KR102259236B1 - Composition of carbon nanotube paste for flat heating element device, flat heating element device comprising the same and film heater for preventing winter damage of water pipe using carbon nanotube - Google Patents

Abstract

The present invention relates to a composition for a carbon nanotube-containing paste for a planar heating element to provide increased wear resistance, adhesion, and temperature uniformity, and a planar heating element and carbon nanotube-based film heater for preventing winter damage of water pipes including the same. More specifically, the component comprises: conductive particles including carbon nanotube particles and graphene particles; a mixed binder in which hexamethylene diisocyanate, polyvinyl acetal, and a phenol-based resin are mixed; organic solvents; a dispersant; and mica modified with titanium dioxide. The carbon nanotube particles include silane functional groups formed by treating heat-treated carbon nanotubes with silane.

Description

Planar heating element paste composition comprising carbon nanotubes, planar heating element including the same and a film heater for preventing freeze based on carbon nanotubes TECHNICAL FIELD [0002] Composition of carbon nanotube paste for flat heating element device, flat heating element device comprising the same and film heater for preventing winter damage of water pipe using carbon nanotube}

The present invention relates to a planar heating element paste composition comprising carbon nanotubes having heat resistance even at a temperature of about 300° C., a planar heating element including the same, and a carbon nanotube-based antifreeze film heater.

When the temperature in winter falls below freezing, there is a concern about freezing of various piping systems. Therefore, in order to prevent freezing of the piping system, conventionally, a hot wire is used to prevent freezing. Typical products for freeze protection can be divided into hot wire heaters and metal heaters.

A heated wire heater is a cable whose calorific value changes according to the temperature, and is designed to automatically increase or decrease the calorific value according to changes in ambient temperature. In such a heated wire heater, if leakage current flows outside due to damage to the insulation coating, there is a possibility of electric shock and fire due to a short circuit, and if it is kept warmer than necessary with nonwoven fabric or Styrofoam, there is a possibility of fire due to deterioration of the insulator due to heat storage. In addition, there is a high possibility that moisture penetrates into the damaged part of the insulator to cause a spark discharge, or the insulating coating without flame retardant performance is melted and ignited, and if the heater is damaged, the entire construction must be repeated.

Metal heaters have PTC (Positive Temperature Coefficient) characteristics and reduce the risk of fire by using metal materials. However, due to the inrush current, the design of the electric load increases, the power efficiency decreases, and the heat transfer efficiency is very low due to the narrow heating area. There is a problem in that the service life of the insulation material is shortened due to heat curing of the contact part between the heater and the insulation material.

On the other hand, carbon nanotubes have characteristics such as anti-static, electromagnetic wave shielding, radar wave absorption, sound insulation, soundproofing, heat dissipation, and heat generation, so they are widely applied to functional materials, and are used in electricity, electronics, automobiles, ships, aircraft, sports, and military applications. It is used as an additive for parts and materials in various fields. Recently, studies on planar heating elements based on carbon nanotubes are being actively conducted.

Unlike a linear heating element, a planar heating element is a relatively safe heating element with a high heating effect by generating uniform heat on the surface. A planar heating element using a carbon-based material is manufactured as a paste formed by mixing a binder with a conductive carbon-based powder such as carbon, graphite, carbon black, carbon nanotube, etc. Conductivity, workability, adhesiveness, scratch resistance, etc. are determined according to this.

As a prior art, with respect to a planar heating element paste composition containing carbon nanotubes having heat resistance even at a temperature of about 300° C., Patent Registration No. 2049266 discloses conductive particles including carbon nanotube particles and graphite particles; a mixed binder in which epoxy acrylate or hexamethylene diisocyanate, polyvinyl acetal and phenolic resin are mixed; organic solvents; and a planar heating element paste composition comprising a dispersant.

However, for the commercialization of the prior art, it is necessary to improve durability such as temperature uniformity and abrasion resistance, and it is also necessary for the paste composition to be adhered to the polyimide film as a support with strong binding force during long-term heat at high temperature.

