Wire and cable sheath material and preparation method thereof

Abstract

The invention relates to the technical field of electric wires and cables, and discloses an electric wire and cable sheath material and a preparation method thereof, the electric wire and cable sheath material comprises the following raw materials by mass: 80-120 parts of polyolefin, 15-20 parts of an ethylene-vinyl acetate copolymer, 20-30 parts of a composite flame retardant filler, 0.4-1.2 parts of a lubricant, 2-4 parts of an ultraviolet light absorber, 1-3 parts of an antioxidant and 1-2 parts of a light stabilizer. The wire and cable sheath material prepared by taking polyolefin resin as a matrix, adding the composite flame-retardant filler and compounding the ethylene-vinyl acetate copolymer, the lubricant, the ultraviolet light absorber, the antioxidant and the light stabilizer has relatively good mechanical property and flame retardance, and the composite flame-retardant filler can be uniformly dispersed in the wire and cable sheath material; the synergistic improvement of the flame retardant property and the mechanical property is realized.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, specifically to a wire and cable sheath material and its preparation method. Background Technology

[0002] As the outermost protective structure of a cable, the cable sheath needs to maintain stable performance over a long period of time under complex and ever-changing environmental conditions to ensure the safe operation of the cable system. With the development of power networks towards high voltage and large capacity, and the evolution of communication networks towards high speed and large bandwidth, the service environment of cables is becoming increasingly harsh, which puts forward more stringent requirements on the durability of sheath materials.

[0003] Polyolefins, as the matrix material for wire and cable sheathing, possess excellent insulation properties, weather resistance, processing performance, and economy, and are widely used in the wire and cable industry. However, when faced with extreme high-temperature environments such as fires, polyolefin materials exhibit serious fire resistance defects. Ammonium polyphosphate and fly ash can significantly enhance the flame retardant and mechanical properties of wire and cable sheathing materials, but ammonium polyphosphate and fly ash have poor compatibility with the matrix of wire and cable sheathing materials and are prone to agglomeration and precipitation in the sheathing materials, affecting the flame retardant and mechanical properties of the wire and cable sheathing materials. Summary of the Invention

[0004] This invention provides a wire and cable sheath material and its preparation method, which solves the problem of poor flame retardant and mechanical properties of wire and cable sheath materials.

[0005] The technical solution of the present invention: A type of wire and cable sheath material, comprising the following raw materials in parts by weight: 80-120 parts of polyolefin, 15-20 parts of ethylene-vinyl acetate copolymer, 20-30 parts of composite flame retardant filler, 0.4-1.2 parts of lubricant, 2-4 parts of ultraviolet absorber, 1-3 parts of antioxidant, and 1-2 parts of light stabilizer; Among them, the composite flame retardant filler is obtained by grafting polyvinyl alcohol onto melamine-formaldehyde resin and then reacting it with modified fly ash and tannic acid. Modified fly ash is obtained by mixing and reacting fly ash, glucose and carboxymethyl cellulose, and then loading ammonium polyphosphate. A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix polyolefin, ethylene-vinyl acetate copolymer, composite flame retardant filler, lubricant, ultraviolet absorber, antioxidant and light stabilizer for 5-10 minutes to obtain a mixture; S2. The mixture is fed into a twin-screw extruder, melt-extruded, granulated, cooled, and pelletized to obtain wire and cable sheath material.

[0006] Furthermore, the temperature of the twin-screw extruder is 125-135℃ in zone one, 145-155℃ in zone two, 160-170℃ in zone three, 165-175℃ in the die head, and the screw speed is 30-40 rpm.

[0007] Furthermore, the polyolefin is low-density polyethylene.

[0008] Furthermore, the vinyl acetate content in the ethylene-vinyl acetate copolymer is 16-20 wt%.

[0009] Furthermore, the lubricant is selected from any one of zinc stearate, calcium stearate, vinyl bis-stearamide, and epoxidized soybean oil.

[0010] Furthermore, the ultraviolet absorber is selected from ultraviolet absorber UV-328 or ultraviolet absorber UV-9.

[0011] Furthermore, the antioxidant is selected from any one of antioxidant DLTDP, antioxidant 1010, antioxidant 168 and antioxidant 264.

[0012] Furthermore, the light stabilizer is selected from any one of the light stabilizers HALS-62, 944, and UV-3853.

