A high-voltage cable material, cable and preparation method resistant to 105 °C

Abstract

The present invention discloses a high-voltage cable material, a cable and a preparation method thereof that are resistant to 105°C. The high-voltage cable material resistant to 105°C is characterized in that the raw materials contained by weight are: 85-90 parts of low-density polyethylene, 8-10 parts of modified nano-inorganic powder, 0.5-0.8 parts of maleic anhydride, 1.5-2.5 parts of cross-linking agent, 0.2-0.5 parts of co-cross-linking agent, and 0.3-0.5 parts of antioxidant; the modified nano-inorganic powder is obtained by modification using epoxy resin and polyarylene sulfide resin under the dispersion action of styrene maleic anhydride copolymer; by dispersing epoxy resin and polyarylene sulfide resin in low-density polyethylene, curing and melting are achieved during high-temperature cross-linking, filling the micropores generated by the decomposition of the cross-linking agent and forming an interface with high temperature and high pressure resistance, significantly improving the breakdown field strength and high temperature resistance of cross-linked polyethylene.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer cable materials, and particularly relates to a high-voltage cable material resistant to 105 °C, a cable and a preparation method thereof. Background Art

[0002] As an important technical symbol of the current power grid, high-voltage power transmission technology poses extremely high requirements for the industry. With the gradual increase in the transmission voltage level, the requirements for the voltage resistance level and temperature resistance level of cable materials are getting higher and higher. At present, it is urgent to solve the stability and effectiveness of cable materials under high voltage and high temperature through cross-industry means.

[0003] Crosslinked polyethylene (XLPE) can withstand large currents, high voltages, strong electromagnetic fields, etc. due to its good electrical properties, large insulation resistance, low dielectric loss tangent value, high breakdown strength, etc. At present, it has become the mainstream insulation material for high-voltage cables. According to the mature technology of crosslinked polyethylene (XLPE) insulation cable materials, the long-term maximum allowable temperature grade of crosslinked polyethylene cables is set at 90 °C, which is based on the comprehensive consideration of the thermal stability of its materials, mechanical properties and cable design. The maximum temperature of the cable during short-term overload shall not exceed 130 °C; the maximum temperature of the cable during short circuit shall not exceed 250 °C, and the duration shall not exceed 5 seconds. These technical standards ensure that the cable can operate safely and reliably under normal working conditions.

[0004] However, with the increase in the service time of the cable, the crosslinked polyethylene (XLPE) insulation material often undergoes thermal aging. The small groups generated by thermal aging will further ionize under the action of the electric field. Especially in high-voltage cables, it is extremely easy to cause the rapid accumulation of charges inside the insulating material. Due to the accumulation of space charges inside the insulating material, the insulating layer will age rapidly, and ultimately the cable insulating layer will fail and cannot operate stably and safely. Obviously, for some environments with high-temperature operation such as aerospace, shipbuilding, military industry, boilers, oil refineries, metallurgical plants, fertilizer plants, glass plants, etc., the temperature resistance grade of the existing crosslinked polyethylene (XLPE) insulation material is even more difficult to meet the requirements. If the temperature resistance grade of the crosslinked polyethylene (XLPE) insulation material is increased to 125 °C, it can not only increase the service life and safety stability of the cable, but also apply the cable with crosslinked polyethylene (XLPE) as the insulation material in a wider range.

[0005] In the prior art, the long-term allowable operating temperature of cross-linked polyethylene (XLPE) insulating materials is 90 °C. Moreover, the conductivity of cross-linked polyethylene will change significantly with charge accumulation and temperature gradient, affecting the performance of the insulating material. Technicians reduce impurities by controlling the cleanliness of cross-linked polyethylene to maximize the characteristics of the material itself. The long-term heat resistance performance of the material is determined by the characteristics of the polyethylene material. It is difficult to reach a long-term tolerance of 105 °C and the polyethylene needs to be modified. According to the publicly available technology, inorganic nanoparticles have been used to improve the dielectric properties and heat resistance of polyethylene, but the dispersion performance of the nanoparticles is limited and it is difficult to achieve the designed effect. Especially when a single nanoparticle is dispersed, aggregation is extremely likely to occur, resulting in a decrease in dielectric properties. There are also cases where graft modification is used to introduce functional groups to modify polyethylene to improve its high-voltage resistance and high-temperature resistance. However, the high-temperature resistance is not ideal.

