Preparation process and application of ultra-low temperature curing polyester material

Abstract

The present invention relates to the technical field of low-temperature curing polyester powder coating research and development, and discloses a preparation process and application of ultra-low-temperature curing polyester materials, including: synthesizing a latent curing accelerator containing an imidazole group or a latent curing accelerator containing an imidazole group and a quaternary ammonium salt group; modifying a polyester resin with a latent curing accelerator to prepare an ultra-low-temperature curing polyester resin; and baking and curing the ultra-low-temperature curing polyester resin and a curing agent TGIC at 130 to 160°C for 10 to 20 minutes to prepare an ultra-low-temperature curing polyester material. The present invention provides a process for preparing an ultra-low-temperature curing polyester resin, and an ultra-low-temperature curing polyester material is prepared according to the process, which can achieve the technical function of ultra-low-temperature curing while maintaining excellent room temperature storage stability.

Description

Technical Field

[0001] The invention relates to the technical field of research and development of low-temperature curing polyester powder coatings, and in particular to a preparation process and application of an ultra-low-temperature curing polyester material. Background Art

[0002] Polyester powder coatings have always played an important role in industry and civil applications due to their zero VOC, excellent comprehensive performance, and low cost. At present, polyester powder coatings are widely used in household appliances, mechanical equipment, anti-corrosion pipelines, and building materials. However, the recommended construction conditions for ordinary thermosetting powder coatings are mostly (180~210℃)×(10~30min). This is because conventional polyester powder coatings need to be cured at high temperatures of 180~210℃ to make the performance of the coating meet the requirements of use, which seriously limits the expansion of its application range.

[0003] At present, the main ways to achieve low-temperature curing of polyester powder coatings include: (1) selecting suitable monomers and synthesizing polyester resins that can achieve low-temperature curing; (2) selecting appropriate types of curing agents; (3) selecting appropriate types of curing accelerators. For example, the patent with publication number CN116041676A discloses a polyester resin for low-temperature TGIC curing powder coatings and a preparation method thereof. The branching degree and the activity of the terminal carboxyl group of the polyester resin are effectively improved by using trihydroxyethyl isocyanurate monomer, and triglycidyl isocyanurate (TGIC) is used as a curing agent and an onium salt is used as a curing accelerator to achieve low-temperature curing performance of the polyester resin.

[0004] The search found that alkaline compounds (imidazoles, amine compounds) and onium salts (quaternary ammonium salts, quaternary phosphonium salt compounds) are common curing accelerators, which can effectively reduce the curing temperature when added to polyester powder coatings. While highly active curing accelerators promote high-temperature curing of resins, they often affect the room temperature storage stability of the system, reduce the applicability of the material, are not conducive to long-term storage of single-component formulas, and bring great inconvenience to industrial production. Therefore, modifying the curing accelerator to improve its latency is of great research significance for the application of polyester materials. In addition, studies have found that a variety of curing accelerators can synergistically reduce the curing temperature of polyester powder coatings.

[0005] The present invention cites the following references: Shandong University's doctoral dissertation "Preparation of Inorganic-Organic Nanocomposites and Study on 3D Printing Performance" discloses the structure and preparation method of monobromotrisilylcyclohexyl polyhedral oligomeric silsesquioxane (POSS-Br). Summary of the invention

[0006] The present invention provides a preparation process and application of an ultra-low temperature curing polyester material, designs and synthesizes a novel latent curing accelerator, and the novel latent curing accelerator can reduce the curing temperature of the polyester material, achieve the technical goal of curing at ultra-low temperatures, and enhance the storage stability of the polyester material at room temperature through the reversibility of the Michael addition reaction.

[0007] A preparation process of an ultra-low temperature curing polyester material comprises the following steps:

[0008] Step 1: Synthesize a latent curing accelerator containing an imidazole group, the general chemical formula of which is:

[0009]

[0010] Alternatively, a latent curing accelerator containing an imidazole group and a quaternary ammonium salt group is synthesized, and its general chemical formula is:

[0011]

[0012] Step 2: preparing an ultra-low temperature curing polyester resin, wherein the raw materials of the polyester resin include: neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 1,6-hexanediol, trimethylolpropane, terephthalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, a capping agent, a catalyst, a stabilizer, a composite antioxidant and a latent curing accelerator synthesized in step 1;

[0013] Step 3: After the ultra-low temperature curing polyester resin and the curing agent TGIC are evenly mixed, the mixture is baked and cured at 130-160° C. for 10-20 minutes to prepare an ultra-low temperature curing polyester material.

