JPH07124470A - Molded adsorbent - Google Patents

Abstract

PURPOSE:To obtain a molded adsorbent making use of merits of a hot-melt synthetic resin used as a binder, high in strength before drying and dry strength in the production process of a molding and excellent in dimensional stability. CONSTITUTION:The molded adsorbent molded by mainly using activated carbon contains 0.3-10wt.% pulp like or fibril like aramid fiber as the binder per total weight of the components of the molded adsorbent except total binder and 2-10wt.% polyethylene having a lower m.p. than the m.p. or thermal decomposition starting temp. of the aramid fiber, and the activated carbon is bonded by the entanglement of the pulp like or fibril like aramid fiber and the melting of the polyethylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded adsorbent used for adsorbing and removing coloring substances, odorous components and other harmful substances contained in a gas phase or a liquid phase.

[0002]

2. Description of the Related Art A conventional molded adsorbent (hereinafter simply referred to as "molded body")
(Also called) as a binder (binder) using a heat-melting synthetic resin (powder or fibrous) such as polyethylene or polypropylene, which is thermally fused to bond (bond) activated carbons to each other. Are known. And this thing was manufactured as follows. That is, for example, in the case of a molded body containing fibrous activated carbon as a main component, 10 to 25% by weight of a heat-meltable fibrous synthetic resin is mixed with the total weight of the component to form a uniform aqueous slurry. After preparing, dipping a molding die in this liquid, stacking a predetermined amount of solid content on the mold surface by a suction method and taking out from the liquid, dehydration treatment to obtain a wet (wet) shaped body, Is taken out from the molding die, heated to a predetermined temperature in a state of being loaded in a drying die (mold frame), and the binder is heat-melted to bond and dry the activated carbons. The molded adsorbent thus obtained uses a heat-meltable synthetic resin as a binder, so it does not lose its shape even after being immersed in water for a long time. ) And high wet heat strength.

[0003]

However, the above-mentioned molded product has a remarkably low shape-retaining strength at the stage of the wet-shaped molded product (molded product before drying) in the manufacturing process thereof, and when gripped by hand, There was a difficulty in handling, such as deformation and deformation if not done carefully. Therefore, there has been a problem that the production efficiency or the yield is poor accordingly. Further, in the heating and melting and drying steps, unless a dry mold is used as described above, when a fibrous heat-melting synthetic resin (polyethylene, polypropylene) which is general as a binder is used, The shrinkage of the molded product after drying is as large as 10 to 15%, and it may expand by 5% or more depending on the heating conditions. Therefore, it is not possible to expect high precision of the size of the molded adsorbent (product). there were. In addition, as described above, a separate drying mold is required, and therefore, it is necessary to prepare the same number of moldings to be dried in one drying step, which is one of the causes of cost increase.

Under the circumstances, the inventors of the present application produced various samples of the molded body containing activated carbon as a main component by using various materials as the binder, and repeated the test. I found it. That is, an appropriate amount of pulp-like or fibril-like aramid fiber is used as a binder, and in the case where activated carbon is bonded by entanglement of the fiber, strength is obtained even in a wet shaped product before drying in the manufacturing process. Extremely high. Moreover, in the case where the aramid fiber is bound by its entanglement without melting, even if it is dried without using a drying mold, the shrinkage or expansion stops within a few percent, and the dimensional stability is extremely high. It was found that it was high and the strength after drying (product) was also high. When aramid fibers that are not in the form of pulp or fibrils are used as the binder, the strength before drying (at the time of wet) is extremely low, and heating, melting, and drying are performed using a drying mold. It was found that even when it was carried out, sufficient dry strength was not obtained, and the dimensional stability was extremely insufficient.

Thus, the inventors of the present application repeated various tests, and as a binder, in addition to the heat-meltable synthetic resin,
By using an appropriate amount of pulp-like or fibril-like aramid fibers, the molded product as a product has extremely high wet strength and wet heat strength, as well as its (handling) strength before drying in the manufacturing process of the molded product, and dryness. It was found that a molded adsorbent having a high strength and an excellent dimensional stability (accuracy) can be obtained. The present invention has been devised based on these findings, taking advantage of the advantage of using a heat-meltable synthetic resin as a binder, and the strength before drying (handling) in a manufacturing process of a molded body, It is an object of the present invention to obtain a molded adsorbent having high dry strength and excellent dimensional stability (accuracy).

