JP2015029770A - Air cleaning filter medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air cleaning filter medium having a low gas transmission resistance, excellent deodorizing performances of aldehydes and hydrocarbon-based gases, high peeling strength, excellent pleatability, and favorable in-use contaminant visual recognizability.SOLUTION: The provided air cleaning filter medium is an air cleaning filter medium obtained by sandwiching, between cover layers, a mixture of activated carbon, a hydrazide compound-supported silica gel, and a thermoplastic resin wherein the activated carbon and hydrazide compound-supported silica gel within the mixture are adhered and fixed between the cover layers based on the melting of the thermoplastic resin, wherein the weight ratio of the hydrazide compound-supported silica gel content with respect to the activated carbon within the mixture is 1-100, wherein the average particle diameter ratio and filling density ratio of the silica gel with respect to the activated carbon within the mixture are respectively 0.5-2.0 and 0.5-2.0, and wherein the respective average particle diameters of the activated carbon and silica gel within the mixture are each at least 100 μm.

Description

  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 the ventilation resistance increases due to the high packing density of the porous body. In addition, the ratio of the activated carbon must be 50% by mass or more of the total deodorant, and when used as an air purifying filter medium, the activated carbon is black, so the color tone becomes dark and dust in the environment is collected and clogged. There was a problem that the appearance could not be discerned even when it was awake.

Japanese Patent Laid-Open No. 11-5058 Japanese Patent Laid-Open No. 3-98642 JP 2001-218824 A JP 2010-58075 A JP 2008-148804 A

  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) An air cleaning filter medium in which a mixture of activated carbon, silica gel carrying a hydrazide compound and a thermoplastic resin is sandwiched between cover layers, and the silica gel carrying activated carbon and a hydrazide compound in the mixture is heated The adhesive is fixed between the cover layers by melting the plastic resin, and the content of the silica gel carrying the hydrazide compound in the mixture is 1 to 100 by weight with respect to the activated carbon, and the silica gel relative to the activated carbon in the mixture The ratio of average particle diameter is 0.5 to 2.0, the ratio of packing density is 0.5 to 2.0, and the average particle diameter of activated carbon and silica gel in the mixture is 100 μm or more, respectively. Filter media.
(2) The air-cleaning filter medium according to (1), wherein the hydrazide compound is adipic acid dihydrazide.

  The air cleaning filter medium according to the present invention has low ventilation resistance, excellent deodorization performance of aldehydes and hydrocarbon gases, high peel strength, excellent pleatability, and good visibility of dirt during use. It is a filter medium for cleaning.

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. It is the schematic of the peeling strength measurement in this invention.

  Hereinafter, the present invention will be described in detail.

  The air cleaning filter medium of the present invention contains 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. As the silica gel used in the present invention, any silica gel obtained by any method can be preferably used as long as desired characteristics can be obtained.

  The silica gel used in the present invention is required to have an average particle size of 100 μm or more, and preferably 200 to 600 μm. When the average particle size is less than 100 μm, it is advantageous for obtaining an adsorption rate. However, when silica gel particles are immobilized between cover layers and used as an air cleaning filter medium, the amount used is increased in order to secure an adsorption capacity. Since the packing density becomes high, 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, still more preferably 30 to 80 nm, and most preferably 40 to 70 nm. preferable. If it is less than 12 nm, pores are likely to be clogged at the time of drug attachment, which is disadvantageous in terms of reaction rate, and physical adsorption force due to intermolecular force between the walls increases, so unintentional adsorption and desorption of odors. growing. 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, and more specifically, is determined using an adsorption side isotherm obtained by a nitrogen adsorption method at 77 Kelvin (liquid nitrogen temperature). In this method, since it is not always necessary to obtain the total pore volume, evaluation and analysis are facilitated when the large pore silica gel of the present invention is used.

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, preferably 20~1000m ² / g in specific surface area is calculated by the nitrogen adsorption BET method at 77 Kelvin, more preferably 35~500m ² / g, more preferably 50~400m ² / g, 70~300m ² / g is most preferred. If it is less than 20 m ² / g, there is a problem that the aldehyde removal rate decreases, and if it exceeds 1000 m ² / g, the amount of odor physical adsorption 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, C1-C12 linear alkyl groups, such as an n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, can be mentioned. 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 and bromine, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a tert-butyl group, and an iso group. -C1-C4 linear or branched alkyl groups, such as a butyl group, etc. can be mentioned.

