KR20200106716A - Method for manufacturing few layer graphene, and method for manufacturing ptc positive temperature heating element comprising graphene-containing polymer nanocomposite - Google Patents

Abstract

The present invention relates to a method for manufacturing few-layer graphene, and a method for manufacturing a PTC positive temperature heating element using a graphene-based nanocomposite material including graphene obtained therefrom. Particularly, the method for manufacturing few-layer graphene includes the steps of: heat treating graphite; and carrying out mechanical exfoliation of the heat treated graphite to obtain few-layer graphite having 2-9 layers. In addition, the method for manufacturing a PTC positive temperature heating element includes the steps of: mixing the few-layer graphene having 2-9 layers and obtained by the above-mentioned method with a polymer binder to prepare a graphene-based PTC positive temperature heating paste; and printing or coating the graphene-based PTC positive temperature heating paste to obtain a PTC positive temperature heating element using a graphene-based polymer nanocomposite material.

Description

Manufacturing method of graphene and method of manufacturing PTC constant temperature heating element including graphene-based polymer nanocomposite material{METHOD FOR MANUFACTURING FEW LAYER GRAPHENE, AND METHOD FOR MANUFACTURING PTC POSITIVE TEMPERATURE HEATING ELEMENT COMPRISING GRAPHENE-CONTAINING POLYMER NANOCOMPOSITE}

The present invention is a method of manufacturing a low-layer graphene (few layer graphene) of 2 to 9 layers, and a method of manufacturing a high-efficiency PTC constant temperature heating element including a graphene-based polymer nanocomposite material having improved PTC (positive temperature coefficient) strength by adding the same And, it relates to a PTC constant temperature heating element having a magnetic temperature control characteristic manufactured through it.

In recent years, as research and development of energy-saving heating materials and heating elements using the same has been accelerated, the development of new technologies for minimizing leakage currents due to wet construction has emerged.

Until now, a wire heater has been mainly used as a heating element for heating in a wet construction method. However, since the onboard heating element is made of a heating material such as Ni-Cr and Fe-Ni-Cr, the thermal efficiency is low due to the onboard heating, so the power consumption is relatively high, and due to the series circuit configuration, the circuit in one place is open. If it is, there is a difficulty in maintenance, such as the entire heating element does not generate heat. In addition, there is a high risk of damage to the heating element and fire due to abnormal heating phenomena such as local overheating such as heat collection, and the stability of the product is lacking.

On the other hand, carbon-based surface heating elements have superior thermal efficiency compared to linear heating elements, but since conductive particles such as carbon black are applied as resistance heating sources, resistance values change greatly due to repeated use and abnormalities such as local overheating such as heat collection. Due to the heating phenomenon, there is a high risk of damage to the heating element and fire, and the stability of the product is lacking.

In order to secure stability, a temperature control system such as an overheating prevention sensor has been devised for the linear heating element and the planar heating element, but it causes abnormal heating phenomena such as local overheating such as heat collection. The main path of abnormal heating phenomenon occurs from thermal insulation, heat storage, and overheating. In particular, as the temperature of the heat storage unit rises rapidly, local overheating of the heating element damages the finishing material, causing an electric fire.

Particularly, when overcoming the problem of the shipboard heating element currently being constructed for wet use and using a planar heating element with relatively excellent thermal efficiency as a heating element for wet construction, the leakage current breaker may operate due to a sharp increase in leakage current than the shipboard heating element. .

This is because the existing planar heating elements are mostly made of PET film for electrical insulation and flame retardant purposes and have been mainly used in dry construction. In addition, strong alkalinity in contact with the cement mortar floor during wet construction and the PET film of the planar heating element have weak disadvantages such as moisture or condensation due to the waterproofness due to interfacial contact with a wider construction floor than the linear heating element.

On the other hand, in Korean Patent No. 10-1168906 (2012.07.20) by the present applicant, a constant temperature heating element using a polymer PTC constant temperature heating ink applied with a PET film was proposed, and a polymer PTC by adjusting the amount of various dopants added. A solution to problems such as improvement of characteristics and stabilization of room temperature resistance has been disclosed, and the product has already been commercialized with this registered patent and exported to the United States. However, while the above registered patented technology is safe from the risk of energy saving and electric fire due to the self-temperature control characteristic of the polymer PTC constant temperature heating element, the above-described difficulties are encountered in applying it to wet construction for heating.

Accordingly, the applicant of the present invention has proposed a wet planar heating element using a polymer PTC constant temperature heating ink to minimize leakage current and induced current in Korean Patent No. 10-1593983.

However, as requirements for energy efficiency and stability due to heat generation are gradually expanding, development of a next-generation high-efficiency PTC constant temperature heating ink and a heating element using the same is required.

