JPH1147522A - Filter paper for air purification filter, method for producing filter paper, and air purification filter using filter paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide filter paper for air purification filters which has the dust removing function of a filter paper (HEPA) for high performance of air purification, a method for producing such filter paper, and an air purification filter made of such filter paper. SOLUTION: Damp paper is produced by a wet paper manufacturing method from an aqueous suspension containing 100 pts.wt. of a glass fiber with not shorter than 0.3 μm and shorter than 2.0 μm average fiber diameter and 5-40 pts.wt. of an activated carbon fiber with 500-1,300 m<2> /g specific surface area, not shorter than 5 μm and shorter than 15 μm fiber diameter, and 1-20 mm fiber length, 1-7 pts.wt. of an adhesive is deposited on the damp paper, and then the resultant damp paper is dried to give filter paper for air purification filters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter paper for an air purifying filter, a method for producing the same, and an air purifying filter using the filter paper, and more particularly to a filter paper for a high-performance air purifying filter used in a clean room and the like, and its production. The present invention relates to a method and an air cleaning filter using the filter paper.

[0002]

2. Description of the Related Art Conventionally, glass fiber-made so-called "high-performance air purifying filters" are used in fields such as clean rooms, clean benches and aseptic chambers which need to remove ultra-fine dust and the like which require a high level of clean environment. Filter paper "is used. The "filter paper for high-performance air purifying filter"
MIL-STD 0.3 μm dioctyl phthalate particles as defined in MIL-F-51079C (abbreviation:
(DOP particles) exhibiting a property of 99.97% or more under conditions of a surface wind velocity of 5.33 cm / sec.
(High Efficiency Particulate Air filter) is defined as a glass fiber filter paper.

[0003] Japanese Patent Application Laid-Open No. 4-284803 discloses a high performance air purifier which maintains the collection efficiency of the conventional glass fiber filter paper for HEPA and improves the drawback that the pressure loss of the conventional glass fiber filter paper for HEPA is high. A filter paper for the filter is shown. The filter paper for a high-performance air purifying filter described in the publication includes a glass chopped strand fiber having a glass fiber composition of 10 to 50% by weight and a fiber diameter of 10 μm or less;
And a glass fiber filter paper made of 90 to 50% by weight of ultrafine glass fibers and having the above-mentioned HEPA characteristics and low pressure loss. However, the above-mentioned conventional "high-performance air purification filter paper" (HEPA) has a problem that it has a dust removing function but no deodorizing function.

On the other hand, Japanese Patent Application Laid-Open No. H2-115013 discloses that 40 to 70% by weight of activated carbon fiber and 2% of glass fiber are used.
By mixing and containing 0 to 40% by weight and an adhesive of 1 to 4% by weight, it has the same dust removing function as a conventional filter filter for medium-performance air purification, has a small pressure loss, and has a deodorizing function. It shows that the obtained filter paper for a medium-performance filter was obtained. However, the filter paper for air purification of this publication has a medium performance, and there is a problem that the collection efficiency of ultrafine dust and the like is lower than that of the filter paper for high performance air purification.

Japanese Patent Application Laid-Open No. 7-289828 discloses that activated carbon fiber is 10 to 40% by weight, and the average fiber diameter is 2 to 40%.
10% by weight or more of 3 μm glass fiber and 4 to 6 of adhesive
It is shown that by mixing and mixing by weight%, a tensile strength can be secured, pressure loss can be suppressed low, and a filter paper for a medium-performance filter having a deodorizing function is obtained. However, the filter paper for air purification of this publication has a medium performance, and there is a problem that the collection efficiency of ultrafine dust and the like is lower than that of the filter paper for high performance air purification.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention
L-STD MIL-F-51079C "Filter paper for high-performance air purification" (HEPA) specified in L-STD MIL-F-51079C, which has a dust-removing performance and is provided with an adsorption function such as deodorization, and a method for producing the filter paper. It is an object to provide an air cleaning filter using the filter paper.

