Preparation method of semiconductive shielding filling material for cable

Abstract

The invention discloses a preparation method of a semiconductive shielding filling material for a cable, and the method comprises the following steps: S1, preparing a composite rod which sequentially comprises a conductive core material, a diffusion barrier layer and an insulation permeation base material from inside to outside, or the composite rod sequentially comprises the conductive core material, the insulation permeation base material and the diffusion barrier layer from inside to outside; s2, drying the composite rod to cure the composite rod; s3, carrying out high-temperature calcination on the dried and cured composite rod; and S4, cooling the composite rod subjected to high-temperature calcination, partially or completely taking out the residual conductive core material in the cooled composite rod, and sequentially crushing, grinding and screening the composite rod from which the residual conductive core material is taken out to obtain the semiconductive shielding filling material for the cable. The resistivity of the prepared semi-conductive shielding filling material for the cable can be accurately regulated and controlled, and the prepared semi-conductive shielding filling material for the cable is stable in performance.

Description

Technical Field

[0001] The invention belongs to the technical field of shielding materials, and in particular relates to a method for preparing a semi-conductive shielding filling material for cables. Background Art

[0002] Semi-conductive shielding filling materials for cables are prepared by adding conductive fillers to insulating base materials. Current conductive fillers are mainly concentrated in carbon-based materials (such as graphene, carbon nanotubes), metals and metal oxides. Current semi-conductive shielding filling materials for cables have problems such as narrow resistivity control range, low resistivity control accuracy, and poor performance stability. The reasons are:

[0003] Current semi-conductive shielding filling materials for cables are mostly prepared by chemical doping or physical blending processes, which makes it difficult to achieve precise construction of a conductive network. Specifically, the traditional chemical doping process is limited by the solid solubility limit of the conductive filler in the insulating matrix, resulting in low resistivity adjustment sensitivity of the semi-conductive shielding filling material for cables, which in turn leads to inaccurate resistivity control of the semi-conductive shielding filling material for cables. In addition, the traditional chemical doping process also has the problem of uneven distribution and poor dispersion of the conductive filler in the insulating matrix. Mechanical stirring or ultrasonic dispersion as traditional physical blending processes will cause the nanoparticles of carbon nanotubes to agglomerate, which will lead to the breakage of the conductive network of the semi-conductive shielding filling material for cables, which will lead to fluctuations in the resistivity of the semi-conductive shielding filling material for cables, and poor performance stability, which will lead to local discharge of the cable shielding layer and threaten the safety of high-voltage power transmission. In addition, some current semi-conductive shielding filling materials for cables are also prepared by chemical vapor deposition, specifically growing a carbon nanotube layer on the surface of the substrate. The disadvantage is that the equipment investment is high and it is only applicable to flat substrates.

[0004] In emerging fields such as new energy cables and flexible electronics, there is an urgent demand for semi-conductive shielding filling materials for cables with controllable resistivity and stable performance. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a method for preparing a semi-conductive shielding filling material for cables, which can accurately control the resistivity of the prepared semi-conductive shielding filling material for cables, and the performance of the prepared semi-conductive shielding filling material for cables is stable.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for preparing a semi-conductive shielding filling material for a cable, comprising the following steps:

[0008] S1. Prepare a composite rod; the composite rod comprises, from the inside to the outside, a conductive core material, a diffusion barrier layer, and an insulating permeable substrate, wherein the diffusion barrier layer is used to reduce the diffusion depth of metal atoms in the conductive core material into the insulating permeable substrate; or the composite rod comprises, from the inside to the outside, a conductive core material, an insulating permeable substrate, and a diffusion barrier layer, wherein the diffusion barrier layer is used to increase the element content of metal atoms in the conductive core material that penetrate into the insulating permeable substrate;

[0009] S2. Drying the composite rod to solidify the composite rod;

[0010] S3, calcining the dried and solidified composite rod at high temperature;

[0011] S4. Cooling the composite rod after high-temperature calcination, partially or completely removing the conductive core material remaining in the cooled composite rod, and crushing, grinding and sieving the composite rod with the residual conductive core material removed in sequence to obtain a semi-conductive shielding filling material for cables.

[0012] Furthermore, in step S1: the conductive core material is made of one of copper, nickel-plated copper or silver-plated copper; the diffusion barrier layer includes multiple layers of mica tape, and the mica tape is one of phlogopite tape, calcined mica tape or synthetic mica tape; the insulating permeable substrate is an inorganic fiber filament composite alumina gel solid or an inorganic fiber filament composite silica gel solid.

