Microporous material and a method of making same

Abstract

A method for producing a microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a filler; providing a processing plasticizer; adding the filler to the UHMWPE in a mixture being in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight; adding the processing plasticizer to the mixture; extruding the mixture to form a sheet from the mixture; calendering the sheet; extracting the processing plasticizer from the sheet to produce a matrix comprising UHMWPE and the filler distributed throughout the matrix; stretching the microporous material in at least one direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix; and subsequently calendering the stretched microporous matrix to produce a microporous material which exhibits improved physical and dimensional stability properties over the stretched microporous matrix.

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         11 . A microporous material made from a precursor material where said microporous material has a reduction of thickness of 5% or more from said precursor material;
 said microporous material comprises: an ultrahigh molecular weight polyethylene (UHMWPE) and a particulate silica filler distributed throughout said microporous material;   where said filler constitutes from about 5 percent to 95 percent by weight of said microporous material;   where said microporous material has a network of interconnecting pores communicating throughout said microporous material, said pores constituting at least 45 percent by volume of said microporous material;   said microporous material has a machine direction (MD) tensile strength of greater than 25 N/mm 2 ; and   said microporous material has a wet out time of less than 180 seconds.   
     
     
         12 . The microporous material according to  claim 11 , where said microporous material has a machine direction (MD) tensile strength of greater than 35 N/mm 2 . 
     
     
         13 . The microporous material according to  claim 11 , where said microporous material has a machine direction (MD) tensile strength of greater than 50 N/mm 2 . 
     
     
         14 . A microporous material where said microporous material comprises: an ultrahigh molecular weight polyethylene (UHMWPE) and a particulate filler distributed throughout said microporous material;
 where said filler constitutes from about 5 percent to 95 percent by weight of said microporous material;   where said microporous material has a network of interconnecting pores communicating throughout said microporous material, said pores constituting at least 25 percent by volume of said microporous material, these pores create a pore distribution;   where said microporous material has no pores greater in size than 1.0 micrometers; and   where change in volume divided by log d for the pores of this microporous material is less than 2 cc/g for the entire pore distribution.   
     
     
         15 . The microporous material according to  claim 14 , where the shrink in the machine direction is less than 10%. 
     
     
         16 . The microporous material according to  claim 14 , where said microporous material has an machine direction (MD) tensile strength of greater than 25 N/mm 2 . 
     
     
         17 . The microporous material according to  claim 14 , where said filler is selected from the group consisting essentially of: silica, mica, montmorillonite, kaolinite, asbestos, talc, diatomaceous earth, vermiculite, natural and synthetic zeolites, cement, calcium silicate, clay, aluminum silicate, sodium aluminum silicate, aluminum polysilicate, alumina silica gels, glass particles, carbon black, activated carbon, carbon fibers, charcoal, graphite, titanium oxide, lead oxide, tungsten, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, and magnesium carbonate. 
     
     
         18 . The microporous material according to  claim 17 , where said filler is selected from the group consisting essentially of: silica, precipitated silica, silica gel, fumed silica, mica, talc, diatomaceous earth, carbon black, activated carbons, carbon fibers, titanium oxide and calcium carbonate. 
     
     
         19 . The microporous material according to  claim 14  where said UHMWPE is mixed with a high density (HD) polyethylene to produce a polyolefin mixture, where said polyolefin mixture has at least 50% UHMWPE by weight of said polyolefin mixture; where said filler to said polyolefin mixture is in a range of from 1:9 to 15:1 filler to polyolefin mixture by weight and where said matrix comprises UHMWPE and HD polyethylene and said particulate filler distributed throughout said matrix. 
     
     
         20 . The microporous material according to  claim 19 , where said microporous material has a machine direction (MD) tensile strength of greater than 25 N/mm 2 . 
     
     
         21 . A microporous material where said microporous material comprising: an ultrahigh molecular weight polyethylene (UHMWPE) and a particulate filler distributed throughout said microporous material;
 where said filler constitutes from about 5 percent to 95 percent by weight of said microporous material;   where said microporous material has a network of interconnecting pores communicating throughout said microporous material, said pores constituting at least 25 percent by volume of said microporous material;   where said microporous material has no pores greater in size than 0.50 micrometers; and   where said median pore size is between or equal to 0.01 and 0.3 micrometers and the pores vary in size by plus or minus 0.2 micrometers or less.   
     
     
         22 . The microporous material according to  claim 21 , where shrink in the machine direction is less than 10%. 
     
     
         23 . The microporous material according to  claim 21 , where said microporous material has a machine direction (MD) tensile strength of greater than 25 N/mm 2 . 
     
     
         24 . The microporous material according to  claim 21 , where said filler is selected from the group consisting essentially of: silica, mica, montmorillonite, kaolinite, asbestos, talc, diatomaceous earth, vermiculite, natural and synthetic zeolites, cement, calcium silicate, clay, aluminum silicate, sodium aluminum silicate, aluminum polysilicate, alumina silica gels, glass particles, carbon black, activated carbon, carbon fibers, charcoal, graphite, titanium oxide, iron oxide, copper oxide, zinc oxide, lead oxide, tungsten, antimony oxide, zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, and magnesium carbonate. 
     
     
         25 . The microporous material according to  claim 24 , where said filler is selected from the group consisting essentially of: silica, precipitated silica, silica gel, fumed silica, mica, talc, diatomaceous earth, carbon black, activated carbons, carbon fibers, titanium oxide and calcium carbonate. 
     
     
         26 . The microporous material according to  claim 21  where said UHMWPE is mixed with a high density (HD) polyethylene to produce a polyolefin mixture, where said polyolefin mixture has at least 50% UHMWPE by weight of said polyolefin mixture; where said filler to said polyolefin mixture is in a range of from 1:9 to 15:1 filler to polyolefin mixture by weight and where said matrix comprises UHMWPE and HD polyethylene and said particulate filler distributed throughout said matrix. 
     
     
         27 . The microporous material according to  claim 26 , where said microporous material has a machine direction (MD) tensile strength of greater than 25 N/mm 2 . 
     
     
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