Flame-retardant polyethylene sheath material for B1 flame-retardant grade high-voltage cable and preparation method of flame-retardant polyethylene sheath material

Abstract

The invention discloses a flame-retardant polyethylene sheath material for a B1 flame-retardant grade high-voltage cable and a preparation method of the flame-retardant polyethylene sheath material. The sheath material is prepared from the following raw materials in parts by weight: 15-20 parts of a polyolefin elastomer, 10-15 parts of linear low-density polyethylene resin, 5.0-10 parts of a compatilizer, 45-55 parts of a halogen-free flame retardant, 10-15 parts of a charring agent, 0.5-1.0 part of an antioxidant, 1.0-2.0 parts of a lubricant and 1.0-2.0 parts of carbon black. The preparation method comprises the following steps: banburying and mixing the raw materials, pressurizing and plasticizing (the pressure is greater than or equal to 25MPa, the final temperature is 200-220 DEG C, and the materials are turned over at 120 DEG C, 160 DEG C and 180 DEG C in sections), and granulating through a twin-screw extruder (140-180 DEG C) and a single-screw extruder (90-140 DEG C) in series. The sheath material has excellent flame retardance (full of B1 grade of GB 31247-201), high electrical property (the volume resistivity at 20 DEG C is greater than or equal to 1.2 * 10 < 16 > omega.m) and mechanical strength, and is suitable for protection of 66kV and above high-voltage cables.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable materials, in particular to a B1 flame-retardant grade high-voltage cable flame-retardant polyethylene sheath material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the national economy, the demand for wire and cable is growing rapidly, and the quality requirements for wire and cable in various fields are gradually increasing. The implementation of GB 31247-2014 standard makes B1 flame-retardant grade low smoke halogen-free a research hotspot in the wire and cable industry.

[0003] In the fields of medium and low voltage power cables, optical communication cables and electrical equipment wires, B1 flame-retardant grade low smoke halogen-free product technology is relatively mature. However, for high-voltage cables, especially 66kV and above high-voltage cables, due to their large outer diameter and high electrical performance requirements, the flame-retardant performance of the sheath material faces higher challenges.

[0004] Currently, high-voltage cable sheaths generally use high electrical performance polyvinyl chloride or (flame-retardant) polyethylene as sheath material. Polyvinyl chloride cannot achieve halogen-free and low smoke requirements due to the presence of a large amount of chlorine elements. The existing flame-retardant polyethylene sheath material, although can meet the requirements of bundle burning, low smoke and halogen-free to some extent, such as meeting the requirements of ST12 sheath material in IEC60840-2020, IEC60627-2022 and GB / T 11017-2024 standards, but has deficiencies in B1 flame-retardant grade. For example, the sheath for low smoke halogen-free high-voltage cable introduced in CN 11628537A and CN 104945728A can meet the basic requirements of ST12, but does not involve the research of B1 flame-retardant grade, and cannot meet the demand of high-voltage cable for B1 flame-retardant grade.

[0005] Therefore, it has become a problem to be solved in the field to develop a flame-retardant polyethylene sheath material for high-voltage cable that can meet B1 flame-retardant grade. SUMMARY

[0006] The purpose of the present application is to provide a B1 flame-retardant grade high-voltage cable flame-retardant polyethylene sheath material and a preparation method thereof, to solve the problem that the flame-retardant polyethylene in the prior art cannot meet the B1 flame-retardant grade when used in high-voltage cables.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A B1 flame-retardant grade high-voltage cable flame-retardant polyethylene sheath material is prepared from the following raw materials by weight:

[0009] Polyolefin elastomer 15-20;

[0010] Linear low density polyethylene resin 10-15;

[0011] Compatibilizer 5.0-10;

[0012] Halogen-free flame retardant 45-55;

[0013] Charring agent 10-15;

[0014] Antioxidant 0.5-1.0;

[0015] Lubricant 1.0-2.0;

[0016] Carbon black 1.0-2.0;

[0017] The polyolefin elastomer has a melt index of 0.5-5.0 g / 10 min at 190℃ / 2.16 kg, a tensile breaking strength ≥ 20 MPa, and a volume resistivity ≥ 1.0 x 10 16 Ω·cm at 190℃ / 2.16 kg; the halogen-free flame retardant is a chemical magnesium hydroxide; and the charring agent is a combination of organic nano-montmorillonite and sepiolite in a weight ratio of (1-2):1.

