An Acrylic Polyester Resin and An Aqueous Coating Composition Containing the Same

Abstract

There is described an acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material. The polyester material is obtainable by polymerizing (i) a polyacid component, with (ii) a polyol component, including2,2,4,4-tetraalkyl-cyclobutane-1,3-diol. One of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality. Also provided is an aqueous coating composition comprising the acrylic polyester resin and a metal packaging containing coated with the composition.

Claims

1. An acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality.

2. An aqueous coating composition, the aqueous coating composition comprising: a) an acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality, b) a crosslinking material.

3. A metal packaging container coated on at least a portion thereof with a coating, the coating being derived from an aqueous coating composition, the aqueous coating composition comprising: a) an acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality, b) a crosslinking material.

4. A packaging coated on at least a portion thereof with a coating, the coating being derived from an aqueous coating composition, the aqueous coating composition comprising: a) an acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality, b) a crosslinking material.

5. A resin, coating composition or packaging according to any of claims 1 to 4, wherein the functional monomer comprises an ethylenically unsaturated monomer.

6. A resin, coating composition or packaging according to any of claims 1 to 5, wherein the functional monomer is selected from one or more of the following: maleic acid, maleic anhydride, fumaric acid, itaconic anhydride, itaconic acid, citraconic anhydride, citraconic acid, aconitic acid, aconitic anhydride, oxalocitraconic acid, oxalocitraconic anhydride, mesaconic acid, mesaconic anhydride, phenyl maleic acid, phenyl maleic anhydride, t-butyl maleic acid, t-butyl maleic anhydride, monomethyl fumarate, monobutyl fumarate, nadic acid, nadic anhydride, methyl maleic acid, methyl maleic anhydride.

7. A resin, coating composition or packaging according to any of claims 1 to 6, wherein the functional monomer is selected from one or more of the following: maleic acid, maleic anhydride, fumaric acid, itaconic anhydride, itaconic acid, citraconic anhydride, citraconic acid, aconitic acid, aconitic anhydride, oxalocitraconic acid, oxalocitraconic anhydride, mesaconic acid, mesaconic anhydride, phenyl maleic acid, phenyl maleic anhydride, t-butyl maleic acid, t-butyl maleic anhydride, monomethyl fumarate, monobutyl fumarate, nadic acid, nadic anhydride, methyl maleic acid, methyl maleic anhydride, trimethylolpropane monoallyl ether.

8. A resin, coating composition or packaging according to any of claims 1 to 7, wherein the functional monomer is present as a proportion of the dry weight of the polyol or polyacid component, such as the polyacid component, in an amount of between 0.5 and 10 wt %, suitably between 1 and 5 wt %.

9. A resin, coating composition or packaging according to any of claims 1 to 8, wherein the polyacid component comprises from one or more of the following: maleic acid; fumaric acid; itaconic acid; adipic acid; azelaic acid; succinic acid; sebacic acid; glutaric acid; decanoic diacid; dodecanoic diacid; phthalic acid; isophthalic acid; 5-tert-butylisophthalic acid; tetrachlorophthalic acid; tetrahydrophthalic acid; trimellitic acid; naphthalene dicarboxylic acid; naphthalene tetracarboxylic acid; terephthalic acid; hexahydrophthalic acid; methylhexahydrophthalic acid; dimethyl terephthalate; cyclohexane dicarboxylic acid; chlorendic anhydride; 1,3-cyclohexane dicarboxylic acid; 1,4-cyclohexane dicarboxylic acid; tricyclodecane polycarboxylic acid; endomethylene tetrahydrophthalic acid; endoethylene hexahydrophthalic acid; cyclohexanetetra carboxylic acid; cyclobutane tetracarboxylic; a monomer having an aliphatic group containing at least 15 carbon atoms; esters and anhydrides of all the aforementioned acids and combinations thereof.

10. A resin, coating composition or packaging according to any of claims 1 9, wherein the polyacid component comprises one or more of the following: dimethyl terephthalate, isophthalic acid, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid.

11. A resin, coating composition or packaging according to any of claims 1 to 10, wherein the polyacid component comprises one or more of the following: isophthalic acid, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid.

12. A resin, coating composition or packaging according to any of claims 1 to 11, wherein the polyacid component comprises one or more of the following: dimethyl terephthalate, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid and a monomer having an aliphatic group containing at least 15 carbon atoms, such as a dimer fatty acid, suitably a dimer fatty acid comprising 18 to 50 carbon atoms, such as a dimer fatty acid comprising 20 to 46 carbon atoms, or a dimer fatty acid comprising from 22 to 44 carbon atoms, for example a dimer fatty acid comprising from 24 to 42 carbon atoms, a dimer fatty acid comprising from 26 to 40 carbon atoms, a dimer fatty acid comprising from 28 to 38 carbon atoms, or a dimer fatty acid comprising from 30 to 38 carbon atoms;

13. A resin, coating composition or packaging according to any of claims 1 to 12, wherein the polyacid component comprises one or more of the following isophthalic acid, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid and a monomer having an aliphatic group containing at least 15 carbon atoms, such as a dimer fatty acid, suitably a dimer fatty acid comprising 18 to 50 carbon atoms, such as a dimer fatty acid comprising 20 to 46 carbon atoms, or a dimer fatty acid comprising from 22 to 44 carbon atoms, for example a dimer fatty acid comprising from 24 to 42 carbon atoms, a dimer fatty acid comprising from 26 to 40 carbon atoms, a dimer fatty acid comprising from 28 to 38 carbon atoms, or a dimer fatty acid comprising from 30 to 38 carbon atoms.

14. A resin, coating composition or packaging according to any of claims 1 to 13, wherein the 2,2,4,4-tetraalkylcyclobutane-1,3-diol (TACD) is according to the structure: ##STR00017## wherein R1, R2, R3, and R4 each independently represent an alkyl radical, for example, a lower alkyl radical having 1 to 8 carbon atoms; or 1 to 6 carbon atoms, or 1 to 5 carbon atoms, or 1 to 4 carbon atoms, or 1 to 3 carbon atoms, or 1 to 2 carbon atoms, or 1 carbon atom.

