Semiconductive shielding material composition and application, semiconductive shielding material and preparation method and application thereof

Abstract

The present invention relates to the technical field of power cables, and discloses a semiconductive shielding material composition and application, a semiconductive shielding material and its preparation method and application. The composition includes: a base resin, an amino polymer grafted carbon nanotube, a conductive carbon black and a cross-linking agent; wherein the amount of the base resin is 55-85 parts by weight, the amount of the amino polymer grafted carbon nanotube is 0.1-10 parts by weight, the amount of the conductive carbon black is 5-40 parts by weight, and the amount of the cross-linking agent is 0.5-2 parts by weight; the grafting rate of the amino polymer in the amino polymer grafted carbon nanotube is 5-15wt%. In the composition, the carbon nanotube grafted with a specific content of amino polymer is used as a second filler, and components such as conductive carbon black and base resin are coordinated with each other. While reducing the amount of conductive filler, the PTC effect of the semiconductive shielding material prepared by the composition is improved, and the mechanical properties and electrical properties of the semiconductive shielding material are improved.

Description

Technical Field

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

[0002] The semiconductive shielding layer in high-voltage cables is located between the conductor and insulation layer. It serves to uniformly distribute the electric field within the cable structure and reduce the gap between the metal core and the insulation layer. For power transmission cables with rated voltages above 1.8 / 3.0 kV, cables using cross-linked polyethylene (XLPE) and polyethylene (PE) insulation must have a conductor shield to uniformly distribute the electric field. Semiconductive shielding materials consist of a polymer matrix and conductive fillers. Within the temperature range of 23-90°C, the volume resistivity of semiconductive composite materials gradually increases with increasing temperature, exhibiting a positive temperature coefficient (PTC) property. The PTC coefficient is often expressed as the ratio of the resistivity (or maximum resistivity) at 90°C to the resistivity at 23°C. This PTC effect is generally believed to be caused by a mismatch in the thermal expansion coefficients of the polymer matrix and the conductive filler. At low temperatures, the conductive filler forms a conductive network throughout the matrix, resulting in low material resistance. As the temperature rises, the greater thermal expansion coefficient of the polymer matrix increases the distance between the conductive filler particles, disrupting the conductive network and increasing the resistance. When the material cools, the polymer shrinks, the distance between the conductive filler particles decreases, and the conductive network is rebuilt, restoring conductivity. The PTC effect has a significant negative impact on the semi-conductive shielding layer, which is mainly reflected in three aspects. First, as the resistivity of the semi-conductive layer increases, its ability to uniformly distribute the electric field weakens, and the semi-conductive layer cannot play its original role. Second, as the resistivity of the semi-conductive layer increases, its heat generation also increases, causing local overheating and interface melting, which seriously threatens the safety of the cable. Third, due to the increased heat generation of the semi-conductive layer, power losses during transportation increase. Therefore, for the stable operation of the cable, the PTC effect of the semi-conductive layer must be weakened.

[0003] Carbon nanotubes (CNTs) are one-dimensional carbon nanomaterials composed of carbon atoms, similar to graphene nanosheets, with a tubular structure. SWCNTs typically have diameters between 0.5 and 3 nm, while MWCNTs range from a few to tens of nanometers. Their conductivity is significantly superior to that of materials like graphene and carbon black, and the thinner the tube, the longer it is. By introducing a second conductive filler with a large aspect ratio, CNTs are an effective way to reduce the carbon black filler content and mitigate the PTC effect of semiconductive shielding materials. However, the one-dimensional CNT tubular structure is prone to entanglement in the matrix resin, making it difficult to form an effective conductive network within the matrix. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem of high PTC effect of semi-conductive shielding materials for medium and high voltage cables in the prior art, and to provide a semi-conductive shielding material composition and application, a semi-conductive shielding material and its preparation method and application. In the composition, carbon nanotubes grafted with a specific content of amino polymer are used as the second filler, which cooperates with conductive carbon black and matrix resin and other components. While reducing the amount of conductive filler, the PTC effect of the semi-conductive shielding material prepared by the composition is improved, and the mechanical properties and electrical properties of the semi-conductive shielding material are improved.

[0005] In order to achieve the above object, the first aspect of the present invention provides a semiconductive shielding material composition, wherein the composition comprises:

[0006] Base resin, amino polymer grafted carbon nanotubes, conductive carbon black and crosslinking agent;

[0007] Among them, the amount of the base resin is 55-85 parts by weight, the amount of the amino polymer grafted carbon nanotubes is 0.1-10 parts by weight, the amount of the conductive carbon black is 5-40 parts by weight, and the amount of the cross-linking agent is 0.5-2 parts by weight; the grafting rate of the amino polymer in the amino polymer grafted carbon nanotubes is 5-15wt%.

[0008] The second aspect of the present invention provides a semiconductive shielding material prepared from the above-mentioned semiconductive shielding material composition.

[0009] A third aspect of the present invention provides a method for preparing the above-mentioned semiconductive shielding material, wherein the preparation method comprises:

[0010] S1. Mixing, extruding, and granulating the components of the semiconductive shielding material composition except the crosslinking agent to obtain a granular material;

[0011] S2. Mixing and absorbing the granular material and a cross-linking agent to obtain the semi-conductive shielding material.

[0012] A fourth aspect of the present invention provides a use of the semiconductor shielding material composition or the semiconductor shielding material in a high-voltage cable.

