Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF INVENTION
FLASH-SPINNING PROCESS AND SOLUTION
This application claims benefit of priority from Provisional application
No. 60/150,002, filed August 20, 1999.
FIELD OF THE INVENTION
This invention relates to flash-spinning of polymeric plexifilamentary
film-fibril strands. More particularly, this invention relates to a spin fluid
that may be
used with existing commercial flash-spinning equipment with minimum changes in
the equipment.
BACKGROUND OF THE INVENTION
In the process for making flash-spun fibers, as disclosed in U.S. Pat.
No. 3,081,519 to Blades et al. assigned to E.I. du Pont de Nemours and
Company,
Wilmington, DE (hereafter DuPont), a solution of fiber-forming polymer in a
liquid
spin agent that is not a solvent for the polymer below the liquid's normal
boiling point,
is maintained at a temperature above the normal boiling point of the liquid
and at
autogenous pressure or greater, and is then spun into a zone of lower
temperature and
substantially lower pressure to generate plexifilamentary filin-fibril
strands. As
disclosed in U.S. Pat. No. 3,227,794 to Anderson et al. (assigned to DuPont),
the
flash-spinning process requires a spin agent that: (1) is a non-solvent to the
polymer
below the spin agent's normal boiling point; (2) forms a solution with the
polymer at
high pressure; (3) forms a desired two-phase dispersion with the polymer when
the
solution pressure is reduced slightly in a letdown chamber; and (4) flash
vaporizes
when released from the letdown chamber into a zone of substantially lower
pressure.
Commercial spunbonded products made from polyethylene
plexifilamentary film-fibril strands have been produced by flash-spinning a
spin fluid
comprised of polyethylene in a trichlorofluoromethane spin agent.
Unfortunately,
trichlorofluoromethane is considered to be a stratospheric ozone depletion
chemical,
and therefore, there is a need for alternative spin agents for use in the
flash-spinning
process.
The Ozone Depletion Potential ("ODP") for a compound is a relative
measure of the expected impact of the compound on the depletion of
stratospheric
ozone when the compound is released as a gas into the atmosphere as compared
to the
impact expected from the release of the same mass of trichlorofluoromethane
gas.
ODP values are used to compare the relative impacts of the release of
different gases
upon the Earth's ozone layer. The ODP values are generally calculated by
methods
like those described in Chapter 13 of "Scientific Assessment of Ozone
Depletion:
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1994," Report No. 37 of the World Meteorological Organization's Global Ozone
Research and Monitoring Project.
The Global Warming Potential ("GWP") for a compound is a relative
measure of the expected impact on the greenhouse warming of the Earth's
atmosphere
when the compound is released as a gas into the atmosphere as compared to the
impact expected from the release of the same mass of carbon dioxide gas into
the
atmosphere. GWP is dependent on the degree of absorbance of longwave radiation
(infared) by the compound, and the expected lifetime of the compound in the
atmosphere. GWP values are generally calculated by methods like those
described in
Chapter 13 of "Scientific Assessment of Ozone Depletion: 1994," Report No. 37
of
the World Meteorological Organization's Global Ozone Research and Monitoring
Proj ect.
In the flash-spinning process, the liquid spin agent is vaporized after
passing through the spin orifice. The gaseous spin agent is conventionally
collected,
condensed, purified, and then recycled into the spin agent feed stream for the
flash-
spinning process. However, it is likely that a certain amount of the gaseous
spin agent
will escape to the atmosphere at some point. Accordingly, there is a need to
find a
spin agent that works well in the flash-spinning process that also has a very
low ODP,
a very low GWP, a boiling point of less than 100° C, and either no
flash point or a
flash point greater than 0° C.
U.S. Patent 5,032,326 to Shin (assigned to DuPont) discloses an
alternative flash-spinning spin agent, namely, dichloromethane (also referred
to as
methylene chloride) and a halocarbon co-spin agent having a boiling point
between
0°C and -50°C.
Published Japanese Application JP5263310-A (published 10/12/93)
discloses that three-dimensional flash-spun fibers made from polymer dissolved
in
mixtures of spin agents where the major component of the spin agent mixture is
selected from the group consisting of dichloromethane, dichloroethylene, and
bromochloromethane, and the minor component of the spin agent mixture is
selected
from the group consisting of dodecafluoropentane, decafluoropentane, and
tetradecafluorohexane.
U.S. Patent 5,672,307 (assigned to DuPont) discloses a process for
flash-spinning plexifilamentary film-fibril strands from polyolefin polymer
dissolved
in mixtures of spin agents where the major component of the spin agent mixture
is
selected from the group consisting of dichloromethane and dichloroethylene,
and the
minor component of the spin agent mixture is selected from the group
consisting of
hydrofluoroethers and cyclic perfluorinated hydrocarbons, wherein the minor
compontent of the spin agent has 3 to 7 carbon atoms and an atmospheric
boiling
point between 15° C and 100° C.
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U.S. Patent 5,874,036 (assigned to DuPont) discloses a process for
flash-spinning plexifilamentary film-fibril strands from polyolefin polymer
dissolved
in mixtures of spin agents where the major component of the spin agent mixture
is
selected from the group consisting of dichloromethane and dichloroethylene,
and the
S minor component of the spin agent mixture is a cyclic partially fluorinated
hydrocarbon having 4 to 7 carbon atoms and an atmospheric boiling point
between
15° C and 100° C.
The co-spin agents disclosed in the four patent publications discussed
above do not exhibit the desired combination of having a very low ODP, a very
low
GWP, a boiling point of less than 100° C, and either no flash point or
a flash point
greater than 0° C. Accordingly, there is a need for an alternative co-
spin agent for use
in the flash-spinning process, which co-spin agent has a very low ODP, a very
low
GWP, a boiling point of less than 100° C, and either no flash point or
a flash point
greater than 0° C.
