KR20040082835A - semi-electric-composition for high-pressure cable - Google Patents

Abstract

PURPOSE: A semiconductive composition for a high voltage cable is provided to optimize scorch time, a degree of crosslinking and mechanical and electric properties, to improve blooming properties and to reduce impurities by using a cresol-based antioxidant. By using the semiconductive composition, excellent interfacial properties are obtained in long-term use at high temperature. CONSTITUTION: The semiconductive composition for a high voltage cable, which can both used in the inner and the outer semiconductive layers comprises: 100pts.wt of a polyethylene acrylate copolymer having 10-20wt% of the acrylate content and 1.8-8g/10min of melt index or 100pts.wt of a matrix resin where a polyethylene acrylate copolymer having 10-20wt% of the acrylate content and 1.8-8g/10min of melt index is blended with any one of polyethylene butylacrylate having 25-40wt% of the acrylate content and 15-300g/10min of melt index and polyethylene ethylacrylate having 15-30wt% of the ethylacrylate content and 15-300g/10min. of melt index; 45-70pts.wt of a carbon black; 0.1-5pts.wt of a process oil; 0.2-2pts.wt of a crosslinking agent; and a cresol-based antioxidant being used alone or together with a phenol-based antioxidant, in which the cresol-based antioxidant is 4,6-bis(octylthiomethyl)-o-cresol.

Description

Semi-electric composition for high-pressure cable

The present invention relates to a semiconductive composition for a high voltage cable, and more particularly to a semiconductive composition for a high voltage cable that can be applied simultaneously as a material of the inner semiconducting layer and a material of the outer semiconducting layer.

Semiconducting materials for high voltage cables of 66 kV or more are classified into an inner semiconducting layer (hereinafter referred to as an inner diagram) and an outer semiconducting layer (hereinafter referred to as an outer diagram) according to their use.

Since the internal resistance is located between the conductor and the insulator, the adhesiveness with the metal such as aluminum (Al) or copper (Cu) should be excellent, as well as the conformity with the insulator made of crosslinked polyethylene. In addition, the electrical stability of long-term use should be secured.

On the other hand, the outer diameter as well as the degree of consistency with the insulator and the electrical stability while ensuring excellent mechanical properties while ensuring the stability of long-term use.

Such semiconducting materials are suitable for application of carbon black, antioxidants, crosslinking agents and crosslinking aids to polyethylene resins, in particular ethylene vinyl acetate resins or ethylene ethyl acrylate resins alone or blended matrix resins. It is manufactured through.

That is, the ethylene copolymer resin is a base, and carbon black corresponding to about 40 to 80 parts by weight is added thereto, and a small amount of an antioxidant, a crosslinking agent, and a crosslinking aid are added. By determining the degree of crosslinking, it becomes a major factor in determining the electrical and mechanical properties after cable extrusion.

At this time, when the content of the crosslinking agent is small, sufficient mechanical and electrical properties cannot be secured.

In addition, when the content of the crosslinking agent increases, the crosslinking agent that does not participate in the crosslinking reaction in the semiconducting layer of the cable, which has been completed until the crosslinking tube process, functions as an impurity. Intermediate junction box and terminating junction box are connected. When heat is applied using a torch, additional crosslinking occurs, which causes problems such as generation of an electric tree under the influence of crosslinking byproducts such as acetophenone and cumyl alcohol. .

On the other hand, when the same cross-linking agent is applied, the cross-linking degree after the extrusion process is known to be about 5% lower than the cross-linking degree of the internal resistance. This is because the effect of increasing the crosslinking agent content of the actual internal resistance occurs.

Therefore, in order to optimize the degree of crosslinking of the inner and outer canal to the same level, it is generally applied by adding about 0.1 to 0.3 parts by weight of the cross-linking agent content of the outer canal, and accordingly, it is necessary to separate the production of the inner and outer canals. Will be produced

Therefore, in the process of producing the internal and external uses, the crosslinking agent content is differently applied or used as materials of different base resins in order to meet the characteristics required by the internal and external degrees. Compared to the use of the same material, the management cost increases due to the dual quality control, and the high voltage cable producer using the same material has the inconvenience of increasing the cost and the dual management.

On the other hand, the internal and external use is mainly used alone or blended with ethylene vinyl acetate or ethylene-α copolymer resin, using carbon black and antioxidants, crosslinking agents, etc., and adding a small amount of other ethylene-propylene-diene monomer In some cases.

