JPH0977934A - Electrical insulating composition and insulated electrical wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrical insulating composition excellent in electric strength properties, electrical properties (low electrostatic capacity), workability, and flexibility and an insulated electric wire wherein the same is used as an insulator. SOLUTION: This electrical insulating composition comprises 100 pts.wt. nonpolar polyolefin polymer mixture whose main component is an ethylene/ propylene rubber and 20 to 200 pts.wt. polyolefin powder having a particle diameter of 600μm or less and a crystalline melting temperature of 120 deg.C or more. The insulated electrical wire has a conductor whose circumference is provided with a crosslinked coating layer made of that electrical insulating composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrical insulating composition having excellent withstand voltage characteristics, electrical characteristics, processability and flexibility, and particularly to home electric appliances, OA equipment, gas appliances using the same. , An insulated wire suitable as an electric wire for a high-voltage circuit used in an automobile or the like.

[0002]

2. Description of the Related Art Nonpolar polyolefins such as polyethylene-based polymers and ethylene-propylene rubber mixtures have been widely used as insulators for insulated wires since they are inexpensive and have good processability.

[0003]

However, in the case of polyethylene-based polymers, in addition to processability, they have high withstand voltage characteristics and electrical characteristics (low capacitance),
Since it is inferior in flexibility, it is difficult to overdense the insulated wire using this as an insulator. On the other hand, in the case of the ethylene-propylene rubber mixture, in addition to the processability, the flexibility is excellent, but the impurities contained in the inorganic powder such as talc and clay that are blended for the purpose of improving the processability are Originally, the withstand voltage characteristics and electrical characteristics of ethylene-propylene rubber, which are lower than those of polyethylene-based polymers, are further deteriorated.

The present invention has been made on the basis of the above points, and an object thereof is to obtain excellent withstand voltage characteristics,
An object of the present invention is to provide an electrical insulating composition having electrical characteristics (low capacitance), processability and flexibility, and an insulated wire using the same as an insulator.

[0005]

In order to achieve the above object, the electrical insulating composition according to the present invention has a particle size of 600 μm or less based on 100 parts by weight of a nonpolar polyolefin polymer mixture mainly composed of ethylene-propylene rubber. It is characterized by containing 20 parts by weight or more and 200 parts by weight or less of a polyolefin powder having a crystalline melting point of 120 ° C. or more.

An insulated wire according to another aspect of the present invention has a particle size of 600 μm or less and a crystal melting point of 120 ° C. or more with respect to 100 parts by weight of a nonpolar polyolefin polymer mixture mainly composed of ethylene-propylene rubber. A cross-linking coating layer made of an electrically insulating composition containing 20 parts by weight or more and 200 parts by weight or less of the polyolefin powder is provided on the outer circumference of the conductor.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The non-polar polyolefin polymer mixture mainly composed of ethylene-propylene rubber used in the present invention means, for example, ethylene-propylene rubber alone or ethylene-propylene rubber, which is provided with processability and hardness adjustment. For the purpose of
For example, a polyolefin polymer at 0 ° C. or lower is added. The mixture may contain an ester monomer component derived from a polyolefin polymer, an α-olefin monomer component, or the like in a small amount of 5% by weight or less.
As the ethylene-propylene rubber, other than a copolymer of ethylene and propylene, as a third component,
Ethylidene norbornene, dicyclopentadiene, 1,
Examples thereof include those obtained by copolymerizing 4-hexadiene and the like. These may be used alone or in combination of two or more.

