Mica tape special for fire-resistant cable and forming process of mica tape

Abstract

The invention relates to the technical field of cable materials, in particular to a mica tape special for a fire-resistant cable and a forming process of the mica tape. The invention discloses an epoxy modified mica composite material which is composed of 65-80 parts of synthetic mica powder, 12-22 parts of a composite bonding system, a zinc 2-ethylhexanoate curing agent accounting for 8% of the total mass of the composite bonding system, an alkali-free glass fiber cloth reinforcing base material with the mass per unit area being 22 g / m < 2 > and the thickness being 0.028 mm and 5-6 parts of an epoxy modified resin composition surface adhesive layer. According to the special mica tape for the fire-resistant cable and the forming process of the special mica tape, systematic optimization is carried out aiming at many defects in the prior art, leap-type improvement of the comprehensive performance of the fire-resistant mica tape is achieved, and the special mica tape has remarkable technical advantages and practical value.

Description

Technical Field

[0001] This invention relates to the field of cable material technology, specifically to a mica tape for fire-resistant cables and its molding process. Background Technology

[0002] Fire-resistant mica tape, as the core insulating and fire-resistant component of fire-resistant cables, directly determines the operational stability of the cable in high-temperature fire environments and is widely used in fields with stringent fire safety requirements, such as power transmission and rail transportation. Currently, the production and preparation of existing fire-resistant mica tape still suffers from many technical shortcomings, making it difficult to meet the high-specification requirements of high-voltage cables.

[0003] Existing products often use a single resin for their bonding system, which presents an inherent contradiction between temperature resistance and bonding strength. If temperature resistance is prioritized, the bonding strength is insufficient and the layers are easily peeled off. If the bonding strength is improved, the temperature resistance decreases, and the degree of crosslinking after curing is low, resulting in a significant decline in mechanical properties after thermal aging.

[0004] In terms of filler application, traditional solutions often involve directly adding unmodified fillers, which easily leads to agglomeration and weak interfacial bonding with the resin. This fails to effectively improve properties such as thermal conductivity and flame retardancy, and the use of a single filler makes it difficult to achieve synergistic optimization of multiple properties. The substrate is often made of a single material, resulting in poor overall structural stability and a tendency to crack and delaminate after thermal cycling. Furthermore, existing production processes are relatively crude, lacking precise filler dispersion and segmented curing processes. The matching degree between coating and curing parameters is low, leading to poor product performance consistency. In addition, post-processing is inadequate, making the product susceptible to moisture absorption and deterioration during storage, and resulting in insufficient corrosion resistance and weather resistance.

[0005] Furthermore, existing technological improvements are mostly focused on local adjustments to single modules, with no collaborative design between components. This makes it impossible to address shortcomings in overall performance and makes it difficult to meet the multiple performance requirements of high-voltage cables, such as fire resistance, insulation, and mechanical properties. Summary of the Invention

[0006] The primary objective of this invention is to provide a mica tape for fire-resistant cables and its molding process.

[0007] A further objective of this invention is to provide a mica tape specifically for fire-resistant cables, comprising, by weight, 65-80 parts synthetic mica powder, 12-22 parts composite bonding system, 8% by weight of zinc 2-ethylhexanoate curing agent, 22 g / m² alkali-free glass fiber cloth reinforcing substrate with a thickness of 0.028 mm, and 5-6 parts by weight of epoxy modified resin composition surface adhesive layer; the composite bonding system is composed of silicone resin and epoxy modified resin in a mass ratio of 1:1 to 3:1; the synthetic mica powder is obtained by magnetic separation to remove iron in a 12000 Gauss magnetic field, hydraulic classification, hot pressing and peeling at 300 degrees Celsius and 0.8 MPa, and wet papermaking, with a flake diameter D50 of 35-45 micrometers; the epoxy modified resin composition has a solid content of 10% to 12%.

[0008] Preferably, it further includes 3 parts of nano-silica filler modified with diphenylmethane diisocyanate, the amount of the modifier diphenylmethane diisocyanate added is 0.15 parts, and the particle size of the nano-silica filler is 20 nanometers.

[0009] Preferably, the reinforcing substrate is replaced by a composite substrate with a total thickness of 0.03 mm. The composite substrate is formed by hot pressing a 0.028 mm thick alkali-free glass fiber cloth and a 0.002 mm thick polyimide film together. It also includes 6-8 parts of micron boron nitride-nano graphene composite functional filler modified with diphenylmethane diisocyanate. The amount of diphenylmethane diisocyanate added is 0.3-0.4 parts. The particle size of the micron boron nitride is 1 micron. The thickness of the nano graphene is 0.8 nanometers.

[0010] Preferably, in the micron boron nitride-nano graphene composite functional filler, the mass ratio of micron boron nitride to nano graphene is 5:1.

[0011] Preferably, the mica tape surface is coated with a 0.5 g / m² o-hydroxybenzoate UV-resistant coating.

