Curing agent for environment-friendly polyurethane resin powder coating and application of curing agent

Abstract

The invention discloses a curing agent for an environment-friendly polyurethane resin powder coating and application of the curing agent, and the curing agent is prepared by adopting the following method: under the protection of nitrogen, adding an I PD I tripolymer and DMAC into a flask, uniformly stirring, heating to 120 DEG C, adding a DMAC solution of a DOPO-based intermediate, keeping the temperature, stirring and reacting for 2-4 hours, adding hydroxyl-terminated polyborosiloxane into the flask, stirring and reacting for 2-4 hours, and cooling to room temperature to obtain the curing agent for the environment-friendly polyurethane resin powder coating. The curing agent for the polyurethane resin powder coating is prepared by the following steps: adding a DMAC solution of an imidazolyl sealing agent into a reaction kettle, carrying out heat-preservation stirring reaction for 1-2 hours, cooling to 100 DEG C, dropwise adding the DMAC solution of the imidazolyl sealing agent, carrying out heat-preservation reaction until the content of-NCO in the system is less than 0.6% after dropwise adding, stopping the reaction, carrying out reduced pressure distillation to remove DMAC, cooling to room temperature, crushing a distillation product, adding an initiator, and uniformly stirring and mixing, so that the curing agent for the polyurethane resin powder coating is obtained. The mechanical property and the flame retardant property of a polyurethane coating film can be enhanced, and the polyurethane coating film is endowed with good self-repairing performance.

Description

Technical Field

[0001] The invention belongs to the technical field of curing agents, and in particular relates to a curing agent for an environmentally friendly polyurethane resin powder coating and application thereof. Background Art

[0002] Powder coatings and their coating technology are a rapidly developing new variety, new process and new technology, which have many advantages that solvent-based coatings cannot match. Among them, polyurethane powder coatings have many excellent properties. The coating film has high gloss, excellent decorative properties, strong wear resistance, good adhesion, and good weather resistance, corrosion resistance, electrical properties and mechanical properties. It can play an advantageous role in many fields of industry, agriculture, transportation and aerospace industry.

[0003] Polyurethane powder coatings are composed of resins, curing agents, curing catalysts, pigments and fillers. The molecular structure of the resin can be expressed as HO-R-OH, where R represents the main chain of the macromolecule and -OH is a reactive functional group. Common resins are polyester resins with hydroxyl groups, acrylic resins containing hydroxyl groups and hydroxyl polyethers. The main component of the curing agent is blocked isocyanate. Blocked isocyanate is a class of compounds with one or more terminal isocyanate groups (-NCO) and whose -NCO groups are blocked by a blocking agent that cannot be unblocked at low temperatures. This compound is chemically stable at room temperature, but at higher temperatures, the blocked isocyanate will unblock into free isocyanate groups and blocking agents, and regain reactive activity. Although existing blocked isocyanate blocking agents can provide lower unblocking temperatures and obtain higher curing efficiency, the release of the blocking agent after unblocking will cause environmental pollution problems and easily cause adverse effects on the environment. Therefore, providing an environmentally friendly curing agent for polyurethane resin powder coatings is a technical problem that needs to be solved at present. Summary of the invention

[0004] The purpose of the present invention is to provide an environmentally friendly polyurethane resin powder coating curing agent and application thereof, so as to solve the problem that the sealing agent released after unsealing in the existing polyurethane resin powder coating curing agent will cause environmental pollution.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first aspect of the present invention provides an environmentally friendly polyurethane resin powder coating curing agent, wherein the environmentally friendly polyurethane resin powder coating curing agent is prepared by the following method:

[0007] Under nitrogen protection, IPD I trimer and DMAC (N, N-dimethylacetamide) are added to a flask, stirred evenly, and then heated to 120°C, and the DMAC solution of the DOPO-based intermediate is added, and the reaction is stirred and kept warm for 2-4 hours. The terminal hydroxyl polyborosiloxane is added to the flask, and the reaction is stirred and kept warm for 1-2 hours. The temperature is lowered to 100°C, and the DMAC solution of the imidazole-based blocking agent is added dropwise. After the addition is completed, the reaction is kept warm until the -NCO content in the system is less than 0.6%, and the reaction is stopped. The DMAC is removed by vacuum distillation, and after cooling to room temperature, the distillation product is crushed and added to the initiator, and the mixture is stirred and mixed evenly to obtain an environmentally friendly polyurethane resin powder coating curing agent.