[0013] Furthermore, the composite flame-retardant filler is prepared by the following steps: A1. Add fly ash, glucose and carboxymethyl cellulose to deionized water, stir evenly, filter, dry and place in a tube furnace, add potassium hydroxide solution, purge with nitrogen, carbonize at 800-900℃ for 3-5 hours, cool to room temperature, take out, wash and dry to obtain fly ash loaded with porous carbon. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. After negative pressure, take it out and dry it to remove moisture to obtain modified fly ash. A3. Mix polyvinyl alcohol aqueous solution, melamine formaldehyde prepolymer solution and deionized water evenly, add hydrochloric acid solution to adjust pH, stir the reaction, add sodium hydroxide aqueous solution to adjust pH, pass ammonia gas, continue the reaction, filter, wash and dry to obtain polyvinyl alcohol-melamine formaldehyde resin. A4. Modified fly ash and tannic acid are added to acetone and stirred to mix. Polyvinyl alcohol-melamine formaldehyde resin is added and stirring is continued. After filtration and drying, composite flame retardant filler is obtained.

[0014] Furthermore, in the A1 reaction process described above, carboxymethyl cellulose acts as a binder, enabling glucose to adhere to the surface of fly ash. After high-temperature carbonization, the glucose decomposes to form a dense carbon layer. Potassium hydroxide solution acts as an activator, forming channels on the surface of the dense carbon layer, thus achieving the synthesis of a porous carbon structure on the surface of fly ash. During the high-temperature carbonization process, the metal ions contained in the fly ash can also combine with the carbon elements produced by the carbonization of glucose and carboxymethyl cellulose to form metal carbides, resulting in fly ash loaded with porous carbon.

[0015] Furthermore, in the A2 reaction process described above, ammonium polyphosphate dissolves in deionized water to form an aqueous solution of ammonium polyphosphate. The fly ash loaded with porous carbon has a large number of porous structures, which can adsorb the aqueous solution of ammonium polyphosphate into the pores of the porous carbon. After drying to remove moisture, the ammonium polyphosphate powder is loaded into the pores of the fly ash loaded with porous carbon, thus obtaining modified fly ash.

[0016] Furthermore, during the A3 reaction process described above, under acidic conditions, the hydroxyl groups contained in the melamine-formaldehyde prepolymer can undergo an etherification reaction with the hydroxyl groups of polyvinyl alcohol, thereby enabling polyvinyl alcohol to be grafted onto the melamine-formaldehyde resin to obtain polyvinyl alcohol-melamine-formaldehyde resin.

[0017] Furthermore, during the A4 reaction process described above, tannic acid contains a large number of phenolic hydroxyl groups, which have good adhesion properties and can adhere to the surface of modified fly ash. Tannic acid can also be combined with polyvinyl alcohol-melamine formaldehyde resin through hydrogen bonds, so that polyvinyl alcohol-melamine formaldehyde resin coats the surface of modified fly ash, resulting in a composite flame retardant filler.

[0018] Further, in step A1, the mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water and potassium hydroxide solution is (4-5):(3-4):(1.5-2):(70-80):(3-3.5).

[0019] Further, in step A2, the mass ratio of ammonium polyphosphate, deionized water, and fly ash loaded with porous carbon is (1.5-2):(20-30):(4.5-5).

[0020] Further, in step A3, the mass ratio of polyvinyl alcohol aqueous solution, melamine formaldehyde prepolymer solution and deionized water is (1.2-1.4):(1.1-1.5):(20-30).

[0021] Further, in step A4, the mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin is (4.2-4.7):(1.2-1.5):(50-60):(2.3-2.5).

[0022] The present invention has the following beneficial effects: (1) In the technical solution of the present invention, fly ash, glucose and carboxymethyl cellulose are mixed and reacted, and then carbonized at high temperature to achieve the synthesis of a porous carbon structure on the surface of fly ash. On the one hand, during the high-temperature carbonization process, the metal ions (Ca) contained in the fly ash are released. 2+ Mg 2+ Fe 3+ The carbon compounds (such as calcium carbide, magnesium carbide, and iron carbide) can combine with the carbon elements produced by the carbonization of glucose and carboxymethyl cellulose to form metal carbides, thereby adsorbing and fixing metal ions in fly ash that are prone to sedimentation. This prevents metal ions from precipitating into the wire and cable sheathing material, which would affect the flame retardancy and mechanical properties of the material. Furthermore, the synthesized porous carbon structure serves as an adsorption site for ammonium polyphosphate, which is beneficial for loading ammonium polyphosphate onto the surface of fly ash and improving flame retardancy. On the other hand, fly ash contains a large amount of silicon, which can also combine with the carbon elements produced by the carbonization of glucose and carboxymethyl cellulose to form silicon carbide, improving the mechanical properties of the wire and cable sheathing material. Moreover, porous carbon and fly ash, as rigid inorganic fillers, have high modulus and thermal stability, which can effectively bear stress and improve the tensile strength of the material.

