High-temperature-resistant organic silicon insulating paint for ZnO resistor disc as well as preparation method and application of high-temperature-resistant organic silicon insulating paint

Abstract

The invention provides a high-temperature-resistant organic silicon insulating coating for a ZnO resistor disc as well as a preparation method and application of the high-temperature-resistant organic silicon insulating coating, and belongs to the field of insulating coatings. The organic silicon insulating paint comprises the following components: 60-90% of liquid silicon resin; 0-20% of a heat-resistant filler; 1 to 10% of a silane coupling agent; 1 to 10% of butyl titanate; and 3-10% of an adhesion promoter. A main chain structure in organic silicon molecules of the silicon resin is a Si-O bond formed by alternately connecting silicon (Si) and oxygen (O) atoms, and the bond has relatively high bond energy and good flexibility, so that a resin coating system has relatively good heat resistance and the like. The problems that existing organic and inorganic insulating coatings are poor in heat resistance, prone to corrosion when meeting water and the like can be solved, the provided insulating paint can be used for ZnO resistor discs with various diameters, the resistor discs are not limited to a cake shape and a ring shape, and the insulating paint is particularly well applied to the ZnO resistor discs with high voltage gradients.

Description

Technical Field

[0001] The invention relates to the technical field of insulating coatings, and in particular to a high-temperature resistant organic silicon insulating coating for a ZnO resistor sheet, and a preparation method and application thereof. Background Art

[0002] Zinc oxide resistors are an important part of zinc oxide arresters, and their external insulation plays a vital role in their electrical performance. In the zinc oxide (ZnO) resistor industry, there are two main insulation methods commonly used: one is an organic insulation coating that uses epoxy resin as the main body and adds inorganic fillers to improve the insulation strength of the coating; the other is a glass glaze inorganic insulation coating composed of multiple metal oxides and obtained by heat treatment.

[0003] For existing organic insulating coatings, epoxy resin coatings can meet the insulation and temperature requirements of conventional voltage gradient ZnO resistors. However, when the surface temperature of the resistor ZnO exceeds 200°C, the coating will fail. Since the energy generated by the action during the electrical test will cause the temperature of the resistor to rise rapidly in an instant, the temperature resistance of epoxy resin cannot meet the requirements. Therefore, its protection ability is limited for high-gradient ZnO resistors with high energy density. For inorganic glass glaze coatings, although this side insulation method can meet the temperature requirements, on the one hand, after spraying the glass glaze precursor, the resistor needs to be subjected to high-temperature heat treatment at 500°C-600°C to vitrify the coating. This process has a high temperature and consumes a lot of energy, resulting in energy waste, which is not conducive to energy conservation and emission reduction. At the same time, after the heat treatment process, the resistor will have the risk of increased leakage current; on the other hand, the glass glaze is not resistant to water corrosion, which puts forward high requirements on the storage environment and transportation environment, and is inconvenient for storage and transportation to a certain extent.

[0004] It can be seen that the existing organic insulating coating and inorganic glass glaze coating have some problems in practical application. Among them, the above-mentioned organic insulating coating has poor high temperature resistance. When the surface temperature of the ZnO resistor exceeds 200°C, the coating has the risk of failure, which is not conducive to application. Summary of the invention

[0005] In view of the shortcomings of the existing ZnO resistor organic insulating coating, such as poor high temperature resistance, the present invention provides a high temperature resistant organic silicon insulating coating for ZnO resistor, a preparation method and application thereof. The organic silicon insulating coating provided by the present invention is applied to the external insulation of ZnO resistor, has good heat resistance, and thus makes the resistor have a higher gradient, etc.

[0006] In order to solve the above technical problems, the present invention provides a high temperature resistant organic silicon insulating coating for ZnO resistor, comprising the following components by weight:

[0007] 60-90% liquid silicone;

[0008] 0-20% heat-resistant filler;

[0009] 1-10% silane coupling agent;

[0010] 1-10% butyl titanate;

[0011] 3-10% adhesion promoter.

