A method for preparing a high temperature resistant flame retardant radio frequency coaxial cable

Abstract

The invention discloses a method for preparing a high temperature resistant flame retardant radio frequency coaxial cable. The high temperature resistant flame retardant radio frequency coaxial cable comprises a conductor, an insulating layer, a shielding layer and a sheath layer. The sheath layer comprises the following raw materials in parts by weight: 40 to 60 parts of polyvinyl chloride resin, 10 to 15 parts of EVA resin, 5 to 8 parts of glass fiber, 3 to 5 parts of expansion flame retardant, 0.5 to 2 parts of synergistic flame retardant, 4 to 6 parts of kaolin, 0.1 to 0.5 parts of coupling agent, and 1 to 3 parts of plasticizer. , 0.5 to 2 parts of lubricant, and 0.1 to 0.5 parts of antioxidant. The present invention prepares an intumescent flame retardant rich in P and N by polycondensing 5-nitrofurfural and ethylenediamine with hypophosphorous acid, and obtains a synergistic flame retardant used in combination with chitosan phosphate after ZIF-8 is adsorbed with chitosan phosphate and hyperbranched polysiloxane is grafted on the surface thereof. The sheath layer and the high-temperature resistant and flame-retardant radio frequency coaxial cable having the sheath layer have excellent flame retardant properties through the compounding of the intumescent flame retardant and the synergistic flame retardant.

Description

Technical Field

[0001] The invention belongs to the technical field of cable material preparation, and in particular relates to a method for preparing a high-temperature resistant and flame-retardant radio frequency coaxial cable. Background Art

[0002] Wires and cables play a key role as a medium in power transmission and are widely used in the fields of electricity, construction, communications, automobiles, and aviation. They provide electrical equipment with power transmission, information transmission, and other purposes. They are essential carriers for realizing the development of an electrified, information-based, and intelligent society, and play an important role in promoting the development of the national economy. PVC has excellent strength, toughness, thermal stability, electrical insulation, and aging resistance, and is widely used in the sheath layer of wires and cables. Polyvinyl chloride (PVC) is widely used as a sheath material for cable systems because of its low price, excellent strength, toughness, thermal stability, electrical insulation, and aging resistance. However, PVC is generally added with flammable plasticizers during processing to reduce its flame retardant properties. PVC cables burn in a fire environment to generate a large amount of heat that harms personal safety, and also release toxic gases that cause secondary damage to the human body.

[0003] Adding flame retardants to PVC cables can effectively improve the flame retardant properties of PVC insulation sheaths. There are many types of flame retardant additives, which can be roughly divided into halogen flame retardants, metal hydroxides, phosphorus flame retardants, silicon flame retardants, nitrogen flame retardants, nano flame retardants and bio-based flame retardants. In recent years, intumescent flame retardants (IFRs) have been widely used in the flame retardant modification of polyolefin materials due to their advantages of low smoke, non-toxicity and no droplets. However, in order to achieve a better flame retardant effect, it is necessary to dope more IFR in the polymer matrix. Too much inorganic flame retardant will aggregate in the polymer, affecting the comprehensive performance of the material. Therefore, there is an urgent need for an intumescent flame retardant with a high phosphorus and nitrogen content to reduce the amount of flame retardant added in PVC cables to improve the performance of PVC cables. Summary of the invention

[0004] In order to solve the deficiencies mentioned in the above-mentioned background technology, the purpose of the present invention is to provide a method for preparing a high-temperature resistant and flame-retardant radio frequency coaxial cable, wherein 5-nitropurfural and ethylenediamine are polycondensed and reacted with hypophosphorous acid to obtain an intumescent flame retardant rich in P and N, and ZIF-8 is adsorbed with chitosan phosphate and hyperbranched polysiloxane is grafted on the surface to obtain a synergistic flame retardant used therewith, and the sheath layer and the high-temperature resistant and flame-retardant radio frequency coaxial cable having the sheath layer have excellent flame retardant properties through the compounding of the intumescent flame retardant and the synergistic flame retardant.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a high-temperature resistant and flame-retardant radio frequency coaxial cable, the high-temperature resistant and flame-retardant radio frequency coaxial cable comprising a conductor, an insulating layer, a shielding layer and a sheath layer, the conductor being a copper-aluminum composite tube, the insulating layer being coated on the outer wall of the conductor, the insulating layer being foamed polyethylene, the shielding layer surrounding the outer wall of the insulating layer, the shielding layer being an annular copper tube coaxial with the conductor, the sheath layer being coated on the outer wall of the shielding layer, the sheath layer comprising the following raw materials in parts by weight: 40-60 parts of polyvinyl chloride resin, 10-15 parts of EVA resin, 5-8 parts of glass fiber, 3-5 parts of intumescent flame retardant, 0.5-2 parts of synergistic flame retardant, 4-6 parts of kaolin, 0.1-0.5 parts of coupling agent, 1-3 parts of plasticizer, 0.5-2 parts of lubricant, and 0.1-0.5 parts of antioxidant;

