JPS6027129B2 - Method for manufacturing electrical insulators - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an electrical insulator, and more particularly to a method for producing an electrical insulator by vulcanizing a specific compounded rubber.

Ethylene-Q-olefin-diolefin copolymer rubber,
Ethylene-Q-olefin copolymer rubber, etc.
Vulcanized product obtained from olefin copolymer rubber Due to its rubber structure, it has excellent heat resistance, ozone resistance, chemical resistance, and electrical insulation, and is flexible, so it is resistant to mechanical vibration. It is used as an electrical insulator around automobile engines, such as the black cap of automobile engines, ignition caps, distribution caps, and insulation layers of ignition cables, which are exposed to intense high-temperature atmospheres. Furthermore, it is suitably used as an electrical insulator such as an insulating layer for ordinary power transmission wires.

Such electrical insulators are made of a vulcanized compound containing ethylene-Q-olefin copolymer rubber, a softener, an inorganic filler, a vulcanizing agent, a vulcanization accelerator, or a vulcanization aid. Once the rubber is prepared, the compounded rubber is molded and vulcanized to produce an electrical insulator through a process depending on the use of each electrical insulator. The present invention relates to a method for producing electrical insulators by vulcanizing such compounded rubber. Recently, due to automobile exhaust gas regulations, engine temperatures have increased due to improvements in combustion efficiency, and the temperature around the engine, which used to be below 100 degrees Celsius, is now exposed to higher temperatures than before, to over 10,000 degrees Celsius. Therefore, electrical insulators used around engines are required to have even higher heat resistance, but vulcanizates obtained from conventionally known ethylene-Q-olefin copolymer rubber compositions do not meet this requirement. The inventor has found that the requirements are not met.

For example, in Japanese Patent Publication No. 49-16259, a composition comprising an ethylene-propylene-gene copolymer rubber, a mineral filler, a peroxide, and a specific compound such as a quinone dioxime compound, a nitroso compound, or a nitro compound is described as a special compound. Discloses a method for producing a vulcanizate with excellent heat resistance. However, in the description of the publication,
When left at 120 qo for 7 days, the vulcanizate elongates and its strength decreases to less than 90% of its initial value.According to the inventor's experiments, the vulcanizate was subjected to an accelerated heat resistance test, that is, when left at 160 qo for 7 days. Both elongation and strength decreased to less than 50% of their initial values, and the degree of deterioration was severe, and the original flexibility and strength of ethylene-Q-olefin rubber vulcanizates could not be maintained for long periods at high temperatures of around 120°C. Therefore, it was not suitable as an electrical insulator around future automobile engines. Furthermore, since electrical wires for ships, i.e., marine electrical wires, require particular flexibility due to the complicated wiring inside the ship, vulcanized products of ethylene-Q-olefino copolymer rubber are preferably used as the insulation layer for marine electrical wires. However, due to the nature of ships being carried at sea for long periods of time, breakdowns in marine electrical cables cannot be tolerated, and there are particularly strict requirements regarding the durability of the insulation layer of marine electrical cables, and further improvements in durability are desired. Ta.

Therefore, the present inventor has discovered that a vulcanized product of a specific compounded rubber using ethylene-bi-olefin copolymer rubber has appropriate mechanical strength as an electrical insulator and exhibits excellent heat resistance. This discovery led to the present invention.

. That is, the present invention is a method for producing an electrically insulating material, which is characterized in that, in producing the electrically insulating material by vulcanizing the compounded rubber, a compounded rubber that satisfies all of the following foot (skin) conditions is used. . (1) Ethylene whose molar ratio of ethylene unit content and Q-olefin unit content (ethylene/Q-olefin) is 50/50 and 95/5, and whose iodine number is 4 and 75. Q-olefin-gen copolymer rubber A, which does not substantially contain double bonds and has a molar ratio of ethylene unit content to Q-olefin unit content (ethylene/Q-olefin) of 50/50.
Ethylene-Q-olefin copolymer rubber B, which is none and 95-5, weight ratio (copolymer rubber A/copolymer rubber B)
Contains 55/45 without and 90/10. (
0) The total amount of English polymer rubber A and copolymer rubber B in the compounded rubber is 30 to 8 tonne weight percent.

