Modifier and preparation method thereof, modified carbon nanotube and preparation method thereof, polyolefin composite material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a modifier and a preparation method thereof, a modified carbon nanotube and a preparation method thereof, and a polyolefin composite material and a preparation method thereof. The modifier has a structure as shown in a formula (I). The modifier has a flame-retardant functional structure and an active double-bond structure, the dispersity and interface bonding force of the modified carbon nanotubes prepared by using the modifier in a polyolefin matrix are remarkably improved, and the polyolefin composite material is endowed with excellent mechanical properties and flame retardance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and particularly to modifiers and their preparation methods, modified carbon nanotubes and their preparation methods, and polyolefin composite materials and their preparation methods. Background Technology

[0002] While research on carbon nanotube-reinforced polyolefin composites has made some progress, many technical bottlenecks remain to be addressed. For example, traditional methods typically involve physical blending to directly disperse carbon nanotubes into the polyolefin matrix. However, due to the inertness and tendency of carbon nanotubes to agglomerate, their dispersion in the polymer matrix is ​​poor, resulting in weak interfacial bonding and severely limiting the improvement of mechanical properties. While silane coupling agent modification, commonly used in related technologies, can partially improve dispersion, the modified carbon nanotubes and matrix still primarily rely on physical adsorption, resulting in limited interfacial bonding strength and failing to impart specific functions to the material. Furthermore, related technologies struggle to simultaneously achieve the synergistic effects of efficient carbon nanotube dispersion, strong interfacial bonding, and functional modification. Therefore, when faced with high carbon nanotube content, existing composite materials generally exhibit deteriorated processing fluidity and decreased mechanical properties. Besides the deficiencies in dispersion and interfacial bonding, existing composite materials also generally suffer from insufficient flame retardant properties. Related technologies often employ additive flame retardants, which suffer from problems such as large addition amounts, easy migration and precipitation, and negative impacts on material mechanical properties. Summary of the Invention

[0003] This invention provides a modifier and its preparation method, a modified carbon nanotube and its preparation method, and a polyolefin composite material and its preparation method. The modifier possesses a flame-retardant functional structure and an active double bond structure. The modified carbon nanotubes prepared using this modifier exhibit significantly improved dispersibility and interfacial bonding in a polyolefin matrix, and also endow the polyolefin composite material with excellent mechanical and flame-retardant properties.

[0004] The first aspect of the present invention provides a modifier having the structure shown in formula (I).

[0005]

[0006] The modifier provided by this invention has a flame-retardant functional structure and an active double bond structure. The active double bond structure can undergo a grafting reaction with the polyolefin molecular chain to form a stable chemical bond connection, thereby improving the dispersibility and interfacial bonding of carbon nanotubes. The flame-retardant functional structure contained in the modifier can also solve the problem of easy migration and precipitation of traditional additive flame retardants.

[0007] A second aspect of the present invention provides a method for preparing the modifier described in the first aspect, comprising: subjecting a first intermediate having the structure shown in formula (II) and a second intermediate having the structure shown in formula (III) to a first reaction to obtain the modifier;

[0008]

[0009] Thus, the phospholipid group of the first intermediate undergoes a nucleophilic substitution reaction with the amino group of the second intermediate to obtain the modifier.

[0010] According to an embodiment of the present invention, the mass ratio of the first intermediate to the second intermediate is (13-14):(14-16). This improves product selectivity and reduces the occurrence of side reactions.

[0011] According to an embodiment of the present invention, the temperature of the first reaction is 70°C-80°C, and the time is 3-4 hours. This allows the reaction to proceed fully.

[0012] According to an embodiment of the present invention, the method further includes the following steps for preparing the first intermediate: subjecting pentaerythritol and phosphorus oxychloride to a second reaction to obtain a precursor; and subjecting the precursor to water to a third reaction to obtain the first intermediate.

[0013] According to an embodiment of the present invention, the mass ratio of pentaerythritol, phosphorus oxychloride, and water is (13-14):(13-14):(0.5-1). This improves product selectivity and reduces the occurrence of side reactions.

[0014] According to an embodiment of the present invention, the method further includes the following steps for preparing the second intermediate: mixing β-(acryloyloxy)propionic acid, melamine, a dehydrating agent, and a catalyst, and carrying out a fourth reaction to obtain the second intermediate.

[0015] According to an embodiment of the present invention, the mass ratio of β-(acryloyloxy)propionic acid, melamine, dehydrating agent, and catalyst is (14-18):(6-8):(22-25):(1-2). This improves product selectivity and reduces the occurrence of side reactions.

