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

Abstract

The invention relates to the technical field of power cables, and discloses a shielding material composition, a shielding material and a preparation method thereof, and a shielding material and application thereof, the shielding material composition comprises the following components by weight: 55-73 parts of 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 dispersing agent A is an anionic dispersing agent, and the weight-average molecular weight of the dispersing agent A is 1-150 thousand g / mol; the dispersing agent B is a nonionic dispersing agent. When the proportion of the polyolefin resin, the conductive filler, the cross-linking agent, the dispersing agent, the lubricating agent and the antioxidant in the shielding material composition meets the range required by the invention, the prepared shielding material has the characteristics of smooth surface, low volume resistivity, high mechanical property and low PTC (Positive Temperature Coefficient) coefficient.

Description

Technical Field

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

[0002] The surface finish of the extruded product of the semiconductive shielding material is a key index for evaluating the quality of the semiconductive shielding material, which determines its applied voltage level. High-voltage cables have extremely strict requirements for the surface finish of the semiconductive shielding layer. Tiny impurities or defects on its surface may cause partial discharge, initiate the growth of electrical trees, and pose potential safety hazards. At the same time, the high-voltage semiconductive shielding material should maintain high mechanical properties, low volume resistivity and positive temperature resistance effect to ensure its effect of supporting and homogenizing the electric field. The surface finish evaluation method mainly involves observing the extruded strip-shaped sample and statistically analyzing the height and width of the surface protrusions. Therefore, the semiconductive shielding material for high-voltage cables needs to ensure high surface finish, high mechanical properties, and low volume resistivity and positive temperature resistance effect, which is also one of the key problems to be solved in the preparation of shielding materials for high-voltage cables. At present, the surface finish of the semiconductive shielding material is low, the mechanical properties are low, and the volume resistivity and positive temperature resistance effect are high, making it difficult to meet the requirements of cable materials under high voltage levels. Summary of the Invention

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

[0004] To achieve the above purpose, the first aspect of the present invention provides a shielding material composition, wherein the shielding material composition includes 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; Among them, the dispersant A is an anionic dispersant, and the weight-average molecular weight of the dispersant A is 1 - 150,000 g / mol; The dispersant B is a non-ionic dispersant.

[0005] The second aspect of the present invention provides a preparation method of a shielding material, wherein the preparation method includes: S1. Blend the components in the above shielding material composition except the crosslinking agent to obtain a blend; S2. After pelletizing and drying the blend, a semi-finished material is obtained. S3. After mixing the semi-finished material with a crosslinking agent, a shielding material is obtained.

[0006] The third aspect of the present invention provides a shielding material made by the above method.

[0007] The fourth aspect of the present invention provides a shielding material, which is made by crosslinking the above shielding material.

[0008] The fifth aspect of the present invention provides an application of the above shielding material composition, or the above shielding material, or the above shielding material in high-voltage power cables.

[0009] Through the above technical solutions, the shielding material composition, shielding material and preparation method, shielding material and its application provided by the present invention have the following beneficial effects.

[0010] The shielding material composition of the present invention contains an anionic dispersant and a non-ionic dispersant with specific molecular weights. Under the synergistic effect of the two dispersants, it can effectively prevent the self-aggregation of conductive fillers, making the conductive fillers more fully dispersed and effectively distributed in the polyolefin resin; the prepared shielding material has a developed conductive network and a smooth surface, without protrusions and mechanical stress points caused by the aggregation of conductive fillers; when the ratios of polyolefin resin, conductive filler, crosslinking agent, dispersant, lubricant and antioxidant in the shielding material composition meet the ranges required by the present invention, the prepared shielding material has the characteristics of a smooth surface, low volume resistivity, high mechanical properties and low PTC coefficient. Detailed Embodiments

[0011] The endpoints and any values disclosed in this article for a range are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, between the endpoints of each range and a single point value, and between single point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0012] The first aspect of the present invention provides a shielding material composition, wherein 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 non-ionic dispersant.

