JP5872531B2 - High dielectric constant rubber composition and power cable parts - Google Patents

Description

  The present invention relates to a high dielectric constant rubber composition and a power cable component.

  In order to relax the electric field, power cable components such as a tape and a tube are usually arranged in a portion where the electric field irregularity portion such as a connection portion or a termination portion of the power cable is likely to become. These parts are generally composed of a high dielectric rubber composition, and this high dielectric rubber composition is required to have a high relative dielectric constant in order to increase the electric field relaxation effect.

  As a high dielectric rubber composition used to form such a power cable component, for example, Patent Document 1 listed below discloses a high dielectric compound in which a high dielectric constant filler such as barium titanate powder and process oil are blended with EPDM rubber. A rubber composition is disclosed.

JP 2003-174719 A

  However, the high dielectric constant rubber composition described in Patent Document 1 has the following problems.

  That is, although the high dielectric constant rubber composition described in Patent Document 1 has excellent processability, there is room for improvement in terms of electrical characteristics of power cable components obtained using the high dielectric constant rubber composition. was there.

  The present invention has been made in view of the above circumstances, and provides a high dielectric constant rubber composition and a power cable component that have excellent processability and can sufficiently improve the electrical characteristics of the power cable component. The purpose is to do.

  The present inventor has studied to solve the above problems. First, in order to increase the relative dielectric constant of the high dielectric constant rubber composition described in Patent Document 1, it was considered to add a large amount of high dielectric filler. However, in this case, in a power cable component obtained by using a high dielectric constant rubber composition, an increase in dielectric loss tangent (tan δ), a decrease in insulation resistance, and the like may occur. In other words, the electrical characteristics of power cable components may be reduced. Here, the inventor considered this cause as follows. That is, since EP rubber and silicone rubber are non-polar, the familiarity between the interface of non-polar rubber such as EP rubber and silicone rubber and the interface of high dielectric filler such as polar barium titanate powder is poor. For this reason, a gap is easily generated between the high dielectric constant filler and the nonpolar rubber. Therefore, when an AC voltage is applied to the power cable component, the polar component of the filler follows the AC voltage. As a result, the present inventor thought that tan δ would increase or the insulation resistance would decrease. Accordingly, as a result of further earnest research, the inventor blended titanate at a predetermined ratio with respect to 100 parts by mass of the base resin, and also included a polar group-containing resin having a nonpolar hydrocarbon rubber and a polar group. It is found that the above-mentioned problems can be solved by containing hydrocarbon-based rubber, polar group-containing resin and liquid hydrocarbon at a predetermined ratio in a base resin composed of styrene and liquid hydrocarbon, and completes the present invention. It came to.

That is, in the present invention, the main chain containing 10 to 70% by mass of hydrocarbon rubber and ethylene as a structural unit is provided with only a functional group containing a polar group as a side chain, and the functional group containing the polar group is A base resin composed of 20 to 70% by weight of a polar group-containing resin which is a maleic anhydride group or a carboxylic acid group, and 10 to 70% by weight of a liquid hydrocarbon; and a titanate, wherein the titanate is The high dielectric constant rubber composition is blended at a ratio of 50 to 500 parts by mass with respect to 100 parts by mass of the base resin, and the liquid hydrocarbon is in a liquid state at a temperature of at least 20 to 30 ° C.

  The high dielectric constant rubber composition of the present invention has excellent processability and can sufficiently improve the electrical characteristics of power cable components.

  In addition, this inventor estimates as follows about the reason for which the said effect is acquired.

  That is, a polar group-containing resin can be interposed between the polar titanate and the nonpolar hydrocarbon rubber, and the interface between the polar titanate and the nonpolar hydrocarbon rubber Is improved by the polar group contained in the polar group-containing resin. For this reason, the gap between the titanate interface and the hydrocarbon rubber interface can be made sufficiently small. Therefore, even if an AC voltage is applied to the power cable component, the polar component of titanate is sufficiently suppressed from following the AC voltage. For this reason, an increase in tan δ is suppressed and a decrease in insulation resistance is suppressed. As a result, according to the high dielectric constant rubber composition of the present invention, the present inventor presumes that it has excellent processability and can sufficiently suppress a decrease in electrical characteristics of power cable components. .

  In the high dielectric constant rubber composition, the titanate is preferably calcium titanate.

  In this case, compared with the case where the titanate is a titanate other than calcium titanate, even if the same mass proportion as the titanate other than calcium titanate is blended with the base resin, The relative dielectric constant can be further increased. In other words, when the titanate is calcium titanate, the relative permittivity of the power cable component can be efficiently increased with a small amount as compared with a case where the titanate is a titanate other than calcium titanate.

