Polyester and coatings

Abstract

The present disclosure relates to a polyester formed by the reaction of a plurality of monomers, and the monomers include: 7 to 20 mole parts of (a) an aliphatic triol monomer; 40 to 80 mole parts of (b) a first diol monomer; 12 to 40 mole parts of (c) a second diol monomer; and 100 mole parts of (d) an aliphatic dicarboxylic acid monomer or an aliphatic acid anhydride monomer. The chemical structure of (b) the first diol monomer is as follows: or wherein each R 1 is the same. The chemical structure of (c) the second diol monomer is as follows: wherein R 6 is different from R 7 ​

Description

Technical Field

[0001] The present disclosure relates to polyesters, and more particularly to the monomers used therein. Background Art

[0002] Japan and the European Union have announced achieving carbon neutrality or net zero carbon emissions by 2050, and using biomass and highly durable materials is one of the ways to reduce carbon emissions. Traditional polyesters have the worst weather resistance and thus are not highly priced. To increase the value of polyesters, improving their weather resistance is the fastest way. On the other hand, reducing volatile organic compounds (VOCs) is a global trend, and regulations in the European Union and California in the United States require reducing the VOCs in coatings. However, the VOCs in coatings mainly come from solvents, and usually reducing the solvents may increase the viscosity of the coatings and make them unusable. In summary, there is an urgent need to develop new polyester materials to produce polyester coatings with high solid content (low VOC), low viscosity, high biomass content, and high weather resistance, so as to increase the value of polyesters. Summary of the Invention

[0003] The polyester provided by an embodiment of the present disclosure is formed by reacting multiple monomers, and the monomers include: 7 to 20 molar parts of (a) an aliphatic triol monomer; 40 to 80 molar parts of (b) a first diol monomer; 12 to 40 molar parts of (c) a second diol monomer; and 100 molar parts of (d) an aliphatic dicarboxylic acid monomer or an aliphatic acid anhydride monomer. The chemical structure of (b) the first diol monomer is: where n is an integer from 2 to 10, a, b, c, and d are each integers from 0 to 6, and a + b + c + d ≠ 0; R 0 is an alkylene group of C 2-5 ; R 1 is H or an alkyl group of C 1-6 , and each R 1 is the same; R 2 is H or an alkyl group of C 1-6 , and each R 2 is the same; R 3 is H or an alkyl group of C 1-6 , and each R 3 is the same; R 4 is H or an alkyl group of C 1-6 , and each R 4 is the same; R 5 is H or an alkyl group of C 1-6 , and each R 5 is the same. The chemical structure of (c) the second diol monomer is: where e, f, g, and h are each integers from 0 to 6, and e + f + g + h ≠ 0; and R 6 is H or an alkyl group of C 1-6 , R 7is H or C 1-6 is an alkyl group, and R 6 is different from R 7 ; and R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , and R 15 are each H or an alkyl group of C 1-6 .

[0004] The coating provided by an embodiment of the present disclosure includes: 100 parts by weight of the above polyester; and 5 to 40 parts by weight of a hardener. Description of the Drawings

[0005] None. Detailed Description of the Embodiments

[0006] To make the objectives, technical solutions, and advantages of the present disclosure clearer and more understandable, the present disclosure will be further described in detail below in conjunction with specific embodiments.

[0007] The polyester provided by an embodiment of the present disclosure is formed by reacting multiple monomers, and the monomers include 7 to 20 mole parts of (a) an aliphatic triol monomer; 40 to 80 mole parts of (b) a first diol monomer; 12 to 40 mole parts of (c) a second diol monomer; and 100 mole parts of (d) an aliphatic dicarboxylic acid monomer or an aliphatic anhydride monomer.

[0008] In some embodiments, the (a) aliphatic triol monomer includes glycerol, trimethylolpropane, 1,1,1-trimethylolethane, polycaprolactone triol, stigmastane-3,5,6-triol, (5alpha)-cholestane-3,5,6-triol, the above ethoxylated or propoxylated derivatives, or a combination of the above. If the amount of the (a) aliphatic triol monomer is too low, the molecular weight of the polyester is too low or the durability is insufficient. If the amount of the (a) aliphatic triol monomer is too high, the viscosity of the polyester is too high or gelling occurs during the reaction.

