JP2013082813A - Semiconductive resin composition, and power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductive resin composition that has good moldability for forming a molded article having a volume resistivity of 1×10Ω cm or less without losing characteristics as a molded article, and to provide a molded article obtained using the same.SOLUTION: The semiconductive resin composition is produced by mixing (A) 100 pts.mass of ethylene-propylene diene rubber, (B) 20 to 70 pts.mass of conductive carbon black, and (C) 2 to 7 pts.mass of an organic peroxide cross-linking agent. The power cable is provided with a semiconductive layer obtained using the semiconductive resin composition.

Description

  The present invention relates to a semiconductive resin composition and a power cable provided with a semiconductive layer formed using the composition.

In a conventional power cable, particularly a high voltage power cable, at the interface between the insulating layer covering the conductor and the conductor, the electric field concentration is reduced and partial discharge is prevented in order to reduce the concentration of the electric field. A semiconductive layer is provided on both outer sides. Here, the insulating layer refers to, for example, a layer having a volume resistivity of 1 × 10 ¹³ Ω · cm or more. The semiconductive layer is made of a material having a volume resistivity of 1 × 10 ⁵ Ω · cm or less, and is usually a molded product of semiconductive rubber.

  As a method for producing a semiconductive molded product such as a semiconductive layer, a method of molding using a semiconductive resin composition containing a conductive material such as carbon black has been heretofore known (for example, see Patent Document 1). ) Is well known.

JP-A-4-31745

However, the conventional manufacturing method focuses on setting the volume resistivity of the semiconductive molded product to 1 × 10 ⁵ Ω · cm or less, and the semiconductive resin composition has moldability at the time of manufacture. There was a problem of being inferior. More specifically, when a large amount of a conductive material such as carbon black is blended in order to lower the volume resistivity, the semiconductive resin composition has a high melt viscosity at the time of molding, so that the extrusion speed is reduced. End up. In addition, such a semiconductive resin composition has a problem that the melt viscosity is likely to fluctuate, so that the production conditions must be adjusted, and the productivity is low. Further, depending on the case, there is a problem that the characteristics of the obtained molded product are impaired.

The present invention has been made in view of the above circumstances, and is a semiconductive material capable of producing a molded product having a volume resistivity of 1 × 10 ⁵ Ω · cm or less with good moldability without impairing the properties of the molded product. An object is to provide a functional resin composition and a molded product obtained using the composition.

To solve the above problem,
In the present invention, (A) 100 parts by mass of ethylene-propylene-diene rubber, (B) 20 to 70 parts by mass of conductive carbon black, and (C) 2 to 7 parts by mass of an organic peroxide crosslinking agent are blended. A semiconductive resin composition is provided.
Such a semiconductive resin composition is such that the blended amount of (B) conductive carbon black is in the above range, so that the melt viscosity is low and the moldability is excellent, and the obtained molded product has the desired semiconductivity. It will be stable. Moreover, the characteristic of a molded article is not impaired because the compounding quantity of (C) organic peroxide type crosslinking agent is the said range. That is, the molded product obtained has a reduced volume resistivity and a good stretchability.
In the semiconductive resin composition of the present invention, the (C) organic peroxide crosslinking agent is preferably dicumyl peroxide.
When the organic peroxide cross-linking agent is dicumyl peroxide, the cross-linking reaction proceeds well, and a molded product having more excellent characteristics can be obtained.
Moreover, this invention provides the electric power cable provided with the semiconductive layer obtained using the semiconductive resin composition of the said invention.
Such a power cable can be easily manufactured because it is excellent in moldability when formed into a semiconductive layer using the semiconductive resin composition. Further, the semiconductive layer has a target volume resistivity without impairing properties as a molded product.

According to the present invention, a semiconductive resin composition capable of producing a molded product having a volume resistivity of 1 × 10 ⁵ Ω · cm or less with good moldability without impairing properties as a molded product, and the composition The molded product obtained using can be provided.

