Polyolefin high polymer blend and ultrahigh-voltage cable using polyolefin high polymer blend

Abstract

The invention belongs to the field of cables, and provides a polyolefin high polymer blend which comprises the following components in parts by weight: 100 parts of polyethylene, 40-60 parts of polyisobutene, 10-20 parts of polystyrene, 30-65 parts of an additive, 1-5 parts of a plasticizer, 10-50 parts of a flame-retardant compounding agent, 1-3 parts of a lubricant, 0.5-2 parts of a cross-linking agent and 0-1 part of a performance additive, the invention further provides an ultrahigh-voltage cable which comprises a plurality of cable cores, and a filling layer, a flame-retardant layer, a first inner sheath, an insulation reinforcing layer, a semiconductor insulation shielding layer, a metal shielding layer, a second inner sheath, an armor layer and an outer sheath are sequentially arranged outside the cable cores. The first inner sheath, the second inner sheath and the outer sheath are all made of the polyolefin high polymer blend provided by the invention. The ultrahigh-voltage cable is improved from the aspects of material and structure, the insulativity and electric breakdown resistance of the ultrahigh-voltage cable are improved, the actual service life of the ultrahigh-voltage cable is prolonged, the flame retardance is also improved, and the ultrahigh-voltage cable is suitable for large-scale popularization.

Description

Technical Field

[0001] The invention belongs to the field of cables, and relates to an ultra-high voltage cable, in particular to a polyolefin high polymer blend and an ultra-high voltage cable using the polyolefin high polymer blend. Background Art

[0002] Wires and cables are essential basic products in power infrastructure construction, new smart grids, and new energy industries. Ultra-high voltage cables are a type of power cable, which refers to power cables used to transmit power between 275kv and 800kv, and are mostly used in power transmission and distribution.

[0003] The thickness of the insulation layer of the ultra-high voltage cable is much greater than that of ordinary wires and cables to prevent high voltage breakdown. When there is moisture and other inducing factors in the insulation layer of the cable, such as impurities, protrusions or space charges, the insulation layer will form some micro channels under the action of moisture and electric field. These micro channels are mostly tree-like structures, also known as "water trees". Water trees are the main factor inducing damage to high-voltage cables. This is because when the ultra-high voltage cable is working normally, water molecules will continue to gather in defective parts under the action of the electric field, causing mechanical damage to the insulation layer, thereby expanding the damage to the insulator. The insulation of ultra-high voltage cables is directly related to their actual performance and life. Therefore, in order to meet the requirements of the insulation performance of ultra-high voltage cables in applicable scenarios, reasonable improvements can be made to ultra-high voltage cables in terms of materials and structures to improve the actual performance of ultra-high voltage cables as a whole, extend the actual service life of cables, and reduce power maintenance costs. Summary of the invention

[0004] In view of the technical problems existing in the above-mentioned cable materials and ultra-high voltage cables, the present invention proposes a polyolefin polymer blend which has a reasonable design, good flame retardancy and insulation properties and is beneficial to extending the actual service life of the ultra-high voltage cable, and an ultra-high voltage cable using the polyolefin polymer blend.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is that a polyolefin polymer blend provided by the present invention comprises the following components by weight: 100 parts of polyethylene, 40-60 parts of polyisobutylene, 10-20 parts of polystyrene; 30-65 parts of additives, 1-5 parts of plasticizers, 10-50 parts of flame retardant compounding agents, 1-3 parts of lubricants, 0.5-2 parts of cross-linking agents and 0-1 parts of modifying aids; the additives include 1-5 parts of microcrystalline wax, 25-50 parts of industrial carbon black and 5-10 parts of internal plasticizers; the modifying aids are used to inhibit water trees and include 0.2-1 parts of sorbitol and 0.5-1 parts of antioxidants.

[0006] Preferably, the internal plasticizer is a highly active low molecular weight polyisobutylene.

[0007] Preferably, the flame retardant compound comprises ammonium polyphosphate, pentaerythritol, melamine, coal and montmorillonite.

[0008] An ultra-high voltage cable comprises a plurality of cable cores, wherein the cable cores comprise conductors and an insulating layer and a shielding layer arranged outside each conductor, a filling layer, a flame retardant layer, an insulating reinforcement layer, a semiconductor insulating shielding layer, a metal shielding layer, an armor layer and an outer sheath are arranged outside the plurality of cable cores, a first inner sheath is arranged between the flame retardant layer and the insulating reinforcement layer, a second inner sheath is arranged between the metal shielding layer and the armor layer, and the first inner sheath, the second inner sheath and the outer sheath are all made of a polyolefin polymer blend provided by the present invention.

