SAPONIFICATION METHOD OF CROSSLINKED ACRYLONITRILE GRANULAR POLYMER USING ALKALINE SAPONIFYING AGENT AND WEAK ACIDIC CATION EXCHANGE BODY OBTAINED BY THE METHOD

摘要

PURPOSE: Provided are a method for saponifying a crosslinked acrylonitrile granular polymer and a weak acidic cation exchange body obtained by the method which has little inherent color and is reduced in remaining nitrogen amount. CONSTITUTION: Te method comprises the steps of starting the saponification by using an alkaline saponifying agent at a temperature (T1) of 70-120 deg.C; and terminating the saponification at a temperature (T2) of 120-180 deg.C higher than T1 by 10 deg.C or more when the degree of saponification reaches 65 % or more. Preferably the alkaline saponifying agent is added to the aqueous suspension of an acrylonitrile granular polymer at T1. Preferably the acrylonitrile granular polymer is crosslinked by using divinyl ether or poly(vinyl ether), and the divinyl ether comprises the compound represented by the formula 1, wherein R is -CnH2n-, -(CmH2m-O)p-CmH2m- or -CH2-C6H4-CH2-; n>=2; m is 2-8; and p>=1.