[0007] The preparation method of the high temperature resistant flame retardant radio frequency coaxial cable comprises the following steps:

[0008] S1. After the copper-aluminum composite tube is paid out from the pay-off rack, it is straightened and drawn to a diameter of 8 to 10 mm, and then the metal wire is cleaned to remove copper powder and impurities on the surface;

[0009] S2, mixing low-density polyethylene, high-density polyethylene and a foaming agent as insulating layer materials in a foaming extruder, injecting nitrogen gas under high pressure into the mixture in a molten state, and after the mixture is fully mixed, extruding it through a die head and coating it on the outside of the metal wire conductor to form an insulating layer;

[0010] S3, clean the copper strip with a thickness of 0.2-0.8 mm, cut it according to the product size and curl it, use a longitudinal wrapping machine to shape the copper strip into a tube, introduce the conductor with an extruded insulation layer into the copper strip longitudinally wrapped tube, and finally weld, draw and corrugate the formed tube to form a closed spiral shielding layer;

[0011] S4. The raw materials of the sheath layer are mixed evenly by a high-speed mixer, and then melt-extruded by a single-screw or twin-screw extruder at 140-160° C. to coat the outer wall of the shielding layer to obtain the high-temperature resistant and flame-retardant radio frequency coaxial cable.

[0012] Further preferably, the intumescent flame retardant is a phosphorus-nitrogen intumescent flame retardant rich in P and N elements, which is prepared by polycondensing 5-nitrofurfural and ethylenediamine and reacting with hypophosphorous acid, and the chemical reaction formula is as follows:

[0013]

[0014] Further preferably, the preparation method of the intumescent flame retardant specifically comprises the following steps:

[0015] (1) dissolving 5-nitrofurfural in anhydrous ethanol at a solid-liquid ratio of 1:8-12, stirring and heating to 60-80° C., slowly dropping ethylenediamine solution into the above solution, keeping the temperature for reaction for 2-4 hours, standing for 8-12 hours, filtering, washing and drying to obtain an intermediate product;

[0016] (2) The intermediate product is dissolved in anhydrous ethanol at a solid-liquid ratio of 1:8-12, and the mixture is heated to 60-80° C. with stirring, and hypophosphorous acid is slowly added to the solution. The mixture is refluxed for 12-18 hours under the protection of nitrogen. The product is evaporated to remove the solvent, and then dissolved in sodium hydroxide and precipitated with hydrochloric acid solution, filtered, washed, and dried to obtain the intumescent flame retardant.

[0017] Further preferably, the molar ratio of 5-nitrefurfural, ethylenediamine and hypophosphorous acid is 2:1:2.

[0018] Further preferably, the synergistic flame retardant is a modified ZIF-8 material, which is prepared by ZIF-8 adsorbing chitosan phosphate and then grafting hyperbranched polysiloxane on the surface, and the preparation method thereof comprises the following steps:

[0019] A. Dissolve zinc acetate and 2-methylimidazole in anhydrous methanol respectively, slowly add the 2-methylimidazole solution to the zinc acetate solution at room temperature, stir and react for 4-6 hours, centrifuge and wash and dry to obtain ZIF-8;

[0020] B. Dissolve 2-carboxyethylphenyl hypophosphorous acid in deionized water, then add chitosan to the 2-carboxyethylphenyl hypophosphorous acid solution, heat in a water bath to 55-65° C., stir and react for 4-6 hours, add anhydrous ethanol to precipitate the product, filter and dry to obtain chitosan phosphate;

