Adhesion promoting photoinitiators for UV cured coatings over metal surfaces
View Patent ↗Compounds containing both photoinitiator moieties and adhesion promoting moieties and coating formulations containing them are disclosed, in particular, durable UV cured primer layers for coil coatings. One embodiment includes a coated metal surface which comprises a metal substrate with at least one surface immediately adjacent to a coating layer comprising a photoinitiator chemically bound to an adhesion promoter is disclosed.
1. A coated metal surface which comprises
a) a metal of steel or aluminum with at least one surface which is immediately adjacent to a coating layer obtained by photocuring a coating composition comprising
b) one or more ethylenically unsaturated monomers, oligomers or prepolymers, and
c) from about 0.05 to about 25% by weight, based on the total weight of the coating layer solids, of one or more compounds selected from the group consisting of
wherein the coating layer is cured under a light with wavelength from about 200 nm to about 450 nm.
2. A coated metal surface according to claim 1 , wherein component b) comprises one or more acrylate monomers, oligomers or prepolymers.
3. A coated metal surface according to claim 1 which also comprises 5-25 weight percent, based on total solids, of an additional photoinitiator or photoinitiator blend.
4. A coated metal surface according to claim 3 , wherein the additional photoinitiator or photoinitiator blend comprises one or more compounds selected from the group consisting of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-Hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, 2-Hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methylpropan-1-one, benzophenone and 1-hydroxycyclohexyl phenyl ketone.
5. A coated metal surface according to claim 4 , wherein the additional photoinitiator or photoinitiator blend comprises one or more compounds or blends selected from the group consisting of
a blend of 20% by weight phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide and 80% by weight 2-hydroxy-2-methyl-1-phenyl-1-propanone;
2-Hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one;
2-Hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methylpropan-1-one;
a blend of 50 weight % benzophenone and 50 weight % 1-hydroxycyclohexyl phenyl ketone;
Phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide;
1-Hydroxycyclohexyl phenyl ketone; and
2-Hydroxy-2-methyl-1-phenyl propan-1-one.
6. A coated metal surface according to claim 3 , wherein the additional photoinitiator or photoinitiator blend comprises the blend 50 weight % benzophenone and 50 weight % 1-hydroxycyclohexyl phenyl ketone or the compound phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide.