JP2013094367A - Air cleaning filter material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter material for a pleated filter with a low ventilation resistance and a large dust holding amount, and with a small amount of dropping activated charcoal in a pleating process.SOLUTION: The air cleaning filter material includes activated charcoal and thermoplastic resin between cover layers. The air cleaning filter material is made from palm shell activated charcoal whose average particle size is 400-800 μm and whose hardness by JIS K 1474 is at least 90%. The average fiber diameter of fibers constituting a cover layer on the upstream side is 20-100 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).

  Such adsorptive filter media can provide an adsorbent sheet that is low in cost and excellent in air permeability. However, since the adhesion between the adsorbent layer and the base sheet is weak, peeling is likely to occur, and when external force is applied by pleating, etc. When exposed to air flow, there were problems in practical use such as a large dropout of the adsorbent.

  In order to solve this problem, for example, an adsorbent sheet in which an adsorbent layer and a substrate are bonded using an adhesive sheet is disclosed (for example, Patent Document 2). However, such an adsorbent sheet has a problem that the adhesive sheet impairs the air permeability and increases the air resistance, and further, the adhering surface tends to clog the dust or impedes the adsorbing performance.

Japanese Patent Laid-Open No. 11-5058 JP 2002-273123 A

  The present invention has been made against the background of the above-described problems of the prior art, and provides an air purifying filter medium having low ventilation resistance, a large dust holding amount, and a small amount of activated carbon falling off during pleating.

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 containing activated carbon and a thermoplastic resin between cover layers, wherein the activated carbon is made of coconut shell activated carbon having an average particle diameter of 400 to 800 μm and a hardness of 90% or more according to JIS K 1474, and an upstream cover layer The filter medium for air cleaning whose average fiber diameter of the fiber which comprises is 20-100 micrometers.
2. A filter unit in which the filter medium is formed into a pleated shape.

  The air-cleaning filter medium according to the present invention can provide an air-cleaning filter medium having a low ventilation resistance, a large dust holding amount, and a small amount of activated carbon falling off during pleating.

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 schematic diagram of the filter unit used for activated carbon dropout amount measurement in the present invention.

Hereinafter, the present invention will be described in detail.
The air-cleaning filter medium of the present invention is an air-cleaning filter medium containing activated carbon and a thermoplastic resin between cover layers. The cover layer used in the present invention may be woven or non-woven. The average fiber diameter of the fibers constituting the upstream cover layer is 20 to 100 μm, preferably 20 to 60 μm, and 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 smaller than 20 μm, the gap between the fibers becomes narrow, dust in the air accumulates on the cover layer, and airflow resistance Soars. When the average fiber diameter is larger than 100 μm, the activated carbon particles pop out or fall off particularly during pleating.

  On the other hand, the average fiber diameter of the fibers constituting the downstream cover layer is not particularly limited, but is preferably 10 to 30 μm in consideration of dropping off of the activated carbon. If it is smaller than 10 μm, the ventilation resistance is high, and if it is larger than 30 μm, the activated carbon falls off.

  The filling density of the fiber part 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 mm to 3.0 mm. If it 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.

The cover layer of the present invention preferably has a basis weight of 15 to 100 g / m ² , more preferably 20 to 80 g / m ² . If it is less than 15 g / m ² , the activated carbon and the thermoplastic resin are likely to escape. If it exceeds 100 g / m ² , the sheet thickness increases, and the structural resistance in the case of a pleated unit increases.

  The fiber material constituting the cover layer of the present invention is not particularly specified, such as polyolefin, rayon, polyester, polyamide, polyurethane, acrylic, polyvinyl alcohol, polycarbonate, etc. The mixed fiber may be used. In addition, a charged non-woven fabric, so-called electret sheet, which can increase the effect of removing submicron particles such as tobacco smoke particles, carbon particles, and sea salt particles can also be used as a substrate. This is because, by using the electret sheet as a base material, it is possible to prevent dust and the like from entering the adsorption layer and block the pores in the adsorption layer, thereby extending the filter life.

