JP6445485B2 - Semiconductive resin composition and power cable using the same - Google Patents

Description

  The present invention relates to a semiconductive resin composition and a power cable using the same.

High voltage power cables are electrically insulated from the outside by covering the surface of the conductor with an insulating layer, and this insulating layer is also provided with a semiconductive layer on the surface to smooth the surface potential and prevent discharge. Like to do. For this reason, it is preferable that the semiconductive layer has a lower volume resistivity. In general, carbon is blended in the semiconductive layer, and this carbon causes the semiconductive layer to exhibit conductivity by forming a chain. Therefore, a large amount of carbon is blended in the semiconductive layer to chain a large number of carbons, and as a result, a sufficiently low resistance has been realized in the semiconductive layer. In this specification, “semiconductive” means that the volume resistivity is in the range of 1 × 10 ⁰ to 1 × 10 ⁴ [Ω · cm].

  As a resin composition used for such a semiconductive layer, for example, a semiconductive resin composition described in Patent Document 1 below is known. In Patent Document 1 below, 40 conductive carbon blacks are added to 100 parts by mass of an olefin polymer containing 30 to 80% by mass of an ethylene / α-olefin / non-conjugated polyene copolymer such as an ethylene vinyl acetate copolymer. A semiconductive resin composition is disclosed that is blended at a ratio of ˜90 parts by mass and crosslinked with an olefin polymer.

JP2011-46891A (Claim 1 and paragraph 0046)

  However, the semiconductive resin composition described in Patent Document 1 has the following problems.

  That is, although the semiconductive resin composition described in Patent Document 1 has a sufficiently low resistance, it has room for improvement in terms of heat aging resistance.

  For this reason, a semiconductive resin composition having a sufficiently low resistance and excellent heat aging resistance has been demanded.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductive resin composition having sufficiently low resistance and excellent heat aging resistance, and a power cable using the same. To do.

  The present inventor has intensively studied to solve the above problems. As a result, the present inventor, in a semiconductive resin composition containing a base resin and carbon, comprises the base resin only with an ethylene vinyl acetate copolymer, and specifies the compounding amount of carbon with respect to 100 parts by mass of the base resin. It was found that the above-mentioned problems can be solved by setting the range and the gel fraction of the base resin to a specific value or more.

That is, the present invention is a semiconductive resin composition comprising a base resin composed only of an ethylene vinyl acetate copolymer and carbon, wherein the carbon is in a proportion of 35 parts by mass or more with respect to 100 parts by mass of the base resin. And a vinyl acetate content in the ethylene vinyl acetate copolymer is 20 to 33% by mass, and the gel fraction of the base resin is 17 to 52% .

  According to the semiconductive resin composition of the present invention, it is possible to have sufficiently low resistance and excellent heat aging resistance.

  The semiconductive resin composition further includes an anti-aging agent, the carbon is blended at a ratio of 55 parts by mass or more with respect to 100 parts by mass of the base resin, and the anti-aging agent is based on 100 parts by mass of the base resin. Is preferably blended at a ratio of 1.5 parts by mass or less.

  In this case, the resistance of the semiconductive resin composition can be more sufficiently lowered.

  In the said semiconductive resin composition, the said carbon is mix | blended in the ratio of 65 mass parts or less with respect to 100 mass parts of said base resins, and the said anti-aging agent is comprised with a hindered phenol type anti-aging agent. Is preferred.

  In this case, the flexibility of the semiconductive resin composition can be further improved while sufficiently reducing the resistance of the semiconductive resin composition.

  In the semiconductive resin composition, the carbon is preferably composed of furnace black.

  In this case, when a semiconductive resin composition is used as a semiconductive layer in a power cable having a conductor, an insulating layer provided so as to surround the conductor, and a semiconductive layer provided so as to surround the insulating layer In addition, it is possible to easily peel the semiconductive layer from the insulating layer when the power cable is centered compared to the case where the carbon is made of carbon other than furnace black.