[0021] C. Add the ZIF-8 obtained in step A to ionized water for ultrasonic dispersion for 20 to 30 min to obtain a ZIF-8 dispersion, add the chitosan phosphate obtained in step B to the ZIF-8 dispersion, stir at a rate of 150 to 200 r / min for 1 to 3 h, wash, filter, and then dry to obtain chitosan phosphate-loaded ZIF-8;

[0022] D. Add N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to deionized water and stir to mix, heat in a water bath to 55-65° C. and stir to react for 6-10 hours, obtain a viscous liquid under the autocatalysis of amino groups, and vacuum dry to obtain a hyperbranched polysiloxane;

[0023] E. Add the chitosan phosphate-loaded ZIF-8 into anhydrous methanol and ultrasonically disperse it for 20 to 30 minutes to obtain a chitosan phosphate-loaded ZIF-8 dispersion, dissolve the hyperbranched polysiloxane in anhydrous methanol, slowly drop the hyperbranched polysiloxane solution into the chitosan phosphate-loaded ZIF-8 dispersion, stir for 8 to 12 hours, and wash and dry to obtain the synergistic flame retardant.

[0024] Further preferably, in step C, the mass ratio of ZIF-8 to chitosan phosphate is 2-3:7-8.

[0025] More preferably, the coupling agent is one or more of a silane coupling agent, a titanate coupling agent, and a zirconium coupling agent.

[0026] More preferably, the plasticizer is selected from one or more of dibutyl phthalate, dioctyl phthalate, dioctyl terephthalate, dioctyl adipate, chlorinated paraffin, phosphate ester, and epoxidized soybean oil.

[0027] More preferably, the lubricant is one or more of stearate, paraffin and polyethylene wax.

[0028] More preferably, the antioxidant is one or more of antioxidant 1010 , antioxidant 168 , and antioxidant 300 .

[0029] Beneficial effects of the present invention:

[0030] The present invention uses 5-nitrofurfural and ethylenediamine to react with hypophosphorous acid to prepare an intumescent flame retardant rich in P and N. During the combustion process, the intumescent flame retardant of the present invention undergoes intramolecular and intermolecular dehydration and cross-linking reactions, and the generated inert gas is released into the gas phase to play a role in diluting oxygen and combustible volatiles. PhO, PO, and PO2 free radicals generated by further pyrolysis can capture H and HO free radicals in the gas phase, hindering the chain reaction of combustion in the condensed phase. P-OH protonic acid promotes random chain breaking of polyvinyl chloride, reduces the melt viscosity and molecular weight of the composite material, accelerates the generation of molten droplets at a lower temperature, and the generated flameless molten droplets take away part of the heat, promoting flame self-extinguishing. At the same time, phosphorus-containing intermediates such as polyphosphoric acid generated by pyrolysis of the intumescent flame retardant catalyze the dehydration and carbonization of the polyvinyl chloride matrix, and the dense carbon layer formed plays a role as a physical barrier, reducing the heat release of the composite material.

[0031] The intumescent flame retardant of the present invention improves the flame retardant performance of polyvinyl chloride by exerting a flame retardant effect in the gas phase and the solid phase, but the smoke and toxic gas release of the composite material is not improved. Therefore, the present invention further obtains a synergistic flame retardant used in combination with the chitosan phosphate after adsorbing the chitosan phosphate on ZIF-8. Zeolite imidazole skeleton-8 is a subclass of MOFs. ZIF-8 produces ZnO during the combustion process, which can inhibit the release of toxic smoke and catalyze the formation of a graphite carbon layer, thereby avoiding the combustion of the bottom polymer. On the one hand, the chitosan phosphate can be used as a carbon source in the intumescent flame retardant system, and on the other hand, its P element further improves the flame retardant effect. At the same time, a hyperbranched polymer with Si-O-Si as the main structure is grafted on the surface. The synergistic effect of silicon and nitrogen is utilized. The various non-flammable gases produced by the nitrogen element dilute the surrounding oxygen concentration, and the silicon element gathers in the gap to form a continuous and compact silicon carbon layer.

