A flame-retardant carbon nanotube conductive material and its preparation process

Abstract

The present invention relates to the technical field of carbon nanotube modification, specifically a flame-retardant carbon nanotube conductive material and a preparation process thereof. The method comprises the following steps: S1: reacting chlorinated carbon nanotubes with 4-aminobenzophenone and DOPO in sequence to obtain DOPO-carbon nanotubes; S2: reacting chain polyphosphazenes with (1-hydroxyallyl)trimethylsilane and oxetane-3-thiol in sequence to obtain oxacyclic-chain polyphosphazenes; and S3: mixing DOPO-carbon nanotubes, oxacyclic-chain polyphosphazenes, and pyrrole to prepare the flame-retardant carbon nanotube conductive material.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanotube modification, in particular to a flame-retardant carbon nanotube conductive material and a preparation process thereof. Background Art

[0002] Carbon nanotubes are excellent conductive materials, with electrical conductivity comparable to that of metal conductors. However, they also have the problem of agglomeration. If carbon nanotubes are used directly as negative electrode materials, the cations on the carbon nanotube surface will be constrained, resulting in a decrease in their electrical conductivity and failure to fully utilize their conductive properties.

[0003] Therefore, modifying carbon nanotubes to enhance their dispersibility and improve their electrical conductivity is crucial. Furthermore, with the rapid development of modern industry, the demands placed on materials are increasing, and multifunctionalization has become a key area of ​​materials research. Improving the dispersion of carbon nanotubes while enhancing their other properties or imparting them with additional superior properties can significantly expand the potential applications of carbon nanotubes.

[0004] Based on this, the present invention provides a flame-retardant carbon nanotube conductive material that improves the dispersibility of carbon nanotubes and enhances their conductivity, as well as the flame retardancy of carbon nanotubes and the safety of carbon nanotubes when used as a conductive material. Summary of the Invention

[0005] The purpose of the present invention is to provide a flame retardant carbon nanotube conductive material and a preparation process thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A preparation process of a flame-retardant carbon nanotube conductive material comprises the following steps:

[0008] S1: Acylation of carbon nanotubes reacts with 4-aminobenzophenone and DOPO in sequence to obtain DOPO-carbon nanotubes:

[0009] S11: adding carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid into a reaction container, stirring and mixing, then heating to 50-100° C. and soaking for 1-6 hours, finally filtering, washing with water until the pH of the washing solution is neutral, and drying to obtain acidified carbon nanotubes;

[0010] S12: adding the acidified carbon nanotubes and thionyl chloride into a reaction vessel, stirring and mixing uniformly, then heating to 50-70° C. and continuing stirring for 1-24 hours, stopping stirring, and finally removing excess thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes;

[0011] S13: adding acyl chloride carbon nanotubes and 4-aminobenzophenone into a reaction vessel containing toluene, and reflux reacting at room temperature for 24 to 72 hours, stopping the reaction, and finally filtering, washing, and drying to obtain benzophenone-carbon nanotubes;

[0012] S14: Under a nitrogen atmosphere, benzophenone-carbon nanotubes and DOPO are added to a reaction vessel containing toluene, stirred and mixed evenly, and then heated to 150-180° C. and stirred for reaction for 1-3 hours, stopping the reaction, and finally filtering, washing, and drying to obtain DOPO-carbon nanotubes;

[0013] S2: The chain polyphosphazene reacts with (1-hydroxyallyl)trimethylsilane and oxetane-3-thiol in sequence to obtain an oxetane-chain polyphosphazene:

[0014] S21: Under a nitrogen atmosphere, hexachlorocyclotriphosphazene, trichlorobenzene, aminosulfonic acid, and calcium sulfate dihydrate are added to a reaction vessel, stirred and heated to 170-190° C., then the nitrogen is stopped, the temperature is continued to be raised to 210±1° C. and stirred for 0.5-2 h, the reaction is stopped, and the temperature is cooled to 100-110° C., sufficient n-heptane is added to the reaction vessel to precipitate, and finally filtered, washed, and dried to obtain a chain polyphosphazene;

[0015] S22: Under a nitrogen atmosphere, the chain polyphosphazene and (1-hydroxyallyl)trimethylsilane are added to a reaction vessel containing dimethylformamide, and the mixture is stirred and mixed uniformly. Tetrabutylammonium bromide is then added thereto, and the mixture is heated to 60-80° C. and refluxed for 6-24 hours. The reaction is stopped, and sufficient n-heptane is added to the reaction vessel to precipitate. The precipitate is filtered, washed, and dried to obtain the allyl-chain polyphosphazene.