It is a schematic sectional drawing which illustrates the power cable provided with the semiconductive layer obtained using the composition concerning the present invention.

<Semiconductive resin composition>
The semiconductive resin composition according to the present invention (hereinafter sometimes abbreviated as “composition”) is 100 parts by mass of (A) ethylene-propylene-diene rubber (hereinafter abbreviated as “EPDM”). (B) 20 to 70 parts by mass of conductive carbon black, and (C) 2 to 7 parts by mass of an organic peroxide crosslinking agent (hereinafter sometimes abbreviated as “crosslinking agent”). It is characterized by. Usually, the volume resistivity of the obtained conductive molded product (hereinafter sometimes abbreviated as “molded product”) is adjusted by the blending amount of (B) conductive carbon black, while (B) conductive When the compounding amount of the functional carbon black is too large, the melt viscosity of the composition increases and the moldability deteriorates. In the present invention, the volume resistivity is adjusted not only by the blending amount of (B) conductive carbon black but also by the blending amount of (C) cross-linking agent, so the blending amount of (B) conductive carbon black can be reduced, Without deteriorating the moldability of the composition, a molded article having a target volume resistivity (that is, semiconductivity) can be obtained.
Hereinafter, the present invention will be described in detail.

  (A) EPDM was obtained by copolymerizing these monomers using ethylene and propylene as main monomers and using a small amount of a non-conjugated diene monomer having a polymerizable unsaturated bond (double bond). It has a double bond in the main chain. (A) EPDM corresponds to a base polymer in the composition according to the present invention.

As the diene monomer, known monomers can be used, and preferred are 5-ethylidene-2-norbornene (ENB), vinylnorbornene (VNB), dicyclopentadiene (DCPD), 1,4-hexadiene (1,4- HD).
The said diene monomer may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose.

(A) As EPDM, a commercial item may be used and what was synthesize | combined according to the well-known method may be used.
(A) EPDM may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose.

  In the composition, the blending amount of (A) EPDM in the total amount of blending components is preferably 40 to 90% by weight, and preferably 50 to 75% by weight. By setting it as such a range, the molded article with a more favorable characteristic is obtained.

(B) The conductive carbon black may be a known one, and preferred examples include acetylene black, furnace black, and ketjen black.
(B) Conductive carbon black may be used individually by 1 type, and may use 2 or more types together. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose.

  In the composition, the amount of (B) conductive carbon black is 20 to 70 parts by mass per 100 parts by mass of (A) the amount of EPDM. By setting it to the lower limit value or more, the obtained molded product has the intended semiconductivity stably. If it is less than the lower limit, the volume resistivity of the molded product tends to increase rapidly, making it difficult to manufacture the molded product with stable quality. On the other hand, by setting it to the upper limit value or less, the melt viscosity of the composition can be reduced, and a composition having good flowability and excellent moldability can be obtained. And since these effects are acquired more notably, it is preferable that the said compounding quantity of (B) electroconductive carbon black is 25-65 mass parts, and it is more preferable that it is 30-60 mass parts.

  (C) The crosslinking agent is not particularly limited as long as it is an organic peroxide type. Etc. can be illustrated. And since a crosslinking reaction advances favorable and the molded article of the more outstanding characteristic is obtained, it is preferable that (C) crosslinking agent is a dialkyl peroxide, and it is more preferable that it is a dicumyl peroxide.

  (C) A crosslinking agent may be used individually by 1 type, and may use 2 or more types together. When two or more types are used in combination, the combination and ratio may be appropriately selected according to the purpose, but one type is usually sufficient.

