Fire resistant copper core polyvinyl chloride insulated cable

Abstract

The application discloses a fireproof copper core polyvinyl chloride insulated cable, and belongs to a shielded control cable. The cable is composed of a plurality of cable cores, and each cable core is composed of a conductor and a polyvinyl chloride fireproof insulation layer. In addition to the core layer composed of the plurality of cable cores, a metal braided shielding layer and a polyvinyl chloride fireproof sheath are sequentially arranged. The KVVP cable is mainly characterized in that the polyvinyl chloride fireproof insulation layer and the polyvinyl chloride fireproof sheath are arranged, so that the cable has the advantages of fireproof class A and heat aging resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of control cables, in particular to a fire-resistant copper core polyvinyl chloride insulated cable. Background Art

[0002] KVVP cable is a kind of copper core polyvinyl chloride insulated polyvinyl chloride sheathed shielded control cable, which is suitable for connection of control, monitoring circuits and protection lines with rated voltage 450 / 750V and below, and is mainly used for suppressing electromagnetic interference. Its structure comprises a copper core conductor, a fire-resistant layer, a polyvinyl chloride insulating layer, a shielding layer and a sheath.

[0003] The industry requires KVVP cables to have the characteristic of high-temperature aging resistance to improve their applicable environments. In the prior art, the main methods for improving the heat resistance of PVC are: 1. Introducing PVC with high chlorine content, such as chlorinated PVC, which is highly corrosive to metals and is rarely used in the cable field. 2. Introducing heat-resistant modifiers or other resins, such as SMA and modified thermoplastic polyurethane (refer to CN119661955A).

[0004] In the prior art, for fire-resistant cables of 450 / 750 specification KVVP cables, according to different fire-resistant grades, Class A fire resistance requires 90 minutes of burning at 950~1000°C, during which the rated voltage is applied throughout the burning process and a 3A current is maintained, and no circuit breakage or breakdown occurs. In addition, if the 15-minute voltage withstand test after flameout is carried out according to regulations and no abnormality is found, the fire resistance can be determined as qualified. However, the oxygen index of generally modified PVC composites for cables can only reach 25~30%, which is due to the addition of plasticizers and other organic additives. It is barely flame-retardant, but it is too hard if no plasticizer is added, and can only be used in rigid PVC cables and other products. Therefore, most of the fire-resistant KVVP or KVV cables sold on the market use mica fire-resistant tapes. However, this will increase the thickness, preparation processes and costs. There are also products that make PVC have fire-resistant properties through ceramic forming modification. However, studies have shown that when PVC contains more ceramic forming agent, especially ceramic forming agents with large specific surface area and containing alkaline substances (metal oxides: iron oxide, magnesium oxide, calcium oxide, aluminum oxide, etc.) or metal impurities such as iron (such as kaolin, talc, sepiolite, montmorillonite, etc.) will deteriorate the high-temperature (above 100°C) aging resistance.

[0005] Therefore, developing a fire-resistant and high-temperature-resistant KVVP cable has a good market prospect. Summary of Invention

[0006] The objective of the present invention is to provide a copper core polyvinyl chloride insulated cable with good fire resistance and high temperature resistance, and also to provide raw materials for a polyvinyl chloride fire-resistant insulating layer and a polyvinyl chloride fire-resistant sheath.

[0007] This invention is achieved through the following technical solution:

[0008] A fire-resistant copper core polyvinyl chloride (PVC) insulated cable is provided. The cable consists of multiple cable cores, each core comprising a conductor and a PVC fire-resistant insulation layer. Surrounding the core layer, which is formed by stranding multiple cable cores, are a metal braided shielding layer and a PVC fire-resistant sheath. The raw materials for the PVC fire-resistant insulation layer and the PVC fire-resistant sheath, by weight percentage, include: PVC A 35-45%, plasticizer 15-25%, inorganic fiber 1-5%, stabilizer 0.5-3%, and refractory masterbatch with a D50 particle size of 80-170 micrometers 30-45%. The refractory masterbatch, by weight percentage, includes: PVC... The composition comprises 15-25% polyvinyl chloride B with a melting point of 1200-2200, 35-55% compound ceramic filler, 3-7% ceramic additive, 10-25% inorganic fiber, 0.5-2.5% irradiation crosslinking agent, 1-4% lubricant, and 0.5-2% stabilizer. The weight ratio of polyvinyl chloride B to irradiation crosslinking agent is (10-30):1. The compound ceramic filler consists of a main component and a minor component. The main component accounts for 55-100% and is low-melting-point glass powder. The minor component is selected from one or more of kaolin, wollastonite, montmorillonite, and talc. The ceramic additive is low-magnesium sepiolite.

