Moisture-resistant epoxy resin composition, and preparation method and application thereof

Abstract

This invention discloses an epoxy resin composition resistant to humid heat aging, its preparation method, and its application, relating to the field of electrical equipment insulation materials. It includes a composite resin system, a mixed anhydride curing agent, and a curing accelerator. The quaternary compounding of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, and alicyclic epoxy resin can balance thermal, mechanical, and electrical properties to a certain extent. The epoxy group POSS can work together with the resin network during the curing process. Subsequently, combined with the MHHPA / HHPA mixed anhydride curing system, this invention solves the problem that existing methods struggle to simultaneously achieve high glass transition temperature, low dielectric loss, low water absorption, and high breakdown field strength retention in humid heat environments, and lack a molecular-scale rigid-flexible co-curable structural design. It is particularly suitable for electrical equipment insulation components such as valve-side bushings of converter transformers used in ±800kV and above ultra-high voltage DC transmission.

Description

Technical Field

[0001] This invention relates to the field of insulating materials for power equipment, specifically to an epoxy resin composition resistant to humid heat aging, its preparation method and application, and is particularly suitable for valve side bushings of converter transformers for ultra-high voltage direct current transmission, composite insulator core rods and other insulating components that have been in long-term service in high temperature, high humidity and strong electric field environments. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) transmission technology is a key technology for achieving long-distance, high-capacity power transmission. Core insulating components such as the valve-side bushings of converter transformers and composite insulator core rods are subjected to long-term high temperature, high humidity, electric field, thermal stress, and mechanical stress coupling conditions, placing extremely high demands on the comprehensive thermal, mechanical, and electrical properties of the insulating materials. While traditional bisphenol A epoxy resin possesses high strength and good process adaptability, it is prone to water absorption in humid and hot environments, leading to increased dielectric loss, decreased glass transition temperature, deterioration of interfacial bonding, and a decline in long-term insulation reliability.

[0003] Existing technologies often employ modification methods such as blending alicyclic epoxy resins, silane-modified inorganic nanofillers, or organosilicon, but these still have the following shortcomings: First, traditional silane-modified inorganic nanofillers are external particle reinforcement methods, which still suffer from limited dispersion stability in the resin system, interface debonding after hygrothermal aging, and an increase in local defects, affecting the long-term maintenance of insulation performance; Second, using only one of hydrogenated bisphenol A type epoxy resin, alicyclic epoxy resin, or organosilicon resin for modification usually only improves one aspect of water absorption, flexibility, or some dielectric properties, making it difficult to simultaneously achieve high glass transition temperature, low dielectric loss, low water absorption, and high breakdown field strength retention; Third, in existing technologies, multiple resins or functional components are often introduced through simple blending, lacking a synergistic structural design that can jointly participate in anhydride curing and maintain network stability after hygrothermal aging, thus limiting the overall performance improvement.

[0004] Therefore, developing a moisture- and heat-resistant epoxy resin system that can be constructed at the molecular scale and is both rigid and flexible and can be co-cured to meet the long-term stable operation requirements of insulating components under harsh service conditions has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing methods are difficult to simultaneously achieve high glass transition temperature, low dielectric loss, low water absorption and high breakdown field strength retention of epoxy resin in humid and hot environments, and lack a synergistic structural design that combines rigidity and flexibility at the molecular scale and can be co-cured. The purpose is to provide an epoxy resin composition resistant to humid and hot aging, its preparation method and application.

[0006] The inventors surprisingly discovered that adding a single resin can only improve one aspect of water absorption, flexibility, or some dielectric properties, and that individual resin components often lead to a significant increase in some indicators while significantly decreasing others. However, a quaternary compound of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, and alicyclic epoxy resin can balance thermal, mechanical, and electrical properties to a certain extent. At the same time, the epoxy group POSS can work together with the resin network during the curing process. Afterwards, combined with a methylhexahydrophthalic anhydride (MHHPA) / hexahydrophthalic anhydride (HHPA) mixed anhydride curing system, the material can maintain a high glass transition temperature, a low increase in dielectric loss, and a high retention rate of breakdown field strength and mechanical properties even after hygrothermal aging, thereby improving the overall insulation performance and long-term service stability of the material.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides an epoxy resin composition resistant to damp heat aging, comprising:

[0009] The composite resin system specifically includes low-chlorinated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS, with a weight ratio of 35-45:15-25:8-15:8-15:1-5.