[0013] Furthermore, in step S1: the inorganic fiber filament composite alumina gel solidified material is an alumina fiber filament composite alumina gel solidified material, and the preparation process is specifically as follows: multiple bundles of longitudinally arranged alumina fiber filaments are impregnated with 5-30wt% alumina gel solution, so that the alumina gel solution penetrates into the gaps between the multiple bundles of alumina fiber filaments, and is dried in an air environment of 150-280°C for 1-6h to solidify the alumina gel solution to form the insulating permeable substrate rich in alumina.

[0014] Furthermore, in step S1: the inorganic fiber filament composite silica gel solidified material is a silica fiber filament composite silica gel solidified material, and the preparation process is specifically as follows: multiple bundles of longitudinally arranged silica fiber filaments are impregnated with 5-30wt% silica gel solution, so that the silica gel solution penetrates into the gaps between the multiple bundles of silica fiber filaments, and is dried in an air environment of 150-280°C for 1-6h to solidify the silica gel solution to form the insulating permeable substrate rich in silica.

[0015] Furthermore,

[0016] When the composite rod includes, from the inside to the outside, a conductive core material, a diffusion barrier layer, and an insulating permeable substrate, step S1 specifically comprises: coating the conductive core material with multiple layers of mica tape, the multiple layers of mica tape cooperate to form a diffusion barrier layer, and coating the insulating permeable substrate on the outside of the diffusion barrier layer to obtain the composite rod;

[0017] When the composite rod includes a conductive core material, an insulating permeable substrate and a diffusion barrier layer from the inside to the outside, step S1 is specifically: coating the insulating permeable substrate on the outside of the conductive core material, and coating the outside of the insulating permeable substrate with multiple layers of mica tape to obtain a composite rod, wherein the multiple layers of mica tape cooperate to form a diffusion barrier layer.

[0018] Furthermore, step S2 specifically includes: heating the composite rod to 150-280° C. and drying it in an air environment for 1-6 hours to solidify the composite rod.

[0019] Furthermore, in step S2: the heating rate of the composite rod is 5°C / min.

[0020] Furthermore, step S3 specifically includes: heating the dried and solidified composite rod to 600-1200° C. and calcining it in air or vacuum environment for 5-500 hours.

[0021] Furthermore, step S3 specifically comprises: directly heating the composite rod that has been dried and solidified but not cooled to room temperature to 600-1200° C. at a heating rate of 3° C. / min and keeping the temperature for 5-500 hours in air or vacuum environment.

[0022] Furthermore, step S4 is specifically as follows: naturally cooling the composite rod after high-temperature calcination to room temperature in the furnace, and partially or completely removing the conductive core material remaining in the cooled composite rod, and crushing and grinding the composite rod with the residual conductive core material removed in turn, and passing it through a 3000 mesh sieve to obtain a semi-conductive shielding filling material for cables.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The preparation method of the semi-conductive shielding filling material for cables in the present invention comprises the following steps: S1, preparing a composite rod; the composite rod comprises a conductive core material, a diffusion barrier layer and an insulating permeable substrate in sequence from the inside to the outside, the diffusion barrier layer being used to reduce the diffusion depth of metal atoms in the conductive core material into the insulating permeable substrate; or the composite rod comprises a conductive core material, an insulating permeable substrate and a diffusion barrier layer in sequence from the inside to the outside, the diffusion barrier layer being used to increase the element content of metal atoms in the conductive core material penetrating into the insulating permeable substrate; S2, drying the composite rod to solidify the composite rod; S3, high-temperature calcining the dried and solidified composite rod; S4, cooling the composite rod after high-temperature calcination, and partially or completely removing the conductive core material remaining in the cooled composite rod, and crushing, grinding and sieving the composite rod with the residual conductive core material removed in sequence to obtain the semi-conductive shielding filling material for cables. The present invention adopts a calcination process for a pre-designed multi-layer heterogeneous material coating structure to precisely control the temperature to prepare a semi-conductive shielding filling material for a cable. By controlling the calcination temperature and time, the diffusion depth of the metal atoms in the conductive core material into the insulating permeable substrate and the diffusion barrier layer is controlled. The diffused metal atoms are oxidized in a high-temperature air environment and react with other substances to form a semi-conductive material. The semi-conductive shielding filling material for a cable is obtained by crushing, grinding and screening. The resistivity of the prepared semi-conductive shielding filling material for a cable can be precisely controlled, and the performance of the prepared semi-conductive shielding filling material for a cable is stable. The present invention has a great influence on the performance of the prepared semi-conductive shielding filling material for a cable. In addition to the calcination temperature and time, the means for controlling the resistivity of the conductive shielding filling material also include: the material and diameter of the conductive core material, the material and thickness of the insulating permeable substrate, the material and thickness of the diffusion barrier layer, the coating order of the diffusion barrier layer and the insulating permeable substrate, the calcination method, and the final retention rate of the residual conductive core material in the composite rod. Through the above control means, the resistivity control range of the semi-conductive shielding filling material for cables can be broadened, and compared with the traditional method of directly adding metal conductive fillers or metal oxide conductive fillers to the insulating substrate, the distribution of metal elements in the semi-conductive shielding filling material for cables prepared by the present invention is more uniform and better dispersed. DETAILED DESCRIPTION

