Polypropylene-based thermoplastic cable shielding material and method of making same

Abstract

The application discloses a polypropylene-based thermoplastic cable shielding material and a preparation method thereof. The polypropylene-based thermoplastic cable shielding material comprises the following components: polypropylene, a compatilizer, carboxyl-modified carbon black, an elastomer, an antioxidant and a lubricant. The compatilizer used in the application can greatly improve the compatibility of the carbon black with the matrix and the dispersibility of the carbon black, and can reduce the use amount of the carbon black and obtain excellent conductivity and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of cable materials, specifically relating to a polypropylene-based thermoplastic cable shielding material and its preparation method. Background Technology

[0002] With economic development and urban construction, my country has built a large-scale power cable network. Currently, the most commonly used insulation material for power cables is cross-linked polyethylene (XLPE). However, XLPE cable production is time-consuming and energy-intensive, and because XLPE is a thermosetting polymer with a unique cross-linked network structure, its insulation layer is difficult to degrade and reuse after decommissioning. As environmental protection and energy conservation become a global trend, thermoplastic polypropylene (PP) has become a research focus due to its excellent electrical and heat resistance properties, such as no need for cross-linking in the production process, simple process, short production cycle, energy consumption reduction of over 50%, and recyclability after decommissioning. While some companies have developed PP insulation materials, research on matching shielding materials is limited. To develop non-cross-linked environmentally friendly PP cables, corresponding PP semi-conductive shielding materials are necessary.

[0003] To achieve a semi-conductive effect, cable shielding materials typically require the addition of a large amount of carbon black, as shown in the formulations and preparation methods used in patents CN113698723A and CN108864527A. However, excessive carbon black content can lead to poor processing performance, mechanical properties, and surface smoothness, as well as poor compatibility with the matrix. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a polypropylene-based thermoplastic cable shielding material and its preparation method. This material significantly improves the compatibility and dispersibility between carbon black and the polypropylene matrix; it reduces the amount of carbon black required while achieving excellent electrical conductivity and mechanical properties.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A polypropylene-based thermoplastic cable shielding material comprises the following components in parts by weight: 100 parts polypropylene, 2-10 parts compatibilizer, 15-30 parts modified carbon black, 5-25 parts elastomer, 0.1-0.5 parts antioxidant, and 0.5-2 parts lubricant.

[0007] In this invention, the compatibilizer is The aziridine in this compatibilizer can undergo a ring-opening reaction with carboxylated carbon black, introducing propylene chains into the carbon black surface in the form of chemical bonds. Since the propylene chains in the reaction product are similar in structure to the polypropylene matrix, it can improve the interfacial bonding between carbon black and the PP matrix and also give the carbon black better dispersibility.

[0008]

[0009] The method for preparing the compatibilizer according to the present invention includes the following steps:

[0010] (1) Add 20-30 wt% sodium hydroxide aqueous solution to the reactor. Heat the mixture to 45-55℃, add 1,2-dibromoethane dropwise while stirring continuously; after the addition is complete, continue stirring for 80-110 minutes, and maintain the temperature at 60-70℃ for 30-60 minutes.

[0011] (2) Cooling, extraction, washing, drying, and distillation to remove solvent.

[0012] As a preferred embodiment, in step (2) of the present invention, after cooling, water and benzene are added to separate the layers. The aqueous phase is extracted with benzene, the organic layer is washed with water and dried with anhydrous magnesium sulfate, and then the solvent is removed by vacuum distillation.

[0013] In this invention, the polypropylene is an ethylene-propylene block copolymer polypropylene, wherein the ethylene content is 8-15% by mass, and the weight-average molecular weight is 35-60*104 g / mol. Suitable examples include, but are not limited to, Dushanzi K8003, Lanzhou Petrochemical EP30R, and Yanshan Petrochemical 4220.

[0014] In this invention, the modified carbon black is carboxylated carbon black, and the carboxylation method is to oxidize the carbon black with nitric acid.

[0015] Preferably, the unmodified carbon black has a particle size of 20-50 nm, an oil absorption value greater than 200 cc / 100 g, and an iodine absorption value greater than 150 g / kg. More preferably, it is acetylene black, and suitable examples include, but are not limited to, Cabot VXC500 and XC72.

[0016] The method for preparing the carboxylated carbon black in this invention includes the following steps:

[0017] S1. Mix and disperse carbon black and concentrated nitric acid for 20-40 minutes; react at 100-120℃ for 16-24 hours.

[0018] S2. Cool, separate, and wash with water until the filtrate is neutral; vacuum dry at 50-70℃.

[0019] The concentrated nitric acid described in this invention has a mass fraction concentration of 63-69 wt%.

