A solvent-free epoxy anhydride impregnating resin, its preparation method and application

Abstract

The application belongs to the technical field of insulating materials, and particularly relates to a solvent-free epoxy anhydride impregnating resin as well as a preparation method and application thereof. The solvent-free epoxy anhydride impregnating resin comprises component A and component B. The component A comprises an epoxy resin and a diluent, and the component B comprises a curing agent, an accelerator and a defoaming agent. The epoxy resin comprises a modified naphthalene type epoxy resin and a bisphenol A type epoxy resin. The solvent-free epoxy anhydride impregnating resin can better balance heat resistance, toughness and dielectric loss.

Description

Technical Field

[0001] This invention belongs to the field of insulating materials technology, and specifically relates to a solvent-free epoxy anhydride impregnating resin, its preparation method, and its application. Background Technology

[0002] Solvent-free epoxy anhydride impregnation resins are widely used in vacuum pressure impregnation (VPI) processes for high-voltage electrical equipment such as motors and transformers due to their excellent electrical insulation properties, low volatility, and good curing characteristics. As electrical equipment develops towards higher power density, higher reliability, and longer lifespan, higher requirements are placed on the heat resistance, crack resistance, and high-temperature dielectric properties of the impregnation resin. Existing solvent-free epoxy anhydride impregnation resins often use high-functionality epoxy resins or epoxy resins containing rigid skeletons to improve the heat resistance index (TI) of the resin system. However, these high-heat-resistant epoxy resins often have excessively high crosslinking density or strong molecular chain rigidity, resulting in brittle cured products that are prone to cracking under thermal cycling or mechanical impact; at the same time, their melt viscosity is usually high, which adversely affects the penetration and ease of operation of the impregnation process.

[0003] CN118813002A uses pretreated bisphenol A and bisphenol F epoxy resins, combined with specific reactive diluents, dispersants, and defoamers, to prepare a low-viscosity, high-purity epoxy anhydride impregnation resin through a specific distillation process and compounding method, and then cures it through a vacuum pressure impregnation process. This improves the resin's electrical properties, mechanical strength, and heat resistance, reduces the system viscosity, enhances the flexibility and thermal shock resistance of the cured product, and lowers production costs, making it a viable alternative to domestically produced resins. However, because it uses ordinary bisphenol A and bisphenol F epoxy resins, the thermal decomposition temperature and glass transition temperature of the crosslinked network after curing are relatively low, making it difficult to meet heat resistance ratings above H. Furthermore, the C12-C14 alkyl glycidyl ethers used contain long-chain alkyl and ether bonds, and the o-tolyl glycidyl ether contains aromatic ether structures; both may increase the dielectric loss factor at high temperatures. CN101864058A uses a room-temperature impregnation type epoxy anhydride heat-resistant resin. It combines molecularly distilled bisphenol A type epoxy resin with a multifunctional, low-viscosity epoxy reactive diluent and a specific curing accelerator to achieve vacuum pressure impregnation and curing at room temperature, avoiding high-temperature curing. This improves the resin's heat resistance and mechanical strength, reduces dielectric loss, and is suitable for thinning insulation in high-voltage motors, extending service life and reducing production costs. However, it cannot effectively absorb thermal stress, and the cured product is prone to cracking under thermal shock conditions.

[0004] Therefore, there is an urgent need to develop a solvent-free epoxy anhydride impregnation resin that combines high heat resistance, excellent crack resistance, and low high-temperature dielectric loss. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a solvent-free epoxy anhydride impregnating resin, its preparation method, and its applications. The solvent-free epoxy anhydride impregnating resin of this invention achieves a better balance between heat resistance, toughness, and dielectric loss.

[0006] In this invention, unless otherwise specified, room temperature refers to 20~25℃.

[0007] The first aspect of the present invention provides a solvent-free epoxy anhydride impregnation resin, comprising component A and component B, wherein component A comprises epoxy resin and diluent, and component B comprises curing agent, accelerator and defoamer; wherein the epoxy resin comprises modified naphthalene-type epoxy resin and bisphenol A-type epoxy resin.

