The chemistry and development of pine tannin adhesives for exterior particleboard

Abstract

Pine tannin-based adhesives obtained by the reaction of polymeric MDI (4,4l'-diphenylmethane diisocyanate) with mildly sulphited pine tannin extract are described.Tolerance limits as regards moisture content resistance, pressing time, proportion of MDI and tannin extract, percentage adhesive solids content and others were studied at laboratory level. Industrial results of extended plant production runs of these adhesive systems showed very encouraging results and are presented. The reactions of polymeric MDI with model compounds representing all the different species in the adhesive systems presented were studied by FT-IR and gave an indication, in water solutions, of which species are likely to react and at what rates. The results obtained also indicate that non-emulsifiable MDI can be successfully used with tannins and other polyols in water solutions. © 1993, Walter de Gruyter. All rights reserved.