[0007]

In order to solve the above-mentioned problems, a filter paper for an air purifying filter according to the present invention comprises:
(1) For 100 parts by weight of glass fiber having an average fiber diameter of 0.3 μm or more and less than 2.0 μm, (2) a specific surface area of 500 to
It contains 1300 m ² / g, 5 to 40 parts by weight of activated carbon fiber having a fiber diameter of 5 μm or more and less than 15 μm, and a fiber length of 1 to 20 mm, and (3) an adhesive of 1 to 7 parts by weight.

[0008] By combining the glass fiber, activated carbon fiber and adhesive having the above structure, MIL-STD
"High-performance air purifying filter paper" (HEPA) specified in MIL-F-51079C and deodorizing performance can be added.

The glass fiber used for the filter paper for an air purifying filter of the present invention contains microfibers having an average fiber diameter of 0.3 to 2.0 μm. This is an important requirement. However, the average diameter of the entire glass fiber is 0.3 to 2.0 μm.
If it is in the range of m, several percent of a large-diameter chopped strand glass fiber may be blended to impart strength to the filter paper. The collection performance of the filter paper is determined by the pressure loss and the collection efficiency, and the higher the pressure loss, the higher the filter efficiency of the filter paper, but the higher the pressure loss, the higher the load on the blower that operates the filter and the higher the energy cost. It is not preferable. Usually, the average fiber diameter of glass fibers is determined in order to design a filter medium according to the purpose of use. When the average fiber diameter of glass fibers is 2.0 μm or more, the collection efficiency is 99.97%.
If it is less than 0.3 μm, the pressure loss is too high, which is not preferable.

In the filter paper for an air cleaning filter of the present invention, the reason why the diameter of the activated carbon fiber is limited to 5 μm or more and less than 15 μm is that if it is less than 5 μm, it becomes difficult to produce the activated carbon fiber, and if it exceeds 15 μm, it is obtained. This is because the processability of the filter paper is deteriorated, and pleating at the time of manufacturing the filter becomes difficult.

In the filter paper for an air purifying filter of the present invention, the specific surface area of the activated carbon fiber is from 500 to 1300 m ² /
The reason for the g is that if it is less than 500 m ² / g, the adsorbing performance such as deodorizing performance is not sufficient, and if it exceeds 1300 m ² / g, the strength of the activated carbon fiber becomes insufficient and the handleability becomes poor.

In the filter paper for an air purifying filter of the present invention, the fiber length of the activated carbon fiber is set to 1 mm to 20 mm because it is difficult to make the fiber length less than 1 mm, the cost becomes high, and it is industrially unsuitable. When the thickness exceeds 20 mm, the water dispersibility of the activated carbon fiber becomes poor, and it becomes difficult to obtain a uniform filter paper.

In the filter paper for an air purifying filter of the present invention, the reason why the equilibrium water content of activated carbon fibers at a relative humidity of 37% is 10% or more is that if it is less than 10%, dispersibility during wet papermaking is poor and uniform filter paper is used. Is difficult to obtain.

It has been empirically known that the collection performance of the filter paper for an air purification filter using ultrafine glass fibers is affected by the variation in the filling of the glass fibers constituting the filter paper. That is, if the dispersion of the filling is large, the dispersion of the pores formed by the glass fibers becomes large, and the maximum diameter becomes large, so that the collection efficiency is reduced and HEPA does not occur. Therefore, in the present invention, uniformly dispersing the activated carbon fibers to be added to the ultrafine glass fibers is an important requirement so as not to lower the collection efficiency.

The activated carbon fiber (AC) used in the present invention
F) is a specific surface area of 500 to 1300 produced by activating polyacrylonitrile-based fibers, cellulose-based fibers, phenol-based fibers, and pitch-based fibers as raw materials by a known method.
m ² / g of fibrous activated carbon. Among these activated carbon fibers, in particular, polyacrylonitrile-based activated carbon fibers are particularly excellent in water dispersibility and become filter paper distributed uniformly, so that the dust removing function of the ultrafine glass fibers is not impaired. Further, since the dispersibility is good at the time of wet papermaking, it does not lump and does not impair the adsorption performance of the activated carbon fiber itself.

