Polyolefin composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer material modification, in particular to a polyolefin composite material and a preparation method and application thereof. The invention provides a polyolefin composite material. The polyolefin composite material is prepared from the following components in parts by weight: 20 to 30 parts of ethylene-vinyl acetate copolymer, 4 to 16 parts of cycloolefin copolymer, 14 to 26 parts of styrene-ethylene-butylene-styrene block copolymer, 1 to 10 parts of compatilizer, 34 to 46 parts of flame retardant, 1 to 3 parts of assistant crosslinker and 0 to 3 parts of other auxiliaries, wherein the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer is greater than or equal to 30%. The polyolefin composite material has the advantages of low cost, excellent organic solvent resistance, salt water resistance and flexibility, and solves the problems of the existing silica gel material in preparation of new energy automobile cables.

Description

Technical Field

[0001] The present application relates to the technical field of polymer material modification, and in particular to a polyolefin composite material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, automotive electrical systems are becoming increasingly complex, and the performance requirements for automotive cables are constantly increasing. Cable outer materials must not only possess excellent electrical insulation and flame retardancy, but also meet multiple requirements, including flexibility, resistance to organic solvents, and resistance to salt water (such as electrolytes). Specifically, during operation, new energy vehicle cables are prone to cracking when exposed to organic solvents. Furthermore, cables may also come into contact with electrolytes, which contain salt, which can degrade the cable's insulation performance.

[0003] Currently, silicone materials are widely used in the industry to manufacture cables for new energy vehicles. For example, Chinese patent application CN117497243A utilizes high-temperature-resistant silicone rubber polymer materials to manufacture a liquid-cooled soft cable. Leveraging the properties of silicone, this cable exhibits excellent flexibility and high-temperature resistance, preventing cracking during long-term use, thereby effectively ensuring the safety of new energy vehicles. However, silicone materials have drawbacks such as high cost and complex processing.

[0004] Therefore, there is an urgent need to develop a cable material that can control costs while having good resistance to organic solvents, salt water and flexibility to meet the application requirements of new energy vehicle cables. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the silicone material used in the prior art for preparing new energy vehicle cables, which cannot be low-cost and resistant to organic solvents, salt water and soft, and to provide a polyolefin composite material.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned polyolefin composite material.

[0007] Another object of the present invention is to provide use of the above polyolefin composite material in the preparation of cables.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions: The present invention protects a polyolefin composite material, comprising the following components in parts by weight: 20-30 parts of ethylene-vinyl acetate copolymer (EVA), 4-16 parts of cycloolefin polymer, 14-26 parts of styrene-ethylene-butylene-styrene block copolymer, 1-10 parts of compatibilizer, 34-46 parts of flame retardant, 1-3 parts of co-crosslinking agent, and 0-3 parts of other additives; Wherein, the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer is ≥30%.

[0009] The present invention adopts ethylene-vinyl acetate copolymer as the main resin. Compared with traditional silicone materials, ethylene-vinyl acetate copolymer has the significant advantages of low cost and simple processing technology.

[0010] In order to make the polyolefin composite material meet basic flame retardant properties, the present invention adds a flame retardant. However, adding a flame retardant to the ethylene-vinyl acetate copolymer will deteriorate the material's resistance to organic solvents and insulation properties after salt water immersion, and cause the material's hardness to be too high.

[0011] The inventors of this invention have discovered that adding a styrene-ethylene-butylene-styrene block copolymer can effectively reduce the material's hardness without degrading the polyolefin composite's resistance to organic solvents and salt water. Furthermore, regulating the VA (vinyl acetate) content in EVA within a specific range not only effectively reduces the material's hardness but also significantly improves its resistance to organic solvents. Regulating the VA content in EVA also helps maintain the material's insulation properties after saltwater immersion.

[0012] The present invention further incorporates a cycloolefin polymer, leveraging its barrier properties to improve the material's resistance to saltwater immersion, maintaining good insulation performance after saltwater immersion. However, the amount of cycloolefin polymer used should be limited, as this can degrade the material's resistance to organic solvents and result in excessive hardness.

[0013] In the present invention, ethylene-vinyl acetate copolymer is used as the base resin, and its content accounts for at least 15wt% of the polyolefin composite material; preferably, the content of the ethylene-vinyl acetate copolymer accounts for 20-28wt% of the polyolefin composite material.

[0014] In the present invention, the amount of ethylene-vinyl acetate copolymer can be specifically 20, 22, 25, 27, or 30 parts by weight; the amount of cycloolefin polymer can be specifically 5, 8, 10, 12, or 15 parts by weight; the amount of styrene-ethylene-butylene-styrene block copolymer can be specifically 15, 18, 20, or 25 parts by weight; the amount of compatibilizer can be specifically 1, 2.5, 5, 7.5, or 10 parts by weight; the amount of flame retardant can be specifically 35, 40, or 45 parts by weight; the amount of cross-linking aid can be specifically 1, 2, or 3 parts by weight; and the amount of other additives can be specifically 0, 1, 1.5, 2, or 3 parts by weight.

