JP2008000652A - Filter medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter medium which can be incinerated and which has high collection efficiency and low pressure loss, and in which dropping of fiber is reduced. <P>SOLUTION: The filter medium containing fiber is obtained from parenchyma cells of plants, and the filter medium at least contains at least one kind of fiber selected from organic and inorganic fibers and fiber obtained from the parenchyma cells of plants. The entire amount of at least one kind of fiber selected from organic and inorganic fibers or a part thereof preferably has fiber of an average fiber diameter of 0.1-5 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to air filters for clean rooms used in the fields of semiconductor manufacturing industry, pharmaceutical manufacturing industry, food industry, hospitals, filter media for filters such as office air conditioners and home air conditioners, engine oil, fuel, water treatment, discharge The present invention relates to a filter medium for liquid filtration such as a processing machine.

  Conventionally, a filter medium for collecting particles in the air or particles in the liquid has (1) excellent air permeability or liquid permeability, low pressure loss, and (2) good collection efficiency. 3) Excellent workability, (4) Less strength drop or fiber dropout during use, (5) Incineration or biodegradability is required from the viewpoint of waste problems. . Filter media are roughly classified into inorganic fiber-containing filter media mainly composed of inorganic fibers such as glass fibers and ceramic fibers, and synthetic fiber-containing filter media mainly composed of polyolefin fibers.

  The inorganic fiber-containing filter medium has an advantage that high collection efficiency can be obtained with a low pressure loss due to the rigidity of the inorganic fiber and the small fiber diameter. However, there is a problem that the rigidity of the inorganic fibers decreases the workability. Moreover, when inorganic fiber falls off when used as an air filter medium, there is a concern about the influence on the human body. When inorganic fibers fall off from a filter material such as an engine oil filter of a machine, there is a concern that the sliding part of the machine may be damaged. Furthermore, there is a waste problem that inorganic fibers cannot be incinerated. Therefore, in the inorganic fiber-containing filter medium, it is desired to reduce the content of the inorganic fiber due to processability, problems due to falling off during use, waste problems, and the like.

  In order to reduce the amount of inorganic fibers, filter media containing organic fibers have been proposed. In addition, a filter medium using biodegradable fibers as organic fibers is disclosed. For example, a filter medium is proposed that is made by adding a cellulose resin to a glass fiber or a ceramic fiber, microfibrillated to a diameter of 1 μm or less, and adding a binder resin (Patent Document 1). As the microfibrillated cellulose fiber, fiber made of wood pulp is used, but since the collection efficiency is low and the binder resin is added during paper making to give strength, pressure loss Had the disadvantage of becoming higher.

  Since the organic fiber-containing filter medium is mainly composed of biodegradable natural fibers or incinerated synthetic fibers, it can be said that it is a filter medium corresponding to the waste problem. In the organic fiber-containing filter medium, an electret filter medium that has been converted to an electret by applying a DC high voltage is used in order to increase the collection efficiency (see Patent Documents 2 and 3). However, the electret filter medium is exposed to high-temperature and high-humidity conditions, and dust accumulates on the filter medium, so that the charge of the filter medium is lowered and it is difficult to maintain good collection efficiency.

  As a means for increasing the collection efficiency, a filter medium containing ultrafine fibers has been proposed. As a filter medium containing ultrafine fibers, there is a nonwoven fabric produced by the melt-blown method, but it is difficult to use alone due to its low mechanical strength, and it is used in combination with spunbonded nonwoven fabrics and woven and knitted fabrics. There has been a problem of an increase in the number of surfaces and manufacturing processes (see Patent Documents 2 and 3).

  Examples of organic fiber-containing filter media that have solved the problems of filter media prepared by the melt blown method include filter media made by mixing fibrillated organic fibers and aggregate fibers, two layers made of thick fibers, and one made of ultrafine fibers. There has been proposed a filter medium made of paper in layers. From the viewpoint of waste problems and collection efficiency, there are filter media using microfibrillated cellulose fibers, bacterial cellulose, and non-wood-derived cellulose as fibrillated organic fibers and ultrafine fibers (Patent Documents 1 and 4). To 6). In these cellulose fibers, the collection efficiency of the filter medium is controlled by the entanglement utilizing hydrogen bonds, the uneven cross-sectional shape of the fibers, and the degree of refinement. However, since the cellulose fiber tends to be in the form of a film, there is a problem that when the pressure loss becomes large or when it is made very fine, it is easy to fall off at the time of processing and using the filter medium.