[0025] A method for preparing a semi-conductive shielding filling material for a cable, comprising the following steps:

[0026] S1. Prepare a composite rod; the composite rod comprises, from the inside to the outside, a conductive core material, a diffusion barrier layer, and an insulating permeable substrate, wherein the diffusion barrier layer is used to reduce the diffusion depth of metal atoms in the conductive core material into the insulating permeable substrate; or the composite rod comprises, from the inside to the outside, a conductive core material, an insulating permeable substrate, and a diffusion barrier layer, wherein the diffusion barrier layer is used to increase the element content of metal atoms in the conductive core material that penetrate into the insulating permeable substrate;

[0027] The conductive core material is made of copper, nickel-plated copper or silver-plated copper; the diffusion barrier layer comprises multiple layers of mica tape, which is one of phlogopite, calcined mica or synthetic mica; the insulating permeable substrate is an inorganic fiber composite alumina gel solidified material or an inorganic fiber composite silica gel solidified material;

[0028] S2. Drying the composite rod to solidify the composite rod;

[0029] S3, calcining the dried and solidified composite rod at high temperature;

[0030] S4. Cooling the composite rod after high-temperature calcination, partially or completely removing the conductive core material remaining in the cooled composite rod, and crushing, grinding and sieving the composite rod with the residual conductive core material removed in sequence to obtain a semi-conductive shielding filling material for cables.

[0031] The present invention adopts a calcination process with precise temperature control on a pre-designed multi-layer heterogeneous material coating structure to prepare a semi-conductive shielding filling material for a cable. By controlling the calcination temperature and time, the diffusion depth of the metal atoms in the conductive core material into the insulating permeation substrate and the diffusion barrier layer is controlled. The diffused metal atoms are oxidized in a high-temperature air environment and react with other substances to form a semi-conductive material. The semi-conductive shielding filling material for a cable is obtained by crushing, grinding and screening. The resistivity of the prepared semi-conductive shielding filling material for a cable can be precisely controlled, and the prepared cable is The performance of the semi-conductive shielding filling material is stable. The control means of the resistivity of the semi-conductive shielding filling material for the prepared cable includes not only the calcination temperature and time, but also includes: the material and diameter of the conductive core material, the material and thickness of the insulating permeable substrate, the material and thickness of the diffusion barrier layer, the coating sequence of the diffusion barrier layer and the insulating permeable substrate, the calcination method, and finally the retention rate of the residual conductive core material in the composite rod. Through the above control means, the resistivity control range of the semi-conductive shielding filling material for the prepared cable can be broadened, and compared with the traditional method of directly adding the conductive core material to the insulating substrate, the resistivity control range of the semi-conductive shielding filling material for the prepared cable can be broadened. The semi-conductive shielding filling material for cables prepared by the present invention has a more uniform distribution of metal elements and better dispersion. For example, when preparing a semi-conductive shielding filling material for cables with a narrow resistivity range by conventional methods, theoretically only 0.1-0.5% of silver powder or copper powder needs to be added. However, since the insulating substrate is in a solid or semi-solid state, the silver powder or copper powder cannot be evenly dispersed in the insulating substrate. Even if some metal oxides are added, the uniformity of the dispersion of the metal elements in the insulating substrate cannot be completely improved, and the performance stability of the semi-conductive shielding filling material for cables cannot be improved. However, the method of the present invention can accurately prepare a semi-conductive shielding filling material for cables with a resistivity close to the required value. When preparing the semi-conductive shielding filling material for cables by the method of the present invention, the diameter of the conductive core material, the thickness of the insulating permeable substrate, and the thickness of the diffusion barrier layer can be designed as needed. The calcination temperature, time, and calcination method can also be designed as needed. This can greatly improve the uniformity of the distribution of metal elements in the semi-conductive shielding filling material for cables and the performance stability of the semi-conductive shielding filling material for cables.