In the composition, the amount of (C) the crosslinking agent is 2 to 7 parts by mass per 100 parts by mass of (A) the amount of EPDM. By setting it as the lower limit value or more, the molded product obtained has a reduced volume resistivity and is 1 × 10 ⁵ Ω · cm or less without deterioration of moldability. This is presumably because (A) EPDM is sufficiently crosslinked, and (B) conductive carbon black is evenly dispersed in the obtained resin. Further, (A) EPDM is sufficiently crosslinked, so that the shape of the molded product can be stably maintained. On the other hand, by setting it as the upper limit value or less, excessive crosslinking is suppressed, and the obtained molded product has good stretchability. Molded articles, which will be described later, obtained from the composition are classified as semiconductive rubber, but excessively cross-linked semiconductive rubber is insufficient in stretchability, and thus its shape is difficult to maintain. is there. Therefore, it lacks the properties as a molded product and is not suitable for practical use.

In addition to (A) EPDM, (B) conductive carbon black, and (C) cross-linking agent, the composition is further blended with (D) other components within a range not impeding the effects of the present invention. But you can.
(D) As another component, a well-known thing can be used suitably, A crosslinking adjuvant, a softener, anti-aging agent, a stabilizer, a filler, a reinforcing agent, a pigment, etc. can be illustrated.
For example, by blending the crosslinking aid, the (A) EPDM crosslinking reaction of the composition can proceed more smoothly.
Moreover, the said composition can be shape | molded more easily by mix | blending the said softener. Moreover, the stability of the obtained molded article is further improved by blending the anti-aging agent or stabilizer.

  (D) One type of other components may be used alone, or two or more types may be used in combination. When using 2 or more types together, the combination and ratio may be appropriately selected according to the purpose.

  In the composition, the ratio of the total blending amount of (A) EPDM, (B) conductive carbon black and (C) cross-linking agent in the total blending component is preferably 75% by mass or more, and 85% by mass. % Or more is more preferable. The upper limit of the ratio is not particularly limited, and may be 100% by mass, but is usually preferably 97% by mass. By setting it to the lower limit value or more, a molded product that is superior in the intended semiconductivity and other characteristics can be obtained. Moreover, the advantageous effect according to the kind of (D) other component is acquired by making it below an upper limit and mix | blending (D) other components.

The said composition can be manufactured by mix | blending (A) EPDM, (B) electroconductive carbon black, (C) crosslinking agent, and (D) other components as needed.
At the time of blending each component, it is preferable to add these components and thoroughly mix them by various means. And each component may be mixed, adding these sequentially, and may be mixed after adding all the components.

The mixing method of each component is not particularly limited, and for example, a known method of mixing for a predetermined time at normal temperature or under heating conditions using a stirring blade, a ball mill, an ultrasonic disperser, a kneader or the like is applied. That's fine.
In addition, when it is desired to knead immediately after the production of the composition and to produce a molded product by heat molding, the kneading may be performed also for the production of the composition.
(D) When a crosslinking aid is used as the other component, the crosslinking aid is preferably blended into the composition immediately before the production of the molded product.

  By setting the blending amount of the crosslinking agent (C) within the above range, the composition should be a molded product having good stretchability, volume resistivity, and other characteristics without deteriorating moldability. Can do. In general, the amount of the crosslinking agent used in the production of the molded product is as small as possible within the range where the crosslinking reaction of the raw material components can be performed to the required level. This is to avoid an increase in the residual amount of impurities derived from the crosslinking agent or the crosslinking agent in the resulting molded article by using the crosslinking agent more than necessary. If these remaining amounts are excessively increased, it is feared that various properties including the mechanical properties of the molded product will be adversely affected. For example, the above-mentioned “JP-A-4-31745” discloses a semiconductive resin composition comprising a crosslinkable resin component, conductive carbon black and a crosslinker, and in such a composition, It is described that the amount of the crosslinking agent is 0.2 to 5 parts by mass per 100 parts by mass of the crosslinking resin component. However, the blending amount of the crosslinking agent that has been confirmed to be specifically effective is only 0.5 parts by mass, and a composition having a greater blending amount than 0.5 parts by mass is not disclosed at all. . On the other hand, in the composition according to the present invention, as will be described later, the blending amount of (C) the crosslinking agent per 100 parts by weight of (A) EPDM is set to 2 to 7 parts by weight. Specifically, it has been confirmed that a molded product having various properties such as stretchability can be obtained. The composition according to the present invention is completely different from the conventional one in that the quality of the molded product is good, although the amount of the (C) crosslinking agent is larger than usual. Furthermore, the composition according to the present invention is not a general conductive material such as (B) conductive carbon black, but (C) the volume resistivity of the molded product is adjusted by adjusting the blending amount of the crosslinking agent. This is an unprecedented advantage in that it can be adjusted. This is because the volume resistivity is adjusted not only by the blending amount of (B) conductive carbon black but also by the blending amount of (C) crosslinking agent, so that the blending amount of (B) conductive carbon black can be reduced.

