Insulation shielding special cable and preparation method thereof

Abstract

The invention discloses an insulation shielding special cable and a preparation method thereof, and belongs to the technical field of special cables. The preparation method is used for solving the technical problems that in the prior art, when a polyethylene insulating material for a cable is prepared, the electrical performance of a polyethylene graft is degraded, and the polyethylene graft is difficult to recycle. A preparation method of an insulation shielding special cable comprises the following steps that silver-copper alloy serves as a conductor, a conductor shielding layer is extruded outside the conductor, and then a steel strip shielding layer is wrapped outside the conductor; the space between the steel belt shielding layer and the wrapping belt is filled with inorganic filler, a modified polyethylene insulating material is melted and extruded outside the wrapping belt, and the insulation shielding special cable is prepared. The preparation method of the modified polyethylene insulating material comprises the following steps: mixing the composite polyethylene, the organic phosphate nucleating agent and the related auxiliary agent to obtain a mixture; melting and extruding the mixture to obtain the modified polyethylene insulating material. The insulation shielding special cable prepared by the invention has the advantages of good mechanical property, insulativity and shielding property.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of special cable, in particular to an insulation shielding special cable and a preparation method thereof. BACKGROUND

[0002] Power cable is a wire and cable product used for transmission and distribution of high-power electric energy on the main line of the power system; the structure of the power cable is generally composed of a conductive core, an insulation layer, a protective layer, a shielding layer, a filler and the like. When applied to the coal mining industry, the power cable should not only have high mechanical properties to resist the harsh environment outside, but also have high insulation and shielding properties to ensure the stability of the power cable operation.

[0003] Polyethylene is a commonly used insulation material for power cables. Patent application CN110240744A discloses a silane cross-linked polyethylene cable insulation material, which comprises polyethylene, polyvinyl alcohol, silane coupling agent, zirconium dioxide and the like; the linear molecular structure is converted into a three-dimensional structure by using silane cross-linked polyethylene, thereby improving the mechanical properties and chemical stability of the prepared cable insulation material. However, the electrical properties of cross-linked polyethylene are deteriorated and cannot be recycled and reused, which causes environmental pollution.

[0004] In view of the technical defects in this regard, a solution is proposed. SUMMARY

[0005] The purpose of the present application is to provide an insulation shielding special cable and a preparation method thereof, which solves the technical problems in the prior art that the prepared grafted polyethylene has deteriorated electrical properties and is difficult to recycle and reuse in order to improve the mechanical properties of the prepared polyethylene.

[0006] The purpose of the present application can be achieved by the following technical solutions: A preparation method of an insulation shielding special cable, prepared by the following steps: S1, silver-copper alloy as a conductor, the conductor is externally extruded with a conductor shielding layer, and then a steel tape shielding layer is wrapped; S2, the steel tape shielding layer and the wrapping tape are filled with inorganic fillers; a modified polyethylene insulation material is melt-extruded outside the wrapping tape to prepare an insulation shielding special cable; The preparation method of the modified polyethylene insulation material is as follows: composite polyethylene, organic phosphate nucleating agent, antioxidant and lubricant are mixed at high speed to obtain a mixture; the mixture is melt-extruded to obtain a modified polyethylene insulation material.

[0007] Further, the preparation method of the composite polyethylene comprises the following steps: A1, porous silica gel is immersed in CrCl3 solution, then titanium ester is added to form a reaction system; the reaction system is reacted at 45-55℃ for 1-2h, and then filtered to obtain a SiO2-TiO2 co-gel carrier; the SiO2-TiO2 co-gel carrier is dried in an air atmosphere to obtain a catalyst precursor; the catalyst precursor is placed in a fluidized bed reactor for calcination to prepare a multi-active metal catalyst; The inorganic chromium salt can be adsorbed on the surface of the porous silica gel carrier; in the constant-temperature water bath process, the titanium ester can also be fixed on the silica gel by reacting with the silicon hydroxyl groups in the silica gel to obtain a SiO2-TiO2 co-gel carrier. The SiO2-TiO2 co-gel carrier is calcined at high temperature to prepare a catalyst for producing polyethylene.