[0009] Sepiolite is a magnesium oxide-containing silicate mineral. Untreated sepiolite has an irregular structure with micropores on its surface. This invention uses alkaline and acid etching to remove alkaline magnesium oxide or other small amounts of metal oxide impurities through the micropores. This increases the silicon content, improving its porcelain-forming properties. Furthermore, the porous and angular nature of the treated sepiolite acts as a core during flame firing, accelerating the porcelain-forming process and preventing collapse and expansion.

[0010] The low-magnesium sepiolite mentioned above is obtained by successively etching sepiolite through alkaline etching, acid etching, water washing, and drying. The specific process is as follows:

[0011] Step 1) Immerse the sepiolite in an alkaline solution at 40~90℃ for 0.5~2 hours, then filter out the solution;

[0012] Step 2) Immerse it in an acid solution at 60~90℃ for 3~6 hours, then filter out the solution;

[0013] Step 3) Wash with water, dry, and disperse by vibration.

[0014] In the alkaline etching step, the alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide, with a mass concentration of 10–50 g / L. In the acid etching step, the acid solution is an aqueous solution of hydrochloric acid or sulfuric acid, with a mass concentration of 20–80 g / L for the hydrochloric acid solution and 60–140 g / L for the sulfuric acid solution. The water used in the water washing step is deionized water.

[0015] Preferably, in the composite ceramic filler, the main component accounts for 75-85% of the composite ceramic filler, and the minor component accounts for 15-25% of the composite ceramic filler.

[0016] The D50 particle size range of ceramic fillers and low-magnesium sepiolite is 6~20 micrometers.

[0017] The irradiation crosslinking agent is selected from any one or more of triallyl isocyanurate, trimethylolpropane triacrylate, and triallyl trimellitate; the stabilizer is selected from any one of organotin stabilizers and calcium-zinc stabilizers (zinc stearate stabilizer, calcium stearate stabilizer); the organotin stabilizer is selected from any one or more of methyltin and butyltin; the calcium-zinc stabilizer is selected from any one or more of zinc stearate, calcium stearate, zinc laurate, and calcium silicate; the inorganic fiber is selected from any one or more of glass fiber, basalt fiber, and mica fiber; the plasticizer is selected from any one or more of dinonyl terephthalate, dioctyl sebacate, dioctyl terephthalate, diisononyl cyclohexane-1,2-dicarboxylate, tributyl acetylacetonate, epoxidized soybean oil, trioctyl trimellitate, and triphenyl phosphate; the lubricant is selected from any one or more of polyethylene wax, oxidized polyethylene wax, stearic acid, and chlorinated paraffin.

[0018] The degree of polymerization of the polyvinyl chloride A is in the range of 800 to 2500.

[0019] The melting point of the low-melting-point glass powder is 400~1000℃.

[0020] The D50 particle size of inorganic powder and refractory masterbatch was tested by a laser particle size analyzer.

[0021] Preferably, the inorganic fiber is selected from basalt fiber.

[0022] The raw materials for the PVC fire-resistant insulation layer and the PVC fire-resistant sheath, calculated by weight percentage, also include 0-1% antioxidant.

[0023] The preparation method of the refractory masterbatch is as follows: polyvinyl chloride B, stabilizer, irradiation crosslinking agent and lubricant are stirred and mixed at 80~120℃, then the composite ceramic filler, ceramic additive and inorganic fiber are added and stirred and mixed at 120~150℃, and finally extruded and granulated at a temperature range of 80~170℃, and then obtained by freeze crushing, sieving and irradiation, wherein the irradiation dose is 3~10Mrad.

[0024] Preparation methods of polyvinyl chloride refractory insulation layer material and polyvinyl chloride refractory sheath material:

[0025] Step 1) Mix polyvinyl chloride A, plasticizer, and stabilizer at 80~120℃;

[0026] Step 2) Add inorganic fibers and refractory masterbatch and stir and mix at 140~180℃ to obtain the preform;

[0027] Step 3) Extrusion granulation, with a temperature range of 80~170℃ to obtain granules.

