A high and low temperature resistant insulating coating and preparation method thereof

Abstract

The present invention relates to the technical field of insulating coatings, and in particular to a high and low temperature resistant insulating coating and a preparation method thereof. The coating comprises 20 to 50 parts of polyimide and / or polyamide-imide, 20 to 40 parts of inorganic filler, 1 to 3 parts of bentonite, 30 to 50 parts of water, 0.1 to 1 part of aqueous dispersant, 0.1 to 1 part of defoamer, 1 to 5 parts of cosolvent and 1 to 3 parts of curing accelerator. The coating provided by the present invention can be cured at 180 to 200°C, effectively reducing energy consumption, and the hardness can reach 5H; it has excellent high and low temperature resistance, a long-term use temperature range of ‑40 to 300°C, high insulation performance, and the surface resistivity of the formed coating is 2.448×10 15 Ω, dielectric loss is only 0.004-0.007, belonging to F to H grade insulation, and the power frequency withstand voltage reaches 1100KV for 5min, with excellent high-voltage resistance, stable temperature resistance and insulation performance, no attenuation, and long service life.

Description

Technical Field

[0001] The invention relates to the technical field of insulating coatings, and in particular to a high and low temperature resistant insulating coating and a preparation method thereof. Background Art

[0002] Insulating coating is a coating that is applied to the surface of a workpiece and forms an organic or inorganic film through physical or chemical cross-linking reactions, which can serve as an insulation layer for the workpiece.

[0003] Especially for outdoor high-voltage insulation components of power grid systems, in extremely cold weather, it is necessary to ensure insulation and also to be resistant to low temperatures for a long time. Existing insulating coatings can meet the requirements for high temperature resistance when the insulation performance meets the requirements, but the low temperature resistance is not ideal. In extremely cold weather, there is a risk of cracking of the coating if it is used for a long time, and the insulation performance will be affected. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a high and low temperature resistant insulating coating and a preparation method thereof. The insulating coating provided by the present invention not only has high temperature resistance that can meet the requirements, but also has good low temperature resistance. The coating coating is not easy to crack under long-term use in a low temperature environment, and the insulating performance is stable.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a high and low temperature resistant insulating coating, which comprises, by weight, 20 to 50 parts of polyimide and polyamide-imide, 20 to 40 parts of inorganic filler, 1 to 3 parts of bentonite, 30 to 50 parts of water, 0.1 to 1 part of aqueous dispersant, 0.1 to 1 part of defoamer, 1 to 5 parts of cosolvent and 1 to 3 parts of curing accelerator;

[0007] The mass ratio of the polyimide to the polyamide-imide is (1-2):1.

[0008] Preferably, the inorganic filler includes one or more of mica powder, titanium dioxide, glass fiber and bentonite.

[0009] Preferably, the particle size of the inorganic filler is 10 to 40 μm.

[0010] Preferably, the aqueous dispersant comprises one or more of polyether-modified polysiloxane, organosilicon gemini surfactant and acetylene glycol surfactant.

[0011] Preferably, the defoaming agent comprises one or more of polysiloxane, modified acrylate and modified mineral oil.

[0012] Preferably, the co-solvent includes one or more of N-butylpyrrolidone, N,N-dimethylethanolamine and N-formylmorpholine.

[0013] Preferably, the curing accelerator is a silane coupling agent containing an epoxy group.

[0014] The present invention provides a method for preparing the high and low temperature resistant insulating coating described in the above scheme, comprising the following steps: mixing the components to obtain the high and low temperature resistant insulating coating.

[0015] Preferably, the mixing comprises: first mixing polyimide, polyamide-imide, inorganic filler, bentonite, water, aqueous dispersant and defoamer under first stirring conditions to obtain a first mixture;

[0016] After ball-milling the first mixed material, a curing accelerator is added to the obtained ball-milled mixed material, and a second mixing is performed under a second stirring condition.

[0017] Preferably, the rotation speeds of the first stirring and the second stirring are independently 500-1000 rpm.

[0018] The present invention provides a high and low temperature resistant insulating coating, which comprises, by weight, 20 to 50 parts of polyimide and polyamideimide, 20 to 40 parts of inorganic filler, 1 to 3 parts of bentonite, 30 to 50 parts of water, 0.1 to 1 part of aqueous dispersant, 0.1 to 1 part of defoamer, 1 to 5 parts of cosolvent and 1 to 3 parts of curing accelerator; the mass ratio of the polyimide to the polyamideimide is (1 to 2): 1. The present invention uses polyimide and polyamideimide as film-forming resins and controls their dosage to overcome the risk of polyimide being easily cracked under low temperature conditions, cooperates with other components, and introduces a curing accelerator. The obtained insulating coating not only has high temperature resistance that can meet the requirements, but also has good low temperature resistance, and the coating is not easy to crack under low temperature long-term use environment, and the insulating performance is stable. In addition, by introducing a curing accelerator, the present invention can reduce the curing temperature of the coating and effectively save energy.

