Mineral fireproof power cable

Abstract

The invention relates to the technical field of mineral cables, and provides a mineral fireproof power cable which sequentially comprises a cable core, a mineral insulating layer, a copper sheath and an outer sheath layer from inside to outside, and the outer sheath layer is prepared from the following raw materials in parts by weight: 95-105 parts of polyethylene, 4-6 parts of a plasticizer, 30-35 parts of composite titanium dioxide, 1-2 parts of an antioxidant and 5-8 parts of a flame retardant; the composite titanium dioxide is titanium dioxide treated by butanedioic anhydride and phthalic anhydride. According to the technical scheme, the problem of poor tensile strength of the polyethylene outer sheath layer of the mineral fireproof power cable in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral cables, and specifically, to a mineral fireproof power cable. Background Art

[0002] In modern power systems, mineral fireproof power cables, with the core structure of "metal sheath + mineral insulation", have become key power transmission guarantees in extreme environments such as high temperature, fire, and corrosion. Such cables usually have a polyethylene outer sheath layer arranged outside the metal copper sheath, and its main function is to provide flexible protection for the cable, enhancing weather resistance, abrasion resistance, and laying convenience.

[0003] With the development of power construction towards high reliability, the problem of insufficient tensile strength of the polyethylene outer sheath layer has gradually become an important bottleneck restricting its application. Existing technologies generally improve its tensile strength by adding inorganic fillers to the polyethylene outer sheath layer. Titanium dioxide has become a commonly used inorganic filler for the polyethylene outer sheath layer due to its dual functions of flame retardant synergism and ultraviolet shielding. However, titanium dioxide is prone to agglomeration in the polyethylene matrix to form stress concentration points, weakening its reinforcing effect as an inorganic filler, resulting in an insignificant improvement in the tensile strength of the polyethylene outer sheath layer. Therefore, it is of crucial significance to develop a mineral fireproof power cable with a high tensile strength of the polyethylene outer sheath layer. Summary of the Invention

[0004] The present invention provides a mineral fireproof power cable, which solves the problem of poor tensile strength of the polyethylene outer sheath layer of mineral fireproof power cables in related technologies.

[0005] The technical solution of the present invention is as follows: The present invention provides a mineral fireproof power cable, which sequentially includes a cable core, a mineral insulation layer, a copper sheath, and an outer sheath layer from the inside to the outside. The raw materials of the outer sheath layer include the following components in parts by weight: 95 - 105 parts of polyethylene, 4 - 6 parts of a plasticizer, 30 - 35 parts of composite titanium dioxide, 1 - 2 parts of an antioxidant, and 20 - 30 parts of a flame retardant; The composite titanium dioxide is titanium dioxide treated with succinic anhydride and phthalic anhydride.

[0006] As a further technical solution, the material of the mineral insulation layer is magnesium oxide.

[0007] In the mineral fire-resistant power cable of the present invention, the magnesium oxide in the mineral insulation layer has an extremely high melting point. In high-temperature environments such as fires, its crystal structure can remain stable and will not soften or deform rapidly due to heat. This enables the magnesium oxide insulation layer to continue to function when the cable is threatened by high temperatures, preventing problems such as short circuits caused by insulation layer failure. Moreover, magnesium oxide is not easily reactive with common chemical substances. In the complex environment where the cable is located, the magnesium oxide insulation layer can resist chemical erosion and maintain the stability of its own performance.

[0008] As a further technical solution, the preparation method of the composite titanium dioxide includes the following steps: Add succinic anhydride and phthalic anhydride to N,N-dimethylformamide, add titanium dioxide, stir, filter, and dry to obtain the composite titanium dioxide.

[0009] As a further technical solution, the mass ratio of the succinic anhydride to the phthalic anhydride is 7-9:2.

[0010] In the mineral fire-resistant power cable of the present invention, the mass ratio of succinic anhydride to phthalic anhydride can be 7:2, 7.1:2, 7.2:2, 7.3:2, 7.4:2, 7.5:2, 7.6:2, 7.7:2, 7.8:2, 7.9:2, 4:1, 8.1:2, 8.2:2, 8.3:2, 8.4:2, 8.5:2, 8.6:2, 8.7:2, 8.8:2, 8.9:2, 9:2, and is preferably 9:2.

