POLYESTERS

Abstract

The present invention provides a polyester which is the reaction product of reactants comprising: (A) an aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms; (B) an aromatic carboxylic acid and/or anhydride; and (C) a polyol. The invention also provides a coating composition comprising the polyester, a method of making the coating composition and the use of at least 2 wt % of a linear aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms as a replacement for at least 2 wt % of an aromatic carboxylic acid and/or anhydride in a polyester composition. This use may improve the UV resistance and/or stability of the polyester composition.

Claims

1. A polyester which is the reaction product of reactants comprising: (A) an aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms; (B) an aromatic carboxylic acid and/or anhydride; and (C) a polyol.

2. A polyester as claimed in claim 1, wherein the weight ratio of (A) to (B) in the polyester is from 0.2:1 to 5:1.

3. A polyester as claimed in claim 1 which has a molecular weight in the range from 500 to 10,000 g/mol.

4. A polyester as claimed in claim 1, wherein (A) is a linear aliphatic dicarboxylic acid comprising from 17 to 27 carbon atoms.

5. A polyester as claimed in claim 1 wherein (A) is obtained by a metathesis reaction.

6. A polyester as claimed in claim 1 wherein the reactants further comprise: (D) an aliphatic dicarboxylic acid comprising less than 16 carbon atoms or a cycloaliphatic carboxylic acid.

7. A polyester as claimed in claim 1 wherein: reactant (B) is selected from benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, trimelletic acid, pyromelletic acid and/or anhydrides thereof; and reactant (C) is a neopentyl polyol.

8. A polyester as claimed in claim 1 wherein the reactants comprise an anhydride selected from trimellitic anhydride, phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl hexahydrophthalic anhydride, succinic anhydride and maleic anhydride and wherein the polyester is water dispersible.

9. A polyester as claimed in claim 1 wherein the reactants further comprise a fatty acid and/or a fatty acid triglyceride and wherein the polyester is an alkyd resin.

10. A polyester as claimed in claim 1 wherein the polyester is for use in a coating composition.

11. A coating composition comprising a polyester as claimed in claim 1.

12. A coating composition as claimed in claim 11 which further comprises at least 10 wt % water.

13. A coating composition as claimed in claim 11 which further comprises at least 5 wt % organic solvent.

14. A method of making a coating composition comprising the steps of: (i) obtaining a polyester as claimed in claim 1; and (ii) including the polyester in a coating composition.

15. A method of improving the UV resistance and/or stability of a polyester composition wherein the polyester composition comprises the reaction product of an aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms, an aromatic carboxylic acid and/or anhydride, and a polyol, comprising replacing at least 2 wt % of an aromatic carboxylic acid and/or anhydride in the polyester composition with at least 2 wt % of a linear aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms, the wt % being on the basis of the total polyester composition, wherein the improvement in the UV resistance and/or stability of the polyester composition is with respect to a polyester composition in which the at least 2 wt % of an aromatic carboxylic acid and/or anhydride in the polyester composition is not replaced with at least 2 wt % of a linear aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms.

16. A method as claimed in claim 15 wherein the improvement in UV resistance and/or stability is determined by measuring the loss of gloss over 500 hours in a cured coating composition comprising the polyester composition.

17. A polyester as claimed in claim 1, wherein the weight ratio of (A) to (B) in the polyester is from 0.5:1 to 2:1.

18. A polyester as claimed in claim 1 wherein (A) is obtained by a self-metathesis reaction.

Description

EXAMPLES

[0083] The present invention will now be described further by way of example only with reference to the following Examples. All parts and percentages are given by weight unless otherwise stated. It will be understood that all tests and physical properties listed have been determined at atmospheric pressure and room temperature (i.e. about 20° C.), unless otherwise stated herein, or unless otherwise stated in the referenced test methods and procedures.

[0084] Compounds as used in the following examples are identified as follows: [0085] Trimethyolpropane (TMP) [0086] Neopentyl glycol (NPG) [0087] Trimellitic anhydride [0088] Adipic acid (C6 dicarboxylic acid) [0089] Isophthalic acid [0090] C18 diacid—linear aliphatic C18 dicarboxylic acid produced according to Example M1 below [0091] C26 diacid—linear aliphatic C26 dicarboxylic acid produced according to Example M2 below [0092] PRIPOL 1006™ dimer fatty diacid—a hydrogenated C36 dimer dicarboxylic acid ex Croda [0093] Cymel™ 303—a methylated melamine resin ex Allnex [0094] TEGO™ Wet 270—a wetting agent ex Evonik [0095] Benzoic acid [0096] Pentaerythritol [0097] Phthalic anhydride [0098] Soya fatty acid [0099] Exxol D40™—dearomatised aliphatic solvent ex Exxon Mobil [0100] Combi APB™—metal combination drier ex Elementis [0101] Meko™—Methyl Ethyl Ketoxime—anti-skinning agent [0102] Dimethylethanolamine [0103] Para-toluenesulfonic acid

