JPH0565961B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to an epoxy semiconductive material, and particularly to an epoxy semiconductive material that can provide a stable electrical resistance value. (b) Prior Art In high-voltage rotating machines, corona generation causes deterioration of insulators, so semiconducting materials are used in slot liners for heavy electric power generation and the like to prevent corona generation. Conventionally, such semiconductive materials have been produced by impregnating a nonwoven fabric made of a mixture of aromatic polyamide fibers and polyester fibers with a heat-resistant semiconductive resin composition such as an epoxy resin or an epoxy ester resin containing carbon black, and curing with heat. A method has been proposed (Japanese Unexamined Patent Publication No. 58-25003). (c) Problems to be solved by the invention However, the coexistence of epoxy resin and carbon black is poor, and it is difficult to uniformly disperse carbon black by simply adding carbon black to epoxy resin and mixing. It is. Therefore, the distribution of carbon black chains in an epoxy semiconductive material made by impregnating a fiber base material with carbon black-containing epoxy resin and curing it is non-uniform, and connects adjacent carbon black chains. The chains are simply formed by larger carbon black aggregates. For this reason, it has been reported that the electrical resistance of epoxy semiconducting materials formed by simply mixing carbon black with epoxy resin becomes high with large variations (Yokogawa Shobo Co., Ltd. 1970, VE
In fact, according to the study results of the present inventors, when epoxy resin and carbon black were mixed for a long time using methods such as three-roll kneading, carbon black The carbon black-containing epoxy resin composition formed aggregates without being uniformly dispersed, and this carbon black-containing epoxy resin composition exhibited significant thixotropy and could not be sufficiently and uniformly impregnated into the fiber base material. Furthermore, the semiconductive material obtained by heating and curing this material has large variations in surface resistivity and volume resistivity, lacks reproducibility, and makes it impossible to obtain a stable resistance value. In particular, semiconductive materials used for the purpose of preventing corona discharge in heavy electric generators include:
Surface resistivity 0.5~20.0KΩ, volume resistivity 2.0~
A material with a resistance of 200.0 KΩ·cm is desired, but a semiconductive material with such characteristics cannot be obtained by simply mixing carbon black and an epoxy resin liquid, and is therefore impractical. (d) Means for Solving the Problems The present inventors used an epoxy resin with excellent heat resistance as a resin component, and created an epoxy half that improves the affinity between this resin and carbon black and has high mechanical strength. Over the years, various studies have been conducted regarding conductive materials. As a result, the diallylphthalate prepolymer is extremely effective in improving the dispersibility of carbon black in epoxy resin, and the mechanical and electrical properties of the resulting epoxy semiconductive material are stable and excellent. The present invention has been completed based on this discovery. That is, the present invention impregnates a fiber base material with a semiconductive epoxy resin composition consisting of an epoxy resin, an epoxy resin curing agent, carbon black, and a diallyl phthalate prepolymer, and then cures the semiconductive epoxy resin composition by impregnating it alone or by laminating two or more sheets. It is characterized by an epoxy semiconducting material made of. The present invention will be explained in detail below. First, the components constituting the semiconductive epoxy resin composition of the present invention will be explained. The epoxy resin used in the present invention has an epoxy equivalent of 50 to 3300 and a number average molecular weight of 300 to 3300.