[0012] In some embodiments, the silicone resin of the liquid silicone resin is one or more of methyl silicone resin, phenyl silicone resin and methylphenyl silicone resin.

[0013] In some embodiments, the room temperature viscosity of the liquid silicone resin is 50-500 mPa·s; the solid content of the liquid silicone resin is 50-60%, and the solvent is toluene.

[0014] In some embodiments, the silane coupling agent is an aminosilane coupling agent, which may be one or more of γ-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0015] In some embodiments, the heat-resistant filler is sericite and / or boron nitride.

[0016] In some embodiments, the heat-resistant filler is sericite with a particle size of 10-30 microns and / or boron nitride with a particle size of 0.1-5 microns.

[0017] In some embodiments, the adhesion promoter is one or more of acrylic compounds, ester compounds and nano-inorganic substances.

[0018] The present invention provides a method for preparing the above-mentioned organosilicon insulating coating, comprising the following steps:

[0019] Mixing a liquid silicone resin and an optional heat-resistant filler according to weight fraction to obtain a first mixture;

[0020] mixing a silane coupling agent, butyl titanate, and an adhesion promoter to obtain a second mixture;

[0021] The first mixture and the second mixture are mixed and prepared before use.

[0022] In some embodiments, the liquid silicone resin and the heat-resistant filler are stirred and mixed by a planetary ball mill or a high-speed stirrer at a rotation speed of 500-600 rpm for 30-60 min.

[0023] The present invention provides the use of the above-mentioned organic silicon insulating coating in the external insulation of a ZnO resistor.

[0024] Compared with the prior art, the organic silicon insulating coating provided by the present invention has liquid silicone resin as the main component, and is added with auxiliary components such as silane coupling agent, butyl titanate and adhesion promoter. In the insulating coating material of the present invention, the main chain structure in the silicone resin organic silicon molecule is a Si-O bond formed by alternating silicon (Si) and oxygen (O) atoms, and this bond has a high bond energy and good flexibility, thereby making its resin coating system have good heat resistance and the like. The present invention can overcome the problems of poor heat resistance and easy corrosion in water of existing organic and inorganic insulating coatings. The insulating coating provided can be used for ZnO resistors of various diameters, and the shape of the resistor is not limited to pancake and ring, and is particularly good for high voltage gradient ZnO resistors.

[0025] In addition, the high temperature resistant organic silicon coating obtained by the present invention can also be widely used in various semiconductor ceramics, and has good application and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the coating position of a resistor sheet in some embodiments of the present invention;

[0027] Figure 2 The thermogravimetric curve of Example 1 of the present invention;

[0028] Figure 3 This is a photograph of the resistor coated with and cured by the organic silicon insulating coating of Example 1 after being tested. DETAILED DESCRIPTION

[0029] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the technical scheme of the present invention is now described in detail below in conjunction with specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0030] The present invention provides a high temperature resistant organic silicon insulating coating for a ZnO resistor, comprising the following components in weight fractions:

[0031] 60-90% liquid silicone;

[0032] 0-20% heat-resistant filler;

[0033] 1-10% silane coupling agent;

[0034] 1-10% butyl titanate;

[0035] 3-10% adhesion promoter.

[0036] The organic silicon insulating coating provided by the present invention is applied to the external insulation of a ZnO resistor and has good heat resistance, thereby making the resistor have a higher gradient, a larger capacity and a high current impact tolerance pass rate.

[0037] The technical solution provided by the embodiment of the present invention first includes a high temperature resistant insulating coating for ZnO resistors, wherein the raw materials thereof mainly consist of: 60%-90% liquid silicone resin and 0-20% heat resistant filler according to mass percentage.

