JPH0221935B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a laminate tape used for high voltage power cables and the like using organic polymer materials used for power transmission and distribution. Cables using organic polymer materials are often used as high voltage power cables. A typical example is a cable that uses cross-linked polyethylene as the insulation material and soft vinyl as the protective sheath. However, when this type of cable is installed underground and used while immersed in water, water seeps into the insulator inside the cable, causing water tree deterioration and dielectric breakdown, which has become a problem in recent years. Recent research has shown that the water tree deterioration phenomenon occurs due to the relationship between moisture accumulated on the inner and outer surfaces of the insulator and the magnitude of the local abrupt electric field in that area. The paths of moisture ingress into the cable insulation include water ingress due to improper waterproofing of the cable end during storage or installation, water ingress due to improper connection of the cable end, water ingress through a damaged part of the protective sheath, and ingress of oil or chemicals into the protective sheath. There are two types of water ingress: water ingress due to so-called accidental factors such as swelling oil that is exposed to aqueous liquid, and water ingress due to factors such as inherent water absorption and water permeability because the protective sheath material is an organic molecular material. The degree of water immersion for soft vinyl and polyethylene is different.
25~90, 16~22g/ ^m2・24hrs, so the water permeability of soft vinyl or polyethylene protective sheathing material depends on the temperature difference, water vapor pressure difference, and concentration outside the sheath, inside the sheath, and even in the length direction of the cable installation route. If there is a difference, water permeates from the higher side to the lower side, and water accumulates on the lower side. Therefore, high-voltage power cables with cross-linked polyethylene insulation exposed to these conditions are associated with water tree deterioration, which poses a problem. As a countermeasure to this problem, lead-sheathed cables are available, but they have the drawbacks of being expensive and inconvenient to handle. When a cable with a protective sheath material is installed underground in a water source, metal tape, such as aluminum or copper tape on one side or both sides, is already effective for blocking water penetration from the outside of the sheath to the insulator. Laminated sheath cables, which are made by attaching a laminated tape made of plastic laminated vertically to the cable core, are well known, and are actually used in communication cables and have been put into practical use and have sufficient water-blocking properties.
These cables use polyethylene for the sheath, and the problem with power cables that generally use PVC as the sheath material is that it is difficult to find a material that will adhere to both the metal tape and the PVC sheath. Also, because of the grounding of metal tape in power cables,
It is necessary to provide a semi-conductive plastic layer on the side of the metal tape that contacts the inner surface of the cable.Tape 1
1. PVC in the overlapped part of the tape when vertically attached.
It was also necessary that the plastic layer bonded to the sheath 10 and the semiconductive plastic layer be sufficiently bonded (for example, see FIG. 1 below). As a result of intensive research, the present inventors have developed the laminated tape by heating an ethylene/vinyl acetate copolymer with an unsaturated alkyd obtained from an unsaturated acid, a saturated acid, a polyhydric alcohol, and an organic peroxide from the tape surface. Three layers: a layer of a modified ethylene vinyl acetate copolymer obtained by kneading, a metal layer, and a layer of a ternary copolymer of ethylene and glycidyl methacrylate or glycidyl acrylate and vinyl acetate made semiconductive by adding carbon. It has been found that a laminated tape characterized by consisting of: can be sufficiently adhered to a PVC sheath, and the overlapped portions of the tapes can also be sufficiently adhered to each other. The present invention will be explained in detail below. FIG. 1 is a cross-sectional view of a power cable using laminated tape, where 10 is a PVC sheath and 11 is a laminated tape. Fig. 2 is a detailed cross-sectional view of the laminated tape of the present invention, and Fig. 1 shows an ethylene/vinyl acetate copolymer heated with an unsaturated acid, an unsaturated alkyd obtained from a saturated acid polyhydric alcohol, and an organic peroxide. Modified ethylene vinyl acetate copolymer obtained by kneading,
2 is a metal layer, and 3 is a copolymer of ethylene and glycidyl methacrylate or glycidyl acrylate and vinyl acetate made semiconductive by adding carbon. The metal of the metal layer 2 above includes lead, aluminum,
Although copper can be used, lead is suitable due to its corrosivity and flexibility. A thickness of 10 to 200 μm is suitable because if the thickness is thin, it will easily break during processing or when bending the cable, and if it is thick, the weight of a single length of tape will increase and the unit price will also increase. If the melting point of the modified ethylene vinyl acetate copolymer No. 1 is too low, it will easily flow due to the heat during sheath extrusion, resulting in uneven adhesion, and if it is too high, it will not be sufficiently melted by the heat during sheath extrusion, resulting in low adhesive strength. A suitable melting point is 80-200°C. A suitable thickness is 10 to 200 μm; if it is thin, the adhesive force with the sheath is insufficient, and if it is 200 μm or more, the adhesive force will be saturated, making it difficult in terms of cost and unnecessary. Acetylene black and Ketchen black EC are suitable as the carbon in 3. A suitable conductivity is 10′ to 10 ⁵ Ω·cm. Also, the thickness of layer 3 is suitable to be 10 to 200 μm; if it is less than 10 μm, the adhesive strength of the overlapped parts of the tapes may not be sufficient or
If the thickness is 200 μm or more, the adhesive force will be saturated, making it difficult in terms of cost and unnecessary. Examples will be described below to help understand the present invention. A 150 mm wide laminate tape with the structure shown in Figure 3 was placed vertically on a cable core made of a 150 mm ² copper conductor (outer diameter 14.7 mm) coated with polyethylene to a thickness of 13 mm and cross-linked, and the overlapping portion of the tape was heated by a hot jet. After crimping with a roller, a PVC sheath was extruded at 200°C to a thickness of 3 mm to create a cable. Note that 1 in Figure 3 is the thickness of modified ethylene vinyl acetate copolymer (Mersene 906B manufactured by Toyo Soda)
2 is a lead thickness of 100 μm, and 3 is a 3-copolymer of ethylene glycidyl methacrylate and vinyl acetate (Bond First 7B manufactured by Sumitomo Chemical Co., Ltd.) with a thickness of 100 μm, to which 30% of Denka Black manufactured by Denki Kagaku is added. As a comparative example, a 150 mm wide laminate tape with the structure shown in Figure 4, which is used for communication cables, was attached vertically to the same cable core as above, and a low density polyethylene sheath was extruded to a thickness of 3 mm at 200°C to make a cable. did. In FIG. 4, 2' is aluminum with a thickness of 100 μm, and 3' is a ternary copolymer of ethylene, glycidyl methacrylate, and vinyl acetate (Bond First 7B manufactured by Sumitomo Chemical) with a thickness of 100 μm. Regarding PVC, use 100 parts of PVC with a degree of polymerization of 1100.
A mixture containing 50 parts of DOP (dioctyl phthalate) and 5 parts of tribasic lead sulfate was used, and low-density polyethylene with a specific gravity of 0.92 and MI2 was used. Regarding the cables of the two parties ○Measurement of the peel strength of the laminated tape 11 and the PVC sheath or low density polyethylene sheath 10 (see Figure 5) Sample width 10 mm, tensile speed 100 mm/min, 180
Measurement of peel strength at the overlapped part of laminated tape 11 (see Figure 6) Sample width 10 mm, tensile speed 100 mm/min, 180 degrees angle ○
The angle 10 in FIG. 6 is a PVC sheath or low density polyethylene. ○C Bending the laminated tape 1 10 times back and forth on a mandrel 12 with a diameter of 470 mm, which is 10 times the outer diameter of the cable approximately 47 mm.
Measurements were made at three points: No. 1 wrinkles and tearing of the metal layer (see Figure 7). The results are shown in Table 1, and the laminate tape of the present invention exhibits adhesive strength greater than that for communication cables, and can withstand practical use.

