ISOCYANATE PHENOLICS WOOD ADHESIVES BY CATALYTIC ACCELERATION OF COPOLYMERIZATION

The reaction of MDI with the hydroxybenzyl alcohol group of phenol-for maldehyde resol (PF resins can he accelerated by the use of catalysts of urethane formation such as triethylamine and dibutyltin dilaureate (DBTDL). A kinetic study for MDI (4,4'-diphenylmethane diisocyanate) a nd p-hydroxybenzyl alcohol as a model compound for phenol-formaldehyde resins confirmed this reaction. These catalysts have been used to upg rade the performance of MDI/phenolic thermosetting wood adhesives for particleboard, in amounts varying between 0.5 % and 2 % of PF resin so lids content. The use of these catalysts allows the use of simpler, us ually slow-reacting, PF resins at pressing times as fast as 5 seconds per mm of board thickness. hence faster than urea-formaldehyde resins. These pressing times are achieved while still mantaining the exterior grade properties of the board.