Cross-linked polyethylene insulated medium and high voltage power cable and preparation method thereof

Abstract

The present invention relates to the technical field of high-voltage power cables, and discloses a cross-linked polyethylene insulated medium- and high-voltage power cable and a preparation method thereof. The cable comprises a conductive core, a first semi-conductive layer, an insulating layer, a second semi-conductive layer, a metal shielding layer and a sheath layer from the inside to the outside. The outer periphery of the conductive core located in the innermost layer is extruded with a first semi-conductive layer, and the outer periphery of the first semi-conductive layer is extruded with an insulating layer; the outer periphery of the insulating layer is extruded with a second semi-conductive layer; the outer periphery of the second semi-conductive layer is provided with a metal shielding layer; the outer periphery of the metal shielding layer is extruded with a sheath layer. The insulating layer is made of cross-linked polyethylene, including the following raw materials in parts by weight: 170-180 parts of low-density polyethylene, 10-12 parts of a cross-linking agent, 1-3 parts of an antioxidant, 5.5-6.5 parts of a voltage stabilizer and 6.5-7.5 parts of an enhancer, wherein the voltage stabilizer is used to suppress the initiation and growth of electrical dendrites, improve the voltage withstand capability of the cable, and the enhancer is used to improve the aging resistance and mechanical properties of the cable.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage power cables, and in particular relates to a cross-linked polyethylene insulated medium- and high-voltage power cable and a preparation method thereof. Background Art

[0002] Medium and high voltage power cables are an indispensable and important part of the power system. They are mainly used for power transmission, distribution and power supply, and can withstand large currents and voltages. The basic structure of medium and high voltage power cables usually consists of a core (conductor core), an insulating functional layer, a shielding functional layer and a protective layer (sheath layer). A typical medium and high voltage power cable usually includes a core, an inner layer, an insulating layer, a shielding layer and an outer sheath layer from the inside out.

[0003] Cross-linked polyethylene medium and high voltage power cables are a common type of medium and high voltage power cables. They refer to medium and high voltage power cables that use cross-linked polyethylene (XLPE) as insulation materials. They have the advantages of good insulation performance, heat resistance, chemical corrosion resistance and high mechanical strength. They are usually used in transmission lines, substations, cable tunnels and other places. The cross-linked polyethylene (XLPE) used as its insulation layer undergoes a specific chemical reaction to cross-link the polyethylene material, thereby improving its physical properties and chemical resistance. During use, they are affected by long-term high-altitude atmosphere and high-temperature environment, and will undergo continuous and irreversible electrical aging. In severe cases, they will lead to insulation breakdown, posing a hidden danger to cable safety.

[0004] The electrical aging of cross-linked polyethylene insulating materials especially refers to the aging caused by the growth of electrical dendrites, which is a cumulative breakdown phenomenon. In the prior art, voltage stabilizers are added to inhibit the growth of electrical dendrites by increasing the starting voltage of electrical dendrites or the field strength of electrical dendrites, but small molecule voltage stabilizers are prone to migration failure. In order to inhibit the light and oxygen aging of cross-linked polyethylene insulating materials, antioxidants are usually tried. Small molecule antioxidants have the problem of migration failure, and insulating fillers added to improve the mechanical properties of insulating materials are prone to agglomeration in the matrix due to the presence of surface active groups. Summary of the invention

[0005] In view of the technical problems existing in the prior art, according to the first aspect of the purpose of the present invention, a cross-linked polyethylene insulated medium and high voltage power cable is proposed, which comprises, from the inside to the outside, a conductive core, a first semi-conductive layer, an insulating layer, a second semi-conductive layer, a metal shielding layer and a sheath layer, wherein the conductive core is located in the innermost layer; the first semi-conductive layer is extruded around the outer periphery of the conductive core; the insulating layer is extruded around the outer periphery of the first semi-conductive layer; the second semi-conductive layer is extruded around the outer periphery of the insulating layer; the metal shielding layer is arranged around the outer periphery of the second semi-conductive layer; finally, the sheath layer is extruded around the outer periphery of the metal shielding layer.

[0006] The insulating layer is made of cross-linked polyethylene-based insulating material, wherein the sterically hindered piperidine structure and benzothiazole structure contained therein synergistically inhibit electrical aging and electrical tree growth of the insulating layer, thereby improving the cable's ability to withstand voltage and insulation life.

[0007] In a further embodiment, the insulating layer is made of cross-linked polyethylene, which is prepared from low-density polyethylene, a cross-linking agent, an antioxidant, a voltage stabilizer and a reinforcing agent, wherein the voltage stabilizer used has at least a benzothiazole structure, a hindered piperidine structure and a carbon-carbon double bond structure.

[0008] In a further embodiment, the enhancer is obtained by modifying nano silicon nitride with a first intermediate, wherein the first intermediate includes a hindered phenol structure and a 3,4-dihydroxybenzene structure, and the hindered phenol structure captures free radicals generated by the thermal oxidative aging reaction of the polymer to generate hydroperoxides and relatively stable phenoloxy free radicals, thereby terminating the thermal oxidative aging reaction of the polymer molecules and inhibiting chain growth;

[0009] The 3,4-dihydroxybenzene structure, the antioxidant 618 containing a phosphite structure that decomposes hydroperoxide, and the hindered phenol structure synergistically inhibit the aging of the matrix and improve the aging resistance of the cable;

[0010] After being modified by the first intermediate, the nano silicon nitride as a thermally conductive insulating filler has reduced agglomeration and is evenly dispersed in the matrix, thereby improving the mechanical properties of the cable and reducing the migration of the first intermediate in the matrix.

[0011] In a further embodiment, the cross-linked polyethylene comprises the following raw materials in parts by weight: 170-180 parts of low-density polyethylene, 10-12 parts of a cross-linking agent, 1-3 parts of an antioxidant, 5.5-6.5 parts of a voltage stabilizer, and 6.5-7.5 parts of a reinforcing agent.

[0012] In a further embodiment, the voltage stabilizer is prepared according to the following process:

[0013] Step A1: In a nitrogen atmosphere, 3-(oxirane-2-ylmethoxy)benzaldehyde and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed and stirred at 40-50° C. for 3-4 hours to obtain a reaction product 1 containing an olefin group;

[0014] Step A2: In a nitrogen atmosphere, add 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid and methanol into a round-bottom flask, start stirring, raise the temperature to 40-50° C., add pyridine and reaction product 1, and react at a constant temperature with stirring for 8-10 hours to obtain reaction product 2;

[0015] Step A3: Add the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide into a flask to obtain a mixed solution a, then add 2,1,3-benzothiadiazole-5-carbonyl chloride to dimethyl sulfoxide to obtain a mixed solution b, slowly dropwise add the mixed solution b into the mixed solution a in an ice-water bath at 0°C, after the dropwise addition is completed, raise the temperature to 40°C, stir the reaction at a constant temperature for 8-10 hours, and distill under reduced pressure to obtain a voltage stabilizer.

[0016] In a further embodiment, in step A1, the ratio of 3-(oxiran-2-ylmethoxy)benzaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran is 0.1 mol: 0.1 mol: 100-120 mL;

[0017] In the step A2, the usage ratio of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, methanol, pyridine and reaction product 1 is 0.1 mol: 140-160 mL: 0.001-0.0012 mol: 0.1 mol;

[0018] In the step A3, the usage ratio of the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide is 0.1 mol: 0.01-0.015 mol: 0.1 mol: 70-80 mL; the usage ratio of 2,1,3-benzothiadiazole-5-carbonyl chloride and dimethyl sulfoxide is 0.1 mol: 20-30 mL; the usage ratio of the mixed solution a to the mixed solution b is 75-85 mL: 25-35 mL.

