A low-smoke and halogen-free extra-high voltage cable sheath material, a cable, and a preparation method thereof

Abstract

The present invention discloses a low-smoke and halogen-free extra-high voltage cable sheath material, a cable, and a preparation method thereof, belonging to the technical field related to cable materials for extra-high voltage applications. The low-smoke and halogen-free extra-high voltage cable sheath material comprises the following components by mass percentage: 15-20% of ethylene-ethyl acrylate copolymer, 20-30% of metallocene polyethylene, 10-15% of high-density polyethylene, 4-6% of maleic anhydride-grafted metallocene polyethylene, 4-6% of maleic anhydride-grafted polyphenylene ether, 30-40% of organosilicon-modified polyphenylene ether powder, 3-5% of charring agent, 1-3% of polyethylene carrier silicone masterbatch, 1-3% of polyphenylene ether carrier silicone masterbatch, and 0.5-1.0% of antioxidant 300. The low-smoke and halogen-free flame-retardant sheath material for extra-high voltage cables of the present invention does not contain phosphorus-based flame retardants, aluminum hydroxide, and magnesium hydroxide, and has high strength, high elongation at break, and high volume resistivity, and the flame retardancy and light transmittance meet the requirements of the extra-high voltage cable sheath.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials for extra-high voltage applications, and specifically to a low-smoke and halogen-free extra-high voltage cable sheath material, a cable, and a preparation method thereof. Background Art

[0002] Extra-high voltage cables refer to power cables used for transmitting electricity above 110 kV. Generally serving as the central hub in large-scale power transmission systems, they are a type of high-voltage cable with relatively high technical content and are mainly used for long-distance power transmission.

[0003] Before the release of the IEC 60840:2020 standard of the international organization - the International Electrotechnical Commission, polyvinyl chloride sheath materials or halogen-containing flame-retardant polyethylene sheath materials were basically used for extra-high voltage cable sheath materials. Although such sheath materials have good tensile strength, elongation at break, and flame-retardant properties, they have environmental problems such as halogen content and large smoke emission. The new IEC 60840:2020 adds ST12 sheath materials, that is, the production of extra-high voltage cable sheaths has begun to require the use of low-smoke and halogen-free flame-retardant sheath materials. The ST12 sheath requires a tensile strength ≥ 12.5 MPa, an elongation at break before and after hot air aging should be ≥ 300%, the flame retardancy of extra-high voltage cables should meet Class A of bundled combustion, and the light transmittance should be ≥ 60%. Due to the large cross-sectional area of extra-high voltage cables, the light transmittance test often fails; due to the high voltage carried by extra-high voltage cables, there are distributed charges in space during normal power transmission. To ensure the safety of personnel around the cables, the insulation of the sheath material for extra-high voltage cables should be at least one order of magnitude higher than that of ordinary cable sheath materials. Ordinary low-smoke and halogen-free flame-retardant sheath materials usually add a large amount of inorganic flame retardants such as aluminum hydroxide or magnesium hydroxide.

[0004] In the prior art, some halogen-free flame-retardant polyethylene sheath materials for extra-high voltage cables use red phosphorus for flame retardancy. Since red phosphorus-based flame retardants generate red phosphorus decomposition gas during molding, there is an odor during mixing and it is prone to combustion, with a large amount of smoke emitted during combustion, and it is not easy to solve the light transmittance problem of extra-high voltage cables. Some low-smoke and halogen-free flame-retardant sheath materials for extra-high voltage cables add a large amount of inorganic flame retardants such as aluminum hydroxide or magnesium hydroxide, resulting in a decrease in the elongation at break of the cable, far lower than the requirement of more than 300% in IEC 60840 - 2020, a decline in mechanical and electrical properties, a slow extrusion speed, and a large current load on the extruder, unable to meet the requirements of extra-high voltage cable sheaths. There are also some thermoplastic halogen-free flame-retardant polyolefin sheath materials for extra-high voltage cables that use polyphosphazene as a flame retardant, and the smoke density of the resulting sheath material is relatively large, and it is not easy to solve the light transmittance problem of extra-high voltage cables.

