CN118588366A - A PVC cable and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of cables and discloses a PVC cable and a preparation method thereof, wherein the PVC cable sequentially comprises a cable core, an insulating layer and a sheath layer from inside to outside, wherein the sheath layer is formed by extruding a polyvinyl chloride sheath material formed by blending and granulating polyvinyl chloride serving as a main raw material and other auxiliary agents such as a flame-retardant additive and a functional filler on the outer side of the insulating layer, and the prepared polyvinyl chloride has good flame-retardant effect, ultraviolet ageing resistance and heat resistance and higher safety and longer service life by utilizing the synergistic effect of the flame-retardant additive and the functional filler.

Description

A PVC cable and preparation method thereof

Technical Field

The present invention relates to the technical field of cables, and in particular to a PVC cable and a preparation method thereof.

Background Art

In recent years, the rapid development of energy transmission, transportation and other fields has led to an increasing demand for cables year by year, and cables have become inseparable from daily life. Generally speaking, the outside of the cable needs to be covered with a sheath layer formed by polymer materials as the main raw material to protect the cable and prevent the cable core from being disturbed. Since polyvinyl chloride (PVC) is cheap, soft, and easy to process into various shapes, it is often used as a sheath material for cables. However, a large amount of plasticizers, heat stabilizers and other additives are often used in the processing of polyvinyl chloride, which leads to a negative effect on the flame retardancy of polyvinyl chloride, which is not conducive to the further development of polyvinyl chloride in the field of cables. In addition, some cables need to work outdoors for a long time, and polyvinyl chloride has poor anti-ultraviolet aging performance. After long-term exposure to sunlight, obvious aging will occur, which will affect the normal operation of the cable. Therefore, it is particularly necessary to improve polyvinyl chloride.

The invention patent with the publication number CN110760139B discloses a high resistivity flame retardant polyvinyl chloride cable material composition, which uses bromine-containing ester liquid as a flame retardant plasticizer and is combined with chlorinated rubber to achieve flame retardant modification of polyvinyl chloride cable materials. However, halogen flame retardant modifiers produce a large amount of smoke and toxic and corrosive gases during combustion, which is very harmful and has been gradually eliminated. In addition, the flame retardant properties of polyvinyl chloride can also be effectively improved by adding inorganic flame retardants, but the flame retardant effect of inorganic flame retardants alone is not good, and a large amount of addition is required to achieve a significant effect, which will affect the mechanical properties of polyvinyl chloride.

Based on this, the present invention provides a polyvinyl chloride sheath material, which has good comprehensive properties such as anti-aging and flame retardancy, and can be directly used to make polyvinyl chloride cables.

Summary of the invention

The object of the present invention is to provide a PVC cable and a preparation method thereof, which solves the problem that polyvinyl chloride is easy to burn and has poor ultraviolet light aging resistance when used as a cable sheath material.

The purpose of the present invention can be achieved through the following technical solutions:

A PVC cable comprises, from inside to outside, a cable core, an insulating layer and a sheath layer; the insulating layer is formed by extruding an insulating material on the outside of the cable core; the sheath layer is formed by extruding a polyvinyl chloride sheath material on the outside of the insulating layer; the insulating material comprises the following components in parts by weight: 20-35 parts of low-density polyethylene, 15-25 parts of ethylene-vinyl acetate copolymer, 5-15 parts of SBS elastomer, 1-3 parts of lubricant, 0.5-1 parts of antioxidant, 10-15 parts of plasticizer, and 10-20 parts of filler; the polyvinyl chloride sheath material comprises the following components in parts by weight: 45-65 parts of polyvinyl chloride, 5-10 parts of powdered chloroprene rubber, 3-6 parts of flame retardant additive, 2-5 parts of functional filler, 6-8 parts of stabilizer, 20-30 parts of plasticizer, 0.5-2 parts of antioxidant, and 1-3 parts of lubricant;

The flame retardant additive is magnesium hydroxide with an organic monomolecular coating layer on the surface; the monomolecular layer structure contains nitrogen, phosphorus and silicon ternary flame retardant elements;

The functional filler is a benzophenone macromolecular ultraviolet absorber.

