Epoxy resin insulating paint, its preparation method and application

Abstract

The application discloses an epoxy resin insulating paint and a preparation method and application thereof. The epoxy resin insulating paint is composed of component A and component B. The preparation raw materials of the component A include solid epoxy resin and polymer slurry. The preparation raw materials of the polymer slurry include liquid epoxy resin, shielding filler and siloxane compound. The preparation raw materials of the component B include polyamide curing agent and phenolic curing agent. The pigment-binder ratio of the epoxy resin insulating paint is 0.9-1.1. The epoxy resin insulating paint has excellent rust-proof performance and good compatibility with insulating oil. In the high-temperature operation process, the coating does not affect the electrical performance of the insulating oil.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coating technology, specifically relating to an epoxy resin insulating varnish, its preparation method, and its application. Background Technology

[0002] Insulating oil is widely used in transformers, instrument transformers, switchgear, rectifier cables, and capacitors, serving as an insulator and heat conductor. Immersion of insulating materials in the oil also provides moisture protection, ensuring the oil's stability, which is of great significance for the use of electrical equipment. Currently, the inner wall of oil-immersed transformers is coated with an inner wall paint for corrosion protection, extending the transformer's service life and preventing rapid corrosion of the transformer metal.

[0003] One requirement for the inner wall paint is that the coating remains stable during the operation of the transformer equipment, and there should be no defects in the paint film such as peeling or blistering. However, it is also important to note that the inner wall paint needs to have good compatibility with the insulating oil to prevent substances in the inner wall paint from contaminating the insulating oil under high-temperature conditions and causing the insulating oil to fail more quickly.

[0004] Existing research has developed a decorative anti-corrosion paint for the inner and outer walls of transformers by preparing the main paint using epoxy-modified acrylic resin and using hexamethylene isocyanate biuret and isophorone diisocyanate trimer as curing agents. The resulting inner wall paint does not peel or bubble when used in high-temperature transformer oil. However, the compatibility of this inner wall paint with transformer insulating oil has not been investigated. It contains a relatively large number of ions, which may slightly precipitate in a sustained high-temperature environment, thus affecting the electrical strength of the insulating oil, such as breakdown voltage and dielectric loss coefficient.

[0005] In summary, developing an epoxy resin varnish with excellent compatibility with insulating oil is a challenging problem that researchers in this field need to explore. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes an epoxy resin insulating varnish. This epoxy resin insulating varnish exhibits stable performance, excellent rust prevention, and good compatibility with insulating oil. During high-temperature operation, the coating will not affect the electrical properties of the insulating oil.

[0007] The present invention also proposes a method for preparing the above-mentioned epoxy resin insulating varnish.

[0008] The present invention also proposes the application of the above-mentioned method for preparing epoxy resin insulating varnish in electrical equipment.

[0009] According to a first aspect of the present invention, an epoxy resin insulating varnish is provided, comprising component A and component B.

[0010] The raw materials for preparing component A include: solid epoxy resin and polymer slurry.

[0011] The raw materials for preparing the polymer slurry include: liquid epoxy resin, shielding filler, and siloxane compound.

[0012] The raw materials for preparing component B include: polyamide curing agent and phenolic curing agent;

[0013] The epoxy value of the solid epoxy resin is 0.48~0.54 mol / 100g;

[0014] The epoxy value of the liquid epoxy resin is 0.2~0.23 mol / 100g;

[0015] The pigment-to-binder ratio in the epoxy resin insulating varnish is 1.4 to 1.7.

[0016] The embodiments of the first aspect of the present invention have at least the following beneficial effects:

[0017] 1. This invention uses epoxy resins with two different epoxy values ​​and polyamide and phenolic curing agents, which improves the toughness and density of the coating, enhances the wettability and high-temperature adhesion of the coating, and prevents peeling.