  More specific examples of the hydrazide compound of 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 include 2-naphthoic acid hydrazide.

Specific examples of the dihydrazide compound, for example, the 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. C1-C12 linear alkylene groups, 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. . Furthermore, various dibasic acid dihydrazide compounds described in Japanese Patent Publication No. 2-4607, 2,4-dihydrazino-6-methylamino-sym-triazine, and the like can also 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 supported by impregnation with the hydrazide compound, the hydrazide compound is dissolved in the solvent and absorbed by spraying and coating on the silica gel, 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 at the same time, the precipitation of the hydrazide compound on the silica gel and the sheet surface and the scattering of the precipitate can be reduced when forming the removal material described later. it can. 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 hydrazide compound solution is sprayed or injected as needed while stirring and mixing with a Henschel mixer and a ribbon mixer, etc., and the solution is absorbed by heating, reduced pressure or combined use in subsequent steps. It is preferable. 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, a good removal material with reduced surface precipitation can be obtained by using this method.

  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 the 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 the silica gel particles. When the amount of the solvent used is less than 5 parts by weight, the adsorption performance is lowered because the penetration into the carrier is insufficient. Further, when the amount of the solvent used is more than 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 preferably 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 supported amount of the hydrazide compound is preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight with respect to 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.

  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, dropout, sheet processability, and the like. Preferably it is 200-600 micrometers. When the average particle size is less than 100 μm, it is advantageous to obtain the adsorption speed. However, when silica gel is fixed between the cover layers and used as a filter medium for air cleaning, it is filled when 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.

  As the activated carbon used in the present invention, it is preferable to use coconut shell activated carbon having a hardness of 90% or more according to the JIS K 1474 activated carbon test method. Coconut shell activated carbon having a hardness of 95% or more is more preferable. 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.

  As the raw material of the activated carbon used in the present invention, coconut shell, wood-based, coal-based, pitch-based and the like are known, but coconut shell is preferable. 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 walls effectively acts on the adsorbed odor molecules, and the adsorbed odor molecules are difficult to desorb. Moreover, since there is little ash content, the odor adsorption performance per weight is also high.

  The toluene adsorption amount 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 odor gas, but cannot absorb low-molecular-weight aldehydes with low boiling point and high polarity, so silica gel carrying hydrazide compound with high adsorption ability of low-molecular-weight aldehydes is used to supplement it. Combined. 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 with respect to the activated carbon in the mixture must be 1 to 100. If it is less than 1, the dust visibility is not inferior, and if it exceeds 100, the hydrocarbon gas This is not preferable because the adsorbing capacity is insufficient.

  The ratio of the average particle diameter of the silica gel to the activated carbon of the air cleaning filter medium of the present invention needs to be 0.5 to 2.0. When the difference in average particle size becomes large, especially when the amount of these adsorbents is small, only the particles with a large particle size come into contact with the cover layers on both sides when fixing between the cover layers. The smaller particles cannot adhere to the cover layer and fall off. Further, since the peel strength is also weakened, it is necessary to select an adsorbent having a close particle size in which the average particle size ratio is in the range of 0.5 to 2.0.

  The ratio of the packing density of the silica gel to the activated carbon of the air cleaning filter medium of the present invention also needs to be 0.5 to 2.0. If the difference between the two increases not only in the average particle diameter but also in the packing density, the adsorbent is separated during sheet formation, which will be described later, which is not preferable. That is, the adsorbent is unevenly distributed due to the difference in packing density when mixing the two, and uniform mixing cannot be performed. If uniform mixing is not possible, variations in adsorption performance and dust visibility will occur in the filter medium and the expected effect cannot be obtained, so the packing density ratio must be 0.5 to 2.0.

The cover layer used for the air cleaning filter medium of the present invention may be a woven or non-woven fibrous structure. 10-100 micrometers is preferable, as for the average fiber diameter of the fiber which comprises the cover layer used as the upstream side at the time of air cleaning, 20-60 micrometers is more preferable, and 20-45 micrometers is more preferable. 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 smaller than 10 μm, the gap between the fibers becomes narrow, dust in the air accumulates on the cover layer, and the ventilation resistance Soars. When the average fiber diameter of the constituent fibers is larger than 100 μm, the adsorbent particles pop out or fall off particularly during pleating.

  The color tone of the fibers constituting the upstream cover layer is preferably a light color with good visibility of dust in the air, and more preferably white or fluorescent. If the color is dark, it cannot be determined even if dust components such as exhaust gas or dust in the air accumulate, and therefore the filter medium may not be replaced even if a large amount of dust accumulates and becomes clogged.