[0019] In a further embodiment, the enhancer is prepared according to the following process:

[0020] Step B1: Add 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile to tetrahydrofuran, start stirring, add Raney nickel and Pd / C, introduce hydrogen, and react under normal pressure with stirring for 48 hours to obtain a primary amino product; add the primary amino product, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, then add methacryloyl chloride to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in an ice-water bath at 0°C, and after the dropwise addition is completed, heat to 40°C, and react with stirring at a constant temperature for 10 hours to obtain a fourth intermediate;

[0021] Step B2: Add the fourth intermediate and anhydrous ethanol into a flask, start stirring, and slowly drop 3,4-methylenedioxyphenylethylamine under nitrogen protection. After the dropwise addition is complete, heat to 105°C, reflux and stir to react for 48 hours, and vacuum dry at 50°C to obtain the third intermediate;

[0022] Step B3: Add the third intermediate and toluene to a tetrahydrofuran solution of lithium aluminum hydride, start stirring, and react at room temperature for 2-3 hours to obtain the second intermediate; add aluminum chloride to nitrobenzene, stir for 10-15 minutes, slowly add the second intermediate, and stir at room temperature for 4-5 hours to obtain the first intermediate;

[0023] Step B4: Add nano aluminum nitride powder to ethanol aqueous solution, stir for 20-30 minutes to obtain mixed solution 3; then add the first intermediate to ethanol aqueous solution, stir for 10-15 minutes to obtain mixed solution 4; add mixed solution 3 and mixed solution 4 to a beaker, ultrasonically disperse for 40-50 minutes, adjust the pH to 6-6.5, then stir and react at 50°C for 10-11 hours, wash with anhydrous ethanol, dry in an oven at 70°C for 12 hours, and grind to obtain the enhancer.

[0024] In a further embodiment, in the step B1, the dosage ratio of 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile, tetrahydrofuran, Raney nickel and Pd / C is 0.1 mol: 70-80 mL: 0.01 mol: 0.01-0.015 mol; the dosage ratio of primary amino product, potassium carbonate and dimethyl sulfoxide is 0.1 mol: 0.015 mol: 75-80 mL; the dosage ratio of methacryloyl chloride and dimethyl sulfoxide is 0.1 mol: 25-30 mL; the dosage ratio of mixed solution 1 and mixed solution 2 is 80-85 mL: 30-35 mL;

[0025] In the step B2, the fourth intermediate, anhydrous ethanol and 3,4-methylenedioxyphenylethylamine are used in a ratio of 0.27 mol: 140-160 mL: 0.1-0.13 mol; in the step B3, the third intermediate, toluene and tetrahydrofuran solution of lithium aluminum hydride are used in a ratio of 0.1 mol: 105-115 mL: 120-130 mL, and the concentration of the tetrahydrofuran solution of lithium aluminum hydride is 1 mol / L; the aluminum chloride, nitrobenzene and the second intermediate are used in a ratio of 2 g: 75 mL: 5 g.

[0026] In the step B4, the dosage ratio of the nano-aluminum nitride powder and the ethanol aqueous solution is 0.1 g: 10 mL; the dosage ratio of the first intermediate and the ethanol aqueous solution is 0.15-0.20 mol: 50-60 mL; the dosage ratio of the mixed solution 3 and the mixed solution 4 is 11-13 mL: 55-65 mL; the volume fraction of the ethanol aqueous solution is 10%;

[0027] During the reaction of step B4, the first intermediate containing two phenolic hydroxyl groups bonds with the active groups on the surface of the nano-aluminum nitride powder, thereby obtaining nano-aluminum nitride modified with the first intermediate, which is the enhancer.

[0028] According to a second aspect of the present invention, a cross-linked polyethylene insulated medium and high voltage power cable prepared according to the aforementioned method is provided, wherein:

[0029] The conductive core is a plurality of twisted copper wires;

[0030] The first semiconductive layer and the second semiconductive layer are both made of ethylene-vinyl acetate copolymer material;

[0031] The metal shielding layer is obtained by spirally wrapping a conductive metal belt made of aluminum around the second semi-conductive layer;

[0032] The sheath layer is made of TPE sheath material.

[0033] According to a third aspect of the present invention, a method for preparing a cross-linked polyethylene insulated medium- and high-voltage power cable is provided, comprising the following steps:

[0034] Step S1, using an extruder to extrude and deposit the first semiconductive layer on the outer periphery of the conductive core;

[0035] Step S2, extruding and depositing the cross-linked polyethylene-based insulating material on the periphery of the first semi-conductive layer to form an insulating layer; wherein the sterically hindered piperidine structure and benzothiazole structure contained in the cross-linked polyethylene-based insulating material synergistically inhibit electrical aging and electrical tree growth of the insulating layer, thereby improving the ability of the cable to withstand voltage and the insulation life;

[0036] Step S3, then extruding and depositing the second semiconductive layer on the periphery of the insulating layer;

[0037] Step S4, wrapping an aluminum conductive metal belt around the outer periphery of the second semi-conductive layer in a spiral form to obtain a metal shielding layer;

[0038] Step S5, finally, the TPE sheath material is extruded and deposited on the outer periphery of the metal shielding layer to obtain a sheath layer, and annealing treatment is performed after extrusion to obtain a cross-linked polyethylene insulated medium and high voltage power cable.

[0039] In combination with the embodiments of the above aspects, the cross-linked polyethylene insulated medium and high voltage power cable proposed by the present invention includes a conductive core, a first semi-conductive layer, an insulating layer, a second semi-conductive layer, a metal shielding layer and a sheath layer from the inside to the outside. The insulating layer is made by cross-linking reaction of cross-linked polyethylene, and the cross-linked polyethylene includes the following raw materials: low-density polyethylene, a cross-linking agent, an antioxidant, a voltage stabilizer and an enhancer. The voltage stabilizer contains a benzothiazole structure, a sterically hindered piperidine structure and a carbon-carbon double bond in its molecule. The carbon-carbon double bond enables the voltage stabilizer to have a cross-linkable site, increases the compatibility and dispersibility of the voltage stabilizer in the matrix, and avoids the migration failure of the voltage stabilizer; the benzothiazole structure has a large electron affinity, which can significantly improve the electric tree initiation field strength of the matrix, and can well inhibit the growth of the electric tree; the sterically hindered piperidine structure can absorb the residual oxygen in the polymer, and the oxidized nitroxide free radical can effectively inhibit the formation of macromolecular free radicals, which not only increases the starting voltage of the electric tree of the matrix, but also cooperates with the benzothiazole structure to inhibit the growth of the electric tree, and can also inhibit the electrical aging of the matrix and extend the insulation life of the matrix. The voltage stabilizer can inhibit the initiation and growth of electrical trees in the insulating material and improve the cable's ability to withstand voltage.

[0040] In the cable structure design of the above embodiment, the reinforcing agent is obtained by modifying nano silicon nitride with the first intermediate. The first intermediate includes a hindered phenol structure and a 3,4-dihydroxybenzene structure. The hindered phenol structure can capture the free radicals generated by the thermal oxidation aging reaction of the polymer, generate hydroperoxides and relatively stable phenol oxygen free radicals, thereby terminating the thermal oxidation aging reaction of the polymer molecules and inhibiting chain growth; the 3,4-dihydroxybenzene structure itself has a strong ultraviolet shielding effect, and together with the antioxidant 618 containing a phosphite structure that decomposes hydroperoxide and the hindered phenol structure, it synergistically inhibits the aging of the matrix and improves the aging resistance of the cable. As an insulating filler with high thermal conductivity, nano silicon nitride, after being modified by the first intermediate, not only reduces the agglomeration phenomenon of nano silicon nitride, but also disperses more evenly in the matrix, thereby improving the mechanical properties of the cable, and also avoids the migration of the first intermediate in the matrix, which can play a better role. The reinforcing agent improves the aging resistance and mechanical properties of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0042] Figure 1 It is a schematic structural diagram of the cross-linked polyethylene insulated medium and high voltage power cable of the present invention.

[0043] Figure 2It is a schematic cross-sectional view of the cross-linked polyethylene insulated medium and high voltage power cable of the present invention.

[0044] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0045] 1. Conductive core; 2. First semi-conductive layer; 3. Insulating layer; 4. Second semi-conductive layer; 5. Metal shielding layer; 6. Sheath layer. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Cross-linked polyethylene insulated medium and high voltage power cables

[0048] Combination Figure 1 , 2 As shown, the cross-linked polyethylene insulated medium and high voltage power cable according to the first aspect of the embodiment of the present invention comprises, from the inside to the outside, a conductive core 1, a first semiconductive layer 2, an insulating layer 3, a second semiconductive layer 4, a metal shielding layer 5 and a sheath layer 6.

