Abstract: Disclosed herein is a polybutylene glycol dimethacrylate which provides various kinds of plastics having good flexibility and low water absorption. Disclosed also herein is a resin composition for cast polymerization which provides molded products which have high heat resistance, good flexibility, and low water absorption, without sacrificing impact resistance and surface hardness. They will find use as optical materials, lenses, etc.

Abstract: Disclosed is a composition comprising(A) 10 to 60 parts by weight of a polybutylene glycol di(meth)acrylate represented by the general formula (I): ##STR1## (B) 20 to 80 parts by weight of a specific urethane poly(meth)acrylate or epoxy poly(meth)acrylate,(C) 5 to 60 parts by weight of a specific mono(meth)acrylate, and(D) 0 to 60 parts by weight of a compound having at least one polymerizable double bond in the molecule,with the total amount of components (A), (B), (C) and (D) being 100 parts by weight. This composition is suitable for the making of plastic lenses because of its excellent properties such as high thermal resistance, high impact resistance, good dyeability, low water absorption and high surface accuracy.

Abstract: An ultraviolet curable ink composition comprising, as main components,(A) a polyurethane poly(meth)acrylate obtained by reacting a polyisocyanate compound of the formula: ##STR1## wherein R.sub.1 is a hydrogen atom or a methyl group, and n is an integer of from 1 to 20, with a hydroxyl group-containing (meth)acrylate, and having, in one molecule, at least two (meth)acryloyl groups and at least two urethane bonds,(B) a radical polymerizable low molecular weight compound, and(C) a photopolymerization initiator.