BRIEF SUMMARY OF THE INVENTION
The present invention is a process for the preparation of
plexifilamentary film-fibril strands of synthetic fiber-forming polymer. The
process
comprises the steps of generating a spin fluid and flash-spinning the spin
fluid at a
pressure that is greater than the autogenous pressure of the spin fluid into a
region of
lower pressure to form plexifilamentary film-fibril strands of the synthetic
fiber-
forming polymer. The spin fluid consists essentially of (a) 5 to 30 wt. % of a
synthetic fiber-forming polymer, (b) a primary spin agent selected from the
group
consisting of hydrocarbons with 4 to 7 carbon atoms, and chlorinated,
brominated and
fluorinated compounds, and (c) a co-spin agent selected from the group
consisting
essentially of fluorinated organic compounds containing 4 to 8 carbon atoms
and a
double bond and having an atmospheric boiling point of less than 100°C.
The co-spin
agent is present in the spin fluid in an amount sufficient to raise the cloud
point
pressure of the spin fluid by at least 50 pounds per square inch (345 kPa).
Preferably the co-spin agent is selected from the group consisting of
perfluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons,
hydrofluoroethers,
hydrofluoroesters, hydrofluoroalcohols, hydrofluoroketones, and mixtures
thereof.
More preferably, the co-spin agent is an unsaturated hydrofluorocarbon, and
most
preferably the co-spin agent is 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
The preferred primary spin agent for use in the process of the invention
is selected from the group of dichloroethylene, dichloroethane,
dichloromethane,
1,1,2-trichloro-2,2-difluoroethane, bromochloromethane, perfluorodecalin,
cyclopentane, n-pentane, cyclohexane, n-hexane, n-heptane, and mixtures
thereof.
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The preferred fiber-forming polymer for use in the process of the
invention is selected from the group consisting of polyolefms, partially
fluorinated
hydrocarbons, and fully fluorinated hydrocarbons. More preferably, the polymer
is a
polyolefin. Most preferably, the spin fluid contains 8 to 18 wt. %
polyethylene
polymer.
According to the preferred embodiment of the inveniton, the co-spin
agent comprises 10 to 80 wt. % of total weight of the primary and co-spin
agents.
Preferably, the co-spin agent has no flash point or a flash point greater than
0° C, an
Ozone Depletion Potential of less than 0.1, and a Global Warming Potential of
less
than 200. More preferably, the co-spin agent has an Ozone Depletion Potential
of less
than 0.05 and a Global Warming Potential of less than 100. Most preferably,
the co-
spin agent has a Global Warming Potential of less than 10. It is further
preferred that
the the co-spin agent be present in the spin fluid in an amount sufficient to
raise the
cloud point pressure of the spin fluid by at least 200 pounds per square inch
( 1379
kPa) and that the co-spin agent have a boiling point greater than 0° C.
The co-spin
agent may include at least one hydrogen atom.
The present invention is also directed to a spin fluid consisting
essentially of (a) 5 to 30 wt. % of a synthetic fiber-forming polymer, (b) a
primary
spin agent selected from the group consisting of hydrocarbons with 4 to 7
carbon
atoms, and chlorinated, brominated.and fluorinated compounds, and (c) a co-
spin
agent selected from the group consisting essentially of fluorinated organic
compounds
containing 4 to 8 carbon atoms and a double bond and having an atmospheric
boiling
point of less than 100°C. The co-spin agent is present in the spin
fluid in an amount
sufficient to raise the cloud point pressure of the spin fluid by at least 50
pounds per
square inch (345 kPa). Preferably the co-spin agent is selected from the group
consisting of perfluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons,
hydrofluoroethers, hydrofluoroesters, hydrofluoroalcohols, hydrofluoroketones,
and
mixtures thereof. More preferably, the co-spin agent is an unsaturated
hydrofluorocarbon, and most preferably the co-spin agent is 3,3,4,4,5,5,6,6,6-
nonafluoro-1-hexene. The preferred primary spin agent of the spin fluid is
selected
from the group of dichloroethylene, dichloroethane, dichloromethane, 1,1,2-
trichloro-
2,2-difluoroethane, bromochloromethane, perfluorodecalin, cyclopentane, n-
pentane,
cyclohexane, n-hexane, n-heptane, and mixtures thereof. The preferred
synthetic
fiber-forming polymer of the spin fluid is selected from the group consisting
of
polyolefins, partially fluorinated hydrocarbons, and fully fluorinated
hydrocarbons.
BRIEF DESCRIPTION OF THE DRAWINGS)
The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate an apparatus for practicing the
process of the
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invention, and the cloud point pressures for various spin fluids over a range
of
temperatures.
Figure 1 is a cross-sectional schematic representation of a spinning
apparatus according to the prior art.
Figure 2 is a plot of the cloud point data for a 10% by weight
polypropylene solution in a spin agent comprised of 100% trans-1,2-
dichloroethylene
and four mixtures of trans-1,2-dichloroethylene and 3,3,4,4,5,5,6,6,6-
nonafluoro-1-
hexene (also referred to as perfluorobutyl ethylene).
Figure 3 is a plot of the cloud point data for an 18% by weight high
density polyethylene solution in a spin agent comprised of 100% cyclopentane
and a
mixture of cyclopentane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
Figure 4 is a plot of the cloud point data for a 20% by weight
HALAR~ fluoropolymer (copolymer of alternating monomer units of ethylene and
chlorotrifluoroethylene) solution in a spin agent comprised of 100% trans-1,2-
dichloroethylene and four mixtures of trans-1,2-dichloroethylene and
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
Figure 5 is a plot of the cloud point data for a 12% by weight
KYNAR~ polyvinylidene fluoride polymer solution in a spin agent comprised of
100% dichloromethane and two mixtures of dichloromethane and 3,3,4,4,5,5,6,6,6-
nonafluoro-1-hexene.