15. A resin, coating composition or packaging according to any of claims 1 to 14, wherein the TACD comprises one or more of 2,2,4,4-tetramethylcyclobutane-1,3-diol (TMCD), 2,2,4,4-tetraethylcyclobutane-1,3-diol (TECD), 2,2,4,4-tetra-n-propylcyclobutane-1,3-diol, 2,2,4,4-tetra-n-butylcyclobutane-1,3-diol, 2,2,4,4-tetra-n-pentylcyclobutane-1,3-diol, 2,2,4,4-tetra-n-hexylcyclobutane-1,3-diol, 2,2,4,4-tetra-n-heptylcyclobutane-1,3-diol, 2,2,4,4-tetra-n-octylcyclobutane-1,3-diol, 2,2-dimethyl-4,4-diethylcyclobutane-1,3-diol, 2-ethyl-2,4,4-trimethylcyclobutane-1,3-diol, 2,4-dimethyl-2,4-diethyl-cyclobutane-1,3-diol, 2,4-dimethyl-2,4-di-n-propylcyclobutane-1,3-diol, 2,4-n-dibutyl-2,4-diethylcyclobutane-1,3-diol, 2,4-dimethyl-2,4-diisobutylcyclobutane-1,3-diol, and 2,4-diethyl-2,4-diisoamylcyclobutane-1,3-diol.

16. A resin, coating composition or packaging according to any of claims 1 to 15, wherein the TACD comprises 2,2,4,4-tetramethylcyclobutane-1,3-diol (TMCD).

17. A resin, coating composition or packaging according to any of claims 1 to 16, wherein the polyol component further comprises one or more of the following: alkylene glycols, such as ethylene glycol; propylene glycol; diethylene glycol; dipropylene glycol; triethylene glycol; tripropylene glycol; hexylene glycol; polyethylene glycol; polypropylene glycol and neopentyl glycol; hydrogenated bisphenol A; cyclohexanediol; propanediols including 1,2-propanediol; 1,3-propanediol; butyl ethyl propanediol; 2-methyl-1,3-propanediol; and 2-ethyl-2-butyl-1,3-propanediol; butanediols including 1,4-butanediol; 1,3-butanediol; and 2-ethyl-1,4-butanediol; pentanediols including trimethyl pentanediol and 2-methylpentanediol; cyclohexanedimethanol; hexanediols including 1,6-hexanediol; caprolactonediol (for example, the reaction product of epsilon-capro lactone and ethylene glycol); hydroxyalkylated bisphenols; polyether glycols, for example, poly(oxytetramethylene) glycol; trimethylol propane; pentaerythritol; di-pentaerythritol; trimethylol ethane; trimethylol butane; dimethylol cyclohexane; bio-derived polyols such as glycerol, sorbitol and isosorbide; and a monomer having an aliphatic group containing at least 15 carbon atoms; or combinations thereof.

18. A resin, coating composition or packaging according to any of claims 1 to 17, wherein the polyol component comprises TACD in combination with 2-methy-1,3 propanediol and/or cyclohexanedimethanol.

19. A resin, coating composition or packaging according to any of claims 1 to 18, wherein the polyol component comprises TMCD in combination with 2-methy-1,3 propanediol and/or cyclohexanedimethanol.

20. A resin, coating composition or packaging according to any of claims 1 to 19, wherein the polyol component comprises one or more polyols having at least three hydroxyl groups, such as one or more selected from trimethylol propane; pentaerythritol; di-pentaerythritol; trimethylol ethane; trimethylol butane; and bio-derived polyols such as one or more selected from glycerol and sorbitol, suitably one or more of trimethylol propane; trimethylol ethane; and trimethylol butane, for example trimethylol propane.

21. A resin, coating composition or packaging according to any of claims 1 to 20, wherein the polyol having at least three hydroxyl groups is present as a proportion of the dry weight of the polyol component in an amount of between 0.1 and 10 wt %, such as between 0.5 and 8 wt % or between 0.7 and 6 wt %, for example between 0.8 and 5 wt % or between 0.9 and 4 wt %, suitably between 1 and 3 wt % or between 1 and 2 wt %.

22. A resin, coating composition or packaging according to any of claims 1 to 21, wherein the polyol component comprises TMCD in combination with 2-methy-1,3 propanediol, cyclohexanedimethanol and/or trimethylolpropane.

23. A resin, coating composition or packaging according to any of claims 1 to 22, wherein the 2,2,4,4-tetraalkylcyclobutane-1,3-diol (TACD) is present as a proportion of the dry weight of the polyol component in an amount of between 10 and 80 wt %, suitably between 10 and 70 wt %, such as between 20 wt % and 60 wt %.

24. A resin, coating composition or packaging according to any of claims 1 to 23, wherein the aliphatic group of the aliphatic group-containing monomer comprises from 18 to 50 carbon atoms, such as from 20 to 46 carbon atoms, from 22 to 44 carbon atoms, from 24 to 42 carbon atoms, from 26 to 40 carbon atoms.

25. A resin, coating composition or packaging according to any of claims 1 to 24, wherein the aliphatic group of the aliphatic group-containing monomer comprises from 28 to 38 carbon atoms, or from 30 to 38 carbon atoms.

26. A resin, coating composition or packaging according to any of claims 1 to 25, wherein the aliphatic group of the aliphatic group-containing monomer is branched and/or comprises a cyclic group.

27. A resin, coating composition or packaging according to any of claims 1 to 26, wherein aliphatic group-containing monomer is a diacid.

28. A resin, coating composition or packaging according to any of claims 1 to 27, wherein the aliphatic group-containing monomer is a dimer fatty acid.

29. A resin, coating composition or packaging according to any of claims 1 to 28, wherein the aliphatic group-containing monomer is the dimerisation product of erucic acid, linolenic acid, linoleic acid, and/or oleic acid.

