贮存稳定的低醛脲醛树脂合成工艺研究

Synthetic technology of urea formaldehyde resin with low content of free formaldehyde and high storage stability

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2 h,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 stabili- ty 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 re- action temperature 90 ℃ , 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 sta- ges 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 ℃, 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.