Reinforced Highly Microporous Polymers

Abstract

The present invention provides microporous polymers and methods for producing and using the same. In particular, microporous polymers of the present invention are highly porous as indicated by a Gurley air permeability flow rate of about 4 seconds or less per mL of air flow per 25 micron of microporous polymer thickness per square inch.

1 . A gelled polymer comprising:
 a gelled polymer matrix having a generally planar surface and a solvent surface tension wherein an average pore size is about 10 μm or less, the gelled polymer including:
 a semi crystalline polymer having a surface free energy; and 
 a solvent in non-wetting relationship to the semicrystalline polymer having at least 70% of a total liquid content of a saturated solution of the polymer, the solvent comprising:
 a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy mixed with a low surface tension liquid being miscible in the high surface tension liquid, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid; 
 the polymer being maintained at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer; and 
 
 a generally planar substrate having a substrate surface free energy at least equal to the solvent surface tension, the generally planar substrate supporting the gelled polymer matrix at the generally planar surface; and 
 a fiber material. 
   
     
     
         2 . The gelled polymer of  claim 1 , wherein the polymer comprises carbon and at least one of a group selected from hydrogen, halogen, oxygen, nitrogen, sulfur and a combination thereof. 
     
     
         3 . The gelled polymer of  claim 1 , wherein the solvent comprises polyvinylidene fluoride, polyvinyl chloride, polylvinylidene fluoride-hexafluoropropylene copolymer and a mixture thereof, such that:
 a high surface tension liquid having a liquid surface tension in excess of the polymer surface free energy; and   a low surface tension liquid that is miscible in the high surface tension liquid, the low surface tension liquid:
 having a low surface tension that is lower than the solvent surface tension, and 
 being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid. 
   
     
     
         4 . The gelled polymer of  claim 1 , the fiber material comprising single fibers. 
     
     
         5 . The gelled polymer of  claim 1 , the fiber material comprising stranded rovings. 
     
     
         6 . The gelled polymer of  claim 1 , the fiber material comprising woven cloth. 
     
     
         7 . The gelled polymer of  claim 1 , the fiber material comprising non-woven mats. 
     
     
         8 . A method of producing a microporous polymer comprising:
 forming an approximately saturated solution from a polymer by adding a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy, to the polymer previously dissolved in a low surface tension liquid, the low surface tension liquid being miscible in the high surface tension liquid to form a solvent, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid; the forming being conducted at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer, wherein the approximately saturated solution comprises a solvent and a polymer material that is dissolved in the solvent,   placing the polymer solution in a layer at the forming temperature;   adding a fiber material to the polymer solution;   urging the solvent into a non-wetting relation to the polymer by increasing the surface tension of the solvent to form a gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer; and   evaporating, at a temperature not to exceed the forming temperature, the solvent from the gelled polymer to form a film defining a plurality of pores, such that sufficient solvent is removed from the gelled polymer to form the film defining the plurality of pores at a temperature near or below the forming temperature, the remaining solvent is removed at temperatures not to exceed the melt temperature of the polymer.   
     
     
         9 . The method of  claim 8 , the fiber material comprising single fibers. 
     
     
         10 . The method of  claim 8 , the fiber material comprising stranded rovings. 
     
     
         11 . The method of  claim 8 , the fiber material comprising woven cloth. 
     
     
         12 . The method of  claim 8 , the fiber material comprising non-woven mats. 
     
     
         13 . The method of  claim 8 , wherein the solubility of the polymer material in the solution is about 25% v/v or less relative to the total volume of the solvent in the solution. 
     
     
         14 . The method of  claim 8 , wherein the ratio of the low surface tension liquid relative to the high surface tension liquid is about 99:1 v/v or less. 
     
     
         15 . The method of  claim 8 , wherein
 the plurality of pores encompass a void volume having a void volume ratio between the void volume and the combined volume total of the polymer material and the solvent; and   the void volume ratio is substantially similar to a relative volumetric ratio between the low surface tension liquid and a combined volume total of the polymer material and the solvent.   
     