[0038] Silicone resin is an organic silicon polymer with a cross-linked structure such as Si-O bonds. It is a common insulating heat-resistant coating material in recent years, and its heat resistance is better than that of epoxy resin system. The embodiment of the present invention mainly uses liquid silicone resin to form an organic silicon insulating coating, and its weight percentage is preferably 65%-80% (can be 70%, 75%, 80%, etc.); the liquid silicone resin can be one or more of methyl silicone resin, phenyl silicone resin and methylphenyl silicone resin. Methylphenyl silicone resin belongs to organic silicone resin, and its main components include methyl and phenyl siloxane segments, and have excellent high temperature resistance, electrical insulation and weather resistance. Further, the room temperature viscosity of the liquid silicone resin can be 50-500mPa·s, preferably 60-400mPa·s; the solid content of the liquid silicone resin is generally 50-60%, and the solvent is toluene, and commercially available products can be used.

[0039] Some embodiments of the present invention may not use heat-resistant fillers, or may use heat-resistant fillers to improve performance and reduce costs. The weight percentage of the heat-resistant filler is further 0-10%, for example, 1-8%; the type is preferably sericite and / or boron nitride, and more preferably sericite. Sericite is a type of mica, which is a silicate material with a layered structure; sericite is in the form of fine flakes (generally <0.01mm) and has good thermal insulation properties. The chemical formula of boron nitride is BN, and it has a variety of crystal structures. Preferably, the heat-resistant filler is sericite with a particle size of 10μm-30μm and / or boron nitride with a particle size of 0.1μm-5μm, which is more conducive to application.

[0040] Furthermore, the organic silicon insulating coating described in the embodiment of the present invention comprises: 1%-10%, preferably 2-8% of silane coupling agent, 1%-10%, preferably 2-7% of butyl titanate, and 3%-10%, preferably 4-9% of adhesion promoter.

[0041] Wherein, the silane coupling agent is an aminosilane coupling agent, which can be one or more of γ-aminopropyltriethoxysilane (γ-APS, 3-(aminopropyl)triethoxysilane), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; preferably 3-(aminopropyl)triethoxysilane, which is referred to as γ-aminopropyltriethoxysilane, with a molecular weight of 236.34. Some specific structural formulas of the silane coupling agent are as follows:

[0042]

[0043] The above-mentioned silane coupling agent contains a silanol group capable of forming a chemical bond with an inorganic substrate, and also has an organic functional group compatible with an organic resin, etc. Meanwhile, the butyl titanate enhances the adhesion of the coating by providing a titanate group capable of forming a chemical bond with the substrate.

[0044] The interfacial bonding between a single silicone resin system and a substrate material is not ideal, but the present invention uses an adhesion promoter in combination with silicone resin to achieve better adhesion effects, etc. The adhesion promoter is a type of chemical additive used to improve the adhesion between a coating, adhesive or other coating material and the surface of a substrate, preferably one or more of acrylic compounds, ester compounds and nano-inorganic substances, further enhancing the interaction between the interfaces and improving the adhesion and durability of the organic silicon insulating coating. The ester compound includes titanate, zirconate, phosphate, etc., preferably tetraisopropyl titanate.

[0045] In a specific embodiment of the present invention, the acrylic compound is acrylic acid, methacrylic acid and its derivatives, which can form good adhesion with various substrates through free radical polymerization. In addition, tetraisopropyl titanate and γ-aminopropyl triethoxysilane added in the system can hydrolyze alkoxy groups into hydroxyl groups during the molding process, which can promote the wettability between the coating and zinc oxide, and they can form Ti-O-Zn and Si-O-Zn bonds on the surface of zinc oxide to improve the bonding force between the two. Furthermore, the active groups hydroxyl and amino groups can change the molecular polarity, promote the formation of strong intermolecular forces such as hydrogen bonds between the coating and the zinc oxide sheet, and at the same time, combined with nano inorganic substances such as nano silicon dioxide or nano calcium carbonate, they can increase the cohesive energy and high temperature resistance of the coating through mechanical anchoring, thereby ensuring the improvement of adhesion in applications of high temperature resistance or harsh environments.

[0046] The present invention provides a method for preparing the above-mentioned organic silicon insulating coating, comprising the following steps:

[0047] Mixing a liquid silicone resin and an optional heat-resistant filler according to weight fraction to obtain a first mixture;

[0048] mixing a silane coupling agent, butyl titanate, and an adhesion promoter to obtain a second mixture;

[0049] The first mixture and the second mixture are mixed and prepared before use.

