Flame-retardant cable with low capacitance growth rate and preparation process thereof

Abstract

The invention discloses a flame-retardant cable with low capacitance growth rate and a preparation process thereof, the flame-retardant cable with low capacitance growth rate comprises a conductor, an inner wrapping layer, an inner insulating layer, a shielding layer, an outer wrapping layer and an outer insulating layer which are sequentially arranged from inside to outside, and the flame-retardant cable adopts a composite cross-linked polyethylene inner insulation and composite cross-linked polyethylene outer insulation structure, the main material of double-layer insulation is cross-linked polyethylene, and a flame-retardant master batch and a nano oxide composite water-blocking agent which are independently researched and developed are added. According to the flame-retardant cable with the low capacitance growth rate, the long-term operation stability of the cable in some specific places (such as a long-term humid environment and a high-humidity industrial scene) can be guaranteed, and meanwhile the flame-retardant cable has good flame-retardant performance.

Description

Technical Field

[0001] The present invention relates to the technical field of flame-retardant cables, and in particular to a flame-retardant cable with a low capacitance growth rate and a preparation process thereof. Background Art

[0002] In the field of power cables, the performance of insulation materials directly impacts safe cable operation and power transmission efficiency. Currently, the selection of cable insulation materials often prioritizes conventional performance indicators such as insulation and heat resistance, while overlooking the cable's long-term operational stability in harsh environments such as humidity and water immersion. Traditional low-voltage cables experience a significant increase in capacitance when exposed to water, significantly reducing power transmission efficiency. In power transmission scenarios, high-capacitance cables used in AC systems generate large charging currents, leading to increased reactive power losses. For example, a 110kV cable has a capacitance of approximately 0.15μF per kilometer. At a frequency of 50Hz, this charging current can reach 8A per kilometer, necessitating the deployment of additional reactive power compensation equipment. Furthermore, during long-distance power transmission, the capacitive current induced by the capacitors can cause voltage increases at the end terminals, necessitating the use of reactors for balancing and regulation.

[0003] Currently, cross-linked polyethylene (XLPE) is a commonly used insulating material in the power cable field. However, not only does this material have significant shortcomings in adaptability to humid and submerged environments, its capacitance value easily increases, resulting in reduced power transmission efficiency, and its inherent flame retardancy also severely restricts its application. XLPE forms a three-dimensional network structure through cross-linking, and its molecular chains are mainly composed of carbon (C) and hydrogen (H). It does not contain flame retardant elements such as halogens (such as chlorine and bromine) or phosphorus. As a pure hydrocarbon, XLPE reacts easily with oxygen at high temperatures, releasing large amounts of heat and continuously burning. XLPE's limiting oxygen index (LOI) is only 18%, far below the flame retardant material requirement of 26% or more. This indicates that in air (oxygen concentration is approximately 21%), XLPE material is extremely easy to ignite and the fire is likely to spread continuously. At the same time, the carbon content of XLPE material is as high as 85%, which releases a large amount of heat energy when burning, further accelerating the spread of flames. This uncontrollable flame retardant property brings unpredictable safety hazards to electrical systems, significantly increases the risk of accidents such as electrical fires, and greatly reduces the effectiveness and reliability of electricity safety management. Summary of the Invention

[0004] In order to solve the above technical problems, the primary purpose of the present invention is to provide a flame-retardant cable with a low capacitance growth rate, which is suitable for long-term humid environments and high-humidity industrial scenarios.

[0005] Another object of the present invention is to provide a process for preparing a flame-retardant cable with a low capacitance growth rate.

[0006] The present invention is achieved through the following technical solutions:

[0007] A flame-retardant cable with low capacitance growth rate, comprising a conductor, an inner wrapping layer, an inner insulating layer, a shielding layer, an outer wrapping layer, and an outer insulating layer, which are arranged in sequence from the inside to the outside;

[0008] The material of the inner insulating layer is cross-linked polyethylene, a flame retardant masterbatch and a nano-oxide composite water-blocking agent, and the mass ratio of the cross-linked polyethylene, the flame retardant masterbatch and the nano-oxide composite water-blocking agent is (80-85):(13-18):(1-6); the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