[0009] The chemical structure of the above (b) first diol monomer is as follows: where n is an integer from 2 to 10; a, b, c, and d are each integers from 0 to 6, and a + b + c + d ≠ 0; R 0 is an alkylene group of C 2-5 ; R1 is H or an alkyl group of C 1-6 , and each R 1 is the same; R 2 is H or an alkyl group of C 1-6 , and each R 2 is the same; R 3 is H or an alkyl group of C 1-6 , and each R 3 is the same; R 4 is H or an alkyl group of C 1-6 , and each R 4 is the same; R 5 is H or an alkyl group of C 1-6 , and each R 5 is the same. In some embodiments, (b) the first diol monomer includes ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, tripropylene glycol, or a combination thereof. If the amount of (b) the first diol monomer is too low, the molecular weight of the polyester is insufficient and the physical properties such as hardness are poor. If the amount of (b) the first diol monomer is too high, the viscosity of the polyester is too high or the weather resistance is poor.

[0010] The chemical structure of the above (c) second diol monomer is as follows: wherein e, f, g, and h are each an integer from 0 to 6, and e + f + g + h ≠ 0; and R 6 is H or an alkyl group of C 1-6 , R 7 is H or an alkyl group of C 1-6 , and R 6 is different from R 7 ; and R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , and R 15 are each H or an alkyl group of C 1-6 . In some embodiments, (c) the second diol monomer includes 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, butane-1,3-diol, 2-methylpentane-2,4-diol, 2-methyl-2-propyl-1,3-propanediol, or a combination thereof. If the amount of (c) the second diol monomer is too low, the viscosity of the polyester is too high. If the amount of (c) the second diol monomer is too high, the molecular weight of the polyester is not high, resulting in insufficient physical properties.

[0011] In some embodiments, the (d) aliphatic diacid monomer or aliphatic anhydride monomer includes hydrogenated phthalic 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, suberic acid, azelaic acid, sebacic acid, tridecanedioic acid, tartaric acid, or a combination thereof.

[0012] In some embodiments, the (a) aliphatic triol monomer, (b) first diol monomer, (d) aliphatic diacid monomer or aliphatic anhydride monomer, or a combination thereof is a biomass material. For example, the (a) aliphatic triol monomer can be biomass glycerol, and the (b) first diol monomer can be biomass ethylene glycol. The (d) aliphatic diacid monomer or aliphatic anhydride monomer can be biomass succinic acid. When the above monomers are biomass materials, the biomass content of the polyester can be increased. For example, the biomass content of the polyester can be increased to > 25%, which meets the BioPreferred label requirement (> 22%).

[0013] In some embodiments, the weight-average molecular weight of the polyester (hereinafter referred to as the weight-average molecular weight Mw) is from 4,500 to 90,000. The above weight-average molecular weight is measured by gel permeation chromatography (GPC) using polystyrene (PS, weight-average molecular weights Mw are 498, 1,220, 8,670, 19,100, 62,500, 125,000, 554,000, 1,170,000) as the standard. If the weight-average molecular weight of the polyester is too low, the weather resistance and physical properties of the polyester are poor. If the weight-average molecular weight of the polyester is too high, the viscosity of the polyester is too high or gelling occurs during the reaction. In some embodiments, the polyester can be applied to coatings. When the solid content of the polyester diluted in xylene is 75 wt%, the bubble viscosity at 25 °C can be maintained at Y to Z3. It should be noted that the measurement standard for the bubble viscosity is CNS 15200-2-2. If the bubble viscosity of the above-diluted polyester (75 wt%) is too low, paint sagging is likely to occur. If the bubble viscosity of the above-diluted polyester (75 wt%) is too high, it cannot be coated. Additionally, in some embodiments, when the bubble viscosity of the polyester is between X and Z3, it can be applied to inks, adhesives, or glass fiber reinforced plastics.

[0014] In some embodiments, the carbon spectrum ( 13 13C NMR) of the above polyester has a signal integral value of C1 at 39 ppm to 40 ppm, a signal integral value of C2 at 37 ppm to 39 ppm, and a signal integral value of C3 at 33 ppm to 35 ppm. C1 corresponds to an ester group formed by the reaction of one (a) aliphatic triol monomer and one (d) aliphatic diacid monomer or aliphatic anhydride monomer, C2 corresponds to two ester groups formed by the reaction of one (a) aliphatic triol monomer and two (d) aliphatic diacid monomers or aliphatic anhydride monomers, and C3 corresponds to three ester groups formed by the reaction of one (a) aliphatic triol monomer and three (d) aliphatic diacid monomers or aliphatic anhydride monomers. The esterification degree (i.e., the crosslinking degree) E of the (a) aliphatic triol monomer can be defined as E = (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3), and E can be from 2.07 to 2.50. When E is less than 2.07, it means that the esterification degree is low. If the esterification degree is insufficient, the weather resistance of the coating formed by the polyester is poor. When E is greater than 2.50, it means that the esterification degree is high. If the esterification degree is too high, the viscosity of the formed polyester is too high or even gelling occurs.

