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

Abstract

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

Description

Polypropylene-based semiconductive shielding material, preparation method thereof and cable TECHNICAL FIELD

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

[0002] High-voltage cable power transmission has the characteristics of long distance, large capacity and low loss, and is the core electrical equipment for urban power transmission, cross-river and offshore power transmission. Among them, the semiconductive shielding layer is an important part of the high-voltage cable, which has the functions of eliminating defects between the metal conductor and the insulating layer and uniformly distributing the interface electric field. Its existence has an important guarantee effect on the long-term operation, safety and stability of the cable.

[0003] At present, cross-linked polyethylene (XLPE) is usually used as the base resin in the semiconductive shielding layer, which has excellent electrical insulation and high temperature resistance. However, XLPE has the disadvantages of high production equipment cost, easy mixing of impurities in the manufacturing process and difficult recycling. Therefore, finding or developing substitutes to make up for these shortcomings is one of the important directions of current research and development. Polypropylene resin (PP) is an environmentally friendly material, but its high hardness and brittleness also limit its application. At present, a certain proportion of low modulus elastomer is usually added to reduce the hardness of polypropylene. However, the addition of a large amount of elastomer also has the disadvantages of cost increase and uneven distribution of conductive carbon black in the semiconductive shielding material, which affects the mechanical strength of the shielding material. SUMMARY

[0004] Therefore, the present application provides a polypropylene-based semiconductive shielding material, a preparation method thereof and a cable. The polypropylene-based semiconductive shielding material provided by the present application has excellent compatibility between the polypropylene resin and the ethylene-propylene copolymer elastomer, which can effectively reduce the use of elastomer and make it have the advantages of low cost, excellent mechanical strength and electrical performance.

[0005] In a first aspect, the present application provides a polypropylene-based semiconductive shielding material. The preparation raw materials of the polypropylene-based semiconductive shielding material comprise the following components in parts by weight: 34-63 parts of polypropylene resin, 7-28 parts of ethylene-propylene copolymer elastomer, and 20-30 parts of conductive carbon black.

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

[0007] The carbon black oil absorption value of the conductive carbon black is 145-150 mL / 100g.

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

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

[0010] (1) the rubber phase in the polypropylene resin accounts for 18% to 22% by mass;

[0011] (2) the rubber phase in the polypropylene resin is ethylene-propylene rubber;

[0012] (3) the rubber phase in the polypropylene resin 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 under a load of 230℃ x 2.16 kg;

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

[0016] In one embodiment, the polypropylene-based semiconductive shielding material further comprises a functional additive, which comprises one or more of an antioxidant, a lubricant, and a dispersant.

[0017] In one embodiment, the polypropylene-based semiconductive shielding material comprises, by weight fraction, the following components: 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 comprises one or more of hindered phenol antioxidant, phosphite antioxidant, and thio-phenol antioxidant;

[0020] (2) the lubricant comprises one or more of zinc stearate and pentaerythritol;

[0021] (3) the dispersant comprises one or more of oleic acid amide and ethylene bis-stearyl amide.

[0022] In a second aspect, the application provides a preparation method of the polypropylene-based semiconductive shielding material according to any one of the embodiments of the first aspect of the application, comprising the following steps:

[0023] The raw materials are selected according to the weight ratio, and the polypropylene-based semiconductive shielding material is prepared after melt blending.

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

[0025] The temperature of the melt blending is 180-220℃.

[0026] In a third aspect, the application provides a cable comprising the polypropylene-based semiconductive shielding material according to any one of the embodiments of the first aspect of the application.

[0027] The application has the following advantages:

[0028] The polypropylene-based semiconductive shielding material provided by the application uses 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 a moderate mechanical strength and effectively resist the molecular chain movement at high temperatures, so as to ensure the heat resistance of the polypropylene-based semiconductive shielding material. Meanwhile, the non-crystalline region can give the polypropylene resin a moderate toughness.

[0029] The ethylene-propylene copolymer elastomer with a specific ethylene content can ensure sufficient elasticity, ensure overall heat resistance, and improve the impact resistance of the polypropylene resin. The polypropylene resin and the ethylene-propylene copolymer elastomer have good compatibility, which can effectively reduce the phase interface between the components, which is conducive to reducing the addition amount of the ethylene-propylene copolymer elastomer and uniformly dispersing the conductive carbon black. Further, the conductive carbon black with an oil absorption value of 145-150 mL / 100g has a moderate structure degree, which can form an effective conductive network. In summary, the application selects specific polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black, and reasonably matches the weight ratio of each component, so as to obtain a polypropylene-based semiconductive shielding material with excellent mechanical properties, electrical properties and heat resistance. DETAILED DESCRIPTION

[0030] The polypropylene-based semiconductive shielding material, the preparation method thereof and the cable of the application are further described in detail below in combination with specific embodiments. The application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the application more thorough and comprehensive.