[0016] A third aspect of the present invention provides a method for preparing modified carbon nanotubes, comprising: subjecting an amination reagent and carbon nanotubes to a fifth reaction to obtain amination-treated carbon nanotubes; and subjecting the amination-treated carbon nanotubes and a modifier to a sixth reaction to obtain the modified carbon nanotubes; wherein the modifier comprises the modifier described in the first aspect or a modifier prepared according to the method described in the second aspect. Thereby, the phospholipid groups in the structure of the modifier react with the amino groups in the amination-treated carbon nanotubes to obtain the modified carbon nanotubes.

[0017] According to an embodiment of the present invention, the mass ratio of the amination reagent to the carbon nanotubes is (10-20):(1-2). Therefore, the resulting amination-treated carbon nanotubes have a high content of amino groups.

[0018] According to an embodiment of the present invention, the mass ratio of the aminated carbon nanotubes to the modifier is (2-3):(25-30). Therefore, the resulting modified carbon nanotubes have a high content of modified chemical structures, thereby improving the dispersibility and interfacial bonding of carbon nanotubes in the polyolefin matrix.

[0019] According to an embodiment of the present invention, the temperature of the fifth reaction is 180°C-190°C, and the time is 10h-12h. This allows the reaction to proceed fully.

[0020] According to an embodiment of the present invention, the temperature of the sixth reaction is 60°C-70°C, and the time is 3-4 hours. This allows the reaction to proceed fully.

[0021] According to an embodiment of the present invention, the carbon nanotubes include multi-walled carbon nanotubes. Therefore, multi-walled carbon nanotubes are more robust and can withstand higher pressures.

[0022] A fourth aspect of the present invention provides a modified carbon nanotube prepared according to the method described in the third aspect. This modified carbon nanotube exhibits excellent dispersibility and interfacial bonding in a polyolefin matrix.

[0023] A fifth aspect of this invention provides a polyolefin composite material, comprising, by weight, 30-50 parts ethylene vinyl acetate, 20-40 parts low-density polyethylene, 10-20 parts polyethylene elastomer, 5-10 parts modified carbon nanotubes, 0.1-0.5 parts antioxidant, 0.5-1 part lubricant, and 0.5-0.8 parts crosslinking agent; wherein the modified carbon nanotubes include modified carbon nanotubes prepared according to the method described in the third aspect or modified carbon nanotubes as described in the fourth aspect. This polyolefin composite material exhibits excellent mechanical properties and flame retardant properties.

[0024] The sixth aspect of the present invention provides a method for preparing the polyolefin composite material described in the fifth aspect, comprising: preparing a mixture comprising ethylene vinyl acetate, low-density polyethylene, polyethylene elastomer, antioxidant, and lubricant; adding modified carbon nanotubes and a crosslinking agent to the mixture; and mixing to obtain a premix; and subjecting the premix to a kneading treatment, a granulation treatment, and an injection molding treatment to obtain the polyolefin composite material.

[0025] According to an embodiment of the present invention, the mixing treatment is performed at a temperature of 120°C-150°C for 8-10 minutes. This optimizes the physical properties of the polyolefin composite material and improves product quality.

[0026] According to an embodiment of the present invention, the injection molding temperature is 180℃-200℃. This allows the melt to have good fluidity, improving product quality.

[0027] According to an embodiment of the present invention, the injection molding process is carried out at a pressure of 30 MPa-50 MPa. This allows the melt to be fully compacted within the mold cavity, reducing internal porosity and defects, and improving the density and strength of the product.

[0028] According to an embodiment of the present invention, the injection molding speed is 30 mm / s-60 mm / s. This allows the melt to fill the mold cavity uniformly, reducing air bubbles and voids in the melt and improving product quality.

[0029] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] To facilitate understanding of the invention, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0035] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0036] The first aspect of the present invention provides a modifier having the structure shown in formula (I).

[0037]

[0038] The modifier provided by this invention has flame-retardant groups and an active double bond structure. When the aforementioned modifier is used to modify carbon nanotubes and prepare polyolefin composites, the active double bond structure can undergo a grafting reaction with the polyolefin molecular chains during processing to form stable chemical bonds. This not only gives the carbon nanotube surface a good polymer compatibility shell, effectively reducing interfacial energy and preventing nanotube aggregation, but also allows the grafted polymer segments to form chain entanglement with the matrix molecular chains, creating a physical cross-linking network that further stabilizes the dispersion state. At the same time, the covalent bonding between the double bonds and the polyolefin constructs an efficient molecular-level stress transfer channel at the carbon nanotube-matrix interface. When the polyolefin composite is subjected to external force, the load can be directly transferred to the high-strength carbon nanotubes through chemical bonds, significantly enhancing the interfacial bonding strength. This strong interfacial interaction not only improves the overall performance of the material, but also effectively inhibits crack propagation, thereby improving the toughness of the material. In addition, the flame-retardant groups of the modifier play multiple roles when heated: on the one hand, they promote the char formation of polymers, forming a dense char layer to insulate against heat and oxygen; on the other hand, they decompose to produce phosphoric acid substances, which capture free radicals in the gas phase to interrupt the combustion chain reaction; and the carbon nanotube network enhances the strength of the char layer, forming a skeleton-barrier synergistic flame-retardant system. The introduction of double bonds improves the uniformity and stability of the distribution of flame-retardant groups in the material, thereby effectively alleviating the migration and precipitation problems of traditional flame retardants.

