Semi-conductive oil-resistant low-smoke low-halogen PVC (polyvinyl chloride) sheath material for ultrahigh-voltage cable and preparation method of PVC sheath material

Abstract

The invention relates to a PVC (polyvinyl chloride) sheath material for a semi-conductive oil-resistant low-smoke low-halogen ultrahigh-voltage cable and a preparation method of the PVC sheath material. The PVC sheath material comprises the following raw material components in parts by weight: 100 parts of PVC resin; 35-55 parts of a composite plasticizer; 4-10 parts of a compound stabilizer; 25 to 35 parts of semi-conductive filler; 8-20 parts of an oil resistant modifier; 20 to 40 parts of a low-smoke low-halogen flame retardant synergist; 0.8 to 2.0 parts of a lubricant; 0.3 to 1.0 part of an antioxidant; and 0.5 to 2.0 parts of a silane coupling agent. The following synergistic effects are generated: (1) semiconduction is controllable: the volume resistivity is not greater than 1 * 10 < 2 > omega.cm, the electric field is homogenized, and partial discharge is inhibited; (2) excellent oil resistance: the volume change of IRMS903 oil at 100 DEG C * 96h is less than or equal to 10%, and the retention rate of strength and elongation is greater than or equal to 85%; (3) the smoke density is low, the halogen release is less, and VW-1 / bunched flame retardance is realized; and (4) mechanical property, heat aging resistance, weather resistance and processability are balanced, and the extrusion of the ultrahigh-voltage cable is adapted.

Description

Technical Field

[0001] This invention belongs to the field of cable sheathing material technology, and relates to a PVC sheathing material, specifically a PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables and its preparation method. Background Technology

[0002] Ultra-high voltage cables typically refer to power cables used to transmit power at 110kV or higher. They are generally used as central hubs in large power transmission systems and are primarily used for long-distance power transmission.

[0003] Ultra-high voltage (UHV) cable sheaths must meet performance requirements including electric field homogenization, mechanical protection, oil and chemical resistance, flame retardancy, low smoke, and low halogen content. Existing PVC sheaths generally suffer from the following problems: 1. Poor semi-conductive stability and large resistivity fluctuations, leading to uneven electric field and potential partial discharge; 2. Insufficient oil resistance, resulting in significant swelling and mechanical degradation after oil immersion; 3. Difficulty in balancing flame retardancy with smoke and halogen release, posing a high fire risk; 4. Incompatibility between processability and long-term heat aging and weather resistance. Conventional formulations cannot simultaneously meet the stringent requirements of UHV systems for electrical performance, environmental adaptability, and safety and environmental protection. Summary of the Invention

[0004] In view of the shortcomings of existing technical approaches, the purpose of this invention is to provide a PVC sheath material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0005] To achieve the above objectives, the present invention provides a PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables, comprising the following raw material components in parts by weight: 100 parts of PVC resin; 35-55 parts of compound plasticizer; 4-10 parts of composite stabilizer; 25-35 parts of semi-conductive filler; 8-20 parts of oil-resistant modifier; 20-40 parts of low-smoke, low-halogen flame retardant synergist; Lubricant 0.8~2.0 parts; Antioxidant 0.3~1.0 parts; 0.5 to 2.0 parts of silane coupling agent.

[0006] Preferably, the PVC resin is a mixture of one or more components selected from those with a degree of polymerization of 1300 to 2500.

[0007] Optimally, the composite plasticizer is a mixture of at least two selected from DOTP, DPHP, TOTM and ESO; the composite plasticizer is a mixture of DOTP, TOTM and epoxidized soybean oil in a mass ratio of 1~2:1~2:0.5.

[0008] Optimally, the composite stabilizer is a mixture of at least two selected from calcium-zinc stabilizers, rare earth stabilizers, and hydrotalcite.

[0009] Ideally, the semiconductive filler is a mixture of one or more components selected from conductive carbon black, graphite, and carbon nanotubes.

[0010] Optimally, the oil-resistant modifier is a mixture of one or more components selected from carboxylated nitrile rubber and maleic anhydride-grafted SEBS.

