JPH09249772A - Semiconductive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an easily peelable semiconductive resin composition improved in tree resistance without detriment to heat resistance and mechanical strengths by using a methylphenylsilicone oil. SOLUTION: This composition comprises a methylphenylsilicone oil. This is produced by mixing 100 pts.wt. polyolefin base resin with 10-100 pts.wt. conductivity improver, 5-30 pts.wt. filler and 1-10 pts.wt. methylphenylsilicone oil. The methylphenylsilicone oil should have a viscosity of 1-500mPa/sec. The composition is used to form the semiconductive layer of a crosslinked polyethylene insulated power cable.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductive resin composition used for a semiconductive layer of a power cable.

[0002]

2. Description of the Related Art Insulated wire cores for crosslinked polyethylene insulated cables have the purpose of relaxing electric field concentration and preventing partial discharge at the interface between the insulating layer and the conductor or at the interface between the insulating layer and the metal shielding layer.
A semiconductive layer is provided inside and outside the insulating layer. This semiconductive layer is formed by a semiconductive resin composition obtained by mixing an ethylene-vinyl acetate copolymer, carbon black, and a filler as a base resin.

However, this resin composition has a drawback that it is difficult to peel off. Therefore, when the outer semiconductive layer is stripped off by a work of connecting a power cable using such a composition for the semiconductive layer, carbon black is apt to remain in the insulating layer after stripping, There was a defect that residual carbon black causes a decrease in insulation resistance and the generation of trees. As a method for solving this drawback, there is a method of lowering the crosslinking degree of the ethylene-vinyl acetate copolymer contained, or a method of increasing the vinyl acetate component in the copolymer. It is accompanied by a decrease in mechanical strength and heat resistance.

As a method for solving such a drawback, a method of adding dimethylpolysiloxane (silicone oil) has been proposed (JP-A-56-118435). According to this method, the effect of improving releasability can be obtained without lowering the mechanical strength. However, as a result of various studies, it has been found that the power cable using the resin composition according to the related art for the semiconductive layer is inferior in tree resistance.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductive resin composition which is not easily deteriorated in heat resistance and mechanical strength and which is excellent in tree resistance and easily peeled off. .

[0006]

In order to solve the above problems, the semiconductive resin composition of the present invention contains methylphenyl silicone oil as a component. This methylphenyl silicone oil has a viscosity of 1 mPa / sec or more 50
It is necessary to be less than 0 mPa / sec. When a semiconductive layer of a power cable is formed by using a semiconductive resin composition containing a methylphenyl silicone oil having a viscosity of less than 1 mPa / sec, slipperiness is too good and kneading and manufacturing becomes difficult. Is improved, but it may cause the appearance to be roughened, which may deteriorate the tracking property and cause trees. On the other hand, a semiconductive resin composition containing a methylphenyl silicone oil having a viscosity of more than 500 mPa / sec has poor releasability.

Further, the content of the methylphenyl silicone oil must be 1 part by weight or more and 10 parts by weight or less when the base resin is 100 parts by weight. If it is less than 1 part by weight, a good effect of improving the peelability cannot be obtained, and if it is more than 10 parts by weight, the slipperiness is so good that the kneading and manufacturing becomes difficult.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the semiconductive resin composition of the present invention, a polyolefin resin is used as the base resin from the viewpoint of affinity with the crosslinked polyethylene forming the insulating layer. Examples of such polyolefin base resin include low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, chlorinated polyethylene, and peroxides thereof. Examples of the crosslinkable polymer include a physical crosslinking agent. In addition, ethylene-
When the vinyl acetate copolymer is used, it is desirable to use one having a vinyl acetate content of 10% by weight or more and 50% by weight or less. If the content of vinyl acetate is less than 10% by weight, the releasability is extremely deteriorated, and if the content of vinyl acetate is more than 50% by weight, the heat resistance is deteriorated and the molding process for electric power cables is endured. Absent.

As the conductivity-imparting agent, it is preferable to use a carbon black-based conductive material such as furnace black, acetylene black or Ketjen black for uniform dispersibility,
It is desirable in terms of conductivity and durability. The addition amount of these carbon blacks is preferably 10 parts by weight or more and 100 parts by weight or less, based on 100 parts by weight of the base resin. When it is less than 10 parts by weight, sufficient conductivity cannot be obtained, and when it is 100 parts by weight or more, extrusion moldability is remarkably deteriorated, and sufficient strength is obtained when it is used as a semiconductive layer of a power cable. I can't.

The semiconductive resin composition according to the present invention may contain organic peroxides (dicumyl peroxide, perhexin, etc.), antioxidants, processing aids, etc. as fillers. desirable. Such a filler is preferably added in an amount of 5 parts by weight or more and 30 parts by weight or less, based on 100 parts by weight of the base resin. 5
If it is less than part by weight, a sufficient addition effect cannot be obtained, and
If it is 30 parts by weight or more, the workability is significantly reduced.

The semiconductive resin composition of the present invention can be obtained by sufficiently kneading the above-mentioned raw materials with a kneading means such as a roll mill or a kneader. The temperature in this kneading step is preferably 120 ° C. or higher and 150 ° C. or lower. 1
If the temperature is less than 20 ° C, it is difficult to sufficiently knead, while 15
If it is 0 ° C or higher, there is a risk of deterioration or thermal decomposition.

