KR0136110B1 - Halocarbons for flash spinning of polymeric plexifilaments - Google Patents

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Description

Halocarbons for Flash Spinning Polymeric Flexifilments

The present invention relates to a method of flash spining polymeric film-fibrils strands. In particular, the present invention relates to a process for improving the process of flash spinning strands from liquids that do not adversely affect ozone on earth even when released into the atmosphere.

Blades and White, US Pat. No. 3,081,519, discloses a flash spinning method for making flexiformed film-fibrillated strands from fiber forming polymers. Below the standard boiling point, the polymer solution in the liquid in which the polymer does not dissolve is extruded into a medium that is significantly low and low temperature at temperatures above and above the standard boiling point of the liquid and at either self or high pressure. This flash spinning causes the liquid to evaporate, thereby cooling the extrudate which forms the film's flexi filamentous film-fibril strand. Preferred polymers include crystalline hydrocarbon polymers such as polyethylene and polypropylene.

According to the above-mentioned patent document, a solution suitable for flash spinning has (a) a boiling point of 25 ° C. to the melting point of the polymer; (b) hardly react with the polymer at the extrusion temperature; (c) be soluble to the polymer under the pressure and temperature mentioned in the patent document (ie, this extrusion temperature and extrusion pressure are 165 to 225 ° C. and 545 to 1490 psia, respectively); (d) dissolve the polymer below 1% below the standard boiling point; A solution must be formed in which phase separation occurs rapidly during extrusion so that a lack of solvent can form a polymer phase that does not plasticize the polymer. Depending on the specific polymer used, the following liquids may be used in the flash spinning process: aromatic hydrocarbons (eg benzene, toluene, etc.); Aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane, isomers and homologues thereof; Alicyclic hydrocarbons such as cyclohexane; Unsaturated hydrocarbons; Halogenated hydrocarbons such as methylene chloride, carbon tetrachloride, chloroform, ethyl chloride, methyl chloride and the like; Alcohol; ester; ether; Ketones; Nitrile; amides; Fluorocarbons; Sulfur dioxide; Carbon disulfide; Nitromethane; Water and mixtures of these liquids, the patent document also schematically describes certain principles that help to establish optimal spinning conditions for obtaining flexi filamentous strands. The patent document also states that the flash spinning solution may further contain liquefied gas (eg nitrogen, carbon dioxide, helium, hydrogen, methane, propane, butane, ethylene, propylene, butene, etc.). Preferred liquefied gases for improving flexifilment fibrillation are poorly soluble gases dissolved at a concentration of less than 7% in polymer solutions under spinning conditions. Prior to extrusion, conventional additives such as antioxidants, UV stabilizers, dyes, pigments and the like may also be added to the solution.

Drawings similar to those of blades and whites for selecting the spinning conditions of flexifiltrated strands are described in the literature (US Pat. No. 3,227,794 to Anderson and Romano). The graph shows spinning pressure versus spinning temperature for a solution of 10-16% by weight of linear polyethylene in trichlorofluoromethane. The patent also provides a solution of 14% by weight of high density linear polyethylene in trichlorofluoromethane at a temperature of about 185 ° C. and a pressure of about 1655 psia and then a let-down chamber at a temperature of 185 ° C. and a pressure of 1065 psia. Flash spinning from the chamber is described in detail. Very similar temperatures, pressures, and concentrations were used when commercially flashing polyethylene into flexifilmented film-fibril strands and then converting them into sheet structures.

Trichlorofluoromethane is a very useful solvent for flash spinning polyethylene into film-fibril strands per flexi filament and is a solvent used in the commercial manufacture of strands on polyethylene flexi filaments, but the ozone on earth is due to the release of such halocarbons into the atmosphere. It is a serious cause of exhaustion. A general description of the problem of ozone depletion is described, for example, in P. S. Zurrer, Search Intensifies for Alternative to Ozone-Depleting Hhlocarbons, Chemical Engineering News. pages 17-20 (February 8, 1988).

