Flame-retardant carbon nanotube conductive material and preparation process thereof

Abstract

The 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. Comprising the following steps: S1, sequentially reacting an acylating chlorination carbon nanotube with 4-aminobenzophenone and DOPO (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) to obtain a DOPO-carbon nanotube; s2, the chain polyphosphazene is subjected to a reaction with (1-hydroxyl allyl) trimethylsilane and oxetane 3-sulfydryl in sequence, and oxetane-chain polyphosphazene is obtained; s3, mixing the DOPO-carbon nano tube, oxygen heterocyclic ring-chain polyphosphazene and pyrrole to react, so as to prepare the flame-retardant carbon nano tube conductive material.

Description

Technical Field

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

[0002] Carbon nanotubes are a very good conductive material, and their conductive performance can be comparable to that of metal conductors. However, carbon nanotubes also have the problem of easy agglomeration. If carbon nanotubes are directly used as the negative electrode material, the cations on the surface of the carbon nanotubes will be restricted, which will lead to a decline in their conductive performance and cannot fully exert their conductive characteristics.

[0003] Therefore, it is quite important to modify carbon nanotubes to enhance their dispersibility and improve their conductive performance. In addition, with the rapid development of modern industry, there are more and more requirements for materials, and the multi-functionalization of materials has gradually become an important direction in material research. That is, while improving the dispersion performance of carbon nanotubes, enhancing their other properties or endowing them with other excellent properties can actively play a role in broadening the application potential of carbon nanotubes.

[0004] Based on this, the present invention will provide a flame-retardant carbon nanotube conductive material. This flame-retardant carbon nanotube conductive material not only improves the dispersibility of carbon nanotubes and enhances their conductive performance, but also improves the flame retardancy of carbon nanotubes and enhances the safety when carbon nanotubes are used as conductive materials. 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 to solve the problems raised in the prior art.

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

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

[0008] S1: The acyl chloride carbon nanotubes react with 4-aminobenzophenone and DOPO in sequence to obtain DOPO-carbon nanotubes:

[0009] S11: Add carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid into a reaction vessel, stir and mix evenly, then heat up to 50-100 °C for soaking treatment for 1-6 h, and finally filter, wash with clear water until the pH of the washing solution is neutral, and dry to obtain acidified carbon nanotubes;

[0010] S12: Add the acidified carbon nanotubes and thionyl chloride into a reaction vessel, stir and mix evenly, then heat up to 50-70 °C and continue stirring for 1-24 h, stop stirring, and finally remove the excess thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes;

[0011] S13: Add the carbon nanotubes with acyl chloride groups and 4-aminobenzophenone into a reaction vessel filled with toluene, reflux at room temperature for 24 - 72 h, stop the reaction, and finally obtain benzophenone-carbon nanotubes through filtration, washing, and drying.

[0012] S14: Under a nitrogen atmosphere, add benzophenone-carbon nanotubes and DOPO into a reaction vessel filled with toluene, stir and mix evenly, then heat to 150 - 180 °C and stir for 1 - 3 h, stop the reaction, and finally obtain DOPO-carbon nanotubes through filtration, washing, and drying.

[0013] S2: The chain-like polyphosphazene reacts with (1-hydroxyallyl)trimethylsilane and 3-mercaptooxetane in sequence to obtain oxacyclic-chain-like polyphosphazene:

[0014] S21: Under a nitrogen atmosphere, add hexachlorocyclotriphosphazene, trichlorobenzene, sulfamic acid, and calcium sulfate dihydrate into a reaction vessel, stir and heat to 170 - 190 °C, then stop introducing nitrogen and continue heating to 210 ± 1 °C and stir for 0.5 - 2 h, stop the reaction, wait until the temperature drops to 100 - 110 °C, add a sufficient amount of n-heptane into the reaction vessel to precipitate, and finally obtain chain-like polyphosphazene through filtration, washing, and drying.

[0015] S22: Under a nitrogen atmosphere, add chain-like polyphosphazene and (1-hydroxyallyl)trimethylsilane into a reaction vessel filled with dimethylformamide, stir and mix evenly, then add tetrabutylammonium bromide, heat to 60 - 80 °C and reflux for 6 - 24 h, stop the reaction, add a sufficient amount of n-heptane into the reaction vessel to precipitate, and finally obtain allyl-chain-like polyphosphazene through filtration, washing, and drying.