[0018] 2. The coating exhibits excellent adhesion, strong wettability, strong shielding ability, and superior chemical resistance. It can be continuously immersed in insulating oil without peeling off. 3. The formulation has simple components, excellent compatibility with insulating oil, no leaching components, and the coating does not affect the electrical properties of the insulating oil. 4. The use of siloxane compounds in the polymer slurry to modify the shielding filler improves the dispersibility and coating properties of the shielding filler and epoxy. Liquid epoxy resin forms a thick film after curing with high crosslinking density, achieving a dense coating. Its slow drying speed and low molecular weight facilitate wettability and good adhesion, while solid epoxy resin has a high molecular weight and better flexibility. The above formulation system has simple and stable components, eliminates leaching issues, and does not affect the properties of the insulating oil. Within the pigment-to-binder ratio range of this invention, the film exhibits good density, resulting in strong shielding ability and good chemical resistance. The pigment-to-binder ratio is calculated as follows: the mass of the material solids in the shielding filler divided by the sum of the mass solids in the solid epoxy resin, the liquid epoxy resin, the polyamide curing agent, and the phenolic curing agent.

[0019] In some embodiments of the present invention, the raw materials for preparing the polymer slurry further include a solvent, wherein the solvent includes at least one of xylene, methyl isobutyl ketone and propylene glycol methyl ether.

[0020] In some embodiments of the present invention, the raw materials for preparing the polymer slurry, by weight, include: 14-24 parts of liquid epoxy resin, 45-55 parts of shielding filler, 0.3-1 parts of siloxane compound, and 6-10 parts of solvent.

[0021] In some embodiments of the present invention, the siloxane compound includes at least one of aliphatic epoxy silanes and alicyclic epoxy silanes.

[0022] In some embodiments of the present invention, the siloxane compound includes at least one of: n-octyltriethoxysilane, isopropoxytris(dioctylpyrophosphoryloxy)titanate, 3-(2,3-epoxypropyl)propyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0023] Among the aforementioned siloxane compounds, n-octyltriethoxysilane and isopropoxytris(dioctylpyrophosphoryloxy)titanate have an alkoxysilane (hydrophilic structure) at one end. Under the action of surface moisture in the shielding filler, they undergo hydrolysis, and the silicon-oxygen bond combines with the hydroxyl group.

[0024] In some embodiments of the present invention, the siloxane compound includes: 3-(2,3-epoxypropyl)propyltrimethoxysilane.

[0025] 3-(2,3-epoxypropyl)propyltrimethoxysilane can react with epoxy resin to form siloxane bonds and polyether chains. The polyether chains are softer than the siloxane chains, while the siloxane chains possess a certain degree of rigidity. The polyether chains can fully expand in the mixture of the shielding filler and epoxy resin, creating tiny gaps between the filler particles. These gaps facilitate the dispersion of the shielding filler particles, reduce the possibility of filler aggregation, and improve the interfacial compatibility between the shielding filler and epoxy resin. The rigidity of the siloxane chains helps maintain the stability of these gaps. Therefore, 3-(2,3-epoxypropyl)propyltrimethoxysilane, as a silane modifier, helps improve the dispersibility and interfacial compatibility of the filler and resin by forming siloxane bonds and polyether chains, thereby enhancing the overall performance of the composite material.

[0026] In some embodiments of the present invention, the shielding filler in the polymer slurry includes at least one of talc, barium sulfate, and titanium dioxide.

[0027] In some embodiments of the present invention, the shielding filler in the polymer slurry includes talc, barium sulfate and titanium dioxide; the weight ratio of the talc, the barium sulfate and the titanium dioxide is 3~5:25~35:15~18 by weight.

[0028] In some embodiments of the present invention, the raw materials for preparing component A further include pigments and fillers; the pigments and fillers include at least two of talc, barium sulfate, and titanium dioxide.

[0029] Talc powder acts as a sealant in the coating, barium sulfate acts as a filler without affecting the density of the coating, and titanium dioxide acts as a colorant and a masking agent. The titanium dioxide of this invention is an uncoated rutile titanium dioxide, which avoids the introduction of excess ions that could affect the compatibility with the insulating oil.

[0030] In some embodiments of the present invention, the raw materials for preparing component A also include an anti-settling agent.

