JPH05230185A - Electrically insulating composite sheet material having excellent flexibility - Google Patents

Abstract

PURPOSE:To obtain the subject inexpensive material having heat resistance comparable to those of heat-based aromatic aramid-based polymer widely useful as a heat-resistance insulating material comprising a specific epoxy resin, a curing agent of a polycarboxylic acid polyanhydride and reinforcing fibers. CONSTITUTION:The objective material comprises (A) an epoxy resin (preferably bisphenol A type epoxy resin) having 150-300g/eq epoxy equivalent, (B) a curing agent of a polycarboxylic acid of the formula ((m) is 8-20; (n) is 2-20), (C) reinforcing fibers, (D) a latently curing promoter (preferably latently amine adduct- based promoter and/or latently imidazole-based promoter) and (E) an inorganic filler subjected to surface treatment preferably with a silane coupling agent and has >=3 hours pot life during melt blending at 80 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite sheet material which gives a cured product having flexibility and excellent heat resistance, crack resistance and electric insulation. The composite sheet material is a dry transformer or a motor. It is also useful as a material for insulating sheets used in generators and the like.

[0002]

2. Description of the Related Art The most commonly used flexible heat-resistant insulating sheet material used for the above-mentioned insulating applications is Dupo, which is marketed under the trade name "Nomex".
It is a product of NT. This sheet is a meta-aromatic aramid-based polymer of the following structural formula

[0003]

[Chemical 2]

A heat-resistant insulating sheet, which is made of paper made from short fibers and formed into a paper form, and which has excellent heat resistance and electrical insulation properties as well as excellent mechanical strength. Widely used as a material.

However, this insulating sheet material has the drawback that it is very expensive and, in addition, it is hygroscopic so that its electrical insulating property is deteriorated after a relatively short period of use. Is a paper made from short fibers and has innumerable inter-fiber voids, so it cannot be said that the electric insulation of the material itself is fully utilized, and the dielectric breakdown strength is also likely to be insufficient.

[0006]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances, and its purpose is to use an inexpensive epoxy resin as a main component for an insulating sheet material for a generator or the like. Even in such a case, it is intended to provide a composite sheet material having heat resistance and electric insulation that can be sufficiently put into practical use and having good flexibility. Another object of the present invention is to
It has a long pot life in the melt-kneading state, improves the handling workability when it is heat-formed into a sheet shape, and further suppresses the shrinkage during curing and reduces the thermal expansion of the cured product. It is intended to provide a material that gives a composite sheet having excellent radiation properties.

[0007]

[Means for Solving the Problems] The composite sheet material according to the present invention, which has been able to solve the above problems, includes an epoxy resin having an epoxy equivalent of 150 to 300 g / eq or less, and the following general formula [I]

[0008]

[Chemical 3]

It is a composite material excellent in flexibility, electric insulation and dielectric breakdown, which contains a polycarboxylic acid polyanhydride curing agent represented by and a reinforcing fiber as main constituents. Above all, the epoxy equivalent of epoxy resin is 150-30
By using 0 g / eq of bisphenol A type epoxy resin, bisphenol F type epoxy resin or phenol novolac type epoxy resin, it is possible to obtain a composite sheet material having extremely excellent mechanical and electrical properties.

If a latent curing accelerator (preferably an amine adduct-based or imidazole-based curing accelerator) is blended in addition to the above-mentioned constituents, the pot life at the time of heat-melt kneading can be extended, and the composite If it is possible to obtain a material for forming a composite sheet that is excellent in handling workability during forming into a sheet, and if an inorganic filler (preferably surface-treated with a silane coupling agent) is added as another component, Further, the curing shrinkage is suppressed and the thermal expansion coefficient of the cured product is also suppressed to be low. As a result, it is possible to obtain a material which gives a composite sheet having high thermal conductivity and excellent heat dissipation.