[0009] Preferably, a double-layer dry tape wrapping layer is provided between the second inner sheath and the armor layer.

[0010] Preferably, the dry belt wrapping layer comprises a flat belt sleeve, the inner surface of the flat belt sleeve is provided with a wire mesh layer, and the surface of the wire mesh layer is provided with a dry powder spray coating.

[0011] Preferably, edge bands are formed on both sides of the flat belt sleeve by rolling, and a plurality of spacing bands formed by rolling are arranged between the edge bands, and the spacing bands divide the interior of the flat belt sleeve into interlayers distributed along its length direction.

[0012] Preferably, the number of the cable cores is 4 and a positioning core is provided in the center of the 4 cable cores, the side of the positioning core is a curved surface matching the side of the cable core, the inner wall of the positioning core is 4 paraboloids extruded symmetrically in pairs, and the 4 paraboloids constitute a star-shaped hole located in the center of the positioning core.

[0013] Preferably, the side edges of the positioning core are provided with a plurality of fractures evenly spaced along the length direction thereof.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are:

[0015] 1. The polyolefin polymer blend provided by the present invention can improve the electrical breakdown resistance and insulation performance of the material by blending polyethylene, polyisobutylene and polystyrene, and the additive components can improve the flame retardancy, corrosion resistance and insulation of the material; the use of modified additives can improve the water tree inhibition performance of the material, and can further improve the insulation of the material, which is beneficial to improving the electrical breakdown resistance of the cable.

[0016] 2. The ultra-high voltage cable provided by the present invention adopts a first inner sheath, a second inner sheath and an outer sheath as multi-layer protection, and is made of a polyolefin polymer blend provided by the present invention, which can cooperate with the insulation reinforcement layer and the semiconductor insulation shielding layer inside the cable to further improve the insulation of the cable, which is beneficial to improving the anti-puncture performance of the cable, thereby helping to extend the actual service life of the cable.

[0017] 3. The present invention proposes improvements to the ultra-high voltage cable in terms of materials and structure, which can effectively improve the insulation and electrical breakdown resistance of the ultra-high voltage cable, which is beneficial to extending its actual service life, and the flame retardant performance is also improved. The design is reasonable and suitable for large-scale promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A cross-sectional view of an ultra-high voltage cable provided by the present invention;

[0020] Figure 2 A partial unfolded view of the drying belt wrapped layer provided by the present invention;

[0021] Figure 3 A partial axonometric view of the positioning core provided by the present invention;

[0022] Figure 4 A composition table of a polyolefin polymer blend provided in Examples 1 to 7;

[0023] Figure 5 A performance table of a polyolefin polymer blend provided in Examples 1 to 7;

[0024] In the above figures, 1, cable core; 2, filling layer; 3, flame retardant layer; 4, first inner sheath; 5, insulation reinforcement layer; 6, semiconductor insulation shielding layer; 7, metal shielding layer; 8, second inner sheath; 9, dry tape wrapping layer; 91, flat tape sleeve; 92, wire mesh layer; 93, edge banding tape; 94, spacing tape; 10, armor layer; 11, outer sheath; 12, positioning core; 121, star-shaped hole; 122, fracture. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict. For the convenience of description, if the words "upper", "lower", "left" and "right" appear below, they only indicate that the upper, lower, left and right directions are consistent with the accompanying drawings themselves, and do not limit the structure.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0027] Embodiments 1 to 7, as Figures 4-5 As shown, the performance of a polyolefin polymer blend provided by the present invention under different components, wherein the unit of each component is part. Specifically:

[0028] Example 1. A polyolefin polymer blend provided in this example includes the following components by weight: 100 parts of polyethylene, 55 parts of polyisobutylene, and 10 parts of polystyrene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricants, 0.5 parts of cross-linking agents, and 0.2 parts of modifying aids; the additives include 2 parts of microcrystalline wax, 30 parts of industrial carbon black, and 8 parts of internal plasticizers; the modifying aids are used to inhibit water trees and include 0.1 parts of sorbitol and 0.1 parts of antioxidants.