Accordingly, the inventors of the present inventors have developed a planar heating element paste composition having high heat resistance of 300°C or higher as a heating element capable of low-voltage, low-power driving and excellent bending resistance and environmental resistance. It has excellent pipe heat transfer rate, low heat loss rate, and low consumption compared to heating wire and metal heater. While researching a planar heating element paste composition containing carbon nanotubes that can satisfy all temperature uniformity, abrasion resistance and adhesion for the commercialization of a planar heating element paste composition that can save energy with electric power, silane in the planar heating element paste composition The present invention was completed by confirming that abrasion resistance, adhesion and temperature uniformity were improved when carbon nanotubes having functional groups and mica modified with titanium dioxide were included.

Republic of Korea Patent No. 2049266 (Announcement Date 2019. 11. 21)

Therefore, an object of the present invention is a planar heating element paste composition having heat resistance even at a temperature of about 300 ° C. A planar heating element paste composition comprising carbon nanotubes that can satisfy all of abrasion resistance, adhesion and temperature uniformity, a planar heating element comprising the same and It is to provide a film heater for antifreeze based on carbon nanotube.

Another object of the present invention is a heating element capable of low-voltage, low-power driving and excellent bending resistance and environmental resistance. It is a paste composition for a planar heating element having high heat resistance of 300° C. or higher. It has excellent pipe heat transfer rate, low heat loss rate, and lower than that of hot wire and metal heater. An object of the present invention is to provide a planar heating element paste composition containing carbon nanotubes that can save energy with power consumption, a planar heating element including the same, and a carbon nanotube-based antifreeze film heater.

In order to achieve the above object, the planar heating element paste composition comprising carbon nanotubes according to an embodiment of the present invention includes conductive particles including carbon nanotube particles and graphene particles; hexamethylene diisocyanate, polyvinyl acetal, and a mixed binder in which a phenol-based resin is mixed; organic solvents; dispersant; and mica modified with titanium dioxide; wherein the carbon nanotube particles have a silane functional group formed by treating the heat-treated carbon nanotube with silane.

In addition, in the planar heating element paste composition comprising carbon nanotubes according to an embodiment of the present invention, based on 100 parts by weight of the planar heating element paste composition, the carbon nanotube particles are 0.5 to 7 parts by weight and the graphene particles are It is characterized in that it contains 2 to 25 parts by weight.

The planar heating element comprising carbon nanotubes according to an embodiment of the present invention is characterized in that it is formed by printing the planar heating element paste composition including the carbon nanotubes on a polyimide film.

The carbon nanotube-based antifreeze film heater according to an embodiment of the present invention includes the planar heating element.

According to the planar heating element paste composition comprising carbon nanotubes of the present invention, there is an excellent effect of improving abrasion resistance, adhesion and temperature uniformity by including carbon nanotubes having a silane functional group and mica modified with titanium dioxide.

In addition, the planar heating element paste composition comprising the carbon nanotubes of the present invention is a heating element that is capable of low voltage and low power driving and has excellent withstand voltage, durability, bending resistance, and environmental resistance characteristics. Because of this excellent and low heat loss rate, it is possible to save energy with lower power consumption compared to heating wires and metal heaters, and the construction cost is reduced due to the space-time space approximately twice wider than that of metal heaters, and it has the advantage of realizing low manufacturing cost.

1 is a test article (FIG. 1 a) and a withstand voltage test equipment (FIG. 1 b) for a withstand voltage test of a carbon nanotube-based anti-freeze film heater including a planar heating element according to an embodiment of the present invention.

Since the present invention can apply various transformations and can have various embodiments, preferred embodiments will be described in detail.

The planar heating element paste composition according to an embodiment of the present invention includes conductive particles including carbon nanotube particles and graphene particles, a mixed binder, an organic solvent, a dispersant and mica modified with titanium dioxide, and the carbon nanotube particles is characterized in that it has a silane functional group formed by treating the heat-treated carbon nanotube with silane.

The carbon nanotube particles may be selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or mixtures thereof. For example, the carbon nanotube particles may be multi-wall carbon nanotubes. When the carbon nanotube particles are multi-walled carbon nanotubes, the diameter may be 5 nm to 20 nm, and the length may be 3 μm to 40 μm.