[0011] In the outer sheath layer of the mineral fire-resistant power cable of the present invention, when preparing the composite titanium dioxide, optimizing the mass ratio of succinic anhydride to phthalic anhydride helps to further improve the tensile strength of the outer sheath layer. Considering that succinic anhydride has a small molecular weight and good diffusibility, and phthalic anhydride has a relatively complex molecular structure and good coverage, the inventor found that when the mass ratio of succinic anhydride to phthalic anhydride is 7-9:2, the tensile strength of the outer sheath layer is better. The analysis shows that within this mass ratio range, the composite effect of succinic anhydride and phthalic anhydride on titanium dioxide is better. The surface polarity of the composite titanium dioxide will neither affect the dispersion performance of titanium dioxide itself nor help to improve its compatibility with the matrix, thereby further enhancing the strengthening effect of titanium dioxide on the tensile strength of the outer sheath layer.

[0012] As a further technical solution, the mass ratio of the succinic anhydride to N,N-dimethylformamide is 1:20-25; The total mass ratio of the succinic anhydride and the phthalic anhydride to the mass of the titanium dioxide is 1:8-10.

[0013] In the outer sheath layer of the mineral fire-proof power cable of the present invention, when preparing the composite titanium dioxide, when the mass ratio of succinic anhydride to N,N-dimethylformamide is 1:20 - 25, an appropriate amount of N,N-dimethylformamide can evenly disperse succinic anhydride and phthalic anhydride in the system, ensuring sufficient contact with titanium dioxide. The ratio of the total mass of succinic anhydride and phthalic anhydride to the mass of titanium dioxide is 1:4 - 5. Within this range of 1:4 - 5, the acid anhydride can moderately compound with titanium dioxide to form a suitable functional group density and distribution, enabling the composite titanium dioxide to have good dispersibility in the polyethylene matrix and strong interaction with polyethylene.

[0014] As a further technical solution, during the stirring, the temperature is 90 - 95°C, the rotation speed is 300 - 500 rpm, and the time is 3 - 4.5 h.

[0015] In the outer sheath layer of the mineral fire-proof power cable of the present invention, when preparing the composite titanium dioxide, the stirring temperature can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C. The temperature range of 90 - 95°C can not only ensure the compounding speed but also the compounding effect. When the stirring rotation speed is 300 - 500 rpm, succinic anhydride and phthalic anhydride can be evenly dispersed in N,N-dimethylformamide and fully contact with titanium dioxide, making the compounding more uniform. Within the time range of 3 - 4.5 h, it ensures more sufficient compounding of succinic anhydride and phthalic anhydride with titanium dioxide.

[0016] As a further technical solution, the titanium dioxide includes first titanium dioxide and second titanium dioxide; The particle size of the first titanium dioxide is 10 - 30 μm; The particle size of the second titanium dioxide is 80 - 100 nm.

[0017] In the outer sheath layer of the mineral fire-proof power cable of the present invention, the first titanium dioxide can directly bear part of the impact force by virtue of its larger size and disperse it to the surrounding polyethylene molecular chains. The second titanium dioxide has a smaller particle size and can generate more interactions with the polyethylene molecular chains. When an impact occurs, this close interaction can prevent the relative sliding of the polyethylene molecular chains, increase the internal friction of the material, thereby consuming more impact energy. At the same time, the role of filling voids makes the microstructure of the material more dense, reducing the defects that may cause stress concentration and avoiding cracks caused by stress concentration under the impact, further improving the impact resistance of the material. Therefore, the titanium dioxide with a particle size of 10 - 30 μm and the titanium dioxide with a particle size of 80 - 100 nm act synergistically to improve the impact strength of the outer sheath layer of the mineral fire-proof power cable.

[0018] As a further technical solution, the mass ratio of the first titanium dioxide to the second titanium dioxide is 2-3:1.

[0019] In the outer sheath layer of the mineral fire-proof power cable of the present invention, the mass ratio of the first titanium dioxide to the second titanium dioxide can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1. When the mass ratio is 2-3:1, the first titanium dioxide can form a relatively dense skeleton structure to provide the main impact resistance support for the outer sheath layer, and the second titanium dioxide can fully fill the gaps between the skeletons. The cooperation of the first titanium dioxide and the second titanium dioxide makes the microstructure of the outer sheath layer more dense.