30. A resin, coating composition or packaging according to any of claims 1 to 29, wherein the polyacid component and/or the polyol component comprises a sulfonated monomer.

31. A resin, coating composition or packaging according to any of claims 1 to 30, wherein the sulfonated monomer comprises one or more of: 5-(sodiosulfo)-isophthalic acid, dimethyl 5-(sodiosulfo)isophalate, 5-(lithiosulfo)isophthalic acid, bis(2-hydroxyethyl)-5-(sodiosulfo)isophthalate.

32. A resin, coating composition or packaging according to any of claims 1 to 31, wherein the polyester material comprises an Mn from 1,000 Daltons (Da=g/mole) to 15,000 Da, suitably from 2,000 Da to 10,000 Da, such as from 3,000 Da to 8,000 Da, or even from 4,000 to 7,000 Da.

33. A resin, coating composition or packaging according to any of claims 1 to 32, wherein the polyester material has a gross OHV of from 0 to 120 mg KOH/g, suitably from 5 to 100 mg KOH/g, such as from 5 to 80 mg KOH/g, or from 5 to 50 mg KOH/g, or from 7 to 40 mg KOH/g, suitably from 10 to 30 mg KOH/g or 10 to 20 mg KOH/g.

34. A resin, coating composition or packaging according to any of claims 1 to 33, wherein the polyester material has an AV from 0 to 20 KOH/g, suitably from 0 to 10 mg KOH/g, such as less than 5 or even less than 3.

35. A resin, coating composition or packaging according to any of claims 1 to 34, wherein the polyester material has a Mn of from 3,000 to 8,000 Da, a gross OHV of from 5 to 50 mg KOH/g and an acid value of from 0 to 10 mg KOH/g.

36. A resin, coating composition or packaging according to any of claims 1 to 35, wherein the polyester material has a Mn of from 4,000 to 7,000 Da, a gross OHV of from 10 to 20 mg KOH/g and an acid value of less than 5 mg KOH/g.

37. A resin, coating composition or packaging according to any of claims 1 to 36, wherein the acrylic polyester resin is formed from the polyester material and an acrylic modification polymer in a weight ratio of from 95 wt % to 55 wt % polyester material to from 45 wt % to 5 wt % acrylic modification polymer, such as from 90 wt % to 55 wt % polyester material to from 45 wt % to 10 wt % acrylic modification polymer, or from 90 wt % to 55 wt % polyester material to from 45 wt % to 10 wt % acrylic modification polymer, such as a weight ratio of from 90 wt % to 60 wt % polyester material to from 40 wt % to 10 wt % acrylic modification polymer, such as a weight ratio of from 85 wt % to 65 wt % polyester material to from 35 wt % to 15 wt % acrylic modification polymer.

38. A resin, coating composition or packaging according to any of claims 1 to 36, wherein the acrylic polyester resin is formed from the polyester material and an acrylic modification polymer in a weight ratio of between 85 wt % and 55 wt % polyester material to between 45 wt % and 15 wt % acrylic modification polymer.

39. A resin, coating composition or packaging according to any of claims 1 to 38, wherein an acrylic modification polymer is polymerized in the presence of the polyester material to form an acrylic modified polyester resin.

40. A resin, coating composition or packaging according to any of claims 1 to 39, wherein the acrylic modification polymer is formed from one or more of the following monomers: methyl(meth)acrylate, ethyl(meth)acrylate, butyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyethyl (meth)acrylate, 2-ethyl hexyl(meth)acrylate, (meth)acrylic acid; cyclohexyl (meth)acrylate, allyl (meth)acrylate, dimethylamino ethyl methacrylate. butylamino ethyl (meth)acrylate, HEMA phosphate (such as ethylene glycol methacrylate phosphate).

41. A resin, coating composition or packaging according to any of claims 1 to 40, wherein the acrylic monomers comprise a hydroxyl functional monomer, such as hydroxyethyl (meth)acrylate.

42. A resin, coating composition or packaging according to any of claims 1 to 41, wherein the hydroxyl functional monomer is present by dry weight of the acrylic modification polymer in an amount of between 5 and 40 wt %, such as between 5 and 30 wt % or between 10 and 20 wt %.

43. A resin, coating composition or packaging according to any of claims 1 to 42, wherein the acrylic polyester resin, which may be an acrylic modified polyester resin, is present in the aqueous coating composition in an amount of between 50 to 99 wt % (based on dry weight of the aqueous coating composition), suitably, in an amount of between 60 to 95 wt % (based on dry weight of the aqueous coating composition).

44. A resin, coating composition or packaging according to any of claims 1 to 43, wherein the acrylic monomers comprise a ratio of methacrylate monomers to acrylate monomers of at least 1:1, such as at least 2:1 or at least 3:1 or at least 4:1, suitably at least 5:1.

45. A resin, coating composition or packaging according to any of claims 1 to 44, wherein the acrylic polyester resin has a Mn from 1,000 Daltons (Da=g/mole) to 15,000 Da, suitably from 2,000 Da to 10,000 Da, such as from 3,000 Da to 8,000 Da, or even from 4,000 to 7,000 Da.

46. A resin, coating composition or packaging according to any of claims 1 to 45, wherein the acrylic polyester resin has a gross OHV from 0 to 120 mg KOH/g, such as from 5 to 100 mg KOH/g, or from 10 to 60 mg KOH/g, or even from 10 to 50 mg KOH/g, such as from 10 to 30 mg KOH/g.

47. A resin, coating composition or packaging according to any of claims 1 to 46, wherein the acrylic polyester resin has an AV from 10 to 80 KOH/g, such as from 20 to 70 mg KOH/g, suitably from 30 to 60 mg KOH/g.

48. A resin, coating composition or packaging according to any of claims 1 to 47, wherein the acrylic polyester resin, which may be an acrylic modified polyester resin, has a Mn of 3,000 to 9,000 Da, a gross OHV of from 10 to 50 mg KOH/g and an AV of from 20 to 70 mg KOH/g.