  On the other hand, the average fiber diameter of the fibers constituting the cover layer on the downstream side is not particularly limited, but is preferably 10 to 30 μm in consideration of the dropping of the adsorbent. When the average fiber diameter of the constituent fibers is smaller than 10 μm, the airflow resistance is increased, and when it is larger than 30 μm, the adsorbent is detached.

  The filling density of the fiber structure constituting the cover layer of the present invention is preferably 0.05 g / cc or more. If the packing density is lower 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. When the thickness is smaller than 0.1 mm, there is a concern that the activated carbon may come off or fall off when the spot weight is taken into consideration. When the thickness is larger than 3.0 mm, the thickness of the entire filter medium is too large, and the structural resistance becomes large when the pleated unit is used. As a result, the ventilation resistance of the entire unit becomes too high, which causes a practical problem.

Cover layer of the present invention preferably has a basis weight is ^{15~100g / m 2, 20~80g / m} 2 is more preferable. 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.

  In the cover layer of the present invention, 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 can be used. By using the electret sheet as a cover layer, dust and the like enter the adsorbent layer composed of activated carbon, silica gel, and thermoplastic resin to prevent clogging of the pores of the activated carbon and silica gel in the adsorbent layer, This is because 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. Among these, a polyester resin is preferable because it has a high oxygen index (LOI value) and has a great effect on improving flame retardancy as a filter medium. Moreover, if it is the same material as a cover layer, there exists an effect which adhesiveness improves more.

  The size of the thermoplastic resin of the present invention is preferably a powder and an average particle size of 1 to 40 μm. An average particle size of 5 to 30 μm is more preferable. Further, it is more preferable that 95% by weight or more is included in the range of the average particle diameter of 1 to 40 μm. If the average particle size is within this range, the thermoplastic resin can reduce the 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 powdery, but examples thereof include spherical, crushed, and fibrous shapes. 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 an MI value described in JIS K-7210, preferably 1 to 80 g / 10 min, more preferably 3 to 30 g / 10 min. 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 1 to 40% by weight and more preferably 3 to 30% by weight with respect to the activated carbon. 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.

  Examples of methods for adjusting the particle size of powdered and granular thermoplastic resins include mechanical pulverization, freeze pulverization, and chemical adjustment methods. Moreover, although it can finally screen and obtain a fixed particle size, if it is a method which can ensure a fixed particle size, it will not specifically limit.

  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. Further, 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 structural unit of the air-cleaning filter medium of the present invention is an upstream cover layer / silica gel, a mixture of activated carbon and a thermoplastic resin / downstream cover layer.
The basic manufacturing method of the air cleaning filter medium will be described. First, activated carbon, silica gel on which a hydrazide compound is supported, 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 about 5 to 20 ° C higher than the melting point of the powdered thermoplastic resin.

  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 the lamination, 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. An air cleaning filter medium can also be obtained by spraying the mixed powder or using it for the cover layer and carrying out 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 produce a sheet by finally hot pressing, a hot press method between rolls or a flat bed laminating method in which the upper and lower parts are sandwiched between flat heat belt conveyors can be used. 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, 40 to approximately 10 to 60 mm for large filter units often installed in building air conditioning applications due to the normal internal space. About ~ 400 mm is preferable considering the storage space.

  The pleat peak apex distance 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 by the following methods.

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

(Average particle size)
For activated carbon and silica gel, the mass average diameter based on the JIS K 1474 activated carbon test method was defined 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)
A sample of 200 mm × 200 mm is used, left in a constant temperature bath at 80 ° C. for 30 minutes, and then left 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)
With 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 flow rate through the filter medium is 50 cm / sec. It was resistance.

(Thickness)
Measurement was performed 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.

(Packing density)
The packing density was measured based on JIS K 1474 (2007) activated carbon test method.

(Peel strength)
Measurement is performed as shown in FIG. The test piece has a width of 50 mm, a length of 200 mm, and a tensile speed of 100 mm / min. The L dimension in FIG. 4 is 200 mm at the start and 280 mm at the end (peeling amount 40 mm), and the average value therebetween is the peeling strength. The strength was measured using an autograph manufactured by Shimadzu Corporation.

(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.