[0006] In order to adapt to the continuous improvement of the grid voltage level, ensure the insulation of the cable at a higher temperature, and ensure the stability, reliability, and safety of the grid operation, the present invention proposes a cable material that can withstand a temperature of 105 °C. Summary of the Invention

[0007] To improve the high-voltage resistance characteristics and long-term high-temperature stability of cross-linked polyethylene used as a cable material, the present invention discloses a high-voltage cable material that can withstand a temperature of 105 °C, aiming to further improve the long-term tolerance temperature level of the cross-linked polyethylene cable material and ensure the service life and safe operation of the cable.

[0008] The technical solution of the present invention is as follows:

[0009] According to one aspect of the present invention, first, a high-voltage cable material that can withstand a temperature of 105 °C is provided, which is characterized by containing the following raw materials by weight: 85-90 parts of low-density polyethylene, 8-10 parts of modified nano-inorganic powder, 0.5-0.8 parts of maleic anhydride, 1.5-2.5 parts of cross-linking agent, 0.2-0.5 parts of co-cross-linking agent, and 0.3-0.5 parts of antioxidant; wherein: the modified nano-inorganic powder is a nano-inorganic powder modified by epoxy resin combined with polyarylene sulfide resin under the dispersion action of styrene maleic anhydride copolymer.

[0010] Preferably, the modified nano-inorganic powder is obtained by grinding and dispersing nano-inorganic powder, epoxy resin, polyarylene sulfide resin, and styrene maleic anhydride copolymer in a mass ratio of 100:20-30:20-25:0.2-0.3. By introducing the modified nano-inorganic powder into low-density polyethylene, the modified nano-inorganic powder is evenly dispersed in the low-density polyethylene, inhibiting charge accumulation, hindering the thermal movement of polymer segments, reducing the possibility of thermal decomposition, and significantly improving the breakdown field strength and heat resistance of the cable material.

[0011] Styrene maleic anhydride copolymer (SMA) is a polymer material synthesized by copolymerization of styrene and maleic anhydride, which has good thermal stability and can effectively depolymerize and disperse nano-inorganic powder.

[0012] Preferably, the polyarylene sulfide resin is at least one of powdered polyphenylene sulfide (PPS) and polyarylene sulfide sulfone (PASS). The polyarylene sulfide resin is a kind of polymer with a main chain structure of alternating sulfur and aryl structures, which has good high-temperature resistance. The polyarylene sulfide resin is usually in fine powder form and is easy to be ground into fine powder. By grinding with epoxy resin and nano-inorganic powder, the nano-inorganic powder is dispersed and modified under the dispersion action of styrene maleic anhydride copolymer, so as to promote the dispersion in low-density polyethylene. At the same time, the interface of the polyarylene sulfide resin and epoxy resin dispersed in low-density polyethylene is increased, which is significant for improving the high-temperature resistance of crosslinked polyethylene.

[0013] Particularly preferably, the melt index of the polyarylene sulfide resin is greater than 200 g / 10 min. The polyarylene sulfide resin is usually a high melt index resin, and the melt index of the existing common polyarylene sulfide resin can even reach 1200 - 2000 g / 10 min; when the polyarylene sulfide resin is dispersed in low-density polyethylene, in the crosslinking process at a high temperature of 280 - 320 °C, the decomposition products of the crosslinking agent cause micropores to appear in the insulating material. At this temperature, the polyarylene sulfide resin dispersed in low-density polyethylene begins to melt and flow, filling the micropores generated by the crosslinking of low-density polyethylene, reducing the accumulation of space charge during high-voltage transmission, and at the same time forming a high-temperature resistant interface, so as to improve the breakdown field strength and temperature resistance of crosslinked polyethylene.

[0014] Preferably, the epoxy resin is an epoxy resin with an epoxy value of 0.1 - 0.6 eq / 100 g. Particularly preferably, bisphenol A epoxy resin is used, which basically does not produce small molecule volatiles during curing and has high toughness and heat resistance after curing. When the epoxy resin is dispersed in low-density polyethylene, in the high-temperature crosslinking stage, the epoxy resin thermally cures, enhancing the breakdown field strength and temperature resistance of crosslinked polyethylene.