[0032] Therefore, the compounding of the intumescent flame retardant and the synergistic flame retardant prepared by the present invention enables the sheath layer and the high temperature resistant flame retardant radio frequency coaxial cable having the sheath layer to have excellent flame retardant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 It is the infrared spectrum of the intermediate product and the intumescent flame retardant prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] A P- and N-rich intumescent flame retardant is prepared by polycondensing 5-nitrofurfural and ethylenediamine and reacting with hypophosphorous acid, and the chemical reaction formula is as follows:

[0038]

[0039] The preparation method specifically comprises the following steps:

[0040] (1) 10.3 g of 5-nitrofurfural was dissolved in 100 ml of anhydrous ethanol, heated to 70° C. with stirring, and 25 ml of 1.5 mol / L ethylenediamine solution was slowly added dropwise to the solution. The mixture was kept warm for 3 h, allowed to stand for 10 h, and then filtered, washed, and dried to obtain 12.6 g of an intermediate product.

[0041] (2) The intermediate product was dissolved in 150 ml of anhydrous ethanol, stirred and heated to 70° C., 4.8 g of hypophosphorous acid was slowly added to the above solution, and refluxed for 16 h under the protection of nitrogen. The product was evaporated to remove the solvent and then dissolved in sodium hydroxide and precipitated with hydrochloric acid solution, filtered, washed and dried to obtain 14.1 g of the intumescent flame retardant.

[0042] The infrared spectra of the intermediate product and the intumescent flame retardant prepared in this example were collected by KBr tabletting. The scanning number was set to 32, and the spectrum collection range was 400-4000 cm -1, the optical frequency is 1cm -1 The infrared spectrum is as follows: Figure 1 As shown (1a is the intermediate product, 1b is the expansion flame retardant).

[0043] Depend on Figure 1 (a) It can be seen that in the infrared spectrum of the intermediate product, 1300 cm -1 The left and right sides correspond to the characteristic peaks of the furan oxide ring, 1550cm -1 The left and right sides correspond to the characteristic peaks of nitro groups, 1630 cm -1 The left and right sides correspond to the characteristic peaks of the C=N double bond, indicating that the -CHO of 5-nitrefuraldehyde and the -NH2 of ethylenediamine reacted successfully.

[0044] Depend on Figure 1 (b) It can be seen that in the infrared spectrum of the intumescent flame retardant, 2385 cm -1 The left and right sides correspond to the characteristic peaks of pH, and the peaks at 1630 cm in the intermediate product spectrum -1 The C=N characteristic peaks around 1280cm disappeared, indicating that the pH in the hypophosphorous acid reacted with the C=N in the intermediate product. -1 、1050cm -1 and 970cm -1 The absorption peaks appearing at correspond to the characteristic peaks of P=O, PO and P-OH.

[0045] The elemental composition of the intumescent flame retardant was analyzed using an element analyzer, and the contents of C, N, and H in the sample were determined by a high-temperature combustion method. The data obtained are shown in Table 1 below.

[0046] Table 1 Elemental analysis results of intumescent flame retardants

[0047]

[0048] Example 2

[0049] A synergistic flame retardant, the synergistic flame retardant is a modified ZIF-8 material, which is prepared by ZIF-8 adsorbing chitosan phosphate and then grafting hyperbranched polysiloxane on the surface. The preparation method thereof comprises the following steps:

[0050] A. Dissolve 2.2 g zinc acetate and 6.5 g 2-methylimidazole in 250 ml anhydrous methanol respectively, slowly add the 2-methylimidazole solution dropwise to the zinc acetate solution at room temperature, stir and react for 5 h, centrifuge and wash and dry to obtain ZIF-8;

[0051] B. Dissolve 2.3 g of 2-carboxyethylphenyl hypophosphorous acid in 120 ml of deionized water, then add 4.5 g of chitosan to the 2-carboxyethylphenyl hypophosphorous acid solution, heat to 605° C. in a water bath, stir and react for 5 h, add anhydrous ethanol to precipitate the product, filter and dry to obtain chitosan phosphate;

[0052] C. Add 3.1 g of ZIF-8 obtained in step A to 100 ml of ionized water and ultrasonically disperse for 25 min to obtain a ZIF-8 dispersion. Add 7.2 g of chitosan phosphate obtained in step B to the ZIF-8 dispersion, stir at a rate of 180 r / min for 2 h, wash, filter, and then dry to obtain chitosan phosphate-loaded ZIF-8.

