糖基三聚氰胺甲醛树脂木材胶黏剂的研究进展

Research Progress on Sugar-based Melamine Formaldehyde Resin asWood Adhesives

三聚氰胺甲醛树脂由三聚氰胺和甲醛在碱性催化剂条件下缩聚而成,是三大醛基热固性胶黏剂之一,其产量在木材胶黏剂中排名第三。该树脂具有黏结强度高、硬度高、耐沸水性好、热稳定性好、低温固化能力强和耐磨性能突出等优点,但也存在脆性高、储存期短、生产成本高等缺点,以致长期以来其工业应用受到一定的限制。因此,探索低成本和高性能且环保兼顾的三聚氰胺甲醛树脂改性方法具有一定的现实意义。糖类具有价廉物广的特点,可在一定条件下分解为具有羟基和醛基的活性单体,能与氨基或甲醛反应,缩短缩合时间,还具有增强韧性和提高热稳定性的特性。本文综述了以蔗糖、麦芽糖和葡萄糖为原料合成糖基三聚氰胺甲醛树脂木材胶黏剂的研究进展,并对合成机理、胶合强度、热稳定性和游离甲醛含量等进行探讨,希望为糖基三聚氰胺甲醛共聚树脂的开发以及糖类的高价值利用提供理论支持。

Melamine formaldehyde resin (MF), commonly synthesized by the polycondensation of melamine and formaldehyde under alkaline catalyst conditions, belongs to one of the three major aldehyde-based thermosetting adhesives and ranks No.3 of the adhesives with most consumption in global wood industry. MF has many excellent performances, such as strong bonding strength, high hardness, good boiling water resis- tance , excellent thermal stability, wonderful low-temperature curing ability, and outstanding wear resistance. Meanwhile, MF also has some shortcomings which have been for a long time limiting its industrial applications to some extent, e.g., brittleness, short shelf life, high price, etc. Therefore, it is of vital practical significance to seek low-cost, high-performance and eco-friendly methods of modifying MF. Sugars are a kind of natural renewable substances with low cost and wide source, and more importantly, capability of being decomposed into active monomers with hydroxyl and aldehyde groups under suitable conditions. These monomers can react with formaldehyde or amino-group, which results in reduced condensation time. The addition of sugar can also improve the toughness and thermal stability of the products, and hence is a potential method to overcome the inherent brittleness of MF. This article reviews recent research on sugar including sucrose, maltose and glucose, used as the raw materials to synthesize sugar-based melamine formaldehyde resins. It also gives detailed description about the authors’ understanding of the synthetic mechanism, and summary of bonding strength, thermal stability and free formaldehyde content of sugar-based melamine formaldehyde resins . This work is expected to provide theoretical support for the high-value utilization of sugar and the development of sugar-based melamine formaldehyde copolymer adhesives.