[0039] A second aspect of the present invention provides a method for preparing the modifier described in the first aspect, comprising: subjecting a first intermediate having the structure shown in formula (II) and a second intermediate having the structure shown in formula (III) to a first reaction to obtain the modifier;

[0040]

[0041] Thus, the phospholipid group of the first intermediate undergoes a nucleophilic substitution reaction with the amino group of the second intermediate to obtain the modifier.

[0042] According to a specific embodiment of the present invention, the mass ratio of the first intermediate to the second intermediate is (13-14):(14-16). As some specific examples, the mass ratio of the first intermediate to the second intermediate can be 13:14, 13:16, 14:14, 14:16, etc. This can improve product selectivity and reduce the occurrence of side reactions.

[0043] According to a specific embodiment of the present invention, the temperature of the first reaction is 70°C-80°C, and the time is 3-4 hours. As some specific examples, the temperature of the first reaction can be 70°C, 75°C, 80°C, etc., and the time can be 3 hours, 3.5 hours, 4 hours, etc. This allows the reaction to proceed fully.

[0044] According to a specific embodiment of the present invention, the method further includes the following steps for preparing the first intermediate: subjecting pentaerythritol and phosphorus oxychloride to a second reaction to obtain a precursor; and subjecting the precursor to water to a third reaction to obtain the first intermediate.

[0045] During the reaction, pentaerythritol undergoes a phosphorylation reaction with phosphorus oxychloride, where the phosphorus atom of phosphorus oxychloride combines with the hydroxyl group of pentaerythritol to form a phosphoryl chloride intermediate, which is subsequently hydrolyzed to generate a phosphate ester compound. The specific reaction process can be seen in the following reaction equation:

[0046]

[0047] According to specific embodiments of the present invention, the mass ratio of pentaerythritol, phosphorus oxychloride, and water is (13-14):(13-14):(0.5-1). As some specific examples, the mass ratio of pentaerythritol, phosphorus oxychloride, and water can be 13:13:0.5, 14:14:1, etc. This can improve product selectivity and reduce the occurrence of side reactions.

[0048] Specifically, the preparation of the first intermediate can be carried out as follows: pentaerythritol, phosphorus oxychloride, and acetonitrile solvent are mixed, and the temperature is raised to 60℃-70℃ under a protective atmosphere. The reaction is carried out for 2h-3h. After the reaction is completed, the mixture is cooled to room temperature, washed and dried, and the precursor is transferred to N,N-dimethylformamide. Under a protective atmosphere, the temperature is raised to 70℃-80℃, and then distilled water is slowly added dropwise. The reaction is carried out for 1h-2h to obtain the first intermediate.

[0049] According to a specific embodiment of the present invention, the method further includes the following steps for preparing the second intermediate: mixing β-(acryloyloxy)propionic acid, melamine, a dehydrating agent, and a catalyst, and carrying out a fourth reaction to obtain the second intermediate.

[0050] During the reaction, β-(acryloyloxy)propionic acid undergoes a condensation reaction with melamine, as shown in the following reaction equation:

[0051]

[0052] According to specific embodiments of the present invention, the mass ratio of β-(acryloyloxy)propionic acid, melamine, dehydrating agent, and catalyst is (14-18):(6-8):(22-25):(1-2). As some specific examples, the mass ratio of β-(acryloyloxy)propionic acid, melamine, dehydrating agent, and catalyst can be 14:6:22:1, 18:8:25:2, etc. This improves product selectivity and reduces the occurrence of side reactions.

[0053] According to specific embodiments of the present invention, the type of dehydrating agent is not particularly limited, and as some specific examples, it includes, but is not limited to, N,N'-dicyclohexylcarbodiimide.

[0054] According to specific embodiments of the present invention, the type of catalyst is not particularly limited, and as some specific examples, it includes, but is not limited to, 4-dimethylaminopyridine.

