Self-repairing bio-based polyester resin for matte powder coating as well as preparation method and application of self-repairing bio-based polyester resin

Abstract

The invention relates to the technical field of high polymer materials, and discloses self-repairing bio-based polyester resin for a matte powder coating as well as a preparation method and application of the self-repairing bio-based polyester resin. The bio-based polyester resin is prepared from the following preparation raw materials in percentage by mole: 20 mol% to 40 mol% of bio-based flexible diol, 20 mol% to 35 mol% of bio-based furandicarboxylic acid, 10 mol% to 25 mol% of isosorbide, 5 mol% to 25 mol% of itaconic acid, 1 mol% to 15 mol% of long-chain bio-based aliphatic dibasic acid, 1 mol% to 10 mol% of bio-based citric acid, 0.1 mol% to 2.0 mol% of zinc acetylacetonate, 0.1 mol% to 1.0 mol% of a microcapsule corrosion inhibitor, 0.1 mol% to 1.0 mol% of an esterification catalyst and 0.1 mol% to 1.5 mol% of an antioxidant. The bio-based polyester resin does not contain petroleum-based monomers and is high in biochar content.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a self-healing bio-based polyester resin for matte powder coatings, its preparation method, and its application. Background Technology

[0002] The polyester resin used for indoor matte powder coatings is mainly cured using a polyester / epoxy hybrid system. The resulting coating has excellent fineness and extremely low matte gloss, and is widely used in home appliances, automobiles, metal furniture and other fields. However, existing matte powder coatings have certain defects: (1) The hybrid polyester resin generally uses trimellitic anhydride (TMA) as the core monomer of high acid value polyester. TMA is a petroleum derivative and has certain toxicity risks. During high-temperature processing, it will release benzene ring volatiles restricted by the EU REACH regulation, and the residual monomer is easy to migrate, causing the coating to yellow; (2) The petroleum-based carbon footprint of conventional hybrid polyester resins reaches 8.2 kg CO2 / kg resin; (3) The hybrid polyester used for matte powder coatings has a single function and lacks self-healing ability. Scratches caused by external impact will cause electrochemical corrosion to spread, eventually causing the coating to lose its protective function.

[0003] Bio-based monomers (such as 2,5-furandicarboxylic acid and isosorbide) can replace petroleum raw materials to reduce the negative impact of TMA. However, matte powder coatings using bio-based monomers still have the following problems: (1) Insufficient corrosion resistance. The acid value of traditional bio-based polyester is 30-40 mg KOH / g, the polyester bond density is low, and the water vapor transmission rate is greater than 25 g / (m 2·day), about 40% higher than petroleum-based, the coating is more susceptible to the penetration of corrosive media; (2) conflict in matting performance, due to the large difference in the reactivity of bio-based monomers, it is difficult to reproduce the microphase separation matting effect of TMA compared with conventional mixed polyester, resulting in the coating being unable to matte or poorly matted, failing to meet consumers' demand for matte powder or no-gloss powder; (3) lack of self-healing mechanism, existing bio-based polyesters mainly rely on the addition of external repair agents (such as microcapsule dicyclopentadiene) to achieve self-healing function, but this additive needs to be triggered under conditions higher than 120°C, which is harsh, and the repair efficiency is less than 60%, while the external repair agent cannot form a strong interface with the polyester resin matrix. It is easily damaged during the extrusion of powder coatings and cannot meet the actual use requirements of matte powder coatings; (4) Corrosion resistance and self-healing performance conflict. Generally, resins with good corrosion resistance require rigid segments and molecular structures with high crosslinking density. Although bio-based rigid structures can improve density, they will inhibit the movement of polyester segments and form a dense barrier layer. Self-healing coatings require resins with low crosslinking density and more flexible segments. Although bio-based flexible monomers (such as 1,3-propanediol) can promote chain movement and allow molecular chain diffusion and recombination, they will reduce the corrosion resistance of the coating. This is essentially due to the fundamental contradiction in molecular structure design and the intrinsic characteristics of bio-based monomers, which are difficult to overcome. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one object of the present invention is to provide a bio-based polyester resin.

[0005] A second objective of this invention is to provide a method for preparing this bio-based polyester resin.

[0006] The third objective of this invention is to provide a matte powder coating.

[0007] The fourth objective of this invention is to provide a coating.

[0008] The fifth objective of this invention is to provide the application of the bio-based polyester resin, or a matte powder coating.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a bio-based polyester resin, comprising, by molar percentage, the following raw materials: 20 mol%-40 mol% bio-based flexible diol, 20 mol%-35 mol% bio-based furanyl dicarboxylic acid, 10 mol%-25 mol% isosorbide, 5 mol%-25 mol itaconic acid, 1 mol%-15 mol% long-chain bio-based aliphatic dicarboxylic acid, 1 mol%-10 mol% bio-based citric acid, 0.1 mol%-2.0 mol% zinc acetylacetonate, 0.1 mol%-1.0 mol% microencapsulated corrosion inhibitor, 0.1 mol%-1.0 mol% esterification catalyst, and 0.1 mol%-1.5 mol% antioxidant.

[0010] In some embodiments of the present invention, the bio-based polyester resin comprises, by molar percentage, the following raw materials: 26 mol%-36 mol% bio-based flexible diol, 22 mol%-32 mol% bio-based furanyl dicarboxylic acid, 11 mol%-21 mol% isosorbide, 9 mol%-19 mol% itaconic acid, 2 mol%-12 mol% long-chain bio-based aliphatic dicarboxylic acid, 1 mol%-8 mol% bio-based citric acid, 0.8 mol%-1.5 mol% zinc acetylacetonate, 0.1 mol%-0.5 mol% microencapsulated corrosion inhibitor, 0.1 mol%-0.5 mol% esterification catalyst, and 0.3 mol%-1 mol% antioxidant.

[0011] Specifically, the bio-based citric acid described in this invention refers to citric acid obtained through bio-fermentation. Compared with non-bio-based citric acid prepared by chemical synthesis, bio-based citric acid has fewer byproducts and higher purity.

[0012] In some embodiments of the present invention, the bio-based polyester resin has an acid value of 50-80 mgKOH / g, a hydroxyl value of 5-50 mgKOH / g, a glass transition temperature (Tg) of 40-70℃, and a viscosity of 1000-5000 mPa·s at 200℃.