[0011]

As described above, in the present invention, the epoxy resin having an epoxy equivalent of 150 to 300 g / eq is used as the base resin, and the polycarboxylic acid polyanhydride represented by the general formula [I] is used as the curing agent. By combining these with reinforcing fibers, a composite sheet material which gives a cured product having excellent electrical insulation and strength and flexibility, and further other components to this material are obtained. By blending a latent curing accelerator and an inorganic filler as
It is possible to obtain a composite material that has a long pot life to improve handling workability and that provides a cured sheet with improved heat transfer characteristics.

In the present invention, the epoxy resin has an epoxy equivalent of 150 to 300 g / eq, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin,
Resorcinol type epoxy resin, hexahydrobisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, polypropylene glycol diglycidyl ester, phthalic acid diglycidyl ester, bisphenol hexachloroacetone diglycidyl ether and the like can be mentioned. Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin and phenol novolac type epoxy resin are particularly preferable. These may be used alone or, if necessary, may be used in combination of two or more kinds.

The bisphenol A type epoxy resin is, for example, "DER331" manufactured by Dow Chemical Co., "GY260", "GY280" manufactured by Ciba-Geigy Co., Ltd., "Epicoat 828" manufactured by Yuka Shell Epoxy Co., Ltd .; bisphenol F type epoxy resin. Is, for example, "Epicote 807" manufactured by Yuka Shell Epoxy Co .; Phenol novolac type epoxy resin is, for example, "DEN431" manufactured by Dow Chemical Co.,
It can be obtained as "DEN438" or the like.

If the epoxy equivalent is less than 150 g / eq,
The heat resistance and flexibility of the obtained composite sheet material become poor, while those exceeding 300 g / eq are solid at room temperature or have extremely high viscosity, and are not only difficult to handle, but also reinforced fibers. It also becomes difficult to penetrate into the cured product, and voids are formed in the cured product, resulting in poor strength and flexibility. Therefore, in the present invention, an epoxy equivalent of 150 to 300 g / eq must be used. When two or more kinds of epoxy resins are used in combination, the combined ratio may be adjusted so that the average value thereof is 150 to 300 g / eq.

The polycarboxylic acid polyanhydride used as a curing agent has a function of increasing the inter-crosslinking distance to give flexibility to the cured product, and is represented by the above general formula [I]. Collective polymers are collectively referred to. In the general formula [I], if m and n are too large, the cured product tends to have insufficient strength, and if too small, the flexibility of the cured product tends to be insufficient. It is desirable to use those having 20, n of 2 to 20. Preferred polycarboxylic acid polyanhydrides satisfying these requirements include polycarboxylic acid anhydrides such as polydodecanedioic acid polyanhydride and polyeicosanedioic acid polyanhydride, for example, "SL-12AH" and "SL-12" manufactured by Okamura Oil Co., Ltd. -20 AH "and the like.
These may be used alone or in combination of two or more. The amount of the polycarboxylic acid polyanhydride curing agent is preferably 30 to 200 parts by weight, more preferably 50 to 150 parts by weight, based on 100 parts by weight of the epoxy resin.

Next, the reinforcing fiber is a compound to further enhance the physical properties of the cured product, particularly strength and flexibility, and is an inorganic fiber such as glass fiber, asbestos fiber or carbon fiber,
Also, organic fibers such as polyamide fibers, polyamideimide fibers, aramid fibers, polyester fibers, polyphenylene sulphite fibers and polystyrene fibers can be used alone or in combination of two or more kinds. These can be compounded as short fibrous materials, but in order to exert the reinforcing effect more effectively, long fibers are matted,
It is preferable to use it in the form of woven / knitted fabric or non-woven fabric.

The composite ratio of the reinforcing fiber and the epoxy resin composition (the sum of the epoxy resin and the curing agent) is not particularly limited,
The content may be appropriately selected depending on the application, required characteristics, etc., but it is preferably in the range of 10 to 90% by weight, more preferably 20 to 80% by weight in the content of the reinforcing fibers in the total amount of the composite sheet material. Good.

