JPH0524603B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a polyethylene insulated power cable with excellent heat resistance and dielectric breakdown strength, particularly dielectric breakdown strength at high temperatures, and a method for manufacturing the same. <Prior Art> Conventional power cables of this type generally have a crosslinked insulator made of low density polyethylene crosslinked with an organic peroxide. <Problems to be solved by the invention> However, in the case of this power cable, low-density polyethylene has a low crystal melting point of 100 to 110°C, so when the operating temperature reaches 80 to 90°C or higher, the crystals partially melt. The dielectric breakdown strength of the cross-linked insulator decreases. In addition, when the temperature exceeds the crystal melting point, the thermal expansion becomes large.
Particularly in the case of high-voltage cables where the insulator is thick, thermal expansion can cause mechanical troubles. Compared to such low-density polyethylene, filamentary low-density polyethylene and high-density polyethylene are materials with a higher crystal melting point and higher crystallinity and higher dielectric breakdown strength, but have the disadvantage that crosslinking is difficult. This is especially difficult when the insulation thickness is large. Furthermore, when attempting to crosslink this type of material with an organic peroxide such as dicumyl peroxide, the extrusion temperature must be set at 140 to 150°C or higher due to the high crystal melting point, which causes the problem of scorching of the insulator. arise. On the other hand, at low temperatures below 140 to 150°C, problems arise such as insufficient melting and inability to extrude. From the above points, it is desired to solve these problems. <Means for solving the problems> The present invention solves these problems.
The gist of the first invention, the power cable, is as follows:
In the composition of the insulator, linear low-density polyethylene or high-density polyethylene is used according to the formula

Crosslinking is carried out using a crosslinking agent represented by the following formula, and triallyl cyanurate is further added if necessary. Furthermore, in the method for manufacturing a cable, which is the second invention, the above-mentioned object is achieved by extruding and coating the above-mentioned composition onto a conductor at a temperature of 140 to 190°C, and then crosslinking at a temperature of 210°C or higher. The aim is to obtain a power cable that will Hereinafter, the present invention will be explained in more detail. First, in the present invention, it is used as a crosslinking agent for linear low density polyethylene or high density polyethylene. formula

The compound represented by [Formula] has a 1 minute half-life temperature of 220℃, 10
It is a crosslinking agent with a time half-life temperature of 143°C and superior high temperature stability compared to conventional organic peroxides.
It has excellent extrusion stability as a crosslinking agent for the polyethylene, and the obtained insulator also has excellent dielectric breakdown strength, especially at high temperatures. The amount added is 100% of the polyethylene
The amount is 1 to 4 parts by weight. If the amount added is less than 1 part by weight, it is difficult to obtain a sufficient crosslinked product, and if it exceeds 4 parts by weight, the crosslinking effect is saturated and the dielectric properties are deteriorated due to the crosslinking agent residue. This is because the problem of time scorch occurs. In addition, it is preferable to use 0.2 to 3.0 parts by weight of triallyl cyanurate as a crosslinking aid in the crosslinking agent. Although the crosslinking efficiency can be improved by adding this triallyl cyanurate,
If the amount added exceeds the above range, no improvement in crosslinking efficiency will be observed at the lower limit, and if the upper limit is exceeded, the crosslinking efficiency will be saturated and at the same time, crosslinking will be promoted, causing the problem of scorch in the insulator. This is because it occurs. It has been confirmed that the power cable using the following cross-linked polyethylene as an insulator has 40 to 80% higher dielectric breakdown strength at high temperatures (e.g. 130°C) compared to conventional power cables of this type. It was done. Next, a cable manufacturing method, which is the second invention of the present invention, will be described. It has been confirmed that in order to obtain the power cable described above, it is preferable to set specific manufacturing conditions. That is, for linear low density polyethylene or high density polyethylene, the formula

