Bipolar membrane and process for producing the same

A bipolar membrane in which a cation-exchange membrane and an anion-exchange membrane are joined together, characterized in that particles of a basic metal chloride are distributed in the interface between said cation-exchange membrane and said anion-exchange membrane,

• wherein the particles of said basic metal chloride are distributed in an amount of 0.1 to 1 g/m2, wherein said basic metal chloride is a polyvalent metal chloride to which hydroxide ions are introduced, and the degree of hydroxide ion introduction is 20 to 90%,
• wherein the particles of said basic metal chloride have a number average particle diameter of 0.05 μm to 10 μm,
• wherein the bipolar membrane (1 cm2) has no separated portion where blisters have evolved on its surface, after being dipped in an aqueous solution of 6.0 mol/L of sodium hydroxide at 25° C. for one hour, taken out from the aqueous solution, dipped in pure water maintained at 25° C. for one hour, and taken out from the pure water,
• wherein the cation-exchange membrane is formed of a resin that has a cation-exchange group introduced into an aromatic ring present in a main chain or a side chain thereof,
• wherein the anion-exchange membrane is formed of a resin that has an anion-exchange group introduced into an aromatic ring present in a main chain or a side chain thereof,
• wherein the metal contained in said basic metal chloride is Sn or Ru.