  The fiber orientation of the cover layer of the present invention is not particularly limited, and may be any of a random shape, a cloth shape, and a parallel shape as long as it is a nonwoven fabric, for example.

  In the present invention, a thermoplastic resin is used for adhesion between the cover layer and the activated carbon layer. Examples of the thermoplastic resin include polyolefin-based, polyamide-based, polyurethane-based, polyester-based, ethylene-acrylic copolymer, polyacrylate, polyarene, polyacrylic, polydiene, ethylene-vinyl acetate, PVC, PS, and the like.

  As for the size of the thermoplastic resin, the powdery resin preferably has an average particle size of 1 to 40 μm (hereinafter sometimes referred to as “powdered thermoplastic resin”). More preferably, it is 5-30 micrometers. More preferably, it is 95% by weight or more in the range of 1 to 40 μm. If the particle size is in such a range, the thermoplastic resin can reduce the clogging of the surface pores of the activated carbon, while pre-adhesion to the activated carbon by van der Waals force or electrostatic force is effectively made when mixed with activated carbon, It is because it can disperse | distribute uniformly and the adhesiveness in an activated carbon layer and a cover layer can be made favorable.

  The shape of the powdered thermoplastic resin is not particularly limited, but examples thereof include a spherical shape, a crushed shape, and a fibrous shape. The melting point of the powdered thermoplastic resin is preferably 80 ° C. or higher in consideration of the environmental temperature in the room of a moving vehicle or the like. More preferably, it is 90 ° C. or higher.

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

It is preferable to use the thermoplastic resin in an amount of 1 to 50% by weight with respect to the activated carbon in both powder and granular form. More preferably, it is 3 to 30% by weight. 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 the method for adjusting the particle size of the thermoplastic powder resin in both powder and granular form include mechanical pulverization, freeze pulverization, and chemical adjustment. 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 structural unit of the air-cleaning filter medium of the present invention is an upstream cover layer / active carbon and a powdered thermoplastic resin mixed powder / downstream cover layer. Of course, it is also possible to dispose a mixed powder of activated carbon and powdered thermoplastic resin in the laminate and repeatedly laminate and integrate the cover layers.

  The average particle diameter of the activated carbon used for the air cleaning filter medium of the present invention is the mass average diameter based on the JIS K 1474 activated carbon test method in consideration of air permeability, dust retention, adsorbent dropout, sheet processability, and the like. 400 to 800 μm. Preferably, it is 450-750 micrometers. If the average particle size is less than 400 μm, the ventilation resistance becomes too high to obtain a certain deodorizing performance, and at the same time the sheet filling density tends to be high, which may cause an early increase in the ventilation resistance when supplying dust. It is not preferable. When the average particle diameter exceeds 800 μm, the deodorizing performance is extremely lowered, and the thickness is increased, so that the structural resistance as a pleat unit is increased, which is not preferable. In addition, said granular activated carbon can be obtained by carrying out predetermined particle size adjustment using a normal classifier.

  The activated carbon used for the air cleaning filter medium of the present invention is coconut shell activated carbon having a hardness of 90% or more according to the JIS K 1474 activated carbon test method. Preferred is coconut shell activated carbon having a hardness of 95% or more. When the hardness 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.

  In addition to coconut shells, wood-based, coal-based, pitch-based, etc. are known as activated carbon raw materials, but the pores of coconut shell activated carbon have a large proportion of small pores compared to other raw materials, Some ash is also low. 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 amount of toluene adsorbed when measured in accordance with JIS K 1474 of the activated carbon used for the air cleaning filter medium of 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.

It is preferable that the weight per layer of the activated carbon used in the air-cleaning filter medium of the present invention is in the range of ^{20 to} 500 g / m ² . This is because, within such a range, not only sufficient adsorption performance can be obtained, but also the ventilation resistance can be kept low.

