Low-temperature curing insulating powder coating as well as preparation method and application thereof

Abstract

The invention discloses a low-temperature curing insulating powder coating as well as a preparation method and application thereof. The low-temperature curing insulating powder coating is prepared from the following raw materials: epoxy resin, a curing agent, nano boron nitride, a flatting agent, a degassing agent, barium sulfate, wollastonite powder, an accelerant and pigment. By optimizing the components and the component proportion, the low-temperature curing powder coating can be cured at the low temperature of 120-140 DEG C, and compared with a traditional high-temperature curing powder coating at the temperature of 180-200 DEG C, the curing temperature is reduced by 40-60 DEG C, and the energy-saving effect is remarkable. According to the invention, nano boron nitride is added as a functional filler, so that the insulating property of a coating is obviously improved, and the coating formed by the prepared powder coating has high hardness and toughness, is not easy to cut through in a winding process, can be used for a long time in an environment of 180 DEG C, has a performance retention rate of 90% or more, meets the requirements of H-grade insulating materials, and has excellent salt spray resistance; and the method has relatively good applicability on the whole.

Description

Technical Field

[0001] This invention relates to the field of powder coating preparation, and more specifically, to a low-temperature curing insulating powder coating, its preparation method, and its application. Background Technology

[0002] Powder coatings contain 100% solid components, unlike traditional liquid coatings. They are completely free of chemical solvents, causing no environmental pollution or harm to human health, making them a relatively environmentally friendly product. With the development of the electronics industry and new energy vehicles, the demand for new functional insulating powder coatings is increasing. Unlike traditional powder coatings, powder coatings used for electrical insulation require excellent film-forming properties, high breakdown voltage, thin coating thickness, and low-temperature curing. Especially for motor stators and rotors, as core components of motors, their insulation, protection, and durability are crucial to motor performance. Due to their superior performance, powder coatings are gradually replacing traditional coating technologies (such as solvent-based coatings) and becoming the mainstream choice for coating motor components. For example, Chinese patent application CN202211387464.3 discloses a low-temperature curing thin-film insulating powder coating and its preparation method. It uses a composite of rod-shaped or needle-shaped inorganic fillers and organic fiber fillers as a resin reinforcement system. Utilizing the anisotropy of the fiber fillers, an ordered orientation is formed during melt extrusion. A low-temperature curing system and auxiliary materials such as leveling agents, defoamers, and pigments are selected to obtain a novel thin-film high-strength electrically insulating powder coating with stable film-forming properties. Another example is Chinese patent application CN202210364312.5, which discloses a low-temperature rapid-curing insulating powder coating, its preparation method, and its applications. It can be used for insulating and fixing coils of various small and medium-sized DC motors and power tools. The application method is simple, avoiding the need for liquid drip-curing after winding the motor core or power tool coils, greatly improving the production efficiency of small and medium-sized DC motors.

[0003] In practical production applications, low-temperature curing insulating powder coatings for industrial motor stators and rotors still have the following shortcomings: 1. Curing temperature remains high: The curing temperature of some low-temperature curing powder coatings is still above 160℃, failing to fully meet energy-saving requirements. 2. Insufficient insulation performance: Under low-temperature curing conditions, the insulation performance of the coating, especially the high-voltage insulation performance, is difficult to meet the requirements of Class H insulation materials. 3. Mechanical properties need improvement: The hardness, toughness, and adhesion of low-temperature curing coatings are often inferior to those of high-temperature curing coatings, affecting the service life of the motor. 4. Easily cut during winding: Existing low-temperature curing powder coatings are easily cut during winding, leading to insulation failure. Therefore, the aforementioned technical problems still exist in the existing technology and urgently need to be solved. Summary of the Invention

[0004] In order to solve one of the above problems, this invention provides a low-temperature curing insulating powder coating, its preparation method, and its application. The specific technical solution is as follows:

[0005] A low-temperature curing insulating powder coating, wherein the low-temperature curing insulating powder coating comprises the following raw materials in parts by weight:

[0006] 45-70 parts epoxy resin, 5-20 parts curing agent, 3-10 parts nano boron nitride, 1-2 parts leveling agent, 1-2 parts degassing agent, 15-40 parts barium sulfate, 10-25 parts wollastonite powder, 0.1-0.8 parts accelerator, and 0.8-25 parts pigment.