A convenient test method for determining whether a given solvent is suitable for flash spinning a given polymer is described in the literature (US Pat. No. 3,655,498 to Woodell). This test method has been widely used by the vast majority of manufacturers around the world to make flash spun polyethylene products to determine whether they are suitable as an alternative to trichlorofluoromethane solvents for producing strands per flexifilament. In this test, a mixture of polymer and solvent (wherein the solvent content is calculated to produce about 10% by weight of a solution) is sealed in a thick walled glass tube (this mixture is about 1 of the tube volume). / 3 to 1/2), the mixture is heated at its own pressure. Test temperatures typically range from about 100 ° C. up to the critical temperature of the liquid being tested. Woodell states that the solvent power is too low if it is not formed at any temperature below the solvent critical temperature Tc (or lower polymer decomposition temperature) in the tube of the single phase flowable solution. Conversely, if a solution of a single phase is formed at a certain temperature below Tc but the solution cannot be converted to two liquid phases when it is heated to a higher temperature (still below Tc), its solvent power is too high. Solvents in which the high solvent strength does not correspond to these anodic ends may be suitably prepared by diluting with a nonsolvent or optionally a good solvent additive. After selecting a suitable solvent or solvent mixture, the behavior of the single phase and two liquid phase boundaries of this solvent or mixture can be determined as a function of temperature and pressure at different concentrations of polymer as described by Anderson and Romano.

It is an object of the present invention to provide an improved method of flash spinning fiber forming polyolefins into plexiglass filamentous strands without the risk of global ozone depletion due to solvents.

The present invention dissolves polyethylene in a halocarbon spinning solution under a temperature range of 130 to 210 ° C. and a pressure of 3000 psia or more to form a spinning solution containing 10 to 20% by weight of polyethylene based on the weight of the solution. In the method of flash spinning the plexiglass filamentous film-fibrils strand by flash spinning at substantially lower temperature and pressure, halocarbons are 1,1-dichloro-2,2,2-trifluoroethane and 1, Provided is an improved method characterized by selecting from the group consisting of 2-dichloro-1,2,2-trifluoroethane.

The present invention dissolves polyethylene in a halocarbon spinning solution at a temperature in the range of 130 to 210 ° C. and a pressure of 1800 psia or more to form a spinning solution containing 10 to 20% by weight of polyethylene based on the weight of the solution. In which the halocarbons are 1,1-dichloro-2,2-difluoroethane and 1,2- in the flash spinning of the plexi-filament-like film-fibrils strands by flash spinning at substantially lower temperatures and pressures. An improved process is characterized by selecting from the group consisting of dichloro-1,1-difluoroethane.

The present invention dissolves polyethylene in a halocarbon spinning solution under a temperature range of 130 to 210 ° C. and a pressure of at least 2000 psia to form a spinning solution containing 10 to 20% of polyethylene, based on the weight of the solution. A method of flash spinning a film-fibrils strand per flexifil by flash spinning at substantially lower temperatures and pressures provides an improvement method wherein the halocarbon is 1,1-dichloro-1-fluoroethane. .

The present invention dissolves polypropylene in a halocarbon spinning solution at a temperature in the range of 130 to 210 ° C. and a pressure of at least 1500 psia to form a spinning solution containing 10 to 20% by weight of polypropylene, based on the weight of the solution. In a method of flash spinning a flexifilament-like film-fibril strand by flash spinning a solution at substantially lower temperature and pressure, wherein halocarbon is 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1,1-dichloro-2,2-difluoroethane, 1,2-dichloro-1,2-difluoroethane and 1,1 An improved process is characterized by selecting from the group consisting of dichloro-1-fluoroethane.

