JPH0197606A - Manufacture of carbon sheet - Google Patents

Abstract

PURPOSE:To improve surface flatness and smoothness by rolling into sheet a kneaded material sandwiched between separable sheets on a press having a thickness control spacer. CONSTITUTION:A roll 2 rolls on a workpiece 3 sandwiched between separable sheets 4 which is placed on a press 1. The workpiece is rolled roughly to a predetermined thickness in the gap between the roll 2 and the press 1. Then, metal spacers 5 for defining the predetermined thickness are placed on the two opposite sides of the rolled sheet 3 which are parallel to the rolling direction, and the sheet 3 is further rolled one time each in four directions perpendicular to each other. The metal spacers 5 should be within a tolerance of + or -0.02mm. In this manner, it is possible to obtain a rolled sheet having a flatness within + or -0.02mm. It is also possible to improve the smoothness of the surface by heating and hardening thermoplastic resin in close contact with the separable sheets 4 at the last stage of rolling.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is mainly used for phosphoric acid fuel cells which require excellent gas and liquid impermeability, corrosion resistance, heat resistance, electronic conductivity, etc. This invention relates to a method for manufacturing dense carbonaceous thin plates used for separators, electrode plates for secondary batteries, etc.

[Prior Art] In a phosphoric acid fuel cell, the entire unit is mechanically clamped, so the separator used is required to have a smooth, flat surface and extremely high flatness accuracy.

The conventionally known impermeable carbon molding method uses graphite powder,
Using either phenolic resin powder or phenolic resin liquid as a binder, a kneaded composition containing these is extruded, rolled, etc., and then cured,
It is fired (see JP-A-60-90805).

In order to obtain a wide thin plate-like molded body with a thickness of about 0.8 sv required for a phosphoric acid fuel cell separator from such a material, it is necessary to further cut the molded body larger than a predetermined size. In order to obtain the required flatness accuracy, precision cutting of the plate surface is required.

[Problems to be Solved by the Invention] According to the above-mentioned conventional method, there are various problems including the forming method in order to obtain an impermeable dense carbonaceous thin plate that requires flatness accuracy and surface smoothness. In particular, problems include flatness accuracy and formation of structural defects due to air entrainment during molding.

In addition, the conventional method requires processing costs and has a low material utilization rate.

[Means for Solving the Problems] The structure of the present invention for solving the above problems is to form a kneaded composition containing carbon powder and a thermosetting resin into a plate shape by roll rolling, and then harden and bake it. In the method for producing a carbonaceous thin plate by rolling the kneaded composition, a releasable thin film is interposed on the upper and lower pressurized surfaces during roll rolling, and a spacer is provided for controlling the thickness after rolling. This is a method for manufacturing a carbonaceous thin plate, which is placed on a stand and rolled from the top with rolls.

That is, the method for producing a dense carbonaceous thin plate according to the present invention is characterized by a rolling improvement method for obtaining flatness accuracy and surface smoothness during roll rolling after extrusion molding of a kneaded composition.

The kneaded composition to be rolled after extrusion molding preferably contains at least one carbon material selected from graphite powder, glassy carbon powder, coke powder, etc., thermosetting resin powder, and thermosetting resin liquid. It is a composition.

After extrusion molding this mixed composition, it is rolled and molded.
After molding into a molded product of the desired shape, it is heated and hardened.

The extruded product is rolled by roll rolling, and in the method of the present invention, the reduction rate in one rolling is 10% to 40 to 90%.
It is preferable to do this every other time. During this roll rolling, a thin releasable film, that is, a hard sheet (polyethylene or polypropylene, etc.) with excellent mold releasability, is interposed on the top and bottom of the molded product, that is, on the pressure surface, to prevent the molded product from adhering to the rolling roll surface and rolling table. It is necessary to do so.

The method of the present invention will be specifically explained with reference to the drawings. FIG. 1 shows a preferred example of roll rolling according to the method of the present invention. A rolling roll 2 is disposed on a rolling table 1, and the rolling roll rotates over the rolled product (molded product) 3 with hard release sheets 4 interposed above and below the rolled product. After adjusting the distance between the rolling rolls and the rolling table and rolling to almost a predetermined thickness, spacers (metal plates) 5 with the same thickness as the predetermined thickness are installed at both ends of the rolled product in a direction perpendicular to the rolls. While applying pressure to the roll while riding on the spacer,
Rolling is performed once in each of four orthogonal directions. However, the metal plate used as a spacer must have an accuracy within ±0.02 mm.