Figure 6 is a plot of the cloud point data for 20% by weight TEFZEL~
copolymer of ethylene and tetrafluoroethylene solution in a spin agent
comprised of
100% dichloromethane, 100% 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, or one of
three
mixtures of dichloromethane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
Figure 7 is a plot of the cloud point data for a 20% by weight
TEFZEL~ copolymer of ethylene and tetrafluoroethylene solution in a spin agent
comprised of 100% trans-1,2-dichloroethylene or one of two mixtures of trans-
1,2-
dichloroethylene and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
Figure 8 is a plot of the cloud point data for a 12% by weight high
density polyethylene solution in a spin agent comprised of 100% trans-1,2-
dichloroethylene or one of five mixtures of trans-1,2-dichloroethylene and
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
Figure 9 is a plot of the cloud point data for a 12% by weight
polyethylene solution in a spin agent comprised of three mixtures of
dichloromethane
and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
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DEFINITIONS
The term "synthetic fiber-forming polymer" as used herein is intended
to encompass the classes of polymers known to be flash-spinnable in the flash-
spinning art.
The term "polyethylene" as used herein is intended to encompass not
only homopolymers of ethylene, but also copolymers wherein at least 85% of the
recurring units are ethylene units such as copolymers of ethylene and alpha-
olephins.
Preferred polyethylenes include linear low density polyethylene and linear
high
density polyethylene. A preferred linear high density polyethylene has an
upper limit
melting range of about 130° to 140°C, a density in the range of
0.94 to 0.98 gram per
cubic centimeter, and a melt index (as defined by ASTM D-1238-57T Condition E)
of
between 0. l and 100, and preferably less than 4.
The term "polypropylene" as used herein is intended to embrace not
only homopolymers of propylene but also copolymers where at least 85% of the
recurring units are propylene units. Preferred polypropylene polymers include
isotactic polypropylene and syndiotactic polypropylene.
The term "polyolefin" as used herein, is intended to mean any of a
series of largely saturated polymeric hydrocarbons composed only of carbon and
hydrogen. Typical polyolefins include, but are not limited to, polyethylene,
polypropylene, polymethylpentene and various combinations of the monomers
ethylene, propylene, and methylpentene.
The term "plexifilamentary" as used herein, means a three-dimensional
integral network of a multitude of thin, ribbon-like, film-fibril elements of
random
length and with a mean film thickness of less than about 4 micrometers and a
median
fibril width of less than about 25 micrometers. In plexifilamentary
structures, the
film-fibril elements are generally coextensively aligned with the longitudinal
axis of
the structure and they intermittently unite and separate at irregular
intervals in various
places throughout the length, width and thickness of the structure to form a
continuous three-dimensional network.
The term "cloud-point pressure" as used herein, means the pressure at
which a single phase liquid polymer solution starts to phase separate into a
polymer-
rich/spin agent-rich two-phase liquid/liquid dispersion.
TEST METHODS
The denier of the strand was determined from the weight of a 15 cm
sample length of strand under a predetermined load.
Tenacity and elongation of the flash-spun strand were determined with an
Instron tensile-testing machine. The strands were conditioned and tested at
70°F
(21°C) and 65% relative humidity. The strands were then twisted to 10
turns per inch
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and mounted in the jaws of the Instron Tester. A two-inch gauge length was
used
with an initial elongation rate of 4 inches per minute ( 10.2 cm/min). The
tenacity at
break is recorded in grams per denier (gpd). The elongation at break is
recorded as a
percentage of the two-inch gauge length of the sample. Modulus corresponds to
the
slope of the stress/strain curve and is expressed in units of gpd.
The apparatus and procedure for determining the cloud point pressures of
a polymer/spin agent combination are those described in U.S. patent 5,147,586
to
Shin et al.
The flash point for a compound is determined in accordance with ASTM
Method D-56-79.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the presently preferred
embodiments of the invention, examples of which are illustrated below. The
present
invention relates to flash-spinning of spin fluids comprising a fiber-forming
polymer
and a novel spin agent to form polymeric plexifilamentary film-fibril strands.
The
general flash-spinning apparatus chosen for illustration of the present
invention is
similar to that disclosed in U.S. Patent 3,860,369 to Brethauer et al., which
is hereby
incorporated by reference. A system and process for flash-spinning a fiber-
forming
polymer is fully described in U.S. Patent 3,860,369, and is shown in Figure 1.
The
flash-spinning process is normally conducted in a chamber 10, sometimes
referred to
as a spin cell, which has a spin agent removal port 1 l and an opening 12
through
which non-woven sheet material produced in the process is removed. A spin
fluid,
comprising a mixture of polymer and spin agent, is provided through a
pressurized
supply conduit 13 to a spinning orifice 14. The spin fluid passes from supply
conduit
13 to a chamber 16 through a chamber opening 15. In certain spinning
applications,
chamber 16 may act as a pressure letdown chamber wherein a reduction in
pressure
causes phase separation of the spin fluid, as is disclosed in U.S. Patent
3,227,794 to
Anderson et al. A pressure sensor 22 may be provided for monitoring the
pressure in
the chamber 16.
The spin fluid in chamber 16 next passes through spin orifice 14. It is
believed that passage of the pressurized polymer and spin agent from the
chamber 16
into the spin orifice generates an extensional flow near the approach of the
orifice that
helps to orient the polymer. When polymer and spin agent discharge from the
orifice,
the spin agent rapidly expands as a gas and leaves behind fibrillated
plexifilamentary
film-fibrils. The gas exits the chamber 10 through the port 11. Preferably,
the
gaseous spin agent is condensed for reuse in the spin fluid.
The polymer strand 20 discharged from the spin orifice 14 is
conventionally directed against a rotating deflector baffle 26. The rotating
baffle 26
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spreads the strand 20 into a more planar web structure 24 that the baffle
alternately
directs to the left and right. As the spread web descends from the baffle, the
web is
electrostatically charged so as to hold the web in a spread open configuration
until the
web 24 reaches a moving belt 32. The web 24 deposits on the belt 32 to form a
batt
34. The belt is grounded to help insure proper pinning of the charged web 24
on the
belt. The fibrous batt 34 may be passed under a roller 31 that compresses the
batt into
a sheet 35 formed with plexifilamentary film-fibril networks oriented in an
overlapping mufti-directional configuration. The sheet 35 exits the spin
chamber 10
through the outlet 12 before being collected on a sheet collection roll 29.
