Finishing of leather

A process for finishing leather by application of an aqueous mixture of at least one dispersed polymeric binder, casein and a crosslinking agent layer by layer, comprising:

• applying an aqueous mixture comprising, based on the weight of solids, from 2 to 15% by weight of one or more polymeric binders, selected from the group of copolymers consisting of:
• (A) 30 to 85% by weight of a C.sub.2 -C.sub.6 -alkyl ester of acrylic or methacrylic acid, 1 to 8% by weight of a carboxyl-containing monomer and 7 to 65% by weight of at least one comonomer selected from the group consisting of acrylonitrile, acrylamide, methacrylamide, vinyl chloride, vinyl acetate, and styrene,
• (B) 50 to 90% by weight of vinylidene chloride, 10 to 50 % by weight of a C.sub.2 -C.sub.4 -alkylester of acrylic or methacrylic acid, 0 to 5% by weight of N-methylolacrylamide or N-methylolmethacrylamide, and 0% or 1 to 5% by weight of acrylamide or methacrylamide,
• (C) 50 to 90% by weight of vinyl chloride, 10 to 50% by weight of a C.sub.1 -C.sub.4 -alkylester of acrylic or methacrylic acid, and 0 to 5% by weight of acrylamide or methacrylamide,
• (D) 80 to 90% by weight of ethyl acrylate, and 10 to 20% by weight of acrylonitrile,
• (E) 90 to 98% by weight of at least one C.sub.1 -C.sub.4 -alkylester of acrylic or methacrylic acid, and 2 to 10% by weight of acrylic or methacrylic acid or an amide thereof, and
• (F) polyesterols of adipic acid and one or more aliphatic diols and polyurethanes prepared from aliphatic, cycloaliphatic, and aromatic diisocyanates and an aliphatic diol,
• and mixtures thereof,
• from 2 to 10% by weight of casein,
• from 2 to 15% by weight of a crosslinking agent which is a condensation product of melamine, urea or mixtures thereof with formaldehyde, or further condensed with glyoxal, the methylol groups of this condensation product being wholly or partly etherified, or a condensation product of dicyandiamide or biuret with formaldehyde, or a condensation of dicyandiamine or biuret with formaldehyde further containing an aziridine compound as additional crosslinking agent,
• ad 100% by weight of water,
• in layers to leather from 2 to 6 times up to a total amount of from 10 to 100 g of solids/m.sup.2 of leather surface area, drying after every application at from 20.degree. to 80.degree. C., and fixing from 1 to 3 times at from 150.degree. to 220.degree. C. in the course of a total contact time of from 0.1 to 5 seconds.