KR20180001993A - Power cable - Google Patents

Abstract

The present invention relates to a power cable. More specifically, the present invention relates to a power cable having an insulating layer made of insulation materials which are eco-friendly and superior in thermal resistance and mechanical strength wherein the insulation materials simultaneously have excellent flexibility, bendability, impact resistance, cold tolerance, burying features, workability and the like which are in a trade-off relation with matter properties of the eco-friendly feature and superior thermal resistance and mechanical strength.

Description

Power cable {Power cable}

The present invention relates to power cables. Specifically, the present invention relates to a resin composition which is environmentally friendly, has excellent heat resistance and mechanical strength, and is made of an insulating material excellent in flexibility, bending property, impact resistance, cold resistance, To a power cable having an insulating layer.

A general power cable may further include a conductor and an insulating layer surrounding the conductor, and may further include 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, and the like .

In recent years, the development of high-capacity cables has been required in accordance with the increasing demand for electric power, and it has become necessary to provide an insulating material for manufacturing an insulating layer having excellent mechanical and electrical characteristics.

Conventionally, a polyolefin-based polymer such as polyethylene, an ethylene / propylene elastic copolymer (EPR), or an ethylene / propylene / diene copolymer (EPDM) has been used as a base resin constituting the insulating material. Such conventional crosslinked resins maintain excellent flexibility and satisfactory electrical and mechanical strength even at high temperatures.

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, when the life of a cable or the like including an insulating layer made of a resin such as the crosslinked polyethylene is shortened, It is impossible to recycle the resin to be disposed of by incineration and is not environmentally friendly.

In addition, when polyvinyl chloride (PVC) is used as the material of the sheath layer, it is difficult to separate it from the crosslinked polyethylene (XLPE) constituting the insulating material, and thus, toxic chlorinated materials are generated during incineration, There are disadvantages.

On the other hand, non-crosslinked high-density polyethylene (HDPE) or low-density polyethylene (LDPE) is eco-friendly because it can recycle the resin constituting the insulating layer at the end of its lifetime, Type polyethylene (XLPE), which is inferior in heat resistance, and its application is very limited due to its low operating temperature.

Therefore, as disclosed in Korean Patent Laid-open Nos. 10-2014-0102408, 10-2014-0126993 and 10-2014-0128584, the heat resistance of the polymer itself is excellent without cross-linking at a melting point of 160 ° C or higher, It may be considered to use a friendly polypropylene resin as a base resin. However, due to insufficient flexibility and flexibility due to the high rigidity of the polypropylene resin, the workability of the cable including the insulation layer produced therefrom is low and the use thereof is limited there is a problem.

1 and 2 schematically show a cross-sectional view and a longitudinal sectional view of a power cable to which an insulation layer including a conventional polypropylene resin is applied.

1 and 2, conventional power cables disclosed in Korean Patent Laid-Open Nos. 10-2014-0102408, 10-2014-0126993, and 10-2014-0128584 include a conductor 1, a conductor An insulating layer 3 surrounding the inner semiconductive layer 2 and containing a non-crosslinked polypropylene resin as a base resin; an outer semiconductive layer 4 surrounding the insulating layer 3; A sheath layer 5 surrounding the outer semiconductive layer 4, and the like.

Here, for the purpose of compacting the outer diameter of the cable, the conductor 1 has a keystone shape in cross section around a single wire having a circular cross section as shown in Figs. 1 and 2 May be a keystone conductor that forms a plurality of conductor layers while arranging a plurality of element wires in the circumferential direction of the cable and realizes a circular cross section as a whole of the conductor or may be a circular compression conductor in which all conductors of all layers are circularly compressed.

In addition, the twisted direction of the conductor layers, that is, the twist direction is alternately applied in the S direction and the Z direction while the layers are different. Here, the circular compression refers to compressing a conductor by passing a twisted wire conductor through a small circular die or the like outside the twisted conductor at the time of twisting the conductor, arranging a concave semicircular roller or the like above and below the twisted wire conductor and applying pressure from the outside. Circular compacted conductors are called circular compacted conductors.

However, the keystone conductors or the circularly-compressed conductors of the conventional cable disclosed in Figs. 1 and 2 are arranged in such a manner that the gaps between the respective strands are minimized and are in an excessively close contact with each other. Thus, the flexibility of the cable is lowered, There is a problem in that the flexibility of the cable as well as the insulation layer of the polypropylene resin is deteriorated so that the flexibility of the cable as a whole is extremely lowered and the workability such as packaging, transportation, installation or installation of the cable is remarkably deteriorated.

In the conventional cable disclosed in Figs. 1 and 2, when a conductor is used without a keystone conductor or a circular compression conductor and an uncompressed normal circular conductor, the twist direction of each conductor layer is changed in the S direction and Z The contact area between the conductor layers is insufficient to increase the resistance of the entire conductor, which inevitably increases the outer diameter of the conductor as a whole.

Accordingly, it is an object of the present invention to provide a resin composition which is environmentally friendly, low in manufacturing cost, and capable of simultaneously satisfying heat resistance and mechanical strength and flexibility, bending property, impact resistance, cold resistance, Cables are in desperate need.

It is an object of the present invention to provide an environmentally friendly power cable.

It is another object of the present invention to provide a power cable capable of simultaneously satisfying heat resistance and mechanical strength and flexibility, bending property, impact resistance, cold resistance, installation property, workability, etc. in trade- do.

