.
11TABLE 11 Plexifilamentary Yarns Comprised of Graft
Ethylene/Methyl Acrylate Copolymer with Oxyethylene Side Chains
Graft Total Polymer Bulk Surface Polymer in total Spin Spin
Concentration concentration Graft Content polymer Temperature
Pressure of F in Fiber of O in Fiber Example Polymer (wt. %) (wt.
%) (.degree. C.) (psi) (wt- %) (wt. %) (wt- %) Comparative None 12
0 185 930 0.3 3.7 Example 7 Example 46 Example 12 15 185 950 1.15
7.8 45 Example 47 Example 12 30 186 1010 2.99 14.1 45
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