Shielding material composition, shielding material and preparation method, shielding material and application thereof

Abstract

The present invention relates to the field of power cable technology, and discloses a shielding material composition, a shielding material and a preparation method, a shielding material and an application thereof. The shielding material composition comprises, by weight, 55-73 parts of a polyolefin resin, 23-40 parts of a conductive filler, 0.5-2 parts of a cross-linking agent, 0.1-1.2 parts of a dispersant A, 0.2-2.5 parts of a dispersant B, 0.5-3 parts of a lubricant, and 0.5-2 parts of an antioxidant; wherein the dispersant A is an anionic dispersant having a weight-average molecular weight of 1-150,000 g / mol; and the dispersant B is a non-ionic dispersant. When the ratio of the polyolefin resin, the conductive filler, the cross-linking agent, the dispersant, the lubricant, and the antioxidant in the shielding material composition meets the required range of the present invention, the prepared shielding material has the characteristics of a smooth surface, low bulk resistivity, high mechanical properties, and a low PTC coefficient.

Description

Technical Field

[0001] The present invention belongs to the technical field of power cables, and in particular relates to a shielding material composition, a shielding material and a preparation method thereof, a shielding material and an application thereof. Background Art

[0002] The surface finish of extruded semi-conductive shielding materials is a key quality indicator and determines their applicable voltage rating. High-voltage cables place extremely stringent requirements on the surface finish of the semi-conductive shielding layer. Minor impurities or defects on the surface can cause partial discharge, triggering electrical treeing and posing safety hazards. High-voltage semi-conductive shielding materials must also maintain high mechanical properties, low volume resistivity, and positive temperature resistance effect to ensure they effectively support and homogenize the electric field. Surface finish evaluation methods primarily involve observing extruded strip samples and performing statistical analysis of the height and width of surface protrusions. Therefore, high-voltage cable semi-conductive shielding materials must ensure high surface finish, high mechanical properties, and low volume resistivity and positive temperature resistance effect. This is one of the key challenges in the production of shielding materials for high-voltage cables. Currently, semi-conductive shielding materials suffer from poor surface finish, low mechanical properties, and high volume resistivity and positive temperature resistance effect, making them difficult to meet the demands of high-voltage cable applications. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems of low surface smoothness, poor mechanical properties, high resistivity and positive temperature resistance effect of existing shielding materials, and to provide a shielding material composition, shielding material and preparation method, shielding material and application thereof. The shielding material made from the shielding material composition has the characteristics of smooth surface, high mechanical properties, low resistivity and low positive temperature resistance effect.

[0004] In order to achieve the above object, the first aspect of the present invention provides a shielding material composition, wherein the shielding material composition comprises, by weight:

[0005] 55-73 parts of polyolefin resin, 23-40 parts of conductive filler, 0.5-2 parts of crosslinking agent, 0.1-1.2 parts of dispersant A, 0.2-2.5 parts of dispersant B, 0.5-3 parts of lubricant, 0.5-2 parts of antioxidant;

[0006] Wherein, the dispersant A is an anionic dispersant, and the weight average molecular weight of the dispersant A is 10,000-150,000 g / mol;

[0007] The dispersant B is a nonionic dispersant.

[0008] A second aspect of the present invention provides a method for preparing a shielding material, wherein the preparation method comprises:

[0009] S1. Blending the components of the shielding material composition except the crosslinking agent to obtain a blend;

[0010] S2, the blend is pelletized and dried to obtain a semi-finished product;

[0011] S3. Mix the semi-finished product with a cross-linking agent to obtain a shielding material.

[0012] A third aspect of the present invention provides a shielding material produced by the above method.

[0013] A fourth aspect of the present invention provides a shielding material, which is made by cross-linking the above-mentioned shielding material.

[0014] A fifth aspect of the present invention provides a use of the above-mentioned shielding material composition, or the above-mentioned shielding material, or the above-mentioned shielding material in a high-voltage power cable.

[0015] Through the above technical solution, the shielding material composition, shielding material and preparation method, shielding material and application thereof provided by the present invention have the following beneficial effects.