[0008] The ratio of epoxy resin and diluent in component A affects the process viscosity of the impregnating resin and the crosslinking density of the final cured product to a certain extent. Epoxy resin (including modified naphthalene-type epoxy and bisphenol A-type epoxy) is the main component forming the three-dimensional network structure, providing heat resistance and mechanical strength; the diluent is used to reduce the system viscosity and increase flexibility. If the epoxy resin content is too high, the resin viscosity will be too high, making it difficult to fully penetrate into the fine gaps of the coil or winding, and the cured product will be brittle. If the epoxy resin content is too low, the crosslinking density will be too low, leading to a significant decrease in heat resistance and mechanical strength. Preferably, component A comprises 60-90 parts of epoxy resin and 10-25 parts of diluent by weight. More preferably, component A comprises 75-85 parts of epoxy resin and 14-22 parts of diluent by weight.

[0009] The curing agent in component B and the epoxy groups in component A determine the crosslinking density and degree of curing. Insufficient curing agent leads to incomplete curing, leaving a large amount of residual epoxy groups, which reduces heat resistance and dielectric properties; excessive curing agent introduces free anhydride into the system, reducing insulation resistance upon moisture absorption. The accelerator is a highly efficient catalyst for the epoxy-anhydride curing reaction; insufficient accelerator results in excessively long curing times and higher curing temperatures, while excessive accelerator leads to an overly vigorous reaction. Preferably, component B comprises 35-50 parts of curing agent, 0.1-1 parts of accelerator, and 0.1-0.5 parts of defoamer by weight. More preferably, component B comprises 40-44 parts of curing agent, 0.5-0.8 parts of accelerator, and 0.15-0.3 parts of defoamer by weight.

[0010] Preferably, the weight ratio of the modified naphthalene-type epoxy resin to the bisphenol A-type epoxy resin is (3~7):1, more preferably (4~6):1.

[0011] In this invention, modified naphthalene-type epoxy resin provides high heat resistance, but it is also rigid and expensive; bisphenol A type epoxy resin (such as NPEL-127E) has moderate flexibility and low viscosity, and good compatibility with modified naphthalene-type resin. By controlling the weight ratio of modified naphthalene-type epoxy resin to bisphenol A type epoxy resin within the aforementioned range, this invention achieves a better balance between heat resistance, toughness, and economy.

[0012] Preferably, the weight ratio of component A to component B is (1.5~3):1, more preferably (2~2.6):1.

[0013] Modified naphthalene-type epoxy resin Preferably, the preparation method of the modified naphthalene-type epoxy resin includes: (1) In the presence of 1,4-dioxane, p-aminophenol and paraformaldehyde undergo a first reaction, followed by the addition of 3-glycidyl etheroxypropyltrimethoxysilane for a second reaction, and finally the removal of 1,4-dioxane to obtain the modified coupling agent. (2) Naphthalene-type epoxy resin, modified coupling agent and dibutyltin dilaurate are modified to obtain modified naphthalene-type epoxy resin.

[0014] The use of modified naphthalene-type epoxy resin in this invention can better increase the heat resistance and toughness of solvent-free epoxy anhydride impregnating resin. Although the tanδ of unmodified naphthalene-type epoxy resin is lower, the heat resistance and toughness are severely reduced, failing to meet the H-class insulation requirements. It is speculated that this is because the modified naphthalene-type epoxy resin, through grafting a rigid benzoxazine structure, can improve the thermal stability and glass transition temperature of the crosslinked network, thereby significantly improving the heat resistance index. At the same time, bisphenol A-type epoxy resin, as a flexible auxiliary component, forms a moderately blended network with the modified naphthalene-type resin, which avoids the excessive brittleness that may result from a single modified resin, and also adjusts the viscosity and cost of the system. The two work synergistically to achieve a balance between high heat resistance, good crack resistance, and acceptable dielectric loss.

[0015] Paraformaldehyde is a polymer of formaldehyde, and its model number is Delrin 100 BK602.

[0016] More preferably, the molar ratio of p-aminophenol to paraformaldehyde is 1:(1~3).