[0010] Mixed anhydride curing agent: including methylhexahydrophthalic anhydride and hexahydrophthalic anhydride, with a mass ratio of 7-9:1-3, and the amount used so that the molar ratio of total epoxy groups to total anhydride groups is 1:0.95-1.05;

[0011] Curing accelerator: 2,4,6-tris(dimethylaminomethyl)phenol, which accounts for 0.3% to 1.0% of the total resin.

[0012] In this scheme, the preferred mass ratio of methylhexahydrophthalic anhydride to hexahydrophthalic anhydride is 8:2, and the preferred molar ratio of total epoxy groups to total acid anhydride groups is 1:1.

[0013] In some preferred embodiments, the low-chlorinated bisphenol A type epoxy resin is a low-hydrolyzable chlorine type bisphenol A diglycidyl ether resin with a hydrolyzable chlorine content ≤1000 ppm.

[0014] In some preferred embodiments, the hydrogenated bisphenol A type epoxy resin is a hydrogenated bisphenol A diglycidyl ether type epoxy resin.

[0015] In some preferred embodiments, the epoxy-terminated methylphenylsiloxane resin contains terminal epoxy groups and a methylphenylsiloxane backbone that participate in the curing reaction; the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

[0016] In some preferred embodiments, the epoxy group POSS is a cage-like silsesquioxane compound containing multiple epoxy reactive groups.

[0017] In some preferred embodiments, the weight ratio of the low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS is 40:18-22:10-13:9-12:2-4.

[0018] Secondly, the present invention provides a method for preparing the above-mentioned epoxy resin composition resistant to damp heat aging, comprising the following steps:

[0019] S1, low-chlorinated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, epoxy-terminated methylphenylsiloxane resin and alicyclic epoxy resin are mixed at 70-90°C for 20-40 minutes under nitrogen protection to obtain a homogeneous resin mixture.

[0020] S2, add pre-dried epoxy group POSS to the resin mixture obtained in step S1, and stir at 90-110℃ for 30-60 minutes to obtain POSS synergistically reinforced resin matrix;

[0021] S3, Add mixed anhydride curing agent: Cool down to 60-75℃, add premixed methyl hexahydrophthalic anhydride and hexahydrophthalic anhydride in proportion to the POSS synergistic reinforced resin matrix obtained in step 2, and continue stirring for 20-40 minutes;

[0022] S4, Add curing accelerator: Cool the mixture obtained in step S3 to 25-40°C, add 2,4,6-tris(dimethylaminomethyl)phenol, and stir for 5-15 minutes;

[0023] S5, Vacuum degassing: The mixture obtained in step S4 is degassed under vacuum conditions;

[0024] S6, Curing: The degassed mixture is poured into a mold and subjected to a stepped temperature curing process to obtain the epoxy resin composition.

[0025] In some preferred embodiments, the heating temperature in step S1 is 80°C and the reaction time is 30 minutes; and / or the time in step S2 is 45 minutes and the reaction temperature is 100°C; and / or the stirring time in step S3 is 30 minutes; and / or the stirring time in step S4 is 10 minutes.

[0026] In some preferred embodiments, the vacuum degree of the vacuum degassing treatment in step S5 is not less than -0.095 MPa, and the time is 15 to 30 minutes; and / or the procedure of the stepped temperature curing treatment in step S6 is: first cure at 125°C for 2 hours, and then cure at 155°C for 5 hours.

[0027] Thirdly, the present invention provides an application of the above-mentioned moisture- and heat-resistant epoxy resin composition in the preparation of insulating components for power equipment, wherein the insulating components for power equipment include valve side bushings of converter transformers for ±800kV and above ultra-high voltage DC transmission, composite insulator core rod insulating components, or other moisture- and heat-resistant insulating components.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. To address the problems of easy agglomeration and interfacial debonding after humid heat in traditional external nanofillers, this invention uses epoxy-based POSS, which can participate in the curing reaction, as a molecular-level cage-like reinforcing component. Unlike conventional inert inorganic nanoparticles, epoxy-based POSS contains epoxy groups on its surface that can participate in the anhydride curing reaction. It can work together with the resin network during the curing process, thereby reducing the problems of particle agglomeration, interfacial defects, and insufficient interfacial stability after humid heat aging that are prone to occur in traditional nanofiller reinforcement methods.