[0050] In a specific embodiment of the present invention, the insulating coating components can be divided into two components, A and B, which need to be prepared separately and then mixed before use. The A component contains liquid silicone resin and heat-resistant filler, which is the first mixture; and the B component contains silane coupling agent, butyl titanate and adhesion promoter, which is the second mixture.

[0051] In some embodiments, the liquid silicone resin and the heat-resistant filler are stirred and mixed by a planetary ball mill or a high-speed stirrer, preferably grinding for 30min-60min at a speed of 500rpm-600rpm to obtain a first mixture that is evenly mixed. In addition, the B component is a silane coupling agent, butyl titanate, and an adhesion promoter, which are stirred by a high-speed stirrer at a speed of 2000rpm-3000rpm to obtain a second mixture that is evenly mixed. The embodiment of the present invention ensures that the adhesion promoter and other components (such as liquid silicone resin, heat-resistant filler, etc.) are fully mixed to form a uniform mixture by pre-mixing the raw material components. The adhesion promoter and other components are evenly mixed using a high-speed stirrer or a ball mill to ensure good dispersibility.

[0052] When it is needed, the embodiment of the present invention further mixes the two components A and B evenly and prepares them for use. In addition, the mass ratio of the two components A and B can be 1:1-5:1.

[0053] In addition, the present invention provides the use of the above-mentioned organic silicon insulating coating in the external insulation of ZnO resistors.

[0054] In the embodiment of the present invention, the ZnO resistor to be coated may be subjected to surface treatment, such as cleaning, roughening or other pretreatment, to increase the adhesion area and adhesion of the coating. In some specific embodiments, the surface of the ZnO resistor to be coated is cleaned with an air gun and preheated for 4 hours at 150°C. In the embodiment of the present invention, there is no special restriction on the diameter and shape of the ZnO resistor, and it can be a resistor of various diameters, and can be applied to a pancake resistor and a ring resistor.

[0055] In the embodiment of the present invention, the above-mentioned component A and component B can be manually stirred evenly to obtain a heat-resistant silicone insulating coating for ZnO resistors. The compressed air pressure of the spray gun is preferably adjusted to 0.4MPa, and the mixed coating liquid is transferred to the spray gun storage tank. The spray gun starts to spray on the surface of the preheated resistor (diameter such as 45mm or 71mm, etc.), and then stops for 10-20s for the second spraying, and the total mass of the coating is controlled to be 4-8g.

[0056] like Figure 1As shown, the embodiment of the present invention can spray the coating on the surface to be sprayed of the pancake-shaped or ring-shaped ZnO resistor, in which the detailed position of the resistor that needs to be covered with the insulating coating is marked. Afterwards, the embodiment of the present invention cures the coating. Appropriate curing temperature and time are essential for forming a stable coating structure. The curing temperature of the present invention preferably adopts a temperature gradient curing mechanism, and heats for two hours at 100°C, 120°C, 140°C, 160°C, 180°C, and 200°C, respectively. During the temperature rise curing process, the moisture in the air removes the alkoxy group to generate silanol group, and a dehydration condensation reaction occurs between the silanol group and the silanol group at high temperature. The generated moisture will further promote the cross-linking reaction.

[0057] After testing, the organic silicon insulating coating is applied to the external insulation of ZnO resistors and has good heat resistance, thereby making the resistors have a higher gradient, etc.

[0058] In order to further understand the present invention, the present invention is described in detail below in conjunction with the examples, and the protection scope of the present invention is not limited by the following examples. In the examples, all raw reagents and materials are commercially available, and the experimental methods without specific experimental conditions are conventional methods and conditions well known in the art.

[0059] Comparative Example 1

[0060] Step 1

[0061] Epoxy resin powder (bisphenol A epoxy resin, brand E-42, epoxy value 0.39 mol / 100 g, commercially available) and solvent dimethyl carbonate were manually mixed at a weight ratio of 1:0.4.