[0015] It is understandable that an appropriate amount of (a) aliphatic triol monomer, (b) first diol monomer, (c) second diol monomer, and (d) aliphatic dicarboxylic acid monomer or aliphatic anhydride monomer can be mixed and then heated to 150°C to 230°C and reacted for 4 to 24 hours to form a polyester. In addition, vacuum can be further applied and the reaction temperature and reaction time can be reduced to achieve a similar effect. It should be noted that if the heating temperature is too high, the reaction time is too long, or the degree of vacuum is too high, the esterification degree of the (a) aliphatic triol monomer may be too high. If the heating temperature is too low or the reaction time is too short, the esterification degree of the (a) aliphatic triol monomer may be insufficient. It should be noted that the above method is only for illustration and not to limit the present disclosure. Those with ordinary knowledge in the technical field can adopt feasible and appropriate steps and process parameters to complete the polymerization.

[0016] The coating provided by an embodiment of the present disclosure includes: 100 parts by weight of the above polyester; and 5 to 40 parts by weight of a hardener. In some embodiments, the hardener includes melamine or isocyanate. Melamine is generally used at high temperatures (120°C to 270°C), and isocyanate is generally used at low temperatures (10°C to 100°C). If the proportion of the hardener is too low, the physical properties of the coating film, such as hardness or weather resistance, are not good. If the proportion of the hardener is too high, the coating film is too soft or cannot form a film.

[0017] In some embodiments, the coating further includes 10 to 30 parts by weight of a solvent. For example, the solvent includes xylene, toluene, aromatic naphtha, ethyl acetate, butyl acetate, methyl isobutyl ketone, acetone, tetrahydrofuran, cyclohexane, cyclohexanone, or a combination of the above. If there is too much solvent, the solid content of the coating will be reduced and the volatile organic compounds (VOCs) will increase. The coating of the present disclosure can have the characteristics of high solid content and low viscosity, and has high weather resistance and high mechanical strength (such as bend resistance and hardness) after forming a coating.

[0018] To make the above content, other purposes, features, and advantages of the present disclosure more obvious and understandable, the following preferred embodiments are specifically given and described in detail as follows:

[0019] [Examples]

[0020] Example 1

[0021] 12 g of trimethylolpropane (0.09 mol), 24 g of ethylene glycol (0.39 mol), 36 g of neopentyl glycol (0.35 mol), 60 g of 2-ethyl-2-butylpropanediol (0.37 mol), 192 g of hydrogenated phthalic anhydride (1.25 mol), and 0.3 g of stannous oxalate were mixed and heated to 210 °C and reacted for 12 hours to form a polyester. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z, approximately 2300 cps) was measured at room temperature of approximately 25 °C according to CNS 15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (16885).

[0022] Example 2

[0023] 20 g of glycerol (0.22 mol), 30 g of ethylene glycol (0.48 mol), 30 g of neopentyl glycol (0.29 mol), 60 g of 2-ethyl-2-butylpropanediol (0.37 mol), 100 g of hydrogenated phthalic anhydride (0.65 mol), 96 g of succinic acid (0.81 mol), and 0.3 g of stannous oxalate were mixed and heated to 210 °C and reacted for 12 hours to form a polyester. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z, approximately 2300 cps) was measured at room temperature of approximately 25 °C according to CNS 15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (11993).

[0024] Example 3-1

[0025] 30 g of trimethylolpropane (0.22 mol), 25 g of ethylene glycol (0.40 mol), 30 g of neopentyl glycol (0.29 mol), 70 g of 2-ethyl-2-butylpropanediol (0.44 mol), 190 g of hydrogenated phthalic anhydride (1.23 mol), and 0.3 g of stannous oxalate were mixed and heated to 210 °C and reacted for 12 hours to form a polyester. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z, approximately 2300 cps) was measured at room temperature of approximately 25 °C according to CNS 15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (18667). The carbon spectrum ( 13 C NMR) of the polyester was measured. The signal integral value at 39 ppm to 40 ppm was C1, the signal integral value at 37 ppm to 39 ppm was C2, and the signal integral value at 33 ppm to 35 ppm was C3. In Example 3-1, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.48.