[0015] Further preferably, the nano-inorganic powder is selected from at least one of MgO, ZnO, Al 2 O 3 、SiO 2 . Particularly, the nano-inorganic powder has a nano size of 20 - 50 nm, and the nano-inorganic powder of this size takes into account both dispersibility and excellent electrical properties. The nano-inorganic powder is uniformly doped into low-density polyethylene after modification and has excellent breakdown field strength.

[0016] According to the present invention, by combining and modifying nano-inorganic powder with epoxy resin and polyarylene sulfide resin, on the one hand, it promotes the efficient dispersion of nano-scale inorganic powder in low-density polyethylene, establishes a nano-interface to inhibit charge accumulation, and improves the heat resistance effect; on the other hand, it promotes the dispersion of epoxy resin and polyarylene sulfide resin. When cross-linked at high temperature, the epoxy resin cures to form an interface resistant to high pressure and high temperature, and the polyarylene sulfide resin melts and flows in situ, filling the micropores generated by the decomposition of the cross-linking agent, significantly improving the breakdown field strength and high-temperature resistance of cross-linked polyethylene.

[0017] Maleic anhydride grafts low-density polyethylene under thermal conditions. The introduced polar groups can prevent the orderly migration of ionized charges and inhibit the formation of space charges under the action of an electric field, significantly improving the breakdown field strength of cross-linked polyethylene.

[0018] Preferably, the antioxidant is a thiodiphenol antioxidant. The thiodiphenol antioxidant can significantly improve the thermal stability of cross-linked polyethylene without damaging the insulation strength. Typically, 4,4'-thiobis(6-tert-butyl-3-methylphenol) can be selected.

[0019] Preferably, the antioxidant is a composition of a hindered phenol antioxidant and a thioester antioxidant. Further preferably, the antioxidant is a combination of a hindered phenol antioxidant and a thioester antioxidant in a mass ratio of 2-3:1. The hindered phenol antioxidant has good thermal stability and processing stability, and effectively prevents the long-term thermal oxidative degradation of the material; typically, antioxidant 1076 and DSTP can be used in combination.

[0020] Preferably, the cross-linking agent is at least one of dicumyl peroxide (DCP) and benzoyl peroxide (BPO).

[0021] Preferably, the co-cross-linking agent is at least one of diallyl phthalate, triallyl cyanurate, and 1,2-polybutadiene.

[0022] On the other hand, according to the present invention, there is provided a method for preparing the above-mentioned high-voltage cable material resistant to 105 °C, which is characterized in that the specific preparation method is as follows:

[0023] (1) Weigh nano-inorganic powder, epoxy resin, polyarylene sulfide resin, and styrene maleic anhydride copolymer according to a mass ratio of 100:20-30:20-25:0.2-0.3, and add them to a closed grinder for grinding and modification to obtain modified nano-inorganic powder;

[0024] (2) Weigh 85 - 90 parts of low - density polyethylene, 8 - 10 parts of modified nano - inorganic powder, 0.5 - 0.8 parts of maleic anhydride, 1.5 - 2.5 parts of cross - linker, 0.2 - 0.5 parts of co - cross - linker, and 0.3 - 0.5 parts of antioxidant by weight using an automatic metering loss - in - weight scale. Then, disperse and mix them at high speed in a high - speed mixer for 30 - 60 min. Pass the mixture through a twin - screw extruder with the screw temperature set at 110 - 120 °C. After hot - melt extrusion into strands, convey them through a chain conveyor belt, cool them with air, and pelletize them to obtain a high - voltage cable material that can withstand 105 °C.

[0025] The high - voltage cable material that can withstand 125 °C is used for the insulation layer of high - voltage cables and needs to be cross - linked at 280 - 320 °C under nitrogen protection. Its insulation layer meets the temperature grade of long - term operation at 105 °C.

[0026] Preferably, in step (1), the closed - type grinder is determined according to the form of the material to be ground. When the epoxy resin is in a brittle solid state, a dry - powder ball mill or a jet mill is used for grinding and dispersion; when the epoxy resin is in a liquid state, a colloid mill or a three - roll mill is used for grinding.

[0027] Preferably, in step (2), the twin - screw extruder selected is a low - L / D ratio co - rotating twin - screw extruder with a screw L / D ratio of 25 / 1 - 30 / 1. It has a lower shear force to prevent the material from overheating and degrading and premature cross - linking.

