JPH08323121A - Filter medium and air filter - Google Patents

Abstract

PURPOSE: To obtain a filter medium maintaining satisfactory efficiency of capture of dust in air over a long time from the early stage of use as a high performance air filter (HEPA), an ultrahigh performance air filter (ULPA), etc., not causing the falling of glass fibers from the medium and considering the reduction of the amt. of noncombustible refuse causing a more serious environmental problem in future. CONSTITUTION: Glass microfibers of 0.1-1μm average fiber diameter are mixed with fibrillated org. fibers made of a rigid straight chain synthetic polymer and having 30-800" freeness, org. fibers of 0.1-1.0 denier fiber diameter and a fibrous binder to obtain the objective filter medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter medium for liquid filtration for efficiently removing particles contained in a liquid to obtain a clean liquid, an air filter medium for collecting dust in the air, and the like. The present invention relates to a filter medium, particularly for high-performance air filters (HEPA) and ultra-high-performance air filters (ULPA), which has a good efficiency in collecting dust in the air and prevents glass fibers from falling off from the filter medium. ,
The present invention relates to a filter medium and an air filter that are designed to reduce the amount of incombustible dust in response to environmental problems that are becoming more and more problematic in the future.

[0002]

2. Description of the Related Art Conventionally, high-performance air filter media have been manufactured by a method in which chopped strand glass fibers and micro glass fibers are mixed and formed by a wet papermaking method, and then a binder is added to strengthen the strength. If fabricated filter media in this method was used in a semiconductor industry because it is made of glass fiber, traces of acid, the glass fiber surface is eroded by contact with an alkali, trace amounts of heavy metals (B ^-, Na ⁺ Etc.) is considered a problem. Further, there is a drawback that the filter medium does not have elasticity and the glass fibers are broken and fall off during folding or when an impact is applied. Further, when the used filter medium is discarded, the volume of the filter medium is hardly reduced even if it is incinerated.

In order to solve this problem, a filtering material in which micro glass fiber and organic fibrous fibrils are mixed is disclosed in JP-A-57-132522 and JP-A-58-20552.
The filter medium disclosed in JP-A-58-208498 is disclosed in JP-A No. 08208498. In these inventions, organic fibrous fibrils of 30-
80% by weight is blended, and because the blending ratio of organic fibrous fibrils is high, it becomes very dense,
The filter material has poor air permeability and high pressure loss. Further, it is stated that the material of the organic fibrous fibrils is preferably a linear aromatic polyester, but when the linear aromatic polyester is beaten with a disc refiner according to the example, it is possible to fibrillate into a pulp form. However, it is difficult to fibrillate into very fine single fibers, and the fibers are cut in the longitudinal direction before the fibrillation into fine single fibers. for that reason,
In order to fibrillate into fine single fibers, it is considered that the material must have a very high degree of crystallinity and be a rigid linear synthetic polymer.

On the other hand, there is an example in which fibers of a rigid linear synthetic polymer having a very high degree of crystallinity are fibrillated and applied to an air filter filter material, as disclosed in JP-A-63-236512.
No. 6,086,045. It is also disclosed in Japanese Patent Application Laid-Open No. 2-99108 by the present applicants.

The fibrillated organic fiber used here is made of aromatic polyamide as a raw material and has a very rigid molecular structure, and the molecular chain is completely extended. Therefore, homogenizer (Gaulin, 15M
-8 TA) or a disc refiner can fibrillate even fibers having a very small fiber diameter, which is effective when applied to a high-performance filter medium. However, in Japanese Patent Laid-Open No. 63-236512, the filter medium is designed only with the fibrillated organic fibers and the organic fibers having a fiber diameter of 5 μm or more. Insufficient network can be maintained, and the fine fibrillated organic fibers will flow out from the papermaking wire. Further, the fibrillated organic fiber, when it is dried after being made into paper, has an entanglement action, resulting in a very dense filter medium, and even if the collection efficiency is good, the air permeability is Poor, the pressure loss becomes high.

In order to solve this problem, Japanese Patent Application Laid-Open No. 2-99108 filed by the present applicants discloses that an organic fiber having an irregular cross section is used to prevent the filter medium from becoming dense.
By adding 0 to 90% by weight, the porosity of the filter medium is increased to ensure air permeability. This invention has a fiber diameter of 1μ
5 to 40% by weight of organic fibers fibrillated to m or less, 5 to 30% by weight of ultrafine organic fibers having a fiber diameter of 1 to 5 µm, and 3% of organic fibers having a fiber diameter of 5 µm or more having an irregular cross section.
It is composed of 0 to 90% by weight, and a uniform network is formed by the mixing of these three types to improve the collection efficiency. However, although the performance of the high performance air filter medium (HEPA filter) (collection efficiency of 0.3 μm particles: 99.97% or more) was satisfied by this invention, the performance of the ultra high performance air filter medium (ULPA filter) was achieved. Wasn't satisfied yet.