[0012] A molding process for preparing the mica tape for fire-resistant cables includes the following steps: (1) Mica powder pretreatment: After removing iron by magnetic separation with a magnetic field of 12000 Gauss and hydraulic classification, natural mica is hot-pressed and peeled off at 300 degrees Celsius and 0.8 MPa, and then wet-made into synthetic mica paper. (2) Preparation of adhesive: Mix silicone resin and epoxy modified resin at a mass ratio of 1:1 to 3:1, add 2-ethylhexanoate zinc curing agent accounting for 8% of the total mass of the composite adhesive system, stir at a speed of 500 rpm for 60 minutes, and adjust the viscosity of the system to 3000 mPa·s using polyether polyol 330N. The amount of polyether polyol 330N added is 2%-3% of the total mass of the composite adhesive system to obtain the composite adhesive system; (3) Coating and bonding: The composite bonding system is coated on one side of the synthetic mica paper at a coating amount of 10 grams per square meter using a slot extrusion coating machine, and then hot-pressed with alkali-free glass fiber cloth at 120 degrees Celsius and 0.3 MPa for 20 seconds. (4) Topcoat coating: Apply an epoxy modified resin composition to the other side of the synthetic mica paper at a coating amount of 5 grams per square meter to form a topcoat layer; (5) Segmented curing: First, pre-curing at 100 degrees Celsius with 2.5 micrometer infrared wavelength for 40 minutes, then final curing with hot air at 180 degrees Celsius for 60 minutes, so that the cross-linking degree of the adhesive layer reaches 92%; (6) Post-processing: The cured substrate is laser-cut into 30 mm wide strips and vacuum-packed with a vacuum degree of -0.09 MPa. Silica gel desiccant is placed inside the packaging, and the amount of silica gel desiccant added is 2 grams per square meter of strip.

[0013] Preferably, when preparing the mica tape, in step (2), before adjusting the viscosity, 3 parts of nano-silica filler modified with diphenylmethane diisocyanate are added, ultrasonically dispersed at 600 watts for 30 minutes, and then stirred at 600 rpm for 80 minutes to adjust the viscosity of the system to 3200 mPa second; in step (3), the coating amount of the composite bonding system is 12 g per square meter, and the hot pressing bonding conditions are 130 degrees Celsius, 0.3 MPa, and 25 seconds; in step (4), the coating amount of the epoxy modified resin composition is 5.5 g per square meter; in step (5), the pre-curing conditions are 110 degrees Celsius and 35 minutes, and the final curing conditions are 190 degrees Celsius and 50 minutes, with the cross-linking degree of the adhesive layer reaching 93%; in step (6), the amount of silica gel desiccant added is 3 g per square meter of tape.

[0014] Preferably, when preparing the mica tape, alkali-free glass fiber cloth and polyimide film are first hot-pressed together at 150 degrees Celsius and 0.5 MPa for 30 seconds to obtain a composite substrate; in step (2), 6-8 parts of diphenylmethane diisocyanate modified micron boron nitride-nano graphene composite functional filler are added, ultrasonically dispersed at 600 watts for 30 minutes, and then stirred at 700 rpm for 90 minutes to adjust the viscosity of the system to 3300 mPa second; in step (3), the coating amount of the composite bonding system is 13 grams per square meter, and it is bonded to the composite substrate at 1 Hot-press bonding for 30 seconds at 40 degrees Celsius and 0.4 MPa; in step (4), the amount of epoxy modified resin composition coated is 6 grams per square meter; in step (5), the pre-curing conditions are 120 degrees Celsius and 30 minutes, and the final curing conditions are 200 degrees Celsius and 45 minutes, with the cross-linking degree of the adhesive layer reaching 94%; in step (6), the cutting width is 35 mm, and after cutting, 0.5 grams per square meter of o-hydroxybenzoic acid phenyl ester anti-UV coating is sprayed, and then vacuum packaging is performed with a vacuum degree of -0.09 MPa, with the amount of silica gel desiccant added being 4 grams per square meter of the tape.

[0015] Preferably, when preparing the mica tape, in step (2), 6 parts of composite functional filler are added, ultrasonically dispersed at 800 watts for 35 minutes, and then stirred at 800 rpm for 70 minutes to adjust the viscosity of the system to 3400 mPa·s; in step (3), a digital twin system is used to control the linear speed at 25 m / min. The digital twin system establishes a simulation model based on the real-time operating parameters of the coating machine and the feedback data of the coating thickness, and adaptively adjusts the pressure and discharge speed of the coating machine. The coating amount of the composite bonding system is 14 g / m², and the hot pressing bonding conditions are 145 degrees Celsius, 0.45 MPa, and 32 seconds; in step (4), the coating amount of the epoxy modified resin composition is 5.8 g / m²; in step (5), FTIR spectroscopy is used at 1720 cm⁻¹. -1 The crosslinking degree is monitored online at the characteristic peak, and the curing parameters are adjusted in real time according to the change of absorbance of the characteristic peak. The pre-curing conditions are 115 degrees Celsius and 32 minutes, and the final curing conditions are 210 degrees Celsius and 48 minutes. The crosslinking degree of the adhesive layer reaches 95%. In step (6), the thickness and flatness of the substrate are detected online with an accuracy of 0.001 mm and then cut into 40 mm wide strips. The strips are vacuum-packed with a vacuum degree of -0.095 MPa and the amount of silica gel desiccant added is 5 grams per square meter of the strip.

[0016] Preferably, the solid content of the epoxy modified resin composition is positively correlated with the coating amount, and the solid content of the epoxy modified resin composition increases by 0.5% for every 0.5 g / m² increase in coating amount.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The mica tape for fire-resistant cables and its molding process provided by this invention systematically optimizes many defects of the existing technology, and achieves a leapfrog improvement in the comprehensive performance of the fire-resistant mica tape, which has significant technical advantages and practical value.

