JP2002338785A - Carbonaceous powder molding material, its preparation process and carbonaceous molded part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbonaceous powder molding material contributing to the manufacture of a carbonaceous molded part having a small electric resistance and a large mechanical strength. SOLUTION: The carbonaceous powder molding material, prepared by mixing a carbonaceous powder and a thermosetting resin, contains a solid dimethylene ether phenolic resin as the essential component of the thermosetting resin, wherein the mixing ratio (mass ratio) of the carbonaceous powder to the thermosetting resin is 92/8 to 70/30. Preferably, the carbonaceous powder contains at least one chosen from an expanded graphite powder, a scaly graphite powder and an artificial graphite powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbonaceous powder molding material containing carbonaceous powder and a thermosetting resin as main components, and a method for producing the same. Further, the present invention relates to a carbonaceous molded product obtained by subjecting the molding material to heat and pressure molding. This molded product is suitable for a carbon electrode, a conductive separator between fuel cells, and the like.

[0002]

2. Description of the Related Art Conventionally, there are the following carbonaceous powder molding materials comprising carbonaceous powder and a thermosetting resin (mainly a phenol resin), and molded articles thereof. (1) A molding material obtained by pressure-kneading a carbonaceous powder and a thermosetting resin and pulverizing the same, and a molded product obtained by heat-press molding or injection molding the same. (2) A molding material obtained by dispersing and mixing a carbonaceous powder and a phenol resin powder in water and drying the mixture, and a molded product obtained by heating and pressing the mixture. (3) a molding material obtained by wet-mixing a carbonaceous powder and a thermosetting resin powder or a thermoplastic resin powder with a solvent and then drying, or a molding material obtained by dry-mixing without using a solvent; Injection molded products. (4) A carbonaceous powder mainly composed of expanded graphite, which does not contain a resin component, and a molded product obtained by compression-molding this as it is at a high pressure.

However, the carbonaceous molded articles obtained by molding the above-mentioned molding materials have various inadequate characteristics. The molding material of (1) is prepared by using a resin with the same mass as the carbonaceous powder in order to uniformly knead the carbonaceous powder and the thermosetting resin. A molded article obtained by molding such a molding material has a large electric resistance. The molding material of (2) is prepared through a heating and drying step for removing moisture, and the curing reaction of the resin proceeds simultaneously with the heating and drying. Since heating and drying are moderate so that the curing reaction does not progress too much,
It is inevitable that the molding material has excessive moisture remaining. A molded product obtained by molding such a molding material has insufficient strength. The molding material of (3) is prepared through a heating and drying process for removing the solvent. However, since heating and drying are refrained for the same reason as in the above (2), the molding material with an excessive amount of solvent remains. I have to be. A molded product obtained by molding such a molding material has insufficient strength. The molding material obtained by dry mixing has no problem of residual solvent, but it is necessary to increase the resin content in order to secure mechanical strength. A molded article obtained by molding such a molding material has a large electric resistance.
Although the carbonaceous powder of (4) can be easily molded in a cold state, it is difficult to secure the strength of the molded product.

[0004]

As described above, the conventional carbonaceous powder molding material is insufficient to reduce the electric resistance and ensure the mechanical strength of a molded article formed from the same. In addition, since the resin content is limited as much as possible to reduce the electric resistance, the moldability cannot be said to be good. In view of the above problems, an object of the present invention is to provide a carbonaceous powder molding material that contributes to the production of a carbonaceous molded article having a small electric resistance and a large mechanical strength. Another object of the present invention is to provide a carbonaceous molded article having a small electric resistance and a large mechanical strength.

[0005]

Means for Solving the Problems The carbonaceous powder molding material according to the present invention for solving the above-mentioned problems is characterized in that a carbonaceous powder molding material obtained by mixing a carbonaceous powder and a thermosetting resin is mainly composed of a thermosetting resin. The curable resin is a dimethylene ether type phenol resin, and the mixing ratio (mass ratio) of the carbonaceous powder and the thermosetting resin is 92/8 to 70/30.

Heretofore, in a carbonaceous powder molding material containing a carbonaceous powder and a phenol resin as main components, attempts have been made to reduce the resin content in order to lower the electric resistance of the molded article. However, when the content of the resin is reduced, the gap between the carbonaceous powder particles cannot be sufficiently filled with the resin at the time of molding, so that the mechanical strength of the molded article decreases. Therefore, in general, a carbonaceous powder and a phenol resin are blended in a mass ratio of 70/30 to 50/50, and care is taken to prevent one of the characteristics of electric resistance and mechanical strength from being extremely deteriorated. I have. Therefore, there is a situation in which one of the characteristics of electric resistance and mechanical strength is insufficient. In the carbonaceous powder molding material according to the present invention, the dimethylene ether type phenol resin selected as the main thermosetting resin has a remarkably low viscosity at the time of molding, and generates little gas at the time of curing. Accordingly, the gap between the carbonaceous powder particles is sufficiently filled with a resin having good fluidity, and good mechanical strength can be imparted to the molded product. At the same time, the resin becomes a thin film,
It is presumed that the electrical resistance can be reduced by bringing the carbonaceous powder particles closer together. Since the resin has good fluidity during molding and generates little gas, moldability is also good. The mixing ratio between the carbonaceous powder and the thermosetting resin is 92/8 to 70/30.
By setting (mass ratio), the characteristic balance between the mechanical strength and the low electric resistance of the molded article becomes good. In order to lower the electrical resistance of the molded article, the carbonaceous powder preferably contains at least one selected from expanded graphite powder, flaky graphite powder, and artificial graphite powder.

