JPH03270734A - Nonwoven fabric-shaped catalyst - Google Patents

Abstract

PURPOSE:To stably hold catalyst particles and to enhance catalytic activity by forming porous fibers having catalyst particles held thereto into a three- dimensional reticulated structure along or along with other fibers to obtain a nonwoven fabric-shaped catalyst. CONSTITUTION:A polymer generating phase separation with respect to a fiber forming polymer and catalyst particles are dispersed in and mixed with the fiber forming polymer and the resulting mixture is spun and stretched to obtain porous fibers having catalyst particles held therein. These porous fibers are formed into a fiber web alone or along with other fibers using a carding machine and this web is subjected to fiber entangling treatment using a needle punching method or a water stream entangling method to form a nonwoven fabric-shaped catalyst having a reticulated structure wherein fibers are entangled three-dimensionally. The fineness of the aforementioned porous fibers is pref. about 0.5-30 denier and the compounding amount of the porous fibers in the nonwoven fabric-shaped catalyst is pref. about 25wt.% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a nonwoven catalyst, and particularly to a nonwoven catalyst used for removing harmful substances contained in gas.

[Conventional Technique] Conventionally, filters made of catalyst particles sintered into a predetermined shape have been used to remove harmful substances contained in exhaust gas and to remove ozone after it has been used for sterilization. However, this sintered filter lacks versatility because its shape is fixed.

For this reason, a non-woven catalyst, in which catalyst particles are supported on a fiber sheet such as a hand-woven cloth, has been proposed as a catalyst whose shape can be easily deformed. However, in conventional nonwoven catalysts, catalyst particles are attached to the fiber surface of the nonwoven fabric using a binder, so if the amount of binder is small, the catalyst particles will fall off, and if the amount of binder is large, the active surface of the catalyst particles will be There was a problem that the processing capacity was reduced due to being covered with binder. Moreover, this nonwoven catalyst has the problem that the binder closes the spaces between the fibers of the nonwoven fabric, resulting in a large pressure loss.

On the other hand, a catalyst containing catalyst particles inside or partially exposed inside a fine fibrous material (Japanese Patent Laid-Open No. 55-9
No. 9345) has been proposed. This catalyst has a catalyst held in a fine fibrous material (also called "bulb-like fibers") obtained by a flash spinning method or a solution shearing method. Since the fine fibrous material has many branched fibrils, the catalyst particles held in the fine fibrous material are easily exposed to the surface due to the thinness of the fibril. Because it was connected to the outside through the fine voids between the fibrils, it was able to exert sufficient catalytic function even though it was held inside the fine fibrous material.

However, this fine fibrous material is so-called bulb-shaped, and it is made into a sheet by papermaking in the same way as paper.
Only a dimensional paper-like product was obtained, and it did not become a catalyst with a three-dimensional three-dimensional structure. Therefore, although sheets using catalysts made of fine fibrous materials have high catalytic functions, they have the drawback of high pressure loss and clogging, resulting in short service life, especially for applications where the processing air volume is large. could not be used.

[VIA Problem to be Solved by the Invention] The present invention has been made to solve the above-mentioned drawbacks of the prior art. An object of the present invention is to provide a small nonwoven catalyst.

[Means for Solving the Problems] In order to solve the above problems, the present invention is characterized in that porous fibers holding catalyst particles in the fibers form a three-dimensional network structure alone or together with other fibers. A non-woven catalyst was provided.

In other words, in the present invention, the catalyst particles are held within the porous fibers, so the catalyst particles are stably held without falling off, and since they are porous, there are many opportunities for contact between the catalyst particles and the object to be treated. Therefore, the catalytic function works well. and,
These porous fibers are longer in length and stronger than the fine fibrous materials shown in the prior art, and therefore can be subjected to fiber entanglement treatment such as needle punch treatment and hydroentanglement treatment. Therefore, it is possible to produce a nonwoven fabric having a three-dimensional network structure using porous fibers, and it is possible to provide a nonwoven fabric catalyst with excellent strength and low pressure loss.

The catalyst particles used in the present invention are not particularly limited and may be appropriately selected depending on the purpose, that is, the object to be treated. For example, when decomposing and removing ozone,
Metals such as platinum, gold, silver, copper, palladium, iron, nickel, cobalt, manganese and their oxides, alumina,
Silica is suitable. The catalyst particles preferably have an average particle size of 0.1 to 20 μm so that they are well dispersed in the porous fibers and the active surface is exposed.

