Electrically insulating resin composition, electrical apparatus using electrically insulating resin composition, and method for manufacturing electrical apparatus using electrically insulating resin composition

Abstract

Peroxide-based radical polymerization initiators used in molds are mostly substances unstable to heat and thus have a short usable period due to decomposition even at room temperature. An electrically insulating resin composition according to the present invention is obtained by mixing and stirring a heated epoxy main agent and a heated curing agent, adding a heated radical agent thereto and stirring, and adding a radical polymerization initiator and a reducing agent thereto and stirring.

Description

Electrically insulating resin composition, electrical device using the electrically insulating resin composition, and method for manufacturing an electrical device using the electrically insulating resin composition

[0001] The present invention relates to an electrical insulating resin composition, an electrical device using the electrical insulating resin composition, and a method for producing an electrical device using the electrical insulating resin composition.

[0002] In power distribution equipment, particularly molded vacuum circuit breakers, ceramic circuit breaker valves must be molded in resin in addition to the many metal parts.However, in many cases, there is a difference in the linear expansion coefficient between resin and ceramic, or between resin and metal, and ceramic and metal often have a lower linear expansion coefficient than the mold resin, which can cause the resin to crack.

[0003] For this reason, in recent years, measures have been taken to prevent cracking by suppressing the linear expansion coefficient of the resin or improving its strength and fracture toughness. It has also become necessary to relieve stress by inserting silicone rubber between the molded resin and the circuit breaker valve. Changing the resin properties is not easy, and these resins are typically expensive.

[0004] Furthermore, when inserting silicone rubber, it is necessary to paint or wrap the valve with expensive silicone, which requires not only the cost of materials but also the process costs of manual and mechanical handling.

[0005] Therefore, some methods have been adopted to add other resin materials to epoxy resin to improve its strength and toughness and prevent cracking. This method also has the advantage of reducing the viscosity of the resin liquid, improving its casting properties. The other resin used is a radically polymerizable monomer with low viscosity, and adding an appropriate radical polymerization initiator to this starts the reaction upon heating, resulting in simultaneous polymerization with the epoxy resin.

[0006] JP 2017-128621 A JP 2019-6847 A

[0007] Patent Document 1 discloses a molding resin material for high-voltage equipment and a method for producing high-voltage equipment that improves the storage stability of the molding resin material, suppresses filler settling, and improves casting properties.

[0008] The molding resin material includes a base material that is liquid at room temperature and contains an epoxy resin having an epoxy equivalent of 200 g / eq or less and a radical polymerization initiator; a curing agent that is liquid at room temperature and contains an acid anhydride and an epoxy resin curing catalyst; and a reactive diluent that is liquid at room temperature and contains an acid anhydride, a radical polymerizable monomer, and a copolymerization agent, and the base material, the curing agent, and the reactive diluent are stored separately.

[0009] This invention describes simultaneous polymerization of an epoxy resin with a styrene-phenylmaleimide copolymer, but does not consider extending the usable period of the radical polymerization initiator.

[0010] Patent Document 2 discloses an electrical insulating resin composition that can improve storage stability during storage, and a high-voltage device using the same.

[0011] The resin composition for electrical insulation is a resin composition for electrical insulation that is used by mixing a first agent, a second agent, and a third agent, in which the first agent contains an epoxy resin, the second agent contains a curing agent, and the third agent has a first capsule containing a copolymerization agent and a second capsule containing a radical polymerizable monomer.

[0012] It is disclosed that each of the first and second capsules is preferably formed from polyethylene, polypropylene, polystyrene, acrylic resin, polyethylene terephthalate, or silica, and that each of the first and second agents preferably contains a filler, and that the filler is preferably at least one selected from the group consisting of crushed crystalline silica, fused silica, and core-shell rubber particles.

[0013] Similarly, radical polymerization agent monomers encapsulated in epoxy resin materials are simultaneously polymerized, but no consideration is given to extending the usable period of the radical polymerization initiator.

