GB191228392A - Improvements in and relating to the Manufacture of Leather and Leather Products. - Google Patents

Abstract

28,392. Spalteholz, W., and Haring, K. Dec. 9. Impregnating - compositions. - Leather, especially of chrome tannage, or an untanned hide or skin is rendered waterproof, non- slipping, resistant to heat, and electrically insulating by a complete removal of its moisture and an impregnation with resinous, asphaltic, or similar substances. " Petrol goudron," that is, the residues from the fractional distillation of petroleum, is a particularly suitable substance. The dehydration after tannage is effected by stretching the hides on frames, immersing them in successive alcohol or acetone baths of increasing strength, and finally distilling off the alcohol in vacuo. A non-fatted flexible chrome leather is thereby produced particularly suitable for tyres in which rubber is employed. The dehydrated material may be impregnated by immersion in a solution of shellac, resin, mastic, rubber, gutta-percha, bituminous substances, coal or lignite tar, or residues from its drv distillation, used singly or mixed in alcohol, benzene, acetone, petroleum-benzene, turpentine, carbon bisulphide or tetrachloride, or any other non-aqueous solvent. The softness of the treated leather or untanned skins may be controlled by adding oils, vaseline, paraffin or other wax, varnish, or the like, or by mixing asphalt with goudron or goudrons of different hardnesses. In alternative processes, the molten materials are used without solvents for the entire impregnation or after a preliminary treatment with dissolved materials. In another process, the dehydrated and evacuated raw or chromed hide is impregnated with a solution of petrol goudron &c., and it is then placed in a molten mass of a substance having a melting-point which is near the boiling- point of the solvent. The molten substance, which replaces the solvent by " diffusion " and fills all the pores, should be soluble in the original solvent. Petrol goudron, paraffin or other wax, and ceresine are suitable materials for this treatment, with or without the addition of linseed, paraffin, or other mineral oil or linseed oil varnish to control the melting-point. During the " diffusion," the contents of the vessel may be agitated; and the process may be assisted by evacuation. A lesser impregnation may be obtained by using molten substances which are insoluble in the original solvent, and in this case a freely mobile bath, such as paraffin wax, should be used. The " diffusion " process may be applied to hides untanned or tanned in any manner, and dehydrated by means of alcohol or. thoroughly dried at a high temperature. As an example, the hides, stretched on frames, dehydrated with alcohol, and treated in vacuo are immersed for ten to fourteen days in benzene containing 33 per cent of natural asphalt or for three to five days in a 40 to 50 per cent solution of hard petrol goudron in benzene. They are then placed in a molten bath of hard petrol goudron melting at 100-108‹ C. and containing 2 to 10 per cent of linseed oil, varnish, or mineral oil. The bath is kept at 80‹ C. for the first twenty-four hours and at 90-95‹ C. for the next twenty-four hours. The excess material is scraped off the hides which are washed with benzene, stocked, rolled, and dressed with a thin asphalt varnish. Ordinary chrome leather, not dehydrated by alcohol, is dried at 50‹ C. and treated for not more than six to eight hours by the above-described process. In the case of colophony, a few days' impregnation in benzene containing 20 to 50 per cent of colophony is followed by immersion in molten ceresine, paraffin, or other wax. In an alternative " diffusion " process, the pure solvent is first introduced into the hide and is then displaced by immersion in the molten bath. Articles such as shoe uppers, tyres, &c. made of untanned or semi-tanned hide may be dehydrated and impregnated by any of the processes.