KR100192125B1 - Resin compositions for controlling ion penetration - Google Patents

Abstract

The present invention relates to an ion permeation inhibiting resin composition, an ion permeation inhibiting resin composition in which an ethylene acrylic resin having ion permeation inhibiting ability is added to a basic resin used for a power cable for underground lines, and the ion permeation inhibiting resin By providing an ion permeation-inhibiting type semiconducting resin composition containing conductive carbon black in the composition, it is possible to reduce the ion permeation characteristics and produce a resin product having a low volume resistance. The resin having such characteristics is useful as a shielding layer of an electric wire. Do.

Description

Ion Permeation Resistant Resin Composition

1 is a view schematically showing an ion permeation measuring apparatus for measuring ion migration properties of a sample on a sheet made of an ion permeation inhibiting resin composition according to Examples and Comparative Examples of the present invention.

The present invention relates to an ion permeation inhibiting resin composition, and more particularly, to an ion permeation inhibiting resin composition in which an ethylene acrylic acid resin having ion permeation inhibiting ability is added to a base resin used for underground cable power cables and the ion permeation. The ion permeation suppression type semiconductive resin composition which added the conductive carbon black to the inhibitory resin composition is related.

In general, power cables for underground lines include outer shields and outer conductors including conductors, conductor strands, inner shields, inner semiconductive layers, insulation layers, and neutral wires. semiconductive layer and sheath, jacket. When a power cable having such a structure is used in the ground, moisture in the ground is attached into the main insulating layer to generate a water tree by interaction with an electric field (see MT Shaw and SH Shaw, Water). treeing in Solid Dielectrics, IEEE Trans, Electr. Insul., EI 19,419-452, 1984).

Sutri is a continuous microcrack failure that occurs inside the main insulation layer, and when viewed under a microscope, it is a tree-shaped name and is known as a major failure cause of power cables for underground lines. Once a tree is generated in the main insulation layer of the power cable, the tree grows due to the application of an electric field. The successive growth of the tree is the result of the continuous microcracks breakdown of the main insulation layer. If such micro crack breakdown continues, the mechanical and electrical properties of the main insulation layer are deteriorated and the main insulation layer is destroyed. Thus, tree tree growth in the main insulation layer of the power cable is a major cause of power cable failure.

As described above, the tree tree generation is caused by moisture migrated from the outside to the main insulating layer, and the water present on the ground and the ground contains various kinds of ionic components. Representative ionic components include calcium, magnesium and potassium, and when these ions are transferred to the main insulating layer together with moisture, these ionic components also grow tree (see MJ Given, RA Fouracre and BH Crichton, The Role of Ions in the Mechansism of Water Tree Growth, IEEE Trans.Electr.Insul., EI-22,151-156, 1987).

In the case of a power cable, the conductor is wrapped in an inner semiconducting layer, and the main insulating layer is wrapped in an outer semiconducting layer. Therefore, moisture penetrating into the power cable from the outside must pass through the semiconducting layer. The composition of the inner and outer semiconducting material is based on ethylenevinylacetate, and is composed of a large amount of additives such as conductive carbon black, antioxidants and processing aids. Conductive carbon black contains many kinds of impurities, some of which are dissolved in water and migrate into the main insulating layer while the moisture passes through the semiconducting layer.

The semiconducting resin used in the existing power cable has ethylene vinyl acetate as the main raw material as described above, but since ethylene vinyl acetate has no ability to trap ionic components mixed with moisture, The migration of ionic components cannot be suppressed.

Therefore, the use of conductive carbon black with very few impurities in the manufacture of semiconducting resins can reduce the content of ionic components transferred into the main insulating layer to some extent. It is not effective because it is a method that can not prevent the ionic component to be transmitted.

It is therefore an object of the present invention to provide a resin composition which has been created to overcome the above-mentioned disadvantages and which has the ability to suppress the transition of ionic components transmitted from the outside into the main insulating layer of the power cable.

In addition, another object of the present invention is to provide an ion permeation inhibitory semiconducting resin composition having ion permeability and semiconductivity by adding conductive carbon black to the ion permeation inhibitory resin composition.

