JPH11124477A - Electrical insulating composition, and wire and cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, having a high initial dielectric breakdown voltage, capable of manifesting excellent, resistance to tree-formation in wet state by compounding an alkyl phenyl ketone solution of a styrene-maleic anhydride copolymer with a polyolefin. SOLUTION: This composition is the one obtained by compounding (B) an alkyl phenyl ketone solution of a styrene-maleic anhydride copolymer with (A) a polyolefin. The component B is preferably a solution comprising the styrene-maleic anhydride copolymer and the alkyl phenyl ketone in the ratio of (30/70)-(70/30) in terms of the weight. The styrene-maleic anhydride copolymer is preferably compounded so that the content of the styrene after the compounding may be 0.05-10.00 wt.%. The alkyl phenyl ketone is preferably the one having phenyl group and ketone bond and acetophenone or the like is exemplified. A wire or cable is provided by coating directly or through other material on a conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating composition and an electric wire or cable formed by coating the electric insulating composition on a conductor directly or via another material.

[0002]

2. Description of the Related Art Polyolefins such as polyethylene and polypropylene are excellent in electrical properties, mechanical properties, chemical resistance and the like. The drawback of these polyolefins is that they are inferior in heat resistance, but their disadvantages can also raise their heat resistance by several tens of degrees by crosslinking.

[0003] For this reason, non-crosslinked polyolefins are mainly used as electrical insulating materials for low-voltage electric wires and cables, and crosslinked polyolefins are widely used mainly as electric insulating materials for high-voltage electric wires and cables.

However, when this cross-linked polyethylene insulated cable for high voltage is used for a long period of time at a wet and high temperature and under a high voltage, a tree-like erosion occurs in the cross-linked polyethylene insulating layer, and when these proceed, the electric power eventually reaches an electric field. It is known that dielectric breakdown will occur.

[0005] Therefore, wire and cable manufacturers are keenly studying the development of a crosslinked polyethylene-based electrical insulating composition capable of preventing such water trees, and some of them have already been put into practical use.

The following has been proposed as such a water-resistant tree-resistant crosslinked polyethylene-based electric insulating composition.

[0007] A crosslinked polyethylene-based electric insulating composition comprising a styrene / maleic anhydride copolymer mixed with polyethylene or an ethylene-based copolymer or a mixture thereof (for example, JP-A-5-325652).

[0008] A crosslinked polyethylene-based insulating composition comprising a mixture of a maleic anhydride-grafted polyethylene, a maleic anhydride-grafted ethylene copolymer, or a mixture thereof with a styrene-maleic anhydride copolymer.

[0009] A crosslinked polyethylene-based insulating composition comprising polyethylene or an ethylene-based copolymer or a mixture thereof, a maleic anhydride-grafted polymer, and a styrene-maleic anhydride copolymer.

[0010]

SUMMARY OF THE INVENTION
Although the water-resistant tree-crosslinked polyethylene-based electrical insulating composition of the above is excellent in intended water-tree resistance, it has a drawback that its initial electrical breakdown voltage is lower than that of a general-purpose polyethylene-based electrical insulating composition.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned drawbacks of the prior art, to provide a high initial electric breakdown voltage and excellent water tree resistance. An object of the present invention is to provide a tree-like electrical insulating composition and electric wires and cables.

[0012]

The gist of the present invention lies in the following two points.

(1) An electrical insulating composition comprising a polyolefin and a styrene / maleic anhydride copolymer, wherein the styrene / maleic anhydride copolymer is an alkylphenylketone of a styrene / maleic anhydride copolymer. An electrical insulating composition characterized by being formulated as a solution.

(2) In an electric wire or cable comprising an electric insulating composition coated on a conductor directly or via another material, the electric insulating composition is composed of polyolefin and styrene.
An electric wire or cable comprising a mixture of an alkyl phenyl ketone solution of a maleic anhydride copolymer.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the electric insulating composition and the electric wires / cables of the present invention will be described.

In the present invention, the alkyl phenyl ketone solution of the styrene / maleic anhydride copolymer is a solution composed of styrene / maleic anhydride copolymer / alkyl phenyl ketone = 30/70 to 70/30 by weight. Is preferred.

In the present invention, the alkyl phenyl ketone preferably has a phenyl group and a ketone bond.