[0023] (2) In the technical solution of the present invention, ammonium polyphosphate powder is adsorbed into the pores of fly ash loaded with porous carbon. The fly ash loaded with porous carbon serves as a carrier for the ammonium polyphosphate powder, which can adsorb more ammonium polyphosphate powder, improve the dispersibility of the ammonium polyphosphate powder in the wire and cable sheath material, and thus improve the flame retardant performance of the wire and cable sheath material. Moreover, the ammonium polyphosphate powder uniformly dispersed in the wire and cable sheath material serves as an intumescent flame retardant, which can significantly enhance the flame retardant performance of the wire and cable sheath material.

[0024] (3) In the technical solution of the present invention, polyvinyl alcohol is grafted onto melamine-formaldehyde resin to form polyvinyl alcohol-melamine-formaldehyde resin. When melamine-formaldehyde resin is heated during combustion, it can decompose to produce non-toxic and harmless inert gases such as nitrogen, which inhibits combustion. Polyvinyl alcohol, as a carbon source, can dehydrate to form a dense carbon layer. At the same time, the water vapor produced plays a role in cooling and oxygen barrier, thereby enhancing the flame retardant performance of wire and cable sheath material.

[0025] (4) In the technical solution of the present invention, polyvinyl alcohol-melamine formaldehyde resin is coated on the surface of modified fly ash by tannic acid. On the one hand, the polyvinyl alcohol molecular chain contained in the polyvinyl alcohol-melamine formaldehyde resin has good compatibility with the polyolefin matrix of the wire and cable sheath material, so that the composite flame retardant filler is uniformly dispersed in the wire and cable sheath material, thereby enhancing the flame retardancy and mechanical properties of the wire and cable sheath material. On the other hand, the polyvinyl alcohol-melamine formaldehyde resin and the modified fly ash form an organic-inorganic flame retardant filler, which has a synergistic flame retardant effect. Moreover, the polyvinyl alcohol-melamine formaldehyde resin provides a large amount of carbon source, and the ammonium polyphosphate in the modified fly ash can catalyze the polyvinyl alcohol-melamine formaldehyde resin to carbon, which significantly improves the flame retardant performance of the wire and cable sheath material.

[0026] (5) In the technical solution of the present invention, the wire and cable sheath material prepared by using polyolefin resin as the matrix, adding composite flame retardant filler, compounding ethylene-vinyl acetate copolymer, lubricant, ultraviolet absorber, antioxidant and light stabilizer has good mechanical properties and flame retardant properties, and the composite flame retardant filler can be uniformly dispersed in the wire and cable sheath material to achieve synergistic improvement of flame retardant properties and mechanical properties. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0029] The polyolefin is low-density polyethylene, grade 1C7A, purchased from Sinopec Yanshan Petrochemical Company.

[0030] The vinyl acetate content in the ethylene-vinyl acetate copolymer is 18 wt%.

[0031] The lubricant is zinc stearate, the ultraviolet absorber is UV-328, the antioxidant is DLTDP, and the light stabilizer is HALS-62; the fly ash particle size is 100μm.

[0032] Carboxymethyl cellulose (product number V32433) and polyvinyl alcohol (product number S25454) were purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0033] The melamine-formaldehyde prepolymer solution is prepared by the following steps: A 37% (w / w) formaldehyde aqueous solution, melamine, and deionized water were mixed evenly. A 20% (w / w) sodium hydroxide aqueous solution was added to adjust the pH to 8.5. The mixture was stirred at 75°C for 60 minutes. During the reaction, a 20% (w / w) sodium hydroxide aqueous solution was added dropwise to maintain the pH of the reaction solution. This yielded a melamine-formaldehyde prepolymer solution. The mass ratio of formaldehyde aqueous solution, melamine, and deionized water was 10:2.5:15.

[0034] Example 1 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 80 parts of low-density polyethylene, 15 parts of ethylene-vinyl acetate copolymer, 20 parts of composite flame retardant filler, 0.4 parts of zinc stearate, 2 parts of ultraviolet absorber UV-328, 1 part of antioxidant DLTDP, and 1 part of light stabilizer HALS-62. A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 5 min to obtain a mixture; S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 125℃, the temperature of the second zone is 145℃, the temperature of the third zone is 160℃, the die temperature is 165℃, and the screw speed is 30rpm.

[0035] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 800°C for 3 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 4:3:1.5:70:3. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. Apply negative pressure at -0.1 MPa for 10 minutes, remove and dry in an oven at 100℃ to remove moisture, to obtain modified fly ash; the mass ratio of ammonium polyphosphate, deionized water and fly ash loaded with porous carbon is 1.5:20:4.5. A3. Mix a 10% (w / w) aqueous solution of polyvinyl alcohol, a melamine-formaldehyde prepolymer solution, and deionized water thoroughly. Add a 10% (w / w) hydrochloric acid solution to adjust the pH to 3. Stir and react at 75°C for 3 hours. Add a 10% (w / w) aqueous solution of sodium hydroxide to adjust the pH to 8. Purge with ammonia gas and continue the reaction for 10 minutes. Filter, wash three times with deionized water, and dry in an oven at 90°C for 4 hours to obtain polyvinyl alcohol-melamine-formaldehyde resin. The mass ratio of polyvinyl alcohol aqueous solution, melamine-formaldehyde prepolymer solution, and deionized water is 1.2:1.1:20. A4. Modified fly ash and tannic acid were added to acetone and stirred at 30°C for 30 min. Polyvinyl alcohol-melamine formaldehyde resin was added and stirred for another 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin was 4.2:1.2:50:2.3.

