Heating film containing carbon nanotubes and preparation method thereof

Abstract

The invention relates to the technical field of heating film preparation, in particular to a heating film containing carbon nanotubes and a preparation method of the heating film. The modified graphene oxide and the pretreated carbon nanotubes are bonded through chemical bonds by taking a silane coupling agent as a'bridge ', so that an inorganic base material is prepared; the inorganic base material ensures the electrical conductivity, the heat-conducting property and the electromagnetic shielding property under the synergistic cooperation of the carbon nanotubes and the graphene; the pretreated inorganic base material is put into a silver nitrate aqueous solution, an oxalic acid aqueous solution is added, and a considerable amount of nano-silver quantum dots are deposited on the surface of the pretreated inorganic base material after a chemical reaction, so that the conductivity of the inorganic base material is further improved; a three-dimensional conductive network is jointly formed by the conductive polymer, the nano-silver quantum dots, the carbon nanotubes and the graphene, so that the compound conductive agent not only has excellent conductive performance, heat-conducting performance and electromagnetic shielding performance, but also has excellent thermal fatigue resistance and thermal damage resistance, and the quality of the heating film is effectively guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of heating film preparation, and in particular to a heating film containing carbon nanotubes and a preparation method thereof. Background Art

[0002] The heating film is a planar heating element composed of an electrical insulating material and a heating resistor material encapsulated therein. When working, it converts electrical energy into thermal energy and transmits the thermal energy outward mainly in the form of radiation. The heating film is a new type of electric heating element that has emerged in recent years. It absorbs the characteristics of two electric heating elements, PTC and conductive coating, and is mainly used for indoor heating and maintaining ambient temperature. Carbon nanotubes have excellent electrical conductivity. When used as a raw material for preparing heating films, they can not only effectively improve the electrical conductivity of the heating film, but also significantly improve its electromagnetic shielding performance.

[0003] A heating film and a preparation method thereof are disclosed in a patent document with application number "CN202111521575.4". The heating film comprises, from bottom to top, a base layer, an electronic paste layer, and a protective layer, and there is a circuit on the surface of the base layer. Although the heating film prepared by this patent document has the advantages of low cost and fast response speed, its own heating efficiency is relatively low, and its high temperature resistance is relatively insufficient. Furthermore, its resistance to thermal fatigue and thermal damage are also relatively poor, which affects the quality and service life of the heating film to a certain extent. Based on this, the present invention provides a heating film containing carbon nanotubes and a preparation method thereof! Summary of the invention

[0004] The purpose of the present invention is to provide a heating film containing carbon nanotubes and a preparation method thereof. The prepared heating film not only has excellent electrical conductivity, thermal conductivity and electromagnetic shielding performance, but also has excellent resistance to thermal fatigue and thermal damage, which effectively guarantees its quality and also extends its service life to a certain extent.

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

[0006] In the first aspect, the present invention provides a method for preparing a heating film containing carbon nanotubes, comprising the following steps: placing a copper foil on the top of a polyimide substrate, and obtaining a substrate layer with a circuit on the surface after etching, and connecting a power pad to the circuit; then printing a conductive paste on the surface of the substrate layer by silk screen printing, and obtaining a conductive paste layer after drying; finally, pasting a polyurethane film on the surface of the conductive paste layer, and obtaining a finished heating film containing carbon nanotubes after heating, curing and punching.

[0007] Furthermore, the conductive paste is composed of the following raw materials in parts by weight: 80 to 85 parts of a composite conductive agent, 80 to 100 parts of dipropylene glycol methyl ether, 5 to 10 parts of bisphenol F epoxy resin, 5 to 8 parts of n-butyl acetate, 2 to 3 parts of tetrahydrophthalic anhydride, 0.3 to 0.6 parts of 2-phenyl-4-methylimidazole, 0.8 to 1.2 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 3 to 5 parts of ethylene glycol diglycidyl ether, 0.5 to 1.0 parts of 3-aminopropyltriethoxysilane and 0.6 to 1.0 parts of polyethylene wax.

