Photocatalyst system and ultraviolet light curable coating compositions containing the same
AssigneePPG Industries, Inc.
InventorGerald W. Gruber
Life of this patent
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Abstract
The oxygen inhibition of the photopolymerization of acrylic resins is reduced by employing a photocatalyst system containing an aromatic ketone and/or aromatic aldehyde photosensitizer having a triplet energy in the range of from about 54 kilocalories per mole to about 72 kilocalories per mole and which promotes polymerization through bimolecular photochemical reactions of the energy donor type and an aromatic ketone photoinitiator which generates a radical pair by way of unimolecular homolysis resulting from photoexcitation. An exemplary photocatalyst system is benzophenone and isobutyl benzoin ether.
Claims20
A photocatalyst system comprising
- a. at least one aromatic ketone or aromatic aldehyde photosensitizer which
- 1. has a triplet energy in the range of from about 54 kilocalories per mole to about 72 kilocalories per mole, and
- 2.
A ultraviolet high curable coating composition comprising:
- a. at least one aromatic ketone or aromatic aldehyde photosensitizer which
- 1.has a triplet energy in the range of from about 54 kilocalories per mole to about 72 kilocalories per mole, and
- 2. promotes photopolymerization through bimolecular photochemical reactions of the energy donor type;
- b. at least one aromatic ketone photoinitiator which generates a radical pair by way of unimolecular homolysis resulting from photoexcitation, at least one number of said radical pair being capable of initiating addition polymerization of acrylic groups, said aromatic ketone photoinitiator being selected from the group consisting of ethyl benzoin ether, isopropyl benzoin ether, butyl benzoin ether, isobutyl benzoin ether, .alpha., .alpha.-diethoxyacetophenone, .alpha., .alpha.-diethoxy-.alpha.-phenylacetophenone, .alpha., .alpha.-dimethoxy-.alpha.-phenylacetophenone, 4,4'-dicarboethoxy-benzoin ethyl ether, benzoin phenyl ether, .alpha.-methylbenzoin ethyl ether, .alpha.-methylolbenzoin methyl ether, .alpha., .alpha., .alpha.-trichloroacetophenone, mixtures of butyl isomers of butyl benzoin ether, and mixtures thereof;
- and
- c. a resin having acrylic unsaturation and capable of being free radially addition polymerized by interaction with said photosensitizer and said photoinitiator upon exposure to ultraviolet light.
A method comprising:
- a. coating a substrate with an ultraviolet light curable coating composition comprising
- 1. at least one aromatic ketone or aromatic aldehyde photosensitizer which
- a. has a triplet energy in the range of from about 54 kilocalories per mole to about 72 kilocalories per mole, and
- b. promotes polymerization through bimolecular photochemical reactions of the energy donor type,
- 2. at least one aromatic ketone photoinitiator which generates a radical pair by way of unimolecular homolysis resulting from photoexcitation, at least one member of said radical pair being capable of initiating addition polymerization of acrylic groups, said aromatic ketone photoinitiator being selected from the group consisting of ethyl benzoin ether, isopropyl benzoin ether, butyl benzoin ether, isobutyl benzoin ether, .alpha., .alpha.-diethoxyacetophenone, .alpha., .alpha.-diethoxy-.alpha.-phenylacetophone, .alpha., .alpha.-dimethoxy-.alpha.-phenylacetophenone, 4,4'-dicarboethoxybenzoin ethyl ether, benzoin phenyl ether, .alpha.-methylbenzoin ethyl ether, .alpha.-methylbenzoin methyl ether, .alpha., .alpha., .alpha.-trichloroacetophenone, mixtures of butyl isomers of butyl benzoin ether, and mixtures thereof,
- and
- 3. a resin having acrylic unsaturation and capable of being free radically addition polymerized by interaction with said photosensitizer and said photoinitiator upon exposure to ultraviolet light;
- and
- b. exposing said coated substrate to ultraviolet light to cure said coating into a hard mar and abrasion resistant film.
Dependencies are inferred from the claim text.