[0006]

To achieve the above object, the present invention relates to a shaped adsorbent formed by molding activated carbon as a main component, wherein the activated carbon is entangled with pulp- or fibril-shaped aramid fibers. And a melting point of the aramid fiber or a melting point lower than the thermal decomposition starting temperature of the aramid fiber is used for fusion by fusion. In the present invention (specification), a pulp-like or fibril-like shape means a short multi-branched shape similar to wood pulp,
It refers to a thin film-shaped or ribbon-shaped structure, a fine dendritic structure in which branching is further developed than this wood pulp, and a structure having a high entanglement property equivalent to or close to these structures. A typical manufacturing method (processing method) for obtaining such a structure is as follows. That is, the pulp-like material is obtained by introducing a solution of an aromatic polymer into a precipitating agent to precipitate it as a fine pulp-like material, and the fibril-like material is a product of the aromatic polymer. It is obtained by treating the fibrous material with a beater, refiner or other special device, but is not limited to those obtained by these production methods.

The aramid fiber is a polyamide fiber composed of an aromatic ring, which is classified into a para type and a meta type depending on the bonding position. In the present invention (specification), the aramid fiber has heat resistance. It may include a pulp-like substance of an aromatic polymer, which is composed of an aromatic polyamideimide, and may contain a small amount of a component other than an aromatic group. Further, the aramid fiber preferably has a free water value of 100 seconds or more and less than 600 seconds. However, the freeness value in this specification is a value (time) for evaluating the freeness of pulp- or fibril-like aramid fibers obtained by the following test method. That is, aramid fibers in the form of pulp or fibrils are adjusted to a 0.3% aqueous dispersion (20 ° C.) to prepare a slurry. Then, 1 L of this is sampled, transferred to a cylindrical container having an inner diameter of 102 mmφ in which a wire mesh of 78 mesh is stretched over the entire bottom surface, and filtered. At this time, the time required for obtaining 500 mL of the filtrate in seconds is referred to as the filtered water value.

In the above invention, the aramid fiber is added in an amount of 0.3 to 10 relative to the total weight of the components of the molded adsorbent excluding the aramid fiber and the heat-meltable synthetic resin.
The heat-meltable synthetic resin (polyethylene, polypropylene, etc.) is preferably 2 to 10% by weight. The hot-melt synthetic resin is particularly preferable because polyethylene or polypropylene is relatively easily melted by heat and is excellent in hygiene safety.

Incidentally, the aramid fiber is not usually melted by heat, and its thermal decomposition starting temperature (or melting point) is 400 ° C. or higher.
On the other hand, the melting points of polyethylene and polypropylene are
The temperatures are about 70 to 135 ° C. and about 155 to 175 ° C., respectively. Further, as the heat-meltable synthetic resin such as polyethylene or polypropylene, it is preferable to use a pulp-like synthetic pulp. Here, the synthetic pulp refers to a material obtained by forming a synthetic polymer into short, multi-branched fibers (pulp-like) similar to wood pulp. This synthetic pulp is in the form of a pulp and therefore has an entanglement property even in the wet state, so that it also has an effect of increasing the strength of the wet molded body. In addition, since it has hydrophilicity and is easily dispersed in water, it has an advantage that it can be mixed evenly without adding a special dispersant or a coagulant.
Moreover, since the fiber length is as short as about 1 to 2 mm, the weight of the activated carbon can be increased, and therefore the adsorption capacity can be improved.

[0010]

The molded adsorbent according to the present invention comprises activated carbon bonded by both means of melting a heat-meltable synthetic resin and intertwining pulp- or fibril-like aramid fibers. That is, since the activated carbon is bonded by melting the heat-meltable synthetic resin, the molded product as a product has extremely high wet strength and wet heat strength. Therefore, it is suitable as an adsorbent (filter) for a water purifier to be reused by use under severe conditions such as being used in an exposed state in water and steam treatment.

