Anhydride-free epoxy resin as well as curing forming method and application thereof

Abstract

The invention relates to the technical field of electrical equipment insulating materials, in particular to anhydride-free epoxy resin and a curing forming method and application thereof.The anhydride-free epoxy resin is prepared from, by weight, 65%-80% of alicyclic epoxy resin, 19%-30% of dimer acid modified epoxy resin, 4%-10% of hydrogenated epoxy resin, 0.5%-5% of latent curing agent, 0.1%-0.5% of accelerant and the balance synergistic accelerant. The anhydride-free epoxy resin prepared by the invention is low in viscosity, and can fully enter gaps of a glass fiber tape winding layer to form a uniform and compact insulating layer; and the system does not contain anhydride, and has the advantages of difficulty in moisture absorption, capability of carrying out a glass fiber winding process for a long time, simplicity in winding operation, smaller odor, higher environmental friendliness and the like.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment insulation materials, specifically to an anhydride-free epoxy resin, its curing method, and its applications. Background Technology

[0002] Dry-type reactors have many advantages, such as small weight, low cost, simple maintenance, and long service life, and their application in power systems is becoming increasingly widespread. Currently, many dry-type reactor coils require the external wrapping of glass fiber bundles impregnated with epoxy resin, resulting in a cured material with excellent overall insulation properties.

[0003] Existing epoxy resins for reactors mainly fall into two categories: the first is an epoxy-anhydride curing system, such as Chinese invention patent application CN121450064A, whose formulation mainly includes epoxy resin, nearly half of which is anhydride curing agent, and a trace amount of curing accelerator; the second mainly consists of epoxy resin and a latent catalytic curing agent. Because the first type of epoxy resin composition contains anhydride curing agent, during long-term glass fiber winding processes, the anhydride curing agent easily absorbs moisture, leading to uneven curing. The cured insulation product is brittle, prone to microcracks, and consequently, easily causes excessively high local temperatures, poor insulation performance, and in severe cases, even inter-turn insulation breakdown. Therefore, preparing the second type of anhydride-free epoxy resin to reduce the material's moisture absorption and enhance the resin's weather resistance during curing becomes particularly important. Summary of the Invention

[0004] To address the problems in the prior art, the first aspect of the present invention provides an anhydride-free epoxy resin, wherein the raw materials for preparation, by weight percentage, comprise: Alicyclic epoxy resins: 65%~80% Dimer acid modified epoxy resin 19%~30% Hydrogenated epoxy resin 4%~10% Latent curing agent 0.5%~5% Accelerator 0.1%~0.5% Synergistic promoters replenish the surplus.

[0005] Anhydride curing agents readily react with environmental moisture to form carboxylic acids, leading to uneven curing and microcracks in the localized curing process. This invention completely abandons traditional anhydride curing agents and replaces them with latent curing agents. Latent curing agents are chemically inert at room temperature and only decompose at high temperatures to produce active amines that trigger curing, thus completely avoiding moisture absorption and ensuring a stable and controllable curing process.

[0006] In some embodiments, the alicyclic epoxy resin includes at least one of 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate.

[0007] Optionally, the alicyclic epoxy resin is 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate.

[0008] Optionally, the alicyclic epoxy resin is 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate, wherein the bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate is up to 50 wt% of the alicyclic epoxy resin.

[0009] Optionally, the alicyclic epoxy resin is 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate in a mass ratio of 1:1.

[0010] In some embodiments, the dimer acid modified epoxy resin has a viscosity of 400-900 cps at 25°C and an epoxy equivalent of 390-470 g / eq.

[0011] Optionally, the dimer acid modified epoxy resin includes C18-unsaturated fatty acid dimer diglycidyl ether.

[0012] Optionally, the C18-unsaturated fatty acid dimer diglycidyl ether is model YD-171 and comes from Guodu Chemical (Kunshan) Co., Ltd.

