Abstract: 'An improvement is described in the process of preparing polymethylene polyphenyl polyamines by condensing aniline and formaldehyde in the presence of an acid catalyst. The improvement entails adding a minor proportion of a polyamine mixture comprising di(aminophenyl)methanes and oligomeric polymethylene polyphenyl polyamines, collectively known as polymethylene polyphenyl polyamines or polymeric MDA, to an intermediate stage of the condensation reaction where the various intermediately formed aminobenzylamines are present. The process lends itself to either a batch or continuous method for preparing the polyamines.The improvement is actually observed in the polymethylene polyphenyl polyisocyanates derived from the polyamines which have substantially reduced color over those polyisocyanates prepared from polyamines prepared via a prior art method. Such color improvements invariably carry over to polyurethane products derived therefrom.

Abstract: Particle boards are currently prepared by treating the particles (e.g. wood chips) with a binder comprising an organic polyisocyanate and, optionally, a release agent and then subjecting the treated particles to a molding process involving heat and pressure. The resulting particle board will generally release well from the caul plates of the press after forming. However, it has been found that the ease of release is enhanced, particularly where the wood particles in the board are derived from hardwood, by utilizing a metal selected from magnesium and zinc in the metallic surfaces of the caul plates or platens which come into contact with the particle board during the application of heat and pressure.