[0030] 2. To address the challenge of achieving high thermal strength (Tg), low water absorption, and low dielectric loss simultaneously with a single modified component, this invention employs a synergistic compound design of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, and alicyclic epoxy resin. This quaternary compound can balance thermal, mechanical, and electrical properties to a certain extent. The low-chlorinated bisphenol A epoxy resin provides a high-rigidity framework and reduces migratable ionic impurities; the hydrogenated bisphenol A epoxy resin and alicyclic epoxy resin help reduce the system's polarity and hygroscopic tendency; and the epoxy-terminated methylphenylsiloxane resin introduces hydrophobic flexible segments, thereby enabling the system to better balance thermal properties, dielectric stability, and resistance to damp heat.

[0031] 3. To address the issues of insufficient synergistic effect and low network stability after hygrothermal aging in existing simple blend systems, this invention further employs an MHHPA / HHPA mixed anhydride curing system, which works synergistically with the aforementioned multi-component epoxy resin and epoxy-based POSS. This approach facilitates the formation of a denser and more stable cured network, enabling the material to maintain a high glass transition temperature, a low increase in dielectric loss, and a high retention rate of breakdown field strength and mechanical properties even after hygrothermal aging, thereby improving the material's overall insulation performance and long-term service stability. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0033] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0034] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of those different embodiments or examples.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Raw material description:

[0038] The low-chlorinated bisphenol A type epoxy resin used in the examples is preferably low-hydrolyzable chlorine type E51, and the epoxy value is preferably 0.51 eq / 100g to 0.54 eq / 100g.

[0039] In the embodiments, the hydrogenated bisphenol A type epoxy resin is preferably a hydrogenated bisphenol A diglycidyl ether type epoxy resin.

[0040] The epoxy-terminated methylphenylsiloxane resin in the embodiments is preferably a siloxane resin containing terminal epoxy groups and methyl and phenyl substituents in the main chain.

[0041] The alicyclic epoxy resin used in the examples is preferably 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

[0042] In the examples, the epoxy-based POSS is preferably a polyepoxy-functionalized cage-type silsesquioxane.

[0043] The curing agent is preferably a mixture of methylhexahydrophthalic anhydride and hexahydrophthalic anhydride in a ratio of 8:2.

[0044] The accelerator is 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30).

[0045] Raw material pretreatment: Epoxy POSS is dried under vacuum at 80-100℃ for 4-8 hours to remove adsorbed water and volatile small molecules.

[0046] To verify the effectiveness of the present invention, a detailed description is provided below through specific embodiments and comparative experiments.

[0047] Example 1: Sample EP-POSS-2

[0048] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0049] S1. Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes to make the resin components mix evenly.

[0050] S2, 8.2 g of epoxy POSS that has been vacuum dried at 90°C for 6 hours is added to the above mixture. The mixture is heated to 100°C and stirred for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix. The weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy POSS is approximately 41:20.7:12:10:1.7.

[0051] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0052] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0053] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and then pour it into a mold.

[0054] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, with a further curing at 175℃ / 2h if necessary. After natural cooling and demolding, the sample number EP-POSS-2 was obtained.

[0055] Example 2: Sample EP-POSS-3

[0056] Based on Example 1, the steps in this example are largely the same as those in Example 1, except that the mass of epoxy-based POSS is 12.3g. The weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin, and epoxy-based POSS is approximately 41:20.7:12:10:2.6.

[0057] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0058] S1. Weigh 200g of low-chlorinated bisphenol A type epoxy resin, 100g of hydrogenated bisphenol A type epoxy resin, 60g of epoxy-terminated methylphenylsiloxane resin and 50g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80℃ under nitrogen protection and stir for 30 minutes to make the resin components evenly mixed.

[0059] S2, add 12.3g of epoxy POSS that has been vacuum dried at 90°C for 6 hours to the above mixture, heat to 100°C and continue stirring for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0060] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0061] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0062] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and then pour it into a mold.

[0063] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding, resulting in sample number EP-POSS-3.

[0064] Example 3: Sample EP-POSS-5

[0065] Based on Example 1, the steps in this example are largely the same as those in Example 1, except that: the mass of epoxy POSS is 20.5g, and the weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy POSS is approximately 41:20.7:12:10:4.3.