[0013] In some preferred embodiments of the present invention, the bio-based polyester resin has an acid value of 60-70 mgKOH / g, a hydroxyl value of 10-25 mgKOH / g, a glass transition temperature (Tg) of 55-65℃, and a viscosity of 1500-2500 mPa·s at 200℃.

[0014] In some embodiments of the present invention, the bio-based polyester resin contains a dynamic network of β-hydroxy esters, and the dynamic transesterification activation energy is ≤100kJ / mol.

[0015] In some preferred embodiments of the present invention, the dynamic transesterification activation energy is ≤85kJ / mol.

[0016] In some embodiments of the present invention, the bio-based polyester resin has a bio-carbon content ≥30 wt%. (Test method is ASTM D6866-22) In some preferred embodiments of the present invention, the bio-based polyester resin has a bio-carbon content of ≥50wt%.

[0017] In some embodiments of the present invention, the bio-based flexible diol is selected from at least one of 1,3-propanediol, 1,2-propanediol, and 1,4-butanediol.

[0018] In some preferred embodiments of the present invention, the bio-based flexible diol is 1,3-propanediol (PDO).

[0019] Specifically, the bio-based flexible diol mentioned in this invention refers to a diol with flexible molecular chains obtained through biological methods.

[0020] In some embodiments of the present invention, the long-chain bio-based aliphatic dicarboxylic acid is selected from at least one of bio-based sebacic acid, azelaic acid, and brassic acid.

[0021] In some preferred embodiments of the present invention, the long-chain bio-based aliphatic dicarboxylic acid is bio-based sebacic acid (SeA).

[0022] In some embodiments of the present invention, the esterification catalyst is selected from at least one of dibutyltin dilaurate, monobutyltin oxide, and tetrabutyl titanate.

[0023] In some preferred embodiments of the present invention, the esterification catalyst is dibutyltin dilaurate.

[0024] In some embodiments of the present invention, the antioxidant is selected from at least one of 2,6-di-tert-butylphenol (BHT), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010), octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (1076), trinonylphenyl phosphite (TNP), and tris(2,4-di-tert-butylphenyl) phosphite (168).

[0025] In some preferred embodiments of the present invention, the antioxidant is antioxidant 1076 and antioxidant 168 in a mass ratio of (1.6-2.4):1.

[0026] In some embodiments of the present invention, the raw materials for preparing the microcapsule corrosion inhibitor include: a core material, a wall material, and an emulsion system; wherein, the core material includes the following components: corrosion inhibitor, functional filler, and oil phase solvent; the wall material includes the following raw materials: polyisocyanate monomer and polyamine monomer; and the emulsion system includes the following components: emulsifier, stabilizer, and water.

[0027] In some embodiments of the present invention, the corrosion inhibitor is selected from mercaptobenzothiazole, benzotriazole, sodium molybdate, or 8-hydroxyquinoline.

[0028] In some preferred embodiments of the present invention, the corrosion inhibitor is mercaptobenzothiazole (MBT).

[0029] In some embodiments of the present invention, the functional filler is selected from silicon nitride nanoparticles, calcium carbonate nanoparticles, or zinc oxide nanoparticles.

[0030] In some preferred embodiments of the present invention, the functional filler is silicon nitride nanoparticles (Si3N4).

[0031] In some embodiments of the present invention, the oil phase solvent is selected from ethyl acetate, toluene, xylene, or liquid paraffin.

[0032] In some preferred embodiments of the present invention, the oil phase solvent is ethyl acetate.

[0033] In some embodiments of the present invention, the polyisocyanate monomer is selected from isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate or hexamethylene diisocyanate.

[0034] In some preferred embodiments of the present invention, the polyisocyanate monomer is isophorone diisocyanate (IPDI).

[0035] In some embodiments of the present invention, the polyamine monomer is selected from diethylenetriamine, ethylenediamine, hexamethylenediamine or triethylenetetramine.

[0036] In some preferred embodiments of the present invention, the polyamine monomer is diethylenetriamine (DETA).

[0037] In some embodiments of the present invention, the emulsifier is selected from sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, or Tween.

[0038] In some preferred embodiments of the present invention, the emulsifier is sodium dodecylbenzenesulfonate (SDBS).

[0039] In some embodiments of the present invention, the stabilizer is selected from polyvinyl alcohol, hydroxyethyl cellulose, or gelatin.

[0040] In some preferred embodiments of the present invention, the stabilizer is polyvinyl alcohol (PVA).

[0041] In some embodiments of the present invention, the microcapsule corrosion inhibitor is prepared by a method comprising the following steps: A1. Dissolve the corrosion inhibitor in the oil phase solvent, then add the polyisocyanate monomer and functional filler to obtain the oil phase; dissolve the emulsifier and stabilizer in water to obtain the aqueous phase; A2. Add the oil phase to the aqueous phase and shear emulsify to obtain an emulsion; A3. Add polyamine monomers and water to the emulsion and react to obtain the microcapsule corrosion inhibitor.

[0042] In some embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the ratio of the corrosion inhibitor, polyisocyanate monomer, functional filler and oil phase solvent is (28-42)g: (12-18)g: (1.2-1.8)g: 100mL.

[0043] In some preferred embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the ratio of the corrosion inhibitor, polyisocyanate monomer, functional filler and oil phase solvent is (31-39)g: (13.5-16.5)g: (1.3-1.5)g: 100mL.

[0044] In some embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the temperature at which the corrosion inhibitor is dissolved in the oil phase solvent is 48-72°C.

[0045] In some preferred embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the temperature at which the corrosion inhibitor is dissolved in the oil phase solvent is 54-66°C.

[0046] In some embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, after adding the polyisocyanate monomer and functional filler, an ultrasonic dispersion operation is further included; the ultrasonic dispersion frequency is 32-48kHz and the time is 8-12min.

[0047] In some preferred embodiments of the present invention, the frequency of the ultrasonic dispersion is 36-44 kHz and the duration is 9-11 min.

[0048] In some embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the ratio of the emulsifier, stabilizer and water is (1.5-2.5)g: (0.8-1.2)g: 100mL.

