Acrylic Polyester Resin and An Aqueous Coating Composition Containing the Same

Abstract

There is described an aqueous coating composition, the aqueous coating composition comprising an acrylic polyester resin, obtainable by grafting an acrylic polymer and a polyester material, the polyester material being obtainable by polymerizing: (i) a polyacid component, with (ii) a polyol component. At least one of the polyacid component and/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. The coating composition further containing a crosslinking material, wherein the crosslinking material comprises material according to formula (I); as shown in claim 1; wherein R.sub.1 is selected from aryl (such as C.sub.4 to C.sub.24 aryl), or aralkyl (such as C.sub.5 to C.sub.25 aralkyl); R.sub.2 to R.sub.5 are each independently hydrogen, alkyl (such as C.sub.1 to C.sub.20 alkyl), aryl (such as C.sub.4 to C.sub.24 aryl), aralkyl (such as 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, alkyl (such as C.sub.1 to C.sub.20 alkyl), aryl (such as C.sub.4 to C.sub.24 aryl), aralkyl (such as C.sub.5 to C.sub.25 aralkyl), alkoxyalkyl (such as C.sub.2 to C.sub.40 alkoxyalkyl) or an alkaryl (such as 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, suitably all of R.sub.2 to R.sub.5, are —CHR.sub.8OR.sub.9.

Claims

1. An aqueous coating composition, the aqueous coating composition comprising: a) an acrylic polyester resin based on the total solid weight of the coating composition, 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, wherein at least one of the polyacid component and/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 based on the total solid weight of the coating composition, wherein the crosslinking material comprises material according to formula (I) ##STR00050## wherein R.sub.1 is selected from aryl, or aralkyl; R.sub.2 to R.sub.5 are each independently hydrogen, alkyl, aryl, aralkyl or —CHR.sub.8OR.sub.9; wherein R.sub.8 and R.sub.9 are each independently hydrogen, alkyl, aryl, aralkyl, alkoxyalkyl or an alkaryl; wherein at least one of R.sub.2 to R.sub.5, is —CHR.sub.8OR.sub.9, wherein the material according to formula (I) forms at least 50 wt % of the crosslinking material of the coating composition; and c) a carrier comprising water and one or more organic solvents; and wherein the majority of the carrier is water and the organic solvent(s) comprise 17 wt % or greater of the total weight of the composition.

2. A packaging coated on at least a portion thereof with a coating, the coating being derived from the aqueous coating composition of claim 1.

3. The coating composition according to claim 1, wherein in the crosslinking material according to formula (I), R.sub.1 is selected from C.sub.4 to C.sub.24 aryl, or C.sub.5 to C.sub.25 aralkyl.

4. The coating composition according to claim 1, wherein the crosslinking material according to formula (I) is selected from one or more of benzoguanamine, butylated benzoguanamine and/or methylated benzoguanamine.

5. The coating composition according to claim 1, wherein the functional monomer comprises an ethylenically unsaturated monomer.

6. The coating composition according to claim 1, wherein the polyacid component comprises a monomer having an aliphatic group containing at least 15 carbon atoms and one or more of the following: dimethyl terephthalate, isophthalic acid, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid.

7. The coating composition according to claim 1, wherein the polyol component comprises one or more of the following: 2-methyl propanediol (2-MPD), 2,2,4,4-tetraalkylcyclobutane-1,3-diol, neopentyl glycol (NPG), 1,4-cyclohexane dimethanol (CHDM), butyl ethyl propane diol (BEPD), trimethylolppropane (TMP) or 1,6 hexanediol.

8. The coating composition according to claim 1, wherein the polyacid component comprises a monomer having an aliphatic group containing at least 15 carbon atoms.

9. The coating composition according to claim 1, wherein the polyester material comprises an Mn from 1,000 Daltons (Da-g/mole) to 15,000 Da.

10. The coating composition according to claim 1, wherein the polyester material has a gross OHV of from 0 to 120 mg KOH/g.

11. The coating composition according to claim 1, wherein an acrylic modification polymer is polymerized in the presence of the polyester material to form an acrylic modified polyester resin.

12. The coating composition according to claim 1, wherein the acrylic monomers comprise a hydroxyl functional monomer.

13. The coating composition according to claim 1, wherein the acrylic polyester resin has an Mn from 1,000 Daltons (Da=g/mole) to 15,000 Da.

14. The coating composition according to claim 1, wherein the acrylic polyester resin has a gross OHV from 0 to 120 mg KOH/g.

15. The coating composition according to claim 1, wherein the crosslinking material according to formula (I) forms at least 60 wt % of the crosslinking material of the coating composition.

16. The coating composition according to claim 1, wherein the aqueous coating composition is substantially free of bisphenol A (BPA), bisphenol F (BPF) and derivatives thereof.

17. The coating composition according to claim 1, wherein the aqueous coating composition is substantially free of styrene.