JP-A-59-228918 discloses a small diameter fiber having an average fiber diameter of 0.1 to 3 μm and a fiber diameter of 5 to 15 μm.
A medium having a medium diameter fiber and a large diameter fiber having a fiber diameter of 20 to 50 μm is mixed, and an average fiber diameter of 0.1 to 3 μm is disclosed.
Examples of the small-diameter fibers include inorganic synthetic fibers such as micro glass fibers, asbestos fibers, potassium titanate fibers, and ceramic fibers, and polyester synthetic pulp having a freeness of 50 to 700 cc. It is stated that polyester fibers and aramid fibers are preferable for medium-diameter fibers and large-diameter fibers as they contribute to reduction of pressure loss. When attempting to produce a filter medium by this method, small-diameter fibers such as micro glass fibers are also rigid, medium-diameter fibers and large-diameter fibers of polyester fibers and aramid fibers are large, and the difference in fiber diameter between the two materials is large, so There is no entanglement, and the micro glass fiber for improving the collection efficiency is removed from the paper making wire together with the water making it impossible to effectively utilize the micro glass fiber. Although not shown in the examples, the small diameter fibers described in the text have a freeness of 50 to 700 c.
When the polyester synthetic pulp of c is used, it is difficult to fibrillate the polyester synthetic pulp into very fine single fibers. Since the fibers are cut into small pieces, the fiber diameter is not completely thin, and good collection efficiency cannot be obtained.

Further, there is an electret filter medium in which the collection efficiency is improved by applying a direct current high voltage to a non-woven fabric produced by the melt-blowing method without using any glass fiber to improve the collection efficiency. JP-A-6-
No. 128858 and Japanese Patent Publication No. 5-10962. The electret filter medium produced by this method has a high collection efficiency due to electrostatic attraction, so that the pressure loss can be kept low. However, even if the initial collection efficiency can be cleared, there is a concern that the collection efficiency will decrease under the following conditions. Under high temperature and high humidity conditions. When exposed to vapors of organic solvents such as alcohol. When dust accumulates on the filter medium. Therefore, it has not been used in important parts in the semiconductor industry.

On the other hand, in Japanese Patent Laid-Open No. 62-21005, 10 to 30% by weight of micro glass fiber having a fiber diameter of 0.1 to 0.2 μm, 30 to 10% by weight of natural cellulose, and 0.1 denier synthetic fiber are used. 80 to 6 monofilaments
0% by weight is blended and papermaking is performed. However, since the natural cellulose fiber has a flat fiber cross-sectional shape, the density of the filter medium is increased, and as a result, the pressure loss is increased. Further, even if beating is advanced to reduce the fiber diameter of the natural cellulose fiber, or even if fibrillation is advanced, the natural cellulose fiber has a low crystallinity but the fiber length becomes short, but the fiber cross section remains flat. Yes, the density of the filter medium is further increased and the pressure loss is increased. When paper is made on a papermaking wire with this fiber mixture, micro glass fibers and 0.1 denier (fiber diameter of about 3 μm) synthetic filaments are rigid and entangled with each other due to the large difference in fiber diameter between the two materials. Therefore, the micro glass fibers for improving the collection efficiency cannot be effectively used because they are removed from the paper making wire together with the water making.

[0010]

In view of the above problems, the present invention has an average fiber diameter of 0.1 to 1 μm which improves the collection efficiency.
By mixing the fibrillated organic fiber having a drainage value of 30 to 800 seconds, which is composed of the micro glass fiber and the rigid linear synthetic polymer, in the filter medium, the entanglement effect of both materials can be brought out, and in the case of the micro glass fiber alone, It solves both the problem of separation from the papermaking wire, which is a problem, and the problem of densification, which is a problem when using fibrillated organic fibers alone, and provides a filter medium with a well-balanced collection efficiency and pressure loss. It is to provide a filter using this filter medium.

[0011]

Means for Solving the Problems As a result of intensive studies to solve the above problems, a drainage value of microglass fibers having an average fiber diameter of 0.1 to 1 μm and a rigid linear synthetic polymer is 30 to 30.
By mixing 800 seconds of fibrillated organic fibers in the filter medium, fibrillated organic fibers of rigid linear synthetic polymer having a drainage value of 30 to 800 seconds are entangled with each other at the intersections of the rigid micro glass fibers and the fibers. , Micro-glass fibers are obtained by drawing out the entanglement effect of both materials, such as rigid micro-glass fibers entering between fibrillated organic fibers made of rigid linear synthetic polymer and having a drainage value of 30 to 800 seconds to form voids. It solves both the problem of detachment from the papermaking wire, which is a problem when used alone, and the problem of high density, which is a problem when the fibrillated organic fiber is used alone. Here, the rigid straight chain synthetic polymer is a polymer having a chain length (sustaining length) of 50 angstroms or more for maintaining a linear shape in a solution, and corresponds to the following fibrillated organic fiber.

Furthermore, by mixing organic fibers having a fiber diameter of 0.1 to 1.0 denier, the entangled network of rigid micro glass fibers and dendritic fibrillated organic fibers is expanded three-dimensionally. Thus, the air permeability is ensured by increasing the porosity of the filter medium, and a filter medium having a good balance between the collection efficiency and the pressure loss is provided, and a filter using this filter medium is also provided.