[0013] This invention combines low-viscosity alicyclic epoxy resin with dimer acid-modified epoxy resin, achieving a significant reduction in system viscosity and optimized wettability. Alicyclic epoxy resin itself has a rigid structure but low viscosity, while the C18 flexible segments of the dimer acid-modified epoxy resin further reduce system viscosity and enhance flowability. The synergistic effect of both allows the resin molecular chains to more easily penetrate the gaps between glass fiber monofilaments, forming a uniform and dense insulating layer.

[0014] In some embodiments, the hydrogenated epoxy resin includes hydrogenated bisphenol A epoxy resin.

[0015] Optionally, the hydrogenated bisphenol A epoxy resin comprises 4,4-(1-methylethylindenyl)dicycloethyl diglyceride ester.

[0016] Optionally, the hydrogenated bisphenol A epoxy resin is of model XY518 and is sourced from Anhui Xinyuan Technology Co., Ltd.

[0017] This invention improves the brittleness and enhances mechanical properties of the cured product by introducing hydrogenated bisphenol A epoxy resin, while maintaining a high crosslinking density. The saturated aliphatic chain structure of hydrogenated bisphenol A effectively disperses stress concentration points and reduces brittle fracture; at the same time, the flexibility of its molecular chain complements the rigid structure of the alicyclic epoxy resin, balancing the hardness and toughness of the cured product and preventing the formation of microcracks.

[0018] In some embodiments, the latent curing agent includes a liquid dicyandiamide latent curing agent.

[0019] Optionally, the liquid dicyandiamide latent curing agent is model TS-SQA918, sourced from Anhui Tiansheng New Materials Co., Ltd.

[0020] In some embodiments, the accelerator includes tertiary amine accelerators.

[0021] Optionally, the tertiary amine accelerator includes at least one of triethylamine, N,N-dimethylbenzylamine, and 2,4,6-tris(dimethylaminomethyl)phenol.

[0022] In some embodiments, the synergistic promoter includes at least one of phenolic synergistic promoters and alcoholic synergistic promoters.

[0023] Optionally, the phenolic synergist includes at least one of bisphenol A, nonylphenol, and p-tert-butylphenol.

[0024] Optionally, the alcohol synergist includes benzpinacol.

[0025] In some embodiments, the method for preparing the anhydride-free epoxy resin includes: mixing and stirring the raw materials evenly to obtain the anhydride-free epoxy resin.

[0026] A second aspect of the present invention provides a method for curing and molding an anhydride-free epoxy resin, comprising at least the following steps: The anhydride-free epoxy resin is cured and molded by gradient heating within a temperature range of 80℃ to 180℃.

[0027] In some embodiments, the gradient temperature step specifically involves curing at 80°C to 90°C for 5 hours, curing at 120°C for 5 hours, curing at 150°C for 5 hours, and finally curing at 180°C for 10 hours.

[0028] A third aspect of the present invention provides an application of an anhydride-free epoxy resin in the insulation system of electrical equipment.

[0029] In some embodiments, the electrical equipment includes a reactor, a current transformer, a medium-voltage switch, or a high-voltage switch.

[0030] Beneficial effects 1. This invention adopts an anhydride-free system design, which is not only less odorous and more environmentally friendly, but also completely eliminates the moisture absorption problem of anhydride. It can be stored in the open for more than 30 days, and the operating window is extended to more than 24 hours. It can be used for insulation treatment of reactors that require long-term glass fiber winding process.

[0031] 2. This invention combines low-viscosity alicyclic epoxy resin with dimer acid-modified epoxy resin, which can significantly reduce the viscosity of the system and optimize its wettability; the viscosity of the system is reduced to 308~442 mPa·s, which can fully wet the gaps between glass fiber monofilaments and avoid insulation defects.

[0032] 3. By introducing hydrogenated bisphenol A epoxy resin, this invention improves the brittleness of the cured product and enhances its mechanical properties while maintaining a high crosslinking density; its tensile strength reaches 40.65~46.25MPa, impact strength 6.5~7.3MPa, and flexural strength 75.0~84.2MPa.