[0053] D. Add N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to deionized water and stir to mix, heat to 60° C. in a water bath and stir to react for 8 h, obtain a viscous liquid under the autocatalysis of amino groups, and vacuum dry to obtain a hyperbranched polysiloxane;

[0054] E. Add 2.2 g of chitosan phosphate-loaded ZIF-8 into 250 ml of anhydrous methanol and ultrasonically disperse for 25 min to obtain a chitosan phosphate-loaded ZIF-8 dispersion; dissolve 2.0 g of hyperbranched polysiloxane in 50 ml of anhydrous methanol; slowly drop the hyperbranched polysiloxane solution into the chitosan phosphate-loaded ZIF-8 dispersion; stir for 10 h; and wash and dry to obtain the synergistic flame retardant.

[0055] Example 3

[0056] A high-temperature resistant and flame-retardant radio frequency coaxial cable includes a conductor, an insulating layer, a shielding layer and a sheath layer. The conductor is a copper-aluminum composite tube, the insulating layer is coated on the outer wall of the conductor, the insulating layer is foamed polyethylene, the shielding layer surrounds the outer wall of the insulating layer, the shielding layer is an annular copper tube coaxial with the conductor, and the sheath layer is coated on the outer wall of the shielding layer.

[0057] The sheath layer comprises the following raw materials in parts by weight: 50 parts of polyvinyl chloride resin, 12 parts of EVA resin, 6 parts of glass fiber, 4 parts of intumescent flame retardant, 1.2 parts of synergistic flame retardant, 5 parts of kaolin, 0.3 parts of silane coupling agent, 1.5 parts of dibutyl phthalate, 0.5 parts of epoxy soybean oil, 1.5 parts of sodium stearate, and 0.2 parts of antioxidant 300;

[0058] The preparation method of the high temperature resistant flame retardant radio frequency coaxial cable comprises the following steps:

[0059] S1. After the copper-aluminum composite tube is paid out from the pay-off rack, it is straightened and drawn to a diameter of 9 mm, and then the metal wire is cleaned to remove copper powder and impurities on the surface;

[0060] S2, mixing low-density polyethylene, high-density polyethylene and a foaming agent as insulating layer materials in a foaming extruder, injecting nitrogen gas under high pressure into the mixture in a molten state, and after the mixture is fully mixed, extruding it through a die head and coating it on the outside of the metal wire conductor to form an insulating layer;

[0061] S3, clean the 0.5mm thick copper strip, cut it according to the product size and curl it, use a longitudinal wrapping machine to shape the copper strip into a tube, introduce the conductor with an extruded insulation layer into the copper strip longitudinally wrapped tube, and finally weld, draw and corrugate the formed tube to form a closed spiral shielding layer;

[0062] S4. The raw materials of the sheath layer are mixed evenly by a high-speed mixer, and then melt-extruded by a single-screw or twin-screw extruder at 150° C. to coat the outer wall of the shielding layer to obtain the high-temperature resistant and flame-retardant radio frequency coaxial cable.

[0063] Example 4

[0064] A high-temperature resistant and flame-retardant radio frequency coaxial cable includes a conductor, an insulating layer, a shielding layer and a sheath layer. The conductor is a copper-aluminum composite tube, the insulating layer is coated on the outer wall of the conductor, the insulating layer is foamed polyethylene, the shielding layer surrounds the outer wall of the insulating layer, the shielding layer is an annular copper tube coaxial with the conductor, and the sheath layer is coated on the outer wall of the shielding layer.

[0065] The sheath layer comprises the following raw materials in parts by weight: 60 parts of polyvinyl chloride resin, 10 parts of EVA resin, 8 parts of glass fiber, 3 parts of intumescent flame retardant, 2 parts of synergistic flame retardant, 4 parts of kaolin, 0.5 parts of titanate coupling agent, 0.5 parts of dioctyl phthalate, 0.5 parts of phosphate ester, 2 parts of paraffin wax, and 0.1 parts of antioxidant 168;

[0066] The preparation method of the high temperature resistant flame retardant radio frequency coaxial cable comprises the following steps:

[0067] S1. After the copper-aluminum composite tube is paid out from the pay-off rack, it is straightened and drawn to a diameter of 10 mm, and then the metal wire is cleaned to remove copper powder and impurities on the surface;

[0068] S2, mixing low-density polyethylene, high-density polyethylene and a foaming agent as insulating layer materials in a foaming extruder, injecting nitrogen gas under high pressure into the mixture in a molten state, and after the mixture is fully mixed, extruding it through a die head and coating it on the outside of the metal wire conductor to form an insulating layer;

[0069] S3, clean the 0.2mm thick copper strip, cut it according to the product size and curl it, use a longitudinal wrapping machine to shape the copper strip into a tube, introduce the conductor with an extruded insulation layer into the copper strip longitudinally wrapped tube, and finally weld, draw and corrugate the formed tube to form a closed spiral shielding layer;

[0070] S4. The raw materials of the sheath layer are mixed evenly by a high-speed mixer, and then melt-extruded by a single-screw or twin-screw extruder at 160° C. to coat the outer wall of the shielding layer to obtain the high-temperature resistant and flame-retardant radio frequency coaxial cable.

