KR20180093808A - Power cable with insulation layer having excellent transparence - Google Patents

Abstract

The present invention relates to a power cable with an insulation layer with improved transparence. The power cable according to an embodiment of the present invention includes: one or more conductors; an inner semiconducting layer surrounding the conductor; the insulation layer surrounding the inner semiconducting layer; an outer semiconducting layer surrounding the insulation layer; a neutral line watertight layer surrounding the outer semiconducting layer; and a sheath layer surrounding the neutral line watertight layer, wherein the insulation layer includes a polypropylene block copolymer and ethylene-octene rubber. The present invention can provide the power cable with an eco-friendly non-crosslinked insulation layer which can be recycled.

Description

POWER CABLE WITH INSULATION LAYER HAVING EXCELLENT TRANSPARENCE BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to power cables. More particularly, the present invention relates to a power cable having an insulating layer that can be operated at a high temperature for a long time and has improved transparency and less bleeding.

Normally, a crosslinked polyethylene resin (XLPE) used as a mainstream as an insulating material of a power cable is excellent in heat resistance, chemical resistance, and electrical properties because it is a thermosetting resin. The method for producing the crosslinked polyethylene resin is a crosslinking and electron beam crosslinking (US Patent No. 4426497 (1984.01.17)) by a chemical reaction using an organic peroxide or silane (US Patent No. 6284178 (Sep. 4, 2011) In recent years, in the large wire industry, crosslinking type by organic peroxide is widely used.

In recent years, there is a demand for a power cable having high transmission capacity capable of being recycled. In order to satisfy this demand, a wire including an insulating layer made of a non-crosslinked polymer resin capable of operating at a maximum allowable temperature of 110 ° C is required.

On the other hand, since the crosslinked polyethylene resin is a thermoset resin prepared by crosslinking polyethylene, it is impossible to recycle the polyethylene resin, and thus it is difficult to dispose of the polyethylene resin, which causes environmental pollution. Further, since the melting point of the crosslinked polyethylene is 90 占 폚 to 115 占 폚, it is difficult to operate at a high temperature of 110 占 폚, which is not suitable as a material for the insulating layer of the power cable.

That is, there is a need to use environmentally friendly non-crosslinkable thermoplastic resins, but the crosslinked polyethylene used mainly at present is a problem because it is not suitable for use as a power cable insulation material because of a remarkably low heat resistance.

As a background of this background, there is a prior art for non-crosslinked polyethylene resin in Korean Patent Laid-Open No. 10-2010-0106871 (Oct. 4, 2010) as insulation material of electric power cable, but due to low shear thinning of resin during actual processing There is a problem that the processability is poor and processing defects occur. In addition, there is a problem that the tracking resistance is poor and the performance is degraded as an insulating layer of an outdoor cable.

Therefore, in order to solve such a problem, it is necessary to develop a power cable capable of operating at a maximum allowable temperature of 110 ° C, including an insulating layer composed of a non-crosslinked polymer composite resin having a high melting point.

It is an object of the present invention to provide a power cable having an eco-friendly non-crosslinked insulating layer which can be recycled.

Another object of the present invention is to provide a power cable including an insulating layer made of a non-crosslinkable resin excellent in heat resistance, low temperature impact resistance, mechanical and electrical properties, and excellent in whitening resistance and transparency.

Another object of the present invention is to provide a power cable having a lower residual amount of catalyst than an ordinary polypropylene composite resin and having excellent electrical characteristics.

One aspect of the present invention relates to a power cable having an insulating layer with improved transparency. In one embodiment, the power cable comprises at least one conductor; An inner semiconductive layer surrounding the conductor; An insulating layer surrounding the inner semiconductive layer; An outer semiconductive layer surrounding the insulating layer; A neutral wire watertight layer surrounding the outer semiconductive layer; And an outer skin layer surrounding the neutral wire watertight layer, wherein the insulating layer comprises a polypropylene block copolymer and an ethylene-octene rubber, wherein the insulating layer comprises 100 parts by weight of a polypropylene block copolymer and an ethylene- And 30 to 80 parts by weight of a polypropylene block copolymer and 20 to 70 parts by weight of an ethylene-octene rubber, wherein the insulating layer has a haze of 90% or less or a total transmittance ) Is more than 80%.

In one embodiment, the haze and light transmittance can be measured according to ASTM D 1003.

