Low-temperature-resistant flame-retardant anti-ultraviolet PVC (polyvinyl chloride) cable sheath composition, preparation method thereof and cable

Abstract

The invention relates to the technical field of cable preparation, in particular to a low-temperature-resistant flame-retardant anti-ultraviolet PVC cable sheath composition, a preparation method thereof and a cable. According to the composition, polyvinyl chloride is used as a matrix, chlorinated polyethylene elastomer, an environment-friendly plasticizer and a calcium-zinc stabilizer are used as auxiliary materials, nanoscale magnesium hydroxide, zinc stannate, passivated zinc borate, sodium tungstate and modified montmorillonite are introduced to form a multi-component synergistic flame-retardant system, and the flame retardance, the low smoke property and the thermal stability of the material are remarkably improved. Meanwhile, through the cooperation of the ultraviolet light absorber and the antioxidant, the weather resistance of the material is enhanced, and the service life of the material is prolonged. The prepared cable sheath material has excellent low-temperature flexibility, flame retardance and smoke suppression performance and ultraviolet aging resistance, and is suitable for high-performance cables in severe environments.

Description

Technical Field

[0001] The present invention relates to the technical field of cable preparation, and particularly relates to a low-temperature resistant, flame-retardant, anti-ultraviolet PVC cable sheath composition, a preparation method thereof, and a cable. Background Art

[0002] Due to its excellent processing performance, mechanical strength, and low cost, polyvinyl chloride (PVC) materials have been widely used in the field of cable sheaths. However, with the increasingly strict requirements for the cable use environment in the fields of electric power, communication, and industrial automation, it is difficult to meet the performance requirements in multiple aspects such as high and low temperature environments, flame retardancy, ultraviolet aging resistance, and low smoke by relying on traditional formulations alone. For example, in a low-temperature environment (such as cold outdoor areas), conventional PVC sheaths are prone to problems such as hardening and cracking; at the same time, in the event of a fire, the flame retardancy efficiency and smoke suppression performance of some traditional PVC sheath materials are insufficient, which may lead to the release of high-concentration toxic smoke during combustion, causing secondary harm. In addition, cables exposed outdoors for a long time also need to withstand ultraviolet irradiation. Without an effective ultraviolet light shielding or absorption system, the sheath material will accelerate aging and cracking, seriously affecting the service life of the cable.

[0003] In order to improve the comprehensive performance of PVC cable sheaths, the industry usually modifies them in the following ways: 1. Adding flexible components such as plasticizers and elastomers: Plasticizers (such as DOA, DOP, etc.) and elastomers (such as chlorinated polyethylene CPE) can endow PVC with certain flexibility and low-temperature tolerance performance. However, excessive use of plasticizers will lead to a decline in the mechanical properties of the material and even plasticizer migration; at the same time, the low-temperature performance improvement of general elastomers is limited and difficult to meet the application requirements in extreme climates; 2. Introducing various inorganic fillers and flame retardants: The typical method is to add magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3), or phosphorus-based flame retardants, etc., to inhibit the thermal decomposition and combustion of PVC at high temperatures. However, single traditional flame retardants are often accompanied by problems such as high filling amounts, easy aggregation, poor smoke control, etc., and may have an adverse impact on mechanical properties; 3. Using ultraviolet absorbers or light stabilizers: Common ultraviolet absorbers such as UV-531, UV-326, etc. can slow down photooxidative degradation to a certain extent, but they often face problems such as easy failure and insufficient compatibility with plasticizers under actual working conditions, resulting in an overall unsatisfactory effect.

