WO2016195009A1

WO2016195009A1 - Air cleaning filter

Info

Publication number: WO2016195009A1
Application number: PCT/JP2016/066386
Authority: WO
Inventors: 禎仁後藤; 健人高見; 増森　忠雄; 北川　義幸
Original assignee: 東洋紡株式会社
Priority date: 2015-06-02
Filing date: 2016-06-02
Publication date: 2016-12-08
Also published as: JPWO2016195009A1; JP6988477B2

Abstract

[Problem] To provide an air cleaning filter that has a low ventilation resistance, shows an excellent performance in deodorizing aldehydes and hydrocarbon-based gases, causes little falling off of deodorant particles and can be easily pleated. [Solution] An air cleaning filter that comprises a homogeneous mixture, said mixture comprising silica gel carrying a hydrazide compound thereon, activated carbon and a thermoplastic resin and being fixed between cover layers, wherein the silica gel and activated carbon are in a crushed state.

Description

Air cleaning media

The present invention relates to an air cleaning filter medium having a deodorizing function.

In recent years, in the fields of automobiles, household filters, and the like, there has been a rapid increase in demands for highly functional and diversified filter media, and many studies have been made on air cleaning filter media having a deodorizing function. And as these air cleaning filter media, a method of forming a sheet using a particulate or fibrous adsorbent and an adhesive is often employed. For example, a mixture of a granular adsorbent and a granular adhesive is provided between base materials. An adsorptive filter medium formed by spraying and heat-bonding this is disclosed (for example, Patent Document 1). *

On the other hand, since aldehydes typified by acetaldehyde generated from exhaust gas and tobacco smoke have a low odor threshold and high toxicity, high-efficiency removal with a deodorizing filter is expected. Since acetaldehyde and formaldehyde have low boiling point and high polarity and are difficult to remove with ordinary activated carbon, amines such as aniline and hydrazine derivatives are attached to activated carbon as a means to improve the adsorption removal performance of lower aldehyde by activated carbon. Have been disclosed (for example, Patent Documents 2 and 3). However, the deodorant material and the air purifying filter using the technology have a problem that the attached chemical gradually deteriorates on the activated carbon, and the aldehyde removal performance is lowered. *

In addition, a method of attaching a hydrazine derivative to an inorganic porous material such as silica gel is disclosed as an aldehyde removing material that does not use activated carbon (for example, Patent Document 4). Such adsorbents are excellent in aldehyde removal performance, but they cannot adsorb hydrocarbon gases such as toluene, xylene, butane, etc., so there is a problem that the removal performance is insufficient particularly as an exhaust gas odor deodorizing filter. It was. *

In order to solve this problem, a deodorant containing an inorganic porous material such as zeolite and a activated carbon impregnated with a hydrazine derivative has been disclosed (for example, Patent Document 5). Although it is possible to deodorize both aldehyde and hydrocarbon gas by using this technology, the particle size of the inorganic porous material is limited to 30 μm or less because it is for supporting on the fiber structure, and the air cleaning When ventilated as a filter medium, there is a problem that ventilation resistance increases due to the high bulk density of the porous body. *

Furthermore, the conventional filter medium containing deodorizing material particles such as activated carbon particles and silica gel particles has a structure in which particles are supported between fiber sheets, and there is a problem that the deodorizing material particles fall off from the fiber gaps.

Japanese Patent Publication “Japanese Patent Laid-Open No. 11-5058” Japanese Patent Publication "JP-A-3-98642" Japanese Patent Publication “JP 2001-218824” Japanese Published Patent Publication “JP 2010-58075” Japanese Patent Publication “JP 2008-148804”

The present invention has been made against the background of the above-mentioned prior art, has low ventilation resistance, is excellent in deodorizing performance of aldehydes and hydrocarbon gases, and has good visibility due to dust adhesion during use. A filter medium for cleaning is provided.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is as follows. 1. A filter medium in which a uniform mixture of silica gel, activated carbon and a thermoplastic resin, in which a hydrazide compound is supported between cover layers, is fixed, and the shape of the silica gel and activated carbon is a crushed shape. . 2. 2. The air cleaning filter medium according to 1 above, wherein the hydrazide compound is adipic acid dihydrazide. 3. 3. The air cleaning filter medium according to 1 or 2 above, wherein one of the cover layers is an electret nonwoven fabric. 4). A filter unit obtained by molding the filter medium according to any one of the above 1 to 3 into a pleated shape.