[0018] Preferably, the polyolefin elastomer is an 8-carbon high-electricity octene-ethylene copolymer; and the linear low density polyethylene resin is a bimodal linear low density polyethylene having a melt index of 0.2-2.0 g / 10 min at 190℃ / 2.16 kg and a tensile breaking strength ≥ 30 MPa.

[0019] Preferably, the compatibilizer is one or a combination of maleic anhydride grafted metallocene polyethylene and maleic anhydride grafted polyolefin elastomer; the maleic anhydride grafted metallocene polyethylene has a melt index of 0.5-2.0 g / 10 min (190℃ / 2.16 kg) and a density of 0.90-0.92 g / cm 3 ; the maleic anhydride grafted polyolefin elastomer has a melt index of 0.5-1.0 g / 10 min (190℃ / 2.16 kg) and a density of 0.860-0.875 g / cm 3 , and a maleic anhydride grafting rate of 1.0%-1.5%.

[0020] Preferably, the halogen-free flame retardant is hexagonal platelet-shaped magnesium hydroxide modified by double-layer coating of ethylene silane and stearic acid, with a particle size ≥ 2500 mesh and a magnesium hydroxide content ≥ 98%.

[0021] Preferably, the organic nano-montmorillonite is high-purity montmorillonite modified by intercalation of a double long-chain alkyl ammonium group.

[0022] Preferably, the antioxidant is a combination of dilauryl thiodipropionate and a multi-hindered phenol in a weight ratio of 2:(0.5-2).

[0023] Preferably, the lubricant is silicone masterbatch with silicone content of 40%-70%; the carbon black is pigment carbon black.

[0024] The application also provides the B1 flame-retardant grade high-voltage cable flame-retardant polyethylene sheath material, which comprises the following steps:

[0025] S1, each component is put into a mixing machine according to a proportion, and is uniformly mixed within 5-10 minutes to obtain a mixed material;

[0026] S2, the mixed material is subjected to pressure mixing and plasticizing: the pressure is controlled to be greater than or equal to 25 MPa, the final mixing temperature is 200-220 DEG C, and the material is turned over at 120 DEG C, 160 DEG C and 180 DEG C respectively to obtain a plasticized material;

[0027] S3, the plasticized material is extruded and granulated through a double-screw extruder (140-180 DEG C) and a single-screw extruder (90-140 DEG C) in series to obtain the required sheath material.

[0028] The application also provides application of the B1 flame-retardant grade high-voltage cable flame-retardant polyethylene sheath material in protection of 66 kV and above high-voltage cables.

[0029] Compared with the prior art, the technical scheme of the application has the following advantages:

[0030] A, the application adopts hexagonal plate crystal type chemical magnesium hydroxide modified by double-layer coating of ethylene silane and stearic acid as a halogen-free flame retardant, the particle size is greater than or equal to 2500 meshes, and the content is greater than or equal to 98%, the specific selection and modification of the flame retardant can effectively improve the flame retardant performance of the sheath material, and the flame retardant has good compatibility with other components.

[0031] B, the application selects organic nano-montmorillonite and sepiolite in a specific proportion as a charring agent, the organic nano-montmorillonite is modified by double-long-chain alkyl ammonium intercalation, can form a dense carbon layer during combustion, cooperates with the flame retardant to ensure the integrity of the sheath after combustion, and further improves the flame retardant effect.

