JP2022083821A - Gas filter function improver - Google Patents

Abstract

To provide a gas filter function improver that improves the trapping ability of a filter.SOLUTION: The inventive gas filter function improver contains cellulose fibers with a median diameter d50 of 1 μm or more, inorganic matter and a dispersion medium.SELECTED DRAWING: None

Description

The present invention relates to a gas filter function improving agent.

Filters such as masks are known to collect pollen, bacteria, viruses and the like.
For example, Patent Document 1 describes an antiviral material containing nanofibers of a polysaccharide.

JP-A-2017-150117

Some filters such as masks on the market have insufficient collection capacity.
Therefore, an object of the present invention is to provide a gas filter function improving agent that improves the collecting ability of the filter.

According to one aspect of the present invention, there is provided a gas filter function improving agent containing a cellulose fiber having a median diameter d ₅₀ of 1 μm or more, an inorganic substance, and a dispersion medium.

According to the present invention, there is provided a gas filter function improving agent that improves the collecting ability of the filter.

The schematic diagram which showed the apparatus which measures the collection efficiency and the initial pressure resistance of a filter sprayed with a gas filter function improver.

Hereinafter, embodiments of the present invention will be described.
The gas filter function improving agent according to the embodiment of the present invention contains a cellulose fiber having a median diameter d ₅₀ of 1 μm or more, an inorganic substance, and a dispersion medium.

The gas filter function improving agent can be used, for example, by spraying or applying to a filter such as a mask filter. The filter described here is a filter that allows gas such as air to pass through.

Cellulose fiber is, for example, a fiber obtained by hydrolyzing and defibrating a plant fiber containing cellulose. The plant fiber containing cellulose is, for example, pulp. The cellulose fiber may be a fiber made of modified cellulose. The modified cellulose is, for example, acetyl cellulose.

The median diameter _d50 of the cellulose fiber is 1 μm or more. The median diameter d50 of the cellulose fiber is preferably in the range of 8 μm to 300 μm, and more preferably in the range of 8 μm to ₁₀₀ μm. If the median diameter d ₅₀ of the cellulose fiber is too small, when applied to the filter, the ventilation resistance of the filter tends to increase, and it tends to be difficult to improve the collection capacity of the filter. If the median diameter d ₅₀ of the cellulose fiber is too large, it tends to be difficult to uniformly disperse the cellulose fiber on the filter when applied to the filter.
The median diameter _d50 of the cellulose fiber is obtained by using, for example, a laser diffraction type particle size distribution measuring device.

The average fiber diameter of the cellulose fiber is preferably in the range of 10 nm to 5000 nm. If the average fiber diameter of the cellulose fiber is too small, the ventilation resistance of the filter tends to increase when the gas filter function improving agent is applied to the filter. When a cellulose fiber having a large average fiber diameter is used, more cellulose fibers are required as compared with the case where a cellulose fiber having a small average fiber diameter is used.
The cellulose fiber is preferably a cellulose nanofiber. Here, the cellulose nanofiber is a cellulose fiber having an average fiber diameter of 100 nm or less. When cellulose nanofibers are used as the cellulose fibers, a network structure composed of the cellulose fibers, the inorganic substance, and the filter can be formed with a smaller mass. The mesh structure will be described later.
The average fiber diameter can be examined using, for example, an electron microscope.

Cellulose fibers having a median diameter d ₅₀ of 1 μm or more have, for example, an average fiber length in the range of 5 μm to 1000 μm. The average fiber length of the cellulose fiber is preferably in the range of 10 μm to 500 μm, more preferably in the range of 20 μm to 500 μm. If the average fiber length of the cellulose fiber is too small, the aeration resistance of the filter tends to increase when applied to the filter, and it tends to be difficult to improve the collection capacity of the filter. If the average fiber length of the cellulose fibers is too large, it tends to be difficult to uniformly disperse the cellulose fibers on the filter when applied to the filter.
The average fiber length can be determined, for example, using an electron microscope.