[0005] Therefore, in view of the limitations of the performance of existing sheath materials for extra-high voltage cables, there is a need for a halogen-free flame-retardant extra-high voltage cable and its sheath material with high mechanical properties and excellent combustion performance. Summary of the Invention

[0006] To solve the existing technical problems, the present invention provides a low-smoke and halogen-free extra-high voltage cable sheath material, a cable, and a preparation method thereof. The prepared cable has a tensile strength ≥ 12.5 MPa, an elongation at break before and after hot air aging ≥ 300%, and the flame retardancy of the extra-high voltage cable should meet Class A of bundled combustion and a light transmittance ≥ 60%, and at the same time has good extrusion performance. The low-smoke and halogen-free extra-high voltage cable sheath material includes the following components by mass percentage: ethylene-ethyl acrylate copolymer 15 - 20%, metallocene polyethylene 20 - 30%, high-density polyethylene 10 - 15%, maleic anhydride-grafted metallocene polyethylene 4 - 6%, maleic anhydride-grafted polyphenylene ether 4 - 6%, organosilicon-modified polyphenylene ether powder 30 - 40%, charring agent 3 - 5%, polyethylene carrier silicone masterbatch 1 - 3%, polyphenylene ether carrier silicone masterbatch 1 - 3%, antioxidant 300 0.5 - 1.0%.

[0007] Preferably or optionally, the charring agent includes 2-ethanolamino-4,6-ethylenediamino-1,3,5-triazine or 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine.

[0008] Preferably or optionally, the preparation method of the organosilicon-modified polyphenylene ether powder includes the following steps:

[0009] Step 1: Dissolve the polyphenylene ether powder in chlorinated alkane at a temperature of 50 - 60 °C to prepare a polyphenylene ether solution;

[0010] Step 2: Add organosilicon to the polyphenylene ether solution in Step 1, add a strong base solution, and stir to obtain an organosilicon-modified polyphenylene ether solution;

[0011] Step 3: Continue to heat the organosilicon-modified polyphenylene ether solution in Step 2 to 80 - 90 °C, and grind it into powder after the solvent volatilizes to obtain the organosilicon-modified polyphenylene ether powder.

[0012] Preferably or optionally, the molar ratio of the organosilicon to the polyphenylene ether powder is 0.9 - 1.1.

[0013] Preferably or optionally, the organosilicon is a low molecular weight hydroxyl-terminated polysiloxane with a molecular weight of 8000 - 10000.

[0014] Preferably or optionally, the strong base solution in Step 2 is an aqueous sodium hydroxide solution with a mass fraction of 30% - 50%.

[0015] Preferably or optionally, the polyphenylene ether powder is a hydroxyl-terminated polyphenylene ether powder.

[0016] A preparation method of a sheath material for a low-smoke and halogen-free extra-high voltage cable, the preparation method being: directly feeding each raw material component into a reciprocating single-screw extruder through a loss-in-weight metering scale system, and carrying out mixing and extrusion granulation under the condition of a temperature of 140 to 190 °C, thereby obtaining the sheath material for the low-smoke and halogen-free extra-high voltage cable.

[0017] A low-smoke and halogen-free extra-high voltage cable, characterized in that the sheath material of the low-smoke and halogen-free extra-high voltage cable is the sheath material for the low-smoke and halogen-free extra-high voltage cable described in any one of the above.

