JPH0366768B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a power cable with excellent heat resistance and low-temperature flexibility. In recent years, polyethylene has been used as a resin insulator for high-voltage power cables, and is known to have advantages in voltage resistance, dielectric properties, processability, etc. This polyethylene has a low melting point and is difficult to use at high temperatures, so cross-linked polyethylene (hereinafter referred to as XLPE), which has undergone cross-linking treatment, is usually used, but in high-voltage power cables, the insulation is thick, so
It relies on chemical crosslinking using peroxide instead of electron beam irradiation. In this case, the polyethylene used is low density polyethylene (LDPE), which has a low melting point (approximately 110°C) and can be extruded at low temperatures, in order to prevent scorch caused by the crosslinking agent during extrusion. Crosslinking after extrusion requires a high-temperature, high-pressure heating medium atmosphere to prevent foaming of the insulator due to the peroxide crosslinking agent, which requires complicated manufacturing equipment. Cross-linking prevents the insulator from flowing at temperatures above the melting point, but the thermal deformation of the insulator significantly increases when the melting point is exceeded. 120-130
℃, usually limited to 70 to 80 ℃ or less. In view of the above drawbacks, the present invention aims to provide a power cable with good heat resistance without using complicated crosslinking equipment. In the provided power cable, an initial boiling temperature of 300% was added to 100 parts by weight of poly-4-methylpentene-1 as the insulator.
It is characterized in that it uses a mixture containing 30 parts by weight or less of a hydrocarbon compound having a temperature of 0.degree. C. or less. Hereinafter, the present invention will be explained in detail with reference to the drawings. In FIG. 1, 1 is a conductor, 2 is an internal semiconducting layer, and 3 is an insulating layer. The resin used for this insulating layer 3 has a high melting point,
Poly-4-methylpentene-1 (hereinafter referred to as TPX) and the like can be cited as a material that satisfies dielectric properties and withstand voltage properties. However, this TPX has difficulty in low-temperature flexibility near room temperature, so by blending a hydrocarbon compound, the low-temperature flexibility is significantly improved without compromising heat resistance, and the thick insulating layer It was confirmed that the material can be processed into a variety of materials, and that its electrical properties are also fully satisfactory. Generally, various grades are known in which TPX contains an appropriate amount of a certain type of hydrocarbon vinyl compound as a copolymer component. However, it is not so good that it can be processed into thick walls, and the hydrocarbon compound of the present invention has made it possible to use TPX for the first time. Hydrocarbon compounds used in the present invention include:
Nonpolar alkylbenzene-based, polybutene-based, mineral oil-based, diphenylethane-based, alkylnaphthalene-based, etc. are preferable, and when even better electrical properties are expected, the above-mentioned hydrocarbon compounds of insulating oil grade may be used. Further, since the extrusion processing temperature of TPX is 250 to 260°C or higher, this hydrocarbon compound preferably has an initial boiling temperature of 300°C or higher due to processing requirements. The number of parts of the hydrocarbon compound is
If the amount exceeds 30 parts by weight per 100 parts by weight of TPX, the blended hydrocarbon compound will cause bleeding, which is undesirable.As for the lower limit, even if the blend is as small as 1 to 2 parts by weight, the effect of low-temperature flexibility will not be achieved. have This is because TPX is a nonpolar hydrocarbon polymer and is a crystalline polymer with a high melting point of 230 to 240°C, so it has good affinity with hydrocarbon compounds with similar chemical structures, and is a type of It is thought that low-temperature flexibility is exhibited by providing a plasticizing effect. In addition, TPX containing hydrocarbon compounds,
Participation inhibitors, copper damage inhibitors, flame retardants, as necessary.
Of course, the same effect can be obtained even if fillers or additives such as corbon black are added. Further, as shown in FIG. 2, a high voltage power cable structure may be provided in which an external semiconducting layer 4 and a shielding layer 5 are provided on an insulating layer 3. As the semiconductive layer, carbon paper, semiconductive cloth, compound for extruded semiconductive layer, etc. are used. Among these, when compound for extruded semiconductive layer is used,