[0013] Through the above technical solution, the semi-conductive shielding material composition and application, the semi-conductive shielding material and its preparation method and application provided by the present invention achieve the following beneficial effects:

[0014] The semi-conductive shielding material composition provided by the present invention uses carbon nanotubes grafted with a specific content of amino polymers as the second filler and combined with conductive carbon black. The one-dimensional carbon nanotubes effectively bridge adjacent carbon black molecules. The amino polymer has large steric hindrance, which can effectively avoid the entanglement of the carbon nanotubes. The organic groups in the polymer enhance the compatibility of the carbon nanotubes with the matrix resin; a more complete conductive network is formed, which greatly improves the PTC effect of the semi-conductive shielding material prepared from the composition and enhances the mechanical and electrical properties of the shielding material.

[0015] Furthermore, by controlling the ball milling speed, temperature and time, the grafting rate of the amino polymer on the carbon nanotubes can be effectively controlled within 5wt%-15wt%, which simplifies the modification method of the carbon nanotubes. At the same time, by controlling the grafting rate, the interfacial compatibility of the carbon nanotubes with weak polar resins such as ethylene butyl acrylate copolymer (EBA) and ethylene vinyl acetate copolymer (EVA) can be effectively improved. While ensuring the structural stability of the carbon nanotubes, the electrical properties of the semi-conductive shielding material prepared from the composition containing the amino polymer grafted carbon nanotubes are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the infrared spectrum of the amino polymer grafted carbon nanotubes and carbon nanotubes prepared in Preparation Example 1. 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 semiconductive shielding material composition, wherein the composition comprises:

[0019] Base resin, amino polymer grafted carbon nanotubes, conductive carbon black and crosslinking agent;

[0020] Among them, the amount of the base resin is 55-85 parts by weight, the amount of the amino polymer grafted carbon nanotubes is 0.1-10 parts by weight, the amount of the conductive carbon black is 5-40 parts by weight, and the amount of the cross-linking agent is 0.5-2 parts by weight; the grafting rate of the amino polymer in the amino polymer grafted carbon nanotubes is 5-15wt%.

[0021] In the present invention, the semi-conductive shielding material composition uses carbon nanotubes grafted with a specific content of amino polymers as the second filler and combined with conductive carbon black. The one-dimensional carbon nanotubes effectively bridge adjacent carbon black molecules. The amino polymers have large steric hindrance and can effectively avoid the entanglement of carbon nanotubes. The organic groups in the polymer enhance the compatibility of the carbon nanotubes with the matrix resin; a more complete and stable conductive network is formed, which inhibits the destruction of the conductive network at high temperature, greatly improves the PTC effect of the semi-conductive shielding material prepared from the composition, and improves the mechanical properties and electrical properties of the semi-conductive shielding material.

[0022] In the present invention, by controlling the grafting rate of the amino polymer on the surface of the carbon nanotubes within the range of 5-15wt%, the compatibility of the carbon nanotubes with the matrix resin can be improved while ensuring the conductivity of the carbon nanotubes. When the grafting rate of the amino polymer is too low, the compatibility of the carbon nanotubes with the matrix resin is poor, making it difficult to form a complete conductive network therein. When the grafting rate of the amino polymer is too high, the intrinsic structure of the carbon nanotubes is destroyed. At the same time, excessive grafting of the non-conductive polymer also leads to a significant decrease in the conductivity of the carbon nanotubes, ultimately deteriorating the electrical performance of the semi-conductive shielding material obtained thereby.

[0023] Furthermore, in the present invention, when the amounts of the matrix resin, amino polymer-grafted carbon nanotubes, conductive carbon black, and crosslinking agent in the semiconductive shielding material composition are controlled to meet the aforementioned ranges, the components are synergistically compounded and mutually regulated, resulting in a synergistic improvement in the electrical properties of the composition and the mechanical properties of the semiconductive shielding material. Specifically, the composition of the present invention can enhance and improve both the mechanical properties and the PTC effect of the semiconductive shielding material without increasing the total amount of conductive filler (including amino polymer-grafted carbon nanotubes and conductive carbon black).

[0024] In a preferred embodiment of the present invention, the amount of the base resin is 60-80 parts by weight, the amount of the amino polymer grafted carbon nanotubes is 0.5-8 parts by weight, the amount of the conductive carbon black is 15-35 parts by weight, and the amount of the crosslinking agent is 0.8-1.5 parts by weight.

[0025] In a preferred embodiment of the present invention, the grafting rate of the amino polymer in the amino polymer-grafted carbon nanotubes is 7-12 wt %.

[0026] According to the present invention, the amino polymer in the amino polymer-grafted carbon nanotubes is selected from polyacrylamide and / or polyethyleneimine.

[0027] In the present invention, the flexible, long molecular chains of the aforementioned specific amino polymers are wrapped around the surfaces of the carbon nanotubes, promoting disentanglement of the carbon nanotubes, preventing agglomeration and / or entanglement of the carbon nanotubes themselves, and thereby improving the dispersibility of the carbon nanotubes. In particular, the aforementioned specific amino polymers have excellent hydrophilicity, and during the grafting modification of the carbon nanotubes, unreacted amino polymers can be removed by washing with ethanol.

[0028] In a preferred embodiment of the present invention, the amino polymer is polyacrylamide.

[0029] In the present invention, there is no particular limitation on the weight average molecular weight and molecular weight distribution of the amino polymer. An amino polymer with a suitable weight average molecular weight or molecular weight distribution can be selected according to actual needs. For example, the weight average molecular weight of the amino polymer is 200,000-1,000,000 g / mol, and the molecular weight distribution is 1.1-1.8.

