Radiation-curable coating composition for improving the surface properties of plastics

1. Radiation-curable coating composition comprising:

A) from 20 to 60 wt. % of at least one oligomer bearing at least one ethylenic unsaturation, wherein said at least one oligomer comprises a urethane (meth)acrylate bearing free isocyanate groups,

B) from 0.1 to 35 wt. % of at least one ethylenically unsaturated monomer having a surface tension measured according to contact angle method NF EN14370 which is lower than 35 mN/m,

C) from 0.1 to 20 wt. % of at least one ethylenically unsaturated monomer with high hydrophilicity having a Hansen solubility parameter δp, calculated according to the method described in “Hansen Solubility Parameters: a user's handbook” by Charles M. Hansen ISBN 068494-1525-5 (chapter I, table 1.1) higher than 4 MPa 1/2 ,

D) 0 to 10 wt. % of at least one photoinitiator,

E) 0 to 75 wt. % of a reactive diluent selected from at least one ethylenically unsaturated monomer other than B) and C) and bearing at least one ethylenically unsaturated group,

F) 0 to 20 wt. % of a phosphoric ester comprising a (meth)acrylate group used as an adhesion promoter and

wherein the sum of wt % of components A+B+C+D+E+F is 100%.

2. Radiation-curable coating composition according to claim 1 , wherein the composition comprises:

A) 20 to 50 wt.-% of said at least one oligomer A), with said oligomer comprising at least one oligomeric segment selected from polyurethane and/or poly(meth)acrylate and/or polyester segments and

B) 0.1 to 30 wt. % of said at least one ethylenically unsaturated monomer B), with said monomer B) being selected from the group consisting of tert-butyl cyclohexyl acrylate, isobornyl acrylate isodecyl acrylate, 3,5,5 trimethyl cyclohexyl acrylate and methacrylate, isooctyl acrylate, octyl decyl acrylate, tridecyl acrylate, lauryl 4EO acrylate (with lauryl bearing 4 ethoxy units) and C 12 -C 15 alkyl methacrylate,

C) 0.5 to 20 wt.-% of said at least one ethylenically unsaturated monomer C), wherein said monomer C) is selected from the group consisting of 2-ethoxyethyl acrylate, 2 (2-ethoxyethoxy)-ethyl acrylate and tetrahydrofufuryl acrylate,

D) 0 to 5 wt.-% of said least one photoinitiator,

E) 5 to 60 wt.-% of said reactive diluent

F) 0 to 15 wt.-% of said phosphoric ester, wherein said phosphoric ester F) comprises monoesters of hydroxyalkyl (meth)acrylates with phosphoric acid.

3. Radiation curable coating composition according to claim 1 , wherein said oligomer A), has a number average molecular weight Mn of from 1000 to 12000 as measured by GPC in THF with polystyrene standard calibration.

4. Radiation-curable coating composition according to claim 1 , wherein the composition comprises components A), B), C) and E).

5. Radiation-curable coating composition according to claim 1 , wherein the composition comprises components A), B), C) and D).

6. Radiation-curable coating composition according to claim 5 , wherein component E).

7. Radiation-curable coating composition according to claim 1 , wherein the composition is a UV and/or an EB-curable composition.

8. Radiation-curable coating composition according to claim 1 , wherein said oligomer A) further comprises polyester acrylate or an acrylic (meth)acrylate oligomer bearing at least two (meth)acrylic groups or a mixture of at least two of them.

9. Radiation-curable coating composition according to claim 1 , wherein said oligomer A) is a urethane (meth)acrylate bearing free isocyanate groups.

10. Radiation-curable coating composition according to claim 9 , wherein said oligomer A) has a content of free isocyanate groups from 0.5 to 20% by weight of —NCO groups.

11. Radiation-curable coating composition according to claim 1 , wherein said oligomer A) is a urethane (meth)acrylate bearing from 2 to 6 (meth)acrylic groups.

12. Radiation curable coating composition according to claim 11 , wherein said urethane (meth)acrylate oligomer comprises polyester segments based on polycaprolactone segments.

13. Radiation curable coating composition according to claim 1 , wherein said oligomer A) further comprises an acrylic (meth)acrylated oligomer.

14. Radiation-curable coating composition according to claim 1 , wherein the composition is a pigmented coating composition.

15. Cured coating resulting from curing by radiation at least one layer of at least one curable coating composition as defined according to claim 1 .

16. Cured coating according to claim 15 , wherein the cured coating is a primer, a base coat or a clear coat.

17. A method of using a coating composition as defined according to claim 1 , comprising applying the coating composition to a substrate and curing the coating composition.

18. The method according to claim 17 , wherein the substrate comprises shaped parts containing plastics.

19. The method according to claim 17 , wherein the composition is used in at least one layer or in one or in multiple layers on said substrate and is cured by UV and/or EB radiation for each of said layers.

20. The method according to claim 17 , wherein said coating composition is used as a primer and/or as a base coat and/or as a clear coat or as a binary or as a ternary combination of these uses on said substrate.

21. The method according to claim 17 , wherein said substrate is a plastic selected from:

thermoplastics,

thermosets, or

mixtures thereof,

fiber-reinforced polymers or composites derived from the thermoplastics or the thermosets or the mixtures thereof.

22. Shaped part comprising a plastic surface coated with at least one layer of a coating resulting from curing by radiation at least one coating composition as defined according to claim 1 .

23. Shaped part according to claim 22 , wherein said coating is a primer and/or a base coat and/or a clear coat.

24. Radiation-curable coating composition according to claim 1 , wherein the composition comprises:

A) from 20 to 50 wt.-% of said at least one oligomer A), wherein said at least one oligomer A) further comprises at least two ethylenic unsaturations,

B) from 0.1 to 30 wt.-% of said at least one ethylenically unsaturated monomer B), wherein said monomer B) is a (meth)acrylate monomer and the surface tension is lower than 32 mN/m,

C) from 0.5 to 20 wt.-% of said at least one ethylenically unsaturated monomer C), wherein said monomer C) is a (meth)acrylate monomer,

D) from 0 to 5 wt.-% of said least one photoinitiator,

E) 5 to 60 wt.-% of said reactive diluent, wherein the least one ethylenically unsaturated group is a (meth)acrylic group, and

F) 0 to 15 wt.-% of said phosphoric ester.

25. Radiation-curable coating composition according to claim 24 , wherein the at least two ethylenic unsaturations of said at least one oligomer A) further comprises (meth)acrylic groups.

26. Radiation-curable coating composition according to claim 11 , wherein said (meth)acrylic groups of said oligomer A) further comprises acrylate groups.