JPS61227305A - Water tight insulation wire - 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 relates to a watertight insulated wire in which the gaps between wires of a stranded wire conductor are filled with a watertight compound, and more specifically, a watertight insulated wire in which the gaps between the wires of a stranded wire conductor are filled with a watertight compound. It is related to.

[Conventional technology and its problems]

Conventionally, in overhead insulated wires, etc., in order to prevent water from entering the stranded conductor and prevent deterioration of the conductor such as stress corrosion,
A watertight insulated wire is used in which the gaps between the wires of a stranded conductor are filled with a watertight compound.

Some types of this watertight compound are filled with a low-viscosity watertight compound made by dissolving polyethylene wax in polybutene oil, but in recent years, so-called dry-type compounds filled with high-viscosity plastic compounds have been introduced in consideration of workability. Watertight insulated wires are often used.

However, if the viscosity is too high, it is difficult to press fit into the stranded wire conductor, necessitating complicated manufacturing methods such as filling when twisting the strands together, and the manufacturing equipment becomes larger.

In addition, some compounds contain low-molecular-weight polyethylene or polyethylene wax to lower the melt viscosity during filling so that they can be press-fitted into stranded wire conductors after twisting. Due to poor adhesion and poor rubber elasticity, even if the wire is initially watertight, when the wire is bent during overhead wiring, separation occurs between the conductor and the watertight compound, causing problems such as loss of watertightness. There is.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and uses a watertight compound that has a melt viscosity that can be press-fitted after twisting wires and has good adhesion to conductors. To provide an insulated wire with excellent watertightness that does not lose its watertightness even when the wire is bent.

[Means to solve the problem]

In order to achieve the above object, the inventors of the present invention have made extensive studies and found that a modified polyolefin adhesive is added to and mixed with an ethylene vinyl acetate copolymer having a melt index of 15 to 200 as a base material. We have discovered that an excellent watertight insulated wire can be obtained by filling the gaps between the strands of a stranded conductor with a watertight compound, and have completed the present invention.

In the present invention, melt index is JIS-6
Measured by the method specified in 760, 1
It refers to the amount of outflow produced in a duram per 10 minutes at 90°C.

Melt index used in the present invention is 15 to 200
The base material of ethylene vinyl acetate copolymer is only one type of ethylene vinyl acetate copolymer whose melt index is within the range of 15 to 200. It includes a mixture having a melt index of 15 to 200 obtained by mixing two or more types of ethylene vinyl acetate copolymers within the range.

In addition, the modified polyolefin adhesive used in the present invention is a synthetic material in which functional groups are introduced into various polyolefins, such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, through graft polymerization to give them adhesive properties with metals and plastics. Refers to resin.

As for the base material of ethylene vinyl acetate copolymer, the larger the melt index, the easier it is to fill, but if it exceeds 200, there is a risk of softening or dripping when the usage temperature becomes high.

Moreover, the tensile strength of the conductor connection portion by the sleeve is also reduced, which is not preferable.

On the other hand, a material having a melt index of less than 15 is not preferable because excessive pressure is required to fill the stranded wire conductor and the manufacturing equipment becomes large.

Furthermore, the ethylene-vinyl acetate copolymer used as the base material for watertight compounds has the ability to
It is desirable to have rubber elasticity that can accommodate the strain caused by this.

When using a mixture of two or more ethylene-vinyl acetate copolymers with a melt index of 2 to 400 as a base material, it is possible to use a mixture of two or more ethylene-vinyl acetate copolymers with a relatively high melt index and low rubber elasticity. Since it can be made to have high fluidity and easy filling at the processing temperature and high rubber elasticity at the use temperature after filling, a watertight insulated wire with better watertightness after bending can be obtained.

The base material of the ethylene vinyl acetate copolymer used in the present invention preferably has a vinyl acetate content of 15 to 45% by weight. The reason for this is that if the content is less than 15% by weight, the flexibility of the conductor will be impaired, and if it is more than 45% by weight, the adhesive force with the insulator will be reduced.

Next, the reason why a modified polyolefin adhesive is used by adding it to a watertight compound is, of course, to increase adhesive strength, and the reason why a modified polyolefin based adhesive is selected as an adhesive is because it is similar to ethylene vinyl acetate. The reason is that the polymer has good compatibility with the base material.

Particularly desirable is a modified ethylene vinyl acetate copolymer obtained by introducing a functional group into an ethylene vinyl acetate copolymer.