[0055] Specifically, the preparation of the second intermediate can be carried out as follows: under a protective atmosphere, β-(acryloyloxy)propionic acid is added to N,N-dimethylformamide, cooled in an ice bath, and then a dehydrating agent and catalyst are added. The mixture is stirred for 30-40 minutes, and then a mixed solution of melamine and N,N-dimethylformamide is added dropwise. The mixture is reacted at 0℃-5℃ for 1-2 hours, and then slowly heated to room temperature for 2-3 hours. After the reaction is completed, the mixture is filtered, the solvent is removed by vacuum distillation, and the mixture is purified to obtain the second intermediate.

[0056] A third aspect of the present invention provides a method for preparing modified carbon nanotubes, comprising:

[0057] (1) The amination reagent and carbon nanotubes undergo a fifth reaction to obtain amination carbon nanotubes.

[0058] According to specific embodiments of the present invention, the mass ratio of the amination reagent to carbon nanotubes is (10-20):(1-2). As some specific examples, the mass ratio of the amination reagent to carbon nanotubes can be 10:1, 10:2, 20:1, 20:2, etc. Thus, the prepared amination carbon nanotubes have a high content of amino groups.

[0059] According to a specific embodiment of the present invention, the temperature of the fifth reaction is 180℃-190℃, and the time is 10h-12h. As some specific examples, the temperature of the fifth reaction can be 180℃, 185℃, 190℃, etc., and the time can be 10h, 11h, 12h, etc. This allows the reaction to proceed fully.

[0060] According to a specific embodiment of the present invention, the carbon nanotubes include multi-walled carbon nanotubes. Therefore, multi-walled carbon nanotubes are more robust and can withstand higher pressures.

[0061] According to specific embodiments of the present invention, the type of amination reagent is not particularly limited, and as some specific examples, it includes, but is not limited to, diamine maleate.

[0062] (2) The aminated carbon nanotubes and the modifier undergo a sixth reaction to obtain the modified carbon nanotubes; wherein the modifier includes the modifier described in the first aspect or the modifier prepared according to the method described in the second aspect. Thus, the phospholipid groups in the modifier structure react with the amino groups in the aminated carbon nanotubes to obtain the modified carbon nanotubes.

[0063] According to specific embodiments of the present invention, the mass ratio of the aminated carbon nanotubes to the modifier is (2-3):(25-30). As some specific examples, the mass ratio of the aminated carbon nanotubes to the modifier can be 2:25, 2:30, 3:25, 3:30, etc. Thus, the prepared modified carbon nanotubes have a high content of modified chemical structures, thereby improving the dispersibility and interfacial bonding of carbon nanotubes in the polyolefin matrix.

[0064] According to a specific embodiment of the present invention, the temperature of the sixth reaction is 60℃-70℃, and the time is 3h-4h. As some specific examples, the temperature of the sixth reaction can be 60℃, 65℃, 70℃, etc., and the time can be 3h, 3.5h, 4h, etc. This allows the reaction to proceed fully.

[0065] A fourth aspect of the present invention provides a modified carbon nanotube prepared according to the method described in the third aspect. This modified carbon nanotube exhibits excellent dispersibility and interfacial bonding in a polyolefin matrix.

[0066] A fifth aspect of this invention provides a polyolefin composite material, comprising, by weight, 30-50 parts ethylene vinyl acetate, 20-40 parts low-density polyethylene, 10-20 parts polyethylene elastomer, 5-10 parts modified carbon nanotubes, 0.1-0.5 parts antioxidant, 0.5-1 part lubricant, and 0.5-0.8 parts crosslinking agent; wherein the modified carbon nanotubes include modified carbon nanotubes prepared according to the method described in the third aspect or modified carbon nanotubes as described in the fourth aspect. This polyolefin composite material exhibits excellent mechanical properties and flame retardant properties.

[0067] A sixth aspect of the present invention provides a method for preparing the polyolefin composite material described in the fifth aspect, comprising:

[0068] ① Prepare a mixture containing ethylene vinyl acetate, low-density polyethylene, polyethylene elastomer, antioxidant, and lubricant. Add modified carbon nanotubes and crosslinking agent to the mixture and mix to obtain a premix.

[0069] According to specific embodiments of the present invention, the type of antioxidant is not particularly limited, and as some specific examples, it includes, but is not limited to, antioxidant 1010.

[0070] According to specific embodiments of the present invention, the type of lubricant is not particularly limited, and as some specific examples, it includes, but is not limited to, zinc stearate.

[0071] According to specific embodiments of the present invention, the type of crosslinking agent is not particularly limited, and as some specific examples, it includes, but is not limited to, dicumyl peroxide.

