Low temperature curing process and coating compositions suitable therefor

Abstract

Coatings may be cured by this process below 50° F. and at temperatures as low as -10° F. Suitable coating compositions comprise a solution in an inert organic solvent of (1) a polyaziridinyl adduct having more than one aziridinyl hydroxyalkyl group per molecule and (2) a coreactant which may be a dicarboxylic acid anhydride or a polyfunctional material having more than one anhydride, .[.oxirane.]. .Iadd.glycidyl.Iaddend., thiol, sulfonic acid or carboxylic group per molecule.

What is claimed is: 
     
       1. A low temperature curing process for the preparation of films and coatings which comprises (a) dissolving a polyaziridinyl adduct having more than one aziridinyl hydroxyalkyl group per molecule and a coreactant for said adduct in a volatile, inert organic solvent to provide a coating solution thereof, wherein said coreactant is a dicarboxylic acid anhydride or a polyfunctional material having more than one anhydride, .[.oxirane.]. .Iadd.glycidyl.Iaddend., sulfonic acid or carboxylic acid group per molecular and wherein the proportions of said adduct to said coreactant on an equivalent basis ranges from about 0.5/1 to about 2/1, respectively;   (b) applying said coating solution in a filmiform layer; and   (c) allowing said solvent to evaporate and the coating composition to cure by exposing said layer to a temperature below about 50° F. for a time sufficient for said adduct and said coreactant to react.   
     
     
       2. The process of claim 1 wherein said solution contains about equivalent proportions of said adduct to said coreactant. 
     
     
       3. The process of claim 1 wherein said curing temperature ranges from about -10° F. to about 50° F. 
     
     
       4. The process of claim 1 wherein said polyaziridinyl adduct is prepared by reacting an alkylenimine with a polyepoxide having more than one glycidyl group per molecule in the proportions of at least about one mole of the alkylenimine per each glycidyl group. 
     
     
       5. The process of claim 4 wherein said polyepoxide is a polyglycidyl ether of a polyhydric alcohol or a polyhyric phenol. 
     
     
       6. The process of claim 5 wherein said polyepoxide is a polyglycidyl ether of a dihydric phenol. 
     
     
       7. The process of claim 6 wherein said dihydric phenol is bisphenol A. 
     
     
       8. The process of claim 4 wherein said alkylenimine is ethylenimine or propylenimine. 
     
     
       9. The process of claim 1 wherein said solution further contains an acid catalyst. 
     
     
       10. A composition which is curable at temperatures below 50° F. consists of a volatile, inert organic solvent solution of (a) a polyaziridinyl adduct having more than one aziridinyl hydroxyalkyl group per molecule, and   (b) a coreactant which is a dicarboxylic acid anhydride or a polyfunctional material having more than one anhydride, .[.oxirane.]. .Iadd.glycidyl.Iaddend., or sulfonic acid group per molecule; wherein the proportions of said adduct to said coreactant on an equivalent basis ranges from about 0.5/1 to about 2/1, respectively.     
     
     
       11. The composition of claim 10 wherein said polyaziridinyl adduct is prepared by reacting an alkylenimine with a polyepoxide having more than one glycidyl group per molecule in the proportions of at least about one mole of the alkylenimine per each glycidyl group. 
     
     
       12. The composition of claim 11 wherein said polyepoxide is a polyglycidyl ether of a polyhydric alcohol or a polyhydric phenol. 
     
     
       13. The composition of claim 12 wherein said polyepoxide is a polyglycidyl ether of a dihydric phenol. 
     
     
       14. The composition of claim 13 wherein said dihydric phenol is bisphenol A. 
     
     
       15. The composition of claim 11 wherein said alkylenimine is ethylenimine or propylenimine. 
     
     
       16. The composition of claim 10 wherein said solution contains about equivalent proportions of said adduct to said coreactant. 
     
     
       17. The composition of claim 10 wherein said coreactant is nadic methyl anhydride or a copolymer of styrene and maleic anhydride. 
     
     
       18. The composition of claim 10 wherein said coreactant is a polyepoxide having more than one glycidyl group per molecule. 
     
     
       19. The composition of claim 18 wherein said polyepoxide is a polyglycidyl ether or a polyhydric phenol or polyhydric alcohol. 
     
     
       20. The composition of claim 10 further consisting of a pigment. 
     
     
       21. The composition of claim 10 further consisting of an acid catalyst. 
     
     
       22. A composition which is curable at temperatures below 50° F. consists of a volatile, inert organic solvent solution of (a) a polyaziridinyl adduct of an alkylenimine and a polyglyicdyl ether of bisphenol A wherein said adduct has more than one aziridinyl hydroxyalkyl ether group per molecule, and   (b) a polyepoxide having more than one glycidyl ether group per molecule; wherein the proportions of said adduct to said polyepoxide on an equivalent basis ranges from about 0.5/1 to about 2/1, respectively.     
     
     
       23. The composition of claim 22 wherein said alkylenimine is ethylenimine or propylenimine. 
     
     
       24. The composition of claim 22 wherein said polyepoxide is a polyglycidyl ether of a dihydric phenol. 
     
     
       25. The composition of claim 22 wherein said solution contains about equivalent proportions of said adduct to said polyepoxide. 
     
     
       26. The composition of claim 22 further consisting of an acid catalyst. 
     
     
       27. The composition of claim 22 further consisting of a pigment.