[0049] In some preferred embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the ratio of the emulsifier, stabilizer and water is (1.8-2.2)g: (0.9-1.1)g: 100mL.

[0050] In some embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the emulsifier and stabilizer are dissolved in water at a temperature of 40-60°C.

[0051] In some preferred embodiments of the present invention, in step A1 of preparing the microcapsule corrosion inhibitor, the emulsifier and stabilizer are dissolved in water at a temperature of 45-55°C.

[0052] In some embodiments of the present invention, in step A2 of preparing the microcapsule corrosion inhibitor, after the oil phase is added to the aqueous phase, a pre-dispersion operation of 1-3 minutes is also included.

[0053] In some embodiments of the present invention, in step A2 of preparing the microcapsule corrosion inhibitor, the rotation speed of the shear emulsification is 5600-8400 rpm, the time is 8-12 min, and the temperature is 23-27℃.

[0054] In some preferred embodiments of the present invention, in step A2 of preparing the microcapsule corrosion inhibitor, the rotation speed of the shear emulsification is 6300-7700 rpm, the time is 9-11 min, and the temperature is 23-27℃.

[0055] In some embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, the ratio of the polyamine monomer, water and emulsion is (0.8-1.2)g: (8-12)mL: 100mL.

[0056] In some preferred embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, the ratio of the polyamine monomer, water and emulsion is (0.9-1.1)g: (9-11)mL: 100mL.

[0057] In some embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, a polyamine monomer and water are added dropwise to the emulsion, and the temperature of the emulsion is 48-84°C.

[0058] In some preferred embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, a polyamine monomer and water are added dropwise to the emulsion, and the temperature of the emulsion is 54-77°C.

[0059] In some embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, the rate of adding polyamine monomers and water is 0.8-1.2 mL / min, and the adding process is accompanied by stirring.

[0060] In some embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, the reaction temperature is 48-84°C and the time is 2-4 hours.

[0061] In some preferred embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, the reaction temperature is 54-77°C and the time is 2.5-3.5h.

[0062] In some embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, the endpoint of the reaction is determined by the change of the emulsion from milky white to pale yellow and translucent.

[0063] In some embodiments of the present invention, in step A3 of preparing the microcapsule corrosion inhibitor, after the reaction is completed, the process further includes centrifugation to collect the microcapsule corrosion inhibitor precipitate, washing, and drying.

[0064] In some embodiments of the present invention, the centrifugation speed is 3200-4800 rpm and the time is 8-12 min.

[0065] In some preferred embodiments of the present invention, the centrifugation speed is 3600-4400 rpm and the time is 8-12 min.

[0066] In some embodiments of the present invention, the washing reagent comprises ethanol and water in a volume ratio of (0.8-1.2):1.

[0067] In some embodiments of the present invention, the drying temperature is 48-72°C and the time is 19-29 hours.

[0068] In some preferred embodiments of the present invention, the drying temperature is 54-66°C and the time is 21-26 hours.

[0069] In some embodiments of the present invention, the microcapsule corrosion inhibitor is a white powder with a particle size of 10-30 μm.

[0070] In some embodiments of the present invention, the microcapsule corrosion inhibitor is terminated with an isocyanate group, and the content of the isocyanate group is 3wt%-10wt%. (The test standard is GB / T 12009.4-2016 Aromatic Isocyanates for Polyurethane Production - Part 4: Determination of Isocyanate Content) A second aspect of the present invention provides a method for preparing the bio-based polyester resin described in the first aspect of the present invention, comprising the following steps: S1. Isosorbide is mixed with bio-based flexible diol, vacuum dehydrated, bio-based furanyl dicarboxylic acid, long-chain bio-based aliphatic dicarboxylic acid and esterification catalyst are added, and the reaction is carried out until the acid value is ≤15mgKOH / g. Then itaconic acid is added and the reaction is continued to obtain the prepolymer. S2. After the prepolymer undergoes a vacuum polycondensation reaction, bio-based citric acid is added, and the reaction is continued until the acid value is 60-70 mgKOH / g. Microencapsulated corrosion inhibitor and esterification catalyst are added, and the reaction is continued until the hydroxyl value is ≤50 mgKOH / g. Zinc acetylacetone and antioxidant are then added to obtain the bio-based polyester resin.

[0071] In some embodiments of the present invention, in step S1, the temperature of vacuum dehydration is 100-120°C, the pressure is -0.06 to -0.1 MPa, and the time is 10-60 min.

[0072] In some embodiments of the present invention, in step S1, after adding bio-based furanyl dicarboxylic acid, long-chain bio-based aliphatic dicarboxylic acid and esterification catalyst, the reaction is carried out under an inert atmosphere and the reaction temperature is 175-185°C.

[0073] In some embodiments of the present invention, the inert atmosphere includes nitrogen.

[0074] In some embodiments of the present invention, in step S1, the temperature is lowered to 135-145°C, the itaconic acid is added, and the reaction is carried out for 60-180 minutes.

[0075] In some embodiments of the present invention, in step S1, the acid value of the prepolymer is ≤30mgKOH / g.

[0076] In some embodiments of the present invention, in step S2, the temperature of the vacuum polycondensation reaction is 195-205℃, the vacuum degree is -0.09~-0.1MPa, and the acid value of the intermediate product after the reaction is completed is ≤10mgKOH / g.

[0077] In some embodiments of the present invention, in step S2, the temperature is lowered to 165-175°C, the bio-based citric acid is added, and the reaction is carried out for 30-180 minutes.

[0078] In some embodiments of the present invention, in step S2, the temperature is lowered to 155-165°C, the microcapsule corrosion inhibitor and esterification catalyst are added, and the reaction is carried out for 60-180 min.

[0079] In some embodiments of the present invention, step S2, after adding the zinc acetylacetonate and antioxidant, further includes stirring for 10-30 minutes.

[0080] In some embodiments of the present invention, in step S2, the zinc acetylacetonate is dissolved in 1wt%-30wt% bio-based flexible diol and then added at a temperature ≤185°C.

[0081] In some preferred embodiments of the present invention, in step S2, the zinc acetylacetonate is dissolved in 1wt%-30wt% bio-based flexible diol and then added at a temperature ≤165°C.

