Radiation curable aqueous compositions

1. A radiation curable aqueous composition comprising at least one ethylenically unsaturated polymer (1) which is the reaction product of

a water-dispersible (meth)acrylic polymer A containing pendant hydroxyl or isocyanate groups, and containing pendant groups capable of rendering the polymer dispersible in aqueous medium either directly or after reaction with a neutralizing agent;

at least one ethylenically unsaturated compound B which can be radically polymerized under irradiation and which attaches to the (meth)acrylic polymer A by an urethane linkage,

wherein, if the (meth)acrylic polymer A contains pendant hydroxyl groups, the ethylenically unsaturated compound B is a compound B1 that is the reaction product of at least one polyisocyanate (b1) and of at least one ethylenically unsaturated compound (b2) containing one functional group capable of reacting with isocyanate groups,

wherein compound (b2) is selected from polyethylenically unsaturated compounds (b21), used alone or in combination with one or more monoethylenically unsaturated compounds (b22), and

wherein, if the (meth)acrylic polymer A contains pendant isocyanate groups, the ethylenically unsaturated compound B is a compound B2 that is an ethylenically unsaturated compound (b2) containing one functional group capable of reacting with isocyanate groups,

wherein compound (b2) is selected from polyethylenically unsaturated compounds (b21), used alone or in combination with one or more monoethylenically unsaturated compounds (b22); and

optionally, at least one neutralizing agent C,

wherein the ethylenically unsaturated polymer (1) has residual hydroxyl functionality.

2. The composition of claim 1 , wherein the (meth)acrylic polymer A contains pendant isocyanate groups, and wherein the weight ratio between polyethylenically unsaturated compounds (b21) and monoethylenically unsaturated compounds (b22) is from 1:0 to 1:1.

3. The composition of claim 1 , wherein compound (b2) is a polyethylenically unsaturated compound.

4. The composition of claim 1 , wherein compound (b2) is a mono-hydroxy poly(meth)acryloyl compound.

5. The composition of claim 1 , wherein the (meth)acrylic polymer A is prepared from polymerizable monomers comprising

at least one (meth)acrylate (a1),

at least one ethylenically unsaturated monomer (a2) selected from a (meth)acrylate (a21) containing at least one hydroxyl functionality and/or from an ethylenically unsaturated monomer containing at least one isocyanate functionality (a22),

at least one ethylenically unsaturated monomer (a3) containing at least one acidic group and/or a salt thereof capable of rendering the polymer dispersible in aqueous medium,

optionally, at least one other ethylenically unsaturated monomer (a4) different from (a1) to (a3) and,

optionally, at least one other ethyelenically unsaturated monomer (a5) different from (a1) to (a4) and having a functional side chain capable to provide additional features to the polymer.

6. The composition of claim 1 comprising at least one further polyethylenically unsaturated compound (2) and/or at least one emulsifier (3).

7. The composition of claim 6 , wherein the polyethylenically unsaturated compound (2) is selected from the group consisting of polyester (meth)acrylates, urethane (meth)acrylates, epoxy (meth)acrylates, polyether (meth)acrylates amino (meth)acrylates, and mixtures thereof.

8. The composition of claim 6 , wherein the emulsifier (3) is selected from the group consisting of anionic surfactants, nonionic surfactants, and mixtures thereof.

9. The composition of claim 1 , wherein the ethylenically unsaturated compound B1 is the reaction product of compounds (b1) and (b2) used in an equivalent ratio of isocyanate to hydroxyl from 1:0.5 to 1:0.75.

10. A coating, an adhesive, an ink or an overprint varnish comprising the composition of claim 1 .

11. An article coated with the composition of claim 1 .

12. A method of coating an article, comprising:

applying the composition of claim 1 to at least one surface of the article in the form of a wet film,

drying or flushing off at least a part of the water comprised in the film, and

curing the film by exposure to high energy radiation.

13. A method of making a coating, an adhesive, an ink or an overprint varnish comprising adding the composition of claim 1 to a coating, an adhesive, an ink or an overprint varnish.