[Table] As a comparative example, a cable was prepared in which the laminate tape for communication cables shown in Fig. 4 was attached vertically to the same cable core as above, and then a PVC sheath was extruded to a thickness of 3 mm at 200°C. Table 2 shows the results of the tests ○A to ○C performed on this cable, but the adhesive strength with the PVC sheath was insufficient, and the laminated tape shown in Figure 3
It can be seen that both the PVC sheath and the laminated tape overlap have sufficient adhesive strength.

[Table] As described above, since the adhesive is selected according to the present invention, it can be applied to power cables using PVC sheaths, and it is possible to obtain sufficient adhesion to the PVC sheath and also sufficient adhesion at the overlapped portions of the tapes.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a power cable using a laminated tape, Fig. 2 is a sectional view of a laminate tape of the present invention, Fig. 3 is a sectional view illustrating an embodiment of the laminate tape of the present invention, and Fig. 4 is a sectional view of a power cable using a laminated tape. Fig. 3 is a cross-sectional view of a laminate tape for comparison with the embodiment of the laminate tape of the present invention; Fig. 5 is a diagram illustrating a method for measuring the peel strength of a laminate tape and a PVC sheath or low-density polyethylene; Fig. 6 7 is a diagram illustrating a method for measuring the peel strength of the overlapping portion of laminated tapes, and FIG. 7 is a diagram illustrating a method for measuring wrinkles and tears when the laminate tape is bent back and forth on a mandrel. DESCRIPTION OF SYMBOLS 1...Modified ethylene vinyl acetate copolymer, 2...Metal layer, 3...Copolymer of ethylene and glycidyl methacrylate or glycidyl acrylate and vinyl acetate as semiconductivity, 10...PVC sheath, 1
1... Laminating tape, 12... Mandrel.

Claims (1)

[Claims] 1. A tape made of metal laminated with plastic on both sides, whose structure consists of an ethylene/vinyl acetate copolymer, an unsaturated acid, an unsaturated alkyd obtained from a saturated acid polyhydric alcohol, and an organic peroxide. A layer of a modified ethylene-vinyl acetate copolymer obtained by heating and kneading with an oxide, a metal layer, and a ternary copolymer of ethylene and glycidyl methacrylate or glycidyl acrylate and vinyl acetate made semiconductive by adding carbon. A laminated tape characterized by consisting of three layers. 2. The laminate tape according to claim 1, wherein the metal layer is a layer of lead or an alloy whose main component is lead. 3. The laminate tape according to claim 2, wherein the metal layer has a thickness of 10 to 200 μm. 4 The plastic layer on each side of the metal layer is 10
The laminate tape according to claim 1, which has a thickness of 200 μm.