18. The coating composition according to claim 1, wherein the aqueous coating composition is substantially free of formaldehyde.

19. The coating composition according to claim 1, wherein the aqueous coating composition further comprises an adhesion promoter.

20. The coating composition according to claim 19, wherein the adhesion promoter comprises an acidic polyester material.

21. The packaging according to claim 2, wherein the packaging comprises a metal packaging container, a food or beverage can; a monobloc aerosol can; a metal cap or closure; a plastic bottle, plastic tube, laminate or flexible packaging.

23. A method of coating at least a portion of a packaging, the method comprising applying a coating composition of claim 1 to at least a portion of the packaging, and curing the aqueous coating composition to form a coating.

24. An electrodepositable coating composition comprising: a) an acrylic polyester resin, based on the total solid weight of the coating composition, 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, wherein at least one of the polyacid component and/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, wherein the acrylic polyester resin is formed in organic solvent, b) a crosslinking material based on the total solid weight of the coating composition, wherein the crosslinking material comprises material according to formula (I) ##STR00051## wherein R.sub.1 is selected from aryl, or aralkyl; R.sub.2 to R.sub.5 are each independently hydrogen, alkyl, aryl, aralkyl or —CHR.sub.8OR.sub.9; wherein R.sub.8 and R.sub.9 are each independently hydrogen, alkyl, aryl, aralkyl, alkoxyalkyl or an alkaryl; wherein at least one of R.sub.2 to R.sub.5, is —CHR.sub.8OR.sub.9, suitably all of R.sub.2 to R.sub.5, are —CHR.sub.8OR.sub.9, wherein the material according to formula (I) forms at least 50 wt % of the crosslinking material of the coating composition; and c) a carrier comprising water and one or more organic solvents; and wherein the majority of the carrier is water and the organic solvent(s) comprise 17 wt % or greater of the total weight of the composition.

25. A powder coating composition, the powder coating composition comprising: a) an acrylic polyester resin based on the total solid weight of the coating composition, 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, wherein at least one of the polyacid component and/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 based on the total solid weight of the coating composition, wherein the crosslinking material comprises material according to formula (I) ##STR00052## wherein R.sub.1 is selected from aryl, or aralkyl; R.sub.2 to R.sub.5 are each independently hydrogen, alkyl, aryl, aralkyl or —CHR.sub.8OR.sub.9; wherein R.sub.8 and R.sub.9 are each independently hydrogen, alkyl, aryl, aralkyl, alkoxyalkyl or an alkaryl; wherein at least one of R.sub.2 to R.sub.5, is —CHR.sub.8OR.sub.9, wherein the material according to formula (I) forms at least 50 wt % of the crosslinking material of the coating composition.

26. The coating composition of claim 1, wherein the polyacid component is substantially free of sulfonated monomer.

27. The packaging of claim 2, wherein the coating is applied to an uncoated or pretreated substrate of the packaging.

28. A packaging coated on at least a portion thereof with a coating, the coating being derived from the aqueous coating composition of claim 1.

29. The packaging of claim 28, wherein the coating is applied to an uncoated or pretreated substrate of the packaging.

30. The packaging of claim 29, wherein the packaging comprises a metal can.

31. The metal can of claim 30, wherein the coated portion comprises an easy open can end.

32. The metal can of claim 30, wherein the coated portion is at least on the interior of the can.

33. A packaging coated on at least a portion thereof with a coating, the coating being derived from the aqueous coating composition of claim 26.

Description

EXAMPLES

Method for the Formation of the Aqueous Coatings

[0463] The details of inventive aqueous coating compositions 1 to 3 and comparative aqueous coating composition 4 are shown in Tables 1 to 4. Coating compositions 1 to 4 show a composition containing a polyester-graft-acrylic (PGA) and a guanamine or melamine based crosslinking material. Comparative coating composition 4 shows a polyester-graft-acrylic and a phenolic resin crosslinking material.

[0464] The polyester material used in coating compositions 1 to 4 was 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 N2 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.

[0465] 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.

[0466] 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.

[0467] The polyester material 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 1 (noted simply as PGA resin 1 in Table 2). Details of the monomers used in the acrylic graft reaction are shown in Table 2.

[0468] The acrylic modified polyester resins were each formed as follows. Half of the amount of the polyester material given in Table 2 was added with 187.78 g of the butyl cellosolve to a vessel with mixing at 350 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 20.30 g of the butyl cellosolve and with continued stirring. 10 minutes after adding the acrylic monomers, about a third of the t-butyl peroctoate initiator amount as shown in Table 2 and 17.90 g of the butyl cellosolve 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 with 20.30 g of the butyl cellosolve. 10 minutes after adding the acrylic monomers, about a third of each of the t-butyl peroctoate initiator amount as shown in Table 2 and 17.98 g of the butyl cellosolve were added over a 30 minute period. The remaining t-butyl peroctoate initiator was then added in two evenly split batches, each batch with 11.98 g of the butyl cellosolve. The first batch was 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 80° C.

