JP2002138386A - Activated carbon fiber sheet and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a high-density activated carbon fiber sheet having excellent handleability, causing neither break nor crack in formation in post processing, in application, or the like, and to provide a method for producing the same. SOLUTION: This activated carbon fiber sheet is a sheet consisting essentially of an activated carbon fiber and a conjugate fiber comprising a high-melting polymer as a core component and a low-melting polymer as a sheath component. The activated carbon fiber is bonded to the sheath component by its fusion with the sheath component of the conjugate fiber. The activated carbon fiber sheet comprises 10-90 mass % of the activated carbon fiber and has 20-300 g/m2 weight and >=0.10 g/cm3 density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated carbon fiber sheet which is obtained by a wet papermaking method using activated carbon fibers as a main component and is suitable as a deodorizing filter and a method for producing the same.

[0002]

2. Description of the Related Art Activated carbon fibers obtained from fibrous materials such as polyacrylonitrile, phenol, rayon, and pitch have a higher adsorption and desorption speed than granular activated carbon, and therefore are not suitable for gas-phase or liquid-phase systems. It is widely used in fields such as removal of odorous components and solvent recovery. However, using the activated carbon fiber as it is often poses a practical problem due to contamination, handling properties, and the like.

[0003] Therefore, there has been proposed a material in which activated carbon fibers are formed into a sheet or the like using a binder or the like. For example, in JP-A-63-283949, a uniform aqueous slurry containing activated carbon fibers and a heat-fusible synthetic resin is dehydrated in a mold, and then heated to form the activated carbon fibers and the heat-fusible synthetic resin. A bonded adsorbent has been proposed. But,
In order to use the heat-fusible synthetic resin, it is necessary to increase the blending amount in order to bond the activated carbon fibers to each other. As a result, the content of the activated carbon fibers in the adsorbent becomes low, and the adsorption performance is reduced. There was a problem.

[0004] In Japanese Patent Application Laid-Open No. 4-197737, a uniform aqueous slurry containing activated carbon fibers, a heat-fusible synthetic resin, and a paper strength enhancing material is dewatered in a mold, and then heated to form activated carbon fibers and heat. An adsorbent in which a fusible synthetic resin is bonded has been proposed. However, this adsorbent has a low adhesiveness due to a small amount of the heat-fusible synthetic resin, and the activated carbon fiber may fall off the adsorbent, or the strength may be insufficient, which may cause a problem in handling during operation.

Further, Japanese Patent No. 3046347 discloses that a composite fiber having a high melting point synthetic resin as a core component and a low melting point synthetic resin as a sheath component and an activated carbon fiber are essential components, and these fibers are contained. The aqueous slurry is made by a wet papermaking method, dried at a temperature higher than the melting point of the sheath component and lower than the melting point of the core component, and after fusion of the activated carbon fibers and the composite fibers, the obtained sheet is heated to a temperature higher than the drying temperature. A filter medium obtained through a step of heat-treating at a temperature lower than the melting point of the core component of the composite fiber, wherein the filter medium contains 50 to 97% by mass of activated carbon fibers based on the sheet weight, and has a basis weight of 50 to 300 g / m. ^2, a filter medium for deodorization having a density of 0.08 g / cm ³ or less and a method for producing the same are disclosed. However, when this filter medium is processed into a corrugate, a corrugate, or the like as a deodorizing filter, the density is too low and it is very difficult to mold. Further, after papermaking, drying at a temperature higher than the melting point of the sheath component and lower than the melting point of the core component, and after fusing the activated carbon fiber and the composite fiber, the obtained sheet is higher than the drying temperature,
The heat treatment is performed at a temperature lower than the melting point of the core component of the conjugate fiber, so that the cost is increased.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and comprises, as main components, an activated carbon fiber and a composite fiber having a high melting polymer as a core component and a low melting polymer as a sheath component. It is an object of the present invention to provide a high-density activated carbon fiber sheet which is free from breakage or cracking at the time of molding or construction and has excellent handleability and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that activated carbon fibers and
After wet papermaking with a high-melting-point polymer as a core component and a composite fiber having a low-melting-point polymer as a sheath component as a main component, the resulting sheet is subjected to a heat treatment at a temperature equal to or higher than the melting point of the sheath component of the composite fiber. The inventors have found that the workability is good at the density, and arrived at the present invention.

