Strong and elastic polyurethane polyurea polycrylates and electron

Abstract

An essentially isocyanate-free polyurethane polyurea polyethylenic oligomer is disclosed which is unusually strong and elastic. This oligomer is the reaction product of: (1) organic diisocyanate; (2) a stoichiometric deficiency of difunctional materials reactive therewith and consisting essentially of: (A) polyoxyalkylene glycol having a molecular weight of from 200 to 1000; (B) dihydric bisphenol-based alkylene oxide adduct containing from 2-10 alkylene groups per molecule; and (C) polyoxyalkylene diprimary amine having a molecular weight of from 150 to 800. In all of these, the alkylene groups contain from 2-4 carbon atoms. Components (A) and (B) are present in a weight ratio of from 1:4 to 9:1 and component (C) is present to supply from 30 to 60 equivalent percent of the total equivalents of component (2). The polyurethane polyurea so-constituted is capped with monohydric ethylenic compound, such as 2-hydroxyethyl acrylate, to provide a molecular weight in the range of about 5,000 to about 30,000. This polyethylenic oligomer is cured by radiation exposure, such as an electron beam, using from 5% to 25%, based on total polymer solids, of polyethylenic polyhydroxyalkyl melamine in which the alkyl group contains from 2-4 carbon atoms and there are an average of from 2.4 to 3.0 hydroxyalkyl groups per molecule, this polyhydroxyalkyl melamine being preferably acrylated to provide at least 2.4 up to about 3.0 acrylate groups per molecule.