[0066] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0067] S1. Weigh 200g of low-chlorinated bisphenol A type epoxy resin, 100g of hydrogenated bisphenol A type epoxy resin, 60g of epoxy-terminated methylphenylsiloxane resin and 50g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80℃ under nitrogen protection and stir for 30 minutes to make the resin components evenly mixed.

[0068] S2, add 20.5g of epoxy POSS that has been vacuum dried at 90°C for 6 hours to the above mixture, heat to 100°C and continue stirring for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0069] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0070] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0071] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and then pour it into a mold.

[0072] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding, resulting in sample number EP-POSS-5.

[0073] Example 4: Sample EP-R35-25-8-15-3

[0074] Based on Example 1, the steps in this example are largely the same as those in Example 1, except that the weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS is 35:25:8:15:3.

[0075] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0076] S1. Weigh 175 g of low-chlorinated bisphenol A type epoxy resin, 125 g of hydrogenated bisphenol A type epoxy resin, 40 g of epoxy-terminated methylphenylsiloxane resin and 75 g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes to make the resin components mix evenly.

[0077] S2, add 15 g of epoxy POSS that has been vacuum dried at 90°C for 6 hours to the above mixture, heat to 100°C and continue stirring for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0078] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0079] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0080] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and then pour it into a mold.

[0081] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding, resulting in sample number EP-R35-25-8-15-3.

[0082] Example 5: Sample EP-R45-15-15-8-3

[0083] Based on Example 1, the steps in this example are largely the same as those in Example 1, except that the weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS is 45:15:15:8:3.

[0084] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0085] S1. Weigh 225 g of low-chlorinated bisphenol A type epoxy resin, 75 g of hydrogenated bisphenol A type epoxy resin, 75 g of epoxy-terminated methylphenylsiloxane resin and 40 g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes to make the resin components mix evenly.

[0086] S1, add 15 g of epoxy POSS that has been vacuum dried at 90°C for 6 hours to the above mixture, heat to 100°C and continue stirring for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0087] S1, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0088] S1, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0089] S1. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and pour it into a mold.

[0090] S1 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding, resulting in sample number EP-R45-15-15-8-3.

[0091] Example 6: Sample EP-R42-18-13-9-3

[0092] Based on Example 1, the steps in this example are largely the same as those in Example 1, except that the weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS is 42:18:13:9:3.

[0093] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0094] S1. Weigh 210 g of low-chlorinated bisphenol A type epoxy resin, 90 g of hydrogenated bisphenol A type epoxy resin, 65 g of epoxy-terminated methylphenylsiloxane resin and 45 g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes to make the resin components mix evenly.

[0095] S2, add 15 g of epoxy POSS that has been vacuum dried at 90°C for 6 hours to the above mixture, heat to 100°C and continue stirring for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0096] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0097] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0098] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes, then pour it into a mold.

[0099] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding, resulting in sample number EP-R42-18-13-9-3.

[0100] Example 7: Sample EP-A73

[0101] Based on Example 1, the steps in this example are roughly the same as those in Example 1, except that the mass ratio of the MHHPA / HHPA mixed anhydride curing agent is 7:3.

[0102] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0103] S1. Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes to make the resin components mix evenly.

[0104] S2, 12.3 g of epoxy POSS that has been vacuum dried at 90°C for 6 hours is added to the above mixture, and the temperature is raised to 100°C and stirred for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0105] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 7:3 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0106] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0107] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and then pour it into a mold.

[0108] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding, resulting in sample number EP-A73.

[0109] Example 8: Sample EP-A91

[0110] Based on Example 1, the steps in this example are roughly the same as those in Example 1, except that the mass ratio of the MHHPA / HHPA mixed anhydride curing agent is 9:1.

[0111] The preparation steps of the epoxy resin composition resistant to humid heat aging are as follows:

[0112] S1. Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, add them to the reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes to make the resin components mix evenly.

[0113] S2, 12.3 g of epoxy POSS that has been vacuum dried at 90°C for 6 hours is added to the above mixture, and the temperature is raised to 100°C and stirred for 45 minutes to fully disperse the epoxy POSS and participate in the formation of the pre-reactive reinforcing matrix.

[0114] S3, then cool to 70°C, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 9:1 according to a total epoxy group to total anhydride group molar ratio of 1:1, and continue stirring for 25 minutes.

