Polyester, polycarboxylated polyester resin, coatings

Abstract

This disclosure provides a polyester formed by reacting multiple monomers, wherein the monomers include: 15 to 20 molar parts of (a) an aliphatic triol monomer; 15 to 35 molar parts of (b) a first diol monomer; 60 to 80 molar parts of (c) a second diol monomer; and 100 molar parts of (d) an aliphatic diacid monomer or an aliphatic anhydride monomer. The polyester can be reacted with a polycarboxyl compound or an anhydride to form a polycarboxyl resin. The polycarboxyl resin can be used to form waterborne coatings.

Description

Technical Field

[0001] This disclosure relates to polyesters and polycarboxylated polyester resins. Background Technology

[0002] Polyester is widely used in coatings, adhesives, and fibers. The synthesis of traditional solvent-based polyester resins is very mature, and the resulting coatings have excellent physical properties. However, solvent-based coatings usually use a large amount of organic solvents to reduce their viscosity in order to facilitate continuous production for subsequent application. Therefore, there are potential risks in production, storage, and use, and they can also have adverse environmental impacts.

[0003] In conclusion, there is an urgent need for new solvent-free resins to solve the above problems. Summary of the Invention

[0004] An embodiment of this disclosure provides a polyester formed by reacting multiple monomers, wherein the monomers include: 15 to 20 molar parts of (a) an aliphatic triol monomer; 15 to 35 molar parts of (b) a first diol monomer; 60 to 80 molar parts of (c) a second diol monomer; and 100 molar parts of (d) an aliphatic diacid monomer or an aliphatic anhydride monomer. The chemical structure of (b) the first diol monomer is as follows: , where R 0 C 2-6 (c) The chemical structure of the second diol monomer is as follows: Where a, b, c, and d are each integers from 0 to 6, and a + b + c + d ≠ 0; R 1 C 1-6 alkyl groups, and each R 1 Same; R 2 For H or C 1-6 alkyl groups, and each R 2 Same; R 3 For H or C 1-6 alkyl groups, and each R 3 Same; R 4 For H or C 1-6 alkyl groups, and each R 4 Same; and R 5 For H or C 1-6 alkyl groups, and each R 5 same.

[0005] One embodiment of this disclosure provides a polycarboxylated polyester resin, wherein the ratio of acid value to alcohol value of the polycarboxylated polyester resin is from 1.2:1 to 2.0:1, and the alcohol value of the polycarboxylated polyester resin is from 35 mg KOH / g to 60 mg KOH / g. The polycarboxylated polyester resin is formed by reacting polyester with a polycarboxylated compound or an anhydride, and the alcohol value of the polyester is from 60 mg KOH / g to 90 mg KOH / g.

[0006] An embodiment of the coating disclosed herein includes 100 parts by weight of an aqueous resin, which is obtained by neutralizing the above-mentioned polycarboxylated polyester resin with alkali; 250 to 300 parts by weight of water; and 25 to 45 parts by weight of a hardener. Detailed Implementation

[0007] The polyester provided in one embodiment of this disclosure is formed by reacting multiple monomers, wherein the monomers include: 15 to 20 molar parts of (a) an aliphatic triol monomer; 15 to 35 molar parts of (b) a first diol monomer; 60 to 80 molar parts of (c) a second diol monomer; and 100 molar parts of (d) an aliphatic diacid monomer or an aliphatic anhydride monomer. If the amount of (a) the aliphatic triol monomer is too low, the molecular weight is not easily increased, and branching points cannot be formed to improve the physical properties of the resin. If the amount of (a) the aliphatic triol monomer is too high, the reaction is difficult to control and gelation is likely to occur. If the amount of (b) the first diol monomer is too low, the viscosity of the resin product will be relatively high. If the amount of (b) the first diol monomer is too high, the molecular weight will be low. If the amount of (c) the second diol monomer is too low, the hydrolysis resistance is poor. If the amount of (c) second diol monomer is too high, the crystallinity of the resin product will be low, and when applied to coatings, the transparency and gloss of the prepared coating will be poor.

