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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。
Polyvinyl acetal type adhesives can be obtained by condensation of polyvinyl alcohol (PVA) with aldehydes, the nature of which depends on the structure of the raw material PVA, degree of hydrolysis, aldehyde chemical structure and degree of acetalization. PVA and glyoxylic acid (non-toxic, tasteless and non-volatile) for acetalization, can be prepared a safe and environmentally friendly polyvinyl glyoxylic resin (PVGa) adhesive. The optimal ratio of n (glyoxylic acid): n (-OH group in PVA), reaction time, reaction temperature and concentration of PVA aqueous solution were used as experimental factors and degree of acetalization was measured. Process conditions. The results showed that the degree of acetalization of PVGa was 39.85 when the reaction temperature was 80 ℃, the concentration of PVA aqueous solution was 15%, n (glyoxylic acid): n (PVA-OH group) = 1: 5 and the reaction time was 40 min %. The moisture absorption capacity of PVGa is 4 ~ 6 times higher than that of PVA. The mechanical properties of PVGa is better than that of PVA, and the weight loss of both is similar.