A weather-resistant bio-based polyester resin, preparation process and application

Abstract

The present invention relates to the technical field of research and development of weather-resistant polyester powder coatings, and discloses a weather-resistant bio-based polyester resin, a preparation process and an application, including: synthesizing a light stabilizer monomer containing a phenolic hydroxyl group, and compounding the light stabilizer monomer containing a phenolic hydroxyl group with ZnO nanoparticles to obtain a light stabilizer with a synergistic effect; using the light stabilizer as a modifier, a polybasic acid containing a 2,5-furandicarboxylic acid component and a polyol as synthesis monomers, and preparing a polyester resin through catalytic esterification and vacuum polycondensation reactions; preparing a powder coating from the polyester resin. The present invention provides a process for preparing a polyester resin, and a weather-resistant bio-based polyester resin is prepared. The powder coating prepared from the polyester resin has excellent weather resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of research and development of weather-resistant polyester powder coatings, and specifically to a weather-resistant bio-based polyester resin, a preparation process and an application thereof. Background Art

[0002] Due to its excellent comprehensive properties, weather resistance, relatively low cost, etc., polyester powder coatings are widely used in outdoor facilities such as buildings, automobiles, and transportation roads. The powder coatings exposed outdoors will undergo aging and degradation due to the influence of various factors. Research has found that photo-oxidative degradation caused by sunlight irradiation is the main factor for the aging failure of the coating.

[0003] Currently, the main ways to improve the weather resistance of polyester resins include: (1) blending or copolymerizing polyester resins (acrylic resins, silicone resins) with monomers, intermediates or polymers with high weather resistance; (2) adding auxiliaries such as ultraviolet absorbers (benzophenone, benzotriazole, triazine compounds); (3) adding nano-inorganic fillers (light shielding agents such as titanium dioxide, zinc oxide, cerium dioxide). For example, the patent with the publication number CN116285680A discloses a polyester resin for low-temperature curing high-toughness super-weather-resistant powder coatings and its preparation method, using a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-di-tert-butyl-4-hydroxyphenyl]methyl]butylmalonate and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxy-resorcinol as an ultraviolet absorber to achieve the ultra-high weather resistance of the polyester resin.

[0004] It is found through retrieval that inorganic ultraviolet light shielding agents have stable chemical properties, good thermal stability, safety, high efficiency, and good durability, but their compatibility with the polymer matrix is poor. Organic ultraviolet absorbers have strong light absorption ability and good compatibility with polymers, but their chemical stability is poor. When they are used alone, the improvement of the weather resistance of materials is limited, but when they are used in combination, the weather resistance of materials can be significantly improved.

[0005] Further retrieval shows that by introducing a carbazole group with a strong intramolecular electron transfer and π-electron conjugation system into the ultraviolet absorber molecule, the light stability of the ultraviolet absorber can be significantly enhanced.

[0006] In addition, the monomers such as polyols and polyacids used in traditional polyester resins generally come from fossil raw materials such as petroleum, coal, and natural gas, which are prone to cause waste of resources and environmental pollution. With the concept of sustainable development deeply rooted in people's hearts, bio-based polyester resins synthesized from biomass raw materials have become a new research hotspot. Among them, furandicarboxylic acid (FDCA) is a biomass raw material containing a rigid aromatic ring in its molecular structure, and it is considered to be a suitable aromatic bio-based monomer substitute for traditional petrochemical-based monomers (terephthalic acid). Summary of the Invention

[0007] The present invention first synthesizes a novel light-stable monomer, and then composites it with nano-zinc oxide to obtain a light stabilizer with a synergistic effect. The light stabilizer is introduced into the polyester matrix to obtain a weather-resistant polyester resin, thereby achieving the technical goal of improving the weather resistance of polyester powder coatings.

[0008] A preparation process of a weather-resistant bio-based polyester resin includes the following steps:

[0009] Step 1: Synthesize a light-stable monomer containing a phenolic hydroxyl group, and composite the light-stable monomer containing a phenolic hydroxyl group with ZnO nanoparticles to obtain a light stabilizer with a synergistic effect;

[0010] Step 2: Prepare raw materials according to the formula of the polyester resin, and then prepare the polyester resin through catalytic esterification and vacuum polycondensation reactions;

[0011] Among them, the formula of the polyester resin is: 35-45 parts by weight of neopentyl glycol, 4-6 parts by weight of 2-butyl-2-ethyl-1,3-propanediol, 0.5-1 part by weight of trimethylolpropane, 20-40 parts by weight of terephthalic acid, 3-5 parts by weight of isophthalic acid, 10-20 parts by weight of 2,5-furandicarboxylic acid, 0.05-1 part by weight of a catalyst, 1-5 parts by weight of trimellitic anhydride, 0.5-5 parts by weight of a light stabilizer, and 0.1-3 parts by weight of a compound antioxidant.