With the above configuration, it is possible to provide a filter medium for air cleaning having low ventilation resistance, excellent deodorizing performance of aldehydes and hydrocarbon gases, less deodorizing material particles, and excellent pleatability.

It is a schematic diagram of the filter medium for air cleaning of this invention. It is a ventilation resistance measuring jig in the present invention. It is a perspective view of the filter unit in the present invention.

Hereinafter, the present invention will be described in detail. The air purification filter medium of the present invention needs to contain silica gel. Since silica gel does not have surface functional groups or impurities derived from natural products unlike activated carbon, it does not react with silica gel even when a chemical for aldehyde adsorption is added, and the chemical can be prevented from deteriorating. Silica gel is an aggregate of primary particles mainly composed of silicon dioxide, and can be obtained by various methods such as a gas phase method, a wet method (precipitation method), and a sol-gel method. The silica gel used in the present invention can be obtained by any method as long as desired characteristics can be obtained. *

The silica gel used in the present invention needs to be in a crushed shape. When it is spherical, when it is supported between the cover layers, not only does the packing density increase and the ventilation resistance increases, but the particles are slippery, so that the particles fall off after forming into a sheet or after pleating. *

The average particle size of the silica gel used in the present invention is preferably 50 μm or more, and more preferably 100 to 600 μm. When the average particle size is less than 50 μm, it is advantageous for obtaining an adsorption rate. However, when silica gel particles are fixed between cover layers and used as a filter medium for air cleaning, if the amount used is increased to ensure the adsorption capacity. Since the packing density is increased, the ventilation resistance is too large to allow ventilation. Furthermore, there is a possibility that dropout and scattering occur easily. *

The pore diameter of the silica gel used in the present invention is preferably 12 to 100 nm, more preferably 20 to 90 nm, further preferably 30 to 80 nm, and most preferably 40 to 70 nm. . If the pore diameter is less than 12 nm, the pores are likely to be clogged at the time of drug addition, which is disadvantageous in terms of reaction rate, and the physical adsorption force due to intermolecular force between the walls increases, so unintentional adsorption of odors And desorption increases. On the other hand, when the pore diameter exceeds 100 nm, it is difficult to obtain a surface area, so that a sufficient deodorization rate cannot be obtained. *

The pore diameter defined in the present invention means a peak diameter obtained by the BJH method. More specifically, the pore diameter is obtained using an adsorption side isotherm obtained by a nitrogen adsorption method at 77 Kelvin (liquid nitrogen temperature). It is done. In this method, since it is not always necessary to obtain the total pore volume, evaluation and analysis are facilitated. *

The silica gel used in the present invention has the above-mentioned pore diameter in order to reduce the action of capillary condensation, and also requires a surface area to develop an adsorption rate useful as a deodorizing material. That is, the specific surface area calculated by the nitrogen adsorption BET method at 77 Kelvin is preferably 20 to 1000 m ² / g, more preferably 35 to 500 m ² / g, and 50 to 400 m ² / g. Is more preferably 70 to 300 m ² / g. When the specific surface area is less than 20 m ² / g, the aldehyde removal rate decreases, and when it exceeds 1000 m ² / g, the physical adsorption amount of odor increases.

The air-cleaning filter medium of the present invention is characterized in that at least one hydrazide compound is supported on silica gel in order to develop adsorption performance for lower aldehydes such as acetaldehyde. *

Examples of the hydrazide compound include a monohydrazide compound having one hydrazide group in the molecule, a dihydrazide compound having two hydrazide groups in the molecule, and a polyhydrazide compound having three or more hydrazide groups in the molecule. Can do. *

Specific examples of the monohydrazide compound include, for example, general formula (1) R—CO—NHNH ₂ [wherein R represents a hydrogen atom, an alkyl group, or an aryl group which may have a substituent. The monohydrazide compound represented by this can be mentioned. In the general formula (1), examples of the alkyl group represented by R include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, Examples thereof include linear alkyl groups having 1 to 12 carbon atoms such as n-octyl group, n-nonyl group, n-decyl group and n-undecyl group. As an aryl group, a phenyl group, a biphenyl group, a naphthyl group etc. can be mentioned, for example, Among these, a phenyl group is preferable. Examples of the substituent for the aryl group include a halogen atom such as a hydroxyl group, fluorine, chlorine, bromine, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, tert-butyl group, iso group. -A linear or branched alkyl group having 1 to 4 carbon atoms such as a butyl group.

