WO2005115586A1

WO2005115586A1 - Medium for mid-performance air filter, process for producing the same and mid-performance air filter

Info

Publication number: WO2005115586A1
Application number: PCT/JP2005/009786
Authority: WO
Inventors: Norikazu Shinya; Yoshinobu Kakizaki; Masaaki Watanabe
Original assignee: Nippon Muki Co., Ltd.
Priority date: 2004-05-28
Filing date: 2005-05-27
Publication date: 2005-12-08

Abstract

A medium for mid-performance air filter that ensures the passage of air by means of voids within a sheet constituting the filter medium, and that without trapping dust disproportionately on its air inlet side, is capable of trapping dust uniformly in the direction of thickness of the filter medium, and that accordingly is capable of prolonging its service life; a process for producing the same; and a mid-performance air filter. There is provided a medium for mid-performance air filter, comprising a sheet having voids formed by causing fragments resulting from bursting of expandable particles to bond surrounding fibers, characterized in that the sheet is composed of 70 to 90 mass% of glass staple fibers of 2 to 8 μm average fiber diameter, 0 to 15 mass% of glass staple fibers of < 2 μm average fiber diameter, 5 to 15 mass% of sticky synthetic fibers of 10 to 35 μm average fiber diameter and 3 to 10 mass% of fragments from expandable particles.

Description

Specification

TECHNICAL FIELD The present invention relates to a medium for a medium performance air filter, a method for producing the same, and a medium performance air filter.

[0001] The present invention relates to a medium-performance air filter used in the purification of clean rooms, office air conditioners, home air conditioners, and the like used in the fields of the semiconductor manufacturing industry, the pharmaceutical manufacturing industry, the food industry, and hospitals. The present invention relates to a high performance air filter medium and a method for producing the same, and a medium performance air filter.

Background art

Conventionally, as a medium-performance air filter, a large-area filter medium is folded in a zigzag shape, and the interval between the filter media is held by a corrugated separator that is an interval holding material to form a filter pack. An air filter housed in a 290 mm box-shaped filter frame is used. Such an air filter has an advantage that it has a long filter life because of a large filter medium area. In addition, a pleated filter pack is formed in which a small space between filter media obtained by folding an electret non-woven fabric or the like in a zigzag shape is maintained by a ribbon material, and, for example, a type in which the filter media is housed in a box-shaped filter frame having a depth of 610 mm. Air filters are also used. This type of air filter has the advantage that dust or the like having the opposite charge is easily adsorbed because the fibers constituting the nonwoven fabric as the filter medium are charged with positive or negative charges. This type of air filter uses the air filter for a long time by frequently changing the filter medium. In addition, for example, as in Patent Document 1, a blow-off type air filter in which a frame is attached to an opening of a bag-shaped filter medium is also used. Such a streamer type air filter also has an advantage that the depth of the filter medium is large and the service life is long because the depth is as large as 610 mm.

[0003] As a filter medium used in the air filter, in addition to the electret nonwoven fabric and the like, a filter medium made of a sheet obtained by adding a binder to synthetic fibers or inorganic fibers and forming the sheet by a wet papermaking method has been used. As such a filter medium for a medium-performance air filter, a filter medium having high dust collection efficiency and high pressure loss and a low pressure loss is desired.

For example, as shown in FIG. 3, a conventional filter medium 10 made of a sheet made of glass fiber or the like by a wet papermaking method is applied to a glass fiber 9 having a relatively small average fiber diameter in a thickness direction of the filter medium. In this case, a gap having a small average pore diameter is formed uniformly, so that there is a problem that a large amount of dust 8 is unevenly collected on the air inflow side, and the pressure loss increases. The filter medium 10 includes a slightly larger average fiber diameter and glass fibers 16.

