JP2000207939A - Electric insulating composition and electric wire cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric insulating composition superior in dielectric breakdown strength as an insulating material and water-tight tree resistance, and an electric cable using it. SOLUTION: An electrical insulating composition (insulating material) 2 is composed by using as a main ingredient straight chain polyethylene which has density of not more than 0.915 g/cm3, a melt index of not more than 5 g/10 min and a melting point of not less than 120 deg.C and is polymerized by using propylene as a copolymer or a blended polymer of the straight chain polyethylene and an ethylene copolymer. An insulating layer comprising such electric insulating composition 2 is provided on the conductor of an electric cable or conductor shielding layer. The insulating layer may be bridged, and thereby thermal deformation rate can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrically insulating composition and an electric wire / cable.

[0002]

2. Description of the Related Art In general, so-called cross-linked polyethylene obtained by cross-linking polyolefin, particularly polyethylene, is widely used as a material of an electric insulator for electric wires and cables. Wires and cables coated with this crosslinked polyethylene have excellent electrical insulation and heat resistance. However, this insulator made of cross-linked polyethylene has a drawback that when used in a wet or submerged atmosphere, water trees are generated inside the insulator, and the excellent electrical insulation performance of the material is greatly reduced.

[0003] Such a water tree is susceptible to defects such as voids and foreign matters in an insulator, and local high electric field portions such as invar (partially having a high degree of polymerization or being crosslinked and having a high molecular weight). It is known that this is caused by aggregation of water in the part.

[0004] Further, even when almost no moisture is present, the starting point of the dielectric breakdown is based on the result of the pre-cutoff test in which the voltage is cut off immediately after the partial discharge is started as a sign of the dielectric breakdown. It has been found that most cases are amba.

[0005] For these reasons, much effort has been made to eliminate these defects in electric wires and cables, and by improving the quality control of resin as a material and the technology of manufacturing electric wires and cables, there has been a great deal of effort. Attempts have been made to suppress the generation of water trees and improve the dielectric breakdown strength.

[0006]

However, at this stage,
It is difficult to completely remove defects such as foreign matter and voids.

Therefore, the present invention has been devised in order to effectively solve the above problems, and an object of the present invention is to reduce the dielectric breakdown strength even if a defect such as a void or a foreign substance occurs in the insulator. It is an object of the present invention to provide a novel electric insulating composition and a new electric wire / cable capable of improving the water tree resistance, especially the bow resistance.

[0008]

In order to achieve the above-mentioned object, the present invention relates to a method for producing a polymer having a density of 0.915 g / cm ³ or less, a melt index of 5 g / 10 min or less, and a melting point of 120 ° C. Provided are an electric insulating composition characterized by containing the above-mentioned linear polyethylene as a main component, and an electric wire / cable having an insulating layer formed with the electric insulating composition.

Further, according to the present invention, the density is 0.915 g / c.
m ³ or less, a melt index of 5 g / 10 min or less, a linear polyethylene having a melting point of 120 ° C. or more polymerized using propylene as a comonomer, an ethylene vinyl acetate copolymer, an ethylene ethyl acrylate copolymer,
Provided are an electric insulating composition containing at least one ethylene copolymer selected from ethylene propylene rubber, ethylene butene rubber, and ethylene octene rubber, and an electric wire / cable having an insulating layer formed from the electric insulating composition.

The electrical insulating composition of the present invention forms an insulating layer by extrusion-coating the outer periphery of a conductor or a conductor shielding layer. The insulating layer may be non-crosslinked,
Crosslinking can further improve heat resistance. As a crosslinking means, a heat crosslinking method by adding an organic peroxide compound such as dicumyl peroxide, or a silane water crosslinking method in which vinyl silane or the like is grafted to a polymer component and brought into contact with moisture in the presence of a silanol condensation catalyst, or the like is employed. it can.

[0011] The present inventors have considered that electric wires and cables are:
As a result of intensive research on polyethylene having improved dielectric breakdown strength and excellent water tree resistance, the above-mentioned density was 0.915.
g / cm ³ or less, melt index 5g / 10mi
n or less, and it was found that a linear polyethylene having a melting point of 120 ° C. or more, which was polymerized (copolymerized) with propylene as a comonomer, was effective, and completed the present invention.

