A mineral fire-resistant power cable

Abstract

The present invention relates to the field of mineral cable technology and proposes a mineral fire-resistant power cable comprising, from the inside out, a cable core, a mineral insulation layer, a copper sheath, and an outer sheath. The outer sheath comprises the following components by weight: 95-105 parts polyethylene, 4-6 parts plasticizer, 30-35 parts composite titanium dioxide, 1-2 parts antioxidant, and 5-8 parts flame retardant. The composite titanium dioxide is titanium dioxide treated with succinic anhydride and phthalic anhydride. This technical solution solves the problem of poor tensile strength of the polyethylene outer sheath in related mineral fire-resistant power cables.

Description

Technical Field

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

[0002] In modern power systems, mineral fire-resistant power cables, with their core structure of "metal sheath + mineral insulation," have become a key guarantee for power transmission in extreme environments such as high temperatures, fires, and corrosion. These cables typically feature a polyethylene outer sheath over a metallic copper sheath, providing flexible protection, enhanced weather resistance, abrasion resistance, and ease of installation.

[0003] As power construction develops towards high reliability, the problem of insufficient tensile strength of the polyethylene outer sheath layer has gradually become a major bottleneck restricting its application. Existing technologies generally improve the tensile strength of the polyethylene outer sheath layer by adding inorganic fillers to it. Titanium dioxide has become a commonly used inorganic filler for the polyethylene outer sheath layer because of its flame retardant synergy and UV shielding effect. However, titanium dioxide easily agglomerates in the polyethylene matrix to form stress concentration points, which weakens the reinforcing effect of its inorganic filler and results in a lack of significant improvement in the tensile strength of the polyethylene outer sheath layer. Therefore, it is of vital importance to develop a mineral fire-resistant power cable with a high tensile strength 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 the mineral fireproof power cable in the related art.

[0005] The technical solutions of the present invention are as follows:

[0006] The present invention provides a mineral fireproof power cable, which comprises, from the inside to the outside, a cable core, a mineral insulation layer, a copper sheath and an outer sheath layer. The outer sheath layer is made of the following components in parts by weight: 95-105 parts of polyethylene, 4-6 parts of plasticizer, 30-35 parts of composite titanium dioxide, 1-2 parts of antioxidant, and 20-30 parts of flame retardant.

[0007] The composite titanium dioxide is titanium dioxide treated with succinic anhydride and phthalic anhydride.

[0008] As a further technical solution, the material of the mineral insulation layer is magnesium oxide.

[0009] The magnesium oxide in the mineral insulation layer of the present invention's fire-resistant mineral power cable has an extremely high melting point. Its crystal structure remains stable in high-temperature environments, such as fires, and it doesn't rapidly soften or deform due to heat. This allows the magnesium oxide insulation layer to continue functioning even when the cable is exposed to high-temperature threats, preventing problems such as short circuits caused by insulation failure. Furthermore, magnesium oxide is less reactive with common chemicals, allowing it to resist chemical attack and maintain stable performance in the complex environments in which the cable operates.

[0010] As a further technical solution, the preparation method of the composite titanium dioxide comprises the following steps:

[0011] Succinic anhydride and phthalic anhydride are added to N,N-dimethylformamide, titanium dioxide is added, the mixture is stirred, filtered, and dried to obtain the composite titanium dioxide.

[0012] As a further technical solution, the mass ratio of the succinic anhydride to the phthalic anhydride is 7-9:2.

[0013] In the mineral fire-proof 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, or 9:2, preferably 9:2.

[0014] In the outer sheath layer of the mineral fireproof power cable of the present invention, optimizing the mass ratio of succinic anhydride and phthalic anhydride during the preparation of the composite titanium dioxide helps further improve the tensile strength of the outer sheath layer. Considering that succinic anhydride has a small molecular weight and good diffusivity, while phthalic anhydride has a relatively complex molecular structure and good coverage, the inventors found that when the mass ratio of succinic anhydride to phthalic anhydride is 7 to 9:2, the tensile strength of the outer sheath layer is even better. Analysis shows that within this mass ratio range, the composite effect of succinic anhydride and phthalic anhydride on titanium dioxide is more excellent. The surface polarity of the composite titanium dioxide does not affect the dispersion properties of the titanium dioxide itself, but also helps improve its compatibility with the matrix, thereby further enhancing the effect of titanium dioxide on the tensile strength of the outer sheath layer.