According to the present invention, the spin agent comprises a mixture of
a primary spin agent and a co-spin agent. The primary spin agent is selected
from the
group consisting of hydrocarbons having four to seven carbon atoms and other
chlorinated, brominated of fluorinated compounds having an ODP less than 0.1
and a
GWP less than 200. The co-spin agent comprises a partially or fully
fluorinated
organic compound containing a double bond. As used herein, the term "primary
spin
agent" refers to the spin agent component having the greatest solubility in
the
polymer. The spin agent mixtures are especially useful when the primary spin
agent
has such a high solubility in the polymer that the cloud-point pressure of a
solution of
5 - 30 wt% polymer (based on the total weight of the spin fluid) in the
primary spin
agent is so close to the bubble point that it is not possible to operate the
flash spinning
process efficiently. For example, the mixed spin agents are particularly
useful when a
solution of the polymer in the primary spin agent has a cloud point pressure
less than
about 2000 lb/in2 (psi)(13790 kPa), and more preferably less than about 1000
psi
(6895 kPa), at the flash spinning temperature, which is generally between T~ -
40 °C
and T~ + 40 °C (T~ = spin agent critical temperature). The co-spin
agent is added to
the primary spin agent in a sufficient amount to raise the cloud-point
pressure of the
polymer solution by at least 50 psi (345 kPa). Preferably, the cloud-point
pressure of
the polymer solution is raised at least 200 psi (1379 kPa) by the addition of
the co-
spm agent.
Examples of suitable primary spin agents include chlorinated solvents
such as trans-1,2-dichloroethylene, cis-1,2-dichloroethylene, 1,l
dichloroethane,
dichloromethane, and 1,1,2-trichloro-2,2-difluoroethane (HCFC-122), brominated
solvents such as bromochloromethane and propyl bromide, fluorinated solvents
such
as perfluorodecalin, and hydrocarbons such as cyclopentane, cyclohexane, n-
hexane,
and n-heptane. Under conditions generally used in flash-spinning processes,
some of
the trans-1,2-dichloroethylene isomerizes to form cis-1,2-dichloroethylene.
Therefore, whenever trans-1,2-dichloroethylene is used herein, it is
understood to
include mixtures of trans- and cis-1,2-dichloroethylene. The preferred primary
spin
agents for flash spinning polyolefins are trans-1,2-dichloroefhylene and
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dichloromethane. HCFC-122 is less preferred due to toxicity issues. The
brominated
solvents are less stable at high temperatures used in flash spinning and
therefore are
also less preferred.
Preferably, the compounds used as primary spin agents in the process of
the invention exhibit a low ozone depletion potential of less than 0.1, and
more
preferably of less than 0.05. The primary spin agents should also exhibit a
low global
warming potential of less than 200, and preferably less than 100, and more
preferably
less than 10. It is further preferred that the primary spin agents of the
invention
exhibit low flammability or combustibility (either no flash point or a flash
point
greater than 0 °C). In addition, the compounds used as primary spin
agents in the
flash-spinning process of the invention preferably have a dielectric strength
of at least
40 kV/cm, and more preferably of at least 60 kV/cm.
According to the preferred embodiment of the invention, the co-spin
agent should be capable of raising the cloud point pressure of the spin fluid
by at least
50 psi (345 kPa) at spin temperatures in the general range of 150° C to
360° C,
depending on the polymer and spin agents) being spun. Preferably, the co-spin
agent
is added to the spin fluid in an amount such that the co-spin agent comprises
from
10% to 80% by weight of the spin agent in the spin fluid. The co-spin agent
should
have an atmospheric boiling point of less than about 100 °C. More
preferably, the co-
spin agent has an atmospheric boiling of between 0°C and 100 °C,
and most
preferably of between about 20°C and about 70°C. The boiling
point of the co-spin
agent should be less than 100°C because the co-spin agent must readily
vaporize
during flash-spinning when the spin fluid is discharged through a spin orifice
into a
zone maintained at approximately atmospheric pressure. The co-spin agent
preferably
has an atmospheric boiling point above 0°C and more preferably above
20°C because
in the flash-spinning process, the spin agent is condensed for reuse after it
flash
vaporizes. If the boiling point of the co-spin agent is below 0°C, it
is difficult and
expensive to condense the co-spin agent for reuse in the flash-spinning
process.
The compounds used as co-spin agents in the process of the invention
have an improved combination of properties making them desirable for use in
flash-
spinning. The compounds exhibit a low ozone depletion potential of less than
0.1,
and more preferably of less than 0.05. The co-spin agents also exhibit a low
global
warming potential of less than 200, and preferably less than 100, and more
preferably
less than 10. The co-spin agents of the invention also exhibit low
flammability or
combustibility (either no flash point or a flash point greater than 0
°C). The
compounds used as co-spin agents in the flash-spinning process of the
invention
preferably have a dielectric strength of at least 40 kV/cm, and more
preferably at least
60 kV/cm.
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The co-spin agents used in the process of the invention are partially or
fully fluorinated organic compounds containing a double bond. Without wishing
to
be bound by theory, it is believed that the presence of the fluorine atoms in
the
compound reduces the flammability of the co-spin agent while the presence of
the
double bond in the compound keeps the global warming potential of the compound
low. Preferred co-spin agents include unsaturated perfluorocarbons,
unsaturated
hydrofluorocarbons, and unsaturated hydrofluoroethers.
Suitable unsaturated perfluorocarbon co-spin agents include perfluoro-2-
pentene and perfluorocyclopentene. Other acyclic perfluoroolefins having from
4 to 8
carbon atoms and from 8 to 16 fluorine atoms, respectively, should have low
flammability, a zero ODP, a low GWP, and a boiling point within the range
required
for a satisfactory flash-spinning co-spin agent. Examples of such compounds
include
perfluoro-1-heptene, CF3CF=CFCF3, CF3CF=CFCF2CF3, CF3CF2CF=CFCF2CF2CF3,
CF3CF=CFCF2CF2CF2CF3, (CF3)2C=CFCF2CF3, (CF3)ZCFCF=CFCF3. Other cyclic
perfluoroolefins having 4 to 8 carbon atoms should have low flammability, a
zero
ODP, a low GWP, and a boiling point within the range required for a
satisfactory co-
spin agent. Examples of such cyclic compounds include perfluorocyclobutene,
perfluorocyclohexene, 1-perfluoroethyl-perfluorocyclobutene, 1-perfluoromethyl-
perfluorocyclopentene, and 1-perfluoroethyl-perfluorocyclobutene.
