Process for the preparation of highly stable liquid carbodiimide-containing polyisocyanate compositions

摘要

Highly stable liquid 4,4'-diphenylmethane diisocyanate (MDI) containing MDI-carbodiimide adducts are prepared by (a) heating MDI at a temperature of from 60 DEG C. to 120 DEG C. for a period of from one hour to ten hours in the presence of tris(chloromethyl)phosphine oxide, (b) stopping the carbodiimide formation by adding thereto a quenchant selected from the group consisting of magnesium chloride hydrate, stannous chloride and trichlorosilane, (c) heating the reaction mixture at a temperature between 60 DEG C. and 120 DEG C. for a period of from 0.5 hour to 6.0 hours, and (d) cooling to room temperature. The resulting compositions are highly stable and may be advantageously employed in the preparation of polyurethane compositions.