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研究了在弱酸-弱碱-弱酸条件下,加入改性剂合成脲醛(UF)树脂胶的工艺过程。实验结果表明,甲醛与尿素的配比[即n(F)/n(U)比值]、体系pH值、尿素的加料方式和改性剂对UF树脂胶中游离甲醛的含量和胶合强度有很大的影响;当n(F)/n(U)=1.06、缩聚反应阶段体系的pH值为4.75～4.80、尿素分3批加入、反应温度为90℃、加入适量的聚乙烯醇(PVA)和三聚氰胺改性剂时,制得的UF树脂胶中游离甲醛的含量不大于0.10%(符合GB/T14 074.16-1993标准中的指标要求)、粘接强度为4.70 MPa且综合性能优良。
The process of synthesizing urea formaldehyde (UF) resin by adding modifier under weak acid - weak base - weak acid condition was studied. The experimental results show that the ratio of formaldehyde to urea [ie, the ratio of n (F) / n (U)], the pH value of the system, the feeding mode of urea and the modifier content of free formaldehyde in UF resin glue and the bonding strength When the ratio of n (F) / n (U) = 1.06, the pH value of the system during the polycondensation reaction is 4.75-4.80, the urea is added in 3 batches, the reaction temperature is 90 ℃, and the appropriate amount of polyvinyl alcohol (PVA) And melamine modifier, the content of free formaldehyde in the prepared UF resin glue is not more than 0.10% (in line with the requirements of GB / T14 074.16-1993 standard), the bonding strength is 4.70 MPa and the comprehensive performance is excellent.