Patent Description:
Flash spinning is a process for producing fibers that involves spinning a polymer from a spin fluid. In the flash spinning process, the spin agent must be recovered and if possible re-used. Recovery and re-use are time and resource extensive operations that if simplified can result in cost savings and quality improvements in the product.

The present inventors have discovered spin agent compositions that allow for simplified spin agent composition processes under more suitable pressure and temperature conditions. These compositions can be used for a broad range of different polymers and blends thereof.

<CIT>, <CIT> and <CIT> each describe mixtures of solvents for spinning, for example, plexifilamentary film-fibril strands or a fibrillated polyolefin network fiber.

In one embodiment the invention is directed to a flash-spin fluid comprising.

wherein the co-spin agent is present in an amount sufficient to form an azeotrope or azeotrope-like composition with the primary spin agent in the spin fluid,.

In another embodiment the invention is directed to a flash-spin fluid comprising.

The flash-spinning may comprise 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 polymer.

The polymer may be selected from the group consisting of polyethylene, polypropylene, polybutene-<NUM>, poly(<NUM>-methyl-<NUM>-pentene), polyvinylidenefluoride, poly (ethylene tetrafluoroethylene), and blends of the foregoing.

In another embodiment the invention is directed to a method for preparing a flash-spin fluid comprising.

In another embodiment, the invention is directed to a method for preparing a flash-spin fluid comprising.

The invention is further directed to the use according to claims <NUM> or <NUM>, and to the method according to claims <NUM> or <NUM>.

When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether such ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range.

The term "polymer" as used herein, generally includes but is not limited to, homopolymers, copolymers (such as for example, block, graft, random and alternating copolymers), terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries.

The term "polyethylene" as used herein is intended to encompass not only homopolymers of ethylene, but also copolymers wherein at least <NUM>% of the recurring units are ethylene units. One preferred polyethylene is high-density polyethylene which has an upper limit of melting range of about <NUM> to <NUM>° C. , a density in the range of <NUM> to <NUM> gram per cubic centimeter, and a melt index (MI) of between <NUM> and <NUM>, preferably less than <NUM>.

The term "polypropylene" is intended to embrace not only homopolymers of propylene but also copolymers where at least <NUM>% of the recurring units are propylene units. Isotactic and syndiotactic polypropylene are preferred forms.

The term "polymer type" refers to the chemical class into which the polymer falls, for example, polyethylene, polypropylene, polyvinylidene fluoride, poly (ethylene tetrafluoroethylene) copolymer, and so on.

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 a median fibril width of less than about <NUM> microns. 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 "spin fluid" refers to the total composition that is spun using the spinning apparatus described herein. Spin fluid includes polymer and spin agent.

The term "spin agent" refers to the solvent or mixture of solvents and any additives, solubility aids and blends therewith that is used to initially dissolve the polymer to form the spin fluid.

The dew point pressure is the pressure at which, at constant temperature, a vapour, vapour mixture, or vapour-gas mixture starts condensing into liquid.

The boiling point pressure is the pressure at which, at constant temperature, a liquid, liquid mixture, or liquid-solution starts to form vapour.

The azeotropic composition is the composition of a mixture of fluids at which the boiling point pressure equals the dew point pressure. In this work, the azeotropic compositions are determined at <NUM> and expressed in mass fractions. Point C on <FIG> corresponds to the azeotropic composition.

"Azeotropic-like compositions" are compositions of fluids which exhibit only small differences between the boiling point pressure and the dew point pressure, i.e. the boiling point pressure is different by less than <NUM>% from the dew point pressure (both expressed in absolute pressure). In this work, the azeotropic-like compositions are determined at <NUM> and expressed in mass fractions. Azeotropic-like compositions correspond to the compositions between and including point A and point B on <FIG>. The phrases "Azeotropic-like" and "azeotrope-like" and "azeotrope like" are used interchangeably herein.

