JP2015059172A - Semiconductive resin composition and power cable - Google Patents

Abstract

To provide a semiconductive resin composition capable of forming a semiconductive resin layer capable of suppressing deterioration of mechanical properties while suppressing temperature dependency of electric resistance, and a power cable using the same.
A semiconductive resin composition in which a carbon material is blended at a ratio of 40 to 80 parts by mass with respect to a total of 100 parts by mass of 50 to 91 parts by mass of a polyolefin resin and 9 to 50 parts by mass of an elastomer. object.
[Selection figure] None

Description

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

  The power cable has a center conductor and an insulating layer surrounding the center conductor. However, in a power cable to which a voltage of 600 V or higher is applied, when the central conductor and the insulating layer are brought into direct contact, the electric field strength between them becomes very large. Therefore, a semiconductive resin layer is usually provided as an electric field relaxation layer between the central conductor and the insulating layer.

  As a semiconductive resin composition for forming such a semiconductive resin layer, for example, in Patent Document 1 below, conductive carbon is blended with a base resin in which an ethylene copolymer (EEA or EVA) and polyethylene are mixed. A semiconductive resin composition is disclosed.

JP-A-61-13738

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

  That is, although the semiconductive resin layer obtained using the semiconductive resin composition described in Patent Document 1 has excellent mechanical properties, the electrical resistance may increase as the temperature increases.

  The present invention has been made in view of the above circumstances, and a semiconductive resin composition capable of forming a semiconductive resin layer capable of suppressing deterioration of mechanical properties while suppressing temperature dependence of electrical resistance, and the same An object is to provide a power cable using the cable.

  This inventor examined the cause which the said subject produces in the semiconductive resin composition of the said patent document 1. FIG. As a result, EVA and EEA used as the base resin in Patent Document 1 are all crystalline resins and have a crystalline portion and an amorphous portion. Here, it is considered that carbon is present in an amorphous part of the base resin and forms a carbon chain that generates conductivity. However, when the temperature of the resin rises, the crystal part melts to become an amorphous part, the carbon distribution spreads, and the degree of carbon chain decreases. Then, it is considered that the electrical resistance of the semiconductive resin layer increases as the temperature increases. In this case, it is considered that the function of the semiconductive resin layer as the electric field relaxation layer is reduced, the electric field strength is remarkably increased between the central conductor and the semiconductive resin layer, and in some cases, dielectric breakdown is caused. Here, it is also conceivable to reduce the electrical resistance at high temperatures by increasing the amount of carbon. However, when the amount of carbon is increased, the melt viscosity of the resin composition increases, and extrusion after kneading of the resin composition becomes difficult. Moreover, the kneading of the resin composition itself may not be possible. Therefore, as a result of further earnest research, the inventor solved the above problem by blending a carbon material at a predetermined ratio with respect to a total of 100 parts by mass of polyolefin resin and elastomer blended at a predetermined ratio. As a result, the present invention has been completed.

  That is, the present invention is a semiconductive material in which a carbon material is blended at a ratio of 40 to 80 parts by mass with respect to a total of 100 parts by mass of 91 to 50 parts by mass of a polyolefin resin and 9 to 50 parts by mass of an elastomer. It is a resin composition.

  With the semiconductive resin composition of the present invention, it is possible to form a semiconductive resin layer that can suppress a decrease in mechanical properties while suppressing the temperature dependence of electrical resistance.

  In addition, this inventor estimates as follows why the temperature dependence of electrical resistance can be suppressed by the semiconductive resin composition of the present invention.

  That is, by blending the polyolefin resin, which is a crystalline resin, with an elastomer, which is a resin having lower crystallinity than that of the polyolefin resin, the proportion of crystal parts in the resin is relatively reduced. The present inventor speculates that the decrease in the degree of the chain of the carbon material due to the dissolution of the portion is suppressed.

  In the said semiconductive resin composition, it is preferable that the crosslinking agent is further mix | blended.

  In this case, the polyolefin resin and the elastomer can be cross-linked by the cross-linking agent. For this reason, it becomes possible for the said semiconductive resin composition to form the semiconductive resin layer which has the more outstanding mechanical characteristic.