[0016] S23: adding allyl-chain polyphosphazene, oxetane-3-thiol and a photoinitiator into a reaction vessel containing dimethylformamide, stirring and mixing uniformly, irradiating under 350-370 nm ultraviolet light for 1-20 minutes to stop the reaction, and finally filtering, washing and drying to obtain oxetane-chain polyphosphazene;

[0017] S3: DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene, and pyrrole are mixed to prepare flame-retardant carbon nanotube conductive materials:

[0018] S31: Add DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene and pyrrole into a reaction vessel filled with dimethylformamide, stir and mix evenly, then add hydrochloric acid to adjust the pH to 4-5, then add ammonium persulfate, stir and react at room temperature for 1-24 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

[0019] Furthermore, the ratio of the carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid is (1-2) g:30 mL:10 mL; wherein the concentration of the concentrated sulfuric acid is ≥96%, and the concentration of the concentrated nitric acid is ≥68%.

[0020] Furthermore, the carbon nanotubes include but are not limited to any one of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.

[0021] Furthermore, the ratio of the acidified carbon nanotubes to the thionyl chloride is (1-5) g:100 mL.

[0022] Furthermore, the mass ratio of the acyl chloride carbon nanotubes to 4-aminobenzophenone is 1:20. The amount of 4-aminobenzophenone needs to be excessive because if the acyl chloride groups on the carbon nanotubes do not react completely, they will directly react with DOPO, which will affect the formation of the target product and reduce the dispersibility of the carbon nanotubes.

[0023] Furthermore, the mass ratio of the benzophenone-carbon nanotubes to DOPO is (0.5-1):5.

[0024] Furthermore, the mass ratio of the hexachlorocyclotriphosphazene, trichlorobenzene, aminosulfonic acid and calcium sulfate dihydrate is (1-2):10:(0.1-0.2):(0.01-0.02).

[0025] Furthermore, the mass ratio of the chain polyphosphazene, (1-hydroxyallyl)trimethylsilane and tetrabutylammonium bromide is (1-2):(5-10):(0.05-0.5).

[0026] Furthermore, the mass ratio of the allyl-chain polyphosphazene, oxetane-3-thiol and photoinitiator is 4:(1-2):(0.15-0.3).

[0027] Furthermore, the mass ratio of the DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene, pyrrole and ammonium persulfate is (0.1-0.3):(0.01-0.05):(1-1.5):(1-1.5).

[0028] In the present invention, the carbon nanotubes are subjected to an acidification treatment to form abundant -COOH groups on their surface, and then the -COOH groups on their surface are subjected to an acylchlorination treatment to obtain acylchlorinated carbon nanotubes; then, the carbon nanotubes are subjected to an amidation reaction with 4-aminobenzophenone to introduce a benzophenone structure on the carbon nanotubes; finally, the active hydrogen on DOPO reacts with the ketone group on the benzophenone structure to prepare DOPO-carbon nanotubes. Among them, the carbon nanotubes after the acidification treatment have improved their dispersion properties, and the introduction of the benzophenone structure on their surface can further enhance their dispersion properties; in addition, benzophenone has hydrogen abstraction ability, and the hydrogen on DOPO is highly active, so the two can easily react. At this time, the benzophenone structure can play a good coupling role, connecting DOPO and the carbon nanotubes together, playing a role in enhancing the flame retardant properties of the carbon nanotubes, and ultimately achieving the purpose of enhancing the dispersibility and flame retardancy of the carbon nanotubes.

