JPS5846517A - Crosslinked polyolefin insulated power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crosslinked polyolefin insulating capsule.
The present invention relates to an improvement in the outer semiconducting layer of a power cable, particularly having an outer semiconducting layer extrusion coated on a crosslinked polyolefin insulator.

Recently, in order to make it easier to peel off the outer semiconductive layer during connection work in this type of electrical capeple, the outer semiconductive layer of the cross-linked polyolefin insulated capeple is mainly made of ethylene-vinyl acetate copolymer, and this is used as a conductive material. It has been proposed to add carbon black to the composition.

Incidentally, conventionally used conductive carbon blacks include 1, acetylene black, Ketjen black, and conductive furnace black.

However, these carbon blacks have problems such as destruction or agglomeration of the carbon structure due to crosstalk conditions, resulting in an increase in volume resistivity, and poor stability. Also, if you increase the amount of carbon black in anticipation of an increase in resistivity, the viscosity of the compound will increase,
There is a pressure increase during cable extrusion and heat generation of the compound in the extruder, resulting in a disadvantage of reduced workability. Furthermore, if acetylene black is used alone, it may become difficult to peel off when a blend insulator of ethylene-vinyl acetate polymer or ethylene-ethyl acrylate copolymer is used. As a solution to this drawback, methods such as blending silicone oil, grease, rubber, silicone block copolymers, etc. are sometimes taken, but these alone are not sufficiently effective, and lubricants and other operating agents are sometimes used. Although it has been proposed to improve the peelability by adding ingredients such as the following, it is insufficient to obtain an appropriate peel strength.

The present invention has been made in view of the above, and its purpose is to provide a crosslinked polyolefin insulating capeple that can provide appropriate releasability to an external semiconductive layer extruded onto a crosslinked polyolefin insulator. There is a particular thing.

A feature of the present invention is that the outer semiconducting layer has a vinyl acetate content of 20%.
A composition whose main components are a total of 50 to 120 parts by weight of conductive carbon black and furnace black to 100 parts by weight of ~45% by weight ethylene-vinyl acetate copolymer, and a lubricant. The point is in the composition.

In addition, as a base resin, the vinyl acetate content is 20 to 4.
The reason why 5% by weight of the ethylene-vinyl acetate copolymer was used is that if it is less than 20% by weight or more than 45% by weight, the peel strength increases and the intended purpose cannot be achieved. Acetylene black is desirable as the conductive carbon black. Furnace flick was used as a filler in order to improve releasability, and this not only significantly improved releasability compared to acetylene black alone, but also improved workability and conductivity. was experimentally confirmed. It should be noted that it is difficult to impart electrical conductivity when using furnace black alone, and when added in a large amount, it causes a decrease in mechanical strength and deterioration in stretchability.

As the lubricant, natural paraffin wax, synthetic polyethylene wax, ester wax, etc. are used alone or in combination.

As a crosslinking agent, commonly used dicumyl peroxide, 1,3-bis-(t-butyl peroxy-isopropal)benzene, 2,5-dimethyl-2,5-di(t-
-butyl peroxy)-hexyne-3, etc.

Furnace black has an average particle size of 60 to 120, and a surface area of 20 to 70rr? /2, PH7-10, oil absorption 0.7
~i, sca7t is good.

Next, examples, comparative examples, and reference examples of the present invention will be described.

Table 1 lists the acid compounds, blending amounts, and test results of the semiconductive compositions of Reference Examples, Examples, and Comparative Examples. In Table 1, the ethylene vinyl acetate copolymer of the semiconductive composition contains 0.5 parts by weight of an antioxidant, a lubricant, and 10 parts by weight of a release agent per 100 parts by weight of the polymer, and further contains crosslinking. 1,6-bis-(t--y
-f le panioxii Z propal) benzene 1.0
Parts by weight are added. In Examples 1 to 5 according to the present invention, the carbon black was acetylene black 40
Total of 80 parts by weight and 40 parts by weight of special furnace black
It is by weight, and the type of special furnace black is different.

