GB723628A - Improvements relating to condensation products, being more especially tanning agents, and their use - Google Patents

Abstract

Tanning agents are prepared by condensing in alkaline solution (a) formaldehyde, (b) polyhydroxyarylsulphone sulphonic acids prepared by heating in vacuo above 150 DEG C. phenol sulphonic acids either alone or with benzene or naphthalene sulphonic acids and (c) polyhydroxyaryl sulphones obtained by heating the component (b) with a phenol in an amount equivalent to the sulphonic acid groups in the component (b), the heating being under the same conditions as specified above. The final products may be further reacted with sulphites, or with naphthalene or tetralin sulphonic acids or soluble condensation products thereof with formaldehyde, to increase their water-solubility. Components (b) and (c) are preferably obtained as a mixture by heating polyhydroxyarylsulphone sulphonic acids with a phenol in amount less than that equivalent ot the sulphonic acid groups present. The phenols used in the preparations may be substituted by halogen or by methyl groups. In examples, (1) phenol sulphonic acid is heated at 160-165 DEG C. and 11-13 mm. pressure until the acidity is reduced to a specified degree, whereupon phenol is added and the heating again continued until the acidity is reduced a further specified amount. The product is made alkaline with caustic soda and condensed at 100-105 DEG C. with formaldehyde for six hours. The reaction mass is diluted, the tanning agent precipitated with sulphuric acid, dissolved in water and acidified with acetic acid; (2) similar to (1) but using cresol instead of phenol; (3) similar to (1) but after-treating the product with sodium bisulphite, preferably under pressure at 150 DEG C., or b -naphthalene sulphonic acid; (4) a mixture of phenol and naphthalene sulphonic acids is heated at 165 DEG C. and 11-13 mm. pressure until the acidity is reduced to a specified degree, whereupon phenol is added and heating continued until the acidity is reduced a further specified amount. The product is condensed with formaldehyde at 100-105 DEG C. in alkaline medium for 7 hours. Toluene may be used instead of naphthalene; (5) a mixture of a naphthylpolyhydroxypolyphenylene sulphone and a polyhydroxypolyphenylenesulphone sulphonic acid is condensed with formaldehyde. The products of the invention are also useful as assistants in dyeing textiles. Specification 683,084 is referred to.