[0032] In the present invention, the innermost copper material, nickel-plated copper material or silver-plated copper material is used as the core material of the conductor, and provides free copper atoms under high-temperature calcination. For the nickel-plated copper material, the nickel plating layer can slow down the migration of copper atoms, and at the same time provide nickel elements for the semi-conductive shielding filling material for the cable finally produced, and effectively control the content of copper elements in the semi-conductive shielding filling material for the cable finally produced. For the silver-plated copper material, the silver plating layer can slow down the migration of copper atoms, and at the same time provide silver elements for the semi-conductive shielding filling material for the cable finally produced, and effectively control the content of copper elements in the semi-conductive shielding filling material for the cable finally produced.

[0033] In the present invention, the inorganic fiber filament composite alumina gel solidified material or the inorganic fiber filament composite silica gel solidified material provides a substrate for the migration and penetration of copper atoms. The copper atoms penetrate into the inorganic fiber filament composite alumina gel solidified material or the inorganic fiber filament composite silica gel solidified material under high-temperature calcination to form the main material component of the semi-conductive shielding filling material for the prepared cable.

[0034] In the present invention, the multi-layer mica tape serves as a diffusion barrier layer, which can prevent the diffusion of copper atoms at a certain temperature and within a certain period of time. If the multi-layer mica tape is coated on the outside of the inorganic fiber composite alumina gel solidified material or the inorganic fiber composite silica gel solidified material, it is used to increase the element content of copper atoms penetrating into the inorganic fiber composite alumina gel solidified material or the inorganic fiber composite silica gel solidified material. When it is necessary to increase the resistivity of the semi-conductive shielding filling material for the prepared cable, the multi-layer mica tape can be coated on the outside of the conductive core material, and the inorganic fiber composite alumina gel solidified material or the inorganic fiber composite silica gel solidified material can be coated on the outside of the multi-layer mica tape to reduce the diffusion depth of copper atoms into the inorganic fiber composite alumina gel solidified material or the inorganic fiber composite silica gel solidified material.

[0035] Among them, in step S1: the inorganic fiber filament composite alumina gel solidified material is an alumina fiber filament composite alumina gel solidified material, and the preparation process is specifically as follows: multiple bundles of longitudinally arranged alumina fiber filaments are impregnated with 5-30wt% alumina gel solution, so that the alumina gel solution penetrates into the gaps between the multiple bundles of alumina fiber filaments, and is dried in an air environment of 150-280°C for 1-6h to solidify the alumina gel solution to form an insulating permeable substrate rich in alumina.

[0036] Among them, in step S1: the inorganic fiber filament composite silica gel solidified material is a silica fiber filament composite silica gel solidified material, and the preparation process is specifically as follows: multiple bundles of longitudinally arranged silica fiber filaments are impregnated with 5-30wt% silica gel solution, so that the silica gel solution penetrates into the gaps between the multiple bundles of silica fiber filaments, and is dried in an air environment of 150-280°C for 1-6 hours to solidify the silica gel solution to form an insulating permeable substrate rich in silica.

[0037] in,

[0038] When the composite rod includes a conductive core material, a diffusion barrier layer, and an insulating permeable substrate in order from the inside to the outside, step S1 specifically comprises: coating the conductive core material with multiple layers of mica tape, the multiple layers of mica tape cooperate to form a diffusion barrier layer, and coating the insulating permeable substrate on the outside of the diffusion barrier layer to obtain the composite rod;

[0039] When the composite rod includes a conductive core material, an insulating permeable substrate and a diffusion barrier layer from the inside to the outside, step S1 is specifically: coating the insulating permeable substrate on the outside of the conductive core material, and coating the insulating permeable substrate with multiple layers of mica tape to obtain a composite rod, wherein the multiple layers of mica tape cooperate to form a diffusion barrier layer.

[0040] Specifically, step S2 includes heating the composite rod to 150-280°C and drying it in air for 1-6 hours to solidify the composite rod. Preferably, in step S2, the heating rate of the composite rod is 5°C / min.

[0041] Step S3 specifically comprises heating the dried and solidified composite rod to 600-1200°C and calcining it in air or vacuum for 5-500 hours. Preferably, step S3 specifically comprises heating the dried and solidified composite rod that has not been cooled to room temperature directly to 600-1200°C at a heating rate of 3°C / min and maintaining the temperature in air or vacuum for 5-500 hours.