A composition containing the compound represented by the formula and triallyl cyanurate added as necessary is extruded onto a conductor at an extrusion temperature of 140 to 190°C, preferably 140°C in the case of linear low density polyethylene. ~190°C, extrusion coating at 150-190°C in the case of high density polyethylene. This is not preferable because if the temperature is below this temperature, sufficient melting and kneading will not be possible and a uniform crosslinked insulator will not be obtained, and if the temperature is higher than the above temperature, scorch will begin to progress. Furthermore, the extrusion-coated insulator is crosslinked at a temperature of 210° C. or higher. This temperature is determined in consideration of a practical time range, and as the crosslinking method, steam crosslinking, nitrogen gas crosslinking, silicone oil or molten salt crosslinking can be used. <Examples> Examples 1 to 12 Linear low-density polyethylene (LLDPE, Urtozex 3010F, manufactured by Mitsui Petrochemicals) and high-density polyethylene (HDPE, Hizexx 3300F, manufactured by Mitsui Petrochemicals) with a melt index of approximately 1.2, A certain amount of anti-aging agent (4,4'-thiobis-
(6-tert-butyl-3-methylphenol)) and Trigonox 107 (manufactured by Kayaku Nouri Co., Ltd.) as a crosslinking agent, and the crosslinking agent and triallyl cyanurate were added in various proportions to prepare compositions. This composition was provided in a three-layer structure as a crosslinked insulator along with inner and outer semiconducting layers on a copper conductor having a conductor cross-sectional area of 200 mm ² to prepare a power cable. For comparison, Comparative Examples 1 to 8 are those that do not meet the conditions of the present invention, and low density polyethylene (LDPE) is cross-linked with dicumyl peroxide (DCP, 0.2 parts by weight added to 100 parts by weight of the polyethylene). A power cable having a similar structure was prepared and designated as Conventional Example 1. Regarding the above power cables, in order to check the dielectric breakdown strength at high temperatures, the impulse breakdown voltage at 130°C, the thermal deformation rate at 140°C, and the gel fraction were also measured. The results are shown in Table 1.

[Table] As is clear from Table 1 above, using LLDPE or HDPE, the formula

The amount of the compound represented by [Formula] and the amount of triallyl cyanurate added if necessary is the same as above.
It can be seen that those in the range of 1 to 4 parts by weight and 0.2 to 3 parts by weight based on 100 parts by weight of LLDPE or HDPE have high dielectric breakdown strength at high temperatures and are less susceptible to heat deformation. Examples 13-17 Insulator extrusion temperature when creating power cables with similar functionality using the compositions of Examples 1-12,
and crosslinking temperature conditions were investigated. The above composition was prepared by adding 2.0 parts by weight of a crosslinking agent (Trigonox 107) and 1.0 parts by weight of triallyl cyanurate to 100 parts by weight of LLDPE or HDPE. still,
For comparison, comparative examples 9 to 13 that do not meet the conditions of the present invention are listed. The results are shown in Table 2.

[Table] As is clear from Table 2 above, the extrusion temperature is
It can be seen that it is preferable that the crosslinking temperature is 140 to 190°C and the crosslinking temperature is 210°C or higher. Note that the conditions of the test items are the same as in Examples 1 to 12. <Effects of the Invention> According to the present invention, as is clear from the above description, it is possible to obtain a polyethylene insulated power cable having excellent heat resistance and dielectric breakdown strength, particularly dielectric breakdown strength at high temperatures, and a method for manufacturing the same. I can do it.

Claims (1)

[Claims] 1. A crosslinked product obtained by adding 1 to 4 parts by weight of a crosslinking agent represented by the formula [formula] to 100 parts by weight of linear low-density polyethylene or high-density polyethylene is used as an insulator on a conductor. Power cable provided. 2. The power cable according to claim 1, wherein 0.2 to 3.0 parts by weight of triallyl cyanurate is added to the crosslinked product. 3 Consisting of 1 to 4 parts by weight of a crosslinking agent represented by the formula [Formula] and 0.2 to 3.0 parts by weight of triallyl cyanurate added as necessary, based on 100 parts by weight of linear low-density polyethylene or high-density polyethylene. 1. A method for producing a power cable, comprising extrusion coating a composition on a conductor at an extrusion temperature of 140 to 190°C, and then crosslinking at a temperature of 210°C or higher.