[0013] In the present invention, the shielding material composition contains an anionic dispersant and a non-ionic dispersant with specific molecular weights. Under the synergistic effect of the two dispersants, it can effectively prevent the self-aggregation of the conductive filler, making the conductive filler more fully dispersed and effectively distributed in the polyolefin resin. The prepared shielding material has a developed conductive network, a smooth surface, and no protrusions and mechanical stress points caused by the aggregation of the conductive filler. When the ratios of the polyolefin resin, conductive filler, crosslinking agent, dispersant, lubricant, and antioxidant in the shielding material composition meet the ranges required by the present invention, the prepared shielding material has the characteristics of a smooth surface, low volume resistivity, high mechanical properties, and a low positive temperature coefficient.

[0014] In the present invention, when the weight-average molecular weight of dispersant A satisfies 10,000 - 150,000 g / mol, it can cooperate synergistically with the ionic dispersant B to make the prepared shielding material have the characteristics of a smooth surface, low volume resistivity, high mechanical properties, and a low PTC coefficient. The weight-average molecular weight of the dispersant A can be any range formed by any two values among 10,000, 15,000, 20,000, 30,000, 50,000, 80,000, 100,000, 120,000, 130,000, 140,000, 150,000 g / mol and the values within the range.

[0015] Further, 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 part 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.

[0016] Further, the weight-average molecular weight of the dispersant A is 50,000 - 100,000 g / mol.

[0017] According to the present invention, the dispersant A is selected from polystyrene sulfonate and / or poly maleic anhydride copolymer.

[0018] In the present invention, when the type of the dispersant A in the shielding material composition meets the above range, the conductive filler can be better dispersed in the polyolefin resin, and the prepared shielding material has the characteristics of a smooth surface, low volume resistivity, high mechanical properties, and a low positive temperature coefficient.

[0019] In the present invention, in the poly maleic anhydride copolymer, the comonomer can be 1-octene or 1-octadecene. In the present invention, the content of the structural unit from the comonomer in the poly maleic anhydride copolymer is 70 - 90 mol%.

[0020] Further, the dispersant A is polystyrene sulfonate.

[0021] According to a preferred embodiment of the present invention, the sulfonation degree of the polystyrene sulfonate is greater than or equal to 85 mol%. When the sulfonation degree of the polystyrene sulfonate meets the above range, the shielding material made of the above composition has higher mechanical properties, lower resistivity and positive temperature coefficient. Further, the sulfonation degree of the polystyrene sulfonate is greater than or equal to 95 mol%.

[0022] According to the present invention, the weight-average molecular weight of the dispersant B is 2 - 3 million g / mol, and it can be any range formed by any two values among 2, 5, 10, 15, 20, 25, 30, 50, 75, 80, 100, 130, 150, 180, 200, 220, 250, 280, 3 million g / mol and the values within the range.

[0023] In the present invention, when the molecular weight of the dispersant B meets the above range, it has the characteristic of inhibiting the aggregation of conductive fillers, bringing the effect of uniform dispersion of conductive carbon black.

[0024] Further, the weight-average molecular weight of the dispersant B is 2 - 2 million g / mol.

[0025] According to the present invention, the dispersant B is polyethylene oxide and / or ethylene oxide - propylene oxide block copolymer.

[0026] In the present invention, in the ethylene oxide - propylene oxide block copolymer, ethylene oxide is 10 - 20 wt% of the total weight of the copolymer, and propylene oxide is 80 - 90 wt% of the total weight of the copolymer.

[0027] In the present invention, when the shielding material composition contains the above types of dispersant B, it has the characteristic of inhibiting the aggregation of conductive fillers, bringing the effect of uniform dispersion of conductive carbon black.

[0028] Further, the dispersant B is polyethylene oxide.

[0029] According to the present invention, the mass ratio of the dispersant A to the dispersant B is 1:1 - 10, and it can be any range formed by any two values among 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:5, 1:6, 1:8, 1:9, 1:10 and the values within the range.

[0030] In the present invention, when the mass ratio of the dispersant A to the dispersant B meets the above range, it has the characteristic of improving the dispersibility of conductive fillers, bringing the effects of high conductivity, good tensile properties and smooth surface of the shielding material.

[0031] Further, the mass ratio of the dispersant A to the dispersant B is 1:2 - 5.