[0042] Among them, step S4 is specifically: the composite rod after high-temperature calcination is naturally cooled to room temperature in the furnace, and the conductive core material remaining in the cooled composite rod is partially or completely removed, and the composite rod with the residual conductive core material removed is crushed and ground in turn, and passed through a 3000 mesh sieve to obtain a semi-conductive shielding filling material for cables.

[0043] Example 1

[0044] S1. Preparation of composite rods:

[0045] S1-1. Prepare the conductive core material: Select a nickel-plated copper rod with a diameter of 5.0 mm, wherein the thickness of the nickel coating on the nickel-plated copper rod is 10 μm;

[0046] S1-2, coating diffusion barrier layer: tightly coat the outer side of the nickel-plated copper rod with two layers of calcined mica tape, each layer of calcined mica tape is 0.15mm thick, and the total thickness of the diffusion barrier layer is 0.30mm;

[0047] S1-3, prepare insulating permeable substrate: select multiple bundles of alumina fibers with a diameter of 10 μm, and the longitudinal arrangement density of the multiple bundles of alumina fibers is 80 bundles / mm 2 , impregnating multiple bundles of longitudinally arranged alumina fiber filaments with a 15wt% alumina gel solution, allowing the alumina gel solution to penetrate into the gaps between the multiple bundles of alumina fiber filaments, ensuring that the gap filling rate between the multiple bundles of alumina fiber filaments is ≥95%, and drying them in an air environment at 280°C for 3 hours to solidify the alumina gel solution, thereby forming an insulating permeable substrate for infiltrating copper atoms;

[0048] S1-4, coating the insulating permeable substrate: coating the prepared insulating permeable substrate on the outside of the diffusion barrier layer, controlling the thickness of the insulating permeable substrate layer to be 0.20 mm, to obtain a composite rod;

[0049] S2. Secondary curing treatment: placing the composite rod in an oven and heating it to 280°C at a heating rate of 5°C / min and drying it in air for 3 hours to cure the composite rod;

[0050] S3, high temperature calcination: the composite rod that has been dried and solidified but not cooled to room temperature is directly heated to 800°C at a heating rate of 3°C / min and kept at this temperature in an air environment for 300h;

[0051] S4. The composite rod after high-temperature calcination is naturally cooled to room temperature in the furnace, and the residual conductive core material inside the cooled composite rod is 100% removed by mechanical stripping. The composite rod with the residual conductive core material is then crushed, ground and passed through a 3000 mesh sieve to obtain a semi-conductive shielding filling material for cables.

[0052] The semi-conductive shielding filling material for cables prepared in Example 1 is referred to as Sample 1#.

[0053] Example 2

[0054] The difference between Example 2 and Example 1 is that:

[0055] In step S1-1: the conductive core material is a nickel-plated copper wire with a diameter of 1.0 mm.

[0056] The semi-conductive shielding filling material for cables prepared in Example 2 is referred to as Sample 2#.

[0057] Example 3

[0058] The difference between Example 3 and Example 1 is that:

[0059] In step S1-2: the outer side of the nickel-plated copper rod is tightly coated with 5 layers of calcined mica tape, each layer of calcined mica tape is 0.3 mm thick, and the total thickness of the diffusion barrier layer is 1.5 mm;

[0060] The semi-conductive shielding filling material for cables prepared in Example 3 is referred to as Sample 3#.

[0061] Example 4

[0062] The difference between Example 4 and Example 1 is that:

[0063] In step S1-3: the diameter of the alumina fiber is 15 μm, and the longitudinal arrangement density of the multiple bundles of alumina fiber is 90 bundles / mm 2 The mass fraction of the alumina gel solution is 30wt%, and the gap filling rate between the multiple bundles of alumina fiber filaments is ≥98%. Compared with Example 1, the density of the formed insulating permeable substrate is larger.

[0064] The semi-conductive shielding filling material for cables prepared in Example 4 is referred to as Sample 4#.

[0065] Example 5

[0066] The difference between Example 5 and Example 1 is that:

[0067] In step S3, the composite rod that has been dried and solidified but not cooled to room temperature is directly heated to 800°C at a heating rate of 3°C / min and kept warm for 300h in a vacuum environment, wherein the vacuum degree is ≤10 -2 Pa.

[0068] The semi-conductive shielding filling material for cables prepared in Example 5 is referred to as Sample 5#.