In the present invention, the reason why the density of the linear polyethylene is set to 0.915 g / cm ³ or less is to reduce the amount of crystals and to reduce shrinkage due to crystallization in the cooling process after extrusion molding. is there. In addition, by polymerizing (copolymerizing) propylene as a comonomer, flexibility can be imparted, and even if there is a foreign substance in the polyethylene, peeling at the interface between the polyethylene and the foreign substance is reduced, and the dielectric breakdown strength and water-tree resistance are improved. it can. The reason for setting the melting point of the linear polyethylene to 120 ° C. or higher is that
One of the test methods specified in IS C3005
This is because the heating deformation rate at 20 ° C. can be reduced.

In the present invention, the above-mentioned linear polyethylene is added to an ethylene-vinyl acetate copolymer, an ethylene ethyl acrylate copolymer, an ethylene methacrylate copolymer,
By blending one or more ethylene copolymers selected from ethylene methyl methacrylate copolymer, ethylene propylene rubber, ethylene butene rubber, and ethylene octene rubber, the water-resistant tree characteristics can be further improved.

In the present invention, as the antioxidant, 2,
2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tellurakis [3- (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate], octadecyl 3- (3,5-di-t-butyl-4)
-Hydroxyphenyl) propionate, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,
5-di-t-butylanilino) -1,3,5-triazine, bis [2-methyl-4- {3-n-alkyl (C ₁₂
Or one or more compounds selected from the group consisting of C ₁₄ ) thiopropionyloxy {-5-t-butylphenyl] sulfide and 4,4′-thiobis (3-methyl-6-tbutylphenol) By adding 0.05 to 1.0 part by weight to 100 parts by weight of polyethylene or the blend polymer of the above-mentioned linear polyethylene and the above-mentioned ethylene-based copolymer, the heat aging resistance can be improved. , 2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tellurakis [3- (3,5-di-tert-butyl-4-) Hydroxyphenyl) propionate], octadecyl 3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate, 2,4-bis- (n-octylthio)
0.05 to 0.5 parts by weight of one or two compounds selected from -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine Selected from diethylene glycol or 100 parts by weight of the above blended polymer) and dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, tetrakis (methylene dodecyl thiopropionate) methane Alternatively, when two or more compounds are used together in an amount of 0.05 to 0.5 parts by weight (based on 100 parts by weight of the linear polyethylene or the blended polymer), the heat aging characteristics can be further improved by a synergistic effect,
Furthermore, a special effect of preventing metal damage can be obtained.

In the present invention, these antioxidants are
Not only can it be supplied and used in the form of a masterbatch kneaded with polyethylene at a high concentration or in the form of a dry blend with polyethylene, but also a vinylalkoxysilane that undergoes a graft reaction when the linear polyethylene or blend polymer is silane-modified. It is also possible to dissolve an antioxidant into the mixture and inject and mix it into the linear polyethylene or the like in the extruder. The amount of each antioxidant added is preferably 0.05 to 1.0 part by weight based on 100 parts by weight of the linear polyethylene or the blended polymer. The effects of preventing oxidation and preventing metal damage are small, and if it exceeds 1.0 part by weight, a so-called bloom phenomenon that precipitates on the surface of polyethylene occurs.

In the present invention, the insulating layer made of the linear polyethylene or the blend polymer is crosslinked,
By setting the degree of cross-linking to 70% or more, the rate of heat deformation at a high temperature can be extremely reduced, and the thinning of the cable at the cable holding portion or the connection portion can be reduced. Crosslinking agents for heat crosslinking include dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and 2,5-dimethyl-2,5-di (t-
Butylperoxy) hexyne-3, α, α′-bis (t
-Butylperoxy-m-isopropyl) benzene, butylcumyl peroxide, isopropylcumyl-t-
A crosslinking agent selected from organic peroxide compounds such as butyl peroxide alone or in combination of two types can be used.