[0009] The present invention provides a flame-retardant cable with low capacitance growth rate, which adopts a composite cross-linked polyethylene inner insulation and a composite cross-linked polyethylene outer insulation structure. The main material of the double-layer insulation is cross-linked polyethylene, and a flame-retardant masterbatch independently developed and a nano-oxide composite water-blocking agent are added. After mixing in a specified proportion, the mixture is extruded onto the outer surface of the sheath through an extruder. The cross-linked polyethylene material forms a three-dimensional network structure through chemical or radiation cross-linking. Although its non-polar molecular chain gives the material high insulation, the micron-level pores (about 0.1-1μm) will become water penetration channels in a long-term water immersion environment. The present invention solves the problem that the water absorption rate of the cross-linked polyethylene material increases after long-term water immersion, resulting in an increase in the dielectric constant and a faster capacitance growth rate by adding a nano-oxide composite water-blocking agent; in addition, in view of the flammable properties of the cross-linked polyethylene material, the flame retardant performance of the cable is ensured by adding a flame-retardant masterbatch independently developed.

[0010] Furthermore, the low capacitance growth rate flame retardant cable is a low capacitance growth rate FT2 flame retardant cable.

[0011] Furthermore, the conductor is a copper conductor.

[0012] Specifically, the conductor adopts a Class B round slightly pressed bare copper conductor in the UL44 standard, with a smooth surface and no burrs, sharp edges, or protruding or broken single wires that damage the insulation.

[0013] Furthermore, a reinforced non-woven fabric is wrapped around the surface of the conductor to obtain an inner wrapping layer.

[0014] Furthermore, the average overlap rate of the inner wrapping layer is 15-20%, and the minimum overlap rate is ≥10%.

[0015] Specifically, a layer of reinforced non-woven fabric is wrapped around the surface of the conductor in the right direction with an overlap rate of 15-20%. The wrapping effect must be smooth and tight.

[0016] Furthermore, the insulating material of the inner insulating layer adopts composite cross-linked polyethylene insulation, with cross-linked polyethylene as the base material, mixed with independently developed flame retardant masterbatch and nano-oxide composite water-blocking agent, and the mixing ratio is (80-85): (13-18): (1-6).

[0017] Specifically, the thickness of the inner insulating layer meets the requirements of RHW-2 in NMX-J-451-ANCE.

[0018] Specifically, there should be no visible defects such as bubbles and sand holes on the cross section of the inner insulating layer.

[0019] Furthermore, the surfactant may be sodium octadecyl sulfate.

[0020] Furthermore, the shielding layer is obtained by wrapping a copper tape around the outer surface of the inner insulating layer.

[0021] Furthermore, the overlapping rate of the shielding layer is 16-21%.

[0022] Specifically, the copper tape is a soft copper tape with a nominal thickness of 0.10 mm, wrapped in a single layer with an overlap rate of 16-21%. The surface of the copper tape should be flat without warping or curling.

[0023] Furthermore, the outer wrapping layer is obtained by wrapping a reinforced non-woven fabric around the outer surface of the shielding layer.

[0024] Furthermore, the average overlap rate of the outer wrapping layer is 15-20%, and the minimum overlap rate is ≥10%.

[0025] Specifically, a layer of reinforced non-woven fabric is wrapped around the surface of the shielding layer in the right direction with an overlap rate of 15-20%. The wrapping effect must be smooth and tight.

[0026] Furthermore, the material of the outer insulating layer is cross-linked polyethylene, a flame retardant masterbatch and a nano-oxide composite water-blocking agent, and the mass ratio of the cross-linked polyethylene, the flame retardant masterbatch and the nano-oxide composite water-blocking agent is (80-85):(13-18):(1-6); the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

[0027] Furthermore, the surfactant may be sodium octadecyl sulfate.

[0028] Specifically, the thickness of the outer insulating layer meets the requirements of RHW-2 in NMX-J-451-ANCE.

[0029] Specifically, there should be no visible defects such as bubbles and sand holes on the cross section of the outer insulating layer.

[0030] A preparation process of the above-mentioned low capacitance growth rate flame-retardant cable comprises the following steps:

[0031] S1. Use reinforced non-woven fabric to wrap around the conductor surface to obtain an inner wrapping layer;

[0032] S2. The cross-linked polyethylene, flame retardant masterbatch and nano-oxide composite water-blocking agent are mixed, the resulting mixture is added to an extruder for extrusion, the resulting inner insulating material is extruded onto the outer surface of the inner wrapping layer, and then cross-linked at 85-95 ° C to obtain an inner insulating layer;

[0033] S3 using copper tape wrapped around the outer surface of the inner insulating layer to obtain a shielding layer;

[0034] S4 using a reinforced non-woven fabric wrapped around the outer surface of the shielding layer to obtain an outer cladding layer;

[0035] S5. Mix cross-linked polyethylene, flame retardant masterbatch and nano-oxide composite water-blocking agent, add the obtained mixed liquid into an extruder for extrusion, extrude the obtained outer insulating material onto the outer surface of the outer winding layer, and then cross-link at 85-95°C to obtain the outer insulating layer, thereby obtaining the low capacitance growth rate flame retardant cable.