Korean Patent Registration No. 10-1168906 Korean Patent Registration No. 10-1593983

J. Mater. Chem. A, 2015, 3, 11700-11715

Accordingly, the present invention prepares a graphene-based PTC constant temperature heating paste by mixing 2 to 9 layers of low-layer graphene prepared by thermal shock and physical peeling method and a polymer binder, and printing or coating it to prepare graphene-based It is intended to provide a method of manufacturing a high-efficiency PTC constant temperature heating element using a polymer nanocomposite material and a high-efficiency PTC constant temperature heating element.

In particular, it is an object of the present invention to provide a high-efficiency PTC constant temperature heating element and a method of manufacturing the same, which has excellent heating characteristics by securing excellent PTC characteristics, and has an increased effect of reducing power consumption, preventing damage to the heating element due to heat collection, and preventing the risk of fire.

However, the problem to be solved by the present application is not limited to the problems mentioned above, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

One aspect of the present application is a first heat treatment step of adding graphite to 200 to 210 °C of normal methyl-2-pyrolidone (NMP) and stirring for 1 to 10 hours; A second heat treatment step of cooling the first heat-treated graphite to a temperature of -10 to 10 °C; And mechanically exfoliating the heat-treated graphite to prepare 2 to 9 layers of low-layer graphene (few layer graphene).

Mechanical peeling of graphite in one aspect of the present invention may include mechanical peeling and dispersion at a speed of 100 to 2,000 rpm using a bead mill, a wet ball mill, a dry stirrer, and a composite stirrer using one or more of them.

In one aspect of the present invention, prior to the first heat treatment step of graphite, a cooling step of cooling the graphite at a temperature of 0 to -100 °C for 20 to 30 hours; may further include.

Another aspect of the present invention is to prepare 2 to 9 layers of low-layer graphene by the method described above; Preparing a graphene-based PTC constant temperature heating paste by mixing graphene and a polymeric binder; And printing or coating a graphene-based PTC constant temperature heating paste to prepare a high-efficiency PTC constant temperature heating element using a graphene-based polymer nanocomposite material; containing, a high-efficiency PTC constant temperature heating element including a graphene-based polymer nanocomposite material Provides a manufacturing method.

In one aspect of the present invention, the polymeric binder is polyethylene, polypropylene, polybutadiene, polyolefin, polyester, polyvinyl chloride, polyvinyl acetate, polyethylene vinyl acetate, polyester-polyethylene vinyl acetate copolymer, polyethylene terephthalate, polystyrene, polyethylene. It includes any one selected from the group consisting of ketone, polyethylene terephthalate glycol, polyethyleneimide, and a composite polymer in which one or more of them are mixed, and the low layer graphene and the polymer binder are mixed in a weight ratio of 2:100 to 40:100. Include.

Printing or coating method in one aspect of the present invention, gravure printing, comma coating, silk screen printing, spray coating, immersion coating, roll coating, Mayer bar coating, blade coating, microgravure coating, slot die coating, slide coating, curtain Coating and any one method selected from the group consisting of a printing or coating method in which one or more of them are mixed.

Another aspect of the present invention provides a high-efficiency PTC constant temperature heating element manufactured by the above manufacturing method.

In another aspect of the present invention, the PTC strength (Intensity) calculated by Equation 1 below of the constant temperature heating element may be 1,000 or more.

[Equation 1] PTC Intensity [%] = (R _100℃ / R _20℃ ) ⅹ 100

(In Equation 1, R _20°C and R _100°C are resistance values (Ω) of the graphene PTC composition measured at 20°C and 100°C, respectively.)

Another aspect of the present invention provides a planar heating element or a heating device including a high-efficiency PTC constant temperature heating element.

The high-efficiency PTC constant temperature heating element using the graphene-based polymer nanocomposite material according to the present invention secures excellent PTC characteristics and has excellent heating characteristics, while reducing power consumption, preventing damage to the heating element due to heat collection, and significantly reducing the risk of fire. It can have an effect.

In addition, due to the excellent characteristics of the high-efficiency PTC constant temperature heating element using the graphene-based polymer nanocomposite material according to the present invention, it can be used as a flexible planar heating element included in automobile seats in the future, or a nano structure that requires precise temperature control. It is possible to manufacture a heating device of excellent quality that can be applied in various fields such as a heating device of

1 is a Transmission Electron Microscope (TEM) image of a low-layer graphene prepared by the method of Example 1. FIG.
FIG. 2 is a TEM image of an impression graphite prepared by the method of Example 2. FIG.
3 is a TEM image of an impression graphite prepared by the method of Comparative Example 1. FIG.
4 is a TEM image of the pulled graphite of Comparative Example 2.
5 is a Raman spectroscopy analysis result of low-layer graphene prepared by the method of Example 1.
6 is an X-ray Photoelectron Spectroscopy (XPS) analysis result of low-layer graphene prepared by the method of Example 1.
7 is an X-ray Diffraction Spectroscopy (XRD) result of low-layer graphene prepared by the method of Example 1.
8 is a result of analyzing the resistance characteristics according to temperature of the graphene-based PTC heating element manufactured by the method of Preparation Example 2 and the carbon black-CNT-based PTC heating element manufactured by the method of Preparation Example 3.