As a method for retaining these catalyst particles in porous fibers, for example, a method of dispersing and mixing catalyst particles and a polymer that causes phase separation with this polymer in a fiber-forming polymer, spinning the mixture, and then stretching the mixture. There is. Immediately after spinning, a polymer that undergoes phase separation from the fiber-forming polymer forms a phase-separated dispersed phase within the fiber-forming polymer. Generates pores. Since the dispersed phase exists near the fiber surface, the pores not only communicate with each other internally but also open to the outside, forming a porous fiber. In addition, the catalyst particles are held with their active surfaces exposed in the numerous pores running within the fibers and on the fiber surface, allowing them to exhibit high catalytic function. As an example of the fiber-forming polymer used here, an acrylic polymer containing 40% by weight or more of acrylonitrile is preferable, and a polymer that undergoes phase separation from this is as follows:
Cellulose acetate and polyvinyl alcohol derivatives remain.

In addition, Ilt! As the porous fibers that retain the medium particles within the fibers, those obtained by other methods can of course also be used. However, in the method of mixing a fiber-forming polymer with catalyst particles and a substance that can be extracted with a solvent, spinning the mixture, and then removing the substance with a solvent, the solvent may have an adverse effect on the activity of the catalyst particles. Further, the method of mixing a foaming agent and catalyst particles with a fiber-forming polymer and foaming it at the same time as spinning requires caution because the fiber strength may decrease.

The fineness of the porous fiber used in the present invention is preferably in the range of 0.5 to 30 denier; if it is smaller than 0.5 denier, the required single fiber strength cannot be maintained sufficiently due to the porous structure, If it is thicker, the degree of exposure of the active surface of the catalyst particle decreases due to the relationship with the size of the catalyst particle, and the catalytic function decreases. In addition, the fiber length of the porous fibers is preferably 20 to 100 cm to ensure sufficient entanglement of the fibers by needle punching treatment, hydroentanglement treatment, etc.; The degree of entanglement becomes worse.

Note that it is desirable that the nonwoven catalyst of the present invention be composed only of the above-mentioned porous fibers, considering its catalytic functions, but if other properties such as strength and durability are particularly required, other fibers may be used. May be mixed with However, even in this case, it is desirable that the porous fibers be contained in the nonwoven catalyst in an amount of 25% by weight or more. Other fibers may be appropriately selected depending on the required properties and are not particularly limited.

The above-mentioned porous fibers are used alone or mixed with other fibers to form a fiber web through a fiber web forming means such as a card machine. After this, the fiber web is subjected to a fiber bonding process such as a needle punching method or a hydroentanglement method, so that the fibers are
A dimensionally entangled network of non-woven catalysts is formed. Since this nonwoven catalyst has a three-dimensional network structure, it has a large contact area with the object to be treated and has a low pressure loss. However, if the degree of entanglement of the fibers is increased too much to increase the density, the pressure loss will naturally increase, so it is desirable that the apparent density of this nonwoven catalyst does not exceed 0.5 g/Cm3. From the relationship, it is desirable that the apparent density of the nonwoven catalyst is 0.003 g/c+n3 or more. In particular, the preferred apparent density of the nonwoven catalyst is 0.
01-0.2 g/cm3.

Although a method of entangling fibers has been described here as a means for producing a nonwoven catalyst with a three-dimensional network structure, the method for producing a nonwoven catalyst of the present invention is not limited to this. Any means may be used as long as a three-dimensional network structure can be obtained. Other methods include the so-called point seal method, in which, after forming a fibrous web of porous fibers, dotted heat-sealed portions are provided at predetermined intervals on the fibrous web. However, even if the fibers have a three-dimensional network structure, binders that bind the fibers can fill the pores of porous fibers, cover the active surface of the catalyst, or form a coating in the spaces between the fibers. This is undesirable because it may cause the formation of

Although the nonwoven catalyst of the present invention obtained in this way has high catalytic activity, it has low pressure loss, so
Not only can it be used to remove harmful substances from ordinary gases, but it can also be applied to fields that require large processing air volumes.