  Moreover, this invention is components for electric power cables obtained using the high dielectric constant rubber composition mentioned above.

  According to the power cable component of the present invention, when it is provided so as to cover a portion where electric field mismatching occurs such as a connection portion connecting the power cables, the increase in tan δ and the decrease in insulation resistance can be sufficiently suppressed. It becomes possible, and the electrical characteristics can be sufficiently improved. Moreover, since the power cable component of the present invention is obtained by using the above-described high dielectric constant rubber composition having excellent processability, it is easy to process and mold. For this reason, since small voids and the like are less likely to occur in the obtained power cable component, an excellent electric field relaxation effect can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the high dielectric constant rubber composition and power cable components which have the outstanding workability and can fully improve the electrical property of the power cable components are provided.

It is a fragmentary sectional view which shows one Embodiment of the components for electric power cables of this invention.

  Hereinafter, an embodiment of a power cable component of the present invention will be described with reference to FIG. FIG. 1 is a partial sectional view showing an embodiment of a power cable component of the present invention, and shows a state where two cables are connected by a cable connecting portion including the power cable component.

  As shown in FIG. 1, the cable connection unit 100 connects two power cables 10. Each of the two power cables 10 includes a central conductor 1, an internal semiconductive layer 2 covering the central conductor 1, an external semiconductive layer 3 covering the internal semiconductive layer 2, and a sheath 4 covering the external semiconductive layer 3. have. More specifically, the power cable 10 is composed of a main body portion and a tip portion provided at one end of the main body portion. Here, the main body is composed of a central conductor 1, an inner semiconductive layer 2, an outer semiconductive layer 3, and a sheath 4. The tip portion is composed of a first portion, a second portion, and a third portion that are sequentially provided in a direction away from the main body portion. The first part is composed of a central conductor 1, an internal semiconductive layer 2 and an external semiconductive layer 3, and the second part is composed of a central conductor 1 and an internal semiconductive layer 2. The third portion is composed only of the central conductor 1.

  The cable connection portion 100 includes a tubular conductive connection tube 5 that compressively connects the central conductor 1 of the third portion at the distal end portions of the two power cables 10, and covers the connection tube 5 and of the distal end portions of the power cable 10. An internal electrode 6 in contact with the internal semiconductive layer 2 of the second portion, an electric field relaxation portion 7 as a power cable component that covers the internal electrode 6 and relaxes the electric field from the internal electrode 6, and an electric field relaxation portion 7 The insulating part 8 to cover and the external electrode 9 which covers the insulating part 8 and contacts the external semiconductive layer 3 which is the first part of the tip part of the power cable 10 are provided.

  Here, the electric field relaxation part 7 is obtained by crosslinking a high dielectric constant rubber composition, and the high dielectric constant rubber composition includes a base resin, a titanate, and a crosslinking agent. The base resin is composed of 10 to 70% by mass of hydrocarbon rubber, 20 to 70% by mass of polar group-containing resin having a polar group, and 10 to 70% by mass of liquid hydrocarbon. Here, the liquid hydrocarbon is in a liquid state at a temperature of at least 20-30 ° C. The titanate is blended at a ratio of 50 to 500 parts by mass with respect to 100 parts by mass of the base resin.

  According to the electric field relaxation unit 7, the electrical characteristics can be sufficiently improved. That is, the increase in tan δ and the decrease in insulation resistance can be sufficiently suppressed. For this reason, according to the cable connection part 100, a dielectric breakdown becomes difficult to occur.

  Next, the high dielectric constant rubber composition will be described in detail.

  As described above, the high dielectric constant rubber composition includes a base resin, a titanate, and a crosslinking agent. The base resin is composed only of hydrocarbon rubber, polar group-containing resin and liquid hydrocarbon. That is, the ratio of the total mass of the hydrocarbon rubber, the polar group-containing resin, and the liquid hydrocarbon in the mass of the base resin is 100% by mass.

<Base resin>
(Hydrocarbon rubber)
The hydrocarbon rubber is a rubber made of hydrocarbon that is in a solid state at least at 20 to 30 ° C. Examples of such rubbers include rubbers containing ethylene as a structural unit such as ethylene propylene diene (EPDM) rubber and ethylene propylene terpolymer (EPT), isoprene rubber (IR), butadiene rubber (BR), butyl rubber (IIR), and the like. Is mentioned. These may be used alone or in combination of two or more. Among these, EPDM rubber is preferable because it has good electrical characteristics and can sufficiently reduce the viscosity.