[0062] Step 2

[0063] The surface of the ZnO resistor (45 mm in diameter) to be coated was cleaned with an air gun and preheated for 4 h at 150°C. The compressed air pressure of the spray gun was adjusted to 0.4 MPa, and the mixed epoxy resin coating liquid was transferred to the spray gun storage tank.

[0064] Step 3

[0065] The spray gun starts to spray on the preheated resistor surface, and then stops for 15 seconds before spraying again. The total mass of the coating is controlled to be 4g.

[0066] Step 4

[0067] The coating was cured by gradient curing, and heated at 100°C, 120°C, 140°C, and 150°C for two hours respectively. After the curing, the film was ground and sprayed onto the aluminum electrode in turn, and the preparation of the test resistor was completed.

[0068] Example 1

[0069] Step 1A Preparation

[0070] 80% of polymethylphenyl silicone resin (viscosity 350 mPa·s) was weighed and transferred into a beaker to obtain component A.

[0071] Step 2B Preparation

[0072] 5% of γ-aminopropyltrimethoxysilane, 5% of butyl titanate, and 10% of an adhesion promoter (tetraisopropyl titanate) were weighed into a container, and ground for 30 minutes using a planetary ball mill at a speed of 500 r / min to obtain component B.

[0073] Step 3

[0074] The surface of the ZnO resistor (45 mm in diameter) to be painted was cleaned with an air gun and preheated at 150°C for 4 hours. Component A and component B were manually stirred to obtain a heat-resistant silicone coating for the ZnO resistor. The compressed air pressure of the spray gun was adjusted to 0.4 MPa, and the mixed coating liquid was transferred to the spray gun storage tank.

[0075] Step 4

[0076] The spray gun starts to spray on the preheated resistor surface, and then stops for 15 seconds before spraying again. The total mass of the coating is controlled to be 5.5 g.

[0077] Step 5

[0078] The coating was cured by gradient curing, and heated for two hours at 100°C, 120°C, 140°C, 160°C, 180°C, and 200°C. After curing, the coating was ground and sprayed onto the aluminum electrode, and the preparation of the test resistor was completed.

[0079] Example 2

[0080] Step 1A Preparation

[0081] 70% of polymethylphenyl silicone resin and 10% of sericite were weighed, transferred to a sealed tank, and ground for 30 minutes using a planetary ball mill at a speed of 500 r / min to obtain component A.

[0082] Step 2B Preparation

[0083] 5% of γ-aminopropyltrimethoxysilane, 5% of butyl titanate, and 10% of an adhesion promoter (tetraisopropyl titanate) were weighed into a container, and ground for 30 minutes using a planetary ball mill at a speed of 500 r / min to obtain component B.

[0084] Step 3

[0085] The surface of the ZnO resistor (45 mm in diameter) to be painted was cleaned with an air gun and preheated at 150°C for 4 hours. Component A and component B were manually stirred to obtain a heat-resistant silicone coating for the ZnO resistor. The compressed air pressure of the spray gun was adjusted to 0.4 MPa, and the mixed coating liquid was transferred to the spray gun storage tank.

[0086] Step 4

[0087] The spray gun starts to spray on the preheated resistor surface, and then stops for 15 seconds before spraying again. The total mass of the coating is controlled to be 4g.

[0088] Step 5

[0089] The coating was cured by gradient curing, and heated for two hours at 100°C, 120°C, 140°C, 160°C, 180°C, and 200°C. After curing, the coating was ground and sprayed onto the aluminum electrode, and the preparation of the test resistor was completed.

[0090] The above resistors to be tested are tested according to the test standard GB / T 11032-2020 or GB / T22389-2023, as shown in the following table.

[0091] Table 1 Resistor test method

[0092]

[0093] The voltage gradient (E) of the resistor is calculated as follows:

[0094] E=U 1mA / H;

[0095] U 1mA is the DC reference voltage of the resistor, in V;

[0096] H is the thickness of the resistor, in mm.