Further preferably, the lubricant is any one of calcium stearate, magnesium stearate or zinc stearate; the antioxidant is any one of antioxidant 168, antioxidant RD or antioxidant 1010; the plasticizer is any one of dioctyl phthalate, dioctyl sebacate or epoxy soybean oil; the filler is any one of calcium carbonate, talc or white carbon black; the stabilizer is calcium zinc stabilizer or barium zinc stabilizer.

A method for preparing a PVC cable comprises the following steps:

Step 1: Prepare insulating materials

Pour low-density polyethylene, ethylene-vinyl acetate copolymer, SBS elastomer, lubricant, antioxidant, plasticizer and filler into a high-speed mixer in sequence, raise the temperature in the mixer to 160-170°C, stir and mix for 30-60 minutes, transfer the materials into an extruder for extrusion granulation after mixing, chop the masterbatch to obtain an insulating material;

Step 2: Preparation of polyvinyl chloride sheath material

Pour polyvinyl chloride, powdered chloroprene rubber, flame retardant additives, functional fillers, stabilizers, plasticizers, antioxidants and lubricants into a high-speed mixer in sequence, raise the temperature in the mixer to 160-170°C, stir and mix for 30-60 minutes, transfer the materials into an extruder for extrusion granulation after mixing, chop the masterbatch to obtain a polyvinyl chloride sheath material;

Step 3: Prepare cables

Use a double-layer co-extrusion extruder to extrude the insulating material on the surface of the conductor. After molding, an insulating layer can be formed. Then, the polyvinyl chloride sheath material is extruded on the outside of the insulating layer. After molding, it is air-cooled and rolled up to obtain the cable.

Further preferably, the flame retardant additive is prepared by the following method:

Add magnesium hydroxide and N,N-dimethylformamide to a reactor filled with nitrogen in sequence, start stirring, and after uniform dispersion, add flame retardant DDP and catalyst to the reactor, stir to dissolve, start heating until the temperature reaches 100-120°C, keep warm for 8-12h, continue to add silazolyl tricyclic glycol to the system, continue stirring for 6-9h, stop heating, wait for the material to cool naturally, separate the product, wash and remove impurities, and completely vacuum dry in a vacuum drying oven at 50-60°C to obtain a flame retardant additive.

More preferably, the average particle size of the magnesium hydroxide is 50 nm.

More preferably, the catalyst is p-toluenesulfonic acid.

In the above technical scheme, the possible mechanism is: magnesium hydroxide contains hydroxyl groups, which can be combined with catalysts and high temperature conditions to condense with the carboxyl groups in the structure of the flame retardant DDP, so that the phosphorus-containing flame retardant DDP is grafted on the surface of the magnesium hydroxide. Since the flame retardant DDP structure contains two equivalents of active carboxyl groups, the flame retardant DDP is used as a bridge, and its bridging effect is utilized to further condense with the hydroxyl groups in the structure of the silatricyclic glycol, and the silatricyclic containing two flame retardant elements of nitrogen and silicon is modified on the surface of the magnesium hydroxide, so that an organic monomolecular coating layer containing the ternary flame retardant elements of nitrogen, phosphorus and silicon is formed on the surface of the magnesium hydroxide, and a flame retardant additive is prepared.

Further preferably, the functionalized filler is prepared by the following method:

2,2',4,4'-Tetrahydroxybenzophenone and toluene are sequentially added to a reactor filled with nitrogen, and stirring is started. After a uniform solution is formed, 1,2-bis(chlorodimethylsilyl)ethane and toluene are mixed to form a reaction solution. The reaction solution is added dropwise to the uniform solution at a controlled dropping rate. After the addition is completed, heating is started to increase the temperature to 60-70°C. After keeping the temperature for 2-4 hours, an acid binding agent is added to the reactor, stirring is continued for 6-8 hours, the solvent is evaporated under reduced pressure, and the material is discharged at a reduced temperature to obtain a functional additive.

Further preferably, the molar ratio of the 2,2',4,4'-tetrahydroxybenzophenone to 1,2-bis(chlorodimethylsilyl)ethane is 1:1.

Further preferably, the dripping rate is 1-2 ml/min.

More preferably, the acid binding agent is triethylamine or pyridine.

In the above technical scheme, the possible mechanism is: the para-hydroxyl group in the structure of 2,2',4,4'-tetrahydroxybenzophenone is highly active and can be substituted with Si-Cl in the structure of 1,2-bis(chlorodimethylsilyl)ethane. Under the action of the acid-binding agent, continuous substitution reactions can occur between them to form alternating long-chain polymer molecules with a block structure, i.e., functional additives.

