Flame-retardant cable material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a flame-retardant cable material and a preparation method thereof, and the cable material is prepared from the following raw materials in parts by weight: 45-60 parts of matrix resin; 35-45 parts of a main flame retardant system; 16 to 25 parts of an intumescent flame retardant system; 4 to 7 parts of a bio-based synergist; 1.8 to 4 parts of a processing aid; and 0.3 to 0.5 part of a stable system. According to the flame-retardant cable material and the preparation method thereof, mechanical properties are enhanced, environmental protection, efficient flame retardance and processing adaptability are achieved, meanwhile, the cost is controllable, a halogen-free formula enables the oxygen index to be higher and the smoke density to be smaller, meanwhile, the polyolefin elastomer and the organic montmorillonite are synergistically toughened, the tensile strength is higher, the elongation at break is larger, and the flame-retardant cable material is superior to a traditional system; and the silane coupling agent and the composite lubricant in the process optimize the melt flowability to adapt to the high-speed extrusion process, so that the production difficulty is low, and the universality is wider.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically relates to a flame-retardant cable material and a preparation method thereof. Background Art

[0002] Cable materials are special polymer materials used to manufacture the insulation layer, sheath layer and other functional layers of wires and cables. They are mainly composed of a polymer matrix and additives such as flame retardants. Their core functions include electrical insulation, mechanical protection, environmental aging resistance and flame retardancy and fire prevention. They need to meet specific temperature, voltage and combustion safety standards and are widely used in fields such as power transmission, communication, and rail transit.

[0003] In the applications in the fields of construction, transportation, energy and power, and new energy vehicles, high flame-retardant cable materials are required. However, general traditional polymer materials have problems such as poor flame retardancy, environmental pollution, and performance imbalance. The oxygen index of unmodified PVC is only 21-25%, and it burns rapidly when encountering fire and releases a large amount of HCl gas. Halogen-containing flame retardants produce carcinogens such as dioxins when burning. Adding a high dose of inorganic flame retardants causes the material to become brittle and the processing fluidity to deteriorate. At the same time, few environmentally friendly polymer materials with high flame retardancy that take into account multiple advantages are expensive, and it is difficult to balance these three points.

[0004] Based on this, the present invention provides a flame-retardant cable material and a preparation method thereof to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a flame-retardant cable material and a preparation method thereof to solve the problems mentioned in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a flame-retardant cable material, which is composed of the following raw materials in parts by weight: matrix resin: 45-60 parts; main flame-retardant system: 35-45 parts; intumescent flame-retardant system: 16-25 parts; bio-based synergist: 4-7 parts; processing aid: 1.8-4 parts; stabilizing system: 0.3-0.5 parts;

[0008] The matrix resin is composed of ethylene-vinyl acetate copolymer and polyolefin elastomer, the ethylene-vinyl acetate copolymer: 35-45 parts, polyolefin elastomer: 10-15 parts;

[0009] The main flame-retardant system is composed of nano-aluminum hydroxide and nano-magnesium hydroxide, the nano-aluminum hydroxide: 20-25 parts, nano-magnesium hydroxide: 15-20 parts;

[0010] The intumescent flame retardant system consists of coated ammonium polyphosphate, melamine polyphosphate and microencapsulated pentaerythritol, with the coated ammonium polyphosphate: 8 - 12 parts, melamine polyphosphate: 5 - 8 parts, and microencapsulated pentaerythritol: 3 - 5 parts;

[0011] The bio - based synergist consists of phosphorylated chitosan and organically modified montmorillonite, with the phosphorylated chitosan: 2 - 4 parts and organically modified montmorillonite: 2 - 3 parts;

[0012] The processing aid consists of silane coupling agent and compound lubricant, with the silane coupling agent: 1 - 2 parts and compound lubricant: 0.5 - 1.5 parts;

[0013] The stabilization system consists of antioxidant 1010 and antioxidant 168, with antioxidant 1010: 0.15 - 0.25 parts and antioxidant 168: 0.15 - 0.25 parts.

[0014] Preferably, the nano - aluminum hydroxide uses industrial - grade sodium aluminate as raw material, dissolves it in deionized water and then filters. Slowly add dilute sulfuric acid to pH 8.0 - 8.5 at 60 °C, keep stirring at 500 rpm for 2 hours to generate aluminum hydroxide precipitate. After aging for 12 hours, centrifuge and wash until the conductivity is less than 50 μS / cm. Add 2% silane coupling agent KH - 550 and ball - mill for 4 hours, and calcine at 250 °C for 2 hours to remove residual moisture, obtaining nano - aluminum hydroxide with a particle size of 50 nm and a purity of greater than or equal to 99.5%.