[0008] Among them, the dosage ratio of IPD I trimer, DMAC, DOPO-based intermediate, terminal hydroxyl polyborosiloxane, imidazole-based blocking agent and initiator is 100g:150-250mL:5.68g:10.68g:85.62g:0.85-1.2g, the DMAC solution of DOPO-based intermediate is composed of DOPO-based intermediate and DMAC according to 5.68g:10mL, and the DMAC solution of imidazole-based blocking agent is composed of imidazole-based blocking agent and DMAC according to 85.62g:100mL.

[0009] The imidazole-based blocking agent is an imidazole-based blocking agent containing an acrylate structure.

[0010] Further, the imidazole-based blocking agent is prepared by the following steps:

[0011] 1H-imidazole-4,5-dimethanol, hydroquinone, DCC (dicyclohexylcarbodiimide), DMAP (4-dimethylaminopyridine) and acrylic acid are added to DMF (N,N-dimethylformamide), heated and stirred at 110-120° C. for 48 hours. After the reaction is completed, DMF is removed by decompression to obtain an imidazole-based blocking agent;

[0012] The dosage ratio of 1H-imidazole-4,5-dimethanol, hydroquinone, DCC, DMAP, acrylic acid and DMF is 40mmol: 0.2-0.3g: 10.32g: 6.11g: 80mmol: 150-200mL. 1H-imidazole-4,5-dimethanol and acrylic acid are used as raw materials, and an imidazole-based sealing agent containing an acrylate structure is obtained through an esterification reaction.

[0013] Further, the hydroxy-terminated polyborosiloxane is prepared by the following steps:

[0014] Add phenylboric acid and dihydroxy-terminated polydimethylsiloxane into a flask, stir at 120-150 rpm for 1 hour at room temperature under nitrogen protection, then heat to 190°C, continue stirring and react for 2-4 hours, and cool to room temperature to obtain hydroxy-terminated polyborosiloxane. The amounts of phenylboric acid and hydroxy-terminated polydimethylsiloxane are set according to a hydroxyl molar ratio of 1:1.1-1.2, the average molecular weight of dihydroxy-terminated polydimethylsiloxane is 500, and phenylboric acid is ground and dried phenylboric acid.

[0015] Further, the DOPO-based intermediate is prepared by the following steps:

[0016] Add DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) into a flask and heat it to 130°C until DOPO is completely melted, cool it to 100°C, add ethylene glycol diglycidyl ether, keep it warm and stir for 10-20 minutes, then add DMAC, heat it to 110°C and stir to react for 3-5 hours, then cool it to 85°C, add methylbutylamine, stir it in a nitrogen atmosphere at 70°C for 12 hours, and finally remove DMAC by distillation under reduced pressure to obtain a DOPO-based intermediate;

[0017] The dosage ratio of DOPO, ethylene glycol diglycidyl ether, DMAC and methyl butylamine is 0.1 mol: 0.1 mol: 500 mL: 0.1 mol. The ring-opening reaction between DOPO, methyl butylamine and ethylene glycol diglycidyl ether is used to obtain a DOPO-based intermediate compound containing nitrogen and phosphorus elements and dihydroxyl groups.

[0018] Furthermore, the initiator is dicumyl peroxide.

[0019] The first aspect of the present invention provides a use of an environmentally friendly polyurethane resin powder coating curing agent, wherein the environmentally friendly polyurethane resin powder coating curing agent is used to cure a hydroxyl polymer to prepare a polyurethane powder coating.

