Patent ID: 7279505

Claim:
A method for producing a radiation-curable prepolymer, comprising the steps of: (I) preparing a melted reaction mixture which is substantially free of a solvent, the melted reaction mixture comprising the components of (a) one or more polyalkylene glycols, (b) one or more branching agents, and (c) at least one di- or polyisocyanate, wherein the stoichiometry of components (a), (b) and (c) in the melted reaction mixture is chosen so that the number of NCO equivalents of component (c) is greater than the sum of OH equivalents of components (a) and (b); (II) reacting components (a) and (b) with component (c) in the melted reaction mixture at a desired temperature to form an isocyanate-capping polyurethane; and (III) reacting the formed isocyanate-capping polyurethane, without intermediate isolation, with a radiation-curable group-capping agent, which is an ethylenically unsaturated monohydroxy compound, to prepare the radiation-curable polyurethane prepolymer, wherein component (a) consists of at least one poly(ethylene glycol) and at least one hydroxy-terminated poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) or poly(propylene glycol)-poly(ethylene glycol)-poly(propylene glycol) tri-block copolymers, wherein component (b) consists of one or more linear or branched aliphatic polyhydroxy compounds of formula (2) R 4 —(OH) x (2) wherein R 4 is a linear or branched C 3 -C 18 aliphatic multi-valent radical and x is a number from 3 to 8, and wherein component (c) consists of one or more diisocyanates of formula OCN—R 5 —NCO (3a), wherein R 5 is a linear or branched C 3 -C 18 -alkylene, an unsubstituted or C 1 -C 4 -alkyl-substituted or C 1 -C 4 -alkoxy-substituted C 6 -C 10 -arylene, a C 7 -C 18 -aralkylene, a C 6 -C 10 -arylene-C 1 -C 2 -alkylene-C 6 -C 10 -arylene, a C 3 -C 8 -cyclo-alkylene, a C 3 -C 8 -cycloalkylene-C 1 -C 6 -alkylene, a C 3 -C 8 -cycloalkylene-C 1 -C 2 -alkylene-C 3 -C 8 -cycloalkylene, or a C 1 -C 6 -alkylene-C 3 -C 8 -cycloalkylene-C 1 -C 6 -alkylene, wherein said ethylenically unsaturated amine is selected from the group consisting of mono-C 1 -C 4 alkylamino-C 1 -C 4 alkyl-acrylates, mono-C 1 -C 4 alkylamino-C 1 -C 4 alkyl-methacrylates, di-C 1 -C 4 alkylamino-C 1 -C 4 alkyl-acrylates and di-C 1 -C 4 alkylamino-C 1 -C 4 alkyl-methacrylates, and wherein said ethylenically unsaturated hydroxy compound is selected from the group consisting of hydroxy-substituted C 1 -C 6 alkylacrylates and hydroxy-substituted C 1 -C 6 alkylmethacrylates.