Acrylic polyester resin and an aqueous coating composition containing the same

Abstract

An acrylic polyester resin is provided by grafting an acrylic polymer with a polyester material. Also provided is an aqueous coating composition with at least the acrylic polyester resin and a metal packaging container coated with the aqueous coating composition.

Claims

1. An acrylic polyester resin, obtained by grafting an acrylic polymer with a polyester material, the polyester material being obtained by polymerizing: i) a polyacid component, with ii) a polyol component, including a diol according to formula (I) ##STR00037## wherein R.sub.1 and R.sub.2 each independently represent a hydrogen radical, a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms, wherein at least one of R.sub.1 or R.sub.2 is a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms; R.sub.3 and R.sub.4 each independently represent a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms, and wherein at least one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality onto the polyester resin, such that an acrylic polymer is grafted with the polyester material via the use of said functionality, and wherein at least one of the polyacid component or the polyol component comprises an aliphatic group-containing monomer that is the dimerisation product of erucic acid, linolenic acid, linoleic acid, and/or oleic acid.

2. The resin of claim 1, wherein the functional monomer comprises an ethylenically unsaturated monomer.

3. The resin of claim 1, wherein the functional monomer is present as a proportion of the dry weight of the polyol or polyacid component in an amount of from 0.5 to 10 wt %.

4. The resin of claim 1, wherein the polyol component comprises trimethylol propane; pentaerythritol; di-pentaerythritol; trimethylol ethane; trimethylol butane; and bio-derived polyols.

5. The resin of claim 1, wherein the diol according to Formula (I) comprises 2,2,4-trimethyl-1,3-pentanediol (TMPD).

6. The resin of claim 1, wherein diol according to Formula (I) is present as a proportion of the dry weight of the polyol component in an amount of 10 and 80% wt.

7. The resin of claim 1, wherein the polyacid component and/or the polyol component comprises a sulfonated monomer.

8. The resin of claim 7, 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.

9. The resin of claim 1, wherein the polyester material comprises an Mn from 1,000 Daltons (Da=g/mole) to 15,000 Da.

10. The resin of claim 1, wherein the acrylic polyester resin is formed from the polyester material and an acrylic modification polymer in a weight ratio of 95 wt % to 55 wt % polyester material to 45 wt % to 5 wt % acrylic modification polymer.

11. The resin of claim 1, wherein the functional monomer comprises a hydroxyl functional monomer.

12. The resin of claim 11, wherein the hydroxyl functional monomer is present by dry weight of the acrylic modification polymer in an amount of 5 and 40 wt %.

13. The resin of claim 1, wherein the functional monomer comprises a ratio of methacrylate monomers to acrylate monomers of at least 1:1, wherein the ratio is calculated as the total number of methacrylate monomers compared to the total number of acrylate monomers across all types of acrylic monomers that form the acrylic polymer.

14. The resin of claim 1, wherein the acrylic polyester resin has a Mn of 1,000 Daltons (Da=g/mole) to 15,000 Da.

15. The resin of claim 1, wherein the acrylic polyester resin has a gross OHV of 0 to 120 mg KOH/g.

16. The resin of claim 1, wherein the acrylic polyester resin has an AV of 10 to 80 KOH/g.

17. The resin of claim 1, wherein the acrylic polyester resin has a Mn of 3,000 to 9,000 Da, a gross OHV of 10 to 50 mg KOH/g and an AV of 20 to 70 mg KOH/g.

18. An aqueous coating composition, the aqueous coating composition comprising: a) an acrylic polyester resin, obtained by grafting an acrylic polymer with a polyester material, the polyester material being obtained by polymerizing: i) a polyacid component, with ii) a polyol component, including a diol according to formula (I) ##STR00038## wherein R.sub.1 and R.sub.2 each independently represent a hydrogen radical, a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms, wherein at least one of R.sub.1 or R.sub.2 is a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms; R.sub.3 and R.sub.4 each independently represent a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms, wherein at least one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality onto the polyester resin, such that an acrylic polymer is grafted with the polyester material via the use of said functionality, b) a crosslinking material comprising material according to the following: ##STR00039## wherein R.sub.1 is selected from C.sub.6 to C.sub.24 aryl, or C.sub.5 to C.sub.25 aralkyl; R.sub.2 to R.sub.5 are each independently hydrogen, C.sub.1 to C.sub.20 alkyl, C.sub.6 to C.sub.24 aryl, C.sub.5 to C.sub.25 aralkyl or CHR.sub.8OR.sub.9; wherein R.sub.8 and R.sub.9 are each independently hydrogen, C.sub.1 to C.sub.20 alkyl, C.sub.6 to C.sub.24 aryl, C.sub.5 to C.sub.25 aralkyl, C.sub.2 to C.sub.40 alkoxyalkyl or C.sub.5 to C.sub.25 alkaryl; wherein at least one of R.sub.2 to R.sub.5, is CHR.sub.8OR.sub.9; and c) water.