[0004] In order to reduce the pressure loss, it is conceivable to reduce the density of the filter medium by using fibers having a large average fiber diameter. However, when a sheet made of only fibers having a large average fiber diameter is used as a filter medium, the gap between the fibers becomes large, and the dust collection efficiency decreases. For this reason, as shown in FIG. 4, Patent Document 2 discloses that a synthetic fiber 11 having a large average fiber diameter, a glass fiber 12 having a small average fiber diameter, and foamable particles are dispersed in a dispersion medium, and the wet papermaking method is used. Thus, a sheet in which a void 13 is formed by foaming expandable particles after forming a sheet-like material is used as a filter medium 15 is disclosed. When the foamable particles are expanded, the fibers constituting the sheet-like material are expanded to form voids 13, and while the voids 13 are maintained, the outer wall 14 of the foamable particles is melted to form a peripheral portion. The fiber is glued.

Patent Document 1: JP-A-7-253028

Patent Document 2: JP-A-9155127

Disclosure of the invention

Problems to be solved by the invention

[0005] As shown in FIG. 4, the filter medium 15 described in Patent Document 2 has a structure in which the density of the filter medium 15 is reduced due to the voids 13 formed by the foaming of the expandable particles. A large mesh structure formed by synthetic fibers 11 having a large average fiber diameter serving as fibers is filled with glass fibers 12 having a small average fiber diameter, and gaps having a small average pore diameter are also uniform in the thickness direction of the filter medium 15. Therefore, the problem that a large amount of dust 8 is trapped unevenly on the air inflow side has not been improved. For this reason, the filter medium 15 has a problem that the pressure loss is high and the life of the filter medium is short. Further, the filter medium 15 has an advantage that an air passage is secured by the voids 13 formed by the foaming of the expandable particles, but the air passage that has been secured is very large, and the skeleton fiber and the skeleton fiber. There was a problem that the synthetic fibers 11 having a large average fiber diameter hindered the pressure loss.

In view of the above, the present invention provides an air passage secured by a void portion in a sheet constituting a filter medium, and uniformly distributes air in the thickness direction of the filter medium without collecting dust in a direction toward an air inflow side. It is another object of the present invention to provide a medium-performance air filter medium, a method for manufacturing the same, and a medium-performance air filter capable of collecting dust and having a longer life.

Means for solving the problem

[0006] A medium-performance air filter according to the present invention, as described in claim 1, is a medium-performance air filter formed of a sheet in which voids are formed by bonding surrounding fibers with fragments obtained by bursting expandable particles. A filter medium, wherein the sheet comprises 70 to 90% by mass of glass short fibers having an average fiber diameter of 2 to 8 m; 0 to 15% by mass of glass short fibers having an average fiber diameter of less than 2 m; It is characterized by comprising 5 to 15% by mass of an adhesive synthetic fiber of 35 m and 3 to 10% by mass of flakes of expandable particles.

Further, the method for producing a medium-performance filter medium for a medium-performance air filter according to the present invention comprises, as described in claim 2, 70 to 90% by mass of glass short fibers having an average fiber diameter of 2 to 8 μm, and an average fiber diameter of less than 2 μm. 0 to 15% by mass of glass short fibers, 5 to 15% by mass of adhesive synthetic fibers having an average fiber diameter of 10 to 35 m, and unfoamed expandable particles 3 to 3 to 20 μm in average particle size 3 to: A sheet is formed using an aqueous dispersion in which LO mass% is dispersed, and the expandable particles are expanded to form a void. Then, the surrounding fibers are debris obtained by bursting the expandable particles. It is characterized in that it is bonded to form a sheet.

Further, a medium-performance air filter according to the present invention uses the filter medium for a medium-performance air filter according to claim 1 as described in claim 3. The invention's effect

[0007] The filter material for a medium-performance air filter of the present invention is a sheet in which voids are formed by adhering surrounding fibers with fragments obtained by bursting foamable particles, and the sheet has an average fiber diameter of 2 to 8 70 to 90% by mass of glass short fibers of m, 0 to 15% by mass of glass short fibers having an average fiber diameter of less than 2 m, and 5 to 15% by mass of adhesive synthetic fibers having an average fiber diameter of 10 to 35 / ζπι. And 3 to 10% by mass of flakes of expandable particles. Therefore, the air gaps in the sheet serve as air passages, so that the air can easily move from the inflow side to the outflow side of the filter medium, and the average fibers constituting the sheet throughout the thickness direction of the filter medium. Dust can be evenly collected in a relatively fine mesh structure formed by short glass fibers having a diameter of 2 to 8 m, and the filter medium made of the sheet can have a long life. In addition, the average fiber diameter is less than 2 m When short glass fibers are mixed, the fine short glass fibers are dispersed by a relatively fine network structure formed by short glass fibers having an average fiber diameter of 2 to 8 m, and the fine glass fibers are small enough not to increase the pressure loss. By forming a mesh structure, dust collection efficiency can be increased over the entire thickness of the filter medium, and the life of the filter medium can be prolonged.

