Coating composition curable with ultraviolet radiation

Abstract

A UV radiation curable primer coating composition curable under a UV radiation emitting lamp or sunlight. The coating demonstrates improved curing time and includes ethylenically unsaturated free radically polymerizable compounds and 0.1% photoiniator or less.

1 . A UV radiation curable primer coating composition comprising 
 a. 5 to 50% by weight of one or more compounds containing one ethylenically unsaturated free-radically polymerizable group per molecule    b. 5 to 50% by weight of one or more compounds containing two or more ethylenically unsaturated free radically polymerizable groups per molecule    c. 1.0 to 60% by weight of one or more pigments, fillers and or dyes    d. 0.1 to 0.95% photoinitiators    e. 0 to 20% by weight of volatile organic solvent and    f. 0.1 to 10% by weight of additives,    wherein said coating is curable to a non-tacky surface under a UVA radiation emitting lamp within 2 minutes and in sunlight within 5 minutes.    
     
     
         2 . A primer coating composition according to  claim 1  wherein the compound A is selected from the group consisting of 1-octene, 1-hexene, 1-decene, vinyl acetate, styrene, alpha-methylstyrene, p-methylstyrene, esters of methacrylic acid and esters of acrylic acid.  
     
     
         3 . A primer coating according to  claim 1  wherein compound A is selected from butyl acrylate, t-butyl acrylate, isobornyl acrylate, isodecyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate and octyl acrylate.  
     
     
         4 . A primer coating composition according to  claim 1  wherein compound B is selected from the group consisting of urethane acrylates, diacrylates, triacrylates, polyfunctional acrylates and mixtures thereof.  
     
     
         5 . A primer coating according to  claim 1  wherein compound B is selected from the group consisting of hexanediol diacrylate, tripropyleneglycol diacrylate, trimethylolpropane triacrylate, alkoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, urethane acrylates and unsaturated polyesters, and mixtures thereof.  
     
     
         6 . A primer coating according to  claim 1  wherein compound B is selected from the group consisting of di- and poly-functional urethane acrylates.  
     
     
         7 . A primer coating composition according to  claim 1  wherein the pigment to binder ratio is between 0.8 and 2.0.  
     
     
         8 . A primer coating composition according to  claim 1  wherein the pigment to binder ratio is between 1.2 and 1.8.  
     
     
         9 . A primer coating composition according to  claim 1  wherein the photoinitiator comprises a compound selected from the group consisting of acyl phospine oxides and benziketals.  
     
     
         10 . A primer coating composition according to  claim 1  wherein said coating is cured by 5 minute exposure to outdoor light having an intensity of 45-65 mJoules/cm 2  and demonstrates 95% post humidity test adhesion.  
     
     
         11 . A process for applying a primer coating composition to a substrate comprising 
 A. applying a UV radiation curable primer to a substrate;    B. curing the primer with a source selected from the group consisting of one or more UV lamps having a UV-B:UV-A ratio of 1:1 or less, and natural outdoor light having a wavelength between 320 and 430 nm, and mixtures thereof,    wherein the UV radiation curable primer comprises    a. 5 to 50% by weight of one or more compounds containing one ethylenically unsaturated free-radically polymerizable group per molecule,    b. 5 to 50% by weight of one or more compounds containing two or more ethylenically unsaturated free radically polymerizable groups per molecule,    c. 1.0 to 60% by weight of one or more pigments, fillers and or dyes,    d. 0.1 to 0.95% photoinitiators,    e. 0 to 20% by weight of volatile organic solvent and    f. 0.1 to 10% by weight of additives.    
     
     
         12 . A process according to  claim 11  wherein the coating applied comprises compound A is selected from the group consisting of 1-octene, 1-hexene, 1-decene, vinyl acetate, styrene, alpha-methylstyrene, p-methylstyrene, esters of methacrylic acid and esters of acrylic acid and mixtures thereof.  
     
     
         13 . A process according to  claim 11  wherein the coating applied comprises compound A selected from butyl acrylate, t-butyl acrylate, isobornyl acrylate, isodecyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate and octyl acrylate and mixtures thereof.  
     
     
         14 . A process according to  claim 11  wherein the coating applied comprises compound B selected from the group consisting of urethane acrylates, urethane diacrylates, tri- and polyfunctional urethane acrylates and mixtures thereof.  
     
     
         15 . A process according to  claim 11  wherein the coating applied comprises a pigment to binder ratio between 0.8 and 2.0.  
     
     
         16 . A process according to  claim 11  wherein the coating applied comprises a pigment to binder ratio between 1.2 and 1.8.  
     
     
         17 . A process according to  claim 11  wherein a UV light source is applied wherein the UVA intensity is from 0.8 to 1.6 Joules/cm 2 , the UVB intensity is from 0.001 to 0.5 Joules/cm 2  and the UVC intensity is from 0.001 to 0.3 Joules/cm 2 .  
     
     
         18 . A process according to  claim 11  wherein the coating is cured under natural light conditions, said light providing an intensity of 5-100 mJoules/cm 2 .  
     
     
         19 . A process according to  claim 11  wherein the substrate to which the coating is applied to a substrate comprising an automotive vehicle.  
     
     
         20 . A process according to  claim 11  wherein the coating process comprises application of the primer coating in the repair of an automotive vehicle.