KR102464398B1 - Method for producing graphene-polymer composite and graphene dispersion, and barrier film using the same - Google Patents

Abstract

Dispersing the graphene oxide powder in a first solvent to prepare a graphene oxide aqueous dispersion, and reducing the graphene oxide aqueous dispersion to form reduced graphene oxide. Provided are a graphene-polymer composite manufacturing method using the graphene dispersion prepared by the graphene dispersion manufacturing method, and a barrier film manufacturing method prepared according to the graphene-polymer composite manufacturing method.

Description

Graphene dispersion and graphene-polymer composite manufacturing method, and barrier film manufacturing method using the same

It relates to a graphene dispersion and a method for manufacturing a graphene-polymer composite, and a method for manufacturing a barrier film using the same.

Graphene has a two-dimensional carbon atomic plane structure in which carbon atomic layers are tightly packed in a hexagonal lattice point plane. Graphene has 311 times stronger tensile strength than steel, 1,000 times faster electron mobility than silicon, 10 times better thermal conductivity than copper, transparent enough to pass 98% of light, and has properties even when bent or stretched. Since this property is maintained, it can be widely used in other nanomaterials, inks, heat dissipation materials, ultra-light materials, energy electrode materials, next-generation semiconductors, and transparent electrodes.

In addition, graphene has a barrier property that blocks the penetration of even small-sized helium. Recently, by using these properties of graphene, it is used in barrier films together with polymers having excellent oxygen and moisture barrier properties, such as polyethylene, polypropylene, and polyvinylidene chloride.

In the case of the conventional method of manufacturing a graphene barrier film, a dispersion such as graphene oxide or reduced graphene oxide is mixed with a polymer solution and coated. When the reduced graphene oxide dispersion and the non-aqueous polymer solution are mixed, if the polar solvent in the reduced graphene oxide dispersion is not completely removed, there is a problem in that the dispersibility of graphene in the reduced graphene oxide/polymer composite solution is reduced, and this Therefore, the demand for a barrier film having excellent oxygen and moisture barrier properties is not met.

Accordingly, there is an increasing demand for a method for manufacturing a barrier film that can solve the problem of lowering the dispersibility of the reduced graphene oxide.

One embodiment is to provide a method for preparing a graphene dispersion having excellent dispersibility and a method for preparing a graphene-polymer composite using the same.

Another embodiment is to provide a method for preparing a barrier film having excellent oxygen barrier properties and improved light transmittance using a method for preparing a graphene-polymer composite.

One embodiment comprises the steps of dispersing graphene oxide powder in a first solvent to prepare an aqueous dispersion of graphene oxide, and removing the first solvent, mixing the graphene oxide aqueous dispersion with a second solvent , It provides a graphene dispersion preparation method comprising the steps of reducing the graphene oxide aqueous dispersion, and preparing a reduced graphene oxide comprising the steps of purifying the reduced graphene oxide aqueous dispersion.

The first solvent may be distilled water or alcohol, and the second solvent may be a basic solvent having a pH of 8 or higher.

The second solvent is dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone, NMP), dimethylacetamide (Dimethylacetamide, DMAC), and dimethylformamide (Dimethylformamide) , DMF) may include at least one of.

The step of dispersing the graphene oxide in the first solvent may be dispersing with a homogenizer at 6,000 rpm for 1 hour.

The concentration of the graphene oxide aqueous dispersion dispersed in the first solvent may be 1 mg/mL.

The reducing of the graphene oxide aqueous dispersion may be reduced by heating the graphene oxide aqueous dispersion to a temperature of 100° C. or higher.

The removing of the first solvent may include removing the supernatant by a centrifugation process.

The step of purifying the reduced graphene oxide aqueous dispersion may include removing moisture through distillation under reduced pressure at a temperature of 80° C. or higher.

Another embodiment is dissolving a polymer resin in a third solvent to prepare a polymer resin solution, mixing the polymer resin solution and the graphene dispersion prepared according to one embodiment to prepare a mixed solution, and the mixing It provides a method for producing a graphene-polymer composite comprising the step of dispersing the solution.

In the mixed solution, a weight ratio of the polymer resin solution and the graphene dispersion may be 2:1 to 10:1.

The third solvent is a solvent different from the second solvent, and the third solvent is tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (N- Methyl-2-Pyrrolidone, NMP), dimethylacetamide (Dimethylacetamide, DMAC), and may include at least one of methylethylketone (Methylethylketone, MEK).

The polymer resin is polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), ethylene vinyl alcohol (EVOH), polyacrylonitrile (Polyacrylonitrile, PAN), and polychloro It may include at least one of trifluoroethylene (Polychlorotrifluoroethylene, PCTFE).

