Reaction injection molded polyurethanes employing aliphatic amine chain extenders

In a process for preparing RIM urethane systems which systems employ a composition which comprises (A) a relatively high molecular weight hydroxyl-containing polyol, (B) a chain extender and (C) a polyisocyanate, a polyisothiocyanate or mixture thereof;

• the improvement which comprises employing as the chain extender, component (B), a mixture comprising
• (1) at least one member selected from the group consisting of
• (a) hydroxyl-containing materials which are essentially free of aliphatic amine hydrogen atoms, have an average OH functionality of from about 2 to about 4 and have an average OH equivalent weight of from about 30 to about 120 and
• (b) aromatic amine-containing materials which are essentially free of aliphatic amine hydrogen atoms and which contain at least two aromatic amine hydrogen atoms and
• (2) at least one aliphatic amine-containing material having at least one primary amine group, an average aliphatic amine hydrogen functionality of from about 2 to about 16 and an average aliphatic amine hydrogen equivalent weight of from about 15 to about 500;
• and wherein
• (i) components (A), (B) and (C) are present in quantities such that the weight percent of the theoretical reaction product of the amine hydrogen atoms of component (B-2) with a stoichiometric quantity of component (C) based upon the total weight of Components (A), (B) and (C) is from about 5 to about 25 and
• (ii) the NCX index is from about 0.6:1 to about 1.50:1 with the proviso that when an NCX trimerization catalyst is also present the index is up to about 5:1.