In order to solve the above problems,

A power cable comprising a stranded conductor including a plurality of strands, an inner semiconductive layer surrounding the stranded conductors, and an insulating layer surrounding the inner semiconductive layer, wherein the stranded conductors have a plurality of strands in a circumferential direction Wherein the plurality of conductor layers include an outermost conductor layer disposed at the outermost layer and at least one conductor inner layer disposed inside the outermost conductor layer, wherein the conductor inner layer is not compressively deformed And the outermost layer is entirely circularly compressed.

Here, the cable conductor has a dropping rate of 75 to 86%.

Further, the power cable has a dot ratio of the outermost layer of the conductor of 90% or more.

The plurality of elemental wires included in the conductor inner layer are circular in cross section and the plurality of elemental wires included in the outermost conductor layer are circular or deformed angular in cross section.

Further, the modified circular shape includes a bent trapezoid, an elliptical shape, or a semicircular shape.

Further, a plurality of element wires included in each of the plurality of conductor layers are twisted together or twisted in the same direction.

If the stranded conductor is an aluminum 1000 series conductor with a nominal cross-sectional area of 185 SQ, the power cable shall have a maximum load of 1,500 N when bending according to 2.4.24 of the standard HD 605 S2 Of the total length of the power cable.

On the other hand, the insulating layer is made of polypropylene as a base resin.

Here, the insulating layer is composed of a mixture of a polypropylene resin (A) and a heterophasic resin (B) in which a propylene copolymer is dispersed in a polypropylene matrix at a weight ratio (A: B) of 3: 7 to 6: 4 And a thermoplastic resin.

Further, the polypropylene resin (A) satisfies all of the conditions a) to i) below.

a) a density of 0.87 to 0.92 g / cm 3 (measured according to ISO 11883),

b) a melt flow rate (MFR) of 1.7 to 1.9 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)

c) a tensile modulus of 930 to 980 MPa (measured at a tensile rate of 1 mm / min)

d) a tensile stress at break of 22 to 27 MPa (measured at a tensile rate of 50 mm / min)

e) tensile strain at yield of 13 to 15% (measured at a tensile rate of 50 mm / min)

f) a charpy impact strength at 0 占 폚 and 23 占 폚 of 1.8 to 2.1 kJ / m2 and 5.5 to 6.5 kJ / m2, respectively,

g) heat distortion temperature of 68 to 72 DEG C (measured at 0.45 MPa),

h) Vicat softening point of 131-136 占 폚 (measured at 50 占 폚 / h and 10N according to specification A50), and

i) Shore D hardness of 63 to 70 (measured according to ISO 868)

And, the above-mentioned heterophasic resin (B) satisfies all of the following conditions a) to j).

a) a density of 0.86 to 0.90 g / cm < 3 > (measured in accordance with ISO 11883)

b) a melt flow rate (MFR) of 0.1 to 1.0 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)

c) tensile stress at break of 10 MPa or more (measured at a tensile rate of 50 mm / min)

d) a tensile strain at break of 13 to 15% (measured at a tensile rate of 50 mm / min)

e) a flexural strength of 95 to 105 MPa

f) a notched izod impact strength at -40 DEG C of 68 to 72 kJ / m2,

g) heat distortion temperature of 38 to 42 DEG C (measured at 0.45 MPa),

h) Vicat softening point of 55 to 59 캜 (measured at 50 캜 / h and 10 N according to Specification A50)

i) a Shore D hardness of 25 to 31 (measured according to ISO 868), and

j) a melting point of 155 to 170 DEG C

The polypropylene resin (A) is a random propylene-ethylene copolymer having an ethylenic monomer content of 1 to 5% by weight based on the total weight of the monomers, and the poly Wherein the propylene matrix is a propylene homopolymer.

Further, the propylene copolymer contained in the heterophasic resin (B) is preferably a propylene-ethylene rubber (PER) having an ethylene monomer content of 20 to 50% by weight and a particle size of 1 m or less based on the total weight of the monomers ) Particles. ≪ / RTI >

Here, the content of the propylene copolymer is 60 to 80% by weight based on the total weight of the heterophasic resin (B).

On the other hand, the above-mentioned heterophasic resin (B) has a melting enthalpy of 25 to 40 J / g as measured by differential scanning calorimetry (DSC).

The insulating layer may further include 0.1 to 0.5 parts by weight of a nucleating agent based on 100 parts by weight of the non-crosslinked thermoplastic resin, wherein the polypropylene resin (A) has a crystal size of 1 to 10 mu m And a power cable.

The insulating layer further comprises 1 to 10 parts by weight of insulating oil based on 100 parts by weight of the non-crosslinked thermoplastic resin.

Further, the insulating layer may further comprise at least one additive selected from the group consisting of antioxidants, impact aids, thermal stabilizers, nucleating agents and acid scavengers in an amount of 0.001 to 10 wt% based on the total weight of the insulating layer. By weight, based on the total weight of the composition.

On the other hand, the non-crosslinked thermoplastic resin preferably has a melting point (Tm) measured by a differential scanning calorimeter (DSC) of 150 to 160 ° C and a melting enthalpy measured by a differential scanning calorimeter (DSC) of 30 to 80 J / g And a power cable.

The power cable includes a stranded conductor including a plurality of strands, an inner semiconductive layer surrounding the stranded conductor, and an insulating layer surrounding the inner semiconductive layer, wherein the stranded conductor has a plurality of strands in the circumferential direction of the center strand Wherein the plurality of conductor layers comprise a conductor outermost layer disposed at the outermost layer and at least one conductor inner layer disposed in the outermost conductor layer, And at least one conductor layer of the conductor inner layer is not circularly compressed.

Further, the insulating layer is made of polypropylene as a base resin.

INDUSTRIAL APPLICABILITY The power cable according to the present invention adopts a non-crosslinked propylene polymer as an insulating layer material, thereby being environmentally friendly and exhibiting heat resistance and mechanical strength.

