A dual-cure bio-based unsaturated polyester primer, method for preparing the same and coating

Abstract

This invention relates to the field of coatings, specifically to a dual-curing bio-based unsaturated polyester primer, composed of the following raw materials in parts by weight: 60-90 parts of dual-curing bio-based unsaturated polyester resin, 0.2 parts of a high-molecular-weight acidic polymer, 0.1 parts of a leveling agent, 2 parts of zinc stearate, 0.5 parts of an anti-settling agent, 0.2 parts of a defoamer, and 10-30 parts of an active acrylic monomer. The introduction of bio-based epoxy resin reduces carbon emissions and decreases the odor of the coating film.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to a dual-curing bio-based unsaturated polyester primer, its preparation, and coatings. Background Technology

[0002] With increasing global environmental awareness, consumers are increasingly demanding environmentally friendly products. Green and low-carbon products are more likely to gain market recognition. However, ordinary unsaturated polyester resins rely on petroleum resources during production, which has a significant impact on the environment. Furthermore, the styrene used in the curing process is toxic and potentially carcinogenic.

[0003] Ordinary unsaturated polyester resins are generally cured by initiating free radical polymerization with an initiator. However, dual-curing bio-based unsaturated polyester resins can be cured by traditional free radical polymerization or under specific conditions, such as ultraviolet radiation or electron beam radiation. This results in more complete and stable curing, reduced VOC release, and some of the resins are biocompatible, making them safer for use in specific environments and having a smaller impact on the ecological environment.

[0004] With the national standard for furniture, "Limits of Hazardous Substances in Furniture" (GB 18584—2024), being mandatory and coming into effect on July 1, 2025, requiring total volatile organic compounds (TVOC) / (mg / m3) ≤ 0.50, oil-based products on the market currently struggle to meet this requirement.

[0005] Patent application CN201610024452.2 discloses "A Dual-Cure Unsaturated Polyester Transparent Primer and Its Preparation Method." This dual-curing unsaturated polyester transparent primer incorporates a TDI adduct curing agent L75 into a PE coating at a ratio of main paint: thinner: initiator: accelerator: curing agent = 100:40:1-2:1-2:30-50. In this formulation, the main paint, through the initiator and accelerator, preferentially reacts with the styrene in the thinner via double bonds. The resulting cross-linking curing reduces intermolecular flow, and the fluidity deteriorates with increasing cross-linking degree. The hydroxyl groups react slowly with the NCO groups in the TDI adduct curing agent L75, and the degree of reaction depends on intermolecular flow. When the reaction reaches a certain point, intermolecular flow becomes almost nonexistent, and the remaining hydroxyl groups after curing are unlikely to react further with the NCO groups in the TDI adduct curing agent L75 for cross-linking, thus resulting in a poorer overall cross-linking degree. Although the TDI adduct curing agent L75 can be cured by moisture, it is not chemically bonded to the polyester, and residual hydroxyl groups remain in the polyester, resulting in poor film durability after formation. Furthermore, the residue of TDI poses a potential risk and could harm human health. Additionally, some of the diluents used in this patent, composed of 30% butyl acetate, 30% styrene, and 40% toluene by weight percentage, release volatile organic compounds during application, which are detrimental to the modern ecological environment. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a dual-curing bio-based unsaturated polyester primer. This primer incorporates bio-based epoxy resin to reduce carbon emissions and decrease film-forming odor. Furthermore, isocyanate is grafted onto the ends of the bio-based unsaturated polyester, forming urethane bonds through a chemical nucleophilic reaction, thus creating a polyurethane system. This system can be directly applied to coatings without the need for a separate curing agent. It achieves enhanced dual curing through both light and moisture curing, thereby improving the mechanical strength and durability of the coating film. Moreover, it achieves a clean odor after curing. The inclusion of a low-concentration oxidant, naphthenic cobalt acid, extends the gelation time of the coating, facilitating application.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A dual-curing bio-based unsaturated polyester primer is composed of the following components in parts by weight: 60-90 parts of dual-curing bio-based unsaturated polyester resin, 0.2 parts of high molecular weight acidic polymer, 0.1 parts of leveling agent, 2 parts of zinc stearate, 0.5 parts of anti-settling agent, 0.2 parts of defoamer, and 10-30 parts of active acrylic monomer.