     
         16 . The method of  claim 8 , wherein the low surface tension liquid is one of a group of a ketone, ester, ether, aldehyde, amine, amide, nitrile, cyanate, nitrite, nitrate, nitro- or nitroso-compound, thiol, sulfide, sulfonium, sulfate, sulfonyl compound, sulfinyl compound, thio-compounds, and a mixture of two or more thereof. 
     
     
         17 . The method of  claim 16 , wherein the ketone is selected from a group consisting of acetone, methyl ethyl ketone, pentanone, hexanone, cyclic ketone, and a mixture of two or more thereof. 
     
     
         18 . The method of  claim 8 , wherein the high surface tension liquid is selected from a group consisting of:
 acetamide, acetophenone, adiponitrile, aniline, benzaldehyde, benzyl benzoate, benzonitrile, benzophenone, bromine, bromobenzene, tribromomethane, bromophenol, carbon disulfide, chloroacetic acid, chlorobenzene, chlorophenol, diethylaniline, diethylene glycol, dimethylaniline, dimethyl phenyl pyrazolane, dimethyl sulfoxide, diphenylamine, ethylaniline, ethylene bromide, ethylene glycol, formamide, formic acid, furfural, y-butyrolactone, glycerin, glycerol, methylaniline, methyl benzoate, methylene iodide, nitric acid, nitrobenzene, nitromethane, phenol, phosphorous tribromide, phosphorous tri-iodide, propylene glycol, pyridine, pyridazine, quinoline, sulfuric acid, tetrabromomethane, toluene, xylene, water, and a mixture of two or more thereof.   
     
     
         19 . The method of  claim 18 , wherein the high surface tension liquid is water. 
     
     
         20 . The method of  claim 8 , wherein the thickness of the layer is about 500 μm or less. 
     
     
         21 . The method of  claim 8 , wherein the urging the solvent into a non-wetting relation to the polymer includes cooling the gelled polymer sufficiently to increase the surface tension of the solvent to be greater than the free surface energy of the polymer. 
     
     
         22 . The method of  claim 8 , wherein the surface tension of the solvent is at least about 35 dynes/cm at 25° C. 
     
     
         23 . The method of  claim 8 , wherein the gelled polymer is formed at a temperature of about 40° C. or less. 
     
     
         24 . The method of  claim 23 , wherein the solvent is removed from the gelled polymer at a temperature of about 30° C. or less. 
     
     
         25 . The method of  claim 8 , wherein the gelled polymer is formed at a temperature of about 5° C. or less relative to forming temperature of the approximately saturated solution. 
     
     
         26 . The method of  claim 8 , wherein the liquid is removed at a temperature of about 5° C. or less relative to the forming temperature of the approximately saturated solution. 
     
     
         27 . The method of  claim 8 , wherein the solubility of the polymer material in the liquid is about 10% v/v or less. 
     
     
         28 . The method of  claim 8  further comprising admixing the solvent and the polymer material to form the approximately saturated solution, wherein the approximately saturated solution is formed by heating the mixture, subjecting the mixture to high shear mixing, or a combination thereof. 
     
     
         29 . A method of forming a polymer film defining a plurality of micropores, the method comprising:
 forming a gelled polymer, wherein the polymer comprises at least about 80% polyvinylidene fluoride, at a forming temperature, by precipitating semicrystaline polymer from a saturated solution of polymer and a solvent wherein the solvent includes:
 a high surface tension liquid having a surface tension not less than the surface free energy of the polymer; and 
 a low surface tension liquid that is miscible in the high surface tension liquid, the low surface tension liquid having a surface tension that is lower than the surface tension of the solvent, and being selected such that:
 the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid; and 
 the low surface tension liquid has a higher vapor pressure than the higher surface tension liquid; 
 
   placing the gelled polymer in a layer on a substrate;   adding fiber material;   urging the solvent into non-wetting relation to the polymer by increasing the surface tension of solvent in the gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, thereby causing the solvent to tend to bead within the gelled polymer.   
     
     
         30 . The method of  claim 29 , the fiber material comprising single fibers. 
     
     
         31 . The method of  claim 29 , the fiber material comprising stranded rovings. 
     
     
         32 . The method of  claim 29 , the fiber material comprising woven cloth. 
     