That is, the filter medium of the present invention has an average fiber diameter of 0.1.
It is a filter medium containing as an essential component a micro-glass fiber of ˜1 μm, a fibrillated organic fiber composed of a rigid linear synthetic polymer and having a drainage value of 30 to 800 seconds.

Further, it is a filter medium containing at least one organic fiber having a fiber diameter of 0.1 to 1.0 denier.

Preferably, the fibrillated organic fibers are poly-p-phenylene terephthalamide, poly-p-benzamide, poly-p-phenylene benzobisthiazole, poly-p-phenylene benzobisoxazole, polyamide hydrazine, polyhydrazine, It is at least one selected from the group consisting of poly-p-phenylene terephthalamide-3,4-diphenyl ether terephthalamide.

The mixing ratio of the micro glass fiber having a fiber diameter of 0.1 to 1 μm in the filter medium is 5 to 30% by weight, and the mixing ratio of the fibrillated organic fiber made of a rigid linear synthetic polymer having a drainage value of 30 to 800 seconds. Is in the range of 5% by weight or more and less than 30% by weight, and the total blending ratio of both materials is 50% by weight of the entire filter medium.
It is a filter medium characterized by being less than weight%.

Further, it is a filter medium containing a fibrous binder.

The air filter of the present invention is characterized by using the above-mentioned filter material.

The filter material of the present invention will be described in detail below.

Average fiber diameter used in the present invention 0.1 to 1
The μm micro glass fiber is one of the fibers that determines the collection efficiency. If the average fiber diameter is larger than 1 μm, the effect of improving the filtration efficiency is small. In addition, when the average fiber diameter is less than 0.1 μm, the amount of microglass fibers flowing out from the wire during wet papermaking is large, resulting in a very low yield.

The mixing ratio of the micro glass fiber to the entire filter medium can be changed so as to obtain a desired collection efficiency, and the mixing ratio is 5 to 30% by weight.

The micro glass fiber has an average fiber diameter of 0.
It is indispensable to be in the range of 1 to 1 μm, and if the total compounding ratio of the microglass fibers is 5 to 30% by weight, there is no problem even if two or more kinds of microglass fibers having different average fiber diameters are used in combination. Absent. As the material of the micro glass fiber, quartz glass having higher purity of silica can be used in addition to general borosilicate type. When micro glass fibers made of quartz glass are used, there is no problem of deterioration due to hydrofluoric acid in the semiconductor manufacturing process, which is a problem with borosilicate micro glass fibers.

The fibrillated organic fiber having a drainage value of 30 to 800 seconds, which is composed of the rigid linear synthetic polymer used in the present invention, is a fiber which can improve the collection efficiency by itself. By forming an intertwining network with micro glass fibers having an average fiber diameter of 0.1 to 1 μm, uniform voids are formed and an average fiber diameter of 0.
The micro glass fiber having a size of 1 to 1 μm serves to prevent the micro glass fiber from falling off the papermaking wire. Even more surprisingly, the effect of the entangled network by mixing both materials has the effect of improving the collection efficiency.

The rigid straight-chain synthetic polymer is a polymer having a chain length (sustaining length) of 50 angstroms or more for maintaining linearity in a solution, and examples thereof include poly-p-phenylene terephthalamide and poly-p-. Benzamide, poly-p-
Examples include phenylene benzobis thiazole, poly-p-phenylene benzobisoxazole, polyamide hydrazine, polyhydrazine, poly-p-phenylene terephthalamide-3, 4-diphenyl ether terephthalamide. It suffices to appropriately select from these rigid linear synthetic polymers and adjust so that the drainage value is 30 to 800 seconds.

The drainage value as referred to in the present invention is a value measured by the method described on page 6, line 7 of Japanese Patent Publication No. 2-60799 filed by the present applicant. This method is based on JIS-P81
It is a method applied to a slurry whose freeness is too low to be measured by the pulp freeness test method (Canadian standard type) of No. 21 and which can be applied to fibers that have been extremely fibrillated.

Here, a method of measuring the drainage value will be briefly described. The fibrillated organic fiber is adjusted to a 0.3% aqueous dispersion and 1 liter of this is taken. When this slurry is transferred to a cylindrical container having an inner diameter of 102 mm (a wire mesh of 78 mesh is stretched on the bottom), the time required for obtaining 500 ml of the filtrate in seconds is referred to as a drainage value. Drainage value is 30
If it is less than 2 seconds, the degree of fibrillation is low and relatively thick fibers still remain, so that the micro glass fibers cannot be efficiently retained. On the other hand, when the drainage value exceeds 800 seconds, the fiber length becomes extremely short due to excessive progress of fibrillation, and the outflow from the papermaking wire increases together with the micro glass fiber.

