Highly flame-retardant semiconductive tape, and method of making and using same

Abstract

The application discloses high-flame-retardant semiconductive wrapping tape, a preparation method and application thereof, and relates to the technical field of cable materials.The high-flame-retardant semiconductive wrapping tape comprises a first reinforcing layer, a semiconductive high-flame-retardant functional layer and a second reinforcing layer which are sequentially stacked and hot-combined into one body, and the semiconductive high-flame-retardant functional layer comprises PA11, PA1010, PA6, linear low-density polyethylene, maleic anhydride grafted polyethylene, conductive carbon black, carboxylated multi-walled carbon nanotubes, magnesium hydroxide and aluminum hydroxide which are surface treated by amino silane, melamine polyphosphate, zinc borate, mica, an antioxidant and a lubricant.The application further discloses a preparation method of the high-flame-retardant semiconductive wrapping tape and application thereof in an ultrahigh-voltage cable or a large-interface medium-voltage cable.The wrapping tape has lower resistance, higher mechanical strength, better interlayer bonding performance and better flame-retardant stability under the condition of a relatively thin total thickness.

Description

Technical Field

[0001] This invention belongs to the technical field of cable accessory materials, specifically relating to high flame-retardant semi-conductive wrapping tape, its preparation method, and its application. Background Technology

[0002] In ultra-high voltage cables and large-interface medium-voltage cables, semi-conductive wrapping tape is typically used outside the conductor shielding layer, outside the insulated core, or other areas requiring auxiliary electric field homogenization, shielding, and binding. Besides requiring low surface and volume resistivity, this type of tape also needs to consider mechanical strength, flexibility, wrapping stability, and a certain degree of flame retardancy to meet the requirements of long-term operation and use under fire conditions.

[0003] In the prior art, one type of solution is the single-layer thermoplastic semi-conductive nylon tape approach. For example, CN105295364B discloses a semi-conductive nylon tape for cable shielding, whose raw material system includes PA11, PA1010, PA6, linear low-density polyethylene, maleic anhydride-grafted polyethylene, conductive materials, flame retardants, fillers, reinforcing fibers, and surface modifiers, and provides thickness windows of 0.08–0.12 mm, 0.10–0.14 mm, and 0.12–0.16 mm. This type of solution mainly focuses on the conductivity, heat resistance, and processability of the single-layer material system.

[0004] Another type of solution involves a fabric skeleton combined with a coating or impregnation method using semi-conductive flame-retardant adhesive. For example, CN101950623A discloses a semi-conductive flame-retardant tape for cables, comprising a skeleton and a semi-conductive flame-retardant adhesive applied outside the skeleton; the skeleton can be made of fiberglass cloth, nylon fiber cloth, or polyester fiber cloth, and the semi-conductive flame-retardant adhesive can be an adhesive such as acrylic polymer or polyurethane, combined with flame retardants such as magnesium hydroxide, aluminum hydroxide, zinc borate, ammonium polyphosphate, and melamine. This type of solution essentially relies on the surface adhesive layer to impart semi-conductive and flame-retardant functions.

[0005] Another type of solution uses a multi-layer semi-conductive nylon tape. For example, CN206711624U discloses a semi-conductive nylon tape for cables, comprising a flame-retardant base fabric, an upper epoxy resin adhesive layer and an upper semi-conductive layer on the upper surface, and a thermal insulation layer, a waterproof layer, a lower epoxy resin adhesive layer and a lower semi-conductive layer on the lower surface. This type of solution focuses more on waterproofing, thermal insulation, and adhesion structure.

[0006] In addition, there is also a surface-coated type of high flame-retardant and fire-resistant wrapping tape. For example, CN112562906A discloses an antistatic high flame-retardant, fire-resistant and anti-oxidation wrapping tape, the surface of which is coated with an antistatic high flame-retardant, fire-resistant and anti-oxidation coating, achieving semi-conductive, high flame-retardant and fire-resistant properties through the surface coating.

[0007] Although the aforementioned existing technologies have made improvements in various directions, such as single-layer thermoplastic, surface adhesive, multi-layer adhesion, and surface spraying, the following shortcomings still exist: single-layer thermoplastic semiconductive tapes are difficult to simultaneously achieve flame retardancy, structural stability, and wrapping construction stability under thin-film conditions; the functional layers of coated or sprayed tapes rely more on the surface adhesive or coating, which are prone to interfacial stability and surface durability issues under long-term thermal exposure; existing multi-layer solutions rely more on epoxy adhesive layers, thermal insulation layers, or waterproof layers, and have not yet undergone systematic optimization around the semiconductivity, flame retardancy, and interlayer stability of thermal composites under thin-film conditions.