[0015] As a further technical solution, the mass ratio of succinic anhydride to N,N-dimethylformamide is 1:20-25;

[0016] The mass ratio of the total mass of the succinic anhydride and phthalic anhydride to the titanium dioxide is 1:8-10.

[0017] In the outer sheath of the mineral fireproof 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 the succinic anhydride and phthalic anhydride in the system, ensuring sufficient contact with the 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 anhydrides can moderately composite with the titanium dioxide, forming an appropriate functional group density and distribution, resulting in good dispersion of the composite titanium dioxide in the polyethylene matrix and strong interaction with the polyethylene.

[0018] 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 hours.

[0019] During the preparation of the composite titanium dioxide in the outer sheath layer of the mineral fireproof power cable of the present invention, the stirring temperature can be 90°C, 91°C, 92°C, 93°C, 94°C, or 95°C. A temperature range of 90-95°C ensures both the composite speed and composite effect. A stirring speed of 300-500 rpm allows succinic anhydride and phthalic anhydride to be evenly dispersed in N,N-dimethylformamide and fully contacted with the titanium dioxide, ensuring a more uniform composite. A time range of 3-4.5 hours ensures that the succinic anhydride and phthalic anhydride are fully composited with the titanium dioxide.

[0020] As a further technical solution, the titanium dioxide includes a first titanium dioxide and a second titanium dioxide;

[0021] The particle size of the first titanium dioxide is 10-30 μm;

[0022] The particle size of the second titanium dioxide is 80-100 nm.

[0023] In the outer sheath layer of the mineral fireproof 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 produce 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 friction inside the material, and thus consume more impact energy. At the same time, the effect of filling the gaps makes the microstructure of the material denser, reduces defects that may cause stress concentration, avoids cracks due to stress concentration under impact, and further improves the material's ability to resist impact. Therefore, titanium dioxide with a particle size of 10~30μm and titanium dioxide with a particle size of 80~100nm work synergistically to improve the impact strength of the outer sheath layer of the mineral fireproof power cable.

[0024] As a further technical solution, the mass ratio of the first titanium dioxide to the second titanium dioxide is 2-3:1.

[0025] In the outer sheath layer of the mineral fire-resistant 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, or 3:1. When the mass ratio is between 2 and 3:1, the first titanium dioxide can form a relatively dense skeleton structure, providing primary impact resistance support for the outer sheath layer, while the second titanium dioxide can fully fill the gaps between the skeletons. The combination of the first titanium dioxide and the second titanium dioxide makes the microstructure of the outer sheath layer more compact.

[0026] As a further technical solution, the plasticizer includes one or more of dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate.

[0027] Among the raw materials of the outer sheath layer of the mineral fireproof power cable of the present invention, the plasticizer can be any one or more conventional plasticizers, and can be one or more of dioctyl adipate, dibutyl sebacate, tributyl citrate, dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate, preferably one or more of dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate.

[0028] As a further technical solution, the antioxidant includes one or more of antioxidant 330, antioxidant 168, and antioxidant 1035.

[0029] In the raw materials of the outer sheath layer of the mineral fire-resistant 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 one or more of antioxidant 330, antioxidant 168, and antioxidant 1035.

[0030] As a further technical solution, the flame retardant includes one or more of magnesium hydroxide, aluminum hydroxide, and zinc borate.

[0031] Among the raw materials for the outer sheath layer of the mineral fireproof 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 one or more of magnesium hydroxide, aluminum hydroxide, and zinc borate.

[0032] The present invention also provides a method for preparing a mineral fireproof power cable, which is used to prepare the mineral fireproof power cable, comprising the following steps:

[0033] S1. Copper sheath is installed on the outside of the cable core;

[0034] S2, pouring magnesium oxide powder between the copper sheath and the cable core to form a mineral insulation layer;

[0035] S3. Mixing the raw materials of the outer sheath layer and extruding the mixture outside the copper sheath to obtain the mineral fireproof power cable.

[0036] The working principle and beneficial effects of the present invention are:

[0037] In the present invention, titanium dioxide is composite-treated with succinic anhydride and phthalic anhydride, thereby improving the tensile strength of the outer sheath layer of the mineral fireproof power cable. Different from the direct addition of titanium dioxide to the outer sheath layer of the existing mineral fireproof power cable, the present invention uses succinic anhydride and phthalic anhydride to treat titanium dioxide, which, on the one hand, reduces the surface hydroxyl groups of titanium dioxide, improves the dispersibility between titanium dioxides, and avoids the formation of stress concentration points in the polyethylene matrix due to agglomeration of titanium dioxide. On the other hand, the polarity of titanium dioxide is reduced, so that the compatibility of titanium dioxide with the polyethylene matrix is better and the bonding with polyethylene is tight. When tension acts on the outer sheath layer, the relative sliding of polyethylene molecular chains can be effectively prevented, so that the outer sheath layer can withstand greater tension, thereby improving the tensile strength of the outer sheath layer of the mineral fireproof power cable. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] In the following examples 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.