That is, the gist of the present invention is as follows. (1) A sheet mainly composed of activated carbon fibers and a composite fiber having a high-melting polymer as a core component and a low-melting polymer as a sheath component, wherein the activated carbon fibers are bonded by fusion with the sheath component of the composite fiber. 10 to 90% by mass of activated carbon fiber
Containing, and having a basis weight of 20 to 300 g / m ² and a density of 0.1
An activated carbon fiber sheet characterized by being at least 0 g / cm ³ . (2) Activated carbon fiber and a high-melting polymer as a core component, an aqueous slurry containing a composite fiber having a low-melting polymer as a sheath component as a main component is formed by a wet papermaking method, and then the sheath component of the composite fiber is produced. Above the melting point, (melting point of core component -20) ° C
The method for producing an activated carbon fiber sheet according to the above (1), wherein the activated carbon fiber sheet is heat-treated at the following temperature.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The activated carbon fiber sheet of the present invention comprises, as main components, activated carbon fibers and composite fibers (hereinafter, referred to as binder fibers) having a high-melting polymer as a core component and a low-melting polymer as a sheath component, and the activated carbon fibers are preferably uniform. It is bonded by fusion to the sheath component of the binder fiber in a dispersed state. In the present invention, the low-melting polymer basically refers to a polymer having a lower melting point than the high-melting polymer, but in the case of a polymer not showing a clear melting point, a polymer having a lower softening point than the high-melting polymer. .

In the present invention, the basis weight of the activated carbon fiber sheet needs to be ²⁰ to 300 g / m ² , especially 30 g / m ^2.
~250g / m ² is preferred. If the basis weight of the sheet is less than 20 g / m ² , the uniform weight of the sheet will increase, and a uniform sheet cannot be obtained. On the other hand, if it exceeds 300 g / m ² , heat treatment after wet papermaking becomes difficult, and further post-processing becomes difficult. Then, the density of the sheet is 0.10 g / cm ³ or more, preferably must be a 0.12~0.30g / cm ^3, 0.10g /
If it is less than cm ³ , post-processing becomes very difficult.

The binder fibers used in the present invention include, for example, a polyolefin fiber having a core of polypropylene and a sheath of modified polyethylene, a fiber having a core of polyethylene terephthalate and a sheath of polyolefin,
Core-sheath composite fibers having a core having a melting point (softening point) lower than the core melting point, such as a polyester-based polyester having a core made of polyethylene terephthalate and a sheath made of polyester having a low melting point (low softening point). Among these, polyester-based composite fibers marketed by Unitika Fiber Co., Ltd. under the trademark of Melty are preferred.

The average fiber length of the binder fibers is desirably 1 to 50 mm, and particularly desirably 3 to 25 mm. If the average fiber length is shorter than 1 mm, the strength of the sheet tends to decrease. If the average fiber length exceeds 50 mm, the dispersion state in water deteriorates, and the uniformity of the activated carbon fibers and the binder fibers decreases. The average fiber diameter of the binder fiber is 2 to 100 μm.
m, particularly preferably 5 to 50 μm. Average fiber diameter is 100
When the thickness exceeds μm, it becomes difficult to sufficiently capture activated carbon fibers even when fusion is performed.

Next, the activated carbon fibers used in the present invention are:
The type is not particularly limited and can be selected according to the purpose such as the field of use of the sheet. For example, polyacrylonitrile type, rayon type, phenolic resin type, coal pitch type, petroleum pitch type etc.
After carbonization as desired, any activated carbon fiber produced by activating by holding at a predetermined temperature and for a predetermined time in an atmosphere containing water vapor and carbon dioxide can be used. Activated carbon fibers made from pitch are advantageous in that the theoretical carbonization yield is high. In addition, activated carbon fibers for removing acidic gases, activated carbon fibers for removing alkaline gases, activated carbon fibers for removing lower aldehydes, etc., or special activated carbon fibers impregnated with agents such as silver or platinum for imparting antibacterial properties and other properties. Activated carbon fibers impregnated with a metal can also be used according to the purpose.

The average fiber diameter of the activated carbon fibers is 3
It is preferably 0 μm or less, particularly preferably 5 to 20 μm. If the average fiber diameter exceeds 30 μm, breakage is likely to occur, and molding processing becomes difficult. The average fiber length of the activated carbon fiber is 0.5 to 50 m.
m is desirable, and particularly preferably 3 to 25 mm. If the average fiber length is less than 0.5 mm, it is difficult to impart sufficient strength to the sheet, and if it exceeds 50 mm, dispersion in water becomes worse,
The uniformity of mixing of the activated carbon fiber and the binder fiber is likely to be reduced.