[0049] like Figure 2 As shown, the conductive core 1 is located in the innermost layer, the outer periphery of the conductive core 1 is extruded with a first semiconductive layer 2, the outer periphery of the first semiconductive layer 2 is extruded with an insulating layer 3, the outer periphery of the insulating layer 3 is extruded with a second semiconductive layer 4, the outer periphery of the second semiconductive layer 4 is provided with a metal shielding layer 5, and finally, the outer periphery of the metal shielding layer 5 is extruded with the sheath layer 6 shown.

[0050] The aforementioned insulating layer 3 is made of cross-linked polyethylene-based insulating material, wherein the sterically hindered piperidine structure and benzothiazole structure contained therein synergistically inhibit electrical aging of the insulating layer and growth of electrical dendrites, thereby improving the cable's ability to withstand voltage and insulation life.

[0051] Insulation layer

[0052] As an optional embodiment, the insulating layer is made of cross-linked polyethylene through a cross-linking reaction. The cross-linked polyethylene is prepared from low-density polyethylene, a cross-linking agent, an antioxidant, a voltage stabilizer and a reinforcing agent, wherein the voltage stabilizer used has at least a benzothiazole structure, a hindered piperidine structure and a carbon-carbon double bond structure.

[0053] As an optional embodiment, the aforementioned cross-linked polyethylene comprises the following raw materials in parts by weight: 170-180 parts of low-density polyethylene, 10-12 parts of a cross-linking agent, 1-3 parts of an antioxidant, 5.5-6.5 parts of a voltage stabilizer, and 6.5-7.5 parts of a reinforcing agent.

[0054] Stabilizer

[0055] As an optional embodiment, the voltage stabilizer has at least a benzothiazole structure, a hindered piperidine structure and a carbon-carbon double bond structure.

[0056] The carbon-carbon double bond provides the voltage stabilizer with cross-linkable sites, increases the compatibility and dispersibility of the voltage stabilizer in the matrix, and avoids the migration and failure of the voltage stabilizer. The benzothiazole structure has a large electron affinity, which can significantly increase the initiation field strength of the matrix's electrical dendrites and effectively inhibit the growth of electrical dendrites. The sterically hindered piperidine structure can absorb the residual oxygen in the polymer, and the oxidized nitroxide free radicals can effectively inhibit the formation of macromolecular free radicals, which not only increases the matrix's electrical dendrite initiation voltage, but also synergizes with the benzothiazole structure to inhibit the growth of electrical dendrites, and can also inhibit the electrical aging of the matrix and extend the insulation life of the matrix.

[0057] Thus, the voltage stabilizer can inhibit the initiation and growth of electrical trees in the insulating material, thereby improving the cable's ability to withstand voltage.

[0058] As an example of a voltage stabilizer, the aforementioned voltage stabilizer is prepared according to the following process:

[0059] Step A1: In a nitrogen atmosphere, 3-(oxirane-2-ylmethoxy)benzaldehyde and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed and stirred at 40-50° C. for 3-4 hours to obtain a reaction product 1 containing an olefin group;

[0060] Step A2: In a nitrogen atmosphere, add 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid and methanol into a round-bottom flask, start stirring, raise the temperature to 40-50° C., add pyridine and reaction product 1, and react at a constant temperature with stirring for 8-10 hours to obtain reaction product 2;

[0061] Step A3: Add the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide into a flask to obtain a mixed solution a, then add 2,1,3-benzothiadiazole-5-carbonyl chloride to dimethyl sulfoxide to obtain a mixed solution b, slowly dropwise add the mixed solution b into the mixed solution a in an ice-water bath at 0°C, after the dropwise addition is completed, raise the temperature to 40°C, stir the reaction at a constant temperature for 8-10 hours, and distill under reduced pressure to obtain a voltage stabilizer.

[0062] As an optional embodiment, in the aforementioned step A1, the usage ratio of 3-(oxiran-2-ylmethoxy)benzaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran is 0.1 mol:0.1 mol:100-120 mL.

[0063] In the aforementioned step A2, the usage ratio of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, methanol, pyridine and reaction product 1 is 0.1 mol:140-160 mL:0.001-0.0012 mol:0.1 mol.

[0064] In the aforementioned step A3, the usage ratio of the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide is 0.1 mol: 0.01-0.015 mol: 0.1 mol: 70-80 mL; the usage ratio of 2,1,3-benzothiadiazole-5-carbonyl chloride and dimethyl sulfoxide is 0.1 mol: 20-30 mL; the usage ratio of the mixed solution a to the mixed solution b is 75-85 mL: 25-35 mL.

[0065] Enhancer

[0066] As an optional embodiment, the enhancer is obtained by modifying nano silicon nitride with a first intermediate, wherein the first intermediate includes a hindered phenol structure and a 3,4-dihydroxybenzene structure.

[0067] As an optional embodiment, the aforementioned enhancer is obtained by modifying nano silicon nitride with a first intermediate, and the aforementioned first intermediate includes a hindered phenol structure and a 3,4-dihydroxybenzene structure.

[0068] Among them, the free radicals generated by the thermal oxidative aging reaction of the polymer are captured by the hindered phenol structure to generate hydroperoxides and relatively stable phenoloxyl radicals, thereby terminating the thermal oxidative aging reaction of the polymer molecules and inhibiting chain growth.

[0069] The 3,4-dihydroxybenzene structure, the antioxidant 618 containing a phosphite structure that decomposes hydroperoxide, and the hindered phenol structure synergistically inhibit matrix aging and improve the aging resistance of the cable.

[0070] After being modified by the first intermediate, the nano silicon nitride as a thermally conductive insulating filler has reduced agglomeration and is evenly dispersed in the matrix, thereby improving the mechanical properties of the cable and reducing the migration of the first intermediate in the matrix.

[0071] As an optional embodiment, the aforementioned enhancer is prepared according to the following process:

[0072] Step B1: Add 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile to tetrahydrofuran, start stirring, add Raney nickel and Pd / C, introduce hydrogen, and react under normal pressure with stirring for 48 hours to obtain a primary amino product; add the primary amino product, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, then add methacryloyl chloride to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in an ice-water bath at 0°C, and after the dropwise addition is completed, heat to 40°C, and react with stirring at a constant temperature for 10 hours to obtain a fourth intermediate;

[0073] Step B2: Add the fourth intermediate and anhydrous ethanol into a flask, start stirring, and slowly drop 3,4-methylenedioxyphenylethylamine under nitrogen protection. After the dropwise addition is complete, heat to 105°C, reflux and stir to react for 48 hours, and vacuum dry at 50°C to obtain the third intermediate;

[0074] Step B3: Add the third intermediate and toluene to a tetrahydrofuran solution of lithium aluminum hydride, start stirring, and react at room temperature for 2-3 hours to obtain the second intermediate; add aluminum chloride to nitrobenzene, stir for 10-15 minutes, slowly add the second intermediate, and stir at room temperature for 4-5 hours to obtain the first intermediate;

[0075] Step B4: Add nano aluminum nitride powder to ethanol aqueous solution, stir for 20-30 minutes to obtain mixed solution 3; then add the first intermediate to ethanol aqueous solution, stir for 10-15 minutes to obtain mixed solution 4; add mixed solution 3 and mixed solution 4 to a beaker, ultrasonically disperse for 40-50 minutes, adjust the pH to 6-6.5, then stir and react at 50°C for 10-11 hours, wash with anhydrous ethanol, dry in an oven at 70°C for 12 hours, and grind to obtain the enhancer.

[0076] As an optional embodiment, in the aforementioned step B1, the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile, tetrahydrofuran, Raney nickel and Pd / C is 0.1 mol: 70-80 mL: 0.01 mol: 0.01-0.015 mol; the usage ratio of primary amino product, potassium carbonate and dimethyl sulfoxide is 0.1 mol: 0.015 mol: 75-80 mL; the usage ratio of methacryloyl chloride and dimethyl sulfoxide is 0.1 mol: 25-30 mL; the usage ratio of mixed solution 1 and mixed solution 2 is 80-85 mL: 30-35 mL.