(Mountain) The Mooney viscosity of the copolymer rubber A and the copolymer rubber B is 15 to 80.

(W) An organic peroxide is used as a vulcanizing agent, and the amount used is 100% of the total amount of copolymer rubber A and copolymer rubber B.
Use 0.003 parts by mole and 0.02 parts by mole based on parts by weight. (V) 0.003% of the vulcanization aid per 10 parts by weight of the total amount of polymeric rubber A and copolymer rubber B;
Use 0.02 mole part.

(W) Antioxidant copolymerized rubber A and copolymerized rubber B
Use 0.5 parts by weight or 4 parts by weight for a total of 10 parts by weight.

(Blood) The amount of inorganic filler used is 100% or 2% per 10 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.
Must be 0 parts by weight.

(Skin) The blending amount of the softener is 2 parts by weight or less per 10 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.

By adding this specific rubber compound,
At room temperature, stress at break is 30, 250k9/2, elongation at break is 50, 1000%, surface hardness (JISA)
It is possible to obtain a vulcanizate with suitable physical properties as an electrical insulator, such as 40 None, 75 Volume Specific Resistance 1 x 1, and 40 Skin or higher, and these physical property values are as follows:
It exhibits amazing heat resistance, retaining more than 95% of its initial value even after being left at 120 qo for 7 days, and virtually retaining almost its initial value even after being left at 120 qo for 20 days. It has suitable physical properties and heat resistance as an insulating layer for objects such as plug caps, ignition caps, distributor caps, and ignition cables, and when used as an insulating layer for marine electric wires, it can be used for long periods of time. guarantee.

Of course, it is also suitable as an insulating layer for ordinary power transmission wires.
The copolymer rubber A of the present invention is a copolymer rubber consisting of ethylene, Q-olefin, and olefin.The content of ethylene units and the content of Q-olefin are 50/50 in molar ratio (ethylene/Q-olefin). 95/5,
The Q-olefin is preferably 65/25 to 95/5, such as propylene, butene-1, bentene-1
, hexene-1, octene-1, etc., among which propylene and butene-1 are preferred. Diolefins include isoprene, putadiene, 1,4-pentadiene, 1,4-hexadiene, divinylbenzene,
Dicyclobentadiene, methylene norbornene, ethylidene norporene, etc. can be mentioned, but 1.4
-Hexadiene and ethylidene norbornene are preferably used, and ethylidene norbornene is particularly preferably used. The content of diolefin units in copolymer rubber A is from 4 to 75, preferably from 8 to 40, in terms of iodine value. Copolymer rubber B of the present invention is an ethylene-Q-olefin copolymer rubber that does not substantially contain double bonds in its molecular region. Substantially not containing double bonds in the molecular chain means that the iodine value of copolymer rubber B is 2 or less. Such rubbers are obtained, for example, by copolymerizing ethylene and Q-olefin under a Ziegler catalyst, but a small amount of double bonds may exist in the molecular chain due to disproportionation reactions, etc. The copolymer rubber usually has an iodine value of 2 or less and can be suitably used as the copolymer rubber B of the present invention. The ethylene unit content and Q-olefin unit content contained in copolymer rubber B are in a molar ratio (ethylene/Q-olefin) of 50/50 to 95/5, preferably 65/25 to 95/5, Q -Olefins include propylene, butene-1, bentene-1,
Examples include hexene-1 and octene-1, among which propylene and butene-1 are preferably used. The Mooney viscosity (ML, 14,100°C) of copolymer rubber A and copolymer rubber B used in the present invention is 15% and 80%.
Preferably, 20 and 60 are examples.

