Patent ID: 7226621

Claim:
A formulation for tanning made by the process comprising: (a) adding sodium dichromate or potassium dichromate to water to provide an aqueous solution, to which solution is further added sulfuric acid to provide chromium III acid sulfate complex present in an acidic aqueous solution; (b) providing a mixture of a first, second and third copolymers, wherein the first copolymer is a copolymer having a molecular weight between the range of 500 to 10,000, wherein the first copolymer is a vinyl acid/ester based copolymer, the vinyl acid or ester being selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxypropyl acrylate and vinyl acetate; the second copolymer is a copolymer having a molecular weight between the range of 500 to 10,000, wherein the second copolymer is a condensate of formaldehyde and aromatic sulfonic acid, the copolymer having a saturated carbon bridging the aromatic rings in the copolymer; the third copolymer is a copolymer having a molecular weight between the range of 500 to 10,000, wherein the third copolymer is a condensate of acrylonitrile, acrylamide or N-methylacrylamide with an agent selected from the group consisting of urea, formaldehyde, melamine and dicyandiamide; and (c) adding the mixture of the first, second and third copolymers to the acidic aqueous solution from step (a) and heating to a temperature of about 40 to 60° C. for about 1.5 to 5 hours and then cooled to room temperature to a obtain a formulation for tanning; wherein the combined amount of the first copolymer, second copolymer and third copolymer is 1 to 10 wt % based on the weight of the acidic aqueous solution from step (a), and the formulation for tanning has a Cr 2 O 3 content of 12 to 18% and a basicity of between 10% and 20%.