Further, since the sheet contains 3 to 10% by mass of fragments of the expandable particles, the fragments of the ruptured expandable particles strongly adhere to the surrounding fibers so as not to deteriorate the air permeability, and reduce the strength of the filter medium. Can be improved.

According to the method for producing a filter material for a medium-performance air filter of the present invention, since the surrounding fibers are bonded by the fragments obtained by rupture of the expandable particles, compared with the case where the fibers are bonded only by the adhesive synthetic fibers. Thus, the strength of the sheet is improved, and a long-life filter medium can be manufactured. The medium-performance air filter using the filter medium for a medium-performance air filter of the present invention has a high filter medium strength, so that the life of the filter medium is about twice as long as when a sheet made of conventional glass fiber is used as the filter medium. The filter can be made long, and a medium-performance air filter using the filter medium can be compactly formed.

Brief Description of Drawings

[0008] [Fig. 1] (a) a sheet before foaming of expandable particles serving as a filter material for a medium-performance air filter of the present invention, (b) a sheet in which the expandable particles are expanded, and (c). Conceptual diagram showing a sheet in which effervescent particles have been ruptured

FIG. 2 is a conceptual diagram showing a state in which air is passed through a medium-performance air filter medium of the present invention. FIG. 3 is a conceptual diagram showing a state in which air is passed through a conventional filter medium.

FIG. 4 is a conceptual diagram showing a state in which air is passed through a filter medium having a gap in a conventional sheet.

Explanation of symbols

[0009] 1 Sheets used as filter media for medium-performance air filters

2 Core-sheath type synthetic fibers that are adhesive synthetic fibers

3 C glass short fiber with average fiber diameter of 4 μm

3 'Short C glass fiber with average fiber diameter of 0.8 μm

4 Unfoamed heat-expandable microcapsules 5 Microcapsules foamed by thermal expansion

6 Void

7 Ruptured microcapsule fragments

8 dust

9 Glass fiber

10 Filter media

11 Synthetic fiber with large average fiber diameter

12 Small average fiber diameter! / Short glass fiber

13 Void

14 Exterior wall

15 Filter media

16 Slightly larger average fiber diameter! / Glass fiber

BEST MODE FOR CARRYING OUT THE INVENTION

The filter material for a medium-performance air filter according to the present invention is a sheet that forms voids by adhering surrounding fibers with debris obtained by bursting foamable particles, and the sheet has an average fiber diameter of 2 70 to 90% by mass of glass short fibers of up to 8 μm, 0 to 15% by mass of glass short fibers having an average fiber diameter of less than 2 m, and adhesive synthetic fibers having an average fiber diameter of 10 to 35 / ζπι 5 to 15 % By mass, and 3 to 10% by mass of foam particles.

The reason why 70 to 90% by mass of short glass fibers having an average fiber diameter of 2 to 8 m is blended in the sheet is that if the blending amount is less than 70% by mass, the fragments of adhesive synthetic fibers and foamable particles are combined. However, if the average fiber diameter exceeds 8 m or the blending amount exceeds 90% by mass, the adhesive synthetic fiber and the particles of the expandable particles may be reduced. This is because there is a problem that the strength of the filter medium is reduced due to a reduced amount of the compound. In order to reduce the gap between the fibers in the sheet and to improve the dust collection efficiency in a range where the pressure loss is not increased, a part of the short glass fibers is blended in an amount of 0 to 15% by mass to obtain an average fiber. Short glass fibers with a diameter of less than 2 m can also be used. In order to use stable quality glass short fibers, it is preferable to use those having an average fiber diameter of 0.3 m or more. As the short glass fiber, those formed by a steam spraying method, a spying method, a fire insertion method, a rotary method, or the like can be used.

