KR102278262B1 - Power cable - Google Patents

Abstract

The present invention relates to a power cable. Specifically, the present invention effectively suppresses peeling of the overlapping portions of both ends of the metal laminate even when moisture permeates and external physical shocks or temperature changes, and has a watertight layer that is lightweight and has excellent corrosion resistance, and has excellent interlayer adhesion. It relates to a structurally stable power cable.

Description

power cable

The present invention relates to a power cable. Specifically, the present invention effectively suppresses peeling of the overlapping portions of both ends of the metal laminate even when moisture permeates and external physical shocks or temperature changes, and has a watertight layer that is lightweight and has excellent corrosion resistance, and has excellent interlayer adhesion. It relates to a structurally stable power cable.

Power cables, such as submarine cables and underground cables, generally include a watertight layer that suppresses penetration of moisture from the outside.

1 schematically shows a cross-sectional structure of a power cable disclosed in US Patent Publication No. 4,501,928. As shown in Figure 1, a conventional power cable has a conductor (1), an inner semiconducting layer (2), an insulating layer (3), an outer semiconducting layer (4), a metal shielding layer (5), and a semiconducting tape (6) , the watertight layer 7 , and the outer jacket 8 may have a structure including these components in the order.

Here, when a metal laminate coated with polyethylene, polyvinyl chloride, etc. on both sides of the metal foil is used as the watertight layer 7 , as shown in FIG. 1 , the amount of the metal laminate to realize better watertight properties The ends overlap each other, and a hot melt adhesive may be applied between the overlapping metal laminates.

However, the conventional hot melt adhesive has insufficient adhesive strength, and in particular, when moisture that has passed through the outer jacket 8 penetrates or an external physical impact or temperature change is applied to the cable, there is a problem in that the adhesive strength is significantly reduced.

Furthermore, when the metal foil is a lead foil, the weight of the lead foil is heavy and the lightness of the cable may be reduced, and when the metal foil is a lightweight aluminum foil, the aluminum foil is vulnerable to corrosion. have.

In addition, the water-tight layer 7 applied to the conventional power cable has insufficient adhesion with the outer jacket 8, so that the water-tight layer 7 and the outer jacket 8 are separated from each other due to external physical impact and temperature change. There is a problem of peeling.

On the other hand, the power cables disclosed in Japanese Patent Application Laid-Open Nos. 1994-309948, 2001-023453 and 2014-032912, and US Patent Publication No. 2012-0080213, etc. to improve the adhesion between the watertight layer and the outer jacket. An adhesive layer is additionally included between them, or the watertight layer consists of a metal layer and an adhesive auxiliary layer applied to the surface of the metal layer, but the adhesive layer or the adhesive auxiliary layer has a sharp decrease in adhesive strength due to moisture that has passed through the outer jacket. There is a problem in that interlayer peeling occurs or, in particular, adhesion and peeling strength are significantly reduced due to external physical impact.

Therefore, even when moisture penetrates, peeling of the overlapping portions at both ends is effectively suppressed even when external physical shocks or temperature changes, and it is lightweight and has a watertight layer with excellent corrosion resistance, and structurally stable power cables with excellent interlayer adhesion are desperately needed. It is being demanded.

An object of the present invention is to provide a power cable having a watertight layer in which peeling of overlapping portions at both ends is effectively suppressed even when moisture penetrates and even when external physical shock or temperature change.

Another object of the present invention is to provide a power cable having a watertight layer that is lightweight and has excellent corrosion resistance.

Furthermore, an object of the present invention is to provide a structurally stable power cable having excellent interlayer adhesion.

In order to solve the above problems, the present invention,

A center conductor, an inner semiconducting layer surrounding the center conductor, an insulating layer surrounding the inner semiconducting layer, an outer semiconducting layer surrounding the insulating layer, a metal shielding layer surrounding the outer semiconducting layer, a watertight layer surrounding the metal shielding layer, the an outer jacket surrounding the watertight layer, wherein the watertight layer is formed by a metal laminate including a metal foil and an adhesive auxiliary layer laminated on the metal foil, both ends of the metal laminate overlap and the metal in the overlapping region The lower surface of one end of the laminate and the upper surface of the other end of the laminate are respectively adhered to the hot melt adhesive layer formed by the hot melt adhesive,

It provides a power cable having a peel force residual ratio of 50% or more defined by Equation 1 below.

[Equation 1]

Residual peel force = final peel force/initial peel force × 100

In Equation 1 above,

The initial peel force is the peel force of the hot melt adhesive layer to the metal laminate measured at room temperature,

The final peel strength is the peel strength of the hot melt adhesive layer to the metal laminate after being immersed in a basic aqueous solution of pH 8.5 at 80° C. for 300 hours.