The present invention further comprises a fiber-forming polyolefin at a temperature of 130 to 210 ° C. and a pressure of at least 1000 psia, containing 2 to 25% of hydrocarbon or 5 to 50% of methylene chloride cosolvent of the total weight of the spinning solution. Dissolved in a halocarbon spinning solution to form a spinning solution containing 10 to 20% by weight of fiber-forming polyethylene based on the weight of the solution, and then flash spinning the solution to substantially lower temperature and pressure to form a flexifilment In the method of flash spinning the film-fibril strand, the halocarbon is 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, Characterized in that it is selected from the group consisting of 1,1-dichloro-2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane To provide an improved method.

The present invention is essentially a fiber-forming polyolefin of 10 to 20% by weight or 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1, Liquid containing halocarbon selected from the group consisting of 1-dichloro-2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane It provides a novel solution consisting of 80 to 90% by weight.

The invention essentially comprises 10 to 20% by weight of fiber-forming polyolefins and 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1, 80-90 halocarbon liquid selected from the group consisting of 1-dichloro-2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane It provides a novel solution consisting of weight percent.

As used herein, the term polyolefin refers to a group of ring-opened polymeric hydrocarbons consisting mostly of carbon and hydrogen and mostly saturated. Typical polyolefins include, but are not limited to, polyethylene, polypropylene, and polymethylpentene. Typically, polyethylene and polypropylene are polyolefins which are preferably used in the process of the present invention.

Polyethylene as used herein includes homopolymers of ethylene as well as copolymers in which at least 85% of the repeating units are ethylene units. Preferred polyethylenes are homopolymeric linear with an upper melting range of about 130 to 135 ° C., a density of 0.94 to 0.98 g / cm ³ and a melt index (as defined by ASTM D-1238-57T, conditions) of 0.1 to 6.0 Polyethylene.

The term polypropylene includes not only propylene homopolymers but also copolymers that are propylene units of at least 85% of the repeating units.

As used herein, the term flexifilamental film-fibrils strand is a three-dimensional array of thin, ribbon-like film fibrils that are not uniform in length and have an average thickness of about 4 μm or less along the longitudinal axis of the strand. The strand is characterized as an integrated network structure. The film-fibrils component is intermittently integrated and separated at irregular intervals at various locations throughout the length, width, and thickness of the strand to form a three-dimensional network structure. Such strands are described in more detail in US Pat. No. 3,081,519 (Blades and White and 3,227,794 (Anderson and Romano)).

SUMMARY OF THE INVENTION The present invention provides an improved method for producing a flexi filamentous film-fibril strand of fiber forming polyolefin from a halocarbon spinning solution containing 10 to 20% by weight of fiber forming polyolefin. The fiber-forming polyolefin (e.g., linear polyethylene) is dissolved in a spinning solution containing halocarbons to form a spinning solution containing 10 to 20% by weight of linear polyethylene, based on the weight of the solution, and then the spinning solution itself. Under pressure above pressure, flash to a region with substantially lower temperature and pressure in the temperature range of 130 to 210 ° C.

The main improvements of the present invention are 1,1-dichloro-2,2,2-trifluoroethane (HC-123), 1,2-dichloro-1,2,2-trifluoroethane (C-123a), 1,1-dichloro-2,2-difluoroethane (HC-132a), 1,2-dichloro-1,1-difluoroethane (C-132b) and 1,1-dichloro-1-fluoro Requires a halocarbon selected from the group consisting of ethane (HC-141b).

The notation in parentheses is used as an abbreviation for the chemical formula of halocarbons. The table below shows the boiling point (Tbp), critical temperature (Tcr) and critical pressure (Pcr) at known standard pressures for selected halocarbons and known solvents. In the table, the solubility described under the designation indicates whether a 10% polyethylene solution can be formed in halocarbon at a temperature of 130 to about 225 ° C. under its own pressure.