Further, the content of the activated carbon fiber in the activated carbon fiber sheet of the present invention must be 10 to 90% by mass, preferably 40 to 80% by mass. When the content of the activated carbon fiber is less than 10% by mass, the adsorption performance is insufficient, and
If it exceeds 0% by mass, the adsorption performance is good but the strength is insufficient.

Next, a method for producing the activated carbon fiber sheet of the present invention will be described. First, an activated carbon fiber and a binder fiber are dispersed and mixed in water to prepare an aqueous slurry. As a result, the activated carbon fiber and the binder fiber having the high melting point polymer as the core component and the low melting point polymer as the sheath component are sufficiently dispersed and mixed, and both fibers are uniformly dispersed and composited.

Next, the aqueous slurry is made into a sheet by a wet papermaking method to form a sheet. That is, it is preferable that the sheet is formed by using a paper machine or the like, and solid-liquid separated in such a manner that solids in water are formed into a sheet in the manner of paper making. The activated carbon fiber sheet of the present invention is obtained by subjecting the obtained wet sheet to a heat treatment at a temperature not lower than the melting point of the sheath component of the binder fiber and not higher than (melting point of the core component−20) ° C.

In the present invention, if necessary, to increase the density of the activated carbon fiber sheet obtained by the heat treatment, the surface pressure is set to 0.1.
It is also possible to heat under a pressing pressure of not less than kgf / cm ² and then cool while maintaining the pressing pressure.

Further, in order to improve the strength of the sheet after papermaking, it can be produced by adding synthetic pulp to an aqueous slurry. The synthetic pulp is a pulp-like multibranched fiber made of a thermoplastic polymer such as polyolefin, polyacryl, polyimide, aromatic polyamide, and wholly aromatic polyester. Since these synthetic pulp have a very strong power of capturing other materials when dispersed in water, a sheet having high strength can be produced by a wet papermaking method by adding a small amount of synthetic pulp.

In preparing the aqueous slurry, for example, a binder may be used as necessary. It is preferable to add less than 3% by weight, especially less than 1% by weight, of the binder as a solid component. Examples of the binder include a bound sulfonium group, an isothiouronium group, a pyridinium group,
Polymer latex comprising a substantially water-insoluble organic polymer having an attached anionic or cationic charge, such as an acrylic polymer or a styrene-butadiene polymer containing quaternary ammonium, sulfate, sulfonate or carboxylate groups. And the like.

Furthermore, in the method using this binder,
It is preferable to use an organic coagulant in combination. Suitable organic coagulants include various organic coagulants such as aluminum polychloride (aluminum hydroxychloride), partially hydrolyzed polyacrylamide, modified cationic polyacrylamide, diallyldiethylammonium chloride, and the like. The amount of the coagulant added is less than 3% by weight of the sheet, preferably less than 1% by weight. Further, in order to improve dispersibility, a slurry viscosity modifier such as xanthan gum can be used. The amount of such a thickener added is preferably less than 2% by mass of the activated carbon fiber sheet.

The activated carbon fiber sheet of the present invention can be used as it is, but since it has excellent post-processability and flexibility, it can be formed into, for example, a corrugated sheet (corrugated).
It can also be suitably used for producing a honeycomb by a corrugating method.

[0023]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. The evaluation of each characteristic in the examples was performed by the following method. Further, all the percentages described in the examples are mass%. (1) Specific surface area It was measured by a BET multipoint method using nitrogen as the substance to be adsorbed. (2) Theoretical specific surface area Assuming that the mass of activated carbon fiber contained in 1 g of sheet is L and the specific surface area of activated carbon fiber is Tm ² / g, the theoretical specific surface area is
(m ² / g sheet) = L × T. (3) Evaluation of processability A trapezoidal cell shape having a cell pitch of 10 mm, a cell height of 5 mm, and a line width of 0.5 mm was processed by a corrugator and evaluated. (4) Iodine adsorption amount 1.00 g of the sheet was treated with a 0.05N iodine solution (temperature 2).
8 ° C) for 30 minutes, and a residual iodine concentration of 2.5 g /
The iodine adsorption amount in liter was measured.