Specific examples of the hydrazide compound represented by the general formula (1) include lauric acid hydrazide, salicylic acid hydrazide, form hydrazide, acetohydrazide, propionic acid hydrazide, p-hydroxybenzoic acid hydrazide, naphthoic acid hydrazide, 3-hydroxy- Examples thereof include 2-naphthoic acid hydrazide. *

Specific examples of the dihydrazide compound include, for example, general formula (2) H ₂ NHN—X—NHNH ₂ [wherein X represents a group —CO— or a group —CO—A—CO—. A represents an alkylene group or an arylene group. The dihydrazide compound represented by this can be mentioned. In the general formula (2), examples of the alkylene group represented by A include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, and a nonamethylene group. And linear alkylene groups having 1 to 12 carbon atoms such as a decamethylene group and an undecamethylene group. Examples of the substituent for the alkylene group include a hydroxyl group. Examples of the arylene group include a phenylene group, a biphenylene group, a naphthylene group, an anthrylene group, and a phenanthrylene group. Among these, a phenylene group and a naphthylene group are preferable. Examples of the substituent of the arylene group include the same substituents as the aryl group.

Specific examples of the dihydrazide compound represented by the general formula (2) include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, and dodecane-2-acid dihydrazide. Dibasic acid dihydrazides such as maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, dimer acid dihydrazide, 2,6-naphthoic acid dihydrazide, etc. . Further, various dibasic acid dihydrazide compounds described in JP-B-2-4607, 2,4-dihydrazino-6-methylamino-sym-triazine, and the like can be used as the dihydrazide of the present invention. *

Specific examples of the polyhydrazide compound include polyacrylic hydrazide. Among these, dihydrazide compounds are preferable, dibasic acid dihydrazide is particularly preferable, and adipic acid dihydrazide is even more preferable. *

The said hydrazide compound can be used individually by 1 type or in mixture of 2 or more types. *

The method for supporting the hydrazide compound on the silica gel is not particularly limited as long as the desired properties can be obtained. For example, a method of mixing the hydrazide compound in silica sol and supporting it on the primary particle surface and drying and solidifying it, The silica gel is dissolved in a solvent and impregnated and supported by a hydrazide compound, the hydrazide compound is dissolved in a solvent and sprayed or applied to the silica gel to absorb, and the solvent is dried in subsequent steps. As the solvent, an appropriate one can be selected in consideration of the characteristics and workability of the hydrazide compound. Among these, it is preferable to use an aqueous solvent from the viewpoint of safety and workability.

A more preferable loading treatment method is a method in which a drug solution with less water retention is absorbed and mixed while stirring and mixing in a container, and the particle dispersibility is maintained by stirring and mixing or a fluidized bed in the subsequent drying step. By using this method, aggregation and fixation due to a solution in which the particles are cross-linked can be reduced, and precipitation of the hydrazide compound on the silica gel and the surface of the sheet and scattering of the precipitate can be reduced when forming the filter medium described later. . Furthermore, there is also an effect of improving particle adhesion due to a decrease in drug precipitates or fine powder during sheet processing. *

As a more specific example of support, the solution is absorbed by spraying or injecting the hydrazide compound solution while stirring and mixing with a Henschel mixer or a ribbon mixer, etc., and heating, decompression, or a combination thereof is used in subsequent steps. It is preferable to dry by. Since the hydrazide compound and the silica gel as the carrier are also hydrophilic, they are inferior in the equilibrium adsorption force of the drug as compared with activated carbon. Therefore, by using this method, a good filter medium with reduced surface precipitation can be obtained. *

In the case of carrying by the stirring and mixing method, appropriate conditions can be used depending on the characteristics of the apparatus and silica gel. More specifically, the amount of solvent used is preferably 5 to 300 parts by weight, more preferably 10 to 250 parts by weight, still more preferably 20 to 200 parts by weight, and most preferably 50 to 150 parts by weight with respect to 100 parts of silica gel particles. When the amount of solvent used is less than 5 parts by weight, the permeation into the carrier becomes insufficient and the adsorption performance is lowered. Further, when the amount of the solvent used exceeds 300 parts by weight, the silica gel is saturated, so that chemical precipitation and aggregation occur on the surface, and much energy is required for drying. In view of the pore volume of silica gel, the solvent volume is generally 5% to 200%, more preferably 10% to 150%, and more preferably 20 to 110% of the total pore volume. Is more preferable. *

