KR20060005904A - Materials for shaping a separator of a fuel cell and the separator for the fuel cell made therefrom - Google Patents

Abstract

The present invention generally relates to improved molding materials for separators for fuel cells. More specifically, the present invention relates to a powder type molding material of a separator for fuel cells in which an antistatic agent powder is added to and mixed with a conductive carbon material, an epoxy resin, and a curing agent powder. The present invention also provides a fuel cell separator formed by using a fuel cell molding material in which a conductive carbon material, an epoxy resin, a curing agent, and an antistatic agent are finely ground, and then each powder is dry mixed and uniformly dispersed. . According to the molding material of the present invention, a separator for a fuel cell having high moldability at the same time as conductivity and mechanical strength is obtained.

Fuel cell, separator, molding material, conductive carbon material, epoxy resin, antistatic agent, hardener

Description

Molding material of fuel cell separator and fuel cell separator manufactured therefrom {MATERIALS FOR SHAPING A SEPARATOR OF A FUEL CELL AND THE SEPARATOR FOR THE FUEL CELL MADE THEREFROM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder type molding material capable of producing a separator for fuel cells, which contains powders such as conductive carbon materials, epoxy resins, and curing agents.

Fuel cells that obtain electric energy by electrochemical reactions between carbon and hydrogen are expected to be used as next-generation energy substitutes for petroleum and the like because they are environmentally friendly and can use raw materials indefinitely. In particular, the application of automobiles that do not emit exhaust gas to the atmosphere is in practical use.

As a conventional technique, Japanese Laid-Open Patent Publication No. 2001-335695 discloses 10 to 25% by weight of thermosetting resin, 70 to 85% by weight of graphite, and an average particle diameter of graphite to provide a thermosetting resin molding material having excellent moldability and conductivity. The thermosetting resin molding material which consists of 0.1-3 weight% of spherical silica which is 1/20 or less is proposed. As the manufacturing method, a method of uniformly mixing graphite, spherical silica, finely pulverized thermosetting resin and a release agent with a Henschel mixer is used. This mixed composition can be molded as it is, but in order to impart uniform conductivity and mechanical strength and the like, and to increase moldability, the mixed composition is crushed into a molding material. It is also possible to make it granular as needed.

As described above, this publication states that "graphite, spherical silica, finely pulverized thermosetting resin and a releasing agent are uniformly mixed with a Henschel mixer", but the mixed dispersion using this molding material is graphite, spherical silica, finely pulverized. Since the charge distribution of each material powder particle of a thermosetting resin and a mold release agent is not uniform, it is thought that it will be difficult to mix uniformly.

Accordingly, the present invention provides a molding material of a fuel cell separator having improved uniform mixing and dispersibility of conductive carbon materials, epoxy resins, hardeners, and the like, and thus, a fuel cell separator having improved conductivity, mechanical strength, formability, and the like. For the purpose of

In one aspect, the present invention provides a powder-shaped molding material for a separator for a fuel cell in which an antistatic agent is added to and mixed with a conductive carbon material, an epoxy resin, and a powder of a curing agent.

As a preferable specific example of such an aspect, the average particle diameter of each powder of an electroconductive carbon material, an epoxy resin, a hardening | curing agent, and an antistatic agent is 0.5-20 micrometers.

In another preferred embodiment, the angle of repose (fluidity) of the molding material powder of the separator is 15 to 30 degrees.

In another preferred embodiment, the apparent density of the molding material powder of the separator is from 0.05 to 0.55 g / cm 3.

As the conductive carbon material, it is possible to use one or more kinds of natural graphite such as flaky graphite and bulk graphite, artificial graphite, acetylene black and carbon black. The usage-amount can use 65-97 weight part. If the amount is less than 65 parts by weight, the conductivity of the separator is lowered. When the amount exceeds 97 parts by weight, the conductivity is high, but the mechanical strength of the separator is lowered. The preferred amount is 75 to 90 parts by weight.