[0014] Preferably, the preparation method of the latent curing accelerator containing imidazole groups is: utilizing the Michael addition reaction mechanism, catalyzing the conjugate addition reaction of 2-substituted imidazole monomer and diethyl fumarate by alkaline substances, to generate the latent curing accelerator containing imidazole groups;

[0015] The 2-substituted imidazole monomer is one of imidazole, 2-methylimidazole, 2-isopropylimidazole and 2-tert-butylimidazole.

[0016] Preferably, the latent curing accelerator containing an imidazole group and a quaternary ammonium salt group is a latent curing accelerator A2, and the preparation method of the latent curing accelerator A2 is:

[0017] Step S3-1: generating an imidazole tertiary amine monomer by a nucleophilic substitution reaction between the bromine functional group of 4-bromoimidazole and the hydroxyl functional group of 3-dimethylamino-1-propanol;

[0018] Step S3-2: utilizing a nucleophilic substitution reaction mechanism to generate an imidazole quaternary ammonium salt monomer by reacting the tertiary amine group of the imidazole tertiary amine monomer with the halogen atom of 1-bromobutane;

[0019] Step S3-3: using the Michael addition reaction mechanism, a conjugate addition reaction of the imidazole quaternary ammonium salt monomer and diethyl fumarate is catalyzed by an alkaline substance to generate a latent curing accelerator A2.

[0020] Preferably, the latent curing accelerator containing an imidazole group and a quaternary ammonium salt group is a latent curing accelerator A3, and the preparation method of the latent curing accelerator A3 is:

[0021] Step S4-1: utilizing a nucleophilic substitution reaction mechanism, a quaternization reaction is carried out between the tertiary amine group of the imidazole tertiary amine monomer and the bromine atom of the monobromotrisilylcyclohexyl polyhedral oligomeric silsesquioxane to generate a POSS imidazole quaternary ammonium salt monomer;

[0022] Step S4-2: using the Michael addition reaction mechanism, a conjugate addition reaction of POSS imidazole quaternary ammonium salt monomer and diethyl fumarate is catalyzed by an alkaline substance to generate a latent curing accelerator A3.

[0023] Preferably, the alkaline substance is one of sodium ethoxide, sodium hydride, potassium tert-butoxide, triethylamine, and 8-diazabicycloundec-7-ene.

[0024] Preferably, the formula of the ultra-low temperature curing polyester resin in step 2 is: 35-45 parts by weight of neopentyl glycol, 4-6 parts by weight of 2-butyl-2-ethyl-1,3-propanediol, 5-10 parts by weight of 1,6-hexanediol, 0.5-2 parts by weight of trimethylolpropane, 40-60 parts by weight of terephthalic acid, 5-10 parts by weight of adipic acid, 1-5 parts by weight of 1,4-cyclohexanedicarboxylic acid, 1-5 parts by weight of isophthalic acid, 1-5 parts by weight of a capping agent, 0.05-2 parts by weight of a catalyst, 0.05-1 parts by weight of a stabilizer, 0.1-2 parts by weight of a composite antioxidant, and 0.1-3 parts by weight of a latent curing accelerator.

[0025] Preferably, the end-capping agent is trimellitic anhydride or adipic anhydride;

[0026] Preferably, the catalyst is monobutyltin oxide 4100 or stannous oxalate;

[0027] Preferably, the stabilizer is triphenyl phosphite;

[0028] Preferably, the composite antioxidant includes antioxidant 168 and antioxidant 1010.

