A cross-linked polyolefin insulating material and its preparation method and application

Abstract

The present invention belongs to the technical field of polymer materials, and specifically discloses a cross-linked polyolefin insulating material and a preparation method and application thereof. The present invention adds silane grafts to the raw materials for preparation, which can effectively inhibit the hydrolysis of thermal conductive fillers, so that the thermal conductive effect of the cross-linked polyolefin insulating material can be effectively exerted. The cross-linked polyolefin insulating material of the present invention not only ensures the basic mechanical properties of the material, but also has good flame retardant properties and thermal conductivity. At the same time, the insulation volume resistivity also meets the standards, and has practical application value as a thermal conductive insulating material for charging piles.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a cross-linked polyolefin insulating material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the new energy vehicle market, people's demand for fast charging of new energy vehicles is also increasing. In order to achieve the purpose of fast charging, it is necessary to increase the power supply. High power supply accompanied by high charging current will cause the heat generation of the charging conductor to increase significantly. The charging conductor can be cooled by liquid cooling charging pile technology to avoid overheating of the charging conductor. Polyolefin (PO) is a common insulating material. It has the characteristics of low price, easy processing and molding, and excellent comprehensive performance. It is widely used. However, the thermal conductivity of polyolefin insulation material is usually only 0.2-0.3W / (m·k). As one of the preparation materials for charging cables, it cannot meet the heat dissipation requirements of charging conductors.

[0003] The thermal conductivity of polyolefin materials is usually increased by adding thermally conductive fillers, and commonly used thermally conductive fillers include aluminum oxide, magnesium oxide, zinc oxide, iron oxide, etc. However, the thermal conductivity efficiency of these thermally conductive fillers is still low, and it is generally necessary to add a large amount of thermally conductive fillers to achieve the purpose of improving the thermal conductivity of the material. Due to the actual insulation and mechanical properties required by the material, the thermal conductivity of the material finally obtained is not high. In addition, for relatively efficient thermally conductive fillers (including aluminum nitride, boron nitride, silicon carbide, etc.), such as aluminum nitride, which is one of the most commonly used thermally conductive fillers, it is easy to absorb moisture and deteriorate, resulting in the loss of its high thermal conductivity. Summary of the invention

[0004] In view of the problem of poor thermal conductivity of polyolefin insulating materials involved in the above-mentioned prior art, the present invention provides a cross-linked polyolefin insulating material and a preparation method and application thereof.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A cross-linked polyolefin insulating material comprises the following components in parts by weight: 40-50 parts of polyolefin resin, 5-10 parts of maleic anhydride grafts, 40-70 parts of flame retardants, 20-40 parts of thermal conductive fillers, 0.5-1 parts of silane coupling agents, 2-5 parts of silane grafts, 1-2 parts of cross-linking aids, and 0.5-1 parts of antioxidants.

[0007] As a preferred embodiment of the present invention, the silane graft is at least one of PE silane graft, EVA silane graft, POE silane graft, EVA / POE silane graft, PE / EVA silane graft, PE / POE silane graft

[0008] The invention adds silane grafted materials to the raw materials for preparation, which can effectively inhibit the hydrolysis of the heat-conducting filler and effectively exert the heat-conducting effect of the cross-linked polyolefin insulating material.

[0009] As a preferred embodiment of the present invention, the cross-linked polyolefin insulation material comprises the following components in parts by weight: 40-45 parts of polyolefin resin, 5-7.5 parts of maleic anhydride graft, 60-70 parts of flame retardant, 25-35 parts of thermal conductive filler, 0.5-1 part of silane coupling agent, 3-4 parts of silane graft, 1-2 parts of cross-linking aid, and 0.5-1 part of antioxidant.

[0010] As a preferred embodiment of the present invention, the thermally conductive filler is at least one of aluminum nitride (AlN) and silicon carbide.

[0011] As a preferred embodiment of the present invention, the mass ratio of the thermal conductive filler to the silane coupling agent is (20-60):1.