<Molded product>
The said composition which concerns on this invention can be made into a semiconductive molded article by heat-molding. As the molded article, a semiconductive layer used for covering a power cable is particularly suitable. Such a power cable can be configured in the same manner as a conventional power cable, except that a semiconductive layer obtained by using the composition is provided.

FIG. 1 is a schematic cross-sectional view illustrating a power cable having a semiconductive layer obtained using the composition according to the present invention.
The power cable 1 shown here has a first semiconductive layer 12, an insulating layer 13, a second semiconductive layer 14, a metal shielding layer 15 and a sheath 16 on a conductor 11 from the radially inner side to the outer side. In this order, they are concentric. Here, the first semiconductive layer 12 corresponds to an internal semiconductive layer, and the second semiconductive layer 14 corresponds to an external semiconductive layer.

The conductor 11 is made of, for example, a single metal or an alloy such as copper, a copper alloy, aluminum, or an aluminum alloy.
The first semiconductive layer 12 covers the conductor 11 and is formed using the composition. The thickness of the first semiconductive layer 12 is preferably 0.01 to 3 mm.
The insulating layer 13 covers the first semiconductive layer 12 and is made of, for example, polyethylene or crosslinked polyethylene. The thickness of the insulating layer 13 is preferably 1 to 30 mm.
The second semiconductive layer 14 covers the insulating layer 13 and is formed by using the above composition in the same manner as the first semiconductive layer 12. The thickness of the second semiconductive layer 14 is preferably 0.01 to 3 mm. The first semiconductive layer 12 and the second semiconductive layer 14 may be made of the same material or different materials.
The metal shielding layer 15 covers the second semiconductive layer 14 and is made of a metal such as copper, for example. The thickness of the metal shielding layer 15 is preferably 0.001 to 0.5 mm.
The sheath 16 covers the metal shielding layer 15 and is made of, for example, a resin such as polyvinyl chloride or polyethylene.

  Here, although the power cable 1 is shown with two semiconductive layers, the power cable according to the present invention is not limited to this, and the semiconductive layer is disposed between the conductor layer and the insulating layer. In this case, the number of layers may be 1 or 3 or more, and can be arbitrarily adjusted according to the purpose.

The power cable 1 can be manufactured by the same method as the conventional power cable except that the composition is used. For example, it is as follows.
First, the composition according to the present invention is melt-kneaded using a twin screw extruder, kneader, Banbury mixer or the like, and then extruded onto the conductor 11 using an extruder to coat the conductor 11. At this time, the composition may be subjected to extrusion after being melt-kneaded and pelletized with a granulator.
Since the composition at the time of extrusion has a low melt viscosity, it has good fluidity and is excellent in moldability, such as being able to be rapidly molded into a desired shape.

Next, the composition after coating is heated and crosslinked to complete thermoforming, and the first semiconductive layer 12 is formed.
The heating at this time may be performed by a known method such as spraying water vapor. The heating temperature is preferably 150 to 200 ° C., and the heating time is preferably 1 to 45 minutes. By setting it as such a range, the characteristic of the 1st semiconductive layer 12 becomes more favorable.