[0029] Application of an ultra-low temperature curing polyester material prepared according to the above process in powder coatings;

[0030] The formula of the powder coating is: 45-65 parts by weight of ultra-low temperature curing polyester resin, 3-8 parts by weight of curing agent, 0.5-3 parts by weight of leveling agent, 0.1-2 parts by weight of brightener, 0.1-0.5 parts by weight of benzoin and 10-20 parts by weight of titanium dioxide. Beneficial Effects

[0031] The present invention designs and synthesizes a novel latent curing accelerator containing an imidazole group and / or a quaternary ammonium salt group, and performs a modification treatment on the curing performance of a polyester resin by using the latent curing accelerator to obtain an ultra-low temperature curing polyester resin. The application experiment results of the ultra-low temperature curing polyester resin confirm that the novel latent curing accelerator developed and synthesized by the present invention not only achieves the beneficial technical effect of significantly improving the curing performance of the polyester resin, but also can enhance the storage stability of the polyester material at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 These are the performance test results of powder coatings. DETAILED DESCRIPTION

[0033] Experimental Example 1:

[0034] The latent curing accelerator A1 is synthesized by using the Michael addition reaction mechanism to catalyze the conjugate addition reaction of 2-substituted imidazole monomer and diethyl fumarate with alkaline substances to generate the latent curing accelerator A1, and the chemical structure thereof is:

[0035] ;

[0036] The alkaline substance is one of sodium ethoxide, sodium hydride, potassium tert-butoxide, triethylamine, and 8-diazabicycloundec-7-ene; 8-diazabicycloundec-7-ene is selected in this experimental example;

[0037] The specific experimental steps of the latent curing accelerator A1 are as follows: first, a certain amount of 2-substituted imidazole monomer is dissolved in 20 mL of acetonitrile, and stirred at room temperature until it is completely dissolved to obtain a 2-substituted imidazole monomer solution, and then 1.7 g of diethyl fumarate is dissolved in 30 mL of acetonitrile, and stirred at room temperature until it is completely dissolved to obtain a diethyl fumarate solution. Then, the 2-substituted imidazole monomer solution and the diethyl fumarate solution are added to a three-necked flask, and stirred and mixed at room temperature for 30 minutes, and then 1.5 mL of 8-diazabicycloundec-7-ene is slowly added dropwise to the three-necked flask, and the reaction is kept stirring at room temperature for 2 hours, and the acetonitrile is removed by rotary evaporation, and the solution is dissolved in chloroform, washed with saturated sodium chloride solution and deionized water, dried over anhydrous magnesium sulfate, and the chloroform is removed by rotary evaporation to obtain a latent curing accelerator A1;

[0038] In the experimental steps for synthesizing the latent curing accelerator A1, when 0.7 g of imidazole is used as the 2-substituted imidazole monomer, the latent curing accelerator A1-Ⅰ is prepared, and its characterization results and structure are as follows:

[0039] 1 H NMR (CDCl3, 400MHz) δ: 1.17-1.29 (dt, 6H), 2.97-3.13 (m, 2H), 4.11-4.23 (m, 4H), 4.89-4.95 (t, 1H, -NC H -), 6.95-6.97(d, 1H), 7.27-7.29(d, 1H), 8.06(s, 1H);

[0040] ;

[0041] In the experimental steps for synthesizing the latent curing accelerator A1, when 0.8 g of 2-methylimidazole is used as the 2-substituted imidazole monomer, the latent curing accelerator A1-II is prepared, and its characterization results and structure are as follows:

[0042] 1 H NMR (CDCl3, 400MHz) δ: 1.15-1.30 (dt, 6H), 2.47 (s, 3H), 2.95-3.12 (m, 2H), 4.09-4.23 (m, 4H), 5.24-5.30 (t, 1H, -NC H -), 7.14-7.16(d, 1H), 7.32-7.34(d, 1H);

[0043] ;

[0044] In the experimental steps for synthesizing the latent curing accelerator A1, when 1.1 g of 2-isopropyl imidazole is used as the 2-substituted imidazole monomer, a latent curing accelerator A1-III is prepared, and its characterization results and structure are as follows:

[0045] 1 H NMR (CDCl3, 400MHz) δ: 1.13-1.32 (m, 12H), 2.94-3.21 (m, 3H), 4.06-4.22 (m, 4H), 5.05-5.13 (t, 1H, -NC H -), 7.38-7.40(d, 1H), 7.53-7.55(d, 1H);

[0046] ;

[0047] In the experimental steps for synthesizing the latent curing accelerator A1, when 1.3 g of 2-tert-butyl imidazole is used as the 2-substituted imidazole monomer, a latent curing accelerator 1-IV is prepared, and its characterization results and structure are as follows:

[0048] 1 H NMR (CDCl3, 400MHz) δ: 1.09-1.28 (m, 15H), 2.92-3.04 (m, 3H), 4.06-4.23 (m, 4H), 4.96-5.08 (t, 1H, -NC H -), 7.46-7.48(d, 1H), 7.60-7.62(d, 1H);

[0049] .