[0008] Furthermore, the preparation method of the dual-curing bio-based unsaturated polyester resin includes the following steps: (1) A mixture of polyol, unsaturated polyacid and antioxidant is subjected to esterification polycondensation reaction, and then bio-based epoxy resin and polymerization inhibitor are added to carry out addition reaction to obtain bio-based unsaturated polyester intermediate. (2) The bio-based unsaturated polyester resin intermediate obtained in step (1) is mixed with isocyanates and the dual-cured bio-based unsaturated polyester resin is obtained by nucleophilic addition reaction.

[0009] Specifically, the raw materials of bio-based unsaturated polyester resin are weighed according to the weight proportions. The polyol, unsaturated polyacid, and antioxidant are mixed and reacted at 160-170℃ for 2-3 hours to obtain a mixture. When the acid value of the system is 160-170mgKOH / g, the polymerization inhibitor and epoxy bio-based resin are added to end-cap and reduce the acid. The temperature is lowered to 100-110℃ and kept at that temperature for 3-4 hours. When the acid value is 5-10mgKOH / g, the temperature is lowered to 80℃ and the acrylic active monomer is added. The temperature is kept at that temperature for 10-20 minutes to obtain the bio-based unsaturated polyester resin intermediate. Weigh out each raw material of the dual-curing bio-based unsaturated polyester resin according to the specified proportions. Mix the isocyanate and bio-based unsaturated polyester intermediates and keep the mixture at 70-80℃ for 4-6 hours. When the NCO value is 5.0-6.5%, stop the reaction by cooling down to 60℃ to obtain the dual-curing bio-based unsaturated polyester resin.

[0010] Further, by weight, the bio-based unsaturated polyester intermediate comprises the following raw materials: 10-40 parts of polyol, 20-50 parts of unsaturated polyacid, 0.15-0.25 parts of polymerization inhibitor, 1.0-2.0 parts of antioxidant, 20-50 parts of bio-based epoxy resin, and 20-50 parts of acrylic active monomer.

[0011] Further, the polyol of the present invention is one or more of diethylene glycol, propylene glycol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, dipropylene glycol, glycerol, methyl propylene glycol, isosorbide, and polyester polyol; the unsaturated polyacid is one or more of maleic anhydride, fumaric acid, fumaric acid, succinic acid, itaconic acid, phthalic anhydride, and sebacic acid; the polymerization inhibitor is hydroquinone monomethyl ether and tert-butylhydroquinone; the bio-based epoxy resin is one or more of epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, cashew phenol epoxy resin, and rosin-based epoxy resin; the acrylic active monomer is one or more of TPGDA, HDDA, DPGDA, and DEGDA; and the antioxidant is BHT, 626, 1010, and triphenyl phosphite.

[0012] Further, by weight, the dual-cured bio-based unsaturated polyester resin comprises the following raw materials: 45-65 parts of isocyanate and 35-55 parts of bio-based unsaturated polyester intermediate.

[0013] Furthermore, the isocyanates described in this invention are one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

[0014] Furthermore, the high molecular weight acidic polymer of the present invention is HP1053 with pigment affinity groups from Anshan Huihong New Material Chemical Co., Ltd., the leveling agent is BYK333 from BYK Chemical, the zinc stearate is TV-V from Dongguan Hanwei Technology Co., Ltd., the anti-settling agent is K200R from Tangshan Sanfu Silicon Industry Co., Ltd., the defoamer is EFKA2720 from BASF, and the active monomer is lauryl acrylate, dodecyl methacrylate, or octadecyl methacrylate from Zhejiang Kangde New Material Co., Ltd.