[0017] More preferably, the amount of 1,4-dioxane used is: 400-600 mL of 1,4-dioxane for every 1 mol of p-aminophenol.

[0018] More preferably, in step (1), the conditions for the first reaction include: stirring at 75~85°C for 20~50 minutes, preferably stirring at 80°C for 30 minutes.

[0019] More preferably, in step (1), 3-glycidyl etheroxypropyltrimethoxysilane is added to the reaction system by dropping, preferably over 20 to 40 minutes.

[0020] More preferably, in step (1), the conditions for the second reaction include: reflux reaction at 100~115°C for 3~5 hours under nitrogen protection.

[0021] The method for removing 1,4-dioxane in step (1) above can be a conventional method in the art, including but not limited to vacuum distillation. This method is a conventional technical means in the art, and the present invention will not elaborate on it.

[0022] Preferably, the epoxy value of the naphthalene-type epoxy resin is 0.5-0.8 equivalents / 100g, more preferably 0.65-0.73 equivalents / 100g, including but not limited to EBA-65 naphthalene-type epoxy resin.

[0023] Preferably, the mass of the modified coupling agent is 3% to 6% of the mass of the naphthalene-type epoxy resin, more preferably 5%.

[0024] Preferably, the mass of the dibutyltin dilaurate is 0.1% to 0.3% of the mass of the naphthalene-type epoxy resin, more preferably 0.15%.

[0025] Preferably, in step (2), the conditions for the modification reaction include: stirring at 115~125°C for 2~3.5 hours under nitrogen protection.

[0026] The modification reaction in step (2) above can be carried out in a conventional reaction vessel in the art. First, naphthalene-type epoxy resin can be added to the reaction vessel, heated to 115~125°C under nitrogen protection, stirred until completely melted, and then the modified coupling agent and dibutyltin dilaurate can be added to continue the modification reaction.

[0027] Bisphenol a-type epoxy resin Preferably, the epoxy equivalent of the bisphenol A type epoxy resin is 170-195 g / eq, more preferably 184-190 g / eq. The bisphenol A type epoxy resin in this invention is commercially available, including but not limited to Nan Ya epoxy resin NPEL-127E. As mentioned above, the bisphenol A type epoxy resin has excellent compatibility with modified naphthalene type epoxy resin and can be combined with the modified naphthalene type epoxy resin to adjust the system viscosity and crosslinking density, enabling the cured product to maintain high thermomechanical properties and electrical insulation properties.

[0028] Diluent Preferably, the diluent comprises aliphatic diol diglycidyl ether.

[0029] More preferably, the aliphatic diol diglycidyl ether is a combination of 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether (preferably with a degree of polymerization of 2 to 4), and neopentyl glycol diglycidyl ether, preferably in a weight ratio of (3 to 5): (2 to 4): (1 to 3).

[0030] In this invention, it was found that using modified naphthalene-type epoxy resin increases the heat resistance of solvent-free epoxy anhydride impregnated resin. However, when the amount of diluent is low, the brittleness of the solvent-free epoxy anhydride impregnated resin increases. In this invention, using a specific amount of diluent not only increases the toughness of the solvent-free epoxy anhydride impregnated resin, but also further increases the heat resistance and other properties of the solvent-free epoxy anhydride impregnated resin by controlling the diluent to be a specific weight ratio of 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether. Possible reasons are: 1,4-Butanediol diglycidyl ether has short chain segments and relatively low polarity, resulting in low viscosity and rapid reactivity; polypropylene glycol diglycidyl ether has long chain segments and contains ether bonds, providing excellent flexibility and thermal shock resistance, but too many ether bonds will increase high-temperature dielectric loss; neopentyl glycol diglycidyl ether contains side methyl groups, which enables the system to have good hydrolytic stability and moderate toughness, but excessive amounts will lead to uneven crosslinking and increased brittleness due to steric hindrance. Controlling the ratio of the three within a specific range can achieve the best balance between reducing process viscosity, toughening and crack resistance, and controlling dielectric loss.

