Polypropylene-based semi-conductive shielding material, preparation method thereof, and cable

Abstract

The present application relates to the technical field of power engineering materials, and specifically to a polypropylene-based semi-conductive shielding material, a preparation method thereof, and a cable. The polypropylene-based semi-conductive shielding material provided in the present application comprises the following components in parts by weight: 34 to 63 parts of polypropylene resin, 7 to 28 parts of ethylene-propylene copolymer elastomer, and 20 to 30 parts of conductive carbon black; wherein the crystallinity of the polypropylene resin is 30% to 35%, and the melting point of the polypropylene resin is 155°C to 160°C; the mass percentage of vinyl in the ethylene-propylene copolymer elastomer is 14% to 18%; and the carbon black oil absorption value of the conductive carbon black is 145 mL / 100g to 150 mL / 100g. In the polypropylene-based semi-conductive shielding material provided in the present application, the polypropylene resin and the ethylene-propylene copolymer elastomer have excellent compatibility, which can effectively reduce the use of elastomer, so that it has the advantages of low cost, mechanical strength and excellent electrical properties.

Description

Technical Field

[0001] The present application relates to the technical field of power engineering materials, and in particular to a polypropylene-based semi-conductive shielding material, a preparation method thereof, and a cable. Background Art

[0002] High-voltage cables, characterized by long distances, large capacity, and low losses, are essential electrical equipment for urban, river-crossing, and offshore power transmission. The semi-conductive shield is a crucial component of high-voltage cables, eliminating defects between the metal conductor and insulation and ensuring uniform interfacial electric field distribution. Its presence plays a crucial role in ensuring the long-term operation, safety, and stability of the cable.

[0003] Currently, cross-linked polyethylene (XLPE) is commonly used as the matrix resin in semi-conductive shielding layers. It offers excellent electrical insulation and high-temperature resistance. However, XLPE suffers from high production equipment costs, easy contamination during the manufacturing process, and difficulty in recycling. Therefore, identifying or developing alternatives to address these shortcomings is a key area of ​​current research and development. Polypropylene resin (PP) is an environmentally friendly material, but its high hardness and brittleness limit its application. Currently, the hardness of PP is typically reduced by adding a certain proportion of low-modulus elastomers. However, the addition of large amounts of elastomers also results in significant cost increases and uneven distribution of conductive carbon black within the semi-conductive shielding material, which compromises its mechanical strength. Summary of the Invention

[0004] Based on this, the present application provides a polypropylene-based semiconductive shielding material, a preparation method thereof, and a cable. The polypropylene-based semiconductive shielding material provided herein has excellent compatibility between the polypropylene resin and the ethylene-propylene copolymer elastomer, effectively reducing the use of the elastomer, thereby achieving the advantages of low cost, excellent mechanical strength, and excellent electrical performance.

[0005] In a first aspect of the present application, a polypropylene-based semiconductive shielding material is provided. The raw materials for preparing the polypropylene-based semiconductive shielding material include the following components, calculated by weight: 34 to 63 parts of polypropylene resin, 7 to 28 parts of ethylene-propylene copolymer elastomer, and 20 to 30 parts of conductive carbon black;

[0006] The crystallinity of the polypropylene resin is 30% to 35%, and the melting point of the polypropylene resin is 155° C. to 160° C. The mass percentage of vinyl in the ethylene-propylene copolymer elastomer is 14% to 18%.

[0007] The conductive carbon black has an oil absorption value of 145 mL / 100 g to 150 mL / 100 g.

[0008] In one embodiment, the polypropylene resin includes a polypropylene matrix and a rubber phase.

[0009] In one embodiment, the polypropylene resin has one or more of the following characteristics:

[0010] (1) In the polypropylene resin, the mass percentage of the rubber phase is 18% to 22%;

[0011] (2) In the polypropylene resin, the rubber phase is ethylene propylene rubber;

[0012] (3) In the polypropylene resin, the rubber phase has a phase size of 0.5 μm to 1.5 μm.