[0008] A2, the first polymerization reactor and the second polymerization reactor are connected in series; the first polymerization reactor is connected to a feeding tank, and the second polymerization reactor is connected to a condenser and a powder discharge bin in sequence; the feeding tank is added with a solvent, ethylene gas, propylene gas and a multi-active metal catalyst, and mixed uniformly to obtain a slurry; the slurry is pumped into the first polymerization reactor for reaction to form a primary polymer; the primary polymer is pumped into the second polymerization reactor for polymerization to obtain a polymer; unreacted gas is recycled back to the first polymerization reactor and the second polymerization reactor; the polymer powder is blown out by nitrogen to obtain a composite polyethylene.

[0009] Further, in step A1, the concentration of the CrCl3 solution is 0.2-0.4mol / L; the amount ratio of the porous silica gel, the CrCl3 solution and the titanium ester is 3-10g:20-30mL:5-10g; the drying temperature of the SiO2-TiO2 co-gel carrier is 45-55℃, and the drying time is 20-30min; the calcination temperature is 600-800℃, the calcination time is 3-4h, and the fluidization gas velocity of the fluidized bed reactor is 0.05-0.1m / s.

[0010] Further, in step A2, the amount ratio of the solvent, ethylene gas, propylene gas and multi-active metal catalyst is 200-300mL:50-100mL:50-100mL:1.2-1.5g; the reaction temperature of the first polymerization reactor is 70-90℃, the reaction pressure is 2.5-3MPa, and the reaction time is 1-2h; the reaction temperature of the second polymerization reactor is 65-80℃, the reaction pressure is 1.5-2.5MPa, and the reaction time is 1.5-2h.

[0011] Further, the preparation method of the organic phosphate nucleating agent comprises the following steps: B1, allyl alcohol and maleic anhydride are mixed and reacted at 70-80℃ for 4-6h to form a primary polymer; an initiator is added to the primary polymer, mixed uniformly, and then reacted at 55-65℃ for 1-2h to form a resin-like product; B2, the resin, toluene, triethylamine and phosphorus oxychloride are mixed, and reacted at 105-110 DEG C for 5-6 hours, then toluene is distilled off at 112-120 DEG C, and the resultant is washed to neutral, and spray-dried at 155-165 DEG C for 5-10 seconds to prepare a solid powder organic phosphate nucleating agent.

[0012] 4 functional maleic anhydride is reacted with 2 functional maleic anhydride, wherein, for maleic anhydride, 2 carboxyl groups provide long chain type molecules, and a primary polymer is obtained.

[0013] Further, in step B1, the ratio of allyl alcohol, maleic anhydride and initiator is 25-35 mL: 5-10 g: 0.1-0.3 g; in step B2, the ratio of the resin, toluene, triethylamine and phosphorus oxychloride is 15-25 g: 50-100 mL: 3-5 mL: 5-8 mL.

[0014] Further, in step S1, the silver content of the silver-copper alloy is 0.1-0.2 wt%, and the material of the conductor shielding layer is galvanized copper; in step S2, the material of the tape is polytetrafluoroethylene, and the inorganic filler is a compound of mica powder and aluminum oxide in a mass ratio of 1:1-2; the temperature of the melt extrusion is 200-220 DEG C.

[0015] Further, the weight ratio of the composite polyethylene, the organic phosphate nucleating agent, the phenolic antioxidant and the zinc stearate is 40-50:3-5:0.5-1:0.5-1; the temperature of the melt extrusion is 165-185 DEG C, and the duration of the melt extrusion is 3-5 minutes.

[0016] As another aspect of the present application, an insulating and shielding special cable is prepared by the preparation method of the insulating and shielding special cable.

[0017] The present application has the following advantages: 1. The insulating and shielding special cable prepared by the present application has the following specific structure: silver-copper alloy as the conductor; the conductor is externally provided with a conductor shielding layer, a steel tape shielding layer and a polytetrafluoroethylene tape in sequence, the compound of mica powder and aluminum oxide is filled between the steel tape shielding layer and the tape, and the modified polyethylene insulating material is externally provided on the tape. The silver-copper alloy as the conductor can optimize the electrical properties of the conductor by doping a small amount of silver, and can meet the requirements of coal mine underground electric wires and cables for signal transmission. In order to shield a large number of electromagnetic interference sources existing in coal mines, the prepared cable needs to have good shielding performance to reduce the influence of external electromagnetic interference on signal transmission. Therefore, the cable prepared by the present application is externally provided with double shielding layers: the conductor shielding layer and the steel tape shielding layer in sequence, and the tape is made of polytetrafluoroethylene material with low dielectric loss.