[0028] In addition, the present invention also provides a cable, which is characterized in that a high - voltage cable material that can withstand 105 °C is used as the insulation layer.

[0029] Furthermore, the present invention also provides a preparation method of the cable, which is characterized in that an inner shield layer, an insulation layer, and an outer shield layer are sequentially extruded and coated on a conductor core by three - layer co - extrusion; after the extrusion and coating are completed, the cable core is obtained through cross - linking treatment at a pressure of 1.0 - 1.2 MPa and a temperature of 280 - 320 °C for 8 - 10 min through a high - temperature nitrogen pipeline; an alloy lead sheath is wound around the cable core, and a sheath is extruded and coated to obtain the cable.

[0030] Preferably, in the preparation method of the cable, the inner shield layer and the outer shield layer use conventional shielding materials in the art or self - made shielding materials.

[0031] Preferably, in the method for preparing the cable, the three-layer co-extrusion extruder is successively an extruder for the inner shielding layer, the insulating layer, and the outer shielding layer, and 65-type, 150-type, and 90-type single-screw extruders are equipped according to the extrusion amount; the processing temperature for the extrusion of the inner and outer shielding layers is set at 100-110°C; the processing temperature for the extrusion of the insulating layer is set as follows: the first stage is 90°C, the second stage is 100°C, the third stage is 105°C, the fourth stage is 105°C, the fifth stage is 110°C, the sixth stage is 110°C, the seventh stage is 110°C, the eighth stage is 115°C, the ninth stage is 115°C, and the tenth stage is 118°C. Among them, the 150-type extruder for extruding the insulating layer is equipped with a vacuum exhaust port, and the vacuum degree is set at 0.06-0.08 MPa, and the volatile components affecting the density of the insulating layer are removed in a timely manner through the vacuum exhaust port.

[0032] The invention effect of a high-voltage cable material, cable and preparation method resistant to 105°C according to the present invention:

[0033] 1. In the present invention, through the dispersion modification of nano-inorganic powder by using epoxy resin and polyarylene sulfide resin under the dispersion action of styrene maleic anhydride copolymer, the effective dispersion of nano-particles is promoted, and nano-sized particles are uniformly doped into low-density polyethylene, improving the breakdown field strength and heat resistance of the material.

[0034] 2. In the present invention, by dispersing epoxy resin and polyarylene sulfide resin in low-density polyethylene, when cross-linking at high temperature, the epoxy resin cures and the polyarylene sulfide resin melts and flows, filling the micropores generated by the decomposition of the cross-linking agent and forming an interface with high temperature and high voltage resistance, significantly improving the breakdown field strength and high temperature resistance of cross-linked polyethylene.

[0035] 3. In the present invention, by introducing maleic anhydride to graft polyethylene, the orderly migration of ionized charges can be prevented, the formation of space charges can be inhibited, and the breakdown field strength of cross-linked polyethylene can be significantly improved.

[0036] 4. The cable material of the present invention improves the stability of the cable in a high-temperature environment, extends the service life of the cable, and ensures the reliable operation of the cable. The manufacturing process is easy to control, has no special requirements for production equipment, and can be directly mass-produced without modifying the existing production line. Specific embodiments

[0037] To enable those skilled in the art to further understand the technical means, technical purposes, and technical effects achieved by the present invention, the present invention will be described in detail below with reference to the embodiments.

[0038] Some basic raw materials used in the implementation scheme:

[0039] Low-density polyethylene: Model 2426H, melt index is 2 g / 10 min (200°C, 5 kg load), produced by CNOOC and Shell Petrochemical Company Limited, Huizhou.

[0040] Polyphenylene sulfide: Model 1130C, white powder, melt index of 250 g / 10 min (316 °C, 5 kg), produced by Zhejiang NHU Co., Ltd.

[0041] Styrene maleic anhydride copolymer: Model BYK - 2013, produced by BYK Chemie GmbH.

[0042] Example 1

[0043] (1) Weigh nano - Al 2 O 3 (with particle size of 20 - 50 nm), epoxy resin E - 20, polyphenylene sulfide (1130C), and styrene maleic anhydride copolymer according to the mass ratio of 100:30:25:0.3. Add them to a closed dry powder ball mill, use zirconia ceramic balls as the grinding medium, and grind for 2 h to obtain modified nano - inorganic powder.