[0469] The acrylic modified polyester resins are formed into aqueous dispersions with the components as shown in Table 3.

[0470] 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. The aqueous dispersions were then allowed to cool to 45-C.

[0471] 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 and blocked DDBSA catalyst were stirred into the aqueous dispersion to form the aqueous coating composition.

TABLE-US-00001 TABLE 1 Polyester Polyester 1 Material — Cyclohexane dimethanol 767.00 Trimethylolpropane 10.40 Isophthalic acid 567.70 Pripol 1010 (C36 Dimer Acid) 634.00 MeHQ 0.18 Maleic anhydride 61.30 Stannous Octoate 1.00 Xylene 98.20 Dowanol DPM 713.00 Properties Initial weight 2036.34 Theoretical water loss 173.53 Final resin weight 1862.81 Total with solids 2673.98 % solids 67.14 Mn 5,651 Mw 25,403 PDI 4.50 AV 1.57 OH 15.6

TABLE-US-00002 TABLE 2 Polyester-graft-acrylic (PGA) Resin PGA resin 1 Material Polyester 1 850.74 Methacrylic acid 67.66 Ethyl methacrylate 62.02 Methyl methacrylate 62.02 2-hydroxyethyl methacrylate 33.83 t-butyl peroctoate 20.43 Butyl cellosolve 288.30 Properties Final % solids 58.19 % polyester 69.90 % acrylic 27.60 % initiator 2.50 AV 31.84 Mn 5,289 Mw 33,328

TABLE-US-00003 TABLE 3 Aqueous Dispersions Aq. Dispersion 1 Materials PGA resin 1 625.00 Dimethylethanolamine 20.97 Deionised water 869.41 Properties % solids 23.91 Acid Value 13.59 Particle size, matersizer, μm 0.432

TABLE-US-00004 TABLE 4 Coating Compositions Com- Example Example Example parative Material Description 1 2 3 Example 4 Aq. polyester grafted 40.00 40.00 40.00 40.00 Dispersion 1 acrylic resin DI Water de-ionized water 4.05 4.09 4.09 2.48 Dowanol solvent 1.13 1.13 1.13 1.09 PnB.sup.1 Cymel 1123.sup.2 benzoguanamine 1.69 1.04 Cymel 1130.sup.3 methylated/ 1.69 butylated melamine Cymel 303.sup.4 methylated 1.69 melamine HRJ-13078.sup.5 phenolic resin 1.74 Nacure 5925.sup.6 blocked catalyst 0.04 0.04 0.04 0.04 Total 46.91 46.94 46.94 45.39 .sup.1available from Dow Chemical .sup.2-4available from Allnex .sup.5available from King

Testing Methods

[0472] 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, conveyor oven for 10 seconds and baked to a peak metal temperature of 450° F. (232° C.).

[0473] The coatings were evaluated for the number of double rubs by hand it took to soften and break through the coating with a rag saturated with methyl ethyl ketone. Their flexibility was evaluated with a wedge bend test. For this test, coated panels were cut into 2 inch by 4.5 inch pieces, with the substrate grain running perpendicular to the long length of the cut panel. They were then bent over a % inch metal dowel along the long length of the panel with the coated side facing out. The bent coupons were then placed onto a block of metal where a wedge was pre-cut out of it with a taper of 0 to % inch along a 4.5 inch length. Once placed in the wedge, each bent coupon was struck with a block of metal which weighed 2.1 kilograms from a height of 11 inches to form a wedge where one end of the coated metal impinged upon itself and a % inch space remained on the opposite end. The wedge bent panels were then placed into an aqueous solution of copper sulfate and hydrochloric acid for two minutes to purposely etch the aluminum panel in areas where the coatings failed and cracked. The etched wedge bent panels were then examined through a microscope at 10× power to determine how far from the impinged end along the bent radii did the coating crack. Flex results are reported as the percentage of cracked area versus total length of the wedge bent panel. The coatings were also evaluated for their ability to adhere to the aluminum panels and to resist blushing in four aqueous solutions.

[0474] 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.

[0475] 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.

[0476] 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 blush and adhesion as described previously.

[0477] 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.

[0478] 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.

[0479] 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.

[0480] The results of these testing methods are provided in Table 5.

TABLE-US-00005 TABLE 5 Results Wedge Bends Acetic Acetic Water Water MEK (% Acid Acid Dowfax Dowfax Joy Joy Retort Retort Coating rubs failure) Blush Adhesion Blush Adhesion Blush Adhesion Blush Adhesion Example 1 100 14 8 4B 9 5B 9 5B 9 5B Example 2 100 23 7 0B 9 5B 9 5B 9 5B Example 3 100 21 7 0B 9 5B 9 5B 8 5B Comparative  2 31 2 0B 6 5B 7 5B 6 5B example 4