In the present invention, a polyolefin powder is contained in the above-mentioned non-polar polyolefin polymer mixture mainly composed of ethylene-propylene rubber. Examples of the polyolefin powder include polyethylene powder and polypropylene powder. In the present invention, among them, the particle diameter is 600 μm or less, preferably 500 μm.
m or less and a crystal melting point of 120 ° C. or more are used. The polyolefin powder having a particle size of more than 600 μm does not disperse uniformly in the non-polar polyolefin polymer mixture mainly composed of ethylene-propylene rubber, and also makes the kneading work extremely difficult. A polyolefin powder having a particle size of more than 500 μm is difficult to be uniformly dispersed in a nonpolar polyolefin polymer mixture mainly composed of ethylene-propylene rubber, and variations in withstand voltage characteristics are likely to occur. Further, a polyolefin powder having a crystal melting point of less than 120 ° C. is melted by self-heating of a non-polar polyolefin polymer mixture mainly composed of ethylene-propylene rubber at the time of kneading, resulting in poor roll adhesiveness and remarkably difficult kneading work. Will be. The "particle size" of the polyolefin powder referred to here is JIS
99 of the powder measured according to the test method of K 5101
% Or more is a value corresponding to the minimum sieving mesh number when passing through a sieving mesh, and the "crystal melting point" is a value measured according to the test method of ASTM D2117.

The content of the polyolefin powder is 20 parts by weight or more and 20 parts by weight or more with respect to 100 parts by weight of the nonpolar polyolefin polymer mixture mainly composed of ethylene-propylene rubber.
0 parts by weight or less. If it is less than 20 parts by weight, the desired high withstand voltage characteristics cannot be obtained, and the kneading process becomes difficult. On the other hand, if it exceeds 200 parts by weight, the extrusion torque of the obtained composition becomes high, the extrusion process becomes difficult, and the flexibility is remarkably lowered.

By incorporating the above-mentioned polyolefin powder into a non-polar polyolefin polymer mixture mainly composed of ethylene-propylene rubber, the excellent flexibility and processability of the conventional ethylene-propylene rubber mixture containing inorganic powder can be obtained. It is possible to impart high withstand voltage characteristics and electrical characteristics equivalent to those of conventional polyethylene-based polymers without impairing them. Therefore, it is no longer necessary to add an inorganic powder containing impurities, which has conventionally been the cause of lowering the withstand voltage characteristics and electrical characteristics of ethylene-propylene rubber mixtures.

In the present invention, in addition to the above components,
A plasticizer, a processing aid, an antioxidant, a cross-linking agent, a cross-linking aid, a coloring agent and the like can be added as appropriate.

The obtained composition is extrusion-coated on the circumference of the conductor using a known extruder, and then crosslinked by high-pressure steam to obtain the insulated wire of the present invention. When cross-linking with high-pressure steam, it is necessary to add a cross-linking agent to the above composition in advance. Examples of the cross-linking agent include organic peroxides such as dicumyl peroxide.

[0013]

EXAMPLES Examples of the present invention will be described below together with comparative examples. In addition, ethylene-propylene-diene terpolymer (EPDM) was used as the ethylene-propylene rubber, and high-density polyethylene powder and low-density polyethylene powder were used as the polyolefin powder. Details of each compounding material are as shown in Table 3.

First, the compounding materials shown in Tables 1 and 2 were
The composition was sufficiently kneaded with a 6-inch open roll maintained at 0 ° C, and the obtained composition was crosslinked at a pressing temperature of 180 ° C with a press machine.
The thickness is about 0.5 after heat-crosslinking under the condition of crosslinking time of 10 minutes.
mm sheets were made. In the case of Comparative Example 4, the high-density polyethylene powder was not uniformly dispersed in EPDM during kneading, and in the case of Comparative Example 5, the low-density polyethylene powder was melted by self-heating of EPDM during kneading. No sheet could be produced.

Next, a total of 10 types of sheets (Examples 1 to 7 and Comparative Examples 1 to 3) thus obtained were used as samples, and the mechanical properties (tensile strength and elongation) were measured. The withstand voltage characteristics (dielectric breakdown voltage), electrical characteristics (electrostatic capacity), and workability (kneading workability) were evaluated. The results are shown in Tables 1 and 2.