[0008] In some embodiments, (a) the aliphatic triol monomer includes glycerol, trimethylolpropane, 1,1,1-trimethylolethane, polycaprolactone triol, stigmasterol-3,5,6-triol, (5alpha)-cholesterol-3,5,6-triol, or a combination thereof.

[0009] In some embodiments, (b) the chemical structure of the first diol monomer is as follows: , where R 0 C 2-6 The straight-chain alkyl group. In other words, (b) the first diol monomer does not have any other substituents on its carbon chain. If R 0 If the carbon number is too high, the viscosity of the resulting polyester can be significantly reduced, but the hardness of the prepared coating will be low and its weather resistance will be significantly worse. For example, (b) the first diol monomer includes ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, or a combination thereof.

[0010] In some embodiments, (c) the chemical structure of the second diol monomer is as follows: Where a, b, c, and d are each integers from 0 to 6, and a + b + c + d ≠ 0, for example, a + b + c + d = 2 to 24; R 1 C 1-6 alkyl groups, and each R 1 Same; R 2 For H or C 1-6 alkyl groups, and each R 2 Same; R 3 For H or C 1-6 alkyl groups, and each R 3 Same; R 4 For H or C 1-6 alkyl groups, and each R 4 Same; and R 5 For H or C 1-6 alkyl groups, and each R 5 Identical. In other words, (c) the second diol monomer must have at least two identical substituents (i.e., R). 1 For example, C 1-6 (The alkyl group) is substituted on the same carbon atom. For example, (c) the second diol monomer includes neopentyl glycol, isopentyl glycol, 3,3-dimethyl-1,5-pentyl glycol, 2,5-dimethyl-2,5-hexanediol, or a combination thereof.

[0011] In some embodiments, (d) the aliphatic dicarboxylic acid monomer or aliphatic anhydride monomer includes hexahydrophthalic anhydride, dodecenylsuccinic anhydride, hexahydro-4-methylphthalic anhydride, methylsuccinic anhydride, itaconic anhydride, 2,3-dimethylmaleic anhydride, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, tridecanoic acid, tartaric acid, or combinations thereof.

[0012] In some embodiments, the alcohol value of the polyester is between 60 mg KOH / g and 90 mg KOH / g. If the alcohol value of the polyester is too low, there are fewer reactive sites, making it difficult to undergo modification or crosslinking reactions. If the alcohol value of the polyester is too high, the coating formed by the coating containing the resin product will have too high a crosslinking density, resulting in poor toughness and easy cracking.

[0013] This disclosure provides a polycarboxylated polyester resin in which the ratio of acid value to alcohol value can be from 1.2:1 to 2:1, for example, from 1.3:1 to 1.9:1, and the alcohol value of the polycarboxylated polyester resin is from 35 mg KOH / g to 60 mg KOH / g. If the ratio of acid value to alcohol value of the polycarboxylated polyester resin is too low, its stability when dispersed in water is poor. If the ratio of acid value to alcohol value of the polycarboxylated polyester resin is too high, the viscosity of the finished resin product is high, which is not conducive to practical applications. If the alcohol value of the polycarboxylated polyester resin is too low, the degree of crosslinking and curing reaction is poor. If the alcohol value of the polycarboxylated polyester resin is too high, the crosslinking density is high, and the coating formed by the coating containing the resin product has poor toughness.

[0014] The aforementioned polycarboxylated polyester resin is produced by reacting polyester with a polycarboxylated compound or an anhydride, wherein the alcohol value of the polyester is between 60 mg KOH / g and 90 mg KOH / g. For example, the polyester can be a commercially available general polyester or the polyester described above in this disclosure, provided that the alcohol value of the polyester is between 60 mg KOH / g and 90 mg KOH / g, and the polycarboxylated polyester resin produced by reacting the polyester with a polycarboxylated compound or anhydride has the aforementioned range of alcohol values ​​and the ratio of acid value to alcohol value.