The ratio A ₁ / A ₂ of the amount A ₂ of the cellulose fiber to the amount A ₁ of the inorganic substance is preferably in the range of 1 to 3000, more preferably in the range of 3 to 100, and 10 to 35. It is particularly preferable that it is within the range. If the ratio A ₁ / A ₂ is too large, the effect of the cellulose fiber is less likely to be noticeable. If the ratio A ₁ / A ₂ is too small, it tends to be difficult to give the filter a high collection capacity.

Examples of the cellulose fiber include the trade names "SELPHYM (registered trademark) C-500", "SELPHYM (registered trademark) C-100" or "SELPHYM (registered trademark) C-25" (all manufactured by Mori Machinery Co., Ltd.). Commercial products such as can be used. All of these commercially available products are cellulose nanofibers.

The amount of the cellulose fiber is preferably in the range of 0.05 parts by mass to 6 parts by mass, and in the range of 0.05 parts by mass to 0.5 parts by mass with respect to 100 parts by mass of the dispersion medium. Is more preferable. If the amount of cellulose fiber is too small, the effect of the cellulose fiber is less likely to be noticeable. If the amount of cellulose fiber is too large, it tends to be difficult to give the filter a high collection capacity.

The inorganic substance preferably contains at least one of a magnesium compound, a titanium compound, a calcium compound and a silicate mineral. Inorganic substances containing at least one of magnesium compounds, titanium compounds, calcium compounds and silicate minerals can give the filter a high collection capacity.

The inorganic material is preferably fibrous, needle-like or scaly.
The fibrous or needle-like inorganic substance has a length-to-diameter ratio of preferably 5 or more, more preferably 50 or more. The fibrous inorganic substance is, for example, a fibrous magnesium compound, a fibrous titanium compound, or a fibrous calcium compound. The fibrous magnesium compound is, for example, fibrous magnesium sulfate. The fibrous titanium compound is, for example, fibrous potassium titanate. The fibrous calcium compound is, for example, fibrous calcium silicate. The needle-shaped inorganic substance is, for example, a needle-shaped calcium compound. The needle-shaped calcium compound is, for example, needle-shaped calcium carbonate.

The fibrous or needle-like inorganic substances have a diameter in the range of 0.5 μm to 10 μm, for example. The fibrous or needle-like inorganic substances are, for example, in the range of 5 μm to 500 μm in length.

The scaly inorganic substance has a thin plate-like shape. The scaly inorganic substance has, for example, a median diameter d50 in the range of 1 μm to ₅₀₀ μm. The scaly inorganic material has, for example, an average thickness in the range of 0.01 μm to 10 μm. The scaly inorganic material has, for example, the ratio of the median diameter _d50 to the average thickness in the range of 5 to 5000. The scaly inorganic substances are, for example, silicate minerals such as talc and mica.

The diameter, length and thickness of the inorganic material can be examined using, for example, an electron microscope.
The median diameter d ₅₀ of the inorganic substance can be obtained by using, for example, a laser diffraction type particle size distribution measuring device.

The inorganic substance is more preferably fibrous or needle-like, and the inorganic substance is particularly preferably fibrous. A gas filter function improver containing a fibrous or needle-like inorganic substance can impart a higher collection ability to the filter than a gas filter function improver containing a scaly inorganic substance. Further, the gas filter function improving agent containing a fibrous inorganic substance can give a higher collecting ability to the filter than the gas filter function improving agent containing a needle-shaped inorganic substance.

The median diameter d50 of the inorganic substance is preferably ₅₀₀ μm or less, more preferably in the range of 1 μm to 500 μm, particularly preferably in the range of 1 μm to 100 μm, and particularly preferably in the range of 20 μm to 40 μm. Is even more preferable. If the median diameter d ₅₀ of the inorganic substance is too small, it tends to be difficult to give the filter a high collection capacity. If the median diameter d ₅₀ of the inorganic substance is too large, it tends to be difficult to uniformly disperse the inorganic substance on the filter when applied to the filter.

The median diameter d ₅₀ of the inorganic substance can be obtained by using, for example, a laser diffraction type particle size distribution measuring device.

The specific gravity of the inorganic substance is preferably in the range of 1 to 4, more preferably in the range of 2 to 3.5. If the specific gravity of the inorganic substance is too large, the inorganic substance tends to precipitate in the dispersion medium. The lower limit of the specific gravity of the inorganic substance is not particularly limited.