[0036] Example 2 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 100 parts of low-density polyethylene, 18 parts of ethylene-vinyl acetate copolymer, 25 parts of composite flame retardant filler, 0.8 parts of zinc stearate, 3 parts of ultraviolet absorber UV-328, 2 parts of antioxidant DLTDP, and 1.5 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 8 min to obtain a mixture; S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 130℃, the temperature of the second zone is 150℃, the temperature of the third zone is 165℃, the die temperature is 170℃, and the screw speed is 35rpm.

[0037] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 850°C for 4 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 4.5:3.5:1.8:75:3.3. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. Apply negative pressure at -0.1 MPa for 10 minutes, remove and dry in an oven at 100℃ to remove moisture, to obtain modified fly ash; the mass ratio of ammonium polyphosphate, deionized water and fly ash loaded with porous carbon is 1.8:25:4.8. A3. Mix a 10% (w / w) polyvinyl alcohol aqueous solution, a melamine-formaldehyde prepolymer solution, and deionized water thoroughly. Add a 10% (w / w) hydrochloric acid solution to adjust the pH to 3. Stir and react at 75°C for 3 hours. Add a 10% (w / w) sodium hydroxide aqueous solution to adjust the pH to 8. Purge with ammonia gas and continue the reaction for 10 minutes. Filter, wash three times with deionized water, and dry in a 90°C oven for 4 hours to obtain polyvinyl alcohol-melamine-formaldehyde resin. The mass ratio of polyvinyl alcohol aqueous solution, melamine-formaldehyde prepolymer solution, and deionized water is 1.3:1.3:25. A4. Modified fly ash and tannic acid were added to acetone and stirred at 30°C for 30 min. Polyvinyl alcohol-melamine formaldehyde resin was added and stirred for another 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin was 4.4:1.3:55:2.4.

[0038] Example 3 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 120 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 30 parts of composite flame retardant filler, 1.2 parts of zinc stearate, 4 parts of ultraviolet absorber UV-328, 3 parts of antioxidant DLTDP, and 2 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 10 min to obtain a mixture. S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 135℃, the temperature of the second zone is 155℃, the temperature of the third zone is 170℃, the die temperature is 175℃, and the screw speed is 40rpm.

[0039] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 900°C for 5 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 5:4:2:80:3.5. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. Apply negative pressure at -0.1 MPa for 10 min, remove and dry in an oven at 100℃ to remove moisture to obtain modified fly ash. The mass ratio of ammonium polyphosphate, deionized water and fly ash loaded with porous carbon is 2:30:5. A3. Mix a 10% (w / w) polyvinyl alcohol aqueous solution, a melamine-formaldehyde prepolymer solution, and deionized water thoroughly. Add a 10% (w / w) hydrochloric acid solution to adjust the pH to 3. Stir and react at 75°C for 3 hours. Add a 10% (w / w) sodium hydroxide aqueous solution to adjust the pH to 8. Purge with ammonia gas and continue the reaction for 10 minutes. Filter, wash three times with deionized water, and dry in a 90°C oven for 4 hours to obtain polyvinyl alcohol-melamine-formaldehyde resin. The mass ratio of polyvinyl alcohol aqueous solution, melamine-formaldehyde prepolymer solution, and deionized water is 1.4:1.5:30. A4. Modified fly ash and tannic acid were added to acetone and stirred at 30°C for 30 min. Polyvinyl alcohol-melamine formaldehyde resin was added and stirred for another 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin was 4.7:1.5:60:2.5.

[0040] Comparative Example 1 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 120 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 30 parts of composite flame retardant filler, 1.2 parts of zinc stearate, 4 parts of ultraviolet absorber UV-328, 3 parts of antioxidant DLTDP, and 2 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 10 min to obtain a mixture. S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 135℃, the temperature of the second zone is 155℃, the temperature of the third zone is 170℃, the die temperature is 175℃, and the screw speed is 40rpm.

