Heat-resistant insulating paint and preparation method thereof

Abstract

The invention discloses a heat-resistant insulating coating and a preparation method of the heat-resistant insulating coating, and belongs to the technical field of coatings. The coating is prepared from the following raw materials in parts by weight: 30 to 40 parts of methyl phenyl polysiloxane resin, 10 to 20 parts of polysiloxane modified bismaleimide resin, 40 to 60 parts of filler, 5 to 10 parts of a curing agent, 0.01 to 0.07 part of a defoaming agent and 0.01 to 0.3 part of a flatting agent. The heat resistance of the insulating paint is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly to a heat-resistant insulating coating and a preparation method thereof. Background Art

[0002] The paint films on the surfaces of motors, transformers, wires, etc. generally adopt the pressure impregnation process. Specifically, the workpieces are pre-dried to remove moisture and then cooled, placed in a vacuum environment, the air and volatiles inside the workpieces are discharged, and relying on the gravity of the paint liquid in the vacuum and the action of applying a certain pressure, the paint liquid rapidly penetrates and fills the inner layer of the insulating structure. This process can obtain a continuous, dense and pinhole-free paint film.

[0003] At present, most impregnating varnishes use epoxy resin as the main resin and acid anhydride as the curing agent. When this impregnating varnish is applied to workpieces such as motors, transformers, and heat conductors that generate heat after long-term use, when the temperature on the workpieces is too high, the flexibility of the epoxy resin becomes poor, resulting in a decline in the insulation performance of the impregnating varnish. Summary of the Invention

[0004] In order to solve the problems in the prior art, the present invention provides a heat-resistant insulating coating and a preparation method thereof. By using methylphenyl polysiloxane resin in combination with polysiloxane-modified bismaleimide resin and filler, the heat resistance of the insulating coating is effectively improved.

[0005] A heat-resistant insulating coating, the coating comprising the following raw materials in parts by weight: 30-40 parts of methylphenyl polysiloxane resin, 10-20 parts of polysiloxane-modified bismaleimide resin, 40-60 parts of filler, 5-10 parts of curing agent, 0.01-0.07 parts of defoaming agent, and 0.01-0.3 parts of leveling agent.

[0006] In a preferred embodiment, the coating comprises the following raw materials in parts by weight: 33-38 parts of methylphenyl polysiloxane resin, 12-16 parts of polysiloxane-modified bismaleimide resin, 45-50 parts of filler, 5-10 parts of curing agent, 0.01-0.07 parts of defoaming agent, and 0.01-0.3 parts of leveling agent.

[0007] In a preferred embodiment, the modification method of the polysiloxane-modified bismaleimide resin comprises the following steps: adding bismaleimide resin and polysiloxane in a weight ratio of (2-4):1 to an excess of acetone, adding a catalytic amount of catalyst, stirring at 50-55°C for 20-24 h, and cooling and then evacuating to remove all acetone to obtain the polysiloxane-modified bismaleimide resin.

[0008] In a preferred embodiment, the polysiloxane used is hydrogen-terminated phenyl polysiloxane.

[0009] In a preferred embodiment, the filler is one or both of nano-aluminum oxide and mica powder.

[0010] In a preferred embodiment, the weight ratio of the nano-aluminum oxide to the mica powder is 1:(1.5 - 2).

[0011] In a preferred embodiment, the mica powder is obtained by modification treatment with a hyperdispersant, and the weight ratio of the mica powder to the hyperdispersant is 5:1.

[0012] In a preferred embodiment, the preparation of the hyperdispersant is to add acrylic monomers and initiators to tetrahydrofuran, react at 60 ± 2 °C for 14 - 17 h, after the reaction is completed, add methanol to precipitate and centrifuge to collect, pour off the supernatant, dissolve with chloroform, and then precipitate with methanol. Repeat the above operations three times to obtain a pure product, and finally dry the product in a vacuum oven at 70 °C for 24 h to obtain the hyperdispersant.