[0032] According to the present invention, the polyolefin resin is selected from ethylene-vinyl acetate copolymer and / or ethylene-acrylate copolymer.

[0033] In the present invention, when the shielding material composition contains the above-mentioned types of polyolefin resins, the conductive filler can be better dispersed in the polyolefin resin, and the shielding material made of the above composition has the characteristics of smooth surface, low volume resistivity, high mechanical properties, and low positive temperature coefficient.

[0034] 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%; the molar content of ethyl acrylate in the ethylene-ethyl acrylate copolymer is 10-20%.

[0035] Further, the polyolefin resin is ethylene-butyl acrylate copolymer.

[0036] According to the present invention, the elongation at break of the polyolefin resin is ≥700%.

[0037] Further, the elongation at break of the polyolefin resin is ≥800%.

[0038] Furthermore, the elongation at break of the polyolefin resin is ≥900%.

[0039] 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 5-10 g / 10 min, and can be any range formed by any two values among 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, 10 g / 10 min and the values within the range.

[0040] Further, the melt index of the polyolefin resin at a temperature of 190 °C and a load of 2.16 kg is 6-8 g / 10 min.

[0041] According to the present invention, the oil absorption value of the conductive filler is 150-200 mL / 100 g, and can be any range formed by any two values among 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, 200 mL / 100 g and the values within the range.

[0042] In the present invention, when the oil absorption value of the conductive filler meets the above range, it indicates that the conductive filler has a relatively high specific surface area and structure degree; the shielding material made of this composition has a lower resistivity and a positive temperature coefficient.

[0043] Furthermore, the oil absorption value of the conductive filler is 180 - 200 mL / 100 g.

[0044] According to the present invention, the conductive filler is conductive carbon black and / or carbon nanotubes.

[0045] In the present invention, when the composition contains the above types of conductive fillers, the shielding material made of the above composition has the characteristic of high conductivity.

[0046] Furthermore, the conductive carbon black is furnace black and / or acetylene black.

[0047] According to the present invention, the average particle size of the conductive carbon black is 30 - 60 nm, and it can be any range formed by any two values among 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm and the values within the range.

[0048] In the present invention, when the average particle size of the conductive carbon black meets the above range, the dispersion of the conductive filler in the shielding material made of the above composition is better, with a developed conductive path, the shielding material has high conductivity, and high mechanical properties.

[0049] Furthermore, the average particle size of the conductive carbon black is 30 - 50 nm.

[0050] 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.

[0051] According to the present invention, the crosslinking agent is an organic peroxide.

[0052] Furthermore, the crosslinking agent is selected from bis(tert - butylperoxyisopropyl)benzene (BIBP) and / or dicumyl peroxide (DCP).

[0053] According to the present invention, the lubricant is selected from at least one of zinc stearate, polyethylene wax, silicone oil, and microcrystalline wax.

[0054] Furthermore, the lubricant is selected from at least one of zinc stearate, polyethylene wax, and microcrystalline wax.

[0055] According to the present invention, the antioxidant is selected from at least one of amine antioxidants, thioester antioxidants, phosphite antioxidants, and hindered phenol antioxidants.

[0056] In the present invention, there is no specific limitation on the specific type of antioxidant. 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 antioxidant is antioxidant 168 and antioxidant 1010.

[0057] In a second aspect of the present invention, a method for preparing a shielding material is provided, wherein the preparation method includes: (1) Blending the components of the above shielding material composition except the crosslinking agent to obtain a blend; (2) After pelletizing and drying the blend, a semi-finished material is obtained; (3) Mixing the semi-finished material with the crosslinking agent to obtain the shielding material.

[0058] According to the present invention, in step S1, the conditions for blending include: the temperature T1 of the feeding section for blending is 80 - 130 °C, the temperature T2 of the mixing section for blending is 170 - 260 °C, and the temperature T3 of the extrusion section for blending is 190 - 250 °C.

[0059] 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.

[0060] Furthermore, in step S1, T3 > T2.

[0061] In the present invention, in step S1, the conditions for blending include: the rotation speed of the extruder is 300 - 600 rpm.