  The present invention further includes a conductor, an insulating layer provided so as to surround the conductor, and a semiconductive layer provided so as to surround the insulating layer, wherein the semiconductive layer is the semiconductive resin composition. It is a power cable composed of objects.

  According to this power cable, since the semiconductive layer is composed of a semiconductive resin composition having a sufficiently low resistance, the surface potential of the semiconductive layer is made uniform, and the discharge of the power cable is suppressed. Is possible.

  According to the present invention, a semiconductive resin composition having sufficiently low resistance and excellent heat aging resistance and a power cable using the same are provided.

It is a partial side view which shows one Embodiment of the power cable of this invention. It is sectional drawing along the II-II line of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

[Power cable]
FIG. 1 is a partial side view showing an embodiment of a power cable according to the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. As shown in FIGS. 1 and 2, the power cable 10 includes a conductor 1, an insulating layer 2 provided so as to surround the conductor 1, and a semiconductive layer 3 provided so as to surround the insulating layer 2. ing.

  Here, the semiconductive layer 3 is comprised with the semiconductive resin composition, This semiconductive resin composition contains the base resin which consists only of an ethylene vinyl acetate copolymer, and carbon. In the semiconductive resin composition, carbon is blended at a ratio of 35 parts by mass or more with respect to 100 parts by mass of the base resin, and the gel fraction of the base resin is 17% or more.

  The semiconductive resin composition can have sufficiently low resistance and excellent heat aging resistance. For this reason, according to the power cable 10, since the semiconductive layer 3 is composed of a semiconductive resin composition having a sufficiently low resistance, the potential of the surface of the semiconductive layer 3 is made uniform, and the power cable 10 It becomes possible to suppress the discharge.

  Hereinafter, the semiconductive resin composition constituting the semiconductive layer 3 will be described in detail.

<Base resin>
As described above, the base resin is composed only of an ethylene vinyl acetate copolymer (hereinafter simply referred to as “EVA”). In this case, it is easier for the base resin to contain a large amount of carbon, and the heat aging resistance is more semiconductive than the case where the base resin is composed of a mixed resin of EVA and other resins than EVA. It can be given to the resin composition.

  In the base resin, at least a part of EVA is crosslinked. That is, in the base resin, all of EVA may be crosslinked, or only a part of EVA may be crosslinked. In the base resin, when only a part of EVA is crosslinked, the base resin contains uncrosslinked EVA. In addition, the crosslinked body obtained by crosslinking EVA is composed of a bonded body in which EVAs are directly bonded to each other.

  EVA is a copolymer of ethylene and vinyl acetate. The vinyl acetate content in EVA is not particularly limited, but is preferably 20 to 46% by mass. In this case, compared with the case where the vinyl acetate content is less than 20% by mass, carbon and EVA can be easily mixed, and the semiconductive layer 3 can be easily peeled from the insulating layer 2 in the power cable 10. The power cable 10 can be easily disassembled. On the other hand, when the vinyl acetate content is 20 to 46% by mass, compared to the case where the vinyl acetate content exceeds 46% by mass, when the raw material kneaded material containing only the EVA and the raw material resin is pelletized. , It becomes difficult for each other to block (aggregate). Therefore, the handling property of pellets is excellent in the process of extruding the semiconductive layer 3 of the power cable 10.

  Further, the gel fraction of the base resin is 17% or more. In this case, compared to the case where the gel fraction of the base resin is less than 17%, the semiconductive resin composition can have a sufficiently lower resistance. However, the gel fraction of the base resin is preferably 92% or less. In this case, the elongation percentage of the semiconductive resin composition is higher than when the gel fraction of the base resin exceeds 92%.

Moreover, it is preferable that the gel fraction Y (%) of the base resin satisfies the following formula (1) with respect to the compounding amount X (part by mass) of carbon with respect to 100 parts by mass of the base resin.

Y ≧ 43926X ^−2.391 (1)

  In this case, the semiconductive resin composition can have a sufficiently lower resistance as compared with the semiconductive resin composition in which the gel fraction of the base resin does not satisfy the above formula (1).