[0008] Therefore, it is still necessary to provide a highly flame-retardant semiconductive tape that combines low resistance, good mechanical properties, high flame retardancy, and good interlayer bonding stability under relatively thin total thickness conditions. Summary of the Invention

[0009] The purpose of this invention is to provide a high flame-retardant semi-conductive wrapping tape, its preparation method, and its application, in order to solve the problem that existing semi-conductive wrapping tapes are difficult to simultaneously achieve semi-conductivity, flame retardancy, mechanical properties, and interlayer bonding stability under thinning conditions. In particular, it improves the comprehensive applicability of existing single-layer thermoplastic wrapping tapes, coated / impregnated wrapping tapes, and sprayed wrapping tapes in long-term service and wrapping construction scenarios.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a highly flame-retardant semi-conductive wrapping tape, comprising a first reinforcing layer, a semi-conductive highly flame-retardant functional layer, and a second reinforcing layer that are sequentially stacked and thermally bonded together. The first and second reinforcing layers are both nylon / polyester composite fiber fabrics, each with a single-layer thickness of 18–30 μm. The nylon / polyester composite fiber fabric is preferably woven or nonwoven, wherein the nylon fibers and polyester fibers can be blended, interwoven, or layered composites. The preferred areal density is 10–40 g / m², and the porosity allows the melt of the intermediate functional layer to partially penetrate into the fiber gaps under pressure during thermal bonding, forming mechanical interlocking, thereby improving the interfacial peel strength and retention rate after thermal aging. The semi-conductive high flame-retardant functional layer comprises, by weight: 40-45 parts PA11, 11-13 parts PA1010, 5-7 parts PA6, 8-10 parts linear low-density polyethylene, 5.5-7.5 parts maleic anhydride-grafted polyethylene, 10.5-12.5 parts conductive carbon black, 0.4-0.8 parts carboxylated multi-walled carbon nanotubes, 14-18 parts magnesium hydroxide and aluminum hydroxide surface-treated with aminosilane, 3.5-5.5 parts melamine polyphosphate, 2.5-4.0 parts zinc borate, 5-8 parts mica, 0.4-0.7 parts antioxidant, and 0.8-1.5 parts lubricant; The total thickness of the highly flame-retardant semi-conductive tape is 0.11–0.13 mm, its surface resistivity is not higher than 500 Ω, and its volume resistivity is not higher than 8 × 10^6 mm. 3 The tensile strength is not less than 170 N / cm, the elongation is not less than 25%, the oxygen index is not less than 34%, and the 180° peel strength between the first or second reinforcing layer and the semiconductive high flame retardant functional layer is not less than 1.2 N / mm.

[0011] Furthermore, the thickness of the first and second reinforcing layers is 20–28 μm, respectively, and the thickness of the semiconductive high flame retardant functional layer is 35–60 μm.

[0012] Furthermore, the weight ratio of the conductive carbon black to the carboxylated multi-walled carbon nanotubes is 15:1 to 30:1.

[0013] Furthermore, the weight ratio of the aminosilane-treated magnesium hydroxide to the aminosilane-treated aluminum hydroxide is 0.9 to 1.1:1, and the total weight ratio of the aminosilane-treated magnesium hydroxide, aluminum hydroxide, melamine polyphosphate, and zinc borate is 1.5:1 to 2.6:1.

[0014] Furthermore, after thermal aging at 145℃ for 168 hours, the surface resistivity increase rate of the high flame-retardant semi-conductive tape is not higher than 20%, the volume resistivity increase rate is not higher than 25%, the 180° peel strength retention rate is not lower than 80%, the tensile strength retention rate is not lower than 80%, and the elongation retention rate is not lower than 75%.

[0015] This invention also provides a method for preparing the above-mentioned high flame-retardant semiconductive tape, comprising the following steps: S1. Dry PA11, PA1010, PA6 and the first and second reinforcing layers at 85-95℃ for 5-7 hours, and dry carboxylated multi-walled carbon nanotubes at 80-90℃ for 2-3 hours. S2. Magnesium hydroxide and aluminum hydroxide are added to an alcohol-water solution containing an aminosilane coupling agent for surface treatment. The amount of the aminosilane coupling agent is 0.6 to 1.2 wt% of the total mass of magnesium hydroxide and aluminum hydroxide. After treatment, the mixture is dried at 100 to 110°C for 1 to 2 hours. S3. PA11, PA1010, PA6, linear low-density polyethylene, and maleic anhydride-grafted polyethylene are added to a high-speed mixer and mixed at 650–850 rpm for 6–10 min. Then, conductive carbon black, carboxylated multi-walled carbon nanotubes, surface-treated magnesium hydroxide and aluminum hydroxide, melamine polyphosphate, zinc borate, and mica are added and mixed at 450–650 rpm for 5–8 min. Finally, antioxidants and lubricants are added and mixed at 300–450 rpm for 2–4 min. Preferably, before adding carboxylated multi-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes are first mixed with a portion of maleic anhydride-grafted polyethylene or PA11 to form a pre-dispersed masterbatch, wherein the content of carboxylated multi-walled carbon nanotubes in the masterbatch is (3–15) wt%. The masterbatch is then added to the high-speed mixing step according to the ratio to improve the dispersion uniformity of carbon nanotubes in the polymer matrix and reduce resistance dispersion. S4. The mixture obtained in step S3 is fed into a twin-screw extruder for melt blending and granulation. The temperature of each zone of the twin-screw extruder is 225-242℃, the screw speed is 180-240rpm, and the vacuum exhaust degree is -0.06--0.09MPa. S5. The granulated material obtained in step S4 is extruded and calendered into a semi-conductive high flame-retardant functional layer film with a thickness of 35-60 μm. S6. Place the semiconductive high flame retardant functional layer film between the first reinforcing layer and the second reinforcing layer, and perform online thermal bonding at 195-210℃ and 0.25-0.55MPa, with a linear velocity of 8-15m / min. S7. After cooling, heat set at 125-155℃ for 40-150s, then cut and rewound to obtain the high flame-retardant semi-conductive tape.