[0062] According to the present invention, in step S1, dispersant A is pre-mixed with the conductive filler and then blended with the polyolefin resin, dispersant B, lubricant, and antioxidant.

[0063] In the present invention, when the above step-by-step mixing method is adopted, it has the characteristics of inhibiting the self-aggregation of the conductive filler and at the same time ensuring good dispersion of the filler in the matrix, bringing about the effects of a well-developed network formed by the conductive filler, high conductivity (low resistivity) of the shielding material, excellent tensile properties, and a smooth surface.

[0064] In the present invention, in step S1, the temperature for pre-mixing is 60 - 100 °C, and the time for pre-mixing is 5 - 12 h.

[0065] In the present invention, in step S2, there is no specific limitation on the pelletizing method, and pelletizing can be carried out in a conventional manner in the art. For example, pelletizing can be performed by a pelletizer.

[0066] In the present invention, there are no special limitations on the drying conditions in step S2, and conventional drying conditions in the art can be adopted. Preferably, the drying temperature is 50 - 60 °C, and the drying time is 1 - 2 h.

[0067] According to the present invention, in step S3, after the crosslinking agent is melted, it is mixed with the semi-finished product material.

[0068] According to the present invention, in step S3, the mixing temperature is 55 - 80 °C, and the mixing time is 10 - 60 min.

[0069] Furthermore, in step S3, the mixing temperature is 60 - 70 °C, and the mixing time is 10 - 40 min.

[0070] In the present invention, after the crosslinking agent is melted, it is mixed with the semi-finished product material in a post-absorption device. Preferably, the rolling speed of the post-absorption device is 1 - 10 rpm, preferably 1 - 5 rpm.

[0071] The third aspect of the present invention provides a shielding material made by the above method.

[0072] The fourth aspect of the present invention provides a shielding material, which is made by crosslinking the above shielding material.

[0073] According to the present invention, the tensile strength of the shielding material is greater than or equal to 13 MPa.

[0074] According to the present invention, the elongation at break of the shielding material is greater than or equal to 250%.

[0075] According to the present invention, the resistivity of the shielding material at 23 °C is less than or equal to 15 Ω·cm.

[0076] Furthermore, the resistivity of the shielding material at 23 °C is less than or equal to 10 Ω·cm.

[0077] According to the present invention, the resistivity of the shielding material at 90 °C is less than or equal to 100 Ω·cm.

[0078] Furthermore, the resistivity of the shielding material at 90 °C is less than or equal to 50 Ω·cm.

[0079] In the present invention, the positive temperature coefficient of the shielding material is less than or equal to 8.

[0080] 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.

[0081] Furthermore, the positive temperature coefficient of the shielding material is less than or equal to 5.

[0082] In the present invention, the shielding material is preferably used for direct current.

[0083] The fifth aspect of the present invention provides an application 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.

[0084] The present invention will be described in detail below through examples.

[0085] In the following examples, the volume resistivity was measured as follows: The measurement was carried out according to the method specified in Part 3 of GB / T 3048.3-2007, Test for Volume Resistivity of Semiconducting Rubber and Plastic Materials. Positive temperature coefficient (PTC coefficient): The ratio of the resistivity of the shielding material at 90 °C to the resistivity at 23 °C. Tensile strength and elongation at break: The measurement was carried out according to the method specified in GB / T 1040.3-2022, and the specimen was a 5A type specimen. Surface protrusions: The test was carried out under an optical scanning device with a high-resolution camera. The scanning speed was 0.05 m 2 / min. The surface of the specimen tape was scanned by the high-resolution camera, and the size and number of surface protrusions were characterized by the results of a sample with a total surface area of about 1 m 2 The number of surface protrusions with a height greater than or equal to 50 μm was recorded. Average particle size of conductive carbon black: Obtained by transmission electron microscopy (TEM). Oil absorption value: The measurement was carried out according to the method specified in GB / T 3780.2-2017. Ethylene-vinyl acetate copolymer (EVA): A commercially available product with the brand name E1770 from Repsol. The melt index at 190 °C and 2.16 kg was 7 g / 10 min, the elongation at break was 800%, and the density was 0.924 g / cm 3 , and the molar content of butyl acrylate was 17%. Ethylene-butyl acrylate copolymer (EBA): A commercially available product with the brand name 2715 from DuPont. The melt index at 190 °C and 2.16 kg was 7 g / 10 min, the elongation at break was 800%, and the density was 0.93 g / cm 3 , and the molar content of ethyl acrylate was 15%. Ethylene-ethyl acrylate copolymer (EEA): A product with the brand name EVA P2805 from Mitsui. The melt index at 190 °C and 2.16 kg was 7 g / 10 min, the elongation at break was 800%, and the density was 0.93 g / cm 3 , and the molar content of vinyl acetate was 28%. Conductive filler: acetylene black, Denka brand DENKA BLACK, oil absorption value is 200mL / 100g, average particle size is 45nm; Conductive filler: furnace black-1, brand ENSACO 250G from Yiruishi Company, oil absorption value is 185mL / 100g, average particle size is 36nm; Conductive filler: furnace black-2, Cabot brand VXC500, oil absorption value is 140mL / 100g, average particle size is 35nm; 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; The types and parameters of dispersant A are shown in Table 1.