Hereinafter, embodiments and examples of the present disclosure will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present disclosure. However, the present application may be implemented in various different forms and is not limited to the embodiments, examples, and drawings described herein. In the drawings, parts not related to the description are omitted in order to clearly describe the present invention.

Throughout the specification, when a certain part "includes" a certain component, it means that other components may be further included, rather than excluding other components unless specifically stated to the contrary.

One aspect of the present application is a first heat treatment step of adding graphite to 200 to 210 °C of normal methyl-2-pyrolidone (NMP) and stirring for 1 to 10 hours; A second heat treatment step of cooling the first heat-treated graphite to a temperature of -10 to 10 °C; And mechanically exfoliating the heat-treated graphite to prepare 2 to 9 layers of low-layer graphene (few layer graphene).

Mechanical peeling of graphite in one aspect of the present invention may include mechanical peeling and dispersion at a speed of 100 to 2,000 rpm using a bead mill, a wet ball mill, a dry stirrer, and a composite stirrer using one or more of them.

In one aspect of the present invention, prior to the first heat treatment step of graphite, a cooling step of cooling the graphite at a temperature of 0 to -100 °C for 20 to 30 hours; may further include.

More preferably, in the case of using graphite cooled to 0 to -100 °C before the first heat treatment step, ΔT ₁ of the graphite cooled through the first heat treatment step of treating NMP at a temperature of 200 to 210 °C is 210 to 300 °C. A level of thermal shock may occur, more preferably at a level of 250 to 300°C. (Here, ΔT ₁ means the difference between the cooling temperature and the first heat treatment temperature (heating NMP temperature).)

In the second heat treatment step of cooling the graphite through the first heat treatment step of treating graphite to NMP at a temperature of 200 to 210 °C to a temperature of -10 to 10 °C, a second thermal shock having a ΔT ₂ of 190 to 220 °C may occur. have. (Here, ΔT ₂ means the difference between the first heat treatment temperature (heating NMP temperature) and the second heat treatment temperature (cooling temperature).)

Due to the first and second thermal shocks or the second thermal shock, the graphene interlayer/intermolecular attraction in the graphite may be weakened, and the NMP having the closest surface energy to the graphite may be easily intercalated. The NMP inserted between the graphite layers through such a single or multi-stage thermal shock step further weakens the inter-molecular attraction between the graphene layers inside the graphite, and then through a mechanical peeling step that proceeds, low-layer graphene at the level of 2 to 9 layers (few layer grapehene). Can be easily manufactured.

Another aspect of the present invention is the steps of preparing 2 to 9 layers of low-layer graphene by the method described above; Preparing a graphene-based PTC constant temperature heating paste by mixing graphene and a polymeric binder; And printing or coating a graphene-based PTC constant temperature heating paste to prepare a high-efficiency PTC constant temperature heating element using a graphene-based polymer nanocomposite material; containing, a high-efficiency PTC constant temperature heating element including a graphene-based polymer nanocomposite material Provides a manufacturing method.

In one aspect of the present invention, the polymeric binder is polyethylene, polypropylene, polybutadiene, polyolefin, polyester, polyvinyl chloride, polyvinyl acetate, polyethylene vinyl acetate, polyester-polyethylene vinyl acetate copolymer, polyethylene terephthalate, polystyrene, polyethylene. It includes any one selected from the group consisting of ketone, polyethylene terephthalate glycol, polyethyleneimide, and a composite polymer in which one or more of them are mixed, and the low layer graphene and the polymer binder are mixed in a weight ratio of 2:100 to 40:100. Include.

Preferably, the polymeric binder may be used by mixing a polyester-based binder and a polyolefin-based binder in a weight ratio of 0.1:10 to 10:0.1, and more preferably, mixing in a weight ratio of 1:5 to 5:1. have.