3800 (gel permeation chromatography method, polystyrene equivalent value) is used in liquid or solid form, but especially those with an epoxy equivalent of 150
450, and a number average molecular weight of 330 to 900 is preferable because a uniform and stable composition can be obtained and handling properties are excellent. In addition, it is desirable to use solid materials with an epoxy equivalent of 450 or more after softening them with a solvent or plasticizer. The types of epoxy resins mentioned above include bisphenol A type epoxy resin, novolac type epoxy resin, bisphenol F type epoxy resin, brominated epoxy resin, cycloaliphatic epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin. , heterocyclic epoxy resins, etc., but in particular bisphenol A epoxy resins, flame-retardant brominated bisphenol A epoxy resins, and novolak epoxy resins have excellent heat resistance and are suitable for electrical applications. This is preferred because good physical and mechanical properties can be obtained. Further, the above epoxy resins may be used in combination as desired. Examples of UV-curable epoxy resins include acrylic esters of epoxy resins, reaction products of acrylic esters of epoxy resins and maleic anhydride, reaction products of epoxy resins and maleic anhydride, and epoxy resins and A reaction product of acrylic acid and methyltetrahydrophthalic anhydride, a reaction product of epoxy resin and 2-hydroxyethyl acrylate,
Examples include a reaction product of an epoxy resin, butylamine, and glycidyl methacrylate, a reaction product of an acrylic acid ester of an epoxy resin and N-methylolamine, a reaction product of an epoxy resin diglycidyl ether and diallylamine, and the like. As the epoxy resin, bisphenol A type, novolac type or alicyclic type is used. Incidentally, in order to obtain sufficient curing characteristics of these ultraviolet curable epoxy resins, it is appropriate to form them into a thin sheet material with a thickness of 0.3 mm or less. Furthermore, the epoxy resin curing agent used in the present invention is one that can cure the above-mentioned epoxy resin at room temperature, by heating, or by irradiation with ultraviolet rays, and its type, combination with a curing accelerator, etc. are not specified. Further, as the curing agent used in the present invention, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, bis(hexamethylene)triamine, 1,3,6-trisaminomethylhexane, dipropylenetriamine, polymethylenediamine, trimethyl Chain aliphatic polyamines such as hexamethylene diamine, polyether diamine, diethylaminopropylamine, bis(4
-amino-3-methylcyclohexine)methane,
Cycloaliphatic polyamines such as N-aminoethylpiperazine, menthene diamine, isophorone diamine, metaxylylene diamine, xylylene diamine trimer, metaphenylene diamine, diaminodiphenylmethane, diaminodiphenylsulfon, etc. Heterocyclic amines of aromatic polyamines, maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, alkenyl succinic anhydride,
Cyclic aliphatic acid anhydrides such as hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylcyclohexenetetracarboxylic anhydride, phthalic anhydride, trimellitic anhydride, ethylene glycol bis(anhydrotrimellitate), glycerol tris( polyamide resin obtained by condensation of dimer acid and polyamine , dicyandiamide, 2-(dimethylaminoethoxy)4-methyl-1,3,2-dioxabornane, 2-methylimidazole, 1-
Benzyl-2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-
Methylimidazole, 1-cyanoethyl-2-udecylimidazolium trimellitate, 1-cyanoethyl-2-phenyl-4,5-di(cyanoethoxymethyl)imidazole, 2-methylimidazolium isocyanurate, 2,4-diamino Examples include imidazoles such as -6-[2-methylimidazolyl-1]-ethyl S triazine, boron trifluoride-amine complexes, and polysulfide resins. They have good compatibility and are generally preferred, and amine curing agents, especially aliphatic amines, and polyamide resins are particularly preferred because they have excellent room temperature curability. Further, in the present invention, a curing accelerating aid is added if desired, and such curing accelerating aids include tertiary amines, Lewis acids, imidazole borate esters, organometallic salts, organometallic compounds, etc. It will be done. In addition, examples of photosensitizers used in ultraviolet curable epoxy resins include benzoin, benzoin methyl ether, benzoin ethyl ether,
Benzoin isopropyl ether, benzoin butyl ether, 2-methylbenzoin, benzophenone, benzoin peroxide, azobisisobutyronitrile, 2-chlorohexanone, Michler's ketone, benzyl, benzyl dimethyl ketal, benzyl diethyl ketal, anthraquinone, methylanthraquinone, diacetyl, acetophenone , diphenyl disulfide, anthracene, etc. The amount of these photosensitizers used is usually 0.05 to 30 parts by weight per 100 parts by weight of the UV-curable epoxy resin. A small amount of auxiliary agent may also be used. Further, in order to improve the thermal stability of the epoxy resin composition, it may be effective to coexist with a known thermal polymerization inhibitor. Specific examples of thermal polymerization inhibitors include para-methoxyphenol, hydroquinone, tertiary-butylcatechol, pyrogallol, phenothiazine, chloranil, naphthylamine, β-naphthol, 2,6-ditertiary-butyl para-cresol, pyridine, nitrobenzene, para-toluidine, methylene blue, etc. The amount used is usually 0.01 to 100 parts by weight of epoxy resin.
