GB569386A - Improvements in or relating to methods of preparing leather and to leather produced thereby - Google Patents

Abstract

569,386. Making leather. AMERICAN CYANAMID CO. May 13, 1943, No. 7655. Convention date, July 25, 1942. [Class 76] Hides and skins are tanned by impregnation with an aqueous solution or dispersion of a water-soluble methylol melamine, which preferably remains soluble in the presence of sodium chloride. 3-10 per cent by weight of the drained and pickled skin of the tanning agent may be used at a pH value of 3-4.5, the pH being adjusted if necessary, as when using a bated skin, by means of sulphuric, hydrochloric or acetic acid. The tanned skins may be fat liquored with a sulphonated vegetable oil, and in one example are finally pigmented with a mixture of colloidal clay, lithopone, Italian talc and white clay. In the examples, the tanning agent is added in stages to a sodium chloride solution with which the skin has been drummed, but in the case of a skin bated with an enzyme bate not followed by preliminary pickling in sodium chloride-sulphuric acid solution, the pH value needs considerable adjustment. Disodium phosphate is also added in the example relating to bated skins. Methylol melamine for use inthe process may be prepared by boiling 1 mol. melamine with 3.5 mols. aqueous 30 per cent formaldehyde at pH 9.0 for 20 mins., cooling and separating and drying the crystals obtained.