[0033] 4. The curing method for anhydride-free epoxy resin provided by the present invention uses a gradient temperature curing process to eliminate internal stress, ensure orderly cross-linking of molecular chains, and achieve synergistic optimization of mechanical and insulation properties; the dielectric loss angle at 150℃ is reduced to 6.546%~8.654%, significantly improving high-temperature insulation stability. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Experimental methods not specifying specific conditions in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0035] Example 1 The first aspect of this example provides an anhydride-free epoxy resin, the raw materials of which include: Alicyclic epoxy resin 70g Dimer acid modified epoxy resin 20g 5g of hydrogenated epoxy resin 5g of latent curing agent Accelerator 0.2g Synergistic promoter 1g.

[0036] The alicyclic epoxy resin is 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate.

[0037] The dimer acid modified epoxy resin is a C18-unsaturated fatty acid dimer diglycidyl ether with a viscosity of 400-900 cps at 25°C, an epoxy equivalent of 390-470 g / eq, and is model YD-171, sourced from Guodu Chemical (Kunshan) Co., Ltd.

[0038] The hydrogenated epoxy resin is 4,4-(1-methylethylindenyl)dicycloethyl diglyceride ester, model XY518, from Anhui Xinyuan Technology Co., Ltd.

[0039] The latent curing agent is a liquid dicyandiamide latent curing agent, model TS-SQA918, from Anhui Tiansheng New Materials Co., Ltd.

[0040] The accelerator is N,N-dimethylbenzylamine.

[0041] The synergistic promoter is benzinolide.

[0042] The preparation method of the anhydride-free epoxy resin includes: mixing and stirring the raw materials at 60°C until uniform to obtain the anhydride-free epoxy resin.

[0043] The second aspect of this example provides a method for curing and molding anhydride-free epoxy resin, including the following steps: The anhydride-free epoxy resin was cured at 85°C for 5 hours, at 120°C for 5 hours, at 150°C for 5 hours, and finally at 180°C for 10 hours.

[0044] The third aspect of this example provides an application of anhydride-free epoxy resin in the insulation system of electrical equipment.

[0045] Example 2 The first aspect of this example provides an anhydride-free epoxy resin, the raw materials of which include: Alicyclic epoxy resin 70g Dimer acid modified epoxy resin 20g 5g of hydrogenated epoxy resin 5g of latent curing agent Accelerator 0.2g Synergistic promoter 1g.

[0046] The alicyclic epoxy resin is 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate, with a mass ratio of 1:1.

[0047] The dimer acid modified epoxy resin is a C18-unsaturated fatty acid dimer diglycidyl ether with a viscosity of 400-900 cps at 25°C, an epoxy equivalent of 390-470 g / eq, and is model YD-171, sourced from Guodu Chemical (Kunshan) Co., Ltd.

[0048] The hydrogenated epoxy resin is 4,4-(1-methylethylindenyl)dicycloethyl diglyceride ester, model XY518, from Anhui Xinyuan Technology Co., Ltd.

[0049] The latent curing agent is a liquid dicyandiamide latent curing agent, model TS-SQA918, from Anhui Tiansheng New Materials Co., Ltd.

[0050] The accelerator is N,N-dimethylbenzylamine.

[0051] The synergistic promoter is benzinolide.

[0052] The preparation method of the anhydride-free epoxy resin includes: mixing and stirring the raw materials at 60°C until uniform to obtain the anhydride-free epoxy resin.

[0053] The second aspect of this example provides a method for curing and molding anhydride-free epoxy resin, including the following steps: The anhydride-free epoxy resin was cured at 85°C for 5 hours, at 120°C for 5 hours, at 150°C for 5 hours, and finally at 180°C for 10 hours.

[0054] The third aspect of this example provides an application of anhydride-free epoxy resin in the insulation system of electrical equipment.

[0055] Comparative Example 1 The first aspect of this example provides an anhydride-free epoxy resin, the raw materials of which include: Alicyclic epoxy resin 95g 5g of latent curing agent Accelerator 0.2g Synergistic promoter 1g.