[0026] Take 100 g of the above polyester solution with a solid content of 75 wt%, add 20 g of the hardener melamine (Allnex Cymel 303) and 37.5 g of TiO₂ (Chemours Ti-Pure R706), and then dilute it with xylene to 75 wt% to form a coating. Coat the coating on a galvanized steel sheet and dry it at 240 °C for 10 minutes to obtain a coating. Test the hardness (H) of the coating according to CNS 10757, test the weather resistance of the coating according to ASTM G154 Cycle 2 (the gloss retention after 1000 hours is about 88%), and detect the T-bend resistance (2T) of the coating according to ASTM D4145.

[0027] Example 3-2

[0028] Similar to Example 3-1, except that the reaction time is reduced to 11.5 hours. The types and amounts of the remaining reactants, as well as the reaction temperature, are the same as those in Example 3-1. After the reaction, add xylene to dilute to a solid content of 75 wt%, and measure the Gardner-type bubble viscosity (Z, about 2300 cps) at room temperature of about 25 °C according to CNS15200-2-2. Use GPC with polystyrene (PS) as the standard to measure the weight-average molecular weight (12251) of the above polyester. Measure the carbon spectrum of the polyester ( 13 C NMR), the signal integral value from 39 ppm to 40 ppm is C1, the signal integral value from 37 ppm to 39 ppm is C2, and the signal integral value from 33 ppm to 35 ppm is C3. In Example 3-2, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.17.

[0029] Take 100 g of the above polyester solution with a solid content of 75 wt%, add 20 g of the hardener (Allnex Cymel 303) and 37.5 g of TiO₂ (Chemours Ti-Pure R706), and then dilute it with xylene to 75 wt% to form a coating. Coat the coating on a galvanized steel sheet and dry it at 240 °C for 10 minutes to obtain a coating. Test the hardness (3H) of the coating according to CNS 10757, test the weather resistance of the coating according to ASTM G154 Cycle 2 (the gloss retention after 1000 hours is about 100%), and detect the T-bend resistance (1T) of the coating according to ASTM D4145.

[0030] Example 3-3

[0031] Similar to Example 3-1, except that the reaction time was reduced to 11 hours. The types and amounts of the remaining reactants, as well as the reaction temperature, were the same as in Example 3-1. After the reaction, xylene was added to dilute to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z1, approximately 2500 cps) was measured at room temperature of about 25 °C according to CNS15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (10251). The carbon spectrum of the polyester was measured ( 13 C NMR), and the signal integral value from 39 ppm to 40 ppm was C1, the signal integral value from 37 ppm to 39 ppm was C2, and the signal integral value from 33 ppm to 35 ppm was C3. In Example 3-3, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.07.

[0032] Take 100 g of the above polyester solution with a solid content of 75 wt%, add 20 g of a hardener (Allnex Cymel 303) and 37.5 g of TiO2 (Chemours Ti-Pure R706), and then dilute with xylene to 75 wt% to form a coating. The coating was applied to a galvanized steel sheet and dried at 240 °C for 10 minutes to obtain a coating. The hardness of the coating was tested according to CNS 10757 (2H), the weather resistance of the coating was tested according to ASTM G154 Cycle 2 (the gloss retention after 1000 hours was about 85%), and the T-bend resistance of the coating was detected according to ASTM D4145 (1T).

[0033] Example 3-4

[0034] Similar to Example 3-1, except that the reaction temperature was increased to 220 °C and the reaction time was reduced to 6 hours. The types and amounts of the remaining reactants were the same as in Example 3-1. After the reaction, xylene was added to dilute to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z1, approximately 2500 cps) was measured at room temperature of about 25 °C according to CNS 15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (7881). The carbon spectrum of the polyester was measured ( 13 C NMR), and the signal integral value from 39 ppm to 40 ppm was C1, the signal integral value from 37 ppm to 39 ppm was C2, and the signal integral value from 33 ppm to 35 ppm was C3. In Example 3-4, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.48.

