JP7079929B2 - Air filter - Google Patents

Description

The present invention relates to an air filter.

As an air filter that adsorbs a gas such as moisture or odor, a filter member in which an adsorbent or the like is supported on a breathable base material is known. As the water adsorbent, for example, silica gel or zeolite is used.

Patent Document 1 discloses a specific filter member in which an adsorbent is supported on a three-dimensional three-dimensional knitted fabric by using a binder as a filter member that absorbs and desorbs a gas by a temperature change. In Patent Document 1, zeolite, silica gel, high silica zeolite and the like are mentioned as adsorbents. According to Patent Document 1, the adsorbed water is desorbed by heating the high silica zeolite at 200 ° C.

Japanese Unexamined Patent Publication No. 2010-069427

In order to desorb water molecules from an adsorbent such as silica gel or zeolite, it is generally necessary to heat the adsorbent to a temperature exceeding 100 ° C., and from the viewpoint of energy saving, an adsorbent that can be regenerated at a lower temperature is required.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an air filter having a reproducible adsorption function at a low temperature.

The air filter of the first embodiment according to the present invention has a structure having a plurality of through holes partitioned by partition walls, and cellulose nanofibers filled in the through holes.
The cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers.

The air filter of the second embodiment according to the present invention is a cellulose nanofibers arranged on or mixed with a support having a breathability formed in a planar shape or a pleated shape. And have
The cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers.

In one embodiment of the air filter of the second embodiment, the cellulose nanofibers are attached to the surface of the support via a binder.

One embodiment of the air filter of the first embodiment and the second embodiment sucks and desorbs a gaseous substance in the gas by aerating a gas through the cellulose nanofibers.

In one embodiment of the air filter of the first embodiment and the second embodiment, the specific surface area of the cellulose nanofibers per unit mass is 40 to 250 m ² / g.

One embodiment of the air filter of the first embodiment and the second embodiment is produced by freeze-drying a cellulose nanofiber dispersion obtained by defibrating a wet pulp fiber by the cellulose nanofiber. It was done.

According to the present invention, it is possible to provide an air filter whose adsorption function can be regenerated at a low temperature.

FIG. 1 is a photograph showing an example of an air filter according to the first embodiment. FIG. 2 is a schematic diagram showing an example of a structure used for the air filter of the first embodiment. FIG. 3 is a schematic view showing another example of the structure used for the air filter of the first embodiment. FIG. 4 is a schematic cross-sectional view showing an example of the air filter of the second embodiment. FIG. 5 is a schematic view showing an example of the support of the air filter of the second embodiment. FIG. 6 is a photograph showing the air filter used in the examples. FIG. 7 is a graph showing the hygroscopic characteristics of the air filters of Examples and Comparative Examples. FIG. 8 is a graph showing the isotherms of water vapor adsorption with the cellulose nanofibers used in the examples and the zeolite used in the comparative examples.

Hereinafter, the air filter according to the present invention will be described. In addition, in order to clarify the explanation, the following description and drawings are omitted or simplified as appropriate. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

FIG. 1 is a photograph showing an example of the air filter of the first embodiment. The air filter 10 of the first embodiment according to the present invention has a structure having a plurality of through holes 12 partitioned by a partition wall 11 and cellulose nanofibers 13 filled in the through holes 12.
The cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers.

In the air filter 10 of the first embodiment, the gas is passed through the cellulose nanofibers by passing the gas in the direction of the through hole 12, and the gaseous substance such as water contained in the gas is the cellulose nano. Adsorbed to the fiber. In the present invention, since the cellulose nanofibers are cotton-like, lump-like, or fine-fiber cellulose nanofibers, the specific surface area per unit mass of the cellulose nanofibers is large, and the adsorption efficiency is excellent. Further, since the gaseous substance adsorbed on the cellulose nanofibers is desorbed by heating at, for example, 100 ° C. or lower, the air filter of the present invention can be easily regenerated.

The structure 14 used for the air filter 10 of the first embodiment will be described with reference to FIGS. 2 and 3. Common to the examples of FIGS. 2 and 3, the structure 14 is a structure 14 in which a plurality of through holes 12 are formed by the partition wall 11, and is usually ventilated in the direction of the through holes 15. The structure 14 may support the cellulose nanofibers to be filled and maintain the shape of the filter. Therefore, the shape of the opening of the through hole is not particularly limited, and may be polygonal, circular, or elliptical. Specifically, for example, it may have a hexagonal honeycomb structure as shown in the example of FIG. 2, a rigid gate honeycomb structure as shown in the example of FIG. 3, a grid shape (not shown), or the like. It may be a shape in which two or more kinds of polygons are combined. Further, as shown in the example of FIG. 1, the shape of the through hole does not have to be a regular polygon, and may be deformed according to the filling amount of the cellulose nanofibers and the like.
The thickness of the structure 14 is not particularly limited, and may be appropriately adjusted in consideration of the use of the air filter, the filling amount of the cellulose nanofibers, and the like. The thickness of the structure 14 can be appropriately set in the range of 1 mm or more and 10 cm or less as an example.