[0032] C, the application optimizes the raw material ratio, and the synergistic effect of the components makes the prepared sheath material not only have excellent flame retardant performance (can pass the B1 grade combustion test in GB 31247-2014 standard), but also have good mechanical properties, electrical properties and thermal aging properties, such as tensile strength greater than or equal to 12.5 MPa, elongation at break greater than or equal to 300%, volume resistivity at 20 DEG C greater than or equal to 5.0 x 10 12 Ω·m, etc.

[0033] D,The preparation method of the application controls the mixing time, pressure, temperature and material overturning time, and the temperature of the double screw and single screw extruders, so as to ensure that the components are fully mixed and plasticized uniformly, which is beneficial to improving the overall performance of the sheath material, and the process is stable and controllable, and is suitable for industrial production.

[0034] E,The sheath material prepared by the application is suitable for 66kV and above high-voltage cable protection, fills the gap that the sheath material for high-voltage cable in the prior art is difficult to meet the B1 flame retardant grade, and has high industrial application value. DETAILED DESCRIPTION

[0035] The application can be implemented in many different forms, and should not be understood as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the inventive concept of the application to those skilled in the art. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0036] Example 1

[0037] The present embodiment provides a B1 flame-retardant grade high-voltage cable flame-retardant polyethylene sheath material, the raw material components and weight parts are as follows: polyolefin elastomer 15; linear low density polyethylene resin 15; compatibilizer 5; halogen-free flame retardant 45; char former 12; antioxidant 0.8; lubricant 1.5; carbon black 1.5. Among them, the polyolefin elastomer is octene-ethylene copolymer, the melt index at 190℃ and 2.16Kg is 0.5g / 10min, the tensile breaking strength is 22MPa, and the volume resistivity is 2.2x10 16 Ω·cm. The linear low density polyethylene resin is a bimodal linear low density polyethylene, the melt index at 190℃ and 2.16Kg is 0.20g / 10min, and the tensile breaking strength is 35MPa. The compatibilizer is a combination of maleic anhydride grafted metallocene polyethylene and maleic anhydride grafted polyolefin elastomer, the weight ratio is 0.5:1, and the maleic anhydride grafting rate is 1.2%. The melt indexes of the two compatibilizers at 190℃ and 2.16Kg are 0.6g / 10min and 0.1g / 10min respectively; the density of the maleic anhydride grafted metallocene polyethylene is 0.91g / cm 3 , and the density of the maleic anhydride grafted polyolefin elastomer is 0.865g / cm 3The halogen-free flame retardant is hexagonal platelet-shaped chemical magnesium hydroxide modified by double-layer coating of vinyl silane and stearic acid, with a magnesium hydroxide content of 98.5% and a particle size of 2500 mesh. The charring agent is a combination of high-purity nano-montmorillonite and sepiolite modified by double-long-chain alkyl ammonium intercalation, with a weight ratio of 1:1. The antioxidant is a combination of dilauryl thiodipropionate and a multi-hindered phenol, with a weight ratio of 2:1. The lubricant is silicone masterbatch with a silicone content of 50%. The carbon black is pigment carbon black.

[0038] The embodiment also provides a preparation method of the B1 flame-retardant grade flame-retardant polyethylene sheath material for high-voltage cables, including the following steps:

[0039] S1, placing the components according to the proportion into the cavity of the internal mixer, uniformly mixing within 6 min to obtain a mixed material;

[0040] S2, pressure plasticizing the mixed material, controlling the pressure to be 25 MPa, and finally controlling the internal mixing temperature to be 210 ℃, and respectively performing material overturning at 120 ℃, 160 ℃ and 180 ℃ to obtain a plasticized material;

[0041] S3, extruding and granulating the plasticized material through a double-screw extruder (140-170 ℃) and a single-screw extruder (100-140 ℃) in series to obtain the required sheath material.