[0029] In this scheme, hexachlorocyclotriphosphazene undergoes ring-opening polymerization to produce a chain polyphosphazene. This is followed by a nucleophilic substitution reaction with (1-hydroxyallyl)trimethylsilane to produce an allyl-chain polyphosphazene, introducing an allyl group into the chain polyphosphazene. Finally, a click reaction occurs with oxetane-3-thiol to produce an oxetane-chain polyphosphazene, introducing an oxetane into the chain polyphosphazene. The chain polyphosphazene, with its backbone composed of nitrogen and phosphorus atoms arranged in alternating single and double bonds, exhibits natural flame retardancy synergy and thermal stability, making it a highly effective flame retardant. In this scheme, an oxygen heterocycle is introduced at the chain end. The ring opening can undergo nucleophilic substitution with pyrrole and -NH- on DOPO-carbon nanotubes, thus connecting pyrrole and carbon nanotubes. Pyrrole can stably and orderly polymerize on the surface of DOPO-carbon nanotubes to form a polypyrrole layer on the outside of the carbon nanotubes, enhancing the conductivity and dispersibility of the carbon nanotubes. In addition, polypyrrole is a flammable substance, and the chain polyphosphazene can give the polypyrrole layer a certain flame retardancy, which in turn acts on the carbon nanotubes. Ultimately, a flame-retardant carbon nanotube conductive material with good dispersibility, flame retardancy and conductivity is prepared.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The flame-retardant carbon nanotube conductive material prepared by the present invention has good dispersibility and will not agglomerate, which would cause the problem of decreased conductivity;

[0032] 2. The flame-retardant carbon nanotube conductive material prepared by the present invention has better conductivity than the original carbon nanotubes;

[0033] 3. The flame-retardant carbon nanotube conductive material prepared by the present invention has good flame-retardant properties, which greatly improves the safety of carbon nanotubes when used as conductive materials. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0035] It should be noted that the purchasers of all raw materials involved in the present invention include, without any special restrictions, illustratively:

[0036] Multi-walled carbon nanotubes with a purity of 99%, a diameter of 50 nm, and a length of 10 μm, product number: 100288, were purchased from Xianfeng Nano Co., Ltd.

[0037] Thionyl chloride was purchased from Changzhou Qidi Chemical Co., Ltd. with a purity of 98%.

[0038] 4-Aminobenzophenone (98%), DOPO (99.5%), CAS No. 35948-25-5, trichlorobenzene (98%), CAS No. 12002-48-1, and tetrabutylammonium bromide (99%) were purchased from JACS-Zhengzhou Jacks Chemical Products Co., Ltd.

[0039] (1-Hydroxyallyl)trimethylsilane with a purity of 96%, CAS number: 95061-68-0, purchased from Custom Chemicals, USA;

[0040] Oxetane-3-mercaptopropane with a purity of 99%, CAS number: 880136-18-5, dimethylformamide with a purity of 99.8%, aminosulfonic acid with a purity of 99%, and pyrrole with a purity of 99% were purchased from Jinjinle (Hunan) Chemical Co., Ltd.

[0041] Hexachlorocyclotriphosphazene with a purity of 98%, product number: S52005, CAS number: 940-71-6, purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0042] Photoinitiator model: IHT-PI EMK, purity 99%, purchased from Hubei Yongkuo Technology Co., Ltd.

[0043] In the following examples, the parts are by mass, with each part being 10 g.

[0044] Example 1: Preparation process of a flame-retardant carbon nanotube conductive material:

[0045] S1: Preparation of DOPO-carbon nanotubes:

[0046] S11: Multi-walled carbon nanotubes, 98 wt% concentrated sulfuric acid, and 68 wt% concentrated nitric acid are added to a reaction vessel in a ratio of 2 g:30 mL:10 mL, stirred and mixed evenly, then heated to 80° C. and soaked for 6 h. Finally, filtered, washed with water until the pH of the washing solution is neutral, and dried to obtain acidified carbon nanotubes;