[0008] Furthermore, the preparation method of the composite conductive agent is:

[0009] Step 1, putting the inorganic substrate into an ethanol aqueous solution with a volume concentration of 50-60% at a solid-liquid ratio of 3-8 mg / mL, adding sodium dodecylbenzene sulfonate with a mass of 2-4% of the ethanol aqueous solution, ultrasonically dispersing for 2-3 hours and then centrifuging it, washing the obtained solid filter material with ethanol for 3-4 times and then drying it to obtain a pretreated inorganic substrate;

[0010] Step 2: Put the pretreated inorganic substrate into a silver nitrate aqueous solution with a mass of 10 to 20 times that of the pretreated inorganic substrate and a concentration of 1 to 1.5 mol / L, mix and stir for 10 to 15 hours, then add a 2 to 3 mol / L oxalic acid aqueous solution, react for 50 to 80 minutes, filter the resulting component, wash the filter cake with ethanol, and then vacuum dry it. The modified inorganic substrate is stored and used for later use.

[0011] Step 3, add 0.2-0.5 mmol / L sodium persulfate aqueous solution to 6-10 mmol / L 3-carboxy-3-hydroxyglutaric acid aqueous solution at a volume ratio of 1:2-4, and add the modified inorganic substrate to the obtained mixed phase at a solid-liquid ratio of 5-10 mg / mL, add 2-aminobenzoic acid with a molar amount of 10-15 times that of 3-carboxy-3-hydroxyglutaric acid after ultrasonic dispersion, mix well and react at a temperature of 120-140°C for 5-8h; after the reaction is completed, cool the product components to room temperature, and then filter, wash with water, wash with alcohol and dry in turn to obtain the composite conductive agent.

[0012] Furthermore, the preparation method of the inorganic substrate is:

[0013] S1. Put graphene oxide into deionized water at a solid-liquid ratio of 3-8 mg / mL, adjust the pH to 4.3-4.8 after ultrasonic dispersion for 2-3 hours, then add silane coupling agent dispersion, mix and stir evenly, and keep warm at 50-65°C for 15-25 hours. After the reaction is completed, cool the resulting components naturally to room temperature, wash with deionized water and freeze-dry, and store the modified graphene oxide for standby use;

[0014] S2. Add the modified graphene oxide into N,N-dimethylformamide at a dosage ratio of 6 to 10 mg / mL, and add pre-treated carbon nanotubes with a mass of 1.5 to 2 times that of the modified graphene oxide. After ultrasonic dispersion for 2 to 5 hours, stir the reaction at 75 to 85° C. for 10 to 15 hours, and then reflux the reaction for 8 to 12 hours. After the reaction is completed, naturally cool the resulting components to room temperature, and then filter, wash and freeze-dry in sequence to obtain the inorganic substrate.

[0015] Furthermore, the preparation method of the silane coupling agent dispersion is: add 3-aminopropyltriethoxysilane into ethanol with a mass of 6 to 10 times that of the silane coupling agent, mix and stir evenly to obtain the silane coupling agent dispersion; and the amount of the silane coupling agent used is 10 to 20% of the mass of the graphene oxide.

[0016] Furthermore, deionized water is used for washing, and the washing times are 4 to 5 times.

[0017] Furthermore, the pressure during freeze drying is 20 to 30 Pa, the temperature is -40 to -50°C, and the freeze drying time is set to 30 to 50 hours.

[0018] Furthermore, the preparation method of the pre-treated carbon nanotubes is: uniformly dispersing the carboxylated single-walled carbon nanotubes in thionyl chloride at a solid-liquid ratio of 2 to 5 mg / mL, ultrasonically dispersing for 2 to 4 hours, and then heat-retaining the reaction at 70 to 85° C. for 15 to 25 hours. After the reaction is completed, naturally cooling it to room temperature, and then filtering, washing with deionized water 3 to 5 times, and vacuum drying in sequence to obtain the pre-treated carbon nanotubes.

