KR102003565B1 - Power cable - Google Patents

Abstract

The present invention relates to power cables. Specifically, the present invention relates to a power cable including an insulating layer made from an insulating composition that is recyclable and environmentally friendly as well as excellent in flexibility, heat resistance, mechanical and electrical properties, and low in manufacturing cost.

Description

Power cable {Power cable}

The present invention relates to power cables. Specifically, the present invention relates to a power cable including an insulating layer made from an insulating composition that is recyclable and environmentally friendly as well as excellent in flexibility, heat resistance, mechanical and electrical properties, and low in manufacturing cost.

A typical power cable includes a conductor and an insulating layer surrounding the conductor. In the case of a high-voltage or ultra-high voltage cable, an inner semiconductive layer between the conductor and the insulating layer, an outer semiconductive layer surrounding the insulating layer, a sheath layer surrounding the outer semiconductive layer May be further included.

In recent years, as the operating temperature of the high voltage cable has been improved from the 90 ° C class to the 110 ° C class, there has been a need for an insulating material for manufacturing an insulating layer that can maintain its inherent mechanical and electrical properties without deteriorating at higher temperatures. Conventionally, a polyolefin-based polymer such as polyethylene, ethylene / propylene elastomeric copolymer (EPR), or ethylene / propylene / diene copolymer (EPDM) has been used as a base resin constituting an insulation material of 90 deg.

However, since the crosslinked polyethylene (XLPE) or the like which has been used as the base resin constituting the insulating material is in a crosslinked form, it is difficult to recycle it, and when polyvinyl chloride (PVC) is used as the material of the sheath layer, (XLPE) or the like, which constitute the carbon nanotubes, and it is not environmentally friendly since toxic chlorinated materials are generated upon incineration.

In addition, non-crosslinked high density polyethylene (HDPE) or low density polyethylene (LDPE) is environmentally friendly such as recyclable, but has a disadvantage that its use is very limited due to its lower operating temperature than crosslinked polyethylene (XLPE).

On the other hand, there is known a technique of using environmentally friendly polypropylene as a base resin capable of improving the operating temperature of the cable to 110 占 폚 level without cross-linking at 160 占 폚 or higher as the melting point of the polymer itself. Here, the term " polypropylene " refers to a high crystalline isotactic polypropylene as a thermoplastic material having excellent mechanical properties.

However, due to the insufficient flexibility due to the high rigidity of the polypropylene, there is a problem that the workability of the cable including the insulation layer produced therefrom is low during the installation work and its application is limited.

In this connection, there is known a technique of mixing polypropylene, which is a base resin, with insulating oil having an aromatic structure, in order to improve the flexibility of the insulating layer made of the polypropylene. However, since the insulating oil having the aromatic hydrocarbon structure is expensive, There is a problem that the manufacturing cost of the cable increases.

Accordingly, there is a need for a power cable including an insulating material for a power cable and an insulating layer made therefrom that is environmentally friendly, has excellent flexibility, heat resistance, mechanical and electrical characteristics, and is low in manufacturing cost .

An object of the present invention is to provide a power cable including an insulating layer made of an environmentally friendly insulating material, which is excellent in heat resistance of itself and can be used as an insulating layer without crosslinking and can be recycled.

It is another object of the present invention to provide a power cable including an insulating layer made of an insulating material with improved flexibility and heat resistance, mechanical and electrical characteristics, and the like.

Furthermore, it is an object of the present invention to provide a power cable including an insulating layer made of an insulating material having a low manufacturing cost.

In order to solve the above problems,

A power cable comprising at least one conductor, an insulating layer surrounding each conductor, and an outermost sheath layer, wherein the insulating layer comprises a non-crosslinked propylene homopolymer, a non-crosslinked propylene copolymer, or a base resin And naphthenic hydrocarbons of the formula C _n H _2n (wherein n is an integer of 20 to 60) in which a cyclic hydrocarbon and an acyclic hydrocarbon are alternately arranged based on 100 parts by weight of the base resin. And 2.5 to 10 parts by weight of the composition.

Here, the power cable is characterized in that the naphthenic hydrocarbon is a monocyclic naphthenic hydrocarbon.

Further, there is provided a power cable characterized in that the loop of the cyclic hydrocarbon is pentagonal or hexagonal.

On the other hand, the base resin includes a non-crosslinked propylene homopolymer and a non-crosslinked propylene copolymer, and the blending ratio of the non-crosslinked propylene homopolymer to the non-crosslinked propylene copolymer is 80:20 to 50:50. Power cable.