[0071] Example 5

[0072] A high-temperature resistant and flame-retardant radio frequency coaxial cable includes a conductor, an insulating layer, a shielding layer and a sheath layer. The conductor is a copper-aluminum composite tube, the insulating layer is coated on the outer wall of the conductor, the insulating layer is foamed polyethylene, the shielding layer surrounds the outer wall of the insulating layer, the shielding layer is an annular copper tube coaxial with the conductor, and the sheath layer is coated on the outer wall of the shielding layer.

[0073] The sheath layer comprises the following raw materials in parts by weight: 40 parts of polyvinyl chloride resin, 15 parts of EVA resin, 5 parts of glass fiber, 5 parts of intumescent flame retardant, 0.5 parts of synergistic flame retardant, 6 parts of kaolin, 0.1 parts of zirconium coupling agent, 1 part of dioctyl terephthalate, 1.5 parts of dioctyl adipate, 0.5 parts of chlorinated paraffin, 0.5 parts of polyethylene wax, and 0.5 parts of antioxidant 1010;

[0074] The preparation method of the high temperature resistant flame retardant radio frequency coaxial cable comprises the following steps:

[0075] S1. After the copper-aluminum composite tube is paid out from the pay-off rack, it is straightened and drawn to a diameter of 8mm, and then the metal wire is cleaned to remove copper powder and impurities on the surface;

[0076] S2, mixing low-density polyethylene, high-density polyethylene and a foaming agent as insulating layer materials in a foaming extruder, injecting nitrogen gas under high pressure into the mixture in a molten state, and after the mixture is fully mixed, extruding it through a die head and coating it on the outside of the metal wire conductor to form an insulating layer;

[0077] S3, clean the 0.8mm thick copper strip, cut it according to the product size and curl it, use a longitudinal wrapping machine to shape the copper strip into a tube, introduce the conductor with an extruded insulation layer into the copper strip longitudinally wrapped tube, and finally weld, draw and corrugate the formed tube to form a closed spiral shielding layer;

[0078] S4. The raw materials of the sheath layer are mixed evenly by a high-speed mixer, and then melt-extruded by a single-screw or twin-screw extruder at 140° C. to coat the outer wall of the shielding layer to obtain the high-temperature resistant and flame-retardant radio frequency coaxial cable.

[0079] Comparative Example 1

[0080] A high-temperature resistant and flame-retardant radio frequency coaxial cable includes a conductor, an insulating layer, a shielding layer and a sheath layer. The conductor is a copper-aluminum composite tube, the insulating layer is coated on the outer wall of the conductor, the insulating layer is foamed polyethylene, the shielding layer surrounds the outer wall of the insulating layer, the shielding layer is an annular copper tube coaxial with the conductor, and the sheath layer is coated on the outer wall of the shielding layer.

[0081] The synergistic flame retardant in the sheath layer raw material is replaced by an equal amount of zinc borate, and the other components and contents are the same as in Example 3. A high temperature resistant flame retardant radio frequency coaxial cable is prepared according to the method in Example 3.

[0082] Comparative Example 2

[0083] A high-temperature resistant and flame-retardant radio frequency coaxial cable includes a conductor, an insulating layer, a shielding layer and a sheath layer. The conductor is a copper-aluminum composite tube, the insulating layer is coated on the outer wall of the conductor, the insulating layer is foamed polyethylene, the shielding layer surrounds the outer wall of the insulating layer, the shielding layer is an annular copper tube coaxial with the conductor, and the sheath layer is coated on the outer wall of the shielding layer.

[0084] The intumescent flame retardant in the raw material of the sheath layer is changed to a combination of ammonium polyphosphate, pentaerythritol and melamine in a mass ratio of 3:1:1, and the other components and contents are the same as in Example 3. The high temperature resistant flame retardant radio frequency coaxial cable is prepared according to the method in Example 3.

