以尿素和甲醛为原料,六次甲基四胺为催化剂,三聚氰胺和聚乙烯醇作改性助剂,硫脲作甲醛捕捉剂,采用弱碱-弱酸工艺,合成出贮存稳定的低醛脲醛树脂.在反应温度为90℃,反应时间为2h,n(尿素)∶n(甲醛)为1.0∶2.0,尿素分2次加入,且缩聚反应阶段尿素加入量为45％(质量分数),改性助剂加入量为2.0％(占原料尿素的质量分数),硫脲添加温度为70℃的优选工艺条件下,合成产品质量中游离甲醛质量分数不超过0.2％,耐水剪切强度高于1.8 MPa,稳定贮存期超过30个月.%The urea formaldehyde resin with low content of free formaldehyde and high storage stability was synthesized by weak base - weak acid process using urea and formaldehyde as materials, hexamine as catalyst, melamine and poly ( vinyl alcohol ) as modifying additive, sulfocarbamide as formaldehyde capture agent. Under the optimum conditions of reaction temperature 90 °C , reaction time 2 h , the mole ratio of urea to formaldehyde 1.0 :2.0, adding urea in two - step mode of addition and condensation stages and the adding mass fraction of urea in conden-sation stage 45% (by total urea) , the adding mass fraction of modifying additive 2. 0% (by urea) , the adding temperature of sulfocarbamide 70 °C , the mass fraction of free formaldehyde in the synthesized product was less than 0. 2% , the water - resisting shear strength was more than 1.8 MPa, and the pot life was more than 30 months.
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