[0031] In a conventional semi-conductive shielding material taking polypropylene resin as a matrix, due to the properties of the polypropylene resin, a large amount of elastomer needs to be added, which not only increases the production cost, but also reduces the heat resistance of the insulating material due to the poor heat resistance of the elastomer.

[0032] Therefore, in a first aspect, the present application provides a polypropylene-based semi-conductive shielding material, the preparation raw materials of the polypropylene-based semi-conductive shielding material include the following components in parts by weight: 34-63 parts of polypropylene resin, 7-28 parts of ethylene-propylene copolymer elastomer, and 20-30 parts of conductive carbon black.

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

[0034] The carbon black oil absorption value of the conductive carbon black is 145-150 mL / 100g.

[0035] It can be understood that the polypropylene resin in the present application can be selected from any value between 34 and 63 parts by weight. Specifically, the weight fraction of the polypropylene resin includes but is 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 fraction of the ethylene-propylene copolymer elastomer can be selected from any value between 7 and 28 parts. Specifically, the weight fraction of the ethylene-propylene copolymer elastomer includes but is 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 fraction 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 ethylene groups in the ethylene-propylene copolymer elastomer can be selected from any value between 14% and 18%. Specifically, the mass percentage of ethylene groups 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 / 100 g and 150 mL / 100 g. Specifically, the carbon black oil absorption value of the conductive carbon black includes, but is not limited to, 145 mL / 100 g, 146 mL / 100 g, 147 mL / 100 g, 148 mL / 100 g, 149 mL / 100 g, or 150 mL / 100 g.

[0038] The polypropylene-based semiconductive shielding material provided by the present application selects 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 a moderate mechanical strength and effectively resist the molecular chain movement at high temperatures, so as to ensure the heat resistance of the polypropylene-based semiconductive shielding material. Meanwhile, the non-crystalline region can give the polypropylene resin a moderate toughness.

[0039] The ethylene-propylene copolymer elastomer with a specific ethylene group content can ensure sufficient elasticity, ensure the overall heat resistance, and improve the impact resistance of the polypropylene resin. The polypropylene resin and the ethylene-propylene copolymer elastomer have good compatibility, which can effectively reduce the phase interface between the components, which is conducive to reducing the addition amount of the ethylene-propylene copolymer elastomer and uniformly dispersing the conductive carbon black. Further, the conductive carbon black with a carbon black oil absorption value of 145 mL / 100 g to 150 mL / 100 g has a moderate structure, which can form an effective conductive network. In summary, by selecting the specific polypropylene resin, ethylene-propylene copolymer elastomer, and conductive carbon black and reasonably matching the weight fractions of the components, the polypropylene-based semiconductive shielding material with excellent mechanical properties, electrical properties, and heat resistance can be obtained.

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

[0041] 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. Meanwhile, 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%. Understandably, the mass percentage of the rubber phase in the polypropylene resin can be any value selected from 18% to 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, the rubber phase in the polypropylene resin is an ethylene-propylene rubber.

[0043] To make the rubber phase in the polypropylene resin uniformly dispersed, the polypropylene resin is effectively toughened. In one example, the phase size of the rubber phase in the polypropylene resin is 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 under a load of 230°C x 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 crystallinity of the ethylene-propylene copolymer elastomer is 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 5% to 15%, which can interpenetrate, entangle, and further interface combine with the amorphous region of the polypropylene resin, thereby enhancing the compatibility between the polypropylene resin and the ethylene-propylene copolymer elastomer.

[0046] In one example, the polypropylene-based semiconductive shielding material further comprises a functional additive, wherein the functional additive comprises one or more of an antioxidant, a lubricant, and a dispersant.

[0047] In one example, the polypropylene-based semiconductive shielding material comprises, by weight, 34-63 parts of polypropylene resin, 7-28 parts of ethylene-propylene copolymer elastomer, 20-30 parts of conductive carbon black, 0.5-1 part of antioxidant, 1-2 parts of lubricant, and 2-4 parts of dispersant.

