JP7247721B2 - Electrical insulation composition and power cable - Google Patents

Description

The present disclosure relates to electrical insulation compositions and power cables.

Due to its excellent insulating properties, polyethylene is widely used as a base resin of an electrical insulating composition forming an insulating layer in power cables and the like (for example, Patent Document 1).

JP-A-57-69611

Water trees can occur in the insulation layer when a power cable is energized in a wet or flooded environment. Therefore, it is required to improve the water tree resistance of the insulating layer.

An object of the present disclosure is to provide a technique capable of improving water tree resistance while ensuring cable properties.

According to one aspect of the present disclosure,
100 parts by mass of a base resin containing polyethylene,
0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene;
0.05 parts by mass or more and 1.0 parts by mass or less of fatty acid amide;
An electrical insulating composition is provided having:

According to another aspect of the present disclosure,
a conductor;
an insulating layer provided to cover the outer periphery of the conductor;
with
The insulating layer contains 100 parts by mass of a base resin containing polyethylene, 0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of an α-aromatic substituted α-methylalkene, and 0.05 parts by mass of a fatty acid amide. There is provided a power cable composed of an electrical insulating composition having at least 1.0 part by mass and no more than 1.0 part by mass.

According to the present disclosure, it is possible to improve water tree resistance while ensuring cable properties.

1 is a schematic cross-sectional view orthogonal to the axial direction of a power cable according to an embodiment of the present disclosure; FIG.

[Description of Embodiments of the Present Disclosure]
<Knowledge acquired by the inventors, etc.>
First, the outline of knowledge obtained by the inventors will be described.

Power cables may be laid, for example, in wet or flooded environments. Under such circumstances, when a given electric field is applied to the insulating layer of the power cable, water trees can occur in the insulating layer. The occurrence of water trees in the insulation layer can degrade the insulation of the power cable.

Water trees are generated, for example, by the following mechanism. That is, in wet or flooded environments, water can penetrate into the insulation layer of the power cable. When water enters the insulating layer while the power cable is being energized, the water aggregates in the portion of the insulating layer where local electric field concentration occurs. Examples of localized electric field concentrations include voids in the insulating layer, foreign matter, and interface irregularities between the insulating layer and the semiconducting layer. When water condenses in such a localized electric field concentration portion, mechanical distortion occurs around the water condensed portion due to the pressure increase of the condensed water. As a result, tree-like or bow-tie-like water trees develop in the insulating layer.

Conventionally, in order to suppress the generation of water trees in the insulating layer of power cables, various techniques have been studied, such as the above-mentioned Patent Document 1, for example.

However, in recent years, the specifications required for power cables laid under wet or flooded environments have become stricter. Alternatively, there is a demand for simplifying the configuration of power cables laid under wet or flooded environments to reduce the cost of the power cables. For these reasons, a power cable with improved water tree resistance is desired.

Accordingly, the inventors of the present invention have investigated materials to be added to the electrical insulating composition that constitutes the insulating layer of the power cable. Specifically, among various materials to be added to the electrical insulating composition, unsaturated dimers of α-aromatic substituted α-methylalkenes and fatty acid amides were investigated. As a result of investigation, it was found that the number density of water trees generated in the insulating layer can be reduced by adding either an unsaturated dimer of α-aromatic substituted α-methylalkene or a fatty acid amide. Do you get it.

As a result of further intensive studies by the present inventors, it was found that the addition of both the unsaturated dimer of the α-aromatically substituted α-methylalkene and the fatty acid amide significantly improves the water tree resistance. I found what I can do. Specifically, the present inventors have found that the maximum length of water trees generated in the insulating layer can be shortened, and the number density of water trees generated in the insulating layer can be significantly reduced.

The present disclosure is based on the above findings found by the inventors.

<Embodiments of the Present Disclosure>
Next, embodiments of the present disclosure are listed and described.

[1] An electrical insulating composition according to one aspect of the present disclosure,
100 parts by mass of a base resin containing polyethylene,
0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene;
0.05 parts by mass or more and 1.0 parts by mass or less of fatty acid amide;
have
According to this configuration, it is possible to remarkably improve the water tree resistance while ensuring various cable characteristics.

[2] In the electrical insulating composition according to [1] above,
The electrical insulating composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was immersed in a 1 N NaCl aqueous solution at room temperature. When an AC electric field with a commercial frequency of 4 kV / mm is applied for 1000 hours,
The maximum length of water trees occurring in the electrical insulating composition is less than 200 μm.
According to this configuration, dielectric breakdown of the insulating layer due to water trees can be stably suppressed.

[3] In the electrical insulating composition according to [1] or [2] above,
The electrical insulating composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was immersed in a 1 N NaCl aqueous solution at room temperature. When an AC electric field with a commercial frequency of 4 kV / mm is applied for 1000 hours,
The concentration of the number of water trees generated in the electrical insulating composition and having a length of 30 μm or more is less than 200/cm ³ .
According to this configuration, dielectric breakdown of the insulating layer due to water trees can be stably suppressed.

[4] In the electrical insulating composition according to any one of [1] to [3] above,
The fatty acid amide consists of a fatty acid monoamide.
According to this configuration, it is possible to improve the effect of suppressing the local concentration of water by the polar groups.

[5] In the electrical insulating composition according to any one of [1] to [4] above,
The fatty acid amide comprises an unsaturated fatty acid amide.
According to this configuration, electrons can be trapped in the dispersed unsaturated bond portions (double bonds), and local electric field concentration can be suppressed.

[6] In the electrical insulating composition according to any one of [1] to [5] above,
It has a cross-linking agent containing an organic peroxide.
According to this configuration, the base resin can be crosslinked by the crosslinking agent. This can improve the mechanical and electrical properties of the electrical insulating composition.

[7] In the electrical insulating composition according to any one of [1] to [5] above,
The base resin is crosslinked.
This configuration can improve the mechanical properties and electrical properties of the electrical insulating composition.

[8] In the electrical insulating composition according to any one of [1] to [7] above,
The ratio of the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene to the content of the fatty acid amide is more than 0.5 and less than 15.
According to this configuration, it is possible to obtain a sufficiently pronounced effect of suppressing water tree by both the fatty acid amide and the unsaturated dimer. In addition, it is possible to stably suppress an increase in dielectric loss tangent and a decrease in tensile properties of the insulating layer (a decrease in tensile strength and a decrease in tensile elongation).

[9] A power cable according to another aspect of the present disclosure,
a conductor;
an insulating layer provided to cover the outer periphery of the conductor;
with
The insulating layer contains 100 parts by mass of a base resin containing polyethylene, 0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of an α-aromatic substituted α-methylalkene, and 0.05 parts by mass of a fatty acid amide. 1.0 parts by mass or more and not less than 1.0 parts by mass.
According to this configuration, it is possible to remarkably improve the water tree resistance while ensuring various cable characteristics.

[Details of the embodiment of the present disclosure]
Next, one embodiment of the present disclosure will be described below with reference to the drawings. The present invention is not limited to these exemplifications, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

<One embodiment of the present disclosure>
(1) Electrical insulation composition The electrical insulation composition of the present embodiment is a material that constitutes the insulation layer 130 of the power cable 10 described later. It has saturated dimers, fatty acid amides, and other additives.

