KR102078974B1 - Manufacturing method of carbon papers having excellent thermal conductivity and carbon papers manufactured therefrom - Google Patents

Abstract

According to the present invention, a method for manufacturing carbon paper having an excellent thermal conductivity can improve thermal conductivity of carbon paper by simply coating a thermal conductor on a surface of carbon fibers without complex or expensive additional factors. The method comprises: a first step of melting phenol resin solid content and thickeners in an alcohol-based solvent to manufacture a phenol resin melt solution; a second step of dispersing zinc oxide (ZnO) powders in the phenol resin melt solution; a third step of impregnating carbon fiber non-woven fabrics in the phenol resin melt solution having zinc oxide powders dispersed therein; a fourth step of drying the impregnated carbon fiber non-woven fabrics; a fifth step of carbonizing the dried carbon fiber non-woven fabrics and selectively placing a zinc oxide layer on a surface of the carbon fibers; and a sixth step of graphitizing the carbonized carbon fiber non-woven fabrics to coat the zinc oxide layer on the surface of carbon fibers.

Description

Manufacturing method of carbon paper having excellent thermal conductivity and carbon paper manufactured therefrom {MANUFACTURING METHOD OF CARBON PAPERS HAVING EXCELLENT THERMAL CONDUCTIVITY AND CARBON PAPERS MANUFACTURED THEREFROM}

The present invention relates to carbon paper having excellent thermal conductivity, and more particularly, to a method for producing carbon paper having excellent thermal conductivity in the surface direction (IN-PLANE) and a carbon paper prepared therefrom.

Carbon fiber is a material having excellent mechanical properties, and is generally composed of carbon fiber reinforced plastic (CFRP) together with a matrix resin. As CFRP, which is a substrate utilizing excellent mechanical properties of carbon fiber, is used in various ways, lightweight and high strength of existing materials are being achieved. In addition, there are also fields that use special properties such as X-ray permeability, electrical conductivity, and thermal conductivity of carbon fiber. A gas diffusion layer (GDL) of a fuel cell is a representative example of utilizing the functional characteristics of carbon fiber.

The fuel cell using the gas diffusion layer is an eco-friendly energy that uses electrical energy generated when oxygen ions and hydrogen ions are combined. The fuel cell can be used for electric power of one household or one building from small fuel cells installed in drones for automobiles and cargoes. Even large fuel cells to be produced are spread in various scales. Many substrates are used in such fuel cells, among which the gas diffusion layer functions to uniformly supply oxygen or hydrogen gas and discharge water, a byproduct of power generation. Since the gas diffusion layer requires excellent thermal conductivity, electrical conductivity and weather resistance, strength, fatigue resistance, and the like, carbon fibers having excellent strength, dimensional stability, and thermal and electrical characteristics are widely used as materials for the gas diffusion layer. At this time, because the gas or water must be permeated, the gas diffusion layer requires pores. Therefore, the carbon fiber is cut into a length of 6 to 50 mm, and then manufactured by using a wet nonwoven fabric.

When producing electricity, the gas diffusion layer is required to have high thermal conductivity in order to sufficiently discharge heat accumulated inside the fuel cell and to maintain an optimal power generation temperature. At this time, if the heat diffusion of the gas diffusion layer is not smooth, it also affects the water discharge, and thus the power generation condition is out of the optimum point, which greatly affects the efficiency of the fuel cell and the lifetime. Therefore, there is a need for a method of improving the thermal conductivity of the gas diffusion layer in order to improve the performance of the fuel cell.

However, the conventional technology requires a separate process for the basic carbon paper manufacturing process to improve the thermal conductivity, and the process is costly and time consuming because the process is such as vacuum deposition or plating to add a thermal conductor. Korean Unexamined Patent Publication No. 10-2017-0108474 relates to a method of manufacturing conductive carbon paper, and discloses carbon paper having excellent electrical conductivity and soft conductivity. However, the patent also increases the thermal conductivity and electrical conductivity by forming a conductive metal film by vacuum deposition, plating, or the like, and thus has a problem in that time and cost are increased. In addition, even if the additive is introduced through a relatively simple process, the effect of improving the thermal conductivity has a very insignificant problem.

Republic of Korea Patent Publication No. 10-2017-0108474

The present invention has been made to solve the above problems, the object of the present invention to improve the thermal conductivity of the carbon paper through a method that requires a relatively low time and cost to improve the performance in the field where the carbon paper is applied It is an object of the present invention to provide a method for producing carbon paper having excellent thermal conductivity and a carbon paper prepared therefrom.

Another object of the present invention is to provide a method for producing carbon paper having excellent thermal conductivity and a carbon paper manufactured therefrom, which can be expected to improve performance such as fuel cell efficiency as a gas diffusion layer of a fuel cell.

The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiments.

The above object is a first step of preparing a phenol resin melt by dissolving a phenol resin solids and thickener in an alcohol solvent, a second step of dispersing zinc oxide (ZnO) powder in the phenol resin melt, zinc oxide powder dispersed phenol resin A third step of impregnating the carbon fiber nonwoven fabric with the melt, a fourth step of drying the impregnated carbon fiber nonwoven fabric, a fifth step of carbonizing the dried carbon fiber nonwoven fabric to selectively place a zinc oxide layer on the surface of the carbon fiber, and carbonization It is achieved by a method of producing a carbon paper having excellent thermal conductivity, comprising a sixth step of graphitizing the carbon fiber nonwoven fabric to coat a zinc oxide layer on the surface of the carbon fiber.

