A modified polyester resin for powder coating and preparation method thereof

Abstract

The invention discloses a modified polyester resin for powder coating and a preparation method thereof, belonging to the technical field of powder coating, and the preparation method comprises the following steps: mixing diol, modified hexagonal boron nitride, dibasic acid and catalyst, introducing nitrogen protection, heating to 235-250°C for reaction and heat preservation; when the acid value of the resin reaches 6-12 mgKOH / g, cooling to 190-210°C, adding an acidolysis agent, heating to 240-250°C for end-capping reaction, and controlling the acid value of the polyester to be 40-48 mgKOH / g; performing vacuum polycondensation reaction at -0.094 to -0.1 MPa, and controlling the acid value of the resin to be 25-30 mgKOH / g; cooling to 200-220°C, adding a curing accelerator and an antioxidant, stirring evenly, cooling, and obtaining a modified polyester resin. The obtained modified polyester resin has excellent mechanical properties, thermal stability, heat dissipation and thermal conductivity, and flame retardant properties.

Description

Technical Field

[0001] The invention belongs to the technical field of powder coatings, and particularly relates to a modified polyester resin for powder coatings and a preparation method thereof. Background Art

[0002] Powder coating is a solid powdered synthetic resin coating composed of solid resin, pigment, filler and additives. Unlike traditional liquid coating, it does not use solvent or water as dispersion medium. It is an environmentally friendly, economical, efficient and VOC-free green coating. It is widely used in metal coating, architectural decoration, electrical and electronic product coating, furniture manufacturing, pipeline coating and other fields.

[0003] At present, with the rapid development of modern science and technology of materials and metals, the design and production of instruments, components, etc. are developing towards miniaturization and lightweight. The large amount of heat generated will directly affect the working stability and complete reliability of electronic devices. Therefore, higher requirements are put forward for the heat dissipation performance and thermal conductivity of powder coatings. At present, in order to improve the heat dissipation performance of powder coatings, various heat dissipation additives are often added therein, including graphene, carbon nanotubes, aluminum nitride, silicon carbide, etc. The principle of heat conduction of these traditional heat dissipation additives is roughly: its own high thermal conductivity or forming a connecting channel inside the polymer matrix to improve the heat dissipation effect. However, the prepared powder coating has a large filler content and large particles, which leads to the coating surface becoming more and more rough and the structure tends to be loose. The base material cannot wrap the filler, and a simple filler accumulation phenomenon occurs. The arrangement also tends to be disordered, which will destroy this "heat channel" instead, resulting in poor overall heat dissipation effect of the powder coating, and the final prepared powder coating has poor comprehensive performance. The Chinese patent application document with patent application number CN108300136A discloses a preparation method and product of graphene heat dissipation coating, whose formula consists of epoxy resin, polyester resin, polysiloxane resin, curing agent, curing accelerator, leveling agent, degassing agent, brightening agent, carbon black, carbon nanotubes, graphene, and filler. The components are subjected to the processes of batching → premixing → melt extrusion in temperature sections → tableting → crushing → screening to obtain graphene heat dissipation powder coating. The added graphene is micron-sized and is difficult to be fully dispersed in the powder coating. The thermal conductivity and heat dissipation performance of the obtained heat dissipation coating are poor.

[0004] Therefore, how to improve the heat dissipation performance of polyester powder coatings and expand its application areas is of great significance. Summary of the invention

[0005] The object of the present invention is to provide a modified polyester resin for powder coating and a preparation method thereof, so as to solve the problem of poor heat dissipation performance of polyester powder coating in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a modified polyester resin for powder coatings, comprising the following steps:

[0008] S1. Add hydroxylated hexagonal boron nitride to deionized water, heat to 95-100°C, stir and disperse to obtain a mixed solution, cool to room temperature, add modified polyethylene glycol, stir for 0.5-1h, introduce nitrogen protection, continue stirring and reacting at 18-20°C until the pH value is 7-7.3, stop stirring, filter, wash, and dry to obtain modified hexagonal boron nitride; the modified hexagonal boron nitride is prepared by chemical reaction of modified polyethylene glycol and hydroxylated hexagonal boron nitride, wherein polyethylene glycol is prepared by polyethylene glycol and polyphosphoric acid The modified polyethylene glycol is prepared by an esterification reaction, and both ends of the modified polyethylene glycol molecule contain active groups. One end can form a chemical bond with the surface of the hexagonal boron nitride nanoparticles, thereby reducing the surface energy of the hexagonal boron nitride, improving the compatibility of the hexagonal boron nitride with the polyester matrix, and improving its dispersion performance; the other end can react with the terminal carboxyl / hydroxyl group of the polyester, so that the interface between the polyester resin and the hexagonal boron nitride nanoparticles undergoes a chemical reaction on a molecular scale, further improving the uniform dispersion of the hexagonal boron nitride in the polyester matrix.

[0009] S2, mixing diol, modified hexagonal boron nitride, dibasic acid and catalyst, introducing nitrogen protection, heating to 235-250°C for reaction and keeping warm;

[0010] S3, when the acid value of the resin reaches 6-12 mgKOH / g, cool to 190-210°C, add an acidolysis agent, and heat to 240-250°C for end-capping reaction to control the acid value of the polyester at 40-48 mgKOH / g;

[0011] S4, performing vacuum polycondensation reaction at a vacuum degree of -0.094 to -0.1 MPa, and controlling the acid value of the resin to be 25 to 30 mgKOH / g;

[0012] S5. Cool down to 200-220° C., add curing accelerator and antioxidant, stir evenly, and cool to room temperature to obtain modified polyester resin.

[0013] Furthermore, the usage ratio of diol, modified hexagonal boron nitride, dibasic acid, catalyst, acidolysis agent, curing accelerator and antioxidant is 28-35g: 8-12g: 45-55g: 0.05-0.15g: 4-12g: 0.03-0.05g: 0.01-0.02g.

[0014] Furthermore, the usage ratio of hydroxylated hexagonal boron nitride, deionized water and modified polyethylene glycol in S1 is 16.5-16.8 g: 300 mL: 7.2-7.5 mL.

[0015] Furthermore, the modified polyethylene glycol described in S1 is prepared by the following steps:

[0016] The polyethylene glycol and polyphosphoric acid are mixed, stirred and reacted at 90-92° C. for 3-3.5 hours, and cooled to room temperature to obtain modified polyethylene glycol; wherein the dosage ratio of the polyethylene glycol to the polyphosphoric acid is 5.0-5.2 g:0.56-0.58 g.

[0017] Furthermore, the diol is at least one of neopentyl glycol, 1,3-propylene glycol, hexylene glycol, 1,4-cyclohexanedimethanol, and ethyl butyl propanediol.

[0018] Furthermore, the dibasic acid is at least one of terephthalic acid, isophthalic acid, adipic acid, and 1,4-cyclohexane dicarboxylic acid.

[0019] Furthermore, the catalyst is one of an organic tin catalyst and a titanium catalyst; the acidolysis agent is one of isophthalic acid, adipic acid, and phthalic anhydride.

[0020] Furthermore, the curing accelerator is at least one of tetraethylammonium bromide, tetrabutylammonium bromide, and benzyltriethylammonium chloride; and the antioxidant is at least one of hindered phenol antioxidants and phosphite antioxidants.

[0021] Further, the hydroxylated hexagonal boron nitride in S1 is prepared by the following steps:

[0022] Hexagonal boron nitride and sodium cholate are added into deionized water, ultrasonically dispersed, centrifuged, filtered and separated, and dried to obtain hydroxylated hexagonal boron nitride; wherein the dosage ratio of hexagonal boron nitride, sodium cholate and deionized water is 1g:0.01g:40mL.

[0023] The second aspect of the present invention provides a modified polyester resin for powder coating obtained by the preparation method described in the first aspect.

[0024] Beneficial effects of the present invention:

[0025] The modified polyester resin prepared in the present invention is prepared from diol, modified hexagonal boron nitride, dibasic acid, catalyst, acidolysis agent, curing accelerator and antioxidant. The toughness, hardness and thermal stability of the polyester resin are increased by introducing the modified hexagonal boron nitride in the preparation process of the polyester resin. In addition, the modified polyethylene glycol molecular chain grafted on the surface contains phosphorus, which gives the polyester resin flame retardant properties, further expanding the application field of the modified polyester resin.