[0082] A third aspect of the present invention provides a matte powder coating comprising the bio-based polyester resin described in the first aspect of the present invention; wherein the bio-based polyester resin comprises 28%-42% by mass.

[0083] In some embodiments of the present invention, the matte powder coating further comprises, by weight percentage: 28%-42% curing agent, 0.8%-1.2% leveling agent, 0.1%-0.8% degassing agent, 20%-30% matting filler, 0.5%-1.5% coloring pigment and 1.5%-2.5% matting agent.

[0084] In some embodiments of the present invention, the curing agent includes epoxy resin.

[0085] In some embodiments of the present invention, the degassing agent includes benzoin.

[0086] In some embodiments of the present invention, the matting filler comprises matting barium.

[0087] In some embodiments of the present invention, the coloring pigment includes carbon black.

[0088] A fourth aspect of the present invention provides a coating formed from the matte powder coating described in the third aspect of the present invention.

[0089] In some embodiments of the present invention, during the coating formation process, the curing temperature of the matte powder coating is 145-215°C, and the curing time is 16-24 min.

[0090] In some preferred embodiments of the present invention, during the coating formation process, the curing temperature of the matte powder coating is 160-200°C and the curing time is 18-22 min.

[0091] The fifth aspect of the present invention provides the application of the bio-based polyester resin described in the first aspect of the present invention, or the matte powder coating described in the third aspect of the present invention, in the surface coating of electrical appliances, automobiles, office supplies, and metal materials.

[0092] The basic principles of this invention are explained as follows: 1) The bio-based polyester resin provided by this invention utilizes bio-based furanyl dicarboxylic acid (FDCA) to provide a rigid furan ring and two carboxyl groups, and isosorbide (ISB) to provide a rigid bicyclic structure and β-hydroxy groups. After esterification, a large number of β-hydroxy ester bonds (-O-CO-CH(OH)-) are formed in the polyester backbone. Zinc acetylacetonate, as a zinc ion catalyst, can significantly reduce the activation energy of β-hydroxy ester bond transesterification. This zinc ion catalyst is added in the final stage, and the addition temperature is strictly controlled (below 185°C) to prevent premature deactivation or unnecessary side reactions. The flexible segments provided by bio-based flexible diols and long-chain bio-based aliphatic dicarboxylic acids provide the necessary free volume for molecular chain movement and reconstruction, providing a physical basis for dynamic bond exchange. This allows the coating to show scratches and be heated to 80°C, while the Zn... 2+ Under catalysis, the β-hydroxy ester bonds at the scratch undergo reversible breakage and recombination, allowing the molecular chain segments to move and re-interweave, thereby achieving self-repair of the scratch and solving the problem that traditional high cross-linking density coatings cannot self-repair. 2) The bio-based polyester resin provided by this invention introduces a microcapsule corrosion inhibitor with corrosion inhibitors and pH-responsive functional fillers as core materials, and polyisocyanate monomers and polyamine monomers react to form a polyurethane-polyurea wall material. By controlling the excess of oil-phase polyisocyanate monomers, reactive isocyanate groups remain on the surface of the microcapsules, thereby making the microcapsule corrosion inhibitor end with isocyanate groups (-NCO). This microcapsule corrosion inhibitor is added during the acid hydrolysis stage after polycondensation, at which time the polyester chain contains abundant terminal hydroxyl (-OH) and carboxyl (-COOH) groups. Under the action of an esterification catalyst, the microcapsule surface... The -NCO on the surface reacts with the -OH / -COOH of the polyester chain to form strong urethane or amide bonds, chemically bonding the microcapsules to the polymer network. This prevents the microcapsules from falling off or breaking during powder processing (melt extrusion, pulverization), ensuring their integrity in the final coating and achieving long-lasting corrosion resistance. When the coating is damaged and corrosion occurs, the local pH increases. The functional filler in the microcapsules responds to the high pH environment, causing the wall material to crack and precisely releasing the corrosion inhibitor to the damaged area, forming a protective film and inhibiting the spread of electrochemical corrosion. This, combined with the self-healing function, provides dual protection. 3) The bio-based polyester resin provided by this invention uses bio-based citric acid (CA) as a raw material. Bio-based citric acid contains three carboxyl groups, with an f=3 greater than 2, making it an ideal source of branching points. Instead of being added together with bio-based furanyldicarboxylic acid and functionally long-chain bio-based aliphatic dicarboxylic acid at the initial stage of the reaction, bio-based citric acid is added separately for acid hydrolysis after the polycondensation reaction is basically complete and the chain structure has been initially formed. The reaction is precisely controlled to an acid value of 60-70 mgKOH / g. This means that the three carboxyl groups of bio-based citric acid do not completely react, but rather introduce a controllable number of unevenly distributed branching points on different polyester molecular chains. In the subsequent powder coating curing stage… Regions containing CA branching points (high crosslinking density regions) have high functionality and high crosslinking density, resulting in greater shrinkage during curing. Linear chain regions containing little or no CA branching points (low crosslinking density regions) have lower crosslinking density and less shrinkage. This non-uniformity in crosslinking density leads to differences in shrinkage stress at the microscale during curing, thus forming uniform, fine undulations on the coating surface. When light shines on this surface, diffuse reflection occurs, thereby achieving a matting effect (low gloss), replacing the matting function of traditional petroleum-based TMA. 4) The bio-based polyester resin provided by this invention utilizes bio-based furanyl dicarboxylic acid and isosorbide to provide rigidity and a high glass transition temperature, ensuring the storage stability of the powder and the mechanical strength of the coating; it utilizes long-chain bio-based aliphatic dicarboxylic acid and bio-based flexible diol to provide flexibility, adjust the resin viscosity, and provide segment mobility for dynamic bond exchange, thus balancing rigidity; it utilizes itaconic acid to replace part of the bio-based citric acid to provide acid value, avoiding excessive cross-linking caused by too much bio-based citric acid and sacrificing self-healing properties, and its double bonds can also participate in curing cross-linking to form a denser network, further enhancing corrosion resistance; and it utilizes the bio-based citric acid added later to provide branching to achieve matting; based on the compounding of various rigid monomers, flexible monomers, and functional monomers, the comprehensive performance of the bio-based polyester resin is balanced.

