A flame retardant semi-conductive shielding material and its preparation method and application

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a flame retardant semiconductive shielding material, a preparation method and an application thereof. The flame retardant semiconductive shielding material comprises the following components in parts by weight: 30-50 parts of polyolefin, 5-10 parts of compatibilizer, 60-80 parts of flame retardant, 5-20 parts of conductive filler, 0.5-2 parts of dispersant, 0.5-2 parts of dispersing aid, and 0.5-2 parts of antioxidant; the dispersing aid is a terminal hydroxyl hyperbranched polyester; the number of terminal hydroxyl groups in the terminal hydroxyl hyperbranched polyester is ≥20 / mol, and the molecular weight is >2500g / mol. The flame retardant semiconductive shielding material prepared by the present invention has good mechanical properties, and can obtain good flame retardant properties and meet high light transmittance requirements while ensuring low resistivity of the material.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a flame retardant semi-conductive shielding material and a preparation method and application thereof. Background Art

[0002] Normally, medium and high voltage power cables of 6KV and above generally have a conductor shielding layer and an insulation shielding layer, the main purpose of which is to make the electric field of the conductor core and the insulation layer uniform. The outer semi-conductive shielding layer has good contact with the outer surface of the insulation layer, and at the same potential as the metal sheath, it can avoid partial discharge caused by cracks or defects on the insulation surface.

[0003] Semi-conductive shielding materials on the market are basically filled with carbon black, carbon nanotubes, etc. to improve the conductivity of the material, and the addition ratio is usually high. Such materials are flammable materials themselves, so even if flame retardants are added, the flame retardancy of the materials is not ideal. The existing small amount of halogen-free flame-retardant semi-conductive products have poor flame retardancy, which only indicates that the oxygen index of the material has increased, and there is no positive correlation with the actual bundle combustion. Therefore, it is urgent to develop a semi-conductive shielding material with both high conductivity and flame retardancy. Summary of the invention

[0004] The present invention aims to provide a flame retardant semi-conductive shielding material and its preparation method and application. The flame retardant semi-conductive shielding material has good mechanical properties and can obtain good flame retardant properties and meet the requirements of low smoke density (high light transmittance) while ensuring low resistivity of the material.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a flame retardant semi-conductive shielding material, comprising the following components in parts by weight: 30-50 parts of polyolefin, 5-10 parts of compatibilizer, 60-80 parts of flame retardant, 5-20 parts of conductive filler, 0.5-2 parts of dispersant, 0.5-2 parts of dispersing aid, and 0.5-2 parts of antioxidant; the dispersing aid is a terminal hydroxyl hyperbranched polyester; the number of terminal hydroxyl groups in the terminal hydroxyl hyperbranched polyester is ≥20 / mol, and the molecular weight is >2500g / mol.

[0006] Preferably, the number of terminal hydroxyl groups in the terminal hydroxyl hyperbranched polyester is 20-45 / mol, and the molecular weight is 2600-11500 g / mol.

[0007] The terminal hydroxyl hyperbranched polyester in the present invention can be selected from one or more of H104, H203, H204, H303, H402, and H403 produced by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0008] Preferably, the flame retardant semiconductive shielding material comprises the following components in parts by weight: 40-45 parts of polyolefin, 6-7.5 parts of compatibilizer, 70-75 parts of flame retardant, 10-15 parts of conductive filler, 1-1.5 parts of dispersant, 1-1.5 parts of dispersing aid, and 0.75-1 part of antioxidant.

[0009] Preferably, the mass ratio of the dispersant to the dispersing aid is (1-1.5): (1-1.5).

[0010] Preferably, the content of the dispersant in the flame retardant semi-conductive shielding material is 0.4wt%-1.5wt%.

[0011] Preferably, the content of the dispersing aid in the flame retardant semi-conductive shielding material is 0.4wt%-1.5wt%.

[0012] Preferably, the polyolefin is one or more of ethylene-vinyl acetate copolymer, polyethylene, and POE.

[0013] More preferably, the polyolefin is a mixture of ethylene-vinyl acetate copolymer, polyethylene and POE, and the mass ratio of the ethylene-vinyl acetate copolymer, polyethylene and POE is (1-3): (1-2): (1-2). When the mass ratio of the ethylene-vinyl acetate copolymer, polyethylene and POE is (2-2.5): (1-1.5): 1, the flame retardant semi-conductive shielding material has the best comprehensive effect.

[0014] Preferably, the hydroxyl-terminated hyperbranched polyester comprises an aliphatic or aromatic hydroxyl-terminated hyperbranched polyester.