The "electrical insulating composition" in the present embodiment includes, for example, an uncrosslinked composition that does not contain a crosslinking agent described later, an uncrosslinked composition that includes a crosslinking agent described later, and a crosslinked It contains the composition in a ready state.

(base resin)
The base resin (base polymer) refers to a resin component that constitutes the main component of the electrical insulating composition. The base resin of this embodiment contains polyethylene, for example.

Examples of polyethylene constituting the base resin include low-density polyethylene (LDPE: density of 0.91 g/cm ³ or more and less than 0.93 g/cm ³ ), linear low-density polyethylene (LLDPE: density of 0.945 g/cm ³ Below) medium density polyethylene (MDPE: density of 0.93 g/cm ³ or more and less than 0.942 g/cm ³ ), high density polyethylene (HDPE: density of 0.942 g/cm ³ or more), and the like. Among these, at least one of LDPE and LLDPE is preferred. As a result, it is possible to improve the mechanical properties while improving the insulation of the power cable.

(Unsaturated dimers of α-aromatic substituted α-methylalkenes)
By adding the unsaturated dimer of α-aromatic substituted α-methylalkene to the electrical insulating composition, it is possible to suppress the occurrence of local scorching in the extrusion process of the electrical insulating composition. . In addition, electrons can be trapped in the aromatic ring of the unsaturated dimer of the α-aromatic substituted α-methylalkene to form a stable resonance structure. These can suppress the occurrence of water trees in the insulating layer 130 . In the following, the unsaturated dimer of α-aromatic substituted α-methylalkene may be abbreviated as "unsaturated dimer".

The α-aromatic substituted α-methylalkene monomer is represented by, for example, the following formula (1).

However, R is either an aryl group, an alkaryl group, a halogen-substituted aryl group, or a halogen-substituted alkaryl group. As used herein, the term "alkaryl group" refers to a combination of one or more aryl groups bonded to one or more alkyl groups.

Specifically, the α-aromatic substituted α-methylalkene monomers include, for example, α-methylstyrene, para-methyl-α-methylstyrene, para-isopropyl-α-methylstyrene, meta-methyl- α-methylstyrene, meta-ethyl-α-methylstyrene, ar-dimethyl-α-methylstyrene, ar-chloro-α-methylstyrene, ar-chloro-ar-methyl-α-methylstyrene, ar-diethyl-α -methylstyrene, ar-methyl-ar-isopropyl-α-methylstyrene and the like.

Unsaturated dimers of α-aromatic substituted α-methylalkenes include, for example, unsaturated dimers of α-methylstyrene (2,4-diphenyl-4-methyl-1-pentene). Two or more of the unsaturated dimer of α-methylstyrene and other unsaturated dimers may be used in combination.

In the present embodiment, the content of the unsaturated dimer of α-aromatic substituted α-methylalkene in the electrical insulating composition is, for example, 0.1 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the base resin. It is below the department.

If the content of the unsaturated dimer is less than 0.1 part by mass, the unsaturated dimer may not be sufficiently effective in suppressing water trees. On the other hand, by setting the content of the unsaturated dimer to 0.1 part by mass or more, it is possible to sufficiently obtain the effect of suppressing water tree by the unsaturated dimer. On the other hand, when the content of the unsaturated dimer exceeds 10 parts by mass, the base resin becomes difficult to crosslink, and the gel fraction of the electrical insulating composition decreases. Therefore, the dielectric loss tangent when a predetermined AC electric field is applied may increase, or the tensile properties of the insulating layer 130 may decrease (at least one of a decrease in tensile strength and a decrease in tensile elongation may occur). There is On the other hand, by setting the content of the unsaturated dimer to 10 parts by mass or less, it is possible to crosslink a predetermined amount of the base resin and suppress the decrease in the gel fraction of the electrical insulating composition. As a result, it is possible to suppress an increase in dielectric loss tangent when a predetermined AC electric field is applied, and to suppress a decrease in tensile properties (reduction in tensile strength and shortening in tensile elongation) of the insulating layer 130 .

(Fatty acid amide)
By adding the fatty acid amide to the electrical insulation composition, the fatty acid amide acts as a lubricant, and the fluidity of the electrical insulation composition in the extrusion process of the insulation layer 130 can be improved. Further, by dispersing the fatty acid amide, the dispersed polar groups (hydrophilic groups) can suppress local concentration of water in the electrical insulating composition. Thereby, the occurrence of water trees in the insulating layer 130 can be suppressed.

Fatty acid amides include, for example, saturated fatty acid monoamides, unsaturated fatty acid monoamides, saturated fatty acid bisamides and unsaturated fatty acid bisamides.

Specifically, saturated fatty acid monoamides include, for example, lauric acid amide, palmitic acid amide, stearic acid amide, and hydroxystearic acid amide.

Examples of unsaturated fatty acid monoamides include oleic acid amide and erucic acid amide.

Examples of saturated fatty acid bisamides include methylenebisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, and hexamethylenebisstearic acid. amide, hexamethylenebishydroxystearic acid amide, N,N'-distearyladipic acid amide and the like.

Examples of unsaturated fatty acid bisamides include ethylenebisoleic acid amide, ethylenebiserucic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipic acid amide, N,N'-dioleylsebacic acid amide, and the like. is mentioned.

Two or more of these fatty acid amides may be used in combination.

In this embodiment, the fatty acid amide added to the electrical insulating composition is preferably fatty acid monoamide, for example. This can improve the polarity of the fatty acid amide. As a result, the effect of suppressing the local concentration of water by the polar groups can be improved.

Moreover, in the present embodiment, the fatty acid amide added to the electrical insulating composition is preferably, for example, an unsaturated fatty acid amide. As a result, electrons can be trapped in the dispersed unsaturated bond portions (double bonds), and local electric field concentration can be suppressed.

In this embodiment, the content of the fatty acid amide in the electrical insulating composition is, for example, 0.05 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the base resin.

If the fatty acid amide content is less than 0.05 part by mass, the fatty acid amide may not be sufficiently effective in suppressing water tree formation. On the other hand, by setting the content of the fatty acid amide to 0.05 parts by mass or more, it is possible to sufficiently obtain the water tree suppressing effect of the fatty acid amide. On the other hand, if the content of the fatty acid amide exceeds 1.0 parts by mass, the fatty acid amide may precipitate on the surface of the insulating layer 130 due to the difference in compatibility between the base resin and the fatty acid amide. There is This phenomenon is called "bloom". On the other hand, by setting the content of the fatty acid amide to 1.0 parts by mass or less, it is possible to suppress the occurrence of bloom due to the difference in compatibility between the base resin and the fatty acid amide.

In this embodiment, by adding both the fatty acid amide and the unsaturated dimer of the α-aromatic substituted α-methylalkene described above, their synergistic action significantly improves the water tree resistance. can be made

In the present embodiment, the ratio B/A of the content B of the unsaturated dimer of the α-aromatic substituted α-methylalkene to the content A of the fatty acid amide (hereinafter also referred to as the content ratio B/A) is For example, it is preferably more than 0.5 and less than 15, more preferably 2 or more and less than 9.