[0014] This paper deals with the process and materials used for radical polymerization initiators in epoxy-radical polymerization agent composite resin systems for electrical equipment, particularly molded equipment. Peroxide-based radical polymerization initiators, in particular, are often unstable to heat and decompose even at room temperature, making it impossible to maintain their performance for long periods of time.

[0015] Since peroxides are expensive and require costs for storage and disposal, they must be stable and effective immediately when needed. For this reason, the present invention uses compounds that are stable even at high temperatures and undergo decomposition and cleavage reactions only when a reducing agent is added.

[0016] The above-mentioned object of the present invention is achieved by providing an electrical insulating resin composition which is prepared by mixing and stirring a heated epoxy base resin and a heated curing agent, adding and stirring a heated radical agent, and then adding and stirring a radical polymerization initiator and a reducing agent.

[0017] The present invention aims to extend the usable period of the radical reaction initiator, which is one of the most expensive components of the molding material.

[0018] FIG. 1 is a cross-sectional view of a molded circuit breaker which is a power receiving and distribution device in an example of the present invention. FIG. 2 is a table explaining the components of an epoxy base agent in an example of the present invention. FIG. 3 is a table explaining the components of an acid anhydride curing agent in an example of the present invention. FIG. 4 is a table explaining the components of a radical agent in an example of the present invention. FIG. 5 is a table explaining the components of a radical polymerization initiator in an example of the present invention. FIG. 6 is a diagram explaining a method for producing an electrical insulating resin composition in an example of the present invention.

[0019] Many of the peroxide-based radical polymerization initiators used to prepare epoxy-radical polymerization agent composite resin compositions used in electrical equipment, especially molded equipment, are unstable to heat. Radical polymerization initiators decompose even at room temperature, so they cannot maintain their performance for long periods of time.

[0020] In addition, peroxides are expensive and require costs for storage and disposal, so peroxides must be stable and have the property of being effective immediately when needed.

[0021] For this reason, there is a demand for radical polymerization initiators that are stable even at high temperatures and that undergo decomposition and cleavage reactions only when a reducing agent is added.

[0022] In order to solve the above problems, there are provided an electrical device and a method for producing the same, which uses an organic peroxide that exhibits cleavability due to temperature increase when used in combination with a reducing agent as a radical polymerization initiator in a molding resin.

[0023] If a highly heat-resistant substance is used as the radical polymerization agent, the cleavage reaction does not occur until the reducing agent is mixed, and the radical polymerization initiator can be stored safely for a long period of time.

[0024] Preferably, the epoxy resin base and the curing agent are mixed in advance, and then a mixture of a reducing agent solution and an organic peroxide as a radical polymerization initiator is further mixed with the mixture.

[0025] By using this method, the organic peroxide can remain stable until it is mixed with a reducing agent, extending its usable period and making it easier to manage.

[0026] Preferably, the reducing agent solution and the organic peroxide solution are first mixed after the epoxy resin base resin, curing agent, and radical agent have been sufficiently mixed, and then added to the mixture of the epoxy resin base resin and curing agent, thereby enabling efficient production of an electrical insulating resin composition.

[0027] This method further embodies the method described above, and is the safest and most effective way to utilize the effects of organic peroxides, which are radical polymerization initiators. Because the mixture of the epoxy base resin and curing agent, which is sufficiently heated, is much larger in quantity than the mixture of the radical polymerization initiator and additives, the temperature rises instantly and the reaction begins.

[0028] Preferably, the epoxy resin base is an epoxy prepolymer having a bisphenol A skeleton or a bisphenol F skeleton, and the main filler is crystalline silica or fused silica.

[0029] Bisphenol A is inexpensive and easy to manufacture, so it has the advantage of being supplied cheaply and stably. Bisphenol F is slightly more expensive, but its low viscosity makes it easy to cast resins.

[0030] Crystalline silica is inexpensive, has good thermal conductivity, and has a high linear expansion coefficient, while fused silica is expensive but can reduce the linear expansion coefficient, making it possible to manufacture molds with a linear expansion coefficient that is suited to the material being bonded.By using the epoxy base resin and fillers mentioned above, it is possible to create molds with appropriate performance at low cost.

[0031] Preferably, the hardener is an acid anhydride hardener, and crystalline silica or fused silica is used as the main filler.