[0031] Furthermore, when the amount of diluent is too small, the heat resistance and dielectric properties of the solvent-free epoxy anhydride impregnated resin cannot meet the requirements. When the amount of diluent is too large, it reduces the heat resistance of the solvent-free epoxy anhydride impregnated resin. It is speculated that this is because when the amount of diluent is too large, the flexible segments are excessive, the contribution of the rigid naphthalene ring and oxazine ring is over-diluted, the heat resistance decreases significantly, and the large number of ether bonds causes the dielectric loss to become uncontrolled.

[0032] Curing agent Preferably, the curing agent is selected from alicyclic anhydride curing agents. More preferably, the alicyclic anhydride curing agent includes at least one of methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, and methyltetrahydrophthalic anhydride, and more preferably methyltetrahydrophthalic anhydride. Alicyclic anhydride curing agents (especially methyltetrahydrophthalic anhydride) can give the resin system moderate reactivity, low mixing viscosity, and excellent heat resistance and dielectric properties.

[0033] Accelerator Preferably, the accelerator is selected from at least one of 2-ethyl-4-methylimidazole (2E4MZ), 2-methylimidazole, 1-methylimidazole, 2-phenylimidazole, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), benzyldimethylamine (BDMA), triethylamine, and triphenylphosphine (TPP), more preferably 2-ethyl-4-methylimidazole (2E4MZ). Using the aforementioned accelerator can efficiently catalyze the epoxy-anhydride curing reaction, achieving rapid and complete crosslinking, while maintaining good storage stability and excellent dielectric properties of the resin system.

[0034] Defoaming agent The defoamer may be of conventional types in the art, including but not limited to BYK 057 defoamer.

[0035] A second aspect of the present invention provides a method for preparing a solvent-free epoxy anhydride impregnating resin, the method comprising: S1. Heat the epoxy resin to 75~85℃, then add the diluent and stir at 75~85℃ for 20~40 minutes. Stop heating and cool to room temperature while stirring to obtain component A. S2. Stir the accelerator, curing agent, and defoamer at 65~75℃ for 20~40 minutes, stop heating, and cool to room temperature while stirring to obtain component B.

[0036] In step S2 of this invention, the curing agent and defoamer can be added to the reactor first, heated to 65~75°C, and then the accelerator can be added while stirring, and stirring can continue for 20~40 minutes.

[0037] The third aspect of the present invention provides the application of the solvent-free epoxy anhydride impregnating resin described in the first aspect of the present invention in the preparation of electrical insulating materials, preferably in the application of vacuum pressure impregnation (VPI) insulation treatment of motor coils, transformers or electronic components.

[0038] More preferably, the application includes the following steps: 1) Preheat component A to 60~70℃ and component B to 45~55℃. Then mix component A and component B and stir at 65~75℃ for 15~30 minutes. After that, degas at 65~75℃ and -0.095 MPa vacuum for 15~30 minutes to obtain the impregnation solution. 2) Immerse the workpiece to be impregnated (preferably a stranded pair, coil, or winding) into the impregnation solution for 5-30 seconds, then lift it out and hang it vertically to drip dry for 5-15 minutes; 3) The impregnated workpiece is cured to obtain an insulating product. Preferably, the curing process in step 3) adopts a stepped curing procedure: the temperature is increased to 110-130°C at a rate of 3-10°C / min and held for 1-3 hours; then the temperature is increased to 150-170°C at a rate of 3-10°C / min and held for 2-5 hours; finally, the temperature is increased to 190-210°C at a rate of 3-10°C / min and held for 4-8 hours, and then naturally cooled to room temperature to obtain the insulating product.

[0039] Compared with the prior art, the solvent-free epoxy anhydride impregnation resin of the present invention has at least the following beneficial effects: 1. It has excellent heat resistance and can meet the heat resistance requirements of electrical insulation systems of class H and above.

[0040] 2. It has excellent flexibility, which can overcome the shortcomings of traditional high heat-resistant epoxy anhydride resins, such as high brittleness and easy cracking.