The inorganic material is preferably water-insoluble.

The amount of the inorganic substance is preferably in the range of 0.1 part by mass to 30 parts by mass, and more preferably in the range of 1 part by mass to 4 parts by mass with respect to 100 parts by mass of the dispersion medium. If the amount of minerals is too small, it tends to be difficult to give the filter a high collection capacity. If the amount of inorganic substances is too large, the ventilation resistance of the filter tends to increase when applied to the filter.
The inorganic substance may be one kind or two or more kinds.

The dispersion medium is, for example, water, alcohol, or a mixture of water and alcohol. The alcohol is, for example, ethanol or isopropanol. The dispersion medium may consist of water or a mixture of water and alcohol. When the dispersion medium consists of a mixture of water and alcohol, the proportion of water in the dispersion medium is in the range of 30% by mass to 70% by mass, and the proportion of alcohol in the dispersion medium is in the range of 30% by mass to 70% by mass. It is preferably inside.
The dispersion medium may contain an organic solvent other than alcohol.

The gas filter function improving agent may further contain a dispersant. The dispersant is, for example, an anionic surfactant, a cationic surfactant or a nonionic surfactant.

The amount of the dispersant is preferably in the range of 0.01 parts by mass to 500 parts by mass, and more preferably in the range of 0.01 parts by mass to 20 parts by mass with respect to 100 parts by mass of the inorganic substance. .. The gas filter function improving agent containing a dispersant is superior in dispersibility of the above-mentioned inorganic substances as compared with the gas filter function improving agent containing no dispersant. In addition, the addition of the dispersant suppresses the aggregation of the cellulose fibers.

The gas filter function improving agent may further contain a photocatalyst that exerts a photocatalytic activity by irradiation with visible light. As the photocatalyst, titanium oxide carrying a transition metal ion is preferable. Titanium oxide carrying transition metal ions exhibits photocatalytic activity by irradiation with visible light. As the transition metal ion, an ion of an element belonging to any one of the 8th to 11th groups is preferable, and an iron ion is more preferable. The term "group" used here is "group" in the long-periodic table. Titanium oxide is preferably rod-shaped. The rod-shaped titanium oxide exhibits high photocatalytic activity.

The amount of the photocatalyst is preferably in the range of 0.3 parts by mass to 10000 parts by mass, and more preferably in the range of 0.3 parts by mass to 10 parts by mass with respect to 100 parts by mass of the inorganic substance. The gas filter function improving agent containing a photocatalyst can decompose organic substances such as pollen, bacteria and viruses collected in the filter. If the amount of photocatalyst is too small, the efficiency of decomposition of organic substances such as pollen, bacteria and viruses collected by the filter will be low. If the amount of the photocatalyst is too large, the photocatalyst tends to fall off from the filter when the gas filter function improving agent is applied to the filter.

The average particle size of the photocatalyst is preferably in the range of 100 nm to 200 nm. When the average particle size of the photocatalyst is within the above range, the photocatalyst has a large specific surface area and thus exhibits high photocatalytic ability.
The average particle size of the photocatalyst can be examined using, for example, an electron microscope.

As described above, the gas filter function improving agent can be used by injecting or applying it to a filter such as a mask filter.
Among the commercially available masks, there are masks having a coarse filter, for example, masks having a filter mesh size in the range of 30 μm to 300 μm. Filters for such masks consist of, for example, non-woven fabrics containing at least one of polypropylene and rayon, rayon, polyester, polyurethane, nylon, cotton rags, or cotton gauze. Since the above-mentioned gas filter function improver contains a cellulose fiber having a specific median diameter _d50 and an inorganic substance, it forms a network structure composed of the cellulose fiber, the inorganic substance and the filter in a coarse-grained filter. This mesh structure can reduce the size of the filter mesh. Therefore, the above-mentioned gas filter function improving agent improves the collecting ability of the mask. Further, since the gas filter function improving agent described above contains a cellulose fiber having a specific median diameter _d50 , the expiratory resistance of the filter is unlikely to increase.