[0031] In some embodiments of the present invention, the anti-settling agent includes at least one of fumed silica and polyamide wax.

[0032] In some embodiments of the present invention, the raw materials for preparing component A also include an antifoaming agent.

[0033] In some embodiments of the present invention, the defoamer includes at least one of a polyether-modified polysiloxane defoamer and a fluorinated acrylic defoamer.

[0034] The aforementioned defoamer is a high molecular weight defoamer, which is beneficial for eliminating dark bubbles in the coating and improving the density of the coating.

[0035] In some embodiments of the present invention, the raw materials for preparing component A further include solvent C, wherein solvent C includes at least one of xylene, methyl isobutyl ketone and propylene glycol methyl ether.

[0036] In some embodiments of the present invention, the solid epoxy resin includes South Asia Resin 901X75.

[0037] In some embodiments of the present invention, the liquid epoxy resin includes South Asia Resin 128R.

[0038] In some embodiments of the present invention, the raw materials for preparing component B further include solvent D, wherein solvent D includes at least one of xylene, methyl isobutyl ketone and propylene glycol methyl ether.

[0039] In some embodiments of the present invention, the weight ratio of component A to component B is (2~3):1.

[0040] The above ratio ensures sufficient curing of the system, improves the drying speed and chemical resistance of the insulating varnish, and prevents the escape of epoxy resin and curing agent.

[0041] In some embodiments of the present invention, the weight ratio of the solid epoxy resin to the liquid epoxy resin C is (0.6~1.8):1.

[0042] At the above ratio, the flexibility and cross-linking degree of the insulating varnish are improved, thereby increasing the density of the coating and preventing the varnish film from becoming too brittle.

[0043] In some embodiments of the present invention, the weight ratio of the polyamide curing agent to the phenolic curing agent is (1~2):1.

[0044] The curing agent of the present invention is a mixed curing agent of polyamide and phenolic amine, and the mixing ratio of the two is (1~2):1.

[0045] At the above ratio, polyamide can provide good wettability and pot life, improve adhesion to the substrate, and prevent coating blistering, while phenolic amine provides good density to the coating, improves the chemical resistance of the coating, and prevents the penetration of high-temperature oil.

[0046] In some embodiments of the present invention, the raw materials for preparing component A, by weight, include:

[0047] The raw materials for component B include 15-25 parts of solid epoxy resin and 68-88 parts of polymer slurry; the raw materials for component B include 10-20 parts of polyamide curing agent and 10-15 parts of phenolic curing agent.

[0048] The raw materials for component B include: 15-25 parts of solid epoxy resin and 68-88 parts of polymer slurry; the raw materials for component B include: 10-20 parts of polyamide curing agent, 10-15 parts of phenolic curing agent and 10-20 parts of solvent D.

[0049] In some embodiments of the present invention, the raw materials for preparing component A, by weight, include: 15-25 parts of solid epoxy resin, 68-88 parts of polymer slurry, 0.2-0.4 parts of anti-settling agent, 0.3-0.8 parts of defoamer, and 10-20 parts of solvent C.

[0050] According to a second aspect of the present invention, a method for preparing an epoxy resin insulating varnish is provided, comprising:

[0051] Preparation of component A: The raw materials for preparing component A are mixed, dispersed, heated, and then the viscosity is adjusted.

[0052] Preparation of component B: The raw materials for the preparation of component B are mixed and dispersed and the viscosity is adjusted.

[0053] In some embodiments of the present invention, the preparation method of the epoxy resin insulating varnish includes: preparation of component A: adding liquid epoxy resin, solid epoxy resin, anti-settling agent, defoamer, and solvent C into a reactor, dispersing for 20-50 min, then adding pigments and fillers and dispersing to a fineness of 40-50 μm, controlling the temperature at 50-55°C, adding solvent C to adjust the viscosity, and discharging to obtain component A;

[0054] Preparation of component B:

[0055] After mixing and stirring the polyamide curing agent, phenolic amine curing agent, and solvent D for 30-40 minutes, add a small amount of solvent to adjust the viscosity, and then discharge the material to obtain component B.