[0015] Preferably, the conductive filler is at least one of expanded graphite, carbon nanotubes and graphene.

[0016] Preferably, the compatibilizer is mainly at least one of PE grafts and POE grafts.

[0017] Preferably, the flame retardant is at least one of aluminum hydroxide and magnesium hydroxide.

[0018] Preferably, the dispersant is at least one of stearate, PE wax and silane coupling agent.

[0019] Preferably, the antioxidant is mainly at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris[2,4-di-tert-butylphenyl]phosphite, and distearyl thiodipropionate.

[0020] A method for preparing the flame retardant semiconductive shielding material comprises the following steps:

[0021] Add dispersant to the conductive filler, stir for the first time, add the remaining components except the flame retardant, stir for the second time, then add the flame retardant, continue stirring, then perform banburying, extrusion and granulation to obtain a flame retardant semi-conductive shielding material.

[0022] Preferably, the first stirring time is 3 to 7 minutes, and the second stirring time and the continued stirring time are both 1 to 3 minutes.

[0023] Preferably, the banburying is performed at a temperature of 130-150°C.

[0024] Preferably, the extrusion temperature is 80-120° C., and the rotation speed is 200-300 rpm.

[0025] An application of the flame retardant semi-conductive shielding material in the preparation of power cables.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention adds a specific amount of terminal hydroxyl hyperbranched polyester to the formula components as a dispersing aid. The large number of hydroxyl active groups on the surface of the polyester can effectively combine with the hydroxyl, carboxyl and other active groups on the surface of the conductive filler. The polymer material at the other end and the polyolefin filler also have good compatibility. Combined with the dispersant, efficient dispersion of the conductive filler is achieved, and agglomeration is avoided. Ultimately, excellent conductive properties are achieved under low conductive filler addition (addition amount ≤ 13wt%, minimum 3wt%). At the same time, the surface of the finished wire material obtained by extrusion is smooth and free of granularity, and the negative impact of the conductive filler on the flame retardant properties of the material is greatly reduced.

[0028] (2) The flame-retardant semi-conductive shielding material prepared by the present invention has high flame-retardant properties and can pass through single vertical combustion. Compared with the increase of oxygen index, it is more conducive to the combustion of medium-voltage power cables in bundles, and can be combined with flame-retardant polyethylene materials to increase the probability of medium-voltage power cables in bundles passing through combustion. DETAILED DESCRIPTION

[0029] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0030] In the following examples and comparative examples, unless otherwise specified, the antioxidants were commercially available and the same antioxidants were used in parallel experiments.

[0031] The raw materials used in the examples and comparative examples are shown in Table 1.

[0032] Table 1

[0033]

[0034]

[0035] Examples 1 to 10 and Comparative Examples 1 to 8

[0036] The components and weight proportions of the flame retardant semi-conductive shielding materials of Examples 1 to 10 and Comparative Examples 1 to 8 are shown in Table 2 and Table 3.

[0037] The preparation method of the flame retardant semi-conductive shielding material of Examples 1 to 10 and Comparative Examples 1 to 8 comprises the following steps:

[0038] After adding the conductive filler into the stirring equipment, add the dispersant, stir for 5 minutes, add the remaining components except the flame retardant, stir for 1 minute, then add the flame retardant, stir for 2 minutes, transfer to the internal mixer, mix to 140°C, and then discharge to the twin-screw extruder, extrusion temperature 100°C, rotation speed 250rpm, and then extrude by single screw, granulate, and obtain the flame retardant semi-conductive shielding material.

[0039] Table 2 Component dosage (parts by weight)

[0040]

[0041]

[0042] Table 3 Component dosage in comparative example (parts by weight)

[0043]

[0044] Performance Testing

[0045] The flame retardant semi-conductive shielding materials prepared in Examples 1-10 and Comparative Examples 1-8 were extruded into 10 mm thick sheets using a 50-degree extruder. 2 The bare conductor sample wire was evaluated and irradiated after extrusion, the thermal elongation was controlled at 40-80%, the mechanical properties were tested by wire stripping, and the single vertical burning and smoke density were directly tested using the finished wire; the conductivity test was performed by pressing a 2mm sheet at 180℃×15min, with a pressing pressure of 15MPa. The specific test standards are shown in Table 4, and the performance test results are shown in Table 5.