[0097] Table 2 Electrical test results of Example 1-2

[0098]

[0099] The above test is based on the standard GB / T 11032-2020. The number of samples for the repeated charge transfer test is 10. The table uses n / 10 to represent the pass rate, where n represents the number of resistors that passed the test. The high current test results are the same as above. Failed resistors include high current failure and repeated charge transfer failure.

[0100] Also, see Figure 2 As shown in the thermogravimetric curve, Comparative Example 1 is an insulating coating of epoxy resin, and Example 1 is an insulating coating of silicone resin. Figure 2Thermogravimetric curves can be used to evaluate the thermogravimetric properties of materials by the initial decomposition temperature, i.e., the temperature corresponding to 5% weight loss, and the residual weight of the material after decomposition. The higher the decomposition temperature, the higher the residual weight, indicating better heat resistance. The temperature at which epoxy resin loses 5% weight is 327°C, and the residual weight is 34.50%; the decomposition temperature of silicone resin is higher, the temperature at which it loses 5% weight is 389°C, and the residual weight is 49.64%. It can be seen that the silicone resin system of the present invention has better heat resistance.

[0101] Figure 3 This is an optical photograph of the surface of the resistor that passed the test after the silicone resin system without filler was coated on the resistor surface in Example 1 and cured. It can be seen that the surface is smooth and flat without defects such as cracks and pinholes, indicating that the silicone resin coating system of the present invention has good process performance.

[0102] It can be seen from the above embodiments that the comprehensive effect of the coating components of the embodiments of the present invention, preferably combined with a specific preparation process, can significantly improve the durability, temperature resistance and overall performance of the coating, thereby achieving better adhesion effects and meeting specific application requirements.

[0103] The above examples are only used to illustrate the technical features and implementation process of the present invention, rather than to limit the technical solution of the present invention. It should be pointed out that for ordinary technicians in this field, the present invention can still be modified or replaced by equivalents, and modifications or replacements that do not deviate from the principles of the present invention are all covered by the protection of the present invention.

Claims

1. A high temperature resistant organic silicon insulating coating for ZnO resistor, characterized in that: The components include the following weight fractions: 60-90% liquid silicone; 0-20% heat-resistant filler; 1-10% silane coupling agent; 1-10% butyl titanate; 3-10% adhesion promoter.

2. The organic silicon insulating coating according to claim 1, characterized in that: The silicone resin of the liquid silicone resin is one or more of methyl silicone resin, phenyl silicone resin and methylphenyl silicone resin.

3. The organic silicon insulating coating according to claim 1, characterized in that: The room temperature viscosity of the liquid silicone resin is 50-500 mPa·s; the solid content of the liquid silicone resin is 50-60%, and the solvent is toluene.

4. The organic silicon insulating coating according to any one of claims 1 to 3, characterized in that: The silane coupling agent is an aminosilane coupling agent, which may be one or more of γ-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

5. The organic silicon insulating coating according to any one of claims 1 to 3, characterized in that: The heat-resistant filler is sericite and / or boron nitride.

6. The organic silicon insulating coating according to claim 5, characterized in that: The heat-resistant filler is sericite with a particle size of 10-30 microns and / or boron nitride with a particle size of 0.1-5 microns.

7. The organic silicon insulating coating according to any one of claims 1 to 3, characterized in that: The adhesion promoter is one or more of acrylic compounds, ester compounds and nano inorganic substances.

8. The method for preparing the organosilicon insulating coating according to any one of claims 1 to 7, comprising the following steps: Mixing a liquid silicone resin and an optional heat-resistant filler according to weight fraction to obtain a first mixture; mixing a silane coupling agent, butyl titanate, and an adhesion promoter to obtain a second mixture; The first mixture and the second mixture are mixed and prepared before use.

9. The preparation method according to claim 8, characterized in that: The liquid silicone resin and the heat-resistant filler are stirred and mixed by a planetary ball mill or a high-speed stirrer at a rotation speed of 500-600 rpm for 30-60 minutes.

10. Use of the organic silicon insulating coating as claimed in any one of claims 1 to 7 in external insulation of ZnO resistors.

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