[0015] Furthermore, the melt flow rate of the ethylene-vinyl acetate copolymer measured at 190° C. and 2.16 kg is 3-28 g / 10 min.

[0016] Preferably, the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer is 40% to 80%.

[0017] In the present invention, the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer can be specifically 40%, 50%, 60%, 70%, or 80%.

[0018] More preferably, the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer is 50-70%.

[0019] By regulating the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer within this range, the obtained polyolefin composite material has better softness and organic solvent resistance.

[0020] Furthermore, the melt flow rate of the cycloolefin polymer measured at 230° C. and 2.16 kg is 0.5-25 g / 10 min, specifically 0.5, 1.5, 3, 5, 6, 9, 12, 15, 20, or 25 g / 10 min.

[0021] The melt flow rate of the cycloolefin polymer may be tested according to ASTM D-1238-2010.

[0022] Furthermore, the cycloolefin polymer is a cycloolefin homopolymer and / or a cycloolefin copolymer.

[0023] Preferably, the cycloolefin polymer accounts for 3-16 wt % of the polyolefin composite material.

[0024] Furthermore, the cycloolefin copolymer is a copolymer of ethylene and cycloolefin monomers.

[0025] Furthermore, the cycloolefin monomer is one of norbornene and tetracyclododecene.

[0026] Preferably, the cycloolefin monomer is tetracyclododecene.

[0027] The polyolefin composite material prepared by using tetracyclododecene has better softness.

[0028] Furthermore, the Shore A hardness of the styrene-ethylene-butylene-styrene block copolymer is ≤70 A. The Shore A hardness can be measured according to the test standard ISO 7619-1:2010, and the test conditions are: the length and width of the sample are 50 mm*50 mm, the thickness is 6 mm, and the spring test force holding time is 15 s.

[0029] Preferably, the Shore A hardness of the styrene-ethylene-butylene-styrene block copolymer is 63-65 A.

[0030] By regulating the Shore A hardness of the styrene-ethylene-butylene-styrene block copolymer within this range, the obtained polyolefin composite material has better organic solvent resistance.

[0031] Furthermore, the melt flow rate of the styrene-ethylene-butylene-styrene block copolymer measured at 200°C and 5 kg is 0.5-25 g / 10 min, specifically 0.5, 1.5, 3, 5, 6, 9, 12, 15, 20, or 25 g / 10 min.

[0032] The melt flow rate of the styrene-ethylene-butylene-styrene block copolymer may be tested according to ASTM D-1238-2010.

[0033] Furthermore, the mass content of styrene in the styrene-ethylene-butylene-styrene block copolymer is 10% to 40%, and the mass content of styrene is determined by infrared spectroscopy and nuclear magnetic resonance spectroscopy.

[0034] Preferably, the styrene-ethylene-butylene-styrene block copolymer accounts for 12-27 wt % of the polyolefin composite material.

[0035] Furthermore, the compatibilizer is a maleic anhydride compatibilizer.

[0036] Furthermore, the maleic anhydride grafting rate of the maleic anhydride compatibilizer is 0.5% to 2%, and the grafting rate is measured by infrared spectroscopy.

[0037] Furthermore, the maleic anhydride compatibilizer includes one or both of polyethylene grafted maleic anhydride and SEBS grafted maleic anhydride.

[0038] Furthermore, the flame retardant is a hydroxide flame retardant.

[0039] Furthermore, the flame retardant is a metal hydroxide flame retardant.

[0040] Preferably, the metal hydroxide flame retardant includes one or both of magnesium hydroxide and aluminum hydroxide.

[0041] Preferably, the particle size D of the flame retardant 50 The thickness is 0.8-5 μm, specifically 0.8, 1, 1.5, 2, 4, 5 μm.

[0042] In the present invention, the particle size D of the flame retardant 50 Can be measured by microscopy.

[0043] Furthermore, the auxiliary cross-linking agent includes one or more of triallyl isocyanurate (TAIC), trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TMPTMA).

[0044] Furthermore, the other auxiliary agents include antioxidants and / or colorants.

[0045] Furthermore, the antioxidant includes one or more of hindered phenol antioxidants, hindered amine antioxidants, phosphite antioxidants, diphenylamine antioxidants, and thioether antioxidants.

[0046] Furthermore, the colorant is carbon black.

[0047] The present invention provides a method for preparing the polyolefin composite material, comprising the following steps: The components are mixed evenly to obtain a mixture, the mixture is subjected to banburying, and then melt-extruded and granulated to obtain a polyolefin composite material.