[0019] Furthermore, the thickness of the electronic paste layer is 10-20 μm; the aperture of the nylon screen used in the screen printing process is 250-300 meshes, the drying temperature is 60-75° C., the drying time is 10-25 min; and the heating curing temperature is 170-180° C.

[0020] In a second aspect, the present invention provides a heating film containing carbon nanotubes, which is prepared by the preparation method described above.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the present invention, thionyl chloride is first used to pre-treat carboxylated single-walled carbon nanotubes, and graphene oxide is modified by a silane coupling agent. The modified graphene oxide is then put into N,N-dimethylformamide and the pre-treated carbon nanotubes are added. After ultrasonic dispersion, the two react chemically, and finally the two are chemically bonded through the silane coupling agent as a "bridge" to prepare an inorganic substrate. The inorganic substrate is coordinated with carbon nanotubes and graphene to ensure its electrical conductivity, thermal conductivity and electromagnetic shielding performance.

[0023] The obtained inorganic substrate is put into anhydrous ethanol and sodium dodecylbenzene sulfonate is added, and the pre-treated inorganic substrate is obtained after ultrasonic dispersion. Then the pre-treated inorganic substrate is put into a silver nitrate aqueous solution, and an oxalic acid aqueous solution is added thereto. After chemical reaction, a considerable amount of nano silver quantum dots are deposited on the surface of the pre-treated inorganic substrate, and its conductive properties are further improved. The obtained modified inorganic substrate is then put into a mixed phase consisting of a sodium persulfate aqueous solution and a 3-carboxyl-3-hydroxyglutaric acid aqueous solution, and 2-aminobenzoic acid is added after ultrasonic dispersion. Finally, 2-aminobenzoic acid undergoes polymerization reaction on the surface of the modified inorganic substrate, and the generated conductive polymer is embedded in a topological structure consisting of carbon nanotubes and graphene, and finally a three-dimensional conductive network consisting of conductive polymers, nano silver quantum dots, carbon nanotubes and graphene is formed, so that the prepared composite conductive agent not only has excellent conductive properties, thermal conductivity and electromagnetic shielding properties, and reduces the interference caused by external electromagnetics; it also has excellent thermal fatigue resistance and thermal damage resistance, effectively ensuring the quality and quality of the heating film while also extending its service life to a certain extent. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing a heating film containing carbon nanotubes, comprising the following steps: placing a copper foil on the top of a polyimide substrate, etching to obtain a substrate layer with a circuit on the surface, and connecting a power pad to the circuit; then printing a conductive paste on the surface of the substrate layer by silk screen printing, and drying to obtain a conductive paste layer; finally, pasting a polyurethane film on the surface of the conductive paste layer, and heating, curing and punching to obtain a finished heating film containing carbon nanotubes;

[0027] The thickness of the electronic paste layer is 10 μm; the aperture of the nylon screen used in the screen printing process is 250 meshes; the drying temperature is 60° C. and the drying time is 10 min; and the heating curing temperature is 170° C.

[0028] The conductive paste is composed of the following raw materials in parts by weight: 80 parts of a compound conductive agent, 80 parts of dipropylene glycol methyl ether, 5 parts of bisphenol F epoxy resin, 5 parts of n-butyl acetate, 2 parts of tetrahydrophthalic anhydride, 0.3 parts of 2-phenyl-4-methylimidazole, 0.8 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 3 parts of ethylene glycol diglycidyl ether, 0.5 parts of 3-aminopropyltriethoxysilane and 0.6 parts of polyethylene wax.

[0029] The preparation method of the compound conductive agent is as follows:

[0030] Step 1, putting the inorganic substrate into an ethanol aqueous solution with a volume concentration of 50% at a solid-liquid ratio of 3 mg / mL, adding sodium dodecylbenzene sulfonate with a mass of 2% of the ethanol aqueous solution, ultrasonically dispersing for 2 hours and then centrifuging it, washing the obtained solid filter material with ethanol 3 times and then drying it to obtain a pretreated inorganic substrate;

[0031] Step 2: Put the pretreated inorganic substrate into a silver nitrate aqueous solution with a mass of 10 to 20 times that of the pretreated inorganic substrate and a concentration of 1 to 1.5 mol / L, mix and stir for 10 to 15 hours, then add a 2 to 3 mol / L oxalic acid aqueous solution, react for 50 to 80 minutes, filter the resulting component, wash the filter cake with ethanol, and then vacuum dry it. The modified inorganic substrate is stored and used for later use.