[0019] The results of the examples show that the high and low temperature resistant insulating coating provided by the present invention has excellent high and low temperature resistance, a long-term use temperature range of -40 to 300 ° C, high insulation performance, and a surface resistivity of the formed coating of 2.448×10 15 Ω, the dielectric loss is only 0.004-0.007, belonging to F to H grade insulation, and the power frequency withstand voltage reaches 1100KV for 5min, with excellent high-voltage resistance. In the long-term use process, it has the advantages of stable temperature resistance and insulation performance, no attenuation, and long service life. At the same time, the coating of the present invention belongs to water-based environmentally friendly coating, and there is no VOC emission during the preparation and construction process, which is a real green environmentally friendly coating.

[0020] The coating provided by the invention can be cured by heating at 180-200° C. for 20-30 minutes, the curing temperature is low, and the coating hardness reaches 5H. DETAILED DESCRIPTION

[0021] The present invention provides a high and low temperature resistant insulating coating, which comprises, by weight, 20 to 50 parts of polyimide and polyamide-imide, 20 to 40 parts of inorganic filler, 1 to 3 parts of bentonite, 30 to 50 parts of water, 0.1 to 1 part of aqueous dispersant, 0.1 to 1 part of defoamer, 1 to 5 parts of cosolvent and 1 to 3 parts of curing accelerator;

[0022] The mass ratio of the polyimide to the polyamide-imide is (1-2):1.

[0023] The high and low temperature resistant insulating coating provided by the present invention includes 30 to 50 parts of water by weight. In a specific embodiment, the content of the water may be 30 parts, 35 parts, 40 parts, 45 parts or 50 parts. In the present invention, the water is preferably deionized water.

[0024] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 20 to 50 parts of polyimide and polyamide-imide. In a specific embodiment, it can be 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts or 50 parts. In the present invention, the mass ratio of the polyimide and the polyamide-imide is (1 to 2): 1. In a specific embodiment, it can be 1: 1, 5: 3 or 2: 1. In the present invention, the polyimide has excellent properties such as high temperature resistance, low temperature resistance, low water absorption, high insulation, high strength, high stiffness, low creep and excellent wear resistance. It can withstand high temperatures up to 400°C and low temperatures up to -200°C; but it is relatively brittle and prone to breakage. The coating has the risk of cracking under long-term low temperature conditions. Polyamide-imide also has high cold resistance, heat resistance and insulation performance. The operating temperature ranges from low temperature -195°C to 230°C. It is corrosion-resistant, radiation-resistant, and has good flexibility. The present invention overcomes the risk of low-temperature cracking of single polyimide by using the two together, and gives the insulating coating good high and low temperature resistance and insulation performance.

[0025] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 20 to 40 parts of inorganic filler. In a specific embodiment, the content of the inorganic filler can be 20 parts, 25 parts, 30 parts, 35 parts or 40 parts. In the present invention, the inorganic filler preferably includes one or more of mica powder, titanium dioxide and glass fiber. When there are multiple types, it can be specifically mica powder and glass fiber, mica powder and titanium dioxide, titanium dioxide and glass fiber; when there are multiple types, the present invention has no special requirements for the ratio of each inorganic filler, and any ratio is acceptable. In the present invention, the particle size of the inorganic filler is preferably 10 to 40 μm. In a specific embodiment, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm. The present invention uses one or more of mica powder, titanium dioxide and glass fiber as inorganic fillers to ensure that the coating has good insulation and breakdown resistance. Among them, mica is the general term for layered aluminum silicate, which has good insulation properties and high temperature resistance. Glass fiber has a needle-like structure and has the advantages of good insulation, strong heat resistance, good corrosion resistance, and high mechanical strength.

[0026] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 1 to 3 parts of a curing accelerator. In a specific embodiment, the content of the curing accelerator can be 1 part, 1.5 parts, 2 parts, 2.5 parts or 3 parts. In the present invention, the curing accelerator is preferably a silane coupling agent containing an epoxy group, and more preferably one or more of silane coupling agents KH560, KH561 and MP200. The glass transition temperature of polyimide and polyamideimide resins is 250 to 300°C, and the baking temperature during curing molding needs to be greater than 250°C. In the present invention, by using a silane coupling agent containing an epoxy group, the introduced siloxane group can reduce the glass transition temperature of polyimide and polyamideimide, and can react and crosslink with the imine group in polyimide and polyamideimide during the curing process, thereby accelerating the curing and crosslinking process, and reducing the curing temperature of the paint film from 260°C / 30min to 180 to 200°C / 30min.