In other words, cellulose fibers are used in both inorganic fiber-containing filter media and organic fiber-containing filter media from the viewpoint of waste problems, but filter media that satisfy low pressure loss, high collection efficiency, and processability have been obtained. There is no current situation.
JP 7-116430 A JP-A-5-7713 Japanese Patent Laid-Open No. 6-128858 JP-A-8-229318 JP 2000-153116 A JP-A-6-142422

  This invention is providing the filter medium corresponding to low pressure loss, high collection efficiency, a waste problem, and workability.

The inventors of the present invention have made various studies in order to overcome the above-described problems, and have invented the filter medium of the present invention. That is, the filter medium of the present invention is
(1) a filter medium containing fibers obtained from plant parenchyma cells,
(2) at least one fiber selected from organic fibers and inorganic fibers, a filter medium containing at least fibers obtained from plant parenchyma cells,
(3) The filter medium according to (2), wherein the total amount or a part of at least one kind of fiber selected from organic fibers and inorganic fibers is a fiber having an average fiber diameter of 0.1 μm to 5 μm.

  Fibers obtained from plant parenchyma cells (hereinafter referred to as parenchyma fibers) have a high degree of polymerization, high crystallinity, high modulus of elasticity, and an average fiber diameter of 0.1 μm or less, which is very thin. It is a feature, it is possible to provide a filter medium that is excellent in workability, satisfies a low pressure loss and a high collection efficiency. In addition, parenchymal fibers can be entangled well with both inorganic fibers and organic fibers. Therefore, when mixed with inorganic fibers, paper can be made without adding a binder resin, and processability is also good. In addition, the collection efficiency is high and a low pressure loss can be achieved as compared with conventionally used microfibrillated cellulose fibers and bacterial cellulose fibers derived from wood pulp. The reason is not clear, but it is presumed that the soft cell fibers are less likely to have a film shape or an aggregated structure that completely fills the voids.

  When a filter medium is produced using only soft cell fibers, the filter medium becomes very dense and can be used for a blood filter medium. When used as a filter medium for collecting larger particles, the filter medium is prepared by mixing with fibers having a fiber diameter larger than that of parenchymal fibers. Fibers obtained from plant parenchyma cells are mixed with organic fibers or inorganic fibers having an average fiber diameter of 0.1 to 5 μm, the average fiber diameter of which is obtained from plant parenchymal cells, and these fibers. The fibers are entangled efficiently, making it difficult for the fibers to fall off the papermaking wire of the wet paper machine. In addition, fibers obtained from plant parenchyma cells and these fibers can form a three-dimensional network to construct fine voids. For this reason, collection efficiency can be made high. Moreover, dropping off of organic fibers, inorganic fibers, and parenchyma fibers can be suppressed.

  Fibers obtained from plant parenchyma cells can be incinerated and have biodegradability, so the amount of incombustible waste, which is increasingly regarded as a problem in the future, can be reduced, so that it becomes a filter medium corresponding to environmental problems.

  Fibers obtained from plant parenchyma cells related to the filter medium of the present invention (hereinafter referred to as parenchyma fibers) are treated with alkali on a portion mainly composed of parenchyma cells present in plant stems, leaves, fruits, etc. It is a non-wood fiber that is mainly made of cellulose obtained by, for example, and is insoluble in water. The parenchyma has the characteristic that the secondary wall is not developed.

  In the present invention, in order to obtain plant parenchymal cells, the internal parenchyma of the stem, leaf mesophyll, fruits, etc. may be crushed, but industrially discharged from food processing factories, sugar factories, etc. It is optimal to use juice squeezed from fruit and squeezed squeezed from sugar beet, sugar cane and the like. For example, when using sugar beet squeezed rice cake, the crushed root can be squeezed and the remaining rice cake can be used as it is. When using sugarcane juice cake, a portion containing many parenchyma cells can be obtained by pulverizing bagasse, which is a sugarcane cake, to an appropriate size and passing it through a sieve having an opening of 1 to 2 mm.

  In the present invention, in order to obtain fibers from parenchymal cells, it is preferable to apply a pulping treatment when producing pulp from wood. For example, a kraft pulping method or a soda pulping method in which lignin is decomposed and removed by mixing and heating with an alkali such as sodium hydroxide can be used. Detailed pulping conditions may be appropriately determined in view of the properties of the raw materials, the properties of the target fiber, the yield, and the like. After washing the alkali, bleaching is performed as necessary. Hydrogen peroxide, chlorine dioxide, sodium hypochlorite, oxygen, ozone, etc. can be used as a bleaching agent. After bleaching, it can be washed to obtain a fiber suspension.

