GB353872A - Improvements in the manufacture and production of tanning materials and preparationscontaining the same - Google Patents

Abstract

Water-soluble nitrogenous products useful as tanning agents are obtained by condensing an aliphatic aldehyde with one or more polyhydric phenols, or a mixture thereof with a vegetable tanning material, and urea or a urea derivative at a temperature below 50 DEG C., preferably in the presence of a small quantity of acid condensing agent, the product then being heated if necessary to a temperature not exceeding 100 DEG C. The resulting products are assumed to have the formula R-O-A-NH-CO-NH2 where R is the radicle of the polyhydric phenol and A the alkyl radicle of the aldehyde employed. The aliphatic aldehydes referred to are formaldehyde and acetaldehyde. The polyhydric phenols which may be employed are resorcinol, cresorcinol, phloroglucinol and pyrogallol or less advantageously catechol, quinol or hydroxyquinol. Examples of urea derivatives are semicarbazide, carbazide, thio-urea, monomethyl urea and mono-ethyl urea. The vegetable tanning agents which may be employed include quebracho extract, mangle bark extract, chestnutwood extract or the difficulty soluble phlobaphenes separated from quebracho extract. If products difficulty soluble in water are obtained by using more than half a molecular proportion of formaldehyde for each molecular proportion of polyhydric phenol, they can be rendered soluble by bringing their solutions to dryness in the presence of a small quantity of ammonia, caustic soda or like alkali.