Preferably, the thickener may include at least one or more of polyethylene oxide or polyvinyl alcohol.

Preferably, the first step is 0.01 to 0.2 parts by weight of a thickener composed of at least one of polyethylene oxide or polyvinyl alcohol and 100 parts by weight of an alcohol solvent composed of one or more of methanol, ethanol or isopropyl alcohol, and a phenol resin solid 5 It may be carried out by mixing to 30 parts by weight.

Preferably, the second step may be performed by mixing 5 to 25 parts by weight of zinc oxide powder and 0.05 to 0.5 parts by weight of an acid ester-based dispersant based on 100 parts by weight of an alcohol solvent in a phenol resin melt.

Preferably, zinc oxide (ZnO) is cyclic, the particle diameter may be 0.05 to 5㎛.

Preferably, the fifth step may be carried out by carbonizing the dried carbon fiber nonwoven fabric in an inert gas atmosphere at a temperature of 700 to 900 ℃.

Preferably, the sixth step may be performed by graphitizing the carbonized carbon fiber nonwoven fabric in an argon gas atmosphere at a temperature of 2300 to 2500 ° C.

Preferably, the carbon fiber nonwoven fabric may include at least one of PAN-based, rayon-based or pitch-based carbon fibers.

Preferably, the carbon fibers constituting the carbon fiber nonwoven fabric may have a diameter of 5 to 8 µm and a length of 3 to 30 mm.

Preferably, the basis weight of the carbon fiber nonwoven fabric may be 100 to 200 gsm, and the thickness may be 300 to 750 μm.

Preferably, the step is performed between the fourth step and the fifth step, and may further comprise the step of laminating the carbon fiber nonwoven fabric dried in the fourth step by two or more thermocompression bonding.

Preferably, the step is performed before the third step, it may further comprise the step of producing a carbon fiber nonwoven fabric comprising a carbon fiber and a binder using a wet papermaking method. At this time, preferably, the binder may be 5 to 20% by weight of the carbon fiber.

Moreover, the said objective is achieved by the carbon paper manufactured using the manufacturing method of the carbon paper excellent in the above-mentioned thermal conductivity.

Preferably, the carbon paper may contain 5 to 30% by weight of zinc oxide carbon fiber.

According to the present invention, zinc oxide (ZnO) powder, which is a thermal conductor, is coated on a surface of carbon fiber to improve thermal conductivity inherent in carbon fiber, and zinc oxide is dispersed in a phenol resin composition without any additional process procedure. By producing the carbon paper, the thermal conductivity of the carbon paper can be improved by only a simple process.

In addition, in the present invention, the zinc oxide may be disposed on the carbon fiber nonwoven fabric using a thickener and a dispersant to further improve the thermal conductivity of the carbon paper.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a flowchart of a method of manufacturing carbon paper having excellent thermal conductivity according to an embodiment of the present invention.
2A is a view taken by SEM of the carbon fiber nonwoven fabric prepared in step S104 of FIG. 1, FIG. 2B is a view taken of SEM of the carbon fiber nonwoven fabric prepared in step S105 of FIG. 1, and FIG. A drawing of the carbon fiber nonwoven fabric prepared in step S106 by SEM.
3A is a diagram showing a temperature-time diagram of the precarbonization process of Example 1. FIG.
3B shows a temperature-time diagram of the graphitization process of Example 1. FIG.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are only presented by way of example only to more specifically describe the present invention, it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples. .

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right over" but also when there is another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Also, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

1 is a flowchart of a method of manufacturing carbon paper having excellent thermal conductivity according to an embodiment of the present invention.

Referring to FIG. 1, in the method of preparing carbon paper having excellent thermal conductivity according to an embodiment of the present invention, a first step (S101) of preparing a phenol resin melt and a second step of dispersing zinc oxide powder in a phenol resin melt are performed. (S102), a third step of impregnating a carbon fiber nonwoven fabric with zinc oxide dispersed phenol resin melt (S103), a fourth step of drying the impregnated carbon fiber nonwoven fabric (S104), and a carbonizing non-woven carbon fiber nonwoven fabric A fifth step (S105) and a sixth step (S106) for graphitizing the carbonized carbon fiber nonwoven fabric.

Carbon paper produced through such a manufacturing method can improve the thermal conductivity of the carbon paper by using a material having better thermal conductivity than the carbon fiber, in particular by arranging and coating zinc oxide having excellent thermal conductivity on the surface of the carbon fiber To improve the in-plane thermal conductivity of carbon paper. In addition, the above process may be implemented by adding zinc oxide to the phenol resin in a general carbon paper manufacturing process without any additional process.

First, in the first step (S101) of preparing a phenol resin melt, a phenol resin solid and a thickener are dissolved in an alcohol solvent to prepare a phenol resin melt. More specifically, a phenol resin melt may be prepared by mixing a thickener and a phenol resin solid composed of at least one of polyethylene oxide or polyvinyl alcohol with respect to an alcohol solvent composed of one or more of methanol, ethanol or isopropyl alcohol.

In general, the resin used to prepare carbon paper is a phenol resin. Phenolic resins selected from at least one of novolac or resol type are most commonly used for the production of CARBON-CARBON composites (CC COMPOSITES), such as carbonization efficiency of up to 60% when heated at high temperature in an atmosphere purged with an inert gas. It is resin which becomes. When the phenol resin is carbonized, a carbon structure having a three-dimensional shape made only of the bonds between carbon atoms can be obtained. In the present invention, the carbon fiber nonwoven fabric is impregnated with the phenol resin and then calcined (carbonized and graphitized) to produce carbon paper. .