The activated carbon used in the air cleaning filter medium of the present invention may be used after chemical treatment for the purpose of improving the adsorption performance of polar substances and aldehydes.
Examples of chemicals used in gas chemical treatment include aldehyde gases, nitrogen compounds such as NOx, sulfur compounds such as SOx, and acidic polar substances such as acetic acid such as ethanolamine, polyethyleneimine, aniline, and P-anisidine. , Amine drugs such as sulfanilic acid, sodium hydroxide, potassium hydroxide, guanidine carbonate, guanidine phosphate, aminoguanidine sulfate, 5.5-dimethylhydantoin, benzoguanamine, 2.2-iminodiethanol, 2.2.2 -Nitrotriethanol, ethanolamine hydrochloride, 2-aminoethanol, 2.2-iminodiethanol hydrochloride, P-aminobenzoic acid, sodium sulfanilate, L-arginine, methylamine hydrochloride, semicarbazide hydrochloride, hydrazine, hydroquinone , Hydroxylamine sulfate Permanganate, potassium carbonate, potassium hydrogen carbonate and the like are preferably used. For basic polar substances such as ammonia, methylamine, trimethylamine and pyridine, for example, phosphoric acid, citric acid, malic acid, ascorbine Acid, tartaric acid and the like are preferably used. The chemical treatment is performed by, for example, supporting or attaching a chemical to activated carbon. In addition to directly treating the activated carbon with chemicals, it is possible to impregnate the entire sheet or impregnate the entire sheet by a method such as an ordinary coating method in the vicinity of the sheet surface. At this time, a chemical aqueous solution in which a thickener such as sodium alginate or polyethylene oxide is mixed can be prepared, supported, and attached. This method is effective in supporting and attaching a chemical having low solubility in water and further suppressing the chemical from falling off.

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, or woven fabrics, or may be attached and 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. Also, it is possible to enhance the deodorizing function by imparting a function having adsorption performance to the fibers such as a cover layer and a breathable sheet, for example, by attaching an acid or alkali agent or using ion exchange fibers. .

  The basic manufacturing method of the air cleaning filter medium will be described. First, 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 a mixture temporarily bonded to the activated carbon surface. Next, after spraying this mixed granular material on a cover layer, a breathable sheet (cover layer) is laminated | stacked and a hot press process is implemented. The sheet surface temperature during hot pressing is preferably about 3 to 30 ° C, preferably 5 to 20 ° C higher than the melting point of the thermoplastic powder resin. Alternatively, after spraying a mixed powder in which activated carbon and powdered thermoplastic resin are premixed on the cover layer, a certain amount of granular thermoplastic resin is further sprayed, and a breathable sheet (cover layer) is laminated, A method of performing a heat press treatment or a granular thermoplastic resin fixed in advance to a cover layer, and this sheet as a cover layer described above, a mixed powder in which activated carbon and a powdered thermoplastic resin are premixed thereon It can also be used for spraying or breathable sheets (cover layers) and subjected to hot press treatment to obtain an air cleaning filter medium.

Also, if preheated and pre-bonded with infrared rays or the like before heat treatment, there will be no irregular flow of the mixed powder particles that tend to occur during pressing, and an air purifying filter medium with better dispersibility can be obtained. Can be manufactured. The heat treatment using infrared rays does not cause an air current and the like, can be heated in a state where the mixed powder particles are allowed to stand, and scattering of the mixed powder particles can be prevented.
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 this patent 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 base nonwoven fabric. .

  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, the deodorizing performance and dust holding 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 2 mm or less, 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 nonwoven fabric was taken, and an average value of fiber diameters measured from the photograph at n = 30 was calculated.

(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 .

(Average particle size)
Measurement was carried out based on the JIS K 1474 activated carbon test method to determine the mass average diameter.

(Activated carbon hardness)
The measurement was performed based on the JIS K 1474 activated carbon test method.

(Ventilation resistance)
Measurement was performed under the conditions of a sample size φ75 mm, an effective filtration area φ50.5 mm, and a filter medium passing air velocity of 50 cm / sec using a measurement jig shown in FIG.

(Thickness)
The value when a pressure of 686 Pa was applied was measured.