In the present invention, when performing water crosslinking, the vinylalkoxysilane used in the production of the vinylsilane (vinylalkoxysilane) -modified polymer includes vinyltrimethoxysilane, vinyltriethoxysilane, and the like.
Vinyl triacetoxy silane, vinyl dimethoxymethyl silane, vinyl diethoxy retyl silane, vinyl methoxy dityl silane, vinyl ethoxy dimethyl silane and the like can be mentioned. These may be used alone or in combination of two or more. The radical initiator used in the production of the vinylsilane (vinylalkoxysilane) -modified polymer includes dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, butylcumyl peroxide, isopropylcumyl-t- Butyl peroxide and the like. These may be used alone or in combination of two or more. Here, the amount of the radical initiator used is the above-mentioned linear polyethylene or the above-mentioned blend polymer 100
0.05 to 0.15 parts by weight with respect to parts by weight is desirable,
If the amount is less than 0.05 part by weight, the degree of crosslinking is insufficient, and
If it exceeds 5 parts by weight, there is a problem that voids are generated in the insulator due to decomposition products of the radical initiator.

In the present invention, when the vinylsilane (vinylalkoxysilane) -modified polymer is subjected to a silane water crosslinking reaction to form a water-crosslinked polymer, a silanol condensation catalyst may be optionally used to promote water crosslinking. It can be added and blended in the modified polymer, or can be permeated into the vinylsilane-modified polymer from the surface of the molded product. Examples of such a silanol condensation catalyst generally include carboxylate salts of metals such as tin, zinc, iron, lead, and cobalt, organic bases, inorganic acids, and organic acids. Specifically, dibutyltin dilaurate,
Dibutyltin diacetate, dibutyltin dioctaate,
Inorganic acids such as stannous acetate, stannous carboxylate, lead naphthenate, zinc cabrate, cobalt naphthenate, ethylamine, dibutylamine, hexylamine, pyridine, sulfuric acid, hydrochloric acid, toluenesulfonic acid, acetic acid, stearic acid,
Organic acids such as maleic acid may be mentioned. These are not particularly limited, but are used by adding 0.01 to 0.1 part by weight to 100 parts by weight of the linear polyethylene or the blended polymer.

Further, the following two methods can be mentioned as a method for producing electric wires and cables in which the vinylsilane-modified polymer is water-crosslinked in the presence of the silanol condensation catalyst to obtain a water-crosslinked polymer. One method is a method called two-shot or Sioplus, in which a master batch containing a high concentration of a silanol condensation catalyst is prepared and supplied to an extruder together with a previously prepared vinylsilane-modified polymer to be molded. In another method, a compounding agent containing a silanol condensation catalyst, a radical initiator, and vinylalkoxysilane is supplied to the linear polyethylene or a polymer composition containing the same in an extruder, and a graft reaction of the vinylalkoxysilane onto the polyethylene is carried out. This is a method called one shot or monosil, in which the molding of wire and cable is simultaneously performed in one extruder.

In the present invention, in addition to the above-mentioned compounds, addition of carbon black or additives such as a lubricant and a coloring agent for imparting weather resistance may be used without any problem.

It is also possible to use a watertight conductor filled with a watertight compound as a conductor in order to prevent water running. Further, an insulator shielding layer made of a semiconductive resin composition can be provided on the crosslinked polyethylene insulator.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
The description will be made while comparing an example and a comparative example.

1 to 4 are schematic views showing an enlarged cross section of a specific example of the electric wire / cable of the present invention. FIG. 1 shows a cross section of an electric wire / cable having an insulator 2 made of an insulating layer mainly composed of the electric insulating composition of the present invention on a conductor 1. FIG.
Shows a cross section of a wire / cable comprising a conductor 1, an insulator 2 mainly composed of the electrical insulating composition of the present invention, and a watertight compound 3 filling the space therebetween. FIG. 3 shows an electric wire / cable composed of a conductor 1, an internal semiconductor layer 4 on the conductor 1, and an insulator 2 on the internal semiconductor layer 4 composed of an insulating layer mainly composed of the electric insulating composition of the present invention. 3 shows a cross section. Further, FIG. 4 shows a cross section of a wire / cable comprising a conductor 1, an internal semiconductor layer 4, an insulator 2 mainly composed of the electrical insulating composition of the present invention, and an external semiconductor layer 5.

