JPS58172210A - Manufacture of carbon body for electrode - Google Patents

Abstract

PURPOSE:To increase the gas permeability of a carbon for an electrode and to improve the discharge characteristics by adding a resin which is converted into fibers by shearing force during kneading and vaporized during calcination as a component when a material which is carbonized by calcination is kneaded. CONSTITUTION:A material which is carbonized by calcinating, e.g. polyvinyl chloride or polyvinylidene chloride, graphite, activated carbon or other material which is used optionally, and a resin which is converted into fibers by shearing force during kneading and vaporized during calcination, e.g. polytetrafluoroethylene or polymethyl methacrylate are prepared. These materials are kneaded, molded, and calcined to obtain a carbon body for an electrode with high gas permeability and improved discharge characteristics.

Description

[Detailed description of the invention] The present invention relates to a method for producing a carbon body for electrodes, particularly.

The present invention relates to a suitable method for producing carbon bodies for electrodes, such as carbon bodies for electrodes of air cells and fuel cells, which are desired to have high gas permeability.

It is possible to manufacture carbon bodies for electrodes by using components that carbonize when fired, such as various synthetic resins, along with components used as necessary, such as graphite and activated carbon, through the basic steps of cross-wiring, molding, and firing. It is publicly known.

And like air cells, fuel cells, etc.

Carbon bodies for electrodes that require gas permeability utilize the fine pores that are naturally formed during firing.

However, it is never possible to obtain a satisfactory gas permeability by using only the fine pores as described above.

Therefore, it is important to consider how to artificially increase the gas permeability.

The present invention makes it possible to increase the gas permeability by using a resin that becomes fibrous under the shearing force generated during cross-wires and is dispersed during firing. The present invention provides a method for manufacturing a carbon body for an electrode by cross-wiring, forming, and firing a material that contains at least a component that is carbonized by firing as a main component.
The gist of the present invention is a method for producing a carbon body for an electrode, characterized in that it contains a resin that becomes fibrous due to the shearing force during cross-contact and is dispersed during firing.

First, to give two examples of the components of the materials used in the present invention, components that undergo υ carbonization by firing include polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, and chlorinated polyvinyl chloride. Examples include various synthetic resins such as chlorine-containing resins such as polyethylene and furan resins, and various organic substances such as asphalt, cellulose derivatives, lignin derivatives, gum arabic, and polyvinyl alcohol.

In addition, as an ingredient used as necessary.

Items used primarily to enhance functionality, such as the aforementioned graphite and activated carbon, include platinum, palladium, compounds thereof, and metal phthalocyanine for use as catalysts.

Examples of substances used mainly as auxiliary agents during production include plasticizers, solvents, and stabilizers.

9. The resin (hereinafter referred to as "essential resin"), which is a key component of the present invention, is turned into fibers by the shearing force during kneading and is dispersed during firing.

Examples include polytetrafluoroethylene, polymethyl methacrylate, α-methylstyrene, and trifluorostyrene. Among them, polytetrafluoroethylene is easily used as a fiber and has a high monomer production rate.

The above-mentioned components can be used alone or in combination of two or more.

The usage ratio is also arbitrary, but the key point is that the gas permeability can be sufficiently increased even if the usage ratio of resin is not very large.
For example, in the case of polytetrafluoroethylene, the weight ratio is based on the component that is carbonized by firing (and the component that remains after firing; optionally used component: graphite, etc.).

About 10 inches or less is sufficient. Of course, you can use more than this range, but if you use too much, it will cause strength problems and cracks, so it is better to refrain from using more than 15 inches. If it is too small, there will be no substantial effect, so it is preferably 0.5% or more.

It is preferable to use 1 or more, and it is also true that the usage ratio changes depending on the combination of 9 types of essential resins.

Mixing of materials is done using Henschel mixer and kneader.

Various means such as a roll machine can be used.

Since the present invention utilizes the shearing force generated during this crosstalk,
A roll machine that can obtain a large shearing force by setting the rotation speed, rotation ratio, and gap size of each roll, and can also change the fiberization state by changing the number of rolls, is preferably adopted. It is one of the means.

The kneaded material is molded by various means such as extrusion molding, injection molding, and casting, but it is not necessary that the final shape is formed by the molding.

As will be understood from the Examples described later, the carbon body for electrodes according to the present invention does not need to have pores formed uniformly throughout the body based on the essential resin.

The molded material is fired after undergoing processes such as drying, if necessary. At this time, for the above-mentioned chlorine-containing resin, if the temperature is raised to about 600°C over a long period of time, for example, 10 hours, 20 hours, or 30 hours (of course, it may be longer), the strength will deteriorate. You can get excellent products.

The carbon electrode body after firing is further subjected to formation of a catalyst layer, water repellent treatment, etc. as necessary, and then used as an electrode.

Examples will be explained below, and "part" means 2 parts by weight.

[Example 1] Polyvinyl chloride 6° black
Lead 60
Part activated carbon 60 parts Dioctyl 7-talate (plasticizer) 40 parts Stearate (stabilizer) 4 parts Methyl ethyl ketone (solvent) 150 parts Polytetrafluoroethylene 2 parts The above materials were kneaded using a pressure kneader and a 6-roll machine. . The rotational speed of the three-roll machine is 15 rpm, 45 rpm, 90 rpm starting from the rear roll.
rpm, therefore the rotation ratio is j: 5: 6. Also, what is the diameter of each roll?