[0069] Example 6

[0070] The difference between Example 6 and Example 1 is that:

[0071] In step S1 , the coating order of the diffusion barrier layer and the insulating permeable substrate is changed, that is, the insulating permeable substrate is first prepared, then coated on the outside of the conductive core material, and then coated on the outside of the insulating permeable substrate with the diffusion barrier layer.

[0072] The semi-conductive shielding filling material for cables prepared in Example 6 is referred to as Sample 6#.

[0073] Example 7

[0074] The difference between Example 7 and Example 1 is that:

[0075] In step S1-1: a copper rod with a diameter of 5.0 mm is selected.

[0076] The semi-conductive shielding filling material for cables prepared in Example 7 is referred to as Sample 7#.

[0077] Example 8

[0078] The difference between Example 8 and Example 1 is that:

[0079] In step S1-1: a silver-plated copper rod with a diameter of 5.0 mm is selected, wherein the thickness of the silver coating on the silver-plated copper rod is 10 μm.

[0080] The semi-conductive shielding filling material for the cable prepared in Example 8 is called Sample 8#.

[0081] Example 9

[0082] The difference between Example 9 and Example 1 is that:

[0083] In step S1-2: the calcined mica tape is replaced with a phlogopite mica tape.

[0084] The semi-conductive shielding filling material for cables prepared in Example 9 is called Sample 9#.

[0085] Example 10

[0086] The difference between Example 10 and Example 1 is that:

[0087] In step S1-2: the calcined mica tape is replaced with a synthetic mica tape.

[0088] The semi-conductive shielding filling material for cables prepared in Example 10 is referred to as sample 10#.

[0089] Example 11

[0090] The difference between Example 11 and Example 1 is that:

[0091] In step S1-3: the alumina fiber filaments are replaced with silica fiber filaments, and the alumina gel solution is replaced with silica gel solution.

[0092] The semi-conductive shielding filling material for cables prepared in Example 11 is referred to as Sample 11#.

[0093] Example 12

[0094] The difference between Example 12 and Example 1 is that:

[0095] In step S4: 80% of the remaining conductive core material is removed by mechanical stripping.

[0096] The semi-conductive shielding filling material for cables prepared in Example 12 is referred to as sample 12#.

[0097] Example 13

[0098] The difference between Example 13 and Example 1 is that:

[0099] In step S3: the temperature is raised to 1200°C instead of 800°C.

[0100] The semi-conductive shielding filling material for cables prepared in Example 13 is called Sample 13#.

[0101] Example 14

[0102] The difference between Example 14 and Example 1 is that:

[0103] In step S3: the insulation time of 300 hours is changed to the insulation time of 600 hours.

[0104] The semi-conductive shielding filling material for cables prepared in Example 14 is called sample 14#.

[0105] The material properties of samples 1# to 7# prepared in Examples 1 to 7 were tested according to ASTM D257. The specific results are shown in Table 1.

[0106] Table 1

[0107]

[0108] The material properties of samples 8# to 14# prepared in Examples 8 to 14 were tested according to ASTM D257. The specific results are shown in Table 2.

[0109] Table 2

[0110]

[0111] From Table 1 and Table 2, we can see that

[0112] By comparing the test data of Example 1 and Example 2, it can be seen that in Example 2, due to the high specific surface area of ​​the small-sized nickel-plated copper wire, the deep oxidation of copper atoms is promoted. Therefore, when the diameter of the conductive core material is reduced, the resistivity of the semi-conductive shielding filling material for the prepared cable increases.

[0113] By comparing the test data of Example 1 and Example 3, it can be seen that in Example 3, due to the increase in the total thickness of the diffusion barrier layer, copper atoms are forced to be enriched on the surface of the conductive core material, while the proportion of copper atoms migrating into the insulating permeable matrix is ​​reduced, resulting in an increase in the resistivity of the semi-conductive shielding filling material for the prepared cable.

[0114] By comparing the test data of Example 1 with that of Example 4, it can be seen that in Example 4, by increasing the diameter of the alumina fiber filaments, the longitudinal arrangement density and the mass fraction of the alumina gel solution, when the thickness of the conductive core material, the diffusion barrier layer and the insulating permeable substrate in the composite rod are the same, the resistivity of the prepared semi-conductive shielding filling material for the cable is increased and the stability is improved, which proves that the densification of the insulating permeable substrate can suppress the randomness of the diffusion of copper atoms and achieve a stable jump in the resistivity.