In addition, the power cable according to the present invention can satisfy the flexibility, bending property, impact resistance, cold resistance, installation property, workability and the like even though the insulation layer made of the propylene polymer having high rigidity is applied through the new design of the conductor structure Exhibit excellent effect.

1 schematically shows a cross-sectional structure according to one embodiment of a conventional power cable.
2 schematically shows a longitudinal section of the conventional power cable shown in FIG.
3 schematically shows a cross-sectional structure according to one embodiment of a power cable according to the present invention.
Fig. 4 schematically shows a longitudinal section of the power cable shown in Fig. 3. Fig.
5 schematically shows a cross-sectional structure according to another embodiment of the power cable according to the present invention.
6 schematically illustrates a criterion for estimating the point rate of a conductor in a power cable according to the present invention.
7 schematically shows a criterion for calculating the outermost point of a conductor in a power cable according to the present invention.
Fig. 8 schematically shows a cross-section of an inner semiconductive layer in a stranded conductor in which conductor wires having circular cross-sections are associated.
9 is a graph showing the result of performing a bending test of a cable specimen according to 2.4.24 of the standard HD 605 S2 in the embodiment of the present invention.

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. Like reference numerals designate like elements throughout the specification.

Figures 3 and 4 show cross-sectional and longitudinal cross-sectional structures, respectively, according to one embodiment of a power cable according to the invention.

3 and 4, the power cable according to the present invention includes a conductor 10 made of a conductive material such as copper and aluminum, an insulation layer 30 made of an insulating polymer, An inner semiconductive layer 20 which serves to eliminate the air layer between the conductor 10 and the insulating layer 30 and to relieve the concentration of a local electric field, a shielding function of the cable, An outer semiconductive layer 40 serving to prevent an electric field from being applied, a sheath layer 50 for protecting the cable, and the like.

The dimensions of the conductor 10, the insulating layer 30, the semiconductive layers 20 and 40, and the sheath layer 50 may vary depending on the use of the cable, the transmission voltage, and the like.

The conductor 10 may be formed of a twisted wire conductor in which a plurality of wire strands are associated in order to improve the flexibility, bendability, installation property, workability, etc. of the power cable. And a plurality of conductor layers formed by being arranged in the circumferential direction thereof. Specifically, the plurality of conductor layers may include a conductor outermost layer 12 disposed at the outermost portion and at least one conductor inner layer 11 disposed inside the conductor outermost layer 12. [

At least one layer of the conductor inner layer 11 is not circularly compressed so that the core wires included in the conductor inner layer 11 are circular in cross section while a part of the conductor layer including the conductor outermost layer 12 is circularly compressed, For example, a bent trapezoid, an ellipse, a semicircle, a polygon, or the like. Here, the curved trapezoid means a shape in which a trapezoid is curved like a fan to form a circular shape as a whole, as shown in FIG.

Further, when a conductor layer including the conductor outermost layer 12 is circularly compressed, the strands contained in the circular uncompressed layer inside the circularly compressed layer are also subjected to a compressive force, Since most of the compressive force is applied to the layer and the force is transmitted through the circularly compressed layer to the circular inner uncompressed conductor layer, the force is weakened and the deformation of the element wires contained in the circular uncompressed layer on the inner side It is small, so it is almost circular. Here, the meaning of the prototype is not a mathematical prototype, but means that it can be recognized as a prototype at a glance as a whole, and is used in the same sense in the present invention.

Since voids are formed between the strands so that the cross-section of the strands contained in the layer of unconstrained circularity in the conductor inner layer 11 is circular, the dot ratio of the conductor 10 is 75 to 86%, preferably 80 to 86 %, Whereby it is possible to compensate for the flexibility, bending property, installation property, workability, etc. of the power cable which is lowered by the rigidity of the propylene polymer forming the insulating layer of the power cable. 6, the dot ratio of the conductor 10 is defined as the cross sectional area of the single-wire conductor 10 'having the outer diameter D as the average outer diameter of the stranded conductor 10 formed of the element wire Sectional area of the stranded conductor 10 made of the stranded wire with respect to the area A of the hatched area of the left-side single-stranded conductor 10 'shown in Fig. 6 Area B) (B / A * 100). Here, the average outer diameter of the stranded conductor 10 means the largest outer diameter of the stranded conductor 10 and the arithmetic mean outer diameter of the smallest outer diameter.

As described above, in the case of reducing the point rate of the stranded conductor 10, the total outer diameter of the cable increases, so that the flexibility of the cable may be reduced to some extent. However, The present invention has been accomplished by first discovering that the flexibility enhanced by the voids between the strands constituting the uncompressed layer is greater. This is a whole new approach to changing the material of the layers making up the cable to a more flexible material or reducing the thickness of the layers or the layers stacked thereon, in order to improve flexibility in conventional power cables.

Specifically, the power cable according to the present invention has a structure in which the insulation layer is formed of a composition comprising a polypropylene resin as a base resin by the design of the conductor as described above, and is made of aluminum having a nominal cross-sectional area of 185 SQ 1000 series conductors can measure flexibility (maximum load required when flexing) according to 2.4.24 of the standard HD 605 S2, which is about 1,500 N or less. .