In one embodiment, the insulating layer further comprises an ionic inorganic material, wherein 55 parts by weight to 65 parts by weight of a polypropylene block copolymer, 100 parts by weight of an ethylene- 35 to 45 parts by weight of octene rubber and 0.03 parts by weight or less of an ionic inorganic material.

In one embodiment, the polypropylene block copolymer may comprise from 80 parts by weight to 95 parts by weight of an ethylene-propylene random copolymer and from 5 parts by weight to 20 parts by weight of an ethylene-propylene random block copolymer have.

In one embodiment, the ethylene content in the ethylene-propylene random copolymer is 0.5 wt% to 10 wt%, the ethylene content in the ethylene-propylene rubber is 20 wt% to 60 wt%, and the ethylene- The inherent viscosity ratio of the ethylene-propylene rubber solvent extract (xylene solvent) to the intrinsic viscosity may be 0.5 to 1.1.

In one embodiment, the polypropylene block copolymer has a melt index (MI) of from 1 g / 10 min to 10 g / 10 min as measured according to ASTM D 1238 (230 캜, 2.16 kg) and has a haze measured according to ASTM D 1003 The degree may be less than 5%.

In one embodiment, the polypropylene block copolymer may comprise a matrix in which the ethylene-propylene random block copolymer has been dispersed in an ethylene-propylene rubber having a size of not larger than 0.4 탆.

In one embodiment, the polypropylene block copolymer has a flexural modulus of 7000 kg / cm 2 to 10000 kg / cm 2 as measured in accordance with ASTM D790, a heat distortion temperature measured according to ASTM D648 is 90 ° C to 105 ° C, The melting point may be from 154 캜 to 156 캜.

In one embodiment, the polypropylene block copolymer has a Rockwell hardness of 55 to 63 and a 1/8 "notched Izod impact strength as measured in accordance with ASTM D256 of from 10 kg · cm / cm to 20 kg · cm / cm. < / RTI >

In one embodiment, the ethylene-octene rubber is a copolymer of an ethylene monomer and a 1-octene comonomer, wherein the content of the 1-octene comonomer in the ethylene-octene rubber is 5 wt% to 40 wt%, ASTM D 1238 (MI) of 6 g / 10 min or less as measured on the basis of the melt index (230 DEG C, 2.16 kg).

In one embodiment, the melting point of the insulating layer is between 140 ° C and 160 ° C, and the flexural modulus measured according to the ASTM D790 standard is between 2000 kg / cm 2 and 4000 kg / cm 2.

In one embodiment, one or more neutral lines may be provided between the shell layer and the neutral wire watertight layer.

In one embodiment, the inner semiconductive layer and the outer semiconductive layer may each include a thermoplastic resin composition containing 20 to 40% by weight of carbon black.

In one embodiment, the shell layer comprises polyethylene and the melting temperature may be between 110 ° C and 130 ° C.

According to the present invention, it is possible to provide a power cable having an eco-friendly non-crosslinked insulating layer which can be recycled.

Further, according to the present invention, it is possible to provide a power cable including an insulating layer made of a non-crosslinkable resin excellent in heat resistance, low temperature impact resistance, mechanical and electrical properties, and whitening resistance and transparency.

Further, according to the present invention, it is possible to provide a power cable having a lower residual amount of catalyst than an ordinary polypropylene composite resin and having excellent electrical characteristics.

1 is a view illustrating a power cable according to an embodiment of the present invention.
2 is a cross-sectional view of the power cable of FIG.
FIG. 3A is a view showing a result of stress whitening after orientation crystallization according to Example 1 of the present invention, and FIG. 3B is a view showing a result of stress whitening after orientation crystallization according to Example 2 of the present invention.
FIG. 4A is a graph showing the result of stress whitening after orientation crystallization according to Comparative Example 1, FIG. 4B is a graph showing the result of stress whitening after orientation crystallization according to Comparative Example 2, FIG. 4C is a graph showing stress after orientation crystallization according to Comparative Example 3 Fig.
FIG. 5A shows a power cable according to a first embodiment of the present invention, and FIG. 5B shows a power cable according to a first comparative example of the present invention.

Hereinafter, the present invention will be described in detail. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to be exemplary, self-explanatory, allowing for equivalent explanations of the present invention.

