Styrene-free coating compositions for packaging articles such as food and beverage containers
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 an emulsion-polymerized latex copolymer having copolymer chains of one or more ethylenically-unsaturated monomers and one or more styrene offset monomers. Preferably, the coating composition is substantially free of BPA, PVC, and 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. An inside spray coating composition comprising:
an aqueous carrier; and
an emulsion-polymerized latex copolymer dispersed in the aqueous carrier, wherein the monomers used to produce the emulsion-polymerized latex copolymer are substantially free of BPA, PVC, halogenated monomers, and styrene; and
wherein the emulsion-polymerized latex copolymer is the reaction product of monomers emulsion polymerized in the presence of a polyolefin polymeric surfactant;
wherein the coating composition has an average viscosity ranging from about 5 seconds to about 40 seconds, pursuant to the Viscosity Test;
wherein the coating composition 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; and
wherein the coating composition, when cured, has a glass transition temperature greater than 50° C.
2. The inside spray coating composition of claim 1 , wherein the polyolefin polymeric surfactant comprises a (poly)ethylene (meth)acrylic acid copolymer.
3. The inside spray coating composition of claim 1 , wherein the coating composition, when cured, has a glass transition temperature greater than 60° C.
4. The inside spray coating composition of claim 1 , wherein the coating composition, when cured, has a glass transition temperature greater than 70° C.
5. The inside spray coating composition of claim 1 , wherein the coating composition, when cured, has a glass transition temperature greater than 80° C.
6. The inside spray coating composition of claim 1 , wherein the coating composition is substantially free of formaldehyde and formaldehyde-containing materials.
7. The inside spray coating composition of claim 1 , wherein the polyolefin polymeric surfactant constitutes up to 40% by weight of solids of an aqueous dispersion used to polymerize the reactant monomers.
8. The inside spray coating composition of claim 1 , wherein the monomers comprise one or more first ethylenically-unsaturated monomers each having one or more ethylenically-unsaturated groups, wherein the one or more first ethylenically-unsaturated monomers comprise:
one or more ethylenically-unsaturated, acid-functional monomers;
one or more non-cyclic (meth)acrylates; or
combinations thereof.
9. The inside spray coating composition of claim 8 , wherein the one or more ethylenically-unsaturated, acid-functional monomers constitute at least 1% by weight of the monomers used to produce the emulsion-polymerized latex copolymer.
10. The inside spray coating composition of claim 8 , wherein the one or more non-cyclic (meth)acrylates constitute 10% to 70% by weight of the monomers used to produce the emulsion-polymerized latex copolymer.
11. The inside spray coating composition of claim 8 , wherein the one or more noncyclic (meth)acrylates constitute 20% to 60% by weight of the monomers used to produce the emulsion-polymerized latex copolymer.
12. The inside spray coating composition of claim 8 , wherein the one or more non-cyclic (meth)acrylates comprise a hydroxy-functional non-cyclic (meth)acrylate.
13. The inside spray coating composition of claim 8 , wherein the one or more first ethylenically-unsaturated monomers further comprises one or more multi-functional monomers.
14. The inside spray coating composition of claim 1 , wherein the monomers comprise:
(i) one or more ethylenically-unsaturated, polycyclic monomers;
(ii) one or more ethylenically-unsaturated, monocyclic monomers each having a ring structure with 3-5 atoms in the ring; or
a combination thereof.
15. The inside spray coating composition of claim 14 , wherein a combined concentration of (i) and (ii) is 10% or more by weight of the monomers used to produce the emulsion-polymerized latex copolymer.
16. The inside spray coating composition of claim 14 , wherein the one or more ethylenically-unsaturated, polycyclic monomers are selected from the group consisting of isobornyl (meth)acrylate, norbornane (meth)acrylate, norbornene (meth)acrylate, norbornadiene, tricyclodecenyl (meth)acrylate, isosorbide (meth)acrylate, tricyclodecane (meth)acrylate, bicyclo[4.4.0]decane (meth)acrylate, vinyl variations thereof, and mixtures thereof.
17. The inside spray coating composition of claim 14 , wherein the one or more ethylenically-unsaturated, monocyclic monomers constitute at least 20% by weight of the monomers used to produce the emulsion-polymerized latex copolymer.
18. The inside spray coating composition of claim 1 , wherein the monomers used to produce the emulsion-polymerized latex copolymer are substantially free of oxirane groups.
19. The inside spray coating composition of claim 1 , wherein the coating composition comprises a crosslinking agent.
20. The inside spray coating composition of claim 1 , wherein the monomers used to produce the emulsion-polymerized latex copolymer comprise one or more ethylenically-unsaturated, monocyclic monomers each having a ring structure with 6 or more atoms in the ring.