Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2010
Publication Date: 2/1/2011
Citation: Taylor, M.M., Lee, J., Bumanlag, L.P., Hernandez Balada, E., Brown, E.M. 2011. Treatments to enhance properties of chrome-free (wet white) leather. Journal of American Leather Chemists Association. 106(2):35-43. Interpretive Summary: Upholstery leather, which has been traditionally chrome-tanned, is being replaced by what is typically known as chrome-free leather. Recycling of auto parts, specifically car seats, is driving the momentum towards this type of leather. The chrome-free leathers have a tendency to being flat, empty, or weak and the grain sometimes has an inferior appearance to that seen in chrome-tanned hides. These chrome-free leathers require more filling than normal conventional chrome-tanned leather and thus large amounts of resins and polymers are generally used to improve appearance. In recent studies, we addressed the problems of poor leather quality by utilizing fillers produced from enzymatically-modified waste proteins from sustainable resources, specifically proteins from the leather and dairy industry (such as low quality gelatins and caseins or whey). We demonstrated that these products did indeed fill the leather, did not affect the strength, but did significantly improve subjective properties, such as fullness and color of the leather. In present study, we applied the modified fillers to chrome-free leather, and evaluated the final product with respect to strength and quality. Products were prepared, characterized, and then applied to the chrome-free tanned stock. As seen in previous studies, the strength of the treated chrome-free leather was not significantly different from controls, but there was an improvement in the subjective properties (such as fullness). Electron microscopy images of the leather have suggested a difference in fiber structure between controls and treated samples, with the latter having a more open structure which may contribute to the improved subjective properties. Thus, it has been demonstrated that the properties of chrome-free leather can be improved by using biopolymers produced from enzyme modification of waste proteins.
Technical Abstract: Production of chrome-free or wet white leather, predominantly for upholstery leather, is fast approaching that which has been traditionally tanned with chrome. Recycling of auto parts, specifically the car seats, is driving the momentum towards this type of leather. Wet white leathers are sometimes described as being flat, empty, weak and/or having a poor break and subsequently require more filling than conventional chrome-tanned wet blue. Large amounts of resins, polymers, and syntans are generally used in retanning of wet white leather. In recent studies, we addressed the problems of poor leather quality by utilizing fillers produced from enzymatically-modified waste proteins, specifically those proteins from the leather and dairy industry (low quality gelatins and caseins or whey). We demonstrated that these products did indeed fill the leather, were not removed during washing and while not affecting the mechanical properties, did significantly improve subjective properties, such as handle, fullness, break and color. In this present study, we applied enzymatically modified fillers to wet white leather and evaluated it to see if there was an improvement in the subjective properties. Products were prepared, characterized, and then applied to the wet white tanned stock. After treatment, the hides were retanned, colored, and fatliquored, mechanical properties were determined and subjective analysis was carried out. Scanning electron microscopy (SEM) was also carried out after treatment. As seen in previous studies, the mechanical properties of the treated wet white leather were not significantly different from controls, but there was an improvement in the subjective properties. The data from analysis of the crust will be presented along with microscopy images.