Here, the ungraded propylene copolymer is a copolymer of propylene monomer and ethylene monomer.

Also, the content of the ethylene monomer is 15 mol% or less based on the molar amount of the total monomers constituting the non-crosslinked propylene copolymer.

On the other hand, the insulating composition further comprises 0.2 to 5 parts by weight of an amine-based, dialkyl ester-based, thioester-based or phenol-based antioxidant based on 100 parts by weight of the base resin. do.

And the sheath layer is made from a composition comprising the same base resin as the base resin of the insulating composition.

The power cable may further include an inner semiconductive layer disposed between the conductor and the insulating layer, and an outer semiconductive layer surrounding the insulating layer.

Wherein the inner semiconductive layer, the outer semiconductive layer, or both are fabricated from a semiconductive composition comprising the same base resin as the base resin of the insulating composition.

The power cable according to the present invention is a base resin of the insulating layer constituting the power cable, and it has excellent heat resistance and can be recycled by including non-crosslinked polypropylene which can be used as an insulating layer without crosslinking. .

Further, since the insulating layer constituting the power cable according to the present invention contains specific insulating oil, although the base resin contains polypropylene having insufficient flexibility due to high rigidity, flexibility is improved and heat resistance, mechanical and electrical Characteristics and the like can be maintained.

Further, since the power cable according to the present invention does not include insulating oil having an expensive aromatic hydrocarbon structure as the insulating oil, it is excellent in cost compared to a power cable including an insulating layer made of a conventional insulating material containing the same .

1 is a cross-sectional view schematically showing a cross-sectional structure of a power cable according to the present invention.
2 is a longitudinal sectional view schematically showing a cross-sectional structure of a power cable according to the present invention.

1 and 2 show an embodiment of a power cable according to the present invention.

1 and 2, a power cable according to the present invention includes a conductor 1 made of a conductive material such as copper or aluminum, an insulating layer 3 made of an insulating polymer, (3), thereby suppressing partial discharge at the interface with the conductor (1), eliminating the air layer between the conductor (1) and the insulating layer (3) An outer semiconductive layer 4 serving as a shielding function of the cable and an electric field equivalent to the insulator, a sheath layer 5 for protecting the cable, and the like have.

The inner or outer semiconductive layer (2, 4) of the power cable can be manufactured in a conventional manner and is preferably made of the semiconductive layer (2, 4), the insulating layer (3) (3) which can ensure a good adhesion with the insulating layer (3) so as to prevent peeling of the insulating layer (3). In addition, the inner or outer semiconductive layer (2, 4) may include a conductive filler such as carbon black for anti-conduction properties. In addition, the sheath layer 5 of the power cable may also be made from a composition comprising the same base resin constituting the insulating layer 3.

The dimensions of the conductor 1, the insulating layer 3, the semiconductive layer 2 and 4, and the sheath layer 5 may vary depending on the use of the cable, the transmission voltage, etc. The insulating layer 3, The materials constituting the entire layers (2, 4) and the sheath layer (5) may be the same or different.

The insulating composition forming the insulating layer (3) of the power cable according to the present invention comprises an uncrosslinked polypropylene resin as a base resin.

The polymer constituting the non-crosslinked polypropylene resin may be a copolymer of propylene homopolymer and / or propylene with ethylene or an? -Olefin having 4 to 12 carbon atoms, such as 1-butene, 1-pentene, 4- 1-hexene, 1-octene, 1-decene, 1-dodecene, and combinations thereof, and the like, preferably with ethylene. This is because copolymerization of propylene and ethylene shows a hard and flexible property. Here, the blending ratio of the propylene homopolymer to the propylene copolymer may be, for example, 80:20 to 50:50.

In the propylene copolymer, the content of the comonomer may be 15 mol% or less, preferably 10 mol% or less, based on the total molar amount of the monomers constituting the propylene copolymer. Particularly, a propylene / ethylene copolymer is preferable. Further, the propylene copolymer may be a random copolymer or a block copolymer in which propylene and ethylene and / or? -Olefin are polymerized without regularity. The polypropylene may include a mixture of polyolefin such as low density polyethylene and linear low density polyethylene.

The propylene homopolymer or copolymer preferably has a maximum crystallization temperature of 110 to 125 DEG C (as measured by differential scanning calorimetry (DSC)). If the polypropylene homopolymer and / or the copolymer is melted or aged at a temperature of 90 ° C, which is the continuous operating temperature of the cable, under the aging test conditions (135 or 150 ° C) required by the IEC international standard when the maximum crystallization temperature is less than 110 ° C If the maximum crystallization temperature is higher than 125 ° C, the crystallization rate during cooling tends to increase, and the tensile elongation at room temperature may be lowered.