[0041] 3. It has low dielectric loss, which can ensure long-term insulation reliability. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the following examples and comparative examples: the paraformaldehyde is Delrin 100 BK602; the bisphenol A epoxy resin is Nan Ya Epoxy Resin NPEL-127E. Example

[0044] I. Preparation of modified naphthalene-type epoxy resin: (1) Dissolve p-aminophenol and paraformaldehyde in 1,4-dioxane (1 mol of p-aminophenol is used in 500 mL of 1,4-dioxane) in a molar ratio of 1:2. Under nitrogen protection, stir the reaction at 80 °C for 30 minutes. Then, add 3-glycidyl etheroxypropyltrimethoxysilane dropwise at 80 °C, controlling the dropwise addition to be completed in 30 minutes. After the dropwise addition is completed, heat the reaction mixture to 102±2 °C under nitrogen protection and reflux for 4 hours. After the reaction is completed, remove 1,4-dioxane by vacuum distillation of the resulting reaction solution to obtain the modified coupling agent. (2) Add EBA-65 naphthalene epoxy resin to a reactor, heat to 120°C under nitrogen protection, stir until completely melted, add modified coupling agent and dibutyltin dilaurate, continue stirring at 120°C for 3 hours, stop the reaction, cool to room temperature, take the material, and obtain modified naphthalene epoxy resin; wherein, the mass of modified coupling agent is 5% of the mass of EBA-65 naphthalene epoxy resin, and the mass of dibutyltin dilaurate is 0.15% of the mass of EBA-65 naphthalene epoxy resin.

[0045] II. Preparation of solvent-free epoxy anhydride impregnating resin: S1. By weight, prepare 65 parts of modified naphthalene-type epoxy resin, 15 parts of bisphenol A-type epoxy resin, 8 parts of 1,4-butanediol diglycidyl ether, 6 parts of polypropylene glycol diglycidyl ether (degree of polymerization 3), 4 parts of neopentyl glycol diglycidyl ether, 42 parts of methyltetrahydrophthalic anhydride, 0.6 parts of 2E4MZ accelerator, and 0.2 parts of BYK 057 defoamer; S2. Add the modified naphthalene-type epoxy resin and bisphenol A-type epoxy resin to reactor A and heat to 80°C. Then add 1,4-butanediol diglycidyl ether, polypropylene glycol diglycidyl ether (degree of polymerization 3) and neopentyl glycol diglycidyl ether. Stir at 80±2°C for 30 minutes and then stop heating. Cool to room temperature while stirring to obtain component A. S3. Add methyltetrahydrophthalic anhydride and BYK 057 defoamer to reactor B1, heat to 70±2℃, then add 2E4MZ accelerator while stirring, continue stirring for 30 minutes, stop heating, and cool to room temperature while stirring to obtain component B. Example

[0046] The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnating resin, step S1, by weight, prepares 70 parts of modified naphthalene-type epoxy resin, 10 parts of bisphenol A-type epoxy resin, 6 parts of 1,4-butanediol diglycidyl ether, 5 parts of polypropylene glycol diglycidyl ether (degree of polymerization 3), 3 parts of neopentyl glycol diglycidyl ether, 44 parts of methyltetrahydrophthalic anhydride, 0.6 parts of 2E4MZ accelerator, and 0.2 parts of BYK 057 defoamer.

[0047] The rest is the same as in Example 1. Example

[0048] The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnating resin, step S1, by weight, prepares 60 parts of modified naphthalene-type epoxy resin, 20 parts of bisphenol A-type epoxy resin, 10 parts of 1,4-butanediol diglycidyl ether, 7 parts of polypropylene glycol diglycidyl ether (degree of polymerization 3), 5 parts of neopentyl glycol diglycidyl ether, 40 parts of methyltetrahydrophthalic anhydride, 0.6 parts of 2E4MZ accelerator, and 0.2 parts of BYK 057 defoamer.

[0049] The rest is the same as in Example 1.

[0050] Comparative Example 1 The method of Example 1 is followed, except that in the preparation of the modified naphthalene-type epoxy resin, the modified coupling agent is replaced with KH-550 coupling agent, and the rest is the same as in Example 1. The modified naphthalene-type epoxy resin is obtained, and the solvent-free epoxy anhydride impregnating resin is prepared using the modified naphthalene-type epoxy resin according to the method of Example 1.