[0036] Furthermore, in S1, the conductor is a copper conductor.

[0037] Specifically, in S1, the conductor adopts the Class B round slightly pressed bare copper conductor in the UL44 standard. The surface of the conductor is smooth, without burrs, sharp edges, and protruding or broken single wires that damage the insulation. It can only be transferred to the next process after ensuring that the 20°C DC resistance is qualified.

[0038] Specifically, in S1, the surface of the conductor should be round, uniform, smooth, free of oxidation, burrs, scratches, jumpers, oil stains, dust and other defects that affect product quality.

[0039] Furthermore, in S1, the average overlap rate of the inner wrapping layer is 15-20%, and the minimum overlap rate is ≥10%.

[0040] Specifically, in S1, a layer of reinforced non-woven fabric is wrapped around the surface of the conductor, with the wrapping direction being right, the overlap rate being 15-20%, and the minimum overlap rate being ≥10%. The wrapping effect needs to be smooth and tight, and the wrapping surface must be flat and free of loose or leaking wrapping.

[0041] Furthermore, in S2, the insulating material of the inner insulating layer adopts composite cross-linked polyethylene insulation, with cross-linked polyethylene as the base material, mixed with independently developed flame retardant masterbatch and nano-oxide composite water-blocking agent, and the mixing ratio is (80-85):(13-18):(1-6).

[0042] Specifically, in S2, the thickness of the inner insulating layer meets the requirements of RHW-2 in NMX-J-451-ANCE.

[0043] Specifically, in S2, there should be no visible defects such as bubbles and pinholes on the cross section of the inner insulating layer.

[0044] Furthermore, in S2, the average thickness of the inner insulation layer is 2.7-2.8 mm, the thickness at the thinnest point is ≥2.39 mm, and the insulation eccentricity is ≤20%.

[0045] Specifically, in S2, the screw of the extruder equipment is selected to be of ordinary type with equal distance and unequal depth, the filter mesh is selected to be two pieces of 60 mesh, the specifications and quantity of the filter are matched according to the actual extrusion effect, and the cooling water is cooled in sections to reduce the internal stress of the insulation.

[0046] Specifically, in S2, before extrusion, the cross-linked polyethylene, flame retardant masterbatch, and nano-oxide composite water-blocking agent are mixed and stirred to ensure uniform mixing. After the extruder is kept at a constant temperature for 2-3 hours, the extruder is started to discharge the material. Once plasticization is complete, the die is closed and normal production resumes. After extrusion is completed, the inner insulation material is boiled in water for cross-linking. The boiling temperature is controlled at 85-95°C, and the boiling time is 3-4 hours per millimeter of insulation thickness to ensure sufficient cross-linking of the inner insulation material without affecting its aging performance.

[0047] Specifically, in S2, the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

[0048] Furthermore, in S3, the overlapping rate of the shielding layer is 16-21%.

[0049] Specifically, in S3, a soft copper tape with a nominal thickness of 0.10 mm is used and wrapped in a single layer on the surface of the inner insulation layer with an overlap rate of 16-21%. The surface of the copper tape should be flat without warping or curling.

[0050] Furthermore, in S4, a layer of reinforced non-woven fabric is wrapped around the surface of the shielding layer in a right-hand direction with an overlap rate of 15-20%. The wrapping effect needs to be smooth and tight.

[0051] Furthermore, in S5, the material of the outer insulating layer is cross-linked polyethylene, flame retardant masterbatch and nano-oxide composite water-blocking agent, and the mass ratio of the cross-linked polyethylene, flame retardant masterbatch and nano-oxide composite water-blocking agent is (80-85):(13-18):(1-6);

[0052] Furthermore, in S5, the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

[0053] Specifically, in S5, the thickness of the outer insulating layer meets the requirements of RHW-2 in NMX-J-451-ANCE.

[0054] Specifically, in S5, there should be no visible defects such as bubbles and pinholes on the cross section of the outer insulating layer.

[0055] Furthermore, in S5, the outer insulation layer has an average thickness of 1.7-1.8 mm, a thickness at the thinnest point of ≥1.32 mm, and an insulation eccentricity of ≤20%.