[0020] In this invention, the elastomer is a maleic anhydride-grafted elastomer, selected from one or more of maleic anhydride-grafted ethylene-propylene random copolymer elastomer, maleic anhydride-grafted ethylene-butyl random copolymer elastomer, maleic anhydride-grafted ethylene-hexane random copolymer elastomer, and maleic anhydride-grafted ethylene-octane random copolymer elastomer. The elastomer Mw is preferably 5-13*10⁴ g / mol, and the insertion rate is preferably 27-36 wt%.

[0021] In this invention, the antioxidant is selected from one or more of antioxidant 300, antioxidant 1010 and antioxidant DLTP, preferably antioxidant 300.

[0022] In this invention, the lubricant is selected from one or more of polyethylene wax or white oil, preferably polyethylene wax PEW0363 and / or white oil Ninas 330.

[0023] In this invention, a method for preparing a polypropylene-based thermoplastic cable shielding material includes the following steps: mixing the above-mentioned polypropylene, modified carbon black, elastomer, antioxidant, compatibilizer, and lubricant evenly and adding them to a twin-screw extruder for melt blending and granulation according to the specified ratio, at a temperature of 195-230℃ and a rotation speed of 200-300 r / min.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) A special compatibilizer, aziridine, can react with carboxylated carbon black, and the propylene group at the other end has good compatibility with PP, which can greatly improve the compatibility and dispersibility of carbon black with the matrix.

[0026] (2) The composite material of the present invention can reduce the amount of carbon black used while obtaining excellent electrical conductivity and mechanical properties. It can be recycled and reused, and the preparation method of the present invention is simple and easy to implement, can disperse carbon black very well, and is suitable for mass production. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] Ethylene-propylene block copolymer polypropylene: Dushanzi K8003, Mw is 433,400 g / mol; ethylene content is 10%;

[0029] Ethylene-propylene block copolymer polypropylene: Lanzhou Petrochemical EP30R, Mw is 440,000 g / mol; ethylene content is 10.8%.

[0030] Carbon black: Cabot VXC500.

[0031] Elastomer: DOW7447, ethylene-butene copolymer, Mw is 70,000 g / mol, butene content is 32.7%;

[0032] Elastomer: DOW8100, ethylene octene copolymer, Mw is 110,000 g / mol, octene content is 34.7%.

[0033] Tensile strength and elongation at break: The Instrón tensile tester (INSTRON 5966) was used, and the test method was in accordance with GB / T1040.1 and GB / T1040.2. The thickness was 1.0±0.1 mm and the tensile speed was 200±20 mm / min.

[0034] Volume resistivity: A semiconducting volume resistivity tester (DB-4, Shanghai Peicheng) was used, and the test method was in accordance with GBT3048.3.

[0035] Example 1

[0036] Polypropylene-based thermoplastic cable shielding material comprises the following components by weight: 100 parts polypropylene, 5 parts compatibilizer, 20 parts modified carbon black, 15 parts elastomer, 0.4 parts antioxidant, and 1 part lubricant. The polypropylene is Dushanzi K8003, and the compatibilizer is... The modified carbon black is carboxylated Cabot VXC500, the elastomer is maleic anhydride-grafted ethylene-butene copolymer elastomer DOW7447, the antioxidant is 300, and the lubricant is polyethylene wax PEW0363 and white oil Ninas 330 in a 1:1 mass ratio.

[0037] Compatibilizer preparation

[0038] 50 ml of a 25% sodium hydroxide aqueous solution and 0.01 mol of sodium hydroxide solution were placed in a flat-bottomed flask. The temperature was raised to 50°C, and 0.015 mol of 1,2-dibromoethane was added dropwise while stirring continuously for about 100 min. After the addition was complete, stirring was continued for another 100 min. Then, the temperature was increased to 60°C and maintained for 30 min. The flask was immersed in a cold water bath, and 50 ml of water and 50 ml of benzene were added. After the layers separated, the aqueous phase was extracted with benzene, and the organic layer was washed with water and dried over anhydrous magnesium sulfate. The solvent was then removed by vacuum distillation, yielding the desired product. The NMR structure confirmation data are shown below: 1H NMR (400MHz, CDCl3) 0.90-0.96 (m, 6H), 1.12 (d, 3H), 1.25-1.33 (m, 6H), 1.61-1.65 (m, 5H), 2.79 (m, H).

[0039] Preparation of modified carbon black

[0040] Cabot VXC500 and 66wt% concentrated nitric acid were added to a three-necked flask and ultrasonically dispersed for 30 minutes. After deoxygenation, the mixture was heated and stirred in an oil bath at 100°C for 17 hours. After cooling to room temperature, the mixture was filtered and washed with deionized water until the filtrate was neutral. Finally, the precipitate obtained by filtration was vacuum dried at 60°C to obtain CB-COOH.