[0004] A Chinese invention patent application (publication number: CN102532763A, publication date: July 4, 2012) discloses a chlorinated polyvinyl chloride (CPCV) modified material and its preparation method. The CPCV modified material comprises the following ingredients: 40-90 parts CPCV; 20-70 parts PVC; 5-30 parts modified resin; 1.5-10 parts heat stabilizer; 20-60 parts plasticizer; 1-10 parts antioxidant; 1-10 parts lubricant; 5-40 parts filler; 8-40 parts flame retardant; 8-40 parts flame retardant synergist; and 1-20 parts PVC processing aid. The flame retardant is surface-treated antimony trioxide, aluminum hydroxide, or any mixture thereof, and the flame retardant synergist is zinc borate, ammonium molybdate, or a mixture thereof. CPVC-modified materials offer superior physical and mechanical properties at a relatively lower cost. Compared to CPVC, this invention not only offers superior processability and significantly improved brittleness and impact resistance, but also significantly enhanced heat resistance and flame retardancy (with an oxygen index of approximately 45%, allowing a single strand to burn vertically). However, this patent relies excessively on conventional flame retardants such as antimony trioxide and aluminum hydroxide. The high loading may not only significantly degrade mechanical properties, but also limit the control of smoke and toxicity generated by combustion. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide a low-temperature resistant, flame-retardant and UV-resistant PVC cable sheath composition, by introducing an environmentally friendly calcium zinc stabilizer, a chlorinated polyethylene elastomer, a plasticizer and a specific flame-retardant filler compound system into the PVC matrix. At the same time, with the synergistic effect of multiple flame retardant and smoke suppression systems such as nano-magnesium hydroxide, modified montmorillonite, sodium tungstate and zinc stannate-passivated zinc borate, it can not only form a stable flame retardant protective layer and absorb a large amount of heat during combustion, but also effectively reduce the amount of smoke released. In addition, the combined use of carbon black powder and ultraviolet absorber can significantly improve the weather resistance of the sheath material under outdoor ultraviolet light; and the introduction of silane coupling agent improves the bonding degree between the nano-scale inorganic component and the organic matrix, so that the overall material has high strength, good flexibility and long life characteristics.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A low-temperature-resistant, flame-retardant, and UV-resistant PVC cable sheath composition is prepared by mixing the following raw materials, in parts by weight: 100 parts of polyvinyl chloride resin; 10-15 parts of chlorinated polyethylene elastomer; 4-8 parts of environmentally friendly calcium zinc stabilizer; 15-25 parts of carbon ten plasticizer; 10-15 parts of dioctyl adipate; 10 - 20 parts of nanoscale magnesium hydroxide; 2 - 5 parts of zinc stannate; 3 - 6 parts of passivated zinc borate; 2 - 5 parts of modified montmorillonite; 1 - 3 parts of sodium tungstate; 3 - 5 parts of carbon black powder; 0.2 - 0.5 part of antioxidant; 0.3 - 0.8 part of ultraviolet absorber; 0.5 - 1 part of silane coupling agent.

[0007] Preferably, by weight, the composition is prepared by mixing raw materials of the following components: 100 parts of polyvinyl chloride resin; 12 - 14 parts of chlorinated polyethylene elastomer; 5 - 7 parts of environment-friendly calcium-zinc stabilizer; 18 - 22 parts of decyl phthalate plasticizer; 12 - 14 parts of dioctyl adipate; 12 - 18 parts of nanoscale magnesium hydroxide; 3 - 4 parts of zinc stannate; 4 - 5 parts of passivated zinc borate; 3 - 4 parts of modified montmorillonite; 1.5 - 2.5 parts of sodium tungstate; 3.5 - 4.5 parts of carbon black powder; 0.3 - 0.4 part of antioxidant; 0.4 - 0.7 part of ultraviolet absorber; 0.6 - 0.8 part of silane coupling agent.

[0008] Preferably, the modified montmorillonite is montmorillonite treated by organicization or silanization, and its lamellar structure can be fully compatible with the polyvinyl chloride matrix and the plasticizer system during the mixing process.

[0009] Preferably, the modified montmorillonite is modified montmorillonite treated with a silane coupling agent or a quaternary ammonium salt.

[0010] Preferably, the ultraviolet absorber is selected from UV-531, UV-5411, UV-326 or a mixture thereof; the antioxidant is selected from hindered phenolic antioxidants and / or organophosphite antioxidants.

[0011] Preferably, the silane coupling agent is selected from APTES or GPTMS.

[0012] Furthermore, the present invention also discloses a preparation method of the composition, including the following steps: (1) Premixing: Polyvinyl chloride resin, chlorinated polyethylene elastomer, environment-friendly calcium-zinc stabilizer, C10 plasticizer, dioctyl adipate, antioxidant and ultraviolet absorber are proportionally put into a high-speed mixer, and the stirring temperature is controlled at 80 - 120°C for mixing for 5 - 15 minutes; (2) Adding inorganic fillers and modified components: Nano magnesium hydroxide, zinc stannate, passivated zinc borate, modified montmorillonite, sodium tungstate, carbon black powder and silane coupling agent are added to the above premix, and continue to mix at high speed for 3 - 10 minutes to make each component disperse evenly; (3) Extrusion granulation: The uniformly mixed material is extruded and granulated in a twin-screw extruder, the extrusion temperature is controlled at 160 - 190°C, and the screw speed is 50 - 120 rpm to obtain low-temperature resistant, flame-retardant and ultraviolet-resistant PVC cable sheath pellets.