<Carbon>
The carbon is not particularly limited as long as it has conductivity, and examples of carbon include acetylene black, furnace black, thermal black, and ketjen black. Among these, furnace black is preferable as the carbon. In this case, the semiconductive layer 3 can be easily removed from the insulating layer 2 when the power cable 10 is centered as compared with the case where the carbon is formed of carbon other than furnace black in the semiconductive layer 3 of the power cable 10. It becomes possible to peel.

  As described above, carbon is blended at a ratio of 35 parts by mass or more with respect to 100 parts by mass of the base resin. In this case, the resistance of the semiconductive resin composition can be more sufficiently reduced as compared with the case where the blending ratio of carbon with respect to 100 parts by mass of the base resin is less than 35 parts by mass.

  The blending ratio of carbon with respect to 100 parts by mass of the base resin is preferably 55 parts by mass or more. In this case, the resistance of the semiconductive resin composition can be further reduced as compared with the case where the mixing ratio of carbon to 100 parts by mass of the base resin is less than 55 parts by mass. However, the blending ratio of carbon with respect to 100 parts by mass of the base resin is preferably 65 parts by mass or less. In this case, there is a tendency that the flexibility of the semiconductive resin composition can be further improved as compared with the case where the blending ratio of carbon with respect to 100 parts by mass of the base resin exceeds 65 parts by mass.

  The average particle diameter of carbon is not particularly limited, but is preferably 1 to 30 nm. In this case, the resistance of the semiconductive resin composition can be reduced more sufficiently than when carbon having an average particle size outside the above range is blended with 100 parts by mass of the base resin.

  The semiconductive resin composition may further contain an anti-aging agent.

  The anti-aging agent is preferably blended at a ratio of 2 parts by mass or less with respect to 100 parts by mass of the base resin. In this case, the degree of crosslinking of the semiconductive resin composition can be improved and resistance can be more sufficiently compared with the case where the anti-aging agent is blended at a ratio exceeding 2 parts by mass with respect to 100 parts by mass of the base resin. Can be lowered.

  When the carbon is blended in a proportion of 55 parts by mass or more with respect to 100 parts by mass of the base resin, the antioxidant is blended in a proportion of 1.5 parts by mass or less with respect to 100 parts by mass of the base resin. Is more preferable. In this case, the resistance of the semiconductive resin composition can be more sufficiently lowered. However, the anti-aging agent is preferably blended at a ratio of 0.1 parts by mass or more with respect to 100 parts by mass of the base resin. In this case, the heat aging characteristics of the semiconductive resin composition can be further improved as compared with the case where the anti-aging agent is blended at a ratio of less than 0.1 parts by mass with respect to 100 parts by mass of the base resin.

  The anti-aging agent is not particularly limited, and examples thereof include hindered phenol anti-aging agents, res-hindered phenol anti-aging agents, and semi-hindered phenol anti-aging agents.

  As the hindered phenol-based antioxidant, for example, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2′-thiodiethylbis [3 (3,5 -Di-tert-butyl-4-hydroxyphenyl) propionate] and the like.

  Examples of the hindered phenol anti-aging agent include 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, and the like.

  Examples of the semi-hindered phenol-based antiaging agent include 2,2'-methylene-bis (4-methyl-6-tert-butylphenol).

  Especially, when carbon is mix | blended in the ratio of 65 mass parts or less with respect to 100 mass parts of base resin, it is preferable that an anti-aging agent is comprised with a hindered phenol type anti-aging agent. In this case, compared with the case where the anti-aging agent is composed of an anti-aging agent other than the hindered phenolic anti-aging agent, the resistance of the semi-conductive resin composition is sufficiently reduced while the resistance of the semi-conductive resin composition is sufficiently reduced. Flexibility can be further improved.