The propylene homopolymer or copolymer preferably has a weight average molecular weight (Mw) of 200,000 to 450,000. If the weight average molecular weight (Mw) is less than 200,000, the mechanical properties before and after heating may be lowered. If the weight average molecular weight is more than 450,000, the workability may be lowered due to high viscosity. Furthermore, the propylene homopolymer or copolymer preferably has a molecular weight distribution (Mw / Mn) of 2 to 8. When the molecular weight distribution (Mw / Mn) is less than 2, the workability may be lowered due to the higher viscosity. If the molecular weight distribution is more than 8, the mechanical properties before and after heating may be lowered.

On the other hand, the propylene homopolymer or copolymer may have a melting point of from 0.01 to 1,000 dg / min (measured by ASTM D-1238) and a melting point (Tm) of from 140 to 175 ° C (measured by differential scanning calorimetry (DSC) , A melt enthalpy of 30 to 85 J / g (as measured by DSC), a flexural modulus at room temperature of 30 to 1400 MPa, more preferably 60 to 1000 MPa (measured according to ASTM D790-00) Lt; / RTI >

As described above, in the present invention, the propylene homopolymer or copolymer has a high melting point, exhibits an improved deterioration suppressing property at a higher temperature of the insulating layer made of the propylene homopolymer or copolymer, It is not only capable of providing a power cable with improved operating temperature, but also has the advantage of being environmentally friendly because it is non-crosslinkable and can be recycled.

On the other hand, unlike the non-crosslinked propylene homopolymers or copolymers according to the present invention, conventional crosslinked polymers are not environmentally friendly because they are difficult to recycle, and when cross-linking or scorch occurs early in the production of an insulating layer It is not possible to exhibit a uniform production capacity, which may cause a deterioration in long-term extrudability.

The uncrosslinked propylene homopolymer or copolymer can be prepared by homopolymerization of propylene in the presence of a Ziegler-Natta catalyst having a low stereospecificity or by homopolymerization of propylene with an alpha -olefin other than ethylene or propylene ≪ / RTI > Details of the preparation of the unbiffered propylene homopolymer or copolymer can be found in, for example, Albizzati et al. in "Polypropylene Handbook ", Chapter 2, page 11 on wards (Hanser Publisher, 1996).

The insulating composition constituting the insulating layer 3 of the electric power cable according to the present invention may contain a specific insulating oil in addition to the base resin.

The insulating oil may include naphthenic hydrocarbons. Here, naphthene is a generic term for saturated hydrocarbons having a structure in which carbon atoms are bonded in a ring form in the molecule, and the properties are similar to paraffinic hydrocarbons and may be called cycloparaffins. Particularly, the insulating oil is a mono-cyclic naphthenic hydrocarbon having a general molecular formula of C _n H _2n (where n is an integer of 20 to 60), that is, a cyclic hydrocarbon, And naphthenic hydrocarbons having a structure in which cyclic hydrocarbons are arranged in an alternating manner. Here, the cyclic hydrocarbon may be 3 to 6, preferably pentagonal or hexagonal.

In Formula 1, the large circle is a carbon atom and the small circle is a hydrogen atom.

Wherein the general molecular formula is C _n H _2n-m (wherein n is an integer of 20 to 60 and m is an integer of 4 to 8) and is represented by the following formula (2) In the case where cyclic hydrocarbons are attached to each other in a molecule, that is, an insulating oil having a multi-cyclic structure such as bicyclic or tricyclic has low compatibility with a base resin, The mechanical and electrical properties of the insulating layer produced therefrom may deteriorate.

In Formula 2, the large circle is a carbon atom and the small circle is a hydrogen atom.

When the number of carbon atoms is less than 20, the insulating oil may be vaporized during the extrusion of the insulating layer due to its low molecular weight. When the number of carbon atoms is more than 60, the insulating oil may have a high molecular weight The insulating oil may be eluted during the extrusion of the insulating layer.

In the insulating composition constituting the insulating layer 3 of the power cable according to the present invention, the content of the insulating oil may be 2.5 to 10 parts by weight based on 100 parts by weight of the non-crosslinked propylene homopolymer or copolymer which is a base resin. If the content of the insulating oil is less than 2.5 parts by weight, the insulating layer produced by the insulating composition may not have sufficient flexibility and the cable may not be easily installed. If the content of the insulating oil is 10 wt% There is a problem that the insulating oil leaks out when the insulating layer is extruded, which makes it difficult to manufacture and process the cable.

