JP2002179854A - Resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition useful as a semiconductive layer of a crosslinked polyethylene power cable, having high material strength and excellent peelability of a crosslinked polyethylene. SOLUTION: This resin composition is obtained by compound 60-95 pts.wt. of an ethylene/unsaturated ester copolymer (A) having 10-50 wt.% unsaturated ester content with 40-5 pts.wt. of an saturated styrene-based thermoplastic elastomer (B) having 10-50 wt.% styrene content and 10-100 pts.wt. based on 100 pts.wt. of the total of the components (A) and (B) of electroconductive carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition useful as a power cable semiconductive layer. More specifically, the present invention relates to a resin composition having excellent strength and excellent releasability from a crosslinked polyethylene insulating layer when used as a material for forming a semiconductive layer of a crosslinked polyethylene insulated power cable.

[0002]

2. Description of the Related Art A power cable is constituted by covering an outer periphery of a conductor with an insulating layer sandwiched between inner and outer semiconductive layers, and further covering a shielding layer and a sheath in that order. Polyethylene with excellent electrical properties, especially cross-linked polyethylene, is widely used as an insulating layer from power distribution to ultra-high voltage for power transmission, and a semiconductive layer is generally made of ethylene-vinyl acetate copolymer or Ethylene / unsaturated ester copolymer such as ethylene / ethyl acrylate copolymer mixed with conductive carbon black has a volume resistivity of 10 ⁵ Ω
A semiconductive resin composition of about cm or less is used. The inner semiconductive layer has a function of preventing a partial discharge occurring between the conductor and the insulating layer, and the outer semiconductive layer has a function of preventing a partial discharge generated between the insulating layer and the shielding layer, and relaxing the electric field. .

The semiconductive layer needs to be in close contact with the insulating layer so as not to cause interface delamination when the cable is deformed by an external force. For ease, it must be easy to peel off the polyethylene insulation layer. In this peeling work at the construction site, a cut is made in the semiconductive layer using a special jig, and peeling is performed along the cut.It is important that the peeling is easy and that the material is not cut during the work. It is. However, when the above-described composition of the ethylene / unsaturated ester copolymer which has been conventionally used as the semiconductive layer is used, especially when accompanied by a general crosslinking treatment such as chemical crosslinking or silane crosslinking, the insulating layer is used. However, it could not be said that the film had sufficient performance such as poor peelability of the film and breakage of the semiconductive layer at the time of peeling. For this reason, an improved prescription by adding a special additive has been proposed, but the material cost and processing cost are extremely high, and there is a problem in practical use.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present inventors have
Processability, flexibility, low-temperature properties, moderate adhesion to polyethylene, etc., without substantially impairing the properties required of the semiconductive layer, even when chemically cross-linked or silane cross-linked, the polyethylene insulating layer The study was conducted to obtain an inexpensive resin composition having excellent peelability and material strength. as a result,
It has been found that the object can be achieved by blending an appropriate amount of a specific saturated styrene-based thermoplastic elastomer with the above-mentioned composition of an ethylene / unsaturated ester copolymer conventionally used.

Accordingly, an object of the present invention is to provide a resin composition based on an ethylene / unsaturated ester copolymer which is suitable for a semiconductive layer of a power cable made of polyethylene, particularly a crosslinked polyethylene power cable.

[0006]

According to the present invention, 60 to 95 parts by weight of an ethylene / unsaturated ester copolymer (A) having an unsaturated ester content of 10 to 50% by weight and a styrene content of 10 to 50% by weight. % By weight of a resin composition comprising 40 to 5 parts by weight of a saturated styrene-based thermoplastic elastomer (B) and preferably 100 parts by weight of (A) and (B)
Further, there is provided a resin composition for a power cable semiconductive layer, further comprising 10 to 100 parts by weight of conductive carbon black.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ethylene / unsaturated ester copolymer (A) used in the present invention has an unsaturated ester content of 10 to 50% by weight, preferably 16 to 46% by weight. That is, by using a copolymer containing an appropriate amount of unsaturated ester as a copolymer component, a large amount of conductive carbon black can be compounded with good dispersibility, and the peelability with the crosslinked polyethylene layer is good. It can be. If the unsaturated ester content is less than the above range, the dispersibility and releasability of the carbon black are not sufficient, and if the content is more than the above range, the material strength, heat resistance Etc. are not enough. In consideration of the miscibility of the saturated styrene-based elastomer, processability, and the strength of the semiconductive layer, the copolymer has a melt flow rate at 190 ° C. and a load of 2160 g of 0.1 to 50 g / 10 min. 5-4
It is preferable to use one having 0 g / 10 minutes.

