JP2893322B2 - Liquid epoxy resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid epoxy resin composition, and more particularly, to an epoxy resin composition suitable for insulating and sealing a capacitor.

[0002]

2. Description of the Related Art Generally, a capacitor such as a plastic film capacitor is insulated and sealed with a resin for the purpose of protecting against external environment such as humidity and impact. For insulation sealing of a capacitor, a composition of an epoxy resin or a phenol resin is usually used, and dipping or potting is adopted as an insulation sealing method. Among them, epoxy resin compositions have become mainstream because of their excellent electrical properties and reliability as insulating sealing resins.

[0003] In order for an epoxy resin composition for insulating sealing to effectively exhibit its insulating properties, particularly its insulating properties under high voltage, impregnation, that is, penetration between dielectric films of a capacitor is required. Need to be better. In general, it is known that an epoxy resin composition having a low initial viscosity has a high impregnation property.

As an epoxy resin composition having excellent impregnating properties, bisphenol A type epoxy resin mixed with butyl glycidyl ether or the like as a reactive diluent for lowering the viscosity is used as a main component, and an acid anhydride is used as a curing agent. And a two-part mixed type epoxy resin composition using a curing accelerator is known. However, in such an epoxy resin composition, it is necessary to use a large amount of a diluent in order to reduce the viscosity, and in a flyback transformer used for a television receiver or a display that requires a higher impregnation property. When it is used for a film capacitor embedded in a film, there is a disadvantage that the heat resistance and moisture resistance of the cured product are deteriorated due to the large amount of diluent used for lowering the viscosity. Also,
Bisphenol A-type epoxy resins and the like, which are widely used as epoxy resins, contain impurities such as chlorine due to their production methods, and therefore, capacitors using such resins have a disadvantage that the insulation life is inferior.

[0005] JP-A-1-60624 discloses a liquid epoxy resin composition suitable for impregnation comprising a bisphenol A type epoxy resin and an alicyclic epoxy resin (main component), an acid anhydride and an imidazole compound (curing agent). Liquid epoxy resin compositions have been proposed. However, this epoxy resin composition uses a high-viscosity bisphenol A-type epoxy resin in an amount of 30 to 60% by weight, and thus has good heat resistance and electrical characteristics, but has a high viscosity, and thus is suitable for insulating sealing of a film capacitor. When used, the impregnation is not sufficient.

On the other hand, it is conceivable to use only an alicyclic epoxy resin as a main component and use an acid anhydride and a curing accelerator as a curing agent. However, in this case, although the viscosity of the obtained composition is low, the curability is reduced, and the curing is not completed in a short time at about 120 ° C. at which the film capacitor is cured.

An aromatic diglycidylamine type epoxy resin is known as an epoxy resin having a low viscosity.
However, this alone reduces the pot life of the resulting composition and reduces the heat resistance.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has a low viscosity, a high impregnation property, and good curability and heat resistance. Another object of the present invention is to provide a liquid epoxy resin composition suitable for a film capacitor.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a mixed epoxy resin containing an alicyclic epoxy resin and an aromatic diglycidylamine type epoxy resin as resin components. By using
A liquid epoxy resin that can keep the viscosity of the resulting liquid resin composition low, has a good balance between touch hardening time and curing characteristics and the pot life of the resin composition, and has excellent heat resistance and moisture resistance of the cured product. The present inventors have found that a composition is provided and completed the present invention.

According to the present invention, the content of the alicyclic epoxy resin is 4
0 to 80% by weight, preferably 50 to 70% by weight, and the content of the aromatic diglycidylamine type epoxy resin is 2%.
An epoxy resin composition comprising a mixed epoxy resin component of 0 to 60% by weight, preferably 30 to 50% by weight, and an acid anhydride and a curing accelerator as a curing agent, wherein the initial viscosity of the composition is Is less than 2.0 P (poise) at 23 ° C. in the liquid epoxy resin composition. The present invention also resides in an epoxy resin composition for a capacitor comprising the liquid epoxy resin composition.

The alicyclic epoxy resin has two or more epoxy groups, and has an oxirane ring condensed with an aliphatic ring as at least one of the epoxy groups. The alicyclic epoxy resin used in the present invention is a liquid at normal temperature, specifically, a resin having a viscosity at 25 ° C. of 750 cps or less, preferably 200 to 600 cps, more preferably 350 to 450 cps. . The alicyclic epoxy resin used in the present invention includes 3,4-
Epoxycyclohexylmethyl- (3,4-epoxy)
Examples thereof include cyclohexylcarboxylate, vinylcyclohexene dioxide, bis (3,4-epoxycyclohexylmethyl) adipate, and dicycloaliphatic ester diepoxide. One of these alicyclic epoxy resins may be used alone, or 2
A combination of more than one species may be used.