[0093] Compared with the prior art, the beneficial effects of the present invention are: 1) The bio-based polyester resin provided by this invention does not contain petroleum-based monomers. Its main raw material is derived from biomass, with high biocarbon content, significantly reducing the carbon footprint of the product. Through the construction of a dynamic covalent network of β-hydroxy esters by bio-based furanyl dicarboxylic acid and isosorbide, and under the catalysis of zinc acetylacetonate, the material achieves efficient self-repair capability at a low temperature (80℃ / 20min), with a low repair activation energy (≤100 kJ / mol), effectively repairing coating scratches and extending service life. Due to the use of rigid monomers such as isosorbide, the resin has a high glass transition temperature (Tg>58℃), ensuring that the powder coating prepared from it will not clump during storage and maintains good physical stability. Through the balance of flexible monomers such as long-chain bio-based aliphatic dicarboxylic acids and bio-based flexible diols, the resin has a suitable viscosity in the molten state, which not only ensures processing fluidity but also provides chain segment mobility for self-repair. The microcapsule corrosion inhibitor is firmly connected to the resin backbone through chemical bonding rather than physical blending, avoiding processing damage and providing long-term, intelligent corrosion protection reserves for the coating. 2) The preparation method of bio-based polyester resin provided by this invention, through a stepwise acid hydrolysis process, precisely controls the degree of branching and acid value, creating a non-uniform crosslinking density in the polymer network, thus laying the structural foundation for achieving the microphase separation and matting effect of bio-based polyester, successfully replacing the matting effect of petroleum-based TMA; the addition of zinc acetylacetone catalyst in the low-temperature later stage prevents its high-temperature deactivation, ensuring effective catalysis of dynamic transesterification reaction and guaranteeing the realization of self-repair function; the addition of microcapsule corrosion inhibitor under mild conditions in the later stage of polymerization, and the use of its surface reactive groups (-NCO) to chemically bond with polyester chains, avoids the destruction of microcapsules in the high-temperature polycondensation stage, and solves the interfacial compatibility problem between microcapsules and resin matrix; the use of standard and controllable chemical operations such as vacuum dehydration, nitrogen protection, and programmed temperature rise, combined with indicators such as acid value and hydroxyl value as the reaction endpoint, ensures the repeatability of polymerization reaction and the stability of product quality; 3) The matte powder coating provided by this invention has a low gloss level of 60° (approximately 30 GU), achieving an excellent matte effect. Due to the uniform microphase separation structure induced by bio-based citric acid, the coating surface is delicate, has good leveling properties, no severe orange peel, and high appearance quality. The synergistic effect of self-healing function and bonded microcapsule corrosion inhibitor gives the coating extremely strong corrosion resistance. After 240 hours of salt spray testing, the corrosion spread width is extremely small (1.4-1.5 mm), and the salt spray corrosion inhibition rate is as high as 84% ​​or more, which is far superior to traditional petroleum-based polyester coatings. The coating can pass the 50cm test in both forward and reverse directions, and has good toughness and adhesion, meeting the requirements of coatings for basic mechanical properties. The storage stability rating of the powder coating is 0, and it can still maintain good workability and film-forming properties after long-term storage. Detailed Implementation

[0094] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0095] The microcapsule corrosion inhibitors used in the following examples and comparative examples were prepared by a method comprising the following steps: A11. Dissolve 35g of mercaptobenzothiazole in 100mL of ethyl acetate and stir in a water bath at 60℃ until completely dissolved; add 15g of isophorone diisocyanate and 1.5g of silicon nitride nanoparticles, and disperse using ultrasonication at 40kHz for 10min to form a homogeneous oil phase; A12. Add 8g sodium dodecylbenzenesulfonate and 4g polyvinyl alcohol to 400mL of deionized water, transfer to a 50℃ water bath and stir until completely dissolved to obtain an aqueous phase, and keep warm for later use. A21. Slowly pour the oil phase into the aqueous phase and premix for 2 minutes; then emulsify by high-speed shearing at 7000 rpm for 10 minutes, using an ice-water bath to control the temperature and maintain the emulsion temperature at 25±2℃. A31. Transfer the emulsion to a 70℃ constant temperature water bath and stir at 500 rpm. Slowly add 5g of diethylenetriamine and 50mL of deionized water at a dropping rate of 1mL / min. After the addition is complete, keep the reaction at the temperature for 3 hours. The reaction endpoint is judged when the emulsion changes from milky white to pale yellow and translucent. A32. The reaction solution was allowed to cool naturally to room temperature, and then the microcapsule precipitate was collected by centrifugation (4000 rpm, 10 min). It was then washed three times with ethanol / water (1:1, v / v) to remove residual emulsifier. Finally, it was baked in a vacuum drying oven at 60℃ for 24 h to obtain a white powdery microcapsule corrosion inhibitor (particle size 10-30 μm). The isocyanate group content in the microcapsule corrosion inhibitor was determined to be 3wt%-10wt% according to GB / T 12009.4-2016.

[0096] Example 1 This embodiment prepares a bio-based polyester resin, and the steps are as follows: S11. 15 mol isosorbide and 30 mol 1,3-propanediol were vacuum dehydrated for 30 min at 110 °C and -0.08 MPa. 25 mol bio-based furanyl dicarboxylic acid, 5 mol bio-based sebacic acid, and 0.1 mol dibutyltin dilaurate were added. The mixture was heated to 180 °C under nitrogen protection and reacted until the acid value was ≤15 mg KOH / g. The mixture was then cooled to 140 °C, and 15 mol itaconic acid was added. The mixture was reacted at a constant temperature for 120 min until the acid value was ≤30 mg KOH / g to obtain the prepolymer. S21. Heat to 200℃, maintain vacuum at -0.098MPa, and perform vacuum polycondensation reaction on the prepolymer until the acid value is ≤10mgKOH / g. Then cool to 170℃, add 5mol of bio-based citric acid, and react at a constant temperature for 60min until the acid value is 60-70mgKOH / g. Continue to cool to 160℃, add 0.2mol of microencapsulated corrosion inhibitor and 0.1mol of dibutyltin dilaurate, and react at a constant temperature for 120min until the hydroxyl value is ≤50mgKOH / g. Then add 1.0mol of zinc acetylacetonate, 0.4mol of antioxidant 1076 and 0.2mol of antioxidant 168, stir for 20min, and then discharge and crush to obtain bio-based polyester resin.

