KR101271606B1 - Method of producing polyimide-graphene composite material - Google Patents

Abstract

 The present invention relates to a method for producing a polyimide-graphene composite material which can easily prepare a polyimide-graphene film by coating, comprising: preparing a solvent; Preparing a polyimide and graphene raw material; And forming a dispersion in which the polyimide and graphene raw materials are dissolved in the solvent and the solid content of the graphene and polyimide is 2 to 10 wt%, and the dispersion is uniformly dispersed at low viscosity. In use, the graphene / polyimide dispersion can be highly stable, providing uniform quality to processes based on solution processes.

Description

Method of producing polyimide-graphene composite material {Method of producing polyimide-graphene composite material}

The present invention relates to a method for producing a polyimide-graphene composite material having polyimide and graphene. More specifically, the present invention relates to a method for producing a polyimide-graphene composite material which can easily produce a polyimide-graphene film by coating.

Due to their unique properties, polymers and polymer resins are used in a variety of ways, and applications and research are being actively conducted in universities and industries. Since polyimide has excellent properties that other polymer materials such as heat resistance, insulation, solvent resistance, and low temperature resistance do not have, polyimide, for example, FPC (Flexible Printed), which is an insulating support for electronic and electronic component parts of computers or IC control. It is widely used as a base film for circuit boards and tape automated bonding tapes. In recent years, miniaturization and high functionalization of electric devices are progressed, and the refinement | miniaturization of a wiring pattern and the improvement of the mounting density of the electronic component on a wiring board are calculated | required. As a technology for mounting electronic components, Chip on FPC (COP) and Tape Carrier Package (TCP) technologies have been established, and are already used for packaging display device driving elements of liquid crystal displays (LCDs) and plasma display panels (PDPs), for example. have.

Graphene materials are also expected to be applicable to various fields. Graphene produced by the exfoliation of graphite is composed of sp2 hybrid bonds of carbon as a continuous chemical bond of carbon atoms. The production price is relatively lower than that of carbon nanotubes. On the other hand, graphene has high electrical and thermal conductivity and high mechanical properties, so it is expected to be a representative nanomaterial that can replace carbon nanotubes.

Meanwhile, in order to take advantage of various materials, there is a growing interest in composite materials in which materials are composited. New composite applications require easy fabrication of composites. For example, in order to utilize the composite material in the form of a film, a method for easily manufacturing the same is required.

In order to commercialize a composite having various advantages, it is urgent to develop a manufacturing method that can grasp the characteristics of the composite and express it efficiently, and can easily prepare a composite material exhibiting various physical properties corresponding to user requirements.

In the following prior art document (Patent Document 1: KR2011-0016289A), a carbon nanoplate which is graphene oxide or graphene is chemically and physically dispersed therein, and then manufactured by complexing a composite material using a dispersion. A carbon nanoplatelet composite is disclosed.

KR 2011-0016289 A

The present invention provides a method for producing a composite material of polyimide and graphene.

The present invention provides a method for producing a polyimide graphene composite material having a uniform quality.

The present invention provides a method for producing a polyimide graphene composite material in which residual stress is relaxed.

Method for producing a composite material according to an embodiment of the present invention, the process of preparing a solvent; Preparing a polyimide and graphene raw material; And dissolving the polyimide and graphene raw materials in the solvent, and forming a dispersion such that the solid content of the graphene and polyimide is 2 to 10 wt%. Herein, the method of manufacturing the composite material may include obtaining a graphene and polyimide film by spray coating using the dispersion.

In the forming of the dispersion, polyimide is added and dissolved in a first solvent to form a first dispersion, graphene is added and dissolved in a second solvent to form a second dispersion, and the first and second dispersions are formed. Mixing may be included.

The first solvent is methylene chloride, ethylene chloride, chloroform, chloroform, tetrachloroethane, tetrahydrofurane, THF, dioxane, acetophenone ), Cyclohexanone, meta-cresol, m-Cresol, gamma-butyrolactone, g-Butyrolactone, dimethylformamide (DMF), dimethylacetamide (DMAC) and n-methyl It may include at least one of pyrrolidinone (n-methylpyrrolidone, NMP).