49. A resin, coating composition or packaging according to any of claims 1 to 48, wherein the acrylic polyester resin, which may be an acrylic modified polyester resin, has a Mn of 3,500 to 8,000 Da, a gross OHV of from 10 to 30 mg KOH/g and an AV of from 30 to 60 mg KOH/g.

50. A coating composition or packaging according to any of claims 2 to 49, wherein the crosslinking material comprises one or more of a phenolic resin, benzoguanamine or melamine.

51. A coating composition or packaging according to any of claims 2 to 50, wherein the crosslinking material comprises benzoguanamine.

52. A coating composition or packaging according to any of claims 2 to 51, wherein the aqueous coating composition is substantially free of bisphenol A (BPA), bisphenol F (BPF) and derivatives thereof.

53. A coating composition or packaging according to any of claims 2 to 52 wherein the aqueous coating composition is substantially free of styrene.

54. A coating composition or packaging according to any of claims 2 to 53 wherein the aqueous coating composition is substantially free of formaldehyde.

55. A coating composition or packaging according to any of claims 2 to 54, wherein the aqueous coating composition further comprises an adhesion promoter.

56. A coating composition or packaging according to claim 55, wherein the adhesion promoter comprises an acidic polyester material.

57. A coating composition or packaging according to claim 56, wherein the acidic polyester generally comprises the reaction product of: (a) a polyester having an Mn of 2000 to 10,000, a hydroxyl number of 20 to 75, and an acid value of 15 to 25; the polyester being a polycondensate of: (i) a polyol component comprising a mixture of diols and triols, (ii) a polyacid component comprising an alpha, beta-ethylenically unsaturated polycarboxylic acid, and (b) a phosphorus acid.

58. A coating composition according to any of claims 2 to 57, wherein the coating composition has a solids content of from 10 to 60% by weight of the coating composition, such as from 15 to 50 wt % or suitably from 20 to 40 wt %.

59. A packaging container according to any of claims 3 to 58, wherein the packaging comprises a food or beverage can or aerosol can.

60. A method of forming an acrylic modified polyester resin, the method comprising polymerizing an acrylic modification polymer in the presence of a polyester material, the polyester material being obtainable by polymerizing i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality.

61. A method of preparing an aqueous coating composition, the method comprising dispersing an acrylic modified polyester resin and a crosslinking material in an aqueous medium, the acrylic modified polyester resin being obtainable by grafting an acrylic polymer onto a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality.

62. A method of coating at least a portion of a metal packaging container, the method comprising applying an aqueous coating composition to a metal packaging composition, the aqueous coating composition comprising an acrylic modified polyester resin and a crosslinking material, the acrylic modified polyester resin being obtainable by grafting an acrylic polymer onto a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality, and curing the aqueous coating composition to form a coating.

63. A method of coating at least a portion of a packaging, the method comprising applying an aqueous coating composition to a packaging, the aqueous coating composition comprising an acrylic modified polyester resin and a crosslinking material, the acrylic modified polyester resin being obtainable by grafting an acrylic polymer onto a polyester material, the polyester material being obtainable by polymerizing: i) a polyacid component, with ii) a polyol component, including 2,2,4,4-tetraalkylcyclobutane-1,3-diol wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality, and curing the aqueous coating composition to form a coating.

64. A packaging or method according to any of claims 3 to 63, wherein the packaging is metal packaging, such as a metal can.

Description

EXAMPLES

Actual Experimental DataMethod for the Formation of the Aqueous Coatings

[0303] The details of inventive aqueous coating 1a and 2a, and comparative aqueous coating 3a, are shown in Tables 1 to 4. Coating 1a shows unsaturated, hydroxyl functional polyesters with TMCD. Coating 2a shows unsaturated, hydroxyl functional polyesters with TMCD and a dimer fatty acid (Pripol 1010). Comparative coating 3a shows an unsaturated, hydroxyl functional polyester without TMCD.

[0304] The polyester materials of inventive coatings 1a, 2a and comparative coating 3a were formed as follows. The diol, diacid and catalyst components listed in Table 1 were added as a batch to a vessel with a steam column, distillation head and condenser. The batch temperature is increased to 150? C. with stirring at 400 rpm under an N.sub.2 blanket. Once the temperature reaches 150? C., the batch temperature is increased to 230? C. over a 4 hour period (10? C. steps every 30 minutes), whilst ensuring that the head temperature is below 100? C.

[0305] Once the batch reaches 230? C., the acid value is assessed every hour. When the acid value is less than 15, the batch is cooled to 150? C. and methyl hydroquinone is added, then after 10 minutes, the maleic anhydride is added and the batch temperature increased to 195? C. until the acid value increases up to <20. The batch is then cooled to 130? C. and azeotropically separated using a Dean Stark trap and an addition of xylene.

[0306] The batch is then heated back up to 195? C. When the target AV and cut viscosity is reached the batch is cooled to 150? C. and the Dowanol DPM added. The batch is then held at 150? C. for 1 hour and then poured out.

[0307] The polyester materials formed then underwent a grafting process to graft acrylic onto the unsaturated functionality of the backbone of the polyester (imparted by the maleic anhydride) to form acrylic modified polyester resins 1a, 2a and 3a (noted simply as PGA resins 1a to 3a in Table 2). Details of the monomers used in the acrylic graft reaction are shown in Table 2.

[0308] The acrylic modified polyester resins were each formed as follows. Half of the amount of the polyester material given in Table 2 was added to a vessel with mixing at 225 rpm and heated to 120? C. Once at 120? C., half of total amount of each acrylic monomer as shown in Table 2 was added over a period of 40 minutes with continued stirring. 10 minutes after adding the acrylic monomers, about a third of each of the t-butyl peroctoate initiator and Dowanol DPM amounts as shown in Table 2 were added. The remaining amount of the polyester material was then added and the solution heated back to 120? C. At this stage the solution is homogeneous and has good mixing. Then the remaining acrylic monomers were added over 40 minutes. 10 minutes after adding the acrylic monomers, about a third of each of the t-butyl peroctoate initiator and Dowanol DPM amounts as shown in Table 2 were added over a 30 minute period. The remaining t-butyl peroctoate initiator and Dowanol DPM was then added in two evenly split batches, the first batch being added over 5 minutes and the mixture then held at 120? C. for 30 minutes before addition of the second batch over 5 minutes and then held at 120? C. for 30 minutes. The reaction mixture is then cooled to below 100? C.