[0028] This invention also relates to a method for preparing a fire-resistant copper core polyvinyl chloride insulated cable:

[0029] (1) A cable core is obtained by extruding a polyvinyl chloride fire-resistant insulation layer around a copper wire core;

[0030] (2) Wrap multiple cable cores with a metal braided shielding layer, and then extrude a polyvinyl chloride fire-resistant sheath to obtain a fire-resistant copper core polyvinyl chloride insulated cable.

[0031] The present invention also relates to a refractory masterbatch for a polyvinyl chloride refractory insulation layer, comprising, by weight percentage: 15-25% polyvinyl chloride B with a degree of polymerization of 1200-2200, 35-55% compound ceramic filler, 3-7% ceramic additive, 10-25% inorganic fiber, 0.5-2.5% irradiation crosslinking agent, 1-4% lubricant, and 0.5-2% stabilizer. The weight ratio of polyvinyl chloride B to irradiation crosslinking agent is (10-30):1. The compound ceramic filler is composed of a main component and a minor component, with the main component accounting for 55-100%. The main component is low-melting-point glass powder, and the minor component is selected from one or more of kaolin, wollastonite, montmorillonite, and talc. The ceramic additive is low-magnesium sepiolite.

[0032] The technical measures of this invention have the following advantages compared with the prior art:

[0033] (1) The refractory masterbatch of the present invention has the following characteristics: 1. A specific content of low-magnesium sepiolite can promote the ceramic-forming performance of ceramic fillers, especially promoting the ceramicization of low-melting-point glass powder. 2. A specific content of inorganic fibers can prevent collapse before ceramicization. 3. High-polymerization-degree PVC is selected and the degree of crosslinking is controlled so that the refractory masterbatch inhibits the release of ceramic fillers into the resin matrix during processing to improve high-temperature aging resistance. At the same time, a suitable degree of crosslinking can maintain flexibility and not significantly reduce the elongation at break. A suitable degree of crosslinking also gives the refractory masterbatch a certain degree of softness and plasticity, ensuring that a smooth cable sheath is obtained. 4. Refractory masterbatch with a suitable particle size can simultaneously achieve the advantages of fire resistance and smooth cable sheath. 5. A suitable particle size is the key to simultaneously obtaining fire resistance, tensile properties, heat aging resistance, and smooth cable sheath.

[0034] (2) The polyvinyl chloride refractory insulation material of the present invention also contains a specific amount of inorganic fiber. During the processing, the fiber can penetrate into the refractory masterbatch to form a stable ceramic network, preventing it from collapsing and deforming before it is ceramicized by flame. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit of the present invention. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0036] Example of a fire-resistant copper core polyvinyl chloride cable of the present invention: Cable core: 1 copper conductor (cross-sectional area 6mm²) 2 The cable has a 0.9mm thick PVC fire-resistant insulation layer, is made of 37 stranded cores, and features a copper fiber braided tape (single wire diameter 0.30mm, braiding density 82%) and a 2.4mm thick PVC fire-resistant sheath.

[0037] Materials used in the experiment:

[0038] PVC-1: Degree of polymerization 1000, TL1000, Tianjin LG Bohai Chemical Co., Ltd.

[0039] PVC-2: Polymerization degree 1600, cable grade PVC, purchased from Ningbo Zihong Plastics Co., Ltd.

[0040] PVC-3: Degree of polymerization 2150, cable grade PVC, purchased from Ningbo Zihong Plastics Co., Ltd.

[0041] PVC-4: Degree of polymerization 2500, cable grade PVC, purchased from Ningbo Zihong Plastics Co., Ltd.

[0042] Sepiolite-1: Screened D50 particle size 8.7 microns, ADINS® Clay 20, purchased from TOLSA.

[0043] Sepiolite-2: Purchased from Leibao Sepiolite Processing Co., Ltd., Wolong District, Nanyang City.

[0044] Low melting point glass powder: screened D50 particle size 10 microns, CA450, purchased from Guangzhou Geliner New Materials Co., Ltd.

[0045] Kaolin: Screened with a D50 particle size of 12 microns, purchased from Hebei Huishun Mining Co., Ltd.

[0046] Montmorillonite: screened with a D50 particle size of 15 micrometers, purchased from Zhejiang Fenghong.