[0029] Example 2. A polyolefin polymer blend provided in this example includes the following components by weight: 100 parts of polyethylene, 20 parts of polyisobutylene, and 10 parts of polystyrene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricant, 0.5 parts of cross-linking agents, and 0.2 parts of modifying aids; the additives include 2 parts of microcrystalline wax, 30 parts of industrial carbon black, and 8 parts of internal plasticizers; the modifying aids are used to inhibit water trees and include 0.1 parts of sorbitol and 0.1 parts of antioxidants.

[0030] Example 3. A polyolefin polymer blend provided in this example comprises the following components by weight: 100 parts of polyethylene, 10 parts of polystyrene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricants, 0.5 parts of cross-linking agents and 0.2 parts of modifying aids; the additives comprise 2 parts of microcrystalline wax, 30 parts of industrial carbon black and 8 parts of internal plasticizers; the modifying aids are used to inhibit water trees and comprise 0.1 parts of sorbitol and 0.1 parts of antioxidants.

[0031] Example 4. A polyolefin polymer blend provided in this example includes the following components by weight: 100 parts of polyethylene, 55 parts of polyisobutylene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricants, 0.5 parts of cross-linking agents and 0.2 parts of modifying aids; the additives include 2 parts of microcrystalline wax, 30 parts of industrial carbon black and 8 parts of internal plasticizers; the modifying aids are used to inhibit water trees and include 0.1 parts of sorbitol and 0.1 parts of antioxidants.

[0032] Example 5. A polyolefin polymer blend provided in this example includes the following components by weight: 100 parts of polyethylene, 55 parts of polyisobutylene, and 10 parts of polystyrene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricants, 0.5 parts of cross-linking agents, and 0.2 parts of modifying agents; the additives include 2 parts of microcrystalline wax and 38 parts of industrial carbon black; the modifying agents are used to inhibit water trees and include 0.1 parts of sorbitol and 0.1 parts of antioxidants.

[0033] Example 6. A polyolefin polymer blend provided in this example includes the following components by weight: 100 parts of polyethylene, 55 parts of polyisobutylene, 10 parts of polystyrene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricant and 0.5 of cross-linking agent; the additives include 2 parts of microcrystalline wax, 30 parts of industrial carbon black and 8 parts of internal plasticizer.

[0034] Example 7. A polyolefin polymer blend provided in this example includes the following components by weight: 100 parts of polyethylene, 55 parts of polyisobutylene, and 10 parts of polystyrene; 40 parts of additives, 2 parts of plasticizers, 50 parts of flame retardant compounding agents, 1 part of lubricant, 0.5 parts of cross-linking agents, and 0.2 parts of modifying aids; the additives include 2 parts of microcrystalline wax, 30 parts of industrial carbon black, and 8 parts of internal plasticizers; the modifying aids include 0.2 parts of antioxidants.

[0035] Examples 1 to 4 form a control group: by controlling the mixing ratio of polyisobutylene and polystyrene in the cable material, a breakdown test, a tensile strength test, a break elongation test, a heat resistance test and a flame retardancy test were carried out, from which it can be seen that the insulation performance of the cable can be effectively improved by adding polyisobutylene and polystyrene. The chemical structure, low chlorine content and high purity of polyisobutylene effectively prevent its oxidation and gas precipitation under electrical stress, which is beneficial to improving the electrical breakdown resistance of the cable, and polyisobutylene can improve the coloring performance of the cable product.

[0036] Examples 1 and 5 form a control group; through the comparison, it can be seen that the elongation at break and tensile strength of the polyolefin polymer blend containing internal plasticizer are higher, and the mixing ratio of the internal plasticizer is beneficial to improving the mechanical properties of the cable material. Regarding the microcrystalline wax in the additive, the migration speed of the microcrystalline wax in the rubber is relatively slow, the time to form a protective film is slightly longer, and the protection period is longer, which is beneficial to improving the anti-aging performance of the cable, and is also beneficial to improving the moisture-proof sealing of the cable. The appropriate amount of industrial carbon black mixed can improve the surface smoothness of the cable and has a positive effect on inhibiting the water tree of the cable, so it can improve the anti-puncture performance of the ultra-high voltage cable when the electric field is enhanced.

[0037] Examples 1, 6, and 7 form a control group: Since the sorbitol nucleating agent can reduce the size of spherulites, water trees are not easy to develop, the probability of initiation and the length of water trees are greatly reduced, and the development of water trees in the cable material can be inhibited; at the same time, through the comparison, it can be seen that the sorbitol in the modification auxiliary agent can effectively improve the insulation performance and electrical breakdown resistance of the cable material, and complement the antioxidant to improve the mechanical properties, heat resistance and flame retardancy of the cable.