[0050] Experimental Example 2:

[0051] The synthesis route of latent curing accelerator A2 is as follows:

[0052] ;

[0053] The synthesis method of latent curing accelerator A2 is as follows:

[0054] (1) The bromine functional group of 4-bromoimidazole and the hydroxyl functional group of 3-dimethylamino-1-propanol undergo nucleophilic substitution reaction to generate an imidazole-based tertiary amine monomer. The specific experimental steps are as follows: 4.5 g of 4-bromoimidazole, 10 mL of a 30 wt% sodium hydroxide aqueous solution and 100 mL of N,N-dimethylformamide are added to a three-necked flask, and stirred and dissolved for 30 min under nitrogen protection and mechanical stirring. Then, 5 mL of tetrabutylammonium hydrogen sulfate and 3.6 mL of 3-dimethylamino-1-propanol are added dropwise to the three-necked flask in sequence, and the temperature is raised to 70° C. and stirred for reaction for 6 h. After cooling, the solvent is distilled off and dried to obtain an imidazole-based tertiary amine monomer.

[0055] (2) Using the nucleophilic substitution reaction mechanism, the tertiary amine group of the imidazole tertiary amine monomer reacts with the halogen atom of 1-bromobutane to generate an imidazole quaternary ammonium salt monomer. The specific experimental steps are as follows: 3.4 g of the imidazole tertiary amine monomer and 80 mL of cyclohexane are added to a three-necked flask, and the temperature is raised to 40°C under nitrogen protection and mechanical stirring. After the temperature stabilizes, 10 mL of 1-bromobutane solution (prepared from 2.8 g of 1-bromobutane and 20 mL of cyclohexane) is added dropwise to the three-necked flask, and the reaction is maintained at 40°C with stirring for 10 hours. After cooling, the mixture is rotary evaporated, washed with ethyl acetate, and vacuum dried to obtain an imidazole quaternary ammonium salt monomer.

[0056] (3) Using the Michael addition reaction mechanism, a conjugate addition reaction of imidazole quaternary ammonium salt monomer and diethyl fumarate was catalyzed by alkaline substances to generate a latent curing accelerator A2. The specific experimental steps are as follows: In the experimental steps for synthesizing the latent curing accelerator A1, when 3.1 g of imidazole quaternary ammonium salt monomer was used as the 2-substituted imidazole monomer, the latent curing accelerator A2 was prepared. The characterization results are as follows:

[0057] 1 H NMR (CDCl3, 400MHz) δ: 0.91-0.94(t, 3H), 1.13-1.22(dt, 6H), 1.40-1.48(m, 2H), 1.73-1.80(m, 2H), 2.25-2.35(m, 2H), 2.94-3.30(m, 12H), 4.06-4.25(m, 6H), 5.15-5.21(t, 1H, -NC H -), 7.91(s, 1H), 8.36(s, 1H);

[0058] The alkaline substance is one of sodium ethoxide, sodium hydride, potassium tert-butoxide, triethylamine, and 8-diazabicycloundec-7-ene; 8-diazabicycloundec-7-ene is selected in this experimental example.

[0059] Experimental Example 3:

[0060] The latent curing accelerator A3 is synthesized as follows:

[0061] (1) Using the nucleophilic substitution reaction mechanism, the tertiary amine group of the imidazole tertiary amine monomer reacts with the bromine atom of monobromotrisilylcyclohexyl polyhedral oligomeric silsesquioxane (POSS-Br) to generate POSS imidazole quaternary ammonium salt monomer. The specific experimental steps are as follows: 0.9 g of imidazole tertiary amine monomer and 20 mL of tetrahydrofuran are added to a three-necked flask, and the temperature is raised to 40°C under nitrogen protection and mechanical stirring. After the temperature stabilizes, 50 mL of POSS-Br solution (prepared from 5.6 g of POSS-Br and 50 mL of tetrahydrofuran) is added dropwise to the three-necked flask, and the reaction is maintained at 40°C with stirring for 10 hours. After cooling, the mixture is rotary evaporated, washed with ethyl acetate, and vacuum dried to obtain POSS imidazole quaternary ammonium salt monomer.