[0032] Step 3, add 0.2mmol / L sodium persulfate aqueous solution to 6mmol / L 3-carboxy-3-hydroxyglutaric acid aqueous solution at a volume ratio of 1:2, and add the modified inorganic substrate to the obtained mixed phase at a solid-liquid ratio of 5mg / mL, add 2-aminobenzoic acid with a molar amount of 10 times that of 3-carboxy-3-hydroxyglutaric acid after ultrasonic dispersion, mix well and react at 120°C for 5h; after the reaction is completed, cool the product components to room temperature, and then filter, wash with water, wash with alcohol and dry to obtain the composite conductive agent.

[0033] The preparation method of the inorganic substrate is:

[0034] S1. Put graphene oxide into deionized water at a solid-liquid ratio of 3 mg / mL, adjust the pH to 4.3 after ultrasonic dispersion for 2 hours, then add silane coupling agent dispersion, mix and stir evenly, and keep the mixture at 50°C for 15 hours. After the reaction is completed, cool the resulting components naturally to room temperature, wash with deionized water and freeze-dry, and store the modified graphene oxide for later use;

[0035] The preparation method of the silane coupling agent dispersion is as follows: 3-aminopropyltriethoxysilane is added into ethanol with a mass that is 6 times of the mass of 3-aminopropyltriethoxysilane, and the mixture is mixed and stirred to obtain the silane coupling agent dispersion; and the amount of the silane coupling agent used is 10% of the mass of the graphene oxide;

[0036] S2. Add the modified graphene oxide into N,N-dimethylformamide at a dosage ratio of 6 mg / mL, and add pre-treated carbon nanotubes with a mass 1.5 times that of the modified graphene oxide, and after ultrasonic dispersion for 2 hours, stir and react at 75° C. for 10 hours, and then reflux and react for 8 hours; after the reaction is completed, naturally cool the resulting components to room temperature, and then filter, wash and freeze-dry in sequence to obtain an inorganic substrate;

[0037] Deionized water was used for washing, and the number of washing times was 4 times;

[0038] The pressure during freeze drying was 20 Pa, the temperature was -40 °C, and the freeze drying time was set to 50 h;

[0039] The preparation method of the pre-treated carbon nanotubes is as follows: the carboxylated single-walled carbon nanotubes are uniformly dispersed in thionyl chloride at a solid-liquid ratio of 2 mg / mL, and then the mixture is ultrasonically dispersed for 2 hours and then kept warm for 15 hours at 70°C. After the reaction is completed, the mixture is naturally cooled to room temperature, and then filtered, washed with deionized water for 3 times, and vacuum dried to obtain the pre-treated carbon nanotubes; wherein the single-walled carbon nanotubes have a diameter of 4.0 nm and a length of 35 μm.

[0040] Example 2

[0041] The preparation method of a heating film containing carbon nanotubes provided in this embodiment is basically the same as that in embodiment 1, except that the specific composition of the conductive paste used in the heating film and the preparation method of the compound conductive agent are not exactly the same. The specific composition of the conductive paste used in the heating film and the preparation method of the compound conductive agent in this embodiment are as follows:

[0042] The conductive paste is composed of the following raw materials in parts by weight: 80 parts of a compound conductive agent, 90 parts of dipropylene glycol methyl ether, 8 parts of bisphenol F epoxy resin, 6 parts of n-butyl acetate, 2.5 parts of tetrahydrophthalic anhydride, 0.5 parts of 2-phenyl-4-methylimidazole, 1 part of bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, 4 parts of ethylene glycol diglycidyl ether, 0.8 parts of 3-aminopropyltriethoxysilane and 0.8 parts of polyethylene wax.