[0040] Example 1

[0041] A mineral fireproof power cable comprises, from the inside out, a cable core, a mineral insulation layer, a copper sheath, and an outer sheath layer. The outer sheath layer is made of 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.

[0042] The preparation method of composite titanium dioxide comprises the following steps:

[0043] Succinic anhydride and phthalic anhydride in a mass ratio of 11:2 were added to N,N-dimethylformamide (the mass ratio of succinic anhydride to N,N-dimethylformamide was 1:25), and the first titanium dioxide was added (the mass ratio of the total mass of succinic anhydride and phthalic anhydride to the first titanium dioxide was 1:10), and the mixture was stirred at 120°C and 500 rpm for 1 hour, filtered, and dried to obtain a composite titanium dioxide;

[0044] The preparation method of the mineral fireproof power cable comprises the following steps:

[0045] S1. Copper sheath is installed on the outside of the cable core;

[0046] S2, pouring magnesium oxide powder between the copper sheath and the cable core to form a mineral insulation layer;

[0047] S3. Mix the outer sheath layer material and extrude it outside the copper sheath to obtain a mineral fireproof power cable.

[0048] Example 2

[0049] A mineral fireproof power cable comprises, from the inside out, a cable core, a mineral insulation layer, a copper sheath, and an outer sheath layer. The outer sheath layer is made of 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.

[0050] The preparation method of composite titanium dioxide comprises the following steps:

[0051] Succinic anhydride and phthalic anhydride in a mass ratio of 3:1 were added to N,N-dimethylformamide (the mass ratio of succinic anhydride to N,N-dimethylformamide was 1:20), and the first titanium dioxide was added (the mass ratio of the total mass of succinic anhydride and phthalic anhydride to the first titanium dioxide was 1:8), and the mixture was stirred at 100°C and 300 rpm for 1.5 hours, filtered, and dried to obtain composite titanium dioxide;

[0052] The preparation method of the mineral fireproof power cable comprises the following steps:

[0053] S1. Copper sheath is installed on the outside of the cable core;

[0054] S2, pouring magnesium oxide powder between the copper sheath and the cable core to form a mineral insulation layer;

[0055] S3. Mix the outer sheath layer material and extrude it outside the copper sheath to obtain a mineral fireproof power cable.

[0056] Example 3

[0057] The only difference between this embodiment and embodiment 2 is that the mass ratio of succinic anhydride to phthalic anhydride in this embodiment is 5:1.

[0058] Example 4

[0059] The only difference between this embodiment and embodiment 2 is that the mass ratio of succinic anhydride to phthalic anhydride in this embodiment is 7:2.

[0060] Example 5

[0061] The only difference between this embodiment and embodiment 2 is that the mass ratio of succinic anhydride to phthalic anhydride in this embodiment is 9:2.

[0062] Example 6

[0063] The only difference between this embodiment and embodiment 5 is that the first titanium dioxide in this embodiment is replaced by mixed titanium dioxide of equal mass, and the mixed titanium dioxide includes the first titanium dioxide and the second titanium dioxide in a mass ratio of 2:1.

[0064] Example 7

[0065] The only difference between this embodiment and embodiment 5 is that the first titanium dioxide in this embodiment is replaced by mixed titanium dioxide of equal mass, and the mixed titanium dioxide includes the first titanium dioxide and the second titanium dioxide in a mass ratio of 3:1.

[0066] Example 8

[0067] The only difference between this embodiment and embodiment 5 is that the first titanium dioxide in this embodiment is replaced by a second titanium dioxide of equal mass.

[0068] Comparative Example 1

[0069] The only difference between this comparative example and Example 2 is that the preparation method of the composite titanium dioxide in this comparative example includes the following steps:

[0070] Succinic anhydride was added to N,N-dimethylformamide (the mass ratio of succinic anhydride to N,N-dimethylformamide was 1:20), and the first titanium dioxide was added (the mass ratio of succinic anhydride to titanium dioxide was 1:8). The mixture was stirred at 100°C and 300 rpm for 1.5 hours, filtered, and dried to obtain composite titanium dioxide.