It is important for the activated carbon fiber used in the present invention to have the above-mentioned properties in combination, in order to obtain HEPA having good trapping performance. In particular, the dispersibility of activated carbon fiber is
This greatly affects the collection performance, and if the dispersion is poor, a leak occurs from the lump of the activated carbon fiber, and the dust removal performance as HEPA cannot be achieved.

In the filter paper for an air purifying filter of the present invention, the adhesive (binder) may be acrylic, vinyl acetate, urethane, epoxy, polyester, or SBR.
, NBR latex or polyvinyl alcohol,
A paper strength agent generally used in papermaking processes such as starch, or a fibrous material such as a polyvinyl alcohol fibrous binder of a wet heat fusion type, a low melting point polyethylene terephthalate, denatured polypropylene, or a denatured polyester fiber using denatured polyester in the sheath part. A binder or the like is used alone or in combination. In order to impart water repellency to the filter paper, a water repellent such as a silicon-based, fluorine-based, or paraffin-based water repellent may be used in combination.

The amount of the adhesive to be added is preferably 1 to 7 parts by weight with respect to 100 parts by weight of glass fiber having an average fiber diameter of 0.3 μm or more and less than 2.0 μm. Practical strength cannot be imparted, and if it is 7 parts by weight or more, the webbing state of the adhesive increases between the constituent fibers of the filter paper, and the pressure loss becomes too high, which is not preferable.

The first method for producing the filter paper for an air purifying filter of the present invention is as follows.
specific surface area of 50 parts by weight of glass fiber of less than 50 m
An aqueous suspension containing 0 to 1300 m ² / g, a fiber diameter of 5 μm or more and less than 15 μm, 5 to 40 parts by weight of an activated carbon fiber having a fiber length of 1 to 20 mm, and an adhesive of 1 to 7 parts by weight is wet-processed. It is characterized by drying after papermaking.

The second method for producing the filter paper for an air purifying filter of the present invention is a method for producing an average fiber diameter of 0.3 μm to 2.0 μm.
specific surface area of 50 parts by weight of glass fiber of less than 50 m
0-1300 m ² / g, fiber diameter 5 μm or more and less than 15 μm, 5 to 40 parts by weight of an aqueous suspension containing activated carbon fibers having a fiber length of 1 to 20 mm in an amount of 5 to 40 parts by weight. It is characterized in that 7 parts by weight are adhered and then dried.

That is, the filter paper for an air purifying filter of the present invention is obtained by dispersing the fiber constituting the filter paper in water using a pulper or the like, wet-making the slurry with a paper machine to obtain a wet paper, and then drying the wet paper. It is. In the process of dispersing the raw fiber, in order to improve dispersibility, sulfuric acid is used to adjust pH 2
A method of adjusting the pH in the range of 4 is used, but a surfactant having a neutral pH and a dispersant may be used.

The method for applying the adhesive includes an internal addition method in which the adhesive is mixed at the time of dispersion, and an external addition method in which the adhesive is attached to wet paper obtained by a paper machine and then dried. The effect of the present invention does not change even if
If the total amount of the adhesive is 1 part by weight or more and 7 parts by weight or less, the internal addition method and the external addition method may be used in combination. The method of application by the external addition method is not particularly limited, but a method of immersing a wet paper in the adhesive liquid, a method of spraying the wet paper with a spray, a method of attaching the adhesive liquid to a roll and transferring the wet paper to the wet paper, etc. Is used.

As a drying method, it is desirable to dry at 110 to 150 ° C. using a hot air drier, a roll drier or the like.

[0024]

The test method used in each of the following examples was performed as follows.

Pressure loss Air was passed through a filter paper having an effective area of 100 cm ^{2 at} a surface wind velocity of 5.33 cm / sec, and the differential pressure at that time was measured with a fine differential pressure gauge.

DOP Collection Efficiency Air containing polydisperse DOP particles generated by a Ruskin nozzle is applied to a filter paper having an effective area of 100 cm ^{2 at} a surface wind velocity of 5.33 c.
The DOP collection efficiency when ventilation was performed at m / sec was measured with a laser particle counter manufactured by Rion. The target particle size was measured at 0.3 μm.