[0115] S4, after cooling to room temperature, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes.

[0116] S5. Degas the mixture under a vacuum of -0.098 MPa for 20 minutes and then pour it into a mold.

[0117] S6 was cured using a stepped curing process of 125℃ / 2h + 155℃ / 5.5h, followed by natural cooling and demolding to obtain sample number EP-A9.

[0118] Comparative Example 1: Pure low-chlorinated bisphenol A type epoxy resin system

[0119] Weigh 400 g of low-chlorinated bisphenol A type epoxy resin. Based on a total epoxy group to total anhydride group molar ratio of 1:1, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2. Stir at 70℃ for 25 minutes. After cooling, add DMP-30 at 0.6% of the total resin mass and stir for 10 minutes. After vacuum degassing, pour the mixture and cure at 120℃ / 2h + 150℃ / 5h to obtain sample number LC-E51.

[0120] Comparative Example 2: Low-chlorinated bisphenol A / hydrogenated bisphenol A binary system

[0121] Weigh 260 g of low-chlorinated bisphenol A type epoxy resin and 150 g of hydrogenated bisphenol A type epoxy resin, add them to a reaction vessel, heat to 80°C under nitrogen protection and stir for 30 minutes.

[0122] Subsequently, MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 8:2 was added according to a total epoxy group to total anhydride group molar ratio of 1:1, and stirring was continued for 25 minutes. After cooling, DMP-30 was added, and stirring was carried out for 10 minutes. After vacuum degassing, the mixture was poured and cured in the same way to obtain sample number LC-HBPA.

[0123] Comparative Example 3: Quaternary composite resin system, without POSS

[0124] Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, and stir at 80℃ for 30 minutes to mix evenly.

[0125] Then, add the premixed MHHPA / HHPA mixed anhydride curing agent at a mass ratio of 8:2, and continue stirring for 25 minutes. After cooling, add DMP-30, stir for 10 minutes, degas under vacuum, and pour. Curing is performed in the same way to obtain sample number Blend-4.

[0126] Comparative Example 4: Quaternary composite resin system + KH-560 modified nano-silica

[0127] Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, and stir at 80°C for 30 minutes.

[0128] Add 12.3 g of KH-560 modified nano silica, ultrasonically disperse at 80℃ for 20 minutes and continue stirring for 20 minutes.

[0129] Then, add the premixed MHHPA / HHPA mixed anhydride curing agent at a mass ratio of 8:2, and continue stirring for 25 minutes. After cooling, add DMP-30, stir for 10 minutes, degas under vacuum, pour, and cure in the same way to obtain sample number SiO2-3.

[0130] Comparative Example 5: Quaternary composite resin system + acrylic functionalized POSS

[0131] Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, and stir at 80°C for 30 minutes.

[0132] Add 12.3 g of acrylic acid-functionalized POSS and heat to 100°C while stirring for 45 minutes.

[0133] Then, add the premixed MHHPA / HHPA mixed anhydride curing agent at a mass ratio of 8:2, and continue stirring for 25 minutes. After cooling, add DMP-30, stir for 10 minutes, degas under vacuum, pour, and cure in the same way to obtain sample number MA-POSS-3.

[0134] Comparative Example 6: Quaternary composite resin system + epoxy group POSS + single MHHPA

[0135] Weigh 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin and 50 g of alicyclic epoxy resin, and stir at 80°C for 30 minutes.

[0136] Add 12.3 g of pre-dried epoxy POSS and heat to 100°C while stirring for 45 minutes.

[0137] Subsequently, only MHHPA was added as a curing agent, mixed at a total epoxy group to total anhydride group molar ratio of 1:1, and stirred for another 25 minutes. After cooling, DMP-30 was added, stirred for 10 minutes, vacuum degassed, and then poured. Curing was performed using the same method to obtain sample number EP-POSS-M.

[0138] Comparative Example 7: Quaternary composite resin system + epoxy group POSS + mixed acid anhydride in a weight ratio of 6:4

[0139] Weigh out 200 g of low-chlorinated bisphenol A type epoxy resin, 100 g of hydrogenated bisphenol A type epoxy resin, 60 g of epoxy-terminated methylphenylsiloxane resin, and 50 g of alicyclic epoxy resin, and mix them thoroughly at 80℃ for 30 minutes. Add 12.3 g of pre-dried epoxy group POSS, heat to 100℃, and stir for 45 minutes. Then, according to a total epoxy group to total anhydride group molar ratio of 1:1, add MHHPA / HHPA mixed anhydride curing agent premixed at a mass ratio of 6:4, and continue stirring for 25 minutes. After cooling, add DMP-30, stir for 10 minutes, degas under vacuum, pour, and cure using the same method to obtain sample number EP-A64.

