Patent ID: 7879957

Claim:
A process for producing an amphoteric electrolyte resin by continuous polymerization, comprising the steps of: feeding, from a mixture supply port, a monomer mixture containing 0.01 to 10% by weight of at least one radically polymerizable basic monomer(s) including a nitrogen atom, 0.01 to 35% by weight of at least one radically polymerizable acidic monomer(s) having a carboxyl group and 45 to 99.98% by weight of a monomer(s) capable of copolymerizing with these monomers, or a mixture of the monomer mixture and a polymerization initiator and/or an organic solvent having a boiling point of 80° C. or higher and contained in an amount of 10% by weight or less to the total weight of the monomers, into a reaction zone composed of four polymerization zones independently providing the mixture temperatures of T 1 , T 2 , T 3 and T 4 which satisfy the following expressions: T 1 =50 to 160° C., T 2 =70 to 190° C., T 3 =70 to 250° C., T 4 =70 to 270° C., and T 1 <T 2 , T 2 <T 3 and T 3 <T 4 ; and continuously passing the mixture through the reaction zone with stirring while the residence time in each of the polymerization zones is controlled to 5 to 20 minutes; whereby a copolymer is produced in a reaction yield of 85% or higher in one passage through the reaction zone, and an amphoteric electrolyte resin having a number average molecular weight of 700 to 6,000 and a Mw/Mn ratio of 1.5 to 10 can be obtained.