As the aromatic diglycidylamine type epoxy resin used in the present invention, those which are liquid at ordinary temperature,
Specifically, the viscosity at 25 ° C. is 250 cps or less, preferably 10 to 200 cps, more preferably 30 to 16 cps.
It is preferably 0 cps. Examples of the aromatic glycidylamine type epoxy resin used in the present invention include diglycidylamine derivatives of aromatic amines. Specifically, N, N-di (glycidyl) -o-toluidine, N, N -Di (glycidyl) aniline and the like. One of these aromatic diglycidylamine type epoxy resins may be used alone, or two or more thereof may be used in combination.

The acid anhydride used as a curing agent in the present invention can be arbitrarily selected from those commonly used as epoxy resin curing agents. The acid anhydride used in the present invention is preferably a liquid at normal temperature, specifically, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride,
Dodecenyl succinic anhydride, methyl endmethylene tetrahydrophthalic anhydride and the like can be mentioned. In addition, acid anhydrides that are solid at room temperature, such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methylcyclohexene dicarboxylic anhydride, as long as the impregnation of the epoxy resin composition of the present invention is not adversely affected. Etc. can be used. When an acid anhydride that is solid at room temperature is used, it is preferable that the acid anhydride be dissolved in a liquid acid anhydride at room temperature and used as a mixture that is liquid at room temperature. The compounding amount of the acid anhydride is not particularly limited as long as it is an effective amount capable of exhibiting the effect as a curing agent, but is usually 0.5 to 0.5 to 1 equivalent of the epoxy group in the epoxy resin component.
It is preferable to use a ratio such that an acid anhydride equivalent of 1.5 is obtained.

[0014] The curing accelerator is a compound having a function of accelerating the curing reaction when the epoxy resin is cured with an acid anhydride. Examples of the curing accelerator used in the present invention include tertiary amines such as benzyldimethylamine and 2,4,6-tris (dimethylaminomethyl) phenol, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2. Known compounds such as imidazoles such as -ethyl-4-methylimidazole, organic phosphine compounds such as triphenylphosphine, tertiary amine salts, quaternary ammonium salts, phosphonium salts, and metal salts such as tin octylate. it can. It is preferable to use the curing accelerator in an amount of 0.1 to 3.0 parts by weight based on 100 parts by weight of the epoxy resin.

Various additives can be added to the liquid epoxy resin composition of the present invention as long as the viscosity is not adversely affected. Examples of such additives include silicone-based and fluorine-based antifoaming agents, and silane coupling agents such as γ-glycidoxypropyltrimethoxysilane.

The liquid epoxy resin composition of the present invention has a high glass transition temperature, excellent electrical properties, a low viscosity and a good impregnation property, and thus is suitable as a resin composition for (film) capacitors. is there. For example, the cured product of the liquid epoxy resin composition of the present invention is excellent in the strength of dielectric breakdown, and the strength of the dielectric breakdown at DC is 50 kV /
mm or more. Therefore, by using the liquid epoxy resin composition of the present invention as a resin composition for a capacitor, in a capacitor using a normal resin composition, the capacitor is broken even when a voltage is applied at which insulation is destroyed. The effect of not being performed can be achieved.

[0017]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Examples and Comparative Examples The components (parts by weight) shown in Tables 1 and 2 were blended to obtain a liquid epoxy resin composition. For each composition, impregnating property, curability, pot life, heat resistance, moisture resistance and strength of dielectric breakdown were measured as described below, and the performance was evaluated.

(1) Impregnating property Each composition was adjusted to 23 ° C., and the viscosity immediately after mixing (initial viscosity) was measured with a B-type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.). The lower the initial viscosity, the better the impregnating property. Therefore, the initial viscosity was classified as follows, and the case corresponding to A was evaluated as having good impregnating property. Less than 2P: A, 2P-4P: B, 4P
Ultra: C.

(2) Curability 10 g of each composition was placed in a metal can, and the time during which the resin surface did not stick to the touched object (touch hardening time) was measured in a dryer at 120 ° C. The faster the touch hardening time, the better the curability. Therefore, the finger touch hardening time was classified as follows, and the case corresponding to A was evaluated as having good hardening. Less than 20 minutes: A, 20 to 30 minutes: B, more than 30 minutes: C.