Here, the hot melt adhesive provides a power cable, characterized in that it includes a hot melt adhesive or a pressure sensitive adhesive having a creep resistance temperature and a softening temperature of 80° C. or higher.

In addition, the hot melt adhesive provides a power cable, characterized in that it contains polyamide, polyethylene vinyl acetate, rubber-based resin, or a combination thereof.

And, the metal foil is a copper foil, the thickness of the copper foil is 0.05 to 0.38 mm, and the thickness of the auxiliary adhesive layer is 0.05 to 0.1 mm, it provides a power cable.

On the other hand, the adhesive auxiliary layer is an adhesive having an adhesive strength such that the residual ratio of the peel force of the outer jacket with respect to the metal foil measured after immersing the power cable in a basic aqueous solution of pH 8.5 at a temperature of 80 ° C. is 70% or more. It provides a power cable, characterized in that it comprises.

Here, the adhesive forming the auxiliary adhesive layer provides a power cable, characterized in that it comprises a copolymer or blend resin of an olefin and a polar monomer.

In addition, the polar monomer is a vinyl ester monomer of vinyl acetate or vinyl versatate, a vinyl-unsaturated carboxylic acid monomer of methacrylic acid, acrylic acid, maleic acid or itaconic acid, an acrylic monomer of (meth)acrylate or alkyl (meth)acrylate It provides a power cable, characterized in that.

And, the content of the polar monomer, based on the total weight of the random copolymer resin, it provides a power cable, characterized in that 5 to 25% by weight.

Further, the random copolymer resin of the olefin and the polar monomer is ethylene acrylic acid (EAA), ethylene vinyl acetate (EVA) or ethylene butyl acrylate (EBA), characterized in that, provides a power cable.

On the other hand, the outer jacket includes a high-density polyethylene (HDPE) resin, it provides a power cable, characterized in that the thickness of 0.1 to 8 mm.

In addition, the metal shielding layer includes a first semiconducting tape layer cross-wound on the outer semi-conducting layer, a metal layer disposed on the first semi-conducting tape layer and including a plurality of copper neutral wires, and a second semi-conducting layer cross-wound on the metal layer. It provides a power cable, characterized in that it comprises a tape layer.

Further, the insulating layer provides a power cable, characterized in that made of cross-linked polyethylene (XLPE).

On the other hand, the inner semiconducting layer, the insulating layer and the outer semiconducting layer provides a power cable, characterized in that made of a base resin of a similar series.

In addition, it provides a power cable, characterized in that it further comprises an adhesive layer surrounding the buffer layer and the buffer layer surrounding the watertight layer.

And, the buffer layer has a melting point of 80° C. or more, a density of 0.85 to 0.94, and a hardness (shore A) of 65 or more. It provides a power cable, characterized in that it comprises a resin.

Here, the buffer layer provides a power cable, characterized in that it comprises at least one ethylene copolymer selected from the group consisting of ethylene butyl acrylate (EBA), ethylene vinyl acetate (EVA) and ethylene acrylic acid (EAA).

In addition, the thickness of the buffer layer is characterized in that 1 to 3 mm, it provides a power cable.

On the other hand, the adhesive layer includes a resin having a density of 0.90 or more and a crystallinity of more than 50%, and does not include an additive for forming a moisture migration path, and provides a power cable.

Here, the adhesive layer provides a power cable, characterized in that it comprises a resin having a crystallinity of 60% or more.

In addition, the adhesive layer provides a power cable, characterized in that it comprises a high-density polyethylene (HDPE) resin.

Furthermore, the thickness of the adhesive layer provides a power cable, characterized in that 1 to 6 mm.

In the power cable according to the present invention, a hot-melt adhesive having specific properties is applied to the overlapping portions of both ends of the metal laminate constituting the watertight layer, so that moisture permeates or the adhesive force between the metal laminates in the overlapping portion despite external physical impact or temperature change It shows an excellent effect to maintain

In addition, the power cable according to the present invention exhibits excellent effects in light weight and corrosion resistance by the lightweight metal foil constituting the watertight layer and the resin coated on the surface of the metal foil.

Furthermore, the power cable according to the present invention exhibits an excellent structurally stable effect due to excellent interlayer adhesion even in an external physical impact or temperature change by a buffer layer and an adhesive layer made of a specific material applied between the watertight layer and the outer jacket.