[0043] The preparation method of the compound conductive agent is as follows:

[0044] Step 1, putting the inorganic substrate into an ethanol aqueous solution with a volume concentration of 55% at a solid-liquid ratio of 5 mg / mL, adding sodium dodecylbenzene sulfonate with a mass of 3% of the ethanol aqueous solution, ultrasonically dispersing for 2 hours and then centrifuging it, washing the obtained solid filter material with ethanol 4 times and then drying it to obtain a pretreated inorganic substrate;

[0045] Step 2: Put the pretreated inorganic substrate into a silver nitrate aqueous solution with a mass 15 times that of the pretreated inorganic substrate and a concentration of 1 mol / L, mix and stir for 12 hours, then add a 2 mol / L oxalic acid aqueous solution, react for 60 minutes, filter the resulting components, wash the filter cake with ethanol, and then vacuum dry it. The modified inorganic substrate is stored and used for later use.

[0046] Step 3, add 0.3 mmol / L sodium persulfate aqueous solution to 8 mmol / L 3-carboxy-3-hydroxyglutaric acid aqueous solution at a volume ratio of 1:3, and add the modified inorganic substrate to the obtained mixed phase at a solid-liquid ratio of 8 mg / mL, and add 2-aminobenzoic acid with a molar amount of 10 times that of 3-carboxy-3-hydroxyglutaric acid after ultrasonic dispersion. After mixing evenly, react at 130°C for 6 hours; after the reaction is completed, cool the product components to room temperature, and then filter, wash with water, wash with alcohol and dry them in turn to obtain the composite conductive agent.

[0047] The preparation method of the inorganic substrate is:

[0048] S1. Put graphene oxide into deionized water at a solid-liquid ratio of 5 mg / mL, adjust the pH to 4.5 after ultrasonic dispersion for 2.5 hours, then add the silane coupling agent dispersion, mix and stir evenly, and keep the mixture at 60°C for 20 hours. After the reaction is completed, cool the resulting components naturally to room temperature, wash with deionized water and freeze-dry, and store the modified graphene oxide for later use;

[0049] The preparation method of the silane coupling agent dispersion is as follows: 3-aminopropyltriethoxysilane is added into ethanol with a mass of 8 times that of 3-aminopropyltriethoxysilane, and the mixture is mixed and stirred to obtain the silane coupling agent dispersion; and the amount of the silane coupling agent is 15% of the mass of the graphene oxide;

[0050] S2, adding the modified graphene oxide into N,N-dimethylformamide at a dosage ratio of 8 mg / mL, and adding pre-treated carbon nanotubes with a mass 1.5 times that of the modified graphene oxide, and ultrasonically dispersing for 3 hours, stirring and reacting at 80° C. for 12 hours, and then reflux for 10 hours; after the reaction is completed, the resulting components are naturally cooled to room temperature, and then filtered, washed and freeze-dried in sequence to obtain an inorganic substrate;

[0051] Deionized water was used for washing, and the washing times were 5 times;

[0052] The pressure during freeze drying was 25 Pa, the temperature was -45 °C, and the freeze drying time was set to 40 h;

[0053] The preparation method of pretreated carbon nanotubes is as follows: carboxylated single-walled carbon nanotubes are uniformly dispersed in thionyl chloride at a solid-liquid ratio of 4 mg / mL, ultrasonically dispersed for 3 hours, and then kept warm for reaction at 80°C for 20 hours. After the reaction is completed, it is naturally cooled to room temperature, and then filtered, washed with deionized water 5 times, and vacuum dried in sequence to obtain pretreated carbon nanotubes.

[0054] Example 3

[0055] The preparation method of a heating film containing carbon nanotubes provided in this embodiment is basically the same as that in embodiment 1, except that the specific composition of the conductive paste used in the heating film and the preparation method of the compound conductive agent are not exactly the same. The specific composition of the conductive paste used in the heating film and the preparation method of the compound conductive agent in this embodiment are as follows:

[0056] The conductive paste is composed of the following raw materials in parts by weight: 85 parts of a composite conductive agent, 100 parts of dipropylene glycol methyl ether, 10 parts of bisphenol F epoxy resin, 8 parts of n-butyl acetate, 3 parts of tetrahydrophthalic anhydride, 0.6 parts of 2-phenyl-4-methylimidazole, 1.2 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 5 parts of ethylene glycol diglycidyl ether, 1.0 parts of 3-aminopropyltriethoxysilane and 1.0 parts of polyethylene wax.