[0041] The composite flame-retardant filler is prepared by the following steps: A1. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash and stir evenly. Apply negative pressure at -0.1MPa for 10 minutes. Remove the fly ash and dry it in an oven at 100℃ to remove moisture, thus obtaining modified fly ash. The mass ratio of ammonium polyphosphate, deionized water and fly ash is 2:30:5. A2. Mix a 10% (w / w) polyvinyl alcohol aqueous solution, a melamine-formaldehyde prepolymer solution, and deionized water thoroughly. Add a 10% (w / w) hydrochloric acid solution to adjust the pH to 3. Stir and react at 75°C for 3 hours. Add a 10% (w / w) sodium hydroxide aqueous solution to adjust the pH to 8. Purge with ammonia gas and continue the reaction for 10 minutes. Filter, wash three times with deionized water, and dry in a 90°C oven for 4 hours to obtain polyvinyl alcohol-melamine-formaldehyde resin. The mass ratio of polyvinyl alcohol aqueous solution, melamine-formaldehyde prepolymer solution, and deionized water is 1.4:1.5:30. A3. Modified fly ash and tannic acid were added to acetone and stirred at 30°C for 30 min. Polyvinyl alcohol-melamine formaldehyde resin was added and stirred for another 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin was 4.7:1.5:60:2.5.

[0042] Comparative Example 2 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 120 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 30 parts of composite flame retardant filler, 1.2 parts of zinc stearate, 4 parts of ultraviolet absorber UV-328, 3 parts of antioxidant DLTDP, and 2 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 10 min to obtain a mixture. S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 135℃, the temperature of the second zone is 155℃, the temperature of the third zone is 170℃, the die temperature is 175℃, and the screw speed is 40rpm.

[0043] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 900°C for 5 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 5:4:2:80:3.5. A2. Mix a 10% (w / w) polyvinyl alcohol aqueous solution, a melamine-formaldehyde prepolymer solution, and deionized water thoroughly. Add a 10% (w / w) hydrochloric acid solution to adjust the pH to 3. Stir and react at 75°C for 3 hours. Add a 10% (w / w) sodium hydroxide aqueous solution to adjust the pH to 8. Purge with ammonia gas and continue the reaction for 10 minutes. Filter, wash three times with deionized water, and dry in a 90°C oven for 4 hours to obtain polyvinyl alcohol-melamine-formaldehyde resin. The mass ratio of polyvinyl alcohol aqueous solution, melamine-formaldehyde prepolymer solution, and deionized water is 1.4:1.5:30. A3. Add porous carbon-loaded fly ash and tannic acid to acetone, stir and mix at 30°C for 30 min, add polyvinyl alcohol-melamine formaldehyde resin, continue stirring for 30 min, filter, and dry in an oven at 70°C for 10 min to obtain a composite flame-retardant filler; the mass ratio of porous carbon-loaded fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin is 4.7:1.5:60:2.5.

[0044] Comparative Example 3 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 120 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 30 parts of composite flame retardant filler, 1.2 parts of zinc stearate, 4 parts of ultraviolet absorber UV-328, 3 parts of antioxidant DLTDP, and 2 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 10 min to obtain a mixture. S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 135℃, the temperature of the second zone is 155℃, the temperature of the third zone is 170℃, the die temperature is 175℃, and the screw speed is 40rpm.

[0045] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 900°C for 5 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 5:4:2:80:3.5. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. Apply negative pressure at -0.1 MPa for 10 min, remove and dry in an oven at 100℃ to remove moisture to obtain modified fly ash. The mass ratio of ammonium polyphosphate, deionized water and fly ash loaded with porous carbon is 2:30:5. A3. Mix the melamine-formaldehyde prepolymer solution and deionized water evenly, add 10% hydrochloric acid solution to adjust the pH to 3, stir and react at 75℃ for 3 hours, then add 10% sodium hydroxide aqueous solution to adjust the pH to 8, introduce ammonia gas, and continue the reaction for 10 minutes. After filtration, wash three times with deionized water, and dry in an oven at 90℃ for 4 hours to obtain melamine-formaldehyde resin; the mass ratio of melamine-formaldehyde prepolymer solution to deionized water is 1.5:30. A4. Modified fly ash and tannic acid were added to acetone and stirred at 30°C for 30 min. Polyvinyl alcohol-melamine formaldehyde resin was added and stirred for another 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin was 4.7:1.5:60:2.5.

[0046] Comparative Example 4 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 120 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 30 parts of composite flame retardant filler, 1.2 parts of zinc stearate, 4 parts of ultraviolet absorber UV-328, 3 parts of antioxidant DLTDP, and 2 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 10 min to obtain a mixture. S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 135℃, the temperature of the second zone is 155℃, the temperature of the third zone is 170℃, the die temperature is 175℃, and the screw speed is 40rpm.