  The fiber obtained by the pulping treatment can be used as it is, but the fibrillation treatment is preferable because the specific surface area is increased and the uniformity is increased. For fibrillation treatment, refiner, beater, mill, grinding device, rotary blade homogenizer that applies shear force with high-speed rotary blade, shear between cylindrical inner blade rotating at high speed and fixed outer blade Double-cylindrical high-speed homogenizer that generates force, ultrasonic crusher that is refined by ultrasonic impact, a pressure difference of at least 3000 psi is applied to the fiber suspension, and a small-diameter orifice is passed to increase the speed. A high-pressure homogenizer or the like that applies a shearing force or a cutting force to the fibers by colliding and rapidly decelerating can be used.

  The average fiber diameter of the parenchyma fibers according to the present invention is 0.1 μm or less. The fiber length is 1 to 20 μm. The average fiber diameter referred to here is an average value of values obtained by observing the fibers with a scanning electron microscope and measuring the thickness at 50 locations. The fiber length is a value calculated as a volume average particle diameter when the fiber slurry is measured with a light scattering particle size distribution measuring apparatus.

  Examples of the inorganic fiber used in the present invention include glass fiber, alumina fiber, lock fiber, stainless steel fiber, etc. Among them, alumina fiber and glass fiber are preferable, and glass fiber is more preferable.

  The organic fibers according to the present invention are wood pulp, hemp pulp, cotton linter, lint, mercerized pulp, hemp pulp, and regenerated fibers are lyocell fiber, rayon fiber, cupra fiber, and semi-synthetic fiber is acetate. Fibers, triacetate fibers, promix fibers are synthetic fibers such as polyolefin fibers, polyamide fibers, polyacrylic fibers, vinylon fibers, vinylidene chloride fibers, polyvinyl chloride fibers, polyester fibers, aramid fibers, urethane. Examples thereof include fibers such as fiber, benzoate fiber, polyclar fiber, and phenol fiber. In addition to the above fibers, wood fibers such as straw pulp, bamboo pulp, kenaf pulp, and herbs are included as plant fibers. Some or all of them have a heat-fusing binder component. Even if these fibers are fibrillated, there is no problem as long as they do not impair liquid permeability and air permeability. Furthermore, pulp fibers obtained from waste paper, waste paper, and the like are also included. In addition, irregular cross-section fibers such as T-shaped, Y-shaped, triangular, etc. and crimped fibers can also be included to ensure air permeability and liquid permeability.

  In the present invention, the organic fiber and the inorganic fiber are not limited to one type of fiber diameter, and fibers having two or more types of fiber diameters can be used in combination. By blending fibers having two or more types of fiber diameters, a uniform air gap inside the filter medium is formed, so that the filter medium has excellent collection efficiency.

  Furthermore, when all or part of the organic fiber having crimpability is contained, the density of the filter medium can be lowered while maintaining the network with the soft cell fibers, and the space volume inside the filter medium can be widened, and the collection efficiency It is possible to play a role in balancing life with life.

  In the present invention, a heat-fusible binder fiber may be used as part of the organic fiber. Examples of the heat-fusible binder fiber include composite fibers such as a core-sheath fiber (core-shell type), a parallel fiber (side-by-side type), and a radial split fiber. Since the composite fiber hardly forms a film, the mechanical strength can be improved while maintaining the space of the filter medium. Examples of the heat-fusible binder fiber include polypropylene short fibers, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), polypropylene (core) and polyethylene (sheath). ), A combination of a high melting point polyester (core) and a low melting point polyester (sheath), and the like. In addition, single fibers (fully fused type) composed only of low melting point resins such as polyethylene and polyester, and vinylon-based and polyvinyl alcohol (PVA) -based fibrous binders are easy to form a film in the drying process of the filter medium, It can be used as long as the properties are not impaired. The fiber diameter of the heat-fusible binder fiber is not particularly limited, but is preferably 5 μm to 40 μm, more preferably 7 μm to 30 μm.

  In the filter medium (2) of the present invention, the average fiber diameter of organic fibers and inorganic fibers is not particularly limited. Considering the operability and the filtering efficiency when making paper by the wet papermaking method, the fiber diameter is preferably 0.1 μm to 50 μm, more preferably 0.1 μm to 30 μm.