[0048] It is appreciated that the antioxidant can be selected from any value between 0.5-1 parts by weight. Specifically, the antioxidant can be, but not limited to, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1 part. The lubricant can be, but 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 dispersant can be, but 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] The antioxidant can effectively capture free radicals, inhibit or delay the degradation of the material due to oxidation during processing and use, and prolong the service life of the semiconductive shielding material. In one example, the antioxidant comprises one or more of hindered phenolic antioxidants, phosphite antioxidants, and thio-phenolic antioxidants. It is appreciated that the application does not limit the specific types of hindered phenolic antioxidants, phosphite antioxidants, and thio-phenolic antioxidants. For example, the hindered phenolic antioxidant can be exemplified by antioxidant 1010. The phosphite antioxidant can be exemplified by antioxidant 168. The thio-phenolic antioxidant can be exemplified by antioxidant 300.

[0050] The lubricant can reduce the friction coefficient of the semiconductive shielding material during preparation, reduce the heat and wear generated during processing, and reduce the adhesion of the material to the inner wall of the processing equipment, and ensure the surface finish of the semiconductive shielding material. In one example, the lubricant comprises one or more of zinc stearate and pentaerythritol.

[0051] To further increase the dispersibility of the components in the semiconductive shielding material and avoid component agglomeration, the continuity of the conductive network is ensured. In one example, the dispersant comprises one or more of oleic acid amide and ethylene bis-stearyl amide.

[0052] In a second aspect of the application, a method for preparing the polypropylene-based semiconductive shielding material of any one of the examples of the first aspect of the application is provided, comprising the following steps:

[0053] The preparation raw materials are selected according to weight fractions, and the polypropylene-based semi-conductive shielding material is prepared after melt blending.

[0054] In one example, the melt blending method includes one or more of banburying and extruding. It can be understood that banburying can make the preparation raw materials more uniformly mixed; and after extruding, the polypropylene-based semi-conductive shielding material prepared at this time is a granular material.

[0055] In one example, the temperature of melt blending is 180-220°C. Specifically, the temperature of melt blending 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 time of melt blending is 5-10 minutes.

[0057] In one example, the rotation speed of melt blending is 80-150 r / min. Specifically, the rotation speed of 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 preparation method of the polypropylene-based semi-conductive shielding material includes the following steps: the preparation raw materials are selected according to weight fractions, and the polypropylene-based semi-conductive shielding material is prepared after melt blending.

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

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

[0061] Specifically, the equipment for hot-pressing can be selected from a flat vulcanizing machine. The temperature of hot-pressing 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 semi-conductive shielding material can obtain a high-precision molded product.

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

[0063] The semi-conductive shielding material is placed in a flat vulcanizing machine, the temperature of the press plate is set to 170-190℃, and after hot pressing for 10-20 minutes, the semi-conductive shielding material is cooled.

[0064] In a third aspect, the application provides a cable comprising the polypropylene-based semi-conductive shielding material according to any one of the examples of the first aspect.

[0065] The following further specific examples are used to illustrate the application in detail. It should also be understood that the following examples are only used to further illustrate the application, and cannot be understood as limiting the scope of protection of the application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the application are within the scope of protection of the application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range according to the description herein, and do not necessarily have to be limited to the specific values in the following examples.

[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 raw materials for preparation; wherein the crystallinity of the polypropylene resin is 33.4%, the melting point is 156℃, the polypropylene resin comprises 20% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber is 1.3μm.

[0068] The melt index of the ethylene-propylene copolymer elastomer under a load of 230℃×2.16kg is 1.1g / 10min, the mass percentage of ethylene 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 148mL / 100g.

[0070] The polypropylene resin, ethylene-propylene copolymer elastomer and conductive carbon black were 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℃, time 10 minutes, and speed 80r / 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 raw materials for preparation; wherein the crystallinity of the polypropylene resin is 33.4%, the melting point is 156℃, the polypropylene resin comprises 20% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber is 1.3μm.

[0073] The ethylene-propylene copolymer elastomer has a melt index of 1.1 g / 10 min under a load of 230℃x2.16 kg, the mass percentage of ethylene groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

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

[0075] The polypropylene resin, the ethylene-propylene copolymer elastomer and the conductive carbon black are placed in a mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process is as follows: temperature 180℃, time 10 minutes, and 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 are weighed as raw materials for preparation; wherein the crystallinity of the polypropylene resin is 33.4%, the melting point is 156℃, and the polypropylene resin comprises 20% of ethylene-propylene rubber by mass percentage, and the average phase size of the ethylene-propylene rubber is 1.3 μm.