Another embodiment provides a method for producing a barrier film comprising the step of coating and drying the graphene-polymer composite prepared according to the embodiment on a base film.

The graphene-polymer composite may be coated on the base film to a thickness of about 1 μm to about 40 μm.

The base film is polyethylene terephthalate (Polyethyleneterephthalate, PET), polyethylene (Polyethylene, PE), polypropylene (Polypropylene, PP;), polycarbonate (Polycarbonate, PC), polymethyl methacrylate (Polymethyl methacrylate, PMMA), poly Polyimide (PI), Oriented Polypropylene (OPP), Biaxially oriented Polypropylene (BOPP), Polyethylene 2,6-dicarboxyl naphthalate (PEN) , and may include at least one of polyethersulfone (PES), polyester (Polyester), and polystyrene (PS).

The details of other implementations are included in the detailed description below.

The graphene dispersion preparation method according to an embodiment and the graphene-polymer composite preparation method using the same have excellent dispersibility and are stable.

In addition, by coating the graphene-polymer composite prepared by the above method on the film, it is possible to prepare a barrier film having improved oxygen barrier properties and light transmittance.

1 is a graph showing the dispersion stability of graphene dispersions prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 3 according to an embodiment.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Further, when a layer is referred to as being “on” (“on”) another layer or substrate, it may be formed directly on (on) another layer or substrate, or a third layer may be interposed therebetween. . Parts indicated with like reference numerals throughout the specification refer to like elements.

One embodiment is a method for preparing a graphene dispersion, comprising the steps of dispersing graphene oxide powder in a first solvent to prepare an aqueous dispersion of graphene oxide, and reducing the aqueous dispersion of graphene oxide to form reduced graphene oxide includes steps.

The graphene oxide aqueous dispersion preparation method according to an embodiment has a simple process and can be performed under stable conditions, so it can be suitable for mass production, and above all, it is possible to prepare a graphene dispersion with excellent dispersibility.

The graphene oxide powder may include a method of oxidizing graphene by a known method, such as a Hummers method or a Brodie method.

Then, the graphene oxide powder prepared by the known method is dispersed in a first solvent to prepare an aqueous dispersion of graphene oxide.

The step of dispersing the graphene oxide in the first solvent may be a step of adding the graphene oxide powder to the first solvent and dispersing using ultrasonic waves, a high-pressure disperser, a homogenizer, or the like. For example, in order to prevent graphene destruction due to repeated dispersion process application, it may be dispersed at about 6,000 rpm for about 1 hour using a homogenizer.

The first solvent may be a polar solvent such as distilled water or alcohol, but is not limited thereto. For example, the first solvent according to an embodiment may be distilled water.

The concentration of the graphene oxide aqueous dispersion prepared as described above is about 1 mg/mL.

Thereafter, by reducing the graphene oxide aqueous dispersion, a reduced graphene oxide is prepared.

In order to prepare the reduced graphene oxide, first, the first solvent is removed from the prepared graphene oxide aqueous dispersion, and the second solvent is mixed. In one embodiment, in order to remove the first solvent, the supernatant of the graphene oxide aqueous dispersion may be removed by a centrifugation process of about 8,000 rpm or more.

A second solvent is mixed with the graphene oxide aqueous dispersion remaining after removing the first solvent. In one embodiment, the second solvent is a basic solvent having a pH of 8 or higher.

As such, in one embodiment, mixing the basic solvent with the aqueous dispersion of graphene oxide is to activate the repulsive force of functional groups having a negative charge on the surface of the graphene oxide in the basic solvent. That is, it is to prevent the dispersing power of graphene oxide from being lowered.

For example, in one embodiment, the graphene oxide is first dispersed in a polar solvent such as water or ethanol, which is a solvent having the best dispersibility, and then the graphene-polymer complex is formed in an aqueous dispersion of graphene oxide with a secured basicity. A second solvent, which is a solvent, is mixed.

For example, the second solvent is dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone, NMP) dimethylacetamide (Dimethylacetamide, DMAC), and dimethylform It may include at least one of amide (Dimethylformamide, DMF), but is not limited thereto.

On the other hand, the amount of the second solvent used according to the embodiment is not particularly limited, and the amount of the second solvent may be appropriately adjusted according to the content of the third solvent to be added during the production of the graphene-polymer composite thereafter.

After mixing the second solvent in the aqueous dispersion of graphene oxide, the aqueous dispersion of graphene oxide to which the second solvent is added is heated and stirred at a temperature of at least about 100° C. for about 4 hours to perform thermal reduction.

