Preparation of cation-exchange resins

摘要

Relates to cation-exchange resins which contain recurring units which, when in acid form, have the formula and also recurring units which, when in the acid form, have the formula where, in the above formul/m g, R represents hydrogen or a methyl group. Such resins may be prepared by oxidizing, so as to convert the -S-R1-O-R11 groups therein to sulphonic acid groups, and hydrolysing so as to convert the -COOR111 groups therein to carboxyicl acid groups, an insoluble cross-linked synthetic resin which contains recurring units of the formula and also recurring units of the formula where, in the above formul/m g, R represents hydrogen or a methyl group, R1 represents methylene, ethylidene or an isopropylidene group, and R11 and R111 represent alkyl groups. The insoluble cross-linked synthetic resin may be a copolymer of (a) an organic sulphide having the formula CH2=C(R)-S-R1-O-R11 such as vinyl methoxymethyl sulphide, (b) an alkyl ester of acrylic or methacrylic acid, such as ethyl acrylate, and (c) a copolymerizable compound having at least two CH2=C< groups such as divinylbenzene, divinyltoluene, trivinylbenzene, divinylnaphthalene, diallyl phthalate, and ethylene glycol diacrylate or dimethacrylate. Polymerization may be effected in bulk, solution or aqueous suspension or emulsion, preferably in aqueous suspension with the formation of the insoluble copolymers in the shape of small beads, in the presence of a catalyst such as an azo compound, or a peroxide, hydroperoxide or per-salt. The oxidation process may be effected by treating with an aqueous solution of hydrogen peroxide, chlorine, sodium hypochlorite, calcium hypochlorite, nitric acid, potassium permanganate, peracetic acid, performic acid or potassium dichromate. The ester groups may be hydrolysed by treating with a solution of an alkali such as sodium or potassium hydroxide or a quaternary ammonium hydroxide. Specifications 747,765 and 826,659 are referred to.