Study On Preparation And Properties Of Modified Starch Tanning Agent With HRP Catalysis

In this paper, free radical graft copolymerisation of starch and vinylmonomer and the copolymerization of vanillin and gallic acid were carried outusing horseradish peroxidase (HRP) as catalyst. Several different vinylmonomers polymerization and factors that affect the polymerization were studied.The structure of the copolymers was characterized and the reaction mechanismwas researched. The products were used as leather tanning agent, and theapplication effect was studied.Firstly, a new graft copolymerization reaction system of starch andacrylamide (AM) by means of HRP/H2O2/acetylacetone (ACAC), andstarch-polyacrylamide graft copolymer was synthesized. The main factors thataffect the polymerization were discussed and the optimum reaction conditionswere determined as follows:50g degraded starch (wt15%) with9.9g AM in thepresence of HRP/H2O2/ACAC reacted at35°C for5h under system pH7. Theretanning agent Tan-1was obtained. The structure and properties of the retanningagent Tan-1were characterized by FTIR, NMR, UV and SEM, and the resultsshowed that the expected structure of graft copolymer was obtained. Theapplication test indicated that the order of the tanning properties usingcombination tannage was aluminum sulfate, tannic acid, chloride and sodiumsilicate. The application test of different modified starch indicated as follows:grafted methyl methacrylate (MMA) was helpful to improve the tanning propertyof starch modified tanning agents, grafted acrylonitrile (AN) was helpful toimprove the flexibility of leather, grafted hydroxypropyl acrylate (HPA) washelpful to improve the softness of leather, and grafted acrylamide (AM) washelpful to improve the chubbiness of leather.Secondly, hydroxypropyl acrylate-citrate (HPA-CAE) was prepared byesterification of citric acid and hydroxypropyl acrylate. Then a graft copolymerwas synthesized by copolymerization of degraded starch and HPA-CAE using horseradish peroxidase (HRP)/H2O2/acetylacetone (ACAC) as catalyst. Theeffects of amount of HRP, H2O2, ACAC and HPA-CAE on graftingpolymerization were investigated，and the optimum conditions were as follows:50g degraded starch (wt15%) was copolymerized with13.9g HPA-CAE in thepresence of6.4mg HRP/4.7mL H2O2/1.2g ACAC. The retanning agent Tan-2was obtained. The structure of the copolymer was characterized by FTIR andNMR. The applied results showed that the retanned leather had good uniformity,softness and fine grain. It was observed from SEM that Tan-2had gooddispersion effect to fiber.At last, the preparation and application of vanillin and gallic acid copolymer(VGA) and dialdehyde starch were studied. The structure of the products wascharacterized by FTIR and NMR, and the mechanism of polymerization betweenvanillin and gallic acid was advanced. The applied results of combinationtannage using VGA and dialdehyde starch showed that shrinkage temperature (Ts)of tanned leathe increased significantly. The tanned leather had good uniformityfullness softness, strong selecting filling properties and good elasticity. Thetanned leather combined advantage of vegetable tanning and aldehyde tanning.The innovation in this study was that two retanning agents, which wereSt-g-HPA-CAE graft copolymer and vanillin-gallic acid copolymer tanningagent, were synthesized using HRP catalytic polymerization.