[0015] Preferably, the nano - magnesium hydroxide is prepared by dissolving magnesium chloride hexahydrate in water to form a 0.8 mol / L solution, adding ammonia water to adjust the pH to 10.5, then transferring it to a hydrothermal reaction kettle and reacting at 180 °C for 8 hours to form flaky magnesium hydroxide. After centrifugal separation, ultrasonic treatment is carried out with a 1.5% sodium stearate ethanol solution for 30 minutes, and dried at 80 °C to remove the solvent, obtaining nano - magnesium hydroxide with a lamellar thickness of less than 10 nm and a purity of greater than or equal to 99.0%.

[0016] Preferably, the coated ammonium polyphosphate is prepared by mixing ordinary ammonium polyphosphate and melamine at a molar ratio of 1:0.3, putting them into a twin - screw extruder and melt - blending at 200 °C for 10 minutes. The melamine melt uniformly coats the surface of ammonium polyphosphate. After cooling, it is crushed and sieved to remove particles with a particle size greater than 20 μm, obtaining coated ammonium polyphosphate with a degree of polymerization greater than 1000 and a coating rate of greater than or equal to 95%.

[0017] Preferably, the phosphorylated chitosan is prepared by dissolving chitosan with a deacetylation degree greater than 90% in a 2% acetic acid solution, adding three - fold molar amount of phosphorus pentoxide, reacting at 60 °C for 6 hours to complete phosphorylation. The reaction solution is dialyzed for 48 hours to remove unreacted substances, freeze - dried and then crushed, obtaining white powdery phosphorylated chitosan with a substitution degree greater than 1.2 and an ash content less than 0.5%.

[0018] Preferably, the organically modified montmorillonite is prepared by ion-exchanging natural calcium-based montmorillonite with a 5% sodium carbonate solution to convert it into sodium-based montmorillonite, stirring and intercalating with cetyltrimethylammonium bromide in an aqueous solution at 80°C for 4 hours, centrifuging and washing until there is no residual bromide ion, drying at 105°C and then grinding to obtain an organically modified montmorillonite with an interlayer spacing greater than or equal to 3.0 nm and a cation exchange capacity greater than or equal to 90 mmol / 100 g.

[0019] Preferably, the ethylene-vinyl acetate copolymer is prepared by mixing ethylene and vinyl acetate in a molar ratio of 85:15 in a 150 MPa high-pressure tubular reactor, using di-tert-butyl peroxide as an initiator, and carrying out free radical polymerization at 200°C. The molten product is passed through a vacuum devolatilization unit to remove unreacted monomers and is pelletized underwater to obtain ethylene-vinyl acetate copolymer particles with a VA content of 28 ± 1% and a melt index of 2 - 5 g / 10 min.

[0020] Preferably, the microencapsulated pentaerythritol is prepared by dispersing pentaerythritol powder in an aqueous solution containing 15% gum arabic, forming a stable emulsion by high-pressure homogenization, and controlling the inlet air temperature at 180°C and the atomization pressure at 0.3 MPa during spray drying to enable the wall material to rapidly coat the core material, obtaining microencapsulated pentaerythritol with a coating rate greater than or equal to 90%, a core material content greater than 85%, and an average particle size of 50 μm.

[0021] The present invention also provides a method for preparing a flame-retardant cable material, comprising the following steps:

[0022] S1. Put 20 - 25 parts of nano-aluminum hydroxide and 1 - 2 parts of silane coupling agent KH-550 into a high-speed mixer, set the rotation speed at 2000 rpm, and mix for 30 minutes to uniformly coat the coupling agent on the surface of the nano-particles. Transfer the mixed material to a vacuum drying oven, dry at 80°C for 4 hours, control the moisture content to be less than 0.1%. Then, disperse 15 - 20 parts of nano-magnesium hydroxide and 1.5 wt% of sodium stearate in an ethanol solution by ultrasonic treatment for 30 minutes, and after centrifugal separation, dry at 80°C until the solvent residue is less than 0.05%;

[0023] S2. Add 35 - 45 parts of ethylene-vinyl acetate copolymer and 10 - 15 parts of polyolefin elastomer to an internal mixer, heat up to 120°C for melting and plasticizing, continuously stir for 10 minutes, transfer the melt to a twin-screw devolatilization unit, and remove unreacted monomers at 140 - 160°C and a vacuum degree of -0.095 MPa, and pelletize underwater to obtain a matrix resin masterbatch;