[0077] In the aforementioned step B2, the usage ratio of the fourth intermediate, anhydrous ethanol and 3,4-methylenedioxyphenylethylamine is 0.27 mol:140-160 mL:0.1-0.13 mol; in step B3, the usage ratio of the third intermediate, toluene and tetrahydrofuran solution of lithium aluminum hydride is 0.1 mol:105-115 mL:120-130 mL, and the concentration of the tetrahydrofuran solution of lithium aluminum hydride is 1 mol / L; the usage ratio of aluminum chloride, nitrobenzene and the second intermediate is 2 g:75 mL:5 g.

[0078] In the aforementioned step B4, the dosage ratio of nano aluminum nitride powder and ethanol aqueous solution is 0.1 g: 10 mL; the dosage ratio of the first intermediate and ethanol aqueous solution is 0.15-0.20 mol: 50-60 mL; the dosage ratio of mixed solution 3 and mixed solution 4 is 11-13 mL: 55-65 mL; the volume fraction of ethanol aqueous solution is 10%;

[0079] During the reaction of step B4, the first intermediate containing two phenolic hydroxyl groups bonds with the active groups on the surface of the nano-aluminum nitride powder, thereby obtaining nano-aluminum nitride modified with the first intermediate, which is the enhancer.

[0080] Preparation method of cross-linked polyethylene insulated medium and high voltage power cable

[0081] According to a second aspect of an embodiment of the present invention, a method for preparing a cross-linked polyethylene insulated medium- and high-voltage power cable comprises the following steps:

[0082] Step S1, using an extruder to extrude and deposit the first semi-conductive layer on the outer periphery of the conductive core;

[0083] Step S2, extruding and depositing the aforementioned cross-linked polyethylene-based insulating material on the periphery of the first semi-conductive layer to form an insulating layer; wherein the sterically hindered piperidine structure and benzothiazole structure contained in the aforementioned cross-linked polyethylene-based insulating material synergistically inhibit electrical aging and electrical tree growth of the insulating layer, thereby improving the ability of the cable to withstand voltage and the insulation life;

[0084] Step S3, then extruding and depositing the aforementioned second semiconductive layer on the periphery of the insulating layer;

[0085] Step S4, wrapping an aluminum conductive metal tape in a spiral form around the outer periphery of the second semi-conductive layer to obtain a metal shielding layer;

[0086] Step S5, finally, the TPE sheath material is extruded and deposited on the outer periphery of the metal shielding layer to obtain a sheath layer, and annealing treatment is performed after extrusion to obtain a cross-linked polyethylene insulated medium and high voltage power cable.

[0087] As an optional implementation, the conductive core 1 is a plurality of twisted copper wires, in particular, oxygen-free copper soft wire, or tinned oxygen-free copper.

[0088] The first semiconductive layer 2 and the second semiconductive layer 4 are both made of ethylene-vinyl acetate copolymer material. Ethylene-vinyl acetate copolymer is used as the semiconductive shielding material base material and extruded outside the conductive core and the insulating layer to alleviate the defects in the conductor twisting process, improve the radial distribution of the electric field inside the cable, suppress the electric field stress concentration inside the conductor, and improve the shielding and electrical performance.

[0089] The metal shielding layer 5 is obtained by wrapping a conductive metal belt made of aluminum around the second semi-conductive layer 4 in a spiral form, with a wrapping overlap ratio of 30%-45%.

[0090] Combination Figure 1 , 2 The sheath layer 6 is made of a TPE sheath material extruded on the outer surface of the metal shielding layer 5.

[0091] Example 1

[0092] As an example of a voltage stabilizer, its preparation includes the following steps:

[0093] Step A1: In a nitrogen atmosphere, 3-(2-oxirane-1-ylmethoxy)benzaldehyde and methylenetriphenylphosphine were added to anhydrous tetrahydrofuran, and the mixture was refluxed and stirred at 40° C. for 3 h to obtain an olefin-containing reaction product 1; the amount ratio of 3-(2-oxirane-1-ylmethoxy)benzaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran was 0.1 mol: 0.1 mol: 100 mL;

[0094] Step A2: In a nitrogen atmosphere, 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid and methanol were added to a round-bottom flask, the mixture was stirred, the temperature was raised to 40°C, pyridine and reaction product 1 were added, and the mixture was stirred at a constant temperature for 8 hours to obtain reaction product 2; the amount ratio of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, methanol, pyridine and reaction product 1 was 0.1 mol: 140 mL: 0.001 mol: 0.1 mol;

[0095] Step A3: Add the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide into a flask to obtain a mixed solution a, then add 2,1,3-benzothiadiazole-5-carbonyl chloride to dimethyl sulfoxide to obtain a mixed solution b, slowly dropwise add the mixed solution b into the mixed solution a in an ice-water bath at 0°C, after the dropwise addition is completed, heat to 40°C, stir and react at a constant temperature for 8 hours, and distill under reduced pressure to obtain a voltage stabilizer; the amount ratio of the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide is 0.1 mol: 0.01 mol: 0.1 mol: 70 mL; the amount ratio of 2,1,3-benzothiadiazole-5-carbonyl chloride and dimethyl sulfoxide is 0.1 mol: 20 mL; the amount ratio of the mixed solution a to the mixed solution b is 75 mL: 25 mL.

[0096] Example 2

[0097] As an example of a voltage stabilizer, its preparation includes the following steps:

[0098] Step A1: In a nitrogen atmosphere, 3-(2-oxirane-1-ylmethoxy)benzaldehyde and methylenetriphenylphosphine were added to anhydrous tetrahydrofuran, and the mixture was refluxed and stirred at 45°C for 3.5 h to obtain an olefin-containing reaction product 1; the amount ratio of 3-(2-oxirane-1-ylmethoxy)benzaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran was 0.1 mol: 0.1 mol: 110 mL;

[0099] Step A2: In a nitrogen atmosphere, 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid and methanol were added to a round-bottom flask, the mixture was stirred, the temperature was raised to 45°C, pyridine and reaction product 1 were added, and the mixture was stirred at a constant temperature for 9 hours to obtain reaction product 2; the amount ratio of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, methanol, pyridine and reaction product 1 was 0.1 mol: 150 mL: 0.0011 mol: 0.1 mol;

[0100] Step A3: Add the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide into a flask to obtain a mixed solution a, then add 2,1,3-benzothiadiazole-5-carbonyl chloride to dimethyl sulfoxide to obtain a mixed solution b, slowly dropwise add the mixed solution b into the mixed solution a in an ice-water bath at 0°C, after the dropwise addition is completed, heat to 40°C, stir and react at a constant temperature for 8-10 hours, and distill under reduced pressure to obtain a voltage stabilizer; the amount ratio of the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide is 0.1 mol: 0.012 mol: 0.1 mol: 75 mL; the amount ratio of 2,1,3-benzothiadiazole-5-carbonyl chloride and dimethyl sulfoxide is 0.1 mol: 25 mL; the amount ratio of the mixed solution a to the mixed solution b is 80 mL: 30 mL.

