基于氢键自组装的无铬鞣革高分子复鞣体系的构建及其作用机理和调控机制研究

Tanning agent is a sort of key chemistry materials in leather industry. The chrome tanning agent has occupied dominant position for more than 100 years with its unique tanning properties. However, serious environmental pollution could be caused for the low absorption rate of chrome in tanning process， since chrome salt is thought as a toxicant to environment and human. Replacing chrome tanning agent completely or partly with clean materials has being become a hotspot in leather industry. Retanning process, which can influence the commercial value of leather extensively, is regarded as an essential process after leather-tanning. As a sort of the most important retanning chemicals，polymeric retanning agents are able to interact with chrome and leather collagen and give leather versatile properties. The key factor that tradtional polymeric retanning agents can be immobilized to selectively fill among leather collagen is the complexation interaction between chrome and polymeric retanning agents. However, there is not chrome in chrome-free leather at all. If polymeric retanning agents will be used in chrome-free process, they must depend on other interaction to be immobilized among leather collagen. The current situation in leather industry is that there is less fundational science research about special retanning chemical to match chrome-free tanning, which restricts the industry extension of chrome-free tanning process badly. Inspired by the hydrogen bond self-assembly of polymeric supramolecules, an innovative way is put forward in our research: firstly, a series of nonionic amphiphilic block polyurethane copolymers (PUn), similar with the traditional polyurethane retanning agents, will be designed and synthesized, which are switchable in molecular structure and have good surface activity; secondly, polyacrylic acid (PAA)/PUn interpolymer complexes can be formed by the carboxyl of PAA and the ether in polyethylene oxide (PEO) of PUn through inter-hydrogen bonding self-assembly, which could help PAA to penetrate into and to be immobilized among leather collagen. Both of the above two aspects are useful in practical chrome-free process: the PAA and PUn could penetrate fully into the leather collagen at higher pH (pH=4.5-5.0). Then PAA interacted with PUn and collagen by reducing pH and immobilized at lower pH (pH=3.5-4.0), which would finally attain the prospective retanning efficiency. In other words, the key in our research is to use hydrogen bond self-assembly of polymeric supramolecules instead of the complexation between chrome and polymeric retanning agents in order to match chrome-free process. The goal of our research is to provide a theoretical basis for the design and synthesis of novel polymeric retanning agents to match chrome-free process, which will be helpful to extend chrome-free process and reduce the chrome pollution in leather industry, at the same time to accelerate the fundational scicence research of leather chemistry.

本项目针对制革工业铬污染减排面临的关键性基础理论问题，利用氢键自组装原理，在制革工业已有的阴离子性丙烯酸树脂复鞣剂和聚氨酯复鞣剂的研究基础上，通过具有双亲结构的非离子性嵌段型聚氨酯的合成，借助其分子结构中非离子性聚氧乙烯醚链段与阴离子性丙烯酸树脂复鞣剂羧基之间的氢键识别和组装，及其表面活性对复鞣体系渗透能力的促进，首次提出以氢键自组装代替铬盐络合构建制革工业无铬鞣革高分子复鞣体系，并以之为基础，从理论上系统研究分子结构对体系自组装行为的影响及其调控机制，考察复鞣体系与皮胶原的作用机理及在皮纤维中的渗透行为，探讨体系分子及超分子结构与其复鞣性能的构效关系，建立与之相应的清洁化无铬鞣高分子氢键自组装复鞣体系和作用模型。本研究不仅对清洁化制革高分子复鞣体系的基础理论研究具有建设性的理论指导意义，而且对于减轻环境污染，实现生态化制革，促进制革工业的可持续发展都具有重要意义。

本项目针对制革工业铬污染减排面临的关键性基础理论问题，利用氢键自组装原理，在制革工业已有的阴离子性丙烯酸树脂复鞣剂和聚氨酯复鞣剂的研究基础上，设计合成了不同结构的具有双亲结构的非离子性嵌段型聚氨酯（Y型和Gemini型），通过控制复合体系的pH值变化，调控其分子结构中非离子性聚氧乙烯醚链段与阴离子性丙烯酸树脂复鞣剂羧基之间的氢键识别和组装作用，以及上述非离子性嵌段型聚氨酯表面活性对复鞣体系渗透能力具有的明显促进作用，首次在理论上和实践中实现了以氢键自组装代替铬盐络合构建制革工业无铬鞣革高分子复鞣体系的构想，并获得了相应的优化制革工艺。本项目从理论上系统研究分子结构对体系自组装行为的影响及其调控机制，考察复鞣体系与皮胶原的作用机理及在皮纤维中的渗透行为，并通过在无铬鞣革（醛鞣革和植鞣革）中应用探讨体系分子及超分子结构与其复鞣性能的构效关系，建立与之相应的清洁化无铬鞣高分子氢键自组装复鞣体系。本项目首次发现非离子性嵌段型聚氨酯可与醛鞣革中残余的含醛基有机物进一步反应，验证了所构建的清洁化无铬鞣高分子氢键自组装复鞣体系在醛鞣革体系中具有明显降低醛鞣环境风险的可行性。本项目所取得的研究结果不仅对清洁化制革高分子复鞣体系的基础理论研究具有建设性的理论指导意义，而且对于减轻环境污染，实现生态化制革，促进制革工业的可持续发展都具有重要意义。