(Dust retention, dust collection efficiency)
A filter medium veneer is installed in the duct, the atmosphere is ventilated so that the filter medium passing air speed is 50 cm / sec, and 15 kinds of dust described in JIS Z 8901 is loaded at a concentration of 70 mg / m ³ from the upstream side of the filter medium. Dust was loaded until the ventilation resistance increased by 150 Pa from the beginning. The amount of dust collected per unit area of the filter medium at this time was defined as the amount of dust retained.
Moreover, the dust collection efficiency was calculated | required by following Formula.
Dust collection efficiency [%] = Dust retention amount / Dust supply amount x 100

(Activated carbon loss)
The filter medium prepared with a width of 200 mm was subjected to pleating by the Yamatani alternating streaking 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.

(Toluene deodorization performance)
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.

[Example 1]
A thermal bond nonwoven fabric made of polyester fibers having an average fiber diameter of 35 μm, a basis weight of 65 g / m ² , and a thickness of 0.2 mm was used as the upstream cover layer.
As activated carbon, 5% potassium carbonate-impregnated coconut husk granular activated carbon having an average particle diameter of 500 μm, a hardness of 97%, and a BET specific surface area of 1080 m ² / g by nitrogen adsorption method, and an ethylene-acrylic acid copolymer as a thermoplastic powder resin (Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) was weighed at a weight ratio of 10: 1 and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the upstream cover layer so that the total amount was 330 g / m ² (equivalent to activated carbon 300 g / m ² ).
A polyethylene / polyester core-sheath long fiber non-woven fabric (average 20 μm, basis weight 20 g / m ² , thickness 0.2 mm) prepared by the spunbond method is overlaid and sandwiched between Teflon / 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]
A thermal bond nonwoven fabric made of polyester fibers having an average fiber diameter of 45 μm, a basis weight of 60 g / m ² and a thickness of 0.2 mm was used as the upstream cover layer.
As activated carbon, coconut husk granular activated carbon having an average particle size of 730 μm, a hardness of 97%, and a BET specific surface area of 950 m 2 / g by a nitrogen adsorption method, and flow beads EA209 (ethylene-acrylic acid copolymer made by Sumitomo Seika) as a thermoplastic powder resin. , Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) were weighed at a weight ratio of 10: 1 and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the upstream cover layer so that the total amount was 341 g / m ² (equivalent to activated carbon 310 g / m ² ).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Example 3]
A thermal bond nonwoven fabric made of polyester fiber having an average fiber diameter of 40 μm, a basis weight of 65 g / m ² , and a thickness of 0.2 mm is used as an upstream cover layer. ² ) were used in a stacked manner.
As activated carbon, 5% potassium carbonate-impregnated coconut husk granular activated carbon having an average particle size of 560 μm, hardness of 96%, and a BET specific surface area of 1100 m ² / g by nitrogen adsorption method, and ethylene-acrylic acid copolymer ( (Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) were weighed at a weight ratio of 10: 0.3, and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the thermal adhesive sheet laminated with the upstream cover layer so that the total amount was 297 g / m ² (equivalent to 270 g / m ^{2 of} activated carbon).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Example 4]
A thermal bond nonwoven fabric made of polyester fiber having an average fiber diameter of 22 μm, a basis weight of 55 g / m ² , and a thickness of 0.2 mm is used as an upstream cover layer, and from a polyamide spunbond to a heat-adhesive sheet (Kureha Tech Dynac LNS0010, basis weight 10 g / m ² ) were used in a stacked manner.
As activated carbon, 5% potassium carbonate-impregnated coconut husk granular activated carbon having an average particle diameter of 450 μm, a hardness of 96%, and a BET specific surface area of 1020 m ² / g by a nitrogen adsorption method, and an ethylene-acrylic acid copolymer ( (Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) were weighed at a weight ratio of 10: 0.3, and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the heat-adhesive sheet laminated with the upstream cover layer so that the total amount was 275 g / m ² (equivalent to activated carbon 250 g / m ² ).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Example 5]
A thermal bond nonwoven fabric made of polyester fiber having an average fiber diameter of 40 μm, a basis weight of 65 g / m ² and a thickness of 0.2 mm is used as an upstream cover layer, and a polyamide spunbond to a heat-adhesive sheet (Kureha Tech Dynac LNS0010, basis weight 10 g / m). ² ) were used in a stacked manner.