19. The coating composition of claim 18, wherein the crosslinking material comprises one or more of a phenolic resin, benzoguanamine or melamine.

20. The coating composition of claim 18, wherein the aqueous coating composition is substantially free of bisphenol A (BPA), bisphenol F (BPF) and derivatives thereof.

21. The coating composition of claim 18, wherein the aqueous coating composition further comprises an adhesion promoter.

22. The coating composition of claim 18, wherein the coating composition has a solids content of from 10 to 60% by weight of the coating composition.

23. The coating composition of claim 18, wherein the acrylic polyester resin is present in the aqueous coating composition in an amount of 50 to 99 wt % based on dry weight of the aqueous coating composition.

24. 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, obtained by grafting an acrylic polymer with a polyester material, the polyester material being obtained by polymerizing: i) a polyacid component, with ii) a polyol component, including a diol according to formula (I) ##STR00040## wherein R.sub.1 and R.sub.2 each independently represent a hydrogen radical, a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms, wherein at least one of R.sub.1 or R.sub.2 is a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms; R.sub.3 and R.sub.4 each independently represent a lower alkyl radical or an aryl radical having 6 to 12 carbon atoms, wherein at least one of the polyacid component or the polyol component comprises a functional monomer operable to impart functionality onto the polyester resin, such that an acrylic polymer is grafted with the polyester material via the use of said functionality, b) a crosslinking material; c) water, wherein the packaging comprises a food or beverage can or aerosol can.

Description

EXAMPLES

(1) The details of polyester examples 1 to 4 are shown in Table 1. Each of examples 1 to 4 shows unsaturated, hydroxyl functional polyesters with TMPD.

(2) The polyester materials of examples 1 to 4 are formed as follows. The 2-methyl-1,3 propanediol/cyclohexanedimethanol, TMPD, IPA, dibutyl tin oxide, dimethyl terephthalate, hexahydrophthalic anhydride/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.

(3) Once the batch reaches 230? C., the acid value is assessed every hour. When the acid value is less than 20, the batch is cooled to 130? C. and methyl hydroquinone is added where applicable, then after 10 minutes, the maleic anhydride is added, where applicable, and the batch temperature increased to 195? C. until the desired acid value is reached. The batch is then cooled to 150? C. and azeotropically separated using a Dean Stark trap.

(4) The polyester materials of examples 1 to 4 then 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 4). Details of the monomers used in the acrylic graft reaction are shown in Table 2.

(5) The acrylic modified polyester resins were formed as follows.

(6) The polyester material (one of Examples 1 to 4) of charge #1 is added to a vessel with mixing at 225 rpm to a homogeneous mixture and heated to 120? C. Once at 120? C., the acrylate monomers of charge #2 are added over a period of 60 minutes. 10 minutes after adding charge #2, charge #3 was added over 40 minutes. Charge #4 was then added and the temperature increased to 120? C. with stirring increased to 350 rpm. Once the mixture was homogeneous charge #5 was added over 60 minutes. 10 minutes after starting the addition of charge #5, charge #6 was added over 40 minutes. Charge #7 is then added over 5 minutes and the temperature held at 120? C. for 30 minutes with stirring increased to 425 rpm. Charge #8 was added over 5 mintues and the reaction temperature held at 120? C. for 30 minutes. Charge #9 was then added and stirred for 30 minutes. The reaction mixture was then cooled to <80? C.

(7) The acrylic modified polyester resins are formed into aqueous dispersions with the components as shown in Table 3.

(8) The acrylic modified polyester resins are formed into aqueous dispersions by heating the resin to 85? C. under an N.sub.2 blanket. The DMEA is then added with stirring over 15 minutes. Deionized water is then added over 60 minutes and the temperature is kept to <80? C., after which the reaction mixture is stirred for 30 minutes and then cooled.

(9) The aqueous dispersions are formed into aqueous coating compositions with components as shown in Table 4, as follows. The crosslinking material (Cymel 1123-benzoguanamine, 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.