[0016] Furthermore, in step S2, the volume ratio of alcohol to water in the alcohol-water solution is 60:40 to 85:15, and the aminosilane coupling agent is selected from KH-550, KH-560 or a combination thereof; in step S6, the 180° peel strength after online thermal bonding is not less than 1.2 N / mm.

[0017] The present invention also provides the application of the above-mentioned high flame-retardant semi-conductive wrapping tape in ultra-high voltage cables or large-interface medium voltage cables. The high flame-retardant semi-conductive wrapping tape is wrapped around the conductor shielding layer and / or the insulated core with an overlap rate of 15%–25%, and is used in conjunction with the extruded semi-conductive shielding layer for shielding and binding the conductor or insulated core.

[0018] Furthermore, when the cable sample made from the high flame-retardant semi-conductive tape is evaluated for flame retardancy according to GB / T19666-2019 and for fire-resistant line integrity according to GB / T19216.1-2021, the fire resistance retention time shall not be less than 90 minutes.

[0019] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. Compared with single-layer PA-based semiconducting tape, this invention adopts a three-layer thermal composite sandwich structure of a first reinforcing layer / semiconducting high flame-retardant functional layer / second reinforcing layer. With a basically equivalent total thickness, it can simultaneously take into account mechanical properties, wrapping construction stability and semiconducting properties. The outer reinforcing layer mainly bears the wrapping and tensile stress, while the middle continuous thermoplastic functional layer maintains a stable conductive / flame-retardant continuous phase. The thermal composite interface reduces the performance constraints of single-layer materials under thin-film conditions.

[0020] 2. Compared with the conventional conductive network of conductive carbon black and unfunctionalized CNTs, the present invention adopts a functionalized dual conductive network of conductive carbon black and carboxylated multi-walled carbon nanotubes; carboxylated multi-walled carbon nanotubes are more conducive to constructing stable multi-scale conductive pathways in this system.

[0021] 3. Compared with untreated inorganic flame retardants, the present invention uses magnesium hydroxide / aluminum hydroxide surface-treated with aminosilane. The surface treatment of inorganic flame retardants not only improves dispersion, but also improves interfacial bonding and structural stability after aging.

[0022] 4. Compared with non-synergistic flame retardant systems, the present invention adopts a flame retardant synergistic system of treated magnesium hydroxide / aluminum hydroxide, melamine polyphosphate, zinc borate, and mica. It is not a simple superposition of flame retardants, but a synergistic flame retardant effect is formed in the thermoplastic sandwich system of the present invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the layered structure of the high flame-retardant semi-conductive tape of the present invention.

[0025] Figure 2 This is a schematic diagram of the process flow for the preparation method of the high flame-retardant semi-conductive tape of the present invention.

[0026] Reference numerals: 1. First reinforcing layer; 2. Semiconductor high flame retardant functional layer; 3. Second reinforcing layer. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The basic raw material selection and main rules and properties of this invention are as follows: PA11: cable grade; PA1010: cable grade; PA6: extrusion grade; linear low-density polyethylene: MI about 2.0 g / 10 min; maleic anhydride grafted polyethylene: grafting rate 0.8%~1.2%; conductive carbon black: semi-conductive grade; carboxylated multi-walled carbon nanotubes: carboxyl content 1.5%~2.5%; magnesium hydroxide: D50 about 1.8 μm; aluminum hydroxide: D50 about 1.5 μm; aminosilane coupling agent: KH-550; melamine polyphosphate: industrial grade; zinc borate: industrial grade; mica: 1250 mesh; antioxidant: hindered phenol / phosphite compound type; lubricant: fatty acid amides; reinforcing layer: nylon / polyester composite fiber cloth.