In addition, the second solvent is methylene chloride, ethylene chloride, chloroform, chloroform, tetrachloroethane, tetrahydrofurane, THF, dioxane, acetophenone (Acetophenone), cyclohexanone, meta-cresol (m-Cresol), gamma-butyrolactone (g-Butyrolactone), dimethylformamide (DMF), dimethylacetamide (DMAC), n It may include at least one of n-methylpyrrolidone (NMP), distilled water, isopropyl alcohol (IPA), methyl isobutyl ketone and ethanol.

The forming of the dispersion may include at least one of stirring and ultrasonic application.

In particular, the composite material may have a ratio of graphene to polyimide in the range of 2:98 to 12:88.

As described above, according to the embodiment of the present invention, a complex of polyimide and graphene can be prepared by a simple and simple method. In addition, the polyimide-graphene composite in the form of a film can be easily prepared.

According to an embodiment of the present invention, since the dispersion is uniformly dispersed at low viscosity, the graphene / polyimide dispersion can be highly stable, providing uniform quality to processes based on solution processes. The composite produced therefrom may have a uniform quality throughout.

In addition, the prepared composite may be prepared from a polyimide-graphene composite having high thermal conductivity and low residual stress. In addition, the prepared polyimide-graphene composite may be utilized in various electronic components and devices, such as being excellent in heat dissipation and thus may be utilized in heat dissipation sheets.

1 is a process flow diagram of a composite material manufacturing method according to an embodiment of the present invention.
Figure 2 is a photograph of each film produced according to the experimental example of the present invention
3 is an electron micrograph of a polyimide film.
Figure 4 is an electron micrograph of the composite material film prepared according to the experimental example of the present invention.
5 is a residual stress analysis result of each film prepared according to the experimental example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

The composite material prepared according to the embodiment of the present invention includes polyimide and graphene. Polyimide is a high molecular material having an imide ring, and is mainly synthesized using aromatic anhydrides and diamines. Polyimide resins exhibit excellent heat resistance, chemical resistance, abrasion resistance and weather resistance based on the chemical stability of the imide ring, and also exhibit low thermal expansion rate, low breathability, and excellent electrical properties. It has been used extensively in various applications such as high temperature adhesives, engineering plastic materials, aerospace, microelectronics, and optics, and the development of monomers and synthesis methods for more detailed purposes is becoming more diverse and elaborate. As the process progresses, its application range is gradually expanding. Examples of the polyimide resin applied to the inside and outside of articles commonly encountered in the surroundings include flexible circuit boards mainly used inside mobile phones, alignment films and photoresists of LCD TVs and monitors, and O-rings used at high temperatures. In addition to industrial applications such as column chromatography for gas chromatography, a technique for producing Lang-muir-Blodgett (LB) film, which is a monolayer film of a molecular unit using polyimide resin, has been developed and reported. Polyimide can be divided into three types: ① straight chain thermoplastic, ② straight chain non-thermoplastic, and ③ thermosetting according to the molecular structure and molding processability of the finally obtained polymer solid. Straight chain thermoplastics are linear polymers with molecular weights of 1 to 100,000, and are reversible thermoplastic resins capable of injection molding / extrusion molding. The straight chain non-thermoplastic type is a linear polymer having a molecular weight of 100,000 to 100,000 and cannot be melt kneaded because it has no melt flowability or is very bad, and is thus formed by compression / sintering or solution cast / desolvent method. The thermosetting property is obtained by curing reactive monomers (and a combination thereof) or an oligomer prepared by preliminarily polymerizing the monomer (s) and pressurizing the mixture by heating for a predetermined time to obtain a cured molded article which is three-dimensionally crosslinked. The oligomers are referred to as B stage polymers (molecular weights of about 300 to 3,000) and are solid at room temperature but soluble in a solvent and exhibit irreversible thermoplastic. In this embodiment, diamine, 5 (6) -amino-1- (4'aminophenyl) -1,3-trimethylinyne (5 (6) -amino-1- (4 'aminophenyl) -1, Soluble thermoplastic polyimide based on 3-trimethylindane) was used.