[0018] 2. This invention uses a composite bonding system of organosilicon resin and epoxy modified resin, combined with a special curing agent, which effectively solves the inherent contradiction between the temperature resistance and adhesion of a single resin, and achieves synergistic optimization of temperature resistance and interlayer bonding strength. The adhesive layer has a high degree of crosslinking, which greatly improves the thermal aging stability of the product.

[0019] 3. In the application of fillers, this invention avoids the problem of filler agglomeration by performing surface modification treatment on the fillers, enhances the interfacial bonding force between the fillers and the resin, and the combination of micron-nano composite functional fillers forms a synergistic effect, which significantly improves the thermal conductivity, flame retardant performance and mechanical strength of the product.

[0020] 4. The selection of composite reinforcing substrate in this invention improves the overall structural stability of the substrate, so that the product does not crack or delaminate after cold and heat cycling, and its mechanical properties and environmental adaptability are greatly improved.

[0021] 5. The molding process of this invention adopts precise segmented curing, ultrasonic dispersion, intelligent coating control and other means to achieve precise adaptation of each process link, ensuring the consistency and stability of product performance. Online monitoring and high-precision post-processing further optimize product quality and improve weather resistance and storage stability.

[0022] 6. The technical solution of this invention is not a simple superposition of existing technical modules, but a collaborative design of various components and processes. It achieves simultaneous optimization of key properties such as fire resistance, insulation, thermal conductivity, mechanical properties, aging resistance, and corrosion resistance, which can meet the usage requirements of high-voltage cables. Moreover, all raw materials used are industrial-grade products that can be purchased, and the process equipment is conventional production equipment, which has good conditions for industrial implementation and has high promotion and application value. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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. Example

[0024] The core improvement of this embodiment lies in the use of a composite bonding system of silicone resin and epoxy modified resin, combined with zinc 2-ethylhexanoate curing agent.

[0025] Raw material composition (parts by weight): 70 parts synthetic mica powder, flake diameter D50 35 microns, 11 parts silicone resin, 11 parts epoxy modified resin (mass ratio 1:1), 1.76 parts zinc 2-ethylhexanoate (8% of the composite binder by weight), 22 g / m² alkali-free glass fiber cloth (0.028 mm thickness per square meter), and 5 parts epoxy modified resin composition (10% solid content).

[0026] Molding process: Mica powder pretreatment: Natural mica is magnetically separated to remove iron and hydraulically classified under a 12000 Gauss magnetic field. It is then hot-pressed and peeled off under 300 degrees Celsius and 0.8 MPa conditions, and wet-processed to produce synthetic mica paper. Adhesive preparation: Mix silicone resin and epoxy modified resin, add zinc 2-ethylhexanoate, stir at 500 rpm for 60 minutes, and adjust the viscosity to 3000 mPa second with polyether polyol to ensure that the resin and curing agent react fully. Coating and lamination: The adhesive is coated at a rate of 10 grams per square meter using a slot extrusion coating machine and then hot-pressed with mica paper at 120 degrees Celsius and 0.3 MPa for 20 seconds to ensure a tight bond between the layers; Adhesive coating: An epoxy-modified resin composition is coated on the other side of the mica paper at a rate of 5 grams per square meter to improve surface insulation; Segmented curing: 100 degrees Celsius infrared pre-curing for 40 minutes (infrared wavelength 2.5 micrometers), 180 degrees Celsius hot air final curing for 60 minutes (crosslinking degree 92%), ensuring uniform crosslinking of the adhesive layer; Post-processing: Laser slitting to 30 mm width, vacuum packaging with silica gel desiccant inside at -0.09 MPa to prevent moisture absorption and deterioration. Example

[0027] This embodiment adds a nano-silica filler with a surface modified by polyisocyanate to the composite bonding system of Example 1.

[0028] Raw material composition (parts by weight): 65 parts synthetic mica powder, flake diameter D50 40 microns, 18 parts organosilicon resin, 9 parts epoxy modified resin (mass ratio 2:1), 2.16 parts zinc 2-ethylhexanoate (8% of composite binder by weight), 3 parts modified silica (20 nanometer particle size), 0.15 parts polyisocyanate modifier, 22 g / m² alkali-free glass fiber cloth (0.028 mm thickness), and 5.5 parts epoxy modified resin composition (11% solid content).

[0029] Molding process: The mica powder was pretreated in the same way as in Example 1, with a magnetic field strength of 12000 Gauss to ensure the purity and uniformity of the mica powder flakes. Adhesive preparation: After mixing the resin, add zinc 2-ethylhexanoate, stir at 600 rpm for 80 minutes, add modified silica and ultrasonically disperse at 600 W for 30 minutes to ensure uniform dispersion of the filler, adjust the viscosity to 3200 mPa·s to match the coating requirements; Coating and lamination: The amount of composite adhesive applied is 12 grams per square meter, and hot-pressed at 130 degrees Celsius and 0.3 MPa for 25 seconds to extend the holding time and promote the wetting of the filler and adhesive layer; Topcoat coating: 5.5 grams per square meter, compatible with the coating amount of composite adhesive; Segmented curing: Pre-curing at 110 degrees Celsius for 35 minutes, and final curing at 190 degrees Celsius for 50 minutes, with a cross-linking degree of 93%, which enhances the cross-linking degree and strengthens the bonding force; The post-processing is the same as in Example 1 to ensure product storage stability. Example

[0030] Based on Example 2, this embodiment uses micron boron nitride-nano graphene composite functional filler and alkali-free glass fiber cloth-polyimide film composite substrate to improve thermal conductivity and flame retardant properties through the synergistic effect of micron-nano filler.