[0012] As a further preferred embodiment of the present invention, the mass ratio of the thermal conductive filler to the silane coupling agent is (25-40):1.

[0013] As a further preferred embodiment of the present invention, the mass ratio of the thermal conductive filler to the silane coupling agent is 30:1.

[0014] As a preferred embodiment of the present invention, the silane coupling agent is a vinyltrimethoxy silane coupling agent.

[0015] As a preferred embodiment of the present invention, the polyolefin resin includes at least one of ethylene-vinyl acetate copolymer, polyethylene, and polyolefin elastomer.

[0016] As a preferred embodiment of the present invention, the mass ratio of the ethylene-vinyl acetate copolymer, polyethylene and polyolefin elastomer is ethylene-vinyl acetate copolymer: polyethylene: polyolefin elastomer = (0.5-3): (0-3): (0-3).

[0017] As a further preferred embodiment of the present invention, the mass ratio of the ethylene-vinyl acetate copolymer, polyethylene and polyolefin elastomer is ethylene-vinyl acetate copolymer: polyethylene: polyolefin elastomer = (1-2.5): (0-1): (0-1.5).

[0018] As a preferred embodiment of the present invention, the maleic anhydride graft includes at least one of a polyethylene graft (PE graft) and a polyolefin elastomer graft (POE graft).

[0019] The preparation method of silane grafted material comprises the following steps: mixing a material to be grafted and vinyltrimethoxysilane, adding peroxide, extruding and granulating, and drying to obtain the silane grafted material; the material to be grafted comprises at least one of PE, EVA, and POE; the peroxide comprises diisopropylbenzene peroxide; and the extrusion temperature is 100-150°C.

[0020] As a preferred embodiment of the present invention, the flame retardant includes at least one of aluminum hydroxide and magnesium hydroxide.

[0021] As a preferred embodiment of the present invention, the cross-linking auxiliary agent includes at least one of triallyl isocyanurate (TAIC), trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TMPTMA).

[0022] As a preferred embodiment of the present invention, the antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1010), tris[2.4-di-tert-butylphenyl]phosphite (antioxidant 168), and distearyl thiodipropionate.

[0023] The present invention also provides a method for preparing a cross-linked polyolefin insulating material, comprising the following steps:

[0024] (1) subjecting a thermally conductive filler and a silane coupling agent to a surface modification reaction under stirring to obtain a surface-modified thermally conductive filler;

[0025] (2) Premixing and kneading the polyolefin resin, the surface modified thermal conductive filler and the silane grafted material; when the premixed and kneaded mixture reaches the premixed and kneaded temperature, adding the maleic anhydride grafted material, the flame retardant, the crosslinking aid and the antioxidant for kneading; when the kneaded mixture reaches the kneading temperature, extruding and granulating, finally obtaining the crosslinked polyolefin insulating material.

[0026] As a preferred embodiment of the present invention, the stirring speed in step (1) is greater than 5000 rpm / min, and the surface modification reaction time is 3-10 min.

[0027] As a further preferred embodiment of the present invention, the stirring rate in step (1) is 5000-20000 rpm / min, and the surface modification reaction time is 5 min.

[0028] As a preferred embodiment of the present invention, the temperature of the premixing and kneading in step (2) is 100-110°C, and the temperature of the kneading is 130-150°C.

[0029] As a further preferred embodiment of the present invention, the temperature of the premixing and kneading in step (2) is 100°C, and the temperature of the kneading is 130°C.

[0030] As a preferred embodiment of the present invention, in step (2), a twin-screw extruder is used for extrusion at a temperature of 80-120° C. and a rotation speed of 200-300 rpm.

[0031] As a further preferred embodiment of the present invention, in step (2), a twin-screw extruder is used for extrusion at a temperature of 100° C. and a rotation speed of 200 rpm.