It should be noted that the five suitable halocarbons listed above are very special small halocarbon groups suitable for use in the present invention. There are a myriad of halocarbons to choose from. Conventional methods of screening liquids (i.e. by means of polyethylene solubility tests under self pressure as described above) form a solution with polyethylene under its own pressure, and with the prior art solvents set forth above, which have been chosen for further study. In contrast, halocarbons found useful in the present invention are inadequate if they do not dissolve polyethylene under their own pressure. Moreover, in contrast to past flash spinning fluids, none of the halocarbons of the present invention form single phase solutions with polyethylene at the required concentrations and temperatures at pressures below 1500 psia. Of course, these halocarbons have certain properties that known fibrous polyolefin flash spinning liquids may have. For example, these halocarbons also do not substantially react with the polymer at the extrusion temperature. These halocarbons are solvents for fiber-forming polyolefins under certain conditions, so that they can dissolve less than 1% of polymers at temperatures below their standard boiling point, and form polymer phases that cannot plasticize polymers due to lack of solvents. Form a solution that performs rapid phase separation upon extrusion.

In addition to the properties mentioned above, suitable halocarbons for use in the processes and solutions of the present invention

(1) the boiling point is from 0 to 80 ° C;

(2) incompletely fluorinated and / or chlorinated,

(3) low flame resistance,

(4) have a sufficiently large vapor and heat to allow the flexi filaments formed by flash spinning to be cooled quickly;

(5) have suitable thermal and hydrolytic stability for use in flash spinning processes;

(6) Electrostatic insulation sufficiently high in the gas phase for use in conventional spunbonded processes (e.g., US Pat. No. 3,169,899 to Steuver), which form sheets of flexifilment without excess decomposition of halocarbons. Have vandalism,

(7) It should not form a 10% by weight polyethylene solution in the liquid of a single phase in the temperature range of 130 to 225 ° C and a pressure of less than 1500 psia.

Specifically, when using HC-123 and HC-123a, the polyethylene solution may be formed in the halocarbon liquid only at a pressure of 3000 psia or more; When using HC-132a and HC-132a and HC-132b, the polyethylene solution can be formed in the halocarbon liquid only at a pressure of at least 1800 psia; If HC-141b is used, the polyethylene solution can be formed in halocarbon liquids only at a pressure of 2000 psia or higher. Such polypropylene solutions can be produced in the halocarbon spinning liquid of the present invention at a pressure of at least 1,500 psia.

A solution satisfactory as a solution of the polymer and the halocarbon can be produced at a pressure of 1,000 psia or more only when a high solvent power co-solvent is present in the halocarbon spinning liquid.

The properties of halocarbon formulations have been found to be substantially met only by the five halocarbons described above. In order to function similarly to any of these five halocarbons, the other halocarbons must substantially meet all of these properties in order to be suitable for flash spinning fiber-forming polyolefins into high quality plexiglass-like film-fibril strands. .

Even among the five halocarbons suitable for use in the method of the present invention, care must be taken to eliminate certain adverse properties that may be present. For example, for HC-123a, HC-132a, HC-132b and HC-141b, excessively long heating times are avoided in order to minimize the degradation that can result from dehalogenation or hydrolysis of halocarbons. Also note that HC-132b has some indication that it may be a toxic toxin for the reproduction of male animals of the chemical. HC-123 is a preferred halocarbon for use in the process of the present invention because it is relatively free from both of these stability and toxicity issues.

In producing a solution of the fiber-forming polyolefin in the halocarbon liquid of the present invention, the temperature of the mixture of the fiber-forming polyolefin and halocarbon is raised to 130 to 120 ° C. When polyethylene is a polyolefin, the pressure of the mixture is 2,000 psia or more if the halocarbon is HC-141b, 3,000 psia or more if the halocarbon is HC-123 or HC-123a, and HC-132a or HC-132b if the halocarbon is , Is more than 1800psia. When using polypropylene, the pressure is at least 1500 psia, regardless of the halocarbon selected. The mixture described above is maintained under the required pressure until a solution of the fiber forming polyolefin is produced in the liquid. It is usually satisfactory to have a maximum pressure of less than 10,000 psia. After the fiber forming polyolefin has dissolved, the pressure can be reduced slightly and then the flash spinning of the mixture to produce the desired high quality plexiglass filamentous strand structure.

