Preparation of molded lignocellulosic compositions using an emulsifiable polyisocyanate binder and an emulsifiable carboxy functional siloxane internal release agent

In a process for the preparation of particle board wherein wood particles are contacted with a polyisocyanate composition and the treated particles are subsequently formed into boards by the application of heat and pressure, the improvement which comprises imparting internal release properties to said particle board by contacting said wood particles with from 2.5 to 6.5 weight percent, based on oven dried wood particles, of a preblended mixture of a water emulsified polymethylene polyphenyl polyisocyanate, containing from about 20 to 85 percent by weight diphenylmethane diisocyanate, and having a concentration of polyisocyanate of from about 10 to 75 percent by weight in water with a carboxy functional siloxane which has been emulsified with a surface active agent selected from the group consisting of octylphenoxy polyethoxylated ethanols, nonylphenoxy polyethoxylated ethanols and trimethyl nonyl polyethylene glycols, said emulsified carboxy functional siloxane having a concentration of carboxy functional siloxane of from about 0.1 to 90 percent by weight in water said preblended mixture having a concentration of emulsifiable carboxy functional siloxane of between about 0.4 and 6.0 percent by weight based on the emulsifiable polymethylene polyphenyl polyisocyanate.