Shielding material for thermoplastic polyvinyl direct-current power cable and preparation method of shielding material
By using two conductive carbon black composites with different particle sizes as conductive fillers in the polyvinyl matrix resin, the mechanical properties of the semiconductor shielding material of the non-crosslinked polyethylene insulating material in the prior art are solved, and the effects of high conductivity, ultra-smoothness, high toughness and low electric field distortion are achieved, and the electrical characteristics and life of the cable are improved.
Patent Information
- Application Number
- CN202411695281.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-25
- Publication Date
- 2025-03-11
AI Technical Summary
In the prior art, there is a lack of systematic research on the semiconductor shielding material of non-crosslinked polyethylene insulating materials, which leads to excessive conductive carbon black, degraded mechanical properties, uneven distribution of conductive carbon black, and space charge injection in high-voltage DC transmission cables, which limits its application.
Two conductive carbon blacks with different particle sizes (the particle size of the first conductive carbon black is not less than 30 nm, and the particle size of the second conductive carbon black is not more than 15 nm) are used as conductive fillers to improve the dispersion characteristics of conductive carbon black in the matrix resin, ensure that the material has strong mechanical and conductive characteristics, and at the same time, the injection of the shielding layer into the space charge in the insulating layer is suppressed.
It effectively reduces the degree of electric field distortion of the insulation/shielding interface, improves the electrical characteristics of the insulating material, extends the cable life, and improves the voltage level matching of its application.
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Figure CN119591969A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of composite materials, and in particular to a shielding material for a thermoplastic polyethylene-based DC power cable and a preparation method thereof. Background Art
[0002] In recent years, non-cross-linked polyethylene insulation materials have gradually become a research hotspot for cable insulation materials due to their advantages such as low processing energy consumption and recyclability. However, the research and development of matching semi-conductive shielding materials has not been systematically studied, which limits the application of non-cross-linked polyethylene insulation materials. Therefore, it is urgent to study matching non-cross-linked cable semi-conductive shielding materials.
[0003] In high-voltage DC transmission cables, the semi-conductive outer shielding layer wrapped around the main insulation can eliminate the air gap in the sheath and reduce electromagnetic interference, while the inner shielding layer wraps the conductor and is responsible for improving contact performance and uniform interlayer electric field. Compared with the outer shielding layer, it puts forward more stringent requirements on various aspects of the material performance. As a key factor affecting the life of the cable, an excellent semi-conductive shielding material should have high conductivity, ultra-smoothness, high toughness and other qualities that match its application voltage level, and can fit the main insulation that is adapted to it. Generally speaking, the higher the voltage level of the cable, the stricter the requirements for the shielding layer. DC transmission is more likely to accumulate space charge than AC, so the DC cable shielding layer needs to consider the charge injection problem into the insulation accordingly.
[0004] In the current semi-conductive shielding materials for cables, in order to ensure that the shielding materials have strong conductive properties, most of them use excessive amounts of single conductive carbon black. However, the large amount of conductive carbon black added significantly reduces the mechanical properties of the shielding material and causes the distribution of the conductive carbon black in the matrix resin to be uneven. This uneven distribution easily forms numerous and large protrusions on the surface of the semi-conductive shielding layer, thereby increasing the electric field strength at the interface between the shielding layer and the insulating layer, and ultimately causing the accumulation of space charge inside the insulating layer.
[0005] Therefore, it is very necessary to develop shielding materials for thermoplastic polyethylene DC cables and their applications that can inhibit charge injection into the insulation layer and reduce the degree of electric field distortion at the insulation / shielding interface. Summary of the invention
[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a thermoplastic polyethylene-based shielding material for DC power cables and a preparation method thereof. The shielding material of the present invention is suitable for existing thermoplastic polyethylene insulation materials, and effectively reduces the degree of electric field distortion at the insulation / shielding interface and inhibits charge injection into the insulation layer, thereby improving the electrical properties of the insulation material.
[0007] To achieve the above object, the technical solution adopted by the present invention is:
[0008] In a first aspect, the present invention provides a shielding material for a thermoplastic polyethylene-based DC power cable, comprising the following components in parts by weight:
[0009] Polyethylene resin 70-74 parts; filler 22-28 parts; additive 2-6 parts;
[0010] The filler comprises a first conductive carbon black and a second conductive carbon black, wherein the particle size of the first conductive carbon black is not less than 30 nm, and the particle size of the second conductive carbon black is not greater than 15 nm.