[0032] The present invention also provides an application of a cross-linked polyolefin insulating material in a charging pile cable. When the cross-linked polyolefin insulating material is used as a material for preparing the charging pile cable, the charging pile cable can have the advantages of flame retardancy and high thermal conductivity, meeting the requirements of high-power and high-current charging pile cables.

[0033] Compared with the prior art, the present invention has the following beneficial effects: the cross-linked polyolefin insulation material of the present invention has good flame retardancy and thermal conductivity on the basis of ensuring the basic mechanical properties of the material, and the insulation volume resistivity also meets the standard, and has practical application value as a thermal insulation material for charging piles. Among them, the tensile strength of the cross-linked polyolefin insulation material can reach 8-14MPa, the elongation at break can reach 170-280%, and the volume resistivity can reach 1-13 (10 12 Ω·m), oxygen index can reach 26-30, thermal conductivity can reach 0.67-1.3W / (m·K); especially under the optimal conditions, the mechanical properties of cross-linked polyolefin insulation material remain basically unchanged but its thermal conductivity is as high as 0.9-1.3 W / (m·K). DETAILED DESCRIPTION

[0034] To better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific comparative examples and embodiments. Unless otherwise specified, the experimental reagents and instruments involved in the implementation and comparative examples of the present invention are all commonly used ordinary reagents and instruments.

[0035] The raw materials used in the embodiments and comparative examples of the present invention can be directly purchased from the market, or prepared by conventional methods, for example: ethylene-vinyl acetate copolymer (EVA), including but not limited to EVA 7470M purchased from Taiwan Plastics Co., Ltd., China;

[0036] Polyethylene (PE): Exxon, PE 2010PA;

[0037] Polyolefin elastomer (POE): POE 58750, Dow Chemical;

[0038] Maleic anhydride grafted polyolefin elastomer: Nengzhiguang New Materials Technology Co., Ltd., N423;

[0039] Flame retardant: aluminum hydroxide AH-701, Luoyang Zhongchao New Materials Co., Ltd.; magnesium hydroxide S-10, Shreeji Industries;

[0040] Thermal conductive filler: aluminum nitride (AlN), Tokuyama Co., Ltd., Japan;

[0041] Silane coupling agent: KH560 (γ-glycidyloxypropyltrimethoxysilane, a vinyltrimethoxy silane coupling agent), Nanjing Shuguang Chemical Group Co., Ltd.

[0042] Silane grafts: PE silane grafts, EVA silane grafts, POE silane grafts, EVA / POE silane grafts, PE / EVA silane grafts, PE / POE silane grafts, all of which can be prepared by conventional methods or purchased commercially; the preparation process of the silane grafts in this embodiment and the comparative example is as follows: the resin (PE, EVA or POE, total part 100) and vinyltrimethoxysilane (parts 2-3) are mixed and added to a twin-screw extruder through a metering feeder, and peroxide (DCP, part 0.1-0.5) is added by side feeding, the processing temperature is 100-150°C, and the extrusion granulation is followed by drying for 6 hours; in the EVA / POE, PE / EVA, PE / POE grafts, the mass ratio of the two resins is 1:1.

[0043] Cross-linking aid: triallyl isocyanurate (TAIC), commercially available;

[0044] Antioxidant: Antioxidant 1010, Antioxidant 168, commercially available.

[0045] The commercially available raw materials used in the embodiments and comparative examples are all of the same type.

[0046] Examples 1-20

[0047] The raw materials for preparing the cross-linked polyolefin insulating materials of Examples 1-20 are shown in Table 1 below. Their preparation methods are the same, and all include the following steps:

[0048] (1) Preparation of surface-modified thermal conductive filler: AlN powder was introduced into a high-speed mixer (rotation speed was 5000-6000 rpm / min), and KH560 was added and stirred for 5 min to obtain a surface-modified thermal conductive filler;

[0049] (2) According to the proportions in Table 1, polyolefin resin, surface modified thermal conductive filler and silane grafted material are added to an internal mixer, and after internal mixing to 100° C., maleic anhydride grafted material, flame retardant, crosslinking aid and antioxidant are added, and the mixture is continuously mixed. After the temperature of the mixture reaches 140° C., it is transferred to a twin-screw extruder, and granulated by single-screw extrusion at an extrusion temperature of 100° C. and a rotation speed of 200 rpm to obtain the cross-linked polyolefin insulating material.