[0020] Beneficial effects of the present invention:

[0021] The invention provides an environmentally friendly curing agent for polyurethane resin powder coating, which uses a DOPO-based intermediate and an IPD I trimer as raw materials, synthesizes a hyperbranched intermediate through a reaction between a hydroxyl group and an isocyanate group, wherein the DOPO-based intermediate is an A2-type monomer, A is -OH, and the IPD I trimer is a B3-type monomer, B is -NCO, then the hyperbranched intermediate is reacted with a terminal hydroxyl polyborosiloxane, a polyborosiloxane structure is introduced into the system, and finally an imidazole-based blocking agent is used to block the -NCO group in the system, and the curing agent is uniformly mixed with an initiator to obtain the curing agent. The curing agent is easy to use and can be used as a curing agent for polyurethane powder coating, which can not only meet the curing requirements of polyurethane, but also will not cause environmental pollution after the curing agent is unblocked, because the imidazole-based blocking agent in the present case not only has good blocking and unblocking effects, but also can participate in a self-polymerization reaction under the action of the initiator after unblocking due to the presence of unsaturated double bonds, so that the blocking agent is not only retained in the cross-linked network of the coating, reducing the adverse effects on the environment, but also enhancing the cross-linking density of the coating;

[0022] In addition, the curing agent molecular chain contains a polyborosiloxane structure. The presence of the boron-oxygen dynamic bond in the polyborosiloxane can, on the one hand, give the polyurethane coating prepared therefrom good self-healing properties. On the other hand, due to the large bond energy of the boron-oxygen bond, it can synergize with the nitrogen and phosphorus elements in the curing agent system to improve the flame retardant properties of the polyurethane coating. Furthermore, the polyborosiloxane structure has good flexibility, and the hyperbranched polymer has the characteristics of highly branched structure and internal holes, which can improve the mechanical properties of the polyurethane powder coating. In summary, the curing agent for the polyurethane resin powder coating prepared by the present invention can not only improve the mechanical properties and flame retardant properties of the obtained polyurethane coating, but also give it self-healing properties, and is in line with the current development concept of green environmental protection and comprehensive utilization. DETAILED DESCRIPTION

[0023] 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.

[0024] The IPD I trimer in the following examples and comparative examples has an NCO mass fraction of 17.3% and was purchased from Wanhua Chemical.

[0025] Preparation Example 1

[0026] The DOPO-based intermediates are prepared by the following steps:

[0027] 0.1 mol DOPO was added to a flask and heated to 130°C until DOPO was completely melted. The temperature was lowered to 100°C and 0.1 mol ethylene glycol diglycidyl ether was added. After stirring at this temperature for 10 minutes, 500 mL DMAC was added. The temperature was raised to 110°C and stirred for 3 hours. The temperature was then lowered to 85°C, 0.1 mol methylbutylamine was added, and the mixture was stirred in a nitrogen atmosphere at 70°C for 12 hours. Finally, DMAC was removed by distillation under reduced pressure to obtain a DOPO-based intermediate.

[0028] Preparation Example 2

[0029] The DOPO-based intermediates are prepared by the following steps:

[0030] 0.1 mol DOPO was added to a flask and heated to 130°C until DOPO was completely melted. The temperature was lowered to 100°C and 0.1 mol ethylene glycol diglycidyl ether was added. After stirring at this temperature for 20 min, 500 mL DMAC was added. The temperature was raised to 110°C and stirred for 5 h. The temperature was then lowered to 85°C, 0.1 mol methylbutylamine was added, and the mixture was stirred in a nitrogen atmosphere at 70°C for 12 h. Finally, DMAC was removed by distillation under reduced pressure to obtain a DOPO-based intermediate.

[0031] Comparative Example 1

[0032] This comparative example provides an intermediate, which is prepared by the following steps:

[0033] 0.1 mol ethylene glycol diglycidyl ether and 500 mL DMAC were mixed, heated to 110°C and stirred for 3 h, then cooled to 100°C, 0.2 mol methylbutylamine was added, stirred at 70°C in a nitrogen atmosphere for 12 h, and finally DMAC was removed by vacuum distillation to obtain an intermediate.

[0034] Preparation Example 3

[0035] The imidazole-based blocking agent is prepared by the following steps:

[0036] 40 mmol 1H-imidazole-4,5-dimethanol, 0.2 g hydroquinone, 10.32 g DCC, 6.11 g DMAP and 80 mmol acrylic acid were added to 150 mL DMF, heated and stirred at 110°C for 48 h. After the reaction was completed, DMF was removed by decompression to obtain an imidazole-based blocking agent.

[0037] Preparation Example 4

[0038] The imidazole-based blocking agent is prepared by the following steps:

[0039] 40 mmol 1H-imidazole-4,5-dimethanol, 0.3 g hydroquinone, 10.32 g DCC, 6.11 g DMAP and 80 mmol acrylic acid were added to 200 mL DMF, heated and stirred at 120°C for 48 h. After the reaction was completed, DMF was removed by decompression to obtain an imidazole-based blocking agent.