[0056] Specifically, in S5, the screw of the extruder equipment is selected as the ordinary type with equal distance and unequal depth, the filter mesh is selected as two pieces of 60 mesh, the specifications and quantity of the filter are matched according to the actual extrusion effect, and the cooling water is cooled in sections to reduce the internal stress of the insulation.

[0057] Specifically, in S5, before extrusion, the cross-linked polyethylene, flame retardant masterbatch, and nano-oxide composite water-blocking agent are mixed and stirred to ensure uniform mixing. After the extruder is kept at a constant temperature for 2-3 hours, the extruder is started to discharge the material. Once the material is plasticized, the die is closed and production resumes. After extrusion is completed, the outer insulation material is boiled in water for cross-linking. The boiling temperature is controlled at 85-95°C, and the boiling time is 3-4 hours per millimeter of insulation thickness to ensure sufficient cross-linking of the outer insulation material without affecting its aging performance.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] 1. The present invention provides a flame-retardant cable with a low capacitance growth rate, which can ensure the stability of the cable in long-term operation in some specific places (such as humid, submerged environments, etc.), and the flame-retardant cable has good flame retardant properties.

[0060] 2. In terms of insulating materials, the present invention mixes cross-linked polyethylene insulating materials with independently developed nano-oxide composite water-blocking agents and flame-retardant masterbatch formulas. The cross-linked polyethylene material forms a three-dimensional network structure through chemical or radiation cross-linking. Although its non-polar molecular chains give the material high insulation properties, the micron-level pores (about 0.1-1μm) will become water penetration channels in a long-term water immersion environment. The present invention solves the problem of increased water absorption of cross-linked polyethylene materials after long-term water immersion, resulting in an increase in dielectric constant and a faster resistance growth rate by adding independently developed nano-oxide composite water-blocking agents. The molecular chains of cross-linked polyethylene insulating materials are mainly composed of carbon (C) and hydrogen (H), and do not contain flame-retardant elements such as halogens (such as chlorine, bromine) or phosphorus. The material is relatively flammable. By adding the independently developed flame-retardant masterbatch, the present invention can make the cable have excellent flame retardant effects while the cross-linked polyethylene has the original good processability, insulation, and temperature resistance.

[0061] 3. This invention utilizes a double-layer composite structure of inner and outer insulation. The combination of these two layers of composite cross-linked polyethylene creates a redundant protection mechanism. Even if the outer insulation layer is damaged by friction or environmental factors, the inner layer still maintains its basic insulation function. The double-layer structure also disperses electric field stress, reducing the voltage concentration associated with single-layer insulation and improving the cable's withstand voltage by 30-50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a schematic structural diagram of the low capacitance growth rate FT2 flame retardant cable of Example 1.

[0063] Reference numerals: 1, conductor; 2, inner wrapping layer; 3, inner insulating layer; 4, shielding layer; 5, outer wrapping layer; 6, outer insulating layer. DETAILED DESCRIPTION

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0065] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0066] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0067] The cross-linked polyethylene used in the following examples was purchased from Zhejiang Wanma Polymer Materials Group Co., Ltd.

[0068] Example 1

[0069] A low capacitance growth rate FT2 flame retardant cable includes a conductor, an inner wrapping layer, an inner insulation layer, a shielding layer, an outer wrapping layer, and an outer insulation layer arranged in sequence from the inside to the outside. The structural diagram is shown in FIG. Figure 1 As shown in the figure, the rated voltage of this flame retardant cable is 600V, 1 core, and the nominal cross-sectional area is 300MCM.

[0070] The low capacitance growth rate FT2 flame-retardant cable of Example 1 is specifically prepared by the following process:

[0071] S1. Use Class B round, slightly embossed bare copper conductors as specified in the UL44 standard. The conductor surface must be smooth, free of burrs, sharp edges, protruding or broken individual wires that could damage the insulation. Ensure that the 20°C DC resistance meets the requirements for Class B round, slightly embossed bare copper conductors as specified in the UL44 standard before proceeding to the next process. The conductor surface must be round, uniform, smooth, and free of defects such as oxidation, burrs, scratches, jumpers, oil stains, and dust that could affect product quality. Wrap a layer of reinforced non-woven fabric around the conductor surface in a right-hand direction, with an overlap ratio of 15%. Ensure the wrapped surface is smooth and free of loose or leaking wrapping, forming the inner wrapping layer.