  The content of the hydrocarbon-based rubber in the base resin is 10 to 70% by mass. If the content of the hydrocarbon-based rubber in the base resin is less than 10% by mass, the liquid hydrocarbon is likely to bleed from the electric field relaxation portion 7. On the other hand, when the content of the hydrocarbon-based rubber in the base resin exceeds 70% by mass, the ratio of the polar group-containing resin and the liquid hydrocarbon is relatively reduced, so that the electric characteristics of the electric field relaxation portion 7 are sufficiently improved. I can't. Further, since the viscosity of the high dielectric constant rubber composition increases, it becomes difficult to process and mold. For this reason, minute voids or the like are likely to occur in the power cable component, and the electric field relaxation effect is reduced.

  The content of the hydrocarbon-based rubber in the base resin is preferably 30 to 60% by mass, more preferably 30 to 50% by mass.

(Polar group-containing resin)
The polar group-containing resin is not particularly limited as long as it is a resin having a polar group. As such a polar group-containing resin, for example, a main chain containing a hydrocarbon as a structural unit, a resin in which a functional group containing a polar group is provided as a side chain, or a part of the main chain containing a hydrocarbon as a structural unit And those containing a polar group. Examples of the hydrocarbon include ethylene, propylene, and butadiene. Examples of the polar group include a carbonyl group (—CO—). The functional group may have only one polar group or a plurality of functional groups. Examples of the functional group having such a polar group include a maleic anhydride group, a carboxylic acid group (—COOH), an ester group (—COOR), and an acid anhydride group (—CO—O—OC) represented by the following formula. -).

  The content of the polar group-containing resin in the base resin is 20 to 70% by mass. When the content of the polar group-containing resin in the base resin is less than 20% by mass, the electric characteristics of the electric field relaxation unit 7 are deteriorated. On the other hand, if the content of the polar group-containing resin in the base resin exceeds 70% by mass, the workability decreases. The content of the polar group-containing resin in the base resin is preferably 20 to 50% by mass, more preferably 30 to 50% by mass.

(Liquid hydrocarbon)
The liquid hydrocarbon may be a hydrocarbon that is in a liquid state at least at 20 to 30 ° C. Examples of such liquid hydrocarbons include liquid EPDM, process oil, polybutene, and the like. These may be used alone or in combination of two or more. Among these, liquid EPDM is preferable. In this case, when the high dielectric constant rubber composition is subjected to a crosslinking treatment, the liquid EPDM is chemically combined with the hydrocarbon rubber to form a part of the hydrocarbon rubber. Can be improved.

  The content rate of the liquid hydrocarbon in base resin is 10-70 mass%. When the content of the liquid hydrocarbon in the base resin is less than 10% by mass, the processability of the high dielectric constant rubber composition is lowered. On the other hand, when the content rate of the liquid hydrocarbon in the base resin exceeds 70% by mass, the electrical characteristics deteriorate.

  The content of the liquid hydrocarbon in the base resin is preferably 10 to 50% by mass, more preferably 20 to 40% by mass.

<Titanate>
Examples of titanates include titanates having a relative dielectric constant of 200 or more, such as calcium titanate and strontium titanate. You may use these individually or in combination of 2 or more types. Here, the relative dielectric constant refers to a relative dielectric constant measured when an alternating voltage of 10 kHz and 1 V is applied at 30 ° C.

  Of the titanates, calcium titanate is particularly preferred. In this case, compared with the case where a titanate other than calcium titanate is used, the relative permittivity of the electric field relaxation portion 7 can be reduced even if the base resin is blended in the same mass ratio as the titanate other than calcium titanate. Can be higher. In other words, when the titanate is calcium titanate, the relative permittivity of the electric field relaxation portion 7 can be efficiently increased with a small amount as compared with a case where the titanate is a titanate other than calcium titanate.

  The average particle size of the titanate is not particularly limited, but is preferably 0.5 to 5.0 μm because it is easily dispersed uniformly in the base resin, and 0.5 to 2.0 μm. It is more preferable that

  The amount of titanate is 50 to 500 parts by mass with respect to 100 parts by mass of the base resin. When the compounding amount of titanate with respect to 100 parts by mass of the base resin is less than 50 parts by mass, the electric field relaxation effect of the electric field relaxation unit 7 becomes insufficient, and the compounding amount of titanate with respect to 100 parts by mass of the base resin exceeds 500 parts by mass. In this case, the powder component becomes too large to be molded as a resin.