[0018] 2. The modified polyethylene insulation material is obtained by melt extrusion of composite polyethylene, organophosphate nucleating agent, and related additives. A slurry obtained by blending ethylene, propylene, a multi-active metal catalyst, and solvent is transferred to the first polymerization reactor, and then undergoes secondary polymerization in the second polymerization reactor to finally prepare the polymer. Unreacted gases are condensed and recycled to both the first and second polymerization reactors to improve the reaction conversion rate. The high-porosity silica gel carrier has the ability to break down into fragments during the growth of composite polyethylene, ensuring continuous contact with the internal active centers. Titanium and chromium metal elements are chemically reacted and co-loaded within the porous silica gel, synergistically improving the catalytic activity of the prepared multi-active metal catalyst. The synergistic effect of the multi-cycle polymerization process and the active metal catalyst can improve the regularity of the prepared molecular chains.

[0019] 3. The organophosphate nucleating agent prepared in this invention has a similar structure to the composite polyethylene molecule, which facilitates the crystallization and nucleation of the composite polyethylene, thereby increasing the crystal density and promoting grain refinement. Furthermore, the resin-like structure of the organophosphate exhibits good migration resistance, which is beneficial for improving the heat resistance of the prepared composite polyethylene. The polyethylene insulation material prepared in this invention has the advantages of heat oxidation resistance and good mechanical properties. The insulated and shielded special cable with the above-mentioned specific structure has the advantages of good electrical insulation and shielding performance. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0021] The porous silica gel used in Examples 1-3 of this invention is specifically porous silica gel HDG-202A, which was purchased from Jiuding Chemical and has the product number L-CW485. Example 1

[0022] This embodiment provides a method for preparing composite polyethylene for insulating and shielding special cables, including the following steps: A1, 3g of porous silica gel and 20mL of 0.2mol / L CrCl3 solution were added into a 150mL beaker, so that the porous silica gel carrier was immersed in the CrCl3 solution, and then 5g of titanate was added into the beaker. The beaker was transferred to a constant temperature water bath, and constant temperature water bath reaction was carried out at 45℃ for 1h, and then filtration was performed, to obtain a SiO2-TiO2 co-gel carrier. The SiO2-TiO2 co-gel carrier was dried in an air atmosphere at 110℃ for 20min, to obtain a catalyst precursor. The catalyst precursor was placed in a fluidized bed reactor for calcination, the calcination temperature was 600℃, the calcination time was 3h, the fluidized gas velocity of the fluidized bed reactor was 0.05m / s, and finally a multi-active metal catalyst was prepared.

[0023] A2, two 1000mL polymerization reactors with spiral stirrers were connected in series, and were respectively marked as a first polymerization reactor and a second polymerization reactor; the first polymerization reactor was connected to a feed tank, and the second polymerization reactor was connected to a condenser and a powder discharge bin in sequence. 200mL of solvent ethanol was added into the feed tank, and then 50mL of ethylene gas, 50mL of propylene gas and 1.2g of the multi-active metal catalyst were added into the feed tank, and then mixing was performed, to obtain a slurry. The slurry was pumped into the first polymerization reactor for reaction, the reaction temperature of the first polymerization reactor was 70℃, the reaction pressure was 2.5MPa, and the reaction time was 1h, to form a primary polymer. The primary polymer was pumped into the second polymerization reactor, the reaction temperature of the second polymerization reactor was 65℃, the reaction pressure was 1.5MPa, and the reaction time was 1.5h, to obtain a polymer. Excess unreacted gas was recycled back into the first polymerization reactor and the second polymerization reactor through the condenser; the polymer powder entered the powder discharge bin by pressure difference, and then nitrogen was injected into the powder discharge bin to blow out the unremoved reaction monomers in the polymer powder, to obtain the prepared composite polyethylene. Example 2

[0024] The embodiment provides a preparation method of a composite polyethylene for an insulating shielding special cable, and the method comprises the following steps: A1, 3g of porous silica gel and 20mL of 0.2mol / L CrCl3 solution were added into a 150mL beaker, so that the porous silica gel carrier was immersed in the CrCl3 solution, and then 5g of titanate was added into the beaker. The beaker was transferred to a constant temperature water bath, and constant temperature water bath reaction was carried out at 45℃ for 1h, and then filtration was performed, to obtain a SiO2-TiO2 co-gel carrier. The SiO2-TiO2 co-gel carrier was dried in an air atmosphere at 110℃ for 20min, to obtain a catalyst precursor. The catalyst precursor was placed in a fluidized bed reactor for calcination, the calcination temperature was 600℃, the calcination time was 3h, the fluidized gas velocity of the fluidized bed reactor was 0.05m / s, and finally a multi-active metal catalyst was prepared.

