聚乙烯醇缩乙醛酸树脂的研制

聚乙烯醇缩醛型胶粘剂可通过聚乙烯醇(PVA)与醛类缩合而得,其性质取决于原料PVA的结构、水解程度、醛类的化学结构和缩醛化程度等。将PVA与乙醛酸(无毒、无味和不挥发)进行缩醛化反应,可制备出一种安全环保型聚乙烯醇缩乙醛酸树脂(PVGa)胶粘剂。以n(乙醛酸)∶n(PVA中-OH基)比例、反应时间、反应温度和PVA水溶液浓度为试验因素,缩醛度为衡量指标,采用正交试验法优选出制备PVGa的最适宜工艺条件。结果表明:当反应温度为80℃、PVA水溶液浓度为15%、n(乙醛酸)∶n(PVA中-OH基)=1∶5和反应时间为40min时,PVGa的缩醛度为39.85%;PVGa的吸湿性能比PVA高4～6倍,PVGa的力学性能优于PVA,两者的热失重情况基本相似。

Study on preparation of PVGa

Polyvinyl acetal adhesive can be obtained by polycondensation between polyvinyl alcohol(PVA) and aldehyde. The product performances were related to the structure and hydrolysis degree of PVA,chemical structure of aldehyde,degree of acetalation and other factors. A PVGa adhesive with safety and environment friendly was prepared by acetalation between PVA and glyoxylate which has characteristic without toxic,taste and volatilization. With molar ratio of n(glyoxylate)∶n(-OH group in PVA),reaction time,reaction temperature and PVA concentration in water as experiment factors,degree of acetalation as evaluating index,so the optimal process conditions of preparing PVGa were preferred by orthogonal experiment method. The results showed that the degree of acetalation for PVGa was 39.85% when reaction temperature was 80 ℃,PVA concentration in water was 15%,molar ratio of n(glyoxylate)∶n(-OH group in PVA) was 1∶5 and reaction time was 40 min. The moisture absorption content of PVGa was 4-6 times more than of PVA,and the mechanics performances of PVGa were better than of PVA,but the change trends of thermal weight loss between PVGa and PVA were similar.