If the content ratio B/A is less than 0.5, there is a possibility that the significant effect of suppressing water tree by both the fatty acid amide and the unsaturated dimer may not be sufficiently obtained. On the other hand, by setting the content ratio B/A to more than 0.5, it is possible to obtain a sufficiently pronounced effect of suppressing water tree by both the fatty acid amide and the unsaturated dimer. Furthermore, by setting the content ratio B/A to 2 or more, it is possible to stably obtain a conspicuous effect of suppressing water tree by both the fatty acid amide and the unsaturated dimer.

On the other hand, when the content ratio B/A is 15 or more, there is a possibility that the fluidity improving effect of the fatty acid amide cannot be sufficiently obtained. Therefore, it becomes difficult to uniformly disperse the unsaturated dimer, and it may become difficult to improve the gel fraction. Moreover, when the content ratio B/A is 15 or more, the effect of suppressing the local concentration of water by the polar group of the fatty acid amide may not be sufficiently obtained. On the other hand, by setting the content ratio B/A to less than 15, the fluidity improving effect of the fatty acid amide can be sufficiently obtained. Thereby, the unsaturated dimer can be uniformly dispersed, and the gel fraction can be stably improved. As a result, it is possible to stably suppress an increase in dielectric loss tangent and a decrease in tensile properties of the insulating layer 130 (a decrease in tensile strength and a decrease in tensile elongation). Further, by setting the content ratio B/A to less than 15, the effect of suppressing the local concentration of water by the polar group of the fatty acid amide can be sufficiently obtained. This makes it possible to obtain a sufficiently pronounced water tree suppression effect by both the fatty acid amide and the unsaturated dimer. Furthermore, by setting the content ratio B/A to less than 9, it is possible to reliably suppress an increase in the dielectric loss tangent and a decrease in the tensile properties of the insulating layer 130 (decrease in tensile strength and shortening in tensile elongation). . In addition, by setting the content ratio B/A to less than 9, it is possible to stably obtain a conspicuous effect of suppressing water tree by both the fatty acid amide and the unsaturated dimer.

(crosslinking agent)
In this embodiment, the base resin of the electrical insulating composition is preferably crosslinked with, for example, a crosslinking agent. This can improve the mechanical properties (such as tensile properties) and electrical properties of the electrical insulating composition.

As a cross-linking agent added to the electrical insulating composition, for example, an organic peroxide is used. Specifically, examples of organic peroxides include dicumyl peroxide, 1-(2-tert-butylperoxyisopropyl)-1-isopropylbenzene, 1-(2-tert-butylperoxyisopropyl)- 3-isopropylbenzene, 1,3-bis-(tert-butylperoxy-isopropyl)benzene, 2,5-dimethyl-2.5-di(t-butylperoxy)hexane, 2,5-dimethyl-2, 5-(tert-butylperoxy)-hexyne-3 and the like. In addition, you may use combining two or more types among these.

(Other additives)
The electrically insulating composition may further comprise an antioxidant, for example.

Examples of antioxidants include 4,4′-thiobis-(6-t-butyl-3-methylphenol), 2,2-thio-diethylenebis[3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate], pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl 3-(3,5-di-t-butyl-4 -hydroxyphenyl)propionate, 2,4-bis-[(octylthio)methyl]-o-cresol, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t- butylanilino)-1,3,5-triazine, bis[2-methyl-4-{3-n-alkyl(C12 or C14)thiopropionyloxy}-5-t-butylphenyl]sulfide and the like. In addition, you may use combining two or more types among these.

The electrical insulating composition may contain a lubricant other than the fatty acid amide described above as a lubricant. Moreover, the electrical insulating composition may further contain, for example, a coloring agent.

(2) Power Cable Next, the power cable of this embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view orthogonal to the axial direction of the power cable according to this embodiment.

The power cable 10 of this embodiment is configured as a so-called solid insulated power cable. Also, the power cable 10 of the present embodiment is configured to be installed underwater or on the bottom of the water, for example. In addition, the power cable 10 is used for alternating current, for example.

Specifically, the power cable 10 has, for example, a conductor 110 , an inner semi-conductive layer 120 , an insulating layer 130 , an outer semi-conductive layer 140 , a shielding layer 150 and a sheath 160 .

Since the power cable 10 of the present embodiment has the above-described remarkable water tree suppressing effect, for example, it has a metal waterproof layer such as a so-called aluminum covering outside the shielding layer 150. do not have. That is, the power cable 10 of this embodiment is configured with a non-perfect waterproof structure.

(Conductor (Conductive part))
The conductor 110 is configured by twisting a plurality of conductor core wires (conductive core wires) containing pure copper, copper alloy, aluminum, aluminum alloy, or the like, for example.

(Internal semi-conductive layer)
The inner semi-conductive layer 120 is provided so as to cover the outer circumference of the conductor 110 . In addition, the inner semiconducting layer 120 has semiconductivity and is configured to suppress electric field concentration on the surface side of the conductor 110 . The inner semi-conductive layer 120 is conductive with at least one of, for example, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-vinyl acetate copolymer, and the like. of carbon black and

(insulating layer)
The insulating layer 130 is provided so as to cover the outer periphery of the inner semiconductive layer 120 and is made of the electrical insulating composition described above. Insulating layer 130 is crosslinked, for example, by heating after the electrical insulating composition has been extruded, as described above.

(outer semiconducting layer)
The external semi-conductive layer 140 is provided so as to cover the outer circumference of the insulating layer 130 . In addition, the outer semiconductive layer 140 is semiconductive and configured to suppress electric field concentration between the insulating layer 130 and the shielding layer 150 . The outer semi-conductive layer 140 is made of the same material as the inner semi-conductive layer 120, for example.

(shielding layer)
The shielding layer 150 is provided so as to cover the outer periphery of the outer semi-conductive layer 140 . The shielding layer 150 is configured by, for example, winding a copper tape, or is configured as a wire shield by winding a plurality of annealed copper wires or the like. A tape made of rubber-coated cloth or the like may be wound around the inside or outside of the shielding layer 150 .

(sheath)
The sheath 160 is provided so as to cover the outer circumference of the shielding layer 150 . The sheath 160 is made of polyvinyl chloride or polyethylene, for example.

(water tree resistance)
In this embodiment, as described above, both the unsaturated dimer of the α-aromatic substituted α-methylalkene and the fatty acid amide are added to the insulating layer 130, so that the water content of the insulating layer 130 increases. Tree resistance is remarkably improved.

Specifically, in the present embodiment, the electrical insulating composition constituting the insulating layer 130 is immersed in a 1 N NaCl aqueous solution at room temperature (27° C.), and the electrical insulating composition is subjected to a commercial frequency (for example, The maximum length of water trees generated in the electrical insulating composition when an AC electric field of 4 kV/mm (60 Hz) is applied for 1000 hours is, for example, less than 200 μm, preferably 180 μm or less. Thereby, dielectric breakdown of the insulating layer 130 caused by water trees can be stably suppressed.