[0056] The alicyclic epoxy resin is 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate.

[0057] The latent curing agent is a liquid dicyandiamide latent curing agent, model TS-SQA918, from Anhui Tiansheng New Materials Co., Ltd.

[0058] The accelerator is N,N-dimethylbenzylamine.

[0059] The synergistic promoter is benzinolide.

[0060] The preparation method of the anhydride-free epoxy resin includes: mixing and stirring the raw materials at 60°C until uniform to obtain the anhydride-free epoxy resin.

[0061] The second aspect of this example provides a method for curing and molding anhydride-free epoxy resin, including the following steps: The anhydride-free epoxy resin was cured at 85°C for 5 hours, at 120°C for 5 hours, at 150°C for 5 hours, and finally at 180°C for 10 hours.

[0062] Comparative Example 2 This example provides an epoxy resin, and the preparation method of the anhydride-free epoxy resin includes: Weigh 80g of bisphenol A epoxy resin (epoxy equivalent of 190g / eq), add 20g of flexible dimer acid modified epoxy resin (Guodu Chemical YD-171), heat to 80℃ and stir evenly at this temperature to obtain component A. Weigh 80g of methyltetrahydrophthalic anhydride, add 0.2g of accelerator N,N-dimethylbenzylamine, and stir evenly at 60℃ to obtain component B. Before curing, mix components A and B evenly at 80℃, then cure at 85℃ for 5h, 120℃ for 5h, 150℃ for 5h, and finally at 180℃ for 10h.

[0063] Performance testing The cured products obtained after curing and molding processes of each embodiment and comparative example were subjected to performance tests. The test items, conditions and results are shown in Table 1.

[0064] Table 1

[0065] As can be seen from the test results in Table 1, the anhydride-free epoxy resin of the present invention has significant advantages in terms of viscosity, gel time, mechanical properties, insulation properties and storage resistance, providing a better material choice for the insulation system of electrical equipment and having broad application prospects. It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An anhydride-free epoxy resin, characterized in that, The raw materials for preparation, by weight percentage, include: Alicyclic epoxy resins: 65%~80% Dimer acid modified epoxy resin 19%~30% Hydrogenated epoxy resin 4%~10% Latent curing agent 0.5%~5% Accelerator 0.1%~0.5% Synergistic promoters replenish the surplus.

2. The anhydride-free epoxy resin according to claim 1, characterized in that, The alicyclic epoxy resin includes at least one of 3,4-epoxycyclohexyl 3,4-epoxycyclohexyl carboxylate and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate.

3. The anhydride-free epoxy resin according to claim 1, characterized in that, The dimer acid modified epoxy resin has a viscosity of 400-900 cps at 25°C and an epoxy equivalent of 390-470 g / eq.

4. The anhydride-free epoxy resin according to claim 1, characterized in that, The hydrogenated epoxy resin includes hydrogenated bisphenol A epoxy resin.

5. The anhydride-free epoxy resin according to claim 1, characterized in that, The latent curing agent includes a liquid dicyandiamide latent curing agent.

6. The anhydride-free epoxy resin according to claim 1, characterized in that, The accelerators include tertiary amine accelerators.

7. The anhydride-free epoxy resin according to claim 1, characterized in that, The synergistic promoter includes at least one of phenolic synergistic promoters and alcoholic synergistic promoters.

8. A method for curing and molding an anhydride-free epoxy resin according to any one of claims 1-7, characterized in that, At least the following steps are included: The anhydride-free epoxy resin is cured and molded by gradient heating within a temperature range of 80℃ to 180℃.

9. The curing and molding method according to claim 8, characterized in that, The gradient temperature rise step is specifically as follows: curing at 80℃~90℃ for 5 h, curing at 120℃ for 5 h, curing at 150℃ for 5 h, and finally curing at 180℃ for 10 h.

10. An application of the anhydride-free epoxy resin according to any one of claims 1-7, characterized in that, It is used in the insulation system of electrical equipment.

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