[0085] Performance Testing

[0086] The raw materials of the sheath layer in Examples 3 to 5 and Examples 1 to 2 were mixed evenly by a high-speed mixer, and then melt-extruded by a single-screw or twin-screw extruder at 140°C to form a 127×12.7×3.2mm standard specimen, and the horizontal and vertical (UL-94) combustion test was performed according to the ASTMD3801-1996 standard, and the oxygen index test (LOI) was performed according to the ASTM D2863-70 standard. The high-temperature flame-retardant RF coaxial cables prepared in Examples 3 to 5 and Examples 1 to 2 were tested for flame retardancy according to GB12666.5-1990 "Wire and Cable Combustion Test Method", and the data obtained are shown in Table 2 below.

[0087] Table 2 Cable flame retardant performance test

[0088]

[0089] It can be seen from the data in Table 2 that the limiting oxygen index of the sheath layer material of the present invention is greater than 21%, and continuous combustion cannot be maintained in the air. In Comparative Example 1, zinc borate is used to replace the modified ZIF-8 material prepared by the present invention as a synergistic flame retardant component, and the synergistic effect with the intumescent flame retardant is worse than that of Examples 3 to 4. In Comparative Example 2, the most common intumescent flame retardant component currently on the market (ammonium polyphosphate, pentaerythritol, and melamine in a mass ratio of 3:1:1) is used to replace the intumescent flame retardant prepared by the present invention, and its flame retardant effect is also inferior. It can be seen that the combination of the intumescent flame retardant and the synergistic flame retardant prepared by the present invention makes the sheath layer and the high temperature resistant flame retardant RF coaxial cable having the sheath layer have excellent flame retardant properties.

[0090] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a high temperature resistant flame retardant radio frequency coaxial cable, characterized in that: The high temperature resistant flame retardant radio frequency coaxial cable comprises a conductor, an insulating layer, a shielding layer and a sheath layer, wherein the conductor is a copper-aluminum composite tube, the insulating layer is coated on the outer wall of the conductor, the insulating layer is foamed polyethylene, the shielding layer surrounds the outer wall of the insulating layer, the shielding layer is an annular copper tube coaxial with the conductor, the sheath layer is coated on the outer wall of the shielding layer, and the sheath layer comprises the following raw materials in parts by weight: 40-60 parts of polyvinyl chloride resin, 10-15 parts of EVA resin, 5-8 parts of glass fiber, 3-5 parts of expansion flame retardant, 0.5-2 parts of synergistic flame retardant, 4-6 parts of kaolin, 0.1-0.5 parts of coupling agent, 1-3 parts of plasticizer, 0.5-2 parts of lubricant, and 0.1-0.5 parts of antioxidant; The intumescent flame retardant is a phosphorus-nitrogen intumescent flame retardant rich in P and N elements, which is prepared by polycondensing 5-nitrofurfural and ethylenediamine and reacting with hypophosphorous acid, and the chemical reaction formula is as follows: The synergistic flame retardant is a modified ZIF-8 material, which is prepared by adsorbing chitosan phosphate on ZIF-8 and then grafting hyperbranched polysiloxane on the surface; The preparation method of the high temperature resistant flame retardant radio frequency coaxial cable comprises the following steps: S1. After the copper-aluminum composite tube is paid out from the pay-off rack, it is straightened and drawn to a diameter of 8 to 10 mm, and then the metal wire is cleaned to remove copper powder and impurities on the surface; S2, mixing low-density polyethylene, high-density polyethylene and a foaming agent as insulating layer materials in a foaming extruder, injecting nitrogen gas under high pressure into the mixture in a molten state, and after the mixture is fully mixed, extruding it through a die head and coating it on the outside of the metal wire conductor to form an insulating layer; S3, clean the copper strip with a thickness of 0.2-0.8 mm, cut it according to the product size and curl it, use a longitudinal wrapping machine to shape the copper strip into a tube, introduce the conductor with an extruded insulation layer into the copper strip longitudinally wrapped tube, and finally weld, draw and corrugate the formed tube to form a closed spiral shielding layer; S4. The raw materials of the sheath layer are mixed evenly by a high-speed mixer, and then melt-extruded by a single-screw or twin-screw extruder at 140-160° C. to coat the outer wall of the shielding layer to obtain the high-temperature resistant and flame-retardant radio frequency coaxial cable.