Next, the composition for forming the insulating layer is extruded onto the first semiconductive layer 12 using an extruder, and the first semiconductive layer 12 is coated to form the insulating layer 13. In the case where crosslinking is necessary for forming the insulating layer 13, heating may be performed after coating.
Note that the heating for forming the first semiconductive layer 12 may be performed not before the formation of the insulating layer 13 as described above, but simultaneously with the formation of the insulating layer 13 or after the formation of the insulating layer 13.
In addition, the respective compositions for forming the first semiconductive layer 12 and the insulating layer 13 may be extruded all at once by two-layer coextrusion.

Next, the composition according to the present invention is extruded onto the insulating layer 13 by the same method as that for the first semiconductive layer 12 to cover the insulating layer 13.
The composition at the time of extrusion also has excellent flowability because it has a low melt viscosity and can be quickly formed into a desired shape.

Next, the composition after coating is heated and crosslinked in the same manner as in the case of the first semiconductive layer 12, thereby completing the thermoforming and forming the second semiconductive layer 14.
The heating for forming the first semiconductive layer 12 and / or the insulating layer 13 is not performed before the formation of the second semiconductive layer 14 as described above, but during the formation of the second semiconductive layer 14. You may do it at the same time.
Moreover, you may extrude each composition for forming the 1st semiconductive layer 12, the insulating layer 13, and the 2nd semiconductive layer 14 at a stretch by three-layer simultaneous extrusion.

  Next, a metal shielding layer 15 is formed on the second semiconductive layer 14. The metal shielding layer 15 can be formed, for example, by winding a metal tape on the second semiconductive layer 14.

  Next, the power cable 1 is obtained by forming the sheath 16 on the metal shielding layer 15 in the same manner as in the case of the insulating layer 13.

  Here, the semiconductive layer used for covering the power cable has been described as the molded product. However, for other molded products, a molding method is appropriately selected, and the composition is crosslinked under the same heating conditions as described above. Can be manufactured in the same manner. As a molding method other than extrusion molding, a known method such as injection molding or mold molding can be applied.

A molded product obtained by using the composition has a target volume resistivity without impairing properties as a molded product such as stretchability.
For example, the volume resistivity is a value measured by a method based on the Japan Rubber Association standard “SRIS 2301-1969 Conductive Rubber and Plastic Volume Resistivity Test Method” and is 1 × 10 ⁵ Ω · cm or less, preferably 1 × 10 ⁴ Ω · cm or less, more preferably 1 × 10 ³ Ω · cm or less.
Further, the stretchability is a measured value of elongation by a method based on “JIS K 6251”, and is preferably 150% or more, more preferably 170% or more.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples.

[Examples 1-4, Comparative Examples 1-2]
<Manufacture of composition and molded article>
(A) EPDM, (B) conductive carbon black, (C) cross-linking agent, and (D) other components are added so as to obtain the blending amounts shown in Table 1, and a roll kneader (Otake Machinery Co., Ltd.) ) Was used to knead these at 80 ° C. In addition, the blending amount of (D) other components is adjusted as appropriate, and the ratio of the total blending amount of (A) EPDM, (B) conductive carbon black and (C) cross-linking agent in the total blending component is 90. It was made to be -95 mass%.

In addition, the symbol of each component in Table 1 means the following, respectively.
(A) EPDM
(A) -1: EPT3045 (Mitsui Chemicals)
(B) Conductive carbon black (B) -1: Acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.)
(C) Crosslinking agent (C) -1: Dicumyl peroxide (manufactured by Kayaku Akzo)
(D) Other components (D1) Softener (D1) -1: Thumper 2100 (Nihon Sun Oil Co., Ltd.)
(D2) Anti-aging agent (D2) -1: NOCRACK NS-5 (Ouchi Shinsei Co., Ltd.)
(D3) Stabilizer (D3) -1: Zinc flower (Mitsui Metal Mining Co., Ltd.)

  Subsequently, the obtained composition was heated and pressed at 160 ° C. for 40 minutes using a press apparatus (manufactured by Koto Kogyo) to produce a sheet having a thickness of 2 mm as a molded product.