A preferred co-spin agent useful in the present invention is
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene (also known as perfluorobutyl ethylene)
(commercially available from DuPont under the tradename Zonyl~ PFBE), which
has
a GWP of less than about 10, an ozone depletion potential of zero and and no
flash
point. There are other acyclic unsaturated hydrofluorocarbons with limited
hydrogen
atoms that should have low flammability, a zero ODP, a low GWP, and a boiling
point within the range required for a satisfactory flash-spinning co-spin
agent.
Examples of such compounds include CF3(CFZ)nCH=CH2,where n equals 1, 2, 4, 5,
or
6; CF3CH=CHCF3; CF3CF2CH=CHCFZCF3; CF3CH=CHCF2CF3; (CF3)2C=CH2;
CF3CH=CFCFZCF3; CF3CF=CHCF2CF3; 6H-perfluoro-1-hexene; 3,4,4,5,5,5-
hexafluoro-3-(trifluoromethyl)-1-pentene; and 4,5,5,6,6,6-hexafluoro-4-
(trifluoromethyl)-2-hexene.
Cyclic hydrofluoroolefins having 4 to 6 carbon atoms should have low
flammability, a zero ODP, a low GWP, and a boiling point within the range
required
for a satisfactory co-spin agent in the process and spin fluid of the current
invention.
Examples of such cyclic compounds include 1H, 2H-perfluorocyclobutene,
1H, 2H-perfluorocyclopentene, 1H-perfluorocyclobutene, and
1 H-perfluorocyclopentene.
Certain hydrochlorofluorocarbons with low (but not zero) ODPs and low
GWPs that are expected to make satisfactory co-spin agents for the process and
spin
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
fluid of the present invention include 4-chloro-1,1,2-trifluoro-1-butene, and
1-chloro-
2,3,3-trifluorocyclobutene.
Unsaturated hydrofluoroether co-spin agents that should have low
flammability, a zero ODP, a low GWP, and a boiling point within the range
required
for a satisfactory flash-spinning co-spin agent, include the following: 1,2-
dimethoxy-
3,3,4,4,5,5-hexafluorocyclopentene, 1-ethoxy-2,3,3,4,4,5,5-
heptafluorocyclopentene,
1-methoxy(perfluoro-2-methyl-1-propene), CF3CF=CFOCH3, CF3CF=CFOCH2CH3,
(CF3)2C=CFOCH3, CF3CF=C(CF3)OCH2CH3, CF3C(OCH2CH3)=CFCF2CF3.
Other unsaturated compounds that are expected to make satisfactory co-
spin agents in the process and spin fluid of the invention include
hydrofluoroesters,
hydrofluoroalcohols, and hydrofluoroketones with a double bond. The preferred
hydrofluoroesters include CF2=CFC02CH3, CF3CF2C02CH=CH2,
CF3CF=CFCOZCH3, and CF3CF2 CF2C02CH =CH2. The preferred
hydrofluoroalcohols include CF2=CFCHZOH, CF3CF=CFCHZOH,
CF3CF=C(CH3)OH. A preferred hydrofluoroketone is CF3CF=CFCOCH3.
Fiber forming synthetic polymers that can be flash-spun from the spin
agents described above include polyolefins such as polyethylene,
polypropylene,
poly(4-methyl pentene-1), and blends thereof. Such polyolefins can be flash-
spun
from a spin fluid in which the polyolefin is dissolved in a spin agent
comprised of a
primary spin agent such as dichloromethane, dichloroethylene, or HCFC-122, and
a
co-spin agent that is one of the partially or fully fluorinated organic
compounds
containing a double bond that are described above. Preferred spin agents for
polyolefins include mixtures of 1,2-dichloroethylene and 3,3,4,4,5,5,6,6,6-
nonafluoro-
1-hexene, dichloromethane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, and
cyclopentane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene.
Other fiber forming synthetic polymer that can be flash-spun from the
spin agents described above include partially fluorinated hydrocarbon polymers
in
which between 10% and 70% of the total number of hydrogen atoms in the
hydrocarbon polymer are replaced by fluorine atoms. Preferably, the partially
fluorinated hydrocarbon polymers are comprised of at least 80% by weight of
polymerized monomer units selected from ethylene, tetrafluoroethylene,
chlorotrifluoroethylene, vinylidene fluoride and vinyl fluoride. A
particularly
preferred partially fluorinated hydrocarbon polymer is comprised of 40% to 70%
by
weight of polymerized monomer units of tetrafluoroethylene and 10% to 60% by
weight of polymerized monomer units of ethylene, such as a copolymer comprised
of
substantially alternating units of ethylene and tetrafluoroethylene with the
chemical
structure -(CH2CH2)-(CF2CF2)-. Such ethylene/tetrafluoroethylene copolymers
are
disclosed, for example, in U.S. Patents 3,624,250 to Carlson (assigned to
DuPont),
3,870,689 to Modena et al., and 4,677,175 to Ihara et al.
Ethylene/tetrafluoroethylene
11
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copolymer resin is commercially available from DuPont under the tradename
TEFZEL~, which is a registered trademark of DuPont. TEFZEL~ fluoropolymer
resins have melting points between 235° and 280 °C.
Another partially fluorinated hydrocarbon polymer that may be flash-spun
from the spin agents described above is a polymer comprised of greater than
85% to
70% by weight of polymerized monomer units of vinylidene fluoride.