[0016] S23: Add allyl-chain-like polyphosphazene, 3-mercaptooxetane, and a photoinitiator into a reaction vessel filled with dimethylformamide, stir and mix evenly, irradiate under ultraviolet light of 350 - 370 nm for 1 - 20 min, stop the reaction, and finally obtain oxacyclic-chain-like polyphosphazene through filtration, washing, and drying.

[0017] S3: DOPO-carbon nanotubes, oxacyclic-chain-like polyphosphazene, and pyrrole react to prepare a flame-retardant carbon nanotube conductive material:

[0018] S31: Add DOPO-carbon nanotubes, oxacyclic-chain-like 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 at room temperature for 1 - 24 h, and finally obtain a flame-retardant carbon nanotube conductive material through filtration, washing, and drying.

[0019] Furthermore, the proportional relationship among 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 proportional relationship between the acidified carbon nanotubes and thionyl chloride is (1 - 5) g: 100 mL.

[0022] Furthermore, the mass ratio of the acyl chloride-functionalized carbon nanotubes to 4-aminobenzophenone is 1:20; wherein, the dosage of 4-aminobenzophenone needs to be in excess because: if the acyl chloride groups on the carbon nanotubes do not react completely, they will directly react with DOPO subsequently, which will affect the formation of the target product on the one hand and reduce the dispersibility of the carbon nanotubes on the other hand.

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

[0024] Furthermore, the mass ratio of hexachlorocyclotriphosphazene, trichlorobenzene, sulfamic 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-like 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-like polyphosphazene, 3-mercaptooxetane, and photoinitiator is 4:(1 - 2):(0.15 - 0.3).

[0027] Furthermore, the mass ratio of the DOPO-carbon nanotubes, oxacycle-chain-like 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 acidified to form abundant -COOH groups on their surfaces. Then, the -COOH groups on the surfaces are subjected to acyl chlorination treatment to obtain acyl chlorinated carbon nanotubes. Subsequently, an amidation reaction is carried out with 4-aminobenzophenone to introduce a benzophenone structure onto 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 dispersibility of the carbon nanotubes after acidification treatment has been improved, and introducing a benzophenone structure on their surfaces can further enhance their dispersibility. In addition, benzophenone has the ability to abstract hydrogen, and the hydrogen on DOPO has extremely high activity, so the two can easily react. At this time, the benzophenone structure can play a good coupling role, connecting DOPO and carbon nanotubes together, playing a role in enhancing the flame retardant performance of carbon nanotubes, and finally achieving the purpose of enhancing the dispersibility and flame retardancy of carbon nanotubes.

[0029] In the scheme, first, hexachlorocyclotriphosphazene is subjected to ring-opening polymerization to obtain chain-like polyphosphazene. Then, a nucleophilic substitution reaction is carried out with (1-hydroxyallyl)trimethylsilane to obtain allyl-chain-like polyphosphazene, introducing an allyl group onto the chain-like polyphosphazene. Finally, a click reaction is carried out with 3-mercaptooxetane to obtain oxa-ring-chain-like polyphosphazene, introducing an oxetane ring onto the chain-like polyphosphazene. The main chain of the chain-like polyphosphazene is composed of nitrogen and phosphorus atoms arranged alternately with single and double bonds, having natural flame retardant synergy and thermal stability, so it is an efficient flame retardant. In the scheme, by introducing an oxetane ring at its chain end, its ring-opening can undergo nucleophilic substitution with -NH- on pyrrole and DOPO-carbon nanotubes, playing a role in connecting pyrrole and carbon nanotubes. And pyrrole can polymerize stably and orderly on the surface of DOPO-carbon nanotubes to form a polypyrrole layer outside the carbon nanotubes, enhancing the conductivity and dispersibility of the carbon nanotubes. In addition, polypyrrole is a flammable substance, and the chain-like polyphosphazene can endow the polypyrrole layer with certain flame retardancy, and then act on the carbon nanotubes. Finally, a flame retardant carbon nanotube conductive material with good dispersibility, flame retardancy, and conductivity is prepared.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The flame retardant carbon nanotube conductive material prepared by the present invention has good dispersibility and will not show the problem of agglomeration, resulting in a decrease in conductivity.

[0032] 2. The flame retardant carbon nanotube conductive material prepared by the present invention has more excellent conductivity compared with the original carbon nanotubes.