[0104] Test methods used in the following examples are as follows: [0105] Number average molecular weight was determined by end group analysis with reference to the hydroxyl value. [0106] Hydroxyl value is defined as the number of mg of potassium hydroxide equivalent to the hydroxyl content of 1 g of sample, and was measured by acetylation followed by hydrolysation of excess acetic anhydride. The acetic acid formed was subsequently titrated with an ethanolic potassium hydroxide solution. [0107] Acid value is defined as the number of mg of potassium hydroxide required to neutralise the free fatty acids in 1 g of sample, and was measured by direct titration with a standard potassium hydroxide solution. [0108] Konig hardness was measured according to ASTM D4366. [0109] Impact resistance was measured according to ISO 6272-1. [0110] Crosshatch adhesion was measured according to ISO 2409 by visual inspection with damage ratings assigned on the following scale from 0=undamaged to 5=complete damage. [0111] Gloss was measured according to ISO 2813. [0112] UV exposure was performed using ASTM G53 after which at 500 hours the gloss was measured again using the above method. [0113] Chemical resistance was measured according to DIN 12720:1997-10 by visual inspection of spot tests with damage ratings assigned on the following scale from 0=undamaged to 5=complete damage. [0114] Drying time was measured according to ASTM D5895 [0115] Yellowing was measured with the yellowness index according to ASTM E313. Samples were kept in the dark i) for 1 week at room temperature, then ii) in the oven @50° C. for 4 weeks. [0116] Viscosity was measured according to ISO 2555.

Example M1

Production of C18 Diacid

[0117] 100 g methyl oleate (purified by aluminium-oxide treatment) was heated to 100° C. 13 ppm of ([1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinyliden]dichloro[(2-isopropoxy)(5-trifluoracetamido)benzyliden]ruthenium(II)) was dissolved in 1 ml toluene, and this was added to the methyl oleate.

[0118] After 30 seconds 43.6% conversion was reached, and after 120 seconds the reaction equilibrium conversion was reached. The resulting reaction mixture contained 24.8% 9-octadecene, 25.2% 9-octadecenedioic acid dimethyl ester and approximately 50% methyl oleate according to Gas Chromatography analysis. The reaction mixture was treated with a treated clay (Tonsil 210FF, 5 g) while stirring at 80° C. for 60 minutes. This mixture was filtered over filter paper to give an essentially catalyst-free product.

[0119] The catalyst-free product was purified using fractional distillation under vacuum of 2 to 9 mbar, by first distilling off the alkene and methyl oleate, and then collecting dimethyl octadecenedioate in the temperature range of 220-240° C. Gas Chromatography analysis indicated a purity of >95%.

[0120] Purified dimethyl octadecenedioate (200 g) was charged into a 400 ml volume hydrogenation autoclave vessel, 0.18 g palladium 5% on carbon hydrogenation catalyst was added, and the autoclave heated to 160° C. under 15 bar of hydrogen for 45 minutes, after which the hydrogen uptake has stopped, indicating reaction completion. The catalyst was filtered, resulting in dimethyl octadecanedioate, >95% purity according to Gas Chromatography analysis.

[0121] Dimethyl octadecanedioate (150 g) was combined with 300 g methanol, 100 g water and 200 g of a 50% KOH solution in water. This was heated to reflux for 1 h, and subsequently cooled to 55° C. 185 g of an 85% H.sub.3PO.sub.4 solution in 750 ml water was added gradually upon which a solid precipitate was formed which was stirred for 1 h. The solids were filtered off and washed with water until the filtrate had neutral pH as indicated using indicator paper. The solids were dried under vacuum (approx. 10 mbar, 60° C.) until no further mass loss occurred, resulting in 1,18-octadecanedioic acid. In the following examples, this 1,18-octadecanedioic acid will be referred to as C18 diacid.

Example M2

Production of C26 Diacid

[0122] 100 g methyl erucate (purified by aluminium-oxide treatment) was heated to 100° C. 105 ppm of ([1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinyliden]dichloro[(2-isopropoxy)(5-trifluoracetamido)benzyliden]]ruthenium(II) was dissolved in 1 ml toluene, and this was added to the methyl erucate.

