JP2862909B2 - Method for producing carbon molded body - Google Patents

Description

The present invention relates to a method for producing a carbon molded body having mechanical strength and water resistance.

[Problems to be solved by conventional technology and invention]

Activated carbon is widely used as an adsorbent for gas and liquid phases due to its excellent adsorption ability.

For example, it is used for air purification, deodorization, recovery of a solvent in a gas phase or purification of water, decolorization, dissolution, removal of impurities, gas separation, and the like.

For such uses, it is necessary to make the activated carbon into a molded article having a uniform and dense structure having uniform air permeability and liquid permeability, and excellent in mechanical strength, water resistance and the like.

As a method for producing an activated carbon molded body, particularly an activated carbon fiber molded body, conventionally carried out for such a purpose, a molded article is obtained by mixing activated carbon fiber and a heat-fusible synthetic resin fiber such as polyacrylonitrile and then heat-fusing the mixture. Method, a method in which synthetic fibers such as acrylic fiber or the like are made into a felt shape or a woven shape and then activated carbonization by heat treatment or chemical treatment, and a method in which carbon fibers are made into a felt or woven shape and then activated carbonization by heat treatment or chemical treatment. Can be

However, with these methods, it is not possible to obtain an adsorbent having a homogeneous and dense structure, a molded body having sufficient mechanical strength cannot be obtained, and it is necessary to rework to a predetermined shape.
There were many practical disadvantages.

There has also been a demand for a method for producing a carbon molded body made of carbon fiber, carbon black, spherical carbon fine particles, and other various carbon materials having excellent mechanical strength and water resistance.

The present inventors have focused on the thermal decomposition method and thermal crosslinkability of carboxymethylcellulose ammonium salt, and as a result of diligent research to apply this to a method for forming a carbon material, particularly an activated carbon fiber, came to the present invention. Things.

[Means for solving the problem]

That is, the present invention is to impregnate the carbon material with an aqueous solution of carboxymethylcellulose ammonium salt, mold it,
This is a method for producing a carbon molded body, wherein a carboxymethylcellulose ammonium salt is thermally decomposed into carboxymethylcellulose by heating at 300300 ° C. for 3 to 0.5 hours, followed by a crosslinking reaction between carboxymethylcellulose molecules.

As the carbon material of the present invention, any fibrous or powdery carbon material can be used.

Examples of the fibrous carbon material include rayon-based, polyacrylonitrile-based, phenolic resin-based, coal pitch-based, and petroleum pitch-based carbon fibers and activated carbon fibers obtained by activating the carbon fibers. The fiber shape and the like may be appropriately selected according to the purpose of use of the molded article. In the case of activated carbon fibers, those usually used have a fiber diameter of 2 to 30 μm, a fiber length of 0.2 to 20 mm, and a specific surface area of about 300 to 3500 m ² / g.

Powdered carbon materials include powdered and granular materials such as carbon black, coal, coal coke, pitch, pitch coke, graphite, charcoal, and coconut charcoal, and various activated carbon powders and granules activated from these. Can be mentioned. Its shape ranges from almost spherical to amorphous.
The particle size can also be appropriately selected according to the purpose of use of the molded article.

The carboxymethylcellulose ammonium salt used in the present invention is a carboxymethylcellulose in which an ammonium group is bonded to the terminal of a carboxymethyl group, and an example of the chemical structure is shown below.

In the method of the present invention, any of commercially available powdery or granular forms can be used. The viscosity of the 1% aqueous solution measured by a B-type viscometer at 25 ° C. and 60 rpm can be from 1 to 2,000 cps, and preferably from 1 to 500 cps. This is because the operation of impregnating the aqueous solution with the carbon material is easy and has an appropriate binder function.

The concentration of the aqueous solution of carboxymethylcellulose ammonium salt impregnated in the activated carbon is in the range of 1 to 20%, preferably in the range of 2 to 5%. If it is 1% or less, the bonding strength of the carbon material is not sufficient.

The carbon material can be impregnated with the carboxymethylcellulose ammonium salt aqueous solution and formed by various methods. For example, (1) a method in which a carbon material is suspended in an aqueous solution of carboxymethylcellulose ammonium salt in a molding die and then molded by suction dehydration, and (2) an aqueous solution of carboxymethylcellulose ammonium salt is added to the carbon material filled in the molding die. (3) a method of forming by centrifugal dehydration instead of suction dehydration by the method of (1) or (2), and (4) an aqueous carboxymethylcellulose ammonium salt solution on a carbon material. Extrusion molding after addition and kneading, (5) or a method of pressure molding can be mentioned, but the method is not limited thereto.

The formed carbon material molded article impregnated with the aqueous solution of carboxymethyl cellulose ammonium salt is then heated.
The heating temperature is in the range of 100-300C, preferably in the range of 150-250C. This is because carboxymethyl cellulose ammonium salt is free carboxyl group (-COOH) by thermal decomposition
Corresponds to a temperature range that changes to carboxymethylcellulose having Free carboxyl group formed by decomposition as shown in the following formula Is ester-bonded to a hydroxyl group (—OH) in the adjacent carboxymethylcellulose molecular chain to form a crosslinked structure and firmly adhere to each other. The carboxymethylcellulose having a free carboxyl group formed by the decomposition of the ammonium salt and the esterified crosslinked product thereof become insoluble in water, and impart excellent water resistance to the molded article.

