高浓度甲醛和大豆蛋白增强低摩尔脲醛树脂研究

Low mole ratio UF resin enhanced by high concentration formaldehyde and soy-protein

以高浓度甲醛制备摩尔比1.1∶1的脲醛树脂(UF),以降解后的大豆蛋白(DS)为改性剂,并在UF"碱-酸-碱"制备工艺的三个阶段分别加入不同比例的DS进行改性,以增强脲醛树脂的胶合强度。研究结果表明:1相对于普通低摩尔脲醛树脂,高浓度甲醛制备的脲醛树脂固体含量和黏度显著提高,游离甲醛变化不大,但胶合强度提高64%。2高浓度甲醛和DS制备UF:在第一个阶段,加入5%或10%的DS制备的UF胶合强度进一步提高近7%,游离甲醛变化不大;在第二个阶段,加入DS制备的UF胶合强度很低且树脂稳定性差;在第三个阶段,加入DS制备的UF黏度显著提高,游离甲醛有所降低,仅加入量为10%时制备的UF胶合强度有所提高。313C-NMR和FT-IR测试结果表明:在第二个阶段,加入DS制备的UF缩聚反应受阻碍,大量的小分子尿素游离,最终导致树脂较差的稳定性和胶合性能;在第三个阶段,加入的DS主要捕捉树脂未反应的游离甲醛,但最终树脂的交联度不高;在第一个阶段加入DS制备的UF醚键含量有所降低,二羟甲基和亚甲基桥键含量明显增加,树脂具有较高的交联度和缩聚度。4 DMA分析表明:单纯高浓度甲醛制备的UF具有较高的初始胶合强度,但是热稳定性差。高浓度甲醛和DS在第一个阶段改性制备的UF具有较高的热机械性能和较好的热稳定性。

Low mole ratio F/U（1.1 ∶ 1） urea-formaldehyde（UF） resin was prepared with high concentration formaldehyde（UF2）. Hydrolyzed soy protein（DS） was charged into three preparation stages of ＂ alkali-acid-alkali＂ of UF2 resin, respectively. The structure characteristics and thermal mechanical properties of resins were studied by 13C-NMR, FT-IR and DMA. The results indicated that： ① Compared with common resin UF1, UF2 resin had significantly high viscosity and solid content, bonding strength of UF2 resinincreasing by 64%, and free formaldehyde content had no change. ② UF resin prepared with high concentrationformaldehyde and soy-Protein： A： At the first alkali preparation stage, adding 5% or 10% hydrolyzed soy protein into UF2, bonding strength of this UF resin increased by 7% further, and free formaldehyde content had no change. B： At the acid preparation stage, adding hydrolyzed soy protein, the UF resin had poor stability and low bonding strength. C：At the last alkali preparation stage, adding hydrolyzed soy protein into UF2（DS1/UF2）free formaldehyde decreased in some degree, and bonding strength improved only adding 10% hydrolyzed soy protein. ③13C-NMR, FT-IR and DMA results showed that hydroxymethyl（mainly dihydroxy methyl）, content of methylene ether bond and Uron ring increased obviously reduced to high initial strength, low thermal stability and free formaldehyde of UF2 resin. DS1/UF2 resin had high content of dihydroxy methyl, methylene bridge bonds, high degree of polycondensation and crosslinking, offset instability produced by methylene ether bond fracture and rearrangement. Finally, S1/UF2 resin had good thermal mechanical properties and thermostability.