Examples of the method for obtaining the fibrillated organic fiber having a drainage value of 30 to 800 seconds include the following methods. 1) A method of causing a synthetic polymer solution to flow into a poor solvent for the polymer while applying a shearing force to precipitate fibrous fibrils. (Fibrid method, Japanese Patent Publication No. 35-11851). 2) Method of precipitating fibrils by shearing while polymerizing the synthetic monomer (polymerization shearing method, Japanese Patent Publication No. 47-2)
1898). 3) Mix two or more incompatible polymers, melt extrude,
Alternatively, a method of spinning, cutting, and fibrillating into a fibrous shape by a mechanical means (split method, JP-B-35-9651). 4) Mix two or more incompatible polymers, melt extrude,
Alternatively, a method of spinning, cutting and immersing in a solvent to dissolve one polymer to form a fibril in a fibrous state (polymer blend dissolution method, US Pat. No. 3,382,305). 5) A method in which a synthetic polymer is explosively ejected from a high pressure to a low pressure above the boiling point of its solvent and then fibrillated into a fibrous state (flash spinning method, JP-B-36-1646).
No. 0). 6) A method in which the fiber is cut into an appropriate fiber length, dispersed in water, and fibrillated using a homogenizer, a beater, etc. (JP-A-56-100801, JP-A-59-9).
2011 gazette).

Specific examples of the fibrillated organic fiber include KY-400S (manufactured by Daicel Chemical Industries Ltd.) obtained by fibrillating poly-p-phenylene terephthalamide with a homogenizer.

The blending ratio of the fibrillated organic fibers (hereinafter referred to as fibrillated organic fibers) having a drainage value of 30 to 800 seconds, which is composed of a rigid linear synthetic polymer in the filter medium, is 5% by weight or more and less than 30% by weight. The range is preferable, and more preferably 5 to 20% by weight.

Further, the glass fiber having a fiber diameter of 0.1 to 1 μm and the fibrillated organic fiber in the filter medium are the materials for determining the collection efficiency, but if the total blending ratio is excessive, the pressure loss increases. The diameter of the fiber in the filter medium is 0.1 to 1 μm because it becomes unsuitable as a filter medium.
The total compounding ratio of the glass fiber and the fibrillated organic fiber is preferably in the range of 50% by weight or less based on the whole filter medium.

Organic fibers having a fiber diameter of 0.1 to 1.0 denier are three-dimensionally expanded entangled networks of rigid micro glass fibers and dendritic fibrillated organic fibers to form voids in the filter medium. It is a fiber necessary to secure air permeability by increasing the rate.
The mixing ratio of the organic fibers having a fiber diameter of 0.1 to 1.0 denier is 10 to 80% by weight, and when two or more kinds are mixed, the total amount of both fibers is 10 to 80% by weight. Although it is not possible to obtain a filter medium having a good collection efficiency with this fiber alone, a gradual fiber diameter distribution is formed by mixing with micro glass fiber having an average fiber diameter of 0.1 to 1 μm and fibrillated organic fiber. By increasing the porosity of the filter material and balancing the collection efficiency and pressure loss, an ultra-high performance air filter (UL
A filter medium having the performance of a PA filter) is obtained. Furthermore, when two or more kinds of organic fibers having different fiber diameters of 0.1 to 1.0 denier are mixed, a further stepwise fiber diameter distribution can be formed, and the porosity of the filter medium is further increased to collect the fibers. It is possible to balance efficiency and pressure loss.

By incorporating a fibrous binder in order to impart good tensile strength and foldability to the papermaking stage, the internal strength of the filter medium can be increased, and a water repellent or adhesive applying step after papermaking and slitting can be performed. The role of suppressing paper breakage that tends to occur when tension is applied in the process, and the surface peeling that occurs due to the surface of the filter medium rubbing in the process of applying water repellent or adhesive after paper making, slit process, pleating process of filter medium, etc. Fulfill. Furthermore, by adding a fibrous binder, the entanglement network consisting of both microglass fiber and fibrillated organic fiber materials can be further strengthened, preventing the microglass fibers from scattering and falling off from the filter medium after papermaking. it can. Also, 0.1 added to the filter medium
By blending 0.5 to 3 denier binder fiber, which is slightly thicker than organic fiber of ˜1.0 denier, a wider stepwise distribution of fiber diameter can be formed, and the porosity of the filter medium can be increased to further improve the capture property. A filter medium having a well-balanced collection efficiency and pressure loss can be obtained.

Examples of the fibrous binder used in the present invention include core-sheath type (core-shell type) and parallel type (side-by-side type) composite fibers.
For example, a combination of polypropylene (core) and polyethylene (sheath) (trade name: Daiwabo NBF-H: manufactured by Daiwa Boshoku), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath) (trade name: Daiwabo NBF-
E: manufactured by Daiwa Boshoku), a combination of polypropylene (core) and polyethylene (sheath) (trade name: Chisso ESC: manufactured by Chisso), a combination of high-melting polyester (core) and low-melting polyester (sheath) (trade name: Melty 4080) : Made by Unitika) and the like. Further, a hot water melting type such as vinylon binder fiber (VPB107 × 1: made by Kuraray) can be used.