[0309] The acrylic modified polyester resins are formed into aqueous dispersions with the components as shown in Table 3.

[0310] The acrylic modified polyester resins are formed into aqueous dispersions by heating the resin to 90? C., and during heating adding the DMEA with stirring. The mixture was then held for 10 minutes, after which deionized water was added over 60 minutes, maintaining the temperature about 85? C. The aqueous dispersions were then allowed to cool to 45? C.

[0311] The aqueous dispersions are formed into aqueous coating compositions with components as shown in Table 4, as follows. The deionized water, Dowanol PnB, crosslinking material (Cymel 1123benzoguanamine, commercially available from Allnex), and blocked DDBSA catalyst (Nacure 5925, commercially available from King) were stirred into the aqueous dispersion to form the aqueous coating composition.

TABLE-US-00001 TABLE 1 Polyesters Polyester Polyester Comparative 1a 2a Polyester 3a Materials 2-methyl-1,3-propanediol 75.58 824.00 Cyclohexane dimethanol 117.69 TMCD 73.11 39.21 Trimethylolpropane 1.82 1.88 11.24 Isophthalic acid 51.22 121.10 427.00 Pripol 1010 (C36 Dimer Acid) 123.93 Hexahydrophthalic anhydride 38.91 237.00 Dibutyl tin oxide 0.18 0.17 1.12 Cyclohexane-1,4-dicarboxylic acid 110.41 690 MeHQ 0.04 0.036 0.22 Maleic anhydride 12.06 10.55 75.60 Xylene 24.74 21.75 270.20 Dowanol DPM 230.51 284.40 1313.00 Properties Initial weight 361.92 414.21 2265.35 Theoretical weight loss 40.80 32.04 278.17 Final resin weight 321.13 382.17 1987.18 Total with solids 576.33 688.07 3569.27 % solids 55.72 55.54 55.67 Mn 6,160 5,412 5093 Mw 37,341 36,613 28,196 PDI 6.1 6.8 5.5 AV 4.55 1.60 2.59 OH 16.21 15.30 22.23

TABLE-US-00002 TABLE 2 Polyester-graft-acrylic (PGA) Resins PGA PGA Comparative resin 1a resin 2a PGA resin 3a Materials Polyester 1a 286.12 Polyester 2a 276.66 Comparative polyester 3a 599.44 Methacrylic acid 17.72 17.72 49.22 Ethyl methacrylate 16.24 16.24 45.12 Methyl methacrylate 16.24 16.24 45.12 2-hydroxyethyl methacrylate 8.86 8.86 24.62 t-butyl peroctoate 5.32 5.32 14.76 Dowanol DPM 26.58 26.58 230.86 Properties Final % solids 59.00 59.00 59.00 % polyester 70.52 70.52 70.52 % acrylic 27.81 27.81 27.81 % initiator 1.67 1.67 1.67 AV 33.51 38.04 31.40 Mn 6,305 5,771 6,643 Mw 76,799 49,237 72,059

TABLE-US-00003 TABLE 3 Aqueous Dispersions Aq. Aq. Dispersion Dispersion Comp. Aq. 1a 2a Dispersion 3a Materials PGA resin 1a 250.08 PGA resin 2a 241.67 Comparative PGA resin 3a 600.02 Dimethylethanolamine 9.33 9.71 19.50 Deionised water 210.11 213.80 726.00 Properties % solids 24.36 23.44 23.95 Acid Value (on 59% solids) 14.5 13.61 13.22 Particle size, matersizer, ?m 0.128 26.14 12.999 Viscosity 215 77 272

TABLE-US-00004 TABLE 4 Coating Compositions Aq. Comparative Aq. Coating Coating aq. Coating 1a 2a 3a Aq. dispersion 1a 40.00 Aq. dispersion 2a 40.00 Comparative aq. dispersion 3a 35.00 DI Water 3.02 1.25 7.45 Dowanol PnB 1.09 1.04 0.99 Cymel 1123 (benzoguanamine) 1.08 1.04 1.48 Nacure 5925 (blocked DDBSA) 0.04 0.04 0.03 Total 45.23 43.37 44.96

Testing Methods

[0312] Coated panels were obtained by drawing the aqueous coatings over a Zirconium pretreated 5182-H48 aluminum panels using a wire wound rod to obtain dry coating weights of approximately 7.0 mg/square inch (msi). The coated panels were immediately placed into a one-zone, gas-fired, convey or oven for 10 seconds and baked to a peak metal temperature of 450? F. (232? C.).

[0313] Blush resistance measures the ability of a coating to resist attack by various testing solutions. When the coated film absorbs test solution, it generally becomes cloudy or looks white. Blush is measured visually using a scale of 1-10 where a rating of 10 indicates no blush and a rating of 0 indicates complete whitening of the film. Blush ratings of at least 7 are typically desired for commercially viable coatings. The coated panel tested is 2?4 inches (5?10 cm) and the testing solution covers half of the panel being tested so you can compare blush of the exposed panel to the unexposed portion.

[0314] Adhesion testing is performed to assess whether the coating adheres to the substrate. The adhesion test is performed according to ASTM D 3359 Test Method B, using Scotch 610 tape, available from 3M Company of Saint Paul, Minn. Adhesion is generally rated on a scale of 0-5 where a rating of 5 indicates no adhesion failure.

[0315] The Acetic Acid test is designed to measure the resistance of a coating to a boiling 3% acetic acid solution. The solution is prepared by mixing 90 grams of Glacial Acetic Acid (product of Fisher Scientific) into 3000 grams of deionized water. Coated strips are immersed into the boiling Acetic Acid solution for 30 minutes. The strips are then rinsed and cooled in deionized water, dried, and immediately rated for adhesion as described previously.