In the first constitution according to the present invention, the above-mentioned epoxy resin, polycarboxylic acid polyanhydride curing agent and reinforcing fiber are essential constituent components, and accordingly, it has excellent flexibility. In addition, a composite sheet material which gives a cured product having excellent heat resistance, crack resistance and electric insulation can be obtained. However, in addition to these, if a latent curing accelerator and an inorganic filler are used together as other components, the handling workability at the time of molding into a sheet-like product is enhanced and the transmission of the cured product is further enhanced as described in detail below. The thermal characteristics can be improved. Therefore, in the second constitution of the present invention, these latent curing accelerator and inorganic filler are contained as essential components.

First, the latent curing accelerator has a function of suppressing an increase in viscosity in a melt mixed state at the time of forming into a sheet shape and extending a pot life, and various known latent curing accelerators. Although an agent can be used, particularly preferable in combination with the polycarboxylic acid polyanhydride curing agent used in the present invention is an amine adduct-based or imidazole-based curing accelerator, which are used alone. Or two or more kinds may be used in combination. As the amine adduct-based curing accelerator, for example, trade names “Amicure MY-24” and “Amicure MY-H” manufactured by Ajinomoto Co., Inc.
Examples of imidazole-based curing accelerators include Shikoku Kasei Co., Ltd., trade name “Curezol C17Z” (2-heptadecyl imidazole), “Curezol 2PZ” (2-phenylimidazole), Yuka Shell Co., Ltd. trade name “Epicure EMI-24”. (2-Ethyl-4-methylimidazole) and the like are exemplified as preferable ones. The addition amount of these latent curing accelerators may be appropriately determined according to the degree of pot life required, but the standard amount is 0.1 to 100 parts by weight of polycarboxylic acid polyanhydride curing agent.
It is desirable to adjust the content to be 5 parts by weight, more generally 0.5 to 2% by weight, and to adjust the pot life of the composite sheet material at 80 ° C. for 3 hours or more.

The inorganic filler has the function of suppressing shrinkage at the time of curing and reducing the coefficient of thermal expansion of the cured sheet to increase the thermal conductivity and improve heat dissipation. For example, when used as an insulating sheet material or the like. It exhibits the effect of suppressing the thermal deterioration of talc, kaolin, mica, bentonite, silica, calcium carbonate, alumina, hydrated alumina, hydrated magnesium, zirconium silicate, calcium silicate, aluminum silicate, calcium bicarbonate. Preferred are silicon carbide whiskers, potassium titanate whiskers, glass fiber powder and the like.

These inorganic fillers have a silane coupling agent or a titanate-based surfactant on their surface in order to prevent cracks or water from entering at the interface with the epoxy resin which is a component of the vehicle after curing. It is preferable that the wettability with the epoxy resin is enhanced by treating with an aluminum-based surfactant, a zirconium-based surfactant, or the like. From this point of view, the most preferable surface treatment agent is a silane coupling agent, and any of the above-mentioned inorganic fillers exemplified as preferable ones can be easily subjected to silane coupling treatment.

It should be noted that the inorganic filler is preferably subjected to a surface treatment for improving the wettability with the epoxy resin in advance for the above-mentioned reason, but instead of this, the inorganic filler is mixed at the time of kneading to obtain the composite material. It is also possible to add a silane coupling agent or the like. The preferable blending amount for effectively exhibiting the effect of the inorganic filler is in the range of 20 to 60% by weight in the total amount of the composite sheet material.

The essential components of the composite sheet material according to the present invention are as described above, but in order to prevent the occurrence of void defects by suppressing foaming during kneading within a range that does not impair the characteristics of the present invention. It is also possible to add an antifoaming agent, and further to add an appropriate amount of a pigment, a dye, an antioxidant, an antistatic agent, a flame retardant, a release agent and the like.