[0012]

EXAMPLE In this example and comparative example, the base resin is ethylene-vinyl acetate copolymer X700 manufactured by Mitsubishi Chemical.
(Vinyl acetate content 30% by weight), # 3100 manufactured by Mitsubishi Kagaku Co., Ltd. was used as carbon black as a conductivity-imparting agent, and Antage RD manufactured by Kawaguchi Chemical Industry was used as a filler.

Further, in the examples, the release property imparting agent has a viscosity of 0.5, 1, 10, 500 and 700 mPa / sec.
5 kinds of methylphenyl silicone oil (SH550 manufactured by Toray Dow Corning Co., Ltd.) (hereinafter referred to as “MPSi”), and dimethyl silicone oil (TSF4 manufactured by Dow Corning Toray Co., Ltd.) used as a release agent in Comparative Examples.
51-50, viscosity: 50 mPs / sec) (hereinafter "DM
Si)) was prepared.

Resin compositions A to I (Examples 1 to 9) were prepared by mixing these so as to have the compositions shown in Tables 1 and 2 and kneading with a roll mill set at 140 ° C. until uniform.
And resin composition MR (Comparative Examples 1-6) was obtained.

The peel strength of these resin compositions is J
It measured based on IS * K6766. It is said that if the peel strength is 0.3 kg / 10 mm or more and 0.8 kg / 10 mm or less, peeling is easy.

Also, these resin compositions A to I and M to R
Was used to produce an insulated wire core of a crosslinked polyethylene insulated power cable. That is, as shown in the structural diagram of FIG. 1, these resin compositions are applied to the inner and outer semiconductive layers, and the inner semiconductive layer, the insulator (crosslinked polyethylene) and the outer conductive layer are coextruded in three layers at 180 ° C. After molding, this was heated to 200 ° C. in a nitrogen atmosphere and chemically cross-linked to produce 18 kinds of dry cross-linked 6 kV-CV (60 mm ² ) insulated cores (conductor thickness: 9.3 mm, inside). Semi-conductive layer thickness: 1m
m, insulating layer thickness: 3 mm, external semiconductive layer thickness 1 mm).
The appearance of the insulated core obtained at this time was observed. The results are shown in Tables 1 and 2.

Further, the tree resistance of these resin compositions was evaluated. That is, these resin compositions were formed into a sheet having a thickness of 5 mm, and a resin layer of a conductive paint was provided on the bottom surface of the sheet to form a ground side electrode. On the other hand, a water tank was provided on the upper surface of the sheet to form a water electrode. A voltage of 10 kV and 1 kHz was applied to this water electrode for 30 days, the sample was boiled with boiling water, and the developed water tree was observed with a microscope. At this time, the relative number when the number of water trees generated in the comparative sample made of cross-linked polyethylene (XLPE) treated in the same manner was set to 100 was examined.
When the relative number is 20 or less, it is regarded as “good” and is 20
When it was over, it was evaluated as "poor". These results are also shown in Tables 1 and 2.

[0018]

[Table 1]

[0019]

[Table 2]

Further, the semiconductive resin composition A according to the present invention
For the insulation core of a power cable in which a semiconductive layer is formed by using ~ I, when the work of stripping the external semiconductive layer is performed, it can be easily stripped, and the surface of the insulating layer after stripping There was no residual carbon black. On the other hand, the insulated cores using the resin compositions M, P and R were difficult to peel off, and carbon black remained. From these results and Tables 1 and 2, it can be seen that when the semiconductive resin composition according to the present invention is used, an excellent insulated core of a power cable having a semiconductive layer that is easily peeled off can be obtained.

[0021]

INDUSTRIAL APPLICABILITY When the semiconductive resin composition according to the present invention is applied to a semiconductive layer of a crosslinked polyethylene insulated power cable, it has sufficient heat resistance for processing, is excellent in tree resistance, and has an excellent appearance. A power cable having a semiconductive layer having excellent peelability can be obtained.

[Brief description of drawings]

1 is a cross-sectional view of an insulated core of an insulated power cable having a semiconductive layer.

[Explanation of symbols]

 Reference Signs List 1 conductor 2 inner semiconductive layer 3 insulating layer (crosslinked polyethylene) 4 outer semiconductive layer

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 83:04)

Claims (4)

[Claims] 1. A semiconductive resin composition comprising methylphenyl silicone oil as a component. 2. 100 parts by weight of a polyolefin base resin, 10 parts by weight or more and 100 parts by weight or less of a conductivity imparting agent, 5 parts by weight or more and 30 parts by weight or less of a filler, and 1 part by weight or more of methylphenyl silicone oil. The semiconductive resin composition according to claim 1, which is mixed in an amount of 10 parts by weight or less. 3. The semiconductive resin composition according to claim 1 or 2, wherein the viscosity of the methylphenyl silicone oil is 1 mPa / sec or more and 500 mPa / sec or less. 4. A crosslinked polyethylene insulated power cable having a semiconductive layer, wherein the semiconductive layer contains methylphenyl silicone oil.