By "cloud point" it is meant the pressure and temperature at which a clear single phase spin fluid separates into two phases. At the cloud phase a clear spin fluid becomes turbid. The turbidity is determined following the protocol described herein.

<CIT> assigned to E. du Pont de Nemours and Company, Wilmington, Del. (hereafter DuPont) discloses a process for making flash-spun plexifilamentary film-fibril strands from a fiber-forming polymer in a liquid spin agent that is not a solvent for the polymer below the liquid's normal (atmospheric pressure) boiling point. As disclosed in <CIT> (assigned to DuPont), the flash-spinning process requires a spin agent that: (<NUM>) is a nonsolvent to the polymer below the spin agent's normal boiling point; (<NUM>) forms a solution with the polymer at high pressure; (<NUM>) forms a desired two-phase dispersion with the polymer when the solution pressure is reduced slightly in a letdown chamber; and (<NUM>) flash vaporizes when released from the letdown chamber into a zone of substantially lower pressure through a spin orifice.

Dichloromethane (DCM) and cis- or trans-<NUM>,<NUM>-dichloroethylene (DCE) are examples of solvents for polymers, and in particular polyolefins (e.g., polyethylene and polypropylene) that are commercially available. However, their cloud-point pressures are so close to the bubble point that it is not considered feasible to use them alone as spin agents. By employing co-spin agents, the solvent power of the mixture is lowered sufficiently so that flash spinning to obtain the desired plexifilamentary product is readily accomplished.

The present inventors have discovered that it is possible to flash spin a spin fluid of <NUM> to <NUM> wt. % of total spin fluid of polymer, and a spin agent comprising a primary spin agent selected from the group consisting of dichloromethane, cis-<NUM>,<NUM>-dichloroethylene and trans-<NUM>,<NUM>-dichloroethylene, and a co-spin agent comprising <NUM>,<NUM>-perfluorohexane, <NUM>-perfluorohexane, or <NUM>-perfluoroheptane in an azeotropic mixture or azeotropic-like mixture with the primary spin agent.

A study was been performed for the phase behavior and flash spinning of high density polyethylene, polypropylene, polybutene-<NUM>, poly(<NUM>-methyl-<NUM>-pentene), polyvinylidene fluoride and poly(ethylene tetrafluoroethylene) for azeotropic and azeotropic like compositions. The experimental procedure and results are provided below.

The dichloromethane (DCM) used was a high purity grade of <NUM>% purity from Merck. (Dichloromethane , also known as methylene chloride, has a <NPL>. ) Dichloromethane has a molecular weight of <NUM>/mol and an atmospheric boiling point of <NUM>. The dichloromethane is used as received.

The trans-<NUM>,<NUM>-dichloroethylene (t-<NUM>,<NUM>-DCE) used was a high purity grade of <NUM>% purity from Sigma-Aldrich. (Trans-<NUM>,<NUM>-dichloroethylene has a CAS Nr. of <NUM>-<NUM>-<NUM>. ) Trans-<NUM>,<NUM>-dichloroethylene has a molecular weight of <NUM>/mol and an atmospheric boiling point of <NUM>. The trans-<NUM>,<NUM>-dichloroethylene is used as received.

<NUM>,<NUM>-perfluorohexane (<NPL>) was purchased from Apollo Scientific, Units <NUM> & <NUM>, Parkway, Denton, Manchester, M34 3SG, United Kingdom. <NUM>,<NUM>-perfluorohexane is also purchased from Exfluor Research Corporation, <NUM> Double Creek Dr. , Round Rock, TX,<NUM>, United States. <NUM>,<NUM>-perfluorohexane has a purity level of about <NUM>% and used as received. The molecular mass is equal to <NUM>/mol and the atmospheric boiling temperature equals <NUM>. The <NUM>,<NUM>-perfluorohexane was used as received.