[0029] Example 1 See Figure 1 As shown, the high flame-retardant semi-conductive tape of this embodiment includes a first reinforcing layer, a semi-conductive high flame-retardant functional layer and a second reinforcing layer that are sequentially stacked and thermally bonded together. The semi-conductive high flame-retardant functional layer comprises, by weight: 42.0 parts PA11, 12.0 parts PA1010, 6.0 parts PA6, 9.0 parts linear low-density polyethylene, 6.5 parts maleic anhydride-grafted polyethylene, 11.5 parts conductive carbon black, 0.60 parts carboxylated multi-walled carbon nanotubes, 7.5 parts magnesium hydroxide treated with KH-550, 7.5 parts aluminum hydroxide treated with KH-550, 4.5 parts melamine polyphosphate, 3.0 parts zinc borate, 6.0 parts mica, 0.50 parts antioxidant, and 1.00 part lubricant. Both the first and second reinforcing layers are made of nylon / polyester composite fiber cloth, with a single layer thickness of 24μm.

[0030] See Figure 2 As shown, the preparation method of the high flame-retardant semiconductive tape in this embodiment includes the following steps: S1, raw material drying: PA11, PA1010, and PA6 were dried in a 90℃ hot air drying oven for 6 hours, nylon / polyester composite fibers were dried in a 90℃ oven for 4 hours, and carboxylated multi-walled carbon nanotubes were dried in a 85℃ vacuum drying oven for 3 hours. S2. Inorganic flame retardant surface treatment: Take 1000 mL of a mixture of ethanol / deionized water at a volume ratio of 75 / 25, adjust the pH to 4.8 with glacial acetic acid; add KH-550 at a volume of 0.9 wt% of the total mass of magnesium hydroxide and aluminum hydroxide, and pre-hydrolyze in a water bath at 35 °C for 30 min; then add the mixed powder of magnesium hydroxide and aluminum hydroxide, and mechanically stir at 55 °C for 40 min; after filtration, dry in an oven at 105 °C for 1.5 h to obtain the surface-treated flame retardant; S3, High-speed mixing: First, PA11, PA1010, PA6, linear low-density polyethylene, and maleic anhydride-grafted polyethylene are added to a high-speed mixer and mixed at 780 rpm for 8 minutes. Then, conductive carbon black, carboxylated multi-walled carbon nanotubes, surface-treated flame retardant, melamine polyphosphate, zinc borate, and mica are added and mixed at 560 rpm for 6 minutes. Finally, antioxidants and lubricants are added and mixed at 360 rpm for 3 minutes. S4. Blending and granulation: A Φ52 / 44D twin-screw extruder was used, with the temperature zones set sequentially as 225℃ / 230℃ / 234℃ / 236℃ / 238℃ / 240℃ / 240℃ / 238℃, a die head temperature of 236℃, a screw speed of 210 rpm, and a vacuum exhaust degree of -0.08 MPa for extrusion, stranding, and granulation. S5, Film Formation: The granulated material was fed into a flat die casting machine, the melt temperature was set to 232℃, the die head gap was 0.45mm, and the cooling roller temperature was 70℃ to obtain an intermediate functional layer film with a thickness of 52μm. S6, Thermal Composite: The intermediate functional layer film is sandwiched between two layers of nylon / polyester composite fiber cloth. The temperature of the upper composite roller is 202℃, the temperature of the lower composite roller is 198℃, the composite pressure is 0.42MPa, and the linear speed is 12m / min. S7. Heat setting and slitting: After being heat-set in a 140℃ oven for 90 seconds, the tape is cut into 25mm wide strips to obtain a highly flame-retardant semi-conductive tape with a total thickness of 0.128mm.

[0031] Example 2 See Figure 1 As shown, the high flame-retardant semi-conductive tape of this embodiment includes a first reinforcing layer, a semi-conductive high flame-retardant functional layer and a second reinforcing layer that are sequentially stacked and thermally bonded together. The semi-conductive high flame-retardant functional layer comprises, by weight: 42.0 parts PA11, 12.0 parts PA1010, 6.0 parts PA6, 8.8 parts linear low-density polyethylene, 7.2 parts maleic anhydride-grafted polyethylene, 11.5 parts conductive carbon black, 0.60 parts carboxylated multi-walled carbon nanotubes, 7.5 parts magnesium hydroxide treated with KH-550, 7.5 parts aluminum hydroxide treated with KH-550, 4.5 parts melamine polyphosphate, 3.0 parts zinc borate, 6.0 parts mica, 0.50 parts antioxidant, and 1.00 part lubricant. Both the first and second reinforcing layers are made of nylon / polyester composite fiber cloth, with a single layer thickness of 24μm.