Polyvinylidene
fluoride polymer resins with the chemical structure -(CH2CF2)- are
commercially
available from Elf Atochem under the tradename KYNAR~, which is a registered
trademark of Elf Atochem. KYNAR~ fluoropolymer resins have a melting point of
about 170 °C. Another partially fluorinated hydrocarbon polymer that
may be flash-
spun from the spin agents described above is a copolymer of alternating
monomer
units of ethylene and chlorotrifluoroethylene, such as HALAR~ fluoropolymer
resin
obtained from Ausimont. Another partially fluorinated polymer that may be
flash-
spun from the spin agents described above is polyvinyl fluoride.
Figures 2-9 are plots of cloud point pressure vs. temperature for a
number of polymers in various mixtures of a strong primary spin agent
(dichloroethylene, dichloromethane, or cyclopentane) and 3,3,4,4,5,5,6,6,6-
nonafluoro-1-hexene co-spin agent. Where spin agent ratios are expressed
herein, the
first number refers to weight percent of the primary spin agent in the spin
agent
mixture, and the second number refers to the weight percent of the co-spin
agent in
the spin agent mixture.
Figure 2 is a plot of the cloud point data for a solution of a 10% by
weight solution of polypropylene in a spin agent comprised of either a mixture
of
trans-1,2-dichloroethylene and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene at four
different
spin agent weight ratios (50/50, curve 40; 60/40, curve 41; 70/30, curve 42;
and
80/20, curve 43) or 100% trans-1,2-dichloroethylene (curve 44).
Figure 3 is a plot of the cloud point data for an 18% by weight high
density polyethylene solution in a spin agent comprised of 65% cyclopentane
and
35% 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene (curve 46) or 100% cyclopentane
(curve 47).
Figure 4 is a plot of the cloud point data for a 20% by weight
HALAR~ fluoropolymer (copolymer of alternating monomer units of ethylene and
chlorotrifluoroethylene) solution in a spin agent comprised of a mixture of
trans-1,2-
dichloroethylene and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene at four different
spin
agent weight ratios (50/50, curve 50; 60/40, curve 51; 70/30, curve 52; and
80/20,
curve 53) or 100% trans-1,2-dichloroethylene (curve 54).
12
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WO 01/14620 PCT/US00/22729
Figure 5 is a plot of the cloud point data for a 12% by weight
KYNAR~ polyvinylidene fluoride polymer solution in a spin agent comprised of a
mixture of dichloromethane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene at three
different spin agent weight ratios (80/20, curve 55; 85/15, curve 56; and
90/10, curve
57) or 100% dichloromethane (curve 58).
Figure 6 is a plot of the cloud point data for a 20% by weight
TEFZEL~ copolymer solution of ethylene and tetrafluoroethylene in a spin agent
comprised of a mixture of dichloromethane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-
hexene
at 2 different spin agent weight ratios (25/75, curve 61; and 50/50, curve
62), or 100%
3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene (curve 60), or 100% dichloromethane
(curve 63).
Figure 7 is a plot of the cloud point data for a 20% by weight
TEFZEL~ copolymer solution of ethylene and tetrafluoroethylene in a spin agent
comprised of a mixture of trans-1,2-dichloroethylene and 3,3,4,4,5,5,6,6,6-
nonafluoro-1-hexene at 2 different spin agent weight ratios (25/75, curve 66;
and
50/50, curve 67), or 100% trans-1,2-dichloroethylene (curve 68).
Figure 8 is a plot of the cloud point data for a 12% by weight high
density polyethylene solution in a spin agent comprised of a mixture of trans-
1,2-
dichloroethylene and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene at four different
spin
agent weight ratios (65/35, curve 75; 70/30, curve 74; 72.5/27.5, curve 73;
75/25,
curve 72; and 80/20, curve 71), or 100% trans-1,2-dichloroethylene (curve 70).
Figure 9 is a plot of the cloud point data for a 12% by weight high
density polyethylene solution in a spin agent comprised of a mixture of
dichloromethane and 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene at three different
spin
agent weight ratios (75/25, curve 80; 80/20, curve 79, and 85/15, curve 78).
This invention will riow be illustrated by the following non-limiting
examples which are intended to illustrate the invention and not to limit the
invention
in any manner.
EXAMPLES
The apparatus used in the Examples is the spinning apparatus
described in U.S. Patent No. 5,147,586. The apparatus consists of two high
pressure
cylindrical chambers, each equipped with a piston 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 3/32 inch (0.23 cm) diameter
channel
and a mixing chamber 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
13
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
between the two cylinders through the static mixer. A spinneret assembly with
a
quick-acting means for opening the orifice is attached to the channel through
a tee.
The spinneret assembly consists of a lead hole of 0.25 inch (0.63 cm) diameter
and
about 2.0 inch (5.08 cm) length, and a spinneret orifice with a length and a
diameter
S each measuring 30 mils (0.762 mm). The pistons are driven by high pressure
water
supplied by a hydraulic system.
In the tests reported in Examples 1-19, the apparatus described above was
charged with pellets of a polymer and a spin agent. High pressure water was
used to
drive the pistons to generate a mixing pressure of between 1500 and 4500 psig
(10,239 - 30,717 kPa). The polymer and spin agent were then heated to the
mixing
temperature 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 50 psi
(345 kPa) or higher between the two cylinders so as to repeatedly force 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 fluid. The spin fluid temperature was
then
raised to the final spin temperature,.and held there for about 15 minutes or
longer to
equilibrate the temperature, during which time mixing was continued. In order
to
simulate a pressure letdown chamber, the pressure of the spin fluid was
reduced to a
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 is
opened
as rapidly as possible after the opening of the valve between the spin cell
and the
accumulator. This generally takes about one to three seconds. This is intended
to
simulate the letdown chamber effect that is used in larger scale spinning
operations.
The resultant flash-spun product was collected in a stainless steel open mesh
screen
basket. The pressure recorded just before the spinneret (using a computer)
during
spinning is entered as the spin pressure.
It is noted that pressures may be expressed as psig which is pounds per
square inch gage which is approximately 15 psi less than psia (pound per
square inch
absolute). The unit psi is considered the same as psia. For converting to SI
units,
1 psi = 6.9 kPa. In the following tables pressures are reported in psig with
the
corresponding kPa values in parentheses.