Polyester-based binder is a polyester resin having excellent compatibility and adhesion with other component layers of a planar heating element such as polyester-based plastic film (PET film) or nonwoven fabric, and excellent chemical resistance, bending resistance, and printability (workability). Is the main component. More specifically, 5 to 11 wt% of vinyl synthetic resin, 20 to 35 wt% of polyester synthetic resin, 20 to 50 wt% of aromatic hydrocarbon solvent, 20 to 40 wt% of ketone solvent, 0.5 to 1.5 wt% of antifoam, leveling The composition containing 0.5 to 1.5 wt% may be prepared by mechanical stirring in a reactor capable of heating. Vinyl-based synthetic resins include polyvinyl chloride, polyvinyl acetate, and the like, and polyester-based synthetic resins include polyester. Aromatic hydrocarbon solvents include toluene and xylene, and ketone solvents include methyl ethyl ketone and acetone. Preferably, the polyester-based binder is a vinyl-based synthetic resin with 5.03 wt% of polyvinyl chlororide, 5.03 wt% of polyvinyl acetate, and a polyester-based synthetic resin with 30.15 wt% of polyester, and an aromatic hydrocarbon solvent. It is possible to heat a composition containing 24.12 wt% of toluene, 6.03 wt% of methyl ethyl ketone, 28.1 wt% of acetone, 0.5 wt% of an antifoam, and 1 wt% of a leveling agent as a ketone solvent. It can be prepared by mechanical stirring in the reactor.

Polyolefin-based binder is a mixture of crystalline polymers such as polyethylene (PE), polypropylene (PP) and ethylene vinyl acetate (EVA), and in more detail, 1 to 10 wt% of polyethylene, polypropylene Reactor capable of heating a composition containing 1 to 5 wt%, polyethylene vinyl acetate copolymer 5 to 30 wt%, aromatic hydrocarbon solvent 10 to 90 wt%, antifoaming agent 0.5 to 1.5 wt%, leveling agent 0.5 to 1.5 wt% It can be prepared by mechanical stirring within. Preferably, the polyolefin-based binder is polyethylene 2.84 wt%, polypropylene 0.95 wt%, polyethylene vinyl acetate copolymer 9.48 wt%, toluene 56.87 wt% as an aromatic hydrocarbon solvent, xylene 28.44 wt%, antifoaming agent 0.47 wt% %, a composition comprising 0.95wt% of a leveling agent may be prepared by mechanical stirring in a reactor capable of heating.

More preferably, the polymer binder may be a mixture of a polyester-based binder and a polyolefin-based binder in a 1:1 weight ratio.

Printing or coating method in one aspect of the present invention, gravure printing, comma coating, silk screen printing, spray coating, immersion coating, roll coating, Mayer bar coating, blade coating, microgravure coating, slot die coating, slide coating, curtain Coating and any one method selected from the group consisting of a printing or coating method in which one or more of them are mixed.

Another aspect of the present invention provides a high-efficiency PTC constant temperature heating element manufactured by the above manufacturing method.

In another aspect of the present invention, the PTC strength (Intensity) calculated by the following Equation 1 of the constant temperature heating element may be 1,000 or more, preferably 1,000 to 5,000, more preferably 2,000 to 4,000, and even more preferably 3,000 to Can be 4,000.

[Equation 1] PTC Intensity [%] = (R _100℃ / R _20℃ ) ⅹ 100

(In Equation 1, R _20°C and R _100°C are resistance values (Ω) of the graphene PTC composition measured at 20°C and 100°C, respectively.)

Another aspect of the present invention provides a planar heating element or a heating device including a high-efficiency PTC constant temperature heating element. The planar heating element or heating device may further add a commonly used configuration except for the high-efficiency PTC constant temperature heating element using the graphene-based polymer nanocomposite material presented as an embodiment of the present invention. In more detail, there may be an electrode layer, an electrically conductive layer, a waterproof film layer, other heating layer, a metal or non-metal film layer, a nonwoven fabric layer, and the like, and the present invention is not limited thereto.

The electrode layers are formed in a predetermined width on both sides of the PTC constant temperature heating element to control the flow of current between the electrodes to increase the heating temperature of the heating element. The electrode material of the electrode layer may be a conductive polymer such as polyaniline, polypyrrole, and polythiophene; Conductive components such as carbon; At least one selected from the group consisting of metals such as silver, gold, platinum, palladium, copper, aluminum, tin, iron, and nickel may be used. Preferably, copper having excellent thermal conductivity and electrical conductivity is used.

Other heating layers may be stacked together with the PTC constant temperature heating element on the electrode layer, and generate heat when electricity flows. The material is preferably a mixture of any one or two or more of conductive carbon, carbon black, graphene, carbon nanotubes (CNT), graphite, and CNT or graphene on a nonwoven fabric or a heating layer woven with carbon fiber. An impregnated heating layer, a heating layer impregnated with conductive carbon in a nonwoven fabric, and a heating layer prepared by coating CNT or graphene paste or ink on a base film may be further included and used.

