JPH0812821A - Electrical insulating composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition excellent in (high temperature) insulation breakdown, insulation reliability, etc., and useful as, e.g. an insulating material for a large-capacity power cable by blending a specified amount of 3,4-polyisoprene with low-density PE. CONSTITUTION:This electrical insulating composition contains (A) 100 pts.wt. low-density PE and (B) 3 to 50 pts.wt. 3,4-polyisoprene. In addition, the component (A) is preferably low-density PE having 0.2 to 3.0g/10min melt index and 0.915 to 0.925g/cm<3> density respectively measured by the method of JIS K6760 and the component (B) is preferably 3,4-polyisoprene having 0.85 to 0.95g/cm<3>, especially 0.88 to 0.95g/cm<3> density and 150000 to 250000, especially 200000 to 230000 weight-average molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically insulating composition suitable for electrical insulation, particularly a high voltage cable, and a high voltage electrical insulating member such as a connecting portion or a terminal portion thereof.

[0002]

2. Description of the Prior Art Recently,
The voltage class required for power cables is increasing year by year, and higher reliability is required. Conventionally, low-density polyethylene or crosslinked polyethylene has been widely used as an electrically insulating composition for such power cables.
By the way, due to an accident such as a lightning strike on the power cable,
A large voltage may be loaded, although momentarily. Therefore, it is important for the electric insulating material used for the power cable to have a strong resistance to such an accident, and the impact breakdown voltage characteristic (impulse breakdown characteristic) is an important characteristic.

Further, when a large capacity power cable is operated, the heat generated by the conductor causes a high temperature of about 90 ° C., and the insulating layer of these large capacity power cables is required to have good impulse breakdown characteristics even at such a high temperature. To be done. That is, at the time of an accident of the power cable, it is necessary that the insulating layer has excellent impulse breakdown characteristics even in a high temperature state of about 90 ° C.

However, conventional power cables having an insulating layer of low-density polyethylene or cross-linked polyethylene are not always satisfactory in impulse breakdown characteristics, particularly at 90 ° C.

The inventors of the present invention have conducted extensive studies on electrical insulating compositions having good impulse breakdown characteristics, particularly high voltage cables, and electrically insulating compositions suitable as high voltage electrical insulating members for their connecting parts, terminal parts and the like. As a result, it was found that the composition in which 3,4-polyisoprene was blended with low-density polyethylene had a high degree of electrical characteristics, and particularly had extremely good impulse breakdown characteristics and impulse breakdown characteristics at high temperatures. Heading out, the present invention was completed.

[0006]

The above object is achieved by an electrically insulating composition characterized in that 3 to 50 parts by weight of 3,4-polyisoprene are blended with 100 parts by weight of low-density polyethylene. Will be resolved. Preferably JIS
The melt index and the density measured by K6760 are 0.2 to 3.0 g / 10 min and 0.9, respectively.
³ to 4 parts of 3,4-polyisoprene are added to 100 parts by weight of low density polyethylene of 15 to 0.925 g / cm 3.
It is solved by an electrically insulating composition characterized by being mixed in an amount of 50 parts by weight.

[0007]

Function: To 100 parts by weight of low density polyethylene,
By using a composition containing 3 to 50 parts by weight of 3,4-polyisoprene, the composition has high electrical properties, and in particular, the impulse rupture property and the impulsive rupture property at high temperature become extremely good.

Next, the materials used in the present invention will be described in detail. As the low density polyethylene used in the present invention,
A low-density polyethylene by a so-called high-pressure method, for example, ethylene is added with an initiator such as oxygen, peroxide, and azo compound to about 1000 to 2000 atm, 150 to 25 atm.
It was polymerized under the condition of about 0 ° C.

As the low-density polyethylene used in the present invention, known low-density polyethylene can be used as long as it is a low-density polyethylene obtained by a so-called high pressure method.
The melt index measured by K6760 (hereinafter simply referred to as melt index) is 0.1 to
4.0, preferably 0.2-3.0, especially 0.8-1.
3g / 10min, the density measured by JIS K6760 (hereinafter, simply referred to as density) is 0.905 to 0.9
30, preferably 0.915 to 0.925 g / cm ^{3 and} especially 0.918 to 0.922 g / cm ³ . If the melt index is smaller than 0.1 g / 10 min or larger than 4.0 g / 10 min, the moldability tends to be poor. The density is 0.905 g / cm ³
Those smaller than 0.930 g / cm ³ tend to be inferior in impulse fracture strength.