[0057] The preparation method of the compound conductive agent is as follows:

[0058] Step 1, putting the inorganic substrate into an ethanol aqueous solution with a volume concentration of 60% at a solid-liquid ratio of 8 mg / mL, adding sodium dodecylbenzene sulfonate with a mass of 4% of the ethanol aqueous solution, ultrasonically dispersing for 3 hours and then centrifuging it, washing the obtained solid filter material with ethanol 4 times and then drying it to obtain a pretreated inorganic substrate;

[0059] Step 2: Put the pretreated inorganic substrate into a silver nitrate aqueous solution with a mass 20 times that of the pretreated inorganic substrate and a concentration of 1.5 mol / L, mix and stir for 15 hours, then add a 3 mol / L oxalic acid aqueous solution, react for 80 minutes, filter the resulting components, wash the filter cake with ethanol, and then vacuum dry it. The modified inorganic substrate is stored and used for later use.

[0060] Step 3, add 0.5mmol / L sodium persulfate aqueous solution to 10mmol / L 3-carboxy-3-hydroxyglutaric acid aqueous solution at a volume ratio of 1:4, and add the modified inorganic substrate to the obtained mixed phase at a solid-liquid ratio of 10mg / mL, add 2-aminobenzoic acid with a molar amount of 15 times that of 3-carboxy-3-hydroxyglutaric acid after ultrasonic dispersion, mix well and react at a temperature of 140°C for 8h; after the reaction is completed, cool the product components to room temperature, and then filter, wash with water, wash with alcohol and dry in turn to obtain the composite conductive agent.

[0061] The preparation method of the inorganic substrate is:

[0062] S1. Put graphene oxide into deionized water at a solid-liquid ratio of 8 mg / mL, adjust the pH to 4.8 after ultrasonic dispersion for 3 hours, then add silane coupling agent dispersion, mix and stir evenly, and keep warm at 65°C for 25 hours. After the reaction is completed, cool the resulting components naturally to room temperature, wash with deionized water and freeze-dry, and store the modified graphene oxide for standby use;

[0063] The preparation method of the silane coupling agent dispersion is as follows: 3-aminopropyltriethoxysilane is added into ethanol with a mass 10 times that of the silane coupling agent, and the mixture is mixed and stirred to obtain the silane coupling agent dispersion; and the amount of the silane coupling agent used is 20% of the mass of the graphene oxide;

[0064] S2, adding the modified graphene oxide into N,N-dimethylformamide at a dosage ratio of 10 mg / mL, and adding pre-treated carbon nanotubes twice the mass of the modified graphene oxide, after ultrasonic dispersion for 5 hours, stirring and reacting at 85° C. for 15 hours, and then reflux reaction for 12 hours; after the reaction is completed, the resulting components are naturally cooled to room temperature, and then filtered, washed and freeze-dried in sequence to obtain an inorganic substrate;

[0065] Deionized water was used for washing, and the washing times were 5 times;

[0066] The pressure during freeze drying was 30 Pa, the temperature was -50 °C, and the freeze drying time was set to 30 h;

[0067] The preparation method of pretreated carbon nanotubes is as follows: carboxylated single-walled carbon nanotubes are uniformly dispersed in thionyl chloride at a solid-liquid ratio of 5 mg / mL, ultrasonically dispersed for 4 hours, and then kept warm for reaction at 85°C for 25 hours. After the reaction is completed, it is naturally cooled to room temperature, and then filtered, washed with deionized water 5 times, and vacuum dried to obtain pretreated carbon nanotubes.