[0016] The shielding material composition of the present invention contains anionic dispersants and nonionic dispersants of specific molecular weight. Under the synergistic effect of the two dispersants, the self-aggregation of the conductive filler can be effectively prevented, so that the conductive filler is more fully dispersed and effectively distributed in the polyolefin resin; the shielding material prepared has a developed conductive network and a smooth surface, and there are no protrusions and mechanical stress points caused by the aggregation of the conductive filler; when the ratio of the polyolefin resin, conductive filler, crosslinking agent, dispersant, lubricant and antioxidant in the shielding material composition meets the required range of the present invention, the prepared shielding material has the characteristics of smooth surface, low volume resistivity, high mechanical properties and low PTC coefficient. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0018] A first aspect of the present invention provides a shielding material composition, wherein the shielding material composition comprises, by weight:

[0019] 55-73 parts of polyolefin resin, 23-40 parts of conductive filler, 0.5-2 parts of crosslinking agent, 0.1-1.2 parts of dispersant A, 0.2-2.5 parts of dispersant B, 0.5-3 parts of lubricant, 0.5-2 parts of antioxidant;

[0020] Wherein, the dispersant A is an anionic dispersant, and the weight average molecular weight of the dispersant A is 10,000-150,000 g / mol;

[0021] The dispersant B is a nonionic dispersant.

[0022] In the present invention, the shielding material composition contains an anionic dispersant and a nonionic dispersant of a specific molecular weight. The synergistic effect of the two dispersants can effectively prevent the conductive filler from self-aggregating, allowing the conductive filler to be more fully dispersed and effectively distributed in the polyolefin resin. The resulting shielding material has a well-developed conductive network and a smooth surface, without protrusions and mechanical stress points caused by the aggregation of the conductive filler. When the ratio of the polyolefin resin, conductive filler, crosslinking agent, dispersant, lubricant, and antioxidant in the shielding material composition meets the required range of the present invention, the prepared shielding material has the characteristics of a smooth surface, low bulk resistivity, high mechanical properties, and a low positive temperature coefficient.

[0023] In the present invention, when the weight-average molecular weight of dispersant A meets the range of 10,000 to 150,000 g / mol, it can produce a synergistic effect with the ionic dispersant B, so that the shielding material prepared has the characteristics of smooth surface, low volume resistivity, high mechanical properties, and low PTC coefficient. The weight-average molecular weight of the dispersant A can be a range formed by any two values ​​of 10,000, 1.5, 2, 3, 5, 8, 10, 12, 13, 14, and 150,000 g / mol, as well as values ​​within the range.

[0024] Furthermore, the shielding material composition comprises, by weight: 62-72 parts of polyolefin resin, 25-35 parts of conductive filler, 1-1.5 parts of crosslinking agent, 0.2-0.8 parts of dispersant A, 0.4-1.6 parts of dispersant B, 0.5-2.5 parts of lubricant, and 0.5-1.5 parts of antioxidant.

[0025] Furthermore, the weight average molecular weight of the dispersant A is 50,000-100,000 g / mol.

[0026] According to the present invention, the dispersant A is selected from polystyrene sulfonate and / or polymaleic anhydride copolymer.

[0027] In the present invention, when the type of dispersant A in the shielding material composition meets the above range, the conductive filler can be better dispersed in the polyolefin resin, and the shielding material prepared has the characteristics of smooth surface, low volume resistivity, high mechanical properties and low positive temperature coefficient.

[0028] In the present invention, the comonomer in the polymaleic anhydride copolymer may be 1-octene or 1-octadecene. In the present invention, the content of the structural unit derived from the comonomer in the polymaleic anhydride copolymer is 70-90 mol%.

[0029] Furthermore, the dispersant A is polystyrene sulfonate.

[0030] According to a preferred embodiment of the present invention, the degree of sulfonation of the polystyrene sulfonate is greater than or equal to 85 mol%. When the degree of sulfonation of the polystyrene sulfonate meets the above range, the shielding material made from the composition has higher mechanical properties, lower resistivity, and a positive temperature coefficient. Furthermore, the degree of sulfonation of the polystyrene sulfonate is greater than or equal to 95 mol%.

[0031] According to the present invention, the weight average molecular weight of the dispersant B is 2-3 million g / mol, and can be a range formed by any two values ​​of 2, 5, 10, 15, 20, 25, 30, 50, 75, 80, 100, 130, 150, 180, 200, 220, 250, 280, 3 million g / mol, and a value within the range.

[0032] In the present invention, when the molecular weight of the dispersant B satisfies the above range, it has the characteristic of inhibiting the agglomeration of the conductive filler, thereby achieving the effect of uniform dispersion of the conductive carbon black.