Provides the most stable withstand voltage characteristics. In the case of the present invention, it is also possible to improve the adhesion between the insulating layer 3 and the inner and outer semiconductive layers by adding a crosslinking agent to the extruded semiconductive layer compound. As mentioned above, high-voltage power cables are normally required to have high withstand voltage and low inductive loss, but the poly-4-merlepentene-1 used as the insulating layer is compounded with hydrocarbon compounds. As a result, the dielectric dispersion due to the glass transition temperature is typically 40~
The temperature is shifted from 50°C to below room temperature, which is advantageous in terms of dielectric properties. In addition, with ordinary cross-linked polyethylene power cables, since the insulating layer and the agent that forms the insulating layer at the cable joint or terminal part are cross-linked, it is difficult to fuse them together with the resin, and there are areas with poor adhesion at the boundary. However, in the present invention, the resin used for the insulating layer has a high melting point and can be used uncrosslinked.
This is advantageous for forming insulating layers at joints and terminal parts. [Example] The resin for the insulating layer used in the present invention is a powdery MX-001 (manufactured by Mitsui Petrochemical Manufacturing Co., Ltd.) which is highly flexible at low temperatures as TPX, and a hydrocarbon compound with an initial boiling temperature.
Contains 10 parts by weight of heavy alkene at 400℃,
The mixture was mixed in a Henschel mixer at 100 to 110°C, and an antiaging agent and a copper damage inhibitor were added during this mixing to form extruded pellets. Therefore, the conductor (500 mm ² ) was extruded and coated with an extruded semiconductive compound mixed with a crosslinking agent as an internal semiconductive layer, and then the above resin was coated on top of it as an insulating layer at a thickness of 12 mm at an extrusion temperature of 280°C. coating and further outer semiconducting layer (extruded semiconducting compound above)
A power cable was manufactured by sequentially applying a shielding layer and a sheath. In contrast, we experimentally used TPX (MX-001), which does not contain hydrocarbon compounds, as an insulating layer.
I tried to manufacture a power cable with the same structure of the present invention, but
Due to its poor flexibility, it could not be wound onto a drum, making it impossible to obtain a product. In addition, the power cable for comparison was coated with extruded polyethylene as an insulating layer, then crosslinked through a crosslinking zone in a high temperature and high pressure nitrogen gas atmosphere, and as a semiconducting layer an extruded semiconducting compound containing no crosslinking agent was used. I got one with the same structure. The results of measuring various characteristics of each of the above power cables are shown in the table. In the table, the flexural modulus, melting point, embrittlement temperature, tensile strength, and elongation were measured using samples cut from the insulation layer of each power cable.
Since cable processing was not possible for TPX, which does not contain hydrocarbon compounds, measurements were made using sheet samples formed by hot pressing. In addition, in the list of insulating layers, A is TPX containing a hydrocarbon compound,
B indicates TPX containing no hydrocarbon compound, and C indicates crosslinked polyethylene.

[Table] From the table, the low temperature flexibility of the present invention is significantly improved by blending a hydrocarbon compound into TPX, and as a result, the flexural modulus was measured to be close to that of cross-linked polyethylene. , it can be seen that processing into thick insulating layers is easy. In addition, since the present invention has a higher melting point than cross-linked polyethylene cables, the thermal deformation rate is significantly lower.
It was found that the heat resistance was good, and in terms of electrical properties, values comparable to those of cross-linked polyethylene cables were obtained, indicating that it is good as a high-voltage insulated layer power cable.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, with FIG. 1 being a front sectional view thereof and FIG. 2 being a front sectional view of another embodiment. 1... Conductor, 2... Internal semiconducting layer, 3... Insulating layer.

Claims (1)

[Claims] 1. In a power cable in which an internal semiconducting layer and an insulating layer are sequentially provided on a conductor, the insulating layer is made of polyamide.
A power cable characterized by using a mixture of 100 parts by weight of 4-methylpentene-1 and 30 parts by weight or less of a hydrocarbon compound having an initial boiling temperature of 300°C or higher.