[0013] Preferably, the rotation speed of the high-speed mixer is 300 - 1000 rpm, and the mixing process is carried out in an inert gas protection environment.

[0014] Preferably, the temperatures of each section in the twin-screw extruder are set in sequence as follows: the first section is 160 - 165°C, the second section is 165 - 175°C, the third section is 175 - 185°C, and the last section is 180 - 190°C to ensure that modified montmorillonite, sodium tungstate and other additives are fully dispersed in the resin matrix.

[0015] Furthermore, the present invention also discloses a low-temperature resistant, flame-retardant and ultraviolet-resistant PVC cable, which includes a conductor and a sheath prepared from the composition described above.

[0016] The low-temperature resistant, flame-retardant and ultraviolet-resistant PVC cable sheath composition provided by the present invention creatively constructs a composite synergistic flame-retardant system based on nano magnesium hydroxide and supplemented with zinc stannate, passivated zinc borate, sodium tungstate and modified montmorillonite. The above components synergistically act through multiple mechanisms such as physical shielding, endothermic cooling, catalytic carbonization and free radical inhibition, significantly improving the flame-retardant performance of the material and effectively reducing the smoke density and smoke toxicity. The specific synergistic action principle is as follows: (1) Synergy of thermal decomposition and endothermic cooling of nano magnesium hydroxide: The present invention uses nano magnesium hydroxide, which undergoes a rapid thermal decomposition reaction (Mg(OH)2 → MgO + H2O↑) during combustion. The water vapor generated by decomposition can quickly dilute the oxygen and combustible gas concentrations in the combustion zone, and is accompanied by an obvious endothermic effect, effectively reducing the combustion temperature on the material surface and providing a temperature control basis for subsequent flame-retardant effects.

[0017] (2)Synergistic effect of carbonization catalysis and smoke suppression between zinc stannate and passivated zinc borate: In a high-temperature combustion environment, zinc stannate and passivated zinc borate synergistically catalyze the formation of a continuous and dense carbonized protective layer on the PVC matrix. Among them, zinc stannate promotes rapid surface carbonization and inhibits the generation of soot, while passivated zinc borate generates a low-melting-point glassy liquid phase at high temperature, further enhancing the compactness and durability of the carbonized layer, effectively reducing the release rate and concentration of smoke and toxic gases, and improving the overall flame retardancy and safety of the system.

[0018] (3)Synergistic effect of free radical inhibition and smoke reduction by sodium tungstate: As a special free radical scavenger and catalyst, sodium tungstate can effectively capture and terminate hydroxyl radicals (•OH) and hydrogen radicals (•H) generated during the combustion of PVC during the combustion process, significantly reducing the combustion reaction rate. At the same time, sodium tungstate catalyzes the further carbonization of PVC, reducing the release concentration of soot and harmful volatile gases, thereby achieving the dual synergistic effect of gas-phase flame retardancy and smoke suppression.

[0019] (4)Synergistic effect of physical barrier and interface enhancement of modified montmorillonite: In this invention, montmorillonite is surface-modified by silane coupling agent or quaternary ammonium salt to prepare a nano-scale lamellar structure with a large interlayer spacing and good dispersibility. When the modified montmorillonite is heated in the PVC matrix, a dense and stable physical barrier layer is rapidly formed, effectively inhibiting the further diffusion of heat, oxygen and combustible gases. At the same time, the interfacial bonding formed between the modified montmorillonite and PVC through the silane coupling agent effectively improves the mechanical properties of the material and the overall flame retardant stability of the system.

[0020] By using the above-mentioned components in combination, the flame retardant system of this invention realizes the synergistic effect of multiple flame retardant mechanisms such as "solid-phase shielding, endothermic cooling, catalytic carbonization and gas-phase free radical capture", effectively solving the problems of large addition amount, serious loss of mechanical properties, limited control of smoke density and toxicity caused by a single flame retardant component in traditional PVC sheath materials. While significantly improving the flame retardant efficiency of PVC materials, it greatly reduces the smoke concentration and the generation amount of toxic gases during combustion, fundamentally improving the safety and environmental protection of cable materials in a fire environment.