The method of combining the above-mentioned respective raw materials is not particularly limited either, but the polycarboxylic acid polyanhydride curing agent is a solid at room temperature, and the mixture of this and the epoxy resin or the inorganic filler is highly viscous at room temperature. As it is, it is difficult to uniformly compound the reinforcing fibers without voids. Therefore, it is preferable that the mixture of the curing agent, the latent curing accelerator and the epoxy resin be equal to or higher than the melting point of the curing agent (usually about 80 ° C. or higher).
If it is used together with an inorganic filler, it should be uniformly mixed before impregnating the reinforcing fiber, or ketones, glycol ethers, hydrocarbons, chlorinated hydrocarbons, etc. It is possible to consider a method of appropriately diluting with an inert organic solvent, and then impregnating. Considering uniform impregnation, it is preferable to impregnate the heat-melted and kneaded product.

The curing conditions after impregnation are not particularly limited, and the optimum conditions may be selected each time depending on the type and blending ratio of the epoxy resin, the curing agent, and the latent curing accelerator, but usually 60 to 200. It is selected from the range of 0.1 to 72 hours at ℃.
If a suitable pressure is applied with a pressing machine or the like during the curing reaction, the epoxy resin or the like will more reliably infiltrate into the voids between the reinforcing fibers, and a high-performance sheet-shaped cured product with no void defects can be easily obtained.

[0026]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to the following examples. Example 1 100 g of bisphenol A type epoxy resin "DER331" (epoxy equivalent: 190 g / eq) manufactured by Dow Chemical Co. and polydodecanic acid polyanhydride "SL-12A" manufactured by Okamura Oil Co., Ltd.
96 g of "H" was placed in a beaker and uniformly melt-mixed at 100 ° C. This molten mixture was impregnated into a glass fiber cloth “Glavest SBP” manufactured by Olivebest Co., which had been cut into A-4 size, and then pressed at 50 kg / cm ² with a 10-ton small press manufactured by Yasuda Seiki. Heat at 200 ℃ for 2 hours, thickness
A 180 μm composite sheet was obtained.

Example 2 Melt mixing, impregnation and pressurization / heating were carried out in the same manner as in Example 1 except that 0.5 g of imidazole "Epicure EMI-24" manufactured by Yuka Shell Co.
A 180 μm composite sheet was obtained.

Example 3 As the epoxy resin, a phenol novolac type epoxy resin "DEN431" manufactured by Dow Chemical Co. (epoxy equivalent:
178 g / eq) was used, and melt mixing, impregnation and pressurization were carried out in the same manner as in Example 1 except that the amount of the curing agent was 103 g.
It was heated to obtain a composite sheet having a thickness of 180 μm.

Example 4 Polyeicosanedioic acid polyanhydride "SL-20AH" manufactured by Okamura Oil Co., Ltd. was used as a curing agent, and the compounding amount of the curing agent was 132.
Melt mixing, impregnation, pressurization and heating were carried out in the same manner as in Example 1 except that the amount was changed to g to obtain a composite sheet having a thickness of 180 μm.

Example 5 Example 5 except that a bisphenol F type epoxy resin "Epicoat 807" (epoxy equivalent: 174 g / eq) manufactured by Yuka Shell Epoxy Co., Ltd. was used as the epoxy resin, and the amount of the curing agent was 105 g. Melt mixing, impregnation, pressurization and heating were carried out in the same manner as in 1 to obtain a composite sheet having a thickness of 180 μm.

Comparative Example 1 Tetraglycidyl diaminodiphenylmethane "Epicoat 604" manufactured by Yuka Shell Epoxy Co., Ltd. as an epoxy resin
(Epoxy equivalent: 120g / eq)
Melt mixing, impregnation, pressurization and heating were carried out in the same manner as in Example 1 except that the amount was changed to 151 g to obtain a composite sheet having a thickness of 180 μm.

Comparative Example 2 Example 2 except that a bisphenol A type epoxy resin "Epicoat 1004" (epoxy equivalent: 810 g / eq) manufactured by Yuka Shell Epoxy Co., Ltd. was used as the epoxy resin and the amount of the curing agent was changed to 23 g. Melt mixing, impregnation, pressurization and heating were carried out in the same manner as in 1 to obtain a composite sheet having a thickness of 180 μm.

