碱性酚化木质素结构表征及在酚醛树脂中的应用研究

Structural characterization of alkaline phenolic lignin and its application in phenolic formaldehyde resin

采用碱催化酚化改性的方式,增加木质素反应活性位点含量,提高木质素-酚醛树脂木材胶粘剂的反应活性,同时降低树脂中无机盐的含量。将甲醛溶液分三批加入酚化木质素溶液,并在第二批加入的同时加入30%质量分数的氢氧化钠溶液,甲醛加入并反应一定时间后加入尿素,自然降温至40℃以下出料,即得碱性酚化木质素改性酚醛树脂。为证明碱性酚化改性木质素可行,本研究还通过FT-IR、^(1)H-NMR、热裂解-气质联用分析了改性前后木质素的结构变化。研究结果表明:将碱催化酚化改性的木质素酚醛树脂用于木材胶粘剂,其固化速度较酸性酚化改性的木质素酚醛树脂有明显提升,且其粘接强度可提升至1.16 MPa,甲醛释放量仅为0.08 mg/L。

Alkali catalyzed phenolic modification was used to increase the content of reactive sites of lignin,in order to improve the reaction activity of lignin-phenolic formaldehyde resin wood adhesive,and to reduce the content of inorganic salt in the resin.Formaldehyde solution was added into the phenolic lignin solution in three batches,and 30%sodium hydroxide solution was added at the same time in the second batch.After formaldehyde was added and reacted for a certain time,urea was then added,and the temperature was naturally cooled to below40℃for discharging,then the alkaline phenolic lignin modified phenolic formaldehyde resin was obtained.In order to prove the feasibility of alkaline phenolic modification of lignin,the structural changes of lignin before and after modification were analyzed by FT-IR,^(1)H-NMR and pyrolysis GC-MS.The research results showed that,when alkaline catalyzed phenolic modified lignin-phenolic formaldehyde resin was applied in wood adhesive,its curing rate was significantly higher than that of acid phenolic modified lignin-phenolic formaldehyde resin,and its bonding strength could be increased to 1.16 MPa,and the formaldehyde emission was only 0.08 mg/L.