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);
• 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).

A method of producing an aqueous radiation-curable composition comprising at least one high molecular weight ethylenically unsaturated polyurethane (A) and at least one low molecular weight ethylenically unsaturated polyurethane (B), different from polyurethane (A), comprising adding polyurethane (A) into an aqueous composition comprising polyurethane (B), or vice versa,

• wherein the process for producing polyurethane (A) comprises
• forming a polyurethane prepolymer by reacting
• at least one polyisocyanate compound (Ai),
• at least one ethylenically unsaturated compound (Ali) 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, and,
• optionally, one or more polyol (Avi);
• optionally, converting the hydrophilic groups provided by compound (Aiii) into anionic salts by reaction with a neutralizing agent;
• dispersing the polyurethane prepolymer in an aqueous medium;
• and
• reacting the ethylenically unsaturated polyurethane prepolymer with at least one active hydrogen-containing chain extender (Avii), and
• wherein the process for producing polyurethane (B) comprises
• forming a polyurethane prepolymer by reacting
• 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, and
• optionally, one or more polyol (Bvi);
• reacting the polyurethane prepolymer with at least one ethylenically unsaturated compound (Biv) containing essentially one reactive group capable to react with an isocyanate group;
• optionally, converting the hydrophilic groups provided by compound (Biii) into salts by reaction with a neutralizing agent;
• dispersing the polyurethane prepolymer in an aqueous medium;
• and
• optionally, reacting the ethylenically unsaturated polyurethane with at least one active hydrogen containing chain extender (Bvii).