[0033] Furthermore, the weight average molecular weight of the dispersant B is 2-2 million g / mol.

[0034] According to the present invention, the dispersant B is polyethylene oxide and / or an ethylene oxide-propylene oxide block copolymer.

[0035] In the present invention, in the ethylene oxide-propylene oxide block copolymer, ethylene oxide accounts for 10-20 wt% of the total weight of the copolymer, and propylene oxide accounts for 80-90 wt% of the total weight of the copolymer.

[0036] In the present invention, when the shielding material composition includes the above-mentioned dispersant B, it has the characteristic of inhibiting the agglomeration of the conductive filler, thereby achieving the effect of uniform dispersion of the conductive carbon black.

[0037] Furthermore, the dispersant B is polyethylene oxide.

[0038] According to the present invention, the mass ratio of dispersant A to dispersant B is 1:1-10, and can be a range formed by any two values ​​of 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:5, 1:6, 1:8, 1:9, 1:10, or a value within the range.

[0039] In the present invention, when the mass ratio of dispersant A to dispersant B satisfies the above range, the dispersibility of the conductive filler is improved, resulting in the shielding material having high conductivity, good tensile properties and a smooth surface.

[0040] Furthermore, the mass ratio of the dispersant A to the dispersant B is 1:2-5.

[0041] According to the present invention, the polyolefin resin is selected from ethylene-vinyl acetate copolymer and / or ethylene-acrylate copolymer.

[0042] In the present invention, when the shielding material composition contains the above-mentioned type of polyolefin resin, the conductive filler can be better dispersed in the polyolefin resin, and the shielding material made from the above-mentioned composition has the characteristics of smooth surface, low volume resistivity, high mechanical properties and low positive temperature coefficient.

[0043] In the present invention, the molar content of vinyl acetate in the ethylene-vinyl acetate copolymer is 17-28%; the molar content of butyl acrylate in the ethylene-butyl acrylate copolymer is 10-28%; and the molar content of ethyl acrylate in the ethylene-ethyl acrylate copolymer is 10-20%.

[0044] Furthermore, the polyolefin resin is ethylene-butyl acrylate copolymer.

[0045] According to the present invention, the elongation at break of the polyolefin resin is ≥700%.

[0046] Furthermore, the elongation at break of the polyolefin resin is ≥800%.

[0047] Furthermore, the elongation at break of the polyolefin resin is ≥900%.

[0048] According to the present invention, the melt index of the polyolefin resin at a temperature of 190°C and a load of 2.16 kg is 5-10g / 10min, and can be a range formed by any two values ​​of 5g / 10min, 5.5g / 10min, 6g / 10min, 6.5g / 10min, 7g / 10min, 7.5g / 10min, 8g / 10min, 8.5g / 10min, 9g / 10min, and 10g / 10min, as well as a value within the range.

[0049] Furthermore, the polyolefin resin has a melt index of 6-8 g / 10 min at a temperature of 190° C. and a load of 2.16 kg.

[0050] According to the present invention, the oil absorption value of the conductive filler is 150-200 mL / 100 g, and can be a range formed by any two values ​​of 150 mL / 100 g, 155 mL / 100 g, 160 mL / 100 g, 165 mL / 100 g, 170 mL / 100 g, 180 mL / 100 g, 185 mL / 100 g, 190 mL / 100 g, 195 mL / 100 g, and 200 mL / 100 g, as well as a value within the range.

[0051] In the present invention, when the oil absorption value of the conductive filler satisfies the above range, it indicates that the conductive filler has a higher specific surface area and structure; the shielding material made from the composition has a lower resistivity and a positive temperature coefficient.

[0052] Furthermore, the oil absorption value of the conductive filler is 180-200 mL / 100 g.

[0053] According to the present invention, the conductive filler is conductive carbon black and / or carbon nanotubes.

[0054] In the present invention, when the composition contains the above-mentioned conductive filler, the shielding material made from the composition has the characteristic of high conductivity.

[0055] Furthermore, the conductive carbon black is furnace black and / or acetylene black.

[0056] According to the present invention, the average particle size of the conductive carbon black is 30-60 nm, and can be a range formed by any two values ​​of 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, and 60 nm, or a value within the range.