On the other hand, when the gas filter function improving agent contains only one of the cellulose fiber having a predetermined median diameter _d50 and the inorganic substance, it is difficult to improve the collecting ability of the mask. Further, even when the gas filter function improving agent contains both the cellulose fiber and the inorganic substance, if the median diameter d ₅₀ of the cellulose fiber is too small, it is difficult to improve the collecting ability of the mask.

Further, when a fibrous, needle-like or scaly inorganic substance is used as the inorganic substance, since the inorganic substance has anisotropy, it is easy to secure a passage for exhalation. Therefore, the expiratory resistance of the filter is unlikely to increase. In addition, since the specific surface area of fibrous, needle-like or scaly inorganic substances is relatively large, such inorganic substances tend to collect pollen, bacteria, viruses and the like.

Further, since the dispersant is an organic substance like pollen, bacteria and viruses, the activity of the photocatalyst can be reduced. On the other hand, since the above-mentioned photocatalyst exhibits photocatalytic activity by irradiation with visible light, if the gas filter function improving agent contains the above-mentioned dispersant and the above-mentioned photocatalyst, when the gas filter function improving agent is applied to the filter, The photocatalyst decomposes the dispersant by irradiation with visible light. When the dispersant is decomposed, pollen, bacteria, viruses, etc. can be collected by the filter and decomposed by the photocatalyst at the position occupied by the dispersant on the filter, and the collecting ability of the filter and the activity of the photocatalyst are improved. do.

The above-mentioned gas filter function improving agent can be used for filters other than the mask filter. Such a filter is, for example, an air purifier filter or an air conditioner filter.

Examples are described below.
<Preparation of gas filter function improver>
<Example 1>
First, 98.2 parts by mass of a dispersion medium, 1 part by mass of an inorganic substance, 0.3 parts by mass of a cellulose fiber and 0.5 parts by mass of a dispersant were mixed to prepare a gas filter function improving agent.
A mixture of water and alcohol is used as the dispersion medium, ethanol is used as the alcohol, fibrous magnesium sulfate is used as the inorganic substance, and "SELPHYM (registered trademark) C-500" (morimachinery) is used as the cellulose fiber. Co., Ltd.) was used, and an anionic surfactant was used as the dispersant. The amount of ethanol was 50.0 parts by mass. The fibrous magnesium sulfate has a median diameter d ₅₀ of 30 μm and a fiber length in the range of 8 to 100 μm. The median diameter d50 of "SELPHYM (registered trademark) C- ₅₀₀ " is 100 μm.

<Examples 2 to 23 and Comparative Examples 1 to 8>
The gas filter function improving agents according to Examples 2 to 23 and Comparative Examples 1 to 8 were prepared by the same method as described for Example 1 except that the composition was changed as described in Tables 1 to 8.

The cellulose nanofibers (C-500) in Tables 1 to 6 and 8 are the same as the cellulose fibers used in Example 1. The fibrous magnesium sulfate in Tables 1 to 6 and Table 8 is the same as the fibrous magnesium sulfate used in Example 1. The needle-shaped calcium carbonate in Table 1 has a median diameter d ₅₀ of 4 μm and a length in the range of 5 to 50 μm. The talc (d ₅₀ : 4 μm) in Tables 1 and 7 has a median diameter d ₅₀ of 4 μm. The mica (d ₅₀ : 20 μm) in Tables 1 and 7 has a median diameter d ₅₀ of 20 μm. The mica (d ₅₀ : 40 μm) in Tables 1 and 7 has a median diameter d ₅₀ of 40 μm. The heavy calcium carbonate (d ₅₀ : 1.6 μm) in Tables 1 and 7 is an amorphous heavy calcium carbonate, and the median diameter d ₅₀ is 1.6 μm. The light calcium carbonate (d ₅₀ : 2 μm) in Table 1 has a median diameter d ₅₀ of 2 μm.