In the present invention, a phenol resin composed of at least one of novolac or resol type is diluted with an alcohol composed of at least one of methanol, ethanol or isopropyl alcohol. At this time, rather than using alcohol alone, a thickener is added to ensure dispersion stability of the zinc oxide powder to be described later. Polyethylene oxide (PEO) or polyvinyl alcohol (PVA) is used as a thickener because it can be effectively melted in an alcohol solvent to increase the viscosity. In addition, the content of polyethylene oxide (PEO) or polyvinyl alcohol (PVA) is preferably used in 0.01 to 0.2 parts by weight of 100 parts by weight of the alcohol solvent. If the content of the thickener is less than 0.01 parts by weight, there is no thickening effect. If the content of the thickener is greater than 0.2 parts by weight, it is difficult to control the picking amount of the phenol resin and bubbles in the impregnation process after carbon nonwoven fabric impregnation. It is undesirable because it can act as a defect on the paper.

Although the phenol resin is diluted and used in the alcohol solution containing such a thickener, it is preferable to use 5 to 30 weight part of phenol resin solids in 100 weight part of alcohol solvents. If the content of solid phenolic resin is less than 5 parts by weight, the amount picked during carbon fiber nonwoven impregnation decreases. As a result, the function of concentrating the carbon fiber is reduced, resulting in lowered physical properties such as strength and rigidity of the carbon paper substrate, thermal conductivity and electricity. Can cause a decrease in conductivity. In addition, when the content of the phenol resin solid content exceeds 30 parts by weight, the carbon fiber nonwoven fabric is picked up excessively during the impregnation, resulting in loss of material and energy in the post-impregnation process, and the thickness of the carbon paper becomes excessively thick. And limitations in the field of application. In particular, when the carbon paper according to the present invention is used in the gas diffusion layer (GDL) when the content of the phenol resin solids exceeds 30 parts by weight, gas or moisture cannot be discharged, which causes a problem in function.

Next, in the second step S102 of dispersing the zinc oxide powder in the phenol resin melt, the zinc oxide powder and the acid ester dispersant are mixed with the phenol resin melt in the first step S101.

In the present invention, zinc oxide is used as the metal oxide having excellent thermal conductivity. Zinc oxide has a thermal conductivity of 60 to 100 W / mK, which is superior to that of general carbon fibers, and thus improves thermal conductivity compared to conventional carbon paper. The zinc oxide has a melting point of 800 ° C. In the step S106).

Zinc oxide used in the present invention may be provided as a powder (particles) of several μm or less, and preferably used in the form of a cyclic (spherical) particle size of 0.5 to 5 μm. If the particle diameter is less than 0.5㎛ the zinc oxide particles are aggregated together in the process of supplying the zinc oxide powder, and if more than 5㎛ the efficiency of being selectively disposed on the surface of the carbon fiber having a diameter of the filament 7㎛ level. In addition, when zinc oxide is in the form of a rod, fiber, or flake that is not cyclic, the fluidity between the dense carbon fibers is inferior, so that zinc oxide is preferably cyclic.

In the present invention, the carbon fiber nonwoven fabric is made of carbon paper after the impregnation in the phenolic resin solution through a firing process. At this time, the thermal conductivity of the carbon fiber used is 10W / mK in the longitudinal direction, since short fibers of 3 to 30mm are used in the present invention, zinc oxide is coated on the surface of the carbon fiber in order to improve the thermal conductivity of the carbon fiber.

Zinc oxide is dispersed and applied to the phenol resin solution in a powder state, which is picked together with the phenol resin while impregnating a carbon fiber nonwoven fabric in step S103 described later. At this time, the zinc oxide used is preferably 5 to 25 parts by weight based on 100 parts by weight of the alcohol solvent contained in the phenol resin melt of the first step (S101). If the content of zinc oxide is less than 5 parts by weight, the thermal conductivity of carbon fiber will increase less. If it is more than 25 parts by weight, the aggregation of zinc oxide will occur and the probability of being selectively placed on the surface of carbon fiber will be reduced. The effect of lowering the thermal conductivity increase may be generated.

In addition, an acid ester-based dispersant may be used in the phenol resin solution in which the zinc oxide powder is dispersed, for stable dispersion of zinc oxide. In the present invention, it is preferable that the acid ester-based dispersant is contained 0.05 to 0.5 parts by weight based on 100 parts by weight of the alcohol solvent contained in the melt of the phenol resin of the first step (S101). When the amount of the acid ester-based dispersant is less than 0.05 parts by weight, the function as a dispersant is insignificant, and when it is more than 0.5 parts by weight, it may generate bubbles in the solution or act as an impurity in the manufacture of carbon paper. It is desirable to.

The method may further include preparing a carbon fiber nonwoven fabric by a wet papermaking method before performing the third step described below. Using wet papermaking method for the carbon fiber and the binder, a wet carbon fiber nonwoven fabric may be prepared and used as the carbon fiber nonwoven fabric in step S103. Specific description of the carbon fiber nonwoven fabric will be described together in step S103 described later.

