GB608516A - Improvements relating to cation-exchange resins - Google Patents

Abstract

Cation-exchange resins are prepared by condensing in alkaline solution a sulphited tannin other than myrobalans (or such a tannin and a sulphiting agent such as sodium sulphite or metabisulphite, sulphur dioxide and alkali, or mixtures thereof), phenol, hydroquinone, catechol or resorcinol or mixtures thereof, and an aldehyde, e.g. formaldehyde, the additional phenol being present in the proportion of 0.62 to 1.5 mols. per atom of sulphur introduced as sulphited tannin or as sulphiting agent and the tannin being so highly sulphited or the sulphiting agent being present in such large proportion that in the absence of the additional phenol a soft and colour-throwing product would be obtained. The proportion of sulphiting agent to tannin may be equivalent to 0.64 to 1.12 (preferably 0.88) gram-atoms of sulphur per 100 gms. of tannin. In a modification, part of the sulphited tannin is replaced by a water-soluble sulphonated phenol, cresol, catechol, hydroquinone or a mixture thereof, the proportion of sulphited tannin to sulphonated phenol being at least 3 : 2, and 1/2 to 1 1/2 mols. additional mono- or di-hydric phenol is present per mol. of sulphonated phenol. Tannins specified are quebracho, gambier and mimosa. During or subsequent to drying, the resins may be heattreated above 120 DEG C. In examples: (1) quebracho tannin is heated with sodium metabisulphite in alkaline solution, then condensed with phenol and paraformaldehyde; (2) resorcinol is condensed with formaldehyde in the presence of caustic soda, then quebracho tannin, sodium metabisulphite, phenol and paraformaldehyde added and further condensed; (3) and aqueous solution of quebracho tannin, sodium metabisulphite and caustic soda was mixed with sulphonated phenol, and condensed with phenol and paraformaldehyde. Specifications 450,308, 474,361 and 588,380 are referred to.