[0316] The Dowfax test is designed to measure the resistance of a coating to a boiling detergent solution. The solution is prepared by mixing 5 grams of DOWFAX 2A1 (product of Dow Chemical) into 3000 grams of deionized water. Coated strips are immersed into the boiling Dowfax solution for 15 minutes. The strips are then rinsed and cooled in deionized water, dried, and immediately rated for blush and adhesion as described previously.

[0317] The Joy test is designed to measure the resistance of a coating to a hot 180? F. (82? C.) Joy detergent solution. The solution is prepared by mixing 30 grams of Ultra Joy Dishwashing Liquid (product of Procter & Gamble) into 3000 grams of deionized water. Coated strips are immersed into the 180? F. (82? C.) Joy solution for 15 minutes. The strips are then rinsed and cooled in deionized water, dried, and immediately rated for blush and adhesion as described previously.

[0318] The DI Water Retort test is designed to measure the resistance of a coating to deionized water. Coated strips are immersed into the deionized water and placed in a steam retort for 30 minutes at 250? F. (121? C.). The strips are then cooled in deionized water, dried, and immediately rated for blush and adhesion as described previously.

[0319] The results of these testing methods are provided in Table 5.

[0320] Aqueous dispersions produced according to the compositions of Tables 1 to 4 and the associated methods were also tested for hot room stability by exposing the dispersions to 120? F. for two weeks. The results of the hot room stability test are provided in Table 6.

TABLE-US-00005 TABLE 5 Results Acetic Acid Dowfax Dowfax Joy Joy Water Retort Water Retort Coating Adhesion Blush Adhesion Blush Adhesion Blush* Adhesion Example 1 3B 9 5B 9 5B 9 5B Example 2 4B 9 5B 9 5B 8 5B Comp. Av. 3B 9 5B 9 5B 9 5B Coating 1 *Any result above 7 is acceptable for a commercial coating composition

TABLE-US-00006 TABLE 6 Hot Room Stability Results Aq. dispersion Aq. dispersion Comp aq. 1a 2a dispersion 3a Particle Initial 0.122 17.184 3.898 size, ?m After 2 weeks 0.122 14.468 1.087 at 120? F. % reduction 0% 16% 62% Mn Initial 6,235 5,472 6,471 After 2 weeks 4,904 4,759 5,123 at 120? F. % reduction 21% 13% 21%

Theoretical Embodiments

[0321] The details of examples 1 to 8 are shown in Table 7. Each of examples 1 to 8 shows the components of a polyester material. Examples 1 to 4 show unsaturated, hydroxyl functional polyesters with TMCD and 5-SSIPA. Examples 5 to 8 show unsaturated, hydroxyl functional polyesters with TMCD, but without 5-SSIPA.

[0322] The polyester materials of examples 1 to 8 are formed as follows. The 2-methyl-1,3 propanediol, TMCD, cyclohexanedimethanol, 5-SSIPA, dibutyl tin oxide, dimethyl terephthalate, hexahydrophthalic anhydride and cyclohexane 1,4-dicarboxylic acid are added as a batch to a vessel with a steam column, distillation head and condenser. The batch temperature is increased to 150 C with stirring at 400 rpm under an N.sub.2 blanket. Once the temperature reaches 150 C, the batch temperature is increased to 230 C over a 4 hour period (10 C steps every 30 minutes), whilst ensuring that the head temperature is below 100 C.

[0323] Once the batch reaches 230 C, the acid value is assessed every hour. When the acid value is less than 15, the batch is cooled to 150 C and methyl hydroquinone is added, then after 10 minutes, the maleic anhydride is added and the batch temperature increased to 195 C until the acid value increases to about 20. The batch is then cooled to 130 C and azeotropically separated using a Dean Stark trap.

[0324] The polyester materials of examples 1 to 8 undergo a grafting process to graft acrylic onto the unsaturated functionality of the backbone of the polyester (imparted by the maleic anhydride) to form acrylic modified polyester resins 1 to 8 (noted simply as resins 1 to 8 in Table 2). Details of the monomers used in the acrylic graft reaction are shown in Table 8.

[0325] The acrylic modified polyester resins were formed as follows. The polyester material (of Examples 1 to 8) is added to a vessel with mixing at 225 rpm and heated to 120 C. Once at 120 C, the acrylate monomers are added over a period of 75 minutes with continued stirring. Then the Dowanol DPM and t-butyl peroctoate initiator is added over a period of 90 minutes and the reaction held at 120 C for a further 45 minutes. The reaction mixture is then cooled to below 80 C.

[0326] The acrylic modified polyester resins are formed into aqueous dispersions with the components as shown in Table 9.

[0327] The acrylic modified polyester resins are formed into aqueous dispersions by heating the resin to 80 to 85 C, then slowly adding deionized water to the resins (over a period of about 60 minutes), with the elevated temperature (80 to 85 C) maintained, then stirring the dispersed mixture for a further 60 minutes at 80 to 85 C. The aqueous dispersions are then cooled.

[0328] In forming the aqueous dispersions where the polyester material does not include a sulfonated monomer, dimethylethanol amine is added to the heated (80 to 85 C) acrylic modified polyester resin and stirred for 10 minutes until homogeneous, prior to adding the deionized water. Otherwise, the process is the same.

[0329] The aqueous dispersions are formed into aqueous coating compositions with components as shown in Table 10, as follows. The crosslinking material (Cymel 1123benzoguanamine, commercially available from Allnex), blocked DDBSA catalyst (Nacure 5925, commercially available from King) and wax additive (Michem Lube 160, commercially available from Michelman) are stirred into the water dispersed PGA dispersion to form an aqueous coating composition.

