KR20220068666A - Resin composition for insulation of eco-friendly power cables - Google Patents

Abstract

The present invention provides a composition for an insulation layer of a power cable which has excellent heat resistance, low-temperature impact resistance, flexibility, and electrical properties and is recyclable. The present invention provides a resin composition for an insulation layer of a power cable which comprises: 90 to 99 parts by weight of a propylene block copolymer including an ethylene-propylene rubber block; 1 to 10 parts by weight of a linear low-density polyethylene; and 0.01 to 0.1 parts by weight of a β-nucleating agent.

Description

Resin composition for insulation of eco-friendly power cables

The present invention relates to a resin composition for an insulating layer of an eco-friendly power cable, and more particularly, to a resin composition for an insulating layer of an eco-friendly power cable that has excellent flexibility and electrical properties and is recyclable.

As the insulation material of the cable, a material obtained by crosslinking polyethylene (PE), polyvinyl chloride (PVC), ethylene/propylene elastic copolymer (EPR), etc. is mainly used. Among them, cross-linked polyethylene (XLPE) converts the linear molecular structure of polyethylene into a three-dimensional network structure through a cross-linking process. It has been used as a cable insulation layer. However, in the case of cross-linked polyethylene, since it is a cross-linked polymer, recycling is impossible, and in order to dispose of it, it has to be incinerated, which is somewhat unfriendly to the environment.

Meanwhile, research on an environmentally friendly insulating layer that can be recycled using non-crosslinked high-density polyethylene (HDPE) or low-density polyethylene (LDPE) has also been conducted, but its use is somewhat limited due to inferior heat resistance compared to cross-linked polyethylene. There is this.

Accordingly, the development of an insulating layer using a polypropylene (PP) material that is easy to recycle and has high heat resistance is being developed. Compared with cross-linked polyethylene, polypropylene has a simpler manufacturing method and is environmentally friendly in a non-cross-linked form, does not generate toxic substances such as methane gas and various by-products during the manufacturing process, and also produces greenhouse gases such as carbon dioxide (CO ₂ ) generated during the manufacturing process. It is possible to reduce about 30% compared to cross-linked polyethylene. In addition, polypropylene is recyclable, and it is strong against heat, so the power transmission capacity can be increased.

As such, it may be considered to use environmentally friendly polypropylene as a base resin because the polymer itself has excellent heat resistance without crosslinking at a melting point of 160° C. or higher. However, due to low flexibility due to high rigidity, polypropylene has poor workability when installing cables including an insulating layer manufactured therefrom, and its use is limited due to insufficient electrical properties compared to cross-linked polyethylene. there is a problem to be

In order to overcome this limitation, a technology related to a resin composition for an insulating layer of a power cable made of polypropylene has been developed.

Korean Patent Laid-Open No. 10-2019-0016667 discloses an insulation composition for a high voltage cable, including a base resin and an additive, wherein the base resin is a copolymer resin of an ethylene monomer and a polar monomer, a polypropylene resin, a polyolefin elastomer, and maleic anhydride. Disclosed is an insulation composition for a high voltage cable comprising a grafted polyolefin-based resin blending resin, and Korean Patent No. 1163432 discloses (a) isotactic propylene homopolymers (A) and (b) A random propylene-butene copolymer having a 1-butene content (B) or a random propylene-ethylene copolymer having an ethylene content (B') was disclosed for polypropylene, and Korean Patent Laid-Open No. 10-2016-0180197 An ethylene-propylene block copolymer in which (a) a propylene homopolymer or an ethylene-propylene random copolymer and (b) an ethylene-propylene rubber copolymer was polymerized stepwise in a reactor was disclosed, but excellent flexibility and electrical properties were simultaneously satisfied can't make it

An object of the present invention is to provide a resin composition for an insulating layer of an eco-friendly power cable that simultaneously satisfies excellent flexible properties and electrical properties as a resin composition for an insulating layer of a power cable that can be recycled.