[0097] In step S21, zinc acetylacetonate is dissolved in 5 wt% 1,3-propanediol and then added, with the temperature strictly controlled to ≤165℃.

[0098] Example 2 This embodiment prepares a bio-based polyester resin, and the steps are as follows: S11. 11 mol of isosorbide and 26 mol of 1,3-propanediol were vacuum dehydrated for 20 min at 100 °C and -0.06 MPa. 32 mol of bio-based furanyl dicarboxylic acid, 12 mol of bio-based sebacic acid, and 0.05 mol of dibutyltin dilaurate were added. The mixture was heated to 175 °C under nitrogen protection and reacted until the acid value was ≤15 mg KOH / g. The mixture was then cooled to 135 °C, and 19 mol of itaconic acid were added. The mixture was reacted at a constant temperature for 180 min until the acid value was ≤30 mg KOH / g to obtain the prepolymer. S21. Heat to 195℃, maintain vacuum at -0.09MPa, and perform vacuum polycondensation reaction on the prepolymer until the acid value is ≤10mgKOH / g. Then cool to 165℃, add 8 mol of bio-based citric acid, and react at a constant temperature for 90 min until the acid value is 60-70mgKOH / g. Continue to cool to 155℃, add 0.4 mol of microencapsulated corrosion inhibitor and 0.08 mol of dibutyltin dilaurate, and react at a constant temperature for 60 min until the hydroxyl value is ≤50mgKOH / g. Then add 0.8 mol of zinc acetylacetonate, 0.2 mol of antioxidant 1076 and 0.1 mol of antioxidant 168, stir for 10 min, and then discharge and crush to obtain bio-based polyester resin.

[0099] In step S21, zinc acetylacetonate is dissolved in 2wt% 1,3-propanediol and then added, with the temperature strictly controlled to ≤165℃.

[0100] Example 3 This embodiment prepares a bio-based polyester resin, and the steps are as follows: S11. 21 mol of isosorbide and 36 mol of 1,3-propanediol were vacuum dehydrated for 60 min at 120 °C and -0.1 MPa. 22 mol of bio-based furanyl dicarboxylic acid, 2 mol of bio-based sebacic acid, and 0.12 mol of dibutyltin dilaurate were added. The mixture was heated to 185 °C under nitrogen protection and reacted until the acid value was ≤15 mg KOH / g. The mixture was then cooled to 145 °C, and 9 mol of itaconic acid were added. The mixture was reacted at a constant temperature for 60 min until the acid value was ≤30 mg KOH / g to obtain the prepolymer. S21. Heat to 205℃, maintain vacuum at -0.1MPa, and perform vacuum polycondensation reaction on the prepolymer until the acid value is ≤10mgKOH / g. Then cool to 175℃, add 1 mol of bio-based citric acid, and react at a constant temperature for 180 min until the acid value is 60-70mgKOH / g. Continue to cool to 165℃, add 0.5 mol of microencapsulated corrosion inhibitor and 0.12 mol of dibutyltin dilaurate, and react at a constant temperature for 180 min until the hydroxyl value is ≤50mgKOH / g. Then add 1.5 mol of zinc acetylacetonate, 0.6 mol of antioxidant 1076 and 0.3 mol of antioxidant 168, stir for 30 min, and then discharge and crush to obtain bio-based polyester resin.

[0101] In step S21, zinc acetylacetonate is dissolved in 10 wt% 1,3-propanediol and then added, with the temperature strictly controlled to ≤165℃.

[0102] Comparative Example 1 This comparative example prepares a polyester resin containing trimellitic anhydride, and the steps are as follows: 31.7 mol neopentyl glycol, 15.9 mol diethylene glycol, and 0.1 mol monobutyltin oxide were added to the reactor and rapidly heated to 120 °C to dissolve them at a rate of 90 °C / h. Then, stirring and nitrogen were introduced. Next, 44.9 mol terephthalic acid was added, and the temperature was programmed to 190 °C for esterification at a rate of 8.3 °C / h. The reaction was held at 190 °C for 1 h, and then gradually increased to 240 °C at a rate of 10 °C / h. / h, after reaching the specified temperature, keep it at that temperature for 4h; then lower the temperature to 230℃, add 4mol isophthalic acid, and keep it at that temperature for 4h; then lower the temperature to 205℃ for compression polymerization, and react at -0.094MPa for 2h; then add 3.5mol trimellitic anhydride for end-capping, keep it at that temperature for 1h, then add 0.6mol antioxidant 1076 and 0.3mol antioxidant 168, and finally lower the temperature to 200℃ to discharge the material, obtaining polyester resin.

[0103] Comparative Example 2 This comparative example prepares a bio-based polyester resin, which differs from Example 1 in that it does not contain a microencapsulated corrosion inhibitor. The steps are as follows: S11. 15 mol isosorbide and 30 mol 1,3-propanediol were vacuum dehydrated for 30 min at 110 °C and -0.08 MPa. 25 mol bio-based furanyl dicarboxylic acid, 5 mol bio-based sebacic acid, and 0.1 mol dibutyltin dilaurate were added. The mixture was heated to 180 °C under nitrogen protection and reacted until the acid value was ≤15 mg KOH / g. The mixture was then cooled to 140 °C, and 15 mol itaconic acid was added. The mixture was reacted at a constant temperature for 120 min until the acid value was ≤30 mg KOH / g to obtain the prepolymer. S21. Heat to 200℃, maintain vacuum at -0.098MPa, and perform vacuum polycondensation reaction on the prepolymer until the acid value is ≤10mgKOH / g. Then cool to 170℃, add 5 mol of bio-based citric acid, and react at a constant temperature for 60 min until the acid value is 60-70mgKOH / g. Continue to cool to 160℃, add 0.1 mol of dibutyltin dilaurate, and react at a constant temperature for 120 min until the hydroxyl value is ≤50mgKOH / g. Then add 1.0 mol of zinc acetylacetonate, 0.4 mol of antioxidant 1076 and 0.2 mol of antioxidant 168, stir for 20 min, and then discharge and crush to obtain bio-based polyester resin.