  In the semiconductive resin composition, it is preferable that the polyolefin resin is composed of at least one of an ethylene vinyl acetate copolymer and ethylene ethyl acrylate, and the elastomer is composed of EP rubber.

  In this case, the said semiconductive resin composition can form effectively the semiconductive resin layer which can suppress the fall of a mechanical characteristic, suppressing the temperature dependence of electrical resistance.

  Further, the present invention provides a power cable including at least a central conductor, a semiconductive resin layer covering the central conductor, and an insulating resin layer covering the semiconductive resin layer, wherein the semiconductive resin layer is the semiconductive resin layer. It is a power cable obtained by crosslinking a conductive resin composition.

  According to the power cable of the present invention, the semiconductive resin layer can suppress the temperature dependence of the electrical resistance. That is, even when a high voltage is applied to the power cable and the power cable is in a high temperature state, the occurrence of dielectric breakdown in the semiconductive resin layer is sufficiently suppressed. For this reason, it is possible to extend the life of the power cable. Moreover, since a semiconductive resin layer is obtained by bridge | crosslinking a semiconductive resin composition, it can also suppress sufficiently the fall of the mechanical characteristic of a semiconductive resin layer and by extension, the mechanical characteristic of an electric power cable.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductive resin composition which can form the semiconductive resin layer which can suppress the fall of a mechanical characteristic, suppressing the temperature dependence of electrical resistance, and a power cable using the same are provided. The

It is sectional drawing which shows one Embodiment of the power cable of this invention.

  Hereinafter, an embodiment of a power cable of the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing an embodiment of a power cable according to the present invention.

  As shown in FIG. 1, the power cable 100 surrounds the center conductor 1, the inner semiconductive resin layer 2 surrounding the center conductor 1, the insulating layer 3 surrounding the inner semiconductive resin layer 2, and the insulating layer 3. An external semiconductive resin layer 4 and an insulating sheath 5 surrounding the external semiconductive resin layer 4. Here, the insulating layer 3 is disposed outside the internal semiconductive resin layer 2 and inside the external semiconductive resin layer 4 so as to be in contact with both the internal semiconductive resin layer 2 and the external semiconductive resin layer 4. Is provided. The sheath 5 is provided outside the external semiconductive resin layer 4 so as to be in contact with the external semiconductive resin layer 4.

  The inner semiconductive resin layer 2 and the outer semiconductive resin layer 4 are obtained by cross-linking the semiconductive resin composition. The semiconductive resin composition includes a polyolefin resin, an elastomer, and a carbon material. And a crosslinking agent. Here, the carbon material is blended at a ratio of 40 to 80 parts by mass with respect to 100 parts by mass in total of 91 to 50 parts by mass of the polyolefin-based resin and 9 to 50 parts by mass of the elastomer.

  According to this power cable 100, the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 can suppress the temperature dependence of the electrical resistance. That is, even when a high voltage is applied to the power cable 100 and the power cable 100 is in a high temperature state, the occurrence of dielectric breakdown in the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 is sufficiently suppressed. For this reason, the lifetime of the power cable 100 can be extended. Further, since the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 are obtained by cross-linking the semiconductive resin composition, the mechanical characteristics of the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 and thus the power cable It is possible to sufficiently suppress the decrease in mechanical properties of 100.

  Next, the center conductor 1, the internal semiconductive resin layer 2, the external semiconductive resin layer 4, the insulating layer 3, and the sheath 5 will be described in detail.

<Center conductor>
The center conductor 1 may be composed of only one strand or may be composed of a plurality of strands bundled together. Moreover, the center conductor 1 is not specifically limited about a conductor diameter, the material of a conductor, etc., It can determine suitably according to a use.

<Internal semiconductive resin layer and external semiconductive resin layer>
The internal semiconductive resin layer 2 and the external semiconductive resin layer 4 are obtained by crosslinking a semiconductive resin composition. As described above, the semiconductive resin composition includes a polyolefin-based resin, an elastomer, a carbon material, and a crosslinking agent.