[0012] Preferably, the light stabilizer is Light Stabilizer I, and the preparation method of the Light Stabilizer I is as follows:

[0013] Step S2-1: Using the Grignard reaction mechanism, with iodine as an initiator, 9-(4-bromophenyl)carbazole first reacts with metallic magnesium to generate Grignard reagent a, and then Grignard reagent a undergoes a coupling reaction with cyanuric chloride to synthesize carbazolyl triazine monomer a; wherein, the molar ratio of Grignard reagent a to cyanuric chloride is controlled to be 1:1;

[0014] Step S2-2: Using the Friedel-Crafts reaction mechanism, under the catalysis of a Lewis acid, carbazolyl triazine monomer a undergoes an electrophilic substitution reaction with resorcinol to synthesize Light Stabilizer I;

[0015] Step S2-3: Based on the epoxy-phenolic hydroxyl ring-opening reaction mechanism, Light Stabilizer I is used to modify KH560-modified ZnO nanoparticles to prepare Light Stabilizer I.

[0016] Preferably, the light stabilizer is Light Stabilizer II, and the preparation method of the Light Stabilizer II is as follows:

[0017] Step S3-1: Using the Grignard reaction mechanism, with iodine as the initiator, 9-(4-bromophenyl)carbazole first reacts with metallic magnesium to generate Grignard reagent b, and then Grignard reagent b undergoes a coupling reaction with cyanuric chloride to synthesize the carbazolyltriazine monomer b; wherein, the molar ratio of Grignard reagent b to cyanuric chloride is controlled to be 2:1;

[0018] Step S3-2: Using the Friedel-Crafts reaction mechanism, under the catalytic action of a Lewis acid, the carbazolyltriazine monomer b undergoes an electrophilic substitution reaction with resorcinol to generate the light stabilizer monomer II;

[0019] Step S3-3: Based on the epoxy-phenolic hydroxyl ring-opening reaction mechanism, the light stabilizer monomer II is used to modify the KH560-modified ZnO nanoparticles to prepare the light stabilizer II.

[0020] Preferably, the light stabilizer is light stabilizer III, and the preparation method of this light stabilizer III is: First, synthesize the light stabilizer monomer I and the light stabilizer monomer II, and then physically blend the light stabilizer monomer I, the light stabilizer monomer II with ZnO nanoparticles to prepare the light stabilizer III.

[0021] Preferably, the preparation method of the polyester resin in step two is:

[0022] Step S5-1: Mix neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol and trimethylolpropane evenly, heat and melt them, add terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid and a catalyst, raise the temperature to 220-240 °C and stir until the acid value is 5-7 mg KOH / g;

[0023] Step S5-2: Cool down to 210-230 °C and add a capping agent, keep the temperature at 210-230 °C until the acid value reaches 30-40 mg KOH / g, then vacuumize, and stir until the acid value is 20-30 mg KOH / g;

[0024] Step S5-3: Cool down to 190-200 °C, add the light stabilizer and the compound antioxidant to prepare the polyester resin.

[0025] Preferably, the catalyst is monobutyltin oxide 4100 or stannous oxalate;

[0026] Preferably, the capping agent is trimellitic anhydride or adipic anhydride;

[0027] Preferably, the compound antioxidant includes antioxidant 168 and antioxidant 1010.

[0028] Application of a weather-resistant bio-based polyester resin prepared according to the above process in powder coatings;

[0029] Preferably, the formulation of the powder coating is as follows: 45 to 60 parts by weight of a weather-resistant bio-based polyester resin, 3 to 8 parts by weight of a curing agent, 0.5 to 3 parts by weight of a leveling agent, 0.1 to 2 parts by weight of a brightening agent, 0.1 to 0.5 parts by weight of benzoin, and 2 to 10 parts by weight of titanium dioxide.

[0030] Preferably, the light retention rate of the powder coating is 75 to 95% and the color difference is 0.3 to 1.0.

