Study On Synthesis And Application Of Acrylic Retanning Agents Used In High Elastic Leather

Retanning is critical to attaining the required physical properties for leather products, during which acrylic polymers are commonly used. Acrylic polymer retanning agents have proliferated worldwide because they are products with low cost but high performance. Besides, it can reduce the dosage of chrome in leather process, which is of little quantity on the earth and can cause severe pollution. Elasticity is an important property of leather products. There is a lack of information, however, regarding performance of acrylic polymer retanning agents in terms of elasticity of the resultant leather. Nor is much known regarding effective methods to measure the elasticity. Most of the researchers dealing with acrylic retanning agents concerned on the preparation of a new polymer which endow leather with a special property. But few of them studied the effect of different acrylic monomers and its dosage on leather properties, especially on elasticity.The way to measure leather elasticity was discussed. Different acrylic polymer retanning agents were synthesized with acrylic acid as the primary monomer and eight other acrylate monomers (MAA-methyl acrylic acid, EA-ethyl acrylate, BA- butyl acrylate, VAc-vinyl acetate, MA-methyl acrylate, AM-acrylamide, IA-Itaconic acid, HEA- 2-Hydroxyethyl acrylate) as co-monomers. The eight copolymers were applied in the retanning process separately and elasticity and other properties of the resultant leather was determined. Three comonomers were selected from eight of them and their dosage was discussed. XRD analysis was occupied to explain the crystallinity of copolymers. The effect of dosage of initiator on viscosity, crystallinity and Young's modulus of resultant leather. FT-IR and DSC analysis were occupied to explain the structure of the selected copolymer. The factors in retanning process were determined by orthogonal tests. The polymer was compared with chrome tannage and RST retanning agent, and TEM was introduced to scan the resultant leather. Copolymers containing three or four monomers were synthesised and the dosage of copolymer was discussed and they were characterized by FT-IR, DSC and XRD. Three samples were selected was they were used in a plant; the resultant leather was also scanned under SEM.The results showed that leather elasticity could be tested by calculating Young's modulus of the elastic deformation, which was a variable region on the load-displacement curve, and Young's modulus of the elastic deformation could serve as an independent parameter in characterizing leather's physical properties. The relation between the elasticity and the dosage of copolymer was determined, and it revealed that every co-monomer had an optimum dosage at which level the resultant leather showed the lowest Young's modulus. Then the effects of the eight co-monomers on leather elasticity were compared under the same condition. It showed that the soft co-monomers, BA and EA, contributed more in leather elasticity than other selected co-monomers. It also showed some orderliness on other leather properties.The dosage of these three were analysed and the results showed that they revealed best elasticity when the dosage was 9%, 2%, 7.5%. XRD analysis showed that the crystallinity reduced with the introduction of the comonomers. The higher viscosity the copolymers had, the lower Young's modulus the resultant leather would be when the ration of base monomer and comonomer was changed. The higher dosage of initiator, the higher crystallinity the copolymer had, while the viscosity was lower. The results showed the best application result occurred when the dosage of BA and initiator were 2% and 10% respectively. The higher dosage of initiator, the higher crystallinity the copolymer had, while the viscosity was lower. FTIR and DSC analysis showed the polymer was a copolymer of two monomers and its best application dosage, time, liquid ratio, temperature was 1.5%, 30min, 1:1, 30℃. The comparision revealed the copolymer had a similar effect in leather elasticity with the other two. The TEM showed the fiber bundles processed by the copolymer was dispersed sufficiently.The optimum dosage of VAc and EA was 0.5% and 8% respectively when Copolymers containing three monomers were synthesised and the AA/BA/EA polymers showed a better result. HEA and VAc were introduced into further study and the proper dosage was 5% and 5% respectively. AA/BA/EA polymer, AA/BA/EA/HEA polymer, AA/BA/EA/VAc polymer samples were used in a plant and the last to showed better effect than R556, while they showed no better than R83. THE SEM showed the fibers were scattered thoroughly.