     
         33 . The method of  claim 29 , the fiber material comprising non-woven mats. 
     
     
         34 . The method of  claim 29 , wherein urging the solvent into a non-wetting relationship to the polymer includes cooling the gelled polymer below a gelled polymer melting point. 
     
     
         35 . The method of  claim 29 , further comprising:
 removing a portion of the solvent from the gelled polymer at a temperature not to exceed the forming temperature thereby forming a polymer film defining at least one pore.   
     
     
         36 . The method of  claim 35 , further comprising:
 upon formation of a polymer film defining at least one pore, removing solvent from the gelled polymer at a temperature not to exceed the melt temperature of the polymer.   
     
     
         37 . A gelled polymer comprising:
 a gelled polymer matrix having a generally planar surface and a solvent surface tension, the gelled polymer including a semicrystalline polymer comprising a halogen, having a surface free energy; and   a solvent in non-wetting relationship to the semicrystalline polymer having at least 70% of a total liquid content of a saturated solution of the polymer, the solvent comprising:
 a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy mixed with a low surface tension liquid being miscible in the high surface tension liquid, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid; and 
 the polymer being maintained at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer; 
   fiber material; and   a generally planar substrate having a substrate surface free energy at least equal to the solvent surface tension, the generally planar substrate supporting the gelled polymer matrix at the generally planar surface.   
     
     
         38 . The gelled polymer of  claim 37 , the fiber material comprising single fibers. 
     
     
         39 . The gelled polymer of  claim 37 , the fiber material comprising stranded rovings. 
     
     
         40 . The gelled polymer of  claim 37 , the fiber material comprising woven cloth. 
     
     
         41 . The gelled polymer of  claim 37 , the fiber material comprising non-woven mats. 
     
     
         42 . The gelled polymer of  claim 37 , wherein the halogen is selected from a group consisting of chloride, fluoride, and a mixture thereof. 
     
     
         43 . A method of producing a microporous polymer comprising:
 forming, at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of an approximately saturated solution or a melt temperature of the polymer, wherein the approximately saturated solution comprises a solvent and a polymer material that is dissolved in the solvent, an approximately saturated solution from a polymer by adding a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy, to the polymer previously dissolved in a low surface tension liquid, the low surface tension liquid being miscible in the high surface tension liquid to form a solvent, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid;   adding a fiber material;   urging the solvent into non-wetting relationship with the polymer includes evaporating the low surface tension liquid;   urging the solvent into a non-wetting relation to the polymer by increasing the surface tension of the solvent to form a gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer; and   evaporating, at a temperature not to exceed the forming temperature, the solvent from the gelled polymer to form a film defining a plurality of pores.   
     
     
         44 . A method of forming a polymer film defining a plurality of micropores, the method comprising:
 forming a gelled polymer, wherein the polymer comprises at least about 80% polyvinylidene fluoride, at a forming temperature, by precipitating semicrystaline polymer from a saturated solution of polymer and a solvent;   placing the gelled polymer in a layer on a substrate;   adding a fiber material;   urging the solvent into non-wetting relation to the polymer by increasing the surface tension of solvent in the gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer precipitating the polymer by mechanical removal of the solvent from the gelled polymer.   
     
     
         45 . A method of producing a microporous polymer comprising:
 forming an approximately saturated solution from a polymer by adding a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy, to the polymer previously dissolved in a low surface tension liquid, the low surface tension liquid being miscible in the high surface tension liquid to form a solvent, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid; the forming being conducted at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer, wherein the approximately saturated solution comprises a solvent and a polymer material that is dissolved in the solvent, the low surface tension liquid being selected to have a higher vapor pressure than the high surface tension liquid, thereby allowing the low surface tension liquid to evaporate at a faster rate than the high surface tension liquid from the gelled polymer;   adding a fiber material;   placing the polymer solution in a layer at the forming temperature;   urging the solvent into a non-wetting relation to the polymer by increasing the surface tension of the solvent to form a gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer, the urging including evaporating the low surface tension liquid; and   evaporating, at a temperature not to exceed the forming temperature, the solvent from the gelled polymer to form a film defining a plurality of pores.