[0032] Amine-based curing agents are also often used as curing agents for epoxy resins, but because they are highly reactive and difficult to handle outside the room temperature range, it is preferable to use acid anhydride-based curing agents for resin molded products that are intended to be cured by heat.As mentioned above, it is desirable to change the composition of the added silica depending on the characteristics that the mold should have.

[0033] Preferably, the organic peroxide used is any one of t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, or a mixture thereof.

[0034] These organic peroxides are stable to heat and do not easily decompose when used alone, but they only become thermally decomposable when used in combination with a reducing agent.

[0035] Preferably, the reducing agent is a mild reducing agent such as ferrous sulfate, sulfite, tin chloride, 3,4,5-trihydroxybenzoic acid, oxalic acids, or formic acids, or a mixture containing any one of the reducing agents described above, or a solvent for dispersing these.

[0036] All of the reducing agents listed above are mild reducing agents, and do not have strong toxicity, explosiveness, or other violent reactivity when used alone.

[0037] A series of examples relating to the present invention are set out below.

[0038] FIG. 1 is a cross-sectional view of a molded circuit breaker, which is an electric power receiving and distribution device, and is one example of electric equipment according to an embodiment of the present invention.

[0039] The molded circuit breaker is composed of a vacuum circuit breaker body 10 surrounded by a dotted line, a metal electrode 11, a metal part 12, a hardened molded resin 14 indicated by diagonal lines, and a movable electrode 15. Here, a method for manufacturing the molded resin 14 will be described.

[0040] FIG. 2 is a table illustrating the components of the epoxy base resin in the examples of the present invention.

[0041] As shown in FIG. 2, 10 kg of epoxy base compound A has a composition of 25% bisphenol A type epoxy prepolymer, 5% bisphenol F type epoxy prepolymer, 40% crystalline silica, and 30% fused silica.

[0042] FIG. 3 is a table illustrating the components of the acid anhydride curing agent in the examples of the present invention.

[0043] As shown in Figure 3, 10 kg of acid anhydride hardener B has a composition of 15% cyclic acid anhydride (4-methylhexahydrophthalic anhydride), 15% cyclic acid anhydride (5-methylhexahydrophthalic anhydride), 40% crystalline silica, and 30% fused silica.

[0044] FIG. 4 is a table illustrating the components of the radical agent in an embodiment of the present invention.

[0045] As shown in FIG. 4, 1 kg of radical agent C having a composition of 30% styrene monomer, 30% phenylmaleimide, acid anhydride, and 40% B was used.

[0046] FIG. 5 is a table illustrating the components of the radical polymerization initiator (including the reducing agent) in the examples of the present invention.

[0047] The radical polymerization initiator used was 1 g of a 98% solution of t-butyl hydroperoxide, and the reducing agent used was 1 g of a 2 wt % solution of ferrous sulfate.

[0048] FIG. 6 is a diagram illustrating a method for producing an electrical insulating resin composition in an embodiment of the present invention.

[0049] First, the metal electrode 11 and other components that are the core material other than the molded portion in Fig. 1 are assembled into a mold 66. Next, the mold is heated and the temperature is raised to 80°C over 8 hours.

[0050] Epoxy base A and acid anhydride B are placed in tanks 60 and 61 and heated to 60° C. over a period of about two hours. Once the mold and resin are sufficiently heated, epoxy base A and acid anhydride B are mixed in a mixer 63.

[0051] Once sufficient stirring has been achieved, 1 kg of radical agent C is heated to 60° C. in tank 62 and added to stirrer 63, and the mixture is vacuum degassed at a pressure of 400 Pa while stirring. The vacuum degassing time is about 10 minutes at 400 Pa.

[0052] Next, a solution of t-butyl hydroperoxide as a radical polymerization initiator and ferrous sulfate as a reducing agent is placed in a test tube 64 and vigorously shaken. After about one minute, the mixture is dropped into the mixture from the inlet of a stirrer 63, and the mixture is stirred for another 10 minutes or so and degassed under vacuum at a pressure of 400 Pa.