[0123] After 30 seconds the reaction equilibrium conversion was reached. The resulting reaction mixture contained 20.6% 9-octadecene, 28.4% 13-hexacosenedioic acid dimethyl ester and approximately 50% methyl erucate according to Gas Chromatography analysis.

[0124] In order to produce 1,26-hexacosanediacid (C26 diacid) from this reaction mixture, the same steps were followed as given above in Example M1 for octadecanedioic acid (C18 diacid).

[0125] However, the fractional distillation step was modified in that the product (dimethyl hexacosenedioiate) remained in the bottom fraction of the distillation due to its high molecular weight. In the following examples, the 1,26-hexacosanedioic acid produced by this example will be referred to as C26 diacid.

Comparative Example PES1

A Polyester Not According to the Invention

[0126] 26 parts by weight of trimethylolpropane, 120.8 parts of neopentyl glycol, 56.4 parts of adipic acid, and 128.4 parts of isophthalic acid were introduced into a four-necked flask equipped with a reflux condenser, thermometer, stirring means and nitrogen inlet tube. The temperature was raised to 150° C., after which it was further raised to 230° C. in 3.5 hours and condensation accompanied by the elimination of water was carried out until the polyester acid value fell below 10. Subsequently, the reaction temperature was lowered to 150° C. and, after introducing 24.7 parts of trimellitic anhydride, the temperature was raised to 160-170° C. and this reaction temperature was then maintained for 30 minutes. Next, the temperature was increased to 180° C. and the reaction continued at this temperature. Once the polyester acid value had attained the planned acid value of 45-50, the reaction temperature was lowered to 120° C. and 77 parts of ethylene glycol monobutyl ether was added. A polyester resin (PES1) of 80 wt % solids was produced.

Example PES2

A Polyester Including C18 Diacid

[0127] 18.6 parts by weight of trimethylolpropane, 86.1 parts of neopentyl glycol, 40.3 parts of adipic acid, and 164.9 parts of C18 diacid (from Example M1) were introduced into a four-necked flask equipped with a reflux condenser, thermometer, stirring means and nitrogen inlet tube. The temperature was raised to 150° C., after which it was further raised to 230° C. in 3.5 hours and condensation accompanied by the elimination of water was carried out until the polyester acid value fell below 10. Subsequently, the reaction temperature was lowered to 150° C. and, after introducing 17.6 parts of trimellitic anhydride, the temperature was raised to 160-170° C. and this reaction temperature was then maintained for 30 minutes. Next, the temperature was increased to 180° C. and the reaction continued at this temperature. Once the polyester acid value had attained the planned acid value of 45-50, the reaction temperature was lowered to 120° C. and 75 parts of ethylene glycol monobutyl ether was added. A polyester resin (PES2) of 80 wt % solids was produced.

Example PES3

A Polyester Including C18 Diacid

[0128] 21.1 parts by weight of trimethylolpropane, 98.1 parts of neopentyl glycol, 104.2 parts of isophthalic acid and 85 parts of C18 diacid (from Example M1) were introduced into a four-necked flask equipped with a reflux condenser, thermometer, stirring means and nitrogen inlet tube. The temperature was raised to 150° C., after which it was further raised to 230° C. in 3.5 hours and condensation accompanied by the elimination of water was carried out until the polyester acid value fell below 10. Subsequently, the reaction temperature was lowered to 150° C. and, after introducing 23.6 parts of trimellitic anhydride, the temperature was raised to 160-170° C. and this reaction temperature was then maintained for 30 minutes. Next, the temperature was increased to 180° C. and the reaction continued at this temperature. Once the polyester acid value had attained the planned acid value of 45-50, the reaction temperature was lowered to 120° C. and 75 parts of ethylene glycol monobutyl ether was added. A polyester resin (PES3) of 80 wt % solids was produced.

Comparative Example PES4

A Polyester Not According to the Invention

[0129] 21.1 parts by weight of trimethylolpropane, 96.1 parts of neopentyl glycol, 119 parts of isophthalic acid and 84.9 parts of C36 diacid (PRIPOL 1006) were introduced into a four-necked flask equipped with a reflux condenser, thermometer, stirring means and nitrogen inlet tube. The temperature was raised to 150° C., after which it was further raised to 230° C. in 3.5 hours and condensation accompanied by the elimination of water was carried out until the polyester acid value fell below 10. Subsequently, the reaction temperature was lowered to 150° C. and, after introducing 24.8 parts of trimellitic anhydride, the temperature was raised to 160-170° C. and this reaction temperature was then maintained for 30 minutes. Next, the temperature was increased to 180° C. and the reaction continued at this temperature. Once the polyester acid value had attained the planned acid value of 45-50, the reaction temperature was lowered to 120° C. and 75 parts of ethylene glycol monobutyl ether was added. A polyester resin (PES4) of 80 wt % solids was produced.