[0140] Performance Tests and Results

[0141] Thermal, mechanical, and electrical properties of each sample were tested, and the performance changes after aging in boiling water at 100℃ for 0 days and 8 days were investigated. The test results are shown in Table 1.

[0142] Table 1 Comparison of epoxy resin sample properties

[0143]

[0144] As can be seen from Table 1:

[0145] Combining Comparative Example 1 and Comparative Example 2, the water absorption rate of Comparative Example 2 decreased from 0.54% to 0.32% and the dielectric loss factor decreased from 0.044 / 0.061 to 0.037 / 0.051 compared to Comparative Example 1. This indicates that hydrogenated bisphenol A epoxy resin helps reduce the polarity of the system and inhibit moisture absorption. However, its Tg decreased from 151.0 / 136.2℃ to 146.8 / 129.6℃ and its flexural strength decreased from 98.5 / 72.8 MPa to 94.2 / 73.9 MPa. This shows that while adding this component can reduce polarity, it also reduces other properties, making it difficult to simultaneously achieve both system rigidity and thermal stability, resulting in only a localized improvement.

[0146] Comparative Example 3 shows that the quaternary blend of low-chlorinated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, epoxy-terminated methylphenylsiloxane resin and alicyclic epoxy resin can balance thermal, mechanical and electrical properties to a certain extent, and all properties are improved. However, the retention rates of flexural strength and breakdown field strength after damp heat aging are still only 81.1% and 82.2%, respectively, indicating that simple multi-component blending is still insufficient to establish a highly stable damp heat resistant insulation network.

[0147] Comparative Example 4 shows that after using KH-560 modified nano-silica, the Tg increased significantly from 169.5℃ to 184.1℃, and the initial flexural strength increased from 109.4 MPa to 124.8 MPa, indicating that nano-silica has a significant enhancing effect on the rigidity and initial mechanical properties of the system. However, at the same time, its breakdown field strength after aging decreased from 43.3 / 35.6 kV / mm to 41.8 / 30.9 kV / mm, the breakdown field strength retention rate decreased from 82.2% to 73.9%, and the dielectric loss factor increased from 0.033 / 0.046 to 0.041 / 0.060. This shows a clear trade-off between a sharp increase in thermal and initial mechanical properties and a sharp decrease in damp-heat dielectric stability, indicating that the effect brought by this component is still a conventional single-item enhancement, rather than a comprehensive synergistic improvement.

[0148] Comparative Example 5 shows that the use of acrylic functionalized POSS also exhibits a similar trend, namely, the initial Tg and flexural strength are improved, but the breakdown field strength retention rate decreases and the dielectric loss increases after aging. This indicates that the functional group matching of this type of POSS in the anhydride-cured epoxy insulation system is insufficient, and it cannot achieve the stable synergistic enhancement of the present invention.

[0149] Comparative Example 6 particularly illustrates that even with the introduction of epoxy-based POSS, if a single MHHPA curing system is still used, the initial Tg of the material can increase to 186.7℃ and the initial flexural strength to 127.6 MPa, demonstrating the significant improvement of rigidity and initial thermal properties by epoxy-based POSS. However, after aging in boiling water at 100℃ for 8 days, its Tg drops to 150.8℃, the flexural strength retention rate is only 70.1%, the breakdown field strength retention rate is only 71.4%, the dielectric loss factor increases to 0.062, and the water absorption rate also increases to 0.19%. These results indicate that the addition of epoxy-based POSS alone mainly improves initial performance, rather than the overall stability improvement after hygrothermal aging, and may even lead to a significant deterioration in electrical and insulation retention properties due to insufficient matching of the curing system.

[0150] In Comparative Example 6, since the system still contains epoxy group POSS, its initial Tg and initial flexural strength are relatively high, indicating that epoxy group POSS can improve the initial rigidity of the system. However, since its curing agent is only a single MHHPA, rather than the MHHPA / HHPA mixed anhydride system described in this invention, its stability under humid and hot conditions is insufficient. This ultimately manifests as a significant decrease in Tg after aging, low retention rates of flexural strength and breakdown field strength, increased dielectric loss factor, and high water absorption.