[0015] In some embodiments, the polyester is the aforementioned polyester, and the molar ratio of the (d) aliphatic diacid monomer or aliphatic anhydride monomer used to form the aforementioned polyester to the aforementioned polycarboxylic acid compound or anhydride is 100:11 to 100:18. If the amount of polycarboxylic acid compound or anhydride is too low, the acid value of the polycarboxylic polyester resin will be too low, resulting in insufficient stability of its aqueous dispersion after alkali neutralization. If the amount of polycarboxylic acid compound or anhydride is too high, the acid value of the polycarboxylic polyester resin will be too high, resulting in a significant increase in resin viscosity.

[0016] In some embodiments, the aforementioned polycarboxylic acid compounds or anhydrides include benzotriglycerid acid, trimellitic anhydride, pyromellitic terephthalic anhydride, or combinations thereof. In some embodiments, the weight-average molecular weight (MAM) of the aforementioned polycarboxylic polyester resin may be between 2000 and 20000 g / mol. If the MAM of the polycarboxylic polyester resin is too low, its solvent resistance and weather resistance will be poor. If the MAM of the polycarboxylic polyester resin is too high, it will be difficult to form a stable aqueous dispersion.

[0017] The coating provided in one embodiment of this disclosure comprises 100 parts by weight of an aqueous resin; 250 to 300 parts by weight of water; and 25 to 45 parts by weight of a hardener. The aqueous resin is formed by neutralizing the above-mentioned polycarboxylated polyester resin with an alkali. In some embodiments, the alkali may be triethylamine, ammonia, dimethylethanolamine, ethyl diisopropylamine, or a combination thereof. If the amount of water is too low, the coating viscosity is high and it is difficult to apply. If the amount of water is too high, the coating will not easily wet the substrate due to the high surface tension of water, and the coating is prone to pinholes. If the amount of hardener is too low, the film hardness or weather resistance will be poor. If the amount of hardener is too high, the film will be too soft or unable to form a film. In some embodiments, the hardener includes melamine or isocyanate. Melamine is generally used at high temperatures (120°C to 270°C), while isocyanate is generally used at low temperatures (10°C to 100°C).

[0018] In some embodiments, the coating may further include 1 to 150 parts by weight of pigment to alter the color of the coating film. For example, the pigment may be titanium dioxide, cobalt blue, chrome green, or other suitable pigments.

[0019] In some embodiments, the coating may further include 0.05 to 2 parts by weight of additives such as leveling agents, film-forming agents, defoamers, dispersants, antibacterial agents, or combinations thereof, to further improve the properties of the coating.

[0020] To make the foregoing contents and other objects, features and advantages of this disclosure more apparent and understandable, embodiments are provided below for detailed explanation:

[0021] Example

[0022] Example 1

[0023] Ethylene glycol (20 g), neopentyl glycol (90 g), trimethylolpropane (30 g), hexahydrophthalic anhydride (190 g), and stannous oxalate (0.3 g) were mixed and heated to 220 °C and reacted for 4 hours. After the reaction was completed, xylene was added to dilute to a solid content of 75% to obtain polyester (1). The acid value (<10 mg KOH / g) and alcohol value (77.8 mg KOH / g) of polyester (1) were measured using an automatic potentiometric titrator. The weight-average molecular weight (10208 g / mol) of polyester (1) was measured using GPC mixed with polystyrene (PS) as a standard.

[0024] Trimeric triglyceride (42 g) was added to polyester (1) (300 g), and the mixture was heated to 140°C and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (62.8 mg KOH / g) and alcohol value (48.3 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.30:1. Using GPC mixed with polystyrene (PS) as a standard, the weight-average molecular weight (11360 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The stability of the above dispersion in an oven at 50°C was greater than 7 days.

[0025] A water-based coating was prepared by adding 100 g of dispersion to a hardener (Allnex Cymel 303, 11 g from Qinglin Enterprises), TiO2 (Ti-Pure R960, 51 g from Xunmao Chemical), and a leveling agent (ADDITOL-XW-395, 0.2 g from Qinglin Enterprises). The dispersion was then diluted with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain a coating layer. The coating adhesion (5B) was tested using ASTM D3359, and the coating adhesion still reached 5B after being immersed in boiling water for 2 hours. The coating hardness (2H) was tested using ASTM D3363, the coating resistance to T-bending (2T) was tested using ASTM D4145, and the coating resistance to organic solvents was tested using ASTM D5402 (by wiping with 1 kg of MEK-saturated cotton for more than 100 times). The coating has a König hardness of 215.3 seconds, and its accelerated weathering test (ASTM G154 cycle 2) reaches 1293 hours. Commercially available water-based coatings, such as PPG Aquacron® 880, typically only achieve about 250 hours of weathering resistance.

