Polyurethane-wood composite, useful for making blocks and boards of high flame resistance, comprises wood particles or fibers and, as binder, isocyanate-containing prepolymer

摘要

Polyurethane-wood composite (A) comprises (a) 50-97.5wt.% wood particles, including fibers (X); (b) 50-2.5wt.% solid, isocyanate-containing prepolymer (PP), based on polyurethane solvolyzate and polyisocyanate; (c) 0-25% other solid additives, including fillers, flame-proofing agents and/or colors; (d) 0-25% other milled polymers, including polyurethanes (PU), polyisocyanurates and/or melamine resins and/or (e) optionally a covering film, on one or both sides of the composite. An independent claim is included for preparing (A) by subjecting a mixture of wood particles and a finely-milled isocyanate-containing oligourethane (produced by polyurethane solvolysis and with 0.5-15wt.% free isocyanate groups), solid at room temperature and containing catalysts, to pressure and temperature for 1-60 minutes.