Examples 1 to 3 Activated carbon fibers (Adol A-10, fiber length 6 mm, specific surface area 10
00m ² / g, manufactured by Adol) was added to water to prepare a 0.3% concentration, and the mixture was dispersed with an SV type reciprocating reversing stirrer (Agita, manufactured by Shimazaki Seisakusho). A core-sheath type polyester binder fiber (melt 4080, 2.2 dtex × 5 mm, manufactured by Unitika Ltd.) having a melting point of the core of 250 ° C. was added and mixed while stirring with an agitator. At this time, the mixing ratio of activated carbon fiber / polyester binder fiber was 70/30.
(Example 1), 65/35 (Example 2) and 50/50 (Example 3) were prepared at three levels.

Next, water was added to the slurry, and
Was diluted to 0.1% dry weight of 150 g / m ² sheets - preparative square handsheet device - after papermaking with (wire mesh 80 mesh screen size 25 cm × 25 cm), dried and pressed, further hot-air drying of 160 ° C. 1 in the plane
Heat treatment was performed for 0 minutes to obtain an activated carbon fiber sheet.

Example 4 An activated carbon fiber sheet having a basis weight of 40 g / m ² was obtained in the same manner as in Example 3.

Comparative Example 1 A sheet was prepared in the same manner as in Example 3 of Japanese Patent No. 3046347. That is, activated carbon fiber (Adol A
-10, fiber length 6mm, specific surface area 1000m ² / g, manufactured by Adol)
Was added to water to adjust the concentration to 0.3%, and dispersed with an SV type reciprocating reversing stirrer (Agita, manufactured by Shimazaki Seisakusho). As a binder fiber, the softening point of the sheath was 80 ° C and the melting point of the core was 2 ° C.
A core-sheath type polyester binder fiber (melty 4080, 2.2 dtex × 5 mm, manufactured by Unitika) at 50 ° C. was added and mixed while stirring with an agitator to obtain a slurry. Also,
At this time, the mixing ratio of activated carbon fiber / polyester binder fiber was set to 70/30.

Next, water was added to the above slurry, and
After diluting to 0.1%, the sheet with a dry weight of 200 g / m ² was paper-made with a square-shaped hand paper making machine (wire mesh 80 mesh-wire mesh size 25 cm x 25 cm), dewatered and pressed using a 110 ° C cylinder dryer. And dried. Thereafter, an air dryer was set at 190 ° C., and heat treatment was performed at a wind speed of 5 m / s for 1 minute to obtain an activated carbon fiber sheet suitable as a filter medium for deodorization.

Example 5 An activated carbon fiber sheet was produced in the same manner as in Example 2. However, the core of the binder fiber is polypropylene (melting point 160
℃), using a sheath of modified polyolefin (melting point 100 ℃) fiber (NBF fiber, E type, 2.2 dtex × 5 mm, manufactured by Daiwa Spinning Co., Ltd.), heat treatment at 135 ℃ for 20 minutes, 100 g of basis weight / m ² of activated carbon fiber sheet was obtained. Example 1
Table 1 shows the physical properties of the activated carbon fiber sheets obtained in Comparative Examples 1 to 5 and Comparative Example 1.

[0030]

[Table 1]

As is apparent from Table 1, the activated carbon fiber sheet of the present invention has a high density and a large specific surface area. Therefore, it is understood that the adsorption performance, that is, the deodorizing ability is not impaired. On the other hand, in Comparative Example 1, since the specific surface area of the sheet is small, the adsorption performance is inferior.
Next, regarding the evaluation of workability, the sheets of Examples 1 to 5 could be processed without any problem, but the sheet of Comparative Example 1 was insufficient in strength due to low density, and the sheet was broken during processing and could not be processed. Was.

[0032]

The activated carbon fiber sheet of the present invention does not break or crack at the time of molding or construction in post-processing because of its high density, and is excellent in handleability. Further, according to the method for producing an activated carbon fiber sheet of the present invention, it is possible to stably produce an activated carbon fiber sheet having the above advantages.

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Claims (2)

[Claims] 1. A sheet mainly comprising activated carbon fibers and a composite fiber having a high-melting polymer as a core component and a low-melting polymer as a sheath component, wherein the activated carbon fibers are fused with the sheath component of the composite fibers. And activated carbon fiber is
An activated carbon fiber sheet containing 90% by mass, having a basis weight of 20 to 300 g / m ² and a density of 0.10 g / cm ³ or more. 2. An aqueous slurry mainly comprising activated carbon fiber and a composite fiber having a high-melting polymer as a core component and a low-melting polymer as a sheath component is subjected to papermaking by a wet papermaking method. The method for producing an activated carbon fiber sheet according to claim 1, wherein the heat treatment is performed at a temperature not lower than the melting point of the component and not higher than (melting point of the core component-20) ° C.