[0033] 3. The flame retardant carbon nanotube conductive material prepared by the present invention has good flame retardant performance, greatly improving the safety of carbon nanotubes when used as a conductive material. Detailed implementation mode

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] It should be noted that there are no special restrictions on the purchasing manufacturers of all raw materials involved in the present invention. Exemplarily, they include:

[0036] The multi-walled carbon nanotubes have a purity of 99%, a diameter of 50 nm, a length of 10 μm, article number: 100288, and are purchased from Xianfeng Nano Co., Ltd.;

[0037] Thionyl chloride has a purity of 98% and is purchased from Changzhou Qidi Chemical Co., Ltd.;

[0038] 4-Aminobenzophenone has a purity of 98%, DOPO has a purity of 99.5%, CAS number: 35948-25-5, trichlorobenzene has a purity of 98%, CAS number: 12002-48-1, tetrabutylammonium bromide has a purity of 99%, and all are purchased from JACS-Zhengzhou Jacks Chemical Products Co., Ltd.;

[0039] (1-Hydroxyallyl)trimethylsilane has a purity of 96%, CAS number: 95061-68-0, and is purchased from American Custom Chemicals Corporation;

[0040] Oxetane-3-thiol has a purity of 99%, CAS number: 880136-18-5, dimethylformamide has a purity of 99.8%, sulfamic acid has a purity of 99%, pyrrole has a purity of 99%, and all are purchased from Jinjinle (Hunan) Chemical Co., Ltd.;

[0041] Hexachlorocyclotriphosphazene has a purity of 98%, article number: S52005, CAS number: 940-71-6, and is purchased from Shanghai Yuanye Bio-Technology Co., Ltd.;

[0042] The photoinitiator model: IHT-PI EMK, has a purity of 99% and is purchased from Hubei Yongkuo Technology Co., Ltd.;

[0043] In the following embodiments, the parts are by mass, and each part is 10 g.

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

[0045] S1: Prepare DOPO-carbon nanotubes:

[0046] S11: Add multi-walled carbon nanotubes, 98 wt% concentrated sulfuric acid, and 68 wt% concentrated nitric acid into a reaction vessel at a ratio of 2 g: 30 mL: 10 mL, stir and mix evenly, then heat up to 80 °C for soaking treatment for 6 h, and finally filter, wash with clear water until the pH of the washing solution is neutral, and dry to obtain acidified carbon nanotubes;

[0047] S12: Add acidified carbon nanotubes and thionyl chloride into a reaction vessel at a ratio of 4 g: 100 mL, stir and mix evenly, then heat up to 55 °C and continue stirring for 12 h, stop stirring, and finally remove the excessive thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes;

[0048] S13: Add 10 parts of acyl chloride carbon nanotubes and 200 parts of 4-aminobenzophenone into a reaction vessel containing an appropriate amount of toluene, reflux and react at room temperature for 72 h, stop the reaction, and finally filter, wash, and dry to obtain benzophenone-carbon nanotubes;

[0049] S14: Under a nitrogen atmosphere, add 10 parts of benzophenone-carbon nanotubes and 62.5 parts of DOPO into a reaction vessel containing an appropriate amount of toluene, stir and mix evenly, then heat up to 175 °C and stir and react for 2 h, stop the reaction, and finally filter, wash, and dry to obtain DOPO-carbon nanotubes;

[0050] S2: Prepare oxacycle-chain polyphosphazene:

[0051] S21: Under a nitrogen atmosphere, add 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 part of amidosulfonic acid, and 0.019 part of calcium sulfate dihydrate into a reaction vessel, stir and heat up to 180 °C, then stop introducing nitrogen, continue to heat up to 210 ± 1 °C and stir and react for 2 h, stop the reaction, wait until the temperature drops to 100 °C, add a sufficient amount of n-heptane into the reaction vessel, precipitate, and finally filter, wash, and dry to obtain chain polyphosphazene;

[0052] S22: Under a nitrogen atmosphere, add 2 parts of chain polyphosphazene and 8 parts of (1-hydroxyallyl) trimethylsilane into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 0.3 part of tetrabutylammonium bromide thereto, then heat up to 70 °C and reflux and react for 12 h, stop the reaction, add a sufficient amount of n-heptane into the reaction vessel, precipitate, and finally filter, wash, and dry to obtain allyl-chain polyphosphazene;

[0053] S23: Add 2 parts of allyl-chain polyphosphazene, 0.75 part of 3-mercaptooxetane, and 0.13 part of photoinitiator into a reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, irradiate under ultraviolet light at 350 nm for 10 min, stop the reaction, and finally filter, wash, and dry to obtain oxacyclic-chain polyphosphazene;

[0054] S3: Prepare a flame-retardant carbon nanotube conductive material:

[0055] S31: Add 10 parts of DOPO-carbon nanotubes, 1.5 parts of oxacyclic-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 an aqueous solution of 10 wt% ammonium persulfate (prepared by adding 65 parts of ammonium persulfate to clear water), stir and react at room temperature for 12 h, and finally filter, wash, and dry to obtain a flame-retardant carbon nanotube conductive material.