[0013] In a preferred embodiment, the acrylic monomers are composed of n-butyl methacrylate and 2-hydroxyethyl methacrylate with a weight ratio of 1:(1 - 1.2).

[0014] The second aspect of the present invention is to provide a preparation method of the heat-resistant insulating coating as described above, including the following steps: After stirring and mixing the filler with methylphenyl polysiloxane resin and polysiloxane-modified bismaleimide resin, add an antifoaming agent and a leveling agent and stir and mix evenly, and then add a curing agent to obtain a heat-resistant insulating filler.

[0015] In summary, the present invention has the following beneficial effects: 1. When the methylphenyl polysiloxane resin and the polysiloxane-modified bismaleimide resin are used as the resin matrix in this application, due to the presence of polysiloxane between the two, the compatibility of the two is effectively improved, thereby improving the heat resistance of the coating. And the addition of the polysiloxane-modified bismaleimide resin can enhance the adhesion of the coating and the flexibility of the coating. The reason is that during the modification process of the polysiloxane-modified bismaleimide resin, strong chemical bonds such as covalent bonds or hydrogen bonds may be formed between the polysiloxane and the bismaleimide resin. The existence of this chemical bond significantly enhances the binding force between the coating and the substrate, thereby improving the adhesion of the coating.

[0016] 2. When the hydrogen-terminated phenyl polysiloxane is used to modify the bismaleimide resin, the flexible Si-O-Si chain segments in the hydrogen-terminated phenyl polysiloxane are dispersed in the cross-linked network of the bismaleimide resin, and by absorbing impact energy and hindering crack propagation, the toughness is significantly improved. Moreover, when the hydrogen-terminated phenyl polysiloxane is used to modify the bismaleimide resin, the cross-linking density of the bismaleimide resin can be reduced, and the viscosity of the prepolymer can be lowered, which is more conducive to impregnation.

[0017] 3. After using modified mica powder and nano-aluminum oxide, the heat resistance of the coating can be guaranteed. At the same time, after the mica powder is modified, its dispersion performance in the resin is improved. Moreover, the multi-layer structure of the mica powder can increase the sealing property of the coating film, thus reducing atomic migration and improving the insulation electrical property of the film at high temperatures. Detailed implementation manners

[0018] The present invention will be further described in detail below with reference to the embodiments. All reagents not indicating the manufacturer are conventional reagent products that can be obtained through commercial purchase.

[0019] Among them, the bismaleimide resin uses N,N'-(4,4'-methylenediphenyl) bismaleimide, with the CAS number 13676-54-5 and the molecular weight of 358.347; The polysiloxane uses hydrogen-terminated phenyl polysiloxane, with the CAS number 68952-30-7 and the molecular weight of 302.51568; Preparation Example 1.1 A modification method of polysiloxane-modified bismaleimide resin includes the following steps: Add 2 kg of N,N'-(4,4'-methylenediphenyl) bismaleimide resin and 1 kg of hydrogen-terminated phenyl polysiloxane into 6 kg of acetone, then add 0.2 kg of chloroplatinic acid and stir at 50 °C for 20 h. After cooling, evacuate until all the acetone is removed to obtain the polysiloxane-modified bismaleimide resin.

[0020] Preparation Example 1.2 A modification method of polysiloxane-modified bismaleimide resin includes the following steps: Add 3 kg of N,N'-(4,4'-methylenediphenyl) bismaleimide resin and 1 kg of hydrogen-terminated phenyl polysiloxane into 7 kg of acetone, then add 0.3 kg of chloroplatinic acid and stir at 55 °C for 24 h. After cooling, evacuate until all the acetone is removed to obtain the polysiloxane-modified bismaleimide resin.