As the other film layer, at least one selected from a metal, non-metal, or mixed metal-non-metal film may be additionally attached to one or more layers. An air layer may be formed on a metal, non-metal, or metal-non-metal mixed film. The metal film may include aluminum, copper, and the like, a polymer or ceramic as the non-metal film, and an aluminum-polymer or aluminum-ceramic may be selectively used as the metal-non-metal mixed film. Specifically, the polymer film is preferably polyethylene terephthalate, and the metal-nonmetal mixed film is preferably aluminum-polyethylene terephthalate, but is not limited thereto. The metal, non-metal, or metal-non-metal mixed film may be attached to one or both surfaces of the outermost surface of the heating element, but is not limited thereto, and one or more layers may be added between various layers of the heating element.

In addition, in order to minimize leakage current due to an increase in a large area during construction of the heating element, a waterproof film layer and a nonwoven fabric layer interposed between the heating element and the waterproof film layer may be further included on both sides of the heating element.

The waterproof film layer is used for the purpose of minimizing the leakage current generated by the increase in the large area during wet construction and to provide waterproofness during wet construction. The material may be used without limitation as long as it is a material that can impart insulation and waterproof properties, and specifically, polyethylene terephthalate, polypropylene, polyester, polystyrene, polyether ketone, polyethylene terephthalate glycol, and polyethyleneimide. One selected from the group consisting of can be used.

The nonwoven layer is formed of fibers, and a plurality of pores formed between the fibers and irregularities may be further formed on the surface. Leakage current can be prevented through the air pockets due to pores and irregularities of the nonwoven fabric. The fibers forming the nonwoven base material may have an average diameter of 0.1 μm to 10 μm. Fibers are polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as aramids, polyacetals, polycarbonates, polyimides, polyetheretherketones, polyethersulfones, poly It may be formed of phenylene oxide, polyphenylene sulfide, polyethylene naphthalene, etc., but is not limited thereto.

Each of the structural layers includes T-die method, inflation method, extrusion lamination, coextrusion lamination; It can be laminated using an adhesive method such as dry lamination, sandwich lamination, or thermal lamination using adhesives such as polyurethane, unsaturated polyester, and epoxy resin, and more preferably, dry lamination using a polyurethane adhesive and an isocyanate curing agent is used. I can.

Hereinafter, the present application will be described in more detail using examples, but the present application is not limited thereto.

[Example 1] Preparation of low-layer graphene (few layer graphene)

200g of pulled graphite (d50: 20㎛, carbon content: at least 99.5%) was treated in a freezer set at -80℃ for 24 hours.

200 g of impression graphite treated at -80°C boiled inside a reactor equipped with a gas condenser (double jacket reactor in which cooling water circulates; N-Methyl-2-pyrrolidone; bp.204) ℃) momentarily put into 1L and heat-treated while stirring for 2 hours, and then rapidly cooled to 4°C.

A counter rotating bead mill equipped with a disk coupled to a zirconia ceramic bead and a rotating shaft of heated and cooled impression graphite, processing capacity: up to 1.8L / bead: zirconia (ZrO ₂ ), φ0 Low-layer graphene of 2 to 9 layers by mechanical peeling and dispersion for 3 hours by centrifugal force by rotation of the original plate at .8mm, filling amount 950g) (Mix. 150~200rpm / Agitator 1,500~1,700rpm) (few layer grapheme) was prepared.

[Example 2]

200 g of impression graphite stored at room temperature was instantaneously added to 1 L of NMP at 204° C. inside a reactor equipped with a gas condensing device as in Example 1, followed by heat treatment while stirring for 2 hours, and then quenched to 4° C.

Thereafter, the impression graphite was mechanically peeled and dispersed for 3 hours in a bead mill device as in Example 1 to prepare a multilayer graphene.

[Comparative Example 1]

200 g of impression graphite stored at room temperature was mixed with 1 L of NMP at room temperature, and mechanical peeling and dispersion were performed for 3 hours in a bead mill device as in Example 1.

[Comparative Example 2]

200 g of raw material of impression graphite stored at room temperature was prepared and compared with the low-layer graphene of the present application prepared previously.

[Production Example 1]

To 12% by weight (wt) of the low-layer graphene prepared in Example 1, 22% by weight of polyester as a polyester-based binder, 4.7% by weight of polyethylene as a polyolefin-based binder, 1.6% by weight of polypropylene, and 15.7% by weight of polyethylene vinyl acetate %, toluene 29.3 wt% and xylene 14.7 wt% as solvent, Fatty acid modified polyester (Fatty acid modified polyester) as a dispersant was added at 1 phr (parts per hundred rubber) relative to the total polymer binder content, and further dispersion and peeling were performed for 1 hour in a counter rotating bead mill.