[0011] In the present invention, two kinds of conductive carbon black are selected as conductive fillers, which improves the dispersion characteristics of the conductive carbon black in the matrix resin, and improves the smoothness of the shielding / insulating interface while ensuring that the material has strong mechanical properties, thereby effectively inhibiting the injection of space charges from the shielding layer into the insulating layer, effectively reducing the degree of electric field distortion in the insulating layer, and thus improving the electrical properties of the insulating material.
[0012] Preferably, the thermoplastic polyethylene-based DC power cable shielding material comprises the following components in parts by weight:
[0013] Polyethylene resin 71-72 parts; filler 24-26 parts; additive 3-4 parts.
[0014] More preferably, the thermoplastic polyethylene-based shielding material for DC power cable comprises the following components in parts by weight:
[0015] 71.5 parts of polyethylene resin; 25 parts of filler; 3.5 parts of additives.
[0016] Preferably, the particle size of the first conductive carbon black is 30-40 nm, more preferably any one or both of 30 nm, 32 nm, 34 nm, 35 nm, 36 nm, 38 nm and 40 nm.
[0017] Preferably, the particle size of the second conductive carbon black is 5-15 nm, more preferably any one or both of 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm and 15 nm.
[0018] Preferably, the weight ratio of the first conductive carbon black to the second conductive carbon black in the filler is (85-90):(10-15), and more preferably 90:10.
[0019] Preferably, the polyethylene resin is a linear low-density polyethylene, and the melt index of the polyethylene resin at 190° C. / 2.16 kg is 0.15-0.25 g / 10 min.
[0020] Preferably, the auxiliary agent includes 0.5-1 parts of antioxidant and 2-4 parts of dispersant.
[0021] More preferably, the auxiliary agent includes 0.5 parts of antioxidant and 3 parts of dispersant.
[0022] Preferably, the antioxidant includes at least one of antioxidant 300 , antioxidant 1010 , and antioxidant 168 .
[0023] Preferably, the dispersant includes at least one of white oil, ethylene bisstearamide and oleamide.
[0024] In a second aspect, the present invention further provides a method for preparing a shielding material for a thermoplastic polyethylene-based DC power cable, comprising the following steps:
[0025] The polyethylene resin, filler and additive are uniformly mixed according to a proportion, and then melt-blended and extruded in an extruder, compressed, pelletized and dried to obtain a thermoplastic polyethylene-based shielding material for DC power cables.
[0026] Preferably, the temperature of the melt blending extrusion is 150-180°C and the rotation speed is 40-50r / min.
[0027] Preferably, the drying temperature is 60-80°C and the drying time is 20-24h.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] The present invention selects two kinds of conductive carbon blacks to be compounded as conductive fillers. The two different conductive carbon blacks produce a synergistic effect, which improves the dispersion characteristics of the conductive carbon black in the matrix resin. On the premise of ensuring that the material has strong mechanical properties, the smoothness of the shielding / insulating interface is improved, and the degree of electric field distortion in the insulating layer is reduced, thereby effectively inhibiting the injection of space charges from the shielding layer into the insulating layer, thereby achieving the purpose of improving the electrical properties of the cable insulation and the shielding composite layer. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 The spatial charge distribution diagram of the thermoplastic polyethylene insulating material pressurized for 1 min to 60 min using the semiconductive shielding materials prepared in Example 1, Comparative Example 3 and Comparative Example 5 as electrodes.
[0031] Figure 2 The electric field distribution diagram of the thermoplastic polyethylene insulating material pressurized for 1 min to 60 min using the semiconductive shielding materials prepared in Example 1, Comparative Example 3 and Comparative Example 5 as electrodes.
[0032] Figure 3Space charge comparison diagram of thermoplastic polyethylene insulation material pressurized for 60 minutes using the semiconductive shielding materials prepared in Example 1, Comparative Example 3 and Comparative Example 5 as electrodes. DETAILED DESCRIPTION
[0033] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.