  In the filter medium (3) of the present invention, micro glass fibers can be preferably used as inorganic fibers having an average fiber diameter of 0.1 μm to 5 μm. The micro glass fiber is an ultrafine glass fiber manufactured by a steam spraying method, a spinning method, a flame insertion method, a rotary method, or the like, and generally has an average fiber diameter of 5 μm or less. In the present invention, 3 μm or less is more preferable.

  In the filter medium (3) of the present invention, it is preferable to use fibrillated organic fibers as the organic fibers having an average fiber diameter of 0.1 μm to 5 μm. A part of the fibrillated organic fiber is preferably fibrillated to a fiber diameter of 1 μm or less. Examples of the fibrillated organic fiber include those treated by the method shown below.

1) A method in which a synthetic polymer solution is allowed to flow in a poor solvent of the polymer while applying a shearing force to precipitate a fibrous fibrin (fibrid method),
2) A method of precipitating fibrils by polymerization while polymerizing the synthetic monomer (polymerization shearing method),
3) A method in which two or more incompatible polymers are mixed, melt-extruded, or spun, and fibrillated by mechanical means after cutting (split method).
4) Method of mixing two or more incompatible polymers, melt-extruding or spinning, immersing in a solvent after cutting, dissolving one polymer, and fibrillating into a fiber (polymer blend dissolution method) ,
5) A method in which the synthetic polymer is expelled from the high pressure measurement to the low pressure measurement after the boiling point of the solvent is exceeded, and then fibrillated into a fibrous form (flash spinning method).
6) A method in which a fiber is cut into an appropriate fiber length, dispersed in water, and fibrillated using a homogenizer, a beater, or the like.

  The 0.1 to 5 μm fibrillated organic fiber is preferably as rigid as possible, and is particularly preferably a fiber made of a material called a rigid linear synthetic polymer. A rigid linear synthetic polymer is a polymer having a chain length (sustained length) of 50 angstroms or more that maintains linearity in solution. For example, poly (p-phenylene terephthalamide), poly (p-benzamide) , Poly (p-phenylenebenzobisthiazole), poly (amide hydrazine), polyhydrazine, poly (p-phenylene terephthalamide-3,4-diphenyl ether terephthalamide), and the like.

  Moreover, as a fibrillated organic fiber of 0.1-5 micrometers, the lyocell fiber which used the cellulose fiber as a raw material can also be used. In the present invention, “Lyocell” is a fiber term defined in ISO standards and Japanese JIS standards, and is “cellulose cellulose obtained by spinning in an organic solvent directly without passing through a cellulose derivative”. . Features of the lyocell fiber include excellent wet strength, easy fibrillation, and easy strength when formed into a sheet by hydrogen bonds derived from cellulose fibers.

  Lyocell fiber is beater, dispersion equipment such as beater, PFI mill, single disc refiner (SDR), double disc refiner (DDR), ball mill, dyno mill, etc. used for dispersing and crushing pigment, etc. Can be fibrillated. Since lyocell fiber is a raw material of cellulose fiber, it has a characteristic that strength improvement by hydrogen bonding can be expected even after fibrillation.

  When fibers obtained from plant parenchyma cells and lyocell fibers of 0.1 to 5 μm are used in combination, both materials are biodegradable, so that they become biodegradable filter media. In that case, it is preferable to use a biodegradable material for the fiber or resin to be a binder as necessary.

  In an organic fiber or an inorganic fiber having an average fiber diameter of 0.1 μm to 5 μm, a more preferable average fiber diameter is 0.1 μm to 3 μm. More preferably, it is 0.1 micrometer-1 micrometer. When the average fiber diameter is less than 0.1 μm, the outflow from the papermaking wire is increased along with the soft cell fibers. In addition, when the thickness exceeds 5 μm, it is difficult to form a good network due to the large difference from the fiber diameter of the parenchyma fibers, and the outflow of the parenchyma fibers from the papermaking wire may increase, and the good collection Efficiency may be difficult to obtain. Also, the parenchyma fibers and other fibers may fall off when using the filter medium.

  A method for producing the filter medium is not particularly limited, but a paper slurry is prepared by wet papermaking, in which only soft cell fibers or a mixture of soft cell fibers and at least one fiber selected from organic fibers and inorganic fibers are dispersed and mixed in water. And a method of manufacturing the same.

  In addition, since soft cell fibers are used, papermaking is possible in wet papermaking without adding a binder in the slurry. However, various binders can be applied depending on the use of the filter medium or for the purpose of improving strength and waist (hardness). As the binder to be used, for example, latex such as acrylic, epoxy, vinyl acetate, polyester, NBR, and SBR, PVA, starch, phenol resin, and the like can be used alone or in combination of two or more. Moreover, it is possible to mix | blend dye, a pigment, a water repellent, a flame retardant, etc. in the range which does not inhibit the performance of a filter medium.

