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以酸-碱-酸-碱工艺合成一种聚乙烯醇(PVA)、三聚氰胺改性脲醛树脂,研究了原料配比、pH值、反应时间等对产品性能的影响。结果发现,当n甲醛:n尿素=1.6:1,聚乙烯醇加入量为甲醛和尿素总质量的1%,三聚氰胺加入量为甲醛和尿素总质量的3%,酸性条件下pH=5.5,碱性条件pH=8.5～9.0,反应温度为80℃左右时,合成的脲醛树脂的机械强度较好,游离甲醛的含量较低。
A kind of polyvinyl alcohol (PVA) and melamine modified urea formaldehyde resin were synthesized by acid - alkali - acid - alkali process. The effects of raw materials ratio, pH value and reaction time on the product performance were studied. The results showed that when n formaldehyde: n urea = 1.6: 1, the addition of polyvinyl alcohol was 1% of the total mass of formaldehyde and urea, the melamine was added to 3% of the total mass of formaldehyde and urea, the pH was 5.5 under acidic conditions, Under the condition of pH = 8.5-9.0 and reaction temperature about 80 ℃, the mechanical strength of the synthesized urea-formaldehyde resin is better and the content of free formaldehyde is lower.