[0047] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 900°C for 5 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 5:4:2:80:3.5. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. Apply negative pressure at -0.1 MPa for 10 min, remove and dry in an oven at 100℃ to remove moisture to obtain modified fly ash. The mass ratio of ammonium polyphosphate, deionized water and fly ash loaded with porous carbon is 2:30:5. A3. Modified fly ash and tannic acid were added to acetone and stirred at 30°C for 30 min. Polyvinyl alcohol was added and stirring was continued for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, tannic acid, acetone and polyvinyl alcohol was 4.7:1.5:60:2.5.

[0048] Comparative Example 5 A type of wire and cable sheath material comprises the following raw materials in parts by weight: 120 parts of low-density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 30 parts of composite flame retardant filler, 1.2 parts of zinc stearate, 4 parts of ultraviolet absorber UV-328, 3 parts of antioxidant DLTDP, and 2 parts of light stabilizer HALS-62; A method for preparing a wire and cable sheath material includes the following preparation steps: S1. Mix low-density polyethylene, ethylene-vinyl acetate copolymer, composite flame retardant filler, zinc stearate, ultraviolet absorber UV-328, antioxidant DLTDP and light stabilizer HALS-62 for 10 min to obtain a mixture. S2. The mixture is fed into a twin-screw extruder, and after melt extrusion, granulation, cooling, and pelletizing, wire and cable sheath material is obtained; wherein, the temperature of the first zone of the twin-screw extruder is 135℃, the temperature of the second zone is 155℃, the temperature of the third zone is 170℃, the die temperature is 175℃, and the screw speed is 40rpm.

[0049] The composite flame-retardant filler is prepared by the following steps: A1. Fly ash, glucose, and carboxymethyl cellulose were added to deionized water and stirred at 65°C for 30 min. After filtration, the mixture was dried in an oven at 70°C for 10 min, placed in a tube furnace, and a 30% potassium hydroxide solution was added. Nitrogen gas was introduced, and the mixture was carbonized at 900°C for 5 h. After cooling to room temperature, the mixture was removed, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain fly ash loaded with porous carbon. The mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water, and potassium hydroxide solution was 5:4:2:80:3.5. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. Apply negative pressure at -0.1 MPa for 10 min, remove and dry in an oven at 100℃ to remove moisture to obtain modified fly ash. The mass ratio of ammonium polyphosphate, deionized water and fly ash loaded with porous carbon is 2:30:5. A3. Mix a 10% (w / w) polyvinyl alcohol aqueous solution, a melamine-formaldehyde prepolymer solution, and deionized water thoroughly. Add a 10% (w / w) hydrochloric acid solution to adjust the pH to 3. Stir and react at 75°C for 3 hours. Add a 10% (w / w) sodium hydroxide aqueous solution to adjust the pH to 8. Purge with ammonia gas and continue the reaction for 10 minutes. Filter, wash three times with deionized water, and dry in a 90°C oven for 4 hours to obtain polyvinyl alcohol-melamine-formaldehyde resin. The mass ratio of polyvinyl alcohol aqueous solution, melamine-formaldehyde prepolymer solution, and deionized water is 1.4:1.5:30. A4. Add modified fly ash to acetone and stir at 30°C for 30 min. Add polyvinyl alcohol-melamine formaldehyde resin and continue stirring for 30 min. After filtration, dry in an oven at 70°C for 10 min to obtain a composite flame retardant filler. The mass ratio of modified fly ash, acetone and polyvinyl alcohol-melamine formaldehyde resin is 6.2:60:2.5.

[0050] The performance of the wire and cable sheath materials prepared in Examples 1-3 and Comparative Examples 1-5 was then tested.

[0051] The above-prepared wire and cable sheath material was made into a standard sample strip using an injection molding machine: length × width × thickness = 120mm × 10mm × 4mm.

[0052] Flame retardant performance testing: The oxygen index of wire and cable sheathing materials was tested according to GB / T2406.2-2009 "Determination of burning behavior by oxygen index method for plastics - Part 2: Room temperature test". The specific standards for the vertical burning rating test are as follows: 1. Fix the standard sample vertically on the bracket, with the lower end 10mm from the bottom of the combustion chamber and 10mm from the top of the Bunsen burner. The longitudinal axis of the standard sample should coincide with the flame axis, without any skew or looseness; 2. Flame calibration: Ignite the Bunsen burner and adjust the flame height to 20±2mm, with the tip of the blue flame cone contacting the lower edge of the sample; 3. Aim the flame at the center of the lower end of the standard sample, burn for 10 seconds, and then quickly remove it. Record the flaming burning time (t1). After the flame extinguishes, wait 10 seconds and then apply the flame again for 10 seconds. Record the flaming time (t2) and the flameless burning time (t3).

[0053] Throughout the process, observe whether the dripping material ignites the absorbent cotton. During combustion, the sample melts and drips. Gently push the dripping material away from the bottom of the sample with a blowtorch. If any sample breaks within the gauge length or burns to the fixture, the result for that sample is invalid. Repeat the above method for testing.

