JPH0555183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a method for producing a three-dimensional, integrally formed adsorbent using activated carbon fibers.

<Prior art and its problems> Activated carbon fibers (also referred to as activated carbon fibers or fibrous activated carbon) have been used as adsorbents since around 1975. Activated carbon fibers have a larger surface area per unit weight than conventionally used granular activated carbon, and have smaller pore diameters and a sharper distribution.
Due to its excellent adsorption properties, it is attracting attention as a new adsorbent.

However, activated carbon fibers (1) have a low bulk density, making it difficult to increase the amount of adsorption per unit volume;

(2) Activated carbon fibers are extremely weak because there are countless angstrom-sized pores on the surface of the thin fibers with a diameter of 2 to 30 microns. For example, if you rub it once or twice with your fingertips, it will easily become powdery.

Therefore, it is desired to establish a method for manufacturing a shaped adsorbent having a high bulk density using activated carbon fibers having weak mechanical properties and low bulk density.

The following are known as gas phase and liquid phase adsorbents using activated carbon fibers, but none of them have been able to achieve the above-mentioned problems.

(1) There is an adsorbent in which activated carbon fibers and thermofusible synthetic resin fibers are blended or mixed and then heated to fuse or bond them together (for example, see Japanese Patent Application Laid-Open No. 56-24151). .

The obtained adsorbent can be used for deodorizing and purifying air, recovering and concentrating solvents from the gas phase, liquid phase processing (removal of chlorine, decolorization, deodorization, etc.), separation of simple gases (molecular sieves), etc. used.

However, this method has a high bulk density.
It is difficult to produce adsorbents with a dense three-dimensional structure.
Furthermore, a loss occurs during the cutting process, and reprocessing to a predetermined shape is required, resulting in high costs.

(2) Organic fibers such as acrylic fibers and phenolic resin fibers are needle-punched into felt or non-woven fabrics, or these fibers are made into threads;
There are adsorbents that are made into textiles and then activated carbonized by heat treatment or chemical treatment.

The activated carbon fiber structure thus obtained has an extremely large number of micropores with a diameter of about 10 to 40 angstroms, and a specific surface area of about 700 to 2500 m ² /g. Therefore, the strength of the structure is significantly reduced to about 1/10 of the strength of the original felt-like or woven structure, and it is likely to collapse or break during use.

Even with this method, it is difficult to produce an adsorbent with a high bulk density and a dense three-dimensional structure.

(3) Carbon fibers are needle-punched to make felt or non-woven fabric, or thread-like, then made into woven fabric, and then activated carbonized by heat treatment or chemical treatment to make an adsorbent.

In this case as well, since the strength of the obtained structure is low, there are practical difficulties similar to those in (2) above, and it is difficult to produce an adsorbent with a dense three-dimensional structure and a high bulk density.

<Means for Solving the Problems> Activated carbon fibers have excellent adsorption properties, low mechanical strength, and low bulk density. The present inventor has conducted various studies to develop a molded adsorbent with a high bulk density and a dense three-dimensional structure using activated carbon fibers having such properties. An aqueous slurry containing a heat-melting synthetic resin (which may be in the form of fibers or powder; the same applies hereinafter) to be used as a bonding material for bonding the When a hot-melt synthetic resin is melted by suction molding, dehydration, and heating, a molded adsorbent that can substantially solve or significantly alleviate the problems of the prior art can be obtained. I found out that it can be done.

That is, the present invention provides a method for producing a shaped adsorbent as follows: Contains activated carbon fibers and a heat-melting synthetic resin, and the content of the heat-melting synthetic resin is 0.2 parts by weight per 100 parts by weight of the activated carbon fibers. By suction-molding a homogeneous slurry having an amount of at least 40 parts by weight using a mold having a large number of suction holes, dehydrating it, and then heating it,
A method for producing an integrally molded adsorbent with a three-dimensional structure having a papermaking structure in which activated carbon fibers are randomly bonded and held by a heat-melting synthetic resin.

In the present invention, an adsorbent having a paper-making structure refers to an adsorbent having a dense structure in which the fibers constituting the adsorbent are randomly arranged like thick Japanese paper.

The adsorbent having a three-dimensional structure refers to an adsorbent having a shape other than a flexible thin adsorbent having a thickness of approximately 3 mm or less, such as a sheet or tape shape. Specifically, the shapes include cylinders, prismatic materials, elliptical cylinders, truncated cones, truncated pyramids, pellets, rectangular parallelepipeds, cubes, etc., and shapes with holes in these (for example, the above-mentioned columnar materials). A cylindrical adsorbent having a through hole that is open on the upper and lower surfaces of the columnar body and whose central axis is the central axis of the columnar body.

