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. At least one of the polyacid component and/or the polyol component comprises a monomer having an aliphatic group containing at least 15 carbon atoms. 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. Also provided is an aqueous coating composition comprising the acrylic polyester resin and a packaging coated with the composition.

Claims

1. An aqueous coating composition comprising: a) a graft 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, wherein at least one of the polyacid component and/or the polyol component comprises a monomer having an aliphatic group containing at least 15 carbon atoms; wherein the polyester material has a gross hydroxyl value of 7 to 40 mg KOH/g; wherein the aliphatic group-containing monomer is a dimer fatty acid; 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 is grafted with the polyester material via the use of said functionality, b) a crosslinking material.

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

4. The coating composition of claim 1, wherein the aliphatic group of the aliphatic group-containing monomer comprises from 18 to 50 carbon atoms.

5. The coating composition of claim 1, wherein the aliphatic group-containing monomer is the dimerization product of erucic acid, linolenic acid, linoleic acid, and/or oleic acid.

6. The coating composition of claim 1, wherein the polyacid component comprises the aliphatic group-containing monomer and one or more of the following: dimethyl terephthalate, isophthalic acid, hexahydrophthalic anhydride, cyclohexane 1,4-dicarboxylic acid.

7. The coating composition of claim 1, wherein the polyol component comprises 2,2,4,4-tetraalkylcyclobutane-1,3-diol (TACD), alkylene glycol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, hydrogenated bisphenol A, cyclohexanediol, propanediol, 1,2-propanediol, 1,3-propanediol, butyl ethyl propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, butanediol, 1,4-butanediol, 1,3-butanediol, 2-ethyl-1,4-butanediol, pentanediol, trimethyl pentanediol, 2-methylpentanediol, cyclohexanedimethanol, hexanediol, 1,6-hexanediol, caprolactonediol, hydroxyalkylated bisphenol, polyether glycol, poly(oxytetramethylene) glycol, trimethylol propane, pentaerythritol, di-pentaerythritol, trimethylol ethane, trimethylol butane, dimethylol cyclohexane, bio-derived polyols, glycerol, sorbitol, and/or isosorbide.

8. The coating composition of claim 1, wherein the polyol component comprises 2-methyl propanediol (2-MPD), 2,2,4,4-tetraalkylcyclobutane-1,3-diol, 2,2,4,4-tetramethylcyclobutane-1,3-diol (TMCD), neopentyl glycol (NPG), 1,4-cyclohexane dimethanol (CHDM), butyl ethyl propane diol (BEPD), trimethylolpropane (TMP), and/or 1,6 hexanediol.

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

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

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

12. The coating composition of claim 1, wherein the crosslinking material comprises one or more of a phenolic resin, melamine, benzoguanamine or aminoplast resin.

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

14. The coating composition of claim 1, wherein the aqueous coating composition further comprises an adhesion promoter.

15. The coating composition of claim 14, wherein the adhesion promotor comprises an acidic polyester material.

16. The coating composition of claim 15, wherein the acidic polyester material 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.

17. The coating composition of claim 1, wherein the coating composition has a solids content of from 10 to 60%, 15 to 50 wt %, or 20 to 40 wt % by weight of the coating composition.

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

19. The coating composition of claim 1 is an electrodeposited coating composition.

20. A powder coating composition, the powder coating composition comprising: a) a graft 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, wherein at least one of the polyacid component and/or the polyol component comprises a monomer having an aliphatic group containing at least 15 carbon atoms; wherein the aliphatic group-containing monomer is a dimer fatty acid; 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 is grafted with the polyester material via the use of said functionality, wherein the polyester material has a gross hydroxyl value of 5 to 50 mg KOH/g; b) a crosslinking material.

Description

EXAMPLES

(1) Method for the Formation of the Aqueous Coatings

(2) The details of inventive aqueous coating 1 and comparative aqueous coating 2 are shown in Tables 1 to 4. Coating 1 shows unsaturated, hydroxyl functional polyesters formed from monomers including a monomer having at least 15 carbon atoms (Pripol 1010). Comparative coating 2 shows an unsaturated, hydroxyl functional polyester without a monomer having at least 15 carbon atoms.

