JPS63190206A - Insulating material composition for wire and cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention improves the degree of crosslinking and reduces scorch by using polyethylene having a specific structure as a base insulating material for insulating compositions such as electrical cables. The present invention relates to an insulator composition for electric wires and cables that is excellent in preventing

<Prior art> Conventionally, in order to improve the degree of crosslinking of polyethylene insulators such as electrical cables, it has been necessary to add a large amount of dicumyl peroxide (hereinafter abbreviated as DCP), which is an organic peroxide. It is being done.

<Problems to be solved by the invention> However, if too much DCP is added, scorch (early vulcanization) will occur during extrusion, making it impossible to extrude for a long time, or causing damage to the surface of the extruded insulator. Minor unevenness (rough skin) may occur. Furthermore, in the case of this DCP, cumyl alcohol (CA) and acetophenone (AP) are generated by thermal decomposition during crosslinking, and this cumyl alcohol is secondarily decomposed by reheating during mold jointing of the cable, etc. , α-methylstyrene (α-MS) and water (moisture)
・It becomes.

It is believed that this water condenses in the polyethylene insulator and causes water trees when an electric field is applied, lowering the breakdown voltage of the insulator.

Therefore, the present inventors conducted extensive studies in search of an insulator composition that has a sufficient degree of crosslinking (gel fraction %) and does not cause scorch, rough skin, or even water tree formation.
Low density polyethylene with specific properties, i.e. terminal carbon-carbon double bonds (e.g. CH,=CHR structure, where R
(polyethylene polymer) is 0 per 1000 carbon atoms.
．． When using low density polyethylene with 7 to 1°5 pieces,
It has been found that good results can be obtained without significantly increasing the amount of DCP added.

The present invention has been completed based on this point.

Means for Solving the Problems and Their Effects> The characteristic feature of the present invention is that polyethylene having terminal carbon-carbon double bonds of 0.7 to 1.5 per 1000 carbon atoms is 1.0 to 3.0 parts by weight of an organic peroxide and 0.10 to 0.35 parts by weight of an oxidative deterioration inhibitor. More preferably, this low density polyethylene also has a melt flow ratio (hereinafter abbreviated as M, F, R) of 0.
．． It is good if it is 5-7.0.

The polyethylene used in the present invention is preferably, for example, low-density polyethylene, and if the terminal carbon-carbon double bonds are less than 0.7 per 1000 carbon atoms, the number is too small and a sufficient degree of crosslinking cannot be obtained. First, it is not preferable because it requires an increase in the amount of DCP, and conversely, if it exceeds 1.5, crosslinking is promoted too much and scorch occurs, which is not preferable. Therefore, in the present invention, as described above, the range is set to 0.7 to 1.5 carbon atoms per 1000 carbon atoms.

In addition, in this low density polyethylene in which the number of terminal carbon-carbon double bonds is 0.7 to 1.5 per 1000 carbon atoms, M, F, and R are further set in the range of 0.5 to 7.0. This is because if it is less than 0.5, scorch tends to occur during extrusion, whereas if it exceeds 7.0, uneven thickness will occur when a thick insulator layer is extruded.

Low-density polyethylene with the above characteristics allows organic peroxide,
For example, even if the amount of DCP added is relatively small, sufficient degree of crosslinking (
For example, a gel fraction of about 75% to 90%) was obtained, and the amount added was 1.0 to 3.0 parts by weight because if it was less than 1.0 parts by weight, a sufficient degree of crosslinking could not be obtained. Moreover, if the amount exceeds 3.0 parts of sodium bicarbonate, scorch will occur and a large amount of water will be generated due to secondary decomposition, which is undesirable.

In addition, examples of organic peroxides other than the above DCP include, for example, 2
．． 5-dimethyl-2,5-di(t-butylperoxy)
Examples include hexyne-3, di-t-butyl peroxide, and the like.

The oxidative deterioration inhibitor used in the present invention is 4.4'
-thiobis(3-methyl-6-t-butyl-phenol, bis[2-methyl-4-(3-n-alkyl(C+z
or C34) thiopropionyloxy)-5-t-butylphenyl] sulfide, and the amount added is 0.10 to 0.35 parts by weight.
If it is less than 0 parts by weight, a sufficient deterioration prevention effect cannot be obtained;
．． This is because if it exceeds 35 parts by weight, bloom will occur.

<Example I> Next, low-density polyethylene, organic peroxide, and oxidative deterioration inhibitor were blended in various proportions to create an insulator with a measured height (Nα■ to ■) that satisfies the conditions of the present invention. The compositions and insulating compositions with comparative height measurements (Nα■ to ■) lacking the conditions of the present invention were prepared as shown in Table 1, and various property tests were conducted. The results are also listed in Table 1.

The scorch time is T on the rheometer. Evaluated by value. In Table 1, T. : Time to reach 10% of maximum torque, T. 2 represents the time required to reach 90% of the maximum torque.

From Table 1 above, the actual height measurement No., ■ and the comparative height measurement Nα■,
When comparing Example No., ■ and comparative height measurement Nα■, and Example product No. 2, and comparison height measurement No., is slightly shorter, which shows that it is better.

<Example ■> A 66Kv, lX250mm2 cable was manufactured using an insulator made of a composition with the above-mentioned actual height measurement No. ■ and the comparative height Nα■, and the insulator was removed and heated (160"CX
conditions such as 4 hours), and the amount of water generated was measured. The results were 600 ppm for comparative height measurement Nα■, whereas it was 220 ppm for actual height measurement No. ■.

This result shows that in the case of the present invention, the effect of suppressing moisture generation is sufficiently achieved.

<Effects of the Invention> As is clear from the above description, according to the present invention, in an insulating composition using polyethylene, for example, low-density polyethylene, as an insulating material, the structure of the low-density polyethylene is A sufficient degree of crosslinking can be obtained by specifying a material having 0.7 to 1.5 double bonds per 1000 carbon atoms and using an appropriate amount of an organic peroxide as a crosslinking agent and an oxidative deterioration inhibitor. When the organic peroxide is DCP, this DCP
It is possible to provide an excellent insulating composition for electric wires and cables, which has a large water tree prevention effect that significantly reduces the amount of water generated as a secondary decomposition product, that is, prevents a drop in dielectric breakdown voltage. .

Claims (2)

[Claims] (1) 100 parts by weight of polyethylene having 0.7 to 1.5 terminal carbon-carbon double bonds per 1000 carbon atoms, 1.0 to 3.0 parts by weight of an organic peroxide, and oxidized An insulating composition for electric wires and cables, comprising 0.10 to 0.35 parts by weight of a deterioration inhibitor. (2) The insulator composition for electric wires and cables according to claim 1, wherein the low-density polyethylene has a melt flow ratio of 0.5 to 7.0.