As such, unlike the reduction process using a conventional reducing agent, an additional process in which the residual reducing agent must be removed by performing the thermal reduction according to an embodiment is unnecessary.

Next, in order to remove the remaining amount of the first solvent that may exist in the reduced graphene oxide mixed solution, the step of purifying the reduced graphene oxide aqueous dispersion may be further included. For example, it can be removed through a reduced pressure distillation method at a temperature of 80 °C or higher. Likewise, In one embodiment, there is no need for an additional process of purification by adding other additives in the prior art.

Another embodiment provides a method for preparing a graphene-polymer composite using the graphene dispersion prepared according to the above method.

In the graphene-polymer composite manufacturing method according to an embodiment, for the dispersion stability of graphene, a third solvent different from the first to second solvents used in preparing the graphene dispersion is used. In one embodiment, the dispersibility of the graphene dispersion can be improved by using a solvent used for preparing the graphene dispersion and a solvent used for dissolving the polymer differently.

First, a polymer resin is dissolved in a third solvent to prepare a polymer resin solution. The third solvent according to an embodiment is a solvent different from the second solvent, for example, the third solvent is tetrahydrofuran (THF); Dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone, NMP) may include at least one of dimethylacetamide (Dimethylacetamide, DMAC), but is limited thereto not.

Polymer resin according to one embodiment is polyvinylidene chloride (Polyvinylidene chloride, PVDC), polyvinyl alcohol (Poly vinyl alcohol, PVA), ethylene vinyl alcohol (Ethylene vinyl alcohol, EVOH), polyacrylonitrile (Polyacrylonitrile, PAN) , and polychlorotrifluoroethylene (PCTFE) It may include at least one of, but is not limited thereto.

In this case, the content of the polymer resin with respect to the total content of the third solvent is preferably about 40 wt% or less. When the polymer resin within the above range is mixed, the workability such as the preparation of the mixed solution of the graphene dispersion and the polymer resin and the coating property is excellent.

Thereafter, a mixed solution is prepared by mixing the graphene dispersion prepared as described above and the polymer resin solution, and the mixed solution is stirred. For example, the mixed solution may be stirred at room temperature for about 30 minutes. In addition, after the stirring step, the bubble removal process may be performed for about 5 minutes to about 20 minutes under the conditions of about 1,000 rpm to about 3,000 rpm.

In this case, the polymer resin solution and the graphene dispersion may be included in a weight ratio of about 2:1 to about 10:1. When the polymer resin solution and the reduced graphene oxide dispersion are mixed in the above range, the dispersibility is stable.

Another embodiment provides a barrier film manufacturing method using the graphene-polymer composite prepared according to the above manufacturing method.

In one embodiment, the graphene-polymer composite prepared as described above is coated on a base film and dried.

In the step of coating and drying the graphene-polymer composite on the base film, the film may be a film whose surface is coated with a urethane primer. When the graphene-polymer composite is coated on a film coated with a urethane primer (surface treatment), the reduced graphene oxide and the polymer resin coated on the film may not be easily peeled off due to improved adhesion. In addition, in order to improve adhesion, the film may be further subjected to a surface treatment such as plasma or corona.

The coating may be micro gravure coating, slot die coating, bar coating, spin coating, etc., but is not limited thereto.

The graphene-polymer composite may be coated on the base film to a thickness of about 1 μm to about 40 μm. It is possible to manufacture a barrier film excellent in both light transmittance and oxygen barrier properties of the film when it is coated to a thickness within the above range.

The drying may be performed in a vacuum oven, or may be dried using a heat gun or a hot plate, but the drying method is not limited thereto. For example, the drying step may be carried out at 60 to 120 for 2 hours to 5 hours.

The base film is polyethylene terephthalate (Polyethyleneterephthalate, PET), polyethylene (Polyethylene, PE), polypropylene (Polypropylene, PP;), polycarbonate (Polycarbonate, PC), polymethyl methacrylate (Polymethyl methacrylate, PMMA), poly Polyimide (PI), Oriented Polypropylene (OPP), Biaxially oriented Polypropylene (BOPP), Polyethylene 2,6-dicarboxyl naphthalate (PEN) , and may include at least one of polyethersulfone (PES), polyester (Polyester), and polystyrene (PS).

The barrier film manufacturing method according to the exemplary embodiment can provide a barrier film having excellent oxygen barrier properties and improved light transmittance.

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited by the following examples.

graphene Dispersion Preparation

production example One

Prepare graphene oxide powder prepared by Brodie's method.