The cellulose nanofiber (C-100) in Table 2 indicates "SELPHYM (registered trademark) C-100" (manufactured by Mori Machinery Co., Ltd.). The median diameter d50 of this cellulose fiber is ₄₀ μm. The cellulose nanofiber (C-25) in Table 2 indicates "SELPHYM (registered trademark) C-25" (manufactured by Mori Machinery Co., Ltd.). The median diameter _d50 of this cellulose fiber is 8 μm. TEMPO-oxidized CNF in Table 2 indicates TEMPO-oxidized cellulose nanofibers. When the median diameter d ₅₀ of TEMPO oxidized CNF was measured, the median diameter d ₅₀ was less than the detection limit. The detection limit of the laser diffraction type particle size distribution measuring device used for the measurement of the median diameter d ₅₀ was 0.1 μm. The TEMPO oxidized CNF has a fiber length in the range of 0.5 to 1.0 μm. The talc (d ₅₀ : 20 μm) in Table 7 has a median diameter d ₅₀ of 20 μm. The heavy calcium carbonate (d ₅₀ : 20 μm) in Table 7 is an amorphous heavy calcium carbonate, and the median diameter d ₅₀ is 20 μm.
Further, the gas filter function improving agents according to Examples 2 to 23 and Comparative Examples 1 to 8 were prepared so that the amount of ethanol was 50.0 parts by mass.

<Making a filter to which a gas filter function improver is applied>
The gas filter function improving agent according to Example 1 was sprayed onto the filter to obtain a gas filter function improving agent applied filter according to Example 1. As the filter, a non-woven fabric made of polypropylene and rayon was used.
Examples 2 to 23 and Examples 2 to 23 and the same method as described for the gas filter function improver application filter according to Example 1 except that the gas filter function improver according to Examples 2 to 23 and Comparative Examples 1 to 8 were used. The gas filter function improving agent application filter according to Comparative Examples 1 to 8 was obtained.

<Measurement of collection efficiency and initial pressure resistance>
Using the apparatus shown in FIG. 1, the collection efficiency and the initial pressure resistance of the gas filter function improving agent applied filter were investigated. Hereinafter, this device will be described.

FIG. 1 is a schematic diagram showing a device for measuring the collection efficiency and the initial pressure resistance of a filter to which a gas filter function improving agent is applied. The device 1 shown in FIG. 1 includes a particle accommodating unit 2, a collecting unit 3, a suction machine 4, a differential pressure gauge 5, a tube 6, a tube 7, a tube 8, and a tube 9.

The particle accommodating unit 2 is a container accommodating test particles. This container contains about 100 mg of test particles. The average particle size of the test particles is 10 μm. This container has an open top. One end of the tube 6 is connected to the opening of this container.

The collecting unit 3 is a container in which the filter 31 is installed. The filter 31 is provided in the center of the collection unit 3 and divides the internal space of the container into an upper space and a lower space. This container is provided with an inflow port connecting the upper space and the external space directly above the filter 31. The other end of the pipe 6 is connected to this inflow port. This container is provided with an outlet that connects the lower space and the external space. One end of the pipe 7 is connected to this outlet. This container is provided with a first vent that connects the upper space and the external space, and a second vent that connects the lower space and the external space. One end of the pipe 8 is connected to the first vent, and one end of the pipe 9 is connected to the second vent.

The suction machine 4 is a device for sucking air. The suction machine 4 has a suction port, and the other end of the pipe 7 is connected to the suction port.

The differential pressure gauge 5 is a device for measuring the pressure difference between the pressure in the upper space and the pressure in the lower space of the collecting unit 3. The differential pressure gauge 5 has a first vent and a second vent. The other end of the pipe 8 is connected to the first vent of the differential pressure gauge 5. The other end of the pipe 9 is connected to the second vent of the differential pressure gauge 5.

The device for measuring the collection efficiency and the initial pressure resistance of the filter to which the gas filter function improving agent is applied has been described above.

Next, a method for measuring the collection efficiency and the initial pressure resistance of the gas filter function improving agent-applied filter using the above-mentioned device 1 will be described.

First, the mass of the gas filter function improving agent applied filter and the mass of the particle accommodating portion 2 according to Example 1 were measured.
Next, the gas filter function improving agent application filter was installed inside the collecting unit 3 so that the surface sprayed with the gas filter function improving agent faces the upper space of the collecting unit 3.