In addition, since the activated carbon is bound by entanglement of aramid fibers in the form of pulp or fibrils, the shape-retaining force of the wet shaped body (molded body before drying) in the manufacturing process of the molded body is improved. It is high and its strength is retained even when it is dried. Therefore, the handling (handling) is good, and the production efficiency can be improved accordingly. Further, the pulp-like or fibril-like aramid fiber has a function of aggregating substances such as activated carbon in the aqueous slurry, so that the molded body is homogenized, and therefore high quality of the product is expected. . Moreover, unlike organic substances such as pulp and hemp, aramid fibers are far superior to pulp and hemp in that they are less likely to rot or lose shape when used in water (wet state).

[0012] Further, since it is a structure in which pulp- or fibril-like aramid fibers are entangled with each other without being formed by only the heat-melting of the heat-melting synthetic resin, the structure can be manufactured without requiring a dry mold. can do. Therefore, the process (equipment) can be simplified,
The manufacturing cost can be reduced, the shrinkage (expansion) associated with drying can be reduced, and a molded product with high dimensional stability can be obtained.

Further, in the present invention, the aramid fiber is used in combination with the heat-meltable synthetic resin, and since the aramid fiber is in the form of pulp or fibril, it has a strong binding force, and therefore, the heat of the prior art is reduced. The amount (composition ratio) of the heat-meltable synthetic resin used can be markedly reduced as compared with the case where the heat-meltable synthetic resin is bonded only by heat melting. Therefore, the use ratio of the binder can be reduced as compared with the case where only the hot-melt synthetic resin is used, so that the adsorbing ability as the molded adsorbent can be enhanced. The percentage of binder used is
It may be set appropriately according to the application of the molded adsorbent.

Generally, with respect to the total weight of the components of the molded adsorbent except for the pulp- or fibril-like aramid fiber and the heat-meltable synthetic resin (hereinafter, also referred to as total binder),
The amount of the heat-meltable synthetic resin is about 2 to 10% by weight, and the aramid fiber in the form of pulp or fibril is 0.3 to 10%.
It is good to set it as about% by weight. 2% by weight of heat-meltable synthetic resin
If it is less than, wet resistance and wet heat resistance will be insufficient,
This is because if it exceeds 10% by weight, the adsorption performance is deteriorated. If the pulp-like or fibril-like aramid fiber is less than 0.3%, the handling strength before drying, the dry strength, and the dimensional stability in the manufacturing process of the molded body are insufficient, and if it exceeds 10%. Is unnecessary.

[0015]

EXAMPLES Examples embodying the present invention and manufacturing methods thereof will be described in detail. However, in the molded adsorbent of this example, the activated carbon is a mixture of granular activated carbon and fibrous activated carbon, and an antibacterial material is added as an additive,
The specific contents (composition) and blending ratio are as follows. The molded adsorbent in this example is for a water purifier, is formed in a hollow cylindrical shape, and has an outer diameter of 65 mm,
The wall thickness is set to 15 mm and the length is set to 250 mm. That is, the granular activated carbon is a coconut shell type activated carbon mainly composed of micropores, having a grain size of 0.18 to 0.36 mm and a specific surface area of 1550 m @ 2 / g or more. By the way, this product has a high ability to adsorb odorous components and the like, and is suitable for water purifiers. Further, the fibrous activated carbon is a coal pitch type in this example, and the fiber thickness is 10 μm.
It has a specific surface area of 1500 m @ 2 / g or more and a length of about 0.5 mm.
This is relatively inexpensive as fibrous activated carbon, has a high adsorption performance (speed), and can adsorb a substance having a molecular diameter smaller than that of granular (powdered) activated carbon. And
The antibacterial material is an antibacterial zeolite (powder) obtained by adding antibacterial metal ions to zeolite. This product is suitable for water purifiers because it has a function of preventing the growth of bacteria in the residual water in the molded body and has high safety. The mixing ratio (weight) in these examples is 45:45:10.
It is set to (wt%).