[0040] Comparative Example 2

[0041] This comparative example provides a blocking agent, which is methyl ethyl ketone oxime.

[0042] Example 5

[0043] An environmentally friendly polyurethane resin powder coating curing agent is prepared by the following method: under nitrogen protection, 100 g of IPD I trimer and 150 mL of DMAC are added to a flask, stirred evenly, and then heated to 120° C., 5.68 g of the DOPO-based intermediate of Preparation Example 1 and 10 mL of DMAC solution are added, and the mixture is stirred and reacted for 2 h, 10.68 g of terminal hydroxyl polyborosiloxane is added to the flask, stirred and reacted for 1 h, cooled to 100° C., and a solution consisting of 85.62 g of the imidazole-based blocking agent of Preparation Example 3 and 100 mL of DMAC is added dropwise, and after the addition is completed, the mixture is stirred and reacted until the -NCO content in the system is less than 0.6%, the reaction is stopped, and the DMAC is removed by reduced pressure distillation, and after cooling to room temperature, the distillation product is crushed and 0.85 g of initiator is added, and the mixture is stirred and mixed for 1 h, so as to obtain an environmentally friendly polyurethane resin powder coating curing agent.

[0044] Hydroxyl-terminated polyborosiloxane is prepared by the following steps:

[0045] Add phenylboric acid and dihydroxy-terminated polydimethylsiloxane into a flask, stir at 120 rpm for 1 hour at room temperature under nitrogen protection, then heat to 190°C, continue stirring and react for 2 hours, and cool to room temperature to obtain hydroxy-terminated polyborosiloxane. The amounts of phenylboric acid and hydroxy-terminated polydimethylsiloxane are set according to a hydroxyl molar ratio of 1:1.1. The average molecular weight of dihydroxy-terminated polydimethylsiloxane is 500, and phenylboric acid is ground and dried phenylboric acid.

[0046] The initiator is dicumyl peroxide.

[0047] Example 6

[0048] An environmentally friendly polyurethane resin powder coating curing agent is prepared by the following method: under nitrogen protection, 100g of IPD I trimer and 200mL of DMAC are added to a flask, stirred evenly, and then heated to 120°C, 5.68g of the DOPO-based intermediate of Preparation Example 2 and 10mL of DMAC solution are added, and the mixture is stirred and reacted for 3h, 10.68g of terminal hydroxyl polyborosiloxane is added to the flask, and the mixture is stirred and reacted for 1.5h, cooled to 100°C, and a solution consisting of 85.62g of the imidazole-based blocking agent of Preparation Example 3 and 100mL of DMAC is added dropwise, and after the addition is completed, the mixture is stirred and reacted until the -NCO content in the system is less than 0.6%, the reaction is stopped, and the DMAC is removed by reduced pressure distillation. After cooling to room temperature, the distillation product is crushed and 1.0g of initiator is added, and the mixture is stirred and mixed for 1.5h to obtain an environmentally friendly polyurethane resin powder coating curing agent.

[0049] Hydroxyl-terminated polyborosiloxane is prepared by the following steps:

[0050] Add phenylboric acid and dihydroxy-terminated polydimethylsiloxane into a flask, stir at 140 rpm for 1 hour at room temperature under nitrogen protection, then heat to 190°C, continue stirring and react for 3 hours, and cool to room temperature to obtain hydroxy-terminated polyborosiloxane. The amounts of phenylboric acid and hydroxy-terminated polydimethylsiloxane are set according to a hydroxyl molar ratio of 1:1.1. The average molecular weight of dihydroxy-terminated polydimethylsiloxane is 500, and phenylboric acid is ground and dried phenylboric acid.

[0051] The initiator is dicumyl peroxide.