[0025] A2, two 1000 mL polymerization reactors equipped with helical stirrers are connected in series, and are respectively marked as a first polymerization reactor and a second polymerization reactor; the first polymerization reactor is connected to a feeding tank, and the second polymerization reactor is connected to a condenser and a powder discharge bin in sequence. 250 mL of solvent ethanol is added to the feeding tank, and then 80 mL of ethylene gas, 80 mL of propylene gas and 1.3 g of the multi-active metal catalyst are added to the feeding tank, and mixed to obtain a slurry. The slurry is pumped into the first polymerization reactor for reaction, the reaction temperature of the first polymerization reactor is 80℃, the reaction pressure is 2.8 MPa, and the reaction time is 1.5 h, to form a primary polymer. The primary polymer is pumped into the second polymerization reactor, the reaction temperature of the second polymerization reactor is 75℃, the reaction pressure is 2 MPa, and the reaction time is 1.8 h, to obtain a polymer. The excess unreacted gas is recycled back into the first polymerization reactor and the second polymerization reactor through the condenser; the polymer powder enters the powder discharge bin by pressure difference, and nitrogen is injected into the powder discharge bin to blow out the unremoved reaction monomers in the polymer powder, to obtain the prepared composite polyethylene. Example 3

[0026] The embodiment provides a preparation method of a composite polyethylene for an insulating shield special cable, and the method comprises the following steps: A1, 10 g of porous silica gel and 30 mL of 0.4 mol / L CrCl3 solution are added to a 150 mL beaker, so that the porous silica gel carrier is immersed in the CrCl3 solution, and then 10 g of titanate is added to the beaker to form a reaction system. The beaker is transferred to a constant temperature water bath pot, and constant temperature water bath reaction is carried out at 55℃ for 2 h, and then filtration is performed to obtain a SiO2-TiO2 co-gel carrier. The SiO2-TiO2 co-gel carrier is dried in an air atmosphere at 120℃ for 30 min to obtain a catalyst precursor. The catalyst precursor is placed in a fluidized bed reactor for calcination, the calcination temperature is 800℃, the calcination time is 4 h, the fluidization gas velocity of the fluidized bed reactor is 0.1 m / s, and finally a multi-active metal catalyst is prepared.

[0027] A2, two 1000mL polymerization reactors equipped with helical stirrers are connected in series, and are respectively marked as a first polymerization reactor and a second polymerization reactor; the first polymerization reactor is connected to a feed tank, and the second polymerization reactor is connected to a condenser and a powder discharge bin in sequence. 300mL of solvent ethanol is added to the feed tank, and then 100mL of ethylene gas, 100mL of propylene gas and 1.5g of multi-active metal catalyst are added to the feed tank, mixed to obtain a slurry. The slurry is pumped into the first polymerization reactor for reaction, the reaction temperature of the first polymerization reactor is 90℃, the reaction pressure is 3MPa, and the reaction time is 2h to form a primary polymer. The primary polymer is pumped into the second polymerization reactor, the reaction temperature of the second polymerization reactor is 80℃, the reaction pressure is 2.5MPa, and the reaction time is 2h to obtain a polymer. The excess unreacted gas is recycled back to the first polymerization reactor and the second polymerization reactor through the condenser; the polymer powder enters the powder discharge bin by pressure difference, and nitrogen is injected into the powder discharge bin to blow out the unremoved reaction monomer in the polymer powder to obtain the prepared composite polyethylene. Example 4

[0028] The present embodiment provides a preparation method of a modified polyethylene insulation material for insulated shield special cables, comprising the following steps: B1, 25mL of allyl alcohol and 5g of maleic anhydride are added to a 250mL three-necked flask for mixing, the reaction temperature of the three-necked flask is set to 70℃, and the stirring speed is 100r / min, and the reaction is carried out for 4h to form a primary polymer. 0.1g of azobisisobutyronitrile is further added to the three-necked flask for mixing, and the three-necked flask is continuously reacted at 55℃ for 1h to form a resin-like substance.