Next, in the third step (S103) of impregnating the carbon fiber nonwoven fabric with the zinc oxide-dispersed phenol resin melt, the carbon oxide nonwoven fabric is impregnated with the zinc oxide-dispersed phenol resin melt, and the zinc oxide is combined with the phenol resin. Picked on a nonwoven fabric. At this time, the amount of zinc oxide picked after impregnating the carbon fiber nonwoven fabric is preferably 10 to 30% by weight relative to 100 weight of the carbon fiber in terms of dispersion in the carbon paper and improvement of thermal conductivity. If the amount of zinc oxide picked is less than 10% by weight, the thermal conductivity increase of carbon fiber is small, and if it exceeds 30% by weight, aggregation between the zinc oxide particles may occur, which may act as a defect in the carbon paper.

As the carbon fiber used in the present invention, any one or more carbon fibers of PAN, rayon, and pitch systems may be used. At this time, the filament diameter of the carbon fiber is 5 to 8㎛ and the shape of chopped to a length of 3 to 30mm is preferred. If the filament diameter of the carbon fiber is less than 5㎛, the length is longer than the thickness, which is disadvantageous in the water dispersion, and if it exceeds 8㎛, the density of the nonwoven fabric is reduced, and the balance between the strength, thermal conductivity, and porosity of the carbon paper is broken down. There is a problem that physical properties are not expressed.

In this case, when the length of the carbon fiber is less than 3 mm, the denseness of the carbon fiber resin paper is excessively increased, and the porosity of the carbon paper falls, which may not be smooth when gas and water are discharged when the carbon paper is used as the gas diffusion layer. In addition, when the thickness exceeds 30 mm, the fibers are intertwined with each other during formation of the sheet, which may inhibit even dispersion, which is not preferable because the variation of physical properties increases for each position of the carbon paper surface.

In addition, it is preferable to use the nonwoven fabric manufactured by the wet papermaking method as carbon fiber. At this time, at least one or more of the low-melting-point PET fiber (LM company) and PVA fiber cut to 6mm length is used as a binder to compensate for the binding force of the carbon fiber nonwoven fabric, and the amount of the binder is 5 to 20% by weight of the carbon fiber constituting the nonwoven fabric. It is preferable.

Next, in the fourth step (S104) of drying the impregnated carbon fiber nonwoven fabric, the remaining solvent is dried in the impregnated carbon fiber nonwoven fabric. At this time, the drying temperature is preferably 100 to 140 ℃. If the drying temperature is less than 100 ℃ the residual solvent is not sufficiently dried, if the temperature exceeds 140 ℃ has a problem that may cause a fire due to the solvent.

At this time, the final basis weight of the carbon fiber nonwoven fabric is preferably 100 to 200 gsm based on the carbon fiber, the thickness is preferably 300 to 750㎛. When the thickness of the carbon fiber nonwoven fabric is less than 300㎛, the physical properties of the carbon paper is insufficient, and when it is used as the gas diffusion layer when the thickness of more than 750㎛ may not smooth the movement of gas and moisture can reduce the performance of the fuel cell.

Therefore, if the basis weight and thickness of the carbon fiber nonwoven fabric do not satisfy the above-mentioned range, the step of laminating the carbon fiber nonwoven fabric dried in the fourth step by thermocompression bonding between the fourth step and the fifth step is further performed. It may include. In this case, by stacking two or more sheets of the dried carbon fiber nonwoven fabric prepared in the fourth step by applying heat and pressure, it is possible to determine the carbon paper thickness after the firing process (S105, S106) to be described later.

Next, in the fifth step S105 of carbonizing the dried carbon fiber nonwoven fabric and the sixth step S106 of graphitizing the carbonized carbon fiber nonwoven fabric, the carbon fiber nonwoven fabric impregnated with phenol resin mixed with zinc oxide is calcined. Carbon paper is prepared.

First, a fifth step S105 of carbonizing a dried carbon fiber nonwoven fabric, which is a pre-carbonization process performed before graphitization, is performed. In this case, in order to block the combustion of the phenol resin, it is preferable to carry out purging the inside of the carbonization furnace at a flow rate of 90 L / min with nitrogen (N ₂ ) or argon (Ar) gas, which is an inert gas. The temperature of the inert gas atmosphere is preferably less than 1000 ° C, more preferably 700 to 900 ° C. If the temperature of the inert gas atmosphere is less than 700 ℃ there is a problem that a large number of atoms other than carbon can remain, and if it exceeds 900 ℃ has a problem that pyrolysis and intact carbonization of the inert gas is impossible.

Zinc oxide particles are selectively disposed on the surface of the carbon fiber in the step S105, which is a total carbonization process, and may be selectively disposed because the thermal conductivity of the carbon fiber is better than that of the phenol resin and thus the fluidity is higher near the carbon fiber.

In addition, since the exhaust gas is generated as the phenol resin is thermally decomposed at step S105, which is a total carbonization process, a process of removing the exhaust gas may be further included. After the exhaust gas is discharged, the graphitization process (step S106) to be described later may minimize the impurities and maximize the carbonization yield of the phenol resin to improve the quality of the carbon paper. In addition, in the total carbonization process (step S105), the surface of the carbon paper may be uneven due to the exhaust gas discharge. In order to prevent the carbonization, the total carbonization process may be performed while pressing with a carbon coating film.