As said epoxy resin, it is possible to use bisphenol-types, such as bisphenol-A type and bisphenol F-type, various novolak-type, a biphenyl type, and a biphenyl ether type. Especially, what can be powdered in a solid phase is preferable. The usage-amount can use 5-35 weight part. If the amount is less than 5 parts by weight, the mechanical strength of the separator is lowered. If the amount exceeds 35 parts by weight, the conductivity of the separator is lowered. The preferred amount is 10 to 20 parts by weight.

It is possible to use an acid anhydride type, an amine type, and a phenol type as a hardening | curing agent. Considering the heat resistance of the molded article, novolak-type phenolic resin is preferable. Especially, what can be powdered in a solid phase is good. The usage-amount can use 5 to 70% with respect to an epoxy resin. If the amount used is less than 5%, the curing is insufficient, and if the amount exceeds 70%, the curing becomes easy and the use time is shortened, making the work easier. The preferred amount is 20-50%.

As the curing accelerator, it is possible to use an imidazole series, a polyamide series or an organophosphorus series.

As the antistatic agent, it is possible to use a general antistatic agent used as a raw material of the electrophotographic toner. By adding a small amount of the antistatic agent powder to the conductive carbon material, the epoxy resin, and the powder of the curing agent and stirring it, the surface of the conductive carbon material, the epoxy resin, and the powder particles of the curing agent are made to have the same charge to uniformly distribute the charge, and conduct electricity at the repulsive force. It is possible to uniformly mix and disperse the powder of each material of the carbon material, the epoxy resin and the curing agent. By uniformly mixing and dispersing the respective powders of the conductive carbon material, the epoxy resin, and the curing agent, it is possible to increase the conductivity, mechanical strength, and the like of the fuel cell separator formed by these.

Examples of antistatic agents include metal complexes and metal oxides of nigrosine antistatic agents, quaternary ammonium salts, and monoazo dyes as antistatic agents. ) It is possible to use a metal complex system of mono azo dye with reaction, a metal silicylic acid system, and a metal salicylic acid system with metal oxide (powder) reaction. In particular, the metal complex system antistatic agent with metal oxide (powder) reaction is preferable because it has a particle size. The usage-amount can use 0.1-5.0% with respect to the total compounding quantity of an electroconductive carbon material, an epoxy resin, and a hardening | curing agent. If it is less than 0.1%, the effect of dispersion is low, and even if it exceeds 5.0%, the effect of dispersion is the same. In particular, 0.5 to 3% is preferable.

If necessary, silica, barium sulfate, alumina, magnesium oxide, potassium carbonate, mica, kaolin, bentonite, aluminum hydroxide and the like are added to conductive carbon materials, epoxy resins, hardeners, and antistatic agents to form the molding material powder of the fuel cell separator. It is possible to use on.

The average particle diameter of an electroconductive carbon material, an epoxy resin, a hardening | curing agent, and an antistatic agent powder is 0.2-20 micrometers. If the particle diameter is less than 0.2 µm, the diameter of the particles is too small, so that uniform dispersion of each powder of the conductive carbon material, the epoxy resin, the curing agent, and the antistatic agent becomes difficult. When it exceeds 20 micrometers, the mechanical strength of a separator will fall.

As described above, the angle of repose (fluidity) of the molding material powder of the separator is 15 to 30 degrees. If the angle of repose is within this range, it can be stably added to the heating press molding machine.

The apparent density of the molding material powder of the separator is 0.05 to 0.55 g / cm 3. If it is less than 0.05 g / cm <3> or more than 0.55 g / cm <3>, uniform dispersion of a raw material will become difficult, and the mechanical strength of a separator will become low.