[0031] Beneficial effects

[0032] First, a light-stable monomer containing phenolic hydroxyl groups was synthesized in the present invention. Then, based on the epoxy-phenolic hydroxyl ring-opening reaction mechanism, the light-stable monomer was used to modify KH560-modified ZnO nanoparticles to prepare a light stabilizer. Finally, the polyester resin was modified with the light stabilizer. Thus, the prepared powder coating can effectively extend the outdoor service life of the powder coating; that is, the present invention provides a new and effective method for improving the weather resistance of polyester powder coatings. Description of the drawings

[0033] Figure 1 is the synthesis route of light-stable monomer I;

[0034] Figure 2 is the 1H NMR spectrum of light-stable monomer I;

[0035] Figure 3 is the synthesis route of light-stable monomer II;

[0036] Figure 4 is the 1H NMR spectrum of light-stable monomer II;

[0037] Figure 5 are the experimental results of the weather resistance of the powder coating. Detailed implementation manners

[0038] Experimental example 1:

[0039] Synthesize light-stable monomer I, as Figure 1 shown, and its synthesis route is as follows:

[0040] Step 1: Using the Grignard reaction mechanism, with iodine as the initiator, 9-(4-bromophenyl)carbazole first reacts with metallic magnesium to generate Grignard reagent a. Then, 1 molar equivalent of Grignard reagent a undergoes a coupling reaction with 1 molar equivalent of cyanuric chloride to synthesize carbazolyl triazine monomer a. The specific experimental steps are as follows: Add 0.3 g of magnesium powder, 0.1 g of iodine, and 20 mL of tetrahydrofuran into a four-necked flask. Under mechanical stirring, heat up to 70 °C. Then, slowly drip 10 mL of 9-(4-bromophenyl)carbazole solution (prepared from 3.3 g of 9-(4-bromophenyl)carbazole and 10 mL of tetrahydrofuran) into the four-necked flask, maintain reflux at 70 °C for 2 h. After cooling, slowly drip the above liquid into a four-necked flask containing 2.0 g of cyanuric chloride and 20 mL of tetrahydrofuran (control the temperature not exceeding 30 °C), heat up to 50 °C and stir for 1 h. Rotate and evaporate to remove the solvent, add deionized water, filter, and recrystallize with dichloromethane to obtain carbazolyl triazine monomer a;

[0041] Step 2: Using the Friedel-Crafts reaction mechanism, under the catalysis of Lewis acid, carbazolyl triazine monomer a undergoes an electrophilic substitution reaction with resorcinol to synthesize light-stable monomer I;

[0042] Among them, the Lewis acid is selected from one of aluminum trichloride, iron trichloride, tin tetrachloride, and zinc dichloride; in this experimental example, aluminum trichloride is selected;

[0043] The specific experimental steps for synthesizing light-stable monomer I are as follows: Add 3.9 g of carbazolyl triazine monomer a, 1.5 g of anhydrous aluminum trichloride, 2.2 g of resorcinol, and 50 mL of chlorobenzene into a four-necked flask, heat up to 80 °C and stir for 3 h. After cooling, add an ice-water mixture, heat under reflux, separate the chlorobenzene, filter, wash with deionized water, and dry to obtain light-stable monomer I. Its nuclear magnetic resonance hydrogen spectrum (solvent: CDCl 3 3, frequency: 400 MHz) is as Figure 2 shown.

[0044] Experimental Example Two:

[0045] Synthesize light-stable monomer II, as Figure 3 shown, and its synthetic route is as follows:

[0046] Step 1: Using the Grignard reaction mechanism, with iodine as the initiator, 9-(4-bromophenyl)carbazole first reacts with metallic magnesium to generate Grignard reagent b. Then, 2 molar equivalents of Grignard reagent b undergo a coupling reaction with 1 molar equivalent of cyanuric chloride to synthesize carbazolyl triazine monomer b;

[0047] The difference between the experimental method of carbazolyl triazine monomer b and the synthesis of carbazolyl triazine monomer a is only that: 1.0 g of cyanuric chloride is used to replace 2.0 g of cyanuric chloride;

[0048] Step 2: Using the Friedel-Crafts reaction mechanism, under the catalysis of Lewis acid, the carbazolyl triazine monomer b undergoes an electrophilic substitution reaction with resorcinol to generate the light-stable monomer II;

[0049] The experimental method for synthesizing the light-stable monomer II only differs from that for synthesizing the light-stable monomer II in that: 12 g of the carbazolyl triazine monomer b is used to replace 3.9 g of the carbazolyl triazine monomer a, and its nuclear magnetic resonance hydrogen spectrum (solvent: CDCl 3 , frequency: 400 MHz) is as Figure 4 shown.