1 schematically shows a cross-sectional structure according to an embodiment of a conventional power cable.
2 is a cross-sectional view schematically showing a cross-sectional structure according to an embodiment of a power cable according to the present invention.
3 is a longitudinal cross-sectional view schematically showing a cross-sectional structure according to an embodiment of a power cable according to the present invention.
4 schematically shows the cross-sectional structure of the watertight layer 70 in the power cable according to 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 and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art. Like reference numerals refer to like elements throughout.

2 and 3 schematically show a cross-sectional structure of an embodiment of a power cable according to the present invention. 2 and 3, the power cable according to the present invention has a center conductor 10, an inner semiconducting layer 20 surrounding the center conductor 10, and an insulating layer surrounding the inner semiconducting layer 20 ( 30), an outer semiconducting layer 40 surrounding the insulating layer 30, a first semiconducting tape layer 51, a metal layer 60 and a second semiconducting tape layer 52 surrounding the outer semiconducting layer 40 ) may include a metal shielding layer composed of, a watertight layer 70 surrounding the metal shielding layer, and an outermost outer jacket 100 .

In addition, the power cable according to the present invention protects the watertight layer 70 from an external impact to the adhesive layer 90 and the cable for improving the adhesion between the watertight layer 70 and the outer jacket 100 . And even when the external impact is applied, it may further include a buffer layer 80 and the like to maintain the adhesive force between the watertight layer 70 and the adhesive layer 90 .

4 schematically shows the cross-sectional structure of the watertight layer 70 in the power cable according to the present invention. The watertight layer 70 serves to inhibit the penetration of moisture penetrating through the outer jacket 100 into the insulating layer 30 . As shown in FIG. 4 , the watertight layer 70 is formed by a metal laminate including a metal foil 72 , for example, a copper foil and an adhesive auxiliary layer 71 laminated on the metal foil 72 . can be

In the watertight layer 70 , the copper foil as the metal foil 72 has superior corrosion resistance compared to the conventional aluminum foil layer, and has the advantage of being lightweight compared to the conventional lead foil layer. An auxiliary adhesive layer 71 is formed on the metal foil 72 . Since adhesion between the metal foil 72 and the buffer layer 80 or the adhesive layer 90 is not easy, an adhesive auxiliary layer 71 made of a resin that can easily adhere to them is placed on the metal foil 72 . Lamination.

The thickness of the metal foil 72 may be, for example, about 0.05 to 0.38 mm, and the thickness of the adhesion auxiliary layer 71 may be, for example, about 0.05 to 0.1 mm. The adhesive auxiliary layer 71 should be formed as thin as possible in order to avoid a negative influence on the electrical characteristics of the cable.

Here, the lamination method of the adhesion auxiliary layer 71 is not particularly limited, and for example, a method such as deposition, electro deposition, or extrusion may be used. The adhesive auxiliary layer 71 is the watertight layer 70 and the outer jacket 100 or the watertight layer 70 and the buffer layer 80 even under severe conditions in which an impact is applied from the outside of the cable or the temperature changes rapidly. ) or a function of maintaining a close adhesion of the adhesive layer 90 and a function of suppressing corrosion of the metal foil 72 .

The adhesion auxiliary layer 71 is the outer jacket 100 or the metal foil 72 for the metal foil 72 measured after immersing the power cable in a basic aqueous solution of pH 8.5 at a temperature of 80° C. for 7 days. It may be made of an adhesive having an adhesive force such that the residual peel force of the adhesive layer 90 is 70% or more. The peel force residual ratio is the outer jacket for the metal foil 72 after immersion of the power cable with respect to the initial value of the peel force of the outer jacket 100 with respect to the metal foil 72 before the immersion of the power cable ( 100) means the ratio of the peel force values.

When the residual peel force is less than 70%, the close adhesion between the watertight layer 70 and the outer jacket 100 cannot be maintained under severe conditions in which an impact is applied from the outside of the cable or the temperature is rapidly changed.

For example, the auxiliary adhesion layer 71 may be formed of an adhesive including an acrylic resin, an olefin-based resin, preferably, a random copolymer resin of an olefin and a polar monomer as a base resin. The auxiliary adhesive layer 71 may be formed by a general coating process such as spraying, impregnation, or extrusion.

The polar monomer may include vinyl ester monomers such as vinyl acetate and vinyl versatate; vinyl-unsaturated carboxylic acid monomers such as methacrylic acid, acrylic acid, maleic acid, and itaconic acid; (meth) acrylate, may include an acrylic monomer such as alkyl (meth) acrylate or a combination thereof, and the content of the polar monomer is 5 to 25 wt %, preferably 5 to 25 wt % based on the total weight of the resin to 20% by weight.