[0013] In one embodiment, the ethylene-propylene copolymer elastomer has one or more of the following characteristics:

[0014] (1) The ethylene-propylene copolymer elastomer has a melt index of 1 g / 10 min to 1.2 g / 10 min at 230° C. and a load of 2.16 kg;

[0015] (2) The crystallinity of the ethylene-propylene copolymer elastomer is 5% to 15%.

[0016] In one embodiment, the raw materials for preparing the polypropylene-based semi-conductive shielding material further include functional additives, and the functional additives include one or more of antioxidants, lubricants, and dispersants.

[0017] In one embodiment, the raw materials for preparing the polypropylene-based semi-conductive shielding material include the following components, in parts by weight: 34 to 63 parts of polypropylene resin, 7 to 28 parts of ethylene-propylene copolymer elastomer, 20 to 30 parts of conductive carbon black, 0.5 to 1 part of antioxidant, 1 to 2 parts of lubricant, and 2 to 4 parts of dispersant.

[0018] In one embodiment, the polypropylene-based semiconductive shielding material has one or more of the following characteristics:

[0019] (1) The antioxidant includes one or more of hindered phenol antioxidants, phosphite antioxidants and thiophenol antioxidants;

[0020] (2) The lubricating oil includes one or more of zinc stearate and pentaerythritol;

[0021] (3) The dispersant includes one or more of oleamide and ethylene bisstearamide.

[0022] In a second aspect of the present application, there is provided a method for preparing the polypropylene-based semiconductive shielding material according to any one of the embodiments of the first aspect of the present application, comprising the following steps:

[0023] The raw materials are selected according to weight proportions, melt-blended, and then the polypropylene-based semi-conductive shielding material is prepared.

[0024] In one embodiment, the melt blending method includes one or more of banburying and extrusion; and / or,

[0025] The temperature of the melt blending is 180°C to 220°C.

[0026] The third aspect of the present application provides a cable, comprising the polypropylene-based semi-conductive shielding material described in any embodiment of the first aspect of the present application.

[0027] This application has the following beneficial effects:

[0028] The polypropylene-based semi-conductive shielding material provided in the present application is prepared by selecting a polypropylene resin with a specific crystallinity and a specific melting point. At this time, the crystalline region in the polypropylene resin can give the polypropylene resin moderate mechanical strength and can effectively resist the movement of molecular chains at high temperatures to ensure the heat resistance of the polypropylene-based semi-conductive shielding material; at the same time, the non-crystalline region can give the polypropylene resin moderate toughness.

[0029] Ethylene-propylene copolymer elastomer with a specific ethylene content can ensure sufficient elasticity, ensure its overall heat resistance, and improve the impact resistance of polypropylene resin. The above-mentioned polypropylene resin and ethylene-propylene copolymer elastomer have good compatibility, which can effectively reduce the phase interface between the components, which is conducive to reducing the amount of ethylene-propylene copolymer elastomer added and making the conductive carbon black evenly dispersed. Furthermore, the conductive carbon black with a carbon black oil absorption value of 145 mL / 100g~150 mL / 100g has a moderate degree of structure and can form an effective conductive network. In summary, the present application can obtain a polypropylene-based semi-conductive shielding material with excellent mechanical properties, electrical properties and heat resistance by selecting specific polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black, and by reasonably matching the weight proportions of each component. DETAILED DESCRIPTION

[0030] The following, in conjunction with specific examples, provides a further complete and clear description of the polypropylene-based semiconductive shielding material, its preparation method, and the cable of this application. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of this application.

[0031] Traditional semi-conductive shielding materials based on polypropylene resin often require the addition of more elastomers due to the properties of polypropylene resin. This not only increases production costs, but also reduces the heat resistance of the insulating material due to the poor heat resistance of the elastomer.

[0032] Based on this, the first aspect of the present application provides a polypropylene-based semiconductive shielding material, wherein the raw materials for preparing the polypropylene-based semiconductive shielding material include the following components, calculated by weight: 34 to 63 parts of polypropylene resin, 7 to 28 parts of ethylene-propylene copolymer elastomer, and 20 to 30 parts of conductive carbon black;

[0033] The crystallinity of the polypropylene resin is 30% to 35%, and the melting point of the polypropylene resin is 155° C. to 160° C. The mass percentage of vinyl in the ethylene-propylene copolymer elastomer is 14% to 18%.