Each of the insulating compositions shown in Examples 1 to 8 and Comparative Examples 1 to 4 in Table 1 was coated on a 60 mm ² soft copper stranded wire by 2.
Extruded as a 5 mm thick insulating layer.

Further, the insulating compositions shown in Examples 9 to 24 and Comparative Examples 5 to 10 in Tables 2 and 3 were coated on a 60 mm ² soft copper stranded wire together with an inner semiconductive layer having a thickness of 0.7 mm and a thickness of 4.5 mm. Extruded.

The details of this step are as follows.

A composition having the composition shown in Table 2 was heated at 120 ° C.
The mixture was kneaded with a hot roll to form a sheet, and pelletized with a pelletizer. Then, the pellets were introduced into an extruder,
As shown in FIG. 4, 0.7 m in annealed copper twisted line of 60 mm ²
4.5 m with internal semiconductive layer and external semiconductor layer
Extruded as an m-thick insulating layer. After this, crosslinking is immediately performed in a dry crosslinking tube using nitrogen gas as a medium.
The cable was completed by cooling and used as a sample.

Further, a linear polyethylene as shown in Table 3 and other components (excluding vinyltrimethoxysilane and dicumyl peroxide) were dry-blended in advance and charged into a 130 mm extruder at about 200 ° C. Vinyl trimethoxysilane and dicumyl peroxide were injected from the lower part of the hopper of the extruder. In this extruder, mixing, vinylsilane graft reaction, and cable molding were simultaneously performed.

After forming the cable in this way, 8
The sample was allowed to stand in an atmosphere of 0 ° C. and 95% water vapor for 24 hours to be crosslinked with water to obtain a sample.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

The extrudability of each of these samples was evaluated from the appearance, and the heat deformation ratio and the like were examined by the following methods.

The heating deformation rate conformed to JIS C3005. The heating deformation rate of the cable sample at 120 ° C. is 25
% Or less as "good" and those exceeding 25% as "bad".

[0035] The shrink-back is performed by
The amount of shrinkage when heated to 0 ° C was measured, and the value at that time was 1
% Or less, and 1% or more was rated x.

The evaluation test of bow titley characteristics was performed by immersing the above-mentioned sample injected into the conductor in warm water of 90 ° C. and applying an AC voltage of 90 KV at 50 Hz between the body and water for 500 days. After 500 days, the cable section was sliced thinly, stained by boiling with an aqueous methylene blue solution, and the length of the bow title tree and the number of bow title trees having a size of 200 μm or more were counted using an optical microscope.

The metal damage / deterioration characteristic was measured at 135 ° C. for 7 days in accordance with the standard of IEC502, and then compared with the initial tensile strength and elongation.
Those that entered the range of 5% were judged to be acceptable. In addition, in the case where the conductor was directly coated with the insulator, in addition to the determination of the tensile properties, the discoloration of the portion in contact with the copper conductor was examined, and those having no discoloration were accepted.

As shown in Table 1, Examples 1 to 8 have good extruded appearance, small heat deformation rate and small shrinkback, and all properties including bow titleries are good.

Further, those in which an antioxidant is used in combination as in Examples 3 to 6 also have good copper damage deterioration characteristics.

On the other hand, Comparative Example 1 using a linear polyethylene having a high density outside the specified range of the present invention has good heat denaturation properties, but has a large shrinkback and poor bow titley properties. Further, those having a low melting point, such as Comparative Examples 2 and 3, have inferior heat deformation characteristics. In addition, when an antioxidant is added in an amount exceeding a specified amount, the bloom becomes large. In Comparative Example 4, the comonomer was butene-1, but the bow titley characteristics were inferior.

Tables 2 and 3 show the cases where the insulating layer is an insulating layer composed of a cross-linked polymer and a water-cross-linked polymer, respectively. Examples 9 to 24 have good extruded appearance, small heat deformation rate and small shrink-back. In addition, all properties including bow titleries are good.