[0047] Wollastonite: Screened D50 particle size 19 microns, commercially available.

[0048] Talc powder: AH-1250, screened D50 particle size 10 microns, purchased from Guangxi Longsheng Huamei Talc Development Co., Ltd.

[0049] Basalt fiber: length range 2-8mm, diameter 10-13 microns, purchased from Sichuan Aerospace Tuoxin Basalt Industry Co., Ltd.

[0050] Short-cut fiberglass: 3-6 mm in length, 13 micrometers in diameter, purchased from China Jushi.

[0051] Dioctyl terephthalate (DOTP): Purchased from Jinan Runtian Chemical Co., Ltd.

[0052] Epoxidized soybean oil (ESO): Purchased from Jinan Runtian Chemical Co., Ltd.

[0053] Polyethylene wax: AC-617A, melting point 105℃, purchased from Honeywell.

[0054] Trimethylolpropane triacrylate (TMPTMA): CAS15625-89-5, molecular weight 296.316, commercially available.

[0055] Triallyl isocyanurate (TAIC): CAS202-936-7, molecular weight 249.27, commercially available.

[0056] Zinc stearate stabilizer: commercially available.

[0057] Preparation method of low magnesium sepiolite: Sepiolite (-1 or -2) is immersed in a 25 g / L sodium hydroxide aqueous solution and etched at 70°C for 45 minutes, then the solution is filtered off; then it is immersed in a 40 g / L sulfuric acid aqueous solution and etched at 80°C for 3.5 hours, then the solution is filtered off; finally, it is washed three times with deionized water, dried, dispersed by vibration, and sieved.

[0058] Table 1: Parameters of Low-Magnesium Sepiolite

[0059]

[0060] Calcined sepiolite: Sepiolite-1 is placed in a muffle furnace and baked at 800℃ for 2 hours. After drying, it is vibrated and dispersed, and then sieved to a D50 particle size of 15 micrometers.

[0061] Alkali etching of sepiolite: Sepiolite-1 is immersed in a 25g / L sodium hydroxide aqueous solution and etched at 70℃ for 45 minutes. The solution is then filtered off, and the product is washed three times with deionized water, dried, vibrated and dispersed, and sieved to a D50 particle size of 14 micrometers.

[0062] Acid etching of sepiolite: Sepiolite-1 is immersed in a 40g / L sulfuric acid aqueous solution and acid etched at 80℃ for 3.5 hours. The solution is then filtered off, and the product is washed three times with deionized water, dried, vibrated and dispersed, and sieved to a D50 particle size of 18 micrometers.

[0063] Preparation method of refractory masterbatch: Polyvinyl chloride, stabilizer, irradiation crosslinking agent, and polyethylene wax are stirred and mixed at 90~110℃. Then, ceramic filler, ceramic additive, and inorganic fiber are added and stirred and mixed at 130~140℃. Finally, the mixture is extruded and granulated (temperature settings for each zone: 80~100℃, 100~120℃, 150~170℃, 160~180℃, 160~180℃, 170~190℃). The refractory masterbatch is then obtained by cryogenic pulverization, sieving, and irradiation (irradiation dose of 5.5 Mrad; B-11 is not irradiated).

[0064] Table 2: Parameters A of Refractory Masterbatch (%)

[0065]

[0066] Table 3: Parameters B of Refractory Masterbatch (%)

[0067]

[0068] Table 4: Parameters B of Refractory Masterbatch (%)

[0069]

[0070] Preparation method of polyvinyl chloride refractory sheath material: Polyvinyl chloride, plasticizer, and stabilizer are stirred and mixed at 100~110℃; basalt fiber and refractory masterbatch are added and stirred and mixed at 150~170℃ to obtain preform; extrusion granulation is carried out, with the temperature set as follows: Zone 1 70~90℃, Zone 2 90~110℃, Zone 3 140~160℃, Zone 4 150~160℃, Zone 5 150~170℃, Zone 6 160~180℃.

[0071] Test methods for various properties of polyvinyl chloride refractory sheathing materials:

[0072] (1) Refractory Class A: Refer to GB 12666.6-Class A test, continuously burn at a flame temperature of 950~1000℃ for 90min, apply rated voltage and 3A additional current throughout the combustion process, and observe whether breakdown or open circuit occurs. If the above test is passed, after the test, observe whether the surface of the carbon layer or porcelain layer at the burning point is flat (such as cavitation or collapse, cavitation or collapse less than 0.2mm is slight deformation, cavitation or collapse more than 0.3mm is obvious deformation). If there is no deformation or slight deformation, it indicates that the porcelain formation is fast and the porcelain formation process does not shrink.