[0027] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 1 to 3 parts of bentonite. In a specific embodiment, the content of the bentonite can be 1 part, 1.5 parts, 2 parts, 2.5 parts or 3 parts. In the present invention, the particle size of the bentonite is preferably 10 to 40 μm. In a specific embodiment, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm. In the present invention, the bentonite is a natural mineral with montmorillonite as the main component, which has the effects of anti-sedimentation, thickening and anti-sagging, etc., and can make the prepared coating more uniform and have a longer storage period.

[0028] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 0.1 to 1 part of an aqueous dispersant. In a specific embodiment, the content of the aqueous dispersant can be 0.1 part, 0.3 part, 0.5 part, 0.7 part, 0.8 part or 1 part. In the present invention, the aqueous dispersant preferably includes one or more of polyether-modified polysiloxane, organosilicon twin structure surfactant and acetylene glycol surfactant. The present invention utilizes an aqueous dispersant to evenly disperse the components.

[0029] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 0.1 to 1 part of defoamer. In a specific embodiment, the content of the defoamer can be 0.1 part, 0.3 part, 0.5 part, 0.7 part, 0.8 part or 1 part. The present invention has no special requirements for the specific type of the defoamer, and a defoamer well known in the art can be used, such as one or more of polysiloxane, modified acrylate and modified mineral oil.

[0030] Based on the mass fraction of the water, the high and low temperature resistant insulating coating provided by the present invention includes 1 to 5 parts of a co-solvent. In the present invention, the co-solvent preferably includes one or more of N-butylpyrrolidone, N,N-dimethylethanolamine and N-formylmorpholine. In a specific embodiment, the content of the co-solvent can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts. In the present invention, the role of the co-solvent is to adjust the viscosity of the coating and ensure the leveling and construction properties of the paint film.

[0031] The present invention uses polyimide and polyamide-imide as film-forming agents and controls their dosage, and cooperates with other components to obtain a high and low temperature resistant insulating coating that not only has high temperature resistance that meets the requirements, but also has good low temperature resistance. The coating is not easy to crack under long-term low temperature use conditions, and the insulating performance is stable.

[0032] The present invention provides a method for preparing the high and low temperature resistant insulating coating described in the above scheme, comprising the following steps: mixing the components to obtain the high and low temperature resistant insulating coating.

[0033] In the present invention, the mixing preferably includes:

[0034] The polyimide, polyamide-imide, inorganic filler, bentonite, water, aqueous dispersant and defoamer are first mixed under first stirring conditions to obtain a first mixture;

[0035] After ball-milling the first mixed material, a curing accelerator is added to the obtained ball-milled mixed material, and a second mixing is performed under a second stirring condition.

[0036] In the present invention, the rotation speeds of the first stirring and the second stirring are preferably independently 500-1000 rpm; in a specific embodiment, the rotation speeds of the first stirring and the second stirring may be 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm. In the present invention, the time of the first stirring is preferably 1-3 hours, and in a specific embodiment, it may be 1 hour, 2 hours or 3 hours. In the present invention, the first mixing is preferably carried out in a stirring tank. The present invention preferably adds polyimide and polyamide-imide, inorganic filler, bentonite, water, aqueous dispersant and defoamer into a stirring tank in sequence, and sets the stirring speed and time for the first mixing.

[0037] In the present invention, the rotation speed of the ball mill is preferably 100-200 r / min, and the time is preferably 2-3 h; in a specific embodiment, the rotation speed of the ball mill can be 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm or 200 rpm, and the ball milling time can be 2 h, 2.5 h or 3 h.

[0038] In the present invention, the second stirring time is preferably 0.5 to 1 h; in a specific embodiment, the second stirring time can be 0.5 h, 0.75 h or 1 h.

[0039] The high and low temperature resistant insulating coating and the preparation method thereof provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] The raw material information and particle size in the following examples are shown in Table 1.

[0041] Table 1 Raw material information

[0042]

[0043] Note: The ratios in Table 1 are mass ratios.

[0044] Examples 1 to 3

[0045] According to the formula in Table 1, polyimide resin, polyamide-imide resin, mica powder, glass fiber, bentonite, deionized water, aqueous dispersant and defoamer were added to a mixing tank in sequence, the speed was set to 600 rpm, the time was 1 hour, and a first mixture was obtained.

[0046] The first mixed material was added into a ball mill, the speed of the ball mill was set to 100 r / min, and the ball milling time was set to 2 h to obtain a ball milled mixed material.

[0047] The curing accelerator is added to the ball-milled mixture under stirring conditions, the rotation speed is set to 600 rpm, and the time is 0.5 h to obtain the high and low temperature resistant insulating coating.