As described above, the dielectric oil has a high rigidity and improves the flexibility of the insulating layer made of an insulating composition comprising a low-flexibility polypropylene resin as a base resin, and the polypropylene resin is essentially They have excellent heat resistance, mechanical and electrical properties. Further, since the insulating oil has the same or rather superior flexibility, heat resistance, mechanical and electrical properties as the conventional insulating oil having an aromatic hydrocarbon structure, the cost is much lower, thereby exhibiting an excellent effect of reducing the manufacturing cost of the cable.

The insulating composition constituting the insulating layer 3 of the power cable according to the present invention may further include other additives such as an antioxidant in addition to the base resin and the insulating oil. The antioxidant may be an amine-based, dialkyl ester-based, thioester-based or phenol-based antioxidant. Examples of the antioxidant include distearylthio-propionate, pentaerythry-tetrakis [3- Dihydroxyphenyl) propionate], [3- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propanoyloxy] -2 (3,5-di-t-butyl-4-hydroxyphenyl) propanoyloxymethyl] propyl] Phenyl) propanoate, thiodiethylenebis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 3,5-bis (1,1-dimethylethyl) -4- hydroxybenzenepropionic acid Octadecyl ester, propionic acid, 3,3'-thiobis-1,1'-dioctadecyl ester, and the like. Here, the content of each of the other additives such as the antioxidant may be 0.2 to 5 parts by weight based on 100 parts by weight of the base resin.

[Example]

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

An insulating composition was prepared according to the components and their contents shown in Table 1 below, and each sample sheet having a thickness of 2 mm and a size of 30 cm x 30 cm was produced by using a hot press. Here, the unit relating to the content of the constituent components is parts by weight.

Constituent
Example Comparative Example One One 2 3 4 5 Base resin 100 100 100 100 100 100 Monocyclic naphthenic oil (C ₃₀ H ₆₀ ) 5 - - - One 13 Monocyclic naphthenic oil (C ₁₀ H ₂₀ ) - 5 - - - - Monocyclic naphthenic oil (C ₈₀ H ₁₆₀ ) - - 5 - - - Multicyclic naphthenic oil (C ₃₀ H ₅₄ ) - - - 5 - -

- Base resin: A 50:50 mixture of polypropylene (manufacturer: Basel, product name: Q200) and an ethylene-propylene copolymer resin (manufacturer: SK General Chemicals, product name: R520Y)

- Mono cyclic naphthenic oil (C ₃₀ H ₆₀ ): Insulated oil No. 4 (Dongnam Petrochemical)

- Mono cyclic naphthenic oil (C ₁₀ H ₂₀ ): Insulating oil No.1 (Dongnam Petrochemical)

- Mono cyclic naphthenic oil (C ₈₀ H ₁₆₀ ): Insulating oil No. 6 (Dongnam Petrochemical)

- Multicyclic naphthenic oil (C ₃₀ H ₅₄ ): Insulating oil No. 35 (Dongnam Petrochemical)

≪ Evaluation of physical properties of sheet &

1) Evaluation of Mechanical Properties at Room Temperature

Tensile strength and tensile elongation were measured at room temperature and at a tensile rate of 250 mm / min for each of the sample sheets prepared in Example 1 and Comparative Examples 1 to 5 according to IEC-60811-1-1 standard. According to the above specification, the tensile strength should be 1.27 kgf / mm 2 or more, and the tensile elongation should be 200% or more.

2) Evaluation of mechanical properties after heating

Each of the sample sheets prepared in Example 1 and Comparative Examples 1 to 5 was heated and aged at 150 ° C for 168 hours, and mechanical properties were measured in the same manner as in the mechanical and 1) room temperature mechanical property measurement. Here, the tensile strength and the tensile elongation percentage should be 75% or more, respectively.

3) Flexural strength evaluation

Flexural strength of each sample sheet prepared in Example 1 and Comparative Examples 1 to 5 was measured according to IEC 60811-1-1 standard. The lower the value, the more flexible the insulation layer and the cable, And the like.

4) Evaluation of dielectric breakdown strength

The dielectric breakdown strength was measured for each of the sample sheets prepared in Example 1 and Comparative Examples 1 to 5 according to the ASTM D149 standard, and the higher the value, the better the electrical characteristics are considered.

Flexibility, mechanical and electrical properties of each of the sample sheets prepared in Example 1 and Comparative Examples 1 to 5 were evaluated according to the physical property evaluation method of the sheet described above, and the results are shown in Table 2 below.