As the graphene particles, commercially available graphene particles may be used, and the thickness is preferably 10 nm or less, and the diameter is preferably 25 μm or less. Graphene is a structure in which carbon atoms are composed of one layer of atoms on a two-dimensional plane, and is an excellent conductive material as well as very stable and excellent electrical, mechanical, and chemical properties.

The mixed binder functions to allow the planar heating element paste composition to have heat resistance even in a temperature range of about 300 ° C. Epocy acrylate or hexamethylene diisocyanate, polyvinyl acetal And phenolic resin (Phenol resin) has a mixed form.

For example, the mixed binder may be a mixture of epoxy acrylate, polyvinyl acetal, and a phenol-based resin, or a mixture of hexamethylene diisocyanate, polyvinyl acetal, and a phenol-based resin. In the present invention, by increasing the heat resistance of the mixed binder, even when heat is generated at a high temperature of about 300° C., there is no change in resistance of the material or damage to the coating film.

Here, the phenolic resin means a phenolic compound including phenol and phenol derivatives. For example, the phenol derivative is p-cresol (p-Cresol), o-guaiacol (o-Guaiacol), creosol (Creosol), catechol (Catechol), 3-methoxy-1,2-benzenediol (3 -methoxy-1,2-Benzenediol), Homocatechol, Vinylguaiacol, Syringol, Iso-eugenol, Methoxyeugenol, o -Cresol (o-Cresol), 3-methyl-1,2-benzenediol (3-methyl-1,2-Benzenediol), (z) -2-methoxy-4- (1-propenyl) -phenol ( (z)-2-methoxy-4-(1-propenyl)-Phenol), 2,6-diethoxy-4-(2-propenyl)-phenol (2,6-dimethoxy-4-(2-propenyl) -Phenol), 3,4-dimethoxy-phenol (3,4-dimethoxyPhenol), 4-ethyl-1,3-benzenediol (4-ethyl-1,3-Benzenediol), Resole phenol, 4 -Methyl-1,2-benzenediol (4-methyl-1,2-Benzenediol), 1,2,4-benzenetriol (1,2,4-Benzenetriol), 2-methoxy-6-methylphenol ( 2-Methoxy-6-methylphenol), 2-methoxy-4-vinylphenol (2-Methoxy-4-vinylphenol) or 4-ethyl-2-methoxy-phenol (4-ethyl-2-methoxy-Phenol), etc. and is not limited thereto.

The mixing ratio of the mixed binder may be 10 to 150 parts by weight of polyvinyl acetal resin and 10 to 500 parts by weight of phenolic resin based on 100 parts by weight of epoxy acrylate or hexamethylene diisocyanate.

The organic solvent is for dispersing the conductive particles and the mixed binder, carbitol acetate, butyl carbotol acetate, DBE (dibasic ester), ethyl carbitol, ethyl carbitol acetate, dipropylene It may be a mixed solvent of two or more selected from glycol methyl ether, cellosolve acetate, butyl cellosolve acetate, butanol and octanol.

On the other hand, the process for dispersion can be applied by various methods commonly used, for example, through ultrasonic treatment (Ultra-sonication), roll mill (Roll mill), bead mill (Bead mill) or ball mill (Ball mill) process. can be done

The dispersing agent is to make the dispersion more smooth, and a general dispersing agent used in the art such as BYK, an amphoteric surfactant such as Triton X-100, or an ionic surfactant such as SDS may be used.

In the planar heating element paste composition configured as described above, the carbon nanotube particles are 0.5 to 7 parts by weight, the graphene particles are 2 to 20 parts by weight, and the organic solvent is 38 to 92 parts by weight based on 100 parts by weight of the planar heating element paste composition. , 5 to 25 parts by weight of the mixed binder, 0.5 to 5 parts by weight of the dispersant, and 2 to 6 parts by weight of mica modified with titanium dioxide.

The present invention additionally provides a planar heating element formed by screen printing, gravure printing or comma coating of the planar heating element paste composition according to the above-described embodiments of the present invention on a substrate.