(Example 1) Acrylic polymerization stop containing 90% acrylonitrile 92.
In a dimethylformamide solution with a polymer concentration of 22% consisting of 5 parts of cellulose acetate and 7.5 parts of cellulose acetate (average degree of polymerization 150), 10 parts of catalyst particles (manufactured by Ebara Jitsugyo ■) with an average particle diameter of 10 μm mainly composed of manganese dioxide were added. Disperse and mix. Next, this solution was spun into a 63% aqueous dimethylformamide solution at 15°C, followed by first stretching, washing with water, drying, second stretching,
A porous fiber in which catalyst particles were retained was produced by heat shrinking.

The porous fibers were passed through a carding machine to form a fiber web with a basis weight of 100 g/a'' consisting of 100% porous fibers, and then needle punched at a needle density of 80/(a)2 to form a three-dimensional fiber. apparent density of entangled 0.02g
/cm'' of non-woven catalyst was obtained.

Using this nonwoven catalyst, an experiment was conducted to decompose and remove ozone gas as follows.

First, the nonwoven catalyst was cut into pieces of 800c+n' (weight of nonwoven catalyst: 8.0 g, weight of catalyst particles: 08 g), and this was placed in an ozone gas flow path. Next, ozone gas of 115±10 ppm was flowed through channel No. 20 at a rate of 1.5 liters/min, and the ozone concentration before and after passing through the nonwoven catalyst was measured to determine the ozone decomposition rate.

The results are shown in Table 1.

Note that the ozone decomposition rate was expressed as a percentage by dividing the difference in ozone concentration before and after passing through the nonwoven catalyst by the ozone concentration before passing.

(Example 2) A mixture of 50% of the rolled porous fibers and 50% of acrylic fibers used in Example 1 was used, and a card machine was used to create
/l" fiber web was produced. Next, this m-fiber nib was subjected to needle punching at a needle density of 80/cs" to obtain an apparent density of 0.02 in which am was three-dimensionally entangled.
A nonwoven catalyst of g/co+' was obtained.

Using this nonwoven catalyst cut into pieces of 800 cm (weight of nonwoven catalyst: 8.0 g, weight of catalyst particles: 0.8 g), an experiment for decomposition and removal of ozone gas was conducted in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example, 2) A sintered body of sintered catalyst particles mainly composed of manganese dioxide (manufactured by Nippon Shokubai Chemical Co., Ltd.) 7.28 g,
Prepare 41.6g. Next, these sintered bodies were placed in an ozone gas flow path, and an experiment for decomposition and removal of ozone gas was conducted in the same manner as in Example 1. The results are shown in Table 1.

The sintered body used had a cross-sectional area perpendicular to the flow path of the sintered body that was the same as the area of the nonwoven catalyst of Example 1.

Table 1 As is clear from Table 1, the sintered body consisting only of catalyst particles and the non-woven catalyst of the present invention are similar in weight (Example 1.2 and Comparative Example 1). has a high decomposition rate,
It can be seen that it is excellent in removing ozone. This means that
Considering that the amount of catalyst particles contained in the non-woven catalyst is about ten tenths of the weight of the non-woven catalyst, this indicates that the catalyst of the present invention is working with remarkable efficiency.

[Effects of the Invention] Since the present invention has the configuration described above, it has the following effects.

(2) Since the catalyst particles are retained within the porous fibers, the catalyst particles do not fall off and are stably retained.

(2) In addition, the catalyst particles are held within the porous fibers, and the fibers form a three-dimensional network structure, so the contact area with the processing gas is large and the catalyst activity is high.

■Since the pores Ili & 1 have a three-dimensional network structure, space between fibers is secured and pressure loss is low.

■Thus, processing is possible even with a large flow rate of processing gas, and the service life is long.

■Also, since it has the above structure, it has excellent strength and there are no problems in handling.

As described above, the nonwoven catalyst of the present invention exhibits excellent effects, and is particularly useful for removing harmful substances in gases such as harmful substances in exhaust gas and decomposition of ozone in ozone gas. It is.

Claims (3)

[Claims] (1) A nonwoven catalyst characterized in that porous fibers holding catalyst particles in the fibers form a three-dimensional network structure alone or together with other fibers. (2) The nonwoven catalyst according to claim 1, which has an apparent density of 0.003 to 0.5 g/cm^3. (3) The nonwoven catalyst according to claim 1 or 2, wherein the three-dimensional network structure is formed by entangling fibers.