As shown in FIG. 3, the outermost layer 12 of the conductor is compressed to be circular, so that the end of the outermost strands of the outermost layer is deformed to reduce the gap between the strands. As a result, Even when the inner semiconductive layer 20 disposed on the outer surface is formed to have a small thickness, it can be formed into a circular shape having no bending as a whole, so that it is possible to prevent unevenness of the electric field due to bending and also to prevent local field concentration. Here, the dot rate of the conductor outermost layer 12 may be 90% or more, and preferably 93% or more. 7, the dot ratio of the conductor outermost layer 12 refers to an outer diameter D equal to the average outer diameter of the conductor outermost layer 12 and an inner diameter d equal to the average inner diameter of the conductor outermost layer 12 (The area B 'of the hatched area in the right twisted wire conductor 10 shown in FIG. 7) of the cross-sectional area of the outermost layer 12 conductor strands to the cross-sectional area A' of the donut- (B '/ A' * 100). Here, the average outer diameter of the conductor outermost layer 12 means the largest outer diameter of the conductor outermost layer 12 and the arithmetic mean outer diameter of the smallest outer diameter, and the average inner diameter of the conductor outermost layer 12 is Means the arithmetic mean inner diameter of the largest inner diameter and the smallest inner diameter of the outer layer 12.

 As shown in FIG. 8, when the core wires included in the conductor outermost layer 120 are not circularly compressed and the cross-section is circular like the core wires included in the conductor inner layer 110, the gap between the core wires is large When the inner semiconductive layer 200 is extrusion-molded on the outer surface of the conductor outermost layer 120, the inner semiconductive layer 200 can not be formed in a circular shape as a whole by filling the gap between the strands, The thickness of the inner semiconductive layer 200 must be thick in order to form a circular shape as a whole. In this case, the outer diameter of the power cable is unnecessarily large There is an increasing problem. Here, when the dot percent of the conductor outermost layer 12 is less than 90%, the conductor outermost layer 12 is not properly circularly compressed, so that there is a problem that the function of relaxing the electric field concentration can not be sufficiently performed do.

Also, as described above, when the voids between the strands of the stranded conductor become large and the dotted rate of the whole stranded conductor becomes small, the contact area between the stranded conductors becomes small, and the resistance of the cable conductor as a whole increases.

To improve this, the plurality of conductor layers included in the stranded conductor 10 may be formed by twisting the conductor layers in the twisted direction (twist direction) in any one of the directions, that is, the S direction or the Z direction have. Even if only the outermost conductors are circularly compressed and the core wires of the inner layer are not circularly compressed but retain their original shape, the twist direction of each conductor layer is alternately applied in the S direction and the Z direction alternately The contact area between the interlayer conductor wires is reduced and the conductor resistance is relatively increased. In the present invention, since the twisted directions of the respective conductor layers are all the same, the wires of each inter-layer conductor can be twisted in a continuous contact state, so that the contact area of the conductor wires between the conductor layers increases, It is possible to compensate for the increase in resistance by the proportion. If the percentage of the conductor 10 is 86% or more, the flexibility of the cable can not be ensured. If the percentage of the conductor 10 is 75% or less, the resistance of the conductor becomes large, A satisfactory conductor resistance can not be ensured even if it is twisted in the same direction. Therefore, in order to lower the resistance to a proper level, the size of the conductor must be increased. When the size of the conductor is increased, flexibility becomes poor, do.

The insulating layer 30 of the power cable according to the present invention may comprise a non-crosslinked thermoplastic resin blended with a polypropylene resin and (B) a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix have.

The polypropylene resin (A) may comprise a propylene homopolymer and / or a propylene copolymer, preferably a propylene copolymer. The propylene homopolymer refers to a polypropylene formed by polymerization of propylene at 99 wt% or more, preferably 99.5 wt% or more, based on the total weight of the monomers.

The propylene copolymer is obtained by copolymerizing propylene with ethylene or an? -Olefin having 4 to 12 carbon atoms, such as 1-butene, 1-pentene, 4-methyl-1-pentene, Dodecene, and combinations thereof, and the like, preferably a copolymer with ethylene. This is because copolymerization of propylene and ethylene shows a hard and flexible property.

The propylene copolymer may include a random propylene copolymer and / or a block propylene copolymer, preferably a random propylene copolymer, and more preferably a random propylene copolymer. The random propylene copolymer means a propylene copolymer in which propylene monomer and other olefin monomers are alternately arranged. The random propylene copolymer is preferably a random propylene copolymer comprising 1 to 10% by weight, preferably 1 to 5% by weight, more preferably 3 to 4% by weight, based on the total monomer weight of ethylene monomer.

The random propylene copolymer preferably has a density of from 0.87 to 0.92 g / cm 3 (measured according to ISO 11883), a melt flow rate (MFR) of from 1.7 to 1.9 g / 10 min (Measured at a tensile rate of 1 mm / min), a tensile stress of 22 to 27 MPa (measured at a tensile rate of 50 mm / min), a tensile strain of 13 to 15% (Measured at a tensile rate of 50 mm / min), a Charpy impact strength at 0 占 폚 and 23 占 폚 of 1.8 to 2.1 kJ / m2 and 5.5 to 6.5 kJ / m2, a heat distortion temperature of 68 to 72 占 폚 , A Vicat softening point of 131 to 136 占 폚 (measured at 50 占 폚 / h and 10 N according to Specification A50) and a Shore D hardness of 63 to 70 (measured according to ISO 868).

The random propylene copolymer can improve mechanical strength such as tensile strength of the insulating layer 30 to be formed and is suitable for a transparent molded article because of its high transparency and has a relatively high crystallization temperature Tc, It is possible to shorten the time required for cooling after the layer 30 is extruded to improve the production yield of the cable and to minimize the shrinkage and thermal deformability of the insulating layer 30 and to reduce the cable manufacturing cost There is an advantage that can be saved.