[0031] Raw material composition (parts by weight): 75 parts synthetic mica powder, flake diameter D50 40 micrometers, 10 parts silicone resin, 5 parts epoxy modified resin (mass ratio 2:1), 1.2 parts zinc 2-ethylhexanoate (8% of composite binder by weight), 8 parts composite functional filler, 6.67 parts modified boron nitride, 1.33 parts graphene (1 micrometer particle size), 0.8 nanometer thickness (all modified with polyisocyanate), 0.4 parts modifier, composite reinforcing substrate alkali-free glass fiber cloth and polyimide film composite with a total thickness of 0.03 mm, and 6 parts epoxy modified resin composition with a solid content of 12%.

[0032] Molding process: The mica powder pretreatment is the same as in Example 1 to ensure the quality of the base material; Adhesive preparation: Mix the resin and curing agent for 30 minutes, add the composite functional filler and ultrasonically disperse for 30 minutes at 600 watts to ensure that the two fillers are uniformly mixed and stably dispersed. Stir at 700 rpm for 90 minutes to achieve a viscosity of 3300 mPa·s, thereby strengthening the interfacial bonding between the filler and the resin. Composite substrate pretreatment: Hot pressing at 150 degrees Celsius and 0.5 MPa for 30 seconds to tightly bond the glass fiber cloth and polyimide film and improve the overall stability of the substrate; Coating and lamination: The amount of composite adhesive applied is 13 grams per square meter, and hot-pressing at 140 degrees Celsius and 0.4 MPa for 30 seconds promotes interlayer fusion by increasing pressure and temperature; Topcoat coating: 6 grams per square meter, matching the surface characteristics of the composite substrate; Segmented curing: Pre-curing at 120 degrees Celsius for 30 minutes, and final curing at 200 degrees Celsius for 45 minutes, achieving a crosslinking degree of 94%, further improving the crosslinking quality of the adhesive layer; Post-processing: 35 mm wide cutting, spraying with o-hydroxybenzoic acid phenyl ester anti-UV coating, spraying amount 0.5 g per square meter, vacuum packaging to improve the product's weather resistance. Example

[0033] Based on the synergistic system of Example 3, this embodiment achieves precise adaptation of each process step by step feeding process, digital twin system control of coating and composite process, and online monitoring of crosslinking degree by FTIR spectroscopy.

[0034] Raw material composition (parts by weight): 80 parts synthetic mica powder, flake diameter D50 45 micrometers, 9 parts organosilicon resin, 3 parts epoxy modified resin (mass ratio 3:1), 0.96 parts zinc 2-ethylhexanoate (8% of the composite binder by weight), 6 parts composite functional filler, 4.8 parts modified boron nitride, 1.2 parts graphene, 0.3 parts polyisocyanate modifier, composite reinforcing substrate (same as in Example 3), and 5.8 parts epoxy modified resin composition with a solid content of 11%.

[0035] Molding process: The mica powder pretreatment is the same as in Example 1, but the mica powder flake size is optimized to increase the bulk density; Adhesive preparation: The resin and curing agent are added in steps and stirred for 30 minutes to ensure initial reaction. Then, the composite functional filler is added and ultrasonically dispersed at 800 watts for 35 minutes to improve dispersion uniformity. The mixture is stirred at 800 rpm for 70 minutes to achieve a viscosity of 3400 mPa·s. Step-by-step operation avoids filler agglomeration. The composite substrate pretreatment is the same as in Example 3 to ensure stable substrate performance; Coating and lamination: The digital twin system controls the linear speed at 25 meters per minute, the coating amount at 14 grams per square meter, the temperature at 145 degrees Celsius and the pressure at 0.45 MPa for 32 seconds. The system adaptively adjusts the pressure and speed of the coating machine based on the real-time monitored coating thickness to ensure uniform coating. Topcoat application: 5.8 grams per square meter, precisely matching the amount of composite adhesive used; Segmented curing: FTIR online monitoring shows pre-curing at 115 degrees Celsius for 32 minutes and final curing at 210 degrees Celsius for 48 minutes, with a crosslinking degree of 95%. Curing parameters are adjusted in real time to ensure stable crosslinking degree. Post-processing: 0.001 mm precision online inspection, 40 mm wide slitting, -0.095 MPa vacuum packaging, silica gel desiccant dosage of 5 grams per square meter of strip, strict control of product appearance and storage conditions.

[0036] Comparative Example 1: Raw material composition: 70 parts synthetic mica powder, 22 parts epoxy modified resin, 1.76 parts zinc 2-ethylhexanoate, the rest are the same as in Example 1; A single epoxy adhesive without silicone resin is cured at a constant temperature of 180 degrees Celsius for 90 minutes without segmentation, simulating the existing single resin adhesive system.

[0037] Comparative Example 2: Raw material composition: 75 parts synthetic mica powder, 10 parts organosilicon resin, 5 parts epoxy modified resin, 1.2 parts zinc 2-ethylhexanoate, the rest are the same as in Example 3; The mixture was stirred at 600 rpm without any functional filler or ultrasonic dispersion step, simulating existing technologies with no filler or improperly added filler.