[0051] Comparative Example 2 The method of Example 1 is the same, except that in the preparation of the solventless epoxy anhydride impregnation resin, EBA-65 naphthalene-type epoxy resin is used instead of the modified naphthalene-type epoxy resin in Example 1.

[0052] The rest is the same as in Example 1.

[0053] Comparative Example 3 The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnation resin, the amount of 1,4-butanediol diglycidyl ether is 14 parts, polypropylene glycol diglycidyl ether (degree of polymerization 3) is 2 parts, and neopentyl glycol diglycidyl ether is 2 parts.

[0054] The rest is the same as in Example 1.

[0055] Comparative Example 4 The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnation resin, the amount of 1,4-butanediol diglycidyl ether is 2 parts, polypropylene glycol diglycidyl ether (degree of polymerization 3) is 14 parts, and neopentyl glycol diglycidyl ether is 2 parts.

[0056] The rest is the same as in Example 1.

[0057] Comparative Example 5 The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnation resin, the amount of 1,4-butanediol diglycidyl ether is 2 parts, polypropylene glycol diglycidyl ether (degree of polymerization 3) is 2 parts, and neopentyl glycol diglycidyl ether is 14 parts.

[0058] The rest is the same as in Example 1.

[0059] Comparative Example 6 The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnation resin, the amount of 1,4-butanediol diglycidyl ether is 4 parts, polypropylene glycol diglycidyl ether (degree of polymerization 3) is 2 parts, and neopentyl glycol diglycidyl ether is 2 parts.

[0060] The rest is the same as in Example 1.

[0061] Comparative Example 7 The method of Example 1 differs in that, in the preparation of the solvent-free epoxy anhydride impregnation resin, the amount of 1,4-butanediol diglycidyl ether is 18 parts, polypropylene glycol diglycidyl ether (degree of polymerization 3) is 12 parts, and neopentyl glycol diglycidyl ether is 8 parts.

[0062] The rest is the same as in Example 1.

[0063] Performance testing Sample preparation: After preheating component A to 65°C and component B to 50°C, they were added to a mixer and stirred at 70°C for 20 minutes. Then, the mixture was degassed at 70°C and under a vacuum of -0.095 MPa for 20 minutes to obtain a solvent-free epoxy anhydride impregnating resin. Using 1.2 mm bare copper wire (annealed state), twisted 20-24 strands per meter, with a length of 300 mm, and removing 10 mm of insulation from both ends, the stranded wire pairs were vertically immersed in solvent-free epoxy anhydride impregnation resin for 10 seconds, then slowly lifted out and hung vertically to drip dry for 10 minutes before being placed in an air-circulating oven and treated at 200±2℃ for 48 hours to obtain stranded wire pair sample A. Sample A is a sample that has undergone special high-temperature curing treatment for accelerated thermal aging evaluation.

[0064] Using 1.2mm bare copper wire (annealed state), twisted 20-24 strands per meter, with a length of 300mm, and removing 10mm of insulation from both ends, the stranded wire pair was vertically immersed in solvent-free epoxy anhydride impregnation resin. After immersion for 10 seconds, it was slowly lifted out for curing (step curing: room temperature temperature increased to 120℃ at 5℃ / min / holding for 2h → temperature increased to 160℃ at 5℃ / min / holding for 4h → temperature increased to 200℃ at 5℃ / min / holding for 6h), stranded wire pair sample B was obtained.

[0065] Temperature index (TI) determination by hot-spot tilt method: Reference standards GB / T11026.1-2016, JB / T 1544-2015, and GB / T 1408.1-2016.

[0066] Take a portion of the insulating layer of sample A, machine it into 100-150 mesh powder, test it in TGA (normal pressure dry air, 5℃ / min), obtain the thermogravimetric curve, and calculate the apparent activation energy and the slope b of the thermal lifetime equation. Twenty-one samples A were taken and aged at 240°C. Every 72 hours, the samples were removed and placed at (23±2)℃ / RH (50±5)% for 6 hours. Then, a withstand voltage test (1.0kV, 1s) was conducted in accordance with GB / T1408.1-2016. During the withstand voltage test, the insulation layer was removed from both ends of the sample (exposing the conductor), and the sample was bent outward into a "V" shape. The upper end was then separated and fixed. The cumulative number of failures was recorded. If more than 11 samples failed the withstand voltage test, the material was deemed to have reached the failure endpoint. The temperature index was calculated according to JB / T1544-2015, taking into account the combined data of thermogravimetric analysis and isothermal aging.