[0018] Beneficial effects:

[0019] The present invention provides a low-smoke and halogen-free extra-high voltage cable sheath material, a cable, and a preparation method thereof. In the present invention, a polyphenylene ether-modified sheath material is adopted, including maleic anhydride-grafted polyphenylene ether, organosilicon-modified polyphenylene ether powder, polyphenylene ether carrier silicone masterbatch, and a condensation reaction of the organosilicon-modified polyphenylene ether powder, so that the organosilicon is covalently incorporated into the polyphenylene ether molecular chain, improving the dispersibility and processing performance of the polyphenylene ether. The low-smoke and halogen-free flame-retardant sheath material for the extra-high voltage cable prepared by the present invention does not contain a phosphorus-based flame retardant, aluminum hydroxide, and magnesium hydroxide, and has high strength, high elongation at break, high volume resistivity, and the flame retardancy and light transmittance meet the requirements of the extra-high voltage cable sheath. Specific embodiments

[0020] In the following description, a large number of specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some well-known technical features in the art are not described.

[0021] The following combines examples to further illustrate the present invention. The examples are intended to explain the present invention and should not be construed as limiting the present invention. For those not specifying specific technical and reaction conditions in the examples, the techniques or conditions described in the literature in the art or the product specifications can be followed. Any reagent, instrument, or equipment not specifying the manufacturer can be obtained commercially.

[0022] Example 1

[0023] The sheath material for the low-smoke and halogen-free extra-high voltage cable, by mass percentage, includes the following components: ethylene-ethyl acrylate copolymer 15%, metallocene polyethylene 25%, high-density polyethylene 10%, maleic anhydride-grafted metallocene polyethylene 5%, maleic anhydride-grafted polyphenylene ether 5%, organosilicon-modified polyphenylene ether powder 32%, charring agent 2-ethanolamine-4,6-ethylenediamino-1,3,5-triazine 3%, polyethylene carrier silicone masterbatch 2%, polyphenylene ether carrier silicone masterbatch 2%, and 1% of antioxidant 300.

[0024] Due to the low dielectric constant and dielectric loss of polyphenylene ether, low moisture absorption rate, good flame retardancy and self-extinguishing property, as well as excellent mechanical properties, heat resistance and high-temperature creep properties, it is widely used in the fields of electronics and electrical appliances, automobiles, construction, military industry, etc. However, polyphenylene ether has a high melt viscosity, poor fluidity, and is difficult to process and form. In order to improve its processability, it must be modified.

[0025] Silicone has excellent thermal stability, oxidation stability, hydrophobicity, good flexibility and flame retardancy due to the large bond energy of the Si-O bond, and can improve the processing performance and heat resistance of the substrate. By using polymerization, grafting and cross-linking technologies to introduce silicon-containing groups into the polymer molecular chain, the obtained silicon-containing flame-retardant polymer not only has the characteristics of flame retardancy, heat resistance, oxidation resistance and non-flammability, but also has high moisture resistance and molecular flexibility, and the processing performance is also improved.

[0026] In this embodiment, through the condensation reaction of silicone-modified polyphenylene ether powder, silicone is covalently bonded to the polyphenylene ether molecular chain, which not only solves the problems of difficult compounding and uneven dispersion when the silicone flame retardant and polyphenylene ether are added to the material in a physical mixing form, but also improves the problem of poor fluidity of polyphenylene ether, making the material have good extrusion processing performance.

[0027] The preparation method of silicone-modified polyphenylene ether powder includes the following steps:

[0028] Dissolve the polyphenylene ether powder in chloroalkane to prepare a polyphenylene ether solution; add silicone to the polyphenylene ether solution, add a strong base solution, and stir to obtain a silicone-modified polyphenylene ether solution; continue to heat the silicone-modified polyphenylene ether solution until the solvent evaporates and then grind it into powder to obtain silicone-modified polyphenylene ether powder.

[0029] The preparation method of a low-smoke and halogen-free extra-high voltage cable sheath material is as follows: Pass each raw material component through a loss-in-weight metering scale system and directly enter a reciprocating single-screw extruder for mixing and extrusion granulation, and then the low-smoke and halogen-free extra-high voltage cable sheath material of this embodiment is obtained.

