JPS621698Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention uses a layer made of foam insulation as the inner layer.
This invention relates to a two-layer insulated wire having a layer made of a non-foamed solid insulator as an outer layer. Double-layer insulated wires can be used as wires for communication cables because the insulation thickness can be reduced by making the inner layer highly foamed, and the mechanical strength can be improved by providing a solid layer on the outer layer. ,
It has become widely used. In these electric wires for communication cables, a required amount of antioxidant is always added to the insulating composition in order to maintain weather resistance. Particularly when using a copper conductor, addition of a copper damage stabilizer in addition to an antioxidant is very effective. However, even cables using electric wires treated with these stabilizer formulations will deteriorate over a long period of time at high temperatures of 40 to 70 degrees Celsius, and the antioxidants and copper damage stabilizers in the insulation composition will be subject to diffusion phenomena caused by heat. This tends to cause a bleed phenomenon and reduce the weather resistance of the insulating composition. Furthermore, in cables that contain waterproofing fillers between the insulated cores, the waterproofing filler can swell the insulation composition of the wire and leach stabilizers and other components from the insulation composition. There was a risk that the weather resistance of the insulating composition would be significantly reduced. The present invention has been devised to overcome these drawbacks. Generally, materials used as insulating compositions for electric wires for communication cables include low-density polyethylene, high-density polyethylene, and polypropylene. The persistence of antioxidants, copper damage stabilizers, etc. in these insulating compositions is controlled by the diffusion rate based on the morphology of crystalline/amorphous regions.For example, at room temperature, high-density polyethylene with few amorphous regions It has been found to exhibit better retention than low density polyethylene. Furthermore, in a cable using a waterproof filler, the difference in compatibility between the antioxidant and the copper damage stability with respect to the waterproof filler that has penetrated into the insulating composition by swelling greatly affects its persistence.
Therefore, in order to improve the persistence of stabilizers such as antioxidants and copper damage stabilizers in insulation compositions, by adding an appropriate amount of a copolymer of ethylene and carboxylic acid or ethylene and carboxylic acid ester, stabilizers such as antioxidants and copper damage stabilizers can be added. The idea was to take advantage of the fact that the compatibility (solubility) of Table 1 shows the residual effect of the antioxidant (in this case, using the product name Santonox R) in relation to the vinyl acetate content in the ethylene-vinyl acetate copolymer. It can be seen that it is effective. It has also been found that a blend system of polyethylene and ethylene vinyl acetate copolymer has similarly good residual effects.

[Table] Left in the tank. )
If we consider only the persistence of the stabilizer in the insulating composition, then both the inner foam layer and the outer solid layer of the two-layer foam insulating layer should be made of polar polyolefin such as ethylene-vinyl acetate copolymer. The most effective way is to add
Considering the electrical properties of the insulating composition such as dielectric constant, dielectric loss, volume resistivity, and withstand voltage, as well as high-speed extrudability in manufacturing, polyolefin with a polar group is added only to the outer solid insulating layer. This is desirable. In this case, the persistence of the stabilizer in the outer solid layer is sufficiently high, so that its own weather resistance is sufficiently maintained, and migration of the stabilizer in the inner foam layer to the outer layer is also suppressed. As a whole, an insulator with very good weather resistance is formed. Furthermore, it was confirmed that the electrical characteristics were hardly affected. Embodiments of the present invention will be described in detail below. As shown in Figure 1, a foamed insulating layer 2 and a non-foamed solid insulating layer 3 are provided on the conductor 1, but in reality, 0.5 mm annealed copper wire is used as the conductor, and the foamed insulating material has a high density.
High-density polyethylene with a melt index of ^0.45 containing 0.5% of ADCA (azodicarbonamide) as a foaming agent was used as a solid insulating material, and the high-density polyethylene alone (A ) and 10% ethylene-vinyl acetate copolymer blended with the polyethylene (B) 2
Seeds were prepared and two types of double-layer insulated wires with a foaming degree of 40% were manufactured. The amount of stabilizer in the ethylene vinyl acetate copolymer is determined by the OIT with high density polyethylene (A).
The OIT value of the blended high-density polyethylene (B) is also lower than that of the high-density polyethylene (A) alone. The double-layer insulated wire produced as described above was wrapped around a rod of its own diameter and tested for cracking of the insulator in an air oven at 110°C. ) and then a differential scanning calorimeter (Differential
The oxidation induction time was examined using a scanning calorimeter. The results are shown in Table 2.

[Table] From these results, it is clear that the blend of 10% ethylene-vinyl acetate copolymer (B) has better insulation both in self-diameter winding deterioration and in the oxidation induction period after being left in a waterproofing filler at 70°C. It can be seen that the stabilizer remains in the composition well. Further, the blending amount of the ethylene vinyl acetate copolymer depends on the vinyl acetate content contained in the ethylene vinyl acetate copolymer. In addition to ethylene-vinyl acetate copolymers, ethylene and carboxylic acid or ethylene and carboxylic acid esters, such as ethylene-ethyl acrylate copolymer (EEA) and ethylene-acrylic acid copolymer (EAA), which also have polar groups, can be used. Copolymers can be used as well. As described above, the double-layer insulated wire of the present invention has excellent weather resistance and is particularly suitable for cables containing waterproof fillers.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the double-layer insulated wire of the present invention.
2 indicates a conductor, 2 indicates a foamed insulating layer, and 3 indicates a non-foamed insulating layer.

Claims (1)

[Claims for Utility Model Registration] (1) A double-layer insulated wire in which a conductor is provided with a layer made of a foamed insulator as an inner layer and a layer made of a non-foamed insulator as an outer layer, the outer layer material being non-polar polyolefin. A double-layer insulated wire characterized by being made of a blended material of ethylene and carboxylic acid or a copolymer of ethylene and carboxylic acid ester. (2) Utility model registration claim 2 described in paragraph (1), characterized in that the copolymer of ethylene and carboxylic acid ester is an ethylene-vinyl acetate copolymer.
Layer insulated wire.