[0026] The preparation method of the modified polyester resin for powder coating provided by the present invention has a simple preparation process, readily available raw materials, and is suitable for large-scale production. The prepared modified polyester resin for powder coating has excellent mechanical properties, thermal stability, heat dissipation and thermal conductivity, and flame retardant properties. Furthermore, the polyester resin powder coating prepared from the modified polyester resin provided by the present invention has excellent heat dissipation capacity, mechanical properties, flame retardant properties and other characteristics, and has potential application value in the fields of electronic appliances, fire fighting equipment, building materials, automobiles, etc. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the embodiments and comparative examples of the present invention:

[0029] The organotin catalyst used was monobutyltin oxide, purchased from Tianjin Xiensi Biochemical Technology Co., Ltd.;

[0030] The hindered phenol antioxidants used were antioxidant 1010, neopentyl glycol, and terephthalic acid, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0031] The polyethylene glycol (1000) and tetraethylammonium bromide used were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0032] The hydroxylated hexagonal boron nitride used is prepared by the following steps:

[0033] 1 g of hexagonal boron nitride and 0.01 g of sodium cholate were added to 40 mL of deionized water, ultrasonically dispersed for 3.5 h, centrifuged, filtered and separated, and dried in an oven at 60° C. to obtain hydroxylated hexagonal boron nitride.

[0034] The modified polyethylene glycol used is prepared by the following steps:

[0035] 5.0 g of polyethylene glycol (1000) and 0.56 g of 2-carboxyethylphenylphosphinic acid were mixed, stirred and reacted at 90° C. for 3 h, and cooled to room temperature to obtain modified polyethylene glycol.

[0036] Example 1

[0037] This embodiment provides a method for preparing a modified polyester resin for powder coating, comprising the following steps:

[0038] S1. Add 16.5 g of hydroxylated hexagonal boron nitride to 300 mL of deionized water, heat to 95 ° C, stir and disperse to obtain a mixed solution, cool to room temperature, add 7.2 mL of modified polyethylene glycol, stir for 0.5 h, introduce nitrogen protection, continue stirring and react at 18 ° C until the pH value is 7, stop stirring, filter, wash, and place in an oven at 80 ° C to dry for 12 h to obtain modified hexagonal boron nitride;

[0039] S2, 30g of neopentyl glycol, 8g of modified hexagonal boron nitride, 50g of terephthalic acid and 0.05g of monobutyltin oxide were mixed, nitrogen was introduced for protection, the temperature was raised to 235°C for reaction and the temperature was kept;

[0040] S3, when the acid value of the resin reaches 6 mgKOH / g, cool to 190°C, add 4 g adipic acid, and heat to 240°C for end-capping reaction to control the acid value of the polyester at 40 mgKOH / g;

[0041] S4, performing vacuum polycondensation reaction at a vacuum degree of -0.094 MPa, and controlling the acid value of the resin at 25 mgKOH / g;

[0042] S5. Cool down to 200° C., add 0.03 g of tetraethylammonium bromide and 0.01 g of antioxidant 1010, stir evenly, and cool to room temperature to obtain a modified polyester resin.

[0043] The modified polyester resin for powder coating is prepared by the above steps.

[0044] Example 2

[0045] Compared with Example 1, the only difference is:

[0046] S1. Add 16.6 g of hydroxylated hexagonal boron nitride to 300 mL of deionized water, heat to 95 ° C, stir and disperse to obtain a mixed solution, cool to room temperature, add 7.3 mL of modified polyethylene glycol, stir for 0.5 h, pass nitrogen protection, continue stirring and react at 18 ° C until the pH value is 7, stop stirring, filter, wash, and place in an oven at 80 ° C to dry for 12 h to obtain modified hexagonal boron nitride.

[0047] Example 3

[0048] Compared with Example 1, the only difference is:

[0049] S1. Add 16.8 g of hydroxylated hexagonal boron nitride to 300 mL of deionized water, heat to 95 ° C, stir and disperse to obtain a mixed solution, cool to room temperature, add 7.5 mL of modified polyethylene glycol, stir for 0.5 h, pass nitrogen protection, continue stirring and react at 18 ° C until the pH value is 7, stop stirring, filter, wash, and place in an oven at 80 ° C to dry for 12 h to obtain modified hexagonal boron nitride.