[0030] In a specific embodiment of the present invention, the organic group content in the amino polymer is 15-35wt%. In the present invention, when selecting an amino polymer with an organic group content that meets the above range, it can ensure that the amino compound contains sufficient organic groups so that the amino polymer can be effectively grafted onto the carbon nanotubes, while avoiding too high an organic group content, which may cause excessive organic groups to remain in the amino polymer-grafted carbon nanotubes and lead to the aggregation of the amino polymer-grafted carbon nanotubes again.

[0031] In a more preferred embodiment of the present invention, the content of organic groups in the amino polymer is 20-30 wt%.

[0032] In the present invention, the organic group mainly refers to an amino group.

[0033] According to the present invention, the average diameter of the carbon nanotubes in the amino polymer grafted carbon nanotubes is 4-20 nm, and the aspect ratio is 50-10. 6 , conductivity greater than or equal to 500S / cm, BET specific surface area of ​​200-500 m 2 / g.

[0034] In the present invention, when carbon nanotubes whose average diameter, aspect ratio, conductivity and BET meet the above-mentioned ranges are used, the carbon nanotubes have a large specific surface area and high surface activity. When they are used in a semi-conductive shielding material composition, they are easy to achieve uniform dispersion in the polymer matrix and less agglomeration, and can effectively form a three-dimensional conductive network in the matrix resin, thereby improving the conductivity of the shielding material prepared from the composition.

[0035] Furthermore, the average diameter of the carbon nanotubes in the amino polymer grafted carbon nanotubes is 5-15 nm, and the aspect ratio is 10 3-10 5 , conductivity is 1000-10,000 S / cm, BET specific surface area is 300-500 m 2 / g.

[0036] In the present invention, the carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0037] According to the present invention, the amino polymer grafted carbon nanotubes are prepared according to the following method:

[0038] In a ball mill, a mixture of carbon nanotubes and amino polymer is ball-milled, washed with alcohol and water in sequence, and dried to obtain the amino polymer-grafted carbon nanotubes;

[0039] The ball milling speed is 150-250 r / min; the ball milling time is 2-4 h; and the ball milling temperature is 30-60°C.

[0040] Furthermore, the ball milling speed is 200-250 r / min; the ball milling time is 2-3.5 h; and the ball milling temperature is 40-60° C.

[0041] In the present invention, there is no particular limitation on the type of ball mill, and conventional ball mills in the art, such as a planetary ball mill, can be used.

[0042] In the present invention, there is no particular limitation on the amount of the amino polymer and the carbon nanotubes, as long as the amount of the amino polymer and the carbon nanotubes is such that the grafting rate of the amino polymer in the amino polymer-grafted carbon nanotubes is 5-15 wt %, preferably 7-12 wt %.

[0043] In the present invention, alcohol and water are sequentially used to wash the ball-milled product, thereby removing the incompletely reacted amino polymer and obtaining purified amino polymer-grafted carbon nanotubes.

[0044] In one embodiment of the present invention, the ball-milled product is washed and centrifuged with alcohol, such as ethanol, until the supernatant is colorless, and then the solid phase obtained by centrifugation is washed and centrifuged with water to replace the alcohol.

[0045] In the present invention, there is no particular limitation on the drying method or drying conditions, as long as the washed product is fully dried. For example, freeze drying can be used and carried out according to conventional conditions in the art, as long as the amino polymer-grafted carbon nanotubes can be fully dried.

[0046] In the present invention, there is no particular limitation on the type of matrix resin, and conventional polymer materials in the art that can be used to prepare semiconductive shielding materials can be used, such as at least one of ethylene-butyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-vinyl acetate copolymer. There are no particular requirements for the melt index, density, elongation at break, etc. of the matrix resin, as long as the semiconductor shielding material prepared therefrom can meet the performance requirements of the high-voltage cable. For example, the matrix resin has a melt index of 3-25 g / 10 min at 190°C and 2.16 kg, and a density of 0.8-1 g / cm -3 , the elongation at break is 500-900%.

[0047] Furthermore, in the present invention, for the above-mentioned matrix resins, in order to balance the mechanical properties of the shielding material and the compatibility between the matrix resin and the filler, preferably, the content of the ethylene structure in the copolymer is 75-95 wt%.

[0048] According to the present invention, the average particle size of the conductive carbon black is 20-80 nm, and the BET specific surface area is 50-150 m 2 / g, iodine absorption value is 55-75mg / g, and oil absorption value is 140-210cc / 100g.

[0049] In the present invention, the conductive carbon black whose average particle size, BET, iodine absorption value and oil absorption value meet the above ranges has a large specific surface area. When used in a semi-conductive shielding material composition, it can improve the dispersibility of the conductive carbon black in the matrix resin, thereby improving the electrical properties of the shielding material prepared from the composition.

[0050] Furthermore, the average particle size of the conductive carbon black is 25-60 nm, and the BET specific surface area is 50-100 m 2 / g, iodine absorption value is 60-75mg / g, and oil absorption value is 160-205cc / 100g.

[0051] In the present invention, there is no particular limitation on the specific type of the conductive carbon black, as long as the average particle size, BET specific surface area and oil absorption value of the conductive carbon black meet the requirements of the present invention.

[0052] According to the present invention, the cross-linking agent is an organic peroxide.

[0053] In the present invention, there is no particular limitation on the specific type of the peroxide crosslinking agent, which may be a conventional peroxide crosslinking agent in the art, such as at least one of BIBP, DCP, and bis(2-pentyl)sulfurizer.