[0029] B2, in a 250mL three-necked flask equipped with a mechanical stirrer, a constant pressure dropping funnel and a thermometer, 15g of the resin-like substance, 50mL of toluene and 3mL of triethylamine are sequentially added, and then 5mL of phosphorus oxychloride is added dropwise, and the reaction is carried out at 105℃ for 5h, and then toluene is distilled off at 112℃ to obtain a reaction product. The reaction product is washed with deionized water until neutral, and then spray dried at 155℃ for 5s to obtain a solid powder organic phosphate nucleating agent.

[0030] B3, according to the weight parts, 40 parts of the composite polyethylene prepared in Example 1, 3 parts of the organic phosphate nucleating agent, 0.5 parts of the phenolic antioxidant 1010 and 0.5 parts of zinc stearate are added to a high-speed mixer, and high-speed stirring is carried out at 2000r / min for 3min to obtain a mixture. The mixture is added to a twin-screw extruder for melt blending and extrusion, the temperature of the melt blending is 165℃, the time of the melt blending is 3min, and finally a modified polyethylene insulation material is prepared. Example 5

[0031] The embodiment provides a preparation method of modified polyethylene insulating material for special insulated shielded cable, and comprises the following steps: B1, 30mL of allyl alcohol and 8g of maleic anhydride are mixed in a 250mL three-necked flask, the reaction temperature of the three-necked flask is set to 75 DEG C, and the three-necked flask is stirred at 150r / min for 5h to form a primary polymer. 0.2g of azobisisobutyronitrile is further added into the three-necked flask, and the three-necked flask is continuously reacted at 60 DEG C for 1.5h to form a resin-like substance.

[0032] B2, 20g of the resin-like substance, 80mL of toluene and 4mL of triethylamine are sequentially added into a 250mL three-necked flask provided with a mechanical stirrer, a constant pressure dropping funnel and a thermometer, and then 6mL of phosphorus oxychloride is added dropwise, reaction is carried out at 108 DEG C for 5.5h, toluene is removed by distillation at 118 DEG C, and a synthesis product is generated. The reactants are washed with deionized water until neutral, and are spray dried at 160 DEG C for 6s to prepare a solid powder organic phosphate nucleating agent.

[0033] B3, 45 parts of the composite polyethylene prepared in the embodiment 2, 4 parts of the organic phosphate nucleating agent, 0.6 parts of the phenolic antioxidant 1010 and 0.7 parts of zinc stearate are added into a high-speed mixer, and are stirred at 2335r / min for 5min to obtain a mixture. The mixture is added into a double-screw extruder for melt blending and extrusion, the temperature for melt extrusion is 175 DEG C, the time for melt extrusion is 4min, and finally the modified polyethylene insulating material is prepared. Embodiment

[0034] The embodiment provides a preparation method of modified polyethylene insulating material for special insulated shielded cable, and comprises the following steps: B1, 30mL of allyl alcohol and 8g of maleic anhydride are mixed in a 250mL three-necked flask, the reaction temperature of the three-necked flask is set to 75 DEG C, and the three-necked flask is stirred at 150r / min for 5h to form a primary polymer. 0.2g of azobisisobutyronitrile is further added into the three-necked flask, and the three-necked flask is continuously reacted at 60 DEG C for 1.5h to form a resin-like substance.

[0035] B2, 20g of the resin-like substance, 80mL of toluene and 4mL of triethylamine are sequentially added into a 250mL three-necked flask provided with a mechanical stirrer, a constant pressure dropping funnel and a thermometer, and then 6mL of phosphorus oxychloride is added dropwise, reaction is carried out at 108 DEG C for 5.5h, toluene is removed by distillation at 118 DEG C, and a synthesis product is generated. The reactants are washed with deionized water until neutral, and are spray dried at 160 DEG C for 6s to prepare a solid powder organic phosphate nucleating agent.

[0036] B3, 50 parts of the composite polyethylene prepared in Example 3, 5 parts of the organic phosphate nucleating agent, 01 part of the phenolic antioxidant 1010, and 1 part of zinc stearate were added into a high-speed mixer, and stirred at 3000 r / min for 5 min to obtain a mixture. The mixture was added into a twin-screw extruder for melt blending and extrusion, the temperature for melt extrusion was 185℃, and the time for melt extrusion was 5 min, thereby finally obtaining the modified polyethylene insulation material. Example 6

[0037] The embodiment provides a preparation method of an insulated shielding special cable, and the method comprises the following steps: S1, the silver copper alloy is used as the conductor, the silver content of the silver copper alloy is 0.1 wt%, and the diameter of the conductor is 20 mm. A conductor shielding layer is extruded and wrapped outside the conductor, and a steel tape shielding layer is further wrapped outside the conductor shielding layer; the conductor shielding layer is a zinc-plated copper shielding layer, and the thickness of the conductor shielding layer is 2 mm.