[0030] Example 2

[0031] Compared with Example 1, the difference in this embodiment is that the mass percentages of the following components change: 30% of silicone-modified polyphenylene ether powder, 5% of charring agent, and the remaining steps and components are the same as those in Example 1.

[0032] Example 3

[0033] This example is different from Example 1 in that the mass percentages of the following components change: ethylene-ethyl acrylate copolymer 20%, metallocene polyethylene 15%, organosilicon-modified polyphenylene ether powder 37%, the charring agent is 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine, and the remaining steps and components are the same as those in Example 1.

[0034] Example 4

[0035] This example is different from Example 1 in that the mass percentages of the following components change: ethylene-ethyl acrylate copolymer 20%, metallocene polyethylene 15%, organosilicon-modified polyphenylene ether powder 35%, charring agent 5%, the charring agent is 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine, and the remaining steps and components are the same as those in Example 1.

[0036] Comparative Example 1

[0037] This example is different from Example 1 in that the sheath material for low-smoke halogen-free extra-high voltage cables, by mass percentage, includes the following components: ethylene-ethyl acrylate copolymer 20%, metallocene polyethylene 15%, high-density polyethylene 10%, maleic anhydride-grafted metallocene polyethylene 5%, maleic anhydride-grafted polyphenylene ether 5%, organosilicon 5%, polyphenylene ether powder 30%, charring agent 5%, polyethylene carrier silicone masterbatch 2%, polyphenylene ether carrier silicone masterbatch 2%, 1% antioxidant 300, the charring agent is 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine, and the remaining steps and components are the same as those in Example 1.

[0038] Comparative Example 2

[0039] The sheath material for low-smoke halogen-free extra-high voltage cables in this example, by mass percentage, includes the following components: ethylene-ethyl acrylate copolymer 20%, metallocene polyethylene 15%, high-density polyethylene 10%, maleic anhydride-grafted metallocene polyethylene 5%, maleic anhydride-grafted polyphenylene ether 5%, organosilicon 5%, polyphenylene ether powder 32%, charring agent 3%, polyethylene carrier silicone masterbatch 2%, polyphenylene ether carrier silicone masterbatch 2%, 1% antioxidant 300, and the charring agent is 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine.

[0040] The remaining steps and components are the same as those in Example 1.

[0041] Table 1 below shows the content comparison of each component in Examples 1-5 and Comparative Examples 1-2.

[0042] Table 1. Content Comparison of Components in Each Example and Comparative Example

[0043]

[0044] Result Test

[0045] 1. Performance comparison tests were conducted on the mechanical properties (including tensile strength and elongation at break), combustion properties (flaming combustion smoke density and oxygen index), and electrical properties (volume resistivity) of the low-smoke and halogen-free extra-high voltage cables in each example and comparative example. The results are shown in Table 2 below.

[0046] 2. The low-smoke and halogen-free extra-high voltage cables prepared in each example and comparative example were subjected to performance tests under the specifications of the extra-high voltage cable WDZA-YJLW03-64 / 110 kV -1 ×800. The cable performance test data of each example and comparative example are shown in Table 3. (ZA - Class A flame retardant; WD - low-smoke and halogen-free type; YJLW03 - cross-linked polyethylene insulated corrugated aluminum sheath polyethylene outer sheath cable; rated voltage of power cable: 64 / 110 kV; nominal cross-section: 800 mm 2 ).

[0047] Table 2. Comparative test results of the sheath performance of each example and comparative example

[0048] Test items Unit Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Tensile strength MPa 26 24 21 20 20 18 Elongation at break ％ 560 530 490 420 210 170 Smoke density - 64 66 52 55 71 76 Oxygen index ％ 32 35 37 39 29 31 Volume resistivity Ω·m <![CDATA[6.5×10 15 > <![CDATA[5.4×10 15 > <![CDATA[1.2×10 15 > <![CDATA[1.0×10 15 > <![CDATA[0.7×10 15 > <![CDATA[8.2×10 14 >