[0072] S2. Choose a standard type with equal spacing and unequal depth for the extruder screw. Use two 60-mesh filters. The filter specifications and quantity should be matched to the actual extrusion effect. Cooling water should be cooled in sections to reduce internal stress in the insulation. Before extrusion, mix and stir the cross-linked polyethylene, flame retardant masterbatch (18 parts of magnesium hydroxide, 7 parts of aluminum hydroxide, 2 parts of tribasic lead sulfate, 1 part of dibasic lead phosphite, 0.5 parts of paraffin, 30 parts of phthalate, 8 parts of nano-montmorillonite), and nano-oxide composite water-blocking agent (31 parts of nano-silicon oxide, 18 parts of nano-iron oxide, 38 parts of nano-calcium carbonate, 26 parts of nano-aluminum oxide, 7 parts of sodium octadecyl sulfate, and 44 parts of deionized water) to ensure uniform mixing (the mass ratio of cross-linked polyethylene, flame retardant masterbatch, and nano-oxide composite water-blocking agent is 82:15:3). After the extruder is kept at a constant temperature for 2 hours, start the extruder discharge. After good plasticization, close the die head and proceed with normal production. After extrusion, the inner insulation material is boiled in water for crosslinking at 90°C for three hours per millimeter of insulation thickness to ensure sufficient crosslinking without affecting its aging performance. The resulting inner insulation material is then applied to the outer surface of the inner wrapping layer to form an inner insulation layer. The thickness of the inner insulation layer meets the RHW-2 requirements of NMX-J-451-ANCE, reaching 2.7 mm and with an insulation eccentricity of ≤20%.

[0073] S3. Use soft copper tape with a nominal thickness of 0.10mm. Wrap it in a single layer on the outer surface of the inner insulation layer with an overlap rate of 20%. The surface of the copper tape should be flat without warping or curling to obtain a shielding layer.

[0074] S4. Wrap a layer of reinforced non-woven fabric on the surface of the shielding layer in an overlapping manner to the right, with an overlap rate of 15%. The wrapped surface must be flat and free of loose or leaking wrapping to obtain the outer wrapped layer.

[0075] S5. Choose a standard type with equal spacing and unequal depth for the extruder screw. Use two 60-mesh filters. The filter specifications and quantity should be matched to the actual extrusion effect. Cooling water should be cooled in sections to reduce internal stress in the insulation. Before extrusion, mix and stir the cross-linked polyethylene, flame retardant masterbatch (18 parts of magnesium hydroxide, 7 parts of aluminum hydroxide, 2 parts of tribasic lead sulfate, 1 part of dibasic lead phosphite, 0.5 parts of paraffin, 30 parts of phthalate, 8 parts of nano-montmorillonite), and nano-oxide composite water-blocking agent (31 parts of nano-silicon oxide, 18 parts of nano-iron oxide, 38 parts of nano-calcium carbonate, 26 parts of nano-aluminum oxide, 7 parts of sodium octadecyl sulfate, and 44 parts of deionized water) to ensure uniform mixing of the materials (the mass ratio of cross-linked polyethylene, flame retardant masterbatch, and nano-oxide composite water-blocking agent is 82:15:3). After ensuring that the extruder is kept at a constant temperature for 2 hours, start the extruder discharge. After good plasticization, close the die head and proceed with normal production. After extrusion, the inner insulation material is boiled in water for crosslinking at a temperature of 90°C for three hours per millimeter of insulation thickness to ensure sufficient crosslinking of the outer insulation material without affecting the aging performance of the inner insulation material. The resulting inner insulation material is then applied to the outer surface of the inner wrapping layer to form an outer insulation layer. The thickness of the outer insulation layer meets the RHW-2 requirements of NMX-J-451-ANCE, reaching 1.7 mm, with an insulation eccentricity of ≤20%, ultimately resulting in the low capacitance growth flame-retardant cable.

[0076] Test Case

[0077] The following performance tests were performed on the low capacitance growth rate FT2 flame retardant cable of Example 1:

[0078] The dielectric constant was tested according to UL44 standard (test temperature 90°C, after immersion in water for 24 hours). The technical requirement is not more than 6, and the test result is 2.2.

[0079] The capacitance growth rate was tested according to UL44 standard (90℃, 3.15kV / nm). The capacitance was tested after immersion in water for 1 day, 7 days and 14 days. The capacitance growth rate (C 14 The technical requirement of capacitance growth rate (C -C1) / C1 is no more than 10%, and the test result is 1%; the capacitance growth rate (C 14 -C7) / C1 technical requirement is no more than 4%, and the test result is 0.4%.