[0047] S12: adding the acidified carbon nanotubes and thionyl chloride in a ratio of 4 g:100 mL into a reaction vessel, stirring and mixing uniformly, then heating to 55° C. and continuing stirring for 12 h, stopping stirring, and finally removing excess thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes;

[0048] S13: adding 10 parts of acyl chloride carbon nanotubes and 200 parts of 4-aminobenzophenone to a reaction vessel containing an appropriate amount of toluene, and refluxing the reaction at room temperature for 72 hours, stopping the reaction, and finally filtering, washing, and drying to obtain benzophenone-carbon nanotubes;

[0049] S14: Under a nitrogen atmosphere, 10 parts of benzophenone-carbon nanotubes and 62.5 parts of DOPO were added to a reaction vessel containing an appropriate amount of toluene, and the mixture was stirred and mixed evenly. The mixture was then heated to 175°C and stirred for 2 hours. The reaction was stopped, and the mixture was filtered, washed, and dried to obtain DOPO-carbon nanotubes.

[0050] S2: Preparation of oxygen heterocyclic-chain polyphosphazene:

[0051] S21: Under a nitrogen atmosphere, 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 parts of aminosulfonic acid and 0.019 parts of calcium sulfate dihydrate were added to a reaction vessel, stirred and heated to 180°C, then the nitrogen was stopped, the temperature was continued to be raised to 210±1°C and stirred for 2h, the reaction was stopped, and the temperature was cooled to 100°C. Sufficient n-heptane was added to the reaction vessel to precipitate, and finally filtered, washed and dried to obtain a chain polyphosphazene;

[0052] S22: Under a nitrogen atmosphere, 2 parts of the chain polyphosphazene and 8 parts of (1-hydroxyallyl)trimethylsilane were added to a reaction vessel containing an appropriate amount of dimethylformamide, and the mixture was stirred and mixed uniformly. 0.3 parts of tetrabutylammonium bromide was then added thereto, and the mixture was heated to 70° C. and refluxed for 12 hours to stop the reaction. Sufficient n-heptane was added to the reaction vessel to precipitate, and the precipitate was finally filtered, washed, and dried to obtain an allyl-chain polyphosphazene;

[0053] S23: 2 parts of allyl-chain polyphosphazene, 0.75 parts of oxetane-3-thiol and 0.13 parts of photoinitiator are added to a reaction vessel containing an appropriate amount of dimethylformamide, stirred and mixed evenly, and irradiated under 350 nm ultraviolet light for 10 minutes to stop the reaction. Finally, the mixture is filtered, washed and dried to obtain oxetane-chain polyphosphazene;

[0054] S3: Preparation of flame-retardant carbon nanotube conductive materials:

[0055] S31: Add 10 parts of DOPO-carbon nanotubes, 1.5 parts of oxygen heterocycle-chain polyphosphazene and 65 parts of pyrrole into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 1 mol / L hydrochloric acid to adjust the pH to 5, then add 10 wt% ammonium persulfate aqueous solution (prepared by adding 65 parts of ammonium persulfate to clean water), stir and react at room temperature for 12 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

[0056] Example 2: Preparation process of a flame-retardant carbon nanotube conductive material:

[0057] S1: Preparation of DOPO-carbon nanotubes:

[0058] S11: Multi-walled carbon nanotubes, 98 wt% concentrated sulfuric acid, and 68 wt% concentrated nitric acid are added to a reaction vessel in a ratio of 2 g:30 mL:10 mL, stirred and mixed evenly, then heated to 80° C. and soaked for 6 h. Finally, filtered, washed with water until the pH of the washing solution is neutral, and dried to obtain acidified carbon nanotubes;

[0059] S12: adding the acidified carbon nanotubes and thionyl chloride in a ratio of 4 g:100 mL into a reaction vessel, stirring and mixing uniformly, then heating to 55° C. and continuing stirring for 1 hour, stopping stirring, and finally removing excess thionyl chloride by rotary evaporation to obtain chlorinated carbon nanotubes;