Here, the substrate is polycarbonate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, cellulose ester, nylon, polypropylene, polyacrylonitrile, polysulfone, polyester sulfone, polyvinylidene fluoride , glass, ceramic, SUS, copper or aluminum substrates may be used, but not limited to those listed above. The substrate may be appropriately selected according to the application field of the heating element or the temperature of use, and preferably, polyimide having excellent insulation performance (3 kv) and high temperature (350° C.) performance may be selected.

The planar heating element is printed on the substrate in a desired pattern through screen printing or gravure printing of the planar heating element paste composition according to embodiments of the present invention, and after drying and curing, printing and drying a silver paste or conductive paste on the substrate It can be formed by forming an electrode by curing /curing. Alternatively, after printing and drying/curing the silver paste or conductive paste, it is also possible to form the planar heating element paste composition according to the embodiments of the present invention on the top by screen printing or gravure printing.

Hereinafter, the present invention will be described in more detail through examples, but the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

<Example>

The planar heating element paste composition according to an embodiment of the present invention is composed of conductive particles including carbon nanotube particles and graphene particles, a mixed binder, an organic solvent, a dispersant, and mica modified with titanium dioxide.

A carbon nanotube having a silane functional group was prepared as follows.

- heat treatment step

In this step, the process of heat-treating the carbon nanotube is made. ^{Specifically, the heat treatment was performed under a pressure of 10 -7} mmHg in a vacuum at a high frequency, and was performed at a temperature of 1,200° C. for 1 hour, thereby improving the crystallinity of the carbon nanotubes. As the carbon nanotube, a multi-walled carbon nanotube (MWCNT, CM280) was used, and the carbon nanotube may have a diameter of 5 nm to 20 nm and a length of 90 μm to 100 μm. The carbon nanotube is preferably provided in an amount of 1 to 2 parts by weight, which is that if the carbon nanotube is less than 1 part by weight, the resistance of the planar heating element may increase and the current may be disconnected, and if it exceeds 2 parts by weight, flexibility and elasticity are reduced or This is because there is a problem in that it is difficult to manufacture with a paste.

- Silanization treatment step

In this step, a process of silanizing the carbon nanotubes heat-treated through the heat treatment step using silane is performed. Silanization treatment step is carbon nanotube acid treatment step; A first mixing solution stirring step; silanol solution preparation step; a second stirring step of the mixed solution; A process of sequentially silanizing the carbon nanotubes is performed through the heat treatment step.

In the carbon nanotube acid treatment step, an acid treatment with aqua regia is performed on the carbon nanotubes heat-treated through the heat treatment step. Here, aqua regia may be prepared with strong acid (sulfuric acid: nitric acid = 7:3) and acid treatment may be performed, and the acid treatment was performed under ultrasonic waves (50 Hz to 60 Hz, 350 W) for 1 to 2 hours. This is because, when the ultrasonic treatment time exceeds 2 hours, the crystallinity of the carbon nanotubes is rather deteriorated. Then, the mixture of sulfuric acid and nitric acid is stirred at a temperature of 80° C. for 1 hour, neutralized to pH 7, filtered, and dried at a temperature of 70° C. for 24 hours. Through this, the dispersibility of the carbon nanotubes and the miscibility with the polymer film are improved.

In the first mixed solution stirring step, the first mixed solution prepared by mixing N-[3-(trimethoxysilyl)propyl]aniline), water and ethanol is stirred for 20 minutes to Stirring is performed for 30 minutes. Specifically, the first mixed solution is prepared by mixing 855 ml of distilled water, 95 ml of ethanol, and 50 ml of N-[3-(trimethoxysilyl)propyl]aniline), and thus prepared The first mixed solution is sufficiently stirred so that each component can be uniformly mixed for 20 to 30 minutes.