Then, toluene diisocyanate (TDI, Toluene Diisocianate) as a curing agent was added 5 phr compared to the content of the polyester-based binder, and dicumyl peroxide (DCP, Dicumyl Peroxide) as a crosslinking agent was added 2 phr compared to the polyolefin-based polymer content. ) Was prepared. The contents of the components are shown in Table 1 below.

Ingredients Composition [wt%] additive Graphene 12 * Dispersant 1phr (input when mixing ingredients)
* Hardener 5phr (add after mixing ingredients)
* Crosslinking agent 2phr (input after mixing components) Polyester binder 22 Polyolefin binder 22 Solvent 44 Sum 100

The prepared graphene-based PTC ink (paste) was applied to a substrate, and silkscreen printed in a manner of processing at 130° C. for 15 minutes to prepare a graphene-based PTC heating element (coating film) having a thickness of 1 μm.

[Production Example 2]

In Preparation Example 1, a graphene-based PTC ink (paste) was prepared using the same composition as in Preparation Example 1, except that the content of graphene was changed to 1.5 wt% and the polyolefin-based binder was mixed to 32.5 wt%. . The contents of the components are shown in Table 2 below.

Ingredients Composition [wt%] additive Graphene 1.5 * Dispersant 1phr (input when mixing ingredients)
* Hardener 5phr (add after mixing ingredients)
* Crosslinking agent 2phr (input after mixing components) Polyester binder 22 Polyolefin binder 32.5 Solvent 44 Sum 100

The prepared graphene-based PTC ink (paste) was silkscreen printed under the same conditions as in Preparation Example 1 to prepare a graphene-based PTC heating element (coating film) having a thickness of 1 μm.

[Production Example 3]

In Preparation Example 1, a carbon black/CNT-based PTC ink (paste) was prepared using the same composition, except that 9 wt% of acetylene carbon black and 3 wt% of carbon nanotubes (CNT) were changed instead of 12 wt% of graphene. The contents of the components are shown in Table 3 below.

Ingredients Composition [wt%] additive Acetylene carbon black 9 * Dispersant 1phr (input when mixing ingredients)
* Hardener 5phr (add after mixing ingredients)
* Crosslinking agent 2phr (input after mixing components) Carbon nanotube 3 Polyester binder 22 Polyolefin binder 22 Solvent 44 Sum 100

The prepared carbon black/CNT-based PTC ink (paste) was silkscreen-printed under the same conditions as in Preparation Example 1 to prepare a carbon black/CNT-based PTC heating element (coating film) having a thickness of 1 μm.

[Experimental Example 1] Evaluation of transmission electron microscope (TEM) images of graphene and impression graphite of Examples 1 to 2 and Comparative Examples 1 to 2

In order to confirm the shape such as the number of graphene layers of graphene and impression graphite of Examples 1 to 2 and Comparative Examples 1 to 2, the image was confirmed through TEM analysis, and this was shown in FIGS. 1 to 4.

1 is a Transmission Electron Microscope (TEM) image of the low-layer graphene prepared in Example 1, and it was confirmed that low-layer graphene at the level of 3 to 4 layers or 7 to 8 layers was prepared through this.

FIG. 2 is a TEM image of the multilayered graphene prepared in Example 2, and it was confirmed that the peeling of the impression graphene was less than that of the low-layered graphene of Example 1, so that a multilayered graphene having about 10 layers of graphene was formed. .

Figure 3 is a TEM image of the impression graphite prepared in Comparative Example 1, it was confirmed that the peeling of the graphene layer constituting the graphite was hardly achieved by only physical peeling, and FIG. 4 is the impression graphite prepared in Comparative Example 2 Is a TEM image of.

As shown in Figs. 1 to 4, it was confirmed that the low-layer graphene prepared according to an embodiment of the present invention is a low-layer graphene in which less than 10 layers of graphene are stacked.

[Experimental Example 2] Component evaluation of low-layer graphene prepared in Example 1

In order to confirm the composition of the low-layer graphene prepared in Example 1, Raman Spectroscopy analysis, X-ray Photoelectron Spectroscopy (XPS) analysis, and X-ray Diffraction Spectroscopy, XRD ) Analysis was carried out, and it is shown in FIGS. 5 to 7.

Figure 5 is confirmed the D peak of the Raman spectroscopy results in yes 1350cm- showing a G peak and yes deformation or oxidation of a pin at 1580cm- ¹ is characterized by detecting at the pin ^1. In addition, it was confirmed that the D/G ratio was 0.286, which was differentiated from the existing graphene.

