Microporous sheet product and methods for making and using the same

Abstract

Microporous sheet product and methods of making and using the same. In one embodiment, the microporous sheet product is made by a process that includes melt-extruding a sheet material using an extrusion mixture that includes a thermoplastic polymer, a non-cross-linked elastomer having a molecular weight of at least 50,000 Da, and a compatibilizing agent. By way of example, the thermoplastic polymer may be a polyolefin, the non-cross-linked elastomer may be a polyisobutylene, and the compatibilizing agent may be mineral spirits. After extrusion, the sheet material may be cooled, and the sheet material may be stretched. The microporous sheet product may be used, for example, as a battery separator, as a food packaging material, as a diffusion barrier in the ultrafiltration of colloidal matter, and in disposable garments.

What is claimed is: 
     
         1 . A microporous sheet product made by a method comprising (a) dissolving a cyclic olefin copolymer and a non-cross-linked elastomer in a solvent to form a homogeneous solution, the non-cross-linked elastomer having a molecular weight of at least 50,000 Da; and (b) forming a sheet material with the homogeneous solution. 
     
     
         2 . The microporous sheet product as claimed in  claim 1  wherein the forming step comprises forming the sheet material with the homogeneous solution using a solvent cast technique. 
     
     
         3 . The microporous sheet product as claimed in  claim 1  wherein the solvent is mineral spirits. 
     
     
         4 . The microporous sheet product as claimed in  claim 1  wherein the solvent comprises at least one hydrocarbon. 
     
     
         5 . The microporous sheet product as claimed in  claim 1  wherein the non-cross-linked elastomer is polyisobutylene. 
     
     
         6 . The microporous sheet product as claimed in  claim 1  wherein the non-cross-linked elastomer has a molecular weight between 200,000 Da and 10,000,000 Da. 
     
     
         7 . The microporous sheet product as claimed in  claim 1  wherein the microporous sheet product has a resistivity below about 100 ohm-cm as tested in a 30% KOH solution. 
     
     
         8 . The microporous sheet product as claimed in  claim 1  further comprising, after step (b), the step of removing the solvent from the sheet material. 
     
     
         9 . The microporous sheet product as claimed in  claim 8  wherein the microporous sheet product has a pore size of about 0.001 to 5 microns. 
     
     
         10 . The microporous sheet product as claimed in  claim 1  wherein the homogeneous solution further comprises a filler. 
     
     
         11 . The microporous sheet product as claimed in  claim 1  wherein the dissolving step comprises dissolving the cyclic olefin copolymer and the non-cross-linked elastomer in the solvent to form the homogeneous solution at standard temperature and pressure conditions and wherein forming step comprises forming the sheet material with the homogeneous solution using a solvent dissolution membrane cast technique. 
     
     
         12 . A method of making a microporous sheet product, the method comprising the steps of:
 (a) dissolving a cyclic olefin copolymer and a non-cross-linked elastomer in a solvent to form a homogeneous solution, the non-cross-linked elastomer having a molecular weight of at least 50,000 Da; and   (b) forming a sheet material with the homogeneous solution using a solvent cast technique.   
     
     
         13 . The method as claimed in  claim 12  wherein the solvent cast technique comprises casting the homogeneous solution on a battery electrode. 
     
     
         14 . The method as claimed in  claim 12  wherein the solvent cast technique comprises casting the homogeneous solution on a porous film. 
     
     
         15 . The method as claimed in  claim 12  wherein the solvent is mineral spirits. 
     
     
         16 . The method as claimed in  claim 12  wherein the solvent comprises at least one hydrocarbon. 
     
     
         17 . The method as claimed in  claim 12  wherein the non-cross-linked elastomer is polyisobutylene. 
     
     
         18 . The method as claimed in  claim 12  wherein the non-cross-linked elastomer has a molecular weight between 200,000 Da and 10,000,000 Da. 
     
     
         19 . The method as claimed in  claim 12  further comprising, after step (b), the step of removing the solvent from the sheet material. 
     
     
         20 . The method as claimed in  claim 12  wherein the dissolving step comprises dissolving the cyclic olefin copolymer and the non-cross-linked elastomer in the solvent to form the homogeneous solution at standard temperature and pressure conditions and wherein forming step comprises forming the sheet material with the homogeneous solution using a solvent dissolution membrane cast technique. 
     
     
         21 . A method of separating the electrodes of a battery, the method comprising positioning the microporous sheet product of  claim 1  between the electrodes. 
     
     
         22 . The method as claimed in  claim 21  wherein the microporous sheet product positioned between the electrodes is unstretched.