KR19980021663A - Semiconductive Resin Composition - Google Patents

Abstract

The present invention provides a semiconducting resin composition for a high-voltage power cable comprising a base resin of an ethylene-vinyl acetate copolymer, conductive carbon black, an antioxidant, and a crosslinking agent, wherein the bonded acrylonitrile content is 25 to 40 weight percent, 5-20% by weight of acrylonitrile butadiene rubber having a Mooney viscosity (M _{L1 + 4} , 100 ° C.) of 40 to 65 and satisfying the condition of having a volatile component of less than 1 percent. It provides a semiconductive resin composition for a high voltage power cable, which is made by adding a part.

The resin composition according to the present invention has excellent mechanical properties while maintaining an equivalent volume resistivity compared to the conventional composition, and is particularly excellent in the peeling property which is most important in the external semiconductive resin composition.

Description

Semiconductive Resin Composition

The present invention relates to a semiconductive resin composition, and more particularly to a semiconductive resin composition suitable for forming an outer semiconducting layer of an organic polymer power cable, for example, a high voltage power cable such as a crosslinked polyethylene insulated power cable. .

In general, insulated power cables are locally concentrated due to electrical stress, such as moisture coming from the outside during fabrication, ions inside, or protrusions present at the interface between the insulator and the outer sheath, causing breakdown of the insulator. As a result, the cable life will eventually be reduced.

Therefore, in order to prevent shortening of the lifespan of such cables, breakage of the insulator should be suppressed. In order to prevent the generation of moisture, protrusions, etc., which are one of the causes of insulation breakdown, when the cable is manufactured or when the cable is installed around the flow of water, the amount of moisture flowing into the insulation from the outside is suppressed. An external semiconducting layer is installed between the insulator and the outer cover to buffer the sieve interface.

Normally, the outer semiconducting layer should have proper conductivity, as well as the role of the inner semiconducting layer, to disperse the electrical stress, and also have to have adequate strippability because the outer sheath should be peeled off during the cable connection work.

Conventionally, the external semiconducting resin composition used for a high voltage power cable was manufactured by mix | blending these in fixed ratio using ethylene-vinyl acetate copolymer as a base resin, and electroconductive carbon black as an electroconductivity imparting agent.

However, the resin composition as described above is excellent in terms of mechanical properties and volume resistivity, but poor peeling properties, in order to improve this, a method of changing the composition of the base resin and increasing the carbon black content has been attempted. Such an attempt causes a problem in productivity due to a decrease in workability due to a decrease in mechanical properties and a rise in viscosity of the final product, and a problem in that the volume resistivity at high temperature is deteriorated.

MEANS TO SOLVE THE PROBLEM The present inventors researched in order to solve the said problem, and came to complete this invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide an external semiconducting resin composition for a high-voltage power cable that has proper peeling properties to facilitate cable peeling operation without increasing carbon black content and has excellent mechanical properties. .

In order to achieve the above object, in the present invention, first, acrylonitrile butadiene rubber is added to a base resin made of ethylene-vinyl acetate copolymer for the purpose of imparting proper peeling force to the outer semiconducting layer of a high-voltage power cable. Compared to the above, the peeling force can be easily controlled and the mechanical properties can be improved while maintaining the same volume resistivity.

That is, according to the present invention, in the semiconductive resin composition for a high-voltage power cable comprising a base resin made of ethylene-vinyl acetate copolymer, conductive carbon black, an antioxidant, and a crosslinking agent, the bonded acrylonitrile content is 25 to 40. Acrylonitrile butadiene rubber satisfying the conditions of weight percent, Mooney viscosity (M _{L1 + 4} , 100 ° C.) of 40 to 65 and a volatile component of less than 1 percent, based on 100 parts by weight of the base resin described above. Provided is a semiconductive resin composition comprising 5 to 20 parts by weight.

The conductive carbon black, antioxidant, and crosslinking agent which are the other components in the resin composition by this invention add each well-known thing in a well-known ratio.