The polypropylene resin (A) may have a weight average molecular weight (Mw) of 200,000 to 450,000. Further, the polypropylene resin (A) has a melting point (Tm) of 140 to 175 캜 (measured by a differential scanning calorimeter (DSC)), a melting enthalpy of 50 to 100 J / g May be 30 to 1,000 MPa, preferably 60 to 1,000 MPa (measured in accordance with ASTM D790).

The polypropylene resin (A) can be polymerized under conventional stereospecific Ziegler-Natta catalysts, metallocene catalysts, restrained geometric catalysts, other organometallic or coordination catalysts, preferably Ziegler-Natta catalysts or metallocenes Can be polymerized under a catalyst. Here, the metallocene is a generic name of a bis (cyclopentadienyl) metal, which is a novel organometallic compound in which cyclopentadiene and a transition metal are bonded in a sandwich structure. The general formula of the simplest structure is M (C ₅ H ₅ ) ₂ , M is Ti, V, Cr, Fe, Co, Ni, Ru, Zr, Hf, etc.). Since the amount of catalyst remaining in the polypropylene polymerized under the metallocene catalyst is as low as about 200 to 700 ppm, it is possible to suppress or minimize the deterioration of the electrical characteristics of the insulating composition including the polypropylene due to the residual amount of the catalyst.

Although the polypropylene resin (A) has a high melting point due to its own melting point, the polypropylene resin (A) can exhibit sufficient heat resistance to provide a power cable having an improved continuous use temperature and is environmentally friendly And exhibits excellent effects. On the other hand, the conventional crosslinked resin is not environmentally friendly because it is difficult to recycle, and when crosslinking or scorch occurs early in forming the insulating layer 30, the resin can not exhibit uniform production capability, . ≪ / RTI >

In the heterophasic resin (B) in which the propylene copolymer is dispersed in the polypropylene matrix, the polypropylene matrix may be the same as or different from the polypropylene resin (A), preferably a propylene homopolymer And more preferably a propylene homopolymer alone.

In the above-mentioned heterophasic resin (B), the propylene copolymer dispersed in the polypropylene matrix (hereinafter referred to as 'dispersed propylene copolymer') is substantially amorphous. Here, the amorphous propylene copolymer means that the propylene copolymer has a residual crystallinity with a melting enthalpy of less than 10 J / g. The dispersed propylene copolymer is selected from the group consisting of ethylene and C _{4 -8} alpha-olefins such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, And may include one or more comonomers.

The dispersed propylene copolymer may be 60 to 90 wt%, preferably 65 to 80 wt%, based on the total weight of the heterophasic resin (B). If the content of the dispersed propylene copolymer is less than 60% by weight, the flexibility, bending property, impact resistance and cold resistance of the formed insulating layer 30 may be insufficient, while if it exceeds 90% by weight, 30 may have insufficient heat resistance, mechanical strength, and the like.

The dispersed propylene copolymer may be a propylene-ethylene rubber (PER) or propylene-ethylene diene rubber (EPDM) containing 20 to 50 wt%, preferably 30 to 40 wt% of ethylene monomer based on the total weight of monomers . When the content of the ethylene monomer is less than 20% by weight, the insulation layer 30 formed may be excellent in flexibility, bending property and impact resistance but may be insufficient in cold resistance, etc. If the ethylene monomer content is more than 50% by weight, , Heat resistance and mechanical strength are excellent, but flexibility and the like may be lowered.

In the present invention, the particle size of the dispersed propylene copolymer may be 1 占 퐉 or less, preferably 0.9 占 퐉 or less, and more preferably 0.8 占 퐉 or less. Such a particle size of the dispersed propylene copolymer can ensure uniform dispersion of the dispersed propylene copolymer in the polypropylene matrix and improve the impact strength of the insulating layer containing the dispersed propylene copolymer. In addition, the particle size improves the likelihood of stopping already formed cracks or cracks while reducing the risk of fracture initiated by the particles.

The heterophasic resin (B) preferably has a melt flow rate (MFR) of 0.2 to 1.0 g / 10 min, preferably 0.8 g / 10 min, measured according to ISO 1133 at 230 DEG C and a load of 2.16 kg / 10 min, a tensile stress at break of 10 MPa or more, a tensile strain at break of 490% or more, a bending strength of 95 to 105 MPa, a notched Izod impact strength of 68 to 72 kJ / (Measured at 50 占 폚 / h and 10 N according to A50), a Shore D hardness of 25 to 31 (measured according to ISO 868), a heat distortion temperature of 38 to 42 캜 (measured at 0.45 MPa), a Vicat softening point of 55 to 59 캜 (Measured by differential scanning calorimetry (DSC)) and a melting enthalpy of 25 to 40 J / g (as measured by DSC).

The density of the heterophasic resin (B) may be 0.86 to 0.90 g / cm3, preferably 0.88 g / cm3, as measured according to ISO 11883, In turn, impact strength and shrinkage properties are affected.

Since the above-mentioned heterophasic resin (B) contains non-crosslinked polypropylene, it is possible to improve the heat resistance of the insulating layer 30 formed of a polypropylene matrix that is environmentally friendly and highly heat-resistant, The flexibility, the bending property, the impact resistance, the cold resistance, the installation property, the workability, etc. of the insulating layer 30 lowered by the rigidity of the resin (A) can be improved.

The weight ratio (A: B) of the polypropylene resin (A) and the heterophasic resin (B) may be 3: 7 to 6: 4, preferably 5: 5. If the weight ratio is less than 3: 7, mechanical strength such as tensile strength of the insulating layer 30 may be insufficient. If the weight ratio is more than 6: 4, flexibility, bending property, impact resistance, It may be insufficient.