[0052] Example 7

[0053] An environmentally friendly polyurethane resin powder coating curing agent is prepared by the following method: under nitrogen protection, 100g of IPD I trimer and 250mL of DMAC are added to a flask, stirred evenly, and then heated to 120°C, 5.68g of the DOPO-based intermediate of Preparation Example 2 and 10mL of the DMAC solution are added, and the mixture is stirred and reacted for 4h, 10.68g of terminal hydroxyl polyborosiloxane is added to the flask, and the mixture is stirred and reacted for 2h, and the temperature is lowered to 100°C, and a solution consisting of 85.62g of the imidazole-based blocking agent of Preparation Example 4 and 100mL of DMAC is added dropwise, and after the addition is completed, the mixture is stirred and reacted until the -NCO content in the system is less than 0.6%, the reaction is stopped, and the DMAC is removed by reduced pressure distillation. After cooling to room temperature, the distillation product is crushed and 1.2g of an initiator is added, and the mixture is stirred and mixed for 2h to obtain an environmentally friendly polyurethane resin powder coating curing agent.

[0054] Hydroxyl-terminated polyborosiloxane is prepared by the following steps:

[0055] Add phenylboric acid and dihydroxy-terminated polydimethylsiloxane into a flask, stir at 150 rpm for 1 hour at room temperature under nitrogen protection, then heat to 190°C, continue stirring and react for 2-4 hours, and cool to room temperature to obtain hydroxy-terminated polyborosiloxane. The amounts of phenylboric acid and hydroxy-terminated polydimethylsiloxane are set according to a hydroxyl molar ratio of 1:1.2, the average molecular weight of dihydroxy-terminated polydimethylsiloxane is 500, and phenylboric acid is ground and dried phenylboric acid.

[0056] The initiator is dicumyl peroxide.

[0057] Comparative Example 3

[0058] Compared with Example 5, the DOPO-based intermediate in Example 5 was replaced by the product prepared in Control Example 1, and the remaining raw materials and preparation process were the same as in Example 5.

[0059] Comparative Example 4

[0060] Compared with Example 5, the imidazole blocking agent in Example 5 is replaced by the substance in Control Example 2, and the remaining raw materials and preparation process are the same as in Example 5.

[0061] Comparative Example 5

[0062] Compared with Example 5, the step of "adding 12.4 g of terminal hydroxyl polyborosiloxane into the flask, and stirring and reacting for 1 hour at a temperature keeping warm" in Example 5 is removed, and the remaining raw materials and preparation process are the same as in Example 5.

[0063] The environmentally friendly polyurethane resin powder coating curing agent obtained in Examples 5-7 and Comparative Examples 3-5 was used as the curing component. The raw materials were weighed according to the formula in Table 1, added to a high-speed mixer, stirred at a speed of 1500 rpm for 1 hour, and then transferred to a twin-screw extruder for melt extrusion. The temperature of the first zone was 110°C and the temperature of the second zone was 125°C. After the extrusion was completed, it was cooled to room temperature and sent to a grinder for grinding. The grinding conditions were a main machine speed of 8500 r / min and a secondary mill speed of 6500 r / min. The polyurethane powder coatings obtained in Examples 8-10 and Comparative Examples 6-8 were obtained. The obtained polyurethane powder coatings were electrostatically sprayed on the surface of a steel plate, cross-linked and cured at a curing temperature of 200°C and a curing time of 10 min. The coating thickness was 50 μm.

[0064] Table 1

[0065]

[0066]

[0067] Note:

[0068] 1: Hydroxyl-terminated polyester resin, produced by Zhejiang Tiansong Group Co., Ltd.;

[0069] 2: Polyacrylate leveling agent, produced by Worleee of Germany;

[0070] 3: Defoaming agent, commercially available industrial grade;

[0071] 4: Carbon black, produced by Mitsubishi Chemical Corporation of Japan;

[0072] 5: Filler, produced by Shaanxi Fuhua Chemical Co., Ltd.

[0073] The coatings obtained in Examples 8-10 and Comparative Examples 6-8 were tested, and the pencil hardness of the coating was tested with reference to standard GB6739-86. Impact resistance test: impact resistance was tested with reference to standard GB / T1732-2020. Smoke emission during baking and curing: when the coating was cured, observe with the naked eye whether smoke was emitted, and if so, the environment was polluted. A combustion test was performed on the prepared coating with reference to GB / T2408-2008, and the flame retardant effect was characterized by the limiting oxygen index. Repairability: a crack 5 cm long and 500 microns wide was cut in the middle of the coating along the direction perpendicular to the tensile axis, and a slight force was applied on both sides to make the fracture contact. The crack was healed for 12 hours at room temperature to observe whether it was healed. The results are shown in Table 2:

[0074] Table 2

[0075]

[0076]

[0077] It can be seen from the data recorded in Table 2 that compared with the curing agents prepared in Comparative Examples 6, 7 and 8, the curing agents for environmentally friendly polyurethane resin powder coatings prepared in Examples 8, 9 and 10 are more environmentally friendly, and can enhance the mechanical properties and flame retardant properties of the polyurethane coating and give it good self-healing properties.