[0071] Comparative Example 2

[0072] The only difference between this comparative example and Example 2 is that the preparation method of the composite titanium dioxide in this comparative example includes the following steps:

[0073] Phthalic anhydride was added to N,N-dimethylformamide (the mass ratio of phthalic anhydride to N,N-dimethylformamide was 1:20), and the first titanium dioxide was added (the mass ratio of phthalic anhydride to titanium dioxide was 1:8). The mixture was stirred at 100°C and 300 rpm for 1.5 hours, filtered, and dried to obtain composite titanium dioxide.

[0074] Comparative Example 3

[0075] The only difference between this comparative example and Example 2 is that the composite titanium dioxide in this comparative example is replaced by the first titanium dioxide of the same mass.

[0076] Experimental Example 1

[0077] The outer sheath layers of the mineral fire-resistant power cables produced in Examples 1-5 and Comparative Examples 1-3 were tested for tensile strength according to the method specified in GB / T 1040.1-2018, "Determination of Tensile Properties of Plastics - Part 1: General Principles." The test speed was 20 mm / min, and the specimen size was a dumbbell-shaped 2 × 4 mm. The test results are shown in Table 1.

[0078] Table 1 Tensile strength test results

[0079]

[0080] As can be seen from Table 1, the tensile strength of the outer sheath layer of the mineral fire-resistant power cable prepared in Examples 1 to 5 of the present invention reaches above 12.7 MPa. Therefore, in the present invention, titanium dioxide is treated with succinic anhydride and phthalic anhydride to improve the tensile strength of the outer sheath layer of the fire-resistant power cable.

[0081] Experimental Example 2

[0082] The outer sheath layers of the mineral fireproof power cables prepared in Examples 5 to 8 were tested for Izod notched impact strength according to the method specified in GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics," with the notch being Type A. The test results are shown in Table 2.

[0083] Table 2 Izod notched impact strength test results

[0084]

[0085] As shown in Table 2, the Izod notched impact strength of the outer sheath layer of the mineral fireproof power cable prepared in Examples 6 to 7 of the present invention reaches 31.4 kJ / m 2 As described above, therefore, the present invention uses two types of titanium dioxide particle sizes to improve the impact strength of the outer sheath layer of the mineral fireproof power cable.

[0086] Experimental Example 3

[0087] The outer sheath of the mineral fireproof power cable prepared in Examples 1 and 2 was tested for oxygen index according to the method specified in GB / T 2406.2-2009, "Determination of Combustion Behavior of Plastics by Oxygen Index Method - Part 2: Room Temperature Test." The test results are shown in Table 3.

[0088] Table 3 Oxygen index test results

[0089]

[0090] The above are only 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 should be included in the scope of protection of the present invention.

Claims

1. A mineral fireproof power cable, characterized in that: The cable comprises, from the inside to the outside, a cable core, a mineral insulation layer, a copper sheath and an outer sheath layer. The outer sheath layer comprises the following components in parts by weight: 95-105 parts of polyethylene, 4-6 parts of plasticizer, 30-35 parts of composite titanium dioxide, 1-2 parts of antioxidant, and 20-30 parts of flame retardant. The composite titanium dioxide is titanium dioxide treated with succinic anhydride and phthalic anhydride; The preparation method of the composite titanium dioxide comprises the following steps: Succinic anhydride and phthalic anhydride are added to N,N-dimethylformamide, titanium dioxide is added, stirred, filtered, and dried to obtain the composite titanium dioxide; The mass ratio of the succinic anhydride to the phthalic anhydride is 7-9:2; The mass ratio of 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 titanium dioxide is 1:8-10.

2. A mineral fireproof power cable according to claim 1, characterized in that: The material of the mineral insulation layer is magnesium oxide.

3. The mineral fireproof power cable according to claim 1, characterized in that: During the stirring, the temperature is 90-95° C., the rotation speed is 300-500 rpm, and the time is 3-4.5 hours.

4. The mineral fireproof power cable according to claim 1, characterized in that: The titanium dioxide includes a first titanium dioxide and a 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.

5. The mineral fireproof power cable according to claim 4, characterized in that: The mass ratio of the first titanium dioxide to the second titanium dioxide is 2-3:

1.

6. A mineral fireproof power cable according to any one of claims 1 to 5, characterized in that: The plasticizer includes one or more of dioctyl phthalate, diisononyl phthalate, and dioctyl terephthalate.

7. A mineral fireproof power cable according to any one of claims 1 to 5, 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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