GB1353024A - Tanning - Google Patents

Abstract

1353024 Tanning hides NATIONAL RESEARCH DEVELOPMENT CORP 21 July 1971 [24 July 1970] 35994/70 Addition to 1227532 Heading C6C Leather with good hydrophobic properties is obtained by a tanning process in which hide or skin is treated firstly with a basic salt of a multivalent metal, secondly, under alkaline conditions, with an organic compound having a long chain aliphatic group with at least six C atoms in the chain, and at least one reactive group capable of entering into a complex with a basic salt of a multivalent metal, and thirdly with a salt of a multivalent metal. The first stage may be carried out on stock which has the hair or wool intact, or has been prepared by conventional pre-tanning processes, or has been previously tanned, e.g. by vegetable tanning. Suitable basic salts are those of mineral acids, e.g. sulphuric, and metals having a valency of three or more, e.g. chromium, aluminium, zirconium or cerium. The salt may be "masked" with certain organic acid salts to form a mixed salt of modified reactivity but still capable of reacting with the organic compound. The organic compound, which is adjusted to the required pH of e.g. 7À5 to 9 by addition of organic bases or inorganic alkalis such as sodium carbonate or ammonia, preferably contains two or more long chain aliphatic groups with from six to thirty-six C atoms in the chain. The reactive group, of which there may be more than one, may be chloro, nitro, sulphonate, phosphate, borate, citrate, thiocyanate, sulphate, amino or carboxyl. Mixtures of different organic compounds may be used, and suitable ones are alkali metal, ammonium or organic base salts of long chain aliphatic carboxylic acids, e.g. oleic, palmitic and stearic acids; half esters of long chain dicarboxylic acids; salts of sulphonated or sulphated long chain mono-carboxylic acids, e.g. ammonium, sodium and potassium salts of sulphonated or sulphated oleic and palmitic acids; sulphonated or sulphated triglycerides, e.g. medium sulphated cod oil and lightly sulphated cold test neatsfoot oil; and long chain aliphatic amino acids. The treatment with the organic compound may be carried out in the presence of a water soluble or water miscible alcohol or liquid hydrocarbon. The salt for the third stage may be a basic salt of chromium, aluminium, zirconium or cerium &c, or a normal salt e.g. a copper, zinc, zirconium, aluminium or nickel sulphate. The salt may be "masked" with a formate, acetate phthalate, citrate &c. Dyeing may be performed before or after the third stage. Softer leathers are obtained by using a small amount of hydrocarbon solvent or a straight oil, &c., neatsfoot or sperm oil, emulsified in the organic compound.