[0054] In the present invention, in order to improve the processing performance of the shielding material, preferably, the compound further comprises a dispersant, wherein the amount of the dispersant is 0.2-2 parts by mass, preferably, the amount of the dispersant is 0.5-1.5 parts by mass.

[0055] In the present invention, there is no particular limitation on the specific type of the dispersant, and the dispersant may be a conventional dispersant in the art, such as at least one of microcrystalline wax, white oil, and silicone masterbatch.

[0056] In the present invention, in order to improve the aging resistance of the semiconductive shielding material, preferably, the composition further comprises an antioxidant, wherein the amount of the antioxidant is 0.2-2 parts by mass, preferably, the amount of the antioxidant is 0.5-1.5 parts by mass.

[0057] In the present invention, there is no particular limitation on the specific type of antioxidant, and it can be a conventional antioxidant in the art, such as at least one of the antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ), antioxidant 1010 and antioxidant 300.

[0058] In the present invention, in order to improve the flowability of the shielding material, preferably, the composition further comprises a lubricant, wherein the amount of the lubricant is 0.2-2 parts by weight, preferably, the amount of the lubricant is 0.4-1.5 parts by weight.

[0059] In the present invention, there is no particular limitation on the specific type of lubricant, and the lubricant may be a conventional lubricant in the art, such as at least one of zinc stearate, ethylene bis stearamide, and pentaerythritol.

[0060] The second aspect of the present invention provides a semiconductive shielding material prepared from the above-mentioned semiconductive shielding material composition.

[0061] In the present invention, the semiconductive shielding material prepared by using the above-mentioned semiconductive shielding material composition has low PTC effect and excellent electrical and mechanical properties.

[0062] Specifically, the PTC coefficient of the semi-conductive shielding material is 3-6.

[0063] The tensile strength of the semi-conductive shielding material is greater than or equal to 16MPa, and the elongation at break is 180-250%.

[0064] The volume resistivity of the semi-conductive shielding material at 23°C is 5-20Ω·cm.

[0065] The volume resistivity of the semi-conductive shielding material at 90°C is 30-125Ω·cm.

[0066] A third aspect of the present invention provides a method for preparing the above-mentioned semiconductive shielding material, wherein the preparation method comprises:

[0067] S1. Mixing, extruding, and granulating the components of the semiconductive shielding material composition except the crosslinking agent to obtain a granular material;

[0068] S2. Mixing the granular material and the cross-linking agent and absorbing them to obtain the semi-conductive shielding material.

[0069] The raw materials for preparing the semiconductor shielding material in the third aspect of the present invention adopt the composition described in the first aspect of the present invention. The types of raw materials in the third aspect of the present invention are exactly the same as those described in the first aspect of the present invention. In order to avoid repetition, the present invention will not be described in detail in the third aspect, and those skilled in the art should not understand it as a limitation of the present invention.

[0070] In the present invention, the semiconductive shielding material obtained by mixing, extruding, granulating and absorbing the semiconductive shielding material composition described in the first aspect of the present invention has low PTC effect and excellent electrical and mechanical properties.

[0071] According to the present invention, the amino polymer grafted carbon nanotubes are prepared according to the following steps:

[0072] In a ball mill, a mixture of carbon nanotubes and amino polymer is ball-milled, washed with alcohol and water in sequence, and dried to obtain the amino polymer-grafted carbon nanotubes;

[0073] The ball milling speed is 150-250 r / min; the ball milling time is 2-4 h; and the ball milling temperature is 30-60°C.

[0074] In the present invention, the inventors have discovered that by using ball milling in a ball mill to graft amino polymers onto the surface of carbon nanotubes, the grafting rate on the carbon nanotube surface can be quantitatively controlled by controlling the ball milling temperature, rotation speed and time, effectively avoiding the grafting of amino polymers that causes damage to the carbon nanotube structure and the resulting decrease in conductive performance.

[0075] In the present invention, the inventors have found that increasing the ball milling temperature can reduce the reaction activation energy and accelerate the formation of chemical bonds (such as free radical grafting); however, too high a temperature may trigger side reactions, such as oxidation of the carbon black surface to generate too much -COOH, which reduces conductivity. High rotation speed enhances collision energy and promotes the formation of surface defects of carbon black (increases active sites). Too high a rotation speed leads to local overheating or particle refinement, resulting in poor processability. Based on this, the present invention adopts a simple low-speed and slow-speed ball milling method to modify carbon nanotubes. By coordinated control of the ball milling time, ball milling temperature and ball milling speed, the grafting rate of amino polymers on the surface of carbon nanotubes can be regulated within 5wt%-15wt%. The amino groups in the polymer are utilized to enhance the interfacial compatibility with the polar matrix resin, thereby promoting the formation of a conductive network. The steric hindrance effect between polymers on the surface of carbon nanotubes and the intermolecular repulsion are combined to avoid entanglement of carbon nanotubes, thereby improving the compatibility with ethylene-acrylic acid copolymers.

[0076] Furthermore, the ball milling speed is 200-250 r / min; the ball milling time is 2-3.5 h; and the ball milling temperature is 40-60° C.

[0077] In the present invention, there is no particular limitation on the type of ball mill, and conventional ball mills in the art, such as a planetary ball mill, can be used.

[0078] In the present invention, there is no particular limitation on the amount of the amino polymer and the carbon nanotubes, as long as the amount of the amino polymer and the carbon nanotubes is such that the grafting rate of the amino polymer in the amino polymer-grafted carbon nanotubes is 5-15 wt %, preferably 7-12 wt %.