In the present invention, the amount of hydrazide compound supported on silica gel is preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight, based on 100 parts of silica gel. If the amount is less than 1 part by weight, the removal capacity and speed become insufficient, and if it exceeds 100 parts by weight, the pores of the silica gel become clogged, and the removal capacity and speed, which are combined effects with the porous body, cannot be obtained. *

Examples of the activated carbon used in the present invention include coconut shells, wood-based materials, coal-based materials, and pitch-based materials, with coconut shells being preferred. The fine pores of coconut shell activated carbon have a large proportion of small pores compared to other raw materials, and the amount of ash that is an impurity is also small. That is, since the coconut shell activated carbon has small pores, the intermolecular force with the pore wall effectively acts on the adsorbed odor molecules, and it is difficult to desorb the adsorbed odor molecules. Moreover, since there is little ash content, the odor adsorption performance per weight is also high. *

The shape of the activated carbon used in the present invention needs to be a crushed shape. When it is spherical, when it is supported between the cover layers, the packing density increases and the airflow resistance increases, and the particles are slippery, so that the particles fall off after forming into a sheet or after pleating. The pulverized activated carbon can be obtained by mechanically pulverizing coconut shell activated carbon with a ball mill or a crusher. *

The average particle diameter of the activated carbon used in the present invention is 100 μm or more in terms of mass average diameter based on the JIS K 1474 activated carbon test method in consideration of air permeability, dust retention, detachability, sheet processability, and the like. And more preferably 200 to 600 μm. When the average particle size is less than 100 μm, it is advantageous to obtain the adsorption rate. However, when silica gel is fixed between the cover layers and used as a filter medium for air cleaning, it is filled if the amount used is increased to secure the adsorption capacity. Density increases and ventilation resistance is too high to vent. Furthermore, there is a possibility that dropout and scattering occur easily. In addition, said granular activated carbon can be obtained by carrying out predetermined particle size adjustment using a normal classifier. *

The activated carbon used in the present invention is preferably coconut shell activated carbon having a hardness of 90% or more according to JIS K 1474 activated carbon test method, more preferably coconut shell activated carbon having a hardness of 95% or more. If the hardness of the activated carbon is less than 90%, the activated carbon is crushed during sheet processing or pleating, and the activated carbon falls off from the filter medium surface or the pleat apex. *

The amount of toluene adsorbed when measured according to JIS K 1474 of the activated carbon used in the present invention is preferably 20% by weight or more. This is because high adsorption performance is required for nonpolar gaseous and liquid substances such as malodorous gases. *

In the air cleaning filter medium of the present invention, a mixture of activated carbon, silica gel, and a thermoplastic resin is sandwiched between cover layers, and the silica gel carries a hydrazide compound. The activated carbon and silica gel are bonded together, and the cover layer and the adsorbent are bonded. *

In the air purifying filter medium of the present invention, it is necessary to use in combination silica gel carrying activated carbon and a hydrazide compound as an adsorbent. Activated carbon alone can adsorb hydrocarbon-based odorous gases, but cannot absorb low-molecular-weight aldehydes with low boiling point and high polarity. For this purpose, silica gel carrying hydrazide compound with high adsorption performance of low-molecular-weight aldehydes. Use together. As a result, it becomes possible to deodorize various odors in a balanced manner. *

Furthermore, when the activated carbon is used alone, the filter medium becomes black, so even if dust accumulates during air cleaning, the dust cannot be visually recognized, and even if clogging due to dust accumulation occurs, it may not be noticed. The weight ratio of the content of the silica gel on which the hydrazide compound is supported relative to the activated carbon in the mixture must be 1 to 100. If it is less than 1, the dust visibility is poor, and if it exceeds 100, the adsorption of hydrocarbon gas Lack of ability. *

The cover layer used for the air cleaning filter medium of the present invention may be a woven or non-woven fibrous structure. The average fiber diameter of the fibers constituting the cover layer on the upstream side during air cleaning is preferably 10 to 100 μm, more preferably 20 to 60 μm, and even more preferably 20 to 45 μm. Since the upstream cover layer is the inflow surface of the air to be treated, if the average fiber diameter of the constituent fibers is less than 10 μm, the gap between the fibers is also narrowed, dust in the air accumulates on the cover layer, and the ventilation Resistance soars. When the average fiber diameter of the constituent fibers exceeds 100 μm, the adsorbent particles jump out or fall off particularly during pleating. *