[0101] Example 3

[0102] As an example of a voltage stabilizer, its preparation includes the following steps:

[0103] Step A1: In a nitrogen atmosphere, 3-(2-oxirane-1-ylmethoxy)benzaldehyde and methylenetriphenylphosphine were added to anhydrous tetrahydrofuran, and the mixture was refluxed and stirred at 50° C. for 4 h to obtain an olefin-containing reaction product 1; the amount ratio of 3-(2-oxirane-1-ylmethoxy)benzaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran was 0.1 mol: 0.1 mol: 120 mL;

[0104] Step A2: In a nitrogen atmosphere, 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid and methanol were added to a round-bottom flask, the mixture was stirred, the temperature was raised to 50°C, pyridine and reaction product 1 were added, and the mixture was stirred at a constant temperature for 10 hours to obtain reaction product 2; the amount ratio of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, methanol, pyridine and reaction product 1 was 0.1 mol: 160 mL: 0.0012 mol: 0.1 mol;

[0105] Step A3: Add the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide into a flask to obtain a mixed solution a, then add 2,1,3-benzothiadiazole-5-carbonyl chloride to dimethyl sulfoxide to obtain a mixed solution b, slowly dropwise add the mixed solution b into the mixed solution a in an ice-water bath at 0°C, after the dropwise addition is completed, heat to 40°C, stir and react at a constant temperature for 10 hours, and distill under reduced pressure to obtain a voltage stabilizer; the amount ratio of the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide is 0.1 mol: 0.015 mol: 0.1 mol: 80 mL; the amount ratio of 2,1,3-benzothiadiazole-5-carbonyl chloride and dimethyl sulfoxide is 0.1 mol: 30 mL; the amount ratio of the mixed solution a to the mixed solution b is 85 mL: 35 mL.

[0106] Example 4

[0107] As an example of an enhancer, its preparation includes the following steps:

[0108] Step B1: Add 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile to tetrahydrofuran, start stirring, add Raney nickel and Pd / C, introduce hydrogen, and react under normal pressure with stirring for 48 hours to obtain a primary amino product; add the primary amino product, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, then add methacryloyl chloride to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in an ice-water bath at 0°C, and after the dropwise addition is completed, heat to 40°C, and react with stirring at a constant temperature for 10 hours. , that is, the fourth intermediate is obtained; the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile, tetrahydrofuran, Raney nickel and Pd / C is 0.1mol:70mL:0.01mol:0.01mol; the usage ratio of primary amino product, potassium carbonate and dimethyl sulfoxide is 0.1mol:0.015mol:75mL; the usage ratio of methacryloyl chloride and dimethyl sulfoxide is 0.1mol:25mL; the usage ratio of mixed solution 1 and mixed solution 2 is 80mL:30mL;

[0109] Step B2: Add the fourth intermediate and anhydrous ethanol into a flask, start stirring, and slowly drop 3,4-methylenedioxyphenylethylamine (supplier: Wuhan Kemik Biopharmaceutical Technology Co., Ltd.) under nitrogen protection. After the dropwise addition is completed, heat to 105°C, reflux and stir to react for 48 hours, and vacuum dry at 50°C to obtain the third intermediate; the usage ratio of the fourth intermediate, anhydrous ethanol and 3,4-methylenedioxyphenylethylamine is 0.27 mol:140 mL:0.1 mol;

[0110] Step B3: Add the third intermediate and toluene to a tetrahydrofuran solution of lithium aluminum hydride, start stirring, and react at room temperature for 2 hours to obtain a second intermediate; add aluminum chloride to nitrobenzene, stir for 10 minutes, slowly add the second intermediate, and stir at room temperature for 4 hours to obtain a first intermediate; the dosage ratio of the third intermediate, toluene and the tetrahydrofuran solution of lithium aluminum hydride is 0.1 mol: 105 mL: 120 mL, and the concentration of the tetrahydrofuran solution of lithium aluminum hydride is 1 mol / L; the dosage ratio of aluminum chloride, nitrobenzene and the second intermediate is 2 g: 75 mL: 5 g;

[0111] Step B4: Add nano aluminum nitride powder to ethanol aqueous solution, stir for 20 minutes to obtain mixed solution 3; then add the first intermediate to the ethanol aqueous solution, stir for 10 minutes to obtain mixed solution 4; add mixed solution 3 and mixed solution 4 to a beaker, ultrasonically disperse for 40 minutes, adjust the pH to 6, and then stir and react at 50°C for 10 hours, wash with anhydrous ethanol, dry in an oven at 70°C for 12 hours, and grind to obtain an enhancer; the dosage ratio of nano aluminum nitride powder and ethanol aqueous solution is 0.1g:10mL; the dosage ratio of the first intermediate and ethanol aqueous solution is 0.15mol:50mL; the dosage ratio of mixed solution 3 to mixed solution 4 is 11mL:55mL; the volume fraction of ethanol aqueous solution is 10%.

[0112] Example 5

[0113] As an example of an enhancer, its preparation includes the following steps:

[0114] Step B1: Add 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile to tetrahydrofuran, start stirring, add Raney nickel and Pd / C, introduce hydrogen, and react under normal pressure with stirring for 48 hours to obtain a primary amino product; add the primary amino product, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, then add methacryloyl chloride to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in an ice-water bath at 0°C, and after the dropwise addition is completed, heat to 40°C, and react with stirring at a constant temperature for 10 hours. , that is, the fourth intermediate is obtained; the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile, tetrahydrofuran, Raney nickel and Pd / C is 0.1mol:75mL:0.01mol:0.02mol; the usage ratio of primary amino product, potassium carbonate and dimethyl sulfoxide is 0.1mol:0.015mol:77mL; the usage ratio of methacryloyl chloride and dimethyl sulfoxide is 0.1mol:27mL; the usage ratio of mixed solution 1 and mixed solution 2 is 82mL:32mL;

[0115] Step B2: Add the fourth intermediate and anhydrous ethanol into a flask, start stirring, and slowly drop 3,4-methylenedioxyphenylethylamine (supplier: Wuhan Kemik Biopharmaceutical Technology Co., Ltd.) under nitrogen protection. After the dropwise addition is completed, heat to 105°C, reflux and stir to react for 48 hours, and vacuum dry at 50°C to obtain the third intermediate; the usage ratio of the fourth intermediate, anhydrous ethanol and 3,4-methylenedioxyphenylethylamine is 0.27 mol:150 mL:0.12 mol;

[0116] Step B3: Add the third intermediate and toluene to a tetrahydrofuran solution of lithium aluminum hydride, start stirring, and react at room temperature for 2.5 hours to obtain a second intermediate; add aluminum chloride to nitrobenzene, stir for 12 minutes, slowly add the second intermediate, and stir at room temperature for 4.5 hours to obtain a first intermediate; the dosage ratio of the third intermediate, toluene and the tetrahydrofuran solution of lithium aluminum hydride is 0.1 mol: 110 mL: 125 mL, and the concentration of the tetrahydrofuran solution of lithium aluminum hydride is 1 mol / L; the dosage ratio of aluminum chloride, nitrobenzene and the second intermediate is 2 g: 75 mL: 5 g;

[0117] Step B4: Add nano aluminum nitride powder to ethanol aqueous solution, stir for 25 minutes to obtain mixed solution 3; then add the first intermediate to the ethanol aqueous solution, stir for 12 minutes to obtain mixed solution 4; add mixed solution 3 and mixed solution 4 to a beaker, ultrasonically disperse for 45 minutes, adjust the pH to 6.2, and then stir and react at 50°C for 10.5 hours, wash with anhydrous ethanol, dry in an oven at 70°C for 12 hours, and grind to obtain an enhancer; the dosage ratio of nano aluminum nitride powder and ethanol aqueous solution is 0.1g:10mL; the dosage ratio of the first intermediate and ethanol aqueous solution is 0.17mol:55mL; the dosage ratio of mixed solution 3 to mixed solution 4 is 12mL:60mL; the volume fraction of ethanol aqueous solution is 10%.