[0042] Example 2

[0043] The embodiment provides a B1 flame-retardant grade flame-retardant polyethylene sheath material for high-voltage cables, raw material components and weight parts of which are as follows: polyolefin elastomer 20; linear low-density polyethylene resin 10; compatibilizer 8; halogen-free flame retardant 50; charring agent 10; antioxidant 0.6; lubricant 2.0; carbon black 2.0. Among them, the polyolefin elastomer is octene-ethylene copolymer, the melt index at 190 ℃ and 2.16 Kg is 0.9 g / 10 min, the tensile breaking strength is 21 MPa, and the volume resistivity is 1.2 x 10 16 Ω·cm. The linear low-density polyethylene resin is bimodal linear low-density polyethylene, the melt index at 190 ℃ and 2.16 Kg is 1.00 g / 10 min, and the tensile breaking strength is 33 MPa. The compatibilizer is maleic anhydride grafted metallocene polyethylene, the maleic anhydride grafting rate is 1.0%, the melt index at 190 ℃ and 2.16 Kg is 1.0 g / 10 min, and the density is 0.90 g / cm 3The halogen-free flame retardant is hexagonal lamellar magnesium hydroxide chemically modified with a double-layer coating of ethylene silane and stearic acid, with a magnesium hydroxide content of 99% and a particle size of 3000 mesh. The charring agent is a combination of high-purity nano-montmorillonite and sepiolite modified with dual long-chain alkylammonium intercalation, in a weight ratio of 1:1. The antioxidant is a combination of dilaurate thiodipropionate and poly-hindered phenols, in a weight ratio of 2:0.5. The lubricant is silicone masterbatch with a silicone content of 40%. The carbon black is pigment carbon black.

[0044] This embodiment also provides a method for preparing flame-retardant polyethylene sheath material for B1 flame-retardant grade high-voltage cables, including the following steps:

[0045] S1. Place each component into the internal mixer cavity according to the proportion, and mix evenly within 8 minutes to obtain a mixture.

[0046] S2. The mixture is pressurized and plasticized, with the pressure controlled at 30MPa and the final mixing temperature at 220℃. The material is then turned over at 120℃, 160℃ and 180℃ respectively to obtain the plasticized material.

[0047] S3. The plasticized material is extruded and granulated by a twin-screw extruder (150-180℃) and a single-screw extruder (110-140℃) in series to obtain the required sheath material.

[0048] Example 3

[0049] This embodiment provides a flame-retardant polyethylene sheathing material for high-voltage cables with a B1 flame-retardant rating. The raw material components and their weight parts are as follows: polyolefin elastomer 18; linear low-density polyethylene resin 12; compatibilizer 10; halogen-free flame retardant 45; charring agent 12; antioxidant 0.5; lubricant 1.5; carbon black 1.5. The polyolefin elastomer is an octene-ethylene copolymer with a melt index of 5.0 g / 10 min at 190℃ and 2.16 kg, a tensile breaking strength of 23 MPa, and a volume resistivity of 1.9 × 10⁻⁶. 16 The linear low-density polyethylene resin is a bimodal linear low-density polyethylene with a melt index of 2.00 g / 10 min at 190 °C and 2.16 kg, and a tensile breaking strength of 31 MPa. The compatibilizer is a combination of maleic anhydride-grafted metallocene polyethylene and maleic anhydride-grafted polyolefin elastomer in a 1:1 weight ratio, with a maleic anhydride grafting rate of 1.5%. The melt indices of the two compatibilizers at 190 °C and 2.16 kg are 1.2 g / 10 min and 0.4 g / 10 min, respectively; the density of the maleic anhydride-grafted metallocene polyethylene is 0.92 g / cm³. 3 The density of maleic anhydride-grafted polyolefin elastomer is 0.875 g / cm³. 3The halogen-free flame retardant is hexagonal platelet-shaped chemical magnesium hydroxide modified by double-layer coating of vinyl silane and stearic acid, with a magnesium hydroxide content of 98% and a particle size of 2800 mesh. The charring agent is a combination of high-purity nano-montmorillonite and sepiolite modified by double-long-chain alkyl ammonium intercalation, with a weight ratio of 1.5:1. The antioxidant is a combination of dilauryl thiodipropionate and a multi-hindered phenol, with a weight ratio of 2:2. The lubricant is silicone masterbatch with a silicone content of 70%. The carbon black is pigment carbon black.