  The amount of titanate added to 100 parts by mass of the base resin is preferably 100 to 500 parts by mass, and more preferably 250 to 400 parts by mass.

<Crosslinking agent>
The crosslinking agent contained in the high dielectric constant rubber composition is not particularly limited as long as it can crosslink the base resin. 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 0.5-4.0 mass parts with respect to a total of 100 mass parts of base resin. When the blending amount of the crosslinking agent with respect to 100 parts by mass of the base resin is within the above range, the degree of crosslinking is increased and the heat resistance is improved as compared with the case of less than 0.5 parts by mass. On the other hand, when the blending amount of the crosslinking agent with respect to 100 parts by mass of the base resin is within the above range, moderate elongation and hardness can be obtained as compared with the case where it exceeds 4.0 parts by mass.

  The high dielectric constant rubber 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, etc. as necessary. May be included.

  A high dielectric constant rubber composition is obtained by kneading a base resin, titanate, and, if necessary, an additive other than a 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.

  Next, an example of the manufacturing method of the cable connection part 100 mentioned above is demonstrated.

  First, two power cables 10 and a connecting pipe 5 are prepared. As described above, the power cable 10 includes a main body portion and a tip portion. Then, the central conductor 1 of the third portion at the tip of the two power cables 10 is inserted into the connecting pipe 5 and the connecting pipe 5 is compressed to compress the tip of the two power cables 10 into the connecting pipe 5. The center conductor 1 is fixed.

  Next, a tape made of the internal semiconductive resin composition is wound around the connection pipe 5. At this time, the tape is also wound around the inner semiconductive layer 2 at the second portion of the tip of the power cable 10 so as to be in contact with the inner semiconductive layer 2. The internal electrode 6 is obtained by crosslinking the tape as necessary, and the internal semiconductive layers 2 of the two power cables 10 are connected to each other by the internal electrode 6.

  Next, a tape made of the above-described high dielectric constant rubber composition is wound around the internal electrode 6. At this time, this tape is also wound around the inner semiconductive layer 2 of the second portion at the tip of the power cable 10. And the electric field relaxation part 7 is obtained by bridge | crosslinking this tape. At this time, the crosslinking treatment temperature of the tape may be, for example, 150 to 200 ° C., and the crosslinking treatment time may be, for example, 0.25 to 1 hour.

  Next, a tape made of an insulating material is wound around the electric field relaxation portion 7. At this time, this tape is also wound around the inner semiconductive layer 2 of the second portion at the tip of the power cable 10. And the insulating part 8 is obtained by bridge | crosslinking a tape as needed.

  Finally, a tape made of an external semiconductive resin composition is wound around the insulating portion 8. At this time, the tape is also wound around the outer semiconductive layer 3 which is the first portion of the tip of the power cable 10 so as to be in contact with the outer semiconductive layer 3. Then, the external electrode 9 is obtained by crosslinking the tape as necessary, and the external semiconductive layers 3 of the two power cables 10 are connected to each other by the external electrode 9.

  The cable connection part 100 is obtained as described above.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the high dielectric constant rubber composition contains a crosslinking agent, but the crosslinking agent is not necessarily required. For example, when the base resin is crosslinked by electron beam irradiation or the like, the high dielectric constant rubber composition may not contain a crosslinking agent.

  Moreover, in the said embodiment, although the high dielectric constant rubber composition of this invention is used as an electric field relaxation part in the cable connection part which connects two electric power cables, the high dielectric constant rubber composition of this invention is Any portion can be used as long as it easily becomes an electric field irregular portion of the power cable as the electric field relaxation portion. For example, since the terminal portion of the power cable tends to be an electric field irregularity portion, the high dielectric constant rubber composition of the present invention can also be applied as an electric field relaxation portion in the terminal portion of the power cable.

  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.

The following materials were used as raw materials for the high dielectric constant rubber composition.
(1) Hydrocarbon rubber EPDM (manufactured by Mitsui Chemicals, trade name “EPT X4010M”, solid state at 20-30 ° C.)
(2) Polar group-containing resin maleic anhydride modified polyethylene (Mitsui Chemicals, trade name “Tuffmer MA9015”)
(3) Liquid hydrocarbon (3-1) Liquid EPDM (Mitsui Chemicals, trade name “Mitsui EPT PX-068”, liquid state at 20-30 ° C.)
(3-2) Process oil (manufactured by Sun Japan Oil Company, trade name “Samper 2280”, liquid state at 20-30 ° C.)
(4) Calcium titanate titanate (Fuji Titanium Industry Co., Ltd., trade name “Calcium titanate CT”, average particle size 2 μm)
(5) Cross-linking agent dicumyl peroxide: Park mill D (manufactured by NOF Corporation)