[0044] (2) Weigh 85 parts of low - density polyethylene (2426H), 10 parts of modified nano - inorganic powder, 0.5 part of maleic anhydride, 1.8 parts of DCP cross - linker, 0.2 part of triallyl cyanurate co - cross - linker, 0.3 part of 1076 antioxidant, and 0.1 part of DSTP antioxidant by weight using an automatic weighing loss feeder. Disperse and mix them at a high speed of 700 r / min in a high - speed mixer for 45 min, and extrude through a co - rotating twin - screw extruder with a screw length - diameter ratio of 25 / 1. The screw temperature is set as follows: the first section is 110 °C, the second section is 110 °C, the third section is 115 °C, the fourth section is 115 °C, the fifth section is 118 °C, the sixth section is 120 °C, the seventh section is 110 °C, the eighth section is 115 °C, the ninth section is 115 °C, and the tenth section is 118 °C. After hot - melt extrusion, draw into strips, convey through a chain conveyor belt, air - cool, and pelletize to obtain a high - voltage cable material resistant to 105 °C.

[0045] Example 2

[0046] (1) Weigh nano - MgO (with particle size of 20 - 50 nm), epoxy resin E - 12, polyphenylene sulfide (1130C), and styrene maleic anhydride copolymer according to the mass ratio of 100:25:25:0.3. Add them to a closed dry powder ball mill, use zirconia ceramic balls as the grinding medium, and grind for 1 h to obtain modified nano - inorganic powder.

[0047] (2)Weigh 90 parts of low-density polyethylene (2426H), 10 parts of modified nano-inorganic powder, 0.8 part of maleic anhydride, 2.0 parts of DCP crosslinking agent, 0.5 part of diallyl phthalate co-crosslinking agent, 0.3 part of antioxidant 1076, and 0.1 part of antioxidant DSTP by weight using an automatic metering loss-in-weight scale. Mix them at a high speed of 700 r / min in a high-speed mixer for 30 min, and extrude them through a co-rotating twin-screw extruder with a screw length-diameter ratio of 25 / 1. Set the screw temperature as follows: the processing temperature for the first section is 110 °C, the second section is 110 °C, the third section is 115 °C, the fourth section is 115 °C, the fifth section is 118 °C, the sixth section is 120 °C, the seventh section is 110 °C, the eighth section is 115 °C, the ninth section is 115 °C, and the tenth section is 118 °C. After hot-melt extrusion into strands, conveying by a chain conveyor belt, air cooling, and pelletizing, a high-voltage cable material resistant to 105 °C is obtained.

[0048] Example 3

[0049] (1)Weigh nano-SiO 2 (with a particle size of 20 - 50 nm), epoxy resin E-44, polyphenylene sulfide (1130C), and styrene maleic anhydride copolymer in a mass ratio of 100:30:20:0.2, and add them to a three-roll grinder and grind for 2 h to obtain a modified nano-inorganic powder;

[0050] (2)Weigh 85 parts of low-density polyethylene (2426H), 10 parts of modified nano-inorganic powder, 0.8 part of maleic anhydride, 1.8 parts of DCP crosslinking agent, 0.4 part of diallyl phthalate co-crosslinking agent, and 0.4 part of antioxidant 4,4'-thiobis(6-tert-butyl-3-methylphenol) (a thio-bisphenol antioxidant) by weight using an automatic metering loss-in-weight scale. Mix them at a high speed of 700 r / min in a high-speed mixer for 60 min, and extrude them through a co-rotating twin-screw extruder with a screw length-diameter ratio of 25 / 1. Set the screw temperature as follows: the processing temperature for the first section is 110 °C, the second section is 110 °C, the third section is 115 °C, the fourth section is 115 °C, the fifth section is 118 °C, the sixth section is 120 °C, the seventh section is 110 °C, the eighth section is 115 °C, the ninth section is 115 °C, and the tenth section is 118 °C. After hot-melt extrusion into strands, conveying by a chain conveyor belt, air cooling, and pelletizing, a high-voltage cable material resistant to 105 °C is obtained.

