Coating compositions comprising diisocyanate chain extended bisaspartates

Abstract

This invention relates to a coating composition, a method for coating of a metallic substrate as well as the use of the coating in a two-component coating composition.

The invention claimed is: 
     
       1. A coating composition comprising:
 a) a chain-extended aspartate prepolymer, wherein the chain-extended aspartate prepolymer
 x) is free of isocyanate groups, 
 xi) has an NH equivalent weight of from 250 to 1,000 g, and 
 xii) is a reaction product of
 i) a mixture comprising at least one di-aspartic acid ester and at least one amino-functional mono-aspartic acid ester, wherein the molar ratio between the at least one di-aspartic acid ester and the at least one amino-functional mono-aspartic acid ester is from 99.5:0.5 to 50:50, and 
 ii) at least one polyisocyanate, 
 
 
 b) at least one curing agent having free isocyanate groups, and 
 c) at least one UV absorber consisting of oxanilide or a derivative thereof and/or benzotriazole or a derivative thereof. 
 
     
     
       2. The coating composition of  claim 1 , wherein the at least one di-aspartic acid ester and/or the at least one amino-functional mono-aspartic acid ester is/are a reaction product of at least one dialkyl maleate and/or dialkyl fumarate and at least one primary diamine. 
     
     
       3. The coating composition of  claim 2 , wherein the at least one dialkyl maleate is selected from the group consisting of dimethyl maleate, diethyl maleate, di-n-butyl maleate, di-iso-butyl maleate, di-tert-butyl maleate, diamyl maleate, di-n-octyl maleate, dilauryl maleate, dicyclohexyl maleate, and di-tert-butylcyclohexyl maleate and/or the at least one dialkyl fumarate is selected from the group consisting of dimethyl fumarate, diethyl fumarate, di-n-butyl fumarate, di-iso-butyl fumarate, di-tert-butyl fumarate, diamyl fumarate, di-n-octyl fumarate, dilauryl fumarate, dicyclohexyl fumarate, and di-tert-butylcyclohexyl fumarate. 
     
     
       4. The coating composition of  claim 2 , wherein the at least one primary diamine is selected from the group consisting of ethylene diamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,3-diaminopentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethylhexane, 2,2,4-trimethyl-1, 6-diaminohexane, 2,4,4-trimethyl-1, 6-diaminohexane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,3-cyclohexane diamine, 1,4-cyclohexane diamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 2,4-hexahydrotolylene diamine, 2,6-hexahydrotolylene diamine, 2,4′-diamino-dicyclohexyl methane, 4,4′-diamino-dicyclohexyl methane, 3,3′-dialkyl-4, 4′-diaminodicyclohexylmethanes, 3, 3′-dimethyl-4, 4′-diaminodicyclohexyl methane, 3,3′-diethyl-4,4′-diaminodicyclohexylmethane, 2-methyl-1,5-pentanediamine, 1,3-xylenediamine, 1,4 xylylenediamine, tetramethyl xylylenediamine, and 4,4′-diaminodicyclohexyl methane (PACM). 
     
     
       5. The coating composition of  claim 1 , wherein the at least one di-aspartic acid ester and/or the at least one amino-functional mono-aspartic acid ester has/have been obtained by reacting at least one dialkyl maleate and/or dialkyl fumarate and at least one primary diamine in an equivalent ratio of dialkyl maleate and/or dialkyl fumarate to primary diamine from 2:1 to 1:4. 
     
     
       6. The coating composition of  claim 5 , wherein the at least one dialkyl maleate is selected from the group consisting of dimethyl maleate, diethyl maleate, di-n-butyl maleate, di-iso-butyl maleate, di-tert-butyl maleate, diamyl maleate, di-n-octyl maleate, dilauryl maleate, dicyclohexyl maleate, and di-tert-butylcyclohexyl maleate and/or the at least one dialkyl fumarate is selected from the group consisting of dimethyl fumarate, diethyl fumarate, di-n-butyl fumarate, di-iso-butyl fumarate, di-tert-butyl fumarate, diamyl fumarate, di-n-octyl fumarate, dilauryl fumarate, dicyclohexyl fumarate, and di-tert-butylcyclohexyl fumarate. 
     