On the other hand, the hot-melt synthetic resin as a binder is polyethylene, and in this example, a fibrous resin having a denier of 2 to 5 and a fiber length of 3 to 5 mm is used, except for all binders. (Component) 3% by weight based on the total weight. In this example, the aramid fiber as a binder is a meta type having a short multi-branched, thin film, or ribbon-like structure similar to wood pulp, and its particle diameter (width) is 1 ~ 200 μm
And the length is adjusted to an average of 1 to 3 mm. Also, the drainage value is about 275 seconds. However, this amount is 5% by weight in this example with respect to the total weight excluding the total binder.

The thus-prepared material is sequentially poured into water stored in a pulper with stirring to form an aqueous slurry, which is then sent to a slurry concentration adjusting tank.
The amount of water is adjusted to form a uniform aqueous slurry having a concentration of 0.5%, and if necessary, an appropriate additive material (chemical agent) is added and the mixture is sent to a molding tank. In this process, pulp- or fibril-shaped aramid fibers have a function of coagulating the activated carbon and the antibacterial material in the slurry. Then, a predetermined molding die is dipped in the slurry in the molding tank, a predetermined amount of solid content is laminated on the mold surface by a suction (vacuum molding) method, taken out from the liquid, dehydrated, and removed from the mold. Then, a wet shaped body is obtained. The wet-shaped molded body (molded body before drying) in the process of manufacturing the molded body in this example thus obtained is
The activated carbon is bound by the entanglement of aramid fibers in the form of pulp or fibrils, and the shape is maintained, so the handling strength is extremely high, and there is almost no deformation or deformation during demolding, so handling is extremely difficult. It became easier.

Next, the wet shaped body is not loaded into a dry mold, but at a predetermined temperature (below the temperature at which pyrolysis of aramid fiber begins (400 ° C.) and above the melting point of polyethylene (130 ° C.)), In this example, it was kept at 140 ° C. for 5 hours, heated and dried. By this heating, only this polyethylene in the binder is thermally melted, the activated carbons are bonded to each other, and only water is removed by evaporation. A high-strength dry shaped product, ie, a shaped adsorbent (product), in which activated carbon is bonded by entanglement of aramid fibers in the form of pulp or fibrils can be obtained.
In this example, the shrinkage during drying could be maintained at about 0.5 to 1% without the need for a drying type.

As a comparative example, 10 samples of the same size and shape were used under the same conditions as those of the above-mentioned examples except that pulp- or fibril-shaped aramid fibers (meta type) were not included as a binder. Individually produced and compared with each other in handling strength. As a result, the unacceptable deformation and deformation (defect in appearance) at the time of demolding was 0% in this example, but was 100% in the comparative example. Further, such a defect is caused in the present invention when the pulp-like or fibril-like aramid fiber (meta type) is 0.2% by weight with respect to the total weight of the components of the molded body excluding all binders. It was 25%, but when it was 0.3% by weight, it became almost 0%. By the way, in the case of this example, the shape was not deformed even after being continuously immersed in boiling water for 12 hours. When the amount of the heat-fusible synthetic resin (polyethylene) was 1% by weight based on the total weight of the components of the molded product excluding all binders, the shape began to collapse after 2 to 3 hours. There was one, but in the case of 2% by weight, 3
It has been confirmed that the shape does not collapse even after the duration of time.

Further, in this example, since the inexpensive granular (powdered) activated carbon was mixed in an appropriate amount ratio, the cost could be remarkably reduced. As a matter of course, this mixing ratio can be set to an appropriate value. However, when granules are used for the activated carbon, the particle size is 0.18 to
It is good to use 0.36 mm. This is because when the content is in this range, vacuum molding is possible, the water flow performance is not deteriorated, and a sufficient specific surface area (activated carbon adsorption area) can be maintained.