[0050] The embodiment also provides a preparation method of the flame-retardant polyethylene sheath material for B1 flame-retardant grade high-voltage cables, including the following steps:

[0051] S1, placing the components according to the proportion into the cavity of the internal mixer, uniformly mixing within 5 min to obtain a mixed material;

[0052] S2, pressure plasticizing the mixed material, controlling the pressure to be 28 MPa, and finally controlling the internal mixing temperature to be 200 ℃, and respectively performing material overturning at 120 ℃, 160 ℃ and 180 ℃ to obtain a plasticized material;

[0053] S3, extruding and granulating the plasticized material through a double-screw extruder (140-180 ℃) and a single-screw extruder (100-140 ℃) in series to obtain the required sheath material.

[0054] Example 4

[0055] The embodiment provides a flame-retardant polyethylene sheath material for B1 flame-retardant grade high-voltage cables, raw material components and weight parts of which are as follows: polyolefin elastomer 10; linear low-density polyethylene resin 14; compatibilizer 8.0; halogen-free flame retardant 55; charring agent 15; antioxidant 1.0; lubricant 1.0; carbon black 1.0. Among them, the polyolefin elastomer is octene-ethylene copolymer, the melt index at 190 ℃ and 2.16 Kg is 2.8 g / 10 min, the tensile breaking strength is 27 MPa, and the volume resistivity is 5.5 x 10 16 Ω·cm. The linear low-density polyethylene resin is bimodal linear low-density polyethylene, the melt index at 190 ℃ and 2.16 Kg is 0.30 g / 10 min, and the tensile breaking strength is 40 MPa. The compatibilizer is maleic anhydride grafted polyolefin elastomer, the maleic anhydride grafting rate is 1.3%, the melt index at 190 ℃ and 2.16 Kg is 0.3 g / 10 min and 0.4 g / 10 min, and the density is 0.870 g / cm 3The halogen-free flame retardant is hexagonal platelet-shaped chemical magnesium hydroxide modified by double-layer coating of ethylene silane and stearic acid, the content of magnesium hydroxide is 99.2%, and the particle size is 3000 mesh. The charring agent is a combination of high-purity nano-montmorillonite and sepiolite modified by double-long-chain alkyl ammonium intercalation, with a weight ratio of 2:1. The antioxidant is a combination of dilauryl thiodipropionate and polyhydric hindered phenol, with a weight ratio of 2:1.5. The lubricant is silicone masterbatch with a silicone content of 60%. The carbon black is pigment carbon black.

[0056] The embodiment also provides a preparation method of a B1 flame-retardant grade flame-retardant polyethylene sheath material for high-voltage cables, including the following steps:

[0057] S1, placing the components in the cavity of the internal mixer according to the proportion, uniformly mixing within 10 min, and obtaining a mixed material;

[0058] S2, pressurizing and plasticizing the mixed material, controlling the pressure to be 35 MPa, and finally controlling the internal mixing temperature to be 220 DEG C, and respectively performing material overturning at 120 DEG C, 160 DEG C and 180 DEG C, and obtaining a plasticized material;

[0059] S3, the plasticized material is extruded and granulated by a double-screw extruder (150-180 DEG C) and a single-screw extruder (120-140 DEG C) in series, and the required sheath material is obtained.

[0060] The cable materials prepared in examples 1-4 are respectively subjected to performance tests according to relevant national standards, and the obtained relevant performance results are shown in table 1.

[0061] Table 1: Performance test results of each example

[0062]

[0063] The cable materials prepared in each example are used to prepare high-voltage cables, and the cable specifications are WDZA-YJLW03-127 / 220kV 1*2500mm 2 , and the cable combustion test results of each example are shown in table 2.