[0062] (2) Using the Michael addition reaction mechanism, the conjugate addition reaction of POSS imidazole quaternary ammonium salt monomer and diethyl fumarate was catalyzed by alkaline substances to generate a latent curing accelerator A3. The specific experimental steps are as follows: 6.5 g of POSS imidazole quaternary ammonium salt monomer was dissolved in a mixed solution of 20 mL of acetonitrile and 20 mL of tetrahydrofuran, and stirred at room temperature until completely dissolved to obtain a POSS imidazole quaternary ammonium salt monomer solution; 0.9 g of diethyl fumarate was dissolved in 20 mL of acetonitrile, and stirred at room temperature until completely dissolved to obtain a diethyl fumarate solution; the imidazole solution and the diethyl fumarate solution were added to a three-necked flask, stirred and mixed at room temperature for 30 minutes, and then 1.0 mL of 8-diazabicycloundec-7-ene was stirred at room temperature for 2 h, the solvent was removed by rotary evaporation, dissolved in chloroform, washed with saturated sodium chloride solution and deionized water in turn, dried over anhydrous magnesium sulfate, and chloroform was removed by rotary evaporation to obtain a latent curing accelerator 3, the characterization results and structure of which are as follows:

[0063] 1 H NMR (CDCl3, 400MHz) δ: 1.05-1.18 (dt, 6H), 1.49-2.07 (m, 79H), 2.35-2.37 (m, 2H), 2.68-2. 70(m,2H),2.97-3.44(m,12H),4.05-4.11(m,6H),5.20-5.22(t,1H,-NC H -), 7.90(s, 1H), 8.27(s, 1H);

[0064] ;

[0065] The alkaline substance is one of sodium ethoxide, sodium hydride, potassium tert-butoxide, triethylamine, and 8-diazabicycloundec-7-ene; 8-diazabicycloundec-7-ene is selected in this experimental example. Embodiment 1:

[0066] The preparation of ultra-low temperature curing polyester resin comprises the following steps:

[0067] Step 1: According to the formula of the ultra-low temperature curing polyester resin in Table 1, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 1,6-hexanediol and trimethylolpropane are first put into a reaction kettle, heated to melt, filled with nitrogen and stirred, and then terephthalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid and monobutyltin oxide 4100 are added, and the temperature is raised to 240° C. to keep the reaction until the acid value reaches 15.4 mgKOH / g;

[0068] Step 2: Cool down to 220°C and add triphenyl phosphite, isophthalic acid and trimellitic anhydride, start stirring, keep warm at 220°C until the acid value is 47.2 mgKOH / g; start the vacuum pump, slowly evacuate at 220°C to a vacuum degree of -0.1 MPa, maintain for 2 hours, so that the acid value is 30.8 mgKOH / g;

[0069] Step 3: Cool down to 200°C, add antioxidant 168 and antioxidant 1010, keep reacting for 40 minutes, continue to cool down to 120°C, add latent curing accelerator, keep for 20 minutes, and obtain ultra-low temperature curing polyester resin;

[0070] The acid value is tested according to GB / T 6743-2008 "Determination of partial acid value and total acid value of polyester resins for plastics, paints and varnishes".

[0071] In the experimental steps for synthesizing the ultra-low temperature curing polyester resin, when the latent curing accelerators A1-Ⅰ, A1-Ⅱ, A1-Ⅲ, A1-Ⅳ, A2, A3 are used, the ultra-low temperature curing polyester resins P1-Ⅰ, P1-Ⅱ, P1-Ⅲ, P1-Ⅳ, P2, P3 are prepared in sequence; when the latent curing accelerator is not used, the conventional polyester resin is prepared.

