JPS60112204A - Conductive composition for 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 [Background and Objects of the Invention] The present invention relates to a conductive composition used for forming an inner conductive layer or an outer conductive layer of an electric power cable.

Conventionally, conductive compositions used to form the internal conductive layer and external conductive layer of power cables are generally made by mixing ethylene-based polymers such as ethylene vinyl acetate copolymer with acetylene black as a conductivity imparting agent. It has been used.

However, in order to obtain sufficient conductivity, it is necessary to mix a large amount of conductivity imparting agent, which increases the viscosity of the composition and makes extrusion difficult under severe processing conditions, such as extrusion at high speed. It becomes difficult.

To solve this problem, the viscosity of the composition can be lowered by using a furnace black such as HAF, FEF, or SRF, but on the other hand, the dispersion is not sufficient and coarse particles are generated on the surface of the conductive layer, which deteriorates the electrical properties. The problem is that it significantly reduces the amount.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a conductive composition that has excellent extrusion processability, reduces generation of coarse particles, and can provide sufficient conductivity. .

[Summary of the invention] The conductive composition of the present invention has an arithmetic mean particle diameter of 25 to 40 mμ, an iodine adsorption amount of 40 to 60 mg/g, and a DBP oil absorption amount (JISA method) based on 100 parts by weight of the ethylene polymer.
120-150m1/100g of furnace carbon black alone or in combination with acetylene black
It is characterized by containing 0 parts by weight or more.

In the present invention, the ethylene polymer refers to the entire polymer containing ethylene in the molecular chain, such as polyethylene,
Ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene methyl acrylate copolymer, ethylene propylene copolymer, ethylene butene copolymer,
Such as ethylene pentene copolymer. Furthermore, it also includes those grafted with styrene, acrylate, acrylonitrile, etc. These can be used alone or in combination of two or more.

The conductivity imparting agent used in the present invention is furnace carbon black whose arithmetic mean particle diameter, iodine adsorption amount, and DBP oil absorption amount are within a specific range, and this can be used alone or in combination with acetylene black. Ru.

The arithmetic mean particle diameter must be in the range of 25 to 40 mμ; if it is less than 25 mμ, the viscosity will increase when kneaded with a polymer, resulting in poor processability; if it exceeds 40 mμ, sufficient conductivity cannot be imparted. Moreover, it is more effective to sieve to remove those of 149 mμ or more.

The amount of iodine adsorbed must be in the range of 40 to 60 mg/g; if it is less than 4.0 mg/g, sufficient conductivity cannot be imparted, and if it exceeds 60 mg/g, the viscosity will increase and processability will be impaired. Getting worse.

DBP oil absorption (JISA method) is 120-160ml
/ 100 g, 120 m1
/100g or less, sufficient conductivity cannot be imparted, and 150g
When m1/100g is exceeded, dispersion in the polymer deteriorates and coarse particles are likely to be formed.

By using furnace carbon black in such a specific range, it is possible to form a conductive layer that has good dispersion in the polymer, excellent processability, and sufficient conductivity.

The amount of furnace carbon black mixed into the ethylene polymer must be 40 parts by weight or more per 100 parts by weight of the ethylene polymer, and if it is less than this, sufficient conductivity cannot be imparted. The upper limit is not particularly limited since it varies depending on the desired conductivity and the type of polymer, but it is 120 parts by weight considering processability.

When used in combination with acetylene black, the total amount of both may be 40 parts by weight or more, but it is preferable that the amount of acetylene black is the same as that of furnace black or less.

The conductive composition of the present invention may be crosslinkable or non-crosslinkable. In the case of crosslinking, dicumyl peroxide, 1,3-bis(t-butyl peroxy isopropyl)benzene, 2,5-
It is appropriate to mix a dialkyl peroxide represented by dimethyl-2,5-di(t-butyl peroxy)hexyne-3.

In the present invention, in addition to the above-mentioned components, lubricants, antioxidants, etc. may be mixed in the same manner as in conventional compositions.

As the lubricant, it is preferable to use one or more of stearic acid, metal acids and esters, fatty acid amides made of stearic acid, oleic acid, and ethylenediamine, and saturated hydrocarbon oligomers with a molecular weight of 10,000 or less.

As the antioxidant, one type or one of those used for rubber or polyolefins such as 4'-thiobis(3-methyl-6-t-butylphenol) and N,N'-diphenyl-p-phenylenediamine may be used. Two or more types can be used in combination.

[Embodiments of the invention] Various carbon blacks as shown in Table 1 were prepared.

Next, various ingredients were mixed using a panburi kneader at the proportions shown in Table 2. This mixture was put into a 65 mm extruder and extruded to a thickness of 1 mm to cover the outer periphery of a core coated with a cross-linked polyethylene insulator to a thickness of 6 mm on the circumference of a copper conductor having a cross-sectional area of 150 mv/. The temperature setting of the extruder goes from the feed section to the metering section, and the barrel zone C1=
100℃, C2=110℃, C3=115℃, Dice=
The temperature was 120°C. Also, the screw is L/D=22,
One with a rotation speed of 2 Orpm was used.

After extrusion coating, crosslinking was carried out by heating in a nitrogen gas atmosphere at 250°C.

The evaluation results for the conductive composition and the obtained power cable are shown in the lower column of Table 2.

Table 1 In the evaluation shown in Table 2, the Mooney viscosity was measured for the uncrosslinked mixture, and those with a 4-minute value of 50 points or less after heating one molecule were designated as O5, and those with a higher value of 50 points or less were designated as X.

Coarse particles with a diameter of 100 μm or more were visually counted on the extrusion surface, and those with 10 pieces/100 crf or less were rated ○, and those with more than 10 pieces/100 crf were rated ×.

Volume resistivity was measured in a constant temperature bath at 90°C, and was measured at 5°0 x 1
Those below 0 Ω·Cm were marked ○, and those above this were marked ×.

Examples 1 to 8, which fall within the scope of the present invention, were good in all properties. However, in Comparative Example 1 where the furnace carbon content was below the specified value, satisfactory conductivity could not be obtained.
Comparative Example 2 in which acetylene black was used alone had a large Mooney viscosity and poor extrusion processability. Further, in Comparative Examples 3 to 8, both or one of the characteristics of appearance due to coarse particles and conductivity due to significant volume resistance are insufficient.

[Effects of the Invention] As explained above, the present invention provides a conductive composition using special furnace black as a conductivity imparting agent, which has excellent extrusion processability, can prevent poor appearance due to coarse particles, Moreover, it becomes possible to form a conductive layer having excellent conductivity.

Claims (1)

[Claims] (1) Arithmetic mean particle diameter 25-40 mμ, iodine adsorption amount 40-60 mg/100 parts by weight of ethylene polymer
g, DBP oil absorption 11 (JISA method) 120-150ml
1. An electrically conductive composition for power cables, comprising 40 parts by weight or more of /100 g of furnace carbon black alone or in combination with acetylene black.