[0050] Comparative Examples 1-5

[0051] The preparation method of the cross-linked polyolefin insulating material of Comparative Examples 1-5 comprises the following steps:

[0052] (1) Preparation of surface-modified thermal conductive filler: AlN powder was introduced into a high-speed mixer (rotation speed was 5000-6000 rpm / min), and KH560 was added and stirred for 5 min to obtain a surface-modified thermal conductive filler;

[0053] (2) According to the proportions in Table 2, polyolefin resin, thermal conductive filler (the surface-modified thermal conductive filler obtained in step (1) or aluminum nitride not modified in step (1)) and silane grafted material are added to an internal mixer, and after internal mixing at 100° C., maleic anhydride grafted material, flame retardant, cross-linking aid and antioxidant are added, and the mixture is continuously mixed. After the temperature of the mixture reaches 140° C., it is transferred to a twin-screw extruder, and granulated by a single-screw extruder at an extrusion temperature of 100° C. and a rotation speed of 200 rpm to obtain the insulating material.

[0054] Table 1 Raw materials and contents of cross-linked polyolefin insulation materials of Examples 1-19

[0055]

[0056] Table 2 Raw materials and contents of cross-linked polyolefin insulation materials prepared in Comparative Examples 1-4

[0057]

[0058] Performance Testing Methods

[0059] The insulating materials extruded and granulated in the examples and comparative examples were extruded into 10 mm thick using a 50-degree extruder. 2 The bare conductor sample wire is then irradiated, and the thermal extension is controlled at 40-80% to obtain the test sample. The test samples are respectively subjected to mechanical property stripping test, single vertical burning, smoke density and conductivity test. Among them, the conductivity test adopts 180℃×15min pressing 2mm sheet test, and the pressing pressure is 15MPa. The specific test method is carried out according to the method in Table 3 below, and the test results are shown in Table 4.

[0060] Table 3 Test items and standards for examples and comparative examples

[0061]

[0062] Table 4 Performance test results of cross-linked polyolefin insulation materials of examples and comparative examples

[0063]

[0064] It can be seen from Example 1 and Comparative Example 1 that the addition of silane grafted materials in the present invention can effectively inhibit the hydrolysis of the thermally conductive filler, so that the thermal conductivity of the material can be effectively exerted.

[0065] It can be seen from Examples 1 and 8-12 that different types of silane grafts have an effect on thermal conductivity, among which the sea-island structure formed by PE / EVA is more beneficial to thermal conductivity and is superior to silane grafts of other polyolefin systems.

[0066] It can be seen from Example 1 and Comparative Example 2 that the surface improvement of the silane coupling agent can inhibit the hydrolysis of the thermally conductive filler to a certain extent, and it and the silane grafted material can improve the thermal conductivity of the material together.

[0067] It can be seen from Examples 2-5 that as the amount of thermally conductive filler increases, the thermal conductivity increases accordingly, but the elongation at break decreases.

[0068] From the analysis of Examples 1, 2-5 and 20, it can be seen that the mass ratio of thermal conductive filler to silane coupling agent has an effect on the cross-linked polyolefin insulation material. The preferred mass ratio of aluminum nitride to silane coupling agent is (25-40):1, at which time the thermal conductivity of the cross-linked polyolefin insulation material is better.

[0069] From the comparative analysis of Examples 5-7, it can be seen that when aluminum hydroxide and the thermal conductive filler aluminum nitride are combined, the thermal conductivity of the material is higher than the thermal conductivity of magnesium hydroxide and aluminum nitride.