[0034] The conductive carbon black has an oil absorption value of 145 mL / 100 g to 150 mL / 100 g.

[0035] It is understandable that in the application, the weight parts of polypropylene resin can be selected from any numerical value between 34 parts~63 parts. Specifically, the weight parts of polypropylene resin include but are not limited to 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 45 parts, 48 ​​parts, 50 parts, 53 parts, 55 parts, 56 parts, 57 parts, 58 parts, 60 parts, 62 parts or 63 parts. The weight parts of ethylene-propylene copolymer elastomer can be selected from any numerical value between 7 parts~28 parts. Specifically, the weight parts of ethylene-propylene copolymer elastomer include but are not limited to 7 parts, 8 parts, 9 parts, 12 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 20 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts or 28 parts. Specifically, the weight percentage of the conductive carbon black includes, but is not limited to, 20 parts, 22 parts, 25 parts, 28 parts, 29 parts or 30 parts.

[0036] The crystallinity of the polypropylene resin can be selected from any value between 30% and 35%. Specifically, the crystallinity of the polypropylene resin includes but is not limited to 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.2%, 33.3%, 33.4%, 33.5%, 33.6%, 33.8%, 34%, 34.3%, 34.6%, 34.8%, 34.9% or 35%. The melting point of the polypropylene resin can be selected from any value between 155°C and 160°C. Specifically, the melting point of the polypropylene resin includes but is not limited to 155°C, 156°C, 157°C, 158°C, 159°C or 160°C. The mass percentage of vinyl in the ethylene-propylene copolymer elastomer can be selected from any value between 14% and 18%. Specifically, the mass percentage of vinyl group in the ethylene-propylene copolymer elastomer includes but is not limited to 14%, 14.5%, 14.8%, 15%, 15.2%, 15.5%, 15.8%, 16%, 16.5%, 16.8%, 17%, 17.5%, 17.8% or 18%.

[0037] The carbon black oil absorption value of the conductive carbon black can be selected from any value between 145 mL / 100g and 150 mL / 100g. Specifically, the carbon black oil absorption value of the conductive carbon black includes but is not limited to 145 mL / 100g, 146 mL / 100g, 147 mL / 100g, 148 mL / 100g, 149 mL / 100g, or 150 mL / 100g.

[0038] The polypropylene-based semi-conductive shielding material provided in the present application is prepared by selecting a polypropylene resin with a specific crystallinity and a specific melting point. At this time, the crystalline region in the polypropylene resin can give the polypropylene resin moderate mechanical strength and can effectively resist the movement of molecular chains at high temperatures to ensure the heat resistance of the polypropylene-based semi-conductive shielding material; at the same time, the non-crystalline region can give the polypropylene resin moderate toughness.

[0039] Ethylene-propylene copolymer elastomer with a specific ethylene content can ensure sufficient elasticity, ensure its overall heat resistance, and improve the impact resistance of polypropylene resin. The above-mentioned polypropylene resin and ethylene-propylene copolymer elastomer have good compatibility, which can effectively reduce the phase interface between the components, which is conducive to reducing the amount of ethylene-propylene copolymer elastomer added and making the conductive carbon black evenly dispersed. Furthermore, the conductive carbon black with a carbon black oil absorption value of 145 mL / 100g~150 mL / 100g has a moderate degree of structure and can form an effective conductive network. In summary, the present application can obtain a polypropylene-based semi-conductive shielding material with excellent mechanical properties, electrical properties and heat resistance by selecting specific polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black, and by reasonably matching the weight proportions of each component.

[0040] In one example, the polypropylene resin includes a polypropylene matrix and a rubber phase.

[0041] Defining the mass percentage of the rubber phase in the polypropylene resin plays an important role in ensuring the crystallinity and melting point of the polypropylene resin. At the same time, the rubber phase can also absorb and disperse stress, reduce stress concentration, and improve the brittleness of the polypropylene matrix. In one example, the mass percentage of the rubber phase in the polypropylene resin is 18% to 22%. It is understandable that the mass percentage of the rubber phase in the polypropylene resin can be selected from any value between 18% and 22%. Specifically, the mass percentage of the rubber phase in the polypropylene resin includes but is not limited to 18%, 19%, 20%, 21% or 22%.