[0011] Ideally, the low-smoke, low-halogen flame retardant synergist is a mixture of one or more of aluminum hydroxide, magnesium hydroxide, zinc borate, and ammonium octamolate.

[0012] Preferably, the lubricant is a mixture of one or more components selected from PE wax, stearic acid, and oxidized polyethylene wax.

[0013] Optimally, the antioxidant is a mixture of one or more selected from antioxidant 1010 and antioxidant 168; the silane coupling agent is a mixture of one or more selected from KH-550, KH-560 and KH-570.

[0014] Another objective of this invention is to provide a method for preparing the above-mentioned semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cable PVC sheath material, comprising the following steps: (a) The PVC resin, composite stabilizer, antioxidant, silane coupling agent and composite plasticizer of the specified amounts are stirred and mixed at 80~95°C; (b) Add the formulated amounts of the semiconductive filler, oil-resistant modifier, low-smoke low-halogen flame retardant synergist and lubricant to the product of step (a), and heat to 100~120°C for stirring and mixing; (c) The product from step (b) is added to a twin-screw extruder for granulation, pelletizing, cooling, air drying, screening and packaging. The process parameters of the twin-screw extruder are: Zone 1 120~135℃, Zone 2 135~150℃, Zone 3 145~165℃, and Die Head 155~165℃.

[0015] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art: The PVC sheath material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables of the present invention, by accurately selecting appropriate types and weights of each component, produces the following synergistic effects: (1) Controllable semi-conductivity: volume resistivity not greater than 1×10 2Ω·cm, electric field homogenization, suppression of partial discharge; (2) Excellent oil resistance: IRMS903 oil volume change ≤10% at 100 degrees*96h, strength and elongation retention rate ≥85%; (3) Low smoke and low halogen flame retardancy: low smoke density and low halogen release, flame retardant through VW-1 / bundling; (4) Excellent comprehensive performance: mechanical, heat aging resistance, weather resistance and processability are balanced, suitable for ultra-high voltage cable extrusion. Detailed Implementation

[0016] This invention relates to a semi-conductive, oil-resistant, low-smoke, low-halogen PVC sheathing material for ultra-high voltage cables, comprising the following raw material components in parts by weight: 100 parts PVC resin; 35-55 parts composite plasticizer; 4-10 parts composite stabilizer; 25-35 parts semi-conductive filler; 8-20 parts oil-resistant modifier; 20-40 parts low-smoke, low-halogen flame retardant synergist; 0.8-2.0 parts lubricant; 0.3-1.0 parts antioxidant; and 0.5-2.0 parts silane coupling agent. By precisely selecting appropriate types and weights of each component, the following synergistic effects are achieved: (1) Controllable semi-conductivity: volume resistivity not greater than 1×10⁻⁶. 2 Ω·cm, electric field homogenization, suppression of partial discharge; (2) Excellent oil resistance: IRMS903 oil volume change ≤10% at 100 degrees*96h, strength and elongation retention rate ≥85%; (3) Low smoke and low halogen flame retardancy: low smoke density and low halogen release, flame retardant through VW-1 / bundling; (4) Excellent comprehensive performance: mechanical, heat aging resistance, weather resistance and processability are balanced, suitable for ultra-high voltage cable extrusion.

[0017] The degree of polymerization of the PVC resin is 1300-2500; preferably, the PVC resin is a mixture of one or more components selected from SG-3 and SG-1. The composite plasticizer is a mixture of at least two components selected from DOTP (dioctyl terephthalate), DPHP (dipropyl heptyl phthalate), TOTM (trioctyl trimellitate), and ESO (epoxidized soybean oil); preferably, the composite plasticizer is a mixture of DOTP, TOTM, and epoxidized soybean oil in a mass ratio of 1-2:1-2:0.5. The composite stabilizer is a mixture of at least two components selected from calcium-zinc stabilizers, rare earth stabilizers, and hydrotalcite (preferably a mixture of calcium-zinc stabilizers and rare earth stabilizers in a mass ratio of 1-10:1). The semi-conductive filler is a mixture of one or more components selected from conductive carbon black, graphite, and carbon nanotubes. The oil-resistant modifier is a mixture of one or more components selected from carboxylated nitrile rubber and maleic anhydride-grafted SEBS. The low-smoke, low-halogen flame retardant synergist is a mixture selected from one or more of aluminum hydroxide (ATH), magnesium hydroxide (MH), zinc borate, and ammonium octamolate (preferably in a mass ratio of 1-3:1-3:1-2). The lubricant is a mixture selected from one or more of PE wax, stearic acid, and oxidized polyethylene wax (preferably a mixture of PE wax and stearic acid in a mass ratio of 1:1-3). The antioxidant is a mixture selected from one or more of antioxidant 1010 and antioxidant 168; the silane coupling agent is a mixture selected from one or more of KH-550, KH-560, and KH-570.