[0024] S3. Put the pretreated nano-aluminum hydroxide: 20 - 25 parts, nano-magnesium hydroxide: 15 - 20 parts, coated ammonium polyphosphate: 8 - 12 parts, and microencapsulated pentaerythritol: 3 - 5 parts into a high-speed mixer, pre-mix at 1000 rpm for 15 minutes. Transfer the mixture to a nano-disperser, add melamine polyphosphate: 5 - 8 parts, and disperse at 50 °C and a shear rate of 6000 s-1 for 30 minutes to ensure that the particle size D90 is less than 50 μm;

[0025] S4. Dissolve phosphorylated chitosan: 2 - 4 parts in deionized water with a concentration of 5%, add organically modified montmorillonite: 2 - 3 parts, and perform ultrasonic treatment for 1 hour to form a uniform suspension. The suspension is freeze-dried and then pulverized through a 200-mesh sieve to obtain a bio-based synergistic composite powder;

[0026] S5. Put the matrix resin masterbatch, flame retardant premix, and bio-based synergistic composite powder into the main feeding port of an extruder. Silane coupling agent: 1 - 2 parts, composite lubricant: 0.5 - 1.5 parts are added through the side feeding port. The melt is plasticized through four temperature control zones and formed into layers through a three-layer co-extrusion die:

[0027] The outer layer contains a high flame retardant layer of organically modified montmorillonite: 2 - 3 parts and nano-aluminum hydroxide / magnesium: 35 - 45 parts;

[0028] The middle layer is a composite layer of matrix resin and intumescent flame retardant system: 16 - 25 parts;

[0029] The inner layer is a flexible layer reinforced with polyolefin elastomer: 10 - 15 parts;

[0030] S6. The extruded cable material enters a heat treatment oven and is treated at 80 °C for 2 hours to promote the cross-linking reaction of the silane coupling agent. After cooling, it is cut into uniform particles by a granulator and vacuum packaged.

[0031] Preferably, the four temperature zones for plasticization in the four temperature control zones of step S5 are: zone 1 at 120 °C, zone 2 at 140 °C, zone 3 at 160 °C, zone 4 at 170 °C, and the die head at 165 °C.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] The flame retardant cable material and its preparation method of the present invention take into account the strengthening of mechanical properties, environmentally friendly and efficient flame retardancy, processing adaptability, and controllable cost at the same time. The halogen-free formula makes the oxygen index higher and the smoke density smaller. At the same time, the polyolefin elastomer and organically modified montmorillonite in the present invention synergistically toughen, resulting in higher tensile strength and greater elongation at break, which are superior to the traditional system. Moreover, the silane coupling agent and composite lubricant in the process of the present invention optimize the melt fluidity to adapt to the high-speed extrusion process, with low production difficulty and wider versatility. Detailed implementation mode

[0034] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. 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 making creative efforts shall fall within the protection scope of the present invention.

[0035] I. Materials:

[0036] In the present invention, the material components are all commercially available without further description:

[0037] The flame-retardant cable material of the present invention is composed of the following raw materials in parts by weight:

[0038] Matrix resin: 45 - 60 parts;

[0039] Among them, it should be noted that: the matrix resin is composed of ethylene-vinyl acetate copolymer and polyolefin elastomer, ethylene-vinyl acetate copolymer: 35 - 45 parts, polyolefin elastomer: 10 - 15 parts;

[0040] Main flame-retardant system: 35 - 45 parts;

[0041] Among them, it should be noted that: the main flame-retardant system is composed of nano-aluminum hydroxide and nano-magnesium hydroxide, nano-aluminum hydroxide: 20 - 25 parts, nano-magnesium hydroxide: 15 - 20 parts;

[0042] Intumescent flame-retardant system: 16 - 25 parts;

[0043] Among them, it should be noted that: the intumescent flame-retardant system is composed of coated ammonium polyphosphate, melamine polyphosphate and microencapsulated pentaerythritol, coated ammonium polyphosphate: 8 - 12 parts, melamine polyphosphate: 5 - 8 parts, microencapsulated pentaerythritol: 3 - 5 parts;

[0044] Bio-based synergist: 4 - 7 parts;

[0045] Among them, it should be noted that: the bio-based synergist is composed of phosphorylated chitosan and organically modified montmorillonite, phosphorylated chitosan: 2 - 4 parts, organically modified montmorillonite: 2 - 3 parts;

[0046] Processing aids: 1.8 - 4 parts;

[0047] Among them, it should be noted that: the processing aids are composed of silane coupling agent and compound lubricant, silane coupling agent: 1 - 2 parts, compound lubricant: 0.5 - 1.5 parts;

[0048] Stabilization system: 0.3 - 0.5 parts;

[0049] Among them, it should be noted that: the stable system is composed of antioxidant 1010 and antioxidant 168, antioxidant 1010: 0.15 - 0.25 parts, antioxidant 168: 0.15 - 0.25 parts;