[0020] As a further technical solution, the plasticizer includes one or more of dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate.

[0021] In the raw materials of the outer sheath layer of the mineral fire-proof power cable of the present invention, the plasticizer can be any one or more of conventional plasticizers, and can be one or more of dioctyl adipate, dibutyl sebacate, tributyl citrate, dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate. Preferably, it is one or more of dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate.

[0022] As a further technical solution, the antioxidant includes one or more of antioxidant 330, antioxidant 168, and antioxidant 1035.

[0023] In the raw materials of the outer sheath layer of the mineral fire-proof power cable of the present invention, the antioxidant can be any one or more of conventional antioxidants, and can be one or more of antioxidant 330, antioxidant 168, antioxidant 1035, antioxidant 1010, and antioxidant 2246. Preferably, it is one or more of antioxidant 330, antioxidant 168, and antioxidant 1035.

[0024] As a further technical solution, the flame retardant includes one or more of magnesium hydroxide, aluminum hydroxide, and zinc borate.

[0025] In the raw materials of the outer sheath layer of the mineral fire-proof power cable of the present invention, the flame retardant can be any one or more of conventional flame retardants, and can be one or more of antimony trioxide, barium metaborate, magnesium hydroxide, aluminum hydroxide, and zinc borate. Preferably, it is one or more of magnesium hydroxide, aluminum hydroxide, and zinc borate.

[0026] The present invention also provides a preparation method of a mineral fire-proof power cable for preparing the above-mentioned mineral fire-proof power cable, which includes the following steps: S1. A copper sheath is provided outside the cable core; S2. Magnesium oxide powder is poured between the copper sheath and the cable core to form a mineral insulation layer; S3. The raw materials of the outer sheath layer are kneaded and extruded outside the copper sheath to obtain the mineral fire-proof power cable.

[0027] The working principle and beneficial effects of the present invention are as follows: In the present invention, titanium dioxide is subjected to composite treatment with succinic anhydride and phthalic anhydride, which improves the tensile strength of the outer sheath layer of the mineral fire-proof power cable. Different from directly adding titanium dioxide in the outer sheath layer of the existing mineral fire-proof power cable, in the present invention, titanium dioxide is treated with succinic anhydride and phthalic anhydride. On the one hand, the surface hydroxyl groups of titanium dioxide are reduced, the dispersibility between titanium dioxides is improved, and the formation of stress concentration points in the polyethylene matrix due to agglomeration of titanium dioxide is avoided. On the other hand, the polarity of titanium dioxide is reduced, making the compatibility between titanium dioxide and the polyethylene matrix better, and the combination between titanium dioxide and polyethylene is tight. When a tensile force acts on the outer sheath layer, the relative sliding of polyethylene molecular chains can be effectively prevented, enabling the outer sheath layer to withstand a greater tensile force. Therefore, the tensile strength of the outer sheath layer of the mineral fire-proof power cable is improved. Specific embodiments

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0029] In the following embodiments and comparative examples, the average particle size of the first titanium dioxide is 20 μm; the average particle size of the second titanium dioxide is 90 nm, and the model of polyethylene is 2102TN00.

[0030] Example 1 A mineral fire-proof power cable includes, from inside to outside, a cable core, a mineral insulation layer, a copper sheath, and an outer sheath layer in sequence. The raw materials of the outer sheath layer include the following components in parts by weight: 105 parts of polyethylene, 3 parts of dioctyl phthalate, 3 parts of diisononyl phthalate, 35 parts of composite titanium dioxide, 1 part of antioxidant 330, 1 part of antioxidant 168, 15 parts of magnesium hydroxide, and 15 parts of aluminum hydroxide; The preparation method of the composite titanium dioxide includes the following steps: Add succinic anhydride and phthalic anhydride with a mass ratio of 11:2 into N,N-dimethylformamide (the mass ratio of succinic anhydride to N,N-dimethylformamide is 1:25), add the first titanium dioxide (the total mass of succinic anhydride and phthalic anhydride to the mass of the first titanium dioxide is 1:10), stir at 120 °C at a speed of 500 rpm for 1 h, filter, and dry to obtain composite titanium dioxide; The preparation method of a mineral fire-resistant power cable comprises the following steps: S1. Set a copper sheath outside the cable core; S2. Pour magnesium oxide powder between the copper sheath and the cable core to form a mineral insulation layer; S3. Knead the outer sheath layer material and extrude it outside the copper sheath to obtain a mineral fire-resistant power cable.

