Bipolar membrane

Abstract

A bipolar membrane in which a cation-exchange membrane and an anion-exchange membrane are joined to each other, wherein a leakage ratio of gluconic acid at 60° C. is not more than 1.0%, and the cation-exchange membrane is supported by a polyolefin reinforcing member and, further, contains a polyvinyl chloride.

1 . A bipolar membrane in which a cation-exchange membrane and an anion-exchange membrane are joined to each other,
 wherein a leakage ratio of gluconic acid at 60° C. is not more than 1.0%, and said cation-exchange membrane is supported by a polyolefin reinforcing member and, further, contains a polyvinyl chloride.   
     
     
         2 . The bipolar membrane according to  claim 1 , wherein an area ratio of a portion where the cation-exchange membrane and the anion-exchange membrane are peeled off is not more than 20% after the bipolar membrane is dipped in a 6N sodium hydroxide aqueous solution of 25° C. for one hour and then in pure water of 25° C. for another one hour. 
     
     
         3 . The bipolar membrane according to  claim 1 , wherein the cation-exchange membrane contains said polyvinyl chloride in an amount of 10 to 45% by mass. 
     
     
         4 . A method of producing a bipolar membrane including a step of forming a cation-exchange membrane, and a step of forming an anion-exchange membrane on the surface of said cation-exchange membrane; wherein
 the step of forming said cation-exchange membrane includes:   a step of impregnating a polyolefin reinforcing member with a polymerizable composition obtained by mixing a polyvinyl chloride (A) and a polymerization-curable component (B) that contains a monomer (b1) having a cation-exchange group or a monomer (b2) having a reaction group capable of introducing a cation-exchange group; and   a step of forming a membrane of a cation-exchange resin that contains the polyvinyl chloride or of a cation-exchange resin precursor resin by polymerization-curing said polymerizable composition at a temperature of not lower than 100° C.; and, further, as required,   a step of introducing a cation-exchange group into the cation-exchange resin precursor resin.   
     
     
         5 . The method of producing the bipolar membrane according to  claim 4 , further including:
 a step of impregnating a polyolefin reinforcing member with the polymerizable composition obtained by mixing the polyvinyl chloride (A) and the monomer (b1) having a cation-exchange group; and   a step of forming a membrane of the cation-exchange resin that contains the polyvinyl chloride by the polymerization curing at a temperature of not lower than 100° C.   
     
     
         6 . The method of producing the bipolar membrane according to  claim 4 , further including:
 a step of impregnating a polyolefin reinforcing member with the polymerizable composition obtained by mixing the polyvinyl chloride (A) and the monomer (b2) having a reaction group capable of introducing a cation-exchange group;   a step of forming the membrane of said cation-exchange resin precursor resin by the polymerization curing at a temperature of not lower than 100° C.; and   a step of introducing a cation-exchange group by acting a cation-exchange group introducing agent upon said cation-exchange resin precursor resin.   
     
     
         7 . The method of producing the bipolar membrane according to  claim 4 , wherein the step of forming the anion-exchange membrane on the surface of said cation-exchange membrane includes:
 a step of applying a polar organic solvent solution of the anion-exchange resin on the surface of said cation-exchange membrane; and   a step of removing the polar organic solvent.   
     
     
         8 . The method of producing the bipolar membrane according to  claim 4 , wherein the step of forming the anion-exchange membrane on the surface of said cation-exchange membrane includes:
 a step of applying, on the surface of said cation-exchange membrane, a polar organic solvent solution of an anion-exchange resin precursor resin having a reaction group capable of introducing the anion-exchange group;   a step of forming a membrane of said anion-exchange resin precursor resin on the surface of said cation-exchange membrane by removing the polar organic solvent; and   a step of introducing the anion-exchange group into said anion-exchange resin precursor resin.   
     
     
         9 . The method of producing the bipolar membrane according to  claim 4 , wherein the step of forming the anion-exchange membrane on the surface of said cation-exchange membrane includes:
 a step of applying, on the surface of said cation-exchange membrane, a polar organic solvent solution that contains an anion-exchange resin precursor resin having a reaction group capable of introducing the anion-exchange group and an anion-exchange group introducing agent; and   a step of removing the polar organic solvent.