1201EB, one gap was set to 0.02 m, the temperature was 105° C., and the number of rolls was 40.

The kneaded material is in a state in which it is substantially free of solvent, and is molded into a ram-type extrusion molding machine with a wall thickness of 1.5111 mm using a Kipler car plate with a center bin.
It was extruded into a hollow rod-shaped body (outer diameter 4 II (φ), inner diameter 1 stroke (φ)). In addition, when the extruded hollow rod-shaped body was cut and its surface was observed under a microscope, it was found that it was approximately 0.01 to 0.
．． A network of fibrous bodies having a diameter of 5 μm was present.

After heating the hollow rod-shaped body in air from room temperature to 500°C over 15 hours, it was placed in a closed container.

A firing treatment was performed at 700°C for 1 hour.

[Examples 2 to 4] All examples were the same as in Example 1 except that the amount of polytetrafluoroethylene used was changed to 5 parts, 1 part, and 20 parts.
Examples 2 and 3.4 were prepared in the same manner as above.

[Example 5] Everything was the same as in Example 1 except that 2 parts of polymethyl methacrylate was used instead of polytetrafluoroethylene.

[Examples 6 and 7] Examples 6 and 7 were prepared in the same manner as in Example 5 except that the amount of polymethyl methacrylate used was changed to 5 parts and 10 parts.

[Example 8] Polyvinyl chloride 30 parts black
Lead 40
1 part dioctyl phthalate (plasticizer) 15 parts stearate (stabilizer) 2 parts methyl ethyl ketone (solvent) 80 parts polytetrafluoroethylene 5 parts The above materials were kneaded in the same manner as in Example 1 (below).

materials (referred to as ■).

Polyvinyl chloride 35 parts black
Lead 10
Part activated carbon 50 parts Dioctyl phthalate (plasticizer) 20 parts Stearate (stabilizer) 2 parts Methyl ethyl ketone (solvent) 80 parts The above materials were kneaded in the same manner as in Example 1 (below).

materials (called "materials").

First, put material ■ into the extrusion molding machine used in Example 1.
Next, material I was added and extruded in the same manner as in Example 1. As a result, by utilizing the flow of material in the extrusion molding machine, the inner layer part (thickness 1.OIll) made of material (1),
A multilayer hollow rod-shaped body consisting of an outer layer portion (thickness: 0.5 m) made of material (1) was obtained, and this was heat-treated to the firing temperature in the same manner as in Example 1.

[Comparative Example 1] Everything was the same as in Example 1 except that polytetrafluoroethylene was not used.

[Comparative Example 2] The same procedures as in Example 8 were carried out except that polytetrafluoroethylene was not used.

The tips of the hollow carbon rods obtained on each side were sealed with silicone rubber, and the length of the unsealed part was set to 4011, and 860To
Air at rr pressure is pumped into the hollow part (100 Torr difference) L,
The amount of air permeating through the entire surface of the unsealed part with a length of 40111 was investigated. These results are calculated based on the apparent specific gravity (Note 1) and specific surface area (Note 2).
) are shown in Table-1.

Table 1 Note 1: Apparent specific gravity was calculated by dividing 1 weight (measured with a direct scale) by volume (measured with a dial caliper).

Note 2: Specific surface area was measured by the BET method using low-temperature nitrogen adsorption.

In addition, in order to investigate the performance as an electrode, a petroleum benzene solution containing 10% paraffin was sprayed on the surface of each hollow carbon rod obtained on each side, and the petroleum benzene was volatilized to make it water repellent, and the tip was made with silicone rubber. The one sealed with is used as the positive electrode,
An air battery was constructed. The negative electrode was a cylindrical container with an inner diameter of 20Ws (φ) made of 99.9% zinc, the electrolyte was a 15% hydroxide tlllum solution, and the length of the positive electrode was 40'1lli in the unsealed silicon part. The length in liquid is 301B, and the load resistance is 100Ω.

The positive electrode was located in the center of the negative electrode.

The obtained discharge characteristics are shown in Table 2.

(Note) In Table 2, the initial voltage is measured under stable conditions 5 minutes after the start of discharge. is not balanced). Also, ,O,
Values such as 1V decrease and 02■ decrease were measured from the start of discharge. It shows the amount of decrease from the initial voltage in terms of time.

As can be seen from the above, according to the present invention, the gas permeability of the carbon material for electrodes can be increased, and the discharge characteristics of the battery can be improved. In addition, according to the present invention, it is possible to increase the specific surface area, so
Also suitable for other batteries that do not require gas permeability [can be used extensively] Patent applicant Pentel Co., Ltd.

Claims (1)

[Claims] When manufacturing a carbon body for electrodes by cross-wiring, forming, and firing a material that contains at least a component that carbonizes when fired, the component in the material is formed into fibers by the shearing force during cross-wiring, and is dispersed during firing. 1. A method for producing a carbon body for an electrode, characterized in that it contains a resin that causes