[0057] In the present invention, when the average particle size of the conductive carbon black satisfies the above range, the shielding material prepared from the above composition has better dispersion of the conductive filler, has a developed conductive path, and has high conductivity and high mechanical properties.

[0058] Furthermore, the average particle size of the conductive carbon black is 30-50 nm.

[0059] According to the present invention, the average length of the carbon nanotubes is 1-5 μm, and the aspect ratio is 100-200. Preferably, the average length of the carbon nanotubes is 1-3 μm, and the aspect ratio is 140-180.

[0060] According to the present invention, the cross-linking agent is an organic peroxide.

[0061] Furthermore, the cross-linking agent is selected from di-tert-butylperoxyisopropylbenzene (BIBP) and / or diisopropylbenzene peroxide (DCP).

[0062] According to the present invention, the lubricant is selected from at least one of zinc stearate, polyethylene wax, silicone oil and microcrystalline wax.

[0063] Furthermore, the lubricant is selected from at least one of zinc stearate, polyethylene wax and microcrystalline wax.

[0064] According to the present invention, the antioxidant is selected from at least one of amine antioxidants, thioester antioxidants, phosphite antioxidants and hindered phenol antioxidants.

[0065] In the present invention, the specific type of antioxidant is not particularly limited. Preferably, the antioxidant is selected from at least one of Antioxidant RD (amine antioxidant), Antioxidant 300 (thioester antioxidant), Antioxidant 168 (phosphite antioxidant), and Antioxidant 1010 (hindered phenol antioxidant). Preferably, the antioxidants are Antioxidant 168 and Antioxidant 1010.

[0066] A second aspect of the present invention provides a method for preparing a shielding material, wherein the preparation method comprises:

[0067] (1) Blending the components of the shielding material composition except the crosslinking agent to obtain a blend;

[0068] (2) The blend is pelletized and dried to obtain a semi-finished product;

[0069] (3) The semi-finished product is mixed with a cross-linking agent to obtain a shielding material.

[0070] According to the present invention, in step S1, the blending conditions include: the temperature T1 of the feeding section of the blending is 80-130°C, the temperature T2 of the mixing section of the blending is 170-260°C, and the temperature T3 of the extrusion section of the blending is 190-250°C.

[0071] In the present invention, when the blending conditions meet the above ranges, it is beneficial to obtain a shielding material with high mechanical properties, low resistivity and low positive temperature coefficient.

[0072] Furthermore, in step S1, T3>T2.

[0073] In the present invention, in step S1, the blending conditions include: the rotation speed of the extruder is 300-600 rpm.

[0074] According to the present invention, in step S1, the dispersant A is pre-mixed with the conductive filler and then blended with the polyolefin resin, the dispersant B, the lubricant and the antioxidant.

[0075] In the present invention, when the above-mentioned step-by-step mixing method is adopted, it has the characteristics of suppressing the self-aggregation of the conductive filler while ensuring that the filler is well dispersed in the matrix, resulting in a well-developed network formed by the conductive filler, high conductivity (low resistivity) of the shielding material, excellent tensile properties and a smooth surface.

[0076] In the present invention, in step S1, the premixing temperature is 60-100° C., and the premixing time is 5-12 hours.

[0077] In the present invention, in step S2, there is no particular limitation on the pelletizing method, and pelletizing can be performed according to conventional methods in the art. For example, pelletizing can be performed using a pelletizer.

[0078] In the present invention, there is no particular limitation on the drying conditions in step S2, and conventional drying conditions in the art may be used. Preferably, the drying temperature is 50-60° C., and the drying time is 1-2 hours.

[0079] According to the present invention, in step S3, the cross-linking agent is melted and then mixed with the semi-finished product.

[0080] According to the present invention, in step S3, the mixing temperature is 55-80° C., and the mixing time is 10-60 min.

[0081] Furthermore, in step S3, the mixing temperature is 60-70° C., and the mixing time is 10-40 min.

[0082] In the present invention, the cross-linking agent is melted and then mixed with the semi-finished product in a post-absorption device. Preferably, the rolling speed of the post-absorption device is 1-10 rpm, preferably 1-5 rpm.

[0083] A third aspect of the present invention provides a shielding material produced by the above method.

[0084] A fourth aspect of the present invention provides a shielding material, which is made by cross-linking the above-mentioned shielding material.

[0085] According to the present invention, the tensile strength of the shielding material is greater than or equal to 13 MPa.