<NUM>-perfluorohexane (<NPL>) was purchased from Apollo Scientific, Units <NUM> & <NUM>, Parkway, Denton, Manchester, M34 3SG, United Kingdom. The molecular mass is equal to <NUM>/mol and the reported boiling temperature by the Apollo Scientific equals <NUM>. The <NUM>-perfluorohexane is used as received.

<NUM>-perfluoroheptane (<NPL>) was purchased from Apollo Scientific, Units <NUM> & <NUM>, Parkway, Denton, Manchester, M34 3SG, United Kingdom. The molecular mass is equal to <NUM>/mol and the reported atmospheric boiling temperature by the manufacturer is <NUM>. The <NUM>-perfluoroheptane is used as received.

The polyethylene was a commercial grade high density polyethylene (HDPE) from Total - refining and chemicals, grade <NUM> with a density of <NUM>/cm3 (ISO <NUM>), melt flow index of <NUM> (ISO <NUM>/D, <NUM>/<NUM>) and <NUM> (ISO <NUM>/G, <NUM>/<NUM>).

The polypropylene (PP) used in the examples is a commercial grade Total PPH <NUM> from Total Chemicals. The MFR is <NUM>/<NUM> (ISO <NUM>, <NUM>-<NUM>).

Polybutene-<NUM> (PB-<NUM>) used was the commercial grade PB-<NUM><NUM> from Lyondell-Basell. The density is <NUM>/cm3 and MFR is <NUM>/<NUM> (ISO <NUM>/D, <NUM>, <NUM>). The PB-<NUM> was used as received.

The poly(<NUM>-methyl-<NUM>-pentene) (P4M1P) used is a medium molecular weight grade purchased from Sigma-Aldrich Chemie GmbH. The Product number is <NUM>. The reported melting point is <NUM>. Poly(<NUM>-methyl-<NUM>-pentene) is also known as polymethylpentene (PMP).

Polyvinylidene fluoride (PVDF) was performed with Kynar® <NUM>, Kynar® <NUM> and Kynar® <NUM> grades from Arkema. The Kynar® <NUM> has a specific gravity of <NUM>-<NUM>/cm<NUM> (ASTM D792 <NUM>), melting point of <NUM>-<NUM> and melt flow rate of <NUM>-<NUM>/<NUM> (ASTM D1238, <NUM>°F, <NUM> load). Kynar® <NUM> has specific gravity of <NUM>-<NUM>/cm3 (ASTM D792 <NUM>), melting point of <NUM>-<NUM> and melt flow rate of <NUM>-<NUM>/<NUM> (ASTM D1238, <NUM>°F, <NUM> load). Kynar® <NUM> has specific gravity is <NUM>-<NUM>/cm3 (ASTM D792 <NUM>), melting point of <NUM>-<NUM> and melt flow rate of <NUM>-<NUM>/<NUM> (ASTM D1238, <NUM>°F, <NUM> load).

The ethylene tetrafluoroethylene used in the examples is commercial grade Tefzel® <NUM> from DuPont de Nemours. Ethylene tetrafluoroethylene is also known as poly(ethene-co-tetrafluoroethene) or poly(ethylene tetrafluoroethylene). Reported technical properties are a nominal melting point of <NUM>-<NUM> (ASTM D3418), Flow rate of <NUM>/<NUM> (ASTM D3159) and a specific gravity <NUM> (ASTM D792).

All polymers are used as received. Polymers were dried during a minimum of <NUM> hours in a vacuum over of <NUM> mbar and temperature of about <NUM>-<NUM> before being used.

