GB362797A - Improvements relating to tanning substances - Google Patents

Abstract

A sulphonated phenol (or a sulphonated phenol derivative) is condensed with formaldehyde (or a compound which yields formaldehyde) at a raised temperature and in strongly acid solution in the presence of one or more aromatic oxycarboxylic acids and urea (or a compound which yields urea). The neutralized products show the general reactions of tanning substances, and can be used alone or in combination with other tanning agents; silk can be loaded by means of the products without change of colour. According to the examples, (1) crude cresol and sulphuric acid are heated at 105 DEG C., diluted, cooled to 50 DEG C., and treated with gallic acid, urea, and formaldehyde solution with further heating; the acidity of the product is reduced by addition of caustic soda; (2) as in example 1, using salicylic acid instead of gallic acid; (3) phenol and sulphuric acid are heated to 110 DEG C., diluted, cooled to 40-50 DEG C., and treated with o-cresotinic acid and a filtrate obtained from calcium cyanamide and water; formaldehyde solution is then added, the temperature is raised to 90-95 DEG C., and the mixture finally neutralized with ammonia; (4) as in example 2, except that methylal is used instead of formaldehyde, and the reaction product is salted out with common salt and sodium carbonate, separated, and dried; (5) as in example 1, except that salicylic acid is used instead of cresol.