  The above-mentioned semiconductive resin composition is an inorganic filler, processing aid, cross-linking aid, flame retardant, ultraviolet absorber, softener, plasticizer, lubricant as necessary, as long as the effects of the present invention are not impaired. Such additives may be further included as necessary.

[Power cable manufacturing method]
Next, a method for manufacturing the power cable 10 described above will be described.

<Conductor>
First, the conductor 1 is prepared. The conductor 1 may be configured by only one strand, or may be configured by bundling a plurality of strands. Moreover, the conductor 1 is not specifically limited about a conductor diameter, the material of a conductor, etc., It can determine suitably according to a use.

<Insulating layer>
Next, the insulating layer 2 is formed so as to surround the conductor 1. The insulator used for the insulating layer 2 is not particularly limited, but as such an insulator, for example, an insulating resin composition containing a polyolefin resin can be used.

<Semiconductive layer>
Next, the semiconductive layer 3 is formed so as to surround the insulating layer 2. The semiconductive layer 3 is obtained by, for example, kneading a raw material resin made only of EVA and a raw material containing carbon, extruding a tube-shaped kneaded material and continuously covering the insulating layer 2, and then crosslinking the raw material resin. Can be formed. At this time, the crosslinking is performed so that the gel fraction of the base resin obtained by crosslinking the raw resin becomes 17% or more.

  The kneading can be performed by a kneading machine such as a Banbury mixer, a tumbler, a pressure kneader, a kneading extruder, a twin screw extruder, or a mixing roll. In addition, as a crosslinking method, a crosslinking agent is added to the raw material and the kneaded product is heated after extrusion to crosslink the raw material resin, or a crosslinking agent is not added to the raw material and the kneaded product is extruded after extrusion. An electron beam crosslinking method or the like in which a raw material resin is crosslinked by irradiating an electron beam can be used. Of these, the chemical crosslinking method is preferably used as the crosslinking method.

  In the production method of the semiconductive resin composition, when a chemical crosslinking method is used as a crosslinking method, the crosslinking agent included in the raw material is not particularly limited as long as the raw material resin can be crosslinked. Are, for example, dicumyl peroxide and di-tert-butyl peroxide.

  Moreover, the crosslinking conditions in the case of using a chemical crosslinking method should just be the conditions from which the gel fraction of the raw material resin in the said semiconductive resin composition will be 17% or more. Specifically, the crosslinking may be performed under the crosslinking conditions of 140 to 200 ° C. and 5 to 160 minutes.

  When manufacturing the said semiconductive resin composition, it is preferable that the compounding quantity of the carbon with respect to 100 mass parts of raw material resin shall be 70 mass parts or less in a semiconductive resin composition. In this case, the Mooney viscosity of the raw material is reduced, the workability of the raw material is further improved, and the semiconductive resin composition can be easily produced.

  The power cable 10 is obtained as described above.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the semiconductive layer 3 is formed by continuously covering the insulating kneaded material with the tube-shaped kneaded material and then cross-linking the raw material resin in the kneaded material. The semiconductive layer 3 may be formed by winding the semiconductive resin composition thus wound around the insulating layer 2.

  In the said embodiment, although the semiconductive resin composition is applied to the semiconductive layer of an electric power cable, the use of the semiconductive resin composition of this invention is not limited to the semiconductive layer of an electric power cable. Absent. For example, the semiconductive resin composition of the present invention can also be used for applications such as antistatic plastic products.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Examples 1-10 and Comparative Examples 1-4)
The raw material resin is melted with an oil roll heated to 100 ° C. (product name “Oil Roll 152Φ × 390L”, manufactured by Otake Machinery Co., Ltd.), and carbon, an antioxidant and a crosslinking aid are added to 100 parts by mass of the raw material resin. After blending in the blending amounts shown in Tables 1 to 3 (units are parts by mass) and sufficiently kneading, the temperature is lowered to about 90 ° C., and the crosslinking agents are listed in Tables 1 to 3 (units are parts by mass) The raw material was obtained by blending. The raw materials were kneaded to obtain a kneaded product.