After adding distilled water to the graphene oxide powder to prepare an aqueous dispersion of graphene oxide having a concentration of about 1 mg/mL, the graphene oxide was treated at 6,000 rpm for about 1 hour using a homogenizer. An aqueous dispersion was prepared.

Thereafter, in order to remove the remaining amount of water in the graphene oxide aqueous dispersion, the supernatant is removed using a centrifuge, and dimethyl sulfoxide (DMSO) is mixed and stirred at about 100° C. for about 4 hours to thermal reduction. proceeded.

The residual amount of water remaining in the reduced graphene oxide dispersion was removed through distillation under reduced pressure at about 80° C., thereby preparing a reduced graphene oxide dispersion.

Comparative Preparation Example One

After adding tetrahydrofuran (THF) as an organic solvent to the graphene oxide powder prepared in the same manner as in Preparation Example 1, at a concentration of about 1 mg/mL A graphene oxide dispersion was prepared by treatment at 6,000 rpm for about 1 hour using a homogenizer.

Comparative Preparation Example 2

After an alkyl group is formed on the surface of graphene oxide after acid treatment, it is added to tetrahydrofuran (THF), an organic solvent, and is about 1 at 6,000 rpm using a homogenizer at a concentration of about 1 mg/mL. A graphene oxide dispersion was prepared by treatment for about an hour.

Comparative Preparation Example 3

Graphene nanosheet (GnP, Graphene nano Platelet) was added to tetrahydrofuran (THF) as an organic solvent, A graphene dispersion was prepared by treatment at 6,000 rpm for about 1 hour at a concentration of about 1 mg/mL using a homogenizer).

Rating 1: graphene Dispersibility evaluation of dispersions

1 is a graph of measuring the dispersibility (TSI) of graphene dispersions prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 3 at room temperature for 1 day (24h) through Turbiscan.

1, it can be confirmed that the reduced graphene oxide dispersion of Preparation Example 1 according to an embodiment has very good dispersibility in the organic solvent tetrahydrofuran (THF), as compared to Comparative Preparation Examples 1 to 3 have. As the dispersibility is more stable, there is no change in the dispersibility value. Referring to FIG. 1 , in the graphene dispersion of Preparation Example 1, no large change in dispersibility with time is observed, so the organic solvent (THF) of Preparation Example 1 It can be seen that the dispersion is stable.

graphene -Manufacture of polymer complexes and barrier film manufacturing

Example One

Polyvinylidene chloride (PVDC) resin is added to THF and completely dissolved at 80° C. to prepare a polymer resin solution. Mixing the graphene dispersion of Preparation Example 1 with the polymer resin solution, After dispersing 5 times at a pressure of 500 bar using a high-pressure disperser equipment, a graphene-polymer composite was prepared.

At this time, the weight ratio of the PVDC resin solution and the graphene dispersion of Preparation Example 1 is about 1:0.2.

The graphene-polymer composite prepared as described above was bar-coated on a 125 μm PET film (surface treated with a urethane primer) to have a coating thickness of 5 μm, and dried at 90° C. for 3 hours to prepare a barrier film.

comparative example One

A barrier film was prepared in the same manner as in Example 1, except that the graphene dispersion of Preparation Example 1 was not used.

comparative example 2

A barrier film was prepared in the same manner as in Example 1, except that the graphene dispersion of Comparative Preparation Example 3 was used instead of the graphene dispersion of Preparation Example 1.

comparative example 3

Except that the weight ratio of the polymer resin solution and the graphene dispersion of Preparation Example 1 is about 1:0.05 A barrier film was prepared in the same manner as in Example 1.

comparative example 4

A barrier film was prepared in the same manner as in Example 1, except that the weight ratio of the polymer resin solution and the graphene dispersion of Preparation Example 1 was about 1:0.6.

Rating 2: barrier Evaluation of film properties

The barrier films prepared according to Example 1 and Comparative Examples 1 to 4 were measured for light transmittance based on ASTM E1164 using an NDH-7000 haze meter equipment, and the results are shown in Table 1 below.

In addition, the barrier films prepared according to Example 1 and Comparative Examples 1 to 4 were measured for oxygen permeability based on ASTM F1307 using Mocon's OX-TRAN 10X equipment, and the results are shown in Table 1 below.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Light transmittance (%) 92.5 89.27 90.19 - 90.23 oxygen permeability
(cc/m ² days) 1.12 1.34 1.15 - 0.69 coating thickness
(μm) 5 5 5 5 5

Referring to Table 1, when coated with the same thickness on the PET film as the base film, in Example 1 according to one embodiment, compared to Comparative Example 1 in which only PVDC was coated on the PET film, the oxygen permeability was about half or more decrease can be seen.

