Coating composition for metal substrates

Abstract

The present invention provides novel packaging coating compositions, e.g., food and beverage cans. Preferred cans typically comprise a body portion and an end portion, wherein at least one of the body and end portions are aluminum and are coated on at least one major surface with a coating composition of the present invention. Suitable coating compositions of the present invention comprise: one or more polyester resins, wherein at least one of the polyester resins has a glass transition temperature (‘Tg’) less than about 50° C., and wherein the polyester resin is formed by the reaction of one or more polyacid molecules and one or more polyol molecules; and a crosslinker. Preferred compositions are substantially free of mobile BPA and aromatic glycidyl ether compounds, e.g., BADGE, BFDGE and epoxy novalacs (e.g., NOGE) and more preferred compositions are also substantially free of bound BPA and aromatic glycidyl ether compounds. In more preferred embodiments (e.g., alcoholic beverage cans), the polyol molecules used to make the polyester resin are substantially free of NPG. The present invention also provides a method of making such cans.

What is claimed is: 
     
         1 - 25 . (canceled) 
     
     
         26 . A beverage can end coating composition comprising:
 between about 60 and 95 weight percent of one or more polyester resins, based on solids content of the coating composition, wherein the one or more polyester resins are formed by reaction of one or more polyacid molecules and one or more polyol molecules, and wherein the one or more polyols are substantially free of NPG;   a crosslinker comprising a benzoguanamine-formaldehyde resin; and   a lubricant;   wherein the coating composition includes between 10 to 50% solids, and wherein the coating composition, when applied to a cleaned and chrome-treated aluminum panel and cured for 14 seconds to a 249° C. peak metal temperature to achieve a dried film thickness of approximately 7.5 milligram per square inch and formed into a fully converted 202 standard opening beverage can end, passes less than 5 milliamps of current while being exposed for 4 seconds to an electrolyte solution containing 1% by weight of NaCl dissolved in deionized water.   
     
     
         27 . The coating composition of  claim 26 , wherein the coating composition, when applied to a cleaned and chrome-treated aluminum panel and cured for 14 seconds to a 249° C. peak metal temperature to achieve a dried film thickness of approximately 7.5 milligram per square inch and formed into a fully converted 202 standard opening beverage can end, passes less than 1 milliamps of current while being exposed for 4 seconds to an electrolyte solution containing 1% by weight of NaCl dissolved in deionized water. 
     
     
         28 . The coating composition of  claim 26 , wherein the coating composition is substantially free of BPA and aromatic glycidyl ether compounds. 
     
     
         29 . The coating composition of  claim 26 , wherein the coating composition is not made using PVC compounds. 
     
     
         30 . The coating composition of  claim 26 , wherein the lubricant comprises a Carnauba wax. 
     
     
         31 . The coating composition of  claim 26 , wherein the lubricant comprises a polyethelene type lubricant. 
     
     
         32 . The coating composition of  claim 26 , wherein the lubricant is present in the coating composition in an amount of about 0.1 to about 2%, by weight of nonvolatile material. 
     
     
         33 . The coating composition of  claim 26 , wherein the one or more polyester resins include at least one polyester resin that has a glass transition temperature of less than 50° C. 
     
     
         34 . The coating composition of  claim 26 , wherein the one or more polyester resins include at least one polyester resin that has a glass transition temperature of less than 25° C. 
     
     
         35 . The coating composition of  claim 33 , wherein the one or more polyester resins further include at least one polyester resin having a glass transition temperature of greater than 50° C. 
     
     
         36 . The coating composition of  claim 34 , wherein the one or more polyester resins further include at least one polyester resin having a glass transition temperature of greater than 50° C. 
     
     
         37 . The coating composition of  claim 26 , wherein the coating composition, when applied to a cleaned and chrome-treated aluminum panel and cured for 14 seconds to a 249° C. peak metal temperature to achieve a dried film thickness of approximately 7.5 milligram per square inch, exhibits feathering of about 0.9 mm to about 0.1 mm. 
     
     
         38 . The coating composition of  claim 26 , wherein the coating composition includes a catalyst to increase the rate of cure. 
     
     
         39 . The coating composition of  claim 26 , wherein the coating composition includes a catalyst selected from one or more of strong acids, quaternary ammonium compounds, phosphorous compounds, tin compounds, or zinc compounds. 
     
     
         40 . The coating composition of  claim 26 , wherein the coating composition includes a dodecylbenzene sulphonic acid catalyst. 
     
     
         41 . The coating composition of  claim 26 , wherein the benzoguanamine-formaldehyde resin comprises a fully alkylated benzoguanamine-formaldehyde resin. 
     
     
         42 . The coating composition of  claim 26 , wherein the coating composition includes at least 5% by weight of benzoguanamine-formaldehyde resin, based upon the total weight of the resin solids in the coating composition. 
     
     
         43 . The coating composition of  claim 26 , wherein the coating composition includes an acrylic resin. 
     
     
         44 . The coating composition of  claim 26 , wherein the acrylic resin is present in an amount of less than about 20% by weight, based upon the total weight to the resin solids in the coating composition. 
     
     
         45 . The coating composition of  claim 26 , wherein the one or more polyols comprise one or more of ethylene glycol, cyclohexane dimethanol, or 2-methyl 1,3-propanediol, and wherein the one or more polyacids comprise one or more of sebacic acid, terephthalic acid, and isophthalic acid. 
     
     
         46 . The coating composition of  claim 26 , wherein the one or more polyacids are selected from one or more of adipic, azelaic, cyclohexane dicarboxylic, fumaric, isophthalic, maleic, phthalic, sebacic, succinic, terephthalic acids and anhydrides and esters thereof. 
     
     
         47 . The coating composition of  claim 46 , wherein the one or more polyacids include maleic anhydride. 
     
     
         48 . The coating composition of  claim 26 , wherein the coating composition includes from between 10 to 30% by weight of crosslinker, based upon the total weight of resin solids in the coating composition. 
     
     
         49 . The coating composition of  claim 48 , wherein the coating composition includes from 20 to 40% solids. 
     
     
         50 . The coating composition of  claim 49 , wherein the coating composition is completely free of BPA and aromatic glycidyl ether compounds and is not made using PVC compounds; wherein the coating composition includes a catalyst to increase the rate of cure; and wherein the one or more polyester resins have a number average molecular weight between about 5,000 and 20,000 Daltons. 
     
     
         51 . An aluminum beverage can end having an interior coating formed from the coating composition of  claim 26 , wherein the coating is substantially free of BPA and aromatic glycidyl ether compounds. 
     
     
         52 . A method comprising causing the coating composition of  claim 26  to be used on a beverage can end.