(Polyolefin resin)
The polyolefin resin is not particularly limited. Examples of such polyolefin resins include polyethylene, polypropylene, ethylene vinyl acetate copolymer (EVA), and ethylene ethyl acrylate (EEA). These can be used alone or in combination of two or more. Especially, it is preferable that polyolefin resin is comprised by at least one of EVA and EEA. In this case, the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 can effectively suppress the deterioration of mechanical properties while effectively suppressing the temperature dependence of the electrical resistance.

  The crystallinity of the polyolefin resin is not particularly limited, but is preferably 10 to 40%. When the crystallinity is within the above range, the mechanical properties of the semiconductive resin composition are further improved as compared with the case where the crystallinity is less than 10%. Moreover, when the degree of crystallinity is within the above range, the semiconductive resin composition can more sufficiently suppress the temperature dependence of electrical resistance than when it exceeds 40%. In the present specification, the “crystallinity” refers to a value obtained from the heat of fusion measured by a differential scanning calorimeter.

(Elastomer)
The elastomer may be a resin having a crystallinity lower than that of the polyolefin resin, and is not particularly limited, but is preferably 0 to 20%. In particular, the crystallinity of the elastomer is preferably 0%. Examples of the elastomer include EP rubber and nitrile rubber.

  The EP rubber is composed of at least one of ethylene-propylene copolymer (EPM) and ethylene-propylene-diene terpolymer (EPT). Examples of the diene contained in the terpolymer include 5-ethylidene-2-norbornene, 1,4-hexadiene, and dicyclopentadiene. The above EP rubbers may be used alone or in combination of two or more.

  In a total of 100 parts by mass of the polyolefin resin and the elastomer, the amount of the elastomer is 9 to 50 parts by mass. When the blending amount of the elastomer is less than 9 parts by mass, the temperature dependency of the electrical resistance cannot be sufficiently suppressed. When the blending amount of the elastomer exceeds 50 parts by mass, it becomes impossible to suppress a decrease in mechanical strength.

  The blending amount of the elastomer is preferably 23 to 33 parts by mass in a total of 100 parts by mass of the polyolefin resin and the elastomer.

(Carbon material)
The carbon material contained in the semiconductive resin composition is not particularly limited as long as it imparts sufficient conductivity to the semiconductive resin composition. Examples of the carbon material include carbon black, graphite, glassy carbon, carbon fiber, and carbon nanotube. These can be used alone or in combination of two or more. Among these, carbon black is particularly preferable.

  The compounding quantity of the carbon material with respect to a total of 100 parts by mass of the polyolefin resin and the elastomer is 40 to 80 parts by mass. When the blending amount of the carbon material with respect to 100 parts by mass of the polyolefin resin and the elastomer is less than 40 parts by mass, the temperature dependency of the electrical resistance cannot be sufficiently suppressed. When the blending amount of the carbon material with respect to 100 parts by mass of the polyolefin-based resin exceeds 80 parts by mass, the melt viscosity of the semiconductive resin composition increases, and extrusion after kneading of the semiconductive resin composition becomes difficult. Alternatively, kneading of the semiconductive resin composition itself cannot be performed.

  The blending amount of the carbon material with respect to 100 parts by mass of the total of the polyolefin-based resin and the elastomer is preferably 60 to 75 parts by mass.

(Crosslinking agent)
The crosslinking agent contained in the semiconductive resin composition is not particularly limited as long as it can crosslink the polyolefin resin and the elastomer. Examples of such crosslinking agents include organic peroxides such as dialkyl peroxides, diacyl peroxides, ketone peroxides, hydroperoxides, peroxyketals, alkyl peresters, and carbonates, And sulfur.

  Specific examples of the organic peroxide include dicumyl peroxide (DCP), 1,3-bis (t-butylperoxyisopropyl) benzene, and 2,5-dimethyl-2,5- (t-butyl). Peroxy) -3-hexyne, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2 , 5-Dibenzoylperoxyhexane, n-butyl-4,4-bis (t-butylperoxy) valerate, t-butylperoxybenzoate, 1,4-bis [(t-butylperoxy) isopropyl] Benzene, t-butylcumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, di-t-butylper Kisaido, and the like. These may be used alone or in combination of two or more.

