Coating composition curable with ultraviolet radiation
A UV radiation curable primer coating composition curable under a UV radiation emitting lamp or sunlight. The coating demonstrates improved curing time and includes ethylenically unsaturated free radically polymerizable compounds and 0.1% photoinitiator or less.
1. A UV radiation curable primer coating composition comprising:
(a) one or more compounds containing one ethylenically unsaturated free-radically polymerizable group per molecule;
(b) 5 to 50% by weight of compounds containing two or more ethylenically unsaturated free radically polymerizable groups per molecule comprising a difunctional urethane acrylate and a hexafunctional urethane acrylate;
(c) 1.0 to 60% by weight of one or more pigments, fillers and/or dyes;
(d) 0.1 to 0.95 % photoinitiators;
(e) 0 to 20% by weight of volatile organic solvent; and
(f) 0.1 to 10% by weight of additives,
wherein said coating composition is curable to a non-tacky surface under a UVA radiation emitting lamp within 2 minutes and in sunlight within 5 minutes.
2. A primer coating composition according to claim 1 , comprising 0.1 to 0.5% by weight photoinitiators.
3. A primer coating composition according to claim 1 wherein component (a) is selected from the group consisting of butyl acrylate, t-butyl acrylate, isobomyl acrylate, isodecyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate, octyl acrylate.
4. A primer coating composition according to claim 1 wherein component (b) further comprises a member selected from the group consisting of diacrylates, triacrylates, polyfunctional acrylates and mixtures thereof.
5. A primer coating composition according to claim 1 wherein component (b) further comprises a member selected from the group consisting of hexanediol diacrylate, tripropyleneglycol diacrylate, trimethylolpropane triacrylate, alkoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, unsaturated polyesters, and mixtures thereof.
6. A primer coating composition according to claim 1 wherein component (b) further comprises tripropylene glycol diacrylate.
7. A primer coating composition according to claim 1 wherein the pigment to binder ratio is between 1.2 and 1.8.
8. A primer coating composition according to claim 1 wherein the photoinitiator comprises a compound selected from the group consisting of acyl phosphine oxides and benzyl ketals.
9. A primer coating prepared by curing the primer coating composition according to claim 1 wherein said primer coating composition is cured to a tack free surface on a metal substrate by 5 minutes' exposure to outdoor light having an intensity of 45-65 mJoules/cm 2 and demonstrates 95% post humidity test adhesion.
10. A process for applying a primer coating to a substrate consisting essentially of:
A. applying a UV radiation curable primer coating composition according to claim 1 to a substrate;
B. curing the applied coating composition with a source selected from the group consisting of one or more UV lamps having a UV-B:UV-A ratio of 1:1 or less, natural outdoor light having a wavelength between 320 and 430 nm, and mixtures thereof.
11. A process according to claim 10 wherein the coating composition applied comprises 0.1 to 0.5% by weight photoinitiators.
12. A process according to claim 10 wherein the coating composition applied comprises compound A selected from butyl acrylate, t-butyl acrylate, isobornyl acrylate, isodecyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate and octyl acrylate and mixtures thereof.
13. A process according to claim 10 wherein component (b) further comprises a member selected from the group consisting of diacrylates, triacrylates, polyfunctional acrylates and mixtures thereof.
14. A process according to claim 10 wherein component (b) further comprises a member selected from the group consisting of hexanediol diacrylate, tripropyleneglycol diacrylate, trimethylolpropane triacrylate, alkoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, unsaturated polyesters, and mixtures thereof.
15. A process according to claim 10 wherein the coating composition applied comprises a pigment to binder ratio between 1.2 and 1.8.
16. A process according to claim 10 wherein a UV light source is applied wherein the UVA intensity is from 0.8 to 1.6 Joules/cm 2 , the UVB intensity is from 0.001 to 0.5 Joules/cm 2 and the UVC intensity is from 0.001 to 0.3 Joules/cm 2 .
17. A process according to claim 10 wherein the applied coating composition is cured under natural light conditions, said light providing an intensity of 5-100 mJoules/ cm 2 .
18. A process according to claim 10 wherein the substrate to which the coating composition is applied to a substrate comprising an automotive vehicle.
19. A process according to claim 10 wherein the coating process comprises application of the primer coating in the repair of an automotive vehicle.