FIG. 1 is a view showing a power cable according to an embodiment of the present invention, and FIG. 2 is a sectional view of the power cable of FIG. 1. A power cable 100 having an insulating layer with improved transparency according to an embodiment of the present invention includes at least one conductor (or an electric conductor) 110; An inner semiconductive layer 120 surrounding the conductor 110; An insulating layer 130 surrounding the inner semiconductive layer 120; An outer semiconductive layer 140 surrounding the insulating layer 130; A neutral wire tightness layer 150 surrounding the outer semiconductive layer 140; And an outer layer 160 surrounding the neutral conductor water tight layer 150. The insulating layer 130 comprises a polypropylene block copolymer and an ethylene-octene rubber, and the insulating layer 130 comprises a polypropylene block copolymer And 30 to 80 parts by weight of a polypropylene block copolymer and 20 to 70 parts by weight of an ethylene-octene rubber with respect to 100 parts by weight of the sum of the ethylene-octene rubber and the ethylene- ) Is 90% or less, or the total transmittance is 80% or more.

In one embodiment, the haze and light transmittance can be measured according to ASTM D 1003.

The power cable 100 according to an exemplary embodiment of the present invention can transmit a high voltage of 20 kV or more and can be stably used for a long time and is made of an eco-friendly resin that stably insulates the conductor 110, .

The electrical conductor 110 may be a rod or a stranded multi-wire, and may be a metallic material that is electrically conductive, and may specifically include aluminum or copper. The conductor 110 may have a circular cross-section, an outer diameter of 10 mm to 25 mm, and a thickness of the insulation layer 130 may be 6 mm to 8 mm. Specifically, the conductor 110 has a circular cross-sectional area, an outer diameter is 11.4 mm to 23.5 mm, and a thickness of the insulating layer 130 is 6 mm to 7.5 mm.

The power cable 100 according to an embodiment of the present invention may be provided in a circular shape having an outer diameter of 10 mm to 25 mm according to a nominal cross-sectional area. As the nominal cross-sectional area of the power cable 100 increases, 110 is also increased, and thus the maximum permissible current for transmission is also increased.

For example, in the 22.9 kV eco-friendly full power aluminum cable 100, the thickness of the insulating layer can be set to 6.8 mm, and the thickness of the insulating layer 130 can be determined by the withstand voltage value and the dielectric breakdown strength of the cable have. The calculation standard of the insulation layer thickness is determined by a larger value determined from the thickness determined from the AC voltage and the thickness determined from the impact voltage of the brain. When the insulation thickness of the 22.9 kV class power cable 100 exceeds 8 mm, And the workability of construction and construction is lowered. Specifically, the thickness of the insulating layer 110 may be 6.22 mm to 7.37 mm.

The inner semiconductive layer 120 is formed on the outer surface of the electrical conductor 110 and the outer semiconductive layer 140 is surrounded on the outer surface of the semiconductive semiconductive layer 120. The inner semiconductive layer 120, The insulating layer 130 may be interposed between the first electrode layer 140 and the second electrode layer 140.

The inner semiconductive layer 120 and the outer semiconductive layer 140 may have a volume resistivity value of less than 500 Ω · m, preferably less than 20 Ω · m at room temperature as a semiconductive layer on both sides, The inner semiconductive layer 120 and the outer semiconductive layer 140 may each include a thermoplastic resin composition containing 20 to 40% by weight of carbon black. For example, the thermoplastic resin may include a polypropylene polymer. For example, the inner semiconductive layer 120 and the outer semiconductive layer 140 may be formed by dispersing 20 to 40% by weight of carbon black in the polypropylene polymer, respectively.

The inner semiconductive layer 120 may be interposed between the conductor 110 and the insulating layer 130. The inner semiconductive layer 120 can prevent electric field relaxation and partial discharge of the surface of the conductor, and the outer semiconductive layer 140 serves to protect the insulating layer in addition to the field relaxation. The neutral wire tightness layer 150 may include a semiconductive inflatable tape, and the semiconductive inflatable tape may be inflated (swollen) by absorbing moisture.

The outer surface of the neutral wire watertight layer 150 may be provided so as to be surrounded by the outer skin layer 160. The outer skin layer 160 may include polyethylene and may have a melting temperature of 110 ° C to 130 ° C (the melting temperature may be tested at a heating rate of 20 ° C / min according to KS M ISO 11357-3). Specifically, (160) may have a melting temperature of 118 ° C to 128 ° C.

The power cable 100 uses a material such as polyvinyl chloride (PVC) having excellent flame retardancy when it is installed in the air or a power socket as the outer layer 160. In other cases, the outer layer 160 is made of polyethylene (PE).

One or more neutral lines 170 may be provided between the outer shell layer 160 and the neutral conductor water tight layer 150. The neutral line 170 may be an interlocking line and may include a plurality of wires having a circular cross section having an outer diameter of approximately 0.1 to 0.15 times the outer diameter of the conductor 110.