[0130] Properties of PES1 to PES4

[0131] A comparison of various properties of the polyesters PES1 to PES4 is given in Table 1 below.

TABLE-US-00001 TABLE 1 properties of PES1 to PES 4 PES1 PES2 PES3 PES4 Acid value (mg KOH/g) 48.5 42 44 44 OH-value (mg KOH/g) 85.5 84.5 85.3 85 Molecular weight number average 1343 1344 1344 1348 (g/mol) Adipic acid (wt % on resin) 18 14 — — Isophthalic acid (wt % on resin) 41 — 35 38 C18-diacid (wt % on resin) — 55 28 — C36-diacid (wt % on resin) — — — 25 Adipic acid (mol % on resin) 14 15 — — Isophthalic acid (mol % on resin) 30 — 30 44 C18-diacid (mol % on resin) — 28 13 — C36-diacid (mol % on resin) — — — 7

Examples WB1 to WB4

Production of Water-Based Compositions from PES1 to PES4

[0132] To 100 parts by weight of each polyester resin PES1 to PES4 with a temperature of 50° C., 6.6 parts of dimethylethanolamine was slowly added while stirring and then a thorough stirring was performed. Next, 155 parts of deionized water was added and well-mixed therein, and a water-soluble or water-dispersible polyester resin was obtained. These water-based compositions WB1 to WB4 yielded a 40 wt % non-volatile material with a pH of 8-8.5.

Examples C1 to C4

Production and Evaluation of Coating Compositions from WB1 to WB4

[0133] To 100 parts by weight of WB1 to WB4, 6.9 parts of Cymel® 303 was slowly added while stirring and then thorough stirring was performed. Next, 0.5 wt % of the catalyst p-toluenesulfonic acid (50 wt % in ethanol) and 1 wt % of the wetting agent TEGO® Wet 270 were added. The resulting coating compositions are referred to as C1 to C4.

[0134] Coating compositions C1 to C4 were applied wet in a 50 μm layer to a steel Q panel (QD-36) and cured for 10 minutes at 160° C. Various properties of the cured coatings were evaluated and the results are given in Table 2 below.

TABLE-US-00002 TABLE 2 properties of cured coatings C1 to C4 C1 C2 C3 C4 König Hardness (s) 176 175 170 150 Impact resistance (kg .Math. cm) @ RT a) direct 200 200 200 200 b) indirect 200 200 200 200 Crosshatch adhesion .sup.1) 0 0 0 0 Gloss 20° (GU) 89 90 97 97 Loss of Gloss 20° −80% −11% −50% −40% after UV exposure over 500 h .sup.2) Chemical resistance .sup.3) to: Ammonia (10%) (2 min) 1 0 0 0 EtOH (50%) (1 hour) 1-2 0 0 0 Acetic acid (1 h) 2-3 2-3 2-3 2-3 Acetone (10 s) 2 0-1 0-1 0-1 Ethylacetate (10 s) 2 0-1 0-1 0-1 Water (16 h) 0 0 0 0 .sup.1) Crosshatch adhesion: damage ratings (0 = undamaged and 5 = complete damage) .sup.2) UV exposure according to ASTM G53: UV-B, cycle 8 h light @ 40° C./8 h dark @ 60° C. .sup.3) Chemical resistance: damage ratings (0 = undamaged and 5 = complete damage).

[0135] It can be seen from the results in Table 2 that the coating C2 based on PES2 (including linear aliphatic C18 diacid) exhibits a similar Konig hardness as C1 based on PES1 which includes an aromatic diacid (isopthalic acid) instead of C18 diacid. C2 also has similar or improved chemical resistance when compared with C1. Furthermore it can be seen from the results that coating C2 exhibits a similar initial gloss as C1. However after being exposed to UV-B in a cycle of 8 h light @40° C. and 8 h dark @60° C. for 500 h, a significant loss of gloss is noticed with the C1 coating (−80%) whereas the C2 coating exhibits only a small loss of gloss (−11%). This indicates that the inclusion of the C18 diacid as replacement for an aromatic diacid maintains the hardness and chemical resistance of a cured coating while improving its UV resistance and/or stability.

