Preparation Protein-based Surfactants With Leather Wastes

After nearly 30 years’ development, China’s leather industry has made great progress and become a big leather country in the word. Leather industry promotes China’s economic development, but also generates tons wastes at the same time. According to the statistics that 1.4 million tons wastes were produced annually at the expense of producing 170 million pieces of leather. How to reuse those wastes reasonablely is becoming the focus. In this paper, the protein-based anionic surfactants(PAS) are synthesized via the condensation reaction of hydrolysate and oleoyl chloride. It will effectively promote the sustainable development of leather industry when applied to the leather degreasing.In this paper, leather scraps were hydrolyzed respectively with sodium hydroxide and calcium hydroxide, then, the properties of hydrolysate, such as hydrolysis yield, chromium content and peptide size distribution are analyzed to find out the optimal hydrolysis conditions. In the follow-up process, creatively using n-hexane as oleoyl chloride solvent to react with polypeptide. The properties of peptides-based surfactants of different molecular chain length, such as foaming power, emulsifying, wetting force, surface tension and degreasing ability were analyzed.Results show that leather scraps hydrolyze by sodium hydroxide have higher production rate(82%), but the ability of dechroming is poor(chromium content at about 20ug/ml), chromium concentration at about 20ug/ml. On the contrary, hydrolysate has low chromium content(at about 5ug/ml) and hydrolysis rate is low(68%), when using calcium oxide. Alkali dosage is the notable factor that affect the molecular weight of peptide extracted from leather hydrolysis liquid using sodium hydroxide, but hydrolysis time for calcium oxide. In the condensation reaction, using n-hexane as oleoyl chloride solvent, when the proportion of n-hexane and oleoyl chloride is 3:5, the yield can reach 72%. Performance tests show that protein-based surfactant’s emulsifying ability increased but ability to reduce the surface tension of solution decreased with increase of the peptide chain length. In the pig skin degreasing experiments, when the dosage of protein-based surfactants reach 3% and compound with OP-10, the degreasing rate can be up to 87%, which is close to the market degreasing agent 426.