谷朊蛋白的改性及其作为纸张增强剂的性能

Modification of Wheat Gluten and Its Application in Paper Making as Paper Strength Agent

采用廉价可生物降解的小麦谷朊蛋白为原料,经过羟甲基化和阳离子化改性合成类似聚酰胺聚胺环氧氯丙烷(PPE)的纸张增强剂。经改性后,谷朊蛋白带有氮杂环丁烷结构、表氯醇和环氧基团3种功能基团,可与纤维形成共价键,且能发生自身交联,在纤维周围形成三维交联网络结构,提高纸张干、湿强度。通过单因素试验,研究了甲醛、甲酸、温度、反应时间和环氧氯丙烷5种反应因素对纸张强度的影响。优化合成条件下制备改性谷朊蛋白可使纸张干抗张强度提高35%,湿强保留率达20%。改性后谷朊蛋白显阳离子性,加入纸浆中,可使得浆料体系Zeta电位升高,改善浆料的留着率,明显提高纸张强度。结果表明,经羟甲基化和环氧氯丙烷加成改性的谷朊蛋白可以作为纸张的干强剂和湿强剂。

Wheat gluten, a kind of cheap and reproducible agricultural by-products, was modified to produce a new paper strength agent similar to polyamide polyamine epichlorohydrin （PPE） synthesized from petroleum resources. The modification reaction included hydroxymethylation of gluten and cationic activation with epichlorohydrin. The modified wheat gluten contains three kinds of functional groups, hydroxy-azetidinium, Chlorohydrin and epoxy groups. Those groups can bond with the fibers of pulp to form three-dimensional networks around the fibers, improving paper strength. The hydroxymethylation of gluten was carried on in the suspension of 5% gluten with 1% formic acid and 0. 7% formaldehyde under 70 ℃, and then cationic activation with 8% epichlorohydrin under 60 ℃. The modified gluten carries cationic charges, which can increase the Zeta potential and retention of pulp slurry, and improve the physical properties of hand sheets. The gains of dry strength and wet strength of hand sheet were 35% and 20% respectively when 5% modified gluten was used in the pulp slurry.