Method for making urethane-terminated polycarbodiimides and products thereof

Claim 1

A urethane-terminated polycarbodiimide prepared by: 1 reacting at a temperature of no more than about 50° C. an arylene diisocyanate in which the isocyanate groups are of unequal reactivity and being selected from the group consisting of toluene 2,4-diisocyanate, 2-methyl napthalene 1,5-diisocyanate, 3-methyl-4,4'-diisocyanatodiphenylmethane, 3-chloro-4,4'-diisocyanatodiphenylmethane, 3-methoxy-4,4'-diisocyanatodiphenylmethane, 2,4-diisocyanatochlorobenzene, cumene 2,4-diisocyanate, m-xylene 2,5-diisocyanate and 3,5-dimethylbiphenyl-4,4'-diisocyanate with a stoichiometric deficiency of a primary or secondary aliphatic alcohol selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, secondary buyl alcohol, isoamyl alcohol, n-hexanol, cyclohexanol, 2-chloro-1-propanol, 2-octanol, methylphenylcarbinol, benzyl alcohol, diethylene glycol mono-n-butyl ether, cinnamyl alcohol and 2-ethyl hexanol to convert less than all of the isocyanate groups to urethane groups; 2 cooling the mixture to near room temperature; and 3 admixing therewith a carbodiimide-forming catalyst and polymerizing the partially urethane-terminated arylene diisocyanate to a urethane-terminated polycarbodiimide that exhibits a single N═C═N peak at 2130 cm. -1 and is free of other peaks in the 2000 to 2500 cm. -1 band under infra-red inspection.