[0050] Experimental Example 3:

[0051] Preparation of KH560-modified ZnO nanoparticles: Add 1.5 g of zinc oxide nanoparticles, 10 mL of deionized water, and 40 mL of absolute ethanol to a three-necked flask, stir and dissolve at room temperature for 30 min, and ultrasonically disperse for 30 min. Then, add 10 mL of KH560 silane coupling agent solution (prepared from 0.3 g of KH560 silane coupling agent and 10 mL of absolute ethanol) dropwise to the three-necked flask, raise the temperature to 70 °C, stir and react for 2 h, filter by suction, and dry under vacuum to obtain KH560-modified ZnO nanoparticles;

[0052] Among them, the zinc oxide nanoparticles are nano-zinc oxide purchased from Aladdin Reagent Network, with the product number Z112847, and its specification or purity is 99.9% metals basis, 30 ± 10 nm.

[0053] Example 1:

[0054] Preparation of light stabilizer I: Based on the epoxy-phenolic hydroxyl ring-opening reaction mechanism, the light-stable monomer I is used to modify the KH560-modified ZnO nanoparticles to prepare the light stabilizer I;

[0055] The specific experimental steps for preparing the light stabilizer I are as follows: Add 10 g of KH560-modified ZnO nanoparticles and 50 mL of N,N-dimethylformamide to a three-necked flask, rapidly stir and mix at room temperature for 30 min. Then, add 10 mL of the mixed solution of the light-stable monomer I and sodium hydroxide (prepared from 3 g of the light-stable monomer I, 0.5 g of sodium hydroxide, and 10 mL of N,N-dimethylformamide) to the three-necked flask, raise the temperature to 90 °C, stir and react for 3 h, cool to room temperature, centrifuge, wash and centrifuge repeatedly with ethanol, and dry in a vacuum oven to obtain the light stabilizer I.

[0056] Example 2:

[0057] Preparation of Light Stabilizer Ⅱ: Based on the ring-opening reaction mechanism of epoxy-phenolic hydroxyl group, light-stable monomer Ⅱ was used to modify KH560-modified ZnO nanoparticles to prepare Light Stabilizer Ⅱ;

[0058] The difference between the preparation method of Light Stabilizer Ⅱ and that of Light Stabilizer Ⅰ is only that: Light-stable monomer Ⅱ is used to replace Light-stable monomer Ⅰ.

[0059] Example 3:

[0060] Preparation of Light Stabilizer Ⅲ: Physical blending of Light-stable monomer Ⅰ, Light-stable monomer Ⅱ and ZnO nanoparticles was carried out to prepare Light Stabilizer Ⅲ.

[0061] The specific experimental steps for preparing Light Stabilizer Ⅲ are as follows: 10 g of ZnO nanoparticles, 1.5 g of Light-stable monomer Ⅰ, 1.5 g of Light-stable monomer Ⅱ and 50 mL of N,N-dimethylformamide were added to a three-necked flask, rapidly stirred and mixed at room temperature for 30 min, the solvent was removed by rotary evaporation, and vacuum drying was carried out to obtain Light Stabilizer Ⅲ.

[0062] Example 4:

[0063] Preparation of Polyester Resin Ⅰ includes the following steps:

[0064] Step 1: According to the formula of Polyester Resin Ⅰ in Table 1, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol and trimethylolpropane were first put into a reaction kettle, heated and melted, filled with nitrogen and stirred, then terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid and monobutyltin oxide 4100 were added, and the temperature was raised to 235 °C and the reaction was maintained until the acid value was 6.8 mgKOH / g;

[0065] Step 2: The temperature was lowered to 220 °C and trimellitic anhydride was added, and it was kept at 220 °C until the acid value was 35.2 mgKOH / g, then the vacuum was pumped at 220 °C to a vacuum degree of -0.1 MPa and maintained for 3 h, so that the acid value was 27.8 mgKOH / g and the hydroxyl value was 11.4 mgKOH / g;

[0066] Step 3: The temperature was lowered to 200 °C, Light Stabilizer Ⅰ, antioxidant 168 and antioxidant 1010 were added, and the reaction was maintained for 40 min to obtain Polyester Resin Ⅰ;

[0067] Among them, the acid value was tested according to GB / T 6743-2008 Determination of Part Acid Value and Total Acid Value of Polyester Resins for Plastics, Paint Bases for Paints and Varnishes.