[0068] Comparative Example 1: The difference between this embodiment and Example 1 is that in this embodiment, an equal amount of modified inorganic substrate is used to replace the compound conductive agent, and it is used as a raw material for preparing conductive paste and heating film.

[0069] Comparative Example 2: The difference between this embodiment and embodiment 1 is that in this embodiment, an equal amount of inorganic base material is used to replace the compound conductive agent, and it is used as a raw material for preparing conductive paste and heating film.

[0070] Performance test: The relevant performances of the heating film samples prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested as follows:

[0071] 1. The test standard for the heating film temperature after heating is GB / T28204-2011.

[0072] 2. The test standard for the electric heat conversion efficiency of heating film is GB / T4654-2008.

[0073] 3. Resistance change rate test: The heating film samples prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested respectively, wherein the resistance change rate of the heating film was measured by heating to 100°C at rated power, then performing low temperature treatment, cooling to 0°C, taking out after thermal equilibrium, restoring to room temperature, and continuing to heat it, and repeating this cycle 100 times. The resistance of the heating film after 100 thermal cycles (Ω) was measured. 1 ) and resistance before thermal cycling (Ω 0 ) change rate (h%), the resistance change rate is as follows:

[0074] h%=(Ω 1 -Ω 0 )×100% / Ω 0

[0075] 4. Surface temperature change rate test: Before the thermal cycle test, the heating film surface temperature T 0 , and after the above 100 thermal cycles, the surface temperature of the heating film is T after heating for 2 minutes at the same rated power. 1 , the surface temperature change rate (T%) is as follows:

[0076] T%=(T 1 -T 0 )×100% / T 0

[0077] The test data obtained are recorded in the following table:

[0078]

[0079] By comparing and analyzing the relevant data in the table, it can be seen that the heating film prepared by the present invention not only has excellent electrical conductivity, thermal conductivity and electromagnetic shielding performance, reducing the interference caused by external electromagnetics; it also has excellent resistance to thermal fatigue and thermal damage, effectively ensuring its quality and quality while also extending its service life to a certain extent. This shows that the heating film containing carbon nanotubes and the preparation method thereof provided by the present invention have a broader market prospect and are more suitable for promotion.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0081] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a heating film containing carbon nanotubes, characterized in that: The following steps are involved: A copper foil is placed on top of a polyimide substrate, and after etching, a base layer with a circuit on the surface is obtained, and a power pad is connected to the circuit; then a conductive paste is printed on the surface of the base layer by silk screen printing, and a conductive paste layer is obtained after drying; finally, a polyurethane film is pasted on the surface of the conductive paste layer, and after heating, curing and punching, a finished heating film containing carbon nanotubes is obtained.

2. The method for preparing a heating film containing carbon nanotubes according to claim 1, characterized in that: The conductive paste is composed of the following raw materials in parts by weight: 80 to 85 parts of a composite conductive agent, 80 to 100 parts of dipropylene glycol methyl ether, 5 to 10 parts of bisphenol F epoxy resin, 5 to 8 parts of n-butyl acetate, 2 to 3 parts of tetrahydrophthalic anhydride, 0.3 to 0.6 parts of 2-phenyl-4-methylimidazole, 0.8 to 1.2 parts of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 3 to 5 parts of ethylene glycol diglycidyl ether, 0.5 to 1.0 parts of 3-aminopropyltriethoxysilane and 0.6 to 1.0 parts of polyethylene wax.