[0042] In one example, in the polypropylene resin, the rubber phase is ethylene propylene rubber.

[0043] To achieve uniform dispersion of the rubber phase in the polypropylene resin and effectively toughen the polypropylene resin, in one example, the rubber phase in the polypropylene resin has a phase size of 0.5 μm to 1.5 μm. Specifically, the phase size of the rubber phase in the polypropylene resin includes, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, or 1.5 μm.

[0044] In one example, the melt index of the ethylene-propylene copolymer elastomer at 230°C and a load of 2.16 kg is 1 g / 10 min to 1.2 g / 10 min. Specifically, the melt index of the ethylene-propylene copolymer elastomer includes but is not limited to 1 g / 10 min, 1.05 g / 10 min, 1.08 g / 10 min, 1.1 g / 10 min, 1.12 g / 10 min, 1.15 g / 10 min, 1.18 g / 10 min, or 1.2 g / 10 min.

[0045] In one example, the ethylene-propylene copolymer elastomer has a crystallinity of 5% to 15%. Specifically, the crystallinity of the ethylene-propylene copolymer elastomer includes, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. The crystallinity of the ethylene-propylene copolymer elastomer is limited to 5% to 15%, so that the amorphous regions present therein can interpenetrate and entangle with the amorphous regions of the polypropylene resin, thereby achieving a closer interfacial bonding and enhancing the compatibility between the polypropylene resin and the ethylene-propylene copolymer elastomer.

[0046] In one example, the raw materials for preparing the polypropylene-based semi-conductive shielding material further include functional additives, and the functional additives include one or more of antioxidants, lubricants, and dispersants.

[0047] In one example, the raw materials for preparing the polypropylene-based semi-conductive shielding material include the following components, in parts by weight: 34 to 63 parts of polypropylene resin, 7 to 28 parts of ethylene-propylene copolymer elastomer, 20 to 30 parts of conductive carbon black, 0.5 to 1 part of antioxidant, 1 to 2 parts of lubricant, and 2 to 4 parts of dispersant.

[0048] It is understandable that the weight parts of the antioxidant can be selected from any value between 0.5 part and 1 part. Specifically, the weight parts of the antioxidant include but are not limited to 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1 part. The weight parts of the lubricant include but are not limited to 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.5 parts, 1.6 parts, 1.8 parts, 1.9 parts or 2 parts. The weight parts of the dispersant include but are not limited to 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts or 4 parts.

[0049] Antioxidants can effectively capture free radicals, inhibit or delay the degradation of materials due to oxidation during processing and use, and extend the service life of semi-conductive shielding materials. In one example, the antioxidant includes one or more of hindered phenol antioxidants, phosphite antioxidants, and thiophenol antioxidants. It is understandable that the present application does not limit the specific types of hindered phenol antioxidants, phosphite antioxidants, and thiophenol antioxidants. For example, hindered phenol antioxidants can be exemplified by antioxidant 1010. Phosphite antioxidants can be exemplified by antioxidant 168. Thiophenol antioxidants can be exemplified by antioxidant 300.

[0050] Lubricating oil can reduce the friction coefficient of the semi-conductive shielding material during the preparation process, reduce heat and wear generated during processing, and reduce material adhesion to the inner walls of processing equipment, while ensuring the surface finish of the semi-conductive shielding material. In one example, the lubricating oil includes one or more of zinc stearate and pentaerythritol.

[0051] To further increase the dispersibility of the components in the semi-conductive shielding material, avoid component agglomeration, and ensure the continuity of the conductive network, in one example, the dispersant includes one or more of oleamide and ethylene bisstearamide.

[0052] In a second aspect of the present application, there is provided a method for preparing the polypropylene-based semiconductive shielding material as described in any example of the first aspect of the present application, comprising the following steps:

[0053] The raw materials are selected according to weight proportions, melt-blended, and then the polypropylene-based semi-conductive shielding material is prepared.