Graphene is a carbon nano material with one layer of graphite stripped off. In other words, graphite has a structure in which carbon layers are stacked in a hexagonal honeycomb shape, and graphene may be regarded as the thinnest layer of graphite. Graphene, a carbon allotrope, is a nanomaterial composed of carbon number 6, such as carbon nanotubes and fullerenes. It has a two-dimensional planar shape, and its thickness is 0.2nm (1nm is 1m / 1 billion) or 2m / 10 billion, which is extremely thin and has high physical and chemical stability. It is 100 times more electricity than copper, and can transfer electrons 100 times faster than single crystal silicon, which is mainly used as a semiconductor. The strength is more than 200 times stronger than steel, and more than twice the thermal conductivity of diamond, which boasts the highest thermal conductivity. In addition, it has excellent elasticity and does not lose its electrical properties even when stretched or bent. Due to these characteristics, graphene is evaluated as a material that surpasses carbon nanotubes, which is emerging as a next-generation new material, and is more likely to be applied industrially since it has a uniform metallicity than carbon nanotubes. In addition, graphene is attracting attention as a future new material in the electronic information industry that can make bendable displays, electronic paper, wearable computers and the like. In this example, graphene was prepared by exfoliating graphite with strong acid and thermal expansion at high temperature.

The polyimide-graphene composite material prepared according to the embodiment of the present invention is prepared using a low viscosity dispersion in which the graphene and polyimide are dissolved in a solution, so that the two materials are uniformly dispersed. It can be produced in various forms such as sheets, films, and bulk.

1 is a process flowchart of a composite material manufacturing method according to an embodiment of the present invention.

Referring to Figure 1, the composite manufacturing method according to an embodiment of the present invention is a process for preparing a solvent, preparing a polyimide and graphene, by dissolving the polyimide and graphene raw material in the solvent and controlling the solids content Forming a dispersion.

First, prepare raw materials. That is, polyimide and graphene, and a solvent for dissolving them are prepared, respectively. The polyimide is diamine, 5 (6) -amino-1- (4'aminophenyl) -1,3-trimethylinyne (5 (6) -amino-1- (4 'aminophenyl), as described above. Soluble thermoplastic polyimide based on) -1,3-trimethylindane) is used, and graphene is prepared by exfoliating graphite with strong acid and thermal expansion at high temperatures.

Here, the graphene may be manufactured according to the method of Staudenmaier. For example, 5 g of graphite powder, 90 mL of sulfuric acid at a volume ratio of 2: 1, and 45 mL of nitric acid were added to a two-necked round flask, and 25 g of potassium chlorate was slowly added at around 0 ° C, followed by stirring at room temperature for 3 days. The solution is washed and filtered several times, neutralized to pH around 6, dried in vacuo at 80 ° C. and crushed. The dried graphite oxide prepared by the above method is heat-treated for 5 minutes in an electric furnace at 500 ° C. to 1000 ° C., preferably 1000 ° C., in an argon gas atmosphere to obtain graphene in which each layer of graphite is thinly thin. Of course, the method for producing graphene is not particularly limited.

The solvent selects a liquid that can dissolve each solid raw material. Solvents to be dissolved by adding polyimide include methylene chloride, ethylene chloride, ethylene chloride, chloroform, tetrachloroethane, tetrahydrofuran (THF), which are soluble in polyimide. Dioxane, Acetophenone, Cyclohexanone, Meta-cresol, Gamma-butyrolactone, Dimethylformamide, Dimethylformamide At least one of acetamide (Dimethylacetamide, DMAC) and n-methylpyrrolidinone (NMP) is used. In addition, at least any one of the solvents for dissolving the polyimide may be used as the solvent for dissolving the graphene. In addition, distilled water, isopropyl alcohol (IPA), methyl having solubility in graphene may be used. At least one of isobutyl ketone (MethylIsoButylKetone) and ethanol may be used. These solvents may be used alone or in a proportion of the mixed solution.