[0072] Specifically, step ① can be performed as follows: first mix ethylene vinyl acetate, low-density polyethylene, and polyethylene elastomer for 2-3 minutes to initially disperse them; then add antioxidants and lubricants, and continue mixing for 2-3 minutes until uniform; next, add modified carbon nanotubes and mix for 5-6 minutes; finally, add crosslinking agent and mix for 2-3 minutes. The mixture is then passed through a 60-mesh sieve to obtain a premix.

[0073] ② The premixed material is subjected to mixing, granulation and injection molding to obtain the polyolefin composite material.

[0074] According to a specific embodiment of the present invention, the mixing treatment temperature is 120℃-150℃, and the time is 8min-10min. This optimizes the physical properties of the polyolefin composite material and improves product quality.

[0075] According to a specific embodiment of the present invention, the injection molding temperature is 180℃-200℃. This allows the melt to have good fluidity, improving product quality.

[0076] According to a specific embodiment of the present invention, the injection molding process is carried out at a pressure of 30 MPa-50 MPa. This allows the melt to be fully compacted within the mold cavity, reducing internal porosity and defects, and improving the density and strength of the product.

[0077] According to a specific embodiment of the present invention, the injection molding speed is 30 mm / s-60 mm / s. This allows the melt to fill the mold cavity uniformly, reducing air bubbles and voids in the melt and improving product quality.

[0078] Specifically, step ② can be performed as follows: the premixed material is added to a mixer for mixing, discharged and cooled to room temperature, then extruded and granulated through a twin-screw extruder, and finally injection molded through a screw injection molding machine to obtain a polyolefin composite material.

[0079] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0080] Example 1

[0081] This embodiment provides a polyolefin composite material and its preparation method, including the following steps:

[0082] S1: The preparation of modified carbon nanotubes, the specific steps are as follows:

[0083] S11: Grind and mix 10 parts of maleic diamine and 1 part of multi-walled carbon nanotubes. After purging nitrogen for 10 min, raise the temperature to 190℃ and stir for 10 h. After the reaction is complete, wash and dry to obtain aminated carbon nanotubes.

[0084] S12: Mix 13 parts pentaerythritol, 13 parts phosphorus oxychloride, and 250 parts acetonitrile solvent. Under a protective atmosphere, raise the temperature to 60°C and react for 2 hours. After the reaction is complete, cool to room temperature, wash and dry, and transfer to 120 parts N,N-dimethylformamide. Under a protective atmosphere, raise the temperature to 70°C and then slowly add 0.5 parts distilled water. React for 1 hour to obtain the first intermediate.

[0085] S13: Under a protective atmosphere, 14 parts of β-(acryloyloxy)propionic acid were added to 120 parts of N,N-dimethylformamide and cooled in an ice bath. Then, 22 parts of N,N'-dicyclohexylcarbodiimide and 1 part of 4-dimethylaminopyridine were added and stirred for 30 min. Then, a mixed solution of 6 parts of melamine and 30 parts of N,N-dimethylformamide was added dropwise and reacted at 0 °C for 1 h. Then, the temperature was slowly raised to room temperature and reacted for 2 h. After the reaction was completed, the mixture was filtered, the solvent was removed by vacuum distillation, and the product was purified to obtain the second intermediate.

[0086] S14: Mix 14 parts of the second intermediate, 13 parts of the first intermediate, and 200 parts of dimethyl sulfoxide, raise the temperature to 70°C, and react for 3 hours. After the reaction is complete, cool to room temperature and perform post-treatment to obtain the modifier. Then mix it with 2 parts of aminated carbon nanotubes and 250 parts of N,N-dimethylformamide, raise the temperature to 60°C, and react for 3 hours. Filter, wash, and dry to obtain modified carbon nanotubes.

[0087] S2: Mix 30 parts ethylene vinyl acetate, 20 parts low-density polyethylene, and 10 parts polyethylene elastomer for 2 minutes to initially disperse them; then add 0.1 parts antioxidant (antioxidant 1010) and 0.5 parts lubricant (zinc stearate), and continue mixing for 2 minutes until homogeneous; next, add 5 parts modified carbon nanotubes and mix for 5 minutes; finally, add 0.5 parts crosslinking agent (diisopropylbenzene peroxide), mix for 2 minutes, and pass the mixture through a 60-mesh sieve to obtain a premix.

[0088] S3: Add the premixed material to the internal mixer and mix at 120°C for 8 minutes. After discharging, cool to room temperature and then extrude and granulate through a twin-screw extruder. Finally, injection mold through a screw injection molding machine (temperature 180°C, pressure 30MPa, speed 30mm / s) to obtain a polyolefin composite material.