[0104] In step S21, zinc acetylacetonate is dissolved in 5 wt% 1,3-propanediol and then added, with the temperature strictly controlled to ≤165℃.

[0105] Comparative Example 3 This comparative example prepares a bio-based polyester resin, which differs from Example 1 in that the bio-based citric acid is added before polycondensation. The steps are as follows: S11. 15 mol isosorbide and 30 mol 1,3-propanediol were vacuum dehydrated for 30 min at 110 °C and -0.08 MPa. 25 mol bio-based furanyl dicarboxylic acid, 5 mol bio-based sebacic acid, and 0.1 mol dibutyltin dilaurate were added. The mixture was heated to 180 °C under nitrogen protection and reacted until the acid value was ≤15 mg KOH / g. The mixture was then cooled to 140 °C, and 15 mol itaconic acid and 5 mol bio-based citric acid were added. The mixture was reacted at a constant temperature for 120 min until the acid value was ≤80 mg KOH / g to obtain the prepolymer. S21. Heat to 200℃, maintain vacuum at -0.098MPa, and perform vacuum polycondensation reaction on the prepolymer until the acid value is 60-70mgKOH / g; then cool to 160℃, add 0.2mol microencapsulated corrosion inhibitor and 0.1mol dibutyltin dilaurate, and react at a constant temperature for 120min until the hydroxyl value is ≤50mgKOH / g; then add 1.0mol zinc acetylacetonate, 0.4mol antioxidant 1076 and 0.2mol antioxidant 168, stir for 20min and then discharge and crush to obtain bio-based polyester resin.

[0106] In step S21, zinc acetylacetonate is dissolved in 5 wt% 1,3-propanediol and then added, with the temperature strictly controlled to ≤165℃.

[0107] Comparative Example 4 This comparative example prepares a bio-based polyester resin, which differs from Example 1 in that zinc acetylacetone is not added. The steps are as follows: S11. 15 mol of isosorbide and 30 mol of 1,3-propanediol were vacuum dehydrated for 30 min at 110 °C and -0.08 MPa. 25 mol of bio-based furanyl dicarboxylic acid, 5 mol of bio-based sebacic acid, and 0.1 mol of dibutyltin dilaurate were added. The mixture was heated to 180 °C under nitrogen protection and reacted until the acid value was ≤15 mg KOH / g. The mixture was then cooled to 140 °C, and 15 mol of itaconic acid were added. The mixture was reacted at a constant temperature for 120 min until the acid value was ≤30 mg KOH / g to obtain the prepolymer. S21. Heat to 200℃, maintain vacuum at -0.098MPa, and perform vacuum polycondensation reaction on the prepolymer until the acid value is ≤10mgKOH / g. Then cool to 170℃, add 5mol of bio-based citric acid, and react at a constant temperature for 60min until the acid value is 60-70mgKOH / g. Continue to cool to 160℃, add 0.2mol of microencapsulated corrosion inhibitor and 0.1mol of dibutyltin dilaurate, and react at a constant temperature for 120min until the hydroxyl value is ≤50mgKOH / g. Then add 0.4mol of antioxidant 1076 and 0.2mol of antioxidant 168, stir for 20min, and then discharge and crush to obtain bio-based polyester resin.

[0108] Application examples Matte powder coatings were prepared using the polyester resins from Examples 1-3 and Comparative Examples 1-4 as raw materials. The composition of the matte powder coatings is shown in Table 1 below: Table 1. Components and content (g) of matte powder coatings in application examples.

[0109] The preparation steps for matte powder coatings are as follows: According to the formula of matte powder coating in Table 1, the materials are weighed and premixed, and then melt-extruded, pressed, cooled and crushed, and sieved to obtain matte powder coating 1-7.

[0110] Performance testing 1. The acid value, viscosity, and glass transition temperature of the polyester resins in Examples 1-3 and Comparative Examples 1-4 were tested. The acid value was tested according to GB / T6743-2008 "Determination of Acid Value and Total Acid Value of Polyester Resins for Plastics, Paints and Varnishes". The viscosity was measured at 200℃ according to ASTM D4287-88 using the ICI cone plate method. The glass transition temperature was tested according to GB / T 19466.2-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 2: Determination of Glass Transition Temperature". The hydroxyl value was tested according to ASTM E1899-23 "Standard Test Method for Determination of Hydroxyl Groups Using the Reaction with p-Toluenesulfonyl Isocyanate (TSI) and Tetrabutylammonium Hydroxide Potentiometric Titration". The test results are shown in Table 2. Table 2. Acid value, viscosity, and glass transition temperature of the polyester resins in Examples 1-3 and Comparative Examples 1-4

[0111] Table 2 shows the acid value, viscosity, and glass transition temperature of the polyester resins in Examples 1-3 and Comparative Examples 1-4. As can be seen from Table 2, the present invention utilizes bio-based furanyl dicarboxylic acid and isosorbide to provide a high glass transition temperature, and the resulting bio-based polyester resin has a glass transition temperature greater than 58°C. Long-chain bio-based aliphatic dicarboxylic acids and bio-based flexible diols are used to provide flexibility, and the resin viscosity is adjusted to 1700-2400 mPa·s (200°C). The hydroxyl value of the bio-based polyester resin is strictly controlled to be ≤50 mgKOH / g to avoid excessive reaction between the terminal hydroxyl groups and the -NCO of the microcapsules, leading to gelation of the system, or too rapid reaction with the curing agent affecting leveling and matting, and excessive crowding of the β-hydroxy ester dynamic network, hindering chain segment movement and impairing self-repair function.