The material of the partition wall 11 is not particularly limited, and may be appropriately selected from those used in known air filters. For example, in addition to metals such as aluminum, stainless steel and iron, ceramics such as alumina and silica, resins such as polyester, nylon and acrylic, glass fiber, cellulose paper and the like can be used. The partition wall 11 may be made of a material having breathability or may be made of a material having no breathability.

The air filter 10 of the second embodiment will be described with reference to FIGS. 4 and 5. The air filter 10 of the second embodiment according to the present invention is a mixture of a breathable support 16 formed into a planar or pleated shape (see FIG. 5) on the support or with the support. With the cellulose nanofibers 13 arranged in
The cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers.

In the air filter 10 of the second embodiment, the cellulose nanofibers 13 may be laminated on the support 16 as shown in the example of FIG. 4, and the fine fiberized cellulose nanofibers may be laminated. It may enter the ventilation hole of the support 16 and adhere to the surface in the ventilation port. When the cellulose nanofibers adhere to the surface of the support 16, they may adhere to the surface of the support 16 via a binder.

The support used for the air filter 10 of the second embodiment is appropriately selected from those made of a breathable material. Examples thereof include metal fibers such as aluminum, stainless steel and iron, ceramic fibers such as alumina and silica, resin fibers such as polyester, nylon and acrylic, glass fibers and fibrous materials such as cellulose paper.
Further, a support containing cellulose nanofibers may be used by mixing cellulose nanofibers with each of the above materials.

Next, the cellulose nanofibers common to the air filter of the first embodiment and the air filter of the second embodiment will be described.
In the present invention, the cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers. Since the specific cellulose nanofilter has a large specific surface area, it has excellent adsorption performance for gaseous substances. The cellulose nanofilter used in the present invention preferably has a specific surface area of 40 m ² / g or more and 250 m ² / g or less and a fiber diameter of 50 to 700 nm per unit mass.

In the present invention, the cellulose nanofibers include not only cellulose but also partially modified cellulose. For example, some of the hydroxyl groups in the cellulose molecule are oxidized to aldehyde group, carboxyl group, etc., esterified such as nitrate ester, acetate ester, phosphoric acid ester, etc., methyl ether, hydroxypropyl ether, carboxy. Includes those substituted with other substituents, such as those etherified, such as methyl ether. Further, in the present invention, the cellulose nanofibers form a bundle of two or more cellulose molecular chains. When two or more bundles of cellulose molecular chains are formed, it means that two or more cellulose molecular chains are aggregated to form an aggregate called a microfibril.

A method for manufacturing cellulose nanofibers will be described. The cellulose nanofibers used in the present invention are preferably produced by freeze-drying a cellulose nanofiber dispersion obtained by defibrating wet pulp fibers. According to the production method, cotton-like or lumpy cellulose nanofibers having a large specific surface area can be produced.

The pulp fiber used as a raw material in the present invention is not particularly limited, and wood pulp such as broadleaf tree and coniferous tree; non-wood pulp such as straw, bagus, kenaf, bamboo, reed, 楮, flax; sulfite pulp, deinked pulp and the like. Waste paper pulp; can be appropriately selected from mechanical pulps such as ground pulp, pressurized crushed wood pulp, refiner crushed wood pulp, thermomechanical pulp, chemothermomechanical pulp, chemimechanical pulp, and chemigrand pulp (CGP). Pulp fiber is powdered cellulose obtained by crushing these pulps with a homogenizer, a mill, or the like.

If necessary, the powdered cellulose may be dispersed in water and then an oxidation catalyst and an oxidizing agent may be added to carry out an oxidation reaction. Examples of the oxidation catalyst include N-oxyl compounds such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). In addition, examples of the copolymerizer include alkali metal hypohalites and the like. In the present invention, cellulose nanofibers having a large specific surface area can be produced without performing an oxidation reaction.

Next, water is added to the powdered cellulose, and the fiber is defibrated in a wet state. In the present invention, it is preferable that the cellulose nanofibers are defibrated mechanically. As a defibration method, for example, a ball mill, a jet mill, or the like can be used, and it is particularly preferable to defibrate with a jet mill.

Then, by freeze-drying the defibrated cellulose nanofibers, cotton-like or lumpy, porous cellulose nanofibers can be obtained. Further, by dispersing and refining the cellulose nanofibers, fine fibrous cellulose nanofibers can be obtained.

The air filter of the present invention can be made into a filter having excellent hygroscopicity by using the cellulose nanofibers having a large specific surface area thus obtained. Further, since the gaseous substance adsorbed on the cellulose nanofibers is desorbed by heating at 100 ° C. or lower, and further at 70 ° C. or lower, the air filter of the present invention can regenerate the adsorption function at a low temperature.

The air filter of the present invention can be suitably used as an air filter for a known dehumidifying / humidity controlling device. Further, it can be used as a pre-filter for dehumidification and humidity control by installing it at an intake port of an existing air conditioner.

Hereinafter, the present implementation will be described in detail with reference to Examples and Comparative Examples, but the present implementation is not limited to the following Examples.