[0049] Table 3. Test results of WDZA-YJLW03-64 / 110 kV-1×800

[0050] Test items Unit Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Tensile strength MPa 22 20 16 15 14 11 Elongation at break ％ 470 420 410 370 140 120 Bunched burning - Class A Class A Class A Class A Class B Class A Light transmittance ％ 67 65 73 69 62 58

[0051] As can be seen from Table 2 and Table 3, the mechanical properties (including tensile strength and elongation at break), combustion properties (flaming combustion smoke density and oxygen index), and electrical properties (volume resistivity) of the low-smoke and halogen-free flame retardant sheath materials for the extra-high voltage cables in each example are not inferior to those of Comparative Examples 1 - 2. Comparative Examples 1 and 2 used silicone and polyphenylene ether powder, rather than the polyphenylene ether modified by silicone condensation in the examples. Therefore, the dispersion and processing performance of polyphenylene ether in the system are poor, and the properties of its cable sheath materials are lower than those of each example. The low-smoke and halogen-free extra-high voltage cables prepared in each example have high strength, high elongation at break, and high volume resistivity, and their flame retardancy and light transmittance meet the requirements of the extra-high voltage cable sheath.

[0052] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

Claims

1. A sheath material for low-smoke and halogen-free extra-high voltage cables, characterized in that, by mass percentage, it comprises the following components: ethylene-ethyl acrylate copolymer 15-20%, metallocene polyethylene 20-30%, high-density polyethylene 10-15%, maleic anhydride grafted metallocene polyethylene 4-6%, maleic anhydride grafted polyphenylene ether 4-6%, organosilicon-modified polyphenylene ether powder 30-40%, charring agent 3-5%, polyethylene carrier silicone masterbatch 1-3%, polyphenylene ether carrier silicone masterbatch 1-3%, antioxidant 3000 0.5-1.0%; The preparation method of the organosilicon-modified polyphenylene ether powder comprises the following steps: Step 1: Dissolve the polyphenylene ether powder in chlorinated alkane at a temperature of 50-60°C to prepare a polyphenylene ether solution; the polyphenylene ether powder is a hydroxyl-terminated polyphenylene ether powder; Step 2: Add organosilicon to the polyphenylene ether solution in Step 1, add a strong base solution, and stir to obtain an organosilicon-modified polyphenylene ether solution; the organosilicon is a hydroxyl-terminated polysiloxane with a molecular weight of 8000-10000; the molar ratio of the organosilicon to the hydroxyl-terminated polyphenylene ether powder is 0.9-1.1; Step 3: Continue to heat the organosilicon-modified polyphenylene ether solution in Step 2 to 80-90°C, and grind it into powder after the solvent volatilizes to obtain the organosilicon-modified polyphenylene ether powder.

2. A sheath material for low-smoke and halogen-free extra-high voltage cables according to claim 1, characterized in that, the charring agent comprises 2-ethanolamine-4,6-ethylenediamine-1,3,5-triazine or 2,4-diamino-6-hydroxyethylamino-1,3,5-triazine.

3. A sheath material for low-smoke and halogen-free extra-high voltage cables according to claim 1, characterized in that, the strong base solution in Step 2 is an aqueous sodium hydroxide solution with a mass fraction of 30%-50%.

4. A preparation method of a sheath material for low-smoke and halogen-free extra-high voltage cables, characterized in that, the preparation method for preparing the sheath material for low-smoke and halogen-free extra-high voltage cables as described in any one of claims 1-3 is: directly feed each raw material component into a reciprocating single-screw extruder through a loss-in-weight metering scale system, and carry out mixing and extrusion granulation under the condition of a temperature of 140-190°C.

5. A low-smoke and halogen-free extra-high voltage cable, characterized in that, the sheath material of the low-smoke and halogen-free extra-high voltage cable is the sheath material for low-smoke and halogen-free extra-high voltage cables as described in any one of claims 1-3.

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