[0041] The preparation method of the polypropylene-based thermoplastic cable shielding material in this embodiment is as follows: the above-mentioned polypropylene, modified carbon black, elastomer, antioxidant, compatibilizer and lubricant are mixed evenly and added to a twin-screw extruder for melt blending and granulation according to the ratio. The temperature of the extruder is 200-220℃ and the speed is 250r / min.

[0042] Example 2

[0043] Polypropylene-based thermoplastic cable shielding material comprises the following components by weight: 100 parts polypropylene, 5 parts compatibilizer, 25 parts modified carbon black, 15 parts elastomer, 0.4 parts antioxidant, and 1 part lubricant. The polypropylene is Lanzhou Petrochemical EP30R, and the compatibilizer is... The modified carbon black is the modified carboxylated carbon black in Example 1, the elastomer is maleic anhydride-grafted ethylene octene copolymer elastomer DOW8100, the antioxidant is 300, and the lubricant is polyethylene wax PEW0363 and white oil Ninas 330 in a 1:1 mass ratio.

[0044] Polypropylene-based thermoplastic cable shielding material was prepared according to the method in Example 1.

[0045] Comparative Example 1

[0046] The method is the same as in Example 1, except that the compatibilizer used in this method is polypropylene grafted glycidyl methacrylate (PP-g-GMA), and the rest of the formulation and preparation method are the same.

[0047] Comparative Example 2

[0048] The method is the same as in Example 2, except that the carbon black used in this method is ordinary carbon black Cabot VXC500 without carboxylation treatment, and the rest of the formulation and preparation method are the same.

[0049] The performance test results are shown in Table 1.

[0050] Table 1 Performance Test Results

[0051]

Claims

1. A polypropylene-based thermoplastic cable shielding material, comprising the following components in parts by weight: 100 parts polypropylene, 2-10 parts compatibilizer, 15-30 parts modified carbon black, 5-25 parts elastomer, 0.1-0.5 parts antioxidant, and 0.5-2 parts lubricant. The compatibilizer is ; The modified carbon black is carboxylated carbon black.

2. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The method for preparing the compatibilizer includes the following steps: (1) Add 20-30 wt% sodium hydroxide aqueous solution to the reactor. Heat the mixture to 45-55℃, add 1,2-dibromoethane dropwise while stirring continuously; after the addition is complete, continue stirring for 80-110 minutes, and maintain the temperature at 60-70℃ for 30-60 minutes. (2) Cooling, extraction, washing, drying, and distillation to remove solvent.

3. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The polypropylene mentioned is an ethylene-propylene block copolymer polypropylene, wherein the ethylene content is 8-15% by mass and the weight average molecular weight is 35-60*10. 4 g / mol.

4. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The polypropylene is one or more of Dushanzi K8003, Lanzhou Petrochemical EP30R, and Yanshan Petrochemical 4220.

5. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The method for preparing the modified carbon black includes the following steps: a) Mix and disperse carbon black and concentrated nitric acid, and react at 100-120℃ for 16-24 hours; b) Cool, separate, wash with water until the filtrate is neutral, and dry.

6. The polypropylene-based thermoplastic cable shielding material according to claim 5, characterized in that, The carbon black in step a) has a particle size of 20-50 nm, an oil absorption value greater than 200 cc / 100 g, and an iodine absorption value greater than 150 g / kg.

7. The polypropylene-based thermoplastic cable shielding material according to claim 6, characterized in that, The carbon black is acetylene black.

8. The polypropylene-based thermoplastic cable shielding material according to claim 6, characterized in that, The carbon black is Cabot VXC500 and / or XC72.

9. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The elastomer is a maleic anhydride-grafted elastomer.

10. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The elastomer is selected from one or more of the following: maleic anhydride-grafted ethylene-propylene random copolymer elastomer, maleic anhydride-grafted ethylene-butyl random copolymer elastomer, maleic anhydride-grafted ethylene-hexane random copolymer elastomer, and maleic anhydride-grafted ethylene-octane random copolymer elastomer.

11. The polypropylene-based thermoplastic cable shielding material according to claim 1, characterized in that, The Mw of the elastomer is 5-13*10 4 g / mol, with an insertion rate of 27-36 wt%.

12. A method for preparing the polypropylene-based thermoplastic cable shielding material according to any one of claims 1-11, comprising the following steps: Polypropylene, modified carbon black, elastomer, antioxidant, compatibilizer, and lubricant are added to a twin-screw extruder for melt blending and granulation at a temperature of 195-230℃ and a speed of 200-300 r / min.

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