[0078] The ethylene-propylene copolymer elastomer has a melt index of 1.1 g / 10 min under a load of 230℃x2.16 kg, the mass percentage of ethylene groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

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

[0080] The polypropylene resin, the ethylene-propylene copolymer elastomer and the conductive carbon black are placed in a mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process is as follows: temperature 180℃, time 10 minutes, and 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 are weighed as raw materials for preparation; wherein the crystallinity of the polypropylene resin is 33.4%, the melting point is 156℃, and the polypropylene resin comprises 20% of ethylene-propylene rubber by mass percentage, and the average phase size of the ethylene-propylene rubber is 1.3 μm.

[0083] The ethylene-propylene copolymer elastomer has a melt index of 1.1 g / 10 min under a load of 230℃x2.16 kg, the mass percentage of ethylene groups in the ethylene-propylene copolymer elastomer is 15%, and the crystallinity is 9%.

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

[0085] The polypropylene resin, the ethylene-propylene copolymer elastomer and the conductive carbon black are placed in a Banbury mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process is as follows: temperature 180℃, time 10 minutes, and rotating speed 80r / min.

[0086] Example 5

[0087] 46 parts of polypropylene resin, 24 parts of ethylene-propylene copolymer elastomer and 30 parts of conductive carbon black are weighed as raw materials for preparation; wherein the crystallinity of the polypropylene resin is 30%, and the melting point is 155℃, the polypropylene resin comprises 22% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber is 1.3μm.

[0088] The melt index of the ethylene-propylene copolymer elastomer under 230℃×2.16kg load is 1.2g / 10min, the mass percentage of ethylene group in the ethylene-propylene copolymer elastomer is 14%, and the crystallinity is 5%.

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

[0090] The polypropylene resin, the ethylene-propylene copolymer elastomer and the conductive carbon black are placed in a Banbury mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process is as follows: temperature 180℃, time 10 minutes, and rotating speed 80r / min.

[0091] Example 6

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

[0093] The melt index of the ethylene-propylene copolymer elastomer under 230℃×2.16kg load is 1g / 10min, the mass percentage of ethylene group in the ethylene-propylene copolymer elastomer is 18%, and the crystallinity is 5%.

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

[0095] The polypropylene resin, the ethylene-propylene copolymer elastomer and the conductive carbon black are placed in a Banbury mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process is as follows: temperature 180℃, time 10 minutes, and rotating speed 80r / min.

[0096] Comparative Example 1

[0097] Take 70 parts of polypropylene resin and 30 parts of conductive carbon black as raw materials; wherein, the crystallinity of the polypropylene resin is 33.4%, and the melting point is 156℃, the polypropylene resin includes 20% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber is 1.3μm.

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

[0099] The polypropylene resin and the 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: temperature 180℃, time 10 minutes, and speed 80r / min.

[0100] Comparative Example 2

[0101] Take 46 parts of polypropylene resin, 24 parts of ethylene-octene copolymer elastomer and 30 parts of conductive carbon black as raw materials; wherein, the crystallinity of the polypropylene resin is 33.4%, and the melting point is 156℃, the polypropylene resin includes 20% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber is 1.3μm.

[0102] The melt index of the ethylene-octene copolymer elastomer under 230℃×2.16kg load is 2.5g / 10min, the mass percentage of octene 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 148mL / 100g.

[0104] The polypropylene resin, the ethylene-octene copolymer elastomer and the 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: temperature 180℃, time 10 minutes, and speed 80r / min.

[0105] Comparative Example 3

[0106] Take 46 parts of polypropylene resin, 24 parts of ethylene-octene copolymer elastomer and 30 parts of conductive carbon black as raw materials; wherein, the crystallinity of the polypropylene resin is 33.4%, and the melting point is 156℃, the polypropylene resin includes 20% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber is 1.3μm.

[0107] The melt index of the ethylene-octene copolymer elastomer under 230℃×2.16kg load is 2.5g / 10min, the mass percentage of octene group in the ethylene-propylene copolymer elastomer is 38%, and the crystallinity is 6%.