[0050] Example 4

[0051] Compared with Example 1, the only difference is:

[0052] S2. 30 g of neopentyl glycol, 12 g of modified hexagonal boron nitride, 50 g of terephthalic acid and 0.05 g of monobutyltin oxide are mixed, nitrogen is introduced for protection, and the temperature is raised to 235° C. for reaction and kept warm.

[0053] Example 5

[0054] Compared with Example 1, the only difference is:

[0055] S2. 34 g of neopentyl glycol, 10 g of modified hexagonal boron nitride, 52 g of terephthalic acid and 0.1 g of monobutyltin oxide are mixed, nitrogen is introduced for protection, and the temperature is raised to 235° C. for reaction and kept warm.

[0056] Example 6

[0057] Compared with Example 1, the only difference is:

[0058] S3. When the acid value of the resin reaches 8 mgKOH / g, cool to 190°C, add 5 g of adipic acid, and heat to 240°C for end-capping reaction to control the acid value of the polyester at 40 mgKOH / g.

[0059] Example 7

[0060] Compared with Example 1, the only difference is:

[0061] S3. When the acid value of the resin reaches 12 mgKOH / g, cool to 210°C, add 10 g of adipic acid, and heat to 250°C for end-capping reaction to control the acid value of the polyester at 48 mgKOH / g.

[0062] Example 8

[0063] Compared with Example 1, the only difference is:

[0064] S4. Perform vacuum polycondensation reaction at a vacuum degree of -0.094 MPa, and control the acid value of the resin to be 30 mgKOH / g.

[0065] Example 9

[0066] Compared with Example 1, the only difference is:

[0067] S4. Carry out vacuum polycondensation reaction at a vacuum degree of -0.1 MPa, and control the acid value of the resin at 25 mgKOH / g.

[0068] Example 10

[0069] Compared with Example 1, the only difference is:

[0070] S5. Cool down to 220° C., add 0.03 g of tetraethylammonium bromide and 0.01 g of antioxidant 1010, stir evenly, and cool to room temperature to obtain a modified polyester resin.

[0071] Embodiment 11

[0072] Compared with Example 1, the only difference is:

[0073] S5. Cool down to 215° C., add 0.045 g of tetraethylammonium bromide and 0.015 g of antioxidant 1010, stir evenly, and cool to room temperature to obtain a modified polyester resin.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a modified polyester resin for powder coating, comprising the following steps:

[0076] S1, 30g of neopentyl glycol, 8g of hexagonal boron nitride, 50g of terephthalic acid and 0.05g of monobutyltin oxide were mixed, nitrogen was introduced for protection, the temperature was raised to 235°C for reaction and the temperature was kept;

[0077] S2. When the acid value of the resin reaches 6 mgKOH / g, cool to 190°C, add 4 g adipic acid, and heat to 240°C for end-capping reaction to control the acid value of the polyester at 40 mgKOH / g;

[0078] S3, carrying out vacuum polycondensation reaction at a vacuum degree of -0.094 MPa, and controlling the acid value of the resin at 25 mgKOH / g;

[0079] S4, cooling to 200°C, adding 0.03g tetraethylammonium bromide and 0.01g antioxidant 1010, stirring evenly, cooling to room temperature, and obtaining a modified polyester resin.

[0080] The modified polyester resin for powder coating is prepared by the above steps.

[0081] Comparative Example 2

[0082] This comparative example provides a method for preparing a modified polyester resin for powder coating, comprising the following steps:

[0083] S1. Add 16.5 g of hydroxylated hexagonal boron nitride to 300 mL of deionized water, heat to 95 ° C, stir and disperse to obtain a mixed solution, cool to room temperature, add 7.2 mL of polyethylene glycol, stir for 0.5 h, introduce nitrogen protection, continue stirring and react at 18 ° C until the pH value is 7, stop stirring, filter, wash, and place in an oven at 80 ° C to dry for 12 h to obtain modified hexagonal boron nitride;

[0084] S2, 30g of neopentyl glycol, 8g of modified hexagonal boron nitride, 50g of terephthalic acid and 0.05g of monobutyltin oxide were mixed, nitrogen was introduced for protection, the temperature was raised to 235°C for reaction and the temperature was kept;

[0085] S3, when the acid value of the resin reaches 6 mgKOH / g, cool to 190°C, add 4 g adipic acid, and heat to 240°C for end-capping reaction to control the acid value of the polyester at 40 mgKOH / g;

[0086] S4, performing vacuum polycondensation reaction at a vacuum degree of -0.094 MPa, and controlling the acid value of the resin at 25 mgKOH / g;

[0087] S5. Cool down to 200° C., add 0.03 g of tetraethylammonium bromide and 0.01 g of antioxidant 1010, stir evenly, and cool to room temperature to obtain a modified polyester resin.