In summary, the apparatus used consisted of two high pressure cylindrical chambers, each equipped with a piston which is adapted to apply pressure to the contents of the vessel. The cylinders have an inside diameter of <NUM> inch (<NUM>×<NUM>-<NUM> m) and each has an internal capacity of <NUM> cubic centimeters. The cylinders are connected to each other at one end through a <NUM>/<NUM> inch (<NUM>×<NUM>-<NUM> m) diameter channel and a mixing chamber containing a series of fine mesh screens used as a static mixer. In the channel a Type J thermocouple is in contact with the spin fluid to record the temperature. Mixing is accomplished by forcing the contents of the vessel back and forth 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 <NUM> inch (<NUM>×<NUM>-<NUM> m) diameter and about <NUM> inch (<NUM>×<NUM>-<NUM> m) length, and a spinneret orifice of <NUM> inch (<NUM>×<NUM>-<NUM> m) diameter and <NUM> inch (<NUM>×<NUM>-<NUM> m) length. A pressure transmitter is mounted in the lead hole to measure the pressure of the spin fluid. The pistons are driven by high pressure hydraulic system.

In operation, the apparatus was charged with polymer pellets and spin agent and a pressure of at least <NUM> barg is applied to the pistons to compress the charge and avoid the spin fluid from boiling during subsequent heating. The contents then were heated to mixing temperature and held at that temperature for about <NUM> to <NUM> minutes during which time a differential pressure was alternatively established between the two cylinders to repeatedly force the contents through the mixing channel from one cylinder to the other to provide mixing and effect formation of a spin fluid. The spin fluid temperature was then raised to the final spin temperature, and held there for about <NUM> to <NUM> minutes to equilibrate the temperature. The pressure of the spin fluid is kept above the cloud point pressure during mixing and during the raise from the mixing temperature to the spin temperature. Mixing is continued throughout this period. In addition, the pressure transducer in the lead hole is calibrated at the spin temperature. The accumulator pressure was set to that desired for spinning at the end of the mixing cycle to simulate the letdown chamber effect. Next, the valve between the spin cell and the accumulator is opened, and then the spinneret orifice is opened immediately thereafter in rapid succession. It usually took about two to five seconds to open the spinneret orifice after opening the valve between the spin cell and the accumulator. This time should correspond to the residence time in the letdown chamber. When letdown chambers are used, the residence time in the chamber is usually <NUM> to <NUM> seconds. However, it has been determined that residence time does not have much effect on fiber morphology and/or properties as long as it is greater than about <NUM> second but less than about <NUM> seconds. 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 was entered as the spin pressure.

For cloud-point pressure determination, the spinneret assembly was replaced with a view cell assembly containing a <NUM>/<NUM> inch (<NUM>×<NUM>-<NUM> m) diameter high pressure sight glass, through which the contents of the cell could be viewed as they flow through the channel. The window was lighted by means of a fiber optic light guide, while the content at the window itself was displayed using a digital camera. In the cell a Type J thermocouple is located about <NUM> behind the high pressure sight glass. The Type J thermocouple and a pressure measuring device located in close proximity to the window provide the pressure and temperature details of the cell behind the sight glass respectively. The temperature and pressure of the contents at the window were continuously monitored by a computer. When a clear, homogeneous polymer-spin liquid mixture was established after a period of mixing, the temperature was held constant, and the differential pressure applied to the pistons was equalized, so that the pistons stopped moving. Then the pressure applied to the contents of the view cell was gradually decreased until a second phase formed in the view cell behind the high pressure sight glass. This second phase can be observed through the sight glass in the form of cloudiness of the once clear, homogeneous polymer-spin liquid mixture. The temperature and pressure was measured by the Type J thermocouple and pressure transducer at the condition where the thermocouple is no longer visible. This pressure is the phase separation pressure or the cloud-point pressure at that temperature for that polymer-spin liquid mixture. For an approximate constant temperature typically two or three measurements are performed. Once these data are recorded, mixing was again resumed, while the content was heated to the temperature where the next phase separation pressure or cloud-point pressure has to be measured.