[0007] Furthermore, the epoxy resin is a low softening point epoxy resin with an epoxy equivalent of 200-550 g / mol and a softening point of 40℃~75℃.

[0008] Furthermore, the curing agent is a liquid curing agent;

[0009] The curing agent is one or a combination of two of polyamide and polyetheramine;

[0010] The active hydrogen equivalent of the curing agent is 60–140 g / eq.

[0011] Furthermore, the boron nitride nanoparticles have a particle size of 50 nm to 200 nm and a specific surface area of ​​10 m². 2 / g~30m 2 / g.

[0012] Furthermore, the leveling agent is one or a combination of two of the following: acrylate copolymer leveling agents and silicone leveling agents.

[0013] Furthermore, the degassing agent is one or a combination of two of modified silicone oil and benzoin.

[0014] Furthermore, the promoter is one or a combination of two of benzyltriethylammonium chloride and 2-methylimidazole.

[0015] In addition, the present invention also provides a method for preparing a low-temperature curing insulating powder coating, the preparation method comprising the following steps:

[0016] Epoxy resin, nano boron nitride, leveling agent, degassing agent, barium sulfate, wollastonite powder, accelerator and pigment are mixed evenly to obtain a solid mixture;

[0017] The solid mixture is melt-extruded through a twin-screw extruder to obtain the extrudate.

[0018] The base material and curing agent are added separately to a two-component polyurea spray gun, heated to 70℃~95℃, mixed and then sprayed onto a material collection plate in a strong cooling zone. The material is collected, cooled to room temperature, crushed, ground into powder using a pulverizer, and then sieved through a 120~140 mesh screen to obtain a low-temperature curing insulating powder coating.

[0019] Furthermore, the screw speed of the twin-screw extruder is 800 r / min to 1000 r / min, and the melt extrusion temperature is 60℃ to 90℃.

[0020] In addition, the present invention also provides an application of a low-temperature curing insulating powder coating, wherein the application is the application of the low-temperature curing insulating powder coating in the insulation protection of the stator and rotor of an industrial motor; wherein the application is to apply the coating to the surface of the motor stator and / or rotor by electrostatic dip coating and cure it at a temperature of 120℃~140℃ for 20min~30min.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention, through optimized composition and ingredient ratios, enables curing at a low temperature of 120-140℃. Compared to traditional high-temperature curing powder coatings of 180-200℃, the curing temperature is reduced by 40-60℃, resulting in significant energy savings. According to test data, approximately 10% energy savings are achieved for every 10℃ reduction in curing temperature; therefore, this invention can reduce energy consumption by 30-40%.

[0023] 2. This invention significantly improves the insulation performance of the coating by adding nano-boron nitride as a functional filler. Test results show that the powder coating of this invention, under low-temperature curing conditions, has an insulation withstand voltage of over 6000V and a leakage current of less than 1mA, fully meeting the insulation requirements of industrial motor stators and rotors.

[0024] 3. The powder coating prepared by this invention forms a coating with high hardness and toughness, making it difficult to be cut during winding. Test results show that the coating has a pencil hardness of H or higher, an impact resistance of 50 kg·cm or higher, and an adhesion rating of 5B, effectively protecting the motor stator and rotor from mechanical damage.

[0025] 4. The powder coating of this invention, after curing, forms a coating that can be used for a long time in an environment of 180°C with a performance retention rate of over 90%, meeting the requirements of Class H insulation materials. Even after a 500-hour heat resistance test at 180°C, the coating only shows slight yellowing, and all performance indicators remain good.

