JP2889267B2 - Composition for forming semiconductive layer for power cable - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a composition for forming a semiconductive layer for a power cable, and particularly to an excellent semiconductive layer formation useful for forming an outer semiconductive layer of a crosslinked polyethylene insulated power cable. It relates to a composition.

[Conventional technology]

In recent years, cables with so-called free stripping properties, in which the external semiconductive layer can be easily peeled off and removed from the insulator in order to simplify the terminal treatment work and connection work of power cables such as cross-linked polyethylene and shorten the time, have begun to spread. I have.

This outer semiconductive layer is disclosed in Japanese Patent Publication No.
As disclosed in JP-A-3-32204, many proposals have been made to form a composition containing a chlorine-based polymer or an ethylene / vinyl acetate copolymer as a main component.

Although the above polymer has a good function in terms of free stripping properties, its half-surface chlorine-based polymer has poor extrudability and thermal stability due to chemical cross-linking that normally passes through high-pressure steam pipes at around 200 ° C. It is bad and easily deteriorates.

Similarly, the ethylene-vinyl acetate copolymer has poor heat resistance and is decomposed during the crosslinking step to generate acetic acid, which is liable to be broken due to a decrease in strength and corrodes the copper tape of the shielding layer provided on the cable.

In the case of chemical crosslinking which has been widely used in the past, if no crosslinking device is provided, the equipment investment cost becomes large and it cannot be easily manufactured.

Furthermore, in the conventional semiconductive composition, the carbon black particles are uniformly kneaded in the base polymer in the mixing step, and there is a large amount of carbon aggregation because the carbon black particles do not disperse.However, the dispersion can be improved and the carbon aggregation can be reduced. Is an issue.

[Problems to be solved by the invention]

The object of the present invention is to use a resin material such as a chlorine-based polymer or an ethylene-vinyl acetate copolymer, which does not have good heat stability and heat resistance, and that a high share is applied during kneading to completely eliminate carbon bumps. An object of the present invention is to provide a composition for a semiconductive layer having free stripping properties of a crosslinked polyethylene insulated power cable without having the same.

[Means for solving the problem]

The present invention relates to a method for producing a conductive material based on 100 parts by weight of a resin material comprising 30 to 70% by weight of a polymer obtained by silane grafting of an ethylene-α olefin copolymer and 70 to 30% by weight of an ethylene-α olefin copolymer. Carbon black 15 ~ 70
A semiconductive layer forming composition for a power cable, wherein the composition is prepared by uniformly mixing parts by weight.

As the α-olefin of the ethylene-α-olefin copolymer used by silane grafting in the present invention,
For example, C ₃ -C _12, polypropylene, butene-1, pentene-1, hexene-1, heptene-1, octene -
1,4-methylpentene-1,4-methylhexene-1,
4-4-dimethylpentene-1, nonene-1, decene-
1, undecene-1 and dodecene-1 and the like.

Particularly preferred are butene-1, pentene-
1, hexene-1, heptene-1, 4-methylpentene-
One is raised.

The silane grafter used in the present invention is obtained by adding the above-mentioned olefin resin to the olefin resin represented by the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R 'is an aliphatic unsaturated group. It is obtained by reacting an organic silane represented by a monovalent hydrocarbon group other than a saturated hydrocarbon or the same as Y) under a free radical-generating compound. This uses a known method disclosed in JP-B-57-24373, JP-B-48-1711, JP-A-50-24342 and the like. Specifically, for example, a vinyltriene based on a polyolefin resin is used. It can be obtained by using methoxysilane or the like in combination with an organic peroxide having a strong polymerization initiating action such as DCP (dicumyl peroxide). The amount of the silane grafter is preferably 30% by weight or more based on 100% by weight of the resin, and if it is less than 30%, the shape retention characteristics at high temperatures and the heat deformation rate deteriorate.

In addition, the degree of crosslinking of the silane graftmer is expressed as gel fraction in terms of gel fraction as xylene-insoluble residue.
20% to 80% by weight is preferred. When the gel fraction is 20% by weight or less, the shape retention at high temperatures and the heat deformation rate are poor, and when the gel fraction is 80% by weight or more, the moldability is poor.

Also, the amount of conductive carbon black is 15-70% by weight.
The reason is that if it is less than 15 parts by weight, the conductivity is low and the function as a semiconductive layer cannot be provided, and if it exceeds 70 parts by weight, the extrudability deteriorates and the mechanical strength decreases. This is because it is easily broken.

As the type of carbon black, any of Ketjen black, furnace black, acetylene black and the like may be used, but carbon black having a large specific surface area for adsorption is more effective.

Of course, if necessary, an antioxidant, a lubricant and the like can be added.

〔Example〕

A silane-grafted polymer was prepared with the composition shown in Table 1. The ethylene-butene-1 copolymer used was CN2008, MFR 2.1 g / 10 min, manufactured by Sumitomo Chemical Co., Ltd.

Next, various compositions were prepared as shown in Table 2. The ethylene-butene-1 copolymer in Table 2 is also CN2002, MFR 2.2 g / 10 min, manufactured by Sumitomo Chemical Co., Ltd.

In order to prevent the material temperature from rising rapidly during kneading,
Water was passed through the jacket of the Banbury mixer, batch-poured, kneaded until the material temperature reached 150 ° C., and pelletized.

Granulated pellets are extruded with 65mmφ extruder (insulating material) and 40mm
A rod-shaped two-color molded product was formed with a φ extruder (semiconductive material).

As for the free stripping property, a test piece was taken from the molded product with a width of 1 inch, and the peel strength was measured by an autograph.

The gel fraction was measured as a residue obtained by treating a molded article with hot water at 80 ° C. for 2 hours and immersing the molded article in xylene at 120 ° C. for 20 hours.

The heating deformation rate was measured according to JISK6723. Regarding the thermal stability, those which began decomposition within 15 minutes when kneaded at 200 ° C. with a Brabender plastograph were evaluated as X, and those having 15 minutes or more were evaluated as ○.

[Effects of the Invention] From the above evaluations, a favorable composition was obtained as a semiconductive layer forming composition for power cables having good heat resistance and free stripping properties.

Claims (1)

(57) [Claims] An electroconductive material is used for 100 parts by weight of a resin material comprising 30 to 70% by weight of a polymer obtained by silane grafting an ethylene-α-olefin copolymer and 70 to 30% by weight of an ethylene-α-olefin copolymer. Carbon black 15-70
What is claimed is: 1. A composition for forming a semiconductive layer for a power cable, wherein the composition is prepared by uniformly mixing parts by weight.