Method of using mixed aliphatic/aromatic polycarbodiimides

A method of preparing a cross-linkable composition comprising admixing:

• (a) a carboxylated latex,
• (b) a cross-linking catalyst, and
• (c) a mixed aliphatic and aromatic polycarbodiimide prepared by a process comprising 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.degree. to about 160.degree. 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.degree. to about 160.degree. 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 ranges 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.