[0026] Example 2

[0027] Ethylene glycol (20 g), neopentyl glycol (90 g), trimethylolpropane (30 g), hexahydrophthalic anhydride (190 g), and stannous oxalate (0.3 g) were mixed and heated to 210 °C and reacted for 12 hours. After the reaction was completed, xylene was added to dilute to a solid content of 75% to obtain polyester (2). The acid value (<10 mg KOH / g) and alcohol value (78.2 mg KOH / g) of polyester (2) were measured using an automatic potentiometric titrator. The weight-average molecular weight (12749 g / mol) of polyester (2) was measured using GPC mixed with polystyrene (PS) as a standard.

[0028] Trimeric trioxide (36 g) was added to polyester (2) (300 g), and the mixture was heated to 140°C and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (79.3 mg KOH / g) and alcohol value (41.9 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.89:1. Using GPC mixed with polystyrene (PS) as a standard, the weight-average molecular weight (14286 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The stability of the above dispersion in an oven at 50°C was greater than 7 days.

[0029] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 18 g), TiO2 (Ti-Pure R960, 55 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating. The coating's adhesion (5B) was tested using ASTM D3359. The coating's hardness (3H) was tested using ASTM D3363, its resistance to T-bending (3T) was tested using ASTM D4145, and its resistance to organic solvents was tested using ASTM D5402 (by wiping with 1 kg of MEK-saturated cotton for more than 100 times). The König hardness of the coating was 204.1 seconds.

[0030] Example 3

[0031] Ethylene glycol (20 g), neopentyl glycol (90 g), trimethylolpropane (30 g), hexahydrophthalic anhydride (190 g), and stannous oxalate (0.3 g) were mixed and heated to 210 °C and reacted for 10 hours. After the reaction was completed, xylene was added to dilute to a solid content of 75% to obtain polyester (3). The acid value (<10 mg KOH / g) and alcohol value (76.6 mg KOH / g) of polyester (3) were measured using an automatic potentiometric titrator. The weight-average molecular weight (4828 g / mol) of polyester (3) was measured using GPC mixed with polystyrene (PS) as a standard.

[0032] Trimeric trioxide (35 g) was added to polyester (3) (300 g), heated to 140°C, and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (60.9 mg KOH / g) and alcohol value (43.3 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.40:1. Using GPC mixed with polystyrene (PS) as a standard, the weight-average molecular weight (5404 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The stability of the above dispersion in an oven at 50°C was greater than 7 days.

[0033] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 10 g), TiO2 (Ti-Pure R960, 49 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating layer. The coating adhesion (5B) was tested according to ASTM D3359. The coating hardness (H) was tested according to ASTM D3363, the coating resistance to T-bending (1T) was tested according to ASTM D4145, and the coating resistance to organic solvents was tested according to ASTM D5402 (by wiping with 1 kg of MEK-saturated cotton for 70 cycles). The coating's König hardness was 190.3 seconds, and its accelerated weathering test (ASTM G154 cycle 2) reached 780 hours.

[0034] Example 4

[0035] Polyester 50558-R-70 purchased from Changxing Materials was used as polyester (4). The acid value (<10 mg KOH / g) and alcohol value (85.71 mg KOH / g) of polyester (4) were measured using an automatic potentiometric titrator. The weight-average molecular weight (11822 g / mol) of polyester (4) was measured using GPC mixed with polystyrene (PS) as a standard.

[0036] Trimeric trioxide (27 g) was added to polyester (4) (300 g), and the mixture was heated to 140°C and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (80.1 mg KOH / g) and alcohol value (42.8 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.87:1. Using GPC mixed with polystyrene (PS) as a standard, the weight-average molecular weight (13359 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and the aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The stability of the above dispersion in an oven at 50°C was greater than 7 days.