Generally, crosslinked polyethylene is used as an insulating layer in a power cable. Since crosslinked polyethylene is used for crosslinking using organic peroxide, it is impossible to recycle the crosslinked polyethylene and the melting point is low. Thus, when a power cable is operated at a high temperature of 110 ° C or more The power cable may be deformed and melted. Further, when polypropylene is used as the insulating layer of the power cable, the polypropylene has a melting point higher than that of the crosslinked polyethylene at a melting point of 150 ° C or higher, so that the polypropylene can operate at a high temperature. However, There is a disadvantage that it is not suitable for installing a power cable because of lack of flexibility.

The power cable 100 according to this embodiment may include an insulating layer 130 made by blending one or more novel polymeric resins. The insulating layer 130 may include a non-crosslinked thermoplastic polymer resin.

The insulating layer 130 may be made by blending two different resins, for example, the different resins may include a polypropylene block copolymer and an ethylene-octene rubber, and the polypropylene block copolymer and the ethylene- The octene rubber may be a non-crosslinkable polymer.

In an embodiment, the insulating layer 130 may further comprise an ionic inorganic material. For example, the insulating layer 130 may be formed by blending 30 to 80 parts by weight of a polypropylene block copolymer, 20 to 70 parts by weight of an ethylene-octene rubber with respect to 100 parts by weight of the sum of the polypropylene block copolymer and the ethylene- And 0.03 parts by weight or less of an ionic inorganic material.

When the polypropylene block copolymer is contained in an amount exceeding 80 parts by weight based on 100 parts by weight of the sum of the polypropylene block copolymer and the ethylene-octene rubber, the mechanical strength of the power cable 100 is increased, When the polypropylene block copolymer is contained in an amount of less than 30 parts by weight, a heat deformation rate is increased and a phenomenon such as pressing of the power cable occurs.

When the ethylene-octene rubber is contained in an amount of less than 20 parts by weight based on 100 parts by weight of the sum of the polypropylene block copolymer and the ethylene-octene rubber, flexibility of the power cable is lowered, - When the octene rubber is contained in an amount exceeding 70 parts by weight, the mechanical strength such as corrosion resistance and weather resistance is lowered, which is a problem.

In order to further improve the electrical insulation property of the insulating layer 130, suppress the whitening phenomenon, and improve the process efficiency, the insulating layer 130 may be formed of a polypropylene 55 to 65 parts by weight of a polypropylene block copolymer, 35 to 45 parts by weight of an ethylene-octene rubber, and 0 to 0.03 parts by weight of an ionic inorganic substance, based on 100 parts by weight of the sum of the block copolymer and the ethylene- More preferably 60 parts by weight of a polypropylene block copolymer, 40 parts by weight of an ethylene-octene rubber and 0.03 part by weight of an ionic inorganic material.

The insulating layer 130 may further include the ionic inorganic material. The ionic inorganic material may be one derived from a residue of a catalyst component used in the production of an insulating layer using the polypropylene block copolymer and ethylene-octene rubber, and an additive such as an antioxidant. For example, the ionic inorganic material may include at least one of magnesium (Mg), aluminum (Al), phosphorous (P), silicon (Si), calcium (Ca), and zinc (Zn).

The ionic inorganic material may be contained in an amount of more than 0 to 0.03 parts by weight based on 100 parts by weight of the sum of the polypropylene block copolymer and the ethylene-octene rubber. For example, 0 to 0.03 part by weight. When it is included in the above-mentioned range, the electric field is not concentrated due to the fine particles and voids, and thus the electrical characteristics are excellent and the mechanical strength and flexibility such as impact resistance can be excellent.

The whitening phenomenon is caused by a crack caused by a micro void, and when the whitening phenomenon occurs, the transparency is lowered and the whitening resistance and impact resistance are lowered. Specifically, when the content of the ionic inorganic material increases, the insulation performance is lowered to lower the electrical characteristics of the power cable. In the case of operating the power cable at a high temperature, the deterioration of the power cable is accelerated. .

On the other hand, the insulating layer according to the embodiment of the present invention can reduce the crystal size of the insulating layer polymer resin including the polypropylene block copolymer and the ethylene-octene rubber, thereby improving the light transmittance and suppressing the occurrence of whitening.

In the present invention, the ethylene-propylene rubber may be in the form of a heterophasic copolymer. The heterophasic copolymer may be in the form of an elastomeric domains of an ethylene-propylene rubber dispersed in a matrix of a polypropylene homopolymer or a polypropylene copolymer.

