Treatment of wet blue with fillers produced from quebracho-modified gelatin

Authors: Taylor, Maryann; Medina, Marjorie; Lee, Joseph - Joe; Bumanlag, Lorelie; Brown, Eleanor - Ellie; Liu, Cheng Kung

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2012
Publication Date: 12/1/2012
Citation: Taylor, M.M., Medina, M.B., Lee, J., Bumanlag, L.P., Brown, E.M., Liu, C. 2012. Treatment of wet blue with fillers produced from quebracho-modified gelatin. Journal of American Leather Chemists Association. 107(12):416-421.

Interpretive Summary: In recent studies, we successfully addressed the problems of poor leather quality by utilizing fillers produced from the reaction of gelatin with tannins, which are compounds isolated from plant materials, and are used in the vegetable tanning of hides to make leather. We explored whether gelatin, when modified using these compounds, could give products with properties that might have application in leather processing. We used quebracho, a vegetable tannin, and demonstrated that gelatin could be modified to make products that had increased melting points, high viscosities, and polymer-like behavior. In this continuing study, we applied these products to hides as fillers, and made modifications to conventional processes to further clarify the effect that these fillers had on improved leather quality. We found that after retanning, coloring and fatliquoring, the resulting leather continued to have, in spite of modifications, superior subjective properties when compared to control samples and that the strength and other mechanical properties of the treated samples were not significantly different than control samples. Furthermore, by using a modification of a technique developed at this laboratory for analyses of foods and beverages, we were able to determine the uptake of the gelatin/quebracho product. We showed that about 55% of the product was taken up by the hide and that the reaction was complete in about 4 h. Thus gelatin, a byproduct from the leather-making process, modified with quebracho, a commonly used sustainable tanning agent, could be utilized to improve crust leather products in the retanning, coloring and fatliquoring process.

Technical Abstract: Gelatin modified with quebracho to produce high molecular weight, high viscosity products was investigated as a filler in leather processing. The uptake of quebracho/gelatin product by the wet blue was on the average about 55% of the 10% gelatin/quebracho product offered; the reaction appeared to be complete after about 4 h. The uptake of quebracho alone by the wet blue was run as a control; after 2 h almost 100% of the quebracho was taken up by the hide. As a second control, the effect of eliminating vegetable tannins (quebracho and mimosa) from the retan, color, and fatliquor (RCF), on properties of the crust was tested. Epi-fluorescent imaging and scanning electron microscopy (SEM) results indicated distinctive differences between the two control samples and the gelatin/quebracho treated hide. The gelatin/quebracho treated samples had superior subjective properties when compared to untreated controls; differences in mechanical properties were dependent on whether vegetable tannin was present or absent in RCF. Thus a filler produced from a common vegetable tannin (quebracho) and a waste product from the leather industry (gelatin) can add economic value to leather by improving its quality.