Crosslinked coating compositions for packaging articles such as food and beverage containers

Abstract

A method of forming a coating on a food or beverage container, which includes spraying a coating composition onto an interior surface of the food or beverage container, where the coating composition includes a latex copolymer and a metal drier or crosslinking agent. The latex copolymer is a reaction product of monomers that include (a) one or more styrene-mimicking monomers containing one or more cyclic groups and one or more ethylenically-unsaturated groups, at least a portion of such styrene-mimicking monomers being polycyclic monomers containing ring unsaturation, and (b) one or more other ethylenically-unsaturated monomers. Preferably, the coating composition is substantially free of each of BPA, PVC, other halogenated monomers, and optionally styrene. The method may also include curing the sprayed coating composition, thereby providing the coating on the interior surface of the food or beverage container.

1 . A method of forming a coating on a food or beverage container, the method comprising:
 receiving a coating composition having an acrylic copolymer dispersed in a liquid carrier and mixed with one or both of a metal drier or crosslinking agent, wherein the acrylic copolymer is a reaction product of:
 one or more monomers containing one or more cyclic groups and one or more ethylenically-unsaturated groups, at least a portion of such crosslinkable monomers being polycyclic monomers containing ring unsaturation, and 
 one or more other ethylenically-unsaturated monomers; and 
   applying the coating composition to a substrate prior to or after forming the substrate into a food or beverage container, or a portion thereof.   
     
     
         2 . The method of  claim 1 , wherein applying the coating composition to the substrate comprises:
 spraying the coating composition onto an interior surface of the food or beverage container; and   curing the sprayed coating composition to substantially remove the aqueous carrier, and provide the coating on the interior surface of the food or beverage container.   
     
     
         3 . The method of  claim 1  or  2 , wherein the average viscosity of the coating composition ranges from about 15 seconds to about 25 seconds, pursuant to the Viscosity Test. 
     
     
         4 . The method of  claim 2 , wherein the coating composition is spray applied onto an interior surface of an aluminum beverage can including a body portion and a bottom end portion, and where the cured coating has a coating thickness ranging of from about 0.7 milligrams/square-inch (mg/inch 2 ) (0.11 mg/cm 2 ) to about 2.5 mg/inch 2  (0.39 mg/cm 2 ). 
     
     
         5 . The method of any of the preceding claims, wherein the monomers used to produce the acrylic copolymer are substantially free of each of BPA, PVC and other halogenated monomers. 
     
     
         6 . The method of any of the preceding claims, wherein the monomers used to produce the acrylic copolymer are substantially free of styrene. 
     
     
         7 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation constitute at least 1% by weight of the monomers used to produce the any of the preceding claims copolymer. 
     
     
         8 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation constitute less than 50% by weight of the monomers used to produce the emulsion-polymerized latex copolymer. 
     
     
         9 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation comprise bridged cyclic groups. 
     
     
         10 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation comprise (meth)acrylate monomers. 
     
     
         11 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation comprise (meth)acrylamide or vinyl acetate monomers. 
     
     
         12 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation comprise octahydronapthalene (meth)acrylate, norbornene (meth)acrylamide, tricyclodecenyl (meth)acrylamide, octahydronapthalene (meth)acrylamide, tricyclodecenyl vinyl acetate, norbornene vinyl acetate, octahydronapthalene vinyl acetate, other vinyl variations thereof, or a mixture thereof. 
     
     
         13 . The method of any of the preceding claims, wherein the polycyclic monomers containing ring unsaturation comprise norbornene (meth)acrylate or tricyclodecenyl (meth)acrylate. 
     
     
         14 . The method of any of the preceding claims, wherein the one or more other ethylenically-unsaturated monomers are each substantially free of cyclic groups. 
     
     
         15 . The method of any of the preceding claims, wherein the one or more other ethylenically-unsaturated monomers comprise:
 one or more ethylenically-unsaturated, acid- or anhydride-functional monomers;   one or more non-cyclic (meth)acrylates; or   combinations thereof.   
     
     
         16 . The method of  claim 15 , wherein the one or more ethylenically-unsaturated, acid-functional monomers constitute at least 3% by weight of the acrylic copolymer, based on the total weight of the monomers used to produce the acrylic copolymer. 
     
     
         17 . The method of  claim 15 , wherein the one or more non-cyclic (meth)acrylates have a concentration ranging from 10% by weight to 70% by weight, based on the total weight of the monomers used to produce the acrylic copolymer. 
     
     
         18 . The method of  claim 15 , wherein the one or more other ethylenically-unsaturated monomers comprise one or more oxirane-functional monomers. 
     