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

[0057] S1: Prepare DOPO-carbon nanotubes:

[0058] S11: Add multi-walled carbon nanotubes, 98 wt% concentrated sulfuric acid, and 68 wt% concentrated nitric acid into a reaction vessel in a ratio of 2 g:30 mL:10 mL, stir and mix evenly, then heat up to 80 °C and soak for 6 h, and finally filter and wash with clear water until the pH of the washing liquid is neutral, and dry to obtain acidified carbon nanotubes;

[0059] S12: Add acidified carbon nanotubes and thionyl chloride into a reaction vessel in a ratio of 4 g:100 mL, stir and mix evenly, then heat up to 55 °C and continue stirring for 1 h, stop stirring, and finally remove the excess thionyl chloride by rotary evaporation to obtain acyl chloride carbon nanotubes;

[0060] S13: Add 10 parts of acyl chloride carbon nanotubes and 200 parts of 4-aminobenzophenone into a reaction vessel containing an appropriate amount of toluene, reflux and react at room temperature for 72 h, stop the reaction, and finally filter, wash, and dry to obtain benzophenone-carbon nanotubes;

[0061] S14: Under a nitrogen atmosphere, add 10 parts of benzophenone-carbon nanotubes and 50 parts of DOPO into a reaction vessel containing an appropriate amount of toluene, stir and mix evenly, then heat up to 175 °C and stir and react for 2 h, stop the reaction, and finally filter, wash, and dry to obtain DOPO-carbon nanotubes;

[0062] S2: Prepare oxacyclic-chain polyphosphazene:

[0063] S21: Under a nitrogen atmosphere, 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 part of sulfamic acid, and 0.019 part of calcium sulfate dihydrate are added into a reaction vessel, stirred and heated to 180 °C, then the nitrogen supply is stopped, and the temperature is continuously raised to 210 ± 1 °C and stirred for reaction for 2 h. The reaction is stopped. After cooling to 100 °C, sufficient n-heptane is added into the reaction vessel to precipitate a solid. Finally, after filtration, washing, and drying, a chain-shaped polyphosphazene is obtained.

[0064] S22: Under a nitrogen atmosphere, 2 parts of the chain-shaped polyphosphazene and 5 parts of (1-hydroxyallyl)trimethylsilane are added into a reaction vessel containing an appropriate amount of dimethylformamide, stirred and mixed evenly, then 0.3 part of tetrabutylammonium bromide is added thereto, and then the temperature is raised to 70 °C and refluxed for reaction for 12 h. The reaction is stopped. Sufficient n-heptane is added into the reaction vessel to precipitate a solid. Finally, after filtration, washing, and drying, an allyl-chain-shaped polyphosphazene is obtained.

[0065] S23: 2 parts of the allyl-chain-shaped polyphosphazene, 0.5 part of oxetane-3-thiol, and 0.13 part of a photoinitiator are added into a reaction vessel containing an appropriate amount of dimethylformamide, stirred and mixed evenly, irradiated under ultraviolet light at 350 nm for 10 min, the reaction is stopped, and finally, after filtration, washing, and drying, an oxacyclic-chain-shaped polyphosphazene is obtained.

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

[0067] S31: 10 parts of DOPO-carbon nanotubes, 0.5 part of the oxacyclic-chain-shaped polyphosphazene, and 50 parts of pyrrole are added into a reaction vessel containing an appropriate amount of dimethylformamide, stirred and mixed evenly, then 1 mol / L hydrochloric acid is added thereto to adjust the pH to 5, then an aqueous solution of 10 wt% ammonium persulfate (prepared by adding 65 parts of ammonium persulfate to clear water) is added thereto, and stirred at room temperature for reaction for 12 h. Finally, after filtration, washing, and drying, a flame-retardant carbon nanotube conductive material is obtained.