In an embodiment of the present invention, a homopolymer refers to a polymer having one type of repeating unit, and a copolymer means a polymer having two or more types of repeating units.

In one embodiment, the polypropylene block copolymer comprises 80 to 95 parts by weight of an ethylene-propylene random copolymer and 5 to 20 parts by weight of an ethylene-propylene random copolymer in an ethylene-propylene random block copolymer Polymer.

The ethylene-propylene copolymer can be polymerized by simultaneously injecting ethylene and propylene in a polymerization reactor. The polymerization method of the ethylene-propylene copolymer may be prepared by a method known in the art.

The ethylene-propylene rubber is polymerized in the presence of the ethylene-propylene random copolymer in a series of polymerization reaction apparatuses subsequent to the preparation of the ethylene-propylene random copolymer. The polymerization method of the ethylene-propylene rubber can be produced by a method known in the art.

When the ethylene-propylene random copolymer is contained in an amount of less than 80 parts by weight based on the total weight of the polypropylene block copolymer, the crystallinity of the polypropylene block copolymer resin is lowered and the heat resistance is lowered. The impact resistance sharply decreases.

The ethylene content in the ethylene-propylene random copolymer may be from 0.5 wt% to 10 wt%. When the content of ethylene is less than 0.5% by weight, the degree of crystallization of the copolymer may be high or the compatibility with the ethylene-propylene rubber may be deteriorated and the transparency and whitening resistance may be deteriorated. When the ethylene content exceeds 10% by weight, The mechanical strength such as heat resistance is lowered.

The amount of ethylene in the ethylene-propylene rubber may be 20 wt% to 60 wt%. When ethylene is contained in an amount of less than 20% by weight, physical properties such as elasticity and impact resistance are deteriorated. When the ethylene content is more than 60% by weight, flexibility of the ethylene-propylene rubber may be lowered.

In the specific examples, the intrinsic viscosity ratio of the solvent extract of ethylene-propylene rubber (xylene solvent) to the intrinsic viscosity of the ethylene-propylene random copolymer (intrinsic viscosity of the solvent extract of ethylene-propylene rubber / ethylene- Intrinsic viscosity of the polymer) may be 0.5 to 1.1. When the intrinsic viscosity ratio is out of the above range, the compatibility between the ethylene-propylene random block copolymer and the ethylene-propylene rubber is lowered, and the moldability of the product such as the ethylene-propylene rubber is aggregated .

The polypropylene block copolymer is prepared by adding to the matrix comprising an ethylene-propylene random block copolymer an ethylene-propylene rubber having a size of 0.4 m or less, preferably 0.01 to 0.4 m, ≪ / RTI > If the size of the ethylene-propylene rubber is larger than 0.4 mu m, the moldability is lowered and the dispersed phase larger than the visible light wavelength is increased, and transparency may be lowered.

In the present specification, the "size" may mean the "maximum length" of the ethylene-propylene rubber.

In embodiments, the polypropylene block copolymer has a melt index (MI) of from 1 g / 10 min to 10 g / 10 min measured according to ASTM D 1238 (230 캜, 2.16 kg) and a haze measured according to ASTM D 1003 Can be less than 5%. When the melt index (MI) is less than 1 g / 10 min, the fluidity is lowered and the power cable is not suitable for molding. If the melt index is more than 10 g / 10 min, the viscosity is too low to control the thickness of the produced power cable uniformly .

The polypropylene block copolymer has a flexural modulus of 7000 kg / cm 2 to 10000 kg / cm 2 as measured according to ASTM D790, a heat distortion temperature measured according to ASTM D648 of 90 ° C to 105 ° C, a melting point of 154 ° C / RTI > to < RTI ID = In one embodiment, the polypropylene block copolymer has a Rockwell hardness of 55 to 63 and a 1/8 "notched Izod impact strength as measured in accordance with ASTM D256 of from 10 kg · cm / cm to 20 kg · cm / cm. < / RTI >

The insulating layer 130 may be prepared by mixing the polypropylene block copolymer and ethylene-octene rubber at a predetermined ratio. Wherein the ethylene-octene rubber is a copolymer of an ethylene monomer and a 1-octene comonomer, the content of the 1-octene comonomer in the ethylene-octene rubber is 5 wt% to 40 wt%, ASTM D 1238 (230 DEG C, 2.16 kg) may have a melt index (MI) of 6 g / 10 min or less. Specifically, the content of the 1-octene comonomer in the ethylene-octene rubber may be 5.5% by weight, 7.6% by weight, 28% by weight and 39% by weight. The ethylene-octene rubber may have a glass transition temperature (Tg) of -30 占 폚 or lower.

