Ultraviolet curable coatings for optical glass fiber base on a polyfunctional core

Claim 1

A volatile solvent-free ultraviolet curing liquid coating composition which, when cured with ultraviolet light, provides a coating adapted for the buffer coating of optical glass fiber, said coating composition consisting essentially of (I) a photoinitiator, (II) an acrylate functional liquid that is either sufficient monoacrylate monomer liquid, the homopolymer of the monomer having a glass transition temperature below 0°C., to provide the liquidity needed for coating application, or a linear aliphatic diacrylate in which the two acrylate groups are separated by a chain of at least 6 carbon atoms or by a molecular weight of at least 400 up to 4000, and (III) an acrylate-terminated polyurethane oligomer based on a trifunctional core, said oligomer (III) being the reaction product of (A) an organic diisocyanate with (B) a high molecular weight trifunctional triamine providing said core and having three linear branches with an amine terminal group on each branch, each of said branches having an average molecular weight from 1000 to 2500 and (C) a monoisocyanate functional acrylate, each branch leading to an acrylate-functional terminal group.