An integrally formed adsorbent excludes adsorbents made by laminating sheet-like, tape-like, etc. adsorbents using adhesives, etc., and more specifically, adsorbents with a three-dimensional structure. Refers to something obtained by molding all or part of an adsorbent at once. What is a shaped adsorbent?
This means that the adsorbent is shaped using a mold during manufacture.

In the present invention, activated carbon fibers are not particularly limited and may be selected appropriately depending on the field of use of the adsorbent, but usually the fiber diameter is about 2 to 30 μm, the fiber length is about 0.5 to 10 mm, and the pore diameter is 8. ~Has micropores of about 20 angstroms and a specific surface area of 500~
It is preferable to use one with a surface area of about 2500 m ² /g. Further, its origin is not limited either, and it may be any one of rayon-based, polyacrylonitrile-based, phenol resin-based, coal pitch-based, petroleum pitch-based, and the like.

The heat-melting synthetic resin used to join and integrate the activated carbon fibers is preferably one with a melting point of about 50 to 200°C, such as polyethylene, polypropylene,
polyvinyl alcohol, polyacrylonitrile,
Examples include polyester, and polyacrylonitrile is particularly suitable. As the heat-melting synthetic resin, it is more preferable to use a filamentous (fiber-like) resin because it less likely blocks the pores of the activated carbon. As the heat-melting synthetic resin thread, the thread diameter is 5~
Preferably, the thickness is about 100 μm and the length is about 0.5 to 10 mm. As the heat-melting synthetic resin thread, one having a structure in which the surface of a high-melting point fiber thread that does not melt or change in quality at the heating temperature during production of the molded adsorbent body is coated with a heat-melting synthetic resin may be used.

The blending amount of the heat-melting synthetic resin to 100 parts by weight of activated carbon fiber is about 0.2 to 40 parts by weight, preferably
The amount should be approximately 0.2 to 20 parts by weight. If the amount of the heat-melting synthetic resin is too small, the strength of the molded adsorbent will be low, and if the amount is too large, the pores of the activated carbon fibers will be blocked and the porosity will decrease. When the molded article requires a certain degree of strength, contains a large amount of activated carbon fiber, and exhibits its properties, the appropriate amount of the hot-melt synthetic resin is about 5 parts by weight.

The method for manufacturing the shaped adsorbent of the present invention will be specifically explained below.

First, a uniform aqueous slurry containing activated carbon fibers and a heat-melting synthetic resin in a predetermined ratio is prepared. The concentration of individual particles in the aqueous slurry is not particularly limited, but from the viewpoint of ease of handling, ease of molding, etc., it is preferably about 0.1 to 2% by weight. When preparing the slurry, mechanical dispersion or stirring is performed according to a conventional method, if necessary. Further, dispersants, stabilizers, viscosity modifiers, paper strength enhancers, retention aids, etc. may be added as long as they do not impede the performance of the shaped adsorbent. The homogeneous aqueous slurry thus obtained is shaped.

The molding is preferably carried out under reduced pressure while preliminary dehydration is performed, such as by suction molding. More specifically, for example, in the case of manufacturing a cylindrical body, a mold having a cylindrical core body sealed at both ends with blind flanges and having a large number of suction holes on the surface is immersed in the slurry. Then, by sucking the slurry with a pump through a suction nozzle provided at one end of the flange, fiber components are randomly integrated and formed on the surface of the core body. If the length of the cylindrical product is short, it is also possible to form the fibrous components randomly by suctioning from the end face. In the case of a molded adsorbent having a three-dimensional structure without holes, it can be molded by suction using a mold having small suction holes on at least one side. Suction molding can also be carried out by supplying slurry to a mold and dewatering it without embedding the mold in the slurry.

The molded body in a wet state is dehydrated as desired, and then heated at a temperature depending on the heat-melting synthetic resin used, and the molded body is integrated by melting the synthetic resin and dried. Thus, a shaped adsorbent of the present invention is obtained. The heating temperature varies depending on the temperature at which the resin becomes adhesive and the resin used, but it is preferably about 40 to 60°C higher than the softening point.