In the electrical insulator of the present invention, it is necessary to avoid the use of a softener as much as possible because it reduces heat resistance. Therefore, copolymer rubber with a Mooney viscosity of 80 or more has poor roll processability when preparing compounded rubber. It is not used because it is low. Further, in the case of a copolymer rubber having a Mooney viscosity of 15 or less, the strength of the vulcanizate decreases. In the present invention, the weight ratio of copolymer rubber A and copolymer rubber B is 55/45 to 90/10, preferably 60/40 to 80/20.

Even if the usage ratio is 95/5 or more, ie, a large amount of copolymer rubber A is used, and even if the ratio is 60/40 or less, ie, a large amount of copolymer rubber B is used, a vulcanizate with excellent heat resistance cannot be obtained. In the present invention, an organic peroxide is used as a vulcanizing agent.

Sulfur, organic sulfur compounds, organic peroxides, etc. are usually used as vulcanizing agents for rubber, but when other bulking agents are used without using organic peroxides, the heat resistance of the vulcanizing agent is Inferior. Examples of organic peroxides used in the present invention include tert-butyl hydroperoxide, cumene hydroperoxide, and diisof.

Alkyl doloberoxides such as lopylbenzene hydroperoxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5 dihydroberoxyhexane, 2,5-dimethyl-2,5 dihydroberoxyhexine-3, etc. Class; di-tert-butyl peroxide, di-tert-amyl peroxide, tert-butyl cumyl peroxide, dicumyl peroxide, 1,4-1 (or 1,3-1) di-tert-butyl peroxyisobro Bilbenzene, 2,2-di-butylberoxybutane, 2,5-dimethyl-2,5
-di(tert-butylberoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylberoxy)hexane-3, ropetyl-4,4-di-tert-butyl parerate, 1
, 1-di-tert-butylberoxycyclohexane, di-tert-butylberoxy-3,3,5-trimethylcyclohexane, 2,2-bis(4,4-di-tert-butylberoxycyclohexyl)propane, etc. Beroxides; diacetyl peroxide, dibrobionyl peroxide, dioctanoyl peroxide, 3,5,
5-trimethylhexanoyl peroxide, dideca/yl peroxide, dilauroyl peroxide, stearoyl peroxide, dibenzoyl peroxide, gp
- Diacyl peroxides such as chlorobenzoyl peroxide, di-2,4-dichlorobenzoyl peroxide, and succinic acid peroxide; tert-butyl peroxyacetate, tert-butyl peroxy isobutyrate, tert-butyl peroxy malei ipiparate, tert-butyl peroxyquaside, tert-butyl peroxyneodecanoate, tert-butyl peroxybenzoate, di-tert-butyl diberoxy phthalate, tert-butyl peroxylaurate, 2,5-dimethyl Examples include peroxyesters such as -2,5-di(benzoylberoxy)hexane and tert-butylberoxyisopropyl carbonate; ketone peroxides such as dicyclohexanone peroxide; and mixtures thereof. Among them, it is preferable to use organic peroxides whose temperature giving a half-life of 1 minute is in the range of 130oo to 200qo, especially n-butyl-4,4-ditert-butylvalerate, dicluberoxide, and 2,5-dimethyl. -2,5-di(tert-butylberoxy)hexane, 2,5-dimethyl-2,5-di(benzoylberoxy)hexane, 2,5-dimethyl-2
, 5-di(tert-butylberoxy)hexyne-2, di-tert-butylperoxide, 1,1-di-tert-butylberoxy-3,3,5-trimethylcyclohexane, tert-butyl hydroperoxide, etc. Organic peroxides are preferably used. In the present invention, such an organic peroxide is present in an amount of 0.003 to 0.02 mole part, preferably 0.0 to 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.
Without 05, 0.015 mol part was used.

If it is less than 0.003 mole part, not only the strength will decrease but also the heat resistance will be inferior.

If 0.02 mole part or more is used, heat resistance will decrease.

In the present invention, a vulcanization aid is blended together with peroxide as a vulcanizing agent.