Usually, 20-40 weight part of conductive carbon black is used with respect to 100 weight part of base resins of an ethylene-vinyl acetate copolymer, The mixing ratio of antioxidant and a crosslinking agent is not restrict | limited, An appropriate amount is added as needed. use.

The base resin used in the present invention is an ethylene-vinyl acetate copolymer having a melt index in the range of 1 to 30 g / 10 minutes, and a vinyl acetate content in the range of 20 to 40 weight percent.

On the other hand, as the acrylonitrile butadiene rubber added to the base resin to create a unique effect of the present invention is a combined acrylonitrile content of 25 to 40% by weight, Mooney viscosity (M _{L1 +4} , 100 ℃ ) Is 40 to 65, it is preferred to use a volatile component of less than 1 percent. It is preferable to add 5-20 weight part of such acrylonitrile butadiene rubber with respect to 100 weight part of said base resins. If the added amount of the acrylonitrile butadiene rubber is less than 5 parts by weight, the desired peeling force cannot be obtained. If the amount of the acrylonitrile butadiene rubber is less than 5 parts by weight, the peeling property is higher than the desired peeling force, and the cable is peeled off so easily that a problem occurs in the cable maintenance itself. .

In addition, as long as the carbon black used by this invention is produced with electroconductive carbon black, a well-known thing can be used as it is. In addition, the antioxidant and crosslinking agent used by this invention can use a well-known antioxidant and crosslinking agent as it is.

Examples of primary antioxidants include 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2 , 2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-nonylphenol), 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,6-di-tert-butyl-paracresol, tetra Bis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane and the like.

Examples of secondary antioxidants include di-lauryl sulfide, di-laurylthio-di-propionate, tetramethylthiuram di-sulfide and the like.

Per-butyl peroxide etc. are mentioned as a crosslinking agent.

Next, the Example of this invention is described. However, these examples are provided only to make the understanding of the present invention easier, and the present invention is not limited to these examples.

Example 1

Ethylene-vinyl acetate copolymer as the base resin (vinyl acetate content:

28%, melt index: 3.0) 6 kg; 900 g of acrylonitrile butadiene rubber that satisfies the condition that the bound acrylonitrile content is 33 weight percent, the Mooney viscosity (M _{L1 + 4} , 100 ° C.) is 54 and the volatile component is 0.8 percent; As carbon black, 3.9 kg of conductive carbon black (particle size; 30 nm); 60 g of 4,4'-thiobis (3-methyl-6-tert-butylphenol) as a primary antioxidant; 42 g of di-stearylthiodipropionate as a secondary antioxidant; And 90 g of per-butyl peroxide was added as a crosslinking agent to obtain a semiconductive resin composition, which was kneaded in a pressurized kneader, and then pelletized through an extruder.

Peel strength, breaking tensile strength, breaking elongation, and volume resistivity of the test pieces were measured and shown in Table 1 below.

Comparative Example 1

Except not adding acrylonitrile butadiene rubber was carried out under the same conditions as in Example 1 to obtain a semiconductive resin composition, which was kneaded in a pressurized kneader and then pelletized through an extruder. Peel strength, breaking tensile strength, breaking elongation, and volume resistivity of the test pieces were measured and shown in Table 1 below.

Comparative Example 2

A semiconductive resin composition was obtained under the same conditions as in Comparative Example 1 except that the carbon black content was increased to 4.8 kg, which was kneaded in a pressurized kneader and then pelletized through an extruder. Peel strength, breaking tensile strength, breaking elongation, and volume resistivity of the test pieces were measured and shown in Table 1 below.

Comparative Example 3

Except for using 6kg of ethylene-vinyl acetate copolymer (vinyl acetate content: 33%, melt index: 5.0) as the base resin, the reaction was carried out under the same conditions as in Comparative Example 2 to obtain a semiconductive resin composition, which was pressurized After kneading in the prepared pellet state through an extruder. Peel strength, breaking tensile strength, breaking elongation, and volume resistivity of the test pieces were measured and shown in Table 1 below.