In the above examples, the activated carbon was a mixture of granular activated carbon and fibrous activated carbon, but in the present invention, granular (powdered) activated carbon or fibrous activated carbon alone is also used as activated carbon. Can be materialized. It is also possible to use activated carbon in other forms such as flakes. The activated carbon may be appropriately selected and used depending on the application of the molded adsorbent such as petroleum pitch.
By the way, in the case of fibrous activated carbon, the fiber diameter is 2 to
30 μm, fiber length 0.5 to 10 mm, radius 8 to 20
It has pores of about angstrom and has a specific surface area of 150.
It is preferable to use one having a size of 0 to 2500 m @ 2 / g.

On the other hand, polyethylene as the binder may be powder, but preferably fibrous,
More preferably, it is fibrous, and pulp-like (synthetic pulp) is preferable. In addition, regardless of powder or fibrous material, suitable heat-melting synthetic resin such as polypropylene may be used instead of polyethylene. As for the fibrous heat-melting synthetic resin, for example, a fiber having a double structure in cross section in which polyethylene is applied (coated) to the surface of polyester fiber (core material) can be used. In this product, the melting point of the core material is higher than that of polyethylene on the surface side, and only the surface is melted at a temperature between the melting points, and activated carbon or the like is fused and bonded. Polyethylene as a binder also acts as a substitute for wet strength agents.

The pulp-like or fibril-like aramid fiber as the binder is preferably such that the entanglement is high, and the freeness value is preferably 100 seconds or more and less than 600 seconds, particularly 150 seconds or more and less than 500 seconds. Are preferred. If it is less than 100 seconds, the strength of the molded article will be low, and 6
This is because if it is 00 seconds or more, the drainage during suction molding becomes poor. Further, the higher the degree of fibrillation, the easier the polyethylene (powder) and wet paper strength enhancer (liquid) are aggregated, and therefore polyethylene (powder) and wet paper strength enhancer (liquid) during slurry suction molding. The yield of can be improved. That is, the ratio of the polyethylene (powder) and the wet paper strength enhancer (liquid) mixed in the slurry through the molding die surface (water passage hole) during the suction molding becomes small.

In the above embodiments, the meta-type pulp- or fibril-shaped aramid fibers are used, but para-type aramid fibers may be used as long as they are pulp- or fibril-shaped. In addition, regardless of the meta type and the para type, the higher the entanglement property of the aramid fiber is, the better. In both of the meta type and the para type, the fiber has a particle diameter (width) in a pulp-like or fibril-like state. Is preferably in the range of 1 to 200 μm and has an average length of about 0.1 to 3 mm, and particularly preferably an average length of about 0.2 to 2 mm from the viewpoint of maintaining the strength of the molded product. Further, a free water value of 100 seconds or more and less than 600 seconds is preferable, and a free water value of 150 seconds or more and less than 500 seconds is particularly preferable in terms of strength retention or workability of the molded product.

In the previous example, instead of the meta-type aramid fiber (freezing value of about 275 seconds), the para-type aramid fiber (freezing value of about 250 seconds) was used.
Although a molded adsorbent (product) was obtained, the shrinkage of the adsorbent itself during drying could be maintained at about 0.5 to 1% even when the drying mold was not used. In addition, the handling strength was compared in the same manner as before, but unacceptable deformation and deformation (defect in appearance) during demolding.
Was 0% in this example as well. Further, such a defect is caused in the present invention when the pulp-like or fibril-like aramid fiber (para type) is 0.2 wt% with respect to the total weight of the components of the molded body excluding all binders.
It was 25%, but when it was 0.3% by weight, it was almost 0%.
Became.

The mixing ratio of the aramid fibers in the form of pulp or fibrils may be appropriately set according to the application of the molded adsorbent, but the adsorbent for a water purifier for purifying and filtering water. When used for, with respect to the total weight of the components of the molded adsorbent except the pulp-like or fibril-like aramid fibers and the heat-meltable synthetic resin,
About 0.5 to 7% by weight is suitable for both the meta type and the para type. It should be noted that the higher the mixing ratio, the higher the strength, but the lower the adsorption capacity. On the other hand, when the blending ratio is small, the opposite is true. However, the smaller the size, the better in order to reduce shrinkage due to drying. When this ratio is set to 10% by weight based on the total weight of the components of the molded adsorbent excluding all the binders in the above-mentioned examples, 0.7 to 2
%, And 0.2 to 0.5 when 3% by weight
The shrinkage rate was about%.