[0031] Example 2 A mineral fire-resistant power cable, from inside to outside, comprises a cable core, a mineral insulation layer, a copper sheath and an outer sheath layer. The raw materials of the outer sheath layer comprise the following components in parts by weight: 95 parts of polyethylene, 4 parts of dioctyl terephthalate, 30 parts of composite titanium dioxide, 1 part of antioxidant 1035, and 20 parts of zinc borate; The preparation method of the composite titanium dioxide comprises the following steps: Add succinic anhydride and phthalic anhydride with a mass ratio of 3:1 into N,N-dimethylformamide (the mass ratio of succinic anhydride to N,N-dimethylformamide is 1:20), add the first titanium dioxide (the total mass of succinic anhydride and phthalic anhydride to the mass of the first titanium dioxide is 1:8), stir at 100 °C at a speed of 300 rpm for 1.5 h, filter, and dry to obtain composite titanium dioxide; The preparation method of a mineral fire-resistant power cable comprises the following steps: S1. Set a copper sheath outside the cable core; S2. Pour magnesium oxide powder between the copper sheath and the cable core to form a mineral insulation layer; S3. Knead the outer sheath layer material and extrude it outside the copper sheath to obtain a mineral fire-resistant power cable.

[0032] Example 3 The difference between this example and Example 2 is only that the mass ratio of succinic anhydride and phthalic anhydride in this example is 5:1.

[0033] Example 4 The difference between this example and Example 2 is only that the mass ratio of succinic anhydride and phthalic anhydride in this example is 7:2.

[0034] Example 5 The difference between this example and Example 2 is only that the mass ratio of succinic anhydride to phthalic anhydride in this example is 9:2.

[0035] Example 6 The difference between this example and Example 5 is only that the first titanium dioxide in this example is replaced with an equal mass of mixed titanium dioxide, and the mixed titanium dioxide includes first titanium dioxide and second titanium dioxide with a mass ratio of 2:1.

[0036] Example 7 The difference between this example and Example 5 is only that the first titanium dioxide in this example is replaced with an equal mass of mixed titanium dioxide, and the mixed titanium dioxide includes first titanium dioxide and second titanium dioxide with a mass ratio of 3:1.

[0037] Example 8 The difference between this example and Example 5 is only that the first titanium dioxide in this example is replaced with an equal mass of second titanium dioxide.

[0038] Comparative Example 1 The difference between this comparative example and Example 2 is only that the preparation method of the composite titanium dioxide in this comparative example includes the following steps: Add succinic anhydride to N,N-dimethylformamide (the mass ratio of succinic anhydride to N,N-dimethylformamide is 1:20), add the first titanium dioxide (the mass ratio of succinic anhydride to titanium dioxide is 1:8), stir at 100 °C at a speed of 300 rpm for 1.5 h, filter, and dry to obtain the composite titanium dioxide.

[0039] Comparative Example 2 The difference between this comparative example and Example 2 is only that the preparation method of the composite titanium dioxide in this comparative example includes the following steps: Add phthalic anhydride to N,N-dimethylformamide (the mass ratio of phthalic anhydride to N,N-dimethylformamide is 1:20), add the first titanium dioxide (the mass ratio of phthalic anhydride to titanium dioxide is 1:8), stir at 100 °C at a speed of 300 rpm for 1.5 h, filter, and dry to obtain the composite titanium dioxide.

[0040] Comparative Example 3 The difference between this comparative example and Example 2 is only that the composite titanium dioxide in this comparative example is replaced with an equal mass of the first titanium dioxide.

