Radiation curable compositions

1. An ethylenically unsaturated hydroxyl-terminated polyurethane (I) obtained by reacting

(i) at least one ethylenically unsaturated compound (A) containing at least two reactive groups capable of reacting with isocyanate groups and at least one ethylenically unsaturated group,

wherein the ethylenically unsaturated hydroxyl-terminated polyurethane (I) has the at least one ethylenically unsaturated compound (A) is incorporated into its backbone;

(ii) at least one saturated alcohol component (B) comprising:

(iia) at least one saturated hydroxylated compound (B1) containing hydrophilic groups capable of rendering the polyurethane dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt, and at least one compound (B2) that is selected from saturated polyester polyols (B21) and/or from saturated polycarbonate polyols (B22);

and/or

(iib) at least one compound (B3) that is selected from saturated polyester polyols (B31) containing compound (B1) moieties and/or from saturated polycarbonate polyols (B32) containing compound (B1) moieties; and, optionally, one or more of compounds (B1) and/or (B2)

wherein at least one of (B2) and (B3) is incorporated into the backbone of the ethylenically unsaturated hydroxyl-terminated polyurethane (I);

(iii) optionally, at least one ethylenically unsaturated compound (C) containing essentially one reactive group capable of reacting with isocyanate groups; and

(iv) at least one polyisocyanate (D);

wherein the reactive groups capable of reacting with isocyanate groups are hydroxyl groups,

wherein compound (A) is used in an amount of from 25 to 65% by weight, relative to the total weight of the polyurethane (I), and

wherein the polyurethane (I) has a hydroxyl value of between 5 and 60 mg KOH/g.

2. The polyurethane according to claim 1 , wherein relative to the total weight of the polyurethane (I), the from 25 to 65% by weight of compounds (A) are reacted with from 10 to 40% by weight of components (B), from 0 to 20% by weight of compounds (C), and from 15 to 40% by weight of compounds (D).

3. The polyurethane according to claim 1 , wherein component (B) consists of at least one compound (B1) and at least one compound (B2), and wherein compounds (B2) are used in an amount of at least 3% by weight, relative to the total weight of the polyurethane (I).

4. The polyurethane according to claim 1 , wherein component (B) consists of at least one compound (B3) and, optionally, at least one of compounds (B1) and/or (B2), and wherein the total amount of compounds (B3) and of compounds (B2) if present is at least 5% by weight, relative to the total weight of the polyurethane (I).

5. The polyurethane according to claim 1 , wherein compounds (A) through (D) are used in such an amount that the ratio between the isocyanate groups and between the reactive groups capable of reacting with said isocyanate groups is between 0.5 and 0.95.

6. The polyurethane according to claim 1 , wherein the isocyanate content is between 0 and 0.05% based on the weight of the polyurethane (I).

7. The polyurethane according to claim 1 , wherein compounds (A) are obtained from the reaction of diglycidyl compounds with (meth) acrylic acid.

8. The polyurethane according to claim 1 , wherein compound (B1) is selected from aliphatic saturated mono-, di- and/or or tri carboxylic acids having at least two hydroxyl groups per molecule and wherein compound (B2) is selected from saturated polyester polyols and/or saturated polycarbonate polyols with a molecular weight of from 500 to 5000 daltons.

9. The polyurethane according to claim 1 , wherein compound (C) is selected from (meth)acryloyl mono-hydroxy compounds.

10. The polyurethane according to claim 1 , wherein compound (D) is selected from aliphatic and/or cycloaliphatic isocyanates.

11. The polyurethane according to claim 1 , wherein compound (D) is 1,6-hexane diisocyanate.

12. A radiation curable composition comprising at least one polyurethane (I) according to claim 1 .

13. The composition according to claim 12 comprising, relative to the total amount of polyurethane (I) and of compounds (E), from 60 to 100% by weight of the polyurethane (I), and, optionally from 0 to 40% by weight of at least one (meth) acryloyl-compound (E) with a hydroxyl value of less than 25.

14. The composition according to claim 12 which is an aqueous composition having a total solids content of at least 35% by weight.

15. The composition according to claim 12 , which is produced according to a solvent free process.

16. A coating composition, ink or varnish comprising at least one polyurethane (I) according to claim 1 or a radiation curable composition comprising at least one polyurethane (I) according to claim 1 .

17. An article coated, entirely or in part, with a coating composition according to claim 16 .

18. The polyurethane according to claim 1 , wherein compounds (A) are selected from the group consisting of polyester (meth)acrylates comprising hydroxyl groups, polyepoxy (meth)acrylates comprising hydroxyl groups, and mixtures thereof.

19. The polyurethane according to claim 1 , wherein compounds (A) through (D) are used in such an amount that the ratio between the isocyanate groups and between the reactive groups capable of reacting with said isocyanate groups is between 0.6 and 0.95.