[0079] In the present invention, alcohol and water are sequentially used to wash the ball-milled product, thereby removing the incompletely reacted amino polymer and obtaining purified amino polymer-grafted carbon nanotubes.

[0080] In one embodiment of the present invention, the ball-milled product is washed and centrifuged with alcohol, such as ethanol, until the supernatant is colorless, and then the solid phase obtained by centrifugation is washed and centrifuged with water to replace the alcohol.

[0081] In the present invention, there is no particular limitation on the drying method or drying conditions, as long as the washed product is fully dried. For example, freeze drying can be used and carried out according to conventional conditions in the art, as long as the amino polymer-grafted carbon nanotubes can be fully dried.

[0082] In the present invention, there is no particular limitation on the equipment used for mixing the components other than the cross-linking agent in the semiconductive shielding material. The mixing can be performed in conventional equipment in the art, such as an internal mixer.

[0083] In the present invention, there is no particular limitation on the mixing conditions of step S1, and the mixing can be carried out according to conventional conditions in the art, as long as the components are fully mixed. For example, the mixing temperature is 140-170° C., and the mixing time is 12-25 min.

[0084] In the present invention, the extrusion and granulation in step S1 can be carried out in conventional equipment in the art, such as a twin-screw extruder or a reciprocating single-screw extruder.

[0085] According to the present invention, step S1 comprises:

[0086] premixing the amino polymer grafted carbon nanotubes with conductive carbon black to obtain a premix;

[0087] The premix, base resin, optional antioxidant, optional lubricant and optional dispersant are mixed, extruded and granulated to obtain the granular material.

[0088] In the present invention, the amino polymer grafted carbon nanotubes and the conductive carbon black are pre-mixed in advance, so that a multi-dimensional composite structure can be formed between the amino polymer grafted carbon nanotubes and the conductive carbon black. The pre-mixed semi-conductive shielding material composition can further improve the conductive performance of the shielding material prepared from the composition.

[0089] According to the present invention, the premixing is carried out at 200-1000 r / min for 3-20 min.

[0090] Furthermore, the premix is ​​mixed at 300-800 r / min for 5-15 min.

[0091] According to the present invention, in step S2, the absorption conditions include: the absorption temperature is 50-80° C., and the absorption time is 2-6 hours.

[0092] In the present invention, the absorption is carried out under the above conditions, the absorption temperature is low and the absorption time is short, which can make the composition completely cross-linked while avoiding over-cross-linking.

[0093] Furthermore, the absorption conditions include: the absorption temperature is 60-75° C., and the absorption time is 2-4 hours.

[0094] A fourth aspect of the present invention provides a use of the semiconductor shielding material composition or semiconductor shielding material in a high-voltage cable.

[0095] The present invention will be described in detail below by way of examples.

[0096] The tensile strength and elongation at break of the semi-conductive shielding material are measured using a universal testing machine in accordance with GB / T1040.3-2022.

[0097] The volume resistivity of the semi-conductive shielding material is measured by a rubber semi-conductive resistance tester according to the test standard GB / T3048-2007 Part 3 Volume Resistivity Test of Semi-conductive Rubber and Plastic Materials;

[0098] The PTC coefficient of the semi-conductive shielding material is measured using a rubber semi-conductive resistance tester, and the PTC coefficient = 90°C volume resistivity / 23°C volume resistivity.

[0099] The grafting rate of the amino polymer in the amino polymer grafted carbon nanotubes is measured by a thermogravimetric method. The test temperature range is 35-800° C. in a nitrogen atmosphere. The weight loss rate is the grafting rate of the amino polymer.

[0100] Conductive carbon black 1: Cabot Corporation brand VXC500 commercial product, average particle size 35nm, oil absorption value 148 / 100g, BET value 59m 2 / g;

[0101] Conductive carbon black 2: Commercially available product from Yiruishi Co., Ltd., brand 250G, with an average particle size of 45 nm, an oil absorption value of 178 cc / 100 g, and a BET value of 61 m 2 / g;

[0102] Ethylene butyl acrylate: a commercial product sold by Repsol under the brand name E1770; melt index at 190°C and 2.16 kg is 7 g / 10 min, elongation at break is 800%, and density is 0.924 g / cm 3 , the ethylene structure content is 83wt%;

[0103] Ethylene vinyl acetate: commercially available from Yangzi Petrochemical Company under the designation EVA V5110J; melt index 4 g / 10 min at 190°C and 2.16 kg, elongation at break 650%, density 0.923 g / cm 3 , the ethylene structure content is 77wt%;

[0104] Other raw materials used in the examples and comparative examples are all commercially available.

[0105] In the following examples and comparative examples, 1 part = 1 g.

[0106] Preparation Example 1

[0107] Multi-walled carbon nanotubes (with an average diameter of 10 nm and an aspect ratio of 10 4 , conductivity 6000 S / cm, BET specific surface area 300 m 2A mixture of 1:1 (weight-average molecular weight, 500,000 g / mol, molecular weight distribution, 1.3, and 22 wt% amino group content) was prepared. The mixture was poured into a nylon ball mill, which was then fixed on a planetary ball mill for milling at 250 r / min and 40°C for 2 hours. The mixture was then washed repeatedly with ethanol and centrifuged. After the solution became colorless, it was washed with water and centrifuged twice to displace the ethanol. The mixture was then freeze-dried to obtain amino polymer-grafted carbon nanotubes (CNT1). Testing showed that the amino polymer grafting rate in the CNT1 was 7.69 wt%.