[0011] In the sheet, 5 to 15% by mass of the adhesive synthetic fiber having an average fiber diameter of 10 to 35 µm is blended when the amount is less than 5% by mass or the average fiber of the adhesive synthetic fiber. If the diameter is less than 10 μm, the bonding area with the short glass fiber is reduced, and the bonding strength is insufficient. If the blending amount exceeds 15% by mass or the average fiber diameter of the adhesive synthetic fiber exceeds 35 μm, a film is formed between the fibers when the resin is melted and turned into a binder, and the pressure of the filter medium is reduced. This is because the higher the loss, the shorter the filter life.

As the adhesive synthetic fiber, a core-sheath type synthetic fiber can be used. For example, a core-sheath type synthetic fiber using polyester as the core component and a modified polyester having a low melting point as the sheath component (for example, N720 manufactured by Kuraray Co., Ltd.), or a core-sheath type using polyester as the core component and polyethylene as the sheath component Use of synthetic fibers (for example, N710 manufactured by Kuraray Co., Ltd.) is possible. The adhesive synthetic fibers are not limited to core-sheath type synthetic fibers. For example, synthetic fibers made of thermoplastic resin such as acrylic resin, polyester resin and polyolefin resin, and thermosetting materials such as epoxy resin Synthetic fibers made of fats and the like can also be used.

[0013] The content of 3 to 10% by mass of the shards of the expandable particles in the sheet is less than 3% by mass. There is a problem that the strength of the filter medium becomes weaker when the amount of the filter medium adhered to the fiber is small. When the amount exceeds 10% by mass, the strength of the filter medium is increased, but the amount of fragments of the ruptured expandable particles is increased, and the glass material is reduced. A large amount of explosive foamed particles adhere to the gaps between the short fibers and the adhesive synthetic fibers, resulting in poor air permeability, high pressure loss, and short filter media life.

Next, a method for producing a medium-performance air filter medium of the present invention will be described.

According to the production method of the present invention, a wet papermaking method using an aqueous dispersion in which unfoamed expandable particles having an average particle size of 3 to 20 μm are dispersed in the glass short fibers and the adhesive synthetic fibers of the above-mentioned composition. After forming a void portion by foaming the expandable particles to form a void portion, a filter medium for a neutral air filter formed of a sheet in which surrounding fibers are adhered by fragments of the expandable particles is ruptured. Manufacture. In addition, the use of unexpanded expandable particles having an average particle size of 3 to 20 / 、 πι is due to the fact that the average particle size of the unexpanded expandable particles is less than 3 m. However, there is a problem that it is not possible to form a sufficiently large void in the filter medium because the coefficient of expansion of the filter medium is low.If the average particle size exceeds 20 m, the voids become large. Although the trapping efficiency is improved, a large amount of ruptured expandable particles adhere to the interstices between the fibers, resulting in a problem that the pressure loss increases and the life of the filter medium is shortened.

[0015] The expandable particles used have a particle diameter of about 4 to 5 times and a volume of about 50 to 100 times when expanded by foaming.

As the expandable particles, polystyrene, polyvinyl chloride, polyvinyl chloride, zirride, or a copolymer of these, a heat-expandable gas such as ethane, ethylene, propane, butane, or isobutane was included on the outer wall. Things can be used. In particular, acrylonitrile monomethyl methacrylate (MMA) was used on the outer wall of the expandable particles, and isobutane was used as the heat-expandable gas contained in the expandable particles due to the degree of expansion of the expandable particles and the degree of adhesion between the expanded expandable particles and the short glass fibers. It is preferred to use expandable particles. When the heat-expandable expandable particles are used, the expandable particles expand by heating, and the expandable particles burst, and the encapsulated heat-expandable gas is released to the outside. Fragments of the ruptured expandable particles melt and firmly adhere to the surrounding fiber surface and Z or intersection. Note that the mass of the expandable particles hardly changes before and after the gas is released to the outside.