[0021] Furthermore, by introducing a composite plasticizer system of chlorinated polyethylene elastomer (CPE), decane plasticizer, and dioctyl adipate, the present invention effectively improves the flexibility and impact resistance of the PVC sheath material in low-temperature environments, effectively solving the technical problems of easy hardening and cracking of traditional PVC cable sheaths under low-temperature conditions, enabling the material to be stably used in extreme environments with temperatures as low as -40°C or even lower. At the same time, the modified montmorillonite used in the present invention has been organically modified with a silane coupling agent or quaternary ammonium salt, effectively improving its compatibility with the PVC matrix, enabling the nano-montmorillonite platelets to be fully exfoliated and uniformly dispersed in the polymer matrix, thereby significantly enhancing the flame-retardant synergistic effect and mechanical strength of the material. In addition, silane coupling agents (such as APTES or GPTMS) further improve the interfacial bonding strength between other inorganic additives such as nano-magnesium hydroxide and sodium tungstate and the PVC resin, effectively preventing the agglomeration of additives, and further optimizing the processing performance and stability of the material.

[0022] In summary, the low-temperature resistant, flame-retardant, and ultraviolet-resistant PVC cable sheath composition provided by the present invention successfully realizes the synergistic improvement of comprehensive properties such as high-efficiency flame retardancy, low smoke and toxicity suppression, excellent low-temperature flexibility, and remarkable ultraviolet aging resistance. It is applicable to the application of cable outer sheaths in extreme climate environments and special requirement occasions, and has significant economic and social benefits. Detailed Embodiments

[0023] The following combines the embodiments of the present invention, and clearly and completely describes the technical solutions in the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] I. Preparation of Embodiments and Comparative Examples The raw material sources of the embodiments and comparative examples of the present invention are shown in Table 1.

[0025] Table 1 Specific sources of main raw materials in embodiments and comparative examples

[0026] The following conducts performance comparisons through Embodiment 1 - Embodiment 3 and Comparative Example 1 - Comparative Example 6, and the formulations are shown in Table 2 and Table 3. To verify the significant improvement effect of the synergistic flame-retardant system on the flame-retardant, low-smoke, ultraviolet-resistant, and low-temperature properties of the material.

[0027] Table 2 Raw material components (parts by weight) of the embodiments

[0028] Table 3 Raw material components (parts by weight) of the comparative examples

[0029] The preparation methods of Examples 1 - 3 and Comparative Examples 1 - 6 are as follows, and if a certain raw material is not used, it is omitted: (1) Premixing: Polyvinyl chloride resin, chlorinated polyethylene elastomer, environment-friendly calcium-zinc stabilizer, C10 plasticizer, dioctyl adipate, antioxidant, and ultraviolet absorber were put into a high-speed mixer in proportion, and the stirring temperature was controlled at 105°C and mixed for 10 minutes; (2) Adding inorganic fillers and modified components: Nano magnesium hydroxide, zinc stannate, passivated zinc borate, modified montmorillonite, sodium tungstate, carbon black powder, and silane coupling agent were added to the above premixed material, and high-speed mixing was continued for 8 minutes to make each component disperse evenly; (3) Extrusion granulation: The uniformly mixed material was extruded and granulated in a twin-screw extruder, the extrusion temperature was controlled at 180°C, and the screw speed was 80 rpm to obtain low-temperature resistant, flame-retardant, and ultraviolet-resistant PVC cable sheath pellets.

[0030] Comparative Example 7 was Example 1 disclosed in Chinese Patent Application (Publication No.: CN102532763A, Publication Date: July 4, 2012).

[0031] II. Test Methods The following are the specific processes and reference standards of the test methods involved in the examples and comparative examples: (I). Flame-retardant performance test method 1. Oxygen index (LOI) test Basis standard: GB / T 2406.2 - 2009 "Plastics - Determination of burning behavior by the oxygen index method"; Instrument and equipment: Oxygen index tester (such as JF-3 oxygen index determinator); Specimen specification: Long strip specimen (length 100 mm × width 10 mm × thickness 3 mm); Test process: The specimen was vertically fixed in the test fixture, and the top of the specimen was ignited; the ratio of oxygen and nitrogen was adjusted to determine the lowest oxygen concentration required for the specimen to burn continuously for exactly 3 minutes; the test was repeated 3 times, and the average value was the oxygen index of the sample.

[0032] 2. Vertical burning rating test (UL-94) Basis standard: GB / T 2408 - 2008 (equivalent to UL-94) "Plastics - Determination of burning performance - Vertical method"; Instrument and equipment: UL-94 vertical burning tester; Specimen specification: length 125 mm × width 13 mm × thickness 3 mm; Test procedure: Vertically fix the specimen in the combustion chamber, with the bottom end 10 mm away from the top of the burner; Apply the flame (20 mm in height) to the bottom end of the specimen twice, each time for 10 seconds; Observe the afterflame and afterglow time after removing the heat source, and whether the dripping ignites the bottom absorbent cotton; Evaluate the grade according to the afterflame, afterglow, and dripping conditions: V-0, V-1, V-2, etc.