[0112] 2. Using an electrostatic spray gun, the matte powder coatings 1-7 prepared in the application examples were sprayed onto the tinplate substrate and cured at 180°C for 20 minutes to form coatings 1-7. The following performance tests were performed on the coatings: Impact strength: Tested according to GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film"; Matte gloss: The test was conducted in accordance with GB / T 9754-2007 "Determination of 20°, 60° and 85° specular gloss of paint films without metallic pigments". Leveling rating: The leveling effect is rated according to the leveling effect rating standard of the Powder Coatings Institute (PCI); the PCI leveling rating is 1-10, and the higher the value, the better the leveling performance. Storage stability: Tested in accordance with GB / T 21782.8-2008 "Powder Coatings Part 8: Evaluation of Storage Stability of Thermosetting Powders"; Copper Accelerated Acetic Acid Salt Spray Corrosion Test (CASS): The test shall be conducted in accordance with GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; Biochar content: Tested according to ASTM D6866-22; Activation energy: determined experimentally using dynamic thermomechanical analysis (DMA) combined with the Arrhenius equation; Salt spray corrosion inhibition rate: An "X"-shaped scratch is made on the cured coating sample with a sharp blade, penetrating to the substrate. The scratched sample is then placed in an 80℃ oven for 20 minutes for self-healing. Samples that have undergone the 80℃ / 20min self-healing treatment and those that have not are placed in a salt spray test chamber for accelerated corrosion testing at 35±2℃, simulating normal temperature conditions. After 240 hours of testing, the samples are removed, and the corrosion width at the scratch edge is measured. The corrosion is then determined using the formula... The salt spray corrosion inhibition rate was calculated, where D0 is the corrosion width (mm) of the scratch that was not repaired at 80℃. rep The corrosion width (mm) of the scratch after repair treatment at 80℃.

[0113] Table 3 Performance test results of matte powder coatings 1-7 in application examples

[0114] Table 3 shows the performance test results of the coatings formed by matte powder coatings 1-7 in the application examples. As can be seen from Table 3, the bio-based polyester resin synthesized by the present invention through dynamic ester bond design to construct a β-hydroxy ester network, and by introducing microcapsule corrosion inhibitors and optimizing the stepwise acid hydrolysis process, compared with conventional matte polyesters, does not contain petroleum-based monomers, has a high bio-carbon content, and the powder coatings prepared therefrom have excellent matting properties, storage stability and corrosion resistance, while also having self-healing function, further improving the corrosion resistance of the coating.

Claims

1. A bio-based polyester resin, characterized in that, The preparation raw materials include, in terms of mole percentage, 20-40 mole percent of a bio-based flexible diol, 20-35 mole percent of a bio-based furandicarboxylic acid, 10-25 mole percent of isosorbide, 5-25 mole percent of itaconic acid, 1-15 mole percent of a long-chain bio-based aliphatic dibasic acid, 1-10 mole percent of bio-based citric acid, 0.1-2.0 mole percent of zinc acetylacetone, 0.1-1.0 mole percent of a microcapsule corrosion inhibitor, 0.1-1.0 mole percent of an esterification catalyst, and 0.1-1.5 mole percent of an antioxidant.

2. The bio-based polyester resin according to claim 1, characterized in that, The bio-based flexible diol is selected from at least one of 1,3-propanediol, 1,2-propanediol, and 1,4-butanediol; And / or, the long-chain bio-based aliphatic dibasic acid is selected from at least one of bio-based sebacic acid, azelaic acid, and brassylic acid.

3. The bio-based polyester resin according to claim 1, characterized in that, The preparation raw materials of the microcapsule corrosion inhibitor include a core material, a wall material, and an emulsifying system; The core material includes the following components: a corrosion inhibitor, a functional filler, and an oil phase solvent; The wall material includes the following preparation raw materials: a polyisocyanate monomer and a polyamine monomer; The emulsifying system includes the following components: an emulsifier, a stabilizer, and water.

4. The bio-based polyester resin according to claim 3, characterized in that, The corrosion inhibitor is selected from mercaptobenzothiazole, benzotriazole, sodium molybdate, or 8-hydroxyquinoline; And / or, the functional filler is selected from silicon nitride nanoparticles, calcium carbonate nanoparticles, or zinc oxide nanoparticles; And / or, the polyisocyanate monomer is selected from isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, or hexamethylene diisocyanate; And / or, the polyamine monomer is selected from diethylenetriamine, ethylenediamine, hexamethylenediamine, or triethylenetetramine.

5. The bio-based polyester resin according to claim 3 or 4, c h a r a c t e r i z e d in that The microcapsule corrosion inhibitor is prepared by a method including the following steps: A1, dissolving the corrosion inhibitor in the oil phase solvent, then adding the polyisocyanate monomer and the functional filler to obtain an oil phase; dissolving the emulsifier and the stabilizer in water to obtain an aqueous phase; A2, adding the oil phase to the aqueous phase and shearing to emulsify to obtain an emulsion; A3, adding the polyamine monomer and water dropwise to the emulsion and reacting to obtain the microcapsule corrosion inhibitor.

6. The bio-based polyester resin according to claim 5, characterized in that, In step A1, the ratio of the corrosion inhibitor, the polyisocyanate monomer, the functional filler, and the oil phase solvent is (28-42) g: (12-18) g: (1.2-1.8) g: 100 mL; And / or, in step A1, the ratio of the emulsifier, the stabilizer, and water is (1.5-2.5) g: (0.8-1.2) g: 100 mL; And / or, in step A3, the ratio of the polyamine monomer, water, and the emulsion is (0.8-1.2) g: (8-12) mL: 100 mL.

7. The method of producing a bio-based polyester resin according to any one of claims 1 to 6, characterized in that, The method includes the following steps: S1, mixing isosorbide with a bio-based flexible diol, vacuum dehydrating, adding a bio-based furandicarboxylic acid, a long-chain bio-based aliphatic dibasic acid, and an esterification catalyst, and reacting until the acid value is ≤15 mgKOH / g, then adding itaconic acid and continuing to react to obtain a prepolymer; S2, after vacuum polycondensation reaction of the prepolymer, adding bio-based citric acid, reacting until the acid value is 60-70 mgKOH / g, adding microcapsule corrosion inhibitor and esterification catalyst, reacting until the hydroxyl value is ≤50 mgKOH / g, then adding acetylacetone zinc and antioxidant, to obtain the bio-based polyester resin.

8. A matte powder coating characterized in that, The bio-based polyester resin according to any one of claims 1-6; the mass percentage of the bio-based polyester resin is 28%-42%.

9. A coating characterized in that, The matte powder coating according to claim 8 is formed.

10. Application of the bio-based polyester resin according to any one of claims 1-6, or the matte powder coating according to claim 8 in coating of surfaces of electrical appliances, automobiles, office appliances and metal materials.

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