[0151] Comparative Example 7 shows that when the mass ratio of methylhexahydrophthalic anhydride to hexahydrophthalic anhydride is 6:4, deviating from the specified range, the system can still complete curing and obtain certain initial thermal and mechanical properties, but the overall performance after humid heat aging is significantly reduced, manifested as a greater decrease in Tg, a decrease in flexural strength retention and breakdown field strength retention, an increase in dielectric loss factor, and an increase in water absorption. The ratio of the two acid anhydrides in the mixed anhydride affects the stability in a humid heat environment. When the ratio exceeds the specified range, this synergistic relationship is also disrupted, ultimately leading to a decrease in the material's humid heat insulation performance.

[0152] Compared with the above-mentioned examples, Examples 1-8 all exhibited significantly better overall performance, with Example 2 being the most outstanding. Example 2, while maintaining the highest Tg of 189.6 / 178.4℃ and the highest flexural strength retention rate of 95.1%, also achieved the lowest water absorption rate of 0.045%, the lowest dielectric loss factor of 0.023 / 0.027, and the highest breakdown field strength retention rate of 95.1%. Of particular note is that, compared with Comparative Example 6, which also contains epoxy-based POSS, the breakdown field strength of Example 2 after aging jumped from 31.9 kV / mm to 48.7 kV / mm, the dielectric loss factor dropped sharply from 0.062 to 0.027, and the flexural strength retention rate increased significantly from 70.1% to 95.1%. This indicates that the effect of the present invention is not due to the single component epoxy-based POSS itself, but rather to the synergistic effect of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin, epoxy-based POSS, and the MHHPA / HHPA mixed anhydride curing system.

[0153] Furthermore, Examples 4-6 demonstrate that when the weight ratio of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin, and epoxy-based POSS is within the range of 35-45:15-25:8-15:8-15:1-5, the materials exhibit superior overall performance. Specifically, Example 4, with a higher proportion of hydrogenated bisphenol A epoxy resin and alicyclic epoxy resin, exhibits lower water absorption and lower dielectric loss; Example 5, with a higher proportion of low-chlorinated bisphenol A epoxy resin and a higher proportion of epoxy-terminated methylphenylsiloxane resin, exhibits higher initial Tg and higher initial flexural strength; and Example 6 demonstrates a more balanced overall advantage in thermal, mechanical, and electrical properties.

[0154] Furthermore, referring to Examples 2, 7, and 8, it can be seen that when the MHHPA / HHPA mass ratio is within the range of 7:3, 8:2, and 9:1, the materials all exhibit high performance retention rates after damp heat aging, with the 8:2 ratio showing the best overall performance. In comparison, although Examples 7 and 8 still maintain high levels, their aging Tg, breakdown field strength retention rate, and dielectric loss control ability are slightly inferior to 8:2, indicating that 8:2 is a better mixed anhydride ratio. Further referring to Comparative Example 7, it can be seen that when the MHHPA / HHPA mass ratio deviates to 6:4, the flexural strength retention rate, breakdown field strength retention rate, and dielectric loss factor of the material all significantly deteriorate, and the water absorption rate also significantly increases.

[0155] In Comparative Examples 1 and 2, each individual reinforcing component often led to a significant increase in some indicators while a significant decrease in others. However, this invention, through the synergistic design of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin, and epoxy-based POSS, combined with a mixed anhydride curing system, achieves simultaneous improvements in high Tg, low water absorption, low dielectric loss, high mechanical strength retention, and high breakdown field strength retention. It significantly improves the retention of thermal, mechanical, and electrical properties of the epoxy resin composition under boiling water aging conditions at 100°C, exhibiting excellent resistance to damp heat aging.

[0156] In summary, compared to Comparative Examples 1-7, this invention does not simply replace MA-POSS or KH-560 modified nano-SiO2 in the epoxy system. Instead, it employs a combined design of low-chlorinated bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin, epoxy-based POSS, and a MHHPA / HHPA mixed anhydride curing system. This design enables the material to maintain a high glass transition temperature, low water absorption, minimal increase in dielectric loss, and high breakdown field strength retention even after boiling water aging at 100°C. These results demonstrate that the present invention effectively balances improvements in thermal, mechanical, and electrical properties, and exhibits good potential for applications requiring resistance to damp heat aging.