[Production Examples 1-2: Production of Cellulose Nanofibers]
Cellulose nanofibers were obtained by defibrating the sugi pulp material by mechanically crushing it.
In Production Example 1, the pulp suspension was jetted with a nozzle under high pressure conditions, and the suspensions collided with each other under high speed conditions higher than the speed of sound to perform defibration (CNF1).
Further, in Production Example 2, the pulp suspension was ejected by a nozzle under high pressure conditions and collided with a ceramic ball at high speed to perform defibration (CNF2).
Cellulose nanofibers (CNF1 and CNF2) were obtained by freeze-drying each of the suspensions subjected to the above mechanical crushing treatment.
Both CNF1 and CNF2 were cotton-like cellulose nanofibers.

[Measurement of specific surface area of cellulose nanofibers]
The cellulose nanofibers (CNF1 and CNF2) obtained in Production Examples 1 and 2 and the zeolite used in the comparative example described later were measured using a high-performance specific surface area / pore size distribution measuring device ASAP2020 manufactured by Micromeritics, respectively. A water vapor adsorption experiment was conducted under the condition of a temperature of 20 ° C. The specific surface area determined from the adsorption isotherm was 108 m ² / g for CNF1, 107 m 2 / g for CNF ^{2, and 448 m 2 /} g for zeolite.

[Example 1: Manufacture of an air filter]
The air filter 1 of Example 1 was obtained by filling 1 g of the CNF1 into a circular structure having a honeycomb structure made of cellulose and having a diameter of 54 mm. FIG. 6A shows a photograph of the air filter 1.

[Example 2: Manufacture of air filter]
In Example 1, the air filter 2 of Example 2 was obtained in the same manner as in Example 1 except that 1 g of CNF2 was filled instead of CNF1. FIG. 6B shows a photograph of the air filter 2.

[Comparative Example 1]
An air filter of Comparative Example 1 was obtained in the same manner as in Example 1 except that 1 g of 4A type zeolite was used instead of CNF1 in Example 1.

<Hygroscopic characteristics of air filter>
The air filters of Examples and Comparative Examples were regenerated by aerating 70 ° C. air at a speed of 0.22 m / sec for 15 minutes to prepare the air filters. Next, air having a relative humidity of 55% was supplied, and the relative humidity of the air after the air filter was ventilated was measured. The results are shown in FIG.

As shown in FIG. 7, it can be seen that the air filters of Examples 1 and 2 using cellulose nanofibers are superior in hygroscopicity as compared with the air filter of Comparative Example 1 using zeolite.

<Air filter regeneration evaluation>
After evaluating the moisture absorption characteristics, air at 70 ° C. was aerated at a speed of 0.22 m / sec for 15 minutes to regenerate each air filter. Air having a relative humidity of 55% was again supplied to the air filter after ventilation, and the relative humidity of the air after ventilation of the air filter was measured. It was clarified that the air filters of Examples 1 and 2 using the cellulose nanofibers exhibited the same hygroscopic characteristics as the above hygroscopic property evaluation, and the hygroscopic function was regenerated. On the other hand, in the air filter of Comparative Example 1 using zeolite, the regeneration of the hygroscopic function was small in the air at 70 ° C.
As described above, it has been clarified that the air filter of the present invention regenerates the adsorption function under the gentle condition of allowing air at 70 ° C. to pass through.

<Water vapor adsorption isotherm>
FIG. 8 shows the cellulose nanofibers (CNF1 and CNF2) used in Example 1 and the water vapor adsorption isotherm of the zeolite used in Comparative Example 1. In the graph of FIG. 8, the horizontal axis represents relative pressure = (water vapor pressure P at the time of measurement (at equilibrium) / saturated water vapor pressure P ₀ at the measurement temperature), and the vertical axis represents the amount of adsorption per 1 g of cellulose nanofibers or zeolite. Is shown.

As shown in FIG. 8, the equilibrium adsorption amount of zeolite was larger than that of CNF. However, zeolite needs to be heated to 100 ° C or higher for regeneration, and considering the repeated use of the air filter, it has become clear that the air filter of the present invention can construct a dehumidifying system with excellent energy saving. ..

10 Air filter 11 Partition wall 12 Through hole 13 Cellulose nanofiber 14 Structure 15 Ventilation 16 Support

Claims (5)

It has a structure having a plurality of through holes partitioned by a partition wall, and cellulose nanofibers filled in the through holes.
The cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers .
An air filter in which the partition wall is made of a non-breathable material . It has a breathable support molded into a flat shape or a pleated shape, and cellulose nanofibers arranged mixed with the support.
An air filter in which the cellulose nanofibers are cotton-like, lump-like, or fine-fiber-like cellulose nanofibers. The air filter according to claim 1 or 2 , wherein a gas is aerated through the cellulose nanofibers to absorb and desorb a gaseous substance in the gas. The air filter according to any one of claims 1 to 3 , wherein the specific surface area of the cellulose nanofibers per unit mass is 40 to 250 m ² / g. The cellulose nanofibers
The air filter according to any one of claims 1 to 4 , which is produced by freeze-drying a cellulose nanofiber dispersion obtained by defibrating wet pulp fibers.

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