(3) Pot life The sealed components were adjusted to 40 ° C., and the time required for the viscosity to become twice the initial viscosity was taken as the pot life, and the pot life was 4 hours or more. The case was evaluated as having a good pot life.

(4) Heat resistance Each composition was cured at 120 ° C. for 2 hours, and the glass transition temperature of each cured product was measured using a thermal analyzer (manufactured by Rigaku Corporation, DSC measurement apparatus). Since the higher the glass transition temperature, the better the heat resistance, the glass transition temperature was classified as follows, and the case corresponding to A was evaluated as having good heat resistance. 120 ° C or more: A, less than 120 ° C: B.

(5) Moisture resistance Each composition was cured at 120 ° C. for 2 hours, and for each of the obtained cured products, the weight increase rate of the water absorption after 1 hour of boiling was measured according to JIS.
It was measured according to K 6911. The rate of weight increase was classified as follows, and the case corresponding to A was evaluated as having good moisture resistance. 0.5% or less: A, more than 0.5%: B.

(6) Strength of dielectric breakdown Each composition was cured at 120 ° C. for 2 hours, and the strength of dielectric breakdown at a direct current of each cured product obtained was measured. The breakdown strength was classified as follows, and the case corresponding to A was evaluated as having a good breakdown strength. 50 kV / mm or more: A,
Less than 50 kV / mm: B.

[0025]

TABLE 1 Example Comparative Example 1 2 3 1 2 3 4 component composition (parts by weight) Celloxide 2021 80 60 40 100 90 30 0 GOT 20 40 60 0 10 70 100 B-570 110 110 110 110 110 110 110 2E4MZ 1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 Characteristics Impregnation A A A A A A A A Curing A A A C B A A Pot life Good Good Good Good Good Bad Bad Heat resistance A A A A A A C A B A B A A A A A B A B A A A A A B A

The components shown in Table 1 have the following contents.

Celloxide 2021: 3,4-epoxycyclohexylmethyl- (3,4-epoxy) cyclohexylcarboxylate, (manufactured by Daicel Chemical Industries, Ltd.) GOT: N, N-di (glycidyl) -o-toluidine,
(Nippon Kayaku Co., Ltd.) Epicoat 828: Bisphenol A type epoxy resin (Yuoka Shell Epoxy Co., Ltd.) BGE: Butyl glycidyl ether, (Sakamoto Yakuhin Kogyo Co., Ltd.) B-570: Methyltetrahydrophthalic anhydride, 2E4MZ: 2-ethyl-4-methylimidazole,
(Shikoku Chemical Industry Co., Ltd.)

[0028]

Comparative Example 5 67 8 Eight- component composition (parts by weight) celloxide 2021 7050--epicoat 828 30 50 90 80 BGE-- 1020 B-570 100 95 80 80 2E4MZ 1.0 0.95 0.8 0.8 Properties Impregnation BCCA Curability AAAA Pot life Good Good Good Good Heat resistance AACC Moisture resistance AAAC Dielectric breakdown strength AABB .

[0029]

The liquid epoxy resin composition of the present invention has a good impregnation property, a good balance between curability and pot life, and has good heat resistance and moisture resistance of the obtained cured product. Therefore, it is excellent as a resin composition for capacitor insulation sealing.

Continuation of front page (56) References JP-A-61-181819 (JP, A) JP-A-4-275383 (JP, A) JP-A-4-2666976 (JP, A) JP-A-5-279451 (JP, A) (A) Special table 1986-502059 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 59/42 C08G 59/20-59/38 H01G 1/02

Claims (5)

(57) [Claims] An alicyclic epoxy resin content of 40 to 80.
An epoxy resin composition obtained by mixing an acid anhydride and a curing accelerator as a curing agent with respect to a mixed epoxy resin component having an aromatic diglycidylamine-type epoxy resin content of 20 to 60% by weight. A liquid epoxy resin composition, wherein the composition has an initial viscosity of less than 2.0 P (poise) at 23 ° C. 2. The liquid epoxy resin composition according to claim 1, wherein the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl- (3,4-epoxy) cyclohexylcarboxylate. 3. The liquid epoxy resin composition according to claim 1, wherein the aromatic diglycidylamine type epoxy resin is N, N-di (glycidyl) -o-toluidine or N, N-di (glycidyl) aniline. 4. The liquid epoxy resin composition according to claim 1, wherein the acid anhydride is methyltetrahydrophthalic anhydride. 5. An epoxy resin composition for a capacitor, comprising the liquid epoxy resin composition according to claim 1.