TABLE-US-00007 TABLE 7 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Material name 2-Methyl-1,3 Propanediol 339.50 339.50 339.50 339.50 TMCD 542.50 542.50 542.50 542.50 542.50 542.50 542.50 542.50 Cyclohexanedimethanol 542.50 542.50 542.50 542.50 5-SSIPA 245.00 218.80 227.50 236.30 Dibutyl Tin Oxide 1.12 1.12 1.12 1.12 1.12 1.12 1.12 1.12 Dimethyl Terephthalate 385.00 678.10 332.50 647.50 564.38 835.63 503.13 822.50 Hexahydrophthalic anhydride 332.50 332.50 332.50 332.50 Cyclohexane 1,4-dicarboxylic acid 612.50 656.25 612.50 656.25 MeHQ 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 Maleic Anhydride 65.63 65.63 70.00 70.00 65.63 65.63 70.00 70.00 Aromatic 100 269.59 269.59 269.59 269.59 269.59 269.59 269.59 269.59 Dowanol DPM 1312.50 1312.50 1312.50 1312.50 1312.50 1312.50 1312.50 1312.50 Calculated Properties Initial weight 2191.47 2178.34 2372.59 2372.59 2125.84 2117.09 2315.72 2311.34 Theoretical water loss 211.49 176.59 211.71 171.72 244.74 205.79 243.34 204.16 Final Resin weight 1979.98 2001.75 2160.89 2200.88 1881.10 1911.31 2072.38 2107.18 Total (inc solvents) 3562.07 3583.84 3742.97 3782.96 3463.19 3493.39 3654.47 3689.27 Approx Mn 4877.00 5070.00 4939.00 5033.00 4753.00 4785.00 5090.00 5052.00 OH equivalent excess 0.81 0.79 0.88 0.88 0.79 0.80 0.81 0.83

TABLE-US-00008 TABLE 8 Resin 1 Resin 2 Resin 3 Resin 4 Resin 5 Resin 6 Resin 7 Resin 8 Polyester material of Ex. 1 453.9 Polyester material of Ex. 2 453.9 Polyester material of Ex. 3 453.9 Polyester material of Ex. 4 453.9 Polyester material of Ex. 5 453.9 Polyester material of Ex. 6 453.9 Polyester material of Ex. 7 453.9 Polyester material of Ex. 8 453.9 methacrylic acid 28.8 28.8 28.8 28.8 28.8 28.8 28.8 28.8 ethyl methacrylate 45.6 45.6 45.6 45.6 45.6 45.6 45.6 45.6 methyl methacrylate 24.1 24.1 24.1 24.1 24.1 24.1 24.1 24.1 t-butyl peroctoate 5.9 5.9 5.9 5.9 5.9 5.9 5.9 5.9 Dowanol DPM 41.8 41.8 41.8 41.8 41.8 41.8 41.8 41.8 Calculated Properties final % solids 59.00% 59.00% 59.00% 59.00% 59.00% 59.00% 59.00% 59.00% % polyester 70.52% 70.52% 70.52% 70.52% 70.52% 70.52% 70.52% 70.52% % acrylic 27.81% 27.81% 27.81% 27.81% 27.81% 27.81% 27.81% 27.81% % Initiator 1.67% 1.67% 1.67% 1.67% 1.67% 1.67% 1.67% 1.67%

TABLE-US-00009 TABLE 9 Aq. Disp 1 Aq. Disp 2 Aq. Disp 3 Aq. Disp 4 Aq. Disp 5 Aq. Disp 6 Aq. Disp 7 Aq. Disp 8 Resin 1 300 Resin 2 300 Resin 3 300 Resin 4 300 Resin 5 300 Resin 6 300 Resin 7 300 Resin 8 300 Dimethylethanolamine 11.4 11.4 11.4 11.4 Deionized Water 290 290 290 290 278.6 278.6 278.6 278.6 Calculated Properties % solids 59.00% 59.00% 59.00% 59.00% 59.00% 59.00% 59.00% 59.00% Acid Value (on 59% solids) 30 30 30 30 30 30 30 30

