Radiation curable hardcoat with improved weatherability
View Patent ↗Disclosed is a transparent, radiation curable acrylate coating composition comprising (a) at least three polyfunctional acrylate derivatives, (b) a photoinitiator selected from the group consisting of phosphine oxides, ketones, and combinations thereof, (c) a nanoscale filler, and (d) a dibenzoyl resorcinol UV absorber, at least one of said acrylate derivatives being an aliphatic polyester urethane multi-acrylate having an acrylate functionality of at least 5 and an elongation of no greater than 5%, and at least two of said acrylate derivatives being diacrylates, wherein at least one of said diacrylates is an aliphatic Polyester urethane diacrylate having an elongation of greater than 5% and a number average molecular weight of from 500 to about 2500 and wherein another of said diacrylates is a urethane-free diacrylate having a number average molecular weight of from about 150 to about 600.
1. A transparent, radiation-curable acrylate coating composition comprising (a) at least three polyfunctional acrylate derivatives, (b) a photoinitiator selected from the group consisting of phosphine oxides, ketones, and combinations thereof, (c) a nanoscale filler, and (d) a dibenzoyl resorcinol UV absorber, at least one of said acrylate derivatives being an aliphatic polyester urethane multi-acrylate having an acrylate functionality of at least 5 and an elongation of no greater than 5%, and at least two of said acrylate derivatives being diacrylates, wherein at least one of said diacrylates is an aliphatic polyester urethane diacrylate having an elongation of greater than 5% and a number average molecular weight of from about 500 to about 2500 and wherein another of said diacrylates is a urethane-free diacrylate having a number average molecular weight of from about 150 to about 600 wherein the aliphatic polyester urethane multi-acryalte is present in an amount of 10 weight percent to 80 weight percent of a dry coating, wherein the aliphatic polyester urethane diacrylate is present in an amount of 5 weight percent to 50 weight percent of the dry coating, and wherein the urethane-free diacrylate is present in an amount of 3 weight percent to 30 weight percent of the dry coating.
2. The curable acrylate coating composition according to claim 1 wherein the urethane-free diacrylate is selected from the group consisting of alkyldioldiacrylate, hexanediol diacrylate, alkoxylated hexanediol diacrylate, tripropylene glycol diacrylate, polyethylene glycol (400) diacrylate, and combinations thereof.
3. The curable acrylate coating composition according to claim 1 wherein the urethane multi-acrylate having an acrylate functionality of at least 5 is a urethane hexaacrylate.
4. The curable acrylate coating composition according to claim 2 wherein the alkyl moiety on the alkyldiolacrylate contains from four to eight carbons.
5. The curable acrylate coating composition according to claim 1 wherein the phosphine oxide photoinitiator comprises 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide or bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide.
6. The curable acrylate coating composition according to claim 1 wherein said coating composition further comprises (e) a solvent, said solvent being selected from the group consisting of aliphatic alcohols, glycol ethers, cycloaliphatic alcohols, aliphatic esters, cycloaliphatic esters, aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic compounds, halogenated cycloaliphatic compounds, halogenated aromatic compounds, aliphatic ethers, cycloaliphatic ethers, amide solvents, sulfoxide solvents, and combinations thereof.
7. The curable acrylate coating composition according to claim 6 wherein said solvent is 1-methoxy-2-propanol.
8. The curable acrylate coating composition according to claim 1 wherein the dibenzoyl resorcinol UV absorber is 4,6-dibenzoyl resorcinol.
9. The curable acrylate coating composition according to claim 1 wherein the dibenzoyl resorcinol UV absorber is a silylated dibenzoyl resorcinol.
10. The curable acrylate coating composition according to claim 9 wherein the silylated dibenzoyl resorcinol is 4,6-dibenzoyl-2-(3-triethoxysilylpropyl) resorcinol.
11. The curable acrylate coating composition according to claim 4 which additionally comprises (f) a hindered amine light stabilizer.
12. The curable acrylate coating composition according to claim 1 wherein the polyfunctional acrylate derivatives are present in an amount such that the total amount of all polyfunctional acrylates present corresponds to between about 40 and about 80 percent by weight based upon the total weight of the curable acrylate coating composition.
13. The curable acrylate coating composition according to claim 6 wherein said hexafunctional acrylate derivative is present in an amount corresponding to between about 35 and about 50 percent by weight based upon the total weight of the curable acrylate coating composition.
14. The curable acrylate coating composition according to claim 1 wherein said photoinitiator is activated by light having a wavelength of less than about 420 nm.
15. The curable acrylate coating composition according to claim 1 wherein said nanoscale filler is selected from the group consisting of silica, zirconia, titania, alumina, ceria, and mixtures thereof.
16. The curable acrylate coating composition according to claim 1 wherein said nanoscale filler has a particle size of about 10 nanometers to about 250 nanometers.
17. The curable acrylate coating composition according to claim 1 wherein said nanoscale filler has a particle size in the range of between about 15 and about 50 nanometers.
18. The curable acrylate coating composition according to claim 1 wherein said nanoscale filler comprises silica having organic functional groups.
19. The curable acrylate coating composition according to claim 18 wherein said silica having organic functional groups is an acrylate functionalized silica.
20. The curable acrylate coating composition according to claim 6 wherein said nanoscale filler is present in an amount corresponding to between about 2 and about 15 percent by weight based upon the total weight of the coating composition.
21. The curable acrylate coating composition according to claim 1 wherein the ketone photoinitiator comprises 1-hydroxy-cyclohexyl-phenyl ketone.
22. An article coated with the curable acrylate coating composition according to claim 1 .
23. A laminate comprising a substrate and a coating on said substrate, said laminate being produced by coating at least a portion of said substrate with the curable acrylate coating composition according to claim 1 , and curing the coating composition on said substrate.
24. An article being a cured composition on a substrate, wherein said cured composition is produced by radiation curing a curable formulation on said substrate, said curable composition comprising at least three polyfunctional acrylate derivatives, a nanoscale filler, and a UV absorber, at least one of said acrylate derivatives having an acrylate functionality of at least 5 and an elongation of no greater than 5%, and at least two of said acrylate derivatives being diacrylates, wherein at least one of said diacrylates is an aliphatic polyester urethane diacrylate having an elongation of greater than 5% and a number average molecular weight of from 500 to about 2500 and wherein another of said diacrylates is a urethane-free diacrylate having a number average molecular weight of from about 150 to about 600, wherein the aliphatic polyester urethane multi-acryalte is present in an amount of 10 weight percent to 80 weight percent said cured composition, wherein the aliphatic polyester urethane diacrylate is present in an amount of 5 weight percent to 50 weight percent of the cured composition, and wherein the urethane-free diacrylate is present in an amount of 3 weight percent to 30 weight percent of the cured composition, said cured composition having a delta % haze of less than 10 after Taber abrasion testing using CS10F wheels and 500 gram weights for 500 cycles, and said cured composition, after accelerated weathering using a Xenon arc Weather-o-meter to provide UV exposure of 11,000 kJ/m 2 , exhibiting no cracks upon visual inspection, having a percent haze of less than 7, and a yellowness index of less than 4.
25. The article of claim 24 wherein said cured composition is additionally free of cracks, has a percent haze of less than 7, and a yellowness index of less than 4, after 14,000 kJ/m 2 of accelerated xenon arc weathering.
26. The cured composition of claim 24 wherein said substrate comprises polycarbonate.