After finishing step S105 (total carbonization step), a sixth step S106 of graphitizing the carbonized carbon fiber nonwoven fabric which is a graphitization step is performed. In the sixth step, argon (Ar) gas is injected at a flow rate of 90 L / min to graphitize while purging the inside of the carbonization furnace. Nitrogen is not used because it is pyrolyzed at the temperature of the graphitization process. As for the temperature of a graphitization process, 2000 degreeC or more is preferable and 2300-2500 degreeC is more preferable. In particular, when the temperature of the graphitization process is less than 2300 ℃ hexagonal bonds between the carbon atoms are incomplete, there is a problem that the physical properties of the carbon paper is low, if the temperature exceeds 2500 ℃ there is a problem that the production cost of the carbon paper rapidly increases.

In step S106 (graphitization process), the totally carbonized phenol resin leaves almost completely carbon atoms, and the carbon atoms form a hexagonal structure and become close to graphite. In addition, zinc oxide disposed on the surface of the carbon fiber is melted above the melting point (800 ° C.) and coated on the surface of the carbon fiber. The thickness of the carbon paper completed until the graphitization process (step S106) is reduced to 200 to 500 µm, which is a phenomenon caused by the reduction of the volume while removing components other than carbon atoms from the phenol resin through total carbonization and graphitization.

2A is a view taken by SEM of the carbon fiber nonwoven fabric prepared in step S104 of FIG. 1, FIG. 2B is a view taken of SEM of the carbon fiber nonwoven fabric prepared in step S105 of FIG. 1, and FIG. A drawing of the carbon fiber nonwoven fabric prepared in step S106 by SEM.

2A to 2C, in FIG. 2A, in which the carbon fiber nonwoven fabric dried in step S104 is taken with an SEM, the phenol resin 110 is impregnated between the carbon fibers 100 and dispersed in the phenol resin 110. It can be seen that the zinc oxide particles 120 are attached to the surface of the carbon fiber 100. Next, in FIG. 2B, the carbon fiber nonwoven fabric carbonized in step S105 is SEM, and the phenol resin 110 impregnated between the carbon fibers 100 exists as carbonized phenol resin 111 in step S105. Able to know. Next, in FIG. 2C, in which the graphitized carbon fiber nonwoven fabric is SEM photographed in step S106, zinc oxide is melted on the surface of the carbon fiber 100 so that the zinc oxide 121 coated on the surface of the carbon fiber 100 is present. It can be seen that.

In the present invention, by coating zinc oxide on the surface of the carbon fiber through the above steps, there is provided a method for producing carbon paper having excellent thermal conductivity than conventional carbon paper, and the carbon paper produced accordingly.

Hereinafter, the configuration and effects of the present invention will be described in more detail with reference to Examples and Comparative Examples. However, this embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

EXAMPLE

Example 1

1-1. Carbon Fiber Nonwoven Fabric

First, a carbon fiber nonwoven fabric was prepared in the following order.

The carbon fiber was cut into 6 mm length of PANEX-35 non-sizing manufactured by Zoltek, and the binder used was 6 mm length LM PET fiber manufactured by Toray Chemical. The binder fiber was applied to 10% by weight of the carbon fiber, wet paper was prepared by the batch wet paper manufacturing apparatus of the Korea Fiber Research Institute. The wet paper was dried using a drum dryer heated to 130 ° C. in order to improve moisture removal and adhesion between fibers after manufacturing. At this time, the basis weight of the sheet was selected by the carbon fiber nonwoven fabric of 40 gsm by Experimental Example 1 to be described later, using the selected carbon fiber nonwoven fabric cut into a square sheet of 0.01 m ² width following the procedure (1-2 to 1 to 1) -6) was performed.

1-2. Preparation of Phenolic Resin Solution

First, 0.1 parts by weight of PVA was added to 100 parts by weight of ethanol and stirred for 30 minutes using an impeller. Thereafter, 10 parts by weight of phenol resin was added and further stirred for 30 minutes. At this time, PVA used PVA 2288 of KURARAY, and N-3337 of Gangnam Hwaseong was used for phenol resin.

1-3. Preparation of Zinc Oxide Dispersion

Zinc oxide powder (Sigma Aldrich Korea) and DISPERBYK-180 (by BYK Co., Ltd., all DISPERBYK series are manufactured by BYK Co., Ltd.) as an acid ester-based dispersant were added to the phenol resin solution prepared in 1-2, and further stirred for 30 minutes. . At this time, 5 parts by weight of zinc oxide was used in 100 parts by weight of ethanol, 0.1 parts by weight of dispersant.

1-4. Impregnating carbon fiber nonwoven fabric with zinc oxide dispersion

The carbon fiber nonwoven fabric prepared in 1-1 was first immersed in a zinc oxide dispersion prepared in 1-3 for 3 seconds, and then first dried on a net made of SUS 304 material having a 2 mm spacing. The primary drying was carried out until the drops of the zinc oxide dispersion did not fall off, and after completion of the primary drying, the resultant was dried in an oven at 120 ° C. for 60 minutes.

1-5. Impregnation, Lamination of Dried Carbon Fiber Nonwovens

After impregnation at 1-4, the dried carbon fiber nonwoven fabric was heat-pressed and laminated. At this time, three carbon fiber nonwoven fabrics were laminated and treated at 150 ° C. under 1.5 MPa for 30 minutes. The phenol resin which flowed out of the carbon fiber nonwoven fabric after the treatment was scraped off using scissors or the like.

A 120 gsm sample was prepared in which three square carbon fiber nonwoven fabrics having a basis weight of 40 gsm and a width of 0.01 m ² impregnated with phenol resin and zinc oxide were laminated.