The maximum length of water trees generated in the electrical insulating composition is not limited, because the shorter the better. However, in this embodiment, since a predetermined amount of water trees can be generated by the above test, the maximum length of water trees generated in the electrical insulating composition is, for example, 30 μm or more.

Further, in the present embodiment, the electrical insulating composition constituting the insulating layer 130 is immersed in a 1 N NaCl aqueous solution at room temperature (27° C.), and the commercial frequency (eg, 60 Hz) 4 kV is applied to the electrical insulating composition. /mm is applied for 1000 hours, the concentration of the number of water trees generated in the electrical insulating composition and having a length of 30 μm or more is, for example, less than 200/cm ³ , preferably 150/mm. cm ³ or less. Thereby, dielectric breakdown of the insulating layer 130 caused by water trees can be stably suppressed.

The concentration of the number of water trees generated is not limited because the lower the number, the better. However, in this embodiment, since a predetermined amount of water trees can be generated by the above test, the concentration of the number of water trees generated is, for example, 10/cm ³ or more.

(Gel fraction (degree of cross-linking))
In this embodiment, the insulating layer 130 is, for example, crosslinked, as described above. In addition, by setting the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene to 10 parts by mass or less in the electrical insulating composition constituting the insulating layer 130, the gel content of the electrical insulating composition rate decline has been curbed.

Specifically, in the present embodiment, the gel fraction of the electrical insulating composition forming the insulating layer 130 is, for example, more than 68%, preferably 70% or more, and more preferably 74% or more.

The gel fraction of the electrical insulating composition is not particularly limited because the higher the better. However, since the electrical insulating composition contains a predetermined amount of unsaturated dimer of α-aromatic substituted α-methylalkene, the gel fraction of the electrical insulating composition is, for example, 95% or less.

(Dielectric loss tangent)
Here, loss can occur when an alternating electric field is applied to the electrically insulating composition. The loss when an AC electric field is applied includes, for example, leakage current loss, dielectric polarization loss, and partial discharge loss. Due to such losses, the current phase lags behind the lossless current flowing in an ideal electrical insulating composition. The delay angle δ in this case is called the dielectric loss angle, and the tangent is called the dielectric loss tangent (tan δ).

In the present embodiment, the gel fraction of the electrical insulating composition forming the insulating layer 130 is equal to or higher than the predetermined value as described above, so that the dielectric loss tangent becomes small.

Specifically, in the present embodiment, the dielectric loss tangent when an alternating electric field of 9 kV/mm is applied at 90° C. to the electrical insulating composition constituting the insulating layer 130 is, for example, 0.05% or less. .

Note that the dielectric loss tangent is not limited because the smaller the better. However, the electrical insulating composition of the present embodiment has a dielectric loss of, for example, 0.001% or more.

(AC breakdown electric field)
In the present embodiment, the gel fraction of the electrical insulating composition forming the insulating layer 130 is equal to or higher than the predetermined value as described above, thereby ensuring a predetermined AC breakdown electric field.

Specifically, in the present embodiment, the AC breakdown electric field of the electrical insulating composition constituting the insulating layer 130 measured at room temperature (27° C.) is, for example, 55 kV/mm or more, preferably 61 kV/mm or more, or more. Preferably it is 64 kV/mm or more.

Note that the AC breakdown electric field is not particularly limited because the larger the AC breakdown electric field, the better. However, in the electrical insulating composition of the present embodiment, the AC breakdown electric field is, for example, 100 kV/mm or less.

(tensile properties)
In the present embodiment, the gel fraction of the electrical insulating composition forming the insulating layer 130 is equal to or higher than the predetermined value as described above, so that the tensile properties of the electrical insulating composition can be improved.

Specifically, in this embodiment, the tensile strength of the electrical insulating composition forming the insulating layer 130 is, for example, 12.5 MPa or more, preferably 14 MPa or more.

The tensile strength of the electrical insulating composition is not particularly limited because the higher the tensile strength, the better. However, the electrical insulating composition of the present embodiment has a tensile strength of, for example, 50 MPa or less.

Moreover, in the present embodiment, the tensile elongation of the electrical insulating composition forming the insulating layer 130 is, for example, 350% or more, preferably 380% or more, and more preferably 430% or more.

The tensile elongation of the electrical insulating composition is not particularly limited, because the higher the tensile elongation, the better. However, the electrical insulating composition of this embodiment has a tensile elongation of, for example, 1000% or less.

Thus, in this embodiment, predetermined tensile properties can be secured. Thereby, even in an environment where the power cable 10 expands, contracts, or bends, the power cable 10 can be laid appropriately. Specifically, the power cable 10 of the present embodiment can be applied to, for example, an array cable (dynamic cable, riser cable) that is bendably connected to a floating facility underwater.

(Bloom)
In the present embodiment, as described above, by setting the content of the fatty acid amide to 1.0 parts by mass or less, bloom due to the difference in compatibility between the base resin and the fatty acid amide occurs on the surface of the insulating layer 130. Not detected.

(Specific dimensions, etc.)
Although specific dimensions of the power cable 10 are not particularly limited, for example, the diameter of the conductor 110 is 5 mm or more and 60 mm or less, and the thickness of the inner semiconductive layer 120 is 0.5 mm or more and 3 mm or less. , the thickness of the insulating layer 130 is 1 mm or more and 35 mm or less, the thickness of the outer semi-conductive layer 140 is 0.5 mm or more and 3 mm or less, the thickness of the shielding layer 150 is 1 mm or more and 5 mm or less, and the sheath The thickness of 160 is 1 mm or more. The AC voltage applied to the power cable 10 of this embodiment is, for example, 20 kV or more.

(3) Method for Manufacturing Power Cable Next, a method for manufacturing the power cable of the present embodiment will be described. Hereinafter, the step is abbreviated as "S".

(S100: electrical insulation composition preparation step)
First, an electrical insulating composition is prepared.

In the present embodiment, a base resin containing polyethylene, an unsaturated dimer of α-aromatic substituted α-methylalkene, a fatty acid amide, and other additives (crosslinking agent, antioxidant, etc.) are mixed in a Banbury mixer. Mix (knead) with a mixer such as a kneader to form a mixed material. At this time, the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene is, for example, 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the base resin. Also, the content of the fatty acid amide is, for example, 0.05 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the base resin.

After forming the mixed material, the mixed material is granulated by an extruder. Thereby, a pellet-shaped electrical insulating composition that will constitute the insulating layer 130 is formed. The steps from mixing to granulation may be performed collectively using a twin-screw extruder with a high kneading action.

(S200: conductor preparation step)
Meanwhile, a conductor 110 formed by twisting a plurality of conductor core wires is prepared.

(S300: Cable core forming step (extrusion step))
When the electrical insulating composition preparation step S100 and the conductor preparation step S200 are completed, among the three-layer co-extruders, the extruder A that forms the inner semi-conductive layer 120 is loaded with, for example, an ethylene-ethyl acrylate copolymer and a conductive and the composition for the inner semi-conductive layer pre-mixed with the carbon black of .

The above pellet-shaped electrical insulating composition is charged into extruder B for forming insulating layer 130 .