[0032] See Figure 2 As shown, the preparation method of the high flame-retardant semiconductive tape in this embodiment includes the following steps: S1, raw material drying: PA11, PA1010, and PA6 were dried at 92℃ for 6.5 h; nylon / polyester composite fiber cloth was dried at 92℃ for 4.5 h; and carboxylated multi-walled carbon nanotubes were vacuum dried at 86℃ for 2.5 h. S2. Inorganic flame retardant surface treatment: Take 1000 mL of a mixture of ethanol / deionized water (70 / 30 volume ratio) and adjust the pH to 4.6 with glacial acetic acid; add KH-550 at a rate of 1.0 wt% of the total inorganic flame retardant mass and pre-hydrolyze at 38 °C for 35 min; add a mixture of magnesium hydroxide and aluminum hydroxide powder and stir at 58 °C for 45 min; filter and dry at 108 °C for 1.5 h. S3, High-speed mixing: The resin matrix and compatibilizer were first mixed at 760 rpm for 9 min; after adding conductive filler, surface treatment flame retardant, melamine polyphosphate, zinc borate and mica, they were mixed at 540 rpm for 6.5 min; finally, antioxidant and lubricant were added and mixed at 350 rpm for 3.5 min. S4. Blending and granulation: The temperature zones of the twin-screw extruder are set sequentially as follows: 226℃ / 231℃ / 235℃ / 237℃ / 239℃ / 241℃ / 241℃ / 239℃, the die head temperature is 237℃, the screw speed is 200 rpm, and the vacuum exhaust pressure is -0.08 MPa. S5, Film Formation: With a melt temperature of 233℃, a die gap of 0.47mm, and a cooling roller temperature of 72℃, an intermediate functional layer film with a thickness of 53μm was obtained. S6, Thermal Composite: The temperature of the upper composite roller is 205℃, the temperature of the lower composite roller is 201℃, the composite pressure is 0.50MPa, and the linear speed is 10m / min. S7. Heat setting and slitting: Heat-set at 145℃ for 110 seconds, then cut into 25mm wide strips to obtain a highly flame-retardant semi-conductive tape with a total thickness of 0.129mm.

[0033] Example 3 See Figure 1 As shown, the high flame-retardant semi-conductive tape of this embodiment includes a first reinforcing layer, a semi-conductive high flame-retardant functional layer and a second reinforcing layer that are sequentially stacked and thermally bonded together. The semi-conductive high flame-retardant functional layer comprises, by weight: 41.0 parts PA11, 12.0 parts PA1010, 6.0 parts PA6, 8.8 parts linear low-density polyethylene, 6.8 parts maleic anhydride-grafted polyethylene, 11.5 parts conductive carbon black, 0.60 parts carboxylated multi-walled carbon nanotubes, 8.5 parts magnesium hydroxide treated with KH-550, 8.5 parts aluminum hydroxide treated with KH-550, 5.2 parts melamine polyphosphate, 3.8 parts zinc borate, 7.0 parts mica, 0.50 parts antioxidant, and 1.10 parts lubricant. Both the first and second reinforcing layers are made of nylon / polyester composite fiber cloth, with a single layer thickness of 24μm.

[0034] See Figure 2 As shown, the preparation method of the high flame-retardant semiconductive tape in this embodiment includes the following steps: S1, raw material drying: PA11, PA1010, and PA6 were dried at 88℃ for 7 hours; nylon / polyester composite fiber cloth was dried at 88℃ for 5 hours; and carboxylated multi-walled carbon nanotubes were vacuum dried at 82℃ for 3 hours. S2. Inorganic flame retardant surface treatment: Take 1000 mL of a mixture of ethanol / deionized water (80 / 20 volume ratio) and adjust the pH to 4.9 with glacial acetic acid; add KH-550 at a rate of 0.8 wt% of the total inorganic flame retardant mass and pre-hydrolyze at 32 °C for 25 min; add a mixture of magnesium hydroxide and aluminum hydroxide powder and stir at 52 °C for 50 min; filter and dry at 106 °C for 2.0 h. S3, High-speed mixing: The resin matrix and compatibilizer were first mixed at 820 rpm for 8 min; after adding conductive filler, surface treatment flame retardant, melamine polyphosphate, zinc borate and mica, they were mixed at 600 rpm for 7 min; finally, antioxidant and lubricant were added and mixed at 400 rpm for 3 min. S4. Blending and granulation: The temperature zones of the twin-screw extruder are set sequentially as follows: 227℃ / 232℃ / 236℃ / 238℃ / 240℃ / 242℃ / 242℃ / 240℃, with a die head temperature of 238℃, a screw speed of 190 rpm, and a vacuum exhaust pressure of -0.09 MPa. S5, Film Formation: With a melt temperature of 234℃, a die gap of 0.50mm, and a cooling roller temperature of 68℃, an intermediate functional layer film with a thickness of 56μm was obtained. S6, Thermal Composite: The temperature of the upper composite roller is 208℃, the temperature of the lower composite roller is 204℃, the composite pressure is 0.46MPa, and the linear speed is 9m / min. S7. Heat setting and slitting: Heat-set at 150℃ for 120 seconds, then cut into 25mm wide strips to obtain a highly flame-retardant semi-conductive tape with a total thickness of 0.132mm.