Preferably, the base resin of the adhesive forming the adhesion auxiliary layer 71 may be ethylene acrylic acid (EAA), ethylene vinyl acetate (EVA), ethylene butyl acrylate (EBA), or the like.

As shown in FIG. 3 , both ends of the metal laminate may be overlapped in order to realize better watertight properties, and in the overlapping region, the lower surface of one end of the metal laminate and the upper surface of the other end are hot melted. It can be tightly adhered by an adhesive.

The hot melt adhesive does not use any water or solvent and uses 100% thermoplastic resin to be applied to an adherend in a liquid state at a high temperature and cooled within a few seconds after being compressed and cooled within seconds. It may be a hot melt adhesive or a pressure sensitive adhesive. .

The hot melt adhesive does not require a drying process compared to other solvent-type adhesives or water-dispersion adhesives, and has a small working space and a fast bonding speed. In addition, the material of the hot melt adhesive may be, for example, polyurethane, polyamide, polyester, polyethylene vinyl acetate, rubber, and the like, and in general, may further include a wax, an adhesive, a plasticizer, a filler, an antioxidant, and the like.

The hot melt is preferably made of a resin such as polyamide, polyethylene vinyl acetate, or rubber having a creep resistance temperature and a softening temperature of 80° C. or higher for use in a power cable.

After forming a hot melt adhesive layer by applying the hot melt adhesive to the surface of the metal laminate constituting the watertight layer 70, the initial peel force of the hot melt adhesive layer to the metal laminate is measured, and the hot melt adhesive is applied to the metal When the final peel force of the hot melt adhesive layer to the metal laminate was measured after the laminate was immersed in a basic aqueous solution of pH 8.5 at 80° C. for 300 hours, the final peel force/initial peel force × 100 It may be more than 50%.

The central conductor 10 may be made of a single wire made of copper, aluminum, preferably copper, or a stranded wire in which a plurality of conductive wires are combined, and the diameter of the central conductor 10, the diameter of the strands constituting the stranded wire, etc. The included standard may be different depending on the transmission voltage, use, etc. of the power cable including the same, and may be appropriately selected by a person skilled in the art. For example, when the power cable according to the present invention is used for a purpose requiring layingability, flexibility, etc., such as a submarine cable, the center conductor 10 is preferably made of a stranded wire having excellent flexibility rather than a single wire.

The inner semiconducting layer 20 is disposed between the central conductor 10 and the insulating layer 30 to eliminate an air layer causing interlayer lifting of the central conductor 10 and the insulating layer 30, and It performs functions such as alleviating phosphorus electric field concentration. Meanwhile, the outer semiconducting layer 40 functions to apply an equal electric field to the insulating layer 30 , relaxes local electric field concentration, and protects the cable insulating layer from the outside.

In general, in the inner semiconducting layer 20 and the outer semiconducting layer 40, conductive particles such as carbon black, carbon nanotubes, carbon nanoplates, and graphite are dispersed in a base resin, and a crosslinking agent, antioxidant, scorch inhibitor, etc. Formed by extrusion of the additionally added semiconducting composition, the base resin is an insulating composition forming the insulating layer 30 for interlayer adhesion between the semiconducting layers 20 and 40 and the insulating layer 30 It is preferable to use an olefin resin similar to the base resin, for example, a copolymer resin of an olefin and an acrylic monomer, in particular, ethylene butyl acrylate (EBA), ethylene ethyl acrylate (EEA), or the like.

The thickness of the inner and outer semiconducting layers 20 and 40 may be different depending on the transmission voltage of the cable. For example, in the case of a 345 kV power cable, the thickness of the inner semiconducting layer 20 is 1.0 to 2.5 mm. The thickness of the outer semiconducting layer 40 may be 1.0 to 2.5 mm.

The insulating layer 30 may be, for example, a polyolefin resin such as polyethylene or polypropylene as a base resin, and may preferably be formed by extrusion of an insulating composition including a polyethylene resin.

The polyethylene resin may be ultra low density polyethylene (ULDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), or a combination thereof. In addition, the polyethylene resin may be a homopolymer, a random or block copolymer of ethylene and an α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene, or a combination thereof.

In addition, since the insulating composition forming the insulating layer 30 contains a crosslinking agent, the insulating layer 30 is formed by crosslinking polyolefin (XLPO), preferably crosslinked polyethylene (XLPE) during extrusion or after extrusion by a separate crosslinking process. ) can be made. In addition, the insulating composition may further include other additives such as antioxidants, extrudability improvers, and crosslinking aids.

