Aqueous radiation curable polyurethane compositions

An aqueous radiation-curable composition comprising

• at least one high molecular weight ethylenically unsaturated polyurethane (A) obtained from the reaction of
• at least one polyisocyanate compound (Ai),
• at least one ethylenically unsaturated compound (Aii) containing at least two reactive groups capable to react with isocyanate groups,
• at least one hydrophilic compound (Aiii) containing at least one reactive group capable to react with isocyanate groups and which is capable to render the polyurethane prepolymer dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt,
• at least one active hydrogen-containing chain extender (Avii) capable to react with isocyanate groups and provide chain extension, and,
• optionally one or more polyol (Avi),
• wherein the polyurethane (A) has a weight average molecular weight of more than 100000 Dalton;
• and
• at least one low molecular weight ethylenically unsaturated polyurethane (B), different from polyurethane (A), obtained from the reaction of
• at least one polyisocyanate compound (Bi),
• at least one ethylenically unsaturated compound (Bii) containing at least two reactive groups capable to react with isocyanate groups,
• at least one hydrophilic compound (Biii) containing at least one reactive group capable to react with isocyanate groups and which is capable to render the polyurethane prepolymer dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt,
• at least one ethylenically unsaturated compound (Biv) containing one reactive group capable to react with isocyanate groups, and,
• optionally, one or more polyol (Bvi) and/or one or more active hydrogen-containing chain extender (Bvii),
• wherein the polyurethane (B) has a weight average molecular weight of 1000 to 100000 Dalton.