[0056] In some embodiments of the present invention, the preparation method of the polymer slurry includes: heating and dispersing the siloxane compound and the shielding filler, and then adding liquid epoxy resin for reaction.

[0057] In some embodiments of the present invention, the preparation method of the polymer slurry includes: mixing and stirring solvent E and siloxane compound, adding shielding filler, heating to 60-80°C, stirring for 1-2 hours, cooling to 40-50°C, adding liquid epoxy resin, stirring at high speed for 1-2 hours, and cooling for later use.

[0058] According to a third aspect of the invention, an application of the aforementioned epoxy resin insulating varnish in electrical equipment is proposed.

[0059] In some embodiments of the present invention, the electrical equipment includes at least one of a transformer, a current transformer, a switching device, a rectifier cable, and a capacitor. Detailed Implementation

[0060] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0061] In this embodiment, the solid epoxy resin is Nan Ya Resin 901X75.

[0062] The liquid epoxy resin is Nan Ya Resin 128R.

[0063] Example 1

[0064] This embodiment provides an epoxy resin insulating varnish and its preparation method, specifically:

[0065] The preparation method of the polymer slurry is as follows: 8 parts of xylene and 0.5 parts of isopropoxytris(dioctylpyrophosphoryloxy)titanate are added to a dispersion vessel and stirred at 200 r / min for 30 min. Then, 4 parts of talc, 30 parts of barium sulfate, and 16 parts of titanium dioxide are added. The temperature is raised to 80℃ and stirred at 500 r / min for 1 h. After cooling to 40℃, 22 parts of liquid epoxy resin E51 (100% solid content) are added and stirred at 500 r / min for 1 h. After cooling, it is ready for use.

[0066] Preparation of component A of epoxy resin insulating varnish: Add solid epoxy resin, anti-settling agent, defoamer, and solvent xylene into a reactor, disperse for 30 minutes, control the temperature at 50℃, add xylene to adjust the viscosity, and discharge to obtain component A;

[0067] Preparation of component B: Mix polyamide curing agent, phenolic amine curing agent and xylene and stir for 30-40 minutes. Add a small amount of solvent to adjust the viscosity and discharge to obtain component B.

[0068] The amounts of each component in components A and B are shown in Table 1:

[0069] Table 1. Dosage of each component

[0070]

[0071] The pigment-to-binding mass ratio is 0.93, and the weight ratio of component A to component B is 2.4.

[0072] Example 2

[0073] This embodiment provides an epoxy resin insulating varnish and its preparation method, specifically:

[0074] The preparation method of polymer slurry is as follows: 10 parts of methyl isobutyl ketone and 1 part of isopropoxytris(dioctylpyrophosphoryloxy)titanate are added to a dispersion vessel and stirred at 200 r / min for 30 min. Then, 3 parts of talc, 35 parts of barium sulfate and 15 parts of titanium dioxide are added. The temperature is raised to 80℃ and stirred at 500 r / min for 1 h. After cooling to 40℃, 24 parts of liquid epoxy resin E51 are added and stirred at 500 r / min for 1 h. After cooling, it is ready for use.

[0075] Preparation of component A of epoxy resin insulating varnish: Add solid epoxy resin, anti-settling agent, defoamer and solvent C into a kettle and disperse for 20-50 min. Then add pigments and fillers and disperse to a fineness of 40-50 μm. Control the temperature at 50-55℃, add solvent C to adjust the viscosity, and discharge the material to obtain component A.

[0076] Preparation of component B: Mix and stir the polyamide curing agent, phenolic amine curing agent and solvent D for 30-40 minutes, add a small amount of solvent to adjust the viscosity, and discharge to obtain component B.

[0077] The amounts of each component in components A and B are shown in Table 2:

[0078] Table 2. Dosage of each component

[0079]

[0080] The pigment-to-binding mass ratio is 0.93, and the weight ratio of component A to component B is 2.3.