Typically, the concentration of the fiber forming polyolefin in the spinning solution is 10-20% based on the total weight of the liquid and the oil forming polyolefin.

The spinning solution preferably consists of a halocarbon liquid and a fiber forming polyolefin, but if lower pressures are desired during solution preparation and spinning, the spinning solution may contain a second liquid, ie a cosolvent, for the fiber forming polyolefin. have. If the cosolvent is a hydrocarbon solvent such as cyclohexane, toluene, chlorobenzene, hexane, pentane, 3-methylpentane, etc., the concentration of the cosolvent in the mixture of halocarbons and cosolvents is typically 2 to minimize potential flammability problems. To 25% by weight, preferably less than 15% by weight.

However, when methylene chloride is used as cosolvent, the concentration of methylene chloride (ie free fiber forming polyolefin) in the halocarbon / cosolvent mixture is generally 5 to 50% by weight.

Conventional flash spinning additives can be incorporated by known techniques into the spinning mixture. Such additives may act as ultraviolet stabilizers, antioxidants, fillers, dyes and the like.

Various features and characteristics mentioned in the above description and the following examples are determined by the following method.

[Test Methods]

The solubility of polyethylene and polypropylene under their own conditions is measured by a simple sealed tube test, described immediately after the last paragraph of the prior art detailed description of Woodell, US Pat. No. 3,655,498.

The quality of the flexi filamentous film-fibrillated strands prepared in the examples was subjectively evaluated. A rating of 5 indicates that the strands fibrillated better than generally achieved in the conventional manufacture of spunbonded sheets made from flash spun polyethylene strands. Grade 4 indicates that the product is typically as good as the flash spun strand. Grade 3 indicates that the strands are not as good as conventionally flash spun strands. 2 indicates an inadequate strand that is very weakly fibrillated. 1 indicates that no strand is formed. Grade 3 represents the minimum satisfaction that can be used in the method of the present invention. Commercial strand products are about 12.5% of a linear polyethylene solution in trichlorofluoromethane, as described in Lee, US Pat. No. 4,554,207, column 4, lines 63 to 5, line 10, which is incorporated herein by reference. To manufacture.

The surface area of the film-fibrillated strand product per flexifilment is another measure of the degree and purity of fibrillation of the flash spun product. Surface areas are described in S, Brunauer, PH Emmett and E. Telle. J. Am. Chem. Soc., V. 60p 309-319 (1938)], measured by the BET nitrogen adsorption method and reported in m ² / g.

The toughness of the flashed strand is measured using an Instron tension-test apparatus. Condition the strands at 70 ° F and 65% relative humidity.

The denier of the strand is measured from the weight of the strand sample of 15 cm length. Samples are twisted 10 times per inch and placed in the opening of the Instron tester. The lin gauge length and 60% elongation are applied per minute. Toughness at break is reported as g (gpd) per denier.

The present invention is described in an embodiment performed in a batch process using a relatively small apparatus. This batch process is a continuous flash spinning process that can be scaled up and performed using an apparatus of the type described, for example, in US Pat. No. 3,227,794 to Anderson and Romano. You can switch. In this example and table, the process of the present invention is identified by Arabic numerals. Processes identified in capital letters are control processes other than the present invention.

EXAMPLE

For each of Examples 1 to 25 and Control Examples A and B, a high density linear polyethylene having a melt index of 0.76 was used according to the present invention, except Example 7 where a low density linear polyethylene having a melt index of 26 was used. Flash spinning with a film-fiber strand per satisfactory flexifilment.

Two types of instruments are used to prepare and flash spin a mixture of halocarbons and fibrous polyolefins. The instrument indicated by 1 is used in Examples 1, 5 and 16. The instrument shown in II is used for all other examples and control examples.