At this time, the content of the cross-linking agent becomes an important factor indicating the difference between the inner and outer diameters, the content of the cross-linking agent applied to the outer diameter is generally larger than the cross-linking agent content applied to the inner road.

That is, as described above, the crosslinking of the high-pressure cable is performed by applying heat and pressure while the cable extruded through steam crosslinking or the like stays in the crosslinking tube. As a result, the degree of crosslinking after the cable extrusion is about 5% higher than that of the outer diameter based on the material to which the same crosslinking agent content is applied.

However, the same cross-linking agent can be obtained by increasing the content of crosslinking agent to obtain the desired electrical and mechanical properties. The additional crosslinking occurs in the process of acting as an impurity or applying heat when connecting the intermediate junction box or the terminal junction box, thereby causing electrical instability due to the effect of crosslinking by-products.

On the other hand, when applied by reducing the content of the cross-linking agent, the problems caused by the cross-linking by-products and residual cross-linking agent of the internal resistance can be eliminated, but the cross-linking degree of the external can not reach the appropriate degree of cross-linking, there was also a problem that the mechanical and electrical properties are reduced.

In other words, after cable extrusion, the degree of crosslinking of the internal resistance is approximately 5% more than that of the degree of crosslinking of the external canal, thereby increasing the cost and inconvenience of managing the semiconducting material.

The present invention has been made to solve the above problems, by applying the appropriate cross-linking agent content to enable the simultaneous application of internal and external use for high-voltage cable to satisfy the cross-linking properties and mechanical and electrical properties required by the high-voltage cable In providing a semiconductive composition.

It is still another object of the present invention to reduce the electrical properties at the insulation / semiconductor layer interface due to the existing phenolic or amine-based solid-state antioxidants or blooming that may cause deterioration of the scorch and crosslinking properties. By applying 4, 6-bis (octylthiomethyl) -o-cresol instead of 4'-thiobis (thi-butyl) methyl phenol as a liquid antioxidant, a semiconductive composition for a high-voltage cable that can also improve scorch and crosslinking properties In providing.

The present invention devised to solve such a problem is based on 100 parts by weight of polyethylene acrylate copolymer having an acrylate content of 10 to 20% and a melt index of 1.8 to 8 g / 10 min, or polyethylene acrylate having the above conditions. In a copolymer of polyethylene butyl acrylate having an acrylate content of 25 to 40% and a melt index of 15 to 300 g / 10 min, and polyethylene ethyl acrylate having an ethyl acrylate content of 15 to 30% and a melt index of 15 to 300 g / 10 min. 45 to 70 parts by weight of carbon black, 0.1 to 5 parts by weight of processing aids and 0.2 to 2 parts by weight of crosslinking agent, and cresol-based antioxidants alone or in combination with phenolic antioxidants based on 100 parts by weight of the blended matrix resin It is to provide a semiconducting composition for a high pressure cable.

Hereinafter, the semiconductive composition for a high voltage cable according to the present invention will be described in detail.

The present invention relates to a semiconductive composition for a high voltage cable which can be applied simultaneously as an inner semiconducting material and an outer semiconducting material of a high voltage cable.

The semiconducting composition of the high-voltage cable for this purpose is based on 100 parts by weight of the polyethylene acrylate copolymer having an acrylate content of 10 to 20% and a melt index of 1.8 to 8 g / 10 min, or to the polyethylene acrylate copolymer under the above conditions. Either polyethylene butyl acrylate having an acrylate content of 25 to 40% and a melt index of 15 to 300 g / 10 min, or polyethylene ethyl acrylate having an ethyl acrylate content of 15 to 30% and a melt index of 15 to 300 g / 10 min. 45 to 70 parts by weight of carbon black, 0.1 to 5 parts by weight of processing aids and 0.2 to 2 parts by weight of crosslinking agent, and cresol-based antioxidants alone or in combination with phenolic antioxidants are preferably used based on 100 parts by weight of the blended matrix resin. Do.

In addition, it is preferable that the cresol-based antioxidant is used in an amount of 0.3 to 1 part by weight, and the cresol-based antioxidant is preferably 4,6-bisoctyldiomethyl-o-cresol.

At this time, the role of the antioxidant in the semiconducting composition for the high-voltage cable is to prevent aging due to heat of the cable material used for a long time at high temperature.

When the antioxidant is used in an amount of 2 parts by weight or more, the effect of the increase can not be additionally expected, but rather brings about adverse effects such as deterioration of mechanical properties and protrusion.