[0015] On the other hand, the present invention provides a method for preparing a dual-curing bio-based unsaturated polyester primer, comprising the following steps: S1. Weigh the raw materials of bio-based unsaturated polyester resin according to the weight parts, mix the diol, unsaturated polyacid, and antioxidant, and react at 160-170℃ for 2-3 hours to obtain a mixture. When the acid value of the system is 150-165mgKOH / g, add the polymerization inhibitor and epoxy bio-based resin to end-cap and reduce the acid. Cool down to 100-110℃ and keep warm for 3-4 hours. When the acid value is 5-10mgKOH / g, cool down to 80℃ and add the acrylic active monomer. Keep warm for 10-20 minutes to obtain the bio-based unsaturated polyester resin intermediate. S2. Weigh each raw material of the dual-cured bio-based unsaturated polyester resin according to the specified proportions, mix the isocyanate and bio-based unsaturated polyester intermediates, keep the mixture at 70-80℃ for 4-6 hours, and stop the reaction when the NCO value is 5.0-6.5% by cooling down to 60℃ to obtain the dual-cured bio-based unsaturated polyester resin.

[0016] S3. Weigh each component of the dual-curing bio-based unsaturated polyester primer according to the specified weight parts. Add the dual-curing bio-based unsaturated polyester resin to a mixer. Add the high molecular weight acid polymer HP1053, leveling agent, and defoamer at a stirring speed of 400-500 rpm. Stir for 5-10 minutes, then add zinc stearate and anti-settling agent while stirring. Stir at a stirring speed of 1000-1500 rpm for 15-20 minutes. Then add the active acrylic monomer and stir at 500-800 rpm for 5-10 minutes to obtain a mixture. Filter the mixture through a 100-120 mesh filter. The resulting filtrate is the dual-curing bio-based unsaturated polyester primer.

[0017] Thirdly, the present invention also provides a dual-curing bio-based unsaturated polyester coating, comprising: a dual-curing bio-based unsaturated polyester primer, an accelerator, and an initiator mixed uniformly in a mass ratio of 100:0.8:1.2 to obtain the dual-curing bio-based unsaturated polyester coating.

[0018] Furthermore, the accelerator is a 6% cobalt blue water naphthenate.

[0019] Furthermore, the initiator is methyl ethyl ketone peroxide in water.

[0020] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: (1) The present invention introduces epoxy bio-based resin into the molecular structure of dual-curing bio-based unsaturated polyester resin. The epoxy group contains epoxy groups. The acid acts as an initiator or catalyst for the ring-opening reaction. After the ring-opening reaction with the epoxy ring, an intermediate with hydroxyl and carboxyl groups is formed. The carboxyl group undergoes a polycondensation reaction through the hydroxyl group on the polyester chain to form a modified bio-based unsaturated polyester. After the epoxy bio-based resin and acid ring-opening reaction is completed, the end of the product will have a secondary hydroxyl group. The addition of a highly active isocyanate group (-NCO) can react with the secondary hydroxyl group to form a urethane bond. The final isocyanate group (-NCO) residue is 5.0-6.5%. The addition of an initiator to the system can not only initiate double bond polymerization, but also react with moisture in the air to generate amine groups and carbon dioxide. The amine groups further react with unreacted isocyanate groups to form a cross-linked network. The material can form a film on its own under light curing, and the degree of cross-linking can be improved by subsequent moisture curing, thereby improving the mechanical strength and toughness of the film.