[0054] Vertical flammability rating (V) determination: V-0 level: After ignition in 10 seconds, the flaming burning time t1+t2≤10 seconds; the total burning time after two ignitions≤50 seconds; no dripping material ignites the degreased cotton; the sample does not burn to the clamp; Level V-1: After ignition in 10 seconds, the flaming burning time t1+t2≤30 seconds; the total burning time after two ignitions≤250 seconds; no dripping material ignites the degreased cotton; the sample does not burn to the clamp; V-2 level: After ignition in 10 seconds, the flaming burning time t1+t2≤30 seconds; the total burning time after two ignitions≤250 seconds; dripping material is allowed to ignite the degreased cotton; the sample does not burn to the fixture.

[0055] The specific standards for mechanical performance testing are as follows: 1. Condition the standard specimen in an environment of 23℃ and 50% relative humidity for 88 hours. Measure the width and thickness of the standard specimen with calipers, calculate the original cross-sectional area (original cross-sectional area = width × thickness), and mark the original gauge length (L0) on the parallel part of the standard specimen. The gauge length line should be clear and not damage the specimen; 2. Clamp the standard specimen vertically in the testing machine fixture, start the testing machine, set the tensile rate to 50 mm / min, and load until the specimen completely breaks. Record the maximum load (N) and the gauge length (L1) at break; Tensile strength (MPa) = Maximum load (N) / Original cross-sectional area (mm²) 2 Elongation at break = (L1 - L0) / L0 × 100%.

[0056] As shown in Table 1 below.

[0057] Table 1 Performance testing of wire and cable sheathing materials prepared in Examples 1-3 and Comparative Examples 1-5

[0058] As can be seen from the data in Table 1, the wire and cable sheath materials prepared in Examples 1-3 have high flame retardant properties and mechanical properties.

[0059] In Comparative Example 1, replacing the porous carbon-loaded fly ash with a composite flame-retardant filler prepared from fly ash and adding it to the wire and cable sheath material resulted in a decrease in its flame-retardant and mechanical properties. This demonstrates that synthesizing porous carbon structures on the surface of fly ash can adsorb and fix metal ions in fly ash that are prone to sedimentation, preventing the precipitation of metal ions from fly ash into the wire and cable sheath material and affecting its flame-retardant and mechanical properties. Furthermore, the synthesized porous carbon structures serve as adsorption sites for ammonium polyphosphate, which is beneficial for loading ammonium polyphosphate onto the surface of fly ash. In addition, the large amount of silicon in fly ash can combine with the carbon elements produced by the carbonization of glucose and carboxymethyl cellulose to form silicon carbide, thereby improving the mechanical properties of the wire and cable sheath material.

[0060] Comparative Example 2 showed that when modified fly ash was replaced with fly ash loaded with porous carbon, the composite flame-retardant filler was added to the wire and cable sheath material, and its flame-retardant performance decreased. This proves that ammonium polyphosphate powder uniformly dispersed in the wire and cable sheath material, as an intumescent flame retardant, can significantly enhance the flame-retardant performance of the wire and cable sheath material. Moreover, ammonium polyphosphate can catalyze the carbonization of polyvinyl alcohol-melamine formaldehyde resin, which significantly improves the flame-retardant performance of the wire and cable sheath material.

[0061] Comparative Example 3 showed that when the composite flame-retardant filler prepared by replacing polyvinyl alcohol-melamine-formaldehyde resin with melamine-formaldehyde resin was added to the wire and cable sheath material, its flame-retardant and mechanical properties decreased. This proves that polyvinyl alcohol provides a large amount of carbon source, and the ammonium polyphosphate in the modified fly ash can catalyze the carbonization of polyvinyl alcohol, significantly improving the flame-retardant performance of the wire and cable sheath material. Moreover, the polyvinyl alcohol molecular chain has good compatibility with the polyolefin matrix of the wire and cable sheath material, which makes the composite flame-retardant filler uniformly dispersed in the wire and cable sheath material, enhancing the flame retardancy and mechanical properties of the wire and cable sheath material.

[0062] Comparative Example 4 showed that when polyvinyl alcohol-melamine-formaldehyde resin was replaced with a composite flame-retardant filler prepared from polyvinyl alcohol, it was added to the wire and cable sheath material. The flame-retardant and mechanical properties of the filler decreased, which proved that when melamine-formaldehyde resin is heated during combustion, it can decompose to produce non-toxic and harmless inert gases such as nitrogen, which inhibits combustion. It forms an organic-inorganic flame-retardant filler with modified fly ash and has a synergistic flame-retardant effect.