[0070] It can be seen from Examples 1 and 14-19 that the ratio of polyolefin resins EVA, PE and POE has a certain influence on the thermal conductivity of the material, but under the conditions of adding silane grafts and modified aluminum nitride, changing the ratio still obtains a material with good thermal conductivity, and its specific thermal conductivity is 0.67-1.3W / (m·K). The preferred mass ratio of EVA, PE and POE is (1-2.5): (0-1): (0-1.5), at which time the thermal conductivity of the cross-linked polyolefin insulation material is better, specifically 0.98-1.3 W / (m·K).

[0071] The cross-linked polyolefin insulating material of the present invention has good flame retardancy and thermal conductivity on the basis of ensuring the basic mechanical properties of the material, and the insulating volume resistivity also meets the standard, and has practical application value as a thermal conductive insulating material for charging piles.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A cross-linked polyolefin insulating material, characterized in that: It comprises the following components in parts by weight: 40-50 parts of polyolefin resin, 5-10 parts of maleic anhydride graft, 40-70 parts of flame retardant, 20-40 parts of thermal conductive filler, 0.5-1 part of silane coupling agent, 2-5 parts of silane graft, 1-2 parts of cross-linking aid, and 0.5-1 part of antioxidant; the mass ratio of the thermal conductive filler to the silane coupling agent is (20-60): 1; the thermal conductive filler is at least one of aluminum nitride and silicon carbide; the silane graft is at least one of PE silane graft, EVA silane graft, EVA / POE silane graft, PE / EVA silane graft, and PE / POE silane graft; the polyolefin resin comprises at least one of ethylene-vinyl acetate copolymer, polyethylene, and polyolefin elastomer.

2. The cross-linked polyolefin insulating material according to claim 1, characterized in that: The mass ratio of the ethylene-vinyl acetate copolymer, polyethylene and polyolefin elastomer is ethylene-vinyl acetate copolymer: polyethylene: polyolefin elastomer = (0.5-3): (0-3): (0-3).

3. The cross-linked polyolefin insulating material according to claim 2, characterized in that: The mass ratio of the ethylene-vinyl acetate copolymer, polyethylene and polyolefin elastomer is ethylene-vinyl acetate copolymer: polyethylene: polyolefin elastomer = (1-2.5): (0-1): (0-1.5).

4. The cross-linked polyolefin insulating material according to claim 1, characterized in that: Include at least one of the following (a)-(d): (a) the crosslinking aid comprises at least one of triallyl isocyanurate, trimethylolpropane triacrylate and trimethylolpropane trimethacrylate; (b) the antioxidant comprises 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; (C) the flame retardant comprises at least one of aluminum hydroxide and magnesium hydroxide; (d) The maleic anhydride grafted material includes at least one of a polyethylene grafted material and a polyolefin elastomer grafted material.

5. The method for preparing the cross-linked polyolefin insulating material according to any one of claims 1 to 4, characterized in that: The steps include: (1) subjecting a thermally conductive filler and a silane coupling agent to a surface modification reaction under stirring to obtain a surface-modified thermally conductive filler; (2) Premixing and kneading the polyolefin resin, the surface modified thermal conductive filler and the silane grafted material; when the premixed and kneaded mixture reaches the premixed and kneaded temperature, adding the maleic anhydride grafted material, the flame retardant, the crosslinking aid and the antioxidant for kneading; when the kneaded mixture reaches the kneading temperature, extruding and granulating, finally obtaining the crosslinked polyolefin insulating material.

6. The method for preparing a cross-linked polyolefin insulating material according to claim 5, characterized in that: Contain at least one of the following: (a) the stirring speed in step (1) is greater than 5000 rpm / min; (b) the premixing and kneading temperature in step (2) is 100-110°C, and the kneading temperature is 130-150°C; (c) In step (2), a twin-screw extruder is used for extrusion at a temperature of 80-120° C. and a rotation speed of 200-300 rpm.

7. Application of the cross-linked polyolefin insulating material according to any one of claims 1 to 4 in charging pile cables.

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