Here, the reason why the styrene / maleic anhydride copolymer / alkylphenyl ketone = 30 / 70-70 / 30 is used as the alkylphenyl ketone solution of the styrene / maleic anhydride copolymer is as follows. It is.

First, when the styrene / maleic anhydride copolymer is used in an amount of 70 parts or more, the solubility is sharply deteriorated, and as a result, a small amount of insoluble components is generated, which impairs the appearance and electric characteristics.

Conversely, if the styrene / maleic anhydride copolymer is less than 30 parts, the amount of alkyl phenyl ketone is relatively increased, which impairs the mechanical and electrical properties.

In the present invention, the styrene / maleic anhydride copolymer has a styrene content of 0.05 to
It is preferable to mix them so as to be 10.00 wt%. In the present invention, as the polyolefin, polyethylene or ethylene-based copolymer or a mixture thereof,
The graft amount of maleic anhydride is 0.02 to 5.00 wt%
Maleic anhydride-grafted polyethylene or maleic anhydride-grafted ethylene-based copolymer or a mixture thereof, polyethylene or ethylene-based copolymer or a mixture thereof, with maleic anhydride-grafted polymer having a maleic anhydride content of 0.02 to 5; It is preferably a blend obtained by blending so as to be 0.000% by weight.

In the present invention, the maleic anhydride-grafted polymer is preferably maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene copolymer, or a mixture thereof.

In the present invention, examples of the alkylphenyl ketone having a phenyl group and a ketone bond include acetophenone, n-octanophenone, n-decanophenone, laurophenone, n-tetradecanophenone, n-hexadecanophenone and 4 '. -N-octyl acetophenone, 4
-N-octanoylbiphenyl, 1,9-diphenyl-
There are 1,3,6,8-nonatetraen-5-one, 2-isopropoxy-1,2-diphenylethanone and the like. In the present invention, these can be used alone or as a mixture of two or more.

In the present invention, the alkyl phenyl ketone having a phenyl group and a ketone bond is excellent in compatibility with a styrene / maleic anhydride copolymer because of having a phenyl group, and has an overall chemical structure of a crosslinked polyethylene type. Since it is similar to acetophenone, which is one of the residues of decomposition of the cross-linking agent of the electrical insulating composition, the electrical properties of the electrical insulating composition can be improved.

[0025]

EXAMPLES Next, examples of the electric insulating composition and electric wires / cables of the present invention will be described together with comparative examples.

(Preparation of Electrical Insulating Composition and Electric Wire / Cable) First, a raw material was weighed and collected to obtain a compound.

Next, the obtained compound was kneaded with a kneading roll to obtain an electrically insulating composition sheet.

Next, the obtained electrically insulating composition sheet was cut into an electrically insulating composition pellet by a pelletizer.

Next, an inner conductive material is provided directly on the copper stranded conductor having a conductor cross-sectional area of 100 mm ² , the electric insulating composition pellet obtained above on the inner conductive material layer, and the electric insulating composition pellet obtained on the inner insulating material layer A polyethylene insulated power cable was obtained by extruding and covering the external conductive material all together.

Here, the thickness of the internal conductive material is 0.7
mm, 6 mm in total of the electrically insulating composition layer and the outer conductive material layer
Is the thickness.

Next, the obtained polyethylene insulated power cable was guided to a dry vulcanizer using nitrogen gas as a heating medium, and heated and crosslinked to obtain a crosslinked polyethylene insulated power cable.

(Characteristics test of cable) The characteristic test of the cable was carried out with respect to the initial electric breakdown voltage and the resistance to bow titlery. The dielectric loss tangent was also measured for some of the cables.

Initial Electric Breakdown Voltage Test Method The outer semiconductive layer of the obtained cable is grounded, an AC voltage is applied to the copper stranded conductor from 170 kV, and 5 kV every 10 minutes.
The pressure was increased step by step, and the electrical breakdown pressure was measured.

[0034] Test method for bow titley resistance The obtained cable was immersed in warm water of 90 ° C, and 9 kV of alternating current was applied between the copper stranded conductor and the warm water, and was left in that state for 500 days.

After 500 days, the crosslinked polyethylene insulating layer was collected, and the collected crosslinked polyethylene insulating layer was thinly sliced.

Next, the thinly sliced crosslinked polyethylene insulating layer was immersed in an aqueous methylene blue solution and subjected to boiling dyeing.