(Mixing uniformity)
Put a predetermined amount of activated carbon and silica gel into a hoop shaker (manufactured by Kyomachi Sangyo Vehicle Co., Ltd.), take out after stirring for 15 minutes, visually check the color uniformity, and make uniform uniform and defective non-uniform. .

(Dust visibility)
A filter medium veneer is installed in the duct, and the atmosphere is ventilated so that the flow speed of the filter medium passing air is 50 cm / sec. From the upstream side of the filter medium, 15 g of dust according to JIS Z 8901 is 0.5 g at a concentration of 70 mg / m ³ . / M ^{2 was} applied, and the degree of dust adhesion was confirmed by visual observation.

[Example 1]
A spunbonded nonwoven fabric composed of white polyethylene terephthalate fibers having an average fiber diameter of 27 μm, a basis weight of 30 g / m ² , and a thickness of 0.2 mm was used as the upstream cover layer.
An average particle diameter of 350 μm as activated carbon, a JIS K 1474 (2007) activated carbon test method with a packing density of 0.44 g / cc, a BET specific surface area of 950 m ² / g, a coconut shell granular activated carbon, and an average particle diameter of 300 μm as JIS K 1474 (2007) Type A silica gel having a packing density of 0.69 g / cc and a BET specific surface area of 610 m ² / g supported by 5 parts by weight of adipic acid dihydrazide on 100 parts by weight of silica gel, thermoplastic powder Low density polyethylene resin (average particle size 20 μm, MI 24 g / 10 min, melting point 106 ° C.) as a resin is weighed at a weight ratio of 40:60:20, and 15 minutes by a hoop shaker (manufactured by Kyomachi Sangyo Vehicle Co., Ltd.) Stir and mix. This mixed powder was uniformly sprayed on the upstream cover layer so that the total amount was 100 g / m ² .
A white core-sheath type composite fiber spunbonded nonwoven fabric (average fiber diameter 20 μm, basis weight 20 g / m ² , thickness 0.2 mm) composed of polyethylene as the sheath and polyethylene terephthalate as the sheath is laminated as a downstream cover layer, and Teflon (registered) (Trademark) / Glass was sandwiched between glass belts, the belt interval was set to 0.5 mm, and the pressure was set to 100 kPa. Thereafter, it was cooled to obtain a desired air cleaning filter medium.

[Example 2]
The same silica gel and thermoplastic resin as in Example 1 were used except that coconut shell activated carbon having an average particle diameter of 350 μm, a packing density of 0.55 g / cc and a BET specific surface area of 900 m ² / g was used as the activated carbon, and the weight ratio thereof was 10 : Weighed at 90:20, and in the same manner as in Example 1, an air cleaning filter medium was obtained.

[Example 3]
Coconut shell activated carbon having an average particle diameter of 520 μm, a packing density of 0.49 g / cc and a BET specific surface area of 900 m ² / g is used as the activated carbon, and an average particle diameter of 450 μm, a packing density of 0.62 g / cc and a BET specific surface area of 600 m ² as silica gel. The same thermoplastic resin as in Example 1 was used except that 5 wt% of adipic acid dihydrazide was supported on / g A-type silica gel, and these weight ratios were weighed at 20:80:20. In the same manner as in Example 1, an air cleaning filter medium was obtained.

[Example 4]
The same activated carbon as in Example 1 except that a silica gel having an average particle diameter of 450 μm, a packing density of 0.62 g / cc, and a BET specific surface area of 600 m ² / g of A-type silica gel carrying 5% by weight of adipic acid dihydrazide is used. And a thermoplastic resin were weighed at a weight ratio of 2:80:20, and an air cleaning filter medium was obtained in the same manner as in Example 1.

[Example 5]
The same activated carbon, silica gel and thermoplastic resin as in Example 1 were used, and their weight ratio was weighed at 5:95:20, and an air cleaning filter medium was obtained in the same manner as in Example 1.

[Comparative Example 1]
Coconut shell activated carbon having an average particle diameter of 650 μm, a packing density of 0.49 g / cc and a BET specific surface area of 900 m ² / g is used as the activated carbon, and an average particle diameter of 250 μm, a packing density of 0.71 g / cc and a BET specific surface area of 600 m ² as silica gel. The same thermoplastic resin as in Example 1 was used except that 5 wt% of adipic acid dihydrazide was supported on / g A-type silica gel, and these weight ratios were weighed at 20:80:20. In the same manner as in Example 1, an air cleaning filter medium was obtained.