[0048] Comparative Example 1

[0049] The only difference from Example 1 is that polyamide-imide is not used, and the rest is the same as Example 1.

[0050] Comparative Example 2

[0051] The only difference from Example 1 is that no curing accelerator is used, and the rest is the same as Example 1.

[0052] Table 2 Formulations of Examples 1 to 3 and Comparative Examples 1 to 2

[0053] Main ingredients of the formula Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Polyimide 25 20 20 40 25 Polyamide-imide 15 20 10 - 15 Mica powder 10 5 15 10 10 Fiberglass 30 25 15 30 30 Bentonite 1 2 1 1 1 Deionized water 15 25 35 15 15 Defoaming agent 1 0.5 0.5 1 1 Aqueous Dispersants 1 1 0.5 1 1 Solvent 1.5 1.5 3 1.5 2.5 Curing accelerator 1 1 0.5 1 -

[0054] Performance Test:

[0055] The insulating coatings of Examples 1 to 3, Comparative Examples 1 to 2 and Commercial Products 1 to 2 were sprayed on the copper plates to be tested, pre-baked at 80°C for 10 min, baked at 180°C, 200°C or 260°C for 30 min, cooled to room temperature, and obtained a dry film with a thickness of 50 μm. The dry film was tested for performance. Each test of each sample was repeated three times, and the average value was taken.

[0056] The test results are shown in Tables 3 to 9.

[0057] Table 3 Pencil hardness properties of examples, comparative examples and commercially available products

[0058]

[0059]

[0060] Table 4 Adhesion properties of examples, comparative examples and commercially available products

[0061]

[0062] Table 5 High and low temperature cycle resistance performance of the embodiments, comparative examples and commercially available products

[0063]

[0064] Table 6 Surface resistivity (Ω) of the embodiments, comparative examples and commercially available products

[0065]

[0066] Table 7 Surface resistivity (Ω) of the embodiment, comparative example and commercially available product before and after high and low temperature cycle test

[0067]

[0068] Table 8 Power frequency withstand voltage test results of the embodiments, comparative examples and commercially available products

[0069]

[0070] Table 9 Dielectric loss test results of examples, comparative examples and commercially available products

[0071]

[0072] It can be seen from Tables 3 to 9 that the coating provided by the present invention has excellent high and low temperature resistance and insulation and high voltage resistance, and the insulation performance is stable; Table 3 shows that the curing accelerator can effectively reduce the curing temperature, Table 5 shows that the coating provided by the present invention can be used for a long time in a low temperature environment without cracking, and Table 6 shows that the coating provided by the present invention has a stable surface resistivity after the high and low temperature cycle test.

[0073] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high and low temperature resistant insulating coating, characterized in that: Calculated by mass, it includes 20-50 parts of polyimide and polyamide-imide, 20-40 parts of inorganic filler, 1-3 parts of bentonite, 30-50 parts of water, 0.1-1 part of aqueous dispersant, 0.1-1 part of defoamer, 1-5 parts of cosolvent and 1-3 parts of curing accelerator; The mass ratio of the polyimide to the polyamide-imide is (1-2):

1.

2. The high and low temperature resistant insulating coating according to claim 1, characterized in that: The inorganic filler includes one or more of mica powder, titanium dioxide, glass fiber and bentonite.

3. The high and low temperature resistant insulating coating according to claim 1, characterized in that: The particle size of the inorganic filler is 10 to 40 μm.

4. The high and low temperature resistant insulating coating according to claim 1, characterized in that: The aqueous dispersant includes one or more of polyether-modified polysiloxane, silicone gemini surfactant and acetylene glycol surfactant.

5. The high and low temperature resistant insulating coating according to claim 1, characterized in that: The defoaming agent includes one or more of polysiloxane, modified acrylate and modified mineral oil.

6. The high and low temperature resistant insulating coating according to claim 1, characterized in that: The co-solvent includes one or more of N-butylpyrrolidone, N,N-dimethylethanolamine and N-formylmorpholine.

7. The high and low temperature resistant insulating coating according to claim 1, characterized in that: The curing accelerator is a silane coupling agent containing an epoxy group.

8. The method for preparing the high and low temperature resistant insulating coating according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: mixing the components to obtain the high and low temperature resistant insulating coating.

9. The preparation method according to claim 8, characterized in that: The mixing comprises: first mixing polyimide, polyamide-imide, inorganic filler, bentonite, water, aqueous dispersant and defoamer under first stirring conditions to obtain a first mixture; After ball-milling the first mixed material, a curing accelerator is added to the obtained ball-milled mixed material, and a second mixing is performed under a second stirring condition.

10. The preparation method according to claim 8, characterized in that: The rotation speeds of the first stirring and the second stirring are independently 500 to 1000 rpm.

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