[0086] According to the present invention, the elongation at break of the shielding material is greater than or equal to 250%.

[0087] According to the present invention, the resistivity of the shielding material at 23° C. is less than or equal to 15Ω·cm.

[0088] Furthermore, the resistivity of the shielding material at 23° C. is less than or equal to 10Ω·cm.

[0089] According to the present invention, the resistivity of the shielding material at 90° C. is less than or equal to 100Ω·cm.

[0090] Furthermore, the resistivity of the shielding material at 90° C. is less than or equal to 50Ω·cm.

[0091] In the present invention, the positive temperature coefficient of the shielding material is less than or equal to 8.

[0092] In the present invention, the positive temperature coefficient of the shielding material refers to the ratio of the resistivity of the shielding material at 90°C to the resistivity at 23°C.

[0093] Furthermore, the positive temperature coefficient of the shielding material is less than or equal to 5.

[0094] In the present invention, the shielding material is preferably used for direct current.

[0095] A fifth aspect of the present invention provides a use of the above-mentioned shielding material composition, or the above-mentioned shielding material, or the above-mentioned shielding material in a high-voltage power cable.

[0096] The present invention will be described in detail below through examples.

[0097] In the following examples, the volume resistivity was measured according to the method specified in Part 3 of GB / T 3048.3-2007, Volume Resistivity Test for Semi-Conductive Rubber and Plastic Materials.

[0098] Positive temperature coefficient (PTC coefficient): the ratio of the resistivity of the shielding material at 90°C to the resistivity at 23°C;

[0099] Tensile strength and elongation at break: measured in accordance with the method specified in GB / T 1040.3-2022, using a 5A type specimen;

[0100] Surface protrusion: Tested with an optical scanning device with a high-resolution camera, with a scanning speed of 0.05m 2 / min, the surface of the sample strip is scanned by a high-resolution camera, and the size and number of surface protrusions are characterized based on the total surface area of ​​about 1m 2 For samples, record the number of surface protrusions with a height greater than or equal to 50 μm;

[0101] Average particle size of conductive carbon black: obtained by transmission electron microscopy (TEM);

[0102] Oil absorption value: measured according to the method specified in GB / T 3780.2-2017;

[0103] Ethylene-vinyl acetate copolymer (EVA): a commercial product sold by Repsol under the brand name E1770; melt index at 190°C and 2.16 kg: 7 g / 10 min, elongation at break: 800%, density: 0.924 g / cm 3 , the molar content of butyl acrylate is 17%;

[0104] Ethylene-butyl acrylate copolymer (EBA): commercially available from DuPont under the designation 2715; melt index at 190°C and 2.16 kg: 7 g / 10 min, elongation at break: 800%, density: 0.93 g / cm 3 , the molar content of ethyl acrylate is 15%;

[0105] Ethylene ethyl acrylate copolymer (EEA): Mitsui brand EVA P2805, with a melt index of 7 g / 10 min at 190°C and 2.16 kg, an elongation at break of 800%, and a density of 0.93 g / cm 3 , the molar content of vinyl acetate is 28%;

[0106] Conductive filler: acetylene black, Denka brand DENKA BLACK, oil absorption value is 200mL / 100g, average particle size is 45nm;

[0107] Conductive filler: Furnace Black-1, brand ENSACO 250G from Yiruishi Company, oil absorption value is 185mL / 100g, average particle size is 36nm;

[0108] Conductive filler: furnace black-2, Cabot brand VXC500, oil absorption value is 140mL / 100g, average particle size is 35nm;

[0109] Conductive filler: carbon nanotubes, brand NC7000 from a Belgian company, oil absorption value of 200 mL / 100 g, length of carbon nanotubes 1.5 μm, aspect ratio 160;

[0110] The types and parameters of dispersant A are shown in Table 1.

[0111] Table 1

[0112]

[0113] Dispersant B: polyethylene oxide (PEO), P101345 from Aladdin, with a weight-average molecular weight of 2 million g / mol.

[0114] Dispersant B: ethylene oxide-propylene oxide block copolymer (ethylene oxide is 15 wt% of the total weight of the copolymer, and propylene oxide is 85 wt% of the total weight of the copolymer), BASF Tetronic 901, with a weight-average molecular weight of 20,000 g / mol.