[0035] Take 100 g of the above polyester solution with a solids content of 75 wt%, add 20 g of a hardener (Allnex Cymel 303) and 37.5 g of TiO₂ (Chemours Ti-Pure R706), and then dilute it to 75 wt% with xylene to form a coating. Coating the coating on a galvanized steel sheet and drying it at 240 °C for 10 minutes to obtain a coating. Test the hardness of the coating (2H) according to CNS 10757, and detect the T-bend resistance of the coating (1T) according to ASTM D4145.

[0036] Example 4

[0037] Take 20 g of bioglycerol (0.22 mol), 37 g of ethylene glycol (0.60 mol), 45 g of neopentyl glycol (0.43 mol), 30 g of 2-ethyl-2-butylpropanediol (0.19 mol), 110 g of hydrogenated phthalic anhydride (0.71 mol), 95 g of bio-succinic acid (0.80 mol), and mix with 0.3 g of stannous oxalate, then heat to 210 °C and react for 12 hours to form a polyester. After the reaction is completed, add xylene to dilute to a solids content of 75 wt%, and measure the Gardner bubble viscosity (Y, about 2000 cps) at room temperature of about 25 °C according to CNS 15200-2-2. Measure the weight-average molecular weight (4880) of the above polyester with GPC using polystyrene (PS) as a standard. The bio-content (ASTM D6866) of the above polyester is 27.47%.

[0038] Take 100 g of the above polyester solution with a solids content of 75 wt%, add 20 g of a hardener (Allnex Cymel 303) and 37.5 g of TiO₂ (Chemours Ti-Pure R706), and then dilute it to 75 wt% with xylene to form a coating. Coating the coating on a galvanized steel sheet and drying it at 240 °C for 10 minutes to obtain a coating. Test the hardness of the coating (3H) according to CNS 10757, test the weather resistance of the coating (the gloss retention after 1000 hours is about 80%) according to ASTM G154 Cycle2, and detect the T-bend resistance of the coating (0T) according to ASTM D4145.

[0039] Example 5

[0040] 30 g of trimethylolpropane (0.22 mol), 32 g of ethylene glycol (0.52 mol), 70 g of 2-ethyl-2-butylpropanediol (0.44 mol), 190 g of hydrogenated phthalic anhydride (1.23 mol) were mixed with 0.3 g of stannous oxalate, and then heated to 210 °C and reacted for 12 hours to form a polyester. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%, and the Gardner-type bubble viscosity (X, about 1400 cps) was measured at about 25 °C at room temperature according to CNS15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight (5910) of the above polyester was measured.

[0041] Comparative Example 1-1

[0042] 10 g of trimethylolpropane (0.07 mol), 15 g of ethylene glycol (0.24 mol), 60 g of neopentyl glycol (0.58 mol), 15 g of 2-ethyl-2-butylpropanediol (0.09 mol), 160 g of hydrogenated phthalic anhydride (1.04 mol) were mixed with 0.3 g of stannous oxalate, and then heated to 210 °C and reacted for 12 hours to form a polyester. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z4, about 6500 cps) was measured at about 25 °C at room temperature according to CNS 15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight (1534) of the above polyester was measured. Due to the too low proportion of the second diol monomer, the viscosity of the polyester was too high and the weight-average molecular weight was insufficient.

[0043] Comparative Example 1-2

[0044] 4 g of trimethylolpropane (0.03 mol), 20 g of ethylene glycol (0.32 mol), 60 g of neopentyl glycol (0.58 mol), 20 g of 2-ethyl-2-butylpropanediol (0.12 mol), 160 g of hydrogenated phthalic anhydride (1.04 mol) were mixed with 0.3 g of stannous oxalate, and then heated to 210 °C and reacted for 12 hours to form a polyester. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight (883) of the above polyester was measured. Due to the too low proportion of the second diol monomer, the molecular weight of the polyester was insufficient.

[0045] Comparative Example 2

[0046] 40 g of glycerol (0.43 mol), 41 g of ethylene glycol (0.66 mol), 40 g of neopentyl glycol (0.38 mol), 200 g of hydrogenated phthalic anhydride (1.30 mol), and 0.3 g of stannous oxalate were mixed and heated to 210 °C and reacted for 12 hours. The above reaction gelled and it was impossible to measure its bubble viscosity and molecular weight.