[0037] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 18 g), TiO2 (Ti-Pure R960, 60 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating layer. The coating adhesion (5B) was tested according to ASTM D3359. The coating hardness (3H) was tested according to ASTM D3363, the coating resistance to T-bending (3T) was tested according to ASTM D4145, and the coating resistance to organic solvents was tested according to ASTM D5402 (by wiping with 1 kg of MEK-saturated cotton for more than 100 times). The König hardness of the coating was 195.7 seconds.

[0038] Example 5

[0039] Ethylene glycol (20 g), neopentyl glycol (90 g), trimethylolpropane (30 g), hexahydrophthalic anhydride (190 g), and stannous oxalate (0.3 g) were mixed and heated to 210 °C and reacted for 10 hours. After the reaction was completed, xylene was added to dilute to a solid content of 75% to obtain polyester (5). The acid value (<10 mg KOH / g) and alcohol value (76.6 mg KOH / g) of polyester (5) were measured using an automatic potentiometric titrator. The weight-average molecular weight (4828 g / mol) of polyester (5) was measured using GPC mixed with polystyrene (PS) as a standard.

[0040] Trimellitic acid (39 g) was added to polyester (5) (300 g), heated to 165°C, and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (70.6 mg KOH / g) and alcohol value (37.1 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.90:1. Using GPC in combination with polystyrene (PS) as a standard, the weight-average molecular weight (5881 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The stability of the above dispersion in an oven at 50°C was greater than 7 days.

[0041] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 10 g), TiO2 (Ti-Pure R960, 49 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating. The coating adhesion (5B) was tested according to ASTM D3359. The coating hardness (2H) was tested according to ASTM D3363, the coating resistance to T-bending (1T) was tested according to ASTM D4145, and the coating resistance to organic solvents was tested according to ASTM D5402 (by wiping 94 times with 1 kg of MEK-saturated cotton). The König hardness of the coating was 179.6 seconds.

[0042] Comparative Example 1

[0043] Similar to Example 1, the difference lies in the addition of a larger amount of trimellitic anhydride (59 g) to polyester (1) (300 g), followed by heating to 140°C and reacting for 1 hour to form a polycarboxylated polyester resin. The acid value (93.9 mg KOH / g) and alcohol value (24.1 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 3.89:1. Using GPC in combination with polystyrene (PS) as a standard, the weight-average molecular weight (12128 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The stability of the above dispersion in an oven at 50°C was greater than 7 days.

[0044] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 11 g), TiO2 (Ti-Pure R960, 51 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating. The coating adhesion (1B) was tested according to ASTM D3359. The coating's resistance to T-bending (>5T) was tested according to ASTM D4145, and the coating was found to be too hard and brittle. The coating's resistance to organic solvents was tested according to ASTM D5402 (wiping with 1 kg of MEK-saturated cotton for more than 100 times). The König hardness of the coating was 128.7 seconds.

[0045] Comparative Example 2

[0046] Ethylene glycol (20 g), neopentyl glycol (90 g), trimethylolpropane (30 g), hexahydrophthalic anhydride (190 g), and stannous oxalate (0.3 g) were mixed and heated to 180 °C for 4 hours. After the reaction was completed, xylene was added to dilute to a solid content of 75% to synthesize polyester (6). The acid value (<10 mg KOH / g) and alcohol value (159 mg KOH / g) of polyester (6) were measured using an automatic potentiometric titrator. The weight-average molecular weight (1000 g / mol) of polyester (6) was measured using GPC combined with polystyrene (PS) as a standard.

[0047] Trimeric trioxide (115 g) was added to polyester (6) (300 g), heated to 150°C and reacted for 40 minutes, then heated to 180°C to confirm that gelation had not occurred (i.e., a polycarboxylated polyester resin was formed). The acid value (80.0 mg KOH / g) and alcohol value (14.1 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 5.67:1. Using GPC mixed with polystyrene (PS) as a standard, the weight-average molecular weight (1326 g / mol) of the above polycarboxylated polyester resin was measured. However, the viscosity of this polycarboxylated polyester resin was too high to be water-soluble and converted into a water-based resin.