6 is a result of XPS analysis of low-layer graphene prepared by the method of Example 1, by measuring the binding energy (eV) of the carbon peak and the oxygen peak, through which carbon (C _1s ) and oxygen (0 _1s) The atomic content of) was calculated. More detailed atomic contents of carbon and oxygen are shown in Table 4 below.

Sample name C _1S O _1S Binding energy (BE) (eV) Atomic content (AT.%) Binding energy (BE) (eV) Own content (AT.%) Example 1 284.6 96.82 532.71 3.18

It was confirmed that graphene was formed through Example 1 through the XPS measurement result, which was consistent with the previously measured Raman spectroscopy measurement result.

7 is a result of XRD analysis of the low-layer graphene prepared by the method of Example 1, 2 Theta, which is characteristic of graphene, is found near the (002) plane peak found at about 26 degrees and the (002) plane peak found at about 54 degrees ( 004), a peak was confirmed. By analyzing the (002) peak, it was confirmed that the interlayer distance (d) of the low-layer graphene of Example 1 was 3.4 Å, and also, the TEM measurement result of Example 1 as shown in FIG. 1 through this XRD analysis result In the same way, it was confirmed that low-layer graphene of less than 10 layers was formed.

[Experimental Example 3] PTC heating element composition coating resistance characteristics analysis of Preparation Examples 1 to 3

The PTC heating elements (composition coating) of Preparation Examples 1 to 3 were formed in a width, length, and thickness of W45mm*L45mm*T1.0㎛ by silkscreen printing, and a 4-point resistance value was measured at room temperature, and thus measured. The electrical conductivity was compared by applying the correction factor (4.532) to the calculated value to calculate the sheet resistance, and the results are shown in Table 5 below.

PTC heating element (PTC composition coating film) Drying condition Film thickness Resistance value Temperature time 4-point measurement Sheet resistance Manufacturing Example 1 130 ℃ 15 minutes 1.0 μm 1.2~1.3 kΩ 5.44~5.89 kΩ Manufacturing Example 3 1.0 μm 9.8~10.8 kΩ 44.41~48.95 kΩ

* Sheet resistance = measured value X correction factor (4.532)

As shown in Table 5, when containing the same content of conductive fine particles (Preparation Example 1 is low-layer graphene, Preparation Example 3 is carbon black and CNT) Preparation comprising the low-layer graphene prepared in Example 1 of the present invention It was confirmed that the PTC heating element (composition coating film) of Example 1 had a 4-point measured resistance value or a sheet resistance value corrected for it was 7.5 to 9.0 times lower than that of the PTC (composition coating film) of Preparation Example 3. Therefore, compared to the case where the existing carbon black or CNT is included as conductive fine particles, the PTC constant temperature heating ink (paste) of Preparation Example 1 of the present invention and the heating element manufactured using the same are limited in the filling rate of conductive particles (filling of conductive particles It was confirmed that if the rate is more than the limit, the dispersion stability of the conductive ink is not good), and the PTC characteristic (magnetic temperature control) can be increased.

In addition, by performing a resistance change (RT) test according to the temperature of the existing PTC heating element and the PTC constant temperature heating element in Preparation Example 2, which reduced the filling rate of the conductive particles compared to Preparation Examples 1 and 3, the resistance characteristics for each temperature were measured. In comparison, it is shown in Figure 8 and Table 6 below. In more detail, the PTC constant temperature heating elements of Preparation Example 2 and Preparation Example 3 were cut into W303mm*L500m in the oven, respectively, and the wires connected to the electrodes of each sample were pulled out of the oven and placed outside the oven. Connected to the meter instrument. Thereafter, the change in resistance of the PTC constant temperature heating element was measured using a digital multimeter device while increasing the oven temperature by 10°C to 20-100°C.

Temp.
[℃] Manufacturing Example 2
R [Ω] Manufacturing Example 3
R [Ω] 20 940 950 30 1,067 1,058 40 1,390 1,325 50 1,754 1,668 60 3,856 2,116 70 6,598 2,900 80 12,135 4,334 90 20,872 7,411 100 31,003 10,302 PTC Intensity
[%] 3,298 1,084 ☞ PTC Intensity [%] = (R _100℃ / R _20℃ ) ⅹ 100

As shown in Figure 8 and Table 6, in the case of the graphene-based PTC constant temperature heating body Preparation Example 2, the initial resistance at 20 ℃ was 940Ω, up to 50 ℃ resistance value similar to Preparation Example 3 containing CNT, etc. And showed similar heating characteristics. However, from 60°C, the resistance of the PTC heating element manufactured in Preparation Example 2 was 3,856Ω, which was increased to about 1.8 times compared to 2,116Ω in Preparation Example 3, and about 3 times higher resistance than Preparation Example 3 at 100°C. Showed shame.