The optimal heating time depends on the superheat temperature, but is 0.5 to 3
It is within a range of time, and an appropriate temperature and time at which the thermal decomposition and the esterification crosslinking reaction sufficiently occur may be selected. Heating to a high temperature requires a shorter time, but at the same time, thermal decomposition of carboxymethylcellulose occurs. Therefore, it is most preferable to perform the reaction at 180 ° C. for about 2 hours. In this heat treatment, ammonia gas is generated by thermal decomposition of carboxymethylcellulose ammonium salt, and this gas generation is useful for imparting uniform air permeability and liquid permeability to the carbon molded body.

In the carbon molded article of the present invention, particularly in the activated carbon fiber molded article, in addition to the activated carbon fiber alone, carbon fiber, glass fiber,
Mix appropriate amounts of inorganic fibers such as alumina fibers, polyamide fibers, high melting point polyethylene fibers, high melting point polypropylene fibers, synthetic fibers such as high melting point polyacrylonitrile fibers, semi-synthetic fibers such as rayon, and pulp fibers according to the purpose. Needless to say, it can be manufactured.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the manufacturing method of the carbon molded object of this invention, a water-resistant molded object with high uniformity and high mechanical strength is obtained. In particular, since activated carbon fiber and carbon fiber molded products have uniform air permeability and liquid permeability, these molded products are widely used as filters for water purifiers, filters for air purifiers and air conditioners, and adsorbents for solvent recovery in the gas phase. Can be used.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 A powdery carboxymethyl cellulose ammonium salt (CMC Daicel <Ammonium> DN-LL, manufactured by Daicel Chemical Industries, Ltd.) having a 1% aqueous solution viscosity (25 ° C., B-type viscometer, 60 rpm) of 10 cps or less is dissolved in water. Thus, a 5% aqueous solution was prepared.

1000 ml of this carboxymethylcellulose ammonium salt aqueous solution is placed in a commercial cutter mixer, into which flocculent activated carbon fiber (fiber diameter 10-15 μm, specific surface area 700-2500 m
100 g of ² / g, pitch type), disperse and suspend in a carboxymethylcellulose ammonium salt aqueous solution while stirring the flocculent activated carbon fiber to a fiber length of 1 to 5 mm by stirring a commercial cutter mixer A good slurry was obtained.

Next, the slurry was poured into a hollow cylindrical molding die (outside diameter 30 mm, inside diameter 18 mm, hollow section system 14 mm, height 300 mm) equipped with a perforated plate for suction dehydration at the bottom, and then suction dewatered from the bottom. Molded. The formed infiltrated hollow cylindrical body was taken out of the mold, dried at 100 ° C. for 2 hours, and heated at 180 ° C. for 2 hours.

The dimensions of the obtained activated carbon fiber molded body were 18.7 mm in inner diameter, 29.9 mm in outer diameter, and 107.5 mm in length, and its physical properties were bulk density of 0.234.
g / cc and crushing strength 24.0 kg / cm ² .

Example 2 A hollow cylindrical activated carbon fiber molded body was produced in the same manner as in Example 1, except that the concentration of the carboxymethylcellulose ammonium salt aqueous solution was changed to 3%.

The dimensions of the obtained molded body are 18.3 mm in inner diameter, 29.5 mm in outer diameter,
The length was 92.1 mm, the bulk density was 0.214 g / cc, and the crushing strength was 21.1 kg / cm ² .

Example 3 The viscosity of a 1% aqueous solution (25 ° C., B-type viscometer, 60 rpm) was 10 cps.
The following powdery carboxymethylcellulose ammonium salt (CMC Daicel <ammonium> DN-LL, manufactured by Daicel Chemical Industries, Ltd.) was dissolved in water to prepare a 3% aqueous solution.

1000 ml of this carboxymethylcellulose ammonium salt aqueous solution is placed in a commercial cutter mixer, into which flocculent activated carbon fiber (fiber diameter 10-15 μm, specific surface area 700-2500 m
50 g of ² / g, pitch type) and 50 g of flocculent carbon fiber (fiber diameter: 13 μm, tensile strength: 80 kg / mm ² , specific gravity: 1.65, pitch type) 5m
While beating to obtain m, the mixture was dispersed and suspended in an aqueous solution of carboxymethylcellulose ammonium salt to obtain a uniform slurry.

Next, the slurry is poured into a hollow cylindrical molding die (outer diameter 46 mm, inner diameter 16 mm, hollow part diameter 12 mm, height 300 mm) provided with a perforated plate for suction dehydration at the bottom, and then suction dewatered from the bottom. Molded. The molded wet hollow cylindrical body was taken out of the mold, dried at 100 ° C. for 2 hours, and heated and sintered at 180 ° C. for 2 hours.

The dimensions of the obtained carbon fiber-containing activated carbon fiber molded body were 16.0 mm in inner diameter, 45.2 mm in outer diameter, 0.248 g / cc in bulk density, and 32 k in crushing strength.
g, 6.8 kg / cm ² , flow resistance is 4 l / min, 0.08 kg / cm ²
Met.

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Claims (1)

(57) [Claims] 1. A carbon material which is impregnated with an aqueous solution of carboxymethylcellulose ammonium salt and molded, and then 100-300
A method for producing a carbon molded body, wherein a carboxymethylcellulose ammonium salt is thermally decomposed into carboxymethylcellulose by heating at a temperature of 3 to 0.5 hours for 3 to 0.5 hours, and a cross-linking reaction is performed between carboxymethylcellulose molecules.