[0054] In one example, the melt blending method includes one or more of banburying and extrusion. It is understood that banburying can make the raw materials more evenly mixed; after extrusion, the polypropylene-based semiconductive shielding material prepared is a granular material.

[0055] In one example, the melt blending temperature is 180° C. to 220° C. Specifically, the melt blending temperature includes but is not limited to 180° C., 185° C., 190° C., 195° C., 200° C., 205° C., 210° C., 215° C., or 220° C.

[0056] In one example, the melt blending time is 5 min to 10 min.

[0057] In one example, the speed of the melt blending is 80 r / min to 150 r / min. Specifically, the speed of the melt blending includes but is not limited to 80 r / min, 85 r / min, 90 r / min, 95 r / min, 100 r / min, 105 r / min, 110 r / min, 115 r / min, 120 r / min, 130 r / min, 140 r / min, 145 r / min or 150 r / min.

[0058] In one specific example, the method for preparing the polypropylene-based semi-conductive shielding material includes the following steps: selecting the raw materials according to weight proportions, and melt-blending them to prepare the polypropylene-based semi-conductive shielding material.

[0059] In one example, the method for preparing the polypropylene-based semi-conductive shielding material further includes the step of hot pressing the polypropylene-based semi-conductive shielding material, as follows:

[0060] The polypropylene-based semiconductive shielding material is hot-pressed at 170° C. to 190° C. and cooled.

[0061] Specifically, the hot pressing device can be selected from a flat-plate vulcanizer. The hot pressing temperature includes, but is not limited to, 170°C, 172°C, 173°C, 175°C, 178°C, 180°C, 185°C, 188°C, or 190°C. Hot pressing the polypropylene-based semiconductive shielding material can produce a high-precision molded product.

[0062] In one specific example, the step of hot pressing the polypropylene-based semiconductive shielding material specifically includes:

[0063] The semi-conductive shielding material is placed in a flat plate vulcanizing machine, the pressing plate temperature is set to 170° C. to 190° C., hot pressing is performed for 10 min to 20 min, and then cooling is performed.

[0064] The third aspect of the present application provides a cable, comprising the polypropylene-based semi-conductive shielding material described in any example of the first aspect of the present application.

[0065] The following further specific examples are provided to illustrate the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application belong to the scope of protection of the present application. The specific process parameters and the like in the following embodiments are only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not necessarily limited to the specific values ​​of the embodiments below.

[0066] Example 1

[0067] 63 parts of polypropylene resin, 7 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes 20% by mass of ethylene propylene rubber, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0068] The melt index of the ethylene-propylene copolymer elastomer at 230° C. and a load of 2.16 kg is 1.1 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

[0069] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0070] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0071] Example 2

[0072] 54 parts of polypropylene resin, 16 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes ethylene propylene rubber with a mass proportion of 20%, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0073] The melt index of the ethylene-propylene copolymer elastomer at 230° C. and a load of 2.16 kg is 1.1 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

[0074] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0075] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0076] Example 3

[0077] 46 parts of polypropylene resin, 24 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes ethylene propylene rubber with a mass proportion of 20%, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0078] The melt index of the ethylene-propylene copolymer elastomer at 230° C. and a load of 2.16 kg is 1.1 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

[0079] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0080] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0081] Example 4

[0082] 42 parts of polypropylene resin, 28 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes ethylene propylene rubber with a mass proportion of 20%, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0083] The melt index of the ethylene-propylene copolymer elastomer at 230° C. and a load of 2.16 kg is 1.1 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

[0084] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0085] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0086] Example 5

[0087] 46 parts of polypropylene resin, 24 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 30% and a melting point of 155°C, and the polypropylene resin includes ethylene propylene rubber with a mass proportion of 22%, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0088] The melt index of the ethylene-propylene copolymer elastomer at 230° C. and a load of 2.16 kg is 1.2 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 14%, and the crystallinity is 5%.

[0089] The carbon black oil absorption value of the conductive carbon black is 145 mL / 100 g.

