JPH0317907A - Electric insulation material for electric 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 Field of Application J This invention relates to an electrical insulator for electric wires and cables that can suppress the occurrence of water litter, particularly water litter. [Prior Art] Cross-linked polyethylene has a high degree of electrical insulation, so it is often used as an electrical insulator for electric wires and cables. However, when cross-linked polyethylene insulated wires and cables are used in a humid or waterlogged environment, water trees occur and the electrical insulation performance deteriorates significantly. Water trees occur when water condenses in local high electric field areas such as voids, foreign matter, and irregularities at the interface between the insulator and the semiconducting layer in the cross-linked polyethylene insulator. For this reason, many efforts have been made to eliminate these defects in wire and cable insulation, and improvements in resin quality control and wire and cable manufacturing technology have been shown to be effective in preventing water tree formation. It's improving. However, current technology cannot completely eliminate these defects, and measures to prevent the occurrence of water trees are being investigated from various angles. This invention was made in view of the above-mentioned points, and it is possible to eliminate voids, foreign matter, etc. in the insulator.
Another object of this invention is to provide an electrical insulator for wires and cables that can suppress the occurrence of water trees even if there are defects such as irregularities at the interface between the insulator and the semiconducting layer. [Means and Effects for Solving the Problems] This invention is based on 100 parts by weight of polyethylene, an ethylene copolymer, or a mixture thereof, of a secondary amine having a total carbon number of 10 to 70. O○5~l. It is characterized by the addition of 0.005 to 1.0 parts by weight of O and fatty acid ester, and has greatly improved water resistance, especially pour-tree resistance. [Example] The secondary amine having a total carbon number of 10 or more used in this invention has the following structure. (Total carbon number of R, , R.: 10 or more) Examples of chemicals having such a structure include dioctanylamine, diventanylamine. Didodecylamine, dieicosanylamine, ditridecylamine, dipenecudecylamine, dihebutadecylamine, dihydroxystearylamine, stearylamine, methylstearylamine, dicutatecylamine, dinonadecosanylamine, ditricosanylamine, ditriacon Examples include tanylamine, dimontanylamine, dioleylamine, dilaurylamine, etc. It should be noted that there is no problem even if some atoms such as oxygen, nitrogen, sulfur, etc. or atomic groups consisting of these atoms are included in the structure of R. Additionally, several of these compounds may be used in combination. Here, the total number of carbon atoms is set to 1○ or more because if it is less than 10, it will not be compatible with polyethylene, ethylene copolymer, or a mixture thereof and will precipitate on the surface. The upper limit is not particularly defined, but if it exceeds 70, the effect of the amine in suppressing the occurrence of bow tite tree decreases, so a value of 70 or less is appropriate. Furthermore, the amount of these added is 0.005 parts by weight to 1.0 parts by weight. - If the parts by weight range is exceeded, and due to compatibility limitations, it will precipitate on the surface of the insulator (this phenomenon is called bloom), reducing the quality of the product. Base resins include polyolefins containing ethylene in the majority, such as low-density polyethylene, medium-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, and ethylene-propylene copolymer. One or a combination of two or more of these may be used. As the crosslinking agent, commonly used dicumyl peroxide, l,3-bis-(t-butyl peroxyisobrobyl)benzene, 2.5-dimethyl-2.5
Examples include -di(t-butyl peroxy)-hexyne-3. Crosslinking methods include chemical crosslinking using organic peroxides, silane water crosslinking, and ionizing radiation. If necessary, there is no problem in adding lubricants, colorants, fillers, crosslinking accelerators, etc. The effect of moisture on bow tree is extremely large, and bow tree is also found in cables that are energized in the air and cables that are water-shielded with metal sheaths. These are not caused by moisture seeping in from the outside, but by a small amount of moisture contained inside the cross-linked polyethylene during cable manufacturing. It goes without saying that the insulator of the present invention is effective against such bow ties.

Specific examples will be explained below along with comparative examples. Electrical insulators for wires and cables having the formulations shown in each example in Table 1 were adjusted to have the compositions of Examples 1 to 6 and Comparative Examples 1 to 3. A sheet prepared by kneading the composition of each of these examples with a heated roll at a temperature of 120°C was pelletized using a pelletizer. Place this on conductor 1 with an outer diameter of 3 mm to a thickness of 0.5 mm.
The insulator 3 was extruded and coated with the polyethylene semiconductive layer 2 to a thickness of 2 mm, then crosslinked in a dry crosslinking pipe using nitrogen gas as a heating medium, and then cooled under pressure. Insulated wires 5 were obtained by extrusion coating with the outer semiconductive layer 4, and used as samples of Examples 1 to 6i3 and Comparative Examples 1 to 3. The evaluation method was to heat the electric wire 5 produced as described above to 90°C.
The conductor is immersed in hot water at a temperature of
The voltage was applied for 00 days. This was sliced into thin slices, boiled and stained with a methylene blue aqueous solution, and the presence or absence and number of bow tit trees were examined using an optical microscope. Bloom uses the pellets made before making electric wire 5 as 8.
After being stored in a constant temperature bath at 0°C for 10 days, the surface was observed and evaluated. Table 1 summarizes these evaluation results. As is clear from Table 1, in Examples 1 to 6, in which a limited amount of the additive according to the present invention was added, the occurrence of bowtery was sufficiently suppressed, and no bloom was observed. On the other hand, in Comparative Example 1, in which the above-mentioned additive was not added, and in Comparative Example 2, in which the additive was added in a limited amount, a very large number of bow tit trees occurred. 4 Also,
Comparative Example 3, in which the above additive was added in excess of the limited amount,
Bloom was seen. (The following is a blank space.) [Effects of the Invention] As explained above, the insulator for electric wires and cables of the present invention has defects such as voids and foreign matter in the insulator, and irregularities at the interface between the insulator and the semiconducting layer. However, the occurrence of bow tite trees can be sufficiently suppressed, and an excellent insulator that does not cause blooming can be obtained.

[Brief explanation of the drawing]

The figure shows electric wires and wires to which an embodiment of the electrical insulator of the present invention is applied.
It is a cross-sectional view showing the cable. 1... 2... 3... 4... 5. Conductor: Inner semiconducting layer Insulator: External semiconducting layer Electric wire/cable

Claims (1)

[Claims] The total number of carbon atoms is 10 to 7 per 100 parts by weight of polyethylene, ethylene copolymer, or a mixture thereof.
1. An electrical insulator for wires and cables, characterized in that 0.005 to 1.0 parts by weight of a secondary amine of No. 0 and 0.005 to 1.0 parts by weight of a fatty acid ester are added.