Subsequently, each solid raw material (polyimide, graphene) is completely dissolved in a solvent to bring it into solution. A desired amount of powdered polyimide is added to a first solvent, i.e., a first solvent having solubility in the above-described polyimide, and completely dissolved to form a first dispersion. In addition, a desired amount of graphene powder is added to a second solvent, that is, a second solvent having solubility in the above-described graphene, and completely dissolved to form a second dispersion. At this time, each dispersion is stirred for a sufficient time or by applying ultrasonic waves, so that each solid solute is completely dissolved into a fully dispersed solution. The first dispersion and the second dispersion are mixed to form a dispersion in which polyimide and graphene are uniformly dispersed. In this case, stirring and / or application of ultrasonic waves may be additionally performed to sufficiently mix the first dispersion liquid and the second dispersion liquid. For example, a dispersion treatment may be further improved by carrying out a complex treatment of stirring and sonicating at a temperature around 50 ° C.

In the dispersion thus formed, the solid weight, that is, the content of polyimide and graphene may be variously changed depending on the intended use and required physical properties. For example, the composition of the polyimide and graphene may be prepared in 2 to 10 wt% to prepare a low viscosity dispersion. These low viscosity dispersions are highly stable, providing uniform quality to processes based on solution processes. In this case, the dispersion is used for spray coating, and if the content of polyimide and graphene is too low, less than 2% by weight, the drying process performed after spray coating, that is, the time required to remove the solvent may be longer. As a result, there is a problem that the process efficiency is lowered. In addition, when the content of polyimide and graphene exceeds 10% by weight, the viscosity increases to cause clogging of the fine nozzle, so that the spray coating process itself is stopped or the opening and closing of the nozzle irregularly occurs during the process to prevent film quality. Unevenness may also occur. It is also advantageous to apply a spray coating when the solids content is formulated at 2 to 10% by weight.

In addition, the ratio of graphene to polyimide in the composite material can be variously changed according to required physical properties. For example, the ratio of graphene to polyimide may be in the range of 2:98 to 12:88. If the amount of graphene is too small, the characteristics of graphene, such as conductivity, are not expressed, and if the amount of graphene is too large, excellent properties of polyimide, such as heat resistance, are degraded. The composite material thus prepared may be used to form a coating film on metal surfaces such as carbon steel, stainless steel, aluminum steel, and other alloy steels, thereby improving thermal conductivity and corrosion resistance of the metal.

A composite material such as a composite material film is prepared using the dispersion prepared as described above. A substrate is prepared, and the dispersion is sprayed onto the substrate by a spray method to produce a coating film or a coating film. In this case, when the adhesive property between the substrate and the coating film is required, a metal material such as aluminum, steel, stainless steel, brass, titanium, or the like may be used as the substrate. In the case of using as a support, glass and the like that can easily peel off the coating film due to poor adhesion properties with polyimide may be used. If necessary, the adhesion between the coating film and the substrate may be improved by surface treatment of the glass.

Thereafter, the composite coating film formed on the substrate is dried to obtain a graphene-polyimide composite material. At this time, it is good to dry for 15 hours in a vacuum oven at about 120 ℃. When the composite coating film formed on the substrate is immersed in water, the composite coating film can be easily separated from the substrate.

In the following, specific experimental examples will be described. Using the method described above, a polyimide provided by Ciba Specialty Chemicals and graphene prepared by the above method were dissolved in a solvent, respectively, to prepare a dispersion. At this time, Methylene chloride (purity 98%) was used as the first solvent, methylene chloride (Methylene chloride) was used as the second solvent. Graphene to polyimide ratios were 2:98, 5:95, 8:92, and 12:88 by weight, with a solids content of 5 wt% in the solvent. Thereafter, the glass substrate was spray-coated using the dispersion to obtain a graphene-polyimide composite material film.

In addition, a polyimide film was prepared for comparison with the composite material film. That is, the polyimide-dissolved solution was spray coated on a glass substrate and dried to prepare a polyimide film.

The morphology of the film thus produced was observed and the residual stress behavior was investigated. For each analysis, an electron microscope and a built-in residual stress analyzer were used.