For example, an adhesive consisting of a partially saponified ethylene-vinyl acetate copolymer containing an alloy of acetoxy groups, hydroxyl groups, and carboxyl groups having the chemical structure shown below (manufactured by Shikinichi Yakuhin Kogyo Co., Ltd., Dumilan, C type) is mixed with ethylene vinyl acetate. It is appropriate to add 5 to 30 parts by weight per 100 parts by weight of the copolymer base material.

0(20ωCH30H x-ct-t CH2 x-CH X: Contains a C0OH group.

When the amount of the adhesive is less than 5 parts by weight, the adhesive effect is poor;
If it exceeds 30 parts by weight, the adhesive force with the conductor is too strong.
This is undesirable because when stripping the insulation, the watertight compound remains adhered to the conductor.

In addition to the above-mentioned Dumilan, examples of modified polyolefin adhesives include Atmer (trade name, Mitsui Petrochemical Industries, Ltd.); in this case, per 100 parts by weight of the base material,
It is preferable to add 1 to 10 parts by weight.

Naturally, the present invention also includes a watertight compound to which a small amount of an anti-aging agent or a processing aid is added in addition to the above-mentioned base material and adhesive.

Press-fitting is an efficient method for filling the stranded conductor with the watertight compound, but the method is not limited thereto.

Next, to explain the structure of the present invention using the drawings, FIG. 1 is a cross-sectional view of a watertight insulated electric wire according to the present invention, where 1 is a stranded conductor, 11, 12, and 13 are a center layer, a first layer, The second layer of strands, 2, is a watertight compound prepared by adding and mixing a modified polyolefin adhesive to an ethylene vinyl acetate copolymer base material having a melt index of 15 to 200, and 3 is a crosslinked polyethylene insulator.

In the present invention, the inner layer wire, for example, the center layer wire 11,
Also included are outer layer strands, for example those thicker than the strands 12 and 13 of the first and second layers.

Insulators include all commonly used insulating materials such as cross-linked polyethylene, polyethylene, polyvinyl chloride, and ethylene propylene rubber.

〔Example〕

Examples of the present invention will be described below in comparison with comparative examples.

Each of the watertight insulated wires of the example and comparative example had a diameter of 2,0
A stranded wire conductor made by concentrically twisting 19 FF hard copper wires was filled with a watertight compound having the composition shown in Table 1, and then extruded and coated with weather-resistant cross-linked polyethylene having a thickness of 2.5 WII. Created.

Table 2 shows the results of testing the characteristics of Examples 1 to 7 and Comparative Examples 1 to 5 using the following method.

Test method (a) Initial watertight property: From one end of a 50a II length sample,
A water pressure of 1.0 kQ/d was applied, and 10 samples were checked for water leakage from the other end.

(b) Watertightness after bending: A sample with a length of 50α is
It was wound around half the circumference of a double-diameter mandrel, then unwound, and bent five times, with this back and forth being counted as one time. Thereafter, the same test as the previous water distribution tightness test was conducted, and the same ranking was performed.

(c) Dripping property: Strip off the 3α insulator at one end of a sample with a length of 131, hang it vertically in a constant temperature bath at 100°C with that part facing down, and after 24 hours check whether the filling compound has dripped or not. The results were as follows: O: Not dripped, X: Dropped.

2) Peelability: When stripping the insulation of an insulated wire, various tools are used. A common method is to rotate the wire so that the cutting edge 21 stops slightly before the conductor surface 24, and then rotate the blade 20 around the wire shaft 25 in this state to strip the wire. A tool that can strip the wire continuously in a spiral pattern from the end to the center by applying force to the wire (for example, Furukawa Electric's GS Peeler)
) is also available. In this test, we investigated whether the watertight compound peeled off together with the insulator and did not remain on the conductor when the insulator was removed using the GS peeler.The results were A: The watertight compound was completely removed. B: The watertight compound was completely peeled off. C: The watertight compound adhered to the conductor and tended to remain.

(E) Melt index: The watertight compound used for each sample was subjected to a load of 2.16 OL and the outflow amount for 10 minutes at 190° C. was measured according to the method specified in JIS K 6760.