The non-crosslinked thermoplastic resin contained in the insulating layer 30 of the power cable according to the present invention is excellent in heat resistance, flexibility, bending property, impact resistance, cold resistance, , The combination of the above-mentioned heterophasic resin (B) exhibiting workability and the like, and the above-mentioned characteristics that are in conflict with each other due to their compatibility, that is, heat resistance and mechanical strength and flexibility, flexibility, impact resistance, cold resistance, And exhibits excellent effects that can be achieved at the same time.

Here, the non-crosslinked thermoplastic resin may have a melting point (Tm) of 150 to 160 ° C (as measured by a differential scanning calorimeter (DSC)) and a melting enthalpy of 30 to 80 J / g (as measured by a differential scanning calorimeter have.

If the melting enthalpy of the non-crosslinked thermoplastic resin is less than 30 J / g, it means that the crystal size is small and the crystallinity is low, and the heat resistance and mechanical strength of the cable are lowered. When the melting enthalpy exceeds 80 J / g, And the crystallinity is high, and the electrical characteristics of the insulating layer 30 may be deteriorated.

In the present invention, the insulating layer 30 may further include a nucleating agent in addition to the non-crosslinked thermoplastic resin. The nucleating agent may be a sorbitol-based nucleating agent. That is, the nucleating agent is a sorbitol-based nucleating agent such as 1,3: 2,4-bis (3,4-dimethyl dibenzylidene) sorbitol (1,3: ), Bis (p-methyldibenzulidene) sorbitol, Substituted Dibenzylidene Sorbitol, and mixtures thereof.

The non-crosslinked thermoplastic resin can be cured by heating the non-crosslinked thermoplastic resin. The non-crosslinked thermoplastic resin can be cured by heating the non-crosslinked thermoplastic resin. To 10 mu m, it is possible to improve the electrical characteristics of the insulating layer to be produced, and furthermore, to increase the degree of crystallization by forming a plurality of crystallization sites in which the crystals are formed, thereby improving the heat resistance and mechanical strength of the insulating layer Effect.

Since the nucleating agent has a high melting temperature, injection and extrusion processing should be performed at a high temperature of about 230 ° C, and it is preferable to use two or more sorbitol nucleating agents in combination. When two or more different sorbitol nucleating agents are used in combination, the expression of the nucleating agent can be enhanced even at a low temperature.

The nucleating agent may be contained in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the non-crosslinked thermoplastic resin. If the content of the nucleating agent is less than 0.1 part by weight, heat resistance, electrical and mechanical strength of the non-crosslinked thermoplastic resin and the insulating layer containing the same due to a large crystal size, for example, a crystal size exceeding 10 μm and an uneven crystal distribution While an increase in the surface interface area between the crystal and the amorphous portion of the resin due to too small a crystal size, for example, a crystal size of less than 1 mu m, when the content of the nucleating agent exceeds 0.5 parts by weight The AC dielectric breakdown (ACBD) characteristics and the impulse characteristics of the non-crosslinked thermoplastic resin and the insulating layer including the non-crosslinked thermoplastic resin may be degraded.

In the present invention, the insulating layer 30 may further include insulating oil.

The insulating oil may be mineral oil, synthetic oil, or the like. Particularly, the insulating oil is selected from the group consisting of an aromatic oil composed of an aromatic hydrocarbon compound such as dibenzyltoluene, alkylbenzene and alkyldiphenylethane, a paraffinic oil composed of a paraffinic hydrocarbon compound, a naphthenic oil composed of a naphthenic hydrocarbon compound, Can be used.

On the other hand, the content of the insulating oil may be 1 to 10 parts by weight, preferably 1 to 7.5 parts by weight, based on 100 parts by weight of the non-crosslinked thermoplastic resin, and when the content of the insulating oil is more than 10 parts by weight, The insulation oil may be eluted during the extrusion process of forming the insulation layer 30 on the insulation layer 30, thus making it difficult to process the cable.

As described above, the insulation oil is improved in flexibility and bending property of the insulation layer 30 made of a base resin of a polypropylene resin having a high rigidity and a somewhat low flexibility, And at the same time exhibits an excellent effect of maintaining or improving the excellent heat resistance, mechanical and electrical properties inherent in the polypropylene resin. In particular, the insulating oil exhibits excellent effects of supplementing the somewhat deteriorated processability due to a rather narrow molecular weight distribution when the polypropylene resin is polymerized under a metallocene catalyst.

In the present invention, the insulating layer 30 may further include other additives such as an antioxidant, a shock absorber, a heat stabilizer, a nucleating agent, and acid scavengers. The other additives may be added in an amount of 0.001 to 10% by weight based on the total weight of the insulating layer 30, depending on the type thereof.

On the other hand, the inner semiconductive layer 20 may include a blend resin of a heterophasic resin (B) in which a propylene copolymer is dispersed in the polypropylene matrix and another heterophasic resin (B ') as a base resin. The heterophasic resin (B ') may also include a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix, or the polypropylene matrix contains a propylene laden copolymer, and the heterophasic resin (B' (B ') has a melting point of 140 to 150 DEG C and a load of 2.16 kg and a melting point of 230 DEG C to ISO 1133 The measured melt flow rate (MFR) may be from 6 to 8 g / 10 min.

Also, the content of the heterophasic resin (B) may be 50 to 80 parts by weight, the content of the heterophasic resin (B ') may be 20 to 50 parts by weight based on 100 parts by weight of the base resin, 35 to 70 parts by weight, an antioxidant 0.2 to 3 parts by weight, and the like.

When the content of the heterophasic resin (B ') is less than 50 parts by weight and the content of the heterophasic resin (B') is more than 50 parts by weight, heat resistance and elongation of the inner semiconductive layer (20) When the content of the heterophasic resin (B ') exceeds 80 parts by weight and the content of the heterophasic resin (B') is less than 20 parts by weight, the viscosity of the composition forming the inner semiconductive layer (20) The screw load is increased during extrusion, and the workability may be greatly reduced.

