Autoxidisable architectural coating compositions
View Patent ↗An autoxidisable architectural coating composition suitable for application to surfaces found in and around buildings at ambient temperatures and in natural daylight wherein surface autoxidation of the composition is promoted by a combination of low concentrations of metal ions (especially manganese or vanadium) and 2,2-dimethoxy-1,2-diphenylethan-1-one as photoinitiator. The composition avoids the need to use more than trace amounts cobalt ions which are rumoured to be carcinogenic yet achieves adequately fast rates of autoxidation. Preferably the use of cobalt is avoided altogether. The use of the low concentrations of the other metal ions reduces discoloration of the compositions often to levels below what is achieved using conventional cobalt promoters. Also a modification in which surface autoxidation is promoted by a combination of 2,2-dimethoxy-1,2-diphenylethan-1-one and trace amounts of cobalt ions in the absence of other surface autoxidation promoting metal ions. Finally, a method for applying the autoxidisable coatings to surfaces under ambient temperatures in which they are subject to natural daylight or similar low energy irradiation is disclosed.
1. An autoxidisable architectural coating composition suitable for application to surfaces at ambient temperatures and in natural daylight which composition contains an autoxidisable binder polymer and a promoter system for promoting autoxidation of the autoxidisable binder polymer wherein the system comprises
a) less than 0.01 wt % of cobalt ions based on the weight of the autoxidisable binder polymer in the coating composition,
b) from 0.001 to 0.06 wt % (based on the weight of autoxidisable binder polymer in the coating composition) of metal ions other than cobalt ions being metal ions which promote surface autoxidation,
c) 2,2-dimethoxy-1,2-diphenylethan-1-one
and wherein the binder polymer is free of moieties derived from isocyanate functional ethylenically unsaturated compounds.
2. A coating composition according to claim 1 wherein the composition is free of cobalt ions.
3. A coating composition according to claim 1 wherein the composition contains a sufficient through promoter for the through promoter to provide to the coating composition from 0.5 to 2 wt % of metal ions based on the weight of the autoxidisable binder polymer in the composition.
4. A coating composition according to claim 1 wherein the composition comprises an additional photoinitiator in combination with 2,2-dimethoxy-1,2-diphenylethan-1-one.
5. A coating composition according to claim 4 wherein the additional photoinitiator is camphorquinone.
6. A coating composition according to claim 1 wherein the metal ions other than cobalt are manganese and/or vanadium.
7. A surface coated with a coating according to claim 1 .
8. A method for applying a dried coat of an architectural coating composition to a surface in which a liquid coating of the composition is applied to the surface at ambient temperatures wherein the composition contains an autoxidisable binder polymer and a system for promoting surface autoxidation of the autoxidisable binder polymer and wherein the system as is described in any one of claims 1 and 2 - 6 and the coating composition is exposed to low energy irradiation by light of wavelength in the range 200 to 750 nm.
9. A method according to claim 8 wherein the light is natural daylight.
10. A method according to claim 8 wherein the light is from a 40 to 250 watt source.
11. A coating composition according to claim 3 wherein the composition is free of cobalt ions.
12. A coating composition according to claim 2 wherein the composition contains sufficient through promoter for the through promoter to provide to the coating composition from 0.5 to 2 wt % of metal ions based on the weight of the autoxidisable binder polymer in the composition.
13. A coating composition according to claim 12 wherein the composition comprises an additional photoinitiator in combination with 2,2-dimethoxy-1,2-diphenylethan-1-one.
14. A coating composition according to claim 13 wherein the additional photoinitiator is camphorquinone.
15. A coating composition according to claim 13 wherein the metal ions other than cobalt are manganese and/or vanadium.
16. A coating composition according to claim 12 wherein the surface promoting composition contains from 0.001 to 0.007 wt % of cobalt ions (based on the weight of autoxidisable binder polymer in the coating composition) as its only surface autoxidation promoting metal ions.
17. A coating composition according to claim 1 wherein the 2,2-dimethoxy-1,2-diphenylethan-1-one is present in an amount of from 0.3 to 2.0 wt % based on the weight of the autoxidisable binder polymer in the composition.
18. A coating composition according to claim 1 wherein the autoxidisable binder polymer consists of autoxidisable long oil alkyd present in an amount of 48.06% and polyamide modified autoxidisable alkyd thixotrope present in an amount of 7.33% based on the weight of the coating composition, wherein the 2,2-dimethoxy-1,2-diphenylethan-1-one is present in an amount of 1.02% based on the weight of the autoxidisable binder polymer, and wherein the coating composition further comprises, based on the weight of the autoxidisable binder polymer:
bentonite clay
0.20%;
rutile
30.55%;
aliphatic hydrocarbon
10.46%;
zirconium octoate through dry promoter
0.55%;
calcium octoate through dry promoter
1.60%;
dimethyl silicone
0.10%;
dapro 5005
0.13%.
19. A surface coated with a coating according to claim 18 .