[0118] Example 6

[0119] As an example of an enhancer, its preparation includes the following steps:

[0120] Step B1: Add 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile to tetrahydrofuran, start stirring, add Raney nickel and Pd / C, introduce hydrogen, and react under normal pressure with stirring for 48 hours to obtain a primary amino product; add the primary amino product, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, then add methacryloyl chloride to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in an ice-water bath at 0°C, and after the dropwise addition is completed, heat to 40°C, and react with stirring at a constant temperature for 10 hours. , that is, the fourth intermediate is obtained; the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile, tetrahydrofuran, Raney nickel and Pd / C is 0.1mol:80mL:0.01mol:0.015mol; the usage ratio of primary amino product, potassium carbonate and dimethyl sulfoxide is 0.1mol:0.015mol:80mL; the usage ratio of methacryloyl chloride and dimethyl sulfoxide is 0.1mol:30mL; the usage ratio of mixed solution 1 and mixed solution 2 is 85mL:35mL;

[0121] Step B2: Add the fourth intermediate and anhydrous ethanol into a flask, start stirring, and slowly drop 3,4-methylenedioxyphenylethylamine (supplier: Wuhan Kemik Biopharmaceutical Technology Co., Ltd.) under nitrogen protection. After the dropwise addition is completed, heat to 105°C, reflux and stir to react for 48 hours, and vacuum dry at 50°C to obtain the third intermediate; the usage ratio of the fourth intermediate, anhydrous ethanol and 3,4-methylenedioxyphenylethylamine is 0.27 mol:160 mL:0.13 mol;

[0122] Step B3: Add the third intermediate and toluene to a tetrahydrofuran solution of lithium aluminum hydride, start stirring, and react at room temperature for 3 hours to obtain a second intermediate; add aluminum chloride to nitrobenzene, stir for 15 minutes, slowly add the second intermediate, and stir at room temperature for 5 hours to obtain a first intermediate; the dosage ratio of the third intermediate, toluene and the tetrahydrofuran solution of lithium aluminum hydride is 0.1 mol: 115 mL: 130 mL, and the concentration of the tetrahydrofuran solution of lithium aluminum hydride is 1 mol / L; the dosage ratio of aluminum chloride, nitrobenzene and the second intermediate is 2 g: 75 mL: 5 g;

[0123] Step B4: Add nano aluminum nitride powder to ethanol aqueous solution, stir for 30 minutes to obtain mixed solution 3; then add the first intermediate to the ethanol aqueous solution, stir for 15 minutes to obtain mixed solution 4; add mixed solution 3 and mixed solution 4 to a beaker, ultrasonically disperse for 50 minutes, adjust the pH to 6.5, and then stir and react at 50°C for 11 hours, wash with anhydrous ethanol, dry in an oven at 70°C for 12 hours, and grind to obtain an enhancer; the dosage ratio of nano aluminum nitride powder and ethanol aqueous solution is 0.1g:10mL; the dosage ratio of the first intermediate and ethanol aqueous solution is 0.20mol:60mL; the dosage ratio of mixed solution 3 to mixed solution 4 is 13mL:65mL; ​​the volume fraction of ethanol aqueous solution is 10%.

[0124] Example 7

[0125] like Figure 1 The cross-linked polyethylene insulated medium and high voltage power cable shown in the figure comprises, from the inside to the outside, a conductive core 1, a first semiconductive layer 2, an insulating layer 3, a second semiconductive layer 4, a metal shielding layer 5 and a sheath layer 6, wherein the conductive core 1 is located at the innermost layer; the first semiconductive layer 2 is extruded on the outer periphery of the conductive core 1; the insulating layer 3 is extruded on the outer periphery of the first semiconductive layer 2; the second semiconductive layer 4 is extruded on the outer periphery of the insulating layer 3; the metal shielding layer 5 is arranged on the outer periphery of the second semiconductive layer 4; the sheath layer 6 is extruded on the outer periphery of the metal shielding layer 5;

[0126] The conductive core 1 is a plurality of twisted copper wires; the first semiconductive layer 2 and the second semiconductive layer 4 are both made of ethylene-vinyl acetate copolymer material; the metal shielding layer 5 is obtained by spirally wrapping an aluminum conductive metal tape around the second semiconductive layer 4; the sheath layer 6 is made of TPE sheath material;

[0127] The aforementioned insulating layer 3 is made of cross-linked polyethylene, and the cross-linked polyethylene includes the following raw materials by weight: 170 parts of low-density polyethylene, 10 parts of a cross-linking agent, 1 part of an antioxidant, 5.5 parts of a voltage stabilizer, and 6.5 parts of a reinforcing agent; the aforementioned cross-linking agent is benzoyl peroxide; the aforementioned antioxidant is antioxidant 618;

[0128] The preparation of the cross-linked polyethylene insulated medium and high voltage power cable comprises the following steps:

[0129] Step S1: low-density polyethylene is placed in a rheometer for melt blending, mixed at 105° C. and a rotation speed of 50 r / min for 4 min, then the voltage stabilizer and cross-linking agent obtained in Example 1 are added, mixed for another 3 min, then an antioxidant and the reinforcing agent obtained in Example 4 are added, and finally mixed for 10 min to obtain cross-linked polyethylene;

[0130] Step S2: using an extruder to extrude and deposit the aforementioned first semi-conductive layer on the periphery of the aforementioned conductive core, and then extrude and deposit cross-linked polyethylene on the periphery of the first semi-conductive layer to form an insulating layer; then extrude and deposit the aforementioned second semi-conductive layer on the periphery of the insulating layer; then wrapping an aluminum conductive metal belt in a spiral form around the periphery of the second semi-conductive layer to obtain a metal shielding layer; finally, extruding and depositing a TPE sheath material on the periphery of the metal shielding layer to obtain a sheath layer, and annealing after extrusion to obtain a cross-linked polyethylene insulated medium and high voltage power cable.

[0131] Example 8

[0132] like Figure 1 The cross-linked polyethylene insulated medium and high voltage power cable shown in the figure comprises, from the inside to the outside, a conductive core 1, a first semiconductive layer 2, an insulating layer 3, a second semiconductive layer 4, a metal shielding layer 5 and a sheath layer 6, wherein the conductive core 1 is located at the innermost layer; the first semiconductive layer 2 is extruded on the outer periphery of the conductive core 1; the insulating layer 3 is extruded on the outer periphery of the first semiconductive layer 2; the second semiconductive layer 4 is extruded on the outer periphery of the insulating layer 3; the metal shielding layer 5 is arranged on the outer periphery of the second semiconductive layer 4; the sheath layer 6 is extruded on the outer periphery of the metal shielding layer 5;

[0133] The conductive core 1 is a plurality of twisted copper wires; the first semiconductive layer 2 and the second semiconductive layer 4 are both made of ethylene-vinyl acetate copolymer material; the metal shielding layer 5 is obtained by spirally wrapping an aluminum conductive metal tape around the second semiconductive layer 4; the sheath layer 6 is made of TPE sheath material;

[0134] The insulating layer 3 is made of cross-linked polyethylene, which includes the following raw materials by weight: 175 parts of low-density polyethylene, 11 parts of a cross-linking agent, 2 parts of an antioxidant, 6.0 parts of a voltage stabilizer, and 7.0 parts of a reinforcing agent; the cross-linking agent is benzoyl peroxide; the antioxidant is antioxidant 618;

[0135] The preparation of the cross-linked polyethylene insulated medium and high voltage power cable comprises the following steps:

[0136] Step S1: low-density polyethylene is placed in a rheometer for melt blending, mixed at 107° C. and a rotation speed of 50 r / min for 5 minutes, and then the voltage stabilizer and cross-linking agent obtained in Example 2 are added, and then mixed for another 3 minutes, and then an antioxidant and the reinforcing agent obtained in Example 5 are added, and finally mixed for 12 minutes to obtain cross-linked polyethylene;

[0137] Step S2: using an extruder to extrude and deposit the aforementioned first semi-conductive layer on the periphery of the aforementioned conductive core, and then extrude and deposit cross-linked polyethylene on the periphery of the first semi-conductive layer to form an insulating layer; then extrude and deposit the aforementioned second semi-conductive layer on the periphery of the insulating layer; then wrapping an aluminum conductive metal belt in a spiral form around the periphery of the second semi-conductive layer to obtain a metal shielding layer; finally, extruding and depositing a TPE sheath material on the periphery of the metal shielding layer to obtain a sheath layer, and annealing after extrusion to obtain a cross-linked polyethylene insulated medium and high voltage power cable.

[0138] Example 9

[0139] like Figure 1 The cross-linked polyethylene insulated medium and high voltage power cable shown.

[0140] The conductive core 1 is a plurality of twisted copper wires; the first semiconductive layer 2 and the second semiconductive layer 4 are both made of ethylene-vinyl acetate copolymer material; the aforementioned metal shielding layer 5 is obtained by spirally wrapping an aluminum conductive metal tape around the second semiconductive layer 4; the aforementioned sheath layer 6 is made of TPE sheath material.