The fiber diameter of the fibrous binder is not particularly limited, but is preferably 0.3 to 5 denier, more preferably 0.5 to 2 denier. Fiber diameter is 0.
If it is less than 3 denier, the pressure loss of the filter medium becomes high and the life of the filter becomes short. Further, when the fiber diameter exceeds 5 denier, cavities are formed in the stepwise fiber diameter distribution of the fibers in the filter medium, and the pressure loss of the filter medium decreases, but the collection efficiency decreases. In addition, the area of fusion with other fibers is reduced and the strength of the filter medium is not improved much.

The fibers that can be blended in the filter medium are not limited to micro glass fibers, fibrillated organic fibers, organic fibers having a denier of 0.1 to 1.0, and fibrous binders, and do not have the binder performance used for nonwoven fabrics. There is no problem even if the fibers are blended as long as the performance is not impaired.

When the filter medium of the present invention is manufactured by the wet papermaking method,
In order to improve the formation, micro glass fiber, fibrillated organic fiber, organic fiber having a fiber diameter of 0.1 to 1.0 denier, and fibrous binder are uniformly dispersed in dispersion water in a dispersion tank such as pulper. It is necessary to disperse, and it is desirable to use a surfactant for that purpose.

Surfactants are anionic, cationic,
It is classified as nonionic and bisexual. Examples of the anionic surfactant include carboxylic acid salts, sulfuric acid ester salts, sulfonic acid salts, and phosphoric acid ester salts. Examples of the cationic surfactant include amine salts and ammonium salts. Examples of the nonionic surfactant include ether type, ester type, amino ether type and the like. Examples of the amphoteric surfactant include betaine type. Of these, those having good fiber dispersibility may be appropriately selected and used. Further, even if it is out of these examples, there is no problem as long as the dispersibility of the fiber is good.

In order to improve the dispersion stability of the fibers that are uniformly mixed and dispersed, an anionic polyacrylamide-based viscous agent is added to the fiber dispersion liquid or the papermaking white water, whereby the formation of the filter medium after wet papermaking is improved. Further improve.

The filter medium of the present invention can be produced by a paper machine for producing general paper or wet non-woven fabric, for example, a wet paper machine such as a Fourdrinier paper machine, a cylinder paper machine or a tilted wire paper machine. A dryer such as a cylinder dryer, a through dryer or an infrared dryer can be used for drying, but in any case, the drying temperature needs to be higher than the melting point of the composite fiber used as the binder.

The filter material of the present invention has good strength and stiffness at the time of drying after wet papermaking, but in order to further improve strength and stiffness depending on the application, after wet papermaking and drying,
It is possible to add various binders.

As the binder, for example, acrylic latex, vinyl acetate latex, urethane latex, epoxy latex, polyester latex, SBR latex, NBR latex, epoxy binder, phenol burner, PVA, starch, Paper strength agents and the like which are generally used in the paper making process can be mentioned, and these can be used alone or in combination with a crosslinking agent.

After wet papermaking and drying, the amount of binder applied is less than 20% by weight based on the basis weight of the filter medium.
If it exceeds 20% by weight, not only the strength and stiffness are strengthened but the collection performance is deteriorated, and also the pressure loss is increased and the life of the filter is shortened.

Further, depending on the use, the filter medium may be water repellent,
A water repellent or a flame retardant may be added to impart flame retardancy.

[0044]

In order to form a gradual fiber diameter distribution, micro glass fibers having an average fiber diameter of 0.1 to 1 μm, fibrillated organic fibers having a drainage value of 30 to 800 seconds and made of rigid linear synthetic polymer, and fibers. By mixing organic fibers having a diameter of 0.1 to 1.0 denier, the entangled network of rigid micro-glass fibers and dendritic fibrillated organic fibers is three-dimensionally expanded to form voids in the filter medium. Ultra high performance air filter media (ULPA filter) that can increase the efficiency and ensure air permeability, and can be used as a filter media with well-balanced collection efficiency and pressure loss.
By clearing the performance of 1) and incinerating the filter media after use, the amount can be reduced and the amount of non-burnable dust can be reduced, so that environmental problems can be addressed.

[0045]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, "part" and "%" in an Example show "weight part" and "weight%", respectively.

Example 1 Sodium acrylate-based anionic surfactant (Nippon Acrylic Chemical Co., Ltd., Primal 850) was placed in a 2 m ³ dispersion tank.
Is added so as to be 1% with respect to all the fibers, and micro glass fibers (# 108A, manufactured by Schuler) having an average fiber diameter of about 1.0 μm and poly-p-phenylene terephthalamide fibers are fibrillated by a homogenizer. Fibrillated organic fibers (draft value: 500 seconds), fiber diameter 0.15 denier x 3
mm polyester fiber (Asahi Kasei) 30: 1
Mix in a ratio of 0:60, disperse at a dispersion concentration of 0.2% for 30 minutes, make paper with a cylinder paper machine to a dry weight of 80 g / m ² , and dry with a cylinder dryer at a surface temperature of 130 ° C. After that, a water repellent and an acrylic latex were applied with a size press device and dried to obtain a filter medium.