[0018] The preparation method of the above-mentioned semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cable PVC sheath material includes the following steps: (a) mixing the PVC resin, composite stabilizer, antioxidant, silane coupling agent and composite plasticizer in the prescribed amounts at 80~95℃; (b) adding the semi-conductive filler, oil-resistant modifier, low-smoke, low-halogen flame retardant synergist and lubricant in the prescribed amounts to the product of step (a), and heating to 100~120℃ for mixing; (c) adding the product of step (b) to a twin-screw extruder for granulation, pelletizing, cooling, air drying, screening and packaging, wherein the process parameters of the twin-screw extruder are: zone 1 120~135℃, zone 2 135~150℃, zone 3 145~165℃, and die head 155~165℃.

[0019] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in this industry. Example 1

[0020] This embodiment provides a PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables and its preparation method, comprising the following components: PVC-1300: 100 kg; DOTP+TOTM+ESO: 45 kg (of which DOTP is 19.3 kg, TOTM is 19.3 kg, and ESO is 6.4 kg); calcium-zinc rare earth stabilizer: 6 kg (of which calcium-zinc stabilizer MC90214KA is 5 kg, and rare earth stabilizer KEC is 1 kg); conductive carbon black AC80: 25 kg; carboxyl NBR (carboxyl nitrile butadiene rubber): 8 kg; ATH+MH+zinc borate: 30 kg (of which ATH is 10 kg, MH is 10 kg, and zinc borate is 10 kg); PE wax+stearic acid: 1.2 kg (of which PE wax is 0.4 kg and stearic acid is 0.8 kg); antioxidant 1010: 0.5 kg; silane coupling agent (KH-550): 1.0 kg.

[0021] The preparation method of the above-mentioned PVC sheath material includes the following steps: (a) The PVC resin, composite stabilizer, antioxidant, silane coupling agent and composite plasticizer of the specified amounts are stirred and mixed at 80~95°C; (b) Add the formulated amounts of the semiconductive filler, oil-resistant modifier, low-smoke low-halogen flame retardant synergist and lubricant to the product of step (a), and heat to 100~120°C for stirring and mixing; (c) The product from step (b) is added to a twin-screw extruder for granulation, pelletizing, cooling, air drying, screening and packaging. The process parameters of the twin-screw extruder are: Zone 1 120~135℃, Zone 2 135~150℃, Zone 3 145~165℃, and Die Head 155~165℃ (the above range parameters have virtually no effect on the performance of the product). Example 2

[0022] This embodiment provides a PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables and its preparation method, which is basically the same as that in Example 1, except that it contains the following components: PVC-1300: 100kg; DOTP+TOTM+ESO: 55kg (of which, DOTP is 23.6kg, TOTM is 23.6kg, and ESO is 7.8kg); calcium-zinc rare earth stabilizer: 4kg (of which, calcium-zinc stabilizer MC90214KA is 3.5kg, and rare earth stabilizer KEC is 0.5kg); conductive carbon black: 35kg; carboxyl NBR (carboxyl nitrile butadiene rubber): 20kg; ATH+MH+zinc borate: 40kg (of which, ATH is 15kg, MH is 15kg, and zinc borate is 10kg); PE wax+stearic acid: 2.0kg (of which, PE wax is 0.7kg). kg, stearic acid dosage 1.3 kg); antioxidant 1010: 1.0 kg; silane coupling agent (KH-550): 2.0 kg. Example 3