[0016] In the sheet, as long as the collection efficiency is not lowered and the pressure loss is not increased, filamentous fibers such as ultrafine fibrillated synthetic fibers, natural fibers, and glass long fibers are used. May be blended. In addition, it is also possible to add a surfactant to uniformly disperse the fibers and the like in the dispersion liquid and form a sheet by a wet papermaking method. It is also possible to provide a binder.

Example

Next, an embodiment of the filter medium for a medium-performance air filter of the present invention and a method for manufacturing the filter medium will be described with reference to the drawings, and a comparative example and a conventional example of the filter medium will be described.

Example 1: C-glass short fiber with average fiber diameter of 0.8 μm 3, (MLF # 208 manufactured by Nippon Sheet Glass Co., Ltd.) 10% by mass, and C-glass short fiber with average fiber diameter of 4 μm 3 (W50 manufactured by Mag Co., Ltd.) Core-sheath type synthetic fiber 2 with an average fiber diameter of 17 m and an average fiber length of 5 mm (adhesive polyester, modified polyester sheath, 55% heat shrinkage at 140 ° C, Kuraray 7% by mass and thermally expandable microcapsules 4 having an average particle size of 10 to 20; An aqueous dispersion was prepared by dispersing and mixing 5% by mass of a polymer and Matsumoto Microsphere F-55 manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. in which isobutane was encapsulated in a heat-expandable gas in water. To this aqueous dispersion, a cationic acrylamide adsorbent having a molecular weight of 1.5 million was added to adsorb the heat-expandable microcapsules 4 on the surfaces of the C glass short fibers 3, 3 and the core-sheath type synthetic fibers 2. Supported.

As shown in FIG. 1 (a), the aqueous dispersion was made into a sheet using a normal paper machine, and then subjected to a surfactant treatment. As shown in FIG. 1 (b), the sheet was dried at 140 ° C. to bond the C glass short fibers 3, 3 ′ and the core-sheath type synthetic fiber 2, and to obtain an unexpanded thermal expansion. Foamable microcapsules 4 are foamed about 20 times to form foamed microcapsules 5, and the short C glass fibers 3, 3 'and core-sheath type synthetic fiber 2 are pressed along the spherical surface of the microcapsules 5. Spread out. Then, as shown in FIG. 1 (c) and FIG. 2, the foamed microcapsules 5 are ruptured, and the crushed fragments 7 bond the surrounding C glass short fibers 3, 3 ′ and the core-sheath type synthetic fiber 2 to each other. The sheet 1 having a thickness of 0.71 mm and a basis weight of 92 g / cm ² having a plurality of voids 6 formed therein was used as a medium-performance air filter medium. In addition, in FIG. 2, 8 indicates dust.

Example 2:

C glass short fiber having an average fiber diameter of 4 μm (W50 manufactured by Mag Co., Ltd.) was 73% by mass, and the heat-expandable microcapsules were 10% by mass as expandable particles in the same manner as in Example 1. A sheet having a thickness of 0.86 mm and a basis weight of 9 lgZcm ² was used as a filter medium for a medium-performance air filter.

Example 3:

C-glass short fiber with an average fiber diameter of 0.8 μm (MLF # 208, manufactured by Nippon Sheet Glass Co., Ltd.) is 0% by mass, and C-glass short fiber with an average fiber diameter of 4 μm (W50, manufactured by Mag Co., Ltd.) is 88% by mass. When A sheet having a thickness of 0.70 mm and a basis weight of 90 gZcm ² was used as a medium performance air filter medium in the same manner as in Example 1 except for the above.

Example 4:

Instead of C-glass short fiber 3 with an average fiber diameter of 4 μm (W50 manufactured by Mag Co., Ltd.), C-glass short fiber with an average fiber diameter of 4 μm (NANJING AIXIN FIBREGLASS PRODUCT CO., LTD.) Was used. Except that, in the same manner as in Example 1, a sheet 1 having a thickness of 0.71 mm and a basis weight of 92 g Zcm ² was used as a medium-performance air filter medium.