[0038] S2, inorganic fillers are filled between the steel tape shielding layer and the wrapping tape; the steel tape shielding layer is a zinc-plated steel tape, and the thickness of the steel tape shielding layer is 0.5 mm; the wrapping tape is made of polytetrafluoroethylene, and the thickness of the wrapping tape is 0.5 mm; the inorganic fillers are compounded by mica powder and aluminum oxide according to a mass ratio of 1:1. A modified polyethylene insulation material is melt-extruded outside the wrapping tape, the temperature for melt extrusion is 200℃, and the insulated shielding special cable is prepared. Example 7

[0039] The embodiment provides a preparation method of an insulated shielding special cable, and the method comprises the following steps: S1, the silver copper alloy is used as the conductor, the silver content of the silver copper alloy is 0.15 wt%, and the diameter of the conductor is 18 mm. A conductor shielding layer is extruded and wrapped outside the conductor, and a steel tape shielding layer is further wrapped outside the conductor shielding layer; the conductor shielding layer is a zinc-plated copper shielding layer, and the thickness of the conductor shielding layer is 2.2 mm.

[0040] S2, inorganic fillers are filled between the steel tape shielding layer and the wrapping tape; the steel tape shielding layer is a zinc-plated steel tape, and the thickness of the steel tape shielding layer is 0.6 mm; the wrapping tape is made of polytetrafluoroethylene, and the thickness of the wrapping tape is 0.08 mm; the inorganic fillers are compounded by mica powder and aluminum oxide according to a mass ratio of 1:1. A modified polyethylene insulation material is melt-extruded outside the wrapping tape, the temperature for melt extrusion is 210℃, and the insulated shielding special cable is prepared. Example 8

[0041] The embodiment provides a preparation method of an insulated shielding special cable, and the method comprises the following steps: S1, the silver copper alloy is used as the conductor, the silver content of the silver copper alloy is 0.2 wt%, and the diameter of the conductor is 18 mm. A conductor shielding layer is extruded and wrapped outside the conductor, and a steel tape shielding layer is further wrapped outside the conductor shielding layer; the conductor shielding layer is a zinc-plated copper shielding layer, and the thickness of the conductor shielding layer is 2.5 mm.

[0042] S2, inorganic filler is filled between the steel tape shielding layer and the wrapping tape; the steel tape shielding layer is a galvanized steel tape with a thickness of 0.8 mm; the wrapping tape is made of polytetrafluoroethylene with a thickness of 1 mm; the inorganic filler is a compound of mica powder and aluminum oxide with a mass ratio of 1:1. The wrapping tape is externally fused and extruded with modified polyethylene insulation material, and the temperature of the fusion and extrusion is 220°C, which is the prepared insulation shielding special cable.

[0043] Comparative Example 1 Compared with Example 9, in the preparation of the multi-active metal catalyst of the present comparative example, no titanate is added in step A1.

[0044] Comparative Example 2 Compared with Example 9, in the preparation of the composite polyethylene of the present comparative example, 100 mL of ethylene gas and 100 mL of propylene gas are replaced by 200 mL of ethylene gas in step A2.

[0045] Comparative Example 3 Compared with Example 9, in the present comparative example, the same mass of di(3,4-dimethylbenzyl) sorbitol is used to replace the prepared organic phosphate nucleating agent.

[0046] Performance test: the modified polyethylene insulation material prepared in Examples 7-9 and Comparative Examples 1-3 is cut into several sections to obtain samples, which are still marked as Examples 7-9 and Comparative Examples 1-3. According to GB / T1040-2012 "Determination of tensile properties of plastics", the samples are subjected to thermal oxidative aging test. The thermal oxidative aging temperature is 155°C and the thermal oxidative aging time is 240h.