[0053] At this point, preparation of the molding resin (electrically insulating resin composition) is complete. A vacuum chamber 65 is placed below the tank, and a mold 66 is prepared in which a metal part 12 heated to 80°C is set. The valve 68 of the tank at the top is opened, and the molding resin is poured into the mold 66 from the agitator 63 at the top.

[0054] After it is confirmed that the mold 66 is sufficiently filled with molding resin, the mold 66 containing the molding resin is placed in a thermostatic chamber 65 preheated to 80°C, and the molding resin is cured for approximately eight hours. After this, the mold 66 is removed, and the molding resin is cured for five hours at 120°C.

[0055] This completes the molded circuit breaker as shown in Figure 1. Finally, after checking that there are no bubbles or defects that occurred during molding, the product is sent to the shipping inspection department where it undergoes shipping tests such as a high-voltage test before being completed.

[0056] As described above, since the radical polymerization initiator is not brought into contact with the reducing agent until immediately before molding, the expensive radical polymerization initiator can be prevented from spontaneous decomposition, and the usable period of the radical polymerization initiator can be extended to about one year.

[0057] Furthermore, radical polymerization initiators, which normally have a usable period of only about three months, will no longer be stored in a warehouse with no orders and disposed of when their usable period expires, which reduces disposal costs and is good for the environment. Since it is not an organic acid anhydride, which is particularly highly reactive and decomposes simply by increasing temperature, no special treatment is required when it is disposed of.

[0058] In the above examples, the organic peroxide used as the radical polymerization initiator may be any one of t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, or a mixture thereof.

[0059] In this case, the reducing agent to be combined may be changed, and the same effect can be obtained even if it is one of ferrous sulfate, sulfite, tin chloride, 3,4,5-trihydroxybenzoic acid, oxalic acids, formic acids, or a mixture thereof.

[0060] When selecting a radical polymerization initiator and a reducing agent, it is preferable to confirm an appropriate preheating temperature through a test in advance.

[0061] In the above examples, the same effect can be achieved even if the radical agent is styrene, vinyl monomers, acrylic esters, or a mixture of these. Also, 4-vinyltoluene, an environmentally friendly substitute for styrene, can be used to achieve the same effect.

[0062] Although the above embodiments have been described with reference to molded circuit breakers, the same effects can be achieved with high voltage equipment in general, and in particular, it can be used for molded transformers, molded insulators, distribution boards, etc.

[0063] REFERENCE SIGNS LIST 10 Vacuum circuit breaker body 11 Metal electrode 12 Metal part 13 Mechanical part 14 Molding resin 15 Movable electrode 20 Epoxy base 30 Acid anhydride curing agent 40 Radical agent 50 Radical polymerization initiator and reducing agent 60, 61, 62 Tank 63 Stirrer 64 Test tube 65 Vacuum chamber 66 Mold 68 Valve

Claims

1. An electrical insulating resin composition obtained by mixing and stirring a heated epoxy base and a heated curing agent, adding and stirring a heated radical agent, and then adding and stirring a radical polymerization initiator and a reducing agent.

2. An electrical insulating resin composition according to claim 1, wherein the epoxy base comprises an epoxy prepolymer having a bisphenol A skeleton or a bisphenol F skeleton, crystalline silica, and fused silica.

3. The electrical insulating resin composition according to claim 1, wherein the curing agent comprises 4-methylhexahydrophthalic anhydride, 5-methylhexahydrophthalic anhydride, crystalline silica, and fused silica.

4. The electrical insulating resin composition according to claim 1, wherein the radical agent comprises a styrene monomer, phenylmaleimide, and an acid anhydride.

5. The electrical insulating resin composition according to claim 1, which contains t-butyl hydroperoxide as a radical polymerization initiator and ferrous sulfate as a reducing agent.

6. An electrical device using a molded part obtained by pouring the electrically insulating resin composition according to any one of claims 1 to 5 into a mold in which a ceramic or metal part is placed.

7. A method for manufacturing an electrical device, which comprises pouring the electrical insulating resin composition according to any one of claims 1 to 5 into a mold in which a ceramic or metal part is placed.

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