The crosslinking agent is a silane-based crosslinking agent, or dicumyl peroxide, benzoyl peroxide, lauryl peroxide, t-butyl cumyl peroxide, di(t-butyl peroxyisopropyl) benzene, 2,5 depending on the crosslinking method of the polyolefin. - It may be an organic peroxide-based crosslinking agent such as dimethyl-2,5-di(t-butyl peroxy)hexane or di-t-butyl peroxide. Here, the crosslinking agent may be included in an amount of 1 to 5 parts by weight based on 100 parts by weight of the base resin.

The thickness of the insulating layer 30 may be different depending on the transmission voltage of the power cable. For example, in the case of a 345 kV power cable, the thickness of the insulating layer 30 may be 23.0 to 31.0 mm.

The metal shielding layer is a semiconducting tape layer 50 formed by transversely winding a semiconducting tape on each of the upper and lower portions of the metal layer 60 formed by a plurality of neutral wires made of metal, preferably copper, that is, a first semiconducting tape layer ( 51) and the second semi-conductive tape layer 52 may be formed, and serve as a function of protecting the cable under severe environmental conditions such as the seabed and a path through which the fault current can escape to the outside through the ground when leakage current occurs. carry out

The first semiconducting tape layer 51 performs buffering to suppress deformation of the insulating layer 30 due to the load of the metal layer 60 , and the second semiconducting tape layer 52 is the metal layer The binding of (60) is performed. In addition, the first and second semiconducting tape layers 51 and 52 may be wet and swollen tapes, and in this case, a water blocking function may be performed in parallel. The thickness of the semiconducting tape forming the first and second semiconducting tape layers 51 and 52 may be, for example, about 200 to 1,000 μm.

The thickness of the metal layer 60 forming the metal shielding layer may be, for example, about 1.0 to 3.0 mm, the thickness of the first semi-conductive tape layer 51 is 0.2 to 1.0 mm, and the second semi-conductive tape layer 51 has a thickness of 0.2 to 1.0 mm. The thickness of the tape layer 52 may be 0.85 to 0.95 mm.

The buffer layer 80 is disposed between the water-tight layer 70 and the adhesive layer 90 to absorb an external impact on the cable to prevent damage to the water-tight layer 70 , in particular the metal foil 72 , and interlayer It performs the function of suppressing peeling.

In particular, when the external impact on the cable exceeds a degree that can be absorbed by the buffer layer 80 , a part of the impact is transmitted to the water-tight layer 70 , in particular the metal foil 72 , so that the metal A recessed part is partially formed in the foil 72, and the recessed part may be a passage for moisture penetrating from the outside to move in the longitudinal direction of the cable. The buffer layer 80 is a softer resin than the adhesive layer 90. By including, it is possible to additionally perform a function of suppressing the movement of moisture in the longitudinal direction of the cable by filling the depression.

On the other hand, in the conventional power cable not having the buffer layer 80, when an impact is applied from the outside during its installation, the impact is transmitted to the watertight layer and delamination may occur, especially when a depression is formed in the watertight layer. The depression may be a passage through which moisture permeated from the outside moves in the longitudinal direction.

The buffer layer 80 preferably includes a resin having a melting point of 80° C. or higher, a density of 0.85 to 0.94, and a hardness (shore A) of 65 or higher to withstand heat generated during operation of the cable. When the density of the resin constituting the buffer layer 80 is less than 0.85 and the hardness (shore A) is less than 65, the external shock to the cable cannot be sufficiently absorbed, whereas when the density is greater than 0.94, the metal foil by external shock The depressions that may be formed in (72) cannot be sufficiently filled.

Since the buffer layer 80 is disposed between the water-tight layer 70 , in particular, the adhesion auxiliary layer 71 and the adhesive layer 90 , in order to suppress delamination, the resin included in the buffer layer 80 is the adhesive. Adhesion between the resin included in the auxiliary layer 71 and the resin included in the adhesive layer 90 is advantageous and compatible.

The resin included in the buffer layer 80 is, for example, an ethylene copolymer, preferably at least one selected from the group consisting of ethylene butyl acrylate (EBA), ethylene vinyl acetate (EVA), ethylene acrylic acid (EAA), and the like. It may include a copolymer, and may include a copolymer of ethylene and an α-olefin such as 1-butene, 1-hexene, and 1-octene, or a rubber type.

The thickness of the buffer layer 80 may be 1 to 3 mm. The buffer layer 80 absorbs an external shock to the cable when the thickness of the adhesive layer 90 is less than 1 mm on the premise that the thickness of the adhesive layer 90 is as described below and fills the depression of the watertight layer formed by the external shock. On the other hand, if the thickness is more than 3 mm, the outer diameter of the cable may increase unnecessarily.