<FIG> shows a graph of boiling point pressure of mixtures of dichloromethane and <NUM>,<NUM>-perfluorohexane@ <NUM>, as a function of the weight fraction of dichloromethane. The azeotropic composition of dichloromethane and <NUM>,<NUM>-perfluorohexane at <NUM> corresponds to about <NUM> wt% dichloromethane and about <NUM> wt% <NUM>,<NUM>-perfluorohexane. For a temperature of <NUM> the pressure for the boiling point of the azeotropic composition is equal to <NUM> kPa. For compositions between the azeotropic composition and pure dichloromethane it was found that the pressure associated to the dew point and boiling point are very similar. Azeotrope like compositions with a variation between the dew point and boiling point pressures of less than <NUM> % can be defined from a weight ratio of dichloromethane to <NUM>,<NUM>-perfluorohexane of <NUM>:<NUM> wt% to about <NUM>:<NUM> wt-%.

<FIG> shows the cloud point curve of <NUM> wt% high density polyethylene (HDPE) in a spin agent of dichloromethane and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> wt% composition. <NUM> wt% of high density polyethylene was found soluble in a spin agent of dichloromethane and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were successfully performed using the spinning equipment described for a high density polyethylene polymer concentration of <NUM> wt% from a spin agent of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% PP in a spin agent of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve of <NUM> wt% PP in a spin agent consisting of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% of polypropylene were found soluble in spin agents of dichloromethane and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> and <NUM>:<NUM> ratio by weight, respectively. Flash spin experiments were performed using the spinning equipment for polypropylene polymer concentration for <NUM> and <NUM> wt% from a spin agent of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> and <NUM>:<NUM> ratio by weight, respectively.

<FIG> shows the cloud point curve for <NUM> wt% polybutene-<NUM> (PB-<NUM>) in a spin agent consisting of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve for <NUM> wt% polybutene-<NUM> (PB-<NUM>) in a spin agent consisting of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% of polybutene-<NUM> was found soluble in a spin agent consisting of dichloromethane and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> and <NUM>:<NUM> ratio by weight. Flash spin experiments were performed using the spinning equipment for blends of HDPE and PB-<NUM> with a total concentration of <NUM> and <NUM> wt% from a spin agent of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% PVDF/Kynar® <NUM> in dichloromethane-<NUM>,<NUM>-perfluorohexane corresponding to a composition of <NUM>:<NUM> ratio by weight. <NUM> wt% of PVDF/Kynar® <NUM> was found soluble in mixtures of dichloromethane and <NUM>,<NUM>-perfluorohexane corresponding to a composition of <NUM>:<NUM> wt%. Flash spin experiments were performed using the spinning equipment described in above for a PVDF/Kynar® <NUM> concentration of <NUM> wt% from a spin agent-of DCM and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows a graph of boiling point pressures of mixtures dichloromethane and <NUM>-perfluorohexane @ <NUM>, as a function of the weight fraction of dichloromethane. The azeotropic composition of dichloromethane and <NUM>-perfluorohexane at <NUM> corresponds to about <NUM> wt% dichloromethane and about <NUM> wt% <NUM>-perfluorohexane. The dew point and boiling point at <NUM> for the azeotropic composition is equal to about <NUM> kPa. Azeotropic-like composition with a variation between the dew point and boiling point less than <NUM> % can be defined from a weight ratio of dichloromethane to <NUM>-perfluorohexane of about <NUM>:<NUM> wt% to about <NUM>:<NUM> wt%.

<FIG> shows the cloud point curve of <NUM> wt% polypropylene in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve of <NUM> wt% polypropylene in a spin agent of DCM and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> and <NUM> wt% polypropylene were found soluble in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were performed using the flash spinning equipment described for a polymer concentration of <NUM> wt% PP from a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve for <NUM> wt% polybutene-<NUM> in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% polybutene-<NUM> was found soluble in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% P4M1P in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve of <NUM> wt% P4M1P in a spin agent of DCM and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% poly(<NUM>-methyl-<NUM>-pentene) (P4M1P) was found soluble in a spin agent consisting of dichloromethane and <NUM> -perfluorohexane in a <NUM>:<NUM> ratio by weight and <NUM>:<NUM> ratio by weight, respectively.