[0088] The modified polyester resin for powder coating is prepared by the above steps.

[0089] Comparative Example 3

[0090] This comparative example provides a method for preparing a modified polyester resin for powder coating, comprising the following steps:

[0091] S1, 30g of neopentyl glycol, 50g of terephthalic acid and 0.05g of monobutyltin oxide were mixed, nitrogen was introduced for protection, the temperature was raised to 235°C for reaction and the temperature was kept;

[0092] S2. When the acid value of the resin reaches 6 mgKOH / g, cool to 190°C, add 4 g adipic acid, and heat to 240°C for end-capping reaction to control the acid value of the polyester at 40 mgKOH / g;

[0093] S3, carrying out vacuum polycondensation reaction at a vacuum degree of -0.094 MPa, and controlling the acid value of the resin at 25 mgKOH / g;

[0094] S4, cooling to 200°C, adding 0.03g tetraethylammonium bromide and 0.01g antioxidant 1010, stirring evenly, cooling to room temperature, and obtaining a modified polyester resin.

[0095] The modified polyester resin for powder coating is prepared by the above steps.

[0096] Comparative Example 4

[0097] Compared with Example 1, the only difference is:

[0098] Replace 8 g of modified hexagonal boron nitride in S2 with 6 g of modified hexagonal boron nitride.

[0099] Comparative Example 5

[0100] Compared with Example 1, the only difference is:

[0101] Replace 8 g of modified hexagonal boron nitride in S2 with 15 g of modified hexagonal boron nitride.

[0102] Comparative Example 6

[0103] Compared with Example 1, the only difference is:

[0104] S2. 23 g of neopentyl glycol, 8 g of modified hexagonal boron nitride, 50 g of terephthalic acid and 0.05 g of monobutyltin oxide are mixed, nitrogen is introduced for protection, the temperature is raised to 235° C. for reaction and the temperature is kept.

[0105] Comparative Example 7

[0106] Compared with Example 1, the only difference is:

[0107] S3. When the acid value of the resin reaches 3 mgKOH / g, cool to 190°C, add 4 g of adipic acid, and heat to 240°C for end-capping reaction to control the acid value of the polyester at 35 mgKOH / g.

[0108] Comparative Example 8

[0109] Compared with Example 1, the only difference is:

[0110] S4. Perform vacuum polycondensation reaction at a vacuum degree of -0.094 MPa, and control the acid value of the resin to be 20 mgKOH / g.

[0111] Comparative Example 9

[0112] Compared with Example 1, the only difference is:

[0113] S5. Cool down to 180° C., add 0.03 g of tetraethylammonium bromide and 0.01 g of antioxidant 1010, stir evenly, and cool to room temperature to obtain a modified polyester resin.

[0114] (1) Application of the modified polyester resins obtained in Examples 1 to 11 and Comparative Examples 1 to 9:

[0115] 360 g of the modified polyester resin obtained in Examples 1-11 and Comparative Examples 1-9, 250 g of titanium dioxide, 136 g of matting barium, 18 g of curing agent HAA, 10 g of leveling agent (GLP588), and 4 g of benzoin were weighed and pre-mixed, and the pre-mixed mixture was melt-extruded through a twin-screw extruder, cooled and tableted, crushed and sieved through a 200-mesh sieve to obtain a powder coating.

[0116] (2) The powder coating obtained above was subjected to the following performance tests:

[0117] 1. Impact strength: Impact strength test is carried out according to standard GB / T 1732-2020;

[0118] 2. Gloss: Gloss test is carried out according to standard GB / T 9754-2007, and the test angle is 60°;

[0119] 3. Adhesion: Adhesion test is carried out according to standard GB / T 9286-2021;

[0120] 4. Flame retardancy: flame retardancy grade test is carried out according to standard GB / T 2408-2008;

[0121] 5. Heat dissipation performance: Install the coating on the motor and let the motor run at 90rpm under full load. Test the temperature of the coating surface after running for 2h and 8h respectively.