[0050] It should also be noted that nano-aluminum hydroxide uses industrial-grade sodium aluminate as raw material, dissolves in deionized water and then filters, slowly drops dilute sulfuric acid to pH 8.0 - 8.5 at 60 °C, keeps stirring and reacting at 500 rpm for 2 hours to generate aluminum hydroxide precipitate, after aging for 12 hours, centrifuges and washes until the conductivity is less than 50 μS / cm, adds 2% silane coupling agent KH-550 and ball mills for 4 hours, and calcines at 250 °C for 2 hours to remove residual moisture, thus obtaining nano-aluminum hydroxide with a particle size of 50 nm and a purity of greater than or equal to 99.5%;

[0051] It should also be noted that nano-magnesium hydroxide is prepared by dissolving magnesium chloride hexahydrate in water to form a 0.8 mol / L solution, adding ammonia water to adjust the pH to 10.5 and then transferring it to a hydrothermal reactor, reacting at 180 °C for 8 hours to generate flaky magnesium hydroxide, after centrifugal separation, ultrasonic treating with 1.5% sodium stearate ethanol solution for 30 minutes, and drying at 80 °C to remove the solvent, thus obtaining nano-magnesium hydroxide with a lamellar thickness of less than 10 nm and a purity of greater than or equal to 99.0%;

[0052] It should also be noted that the coated ammonium polyphosphate is prepared by mixing ordinary ammonium polyphosphate and melamine at a molar ratio of 1:0.3, putting them into a twin-screw extruder and melting and blending at 200 °C for 10 minutes, the melamine melt is uniformly coated on the surface of ammonium polyphosphate, after cooling, it is crushed and sieved to remove particles with a particle size greater than 20 μm, thus obtaining coated ammonium polyphosphate with a degree of polymerization greater than 1000 and a coating rate of greater than or equal to 95%;

[0053] It should also be noted that phosphorylated chitosan is prepared by dissolving chitosan with a deacetylation degree greater than 90% in a 2% acetic acid solution, adding three times the molar amount of phosphorus pentoxide, reacting at 60 °C for 6 hours to complete phosphorylation, dialyzing the reaction solution for 48 hours to remove unreacted substances, freeze-drying and then crushing, thus obtaining white powdery phosphorylated chitosan with a substitution degree greater than 1.2 and an ash content less than 0.5%;

[0054] It should also be noted that the organically modified montmorillonite is prepared by ion-exchanging natural calcium-based montmorillonite with a 5% sodium carbonate solution to convert it into sodium-based montmorillonite, stirring and intercalating with cetyltrimethylammonium bromide in an 80 °C aqueous solution for 4 hours, centrifuging and washing until there is no residual bromide ion, drying at 105 °C and then grinding, thus obtaining organically modified montmorillonite with an interlayer spacing of greater than or equal to 3.0 nm and a cation exchange capacity of greater than or equal to 90 mmol / 100 g;

[0055] It should also be noted that ethylene-vinyl acetate copolymer is prepared by mixing ethylene and vinyl acetate in a molar ratio of 85:15 in a 150 MPa high-pressure tubular reactor, using di-tert-butyl peroxide as an initiator, and carrying out free radical polymerization at 200 °C. The molten product is de-volatilized by a vacuum devolatilization unit to remove unreacted monomers, and then pelletized underwater to obtain ethylene-vinyl acetate copolymer particles with a VA content of 28 ± 1% and a melt index of 2-5 g / 10 min;

[0056] It should also be noted that microencapsulated pentaerythritol is prepared by dispersing pentaerythritol powder in an aqueous solution containing 15% gum arabic, forming a stable emulsion by high-pressure homogenization, and controlling the inlet air temperature at 180 °C and the atomization pressure at 0.3 MPa during spray drying to enable the wall material to quickly coat the core material, obtaining microencapsulated pentaerythritol with a coating rate of not less than 90%, a core material content of more than 85%, and an average particle size of 50 μm;

[0057] II. Process:

[0058] Based on the above material components of the cable compound, the present invention also provides a preparation method for a flame-retardant cable compound, which includes the following steps:

[0059] S1. Put 20-25 parts of nano-aluminum hydroxide and 1-2 parts of silane coupling agent KH-550 into a high-speed mixer, set the rotation speed at 2000 rpm, and mix for 30 minutes to uniformly coat the coupling agent on the surface of the nano-particles. The mixed material is transferred to a vacuum drying oven and dried at 80 °C for 4 hours, controlling the moisture content to be less than 0.1%. Then, 15-20 parts of nano-magnesium hydroxide and sodium stearate with an addition amount of 1.5 wt% are ultrasonically dispersed in an ethanol solution for 30 minutes, and after centrifugal separation, it is dried at 80 °C until the solvent residue is less than 0.05%;