In the step of preparing a silanol solution, the first mixed solution stirred through the stirring step of the first mixed solution is heat-treated at a temperature of 55° C. to 60° C. to prepare a silanol solution. Here, heat treatment is performed to increase the temperature of the first mixed solution to a temperature of 55 ° C. to 60 ° C., which must be heat treated to increase to a temperature of 55 ° C. to 60 ° C. Silanol reaction in hydrolysable groups of silane because this happens That is, the silanol reacts with oxygen on the surface of the modified filler to form a hydrogen bond, and thereby serves to improve bondability and mixability between the filler and the polymer film.

In the second mixed solution stirring step, a process of stirring the second mixed solution prepared by mixing the silanol solution prepared through the silanol solution preparation step and the carbon nanotubes acid-treated through the carbon nanotube acid treatment step is performed. . Specifically, by mixing the carbon nanotubes acid-treated through the carbon nanotube acid treatment step with the silanol solution raised to a temperature of 55° C. to 60° C. through the silanol solution preparation step, it reacts with the silanol solution Stir sufficiently for 50 to 60 minutes so that hydrogen bonding occurs. This is because, when stirring for less than 50 minutes, hydrogen bonding cannot be properly induced, and when stirring for more than 60 minutes, the same reaction (hydrogen bonding) is formed.

In the heat treatment step, a process of heat-treating the second mixed solution stirred through the second mixed solution stirring step at a temperature of 110° C. to 130° C. for 3 hours to 4 hours is performed, which is a second mixture stirred through the stirring step This is to induce hydrolysis of the solution surface. As a result, in the second mixed solution stirred through the stirring step, the moisture in the portion where the silanol and hydrogen bonds are formed evaporates, and the bond form is transformed into (C-O-Si, C-O-O-Si).

As described above, carbon nanotubes having a silane functional group were prepared through the silanization treatment step.

Mica modified with titanium dioxide was prepared as follows. In a 500 mL round bottom flask, 2.0 g of mica (Na-form fluorophlogopite) and 200 mL of distilled water were added and magnetically stirred at room temperature for 24 h. 7.0 mmole of titanium tetraisopropoxide (TTIP) was added to a mixed solution of 40 mL of acetic acid and 10 mL of distilled water in a 250 mL beaker, and magnetically stirred at 50 °C for 40 min. The TTIP mixed solution was added to the mica dispersion and magnetically stirred at room temperature for 2 h. The resulting solid material was filtered using a sintered glass filter, washed with distilled water 5 times, and dried in an oven at 60°C. The dried product was calcined in an electric furnace (Thermo Scientific) with varying calcination temperature (600-1000° C.) and calcination time (1-3 h) to obtain mica modified with titanium dioxide.

In order to prepare a planar heating element paste composition according to the present invention, 3 parts by weight of carbon nanotubes having a silane functional group, 2 parts by weight of graphene particles and 4 parts by weight of mica modified with titanium dioxide were added to 41 parts by weight of a carbitol acetate solvent and after adding the BYK dispersant, a dispersion was prepared by ultrasonication for 60 minutes. Then, 6 parts by weight of the mixed binder was added to 41 parts by weight of a carbitol acetate solvent, and then a master batch was prepared through mechanical stirring. Next, the planar heating element paste composition was prepared by first kneading the dispersion and the masterbatch through mechanical stirring, followed by a 3-roll-mill process and second kneading.

<Comparative example>

Comparative Example 1 was performed in the same manner as in Example, but a planar heating element paste composition was prepared using 3 parts by weight of carbon nanotubes instead of 3 parts by weight of carbon nanotubes having a silane functional group.

Comparative Example 2 was carried out in the same manner as in Example, but using 3 parts by weight of mica powder instead of 4 parts by weight of mica modified with titanium dioxide, a planar heating element paste composition was prepared.

Comparative Example 3 was carried out in the same manner as in Example, except that silane was replaced with (3-aminopropyl) ethoxy instead of N- [3- (trimethoxysilyl) propyl] aniline (N- [3- (trimethoxysilyl) propyl] aniline). A planar heating element paste composition was prepared using 3 parts by weight of carbon nanotubes having a silane functional group treated with silane ((3-Aminopropyl) ethoxysilane).