When the content of the carbon black is less than 35 parts by weight, the semiconductive property of the inner semiconductive layer 20 may not be realized, while when the content of the carbon black is more than 70 parts by weight, the composition of the inner semiconductive layer 20 As the viscosity increases, the screw load increases when extruded, and the workability may be greatly reduced.

If the content of the antioxidant is less than 0.2 parts by weight, it may be difficult to secure long-term heat resistance in a high temperature environment. On the other hand, if the content of the antioxidant exceeds 3 parts by weight, the antioxidant may be whitened to the surface of the inner semiconductive layer A blooming phenomenon may occur, which may degrade the anti-conduction characteristic.

The outer semiconductive layer 40 may contain a blending resin of the above-mentioned heterophasic resin (B) and an ethylene copolymer resin as a base resin. The ethylene copolymer resin may include, for example, ethylene butyl acrylate (EBA), ethylene Vinyl acetate (EVA), ethylene ethyl acrylate (EEA), ethylene methyl acrylate (EMA), or the like, or combinations thereof.

Here, the content of the heterophasic resin (B) may be 10 to 40 parts by weight, the content of the ethylene copolymer resin may be 60 to 90 parts by weight based on 100 parts by weight of the base resin, 35 to 70 parts by weight of carbon black, 0.2 to 3 parts by weight of an antioxidant, and the like.

Here, when the content of the heterophasic resin (B) is less than 10 parts by weight and the content of the ethylene copolymer resin is more than 90 parts by weight, it may be difficult to secure the heat resistance in a high temperature environment, (B) is more than 40 parts by weight and the content of the ethylene copolymer resin is less than 60 parts by weight, the adhesion of the outer semiconductive layer (40) to the insulating layer The peeling easiness of the outer semiconductive layer 40 with respect to the layer 30 can be greatly reduced.

When the content of the carbon black is less than 35 parts by weight, the semiconductive property of the external semiconductive layer 20 may not be realized, while when it exceeds 70 parts by weight, the composition of the external semiconductive layer 20 As the viscosity increases, the screw load increases when extruded, and the workability may be greatly reduced.

If the content of the antioxidant is less than 0.2 parts by weight, it may be difficult to ensure the long-term heat resistance of the power cable in a high-temperature environment. On the other hand, if the content of the antioxidant exceeds 3 parts by weight, A blooming phenomenon may occur, which may degrade the anti-conduction characteristic.

[Example]

The power cable specimens as shown in Table 1 below were fabricated and each specimen was evaluated for flexibility by measuring the magnitude of the maximum force required when bending the cable specimen in accordance with 2.4.24 of Specification HD 605 S2, The conductor resistance was measured by a method of applying a uniform current to the conductor wire. 9 shows the results of the load required according to the deflection length indicating the length of the specimen to be bent down by the bending of the cable specimen due to the bending load of the cable specimen for the flexibility evaluation.

Example Comparative Example
Conductor structure
aluminum Aluminum 1000 series Aluminum 1000 series Circular compression Outermost layer only circular compression Full circular compression Outermost floor point rate 94% 94% Overall point rate 80% 94% Outer diameter of conductor (mm) 15.81 15.89 Small diameter (mm)
1st floor / 2nd floor / outermost layer 2.46 / 2.35 / 2.42 2.68 / 2.52 / 2.32 Weight (g / m) 475.6 491.6 Pitch direction
1st floor / 2nd floor / outermost layer S / S / S S / Z / S Pitch (mm)
1st floor / 2nd floor / outermost layer 194.8 / 194.4 / 195.4 156 / 206.5 / 207.2 Insulating layer material Polypropylene Polypropylene Flexibility (maximum force magnitude) Approximately 1,200 N Approximately 2,100 N Conductor resistance (Ω / km) 0.16164 0.16075

* Since the conductor resistance is 0.164 or less, both the example and the comparative example are identical with the nominal cross-sectional area of 185 SQ (nominal cross-sectional area is according to IEC 60228 standard).

As shown in Table 1 and FIG. 9, the power cable of Example 1 according to the present invention, which is specifically designed for each layer of the stranded conductor including a plurality of conductor layers, is made of a polypropylene resin having a stiff, It was confirmed that the flexibility of the power cable of the comparative example was greatly reduced by merely circularly compressing the conductor as a whole, while the flexibility was excellent and the pitch direction of the conductor layer was uniformly applied to minimize the increase of resistance.

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.

10: stranded conductor 20: inner semiconductive layer
30: insulating layer 40: outer semiconductive layer
50: Sheath layer

Claims (21)