3. The method for preparing a heating film containing carbon nanotubes according to claim 2, characterized in that: The preparation method of the composite conductive agent is: Step 1, putting the inorganic substrate into an ethanol aqueous solution with a volume concentration of 50-60% at a solid-liquid ratio of 3-8 mg / mL, adding sodium dodecylbenzene sulfonate with a mass of 2-4% of the ethanol aqueous solution, ultrasonically dispersing for 2-3 hours and then centrifuging it, washing the obtained solid filter material with ethanol for 3-4 times and then drying it to obtain a pretreated inorganic substrate; Step 2: Put the pretreated inorganic substrate into a silver nitrate aqueous solution with a mass of 10 to 20 times that of the pretreated inorganic substrate and a concentration of 1 to 1.5 mol / L, mix and stir for 10 to 15 hours, then add a 2 to 3 mol / L oxalic acid aqueous solution, react for 50 to 80 minutes, filter the resulting component, wash the filter cake with ethanol, and then vacuum dry it. The modified inorganic substrate is stored and used for later use. Step 3, add 0.2-0.5 mmol / L sodium persulfate aqueous solution to 6-10 mmol / L 3-carboxy-3-hydroxyglutaric acid aqueous solution at a volume ratio of 1:2-4, and add the modified inorganic substrate to the obtained mixed phase at a solid-liquid ratio of 5-10 mg / mL, add 2-aminobenzoic acid with a molar amount of 10-15 times that of 3-carboxy-3-hydroxyglutaric acid after ultrasonic dispersion, mix well and react at a temperature of 120-140°C for 5-8h; after the reaction is completed, cool the product components to room temperature, and then filter, wash with water, wash with alcohol and dry in turn to obtain the composite conductive agent.

4. The method for preparing a heating film containing carbon nanotubes according to claim 3, characterized in that: The preparation method of the inorganic substrate is: S1. Put graphene oxide into deionized water at a solid-liquid ratio of 3-8 mg / mL, adjust the pH to 4.3-4.8 after ultrasonic dispersion for 2-3 hours, then add silane coupling agent dispersion, mix and stir evenly, and keep warm at 50-65°C for 15-25 hours. After the reaction is completed, cool the resulting components naturally to room temperature, wash with deionized water and freeze-dry, and store the modified graphene oxide for standby use; S2. Add the modified graphene oxide into N,N-dimethylformamide at a dosage ratio of 6 to 10 mg / mL, and add pre-treated carbon nanotubes with a mass of 1.5 to 2 times that of the modified graphene oxide. After ultrasonic dispersion for 2 to 5 hours, stir the reaction at 75 to 85° C. for 10 to 15 hours, and then reflux the reaction for 8 to 12 hours. After the reaction is completed, naturally cool the resulting components to room temperature, and then filter, wash and freeze-dry in sequence to obtain the inorganic substrate.

5. The method for preparing a heating film containing carbon nanotubes according to claim 4, characterized in that: The preparation method of the silane coupling agent dispersion is as follows: 3-aminopropyltriethoxysilane is added into ethanol with a mass of 6 to 10 times that of the 3-aminopropyltriethoxysilane, and the silane coupling agent dispersion is obtained after mixing and stirring evenly; and the amount of the silane coupling agent used is 10 to 20% of the mass of the graphene oxide.

6. The method for preparing a heating film containing carbon nanotubes according to claim 4, characterized in that: Deionized water is used for washing, and the washing times are 4 to 5 times.

7. The method for preparing a heating film containing carbon nanotubes according to claim 4, characterized in that: The pressure during freeze drying is 20 to 30 Pa, the temperature is -40 to -50°C, and the freeze drying time is set to 30 to 50 hours.

8. The method for preparing a heating film containing carbon nanotubes according to claim 4, characterized in that: The preparation method of the pre-treated carbon nanotubes is as follows: uniformly dispersing carboxylated single-walled carbon nanotubes in thionyl chloride at a solid-liquid ratio of 2-5 mg / mL, ultrasonically dispersing for 2-4 hours, and then heat-retaining the mixture at 70-85° C. for 15-25 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, and then filtered, washed with deionized water for 3-5 times, and vacuum dried to obtain the pre-treated carbon nanotubes.

9. The method for preparing a heating film containing carbon nanotubes according to claim 1, characterized in that: The thickness of the electronic paste layer is 10-20 μm; the aperture of the nylon screen used in the screen printing process is 250-300 meshes, the drying temperature is 60-75° C., the drying time is 10-25 minutes; the heating curing temperature is 170-180° C.

10. A heating film containing carbon nanotubes, characterized in that: The heating film is prepared by the method for preparing a heating film containing carbon nanotubes as described in any one of claims 1 to 9.

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