Comparative Example 1:

The same procedure as in Example 1 was carried out except that the C glass short fiber having an average fiber diameter of 4 μm (W50 manufactured by Mag Co., Ltd.) was 83% by mass, and the thermally expandable microcapsules were 0% by mass as expandable particles. Then, a sheet having a thickness of 0.60 mm and a basis weight of 95 gZcm ² was used as a medium-performance air filter medium.

Comparative Example 2:

The same procedure as in Example 1 was carried out except that the C glass short fiber having an average fiber diameter of 4 μm (W50 manufactured by Mag Co., Ltd.) was 68% by mass, and the thermally expandable microcapsules were 15% by mass as expandable particles. Thus, a sheet having a thickness of 0.91 mm and a basis weight of 88 gZcm ² was used as a medium-performance air filter medium.

Conventional example 1:

A sheet mainly made of glass fiber having an average fiber diameter of 2 μm and made by a commercially available wet papermaking method and having a thickness of 0.36 mm and a basis weight of 64 gZcm ² was used as a filter medium for a medium-performance air filter.

Conventional example 2:

A sheet having a thickness of 0.50 mm and a basis weight of 90 gZcm ² mainly composed of glass fiber having an average fiber diameter of 2 μm and produced by a commercially available wet papermaking method was used as a filter medium for a medium-performance air filter.

Next, for each of the thus obtained medium-performance air filter media of Examples 1-4, Comparative Examples 1-2 and Conventional Examples 1-2, the collection efficiency of the filter media was determined by the following method. The service life of the filter medium was measured, and the measurement results were evaluated. The presence or absence of dust on the outflow side of the filter medium was evaluated. Furthermore, based on these evaluation results, a comprehensive evaluation was made as follows. The results are shown in Table 1. [0027] Collection efficiency:

Atmospheric dust having an average particle size of 0.3 m was passed through a medium-performance air filter medium at a wind speed of 0.5 mZs, and the collection efficiency in accordance with JIS B9908 was measured.

Collection efficiency (%) = (1 downstream particle number Z upstream particle number) X 100

Evaluation criteria: Collection efficiency was 50% or more, ◎, 40-50% was Δ, and less than 40% was X.

[0028] Service life of filter medium:

Based on the method specified in JIS B9908, the service life of the filter medium was measured as follows. Using 15 kinds of powder is tested for powder specified in JIS Z8901, Shi measuring the powder dust holding amount to a final pressure loss 250Pa at wind speed 5. 3 cm / s at a dust concentration of 70 workers 30 mg / m ³ 7

w = w 2 -w 1 (gZ filter unit)

w: Dust retention amount

W: Weight of filter unit at the start of test (g)

W: Filter unit weight at the end of test (g)

2

Evaluation criteria: The life of the filter material for medium-performance air filters of Conventional Example 1 measured according to the above method is 100, and the filter media whose life exceeds 2 times the life of the filter The filter media having a life of less than 2 times was designated as X, and the media having a service life less than 2 times was designated as X.

[0029] Existence of dust on the outflow side:

Using the filter medium subjected to the life test, it was evaluated whether dust adhered to each filter medium on the outflow side. When dust was attached, it was rated as 〇 (presence), and when no dust was attached, it was rated as X (absent).

[0030] Overall rating:

When the collection efficiency and life were all 〇 or ©, ◎ was given. When the collection efficiency was X and the life of the filter was 〇, 〇 was given. When the life of the filter was X, X was given.

[0031] [Table 1] Filter media composition Filter media characteristics Filter media effect

Core-sheath type synthesis

Is the short staple fiber power

Fiber Foamable particles Thickness Per unit area Collection efficiency Outflow side dust Overall evaluation Filter media life

(Mass%)

(Mass ¾) (mass ¾)

(Mass ¾)

Example

Example 〇

Comparative example

Conventional example Commercial product (sheet made of wet-processed glass fiber) 〇

Conventional example Commercial product (sheet made of wet-processed glass fiber) から The results shown in Table 1 revealed the following.