The adhesive layer 90 performs a function of adhering the watertight layer 70 and the buffer layer 80 to the outer jacket 100 and blocks the moisture passing through the outer jacket 100 so that the moisture It functions to suppress a decrease in the peeling force of the adhesive layer 90 with respect to the watertight layer 70 and the buffer layer 80 .

Here, the adhesive layer 90 has a density of 0.90 or more, for example, 0.90 to 0.97, and a crystallinity of more than 50%, for example, more than 50% and less than 90%, preferably made of a resin of 60% or more, and , whereby the melting point may be 100°C or higher, for example, 100 to 140°C.

The adhesive layer 90 has the high density and the high crystallinity, and unlike the outer jacket 100 , water-tightness is improved by not adding an additive such as carbon black that forms a water movement path, so that the water-tight layer by moisture penetration. (87) and it is possible to suppress a decrease in the peeling force of the adhesive layer (90) with respect to the buffer layer (80).

In addition, the thickness of the adhesive layer 90 may be 1 to 6 mm. Here, when the thickness of the adhesive layer 90 is less than 1 mm, the peeling force of the adhesive layer 90 with respect to the water-tight layer 70 and the buffer layer 80 is decreased due to moisture penetration because it does not have sufficient water-repellent properties. On the other hand, when the thickness of the adhesive layer 90 is more than 6 mm, the overall diameter of the power cable is unnecessarily increased, and the plurality of neutral wires forming the metal layer 60 by cooling gradually during cooling after extrusion. A protruding shape may appear on the surface of the outer jacket 100 .

The adhesive layer 90 includes the watertight layer 80 , the buffer layer 80 and the outer jacket 100 for close adhesion with the watertight layer 70 , the buffer layer 80 and the outer jacket 100 . It may be made of a resin of a series similar to the resin forming the resin, for example, an ethylene homopolymer or copolymer, preferably a high-density polyethylene (HDPE) resin.

The outer jacket 100 may include polyethylene, polyvinyl chloride, polyurethane, etc., and a resin of a series similar to that of the resin constituting the adhesive layer 90 in order to maintain a close adhesive force with the adhesive layer 90, For example, it is preferably made of a polyethylene resin, and since it is a layer disposed at the outermost part of the cable, considering the mechanical strength, it is more preferably made of a high-density polyethylene (HDPE) resin. In addition, the outer jacket 100 may include a small amount of an additive such as carbon black, for example, 2 to 3% by weight in order to realize the color of the power cable.

The outer jacket 100 preferably has a thickness of, for example, 0.1 to 8 mm in order to maintain close adhesion with the adhesive layer 90 by first absorbing the shock when an impact is applied to the cable from the outside. Do.

As described above, the power cable according to the present invention is lighter than the conventional power cable by forming the metal foil 72 of the watertight layer 70 with copper foil that is lightweight compared to conventional lead and has excellent corrosion resistance compared to conventional aluminum. and excellent corrosion resistance.

In addition, between the watertight layer 70 and the adhesive layer 90, a buffer layer 80 made of a material constituting these layers and a material that is easy to adhere and has compatibility is disposed, and the watertight layer 70 is adhered By precisely controlling the materials of the auxiliary layer 71 and the adhesive layer 90 , the interlayer adhesion is maximized and delamination caused by moisture penetration is suppressed, and at the same time, an external impact on the cable is transmitted to the watertight layer 70 . to prevent damage to the watertight layer 70 , in particular the metal foil 72 , and furthermore, when a part of the impact on the cable is transmitted to the metal foil 72 to form a partial depression, the buffer layer 80 ) fills the recessed part to suppress the movement of moisture along the recessed part in the longitudinal direction of the cable.

[Example]

1. Preparation of sample sheet overlapping part of watertight layer and evaluation of adhesive properties

A hot melt adhesive sheet was prepared by pressing at 160° C. at 5 MPa, and after preheating the hot melt adhesive sheet and copper foil at 120° C. for 10 minutes, the copper foil was adhered to the top and bottom of the hot melt adhesive sheet at 160° C. Sample sheets of Examples 1 and 2 were prepared by pressing at 5 MPa.

1) Adhesive property evaluation

The initial peel strength of the hot melt adhesive sheet to the copper foil was measured in each of the sample sheets of Examples 1 and 2 at room temperature. In addition, after each sample sheet of Examples 1 and 2 was immersed in an aqueous NaOH solution of pH 8.5 at 80° C. for 300 hours, the final peeling force of the hot melt adhesive sheet to the copper foil was measured. The residual peel force was calculated using the measured values of the initial peel force and the final peel force. The measurement and calculation results are shown in Table 1 below.