The amount is preferably 5 parts by weight. Further, the carbon black used in the present invention is not particularly limited, and specific examples include various conductive carbon blacks such as acetylene black, graphite, and furnace black. Conductive furnace blacks, which have a remarkable sex-imparting effect, are advantageous; commercially available products include HS-500 (manufactured by Asahi Carbon Co., Ltd.) and Ketuchen Black EC (manufactured by Lion Corporation).
and so on. The most significant feature of the present invention is that diallyl phthalate prepolymer is added to the semiconductive epoxy resin composition, which allows carbon black to be uniformly dispersed in the epoxy resin. . The diallyl phthalate prepolymer used in the present invention has good compatibility with the epoxy resin used, has a softening point range of 60 to 120°C, and has a molecular weight of
5000-30000, diallyl phthalate prepolymer with an iodine number of 50-70, or a softening point range of 50-70.
Molecular weight at 100℃ is 5000~30000, iodine value is 70~
100 diallyl phthalate prepolymer. Commercially available products include Daiso Sodap A, Daiso Sodap L (manufactured by Osaka Soda Co., Ltd.), and Daiso Indap (made by Osaka Soda Co., Ltd.), which is a diallyl phthalate prepolymer. The semiconductive epoxy resin composition used in the present invention is obtained by mixing the above-mentioned epoxy resin, epoxy resin curing agent, carbon black, and diallyl phthalate prepolymer in a conventional manner. Per 100 parts by weight of resin, 1 to 50 parts by weight of epoxy resin curing agent, 5 to 150 parts by weight of carbon black, especially 7 to 20 parts by weight,
and diallyl phthalate prepolymer from 1 to 70 parts by weight, particularly preferably from 10 to 40 parts by weight,
Mixing ratios other than this are not preferred because sufficient heat resistance, mechanical strength, and electrical resistance values may not be obtained. Furthermore, in producing the semiconductive epoxy resin composition, instead of the above, carbon black may be uniformly dispersed in diallyl phthalate prepolymer in advance, and this may be blended and mixed into the epoxy resin composition. As the fiber base material used in the present invention, woven fabrics or nonwoven fabrics of polyester fibers, aramid fibers, carbon fibers, glass fibers, etc., as well as nonwoven fabrics made by mixing these materials, are used. The epoxy semiconductive material of the present invention can be produced by manufacturing a prepreg by a conventional method, such as impregnating the above-mentioned semiconductive epoxy resin composition into the above-mentioned fiber base material, and then manufacturing the prepreg singly or by stacking a plurality of prepregs. , is made by curing this. In this case, the prepreg may be produced by a hot melt method that does not use an organic solvent. Alternatively, the material may be prepared by impregnating it with a semiconductive epoxy resin composition and then directly curing it without going through the prepreg state. Furthermore, the semiconductive material of the present invention may be a composite of these prepregs laminated with other metal materials, such as copper foil or iron foil. (e) Effect In the present invention, epoxy resins with poor coexistence -
Although it is not clear why the dispersibility of carbon black is greatly improved by introducing diallylphthalate prepolymer into the carbon black system,
Carbon black has good coexistence with diallyl phthalate prepolymer, and on the other hand, diallyl phthalate prepolymer has good affinity with epoxy resin, so carbon black is a diallyl phthalate prepolymer with good affinity with epoxy resin. The carbon black coated with this diallylphthalate prepolymer is uniformly dispersed in the epoxy resin liquid. In other words, the carbon black is uniformly dispersed in the epoxy resin, and the electrical resistance is stabilized and lowered. It has. (f) Examples Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto. Note that in the following, parts or % mean parts by weight or % by weight. Example 1 As the epoxy resin, bisphenol A type epoxy resin (epoxy equivalent: 450 to 500 g/eq, softening point
64-74℃) 100 parts by weight, 30 parts of trimellitic anhydride as an epoxy resin curing agent, conductive fairness black (HS) as a carbon black.