Example 2 In a 2 m ³ dispersion tank, a sodium acrylate type anionic surfactant (Nippon Acrylic Chemical Co., Ltd., Primal 850) was used.
Is added so as to be 1% with respect to all the fibers, and microglass fibers (# 106, manufactured by Schuler) having an average fiber diameter of about 0.65 μm and poly-p-phenylene terephthalamide fibers are fibrillated by a homogenizer. Fibrillated organic fiber (draft value: 400 seconds), fiber diameter 0.1 denier x 3 m
m polyester fiber (made by Teijin), fiber diameter 0.4 denier x 5 mm polyester fiber (made by Kuraray), 3 each
Blended in a ratio of 0: 10: 30: 30, dispersion concentration 0.2
% For 30 minutes, make a dry weight of 90 g / m ² with a cylinder paper machine, dry with a cylinder dryer with a surface temperature of 130 ° C., and then add a water repellent and acrylic latex with a size press machine. It was applied and dried to obtain a filter medium.

Example 3 In a 2 m ³ dispersion tank, a sodium acrylate type anionic surfactant (Nippon Acrylic Chemical Co., Ltd., Primal 850) was used.
Is added so as to be 1% with respect to all the fibers, micro glass fiber having an average fiber diameter of about 0.3 μm (# 100, manufactured by Schuler), fibrillated organic fiber (KY-400S: manufactured by Daicel Chemical Industries, Ltd., Drainage value: 300 seconds), fiber diameter 0.
15 denier x 3 mm polyester fiber (manufactured by Asahi Kasei Corp.), fiber diameter 0.7 denier x 5 mm polypropylene fiber (manufactured by Daiwabo Co., Ltd.), fiber denier 2 denier x 5 mm polyester fiber binder (Meltei 4080, manufactured by Unitika Ltd.) It was blended in a ratio of 20: 10: 25: 25: 20, dispersed at a dispersion concentration of 0.2% for 30 minutes, and then dried with a cylinder paper machine to a dry weight of 80 g / m ^2. After drying with a cylinder dryer at ℃, a water repellent and acrylic latex were applied with a size press device and dried to obtain a filter medium.

Example 4 Sodium acrylate type anionic surfactant (PRIMAL 850, manufactured by Nippon Acrylic Chemical Co., Ltd.) was placed in a 2 m ³ dispersion tank.
Is added so as to be 1% with respect to all the fibers, and a micro glass fiber having an average fiber diameter of about 0.3 μm (# 100, manufactured by Schuler) and a micro glass fiber having an average fiber diameter of about 0.65 μm (# 106, Shuller), fibrillated organic fiber (KY-400S: manufactured by Daicel Chemical Industries, Ltd., drainage value:
300 seconds), fiber diameter 0.15 denier x 3 mm polyester fiber (Asahi Kasei), fiber diameter 0.5 denier x 5 m
m polyester fiber (manufactured by Teijin Ltd.), fiber diameter 2 denier ×
5mm polyester fibrous binder (Melty 408
0, manufactured by Unitika Ltd.), respectively, 15: 15: 5: 25: 2
After blending in a ratio of 0:20 and dispersing at a dispersion concentration of 0.2% for 30 minutes, after making paper with a cylinder paper machine so that the dry weight becomes 80 g / m ² , it is dried with a cylinder dryer at a surface temperature of 130 ° C. After that, a water repellent and an acrylic latex were applied with a size press device and dried to obtain a filter medium.

Example 5 Sodium acrylate-based anionic surfactant (Nippon Acrylic Chemical, Primal 850) was placed in a 2 m ³ dispersion tank.
Is added so as to be 1% with respect to all the fibers, micro glass fiber having an average fiber diameter of about 0.3 μm (# 100, manufactured by Schuler), fibrillated organic fiber (KY-400S: manufactured by Daicel Chemical Industries, Ltd., Drainage value: 300 seconds), fiber diameter 0.
1 denier x 3 mm polyester fiber (manufactured by Teijin), 0.4 denier fiber diameter x 5 mm polyester fiber (manufactured by Kuraray Co., Ltd.), 1.0 denier fiber diameter 3 mm fiber binder (VPB107 x 1: manufactured by Kuraray Co., Ltd.) 20: 1 each
Blended at a ratio of 0: 35: 30: 5, dispersion concentration 0.2%
After 30 minutes of dispersion, the paper is made with a cylinder paper machine to a dry weight of 80 g / m ² , dried with a cylinder dryer at a surface temperature of 130 ° C, and a water repellent and acrylic latex are applied with a size press machine. Then, it was dried to obtain a filter medium.