     
       7. The coating composition of  claim 5 , wherein the at least one primary diamine is selected from the group consisting of ethylene diamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,3-diaminopentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethylhexane, 2,2,4- and 2,4,4-trimethyl-1, 6-diaminohexane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,3-cyclohexane diamine, 1,4-cyclohexane diamine, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 2,4-hexahydrotolulene diamine, 2,6-hexahydrotoluylene diamine, 2,4′-diamino-dicyclohexyl methane, 4,4′-diamino-dicyclohexyl methane, 3,3′-dialkyl-4, 4′-diaminodicyclohexylmethanes, 3, 3′-dimethyl-4, 4′-diaminodicyclohexyl methane, 3,3′-diethyl-4,4′-diaminodicyclohexylmethane, 2-methyl-1,5-pentanediamine, and 1,3-xylylenediamine, 1,4 xylylenediamine, tetramethyl xylylenediamine, and 4,4′-diaminodicyclohexyl methane (PACM). 
     
     
       8. The coating composition of  claim 1 , wherein the at least one polyisocyanate and/or curing agent having free isocyanate groups is selected from the group consisting of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), 4,4′-diisocyanatocyclohexylmethane, cyclotrimers of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, biurets of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, hexamethylene diisocyanate (HDI), 1-bis(isocyanatocyclohexyl)-methane, 1,1,6,6-tetramethyl-hexamethylene diisocyanate, p- or m-tetramethylxylylene diisocyanate, and 2,2′,5 trimethylhexane diisocyanate. 
     
     
       9. The coating composition of  claim 1 , wherein the mixture of paragraph i) comprises NH and NH 2  groups and wherein the chain-extended aspartate prepolymer has been obtained by reacting the mixture comprising at least one di-aspartic acid ester and at least one amino-functional mono-aspartic acid ester with the at least one polyisocyanate in an equivalent ratio of NH and NH 2  groups in the mixture to NCO groups of the at least one polyisocyanate from 2.0:0.2 to 2.0:1.8. 
     
     
       10. The coating composition of  claim 1 , wherein the chain-extended aspartate prepolymer comprises urea groups and an equivalent ratio of aspartate groups to urea groups from 10:1 to 1:0.9. 
     
     
       11. The coating composition of  claim 1 , wherein
 a) the oxanilide or the derivative thereof is N-(2-ethoxyphenyl)-N-(4-isododecylphenyl) oxamide, and/or 
 b) the benzotriazole or the derivative thereof is selected from the group consisting of benzotriazole, 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, 2-(2-hydroxy-3, 5-di-tert. amyl-phenyl)-2H-benzotriazole, 2 [2-hydroxy-3,5-di (1,1-dimethylbenzyl) phenyl]-2H-benzotriazole, 2-(2-hydroxy-3-tert. butyl-5-iso-octyl propionate)-2H-benzotriazole, and reaction product of 2-(2-hydroxy-3-tert. butyl-5-methyl propionate)-2H-benzotriazole and polyethylene ether glycol having a weight average molecular weight of 300. 
 
     
     
       12. The coating composition of  claim 1 , wherein the coating composition further comprises at least one compound selected from the group consisting of curing catalysts, antioxidants, additives, pigments, extenders, compounds with at least one alkoxy silane group and/or at least one epoxy group, hydroxyl functional binders, acrylics, polyesters, HALS derivatives, inorganic rheology control agents, silica, and organic sag control agents based. 
     
     
       13. The coating composition of  claim 1 , wherein the coating composition is a two-component coating composition. 
     
     
       14. A method for coating of a metallic substrate, the method comprising at least the steps of:
 a) applying the coating composition of  claim 1  to at least a portion of a metallic substrate to be coated, and 
 b) curing the coating composition of step a). 
 
     
     
       15. The method of  claim 14 , wherein multiple layers of coating compositions are applied to at least a portion of the metallic substrate and the multiple layers are applied either wet on wet or by first curing one layer before applying the next layer of the multiple layers. 
     
     
       16. The coating composition of  claim 1 , further comprising an antioxidant component. 
     
     
       17. The coating composition of  claim 16 , wherein the antioxidant component comprises (Al) at least one sterically hindered phenol antioxidant and (A2) at least one organophosphite antioxidant.