Lubricated metallic container stocks and method of preparing the same and applying organic coating thereto

Abstract

Metallic container stocks are lubricated with citric acid esters. The improved lubricated container stocks of the invention are characterized by excellent wettability and adhesion of organic coatings in general and especially epoxy resin coating compositions. The citric acid ester lubricants are pharmacologically safe and are easily applied at low cost by electrostatic deposition and other methods presently used for applying prior art lubricating agents. The method of the invention is especially useful in lubricating tinplate strip, blackplate strip, blackplate strip having a chromium-containing coating thereon, and aluminum strip of container stock gauge with citric acid ester lubricants having the following structural formula: ##STR1## wherein R 1 , R 2 and R 3 are individually selected from the group consisting of hydrogen and alcoholic residual containing 1-18 carbon atoms, R 4 is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-18 carbon atoms, and at least one of R 1 , R 2 and R 3 is an alcoholic residue. The invention further provides a novel method of applying an organic coating on lubricated metallic container stocks.

We claim: .[.1. A metalic container stock having a thin substantially uniform film of a citric acid ester lubricant on at least one surface area thereof, the said citric acid ester lubricant consisting essentially of at least one citric acid ester of an alcohol containing 1-10 carbon atoms and being present in an amount of about 0.05-1.0 gram for each 62,720 square inches of lubricated surface area..]. .[.2. The lubricated container stock of claim 1 wherein the citric acid ester lubricant is present in an amount of about 0.15-0.40 gram for each 62,720 square inches of lubricated surface area..]. .[.3. The lubricated container stock of claim 1 wherein the container stock is selected from the group consisting tinplate, blackplate, blackplate having a chromium-containing coating thereon, and metallic aluminum of container stock gauge..]. .[.4. The lubricated container stock of claim 3 wherein the container stock is blackplate..]. .[.5. The lubricated container stock of claim 3 wherein the container stock is blackplate having a chromium-containing coating thereon..]. .[.6. The lubricated container stock of claim 3 wherein the container stock is metallic aluminum of container stock gauge..]. .[.7. The lubricated container stock of claim 3 wherein the container stock is tinplate..]. .[.8. The lubricated container stock of claim 1 wherein the said film consists essentially of at least one citric acid ester lubricant having the structural formula: ##STR3## wherein R 1 , R 2  and R 3  are individually selected from the group consisting of hydrogen and alcoholic residua containing 1-10 carbon atoms, R 4  is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-10 carbon atoms, and at least one of 
     
        R 1 , R 2  and R 3  is an alcoholic residue..]. .[.9.  The lubricated container stock of claim 8 wherein R 1 , R 2  and R 3  are alcoholic residua containing 1-4 carbon atoms..]. .[.10. The lubricated container stock of claim 8 wherein R 1 , R 2  and R 3  are alcoholic residua containing 1-4 carbon atoms, and R 4  is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-4 carbon atoms..]. .[.11. The lubricated container stock of claim 8 wherein the citric acid ester lubricant consists essentially of at least one substance selected from the group consisting of triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, acetyl tri-2-ethylhexyl citrate, and admixtures thereof..]. .[.12. The lubricated container stack of claim 8 wherein the citric acid ester lubricant consists essentially of acetyl tributyl citrate..]. .[.13. The lubricated container stack of claim 8 wherein the citric acid ester consists essentially of acetyl tributyl citrate and is applied in an amount of about 0.15-0.40 gram for each 62,720 square inches of lubricated surface area..]. .[.14. The lubricated container stock of claim 3 wherein the container stock is tinplate and a film comprising at least one citric acid ester lubricant having the structural formula: ##STR4## wherein R 1 , R 2  and R 3  are individually selected from the group consisting of hydrogen and alcoholic residua containing 1-10 carbon atoms, R 4  is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-10 carbon atoms, and at least one of 
     
     
        R 1 , R 2  and R 3  is an alcoholic residue..]. .[.15.  The lubricated container stock of claim 14 wherein the citric acid ester lubricant is present in an amount of about 0.15-0.40 gram for each 62,720 square inches of lubricated surface area..]. .[.16. The lubricated container stock of claim 14 wherein R 1 , R 2  and R 3  are alcoholic residua containing 1-4 carbon atoms..]. .[.17. The lubricated container stock of claim 14 wherein R 1 , R 2  and R 3  are alcoholic residua containing 1-4 carbon atoms, and R 4  is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-4 carbon atoms..]. .[.18. The lubricated container stock of claim 14 wherein the citric acid ester lubricant comprises at least one substance selected from the group consisting of triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, acetyl tri-2-ethylhexyl citrate and admixtures thereof..]. .[.19. The lubricated container stock of claim 14 wherein the citric acid ester lubricant comprises acetyl tributyl citrate..]. .[.20. The lubricated container stock of claim 19 wherein the citric acid ester lubricant is present in an amount of about 0.15-0.40 gram for each 62,720 square inches of lubricated 
     