[0008] Ethylene / unsaturated ester copolymer (A)
Examples of the unsaturated ester include vinyl esters such as vinyl acetate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate,
Examples thereof include unsaturated carboxylic esters such as isobutyl acrylate, n-butyl acrylate, and methyl methacrylate. Particularly preferred unsaturated esters are vinyl acetate and ethyl acrylate. Such a copolymer can be obtained by radical copolymerization under high temperature and high pressure.

The saturated styrene-based thermoplastic elastomer (B) used in the present invention includes, for example, the releasability from a polyethylene insulating layer and the strength of the semiconductive layer when the resin composition of the present invention is used as a semiconductive layer. In consideration of the above, those having a styrene content of 10 to 50% by weight, preferably 15 to 40% by weight are used. If the styrene content is more than the above range, neither the peelability from the polyethylene insulating layer nor the strength of the semiconductive layer will be satisfactory. In consideration of miscibility with the copolymer (A), processability, and strength of the semiconductive layer, the thermoplastic elastomer (B) has a melt flow rate of 0.1 to 20 g / 230 ° C. and a load of 2160 g. 10 minutes, especially 0.
It is preferable to use one for 2 to 10 g / 10 minutes.

A typical example of the thermoplastic elastomer (B) is
A styrene / (ethylene / butene) / styrene triblock copolymer obtained by hydrogenating the diene polymer part of styrene / butadiene / styrene triblock copolymer (SBS) or styrene / isoprene / styrene triblock copolymer (SIS) Polymer (SEBS) or styrene- (ethylene-propylene) -styrene triblock copolymer (SEPS), which can be easily obtained on the market. As these triblock copolymers, modified products having a functional group may be used.

[0011] Ethylene / unsaturated ester copolymer (A)
The mixing ratio of the styrene-based thermoplastic elastomer (B) and the saturated styrene-based thermoplastic elastomer (B) vary depending on the respective polymerization compositions.
(B) is 40 to 5 parts by weight, and preferably 30 to 10 parts by weight, relative to 70 to 90 parts by weight.
If the blending ratio of the thermoplastic elastomer (B) is too small, the releasability from the polyethylene insulating layer when used as a semiconductive layer is poor, and if the blending amount is too large, the dispersibility of carbon black becomes poor. Not preferred.

When the resin composition comprising (A) and (B) is used as a semiconductive layer, conductive carbon black is blended. As conductive carbon black,
Conventionally used materials can be used for the semiconductive layer for power cables, and examples thereof include well-known carbon black such as Ketjen black, acetylene black, and furnace black. The appropriate amount of the conductive carbon black varies depending on the type thereof, but is determined in consideration of the conductivity required for the semiconductive layer. Generally,
It is blended so that the volume resistivity at room temperature is 10 ⁵ Ω · cm or less, preferably 10 ³ Ω · cm or less.
For example, 10 to 100 parts by weight based on the total 100 parts by weight of (B)
It is in the range of about parts by weight. If the amount is too small, the volume resistivity becomes too high, and if the amount is too large, the tensile strength, elongation, processability, flexibility and the like of the resin composition deteriorate, which is not desirable.

The resin composition of the present invention may contain a crosslinking agent, a crosslinking aid, a silane coupling agent, a silanol condensation catalyst, an antioxidant, a light stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, Various additives such as a property improving agent, a filler, a dispersant, a copper damage inhibitor, and a colorant can be added.

As the crosslinking agent, dicumyl peroxide, butylcumyl peroxide, 2,5-dimethyl-
2,5-bis (t-butylperoxy) hexane, 2,
5-dimethyl-2,5-bis (t-butylperoxy)
Organic peroxides such as hexyne-3, 1,3-bis (t-butylperoxyisopropyl) benzene and the like can be used. Examples of the crosslinking aid include triallyl cyanurate, triallyl cyanurate, N, N'-m-
Phenylene bismaleimide, p, p'-dibenzoylquinone dioxime, p-quinone dioxime and the like can be used. Such a cross-linking agent and / or a cross-linking auxiliary agent is, for example, 0.05 to 3 per 100 parts by weight of (A) and (B).
It is blended in an amount of about parts by weight.