[0035] Example 4 See Figure 1 As shown, the high flame-retardant semi-conductive tape of this embodiment includes a first reinforcing layer, a semi-conductive high flame-retardant functional layer and a second reinforcing layer that are sequentially stacked and thermally bonded together. The semi-conductive high flame-retardant functional layer comprises, by weight: 42.0 parts PA11, 12.0 parts PA1010, 6.0 parts PA6, 8.5 parts linear low-density polyethylene, 6.8 parts maleic anhydride-grafted polyethylene, 12.3 parts conductive carbon black, 0.75 parts carboxylated multi-walled carbon nanotubes, 7.5 parts magnesium hydroxide treated with KH-550, 7.5 parts aluminum hydroxide treated with KH-550, 4.5 parts melamine polyphosphate, 3.0 parts zinc borate, 6.0 parts mica, 0.50 parts antioxidant, and 1.00 part lubricant. Both the first and second reinforcing layers are made of nylon / polyester composite fiber cloth, with a single layer thickness of 23μm.

[0036] See Figure 2 As shown, the preparation method of the high flame-retardant semiconductive tape in this embodiment includes the following steps: S1, raw material drying: PA11, PA1010, and PA6 were dried at 90℃ for 5.5 hours; nylon / polyester composite fiber cloth was dried at 90℃ for 4 hours; and carboxylated multi-walled carbon nanotubes were vacuum dried at 88℃ for 2 hours. S2. Inorganic flame retardant surface treatment: Take 1000 mL of a mixture of ethanol / deionized water at a volume ratio of 78 / 22, adjust the pH to 4.7 with glacial acetic acid; add KH-550 at a rate of 0.9 wt% of the total inorganic flame retardant, and pre-hydrolyze at 36 °C for 30 min; add a mixture of magnesium hydroxide and aluminum hydroxide powder, and stir at 56 °C for 35 min; filter and dry at 103 °C for 1.2 h. S3, High-speed mixing: The resin matrix and compatibilizer were first mixed at 800 rpm for 7 min; after adding conductive filler, surface treatment flame retardant, melamine polyphosphate, zinc borate and mica, they were mixed at 620 rpm for 5 min; finally, antioxidant and lubricant were added and mixed at 330 rpm for 2.5 min. S4. Blending and granulation: The temperature zones of the twin-screw extruder are set sequentially as follows: 225℃ / 229℃ / 233℃ / 235℃ / 237℃ / 239℃ / 239℃ / 237℃, with a die head temperature of 235℃, a screw speed of 225 rpm, and a vacuum exhaust pressure of -0.07 MPa. S5, Film Formation: With a melt temperature of 231℃, a die gap of 0.43mm, and a cooling roller temperature of 66℃, an intermediate functional layer film with a thickness of 50μm was obtained. S6, Thermal Composite: The temperature of the upper composite roller is 198℃, the temperature of the lower composite roller is 195℃, the composite pressure is 0.36MPa, and the linear speed is 14m / min. S7. Heat setting and slitting: Heat-set at 132℃ for 70 seconds, then cut into 25mm wide strips to obtain a highly flame-retardant semi-conductive tape with a total thickness of 0.126mm.

[0037] Comparative Example 1 Compared with Example 1, the difference is that: no first and second reinforcing layers are provided, and the semiconductive high flame retardant functional layer formulation of Example 1 is directly extruded into a single layer of semiconductive tape with a thickness of 0.129 mm; the other raw material formulations and extrusion temperature system are the same as those of Example 1.

[0038] Comparative Example 2 Compared with Example 1, the difference is that 0.60 parts of carboxylated multi-walled carbon nanotubes are replaced with an equal amount of unfunctionalized multi-walled carbon nanotubes; the rest of the formulation and process are the same as in Example 1.

[0039] Comparative Example 3 Compared with Example 1, the difference is that the magnesium hydroxide and aluminum hydroxide treated with KH-550 are replaced with an equal amount of untreated magnesium hydroxide and aluminum hydroxide; the rest of the formula and process are the same as in Example 1.

[0040] Comparative Example 4 Compared with Example 1, the difference is that the flame-retardant synergistic components of 4.5 parts of melamine polyphosphate and 3.0 parts of zinc borate are replaced with 7.5 parts of ordinary melamine; the rest of the formulation and process are the same as in Example 1.