The combined use of a vulcanization aid not only increases the mechanical strength of the vulcanizate, but also improves its heat resistance. Examples of vulcanization aids include quinonedioxime compounds such as p-quinonedioxime and p,pl-dibenzoylquinonedioxime; such as p-dinitrosobenzene, N-methyl-N, and 4-dinitrosomethylaniline. Dinitroso compounds; Nitro compounds such as n-dinitrobenzene, 2,4-dinitrotoluene, etc.; Allyl compounds such as triallyl cinurate, diallyl phthalate, diallyl itaconate, tetraallyloxyethane, etc.: trimethylolburbanne; Methacrylic compounds such as trimethacrylate, ethylene dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol ditacrylate, polyethylene glycol dimethacrylate; and others such as N,N'-phenylene bismaleimide, divinibenzene, divinyltoluene,
and sulfur, among which p-
Preference is given to using quinone dioxime, p,p' dibenzoylquinone dioxime, triallyl cyanurate, polyethylene glycol dimethacrylate, and the like. Such a vulcanization aid is used in a total amount of copolymer rubber A and copolymer rubber B of 1
0.003 to 0.02 mol parts per 00 parts by weight,
Preferably, 0.005 to 0.015 mole part is used. If it is less than 0.003 mole part, the strength and heat resistance will be poor;
．． The use of 0.02 molar parts or more is limitless and may result in poor heat resistance.

An antioxidant is used in the electrical insulating compound rubber of the present invention.

As antioxidants, styrenated phenol, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-p-ethylphenol, 2,4,6 -tri-tert-butylpheno-
1-Hydroxy-3-methyl-4-isobrobylbendene, butyl hydroxyanisole, monotert-butyl-
p-cresol, mono-tertiary petit-m-cresol, 2
, 4-dimethyl-6-tert-butylphenol, butylated bisphenol A, 2,2'-methylene-bis(4-ethyl-6-tert-butylphenol), 4,4'-butyritene-bis(6-methyl-6- tertiary butylphenol)
, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 2,2-methylene-bis(4-ethyl-6-tert-butylphenol), 4,4'-methyl-bis(2,6-di-tert-butylphenol) phenolyl), 2,2
-methylenebis(4-methyl-6-tert-nonylphenol), 4,4'-butylidene-bis(3-methyl-6
-tert-butylphenol), 2,2-iptylidene-bis(4,6-dimethylphenol), 4,4'-thiorbis(3-methyl-6-tert-butylphenol),
Bis(3-methyl-4-hydroxy-5-tert-butylbenzyl) sulfide, 4,4-thiobis(2-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol) butylphenol), 4,4'
-thiobis(6-tert-butyl-3'-methylphenol), 2,2-thio[thiobis-3(3,5-di-
tert-butyl-4-hydroxyphenol) propionate], bis-[3,3-bis(4-hydroxy-3-tert-butylphenol)-butyric acid] glyco-1'
bis[2-[2-hydroxy-5-methyl-3-tert-butyl-penzyl)-4-methyl-6-tert-butylphenyl] terephthalate, 1,3,5-tris(3',5-tert-butyl-penzyl)-4-methyl-6-tert-butyl ester, butyl-4-hydroxybenzyl)
Isocyanurate, N,N'-hexamethylene bis(
3,5-di-tert-butyl-4-hydroxy-hydrocinamide), n-octadecyl-3-(4'-hydroxy-
3,5-di-tert-butylphenol) propionate,
Tetrakis [methylene-3(3,5-di-nibutyl-
4-hydroxyphenyl)propionate]methane, 1,
r-bis(4-hydroxyphenyl)cyclohexane,
2,6-mono(Q-methylbenzyl)phenol, di(
Q-methylbenzyl)phenol, tri(Q-methylbenzyl)phenol, bis(2'-hydroxy-3-tert-butyl-5'-methylbenzyl)4-methyl-fe/
-L, 2,5-di tertiary amylhydroquinone 2,6
-di-tert-butyl-Q-dimethylamino-p-cresol, 2,5-di-tert-butylhydroquinone, 3,5-
Phenolic antioxidants such as diethyl ester of di-tert-butyl-4-hydroxybenzyl phosphate, catechol, hyzoquinone, etc.; 2-mercabutobenzimidazole, zinc salt of 2-mercabutobenzimidazole;
Penzimidazole antioxidants such as 2-mercabutomethylbenzimidazole, zinc salt of 2-mercabutomethylbenzimidazole; dimyristylthiodipropionate, dilaurylthiodipropionate, distearylthiodipropionate , aliphatic thioether antioxidants such as ditridecylthiodipropionate; zinc or nickel salts of dibutyldithiocarbamic acid, zinc salts of diethyldithiocarbamic acid, zinc salts of ethylphenyldithiocarbamic acid, zinc salts of dimethyldithiocarpamic acid; Antioxidants based on metal salts of dithiocarbamic acid such as zinc salts and zinc salts of diamyldiocarbamic acid; 2, 2, 4
-Quinoline antioxidants such as trimethyl-1,2-dihydroquinoline or its polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; other phenothiazine, 4-penzoyloxy-2,2,
6,6-tetramethylpiveridine, bis(2,2,000-
6,6-tetramethyl-4-piveridine) sebacate,
Examples include N-(3'-hydroxybutylidene)-1-naphthylamine. Among these antioxidants, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2,6-di-tert-butyl-4-methylphenol, N-(3'-hydroxybutylidene) Naphthylamine, 2-mercabutobenzimidazole, zinc salt of 2-mercabutomethylbenzimidazole, nickel salt of dibutyldithiocarbamic acid, mono(Q-methylbenzyl)phenol, di(Q-methylbenzyl)phenol,
Preference is given to using tri(Q-methylbenzyl)phenol and mixtures thereof. In the present invention, such an antioxidant is used in an amount of 0.5 to 4 parts by weight, preferably 1 to 3 parts by weight, per 10 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.