[0060] S13: adding 10 parts of acyl chloride carbon nanotubes and 200 parts of 4-aminobenzophenone to a reaction vessel containing an appropriate amount of toluene, and refluxing the reaction at room temperature for 72 hours, stopping the reaction, and finally filtering, washing, and drying to obtain benzophenone-carbon nanotubes;

[0061] S14: Under a nitrogen atmosphere, 10 parts of benzophenone-carbon nanotubes and 50 parts of DOPO were added to a reaction vessel containing an appropriate amount of toluene, and the mixture was stirred and mixed evenly. The mixture was then heated to 175°C and stirred for 2 hours. The reaction was stopped, and the mixture was filtered, washed, and dried to obtain DOPO-carbon nanotubes.

[0062] S2: Preparation of oxygen heterocyclic-chain polyphosphazene:

[0063] S21: Under a nitrogen atmosphere, 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 parts of aminosulfonic acid and 0.019 parts of calcium sulfate dihydrate were added to a reaction vessel, stirred and heated to 180°C, then the nitrogen was stopped, the temperature was continued to be raised to 210±1°C and stirred for 2h, the reaction was stopped, and the temperature was cooled to 100°C. Sufficient n-heptane was added to the reaction vessel to precipitate, and finally filtered, washed and dried to obtain a chain polyphosphazene;

[0064] S22: Under a nitrogen atmosphere, 2 parts of the chain polyphosphazene and 5 parts of (1-hydroxyallyl)trimethylsilane were added to a reaction vessel containing an appropriate amount of dimethylformamide, and the mixture was stirred and mixed uniformly. 0.3 parts of tetrabutylammonium bromide was then added thereto, and the mixture was heated to 70° C. and refluxed for 12 hours to stop the reaction. A sufficient amount of n-heptane was added to the reaction vessel to precipitate, and the mixture was filtered, washed, and dried to obtain an allyl-chain polyphosphazene;

[0065] S23: 2 parts of allyl-chain polyphosphazene, 0.5 parts of oxetane-3-thiol and 0.13 parts of photoinitiator are added to a reaction vessel containing an appropriate amount of dimethylformamide, stirred and mixed evenly, and irradiated under 350 nm ultraviolet light for 10 minutes to stop the reaction. Finally, the mixture is filtered, washed and dried to obtain oxetane-chain polyphosphazene;

[0066] S3: Preparation of flame-retardant carbon nanotube conductive materials:

[0067] S31: Add 10 parts of DOPO-carbon nanotubes, 0.5 parts of oxygen heterocycle-chain polyphosphazene and 50 parts of pyrrole into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 1 mol / L hydrochloric acid to adjust the pH to 5, then add 10 wt% ammonium persulfate aqueous solution (prepared by adding 65 parts of ammonium persulfate to clean water), stir and react at room temperature for 12 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

[0068] Example 3: Preparation process of a flame-retardant carbon nanotube conductive material:

[0069] S1: Preparation of DOPO-carbon nanotubes:

[0070] S11: Multi-walled carbon nanotubes, 98 wt% concentrated sulfuric acid, and 68 wt% concentrated nitric acid are added to a reaction vessel in a ratio of 2 g:30 mL:10 mL, stirred and mixed evenly, then heated to 80° C. and soaked for 6 h. Finally, filtered, washed with water until the pH of the washing solution is neutral, and dried to obtain acidified carbon nanotubes;

[0071] S12: adding the acidified carbon nanotubes and thionyl chloride in a ratio of 4 g:100 mL into a reaction vessel, stirring and mixing uniformly, then heating to 55° C. and continuing stirring for 12 h, stopping stirring, and finally removing excess thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes;

[0072] S13: adding 10 parts of acyl chloride carbon nanotubes and 200 parts of 4-aminobenzophenone to a reaction vessel containing an appropriate amount of toluene, and refluxing the reaction at room temperature for 72 hours, stopping the reaction, and finally filtering, washing, and drying to obtain benzophenone-carbon nanotubes;

[0073] S14: Under a nitrogen atmosphere, 10 parts of benzophenone-carbon nanotubes and 100 parts of DOPO were added to a reaction vessel containing an appropriate amount of toluene, and the mixture was stirred and mixed evenly. The mixture was then heated to 175°C and stirred for 2 hours. The reaction was stopped, and the mixture was filtered, washed, and dried to obtain DOPO-carbon nanotubes.