[0048] Comparative Example 3

[0049] Similar to Example 3, the difference was that a smaller amount of trimellitic anhydride (23 g) was added to polyester (3) (300 g), and the mixture was heated to 140°C and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (52.5 mg KOH / g) and alcohol value (46.7 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.12:1. Using GPC in combination with polystyrene (PS) as a standard, the weight-average molecular weight (5212 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The above dispersion precipitated after about 1 day in an oven at 50°C, indicating insufficient water-based properties.

[0050] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 11 g), TiO2 (Ti-Pure R960, 49 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating. The coating adhesion (4B) was tested according to ASTM D3359. The coating's resistance to T-bending (1T) was tested according to ASTM D4145, and pinholes were observed. The coating's resistance to organic solvents was tested according to ASTM D5402 (by wiping with 1 kg of MEK-saturated cotton for 44 times). The König hardness of the coating was 35.1 seconds.

[0051] Comparative Example 4

[0052] Ethylene glycol (20 g), neopentyl glycol (90 g), trimethylolpropane (40 g), hexahydrophthalic anhydride (190 g), and stannous oxalate (0.3 g) were mixed, heated to 210 °C, and reacted for 6 hours. The mixture was then evacuated to 50 torr and reacted for another 6 hours. After the reaction was complete, xylene was added to dilute the mixture to a solid content of 75%, thus synthesizing polyester (7). The acid value (<10 mg KOH / g) and alcohol value (75.1 mg KOH / g) of polyester (7) were measured using an automatic potentiometric titrator. The weight-average molecular weight (22087 g / mol) of polyester (7) was measured using GPC combined with polystyrene (PS) as a standard.

[0053] Trimeric trioxide (34 g) was added to polyester (7) (300 g), heated to 150°C, and reacted for 1 hour to form a polycarboxylated polyester resin. The acid value (63.6 mg KOH / g) and alcohol value (41.5 mg KOH / g) of the polycarboxylated polyester resin were measured using an automatic potentiometric titrator, i.e., acid value: alcohol value = 1.53:1. Using GPC mixed with polystyrene (PS) as a standard, the weight-average molecular weight (24581 g / mol) of the above polycarboxylated polyester resin was measured. The carboxyl groups of the polycarboxylated polyester resin were neutralized with triethylamine to form a salt, and an aqueous resin was obtained when the pH value reached 7 to 8. Subsequently, deionized water was added under high-speed stirring (2000 rpm) to prepare a dispersion with a solid content of 40%. The above dispersion precipitated in an oven at 50°C after about 5 days.

[0054] A water-based coating was prepared by adding a hardener (Allnex Cymel 303, 18 g), TiO2 (Ti-Pure R960, 55 g), and a leveling agent (ADDITOL-XW-395, 0.2 g) to 100 g of dispersion and diluting the dispersion with deionized water to a solid content of 50%. The water-based coating was applied to a galvanized steel sheet and dried at 200°C for 10 minutes to obtain the coating. The coating's adhesion (5B) was tested using ASTM D3359. The coating's hardness (4H) was tested using ASTM D3363, its resistance to T-bending (4T) was tested using ASTM D4145, and its resistance to organic solvents was tested using ASTM D5402 (by wiping with 1 kg of MEK-saturated cotton for more than 100 times). The König hardness of the coating was 63.8 seconds.

[0055] Comparative Example 5

[0056] Similar to Example 5, trimellitic acid (39 g) was added to polyester (5) (300 g) and heated to 165°C. The difference was that the reaction lasted for 6 hours, resulting in gelation.

[0057] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A polyester formed by reacting a plurality of monomers, wherein the monomers include: 15 to 20 moles of (a) aliphatic triol monomer; 15 to 35 molar parts of (b) the first diol monomer; 60 to 80 molar parts of (c) second diol monomer; and 100 moles of (d) aliphatic dicarboxylic acid monomer or aliphatic anhydride monomer, The chemical structure of the first diol monomer (b) is as follows: , where R 0 C 2-6 alkyl groups; The chemical structure of (c) the second diol monomer is as follows: ， Where a, b, c, and d are each integers from 0 to 6, and a + b + c + d ≠ 0; R 1 C 1-6 alkyl groups, and each R 1 same; R 2 For H or C 1-6 alkyl groups, and each R 2 same; R 3 For H or C 1-6 alkyl groups, and each R 3 same; R 4 For H or C 1-6 alkyl groups, and each R 4 Same; and R 5 For H or C 1-6 alkyl groups, and each R 5 same.

