The Complex Tanning Agent Of Chromium Coordinated With Copolymer And The Method Of Its Preparation

This work aims to eliminate chrome pollution during the leather making process. As a kind of tanning agent, chrome tanning agent plays a indispensable role in the leather making industry. The higher quantity of Cr (III, VI) in the tanning liquid, however, will result in serious environment pollution, which may be destructively. In this work a chrome complex was synthesized as tanning agent. During the leather making process, chrome complexes with polymer, which can greatly increase the assimilation of the chrome for the leather, thus the concentration of dissociated chrome in the waste liquid will be decreased largely under permissible concentration of national standard (≤0.01g/L).In chapter 1, an introduction was carried out, which mainly includes: the character of chrome tanning agent, the mechanism of reaction with collagen and its recent progress, the composing of acrylic acid retanning agent and reaction mechanism, the cleanness of tanning. At last, the outline of this work was presented: synthesizing a kind of polymer complex as tanning agent, which was complexed by polyacrylic acid and chrome, then designing the molecular structure on the property of leather making.In chapter 2, acrylic acid polymer was studied and characterized. Two kinds of polymers were prepared: acrylic acid -methyl acrylic acid — acrylamido-N-2-methylpropane sulfonic acid sodium complex and acrylic acid — trialeic anhydride -acrylamido-N-2-methylpropane sulfonic acid sodium complex. Infrared analysis, TGA and GPC were carried out to characterize the structure of the polymer. The Mark-Houwink parameter K, a of acrylic acid -methyl acrylic acid —acrylamido-N-2-methylpropane sulfonic acid sodium complex was determined. The parameter [ η ] was used to denote the molecular weight. The synthesis of acrylic acid -maleic anhydride - acrylamido-N-2-methylpropane sulfonic acid sodium complexwas optimized and the effect of the dosage of initiator, temperature and concentration of monomer to [η] was also discussed.In chapter 3, tanning agent of the complex was prepared and characterized. The tanning agent was prepared and IR, UV, DSC, TG were used to characterize its structure. The formation of the complex was testified and it presents greater thermal stability than polymer. The effect of different ration of maleic anhydride/acrylic acid, acrylamido-N-2-methylpropane sulfonic acid/acrylic acid and pH to the complex was studied, thus the preparation of the complex was optimized. Chapter 4 is the experiment of leather making. The synthesized complex was used in the process of leather making as tanning agent and the property of the treated leather was tested. The influence of the molecular weight of the polymer and chrome concentration in the complex tanning agent to the tanning efficiency was discussed. The experiment result shows that: the tanning efficiency is highest as [η] reaches 13. 9mg/L, and when the concentration of both the chrome and the polymer compound are 3 wt. % of crude skin, the tanning efficiency is high as well as the concentration of Cr2+ in the waste liquid is 0. 006g/L, which is far from the permissible concentration of national standard(≤0.01g/L). The observation through FE-SEM shows that the uniform dispersion of the fasciculi of collagen in leather tanned with the synthesized complex was obtained and the surface of the leather presented to be round and flexile. In conclusion, the tanning agent using the complex synthesized in this work can greatly increases the assimilation of the chrome for the leather, thus the concentration of dissociated chrome-in the waste liquid will be decreased largely and the pollution to environment was lessened. At the same time, it can work as both main tanning and auxiliary tanning and improves the property of the leather as well.