[0023] This embodiment provides a PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables and its preparation method, which is basically the same as that in Example 1, except that it contains the following components: PVC-1300: 100kg; DOTP+TOTM+ESO: 35kg (of which DOTP is 15kg, TOTM is 15kg, and ESO is 5kg); calcium-zinc rare earth stabilizer: 10kg (of which calcium-zinc stabilizer MC90214KA is 6kg, and rare earth stabilizer KEC is 4kg); conductive carbon black: 30kg; carboxyl NBR (carboxyl nitrile butadiene rubber): 15kg; ATH+MH+zinc borate: 20kg (of which ATH is 5kg, MH is 5kg, and zinc borate is 10kg); PE wax+stearic acid: 0.8kg (of which PE wax is 0.3kg). kg, stearic acid dosage 0.5 kg); antioxidant 1010: 0.3 kg; silane coupling agent (KH-550): 0.5 kg. Example 4

[0024] This embodiment provides a PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables and its preparation method. It is basically the same as that in Example 1, except that the PVC resin is 50 kg each of PVC-1300 and PVC-2500. Example 5

[0025] This embodiment provides a semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cable PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that the semi-conductive filler is a composition of conductive carbon black (AC80) and carbon nanotubes (TUBALLMATRIX814) (wherein, AC80: 20 kg; TUBALLMATRIX814: 5 kg).

[0026] Comparative Example 1 This example provides a PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that the plasticizer is 45 kg DOTP.

[0027] Comparative Example 2 This example provides a PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that no oil-resistant modifier is added.

[0028] Comparative Example 3 This example provides a PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that the low-smoke, low-halogen flame retardant synergist is only a mixture of ATH and MH (wherein, the amount of ATH is 15 kg and the amount of MH is 15 kg).

[0029] Comparative Example 4 This example provides a PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that the PVC resin is PVC-1000.

[0030] Comparative Example 5 This example provides a PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that the stabilizer is only 6 kg of calcium-zinc stabilizer (calcium-zinc stabilizer MC90214KA).

[0031] Comparative Example 6 This example provides a PVC sheath material and its preparation method, which is basically the same as that in Example 1, except that no semi-conductive filler is added.

[0032] Performance tests were conducted on the products of Examples 1-5 and Comparative Examples 1-6 (referencing GB / T8815, GB / T2406, GB / T17650, and GB / T17651), and the results are listed in Table 1.

[0033] Table 1 Performance of products in Examples 1-5 and Comparative Examples 1-6

[0034] Notes: 1. Volume resistivity at 23 degrees Celsius should be tested according to GB / T8815 standard; 2. IRM903 oil at 100 degrees Celsius for 96 hours: volume change should be tested using a 25mm*25mm*2mm sample, and tensile strength should be tested according to GB / T2951 (barbell-shaped); 3. Oxygen index should be tested according to GB / T2406 standard; 4. Smoke density should be tested according to GB / T17651.2 standard; 5. Halogen release should be tested according to GB / T17650.2 standard.

[0035] In Examples 1-3, the test results all fell within the required range. Adjusting the amounts of plasticizer, calcium-zinc stabilizer, semi-conductive filler, carboxyl NBR, and flame retardant had little impact on the various properties of the material. Adjusting the plasticizer only affected the material's hardness; a higher amount of calcium-zinc stabilizer resulted in better thermal stability; a higher amount of semi-conductive filler resulted in lower volume resistivity at 23°C; a higher amount of carboxyl NBR resulted in better oil resistance; and a higher amount of flame retardant resulted in a higher oxygen index.