[0041] Experimental Example 1 The outer sheath layers of the mineral fire-proof power cables prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were tested for tensile strength according to the method specified in GB / T 1040.1-2018 Plastics - Determination of tensile properties - Part 1: General principles. The test speed was 20 mm / min, and the specimen size was a dumbbell shape of 2×4 mm. The test results are shown in Table 1.

[0042] Table 1 Tensile strength test results

[0043] As can be seen from Table 1, the tensile strength of the outer sheath layers of the mineral fire-proof power cables prepared in Examples 1 to 5 of the present invention reached more than 12.7 MPa. Therefore, in the present invention, treating titanium dioxide with succinic anhydride and phthalic anhydride improved the tensile strength of the outer sheath layer of the fire-proof power cable.

[0044] Experimental Example 2 The outer sheath layers of the mineral fire-proof power cables prepared in Examples 5 to 8 were tested for the notched Izod impact strength according to the method specified in GB / T 1843-2008 Plastics - Determination of the notched Izod impact strength. The notch was of Type A. The test results are shown in Table 2.

[0045] Table 2 Notched Izod impact strength test results

[0046] As can be seen from Table 2, the notched Izod impact strength of the outer sheath layers of the mineral fire-proof power cables prepared in Examples 6 to 7 of the present invention reached 31.4 kJ / m 2 above. Therefore, in the present invention, using two particle sizes of titanium dioxide improved the impact strength of the outer sheath layer of the mineral fire-proof power cable.

[0047] Experimental Example 3 The outer sheath layers of the mineral fire-proof power cables prepared in Examples 1 to 2 were tested for the oxygen index according to the method specified in GB / T 2406.2-2009 Plastics - Determination of burning behavior by oxygen index - Part 2: Ambient temperature test. The test results are shown in Table 3.

[0048] Table 3 Oxygen index test results

[0049] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A mineral fire-resistant power cable, characterized in that, It sequentially includes a cable core, a mineral insulation layer, a copper sheath and an outer sheath layer from the inside to the outside. The raw materials of the outer sheath layer include the following components in parts by weight: 95-105 parts of polyethylene, 4-6 parts of a plasticizer, 30-35 parts of composite titanium dioxide, 1-2 parts of an antioxidant, and 20-30 parts of a flame retardant; The composite titanium dioxide is titanium dioxide treated with succinic anhydride and phthalic anhydride.

2. The mineral fire-resistant power cable according to claim 1, characterized in that, The material of the mineral insulation layer is magnesium oxide.

3. The mineral fire-proof power cable according to claim 1, characterized in that, The preparation method of the composite titanium dioxide includes the following steps: Adding succinic anhydride and phthalic anhydride into N,N-dimethylformamide, adding titanium dioxide, stirring, filtering, and drying to obtain the composite titanium dioxide.

4. A mineral fire-resistant power cable according to claim 3, characterized in that, The mass ratio of the succinic anhydride to the phthalic anhydride is 7-9:

2.

5. A mineral fire-resistant power cable according to claim 3, characterized in that, The mass ratio of the succinic anhydride to N,N-dimethylformamide is 1:20-25; The mass ratio of the total mass of the succinic anhydride and phthalic anhydride to the mass of titanium dioxide is 1:8-10.

6. A mineral fire-resistant power cable according to claim 3, characterized in that, When stirring, the temperature is 90-95 °C, the rotation speed is 300-500 rpm, and the time is 3-4.5 h.

7. A mineral fire-resistant power cable according to claim 1, characterized in that, The titanium dioxide includes first titanium dioxide and second titanium dioxide; The particle size of the first titanium dioxide is 10-30 μm; The particle size of the second titanium dioxide is 80-100 nm.

8. A mineral fire-proof power cable according to claim 7, characterized in that, The mass ratio of the first titanium dioxide to the second titanium dioxide is 2-3:

1.

9. A mineral fire-proof power cable according to any one of claims 1 to 8, characterized in that, The plasticizer includes one or more of dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate.

10. A mineral fire-resistant power cable according to any one of claims 1 to 8, characterized in that, The antioxidant includes one or more of antioxidant 330, antioxidant 168, and antioxidant 1035; The flame retardant includes one or more of magnesium hydroxide, aluminum hydroxide, and zinc borate.

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