[0038] In order to enhance the improvement effect of the internal plasticizer on the mechanical properties of the cable material, the internal plasticizer provided by the present invention adopts high-activity low-molecular-weight polyisobutylene. The high-activity low-molecular-weight polyisobutylene plays the role of a lubricant and, in particular, a plasticizer, which can improve the plasticity of the polymer, reduce the melt viscosity and glass transition temperature, and improve the processing performance.

[0039] In order to improve the flame retardant properties of the cable material, the flame retardant compound provided by the present invention includes ammonium polyphosphate, pentaerythritol, melamine, coal and montmorillonite. The flame retardant compound can be obtained by in-situ polymerization with polyethylene, polyisobutylene and polystyrene to obtain a coal-based polyolefin montmorillonite nanocomposite. Ammonium polyphosphate, pentaerythritol and melamine are compounded to form an intumescent flame retardant, which has a flame retardant synergistic effect with coal and montmorillonite; further, due to the small size effect, quantum size effect, surface effect and macroscopic quantum tunneling effect of nanoparticles, many new properties are endowed to the polymer nanocomposite, such as mechanical, thermal, optical, electromagnetic and gas barrier properties, which are significantly improved compared with conventional organic / inorganic composite materials. Therefore, the coal-based polyolefin montmorillonite nanocomposite has significant enhancement and gas barrier properties, can effectively improve the oxygen index of the cable material, and improve the flame retardancy of the cable.

[0040] like Figure 1 , Figure 2 and Figure 3As shown, an ultra-high voltage cable provided by the present invention comprises a plurality of cable cores 1, wherein the cable cores 1 comprise a conductor and an insulating layer and a shielding layer arranged outside each conductor, and a filling layer 2, a flame retardant layer 3, an insulating reinforcement layer 5, a semiconductor insulating shielding layer 6, a metal shielding layer 7, an armor layer 10 and an outer sheath 11 are arranged outside the plurality of cable cores 1. On this basis, the present invention particularly arranges a first inner sheath 4 between the flame retardant layer 3 and the insulating reinforcement layer 5, and a second inner sheath 8 between the metal shielding layer 7 and the armor layer 10, and the first inner sheath 4, the second inner sheath 8 and the outer sheath 11 are all made of a polyolefin polymer blend provided by the present invention. Among them, the first inner sheath 4, the second inner sheath 8 and the outer sheath 11 have good insulation performance and electrical breakdown resistance. They cooperate with the insulation reinforcement layer 5 and the semiconductor insulation shielding layer 6 to increase the insulation layer thickness of the ultra-high voltage cable, and the smoothness of the entire sheath formed is effectively improved, which not only inhibits the development of water trees from the material aspect, but also fully and effectively improves the insulation and electrical breakdown resistance of the cable from the design of the physical structure, thereby extending the actual service life of the ultra-high voltage cable.

[0041] In order to improve the drying performance inside the cable, the present invention provides a double-layer drying tape wrapping layer 9 between the second inner sheath 8 and the armor layer 10. The drying tape wrapping layer 9 can be used as a waterproof barrier to prevent external water vapor from penetrating into the cable and to avoid providing physical conditions for the development of water trees.

[0042] In order to improve the wrapping performance and dry powder adhesion performance of the dry tape wrapping layer 9, the dry tape wrapping layer 9 provided by the present invention includes a flat tape sleeve 91, the inner surface of the flat tape sleeve 91 is provided with a wire mesh layer 92, and the surface of the wire mesh layer 92 is provided with a dry powder spray coating. In this way, the flat characteristic of the flat tape sleeve 91 can be effectively wrapped inside the ultra-high voltage cable to form a continuous and complete wrapping surface on the second inner sheath 8; at the same time, the wire mesh layer 92 can provide a dense spraying base surface, and the densely sprayed dry powder spray coating can make the dry tape wrapping layer 9 have a smaller unit cross-section on the basis of fully exerting the drying performance, and will not form a large range of bulges, and there will be no obvious dry powder falling off on the cable section after cutting.

[0043] Furthermore, the two sides of the flat belt sleeve 91 provided by the present invention are formed into edge bands 93 by rolling, and a plurality of spacing bands 94 formed by rolling are arranged between the edge bands 93, and the spacing bands 94 divide the interior of the flat belt sleeve 91 into interlayers distributed along its length direction. Among them, the spacing bands 94 can improve the independence between adjacent interlayers, and can improve the overall flatness of the flat sleeve during the rolling process, which is conducive to the wrapping process; the rolled edge bands 93 can make the drying belt wrapping layer 9 after wrapping have a certain degree of overlap, so as to better ensure the integrity and continuity of its drying protection range.