[0108] Preparation Example 2

[0109] The method of Preparation Example 1 was followed, except that the ball milling speed was 200 rpm / min, the ball milling temperature was 45°C, and the ball milling time was 3 hours. Amino polymer-grafted carbon nanotubes (CNT2) were obtained. Testing showed that the grafting rate of the amino polymer in the amino polymer-grafted carbon nanotubes (CNT2) was 9.36 wt%.

[0110] Preparation Example 3

[0111] The method of Preparation Example 1 was followed, except that the ball milling speed was 230 rpm / min, the ball milling temperature was 50°C, and the ball milling time was 4 hours. Amino polymer-grafted carbon nanotubes (CNT3) were obtained. Testing showed that the amino polymer grafting rate in the amino polymer-grafted carbon nanotubes (CNT3) was 13.29 wt%.

[0112] Preparation Example 4

[0113] The method of Preparation Example 1 was followed, except that the ball milling speed was 150 r / min, the temperature was 30°C, and the milling time was 3 hours. Amino polymer-grafted carbon nanotubes (CNT4) were obtained. Testing showed that the amino polymer grafting rate in the amino polymer-grafted carbon nanotubes (CNT4) was 6.21 wt%.

[0114] Preparation Example 5

[0115] The method of Preparation Example 1 was followed except that the carbon nanotubes were single-walled carbon nanotubes with an average diameter of 4 nm, an aspect ratio of 3000, a conductivity of 8000 S / cm, and a BET specific surface area of ​​400 m 2 / g; the weight-average molecular weight of polyacrylamide was 1,000,000 g / mol, the molecular weight distribution was 1.8, and the amine content was 22 wt%. The milling speed was 220 r / min, the temperature was 60°C, and the milling time was 3.5 hours. Amino-polymer-grafted carbon nanotubes (CNT5) were obtained. Testing showed that the grafting rate of the amino polymer in the amino-polymer-grafted carbon nanotubes (CNT5) was 10.89 wt%.

[0116] Preparation Example 6

[0117] The method of Preparation Example 1 was followed, except that the amino polymer was polyethyleneimine with a weight-average molecular weight of 600,000 g / mol, a molecular weight distribution of 1.5, and an organic amino group content of 34.9 wt%. The milling temperature was 55°C, the speed was 200 rpm / min, and the milling time was 2.5 hours. Amino polymer-grafted carbon nanotubes (CNT6) were obtained. Testing showed that the amino polymer grafting rate in the amino polymer-grafted carbon nanotubes (CNT6) was 8.87 wt%.

[0118] Preparation Example 7

[0119] The method of Preparation Example 1 was followed, except that the type of carbon nanotubes was changed. Specifically, multi-walled carbon nanotubes were used, which had an average diameter of 20 nm, an aspect ratio of 500, a conductivity of 500 S / cm, and a BET specific surface area of ​​200 m 2 / g. Amino polymer-grafted carbon nanotubes CNT7 were obtained. Testing showed that the grafting rate of amino polymer in the amino polymer-grafted carbon nanotubes CNT7 was 10.23wt%.

[0120] Comparative Preparation Example 1

[0121] The method of Preparation Example 1 was followed, except that the ball milling speed was 100 rpm / min, the ball milling temperature was 20°C, and the ball milling time was 0.5 h. Amino polymer-grafted carbon nanotubes (CNT-D1) were obtained. Testing showed that the grafting rate of the amino polymer in CNT-D1 was 1.35 wt%.

[0122] Comparative Preparation Example 2

[0123] The method of Preparation Example 1 was followed, except that the ball milling speed was 400 rpm / min, the ball milling temperature was 70°C, and the ball milling time was 6 hours. Amino polymer-grafted carbon nanotubes (CNT-D2) were obtained. Testing showed that the amino polymer grafting rate in the amino polymer-grafted carbon nanotubes (CNT-D2) was 25.92 wt%.

[0124] Comparative Preparation Example 3

[0125] The method of Preparation Example 1 was followed, except that polyacrylamide was replaced with an equal mass of ethylamine. Amino polymer-grafted carbon nanotubes (CNT-D3) were obtained. Testing showed that the grafting rate of the amino polymer in the amino polymer-grafted carbon nanotubes (CNT-D3) was 1.67 wt%.

[0126] Comparative Preparation Example 4

[0127] The method of Preparation Example 1 was followed, except that a gravity planetary mixer was used instead of a planetary ball mill, with a stirring time of 2 hours, a temperature of 40°C, and a stirring speed of 250 r / min. Amino polymer-grafted carbon nanotubes (CNT-D4) were obtained. Testing showed that the amino polymer grafting rate in the amino polymer-grafted carbon nanotubes (CNT-D4) was 1.52 wt%.

[0128] From the above results, it can be seen that the preparation examples 1-6 obtained by controlling the ball milling time, ball milling temperature and ball milling speed by the present invention have a grafting rate in the range of 5-15 wt %, which is moderate.

[0129] Figure 1 This is the infrared spectrum of the amino polymer grafted carbon nanotubes and carbon nanotubes obtained in Preparation Example 1. Figure 1 It can be seen that the peaks at 2879 and 2930 cm -1 The peak at 1474 cm is the characteristic absorption peak of methylene stretching vibration. -1 is the characteristic absorption peak of methylene deformation, 1083 cm -1 is the stretching vibration peak of the CN bond, indicating that polyacrylamide was successfully introduced into the CNT surface.