2. The method for preparing a high temperature resistant flame retardant radio frequency coaxial cable according to claim 1, characterized in that: The preparation method of the intumescent flame retardant specifically comprises the following steps: (1) dissolving 5-nitrofurfural in anhydrous ethanol at a solid-liquid ratio of 1:8-12, stirring and heating to 60-80° C., slowly dropping ethylenediamine solution into the above solution, keeping the temperature for reaction for 2-4 hours, standing for 8-12 hours, filtering, washing and drying to obtain an intermediate product; (2) The intermediate product is dissolved in anhydrous ethanol at a solid-liquid ratio of 1:8-12, and the mixture is heated to 60-80° C. with stirring, and hypophosphorous acid is slowly added to the solution. The mixture is refluxed for 12-18 hours under the protection of nitrogen. The product is evaporated to remove the solvent, and then dissolved in sodium hydroxide and precipitated with hydrochloric acid solution, filtered, washed, and dried to obtain the intumescent flame retardant.

3. The method for preparing a high temperature resistant flame retardant radio frequency coaxial cable according to claim 2, characterized in that: The molar ratio of the 5-nitrofurfural, ethylenediamine and hypophosphorous acid is 2:1:

2.

4. The method for preparing a high temperature resistant flame retardant radio frequency coaxial cable according to claim 1, characterized in that: The preparation method of the synergistic flame retardant comprises the following steps: A. Dissolve zinc acetate and 2-methylimidazole in anhydrous methanol respectively, slowly add the 2-methylimidazole solution to the zinc acetate solution at room temperature, stir and react for 4-6 hours, centrifuge and wash and dry to obtain ZIF-8; B. Dissolve 2-carboxyethylphenyl hypophosphorous acid in deionized water, then add chitosan to the 2-carboxyethylphenyl hypophosphorous acid solution, heat in a water bath to 55-65° C., stir and react for 4-6 hours, add anhydrous ethanol to precipitate the product, filter and dry to obtain chitosan phosphate; C. Add the ZIF-8 obtained in step A to ionized water for ultrasonic dispersion for 20 to 30 min to obtain a ZIF-8 dispersion, add the chitosan phosphate obtained in step B to the ZIF-8 dispersion, stir at a rate of 150 to 200 r / min for 1 to 3 h, wash, filter, and then dry to obtain chitosan phosphate-loaded ZIF-8; D. Add N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to deionized water and stir to mix, heat in a water bath to 55-65° C. and stir to react for 6-10 hours, obtain a viscous liquid under the autocatalysis of amino groups, and vacuum dry to obtain a hyperbranched polysiloxane; E. Add the chitosan phosphate-loaded ZIF-8 into anhydrous methanol and ultrasonically disperse it for 20 to 30 minutes to obtain a chitosan phosphate-loaded ZIF-8 dispersion, dissolve the hyperbranched polysiloxane in anhydrous methanol, slowly drop the hyperbranched polysiloxane solution into the chitosan phosphate-loaded ZIF-8 dispersion, stir for 8 to 12 hours, and wash and dry to obtain the synergistic flame retardant.

5. The method for preparing a high temperature resistant and flame retardant radio frequency coaxial cable according to claim 4, characterized in that: In the step C, the mass ratio of ZIF-8 to chitosan phosphate is 2-3:7-8.

6. The method for preparing a high temperature resistant flame retardant radio frequency coaxial cable according to claim 1, characterized in that: The coupling agent is one or more of a silane coupling agent, a titanate coupling agent, and a zirconium coupling agent.

7. The method for preparing a high temperature resistant and flame retardant radio frequency coaxial cable according to claim 1, characterized in that: The plasticizer is selected from one or more of dibutyl phthalate, dioctyl phthalate, dioctyl terephthalate, dioctyl adipate, chlorinated paraffin, phosphate ester, and epoxidized soybean oil.

8. The method for preparing a high temperature resistant and flame retardant radio frequency coaxial cable according to claim 1, characterized in that: The lubricant is one or more of stearate, paraffin and polyethylene wax.

9. The method for preparing a high temperature resistant and flame retardant radio frequency coaxial cable according to claim 1, characterized in that: The antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant 300.

Images