(Examples 1-9 and Comparative Examples 1-3)
The above-mentioned hydrocarbon rubber, polar group-containing resin, liquid hydrocarbon and titanate were blended in the proportions shown in Table 1, and roll kneading was performed at 100 ° C. Next, a crosslinking agent was added to the kneaded material at a ratio shown in Table 1, and roll kneading was performed at 80 ° C. Thus, the high dielectric constant rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 3 were obtained. In Table 1, the unit of the blending amount of hydrocarbon-based rubber, polar group-containing resin, liquid hydrocarbon titanate and crosslinking agent is part by mass.

<Characteristic evaluation>
(Electrical characteristics)
(1) Insulation resistance First, a test piece was prepared as follows.

  First, the high dielectric constant rubber compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 3 were subjected to a crosslinking treatment by pressing at 160 ° C. for 40 minutes using a press machine, and the thickness was 1 mm and the width. A sheet having a length of 100 mm and a length of 100 mm was produced.

  Next, tin foil was affixed with the petrolatum thinly extended on both surfaces of this sheet | seat, and the electrode was formed. A test piece was thus obtained.

A super insulation meter was connected to the test piece, a DC voltage of 500 V was applied at 30 ° C. for 1 minute, and the volume resistivity of the test piece was measured. And about the volume resistivity of Examples 1-9, the increase rate of the volume resistivity on the basis of the comparative example 1 was computed based on the following formula. The results are shown in Table 1.

Volume resistivity increase rate (%)
= 100 × (Volume resistivity of Examples 1 to 9−Volume resistivity of Comparative Example 1) / Volume resistivity of Comparative Example 1

(2) Dielectric loss tangent The above sheet is sandwiched between a pair of electrodes, an AC voltage is applied using a dielectric constant measuring device (product name “E4980A” manufactured by Agilent Technologies), and the relative dielectric constant and dielectric loss tangent are measured at 30 ° C. did. At this time, the amplitude of the AC voltage applied to the sheet was 1 V, and the frequency was 10 kHz. And about the dielectric loss tangent of Examples 1-9, the reduction rate of the dielectric loss tangent on the basis of the comparative example 1 was computed based on the following formula. The results are shown in Table 1.

Reduction rate of dielectric loss tangent (%)
= 100 × (dielectric loss tangent of comparative example 1−dielectric loss tangent of examples 1 to 9) / dielectric loss tangent of comparative example 1

(Processability)
The Mooney viscosity (ML1 + 4, 120 ° C.) at 120 ° C. of the high dielectric constant rubber compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was used as an index of workability. Here, Mooney viscosity was measured based on JISK6300-1.

In Table 1, the acceptance criteria for workability were as follows.

Acceptance criteria: Mooney viscosity is 75 (ML1 + 4, 120 ° C) or less

  As shown in Table 1, the high dielectric constant rubber compositions of Examples 1 to 9 sufficiently improved the electrical characteristics based on Comparative Example 1 compared to the high dielectric constant rubber compositions of Comparative Examples 1 and 2. I found out that Moreover, all of the high dielectric constant rubber compositions of Examples 1 to 9 and Comparative Examples 1 and 2 satisfied the acceptance criteria in terms of workability. On the other hand, the high dielectric constant rubber composition of Comparative Example 3 did not satisfy the acceptance criteria in terms of processability.

  From the above, it was confirmed that the high dielectric constant rubber composition of the present invention has excellent processability and can sufficiently improve the electrical characteristics of power cable components.

  7 ... Electric field relaxation part (components for power cables)

Claims (3)

A main chain containing 10 to 70% by mass of a hydrocarbon-based rubber and ethylene as a structural unit is provided with only a functional group containing a polar group as a side chain, and the functional group containing the polar group is a maleic anhydride group or a carboxyl group. A base resin comprising 20 to 70% by mass of a polar group-containing resin which is an acid group and 10 to 70% by mass of a liquid hydrocarbon;
Containing titanate,
The titanate is blended at a ratio of 50 to 500 parts by mass with respect to 100 parts by mass of the base resin,
A high dielectric constant rubber composition wherein the liquid hydrocarbon is in a liquid state at a temperature of at least 20 to 30 ° C.   The high dielectric constant rubber composition according to claim 1, wherein the titanate is calcium titanate. A power cable component obtained by using the high dielectric constant rubber composition according to claim 1.

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