[0034] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.
[0035] Example 1
[0036] This embodiment discloses a shielding material for a thermoplastic polyethylene-based DC power cable, comprising the following components in parts by weight:
[0037] Polyethylene resin 71.5 parts; filler 25 parts; additives 3.5 parts;
[0038] The polyethylene resin is a linear low-density polyethylene, and the melt index at 190° C. / 2.16 kg is 0.19 g / 10 min.
[0039] The filler comprises a first conductive carbon black and a second conductive carbon black, the particle size of the first conductive carbon black is 35 nm, the particle size of the second conductive carbon black is 10 nm, and the weight ratio of the first conductive carbon black to the second conductive carbon black in the filler is 90:10.
[0040] The auxiliary agent comprises an antioxidant and a dispersant, wherein the antioxidant is 0.5 parts and the dispersant is 3 parts; the antioxidant is antioxidant 300; and the dispersant is white oil.
[0041] This embodiment also discloses a method for preparing a shielding material for a thermoplastic polyethylene-based DC power cable, comprising the following steps:
[0042] S1: Polyethylene resin, fillers and additives are extracted according to the established formula ratio, and then dried in an oven at 60°C for 24 hours.
[0043] S2: After the drying process is completed, the filler is thoroughly mixed with the polyethylene resin and the additives according to the proportion to obtain a mixture while ensuring the uniformity of the mixture.
[0044] S3: The mixture prepared in step S2 is fed into a torque rheometer for molten blending extrusion, followed by compression and granulation. The melt blending extrusion temperature is 150° C. and the rotation speed is 50 r / min.
[0045] S4: Dry the mixed particles generated in step S3 again, keep the oven temperature constant at 60° C. to 80° C., and dry for 24 hours to obtain a thermoplastic polyethylene-based shielding material for DC power cables.
[0046] Example 2
[0047] A shielding material for a thermoplastic polyethylene-based DC power cable, which is different from Example 1 in that the particle size of the first conductive carbon black is 40 nm, and the particle size of the second conductive carbon black is 5 nm, and the rest is the same as Example 1.
[0048] Comparative Example 1
[0049] A shielding material for a thermoplastic polyethylene-based DC power cable, which is different from Example 1 in that the amount of polyethylene resin used is 76.5 parts, the amount of filler used is 20 parts, and the rest is the same as Example 1.
[0050] Comparative Example 2
[0051] A shielding material for a thermoplastic polyethylene-based DC power cable, which is different from Example 1 in that the amount of polyethylene resin used is 66.5 parts, the amount of filler used is 30 parts, and the rest is the same as Example 1.
[0052] Comparative Example 3
[0053] A shielding material for a thermoplastic polyethylene-based DC power cable is different from Example 1 in that the filler includes only one conductive carbon black with a particle size of 35 nm, and the rest is the same as Example 1.
[0054] Comparative Example 4
[0055] A shielding material for a thermoplastic polyethylene-based DC power cable is different from Example 1 in that the filler includes only one conductive carbon black with a particle size of 10 nm, and the rest is the same as Example 1.
[0056] Comparative Example 5
[0057] A shielding material for a thermoplastic polyethylene-based DC power cable is different from Example 1 in that the weight ratio of the first conductive carbon black to the second conductive carbon black in the filler is 80:20.
[0058] Performance Testing
[0059] The performance of the shielding materials prepared in the above embodiments and comparative examples was tested, and the specific test items and test methods are as follows:
[0060] The shielding material was hot pressed at 180°C and 15MPa for 10 minutes on a hot press to obtain a 1mm thick semi-conductive shielding material sample. Then, the 0.2mm non-cross-linked polyethylene insulation material prepared in advance and the 1mm thick semi-conductive shielding material sample were used to prepare an insulation-shielding composite specimen using a hot press for testing.
[0061] 1. Volume resistivity: tested by four-electrode system, refer to GB / T 1551-2009.
[0062] 2. Tensile properties and elongation at break: tested according to the method in standard GB / T 1040.2-2006. At room temperature (25±5°C), stretch at a speed of 100 mm / min until it breaks, and record the tensile strength (MPa) and elongation at break (%).
[0063] The test results are shown in Table 1 below.