<FIG> shows the cloud point curve of <NUM> wt% PVDF/Kynar® <NUM> in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve of 26wt% PVDF/Kynar® <NUM> in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> and <NUM> wt% of PVDF were found soluble in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

Flash spin experiments were performed using the flash-spinning equipment described for polymer concentrations of <NUM> wt% and <NUM> wt% PVDF from a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

In addition, flash spin experiments were performed for a total polymer concentration of 28wt% composed of a blend of PVDF and PB-<NUM> in a <NUM>:<NUM> ratio by weight and a blend of PVDF and P4M1P in a <NUM>:<NUM> ratio by weight from a spin agent of DCM and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% ETFE in a spin agent of dichloromethane and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% of poly (ethylene tetrafluoroethylene) (ETFE) was found soluble in a spin agent of dichloromethane and <NUM> -perfluorohexane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were performed using the spinning equipment described for <NUM> wt% poly (ethylene tetrafluoroethylene) (ETFE) polymer concentration from a spin agent of of dichloromethane and1H-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows a graph of boiling point pressures of dichloromethane and <NUM>-perfluoroheptane mixtures @ <NUM>, as a function of the weight fraction of dichloromethane. The azeotropic composition of dichloromethane and <NUM>-perfluoroheptane at <NUM> corresponds to about <NUM> wt% dichloromethane and about <NUM> wt% <NUM>-perfluoroheptane. The dew point and boiling point at <NUM> for the azeotropic composition is equal to about <NUM> kPa. Azeotrope like composition with a variation between the dew point and boiling point pressure less than <NUM> % can be defined from a weight ratio of dichloromethane to <NUM>-perfluoroheptane of about <NUM>:<NUM> ratio by weight to about <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% high density polyethylene in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <NUM> wt% high density polyethylene was found soluble in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were performed using the spinning equipment described for high density polyethylene polymer concentration of <NUM> wt% from a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% PP in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve of <NUM> wt% PP in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <NUM> wt% and <NUM> wt% of polypropylene were found soluble in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

Flash spin experiments are performed using the flash spinning equipment described for polypropylene polymer concentrations of <NUM> and <NUM> wt% from a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve for <NUM> wt% PB-1in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <NUM> wt% polybutene-<NUM> was found soluble in a spin agent consisting of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were performed using the spinning equipment for blends of HDPE and PB-<NUM> with a total concentration of <NUM> and <NUM> wt% from a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

<FIG> shows the cloud point curve of <NUM> wt% PVDF/Kynar® <NUM> in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <FIG> shows the cloud point curve of <NUM> wt% PVDF/Kynar® <NUM> in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <NUM> wt% PVDF/Kynar® <NUM> was found soluble in spin agents of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> and <NUM>:<NUM> ratio by weight, respectively. Flash spin experiments were performed using the spinning equipment for PVDF/Kynar® <NUM> with a polymer concentration of <NUM> wt% from spin agents consisting of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> and <NUM>:<NUM> ratio by weight, respectively.

<FIG> shows the cloud point curve of <NUM> wt% ETFE in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <NUM> wt% ETFE was found soluble in a spin agent of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were performed using the spinning equipment described before for <NUM>, <NUM> and <NUM> wt% ETFE from a spin agent consisting of DCM and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

<FIG> shows a graph of boiling point pressures of mixtures of trans-<NUM>,<NUM>-dichloroethylene and <NUM>,<NUM>-perfluorohexane @ <NUM>, as a function of the weight fraction of trans-<NUM>,<NUM>-dichloroethylene. The azeotropic composition of trans-<NUM>,<NUM>-dichloroethylene and <NUM>,<NUM>-perfluorohexane at <NUM> corresponds to about <NUM> wt% trans-<NUM>,<NUM>-dichloroethylene and about <NUM> wt% <NUM>,<NUM>-perfluorohexane. The dew point and boiling point at <NUM> for the azeotropic composition is equal to about <NUM> kPa. Azeotropic-like composition with a variation between the dew point and boiling point less than <NUM> % can be defined from a weight ratio of trans-<NUM>,<NUM>-dichloroethylene to <NUM>,<NUM>-perfluorohexane of about <NUM>:<NUM> wt% to about <NUM>:<NUM> wt%.

