JP2000086869A - Epoxy resin composition and coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition excellent in packing property to a thin-wall part as well as in crack resistance and having a high glass transition temperature, and a coil insulated by cast molding the same. SOLUTION: This epoxy resin composition contains as essential components (A) a bifunctional alicyclic epoxy resin, (B) a hydrogenated methylnadic acid curing agent, (C) an imidazole-based curing accelerator and (D) an inorganic filler, and is composed of two packages, that is, a resin component comprising a liquid epoxy resin comprising the component (A) having incorporated therein 25-95 wt.%, based thereon, of (D) the inorganic filler and a liquid curing agent component comprising (B) the curing agent and (C) the curing accelerator. The titled coil is insulated by a cast molded body of the epoxy resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition having excellent crack resistance, moisture resistance, moldability, and excellent electrical properties at high temperatures and high heat resistance, and is cast by the epoxy resin composition. For coils.

[0002]

2. Description of the Related Art Conventionally, electric and electronic parts such as coils are
Cast insulation and resin sealing have been performed to protect it from the external atmosphere and mechanical shock. It is also desired that such electric / electronic parts be used in a stable environment for a long period of time under heat resistance of 100 ° C. or more.

In recent years, as coil devices have become smaller,
Casting resin is required to have even lower viscosity and reliability such as crack resistance and heat resistance after casting to be suitable for filling between coil windings and thin wall moldability. Was. And since the material of the insert to be cast has a smaller coefficient of thermal expansion than the epoxy resin cured product, peeling occurs at the interface between the resin and the cast product after casting, or the resin is cracked, This reduced the reliability of the casting.

Conventionally, a fibrous filler has been added to lower the coefficient of thermal expansion of the cured resin. However, the resin to which the fibrous filler is added is inferior in fluidity and has a thin wall portion. Is inferior in moldability and is not a practically versatile method.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks, and has an excellent filling property of a thin portion, has no defects such as voids, and has a low thermal expansion to prevent cracking. It is an object of the present invention to provide a highly versatile epoxy resin material which is excellent in heat resistance, has a high glass transition temperature, is excellent in heat resistance, and is suitable for coil casting and the like, and a coil which is cast-insulated thereby.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, obtained a bifunctional alicyclic epoxy resin and a hydrogenated methylnadic acid curing agent into an imidazole-based curing accelerator. It has been found that the above-mentioned object is achieved by curing the composition and then filling it with a large amount of an inorganic filler, thereby completing the present invention.

That is, the present invention provides (A) a bifunctional alicyclic epoxy resin, (B) hydrogenated methylnadic acid or its anhydride as a curing agent, (C) an imidazole compound as a curing accelerator and (D) Inorganic filler as an essential component,
(A) a liquid epoxy resin composed of a bifunctional alicyclic epoxy resin, (D) an inorganic filler is blended in a proportion of 25 to 95% by weight, and if necessary, a reactive diluent;
A resin component selectively blended with an antifoaming agent and an antisettling agent,
An epoxy resin composition characterized by comprising two liquids of a liquid curing agent component comprising (B) a hydrogenated methyl nadic acid curing agent and (C) an imidazole-based curing accelerator. Is a coil characterized by being insulated by the casting of the epoxy resin composition.

Hereinafter, the present invention will be described in detail.

As the (A) bifunctional alicyclic epoxy resin used in the present invention, as long as it is an alicyclic compound such as a cyclohexane derivative having two epoxy groups in its molecule,
Generally used materials can be widely used without being limited by the molecular structure, molecular weight and the like. For example, an alicyclic epoxy resin such as a cyclohexane derivative represented by the following general formulas 1 and 2 is preferably used.

[0010]

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[0011]

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Further, these bifunctional alicyclic epoxy resins can be used alone or in combination of two or more.
Further, other commonly used epoxy resin compounds may be used in combination as long as the object of the present invention is not adversely affected. Such an epoxy resin compound is a compound having at least two epoxy groups in the molecule, and can be used without being limited by the molecular structure, molecular weight and the like. Specific examples include aromatic epoxy resins such as epoxy novolak type, biphenyl type, and bisphenol A type.