[0086] Table 1

[0087] Dispersant B: polyethylene oxide (PEO), P101345 from Aladdin, with a weight average molecular weight of 2 million g / mol.

[0088] Dispersant B: ethylene oxide-propylene oxide block copolymer (ethylene oxide is 15wt% of the total weight of the copolymer, and propylene oxide is 85wt% of the total weight of the copolymer), BASF Tetronic 901, with a weight average molecular weight of 20,000 g / mol.

[0089] Other raw materials used in the examples and comparative examples are all commercially available.

[0090] Example 1 By mass, the polyolefin resin is 61 parts, the conductive filler is 35 parts, the dispersant A is 0.5 parts, the dispersant B is 1 part, the lubricant is 0.7 parts, the antioxidant is 0.8 parts and the cross-linking agent is 1 part. The specific selection of raw materials is shown in Table 2.

[0091] The preparation process is as follows: S1: After premixing dispersant A and conductive filler (premixing temperature is 80℃, time is 12h), blend with polyolefin resin, antioxidant, dispersant B and lubricant in a compound single screw extruder. The main engine speed is 400rpm, the feeding section temperature is 80℃, the mixing section temperature is 170℃, and the extrusion section temperature is 190℃ to obtain a blend; 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. S3: Feed the semi-finished material obtained in S2 into the post-absorption system for cross-linking agent mixing, then feed it into the powder removal system, and obtain the shielding material after powder removal. The process conditions of the absorption system are: the mixing temperature is 60 °C, the rolling speed is 1 rpm, and the mixing time is 40 min.

[0092] Example 2 By mass, 62 parts of polyolefin resin, 34 parts of conductive filler, 0.5 part of dispersant A, 1 part of dispersant B, 0.7 part of lubricant, 0.8 part of antioxidant, and 1 part of cross-linking agent. The specific selection of raw materials is shown in Table 2.

[0093] The preparation process is the same as that of Example 1.

[0094] Example 3 By mass, 71 parts of polyolefin resin, 25 parts of conductive filler, 0.2 part of dispersant A, 0.8 part of dispersant B, 0.5 part of lubricant, 1 part of antioxidant, and 1.5 parts of cross-linking agent. The specific selection of raw materials is shown in Table 2.

[0095] The preparation process is as follows: S1: Pre-mix dispersant A with the conductive filler (the pre-mixing temperature is 80 °C and the time is 12 h), then co-mix with polyolefin resin, antioxidant, dispersant B, and lubricant in a double-screw single-screw extruder. The main machine speed is 300 rpm, the feeding section temperature is 90 °C, the mixing section temperature is 200 °C, and the extrusion section temperature is 220 °C to obtain a blend; S2: Granulate the blend obtained in S1 through a granulator, and then conduct a drying treatment. The drying process conditions are: the drying temperature is 50 °C and the drying time is 2 h; obtain the semi-finished material; S3: Feed the semi-finished material obtained in S2 into the post-absorption system for cross-linking agent absorption, then feed it into the powder removal system, and obtain the shielding material after powder removal. The process conditions of the absorption system are: the mixing temperature is 60 °C, the rolling speed is 1 rpm, and the mixing time is 40 min.