[0090] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0091] Example 6

[0092] 46 parts of polypropylene resin, 24 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 35% and a melting point of 160°C, and the polypropylene resin includes 18% by mass of ethylene propylene rubber, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0093] The melt index of the ethylene-propylene copolymer elastomer at 230° C. and a load of 2.16 kg is 1 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 18%, and the crystallinity is 5%.

[0094] The carbon black oil absorption value of the conductive carbon black is 150 mL / 100 g.

[0095] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0096] Comparative Example 1

[0097] 70 parts of polypropylene resin and 30 parts of conductive carbon black were weighed as raw materials for preparation; wherein, the polypropylene resin had a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin included ethylene propylene rubber (EPR) accounting for 20% by mass, and the average phase size of the EPR rubber was 1.3 μm.

[0098] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0099] The polypropylene resin and conductive carbon black are placed in an internal mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0100] Comparative Example 2

[0101] 46 parts of polypropylene resin, 24 parts of ethylene-octene copolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes ethylene propylene rubber with a mass proportion of 20%, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0102] The melt index of the ethylene-octene copolymer elastomer at 230° C. and a load of 2.16 kg is 2.5 g / 10 min. The mass percentage of the octenyl group in the ethylene-propylene copolymer elastomer is 38%, and the crystallinity is 6%.

[0103] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0104] Polypropylene resin, ethylene-octene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0105] Comparative Example 3

[0106] 46 parts of polypropylene resin, 24 parts of ethylene-propylene-diene terpolymer elastomer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes 20% by mass of ethylene propylene rubber, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0107] The melt index of the ethylene-propylene-diene terpolymer elastomer at 230° C. and a load of 2.16 kg is 7.3 g / 10 min. The mass percentage of vinyl groups in the ethylene-propylene copolymer elastomer is 56%, and the crystallinity is 2%.

[0108] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0109] Polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180° C., time 10 minutes, and rotation speed 80 r / min.

[0110] Comparative Example 4

[0111] 46 parts of polypropylene resin, 24 parts of styrene-ethylene-butylene-styrene block copolymer and 30 parts of conductive carbon black were weighed as preparation raw materials; wherein, the polypropylene resin has a crystallinity of 33.4% and a melting point of 156°C, and the polypropylene resin includes ethylene propylene rubber with a mass proportion of 20%, and the average phase size of the ethylene propylene rubber is 1.3 μm.

[0112] The melt index of the styrene-ethylene-butylene-styrene block copolymer at 230° C. and a load of 2.16 kg is 11 g / 10 min. The mass percentage of vinyl groups in the styrene-ethylene-butylene-styrene block copolymer is 35%, and the crystallinity is 20%.

[0113] The carbon black oil absorption value of the conductive carbon black is 148 mL / 100 g.

[0114] Polypropylene resin, styrene-ethylene-butylene-styrene block copolymer and conductive carbon black are melt-blended in an internal mixer to obtain a polypropylene-based semi-conductive shielding material. The melt-blending process is as follows: temperature 180°C, time 10 minutes, and rotation speed 80 r / min.

[0115] The weight parts of each raw material and the properties of the raw materials in the examples and comparative examples are shown in Tables 1 and 2 below.

[0116] Table 1

[0117]

[0118] Table 2

[0119]

[0120] The polypropylene-based insulating materials prepared in the examples and comparative examples were tested for tensile strength, elongation at break, volume resistivity at 23°C, and volume resistivity at 90°C. The corresponding test standards are as follows:

[0121] (1) Tensile strength: tested based on GB / T1040.2;

[0122] (2) Elongation at break: tested based on GB / T1040.2;

[0123] (3) Volume resistivity at 23°C: tested based on GB / T3048.3;

[0124] (4) Volume resistivity at 90°C, tested based on GB / T3048.3; the corresponding test results are shown in Table 3.

[0125] Table 3

[0126]

[0127] As shown in Tables 1-3, while the weight percentage of conductive carbon black remains the same in Comparative Example 1 and Examples 1-4, the performance of the semiconductive shielding material changes significantly as the amount of ethylene-propylene copolymer elastomer added increases. The main reason for the performance changes in the semiconductive shielding material in Comparative Example 1 and Examples 1-4 is that the addition of the ethylene-propylene copolymer elastomer lowers the glass transition temperature (Tg) of the semiconductive shielding material, increasing the mobility of the polymer chains. This makes the material more susceptible to deformation when subjected to external forces, increases its flexibility, and improves its elongation at break.