  In the present invention, surfactants that can be used in the wet papermaking method are classified into anionic, cationic, nonionic, and amphoteric. Examples of the anionic surfactant include carboxylate, sulfate ester salt, sulfonate salt, and phosphate ester salt. Examples of the cationic surfactant include amine salts and ammonium salts. Nonionic surfactants include ether type, ester type, amino ether type and the like. Examples of amphoteric surfactants include betaine types. Of these, those having good fiber dispersibility may be appropriately selected and used.

  In order to improve the dispersion stability of uniformly mixed and dispersed fibers, an anionic polyacrylamide type adhesive is added to the fiber dispersion or papermaking white water to further improve the formation of the filter media after wet papermaking. To do.

  The filter medium of the present invention is a wet paper machine for producing general paper and wet nonwoven fabric, for example, a long net paper machine, a circular net paper machine, a slanted wire type paper machine alone, even between the same model, It may be a multilayer of two or more layers combining different models. In the case of two or more layers, the life of the filter medium is improved by making the upstream side a coarse layer and the downstream side a dense layer.

  For drying, it is possible to use a dryer such as a cylinder dryer, a through dryer, or an infrared dryer. When the heat-fusible binder fiber is blended, it is desirable to dry at a temperature higher than the heat-sealing temperature.

  The filter medium of the present invention is not limited to those obtained by a wet paper machine, but can be laminated with a dry nonwoven fabric, a woven fabric, a film, a porous membrane, and the like.

  Although the filter medium of the present invention has good strength and waist when dried, various binders can be applied after wet papermaking and drying in order to further improve the strength and waist depending on the application.

  Examples of the binder used include acrylic latex, vinyl acetate latex, urethane latex, epoxy latex, SBR latex, phenol resin, and cationic polyacrylamide, amphoteric polyacrylamide of a water-soluble paper strength agent having a cationic group, Examples include cationic acrylamide, amphoteric acrylamide, cationic polyamide, amphoteric polyamide, polyamide polyamine, cationized starch, cationized guar gum, amphoteric guar gum, polyamide epichlorohydrin, and cationized PVA. Cationic polyacrylamide and amphoteric polyacrylamide are preferable, and these can be used alone or in combination of two or more.

  After wet papermaking and drying, the amount of binder applied is less than 20% by mass based on the basis weight of the filter medium. If it exceeds 20% by mass, the strength and waist become stronger, but not only the collection efficiency is lowered, but also the pressure loss is increased and the life of the filter is shortened.

  Further, in order to impart water repellency and flame retardancy to the filter medium depending on the application, a water repellent and a flame retardant may be added.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these at all. The parts and percentages in the examples are based on mass unless otherwise specified. In addition, the pressure loss, collection efficiency, ash content, and filter workability in Examples and Comparative Examples were measured by the following evaluation methods.

[Pressure loss]
For the pressure loss (mmH ₂ O), the ventilation resistance when air was passed through the filter medium at a flow rate of 5.3 cm / sec was obtained from a water column manometer.

[Collection efficiency]
The collection efficiency (%) is that dioctyl phthalate particles having an average particle diameter of 0.3 μm are generated, air containing these particles is aerated (filtered) at a flow rate of 5.3 cm / sec, and air is passed before and after the filter material. Sampling was performed, and the number of each particle was measured with a multi-dust counter.

(Equation 1)
Collection efficiency = {(number of particles before filtration−number of particles after filtration) / number of particles before filtration} × 100

[Ashes after incineration]
The ash content (%) after incineration was calculated from Equation 2 from the mass before and after the filter medium was incinerated by heating in an electric furnace at 900 ° C. for 2 hours.

(Equation 2)
Ash content = (mass of filter medium after incineration / mass of filter medium before incineration) × 100

[Filter workability]
The filter workability indicated the workability when the filter medium was folded in a bellows shape and incorporated into the unit, and the amount of fiber falling off.