     
         19 . The method of  claim 18 , wherein the one or more oxirane-functional monomers are selected from the group consisting of glycidyl acrylate, glycidyl methacrylate, and combinations thereof. 
     
     
         20 . The method of any of the preceding claims, wherein the one or more other ethylenically-unsaturated monomers further comprise one or more multi-functional monomers having two or more ethylenically-unsaturated groups. 
     
     
         21 . The method of any of the preceding claims, wherein the one or more other ethylenically-unsaturated monomers further comprise one or more polymerizable surfactants. 
     
     
         22 . The method of any of the preceding claims, wherein the acrylic copolymer becomes crosslinked by reacting with itself in the presence of the metal drier. 
     
     
         23 . The method of any of the preceding claims, wherein the acrylic copolymer becomes crosslinked by reacting with the crosslinking agent. 
     
     
         24 . The method of any of the preceding  claims 1 , wherein the coating has a glass transition temperature greater than 50° C. 
     
     
         25 . The method of any of the preceding claims, wherein the glass transition temperature of the coating ranges from about 60° C. to about 120° C. 
     
     
         26 . The method of any of the preceding claims, wherein the acrylic copolymer comprises an emulsion-polymerized latex copolymer. 
     
     
         27 . The method of any of the preceding claims, wherein the liquid carrier comprises an aqueous carrier. 
     
     
         28 . The method of  claim 27 , wherein the aqueous carrier comprises water and optionally an organic solvent. 
     
     
         29 . An article comprising a food or beverage container, or a portion thereof, including:
 a metal substrate; and   an inside spray coating disposed on at least a portion of the metal substrate, wherein the coating is produced from a sprayable composition comprising an acrylic copolymer dispersed in a liquid carrier and mixed with one or both of a metal drier or crosslinking agent, wherein the acrylic copolymer is a reaction product of monomers comprising:
 one or more styrene-mimicking monomers containing one or more cyclic groups and one or more ethylenically-unsaturated groups, at least a portion of such styrene-mimicking monomers being polycyclic monomers containing ring unsaturation, and 
 one or more other ethylenically-unsaturated monomers. 
   
     
     
         30 . The article of  claim 29 , wherein the monomers used to produce the emulsion-polymerized latex copolymer are substantially free of each of BPA, PVC, other halogenated monomers, and optionally styrene. 
     
     
         31 . An inside spray coating composition comprising:
 a liquid carrier; and   an acrylic copolymer dispersed in the liquid carrier and mixed with one or both of a metal drier or crosslinking agent, wherein the acrylic copolymer is a reaction product of monomers comprising:
 one or more monomers containing one or more cyclic groups and one or more ethylenically-unsaturated groups, at least a portion of such monomers being polycyclic monomers containing ring unsaturation, and 
 one or more other ethylenically-unsaturated monomers; and 
   
       wherein the coating composition has an average viscosity ranging from about 5 seconds to about 40 seconds, pursuant to the Viscosity Test; and has a resin solids content ranging from about 10% by weight to about 30% by weight, based on a total weight of the coating composition. 
     
     
         32 . The composition of  claim 31 , wherein the monomers used to produce the acrylic copolymer are substantially free of each of BPA, PVC, other halogenated monomers, and optionally styrene. 
     
     
         33 . An emulsion-polymerized latex copolymer, wherein the emulsion-polymerized latex polymer is a reaction product of monomers comprising:
 one or more cross-linking monomers containing one or more cyclic groups and one or more ethylenically-unsaturated groups, at least a portion of such styrene-mimicking monomers being polycyclic monomers containing ring unsaturation, and   one or more other ethylenically-unsaturated monomers, and   
       the copolymer is dispersed in an aqueous carrier and mixed with one or both of a metal drier or crosslinking agent. 
     
     
         34 . The copolymer of  claim 33 , wherein the monomers used to produce the emulsion-polymerized latex copolymer are substantially free of each of BPA, PVC, other halogenated monomers, and optionally styrene. 
     
     
         35 . An acrylic copolymer, wherein the acrylic copolymer is a reaction product of monomers comprising:
 one or more cross-linking monomers containing one or more cyclic groups and one or more ethylenically-unsaturated groups, at least a portion of such styrene-mimicking monomers being polycyclic monomers containing ring unsaturation, and   one or more other ethylenically-unsaturated monomers,   
       wherein when the acrylic copolymer is dispersed in an aqueous carrier and mixed with one or both of a metal drier or crosslinking agent, the acrylic copolymer exhibits an MEK rub test result of 50 rubs or greater.