The low-density polyethylene used in the present invention has an elongation at break of 450 to 800%, especially 550 to 75%.
0%, melting point 100-115 by thermal analysis (DSC) method
It is preferable to use a material having a temperature of ° C, preferably 105 to 110 ° C. If the elongation at break is less than 450% or more than 800%, problems tend to occur in terms of mechanical strength. Melting point by thermal analysis (DSC) method is 1
If it is less than 00 ° C, the mechanical strength tends to be problematic, and if it is higher than 110 ° C, the impulse fracture strength tends to be poor. In addition, the measuring method of the melting point by the thermal analysis (DSC) method is, specifically, a heating rate of 10 ° C./m.
in nitrogen gas atmosphere (100 ml / min).

Among the above, the melt index and the density measured by JIS K6760 are 0.2 to 3.0 g / 10 min and 0.915 to 0.92, respectively.
It is preferably 5 g / cm ³ , particularly JIS K6
Melt index and density measured by 760 are 0.2 to 3.0 g / 10 min and 0.915, respectively.
˜0.925 g / cm ³ and thermal analysis (DS
Those having a melting point of 105 to 110 ° C. according to the method C) are preferable.

Commercial products of the above low-density polyethylene include ZF-30R (melt index 1.1 g / 10 min, density 0.920 g / cm ³ ) manufactured by Mitsubishi Petrochemical Co., Ltd.
HE-30 manufactured by Mitsubishi Petrochemical Co., Ltd. (melt index 0.3 g
/ 10 min, density 0.920 g / cm ³ ), Mitsubishi Yuka Co., Ltd. ZF-50 (melt index 0.7 g / 10 m)
in, density 0.924 g / cm ³ ), UB manufactured by Ube Industries, Ltd.
EC530 (melt index 1.1g / 10mi
n, density 0.920 g / cm ³ ), Sumikasen C-215 (melt index 1.4 g / 10 m, manufactured by Sumitomo Chemical Co., Ltd.)
in, density 0.920 g / cm ³ ), Nippon Oil Co., Ltd. W-
300 (melt index 2.0 g / 10 min, density 0.919 g / cm ³ ) and the like. In particular, ZF-30R manufactured by Mitsubishi Petrochemical Co., Ltd. (melt index 1.1 g / 1
0 min and a density of 0.920 g / cm ³ ) are preferably used.

As the 3,4-polyisoprene used in the present invention, known 3,4-polyisoprene can be used. For example, the density is usually 0.850 to 0.95, especially 0.88 to 0. 0.95 g / cm ³ . The weight average molecular weight is usually 150,000 to 250,000, preferably 180,000 to
It is 230,000, more preferably 20 to 230,000. 3,4
-Polyisoprene usually contains a small amount of 1,4-polyisoprene as an impurity, but the 3,4-polyisoprene used in the present invention may be in a form in which 1,4-polyisoprene is mixed. The content of 3,4-polyisoprene is 3 to 50 parts by weight, preferably 10 to 25, and more preferably 10 to 2 parts by weight with respect to 100 parts by weight of low-density polyethylene.
Add 0 parts by weight. If it is less than 3 parts by weight, the impulse breakdown characteristic tends to deteriorate, and if it is more than 50 parts by weight, the impulse breakdown characteristic tends to deteriorate.

The insulating composition of the present invention may be used after being crosslinked if necessary. In this case, as the cross-linking agent, an organic peroxide such as dialkyl peroxide, dialkoxy peroxide or diacyl peroxide is used. For example, dicumyl peroxide, ditertiary butyl peroxide, etc. may be used appropriately. Further, organic sulfur compounds such as tetramethylthiuram disulfide, dibenzothiazyl disulfide, zinc dibutyldithiodithicarbamine, and mixtures of sulfur with these compounds can be used. Of these, dicumyl peroxide and ditertiary butyl peroxide are preferable.
When the electrically insulating composition of the present invention is crosslinked with a crosslinking agent, the temperature is 150 to 290 ° C., preferably 170 to 250.
The heat treatment may be performed at 10 ° C. for 10 to 120 minutes.

Further, the crosslinking may be a silane crosslinking type. For example, silane compounds such as vinyltrimethoxysilane and vinyltriethoxysilane, and dicumyl oxide, and radical generators such as hydroxypeptyl oxide are grafted onto low-density polyethylene, and the silane-grafted low-density polyethylene is A silanol condensation catalyst such as dibutyltin dilaurate or dibutyltin diacetate may be added and mixed, and crosslinked in the presence of water.