The silane coupling agent is preferably a trialkoxysilane having a carbon-carbon double bond or an epoxy group, and specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxymethylsilane, vinyltris (β- Methoxyethoxysilane), γ-methacryloxypropyltrimethoxysilane, and the like.

As antioxidants, 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis (4-
Methyl-6-t-butylphenol), 4,4′-methylenebis (2,6-di-t-butylphenol),
4'-butylidenebis (6-t-butyl-m-cresol), 1,3,5-tris (3,5-di-t-butyl-
4-hydroxybenzyl) -2,4,6-trimethylbenzene, tetrakis [methylene-3- (3,5-di-t)
-Butyl-4-hydroxyphenyl) propionate]
Methane, n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4,
4'-thiobis (6-t-butyl-m-cresol) and the like can be mentioned.

Compounds such as benzophenone and benzoin are used as ultraviolet absorbers, higher fatty acids and higher fatty acid salts are used as lubricants, higher fatty acid amides are used as processability improvers, silica and clay are used as fillers.
Examples of the copper damage inhibitor include amide compounds and hydrazide compounds.

To prepare the resin composition of the present invention, the copolymer (A), the thermoplastic elastomer (B), the conductive carbon black, and other additives which are added as required are
It can be performed simultaneously or sequentially using a batch-type kneader such as a mixing roll, a Banbury mixer, a Brabender plastograph, a pressure kneader, or a single-screw or twin-screw extruder.

The resin composition according to the present invention can be used as an inner and / or outer semiconductive layer of various power cables. In this case, for example, on the center conductor, or as co-extrusion with the insulating layer resin composition as an internal semiconductive layer,
Alternatively, it can be coated on the center conductor by co-extruding three layers as an internal (external) semiconductive layer together with the resin composition for the external (internal) semiconductive layer and the resin composition for the insulating layer.

[0020]

The present invention will be described in more detail with reference to the following examples. The raw materials used in the examples and comparative examples and methods for evaluating the physical properties of the obtained resin compositions are as follows.

1. Raw materials (1) Ethylene / unsaturated ester copolymer (A) EVA-1: vinyl acetate content 33% by weight, melt flow rate (MFR) (190 ° C, 2160g load) 30
g / 10 minutes ethylene-vinyl acetate copolymer EVA-2: vinyl acetate content 33% by weight, MFR (1
90 ° C, 2160g load) 1g / 10min ethylene / vinyl acetate copolymer

(2) Saturated styrene-based thermoplastic elastomer (B) EL-1: Styrene content 29% by weight, MFR (230
Styrene / (ethylene / butene) / styrene triblock copolymer at 1 g / 10 min at 2 ° C., 2160 g load EL-2: styrene content 80% by weight, MFR (230
Styrene / (ethylene / propylene) / styrene triblock copolymer 1g / 10min.

(3) Other additives: carbon black (trade name: Furnace Carbon BP)
3200 (Cabot Specialty Chemicals
・ DCP: Dicumyl peroxide (trade name: Mitsui DCP)
(Manufactured by Mitsui Chemicals, Inc.) VTMOS: vinyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Antioxidant-1: trade name Irganox 1010 (manufactured by Ciba Specialty Chemicals) Antioxidant-2: trade name Yoshinox SR (4) Substrate ・ LLDPE: density 920 kg / m ³ , MFR (190
Linear low density polyethylene 2g / 10min.

2. Physical property evaluation method (1) Peeling test: LLDPE using a press molding machine and Table 1
After preparing a 1 mm-thick sheet of the resin composition having the composition shown in Table 1, the respective sheets were overlapped, and an adhesive sheet was formed to a thickness of 5 mm using a 1-mm sheet spacer (press condition: 180 ° C. × 3). Min + 20 ° C x 5
Minutes). After half of the adhesive sheet was peeled off, a 180 ° peeling test (sheet width 25 mm, n = 5) was carried out, and judged according to the following criteria. Average adhesive strength State of resin composition at the time of peeling 以上: 1 kg or more and 10 kg or less Complete peeling ×: 1 kg or more and 10 kg or less Partial peeling XX

(2) Strength: Peeling Test The test sample was observed and visually judged according to the following criteria. ：: No breakage of the composition was observed in the peeling test (substantially no elongation of the peeling test piece) ：: No breakage of the composition was observed in the peeling test ×: Composition in the peeling test Items that have been cut off

Example 1 An ethylene / vinyl acetate copolymer, a saturated styrene-based thermoplastic elastomer and other additives were blended in the proportions shown in Table 1, heated and kneaded at a resin temperature of 180 ° C. with a 500 ml mixer, and then rolled. A dispensing sheet was created with a processing machine. A sample for peeling evaluation was prepared by the method described above and evaluated. Table 1 shows the results. As is clear from the results in Table 1, the resin composition of Example 1 has high releasability and strength as a material, and is expected to be used as an actual cable material.