  Specifically, the following materials were used as the raw material resin, carbon, anti-aging agent, crosslinking aid and crosslinking agent.

(1) Raw material resin EVA1: Trade name “Evaflex EV150”, manufactured by Mitsui DuPont Polychemical Co., Ltd., vinyl acetate content: 33%
EVA2: Trade name “Evaflex V523”, manufactured by Mitsui DuPont Polychemical Co., Ltd., vinyl acetate content: 33%
Nitrile Butadiene Rubber (NBR): Trade name “Nipol DN219”, manufactured by Nippon Zeon

(2) Carbon furnace black, trade name “Toka Black # 5500”, manufactured by Tokai Carbon Co., Ltd., average particle size: 25 nm

(3) Anti-aging agent Anti-aging agent 1: Resin hindered phenol-based anti-aging agent, trade name “NOCRACK 300”, Anti-aging agent manufactured by Ouchi Shinsei Chemical Co., Ltd. 2: Hindered phenol-based anti-aging agent, trade name “ Irganox 1010 ", manufactured by BASF

(4) Crosslinking aid TAIC (triallyl isocyanurate), trade name “Tyke”, manufactured by Nippon Kasei Co., Ltd.

(5) Crosslinker DCP (dicumyl peroxide), trade name “Perkadox BC-FF”, manufactured by Kayaku Akzo

  Subsequently, the kneaded material is heated while being pressurized at 160 ° C. for 40 minutes using an electric heat press (product name “VS-216”, manufactured by Koto Kogyo Co., Ltd.) to crosslink the raw resin, A sheet made of a 1 mm semiconductive resin composition was obtained.

  About the sheet | seat of the semiconductive resin composition obtained as mentioned above, the gel fraction was measured based on JISC3005 4.25. The results are shown in Tables 1-3.

[Characteristic evaluation]
About the sheet | seat of the semiconductive resin composition of Examples 1-10 obtained as mentioned above and Comparative Examples 1-4, resistance, heat aging resistance, mechanical characteristics, and evaluation of a softness | flexibility are performed as follows. went. Moreover, about the kneaded material of Examples 1-10 and Comparative Examples 1-4, workability was evaluated as follows.

<Resistance>
Resistance was evaluated based on volume resistivity. The volume resistivity was measured as follows. That is, the sheets of the semiconductive resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4 obtained as described above were cut into a size of 20 mm × 80 mm, and the width of the sheet was 5 mm at each end with a conductive paint. The volume resistivity was measured using a portable Wheatstone bridge (product name: “275597”, manufactured by Yokogawa Electric Corporation) in a thermostatic chamber formed with electrodes and set at 90 ° C. The results are shown in Tables 1-3. The acceptance criteria for volume resistivity were as follows.

(Acceptance criteria) Volume resistivity at 90 ° C is 300 Ω · cm or less

Here, “300 Ω · cm” is a volume resistance indicating that when the semiconductive layer of the power cable is formed by the semiconductive resin composition and this value is exceeded, the risk of discharge increases at a voltage of 6.6 kV. Rate value.

<Heat aging resistance>
Evaluation of heat aging resistance was performed based on the residual elongation rate after heat aging. The elongation percentage after heat aging was measured as follows. That is, the sheets of the semiconductive resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4 obtained as described above were punched with a JIS No. 3 super dumbbell (manufactured by Dumbbell) to produce a JIS No. 3 dumbbell test piece. did. The dumbbell test piece was subjected to a tensile test using a tensile tester (product name “STOROGRAPH-R1”, manufactured by Toyo Seiki Seisakusho), and the elongation before heat aging was measured. In addition, a tensile tester (product name “STOROGRAPH-R1”, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was also used in which the dumbbell specimen was stored in an oven set at 140 ° C. (product name “GEEROVEN”, manufactured by TOYOSEIKI) for 7 days. A tensile test was carried out using, and the elongation after heat aging was measured. Based on the following formula, the residual elongation rate was calculated from the elongation rate before heat aging and the elongation rate after heat aging.