2. The polyester according to claim 1, wherein (a) the aliphatic triol monomer comprises glycerol, trimethylolpropane, 1,1,1-trimethylolethane, polycaprolactone triol, stigmasterol-3,5,6-triol, (5alpha)-cholesterol-3,5,6-triol, or a combination thereof.

3. The polyester according to claim 1, wherein (b) the first diol monomer comprises ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, or a combination thereof.

4. The polyester according to claim 1, wherein (c) the second diol monomer comprises neopentyl glycol, isopentyl glycol, 3,3-dimethyl-1,5-pentylene glycol, 2,5-dimethyl-2,5-hexanediol, or a combination thereof.

5. The polyester according to claim 1, wherein (d) the aliphatic dicarboxylic acid monomer or aliphatic anhydride monomer comprises hexahydrophthalic anhydride, dodecenylsuccinic anhydride, hexahydro-4-methylphthalic anhydride, methylsuccinic anhydride, itaconic anhydride, 2,3-dimethylmaleic anhydride, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, tridecanoic acid, tartaric acid, or a combination thereof.

6. The polyester according to claim 1, wherein the alcohol value of the polyester is from 60 mg KOH / g to 90 mg KOH / g.

7. A polycarboxylated polyester resin, wherein the ratio of acid value to alcohol value of the polycarboxylated polyester resin is from 1.2:1 to 2.0:1, and the alcohol value of the polycarboxylated polyester resin is from 35 mg KOH / g to 60 mg KOH / g. The polycarboxylated polyester resin is formed by reacting a polyester with a polycarboxylated compound or an anhydride, and the alcohol value of the polyester is from 60 mg KOH / g to 90 mg KOH / g.

8. The polycarboxylated polyester resin according to claim 7, wherein the polyester system is formed by reacting a plurality of monomers, and the monomers include: 15 to 20 moles of (a) aliphatic triol monomer; 15 to 35 molar parts of (b) the first diol monomer; 60 to 80 molar parts of (c) second diol monomer; and 100 moles of (d) aliphatic dicarboxylic acid monomer or aliphatic anhydride monomer, The chemical structure of the first diol monomer (b) is as follows: , where R 0 C 2-6 Straight-chain alkyl groups; The chemical structure of (c) the second diol monomer is as follows: ， Where a, b, c, and d are each integers from 0 to 6, and a + b + c + d ≠ 0; R 1 C 1-6 alkyl groups, and each R 1 same; R 2 For H or C 1-6 alkyl groups, and each R 2 same; R 3 For H or C 1-6 alkyl groups, and each R 3 same; R 4 For H or C 1-6 alkyl groups, and each R 4 Same; and R 5 For H or C 1-6 alkyl groups, and each R 5 same.

9. The polycarboxylated polyester resin according to claim 8, wherein the molar ratio of (d) aliphatic dicarboxylic acid monomer or aliphatic anhydride monomer to the polycarboxylated compound or anhydride is 100:11 to 100:

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10. The polycarboxylated polyester resin according to claim 7, wherein the polycarboxylated compound or anhydride comprises benzotriic acid, trimellitic anhydride, pyromellitic tetroxide, or a combination thereof.

11. The polycarboxylated polyester resin according to claim 7, wherein the weight-average molecular weight of the polycarboxylated polyester resin is 2000 to 20000 g / mol.

12. A coating comprising: 100 parts by weight of the aqueous resin is made from the polycarboxylated polyester resin of claim 7 neutralized with alkali; 250 to 300 parts by weight of water; as well as 25 to 45 parts by weight of hardener.

13. The coating according to claim 12, wherein the hardener comprises melamine or isocyanate.

14. The coating according to claim 12, further comprising 1 to 150 parts by weight of pigment.

15. The coating according to claim 12, further comprising 0.05 to 2 parts by weight of an additive.

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