[0067] Crack resistance test: Take three samples B and suspend them vertically in a 250℃ oven for 60 minutes. Remove them within 5 seconds and immerse them completely in a 20℃ water bath. Cool for 30 seconds and remove them. Repeat the above cycle three times. Inspect the insulation layer for cracks using a 10x magnifying glass. Cracks are classified as follows: Grade A: No cracks; Grade B: Minor cracks (≤2 cracks, each ≤2mm in length); Grade C: Severe cracks (>2 cracks or any crack with a length >2mm).

[0068] Dielectric loss factor test: A stranded wire pair was cut from sample B. A metal foil (copper foil, 15 mm wide) was tightly wrapped around the insulation layer of the stranded wire pair as an external electrode, and the exposed end of the wire was used as an internal electrode. Both ends were fixed with high-temperature resistant tape. A uniform tension of about 5 N was applied to ensure tight wrapping without air gaps. The test was conducted at 200±2℃, with a frequency of 50 Hz and an applied voltage of 500V. The tanδ value was read and recorded after stabilization. Three samples were tested, and the average value was taken.

[0069] The test results are shown in Table 1.

[0070] Table 1 Performance Test Results Ti Crack resistance 200° c. tan delta Example 1 188 Class A 0.0075 Example 2 189 Class A 0.0069 Example 3 188 Class A 0.0082 Comparative Example 1 175 Class B 0.0095 Comparative Example 2 170 Class C 0.0055 Comparative Example 3 183 Class B 0.0098 Comparative Example 4 182 Class A 0.0112 Comparative Example 5 184 Class C 0.0071 Comparative Example 6 186 Class C 0.0058 Comparative Example 7 176 Class A 0.0135 As can be seen from the above performance test results, the solvent-free epoxy anhydride impregnating resins in Examples 1 to 3 all exhibited excellent comprehensive performance: the heat resistance index reached above 185, the crack resistance was all Grade A, and the dielectric loss was controlled below 0.0082. This indicates that the modified naphthalene-type epoxy resin in the solvent-free epoxy anhydride impregnating resin of the present invention, combined with three glycidyl ethers in a specific proportion and total amount, can better balance heat resistance, toughness, and dielectric loss.

[0071] The comparative examples, lacking the necessary technical solutions of this invention, showed significantly inferior performance compared to the examples in relevant tests. Comparative Example 1 used a naphthalene-type epoxy resin (non-benzoxazine silane grafted) prepared by other modification methods, while Comparative Example 2 directly used unmodified EBA-65 naphthalene-type epoxy resin. Neither used the modified naphthalene-type epoxy resin of this invention. Consequently, when the final resin was used for impregnation varnish preparation, the heat resistance index of the final cured product was significantly reduced, and the crack resistance decreased. This demonstrates that the modified naphthalene-type epoxy resin of this invention can better increase the heat resistance and toughness of the final cured product within the system of this invention. In Comparative Examples 3-5, the proportions of the three aliphatic glycidyl ethers were not within the preferred range of this invention, resulting in varying degrees of performance degradation. Specifically, the crack resistance was reduced in Comparative Examples 3 and 5, and the dielectric loss exceeded the standard in Comparative Example 4. The results of Comparative Examples 3-5 indicate that the proportions of the three aliphatic glycidyl ethers have a significant impact on toughness and dielectric loss. When the proportions are not within the preferred range of this invention, it leads to a decrease in crack resistance or an excess of dielectric loss. In Comparative Examples 6 and 7, the amount of aliphatic glycidyl ether was not within the optimal range, and the product performance was reduced to varying degrees. Specifically, in Comparative Example 6, the amount of aliphatic glycidyl ether was too small, resulting in a decrease in crack resistance. In Comparative Example 7, the amount of aliphatic glycidyl ether was too large, resulting in a significant decrease in heat resistance index and excessive dielectric loss.

