GB443967A - The manufacture of tanning materials - Google Patents

Abstract

Products useful as tanning - agents are obtained by reacting sulphite cellulose waste liquor (or lignin sulphonic acid) with a dioxydiaryl sulphone and an aliphatic aldehyde. The three reagents may be brought to reaction in an acid, neutral or alkaline medium, or the sulphone and the aldehyde may first be condensed in an alkaline medium and the product then treated with sulphite cellulose liquor, with or without a further addition of aldehyde. Sulphite cellulose liquor which has been freed to some extent from calcium and ferric salts is preferred. In the examples: (1) sulphite cellulose liquor of 35 DEG B<\>e., 4 : 4<1>-dioxydiphenylsulphone, and aqueous formaldehyde are heated to 130 DEG C.; (2) sulphite cellulose liquor of low ash content (24 DEG B<\>e.), 4 : 4<1>-dioxydiphenylsulphone, and aqueous formaldehyde are heated to 90 DEG .; (3) 4 : 4<1>-dioxydiphenylsulphone and formaldehyde solution are heated in the presence of caustic soda, and the product is precipitated with hydrochloric acid, and then heated with sulphite cellulose liquor; a condensation product of 3 : 3<1>-dimethyl-4 : 4<1>-dioxydiphenylsulphone and formaldehyde may also be used; (4) sulphite cellulose liquor of low calcium and ferric salt content (32 DEG B<\>e.) is heated to 108 DEG C. with 4 : 4<1>-dioxydiphenylsulphone and aqueous formaldehyde; the sulphones from equimolecular amounts of phenol and crude cresol or from m-cresol may also be used. Substances which yield formaldehyde, e.g. paraformaldehyde or methylol compounds, may be used in place of formaldehyde. Specification 148,898, [Class 2 (iii)], is referred to. A sample has been furnished under Sect. 2 (5), of a product obtained by heating sulphite cellulose liquor (34 DEG B<\>e.) with 4 : 4<1>-dioxydiphenylsulphone and acetaldehyde.