On the other hand, the average fiber diameter of the fibers constituting the cover layer on the downstream side at the time of air cleaning is not particularly limited, but is preferably 10 to 30 μm in consideration of dropping of the adsorbent. When the average fiber diameter of the constituent fibers is less than 10 μm, the airflow resistance increases, and when it exceeds 30 μm, the adsorbent falls off. *

The packing density of the fiber structure constituting the cover layer of the present invention is preferably 0.05 g / cc or more. When the packing density is less than 0.05 g / cc, heat setting does not work during pleating and it becomes difficult to maintain the pleated shape. More preferably, it is 0.15 g / cc or more. *

The cover layer of the present invention preferably has a thickness of 0.1 to 3.0 mm. If the thickness is less than 0.1 mm, the activated carbon may come off or fall off when considering the uneven appearance. When the thickness exceeds 3.0 mm, the thickness of the entire filter medium is too large, and when the pleated unit is used, the structural resistance increases, and as a result, the ventilation resistance of the entire unit becomes too high, which causes a problem in practice. *

Cover layer of the present invention preferably has a basis weight is 15 ~ 100g / ^{m 2,} more preferably 20 ~ 80g / ^{m 2.} If the basis weight is less than 15 g / m ² , the adsorbent and the thermoplastic resin are likely to come off. When the basis weight exceeds 100 g / m ² , the sheet thickness increases, and the structural resistance in the case of a pleated unit increases.

The fiber material of the fiber structure constituting the cover layer of the present invention is not particularly limited, and materials such as polyolefin, polyester, rayon, polyamide, polyurethane, acrylic, polyvinyl alcohol, and polycarbonate are used. be able to. Among them, if a core-sheath type composite fiber using a low-melting thermoplastic resin component as a sheath component and a high-melting thermoplastic resin component as a core component is used, the sheath component melts at the time of forming a heated sheet, which will be described later. It is preferable because the bonding force is increased. *

For the cover layer of the present invention, it is preferable to use a charged non-woven fabric, so-called electret sheet, which can also increase the removal effect on submicron particles such as tobacco smoke particles, carbon particles and sea salt particles. By using the electret sheet as a cover layer, not only odorous substances but also submicron particles can be removed simultaneously, and the air cleaning effect is further improved. Also, if the electret sheet is installed upstream of the adsorbent, dust etc. will enter the adsorbent layer composed of activated carbon, silica gel, and thermoplastic resin, and the pores of the activated carbon and silica gel in the adsorbent layer will be blocked. This is because the filter life can be prevented and the filter life can be extended. *

The fiber orientation of the fiber structure constituting the cover layer of the present invention is not particularly limited. For example, the fiber orientation may be random, cloth, or parallel as long as it is a nonwoven fabric. *

In the air cleaning filter medium of the present invention, a thermoplastic resin is used for adhesion between the cover layer and the adsorbent, and the material thereof is polyester, polyolefin, polyamide, polyurethane, ethylene-acrylic copolymer, Examples thereof include thermoplastic resins such as polyacrylate, polyarene, polyacryl, polydiene, ethylene-vinyl acetate, PVC, and PS. The size of the thermoplastic resin of the present invention is not particularly limited, but it is preferably powdery and having an average particle size of about 1 to 200 μm. If the average particle size is 1 to 200 μm, the thermoplastic resin can reduce blocking of the surface pores of the adsorbent, while pre-adhesion to activated carbon by van der Waals force or electrostatic force is effective when mixed with the adsorbent. This is because it can be uniformly dispersed, and the adhesiveness in the adsorbent layer and with the cover layer can be improved. *

The shape of the thermoplastic resin of the present invention is not particularly limited as long as it is in a powder form, but a crushed form is preferable because it is less likely to fall off from the cover layer when sprayed onto the cover layer. The melting point of the thermoplastic resin is preferably 80 ° C. or higher, more preferably 90 ° C. or higher in consideration of the environmental temperature in the room of a moving vehicle or the like. *

The fluidity at the time of melting of the thermoplastic resin of the present invention is preferably 1 to 80 g / 10 min, more preferably 3 to 30 g / 10 min in terms of MI value described in JIS K-7210. This is because, within such a range, the adsorbent layer and the cover layer can be firmly bonded while preventing the surface of the adsorbent from being blocked. *

The content of the thermoplastic resin of the present invention is preferably 3 to 100% by weight, more preferably 5 to 70% by weight, based on the adsorbent. This is because a deodorizing filter medium excellent in adhesive strength with the cover layer, ventilation resistance, and deodorizing performance can be obtained within such a range. *