[0074] S2: Preparation of oxygen heterocyclic-chain polyphosphazene:

[0075] S21: Under a nitrogen atmosphere, 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 parts of aminosulfonic acid and 0.019 parts of calcium sulfate dihydrate were added to a reaction vessel, stirred and heated to 180°C, then the nitrogen was stopped, the temperature was continued to be raised to 210±1°C and stirred for 2h, the reaction was stopped, and the temperature was cooled to 100°C. Sufficient n-heptane was added to the reaction vessel to precipitate, and finally filtered, washed and dried to obtain a chain polyphosphazene;

[0076] S22: Under a nitrogen atmosphere, 2 parts of the chain polyphosphazene and 10 parts of (1-hydroxyallyl)trimethylsilane were added to a reaction vessel containing an appropriate amount of dimethylformamide, and the mixture was stirred and mixed uniformly. 0.3 parts of tetrabutylammonium bromide was then added thereto, and the mixture was heated to 70° C. and refluxed for 12 hours to stop the reaction. A sufficient amount of n-heptane was added to the reaction vessel to precipitate, and the precipitate was finally filtered, washed, and dried to obtain an allyl-chain polyphosphazene;

[0077] S23: Add 2 parts of allyl-chain polyphosphazene, 1 part of oxetane-3-thiol and 0.13 parts of photoinitiator into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, irradiate under 350nm ultraviolet light for 10 minutes to stop the reaction, and finally filter, wash and dry to obtain oxetane-chain polyphosphazene;

[0078] S3: Preparation of flame-retardant carbon nanotube conductive materials:

[0079] S31: Add 10 parts of DOPO-carbon nanotubes, 2.5 parts of oxygen heterocycle-chain polyphosphazene and 75 parts of pyrrole into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 1 mol / L hydrochloric acid to adjust the pH to 5, then add 10 wt% ammonium persulfate aqueous solution (prepared by adding 65 parts of ammonium persulfate to clean water), stir and react at room temperature for 12 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

[0080] Based on Example 1, control experiments were carried out, specifically comparative examples 1 to 4, as described below:

[0081] Comparative Example 1: Only multi-walled carbon nanotubes are used as the conductive material.

[0082] Comparative Example 2: In S13, the mass ratio of 4-aminobenzophenone to chlorinated carbon nanotubes is 1:1, and other processes remain unchanged, specifically:

[0083] S13: 10 parts of acyl chloride carbon nanotubes and 10 parts of 4-aminobenzophenone are added to a reaction vessel containing an appropriate amount of toluene, and refluxed at room temperature for 72 hours. The reaction is stopped, and finally filtered, washed, and dried to obtain benzophenone-carbon nanotubes.

[0084] Comparative Example 3: No DOPO was added to modify the benzophenone-carbon nanotubes, and other processes remained unchanged, specifically:

[0085] S3: Preparation of flame-retardant carbon nanotube conductive materials:

[0086] S31: Add 10 parts of benzophenone-carbon nanotubes, 1.5 parts of oxygen heterocycle-chain polyphosphazene and 65 parts of pyrrole into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 1 mol / L hydrochloric acid to adjust the pH to 5, then add 10 wt% ammonium persulfate aqueous solution (prepared by adding 65 parts of ammonium persulfate to clean water), stir and react at room temperature for 12 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

[0087] Comparative Example 4: The chain polyphosphazene was not treated, and other processes remained unchanged, specifically:

[0088] S2: Preparation of chain polyphosphazene:

[0089] S21: Under a nitrogen atmosphere, 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 parts of aminosulfonic acid and 0.019 parts of calcium sulfate dihydrate were added to a reaction vessel, stirred and heated to 180°C, then the nitrogen was stopped, the temperature was continued to be raised to 210±1°C and stirred for 2h, the reaction was stopped, and the temperature was cooled to 100°C. Sufficient n-heptane was added to the reaction vessel to precipitate, and finally filtered, washed and dried to obtain a chain polyphosphazene;