Further, the compounding ratio of the heat-meltable synthetic resin (polyethylene in the above-mentioned examples) will be set appropriately according to the application of the molded adsorbent, but for a water purifier for purifying and filtering water. When used as the adsorbent, the amount of 2 to 5% by weight is appropriate with respect to the total weight of the components of the molded adsorbent excluding all binders. When it is less than 2% by weight, it hardly contributes to improvement of wet heat strength and wet strength as a product. On the other hand, even if it is added in an amount exceeding 5% by weight, the corresponding improvement in wet strength and wet heat strength cannot be expected. Further, it is because the pores of the activated carbon are easily blocked, and the adsorption performance of the shaped adsorbent is deteriorated. In addition, even in the case of using polypropylene instead of polyethylene for the heat-meltable synthetic resin,
It is almost the same.

The shaped adsorbent of the present invention may contain a yield improver, a dry paper strength enhancer, and a coagulant, depending on the application, as long as its performance is not impaired. The fibrous substance (material) may be mixed. Further, in the present invention, an appropriate amount of a wet paper strengthening agent, fibrillated acrylic fiber, pulp-like or fibril-like synthetic fiber, or other binder may be added. Incidentally, as an alternative to the aramid fiber in the form of pulp or fibrils in the present invention,
Pulp-like or fibril-like synthetic fibers can be used as long as they do not melt when heated and dried.

The molded adsorbent according to the present invention is an adsorbent (filter) for a water purifier used for deodorizing and decolorizing drinking water and removing chlorine components, an adsorbent for an air purifier, a solvent in a chemical factory, etc. It can be applied to various applications such as an adsorbent used for the recovery of The shaped adsorbent is not limited to a cylindrical shape with both ends open, but may have a polygonal cross-section such as a square tube shape, a closed end shape (cup shape), or a flat plate shape. It can be embodied as a shape.

[0030]

As is apparent from the above description, the molded adsorbent of the present invention has the following effects. That is, by melting the heat-meltable synthetic resin, there is a merit that the molded product as a product has high wet strength and high wet heat strength, and activated carbon is bonded by entanglement in pulp- or fibril-shaped aramid fibers. Therefore, the binding force is strong and the shape-retaining force of the wet shaped body (the shaped body before drying) in the manufacturing process of the shaped body is high. Therefore, in the past, there was a significant difficulty in handling (workability) such that the shape was apt to be deformed unless it was handled extremely carefully at the time of demolding. Since the occurrence of deformation can be significantly reduced, it is extremely effective in improving workability and productivity. Moreover, its strength is retained even during drying.

Further, since the shrinkage (expansion) during drying is small, it is possible to obtain a molded product having high dimensional stability. Further, since a dry type is not required and the amount (composition ratio) of the heat-meltable synthetic resin used as the binder can be reduced, it is expected that the water permeability and the adsorption capacity of the molded adsorbent will be improved.

Claims (5)

[Claims] 1. A molded adsorbent formed by molding activated carbon as a main component, wherein the activated carbon is entangled with aramid fibers in the form of pulp or fibrils, and the melting point of the aramid fibers or a melting point lower than a thermal decomposition starting temperature is used. A molded adsorbent characterized by being bonded by melting with a heat-meltable synthetic resin. 2. The molded adsorbent according to claim 1, wherein the free water value of the aramid fiber is 100 seconds or more and less than 600 seconds. 3. The heat-meltable synthetic resin containing 0.3 to 10% by weight of the aramid fiber with respect to the total weight of the components of the molded adsorbent excluding the aramid fiber and the heat-meltable synthetic resin. The molded adsorbent according to claim 1 or 2, which contains 2 to 10% by weight. 4. The molded adsorbent according to claim 1, wherein the heat-meltable synthetic resin is polyethylene or polypropylene. 5. The molded adsorbent according to claim 1, wherein the heat-meltable synthetic resin is a pulp-like synthetic fiber.