[0021] Preparation Example 1.3 A modification method of polysiloxane-modified bismaleimide resin includes the following steps: Add 4 kg of N,N'-(4,4'-methylenediphenyl) bismaleimide resin and 1 kg of hydrogen-terminated phenyl polysiloxane into 7 kg of acetone, then add 0.35 kg of chloroplatinic acid and stir at 55 °C for 24 h. After cooling, evacuate until all the acetone is removed to obtain the polysiloxane-modified bismaleimide resin.

[0022] Preparation Example 2.1 A preparation method of modified mica powder includes the following steps: S1. Preparation of hyperdispersant: Dissolve 1 kg of n-butyl methacrylate, 1 kg of 2-hydroxyethyl methacrylate, and 0.032 kg of azobisisobutyronitrile in 10 L of tetrahydrofuran, react at 60 ± 2 °C for 14 h. After the reaction is completed, add methanol for precipitation, centrifuge to collect, pour off the supernatant, dissolve with chloroform, and then precipitate with methanol. Repeat the above operations three times to obtain a pure product. Finally, dry the product in a vacuum oven at 70 °C for 24 h to obtain the hyperdispersant; S2. Add 1 kg of the hyperdispersant obtained above to 5 kg of isopropanol, stir evenly, then add 5 kg of mica powder, stir and mix in a high-speed mixer for 30 min, and then dry to obtain modified mica powder.

[0023] Preparation Example 2.2 A method for preparing modified mica powder, comprising the following steps: S1. Preparation of hyperdispersant: Dissolve 1 kg of n-butyl methacrylate, 1.1 kg of 2-hydroxyethyl methacrylate, and 0.033 kg of azobisisobutyronitrile in 10 L of tetrahydrofuran, react at 60 ± 2 °C for 16 h. After the reaction is completed, add methanol for precipitation, centrifuge to collect, pour off the supernatant, dissolve with chloroform, and then precipitate with methanol. Repeat the above operations three times to obtain a pure product. Finally, dry the product in a vacuum oven at 70 °C for 24 h to obtain the hyperdispersant; S2. Add 1 kg of the hyperdispersant obtained above to 5 kg of isopropanol, stir evenly, then add 5 kg of mica powder, stir and mix in a high-speed mixer for 30 min, and then dry to obtain modified mica powder.

[0024] Preparation Example 2.3 A method for preparing modified mica powder, comprising the following steps: S1. Preparation of hyperdispersant: Dissolve 1 kg of n-butyl methacrylate, 1.2 kg of 2-hydroxyethyl methacrylate, and 0.038 kg of azobisisobutyronitrile in 10 L of tetrahydrofuran, react at 60 ± 2 °C for 16 h. After the reaction is completed, add methanol for precipitation, centrifuge to collect, pour off the supernatant, dissolve with chloroform, and then precipitate with methanol. Repeat the above operations three times to obtain a pure product. Finally, dry the product in a vacuum oven at 70 °C for 24 h to obtain the hyperdispersant; S2. Add 1 kg of the hyperdispersant obtained above to 5 kg of isopropanol, stir evenly, then add 5 kg of mica powder, stir and mix in a high-speed mixer for 30 min, and then dry to obtain modified mica powder.

[0025] Preparation Example 2.4 A method for preparing modified mica powder, which is different from Preparation Example 2.1 in that commercially available hyperdispersant BYK-168 is used to modify mica powder, and the others are the same as Preparation Example 2.1.

[0026] Example 1 A preparation method of a heat-resistant insulating coating, comprising the following steps: After stirring and mixing 4 kg of nano-aluminum oxide, 3 kg of methylphenyl polysiloxane resin (CAS number: 67763-03-5, viscosity at 25°C: 10000 mPa·s), 1 kg of the polysiloxane-modified bismaleimide resin obtained in Preparation Example 1.1, and 5 kg of toluene in a high-speed mixer for 10 min, 0.001 kg of a polyether defoaming agent (viscosity at 25°C: 180 - 600 mPa·s) and 0.001 kg of leveling agent BYK-300 are added and stirred and mixed evenly, and then 0.5 kg of curing agent QXE301 is added to obtain a heat-resistant insulating filler.