As activated carbon, an average particle size of 610 μm, hardness of 96%, 5% potassium carbonate-impregnated coconut husk granular activated carbon having a BET specific surface area of 1100 m ² / g by a nitrogen adsorption method, and an ethylene-acrylic acid copolymer ( (Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) were weighed at a weight ratio of 10: 0.3, and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the thermal adhesive sheet laminated with the upstream cover layer so that the total amount was 297 g / m ² (equivalent to 270 g / m ^{2 of} activated carbon).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Comparative Example 1]
A thermal bond nonwoven fabric made of polyester fibers having an average fiber diameter of 15 μm, a basis weight of 65 g / m ² and a thickness of 0.1 mm was used as the upstream cover layer.
As activated carbon, 5% potassium carbonate-impregnated coconut husk granular activated carbon having an average particle size of 560 μm, a hardness of 96%, and a BET specific surface area of 990 m ² / g by a nitrogen adsorption method, and an ethylene-acrylic acid copolymer ( (Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) were weighed at a weight ratio of 10: 1 and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the heat-adhesive sheet side of the upstream cover layer so that the total amount was 300 g / m ² (equivalent to activated carbon 273 g / m ² ).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Comparative Example 2]
A thermal bond nonwoven fabric made of polyester fibers having an average fiber diameter of 110 μm, a basis weight of 70 g / m ² , and a thickness of 0.2 mm was used as the upstream cover layer.
As activated carbon, an average particle size of 560 μm, hardness of 96%, 5% potassium carbonate-impregnated coconut husk granular activated carbon having a BET specific surface area of 1000 m ² / g by nitrogen adsorption method, and ethylene-acrylic acid copolymer ( (Average particle size 10 μm, MI 9 g / 10 min, melting point 105 ° C.) were weighed at a weight ratio of 10: 1 and stirred and mixed until uniform.
This mixed granular material was uniformly sprayed on the thermal adhesive sheet side of the upstream cover layer so that the total amount was 298 g / m ² (equivalent to activated carbon 271 g / m ² ).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Comparative Example 3]
A thermal bond nonwoven fabric made of polyester fibers having an average fiber diameter of 55 μm, a basis weight of 60 g / m ² , and a thickness of 0.2 mm was used as the upstream cover layer.
As activated carbon, an average particle size of 300 μm, a hardness of 95%, a coconut shell-based granular activated carbon having a BET specific surface area of 1020 m ² / g by a nitrogen adsorption method, and an ethylene-acrylic acid copolymer (average particle size of 10 μm, MI 9 g / 10 min, melting point 105 ° C.) was weighed at a weight ratio of 10: 1 and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the thermal adhesive sheet side of the upstream cover layer so that the total amount was 297 g / m ² (equivalent to 270 g / m ^{2 of} activated carbon).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Comparative Example 4]
A thermal adhesive non-woven fabric made of polyester fiber having an average fiber diameter of 55 μm, a basis weight of 55 g / m ² , and a thickness of 0.2 mm is laminated with a polyamide spunbond heat adhesive sheet (Kureha Tech Dynac LNS0010, basis weight 10 g / m ² ). Used as an upstream cover layer.
As activated carbon, an average particle diameter of 860 μm, a hardness of 96%, a coconut shell granular activated carbon having a BET specific surface area of 968 m ² / g by nitrogen adsorption method, and an ethylene-acrylic acid copolymer (average particle diameter of 10 μm, MI 9 g / 10 min, melting point 105 ° C.) was weighed at a weight ratio of 10: 0.3, and stirred and mixed until uniform.
The mixed powder was uniformly sprayed on the thermal adhesive sheet side of the upstream cover layer so that the total amount was 297 g / m ² (equivalent to 270 g / m ^{2 of} activated carbon).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Comparative Example 5]
A thermal adhesive non-woven fabric made of polyester fiber having an average fiber diameter of 55 μm, a basis weight of 55 g / m ² , and a thickness of 0.2 mm is laminated with a polyamide spunbond heat adhesive sheet (Kureha Tech Dynac LNS0010, basis weight 10 g / m ² ). Used as an upstream cover layer.
As activated carbon, an average particle size of 490 μm, a hardness of 88%, a coconut shell-based granular activated carbon having a BET specific surface area of 1618 m ² / g by a nitrogen adsorption method, and an ethylene-acrylic acid copolymer (average particle size of 10 μm, MI 9 g / 10 min, melting point 105 ° C.) was weighed at a weight ratio of 10: 0.5, and stirred and mixed until uniform.
This mixed granular material was uniformly sprayed on the thermal adhesive sheet side of the upstream cover layer so that the total amount was 275 g / m ² (equivalent to activated carbon 250 g / m ² ).
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