  Although the compounding quantity of a crosslinking agent is not specifically limited, It is preferable that it is 2-4 mass parts with respect to a total of 100 mass parts of polyolefin resin and an elastomer. When the blending amount of the crosslinking agent with respect to the total of 100 parts by mass of the polyolefin-based resin and the elastomer is within the above range, there is an advantage that the degree of crosslinking is increased and the heat resistance is improved as compared with the case of less than 2 parts by mass. On the other hand, when the blending amount of the crosslinking agent with respect to 100 parts by mass in total of the polyolefin resin and the elastomer is within the above range, there is an advantage that moderate elongation and hardness can be obtained as compared with the case where it exceeds 4 parts by mass. .

  The semiconductive resin composition further comprises an anti-aging agent, a stabilizer, a flame retardant, a filler, a surface treatment agent, an anti-drip agent, a processing aid, an activator, a crosslinking aid, an anti-scorch agent, as necessary. May be included.

  The semiconductive resin composition is obtained by kneading a polyolefin resin, an elastomer, a carbon material, and, if necessary, an additive other than the crosslinking agent to obtain a kneaded product, and then kneading the kneaded product by adding a crosslinking agent. Can be obtained. The kneading can be performed with a kneading machine such as a Banbury mixer, a tumbler, a pressure kneader, a kneading extruder, a twin screw extruder, a mixing roll, and the like.

(Insulating layer and sheath)
The insulating material which comprises the insulating layer 3 and the sheath 5 should just show insulation. Examples of such an insulating material include polyethylene resin, polypropylene resin, ethylene-butadiene-diene rubber (EPDM), polyvinyl chloride resin (PVC), polyolefin resin (CPE), ethylene-vinyl acetate copolymer (EVA), Ethylene-ethyl acrylate copolymer (EEA), chloroprene rubber (CR), polyester resin, thermoplastic polyurethane resin (TPU), natural rubber (NR), and the like can be used. These can be used alone or in combination of two or more.

  Among the insulating materials, nonpolar resins such as polyethylene resin, polypropylene resin, and ethylene-butadiene-diene rubber (EPDM) are preferably used.

  Next, an example of a method for manufacturing the above-described power cable 100 will be described.

  For forming the central conductor 1 by the coextrusion molding method, the semiconductive resin composition for forming the internal semiconductive resin layer 2, the insulating material for forming the insulating layer 3, and the external semiconductive resin layer 4. The semiconductive resin composition and the insulating material for forming the sheath 5 are sequentially covered.

  Next, the semiconductive resin composition for forming the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 is crosslinked.

  In this way, the power cable 100 is obtained.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the internal semiconductive resin layer 2 and the external semiconductive resin layer 4 of the power cable 100 are made of the semiconductive resin composition of the present invention. One of the conductive resin layers 4 may be composed of a general semiconductive resin composition that does not satisfy the requirements of the present invention, and only the other may be composed of the semiconductive resin composition of the present invention.

  Moreover, in the said embodiment, although the semiconductive resin composition contains the crosslinking agent, the crosslinking agent is not necessarily required. For example, when the polyolefin resin is cross-linked by electron beam irradiation or the like, the semiconductive resin composition may not contain a cross-linking agent.

  Further, in the above embodiment, the power cable 100 is configured by covering the central conductor 1 with the inner semiconductive resin layer 2, the insulating layer 3, the outer semiconductive resin layer 4 and the sheath 5 in order. May be configured by sequentially covering only the inner semiconductive resin layer 2 and the insulating layer 3 on the central conductor 1.

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

As raw materials for the semiconductive resin composition, the following were used.
(1) Polyolefin resin EVA: EV260 (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd., crystallinity: 15%)
EEA: NUC-6510 (trade name, manufactured by Nihon Unicar)
(2) Elastomer EPDM: EPT3045 (trade name, manufactured by Mitsui Chemicals, Inc., crystallinity: 0%)
(3) Carbon material acetylene black: Denka Black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.)
(4) Crosslinking agent dicumyl peroxide: Park Mill D (manufactured by NOF Corporation)
(5) Anti-aging agent 4,4′-thiobis (3-methyl-6-tert-butylphenol): NOCRACK 300 (Ouchi Shinsei Chemical Co., Ltd.)