In order to achieve the above object, the ion permeation inhibiting resin composition of the present invention is composed of 20 to 95% by weight of ethylene vinyl acetate resin, 5 to 80% by weight of ethylene acrylic acid resin, and 100 parts by weight of an antioxidant and 0 to 5 antioxidants. It is characterized by containing a weight part, 2-15 weight part of processing aids, and 1-5 weight part of organic peroxides.

In addition, the ion permeation inhibiting semiconducting resin composition of the present invention is characterized by consisting of 50 to 70 parts by weight of conductive carbon black to the ion permeation inhibiting resin composition.

Hereinafter, the present invention will be described in more detail.

Ethylene vinyl acetate in the composition of the present invention is preferably a vinyl acetate (vinylacetate) content of 15 to 40% by weight.

As the ethylene acrylic acid resin, a copolymer of ethylene and ethyl acrylic acid is preferably 5 to 40% by weight of acrylic acid. Ethylene acrylic acid resin is added to increase the ion permeability of the base resin. If less than 5 parts by weight is added in a ratio of 100 parts by weight of the base resin, the ion permeation inhibitory ability is insignificant. Ethylene acrylic acid resin sticks to the wall surface of the mixture, resulting in poor kneading property or workability.

As an optional ingredient, conductive carbon black is a conductive filler added to increase the conductivity of ethylene vinyl acetate resin. If it is used in an amount of less than 50 parts by weight relative to 100 parts by weight of the basic resin, the effect as a conductive filler is insignificant. It will promote a decrease in the mechanical properties of the composition, in particular the elongation.

Commercially available examples of conductive carbon black include Cabot's Vulcan XC-72, and other carbon blacks of the same grade may be used.

Antioxidant is an additive which is added to suppress the oxidation reaction occurring during processing or during use.It can be used by mixing the primary antioxidant and the secondary antioxidant for synergistic effect. When used in excess of the weight part, the performance of the peroxide is lowered and the degree of crosslinking is lowered.

Wax or metal stearate may be used as the processing aid. If the amount is less than 2 parts by weight based on 100 parts by weight of the basic resin, the effect as a processing aid is insignificant. Mechanical properties are lowered.

Organic peroxide is a crosslinking agent which is added to crosslink ethylene vinyl acetate, ethylene acrylic acid resin, and a mixture of the two resins. If it is used in an amount of less than 1 part by weight based on 100 parts by weight of the basic resin, the crosslinking effect is insignificant. Mechanical properties are lowered.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to Examples.

The ion measurement apparatus for measuring ion migration of the compositions according to the Examples and Comparative Examples of the present invention used CM60V manufactured by TOA, the schematic diagram of which is shown in FIG. The ion measuring device consists of two glass tubes, and it is designed to place a sheet-like sample of a certain thickness on the junction where the two glass tubes are bonded together, place a rubber ring on both sides, and fix the sheet-shaped sample firmly using a metal plate and screws from the outside. It was. After mounting the sample to prevent moisture from penetrating through the adhesive site from the outside, the joint was wrapped with a waterproof silicone adhesive, and then the test cell was placed in a water bath and the concentration was measured at regular intervals. 0.1 mole of calcium chloride solution was added to the left cell of the apparatus, and deionized distilled water was charged to the right cell. Ion concentration in the right cell was measured using a solution conductivity meter. After loading the sample, the concentration of the right cell was measured periodically for 30 days, and the diffusion coefficient of ions was calculated from the following equations (I) and (II).

In the formula (I), Jd is the flow rate per unit area (mole / cm 2 · sec), D is the diffusion coefficient (cm 2 · sec), C is the concentration (mole) and x is the sample thickness, and dC / dx is the concentration gradient (mole / Cm). Therefore, the diffusion coefficient D can be calculated from equation (II).

Examples 1 to 12 and Comparative Example 1

Each composition ratio of each Example and a comparative example is as Table 1, The composition ratio of this invention shows the weight ratio of each component, when the weight of the whole polymeric resin is 100. In Table 1, ethylene acrylic acid 1 has an acrylic acid content of 6 wt%, ethylene acrylic acid 2 has an acrylic content of 9 wt%, and ethylene acrylic acid 3 has an acrylic content of 20 wt%.

The composition having the composition ratio of Table 1 was soaked at 150 ° C. for 15 minutes using a Benbury mixer, and then kneaded at 120 ° C. for 10 minutes using a roll mill to prepare a resin.