Next, the crosslinked polyethylene insulating layer dyed by boiling was observed under an optical microscope, and the presence or absence and the number of bow title trees were observed.

Dielectric loss tangent test method An AC electric field of 10 kv was applied to the obtained cable, and the dielectric loss tangent was measured.

The results were evaluated as ○ when the dielectric loss tangent was 0.05% or less, and as X when the dielectric loss tangent was 0.05% or more.

Tables 1 and 2 show the formulations of the electrical insulating compositions of Examples and Comparative Examples and the test results of the cables.

Here, in Table 1, acetophenone was used as an alkylphenyl ketone having a phenyl group and a ketone bond, and in Table 2, n-octanophenone was used as an alkylphenyl ketone having a phenyl group and a ketone bond. Features.

FIG. 1 shows a sectional view of the polyethylene insulated power cable of Example 1 thus obtained.

In FIG. 1, 1 is a copper stranded conductor, 2 is an inner conductive material layer, 3 is an electrically insulating composition layer, and 4 is an outer conductive material layer.

[0044]

[Table 1]

[0045]

[Table 2]

As can be seen from Table 1, Comparative Example 1 has a low initial electric breakdown voltage of 260 kv.

Comparative Example 2 had an initial electric breakdown voltage of 300
Although it is slightly better than kv, the dielectric loss tangent is poor.

In Comparative Example 3, the initial electric breakdown voltage was 225.
kv and a low number of bow titleries.

In Comparative Example 4, the initial electric breakdown voltage was 200
kv and the lowest.

In Comparative Example 5, the initial electric breakdown voltage was 210
kv and low.

In Comparative Example 6, the initial electric breakdown voltage was 215
kv and low.

On the other hand, in Examples 1-4 shown in Table 1 and Examples 5-8 shown in Table 2, the initial electric breakdown voltage was 3
It is as high as 30 kv or more, the number of bow titleries is small, and the dielectric loss tangent is good.

[0053]

The electrical insulating composition and the electric wire / cable of the present invention have a remarkably high initial electric breakdown voltage, and have a small number of bow titleries even when used for a long time under high humidity, high temperature and high voltage. In addition, the dielectric loss tangent is good, and is industrially useful.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a polyethylene insulated power cable according to a first embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Copper stranded conductor 2 Internal conductive material layer 3 Electrical insulating composition layer 4 External conductive material layer

Claims (9)

[Claims] An electric insulating composition comprising a polyolefin and a styrene / maleic anhydride copolymer,
The electrical insulating composition according to claim 1, wherein the styrene / maleic anhydride copolymer is blended as an alkylphenylketone solution of the styrene / maleic anhydride copolymer. 2. A solution of styrene / maleic anhydride copolymer in alkyl phenyl ketone, wherein the weight ratio of styrene / maleic anhydride copolymer / alkyl phenyl ketone = 30/7.
2. A solution of 0 to 70/30.
An electrical insulating composition as described in the above. 3. The electrical insulating composition according to claim 1, wherein the alkyl phenyl ketone has a phenyl group and a ketone bond. 4. The compounding amount of the styrene / maleic anhydride copolymer is 0.05 to 10% as the styrene content after compounding.
The electrical insulating composition according to claim 1, wherein the content is 00 wt%. 5. The electrical insulating composition according to claim 1, wherein the polyolefin is polyethylene, an ethylene copolymer or a mixture thereof. 6. The polyolefin is a maleic anhydride-grafted polyethylene or maleic anhydride-grafted ethylene copolymer having a grafting amount of maleic anhydride of 0.02 to 5.00% by weight, or a mixture thereof. The electrical insulating composition according to claim 1. 7. A polyolefin is prepared by adding a maleic anhydride graft polymer to polyethylene or an ethylene-based copolymer or a mixture thereof in an amount of maleic anhydride of 0.02%.
2. The electric insulating composition according to claim 1, wherein the composition is a blend obtained by blending to 5.00 wt%. 8. The electrical insulating composition according to claim 6, wherein the maleic anhydride-grafted polymer is maleic anhydride-grafted polyethylene, maleic anhydride-grafted ethylene-based copolymer, or a mixture thereof. 9. An electric wire or cable comprising an electric insulating composition coated on a conductor directly or via another material, wherein the electric insulating composition is a polyolefin, an alkylphenyl styrene / maleic anhydride copolymer. An electric wire or cable comprising a ketone solution.