The evaluation method is as follows. First, tensile strength and elongation were measured according to JIS C 3005. Ethylene listed in Appendix 1 of the Electrical Appliance and Material Control Law
Tensile strength is 7 based on the standard value of propylene rubber mixture
A pass line was defined as Mpa or higher and elongation of 400% or higher.
The dielectric breakdown voltage was measured according to JIS C 2110. The measurement condition is 5 (2) (a), and the electrode is 7.1.
(1) FIG. 3 was used. Based on the actual value of the polyethylene-based polymer, 40 kv / mm or more was set as the acceptance line. The electrostatic capacity was measured by an LCR meter, in which a sample cut into a size of 70 mm × 70 mm was sandwiched between aluminum plates of the same size and both aluminum plates were used as electrodes. Based on the actual value of the polyethylene-based polymer, 120 pF or less was set as the pass line. Regarding the kneading processability, the state of dispersion of the polyethylene powder during kneading and the state of close contact with the roll were visually confirmed, and when abnormalities were observed, the result was indicated as "poor".

With respect to the extrusion processability in Tables 1 and 2, the above 10 kinds of compositions were used in an electric wire coating extruder having a head temperature of 70 ° C. and a cylinder temperature of 60 ° C.
extrusion coated with 1.0mm thickness on the tin plating annealed copper twisted line of mm ^2, check the appearance state of the time obtained wire visually, those irregularities or roughness was observed on the surface labeled "bad" . Regarding flexibility, a sample was prepared by cutting the electric wire used in the evaluation of extrusion processability to a length of 100 mm, and one end of this sample was fixed in a horizontal state, and the other end had a mass of 20 g. Was hung, and the bending distance with respect to the horizontal plane was measured. As a criterion, a pass line of 55 mm or more was taken into consideration in consideration of workability during wiring.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

As is clear from Tables 1 and 2, the compositions according to the present invention (Examples 1 to 7) all have a tensile strength of 7 Mpa or more, an elongation of 400% or more, and a dielectric breakdown voltage of 40 kv / mm. As above, we have cleared the passing line of electrostatic capacity of 120 pF or less and flexibility of 55 mm or more,
It has a good balance of mechanical properties, withstand voltage properties, electrical properties and flexibility. Regarding workability, no abnormalities were observed during kneading and during extrusion.

On the other hand, Comparative Example 1 containing no high-density polyethylene powder and Comparative Example 2 containing high-density polyethylene powder, but the content of which did not fall within the range of the present invention, were mechanical. The characteristics are remarkably inferior, and the dielectric breakdown voltage is less than 40 kv / mm and the withstand voltage characteristics are inferior. Furthermore, regarding workability, the state of close contact with the roll during kneading was poor, and irregularities were also found on the surface of the obtained electric wire. On the other hand, in Comparative Example 3 in which the content of the high-density polyethylene powder was too large, the dielectric breakdown voltage was 59.4 kv / mm, which showed excellent withstand voltage characteristics, but roughness was observed on the surface of the obtained electric wire. .

Comparative Example 4 is an example in which a high-density polyethylene powder having a particle size of more than 600 μm was contained. This high-density polyethylene powder was uniformly dispersed in EPDM during kneading as described above. However, since the kneading work became extremely difficult, the sheet could not be produced. Further, Comparative Example 5 is an example in which a low-density polyolefin powder having a crystal melting point of less than 120 ° C. is contained, and this also melts the low-density polyethylene powder during kneading due to self-heating of EPDM as described above. However, the sheet could not be prepared because it did not adhere to the roll at all.

In this example, further, a crosslinked electric wire was manufactured using the composition obtained from the compounding materials shown in Table 1. First, a wall thickness of 0.3 m on an aramid fiber core with an outer diameter of 0.7 mm
m ferrite magnet layer is coated, and wire diameter is 0.06m
A resistance conductor having an outer diameter of 1.3 mm was prepared by horizontally winding a metal resistance wire made of a nickel-chromium alloy wire having a resistance of 40 mΩ / m and a resistance value of 40 kΩ / m. Next, on the resistance conductor, the composition obtained in Example 3 in Table 1 was used in an electric wire coating extruder having a head temperature of 70 ° C. and a cylinder temperature of 60 ° C. to have a wall thickness of 1.2 mm.
Was extrusion-coated, and EPDM was extrusion-coated to a wall thickness of 0.75 mm, and then cross-linked by high-pressure steam at 200 ° C. to produce a cross-linked electric wire having a finished outer diameter of 5.2 mm.