The air-cleaning filter medium of the present invention may include components having incidental functions such as antibacterial agents, antifungal agents, antiviral agents, and flame retardants. These components may be kneaded into fibers, non-woven fabrics, and woven fabrics, or may be added or supported by post-processing. For example, by including a flame retardant, FMVSS. It is possible to manufacture a filter medium for air cleaning that meets the standards for retarding flame retardancy defined in 302 and UL flame retardant standards. *

The component having the incidental function may be attached or supported on activated carbon or the like. However, in this case, care must be taken not to impair the original adsorption function of the activated carbon. In addition, it is possible to enhance the deodorizing function by imparting a function having adsorption performance to the fibers of the cover layer, for example, by attaching an acid or alkali chemical or using ion exchange fibers.

The basic manufacturing method of the air cleaning filter medium will be described. First, silica gel on which a hydrazide compound is supported, activated carbon, and a powdered thermoplastic resin are weighed to a predetermined weight, placed in a shaker (stirrer), and stirred at a rotational speed of 30 rpm for about 10 minutes. The moisture content at this time is preferably within 15% of the weight of the mixture. At this point, the powdery thermoplastic resin is temporarily bonded to the activated carbon surface and the silica gel surface on which the hydrazide compound is supported. Next, after spraying this mixture on the cover layer, the cover layer is laminated and a hot press treatment is performed. The sheet surface temperature during hot pressing is preferably about 3 to 30 ° C., more preferably 5 to 20 ° C. higher than the melting point of the powdered thermoplastic resin. *

Alternatively, after spraying a mixed powder premixed with silica gel, activated carbon and powdered thermoplastic resin carrying a hydrazide compound onto the cover layer, a certain amount of granular thermoplastic resin is further sprayed, and the cover layer is further covered. After lamination, a method of performing a heat press treatment, or a granular thermoplastic resin fixed in advance to the cover layer, and this sheet is used as the cover layer described above, and activated carbon and powdered thermoplastic resin are mixed in advance thereon It is also possible to obtain a filter medium for air cleaning by spraying powder or using it for a cover layer and performing a heat press treatment. *

As an alternative method, after spraying a mixed powder in which activated carbon, silica gel supporting a hydrazide compound, and a powdered thermoplastic resin are mixed in advance onto the cover layer, a certain amount of granular thermoplastic resin is further sprayed, and the cover layer After laminating, a method of performing a heat press treatment, or a granular thermoplastic resin is fixed in advance to the cover layer, and this sheet is used as the cover layer described above, and activated carbon and a powdered thermoplastic resin are premixed thereon. It is also possible to obtain a filter medium for air cleaning by spraying the mixed powder or using it for the cover layer and performing a hot press treatment. *

Further, if preheating is performed in advance using infrared rays or the like and temporary bonding is performed before heat treatment, an irregular flow of the mixture that tends to occur during pressing does not occur, and an air purifying filter medium with better dispersibility can be manufactured. The heat treatment using infrared rays does not cause an air current and the like, can be heated while the mixture is left standing, and can prevent the mixture from being scattered. *

In order to finally heat-press and manufacture a sheet, a hot-roll hot-pressing method that is often used, or a flat-bed laminating method that is sandwiched between heat belt conveyors that are flat on the upper and lower sides can be given. The latter is more preferable for producing a more uniform thickness and adhesion. In addition, the combination of the characteristics of the cover layer described in the present invention and the above production method can suppress excessive binding between the activated carbons, and at the same time, can obtain a practically sufficient adhesive strength with the cover layer. *

The air cleaning filter medium obtained in the present invention is suitable for processing into a pleated shape. The method of processing into a pleated shape is not particularly limited, and can be widely used such as a reciprocating method, a rotary method, and a striping method. Since the amount of filter media folded per unit area can be increased by processing into a pleated shape, deodorization performance and dust retention performance can be dramatically improved. *

The thickness of the pleated filter unit using the air-cleaning filter medium of the present invention is preferably 10 to 400 mm. For in-vehicle applications such as built-in car air conditioners and household air purifiers, it is about 10-60mm due to the normal internal space. About 400 mm is preferable from the viewpoint of storage space. *