[0080] Therefore, the low capacitance growth rate FT2 flame retardant cable of Example 1 meets the test requirements of dielectric constant (test temperature 90°C, after immersion in water for 24 hours) in UL44 standard, meets the test requirements of capacitance growth rate in UL44 standard, and meets the FT2 flame retardant test in UL2556.

[0081] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A flame-retardant cable with low capacitance growth rate, characterized in that: It includes a conductor, an inner wrapping layer, an inner insulating layer, a shielding layer, an outer wrapping layer, and an outer insulating layer arranged in sequence from the inside to the outside; The material of the inner insulating layer is cross-linked polyethylene, a flame retardant masterbatch and a nano-oxide composite water-blocking agent, and the mass ratio of the cross-linked polyethylene, the flame retardant masterbatch and the nano-oxide composite water-blocking agent is (80-85):(13-18):(1-6); the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

2. The flame-retardant cable with low capacitance growth rate according to claim 1, characterized in that: The material of the outer insulating layer is cross-linked polyethylene, a flame retardant masterbatch and a nano-oxide composite water-blocking agent, and the mass ratio of the cross-linked polyethylene, the flame retardant masterbatch and the nano-oxide composite water-blocking agent is (80-85):(13-18):(1-6); the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

3. A process for preparing a flame-retardant cable with low capacitance growth rate according to claim 1 or 2, characterized in that: The following steps are involved: S1. Use reinforced non-woven fabric to wrap around the conductor surface to obtain an inner wrapping layer; S2. The cross-linked polyethylene, flame retardant masterbatch and nano-oxide composite water-blocking agent are mixed, the resulting mixture is added to an extruder for extrusion, the resulting inner insulating material is extruded onto the outer surface of the inner wrapping layer, and then cross-linked at 85-95 ° C to obtain an inner insulating layer; S3 using copper tape wrapped around the outer surface of the inner insulating layer to obtain a shielding layer; S4 using a reinforced non-woven fabric wrapped around the outer surface of the shielding layer to obtain an outer cladding layer; S5. Mix cross-linked polyethylene, flame retardant masterbatch and nano-oxide composite water-blocking agent, add the obtained mixed liquid into an extruder for extrusion, extrude the obtained outer insulating material onto the outer surface of the outer winding layer, and then cross-link at 85-95°C to obtain the outer insulating layer, thereby obtaining the low capacitance growth rate flame retardant cable.

4. The preparation process according to claim 3, characterized in that In S1, the average overlap rate of the inner wrapping layer is 15-20%, and the minimum overlap rate is ≥10%.

5. The preparation process according to claim 3, characterized in that: In S2, the average thickness of the inner insulating layer is 2.7-2.8 mm, the thickness at the thinnest point is ≥2.39 mm, and the insulation eccentricity is ≤20%.

6. The preparation process according to claim 3, characterized in that: In S3, copper tape is used to wrap the inner insulation layer in a single layer with an overlapping rate of 16-21%.

7. The preparation process according to claim 3, characterized in that: In S4, a layer of reinforced non-woven fabric is wrapped around the surface of the shielding layer in the right direction with an overlap rate of 15-20%.

8. The preparation process according to claim 3, characterized in that: In S5, the mass ratio of the cross-linked polyethylene, the flame retardant masterbatch and the nano-oxide composite water-blocking agent is (80-85):(13-18):(1-6).

9. The preparation process according to claim 3, characterized in that: In S5, the flame retardant masterbatch includes the following components in parts by weight: 18-22 parts of magnesium hydroxide, 6-9 parts of aluminum hydroxide, 2-3 parts of tribasic lead sulfate, 1-3 parts of dibasic lead phosphite, 0.5-1 part of paraffin, 28-33 parts of phthalate, and 8-10 parts of nano-montmorillonite; the nano-oxide composite water-blocking agent includes the following components in parts by weight: 29-35 parts of nano-silicon oxide, 17-21 parts of nano-iron oxide, 37-42 parts of nano-calcium carbonate, 24-27 parts of nano-aluminum oxide, 5-7 parts of surfactant, and 43-48 parts of deionized water.

10. The preparation process according to claim 3, characterized in that: In S5, the outer insulating layer has an average thickness of 1.7-1.8 mm, a thickness at the thinnest point of ≥1.32 mm, and an insulation eccentricity of ≤20%.

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