Examples 1-3
In Examples 1-3, high density polyethylene having a melt index of 0.75
g/10 min (measured according to ASTM D1238 at 190 °C and 2.16 kg load)
and a
density of 0.95 g/cm3 (Alathon~, obtained from Equistar Chemicals LP of
Houston,
TX) was flash spun using a mixture of trans-1,2-dichloroethylene (DCE) and
Zonyl~
14
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
PFBE (3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont) as the spin
agent.
Spin fluids were prepared having concentrations of high density
polyethylene of 12 weight percent, 14 weight percent, and 10 weight percent
(based
on the total weight of the spin fluid) for Examples 1, 2, and 3, respectively.
The spin
agent was a mixture of 75 wt% trans-1,2-dichloroethylene and 25 wt% PFBE,
based
on the total weight of spin agent. A diphosphite thermal stabilizer (Weston
619F,
from GE Specialty Chemicals) was added at 0.1 weight percent, based on total
spin
agent. The cloud point pressure plot for the spin solution of Example 1 is
shown in
Figure 8 as curve 72.
Plexifilamentary fibers of good quality were obtained by flash spinning
the spin fluids using the spinning conditions given in Table 1.
Example 4
1 S In this example, high density polyethylene having a melt index of 0.75
g/10 min (measured according to ASTM D1238 at 190 °C and 2.16 kg load)
and a
density of 0.95 g/cm3 (Alathon~, obtained from Equistar Chemicals LP of
Houston,
TX) was flash spun using a mixture of dichloromethane and Zonyl~ PFBE
(3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont) as the spin
agent.
A spin fluid was prepared having a concentration of high density polyethylene
of 12
weight percent based on the total weight of the spin fluid. The spin agent was
a
mixture of 80 wt% dichloromethane and 20 wt% PFBE, based on the total weight
of
spin agent. A diphosphite thermal stabilizer (Weston 619F, from GE Specialty
Chemicals) was added at 0.1 weight percent, based on total spin agent. The
cloud
point pressure plot for the spin solution of Example 4 is shown in Figure 9 as
curve
79.
Plexifilamentary fibers of good quality were obtained by flash spinning
the spin fluid using the spinning conditions given in Table 1.
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
' ~ 0 0
w owo
.-,
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16
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WO 01/14620 PCT/US00/22729
Example 5
In this example, Tefzel~ fluoropolymer (grade HT 2129 obtained from
DuPont) was flash spun from a mixture of trans-1,2-dichloroethylene (DCE)and
Zonyl~ PFBE (3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont).
Tefzel~ HT 2129 fluoropolymer is a copolymer of substantially alternating
monomer
units of ethylene and tetrafluoroethylene with a melt flow rate of 7 g/10 min
(measured according to ASTM D3159) and a melting point of about 240 °C.
A spin fluid was prepared having a concentration of 20 v~~t% Tefzel~
fluoropolymer based on the total weight of the spin fluid. The spin agent was
a
mixture of 25 wt% trans-1,2-dichloroethylene and 75 wt% PFBE, based on the
total
weight of spin agent. The cloud point pressure plot for the spin solution of
Example 5
is shown in Figure 7 as curve 66.
Plexifilamentary fibers of good quality were obtained by flash spinning
the spin fluid using the spinning conditions given in Table 2.
Examples 6-8
In Examples 6-8, Tefzel~ fluoropolymer (grade HT 2129 obtained from
DuPont) was flash spun from a mixture of dichloromethane and Zonyl~ PFBE
(3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont). Tefzel~ HT 2129
fluoropolymer is a copolymer of substantially alternating monomer units of
ethylene
and tetrafluoroethylene with a melt flow rate of 7 g/10 min (measured
according to
ASTM D3159) and a melting point of about 240 °C.
Spin fluids were prepared having a concentration of 20 wt% Tefzel~
fluoropolymer based on the total weight of the spin fluid. The spin agent used
in each
of the spin fluids was a mixture of 25 wt% dichloromethane and 75 wt% PFBE,
based
on the total weight of spin agent. The cloud point pressure plot for the spin
solution
of Examples 6-8 is shown in Figure 6 as curve 61.
Different spinning conditions were used for Examples 6-8, as detailed in
Table 2. Plexifilaments of good quality were obtained in every case.
Example 8a
In Example 8a, Tefzel~ fluoropolymer (grade HT 2129 obtained from
DuPont) was flash spun from 100% Zonyl~ PFBE (3,3,4,4,5,5,6,6,6-nonafluoro-1-
hexene, obtained from DuPont). Tefzel~ HT 2129 fluoropolymer is a copolymer of
substantially alternating monomer units of ethylene and tetrafluoroethylene
with a
melt flow rate of 7 g/10 min (measured according to ASTM D3159) and a melting
point of about 240 °C.
17
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
The spin fluid was prepared having a concentration of 20 wt% Tefzel~
fluoropolymer based on the total weight of the spin fluid. The spin agent was
100%
PFBE. The cloud point pressure plot for the spin solution of Example 6 is
shown in
Figure 6 as curve 60.
The spinning conditions and product properties are reported in Table 2.
Plexifilaments of good quality were obtained.
18
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
w ow' M ,-, o, o,
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19
CA 02376499 2002-O1-07
WO 01/14620 PCTlUS00/22729
Ezamples 9-12
In Examples 9-12, Kynar~ polyvinylidene fluoride polymer (grade 760,
obtained from Elf Atochem) was flash spun from a mixture of dichloromethane
and
Zonyl~ PFBE (3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont).
Kynar~ 760 polyvinylidene fluoride polymer resins has a melting point of 165-
170° C and a melt flow rate of 2-4 g/10 min (measured according to ASTM
D1238 at
450 °F (232 °C) and 27.6 pounds (12.5 kg) load).
Spin fluids were prepared having a concentration of 12 wt% Kynar~
fluoropolymer based on the total weight of the spin fluid for Examples 9-11
and
18 wt% for Example 12. The spin agent used in each of the spin fluids was a
mixture
of 85 wt% dichloromethane and 15 wt% PFBE, based on the total weight of spin
agent. A diphosphite thermal stabilizer (Weston 619F, from GE Specialty
Chemicals)
was added at 0.1 weight percent, based on total spin agent. The cloud point
pressure
plot for the spin solution of Examples 9-11 is shown in Figure 5 as curve 56.
