TWI231804B - Processing of high-conductivity and high-impermeability graphite composite - Google Patents

Abstract

The present invention uses a thermosetting resin and a vermicular graphite to produce a composite material, which these two materials are soaked and stirred to mix, then subjected to centrifugal treatment process, drying, and hot pressing to form a component. In the composition, the weight percentage of vermicular graphite is 98% to 25%, preferably 95% to 50%. The present invention has been proved by testing that the volume resistivity thereof can be less than 4x10<-3> Omega-cm and the helium leakage rate thereof can be less than 5x10<-9> torr.l/sec. According to the method of present invention, high-conductivity and high-impermeability components, such as graphite composite plate, unipolar separator, and bipolar separator, etc., for fuel cells can be produced.

Description

1231804 V. Description of the invention (1) —----- (1) Prior technology Ran / 4 Electric Power is a device that directly uses hydrogen-containing fuel and air rolling to generate electricity and heat energy through electrochemical reactions. Because of its low pollution and high efficiency, clean power generation technology can be applied to generator sets, vehicle power, and renewable electricity, etc., and has therefore become a popular target for promotion in the United States, Japan, and Europe in recent years. Bipolar separator (Bipolar current c〇Uect〇r — separat〇r)

It is an important component of Fuel Cell. The main function of the bipolar separator is five: (1) as a fuel gas (such as hydrogen) and oxidant (such as oxygen 02 or air) gas separator, (2 ) Gas guide grooves are distributed on both surfaces of the bipolar separator plate as gas guide grooves' (3) as the current conduction between the cathode and the anode of another battery (ce 1 1), (4) as The current collector (5) can also add a coolant deflector inside the bipolar separator plate to remove the battery volume. It can prevent the fuel gas (such as hydrogen) and the oxidant (such as oxygen) from being mixed. Therefore,

= Must be gas impermeable to gas and high electrical conductivity. Phosphoric acid fuel tanks have problems with acid rot #, especially at high temperatures, so it is particularly difficult to develop bipolar separators. At present, bipolar separators for phosphoric acid fuel cells must withstand operating temperatures up to about 205. (: And long-term electrolyte corrosion. In addition, the dual-core f-panel must also have sufficient bending strength to resist operating pressure and thermal cycling stability. In the use design, I also hope that the bipolar separator plate can do as much as possible Possibly, make the fuel cell smaller, and improve the electrical and thermal conductivity in order to achieve more economical and diversified fuel cells. Graphite materials are currently more commonly used materials for fuel cell bipolar separators, among which graphite materials include Artificial graphite to be processed (such as Japan Toyo Carbon 丨 G_ j 5

Page 4 1231804 V. Description of the invention (graphite, American Poco graphite), carbon powder and thermoplastic polymer composite materials, carbon powder and thermosetting polymer composite materials, etc. For example, U.S. Patents 4,3 0 1,222; 4, 2 1 4,969; 4, 1 97, 1 78; 4, 339, 322; 4,214, 9 6 9 'all mention the production of fuel cell bipolar separator plates. However, the above materials often encounter shortcomings such as brittle, expensive, heavy, difficult to process, low electrical conductivity and high gas permeability. It is too expensive to market a large number of products. The brittle material and high gas permeability make it difficult to make the bipolar separator as thin as possible in order to reduce the fuel volume or the same volume to obtain the maximum energy density. In addition, in the United States ^ 5'846'459, it is mentioned that the uniformity of flexible graphite is improved to facilitate the application in the raw material M # I # = Μ I ^ The raw material is worm-shaped graphite, and the scale: natural graphite powder is used as the raw material. And drying treatment, that is, the miscellaneous medium 1 &amp; ordered a washed graphite from Kyota). Swellable and black, eXpandable graphite powder (eXpandable heating, to obtain a kind of expanded "low_expanded graphlte", the shape of graphite (Vermicula "pure flexible graphite, the overall strength and magnification can reach 100 ~ 50 times. However, Made of high electrical conductivity, low bonding strength between low Weng II, so the electrode separator graphite is very right 2 permeability, high toughness and no need to process dual-derived natural graphite, because: ί = developed: due to Squat worm-like stone: It looks like a piece of maggot, and after compression: the degree of inking and conductivity, and its ink becomes an ideal conductive material, which has better lice and toughness, making it a worm-like stone