[0089] Example 2

[0090] This embodiment provides a polyolefin composite material and its preparation method, including the following steps:

[0091] S1: The preparation of modified carbon nanotubes, the specific steps are as follows:

[0092] S11: Grind and mix 20 parts of maleic diamine and 2 parts of multi-walled carbon nanotubes. After purging nitrogen for 15 minutes, raise the temperature to 190℃ and stir for 12 hours. After the reaction is complete, wash and dry to obtain aminated carbon nanotubes.

[0093] S12: Mix 14 parts pentaerythritol, 14 parts phosphorus oxychloride, and 300 parts acetonitrile solvent. Under a protective atmosphere, raise the temperature to 70°C and react for 3 hours. After the reaction is complete, cool to room temperature, wash and dry, and transfer to 180 parts N,N-dimethylformamide. Under a protective atmosphere, raise the temperature to 80°C and then slowly add 1 part distilled water. React for 2 hours to obtain the first intermediate.

[0094] S13: Under a protective atmosphere, 18 parts of β-(acryloyloxy)propionic acid were added to 160 parts of N,N-dimethylformamide and cooled in an ice bath. Then, 25 parts of N,N'-dicyclohexylcarbodiimide and 2 parts of 4-dimethylaminopyridine were added and stirred for 40 min. Then, a mixed solution of 8 parts of melamine and 40 parts of N,N-dimethylformamide was added dropwise and reacted at 5 °C for 2 h. Then, the temperature was slowly raised to room temperature and reacted for 3 h. After the reaction was completed, the mixture was filtered, the solvent was removed by vacuum distillation, and the product was purified to obtain the second intermediate.

[0095] S14: Mix 16 parts of the second intermediate, 14 parts of the first intermediate, and 250 parts of dimethyl sulfoxide, raise the temperature to 80°C, and react for 4 hours. After the reaction is complete, cool to room temperature and perform post-treatment to obtain the modifier. Then mix it with 3 parts of aminated carbon nanotubes and 300 parts of N,N-dimethylformamide, raise the temperature to 70°C, and react for 4 hours. Filter, wash, and dry to obtain modified carbon nanotubes.

[0096] S2: Mix 50 parts ethylene vinyl acetate, 40 parts low-density polyethylene, and 20 parts polyethylene elastomer for 3 minutes to initially disperse them; then add 0.5 parts antioxidant (antioxidant 1010) and 1 part lubricant (zinc stearate), and continue mixing for 3 minutes until homogeneous; next, add 10 parts modified carbon nanotubes and mix for 6 minutes; finally, add 0.8 parts crosslinking agent (diisopropylbenzene peroxide), mix for 3 minutes, and pass the mixture through a 60-mesh sieve to obtain a premix.

[0097] S3: Add the premixed material to the internal mixer and mix at 150°C for 10 minutes. After discharging, cool to room temperature and then extrude and granulate through a twin-screw extruder. Finally, use a screw injection molding machine to injection mold (temperature 200°C, pressure 50MPa, speed 60mm / s) to obtain a polyolefin composite material.

[0098] Example 3

[0099] This embodiment provides a polyolefin composite material and its preparation method, including the following steps:

[0100] S1: The preparation of modified carbon nanotubes, the specific steps are as follows:

[0101] S11: 15 parts of maleic acid diamine and 1.5 parts of multi-walled carbon nanotubes were ground and mixed. After nitrogen was purged for 12.5 min, the temperature was raised to 190℃ and stirred for 11 h. After the reaction was completed, the mixture was washed and dried to obtain aminated carbon nanotubes.

[0102] S12: Mix 13.5 parts pentaerythritol, 13.5 parts phosphorus oxychloride, and 275 parts acetonitrile solvent. Under a protective atmosphere, raise the temperature to 65°C and react for 2.5 h. After the reaction is complete, cool to room temperature, wash and dry, transfer to 150 parts N,N-dimethylformamide, raise the temperature to 75°C under a protective atmosphere, and then slowly add 0.75 parts distilled water. React for 1.5 h to obtain the first intermediate.

[0103] S13: Under a protective atmosphere, 16 parts of β-(acryloyloxy)propionic acid were added to 140 parts of N,N-dimethylformamide and cooled in an ice bath. Then, 23.5 parts of N,N'-dicyclohexylcarbodiimide and 1.5 parts of 4-dimethylaminopyridine were added and stirred for 35 min. Then, a mixed solution of 7 parts of melamine and 35 parts of N,N-dimethylformamide was added dropwise and reacted at 2.5 °C for 1.5 h. Then, the temperature was slowly raised to room temperature and reacted for 2.5 h. After the reaction was completed, the mixture was filtered, the solvent was removed by vacuum distillation, and the product was purified to obtain the second intermediate.