In the test, after mixing the semiconductive compositions shown in the table, using a compression molding machine, the molding conditions were 120°C, 70V4/m, 5 minutes, and the thickness was 1.0 fin, the length was 110 cm, the width was 160 cm. Rice press sheet and low density polyethylene (melting index M =
1.0, density d = 0.92) 100 parts by weight of insulating crosslinked polyethylene containing 2.0 parts by weight of a crosslinking agent and 0.20 parts by weight of an antioxidant was processed in the same manner as above to reduce the thickness. A press sheet of 3.0 M, 110 fins in length and 130 fins in width was made, and both press sheets were overlapped and heated and pressed at 180°C and 100 Kf/d for 10 minutes using a compression molding machine to produce a laminated sheet. Then, from this laminated sheet, the width is 1
A 2.7M test piece was taken out and used to conduct a tensile test and measure the conductivity of the semiconducting layer.

The peel test was performed using a tensile tester by peeling the semiconductive composition press sheet at a 90 degree angle from the crosslinked polyethylene press sheet at 26°C at a speed of 5001 minutes, and the resistance at that time was measured. Peel strength (Kp/12.'7m
). The elongation of the semiconductive layer was also measured.

This core was used as the first surface layer and crosslinked at a gold vapor pressure of 20 Kg/ca. A shallow scratch was made in the cable core after crosslinking to a width of 12.7 m, and only the external semiconductive layer was peeled off, and the peel strength at that time was measured, and the conductivity of the semiconductive layer was measured.
Results similar to those in Table 1 were obtained.

The figure is a cross-sectional view showing one embodiment of a cross-linked polyolefin insulating capeple of the present invention. As the external semiconducting layer 4, Table 1 Example 1~
The semiconductive composition shown in No. 5 is used.

As described above, the crosslinked polyolefin insulating electrical cable according to the present invention is made of ethylene-vinyl acetate copolymer and conductive carbon black as the outer semiconductive layer 4 which is extruded and coated on the crosslinked polyolefin insulator '3. Since the semiconductive composition containing furnace black is used, the outer semiconductive layer 4 can have appropriate releasability, and the viscosity of the semiconductive composition can be lowered, so that it can be easily removed during extrusion. Problems such as pressure build-up and burning will no longer occur.

In Examples 1 to 5 in Table 1, the total amount of conductive carbon black and special furnace black was 80
The parts by weight are 50 to 50 as mentioned above.
If it is within the range of 120 parts by weight, the same effect can be obtained, and 5 parts by weight.
If it is less than 0 parts by weight, the peel strength will increase and the desired electrical conductivity will not be obtained. ! On the other hand, if the amount exceeds 120 parts by weight, extrusion during coating becomes difficult and tensile strength decreases.

Further, the vinyl acetate content of the ethylene vinyl acetate copolymer is preferably 20 to 45% by weight, and if it is less than 20% by weight or more than 45% by weight, the peel strength cannot be improved. In addition, the special furnace black has an average particle size of 60 to 1'lQ.
w, surface area 20-70-/2, PH7-10, oil absorption 0
．． 7 to 15 CC/f is preferable, and all those shown in Table 1 satisfy the above conditions.

As explained above, according to the present invention, it is possible to provide an external semiconductive layer with appropriate peelability, and it can be made to have good strength, conductivity, and workability, and low mechanical strength. There is an effect.

[Brief explanation of the drawing]

The figure is a cross-sectional view showing one embodiment of the crosslinked polyolefin insulation type capsule of the present invention. 1: conductor, 6: crosslinked polyethylene insulator, 4: outer semiconductive layer.

Claims (1)

[Scope of Claims] 1. An electrical cable having an outer semiconducting layer extrusion coated on a crosslinked polyolefin insulator, wherein the outer semiconducting layer is made of ethylene-vinyl acetate having a vinyl acetate content of 20 to 45% by weight. A total of 5 parts of conductive carbon black and furnace black per 100 parts by weight of the copolymer.
1. A crosslinked polyolefin insulating capeple characterized by comprising a composition containing as a main component 0 to 120 parts by weight and further a lubricant. 2. The furnace black has an average particle diameter of 3o~120o, a surface area of 20~7o-1, a pH of 7~1o. The crosslinked polyolefin insulated capeple according to claim 1, which has an oil absorption of 0.7 to 1.5 cc/l.