[0021] (2) The dual-curing bio-based unsaturated polyester resin uses bio-based epoxy resin. During the synthesis process, the esterification reaction is sufficient, reducing residual small molecule byproducts such as acids or alcohols, and further reducing odor sources. The isocyanate group (-NCO) residue is 5.0-6.5%, ensuring sufficient free radical reactivity. Dual curing ensures that the resin system is fully cross-linked under various conditions (such as light and humidity), reducing the residue of unreacted monomers and avoiding odor caused by the volatilization of small molecules. In the field of PE primer coatings, the dual-curing bio-based unsaturated polyester primer of this invention uses active diluent monomers instead of traditional volatile organic solvents to adjust the viscosity of the resin, which can effectively reduce the viscosity of the resin system. The acrylic monomers can also participate in free polymerization during the curing process to form a cross-linked network instead of volatilizing and escaping, which can greatly reduce the release of volatile organic compounds (VOCs), thereby reducing odor. In addition to the low odor, fast drying speed and good performance of the coating film, it can also reduce dependence on petrochemical resources, reduce harm to the environment and human health, and greatly reduce carbon emissions and volatile organic compound emissions. By replacing VOCs with reactive diluents, improving conversion rates through dual curing, accurately controlling isocyanate residues, and utilizing the low volatility of bio-based raw materials, the coating film reduces the volatilization of unreacted monomers and byproducts, achieving low-odor or odorless characteristics, thus balancing environmental protection and performance requirements. The PE primer coating incorporates a redox system of peroxymethyl ethyl ketone and cobalt salt cycloalkanecobalt acid. The reaction rate is controlled by adjusting the cobalt salt concentration; at low concentrations, the gelation time of the coating can be delayed. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0024] The features and performance of the present invention will be further described in detail below with reference to embodiments. Example 1 1. Dual-curing bio-based unsaturated polyester primer: The mixture of 90 parts of dual-curing bio-based unsaturated polyester resin, 0.2 parts of high molecular weight acidic polymer, 0.1 parts of leveling agent, 2 parts of zinc stearate, 0.5 parts of anti-settling agent, 0.2 parts of defoamer, and 10 parts of active monomer is prepared by uniformly mixing at room temperature.

[0025] 2. A method for preparing a dual-curing bio-based unsaturated polyester resin, comprising the following steps: Preparation of bio-based unsaturated polyester intermediate: 21.5 parts of diethylene glycol, 19.7 parts of maleic anhydride, 7 parts of fumaric acid, and 2 parts of BHT antioxidant were mixed and heated to 160-170℃ for esterification reaction for 2-3 hours to obtain a mixture. When the acid value of the system was 160-170 mgKOH / g, 0.2 parts of hydroquinone monomethyl ether polymerization inhibitor and 27.2 parts of epoxidized soybean oil were added. The temperature was lowered to 100-110℃ and kept for 3-4 hours. When the acid value was 5-10 mgKOH / g, the temperature was lowered to 80℃ and HDDA active monomer was added. The temperature was kept for 10-20 minutes to obtain bio-based unsaturated polyester resin intermediate. Preparation of dual-curing bio-based unsaturated polyester resin: 52 parts of toluene diisocyanate and 48 parts of bio-based unsaturated polyester resin intermediate were added and mixed. The mixture was kept at 70-80℃ for 4-6 hours. When the NCO value was 5.0-6.5%, the mixture was cooled to 60℃ and the reaction was stopped to obtain dual-curing bio-based unsaturated polyester resin.

[0026] Weigh out the components of the dual-curing bio-based unsaturated polyester primer according to the specified weight proportions. Add the dual-curing bio-based unsaturated polyester resin to a mixer. Add the high molecular weight acid polymer HP1053, leveling agent (BYK333 from BYK Chemicals), and defoamer (BASF EFKA 2720) while stirring at 500 rpm. After stirring for 10 minutes, add zinc stearate and anti-settling agent (K200R from Tangshan Sanfu Silicon Industry Co., Ltd.) while stirring. Stir at 1500 rpm for 20 minutes. Then add the acrylic reactive monomer (HDDA) and stir at 800 rpm for 5 minutes to obtain a mixture. Filter the mixture through a 120-mesh filter. The resulting filtrate is the dual-curing bio-based unsaturated polyester primer, denoted as Primer A.