When the ethylene-octene rubber has a melt index of more than 6 g / 10 min, the melt index of the insulating layer is increased to cause a problem in processing the power cable. When the glass transition temperature is higher than -30 ° C, Which is a problem.

Since the ethylene-octene rubber is a copolymer of ethylene and octene and has an excellent low-temperature impact strength as compared with the ethylene-propylene-diene elastomer (EPDM), when the insulating layer 130 is manufactured by mixing with the polypropylene block copolymer The impact strength at low temperature can be improved and the mechanical properties can be further improved.

The flexibility of the power cable 100 can be influenced by the insulation layer 130 and the flexibility of the power cable 100 can be enhanced by the insulation layer 130 in accordance with the ASTM D790 specification of the insulation layer 130 The measured flexural modulus is preferably 2000 kg / cm 2 to 4000 kg / cm 2. The insulating layer 130 may be formed by mixing a polypropylene block copolymer and an ethylene-octene rubber. The polypropylene block copolymer and the ethylene-octene rubber may have a flexural modulus, a mixing ratio, The bending elastic modulus of the insulating layer 130 can be controlled.

The melting point of the insulating layer 130 may be 140 to 160 ° C, and the flexural modulus measured according to ASTM D790 may be 2000 to 4000 kg / cm 2. If the bending modulus of elasticity of the insulating layer 130 is more than 4000 kg / cm 2, the flexibility is lowered and the whitening phenomenon occurs. If the bending modulus of elasticity is less than 2000 kg / cm 2, Can occur.

In this embodiment, the melting point of the insulating layer 130 may be 140 ° C to 160 ° C. Specifically, the melting point of the insulating layer 130 may be 150 ° C or higher, more specifically 150 ° C to 160 ° C. In one embodiment, the melting point of the insulating layer 130 may be 152 캜 or 153 캜. When the melting point of the insulating layer 130 is less than 150 ° C, the occurrence of whitening can be suppressed, but it is difficult to stably operate the power cable 130 for a long time. When the melting point exceeds 160 ° C, There is a problem that the crystal size is large and many whitening phenomena occur. Therefore, in order to stably operate the power cable 100 at a high temperature and control the generation of whitening phenomenon within a predetermined range, the melting point of the insulating layer 130 is preferably 150 ° C to 160 ° C.

Further, the power cable 100 according to the present embodiment can be recycled, eco-friendly, and operated stably even when the melting point is increased and the transmission capacity is increased by using an insulating layer made of a non-crosslinked polymer composite resin It is possible.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Example  And Comparative Example

Example  One

60 parts by weight of a polypropylene block copolymer (product name: CF309, Hanwha Total), 40 parts by weight of ethylene-octene rubber (product name: Engage 8842, Dow Elastomes) and 0.0180 parts by weight of an ionic inorganic substance An insulating layer for an insulating cable was prepared.

Example  2 to 3

An insulating layer was prepared in the same manner as in Example 1, except that the reactive polypropylene and ethylene-octene rubber contents were applied as shown in Table 1 below.

Comparative Example  One

An insulating layer was prepared in the same manner as in Example 1 except that the content of reactive polypropylene and ethylene-octene rubber was applied as shown in Table 1 below.

Comparative Example  2

Except that 60 parts by weight of random polypropylene type polymer (RP242G, Lyondellbasell) and 40 parts by weight of reaction type polypropylene (product name: CA7441A, Lyondellbasell) were applied as shown in the following Table 1 An insulating layer was prepared.

Comparative Example  3

An insulating layer was prepared in the same manner as in Comparative Example 1, except that 100 parts by weight of a random polypropylene-based polymer (RP242G, Lyondellbasell) was applied as shown in Table 1 below.

Comparative Example  4

An insulating layer was prepared in the same manner as in Comparative Example 1, except that crosslinked polyethylene (LS4201, borealis) was used.

The insulation layers of Examples 1 to 3 and Comparative Examples 1 to 4 were each produced with power cables under the same conditions as in Table 2 and the mechanical properties of the insulation layer and the power cable were measured according to the following criteria, Are shown in Tables 1, 3 and 4 below.