[0047] Comparative Example 3-1

[0048] Similar to Example 3-1, except that the reaction time was reduced to 6 hours. The types and amounts of the remaining reactants, as well as the reaction temperature, were the same as those in Example 3-1. After the reaction was completed, xylene was added for dilution to a solid content of 75 wt%, and the Gardner-type bubble viscosity (Z, about 2300 cps) was measured at room temperature of about 25 °C according to CNS15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (9788). The carbon spectrum of the polyester ( 13 C NMR) was measured. The signal integral value from 39 ppm to 40 ppm was C1, the signal integral value from 37 ppm to 39 ppm was C2, and the signal integral value from 33 ppm to 35 ppm was C3. In Comparative Example 3-1, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.04.

[0049] 100 g of the above polyester solution with a solid content of 75 wt% was taken, 20 g of a hardener (Allnex Cymel 303) and 37.5 g of TiO2 (Chemours Ti-Pure R706) were added, and then diluted with xylene to 75 wt% to form a coating. The coating was applied to a galvanized steel sheet and dried at 240 °C for 10 minutes to obtain a coating. The hardness of the coating was tested according to CNS 10757 (3H), the weather resistance of the coating was tested according to ASTM G154 Cycle 2 (the gloss retention after 1000 hours < 40% and the coating peeled off), and the T-bend resistance of the coating was detected according to ASTM D4145 (2T). As can be seen from the above, insufficient reaction time resulted in insufficient esterification degree (i.e., crosslinking degree) of trimethylolpropane, and the weather resistance of the coating was reduced.

[0050] Comparative Example 3-2

[0051] Similar to Example 3-1, except that the reaction temperature was increased to 220 °C and vacuumed to 100 torr, and the reaction time was reduced to 9 hours. The types and amounts of the remaining reactants were the same as those in Example 3-1. After the reaction, xylene was added for dilution to a solid content of 75 wt%, and the Gardner bubble viscosity (Z, about 2300 cps) was measured at about 25 °C (room temperature) according to CNS 15200-2-2. Using GPC with polystyrene (PS) as the standard, the weight-average molecular weight of the above polyester was measured (97406). The carbon spectrum of the polyester was measured ( 13 C NMR), and the signal integral value from 39 ppm to 40 ppm was C1, the signal integral value from 37 ppm to 39 ppm was C2, and the signal integral value from 33 ppm to 35 ppm was C3. In Comparative Example 3-2, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.51. Due to the high vacuum and high reaction temperature, the esterification degree (i.e., crosslinking degree) of trimethylolpropane was too high, resulting in too high weight-average molecular weight and viscosity of the polyester.

[0052] Take 100 g of the above polyester solution with a solid content of 75 wt%, add 20 g of a hardener (Allnex Cymel 303) and 37.5 g of TiO2 (Chemours Ti-Pure R706), and then dilute with xylene to 75 wt% to form a coating. The coating was applied to a galvanized steel sheet and dried at 240 °C for 10 minutes to obtain a coating. The hardness of the coating was tested according to CNS 10757 (2H), and the T-bend resistance of the coating was detected according to ASTM D4145 (1T).

[0053] Comparative Example 3-3

[0054] Similar to Example 3-1, except that it was vacuumed to 50 torr and the reaction time was reduced to 4 hours. The types and amounts of the remaining reactants and the reaction temperature were the same as those in Example 3-1. The polyester formed by the reaction gelled and was not suitable for further applications. The carbon spectrum of the polyester was measured ( 13 C NMR), and the signal integral value from 39 ppm to 40 ppm was C1, the signal integral value from 37 ppm to 39 ppm was C2, and the signal integral value from 33 ppm to 35 ppm was C3. In Comparative Example 3-2, (C1 + 2*C2 + 3*C3) / (C1 + C2 + C3) = 2.7. Due to the vacuum, the esterification degree (i.e., crosslinking degree) of trimethylolpropane was too high, causing the polyester to gel and unable to be used as a coating.

[0055] Comparative Example 4

[0056] Take 30 g of trimethylolpropane (0.22 mol), 25 g of ethylene glycol (0.40 mol), 30 g of neopentyl glycol (0.29 mol), 70 g of 2-ethyl-2-butylpropanediol (0.44 mol), 190 g of phthalic anhydride (1.23 mol), and mix with 0.3 g of stannous oxalate, then heat to 210 °C and react for 12 hours to form a polyester. After the reaction is completed, add xylene to dilute to a solid content of 75 wt%, and measure the Gardner-type bubble viscosity (Z5-Z7, about 10,000 cps to 25,000 cps) at room temperature of about 25 °C according to CNS 15200-2-2. Use GPC with polystyrene (PS) as the standard to measure the weight-average molecular weight (4200) of the above polyester.