[0096] Example 4 By mass, 72 parts of polyolefin resin, 24 parts of conductive filler, 0.2 part of dispersant A, 0.8 part of dispersant B, 0.5 part of lubricant, 1 part of antioxidant, and 1.5 parts of cross-linking agent. The specific selection of raw materials is shown in Table 2.

[0097] The preparation process is as follows: S1: Pre-mix dispersant A with the conductive filler (the pre-mixing temperature is 80 °C and the time is 12 h), then co-mix with polyolefin resin, antioxidant, dispersant B, and lubricant in a double-screw single-screw extruder. The main machine speed is 300 rpm, the feeding section temperature is 130 °C, the mixing section temperature is 230 °C, and the extrusion section temperature is 260 °C to obtain a blend; S2: After the blend obtained in S1 is pelletized by a pelletizer, it is subjected to a drying treatment. The drying process conditions are: drying temperature 50 °C, drying time 2 h; a semi-finished material is obtained. S3: The semi-finished material obtained in S2 is fed into a post-absorption system for cross-linking agent absorption, and then into a powder removal system. After powder removal, a shielded material is obtained. The process conditions of the absorption system are: mixing temperature 60 °C, rolling speed 1 rpm, mixing time 40 min.

[0098] Table 2

[0099] Example 5 The shielded material is prepared according to the method of Example 1, except that dispersant A-1 is replaced by dispersant A-4.

[0100] Example 6 The shielded material is prepared according to the method of Example 1, except that dispersant A-1 is replaced by dispersant A-2.

[0101] Example 7 The shielded material is prepared according to the method of Example 1, except that dispersant A-1 is replaced by dispersant A-3.

[0102] Example 8 The shielded material is prepared according to the method of Example 1, except that there are 0.75 parts of dispersant A-1 and 0.75 parts of dispersant B.

[0103] Example 9 The shielded material is prepared according to the method of Example 1, except that there are 0.15 parts of dispersant A-1 and 1.35 parts of dispersant B.

[0104] Example 10 The shielded material is prepared according to the method of Example 1, except that by mass, there are 61 parts of ethylene-butyl acrylate (EBA), 35 parts of acetylene black, 0.1 part of polystyrene sulfonate A-1, 1.4 parts of polyethylene oxide (PEO), 0.7 part of zinc stearate, 0.8 part of antioxidant 1010, and 1 part of bis(tert-butylperoxyisopropyl)benzene (BIBP).

[0105] Example 11 The shielded material is prepared according to the method of Example 1, except that the conductive filler acetylene black is replaced by furnace black-1.

[0106] Example 12 The shielded material is prepared according to the method of Example 1, except that the conductive filler acetylene black is replaced by furnace black-2.

[0107] Example 13 The shielding material was prepared according to the method of Example 1, except that in the 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 machine 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.

[0108] Example 14 The shielding material was prepared according to the method of Example 6, except that dispersant A-2 was replaced with dispersant A-5.

[0109] Comparative Example 1 The shielding material was prepared according to the method of Example 1, except that there were 75 parts of polyolefin resin and 21 parts of conductive filler.

[0110] Comparative Example 2 The shielding material was prepared according to the method of Example 1, except that dispersant A-1 was not included and there were 1.5 parts of dispersant B.

[0111] Comparative Example 3 The shielding material was prepared according to the method of Example 6, except that dispersant A-2 was replaced with dispersant D-1.

[0112] Comparative Example 4 The shielding material was prepared according to the method of Example 1, except that dispersant A-1 was replaced with dispersant D-2.

[0113] Comparative Example 5 The shielding material was prepared according to the method of Example 1, except that dispersant B was not included and there were 1.5 parts of dispersant A-1.

[0114] Comparative Example 6 The shielding material was prepared according to the method of Example 1, except that there were 2 parts of dispersant A-1 and 3.5 parts of dispersant B.

[0115] Test Example The shielding materials obtained in the examples and comparative examples were made into shielding materials by pressing plates (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.