Beneficial effects of the present invention:

1) The present invention adopts a chemical grafting method to modify the surface of magnesium hydroxide with an organic monomolecular coating layer containing nitrogen, phosphorus and silicon ternary flame retardant elements. After the monomolecular layer coating, the compatibility between magnesium hydroxide and polyvinyl chloride can be improved, so that magnesium hydroxide can be evenly and stably dispersed in the polyvinyl chloride sheath material. By utilizing the magnesium hydroxide inorganic flame retardant and the nitrogen, phosphorus and silicon ternary flame retardant elements grafted on its surface, a synergistic flame retardant effect can be formed, so that the flame retardancy of the polyvinyl chloride sheath material can be greatly improved by adding a small amount of flame retardant additives. According to the test, the limiting oxygen index of the polyvinyl chloride sheath material can reach up to 34.2%, and it has excellent flame retardant properties.

2) The present invention prepares long-chain polymer molecules with block structures as functional additives. Since the structure contains benzophenone structure, the anti-ultraviolet aging performance of polyvinyl chloride sheathing materials can be effectively improved. Moreover, compared with conventional small molecule ultraviolet absorbers, the long-chain polymer molecules are difficult to precipitate, have low volatility, and can exist in polyvinyl chloride sheathing materials for a long time, achieving a long-term anti-ultraviolet aging effect. In addition, a large number of high-energy Si-O bonds will be generated during the substitution reaction, which can effectively improve the heat resistance of polyvinyl chloride sheathing materials. Therefore, the use of the polyvinyl chloride sheathing material prepared by the present invention to make the sheath layer of the cable can effectively improve the safety and service life of the cable.

Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned advantages at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

FIG. 1 is an infrared absorption spectrum of the functionalized filler prepared in Example 1 of the present invention.

FIG2 is a schematic diagram of the structure of a PVC cable;

Reference numerals: 1, cable core; 2, insulation layer; 3, sheath layer.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Example 1

Preparation of polyvinyl chloride sheath material

45 parts of polyvinyl chloride, 5 parts of powdered chloroprene rubber, 3 parts of flame retardant additives, 2 parts of functional fillers, 6 parts of calcium zinc stabilizer, 20 parts of plasticizer dioctyl phthalate, 0.5 parts of antioxidant 168 and 1 part of lubricant calcium stearate are poured into a high-speed mixer in sequence, the temperature in the mixer is increased to 160°C, and the mixture is stirred and mixed for 30 minutes. After mixing, the materials are transferred to an extruder for extrusion and granulation, and the masterbatch is chopped to obtain a polyvinyl chloride sheath material.

The flame retardant additive is prepared by the following method:

To a reactor filled with nitrogen, add 2.5 g of magnesium hydroxide with an average particle size of 50 nm and 240 mL of N,N-dimethylformamide in sequence, start stirring, and after uniform dispersion, add 3.8 g of flame retardant DDP and 1.4 g of p-toluenesulfonic acid to the reactor, stir to dissolve, turn on heating to a temperature of 110°C, and keep warm for 9 hours. Continue to add 2.6 g of tricyclic silazolyl glycol to the system, continue stirring for 8 hours, stop heating, wait for the material to cool naturally, separate the product, wash and remove impurities, and completely dry it in a vacuum drying oven at 50°C to obtain a flame retardant additive.

0.5g of flame retardant additive sample was weighed, and the ester content in the flame retardant additive was tested by soap back titration. The test results showed that the ester content of the sample was 12.87mmol/g. Analysis showed that the above reaction process used the flame retardant DDP as a bridge to bridge magnesium hydroxide and azosilanetriol in the form of esterification condensation, thus forming a large number of ester groups.

The functionalized filler is prepared by the following method:

1.5 g of 2,2',4,4'-tetrahydroxybenzophenone and 80 mL of toluene were added to a reactor filled with nitrogen in sequence, and stirring was started. After a uniform solution was formed, 1.31 g of 1,2-bis(chlorodimethylsilyl)ethane was mixed with 50 mL of toluene to form a reaction solution. The dropping rate was controlled to 1 ml/min, and the reaction solution was added dropwise to the uniform solution. After the addition was completed, heating was started to increase the temperature to 65°C. After keeping warm for 3 hours, triethylamine was added to the reactor, and stirring was continued for 8 hours. The solvent was evaporated under reduced pressure, and the temperature was lowered to discharge the material to obtain a functional additive.