[0141] The insulating layer 3 is made of cross-linked polyethylene, which includes the following raw materials in parts by weight: 180 parts of low-density polyethylene, 12 parts of a cross-linking agent, 3 parts of an antioxidant, 6.5 parts of a voltage stabilizer and 7.5 parts of a reinforcing agent; the aforementioned cross-linking agent is benzoyl peroxide; and the aforementioned antioxidant is antioxidant 618.

[0142] The preparation of the cross-linked polyethylene insulated medium and high voltage power cable comprises the following steps:

[0143] The low-density polyethylene was placed in a rheometer for melt blending, and after mixing for 6 minutes at 110° C. and a rotation speed of 50 r / min, the voltage stabilizer and the crosslinking agent obtained in Example 3 were added, and after mixing for another 3 minutes, an antioxidant and the reinforcing agent of Example 6 were added, and finally mixed for 15 minutes to obtain cross-linked polyethylene;

[0144] An extruder is used to extrude and deposit the first semi-conductive layer on the periphery of the conductive core, and then cross-linked polyethylene is extruded and deposited on the periphery of the first semi-conductive layer to form an insulating layer; then the second semi-conductive layer is extruded and deposited on the periphery of the insulating layer; then an aluminum conductive metal belt is spirally wrapped around the periphery of the second semi-conductive layer to obtain a metal shielding layer; finally, a TPE sheath material is extruded and deposited on the periphery of the metal shielding layer to obtain a sheath layer, and annealing treatment is performed after extrusion to obtain a cross-linked polyethylene insulated medium and high voltage power cable.

[0145] Comparative Example 1

[0146] This comparative example is a commercially available cross-linked polyethylene insulated medium and high voltage power cable.

[0147] Comparative Example 2

[0148] Compared with Example 9, the voltage stabilizer was replaced with 2,1,3-benzothiadiazole-5-ethylene, that is, the hindered piperidine structure was not introduced, and the rest was exactly the same as Example 9 to prepare a cross-linked polyethylene insulated medium and high voltage power cable.

[0149] The preparation process of 2,1,3-benzothiadiazole-5-ethylene is as follows: in a nitrogen atmosphere, 2,1,3-benzothiadiazole-5-carboxaldehyde and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed and stirred at 50°C for 4 hours to obtain 2,1,3-benzothiadiazole-5-ethylene; the dosage ratio of 2,1,3-benzothiadiazole-5-carboxaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran is 0.1 mol: 0.1 mol: 120 mL.

[0150] Comparative Example 3

[0151] Compared with Example 9, the reinforcing agent is replaced with nano-aluminum nitride modified with 2-(3,4-dihydroxyphenyl)ethylamine, that is, the hindered phenol structure is not introduced, and the rest is exactly the same as Example 9 to prepare a cross-linked polyethylene insulated medium and high voltage power cable.

[0152] The preparation process of 2-(3,4-dihydroxyphenyl)ethylamine modified nano aluminum nitride is as follows: adding nano aluminum nitride powder to ethanol aqueous solution and stirring for 30 minutes to obtain mixed solution A; then adding 2-(3,4-dihydroxyphenyl)ethylamine to the ethanol aqueous solution and stirring for 15 minutes to obtain mixed solution B; adding mixed solution A and mixed solution B to a beaker, ultrasonically dispersing for 50 minutes, adjusting the pH to 6.5, stirring and reacting at 50°C for 11 hours, washing with anhydrous ethanol, drying in an oven at 70°C for 12 hours, and grinding to obtain nano aluminum nitride modified with 2-(3,4-dihydroxyphenyl)ethylamine; the amount ratio of nano aluminum nitride powder to ethanol aqueous solution is 0.1g:10mL; the amount ratio of 2-(3,4-dihydroxyphenyl)ethylamine to ethanol aqueous solution is 0.20mol:60mL; the amount ratio of mixed solution A to mixed solution B is 13mL:65mL; ​​the volume fraction of ethanol aqueous solution is 10%.

[0153] In order to test the cross-linked polyethylene insulated medium and high voltage power cable prepared in the present invention, the mechanical properties (tensile strength and elongation at break) of the insulation layer were tested according to GB / T2951-2008 "General Test Methods for Insulation and Sheath Materials of Electric and Optical Cables", and the results are recorded in Table 1.

[0154] Table 1 Comparison of test results

[0155]

[0156] The test method for the average AC breakdown field strength and the average DC breakdown field strength in Table 1 is: apply a linearly increasing AC high voltage or DC high voltage to 100 μm film samples of the insulating layer materials of the cables in Examples 7-9 and Comparative Examples 1-3 at room temperature until the samples break down. According to the method of GB / T11017.1-2014 "Rated voltage 110 kV cross-linked polyethylene insulated power cable and its accessories", the average AC breakdown field strength and the average DC breakdown field strength of 10 samples are obtained respectively, and the results are recorded in Table 1.

[0157] The average electrical tree initiation voltage test method in Table 1 is: the electrical tree initiation voltage test of the insulation layer materials of the cables in Examples 7-9 and Comparative Examples 1-3 is carried out at room temperature using a needle-plate electrode structure, the needle-plate distance is 3 mm, the needle tip curvature radius is 5 μm, the boost mode is linear boost, and the average electrical tree initiation voltage of 10 samples is obtained according to the method of GB / T11017.1-2014 "Rated voltage 110 kV cross-linked polyethylene insulated power cable and its accessories", and the results are recorded in Table 1.

[0158] The aging method in Table 1 is: the insulation layer materials of the cables in Examples 7-9 and Comparative Examples 1-3 are placed in an ultraviolet light with an intensity of 0.89 W / m 2The samples were aged at 50 °C for 500 h, and then the tensile strength retention rate and elongation at break retention rate were determined according to the method of GB / T 2951-2008. The results are recorded in Table 1.

[0159] According to the data in Table 1, compared with Example 1, Example 7, Example 8 and Example 9, it can be seen that the insulating material of the cross-linked polyethylene insulated medium and high voltage power cable prepared by the present invention has higher mechanical properties, pressure resistance and aging resistance than the commercially available cross-linked polyethylene insulated medium and high voltage power cables, thereby improving the mechanical properties, pressure resistance and aging resistance of the cable; compared with Comparative Example 2, Example 9 shows that by using the synthesized voltage stabilizer, the hindered piperidine structure and the benzothiazole structure synergistically inhibit the growth of electrical trees and improve the ability of the cable to withstand voltage; compared with Comparative Example 3, Example 9 shows that the 3,4-dihydroxybenzene structure, the antioxidant 618 containing the phosphite structure and the hindered phenol structure synergistically inhibit the aging of the matrix and improve the aging resistance of the cable.

[0160] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A cross-linked polyethylene insulated medium and high voltage power cable, characterized in that: From the inside to the outside, it comprises a conductive core (1), a first semiconductive layer (2), an insulating layer (3), a second semiconductive layer (4), a metal shielding layer (5) and a sheath layer (6), wherein the conductive core (1) is located at the innermost layer, the first semiconductive layer (2) is extruded around the outer periphery of the conductive core (1), the insulating layer (3) is extruded around the outer periphery of the first semiconductive layer (2), the second semiconductive layer (4) is extruded around the outer periphery of the insulating layer (3), the metal shielding layer (5) is arranged around the outer periphery of the second semiconductive layer (4), and finally, the sheath layer (6) shown is extruded around the outer periphery of the metal shielding layer (5); The insulating layer (3) is made of a cross-linked polyethylene-based insulating material, wherein the sterically hindered piperidine structure and benzothiazole structure contained therein synergistically inhibit electrical aging and electrical tree growth of the insulating layer, thereby improving the voltage withstand capability and insulation life of the cable.

2. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that: The insulating layer is made of cross-linked polyethylene, which is prepared from low-density polyethylene, a cross-linking agent, an antioxidant, a voltage stabilizer and a reinforcing agent, wherein the voltage stabilizer used has at least a benzothiazole structure, a hindered piperidine structure and a carbon-carbon double bond structure.

3. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 2, characterized in that: The reinforcing agent is obtained by modifying nano silicon nitride with a first intermediate, wherein the first intermediate includes a hindered phenol structure and a 3,4-dihydroxybenzene structure, and the hindered phenol structure captures free radicals generated by the thermal oxidation aging reaction of the polymer to generate hydroperoxides and relatively stable phenol oxygen free radicals, thereby terminating the thermal oxidation aging reaction of the polymer molecules and inhibiting chain growth; The 3,4-dihydroxybenzene structure, the antioxidant 618 containing a phosphite structure that decomposes hydroperoxide, and the hindered phenol structure synergistically inhibit the aging of the matrix and improve the aging resistance of the cable; After being modified by the first intermediate, the nano silicon nitride as a thermally conductive insulating filler has reduced agglomeration and is evenly dispersed in the matrix, thereby improving the mechanical properties of the cable and reducing the migration of the first intermediate in the matrix.

4. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 3, characterized in that: The cross-linked polyethylene comprises the following raw materials in parts by weight: 170-180 parts of low-density polyethylene, 10-12 parts of a cross-linking agent, 1-3 parts of an antioxidant, 5.5-6.5 parts of a voltage stabilizer and 6.5-7.5 parts of a reinforcing agent.

5. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 4, characterized in that: The voltage stabilizer is prepared according to the following process: Step A1: In a nitrogen atmosphere, 3-(oxirane-2-ylmethoxy)benzaldehyde and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed and stirred at 40-50° C. for 3-4 hours to obtain a reaction product 1 containing an olefin group; Step A2: In a nitrogen atmosphere, add 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid and methanol into a round-bottom flask, start stirring, raise the temperature to 40-50° C., add pyridine and reaction product 1, and react at a constant temperature with stirring for 8-10 hours to obtain reaction product 2; Step A3: Add the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide into a flask to obtain a mixed solution a, then add 2,1,3-benzothiadiazole-5-carbonyl chloride to dimethyl sulfoxide to obtain a mixed solution b, slowly dropwise add the mixed solution b into the mixed solution a in an ice-water bath at 0°C, after the dropwise addition is completed, raise the temperature to 40°C, stir the reaction at a constant temperature for 8-10 hours, and distill under reduced pressure to obtain a voltage stabilizer.

6. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 5, characterized in that: In the step A1, the usage ratio of 3-(oxiran-2-ylmethoxy)benzaldehyde, methylenetriphenylphosphine and anhydrous tetrahydrofuran is 0.1 mol: 0.1 mol: 100-120 mL; In the step A2, the usage ratio of 2-(2,2,6,6-tetramethylpiperidin-4-yl)acetic acid, methanol, pyridine and reaction product 1 is 0.1 mol: 140-160 mL: 0.001-0.0012 mol: 0.1 mol; In the step A3, the usage ratio of the reaction product 2, pyridine, triethylamine and dimethyl sulfoxide is 0.1 mol: 0.01-0.015 mol: 0.1 mol: 70-80 mL; the usage ratio of 2,1,3-benzothiadiazole-5-carbonyl chloride and dimethyl sulfoxide is 0.1 mol: 20-30 mL; the usage ratio of the mixed solution a to the mixed solution b is 75-85 mL: 25-35 mL.

7. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 5, characterized in that: The enhancer is prepared according to the following process: Step B1: Add 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile to tetrahydrofuran, start stirring, add Raney nickel and Pd / C, introduce hydrogen, and react under normal pressure with stirring for 48 hours to obtain a primary amino product; add the primary amino product, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, then add methacryloyl chloride to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in an ice-water bath at 0°C, and after the dropwise addition is completed, heat to 40°C, and react with constant temperature stirring for 10 hours to obtain a fourth intermediate; Step B2: Add the fourth intermediate and anhydrous ethanol into a flask, start stirring, and slowly drop 3,4-methylenedioxyphenylethylamine under nitrogen protection. After the dropwise addition is complete, heat to 105°C, reflux and stir to react for 48 hours, and vacuum dry at 50°C to obtain the third intermediate; Step B3: Add the third intermediate and toluene to a tetrahydrofuran solution of lithium aluminum hydride, start stirring, and react at room temperature for 2-3 hours to obtain the second intermediate; add aluminum chloride to nitrobenzene, stir for 10-15 minutes, slowly add the second intermediate, and stir at room temperature for 4-5 hours to obtain the first intermediate; Step B4: Add nano aluminum nitride powder to ethanol aqueous solution, stir for 20-30 minutes to obtain mixed solution 3; then add the first intermediate to ethanol aqueous solution, stir for 10-15 minutes to obtain mixed solution 4; add mixed solution 3 and mixed solution 4 to a beaker, ultrasonically disperse for 40-50 minutes, adjust the pH to 6-6.5, then stir and react at 50°C for 10-11 hours, wash with anhydrous ethanol, dry in an oven at 70°C for 12 hours, and grind to obtain the enhancer.

8. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 7, characterized in that: In the step B1, the usage ratio of 3,5-di-tert-butyl-4-hydroxybenzeneacetonitrile, tetrahydrofuran, Raney nickel and Pd / C is 0.1 mol: 70-80 mL: 0.01mol: 0.01-0.015mol; the usage ratio of primary amino product, potassium carbonate and dimethyl sulfoxide is 0.1mol: 0.015mol: 75-80mL; the usage ratio of methacryloyl chloride and dimethyl sulfoxide is 0.1mol: 25-30mL; the usage ratio of mixed solution 1 and mixed solution 2 is 80-85mL: 30-35mL; In the step B2, the fourth intermediate, anhydrous ethanol and 3,4-methylenedioxyphenylethylamine are used in a ratio of 0.27 mol: 140-160 mL: 0.1-0.13 mol; in the step B3, the third intermediate, toluene and tetrahydrofuran solution of lithium aluminum hydride are used in a ratio of 0.1 mol: 105-115 mL: 120-130 mL, and the concentration of the tetrahydrofuran solution of lithium aluminum hydride is 1 mol / L; the aluminum chloride, nitrobenzene and the second intermediate are used in a ratio of 2 g: 75 mL: 5 g; In the step B4, the dosage ratio of the nano aluminum nitride powder to the ethanol aqueous solution is 0.1 g:10 mL; the dosage ratio of the first intermediate to the ethanol aqueous solution is 0.15-0.20 mol:50-60 mL; the dosage ratio of the mixed solution 3 to the mixed solution 4 is 11-13 mL:55-65 mL; the volume fraction of the ethanol aqueous solution is 10%; During the reaction of step B4, the first intermediate containing two phenolic hydroxyl groups bonds with the active groups on the surface of the nano-aluminum nitride powder, thereby obtaining nano-aluminum nitride modified with the first intermediate, which is the enhancer.

9. The cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that: The conductive core (1) is a plurality of twisted copper wires; The first semiconductive layer (2) and the second semiconductive layer (4) are both made of ethylene-vinyl acetate copolymer material; The metal shielding layer (5) is obtained by winding a conductive metal strip made of aluminum in a spiral form around the second semi-conductive layer (4); The sheath layer (6) is made of TPE sheath material.

10. The method for preparing a cross-linked polyethylene insulated medium and high voltage power cable according to claim 1, characterized in that: The steps include: Step S1, using an extruder to extrude and deposit the first semiconductive layer on the outer periphery of the conductive core; Step S2, extruding and depositing the cross-linked polyethylene-based insulating material on the periphery of the first semi-conductive layer to form an insulating layer; wherein the sterically hindered piperidine structure and benzothiazole structure contained in the cross-linked polyethylene-based insulating material synergistically inhibit electrical aging and electrical tree growth of the insulating layer, thereby improving the ability of the cable to withstand voltage and the insulation life; Step S3, then extruding and depositing the second semiconductive layer on the periphery of the insulating layer; Step S4, wrapping an aluminum conductive metal belt around the outer periphery of the second semi-conductive layer in a spiral form to obtain a metal shielding layer; Step S5, finally, the TPE sheath material is extruded and deposited on the outer periphery of the metal shielding layer to obtain a sheath layer, and annealing treatment is performed after extrusion to obtain a cross-linked polyethylene insulated medium and high voltage power cable.

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