[0116] Table 3

[0117] *Performance index: Performance requirements for semi-conductive shielding materials in Appendix B of GB / T 18890.2-2015.

[0118] As can be seen from the results in Table 3, the shielding material made of 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 elongation at break of the shielding material prepared by the preferred embodiment of the present invention is higher than 320%, the volume resistivity at 23°C is less than 13 Ω·cm, and the volume resistivity at 90°C is less than 100 Ω·cm. It can be seen that it has high mechanical properties and low volume resistivity, and the PTC coefficient is also low. There are no surface protrusions larger than 50 μm on the surface of the shielding material.

[0119] Compared with Example 1, in Comparative Example 1, the content of the matrix resin was excessively increased and the content of the conductive filler was decreased. Due to too little conductive filler, the conductive network was not developed, and the resistivity of the conductive material prepared was high, and the volume resistivity at 90°C did not meet the requirements of GB / T 18890.2-2015.

[0120] Compared with Example 1, in Comparative Example 2, dispersant A was not added, 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 properties.

[0121] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope 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; Among them, the dispersant A is an anionic dispersant, and the weight - average molecular weight of the dispersant A is 1 - 150,000 g / mol; The dispersant B is a non - ionic dispersant.

2. The shielding material composition according to claim 1, wherein The weight - average molecular weight of the dispersant A is 5 - 100,000 g / mol; And / or, the dispersant A is selected from polystyrene sulfonate and / or maleic anhydride copolymer; And / or, the sulfonation degree of the polystyrene sulfonate is greater than or equal to 85 mol%.

3. The shielding material composition according to claim 1, wherein The weight - average molecular weight of the dispersant B is 2 - 3,000,000 g / mol; And / or, the dispersant B is polyethylene oxide and / or ethylene oxide - propylene oxide block copolymer; And / or, the mass ratio of the dispersant A to the dispersant B is 1:1 - 10.

4. 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 melt index of the polyolefin resin at a temperature of 190°C and a load of 2.16 kg is 5 - 10 g / 10 min.

5. The shielding material composition according to claim 1, wherein The oil absorption value of the conductive filler is 150 - 200 mL / 100 g; And / or, the conductive filler is conductive carbon black and / or carbon nanotube; And / or, the average particle size of the conductive carbon black is 30 - 60 nm; And / or, the average length of the carbon nanotube is 1 - 5 μm, and the aspect ratio is 100 - 200.

6. The shielding material composition according to claim 1, wherein The crosslinking 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.

7. A preparation method of 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 - 6 except the crosslinking agent to obtain a blend; S2. After pelletizing and drying the blend, a semi - finished material is obtained; S3. Mixing the semi - finished material with the crosslinking agent to obtain a shielding material.

8. The preparation method according to claim 7, wherein, In step S1, the blending conditions include: the temperature T1 of the feeding section for blending is 80 - 130°C, the temperature T2 of the mixing section for blending is 170 - 260°C, and the temperature T3 of the extrusion section for blending is 190 - 250°C; And / or, in step S1, T3 > T2; And / or, in step S1, the dispersant A is pre - mixed with the conductive filler and then blended with the polyolefin resin, dispersant B, lubricant and antioxidant.

9. The preparation method according to claim 7, wherein, In step S3, the crosslinking agent is melted and then mixed with the semi - finished material; And / or, in step S3, the mixing temperature is 55 - 80°C, and the mixing time is 10 - 60 min.

10. A shielding material made by the method according to any one of claims 7 - 9.

11. A shielding material, characterized in that, Made by cross - linking the shielding material according to claim 10.

12. The shielding material according to claim 11, wherein, The tensile strength of the shielding material is greater than or equal to 13 MPa; and / or, the elongation at break of the shielding material is greater than or equal to 250%; and / or, the resistivity of the shielding material at 23 °C is less than or equal to 15 Ω·cm; and / or, the resistivity of the shielding material at 90 °C is less than or equal to 100 Ω·cm.

13. Application of the shielding material composition according to any one of claims 1-6, or the shielding material according to claim 10, or the shielding material according to claim 11 or 12 in a high-voltage power cable.

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