In order to solve the above problems, the present invention provides 90 to 99 parts by weight of a propylene block copolymer comprising an ethylene-propylene rubber block; 1 to 10 parts by weight of linear low density polyethylene; and β-nucleating agent 0.01 to 0.1 parts by weight; provides a resin composition for an insulating layer of a power cable comprising.

In addition, the ethylene-derived repeating unit is contained in 10 to 20% by weight in the propylene block copolymer, and 35 to 55% by weight in the ethylene-propylene rubber block It provides a resin composition for an insulating layer of a power cable .

In addition, the propylene block copolymer has a melting point of 150 to 170° C., a melting enthalpy of 65 to 85 J/g, a melt index (MI, 230° C., 2.16 kg load) of 0.1 to 10 g/10 min, and xylene soluble It provides a resin composition for an insulating layer of a power cable, characterized in that the minute (Xylene soluble) is 20 to 40% by weight in the propylene block copolymer.

In addition, the linear low-density polyethylene has a density of 0.910 to 0.930 g/cm 3 , a melting point of 110 to 130° C., and a melt index (MI, 190° C., 2.16 kg load) of 0.1 to 10 g/10 min. A resin composition for an insulating layer is provided.

In addition, the β-nucleating agent is at least one selected from the group consisting of a calcium salt of dicarboxylic acid, a quinacridone-based organic material, and an aryl amide-based organic material. It provides a resin composition for the insulation layer of a power cable.

In addition The resin composition has a flexural modulus of 500 to 700 MPa measured according to the following method, an AC dielectric breakdown strength of 50 kV/mm or more, and an impulse dielectric breakdown strength of 90 kV/mm or more. To provide a resin composition for an insulating layer.

[Method of measuring flexural modulus]

According to ASTM D790 standard, the span of the specimen (127 × 12.7 × 6.4 mm) is fixed at 100 mm and a flexural load is applied at a rate of 28 mm/min. The measured value is the flexural modulus.

[Method of measuring dielectric breakdown strength]

After preparing the resin composition in a sheet shape with a thickness of 1 mm using a press molding machine, 30 kV is initially applied for 5 minutes according to ASTM D149, and then is increased by 10 kV and maintained for 5 minutes. Continuing until dielectric breakdown occurs, the value obtained by dividing the breakdown voltage by the thickness of the sheet is the AC dielectric breakdown strength, and the sheet is subjected to an impact voltage of 80 kV in positive/negative polarity 10 times each, and then 10 kV Increase by increments and continue to apply three impulse voltages until breakdown occurs, and the value at which breakdown occurs is referred to as impulse dielectric breakdown strength.

The present invention provides a propylene block copolymer including an ethylene-propylene rubber block, a linear low-density polyethylene, and a β-nucleating agent in a specific content ratio to provide a recyclable resin composition for an eco-friendly power cable insulation layer that satisfies both excellent flexible properties and electrical properties. can provide

1 is a view schematically showing a cross-section of a power cable made of a resin composition according to the present invention;
Figure 2 is a photograph showing the result of observing the cross section of the resin composition according to Example 1 and Comparative Example 1 with an optical microscope.

Hereinafter, the present invention will be described in detail through preferred embodiments. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. Accordingly, since the configuration of the embodiments described in the present specification is only the most preferred embodiment of the present invention and does not represent all the technical spirit of the present invention, various equivalents and modifications that can be substituted for them at the time of the present application It should be understood that there may be

The present invention, 90 to 99 parts by weight of a propylene block copolymer comprising an ethylene-propylene rubber block; 1 to 10 parts by weight of linear low density polyethylene; and 0.01 to 0.1 parts by weight of a β-nucleating agent; discloses a resin composition for an insulating layer of a power cable comprising.

Hereinafter, each component of the resin composition for an insulating layer of a power cable according to the present invention will be described in detail.

Polypropylene can be classified into homo polypropylene (H-PP), propylene random copolymer (R-PP) and propylene block copolymer (B-PP). Among them, propylene random copolymer and propylene block copolymer are more suitable for power cables because they have high flexibility and flexibility compared to homopolypropylene. Since there is an advantage of excellent flexural properties, a propylene block copolymer is used in the present invention.