The composition of the present invention may be crosslinked by electron beam irradiation. The electron beam dose is usually 2 to 30 Mr
It is about ad.

Further, when the composition of the present invention is crosslinked, a crosslinking aid may be added. As the crosslinking aid, divinylbenzene, diallyl phthalate, diallyl isophthalate, 4,4'-isopropylidenediphenol bis (diethylene glycol methacrylate) ether, triallyl trimellitate, 2,2'-bis (4-acryloxydiene) Aromatic polyfunctional compounds such as ethoxyphenyl) propane, syn-1,2-polybutadiene, 1,4-
Butanediol diacrylate, N, N'-methylenebisacrylamide, ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, 1,6-hexadiol methacrylate, tetrahexanediol dimethacrylate. Polyfunctional aliphatic compounds such as triallyl isocyanurate, triallyl cyanurate, triacryloylhexahydro-1,3,5-triazine, diacrylchlorendate, and other polyfunctional cyclic compounds, aluminum acrylate , Aluminum methacrylate, zinc acrylate, zinc methacrylate, magnesium acrylate, magnesium methacrylate, calcium acrylate, cal Um methacrylate, zircon acrylate, are exemplified a metal-containing polyfunctional compounds such as zircon methacrylate, these one or more may be added in an amount of about 0.1 to 3.0 parts by weight. Among the above crosslinking assistants, triallyl isocyanurate, triallyl cyanurate, triacryloyl hexahydro-1,3,5-
Triazine is preferred.

The electrically insulative composition prepared by blending 3 to 50 parts by weight of 3,4-polyisoprene with 100 parts by weight of the low-density polyethylene of the present invention is antioxidant to the extent that the object of the present invention is not impaired. Agents, lubricants, stabilizers, fillers, colorants and the like may be added.

Examples of the antioxidant include hindered phenol type antioxidants, amine type antioxidants and the like.
As the hindered phenolic antioxidant, known compounds can be used, for example, tetrakis [methylene-3-
(3,5-di-tert-butyl-4-hydroxyphenol) propionate] (Irganox 1010 manufactured by Ciba-Geigy), 2,2-thio [diethyl-bis-3]
-(3,5-di-tert-butyl-4-hydroxyphenol) propionate] (Ciba Geigy Irganox 1035), 4,4'-thiobis (3-methyl-6-tert-butylphenol) (Ouchi Shinsei Co., Ltd.) Nocrac 300), 4,4'-methylene-bis (3,5
-Di-tert-butylphenol) (Ionox 220 manufactured by British ICI Co., Ltd.), as amine-based antioxidants,
For example, N, N'-di-β-naphthyl-p-phenylenediamine (Nocrack white manufactured by Ouchi Shinko Co., Ltd.), N, N '
-Diphenyl-p-phenylenediamine (Nocrac DP manufactured by Ouchi Shinko Co., Ltd.), N, N'-diisopropyl-p-phenylenediamine (Antioxidant N manufactured by Deyupon)
o. 23), N, N'-bis (1-methyl-heptyl)
-P-phenylenediamine (Eastman chem)
Eastzone 30), phenyl, hexyl-p
-Phenylenediamine (NTO3 manufactured by Pennwalt)
'3'), N, N'-di-β-naphthyl-p-phenylenediamine (Nonfelex F manufactured by Seiko Chemical Co., Ltd.),
N, N'-bis (1-ethyl, 3-methylpentyl)-
p-phenylenediamine (Uniroy's Flexz
on8-L), 2-mercaptomethylbenzimidazole (Nocrac MMB manufactured by Ouchi Shinko Co., Ltd.), 2-mercaptomethylbenzimidazole zinc salt (Nocrac MMBZ manufactured by Ouchi Shinko Co., Ltd.) and the like. Among the above antioxidants, hindered phenolic antioxidants, especially 4,4'-thiobis (3-methyl-6-tert-butylphenol) are preferable.

As the lubricant, conventionally known ones can be widely used, and examples thereof include stearic acid, metal stearates such as zinc stearate, tin stearate, calcium stearate, lead stearate and magnesium stearate, isostearic acid, butyric acid. , Capric acid, caproic acid, lauric acid, oleic acid and their metal salts, fatty acid esters such as vinyl stearate, n-butyl stearate, stearic acid amide, oxystearic acid amide, oleic acid amide, ricinoleic acid, etc. One or more kinds of fatty acid amide, paraffin, etc. are used.