About the produced resin, the ion permeation characteristic value after 30 days at 70 degreeC was measured. The results are shown in Table 2.

When comparing the initial concentration at 70 ℃ and the concentration after 30 days in Table 2, the simple comparison of the concentration after 30 days is not important because the initial concentration at 70 ℃ different from each other. However, the diffusion coefficient of ions, which is calculated from the slope of concentration change over time, is more important because it enables prediction of ion concentration change over time, and both the initial concentration and the concentration after a long time can be considered.

From Table 2, it can be seen that when ethylene acrylic acid is mixed with ethylene vinyl acetate, the concentration and diffusion coefficient of calcium ions measured in the right cell decrease after 70 ° C. and 30 days as the content of ethylene acrylic acid increases. When ethylene acrylic acid is mixed, it is thought that the ion permeation inhibitory capacity of the base resin will become larger with time.

[Examples 13 to 16 and Comparative Example 2]

Each composition ratio of each Example and Comparative Example is as Table 3, after compounding in the same manner as in Example 1 to prepare a resin was measured the calcium ion diffusion coefficient and volume details after 70 ℃, 30 days. The results are shown in Table 3 below.

From Table 3, it can be seen that in Examples 13 to 16 containing ethylene acrylic acid, the diffusion coefficient of calcium ions is smaller than that of Comparative Example 2 in which ethylene acrylic acid is not included, and Examples 13 to 16 show ethylene vinyl. When ethylene acrylic acid is mixed with acetate, it can be seen that as the content of ethylene acrylic acid increases, the diffusion coefficient of calcium ions decreases. Therefore, the ethylene acrylic acid component mixed in ethylene vinyl acetate has the ability to inhibit the permeation of calcium ions, and this ability is more effective as the content of ethylene acrylic acid increases.

On the other hand, when comparing Examples 9 to 12 and Examples 13 to 16, the case of Examples 13 to 16, that is, the case where conductive carbon black was added, was compared with Examples 9 to 12 where no conductive carbon black was added. It can be seen that the permeation inhibiting ability is improved, and it is considered that the conductive carbon black has a function of causing the synergistic effect of the ion permeation inhibiting ability. In addition, the compositions of the present invention have a very low value of the volume resistance of the semi-conducting compound for power cables currently commercially available at room temperature and 90 ℃, respectively, 300 ~ 1,000Ω · ㎝, 400 ~ 2,000Ω · ㎝ for power cables It can be seen that it can be used as a semiconductive material.

In the present invention, calcium chloride was used to measure the migration of calcium ions, but the same method may be applied to other kinds of ions. In this case, the diffusion coefficient of ions may be affected by the size of the ions, and the ion diffusion coefficient decreases as the ion size increases (see T. Bao and J. Tanaka, The Diffusion of Ions in Polyethylene, Proc. 3rd International Conference). on Properties and Applications of Dielectric Materials, Tokyo, Japan, 236-239, 1991).

When the resin composition of the present invention is used as described above, ethylene vinyl acetate resin and ethylene acrylic resin are used as base resins, and by adding conductive carbon black to such base resins, ion permeation characteristics are reduced, and resin products with low volume resistance are manufactured. The resin having such characteristics can be usefully used as a shielding layer of an electric wire.

Claims (5)

100 parts by weight of a basic resin composed of 20 to 95% by weight of ethylene vinyl acetate resin and 5 to 80% by weight of ethylene acrylic acid resin, 0 to 5 parts by weight of antioxidant, 2 to 5 parts by weight of processing aid and 1 to 5 parts by weight of organic peroxide An ion permeation inhibiting resin composition, characterized in that. The ion permeation inhibiting resin composition according to claim 1, further comprising 50 to 70 parts by weight of conductive carbon black. The ion permeation inhibiting resin composition according to claim 1, wherein the ethylene vinyl acetate has a vinyl acetate content of 15 to 40 wt%. The ion permeation inhibiting resin composition according to claim 1, wherein the ethylene acrylic acid resin has an acrylic acid content of 5 to 40 wt%. The ion permeation inhibiting resin composition according to claim 1, wherein the processing aid is wax, metal stearate or a mixture thereof.