The rolled product thus rolled so as not to entrain air into the molded product is heated with the upper and lower hard release sheets in close contact with each other to harden the thermosetting resin.

The temperature for curing this thermosetting resin is 50 to 100°C.
The product is cured to the initial hardening stage in an atmosphere of .

Rolled products that have been hardened are heated for 1000~
By firing at 2000°C, an impermeable dense carbonaceous thin plate can be obtained.

[Function] In the above method of the present invention, a metal plate having a required thickness with an accuracy of ±0.02+am is installed as a spacer at both ends of the rolled product in a direction perpendicular to the roll, and rolled once in each of the four orthogonal directions. By performing this, a rolled product having a flatness accuracy within ±0.02 mm can be obtained.

In addition, during final rolling, the hard release sheets on the upper and lower sides of the rolled product are heated in close contact with each other to harden the thermosetting resin, thereby smoothing the surface.゛Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example] Composition of raw materials Graphite powder (average particle size 4μ) 100 parts by weight powder, powdered phenol resin (manufactured by Sumitomo Durez ■, PR11078)
45 parts by weight liquid phenol resin (manufactured by Sumitomo Durez ■, PR94G
) 50 parts by weight carboxymethyl cellulose 2 parts by weight The above raw materials were mixed and extruded into a thick plate using a screw kneading extruder.

Next, using a 30011III diameter roll rolling mill, the rolling reduction was increased to 40% to 90% in 10% increments until the rolled product was 1. O
Rolling was performed to obtain av. The temperature conditions during rolling were a constant rolling roll of 55°C, a constant rolling table of 25°C, and a rolled product of 40°C.
℃.

During rolling, 0.5-inch thick rigid polyethylene sheets were interposed above and below the extruded product, and the rolling surface was adjusted to l, according to the above rolling reduction ratio.
Roll each time until it reaches O+am thickness, 1
, 2.0im metal plate when rolling 0II1m (accuracy ±0.
02IIla+) as spacers at both ends of the rolled product in a direction perpendicular to the rolling roll.1. Pressure was applied to the rolling rolls, and rolling was performed once in each of four orthogonal directions.

After rolling, the upper and lower hard release sheets were kept in close contact with the molded body and heated to a temperature of 80°C for about 1.0 hours, then the sheets were removed, and the molded body was further heat-treated at 180°C for 1 hour. The thermosetting resin was cured.

This cured product was charged into a firing furnace and heated for 14 hours in a non-oxidizing atmosphere.
Fired at 00℃, thickness 0.8111% 700"'"
A dense carbonaceous thin plate was obtained.

The molded body thus obtained has a flatness accuracy of -1' 0.02
1 or less, the surface smoothing effect was also obtained, and the impermeable carbonaceous thin plate had no structural defects and was excellent.

After firing, the flatness accuracy is within ±0.02a+i, and
The rate at which a molded product with a smooth surface and no structural defects can be obtained is:
The method of the present invention showed a significant improvement of 80% or more, compared to 20-30% in the conventional manufacturing method. The results of the present invention are shown in the table below together with the results of comparative examples (no spacer, no sheet).

(Note 1) Smoothness: 10-point average roughness (JIS B12O
Displayed in 3).

(Note 2) Thickness variation: Indicates the width of thickness variation within one sheet relative to the standard thickness of 0.8'''.

[Effects of the Invention] As explained above, according to the method of the present invention, unlike conventional methods, it is not necessary to cut the molded product after firing to the required thickness again, or to obtain the required flatness accuracy. A dense carbonaceous thin plate having excellent planar precision and smoothness can be easily obtained using conventional equipment without using precision and high precision equipment without cutting the entire surface.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a rolling mill suitable for carrying out the method of the invention. ■... Rolling table, 2... Rolling roll, 3... Rolled product (molded product), 4... Hard release sheet, 5... Spacer (metal plate). Patent applicant: Tokai Carbon Co., Ltd.

Claims (1)

[Claims] In a method of manufacturing a carbon thin plate by forming a kneaded composition containing carbon powder and a thermosetting resin into a plate shape by roll rolling, curing and firing the same, the upper and lower parts of the kneaded composition are A method for producing a carbonaceous thin plate, which comprises placing a releasable thin film on the pressurized surface and placing it on a rolling table having a spacer for controlling the thickness after rolling, and rolling with rolls from above. .