[0027] Example 2 A preparation method of a heat-resistant insulating coating, comprising the following steps: After stirring and mixing 4.5 kg of nano-aluminum oxide, 3.3 kg of methylphenyl polysiloxane resin (CAS number: 67763-03-5, viscosity at 25°C: 10000 mPa·s), 1.2 kg of the polysiloxane-modified bismaleimide resin obtained in Preparation Example 1.1, and 5 kg of toluene in a high-speed mixer for 10 min, 0.003 kg of a polyether defoaming agent (viscosity at 25°C: 180 - 600 mPa·s) and 0.006 kg of leveling agent BYK-300 are added and stirred and mixed evenly, and then 0.6 kg of curing agent QXE301 is added to obtain a heat-resistant insulating filler.

[0028] Example 3 A preparation method of a heat-resistant insulating coating, comprising the following steps: After stirring and mixing 5 kg of nano-aluminum oxide, 3.8 kg of methylphenyl polysiloxane resin (CAS number: 67763-03-5, viscosity at 25°C: 10000 mPa·s), 1.6 kg of the polysiloxane-modified bismaleimide resin obtained in Preparation Example 1.1, and 6 kg of toluene in a high-speed mixer for 10 min, 0.005 kg of a polyether defoaming agent (viscosity at 25°C: 180 - 600 mPa·s) and 0.01 kg of leveling agent BYK-300 are added and stirred and mixed evenly, and then 0.8 kg of curing agent QXE301 is added to obtain a heat-resistant insulating filler.

[0029] Example 4 A preparation method of a heat-resistant insulating coating includes the following steps: 6 kg of nano-aluminum oxide, 4 kg of methylphenyl polysiloxane resin (CAS number: 67763-03-5, viscosity at 25°C: 10000 mPa·s), 2 kg of the polysiloxane-modified bismaleimide resin obtained in Preparation Example 1.1, and 6 kg of toluene are stirred and mixed in a high-speed mixer for 10 min. Then, 0.007 kg of a polyether defoamer (viscosity at 25°C: 180 - 600 mPa·s) and 0.03 kg of a leveling agent BYK-300 are added and stirred and mixed evenly. Subsequently, 1 kg of a curing agent QXE301 is added to obtain a heat-resistant insulating filler.

[0030] Example 5 A preparation method of a heat-resistant insulating coating, which is different from Example 2 in that the polysiloxane-modified bismaleimide resin is the polysiloxane-modified bismaleimide resin obtained in Preparation Example 1.2, and the others are the same as in Example 2.

[0031] Example 6 A preparation method of a heat-resistant insulating coating, which is different from Example 2 in that the polysiloxane-modified bismaleimide resin is the polysiloxane-modified bismaleimide resin obtained in Preparation Example 1.3, and the others are the same as in Example 2.

[0032] Example 7 A preparation method of a heat-resistant insulating coating, which is different from Example 2 in that the total amount of the filler is 4.5 kg, and the filler is composed of nano-aluminum oxide and mica powder with a weight ratio of 1:1.5, specifically 1.8 kg of nano-aluminum oxide and 2.7 kg of mica powder, and the others are the same as in Example 2.

[0033] Example 8 A preparation method of a heat-resistant insulating coating, which is different from Example 2 in that the total amount of the filler is 4.5 kg, and the filler is composed of nano-aluminum oxide and mica powder with a weight ratio of 1:2, specifically 1.5 kg of nano-aluminum oxide and 2 kg of mica powder, and the others are the same as in Example 2.

[0034] Example 9 A preparation method of a heat-resistant insulating coating, which is different from Example 8 in that the mica powder is the mica powder modified in Preparation Example 2.1, and the others are the same as in Example 8.