Mechanism I is a high pressure device comprising a 50 cm ³ volume cylindrical vessel equipped at one end with a cylindrical piston adapted to apply pressure to the contents of the vessel. The other side of the vessel is equipped with a spinneret assembly having an orifice of 0.030 in diameter and 0.060 in length and an attribute means for opening and closing the orifice. Means for measuring pressure and temperature inside the vessel are included. In operation, the vessel is filled with fiber forming polyolefin and halocarbons.

Apply high pressure (eg 4,500 psia) to the filling. The contents are heated at the desired temperature (eg 140 ° C.) for about 1 hour to form a solution, and then the pressure is circulated for about 10 times and mixed. The pressure is then reduced to a pressure suitable for spinning and the spinneret orifice valve is opened. Thus, the resulting flash spinning product is collected.

Instrument II contains a pair of high pressure cylindrical vessels, each equipped with a piston for input application. Each of these containers is similar to the cylindrical container of instrument I, but each has an orifice assembly and two are each coupled to a transport line. The conveying line contains a series of fine mesh screens for mixing the contents of the instrument as it moves the contents through the conveying line from one cylinder to another. The spinneret assembly with an orifice of 0.030 in diameter is coupled to the transport line with an attribute means for opening and closing the orifice. Means for measuring pressure and temperature inside the vessel are included. In operation, the instrument is filled with fibrous forming polyolefins and halocarbons and high pressure is applied to the fill. Thereafter, the contents are heated at the desired temperature for 1 hour and 30 minutes, during which time a differential pressure of about 50 psia is selectively applied in the two cylinders, the contents are repeatedly pressurized through the transport line from one cylinder to the other and mixed. Form a solution. Set the desired pressure for spinning and open the spinneret orifice. The resulting flash spinning product is collected.

All examples and control examples are performed in a similar fashion depending on the instrument used under specific conditions using the specific components shown in the following summarized table. The table also lists the properties of the strands produced by flash spinning.

In Table 1, examples 1-7 describe the use of other halocarbons suitable for the process and solution of the present invention. Control Examples A and B show that some of the same halocarbons were used but under conditions where satisfactory strands could not be produced.

TABLE I

In Table 2, Examples 8-25 describe the use of various cosolvents with halocarbons.

TABLE II

Table II Continued

[Continued Table 2]

[Continued Table 2]

[Continued Table 2]

* ns means no strand is formed.

** nm means not measurable.

+ C ₆ H ₁₂ is cyclohexane.

As can be seen in Example 26 of Table 3, highly fibrillated flexifilments can be obtained from other types of polyolefines using the present invention.

The apparatus and method used in this example is an example of Table II, except that isotactic polypropylene having a melt flow rate of 0.4 sold under the trade name Profax 6823 (Hercules, Inc. Wilmington, DE) is used instead of polyethylene. Same as in

In addition, high mixing temperatures are used to offset the high melting point of the polymer. The conditions used and the properties of the fibers are summarized in Table III. The polymer mixture contains 3.6% by weight of Irganox ^R 1010 (from Ciba-Geigy Corporation, for high molecular weight-inhibited polyphenols) as antioxidant on a polymer basis.

Claims (18)