[0081] Example 3

[0082] This embodiment provides an epoxy resin insulating varnish and its preparation method, specifically:

[0083] The preparation method of the polymer slurry is as follows: 6 parts of propylene glycol methyl ether and 0.3 parts of isopropoxytris(dioctylpyrophosphoryloxy)titanate are added to a dispersion vessel and stirred at 200 r / min for 30 min. Then, 5 parts of talc, 25 parts of barium sulfate and 18 parts of titanium dioxide are added. The temperature is raised to 80℃ and stirred at 500 r / min for 1 h. After cooling to 40℃, 14 parts of liquid epoxy resin E51 are added and stirred at 500 r / min for 1 h. After cooling, it is ready for use.

[0084] Preparation of component A of epoxy resin insulating varnish: Add solid epoxy resin, anti-settling agent, defoamer and solvent into a kettle, disperse for 30 min, control the temperature at 50℃, add solvent to adjust viscosity, discharge the material to obtain component A;

[0085] Preparation of component B: Mix and stir the polyamide curing agent, phenolic amine curing agent and solvent D for 30-40 minutes, add a small amount of solvent to adjust the viscosity, and discharge to obtain component B.

[0086] The amounts of each component in components A and B are shown in Table 3:

[0087] Table 3. Dosage of each component

[0088]

[0089] The pigment-to-binding mass ratio is 0.97, and the weight ratio of component A to component B is 2.5.

[0090] Example 4

[0091] The difference between this embodiment and Example 1 is that 3-(2,3-epoxypropyl)propyltrimethoxysilane is used instead of n-octyltriethoxysilane in Example 1, while the other conditions are the same as in Example 1.

[0092] Comparative Example 1

[0093] This comparative example provides an epoxy resin insulating varnish and its preparation method. The pigment-to-binder ratio of this comparative example is 1.22, the ratio of component A to component B is 2.6:1, and the specific components are shown in Table 4. The other conditions are the same as in Example 1.

[0094] Table 4. Dosage of each component

[0095]

[0096] The pigment-to-binding mass ratio is 1.90, and the weight ratio of component A to component B is 2.6:1.

[0097] Comparative Example 2

[0098] This comparative example provides an epoxy resin insulating varnish and its preparation method. The pigment-to-binder ratio of this comparative example is 1.14, the ratio of component A to component B is 3:1, and it does not include epoxy resin E20 in Example 1. The other conditions are the same as in Example 1.

[0099] Comparative Example 3

[0100] This comparative example provides an epoxy resin insulating varnish and its preparation method. The pigment-to-binder ratio in this comparative example is 1.43, the ratio of component A to component B is 2.6:1, no polyamide curing agent is used, and the other conditions are the same as in Example 1.

[0101] Comparative Example 4

[0102] This comparative example provides an epoxy resin insulating varnish and its preparation method. The pigment-to-binder ratio of this comparative example is 1.47, the ratio of component A to component B is 2.6:1, zinc sulfate is used to replace talc powder as pigment and filler, and the other conditions are the same as in Example 1.

[0103] Test case

[0104] The epoxy resin insulating varnishes prepared in the examples and comparative examples were tested. During board preparation, components A and B were mixed according to the specified ratio, then sprayed to create samples. Specific results are shown in Table 5. The test methods are as follows:

[0105] The coating was sprayed onto the front, back, and sides of a suitably sized steel plate, completely covering the plate. The dried steel plate was then immersed in a sealed glass container filled with insulating oil (experimental group). Another glass container was also filled with insulating oil but without the steel plate (blank group). Both groups of containers were then placed in an oven heated to 105°C and left for one week. The insulating oil was then removed from both containers, and its dielectric loss coefficient was measured. The coefficients of the oil in the blank and experimental groups were compared; the changes in these two coefficients represent the dielectric loss dilution change.

[0106] Color change: as per DL / T 1836.

[0107] Change in dielectric loss coefficient (%): according to DL / T 1836.

[0108] Interfacial tension: as per DL / T 1836.

[0109] Resistance to neutral salt spray: GB / T 1771.