[0130] Example 1

[0131] (1) 0.1 parts of polyacrylamide grafted carbon nanotubes (CNT-1) and 39.9 parts of conductive carbon black 1 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0132] (2) Add 40 parts of the conductive filler mixture, 56 parts of ethylene-butyl acrylate, 1 part of the antioxidant 300, 0.5 parts of the dispersant microcrystalline wax, 1 part of the lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0133] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix evenly. After absorbing at 60°C for 4 hours, a semi-conductive shielding material S1 is obtained.

[0134] Example 2

[0135] (1) 0.5 parts of polyacrylamide grafted carbon nanotubes CNT2 and 34.5 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0136] (2) Add 35 parts of conductive filler mixture, 61 parts of ethylene-butyl acrylate, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0137] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix evenly. After absorbing at 60°C for 4 hours, a semi-conductive shielding material S2 is obtained.

[0138] Example 3

[0139] (1) 0.5 parts of polyacrylamide grafted carbon nanotubes CNT3 and 34.5 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0140] (2) Add 35 parts of conductive filler mixture, 61 parts of ethylene-butyl acrylate, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0141] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix evenly. After absorbing at 60°C for 4 hours, a semi-conductive shielding material S3 is obtained.

[0142] Example 4

[0143] (1) 0.5 parts of polyacrylamide grafted carbon nanotubes CNT4 and 34.5 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0144] (2) Add 35 parts of conductive filler mixture, 61 parts of ethylene-butyl acrylate, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0145] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix evenly. After absorbing at 60°C for 4 hours, the semi-conductive shielding material S4 is obtained.

[0146] Example 5

[0147] (1) 1 part of polyethyleneimine grafted carbon nanotube CNT5 and 29 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0148] (2) Add 30 parts of conductive filler mixture, 66 parts of ethylene-butyl acrylate, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0149] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix them evenly. After absorbing them at 60°C for 4 hours, the semi-conductive shielding material S5 is obtained.

[0150] Example 6

[0151] (1) 2 parts of polyacrylamide carbon nanotubes CNT6 and 23 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0152] (2) Add 25 parts of conductive filler mixture, 71 parts of ethylene-vinyl acetate copolymer, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0153] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix evenly. After absorbing at 60°C for 4 hours, the semi-conductive shielding material S6 is obtained.

[0154] Example 7

[0155] (1) 5 parts of amino polymer grafted carbon nanotubes CNT7 and 15 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0156] (2) Add 20 parts of conductive filler mixture, 76 parts of ethylene-vinyl acetate copolymer, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0157] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix them evenly. After absorbing them at 60°C for 4 hours, the semi-conductive shielding material S7 is obtained.

[0158] Example 8

[0159] (1) 10 parts of polyacrylamide grafted carbon nanotubes CNT2 and 5 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0160] (2) Add 15 parts of conductive filler mixture, 81 parts of ethylene-vinyl acetate copolymer, 1 part of antioxidant 300, 0.5 parts of dispersant microcrystalline wax, 1 part of lubricant zinc stearate, and 0.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and extrude and granulate at 120°C to obtain granules;

[0161] (3) Add 1 part of cross-linking agent BIBP to the obtained granular material and mix them evenly. After absorbing them at 60°C for 4 hours, the semi-conductive shielding material S8 is obtained.

[0162] Comparative Example 1

[0163] A semiconductive shielding material was prepared according to the method of Example 2, except that step (1) was not performed, and in step (2), 35 parts of conductive carbon black 2 was used instead of 35 parts of the conductive filler mixture to obtain a semiconductive shielding material DS1.

[0164] Comparative Example 2

[0165] (1) The process was carried out in accordance with step (1) of Example 2, except that 0.5 parts of unmodified carbon nanotubes were used instead of 0.5 parts of polyacrylamide-grafted carbon nanotubes CNT3.

[0166] (2) Follow step (2) of Example 2.

[0167] (3) Follow step (3) of Example 2 to obtain semiconductor shielding material DS2.

[0168] Comparative Example 3

[0169] Semiconductor shielding material was prepared according to the method of Example 2, except that:

[0170] In step (1), 0.5 parts of amino polymer grafted carbon nanotubes CNT-D1 are used instead of 0.5 parts of polyacrylamide grafted carbon nanotubes CNT3 to prepare semi-conductive shielding material DS3.

[0171] Comparative Example 4

[0172] Semiconductor shielding material was prepared according to the method of Example 2, except that:

[0173] In step (1), 0.5 parts of amino polymer grafted carbon nanotubes CNT-D2 are used instead of 0.5 parts of polyacrylamide grafted carbon nanotubes CNT3 to prepare semi-conductive shielding material DS4.

[0174] Comparative Example 5

[0175] Semiconductor shielding material was prepared according to the method of Example 2, except that:

[0176] In step (1), 0.5 parts of amino polymer grafted carbon nanotubes CNT-D3 are used instead of 0.5 parts of polyacrylamide grafted carbon nanotubes CNT3 to prepare semi-conductive shielding material DS5.

[0177] Comparative Example 6

[0178] Semiconductor shielding material was prepared according to the method of Example 2, except that:

[0179] In step (1), 0.5 parts of amino polymer grafted carbon nanotubes CNT-D4 are used instead of 0.5 parts of polyacrylamide grafted carbon nanotubes CNT3 to prepare semi-conductive shielding material DS6.

