JPH05262912A - Rubber composition for electrical insulation use - Google Patents

Abstract

PURPOSE:To provide the subject composition composed of an ethylene-propylene- diene terpolymer, a calcined clay, a process oil and a quinone dioxime, resistant to the lowering of the volume resistivity and AC breakdown voltage in highly humid atmosphere and having low hardness and excellent elasticity. CONSTITUTION:The objective composition is produced by compounding (A) 100 pts.wt. of an ethylene-propylene-diene terpolymer having a propylene content of >=30wt.% and an iodine value of >=6 with (B) 30-130 pts.wt. of calcined clay, (C) <=30 pts.wt. of a process oil and (D) >=1 pt.wt. of an additive consisting of a p-quinone dioxime of formula I (R1 is H, 1-5C alkyl, etc.; R2 is H or group of formula II) or its derivative and mixing the components at >=160 deg.C in the presence of a vulcanizing agent (preferably dicumyl peroxide, etc.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for electrical insulation, which is mainly used for high voltage insulated wires and terminal parts thereof and which is excellent in electrical insulation and rubber elasticity.

[0002]

2. Description of the Prior Art For insulated high-voltage insulated wires and terminal parts thereof, ethylene-propylene rubber is used as a base, and various fillers, antioxidants, metal oxides, etc. are used in view of electrical characteristics and weather resistance. A rubber composition containing an auxiliary agent is used. A composition using calcium carbonate and aluminum hydroxide as a filler in this kind of application has a problem that the AC breakdown voltage and volume resistivity after immersion in water are lowered, and it is a problem for long-term use in a high-humidity atmosphere. was there.

Therefore, in order to improve these properties, a calcined clay is often used. However, if a large amount of calcined clay is blended, for example, about 100 parts by weight per 100 parts by weight of rubber, the obtained rubber composition will have other properties. Since the rubber hardness is higher than that of a rubber composition containing a filler, when used in an insulated wire, there is a problem in flexibility of the obtained insulated wire, and when used in a terminal product, Insertibility of the terminal product into the cable becomes a problem. As a means to reduce the hardness of the rubber composition, there is a method of low filling or compounding process oil. However, if the filling amount is low, the tensile strength properties decrease, and if a large amount of process oil is compounded, it will lead to bleeding from the molded product. However, it is not practical because of problems such as deterioration of compression set, which is an index of rubber elasticity, and deterioration of tensile strength characteristics.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to reduce the electrical characteristics in a high humidity atmosphere, particularly volume resistivity and AC breakdown voltage, for use in high voltage insulated wires and terminal parts thereof. An object of the present invention is to provide a rubber composition for electrical insulation which has excellent hardness and rubber elasticity.

[0005]

According to the present invention, a calcined clay is added to 100 parts by weight of an ethylene / propylene / diene terpolymer having a propylene content of 30% by weight or more and an iodine value of 6 or more. 30 to 130 parts by weight of process oil
30 parts by weight or less, and the following formula:

[Chemical 3] [Wherein R ₁ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms,
Or an alkyl group having 1 to 5 carbon atoms substituted with one phenyl group, and R ₂ is a hydrogen atom or the following formula:

[Chemical 4] (In the formula, R ₁ represents the same group as described above), and 1 to 10 parts by weight of an additive consisting of p-quinonedioxime or a derivative thereof is blended. The above-described object is achieved by a rubber composition for electrical insulation, which is characterized by being mixed at a temperature of 160 ° C. or higher in the presence of a sulfurizing agent.

[0006]

In the present invention, ethylene and propylene / diene terpolymers mean ethylene, propylene and a diene monomer such as ethylidene norbornene, 1,4.
-A copolymer with hexadiene, dicyclopentanediene and the like. The reason for limiting the propylene content to 30% by weight or more is that if it is less than 30% by weight, the hardness of the terpolymer rubber will be high. The reason for limiting the iodine value to 6 or more is that if it is less than 6, the compression set, which is an index of rubber elasticity, becomes worse. Also, the amount of baking clay is 30 to 130
The reason for limiting the content to parts by weight is that the composition obtained when the amount is less than 30 parts by weight has a low tensile strength, while the composition obtained when the amount is more than 130 parts by weight has too high hardness.

Further, the reason why the process oil is added to the composition is to reduce the hardness of the obtained composition, and the reason why the amount of the process oil is limited to 30 parts by weight or less is that the process oil is added in an amount of more than 30 parts by weight. Bleeding, migration to other products, deterioration of compression set, which is an index of rubber elasticity of the composition, and reduction of tensile strength. Furthermore, the present inventors have added an additive consisting of p-quinonedioxime or a derivative thereof to the above-mentioned composition and set the mixing temperature to 160 ° C. or higher,
It has been found that the compression set is significantly improved. Here, the amount of the additive made of p-quinonedioxime or a derivative thereof is at least 1 part by weight, because the compounding amount of less than 1 part by weight has a small improvement effect. In addition, 10
Almost no increase in the improvement effect is observed even if the amount is more than 100 parts by weight.

An organic peroxide is preferably used as a vulcanizing agent used for vulcanizing the composition of the present invention.
For example, dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-
3, α, α'-bis (t-butylperoxy) -p-diisopropylbenzene, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane and the like. In addition to this, wax, carbon black, an antioxidant, a vulcanization accelerator, and a metal oxide can be added by a known technique as a compounding agent that constitutes the rubber composition.