[0110] Table 5 Performance Tests of Epoxy Resin Insulating Coating

[0111]

[0112] As can be seen from Comparative Example 1, an excessively high pigment-to-binder ratio will cause defects in the coating film. A high pigment-to-binder ratio results in weak internal density of the coating, and the porosity affects the coating's shielding properties, potentially leading to the seepage of transformer oil into the carbon steel substrate, affecting the transformer oil's insulation. A low pigment-to-binder ratio results in insufficient rust prevention, easy blistering after 1000 hours of salt spray testing, and more impurities in the insulating oil leading to more pronounced color changes and greater changes in the dielectric loss coefficient. Poor film sealing (causing iron ions to migrate from the substrate) or the presence of migratory ions in the coating itself are considered contributing factors to color changes.

[0113] Comparing Example 1 and Comparative Example 2, it can be seen that using a single liquid epoxy resin results in good compatibility of the coating with the transformer oil, without affecting its insulation properties. However, the coating exhibits poor physical properties; slight cracking occurs during high and low temperature cycling tests, posing a risk of peeling off in practical applications.

[0114] Comparing Example 1 and Comparative Example 3, it can be seen that using a phenolic amine curing agent with high crosslinking degree and fast reaction speed results in excellent compatibility of the coating with transformer oil, without affecting the insulation properties of the transformer oil. However, the physical properties of the same coating are poor, and blistering occurs in the salt spray resistance, which may be related to the excessively rapid reaction of the phenolic epoxy.

[0115] Comparing Example 1 and Comparative Example 4, it can be seen that the use of anti-rust pigments can improve the salt spray resistance of the coating. However, the coating has poor compatibility with transformer oil, which may be because ions in the anti-rust pigments migrate into the transformer oil, thereby affecting the insulation of the transformer oil.

[0116] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An epoxy resin insulating varnish, characterized in that, It consists of component A and component B. The raw materials for preparing component A include, by weight, 15-25 parts of solid epoxy resin and 68-100 parts of polymer slurry; wherein, the raw materials for preparing the polymer slurry include, by weight, 14-24 parts of liquid epoxy resin, 45-55 parts of shielding filler, 0.3-1 parts of siloxane compound and 6-10 parts of solvent. The shielding filler includes talc, barium sulfate, and titanium dioxide; by weight, the weight ratio of the talc, barium sulfate, and titanium dioxide is 3-5:25-35:15-18. The siloxane compound is isopropoxytris(dioctylpyrophosphoryloxy)titanate, 3 (2,3 At least one of glycidyl(o-propyl)propyltrimethoxysilane; The raw materials for preparing component B include, by weight, 10-20 parts of polyamide curing agent and 10-15 parts of phenolic curing agent; The epoxy value of the solid epoxy resin is 0.48~0.54 mol / 100g; The epoxy value of the liquid epoxy resin is 0.2~0.23 mol / 100g; The pigment-to-binder ratio in the epoxy resin insulating varnish is 0.9~1.1; The weight ratio of component A to component B is (2~3):

1.

2. The epoxy resin insulating varnish according to claim 1, characterized in that, The raw materials for preparing component A also include an anti-settling agent.

3. A method for preparing an epoxy resin insulating varnish as described in claim 1 or 2, characterized in that, include: Preparation of component A: The raw materials for preparing component A are mixed, dispersed, heated, and then the viscosity is adjusted. Preparation of component B: The raw materials for preparing component B are mixed and dispersed and the viscosity is adjusted.

4. The preparation method according to claim 3, characterized in that, The preparation method of the polymer slurry includes: mixing and stirring the solvent and the siloxane compound, adding the shielding filler, heating to 60~80℃, stirring for 1~2h, cooling to 40~50℃, adding the liquid epoxy resin, stirring at high speed for 1~2h, and cooling for later use.

5. The application of an epoxy resin insulating varnish as described in claim 1 or 2 in electrical equipment.

6. The application according to claim 5, characterized in that, The electrical equipment includes at least one of transformers, instrument transformers, switchgear, rectifier cables, and capacitors.

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