低游离甲醛含量脲醛树脂胶粘剂的合成工艺研究

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。

Study on synthetic technology of urea-formaldehyde resin adhesives with low free formaldehyde content

The synthetic technology process of urea-formaldehyde(UF) resin adhesives with modifier was studied under the condition of subacidity-alkalescence-subacidity.The experiment results showed that the influence of the mole ratio of formaldehyde and urea namely n(F)/n(U) ratio],pH value of system,adding urea wise and modifier on free formaldehyde content and agglutinative strength of UF resin were great.The mass fraction of free formaldehyde content was less than 0.10%(met request of GB/T 14 074.16-1993) in UF resin adhesive,the agglutinative strength was 4.70 MPa,and integration performance was better when n(F)/n(U) ratio was 1.06,the pH value of system was between 4.75 and 4.80 in polycondensation reaction stage,urea was appended for three times,reaction temperature was 90 ℃,content of PVA and melamine-modifier were right amount.