Abstract: A formulation for use in chrome-free or chrome tanning is proposed, comprising a clay mineral which, after vigorous stirring for 30 minutes in water at 50° C., has a number average particle diameter of less than 2 ?m or a bimodal size distribution with a first, finely divided fraction whose number average particle diameter is less than 0.5 ?m and a second, coarser fraction whose number average particle diameter is less than 5 ?m, determined in each case by the method according to ISO 13320-1, by combined laser light diffraction and light scattering, the amount of the first, finely divided fraction being from 10 to 90% by weight, and one or more substances from one or more of the following groups: organic polymers, aldehyde tanning agents, sulfone tanning agents, resin tanning agents, phenol tanning agents, fatliquoring agents, vegetable tanning agents, dyes and pigments.

Abstract: Water repellency is imparted to leather and fur skins by a process in which leather or fur skin is treated, before, during or after the retanning, with one or more formulations comprising from 1 to 30% by weight, based on the formulation, of a mixture of polysiloxanes comprising from 10 to 90% by weight, based on the mixture, of one or more carboxyl-containing polysiloxanes, from 90 to 10% by weight, based on the mixture, of one or more carboxyl-free polysiloxanes and from 3 to 25% by weight, based on the formulation, of at least one emulsifier.

Abstract: A semifinished leather product is produced from an animal hide by pretanning with the use of a chromium-free tanning agent and of a clay mineral which, after stirring for 30 minutes in water at 50° C. at a circumferential rotor speed of from 5 to 25 m/s, has a number average particle diameter of less than 2 ?m or a bimodal particle size distribution with a first, finely divided fraction whose number average particle diameter is less than 0.5 ?m and a second, coarser fraction whose number average particle diameter is less than 5 ?m, determined in each case by the method according to ISO 13320-1, by combined laser light diffraction and light scattering, a proportion of the first, finely divided fraction being from 10 to 90% by weight, and drying of the pretanned animal hide to a water content of from 5 to 45% based on the total weight of the semifinished leather product.