[0115] In summary, through the coordinated regulation of the conductive core material size, the diffusion barrier layer thickness, and the densification of the insulating permeable substrate, the resistivity of the semi-conductive shielding filling material for the cable can be reduced to 10 4 -10 6 Precision design spanning three orders of magnitude is achieved within the Ω·cm range, breaking through the technical bottlenecks of the traditional method of directly adding metal conductive fillers or metal oxide conductive fillers to the insulating substrate, which results in a narrow resistivity adjustment range and poor distribution uniformity of metal elements in semi-conductive shielding filling materials for cables.

[0116] By comparing the test data of Example 1 with that of Example 5, it can be seen that when the air environment is adjusted to a vacuum environment during high-temperature calcination, the resistivity of the semi-conductive shielding filling material for the prepared cable shows a significant downward trend. This phenomenon indicates that the vacuum environment has a regulatory effect on the microstructure and interface properties of the material. The vacuum environment effectively inhibits the oxidation behavior of the metal components during the material preparation process, reduces the generation of insulating oxides, and leads to a decrease in resistivity.

[0117] By comparing the test data of Example 1 and Example 6, it can be seen that in Example 6, the diffusion barrier layer is on the outside of the insulating permeable substrate, and the resistivity of the semi-conductive shielding filling material for the prepared cable shows a downward trend. The reason is that compared with the insulating permeable substrate, the diffusion barrier layer has an ultra-high resistivity to form an atomic-level sealing barrier. When the diffusion barrier layer is coated on the outside of the conductive core material, the migration depth of the copper atoms is reduced. When the coating order of the diffusion barrier layer and the insulating permeable substrate is changed, the migration depth of the metal atoms in the conductive core material in the insulating permeable substrate is greater, which reduces the resistivity of the semi-conductive shielding filling material for the prepared cable. This order of magnitude can accurately adapt to the needs of special cables with smaller resistivity tolerance, highlighting the technical value of the coating order.

[0118] By comparing the test data of Example 1 with those of Examples 7-11, it can be found that the material component is the core lever for fine-tuning the resistivity. By changing the type of conductive core material, the type of mica tape in the diffusion barrier layer, and the type of fiber filaments in the insulating permeable substrate, precise adjustment of the resistivity can be achieved within a certain range. At the same time, the coordinated cooperation of multiple components can cover the stringent resistivity requirements of ultra-high voltage cable shielding materials, breaking through the adjustment bottleneck of traditional processes.

[0119] By comparing the test data of Example 1 with that of Example 12, it can be seen that the resistivity of the semi-conductive shielding filling material for cables obtained by changing the removal of 100% of the residual conductive core material inside to 80% of the residual conductive core material inside is greatly reduced. This is because the residual metal phase will significantly change the electrical behavior, and the metal fragments after grinding form a penetrating conductive network, which causes the resistivity to drop sharply. This coarse adjustment mechanism can cover the wide range of needs of ultra-high voltage cable shielding materials, breaking through the limitation of the single resistivity range of the semi-conductive shielding filling material for cables obtained by directly adding metal conductive fillers or metal oxide conductive fillers to the traditional insulating substrate.

[0120] By comparing the test data of Example 1 with that of Example 13, it can be seen that after increasing the calcination temperature, the resistivity of the semi-conductive shielding filling material for the prepared cable decreases. This is because the ultra-high temperature causes the migration rate of copper atoms to accelerate. When the temperature rises, the diffusion coefficient of copper atoms surges. At the same time, the permeability of oxygen in the densified insulating permeable substrate decreases, resulting in the enrichment of copper atoms in the insulating permeable substrate but unable to be fully oxidized, causing the resistivity to decrease. This phenomenon proves that the calcination temperature can be used as a coarse adjustment lever for the resistivity.

[0121] By comparing the test data of Example 1 with that of Example 14, it can be seen that after extending the calcination time, the resistivity of the semi-conductive shielding filling material for the prepared cable decreases. This is because the calcination time dominates the resistivity evolution through the migration depth of copper atoms. Prolonging the calcination time will increase the diffusion depth of copper atoms and reduce the resistivity. This phenomenon proves that the calcination time can be used as a coarse adjustment lever for the resistivity.