In the present invention, the propylene block copolymer is a type of RTPO (Reactor-made Thermoplastic Polyolefins), and may be a reactive polypropylene (Reactor-made Thermoplastic Polypropylene). The reactive polypropylene refers to a polymer having rubber properties, which is polymerized by including a propylene monomer.

In the present invention, the propylene block copolymer may include 60 to 75% by weight of a propylene homopolymer and 25 to 40% by weight of an ethylene-propylene rubber, preferably 65 to 70% by weight of a propylene homopolymer and 30% by weight of an ethylene-propylene rubber to 35% by weight. The propylene block copolymer may be in a form in which ethylene-propylene rubber particles are dispersed in a propylene homopolymer matrix. Specifically, the propylene block copolymer according to the present invention may be a block copolymer in which propylene homopolymer and ethylene-propylene rubber are step-polymerized in a reactor. The propylene block copolymer has ethylene-propylene rubber dispersed in a specific content range, so it has a lower flexural modulus compared to propylene homopolymer, so it can maximize flexibility when applied as an insulating layer of a power cable, and has excellent elasticity to improve impact strength can do it

The propylene block copolymer used in the present invention produces a large amount of ethylene-propylene rubber (EPR) by using a high content of ethylene in a polymerization reactor, and has a higher content than the conventional propylene block copolymer. Since it contains the repeating unit derived from it, it has the advantages of high impact strength and excellent flexibility.

Without wishing to be limited by theory, in general, in the propylene block copolymer prepared in a reactor, the content of repeating units derived from ethylene may be 10 to 20 wt% in the total block copolymer due to technical difficulties, and preferably Preferably, it may be 13 to 16% by weight. In addition, the content of the repeating unit derived from ethylene may be 35 to 55% by weight in the ethylene-propylene rubber block, preferably 40 to 50% by weight. Flexibility, flexural properties and electrical properties can be maximized within the content range of the ethylene-derived repeating unit.

In addition, the propylene block copolymer may have a melting point of 150 to 170 ℃, preferably 160 to 170 ℃. Also, the melting enthalpy may be 65 to 85 J/g, preferably 75 to 85 J/g. When the melting point and melting enthalpy of the propylene block copolymer satisfy the above ranges, flexibility and electrical properties to be implemented in the present invention may be satisfied when applied as an insulating layer of a power cable.

In addition, the propylene block copolymer may have a melt index (MI, 230°C, 2.16 kg load) of 0.1 to 10 g/10min, preferably 0.3 to 5 g/10min, more preferably 0.5 to 2 g/10 min. If the melt index is less than 0.1 g/10 min, the extruder load may be applied during the cable extrusion process, and if it exceeds 10 g/10 min, eccentricity of the insulation layer of the cable molded article may occur.

In addition, in the propylene block copolymer, the amount of xylene soluble (X.S.) in the propylene block copolymer may be 20 to 40% by weight, preferably 25 to 35% by weight. Flexibility, flexural characteristics, and electrical characteristics may be maximized within the content range of the xylene-soluble component.

In the present invention, the propylene block copolymer is included in an amount of 90 to 99 parts by weight, preferably 91 to 97 parts by weight, and more preferably 92 to 96 parts by weight. When the content of the propylene block copolymer is less than 90 parts by weight, electrical properties are deteriorated, and when it exceeds 99 parts by weight, flexibility is reduced.

Since the linear low-density polyethylene (LLDPE) has a low flexural modulus by itself, it serves as a modifier for lowering the flexural modulus of the insulating layer resin composition. The interface between polypropylene crystal spheroids and spheroids is an electrically weak region, and as the interface develops, the electrical properties of polypropylene deteriorate. Therefore, the addition of the linear low-density polyethylene prevents the development of the polypropylene crystal spheroids and the interface between the spheroids to improve electrical properties.