[0068] Table 1 Formulation of Polyester Resin (feed mass m (g))

[0069]

[0070] Afterwards, according to the experimental method of polyester resin I, light stabilizer II was used to replace light stabilizer I to prepare polyester resin II, and light stabilizer III was used to replace light stabilizer I to prepare polyester resin III.

[0071] In order to explore the influence of the bio-based raw material 2,5-furandicarboxylic acid FDCA on the performance of the coating, the following experiments were carried out in this invention:

[0072] Experiment 1: According to the experimental method of polyester resin I, polyester resin a was prepared according to the formula of polyester resin a in Table 1;

[0073] Experiment 2: According to the experimental method of polyester resin I, polyester resin b was prepared according to the formula of polyester resin b in Table 1;

[0074] Experiment 3: According to the experimental method of polyester resin I, polyester resin c was prepared according to the formula of polyester resin c in Table 1.

[0075] Example 5:

[0076] Preparation of powder coating I: According to the formula in Table 2, polyester resin I, curing agent TGIC, leveling agent 588, brightening agent 701, benzoin and titanium dioxide were put into a twin-screw extruder. Through premixing, extrusion, cooling, crushing, grinding and sieving, powder coating I was obtained; Powder coating I was sprayed on an aluminum plate by electrostatic means and cured at 200°C / 15 min;

[0077] Among them, the process parameters of the twin-screw extruder were set as follows: the temperatures of zones 1-3 were 105°C, 140°C, 110°C respectively, and the rotation speed was 35 r / min;

[0078] Table 2 Formula of powder coating I

[0079] Raw material components Charging mass m (g) Polyester resin Ⅰ 51.32 Curing agent TGIC 4.67 Leveling agent 588 0.95 Brightening agent 701 0.95 Benzoin 0.45 Titanium dioxide 7.24

[0080] Afterwards, according to the experimental method of powder coating I, polyester resin II was used to replace polyester resin I to prepare powder coating II, polyester resin III was used to replace polyester resin I to prepare powder coating III, polyester resin a was used to replace polyester resin I to prepare powder coating a, polyester resin b was used to replace polyester resin I to prepare powder coating b, and polyester resin c was used to replace polyester resin I to prepare powder coating c.

[0081] Comparative example:

[0082] Preparation of polyester resin: According to the preparation steps and experimental conditions of polyester resin I, the difference part from the preparation experiment of polyester resin I was only that: light stabilizer I was not used, and polyester resin was prepared;

[0083] Preparation of powder coatings: Use polyester resin to replace polyester resin I in Example 5. Refer to the preparation steps and experimental conditions of powder coating I to prepare the powder coating.

[0084] Performance testing:

[0085] Spray the powder coating on the aluminum plate by electrostatic spraying. After curing at 200 °C in the oven for 15 minutes, take out the sample plate. After the sample plate cools to room temperature, detect the performance of each coating. The test standards are as follows:

[0086] (1) Adhesion is tested according to GB / T 9286-1998 "Paints and varnishes - Cross-cut test for coatings".

[0087] (2) Gloss is tested according to GB / T 9754-2007 "Paints and varnishes - Determination of 20°, 60° and 85° specular gloss of paints without metallic pigments".

[0088] (3) Impact resistance is tested according to GB / T 1732-1993 "Method for the determination of impact resistance of coatings".

[0089] (4) Weather resistance performance is tested according to GB / T 1865-2009 "Paints and varnishes - Artificial weathering and exposure to artificial radiation - Filtered xenon-arc radiation". The specific test steps are as follows: Place the cured coating sample plate in a xenon lamp aging test chamber for 1000 h, take out the sample plate, and detect the gloss retention rate and color difference of the coating.

[0090] The above experimental results are shown in Table 3 below.

[0091] Table 3 Performance experimental results of each powder coating

[0092]

[0093] Based on the test data in Table 3, Figure 5 By comprehensively analyzing the above experimental results, the following conclusions can be drawn:

[0094] Using the light stabilizer developed and synthesized by the present invention to modify the polyester resin for powder coatings has achieved the beneficial technical effect of effectively extending the outdoor service life of powder coatings, and light stabilizers I and II have a significantly better effect on improving the weather resistance performance of powder coatings than light stabilizer III;

[0095] In order to explore the influence of the bio-based raw material 2,5-furandicarboxylic acid FDCA on the coating performance, the present invention has conducted experiments and obtained the following conclusions:

[0096] When introducing bio-based raw material 2,5-furandicarboxylic acid (FDCA) into polyester resin for powder coatings, the dosage range should be controlled within 25% - 35% of the mass of polybasic acid raw materials. Excessive amount will weaken the adhesion to the substrate.