In addition, it interferes with the uniform dispersion of carbon black, which adversely affects mechanical, electrical and protrusion properties.

When the antioxidant is used in a small amount less than 0.3 part by weight, a sufficient antioxidant effect cannot be achieved.

Therefore, in order to simultaneously satisfy the mechanical, electrical and crosslinking properties required by the semiconducting composition for a high voltage cable, optimization of the crosslinking agent content and the antioxidant is essential.

In the present invention, the polyethylene acrylate copolymer, which is the main base resin, aims to improve mechanical properties, electrical properties, appearance, and the like, and the subbase resin, polyethylene butyl acrylate or polyethylene ethyl acrylate, has a decrease in physical properties of the main base resin. It is used for the purpose of improving the workability, such as extrusion characteristics, while minimizing.

At this time, the subbase resin of the polyethylene butyl acrylate or polyethylene ethyl acrylate in the present invention is composed of up to 30 parts by weight based on 100 parts by weight of the main base resin of the polyethylene acrylate copolymer.

The carbon black used in the present invention used acetylene black or high purity furnace black having a sulfur content of 300 ppm or less, and 45 to 70 parts by weight.

In addition, the crosslinking agent is dicumyl peroxide, 2,5-dimethyl-2,5-di-thi-butyl peroxide, di-thi-butylperoxy di-isopropylbenzene, 1-1-bis (ti-butyl Peroxy) -3,3,5-trimethyl-cyclohexane is used.

In addition, when the liquid cresol-based antioxidant is applied, anti-aging characteristics obtained when the existing phenolic or amine-based antioxidants are applied, as well as an increase in scorch time and an improvement in the degree of crosslinking, which are liquid oxidation Associated with a drop in Mooney viscosity through the addition of an inhibitor.

In other words, the antioxidant blended with the main base resin and carbon black also brings the effect of the processing oil, thereby lowering the torque applied between the screw and the semiconducting material during extrusion, thereby lowering the viscosity and thereby causing a relatively long time for scorch to occur. Is increased.

In addition, when a liquid antioxidant such as 4,6-bis (octylthiomethyl) -o-cresol is applied, the side chain is octylthiomethyl, and thus 4,4'-thiobis (thi-butyl) methyl phenol is used. Compared with the liquid antioxidant, the compatibility with the olefin resin is excellent.

In this case, it is possible to secure stable electrical properties between the insulating layer and the semiconducting layer by significantly lowering the possibility of blooming that may occur during long-term use after being prepared as a material of the semiconducting composition, which is an electrical tree It is possible to suppress the occurrence of.

In addition, by applying a liquid antioxidant such as 4, 6-bis (octylthiomethyl) -o-cresol rather than 4,4'- thiobis (thi-butyl) methyl phenol to prevent deterioration of physical properties through blooming, etc. do.

That is, the antioxidant blended with the base resin and carbon black also brings the effect of the processing oil, thereby lowering the torque applied between the screw and the material of the semiconducting composition during extrusion, thereby lowering the viscosity, which results in a time when scorch may occur. Relatively increased.

In addition, when the liquid antioxidant such as 4, 6-bis (octylthiomethyl) -o-cresol is applied, the side chain is composed of octylthiomethyl, and thus 4,4'-thiobis (thi-butyl) methyl phenol is used. Compared to the liquid antioxidants such as the excellent compatibility with the olefin resin.

In this case, it is possible to secure stable electrical properties between the insulating layer and the semiconducting layer by significantly lowering the possibility of blooming that may occur during long-term use after being prepared as a material of the semiconducting composition, which leads to the generation of an electric tree. Appears to inhibit.

Hereinafter, a specific embodiment of the semiconductive composition of the present invention will be described.

Examples 1-4

Ethylene butyl acrylate (1) having a low melt index (7 g / 10 min.) And ethylene butyl acrylate (2) having a high melt index (2) in a ratio of 80:20 for improving workability and having a crosslinking agent content of 0.3 To blend up to 1 part by weight, see Table 1.

Examples 5-8

Ethylene ethyl acrylate having a low melt index is mainly used, ethylene ethyl acrylate having a high melt index is used in a ratio of 80:20, and the content of the crosslinking agent is increased to 0.3 to 1 parts by weight and the antioxidant (4 ) Was blended, see Table 1.