The linear low density polyethylene may have a density of 0.910 to 0.930 g/cm 3 , preferably 0.915 to 0.925 g/cm 3 . In addition, the melting point may be 110 to 130 ℃, preferably 115 to 120 ℃ may be. When the final resin composition is applied as an insulating layer of a power cable within the above density and melting point range, flexibility, flexural properties and electrical properties can be maximized.

In the present invention, the linear low-density polyethylene may be included in an amount of 1 to 10 parts by weight, preferably 3 to 9 parts by weight, and more preferably 4 to 8 parts by weight. When the content of the low-density linear polyethylene is less than 1 part by weight, flexibility is reduced, and when it exceeds 10 parts by weight, flexibility is improved but electrical properties are deteriorated.

The β-nucleating agent changes the polypropylene crystal form to the β form. A typical polypropylene crystal form is an α type, and the α crystal causes a high flexural modulus, which reduces flexibility when the resin composition is applied as a cable. The β-form crystal spheroid has the advantage of being flexible and lowering the flexural modulus of polypropylene. In addition, the electrical resistance of the β crystal is higher than that of the α crystal, which improves the electrical properties of polypropylene.

As the β-nucleating agent, a calcium salt of dicarboxylic acid, a quinacridone-based organic material, or an aryl amide-based organic material may be preferably used, and as a specific example, gamma -quinacridone, delta-quinacridone, quinacridonequinone, indigosol and civatine organic pigment, calcium carbonate modified with dimer aluminate, mixture of calcium stearate and pimelic acid, calcium salt and zinc salt of diacidic acid , diamine of adipic acid or suberic acid, N,N-dicyclohexyl-terephthalamide, N',N'-dicyclohexyl-2,6-naphthalene-dicarboxyamide, tetra-hydrophthalate, etc. , but is not limited thereto.

In the present invention, 0.01 to 0.1 parts by weight of the β-nucleating agent is included in the total resin composition, preferably 0.03 to 0.09 parts by weight, and more preferably 0.04 to 0.08 parts by weight. When the β-nucleating agent content is less than 0.01 parts by weight, the role as a nucleating agent is not sufficiently exhibited, and when it exceeds 0.1 parts by weight, the nucleating agent acts as an impurity, and electrical properties and heat resistance stability may be deteriorated. In this case, the content of ionic impurities in the final resin composition is preferably 200 ppm or less.

In addition to the above components, the resin composition according to the present invention may further contain one or more additives commonly used when applied for an insulating layer of a power cable, preferably an antioxidant, a neutralizing agent or a water tree inhibitor. may include

The antioxidant may be added to suppress yellowing of the resin composition to impart color stability and transparency. Any antioxidant capable of preventing oxidation of the resin composition for the insulating layer of the power cable can be used without limitation, but preferably a hindered phenol-based antioxidant, 4,4'-thiobis (2-t-Butyl-5-methylphenol) (4,4'-thiobis (2-t-butyl-5-methylphenol)), 2,2'-thio-diethyl-bis [3- (3,5) -di-t-butyl-4-hydroxyphenyl) propionate] (2,2'-thio-diethyl-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]), 4,4'-thiobis-(2-methyl-6-t-butylphenol) (4,4'-thiobis(2-methyl-6-t-butylphenol)), 2,2'-thiobis (6- t-Butyl-4-methylphenol) (2,2'-thiobis (6-t-butyl-4-methylphenol)), octadecyl [3- (3,5-di-t-butyl-4-hydroxyphenyl) )propionate](octadecyl[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]) and thiodiethylene-bis[3-(3,5-di-t-butyl-4- At least one antioxidant selected from the group consisting of hydroxyphenyl) propionate] (Thiodiethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate]) may be used.

The neutralizing agent is used to prevent decomposition of the resin composition by effectively removing the catalyst residue remaining after polymerization, and any neutralizing agent capable of preventing decomposition of the resin composition for the insulating layer of the power cable can be used without limitation.

