GB411390A - Improvements in the manufacture and production of synthetic tans - Google Patents

Abstract

Products useful as tanning-agents are prepared by condensing a sulphonated phenol with formaldehyde in the presence of a free ammoniacal base and in the presence or absence of a fixed alkaline substance. The phenolic component may be a sulphonated phenol or phenol homologue, a sulphosalicylic acid, a sulphonated naphthol, or a sulphonated condensation product of the type of p-dioxydiphenylmethane or p-dioxydiphenyldimethylmethane, or halogen derivatives thereof. The ammoniacal base may be ammonia, methylamine and its immediate homologues or the corresponding secondary amines, or amines containing one or more higher radicles such as cyclohexyl, dodecyl or cetyl. The fixed alkaline substance may be caustic potash or soda, calcium hydroxide, potassium or sodium carbonate, or sodium acetate. Formaldehyde and ammonia may be replaced by hexamethylenetetramine, or instead of formaldehyde its equivalents, such as formaldehyde bisulphite or methylene chloride, may be used. In the examples: (1) equal parts of phenol and sulphuric acid are heated to 120 DEG C., mixed with an excess of aqueous ammonia, and then heated to 130--160 DEG C. with formaldehyde solution; cresylic or salicylic acid may be used instead of phenol; (2) cresolsulphonic acid is made slightly alkaline with caustic soda solution and then warmed with hexamethylenetetramine; the products may be prepared for use by dilution and slight acidification, or they may be evaporated on heated rollers or by spray-evaporation.