As such, in the case of Preparation Example 2, the PTC intensity calculated through Equation 1 below was 3,298, which is about three times higher than that of Preparation Example 3 in which the existing conductive particles were applied was 1,084. I could confirm that.

[Equation 1]

PTC Intensity [%] = (R _100℃ / R _20℃ ) ⅹ 100

(In the above formula, R _20°C and R _100°C are resistance values (Ω) of the graphene PTC composition measured at 20°C and 100°C, respectively.)

As described above, when the PTC constant temperature heating element according to the manufacturing example of the present invention is energized under the condition of increasing the temperature, the electric resistance increases and the amount of current decreases, thereby effectively reducing the calorific value, and the PTC constant temperature heating element Through the self-temperature control (or constant temperature heating) characteristic, it is possible to prevent damage to the heating element or the risk of fire due to overheating and overcurrent, and to manufacture a high-efficiency PTC constant temperature heating element having an effect of reducing power consumption.

As described above, the PTC constant temperature heater of the present invention includes low-layer graphene, so that a self-temperature controllable constant temperature heater with improved PTC effect can be efficiently manufactured compared to the PTC constant temperature heater using conventional carbon black, CNT or graphite. , Due to these excellent properties, it is expected to be used as a heating device such as a heating sheet in the future and a nano heating device that needs temperature control, and it can be applied to various other fields.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the scope of the present invention is not limited to the disclosed embodiments, and is interpreted by the claims to be described later, and the meaning and scope of the claims, and all changes or modified forms of technical ideas derived from the equivalent concept It should be construed as being included in the scope of the present invention.

Claims (10)

A first heat treatment step of adding graphite to normal methyl-2-pyrolidone (NMP) at 200 to 210° C. and stirring for 1 to 10 hours;
A second heat treatment step of cooling the first heat-treated graphite to a temperature of -10 to 10 °C; And
Graphene production method comprising a; step of mechanically peeling the heat-treated graphite to produce 2 to 9 layers of low-layer graphene (few layer graphene).
The method of claim 1,
The mechanical exfoliation of the graphite includes mechanical exfoliation and dispersion at a speed of 100 to 2,000 rpm using a bead mill, a wet ball mill, a dry stirrer, and a composite stirrer using one or more of them.
The method of claim 1,
Before the first heat treatment step of the graphite,
A cooling step of cooling the graphite at a temperature of 0 to -100 °C for 20 to 30 hours; further comprising, a method for producing graphene.
Producing 2 to 9 layers of low-layer graphene by the method of any one of claims 1 to 3;
Preparing a graphene-based PTC constant temperature heating paste by mixing the graphene and a polymeric binder; And
Including; printing or coating the graphene-based PTC constant temperature heating paste to prepare a PTC constant temperature heating element using a graphene-based polymer nanocomposite material;
A method of manufacturing a PTC constant temperature heating element including a graphene-based polymer nanocomposite material.
The method of claim 4,
The polymeric binder is polyester, polyethylene vinyl acetate, polyester-polyethylene vinyl acetate copolymer, polyvinyl chloride, polyethylene, polypropylene, polybutadiene, polyolefin, polyvinyl chloride, polyvinyl acetate, polyethylene terephthalate, polystyrene, polyethylene ketone , Polyethylene terephthalate glycol, polyethyleneimide, and any one selected from the group consisting of a composite polymer in which one or more thereof is mixed,
The graphene and the polymeric binder are mixed in a weight ratio of 2:100 to 40:100, a method for producing a PTC constant temperature heating element comprising a graphene-based polymer nanocomposite.
The method of claim 4,
The printing or coating method includes gravure printing, comma coating, silk screen printing, spray coating, immersion coating, roll coating, Mayer bar coating, blade coating, microgravure coating, slot die coating, slide coating, curtain coating, and one or more of these. PTC constant temperature heating element manufacturing method comprising a graphene-based polymer nanocomposite material comprising any one method selected from the group consisting of a mixed printing or coating method.
PTC constant temperature heating element manufactured by the manufacturing method of claim 4.
The method of claim 7,
PTC strength (Intensity) calculated by the following equation 1 of the constant temperature heating element is 1,000 or more, PTC constant temperature heating element.
[Equation 1]
PTC Intensity [%] = (R _100℃ / R _20℃ ) ⅹ 100
(In Equation 1, R _20°C and R _100°C are resistance values (Ω) of the graphene PTC composition measured at 20°C and 100°C, respectively.)
Including the PTC constant temperature heating element of claim 7, planar heating element.
A heating device comprising the PTC constant temperature heating element of claim 7.

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