(f) Adhesion: As shown in Figure 3, a sheet of watertight compound (1n thickness) 32 used for each sample and a polyethylene sheet containing a crosslinking agent are placed on top of the copper tape (1n thickness, 2Sjff width) 31. (2 fll thickness) 33 were sequentially laminated and heated at 170° C. for 10 minutes under a pressure of 5 oklj/d. Using a tensile tester as a sample, grip the unlaminated portions 34 and 35 of the insulator, It was pulled at a speed of 100 fl/min. The results are weak: peeling between the copper tape and the filling compound, the strength of which is 0.5 kq / 2 s y
Suitable for items less than x* width: Items that peel between the copper tape and filling compound, and the strength is greater than 0.5#/2Sff width Strong: Items where the filling compound is torn off and remains on both the copper tape and the insulator (g) Comb elasticity: A sheet with a thickness of 1 fl was prepared from the watertight compound used for each sample, punched out using a JIS No. 3 dumbbell, and stretched to 50% and 100% elongation at a tensile speed of IQ a+/min. The residual elongation was measured 20 minutes after opening, and the results were evaluated according to the following criteria.

Good: The residual elongation after 50% stretching is 7.5% or less, and the residual elongation after 100% stretching is 12.5% or less. Poor: Those that do not satisfy either of the two conditions listed in Table 2. As is clear from the results, all of the watertight insulated wires of the examples of the present invention have only initial watertightness, excellent watertightness after bending, and moderate adhesion between the conductor, watertight compound, and insulator. , good peelability.

In addition, a gripping force test using a retaining clamp and a tensile test on the conductor connection portion using a compression sleeve were also conducted for the samples of each example, but no problems were found.

On the other hand, the watertight insulated wire of the comparative example does not satisfy any of the above characteristics, and the following can be seen from the results.

Comparative Example 1 did not pass the dripping test, but this is probably because the melt index of the watertight compound used was too large.

In addition, Comparative Example 2 did not pass the watertightness test both initially and after bending, but this seems to be due to the fact that no adhesive was mixed into the watertight compound and the base material lacked rubber elasticity. .

Comparative Example 3 also had poor watertightness because no adhesive was used, but
Initial characteristics are better than Comparative Example 2. This seems to be due to the good rubber elasticity of the base material. Comparative Example 4 uses the same compound as Comparative Example 3 in which an adhesive is added to the base material, but since the amount of adhesive added is too large, there is a problem in peelability.

Comparative Example 5 is the same as Comparative Example 2, in which an adhesive is added to the base material with poor rubber elasticity, and although the watertightness is better than Comparative Example 2, the base material has the same defects as Comparative Example 2. , but did not pass the exam.

In addition, when an ethylene vinyl acetate copolymer that has rubber elasticity and can be press-fitted into a stranded wire conductor like the watertight insulated wire of Comparative Example 3 was used without adding an adhesive, there was no variation in watertightness. However, there were some good ones, so we decided to use thermoplastic elastomer from the perspective that if we used a material with more rubber elasticity, we could obtain a good watertight insulated wire without using an adhesive. (Product name: TPE
-8721, manufactured by Sumitomo Chemical) was also prepared, and excellent results were obtained. however,
Materials with high rubber elasticity have a high melt viscosity at processing temperatures and are difficult to fill, so if they are improved by adding an appropriate softener that does not have a negative effect on the insulator, they can be made to have excellent watertightness. It is assumed that an insulated wire is obtained.

〔Effect of the invention〕

As described above, according to the present invention, by using a watertight compound that has a melt viscosity that can be press-fitted into a stranded wire conductor and has good adhesiveness and rubber elasticity, workability during connection can be improved. Problems such as the gripping force caused by the clamp and the tensile strength of the conductor connection portion caused by the sleeve can be solved, and a watertight insulated electric wire can be provided that has excellent watertightness both initially and after bending.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a watertight insulated electric wire of the present invention, FIG. 2 is an explanatory diagram of a peelability test, and FIG. 3 is an explanatory diagram of an adhesion test of a watertight compound. 1...Twisted wire conductor, 2...Watertight compound, 3...
・Insulator, 20...Blade of peeling tool. Figure 1 Figure 2 Figure 3 Figure 1...Twisted conductor 2...Watertight compound 3...Insulator 11...Conductor 12...Conductor 13...Conductor

Claims (1)

[Scope of Claims] 1. A watertight compound made by adding and mixing a modified polyolefin adhesive to a base material of ethylene vinyl acetate copolymer having a melt index of 15 to 200 is filled into the gaps between the wires of a stranded wire conductor. A watertight insulated wire characterized by: 2. The watertight insulated electric wire according to claim 1, wherein the modified polyolefin adhesive is made of a modified ethylene vinyl acetate copolymer obtained by introducing a functional group into an ethylene vinyl acetate copolymer.