[0078] 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", "comprise" or any other variants 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.

[0079] 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. An environmentally friendly polyurethane resin powder coating curing agent, characterized in that: Prepared by the following method: Under nitrogen protection, add IPD I trimer and DMAC into a flask, stir evenly, then heat to 120°C, add DMAC solution of DOPO-based intermediate, keep warm and stir for 2-4h, add terminal hydroxyl polyborosiloxane into the flask, keep warm and stir for 1-2h, cool to 100°C, drop DMAC solution of imidazole blocking agent, keep warm and react until -NCO content in the system is less than 0.6%, stop the reaction, remove DMAC by vacuum distillation, cool to room temperature, crush the distillation product, add initiator, stir and mix evenly, and obtain environmentally friendly polyurethane resin powder coating curing agent; The imidazole-based blocking agent is an imidazole-based blocking agent containing an acrylate structure.

2. The environmentally friendly polyurethane resin powder coating curing agent according to claim 1, characterized in that: The usage ratio of IPDI trimer, DMAC, DOPO-based intermediate, terminal hydroxyl polyborosiloxane, imidazole-based blocking agent and initiator is 100g:150-250mL:5.68g:10.68g:85.617g:0.85-1.2g.

3. The environmentally friendly polyurethane resin powder coating curing agent according to claim 1, characterized in that: The imidazole-based blocking agent is prepared by the following steps: 1H-imidazole-4,5-dimethanol, hydroquinone, DCC, DMAP and acrylic acid were added to DMF, heated and stirred at 110-120°C for 48 hours. After the reaction was completed, DMF was removed by decompression to obtain an imidazole-based blocking agent.

4. The environmentally friendly polyurethane resin powder coating curing agent according to claim 3, characterized in that: The usage ratio of 1H-imidazole-4,5-dimethanol, hydroquinone, DCC, DMAP, acrylic acid and DMF is 40mmol:0.2-0.3g:10.32g:6.11g:80mmo l:150-200mL.

5. The environmentally friendly polyurethane resin powder coating curing agent according to claim 1, characterized in that: Hydroxyl-terminated polyborosiloxane is prepared by the following steps: Add phenylboric acid and double-terminated hydroxyl polydimethylsiloxane into a flask, stir at 120-150 rpm for 1 hour at room temperature under nitrogen protection, then heat to 190°C, continue stirring and react for 2-4 hours, and cool to room temperature to obtain hydroxyl-terminated polyborosiloxane. The amounts of phenylboric acid and hydroxyl-terminated polydimethylsiloxane are set according to a hydroxyl molar ratio of 1:1.1-1.

2.

6. The environmentally friendly polyurethane resin powder coating curing agent according to claim 1, characterized in that: The DOPO-based intermediates are prepared by the following steps: Add DOPO into a flask and heat to 130°C until DOPO is completely melted, cool to 100°C and add ethylene glycol diglycidyl ether, keep warm and stir for 10-20 minutes, then add DMAC, heat to 110°C and stir to react for 3-5 hours, then cool to 85°C, add methylbutylamine, stir in a nitrogen atmosphere at 70°C for 12 hours, and finally remove DMAC by vacuum distillation to obtain a DOPO-based intermediate.

7. The environmentally friendly polyurethane resin powder coating curing agent according to claim 6, characterized in that: The usage ratio of DOPO, ethylene glycol diglycidyl ether, DMAC and methylbutylamine is 0.1 mol: 0.1 mol: 500 mL: 0.1 mol.

8. The environmentally friendly polyurethane resin powder coating curing agent according to claim 1, characterized in that: The initiator is dicumyl peroxide.

9. An environmentally friendly curing agent for polyurethane resin powder coating, characterized in that: The curing agent is used for curing hydroxyl polymer to prepare polyurethane type powder coating.

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