[0157] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An epoxy resin composition resistant to damp heat aging, characterized in that, This includes composite resin systems, mixed acid anhydride curing agents, and curing accelerators. The composite resin system specifically includes low-chlorinated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS, with a weight ratio of 35-45:15-25:8-15:8-15:1-5. Mixed anhydride curing agent: including methylhexahydrophthalic anhydride and hexahydrophthalic anhydride, with a mass ratio of 7-9:1-3, and the amount used so that the molar ratio of total epoxy groups to total anhydride groups is 1:0.95-1.05; Curing accelerator: including 2,4,6-tris(dimethylaminomethyl)phenol, which is 0.3% to 1.0% by mass of the composite resin system.

2. The epoxy resin composition resistant to damp heat aging according to claim 1, characterized in that, The low-chlorinated bisphenol A type epoxy resin is a low-hydrolyzable chlorine type bisphenol A diglycidyl ether resin with a hydrolyzable chlorine content ≤1000 ppm.

3. The epoxy resin composition resistant to damp heat aging according to claim 1, characterized in that, The hydrogenated bisphenol A type epoxy resin is a hydrogenated bisphenol A diglycidyl ether type epoxy resin.

4. The epoxy resin composition resistant to damp heat aging according to claim 1, characterized in that, The epoxy-terminated methylphenylsiloxane resin contains terminal epoxy groups and a methylphenylsiloxane backbone that participate in the curing reaction; the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

5. The epoxy resin composition resistant to damp heat aging according to claim 1, characterized in that, The epoxy group POSS is a cage-type silsesquioxane compound containing multiple epoxy reactive groups.

6. The epoxy resin composition resistant to damp heat aging according to claim 1, characterized in that, The weight ratio of the low-chlorinated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, epoxy-terminated methylphenylsiloxane resin, alicyclic epoxy resin and epoxy-based POSS is 40:18~22:10~13:9~12:2~4.

7. A method for preparing an epoxy resin composition resistant to damp heat aging as described in any one of claims 1-6, characterized in that, Includes the following steps: S1, low-chlorinated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, epoxy-terminated methylphenylsiloxane resin and alicyclic epoxy resin are mixed at 70-90°C for 20-40 minutes under nitrogen protection to obtain a homogeneous resin mixture. S2, add pre-dried epoxy group POSS to the resin mixture obtained in step S1, and stir at 90-110℃ for 30-60 minutes to obtain POSS synergistically reinforced resin matrix; S3, Add mixed anhydride curing agent: Cool down to 60-75℃, add premixed methyl hexahydrophthalic anhydride and hexahydrophthalic anhydride in proportion to the POSS synergistic reinforced resin matrix obtained in step 2, and continue stirring for 20-40 minutes; S4, Add curing accelerator: Cool the mixture obtained in step S3 to 25-40°C, add 2,4,6-tris(dimethylaminomethyl)phenol, and stir for 5-15 minutes; S5, Vacuum degassing: The mixture obtained in step S4 is degassed under vacuum conditions; S6, Curing: The degassed mixture is poured into a mold and subjected to a stepped temperature curing process to obtain the epoxy resin composition.

8. The preparation method according to claim 7, characterized in that, In step S1, the heating temperature is 80°C and the reaction time is 30 minutes; and / or in step S2, the time is 45 minutes and the reaction temperature is 100°C; and / or in step S3, the stirring time is 30 minutes; and / or in step S4, the stirring time is 10 minutes.

9. The preparation method according to claim 7, characterized in that, In step S5, the vacuum degree of the vacuum degassing treatment shall not be lower than -0.095 MPa, and the time shall be 15 to 30 minutes; and / or the procedure of the step-by-step temperature curing treatment in step S6 shall be: first cure at 125°C for 2 hours, and then cure at 155°C for 5 hours.

10. The use of the epoxy resin composition resistant to damp heat aging according to any one of claims 1-6 in the preparation of insulating components for electrical equipment, characterized in that, The insulating components of the power equipment include valve side bushings of converter transformers for ±800kV and above ultra-high voltage DC transmission, composite insulator core rod insulating components, or moisture- and heat-resistant insulating components.

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