In addition, it can be confirmed that Comparative Example 2 containing nano graphene sheets (GnP) as a graphene dispersion has a light transmittance of less than 90% and a high oxygen transmittance, so it is not suitable as a barrier film.

In the case of Example 1 in which a graphene dispersion of an appropriate weight range, for example, 0.2% by weight, was added to the polymer resin solution according to one embodiment, compared with Comparative Example 3 in which only 0.05% by weight of the graphene dispersion was added, It can be seen that the oxygen barrier properties are very good.

On the other hand, in the case of Comparative Example 3 containing about 0.05% by weight of the graphene dispersion with respect to the polymer resin solution, it is not suitable as a barrier film due to high oxygen permeability, and Comparative Example 4 containing about 0.6% by weight of the graphene dispersion In the case of , it is impossible to prepare a barrier film because the graphene content is too high.

Through this, according to one embodiment, it is possible to implement a barrier film excellent in oxygen barrier properties while maintaining light transmittance of 90% or more.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (15)

Dispersing the graphene oxide powder in a first solvent to prepare a graphene oxide aqueous dispersion, and
removing the first solvent;
Mixing at least one of dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), and dimethylformamide (DMF) in the graphene oxide aqueous dispersion, a second solvent,
reducing the graphene oxide aqueous dispersion mixed with the second solvent, and
Preparing a reduced graphene oxide comprising the step of purifying the reduced graphene oxide aqueous dispersion,
A method for preparing a graphene dispersion comprising a. In claim 1,
The first solvent is distilled water or alcohol. delete In claim 1,
The step of dispersing the graphene oxide in the first solvent,
A method for preparing a graphene dispersion by dispersing it with a homogenizer at 6,000 rpm for 1 hour. In claim 1,
A method for preparing a graphene dispersion wherein the concentration of the aqueous dispersion of graphene oxide dispersed in the first solvent is 1 mg/mL. In claim 1,
The step of reducing the graphene oxide aqueous dispersion is,
A method for preparing a graphene dispersion by heating the graphene oxide aqueous dispersion to a temperature of 100° C. or higher. In claim 1,
The step of removing the first solvent,
A method for preparing a graphene dispersion by removing the supernatant by a centrifugation process. In claim 1,
The step of purifying the reduced graphene oxide aqueous dispersion,
A method for preparing a graphene dispersion to remove moisture through distillation under reduced pressure at a temperature of 80° C. or higher. Dissolving a polymer resin in a third solvent to prepare a polymer resin solution,
preparing a mixed solution by mixing the polymer resin solution with the graphene dispersion prepared in any one of claims 1, 2, and 4 to 8; and
dispersing the mixed solution;
A graphene-polymer composite manufacturing method comprising a. In claim 9,
A weight ratio of the polymer resin solution and the graphene dispersion in the mixed solution is 2:1 to 10:1. In claim 9,
The third solvent is a solvent different from the second solvent,
The third solvent is tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone, NMP), dimethylacetamide (Dimethylacetamide, DMAC) , And methyl ethyl ketone (Methylethylketone) graphene comprising at least one of - a polymer composite manufacturing method. In claim 9,
The polymer resin is polyvinylidene chloride (PVDC), polyvinyl alcohol (Poly vinyl alcohol, PVA;), ethylene vinyl alcohol (EVOH), polyacrylonitrile (Polyacrylonitrile, PAN), and poly Polychlorotrifluoroethylene (PCTFE) A graphene-polymer composite manufacturing method comprising at least one of The method for manufacturing a barrier film comprising the step of coating and drying the graphene-polymer composite prepared in claim 9 on a base film. In claim 13,
The graphene-polymer composite is a barrier film manufacturing method that is coated on the base film to a thickness of 1 μm to 40 μm. In claim 13,
The base film is polyethylene terephthalate (PET; polyethyleneterephthalate), polyethylene (PE; Polyethylene), polypropylene (PP; Polypropylene), polycarbonate (PC; polycarbonate), polymethyl methacrylate (PMMA; Poly (methyl methacrylate)) , polyimide (PI; polyimide), oriented polypropylene (OPP; Oriented Polypropylene), biaxially oriented polypropylene (BOPP; Biaxially oriented Polypropylene), polyethylene 2,6-dicarboxyl naphthalate (PEN; Polyethylene 2,6-dicarboxyl) naphthalate), polyethersulfone (PES; polyethersulfone), polyester (Polyester), or polystyrene (PS; Polystyrene) barrier film manufacturing method comprising at least one.

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