The PF value is an indicator of filtration performance of the PF value filter media were determined using the following equation based on the measured value of the collection efficiency and the pressure loss. (The higher the PF value, the higher the collection efficiency with the same pressure loss.)

[0028]

(Equation 1)

Tensile Strength A test piece cut to a width of 1 inch from the longitudinal direction of the filter paper was measured using a constant-speed tensile tester at a span length of 100 mm and a tensile speed of 15 mm / min.

A sample having a toluene adsorption capacity of 1 g was dried at 105 ° C. for 1 hour and then subjected to JIS-K
The toluene adsorption capacity was measured in accordance with 1477-95.

It was measured at an equilibrium water content of 25 ° C. and RH of 37% in accordance with JIS.

Dispersibility of Activated Carbon Fiber The dispersibility of the activated carbon fiber in the filter paper was visually evaluated as good when the dispersibility was good. Those that could not be said were shown in the evaluation of ①.

[0033] Example 1 with respect to the glass fiber to 100 parts by weight of the average fiber diameter of 1.41, a specific surface area of 750 meters ² /
g, fiber diameter 12 μm, fiber length 5 mm, equilibrium moisture content (RH
11% by weight of 16% PAN-based ACF (trade name: Fine Guard, manufacturer: Toho Rayon Co., Ltd.) was blended, defibrated with a pulper at a concentration of 0.5%, sulfuric acid acidic pH 3.5, and then Papermaking was performed with a paper machine to obtain wet paper. Next, an acrylic latex (trade name:
Primal E-358, manufacturer: Nippon Acrylic Chemicals)
1.85 parts by weight of a fluorine-based water repellent (trade name: Light Guard FRG-1, manufacturer: Kyoeisha Chemical) 0.16 parts by weight of an adhesive is applied to wet paper by an external addition method, and then a roll at 130 ° C. The resultant was dried with a dryer to obtain a filter paper having a basis weight of 70 g / m ² and an adhesive amount of 6.2 parts by weight.

Pressure loss, collection efficiency, PF of the obtained filter paper
The values, tensile strength, and toluene adsorption capacity were measured, and the results are shown in Table 1 below.

[0035] Example 2 with respect to the glass fiber to 100 parts by weight of the average fiber diameter of 1.25 .mu.m, a specific surface area of 900 meters ² /
g, fiber diameter 10 μm, fiber length 8 mm, equilibrium moisture content 13%
(Under 37% RH) PAN-based ACF (trade name: Fine Guard, manufacturer: Toho Rayon Co., Ltd.) except that 25 parts by weight were blended in the same manner as in Example 1 above, except that the basis weight was 70 g /%.
m ² , and a filter paper having an adhesive adhesion amount of 6.2 parts by weight was obtained.

Pressure loss, collection efficiency, PF of the obtained filter paper
The values, tensile strength, and toluene adsorption capacity were measured, and the results are shown in Table 1 below.

[0037] Example 3 the glass fiber to 100 parts by weight of the average fiber diameter of 1.41, a specific surface area of 800 m ² /
g, fiber diameter 12 μm, fiber length 10 mm, equilibrium moisture content 14
% (Under 37% RH) of PAN-based ACF (trade name: Fine Guard, manufacturer: Toho Rayon Co., Ltd.), 11 parts by weight,
3.3 parts by weight of a wet / heat dissolving type polyvinyl alcohol fibrous binder (trade name: VPB107-2, manufacturer: Kuraray Co., Ltd.) is blended as the internal adhesive, and the concentration is adjusted to 0.
It was defibrated with a pulper at 5% sulfuric acid acidity pH 3.5, and then made paper with a paper machine to obtain wet paper. Next, a solution concentration of 0.0
14% by weight of a fluorine-based water repellent was applied to wet paper by an external addition method, and then dried with a roll dryer at 130 ° C. to obtain a filter paper having a basis weight of 70 g / m ² and an adhesive adhesion amount of 3.0 parts by weight. .

Pressure loss, collection efficiency, PF of the obtained filter paper
The values, tensile strength, and toluene adsorption capacity were measured, and the results are shown in Table 1 below.