Example 2 As shown in Table 1, the resin composition used in Example 1 was mixed with conductive carbon black, and further subjected to silane crosslinking at a resin temperature of 180 ° C., as in Example 1. Was evaluated. Table 1 shows the results. In general, the chemical cross-linking method used for CV cables and the like is inferior in workability because processing must be performed at a low temperature, but in this mode, operation and processing at a high temperature can be expected to reduce costs. . Further, as is clear from Table 1, even in the case of silane cross-linking, which has conventionally been considered difficult to exhibit releasability, good releasability is obtained without using high VA type EVA having excellent releasability of 1 to 10 kg /. It was confirmed that the adhesive strength was within the range of 25 mm width. High VA
When a type of EVA is used, there are often problems such as poor processing at high temperature, stickiness of molded products, poor electrical characteristics, and the like, but the present composition has an advantage that there is no such problem.

Example 3 A sample having a higher molecular weight than that used in Example 1 was used as an ethylene / vinyl acetate copolymer, and a sample was prepared and evaluated in the same manner as in Example 2. Table 1 shows the results. By using a polymer type ethylene / vinyl acetate copolymer, the strength is improved while maintaining good releasability, and it is expected to meet higher required characteristics.

Comparative Example 1 A sample was prepared and evaluated in the same manner as in Example 1 without blending a styrene-based thermoplastic elastomer. Table 1 shows the results. If the ethylene / vinyl acetate copolymer alone is used as the resin component, sufficient releasability and substrate strength cannot be obtained.

Comparative Example 2 A sample was prepared and evaluated in the same manner as in Example 2 without blending a styrene-based thermoplastic elastomer. Table 1 shows the results. If the ethylene / vinyl acetate copolymer alone is used as the resin component, sufficient releasability and substrate strength cannot be obtained.

Comparative Example 3 A sample was prepared and evaluated in the same manner as in Example 1 using a styrene-based thermoplastic elastomer having a high styrene content. Table 1 shows the results.
If the styrene content of the thermoplastic elastomer is too large, good releasability and composition strength cannot be obtained.

[0032]

[Table 1]

[0033]

Industrial Applicability The resin composition of the present invention is excellent in processability, flexibility, low-temperature properties, moderate adhesion to polyethylene, and excellent in peelability from polyethylene and substrate strength. It is suitable as a semiconductive layer material for cables, especially crosslinked polyethylene power cables.
Even when chemical crosslinking or silane crosslinking is involved, it can be used as an inexpensive high-performance cable material because of good releasability from crosslinked polyethylene and good substrate strength. Such a crosslinked polyethylene power cable using the resin composition of the present invention as a semiconductive layer can be used for medium / low voltage or for high voltage.

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Claims (7)

[Claims] An unsaturated ester content of 10 to 50% by weight.
Ethylene / unsaturated ester copolymer (A) 60-95
A resin composition comprising 40 parts by weight of a saturated styrene-based thermoplastic elastomer (B) having a styrene content of 10 to 50% by weight and a styrene content of 10 to 50% by weight. 2. The resin composition according to claim 1, wherein the saturated styrene-based thermoplastic elastomer (B) is a styrene / (ethylene / butene) / styrene triblock copolymer. 3. The resin composition according to claim 1, wherein the saturated styrene-based thermoplastic elastomer (B) has a melt flow rate at 230 ° C. under a load of 2160 g of 0.1 to 20 g / 10 minutes. 4. The resin composition according to claim 1, wherein 10 to 100 parts by weight of conductive carbon black is blended with respect to 100 parts by weight of the total amount of (A) and (B). 5. The resin composition according to claim 1, which is subjected to a crosslinking treatment. 6. The resin composition according to claim 1, which is used for a power cable semiconductive layer. 7. A power cable having a semiconductive layer formed from the resin composition according to claim 6.