Claims

1. A process for preparing a weather-resistant bio-based polyester resin, characterized in that: The following steps are involved: Step 1: Based on the epoxy-phenolic hydroxyl ring-opening reaction mechanism, the KH560 modified ZnO nanoparticles are modified using photostabilizing monomers I or II containing phenolic hydroxyl groups to obtain a synergistic photostabilizer; The preparation method of light-stable monomer I is as follows: Using the Grignard reaction mechanism and iodine as an initiator, 9-(4-bromophenyl)carbazole first reacts with metal magnesium to generate Grignard reagent a, and then Grignard reagent a and cyanuric chloride undergo a coupling reaction to synthesize carbazole triazine monomer a; wherein the molar ratio of Grignard reagent a to cyanuric chloride is controlled to be 1:1; Using the Friedel-Crafts reaction mechanism, carbazole triazine monomer a and resorcinol undergo electrophilic substitution reaction under the catalysis of Lewis acid to synthesize light-stable monomer Ⅰ. The preparation method of photostable monomer II is as follows: Using the Grignard reaction mechanism and iodine as an initiator, 9-(4-bromophenyl)carbazole first reacts with metal magnesium to generate Grignard reagent b, and then Grignard reagent b reacts with cyanuric chloride to synthesize carbazole triazine monomer b; wherein the molar ratio of Grignard reagent b to cyanuric chloride is controlled to be 2:1; Using the Friedel-Crafts reaction mechanism, under the catalysis of Lewis acid, carbazole triazine monomer b reacts with resorcinol to undergo electrophilic substitution reaction to generate light-stable monomer II. Step 2: preparing raw materials according to the formula of polyester resin, and then preparing polyester resin through catalytic esterification and vacuum polycondensation reaction; The polyester resin has a formula of: 35-45 parts by weight of neopentyl glycol, 4-6 parts by weight of 2-butyl-2-ethyl-1,3-propanediol, 0.5-1 parts by weight of trimethylolpropane, 20-40 parts by weight of terephthalic acid, 3-5 parts by weight of isophthalic acid, 10-20 parts by weight of 2,5-furandicarboxylic acid, 0.05-1 parts by weight of a catalyst, 1-5 parts by weight of trimellitic anhydride, 0.5-5 parts by weight of a light stabilizer, and 0.1-3 parts by weight of a composite antioxidant.

2. The process for preparing a weather-resistant bio-based polyester resin according to claim 1, characterized in that: The light stabilizer is light stabilizer III, and the preparation method of the light stabilizer III is: firstly synthesizing light stabilizer monomer I and light stabilizer monomer II, and then physically blending the light stabilizer monomer I, light stabilizer monomer II and ZnO nanoparticles to prepare light stabilizer III.

3. The process for preparing a weather-resistant bio-based polyester resin according to claim 1, characterized in that: The preparation method of the polyester resin in the step 2 is: Step S3-1: neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol and trimethylolpropane are uniformly mixed and heated to melt, terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid and a catalyst are added, the temperature is raised to 220-240° C. and stirred until the acid value reaches 5-7 mgKOH / g; Step S3-2: Cooling to 210-230° C., adding a capping agent, maintaining the temperature at 210-230° C. until the acid value reaches 30-40 mgKOH / g, evacuating the mixture, and stirring until the acid value reaches 20-30 mgKOH / g; Step S3-3: cooling the temperature to 190-200° C., adding a light stabilizer and a composite antioxidant to prepare a polyester resin.

4. The process for preparing a weather-resistant bio-based polyester resin according to claim 1, characterized in that: The catalyst is monobutyltin oxide 4100 or stannous oxalate; The composite antioxidant includes antioxidant 168 and antioxidant 1010.

5. A weather-resistant bio-based polyester resin prepared by the process according to any one of claims 1 to 4, characterized in that: The weather-resistant bio-based polyester resin is used for powder coatings; The powder coating has a formula of: 45 to 60 parts by weight of a weather-resistant bio-based polyester resin, 3 to 8 parts by weight of a curing agent, 0.5 to 3 parts by weight of a leveling agent, 0.1 to 2 parts by weight of a brightener, 0.1 to 0.5 parts by weight of benzoin and 2 to 10 parts by weight of titanium dioxide.

6. The weather-resistant bio-based polyester resin according to claim 5, characterized in that: The powder coating has a gloss retention rate of 75-95% and a color difference of 0.3-1.0.

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