[Preparation of soft cell fibers]
A commercially available beet pulp consisting of sugar beet squeezed koji was put into a 10 L autoclave. Sodium hydroxide was mixed so that the liquid ratio was 4 L / kg and the effective alkali addition rate per dry dry beet pulp amount was 15% by mass, and the mixture was treated under the conditions of a holding temperature of 120 ° C. and a holding time of 30 minutes. After washing by filtration, the sample concentration was adjusted to 8% by mass, sodium hypochlorite was added to the sample so that the effective chlorine concentration was 2% by mass, the mixture was stirred, bleached at room temperature for 8 hours, and then washed by filtration. Further, the suspension was made into 1% by mass, and 1 L of suspension was treated at 10,000 rpm for 1 minute using a rotary blade type homogenizer (Osterizer, manufactured by Osterizer Co., Ltd.). Obtained.

[Preparation of bacterial cellulose fiber]
Bacterial cellulose is obtained by treating a commercially available Nata de Coco (Fujicco) as a 1% by mass suspension and treating the 1 L suspension at 10,000 rpm for 1 minute using a rotary homogenizer (Osterizer, manufactured by Osterizer). A fiber suspension B was obtained.

[Preparation of microfibrous cellulose fibers]
A commercially available microfibrous cellulose (Cerish KY-100S, manufactured by Daicel Chemical Industries), which uses wood pulp mainly composed of fiber cells as a 1% by mass suspension, is a rotary homogenizer (Osterizer, Osterizer). 1 L suspension was treated at 10,000 rpm for 1 minute to obtain a microfibrous cellulose fiber suspension C.

Example 1
[Manufacture of filter media]
Soft cell fiber suspension A and micro glass fiber having an average fiber diameter of about 0.65 μm (trade name: # 106, manufactured by Schuler), polyester having a fineness of 1.67 dtex (average fiber diameter of about 12.5 μm, fiber length of 5 mm) An aqueous slurry was prepared by mixing so that the mass ratio of the solid content to the fiber (manufactured by Teijin Ltd.) was 10:15:75.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

(Comparative Example 1)
[Manufacture of filter media]
Bacterial cellulose fiber suspension B and micro glass fiber having an average fiber diameter of about 0.65 μm (trade name: # 106, manufactured by Schuler), polyester having a fineness of 1.67 dtex (average fiber diameter of about 12.5 μm, fiber length of 5 mm) An aqueous slurry was prepared by mixing so that the mass ratio of the solid content to the fiber (manufactured by Teijin Ltd.) was 10:15:75.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

(Comparative Example 2)
[Manufacture of filter media]
Microfiber cellulose fiber suspension C and micro glass fiber having an average fiber diameter of about 0.65 μm (trade name: # 106, manufactured by Schuler), fineness of 1.67 dtex (average fiber diameter of about 12.5 μm, fiber length of 5 mm) An aqueous slurry was prepared by mixing with a polyester fiber (manufactured by Teijin Ltd.) so that the mass ratio of the solid content was 10:15:75.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

  The filter media obtained in Example 1 and Comparative Examples 1 and 2 were evaluated according to the above evaluation methods, and the results are shown in Table 1.

The filter medium containing the parenchyma fibers of Example 1 had a low pressure loss and a high collection efficiency. Moreover, the filter processability was also excellent. The filter medium containing the bacterial cellulose fibers of Comparative Example 1 had a low collection efficiency, and the fibers were confirmed to fall off during the filter processing. Moreover, there was much ash content after incineration of the filter medium of the comparative example 1, and it was suggested that the bacterial cellulose fiber may have fallen off at the time of papermaking or processing. The filter medium containing the microfibrous cellulose fibers of Comparative Example 2 had a higher pressure loss than the filter medium of Example 1, and it was found that the microfibrous cellulose fibers inhibited air permeability.

Example 2
[Manufacture of filter media]
An aqueous slurry was prepared by mixing the soft cell fiber suspension A and glass fibers having an average fiber diameter of about 9 μm (fiber length: 6 mm, manufactured by Asahi Glass Co., Ltd.) so that the mass ratio of the solid content was 20:80.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

(Comparative Example 3)
[Manufacture of filter media]
An aqueous slurry was prepared by mixing the bacterial cellulose fiber suspension B and glass fibers having an average fiber diameter of about 9 μm (fiber length 6 mm, manufactured by Asahi Glass Co., Ltd.) so that the mass ratio of the solid content was 20:80.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

(Comparative Example 4)
[Manufacture of filter media]
An aqueous slurry was prepared by mixing the fine fibrous cellulose fiber suspension C and glass fibers having an average fiber diameter of about 9 μm (fiber length: 6 mm, manufactured by Asahi Glass Co., Ltd.) so that the mass ratio of the solid content was 20:80. .