Preparation of the test piece and measurement of peel strength were performed as follows. First, the main insulated XLPE sheet was made 2 mm thick using a press, and the semiconductive sheet was made 1 mm thick. At this time, the press conditions were 110 ° C., 200 kg / kPa, 15 minutes when producing the main insulation XLPE sheet, and 90 ° C., 200 kg / kPa, 10 minutes when producing the semiconducting sheet. Subsequently, a polyester transparent tape is sandwiched between the two sheets described above, and a sheet having a thickness of 3 mm is produced under a press condition of 180 ° C., 200 kg / ㎗, and 15 minutes. After cutting this sheet | seat into width 13mm, and the part containing the transparent tape was isolate | separated, the peeling test was done at the tensile speed of 50 mm / min by 90 degree angle. The peel test was performed until the strip separated 2 inches, and the maximum value up to this time was made peel strength.

The peel strength required as the external semiconducting resin composition for the high voltage power cable is preferably 4 kgf / cm or less.

Physical property evaluation result of semiconductive resin composition Sample item Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Base resin Ethylene-vinyl acetate copolymer (VA = 28%, MI = 3.0) 6.0 kg 6.0 kg of ethylene-vinyl acetate copolymer (VA = 28%, MI = 3.0) 6.0 kg of ethylene-vinyl acetate copolymer (VA = 28%, MI = 3.0) Ethylene-vinyl acetate copolymer (VA = 33%, MI = 5.0) 6.0 kg Acrylonitrile Butadiene Rubber 0.9kg ― ― ― Carbon black 3.9 kg 3.9 kg 4.8 kg 4.8 kg Peel Strength (kgf / cm) 1.5 9.1 1.6 1.5 Tensile Strength at Break (kg / ㎗) 201 172 164 161 Elongation at Break (%) 365 302 285 280 Volume resistivity (nA) 20 ℃ 2.40 × 10 ² 2.58 × 10 ² 1.9 × 10 ² 3.7 × 10 ² 90 ℃ 8.01 × 10 ² 8.14 × 10 ² 6.67 × 10 ² 1.21 × 10 ³

Note) Tensile strength at break is measured according to ASTM D638.

Elongation at break is measured according to ASTM D638.

The volume resistivity is measured at room temperature (20 ° C) and 90 ° C according to ASTM D2305.

Peel strength is measured according to Korea Electric Power Standard ESB 126-650 ~ 657.

VA in the table indicates vinyl acetate content; MI is the melt index.

As can be seen from the results of Table 1, the semiconductive resin composition prepared according to the present invention (Example 1) is equivalent to the conventional composition (Comparative Examples 1 to 3) that does not use acrylonitrile butadiene rubber. While maintaining the volume resistivity, the mechanical properties are excellent, and in particular, the most important peeling property is excellent in the external semiconductive resin composition for a high voltage power cable.

Claims (3)

A semiconducting resin composition for a high voltage power cable comprising a base resin of ethylene-vinyl acetate copolymer, conductive carbon black, an antioxidant, and a crosslinking agent, wherein the bonded acrylonitrile content is 25 to 40 weight percent, and the Mooney viscosity ( Mooney viscosity, M _{L1 + 4} , 100 ° C.) is 40 to 65, and 5 to 20 parts by weight of acrylonitrile butadiene rubber satisfying the condition that the volatile component is less than 1 percent is added based on 100 parts by weight of the base resin. Semiconducting resin composition, characterized in that made. The method of claim 1, The ethylene-vinyl acetate copolymer is a semiconductive resin composition, characterized in that the melt index is in the range of 1 to 30g / 10 minutes, the content of vinyl acetate is in the range of 20 to 40% by weight. The method according to any one of claims 1 to 2, Semiconductive resin composition, characterized in that the base resin is used in an amount of 40 to 70% by weight relative to the total composition.