The hydrogenated methyl nadic acid curing agent (B) used in the present invention is a hydride of methyl nadic acid and / or a hydride of methyl nadic anhydride. The molecular weight and the equivalent of acid anhydride are as follows. There is no particular limitation, and the one represented by the following general formula is optimal.

[0014]

Embedded image The hydrogenated methyl nadic acid curing agent may be used in combination with another acid anhydride curing agent such as methyl tetrahydrophthalic anhydride.

The curing accelerator (C) comprising the imidazole compound used in the present invention may be an imidazole derivative used for accelerating the reaction between epoxy resins or between the epoxy resin and a hydrogenated methylnadic acid curing agent. Any object may be used. Illustrative examples of the curing accelerator include, for example, 2-methylimidazole, 2-methylimidazole,
Undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-
Methyl imidazole and the like can be mentioned. Among these curing agents, 1-benzyl-2-methylimidazole represented by the following formula is preferably used in consideration of the castability and moldability of the resin composition and the heat resistance of the cured product.

[0016]

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As the inorganic filler (D) used in the present invention, those generally used are widely used. Specifically, for example, silica powder, alumina, antimony trioxide, talc, calcium carbonate, titanium white, clay, bengal, glass fiber, carbon fiber and the like can be mentioned, and silica powder and alumina are particularly preferably used. The mixing ratio of the inorganic filler is 25 to the entire resin composition.
It is preferable to mix so as to contain 95% by weight. If the proportion is less than 25% by weight, the linear expansion coefficient of the resin composition is high and the strength is low, which is not preferable. On the other hand, if it exceeds 95% by weight, the fluidity becomes extremely poor and the moldability is poor, which is not preferred. Desirably, by blending 60 to 90% by weight, both low linear expansion property and fluidity can be achieved.

The epoxy resin composition of the present invention comprises a bifunctional alicyclic epoxy resin, a hydrogenated methylnadic acid curing agent, a curing accelerator comprising an imidazole compound and an inorganic filler as essential components. To the extent not inconsistent with the purpose, and if necessary, for example, a reactive diluent such as a monofunctional alicyclic epoxy, a reaction initiator such as an alkylene glycol, a defoaming agent such as silicones and a silane coupling agent, or various An anti-settling agent, a colorant such as carbon black, etc. can be added as appropriate. A general method for preparing the epoxy resin composition of the present invention as a casting material includes the above-mentioned bifunctional alicyclic epoxy resin and a reactive diluent, a reaction initiator, an antifoaming agent, an anti-settling agent, and other additives. An inorganic filler is blended with the liquid epoxy resin blended with the components, and a resin component mixed and heated uniformly by a mixer or the like, and a curing accelerator composed of a hydrogenated methyl nadic acid curing agent and an imidazole compound are mixed with a mixer or the like. Thus, it is possible to obtain a casting material configured as a two-part liquid with a liquid curing agent component that is sufficiently heated and mixed.

The coil in the present invention means a coil utilizing electromagnetic induction and an inductance component of a transformer (transformer), such as a flyback transformer of a television. The casting material thus obtained is used for sealing of general electric parts or electronic parts including coil casting,
When applied to coating, insulation, etc., excellent characteristics and reliability can be imparted.

As a general casting method, there is a vacuum casting method. However, a bifunctional alicyclic epoxy resin, an inorganic filler and other components are blended and mixed with a resin component which is sufficiently uniformly heated and mixed by a mixer or the like. Injection molding, compression molding, etc., by previously mixing two liquids of a liquid curing agent component obtained by heating and mixing a curing accelerator composed of a hydrogenated methyl nadic acid curing agent and an imidazole compound sufficiently and uniformly by a mixer or the like. Casting and molding by other methods are also possible. After sealing by these casting and molding methods, the resin is cured by heating, and finally, a coil casting sealed with the cured product is obtained.

[0021]

The epoxy resin composition of the present invention is obtained by curing a bifunctional alicyclic epoxy resin highly filled with an inorganic filler with a curing accelerator comprising a hydrogenated methyl nadic acid curing agent and an imidazole compound. It is possible to provide an epoxy resin composition which is excellent in crack resistance and heat resistance, excellent in filling of a thin portion of the resin composition, and free of defects such as voids and suitable for coil casting.