2 is a photograph of each film produced. (A) of FIG. 2 is a pure polyimide film, and (b) to (e) of FIG. 2 are graphene to polyimide ratios in order of 2:98, 5:95, 8:92 and 12:88. to be. Pure polyimide film has a yellow color, has a blue color containing graphene, and shows a dark blue color as the amount of graphene increases.

3 is an electron micrograph (SEM) of a pure polyimide film, and FIG. 4 is an electron micrograph (SEM) of a composite material film having a graphene to polyimide ratio of 2:98. (A) and (b) of each photograph photographed the same film by a different magnification. As can be seen in Figure 3, the polyimide film shows a porous morphology. In addition, as shown in Figure 4 it can be seen that the spray-coated polyimide / graphene composite film also exhibits a porous morphology. Even if graphene is introduced, the porous structure and the hydrophobic surface of the polyimide remain intact.

5 is a residual stress analysis result of each film prepared according to the experimental example of the present invention. That is, the results of residual stress analysis of the pure polyimide film (a) and the composite film having a graphene to polyimide ratio of 2:98 (b), 5:95 (c), and 8:92 (d). All samples were subjected to residual stress analysis at an elevated temperature rate of 5 ° C./min from room temperature to 200 ° C., with the same conditions of natural cooling after a 30 minute hold time from the highest temperature (200 ° C.). Both pure polyimide samples and graphene containing samples exhibit typical residual stress behaviors, such as residual stress attenuation by heat treatment, lowest residual stress at maximum temperatures, and the like. Compared with the pure polyimide film, the residual stress of the composite film appears to be relaxed, and it can be seen that the change of the residual stress is low. In addition, the change in the total residual stress is shown in the order of pure polyimide film> graphene 2wt%> graphene 5wt%> graphene 8wt%. From this, it was confirmed that the film prepared with the graphene / polyimide-based dispersion was significantly relieved of the residual stress on the thermal environment compared to the film containing no graphene.

As mentioned above, although this invention was demonstrated with reference to the above-mentioned embodiment and an accompanying drawing, this invention is not limited to this, It is limited by the following claims. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified and modified without departing from the technical spirit of the following claims.

Claims (7)

As a method for producing a composite material,
Preparing a solvent;
Preparing a polyimide and graphene raw material; And
And dissolving the polyimide and graphene raw materials in the solvent, and forming a dispersion such that the solid content of the graphene and polyimide is 2 to 10 wt%.
In the process of forming the dispersion, by adding and dissolving polyimide in a first solvent to form a first dispersion, by adding and dissolving graphene in a second solvent to form a second dispersion, and mixing the first and second dispersion Process for producing a composite material comprising the process. The method according to claim 1,
Obtaining a graphene and polyimide film by spray coating using the dispersion; Method of manufacturing a composite material comprising a. delete The method according to claim 1,
The first solvent is methylene chloride, ethylene chloride, chloroform, chloroform, tetrachloroethane, tetrahydrofurane, THF, dioxane, acetophenone ), Cyclohexanone, meta-cresol, m-Cresol, gamma-butyrolactone, g-Butyrolactone, dimethylformamide (DMF), dimethylacetamide (DMAC) and n-methyl A method for producing a composite material comprising at least one of pyrrolidinone (n-methylpyrrolidone, NMP). The method according to claim 1,
The second solvent is methylene chloride, ethylene chloride, chloroform, chloroform, tetrachloroethane, tetrahydrofurane, THF, dioxane, acetophenone ), Cyclohexanone, meta-cresol, m-Cresol, gamma-butyrolactone, g-Butyrolactone, dimethylformamide (DMF), dimethylacetamide (DMAC), n-methyl Method for producing a composite material comprising at least one of pyrrolidinone (n-methylpyrrolidone, NMP), distilled water, isopropyl alcohol (IPA), methyl isobutyl ketone and ethanol. The method according to claim 1 or 2,
Forming the dispersion process is a composite material manufacturing method comprising at least one of stirring and ultrasonic application method. The method according to claim 1 or 2,
Said composite material having a graphene to polyimide ratio of from 2:98 to 12:88.

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