[0048] Furthermore, the temperature of the banburying is 150-200°C.

[0049] Furthermore, the temperature of the melt extrusion is 135-175° C.; the screw speed of the melt extruder is 50-500 rpm, and the screw aspect ratio is 48-75:1.

[0050] The present invention protects the use of the above-mentioned polyolefin composite material in the preparation of cables.

[0051] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a polyolefin composite material, which can replace the current silicone material as a cable material and has low cost, good resistance to organic solvents and salt water immersion, and softness. DETAILED DESCRIPTION

[0052] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0053] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0054] Ethylene-vinyl acetate copolymer 1# (EVA-40): ELVAX 40L-03, VA content 40%, produced by DuPont; Ethylene-vinyl acetate copolymer 2# (EVA-50): LEVAPREN® 500, 50% VA by mass, produced by Lanxess, Germany; Ethylene-vinyl acetate copolymer 3# (EVA-70): EVA700XL, VA content of 70%, produced by Lanxess, Germany; Ethylene-vinyl acetate copolymer 4# (EVA-28): EVA 00328, VA content 28%, produced by ExxonMobil; Compatibilizer: PE-g-MAH, MC218, produced by Nengzhiguang; Cyclic olefin polymer 1#: ethylene-norbornene copolymer, Topas@ 9506F-500, melt index 6 g / 10 min (230 °C, 2.16 kg), produced by Polyplastics, Japan; Cycloolefin polymer 2#: ethylene-tetracyclododecene copolymer, APL5014CL(04), melt index 1.5 g / 10 min (230 °C, 2.16 kg), produced by Mitsui Chemicals; Cyclic olefin polymer 3#: ethylene-norbornene copolymer, Topas@ 5013F-04, melt index 9 g / 10 min (230°C, 2.16 kg), produced by Polyplastics, Japan; Polyethylene: LLDPE, LLDPE EXCEED 3158CB, produced by ExxonMobil; SEBS1#: Styrene-ethylene-butylene-styrene block copolymer, G1701, styrene content 37 wt%, melt index 1 g / 10 min (200 °C, 5 kg), Shore A hardness 64 A, produced by Kraton Polymers, USA; SEBS2#: Styrene-ethylene-butylene-styrene block copolymer, G1657, styrene content 13 wt%, melt index 8 g / 10 min (200 °C, 5 kg), Shore A hardness 47 A, produced by Kraton Polymers, USA; Other toughening agents: POE elastomer, POE 58750, produced by Dow Chemical; Flame retardant 1#: magnesium hydroxide, H-5, produced by Huber, USA; Flame retardant 2#: aluminum hydroxide, OL-104LEO, produced by Huber, USA; Cross-linking agent: triallyl isocyanurate, commercially available; Other additives: Antioxidant 1010, commercially available.

[0055] The polyolefin composite materials of the embodiments and comparative examples of the present invention were prepared by the following process: The components are uniformly mixed to obtain a mixture, which is then placed in an internal mixer. After internal kneading, the mixture is extruded and granulated through a two-stage single-screw extruder to obtain the polyolefin composite material. The internal mixer is set at a temperature of 150-200°C, and the single-screw extruder is set at a temperature of 135-175°C in each zone.

[0056] Examples 1-11 Examples 1 to 11 provide a series of polyolefin composite materials, and the weight percentages of the components in the formulations are shown in Table 1.

[0057] Table 1: Formulas of Examples 1 to 11

[0058] Comparative Examples 1 to 6 This comparative example provides a series of polyolefin composite materials, and the weight proportions of the components in the formula are shown in Table 2.

[0059] Table 2 Comparative Examples 1 to 6 Formula

[0060] Performance testing of polyolefin composites (1) Test method Organic solvent resistance: The polyolefin composite materials obtained in each embodiment and comparative example were extruded into wires using a wire extruder. The conductor cross-sectional area was 10 mm. 2 The outer diameter of the wire is 6.5 mm. The prepared wire is irradiated and cross-linked at a dose of 15 Mrad. The toluene resistance test is carried out in accordance with the standard ISO 19642-2023: the initial volume V0 of the wire is tested and recorded. After the wire is completely immersed in toluene for 12 hours, the wire is taken out and allowed to stand until the toluene is completely evaporated. The expanded volume V1 is tested and recorded. The volume expansion rate is calculated according to the formula V1 / V0*100%, and the wire is simultaneously observed to see if it cracks during the immersion process. If cracking occurs during the immersion stage, the volume expansion rate will no longer be tested and it will be directly judged as "unsatisfactory organic solvent resistance."