(3) The polyester materials of inventive coating 1 and comparative coating 2 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 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.

(4) 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.

(5) 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.

(6) 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 1 and 2 (noted simply as PGA resins 1 and 2 in Table 2). Details of the monomers used in the acrylic graft reaction are shown in Table 2.

(7) 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.

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

(9) 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.

(10) 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 1123—benzoguanamine, 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.

(11) TABLE-US-00001 TABLE 1 Polyesters Comparative Polyester 1 Polyester 2 Material — 2-methyl-1,3-propanediol — 2157.50 Cyclohexane dimethanol 924.01 — TMCD — — Trimethylolpropane 12.62 29.24 Isophthalic acid 695.38 1117.50 Pripol 1010 (C36 Dimer Acid) 765.03 — Hexahydrophthalic anhydride — 619.50 Dibutyl tin oxide — 2.93 Cyclohexane-1,4-dicarboxylic acid — 1804.50 MeHQ 0.220 0.59 Maleic anhydride 74.44 196.90 Stannous Octoate 1.27 Xylene 118.93 705.50 Dowanol DPM 850.20 509.90 Properties Initial weight 2472.80 5928.76 Theoretical weight loss 212.01 728.01 Final resin weight 2260.79 5200.74 Total with solids 3230.09 6497.11 % solids 70.32 81.01 Mn 5,706 6,120 Mw 30,905 32,547 PDI 5.4 5.3 AV 0.45 0.70 OH 13.87 19.28

(12) TABLE-US-00002 TABLE 2 Polyester-graft-acrylic (PGA) Resins Comparative PGA resin 1 PGA resin 2 Material Polyester 1 1,688.96 — Comparative polyester 2 — 1,657.57 Methacrylic acid 78.8 77.88 Ethyl methacrylate 72.24 71.39 Methyl methacrylate 72.24 71.39 2-hydroxyethyl methacrylate 39.40 38.94 t-butyl peroctoate 36.9 36.88 Dowanol DPM 42.83 545.95 Properties Final % solids 59.00 59.00 % polyester 80.52 79.90 % acrylic 17.81 17.60 % initiator 1.67 2.50 AV 22.50 20.31

(13) TABLE-US-00003 TABLE 3 Aqueous Dispersions Comp. Aq. Aq. Dispersion 1 Dispersion 2 Materials PGA resin 1 1430.00 — Comparative PGA resin 2 — 1525.00 Dimethylethanolamine 33.25 33.08 Deionised water 1701.00 2123.55 Properties % solids 26.00 25.32 Acid Value 9.16 21 Particle size, matersizer, μm 0.290 0.119

(14) TABLE-US-00004 TABLE 4 Coating Compositions Comparative aq. Aq. Coating 1 Coating 2 Aq. dispersion 1 40.00 — Comparative aq. dispersion 2 — 40.00 DI Water 2.31 2.73 Dowanol PnB 1.07 1.13 Cymel 1123 (benzoguanamine) 1.07 1.12 Nacure 5925 (blocked DDBSA) 0.04 0.04 Total 44.49 45.02
Testing Methods

(15) 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.).

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) 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.

(22) The “1% Citric Acid Retort” test measures the resistance of a coating to 1% Citric Acid. Coated strips are immersed into the 1% citric acid solution 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.

(23) The results of these testing methods are provided in Table 5.

(24) TABLE-US-00005 TABLE 5 Results 1% 1% Wedge citric citric Bends Acetic Acetic Water Water acid acid (% Acid Acid Dowfax Dowfax Joy Joy Retort Retort retort retort Coating failure)* Blush Adhesion Blush Adhesion Blush Adhesion Blush Adhesion blush adhesion Example 11 9 4 B 9 5 B 9 5 B 9 5 B 7.5 5 B 1 Comp. 8 9 4 B 9 5 B 9 5 B 9 5 B 3 5 B Av. Coating 1 *Results <15% are acceptable.