Modification Urea-formaldehyde Resin

With the development of modern science and technology, the application of urea-formaldehyde resin adhesives is more widely. This promotes the in-depth research on urea-formaldehyde resin adhesives. Urea-formaldehyde resin adhesives can be prepared simple and the cost is low. But the free formaldehyde content is the main bottleneck in the application of urea-formaldehyde resin adhesives. The theoretical and experimental researches to reduce the free formaldehyde content are the research focus.This paper studies the modification methods of urea-formaldehyde resin adhesives. This paper discusses the capture effect of formaldehyde capture agent, best addition amount, and research the performance of the urea formaldehyde resin adhesive which is prepared by reaction of glyoxal partly replaced formaldehyde with urea.First, not modified with different molar of urea-formaldehyde resin agents are studied. The results show that the performance in all aspects of glue is best when molar ratio is1.2:1.When molar ratio is1.2:1, chooseing sodium thiosulfate, melamine, ammonium acetate, chitosan as modifier, The amout of them are2%of the urea,With the best results is melamine,the second is sodium thiosulfate, chitosan,and ammonium acetate follow them. Adhesive strength and the release of free formaldehyde are improved obviously,when urea-formaldehyde resin is modified by melamine and ulfur and sodium sulfate, the free formaldehyde emission of the plank reachs to the E2class standards.Chooseing sodium thiosulfate as modifier,when we synthesize urea formaldeyde adding a certain amount of melamine and changing the amount of sodium thiosulfate.The study shows that when amount of sodium thiosulfate is3%of urea,the comprehensive performance of uf resin is the best.Joining glyoxal instead of urea formaldehyde and part reactions, the study found that when glyoxal joins in intermediate links and molar ratio of formaldehyde:glyoxal:urea is1.2:0.2:1, the comprehensive performance is very good and reachs E2level, storage period becomes longer, but overall performance has not achieved the best, It still needs further studying.The paper studies blending modified by using formaldehyde-free glue, the study found that Adding bean gum reduce the release of free formaldehyde significantly, even reaches the level of the E0class. Wet strength and dry strength will decline, especially wet strength. It still needs further studying.