The electrically insulating composition of the present invention is kneaded by a conventional kneading means, for example, a Banbury mixer, a Henshur mixer, a kneader, a roll, a blender, etc., and then using a molding machine such as an extruder or an injection molding machine. Specific product shape, for example, electrical insulation layer for electric wires, high voltage cable connection part, high voltage electrical insulation member for equipment such as terminal part, tape, sheet, spacer, plug, socket,
Processed into pipes, insulating rods, various electrical components, circuit components, sealing materials, etc.

When the electrically insulating composition of the present invention is used as an insulating layer of a power cable, it may be formed by a known method. For example, it is continuously formed on the conductor by pressure extrusion or a tubing method. Further, in a power cable of about 66 kv or more, the inner semiconductive layer and the outer semiconductive layer may be appropriately provided. Applying separator tape on the conductor,
A mode in which a sheath layer is further provided on the insulating layer may be used.

When the insulating composition of the present invention is used as an insulator of a power cable, the conductor of the cable is pure copper,
A known conductor such as annealed copper or hard copper may be used. The thickness of the insulating layer may be appropriately designed according to the power transmission capacity, and is, for example, about 1 to 30 mm.

(Examples 1 to 6 and Comparative Examples 1 to 5) The components shown in Table 1 were kneaded at 120 ° C. using a roll mill, and melt-molded in a compression molding machine at 120 ° C. for 15 minutes to give a thickness. 0.
A 3 mm sheet was obtained. In case of crosslinking, 180 ℃
Was heated and pressed for 20 minutes. The sheet was tested for impulse breakdown characteristics at room temperature or 90 ° C.

The compounding agents used in Examples and Comparative Examples are
It is as follows. 1) Low density polyethylene (ZF-30 manufactured by Mitsubishi Petrochemical Co., Ltd.)
R, density 0.920 g / cm ³ , melt index 1.1 g / 10 minutes, elongation at break 740%, melting point 106 ° C. by DSC) 2) 3,4-polyisoprene (Kuraray KM4-K)
1, weight average molecular weight 200,000, containing 20% by weight of 1,4-polyisoprene) 3) cis-1,4-polyisoprene (Kuraray Co., IR
-10) 4) Dicumyl peroxide (DCP manufactured by NOF Corporation) 5) Antioxidant (manufactured by Ouchi Shinko Co., Ltd., N-300, 4, 4 ')
-Thiobis (3-methyl-6-tert-butylphenol))

(Impulse Destruction Characteristic Test) Improved McK
The negative electrode impulse standard wave of 1 × 40 μsec was applied by an eown electrode system at a room temperature and 90 ° C. by a step-up boosting method of applying 5 kv / 3 times, with an initial value of 70% of the expected breakdown voltage. As for the impulse withstand voltage value, data of 10 samples was collected for each condition, and after the Weibull analysis, the destruction value at a destruction probability of 63.3% was used as the impulse withstand voltage value of the sample, and the results are shown in Table 1.

[0027]

[Table 1]

The non-crosslinked insulating composition of the present invention has an impulse breakdown voltage of 20 to 45 kv / mm higher than that of low density polyethylene alone, and an impulse breakdown voltage of 32 to 57 kv even at high temperature (90 ° C.). / Mm larger. Also in the case of cross-linking, the impulse breakdown voltage is 62 to 67 kv / m compared to low density polyethylene alone.
m is large, and the impulse breakdown voltage is 25 to 53 kv / mm large even at a high temperature (90 ° C.).

[0029]

[Effect] The insulating composition of the present invention has good electric characteristics such as electric breakdown strength, particularly good electric breakdown strength at high temperature. Therefore, it is extremely promising as a high-voltage electrical insulator, can be applied as an insulator of a large-capacity power cable, and its reliability is enhanced. Further, since the electric characteristics such as the electric breakdown strength are excellent, it is possible to reduce the number of insulating layers used in the past, and it is possible to reduce the size of the power cable.

Claims (2)

[Claims] 1. An electrically insulating composition comprising 100 parts by weight of low-density polyethylene and 3 to 50 parts by weight of 3,4-polyisoprene. 2. The low density polyethylene is JIS K
Melt index and density measured by 6760 are 0.2-3.0 g / 10 min, 0.91 respectively.
The electrically insulating composition according to claim 1, which has an amount of ⁵ to 0.925 g / cm ³ .