[0051] Example 4

[0052] The cable compound prepared in Example 1 was used as the insulating layer material; conductive carbon black CB3100, high-density polyethylene, and ethylene-vinyl acetate copolymer were melt-blended and pelletized through a single-screw extruder in a mass ratio of 5:60:30 to obtain the shielding material; an inner shielding layer, an insulating layer, and an outer shielding layer were successively extruded and coated on the conductor core through three-layer co-extrusion; 65-type, 150-type, and 90-type single-screw extruders were successively equipped according to the extrusion amount; the processing temperature for the extrusion of the insulating layer was set as follows: the first section at 90 °C, the second section at 100 °C, the third section at 105 °C, the fourth section at 105 °C, the fifth section at 110 °C, the sixth section at 110 °C, the seventh section at 110 °C, the eighth section at 115 °C, the ninth section at 115 °C, and the tenth section at 118 °C; among them, a vacuum exhaust port was arranged between the sixth and seventh sections of the 150-type extruder for extruding the insulating layer, and the vacuum degree was set at 0.08 MPa, and the volatile components affecting the compactness of the insulating layer were timely removed through the vacuum exhaust port; after the extrusion and coating were completed, the cable core was obtained through cross-linking treatment at a pressure of 1.0 MPa and 320 °C for 10 min through a high-temperature nitrogen pipeline; an alloy lead sleeve was wound around the cable core, and a PVC sheath was extruded and coated to obtain the cable.

[0053] Comparative Example 1

[0054] It was implemented according to the scheme of Example 1, except that the modified nano-inorganic powder was not added to the cable compound.

[0055] Comparative Example 2

[0056] It was implemented according to the scheme of Example 1, except that all the epoxy resin was replaced by polyphenylene sulfide when treating the modified nano-inorganic powder.

[0057] Comparative Example 3

[0058] It was implemented according to the scheme of Example 1, except that all the polyphenylene sulfide was replaced by epoxy resin when treating the modified nano-inorganic powder.

[0059] Comparative Example 4

[0060] It was implemented according to the scheme of Example 1, except that maleic anhydride was not added to the cable compound.

[0061] Comparative Example 5

[0062] (1) Weighed nano-Al 2 O 3 (with a particle size of 20 - 50 nm) and styrene maleic anhydride copolymer in a mass ratio of 100:0.3, added them to a closed dry powder ball mill, used zirconia ceramic balls as the grinding medium, and ground for 2 h to obtain the modified nano-inorganic powder;

[0063] (2) 85 parts of low-density polyethylene (2426H), 6.5 parts of modified nano-inorganic powder, 0.5 parts of maleic anhydride, 1.8 parts of DCP crosslinking agent, 0.2 parts of triallyl cyanurate crosslinking agent, 0.3 parts of 1076 antioxidant, and 0.1 parts of DSTP antioxidant were mixed by automatic weight loss weighing, and the mixture was dispersed and mixed in a high-speed mixer at 700 r / min for 45 minutes. The extruder is extruded by a co-rotating twin-screw extruder with a rod length-diameter ratio of 25 / 1. The screw temperatures are set to the following processing temperatures: one section 110°C, two sections 110°C, three sections 115°C, four sections 115°C, five sections 118°C, six sections 120°C, seven sections 110°C, eight sections 115°C, nine sections 115°C, and ten sections 118°C. After hot-melt extrusion drawing, chain conveyor belt conveying, air cooling, and pelletizing, a high-voltage cable material that can withstand 105°C is obtained.

[0064] In Comparative Example 5, only styrene maleic anhydride copolymer was used for dispersion when treating the nano inorganic powder, and no epoxy resin or polyphenylene sulfide was used.

[0065] Performance evaluation test:

[0066] The cable material samples of each group of tests were cross-linked according to two processes, one was cross-linked at conventional 180°C (labeled as type A specimens); the other was cross-linked at 320°C to simulate nitrogen pipelines (labeled as type B specimens). The breakdown field strength of the test specimens and the aging conditions under high temperature conditions were tested to determine the high pressure and high temperature resistance of the cable material.

[0067] Conventional crosslinking process specimen preparation (Type A specimen): The cable materials of Examples 1-3 and Comparative Examples 1-5 are melt-extruded at 110°C through a Φ20 single-screw extruder, and the hot materials are fed into the mold of a flat-plate vulcanizer, and a pressure of 10 MPa is applied at a constant temperature of 110°C to fix the shape, and the pressure is maintained for 10 min; the pressure is increased and maintained at 15 MPa for 10 min; the mold is quickly taken out and transferred to a high-temperature flat-plate vulcanizer at a temperature of 180°C, and a pressure of 15 MPa is applied to react for 25 min to complete the crosslinking reaction, and the reaction is naturally cooled, and the internal stress is eliminated and the by-products of the crosslinking reaction are removed by thermal degassing in a vacuum oven at 80°C for 48 h to obtain a specimen to be tested.