TABLE 1

In this case, the ethylene ethyl acrylate (1) has a melt index of 7, and the content of ethyl acrylate is 15%.

The ethylene ethyl acrylate (2) has a melt index of 275 and an ethyl acrylate content of 25%.

In addition, the antioxidant (1), (2) is a mixture of amine-based and phenol-based antioxidants used to improve the heat resistance.

In particular, the antioxidant (1) is thiodiethylene-bis [3,5-di-butyl-4-hydroxy-phenyl) propionate.

And antioxidant (2) is dioctadecyl 3,3'- thiodipropionate.

In addition, antioxidant (3), (4) is cresol type antioxidant.

Moreover, the antioxidant (3) is 4,4-thiobis (ti-butyl) -m-phenol (cresol) and the antioxidant (4) is 4,6-bis (octylthiomethyl) -o-cresol .

Test Methods

In order to advance this invention, the semiconductive material was kneaded using an open roll or a kneader mixer as kneading equipment.

In addition, by using an electric preheating press to crosslink at 170 ℃ for 20 minutes to prepare a specimen required for test evaluation.

The prepared specimens are summarized in Table 2 below by measuring their mechanical and electrical properties through the following method.

1) Tensile strength and elongation-KSC 3004. 19

2) Volume resistance-IEC 840

3) Crosslinking degree-Grind and weigh the semiconductive material, heat it for 16 hours using xylene solvent under 120 mesh, and then dry in hood for 1 hour. After drying for 2 hours in the oven at 150 ℃ weighing

% Crosslinking = (mass of sample after extraction / sample mass before extraction) * 100

4) Measure at 180 ° C using Mooney Viscometer

5) Determination of blooming after passing through 130 ℃ × 24hrs. In oven (visual + FT-IR analysis)

TABLE 2

Test results of Examples 1 to 8 summarized in Table 2 are the results of the mechanical test and the electrical test selectively among the embodiments of the above-mentioned semiconducting layer materials.

That is, in Examples 1 to 4, the ratio of ethylene butyl acrylate (1) having a low melt index (7 g / 10 min.) And ethylene butyl acrylate (2) having a high melt index (2) to improve processability is 80:20. The content of the crosslinking agent was increased to 0.3 to 1 part by weight and blended.

In Examples 5 to 8, ethylene ethyl acrylate having a low melt index is mainly used, ethylene ethyl acrylate having a high melt index is used in a ratio of 80: 20, and the content of the crosslinking agent is 0.3 to 1 part by weight. It was applied by extension and blended by application of antioxidant (4).

As can be seen from the above results, the mechanical properties of the semiconducting material using the crosslinking aid showed more than equivalent results.

Meanwhile, in Comparative Example 1, ethylene ethyl acrylate having a low melt index is mainly used, ethylene ethyl acrylate having a high melt index is 80: 20, the crosslinking agent is 0.5 parts by weight, and no antioxidant is applied. Without blending.

In Comparative Examples 2 to 4, ethylene ethyl acrylate having a low melt index was mainly used, ethylene ethyl acrylate having a high melt index was used in a ratio of 80: 20, and the content of the crosslinking agent reached 0.3 to 0.8 parts by weight. Used to extend and blended with antioxidants (1), (2) applied.

In Comparative Examples 5 to 7, ethylene ethyl acrylate having a low melt index was mainly used, ethylene ethyl acrylate having a high melt index was used in a ratio of 80: 20, and the content of the crosslinking agent reached 0.3 to 0.8 parts by weight. Used to extend and blended with antioxidant (3).

The semiconductive compositions for ultrahigh voltage cables described in the above examples and comparative examples are extruded as conductors through double extrusion or triple extrusion, and then crosslinked by steam crosslinking or dry crosslinking at 200 ° C. or higher to be used as ultrahigh voltage cables.

As can be seen here, it can be seen that the crosslinking property in the case of applying the cresol-based antioxidant in the Examples shows an increase in scorch time and an excellent crosslinking degree compared to the comparative example with respect to the content change of the crosslinking agent.

As shown in Examples 1 to 4, when applying a cresol-based antioxidant when applying the base resin of ethylene butyl acrylate, even when 0.3 parts by weight of the crosslinking agent is applied, the scorch time is 23 minutes, showing excellent scorch resistance characteristics. Can be.

In addition, the crosslinking also appears to be 60% to 79% level, it is judged that it can be applied as a high voltage cable.