A stranded conductor including a plurality of elementary wires,
An inner semiconductive layer surrounding the stranded conductor,
And an insulation layer surrounding the inner semiconductive layer,
Wherein the stranded conductor includes a plurality of conductor layers formed by arranging a plurality of strands in a circumferential direction of a center strand,
Wherein the plurality of conductor layers includes a conductor outermost layer disposed at an outermost periphery and at least one conductor inner layer disposed inside the outermost conductor layer,
Wherein said conductor inner layer is not compressively deformed, but only the outermost conductor layer is circularly compressed as a whole. The method according to claim 1,
Wherein the branch conductor has a spot rate of 75 to 86%. 3. The method of claim 2,
And a dot ratio of the conductor outermost layer is 90% or more. The method of claim 3,
A plurality of element wires included in the conductor inner layer are circular in cross section,
Wherein a plurality of element wires included in the conductor outermost layer are circular or deformed prisms whose cross section is deformed. 5. The method of claim 4,
Characterized in that the deformed circle comprises a bent trapezoid, elliptical or semicircular. 6. The method according to any one of claims 1 to 5,
And a plurality of element wires included in each of the plurality of conductor layers are twisted together or twisted in the same direction. 6. The method according to any one of claims 1 to 5,
If the stranded conductor is an aluminum 1000 series conductor with a nominal cross-sectional area of 185 SQ, the power cable shall have a maximum load of 1,500 N or less when bending in accordance with 2.4.24 of the standard HD 605 S2 Features, power cable. 6. The method according to any one of claims 1 to 5,
Wherein the insulating layer is made of polypropylene as a base resin. 10. The method of claim 9,
Wherein the insulating layer is a non-crosslinked thermoplastic resin obtained by blending (A) a polypropylene resin and (B) a heterophasic resin in which a propylene copolymer is dispersed in a polypropylene matrix at a weight ratio (A: B) of 3: 7 to 6: 4 A power cable, comprising a resin. 10. The method of claim 9,
Characterized in that the polypropylene resin (A) satisfies all of the conditions a) to i) below.
a) a density of 0.87 to 0.92 g / cm 3 (measured according to ISO 11883),
b) a melt flow rate (MFR) of 1.7 to 1.9 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)
c) a tensile modulus of 930 to 980 MPa (measured at a tensile rate of 1 mm / min)
d) a tensile stress at break of 22 to 27 MPa (measured at a tensile rate of 50 mm / min)
e) tensile strain at yield of 13 to 15% (measured at a tensile rate of 50 mm / min)
f) a charpy impact strength at 0 占 폚 and 23 占 폚 of 1.8 to 2.1 kJ / m2 and 5.5 to 6.5 kJ / m2, respectively,
g) heat distortion temperature of 68 to 72 DEG C (measured at 0.45 MPa),
h) Vicat softening point of 131-136 占 폚 (measured at 50 占 폚 / h and 10N according to specification A50), and
i) Shore D hardness of 63 to 70 (measured according to ISO 868) 10. The method of claim 9,
Wherein said heterophasic resin (B) satisfies all of the following conditions a) to j).
a) a density of 0.86 to 0.90 g / cm < 3 > (measured in accordance with ISO 11883)
b) a melt flow rate (MFR) of 0.1 to 1.0 g / 10 min (measured under a load of 2.16 kg at 230 DEG C in accordance with ISO 1133)
c) tensile stress at break of 10 MPa or more (measured at a tensile rate of 50 mm / min)
d) a tensile strain at break of 13 to 15% (measured at a tensile rate of 50 mm / min)
e) a flexural strength of 95 to 105 MPa
f) a notched izod impact strength at -40 DEG C of 68 to 72 kJ / m2,
g) heat distortion temperature of 38 to 42 DEG C (measured at 0.45 MPa),
h) Vicat softening point of 55 to 59 캜 (measured at 50 캜 / h and 10 N according to Specification A50)
i) a Shore D hardness of 25 to 31 (measured according to ISO 868), and
j) a melting point of 155 to 170 DEG C 10. The method of claim 9,
The polypropylene resin (A) is a random propylene-ethylene copolymer having an ethylenic monomer content of 1 to 5% by weight based on the total weight of the monomers, and the polypropylene matrix (B) Is a propylene homopolymer. 10. The method of claim 9,
The propylene copolymer contained in the heterophasic resin (B) is preferably a propylene-ethylene rubber (PER) particle having an ethylene monomer content of 20 to 50% by weight and a particle size of 1 m or less based on the total weight of monomers Wherein the power cable is a cable. 14. The method of claim 13,
Wherein the content of the propylene copolymer is 60 to 80% by weight based on the total weight of the heterophasic resin (B). 10. The method of claim 9,
Characterized in that said heterophasic resin (B) has a melting enthalpy of from 25 to 40 J / g as measured by differential scanning calorimetry (DSC). 10. The method of claim 9,
Wherein the insulating layer further comprises 0.1 to 0.5 parts by weight of a nucleating agent based on 100 parts by weight of the non-crosslinked thermoplastic resin, and the polypropylene resin (A) has a crystal size of 1 to 10 mu m Power cable. 10. The method of claim 9,
Wherein the insulating layer further comprises 1 to 10 parts by weight of insulating oil based on 100 parts by weight of the non-crosslinked thermoplastic resin. 10. The method of claim 9,
Wherein the insulating layer comprises, based on the total weight of the insulating layer, 0.001 to 10 wt% of at least one other additive selected from the group consisting of antioxidants, impact aids, heat stabilizers, nucleating agents, and acid scavengers Lt; RTI ID = 0.0 >%.≪ / RTI > 10. The method of claim 9,
The non-crosslinked thermoplastic resin has a melting point (Tm) measured by a differential scanning calorimeter (DSC) of 150 to 160 ° C and a melting enthalpy measured by a differential scanning calorimeter (DSC) of 30 to 80 J / g Power cable. A stranded conductor including a plurality of elementary wires,
An inner semiconductive layer surrounding the stranded conductor,
And an insulation layer surrounding the inner semiconductive layer,
Wherein the stranded conductor includes a plurality of conductor layers formed by arranging a plurality of strands in a circumferential direction of a center strand,
Wherein the plurality of conductor layers includes a conductor outermost layer disposed at an outermost periphery and at least one conductor inner layer disposed inside the outermost conductor layer,
Wherein the conductor outermost layer is entirely circularly compressed and at least one of the conductor inner layers is not circularly compressed. 21. The method of claim 20,
Wherein the insulating layer is made of polypropylene as a base resin.

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