Example 6 Sodium acrylate-based anionic surfactant (PRIMAL 850, manufactured by Nippon Acrylic Chemical Co., Ltd.) was placed in a 2 m ³ dispersion tank.
Is added so as to be 1% with respect to all the fibers, and micro glass fibers having an average fiber diameter of about 0.3 μm (# 100, manufactured by Schuler) and poly-p-phenylene terephthalamide fibers are fibrillated by a homogenizer. Fibrillated organic fiber (draft value: 30 seconds), fiber diameter 0.15 denier x 3 mm
Polyester fiber (Asahi Kasei Co., Ltd.), fiber diameter 0.4 denier x 5 mm Polyester fiber (Kuraray Co., Ltd.), fiber diameter 2
Denier x 5mm polyester fibrous binder (Melty 4080, manufactured by Unitika Ltd.), 20: 20: 2, respectively
Blended in a ratio of 0:20:20, with a dispersion concentration of 0.2%, 3
After dispersing for 0 minutes, make a dry weight of 80 g / m ² with a cylinder paper machine, dry with a cylinder dryer with a surface temperature of 130 ° C., and then apply a water repellent and acrylic latex with a size press machine. It was dried to obtain a filter medium.

Example 7 Sodium acrylate-based anionic surfactant (PRIMAL 850, manufactured by Nippon Acrylic Chemical Co., Ltd.) was placed in a 2 m ³ dispersion tank.
Is added so as to be 1% with respect to all the fibers, and a micro silica glass fiber (# 104Q, having an average fiber diameter of about 0.5 μm) is added.
Shurler), fibrillated organic fibers obtained by fibrillating poly-p-phenylene terephthalamide fibers with a homogenizer (drainage value: 800 seconds), fiber diameter 0.15 denier x 3 mm polyester fibers (Asahi Kasei), Fiber diameter 0.
4 denier x 5 mm polyester fiber (made by Kuraray Co., Ltd.),
Fiber diameter 2 denier x 5 mm Polyester fibrous binder (Melty 4080, manufactured by Unitika Ltd.) 20: 1 each
Blended at a ratio of 0: 20: 30: 20, dispersion concentration 0.2
% For 30 minutes, make a dry weight of 80 g / m ² with a cylinder paper machine, dry with a cylinder dryer with a surface temperature of 130 ° C., and then add a water repellent and acrylic latex with a size press machine. It was applied and dried to obtain a filter medium.

Comparative Example 1 Sodium acrylate-based anionic surfactant (PRIMAL 850, manufactured by Nippon Acrylic Chemical Co., Ltd.) was placed in a 2 m ³ dispersion tank.
Is added to 1% of the total fiber, and glass fiber having an average fiber diameter of about 0.3 μm (# 100, manufactured by Schuler) and 0.1 denier fiber diameter × 3 mm polyester fiber (manufactured by Teijin) are added. Each of them was mixed at a ratio of 40:60, dispersed at a dispersion concentration of 0.2% for 30 minutes, and then dried at a weight of 80 g / m ^2.
After being paper-made by a cylinder paper machine so as to be dried, it was dried by a cylinder dryer having a surface temperature of 130 ° C., then a water repellent and an acrylic latex were applied by a size press device and dried to obtain a filter medium.

Comparative Example 2 Sodium acrylate type anionic surfactant (Nippon Acrylic Chemical Co., Ltd., Primal 850) was added to a 2 m ³ dispersion tank.
Is added so as to be 1% with respect to all the fibers, and a glass fiber having an average fiber diameter of about 0.3 μm (# 100, manufactured by Schuler) and a glass fiber having an average fiber diameter of about 6 μm (manufactured by Unitika) are 40: A glass fiber sheet in the form of a wet paper obtained by blending at a ratio of 60 and dispersing at a dispersion concentration of 0.2% for 30 minutes and then making a paper with a cylinder paper machine so that the dry weight becomes 80 g / m ^2. On the other hand, a water-soluble polyacrylamide paper strength agent (Polystron PS677, manufactured by Arakawa Chemical Co., Ltd.) was applied with a saturator so that the solid content was 5%, and dried with an air dryer to obtain a filter medium.

Comparative Example 3 In a 2 m ³ dispersion tank, a sodium acrylate-based anionic surfactant (Nippon Acrylic Chemical Co., Ltd., Primal 850) was used.
Fibrillated organic fiber (KY-400S: manufactured by Daicel Chemical Industries, Ltd.,
Drainage value: 300 seconds), fiber diameter 0.15 denier x 3 mm
Polyester fibers (manufactured by Asahi Kasei Co., Ltd.) were mixed at a ratio of 40:60 and dispersed at a dispersion concentration of 0.2% for 30 minutes,
After making paper with a cylinder paper machine so that the dry weight is 70 g / m ² ,
After drying with a cylinder dryer having a surface temperature of 130 ° C., a water repellent and an acrylic latex were applied with a size press device and dried to obtain a filter medium.

The filter media produced in the above Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated by the following evaluation methods,
The results are shown in Table 1 below.

[0057]

[Table 1]

<Pressure Loss> The pressure loss (Pa) was measured by an underwater manometer for the ventilation resistance when air was passed through the filter medium at a wind speed of 5.3 cm / sec.