[0027] Example 2 1. Dual-curing bio-based unsaturated polyester primer: 85 parts of dual-curing bio-based unsaturated polyester resin, 0.2 parts of high molecular weight acidic polymer, 0.1 parts of leveling agent, 2 parts of zinc stearate, 0.5 parts of anti-settling agent, 0.2 parts of defoamer, and 15 parts of active monomer are mixed evenly at room temperature to obtain the primer.

[0028] 2. A method for preparing a dual-curing bio-based unsaturated polyester resin, comprising the following steps: Preparation of bio-based unsaturated polyester intermediate: 22.5 parts of diethylene glycol, 21.2 parts of maleic anhydride, 7.2 parts of fumaric acid, and 2 parts of BHT antioxidant were mixed and heated to 160-170℃ for esterification reaction for 2-3 hours to obtain a mixture. When the acid value of the system was 160-170 mgKOH / g, 0.2 parts of hydroquinone monomethyl ether polymerization inhibitor and 28.5 parts of epoxidized soybean oil were added. The temperature was lowered to 100-110℃ and kept for 3-4 hours. When the acid value was 5-10 mgKOH / g, the temperature was lowered to 80℃ and 30 parts of HDDA active monomer were added. The temperature was kept for 10-20 minutes to obtain bio-based unsaturated polyester resin intermediate. Preparation of dual-curing bio-based unsaturated polyester resin: 52.2 parts of toluene diisocyanate and 47.8 parts of bio-based unsaturated polyester resin intermediate were added and mixed. The mixture was kept at 70-80℃ for 4-6 hours. When the NCO value was 5.0-6.5%, the mixture was cooled to 60℃ and the reaction was stopped to obtain dual-curing bio-based unsaturated polyester resin.

[0029] Weigh each component of the dual-curing bio-based unsaturated polyester primer according to the specified weight proportions. Add the dual-curing bio-based unsaturated polyester resin to a mixer. Add the high molecular weight acid polymer HP1053, leveling agent, and defoamer at a stirring speed of 500 rpm. After stirring for 10 minutes, add zinc stearate and anti-settling agent while stirring. Stir at a stirring speed of 1500 rpm for 15 minutes. Then add the acrylic reactive monomer and stir at 800 rpm for 5 minutes to obtain a mixture. Filter the mixture through a 120-mesh filter. The resulting filtrate is the dual-curing bio-based unsaturated polyester primer, denoted as Primer B.

[0030] Example 3 Dual-curing bio-based unsaturated polyester primer: 80 parts of dual-curing bio-based unsaturated polyester resin, 0.2 parts of high molecular weight acidic polymer, 0.1 parts of leveling agent, 2 parts of zinc stearate, 0.5 parts of anti-settling agent, 0.2 parts of defoamer, and 20 parts of active monomer are mixed evenly at room temperature to obtain the primer.

[0031] A method for preparing a dual-curing bio-based unsaturated polyester resin includes the following steps: Preparation of bio-based unsaturated polyester intermediate: 22 parts of diethylene glycol, 20.7 parts of maleic anhydride, 6.8 parts of fumaric acid, and 2 parts of BHT antioxidant were mixed and heated to 160-170℃ for esterification reaction for 2-3 hours to obtain a mixture. When the acid value of the system was 160-170 mgKOH / g, 0.2 parts of hydroquinone monomethyl ether polymerization inhibitor and 27.8 parts of epoxidized soybean oil were added. The temperature was lowered to 100-110℃ and kept for 3-4 hours. When the acid value was 5-10 mgKOH / g, the temperature was lowered to 80℃ and 30 parts of HDDA active monomer were added. The temperature was kept for 10-20 minutes to obtain bio-based unsaturated polyester resin intermediate. Preparation of dual-curing bio-based unsaturated polyester resin: 52.9 parts of toluene diisocyanate and 47.1 parts of bio-based unsaturated polyester resin intermediate were added and mixed. The mixture was kept at 70-80℃ for 4-6 hours. When the NCO value was 5.0-6.5%, the mixture was cooled to 60℃ and the reaction was stopped to obtain dual-curing bio-based unsaturated polyester resin.