[0072] Table 1 Formula of ultra-low temperature curing polyester resin

[0073] Embodiment 2:

[0074] Application experiment of ultra-low temperature curing polyester resin: According to the formula in Table 2, ultra-low temperature curing polyester resin, curing agent TGIC, leveling agent 588, brightener 701, benzoin and titanium dioxide were put into a twin-screw extruder (front zone temperature is 120℃, rear zone temperature is 105℃, and speed is 35r / min), and powder coating was obtained through pre-mixing, extrusion, cooling, crushing, grinding and sieving;

[0075] The powder coating stored for 0 days and 30 days was sprayed on the tinplate by electrostatic spraying, and the tinplate was placed in a preheated electric heating box for baking and curing to obtain a polyester coating, and the appearance of the coating film was observed;

[0076] Table 2 Powder coating formulations

[0077]

[0078] In the application experimental steps of the ultra-low temperature curing polyester resin, when the ultra-low temperature curing polyester resin uses ultra-low temperature curing polyester resins P1-Ⅰ, P1-Ⅱ, P1-Ⅲ, P1-Ⅳ, P2, P3, powder coatings C1-Ⅰ, C1-Ⅱ, C1-Ⅲ, C1-Ⅳ, C2, C3 are prepared in sequence; when conventional polyester resin is used to replace the ultra-low temperature curing polyester resin, conventional powder coatings are prepared;

[0079] In order to explore the effect of latent curing accelerator on the storage performance of powder coatings, the present invention conducted the following experiments:

[0080] Experiment 1: In the experimental steps of synthesizing ultra-low temperature curing polyester resin, 2-methylimidazole was used instead of the latent curing accelerator to prepare polyester resin Pa;

[0081] In the application experimental steps of the ultra-low temperature curing polyester resin, polyester resin Pa is used to replace the ultra-low temperature curing polyester resin to prepare powder coating Ca;

[0082] Experiment 2: In the experimental steps of synthesizing ultra-low temperature curing polyester resin, imidazole quaternary ammonium salt monomer was used to replace the latent curing accelerator to prepare polyester resin Pb;

[0083] In the application experimental steps of the ultra-low temperature curing polyester resin, polyester resin Pb is used to replace the ultra-low temperature curing polyester resin to prepare powder coating Cb;

[0084] Experiment 3: In the experimental steps of synthesizing ultra-low temperature curing polyester resin, POSS imidazole quaternary ammonium salt monomer was used to replace the latent curing accelerator to prepare polyester resin Pc;

[0085] In the application experimental steps of the ultra-low temperature curing polyester resin, polyester resin Pb is used to replace the ultra-low temperature curing polyester resin to prepare the powder coating Cc.

[0086] Performance Test:

[0087] 1. The gel time of powder coatings was tested according to the standard GB / T 16995-1997 "Determination of gel time of thermosetting powder coatings at a given temperature". The experimental results are shown in Table 3 below.

[0088] Table 3 Gel time test results of powder coating (test temperature is 140℃)

[0089]

[0090] 2. Gloss retention is tested according to GB / T 1865-2009 “Paints and varnishes - Artificial weathering and artificial radiation exposure to filtered xenon arc radiation”. The experimental results are shown in Table 4 below.

[0091] Table 4 Performance test results of powder coatings

[0092]

[0093] The following conclusions can be drawn from the above experimental results:

[0094] The novel latent curing accelerator developed and synthesized by the present invention can significantly reduce the curing temperature of polyester resin and enhance the storage stability of polyester material at room temperature;

[0095] (2) The new latent curing accelerator containing quaternary ammonium salt functional groups has a better effect on improving the curing performance of polyester resin. The new latent curing accelerator containing both quaternary ammonium salt functional groups and POSS structure has a better improvement effect.