Next, the suction machine 4 was operated to suck air without using the particle accommodating portion 2. After operating the suction machine 4, an initial pressure resistance was obtained as a pressure difference between the pressure in the upper space and the pressure in the lower space of the collecting unit 3 using the differential pressure gauge 5.

Next, the suction machine 4 was operated to suck air while the particle accommodating portion 2 was used. By this suction, the test particles were supplied from the particle accommodating portion 2 to the filter 31. Here, almost the entire amount of the test particles was sucked by the suction machine 4.

Next, the suction machine 4 was stopped, and the gas filter function improving agent application filter was taken out. Then, the mass of the removed gas filter function improving agent application filter and the mass of the particle accommodating portion 2 were measured.
Next, the collection rate (C) of the gas filter function improving agent applied filter was determined by the following formula (1).

In the above formula (1), x1 is the mass of the filter after supplying the test particles, x0 is the mass of the filter before supplying the test particles, and a0 is the particle accommodating portion 2 before supplying the test particles. 1 is the mass of the particle accommodating portion 2 after supplying the test particles.

Next, the filter in the state before spraying the gas filter function improving agent according to Example 1, that is, the untreated filter is also captured by the same method as described for the gas filter function improving agent application filter of Example 1. The collection rate and initial pressure resistance were obtained.

Next, the collection efficiency (E) of the gas filter function improving agent applied filter according to Example 1 was determined by the following formula (2).

In the above formula (2), C1 is the collection rate of the gas filter function improving agent applied filter according to Example 1, and C0 is the collection rate of the untreated filter.

Next, with respect to the gas filter function improving agent application filters according to Examples 2 to 23 and Comparative Examples 1 to 8, the collection efficiency and the initial pressure were obtained by the same method as described for the gas filter function improving agent application filter of Example 1. I got resistance.
The results of measuring the collection efficiency and the initial pressure resistance and the evaluations of the collection efficiency and the initial pressure resistance are summarized in Tables 1 to 7.

Further, except that particles having an average particle diameter of 2.5 μm were used as the test particles, the same method as that for obtaining the collection efficiency and the initial pressure resistance of the gas filter function improving agent applied filter according to Example 1 was used. , The collection efficiency and the initial pressure resistance of the gas filter function improving agent applied filter according to Examples 1 and 15 were obtained. The results are summarized in Table 8.

In the rows of "collection efficiency evaluation" in Tables 1 to 8, "◎" indicates that the collection efficiency was 41% or more, and "○" indicates that the collection efficiency was in the range of 21% to 40%. "△" indicates that the collection efficiency was within the range of 6% to 20%, and "x" indicates that the collection efficiency was 5% or less. .. In the "Initial pressure resistance evaluation" line, "○" indicates that the initial pressure resistance was in the range of 1.3 kPa to 1.7 kPa, and "Δ" indicates that the initial pressure resistance was in the range of 1.8 kPa to 2.5 kPa. It indicates that it was within the range of, and "x" indicates that the initial pressure resistance was 2.6 kPa or more.

As shown in Tables 1 to 6, the gas filter function improving agent application filters according to Examples 1 to 23 were excellent in collection efficiency. In particular, the gas filter function improving agent application filters according to Examples 10, 11 and 15 to 17 were particularly excellent in collection efficiency.

Further, as shown in Tables 1 to 6, the gas filter function improving agent applied filters according to Examples 1 to 23 had a small initial pressure resistance. That is, these gas filter function improver application filters had a small ventilation resistance.

The initial pressure resistance of the untreated filter was 1.3 kPa. As described above, there was no significant difference between the initial pressure resistance of the untreated filter and the initial pressure resistance of the gas filter function improving agent applied filter according to Examples 1 to 23.

On the other hand, the gas filter function improving agent applied filter according to Comparative Example 1 did not contain an inorganic substance, and therefore was not excellent in collection efficiency. Further, the gas filter function improving agent applied filters according to Comparative Examples 2 to 8 did not contain cellulose fibers having a median diameter d ₅₀ of 1 μm or more, and therefore were not excellent in collection efficiency.