[0063] Comparative Example 5 showed that when tannic acid was replaced by a composite flame-retardant filler prepared from modified fly ash, its flame-retardant and mechanical properties decreased. This demonstrates that polyvinyl alcohol-melamine-formaldehyde resin, through tannic acid coating on the surface of modified fly ash, allows the composite flame-retardant filler to be uniformly dispersed in the wire and cable sheath material, enhancing its flame retardancy and mechanical properties. Furthermore, the polyvinyl alcohol-melamine-formaldehyde resin and modified fly ash form an organic-inorganic flame-retardant filler, exhibiting a synergistic flame-retardant effect.

[0064] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0065] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A type of wire and cable sheathing material, characterized in that, The raw materials include the following parts by weight: 80-120 parts of polyolefin, 15-20 parts of ethylene-vinyl acetate copolymer, 20-30 parts of composite flame retardant filler, 0.4-1.2 parts of lubricant, 2-4 parts of ultraviolet absorber, 1-3 parts of antioxidant and 1-2 parts of light stabilizer; The composite flame-retardant filler is obtained by grafting polyvinyl alcohol onto melamine-formaldehyde resin and then reacting it with modified fly ash and tannic acid. The modified fly ash is obtained by mixing and reacting fly ash, glucose and carboxymethyl cellulose, and then loading ammonium polyphosphate.

2. The wire and cable sheath material according to claim 1, characterized in that, The composite flame-retardant filler is prepared by the following steps: A1. Add fly ash, glucose and carboxymethyl cellulose to deionized water, stir evenly, filter, dry and place in a tube furnace, add potassium hydroxide solution, purge with nitrogen, carbonize at 800-900℃ for 3-5 hours, cool to room temperature, take out, wash and dry to obtain fly ash loaded with porous carbon. A2. Add ammonium polyphosphate to deionized water and stir evenly. Add fly ash loaded with porous carbon and stir evenly. After negative pressure, take it out and dry it to remove moisture to obtain modified fly ash. A3. Mix polyvinyl alcohol aqueous solution, melamine formaldehyde prepolymer solution and deionized water evenly, add hydrochloric acid solution to adjust pH, stir the reaction, add sodium hydroxide aqueous solution to adjust pH, pass ammonia gas, continue the reaction, filter, wash and dry to obtain polyvinyl alcohol-melamine formaldehyde resin. A4. Modified fly ash and tannic acid are added to acetone and stirred to mix. Polyvinyl alcohol-melamine formaldehyde resin is added and stirring is continued. After filtration and drying, composite flame retardant filler is obtained.

3. The wire and cable sheath material according to claim 2, characterized in that, In step A1, the mass ratio of fly ash, glucose, carboxymethyl cellulose, deionized water and potassium hydroxide solution is (4-5):(3-4):(1.5-2):(70-80):(3-3.5).

4. The wire and cable sheath material according to claim 2, characterized in that, In step A2, the mass ratio of ammonium polyphosphate, deionized water, and fly ash loaded with porous carbon is (1.5-2):(20-30):(4.5-5).

5. The wire and cable sheath material according to claim 2, characterized in that, In step A3, the mass ratio of the polyvinyl alcohol aqueous solution, melamine formaldehyde prepolymer solution and deionized water is (1.2-1.4):(1.1-1.5):(20-30).

6. The wire and cable sheath material according to claim 2, characterized in that, In step A4, the mass ratio of the modified fly ash, tannic acid, acetone and polyvinyl alcohol-melamine formaldehyde resin is (4.2-4.7):(1.2-1.5):(50-60):(2.3-2.5).

7. The wire and cable sheath material according to claim 1, characterized in that, The polyolefin is low-density polyethylene; The vinyl acetate content in the ethylene-vinyl acetate copolymer is 16-20 wt%.

8. The wire and cable sheath material according to claim 1, characterized in that, The lubricant is selected from any one of zinc stearate, calcium stearate, vinyl distearate and epoxidized soybean oil; The ultraviolet absorber is selected from ultraviolet absorber UV-328 or ultraviolet absorber UV-9.

9. The wire and cable sheath material according to claim 1, characterized in that, The antioxidant is selected from any one of antioxidant DLTDP, antioxidant 1010, antioxidant 168 and antioxidant 264; The light stabilizer is selected from any one of light stabilizer HALS-62, light stabilizer 944 and light stabilizer UV-3853.

10. A method for preparing a wire and cable sheath material according to any one of claims 1-9, characterized in that, The preparation steps include the following: S1. Mix polyolefin, ethylene-vinyl acetate copolymer, composite flame retardant filler, lubricant, ultraviolet absorber, antioxidant and light stabilizer for 5-10 minutes to obtain a mixture; S2. The mixture is fed into a twin-screw extruder, melt-extruded, granulated, cooled, and pelletized to obtain wire and cable sheath material.

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