The water tree inhibitor is added for the purpose of preventing water tree, a form of micro-destruction that gradually grows due to the complex action of moisture and voltage at a voltage below the breakdown voltage. The water tree phenomenon deteriorates the electrical insulating properties of the insulating layer, resulting in a decrease in the lifespan of the insulating layer. The water tree inhibitor may be used without limitation as long as it is a material capable of reducing the combined action of moisture and voltage.

The resin composition for an insulating layer of a power cable according to the present invention may be prepared by mixing and extruding the above components according to a conventional method known in the art. For example, the components may be introduced into a twin-screw extruder and melt-kneaded to prepare a resin composition.

The resin composition for an insulating layer of a power cable according to the present invention has excellent flexibility and electrical properties, is eco-friendly and can be recycled, and specifically has a flexural modulus of 500 to 700 MPa, preferably 600 to 680, measured according to the following method. It may be MPa, the AC breakdown voltage may be 50 kV/mm or more, preferably 52 kV/mm or more, and the impulse breakdown voltage may be 90 kV/mm or more, preferably 93 kV/mm or more. have.

[Method of measuring flexural modulus]

According to ASTM D790 standard, the span of the specimen (127 × 12.7 × 6.4 mm) is fixed at 100 mm and a flexural load is applied at a rate of 28 mm/min. The measured value is the flexural modulus.

[Method of measuring dielectric breakdown strength]

After preparing the resin composition in a sheet shape with a thickness of 1 mm using a press molding machine, 30 kV is initially applied for 5 minutes according to ASTM D149, and then is increased by 10 kV and maintained for 5 minutes. Continuing until dielectric breakdown occurs, the value obtained by dividing the breakdown voltage by the thickness of the sheet is the AC dielectric breakdown strength. Continue to increase kV by kV and apply the impulse voltage three times until breakdown occurs, and the value at which breakdown occurs is referred to as impulse dielectric breakdown strength.

A power cable may be manufactured from the resin composition for an insulating layer of a power cable according to the present invention. 1 schematically shows a cross section of a power cable made of a resin composition according to the present invention.

1, the power cable made of the resin composition for the insulating layer of the power cable according to the present invention includes a conductor (1), an inner semiconducting layer (2) surrounding the conductor (1), and the inner semiconducting layer (2) It includes an insulating layer (3) surrounding the insulating layer (3), an outer semiconducting layer (4) surrounding the insulating layer (3), and a sheath layer (5) surrounding the outer semiconducting layer (4), wherein the insulating layer (3) is in the present invention It may include a resin composition according to the. Except for the insulating layer, since details of each layer constituting the power cable are commonly known to those skilled in the art, detailed descriptions thereof will be omitted in the present invention.

Hereinafter, specific preparation examples, examples and comparative examples according to the present invention will be described.

production example

A propylene homopolymer is prepared by reacting hydrogen and propylene in a loop reactor, and the propylene homopolymer polymerized in the loop reactor and ethylene and propylene are put into a gas phase reactor to conduct a copolymerization reaction of ethylene-propylene in a continuous process to obtain a propylene block copolymer was prepared. In the prepared propylene block copolymer, the ethylene-derived repeating unit was 14.2% by weight in the total copolymer and 42% by weight in the ethylene-propylene rubber (EPR) block, the content of xylene solubles was 31.3% by weight, and the melt index was 1.2 g/10 min, the melting point was 163.7°C, and the melting enthalpy was 77.4 J/g. Melt index, xylene soluble content, melting point and enthalpy of melting of the propylene block copolymer were measured according to the following methods, respectively.

- Melt Index (MI): According to ASTM D1238 standard, it was measured under the conditions of a temperature of 230°C and a load of 2.16 kg.

- Xylene Soluble (X.S.): According to ASTM D5492, the propylene block copolymer is dissolved in boiling xylene, cooled at room temperature, and separated into a part dissolved in xylene and an insoluble part and then dissolved in xylene After evaporating xylene with a hot plate by collecting the separated parts, the weight % of the remaining part was measured.