[0068] Preparation of simulated nitrogen pipeline cross-linked specimens (Type B specimens): The cable materials of Examples 1-3 and Comparative Examples 1-5 were melt-extruded at 110 °C through a Φ20 single-screw extruder. The hot material was taken and fed into the mold of a flat vulcanizing machine, and was shaped under a pressure of 10 MPa at a constant temperature of 110 °C and kept under pressure for 10 min; the pressure was increased and kept under pressure at 15 MPa for 10 min; the prefabricated specimens were transferred to a closed high-temperature device for simulated nitrogen pipeline cross-linking, filled with nitrogen to a pressure of 1.0 MPa, and the temperature was controlled at 320 °C, so that the specimens were cross-linked at high temperature in a nitrogen environment for 10 min, cooled naturally, and thermally degassed at 80 °C in a vacuum oven for 48 h to eliminate internal stress and remove by-products of the cross-linking reaction, and the specimens to be tested were obtained.

[0069] (1)Breakdown strength test:

[0070] The DC breakdown strength of the specimens was tested with reference to the international standard IEC 60243. A column-plate electrode was used, the upper electrode had a diameter of 25 mm, the lower electrode had a diameter of 75 mm, and both electrodes had rounded corners. The specimens were circular specimens with a thickness of 1 mm and a diameter of 100 mm. During the test, the specimens and the electrodes were both immersed in silicone oil. The temperature was controlled at 100 °C, the voltage was increased at a rate of 1 kV / s, the voltage value at breakdown was read, and the breakdown field strength was obtained according to E = U / d, where U was the voltage at breakdown of the specimen and d was the thickness of the specimen. 10 samples were measured for each group of samples, and the breakdown data were analyzed using the two-parameter Weibull distribution. The breakdown field strength corresponding to a 63.2% cumulative failure probability was used as the final data of the breakdown field strength. The test results are shown in Table 1.

[0071] Table 1 Data table of breakdown field strength

[0072]

[0073] From the above test data, for the cable materials of Examples 1-3 during conventional cross-linking (Type A), the introduction of nanoparticles, the high-temperature curing of maleic anhydride-grafted polyethylene and epoxy resin improved the breakdown field strength of the materials. Moreover, during cross-linking at a high temperature of 320 °C with nitrogen filling (Type B), the dispersed polyarylene sulfide resin in the material melted and filled the microvoids generated by cross-linking, and its breakdown field strength was further improved.

[0074] (2)High-temperature resistance performance test:

[0075] The heat resistance stability of the cable materials was detected with reference to JB / T10437. Using the Type B specimens for simulated nitrogen pipeline cross-linking as the test objects, the cable material specimens of Examples 1-3 and Comparative Examples 1-5 were grouped and thermally aged at 135 °C and 150 °C for 168 h and 336 h respectively, and the change rates of tensile strength and elongation at break of the materials were detected; the thermal elongation rate was measured under a load of 0.2 MPa at 200 °C for 15 min; and its high-temperature stability was judged accordingly. The detection results are shown in Table 2.

[0076] Table 2 Data Sheet for Heat Resistance Performance Testing

[0077]

[0078] Through testing, after 168 hours (7 days) of continuous heat aging at 135 °C, its performance meets the temperature resistance requirements of the basic cable. Further, by extending the aging time and increasing the aging temperature to simulate the long-term use of cross-linked polyethylene in a high-temperature environment, the change rate of tensile strength and the change rate of elongation at break are both within 20%, and the load heat elongation is within 100%. It is evaluated that its heat aging performance fully meets the temperature requirements for long-term tolerance at the 105 °C level. It even meets the temperature requirements at the 125 °C level.

[0079] The detailed technical solutions of the present invention have been described in the above embodiments. It should be clear that those skilled in the art can make modification solutions and change solutions without departing from the spirit or scope of the present invention. Therefore, it should be understood that the foregoing is an illustration of the present invention and should not be construed as a limitation.