<FIG> shows the cloud point curve of <NUM> wt% high density polyethylene (HDPE) in a spin agent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% of high density polyethylene was found soluble in a spin agent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were successfully performed using the spinning equipment described for <NUM> wt% PE from a spin agent consisting of t-<NUM>,<NUM>-DCE and <NUM>,<NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows a graph of boiling point pressures of mixtures of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluorohexane @ <NUM>, as a function of the weight fraction of trans-<NUM>,<NUM>-dichloroethylene. The azeotropic composition of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluorohexane at <NUM> corresponds to about <NUM> wt% trans-<NUM>,<NUM>-dichloroethylene and about <NUM> wt% <NUM>-perfluoroheptane. The dew point and boiling point at <NUM> for the azeotropic composition is equal to about <NUM> kPa. Azeotropic-like composition with a variation between the dew point and boiling point less than <NUM> % can be defined from a weight ratio of trans-<NUM>,<NUM>-dichloroethylene to <NUM>-perfluorohexane of about <NUM>:<NUM> wt% to about <NUM>:<NUM> wt%.

<FIG> shows the cloud point curve of <NUM> wt% polypropylene (PP) in a spinagent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. <NUM> wt% of polypropylene was found soluble in a spin agent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight. Flash spin experiments were successfully performed using the spinning equipment described for a polypropylene polymer concentration of <NUM> wt% from a spin agent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluorohexane in a <NUM>:<NUM> ratio by weight.

<FIG> shows a graph of boiling point pressures of mixtures of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluoroheptane @ <NUM>, as a function of the weight fraction of trans-<NUM>,<NUM>-dichloroethylene. The azeotropic composition of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluoroheptane at <NUM> corresponds to about <NUM> wt% trans-<NUM>,<NUM>-dichloroethylene and about <NUM> wt% <NUM>-perfluoroheptane. The dew point and boiling point at <NUM> for the azeotropic composition is equal to about <NUM> kPa. Azeotropic-like composition with a variation between the dew point and boiling point less than <NUM> % can be defined from a weight ratio of trans-<NUM>,<NUM>-dichloroethylene to <NUM>-perfluoroheptane of about <NUM>:<NUM> wt% to about <NUM>:<NUM> wt%.

<FIG> shows the cloud point curve of <NUM> wt% high density polyethylene (HDPE) in a spinagent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight. <NUM> wt% of high density polyethylene was found soluble in a spin agent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

Flash spin experiments were successfully performed using the spinning equipment described for a high density polyethylene polymer concentration of <NUM> wt% from a spin agent of trans-<NUM>,<NUM>-dichloroethylene and <NUM>-perfluoroheptane in a <NUM>:<NUM> ratio by weight.

Claim 1:
A flash-spin fluid comprising
(a) <NUM> to <NUM> wt. % of total spin fluid being a polymer of one or more polymer types,
(b) a primary spin agent selected from the group consisting of dichloromethane, cis-<NUM>,<NUM>-dichloroethylene and trans-<NUM>,<NUM>-dichloroethylene, and
(c) a co-spin agent selected from the group consisting of <NUM>,<NUM>-perfluorohexane, <NUM>-perfluoroheptane, and <NUM>-perfluorohexane,
wherein the co-spin agent is present in an amount sufficient to form an azeotrope or azeotrope-like composition with the primary spin agent in the spin fluid, wherein the azeotropic or azeotrope-like compositions are determined at <NUM>, and wherein the azeotrope-like composition is the composition of fluids wherein the boiling point pressure is different by less than <NUM>% from the dew point pressure.