The distance between the ridge peaks of the filter unit of the present invention is preferably 2 to 30 mm. If it is less than 2 mm, the folds are in close contact with each other and there is a lot of dead space, which makes it impossible to use the sheet efficiently. On the other hand, if it exceeds 30 mm, the filter medium folding area becomes small, and therefore it is not preferable because the removal effect corresponding to the filter thickness cannot be obtained.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and any design change in accordance with the gist of the present invention will be described. It is included in the range. In addition, the numerical value in an Example is the value measured with the following method. *

(Average fiber diameter) A scanning electron micrograph (magnification of 100 to 1000 times) of the cover layer surface was taken, and an average value obtained by measuring the fiber diameter at n = 30 was calculated from the photograph. *

(Average particle diameter) For activated carbon and silica gel, the mass average diameter based on the JIS K 1474 activated carbon test method was taken as the average particle diameter. Moreover, about the thermoplastic resin, D50 median diameter was made into the average particle diameter using the laser diffraction type particle size distribution measuring apparatus (made by Shimadzu Corporation). *

(Weight) Using a 200 mm × 200 mm sample, leave it in a constant temperature bath at 80 ° C. for 30 minutes, and then leave it in a desiccator (desiccant: silica gel) for 30 minutes. Thereafter, the sample was taken out, measured with a chemical balance having a sensitivity of 10 mg, and converted to a weight per m ² .

(Ventilation resistance) Using the measuring jig shown in FIG. 2, the differential pressure between the upstream side and the downstream side when the sample size is φ75 mm, the effective filtration area is φ50.5 mm, and the filter medium passing air velocity is 50 cm / sec. The measured airflow resistance was measured. *

(Thickness) Measured with a dial thickness gauge using a φ75 mm sample. The size of the probe was 50 mm, and the measurement load was 2.94N. *

(Filling density) The filling density was measured based on JIS K 1474 (2007) activated carbon test method. *

(0.3 μm particle collection efficiency) A filter medium is installed in the duct, and the air is vented so that the air filtration speed is 20 cm / second, and the number concentration of 0.3 to 0.5 μm particles upstream and downstream of the filter medium is determined. Measurement was performed with a particle counter, and the particle collection efficiency was calculated using the following equation. Particle collection efficiency (%) = [1- (Downstream concentration / Upstream concentration)] × 100

(Acetaldehyde deodorization efficiency) In an atmosphere of 25 ° C. and 50% relative humidity, 3 ppm of acetaldehyde gas was passed through the test filter medium at a wind speed of 20 cm / sec. One minute after ventilation, the upstream and downstream concentrations of the filter medium are measured with a gas-tech detector tube, and the percentage obtained by dividing the upstream gas concentration by the downstream gas concentration is divided by the upstream gas concentration. It was. The measurement was performed on a filter medium single plate sample cut to 6 cm × 6 cm. *

(Toluene deodorization efficiency) In an atmosphere of 25 ° C and 50% relative humidity, 80 ppm of toluene gas was passed through the test filter medium at a wind speed of 20 cm / sec. One minute after ventilation, the upstream and downstream concentrations of the filter medium are measured with a gas-tech detector tube, and the percentage obtained by dividing the upstream gas concentration by the downstream gas concentration is divided by the upstream gas concentration. It was. The measurement was performed on a filter medium single plate sample cut to 6 cm × 6 cm. *

(Particle dropout amount) The filter medium prepared with a width of 200 mm was subjected to pleat processing by an alternating streaks method so that the pleat folding height was 28 mm. The pleated product was cut at 30 ridges and heat-sealed so that the activated carbon did not fall off from the cut end face. A 200 mm × 30 mm, 1 mm thick non-woven fabric for a frame was applied to a pleat cut product on four surrounding surfaces so that the pleat pitch was equally spaced (FIG. 3). Place the created filter unit horizontally on the ground, let it fall freely on a smooth and clean table from a height of 50 cm, repeat this three times each up and down, measure the weight of the activated carbon dropped from the filter unit, The amount dropped out. *