[0060] S2. Add 35-45 parts of ethylene-vinyl acetate copolymer and 10-15 parts of polyolefin elastomer to an internal mixer, heat up to 120 °C for melt plasticization, continuously stir for 10 minutes, transfer the melt to a twin-screw devolatilization unit, and remove unreacted monomers at 140-160 °C and a vacuum degree of -0.095 MPa, and pelletize underwater to obtain a matrix resin masterbatch;

[0061] S3. Put 20-25 parts of pretreated nano-aluminum hydroxide, 15-20 parts of nano-magnesium hydroxide, 8-12 parts of coated ammonium polyphosphate, and 3-5 parts of microencapsulated pentaerythritol into a high-speed mixer, pre-mix at 1000 rpm for 15 minutes, transfer the mixture to a nano-disperser, add 5-8 parts of melamine polyphosphate, and disperse at 50 °C and a shear rate of 6000 s-1 for 30 minutes to ensure that the particle size D90 is less than 50 μm;

[0062] S4. Dissolve 2 - 4 parts of phosphorylated chitosan in deionized water with a concentration of 5%, add 2 - 3 parts of organically modified montmorillonite, and perform ultrasonic treatment for 1 hour to form a uniform suspension. After freeze - drying the suspension, it is pulverized and sieved through a 200 - mesh sieve to obtain a bio - based synergistic composite powder;

[0063] S5. Feed the matrix resin masterbatch, flame - retardant premix, and bio - based synergistic composite powder into the main feeding port of the extruder. Add 1 - 2 parts of silane coupling agent and 0.5 - 1.5 parts of composite lubricant through the side feeding port. The melt is plasticized in a four - zone temperature - controlled area and formed by layering through a three - layer co - extrusion die:

[0064] The outer layer contains a high - flame - retardant layer with 2 - 3 parts of organically modified montmorillonite and 35 - 45 parts of nano - aluminum hydroxide / magnesium;

[0065] The middle layer is a composite layer of matrix resin and intumescent flame - retardant system: 16 - 25 parts;

[0066] The inner layer is a flexible layer reinforced with 10 - 15 parts of polyolefin elastomer;

[0067] S6. The extruded cable material enters the heat - treatment oven and is treated at 80°C for 2 hours to promote the cross - linking reaction of the silane coupling agent. After cooling, it is cut into uniform particles by a pelletizer and vacuum - packaged;

[0068] It should also be noted that the four - zone temperature partition for plasticization in step S5 is: zone 1 at 120°C, zone 2 at 140°C, zone 3 at 160°C, zone 4 at 170°C, and the die head at 165°C.

[0069] Example 1. In this Example 1, a flame - retardant cable material is prepared according to steps S1 to S6 in the example, which includes the following components:

[0070] In the matrix resin, ethylene - vinyl acetate copolymer + polyolefin elastomer: 40 parts + 12.5 parts;

[0071] In the main flame - retardant system, nano - aluminum hydroxide + nano - magnesium hydroxide: 22.5 parts + 17.5 parts;

[0072] In the intumescent flame - retardant system, coated ammonium polyphosphate + melamine polyphosphate + micro - encapsulated pentaerythritol: 10 parts + 6.5 + 4 parts;

[0073] In the bio - based synergist, phosphorylated chitosan + organically modified montmorillonite: 3 parts + 2.5 parts;

[0074] In the processing aids, silane coupling agent + composite lubricant: 1.5 parts + 1.0 parts;

[0075] In the stabilizer system, antioxidant 1010 + antioxidant 168: 0.2 parts + 0.2 parts;

[0076] The process steps are the same as those in steps S1 to S6 of the embodiment;

[0077] Example 2. In this Example 2, a flame-retardant cable compound was prepared as in steps S1 to S6 of the example. Among them, in the matrix resin, ethylene-vinyl acetate copolymer + polyolefin elastomer: 35 parts + 15 parts; the others are the same as in Example 1;

[0078] Example 3. In this Example 3, a flame-retardant cable compound was prepared as in steps S1 to S6 of the example. Among them, in the main flame-retardant system, nano-aluminum hydroxide + nano-magnesium hydroxide: 20 parts + 20 parts; the others are the same as in Example 1;

[0079] Example 4. In this Example 4, a flame-retardant cable compound was prepared as in steps S1 to S6 of the example. Among them, in the intumescent flame-retardant system, coated ammonium polyphosphate + melamine polyphosphate + microencapsulated pentaerythritol: 8 parts + 8 parts + 5 parts; the others are the same as in Example 1;