[0035] Example 10 A preparation method of a heat-resistant insulating coating, which is different from Example 8 in that the mica powder is the mica powder modified in Preparation Example 2.2, and the others are the same as in Example 8.

[0036] Example 11 A preparation method of a heat-resistant insulating coating, which is different from Example 8 in that the mica powder is the mica powder modified by Preparation Example 2.3, and the others are the same as in Example 8.

[0037] Comparative Example 1 A preparation method of a heat-resistant insulating coating, which is different from Example 2 in that an equal amount of bismaleimide resin is used to replace the polysiloxane-modified bismaleimide resin, and the others are the same as in Example 2.

[0038] Comparative Example 2 A preparation method of a heat-resistant insulating coating, which is different from Example 2 in that an equal amount of epoxy resin (CAS No. 61788-97-4) is used to replace the polysiloxane-modified bismaleimide resin, and the others are the same as in Example 2.

[0039] Comparative Example 3 A preparation method of a heat-resistant insulating coating, which is different from Example 11 in that the mica powder is the mica powder obtained by Preparation Example 2.4, and the others are the same as in Example 11.

[0040] Performance test The heat-resistant insulating coatings obtained from the above examples and comparative examples were tested for heat resistance, insulation performance, adhesion, and flexibility, and the test results are shown in Table 1.

[0041] The adhesion was detected by the cross-cut test method in GB / T9286-2021, where the adhesion grade is 0-5 levels, with 0 being the best and 5 being the worst; the heat resistance was tested according to the relevant regulations in GB / T1735-2009, specifically by heat-treating at 150 °C and 180 °C for 4 h to see if there are any phenomena such as delamination, wrinkling, blistering, and cracking on the coating. If there are no phenomena of air layer, wrinkling, blistering, and cracking, it is considered passed, and if any one of the phenomena of delamination, wrinkling, blistering, and cracking appears, it is considered failed. At the same time, the adhesion of the coating after heat treatment at 150 °C was detected; the volume resistivity was tested according to the relevant regulations in GB / T1410-2006.

[0042] Table 1 Detection results table of insulating coatings As can be seen from Table 1: The insulating coatings obtained from Examples 1-6 of the present application have good adhesion, flexibility, and insulation performance, and can withstand high temperatures of 150 °C at the same time, indicating that the formula of the coating of the present application can effectively obtain good heat resistance.

[0043] Compared with Example 2, in Examples 7-8, when the filler consists of nano-aluminum oxide and mica powder, the flexibility of the insulating coating is improved compared to Example 2. The reason is that when the filler is only nano-aluminum oxide, the coating is more brittle. When the filler consists of nano-aluminum oxide and mica powder together, the lamellar structure of mica powder can enhance the flexibility and anti-cracking performance of the coating. Therefore, the flexibility of the coating obtained in Examples 7-8 is improved. In addition, the lamellar structure of mica powder can delay heat transfer and provide long-term heat insulation effect, so that the insulating coating obtained in Examples 7-8 can withstand high temperature of 180 °C, and the heat resistance performance is significantly improved compared to Example 2.

[0044] Compared with Example 8, in Examples 9-11, after the mica powder is modified, the dispersion effect of mica powder in the resin can be effectively enhanced, so that the adhesion and flexibility of the insulating coating obtained in Examples 9-11 are further improved.

[0045] Compared with Example 2, in Comparative Example 1, when the bismaleimide resin is not modified by polysiloxane, after the insulating coating obtained in Comparative Example 1 is treated at a high temperature of 150 °C, its adhesion is significantly reduced compared to Example 2, and the flexibility of the coating is more significantly reduced compared to Example 2. The reason may be that when the unmodified bismaleimide resin is used, the crosslinking density is high after the coating is cured, and the volume shrinkage rate is relatively large, so internal stress is easily generated, resulting in a decrease in the flexibility of the coating.