Such a method of manufacturing the powder-forming material of the separator for fuel cells of the present invention can be carried out using a grinding and mixing method conventional in the art. In detail, first, the conductive carbon material. The epoxy resin and the curing agent are coarsely pulverized to 50 to 300 μm with a hammer mill, and the finely divided conductive carbon material, the epoxy resin and the hardener powder are respectively finely pulverized to an average particle diameter of 0.2 to 20 μm with a jet mill or the like. do.

Next, each powder of the conductive carbon material, the epoxy resin, the curing agent, and the antistatic agent is placed in a Henschel mixer, for example, and dry mixed at a tip speed of the stirring blade base at a rotational speed of 30 to 60 m / s to obtain a conductive carbon material epoxy resin curing agent. The powder of the molding material of the separator for fuel cell can be produced by dispersing and uniformizing the powder.

In particular, in order to further increase the homogeneous mixing dispersibility, conductivity, and mechanical strength, the conductive carbon material, epoxy resin, curing agent powder, antistatic agent, etc., which are dry mixed and dispersed and uniform, are heated and kneaded with a biaxial kneader or the like, and then cooled. Then, it is also possible to prepare a molding material powder of a separator for a fuel cell having an average particle diameter of 0.2 to 20 µm by fine grinding with a jet mill or the like.

In another aspect, the present invention provides a fuel cell molded using a fuel cell molding material obtained by finely pulverizing each conductive carbon material, an epoxy resin, and a curing agent, and uniformly dispersing the finely ground powder with an antistatic agent powder. Provide a separator. Specifically, the above-mentioned molding material powder of the fuel cell separator of the present invention is introduced into a pressure molding machine, and a pressure of 500 to 1000 kg / cm 2 is applied thereto and simultaneously heated at 130 to 200 for 1 to 5 minutes to form a fuel cell separator. .

In this way, when the molding is carried out using the molding material of the present invention, a separator for a fuel cell to which high moldability is provided at the same time as conductivity and mechanical strength is obtained.

EXAMPLE

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not intended to be limited thereby. Unless otherwise indicated, the terms "parts" used in the following formulations all refer to parts by weight.

Example 1

70 parts of graphite graphite, 20 parts of bisphenol A epoxy resin, and 5 parts of novolak-type phenol resin as a hardening agent were coarsely ground to a mean particle size of 250 μm with a hammer mill, and then a graphite, bisphenol A epoxy resin, a furnace Each coarsely pulverized product of the volacic phenol resin was pulverized with a jet mill so as to have an average particle diameter of 5 m. Next, 0.5 parts of an antistatic agent, which is an iron-coating system of monoazo dye with silica particles with an average particle diameter of 1 µm and finely added to the fine powder of graphite, bisphenol A type epoxy resin and novolak type phenol resin, was placed in a Henschel mixer. Dry mixing was performed at the tip speed of 32 m / s to obtain 95 parts of the molding material powder of the separator for fuel cell.

The apparent density of the molding material powder of this fuel cell separator was 0.09 g / cm 3, the average particle diameter was 5 μm, and the angle of repose (fluidity) was 21 degrees. Here, the measurement of the angle of repose can determine the overall characteristics or the powder engineering behavior of the powder by measuring the fluidity of the particles, the angle of repose was used as a means of measuring the fluidity.

The fuel cell separator was put into a press molding machine and subjected to a pressure of 600 kg / cm 2, and heated at 150 minutes for 2 minutes to form a separator for fuel cell. The volume specific resistance (m * cm) which shows this electroconductivity was 12, and the flexural strength (MPa) which shows mechanical strength was 65.

Comparative Example 1

70 parts of graphite graphite, 20 parts of bisphenol A epoxy resin, and 5 parts of novolak-type phenol resin as a hardening agent are coarsely ground with a hammer mill to have an average particle diameter of 250 μm, and then graphite, bisphenol A epoxy resin, Each coarsely pulverized product of the novolak-type phenolic resin was pulverized with a jet mill so as to have an average particle diameter of 5 mu m. Then, the graphite, bisphenol A type epoxy resin and novolak type phenolic resin powder were added to the Henschel mixer, and dry mixed at the tip speed of the stirring blade base at a rotation speed of 32 m / s to form a molding material for the fuel cell separator. 94 parts of powder were obtained.