In addition, according to this manufacturing method, a shaped adsorbent body that has a certain degree of strength and can be used for practical use as it is can be obtained. The reason why a strong molded adsorbent can be obtained despite the small amount of hot-melt resin used is that fibers are randomly present in the molded adsorbent obtained by the present invention. That is, near the suction surface, the fibers are randomly oriented almost parallel to the suction surface, but as they move away from the suction surface, some of the fibers are randomly attracted and accumulated on the suction surface at various angles. . This seems to be because the fibers sucked at this angle contribute to the shape-retaining effect. However, since activated carbon fibers are inherently weak substances, molded adsorbents obtained using only activated carbon fibers and thermofusible synthetic resin as raw materials may lack strength depending on the purpose of use. In this case, the formed adsorbent may have to be used while being housed in a case. Therefore, in order to obtain a molded adsorbent with higher strength, it is desirable to use non-thermofusible fibers as a reinforcing material.

Non-thermofusible fibers used as reinforcing materials are not particularly limited as long as they do not melt or change in quality at the heating temperature during production of the molded adsorbent, but usually include inorganic fibers such as glass fibers and alumina fibers; polyamide fibers, and high melting point fibers. Synthetic fibers such as polyethylene fibers with a high melting point, polypropylene fibers with a high melting point, and polyacrylonitrile fibers with a high melting point; semi-synthetic fibers such as rayon, pulp fibers, etc. are used. The diameter of the non-thermofusible fiber is 2 to 100 μm from the viewpoint of effectiveness as a reinforcing material.
The length is preferably about 0.5 to 10 mm, and the length is preferably about 0.5 to 10 mm from the viewpoint of dispersibility in the aqueous slurry used in producing the adsorbent and effectiveness as a reinforcing material. It is preferable that the non-thermofusible fiber is blended in an amount of about 5 to 80 parts by weight per 100 parts by weight of activated carbon fiber. If the blending amount is too large, the amount of activated carbon fiber will decrease relatively.
The performance as an adsorbent will deteriorate.

A third adsorbent material such as activated clay, ion exchange fiber, molecular sieve, silica earth, zeolite, silver-impregnated activated carbon, granular activated carbon, powdered activated carbon, etc. may be further added.

When using the molded article of the present invention that has been wet suction molded, it is preferable that the fluid containing the adsorbed substance be allowed to flow in the suction direction during molding. This is because even when the amount of heat-melting synthetic resin used is small, delamination is less likely to occur.

<Effects of the Invention> The shaped adsorbent having a three-dimensional structure obtained by the method of the present invention exhibits the following performance while using activated carbon fibers having low strength and low bulk density.

(1) An adsorbent having a bulk density of about 0.08 to 0.25 g/cm ³ (0.222 g/cm ³ and 0.165 g/cm ³ in the examples) can be obtained.

Depending on how the third fiber is used, 0.40g/
It is also possible to obtain adsorbents with bulk densities as high as cm ³ .

(2) Due to its high bulk density and dense structure, the amount of adsorption per unit volume can be increased, the device can be made more compact, and the fluid containing the adsorbed substance does not pass through during use. The flow rate can be increased.

(3) Since it is integrally molded, it is easy to handle.

(4) Because the activated carbon fibers are densely accumulated and bonded and held together by heat-melting synthetic resin, and because the fibers are randomly present, the fibers have a shape-retaining effect and have arbitrary angles to the suction surface. Because of the presence of activated carbon fibers, the shape of the molded product does not easily collapse even though extremely brittle activated carbon fibers are used.

Furthermore, according to the new manufacturing method of the adsorbent, a molded body having the above-mentioned characteristics can be produced by: (1) When dry molding, activated carbon fiber dust is generated and the working environment is poor; however, the manufacturing method of the present invention Because it is wet-molded, it can be manufactured in a favorable working environment.

(2) Because the slurry in which activated carbon fibers and heat-melting synthetic resin are uniformly dispersed is forcibly sucked into the mold using a mold, a molded product with a high bulk density, that is, a dense three-dimensional structure, can be obtained. . An adsorbent having a dense three-dimensional structure, good air permeability and water permeability, and stable quality can be obtained. In particular, when a hot-melt synthetic resin is used, a molded article with high strength and a specific surface area that does not substantially decrease can be obtained.

Furthermore, when non-thermofusible fibers are blended as reinforcing materials, the strength of the shaped adsorbent is further improved,
Easy to handle.

Furthermore, it is more preferable that the heat-melting synthetic resin is in the form of fibers, since it is less likely to block the pores of the activated carbon.

The adsorbent of the present invention is capable of filtering solid matter in liquid and gas phases, adsorbing and removing trace impurities and harmful components, and
It is effectively used for concentrating useful components by adsorption and desorption. More specifically, it is used as a filter in water purifiers to remove iron rust, malodorous substances, free chlorine, etc. from tap water; as a filter in air purifiers and air conditioners to remove smoke, malodorous substances, etc. and control humidity; chemical It is used in a wide range of fields such as solvent recovery in factories, cleaning industries, etc.; removal of solids from mineral oils and vegetable oils.