<Example 1> Polypropylene fiber (fineness: 2.2 dtex, fiber length: 51 mm) and polyester fiber (fineness: 1.7 dtex, fiber length: 44 mm) are mixed and carded at a weight ratio of 1: 1, and the basis weight is 25 g / m ^2. After producing the mixed fiber web, 3 MPa high-pressure water was continuously sprayed to entangle and dry to prepare a mixed fiber sheet. A nonwoven fabric composed of a core-sheath type composite heat-sealing long fiber (fiber diameter 30 μm) composed of polyester (core) / polyethylene (sheath) having a basis weight of 12 g / m ² is laminated and integrated into this mixed fiber sheet by needle punching. And triboelectric charging was performed to obtain an electret laminated sheet as a downstream layer. An average particle size of 250 μm as activated carbon, a packed density of JIS K 1474 (2007) activated carbon test method having a packing density of 0.43 g / cc, a BET specific surface area of 1500 m ² / g, and an average particle size of 120 μm as silica gel 5 parts by weight of adipic acid dihydrazide was supported on 100 parts by weight of silica gel on crushed A-type silica gel having a packing density of 0.71 g / cc and a BET specific surface area of 610 m ² / g according to JIS K 1474 (2007) activated carbon test method. In addition, as the thermoplastic powder resin, a crushed-shaped ethylene-vinyl acetate copolymer resin (average particle size 150 μm, MI 24 g / 10 min, melting point 100 ° C.) was used, and these were used in a weight ratio of 50:25:25. Weighed and mixed with a hoop shaker (manufactured by Kyomachi Industrial Vehicle Co., Ltd.) for 15 minutes. This mixed powder was uniformly sprayed on the non-woven fabric side made of the heat-bonding long fibers of the electret laminated sheet so that the total amount was 100 g / m ² . A resin-bonded nonwoven fabric (weight per unit area: 40 g / m ² , thickness: 0.2 mm) made of rayon fiber (fiber diameter: 20 μm) is laminated as an upstream side cover layer, and sandwiched between Teflon (registered trademark) / glass belts, The belt interval was set to 0.5 mm and the pressure was set to 100 kPa, and hot pressing was performed at 140 ° C. for 30 seconds. Thereafter, it was cooled to obtain a desired air cleaning filter medium.

<Example 2> An air cleaning filter medium was obtained in the same manner as in Example 1 except that a polypropylene melt blown nonwoven fabric having an average fiber diameter of 7 µm was used as the downstream layer. *

<Comparative Example 1> As a silica gel, an adipic acid dihydrazide is added to a spherical silica gel having an average particle diameter of 125 μm, a packing density of JIS K 1474 (2007) activated carbon test method of 0.75 g / cc, and a BET specific surface area of 610 m ² / g. An air cleaning filter medium was obtained in the same manner as in Example 1 except that 5 parts by weight of 100 parts by weight was used.

<Comparative example 2> Implementation was carried out except that a spherical pitch activated carbon having an average particle size of 250 μm, a packing density of 0.50 g / cc, and a BET specific surface area of 1200 m ² / g in JIS K 1474 (2007) activated carbon test method was used as the activated carbon. In the same manner as in Example 1, an air cleaning filter medium was obtained.

As described above, the air resistance, thickness, collection efficiency, acetaldehyde deodorization efficiency, toluene deodorization efficiency, and particle dropout amount of the air cleaning filter media obtained in Examples and Comparative Examples were evaluated. The measurement results are shown in Table 1. *

In the examples, the ventilation resistance is low, and not only acetaldehyde but also toluene, which is a typical hydrocarbon gas, can be removed, and the collection efficiency is excellent. Since the particle sizes of silica gel and activated carbon, which are deodorizing materials, are in a crushed shape, the amount of deodorizing material particles falling from the filter medium is small even after pleating. On the other hand, in the comparative example, the shape of silica gel or activated carbon is spherical, so the packing density of the particles in the filter medium is high and the ventilation resistance is high, and the deodorant particles are slippery between particles and between the particle and cover layers. The later dropout is large.

The air-cleaning filter medium of the present invention can provide an air-cleaning filter medium with low ventilation resistance, excellent deodorization performance of aldehydes and hydrocarbon gases, and less deodorizing material particles falling off and excellent in pleatability. It can greatly contribute to the industry.

1 Air filter medium 2 Upstream cover layer 3 Activated carbon, silica gel, thermoplastic resin mixed layer 4 Downstream cover layer 5 Pleated unit 6 Frame body

Claims

A filter medium in which a uniform mixture of silica gel, activated carbon and a thermoplastic resin, in which a hydrazide compound is supported between cover layers, is fixed, and the shape of the silica gel and activated carbon is a crushed shape. .
The air-cleaning filter medium according to claim 1, wherein the hydrazide compound is adipic acid dihydrazide.
The air cleaning filter medium according to claim 1, wherein one of the cover layers is made of an electret nonwoven fabric.
A filter unit in which the filter medium according to claims 1 to 3 is molded into a pleat shape.