JP2579493B2 - Insulator composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an insulator composition used for a connection portion of an electric wire or a cable, and more particularly to an insulator which suppresses generation of water trees due to heating during molding. It relates to a composition.

<Prior Art> Conventionally, in order to form a connection portion of an electric wire / cable, a cross-linked polyethylene is heated by molding. And
Dicumyl peroxide (hereinafter referred to as DCP) was generally used as a crosslinking agent for the crosslinked polyethylene.

<Problems to be Solved by the Invention> However, this DCP has the following problems.

When DCP is added in large amounts to improve the degree of crosslinking,
During extrusion, scorch (early crosslinking) occurs, amber (burned resin) is generated in the insulator at the connection portion, and there is a possibility that insulation performance may be reduced.

The DSP becomes cumyl alcohol (hereinafter abbreviated as CA) and acetophenone (abbreviated as AP) at the time of crosslinking, and this CA is decomposed by heat at the time of heating the mold to form α-methylstyrene (hereinafter abbreviated as “A”). α-MS) and water.

This water is agglomerated in the insulator, and when an electric field is applied to the electric wire / cable, it causes water tree generation. This water tree is considered to cause a decrease in the dielectric breakdown voltage of the insulator.

The present invention has been made in view of such a conventional situation, and solves the above-mentioned problems by adding other additives together with DCP in crosslinking of polyethylene.

<Means for Solving the Problems and Their Functions> The feature of the present invention is that the number of terminal carbon-carbon double bonds is 0.7 to 1.5 per 1000 carbon atoms, and the melt flow ratio ( 100 parts by weight of low-density polyethylene having an MFR of 0.5 to 7.0, 0.5 to 3.0 parts by weight of DCP, 0.5 to 1.0 part by weight of triallyl isocyanurate (hereinafter abbreviated as TAIC), and 4,4'-thiobis 0.1-0.6 parts by weight of (6-tertiary-butyl-3-methylphenol) (hereinafter abbreviated as 4,4'-thiobis) in an insulator composition used for connection parts of electric wires and cables.

The amount of DCP used in the present invention is 0.5 to 3.0 parts by weight because a desired degree of crosslinking cannot be obtained if the amount is less than 0.5 part by weight, and if the amount exceeds 3.0 parts by weight, scorch is generated too much. .

Further, the TAIC used in the present invention has a function of suppressing the generation of water at the time of heating the mold, and the compounding amount is set to 0.5 to 1.0 part by weight, when less than 0.5 part by weight, the degree of crosslinking is low. The reason is that almost no effect of suppressing the generation of water is obtained, and if it exceeds 1.0 part by weight, scorch is generated.

In addition, 4,4′-thiobis used in the present invention has a function of suppressing cross-linking and prevents oxidative deterioration.The amount of 0.15 to 0.6 parts by weight is less than 0.15 parts by weight. This is because the effect of suppressing crosslinking is small and scorch occurs.
On the other hand, if it exceeds 0.6 parts by weight, the amount is too large and a sufficient degree of crosslinking cannot be obtained.

In addition, the polyethylene used in the present invention has terminal carbon-carbon double bonds per 1,000 carbon atoms, 0.7 to 1.5,
It is a low-density polyethylene having a melt flow ratio (MFR) of 0.5 to 7.0. Here, the number of terminal carbon-carbon double bonds is set to 0.7 to 1.5 per 1000 carbon atoms, and the melt flow ratio is set to 0.5 to 7.0. This is because the degree is low and if this value exceeds 1.5, scorch occurs. If the melt flow ratio is less than 0.5, scorch is likely to occur. If the melt flow ratio exceeds 7.0, uneven thickness and sagging occur during molding.

<Example I> Next, according to the formulations shown in Table 1, various insulator compositions composed of various products of the present invention (Examples 1 to 3) and comparative products (Comparative Examples 1 to 4) were prepared. The connection portion of the cable was extruded with an extruder for the connection portion and heated by molding to form a connection portion.

The characteristics (scorch time, amount of water generated after extrusion to heating) of each of these connection parts were examined. In addition, the scorch time measurement test and the water generation amount measurement test were performed as follows.

(1) Scorch time measurement test Using a Mooney viscometer, the measurement was performed using the time taken to increase 5 points from the minimum torque value as the scorch time.

(2) Moisture generation measurement test The extrusion was performed by the Karl Fischer method in two stages after extrusion and after heating the mold.

In the above Table 1, each of Examples and Comparative Examples
When compared with the above, the water content in the decomposition residue of the composition is not so large in the extruder, but is large after heating simulating mold heating (160 ° C. × 4 hours). different. In other words, in Examples to
Does not decompose very much, and for Comparative Example 1 to 100 ppm or less, which is the same as the water content of the extruder, CA decomposes to α-MS and water, and the water content is, for example, a comparison between Examples and Comparative Examples. It is about 6 times or more.

In addition, in the gel fraction and scorch time, which are one of the cross-linking properties, when comparing each of the examples to the comparative example, the composition of the examples to have a high degree of cross-linking, and the scorch is the same as the comparative example to. It turns out that it is about the same.

<Example II> Using the compositions of Examples and Comparative Examples in Table 1 above,
A molded joint was applied to the connection part of the 66kv, 1c × 400mm ² CV cable, a long-term energization of 70kv × 6 months was performed, and then the water tree was observed.

As a result, it was confirmed that in the case of the example, the occurrence of water trees was extremely small, and in the case of the comparative example, the occurrence of water trees occurred frequently. That is, it is understood that the occurrence of water trees is effectively suppressed in the product of the present invention.

<Effects of the Invention> As is apparent from the above description, according to the present invention, a high degree of cross-linking is obtained, and scorch is less likely to be generated in water-molding in the case of insulative molding of connection portions of wires and cables. It is possible to provide an excellent insulator composition which exhibits stable performance over a long period without generation of the slag.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshio Niwa 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (56) References JP-A-58-89708 (JP, A) JP-A-51 −136181 (JP, A)

Claims (1)

(57) [Claims] (1) a carbon-carbon double bond having a terminal carbon-carbon double bond of 0.7 to 1.5 per 1000 carbon atoms, and a melt flow ratio (MF
R.) is 0.5 to 7.0 parts by weight, low-density polyethylene is 100 parts by weight, dicumyl peroxide is 0.5 to 3.0 parts by weight, triallyl isocyanurate is 0.5 to 1.0 parts by weight, and 4,4'-thiobis (6-tertiary) is used. -Butyl-3-methylphenol) in an amount of 0.15 to 0.6 parts by weight for use in connection parts of electric wires and cables.