[0090] S3: Preparation of flame-retardant carbon nanotube conductive materials:

[0091] S31: Add 10 parts of DOPO-carbon nanotubes, 1.5 parts of chain polyphosphazene and 65 parts of pyrrole into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 1 mol / L hydrochloric acid to adjust the pH to 5, then add 10 wt% ammonium persulfate aqueous solution (prepared by adding 65 parts of ammonium persulfate to clean water), stir and react at room temperature for 12 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

[0092] Performance test: Conductivity test and flame retardancy test were performed on the carbon nanotube conductive materials corresponding to Examples 1 to 3 and Comparative Examples 1 to 4. The specific test methods are as follows:

[0093] (1) Conductivity test: The conductivity of the carbon nanotube conductive material was measured using a conductivity meter;

[0094] (2) Flame retardancy test: The carbon nanotube conductive material, acetylene black and polyvinylidene fluoride binder were added into a container containing an appropriate amount of N-methylpyrrolidone in a mass ratio of 5:3:2, and ball milled at a speed of 150 r / min until the mixture became viscous to obtain a slurry; the slurry was then coated on a carbon cloth and dried to obtain an electrode sheet; the flame retardancy of the electrode sheet was then tested by direct ignition, and its self-extinguishing time was observed, and the average value of the three times was taken.

[0095] The specific test results are shown in Table 1 below:

[0096] Table 1

[0097]

[0098] Result analysis: It can be seen from the data in Table 1 above that a flame-retardant carbon nanotube conductive material with good conductivity and flame retardancy is prepared in the present invention; in particular, by comparing the embodiment and comparative example 1, it can be clearly seen that the conductivity and flame retardancy of the flame-retardant carbon nanotube conductive material prepared in the present invention are significantly enhanced.

[0099] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A process for preparing a flame-retardant carbon nanotube conductive material, characterized by: The following steps are involved: S1: Acylation of carbon nanotubes reacts with 4-aminobenzophenone and DOPO in sequence to obtain DOPO-carbon nanotubes; The acyl chloride carbon nanotubes undergo an amidation reaction with 4-aminobenzophenone to introduce a benzophenone structure. The 4-aminobenzophenone is in excess to completely react the acyl chloride groups on the carbon nanotubes. The active hydrogen of DOPO then reacts with the ketone group on the benzophenone structure to obtain DOPO-carbon nanotubes. S2: The chain polyphosphazene reacts with (1-hydroxyallyl)trimethylsilane and oxetane-3-thiol in sequence to obtain an oxetane-chain polyphosphazene; The method comprises the following steps: firstly, hexachlorocyclotriphosphazene is subjected to ring-opening polymerization to obtain a chain polyphosphazene; then, a nucleophilic substitution reaction is carried out with (1-hydroxyallyl)trimethylsilane to obtain an allyl-chain polyphosphazene, and an allyl group is introduced into the chain polyphosphazene; finally, a click reaction is carried out with oxetane-3-thiol to obtain an oxetane-chain polyphosphazene, and an oxygen heterocycle is introduced into the chain polyphosphazene; S3: DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene, and pyrrole are mixed to prepare flame-retardant carbon nanotube conductive materials; Among them, the oxygen heterocycle at the chain end of the oxygen heterocycle-chain polyphosphazene opens and undergoes nucleophilic substitution reaction with pyrrole and -NH- on DOPO-carbon nanotubes; pyrrole is stably and orderly polymerized on the surface of DOPO-carbon nanotubes to form a polypyrrole layer outside the carbon nanotubes.

2. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 1, wherein: The specific process of S1 is as follows: S11: adding carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid into a reaction container, stirring and mixing uniformly, then heating to 50-100° C. and soaking for 1-6 hours, and finally filtering, washing and drying to obtain acidified carbon nanotubes; S12: adding the acidified carbon nanotubes and thionyl chloride into a reaction vessel, stirring and mixing uniformly, then heating to 50-70° C. and continuing stirring for 1-24 hours, stopping stirring, and finally removing excess thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes; S13: adding acyl chloride carbon nanotubes and 4-aminobenzophenone into a reaction vessel containing toluene, and reflux reacting at room temperature for 24 to 72 hours, stopping the reaction, and finally filtering, washing, and drying to obtain benzophenone-carbon nanotubes; S14: Under a nitrogen atmosphere, benzophenone-carbon nanotubes and DOPO are added to a reaction vessel containing toluene, and the mixture is stirred to mix evenly. The mixture is then heated to 150-180° C. and stirred for reaction for 1-3 hours. The reaction is stopped, and the mixture is filtered, washed, and dried to obtain DOPO-carbon nanotubes.

3. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 2, wherein: The ratio of the carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid is (1-2) g:30 mL:10 mL; the ratio of the acidified carbon nanotubes and thionyl chloride is (1-5) g:100 mL; the mass ratio of the acyl chloride carbon nanotubes and 4-aminobenzophenone is 1:20; and the mass ratio of the benzophenone-carbon nanotubes and DOPO is (0.5-1):

5.

4. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 3, wherein: The carbon nanotubes include any one of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.

5. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 1, wherein: The specific process of S2 is: S21: Under a nitrogen atmosphere, hexachlorocyclotriphosphazene, trichlorobenzene, aminosulfonic acid, and calcium sulfate dihydrate are added to a reaction vessel, stirred and heated to 170-190° C., then the nitrogen is stopped, the temperature is continued to be raised to 210±1° C. and stirred for 0.5-2 h, the reaction is stopped, and the temperature is cooled to 100-110° C., sufficient n-heptane is added to the reaction vessel to precipitate, and finally filtered, washed, and dried to obtain a chain polyphosphazene; S22: Under a nitrogen atmosphere, the chain polyphosphazene and (1-hydroxyallyl)trimethylsilane are added to a reaction vessel containing dimethylformamide, and the mixture is stirred and mixed uniformly. Tetrabutylammonium bromide is then added thereto, and the mixture is heated to 60-80° C. and refluxed for 6-24 hours. The reaction is stopped, and sufficient n-heptane is added to the reaction vessel to precipitate. The precipitate is filtered, washed, and dried to obtain the allyl-chain polyphosphazene. S23: adding allyl-chain polyphosphazene, oxetane-3-thiol and photoinitiator into a reaction vessel containing dimethylformamide, stirring and mixing uniformly, irradiating under 350-370 nm ultraviolet light for 1-20 min to stop the reaction, and finally filtering, washing and drying to obtain oxetane-chain polyphosphazene.

6. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 5, characterized in that: The mass ratio of the hexachlorocyclotriphosphazene, trichlorobenzene, aminosulfonic acid and calcium sulfate dihydrate is (1-2):10:(0.1-0.2):(0.01-0.02); the mass ratio of the chain polyphosphazene, (1-hydroxyallyl)trimethylsilane and tetrabutylammonium bromide is (1-2):(5-10):(0.05-0.5); the mass ratio of the allyl-chain polyphosphazene, oxetane-3-thiol and photoinitiator is 4:(1-2):(0.15-0.3).

7. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 1, wherein: The specific process of S3 is as follows: S31: Add DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene and pyrrole into a reaction vessel filled with dimethylformamide, stir and mix evenly, then add hydrochloric acid to adjust the pH to 4-5, then add ammonium persulfate, stir and react at room temperature for 1-24 hours, and finally filter, wash and dry to obtain a flame-retardant carbon nanotube conductive material.

8. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 7, wherein: The mass ratio of the DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene, pyrrole and ammonium persulfate is (0.1-0.3):(0.01-0.05):(1-1.5):(1-1.5). 9 . The flame-retardant carbon nanotube conductive material prepared by the process for preparing a flame-retardant carbon nanotube conductive material according to any one of claims 1 to 8 .

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