Comparative Example 3 Melt mixing, impregnation, pressurization and heating were carried out in the same manner as in Example 1 except that 27 g of diaminodiphenylmethane (DDM) was used as the curing agent to obtain a composite sheet having a thickness of 180 μm.

Comparative Example 4 Melt mixing, impregnation, pressurization and heating were carried out in the same manner as in Example 1 except that 98 g of methyl nadic acid anhydride (MNA) was used as the curing agent, and a composite sheet having a thickness of 180 μm was obtained. Obtained. For each composite sheet obtained above, the MIT flex test (JIS
P8115) and electrical breakdown strength test (ASTM D14
9) was performed and the results collectively shown in Table 1 were obtained.

[0035]

[Table 1]

As is clear from Table 1, all of Examples 1 to 5 satisfying the specified requirements of the present invention have excellent flexibility and electrical insulation characteristics, while Comparative Example 1 Is an epoxy resin having an epoxy equivalent of less than 150 g / eq, Comparative Example 2 has an excessive epoxy equivalent of the epoxy resin, and Comparative Examples 3 and 4 have an unsuitable curing agent. However, the flexibility is extremely poor, and the electrical insulating property is also poor. The heat resistance of the composite sheets obtained in Examples 1 to 5 (pyrolysis start temperature; measured by a thermogravimetric analyzer TGA7 manufactured by Perkin Elmer Co., Ltd. at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere, was measured. The weight loss obtained from the weight measurement results is defined as the temperature at which the weight loss becomes 5%, and is 350 ° C. or higher, which is extremely good.

Example 6 100 g of a phenol novolac type epoxy resin “DER431” (epoxy equivalent: 178 g / eq) manufactured by Dow Chemical Co. and polydodecanedioic acid polyanhydride “SL-12A” manufactured by Okamura Oil Co., Ltd.
97 g of "H" was placed in a beaker and uniformly melt-mixed at 100 ° C. The molten mixture was added to the defoaming agent "SN-" manufactured by San Nopco.
352 "(0.1 g) was added, and then 100 g of kaolin" SP-33 (epoxysilane surface-treated product) "manufactured by Tsuchiya Kaolin Co., Ltd. was added and further uniformly mixed. Lastly, 1g of latent imidazole type curing accelerator "CUREZOL C17Z" manufactured by Shikoku Kasei Co., Ltd.
Then, the mixture was mixed uniformly.

The pot life of this molten mixture at 80 ° C. (time until the melt viscosity becomes twice as much as that at the start of measurement) was measured using a B type viscometer “Visco Tester (VT-04)” manufactured by Rion. I asked. Further, the gelation time at 80 ° C. was determined using “Gel Time Tester” manufactured by Yasuda Seiki. The remaining molten mixture was impregnated into a glass fiber paper “Glavest SBP” manufactured by Olivebest Co., which had been cut to A-4 size, and then 30 kg using a 10-ton small press manufactured by Yasuda Seiki Co., Ltd.
While pressurizing at / cm ² , heat at 150 ℃ for 10 minutes to cure,
A composite sheet with a thickness of 200 μm was obtained.

Example 7 As a curing accelerator, 1 g of a latent amine adduct type curing accelerator "Amicure MY-24" manufactured by Ajinomoto Co., Inc. was used and melt-mixed in the same manner as in Example 6 at 80 ° C. The pot life and gelation time of each were determined. The remaining molten mixture was impregnated with glass fiber paper “Glavest SBP” manufactured by Olivebest Co., which had been cut into A-4 size, and then impregnated with a 10-ton small press manufactured by Yasuda Seiki Co., Ltd. at 30 kg / c.
While pressurizing with m ^2, it was heated at 150 ° C. for 30 minutes for curing to obtain a composite sheet with a thickness of 200 μm.