[0122] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a semi-conductive shielding filling material for a cable, characterized in that: The following steps are involved: S1. Prepare a composite rod; the composite rod comprises, from the inside to the outside, a conductive core material, a diffusion barrier layer, and an insulating permeable substrate, wherein the diffusion barrier layer is used to reduce the diffusion depth of metal atoms in the conductive core material into the insulating permeable substrate; or the composite rod comprises, from the inside to the outside, a conductive core material, an insulating permeable substrate, and a diffusion barrier layer, wherein the diffusion barrier layer is used to increase the element content of metal atoms in the conductive core material that penetrate into the insulating permeable substrate; S2. Drying the composite rod to solidify the composite rod; S3, calcining the dried and solidified composite rod at high temperature; S4. Cooling the composite rod after high-temperature calcination, partially or completely removing the conductive core material remaining in the cooled composite rod, and crushing, grinding and sieving the composite rod with the residual conductive core material removed in sequence to obtain a semi-conductive shielding filling material for cables.

2. The method for preparing a semi-conductive shielding filling material for a cable according to claim 1, characterized in that: In step S1: the conductive core material is made of one of copper, nickel-plated copper or silver-plated copper; the diffusion barrier layer includes multiple layers of mica tape, and the mica tape is one of phlogopite tape, calcined mica tape or synthetic mica tape; the insulating permeable substrate is an inorganic fiber composite alumina gel solid or an inorganic fiber composite silica gel solid.

3. The method for preparing a semi-conductive shielding filling material for a cable according to claim 2, characterized in that: In step S1: the inorganic fiber filament composite alumina gel solidified material is an alumina fiber filament composite alumina gel solidified material, and the preparation process is specifically as follows: multiple bundles of longitudinally arranged alumina fiber filaments are impregnated with 5-30wt% alumina gel solution, so that the alumina gel solution penetrates into the gaps between the multiple bundles of alumina fiber filaments, and is dried in an air environment of 150-280°C for 1-6 hours to solidify the alumina gel solution to form the insulating permeable substrate rich in alumina.

4. The method for preparing a semi-conductive shielding filling material for a cable according to claim 2, characterized in that: In step S1: the inorganic fiber filament composite silica gel solidified material is a silica fiber filament composite silica gel solidified material, and the preparation process is specifically as follows: multiple bundles of longitudinally arranged silica fiber filaments are impregnated with 5-30wt% silica gel solution, so that the silica gel solution penetrates into the gaps between the multiple bundles of silica fiber filaments, and is dried in an air environment of 150-280°C for 1-6 hours to solidify the silica gel solution to form the insulating permeable substrate rich in silica.

5. The method for preparing a semi-conductive shielding filling material for a cable according to claim 2, characterized in that: When the composite rod includes, from the inside to the outside, a conductive core material, a diffusion barrier layer, and an insulating permeable substrate, step S1 specifically comprises: coating the conductive core material with multiple layers of mica tape, the multiple layers of mica tape cooperate to form a diffusion barrier layer, and coating the insulating permeable substrate on the outside of the diffusion barrier layer to obtain the composite rod; When the composite rod includes a conductive core material, an insulating permeable substrate and a diffusion barrier layer from the inside to the outside, step S1 is specifically: coating the insulating permeable substrate on the outside of the conductive core material, and coating the outside of the insulating permeable substrate with multiple layers of mica tape to obtain a composite rod, wherein the multiple layers of mica tape cooperate to form a diffusion barrier layer.

6. The method for preparing a semi-conductive shielding filling material for a cable according to claim 2, characterized in that: Step S2 specifically comprises: heating the composite rod to 150-280° C. and drying the composite rod in an air environment for 1-6 hours to solidify the composite rod.

7. The method for preparing a semi-conductive shielding filling material for a cable according to claim 6, characterized in that: In step S2: the heating rate of the composite rod is 5°C / min.

8. The method for preparing a semi-conductive shielding filling material for a cable according to claim 2, characterized in that: Step S3 specifically comprises: heating the dried and solidified composite rod to 600-1200° C. and calcining it in air or vacuum environment for 5-500 hours.

9. The method for preparing a semi-conductive shielding filling material for a cable according to claim 8, characterized in that: Step S3 specifically comprises: directly heating the composite rod that has been dried and solidified but not cooled to room temperature to 600-1200° C. at a heating rate of 3° C. / min and keeping the temperature for 5-500 hours in air or vacuum environment.

10. The method for preparing a semi-conductive shielding filling material for a cable according to claim 2, characterized in that: Step S4 is specifically as follows: the composite rod after high-temperature calcination is naturally cooled to room temperature in the furnace, and the conductive core material remaining in the cooled composite rod is partially or completely removed, and the composite rod with the residual conductive core material removed is crushed and ground in turn, and passed through a 3000 mesh sieve to obtain a semi-conductive shielding filling material for cables.

Images