[0044] In order to improve the positioning performance of the cable core 1 inside the ultra-high voltage cable, the present invention provides four cable cores 1 and a positioning core 12 is provided in the center of the four cable cores 1. The side of the positioning core 12 is a curved surface that matches the side of the cable core 1, and the extrusion position of the adjacent cable cores 1 is positioned by the established curved surface relationship. Taking into account the recycling problem of ultra-high voltage cables, the inner wall of the positioning core 12 designed by the present invention is four paraboloids that are symmetrically extruded in pairs, and the four paraboloids constitute a star-shaped hole 121 located at the center of the positioning core 12. In this way, when recycling ultra-high voltage cables, the working surfaces of the stripping equipment and the cutting equipment are cut from the edge position of the star-shaped hole 121 to separate the four cable cores 1 at the same time, reducing the extrusion force and friction force in the center of the cable, which is conducive to improving the efficiency of recycling the cable core 1.

[0045] Furthermore, the present invention provides a plurality of fractures 122 evenly spaced along the length direction on the side edges of the positioning core 12, and the fractures 122 provide shear openings for the stripping equipment and the cutting equipment to separate the positioning core 12, thereby reducing the stripping resistance and further improving the efficiency of mechanical recovery of the cable core 1.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A polyolefin polymer blend, comprising the following components by weight: 100 parts of polyethylene, 40-60 parts of polyisobutylene, 10-20 parts of polystyrene, 30-65 parts of additives, 1-5 parts of plasticizers, 10-50 parts of flame retardant compounding agents, 1-3 parts of lubricants, 0.5-2 parts of crosslinking agents and 0-1 parts of modification aids; The additives include 1 to 5 parts of microcrystalline wax, 25 to 50 parts of industrial carbon black and 5 to 10 parts of internal plasticizer; The modification aid is used to inhibit water trees and comprises 0.2 to 1 part of sorbitol and 0.5 to 1 part of an antioxidant.

2. A polyolefin polymer blend according to claim 1, characterized in that: The internal plasticizer is a highly active low molecular weight polyisobutylene.

3. A polyolefin polymer blend according to claim 2, characterized in that: The flame retardant compound comprises ammonium polyphosphate, pentaerythritol, melamine, coal and montmorillonite.

4. An ultra-high voltage cable, comprising a plurality of cable cores, wherein the cable cores comprise conductors and an insulating layer and a shielding layer arranged outside each conductor, and the outsides of the plurality of cable cores are provided with a filling layer, a flame retardant layer, an insulating reinforcement layer, a semiconductor insulating shielding layer, a metal shielding layer, an armor layer and an outer sheath, characterized in that: A first inner sheath is arranged between the flame retardant layer and the insulating reinforcement layer, a second inner sheath is arranged between the metal shielding layer and the armor layer, and the first inner sheath, the second inner sheath and the outer sheath are all made of a polyolefin polymer blend as described in any one of claims 1 to 3.

5. An ultra-high voltage cable according to claim 4, characterized in that: A double-layer dry tape wrapping layer is arranged between the second inner sheath and the armor layer.

6. An ultra-high voltage cable according to claim 5, characterized in that: The dry belt wrapping layer comprises a flat belt sleeve, the inner surface of the flat belt sleeve is provided with a wire mesh layer, and the surface of the wire mesh layer is provided with a dry powder spray coating layer.

7. An ultra-high voltage cable according to claim 6, characterized in that: Edge bands are formed on both sides of the flat belt sleeve by rolling, and a plurality of spacing bands formed by rolling are arranged between the edge bands. The spacing bands divide the interior of the flat belt sleeve into interlayers distributed along the length direction thereof.

8. An ultra-high voltage cable according to claim 4 or 7, characterized in that: The number of the cable cores is 4 and a positioning core is arranged in the center of the 4 cable cores. The side of the positioning core is a curved surface matching the side of the cable core. The inner wall of the positioning core is 4 paraboloids extruded symmetrically in pairs. The 4 paraboloids constitute a star-shaped hole located in the center of the positioning core.

9. An ultra-high voltage cable according to claim 8, characterized in that: The side edges of the positioning core are provided with a plurality of fractures evenly spaced and distributed along the length direction thereof.

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