Residual elongation (%) = 100 × Elongation after heat aging / Elongation before heat aging

The results are shown in Tables 1-3. In Tables 1 to 3, the acceptance criteria for the residual elongation rate were as follows. In the tensile test, the tensile speed was 200 mm / min.

(Acceptance criteria) Residual elongation after heat aging is 80% or more

<Processability>
The processability was evaluated based on Mooney viscosity. The Mooney viscosity was measured using the Mooney viscometer (product name “SMV-300RT”, manufactured by Shimadzu Corporation) for the kneaded materials obtained during the production of the semiconductive resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4. ). The results are shown in Tables 1-3. The Mooney viscosity test was conducted using a L-shaped rotor at a measurement temperature of 100 ° C. under conditions of preheating for 1 minute and measurement time of 4 minutes.

<Mechanical properties>
The mechanical properties were evaluated based on the tensile strength. The tensile strength was measured as follows. That is, the sheets of the semiconductive resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4 obtained as described above were punched with a JIS No. 3 super dumbbell (manufactured by Dumbbell) to produce a JIS No. 3 dumbbell test piece. did. The test piece was subjected to a tensile test using a tensile tester (product name “STOROGRAPH-R1”, manufactured by Toyo Seiki Seisakusho), and the tensile strength was measured. The results are shown in Tables 1-3. In the tensile test, the tensile speed was 200 mm / min.

<Flexibility>
Flexibility was evaluated based on the elongation rate. The measurement of the elongation rate was performed as follows. That is, the sheets of the semiconductive resin compositions of Examples 1 to 10 and Comparative Examples 1 to 4 obtained as described above were punched with a JIS No. 3 super dumbbell (manufactured by Dumbbell) to produce a JIS No. 3 dumbbell test piece. did. About this test piece, the tensile test was done using the tensile tester (Product name "STOROGRAPH-R1", the Toyo Seiki Seisakusho make), and the elongation rate was measured. The results are shown in Tables 1-3. In the tensile test, the tensile speed was 200 mm / min.

  From the results shown in Tables 1 to 3, the semiconductive resin compositions of Examples 1 to 10 reached the acceptance criteria for resistance and heat aging resistance. On the other hand, the semiconductive resin compositions of Comparative Examples 1 to 4 did not reach the acceptance criteria for resistance or heat aging resistance.

  From this, it was confirmed that the semiconductive resin composition of the present invention has sufficiently low resistance and excellent heat aging resistance.

DESCRIPTION OF SYMBOLS 1 ... Conductor 2 ... Insulating layer 3 ... Semiconductive layer 10 ... Electric power cable

Claims (5)

A base resin consisting only of an ethylene vinyl acetate copolymer;
A semiconductive resin composition containing carbon,
The carbon is blended at a ratio of 35 parts by mass or more with respect to 100 parts by mass of the base resin,
The vinyl acetate content in the ethylene vinyl acetate copolymer is 20 to 33% by mass,
The semiconductive resin composition whose gel fraction of the said base resin is 17 to 52% . The semiconductive resin composition further comprises an anti-aging agent;
The carbon is blended at a ratio of 55 parts by mass or more with respect to 100 parts by mass of the base resin,
The semiconductive resin composition according to claim 1, wherein the anti-aging agent is blended at a ratio of 1.5 parts by mass or less with respect to 100 parts by mass of the base resin. The carbon is blended at a ratio of 65 parts by mass or less with respect to 100 parts by mass of the base resin,
The semiconductive resin composition according to claim 2, wherein the anti-aging agent comprises a hindered phenol-based anti-aging agent.   The semiconductive resin composition according to any one of claims 1 to 3, wherein the carbon is composed of furnace black. Conductors,
An insulating layer provided so as to surround the conductor;
A semiconductive layer provided so as to surround the insulating layer,
The electric power cable by which the said semiconductive layer is comprised with the semiconductive resin composition as described in any one of Claims 1-4.

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