[0038] Comparative Example 3: Raw material composition: 70 parts synthetic mica powder, 11 parts organosilicon resin, 11 parts epoxy modified resin, 1.76 parts zinc 2-ethylhexanoate, 8 parts unmodified boron nitride, and the rest are the same as in Example 1; A single, unmodified filler was coated and cured at 180 degrees Celsius for 100 minutes, simulating a simple combination of existing modules.

[0039] Comparative Example 4: Raw material composition: 60 parts natural mica powder, 30 parts phenolic resin, 2.4 parts curing agent, single fiberglass cloth with no functional filler, 20 grams per unit area, and a thickness of 0.025 mm per square meter; Traditional roller coating involves applying 16 grams per square meter, curing at a constant temperature of 150 degrees Celsius for 120 minutes, and then naturally cooling and packaging, simulating existing conventional production processes.

[0040] Comparative Example 5: The raw material composition is the same as in Example 4; Process characteristics: Pre-curing at 70 degrees Celsius, final curing at 230 degrees Celsius, coating amount 7 grams per square meter, linear speed 35 meters per minute, the rest is the same as in Example 4, verifying the importance of process parameter adaptation.

[0041] To make the technical solution of this invention clearer and more complete, and to enable those skilled in the art to fully implement this invention, the specific implementation methods of the core raw material preparation, modification process, intelligent control and online monitoring, and auxiliary material addition specifications involved in this invention are now described in further detail: (1) The epoxy modified resin composition of the present invention is composed of bisphenol A type epoxy resin, polyethylene glycol diglycidyl ether and xylene formaldehyde resin in a mass ratio of 6:2:2. The preparation method is as follows: the bisphenol A type epoxy resin is heated to 60 degrees Celsius to melt, polyethylene glycol diglycidyl ether and xylene formaldehyde resin are added in sequence, the mixture is stirred at a speed of 300 rpm for 30 minutes, anhydrous ethanol is added to adjust the solid content to 10%-12%, and the mixture is cooled to room temperature to obtain the final product. The viscosity of the composition is 1500-2000 mPa·s (25 degrees Celsius).

[0042] (2) The polyisocyanate used for surface modification of the filler in this invention is diphenylmethane diisocyanate (MDI). The modification process is as follows: the filler is added to a high-speed mixer, heated to 80 degrees Celsius, diphenylmethane diisocyanate is added according to the ratio, stirred at a speed of 1000 rpm for 40 minutes, cooled to room temperature and discharged. The modified filler surface is grafted with isocyanate groups, and the bonding force with the resin interface is increased by more than 50%.

[0043] (3) The polyether polyol used in this invention is polyether polyol 330N, which is used as a viscosity modifier. The amount added is 2%-3% of the total mass of the composite bonding system. It can achieve precise adjustment of the viscosity of the composite bonding system without affecting the curing reaction and bonding performance of the system.

[0044] (4) The synthetic mica powder of the present invention has a flake diameter D50 of 35-45 micrometers and a bulk density of 0.6-0.8 g / cm³. These physical parameters make the synthetic mica powder tightly stacked between the mica paper layers formed after wet papermaking, resulting in the best fire resistance and insulation performance.

[0045] (5) The control logic of the digital twin system of the present invention is as follows: the thickness data of the coated substrate is collected in real time by a laser thickness gauge, and the data is transmitted to the digital twin simulation model. The model compares the deviation between the actual thickness and the preset thickness, sends an adjustment command to the coating machine, and adjusts the discharge pressure and linear speed of the coating machine in real time, with the deviation controlled within ±0.001 mm; the FTIR spectroscopy method for online monitoring of crosslinking degree is as follows: at 1720 cm⁻¹ -1 At the characteristic peak, when the absorbance of the characteristic peak drops to less than 10% of the initial value, it is determined that the crosslinking degree of the adhesive layer has reached the preset value, and the system automatically stops the curing process.

[0046] (6) The silica gel desiccant described in this invention is a fine-pore spherical silica gel with a water absorption rate of ≥30%. The amount of desiccant added for different specifications of mica tape is 2-5 grams per square meter of tape, which increases synchronously with the increase of the width and thickness of the mica tape. It can effectively prevent the product from absorbing moisture and deteriorating during storage, and the storage validity period can reach more than 24 months.

[0047] (7) The alkali-free glass fiber cloth and polyimide film composite substrate of the present invention has a unit area mass of 22 grams per square meter and a thickness of 0.028 mm, and a unit area mass of 3 grams per square meter and a thickness of 0.002 mm. After hot pressing, the two are not delaminated or wrinkled. The tensile strength of the substrate is increased by 30% compared with that of the single alkali-free glass fiber cloth.

[0048] The technical content of the above supplementary description of the present invention is compatible with the technical solutions in the specific embodiments. All raw materials are industrial-grade products that can be purchased, all process equipment are conventional production equipment, and all operating parameters can be achieved by conventional testing instruments and control equipment. Those skilled in the art can repeat the present invention and obtain the same technical effects based on the entire contents of the present invention specification without making any creative effort.