The polyethylene was dissolved in a halocarbon spinning solution at a temperature of 130-120 ° C. and a pressure of at least 3,000 psia to form a spinning solution containing 10-20% by weight of polyethylene by weight of the solution, and the solution was subjected to substantially lower temperatures and In the method of flash spinning the flexifilament-like film-fibril strand by flash spinning in a pressure zone, the halacarbon is 1,1-chloro-2,2,2-trifluoroethane and 1,2-dichloro-1, And 2,2-trifluoroethane. The polyethylene was dissolved in a halocarbon spinning solution at a temperature of 130-210 ° C. and a pressure of at least 1,800 psia to form a spinning solution containing 10-20 wt.% Polyethylene by weight of the solution, and the solution was subjected to substantially lower temperatures and In a method of flash spinning a flexifilament-like film-fibril strand by flash spinning at a pressure zone, halocarbons are 1,1-chloro-2,2,2-trifluoroethane and 1,1-dichloro-1, And 2,2-trifluoroethane. The polypropylene was dissolved at a temperature of 130 to 210 ° C. and a pressure of at least 2,000 psia to form a spinning solution containing 10 to 20 weight percent polypropylene by weight of the solution, and the solution was substantially lower. 16. A method of flash spinning a plexiglass filamentous film-fibrill strand by flash spinning at temperature and pressure, wherein the halacarbon is 1,1-dichloro-1-fluoroethane. The polypropylene was dissolved at a temperature of 130 to 210 ° C. and a pressure of at least 1,500 psia to form a spinning solution containing 10 to 20 weight percent polypropylene by weight of the solution, and the solution was substantially lower. In the method of flash spinning at a temperature and pressure zone to flash-flexi filamentous film-fibrils strand, the halacarbon is 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro- 1,2,2-trifluoroethane, 1,1-dichloro-2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoro And selected from roethane. The fiber forming polyethylene was dissolved in a halocarbon spinning solution containing 2 to 25% by weight of a hydrocarbon cosolvent of the total weight of the spinning solution at a temperature of 130 to 210 ° C. and a pressure of 1,000 psia or more, thereby providing 10 to 20% by weight of the solution weight. A method of forming a spinning solution containing a fiber-forming polyolefin of the present invention, and flash spinning the solution at substantially lower temperatures and pressures to flash-spin the flexifil-like film-fibrils strands, wherein the halocarbon is 1,1-. Dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1,1-dichloro-2,2, -difluorooethane, 1,2- Dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane. The process of claim 5 wherein the cosolvent is selected from 3-methylpentane, cyclohexane, toluene, pentane, hexane and chlorobenzene. The method of claim 6 wherein the cosolvent comprises less than 15% by weight of the total weight of the spinning liquid. The fiber-forming polyethylene was dissolved in a halocarbon spinning solution containing 5 to 50% by weight of methylene chloride as a cosolvent at a temperature of 130 to 210 ° C. and a pressure of 1,000 psia or more, and 10 to 20 weight of the solution. A method of forming a spinning solution containing a weight percent fiber forming polyolefin and flash spinning the solution at a substantially lower temperature and pressure zone to flash spine the flexi filamentous film-fibrils strand, wherein the halacarbon is 1 , 1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1,1-dichloro-2,2-difluoroethane, 1, Characterized in that it is selected from 2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane. The method of claim 1 wherein the halocarbon is 1,1-dichloro-2,2,2-trifluoroethane. Essentially 10 to 20% by weight of fiber-forming polyolefin with 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1,1-dichloro Liquid containing 80 to 90 halocarbon selected from the group consisting of -2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane Solvent consisting of weight percent. Essentially 10 to 20% by weight of fiber-forming polyolefin with 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, 1,1-dichloro Liquid containing 80 to 90 halocarbon selected from the group consisting of -2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane and 1,1-dichloro-1-fluoroethane Solution by weight. The solution of claim 10 wherein the liquid comprises a hydrocarbon cosolvent that comprises 2-25% by weight of the total weight of halocarbon and cosolvent. The solution of claim 10 wherein the liquid also contains methylene chloride as cosolvent, which accounts for 5-50% by weight of the total weight of halocarbon and methylene chloride. The method according to any one of claims 10, 12 and 13, wherein the halocarbon is 1,1-dichloro-2,2-trifluoroethane. The method of claim 4, wherein the halocarbon is 1,1-dichloro-2,2,2-trifluoroethane. 8. The process of any of claims 5 to 7, wherein the halocarbon is 1,1-dichloro-2,2,2-trifluoroethane. The method of claim 8, wherein the halocarbon is 1,1-dichloro-2,2,2-trifluoroethane. The method of claim 11, wherein the halocarbon is 1,1-dichloro-2,2,2-trifluoroethane.