摘要
目前广泛使用的聚丙烯酸类高吸水材料生物降解性能差,对生态环境造成危害,同时其原料来源于日益枯竭的石油资源。因此,研究可生物降解吸水材料,对于减少环境污染等具有重要意义。丝胶蛋白是一种天然高分子,一般作为制丝生产的废弃物。丝胶蛋白的氨基酸中含有大量极性基团(女-OH、-COOH、-NH2等),具有较好的亲水性、反应活性和生物降解性。如能将丝胶蛋白变废为宝作为生物资源加以利用,研制丝胶蛋白基可生物降解吸水材料,不仅丰富了吸水材料类型,也为丝胶蛋白资源利用提供了一条新途径。
本研究以丝胶(Sericin)为原料,丙烯酸(AA)和丙烯酰胺(AM)为单体,分别以过硫酸铵(APS)和N,N,-亚甲基双丙烯酰胺(MBA)为引发剂和交联剂,采用水溶液聚合的方法,合成了具有生物降解性能的Seric in/PAA-AM复合吸水材料。研究了Sericin/PAA-AM复合吸水材料的合成条件如丝胶蛋白用量、单体配比、交联剂用量、引发剂用量、中和度、反应温度、溶液pH等对复合吸水材料吸水性能的影响,在单因素试验的基础上,设计五因素四水平正交试验获得了最适宜的制备条件：反应温度60℃,反应时间2h,丝胶与单体的配比为1：2,AA和AM的配比为2,引发剂用量为单体用量的2%,交联剂用量为单体用量的03%,中和度为70%,pH为7。复合吸水材料的吸收去离子水倍率为483g/g,吸收自来水倍率为296g/g,吸收0.9%NaCl溶液倍率为52g/g。
考虑到Sericin/PAA-AM复合吸水材料吸水量的不足,尝试把热水沸煮提取的丝胶蛋白再用碱性蛋白酶进一步水解得到不同分子量分布的丝胶溶液,并研究酶解改性处理条件对丝胶蛋白分子量分布的影响。研究表明,酶解浓度越高,丝胶蛋白分子量越小。在此基础上,选择合适的酶解改性丝胶蛋白,进一步与丙烯酸／丙烯酰胺复合单体进行接枝共聚,研制具有生物降解性的酶解丝胶／丙烯酸／丙烯酰胺复合吸水材料,研究不同酶解改性丝胶蛋白复合吸水材料的结构与性能差异,阐明丝胶蛋白结构差异对复合吸水材料的接枝率、吸水性、保水性、生物降解性等的影响机制。研究表明,当碱性蛋白酶和丝胶的质量比为5mg/g时,酶解丝胶/丙烯酸/丙烯酰胺复合吸水材料的接枝率、吸水率、保水率、生物降解均达到最大。在此条件下,经冷冻干燥的酶解丝胶/丙烯酸/丙烯酰胺复合吸水材料吸收去离子水倍率达到896g/g,吸收自来水倍率为424g/g,吸收0.9%NaCl溶液倍率为83g/g。
本研究对于丝胶蛋白基生态功能材料研发具有参考意义。
Present widely-used polyacrylic acid polymer, a kind of superabsorbent polymer (SAP), performs badly on biodegradation, which do harms to cause ecological environment and whose raw material is derived from increasingly exhausted oil. Therefore, researches on biodegradable SAP are of great importance to reducing environmental pollution.
Sericin, a natural polymer, is generally treated as waste in silk prodction. If sericin is recycled and utilized as biological resources, there woulid be considerable social and economic benefits. Amino acids in sericin, which contain abundance polar groups (-OH,-COOH,-NH2etc), have good property in hydropgily, reactivity and biodegradability. The application of sericin to absorbent material field, and graft copolymerization of sericin and propenyl monomer to develop biodegradable SAP, can enrich the types of SAP and offer a new way to expand the utilization of sericin.
Taken sericin as material, acrylic acid (AA) and acrylamide (AM) as monomer, ammonium persulfate (APS) and Methylene bisacrylamid (MBA) as initiator and crosslinker, this research synthesized a biodegradable SAP—Sericin/PAA-AM by polymerization in aqueous solutin. In our work, the synthetic reaction condition was studied including the dosage of sericin, the ratio of monomers, dosage of crosslinker and initiator, neutralization, temperture, and pH etc. After single factor experiment, orthogonal designed experiment of five factors, four levels was adopted to acquire optimal condition as follows:reaction temperture was60℃; reaction time was2h; the mass ratio of sericin to monomer wa1:2; the mass ratio of AA to AM was2:1; the mass ratio of initiator and crosslinker to monomer was2%and0.3%; neutralization degree was70%; pH was7. Water absorbencies of Sericin/PAA-AM in deionized water, tap water and0.9%NaCI solution were483g/g,296g/g and52g/g, respecyively.
Consider inadequate absorption capacity of Sericin/PAA-AM SAP, sericin extracted by boiled-water was hydrolyzed by alkaline protease to different molecular weight of sericin, and the influence of processing conditions of enzymolysis modification was studied on sericin distribution of different molecular weight. It was found that the higher protease concertration, the smaller molecular weight of sericin would be. Furthermore, appropriate enzymolysis sericin was choosed and grafted with AA/AM to produce composite SAP with biodegradability. The differences was studied in structure and performance of this composite SAP, and mechanism of influence of different sericin structures was clarified on grafting percentage, water absorbency, water retaining capacity, biodegradability. The results showed that when the mass ratio of alkaline protease to sericin was5mg/g, APh-Sericin/PAA-AM's capacity reached the highest value, including grafting percentage, water absorbency, retaining capacity and biodegradability. The water absorbency of lyophilized Sericin/PAA-AM was896g/g in deionized water,424g/g in tap water, and83g/g in0.9%NaCl solution.
This research could offer a reference for sericin-based ecological and functional materials.
引文
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