How to measure property

(1) Evaluation of mechanical properties at room temperature and after heating: For each of the power cable specimens prepared in Examples and Comparative Examples, tensile strength and elongation at breaking point of 25 mm / min were measured at room temperature according to IEC-60811-501 Respectively. The heating was carried out at 135 DEG C for 240 hours, and the tensile strength and elongation at break point were measured at a tensile rate of 25 mm / min. The standard of tensile strength after room temperature and after heating shall be 1.27kg / ㎟ or more and the elongation shall be 350% or more.

(2) Heating deformation: Each of the insulating layer specimens prepared in Examples and Comparative Examples was subjected to a test under a constant load at a heating temperature of 130 DEG C for 6 hours according to IEC-60811-508, %.

(3) Internal blowing test: For each of the insulating layer specimens prepared in Examples and Comparative Examples, five internal blowing tests were carried out at -40 DEG C in accordance with KS C 3004 standard, and fracture phenomena were observed in five specimens The more the destruction is not occurred, the better the cold resistance.

(4) Flexural Modulus Test: The flexural modulus of the insulating layers of the above Examples and Comparative Examples was measured according to the ASTM D790 standard, and when the flexural modulus was 2000 kg / cm 2 to 4000 kg / cm 2, the low temperature impact resistance, flexibility, .

(5) Stress-whitening: The insulating layer specimens of the examples and comparative examples were bent at 90 DEG C to check for whitening and cracking.

(6) Orientation-induced crystallization: After orienting the specimen with the universal material testing machine (UTM) for the insulating layers of the examples and comparative examples, the presence of whitening and cracking was visually confirmed.

(7) Light Diffusion (Haze) and Total Transmittance

For the insulating layers of Examples and Comparative Examples, 0.5 mm thick specimens were prepared by using a hot press apparatus according to ASTM D 1003 standard, and the haze and the total transmittance were measured. The results are shown in Table 1 below. A hazemeter (NDH-5000) was used as a test instrument and a white LED was used as a light source. A test light flux of 14 mm ¢ and an incident opening of 25 mm ¢ were used.

FIG. 3A is a view showing a result of stress whitening after orientation crystallization according to Example 1 of the present invention, and FIG. 3B is a view showing a result of stress whitening after orientation crystallization according to Example 2 of the present invention. FIG. 4A is a graph showing the result of stress whitening after orientation crystallization according to Comparative Example 1, FIG. 4B is a graph showing the result of stress whitening after orientation crystallization according to Comparative Example 2, FIG. 4C is a graph showing stress after orientation crystallization according to Comparative Example 3 Fig. 5A shows a power cable according to Embodiment 1 of the present invention, and FIG. 5B shows a power cable according to Comparative Example 1 according to the present invention.

Referring to Tables 1 to 4 together with FIGS. 3A to 5B, in the case of Examples 1 to 3, whitening did not occur, but Comparative Example 1 exhibited excellent electrical properties but was inadequate in impact resistance at low temperatures Whitening occurred after stress whitening and orientation crystallization. Comparative Example 2 was excellent in low-temperature impact resistance and electrical characteristics and did not cause stress whitening. In Comparative Example 3, the impact resistance at low temperature was inadequate and the rigidity was so high that the flexibility was insufficient and whitening occurred after stress whitening and orientation crystallization.

Comparing Example 1, Example 2 and Example 3, it can be seen that the flexural modulus of Examples 1 and 2 is higher than that of Example 3. It was confirmed that the content of the polypropylene block copolymer in Examples 1 and 2 was relatively higher than the content of ethylene-octene rubber.

Comparing Example 1 and Example 2, it was confirmed that the AC insulation breakdown strength of Example 1 is superior even though the contents of the polypropylene block copolymer and the ethylene-octene rubber are similar on both sides. It can be confirmed that this is caused by the fact that the content of the ionic inorganic material is less in the case of Example 1.

That is, it is preferable that a polypropylene block copolymer and an ethylene-octene rubber are mixed and used as an insulation layer of the power cable as in the case of Examples 1 to 3. In this case, the polypropylene block copolymer and the ethylene- It was confirmed that the mixing of the content of the ionic inorganic substances contained in these components within a predetermined controlled range can secure both electrical characteristics, mechanical strength and flexibility.