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer with a surface temperature of 120 ° C. rotating at 1 m / min and the felt after pressing for 5 minutes at a pressure of 98 N / cm with a sheet press to reduce the moisture in the sheet. The filter medium was obtained by sandwiching and drying.

(Comparative Example 5)
[Manufacture of filter media]
An aqueous slurry was prepared by mixing the fine fibrous cellulose fiber suspension C and glass fibers having an average fiber diameter of about 9 μm (fiber length: 6 mm, manufactured by Asahi Glass Co., Ltd.) so that the mass ratio of the solid content was 20:80. Further, 5% by mass of vinyl chloride resin latex as a binder was added to the fiber.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

  The filter media obtained in Example 2 and Comparative Examples 3 to 5 were evaluated according to the above evaluation methods, and the results are shown in Table 2.

  The filter medium containing the parenchyma fibers of Example 2 had a low pressure loss and a high collection efficiency. Moreover, the filter processability was also excellent. The filter medium containing the bacterial cellulose fiber of Comparative Example 3 had a low collection efficiency, and it was confirmed that the fiber was dropped during filter processing. Moreover, there was much ash content after incineration of the filter medium of the comparative example 3, and it was suggested that the bacterial cellulose fiber may have fallen off at the time of papermaking or processing.

  When the filter medium containing the microfibrous cellulose fibers of Comparative Example 4 and the filter medium containing the microfibrous cellulose fibers of Comparative Example 5 and having a binder added during papermaking were compared, the filter medium of Comparative Example 4 was incinerated. There was a lot of ash, and processability and collection efficiency were low. That is, if the binder is not added, it can be said that dropping of the microfibrous cellulose fibers increases. On the other hand, in Example 2, which is a filter medium containing parenchymal fibers, the fibers were prevented from dropping even without adding a binder. The filter medium of Comparative Example 5 had a large pressure loss because a binder was added. Compared with the filter medium of Comparative Example 5, the collection efficiency of the filter medium of Example 2 was excellent.

Example 3
[Manufacture of filter media]
Fibrilized organic fiber (trade name: KY-400S, manufactured by Daicel Chemical Industries, Ltd.) having a mean fiber diameter of about 0.4 μm, using soft cell fiber suspension A and poly-p-phenylene terephthalamide as raw materials, fineness 0.55 dtex Polyester fiber (average fiber diameter: about 7 μm, fiber length: 5 mm) (manufactured by Teijin Ltd.), polyester binder fiber of 2.2 dtex (average fiber diameter: about 14 μm, fiber length: 5 mm) (trade name: Melty 4080, manufactured by Unitika) Was mixed so that the mass ratio of the solid content was 10: 10: 30: 50 to prepare an aqueous slurry.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

Example 4
[Manufacture of filter media]
A homogenizer (15M- manufactured by Gaulin) with an average fiber diameter of about 1.0 μm using soft cell fiber suspension A and poly-p-phenylene terephthalamide (trade name: Kevlar, manufactured by Toray DuPont) as raw materials. 8TA), a fibrillated organic fiber, a polyester fiber (manufactured by Teijin Limited) having a fineness of 0.55 dtex (average fiber diameter of about 7 μm, fiber length of 5 mm), a fineness of 2.2 dtex (average fiber diameter of about 14 μm, fiber length of 5 mm) An aqueous slurry was prepared by mixing the polyester binder fiber (trade name: Melty 4080, manufactured by Unitika) so that the mass ratio of the solid content was 10: 10: 30: 50.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

Example 5
[Manufacture of filter media]
Fibrils treated with a homogenizer (15M-8TA manufactured by Gaulin) to have an average fiber diameter of about 5.0 μm using soft cell fiber suspension A and poly-p-phenylene terephthalamide (trade name: Kevlar) as raw materials. Organic fiber, polyester fiber with a fineness of 0.55 dtex (average fiber diameter of about 7 μm, fiber length of 5 mm), polyester binder fiber with a fineness of 2.2 dtex (average fiber diameter of about 14 μm, fiber length of 5 mm) (trade name) : Melty 4080, manufactured by Unitika Ltd.) to prepare an aqueous slurry by mixing so that the mass ratio of the solid content was 10: 20: 20: 50.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

Example 6
[Manufacture of filter media]
Fibrilization treated with homogenizer (Gaulin 15M-8TA) so that the average fiber diameter is about 1.0 μm using soft cell fiber suspension A and lyocell fiber (fineness 1.7 dtex, fiber length 4 mm) as raw materials. Organic fiber, polyester fiber having a fineness of 0.55 dtex (average fiber diameter of about 7 μm, fiber length of 5 mm) (made by Teijin), polyester binder fiber having a fineness of 2.2 dtex (average fiber diameter of about 14 μm, fiber length of 5 mm) (trade name: An aqueous slurry was prepared by mixing so that the mass ratio of the solid content with Melty 4080 (manufactured by Unitika) was 10: 10: 30: 50.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

