Bipolar membrane
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 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.
2 . The method of producing the bipolar membrane according to claim 1 , 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.
3 . The method of producing the bipolar membrane according to claim 1 , 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.
4 . The method of producing the bipolar membrane according to claim 1 , 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.
5 . The method of producing the bipolar membrane according to claim 1 , 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.
6 . The method of producing the bipolar membrane according to claim 1 , 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.