Comparative Example 4 was carried out in the same manner as in Example, but without using mica modified with titanium dioxide, 5 parts by weight of carbon nanotubes having a silane functional group and 4 parts by weight of graphene particles were used to prepare a planar heating element paste composition.

<Experimental Example 1>

Adhesion strength, temperature uniformity, and coating film hardness were tested by the following test method.

1) Adhesion

The adhesion of the planar heating element paste to the polyimide film was tested in the following way:

- Polyimide film: 200 × 200 mm in size, a planar heating element paste was applied to a thickness of 8 - 10 μm by gravure printing, and cured in a hot air drying furnace at a temperature of 250°C and a time of 1 hr to 3 hr.

- Hot laminating: heating temperature: 300℃, pressure (kgf): 100kgf, pressure time: 1-30min

The Examples and Comparative Examples 1 to 4 were placed on a heating plate and subjected to hot pressing under the conditions described above, and then the adhesive force was measured according to the IPC TM 650 method after being left at room temperature for 1 hour.

2) Temperature uniformity

An IR image camera was used to measure the temperature uniformity of the prepared planar heating element, and the temperature distribution (unit: °C) when the calorific value for 9 points (Sp.1 ~ Sp.9) was measured was measured.

sensor Sp.1 Sp.2 Sp.3 Sp.4 Sp.5 Sp.6 Sp.7 Sp.8 Sp.9 Average Standard Deviation Heat uniformity (%) Example 250 253.1 248.5 251.3 253.4 255.1 247.2 252.8 254.1 251.7 2.5 99.0 Comparative Example 1 254.5 211.5 200.4 250.2 240.5 212.5 236.2 192.4 185.5 220.4 24.1 89.0 Comparative Example 2 220.4 200.5 195.6 249.6 184.5 240.6 252.4 204.7 235.3 220.4 23.7 89.2 Comparative Example 3 247.1 243.6 193.2 203.6 228.3 252.4 185.7 251.4 251.5 228.5 25.6 88.8 Comparative Example 4 235.6 245.5 259.3 185.6 196.7 241.5 206.7 241.3 251.3 229.3 24.6 89.3

*Exothermic uniformity (%) = (1-(standard deviation/average))×100)

3) Film hardness (H)

It was measured according to the standard of ASTM D3363.

It measured by pinching|inserting the pencil for a measurement, and applying a fixed load (1Kg). The measurement results are shown as 9H ~ 1H, F, HB, 1B ~ 6B, and 9H is the hardest, and 6B is the weakest.

division Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Adhesion (kgf/cm) 1.5 0.8 0.7 0.9 0.9 Temperature uniformity (%) 99.0 89.0 89.2 88.8 89.3 Film hardness (H) 5H 3H 3H 2H 2B

As shown in Table 2, Comparative Examples 1 to 3 showed good wear resistance but poor adhesion and temperature uniformity characteristics, and Comparative Example 4 showed poor adhesion, wear resistance and temperature uniformity characteristics, whereas the present invention The example of , shows an excellent effect of improving both adhesion and temperature uniformity along with abrasion resistance.

<Experimental Example 2>

The performance of the carbon nanotube-based antifreeze film heater 270W and the metal heater 375W of the present invention was tested under the following test conditions, and the results are shown in Table 3 below.

test requirements:

- Frozen warehouse: minus 10℃, 96 hours passed

- Steel pipe: 100mm, pipe length: 20m, insulation material: Atylon (25t)

- Carbon nanotube-based antifreeze film heater of the present invention Heating temperature: 250℃, power consumption 4,000W

- Metal heater heating temperature: 110℃, power consumption 5,600W

division Heat transfer rate (%) Heat loss rate (%) After attaching the pipe
Heater surface temperature pipe end water temperature Carbon nanotube-based antifreeze film heater 270W of the present invention 84.9% 15.1% 37.7℃ 8.3℃ Metal Heater 375W 39.6% 60.4% 66.4℃ 4.5℃

According to Table 3, it can be confirmed that the carbon nanotube-based antifreeze film heater of the present invention uses less power, has an excellent heat transfer rate, and has a low heat loss rate compared to a metal heater.