[0115] Other raw materials used in the examples and comparative examples are all commercially available.

[0116] Example 1

[0117] By mass, the following ingredients are used: 61 parts polyolefin resin, 35 parts conductive filler, 0.5 parts dispersant A, 1 part dispersant B, 0.7 parts lubricant, 0.8 parts antioxidant, and 1 part crosslinking agent. See Table 2 for the specific selection of raw materials.

[0118] The preparation process is as follows:

[0119] S1: Dispersant A and conductive filler were premixed (premixing temperature: 80°C for 12 hours) and then blended with polyolefin resin, antioxidant, dispersant B, and lubricant in a compound single-screw extruder. The extruder was operated at 400 rpm, with a feeding section temperature of 80°C, a mixing section temperature of 170°C, and an extrusion section temperature of 190°C to obtain a blend.

[0120] S2: The blend obtained in S1 is pelletized by a pelletizer and then dried. The drying process conditions are: drying temperature 50°C, drying time 2h; and a semi-finished product is obtained.

[0121] S3: The semi-finished product obtained in S2 is sent to the post-absorption system for mixing with a crosslinking agent, and then sent to the powder removal system for powder removal to obtain the shielding material. The process conditions of the absorption system are: mixing temperature 60°C, rolling speed 1 rpm, and mixing time 40 minutes.

[0122] Example 2

[0123] By mass, the following ingredients are used: 62 parts polyolefin resin, 34 parts conductive filler, 0.5 parts dispersant A, 1 part dispersant B, 0.7 parts lubricant, 0.8 parts antioxidant, and 1 part crosslinking agent. See Table 2 for the specific selection of raw materials.

[0124] The preparation process is the same as that in Example 1.

[0125] Example 3

[0126] The raw materials are 71 parts by weight of polyolefin resin, 25 parts of conductive filler, 0.2 parts of dispersant A, 0.8 parts of dispersant B, 0.5 parts of lubricant, 1 part of antioxidant, and 1.5 parts of crosslinking agent. See Table 2 for the specific selection of raw materials.

[0127] The preparation process is as follows:

[0128] S1: Dispersant A and conductive filler were premixed (premixing temperature: 80°C for 12 hours) and then blended with polyolefin resin, antioxidant, dispersant B, and lubricant in a compound single-screw extruder. The extruder speed was 300 rpm, the feeding section temperature was 90°C, the mixing section temperature was 200°C, and the extrusion section temperature was 220°C to obtain a blend.

[0129] S2: The blend obtained in S1 is pelletized by a pelletizer and then dried. The drying process conditions are: drying temperature 50°C, drying time 2h; and a semi-finished product is obtained.

[0130] S3: The semi-finished product obtained in S2 is sent to the post-absorption system for cross-linking agent absorption, and then sent to the powder removal system for powder removal to obtain the shielding material. The process conditions of the absorption system are: mixing temperature 60°C, rolling speed 1 rpm, and mixing time 40 minutes.

[0131] Example 4

[0132] The raw materials are 72 parts by weight of polyolefin resin, 24 parts of conductive filler, 0.2 parts of dispersant A, 0.8 parts of dispersant B, 0.5 parts of lubricant, 1 part of antioxidant, and 1.5 parts of crosslinking agent. See Table 2 for the specific selection of raw materials.

[0133] The preparation process is as follows:

[0134] S1: Dispersant A and conductive filler were premixed (premixing temperature: 80°C for 12 hours) and then blended with polyolefin resin, antioxidant, dispersant B, and lubricant in a compound single-screw extruder. The extruder was operated at 300 rpm, with a feeding section temperature of 130°C, a mixing section temperature of 230°C, and an extrusion section temperature of 260°C to obtain a blend.

[0135] S2: The blend obtained in S1 is pelletized by a pelletizer and then dried. The drying process conditions are: drying temperature 50°C, drying time 2h; and a semi-finished product is obtained.

[0136] S3: The semi-finished product obtained in S2 is sent to the post-absorption system for cross-linking agent absorption, and then sent to the powder removal system for powder removal to obtain the shielding material. The process conditions of the absorption system are: mixing temperature 60°C, rolling speed 1 rpm, and mixing time 40 minutes.

[0137] Table 2

[0138]

[0139] Example 5

[0140] The shielding material was prepared according to the method of Example 1, except that the dispersant A-1 was replaced by the dispersant A-4.