[Comparative Example 6]
A thermal adhesive non-woven fabric made of polyester fiber having an average fiber diameter of 55 μm, a basis weight of 55 g / m ² , and a thickness of 0.2 mm is laminated with a polyamide spunbond heat adhesive sheet (Kureha Tech Dynac LNS0010, basis weight 10 g / m ² ). Used as an upstream cover layer.
As the activated carbon, an average particle size of 550 μm, a hardness of 85%, a coal-based granular activated carbon having a BET specific surface area of 1301 m ² / g by a nitrogen adsorption method, and an ethylene-acrylic acid copolymer (average particle size of 10 μm, MI 9 g / 10 min, melting point 105 ° C.) was weighed at a weight ratio of 10: 0.5, and stirred and mixed until uniform.
The mixed powder and granular material was uniformly sprayed so that the total amount 301 g / m 2 ^(activated carbon 274 g / m ² or equivalent) to the thermal adhesive sheet side of the upstream cover layer.
Subsequent processing was carried out in the same manner as in Example 1 to obtain an air cleaning filter medium.

  As described above, the air-purifying filter media obtained in the examples and comparative examples have been evaluated for ventilation resistance, thickness, dust holding amount, dust collection efficiency, activated carbon dropping amount, and toluene deodorizing performance. The results are shown in Table 1 and Table 2.

In Examples 1 to 4, the airflow resistance is low, and further, the fiber diameter and activated carbon particle size of the upstream cover layer are suitably designed. Therefore, clogging of dust in the upstream cover layer is suppressed, and it is effective for the voids in the activated carbon part. Since dust is retained, the amount of dust retained is large. Since there is no breakage of the cover layer or crushing of the activated carbon at the crease during pleating, the amount of activated carbon falling off is small.
On the other hand, in Comparative Example 1, since the fiber diameter of the upstream cover layer is too small, the amount of activated carbon falling off is small, but the ventilation resistance is high, and the dust holding amount is also very small. In Comparative Example 2, the fiber diameter of the upstream cover layer is too large, and the fall of activated carbon is large. In Comparative Examples 3 and 4, since the hardness of the activated carbon is low, the activated carbon is crushed during the filtering medium processing and the pleating processing, and the amount of falling activated carbon is large.

  As described above, the air-cleaning filter medium of the present invention provides a filter medium having a low airflow resistance, a large dust holding amount, and a small amount of activated carbon falling off during pleating, and contributes greatly to the industry.

DESCRIPTION OF SYMBOLS 1 Air purifying filter medium 2 Upstream cover layer 3 Activated carbon / powdered thermoplastic resin 4 Downstream cover layer 5 Pleated unit 6 Frame

Claims (2)

  An air-cleaning filter medium containing activated carbon and a thermoplastic resin between cover layers, wherein the activated carbon is made of coconut shell activated carbon having an average particle diameter of 400 to 800 μm and a hardness of 90% or more according to JIS K 1474, and an upstream cover layer The filter medium for air cleaning whose average fiber diameter of the fiber which comprises is 20-100 micrometers.   A filter unit obtained by molding the filter medium according to claim 1 into a pleated shape.