GB200262A - Improvements in the manufacture and application of vegetable, mineral and artificial tanning agents - Google Patents

Abstract

The free acid in synthetic tanning agents containing sulphonic-acid groups is neutralized by means of ammonia or an organic base. Suitable organic bases are the amines and the amino-acids, which may be employed in an impure condition as occurring, for example, in the crude mixture of pyridine and quinoline bases obtained in the purification of coal tar, or in the mixture of amino-acids resulting from the hydrolysis of proteid material such as gelatin or hide or leather waste. The tanning agent and the determined quantity of base required for neutralization are heated together at 80 DEG -100 DEG C., an excess of base being generally avoided. The treatment may, however, be carried out under pressure, in which case a small excess of base may be employed which is afterwards neutralized by addition of a weak organic acid. A modification of the process consists in effecting the hydrolysis of proteid material, with consequent production of the amino-acids required for neutralization, by means of the free acid present in the tanning-agent. This hydrolysis may be effected with or without the application of pressure, and with or without catalysts, ferments, or enzymes. Examples are given describing the treatment of synthetic tanning agents of known type with aniline oil, crude pyridine bases, glycine, and with pyridine under pressure; the employment of synthetic tanning agents, with or without the application of pressure, to hydrolyse gelatin and leather shavings; and the production of a synthetic tanning agent by hydrolyzing glue with phenol, condensing the product with formaldehyde, sulphonating, and finally neutralizing with an organic base. Reference has been directed by the Comptroller to Specifications 131,772, [Class 76, Leather], 157,855, and 175,362, [Class 76, Leather].