- Melting point and melting enthalpy: Using a differential scanning calorimeter (DSC), heating to 200°C at a rate of 10°C/min and cooling to -30°C were repeated twice, and the second measured data was used.

Example and comparative example

The mixture composed of the component compositions of Table 1 below was mixed with a mixer for 5 minutes and then extruded with a twin-screw extruder at 190 to 230 ° C. was observed with an optical microscope (observation temperature 134° C., magnification × 100, 2 min), and the results are shown in FIG. 2 . Referring to FIG. 2, in the case of a resin composition for an insulating layer of a power cable comprising a propylene block copolymer including an ethylene-propylene rubber block, a linear low-density polyethylene, and a β-nucleating agent in a specific composition ratio according to the present invention (Example 1) propylene It can be seen that the crystal sphericity is small and uniform compared to the case of the block copolymer alone (Comparative Example 1), and from this, it can be seen that excellent flexible properties and electrical properties can be realized at the same time.

test example

Specimens or sheets were prepared using the prepared resin composition on the pellets, and physical properties were measured according to the following method, and the results are shown in Table 1 below.

[How to measure]

(1) Flexural modulus

According to ASTM D790 standard, the support span of the specimen (127×12.7×6.4 mm) was fixed to 100 mm, and a flexural load was applied at a rate of 28 mm/min. The measured value was used as the flexural modulus. When the flexural modulus is 700 MPa or less, it is judged that flexibility and flexural properties are excellent.

(2) dielectric breakdown strength

After preparing the resin composition in a sheet shape with a thickness of 1 mm using a press molding machine, 30 kV is initially applied for 5 minutes according to ASTM D149, and then is increased by 10 kV and maintained for 5 minutes. Continuing until dielectric breakdown occurs, the value obtained by dividing the breakdown voltage by the thickness of the sheet is the AC dielectric breakdown strength. Increasing by kV and applying the impulse voltage three times was continued until breakdown occurred, and the value at which the breakdown occurred was defined as the impulse dielectric breakdown strength. When the AC breakdown strength is 50 kV/mm or more and the impulse dielectric breakdown strength is 90 kV/mm or more, the electrical properties are judged to be excellent.

(3) ionic impurity content

After measuring the weight of the resin composition, put it in a crucible, ashing in an electric furnace at 400°C for 4 hours and 800°C for 6 hours, and then melt the incinerated sample with a 5 wt% nitric acid solution and fill it in a 100 ml flask, After measuring the concentration of ionic impurities (10 types of Ca, Si, Fe, Al, Zn, Cu, Mg, Na, Ni and K) using an inductively coupled plasma device (ICP-MS), the measured ion concentration The final ionic impurity content was calculated after subtracting the blank concentration obtained from the empty crucible without the incinerated sample.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Propylene block copolymer (parts by weight) 93 95 100 100 93 85 93 Linear low density polyethylene (parts by weight) 7 5 - - 7 15 7 β-nucleating agent
(parts by weight) 0.05 0.07 - 0.05 - - 0.12 flexural modulus
(MPa) 630 670 810 660 740 660 630 AC dielectric breakdown strength
(kV/mm) 54 52 49 52 50 52 47 Impulse dielectric breakdown strength
(kV/mm) 96 93 83 88 89 84 87 Ionic impurity content
(ppm) 159 174 97 155 95 96 263 * main
- Propylene block copolymer: melt index (230℃, load 2.16 kg) 1.2 g/10min, melting point 163.7℃, enthalpy of melting 77.4 J/g
- Linear low-density polyethylene: melt index (190℃, 2.16 kg load) 1.1 g/10min, density 0.920 g/cm ³ , UN315, Lotte Chemical)
- β-nucleating agent: tetra-hydrophthalate-based β-nucleating agent (NAB-82, Copolyman), the content means the content contained in the entire resin composition.

Referring to Table 1, according to the present invention, the resin composition for the insulating layer of the power cable comprising the propylene block copolymer including the ethylene-propylene rubber block, the linear low-density polyethylene, and the β-nucleating agent in a specific composition ratio (Examples 1 and 2) ) is a recyclable resin composition, and it is confirmed that it has excellent flexibility and electrical properties.