[0046] Table 4 Test methods and standards

[0047]

[0048] Table 5 Performance test results

[0049]

[0050] From the data in Table 5, it can be seen that the flame retardant semi-conductive shielding materials prepared in Examples 1 to 10 of the present invention can maintain a relatively high elongation at break, have a relatively low volume resistivity, and can achieve good electrical conductivity. At the same time, they can all pass the single vertical burning test to ensure the requirement of high light transmittance, and it is found that the surface of the finished wire material obtained by extrusion of the present invention is smooth and has no granularity; wherein the elongation at break can be maintained in the range of 193 to 211%, the volume resistivity can be maintained in the range of 53 to 94 Ω·cm, and the smoke density can be achieved in the range of 64 to 78%.

[0051] In comparative example 1, the weight proportion of the polyolefin component added is too much, and the flame retardant performance of the flame retardant semiconductive shielding material obtained is poor and cannot pass the single vertical burning test; the weight proportion of the polyolefin component added in comparative example 2 is too little, and the elongation at break of the flame retardant semiconductive shielding material obtained cannot meet the standard requirements; in comparative examples 3 to 4, no dispersing agent is added or an amphiphilic copolymer is used to replace the terminal hydroxyl hyperbranched polyester, and the flame retardant semiconductive shielding material obtained has a high volume resistivity and poor conductivity, which cannot meet actual application requirements; the weight proportion of the dispersing agent added in comparative examples 5 to 6 is not appropriate, and the conductivity, mechanical properties and flame retardant properties of the flame retardant semiconductive shielding material obtained are all affected; the molecular weight and the number of terminal hydroxyl groups of the terminal hydroxyl hyperbranched polyester selected in comparative example 7 are not appropriate, and the number of terminal hydroxyl groups of the terminal hydroxyl hyperbranched polyester selected in comparative example 8 is not appropriate, resulting in a significant increase in the volume resistivity of the obtained material.

[0052] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A flame retardant semi-conductive shielding material, characterized in that: The invention comprises the following components in parts by weight: 30-50 parts of polyolefin, 5-10 parts of compatibilizer, 60-80 parts of flame retardant, 5-20 parts of conductive filler, 0.5-2 parts of dispersant, 0.5-2 parts of dispersing aid, and 0.5-2 parts of antioxidant; the dispersing aid is a hydroxyl-terminated hyperbranched polyester; the number of terminal hydroxyl groups in the hydroxyl-terminated hyperbranched polyester is ≥20 mol / mol, and the molecular weight is >2500 g / mol; The polyolefin is one or more of ethylene-vinyl acetate copolymer, polyethylene, and POE; The conductive filler is at least one of expanded graphite, carbon nanotubes, and graphene; The dispersant is at least one of stearate, PE wax and silane coupling agent.

2. The flame retardant semi-conductive shielding material according to claim 1, characterized in that: The invention comprises the following components in parts by weight: 40-45 parts of polyolefin, 6-7.5 parts of compatibilizer, 70-75 parts of flame retardant, 10-15 parts of conductive filler, 1-1.5 parts of dispersant, 1-1.5 parts of dispersing aid and 0.75-1 part of antioxidant.

3. The flame retardant semi-conductive shielding material according to claim 1, characterized in that: The terminal hydroxyl hyperbranched polyester includes aliphatic or aromatic terminal hydroxyl hyperbranched polyester.

4. The flame retardant semi-conductive shielding material according to claim 1, characterized in that: At least one of the following (1) to (3): (1) The compatibilizer is mainly at least one of a PE graft and a POE graft; (2) The flame retardant is at least one of aluminum hydroxide and magnesium hydroxide; (3) The antioxidant is mainly at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris[2,4-di-tert-butylphenyl]phosphite, and distearyl thiodipropionate.

5. A method for preparing the flame retardant semiconductive shielding material according to any one of claims 1 to 4, characterized in that: The following steps are involved: Add dispersant to the conductive filler, stir for the first time, add the remaining components except the flame retardant, stir for the second time, then add the flame retardant, continue stirring, then perform banburying, extrusion and granulation to obtain a flame retardant semi-conductive shielding material.

6. The preparation method according to claim 5, characterized in that: The first stirring time is 3 to 7 minutes, and the second stirring and continued stirring time are both 1 to 3 minutes.

7. The preparation method according to claim 5, characterized in that: The banburying is performed at a temperature of 130-150°C.

8. The preparation method according to claim 5, characterized in that: The extrusion temperature is 80-120° C. and the rotation speed is 200-300 rpm.

9. Use of the flame retardant semiconductive shielding material as claimed in any one of claims 1 to 4 in the preparation of power cables.

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