1-6. Firing process (carbon paper manufacturing)

The carbon fiber nonwoven fabric prepared in 1-5 was placed in a high temperature furnace and subjected to total carbonization. At this time, the nitrogen (N ₂ ) gas was carried out while purging at a flow rate of 90 L / min, the temperature was carried out at 850 ℃. The temperature rise rate was 5 ° C / min, the 850 ° C holding time was 6 hours, and after cooling to 200 ° C with the high temperature closed, after reaching 200 ° C, the carbon fiber was opened and the carbonization was completed. The nonwoven fabric was taken out and cooled to 30 ° C at room temperature. At this time, in order to prevent the surface from being bumpy due to the generation of exhaust gas, the carbon coating film was placed on a carbon fiber nonwoven fabric and subjected to total carbonization. The temperature-time diagram of the precarbonization process is shown in FIG. 3A.

The graphitization process was performed after total carbonization. At the time of graphitization, the inside of the ultrahigh temperature furnace was purged with argon (Ar) gas at a flow rate of 90 L / min, and the temperature was performed at 2400 ° C. Temperature rise rate was 5 ℃ / min, 2400 ℃ holding time is 30 minutes, then after cooling to 200 ℃ with the ultra-high temperature closed, after reaching the 200 ℃, the door of the ultra-high temperature to finish the graphitized carbon paper Take out and cooled to 30 ℃ at room temperature to prepare a carbon paper. The temperature-time diagram of the graphitization process is shown in Figure 3b.

Example 2

Carbon paper was prepared in the same manner as in Example 1, except that 0.1 part by weight of PEO was used instead of PVA.

Example 3

Carbon paper was prepared in the same manner as in Example 1 except that 0.1 parts by weight of DISPERBYK-102 was used instead of DISPERBYK-180.

Example 4

Carbon paper was prepared in the same manner as in Example 2 except that 0.1 parts by weight of DISPERBYK-102 was used instead of DISPERBYK-180.

Example 5

Carbon paper was prepared in the same manner as in Example 1, except that 0.1 parts by weight of DISPERPLAST-1150 was used instead of DISPERBYK-180.

Example 6

Carbon paper was prepared in the same manner as in Example 2 except that 0.1 parts by weight of DISPERPLAST-1150 was used instead of DISPERBYK-180.

[Comparative Example]

Comparative Example 1

Carbon paper was prepared in the same manner as in Example 1 except that PVA, zinc oxide powder, and DISPERBYK-180 were not used.

Comparative Example 2

Carbon paper was prepared in the same manner as in Example 1 except that PVA and DISPERBYK-180 were not used.

Comparative Example 3

Carbon paper was prepared in the same manner as in Example 1 except that the DISPERBYK-180 was not used.

[Comparative Example 4]

Carbon paper was prepared in the same manner as in Example 1 except that 0.03 parts by weight of DISPERBYK-180 was used.

[Comparative Example 5]

Carbon paper was prepared in the same manner as in Example 1 except that 0.6 parts by weight of DISPERBYK-180 was used.

Comparative Example 6

A carbon paper was prepared in the same manner as in Example 1 except that 0.1 parts by weight of PEO was used instead of PVA, and DISPERBYK-180 was not used.

Comparative Example 7

Carbon paper was prepared in the same manner as in Example 1 except that PVA was not used.

Comparative Example 8

Carbon paper was prepared in the same manner as in Example 1 except that 0.005 parts by weight of PVA was used.

Comparative Example 9

Carbon paper was prepared in the same manner as in Example 1, except that 0.3 parts by weight of PVA was used.

Comparative Example 10

Carbon paper was prepared in the same manner as in Example 1, except that 0.1 parts by weight of DISPERBYK-102 was used instead of DISPERBYK-180 without using PVA.

Comparative Example 11

Carbon paper was prepared in the same manner as in Example 1, except that 0.1 parts by weight of DISPERPLAST-1150 was used instead of DISPERBYK-180 without using PVA.

Comparative Example 12

Carbon paper was prepared in the same manner as in Example 1, except that 4 parts by weight of zinc oxide powder was used.

Comparative Example 13

Except for using 26 parts by weight of zinc oxide powder, carbon paper was prepared in the same manner as in Example 1.

The specifications of Examples 1 to 6 and Comparative Examples 1 to 13 are as disclosed in Table 1 below.

division ethanol Thickener Phenolic Resin Zinc oxide Dispersant content Kinds content content content Kinds content Example 1 100 PVA 0.1 10 5 DISPERBYK-180 0.1 Example 2 100 PEO 0.1 10 5 DISPERBYK-180 0.1 Example 3 100 PVA 0.1 10 5 DISPERBYK-102 0.1 Example 4 100 PEO 0.1 10 5 DISPERBYK-102 0.1 Example 5 100 PVA 0.1 10 5 DISPERPLAST-1150 0.1 Example 6 100 PEO 0.1 10 5 DISPERPLAST-1150 0.1 Comparative Example 1 100 - - 10 - - - Comparative Example 2 100 - - 10 5 - - Comparative Example 3 100 PVA 0.1 10 5 - - Comparative Example 4 100 PVA 0.1 10 5 DISPERBYK-180 0.03 Comparative Example 5 100 PVA 0.1 10 5 DISPERBYK-180 0.6 Comparative Example 6 100 PEO 0.1 10 5 - - Comparative Example 7 100 - - 10 5 DISPERBYK-180 0.1 Comparative Example 8 100 PVA 0.005 10 5 DISPERBYK-180 0.1 Comparative Example 9 100 PVA 0.3 10 5 DISPERBYK-180 0.1 Comparative Example 10 100 - - 10 5 DISPERBYK-102 0.1 Comparative Example 11 100 - - 10 5 DISPERPLAST-1150 0.1 Comparative Example 12 100 PVA 0.1 10 4 DISPERBYK-180 0.1 Comparative Example 13 100 PVA 0.1 10 26 DISPERBYK-180 0.1

Physical properties of the carbon paper according to Examples 1 to 6 and Comparative Examples 1 to 13 were measured by the following experimental examples, and the results are shown in Table 2.