The infrared absorption spectrum of the functionalized additive was measured at 500-4000 cm ^-1 by the KBr tablet method. The result is shown in Figure 1. After analysis, 3442 cm ^-1 is the characteristic stretching vibration peak of the hydroxyl group, 3000-3100 cm ^-1 is the characteristic stretching vibration peak of the carbon-hydrogen on the benzene ring, 1694 cm ^-1 is the characteristic stretching vibration peak of the carbon-oxygen double bond, and 1058 cm ^-1 is the characteristic stretching vibration peak of silicon-oxygen.

Example 2

Preparation of polyvinyl chloride sheath material

60 parts of polyvinyl chloride, 8 parts of powdered chloroprene rubber, 5 parts of flame retardant additives, 4 parts of functional fillers, 6 parts of barium zinc stabilizer, 25 parts of plasticizer dioctyl sebacic acid, 1 part of antioxidant 1010 and 1.5 parts of lubricant zinc stearate are poured into a high-speed mixer in sequence, the temperature in the mixer is increased to 165°C, and the mixture is stirred and mixed for 40 minutes. After mixing, the materials are transferred to an extruder for extrusion and granulation, and the masterbatch is chopped to obtain a polyvinyl chloride sheath material.

The flame retardant additive and the functional filler are prepared by the preparation method in Example 1.

Example 3

Preparation of polyvinyl chloride sheath material

65 parts of polyvinyl chloride, 10 parts of powdered chloroprene rubber, 6 parts of flame retardant additives, 5 parts of functional fillers, 8 parts of calcium zinc stabilizer, 30 parts of plasticizer epoxy soybean oil, 2 parts of antioxidant RD and 3 parts of lubricant calcium stearate are poured into a high-speed mixer in sequence, the temperature in the mixer is increased to 170°C, and the mixture is stirred and mixed for 60 minutes. After mixing, the materials are transferred to an extruder for extrusion and granulation, and the masterbatch is chopped to obtain a polyvinyl chloride sheath material.

The flame retardant additive and the functional filler are prepared by the preparation method in Example 1.

Comparative Example 1

Preparation of polyvinyl chloride sheath material

60 parts of polyvinyl chloride, 8 parts of powdered chloroprene rubber, 5 parts of magnesium hydroxide, 4 parts of functional filler, 6 parts of barium zinc stabilizer, 25 parts of plasticizer dioctyl sebum, 1 part of antioxidant 1010 and 1.5 parts of lubricant zinc stearate are poured into a high-speed mixer in sequence, the temperature in the mixer is increased to 165°C, and the mixture is stirred and mixed for 40 minutes. After mixing, the materials are transferred to an extruder for extrusion and granulation, and the masterbatch is chopped to obtain a polyvinyl chloride sheath material.

The functionalized filler is prepared by the preparation method in Example 1.

Comparative Example 2

Preparation of polyvinyl chloride sheath material

60 parts of polyvinyl chloride, 8 parts of powdered chloroprene rubber, 4 parts of functional filler, 6 parts of barium zinc stabilizer, 25 parts of plasticizer dioctyl sebacate, 1 part of antioxidant 1010 and 1.5 parts of lubricant zinc stearate were poured into a high-speed mixer in sequence, the temperature in the mixer was increased to 165°C, and the mixture was stirred and mixed for 40 minutes. After mixing, the materials were transferred to an extruder for extrusion and granulation, and the masterbatch was chopped to obtain a polyvinyl chloride sheath material.

The functionalized filler is prepared by the preparation method in Example 1.

Comparative Example 3

Preparation of polyvinyl chloride sheath material

Pour 60 parts of polyvinyl chloride, 8 parts of powdered chloroprene rubber, 5 parts of flame retardant additives, 6 parts of barium zinc stabilizer, 25 parts of plasticizer dioctyl sebum, 1 part of antioxidant 1010 and 1.5 parts of lubricant zinc stearate into a high-speed mixer in sequence, raise the temperature in the mixer to 165°C, stir and mix for 40 minutes, move the materials into an extruder for extrusion and granulation after mixing, chop the masterbatch to obtain a polyvinyl chloride sheath material.