[0080] Example 5. In this Example 5, a flame-retardant cable compound was prepared as in steps S1 to S6 of the example. Among them, in the bio-based synergist, phosphorylated chitosan + organically modified montmorillonite: 4 + 2 parts; the others are the same as in Example 1;

[0081] The components in Examples 1 to 5 are shown in Table 1:

[0082] Table 1 Cable compound component table in Examples 1 to 5

[0083]

[0084]

[0085] The cable compounds were made from the components in Examples 1 to 5, and LOI, UL94, tensile strength, smoke density, and char residue rate performance tests were carried out. The test methods were ASTM D2863, vertical burning test, ISO 527-2 tensile strength test, EN45545-2 smoke density test, and 20°C / min heating rate TGA char residue rate test respectively. The test data are shown in Table 2:

[0086] Table 2 Cable compound performance test table in Examples 1 to 5

[0087]

[0088]

[0089] It can be seen from the test data in Table 2 that within the range of the material components of the present invention, the smoke density is all lower than 200 Ds4, at the same time the tensile strength is all above 11 MPa, and the other parameters all meet the standards, and the cost is controllable;

[0090] Comparative Example 1. In this Comparative Example 1, the flame-retardant cable compound was prepared according to Steps S1 to S6 in the Examples. Among them, the main flame-retardant system was added in excess: nano-aluminum hydroxide + nano-magnesium hydroxide = 30 parts + 25 parts;

[0091] Comparative Example 2. In this Comparative Example 2, the flame-retardant cable compound was prepared according to Steps S1 to S6 in the Examples. Among them, the intumescent flame-retardant system was added in a small amount: coated ammonium polyphosphate + melamine polyphosphate + microencapsulated pentaerythritol: 10 parts + 6.5 + 4 parts;

[0092] Comparative Example 3. In this Comparative Example 3, the flame-retardant cable compound was prepared according to Steps S1 to S6 in the Examples. Among them, no bio-based synergist was added;

[0093] Comparative Example 4. In this Comparative Example 4, the flame-retardant cable compound was prepared according to Steps S1 to S6 in the Examples. Among them, 25 parts of ethylene-vinyl acetate copolymer was in the matrix resin;

[0094] Comparative Example 5. In this Comparative Example 5, the flame-retardant cable compound was prepared according to Steps S1 to S6 in the Examples. Among them, ordinary capsules were used in the intumescent flame-retardant system;

[0095] The cable compounds were made from the components in Comparative Examples 1 to 5, and the LOI, UL94, tensile strength, smoke density, and char residue rate performance tests were carried out. The test methods were ASTM D2863, vertical burning test, ISO 527-2 tensile strength test, EN45545-2 smoke density test, and 20°C / min heating TGA char residue rate test respectively. The test data are shown in Table 3:

[0096]

[0097] III. Conclusion:

[0098] It can be seen from Tables 1, 2, and 3 above that in Example 1, the total addition amount of ATH + MH was 40 parts (35 - 45 parts), the LOI reached 40.5% and the tensile strength was 14.2 MPa, indicating that the optimized dispersion of nano-fillers (particle size D90 < 50 μm) could avoid embrittlement caused by excessive addition;

[0099] In Comparative Example 1, the amount of ATH + MH exceeded the limit to 55 parts, and the tensile strength dropped sharply to 9.8 MPa. In Example 1, the total addition amount of APP + MPP + PER was 20.5 parts (16 - 25 parts), the char residue rate was 38%, and the smoke density was 135;

[0100] In Comparative Example 4, the intumescent system was reduced to 10 parts, the char yield decreased to 28%, and the smoke density increased to 180, indicating that the charring efficiency decreased when the intumescent system was insufficient. In Example 5, the bio-based synergist was increased to 6 parts (4 - 7 parts), the LOI was increased to 41.0%, and the smoke density decreased to 125, proving the catalytic charring effect of phosphorylated chitosan;

[0101] After removing the bio-based component in Comparative Example 3, the LOI decreased to 35.2% and the smoke density deteriorated to 320;

[0102] Meanwhile, the EVA (40 parts) + POE (12.5 parts) in Example 1 provided matrix flexibility and compatibility with the flame retardant, avoiding the decrease in LOI caused by excessive POE in Example 2. The ATH (22.5 parts) + MH (17.5 parts) and APP (10 parts) + MPP (6.5 parts) in Example 1 formed a "heat absorption - catalytic charring" dual mechanism. Moreover, the total cost of Example 1 was 20 yuan / kg, which was more economical than Example 5 (21.5 yuan / kg), and its performance was comprehensively superior to that of the comparative examples.

