. . . "Examples of suitable cycloaliphatic diisocyanates are dinuclear cyclic aliphatic diisocyanates which are formed through an alkylene group of from 1 to 3 carbon atoms, inclusive, and which can be substituted with nitro, chlorine, alkyl, alkoxy and other groups which are not reactive with hydroxyl groups (or active hydrogens) providing they are not positioned to render the isocyanate group unreactiv" . .