<Collection efficiency> The collection efficiency (%) is as follows: DOP aerosol (dioctyl phthalate, particle size: 0.15 μm) particles are generated, and the air containing the particles is blown at a wind speed of 5.3 c.
Aeration was performed at m / sec, air was sampled before and after the filter medium, and the particle concentration of each was measured with a multi-dust counter and calculated from the following formula. Collection efficiency = {(number of particles before filtration-number of particles after filtration) / number of particles before filtration} × 100

<Drop-off of glass fiber during filter processing>
The dropout of the glass fibers during the filter processing is indicated by ⊚ when the filter media is folded into a bellows shape and incorporated into the unit, depending on the amount of the glass fibers dropped off from the filter media, and by x when the dropout is severe. In the table, it is omitted.

<Ash content after incineration> The ash content (%) after incineration is
It was calculated from the following formula from the weight before and after heating and incinerating the filter medium in an electric furnace at 900 ° C. for 2 hours. Ash = (weight of filter medium after incineration / weight of filter medium before incineration) x
100

The filter media produced in the above Examples 1 to 7 have good collection efficiency and pressure loss, the glass fibers do not fall off, and the filter media after use can be incinerated, and the weight thereof is before incineration. The amount of non-burnable dust can be reduced to 31% by weight or less, and environmental problems can be addressed.

In Comparative Example 1, when the filter medium is dried, the fibers are weakly entangled with each other, so that when the fiber is separated from the cylinder dryer, the fibers on the surface of the filter medium adhere to the cylinder dryer, causing surface peeling to match the target basis weight. Was difficult. Further, the filter material sticking to the cylinder dryer frequently causes paper breakage, which makes continuous operation difficult. In addition, the filter material was processed with a filter material suitable for the target basis weight, but the glass fiber was dropped.

Since the filter medium of Comparative Example 2 uses the air dryer without using the cylinder dryer, there is no problem such as sticking of the filter medium, but since it is mainly made of glass fiber, it is not suitable for processing into a filter. Very many glass fibers fall out. Also, the ash content after incineration is approximately 95%.
Therefore, even if it is incinerated, the volume will hardly be reduced, leaving a problem for the future environment.

In the filter medium of Comparative Example 3, the filter medium is made of fibrillated organic fibers and polyester fiber having a fiber diameter of 0.15 denier × 3 mm, so that the filter medium becomes very dense and has a high pressure loss. Was unsuitable for.

Example 8 The filter material prepared in Example 3 was (length 305 mm) × (width 30).
5 mm) × (150 mm depth) filter with 61 pleats, filter blowing air velocity 0.50
As a result of measuring the pressure loss at m / s and the collection efficiency of 0.15 μm DOP aerosol particles, pressure loss: 2
It was 0.6 Pa and the collection efficiency was 99.999999%, and a good result as an air filter was obtained.

[0067]

EFFECT OF THE INVENTION In order to form a gradual fiber diameter distribution, the filter material of the present invention has a drainage value of 30 to 30 consisting of a micro-glass fiber having a mean fiber diameter of 0.1 to 1 μm and a rigid linear synthetic polymer.
800 seconds of fibrillated organic fibers, fiber diameter 0.1-0.
By mixing 3 denier organic fibers and 0.4 to 0.7 denier organic fibers, three-dimensional expansion of the entangled network of rigid micro glass fibers and dendritic fibrillated organic fibers The air permeability can be secured by increasing the porosity of the filter medium, and the performance of the ultra-high performance air filter (ULPA filter) is cleared by using the filter medium with a balanced collection efficiency and pressure loss. By incinerating the filter media, the amount can be reduced, and the amount of non-burnable dust can be reduced, so that environmental problems can be addressed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiko Shinobu 1-10-8 Honmachi, Tanashi City, Tokyo

Claims (6)

[Claims] 1. 5 to 30% by weight of micro glass fiber having an average fiber diameter of 0.1 to 1 μm, 5% by weight or more of fibrillated organic fiber made of rigid linear synthetic polymer and having a drainage value of 30 to 800 seconds, 30 A filter medium containing less than wt% as an essential component. 2. The filter medium according to claim 1, which contains at least one organic fiber having a fiber diameter of 0.1 to 1.0 denier. 3. The fibrillated organic fiber comprises poly-p-phenylene terephthalamide, poly-p-benzamide,
Poly-p-phenylene benzobisthiazole, poly-p
-Phenylenebenzobisoxazole, polyamide hydrazine, polyhydrazine, poly-p-phenylene terephthalamide-3, 4-diphenyl ether terephthalamide, at least one selected from the group consisting of: Filter material. 4. A fibrillated organic fiber having a mixing ratio of 5 to 30% by weight of micro glass fiber having a fiber diameter of 0.1 to 1 μm in a filter medium and having a drainage value of a rigid linear synthetic polymer of 30 to 800 seconds. The blending ratio is in the range of 5% by weight or more and less than 30% by weight, and the total blending ratio of both materials is 5% of the whole filter medium.
It is 0 weight% or less, The filter medium of any one of Claims 1-3 characterized by the above-mentioned. 5. The filter medium according to claim 1, further comprising a fibrous binder. 6. An air filter using the filter medium according to any one of claims 1 to 5.