[0041] Performance testing The high flame-retardant semiconductive tapes prepared in Examples 1-4 and Comparative Examples 1-4 were tested for the following performance indicators. The specific test items and test conditions are as follows: Thickness: A digital thickness gauge was used to measure 5 points along the length of the sample strip and the average value was taken. Surface resistivity: measured using a high resistance meter, with a sample size of 100mm × 25mm; Volume resistivity: Measured using a high-resistivity meter with a volume resistivity fixture; Tensile strength and elongation: tested using an electronic universal testing machine with a clamping distance of 100 mm and a tensile speed of 50 mm / min. 180° peel strength: 180° peel tests were performed on the interface of the first reinforcing layer / intermediate functional layer and the interface of the second reinforcing layer / intermediate functional layer respectively, and the average value of 5 sets was taken for each interface; when it is necessary to give the overall peel strength index of the tape, the smaller value of the test results of the two interfaces is taken as the 180° peel strength of the tape. Thermal aging: 145℃×168h, and the surface resistivity, volume resistivity, peel strength, tensile strength and elongation were measured before and after aging; Oxygen index: Designed and tested according to GB / T2406.2-2009; Flame retardancy evaluation of equivalent cable samples: designed according to GB / T19666-2019; Fire resistance evaluation of equivalent cable samples: Designed according to applicable GB / T19216 series standards; using equivalent samples with rated voltage of 0.6 / 1kV and below and outer diameter exceeding 20mm, designed according to GB / T19216.1-2021; The specific test results are shown in Tables 1, 2, and 3 below: Table 1. Test Results of Structural Parameters Table 2. Initial Performance Parameters Table 3. Heat aging retention performance (145℃×168h) Results Analysis: As can be seen from the comparison between Example 1 and Comparative Example 1, when the total thickness is similar, the three-layer thermal composite sandwich structure significantly improves the overall performance of the wrapping tape. This indicates that the sandwich thermal composite structure is not a simple stacking, but rather takes into account both the conductive continuous phase and the mechanical load-bearing structure under the coupling of the formulation and process of this invention. As can be seen from the comparison between Example 1 and Comparative Example 2, simply replacing the carboxylated multi-walled carbon nanotubes with an equal amount of unfunctionalized multi-walled carbon nanotubes resulted in a significant increase in surface resistance, volume resistance, and the rate of increase in resistance after thermal aging. This indicates that carboxylated multi-walled carbon nanotubes are more conducive to building a stable conductive network in this system. As can be seen from the comparison between Example 1 and Comparative Example 3, the 180° peel strength, the peel strength retention rate after heat aging, and the tensile strength are significantly improved after using surface-treated magnesium hydroxide and aluminum hydroxide. This indicates that the surface treatment of inorganic flame retardants not only affects dispersion, but also affects interfacial bonding and structural durability. As can be seen from the comparison between Example 1 and Comparative Example 4, after adopting the flame retardant synergistic system, the oxygen index and the equivalent sample fire resistance retention time are improved, while the surface resistance remains at a low level. This indicates that the current flame retardant system is not an arbitrary combination of ordinary flame retardants, but rather forms a synergistic flame retardant effect in the thermoplastic sandwich system of the present invention. Comparing Examples 2 to 4, it can be seen that Example 2 is more conducive to improving the interlayer peel strength and its retention rate after aging, Example 3 is more conducive to improving the oxygen index and fire resistance retention time, and Example 4 is more conducive to reducing the surface resistance, volume resistance and its growth rate after thermal aging. This shows that the present invention can achieve adjustable design with different performance focuses through the functional combination of intermediate functional layers under a unified structural platform.

[0042] The tapes obtained in Examples 1-4 are wrapped around the conductor shielding layer of the equivalent cable sample with a 20% overlap rate and are used in conjunction with the extruded semiconductive shielding layer. The sample structure, outer diameter, and rated voltage can be designed according to the target standard by selecting the appropriate parts. When using the above structure, the tape of the present invention can improve the flame retardancy and fire resistance performance of the equivalent sample while maintaining a low resistance. GB / T19666-2019 is the general rule for flame-retardant and fire-resistant wires, cables or optical cables, and GB / T19216.1-2021 is the test method for line integrity of cables or optical cables under flame conditions - Part 1: Flame temperature not lower than 830°C and impact vibration applied to cables with rated voltage of 0.6 / 1kV and below and outer diameter exceeding 20mm.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0044] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high flame-retardant semi-conductive tape, characterized in that, It includes a first reinforcing layer, a semi-conductive high flame-retardant functional layer, and a second reinforcing layer that are sequentially stacked and thermally composited into one unit; The first and second reinforcing layers are both nylon / polyester composite fiber fabrics, with a single layer thickness of 18 to 30 μm. The semi-conductive high flame-retardant functional layer comprises, by weight: 40-45 parts PA11, 11-13 parts PA1010, 5-7 parts PA6, 8-10 parts linear low-density polyethylene, 5.5-7.5 parts maleic anhydride-grafted polyethylene, 10.5-12.5 parts conductive carbon black, 0.4-0.8 parts carboxylated multi-walled carbon nanotubes, 14-18 parts magnesium hydroxide and aluminum hydroxide surface-treated with aminosilane, 3.5-5.5 parts melamine polyphosphate, 2.5-4.0 parts zinc borate, 5-8 parts mica, 0.4-0.7 parts antioxidant, and 0.8-1.5 parts lubricant.

