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United States Department of Agriculture

Agricultural Research Service

Title: Chrome Free Tanning Compositions and Processes

Authors
item Prentiss, William - PRENTISS & SIEGLER
item Siegler, Marcel - PRENTISS & SIEGLER
item Brown, Eleanor

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 5, 2002
Publication Date: February 11, 2003
Citation: PRENTISS, W.C., SIEGLER, M., BROWN, E.M. CHROME FREE TANNING COMPOSITIONS AND PROCESSES. JOURNAL OF AMERICAN LEATHER CHEMISTS ASSOCIATION. 2003. V. 98. P. 63-69.

Interpretive Summary: Upholstery leather is a major export of the American leather industry. The European market has established a need for new tanning agents that are environmentally friendly and produce leathers acceptable for the automotive industry. A procedure in which the hide was treated first with low molecular weight, water-soluble monomers and polymers and then with a crosslinking agent produced leather that met most requirements for upholstery leathers. Development of tanning formulations based on this research may help the American upholstery leather industry to remain globally competitive.

Technical Abstract: Totally organic tannages that start with an aromatic composition that lends itself to secondary reactions or crosslinking are one approach to the reduction or elimination of chrome as the primary tanning agent for leather. Our approach was to focus on the preparation of low molecular weight methacrylic acid copolymers with methacrylate comonomers in order to maintain a rigid rod structure with functional groups extending from the rod. In one series we developed polymerization procedures with an aminomethacrylate monomer, to impart cationic functionality to the tanning molecule, and hydroxyethylmethacrylate to provide hydroxyl functionality for the second stage reaction. In another series methacrolein was the only comonomer, thus providing aldehyde functionality for the second stage reaction. For evaluation shrink temperatures were measured before and after the addition of crosslinking agents to the experimentally tanned stock. The best result for the hydroxyl functionality was 86C obtained with glutaraldehyde, while for the aldehyde functionality the best result was 84C obtained with oxazolidine. While lower than shrink temperatures obtained with chrome tanning, these values are high enough for automotive upholstery leather. Samples of these systems were retanned with a typical upholstery formulation and evaluated. These leathers met the physical requirements for automotive leathers, but we feel the retanning formulations and polymer compositions would need adjustments to improve color matching and to be certain the fat liquors are suitable for fogging tests.

Last Modified: 10/21/2014
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