<Experimental Example 3>

The withstand voltage test of the carbon nanotube-based antifreeze film heater of the present invention was conducted under the following conditions, and as a result, it passed the withstand voltage at DC/AC 3000V (see FIG. 1 ).

test requirements:

- Withstand voltage test of DC/AC 500 ~ 3000V was conducted in units of DC/AC 500V by contacting the probe to the exposed part of the terminal part among the positive terminals and the insulating layer part at the end of the same terminal on the circuit.

<Experimental Example 4>

For the durability test of the carbon nanotube-based anti-freeze film heater of the present invention, an on/off cycle test was performed under the following conditions.

test requirements:

- Using a heat cycle tester, when a voltage of AC 220V is applied to the test item, the cycle was set from 25°C to 95°C for the exothermic temperature range, and 70,000 cycles were performed with ON/OFF as 1 cycle.

Test item name Resistance (Ω) resistance change rate
(%) remark before the exam after the exam Example 545 564 3.486 (564-545)x100/545

Test item name Current (A) electromotive current change rate
(%) remark before the exam after the exam Example 0.425 0.412 3.059 (425-412)x100/425

After testing the on/off cycle of the anti-freeze film heater 70,000 times, the resistance change rate in Table 4 was 3.486% and the electromotive current change rate in Table 5 was 3.059%, showing a low change rate.

On the other hand, the above detailed description should not be construed as restrictive in all aspects, but should be considered as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention.

Claims (4)

heat-treating the carbon nanotubes;
silanizing the heat-treated carbon nanotubes using silane;
preparing a dispersion by adding carbon nanotubes having a silane functional group formed by the silanization treatment, graphene particles, and mica modified with titanium dioxide to a solvent;
Including; adding a mixed binder mixed with hexamethylene diisocyanate, polyvinyl acetal, and a phenolic resin to a solvent, mixing the solvent to which the mixed binder is added with the dispersion, and then stirring;
The step of silanizing the heat-treated carbon nanotubes using silane,
acid-treating the heat-treated carbon nanotubes with aqua regia;
N-[3-(trimethoxysilyl)propyl]aniline (N-[3-(trimethoxysilyl)propyl]aniline) The first mixed solution prepared by mixing silane, water and ethanol for 20 minutes to 30 minutes stirring for minutes;
preparing a silanol solution by heat-treating the stirred first mixed solution at a temperature of 55°C to 60°C;
agitating a second mixed solution prepared by mixing the silanol solution and the acid-treated carbon nanotubes for 50 to 60 minutes; and
Heat-treating the second mixed solution at a temperature of 110° C. to 130° C. for 3 hours to 4 hours; characterized in that it comprises,
Method for producing a planar heating element paste composition comprising carbon nanotubes.
conductive particles including carbon nanotube particles and graphene particles;
a mixed binder in which hexamethylene diisocyanate, polyvinyl acetal and phenolic resin are mixed;
organic solvents;
dispersant; and
Including; mica modified with titanium dioxide;
The carbon nanotube particles are provided with a silane functional group formed by treating the heat-treated carbon nanotube with silane,
The carbon nanotube particles having the silane functional group,
acid-treating the heat-treated carbon nanotubes with aqua regia;
N-[3-(trimethoxysilyl)propyl]aniline (N-[3-(trimethoxysilyl)propyl]aniline) The first mixed solution prepared by mixing silane, water and ethanol for 20 minutes to 30 minutes stirring for minutes;
preparing a silanol solution by heat-treating the stirred first mixed solution at a temperature of 55°C to 60°C;
agitating a second mixed solution prepared by mixing the silanol solution and the acid-treated carbon nanotubes for 50 to 60 minutes; and
Heat-treating the second mixed solution at a temperature of 110°C to 130°C for 3 hours to 4 hours; characterized in that it is prepared including,
A planar heating element paste composition comprising carbon nanotubes.
A planar heating element comprising carbon nanotubes formed by printing the planar heating element paste composition comprising the carbon nanotubes according to claim 2 on a polyimide film.
A film heater for antifreeze based on carbon nanotube comprising a planar heating element according to claim 3 .

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