[0072] The above experimental results further demonstrate the importance of the technical solution defined in this invention to its technical effect.

[0073] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A solvent-free epoxy anhydride impregnation resin, characterized in that, It includes component A and component B. Component A includes epoxy resin and diluent, and component B includes curing agent, accelerator and defoamer. The epoxy resin includes modified naphthalene-type epoxy resin and bisphenol A-type epoxy resin. Methods for preparing modified naphthalene-type epoxy resins include: (1) In the presence of 1,4-dioxane, p-aminophenol and paraformaldehyde undergo a first reaction, followed by the addition of 3-glycidyl etheroxypropyltrimethoxysilane for a second reaction, and finally the removal of 1,4-dioxane to obtain the modified coupling agent. (2) Naphthalene-type epoxy resin, modified coupling agent and dibutyltin dilaurate are modified to obtain modified naphthalene-type epoxy resin.

2. The solvent-free epoxy anhydride impregnating resin according to claim 1, characterized in that, By weight, component A comprises 60-90 parts epoxy resin and 10-25 parts diluent; And / or, component B includes 35-50 parts of curing agent, 0.1-1 parts of accelerator, and 0.1-0.5 parts of defoamer.

3. The solvent-free epoxy anhydride impregnating resin according to claim 1, characterized in that, The weight ratio of the modified naphthalene-type epoxy resin to the bisphenol A-type epoxy resin is (3~7):1; And / or, the weight ratio of component A to component B is (1.5~3):

1.

4. The solvent-free epoxy anhydride impregnation resin according to claim 1, characterized in that, The molar ratio of p-aminophenol to paraformaldehyde is 1:(1~3). And / or, the amount of 1,4-dioxane used is: 400-600 mL of 1,4-dioxane for 1 mol of p-aminophenol.

5. The solvent-free epoxy anhydride impregnation resin according to claim 4, characterized in that, The mass of the modified coupling agent is 3% to 6% of the mass of the naphthalene-type epoxy resin; And / or, the mass of the dibutyltin dilaurate is 0.1% to 0.3% of the mass of the naphthalene-type epoxy resin.

6. The solvent-free epoxy anhydride impregnating resin according to claim 4, characterized in that, The epoxy value of the naphthalene-type epoxy resin is 0.5-0.8 equivalents / 100g.

7. The solvent-free epoxy anhydride impregnating resin according to claim 4, characterized in that, In step (1), the conditions for the first reaction include: stirring the reaction at 75~85℃ for 20~50 minutes; And / or, in step (1), the conditions for the second reaction include: reflux reaction at 100~115°C for 3~5 hours under nitrogen protection; And / or, in step (2), the conditions for the modification reaction include: stirring at 115~125°C for 2~3.5 hours under nitrogen protection.

8. The solvent-free epoxy anhydride impregnating resin according to claim 1, characterized in that, The epoxy equivalent of the bisphenol A type epoxy resin is 170~195 g / eq; And / or, the diluent includes aliphatic diol diglycidyl ether; And / or, the curing agent is selected from alicyclic anhydride curing agents; And / or, the accelerator is selected from at least one of 2-ethyl-4-methylimidazole, 2-methylimidazole, 1-methylimidazole, 2-phenylimidazole, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, triethylamine, and triphenylphosphine.

9. A method for preparing the solvent-free epoxy anhydride impregnating resin according to any one of claims 1 to 8, characterized in that, The preparation method includes: S1. Heat the epoxy resin to 75~85℃, then add the diluent and stir at 75~85℃ for 20~40 minutes. Stop heating and cool to room temperature while stirring to obtain component A. S2. Stir the accelerator, curing agent, and defoamer at 65~75℃ for 20~40 minutes, stop heating, and cool to room temperature while stirring to obtain component B.

10. The use of the solvent-free epoxy anhydride impregnating resin according to any one of claims 1 to 8 in the preparation of electrical insulating materials.