If the amount used is 0.5 parts by weight, the heat resistance will be poor, and if the amount is 4 parts by weight or more, it is wasteful. In the present invention, the inorganic filler is used in an amount of 10 to 20 parts by weight, preferably 30 to 18 parts by weight, based on a total of 10 parts by weight of copolymer rubber A and copolymer rubber B. . If it is less than 1 part by weight, the surface hardness and tensile strength of the vulcanizate will decrease, and if it is more than 20 parts by weight, it will lose flexibility.

Examples of inorganic fillers that can be used include powdered silicic acid, calcium carbonate, talc, clay, and carbon black, but it is preferable to use non-conductive fillers.

When carbon black is unavoidably used as a filler, it should be kept at 15 parts by weight or less based on the total amount of copolymer rubber A and copolymer rubber B of 10 parts by weight. In the present invention, it is preferable to avoid the use of softeners as much as possible.

When it is unavoidably used to improve roll processability, the amount used is 20 parts by weight or less, preferably 15 parts by weight per 10 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.
Keep it below the weight part. If more than 2 parts by weight are used, the heat resistance of the vulcanizate will be significantly reduced.

Softeners that can be used include those commonly used for rubber, such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum softeners such as petrolatum, coal tar, coal tar pitch, etc. Coal tar-based softeners; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, and coconut oil; tall oil;
Waxes such as beeswax, carnaupal wax, and lanolin; Fatty acids and fatty acid salts such as ricinoleic acid, palmitic acid, barium stearate, calcium stearate, and zinc laurate; Synthetic polymer substances such as petroleum resin, atactic polypropylene, and coumaroninden resin. etc. can be given. A common process is usually employed for manufacturing the electrical insulator that is the object of manufacturing the method of the present invention.