[0036] Compared with Example 1, Example 4 shows that when 50 parts each of PVC-1300 and PVC-2500 are used, PVC-2500 has a larger molecular weight, superior heat and oil resistance, and better weather resistance, thus meeting the requirements for PVC sheathing materials for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0037] Compared with Example 1, Example 5 shows that the combination of (AC80) and TUBALLMATRIX 814 carbon nanotubes has equally excellent conductivity with little difference, and can meet the requirements of PVC sheath material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0038] Compared with Example 1, Comparative Example 1 used DOTP (dioctyl terephthalate) as the plasticizer. Due to its small molecular weight, poor heat resistance, and inability to be extracted by oil, it could not meet the requirements of PVC sheath material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0039] Compared with Example 1, without the addition of carboxyl NBR, the NBR swells in oil, resulting in a larger volume and significant changes in strength and elongation. The product fails to protect the cable and does not meet the requirements for PVC sheathing materials for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0040] Compared with Example 1, the flame retardant properties of the composition with added ATH and MH changed significantly in Comparative Example 3. The oxygen index and smoke density (transmittance) decreased, the halogen acid gas increased, the pH value decreased, and the low smoke and low halogen flame retardant index did not meet the requirements.

[0041] Comparing Comparative Examples 4, 5 and Example 1, the PVC-1300 resin was replaced with PVC-1000, which has a smaller molecular weight and lower heat resistance temperature; the stabilizer was replaced with Aidi Ke RUP151NB, which has poor thermal stability. Both directly caused its oil resistance performance to be unqualified, failing to meet the requirements for PVC sheathing materials for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0042] Compared with Example 1, without the addition of semiconductive carbon black, the volume resistivity at 23°C increased significantly, which did not meet the requirements for PVC sheathing material for semiconductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables.

[0043] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables, characterized in that, It comprises the following raw material components in parts by weight: 100 parts of PVC resin; 35-55 parts of compound plasticizer; 4-10 parts of composite stabilizer; 25-35 parts of semi-conductive filler; 8-20 parts of oil-resistant modifier; 20-40 parts of low-smoke, low-halogen flame retardant synergist; Lubricant 0.8~2.0 parts; Antioxidant 0.3~1.0 parts; 0.5 to 2.0 parts of silane coupling agent.

2. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The degree of polymerization of the PVC resin is 1300~2500; Preferably, the PVC resin is a mixture of one or more components selected from SG-3 and SG-1.

3. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The composite plasticizer is a mixture of at least two selected from DOTP, DPHP, TOTM and ESO; Optimally, the composite plasticizer is a mixture of DOTP, TOTM and epoxidized soybean oil in a mass ratio of 1~2:1~2:0.

5.

4. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The composite stabilizer is a mixture of at least two of the following: calcium-zinc stabilizers, rare earth stabilizers, and hydrotalcite.

5. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The semi-conductive filler is a mixture of one or more of conductive carbon black, graphite, and carbon nanotubes.

6. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The oil-resistant modifier is a mixture of one or more components selected from carboxylated nitrile rubber and maleic anhydride-grafted SEBS.

7. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The low-smoke, low-halogen flame retardant synergist is a mixture of one or more of aluminum hydroxide, magnesium hydroxide, zinc borate, and ammonium octamolate.

8. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The lubricant is a mixture of one or more components selected from PE wax, stearic acid, and oxidized polyethylene wax.

9. The PVC sheathing material for semi-conductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to claim 1, characterized in that: The antioxidant is a mixture of one or more of antioxidants 1010 and antioxidant 168; the silane coupling agent is a mixture of one or more of KH-550, KH-560 and KH-570.

10. A method for preparing the PVC sheath material for semiconductive, oil-resistant, low-smoke, low-halogen ultra-high voltage cables according to any one of claims 1 to 9, characterized in that, Includes the following steps: (a) The PVC resin, composite stabilizer, antioxidant, silane coupling agent and composite plasticizer of the specified amounts are stirred and mixed at 80~95°C; (b) Add the formulated amounts of the semiconductive filler, oil-resistant modifier, low-smoke low-halogen flame retardant synergist and lubricant to the product of step (a), and heat to 100~120°C for stirring and mixing; (c) The product from step (b) is added to a twin-screw extruder for granulation, pelletizing, cooling, air drying, screening and packaging. The process parameters of the twin-screw extruder are: Zone 1 120~135℃, Zone 2 135~150℃, Zone 3 145~165℃, and Die Head 155~165℃.

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