TABLE-US-00010 TABLE 10 Aq. Aq. Aq. Aq. Aq. Aq. Aq. Aq. Coating 1 Coating 2 Coating 3 Coating 4 Coating 5 Coating 6 Coating 7 Coating 8 Aq. Disp 1 79.5 wt % Aq. Disp 2 79.5 wt % Aq. Disp 3 79.5 wt % Aq. Disp 4 79.5 wt % Aq. Disp 5 79.5 wt % Aq. Disp 6 79.5 wt % Aq. Disp 7 79.5 wt % Aq. Disp 8 79.5 wt % Cymel 1123 20.00% 20.00% 20.00% 20.00% 20.00% 20.00% 20.00% 20.00% (benzoguanamine) Nacure 5925 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % (blocked DDBSA) Michem Lube 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 160 (wax)
Certain aspects of the invention may be combined in the following combinations. [0330] 1. An acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: [0331] i) a polyacid component, with [0332] ii) a polyol component, including [0333] 2,2,4,4-tetraalkylcyclobutane-1,3-diol [0334] wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality.
2. An aqueous coating composition, the aqueous coating composition comprising: [0335] a) an acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: [0336] i) a polyacid component, with [0337] ii) a polyol component, including [0338] 2,2,4,4-tetraalkylcyclobutane-1,3-diol [0339] wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality, [0340] b) a crosslinking material. [0341] 3. A metal packaging container coated on at least a portion thereof with a coating, the coating being derived from an aqueous coating composition, the aqueous coating composition comprising: [0342] a) an acrylic polyester resin, obtainable by grafting an acrylic polymer with a polyester material, the polyester material being obtainable by polymerizing: [0343] i) a polyacid component, with [0344] ii) a polyol component, including [0345] 2,2,4,4-tetraalkylcyclobutane-1,3-diol [0346] wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted with the polyester material via the use of said functionality, [0347] b) a crosslinking material. [0348] 4. A resin, coating composition or packaging container according to any of aspects 1 to 3, wherein the functional monomer comprises an ethylenically unsaturated monomer. [0349] 5. A resin, coating composition or packaging container according to any of aspects 1 to 4, wherein the functional monomer is selected from one or more of the following: maleic acid, maleic anhydride, fumaric acid, itaconic anhydride, itaconic acid, citraconic anhydride, citraconic acid, aconitic acid, aconitic anhydride, oxalocitraconic acid, oxalocitraconic anhydride, mesaconic acid, mesaconic anhydride, phenyl maleic acid, phenyl maleic anhydride, t-butyl maleic acid, t-butyl maleic anhydride, monomethyl fumarate, monobutyl fumarate, nadic acid, nadic anhydride, methyl maleic acid, methyl maleic anhydride. [0350] 6. A resin, coating composition or packaging container according to any of aspects 1 to 5, wherein the polyacid component comprises one or more of the following: dimethyl terephthalate, isophthalic acid, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid. [0351] 7. A resin, coating composition or packaging container according to any of aspects 1 to 6, wherein the TACD comprises 2,2,4,4-tetramethylcyclobutane-1,3-diol (TMCD). [0352] 8. A resin, coating composition or packaging container according to any of aspects 1 to 7, wherein the polyol component comprises TMCD in combination with 2-methy-1,3 propanediol and/or cyclohexanedimethanol. [0353] 9. A resin, coating composition or packaging container according to any of aspects 1 to 8, wherein the polyacid component and/or the polyol component comprises a sulfonated monomer. [0354] 10. A resin, coating composition or packaging container according to any of aspects 1 to 9, wherein the sulfonated monomer comprises one or more of: 5-(sodiosulfo)-isophthalic acid, dimethyl 5-(sodiosulfo)isophalate, 5-(lithiosulfo)isophthalic acid, bis(2-hydroxyethyl)-5-(sodiosulfo)isophthalate. [0355] 11. A resin, coating composition or packaging container according to any of aspects 1 to 10, wherein the polyester material comprises an Mn from 1,000 Daltons (Da=g/mole) to 15,000 Da. [0356] 12. A resin, coating composition or packaging container according to any of aspects 1 to 11, wherein the acrylic polyester resin is formed from the polyester material and an acrylic modification polymer in a weight ratio of between 85 wt % and 55 wt % polyester material to between 45 wt % and 15 wt % acrylic modification polymer. [0357] 13. A resin, coating composition or packaging container according to any of aspects 1 to 12, wherein an acrylic modification polymer is polymerized in the presence of the polyester material to form an acrylic modified polyester resin. [0358] 14. A resin, coating composition or packaging container according to any of aspects 1 to 13, wherein the acrylic modification polymer is formed from one or more of the following monomers: methyl(meth)acrylate, ethyl(meth)acrylate, butyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyethyl (meth)acrylate, 2-ethylhexyl(meth)acrylate, (meth)acrylic acid; cyclohexyl (meth)acrylate, allyl (meth)acrylate, dimethylamino ethyl methacrylate. butylamino ethyl (meth)acrylate, HEMA phosphate (such as ethylene glycol methacrylate phosphate). [0359] 15. A coating composition or packaging container according to any of aspects 1 to 14, wherein the crosslinking material may comprise one or more of a phenolic resin, benzoguanamine or melamine. [0360] 16. A coating composition or packaging container according to any of aspects 1 to 15, wherein the aqueous coating composition is substantially free of bisphenol A (BPA), bisphenol F (BPF) and derivatives thereof. [0361] 17. A coating composition or packaging container according to any of aspects 1 to 16, wherein the aqueous coating composition is substantially free of styrene. [0362] 18. A coating composition or packaging container according to any of aspects 1 to 17, wherein the aqueous coating composition is substantially free of formaldehyde. [0363] 19. A coating composition or packaging container according to any of aspects 1 to 20, wherein the aqueous coating composition further comprises an adhesion promoter. [0364] 20. A coating composition or packaging container according to aspect 19, wherein the adhesion promoter comprises an acidic polyester material. [0365] 21. A coating composition or packaging container according to aspect 20, wherein the acidic polyester generally comprises the reaction product of: [0366] (a) a polyester having an Mn of 2000 to 10,000, a hydroxyl number of 20 to 75, and an acid value of 15 to 25; the polyester being a polycondensate of: [0367] (i) a polyol component comprising a mixture of diols and triols, [0368] (ii) a polyacid component comprising an alpha, beta-ethylenically unsaturated polycarboxylic acid, [0369] and [0370] (b) a phosphorus acid. [0371] 22. A packaging container according to any of aspects 1 to 21, wherein the packaging container comprises a food or beverage can or aerosol can. [0372] 23. A method of forming an acrylic modified polyester resin, the method comprising polymerizing an acrylic modification polymer in the presence of a polyester material, the polyester material being obtainable by polymerizing [0373] i) a polyacid component, with [0374] ii) a polyol component, including [0375] 2,2,4,4-tetraalkylcyclobutane-1,3-diol [0376] wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality. [0377] 24. A method of preparing an aqueous coating composition, the method comprising dispersing an acrylic modified polyester resin and a crosslinking material in an aqueous medium, the acrylic modified polyester resin being obtainable by grafting an acrylic polymer onto a polyester material, the polyester material being obtainable by polymerizing: [0378] i) a polyacid component, with [0379] ii) a polyol component, including [0380] 2,2,4,4-tetraalkylcyclobutane-1,3-diol [0381] wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality. [0382] 25. A method of coating at least a portion of a metal packaging container, the method comprising applying an aqueous coating composition to a metal packaging composition, the aqueous coating composition comprising an acrylic modified polyester resin and a crosslinking material, the acrylic modified polyester resin being obtainable by grafting an acrylic polymer onto a polyester material, the polyester material being obtainable by polymerizing: [0383] i) a polyacid component, with [0384] ii) a polyol component, including [0385] 2,2,4,4-tetraalkylcyclobutane-1,3-diol [0386] wherein one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality on to the polyester resin, such that an acrylic polymer may be grafted onto the polyester material via the use of said functionality, and curing the aqueous coating composition to form a coating.