On the other hand, when the linear low-density polyethylene and the β-nucleating agent are not included (Comparative Example 1), the flexibility is not good due to the high flexural modulus, and the electrical properties are also significantly reduced, and when the linear low-density polyethylene is not included (Comparative Example 2) Although the flexural modulus is low and the flexibility is excellent, the electrical properties, especially the breaking strength due to the instantaneous impulse current, are lowered, and when the β-nucleating agent is not included (Comparative Example 3), the flexural properties and electrical properties are lowered due to the nature of the α crystal. , However, even if the β-nucleating agent is not included, when the content of the linear low-density polyethylene is increased (Comparative Example 4), the flexibility is improved, but it can be seen that the breaking strength due to the instantaneous impulse current is particularly significantly reduced.

On the other hand, even if the β-nucleating agent is included, when the content is excessive (Comparative Example 5), the flexural properties are still excellent, but the nucleating agent rather acts as an impurity, and the ionic impurity content is significantly increased to 200 ppm or more, resulting in electrical properties and Thermal stability may be deteriorated.

The preferred embodiment of the present invention has been described in detail above. The description of the present invention is for illustrative purposes, and those of ordinary skill in the art to which the present invention pertains will understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Accordingly, the scope of the present invention is indicated by the claims to be described later rather than the above detailed description, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims are included in the scope of the present invention. should be interpreted

Claims (6)

90 to 99 parts by weight of a propylene block copolymer comprising an ethylene-propylene rubber block;
1 to 10 parts by weight of linear low density polyethylene; and
0.01 to 0.1 parts by weight of a β-nucleating agent;
A resin composition for an insulating layer of a power cable comprising a. According to claim 1,
A repeating unit derived from ethylene is
10 to 20% by weight is included in the propylene block copolymer,
The resin composition for the insulating layer of the power cable, characterized in that 35 to 55% by weight is included in the ethylene-propylene rubber block. According to claim 1,
The propylene block copolymer has a melting point of 150 to 170 ° C, a melting enthalpy of 65 to 85 J/g, a melt index (MI, 230 ° C, 2.16 kg load) of 0.1 to 10 g/10 min, and xylene solubles (Xylene soluble) The resin composition for the insulation layer of the power cable, characterized in that 20 to 40% by weight in the propylene block copolymer. According to claim 1,
Linear low-density polyethylene has a density of 0.910 to 0.930 g/cm 3 , a melting point of 110 to 130° C., and a melt index (MI, 190° C., 2.16 kg load) of 0.1 to 10 g/10 min. Insulation of power cables A resin composition for layers. According to claim 1,
The β-nucleating agent is one or more selected from the group consisting of a calcium salt of dicarboxylic acid, a quinacridone-based organic material, and an aryl amide-based organic material, characterized in that A resin composition for an insulating layer of a power cable. According to claim 1,
The resin composition has a flexural modulus of 500 to 700 MPa measured according to the following method, an AC dielectric breakdown strength of 50 kV/mm or more, and an impulse dielectric breakdown strength of 90 kV/mm or more. Resin composition for insulation of:
[Method of measuring flexural modulus]
According to ASTM D790 standard, the span of the specimen (127 × 12.7 × 6.4 mm) is fixed at 100 mm and a flexural load is applied at a rate of 28 mm/min. The measured value is used as flexural modulus.
[Method of measuring dielectric breakdown strength]
After preparing the resin composition in a sheet shape with a thickness of 1 mm using a press molding machine, 30 kV is initially applied for 5 minutes according to ASTM D149, and then is increased by 10 kV and maintained for 5 minutes. Continuing until dielectric breakdown occurs, the value obtained by dividing the breakdown voltage by the thickness of the sheet is the AC dielectric breakdown strength. Continue to increase kV by kV and apply three impulse voltages until breakdown occurs, and the value at which breakdown occurs is referred to as impulse dielectric breakdown strength.

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