[0057] Take 100 g of the above polyester solution with a solid content of 75 wt%, add 20 g of the hardener melamine (Allnex Cymel 303) and 37.5 g of TiO2 (Chemours Ti-Pure R706), and then dilute with xylene to 75 wt% to form a coating. Coat the coating on a galvanized steel sheet and dry at 240 °C for 10 minutes to obtain a coating. Test the weather resistance of the coating according to ASTM G154 Cycle 2 (the gloss retention after 1000 hours is about 10%). As can be seen from the above, if the (d) aliphatic anhydride monomer is replaced with an aromatic anhydride monomer, the weather resistance of the formed coating is poor.

[0058] Comparative Example 5

[0059] Take a commercially available polyester (Changxing 5055, solid content 70 wt%) and concentrate it to a solid content of 75 wt%, and measure the Gardner-type bubble viscosity (Z4 to Z6, about 6500 cps to 15000 cps) at room temperature of about 25 °C according to CNS15200-2-2. As can be seen from the above, commercially available polyesters cannot form coatings with a high solid content and low viscosity.

[0060] Take 100 g of the above polyester solution with a solid content of 75 wt%, add 20 g of the hardener (Allnex Cymel 303) and 37.5 g of TiO2 (Chemours Ti-Pure R706), and then dilute with xylene to 75 wt% to form a coating. Coat the coating on a galvanized steel sheet and dry at 240 °C for 10 minutes to obtain a coating. Test the weather resistance of the coating according to ASTM G154 Cycle 2 (the gloss retention after 1000 hours is about 25%).

[0061] The specific embodiments described above further elaborate on the objective, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A polyester is formed by the reaction of multiple monomers, and these monomers include: 7 to 20 mole parts of (a) aliphatic triol monomer; 40 to 80 mole parts of (b) first diol monomer; 12 to 40 mole parts of (c) second diol monomer; and 100 mole parts of (d) aliphatic dicarboxylic acid monomer or aliphatic acid anhydride monomer; wherein the (b) first diol monomer includes ethylene glycol, propylene glycol, neopentyl glycol, 1,4 - butanediol, or a combination thereof; wherein the (c) second diol monomer includes 2 - butyl - 2 - ethyl - 1,3 - propanediol, 1,2 - propanediol, butane - 1,3 - diol, 2 - methylpentane - 2,4 - diol, 2 - methyl - 2 - propyl - 1,3 - propanediol, or a combination thereof; wherein the carbon spectrum of the polyester has a signal integral value of C1 at 39 ppm to 40 ppm, a signal integral value of C2 at 37 ppm to 39 ppm, a signal integral value of C3 at 33 ppm to 35 ppm, and (C1 + 2×C2 + 3×C3) / (C1 + C2 + C3)=2.07 to 2.

50.

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

3. The polyester according to claim 1, wherein the (d) aliphatic dicarboxylic acid monomer or aliphatic acid anhydride monomer includes hydrogenated phthalic anhydride, dodecenyl succinic anhydride, hexahydro - 4 - methylphthalic anhydride, methyl succinic anhydride, itaconic anhydride, 2,3 - dimethylmaleic anhydride, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, tridecanedioic acid, tartaric acid, or a combination thereof.

4. The polyester according to claim 1, wherein the (a) aliphatic triol monomer, the (b) first diol monomer, the (d) aliphatic dicarboxylic acid monomer or aliphatic acid anhydride monomer, or a combination thereof is a biomass material.

5. The polyester according to claim 1, having a weight - average molecular weight of 4500 to 90000.

6. The polyester according to claim 1, when diluted in xylene with a solid content of 75 wt%, having a bubble viscosity of Y to Z3 at 25°C.

7. A coating, comprising: 100 parts by weight of the polyester according to claim 1; and 5 to 40 parts by weight of a hardener.

8. The coating according to claim 7, wherein the hardener includes melamine or isocyanate.

9. The coating according to claim 7, further comprising 10 to 30 parts by weight of a solvent.

10. The coating according to claim 9, wherein the solvent includes xylene, toluene, aromatic naphtha, ethyl acetate, butyl acetate, methyl isobutyl ketone, acetone, tetrahydrofuran, cyclohexane, cyclohexanone, or a combination thereof.

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