The flame retardant additive is prepared by the preparation method in Example 1.

The polyvinyl chloride sheath materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 were made into composite test specimens, and the following tests were performed respectively:

A. Refer to the national standard GB/T 2406.2-2009, limiting oxygen index, to evaluate the flame retardant effect of polyvinyl chloride sheath materials;

B. Take 10 specimens each, refer to the national standard GB/T 1040.2-2022, randomly select 5 of them for tensile strength test, and place the other 5 in a UV accelerated aging box, set the power of the UV lamp to 40W, and after accelerated aging for 168h, test the tensile strength, calculate the tensile strength retention rate, and evaluate the anti-ultraviolet aging performance of the polyvinyl chloride sheath material;

C. Place the specimen in an oven and set the oven temperature to 150°C. Take it out after heat treatment for 120 hours. Evaluate the heat resistance of the polyvinyl chloride sheath material by calculating the mass loss rate before and after the specimen. The test results are recorded in the following table:

Limiting oxygen index/% Tensile strength retention rate/% Mass loss rate/% Example 1 33.9 93.3 2.9 Example 2 34.2 94.1 2.3 Example 3 34.0 93.8 2.4 Comparative Example 1 26.8 92.5 3.6 Comparative Example 2 24.6 92.0 3.3 Comparative Example 3 32.8 66.7 7.9

By analyzing the data in the table, it can be clearly observed that the polyvinyl chloride sheath material prepared by adding flame retardant additives and functional fillers has a high oxygen index, a high tensile strength retention rate, and a low mass loss rate, and therefore exhibits good flame retardancy, anti-ultraviolet aging performance, and heat resistance.

In contrast, the flame retardant properties of the polyvinyl chloride sheath material prepared by adding only functional fillers in Comparative Example 2 were significantly reduced, and the heat resistance also decreased slightly. It is speculated that the presence of magnesium hydroxide has a positive effect on the heat resistance of the polyvinyl chloride sheath material. The aging resistance and heat resistance of the polyvinyl chloride sheath material prepared by adding only flame retardant additives in Comparative Example 3 were significantly reduced. This is because there is no functional filler, benzophenone cannot be used to absorb ultraviolet rays, and high bond energy silicon oxygen bonds cannot be used to improve heat resistance.

In Comparative Example 1, unmodified magnesium hydroxide was added for filling, and the flame retardancy was significantly reduced, but the anti-ultraviolet aging performance and heat resistance were acceptable.

The polyvinyl chloride sheath material prepared in Example 2 of the present invention is used to prepare a PVC cable, and the method is as follows:

Step 1: Prepare insulating materials

30 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 12 parts of SBS elastomer, 1.5 parts of lubricant zinc stearate, 0.5 parts of antioxidant 1010, 12 parts of plasticizer dioctyl sebacic acid and 15 parts of filler calcium carbonate are sequentially poured into a high-speed mixer, the temperature in the mixer is increased to 170° C., and the mixture is stirred and mixed for 60 minutes. After mixing, the materials are transferred into an extruder for extrusion granulation, and the masterbatch is chopped to obtain an insulating material;

Step 2: Prepare cables

Use a double-layer co-extrusion extruder to extrude the insulating material on the surface of the copper conductor. After molding, an insulating layer can be formed. Then, the polyvinyl chloride sheath material is extruded on the outside of the insulating layer. After molding, it is air-cooled and rolled up to obtain the cable.

Fig. 2 is a schematic diagram of the structure of the cable, which includes, from inside to outside, 1. a cable core; 2. an insulating layer; and 3. a sheath layer.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims (10)