Example 1 Example 2 hot melt Hot Melt Adhesive 1 Hot Melt Adhesive 2 peel force Initial peel force (N/mm) 2.09 1.31 Final Peel Force (N/mm) 1.47 0.76 Residual peel force (%) 70 58

- Hot melt adhesive 1: Amide-based adhesive (Creep resistance temperature: 115℃, softening temperature: 130℃)

- Hot melt adhesive 2: Polyethylene vinyl acetate (Creep resistance temperature: 90℃, softening temperature: 110℃)

As shown in Table 1 above, the power cable according to the present invention having a watertight layer in which a hot melt adhesive having a creep resistance temperature and a softening temperature of 80° C. or higher, respectively, is applied to the overlapping portions of both ends has excellent adhesion even during moisture penetration. was confirmed to be

2. Preparation of watertight layer and adhesive layer sample sheet and evaluation of watertightness and adhesive properties

Adhesive layer (high-density polyethylene with a density of 0.956), copper foil, adhesive auxiliary layer (ethylene vinyl acetate), and adhesive layer by hot pressing under the conditions of a press temperature of 160°C (10 minutes), a cooling temperature of 40°C (10 minutes), and a pressure of 5 MPa. (High-density polyethylene with a density of 0.956) was sequentially laminated to prepare a sample sheet of Example 3 formed. In addition, sample sheets of Examples and Comparative Examples in which litmus paper was inserted between two adhesive layer specimens shown in Table 2 below were prepared.

Suzy Thickness (mm) Example 4 resin 1 1.0 Example 5 resin 1 2.0 Comparative Example 1 resin 1 0.25 Comparative Example 2 resin 1 0.5 Comparative Example 3 resin 2 0.25 Comparative Example 4 resin 2 0.5 Comparative Example 5 resin 2 1.0 Comparative Example 6 resin 2 2.0

- Resin 1: high density polyethylene (density 0.956)

- Resin 2: Ethylene/acrylic acid random copolymer resin (density 0.895)

1) Adhesive property evaluation

The peel force of the outer jacket to the copper foil was measured before and after the sample sheet of Example 3 was immersed in a basic aqueous solution having a pH of 8.5 and a temperature of 80°C. The peel force measurement results are shown in Table 3 below.

before submersion 7 days after submersion 21 days after submersion 42 days after submersion 84 days after submersion Peel force (N/mm) 0.86 0.80 0.77 0.82 0.99 Residual peel force (%) 100 93 89 95 115

As shown in Table 3, the power cable of Example 3 according to the present invention has excellent water-repellent properties and adhesion of the adhesive layer, so that even after submersion, the interlayer adhesion between the water-tight layer and the outer jacket was maintained at 70% or more compared to before submersion. Confirmed.

2) Watertight characteristic evaluation

After immersing the specimens of Examples 4 and 5 and Comparative Examples 1 to 6 in a basic aqueous solution having a pH of 8.5 and a temperature of 80° C., the time until the basic solution passed through the adhesive layer specimen to discolor the litmus paper was measured. The evaluation results are shown in Table 4 below.

time to water penetration Example 4 more than 125 days Example 5 more than 125 days Comparative Example 1 7 days Comparative Example 2 48 days Comparative Example 3 0 days Comparative Example 4 3 days Comparative Example 5 12 days Comparative Example 6 19th

As shown in Table 4, the adhesive layers of Examples 4 and 5 according to the present invention were made of a resin having a density of 0.90 or more and had a thickness greater than or equal to a specific value, so that the water-repellent properties were sufficient.

On the other hand, it was confirmed that the adhesive layers of Comparative Examples 1 to 4 had insufficient water resistance because the thickness was less than the critical value, and the adhesive layers of Comparative Examples 5 and 6 had insufficient water resistance because the density of the resin constituting them was less than the critical value.

Although the present specification has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims described below. will be able to carry out Therefore, if the modified implementation basically includes the elements of the claims of the present invention, it should be regarded as being included in the technical scope of the present invention.