When the polymer resin according to this embodiment is applied to an insulating layer of a power cable, it can be operated at a maximum allowable temperature of 110 ° C at all times and excellent impact resistance can be secured at a low temperature of -40 ° C. Further, the polypropylene block copolymer and the ethylene-octene rubber, which are the constituents of the insulating layer according to the present embodiment, are non-crosslinkable polymers, and when used as an insulating layer of a power cable, their flexibility, mechanical and electrical properties are improved, It is possible to provide an environmentally friendly power cable. In addition, it is possible to control the crystal size of the insulating polymer resin including the polypropylene block copolymer and the ethylene-octene rubber, thereby improving the light transmittance and reducing the whitening phenomenon.

100: power cable 110: conductor
120: inner semiconductive layer 130: insulating layer
140: outer semiconductive layer 150: neutral conductor water-tight layer
160: outer layer 170: Neutral line

Claims (14)

One or more conductors;
An inner semiconductive layer surrounding the conductor;
An insulating layer surrounding the inner semiconductive layer;
An outer semiconductive layer surrounding the insulating layer;
A neutral wire watertight layer surrounding the outer semiconductive layer; And
And an outer skin layer surrounding the neutral water tight layer,
Wherein the insulating layer comprises 30 to 80 parts by weight of a polypropylene block copolymer and 20 to 70 parts by weight of an ethylene-octene rubber with respect to 100 parts by weight of the sum of the polypropylene block copolymer and the ethylene-octene rubber,
Wherein the insulating layer has a total transmittance of 80% or more.
The power cable according to claim 1, wherein the light transmittance is measured according to ASTM D 1003.
The method of claim 1, wherein the insulating layer further comprises an ionic inorganic material,
55 to 65 parts by weight of a polypropylene block copolymer, 35 to 45 parts by weight of an ethylene-octene rubber and 0.03 parts by weight of an ionic inorganic material, based on 100 parts by weight of the sum of the polypropylene block copolymer and the ethylene- Power cables containing less than.
The polypropylene block copolymer according to claim 1, wherein the polypropylene block copolymer comprises 80 to 95 parts by weight of an ethylene-propylene random copolymer and 5 to 20 parts by weight of an ethylene-propylene random block polymer Power cable.
5. The ethylene-propylene random copolymer of claim 4, wherein the ethylene content in the ethylene-propylene random copolymer is 0.5 wt% to 10 wt%, the ethylene content in the ethylene-propylene rubber is 20 wt% to 60 wt%
Wherein the intrinsic viscosity ratio of the ethylene-propylene rubber solvent extract (xylene solvent) to the intrinsic viscosity of the ethylene-propylene random copolymer is 0.5 to 1.1.
The polypropylene block copolymer according to claim 4, wherein the polypropylene block copolymer has a melt index (MI) of 1 g / 10 min to 10 g / 10 min measured according to ASTM D 1238 (230 캜, 2.16 kg) A power cable with a degree of cloudiness of 5% or less.
5. The polypropylene block copolymer according to claim 4,
Wherein the ethylene-propylene random block copolymer is dispersed in an ethylene-propylene rubber having a size of 0.4 mu m or less in a matrix containing the ethylene-propylene random block copolymer.
The polypropylene block copolymer according to claim 1, wherein the polypropylene block copolymer has a flexural modulus in a range of 7000 kg / cm 2 to 10000 kg / cm 2 measured according to ASTM D790 standard, and a heat distortion temperature measured according to ASTM D648 standard is 90 ° C to 105 ° C And a melting point of 154 캜 to 156 캜.
The polypropylene block copolymer according to claim 1, wherein the polypropylene block copolymer has a Rockwell hardness of 55 to 63 and a Izod impact strength of not less than 10 kg · cm / cm to 20 kg · cm / cm measured according to ASTM D256 standard In power cable.
The method of claim 1, wherein the ethylene-octene rubber is a copolymer of an ethylene monomer and a 1-octene comonomer, wherein the content of the 1-octene comonomer in the ethylene-octene rubber is 5 wt% to 40 wt% A power cable having a melt index (MI) measured according to D 1238 (230 캜, 2.16 kg) of not more than 6 g / 10 min.
The power cable according to claim 1, wherein the insulating layer has a melting point of 140 캜 to 160 캜 and a flexural modulus measured according to ASTM D790 of 2000 kg / cm 2 to 4000 kg / cm 2.
The power cable according to claim 1, wherein at least one neutral wire is provided between the shell layer and the neutral wire watertight layer.
The power cable according to claim 1, wherein the inner semiconductive layer and the outer semiconductive layer comprise a thermoplastic resin composition containing 20 to 40 wt% carbon black, respectively.
The power cable according to claim 1, wherein the sheath layer comprises polyethylene and has a melting temperature of 110 ° C to 130 ° C.

Images