[0049] Performance testing and results analysis: Test basis and detailed test methods: (1) Fire resistance temperature test: According to the fire resistance test method in Clause 6.2 of GB / T5019.13-2023, the cable fire resistance test device model CNC-01 is used. The mica tape is wrapped around the conductor of the 10kV cable with a thickness of 1.5 mm. The cable is placed in a combustion furnace and continuously burned at 950 degrees Celsius ± 50 degrees Celsius for 180 minutes. At the same time, a 10kV rated voltage is applied and a withstand voltage tester model YD-2000 is used to continuously monitor the insulation continuity. The highest temperature corresponding to the condition that no breakdown occurs and the insulation resistance is ≥10MΩ is the fire resistance temperature. (2) Breakdown voltage strength test: According to the dielectric strength test method in Clause 5.3 of IEC60371-2, the BDJC-50 oil-immersed breakdown voltage tester was used. The mica tape was cut into 100mm×100mm samples with a thickness of 0.3mm. The samples were placed in transformer oil at 25 degrees Celsius ± 2 degrees Celsius with an electrode diameter of 50mm and a spacing of 2mm. The voltage rise rate was 2kV / s. The voltage value when the sample broke down was recorded. Breakdown voltage strength = breakdown voltage / sample thickness. (3) Tensile strength test: According to the mechanical property test method in Article 7.3 of GB / T19666-2019, the mica tape was cut into dumbbell-shaped specimens of 150mm×25mm with a gauge length of 50mm. The tensile rate was 50mm / min, the ambient temperature was 25 degrees Celsius ± 2 degrees Celsius, and the humidity was 50% ± 5%. The maximum tensile force when the specimen broke was recorded. Tensile strength = maximum tensile force / specimen width; (4) Thermal conductivity test: According to GB / T10297-2015 "Determination of thermal conductivity of non-metallic solid materials by hot wire method", a hot wire thermal conductivity tester model DRL-III was used. The mica tape was cut into 300mm×300mm samples with a thickness of 0.3mm. The ambient temperature was 25 degrees Celsius ± 2 degrees Celsius and the humidity was 50% ± 5%. The hot wire power was 5W / m and the test time was 60s. The thermal conductivity value at steady state was recorded. (5) Flame retardancy rating test: According to UL94-2013 "Test Method for Flammability of Plastic Materials", a horizontal and vertical flame tester model CZF-5 was used. The mica tape was cut into 125mm×13mm×0.3mm samples, placed vertically, and ignited twice at 10s intervals. The burning time, dripping situation and whether the degreased cotton below was recorded. The flame retardancy rating was determined according to the standard. (6) Thermal aging tensile strength retention rate test: According to GB / T2951.12-2008 "General test methods for insulation and sheath materials of cables and optical cables - Part 12: General test - thermal aging test method", the mica tape sample was placed in a thermal aging test chamber (model 401A) and aged at 300 degrees Celsius ± 2 degrees Celsius for 168 hours. After removal, it was placed in an environment of 25 degrees Celsius ± 2 degrees Celsius for 24 hours. The tensile strength after aging was tested according to the above tensile strength test method. Thermal aging tensile strength retention rate = (tensile strength after aging / tensile strength before aging) × 100%; (7) Thermal cycling performance test: According to IEC60068-2-14-2009 "Environmental testing - Part 2-14: Test methods - Test N: Temperature change", a high and low temperature alternating test chamber model GDW-100 was used. The mica tape was cut into 100mm×100mm samples. The cycling conditions were set as follows: -40 degrees Celsius for 2 hours, heating up to 200 degrees Celsius for 2 hours, cooling rate 5 degrees Celsius / min, heating rate 5 degrees Celsius / min, and a total of 10 cycles were performed. After taking it out, the sample surface was visually observed for cracks and delamination. A 5x magnifying glass was used for auxiliary inspection. (8) Corrosion resistance breakdown voltage retention rate test: According to GB / T2951.21-2008 "General test methods for insulation and sheath materials of cables and optical cables Part 21: tests for elastomer mixtures Ozone resistance test Heat extension test Mineral oil immersion test", the mica tape sample was immersed in a 5% sodium chloride aqueous solution at a temperature of 25 degrees Celsius ± 2 degrees Celsius for 72 hours. After being taken out, it was rinsed with distilled water and air-dried for 24 hours. The breakdown voltage strength after corrosion resistance was tested according to the breakdown voltage strength test method described above. Corrosion resistance breakdown voltage retention rate = (breakdown voltage strength after corrosion resistance / breakdown voltage strength before corrosion resistance) × 100%.

[0050] All testing equipment is standard testing equipment that can be purchased on the market. The testing environment conditions can be achieved through conventional environmental control equipment. The preparation size and processing method of the test samples are clearly defined, ensuring that all tests can be completed by those skilled in the art without creative labor.

[0051] The test results are shown in Table 1 below:

[0052] Test Result Analysis: (1) Example 1 overcomes the performance contradiction of single resin through composite bonding system. The fire resistance temperature is significantly improved compared with Comparative Example 1 with single epoxy adhesive and the breakdown voltage strength is greatly improved. It proves that the compounding of organosilicon resin and epoxy modified resin can achieve synergistic optimization of temperature resistance and adhesion. This improvement is not a simple change of resin type, but solves the inherent contradiction that has existed in the prior art for a long time through ratio adaptation and curing agent synergy. Example 2, after adding single modified silica, the thermal conductivity is further improved compared with Example 1 and the tensile strength is improved at the same time. It shows that the filler modified by polyisocyanate can effectively improve the interfacial bonding force and avoid the problem of easy agglomeration and easy peeling of unmodified filler. This effect cannot be obtained by directly adding unmodified filler. Example 3 uses composite functional fillers and composite substrates, which significantly improves the thermal conductivity and tensile strength compared to Comparative Example 2, which uses only a single filler. Furthermore, there is no delamination during thermal cycling, demonstrating the synergistic advantages of micron-nano fillers and composite substrates. This combination is not simply about increasing the types of fillers and the number of substrate layers, but rather about achieving a 1+1>2 technical effect through the adaptation of the characteristics of each component. Example 4 achieves optimal comprehensive performance through precise intelligent process control. The fire resistance temperature is significantly improved compared to Comparative Example 4, which uses conventional technologies. The breakdown voltage strength, thermal aging retention rate, and corrosion resistance retention rate all far exceed the levels of existing technologies. This proves that precise process control and adaptation of each step are key to maximizing performance, rather than simply increasing process parameters.

[0053] (2) Compared with the existing technology combination scheme of Comparative Example 3, the thermal conductivity and tensile strength of Embodiment 3 of the present invention are significantly improved, indicating that the technical solution of the present invention is not a simple superposition of the modules of the existing technology, but forms a synergistic effect of mutual adaptation and mutual promotion. The improvement steps of each embodiment are progressive, from the optimization of the bonding system to the modification of the filler, and then to the synergy of the substrate and the process. Each improvement is aimed at the specific defects of the existing technology, and the subsequent improvement is based on the previous optimization, ultimately achieving a leapfrog improvement in comprehensive performance. Comparative Example 5 suffered a significant performance decline due to the process parameters not being adapted to the system, further verifying the importance of precise matching of the technical links of the present invention. All embodiments meet the usage requirements of 10kV and above high voltage cables, and the raw materials are all industrial-grade procurable products, and the process equipment is conventional production equipment, which is fully capable of industrial implementation.

[0054] (3) It should be noted that the technical improvements of this invention cannot be obtained by those skilled in the art through conventional experiments. In the prior art, problems such as performance contradictions of single resins, uneven dispersion of fillers, and limitations in substrate performance have long existed. Related improvements are mostly concentrated on local adjustments of single modules. However, this invention solves the comprehensive performance shortcomings that cannot be addressed by individual improvements or simple combinations in the prior art through the collaborative design and precise adaptation of multiple modules. Test data show that the technical effect of this invention is not only the improvement of each individual performance, but also the simultaneous optimization of all key performances. This comprehensive breakthrough is impossible to achieve with the prior art. Moreover, the collaborative logic of each improvement link is clear and replicable, providing a brand-new technical path for the performance upgrade of refractory mica tape.

[0055] 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 the specific implementations described. 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.

Claims

1. A mica tape for fire-resistant cables, characterized in that, The composition, by weight, comprises 65-80 parts synthetic mica powder, 12-22 parts composite adhesive system, 8% zinc 2-ethylhexanoate curing agent (by weight of the composite adhesive system), alkali-free glass fiber cloth reinforcing substrate with a unit area mass of 22 g / m² and a thickness of 0.028 mm, and 5-6 parts epoxy modified resin composition surface adhesive layer; the composite adhesive system is composed of silicone resin and epoxy modified resin in a mass ratio of 1:1 to 3:1; the synthetic mica powder is obtained by magnetic separation to remove iron in a 12000 Gauss magnetic field, hydraulic classification, hot pressing and peeling at 300 degrees Celsius and 0.8 MPa, and wet papermaking, and the flake diameter D50 of the synthetic mica powder is 35-45 micrometers; the solid content of the epoxy modified resin composition is 10% to 12%.

2. The mica tape for fire-resistant cables according to claim 1, characterized in that, It also includes 3 parts of nano-silica filler modified with diphenylmethane diisocyanate, the amount of diphenylmethane diisocyanate added is 0.15 parts, and the particle size of the nano-silica filler is 20 nanometers.

3. The mica tape for fire-resistant cables according to claim 1, characterized in that, The reinforcing substrate is replaced by a composite substrate with a total thickness of 0.03 mm. The composite substrate is formed by hot pressing a 0.028 mm thick alkali-free glass fiber cloth and a 0.002 mm thick polyimide film together. It also includes 6-8 parts of micron boron nitride-nano graphene composite functional filler modified with diphenylmethane diisocyanate. The amount of diphenylmethane diisocyanate added is 0.3-0.4 parts. The particle size of the micron boron nitride is 1 micron. The thickness of the nano graphene is 0.8 nanometers.

4. The mica tape for fire-resistant cables according to claim 3, characterized in that, In the micron boron nitride-nano graphene composite functional filler, the mass ratio of micron boron nitride to nano graphene is 5:

1.

5. The mica tape for fire-resistant cables according to any one of claims 1 to 4, characterized in that, The mica tape surface is coated with a UV-resistant coating of 0.5 grams per square meter of phenyl hydroxybenzoate.