In the case of mechanical properties, the tensile strength and the elongation rate increased with increasing crosslinking agent content. However, all of the mechanical properties above 100, which are required for the high-voltage cable, exceeded all of them.

On the other hand, in the volume resistance, when the cross-linking agent content of 0.5 parts by weight or more, except 0.3 parts by weight, the effect of the cross-linking agent content was found to be insignificant.

Therefore, it is considered that there is no problem when applying a cross-linking agent of 0.5 parts by weight or more, and it is considered that application of a cross-linking agent of less than 0.5 parts by weight may be possible depending on the degree of demand for high temperature volume resistance.

In addition, all of the projections were excellent, and the Mooney viscosity value was slightly decreased as the content of the crosslinking agent increased.

In Examples 5 to 8, the change of the properties according to the application of ethylene ethyl acrylate was examined, and as in Examples 1 to 4, it can be seen that excellent scorch time characteristics and crosslinking degree are shown.

Characteristically, in the case of volume resistance, the change according to the content change of the crosslinking degree is very small, and it is judged that there is no problem due to the application of the semiconductive material when the crosslinking agent is applied at the level of 0.3 to 1 part by weight.

In addition, it can be seen that the tensile strength, the elongation rate, the protrusion characteristics, and the Mooney viscosity value show a similar pattern to those of Examples 1 to 4.

Comparative Example 1 showed the characteristic values of the material of the semiconductive composition when no antioxidant was added.

It can be seen that compared to the case of Examples 2 and 6 to which the same amount of crosslinking agent is applied, it shows a very short scorch time.

It can be seen that the crosslinking degree is also about 4 to 5% small, and the high temperature volume resistance is also high, which is determined by the effect of thermal aging of the material of the semiconducting composition.

In addition, it can be seen that the mechanical strength and protrusion characteristics are similar.

In the case of Comparative Examples 2 to 4, the properties of the material of the semiconductive composition according to the addition of phenolic and amine antioxidants can be seen. It can be seen that the time is shown and the crosslinking degree is also relatively small.

As described above, according to the semiconductive composition for a high pressure cable according to the present invention, by applying a cresol-based antioxidant such as 4, 6-bis (octylthiomethyl) -o-cresol, scorch time, crosslinking degree and mechanical / electrical properties It has excellent blooming characteristics and excellent interfacial characteristics with the insulating layer even at high temperature operation for a long time, and minimizes the crosslinking agent content of internal and external parts to secure sufficient crosslinking degree for the high voltage cable. It can be effective.

In addition, it was found that impurities can be minimized by applying cresol-based antioxidants such as 4, 6-bis (octylthiomethyl) -o-cresol, and thus applied simultaneously to the internal semiconductive material and the external semiconductive material. There is also a possible effect.

Claims (4)

In the semiconductive material crosslinked together for the inner semiconducting layer and the outer semiconducting layer of the high-voltage cable, For 100 parts by weight of polyethylene acrylate copolymer having an acrylate content of 10 to 20% and a melt index of 1.8 to 8 g / 10 min, 45 to 70 parts by weight of carbon black, 0.1 to 5 parts by weight of the processing aid and 0.2 to 2 parts by weight of the crosslinking agent; A semiconducting composition for a high voltage cable, wherein the cresol-based antioxidant is used alone or in combination with a phenol-based antioxidant. In the semiconductive material crosslinked together for the inner semiconducting layer and the outer semiconducting layer of the high-voltage cable, Either polyethylene butyl acrylate having an acrylate content of 25 to 40% and a melt index of 15 to 300 g / 10 min, or polyethylene ethyl acrylate having an ethyl acrylate content of 15 to 30% and a melt index of 15 to 300 g / 10 min. With respect to 100 parts by weight of the matrix resin blended with a polyethylene acrylate copolymer having an acrylate content of 10 to 20% and a melt index of 1.8 to 8 g / 10 min, 45 to 70 parts by weight of carbon black, 0.1 to 5 parts by weight of the processing aid and 0.2 to 2 parts by weight of the crosslinking agent; A semiconducting composition for a high voltage cable, wherein the cresol-based antioxidant is used alone or in combination with a phenol-based antioxidant. The method according to claim 1 or 2, The cresol-based antioxidant semiconducting composition for a high-voltage cable, characterized in that using 0.3 to 1 part by weight. The method of claim 3, wherein The cresol-based antioxidant is 4,6-bis octyldiomethyl- five-cresol semiconducting composition for a high-voltage cable, characterized in that.