Further, as shown in Table 8, even when test particles having a particle size of 2.5 μm are used, the gas filter function improving agent-applied filters according to Examples 1 and 15 are both excellent in collection efficiency and have excellent collection efficiency. The ventilation resistance was small.

1 ... device, 2 ... particle accommodating part, 3 ... collecting part, 31 ... filter, 4 ... suction machine, 5 ... differential pressure gauge, 6 ... tube, 7 ... tube, 8 ... tube, 9 ... tube.

According to one aspect of the present invention, a cellulose fiber having a median diameter _d50 of 1 μm or more, an inorganic substance, and a dispersion medium are contained, and the inorganic substance contains at least one of magnesium sulfate, calcium carbonate, talc, and mica, and the inorganic substance is contained. The ratio A ₁ / A ₂ of the amount A ₁ to the amount A ₂ of the cellulose fiber is provided with a gas filter function improving agent in the range of 3 to 100 .

The ratio A ₁ / A ₂ of the amount A ₁ of the inorganic substance to the amount A ₂ of the cellulose fiber is preferably in the range of 1 to 3000, more preferably in the range of 3 to 100, and 10 to 35. It is particularly preferable that it is within the range of. If the ratio A ₁ / A ₂ is too large, the effect of the cellulose fiber is less likely to be noticeable. If the ratio A ₁ / A ₂ is too small, it tends to be difficult to give the filter a high collection capacity.

Further, as shown in Table 8, even when test particles having a particle size of 2.5 μm are used, the gas filter function improving agent-applied filters according to Examples 1 and 15 are both excellent in collection efficiency and have excellent collection efficiency. The ventilation resistance was small.
The inventions described in the original claims are described below.
[1]
A gas filter function improving agent containing a cellulose fiber having a median diameter d ₅₀ of 1 μm or more, an inorganic substance, and a dispersion medium.
[2]
Item 2. The gas filter function improving agent according to Item 1, wherein the median diameter d ₅₀ of the cellulose fiber is in the range of 8 μm to 300 μm.
[3]
Item 2. The gas filter function improving agent according to Item 1 or 2, wherein the median diameter d ₅₀ of the inorganic substance is in the range of 1 μm to 500 μm.
[4]
Item 2. The gas filter function improving agent according to any one of Items 1 to 3, wherein the ratio A ₁ / A ₂ of the amount A ₁ of the inorganic substance and the amount A ₂ of the cellulose fiber is in the range of 1 to 3000.
[5]
Item 6. The gas filter function improving agent according to any one of Items 1 to 4, wherein the inorganic substance contains at least one of a magnesium compound, a titanium compound, a calcium compound and a silicate mineral.

According to one aspect of the present invention, a cellulose fiber having a median diameter _d50 of 1 μm or more, an inorganic substance, and a dispersion medium are contained, and the inorganic substance contains at least one of magnesium sulfate, calcium carbonate, talc, and mica, and the inorganic substance is contained. The ratio A ₁ / A ₂ of the amount A ₁ to the amount A ₂ of the cellulose fiber is in the range of 3 to 100, and the median diameter d ₅₀ of the inorganic substance is in the range of 1 μm to 500 μm, and the inorganic substance is in the range of 1 μm to 500 μm. Is provided with a gas filter function improving agent which is fibrous, needle-like or scaly .

Claims (5)

A gas filter function improving agent containing a cellulose fiber having a median diameter d ₅₀ of 1 μm or more, an inorganic substance, and a dispersion medium. The gas filter function improving agent according to claim 1, wherein the median diameter d ₅₀ of the cellulose fiber is in the range of 8 μm to 300 μm. The gas filter function improving agent according to claim 1 or 2, wherein the median diameter d ₅₀ of the inorganic substance is in the range of 1 μm to 500 μm. The gas filter function improving agent according to any one of claims 1 to 3, wherein the ratio A ₁ / A ₂ of the amount A ₂ of the cellulose fiber to the amount A ₁ of the inorganic substance is in the range of 1 to 3000. The gas filter function improving agent according to any one of claims 1 to 4, wherein the inorganic substance contains at least one of a magnesium compound, a titanium compound, a calcium compound and a silicate mineral.

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