It was confirmed that the filter media of Examples 1 to 4 for medium-performance air filters had a filter life that was at least twice as long as that of the commercially available filter media of Conventional Example 1. Furthermore, it was confirmed that Examples 2 and 4 had good collection efficiency. Examples 1 to 4 medium-performance filter media for air filters have foams in which foamable particles are foamed, and a fragment in which the foamable particles are ruptured has a void portion in which the surface of the surrounding fiber and the Z or intersection are bonded. The voids serve as passages to facilitate the passage of air in the thickness direction of the filter medium, and the fine mesh structure of short glass fibers having an average fiber diameter of 2 to 8 m, which is the main part of the sheet that constitutes the filter medium, It was confirmed that the life of the filter medium was prolonged because dust was collected almost uniformly throughout the thickness direction of the filter medium. Further, when fine glass short fibers having an average fiber diameter of less than 2 / zm are blended as in Examples 1, 2, and 4, this fine glass short fiber force is used to reduce the glass fiber having an average fiber diameter of 2 to 8 m. Dispersed by the relatively fine mesh structure formed by the fibers, a finer mesh structure was formed, and it was confirmed that the efficiency of collecting dust over the entire thickness of the filter medium was increased and the filter medium life was prolonged. Was.

Further, when no short glass fiber having an average fiber diameter of less than 2 / zm is blended at all as in Example 3, although the life of the filter medium is twice as long as the filter medium of Conventional Example 1, the fiber constituting the filter medium is Since the gap between the fibers became large, the dust collection efficiency was lower than in Examples 1, 2, and 4. Also, as in Comparative Example 1, the filter medium containing no expandable particles was the same as the expandable particles. Since no air gap was formed due to the foaming, no air passage was secured in the thickness direction of the filter medium, and the life of the filter medium was shortened as in Conventional Example 1. In the filter medium of Comparative Example 1, voids were formed due to the expansion of the expandable particles because the dust adhering to the air outflow side was ineffective. Therefore, it was speculated that the air passage was not secured and dust was trapped in the filter media on the air inflow side.

Also, as in Comparative Example 2, in the filter medium containing more than 10% by mass of expandable particles, the apparent dust collection efficiency is increased because many voids are formed due to the expansion of the expandable particles. The filter material per unit volume, which is the part that originally collects dust, is reduced, and the dust is collected by the smaller filter medium, resulting in higher pressure loss and the same filter life as in the previous example 1. It was getting shorter.

In addition, even when the basis weight of a commercially available filter medium was the same as in Examples 1 to 4 as in Conventional Example 2, the filter medium had a prolonged service life as in Examples 1 to 4.

Industrial applicability

The present invention relates to a medium-performance air filter medium, a method for manufacturing the medium, and a method for manufacturing a medium-performance air filter, which uniformly collects dust in a relatively fine mesh structure over the entire thickness direction of the filter medium and extends the life of the filter medium. It has industrial applicability in that a high performance air filter can be provided.

Claims

The scope of the claims

[1] A medium-performance air filter medium comprising a sheet in which voids are formed by bonding surrounding fibers with fragments obtained by bursting effervescent particles, wherein the sheet has a mean fiber diameter of 2 to 8 m. 70 to 90% by mass of short fibers, 0 to 15% by mass of glass short fibers having an average fiber diameter of less than 2 m, 5 to 15% by mass of adhesive synthetic fibers having an average fiber diameter of 10 to 35 / zm, and expandable particles Fragment 3 of: A medium-performance air filter medium characterized by comprising LO% by mass.

[2] Adhesion of 70-90% by mass of glass short fibers having an average fiber diameter of 2-8 μm, 0-15% by mass of glass short fibers having an average fiber diameter of less than 2 μm, and 10-35 m of average fiber diameter Unexpanded expandable particles having a synthetic fiber content of 5 to 15% by mass and an average particle size of 3 to 20 μm 3 to: A sheet-like material is formed using an aqueous dispersion in which LO mass% is dispersed, A method for producing a filter material for a medium-performance air filter, comprising: forming a void portion by foaming expandable particles; and bonding a surrounding fiber with a fragment obtained by bursting the expandable particles to form a sheet.

[3] A medium-performance air finoleta, wherein the medium for a medium-performance air filter according to claim 1 is used.