[0032] Weigh each component of the dual-curing bio-based unsaturated polyester primer according to the specified weight proportions. Add the dual-curing bio-based unsaturated polyester resin to a mixer. Add the high molecular weight acid polymer HP1053, leveling agent, and defoamer at a stirring speed of 500 rpm. Stir for 5-10 minutes, then add zinc stearate and anti-settling agent while stirring. Stir at a stirring speed of 1500 rpm for 20 minutes. Then add the acrylic reactive monomer and stir at 800 rpm for 5 minutes to obtain a mixture. Filter the mixture through a 120-mesh filter. The resulting filtrate is the dual-curing bio-based unsaturated polyester primer, denoted as Primer C.

[0033] Experimental Example 1 Primer AC was compared with primers D and E. Primer D was MED4200 (PE low-odor transparent primer) from Beixin Carpoly Coatings Group Co., Ltd., and primer E was MED4202 (PE low-odor transparent primer) from Beixin Carpoly Coatings Group Co., Ltd. The test results are shown in Table 1. Table 1

[0034] As shown in Table 1, primer AC has a low viscosity, so it can be applied directly without adding any thinner. It also has a high solids content, no odor after opening the can, and all its properties are good.

[0035] Example 4 Primer A, cobalt naphthenate blue water, and methyl ethyl ketone peroxide white water were mixed evenly in a mass ratio of 100:0.5:0.6 to obtain a dual-curing bio-based unsaturated polyester coating, denoted as coating A.

[0036] Example 5 Primer B, blue water cobalt naphthenate, and white water methyl ethyl ketone peroxide were mixed evenly in a mass ratio of 100:0.5:0.6 to obtain a dual-curing bio-based unsaturated polyester coating, denoted as coating B.

[0037] Example 6 Primer C, blue water cobalt naphthenate, and white water methyl ethyl ketone peroxide were mixed evenly in a mass ratio of 100:0.5:0.6 to obtain a dual-curing bio-based unsaturated polyester coating, denoted as coating C.

[0038] Comparative Example 1 Carpoly MED4200 (PE low-odor transparent primer), blue water, white water, and matching PE thinner (MEX23) were mixed evenly at a mass ratio of 100:1.2:1.5:40 to obtain an unsaturated polyester coating, denoted as coating D.

[0039] Comparative Example 2 Carpoly MED4202 (PE low-odor transparent primer), blue water, white water, and matching PE thinner (MEX23) were mixed evenly at a mass ratio of 100:1.2:1.5:40 to obtain an unsaturated polyester coating, denoted as coating E.

[0040] Experiment Example 2 Paint AE was sprayed onto the surface of the wood products using a spray gun and left to dry at room temperature for 24 hours. After drying, the crafts or wood products were removed and placed at room temperature to smell their odor. Paint AC was compared with paints D and E, and the test results are shown in Table 2. The test methods for each data in Table 2 are shown below.

[0041] The evaluation method is as follows: Paint film appearance: visual inspection; Gloss: GB 1743-1979 Linshang LS191 specular gloss meter; Hardness: GB6739-86 Coating Hardness Test by Pencil Method; Adhesion: GB1720-1979(1989); Scratch resistance: GB / T 9279.1-2015; Water resistance: GB 1733-1993; Stain resistance: GB / T 23999-2009; Dry heat resistance: GB / T 4893.3-2005; Alkali resistance: GB / T9265-2009; Alcohol resistance: Q / JBL03-2004; Gelatinization time: 25 degrees Celsius in a water bath; Paint film fullness: visual inspection; Paint film transparency: visually assessed; Color difference value (△E*): GB11186.1.2—89; VOC: GB18584-2024GB / T 31106.

[0042] Table 2

[0043] As shown in Table 2, coating AC only requires the addition of a small amount of blue and white water to achieve good performance in all aspects, with no irritating odor and extended gelation time. In contrast, coatings D and E have irritating odors and short gelation times. Furthermore, coating AC is superior to coatings D and E in terms of film color, TVOC, and film fullness.