On the other hand, Comparative Examples 5 and 8, which used a high-density linear polyethylene outside the specified range of the present invention, had good heat deformation properties, but had large shrinkback and poor bow titleries. Comparative Examples 6, 7, 9,
Those having a low melting point, such as 10, also have inferior heat deformation characteristics. In addition, when an antioxidant is added in an amount exceeding a specified amount, the bloom becomes large.

[0043]

As described above, according to the present invention, it is possible to obtain an electric insulating composition and an electric wire / cable having good extrudability, a small heat deformation rate and a small shrink-back, and excellent bow-resistant property.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional schematic view of an embodiment of an electric wire / cable of the present invention.

FIG. 2 is an enlarged schematic sectional view of another embodiment of the electric wire / cable of the present invention.

FIG. 3 is an enlarged schematic sectional view of still another embodiment of the electric wire / cable of the present invention.

FIG. 4 is an enlarged schematic sectional view of still another embodiment of the electric wire / cable of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 2 Insulator 3 Watertight compound 4 Internal semiconductor layer 5 External semiconductor layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junichi Abe 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Power Systems Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Katsushi Hanawa 5 Hidaka-cho, Hitachi City, Ibaraki Prefecture No. 1-1, Hitachi Cable Co., Ltd. H-Taka Plant F-term (reference) 4J002 BB052 BB062 BB072 BB151 BB152 BQ003 EJ066 EK038 EV076 EV077 EV086 FD076 FD077 FD143 FD158 GQ01 5G305 AA02 AA14 AB02 CA04 CB11 CD09

Claims (7)

[Claims] The present invention is characterized in that it mainly contains linear polyethylene having a density of 0.915 g / cm ³ or less, a melt index of 5 g / 10 min or less, and a melting point of 120 ° C. or more polymerized with propylene as a comonomer. Electrical insulating composition. 2. A linear polyethylene having a density of 0.915 g / cm ³ or less, a melt index of 5 g / 10 min or less, a polymerized propylene copolymer having a melting point of 120 ° C. or more, and an ethylene-vinyl acetate copolymer ,
An electrical insulating composition comprising at least one ethylene copolymer selected from an ethylene ethyl acrylate copolymer, ethylene propylene rubber, ethylene butene rubber, and ethylene octene rubber. 3. Antioxidants include 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and pentaerythrityl-tetrakis [3- (3 , 5-Di-t-butyl-4-
Hydroxyphenyl) propionate], octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5- Di-t-butylanilino) -1,3,5-triazine, bis [2-methyl-4- {3-n-alkyl (C ₁₂ or C ₁₄ ) thiopropionyloxy} -5-t-butylphenyl] sulfide, The electrical insulating composition according to claim 1 or 2, comprising at least one selected from 4,4'-thiobis (3-methyl-6-tbutylphenol). 4. Antioxidants such as 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] and pentaerythrityl-tetrakis [3- (3 , 5-Di-t-butyl-4-
Hydroxyphenyl) propionate], octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5- At least one selected from di-t-butylanilino) -1,3,5-triazine, dilaurylthiodipropionate, dimyristylthiodipropionate, distearylthiodipropionate, and tetrakis (methylenedodecylthiopropionate) 3. The electrical insulating composition according to claim 1, which comprises at least one of methane. 5. The method according to claim 5, wherein the density of the conductive material on the conductor or the conductor shielding layer is 0.
915 g / cm ³ or less, melt index 5 g / 1
An electric wire / cable having an insulating layer made of an electrically insulating composition mainly containing linear polyethylene having a melting point of 120 ° C. or higher, which is polymerized using propylene as a comonomer and having a melting point of 0 min or less. 6. On a conductor or a conductor shielding layer, a density of 0.
915 g / cm ³ or less, melt index 5 g / 1
0 min or less, and a linear polyethylene having a melting point of 120 ° C. or higher, which is polymerized using propylene as a comonomer, and ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene propylene rubber, ethylene butene rubber, and ethylene octene rubber. An electric wire or cable comprising an insulating layer made of an electric insulating composition containing at least one selected ethylene copolymer. 7. The electric wire / cable according to claim 5, wherein the insulating layer is cross-linked.