[0104] S14: Mix 15 parts of the second intermediate, 13.5 parts of the first intermediate, and 225 parts of dimethyl sulfoxide, raise the temperature to 75°C, and react for 3.5 h. After the reaction is complete, cool to room temperature and perform post-treatment to obtain the modifier. Then mix it with 2.5 parts of aminated carbon nanotubes and 275 parts of N,N-dimethylformamide, raise the temperature to 65°C, and react for 3.5 h. Filter, wash, and dry to obtain modified carbon nanotubes.

[0105] S2: Mix 40 parts ethylene vinyl acetate, 30 parts low-density polyethylene, and 15 parts polyethylene elastomer for 2.5 minutes to initially disperse them; then add 0.3 parts antioxidant (antioxidant 1010) and 0.75 parts lubricant (zinc stearate), and continue mixing for 2.5 minutes until homogeneous; next, add 7.5 parts modified carbon nanotubes and mix for 5.5 minutes; finally, add 0.65 parts crosslinking agent (diisopropylbenzene peroxide), mix for 2.5 minutes, and pass the mixture through a 60-mesh sieve to obtain a premix.

[0106] S3: Add the premixed material to the internal mixer and mix at 135°C for 9 minutes. After discharging, cool to room temperature and then extrude and granulate through a twin-screw extruder. Finally, injection mold through a screw injection molding machine (temperature 190°C, pressure 40MPa, speed 45mm / s) to obtain a polyolefin composite material.

[0107] Comparative Example 1

[0108] The difference between this comparative example and Example 3 is that the carbon nanotubes were not modified, and flame retardants (magnesium hydroxide, aluminum hydroxide, and zinc borate) were added. The specific steps are as follows:

[0109] S1: Mix 40 parts ethylene vinyl acetate, 30 parts low-density polyethylene, and 15 parts polyethylene elastomer for 2.5 minutes to initially disperse them; then add 15 parts magnesium hydroxide, 15 parts aluminum hydroxide, 3 parts zinc borate, 0.3 parts antioxidant (antioxidant 1010), and 0.75 parts lubricant (zinc stearate), and continue mixing for 2.5 minutes until homogeneous; next, add 7.5 parts carbon nanotubes and mix for 5.5 minutes; finally, add 0.65 parts crosslinking agent (diisopropylbenzene peroxide), mix for 2.5 minutes, and pass the mixture through a 60-mesh sieve to obtain a premix.

[0110] S2: Add the premixed material to the internal mixer and mix at 135°C for 9 minutes. After discharging, cool to room temperature and then extrude and granulate through a twin-screw extruder. Finally, injection mold the material through a screw injection molding machine (temperature 190°C, pressure 40MPa, speed 45mm / s) to obtain a polyolefin composite material.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 3 is that it uses carbon nanotubes modified with a silane coupling agent. The specific steps are as follows:

[0113] S1: 1 part of carbon nanotubes acidified with strong oxidizing acid was mixed with 0.9 parts of γ-aminopropyltriethoxysilane and 23 parts of deionized water and reacted at 80°C. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified carbon nanotubes.

[0114] S2: Mix 40 parts ethylene vinyl acetate, 30 parts low-density polyethylene, and 15 parts polyethylene elastomer for 2.5 minutes to initially disperse them; then add 0.3 parts antioxidant (antioxidant 1010) and 0.75 parts lubricant (zinc stearate), and continue mixing for 2.5 minutes until homogeneous; next, add 7.5 parts modified carbon nanotubes and mix for 5.5 minutes; finally, add 0.65 parts crosslinking agent (diisopropylbenzene peroxide), mix for 2.5 minutes, and pass the mixture through a 60-mesh sieve to obtain a premix.

[0115] S3: Add the premixed material to the internal mixer and mix at 135°C for 9 minutes. After discharging, cool to room temperature and then extrude and granulate through a twin-screw extruder. Finally, injection mold through a screw injection molding machine (temperature 190°C, pressure 40MPa, speed 45mm / s) to obtain a polyolefin composite material.

[0116] Test case

[0117] The properties of the polyolefin composite materials prepared in the examples and comparative examples were tested, and the specific test methods are as follows:

[0118] (1) Tensile strength test

[0119] Tensile strength was measured according to ASTM D638 standard.

[0120] (2) Impact strength test

[0121] Impact strength was measured according to ASTM D256 standard.

[0122] (3) Limiting Oxygen Index Test

[0123] The limiting oxygen index was measured according to ASTM D2863 standard.