[0026] 5. The powder coating of this invention is suitable for automated production processes such as electrostatic spraying. The coating thickness is easy to control, it has good leveling properties, and is free from defects such as pinholes and craters. Simultaneously, its low-temperature curing characteristic shortens the production cycle and improves production efficiency, making it particularly suitable for large-scale industrial production. Overall, it contains no volatile organic solvents, meeting environmental protection requirements. The low-temperature curing process reduces energy consumption and carbon emissions, which is beneficial to environmental protection. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0030] Example 1:

[0031] The raw materials for preparing the low-temperature curing insulating powder coating of Example 1 are shown in Table 1;

[0032] The preparation method of the low-temperature curing insulating powder coating in Example 1 is as follows:

[0033] Epoxy resin, nano boron nitride, leveling agent, degassing agent, barium sulfate, wollastonite powder, accelerator and pigment are added to a high-speed mixer according to the weight parts, and stirred at 1200 r / min for 15 min to obtain a solid mixture.

[0034] The solid mixture is melt-extruded through a twin-screw extruder with a screw speed of 900 r / min and an extrusion temperature of 75°C to obtain the extruded material.

[0035] The extruded material and curing agent are added separately to a two-component polyurea spray gun, heated to 85°C, mixed, and then sprayed onto a material collection plate in a strongly cold zone at -5°C. The material is collected, cooled to room temperature, crushed, ground into powder using a pulverizer, and then sieved through a 130-mesh screen to obtain a low-temperature curing insulating powder coating.

[0036] Application Example 1:

[0037] The powder coating prepared in Example 1 was applied to the surface of the surface-treated motor stator and rotor by an electrostatic dip coating process, and then cured at 130°C for 25 minutes to form an insulating coating.

[0038] Table 1: Raw materials for the preparation of low-temperature curing insulating powder coating in Example 1

[0039]

[0040]

[0041] Example 2:

[0042] The raw materials for preparing the low-temperature curing insulating powder coating of Example 2 are shown in Table 2;

[0043] The preparation method of the low-temperature curing insulating powder coating in Example 2 is the same as that in Example 1;

[0044] The difference between Application Example 2 and Application 1 is that the curing temperature is 125℃ and the curing time is 30min.

[0045] Table 2: Raw materials for the preparation of low-temperature curing insulating powder coating in Example 2

[0046]

[0047]

[0048] Example 3:

[0049] The raw materials for preparing the low-temperature curing insulating powder coating of Example 3 are shown in Table 3;

[0050] The preparation method of the low-temperature curing insulating powder coating in Example 3 is the same as that in Example 1;

[0051] The difference between Application Example 3 and Application 1 is that the curing temperature is 135℃ and the curing time is 20min.

[0052] Table 3: Raw materials for the preparation of low-temperature curing insulating powder coating in Example 3

[0053] Raw material name weight Low softening point epoxy resin 65 Polyamide and polyetheramine mixed curing agent (1:1) 8 Nano boron nitride 4 Acrylic leveling agents 1.2 Modified silicone oil degassing agent 1.8 Barium sulfate 20 Wollastonite powder 22 Benzyltriethylammonium chloride 0.4 carbon black 1

[0054] Comparative Example 1:

[0055] The raw materials for preparing the powder coating in Comparative Example 1 are shown in Table 4.

[0056] The preparation method of the powder coating in Comparative Example 1 is as follows:

[0057] All raw materials are mixed and then melt-extruded through a twin-screw extruder at 140°C. The mixture is then pulverized and sieved through a 130-mesh screen to obtain powder coating.

[0058] Comparative Application 1: The powder coating prepared in Comparative Example 1 was applied to the surface of the motor stator and rotor by electrostatic dip coating process. The coating thickness was controlled at 150 μm, and then cured at 180 °C for 15 min to form a coating.

[0059] Table 4: Raw materials for preparing powder coating of Comparative Example 1

[0060] Raw material name weight Ordinary epoxy resin 70 Dicyandiamide curing agent 8 Micron-sized boron nitride 5 Leveling agent 1.5 Degassing agent 1.5 Barium sulfate 20 Wollastonite powder 20 Accelerator 0.5 pigment 3

[0061] Comparative Example 2:

[0062] Compared with Example 3, Comparative Example 2 did not contain added boron nitride nanoparticles, but was otherwise the same as Example 3.

