Method of making mixed aliphatic/aromatic polycarbodiimides

Claim 1

Method of preparing mixed aliphatic and aromatic polycarbodiimides which comprises the following steps seriatim: (A) charging a mixture of cycloaliphatic or saturated aliphatic mono- and diisocyanates to a reactor with agitation under an inert atmosphere; (B) heating the resultant mixture to about 120° to about 160° C.; (C) adding a catalytic amount of a phospholene oxide catalyst to the reactor; (D) feeding a mixture of a non-reactive solvent and aromatic mono- and/or diisocyanate to the reactor; and (E) maintaining agitation at about 120° to about 160° C. until all of the isocyanate functionality is converted to carbodiimide functionality, with the provisos that: (a) said cycloaliphatic moieties contain 6 to about 10 carbons; (b) said saturated aliphatic moieties contain from about 4 to about 12 carbons; (c) said aromatic moieties contain from 6 to about 16 carbons; (d) The molar ratio of all of the mono-to-diisocyanates range from about 2:1 to about 2:10; and (e) The molar ratio of cycloaliphatic and/or saturated aliphatic isocyanate groups to aromatic isocyanate groups ranges from about 0.5:1 to about 2:1.