[0124] The performance test results of the polyolefin composites prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0125] Table 1

[0126]

[0127] Results analysis:

[0128] Table 1 shows that the tensile strengths of Examples 1, 2, and 3 are 32.5 MPa, 32.7 MPa, and 33.8 MPa, respectively, and the impact strengths are 14.9 kJ / m. 2 15.6 kJ / m 2 and 15.9 kJ / m 2 The limiting oxygen indices were 32.3%, 32.5%, and 33.1%, respectively, all significantly better than Comparative Example 1 (tensile strength 22.6 MPa, impact strength 9.4 kJ / m). 2 The limiting oxygen index was 30.8% (comparative example 1) and the limiting oxygen index was 30.8% (comparative example 2) (tensile strength 25.6 MPa, impact strength 11.3 kJ / m). 2 (Limiting oxygen index 25.7%). This indicates that the modified carbon nanotubes of the present invention not only improve the mechanical properties of the composite material, but also significantly enhance the flame retardant effect, solving the problems of poor dispersion of carbon nanotubes, weak interfacial bonding, and insufficient flame retardant performance in traditional methods.

[0129] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0130] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A modifier, characterized in that, The modifier has the structure shown in formula (Ⅰ).

2. A method for preparing the modifier according to claim 1, characterized in that, include: The first intermediate having the structure shown in formula (II) and the second intermediate having the structure shown in formula (III) are subjected to a first reaction to obtain the modifier; 3. The method according to claim 2, wherein the mass ratio of the first intermediate to the second intermediate is (13-14):(14-16); Optionally, the temperature of the first reaction is 70℃-80℃, and the time is 3h-4h.

4. The method according to claim 2 or 3, characterized in that the method further comprises the step of preparing the first intermediate: The pentaerythritol and phosphorus oxychloride undergo a second reaction to yield the precursor; The precursor and water undergo a third reaction to obtain the first intermediate; Optionally, the mass ratio of pentaerythritol, phosphorus oxychloride, and water is (13-14):(13-14):(0.5-1).

5. The method according to claim 2 or 3, characterized in that the method further comprises the step of preparing the second intermediate: β-(acryloyloxy)propionic acid, melamine, dehydrating agent, and catalyst are mixed and subjected to a fourth reaction to obtain the second intermediate; Optionally, the mass ratio of β-(acryloyloxy)propionic acid, melamine, dehydrating agent, and catalyst is (14-18):(6-8):(22-25):(1-2).

6. A method for preparing modified carbon nanotubes, characterized in that, include: The amination reagent and carbon nanotubes undergo a fifth reaction to obtain amination-modified carbon nanotubes. The aminated carbon nanotubes and the modifier are subjected to a sixth reaction to obtain the modified carbon nanotubes; The modifier includes the modifier according to claim 1 or the modifier prepared by the method according to any one of claims 2-5.

7. The method according to claim 6, characterized in that, The mass ratio of the amination reagent to carbon nanotubes is (10-20):(1-2); Optionally, the mass ratio of the aminated carbon nanotubes to the modifier is (2-3):(25-30); Optionally, the temperature of the fifth reaction is 180℃-190℃, and the time is 10h-12h; Optionally, the temperature of the sixth reaction is 60℃-70℃, and the time is 3h-4h.

8. The method according to claim 6, characterized in that, The carbon nanotubes include multi-walled carbon nanotubes.

9. A modified carbon nanotube prepared by the method according to any one of claims 6-8.

10. A polyolefin composite material, characterized in that, By weight, the polyolefin composite material comprises 30-50 parts ethylene vinyl acetate, 20-40 parts low-density polyethylene, 10-20 parts polyethylene elastomer, 5-10 parts modified carbon nanotubes, 0.1-0.5 parts antioxidant, 0.5-1 part lubricant, and 0.5-0.8 parts crosslinking agent. The modified carbon nanotubes include the modified carbon nanotubes prepared by the method according to any one of claims 6-8 or the modified carbon nanotubes according to claim 9.

11. A method for preparing the polyolefin composite material of claim 10, characterized in that, include: A mixture comprising ethylene vinyl acetate, low-density polyethylene, polyethylene elastomer, antioxidant, and lubricant is prepared. Modified carbon nanotubes and a crosslinking agent are added to the mixture, and the mixture is further mixed to obtain a premix. The premixed material is subjected to mixing, granulation, and injection molding to obtain the polyolefin composite material.

12. The method according to claim 11, characterized in that, The mixing process is performed at a temperature of 120℃-150℃ for 8-10 minutes. Optionally, the temperature of the injection molding process is 180℃-200℃; Optionally, the pressure of the injection molding process is 30MPa-50MPa; Optionally, the injection molding process speed is 30 mm / s to 60 mm / s.

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