JPS62146938A - Electrically semiconductive polyolefin mixture - Google Patents

Abstract

PURPOSE:To obtain an electrically semiconductive mixture having excellent smoothness, by mixing a polyolefin mixture contg. electrically conductive carbon black dispersed therein with a polyolefin. CONSTITUTION:An electrically semiconductive mixture is obtd. by mixing a polyolefin mixture contg. electrically conductive carbon black dispersed therein with a polyolefin. It is preferred that electrically semiconductive carbon black is dispersed in the polyolefin during the course of polymn. and the resulting polyolefin mixture is blended with a polyolefin which is the same kind or a different kind of the polyolefin for the mixture. Pref. carbon black is used in an amount of 5-60wt% based on that of the polyolefin mixture. The amount of carbon black in the electrically semiconductive polyolefin mixture of the polyolefin mixture and the polyolefin is pref. 2-40wt% from the viewpoint of the smoothness of the resulting electrically semiconductive layer.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a polyolefin mixture used for semiconducting layers such as cross-linked polyethylene or ethylene-propylene rubber insulated wires and cables. Our aim is to provide products of superior quality.

<Prior art> Conventionally, in high-voltage cross-linked polyethylene or ethylene-propylene rubber insulated wires and cables, internal semiconducting layers and/or external semiconducting layers have been used to alleviate the surface potential gradient of the insulator and prevent partial discharge. There are layers. .

In order for these semiconducting layers to achieve the above object, it is preferable that the interface between the insulator and the semiconducting layer be smooth.

<Problems to be Solved by the Invention> However, conventional semiconductive layers of this type have minute protrusions on the surface because they use a semiconductive mixture obtained by simply blending conductive carbon black with polyolefin. may occur.

This is undesirable because it tends to become a starting point for the aforementioned partial discharge and the like.

The present invention aims to solve these conventional problems.

<Means for solving the problems and their effects> The feature of the present invention is to prepare a polyolefin mixture in which conductive carbon black is dispersed, and further add a polyolefin of the same type or different type to the polyolefin. There are things to blend.

As a result, a semiconducting material (layer) with excellent smoothness can be obtained.

Furthermore, in the present invention, it is preferable to prepare a polyolefin mixture in which semiconductive carbon black is dispersed during the polymerization process of polyolefin, and further blend this with a polyolefin of the same type or different type as the polyolefin.

In addition, the polyolefins used here include low density polyethylene, high density polyethylene, linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-α olefin copolymer. , ethylene-α-olefin-diene terpolymer, etc., and are used alone or in a blend.

Examples of the conductive carbon black include Ketjen Blank EC (manufactured by Akzo), Palkan XC-72 (manufactured by Caposoto), Toka Black (manufactured by Tokai Carbon), Denka Black (manufactured by Denki Kagaku Kogyo), etc. can be mentioned.

Of course, it is not limited to these.

The amount of conductive carbon black to be added to obtain a polyolefin mixture is preferably in the range of 5 to 60% by weight, and the final product is obtained by blending this mixture with polyolefin. The amount of carbon black in the polyolefin semiconductive mixture is preferably 2 to 40% by weight from the viewpoint of smoothness and conductivity when used as a semiconductive layer for electric wires and cables.

Further, in preparing the polyolefin mixture, it is preferable to knead the polyolefin and conductive carbon black using a mixing roll or the like. Further, a polyolefin mixture in which carbon black is added and mixed during the polymerization process of polyolefin can be obtained, for example, as a Ketjenblack-dispersed polyethylene powder composition manufactured by Idemitsu Kosan Co., Ltd.

Furthermore, various additives such as processing aids, anti-aging agents, crosslinking agents, crosslinking aids, etc. may be added to the above-mentioned semiconductive mixture as necessary.

Now, when the above-mentioned semiconductive mixture is extruded and coated on a conductor as an internal semiconductive layer of a cross-linked polyethylene or ethylene-propylene rubber insulation cable,
An extremely smooth extruded layer is obtained.

This is because, when making a homogeneous mixture of carbon black and polymer, if you try to knead the carbon black and polymer directly, the carbon tends to aggregate and not mix uniformly. On the other hand, in the method of the present invention, in which a mixture containing carbon black is prepared in advance and a mixture is made from this and a polymer, the carbon black in the mixture containing carbon black is completely and uniformly dispersed in advance. This is because even if the carbon black is not mixed, a mixture in which carbon black is uniformly dispersed can be obtained in the end.

Incidentally, if carbon black is not uniformly dispersed, when used in electric wires and cables as described above, or when extruded into a tape shape, minute protrusions will be formed on the surface due to agglomerated carbon black.

<Example> Examples ■～■ Semiconductive mixtures consisting of the formulations shown in Table 1 (Example ■
~■) were extruded into a tape shape with a thickness of 0.5 mm, and its surface smoothness and volume resistivity were examined. The results are shown in the same
Also listed in the table.

In Comparative Examples (1) to (2), semiconductive mixtures prepared by conventional methods were used.

Examples ■~■ A composition obtained by adding 1 part by weight of Perhequin 25B (manufactured by NOF Corporation) as a crosslinking agent to the semiconductive mixture of Examples ■ and ■ above was made into a tape with a thickness of 0.5 mm. Tape at 24℃
Crosslinking was carried out by press heating for 20 minutes (Examples 1 to 2).

In addition, Comparative Examples (1) to (2) were obtained by crosslinking the above-mentioned Comparative Examples (2) and (2) in the same manner.

The surface smoothness, volume resistivity, and gel fraction of each of these Examples (1) to (2) and Comparative Examples (2) to (2) were examined. The results are shown in Table 2.

<Effects of the Invention> As described above, according to the present invention, when extruded as a semiconductive layer for electric wires and cables, for example, the surface smoothness is excellent, and the conventional problems such as micro protrusions do not occur, so partial discharges can be prevented. It is possible to provide a haborioolefin semiconducting mixture with excellent properties free of such problems.

Claims (2)

[Claims] (1) A polyolefin semiconductive mixture characterized by mixing a polyolefin mixture with conductive carbon black dispersed therein and a polyolefin. (2) The semiconductive polyolefin mixture according to claim 1, wherein the polyolefin mixture is a mixture in which conductive carbon black is dispersed in the polyolefin polymerization process.