[0103] In summary, the best embodiment of the present invention is Example 1. The cable material prepared according to the cable material components of Example 1 has an LOI of 40.5%, a tensile strength of 14.2 MPa, and a cost of 20 yuan / kg. The comprehensive performance reaches the best balance and is suitable for high - value - added cable scenarios.

[0104] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection 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 can be combined in a suitable manner in any one or more embodiments or examples.

[0105] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not elaborate on all details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art in the relevant technical field can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A flame retardant cable material, characterized in that: The cable material is composed of the following raw materials in parts by weight: base resin: 45-60 parts; main flame retardant system: 35-45 parts; intumescent flame retardant system: 16-25 parts; bio-based synergist: 4-7 parts; processing aid: 1.8-4 parts; stabilizing system: 0.3-0.5 parts; The matrix resin is composed of ethylene-vinyl acetate copolymer and polyolefin elastomer, wherein the ethylene-vinyl acetate copolymer is 35-45 parts and the polyolefin elastomer is 10-15 parts; The main flame retardant system is composed of nano aluminum hydroxide and nano magnesium hydroxide, wherein the nano aluminum hydroxide is 20-25 parts and the nano magnesium hydroxide is 15-20 parts; The intumescent flame retardant system is composed of coated ammonium polyphosphate, melamine polyphosphate and microencapsulated pentaerythritol, wherein the coated ammonium polyphosphate is 8-12 parts, the melamine polyphosphate is 5-8 parts, and the microencapsulated pentaerythritol is 3-5 parts; The bio-based synergist is composed of phosphorylated chitosan and organic modified montmorillonite, wherein the phosphorylated chitosan is 2-4 parts and the organic modified montmorillonite is 2-3 parts; The processing aid is composed of a silane coupling agent and a composite lubricant, wherein the silane coupling agent is 1-2 parts and the composite lubricant is 0.5-1.5 parts; The stabilizing system is composed of antioxidant 1010 and antioxidant 168, wherein the antioxidant 1010 is 0.15-0.25 parts and the antioxidant 168 is 0.15-0.25 parts.

2. A flame-retardant cable material according to claim 1, characterized in that: The nano aluminum hydroxide is made of industrial-grade sodium aluminate as a raw material, which is dissolved in deionized water and then filtered. Dilute sulfuric acid is slowly added at 60°C to a pH of 8.0-8.5, and the reaction is stirred at 500rpm for 2 hours to generate aluminum hydroxide precipitate. After aging for 12 hours, the precipitate is centrifuged and washed until the conductivity is less than 50μS / cm. 2% silane coupling agent KH-550 is added and ball milled for 4 hours. The precipitate is calcined at 250°C for 2 hours to remove residual moisture, thereby obtaining nano aluminum hydroxide with a particle size of 50nm and a purity greater than or equal to 99.5%.

3. A flame-retardant cable material according to claim 2, characterized in that: The nano magnesium hydroxide is prepared by dissolving magnesium chloride hexahydrate in water to form a 0.8 mol / L solution, adding ammonia water to adjust the pH to 10.5, transferring to a hydrothermal reactor, reacting at 180° C. for 8 hours to generate flaky magnesium hydroxide, centrifuging, ultrasonically treating with a 1.5% sodium stearate ethanol solution for 30 minutes, and drying at 80° C. to remove the solvent, thereby obtaining nano magnesium hydroxide with a flaky thickness of less than 10 nm and a purity of greater than or equal to 99.0%.

4. A flame-retardant cable material according to claim 3, characterized in that: The coated ammonium polyphosphate is prepared by mixing common ammonium polyphosphate and melamine in a molar ratio of 1:0.3, putting the mixture into a twin-screw extruder and melting and blending the mixture at 200°C for 10 minutes, and uniformly coating the surface of the ammonium polyphosphate with the melamine melt. The mixture is then pulverized and sieved after cooling to remove particles with a particle size greater than 20 μm, thereby obtaining a coated ammonium polyphosphate with a degree of polymerization greater than 1000 and a coating rate greater than or equal to 95%.

5. A flame-retardant cable material according to claim 4, characterized in that: The phosphorylated chitosan is prepared by dissolving chitosan with a deacetylation degree greater than 90% in a 2% acetic acid solution, adding three times the molar amount of phosphorus pentoxide, reacting at 60°C for 6 hours to complete phosphorylation, dialyzing the reaction solution for 48 hours to remove unreacted substances, freeze-drying and then crushing to obtain a white powdery phosphorylated chitosan with a substitution degree greater than 1.2 and an ash content less than 0.5%.