The apparent density of the molding material powder of this fuel cell separator was 0.04 g / cm 3, the average particle diameter was 5 μm, and the angle of repose (fluidity) was 31 degrees.

The molding material powder of the fuel cell separator was placed in a pressure molding machine, and a pressure of 600 kg / cm 2 was applied thereto, followed by heating at 150 for 2 minutes to form a fuel cell separator. The volume resistivity (m * cm) which shows this electroconductivity was 15, and the bending strength MPa which shows mechanical strength was 61.

Example 2

84 parts of flaky graphite, 1 part of acetylene black, 10 parts of bisphenol-A epoxy resin, and 6.2 parts of novolak-type phenol resin to which 0.2 parts of 2-imidazole as a curing accelerator were added as a curing agent, respectively, were cut with an average particle diameter of 60 µm. After coarsely pulverizing, each of the coarsely pulverized flaky graphite, acetylene black, bisphenol A type epoxy resin, and novolak type phenolic resin was pulverized to an average particle diameter of 6 mu m as a jet mill. Thus, the finely ground flake graphite, acetylene black, bisphenol A epoxy resin and novolac phenol resin powder and 2 parts of an antistatic agent of chromic salicylate chromium complex having an average particle diameter of 0.8 μm were placed in a Henschel mixer. Dry mixing was carried out at a tip speed of 50 m / s to obtain 100 parts of powder of the molding material of the separator for fuel cell.

The apparent density of the molding material powder of this fuel cell separator was 0.51 g / cm 3, the average particle diameter was 6 μm, and the angle of repose (fluidity) was 24 degrees.

The molding material powder of the fuel cell separator was placed in a press molding machine, pressurized at 1000 kg / cm 2, and heated at 200 for 1 minute to form a separator for fuel cell. The volume specific resistance (m * cm) which shows the electroconductivity of this separator was 13, and the flexural strength (MPa) which shows mechanical strength was 65.

Comparative Example 2

84 parts of flaky graphite, 1 part of acetylene black, 10 parts of bisphenol-A epoxy resin, and 6.2 parts of novolak-type phenol resins containing 0.2 parts of 2-imidazole as a curing accelerator as a curing agent were respectively cut with an average particle diameter of 60 µm. After coarsely pulverizing, powder of coarsely pulverized flaky graphite, acetylene black, bisphenol A epoxy resin and novolak phenol resin was put into a Henschel mixer, and the tip speed of the stirring blade base was set to 50 m / s. Dry mixing was performed to obtain 101 parts of molding material powder of the separator for fuel cell.

The apparent density of the molding material powder of this fuel cell separator was 0.57 g / cm 3, the average particle diameter was 7 μm, and the angle of repose (fluidity) was 34 degrees.

The molding material powder of the fuel cell separator was placed in a press molding machine, pressurized at 1000 kg / cm 2, and heated at 200 for 1 minute to form a separator for fuel cell. The volume intrinsic resistivity (m * cm) which shows the electroconductivity of this separator was 18, and the flexural strength (MPa) which shows mechanical strength was 59.

Example 3

93 parts of graphite graphite, 25 parts of bisphenol F-type epoxy resin, 2 parts of hardener and novolac-type phenol resin, and 2 parts of potassium carbonate as fillers were coarsely pulverized so as to have an average particle diameter of 100 μm by a cutter mill. The pulverized block graphite, bisphenol F type epoxy resin, novolak type phenol resin, and calcium carbonate were each pulverized with a jet mill so as to have an average particle diameter of 5 mu m. Next, fine graphite bisphenol F-type epoxy resin, novolac-type phenolic resin, finely ground powder of calcium carbonate, and 5 parts of positively charged quaternary ammonium salt having an average particle diameter of 3 µm were placed in a Henschel mixer, and the tip speed of the stirring blade base was 40 m /. 121 parts of molding material powder of the separator for fuel cells was obtained by dry mixing at rotation speed of s.