The extruder C for forming the outer semiconductive layer 140 is charged with the outer semiconductive layer composition containing the same material as the inner semiconductive layer electrically insulating composition charged in the extruder A.

Next, the respective extrudates from extruders A to C are led to a common head, and the inner semiconductive layer 120, the insulating layer 130 and the outer semiconductive layer 140 are simultaneously formed on the outer periphery of the conductor 110 from the inside to the outside. Extrude.

After extrusion, at least the insulating layer 130 is crosslinked by heating with radiation from an infrared heater or transferring heat through a heat medium such as high-temperature nitrogen gas or silicone oil in a crosslinking tube pressurized by nitrogen gas or the like. Let After that, the cable core after cross-linking is cooled with water, for example.

Through the cable core forming step S300 described above, a cable core composed of the conductor 110, the inner semiconductive layer 120, the insulating layer 130 and the outer semiconductive layer 140 is formed.

(S400: shielding layer forming step)
Once the cable core is formed, a shielding layer 150 is formed on the outside of the outer semi-conductive layer 140, for example by wrapping a copper tape.

(S500: Sheath forming step)
After the shielding layer 150 is formed, the sheath 160 is formed around the outer periphery of the shielding layer 150 by putting vinyl chloride into an extruder and extruding it.

As described above, the power cable 10 as a solid insulated power cable is manufactured.

(4) Effects According to the Present Embodiment According to the present embodiment, one or more of the following effects can be obtained.

(a) In the present embodiment, by adding an unsaturated dimer of α-aromatic substituted α-methylalkene to the electrical insulating composition, local scorching is prevented during the extrusion process of the electrical insulating composition. can be suppressed. As a result, formation of local electric field concentrations due to scorch can be suppressed. Further, by adding the unsaturated dimer of the α-aromatic substituted α-methylalkene to the electrically insulating composition, electrons are added to the aromatic ring of the unsaturated dimer of the α-aromatic substituted α-methylalkene. can be trapped to form a stable resonance structure. This can suppress the local deviation of electrons, that is, suppress the formation of a local electric field concentration portion. By suppressing the formation of local electric field concentration portions, it is possible to suppress aggregation of water in the electric field concentration portions. As a result, it is possible to suppress the occurrence of dynamic strain due to the water condensation portion. As a result, the occurrence of water trees in the insulating layer 130 can be suppressed.

(b) In the present embodiment, by adding fatty acid amide to the electrical insulation composition, the fatty acid amide acts as a lubricant, and the fluidity of the electrical insulation composition in the extrusion process of the insulation layer 130 can be improved. . Thereby, each material in the electrical insulating composition can be uniformly dispersed. By uniformly dispersing the fatty acid amide in the electrical insulating composition, the polar groups (hydrophilic groups) of the fatty acid amide can be dispersed. As a result, the polar groups disperse water that has entered the electrical insulating composition, and local concentration of water in the electrical insulating composition can be suppressed. By suppressing the local concentration of water, it is possible to suppress the occurrence of dynamic strain caused by the water concentration portion (water condensation portion). As a result, the occurrence of water trees in the insulating layer 130 can be suppressed.

(c) According to the present embodiment, the synergistic effects of (a) and (b) described above can significantly improve water tree resistance.

Here, when only one of the unsaturated dimer of the α-aromatic substituted α-methylalkene and the fatty acid amide is added to the electrical insulating composition, the number of water trees generated in the insulating layer 130 is Although the density is somewhat reduced, the maximum length of water trees that occur in the insulating layer 130 may not be shortened.

In contrast, in the present embodiment, by adding both the unsaturated dimer of the α-aromatic substituted α-methylalkene and the fatty acid amide to the electrical insulating composition, the above (a) and ( The synergistic effect of b) can be obtained. That is, the addition of the fatty acid amide can improve the fluidity of the electrical insulating composition and uniformly disperse the unsaturated dimer of the α-aromatic substituted α-methylalkene in the electrical insulating composition. By uniformly dispersing the unsaturated dimer, the electron trapping effect of the aromatic ring of the unsaturated dimer can be uniformly exhibited, stably suppressing the formation of local electric field concentration areas. can be done. Furthermore, by dispersing water that has penetrated into the electrical insulating composition by means of the polar groups of the fatty acid amide, it is possible to reduce the probability of water concentrating in local electric field concentration areas. Thereby, the generation of water trees in the insulating layer 130 can be stably suppressed. As a result, in this embodiment, the maximum length of water trees generated in the insulating layer 130 can be shortened, and the number density of water trees generated in the insulating layer 130 can be significantly reduced.

By significantly improving the water tree resistance in this way, it can be suitably applied to underwater cables or submarine cables that are constantly exposed to water. Also, by significantly improving the water tree resistance, the configuration of the impermeable layer of the power cable 10 can be simplified. For example, the impermeable layer can be eliminated, or the shielding layer can be configured simply. As a result, the cost of the power cable 10 can be reduced.

(d) By adjusting the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene to 0.1 part by mass or more, the unsaturated dimer can sufficiently suppress the water tree. . On the other hand, by setting the content of the unsaturated dimer to 10 parts by mass or less, it is possible to crosslink a predetermined amount of the base resin and suppress a decrease in the gel fraction of the electrical insulating composition. As a result, it is possible to suppress an increase in dielectric loss tangent when a predetermined AC electric field is applied, and to suppress a decrease in tensile properties (reduction in tensile strength and shortening in tensile elongation) of the insulating layer 130 .

(e) By setting the content of the fatty acid amide to 0.05 parts by mass or more, it is possible to sufficiently obtain the water tree suppressing effect of the fatty acid amide. On the other hand, by setting the content of the fatty acid amide to 1.0 parts by mass or less, it is possible to suppress the occurrence of bloom due to the difference in compatibility between the base resin and the fatty acid amide.

According to the present embodiment, as described in (a) to (e) above, it is possible to improve the water tree resistance while securing various cable properties (electrical properties, tensile properties, and bloom suppression properties). .

(f) The fatty acid amide added to the electrical insulating composition is preferably a fatty acid monoamide. This can improve the polarity of the fatty acid amide. By improving the polarity of the fatty acid amide, the effect of suppressing the local concentration of water by the polar group can be improved. As a result, the generation of water trees in the insulating layer 130 can be stably suppressed.

(g) The fatty acid amide added to the electrical insulating composition is preferably an unsaturated fatty acid amide. As a result, electrons can be trapped in the dispersed unsaturated bond portions (double bonds), and local electric field concentration can be suppressed. By suppressing the formation of local electric field concentration portions, it is possible to suppress aggregation of water in the electric field concentration portions. As a result, the generation of water trees in the insulating layer 130 can be stably suppressed.

<Other embodiments of the present disclosure>
Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present disclosure.

In the above-described embodiment, the case where the base resin contains polyethylene has been described, but the present disclosure is not limited to this case. For example, the base resin may contain an ethylene copolymer. Examples of ethylene copolymers include ethylene-propylene copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-vinyl acetate copolymers, and the like. Two or more of these may be used in combination. By including the ethylene copolymer in the base resin, the dispersibility of the unsaturated dimer of the α-aromatic substituted α-methylalkene and the fatty acid amide can be improved when the electrical insulating composition is mixed.