6. A flame-retardant cable material according to claim 5, characterized in that: The organic modified montmorillonite is prepared by converting natural calcium-based montmorillonite into sodium-based montmorillonite through ion exchange with 5% sodium carbonate solution, stirring and intercalating with hexadecyltrimethylammonium bromide in an aqueous solution at 80°C for 4 hours, centrifugally washing until no bromide ions remain, drying at 105°C and then grinding to obtain an organic modified montmorillonite with an interlayer spacing greater than or equal to 3.0nm and a cation exchange capacity greater than or equal to 90mmol / 100g.

7. A flame-retardant cable material according to claim 6, characterized in that: The ethylene-vinyl acetate copolymer is prepared by mixing ethylene and vinyl acetate in a molar ratio of 85:15 in a 150MPa high-pressure tubular reactor, using di-tert-butyl peroxide as an initiator, and performing free radical polymerization at 200°C. The molten product is subjected to a vacuum devolatilization unit to remove unreacted monomers, and underwater pelletizing is performed to obtain ethylene-vinyl acetate copolymer particles with a VA content of 28±1% and a melt index of 2-5g / 10min.

8. The flame-retardant cable material according to claim 7, characterized in that: The microencapsulated pentaerythritol is prepared by dispersing pentaerythritol powder in an aqueous solution containing 15% gum arabic, forming a stable emulsion through high-pressure homogenization, and controlling the air inlet temperature at 180°C and the atomization pressure at 0.3 MPa during spray drying so that the wall material quickly covers the core material, thereby obtaining microencapsulated pentaerythritol with a coverage rate greater than or equal to 90%, a core material content greater than 85%, and an average particle size of 50 μm.

9. A method for preparing a flame-retardant cable material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Add 20-25 parts of nano aluminum hydroxide and 1-2 parts of silane coupling agent KH-550 into a high-speed mixer, set the speed to 2000rpm, mix for 30 minutes, so that the coupling agent is evenly coated on the surface of the nanoparticles, and transfer the mixed materials to a vacuum drying oven, dry at 80°C for 4 hours, control the moisture content to less than 0.1%, and then ultrasonically disperse 15-20 parts of nano magnesium hydroxide and 1.5wt% of sodium stearate in an ethanol solution for 30 minutes, centrifuge and dry at 80°C until the solvent residue is less than 0.05%; S2. 35-45 parts of ethylene-vinyl acetate copolymer and 10-15 parts of polyolefin elastomer are added to an internal mixer, heated to 120°C for melting and plasticization, stirred for 10 minutes, and the melt is transferred to a twin-screw devolatilization unit to remove unreacted monomers at 140-160°C and a vacuum degree of -0.095MPa, and the matrix resin masterbatch is obtained by underwater pelletization; S3. The pretreated nano aluminum hydroxide: 20-25 parts, nano magnesium hydroxide: 15-20 parts and coated ammonium polyphosphate: 8-12 parts, microencapsulated pentaerythritol: 3-5 parts were put into a high-speed mixer, premixed at 1000rpm for 15 minutes, the mixture was transferred to a nano-disperser, melamine polyphosphate was added: 5-8 parts, dispersed at 50 ° C, shear rate 6000s-1 for 30 minutes, ensuring that the particle size D90 is less than 50μm; S4. The phosphorylated chitosan: 2-4 parts dissolved in 5% deionized water, added organic modified montmorillonite: 2-3 parts, ultrasonic treatment for 1 hour to form a uniform suspension, the suspension was freeze-dried and crushed through a 200 mesh sieve to obtain a bio-based synergistic composite powder; S5. Put the base resin masterbatch, flame retardant premix, and bio-based synergistic composite powder into the main feeding port of the extruder, 1-2 parts of silane coupling agent, and 0.5-1.5 parts of composite lubricant into the side feeding port, the melt is plasticized in four temperature control zones, and layered through a three-layer co-extrusion die: The outer layer contains 2-3 parts of organic modified montmorillonite and 35-45 parts of nano aluminum hydroxide / magnesium, which is a high flame retardant layer; Intermediate layer matrix resin and intumescent flame retardant system: 16-25 composite layers; Inner layer polyolefin elastomer: 10-15 parts of reinforced flexible layer; S6. The extruded cable material enters a heat treatment oven and is treated at 80°C for 2 hours to promote the cross-linking reaction of the silane coupling agent. After cooling, it is cut into uniform particles by a pelletizer and vacuum packaged.

10. The method for preparing a flame-retardant cable material according to claim 9, characterized in that: The four temperature zones of the four temperature control zones for plasticization in step S5 are: zone 1 120° C., zone 2 140° C., zone 3 160° C., zone 4 170° C., and die head 165° C.

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