Then, the molding material powder was kneaded at 120 with a twin-screw kneader or the like, and cooled and finely pulverized with a jet mill or the like to obtain 110 parts of the molding material powder of the separator for fuel cell having an average particle diameter of 6 µm.

The apparent density of the molding material powder of this fuel cell separator was 0.24 g / cm 3, the average particle diameter was 6 μm, and the angle of repose (fluidity) was 17 degrees.

The molding material powder of the fuel cell separator was placed in a press molding machine, and a pressure of 800 kg / cm 2 was applied thereto, followed by heating at 180 for 4 minutes to form a fuel cell separator. The volume specific resistance (m · cm) representing the conductivity of the separator was 11, and the flexural strength MPa representing the mechanical strength was 67.

Comparative Example 3

93 parts of graphite graphite, 25 parts of bisphenol F-type epoxy resin, 2 parts of hardener and novolac-type phenol resin, and 2 parts of potassium carbonate as a filler, coarsely pulverized to a mean particle size of 100 탆 with a cutter mill or the like, and then coarsely crushed Graphite, bisphenol F type epoxy resin, novolak type phenol resin, and calcium carbonate powder were each pulverized with an average particle diameter of 6 mu m with a jet mill. Next, finely ground graphite, bisphenol F-type epoxy resin, novolak-type phenol resin, and calcium carbonate powder were put in a Henschel mixer, and dry mixed at the tip speed of the stirring blade base at a rotation speed of 40 m / s to isolate the fuel cell. 119 parts of powder of the molding material of the board were obtained.

Subsequently, the molding material powder was kneaded at 120 with a twin screw kneader or the like, and after cooling, finely pulverized with a jet mill or the like to obtain 111 parts of molding material powder of the separator for fuel cell having an average particle diameter of 4 m.

The apparent specific gravity of the molding material powder of this fuel cell separator was 0.58 g / cm 3, the average particle diameter was 4 μm, and the angle of repose (flowability) was 32 degrees.

The powder of the molding material of the fuel cell separator is placed in a press molding machine, and a pressure of 800 kg / cm 2 is applied thereto and simultaneously heated at 180 for 4 minutes to form a fuel cell separator. The volume specific resistance (m · cm) representing the conductivity of the separator was 17, and the flexural strength MPa representing the mechanical strength was 60.

Repose Apparent density Volume specific resistance Flexural strength ° (degree) g / cm 3 mΩcm MPa Example 1 21 0.09 12 65 Comparative Example 1 31 0.04 15 61 Example 2 24 0.51 13 65 Comparative Example 2 34 0.57 18 59 Example 3 17 0.24 11 67 Comparative Example 3 32 0.58 17 60

As can be seen from the data shown in Table 1, a molding material mixed and dispersed by adding an antistatic agent to a conductive carbon material, an epoxy resin, a curing agent, and the like has a lower repose angle and volume specific resistance as compared to a molding material mixed and dispersed without an antistatic agent. It was confirmed that the present invention exhibited higher apparent density and flexural strength, which resulted in a homogeneous mixed dispersible molding material, thereby obtaining a fuel cell separator having improved conductivity, mechanical strength, formability, and the like (Examples 1 and 2). . In particular, as a result of further heat kneading, cooling, and pulverizing the molding materials that are uniformly mixed in order to increase the uniformity, the uniform mixing and dispersibility of the molding materials is further improved, thereby improving conductivity, mechanical strength, formability, and the like. It was confirmed that a more improved separator was obtained (Example 3).

