A method for forming chrome-free retanned leather including: (a) contacting wet white (chrome-free tanned hide) with a retanning mixture comprising from 2% to 15%, by solids weight, based on the wet weight of the wet white, of an amphoteric polymer composition comprising amine functional units and acid functional units; and (b) applying a polymeric overcoat containing an acrylic copolymer with one or more metal transition elements, with a thickness of no greater than 100 microns, to the retanned wet white, is provided. The present invention also provides a chrome-free retanned leather formed by the method.

A method for forming chrome-free retanned leather including: (a) contacting wet white (chrome-free tanned hide) with a retanning mixture comprising from 2% to 15%, by solids weight, based on the wet weight of the wet white, of an amphoteric polymer composition comprising amine functional units and acid functional units; and (b) applying a polymeric overcoat containing an acrylic copolymer with one or more metal transition elements, with a thickness of no greater than 100 microns, to the retanned wet white, is provided. The present invention also provides a chrome-free retanned leather formed by the method.

A composition including an acetal of an aldehydic tanning agent for tanning hides and/or pelts, as well as a method for tanning hides and/or pelts in order to produce leather, wherein an acetal of an aldehydic tanning agent is used. By reducing the pH, the aldehydic tanning agent can be released, whereby a tanning step is initiated. The composition according to the invention and the method according to the invention are characterized by lower toxicity compared to conventional compositions and tanning methods based on aldehydic tanning agents. Furthermore, improved penetration of the tanning agents into deeper layers of the hide and/or the pelt is possible, so that particularly homogeneous tanning is achieved.

A method for tanning an animal skin may include: (a) putting the animal skin in contact with a first tanning bath including at least one dialdehyde of general formula OCH(CH).sub.nHCO, wherein n is 0 or an integer number greater than or equal to 1 and less than or equal to 8, and wherein the first tanning bath has a pH greater than or equal to 1 and less than or equal to 5; (b) bringing the pH of the first tanning bath to a pH greater than 5 and less than 8; and/or (c) repeating one or more times the steps (a) and (b) on the animal skin coming from the step (b) using a second or further tanning bath. The first, second, and further tanning baths may be substantially free of surfactants.

A method for tanning an animal skin may include: (a) putting the animal skin in contact with a first tanning bath including at least one dialdehyde of general formula OCH(CH).sub.nHCO, wherein n is 0 or an integer number greater than or equal to 1 and less than or equal to 8, and wherein the first tanning bath has a pH greater than or equal to 1 and less than or equal to 5; (b) bringing the pH of the first tanning bath to a pH greater than 5 and less than 8; and/or (c) repeating one or more times the steps (a) and (b) on the animal skin coming from the step (b) using a second or further tanning bath. The first, second, and further tanning baths may be substantially free of surfactants.

The invention discloses a method for treating an animal substrate comprising: agitating the moistened animal substrate with a treatment formulation and a solid particulate material in a sealed apparatus wherein the treatment formulation comprises a tanning agent or a tannery process agent. The method can comprise applying the tanning agent or tannery process agent to the animal substrate wherein at least some of the agent so applied originates from the treatment formulation. There is also disclosed an animal substrate obtained by the method. The treatment formulation can be aqueous.

The invention discloses a method for treating an animal substrate comprising: agitating the moistened animal substrate with a treatment formulation and a solid particulate material in a sealed apparatus wherein the treatment formulation comprises a tanning agent or a tannery process agent. The method can comprise applying the tanning agent or tannery process agent to the animal substrate wherein at least some of the agent so applied originates from the treatment formulation. There is also disclosed an animal substrate obtained by the method. The treatment formulation can be aqueous.

The invention relates to a poly silsesquioxane-acrylic nanocomposite auxiliary for leather process and its preparation method. By mixing octavinyl silsesquioxane, organic solvent, ammonium persulfate, distilled water and surfactant in one system, and adding acrylic acid dropwise into the mixing system, cooling to adjust pH to obtain poly silsesquioxane-acrylic nanocomposite auxiliary for leather process. The auxiliary obtained in this invention is easily to penetrate into gap of the collagen fibers, and forms nano and micro-scale combination with the leather collagen, which can further improve the multi-point combination of the acrylic polymer with the collagen. Thus, the filling property of the leather that treated by the auxiliary is improved without affect the yield of leather, and the chromium content in the waste water is significantly reduced.

The present invention relates to a process for the tanning of animal hides characterised, compared to currently adopted processes, by the non-adoption of the step known in the industry as pickling. The invention also concerned hides tanned by said process.

The present invention relates to a process for the tanning of animal hides characterised, compared to currently adopted processes, by the non-adoption of the step known in the industry as pickling. The invention also concerned hides tanned by said process.