[0141] Example 6

[0142] The shielding material was prepared according to the method of Example 1, except that the dispersant A-1 was replaced by dispersant A-2.

[0143] Example 7

[0144] The shielding material was prepared according to the method of Example 1, except that the dispersant A-1 was replaced by the dispersant A-3.

[0145] Example 8

[0146] The shielding material was prepared according to the method of Example 1, except that the amount of dispersant A-1 was 0.75 parts and the amount of dispersant B was 0.75 parts.

[0147] Example 9

[0148] The shielding material was prepared according to the method of Example 1, except that the amount of dispersant A-1 was 0.15 parts and the amount of dispersant B was 1.35 parts.

[0149] Example 10

[0150] A shielding material was prepared according to the method of Example 1, except that, by mass, 61 parts of ethylene butyl acrylate (EBA), 35 parts of acetylene black, 0.1 parts of polystyrene sulfonate A-1, 1.4 parts of polyethylene oxide (PEO), 0.7 parts of zinc stearate, 0.8 parts of antioxidant 1010, and 1 part of di-tert-butyl peroxyisopropylbenzene (BIBP) were used.

[0151] Example 11

[0152] The shielding material was prepared according to the method of Example 1, except that the conductive filler acetylene black was replaced by furnace black-1.

[0153] Example 12

[0154] The shielding material was prepared according to the method of Example 1, except that the conductive filler acetylene black was replaced by furnace black-2.

[0155] Example 13

[0156] A shielding material was prepared according to the method of Example 1, except that in preparation process S1, the polyolefin resin, conductive filler, antioxidant, dispersant A, dispersant B, and lubricant were blended in a compound single-screw extruder. The main engine speed was 400 rpm, the feeding section temperature was 80°C, the mixing section temperature was 170°C, and the extrusion section temperature was 190°C to obtain a blend.

[0157] Example 14

[0158] The shielding material was prepared according to the method of Example 6, except that the dispersant A-2 was replaced by the dispersant A-5.

[0159] Comparative Example 1

[0160] A shielding material was prepared according to the method of Example 1, except that: 75 parts of polyolefin resin and 21 parts of conductive filler were used.

[0161] Comparative Example 2

[0162] A shielding material was prepared according to the method of Example 1, except that the dispersant A-1 was not contained and the amount of dispersant B was 1.5 parts.

[0163] Comparative Example 3

[0164] The shielding material was prepared according to the method of Example 6, except that the dispersant A-2 was replaced by the dispersant D-1.

[0165] Comparative Example 4

[0166] The shielding material was prepared according to the method of Example 1, except that the dispersant A-1 was replaced by the dispersant D-2.

[0167] Comparative Example 5

[0168] A shielding material was prepared according to the method of Example 1, except that dispersant B was not contained and the amount of dispersant A-1 was 1.5 parts.

[0169] Comparative Example 6

[0170] The shielding material was prepared according to the method of Example 1, except that the amount of dispersant A-1 was 2 parts and the amount of dispersant B was 3.5 parts.

[0171] Test Case

[0172] The shielding materials obtained in the examples and comparative examples were pressed into shielding materials (180°C, 15 min). The tensile strength, elongation at break, volume resistivity at room temperature (23°C), volume resistivity at 90°C, and PTC coefficient of the shielding materials were tested. The test results are shown in Table 3.

[0173] Table 3

[0174]

[0175] *Performance indicators: Performance requirements for semi-conductive shielding materials in Appendix B of GB / T 18890.2-2015.

[0176] From the results in Table 3, it can be seen that the shielding material made from the shielding material composition of the embodiment of the present application can meet the requirements of GB / T 18890.2-2015. At the same time, the shielding material prepared in the preferred embodiment of the present invention has an elongation at break higher than 320%, a volume resistivity of less than 13Ω·cm at 23°C, and a volume resistivity of less than 100Ω·cm at 90°C. It can be seen that it has high mechanical properties and low volume resistivity, and the PTC coefficient is also low. There is no surface protrusion larger than 50μm on the surface of the shielding material.

[0177] Compared with Example 1, Comparative Example 1 excessively increased the content of the base resin and reduced the content of the conductive filler. Due to the insufficient conductive filler and the underdeveloped conductive network, the resistivity of the conductive material produced was high, and the bulk resistivity at 90°C did not meet the requirements of GB / T 18890.2-2015.