Page 5 1231804 V. Description of the invention (3) (II) Purpose of the invention The purpose of the invention is to produce highly conductive and highly airtight stones for application in fuel cell bipolar separator plates. Lingkou Material Section (3) Technical content, the present invention is a method for producing a highly conductive and high airtight graphite composite material ^] Its main feature is to use a combination of thermosetting resin and worm-like graphite to make a composite material, both of which are soaked Stir mixing, centrifugation process, drying and hot pressing to make a flat plate or bipolar separator plate, the weight ratio of worm-like graphite in the composition is 25% to 98%, preferably 50% to 95%. According to the technology of the present invention, thermosetting resins include polyimide, siiicone resin, epoxy resin, phenoic resin, and furan resin. resin), etc., occupying 2% to 75% by weight, preferably 5% to 50% by weight; mixing the dilute superthermosetting resin and the worm-shaped graphite in a suitable ratio, mixing the two with a mixer, Put the stirred mixture into a centrifuge for centrifugation, then dry the solid after centrifugation, and finally press the hot press into a composite flat plate or single-sided grooved unipolar separator plate or double-sided grooved bipolar separator. Board etc. Example 4: Polyimide resin was diluted with methanol to different proportions of solid content and worm-shaped graphite, respectively, and the worm-like graphite was stirred and mixed with a stirrer, and the stirred mixture was placed in a centrifuge Centrifugation

Page 6 1231804 V. Description of the invention (4)

In 2 minutes, the inner diameter of the centrifuge is 30 cm, the speed is 700 rpm, and the screen is 100 mesh. The worm-shaped graphite after centrifugation is placed in an oven at 200 ° C for 1 hour to dry. Into the mold, a composite material flat plate was pressed by a hot press with a pressure of 160 kg / cm2, a temperature of 320 ° C, and a pressing time of 3 hours. The compacted material was removed, and the density and HP4338B were measured.

Milliohmmeter measures the volume resistivity (Ω-cm), and measures the leak rate (torr.l / sec) with ASM 18 0t helium (He) gas leak detector from ALC TEL, France, as shown in Table 1 ° Table 1. Items, properties of polyimide resin composite worm-like graphite materials

Example 1 Example 2 Example 3 Example 4 Volume resistivity of worm-like graphite (wt%) (Ω-cm) 88.3 8. 98xl0-4 79.4 1. 04x10-3 6 9.7 1. 39xl0-3 6 1. 96xl0-3 leak rate density orr. 1 / sec) (g / cc) 6x1 〇10 1. 58 7χ1010 1. 60 6. 5χ1010 1. 47 5.5x1 Ο10 1. 28

Example 5-11: The same operation method as in step 4, the content of the carcass of DC ^ stone resin (siHcone reSin) in 1NG company in USA was diluted with toluene if it was not proportional to the carcass content and @ Both = after mixing Put the sandalwood mixture into the centrifuge for 2 minutes, and put the worm-shaped graphite after centrifugation in the supply box. . Paul: Two places

1231804, description of the invention (5) 3 dry I ', after drying the worm-like graphite is put into the mold and pressed into a flat plate by a hot press. The pressure is 160 kg / cm2, the temperature is 300 ° C, and the pressing time 1 day: Take out the pressed composite material, its density, volume resistivity and air leakage rate are shown in Table 1. 、 Properties of DC 2 1 〇 04 Shi Xi oxygen resin composite worm-like graphite material Worm-like graphite volume resistivity leak rate density (wt%) (Ω -cm) (torr.1 / sec) (g / cc) 94 · 2 6 · 51χ104 2 · 2x10-10 1.68 89. 5 7 · 74xl〇-4 7χ10π 1. 7 81 · 5 8 · 17xl〇-4 1 · 3xl〇-9 1.65 77. 4 9 · 17xl〇-4 1 · lxlO-9 1. 64 71. 3 1.07xl0-3 9x10-10 1. 59 63 · 3 1 · 32xl0-3 2χ1〇-9 1. 53 50. 4 1 · 91xl0-3 3χ1〇_8 1. 41 Items in Table 2, Example 5 Example 6 Example 7 Example 8 Example 9 Example 1 10 Example 11 Example 1 2-17: The operation mode is the same as that in Example 4 and will be used in the United States. w CORNING's DC805 silicone resin was diluted with methylbenzyl to different proportions of solid content and worm-shaped graphite, respectively. After the two were soaked and mixed with a mixer, the mixture was centrifuged in a centrifuge for 2 minutes to remove excess resin. It was separated from the solvent. The worm-like graphite after centrifugation was placed in an oven and kept at 2 ° C for 2 hours to dry. After drying, the worm-like graphite was put into a mold and pressed into a composite flat plate by a hot press at a pressure of 160 kg / cm2. 250 degrees. (:,Lamination