For example, to obtain electrical insulators for plug caps, ignition caps, distributor caps, etc. around automobile engines, copolymerization is carried out at 90 qo to 15,000 for 10 minutes using a mixer such as a Banbury mixer. After kneading rubber A, copolymer rubber B, an inorganic filler, and if necessary, a softener, etc., the antioxidant and organic peroxide are kneaded using rolls such as open rolls at a temperature of 40°C and 80qo. A vulcanization aid and the like are further mixed to prepare a sheet-like or ribbon-like compounded rubber. This compounded rubber is molded into the shape of the above-mentioned caps using an extrusion molding machine, and at the same time as molding or the molded product is
1 to 6 minutes in a vulcanization tank heated to 220 oo
The above-mentioned caps can be produced by heating for 0 minute, or by heating the compounded rubber at the temperature and for the time at the same time as molding using a hot press.
In addition, when the electrical insulator is an insulating layer of an electric wire, a known method is used, namely, the above-mentioned sheet-like or ribbon-like compounded rubber is
The conducting wire of the current-carrying part, which was separately introduced into the extruder, is coated in a cylindrical shape, and then the integrated conducting wire part and the insulating part are heated to 180 to 22 The sample is continuously introduced into a vulcanization tank heated to 0.5 and 0.0, and is cured by heating for 10 minutes.

This will be explained in detail below using examples.

Copolymer Rubbers Used in Examples and Comparative Examples Table 1 shows a list of copolymer rubbers A (A, to A6) and copolymer rubbers B (B to &) used in Examples and Comparative Examples.

In each case, copolymer rubber A used ethylidene norbornene as the diolefin. Table 1 - Examples 1 to 3, Comparative Examples 1 to 4 Copolymer rubber A and copolymer rubber B in Table 1 were used in the proportions listed in Table 3, and compounded rubber was prepared according to the formulation table in Table 2. After the preparation, a kakimono was obtained.

That is, copolymer rubber A, copolymer rubber B, zinc white, stearic acid, mistronbever talc, SHIEST 8, and YODOPLAST P are combined in Table 2, and the Banbury mixer (Model 00C, Kobe After kneading for 6 minutes using a steel mill (manufactured by Steel Corporation), an antioxidant, a vulcanizing agent, and a vulcanization aid were added, and the mixture was kneaded for 15 minutes using an 8 x 20 inch oven roll at a roll temperature of 40 qo. A sheet of compound rubber on the side was taken out, and this sheet was heat-pressed at 160°C for 30 minutes at a pressure of 150k9/underground to obtain a sheet-like vulcanizate of 12 x 14 x 2 sides. .
A No. 3 dumbbell according to JIS K6301 was punched out from this vulcanizate, and the stress at break TB (k9/ground), elongation at break EB, ( %) was estimated. Furthermore, according to JISK6301, the hardness of the vulcanizate is HS.
, (JISA). These values are shown in Table 3 as initial physical properties. Next, the above-mentioned No. 3 dumbbell was used with Toyo Seiki's "TESTTUBEAGING TESTER"
After exposing each dumbbell to an air atmosphere for 7 days to 6000 and 20 days to 0, stress at break T & (k9/Gaso), elongation at break EZ (%), and hardness were determined in the same manner as above for each dumbbell. ΔTB, ΔEB, and ΔHS with HS2 determined were calculated using the following formula and used as a measure of heat resistance. △TB (%) = Shozo Tatsumi X. Blood △EB (%) = E Saint Ichi Te 3 x. .

. △HS=HS2-HS, Table 2 1) 2-mercaptobenzimidazole (manufactured by Ouchi Shinko Kagaku Co., Ltd.) 2) Polymer of 2,2,4-trimethyl-1,2 dihydroquinoline (manufactured by Ouchi Shinko Kagaku Co., Ltd.) 3) n-butyl-4,4-bis(tert-butylberoxy) parerate (manufactured by NOF Corporation) 4) P,P'-dibenzoylquinone cyoxime (manufactured by Daishinaka Kagaku) 5) 6) SRF carbon black (-Tokai Carbon Kame97)
) Takatsumugi Cervical Fatty Acid Ester (manufactured by Yodogawa Higaku Co., Ltd.) Furthermore, a sample was taken from the sheet-like vulcanizate, and the volume resistivity (DC500V-1 minute value) was determined by the high-pressure Schering bridge method (1000V) according to ASTM D257. The dielectric constant, dielectric strength, and AC breakdown voltage were determined in accordance with JIS K6911.