<Examples> Hereinafter, Examples and Comparative Examples will be shown to further clarify the features of the present invention, but the technical scope of the present invention is not limited to the Examples.

Moreover, the adsorption performance of the shaped adsorbent obtained in each example was almost equivalent to that of the unshaped activated carbon fiber.

Example 1 This will be explained using FIG. 1. 250 parts by weight of activated carbon fiber and 50 parts by weight of wood pulp were mixed with water in water tank 3.
Dispersed in 50,000 parts by weight, the fiber length of both is 0.1 to 5.
After beating until it becomes
Parts by weight were added to obtain a uniform slurry 2.

Next, a cylindrical mold 1 (outer diameter 29 mm, length 2470 mm) with blind flanges 5 and 6 attached to both ends and a large number of small suction holes provided on the circumferential surface of the core body 4 is placed in the water tank 3. The slurry is sucked from inside the core body 4 by a suction pump (not shown) through a suction hose 7 that is immersed and attached to the blind flange 6, and the aqueous slurry is applied around the core body 4 of the mold 1. After attachment, a wet hollow cylinder (inner diameter 29
mm, outer diameter 60 mm, length 2470 mm) was removed from the mold and dried by heating at 140° C. for 120 minutes.

The dimensions of the thus obtained molded adsorbent having a papermaking structure are 28.9 mm in inner diameter, 59.9 mm in outer diameter, and 2468 mm in length, and its physical properties include a density of 0.222 g/cm ³ and an air permeability.
78sec/300c.c. (except that the passing surface is 10mm in diameter)
Measured according to JIS P 8117), filtration speed 168sec/
100 c.c. (measured according to JIS P 3801).

Example 2 150 parts by weight of activated carbon fiber, 40 parts by weight of glass fiber, and 10 parts by weight of polyacrylonitrile fiber with a softening point of about 80°C were dispersed in 5000 parts by weight of water, and each fiber length was
After beating to obtain a uniform slurry to a thickness of 0.1 to 5 mm, a hollow cylindrical molded body was prepared in the same manner as in Example 1, and heated at 130° C. for 120 minutes to obtain a molded adsorbent.

The dimensions of the thus obtained molded adsorbent having a papermaking structure are 29.2 mm in inner diameter, 60.2 mm in outer diameter, and 2468 mm in length, and its physical properties are as follows: basis weight 2560 g/m ² , thickness 15.5 mm,
Density 0.165g/cm ³ , air permeability 22sec/300c.c. (measured in the same manner as Example 1), filtration rate 40sec/100c.c.
(measured in the same manner as in Example 1).

The weight is calculated by dividing the weight of the molded body by the average area π (inner diameter + outer diameter)/2×length when the side surfaces are expanded. The weight of the above product is 886g, and the area is π×(2.92+
6.02) ^{/2×246.8=3466cm2} , so the above value is obtained.

Example 3 Polyacrylonitrile fiber 10 with a softening point of about 80°C was used instead of the polyvinyl alcohol used in Example 1.
A cylindrical molded article was obtained in the same manner as in Example 1, except that part by weight was used, no wood pulp was used, and the length of the core 4 was 500 mm.
Although the strength was weaker than that of the molded product obtained in Example 2, it could be used satisfactorily as an adsorbent for water purifiers and the like.

Comparative Example 1 An aqueous slurry was prepared in the same manner as in Example 2, except that polyacrylonitrile fibers were not used, and molding was performed in the same manner as in Example 1. However, the strength of the molded product was insufficient, and it immediately collapsed. It collapsed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the suction molding method of a molded article of the present invention. 1...Mold, 2...Slurry, 3...Water tank,
4... Core body, 5, 6... Blind flange, 7... Suction hose.

Claims (1)

[Claims] 1. A homogeneous slurry containing activated carbon fibers and a heat-melting synthetic resin, in which the content of the heat-melting synthetic resin is 0.2 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the activated carbon fibers, is By suction molding in a mold with small suction holes, dehydration, and then heating, a three-dimensional structure with a papermaking structure in which activated carbon fibers are randomly bonded and held by a heat-melting synthetic resin is molded into an integral structure. A method for manufacturing a molded adsorbent. 2. The method for producing a shaped adsorbent according to claim 1, wherein the content of the thermofusible synthetic resin is 0.2 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of activated carbon fibers. 3. The method for producing a shaped adsorbent according to claim 1 or 2, wherein the slurry further contains non-thermofusible fibers. 4. The method for producing a shaped adsorbent according to claim 1, 2 or 3, wherein the heat-melting synthetic resin is fibrous.