Experimental Example

(1) Carbon fiber nonwovens basis weight measurement

The basis weight of the carbon fiber nonwoven fabric prepared in 1-1 was measured by the following procedure.

1) Cut the carbon fiber nonwoven into 0.01 m ² squares. Area of carbon fiber nonwoven fabric: A (m ² )

2) Measure the mass of the carbon fiber nonwoven fabric cut in step 1). (W ₁ (g))

3) Thermally decompose the binder material by heat treatment at 450 DEG C for 15 minutes in a purged N ₂ furnace.

4) Cool the carbon fiber nonwoven fabric remaining after pyrolysis in step 3) below 30 ℃, and measure the mass. (W ₂ (g))

5) Calculate the basis weight using Equation 1.

(2) Calculation of picked phenolic resin and zinc oxide after impregnation

After impregnating and drying the carbon fiber nonwoven fabric in 1-4 and laminating by heat pressing at 1-5, the mass of the picked phenolic resin and zinc oxide was calculated by the following procedure.

1) Measure the mass of the sample which completed the lamination process (refer Example 1-5). (W _a (g))

2) The binder material and the phenol resin are burned and removed by heat treatment at 500 ° C. for 30 minutes in an air purged high temperature furnace.

3) After cooling the carbon fiber nonwoven fabric remaining after pyrolysis in step 2), the mass is measured. (W _b (g))

4) The mass of the carbon fiber nonwoven fabric used in Examples 1 to 6 and Comparative Examples 1 to 13 uses the W ₂ value measured in Experimental Example (1).

5) The ratio of the picked phenol resin is calculated using Equation 2.

6) Calculate the ratio of picked zinc oxide using Equation 3.

(3) thermal conductivity measurement

Density was measured using a hydrometer to measure the thermal conductivity of the carbon paper fired in 1-6. The hydrometer was measured using Sartorius' MSA255S-100-DA model using ethanol at 20 ° C. by the Aristotle method. In addition, specific heat was measured using DSC and substituted into the thermal conductivity calculation. DSC was measured using a Q2000 model from TA instruments.

Thermal conductivity was measured using the LFA 457 (laser type) equipment of NETZSCH, the thermal conductivity in the in-plane (thru plane) and the thickness direction (thru plane) was measured, respectively.

Table 2 shows the measured average values of the experimental examples for Examples 1 to 6 and Comparative Examples 1 to 13.

division Phenolic Resin
(wt%) Zinc oxide
(wt%) density
(g / cm ³ ) specific heat
(cal / g ℃) In-plane Thru plane Thermal diffusivity
(mm ² / sec) Thermal conductivity
(W / mK) Thermal diffusivity
(mm ² / sec) Thermal conductivity
(W / mK) Example 1 59.7 19.1 0.423 0.606 13.247 3.433 1.194 0.306 Example 2 59.5 18.5 0.398 0.613 13.360 3.236 1.653 0.403 Example 3 60.8 19.1 0.422 0.618 13.646 3.528 1.195 0.312 Example 4 59.7 18.1 0.397 0.610 12.961 3.139 1.651 0.401 Example 5 59.8 19.3 0.422 0.589 13.838 3.439 1.192 0.296 Example 6 60.1 18.8 0.394 0.598 12.774 3.040 1.650 0.393 Comparative Example 1 62.3 - 0.423 0.454 8.046 1.461 1.074 0.206 Comparative Example 2 61.9 21.1 0.387 0.538 9.668 2.000 1.179 0.248 Comparative Example 3 59.3 18.4 0.411 0.550 10.132 2.358 1.201 0.272 Comparative Example 4 58.9 19.2 0.433 0.599 11.884 3.082 1.088 0.282 Comparative Example 5 58.5 19.1 0.408 0.591 12.141 2.927 1.058 0.255 Comparative Example 6 60.3 17.4 0.400 0.567 10.121 2.295 1.529 0.347 Comparative Example 7 62.2 18.8 0.415 0.610 10.711 2.711 1.220 0.309 Comparative Example 8 61.5 18.6 0.424 0.589 10.996 2.746 1.013 0.253 Comparative Example 9 59.2 18.5 0.419 0.587 11.004 2.706 1.014 0.252 Comparative Example 10 62.2 18.8 0.410 0.612 10.056 2.553 1.220 0.310 Comparative Example 11 62.8 18.6 0.415 0.611 10.051 2.548 1.229 0.312 Comparative Example 12 59.6 17.6 0.416 0.600 12.335 3.079 1.155 0.288 Comparative Example 13 58.9 22.3 0.439 0.588 12.228 3.156 1.148 0.296

As can be seen from Table 2, as a result of applying both the thickener and the dispersant in Examples 1 to 6 according to the present invention, the thermal conductivity in the thickness direction is different from each other, the thermal conductivity in the plane direction compared to Comparative Examples 1 to 13 It can be seen that the increase, which is due to the application of thickeners and dispersants to improve the dispersion and stability of zinc oxide lead to the effect of increasing the thermal conductivity of the carbon paper. In particular, the thermal diffusion rate in the plane direction is remarkably increased, which is a result of zinc oxide being selectively disposed on the surface of the carbon fiber and effectively acting as a thermal conductor.