[0064] Table 1
[0065]
[0066] It can be seen from Example 1 and Comparative Examples 1-2 in Table 1 that the present invention can make the shielding material have excellent mechanical properties and good conductive properties by adding a suitable amount of filler to the polyethylene matrix resin. In Comparative Example 1, the content of polyethylene resin is too much, and only 20% of conductive carbon black filler is added. The conductive network has not been fully established, and the distance between the conductive carbon blacks is large, resulting in a high volume resistivity of the composite material.
[0067] It can be seen from Example 1 and Comparative Examples 3-5 that after two types of conductive carbon black are compounded in a certain ratio in a semi-conductive shielding material and added to the polyethylene matrix resin as a conductive filler, the dispersion of the conductive carbon black in the matrix resin is improved to a certain extent, which is beneficial to improve the smoothness of the shielding / insulation interface, so that the shielding material has both excellent mechanical properties and conductive properties.
[0068] The present invention conducts space charge injection tests on Example 1, Comparative Example 3 and Comparative Example 5 respectively: the electroacoustic pulse method is used to measure the injection characteristics of space charge from the semi-conductive shielding material into the insulating material and the charge accumulation in the insulating material. The semi-conductive shielding material is used as an electrode material and is made into a circular sample with a thickness of 1 mm and a diameter of 20 mm. LLDPE is made into a circular sample with a thickness of 0.2 mm and a diameter of 50 mm. Before the test, the LLDPE sample is short-circuited and placed in an oven for 24 hours to avoid the influence of residual charge on the experiment. Figure 1-3It can be seen that the use of two conductive carbon blacks in a certain ratio as conductive fillers added to the polyethylene matrix resin effectively inhibits the injection of space charges from the shielding layer into the insulating layer, effectively reduces the degree of electric field distortion in the insulating layer, and thus improves the electrical properties of the insulating material. In Comparative Example 5, the charge injection and electric field distortion are more obvious than those in Example 1, which will make the local field strength of the insulating material larger, making it more prone to breakdown.
[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.
Claims
1. A thermoplastic polyethylene-based shielding material for DC power cable, characterized in that: The composition comprises the following components in parts by weight: Polyethylene resin 70-74 parts; filler 22-28 parts; additive 2-6 parts; The filler comprises a first conductive carbon black and a second conductive carbon black, wherein the particle size of the first conductive carbon black is not less than 30 nm, and the particle size of the second conductive carbon black is not greater than 15 nm.
2. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 1, characterized in that: The particle size of the first conductive carbon black is 30-40 nm, and the particle size of the second conductive carbon black is 5-15 nm.
3. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 1, characterized in that: The weight ratio of the first conductive carbon black to the second conductive carbon black in the filler is (85-90):(10-15).
4. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 1, characterized in that: The polyethylene resin is a linear low-density polyethylene, and the melt index of the polyethylene resin at 190° C. / 2.16 kg is 0.15-0.25 g / 10 min.
5. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 1, characterized in that: The thermoplastic polyethylene-based shielding material for DC power cable comprises the following components in parts by weight: Polyethylene resin 71-72 parts; filler 24-26 parts; additive 3-4 parts.
6. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 1, characterized in that: The auxiliary agent includes 0.5-1 parts of antioxidant and 2-4 parts of dispersant.
7. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 6, characterized in that: The antioxidant includes at least one of the antioxidant 300 , the antioxidant 1010 , and the antioxidant 168 .
8. The thermoplastic polyethylene-based shielding material for DC power cable according to claim 6, characterized in that: The dispersant includes at least one of white oil, ethylene bisstearamide and oleamide.
9. The method for preparing the shielding material for thermoplastic polyethylene-based DC power cable according to any one of claims 1 to 8, characterized in that: The following steps are involved: The polyethylene resin, filler and additive are uniformly mixed according to a proportion, and then melt-blended and extruded in an extruder, compressed, pelletized and dried to obtain a thermoplastic polyethylene-based shielding material for DC power cables.
10. The method for preparing a shielding material for a thermoplastic polyethylene-based DC power cable according to claim 9, characterized in that: The temperature of the melt blending extrusion is 150-180° C. and the rotation speed is 40-50 r / min.