Claims

1. A preparation process of ultra-low temperature curing polyester material, characterized in that: The following steps are involved: Step 1: synthesizing a latent curing accelerator, wherein the latent curing accelerator is a latent curing accelerator A2 or a latent curing accelerator A3; The chemical structural formula of the latent curing accelerator A2 is: ； The chemical structural formula of the latent curing accelerator A3 is: ； Step 2: preparing an ultra-low temperature curing polyester resin, wherein the raw materials of the polyester resin include: neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 1,6-hexanediol, trimethylolpropane, terephthalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, a capping agent, a catalyst, a stabilizer, a composite antioxidant and a latent curing accelerator synthesized in step 1; Step 3: After the ultra-low temperature curing polyester resin and the curing agent TGIC are evenly mixed, the mixture is baked and cured at 130-160° C. for 10-20 minutes to prepare an ultra-low temperature curing polyester material.

2. The process for preparing an ultra-low temperature curing polyester material according to claim 1, characterized in that: The preparation method of the latent curing accelerator A2 is as follows: Step S3-1: generating an imidazole tertiary amine monomer by a nucleophilic substitution reaction between the bromine functional group of 4-bromoimidazole and the hydroxyl functional group of 3-dimethylamino-1-propanol; Step S3-2: utilizing a nucleophilic substitution reaction mechanism to generate an imidazole quaternary ammonium salt monomer by reacting the tertiary amine group of the imidazole tertiary amine monomer with the halogen atom of 1-bromobutane; Step S3-3: using the Michael addition reaction mechanism, a conjugate addition reaction of the imidazole quaternary ammonium salt monomer and diethyl fumarate is catalyzed by an alkaline substance to generate a latent curing accelerator A2.

3. The process for preparing an ultra-low temperature curing polyester material according to claim 1, characterized in that: The preparation method of the latent curing accelerator A3 is as follows: Step S4-1: utilizing a nucleophilic substitution reaction mechanism, a tertiary amine group of an imidazole tertiary amine monomer undergoes a quaternization reaction with a bromine atom of a monobromotrisilylcyclohexyl polyhedral oligomeric silsesquioxane to generate a POSS imidazole quaternary ammonium salt monomer; wherein a nucleophilic substitution reaction occurs between a bromine functional group of 4-bromoimidazole and a hydroxyl functional group of 3-dimethylamino-1-propanol to generate an imidazole tertiary amine monomer; Step S4-2: using the Michael addition reaction mechanism, a conjugate addition reaction of POSS imidazole quaternary ammonium salt monomer and diethyl fumarate is catalyzed by an alkaline substance to generate a latent curing accelerator A3.

4. A process for preparing an ultra-low temperature curing polyester material according to claim 2 or 3, characterized in that: The alkaline substance is one of sodium ethoxide, sodium hydride, potassium tert-butoxide, triethylamine, and 1,8-diazabicycloundec-7-ene.

5. The process for preparing an ultra-low temperature curing polyester material according to claim 1, characterized in that: The formula of the ultra-low temperature curing polyester resin in the step 2 is: 35-45 parts by weight of neopentyl glycol, 4-6 parts by weight of 2-butyl-2-ethyl-1,3-propanediol, 5-10 parts by weight of 1,6-hexanediol, 0.5-2 parts by weight of trimethylolpropane, 40-60 parts by weight of terephthalic acid, 5-10 parts by weight of adipic acid, 1-5 parts by weight of 1,4-cyclohexanedicarboxylic acid, 1-5 parts by weight of isophthalic acid, 1-5 parts by weight of a capping agent, 0.05-2 parts by weight of a catalyst, 0.05-1 parts by weight of a stabilizer, 0.1-2 parts by weight of a composite antioxidant, and 0.1-3 parts by weight of a latent curing accelerator.

6. The process for preparing an ultra-low temperature curing polyester material according to claim 1, characterized in that: The end-capping agent is trimellitic anhydride or adipic anhydride; The catalyst is monobutyltin oxide 4100 or stannous oxalate; The stabilizer is triphenyl phosphite; The composite antioxidant includes antioxidant 168 and antioxidant 1010.

7. An ultra-low temperature curing polyester material prepared by the process according to any one of claims 1 to 3, characterized in that: Application of the ultra-low temperature curing polyester material in powder coatings; The formula of the powder coating is: 45-65 parts by weight of ultra-low temperature curing polyester resin, 3-8 parts by weight of curing agent, 0.5-3 parts by weight of leveling agent, 0.1-2 parts by weight of brightener, 0.1-0.5 parts by weight of benzoin and 10-20 parts by weight of titanium dioxide.

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