(10) TABLE-US-00001 TABLE 1 Example Example Example Example 1 2 3 4 Material name 2-methyl-1,3-propanediol 339.5 339.5 Cyclohexanedimethanol 542.5 542.5 TMPD 550.4 550.4 550.4 550.4 IPA 167.8 167.8 167.8 167.8 Dibutyl tin oxide 1.12 1.12 1.12 1.12 Diemethyl terephthalate 669.4 1028.1 651.9 1006.3 Hexahydrophthalic 332.5 332.5 anhydride Cyclohexane-1,4- 689.5 689.5 dicarboxylic acid Maleic anhydride 65.6 65.6 70.0 70.0 MeHQ 0.22 0.22 0.22 0.22 Aromatic 100 269.6 269.6 269.6 269.6 Dowanol DPM 1312.5 1312.5 1312.5 1312.5 Calculated Properties Initial weight 2483.52 2485.27 2673.39 2670.77 Theoretical water loss 280.31 421.48 277.87 238.22 Final resin weight 2203.21 2243.79 2395.53 2432.55 Total (inc solvents) 3785.30 3825.88 3977.61 4014.63 Approx Mn 5,248 5,341 5,208 5,039 OH equivalent excess 0.84 0.84 0.92 0.97

(11) TABLE-US-00002 TABLE 2 Resin 1 Resin 2 Resin 3 Resin 4 Resin 5 Resin 6 Resin 7 Resin 8 Charge #1 Polyester material of example 1 138.69 166.22 Charge #4 Polyester material of example 2 138.69 166.22 Polyester material of example 3 138.69 166.22 Polyester material of example 4 138.69 166.22 Charge #2 Methacrylic acid 9.84 9.84 9.84 9.84 4.89 4.89 4.89 4.89 Charge #5 Ethyl methacrylate 9.02 9.02 9.02 9.02 4.48 4.48 4.48 4.48 Methyl methacrylate 9.02 9.02 9.02 9.02 4.48 4.48 4.48 4.48 Hydroxyethyl methacrylate 4.92 4.92 4.92 4.92 2.44 2.44 2.44 2.44 Charge #3 SEK-534 8.85 8.85 8.85 8.85 8.85 8.85 8.85 8.85 tBuPOc-100% 1.77 1.77 1.77 1.77 1.77 1.77 1.77 1.77 Charge #6 SEK-534 8.85 8.85 8.85 8.85 5.90 5.90 5.90 5.90 tBuPOc-100% 1.77 1.77 1.77 1.77 1.18 1.18 1.18 1.18 Charge #7 SEK-534 5.90 5.90 5.90 5.90 5.90 5.90 5.90 5.90 tBuPOc-100% 1.18 1.18 1.18 1.18 1.18 1.18 1.18 1.18 Charge #8 SEK-534 5.90 5.90 5.90 5.90 5.90 5.90 5.90 5.90 tBuPOc-100% 1.18 1.18 1.18 1.18 1.18 1.18 1.18 1.18 Charge #9 SEK-534 22 22 22 22 0 0 0 0 Calculated Properties Total 400 400 400 400 400 400 400 400 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 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50

(12) TABLE-US-00003 TABLE 3 Aq. Aq. Aq. Aq. Aq. Aq. Aq Aq. dispersion dispersion dispersion dispersion dispersion dispersion dispersion dispersion 1 2 3 4 5 6 7 8 Resin 1 300.00 Resin 2 300.00 Resin 3 300.00 Resin 4 300.00 Resin 5 300.00 Resin 6 300.00 Resin 7 300.00 Resin 8 300.00 Dimethylethanolamine 6.86 6.86 6.86 6.86 6.86 6.86 6.86 6.86 Deionised water 158.93 158.93 158.93 158.93 158.93 158.93 158.93 158.93 Calculated Properties Total 465.79 465.79 465.79 465.79 465.79 465.79 465.79 465.79 Final % solids 38.00 38.00 38.00 38.00 38.00 38.00 38.00 38.00 Acid value (on 59% solids) 15.93 15.93 15.93 15.93 30.3 30.3 30.3 30.3

(13) TABLE-US-00004 TABLE 4 Aq. Aq. Coating Aq. Coating Aq. Coating Aq. Aq. Aq. Aq. Coating 1 2 3 4 Coating 5 Coating 6 Coating 7 Coating 8 Aq. dispersion 1 79.5 wt % Aq. dispersion 2 79.5 wt % Aq. dispersion 3 79.5 wt % Aq. dispersion 4 79.5 wt % Aq. dispersion 5 79.5 wt % Aq. dispersion 6 79.5 wt % Aq. dispersion 7 79.5 wt % Aq. dispersion 8 79.5 wt % Cymel 1123 20.00 wt % 20.00 wt % 20.00 wt % 20.00 wt % 20.00 wt % 20.00 wt % 20.00 wt % 20.00 wt % (benzoguanamine) Nacure 5925 (blocked 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % 0.1 wt % DDBSA) Michem Lube 160 (wax) 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt % 0.4 wt %