[0073] (2) Heat resistance aging: Aging at 100℃ for 168 hours in an air oven, then removing and bringing to room temperature, and testing the elongation at break.

[0074] (3) Elongation at break: Tested according to GB / T 2951.11-2008.

[0075] Table 5: Content (%) of PVC Refractory Insulation / Sheath Material and Experimental Results

[0076]

[0077] Continued from Table 5:

[0078]

[0079] Examples 1 / 6 / 10 / 11 illustrate that the preferred main component of the ceramic filler accounts for 75-85% of the compound ceramic filler. This not only maintains a high elongation at break, but also has good heat aging resistance and does not deform after sintering, indicating that the presence of a certain amount of secondary ceramic agent can improve the rapid ceramic formation.

[0080] Comparative Example 1 shows that when PVC with a lower degree of polymerization is selected, inorganic substances such as ceramic fillers and ceramic additives are easily released during the processing. This not only reduces the heat aging resistance, but also reduces the ceramic forming speed due to the reduced montmorillonite content in the refractory masterbatch, resulting in significant deformation.

[0081] Comparative Example 2 shows that when the degree of polymerization of PVC is high, the elongation at break decreases significantly. The refractory masterbatch has too high toughness, which prevents inorganic fibers from penetrating and makes it easy to collapse during the fire resistance test. In addition, the cable sheath has small bumps.

[0082] Continued from Table 5:

[0083]

[0084] Comparative Examples 3 / 4 / 5 / 6 indicate that untreated sepiolite or sepiolite treated by other methods is unlikely to achieve the effect of promoting porcelain formation. Alkali-etched sepiolite is relatively better, but the carbon layer is also obviously deformed. After testing, Comparative Examples 3 / 4 / 6 can only achieve Class B refractory performance, and the carbon layer at the burning point is obviously uneven after the test.

[0085] Comparative Examples 7-10 show that when kaolin, montmorillonite, wollastonite, and talc are selected as fillers for ceramic PVC, the high-temperature aging resistance of PVC is significantly reduced, and the fire resistance is insufficient.

[0086] Continued from Table 5:

[0087]

[0088] Comparative Example 11 shows that non-crosslinked refractory masterbatch will cause the ceramic-forming agent to disperse during processing, which will reduce the ceramic-forming performance on the one hand and deteriorate the heat aging resistance on the other.

[0089] Comparative Example 12 shows that when the content of irradiation crosslinking agent is too high, the degree of crosslinking will increase. During the processing, inorganic fibers have difficulty penetrating the refractory masterbatch to form a good ceramic network. If the flame burning time is prolonged, the fibers are likely to be broken down by the current. In addition, the cable sheath is not smooth and the initial elongation at break is also low.

[0090] Comparative Example 13 shows that when the content of the irradiation crosslinking agent is too low, the effect is slightly better than that of Comparative Example 11.

[0091] Comparative Example 14 shows that the refractory masterbatch size is too small, and each masterbatch contains less ceramic filler and ceramic additives, which reduces the ceramic performance; at the same time, the ceramic filler in many masterbatches is exposed on the surface, which leads to a significant decrease in heat aging resistance.

[0092] Comparative Example 15 shows that when the particle size of the refractory masterbatch is too large, it will not only significantly reduce the elongation at break and make the cable sheath uneven, but also make it easy for deformation to occur during the fire resistance test.

[0093] Comparative Example 16 shows that the refractory performance does not reach Grade A without low-magnesium talc.

[0094] Comparative Example 17 shows that when the PVC resin matrix does not contain inorganic fibers, it cannot penetrate the refractory masterbatch to form a ceramic network, which is prone to collapse during the firing process, resulting in poor refractory performance.