Spinning conditions for Examples 9-12 are given in Table 3.
Plexifilaments of good quality were obtained in each spin test.
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
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21
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
Examples 13-16
In Examples 13-16, Halar~ fluoropolymer resin (grade 901, obtained
from Ausimont), comprised of a copolymer of ethylene and
chlorotrifluoroethylene,
was flash spun from a mixture of trans-1,2-dichloroethylene and Zonyl~ PFBE
(3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont). Halar~ 901
fluoropolymer resin has a melting point of 240 °C and a melt index of
about 1 g/10
mm.
Spin fluids were prepared having a concentration of 20 wt% Halar~
fluoropolymer based on the total weight of the spin fluid. The spin agent used
in
Examples 13-15 was a mixture of 70 wt% trans-1,2-dichloroethylene (DCE) and 30
wt% PFBE, based on the total weight of spin agent. The spin agent for Example
16
was a mixture of 60 wt% trans-1,2-dichloroethylene and 40 wt% PFBE, based on
the
total weight of spin agent. A diphosphite thermal stabilizer (Weston 619F,
from GE
Specialty Chemicals) was added at 0.1 weight percent, based on total spin
agent. The
cloud point pressure plot for the spin solution of Examples 13-15 is shown in
Figure 4
as curve 52. The cloud point pressure plot for the spin solution of Example 16
is
shown in Figure 4 as curve 51.
Spinning conditions for Examples 13-16 are given in Table 4.
Plexifilaments of good quality were obtained in each spin test.
22
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
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... ~, 0 0 0 0
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~ N ~ N ~ N ~ N
~, ~I r-i r1 v-i
H
,~ x ~ O ~ O ~ O ~ O
w , -~o ~ o ~ o ~ o
U v7o o O o
I .~ ro CLN ~ N ~ N ~ N
x w _.
U o 0 o 0
N N N N
W W W W
M
Cu Ga Ga Ga
N O W O W O f1O LL
M \ M \ M \ c~ \
r-I \ W \ W \ W \ W
O o U o U o U o U
V7 ~ ~ t~ Ca~ La~ Ca
M C ~ l0
>C O
w z
23
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
Examples 17-18
In Examples 17-18, polypropylene (obtained from Montell) having a melt
flow rate of 1.4 g/10 min (measured according to ASTM D1238 at 190 °C
and 2.16 kg
load) and a melting point of 165 °C was flash spun from a mixture of
trans-1,2
dichloroethylene and Zonyl~ PFBE (3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene,
obtained
from DuPont).
Spin fluids were prepared having a concentration of 10 wt%
polypropylene, based on the total weight of the spin fluid. The spin agent
used was a
mixture of 60 wt% trans-1,2-dichloroethylene (DCE) and 40 wt% PFBE, based on
the
total weight of spin agent. A diphosphite thermal stabilizer (Weston 619F,
from GE
Specialty Chemicals) was added at 0.1 weight percent, based on total spin
agent. 'The
cloud point pressure plot for the spin solution of Examples 17 and 18 is shown
in
Figure 2 as curve 41.
Spinning conditions for Examples 17-18 are given in Table 5.
Plexifilaments of good quality were obtained in each spin test.
24
CA 02376499 2002-O1-07
WO 01/14620 PCT/ITS00/22729
N d,
W oWN
r1
O , N
CT~'
p N
O
-r-I
N Q-'~1 N
O H ~T
O r-I N
LL
N O 01
L1 N r1
i
W 0 O O
~ C ~T
C~
i~ U o 0
1 N N
C~
(T Or .-. ~
a,o t~ o
~~., -ri G -rl~ v' ~
n ~ ~r c~
C (1 GL ~o ~
-rl cn c
M ~o
r.r
Ct~ Pa o _ _
O ~ ~ ~ o
-~o m ,--i
U m ,~ ~ o
O C1~ h o~
o
t~
mO
~1
4~
O ~
c
,L~~, A-'-'1O ~ O
... a tn
.fin (1, N
N
.,r
~
O~O ~ O
~ G -riO ~ O
_, C U u mn o ~n
-ri b OaN ~ N
Pa v--I
O O
,~ ~ M f~
CC
U o
H N N
W W
+~ a7 p4
G w Ga
N O LL O
0.i
5 ~ \ V~
\
rI \ W \
W
O o U o
U
v? ~o Ca ~o
CJ
>C O
w z
CA 02376499 2002-O1-07
WO 01/14620 PCT/US00/22729
Example 19
In this example, high density polyethylene having a melt index of
0.75 g/10 min (measured according to ASTM D1238 at 190 °C and 2.16 kg
load)
and a density of 0.95 g/cm3 (Alathon~, obtained from Equistar Chemicals LP of
Houston, TX) was flash spun using a mixture of cyclopentane and Zonyl~ PFBE
(3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, obtained from DuPont) as the spin
agent.
A spin fluid was prepared having a concentration of high density polyethylene
of
18 weight percent based on the total weight of the spin fluid. The spin agent
was
a mixture of 65 wt% cyclopentane and 35 wt% PFBE, based on the total weight of
spin agent. A diphosphite thermal stabilizer (Weston 619F, from GE Specialty
Chemicals) was added at 0.1 weight percent, based on total spin agent. The
cloud
point pressure plot for the spin solution of Example 19 is shown in Figure 3
as
curve 46.
The spin fluid was prepared at a mixing temperature of 200 °C,
mixing time of 20 minutes, with a back pressure of 2500 psig and DP of 250.
Flash spinning was conducted with an accumulator pressure of 1300 psig, spin
pressure of 1150 psig, and spin temperature of 200 °C. Plexifilamentary
fibers of
good quality were obtained having a denier of 262 (100 g load), tenacity of
2.57
grams per denier, modulus of 6.31 grams per denier, and a percent elongation
of
100%.
26