In the above-described embodiment, a case where the power cable 10 does not have a waterproof layer has been described, but the present disclosure is not limited to this case. The power cable 10 may have a simple impermeable layer due to the remarkable water tree suppression effect described above. Specifically, a simple waterproof layer is made of, for example, a metal laminate tape. A metal laminate tape has, for example, a metal layer made of aluminum, copper, or the like, and an adhesive layer provided on one side or both sides of the metal layer. The metal laminate tape is, for example, wound vertically so as to surround the outer circumference of the cable core (more outer circumference than the outer semiconductive layer). The impermeable layer may be provided outside the shielding layer, or may also serve as the shielding layer. With such a configuration, the cost of the power cable 10 can be reduced.

Although the above-described embodiment describes the case where the power cable 10 is configured to be laid underwater or on the bottom of the water, the present disclosure is not limited to this case. For example, the power cable 10 may be configured as a so-called overhead wire (aerial insulated wire).

Next, examples according to the present disclosure will be described. These examples are examples of the present disclosure, and the present disclosure is not limited by these examples.

(1) Preparation of Electrical Insulating Composition Materials of the following samples A1 to A8 and B1 to B7 were mixed by an open roll at 120° C. to obtain electrical insulating compositions.

[Samples A1 to A8]
(base resin)
Low Density Polyethylene (LDPE):
(Density d=0.92 g/cm ³ , MFR=1.0 g/10 min) 100 parts by mass (unsaturated dimer)
Unsaturated dimer of α-methylstyrene (2,4-diphenyl-4-methyl-1-pentene): 0.12 parts by mass or more and 8 parts by mass or less (fatty acid amide)
Stearic acid amide, oleic acid amide, erucic acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide: 0.06 parts by mass or more and 0.9 parts by mass or less (crosslinking agent)
Dicumyl peroxide: 2 parts by mass, or 2,5-dimethyl-2,5-di(t-butylperoxy)hexane: 1.3 parts by mass (antioxidant)
4,4'-thiobis-(6-t-butyl-3-methylphenol): 0.2 parts by mass

[Sample B1]
Made similarly to sample A3 except that it did not contain unsaturated dimers and fatty acid amides.
[Sample B2]
It was prepared in the same manner as sample A3, except that it did not contain fatty acid amide.
[Sample B3]
Prepared similarly to sample A3, except that it does not contain unsaturated dimers.
[Sample B4]
It was prepared in the same manner as sample A3, except that the unsaturated dimer content was 0.05 parts by mass.
[Sample B5]
It was prepared in the same manner as sample A3, except that the unsaturated dimer content was 12 parts by mass.
[Sample B6]
It was prepared in the same manner as sample A3, except that the content of fatty acid amide was 0.02 parts by mass.
[Sample B7]
It was prepared in the same manner as sample A3, except that the content of fatty acid amide was 1.5 parts by mass.

(2) Evaluation Using the electrical insulating composition described above, an insulating sheet was produced according to each evaluation, and each evaluation was performed.

(Evaluation 1: water tree resistance)
After forming the above electrical insulating composition, the electrical insulating composition was pressed by press molding at 120° C. for 10 minutes to prepare two insulating sheets having a thickness of 1 mm. After the insulating sheets were produced, a predetermined semiconductive sheet was sandwiched between two insulating sheets to form a laminated sheet. After forming the laminated sheet, the base resin of the insulating sheet was crosslinked by pressing the laminated sheet at 180° C. for 30 minutes by press molding. Once the insulating sheets were crosslinked, wiring was formed to the semiconducting sheets.

Next, while the laminated sheet was immersed in a 1 N NaCl aqueous solution at room temperature (27° C.), an alternating electric field of 60 Hz and 4 kV/mm was applied to the insulating sheet between the semiconductive sheet and the aqueous solution for 1000 hours.

After applying a predetermined AC electric field, the laminated sheet was dried and boiled and dyed with an aqueous methylene blue solution. After dyeing the laminated sheet, the laminated sheet was sliced at a thickness of 30 μm along the lamination direction (that is, the direction orthogonal to the main surface of the laminated sheet) to form observation slices. After that, the observation slice was observed with an optical microscope to observe water trees generated in the creepage direction of the semiconductive sheet or in the direction perpendicular to the main surface of the semiconducting sheet in the insulating sheet of the observation slice. At this time, the maximum length of water trees generated in the insulating sheet was measured. Also, the concentration of the number of water trees generated in the insulating sheet and having a length of 30 μm or more was measured. In Tables 1 and 2 below, the "maximum water tree length" is obtained by rounding off the length of the longest water tree in 10 randomly selected slices for observation. The "number concentration of water trees" was obtained by rounding off the average value of the number concentration of water trees in 10 randomly sampled slices for observation.

For reference, in the conventional evaluation of water tree resistance, a power cable having an insulating layer made of a predetermined electrical insulating composition is produced, and the power cable is immersed in water to evaluate water tree resistance. . At this time, a shielding layer and a sheath were provided outside the insulating layer of the power cable. Therefore, the insulating layer did not come into direct contact with water. On the other hand, in this example, as described above, the laminated sheet was directly immersed in a predetermined aqueous solution to evaluate the water tree. Therefore, the insulating sheet was brought into direct contact with the aqueous solution. Therefore, the evaluation of water tree resistance in this example was conducted under stricter conditions than the evaluation using the conventional power cable.

(Evaluation 2: Dielectric loss tangent)
After forming the above electrical insulating composition, the electrical insulating composition was pressed by press molding at 180° C. for 30 minutes to prepare an insulating sheet having a thickness of 0.2 mm. At this time, the base resin of the insulating sheet was crosslinked by pressing the insulating sheet at 180° C. for 30 minutes.

Next, using a Schering bridge, an AC electric field of 9 kV/mm was applied to the insulating sheet at 90° C., and the dielectric loss tangent was measured.

(Evaluation 3: AC breakdown electric field)
An insulating sheet similar to Evaluation 2 above was produced. Next, at room temperature (27° C.), an AC voltage of 5 kV was applied to the insulating sheet for 1 minute. After that, a cycle of increasing the AC voltage to the insulating sheet by 1 kV and applying the AC voltage to the insulating sheet for 1 minute was repeated. Then, the electric field was measured when dielectric breakdown occurred in the insulating sheet.

(Evaluation 4: Gel fraction (degree of cross-linking))
After forming the above electrical insulating composition, the electrical insulating composition was pressed by press molding at 180° C. for 30 minutes to prepare an insulating sheet having a thickness of 1 mm. At this time, the base resin of the insulating sheet was crosslinked by pressing the insulating sheet at 180° C. for 30 minutes.

After preparing the insulating sheet, the gel fraction was measured according to JIS C3005. Specifically, first, the mass of the insulating sheet was measured. Next, the insulating sheet was immersed in a predetermined solvent (for example, hot xylene) to dissolve the insulating sheet. At this time, the portion of the insulating sheet where the base resin was crosslinked remained as a gel without dissolving. After dissolving the insulating sheet, the mass of the gel remaining without dissolving was measured. As a result, the "gel fraction" was obtained by calculating the ratio (%) of the remaining gel mass to the mass of the insulating sheet before dissolution.