[0047] 1. 0.2g of the sample of Examples 7-9 and Comparative Examples 1-3 is weighed, a stainless steel mesh with a mass of M1 is weighed, the sample is added to the stainless steel mesh, and the total mass is M2. The stainless steel mesh is completely immersed in a flask containing cyclohexane solution, and the flask is heated in an oil bath at 150°C for 12h. The mesh bag is taken out, washed with anhydrous ethanol, and dried in a vacuum oven. The mass is M3. The calculation formula of crosslinking degree is: P=(M3-M1) / (M2-M1)×100% 2. The samples prepared in Examples 7-9 and Comparative Examples 1-3 are cut into dumbbell-shaped samples with a thickness of 1 mm in turn; according to GB / T1040-2006, the samples are subjected to uniaxial tensile test by using an electronic universal testing machine, and the tensile rate is 10mm / min. The breaking strength and elongation at break values are calculated.

[0048] 3. According to GB / T3048.7 "Test methods for electrical properties of electric wires and cables - Tracking resistance test", the power frequency voltage resistance test was carried out on the insulation and shielding special cables prepared in Examples 7-9 and Comparative Examples 1-3 in turn. The 85kV power frequency voltage resistance effective value was detected to determine whether it reached 1min, and the voltage resistance was qualified if it was greater than or equal to 1min, otherwise it was unqualified.

[0049] 4. According to GB / T3048.13 "Test methods for impulse voltage test of electric wires and cables", the lightning impulse test was carried out on the insulation and shielding special cables prepared in Examples 7-9 and Comparative Examples 1-3 in turn. The test was qualified if there was breakdown or flashover phenomenon when the 185kV lightning impulse withstand voltage was tested, otherwise it was unqualified. The specific test results are shown in Table 1.

[0050] Table 1. Performance detection data of samples

[0051] Data analysis: According to the data in Table 1, the modified polyethylene insulation material prepared in Examples 7-9 and Comparative Examples 1-3 is only the product of the addition polymerization of ethylene and propylene, and the crosslinking degree is low. However, during the addition polymerization process, the prepared active metal catalyst helps to improve the regularity of the molecular chain of the prepared polymer. The melt blending of the composite polyethylene and the organic phosphate nucleating agent helps to nucleate the crystallization of the composite polyethylene, increase the crystallization density and promote the grain refinement, thereby strengthening the mechanical properties of the prepared composite polyethylene, which is manifested by the high values of the tensile strength and elongation at break of the prepared composite polyethylene.

[0052] However, in Comparative Example 1, titanium acid ester was not added when preparing the multi-active metal catalyst, and the synergistic catalytic effect of titanium-chromium metal elements was not formed. Therefore, the tensile strength and elongation at break of the modified polyethylene insulation material prepared in Comparative Example 1 decreased. In Comparative Example 2, the pure ethylene polymer was used to replace the polymer of ethylene and propylene when preparing the composite polyethylene, which caused the mechanical properties of the prepared composite polyethylene to decrease.

[0053] In Comparative Example 3, the organic phosphate nucleating agent was replaced by sorbitol nucleating agent bis(3,4-dimethylbenzyl) sorbitol; the composite polyethylenes prepared by the two nucleating agents had similar tensile strength values and elongation at break values; therefore, the organic phosphate nucleating agent prepared by the present application also has excellent crystallization properties similar to sorbitol nucleating agent.

[0054] The insulated and shielded special cables prepared in Examples 7-9 and Comparative Examples 1-3 of this invention have excellent shielding effectiveness and electrical performance due to the design of the conductor-conductor shielding layer-steel tape shielding layer-wrapping tape-modified polyethylene insulation material structure. As a result, the withstand voltage and partial discharge of the insulated and shielded special cables prepared in Examples 7-9 and Comparative Examples 1-3 have passed the tests.

[0055] The above description is merely an example and illustration of the structure 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 structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0056] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" 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 invention. In this specification, 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.

[0057] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing an insulated and shielded special cable, characterized in that, Includes the following steps: S1. A silver-copper alloy is used as the conductor, with a conductor shielding layer extruded on the outside of the conductor, and then a steel strip shielding layer wrapped around it. S2. Inorganic filler is filled between the steel strip shielding layer and the wrapping tape; modified polyethylene insulation material is melt-extruded outside the wrapping tape to prepare an insulated and shielded special cable. The modified polyethylene insulation material is prepared by: high-speed mixing of composite polyethylene, organophosphate nucleating agent, antioxidant and lubricant to obtain a mixture; melt extrusion of the mixture to obtain the modified polyethylene insulation material.

