JPH02260323A - Power cable - Google Patents

Abstract

PURPOSE:To obtain a semiconductive layer having proper peeling property and adhesion to an insulating layer by blending a specified amount of conductive carbon black to propylene. alpha-olefin copolymer or a blend polymer of this copolymer with a polyolefin polymer other than this. CONSTITUTION:The outer circumference of a conductor 1 is coated with an inner semiconductive layer 2. The inner semiconductive layer 2 is coated with an insulating layer 3. The insulating layer 3 is further successively coated with an outer semiconductive layer 4, a shielding layer 5 and a sheath 6 to form an electric power cable. The outer semiconductive layer 4 is formed by extruding and coating a resin composite in which 10-100 parts by weight cf conductive carbon black is blended to 100 parts by weight of propylene. alpha-olefin copolymer having the propylene content of 40-70% alone or a blend polymer of 5wt.% or more of this copolymer with less than 95wt.% of a polyolefin polymer other than this on the insulating layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a power cable such as a cross-linked polyethylene insulated cable, and the semiconductive layer thereof has improved peelability.

[Conventional technology]

For power cables such as cross-linked polyethylene insulated cables (CV cables), insulating layers made of cross-linked polyethylene or cross-linked ethylene propylene rubber, etc. are It is necessary to make the semiconductive layer easy to peel off. Furthermore, it is also necessary that interfacial peeling between the insulating layer and the semiconducting layer does not occur when an external bending force is applied to the power cable. Therefore, semiconductor 1! The layer needs to have both appropriate releasability and adhesion to the insulating layer.

For this reason, in the past, polyolefin resins such as polyethylene were blended with polar polymers such as polyvinyl chloride, chlorinated polyethylene, and ethylene-vinyl acetate copolymers, fluororesins, and silicone resins to form base polymers, and conductive carbon was added to this base polymer. The semiconductive layer is made of a resin composition containing black, and is made to have appropriate peelability and adhesion to an insulating layer made of a polyolefin resin such as crosslinked polyethylene or crosslinked ethylene propylene rubber.

[Problem to be solved by the invention]

However, in the case of a semiconducting layer made of the above-mentioned resin composition, since this resin composition is a blend of a polyolefin resin and a polar polymer that is inherently poor in compatibility with this polyolefin resin, it is difficult to uniformly conduct wires when cross-wired. It is difficult to disperse, and therefore, when the semiconducting layer obtained from this resin composition is peeled from the insulating layer, directionality is exhibited,
There was a problem in that the cable could not be peeled off in any direction, making it difficult to easily process the ends of the power cable.

[Means to solve the problem]

In this invention, the resin composition forming the semiconductive layer is a propylene content of 40 to 70 mol%, and 100% by weight of a propylene/α-olefin copolymer or a blend polymer of this copolymer and other polyolefin polymers. The above problem was solved by using a material containing 10 to 100 parts by weight of conductive carbon black.

The present invention will be described in detail below.

FIG. 1 shows an example of the power cable of the present invention, and the reference numeral l in the figure represents a conductor. The outer periphery of this conductor 1 is coated with an internal semiconducting layer 2 . This internal semiconducting layer 2 is
This is a bond type semiconductive layer, which is different from the one with good releasability in the present invention. Furthermore, this internal semiconducting layer 2 is coated with an insulating layer 3. The insulating layer 3 is made of a resin composition obtained by extrusion coating a polyolefin resin such as crosslinked polyethylene or crosslinked ethylene propylene rubber, and then crosslinking it by heating.

Furthermore, on this insulating layer 3, an external semiconducting layer 4 and a shielding layer 5 are formed.
and the sheath 6 are covered one after another to form a power cable.

The outer semiconductive layer 4 is made of a propylene/α-olefin copolymer alone having a propylene content of 40 to 70 mol%, or this copolymer is 5% by weight or more, and other polyolefin polymers are 95% by weight or less. 10 to 100 parts of conductive carbon black to 100 parts of blended polymer with
It is formed by extrusion coating the insulating layer 3 with a resin composition containing 100 parts by weight.

The propylene/α-olefin copolymer, which is one component of the base polymer used here, is a block copolymer of propylene and an α-olefin such as ethylene, 1-butene, or 1-hexene, and contains propylene. It is propylene-rich with an amount of 40 to 70 mol%, and preferably has a relatively low crystallinity of 30 to 50%. For example, Mitsui Petrochemical Industries, Ltd.
The product sold as "Tafmar XR" (trade name) is used. As the above α-olefin, ethylene is a particularly preferred co-7mer.

In addition, as the olefin polymer that is the other component of the base polymer, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, etc. -α-olefin copolymer and these two
Among these, ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer are particularly suitable. The ethylene-vinyl acetate copolymer has a vinyl acetate content of 10 to 35
% by weight, and has a melt fluor rate of 1 to 20
Preferably. This ethylene-hinyl acetate copolymer improves the processability of the base polymer and facilitates the dispersion of carbon black into the pace polymer.

Further, as the ethylene-ethyl acrylate copolymer, one having an ethyl acrylate content of about 10 to 25% by weight is preferable in that it imparts appropriate flexibility to the base polymer.