2. The high flame-retardant semi-conductive tape according to claim 1, characterized in that, The thickness of the first and second reinforcing layers is 20-28 μm, respectively, and the thickness of the semi-conductive high flame-retardant functional layer is 35-60 μm.

3. The high flame-retardant semiconductive tape according to claim 1, characterized in that, The weight ratio of the conductive carbon black to the carboxylated multi-walled carbon nanotubes is 15:1 to 30:

1.

4. The high flame-retardant semi-conductive tape according to claim 1, characterized in that, The weight ratio of the aminosilane-treated magnesium hydroxide to the aminosilane-treated aluminum hydroxide is 0.9 to 1.1:1, and the total weight ratio of the aminosilane-treated magnesium hydroxide, aluminum hydroxide, melamine polyphosphate, and zinc borate is 1.5:1 to 2.6:

1.

5. The high flame-retardant semiconductive tape according to claim 1, characterized in that, After being thermally aged at 145℃ for 168 hours, the high flame-retardant semi-conductive tape exhibits a surface resistivity increase rate of no more than 20%, a volume resistivity increase rate of no more than 25%, a 180° peel strength retention rate of no less than 80%, a tensile strength retention rate of no less than 80%, and an elongation retention rate of no less than 75%.

6. The method for preparing the high flame-retardant semiconductive tape according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Dry PA11, PA1010, PA6 and the first and second reinforcing layers at 85-95℃ for 5-7 hours, and dry carboxylated multi-walled carbon nanotubes at 80-90℃ for 2-3 hours. S2. Magnesium hydroxide and aluminum hydroxide are added to an alcohol-water solution containing an aminosilane coupling agent for surface treatment. The amount of the aminosilane coupling agent is 0.6 to 1.2 wt% of the total mass of magnesium hydroxide and aluminum hydroxide. After treatment, the mixture is dried at 100 to 110°C for 1 to 2 hours. S3. Add PA11, PA1010, PA6, linear low-density polyethylene, and maleic anhydride-grafted polyethylene into a high-speed mixer and mix at 650–850 rpm for 6–10 min. Then add conductive carbon black, carboxylated multi-walled carbon nanotubes, surface-treated magnesium hydroxide and aluminum hydroxide, melamine polyphosphate, zinc borate, and mica, and mix at 450–650 rpm for 5–8 min. Finally, add antioxidants and lubricants, and mix at 300–450 rpm for 2–4 min. S4. The mixture obtained in step S3 is fed into a twin-screw extruder for melt blending and granulation. The temperature of each zone of the twin-screw extruder is 225-242℃, the screw speed is 180-240rpm, and the vacuum exhaust degree is -0.06--0.09MPa. S5. The granulated material obtained in step S4 is extruded and calendered into a semi-conductive high flame-retardant functional layer film with a thickness of 35-60 μm. S6. Place the semiconductive high flame retardant functional layer film between the first reinforcing layer and the second reinforcing layer, and perform online thermal bonding at 195-210℃ and 0.25-0.55MPa, with a linear velocity of 8-15m / min. S7. After cooling, heat set at 125-155℃ for 40-150s, then cut and rewound to obtain the high flame-retardant semi-conductive tape.

7. The method for preparing the high flame-retardant semiconductive tape according to claim 6, characterized in that, In step S2, the volume ratio of alcohol to water in the alcohol-water solution is 60:40 to 85:15, and the aminosilane coupling agent is selected from KH-550, KH-560 or a combination thereof; in step S6, the 180° peel strength after online thermal bonding is not less than 1.2 N / mm.

8. The application of the high flame-retardant semi-conductive wrapping tape according to any one of claims 1-5 in ultra-high voltage cables or large-interface medium voltage cables, characterized in that, The high flame-retardant semi-conductive wrapping tape is wrapped around the conductor shielding layer and / or the insulated wire core with an overlap rate of 15%–25%, and is used in conjunction with the extruded semi-conductive shielding layer for shielding and binding the conductor or insulated wire core.

9. The application of the high flame-retardant semi-conductive tape according to claim 8, characterized in that, When the cable sample made from the high flame-retardant semi-conductive tape is evaluated for flame retardancy according to GB / T19666-2019 and for fire-resistant line integrity according to GB / T19216.1-2021, the fire resistance retention time shall not be less than 90 minutes.

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