(Evaluation 5: Tensile properties)
An insulating sheet similar to Evaluation 4 above was produced. Next, the tensile strength and tensile elongation of the insulating sheet were measured according to JIS C3005. Specifically, using a JIS-3 dumbbell, the insulating sheet was pulled at a tensile speed of 200 mm/min to measure the tensile strength and tensile elongation of the insulating sheet.

(Evaluation 6: Bloom)
After holding the pellets of the electrical insulating composition in a constant temperature bath at 80° C. for 10 days, the surfaces thereof were visually observed. The presence or absence of bloom precipitated on the pellet surface was evaluated by observing the pellet. A case where no bloom occurred was rated as "A", and a case where bloom occurred was rated as "B".

(3) Results Using Tables 1 and 2 below, the results of evaluating each sample will be described. In Table 1 below, the unit for the content of the compounding agent is "parts by mass".

As shown in Table 2, sample B1, in which neither the unsaturated dimer nor the fatty acid amide was added, had a high number concentration of water trees and a long maximum water tree length. In samples B2 and B3, to which only one of the unsaturated dimer and the fatty acid amide was added, the concentration of the number of water trees generated was lower than that of sample B1, but the maximum length of the water tree was lower than that of sample B1. was as long as

In contrast, as shown in Table 1, in samples A1 to A8 to which both unsaturated dimers and fatty acid amides were added, the number concentration of water trees generated was significantly lower than in samples B1 to B3. , 150/cm ³ or less. Further, in samples A1 to A8, the maximum water tree length was shorter than in samples B1 to B3, and was 180 μm or less.

According to these results, the addition of both unsaturated dimers and fatty acid amides could shorten the maximum length of water trees generated in the insulating layer due to their synergistic effects. In addition, it was confirmed that the density of the number of water trees generated in the insulating layer could be significantly reduced.

Further, as shown in Table 2, in sample B4 in which the content of the unsaturated dimer was less than 0.1 parts by mass, the concentration of the number of water trees generated was lower than in sample B1, but 200 / cm ³ or more. Also, in sample B4, the maximum length of the water tree was slightly shorter than each of samples B1 to B3, but was over 200 μm.

On the other hand, as shown in Table 1, in samples A1 to A8 in which the unsaturated dimer content was 0.1 parts by mass or more, the number concentration of water trees generated was significantly lower than in sample B4. was Also, in samples A1 to A8, the maximum water tree length was shorter than in sample B4.

According to these results, it was confirmed that the water tree suppressing effect of the unsaturated dimer was sufficiently obtained by setting the content of the unsaturated dimer to 0.1 parts by mass or more.

Moreover, as shown in Table 2, sample B5, in which the content of the unsaturated dimer exceeded 10 parts by mass, had a low gel fraction. Therefore, sample B5 had a large dielectric loss tangent and a low AC breakdown electric field. Moreover, in sample B5, the tensile properties were degraded.

On the other hand, as shown in Table 1, samples A1 to A8, in which the unsaturated dimer content was 10 parts by mass or less, had a gel fraction higher than that of sample B5, ie, 74% or more. As a result, the samples A1 to A8 had a dielectric loss tangent smaller than that of the sample B5, which was 0.05 or less. Further, samples A1 to A8 had an AC breakdown electric field higher than that of sample B5, ie, 64 kV/mm or more. Further, samples A1 to A8 had improved tensile properties as compared to sample B5. Specifically, samples A1 to A8 had a tensile strength of 14 MPa or more and a tensile elongation of 430% or more.

According to these results, by setting the content of the unsaturated dimer to 10 parts by mass or less, it is possible to crosslink a predetermined amount of the base resin and suppress a decrease in the gel fraction of the electrical insulating composition. I confirmed that. As a result, it was confirmed that an increase in dielectric loss tangent when a predetermined AC electric field was applied could be suppressed, and a decrease in tensile properties of the insulating layer could be suppressed.

Further, as shown in Table 2, in sample B6 in which the content of fatty acid amide was less than 0.05 parts by mass, the concentration of the number of water trees generated was lower than in sample B1, but was 200/cm ³ . That was it. Also, in sample B6, the maximum length of the water tree was slightly shorter than each of samples B1 to B3, but was greater than 200 μm.

On the other hand, as shown in Table 1, in samples A1 to A8 in which the fatty acid amide content was 0.05 parts by mass or more, the concentration of the number of water trees generated was significantly lower than in sample B6. Also, in samples A1 to A8, the maximum water tree length was shorter than in sample B6.

According to these results, it was confirmed that the fatty acid amide content of 0.05 parts by mass or more was able to sufficiently obtain the water tree suppressing effect of the fatty acid amide.

Further, as shown in Table 2, bloom occurred in sample B7 in which the content of fatty acid amide exceeded 1.0 parts by mass.

On the other hand, as shown in Table 1, bloom did not occur in samples A1 to A8 in which the content of fatty acid amide was 1.0 parts by mass or less.

According to these results, by setting the content of the fatty acid amide to 1.0 parts by mass or less, it was possible to suppress the occurrence of bloom due to the difference in compatibility between the base resin and the fatty acid amide. confirmed.

Further, as shown in Table 1, in samples A1 to A8, the ratio B/A of the content B of the unsaturated dimer of the α-aromatic substituted α-methylalkene to the content A of the fatty acid amide was 0. It was more than 0.5 and less than 15. By setting the content ratio B/A to more than 0.5, as described above, both the fatty acid amide and the unsaturated dimer were able to stably obtain a conspicuous water tree suppressing effect. It was confirmed. Moreover, it was confirmed that by setting the content ratio B/A to less than 15, the unsaturated dimer could be uniformly dispersed, and the decrease in the gel fraction could be stably suppressed. As a result, it was confirmed that an increase in dielectric loss tangent and a decrease in tensile properties of the insulating layer could be stably suppressed. Further, by setting the content ratio B/A to less than 15, the effect of suppressing the local concentration of water by the polar group of the fatty acid amide enhances the conspicuous effect of suppressing water tree by both the fatty acid amide and the unsaturated dimer. I made sure I got enough.

As described above, according to the samples A1 to A8, it was possible to confirm a remarkable water tree suppressing effect under severe conditions in which the insulating sheet was brought into direct contact with the aqueous solution. Therefore, it was confirmed that the generation of water trees in the insulating layer can be stably suppressed by producing a power cable having an insulating layer composed of each of the electrical insulating compositions of Samples A1 to A8.

<Preferred Embodiment of the Present Disclosure>
Preferred embodiments of the present disclosure will be added below.

(Appendix 1)
100 parts by mass of a base resin containing polyethylene,
0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene;
0.05 parts by mass or more and 1.0 parts by mass or less of fatty acid amide;
An electrical insulating composition having

(Appendix 2)
The electrical insulating composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was immersed in a 1 N NaCl aqueous solution at room temperature. When an AC electric field with a commercial frequency of 4 kV / mm is applied for 1000 hours,
2. The electrical insulating composition according to Claim 1, wherein the maximum length of water trees generated in the electrical insulating composition is less than 200 μm.