[0022]

Next, the effects of the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 100 parts by weight of a bifunctional alicyclic epoxy resin (epoxy equivalent: 200), 580 parts by weight of a fused silica powder, 2 parts by weight of a reaction initiator, and 0.1 part by weight of a silicone-based antifoaming agent were charged into a mixer. And heated and mixed at 70 ° C. to obtain an epoxy resin component.
Separately, hydrogenated methyl nadic acid curing agent (anhydride equivalent 183)
90 parts by weight and 0.7 parts by weight of 1-benzyl-2-methylimidazole were put into a mixer, and heated and mixed at 70 ° C. to obtain a curing agent component.

The epoxy resin component and the curing agent component were mixed to obtain an epoxy resin composition of Example 1.

Examples 2 to 4 In the same manner as in Example 1, the compositions in the epoxy resin component column and the curing agent component column shown in Table 1 were heated and mixed at 70 ° C. to obtain an epoxy resin component and a curing agent component, respectively. Was. The obtained epoxy resin component and curing agent component were mixed to obtain epoxy resin compositions of Examples 2 to 4.

Comparative Examples 1 to 3 The compositions of the epoxy resin component column and the hardener component column shown in Table 1 were heated and mixed at 70 ° C. in the same manner as in the examples to obtain an epoxy resin component and a hardener component, respectively. . The obtained epoxy resin component and the curing agent component were mixed to obtain epoxy resin compositions of Comparative Examples 1 to 3.

The epoxy resin compositions of Examples 1 to 4 and Comparative Examples 1 to 3 obtained above were cast and impregnated in a coil under vacuum at 70 ° C., and then at 110 ° C. for 3 hours and 150 ° C. In ° C
Post-cured for 5 hours. Various tests were performed on these epoxy resin compositions, and the results are shown in Table 2. The epoxy resin composition of the present invention is an epoxy resin composition which is excellent in the filling property of a thin portion, has no defects such as voids, has low linear expansion, and has excellent crack resistance and the like. A remarkable effect could be confirmed.

[0028]

[Table 1] * 1: Epoxy equivalent 200 * 2: Epoxy equivalent 190 * 3: Acid anhydride equivalent 183

[0029]

[Table 2] * 1: Regarding coil impregnating property, the coil was cast into a flyback transformer, post-cured at 110 ° C for 3 hours and further at 150 ° C for 5 hours, and the cut surface of the coil was observed with a microscope. An impregnation rate of 95% or more was judged as good impregnation, and an impregnation rate of less than 95% was judged as poor impregnation.

The number of void defects was described by counting the number of void defects when the impregnation was judged. * 2: Tinplate shears (diameter 5 cm x height 1.5 cm)
Insert a bolt and nut washer into the mold and cast a 30-minute cooling / heating cycle at high temperature (130 ° C) and low temperature (-60 ° C).
The test was given 200 times, and the length of the crack generated in each specimen was measured.

[0031]

As apparent from the above description and Table 2, the epoxy resin composition of the present invention is excellent in the filling property of a thin portion, has no defects such as voids, and has a low linear expansion to prevent cracking. An epoxy resin composition having excellent heat resistance, high glass transition temperature, and excellent heat resistance and suitable for coil casting and the like.

Claims (2)

[Claims] (A) a bifunctional alicyclic epoxy resin,
It comprises (B) hydrogenated methylnadic acid or its anhydride as a curing agent, (C) an imidazole compound as a curing accelerator and (D) an inorganic filler as essential components, and (A) a bifunctional alicyclic epoxy resin. A resin component in which (D) an inorganic filler is blended in a proportion of 25 to 95% by weight with respect to the liquid epoxy resin, and a reactive diluent, an antifoaming agent and an anti-settling agent are selectively blended as required. And a liquid curing agent component comprising (B) a hydrogenated methyl nadic acid curing agent and (C) an imidazole curing accelerator. 2. A coil which is insulated by a casting of the epoxy resin composition according to claim 1.