     
        surface area..]. 21. In a method of applying an organic coating to metallic container stock wherein a layer of an initially fluid organic varnish, lacquer or enamel for the container stock is applied to at least a portion of the surface area of the container stock and thereafter the layer of the initially fluid organic varnish, lacquer or enamel is hardened to form the said organic coating, the improvement which comprises improving the wettability of the said surface area of the container stock by the initially fluid organic varnish, lacquer or enamel by .[.employing thereon as the said lubricant a substantially uniform film.]. .Iadd.applying to the surface area of the container stock only a substantially uniform film of a lubricant .Iaddend.consisting essentially of a citric acid ester of an alcohol containing 1-10 carbon atoms, the citric acid ester being present in an amount of about 0.05-1.0 gram for each 62,720 square inches of lubricated surface area of the container 
     
     
        stock. 22. The method of claim 21 wherein the citric acid ester lubricant is present in an amount of about 0.15-0.40 gram for each 62,720 square 
     
     
        inches of lubricated surface area. 23. The method of claim 21 wherein the metallic container stock is selected from the group consisting of tinplate, blackplate, blackplate having a chromium-containing coating 
     
     
        thereon, and metallic aluminum of container stock gauge. 24. The method of 
     
     
        claim 23 wherein the container stock is blackplate. 25. The method of claim 23 wherein the container stock is blackplate having a 
     
     
        chromium-containing coating thereon. 26. The method of claim 23 wherein 
     
     
        the container stock is metallic aluminum of container stock gauge. 27. The 
     
     
        method of claim 23 wherein the container stock is tinplate. 28. The method of claim 21 wherein the citric acid ester lubricant has the structural formula: ##STR5## wherein R 1 , R 2  and R 3  are individually selected from the group consisting of hydrogen and alcoholic residua containing 1-10 carbon atoms, R 4  is selected from the group consisting of hydroben and carboxylic acid radicals containing 1-10 carbon atoms, and at least one of 
     
     
        R 1 , R 2  and R 3  is an alcoholic residue. 29. The method of claim 28 wherein R 1 , R 2  and R 3  are alcoholic residua 
     
     
        containing 1-4 carbon atoms. 30. The coated metallic container stock 
     
     
        prepared by the method of claim 21. 31. The method of claim 21 wherein the citric acid ester lubricant .[.comprises.]. .Iadd.consists of .Iaddend.at least one substance selected from the group consisting of triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl 
     
     
        citrate, acetyl tri-2-ethylhexyl citrate, and admixtures thereof. 32. The method of claim 21 wherein the citric acid ester lubricant .[.comprises.]. 
     
     
        .Iadd.consists of .Iaddend.acetyl tributyl citrate. 33. The method of claim 21 wherein the citric acid ester .[.comprises.]. .Iadd.consists of .Iaddend.acetyl tributyl citrate and is applied in an amount of about 0.15-0.40 gram for each 62,720 square inches of lubricated surface area. 
     
     
          . The method of claim 21 wherein the citric acid ester is of an alcohol 
     
     
        containing 1-4 carbon atoms. 35. The method of claim 23 wherein the container stock is tinplate and the citric acid ester lubricant has the structural formula: ##STR6## wherein R 1 , R 2  and R 3  are individually selected from the group consisting of hydrogen and alcoholic residua containing 1-10 carbon atoms, R 4  is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-10 carbon atoms, and at least one of 
     
     
        R 1 , R 2  and R 3  is an alcoholic residue. 36. The method of claim 35 wherein the citric acid ester lubricant is present in an amount of about 0.15-0.40 gram for each 62,720 square inches of lubricated 
     
     
        surface area. 37. The method of claim 35 wherein R 1 , R 2  and 
     
     
        R 3  are alcoholic residua containing 1-4 carbon atoms. 38. The method of claim 35 wherein R 1 , R 2  and R 3  are alcoholic residua containing 1-4 carbon atoms, and R 4  is selected from the group consisting of hydrogen and carboxylic acid radicals containing 1-4 carbon 
     
     
        atoms. 39. The method of claim 35 wherein the citric acid ester lubricant comprises at least one substance selected from the group consisting of triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, acetyl tri-2-ethylhexyl citrate, and admixtures thereof. 
     
     
        0. The method of claim 35 wherein the citric acid ester lubricant comprises acetyl tributyl citrate.