Reference Example 1 Example 6 except that 1 g of Imidazole "Epicure EMI-24" manufactured by Yuka Shell Co., Ltd. was used as a curing accelerator.
Melting and mixing were performed in the same manner as in ~ 8, and the pot life at 80 ° C and the gelation time were determined. Further, the remaining molten mixture was impregnated into a glass fiber sheet in exactly the same manner as in Example 1 and then subjected to pressure / heat treatment to obtain a composite sheet having a thickness of 200 μm.

Reference Example 2 The same procedure as in Example 1 was carried out except that 100 g of kaolin "SP-33" manufactured by Tsuchiya Kaolin Co., which was not treated with epoxysilane, was used as the inorganic filler. 200 μm thick after impregnation and pressure / heat treatment
A composite sheet of m 2 was obtained.

Comparative Example 5 Melt mixing, impregnation into a glass fiber sheet and pressure / heat treatment were carried out in the same manner as in Example 1 except that the inorganic filler and the defoaming agent were not used, and the thickness was adjusted. A 200 μm composite sheet was obtained. For each composite sheet obtained above, M
An electric breakdown strength test (ASTM D149) before and after the IT bending test (JIS P8115) and the heat aging test (245 ° C. × 500 hours) was performed, and the results are shown in Table 2 together with the pot life and gelation time.

[0043]

[Table 2]

As is clear from Table 2, Examples 6 and 7 satisfying the requirements of the present invention show a good pot life when the pot life is 3 hours or more, and the cured sheet thereof has good electrical and mechanical properties. Have specific characteristics. On the other hand, Comparative Example 5
Since no inorganic filler is added, the electrical breakdown strength after heat aging is significantly reduced.

Reference Examples 1 and 2 meet the requirements of the present invention, but in Reference Example 1, the effect of extending the pot life is likely to be insufficient because the amount of the curing accelerator added is inappropriate. Workability remains unsatisfactory. Further, in Reference Example 2, since the inorganic filler which is not surface-treated is used, the dispersibility of the filler at the time of kneading the raw materials is poor, and the electrical breakdown strength after heat aging is significantly reduced.

[0046]

EFFECTS OF THE INVENTION The present invention is constructed as described above, and by using polycarboxylic acid polyanhydride as a curing agent for epoxy resin and combining these with reinforcing fibers, strength, flexibility and heat resistance are improved. It is possible to obtain a composite sheet material having excellent properties and excellent electrical insulation properties. Moreover, this composite sheet material has excellent moisture resistance, and there is no fear that the insulating property will be deteriorated due to moisture absorption as seen in known meta-aromatic aramid-based polymers. Further, when an appropriate amount of a latent curing accelerator is added to this composite material as another component, the thickening of the mixture before curing is suppressed, the pot life can be extended, and the handling workability is enhanced. Further, when an appropriate amount of the inorganic filler is blended, shrinkage at the time of curing can be suppressed, the coefficient of thermal expansion of the cured product can be reduced, and the heat dissipation property can be improved to enhance the electric breakdown strength.

Claims (6)

[Claims] 1. An epoxy resin having an epoxy equivalent of 150 to 300 g / eq and the following general formula [I]: An electrically insulative composite sheet material having excellent flexibility, which comprises a polycarboxylic acid polyanhydride curing agent represented by the formula (1) and reinforcing fibers. 2. The composite sheet material according to claim 1, wherein the epoxy resin is at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin and phenol novolac type epoxy resin. 3. A latent curing accelerator and an inorganic filler as a further component.
The composite sheet material according to. 4. The composite sheet material according to claim 3, wherein the latent curing accelerator is a latent amine adduct accelerator and / or a latent imidazole accelerator. 5. The composite sheet material according to claim 3, wherein the inorganic filler is surface-treated with a silane coupling agent. 6. The composite sheet material according to claim 3, which has a pot life of 3 hours or more when melt-kneaded at 80 ° C.