[0009]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples. In these examples, 1. parts by weight of the materials shown in Table 1 excluding the vulcanizing agent (Perhexa 3M-100 manufactured by NOF CORPORATION) were used.
Mixed in a 7 liter Banbury mixer. Various E used
Table 2 shows the characteristic values of P rubber.

[0010]

[Table 1]

[0011]

[Table 2]

A vulcanizing agent was mixed into the composition with an open roll, and the obtained composition was formed into a sheet.
The sheet was press-vulcanized at the temperature of 15 minutes to prepare a test sheet.
In Table 1, the mixed rubber temperature is the rubber temperature at the time of dumping after mixing with a Banbury mixer.

The tensile strength of the composition is JIS K-6301.
According to the tensile test of the vulcanized rubber physical test method of JIS,
This was done using No. 3 dumbbell. Also, the hardness can be measured by J
According to the hardness test of 1 vulcanized rubber physical test method of ISK-630, it was performed using A type. The measurement of compression set is
According to the compression set test of JISK-6301 vulcanized rubber physical test method, heat treatment was performed at 100 ° C. for 70 hours. The volume resistivity was measured by making a pressure-vulcanized sheet of 1 × 160 × 160 mm, and performing this sheet according to the method of JISC2123 (Item 16).

The AC breakdown voltage was measured by applying a conductive paint to the dotted line portion of a test sheet having the shape shown in FIG. 1, placing a spherical electrode with a diameter of 12 mm in the recess, and applying a voltage every 10 minutes. Was stepped up by 1 kv and the voltage up to the dielectric breakdown was measured. The bleeding state from the composition was determined by forming a pressure-vulcanized sheet of 1 × 100 × 100 mm, leaving it at room temperature for 60 days, and then determining the sheet surface by a finger touch test. In the results of the bleeding evaluation shown in Table 1, ◯ indicates that it is completely the same as the original product, Δ indicates that it is slightly raised and slightly sticky, and × indicates that oil is raised on the surface and the stickiness is large.

In Table 1, Experiment Nos. 1 to 6 are examples,
Experiment Nos. 7 to 14 show comparative examples, and Experiment Nos. 15 and 16 show conventional examples. Experiment Nos. 1 to 6 are compositions within the range of the composition of the present invention. The following can be found from Table 1. In Experiment Nos. 1 to 6 (Examples), both the volume resistivity of the composition after immersion in warm water and the AC breakdown voltage were improved as compared with the conventional example. It also has sufficient tensile strength, hardness, and compression set.

Experiment No. 7 (Comparative Example) uses a terpolymer having a propylene content of less than 30% by weight, and the hardness of the composition is increased. Experiment No. 8 (Comparative Example) uses a terpolymer having an iodine value of less than 6, and the composition has poor compression set characteristics. Experiment No. 9 (Comparative Example) is a composition in which the amount of calcined clay is less than 30 parts by weight and the amount of process oil is more than 30 parts by weight, and the tensile strength is reduced. Experiment No.1
0 (Comparative Example) is a composition with a process oil content of more than 30 parts by weight, and the composition has poor compression set characteristics. Experiment
No. 11 (Comparative Example) is a composition having a composition in which the amount of baked clay exceeds 130 parts by weight, and the hardness of the composition is increased. Experiment N
o.12 (Comparative Example) is a composition containing no p, p'-dibenzoylquinone dioxime, and the compression set characteristics of the composition are poor. Experiments Nos. 13 and 14 (comparative examples) were p, p′−
It is a composition in which dibenzoylquinone dioxime is mixed at a mixing temperature lower than 160 ° C., and the compression set characteristics of the composition are deteriorated.

Experiments Nos. 15 and 16 (conventional examples) were compositions obtained by mixing calcium carbonate and aluminum hydroxide as fillers and mixing at 150 ° C., respectively, and both of them had a volume resistivity after immersion in water. And the AC breakdown voltage is significantly reduced.

[0018]

As described above, the rubber composition for electrical insulation of the present invention has electric characteristics after immersion in water, particularly volume resistivity and AC breakdown voltage characteristics, as compared with the conventional rubber composition of the same kind. In addition, it has excellent properties such as compression set and tensile strength, and has a low rubber hardness. In particular, it can be suitably used as an insulating material for electric wires and cables and a terminal material thereof.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a sample sheet used for measuring an AC breakdown voltage.

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Claims (1)

[Claims] 1. A propylene content of 30% by weight or more,
For 100 parts by weight of an ethylene / propylene / diene terpolymer having an iodine value of 6 or more, 30 to 13 calcined clay is added.
0 parts by weight, 30 parts by weight or less of process oil, and the following formula: [Wherein R ₁ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms,
Or an alkyl group having 1 to 5 carbon atoms substituted with one phenyl group, and R ₂ is a hydrogen atom or the following formula: (In the formula, R ₁ represents the same group as the above), and at least 1 part by weight of an additive comprising p-quinonedioxime or a derivative thereof represented by
A rubber composition for electrical insulation, characterized by being mixed at a temperature of 160 ° C. or higher in the presence of a vulcanizing agent.