[0122] The above test results are shown in Table 1:

[0123] Table 1

[0124]

[0125] It can be seen from Table 1 that, compared with the powder coatings prepared from the polyester resins obtained in Comparative Examples 1 to 9, the powder coatings obtained in Examples 1 to 11 have excellent impact resistance, adhesion, gloss, flame retardancy and heat dissipation. It can be seen that the modified polyester resin for powder coatings provided by the present invention has excellent mechanical properties, heat dissipation properties and flame retardancy, and the preparation method is simple and suitable for large-scale production.

[0126] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0127] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a modified polyester resin for powder coating, characterized in that: The following steps are involved: S1. Add hydroxylated hexagonal boron nitride to deionized water, heat to 95-100°C, stir and disperse to obtain a mixed solution, cool to room temperature, add modified polyethylene glycol, stir for 0.5-1h, introduce nitrogen protection, continue stirring and reacting at 18-20°C until the pH value is 7-7.3, stop stirring, filter, wash, and dry to obtain modified hexagonal boron nitride; S2, mixing diol, modified hexagonal boron nitride, dibasic acid and catalyst, introducing nitrogen protection, heating to 235-250°C for reaction and keeping warm; S3, when the acid value of the resin reaches 6-12 mgKOH / g, cool to 190-210°C, add an acidolysis agent, and heat to 240-250°C for end-capping reaction to control the acid value of the polyester at 40-48 mgKOH / g; S4, performing vacuum polycondensation reaction at a vacuum degree of -0.094 to -0.1 MPa, and controlling the acid value of the resin to be 25 to 30 mgKOH / g; S5, cooling to 200-220°C, adding a curing accelerator and an antioxidant, stirring evenly, and cooling to room temperature to obtain a modified polyester resin; Wherein, the modified polyethylene glycol described in S1 is prepared by the following steps: Mixing polyethylene glycol and polyphosphoric acid, stirring and reacting at 90-92° C. for 3-3.5 hours, and cooling to room temperature to obtain modified polyethylene glycol; The dosage ratio of polyethylene glycol to polyphosphoric acid is 5.0-5.2g:0.56-0.58g.

2. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The dosage ratio of diol, modified hexagonal boron nitride, dibasic acid, catalyst, acidolysis agent, curing accelerator and antioxidant is 28-35g: 8-12g: 45-55g: 0.05-0.15g: 4-12g: 0.03-0.05g: 0.01-0.02g.

3. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The dosage ratio of hydroxylated hexagonal boron nitride, deionized water and modified polyethylene glycol in S1 is 16.5-16.8 g: 300 mL: 7.2-7.5 mL.

4. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The diol is at least one of neopentyl glycol, 1,3-propylene glycol, hexylene glycol, 1,4-cyclohexanedimethanol, and ethyl butyl propanediol.

5. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The dibasic acid is at least one of terephthalic acid, isophthalic acid, adipic acid and 1,4-cyclohexane diacid.

6. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The catalyst is one of an organic tin catalyst and a titanium catalyst; the acidolysis agent is one of isophthalic acid, adipic acid, and phthalic anhydride.

7. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The curing accelerator is at least one of tetraethylammonium bromide, tetrabutylammonium bromide and benyltriethylammonium chloride; the antioxidant is at least one of hindered phenol antioxidant and phosphite antioxidant.

8. The method for preparing a modified polyester resin for powder coating according to claim 1, characterized in that: The hydroxylated hexagonal boron nitride in S1 is prepared by the following steps: Hexagonal boron nitride and sodium cholate are added into deionized water, ultrasonically dispersed, centrifuged, filtered and separated, and dried to obtain hydroxylated hexagonal boron nitride; wherein the dosage ratio of hexagonal boron nitride, sodium cholate and deionized water is 1g:0.01g:40mL.

9. A modified polyester resin for powder coating, characterized in that: Prepared by the preparation method described in any one of claims 1 to 8.

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