[0180] Comparative Example 7

[0181] (1) 0.05 parts of polyacrylamide grafted carbon nanotubes CNT3 and 44.95 parts of conductive carbon black 2 were mechanically stirred at a speed of 500 r / min for 10 min to obtain a conductive filler mixture;

[0182] (2) Add 45 parts of conductive filler mixture, 42.5 parts of ethylene-butyl acrylate, 2.5 parts of antioxidant TMQ 300, 2.5 parts of dispersant microcrystalline wax, 2.5 parts of lubricant zinc stearate, and 2.5 parts of ethylene bis stearamide into an internal mixer at 160°C, mix for 20 minutes, and perform internal mixing at 120°C, extrusion granulation, and drying to obtain granules;

[0183] (3) Add 2.5 parts of crosslinking agent BIBP to the obtained granular material and mix them evenly. After absorbing them at 60°C for 4 hours, the semi-conductive shielding material DS7 is obtained.

[0184] The semiconductive shielding materials prepared in the examples and comparative examples were pressed into sheets at 180° C. and 15 MPa to prepare test samples. The properties of the test samples were tested, and the results are shown in Table 1.

[0185] Table 1

[0186]

[0187] As can be seen from Table 1, the semi-conductive shielding material composition uses carbon nanotubes grafted with a specific content of amino polymer as the second filler, which interacts with the conductive carbon black, so that the semi-conductive shielding material prepared from the composition has high tensile strength, high elongation at break, and low PTC coefficient, and the semi-conductive shielding material shows excellent mechanical properties and electrical properties.

[0188] Furthermore, by ball milling, amino polymers are grafted onto the surface of carbon nanotubes. By controlling the ball milling temperature, rotation speed and time, the grafting rate on the carbon nanotube surface can be quantitatively controlled to obtain carbon nanotubes with an amino polymer grafting rate that meets the requirements of the present invention.

[0189] 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 semiconductive shielding material composition, characterized in that: The composition comprises: Base resin, amino polymer grafted carbon nanotubes, conductive carbon black and crosslinking agent; The base resin is used in an amount of 55-85 parts by weight, the amino polymer grafted carbon nanotubes are used in an amount of 0.1-10 parts by weight, the conductive carbon black is used in an amount of 5-40 parts by weight, and the cross-linking agent is used in an amount of 0.5-2 parts by weight; the grafting rate of the amino polymer in the amino polymer grafted carbon nanotubes is 5-15wt%; The amino polymer is selected from polyacrylamide and / or polyethyleneimine.

2. The composition according to claim 1, wherein The grafting rate of the amino polymer in the amino polymer grafted carbon nanotubes is 7-12 wt %; And / or, the average diameter of the carbon nanotubes in the amino polymer grafted carbon nanotubes is 4-20 nm, and the aspect ratio is 50-10 6 , conductivity greater than or equal to 500S / cm, BET specific surface area of ​​200-500 m 2 / g.

3. The composition according to claim 1 or 2, wherein The amino polymer grafted carbon nanotubes are prepared according to the following method: In a ball mill, a mixture of carbon nanotubes and amino polymer is ball-milled, washed with alcohol and water in sequence, and dried to obtain the amino polymer-grafted carbon nanotubes; The ball milling speed is 150-250 r / min; the ball milling time is 2-4 h; and the ball milling temperature is 30-60° C.

4. The composition according to claim 1 or 2, wherein The matrix resin is selected from at least one of ethylene-butyl acrylate copolymer, ethylene-ethyl acrylate copolymer and ethylene-vinyl acetate copolymer; And / or, the average particle size of the conductive carbon black is 20-80 nm, and the BET specific surface area is 50-150 m 2 / g, iodine absorption value is 55-75mg / g, oil absorption value is 140-210cc / 100g; And / or, the cross-linking agent is an organic peroxide.

5. The composition according to claim 1 or 2, wherein The composition further comprises a dispersant, wherein the amount of the dispersant is 0.2-2 parts by weight; And / or, the composition further comprises an antioxidant, wherein the amount of the antioxidant is 0.2-2 parts by weight; And / or, the composition further comprises a lubricant, wherein the amount of the lubricant is 0.2-2 parts by weight.

6. A semiconductive shielding material made from the semiconductive shielding material composition according to any one of claims 1 to 5.

7. A method for preparing the semiconductive shielding material according to claim 6, characterized in that: The preparation method comprises: S1. Mixing, extruding, and granulating the components of the semiconductive shielding material composition according to any one of claims 1 to 5 except the crosslinking agent to obtain a granular material; S2. Mixing and absorbing the granular material and a cross-linking agent to obtain the semi-conductive shielding material.

8. The preparation method according to claim 7, wherein In step S2, the absorption conditions include: the absorption temperature is 50-80°C, and the absorption time is 2-6 hours.

9. The preparation method according to claim 7, wherein Step S1 includes: premixing the amino polymer grafted carbon nanotubes with conductive carbon black to obtain a premix; The premix, base resin, optional antioxidant, optional lubricant and optional dispersant are mixed, extruded and granulated to obtain the granular material.

10. The preparation method according to claim 9, wherein Pre-mix and mix at 200-1000 r / min for 3-20 minutes.

11. The preparation method according to claim 9 or 10, wherein The amino polymer grafted carbon nanotubes are prepared according to the following steps: In a ball mill, a mixture of carbon nanotubes and amino polymer is ball-milled, washed with alcohol and water in sequence, and dried to obtain the amino polymer-grafted carbon nanotubes; The ball milling speed is 150-250 r / min; the ball milling time is 2-4 h; and the ball milling temperature is 30-60° C.

12. Use of the semiconductor shielding material composition according to any one of claims 1 to 5 or the semiconductor shielding material according to claim 6 in a high-voltage cable.

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