[0046] Compared with Example 2, in Comparative Example 2, when epoxy resin is used to replace polysiloxane to modify the bismaleimide resin, after the coating is treated at a high temperature of 150 °C, the adhesion between the coating and the substrate is Grade 4, which is significantly lower than that in Example 2. And after the coating obtained in Comparative Example 2 is treated at a high temperature of 150 °C for 4 hours, wrinkling and cracking phenomena appear on the coating, indicating that the heat resistance performance of the coating obtained in Comparative Example 2 is worse.

[0047] Compared with Example 11, in Comparative Example 3, when the modification of mica powder is treated with the commercially available dispersant BYK-168, after the coating obtained in Comparative Example 3 is treated at 150 °C, the adhesion is worse than that in Example 11, and the flexibility is also lower than that in Example 11. From this, it can be further explained that the super dispersant prepared in this application can effectively improve the dispersion of mica powder, so that the adhesion and flexibility of the coating are better.

[0048] The examples of this specific implementation mode are all preferred examples of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A heat-resistant insulating coating, characterized in that, The coating comprises the following raw materials in parts by weight: 30-40 parts of methylphenyl polysiloxane resin, 10-20 parts of polysiloxane-modified bismaleimide resin, 40-60 parts of filler, 5-10 parts of curing agent, 0.01-0.07 parts of defoamer, and 0.01-0.3 parts of leveling agent.

2. The heat-resistant insulating coating according to claim 1, wherein: The coating comprises the following raw materials in parts by weight: 33-38 parts of methylphenyl polysiloxane resin, 12-16 parts of polysiloxane-modified bismaleimide resin, 45-50 parts of filler, 5-10 parts of curing agent, 0.01-0.07 parts of defoamer, and 0.01-0.3 parts of leveling agent.

3. The heat-resistant insulating coating according to claim 1 or 2, characterized in that: The modification method of the polysiloxane-modified bismaleimide resin comprises the following steps: adding bismaleimide resin and polysiloxane into excessive acetone according to a weight ratio of (2-4):1, adding a catalytic amount of catalyst, stirring at 50-55 °C for 20-24 h, cooling, and then evacuating to remove all acetone to obtain the polysiloxane-modified bismaleimide resin.

4. The heat-resistant insulating coating according to claim 3, characterized in that: The polysiloxane used is hydrogen-terminated phenyl polysiloxane.

5. A heat-resistant insulating coating according to claim 1, wherein: The filler is one or two of nano-aluminum oxide and mica powder.

6. The heat-resistant insulating coating according to claim 7, characterized in that: The weight ratio of the nano-aluminum oxide to the mica powder is 1:(1.5-2).

7. The heat-resistant insulating coating according to claim 6, characterized in that: The mica powder is obtained by modification treatment with a hyperdispersant, and the weight ratio of the mica powder to the hyperdispersant is 5:

1.

8. The heat-resistant insulating paint according to claim 7, wherein: The preparation of the hyperdispersant is as follows: adding acrylic monomers and initiator into tetrahydrofuran, reacting at 60±2 °C for 14-17 h, adding methanol for precipitation after the reaction is completed, centrifuging to collect, pouring off the supernatant, dissolving with chloroform, and then precipitating with methanol. Repeat the above operations three times to obtain a pure product. Finally, dry the product in a vacuum oven at 70 °C for 24 h to obtain the hyperdispersant.

9. The heat-resistant insulating coating according to claim 8, wherein: The acrylic monomers are composed of n-butyl methacrylate and 2-hydroxyethyl methacrylate in a weight ratio of 1:(1-1.2).

10. A method for preparing a heat-resistant insulating coating according to any one of claims 1-9, characterized in that: It comprises the following steps: stirring and mixing the filler with methylphenyl polysiloxane resin and polysiloxane-modified bismaleimide resin, adding a defoamer and a leveling agent, stirring and mixing evenly, and then adding a curing agent to obtain a heat-resistant insulating filler.

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