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

[0109] The polypropylene resin, the ethylene-propylene copolymer elastomer and the conductive carbon black were placed in a Banbury mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process was as follows: temperature 180℃, time 10 minutes, and rotation speed 80r / 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 raw materials for preparation; wherein the crystallinity of the polypropylene resin was 33.4%, the melting point of the polypropylene resin was 156℃, the polypropylene resin included 20% of ethylene-propylene rubber by mass fraction, and the average phase size of the ethylene-propylene rubber was 1.3μm.

[0112] The melt index of the styrene-ethylene-butylene-styrene block copolymer under a load of 230℃x2.16kg was 11g / 10min, the mass percentage of ethylene in the styrene-ethylene-butylene-styrene block copolymer was 35%, and the crystallinity was 20%.

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

[0114] The polypropylene resin, the styrene-ethylene-butylene-styrene block copolymer and the conductive carbon black were placed in a Banbury mixer for melt blending to obtain a polypropylene-based semi-conductive shielding material. The melt blending process was as follows: temperature 180℃, time 10 minutes, and rotation speed 80r / min.

[0115] The weight fractions and properties of the raw materials of the examples and comparative examples are shown in Table 1 and Table 2 as follows.

[0116] Table 1

[0117]

[0118] Table 2

[0119]

[0120] The tensile strength, elongation at break, volume resistivity at 23℃ and volume resistivity at 90℃ of the polypropylene-based insulating material prepared in the examples and comparative examples were tested. 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℃: tested based on GB / T3048.3;

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

[0125] Table 3

[0126]

[0127] As can be seen from Tables 1-3, in Comparative Example 1 and Examples 1-4, the weight fraction of the conductive carbon black is the same, but the fraction of the ethylene-propylene copolymer elastomer added gradually increases, and the performance of the semiconductive shielding material changes significantly. The main reason for the performance change of the semiconductive shielding material in Comparative Example 1 and Examples 1-4 is that the addition of the ethylene-propylene copolymer elastomer reduces the glass transition temperature (Tg) of the semiconductive shielding material, improves the mobility of the polymer chain, so that the material is more likely to deform when subjected to external force, increasing its flexibility and elongation at break.

[0128] In Example 3 and Comparative Examples 2-4, the polypropylene resin and the conductive carbon black are the same, but the elastomer added is different. As can be seen from Example 3 and Comparative Examples 2-4, compared with the same fraction of other elastomers, the mechanical properties of the semiconductive shielding material are significantly improved by adding ethylene-propylene copolymer elastomer with a vinyl mass percentage of 14%-18%. The main reason for this phenomenon is that the ethylene-propylene copolymer elastomer with specific properties defined in the present application can effectively improve the compatibility between it and the polypropylene resin and the conductive carbon black to form a good microphase structure; this enables the elastomer and the polypropylene to effectively transfer the load under external force, thereby improving the overall load-carrying capacity and elongation at break of the semiconductive shielding material; in addition, the uniformity of the distribution of the conductive carbon black also makes the semiconductive shielding material have more excellent electrical properties.

[0129] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, however, as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0130] The above-described embodiments only express several implementation manners of the present application, facilitate specific and detailed understanding of the technical solutions of the present application, but cannot be understood as a limitation on the patent protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by logical analysis, reasoning or limited experiments by the skilled person in the art all belong to the protection scope of the appended claims of the present application. Therefore, the patent protection scope of the present application should be subject to the content of the appended claims, and the description can be used to explain the content of the claims.

Claims

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

2. The polypropylene based semiconductive shielding material of claim 1, wherein, The preparation raw materials of the polypropylene-based semi-conductive shielding material further include functional additives, which include one or more of antioxidants, lubricants, and dispersants.

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

4. The polypropylene based semiconductive shielding material of claim 3, wherein, The polypropylene-based semi-conductive shielding material has one or more of the following characteristics: (1) the antioxidant includes one or more of hindered phenol antioxidants, phosphite antioxidants, and thio phenol antioxidants; (2) the lubricant includes one or both of zinc stearate and pentaerythritol; (3) the dispersant includes one or both of oleic acid amide and ethylene bis-stearyl amide.

5. A process for the preparation of the polypropylene based semiconductive shielding material according to any one of claims 1 to 4, characterized in that, The method includes the following steps: The preparation raw materials are selected according to parts by weight, and the polypropylene-based semi-conductive shielding material is prepared after melt blending.

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 internal mixing and extrusion; and / or The melt blending temperature is 180-220°C.

7. A cable, characterized by The polypropylene-based semi-conductive shielding material of any one of claims 1-6.

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