[0061] Volume resistivity: The polyolefin composite materials obtained in each embodiment and comparative example were pressed on a flat vulcanizer at 180°C for 10 min at a pressure of 15 MPa to produce samples with a length and width of 100 mm * 100 mm and a thickness of 1 mm. The volume resistivity of the samples was first tested at room temperature at a voltage of 1000 V. After the samples were immersed in 70°C salt water for 24 h, the volume resistivity was again tested at a voltage of 1000 V. The order of magnitude of the volume resistivity decrease after soaking in salt water was calculated. The volume resistivity test was carried out in accordance with the standard IEC62631-2024.

[0062] Hardness (Shore A): The polyolefin composite materials obtained in each embodiment and comparative example were pressed on a flat vulcanizer at 180°C for 10 min and a pressure of 15 MPa to produce samples with a length and width of 50 mm*50 mm and a thickness of 6 mm. The test was conducted in accordance with ISO7619-1:2010, and the spring test force was maintained for 15 s.

[0063] (2) Experimental results Table 3 Performance test results of various embodiments and comparative examples

[0064] As shown in Table 3, the polyolefin composite materials prepared in Examples 1 to 11 of the present invention all have the characteristics of softness, salt water resistance, and organic solvent resistance. Specifically, the Shore A hardness is ≤75 A; after immersion in salt water, the volume resistivity decreases by an order of magnitude of ≤1; after immersion in toluene, there is no cracking, and the volume expansion rate is ≤115%. Among them, Example 1 has the best comprehensive performance.

[0065] In Comparative Example 1, since no cycloolefin polymer is added, the volume resistivity of the material decreases by 3 orders of magnitude after soaking in 70°C salt water, which seriously affects its insulation performance. In addition, the volume expansion rate is too high after soaking in toluene, which affects the organic solvent resistance. In Comparative Example 2, since a large amount of cycloolefin polymer is added, the material hardness is too high, and the organic solvent resistance is insufficient, and the composite material cracks. In Comparative Example 3, since ethylene-vinyl acetate copolymer with a low VA content is used, the material hardness is too high, and the organic solvent resistance is insufficient, and the composite material cracks. In Comparative Example 4, since polyethylene is used instead of cycloolefin polymer, the volume resistivity decreases by 2 orders of magnitude after soaking in salt water, which affects the insulation performance. In Comparative Example 5, since no cycloolefin polymer is added and an equal amount of ethylene-vinyl acetate copolymer is used instead, the volume resistivity deteriorates seriously after soaking in salt water, decreasing by 3 orders of magnitude, and the insulation performance deteriorates seriously. In Comparative Example 6, since POE elastomer is used instead of SEBS, the volume resistivity decreases by 2 orders of magnitude after soaking in salt water, which affects the insulation performance. In addition, the organic solvent resistance is insufficient, and cracks occur after soaking in toluene.

[0066] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A polyolefin composite material, characterized in that: The invention comprises the following components in parts by weight: 20-30 parts of ethylene-vinyl acetate copolymer, 4-16 parts of cycloolefin polymer, 14-26 parts of styrene-ethylene-butylene-styrene block copolymer, 1-10 parts of compatibilizer, 34-46 parts of flame retardant, 1-3 parts of co-crosslinking agent, and 0-3 parts of other additives; Wherein, the mass content of vinyl acetate in the ethylene-vinyl acetate copolymer is ≥30%.

2. The polyolefin composite material according to claim 1, characterized in that: The melt flow rate of the cycloolefin polymer measured at 230° C. and 2.16 kg is 0.5-25 g / 10 min.

3. The polyolefin composite material according to claim 1, characterized in that: The cycloolefin polymer is a cycloolefin homopolymer and / or a cycloolefin copolymer.

4. The polyolefin composite material according to claim 3, characterized in that: The cycloolefin copolymer is a copolymer of ethylene and cycloolefin monomers.

5. The polyolefin composite material according to claim 1, characterized in that: The melt flow rate of the styrene-ethylene-butylene-styrene block copolymer measured at 200° C. and 5 kg is 0.5-25 g / 10 min.

6. The polyolefin composite material according to claim 1, characterized in that: The flame retardant is a hydroxide flame retardant.

7. The polyolefin composite material according to claim 1, characterized in that: The compatibilizer is a maleic anhydride compatibilizer.

8. The polyolefin composite material according to claim 1, characterized in that: The auxiliary cross-linking agent includes one or more of triallyl isocyanurate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate.

9. The method for preparing the polyolefin composite material according to any one of claims 1 to 8, characterized in that: The steps include: The components are mixed uniformly to obtain a mixture, the mixture is subjected to banburying, and then melt-extruded and granulated to obtain the polyolefin composite material.

10. Use of the polyolefin composite material according to any one of claims 1 to 8 in the preparation of cables.

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