Example 4 A specific surface area of 1000 m ^{2 was} added to 100 parts by weight of glass fibers having an average fiber diameter of 1.25 μm.
/ G, fiber diameter 10 μm, fiber length 7 mm, equilibrium moisture content 12
% Of PAN-based ACF (trade name: Fine Guard, manufacturer: Toho Rayon Co., Ltd.) except that 25 parts by weight of the filter paper were mixed in the same manner as in Example 3 to obtain a filter paper having an adhesive adhesion amount of 3.0 parts by weight. Was.

Pressure loss, collection efficiency, PF of the obtained filter paper
The values, tensile strength, and toluene adsorption capacity were measured, and the results are shown in Table 1 below.

[0041] [Comparative Example] the glass fiber to 100 parts by weight of the average fiber diameter of 1.41, a specific surface area of 1000 m ² /
g, fiber diameter 18 μm, fiber length 5 mm, equilibrium moisture content 5%
(Under 37% RH) pitch-based activated carbon fiber (trade name: Renoves, manufacturer: Osaka Gas Co., Ltd.) except that 11 parts by weight were blended in the same manner as in Example 1 to obtain a basis weight of 70 g / m ² ,
A filter paper having an adhesive amount of 6.2 parts by weight was obtained.

Pressure loss, collection efficiency, PF of the obtained filter paper
The values, tensile strength, and toluene adsorption capacity were measured, and the results are shown in Table 1 below.

[0043]

[Table 1]

According to Table 1, the fiber diameter is 15 μm or more.
Filter paper using pitch-based activated carbon fiber using an activated carbon fiber having an equilibrium moisture content of less than 10% has poor dispersibility, low collection efficiency, and low adsorption rate of deodorizing components, etc.
It can be seen that the filter paper for an air purifying filter of the present invention has good dispersibility of activated carbon fibers, and therefore has a high collection efficiency and a high adsorption rate of deodorizing components and the like.

[0045]

The filter paper for an air purifying filter of the present invention comprises:
MIL-STD The "high-performance air purification filter paper" (HEPA) specified in MIL-F-51079C has both the dust removal performance and the adsorption function such as deodorization.

Continued on the front page (72) Inventor Tomohiko Soyama 3-5-1 Nishizao, Nagaoka-shi, Niigata Pref.

Claims (8)

[Claims] (1) An average fiber diameter of 0.3 μm or more and 2.0 μm
(2) Specific surface area 500 to 1300 m ² / g, fiber diameter 5 μ
m to less than 15 μm, 5 to 40 parts by weight of activated carbon fiber having a fiber length of 1 to 20 mm, and (3) a filter paper for an air cleaning filter containing 1 to 7 parts by weight of an adhesive. 2. The filter paper for an air purifying filter according to claim 1, wherein the activated carbon fiber has an equilibrium moisture content at a relative humidity of 37% of 10% or more. 3. The filter paper for an air purifying filter according to claim 1, wherein the activated carbon fiber is a PAN type. 4. The collection efficiency of 0.3 μm particles is 99.97.
% Or more and an adsorption capacity for toluene of 1% or more. 5. The method according to claim 1, which is obtained by wet papermaking.
5. The filter paper for an air purifying filter according to 3 or 4. 6. A specific surface area of 500 to 100 parts by weight of glass fibers having an average fiber diameter of 0.3 μm or more and less than 2.0 μm.
An aqueous suspension containing 1300 m ² / g, an active carbon fiber having a fiber diameter of 5 μm or more and less than 15 μm, a fiber length of 1 to 20 mm, 5 to 40 parts by weight, and an adhesive at a ratio of 1 to 7 parts by weight was wet-formed. And then drying the filter paper. 7. A specific surface area of 500 to 100 parts by weight of glass fibers having an average fiber diameter of 0.3 μm or more and less than 2.0 μm.
1300 m ² / g, 5 to less than 15 μm fiber diameter, 5 to 40 parts by weight of an aqueous suspension containing activated carbon fibers having a fiber length of 1 to 20 mm in an amount of 5 to 40 parts by weight.
A method for producing a filter paper for an air purifying filter, wherein 7 parts by weight are adhered and then dried. 8. An air purifying filter using the filter paper for an air purifying filter according to claim 1, 2, 3, 4, or 5.