On the other hand, when comparing Comparative Example 1 and Comparative Example 2, it can be seen that the thermal conductivity in the surface direction slightly increased, but the width is very small to see the effect of the presence or absence of zinc oxide. However, it can be seen that Comparative Examples 3, 6, 7, 10, and 11 to which a thickener or a dispersant are applied have a larger increase in the in-plane thermal conductivity than Comparative Example 2.

Comparative Example 4 having a content of DISPERBYK-180, a dispersant, of 0.03 parts by weight, had a low thermal conductivity compared to Example 1 due to a slight dispersant, and thus a zinc oxide dispersion. Example 5 shows that the thermal conductivity is lower than that of Example 1 due to the excessive dispersant, the dispersant foams in the solution or acts as an impurity, resulting in poor dispersibility of zinc oxide.

Comparative Example 8, the content of PVA as a thickener is 0.005 parts by weight, the content of the thickener is too small to have a thickening effect, so zinc oxide is not picked sufficiently on the carbon fiber nonwoven fabric, so the thermal conductivity is lower than that of Example 1, the content of PVA as a thickener In Comparative Example 9, which is 0.3 parts by weight, it is difficult to control bubbles in the picking amount and impregnation process of the phenol resin due to excessive content of the thickener, and thus it can be seen that the thermal conductivity is lower than that in Example 1.

In Comparative Example 12 having a zinc oxide content of 4 parts by weight, the zinc oxide was too small, so that the thermal conductivity increase effect of zinc oxide was not properly expressed, and thus the thermal conductivity was lower than that of Example 1, and the zinc oxide content was 26 weight. In Comparative Example 13, zinc oxide was excessively contained, so that zinc oxide coagulation occurred and was not evenly disposed on the surface of the carbon fiber, and thus the thermal conductivity was lower than that in Example 1.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of right.

100: carbon fiber
110: phenolic resin
111: carbonized phenolic resin
120: zinc oxide particles
121: zinc oxide coated on carbon fiber surface

Claims (14)

A first step of preparing a phenol resin melt by dissolving a phenol resin solid and a thickener in an alcohol solvent;
Dispersing zinc oxide (ZnO) powder in the phenol resin melt;
A third step of impregnating a carbon fiber nonwoven fabric in the phenol resin melt in which the zinc oxide powder is dispersed;
A fourth step of drying the impregnated carbon fiber nonwoven fabric;
A fifth step of carbonizing the dried carbon fiber nonwoven fabric to selectively arrange a zinc oxide layer on the surface of the carbon fiber; and
A sixth step of graphitizing the carbonized carbon fiber nonwoven fabric to coat the zinc oxide layer by melting the zinc oxide powder on a carbon fiber surface;
Including;
The phenol resin melt is a mixture of 5 to 25 parts by weight of the zinc oxide powder and 0.05 to 0.5 parts by weight of the acid ester-based dispersant based on 100 parts by weight of the alcohol solvent, the carbon paper manufacturing method. The method of claim 1,
The thickener comprises at least one or more of polyethylene oxide or polyvinyl alcohol, method of producing a carbon paper. The method of claim 1,
The first step,
Carbon, a mixture of 0.01 to 0.2 parts by weight of a thickener composed of at least one of polyethylene oxide or polyvinyl alcohol and 5 to 30 parts by weight of phenol resin solids, to 100 parts by weight of an alcohol solvent composed of one or more of methanol, ethanol or isopropyl alcohol. Method of manufacturing paper. delete The method of claim 1,
The zinc oxide (ZnO) is cyclic, the particle diameter is 0.05 to 5㎛, the manufacturing method of the carbon paper. The method of claim 1,
The fifth step,
And carbonizing the dried carbon fiber nonwoven fabric in an inert gas atmosphere at a temperature of 700 to 900 ° C. The method of claim 1,
The sixth step,
And carbonizing the carbonized carbon fiber nonwoven fabric in an argon gas atmosphere at a temperature of 2300 to 2500 ° C. The method of claim 1,
The carbon fiber nonwoven fabric includes at least one or more of the PAN-based, rayon-based or pitch-based carbon fiber, the manufacturing method of the carbon paper. The method of claim 1,
The diameter of the carbon fibers constituting the carbon fiber nonwoven fabric is 5 to 8㎛, length is 3 to 30mm, the manufacturing method of the carbon paper. The method of claim 1,
The basis weight of the carbon fiber nonwoven fabric is 100 to 200gsm, the thickness is 300 to 750㎛, manufacturing method of carbon paper. The method of claim 1,
Carrying out between the fourth and fifth steps, laminating the carbon fiber nonwoven fabric dried in the fourth step by thermocompression bonding of two or more sheets;
Further comprising, the manufacturing method of the carbon paper. The method of claim 1,
A carbon fiber nonwoven fabric which is performed before the third step and comprises a carbon fiber and a binder using a wet papermaking method;
More,
The binder is 5 to 20% by weight of the carbon fiber, the manufacturing method of the carbon paper. The carbon paper produced by using any one of claims 1 to 3 and 5 to 12. The method of claim 13,
The carbon paper is a carbon paper containing zinc oxide 5 to 30% by weight of the carbon fiber.

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