1. A PVC cable, characterized in that it comprises a cable core, an insulating layer and a sheath layer in order from the inside to the outside; the insulating layer is formed by extruding an insulating material on the outside of the cable core; the sheath layer is formed by extruding a polyvinyl chloride sheath material on the outside of the insulating layer; the insulating material comprises the following components in parts by weight: 20-35 parts of low-density polyethylene, 15-25 parts of ethylene-vinyl acetate copolymer, 5-15 parts of SBS elastomer, 1-3 parts of lubricant, 0.5-1 parts of antioxidant, 10-15 parts of plasticizer, and 10-20 parts of filler; the polyvinyl chloride sheath material comprises the following components in parts by weight: 45-65 parts of polyvinyl chloride, 5-10 parts of powdered chloroprene rubber, 3-6 parts of flame retardant additives, 2-5 parts of functional fillers, 6-8 parts of stabilizers, 20-30 parts of plasticizers, 0.5-2 parts of antioxidants, and 1-3 parts of lubricants; The flame retardant additive is magnesium hydroxide with an organic monomolecular coating layer on the surface; the monomolecular layer structure contains nitrogen, phosphorus and silicon ternary flame retardant elements; The functional filler is a benzophenone macromolecular ultraviolet absorber. 2. A PVC cable according to claim 1, characterized in that the lubricant is any one of calcium stearate, magnesium stearate or zinc stearate; the antioxidant is any one of antioxidant 168, antioxidant RD or antioxidant 1010; the plasticizer is any one of dioctyl phthalate, dioctyl sebacate or epoxy soybean oil; the filler is any one of calcium carbonate, talc or white carbon black; the stabilizer is a calcium zinc stabilizer or a barium zinc stabilizer. 3. The method for preparing a PVC cable according to claim 1, characterized in that it comprises the following steps: Step 1: Prepare insulating materials Pour low-density polyethylene, ethylene-vinyl acetate copolymer, SBS elastomer, lubricant, antioxidant, plasticizer and filler into a high-speed mixer in sequence, raise the temperature in the mixer to 160-170°C, stir and mix for 30-60 minutes, transfer the materials into an extruder for extrusion granulation after mixing, chop the masterbatch to obtain an insulating material; Step 2: Preparation of polyvinyl chloride sheath material Pour polyvinyl chloride, powdered chloroprene rubber, flame retardant additives, functional fillers, stabilizers, plasticizers, antioxidants and lubricants into a high-speed mixer in sequence, raise the temperature in the mixer to 160-170°C, stir and mix for 30-60 minutes, transfer the materials into an extruder for extrusion granulation after mixing, chop the masterbatch to obtain a polyvinyl chloride sheath material; Step 3: Prepare cables Use a double-layer co-extrusion extruder to extrude the insulating material on the surface of the conductor. After molding, an insulating layer can be formed. Then, the polyvinyl chloride sheath material is extruded on the outside of the insulating layer. After molding, it is air-cooled and rolled up to obtain the cable. 4. A PVC cable according to claim 1, characterized in that the flame retardant additive is prepared by the following method: Add magnesium hydroxide and N,N-dimethylformamide to a reactor filled with nitrogen in sequence, start stirring, and after uniform dispersion, add flame retardant DDP and catalyst to the reactor, stir to dissolve, start heating to a temperature of 100-120°C, keep warm for 8-12h, continue to add silazolyl tricyclic glycol to the system, continue stirring for 6-9h, stop heating, wait for the material to cool naturally, separate the product, wash and remove impurities, and completely vacuum dry in a vacuum drying oven at 50-60°C to obtain a flame retardant additive. 5 . The PVC cable according to claim 4 , wherein the average particle size of the magnesium hydroxide is 50 nm. 6 . The PVC cable according to claim 4 , characterized in that in step S1 and step S2 , the catalyst is p-toluenesulfonic acid. 7. A PVC cable according to claim 1, characterized in that the functionalized filler is prepared by the following method: 2,2',4,4'-Tetrahydroxybenzophenone and toluene are sequentially added to a reactor filled with nitrogen, and stirring is started. After a uniform solution is formed, 1,2-bis(chlorodimethylsilyl)ethane and toluene are mixed to form a reaction solution. The reaction solution is added dropwise to the uniform solution at a controlled dropping rate. After the addition is completed, heating is started to increase the temperature to 60-70°C. After keeping the temperature for 2-4 hours, an acid binding agent is added to the reactor, stirring is continued for 6-8 hours, the solvent is evaporated under reduced pressure, and the material is discharged at a reduced temperature to obtain a functional additive. 8. A PVC cable according to claim 7, characterized in that the molar ratio of 2,2',4,4'-tetrahydroxybenzophenone to 1,2-bis(chlorodimethylsilyl)ethane is 1:1. 9. A PVC cable according to claim 7, characterized in that the dripping rate is 1-2 ml/min. 10. A PVC cable according to claim 7, characterized in that the acid binding agent is triethylamine or pyridine.