For comparison, a crosslinked electric wire having a conventional structure was also manufactured. That is, a aramid fiber core having an outer diameter of 0.7 mm is coated with a ferrite rubber layer having a thickness of 0.3 mm, and a metal resistance wire made of a nickel chrome alloy wire having a wire diameter of 0.06 mm and a resistance value of 4 kΩ / m is laterally disposed. Wound outer diameter 1.
Polyethylene resin with a thickness of 1.2 on a 3 mm resistive conductor
mm by extrusion coating and EPDM with a wall thickness of 0.75 mm
After extrusion coating, it was crosslinked with high-pressure steam at 200 ° C. to produce a crosslinked electric wire with a finished outer diameter of 5.2 mm.

Here, the two types of cross-linked electric wires thus obtained were used as samples to withstand voltage characteristics (dielectric breakdown voltage),
The electrical characteristics (capacitance) and flexibility were evaluated. The evaluation method is as follows. First, the dielectric breakdown voltage was obtained by stripping both ends of a sample cut to a length of 1200 mm, connecting resistance conductors to each other, and immersing a loop-shaped one in pre-grounded water, and in that state conductor-water. In the meantime, under the condition of pressure rising speed 500 v / sec, 50
An AC voltage of -60 Hz was applied and the effective voltage value (dielectric breakdown voltage) when the insulator was destroyed was measured. The capacitance was measured according to JIS C 3005. Regarding flexibility, a sample cut to a length of 100 mm was used as a sample, one end of this sample was fixed in a horizontal state, and a weight having a mass of 20 g was hung at the other end, and a bending distance with respect to a horizontal plane was measured.

As a result, the crosslinked electric wire using the composition according to the present invention had a dielectric breakdown voltage of 40 kv or more, an electrostatic capacity of 115 pF / m, and a flexibility of 75 mm, while the polyethylene polymer was used. The conventional cross-linked electric wire using is a dielectric breakdown voltage of 40 kv or more and a capacitance of 110
The pF / m and flexibility were 57 mm. According to this, the crosslinked electric wire using the composition according to the present invention has the same high withstand voltage characteristics and electric characteristics (low capacitance) as the conventional crosslinked electric wire using the polyethylene-based polymer. It can be seen that the flexibility of the conventional crosslinked electric wire is also excellent. Therefore, for example, it can be said that it can be suitably used as a high-voltage circuit electric wire in a portion where dense wiring is required.

[0028]

As described in detail above, according to the present invention, a non-polar polyolefin polymer mixture mainly composed of ethylene-propylene rubber is provided with a polyolefin powder having certain specific conditions, that is, a particle diameter of 600 μm or less. By containing a specific amount of a polyolefin powder having a crystalline melting point of 120 ° C. or higher, an electrical insulating composition having a high level of all characteristics of withstand voltage characteristics, electric characteristics, processability and flexibility is obtained. I was able to. Therefore, an insulated electric wire formed by extrusion coating this conductor on the circumference of a conductor and crosslinking it is used for home electric appliances, office automation equipment, gas appliances,
It is suitable as an electric wire for a high voltage circuit used in a portion where dense wiring is required in an automobile or the like.

Claims (2)

[Claims] 1. A particle diameter of 600 μm or less and a crystal melting point of 1 with respect to 100 parts by weight of a nonpolar polyolefin polymer mixture mainly composed of ethylene-propylene rubber.
20 parts by weight or more of polyolefin powder 20 parts by weight or more 200
An electrically insulating composition, characterized in that it contains less than or equal to parts by weight. 2. An insulated wire, wherein a cross-linking coating layer made of the electrical insulating composition according to claim 1 is provided on the outer circumference of a conductor.