The carbonaceous powder molding material according to the present invention has a mixing ratio (mass ratio) of carbonaceous powder and thermosetting resin powder of 9
It is characterized in that it is substantially dry-mixed as 2/8 to 70/30, and dimethylene ether type phenol resin powder is mainly used as the thermosetting resin powder.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a dimethylene ether type phenol resin, which is a main thermosetting resin, is obtained by reacting a phenol and a formalin as main components under an alkali catalyst to form a methylol compound, followed by heat condensation. A solid dimethylene ether type phenol resin obtained by dehydration can be used. If necessary, a curing accelerator such as benzoic acid or maleic acid is added. A phenol resin, an epoxy resin, or the like may be used in combination as a secondary thermosetting resin.

In the present invention, the carbonaceous powder preferably contains at least one selected from flaky graphite powder, expanded graphite powder, and artificial graphite powder. Is also good. The selection of flaky graphite powder is particularly preferred in terms of reducing the electrical resistance of the molded article. Commercial products can be used for the flaky graphite powder and the artificial graphite powder, and the particle size is preferably in the range of 5 to 100 μm. The expanded graphite powder can be manufactured by a known method. For example, scaly graphite is immersed in a mixed solution of sulfuric acid and nitric acid to obtain an acid compound, washed with water, and then rapidly heated at a temperature of 900 ° C. or more to obtain expanded graphite. Thereafter, by compressing and pulverizing, the desired expanded graphite powder can be obtained.

The mixing ratio of the carbonaceous powder and the thermosetting resin (main resin is dimethylene ether type phenol resin) is as follows:
When the resin content decreases, the mechanical strength of the molded article decreases, and when the resin content increases, the electrical resistance of the molded article increases. Therefore, the mass ratio is set to 92/8 to 70/30.

[0011] The molding material is prepared by adding carbonaceous powder and dimethylene ether type phenol resin powder as necessary.
Add a curing accelerator, release agent, surface modifier, other thermosetting resin, etc., and shake them, shaker, mixer,
This is carried out by direct dry mixing using a tumbler, ball mill, thunder crusher or the like. In the dry mixing,
If the amount does not require drying after mixing, a solvent may be added. Such a case is also called dry mixing. The smaller the particle diameter of the dimethylene ether type phenol resin powder, the better, and preferably 75 μm or less.

The molding of the above-mentioned carbonaceous powder molding material is performed by usual compression molding, injection molding or the like. Mold temperature is
Set between room temperature and 300 ° C. The molding may be performed by heating and pressing at the time of molding, or the molding may be performed only by applying pressure, and then the molded product may be removed from the mold and the resin may be cured by heating.
The latter case is convenient because the molding cycle can be shortened.

[0013]

EXAMPLES Examples 1 to 5 and Comparative Examples 1 and 2 Scale-like graphite powder (average particle size 15 μm) or expanded graphite powder (average particle size 30 μm) and commercially available solid dimethylene ether type phenol resin powder (plate flow 45 mm) , Average particle size of 40 μm) was charged into a Henschel mixer with the composition shown in Table 1 and dry-mixed for 5 minutes to obtain a carbonaceous powder molding material. This molding material was put into a mold, and was heated and pressed at a temperature of 180 ° C. and a pressure of 80 MPa for 10 minutes to obtain a carbonaceous molded product.

Conventional Example A flaky graphite powder (average particle size: 15 μm) and a liquid resol-type phenol resin (solid content: 35% by mass) diluted with methanol as required were charged into a Henschel mixer in the composition shown in Table 1 and mixed. Mix for minutes. After mixing, at 80 ° C about 3
After drying for a period of time to remove the solvent, a carbonaceous powder molding material was obtained. This molding material was put into a mold, and was heated and pressed at a temperature of 180 ° C. and a pressure of 80 MPa for 10 minutes to obtain a carbonaceous molded product.

[0015] The molded articles of the above examples (all of them are 125 × 1
The flexural strength, flexural modulus, and electric resistance of the sample (0 × 4 mm) were measured in accordance with JIS-K-6911 and JIS-C-2525. In addition, the appearance of the molded product was evaluated. The results are shown in Table 1.

[0016]

[Table 1]

[0017]

As described above, the carbonaceous powder molding material according to the present invention contributes to providing a carbonaceous molded article having good moldability, high mechanical strength and low electric resistance.

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Claims (4)

[Claims] 1. A carbonaceous powder molding material comprising a mixture of a carbonaceous powder and a thermosetting resin, wherein a main thermosetting resin is a dimethylene ether type phenol resin, and a mixing ratio of the carbonaceous powder and the thermosetting resin. (Mass ratio) is 92/8 to 70
/ 30, a carbonaceous powder molding material. 2. The carbonaceous powder molding material according to claim 1, wherein the carbonaceous powder contains at least one selected from expanded graphite powder, flaky graphite powder, and artificial graphite powder. 3. A substantially dry mixing method in which the mixing ratio (mass ratio) of the carbonaceous powder and the thermosetting resin powder is 92/8 to 70/30, and dimethylene ether type phenol is mainly used as the thermosetting resin powder. A method for producing a carbonaceous powder molding material, characterized by using a resin powder. 4. A carbonaceous molded article obtained by press-molding the carbonaceous powder molding material according to claim 1.