-500, manufactured by Asahi Carbon Co., Ltd.) 15 parts and number average molecular weight as diallyl orthophthalate prepolymer
3300, a softening point of 85°C, and an iodine value of 60, were added to a mixing pot, and then toluene was added to make a resin composition solution with a base of about 50%, and this was mixed in a high-speed disper for 2 hours. By stirring, a semiconductive epoxy resin composition in which carbon black was uniformly dispersed in the epoxy resin was obtained. This composition was impregnated into a polyester nonwoven fabric having a basis weight of 40 g/m ² , a thickness of 0.12 mm, and a fiber thickness of 1 to 2 deniers, and then dried at a temperature of 100°C for 20 minutes to impregnate the semiconductive epoxy resin composition. A prepreg with a volume of 70% was obtained. Five sheets of this prepreg were laminated and heated at 160°C.
Press molded under conditions of time and molding pressure of 50 kg/ ^cm2 , and removed after cooling to a thickness of 0.5 mm, lengthwise,
Epoxy semiconducting materials of the invention were obtained, each having a lateral dimension of 1000 mm. Examples 2 to 13 Examples 2 to 13 were conducted in the same manner as in Example 1 using semiconductive epoxy resin compositions having the compositions shown in Table 1.
epoxy semiconducting material was produced. Comparative Examples 1 to 3 Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 using semiconductive epoxy resin compositions having the compositions shown in Table 1.

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[Table] Table 2 shows the results of investigating various characteristics of each of the above examples and comparative examples.

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[Table] As is clear from Table 2, the epoxy semiconductive material of the present invention has a stable electrical resistance value, and is recognized to be a material with stable quality with little variation. On the other hand, it is recognized that the materials shown in each comparative example have large variations in electrical resistance value, and it is extremely difficult to obtain a desired electrical resistance value. Furthermore, from the evaluation of the compressive strength, by adjusting the blending ratio of the added diallyl phthalate prepolymer in an appropriate amount, the brittleness of the epoxy resin can be eliminated and the compressive strength can be significantly improved. Furthermore, for each example, at a temperature of 120°C, the initial value,
Changes in surface resistivity were measured after 25 hours, 100 hours, and 200 hours, but almost no change was observed. (g) Effects of the Invention The epoxy semiconductive material of the present invention has the above structure and has excellent heat resistance because it uses an epoxy resin with excellent heat resistance as a resin component. Since diallyl phthalate prepolymer is added to improve coexistence with the resin, the dispersibility of carbon black is improved, and as a result, the electrical resistance is stabilized and reduced. Furthermore, if the amount of diallyl phthalate prepolymer added is appropriate, it has the effect of significantly improving the mechanical strength of the epoxy semiconductive material.

Claims (1)

[Claims] 1. A semiconductive epoxy resin composition consisting of an epoxy resin, an epoxy resin curing agent, carbon black, and a diallyl phthalate prepolymer is impregnated into a fiber base material, and the fiber base material is used alone or two or more sheets are laminated, A hardened epoxy semiconducting material. 2 For 100 parts by weight of epoxy resin, 1 to 40 parts by weight of epoxy resin curing agent, 5 to 40 parts by weight of carbon black
150 parts by weight and 1 to 70 parts by weight of diallyl phthalate prepolymer.