The above results are shown in Table 3. Table 3 1 part by weight 2 units: ×lo15○. 3 credits:
Kv/NR Examples 4 to 10 The same operations as in Example 2 were performed except that each copolymer rubber listed in Table 4 was used in place of copolymer rubber A and copolymer rubber B.

The results are shown in Table 4. Table 4 Examples 11 to 17, Comparative Examples 5 and 6 In Example 2, the type and amount of antioxidant, the type and amount of vulcanizing agent, and the type and amount of briquetting aid are as shown in Table 5. The same operation was performed except for the following changes.

The results are shown in Table 5. Table 5 1) Kockel salt of diothyldithiocarbamic acid (manufactured by Ouchi Shinko Kagaku, Ltd.) 2) N-(3'-Hydroquinphthylidene)-1-naphthylamine (manufactured by Ouchi Shinko Kagaku, Ltd.) 3) Mitsui Oil Industry Co., Ltd.)
4) 1,1-di-tert-butylberroquine-3,3,5-
Trimethylcyclohexane (manufactured by NOF Corporation) 5) Triallyrunanurate (Musashino Chemical* Raw Materials) 6) Values are parts by weight based on 100 parts by weight of rubber.

7) The numerical value is the monotower per 100 parts by weight of rubber.

Comparative Example 7 The same operations as in Example 2 were performed except that sulfur was used as the vulcanizing agent in place of the organic peroxide and a compounded rubber was prepared according to the recipe in Table 6. The following results were obtained. Obtained.

Initial physical properties TB=100k9/inhibited EB=570% HB=60 Heat resistance test △TS=-40% △EB=-68% △HS=110 Table 6 1) N-chlorohexyl-2-penzothiazolyl sulfendo Amamide (manufactured by Ouchi Shinko Kagaku Ushio) 2) 2-Mercabutobenzothiazole (manufactured by Ouchi Shinko Kagaku Gendo) 3) Tetramethylthiwalam disulfide (manufactured by Ouchi Shinko Kagaku) 4) Dibentamethylene lentithuram Tetrasulfide (manufactured by Ouchi Shinko Kagaku Gyudo)

Claims (1)

[Scope of Claims] 1. Production of an electrical insulator characterized by using a compounded rubber that satisfies all of the following conditions (I) and (VIII) when producing an electrical insulator by adding a compounded rubber. Method. (I) The molar ratio of ethylene unit content and α-olefin unit content (ethylene/α-olefin) is 50/50.
ethylene-α-olefin-diene copolymer rubber A having a ratio of 4 to 95/5 and an iodine value of 4 to 75, and an ethylene-α-olefin-diene copolymer rubber A containing substantially no double bonds and having an ethylene unit content and an α-olefin unit content. molar ratio of amounts (ethylene/α-
and ethylene-α-olefin copolymer rubber B in which the olefin) is 50/50 to 95/5 in a weight ratio (copolymer rubber A/copolymer rubber B) of 55/45 to 90/10.
It should be included in the proportion of (II) The total amount of copolymer rubber A and copolymer rubber B in the compounded rubber is 30 to 80% by weight. (III) Copolymer rubber A and copolymer rubber B have a Mooney viscosity of 15 to 80. (IV) Using organic peroxide as a vulcanizing agent. Moreover, the amount used is 0.003 to 0.02 parts by mole based on 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B. (V) Add 0.003 parts by weight of the vulcanization aid to 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.
Use between 0.02 mole part and 0.02 mole part. (VI) Copolymerized rubber A and copolymerized rubber B with antioxidant
Use 0.5 to 4 parts by weight per 100 parts by weight of the total amount. (VII) The amount of inorganic filler used is 10 to 20 parts by weight based on 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.
Must be 0 parts by weight. (VIII) The blending amount of the softener is 20 parts by weight or less based on 100 parts by weight of the total amount of copolymer rubber A and copolymer rubber B.