In the measured values shown above, the angle of repose was measured by a powder tester (trade name: manufactured by Hosokawa Micron Co., Ltd.), and the powder tester is a machine capable of measuring the angle of repose by measuring a residual cone angle. The apparent density was ASTM D 1895, the volume specific resistance (mcm) was measured by JIS K 7194, and the flexural strength (MPa) was measured by JIS K 7203, respectively. In addition, the average particle diameter of the molding material powder in the Examples and Comparative Examples was measured using a Coulter multisizer.

As described above, the preferred embodiment through the detailed description and examples of the present invention, the molding material is added to the conductive carbon material, epoxy resin, curing agent and the like and dispersed by dispersing the molding material exhibits uniform mixing dispersibility Since the manufactured separator exhibits improved conductivity, mechanical strength and formability, it is considered that the separator is highly applicable to the field of manufacturing a separator for fuel cells requiring improvement in conductivity, mechanical strength, formability, and the like.

Claims (16)

A powder type molding material for a separator for a fuel cell in which an antistatic agent is added to and mixed with a conductive carbon material, an epoxy resin, and a powder of a curing agent. The powder type molding material for a separator for fuel cell according to claim 1, wherein the average particle diameter of the conductive carbon material, the epoxy resin, the curing agent, the antistatic agent, and the powder is in the range of 0.2 to 20 µm. The powder type molding material for a separator for fuel cell according to claim 1, wherein the angle of repose (fluidity) of the molding material powder of the separator is in a range of 15 to 30 degrees. The powder molding material of the separator for fuel cell according to claim 1, wherein the apparent density of the molding material powder of the separator is in the range of 0.05 to 0.55 g / cm 3. The powdered molding material of the separator for fuel cell according to claim 1, wherein the conductive carbon material comprises at least one of natural graphite, artificial graphite, acetylene black, and carbon black such as flaky graphite and bulk graphite. . The powder type molding material for a separator for fuel cell according to claim 1, wherein the amount of the conductive carbon material is in the range of 65 to 97 parts by weight. The powder molding material of a separator for fuel cells according to claim 1, wherein the epoxy resin includes bisphenol type such as bisphenol A type, bisphenol F type, various novolac type, biphenyl type, and biphenyl ether type. . The powder type molding material for a separator for fuel cell according to claim 1, wherein the epoxy resin is powderable in a solid phase and the amount of the epoxy resin is in the range of 5 to 35 parts by weight. 2. The powder type molding material for a separator for fuel cells according to claim 1, wherein the curing agent includes an acid anhydride type, an amine type, and a phenolic resin. The powder type molding material for a separator for fuel cell according to claim 1, wherein the amount of the curing agent is in the range of 5 to 70% with respect to the epoxy resin. The antistatic agent according to claim 1, wherein the antistatic agent is a nitrosine-based antistatic agent, a quaternary ammonium salt system, and a metal complex system of a monoazo dye which is a negative antistatic agent, a metal complex system of a mono azo dye with a metal oxide (powder) reaction, and silyl. A powder molding material for a separator for a fuel cell, which is selected from a live metal complex system and a metal salicylate complex system with a metal oxide (powder) reaction. The powder type molding material for a separator of a fuel cell according to claim 1, wherein the amount of the antistatic agent is in the range of 0.1% to 5.0% based on the total amount of the conductive carbon material, the epoxy resin, and the curing agent. A fuel cell separator formed by using a fuel cell molding material obtained by finely pulverizing each conductive carbon material, an epoxy resin, and a hardener, and by uniformly dispersing an antistatic agent powder in the fine pulverized powder. The fuel cell separator according to claim 13, wherein the average particle diameter of the conductive carbon material, the epoxy resin, the curing agent, the antistatic agent, and the powder is in the range of 0.2 to 20 µm. The fuel cell separator according to claim 13, wherein the angle of repose (fluidity) of the molding material powder of the separator is in the range of 15 to 30 degrees. The separator for fuel cell according to claim 13, wherein the apparent density of the molding material powder of the separator is in the range of 0.05 to 0.55 g / cm3.