Claims

1. A high voltage cable material capable of withstanding 105°C, characterized in that: The invention comprises the following raw materials by weight: 85-90 parts of low-density polyethylene, 8-10 parts of modified nano inorganic powder, 0.5-0.8 parts of maleic anhydride, 1.5-2.5 parts of cross-linking agent, 0.2-0.5 parts of auxiliary cross-linking agent and 0.3-0.5 parts of antioxidant; wherein the modified nano inorganic powder is obtained by grinding, dispersing and modifying nano inorganic powder, epoxy resin, polyarylene sulfide resin and styrene maleic anhydride copolymer in a mass ratio of 100:20-30:20-25:0.2-0.

3.

2. A high voltage cable material capable of withstanding 105°C according to claim 1, characterized in that: The polyarylene sulfide resin is at least one of powdered polyphenylene sulfide and powdered polyarylene sulfide sulfone.

3. The high voltage cable material capable of withstanding 105°C according to claim 1, characterized in that: The melt index of the polyarylene sulfide resin is greater than 200 g / 10 min.

4. The high voltage cable material capable of withstanding 105°C according to claim 1, characterized in that: The epoxy resin is selected to have an epoxy value of 0.1-0.6 eq / 100g.

5. The high voltage cable material capable of withstanding 105°C according to claim 1, characterized in that: The nano inorganic powder is selected from at least one of MgO, ZnO, Al2O3, and SiO2; the nano inorganic powder has a nano size range of 20-50nm.

6. The high voltage cable material capable of withstanding 105°C according to claim 1, characterized in that: The cross-linking agent is at least one of dicumyl peroxide and benzoyl peroxide; the auxiliary cross-linking agent is at least one of diallyl phthalate, triallyl cyanurate and 1,2-polybutadiene.

7. A method for preparing a high-voltage cable material capable of withstanding 105°C as claimed in any one of claims 1 to 6, characterized in that: The specific preparation method is as follows: (1) weighing nano-inorganic powder, epoxy resin, polyarylene sulfide resin, and styrene maleic anhydride copolymer according to a mass ratio of 100:20-30:20-25:0.2-0.3, adding the mixture into a closed grinder for grinding and modification, and obtaining modified nano-inorganic powder; (2) 85-90 parts of low-density polyethylene, 8-10 parts of modified nano-inorganic powder, 0.5-0.8 parts of maleic anhydride, 1.5-2.5 parts of cross-linking agent, 0.2-0.5 parts of auxiliary cross-linking agent and 0.3-0.5 parts of antioxidant are mixed by automatic weight loss weighing according to weight parts, dispersed and mixed at high speed for 30-60 minutes in a high-speed mixer, and then extruded through a twin-screw extruder with the screw temperature set to 110-120° C., hot-melt extruded into strips, conveyed by a chain conveyor belt, air-cooled and pelletized to obtain a high-voltage cable material that can withstand 105° C.; the twin-screw extruder is a low aspect ratio co-rotating twin-screw extruder with a screw aspect ratio of 25 / 1-30 / 1.

8. A cable, characterized in that: The high-voltage cable material capable of withstanding 105° C. as claimed in any one of claims 1 to 6 is used as the insulating layer.

9. A method for preparing the cable according to claim 8, characterized in that: The inner shielding layer, the insulating layer and the outer shielding layer are sequentially extruded on the conductor core by three-layer co-extrusion; after the extrusion is completed, the cable core is cross-linked at a pressure of 1.0-1.2MPa and 280-320℃ through a high-temperature nitrogen pipeline for 8-10min; an alloy lead sheath is wrapped around the cable core, and a sheath is extruded to obtain a cable; wherein the three-layer co-extrusion extruder is an extruder for the inner shielding layer, the insulating layer and the outer shielding layer, and is equipped with 65 type, 150 type and 9 type in turn according to the extrusion volume 0-type single-screw extruder; the processing temperature for extrusion of inner and outer shielding layers is set at 100-110°C; the processing temperature for extrusion of insulation layer is set as follows: 90°C for the first stage, 100°C for the second stage, 105°C for the third stage, 105°C for the fourth stage, 110°C for the fifth stage, 110°C for the sixth stage, 110°C for the seventh stage, 115°C for the eighth stage, 115°C for the ninth stage, and 118°C for the tenth stage; the 150-type extruder for extruding the insulation layer is equipped with a vacuum exhaust port, and the vacuum degree is set to 0.06-0.08MPa.

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