[0128] In Example 3 and Comparative Examples 2 to 4, the polypropylene resin and the conductive carbon black are the same, but the added elastomers are different. From Example 3 and Comparative Examples 2 to 4, it can be found that the mechanical properties of the semi-conductive shielding material are significantly improved when ethylene-propylene copolymer elastomer with a vinyl mass percentage of 14% to 18% is added compared to other elastomers with the same amount. The main reason for this phenomenon is that the ethylene-propylene copolymer elastomer with specific properties defined in this application can effectively improve its compatibility with the polypropylene resin and the conductive carbon black to form a good microphase structure; this enables the elastomer and polypropylene to effectively transfer loads under the action of external force, thereby improving the overall load-bearing capacity and elongation at break of the semi-conductive shielding material; in addition, the uniform distribution of the conductive carbon black also makes the semi-conductive shielding material have better electrical properties.

[0129] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0130] The embodiments described above only express several implementation methods of the present application, which are convenient for understanding the technical solutions of the present application in a specific and detailed manner, but they cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A polypropylene-based semiconductive shielding material, characterized in that: The raw materials for preparing the polypropylene-based semi-conductive shielding material include the following components in parts by weight: 34 to 54 parts of polypropylene resin, 16 to 28 parts of ethylene-propylene copolymer elastomer, and 20 to 30 parts of conductive carbon black; The polypropylene resin has a crystallinity of 30% to 35% and a melting point of 155° C. to 160° C. The polypropylene resin comprises a polypropylene matrix and a rubber phase. The mass percentage of the rubber phase in the polypropylene resin is 18% to 22%. The rubber phase is ethylene propylene rubber (EPR). The rubber phase has a phase size of 0.5 μm to 1.5 μm. The mass percentage of vinyl in the ethylene-propylene copolymer elastomer is 14% to 18%; the melt index of the ethylene-propylene copolymer elastomer at 230° C. and 2.16 kg load is 1 g / 10 min to 1.2 g / 10 min; and the crystallinity of the ethylene-propylene copolymer elastomer is 5% to 15%. The conductive carbon black has an oil absorption value of 145 mL / 100 g to 150 mL / 100 g.

2. The polypropylene-based semiconductive shielding material according to claim 1, characterized in that: The raw materials for preparing the polypropylene-based semi-conductive shielding material also include functional additives, and the functional additives include one or more of antioxidants, lubricants and dispersants.

3. The polypropylene-based semiconductive shielding material according to claim 2, characterized in that: The raw materials for preparing the polypropylene-based semi-conductive shielding material include the following components, in parts by weight: 34 to 54 parts of polypropylene resin, 16 to 28 parts of ethylene-propylene copolymer elastomer, 20 to 30 parts of conductive carbon black, 0.5 to 1 part of antioxidant, 1 to 2 parts of lubricant, and 2 to 4 parts of dispersant.

4. The polypropylene-based semiconductive shielding material according to claim 3, characterized in that: The polypropylene-based semiconductive shielding material has one or more of the following characteristics: (1) The antioxidant includes one or more of hindered phenol antioxidants, phosphite antioxidants and thiophenol antioxidants; (2) The lubricant includes one or both of zinc stearate and pentaerythritol; (3) The dispersant includes one or both of oleamide and ethylene bisstearamide.

5. A method for preparing the polypropylene-based semiconductive shielding material according to any one of claims 1 to 4, characterized in that: The following steps are involved: The raw materials are selected according to weight proportions, melt-blended, and then the polypropylene-based semi-conductive shielding material is prepared.

6. The method for preparing the polypropylene-based semiconductive shielding material according to claim 5, characterized in that: The melt blending method includes one or both of banburying and extrusion; and / or, The temperature of the melt blending is 180°C to 220°C.

7. A cable, characterized in that: The invention comprises the polypropylene-based semiconductive shielding material according to any one of claims 1 to 6.

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