[0044] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A dual-curing bio-based unsaturated polyester primer, characterized in that; It is composed of the following raw materials in parts by weight: 60-90 parts of dual-curing bio-based unsaturated polyester resin, 0.2 parts of high molecular weight acidic polymer, 0.1 parts of leveling agent, 2 parts of zinc stearate, 0.5 parts of anti-settling agent, 0.2 parts of defoamer, and 10-30 parts of active acrylic monomer.

2. The dual-curing bio-based unsaturated polyester primer according to claim 1, characterized in that, The preparation method of the dual-curing bio-based unsaturated polyester resin includes the following steps: A mixture of polyol, unsaturated polyacid, and antioxidant is subjected to esterification polycondensation reaction, and then bio-based epoxy resin and polymerization inhibitor are added to carry out addition reaction to obtain a bio-based unsaturated polyester intermediate. The dual-curing bio-based unsaturated polyester resin is prepared by mixing a bio-based unsaturated polyester resin intermediate with an isocyanate and then reacting the mixture via a nucleophilic addition reaction.

3. The dual-curing bio-based unsaturated polyester primer according to claim 2, characterized in that, The bio-based unsaturated polyester intermediate comprises the following raw materials in parts by weight: Polyol 10-40 parts, unsaturated polyacid 20-50 parts, polymerization inhibitor 0.15-0.25 parts, antioxidant 1.0-2.0 parts, bio-based epoxy resin 20-50 parts, acrylic active monomer 20-50 parts; The polyol is one or more of diethylene glycol, propylene glycol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, dipropylene glycol, glycerol, methylpropanediol, isosorbide, and polyester polyol. The unsaturated polyacid is one or more of maleic anhydride, fumaric acid, trans-butenedioic acid, succinic acid, itaconic acid, phthalic anhydride, and sebacic acid; The polymerization inhibitor is hydroquinone monomethyl ether or tert-butylhydroquinone; The bio-based epoxy resin is one or more of the following: epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, cashew phenol epoxy resin, and rosin-based epoxy resin. The acrylic active monomer is one or more of TPGDA, HDDA, DPGDA, and DEGDA; The antioxidants are BHT, 626, 1010, and triphenyl phosphite.

4. The dual-curing bio-based unsaturated polyester primer according to claim 1, characterized in that, The dual-curing bio-based unsaturated polyester resin comprises the following raw materials in parts by weight: 45-65 parts of isocyanates, 35-55 parts of bio-based unsaturated polyester intermediates; The isocyanate is one or more of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

5. A method for preparing a dual-curing bio-based unsaturated polyester primer as described in any one of claims 1-4, characterized in that, Includes the following steps: Weigh each raw material according to the specified weight proportions. Add the dual-curing bio-based unsaturated polyester resin to the mixer. Add the high molecular weight acid polymer, leveling agent, and defoamer at a stirring speed of 400-500 prm. Stir for 5-10 minutes, then add zinc stearate and anti-settling agent while stirring. Stir for 15-20 minutes at a stirring speed of 1000-1500 prm. Add the active acrylic monomer and stir for 5-10 minutes at a stirring speed of 500-800 prm to obtain the mixture. Filter the mixture through a 100-120 mesh filter; the resulting filtrate is a dual-curing bio-based unsaturated polyester primer.

6. A dual-curing bio-based unsaturated polyester coating, characterized in that: The mixture comprises the dual-curing bio-based unsaturated polyester primer as described in any one of claims 1-4 or the dual-curing bio-based unsaturated polyester primer prepared by the method described in claim 5, an accelerator, and an initiator, which are mixed uniformly in a mass ratio of 100:0.5:1.

5.

7. The dual-curing bio-based unsaturated polyester coating according to claim 6, characterized in that, The accelerator is cobalt blue naphthenate, and the initiator is methyl ethyl ketone peroxide.

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