[0136] The inclusion of the C18 diacid in PES2 and PES3 results in no decrease of adhesion, chemical resistance and impact properties in coatings C2 and C3 when compared with C1. Coating C3 exhibits a similar hardness when compared with coatings C1 and C2. However, when the C18 diacid in coating C3 is replace with C36 dimer diacid in C4 (from PES4) then the hardness of C4 drops significantly when compared with C3. Without being bound by theory, it is believed that on this basis the C18 diacid of C3 can act as a replacement for aromatic diacid without unduly reducing the hardness of a cured coating, while the C36 dimer diacid of C4 cannot be used in this way without significantly reducing the hardness of the cured coating.

Comparative Example PES5

A Polyester Not According to the Invention

[0137] 10.5 g of benzoic acid, 65.6 g of pentaerythritol, 66 g of phthalic anhydride, 231.7 g of soya fatty acid and 3 wt % of xylene were charged into a reactor equipped with a Dean-stark distillation head, total condenser, agitator, inert gas sparge and thermometer. The mixture was heated to 220-240° C. and esterified until an acid value of approx. 5-10 mg KOH/g was obtained. The resin was cooled to 200° C. and the xylene was removed by means of vacuum distillation. The resulting polyester (alkyd) resin (PES5) was cooled to 100° C. and discharged.

Example PES6

A Polyester Including C18 Diacid

[0138] The procedure of Comparative Example PES5 was repeated using the following ingredients: 6.2 g of benzoic acid, 52.7 g of pentaerythritol, 99.3 g of C18 diacid (from Example M1), 217.2 g of soya fatty acid and 3 wt % of xylene. The resulting polyester (alkyd) resin is PES6.

Example PES7

A Polyester Including C18 Diacid

[0139] The procedure of Comparative Example PES5 was repeated using the following ingredients: 9.7 g of benzoic acid, 60.1 g of pentaerythritol, 33.3 g of C18 diacid (from Example M1), 40 g of phthalic anhydride, 230.9 g of soya fatty acid and 3 wt % of xylene. The resulting polyester (alkyd) resin is PES7.

[0140] Properties of PES5 to PES7

[0141] A comparison of various properties of the polyesters PES5 to PES7 is given in Table 3 below.

TABLE-US-00003 TABLE 3 Properties of PES5 to PES7 PES5 PES6 PES7 Wt (g) Mols Wt (g) Mols Wt (g) Mols Benzoic acid 10.5 0.086 6.2 0.05 9.7 0.08 C18 diacid — — 99.3 0.32 33.3 0.11 Pentaerythritol 65.3 0.48 52.7 0.39 60.1 0.44 Phthalic anhydride 66 0.45 — — 40 0.27 Soya fatty acid 231.7 0.84 217.2 0.78 230.9 0.83 Acid value 9.5 8.9 9.2 (mg KOH/g) Viscosity 740 2864 528 (mPa .Math. s) @ 23° C. 85% solid in xylene Colour (Gardner 63) 4.6 4.6 4.1 Oil Length (%) 69 65 69

Examples C5 to C7

Production and Evaluation of Coating Compositions from PES5 to PES7

[0142] Organic solvent based coating compositions C5 to C7 were prepared from polyesters PES5 to PES7 by preparing the mixtures shown in Table 4 below. All quantities in Table 4 are parts by weight.

TABLE-US-00004 TABLE 4 Coating Compositions C5 to C7 in parts by weight C5 C6 C7 PES5 60 — — PES6 — 60 — PES7 — — 60 Exxsol D40.sup.1) 15 15 15 Combi APB.sup.2) 3.4 3.4 3.4 Meko.sup.3) 0.2 0.2 0.2 .sup.1)Dearomatised aliphatic solvent .sup.2)Metal combination drier .sup.3)Anti-skinning agent

[0143] The coating compositions C5 to C7 were applied wet in a 100 μm layer to a glass panel with an applicator. Various properties of the coatings were evaluated and the results are given in Table 5 below.

TABLE-US-00005 TABLE 5 properties of C5 to C7 C5 C6 C7 Time to Dry (hours:mins) 10:00 2:45 6:00 König Hardness after 1 week 15 56 15 Yellowness index after 4 weeks 12  5 11

[0144] It can be seen from Table 5 that the drying time is improved in C6 and C7 which include C18 diacid when compared with C5 with no C18 diacid. Konig Hardness and yellowness index are similar for C5 (no C18 diacid) and C7 which has some phthalic anhydride replaced by C18 diacid. C6 which has all phthalic anhydride replaced by C18 diacid has better hardness and less yellowing than either C5 or C7.

[0145] It is to be understood that the invention is not to be limited to the details of the above embodiments, which are described by way of example only. Many variations are possible.