(Examples 1-8 and Comparative Examples 1-5)
The above polyolefin resin, elastomer, carbon material, and anti-aging agent were blended in the proportions shown in Tables 1 and 2, and roll kneading was performed at 120 ° C. Next, a crosslinking agent was added to the kneaded material at a ratio shown in Tables 1 and 2, and roll kneading was performed at 100 ° C. Thus, the semiconductive resin compositions of Examples 1 to 8 and Comparative Examples 1 to 5 were obtained. In Tables 1-2, the unit of the compounding quantity of polyolefin resin, an elastomer, a carbon material, a crosslinking agent, and an anti-aging agent is a mass part.

<Characteristic evaluation>
(Temperature dependence of electrical resistance)
First, a test piece was prepared as follows.

  First, the semiconductive resin compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were pressed at 170 ° C. for 15 minutes using a press machine, and the thickness was 2 mm, the width was 20 mm, and the length was 80 mm. A sheet was produced.

  Next, a conductive paste (trade name “Dotite D-362”, manufactured by Fujikura Kasei Co., Ltd.) was applied to each of 5 mm wide regions at both ends of the sheet and dried to form electrodes. A test piece was thus obtained.

A Wheatstone bridge was connected to the test piece, and the electrical resistance of the test piece was measured at each temperature of 30 ° C., 60 ° C., 90 ° C., and 110 ° C. And from these measurement results, the following formula:
Temperature rise ratio of electric resistance = electric resistance at 110 ° C./electric resistance at 30 ° C. The temperature rise ratio of electric resistance was calculated. The results are shown in Tables 1 and 2.

Here, the temperature rise ratio of the electrical resistance was used as an index of the temperature dependence of the electrical resistance. The acceptance criteria for temperature dependence of electrical resistance were as follows.

Acceptance criteria: Temperature rise ratio of electrical resistance is 10 or less

(Mechanical properties)
The sheet was processed into the dimensions of a JIS K6251 No. 3 dumbbell to obtain a test piece. A tensile test was performed on the test piece, and the tensile strength and the tensile elongation were measured. The results are shown in Tables 1 and 2.

Here, tensile strength and tensile elongation were used as indicators of mechanical properties. The acceptance criteria for mechanical properties were as follows.

Acceptance criteria: Tensile strength is 10 MPa or more and tensile elongation is 300% or more

  As shown in Tables 1 and 2, the semiconductive resin compositions of Examples 1 to 8 reached the acceptance criteria in terms of temperature dependence of electrical resistance and mechanical properties. On the other hand, the semiconductive resin compositions of Comparative Examples 1 to 5 did not reach the acceptance criteria in any one of temperature dependency of electrical resistance and mechanical properties.

  From the above, it was confirmed that the semiconductive resin composition of the present invention can form a semiconductive resin layer capable of suppressing the deterioration of mechanical properties while suppressing the temperature dependence of electrical resistance.

DESCRIPTION OF SYMBOLS 1 ... Center conductor 2 ... Internal semiconductive resin layer (semiconductive resin layer)
4. External semiconductive resin layer (semiconductive resin layer)
100 ... Power cable

Claims (4)

  A semiconductive resin composition in which a carbon material is blended in a proportion of 40 to 80 parts by mass with respect to a total of 100 parts by mass of 50 to 91 parts by mass of a polyolefin resin and 9 to 50 parts by mass of an elastomer.   The semiconductive resin composition according to claim 1, further comprising a crosslinking agent. The polyolefin resin is composed of at least one of an ethylene vinyl acetate copolymer and ethylene ethyl acrylate,
The semiconductive resin composition according to claim 1 or 2, wherein the elastomer is composed of EP rubber. A central conductor;
A semiconductive resin layer covering the central conductor;
In a power cable including at least an insulating resin layer covering the semiconductive resin layer,
The electric power cable obtained by the said semiconductive resin layer bridge | crosslinking the semiconductive resin composition as described in any one of Claims 1-3.

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