[0033] (2). Smoke density test According to the standard: GB / T 8323.2-2008 "Plastics - Test method for smoke density - Single-chamber method"; Instrument and equipment: NBS smoke density tester; Specimen specification: Square sheet, size 75 mm × 75 mm × 3 mm; Test procedure: Vertically fix the specimen at a specific position in the combustion chamber, apply a radiant heat source of 25 kW / m² and open flame combustion; Record the change in light transmittance during combustion, and automatically record the curve of smoke density changing with time; Measure and record the maximum smoke density value (Dm) during the combustion of the specimen; Each sample is tested 3 times, and the average value is taken.

[0034] (3). Low-temperature bending performance test According to the standard: GB / T 2951.14-2008 "General test methods for cable insulating and sheathing materials"; Test temperature: -40°C; Instrument and equipment: Low-temperature test chamber, standard bending fixture; Specimen specification: The length of the cable sheath sample is 100 mm; Test procedure: Keep the sample in the low-temperature chamber at -40°C for 4 hours; Take out the sample and quickly bend it 180° around a cylinder with a specified diameter (10 times the outer diameter of the cable) within 10 seconds; Check whether there are cracks or fractures on the surface of the specimen; Each type of sample is tested 3 times, and passing means no cracks or damages occur.

[0035] (4). Anti-ultraviolet aging performance test According to the standard: GB / T 16422.3-2014 "Plastics - Methods of exposure to laboratory light sources - Part 3: Fluorescent ultraviolet lamps"; Instrument and equipment: UV ultraviolet aging test chamber (fluorescent ultraviolet lamp tube, UVA-340); Specimen specification: Dumbbell-shaped specimen, thickness 3 mm, meeting the tensile test requirements of GB / T 1040.2; Testing process: Fix the specimen in a UV aging test chamber, set the irradiation intensity at 0.68 W / m², the blackboard temperature at 60 °C, and perform a light / condensation cycle (8 h of light and 4 h of condensation), and age continuously for 250 hours; measure the tensile strength of the specimen before and after the test, and record the strength retention rate after aging (%): Strength retention rate = (Tensile strength after aging / Initial tensile strength) × 100%; Test 5 specimens for each sample and take the average value.

[0036] (V). Mechanical property testing (auxiliary verification) According to the standard: GB / T 1040.2-2006 "Plastics - Methods of test for tensile properties"; Instrument and equipment: Universal testing machine; Specimen specification: dumbbell-shaped specimen, with a thickness of 3 mm and a length ≥ 150 mm; Testing process: Install the specimen on the universal testing machine, set the grip distance at 100 mm, and the tensile rate at 50 mm / min. Record the maximum tensile strength and elongation at break, and take the average value of 3 specimens.

[0037] (VI). Testing method for thermal aging performance Testing standard: GB / T 2951.12-2008 "General test methods for cable insulating and sheathing materials".

[0038] Testing instruments: Electrothermal constant temperature drying oven, universal testing machine.

[0039] Specimen specification: The same dumbbell-shaped specimen as in the tensile test.

[0040] Testing process: Place the specimen in a constant temperature oven at 100 °C and age continuously for 168 h (7 days); after the aging is completed, cool the specimen to room temperature for 24 h, and measure the tensile strength and elongation at break; calculate the change rate based on the changes in strength and elongation before and after the test.

[0041] In the present invention, if no specific testing method is given, the conventional testing method is adopted.

[0042] The following gives the experimental data of detailed Examples 1 - 3 and Comparative Examples 1 - 7 (as shown in Table 4) to fully present the technical effects of the present invention.

[0043] Table 4 Experimental data of Examples 1 - 3 and Comparative Examples 1 - 7

[0044] Through the systematic comparative experiments of Comparative Examples 1-7 and Examples 1-3, it is proved that the flame retardant system (nanoscale magnesium hydroxide / zinc stannate / passivated zinc borate / modified montmorillonite / sodium tungstate) constructed by the present invention has excellent synergistic effects, and can significantly improve the flame retardancy, smoke suppression performance, low temperature flexibility, thermal stability and anti-ultraviolet aging performance of the PVC cable sheath material, reflecting the technical innovation and outstanding technical effects of the formulation design of the present invention.