<Evaluation of composition>
The obtained composition was subjected to a rheometer test before molding. The rheometer test tests the extrusion characteristics and cross-linking characteristics of the resin composition, and is performed using a torsional vibration type disk vulcanization tester in accordance with “JIS K 6300-2”. A vulcanization curve was created with the vulcanization time assigned to the horizontal axis. The results are shown in Table 2. Each abbreviation regarding the rheometer test in Table 2 means the following.
M _H : Maximum torque value (N · m)
M _L : Minimum value of torque (N · m)
t ₁₀ : Time (minutes) from the start of the test until the torque value reaches 0.1 _MH
t ₉₀ : Time (minutes) from the start of the test until the torque value reaches 0.9 _MH

<Evaluation of molded products>
About the obtained said molded article, the volume resistivity and elongation were measured with the following method. The results are shown in Table 2.
(Volume resistivity)
This was performed in accordance with the Japan Rubber Association standard “SRIS 2301-1969 Conductive Rubber and Plastic Volume Resistivity Test Method”. That is, a molded product is placed on an insulating plate, a pair of electrodes are arranged on the molded product with a spacing of 70 mm, a load and a voltage are evenly applied to these electrodes, and the resistance between the electrodes is measured using a Wheatstone bridge. The volume resistivity (Ω · cm) was determined by measuring the value.
(Elongation)
In accordance with “JIS K 6251”, the molded product was punched into a dumbbell shape to obtain a test piece, and the elongation (%) of the test piece was measured using a tensile tester.

As is clear from the above results, in Examples 1 to 4, the composition had a good rheometer measurement value, a low melt viscosity, these measurement values were stable, and had excellent moldability stably. . The molded product had good volume resistivity and elongation, and was excellent in properties as a semiconductive molded product. For example, the volume resistivity of the molded product showed a value significantly lower than 1 × 10 ⁵ Ω · cm, which is a standard for the upper limit value.
On the other hand, in Comparative Example 1, the elongation of the molded product was remarkably inferior because the amount of the (C) crosslinking agent in the composition was too large. Since such a molded product is easily broken and its shape is difficult to maintain, it is not suitable for practical use. In Comparative Example 2, _ML was remarkably increased due to the excessive amount of (B) conductive carbon black in the composition. M _L is, for example, is an important value as an index of melt viscosity during extrusion of the composition, Comparative Example 2 has poor fluidity of the composition, it was inferior considerably moldability.
In these examples and comparative examples, the elongation of the molded product tended to decrease as the blending amount of (C) the crosslinking agent increased. Moreover, the volume resistivity of the molded product showed a tendency to decrease as the blending amount increased in a region where the blending amount of (C) the crosslinking agent was more than 2 parts by mass. Also, of the rheometer _{measurements,} t _{10, t 90} and _{M L} is (C) shows a tendency to decrease as the amount of crosslinking agent is increased, _{M H} is, the more increased is the amount of crosslinking agent (C) Showed an upward trend.

  The present invention can be used for all semiconductive molded articles, and is particularly useful for forming a semiconductive layer of a power cable.

  DESCRIPTION OF SYMBOLS 1 ... Power cable, 11 ... Conductor, 12 ... 1st semiconductive layer, 13 ... Insulating layer, 14 ... 2nd semiconductive layer, 15 ... Metal shielding layer, 16 ... sheath

Claims (3)

  (A) 100 parts by mass of ethylene-propylene-diene rubber, (B) 20 to 70 parts by mass of conductive carbon black, and (C) 2 to 7 parts by mass of an organic peroxide crosslinking agent are characterized. A semiconductive resin composition.   The semiconductive resin composition according to claim 1, wherein the (C) organic peroxide-based crosslinking agent is dicumyl peroxide.   A power cable comprising a semiconductive layer obtained by using the semiconductive resin composition according to claim 1.

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