[0064] Table 2: Cable combustion test results of each example

[0065]

[0066]

[0067] As shown in table 1, the cable materials prepared in each example meet the various indicators specified in the relevant national standards. As shown in table 2, the high-voltage cables prepared in each example can pass the bundled class A combustion test and the B1 grade combustion test. In summary, the present application effectively overcomes the shortcomings in the prior art and has high industrial utilization value.

[0068] The application is applicable to the prior art.

[0069] Obviously, the above-mentioned embodiments are only examples for clearly illustrating the present application, but not limitation on the embodiments. Based on the above-mentioned description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived from the present application are still within the protection scope of the present application.

Claims

1. A flame-retardant polyethylene sheathing material for high-voltage cables with a B1 flame-retardant rating, characterized in that, It is prepared from the following raw materials in parts by weight: The polyolefin elastomer has a melt index of 0.5-5.0 g / 10 min at 190℃ / 2.16 kg, a tensile breaking strength ≥20 MPa, and a volume resistivity ≥1.0×10⁻⁶. 16 Ω·cm; The halogen-free flame retardant is chemically produced magnesium hydroxide; The charring agent is a composition of organic nano-montmorillonite and sepiolite in a weight ratio of (1-2):

1.

2. The sheath material according to claim 1, characterized in that, The polyolefin elastomer is an octene-ethylene copolymer; the linear low-density polyethylene resin is a bimodal linear low-density polyethylene with a melt index of 0.2-2.0 g / 10 min at 190℃ / 2.16 kg and a tensile breaking strength ≥30 MPa.

3. The sheath material according to claim 1, characterized in that, The compatibilizer is one or a combination of two of maleic anhydride-grafted metallocene polyethylene and maleic anhydride-grafted polyolefin elastomer; wherein the maleic anhydride-grafted metallocene polyethylene has a melt index of 0.5-2.0 g / 10 min (190℃ / 2.16 kg) and a density of 0.90-0.92 g / cm³. 3 The melt index of maleic anhydride-grafted polyolefin elastomer is 0.5-1.0 g / 10 min (190℃ / 2.16 kg), and the density is 0.860-0.875 g / cm³. 3 Furthermore, the maleic anhydride grafting rate is 1.0%-1.5%.

4. The sheath material according to claim 1, characterized in that, The halogen-free flame retardant is hexagonal lamellar magnesium hydroxide modified by double coating with ethylene silane and stearic acid, with a particle size ≥2500 mesh and a magnesium hydroxide content ≥98%.

5. The sheath material according to claim 1, characterized in that, The organic nano-montmorillonite is a high-purity montmorillonite modified by intercalation of two long-chain alkylammonium groups.

6. The sheath material according to claim 1, characterized in that, The antioxidant is a composition of dilaurate thiodipropionate and polyhedral hindered phenols in a weight ratio of 2:(0.5-2).

7. The sheath material according to claim 1, characterized in that, The lubricant is a silicone masterbatch with a silicone content of 40%-70%; the carbon black is pigment carbon black.

8. A flame-retardant polyethylene sheathing material for high-voltage cables with a B1 flame-retardant rating as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Add each component to the internal mixer according to the proportion, and mix evenly within 5-10 minutes to obtain a mixture. S2. Pressurize and plasticize the mixture: control the pressure ≥25MPa, the final mixing temperature 200-220℃, and perform material tumbling at 120℃, 160℃ and 180℃ to obtain the plasticized material. S3. The plasticized material is extruded and granulated by a twin-screw extruder (140-180℃) and a single-screw extruder (90-140℃) in series to obtain the required sheath material.

9. The preparation method according to claim 8, characterized in that, In step S2, the material is turned over at mixing temperatures of 120°C, 160°C, and 180°C.

10. The application of the flame-retardant polyethylene sheathing material for high-voltage cables with a B1 flame-retardant rating as described in any one of claims 1-7 in the protection of high-voltage cables of 66kV and above.

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