(Appendix 3)
The electrical insulating composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was immersed in a 1 N NaCl aqueous solution at room temperature. When an AC electric field with a commercial frequency of 4 kV / mm is applied for 1000 hours,
3. The electrical insulating composition according to Supplementary Note 1 or 2, wherein the concentration of the number of water trees generated in the electrical insulating composition and having a length of 30 μm or more is less than 200/cm ³ .

(Appendix 4)
3. The electrical insulating composition according to any one of appendices 1 to 3, wherein the fatty acid amide is a fatty acid monoamide.

(Appendix 5)
5. The electrical insulating composition according to any one of appendices 1 to 4, wherein the fatty acid amide is an unsaturated fatty acid amide.

(Appendix 6)
6. The electrical insulating composition according to any one of appendices 1 to 5, having a cross-linking agent comprising an organic peroxide.

(Appendix 7)
6. The electrical insulating composition according to any one of appendices 1 to 5, wherein the base resin is crosslinked.

(Appendix 8)
Any one of Appendices 1 to 7, wherein the ratio of the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene to the content of the fatty acid amide is more than 0.5 and less than 15 The electrical insulating composition described.

(Appendix 9)
a conductor;
an insulating layer provided to cover the outer periphery of the conductor;
with
The insulating layer contains 100 parts by mass of a base resin containing polyethylene, 0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of an α-aromatic substituted α-methylalkene, and 0.05 parts by mass of a fatty acid amide. A power cable composed of an electrical insulating composition having at least 1.0 part by mass and at most 1.0 part by mass.

(Appendix 10)
providing an electrically insulating composition;
forming an insulating layer so as to cover the outer periphery of the conductor using the electrical insulating composition;
with
In the step of preparing the electrical insulating composition,
100 parts by mass of a base resin containing polyethylene, 0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene, and 0.05 parts by mass or more of a fatty acid amide1. A method for producing a power cable, comprising mixing 0 parts by mass or less and forming the electrical insulating composition.

10 power cable 110 conductor 120 inner semi-conducting layer 130 insulating layer 140 outer semi-conducting layer 150 shielding layer 160 sheath

Claims (12)

100 parts by mass of a base resin made of at least one of low-density polyethylene and linear low-density polyethylene;
0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene;
0.05 parts by mass or more and 1.0 parts by mass or less of fatty acid amide;
has
The electrical insulating composition, wherein the ratio of the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene to the content of the fatty acid amide is more than 0.5 and less than 15. The electrical insulation composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was directly immersed in a 1 N NaCl aqueous solution at room temperature, and the electrical When an alternating electric field with a commercial frequency of 4 kV / mm was applied to the insulating composition for 1000 hours,
2. The electrical insulating composition of claim 1, wherein the maximum length of water trees occurring in said electrical insulating composition is less than 200 [mu]m. 100 parts by mass of a base resin made of at least one of low-density polyethylene and linear low-density polyethylene;
0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene;
0.05 parts by mass or more and 1.0 parts by mass or less of fatty acid amide;
has
The electrical insulation composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was directly immersed in a 1 N NaCl aqueous solution at room temperature, and the electrical When an alternating electric field with a commercial frequency of 4 kV / mm was applied to the insulating composition for 1000 hours,
The electrical insulating composition, wherein the maximum length of water trees generated in the electrical insulating composition is less than 200 μm. The electrical insulation composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was directly immersed in a 1 N NaCl aqueous solution at room temperature, and the electrical When an alternating electric field with a commercial frequency of 4 kV / mm was applied to the insulating composition for 1000 hours,
The electrical insulating composition according to any one of claims 1 to 3, wherein the number concentration of water trees generated in the electrical insulating composition and having a length of 30 µm or more is less than 200/ ^cm3 . thing. 100 parts by mass of a base resin made of at least one of low-density polyethylene and linear low-density polyethylene;
0.1 parts by mass or more and 10 parts by mass or less of an unsaturated dimer of α-aromatic substituted α-methylalkene;
0.05 parts by mass or more and 1.0 parts by mass or less of fatty acid amide;
has
The electrical insulation composition containing the base resin, the unsaturated dimer of the α-aromatic substituted α-methylalkene, and the fatty acid amide was directly immersed in a 1 N NaCl aqueous solution at room temperature, and the electrical When an alternating electric field with a commercial frequency of 4 kV / mm was applied to the insulating composition for 1000 hours,
The electrical insulating composition, wherein the concentration of the number of water trees generated in the electrical insulating composition and having a length of 30 μm or more is less than 200/cm ³ . 6. The electrical insulating composition according to any one of claims 1 to 5, wherein the fatty acid amide comprises a fatty acid monoamide. 7. The electrical insulating composition according to any one of claims 1 to 6, wherein said fatty acid amide comprises an unsaturated fatty acid amide. 8. The electrical insulating composition according to any one of claims 1 to 7, having a cross-linking agent comprising an organic peroxide. 8. The electrical insulating composition according to any one of claims 1 to 7, wherein the base resin is crosslinked. a conductor;
an insulating layer provided to cover the outer periphery of the conductor;
with
The insulating layer contains 100 parts by mass of a base resin made of at least one of low-density polyethylene and linear low-density polyethylene, and 0.1 mass of an unsaturated dimer of α-aromatic substituted α-methylalkene. part or more and 10 parts by mass or less and fatty acid amide in an amount of 0.05 part by mass or more and 1.0 part by mass or less,
A power cable, wherein the ratio of the content of the unsaturated dimer of the α-aromatic substituted α-methylalkene to the content of the fatty acid amide in the electrical insulation composition is more than 0.5 and less than 15. a conductor;
an insulating layer provided to cover the outer periphery of the conductor;
with
The insulating layer contains 100 parts by mass of a base resin made of at least one of low-density polyethylene and linear low-density polyethylene, and 0.1 mass of an unsaturated dimer of α-aromatic substituted α-methylalkene. part or more and 10 parts by mass or less and fatty acid amide in an amount of 0.05 part by mass or more and 1.0 part by mass or less,
When the electrical insulating composition is directly immersed in a 1 N NaCl aqueous solution at room temperature and an AC electric field with a commercial frequency of 4 kV/mm is applied to the electrical insulating composition for 1000 hours,
A power cable wherein the maximum length of water trees occurring in said electrical insulating composition is less than 200 μm. a conductor;
an insulating layer provided to cover the outer periphery of the conductor;
with
The insulating layer contains 100 parts by mass of a base resin made of at least one of low-density polyethylene and linear low-density polyethylene, and 0.1 mass of an unsaturated dimer of α-aromatic substituted α-methylalkene. part or more and 10 parts by mass or less and fatty acid amide in an amount of 0.05 part by mass or more and 1.0 part by mass or less,
When the electrical insulating composition is directly immersed in a 1 N NaCl aqueous solution at room temperature and an AC electric field with a commercial frequency of 4 kV/mm is applied to the electrical insulating composition for 1000 hours,
The electric power cable, wherein the number concentration of water trees having a length of 30 μm or more generated in the electrical insulation composition is less than 200/cm ³ .

Images