Claims

1. A fire-resistant copper core polyvinyl chloride insulated cable, the cable being composed of multiple cable cores, characterized in that, The cable core consists of a conductor and a fire-resistant polyvinyl chloride insulation layer; outside the core layer, which is composed of multiple cable cores twisted together, are a metal braided shielding layer and a fire-resistant polyvinyl chloride sheath. The raw materials for the PVC refractory insulation layer and the PVC refractory sheath, calculated by weight percentage, include: PVC A 35-45%, plasticizer 15-25%, inorganic fiber 1-5%, stabilizer 0.5-3%, and refractory masterbatch with a D50 particle size of 80-170 micrometers 30-45%; wherein, calculated by weight percentage of the refractory masterbatch, it includes: PVC B with a degree of polymerization of 1200-2200 15-25%, composite ceramic filler 35-55%, and ceramic... The compound ceramic filler comprises 3-7% additives, 10-25% inorganic fibers, 0.5-2.5% irradiation crosslinking agent, 1-4% lubricant, and 0.5-2% stabilizer. The weight ratio of polyvinyl chloride B to irradiation crosslinking agent is (10-30):

1. The compound ceramic filler consists of a main component and a minor component. The main component accounts for 55-100%. The main component is low-melting-point glass powder. The minor component is selected from one or more of kaolin, wollastonite, montmorillonite, and talc. The ceramic additive is low-magnesium sepiolite.

2. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The low-magnesium sepiolite mentioned above is obtained by successively etching sepiolite through alkaline etching, acid etching, water washing, and drying.

3. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, In the aforementioned composite ceramic filler, the main component accounts for 75-85% of the composite ceramic filler, and the minor component accounts for 15-25% of the composite ceramic filler; the D50 particle size range of the ceramic filler and low-magnesium sepiolite is 6-20 micrometers.

4. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The irradiation crosslinking agent is selected from any one or more of triallyl isocyanurate, trimethylolpropane triacrylate, and triallyl trimellitate; the stabilizer is selected from any one of organotin stabilizers and calcium-zinc stabilizers, the organotin stabilizer is selected from any one or more of methyltin and butyltin, the calcium-zinc stabilizer is selected from any one or more of zinc stearate, calcium stearate, zinc laurate, and calcium silicate; the inorganic fiber is selected from any one or more of glass fiber, basalt fiber, and mica fiber; the plasticizer is selected from any one or more of dinonyl terephthalate, dioctyl sebacate, dioctyl terephthalate, diisononyl cyclohexane 1,2-dicarboxylate, tributyl acetylacetonate, epoxidized soybean oil, trioctyl trimellitate, and triphenyl phosphate; the lubricant is selected from any one or more of polyethylene wax, oxidized polyethylene wax, stearic acid, and chlorinated paraffin.

5. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The degree of polymerization of the polyvinyl chloride A is in the range of 800 to 2500.

6. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The melting point of the low-melting-point glass powder is 400~1000℃.

7. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The inorganic fiber is selected from basalt fiber.

8. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The raw materials for the PVC fire-resistant insulation layer and the PVC fire-resistant sheath, calculated by weight percentage, also include 0-1% antioxidant.

9. The fire-resistant copper core polyvinyl chloride insulated cable according to claim 1, characterized in that, The preparation method of the refractory masterbatch is as follows: polyvinyl chloride B, stabilizer, irradiation crosslinking agent and lubricant are stirred and mixed at 80~120℃, then compounded ceramic filler, ceramic additive and inorganic fiber are added, and then extruded and granulated at 120~150℃. Then, the refractory masterbatch is obtained by freeze crushing, sieving and irradiation, wherein the irradiation dose is 3~10Mrad.

10. A refractory masterbatch for polyvinyl chloride refractory insulation layers, characterized in that, The refractory masterbatch comprises, by weight percentage: 15-25% polyvinyl chloride B with a degree of polymerization of 1200-2200, 35-55% composite ceramic filler, 3-7% ceramic additive, 10-25% inorganic fiber, 0.5-2.5% irradiation crosslinking agent, 1-4% lubricant, and 0.5-1.5% stabilizer. The weight ratio of polyvinyl chloride B to irradiation crosslinking agent is (10-30):

1. The composite ceramic filler consists of a main component and a minor component, with the main component accounting for 55-100%. The main component is low-melting-point glass powder, and the minor component is selected from one or more of kaolin, wollastonite, montmorillonite, and talc. The ceramic additive is low-magnesium sepiolite, and the irradiation crosslinking agent is selected from any one or more of triallyl isocyanurate, trimethylolpropane triacrylate, and trimellitic acid triallyl.

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