Page 8 1231804 V. Description of the invention (6) Time 2 hours' Take out the pressed composite material, its density, volume resistivity and air leakage rate are shown in Table 3. Table 3. DC805 Silicone Resin Composite Creepage Item a Worm-like graphite volume resistivity (wt%) (Ω-cm) Example 1 2 93. 2 5.95xl0-4 Example 1 3 89. 3 6. 93xl0 -4 Example 1 4 85. 4 7 · 78χ1〇-4 Example 1 5 75. 0 1 · 01x10-3 Example 1 6 65 · 1 1 · 22xl0-3 Example 1 7 53. 3 1 · 78x10 —3 Nature Leakage Density of Worm Graphite Materials (torr. 1 / sec) (g / cc) 1. Ox 1 Ο 9 1. 68 4 · 0x10-9 1. 7 3 · 0x10-10 1.65 5. 0x1 〇10 1. 64 4 · ΟχΙΟ-η 1. 59 4.0x1ο 11 1. 53 Example 18: The operation mode is the same as that of Examples 1-4. Epoxy resin manufactured by Ciba_Geigy company is 507: 9. 6: Catalyst II 1 0 0: 8 0 ·· 1 After mixing well, dilute with 3 times the weight of acetone, then put the worm-like graphite into the diluted epoxy resin, soak and mix, and place the stirred mixture in a centrifuge for 2 minutes. After centrifugation, the worm-like graphite was placed in an oven at 30 C and kept dry for 0.5 hours. After drying, the worm-like graphite was put into a mold and pressed into a composite flat plate by a hot press at a pressure of 160 kg / ⑽2. ^ 'Pressing f for 2 hours, taking out the pressed composite material, its density, volume resistivity and air leakage rate are shown in Table 4. 、 1231804 V. Description of the invention (7) Table 4. Properties of epoxy resin compound worm-shaped graphite material Item worm-shaped graphite volume resistivity leak rate density (wt%) (Ω-cm) (torr. 1 / sec) (g / cc) Example 1 8 27. 9 3. 68xl0 3 6x1011 1.1 Comparative Examples 1-3: Commercially available flexible graphite, POCO 0 EDM-3 graphite produced by the United States POCO Company, and Toyo Carbon Corporation of Japan Production ^ — 丨 ^ Graphite knives do not measure the subsequent degree, volume resistivity and air leakage rate as shown in Table 5.

Comparative Example 4: Directly putting worm-like graphite into a mold and pressing it into a flat plate with a hot press at a pressure of 100 kg / cm2, a temperature of 200 ° C, and a pressing time of 2 hours, taking out the pressed flexible graphite material, Its density, volume resistivity and air leakage rate are shown in Table 5. Table 5. Properties of graphite materials

Item Worm-like graphite Volume resistivity Leakage rate Density (wt%) (Ω-cm) (torr. 1 / sec) (g / cc) Comparative example 1 100 1.95xl0-3 3x1〇-5 1.10 (Flexible stone Comparative Example 2 Ink) 2. 97xl0-3 2 × 10_3 1. 81 (P0C0 EDM-3) Comparative Example 3 1 · 97 × 10_3 3 × 103 1. 90 (IG-15) Comparative Example 4 100 7 · 55x10-4 1 · 5x10-8 1. 35

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Claims (1)

1231804 / J 丄 ^. „. 1 Jt \ VI. Application for Patent Scope 1. A method for manufacturing a highly conductive and air-tight graphite composite material. The process is to use a thermosetting resin and worm-shaped graphite to make a composite material. The weight ratio of worm-like graphite in the material is 25% to 98%, and the weight ratio of thermosetting resin is 75% to 2%, and the two are made into a composite material by stirring and mixing, centrifugation process, drying and hot pressing. The manufacturing method of the high conductivity and high airtight graphite composite material in the first item of the patent scope, wherein the thermosetting resin can be polyimide, silicone resin and epoxy resin. 2. A method for manufacturing a high-airtight graphite composite material, wherein the composite material may be a flat plate, a single-pole grooved plate with a groove on one side, and a double-pole grooved plate with a groove on both sides.