ABSTRACT
It is estimated that roughly 15-20 million tons of synthetic resins are produced worldwide each year, with most of them used as wood adhesives (Gosselink et al. 2004b, 2004c; Tejado et al. 2007; Imam et al. 2013). These wood adhesives are used to bond wood-based panels such as veneer, strands,
8.1 Introduction ..................................................................................................................................................................... 127 8.2 Species and Properties of Technical Lignins .................................................................................................................. 128
8.2.1 Lignosulphonate................................................................................................................................................... 129 8.2.2 Kraft Lignin ......................................................................................................................................................... 132 8.2.3 Soda Lignin ......................................................................................................................................................... 132 8.2.4 Organosolv Lignin ............................................................................................................................................... 133 8.2.5 Hydrolysis Lignin ................................................................................................................................................ 133 8.2.6 Steam Explosion Lignin ...................................................................................................................................... 134 8.2.7 Ionic Liquids Lignin ............................................................................................................................................ 134
8.3 Utilization of Technical Lignins in Wood Adhesives ...................................................................................................... 134 8.3.1 Lignin-Based Phenol Formaldehyde Resin Adhesive ......................................................................................... 135 8.3.2 Lignin-Based UF Adhesive ................................................................................................................................. 136 8.3.3 Lignin-Based EP Adhesive .................................................................................................................................. 136 8.3.4 Lignin-Based Isocyanate Adhesive ..................................................................................................................... 136 8.3.5 Lignin-Based Green Adhesive ............................................................................................................................. 137
8.4 Modication of Technical Lignins for Adhesive Synthesis ............................................................................................. 137 8.4.1 Methylolation ....................................................................................................................................................... 138 8.4.2 Phenolation .......................................................................................................................................................... 139 8.4.3 Oxidation ............................................................................................................................................................. 139 8.4.4 Demethylation ...................................................................................................................................................... 140 8.4.5 Alkaline Treatment .............................................................................................................................................. 140 8.4.6 Sulphonation ........................................................................................................................................................ 140 8.4.7 Plasma Treatment ................................................................................................................................................ 140 8.4.8 Fractionation .........................................................................................................................................................141 8.4.9 Other Treatment Methods .....................................................................................................................................141
8.5 Concluding Remarks ........................................................................................................................................................141 Acknowledgements ................................................................................................................................................................... 142 References ................................................................................................................................................................................. 142