[Comparative Example 2]
Using the same activated carbon, silica gel and thermoplastic resin as in Example 1, the weight ratio was weighed at 80:20:20, and an air cleaning filter medium was obtained in the same manner as in Example 1.

[Comparative Example 3]
Coconut shell activated carbon having an average particle diameter of 350 μm, a packing density of 0.30 g / cc and a BET specific surface area of 815 m ² / g is used as the activated carbon, and an average particle diameter of 350 μm, a packing density of 0.69 g / cc and a BET specific surface area of 600 m ² is used as the silica gel. The same thermoplastic resin as that used in Example 1 was used except that 5 wt% of adipic acid dihydrazide was supported on / g A-type silica gel, and the weight ratio was weighed at 10:90:20. In the same manner as in Example 1, an air cleaning filter medium was obtained.

[Comparative Example 4]
Coconut shell activated carbon having an average particle diameter of 80 μm, a packing density of 0.63 g / cc and a BET specific surface area of 920 m ² / g is used as the activated carbon, and an average particle diameter of 50 μm, a packing density of 0.72 g / cc and a BET specific surface area of 600 m ² as silica gel. The same thermoplastic resin as that used in Example 1 was used except that 5 wt% of adipic acid dihydrazide was supported on / g A-type silica gel, and the weight ratio was weighed at 10:90:20. In the same manner as in Example 1, an air cleaning filter medium was obtained.

[Comparative Example 5]
An air cleaning filter medium was obtained in the same manner as in Example 1 except that silica gel that did not carry adipic acid dihydrazide was used.

[Comparative Example 6]
An air cleaning filter medium was obtained in the same manner as in Example 1 except that silica gel was not used in Example 1 and the weight ratio of activated carbon to the thermoplastic resin was set to 100: 20.

[Comparative Example 7]
An air cleaning filter medium was obtained in the same manner as in Example 1 except that the weight ratio of silica gel to the thermoplastic resin was set to 100: 20 without using activated carbon in Example 1.

Examples 1 to 5 have low ventilation resistance, can remove not only acetaldehyde but also toluene, which is a hydrocarbon-based gas, and are excellent in dust visibility. Since the average particle diameter and packing density of activated carbon and silica gel are close to each other, the uniformity is high and the peel strength is also high, so that the filter medium does not peel off during pleating.
On the other hand, in Comparative Example 1, since the average particle sizes of the activated carbon and the silica gel were greatly different, poor adhesion with the cover layer was generated and the peel strength was lowered. In Comparative Example 2, since the mixing ratio of the activated carbon was too high, the filter medium was blackened and the visibility during dust loading was poor. In Comparative Example 3, since the packing densities of activated carbon and silica gel differed greatly, both separated during mixing and the uniformity was not sufficient. In Comparative Example 4, since the average particle size of activated carbon and silica gel was small, the ventilation resistance was very high. In Comparative Example 5, since adipic acid dihydrazide was not supported on silica gel, acetaldehyde could not be removed. Since Comparative Examples 6 and 7 contain only one of either adipic acid dihydrazide-supported silica gel or activated carbon, the deodorizing performance was not sufficient.

  The air-cleaning filter medium of the present invention has low ventilation resistance, excellent deodorization performance of aldehydes and hydrocarbon gases, high peel strength, excellent pleatability, and good visibility of dirt during use. It can provide filter media and contributes to the industry.

DESCRIPTION OF SYMBOLS 1 Air purifying filter medium 2 Upstream side cover layer 3 Activated carbon, silica gel, thermoplastic resin mixed layer 4 Downstream side cover layer 5 Pleated unit 6 Frame 7 Activated carbon, silica gel, thermoplastic resin mixed layer 8 Cover layer 9 Chuck

Claims (2)

  A filter medium for air purification in which a mixture of activated carbon, a silica gel carrying a hydrazide compound and a thermoplastic resin is sandwiched between cover layers, wherein the silica gel carrying the activated carbon and the hydrazide compound in the mixture is made of the thermoplastic resin. The content of the silica gel in which the hydrazide compound is supported and fixed between the cover layers by melting is 1 to 100 by weight with respect to the activated carbon, and the average particle diameter of the silica gel with respect to the activated carbon in the mixture The air-cleaning filter medium has a ratio of 0.5 to 2.0, a packing density ratio of 0.5 to 2.0, and an average particle diameter of activated carbon and silica gel in the mixture is 100 μm or more, respectively.   The air cleaning filter medium according to claim 1, wherein the hydrazide compound is adipic acid dihydrazide.