10: conductor 20: inner semiconducting layer
30: insulating layer 40: outer semiconducting layer
50: semiconducting tape layer 60: metal layer
70: watertight layer 80: buffer layer
90: adhesive layer 100: outer jacket

Claims (21)

A center conductor, an inner semiconducting layer surrounding the center conductor, an insulating layer surrounding the inner semiconducting layer, an outer semiconducting layer surrounding the insulating layer, a metal shielding layer surrounding the outer semiconducting layer, a watertight layer surrounding the metal shielding layer, the an outer jacket covering the watertight layer;
The watertight layer is formed by a metal laminate comprising a metal foil and an adhesive auxiliary layer laminated on the metal foil,
Both ends of the metal laminate are overlapped, and in the overlapping region, the lower surface of one end of the metal laminate and the upper surface of the other end are adhered to a hot melt adhesive layer formed by a hot melt adhesive, respectively;
The hot melt adhesive includes a heat melt adhesive or a pressure sensitive adhesive having a creep resistance temperature and a softening temperature of 80° C. or higher,
A power cable having a peel force residual ratio of 50% or more defined by Equation 1 below.
[Equation 1]
Residual peel force = final peel force/initial peel force × 100
In Equation 1 above,
The initial peel force is the peel force of the hot melt adhesive layer to the metal laminate measured at room temperature,
The final peel strength is the peel strength of the hot melt adhesive layer to the metal laminate after being immersed in a basic aqueous solution of pH 8.5 at 80° C. for 300 hours. delete According to claim 1,
The hot melt adhesive is a power cable, characterized in that it comprises polyamide, polyethylene vinyl acetate, a rubber-based resin, or a combination thereof. 4. The method of claim 1 or 3,
The power cable, characterized in that the metal foil is a copper foil, the thickness of the copper foil is 0.05 to 0.38 mm, and the thickness of the adhesive auxiliary layer is 0.05 to 0.1 mm. 4. The method of claim 1 or 3,
The adhesive auxiliary layer includes an adhesive having an adhesive strength such that the residual ratio of the peel force of the outer jacket to the metal foil measured after immersing the power cable in a pH 8.5 basic aqueous solution at a temperature of 80 ° C. is 70% or more Characterized by the power cable. 6. The method of claim 5,
The adhesive forming the auxiliary adhesive layer is characterized in that it comprises a copolymer or blend resin of an olefin and a polar monomer, power cable. 7. The method of claim 6,
The polar monomer is a vinyl ester monomer of vinyl acetate or vinyl versatate, a vinyl-unsaturated carboxylic acid monomer of methacrylic acid, acrylic acid, maleic acid or itaconic acid, (meth) acrylate or an acrylic monomer of alkyl (meth) acrylate. Characterized by the power cable. 8. The method of claim 7,
The content of the polar monomer, based on the total weight of the random copolymer resin, characterized in that 5 to 25% by weight, the power cable. 7. The method of claim 6,
The power cable, characterized in that the random copolymer resin of the olefin and the polar monomer is ethylene acrylic acid (EAA), ethylene vinyl acetate (EVA) or ethylene butyl acrylate (EBA). 4. The method of claim 1 or 3,
The power cable, characterized in that the outer jacket comprises a high density polyethylene (HDPE) resin and has a thickness of 0.1 to 8 mm. 4. The method of claim 1 or 3,
The metal shielding layer includes a first semiconducting tape layer cross wound on the outer semiconducting layer, a metal layer disposed over the first semiconducting tape layer and comprising a plurality of copper neutral wires, and a second semiconducting tape layer cross wound over the metal layer. A power cable comprising a. 4. The method of claim 1 or 3,
The power cable, characterized in that the insulating layer is made of crosslinked polyethylene (XLPE). 4. The method of claim 1 or 3,
The inner semiconducting layer, the insulating layer and the outer semiconducting layer are made of a base resin of a similar series, the power cable. 4. The method of claim 1 or 3,
Power cable, characterized in that it further comprises a buffer layer surrounding the watertight layer and an adhesive layer surrounding the buffer layer. 15. The method of claim 14,
The buffer layer has a melting point of 80° C. or more, a density of 0.85 to 0.94, and a hardness (shore A) of 65 or more, a power cable comprising a resin. 16. The method of claim 15,
The power cable, characterized in that the buffer layer comprises at least one ethylene copolymer selected from the group consisting of ethylene butyl acrylate (EBA), ethylene vinyl acetate (EVA) and ethylene acrylic acid (EAA). 15. The method of claim 14,
The thickness of the buffer layer, characterized in that 1 to 3 mm, power cable. 15. The method of claim 14,
wherein the adhesive layer comprises a resin having a density of at least 0.90 and a crystallinity of greater than 50%, and no additives for forming a moisture migration path. 19. The method of claim 18,
The adhesive layer is characterized in that it comprises a resin having a crystallinity of 60% or more, the power cable. 20. The method of claim 19,
The power cable, characterized in that the adhesive layer comprises a high-density polyethylene (HDPE) resin. 15. The method of claim 14,
The power cable, characterized in that the thickness of the adhesive layer is 1 to 6 mm.

Images