6. A molding process for preparing the mica tape for fire-resistant cables according to claim 1, characterized in that, Includes the following steps: (1) Mica powder pretreatment: After removing iron by magnetic separation with a magnetic field of 12000 Gauss and hydraulic classification, natural mica is hot-pressed and peeled off at 300 degrees Celsius and 0.8 MPa, and then wet-made into synthetic mica paper. (2) Preparation of adhesive: Mix silicone resin and epoxy modified resin at a mass ratio of 1:1 to 3:1, add 2-ethylhexanoate zinc curing agent accounting for 8% of the total mass of the composite adhesive system, stir at a speed of 500 rpm for 60 minutes, and adjust the viscosity of the system to 3000 mPa·s using polyether polyol 330N. The amount of polyether polyol 330N added is 2%-3% of the total mass of the composite adhesive system to obtain the composite adhesive system; (3) Coating and bonding: The composite bonding system is coated on one side of the synthetic mica paper at a coating amount of 10 grams per square meter using a slot extrusion coating machine, and then hot-pressed with alkali-free glass fiber cloth at 120 degrees Celsius and 0.3 MPa for 20 seconds. (4) Topcoat coating: Apply an epoxy modified resin composition to the other side of the synthetic mica paper at a coating amount of 5 grams per square meter to form a topcoat layer; (5) Segmented curing: First, pre-curing at 100 degrees Celsius with 2.5 micrometer infrared wavelength for 40 minutes, and then hot air curing at 180 degrees Celsius for 60 minutes to achieve a cross-linking degree of 92% for the adhesive layer; (6) Post-processing: The cured substrate is laser-cut into 30 mm wide strips and vacuum-packed with a vacuum degree of -0.09 MPa. Silica gel desiccant is placed inside the packaging, and the amount of silica gel desiccant added is 2 grams per square meter of strip.

7. The molding process according to claim 6, characterized in that, When preparing the mica tape according to claim 2, in step (2), before adjusting the viscosity, add 3 parts of nano-silica filler modified with diphenylmethane diisocyanate, disperse it with ultrasonic at 600 watts for 30 minutes, and then stir it at 600 rpm for 80 minutes to adjust the viscosity of the system to 3200 mPa second; in step (3), the coating amount of the composite bonding system is 12 g per square meter, and the hot pressing bonding conditions are 130 degrees Celsius, 0.3 MPa, and 25 seconds; in step (4), the coating amount of the epoxy modified resin composition is 5.5 g per square meter; in step (5), the pre-curing conditions are 110 degrees Celsius and 35 minutes, and the final curing conditions are 190 degrees Celsius and 50 minutes, and the crosslinking degree of the adhesive layer reaches 93%; in step (6), the amount of silica gel desiccant added is 3 g per square meter of tape.

8. The molding process according to claim 6, characterized in that, When preparing the mica tape according to claim 3, firstly, alkali-free glass fiber cloth and polyimide film are hot-pressed together at 150 degrees Celsius and 0.5 MPa for 30 seconds to obtain a composite substrate; in step (2), 6-8 parts of diphenylmethane diisocyanate modified micron boron nitride-nano graphene composite functional filler are added, ultrasonically dispersed at 600 watts for 30 minutes, and then stirred at 700 rpm for 90 minutes to adjust the viscosity of the system to 3300 mPa second; in step (3), the coating amount of the composite bonding system is 13 grams per square meter, and it is bonded to the composite substrate. Hot-press bonding at 140 degrees Celsius and 0.4 MPa for 30 seconds; in step (4), the amount of epoxy modified resin composition coated is 6 grams per square meter; in step (5), the pre-curing conditions are 120 degrees Celsius and 30 minutes, and the final curing conditions are 200 degrees Celsius and 45 minutes, with the cross-linking degree of the adhesive layer reaching 94%; in step (6), the cutting width is 35 mm, and after cutting, 0.5 grams per square meter of o-hydroxybenzoic acid phenyl ester anti-UV coating is sprayed, and then vacuum packaging is performed with a vacuum degree of -0.09 MPa, with the amount of silica gel desiccant added being 4 grams per square meter of the tape.

9. The molding process according to claim 8, characterized in that, When preparing the mica tape according to claim 4, 6 parts of composite functional filler are added in step (2), and the mixture is ultrasonically dispersed at 800 watts for 35 minutes, and then stirred at 800 rpm for 70 minutes to adjust the viscosity of the system to 3400 mPa second. In step (3), a digital twin system is used to control the linear speed at 25 meters per minute. The digital twin system establishes a simulation model based on the real-time operating parameters of the coating machine and the feedback data of the coating thickness, and adaptively adjusts the pressure and discharge speed of the coating machine. The coating amount of the composite bonding system is 14 grams per square meter, and the hot pressing bonding conditions are 145 degrees Celsius, 0.45 MPa, and 32 seconds. In step (4), the coating amount of the epoxy modified resin composition is 5.8 grams per square meter. In step (5), FTIR spectroscopy is used at 1720 cm⁻¹. -1 The crosslinking degree is monitored online at the characteristic peak, and the curing parameters are adjusted in real time according to the change of absorbance of the characteristic peak. The pre-curing conditions are 115 degrees Celsius and 32 minutes, and the final curing conditions are 210 degrees Celsius and 48 minutes. The crosslinking degree of the adhesive layer reaches 95%. In step (6), the thickness and flatness of the substrate are detected online with an accuracy of 0.001 mm and then cut into 40 mm wide strips. The strips are vacuum-packed with a vacuum degree of -0.095 MPa and the amount of silica gel desiccant added is 5 grams per square meter of the strip.

10. The molding process according to any one of claims 6 to 9, characterized in that, The solid content of the epoxy modified resin composition is positively correlated with the coating amount; for every 0.5 g / m² increase in coating amount, the solid content of the epoxy modified resin composition increases by 0.5%.

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