2. The method for preparing an insulated and shielded special cable according to claim 1, characterized in that, The method for preparing the composite polyethylene includes the following steps: A1. Porous silica gel is impregnated in CrCl3 solution, and then titanate is added to form a reaction system; the reaction system is reacted at 45-55℃ for 1-2 hours, filtered, and SiO2-TiO2 co-gel support is obtained; the SiO2-TiO2 co-gel support is dried in air atmosphere to obtain catalyst precursor; the catalyst precursor is placed in a fluidized bed reactor for calcination to prepare a multi-active metal catalyst. A2. A first polymerization reactor and a second polymerization reactor are connected in series; the first polymerization reactor is connected to a feed tank, and the second polymerization reactor is connected in sequence to a condenser and a powder discharge silo; solvent, ethylene gas, propylene gas and multi-active metal catalyst are added to the feed tank and mixed to obtain a slurry; the slurry is pumped into the first polymerization reactor to react and form a primary polymer; the primary polymer is pumped into the second polymerization reactor to polymerize and obtain a polymer; unreacted gas is recycled back to the first and second polymerization reactors; the polymer is blown out with nitrogen to obtain composite polyethylene.

3. The method for preparing an insulated and shielded special cable according to claim 2, characterized in that, In step A1, the concentration of CrCl3 solution is 0.2-0.4 mol / L; the ratio of porous silica gel, CrCl3 solution and titanate is 3-10 g: 20-30 mL: 5-10 g; the drying temperature of SiO2-TiO2 co-gel support is 45-55℃ and the drying time is 20-30 min; the calcination temperature is 600-800℃ and the calcination time is 3-4 h; and the fluidizing gas velocity of the fluidized bed reactor is 0.05-0.1 m / s.

4. The method for preparing an insulated and shielded special cable according to claim 2, characterized in that, In step A2, the ratio of solvent, ethylene gas, propylene gas, and multi-active metal catalyst is 200-300 mL: 50-100 mL: 50-100 mL: 1.2-1.5 g; the reaction temperature of the first polymerization reactor is 70-90℃, the reaction pressure is 2.5-3 MPa, and the reaction time is 1-2 h; the reaction temperature of the second polymerization reactor is 65-80℃, the reaction pressure is 1.5-2.5 MPa, and the reaction time is 1.5-2 h.

5. The method for preparing an insulated and shielded special cable according to claim 1, characterized in that, The preparation method of the organophosphate nucleating agent includes the following steps: B1, allyl alcohol and maleic anhydride are mixed and reacted at 70-80℃ for 4-6 hours to form a primary polymer; an initiator is added to the primary polymer, mixed well, and the reaction is continued at 55-65℃ for 1-2 hours to form a resin-like product. B2, a type of resin, toluene, triethylamine and phosphorus oxychloride are mixed and reacted at 105-110℃ for 5-6 hours. Toluene is then removed by distillation at 112-120℃ to synthesize the product. The product is washed until neutral and spray-dried at 155-165℃ for 5-10 seconds to prepare a solid powder organophosphate nucleating agent.

6. The method for preparing an insulated and shielded special cable according to claim 5, characterized in that, In step B1, the ratio of allyl alcohol, maleic anhydride and initiator is 25-35 mL: 5-10 g: 0.1-0.3 g; in step B2, the ratio of resin, toluene, triethylamine and phosphorus oxychloride is 15-25 g: 50-100 mL: 3-5 mL: 5-8 mL.

7. The method for preparing an insulated and shielded special cable according to claim 1, characterized in that, In step S1, the silver content of the silver-copper alloy is 0.1-0.2wt%, and the material of the conductor shielding layer is zinc-plated copper; in step S2, the material of the wrapping tape is polytetrafluoroethylene, and the inorganic filler is mica powder and alumina compounded in a mass ratio of 1:1-2; the temperature of melt extrusion is 200-220℃.

8. The method for preparing an insulated and shielded special cable according to claim 1, characterized in that, The weight ratio of composite polyethylene, organophosphate nucleating agent, phenolic antioxidant and zinc stearate is 40-50:3-5:0.5-1:0.5-1; the melt extrusion temperature is 165-185℃ and the melt extrusion time is 3-5 min.

9. An insulated shielded special cable prepared by the method of preparing an insulated shielded special cable as described in any one of claims 1-8.

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