[0178] Compared with Example 1, Comparative Example 2 did not add dispersant A, resulting in an increase in the resistivity and PTC coefficient of the shielding material and a decrease in the elongation at break of the mechanical property.

[0179] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A shielding material composition, characterized in that: The shielding material composition comprises, by weight: 55-73 parts of polyolefin resin, 23-40 parts of conductive filler, 0.5-2 parts of crosslinking agent, 0.1-1.2 parts of dispersant A, 0.2-2.5 parts of dispersant B, 0.5-3 parts of lubricant, 0.5-2 parts of antioxidant; Wherein, the dispersant A is an anionic dispersant, and the weight average molecular weight of the dispersant A is 10,000-150,000 g / mol; The dispersant B is a nonionic dispersant; The dispersant A is selected from polystyrene sulfonate and / or polymaleic anhydride copolymer; The dispersant B is polyethylene oxide and / or ethylene oxide-propylene oxide block copolymer.

2. The shielding material composition according to claim 1, wherein The weight average molecular weight of the dispersant A is 50,000-100,000 g / mol.

3. The shielding material composition according to claim 1, wherein The degree of sulfonation of the polystyrene sulfonate is greater than or equal to 85 mol %.

4. The shielding material composition according to claim 1, wherein The weight average molecular weight of the dispersant B is 2-3 million g / mol; And / or, the mass ratio of the dispersant A to the dispersant B is 1:1-10.

5. The shielding material composition according to claim 1, wherein The polyolefin resin is selected from ethylene-vinyl acetate copolymer and / or ethylene-acrylate copolymer; and / or, the elongation at break of the polyolefin resin is ≥700%; And / or, the polyolefin resin has a melt index of 5-10 g / 10 min at a temperature of 190° C. and a load of 2.16 kg.

6. The shielding material composition according to claim 1, wherein The conductive filler has an oil absorption value of 150-200 mL / 100 g; And / or, the conductive filler is conductive carbon black and / or carbon nanotubes.

7. The shielding material composition according to claim 6, wherein The average particle size of the conductive carbon black is 30-60 nm.

8. The shielding material composition according to claim 6, wherein The average length of the carbon nanotubes is 1-5 μm, and the aspect ratio is 100-200.

9. The shielding material composition according to claim 1, wherein The cross-linking agent is an organic peroxide; and / or, the lubricant is selected from at least one of zinc stearate, polyethylene wax, silicone oil and microcrystalline wax; And / or, the antioxidant is selected from at least one of amine antioxidants, thioester antioxidants, phosphite antioxidants and hindered phenol antioxidants.

10. A method for preparing a shielding material, characterized in that: The preparation method comprises: S1. Blending the components of the shielding material composition according to any one of claims 1 to 9 except the crosslinking agent to obtain a blend; S2, the blend is pelletized and dried to obtain a semi-finished product; S3. Mixing the semi-finished product with a cross-linking agent to obtain a shielding material.

11. The preparation method according to claim 10, wherein In step S1, the blending conditions include: the temperature T1 of the feeding section of the blending is 80-130°C, the temperature T2 of the mixing section of the blending is 170-260°C, and the temperature T3 of the extrusion section of the blending is 190-250°C; And / or, in step S1, the dispersant A is pre-mixed with the conductive filler and then blended with the polyolefin resin, the dispersant B, the lubricant and the antioxidant.

12. The preparation method according to claim 11, wherein In step S1, T3>T2.

13. The preparation method according to claim 10, wherein In step S3, the cross-linking agent is melted and then mixed with the semi-finished product; And / or, in step S3, the mixing temperature is 55-80° C., and the mixing time is 10-60 min.

14. A shielding material produced by the method according to any one of claims 10 to 13.

15. A shielding material, characterized in that: The shielding material according to claim 14 is made by cross-linking.

16. The shielding material according to claim 15, wherein The tensile strength of the shielding material is greater than or equal to 13 MPa; and / or, the shielding material has an elongation at break greater than or equal to 250%; and / or, the resistivity of the shielding material at 23° C. is less than or equal to 15Ω·cm; And / or, the resistivity of the shielding material at 90° C. is less than or equal to 100Ω·cm.

17. Use of the shielding material composition according to any one of claims 1 to 9, or the shielding material according to claim 14, or the shielding material according to claim 15 or 16 in a high-voltage power cable.

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