Actinic radiation-curable coating composition
The invention relates to an actinic radiation-curable coating composition comprising a compound having at least two isocyanate groups, a compound having at least two hydroxyl groups, and a photolatent catalyst for the isocyanate-hydroxyl addition reaction, wherein the photolatent catalyst is an organic metal compound comprising a latent catalytically active metal, and wherein the latent catalytically active metal atom in the organic metal compound has no bonds to other metal atoms. The invention further relates to a process for forming a coating on a substrate.
1 . An actinic radiation-curable coating composition comprising a compound having at least two isocyanate groups, a compound having at least two hydroxyl groups, a sensitizer, and a photolatent catalyst for the isocyanate-hydroxyl addition reaction, wherein the photolatent catalyst is an organic metal compound comprising a catalytically active metal, and wherein the catalytically active metal atom in the organic metal compound has no bonds to other metal atoms.
2 . An actinic radiation-curable coating composition according to claim 1 , wherein the catalytically active metal is selected from tin, bismuth, iron, and zirconium.
3 . An actinic radiation-curable coating composition according to claim 2 , wherein the catalytically active metal is tin.
4 . An actinic radiation-curable coating composition according to claim 1 , wherein the photolatent catalyst has at least one organic group attached to the metal via a photolytically cleavable bond.
5 . An actinic radiation-curable coating composition according to claim 4 , wherein the photolatent catalyst has two organic groups attached to the metal via photolytically cleavable bonds.
6 . An actinic radiation-curable coating composition according to claim 4 , wherein the at least one organic group attached to the metal via a photolytically cleavable bond is an aryl group.
7 . An actinic radiation-curable coating composition according to claim 6 , wherein the aryl group is a benzyl group.
8 . An actinic radiation-curable coating composition according to claim 1 , wherein the composition is a clear coat composition.
9 . A process of forming a coating on a substrate comprising the steps of
(a) applying an actinic radiation-curable coating composition comprising a compound having at least two isocyanate groups, a compound having at least two hydroxyl groups, and a photolatent catalyst for the isocyanate-hydroxyl addition reaction, wherein the photolatent catalyst is an organic metal compound comprising a catalytically active metal, and wherein the catalytically active metal atom in the organic metal compound has no bonds to other metal atoms, to a substrate, and
(b) irradiating the applied coating composition with actinic radiation, causing the photolatent catalyst to be activated.
10 . A process according to claim 9 , wherein the actinic radiation-curable coating composition additionally comprises a sensitizer.
11 . A process according to claim 10 , wherein the applied coating composition is irradiated with UV-A radiation.
12 . A process according to claim 9 , wherein the process is implemented for the finishing and refinishing of automobiles and transportation vehicles.
13 . A process according to claim 9 , wherein the formed coating is a layer in a multi-layer lacquer coating.
14 . A process according to claim 9 , wherein the formed coating is a top coat layer in a multi layer lacquer coating.
15 . A kit of parts for the preparation of an actinic radiation-curable coating composition comprising
a) a module A) comprising a compound having at least two isocyanate groups, and
b) a module B) comprising a compound having at least two hydroxyl groups,
and wherein in at least one of the modules A) and B), or in an additional module C), there are present a sensitizer and a photolatent catalyst for the isocyanate-hydroxyl addition reaction, wherein the photolatent catalyst is an organic metal compound comprising a catalytically active metal, and wherein the catalytically active metal atom in the organic metal compound has no bonds to other metal atoms.