[0045] The above is the description of the embodiments of the present invention. Through the above description of the disclosed embodiments, those skilled in the art can implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel points disclosed herein.

Claims

1. A low-temperature resistant, flame-retardant and ultraviolet-resistant PVC cable sheath composition, characterized in that, By weight parts, the composition is prepared by mixing raw materials of the following components: 100 parts of polyvinyl chloride resin; 10 - 15 parts of chlorinated polyethylene elastomer; 4 - 8 parts of environment-friendly calcium-zinc stabilizer; 15 - 25 parts of decyl phthalate plasticizer; 10 - 15 parts of dioctyl adipate; 10 - 20 parts of nanoscale magnesium hydroxide; 2 - 5 parts of zinc stannate; 3 - 6 parts of passivated zinc borate; 2 - 5 parts of modified montmorillonite; 1 - 3 parts of sodium tungstate; 3 - 5 parts of carbon black powder; 0.2 - 0.5 part of antioxidant; 0.3 - 0.8 part of ultraviolet absorber; 0.5 - 1 part of silane coupling agent.

2. The composition according to claim 1, characterized in that, By weight parts, the composition is prepared by mixing raw materials of the following components: 100 parts of polyvinyl chloride resin; 12 - 14 parts of chlorinated polyethylene elastomer; 5 - 7 parts of environment-friendly calcium-zinc stabilizer; 18 - 22 parts of decyl phthalate plasticizer; 12 - 14 parts of dioctyl adipate; 12 - 18 parts of nanoscale magnesium hydroxide; 3 - 4 parts of zinc stannate; 4 - 5 parts of passivated zinc borate; 3 - 4 parts of modified montmorillonite; 1.5 - 2.5 parts of sodium tungstate; 3.5 - 4.5 parts of carbon black powder; 0.3 - 0.4 part of antioxidant; 0.4 - 0.7 part of ultraviolet absorber; 0.6 - 0.8 part of silane coupling agent.

3. The composition according to claim 1, wherein The modified montmorillonite is montmorillonite treated by organicization or silanization, and its lamellar structure can be fully compatible with the polyvinyl chloride matrix and the plasticizer system during the mixing process.

4. The composition according to claim 1, characterized in that, The modified montmorillonite is modified montmorillonite treated with a silane coupling agent or a quaternary ammonium salt.

5. The composition according to claim 1, characterized in that, The ultraviolet absorber is selected from UV-531, UV-5411, UV-326 or a mixture thereof; the antioxidant is selected from hindered phenol antioxidants and / or organophosphite antioxidants.

6. The composition according to claim 1, wherein The silane coupling agent is selected from APTES or GPTMS.

7. A method for preparing the composition according to any one of claims 1-6, characterized in that, It includes the following steps: (1) Premixing: Put polyvinyl chloride resin, chlorinated polyethylene elastomer, environment-friendly calcium-zinc stabilizer, decyl phthalate plasticizer, dioctyl adipate, antioxidant and ultraviolet absorber into a high-speed mixer according to the proportion, control the stirring temperature at 80 - 120 °C, and mix for 5 - 15 minutes; (2) Adding inorganic fillers and modified components: Add nanoscale magnesium hydroxide, zinc stannate, passivated zinc borate, modified montmorillonite, sodium tungstate, carbon black powder and silane coupling agent to the above premixed material, and continue to mix at high speed for 3 - 10 minutes to make each component disperse evenly; (3) Extrusion granulation: Extrude and granulate the uniformly mixed material in a twin-screw extruder, control the extrusion temperature at 160 - 190 °C, and the screw speed at 50 - 120 rpm to obtain low-temperature resistant, flame-retardant and ultraviolet-resistant PVC cable sheath pellets.

8. The preparation method according to claim 7, characterized in that, The rotation speed of the high-speed mixer is 300 - 1000 rpm, and the mixing process is carried out in an inert gas protection environment.

9. The preparation method according to claim 7, characterized in that, The temperatures of each section in the twin-screw extruder are set in sequence as follows: the first section is 160 - 165 °C, the second section is 165 - 175 °C, the third section is 175 - 185 °C, and the last section is 180 - 190 °C, so that the modified montmorillonite, sodium tungstate and other additives are fully dispersed in the resin matrix.

10. A low-temperature resistant, flame-retardant and ultraviolet-resistant PVC cable, characterized in that, The cable includes a conductor and a sheath prepared from the composition according to any one of claims 1-6.

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