[0068] Example 3: A 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 into 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, after filtration, washed with clear water until the pH of the washing solution is neutral, and dried to obtain acidified carbon nanotubes.

[0071] S12: Add acidified carbon nanotubes and thionyl chloride into the reaction vessel at a ratio of 4 g:100 mL, stir and mix evenly, then heat up to 55 °C and continue stirring for 12 h, stop stirring, and finally remove the excessive thionyl chloride by rotary evaporation to obtain acyl chloride-functionalized carbon nanotubes;

[0072] S13: Add 10 parts of acyl chloride-functionalized carbon nanotubes and 200 parts of 4-aminobenzophenone into the reaction vessel containing an appropriate amount of toluene, reflux and react at room temperature for 72 h, stop the reaction, and finally obtain benzophenone-carbon nanotubes through filtration, washing, and drying;

[0073] S14: Under a nitrogen atmosphere, add 10 parts of benzophenone-carbon nanotubes and 100 parts of DOPO into the reaction vessel containing an appropriate amount of toluene, stir and mix evenly, then heat up to 175 °C and stir and react for 2 h, stop the reaction, and finally obtain DOPO-carbon nanotubes through filtration, washing, and drying;

[0074] S2: Prepare oxacyclic-chain polyphosphazene:

[0075] S21: Under a nitrogen atmosphere, add 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 part of sulfamic acid, and 0.019 part of calcium sulfate dihydrate into the reaction vessel, stir and heat up to 180 °C, then stop introducing nitrogen, continue heating up to 210 ± 1 °C and stir and react for 2 h, stop the reaction, wait until the temperature drops to 100 °C, add a sufficient amount of n-heptane into the reaction vessel to precipitate, and finally obtain chain polyphosphazene through filtration, washing, and drying;

[0076] S22: Under a nitrogen atmosphere, add 2 parts of chain polyphosphazene and 10 parts of (1-hydroxyallyl)trimethylsilane into the reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, then add 0.3 part of tetrabutylammonium bromide into it, then heat up to 70 °C and reflux and react for 12 h, stop the reaction, add a sufficient amount of n-heptane into the reaction vessel to precipitate, and finally obtain allyl-chain polyphosphazene through filtration, washing, and drying;

[0077] S23: Add 2 parts of allyl-chain polyphosphazene, 1 part of oxetane-3-thiol, and 0.13 part of photoinitiator into the reaction vessel containing an appropriate amount of dimethylformamide, stir and mix evenly, irradiate under ultraviolet light at 350 nm for 10 min, stop the reaction, and finally obtain oxacyclic-chain polyphosphazene through filtration, washing, and drying;

[0078] S3: Prepare flame-retardant carbon nanotube conductive material:

[0079] S31: Add 10 parts of DOPO-carbon nanotubes, 2.5 parts of oxacycle-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. Next, add an aqueous solution of 10 wt% ammonium persulfate (prepared by adding 65 parts of ammonium persulfate to clear water), stir and react at room temperature for 12 h. Finally, filter, wash, and dry to obtain a flame-retardant carbon nanotube conductive material.

[0080] Based on Example 1 below, control experiments were carried out, specifically Comparative Examples 1-4, as described below:

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

[0082] Comparative Example 2: In S13, the mass ratio of 4-aminobenzophenone to acyl chloride-functionalized carbon nanotubes was 1:1, and other processes remained unchanged. Specifically:

[0083] S13: Add 10 parts of acyl chloride-functionalized carbon nanotubes and 10 parts of 4-aminobenzophenone into a reaction vessel containing an appropriate amount of toluene, reflux and react at room temperature for 72 h, stop the reaction, and finally filter, wash, and dry to obtain benzophenone-carbon nanotubes.

[0084] Comparative Example 3: Without adding DOPO to modify benzophenone-carbon nanotubes, other processes remained unchanged. Specifically:

[0085] S3: Prepare a flame-retardant carbon nanotube conductive material:

[0086] S31: Add 10 parts of benzophenone-carbon nanotubes, 1.5 parts of oxacycle-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. Next, add an aqueous solution of 10 wt% ammonium persulfate (prepared by adding 65 parts of ammonium persulfate to clear water), stir and react at room temperature for 12 h. Finally, filter, wash, and dry to obtain a flame-retardant carbon nanotube conductive material.