Example 7
[Manufacture of filter media]
Polyester fiber (manufactured by Teijin Limited) with soft cell fiber suspension A and fineness of 0.55 dtex (average fiber diameter of about 7 μm, fiber length of 5 mm), polyester binder of fineness of 2.2 dtex (average fiber diameter of about 14 μm, fiber length of 5 mm) An aqueous slurry was prepared by mixing the fibers (trade name: Melty 4080, manufactured by Unitika) so that the mass ratio of the solid content was 20:30:50.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

(Comparative Example 6)
A fibrillated organic fiber (KY-400S, manufactured by Daicel Chemical Industries, Ltd.) having an average fiber diameter of about 0.4 μm made from bacterial cellulose suspension B and poly-p-phenylene terephthalamide (trade name: Kevlar), fineness 0 .55 dtex (average fiber diameter of about 7 μm, fiber length of 5 mm) polyester fiber (manufactured by Teijin Limited), fineness of 2.2 dtex (average fiber diameter of about 14 μm, fiber length of 5 mm) polyester binder fiber (trade name: Melty 4080, Unitika Ltd.) The aqueous slurry was prepared by mixing so that the mass ratio of the solid content to the product was 10: 10: 30: 50.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

(Comparative Example 7)
[Manufacture of filter media]
A fibrillated organic fiber (KY-400S, manufactured by Daicel Chemical Industries, Ltd.) having an average fiber diameter of about 0.4 μm using a microfiber cellulose suspension C and poly-p-phenylene terephthalamide as raw materials, a fineness of 0.55 dtex (average) A polyester fiber (made by Teijin Limited) having a fiber diameter of about 7 μm and a fiber length of 5 mm), and a polyester binder fiber having a fineness of 2.2 dtex (average fiber diameter of about 14 μm, fiber length of 5 mm) (trade name: Melty 4080, manufactured by Unitika Ltd.) An aqueous slurry was prepared by mixing so that the mass ratio of the solid content was 10: 10: 30: 50.

An aqueous slurry corresponding to a dry mass of 70 g / m ² is collected, and the sheet is made with a square hand-making machine (wire mesh 80 mesh, wire mesh size 25 × 25 cm). The sheet is pressed between the cylinder dryer and the felt at a surface temperature of 120 ° C. rotating at 1 m / min after reducing the moisture in the sheet by pressing at a pressure of 98 N / cm for 5 minutes with a sheet press device. The filter medium was obtained by sandwiching and drying.

  The filter media of Examples 3 to 7 and Comparative Examples 6 to 7 were evaluated according to the above evaluation methods, and the results are shown in Table 3.

  The filter medium in which the soft cell fibers of Examples 3 to 6 and the fibrillated organic fibers having an average fiber diameter of 0.1 μm to 5 μm were mixed had high collection efficiency. In addition, the amount of ash after incineration is very low, and since it does not produce incombustible garbage, which is increasingly regarded as a problem in the future, it can cope with environmental problems.

  Since the filter medium of Example 7 did not contain fibrillated organic fibers having an average fiber diameter of 0.1 μm to 5 μm, it was confirmed that the fibers dropped out during processing. Moreover, compared with the filter medium of Examples 3-6, the collection efficiency was a little low. Moreover, the filter medium which mix | blended the cellulose fiber which is not the soft cell fiber of the comparative examples 6 and 7 was a thing with a low collection efficiency compared with the filter medium of Examples 3-7.

  The present invention relates to air filters for clean rooms used in the fields of semiconductor manufacturing industry, pharmaceutical manufacturing industry, food industry, hospitals, filter media for filters such as office air conditioners and home air conditioners, engine oil, fuel, water treatment, discharge The present invention relates to a filtering medium for liquid filtration such as a processing machine and blood.

Claims (3)

  A filter medium containing fibers obtained from plant parenchyma cells.   A filter medium containing at least one fiber selected from organic fibers and inorganic fibers and fibers obtained from plant parenchyma cells.   The filter medium according to claim 2, wherein the total amount or a part of at least one fiber selected from organic fibers and inorganic fibers is a fiber having an average fiber diameter of 0.1 µm to 5 µm.