[0063] The performance of the low-temperature curing insulating powder coating samples prepared in Examples 1-3 and the powder coatings prepared in Comparative Examples 1-2 were tested, and the results are shown in Table 5 below.

[0064] Table 5: Performance Test Results

[0065]

[0066] As shown in Table 5, the low-temperature curing insulating powder coating of this invention achieves performance levels comparable to traditional 180℃ high-temperature curing powder coatings after curing at 125-135℃ for 20-30 minutes. In particular, it meets the requirements of Class H insulation materials in terms of insulation withstand voltage, leakage current, hardness, adhesion, and winding performance. The addition of nano-boron nitride as a functional filler significantly improves the coating's insulation performance. The resulting coating exhibits high hardness and toughness, is not easily cut during winding, can be used long-term in an environment of 180℃, retains over 90% of its performance, meets the requirements of Class H insulation materials, and demonstrates excellent salt spray resistance.

[0067] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-temperature curing insulating powder coating, characterized in that, The low-temperature curing insulating powder coating comprises the following raw materials in parts by weight: 45-70 parts epoxy resin, 5-20 parts curing agent, 3-10 parts nano boron nitride, 1-2 parts leveling agent, 1-2 parts degassing agent, 15-40 parts barium sulfate, 10-25 parts wollastonite powder, 0.1-0.8 parts accelerator, and 0.8-25 parts pigment.

2. The low-temperature curing insulating powder coating according to claim 1, characterized in that, The epoxy resin is a low softening point epoxy resin with an epoxy equivalent of 200-550 g / mol and a softening point of 40℃~75℃.

3. The low-temperature curing insulating powder coating according to claim 1, characterized in that, The curing agent is a liquid curing agent; The curing agent is one or a combination of two of polyamide and polyetheramine; The active hydrogen equivalent of the curing agent is 60–140 g / eq.

4. The low-temperature curing insulating powder coating according to claim 1, characterized in that, The boron nitride nanoparticles have a particle size of 50 nm to 200 nm and a specific surface area of ​​10 m². 2 / g~30m 2 / g.

5. The low-temperature curing insulating powder coating according to claim 1, characterized in that, The leveling agent is one or a combination of two of the following: acrylate copolymer leveling agents and silicone leveling agents.

6. The low-temperature curing insulating powder coating according to claim 1, characterized in that, The degassing agent is one or a combination of two of the following: modified silicone oil and benzoin.

7. The low-temperature curing insulating powder coating according to claim 1, characterized in that, The accelerator is one or a combination of two of benzyltriethylammonium chloride and 2-methylimidazole.

8. A method for preparing a low-temperature curing insulating powder coating, characterized in that, The preparation method is used to prepare the low-temperature curing insulating powder coating as described in any one of claims 1 to 7, and the preparation method includes the following steps: Epoxy resin, nano boron nitride, leveling agent, degassing agent, barium sulfate, wollastonite powder, accelerator and pigment are mixed evenly to obtain a solid mixture; The solid mixture is melt-extruded through a twin-screw extruder to obtain the extrudate. The base material and curing agent are added separately to a two-component polyurea spray gun, heated to 70℃~95℃, mixed and then sprayed onto a material collection plate in a strong cooling zone. The material is collected, cooled to room temperature, crushed, ground into powder using a pulverizer, and then sieved through a 120~140 mesh screen to obtain a low-temperature curing insulating powder coating.

9. The preparation method according to claim 8, characterized in that, The screw speed of the twin-screw extruder is 800 r / min to 1000 r / min, and the melt extrusion temperature is 60℃ to 90℃.

10. An application of a low-temperature curing insulating powder coating, characterized in that, The application is the application of the low-temperature curing insulating powder coating according to any one of claims 1 to 7 in the insulation protection of the stator and rotor of an industrial motor; the application is to apply it to the surface of the motor stator and / or rotor by electrostatic dip coating and cure it at a temperature of 120℃ to 140℃ for 20 min to 30 min.

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