Furthermore, as the polyolefin-based polymer, non-polar polyolefins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), and high-density polyethylene may also be used. be able to.

In addition, when using a blend polymer of the propylene/α-olefin copolymer and other polyolefin polymers as the base polymer, the mixing ratio is 5% by weight or more of the propylene/α-olefin copolymer and 5% by weight or more of the other polyolefin copolymer. The proportion of the polyolefin polymer is 95% by weight or less, preferably the proportion of the propylene/α-olefin copolymer is 30% by weight or more, and the proportion of other polyolefin polymers is 70% by weight or less. Propylene α−
If the olefin copolymer content is less than 5% by weight, the outer semiconducting layer 4
This is inconvenient because it becomes difficult to peel off.

Conductive carbon black is added to such a base polymer to impart electrical conductivity.

As the conductive carbon black here, well-known carbon blacks such as acetylene black and furnace black can be used. The amount of conductive carbon black to be mixed with the base polymer is determined in consideration of the conductivity required of the outer semiconductive layer 4, and is determined in the range of 10 to 100 parts by weight based on 100 parts by weight of the base polymer.

Further, a crosslinking agent, a crosslinking aid, an anti-aging agent, etc. can be added to the resin composition made of the mixture of the base polymer and carbon black, if necessary. As a crosslinking agent, dicumyl peroxide (DCP), 2.5-
Common peroxide crosslinking agents such as dimethyl-2,5-di(t-butylperoxy)hexyne-3 can be suitably used.

The blending amount of the crosslinking agent is approximately 0.2 to 3 parts by weight per 100 parts by weight of the base polymer. In addition, as a crosslinking aid, triallyl isocyanurate, triallyl cyanurate, tetraallyloxyethane TININ'-m
- Phenylene bismaleimide, p, p dibenzoylquinone dioxime, p-quinone dioxime, etc. can be used,
It can be added in an amount of about 0.5 to 3 parts by weight per 100 parts by weight of the base polymer. These crosslinking agents and crosslinking aids may be used in combination, or either one may be used alone. When a crosslinking aid is used alone, a portion of the crosslinking agent in the insulator migrates to the semiconductive layer during crosslinking and reacts with the migrated crosslinking agent to cause crosslinking. In addition, as an anti-aging agent, 4゜4゛-thiobis (6-t-butyl-3-methylphenol) can be used, and zinc stearate, zinc oxide, magnesia, etc. can also be added as necessary. can.

In order to form the outer semiconducting layer 4 using such a composition, an extrusion coating method can be applied in the same manner as the conventional method.

In such a power cable, the outer semiconductive layer 4 is made of a resin composition mainly composed of a propylene/α-olefin copolymer or a polyolefin polymer other than this copolymer and other polyolefin polymers. The insulating layer 3 made of cross-linked ethylene propylene rubber has appropriate adhesion and peelability, and the base polymer itself becomes a homogeneous dispersion system, so that when the semiconducting layer is peeled off, it can be moved in a specific direction. It does not cause any inconvenience such as easy peeling, and can be easily peeled off in any direction as needed.

Hereinafter, the effects of this invention will be clarified by showing examples.

〔Example〕

Resin compositions having the formulations shown in Tables 1 and 2 were prepared as external semiconductive layers. On the conductor (500 m+”), an inner semiconducting layer (thickness IIIP), an insulating layer (°crosslinked polyethylene, thickness 11 m+m), an outer semiconducting layer (thickness 0
. Regarding the obtained power cable, the presence or absence of directionality during peeling of the outer semiconductive layer was investigated. Separately, a sheet piece with a two-layer structure made of this resin composition and crosslinked polyethylene was extruded and its peel force was determined. The results are also shown in Tables 1 and 2.

As is clear from Table 1 below, in the power cable of the present invention, when the semiconducting layer is peeled off, there is no directionality (it can be peeled off in any direction), and the peeling force against the insulating layer is It can be seen that the adhesion is well balanced.

〔Effect of the invention〕

As explained above, the power cable of the present invention has a propylene content of 40 to 70 mol% and 100 parts by weight of a propylene/α-olefin copolymer or a blend polymer of this copolymer and other polyolefin polymer. Since it has a semi-conductive layer made of a resin composition containing 10 to 100 parts by weight of conductive carbon black, it can be easily moved in any direction when peeling the semi-conductive layer from the insulating layer during terminal processing etc. It is possible to peel off as much as necessary, and therefore the terminal processing work can be easily performed. Further, this semiconductive layer has appropriate adhesiveness and appropriate releasability to an insulating layer made of crosslinked polyethylene or the like.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of the power cable of the present invention. 4...Outer semiconducting layer.

Claims (2)

[Claims] (1) 10 to 10 parts by weight of conductive carbon black is added to 100 parts by weight of a propylene/α-olefin copolymer having a propylene content of 40 to 70 mol% or a blend of this copolymer and other polyolefin polymers.
A power cable having a semiconductive layer made of a resin composition containing 100 parts by weight. (2) The proportion of the propylene/α-olefin copolymer is 5% by weight or more, and the proportion of other polyolefin polymers is 9% by weight.
The power cable according to claim 1, wherein the content is 5% by weight or less.