Constituent
Example Comparative Example One One 2 3 4 5 Tensile strength at room temperature (kgf / ㎟) 2.0 2.4

Not measurable


2.1 2.05

Not measurable


Tensile elongation at room temperature (%) 698 660 605 680 Residual tensile strength after heating (%) 81 88 100 90 Renal survival rate after heating (%) 79 58 70 60 Flexural Strength (MPa) 30 37 33 42 Dielectric breakdown strength (kV / mm) 65 57 55 55

As shown in Table 2, the insulating composition of Comparative Example 1 had a low molecular weight (140) of the insulating oil (C ₁₀ H ₂₀ ) contained therein, and after heating, the insulating oil was vaporized and decomposed, (58%) after the heating of the sample sheet is insufficient. In addition, since the insulating oil is decomposed during the sample sheet production process, the flexural strength (37 MPa) of the sheet is high, It was confirmed that the electrical properties were insufficient due to the low strength (57 kV / mm).

The insulating composition of Comparative Example 2 had a large molecular weight (1120) of the insulating oil (C ₈₀ H ₁₆₀ ) contained therein and the insulating oil (C ₃₀ H ₆₀ ) contained in the insulating composition of Comparative Example 5 was excessive Weight portion). Therefore, in the extrusion process for producing the sample sheet, the dielectric oil was eluted and slipping phenomenon occurred in the extruder. As a result, the sample sheet could not be produced and the physical properties could not be measured.

In the insulating composition of Comparative Example 3, since the insulating oil (C ₃₀ H ₆₀ ) contained therein had a polycyclic structure and the mixing property with the base resin was insufficient, the inherent function of the insulating oil could not be exhibited. %) Was less than 75%, and the electrical characteristics were also insufficient due to the low dielectric breakdown strength (55 kV / mm).

Further, the insulation composition of Comparative Example 4 had the lowest flexural strength (55 kV / mm) and the lowest flexural strength (42 MPa) since the content of the insulating oil (C30H60) contained therein was extremely small (1 part by weight) The lowest electrical characteristic was found to be the worst.

On the other hand, the insulating composition of Example 1 exhibited the lowest flexural strength (30 MPa), that is, the highest flexibility, the highest dielectric breakdown strength (65 kV / mm ), That is, the best electrical properties.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. . It is therefore to be understood that the modified embodiments are included in the technical scope of the present invention if they basically include elements of the claims of the present invention.

1: conductor 2: inner semiconductive layer
3: insulating layer 4: outer semiconductive layer
5: Sheath layer

Claims (10)

A power cable comprising at least one conductor, an insulating layer surrounding each conductor, and an outermost sheath layer,
Wherein the insulating layer comprises a base resin comprising a non-crosslinked propylene homopolymer, a non-crosslinked propylene copolymer, or a mixture of both of the base resin and the non-crosslinked propylene copolymer, and a resin having a cyclic hydrocarbon and an acyclic hydrocarbon cross- 2.5 to 10 parts by weight of an insulating oil comprising monocyclic naphthenic hydrocarbons of C _n H _2n wherein n is an integer from 20 to 60. delete The method according to claim 1,
And the ring of the cyclic hydrocarbon is pentagonal or hexagonal. The method according to claim 1,
Characterized in that the base resin comprises a non-crosslinked propylene homopolymer and a non-crosslinked propylene copolymer, and the mixing ratio of the non-crosslinked propylene homopolymer to the non-crosslinked propylene copolymer is 80:20 to 50:50. . 5. The method of claim 4,
Wherein the non-crosslinked propylene copolymer is a copolymer of a propylene monomer and an ethylene monomer. 6. The method of claim 5,
Wherein the content of the ethylene monomer is 15 mol% or less based on the moles of the total monomers constituting the non-crosslinked propylene copolymer. The method according to claim 1,
Wherein the insulating composition further comprises 0.2 to 5 parts by weight of an amine-based, dialkyl ester-based, thioester-based or phenol-based antioxidant based on 100 parts by weight of the base resin. The method according to claim 1,
Wherein the sheath layer is made from a composition comprising the same base resin as the base resin of the insulating composition. The method according to claim 1,
An inner semiconductive layer disposed between the conductor and the insulating layer, and an outer semiconductive layer surrounding the insulating layer. 10. The method of claim 9,
Wherein the inner semiconductive layer, the outer semiconductive layer, or both are fabricated from a semiconductive composition comprising the same base resin as the base resin of the insulating composition.

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