[0087] Comparative Example 4: Without treating the chain polyphosphazene, other processes remained unchanged. Specifically:

[0088] S2: Prepare chain polyphosphazene:

[0089] S21: Under a nitrogen atmosphere, 2.25 parts of hexachlorocyclotriphosphazene, 12.5 parts of trichlorobenzene, 0.19 part of sulfamic acid, and 0.019 part of calcium sulfate dihydrate are added to a reaction vessel, stirred and heated to 180 °C, then the nitrogen supply is stopped, and the temperature is further raised to 210 ± 1 °C and stirred for reaction for 2 h. The reaction is stopped. After cooling to 100 °C, a sufficient amount of n-heptane is added to the reaction vessel to precipitate a solid. Finally, after filtration, washing, and drying, a chain-shaped polyphosphazene is obtained.

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

[0091] S31: 10 parts of DOPO-carbon nanotubes, 1.5 parts of chain-shaped polyphosphazene, and 65 parts of pyrrole are added to a reaction vessel containing an appropriate amount of dimethylformamide, stirred and mixed evenly, then 1 mol / L hydrochloric acid is added to adjust the pH to 5. Then, an aqueous solution of 10 wt% ammonium persulfate (prepared by adding 65 parts of ammonium persulfate to clear water) is added thereto, and the mixture is stirred at room temperature for reaction for 12 h. Finally, after filtration, washing, and drying, a flame-retardant carbon nanotube conductive material is obtained.

[0092] Performance test: Conductivity tests and flame-retardancy tests are carried out 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 is measured using a conductivity meter.

[0094] (2) Flame-retardancy test: The carbon nanotube conductive material is respectively added to a container containing an appropriate amount of N-methylpyrrolidone together with acetylene black and a polyvinylidene fluoride binder in a mass ratio of 5:3:2, and ball-milled at a rotation speed of 150 r / min until the mixture becomes viscous to obtain a slurry. Then, the slurry is coated on a carbon cloth, and after drying, an electrode sheet is obtained. Then, a direct ignition method is used to test the flame-retardancy performance of the electrode sheet, and its self-extinguishing time is observed, and the average value of three measurements is taken.

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

[0096] Table 1

[0097]

[0098] Result analysis: From the data in Table 1 above, it can be seen that a flame-retardant carbon nanotube conductive material with good conductivity and good flame-retardancy is prepared in the present invention; in particular, by comparing Example 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] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A process for preparing a flame-retardant carbon nanotube conductive material, characterized in that: The following steps are involved: S1: Acylation of carbon nanotubes reacts with 4-aminobenzophenone and DOPO in sequence 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; S3: DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene and pyrrole are mixed and reacted to prepare flame-retardant carbon nanotube conductive materials.

2. The process for preparing a flame-retardant carbon nanotube conductive material according to claim 1, characterized in that: 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 evenly, 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 container, stirring and mixing evenly, 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 container filled with toluene, 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 container containing toluene, and the mixture is stirred to be uniform. The mixture is then heated to 150-180° C. and stirred to react 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, characterized in that: 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 dithionyl chloride is (1-5) g:100 mL; the mass ratio of the acyl chloride carbon nanotubes and 4-aminobenzophenone is 1:20; 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, characterized in that: 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, characterized in that: The specific process of S2 is: S21: Under a nitrogen atmosphere, hexachlorocyclotriphosphazene, trichlorobenzene, aminosulfonic acid and calcium sulfate dihydrate are added to a reaction container, 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 reaction for 0.5-2h, the reaction is stopped, and the temperature is cooled to 100-110° C., sufficient amount of n-heptane is added to the reaction container to precipitate, and finally filtered, washed and dried to obtain a chain polyphosphazene; S22: under a nitrogen atmosphere, adding the chain polyphosphazene and (1-hydroxyallyl)trimethylsilane into a reaction vessel containing dimethylformamide, stirring and mixing evenly, adding tetrabutylammonium bromide thereto, and then heating to 60-80° C. and reflux reaction for 6-24 hours, stopping the reaction, adding a sufficient amount of n-heptane into the reaction vessel, precipitating, and finally filtering, washing, and drying 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 evenly, irradiating under 350-370 nm ultraviolet light for 1-20 min, stopping 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, characterized in that: The specific process of S3 is as follows: S31: Add DOPO-carbon nanotubes, oxygen heterocycle-chain polyphosphazene and pyrrole into a reaction container 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, characterized in that: 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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