JP2007038091A - Filter material for air filter and air filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter material for air filters having excellent removal performance both for ionic and organic matter and never causing secondary contamination in the downstream due to decomposition of adsorbed and accumulated organic matter. <P>SOLUTION: The filter material for air filters consists of a chemical reaction layer including a fiber sheet adhered with a chemical which undergoes a neutralization reaction with an ionic substance, and a physical adsorption layer containing a physical adsorbent of a pH of 5-9, by JIS K 1474, laminated in an integrated form. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air filter medium and an air filter that are preferably used for removing gaseous pollutants in air.

  With the increase in airtightness in houses, formaldehyde and volatile hazardous substances (VOC) contained in building materials and paints are not discharged from the house, and so-called sick house syndrome, in which people who inhale these cause chemical sensitivity, is significant. It is a problem. Also, in industrial clean rooms for manufacturing semiconductor devices, microscopic gaseous contaminants that have not been a problem with circuit pattern miniaturization have had a major impact on device characteristics, yield, and reliability. It has become to. In this way, the necessity of removing contaminants in the air is increasing in every scene from general households to advanced industries.

  For removing contaminants in the air, a physical adsorbent such as activated carbon has been generally used. Activated carbon can adsorb and remove organic substances in the air satisfactorily using a large surface area and pore volume. On the other hand, physical adsorbents such as activated carbon have a lower ability to adsorb ionic substances than organic substances. However, in removing air pollutants, it is often necessary to remove not only organic substances but also ionic substances at the same time. For example, ammonia, which is an alkaline substance, is a typical malodorous component, and is known to be a substance that causes poor resolution of a chemically amplified resist in a semiconductor device manufacturing process. Therefore, in order to remove these ionic substances in addition to organic substances, it is common practice to add acidic or alkaline chemicals that neutralize with the ionic substances to physical adsorbents such as activated carbon. Air filter media as shown in (1) to (3) have been proposed.

(1) The activated carbon particles previously charged with acidic chemicals or alkaline chemicals are filled in a tray or arranged three-dimensionally by molding or the like. (Patent Document 1)
(2) Activated carbon particles previously impregnated with acidic chemicals or alkaline chemicals are made into a sandwich sheet with a nonwoven fabric or the like. (Patent Document 2)
(3) Non-attached activated carbon is made into a sheet by a papermaking method or the like, and acidic chemicals or alkaline chemicals are attached to the sheet. (Patent Document 3)
However, these air filters can adsorb both organic substances and ionic substances in the air, but have the following problems.

  (1) The activated carbon surface has a hydrophobic chemical property, which makes it difficult to increase the amount of chemicals added.

  (2) Since the attached chemical covers the activated carbon surface, the organic gas adsorption performance is reduced.

(3) Organic substances adsorbed and held on the activated carbon are decomposed by the catalytic action of the adhering chemicals, and a large amount of decomposition products (decomposition gas) are generated.
Japanese Patent Laid-Open No. 7-16420 JP 7-39553 A Japanese Patent Laid-Open No. 5-132900

  An object of the present invention is to provide a filter medium for an air filter that can efficiently remove both ionic substances and organic substances while minimizing the generation of decomposition products.

  The present invention for solving the above-described problems is characterized by the following (1) to (13).

(1) a chemical reaction layer including a fiber sheet to which a chemical that neutralizes and reacts with an ionic substance, and a physical adsorption layer including a physical adsorbent having a pH of 5 to 9 measured according to JIS K 1474; A filter medium for an air filter, characterized by being laminated and integrated.
(2) The fiber sheet has a BET specific surface area of 0.05 m ² / g or more and a bulk density of 0.5 g / cm ³ or less. Filter media.

(3) The filter material for an air filter according to (1) or (2), wherein the fiber sheet includes ultrafine fibers having a single yarn fineness of 1 dtex or less.
(4) The fiber sheet includes a composite fiber composed of two or more kinds of polymers, and the composite fiber is divided at least in one part, according to any one of (1) to (3) above Air filter media.
(5) The filter sheet for an air filter according to any one of (1) to (4), wherein the fiber sheet includes a polyamide fiber or a composite fiber containing polyamide as a main component.
(6) The filter sheet for an air filter according to any one of (1) to (5), wherein 20 to 80 wt% of the fiber sheet is a heat-adhesive component.
(7) The air filter medium according to any one of (1) to (6), wherein the filter medium is molded into a pleated structure.
(8) The air filter medium according to any one of (1) to (7), wherein the physical adsorption layer is formed by sandwiching the physical adsorbent between fiber sheets.
(9) The air filter medium according to any one of (1) to (8), wherein the physical adsorbent is activated carbon and / or zeolite.
(10) An air filter comprising the air filter medium according to any one of (1) to (9).
(11) An air cleaner comprising the air filter according to (10) above.
(12) A clean room comprising the air filter according to (10).
(13) A semiconductor manufacturing apparatus comprising the air filter according to (10).

  The filter material for an air filter according to the present invention is measured in accordance with JIS K 1474, a chemical reaction layer including a fiber sheet to which a chemical agent that neutralizes and reacts with an ionic substance that is an object to be removed, and an organic substance is removed. Since the physical adsorption layer containing the physical adsorbent having a pH of 5 to 9 is laminated and integrated, the ionic substance and the organic substance can be efficiently removed at the same time. Furthermore, the physical adsorbent has a pH measured in accordance with JIS K 1474 of 5 to 9, that is, no chemical is attached to the physical adsorbent, so that the physical adsorption performance inherent in the physical adsorbent is reduced. Furthermore, it is possible to minimize the generation of decomposition products (decomposition gas such as acetic acid) by the reaction between the adsorbed and accumulated organic substances and the chemicals adhering to the fiber sheet. That is, secondary contamination can be prevented. In addition, since the air filter medium according to the present invention is formed by laminating and integrating the chemical reaction layer and the physical adsorption layer, it is easy to handle and easy to perform post-processing such as pleating. The air filter molded with the air filter medium is lower in cost and space-saving than an air filter in which two types of air filter medium are separately molded and fitted in a frame. .

  As shown in FIG. 1, for example, the filter medium for an air filter of the present invention includes a chemical reaction layer 10 that neutralizes and reacts with an ionic substance to be removed, and a physical adsorption layer 20 that adsorbs and removes organic substances. It has become.

The chemical reaction layer 10 is formed, for example, by adhering a chemical agent that neutralizes with an ionic substance that is a substance to be removed to the fiber sheet 4. The fiber sheet 4 is preferably one having a BET specific surface area per unit volume of 0.05 m ² / g or more and a bulk density of 0.5 g / cm ³ or less in order to improve the adhesion of chemicals. . Further is in the range of ^{0.2~50m 2 /g,0.05g/cm 3 ~0.4g / cm 3} . The BET specific surface area in the present invention is measured by a BET method using nitrogen as an adsorbate, and is measured by a flow type specific surface area measuring device Flowsorb III 2305 manufactured by Shimadzu Corporation. The bulk density is a value obtained by dividing the weight per unit area (weight per unit area) by the thickness measured based on the thickness measurement according to Section 6.1.2 (Method A) of JIS L 1913.

  Increasing the BET specific surface area of the fiber sheet 4 can increase the wetted area when impregnating and applying chemicals and improve the retention of chemicals, but conversely, if too large, adsorbs and holds a large amount of excess organic matter, It reacts with the adhering chemicals and tends to release decomposition products. In addition, if the bulk density of the sheet is reduced, the adhesion amount when impregnating and applying chemicals can be increased, and the air permeability as a filter medium can be increased. However, if it is too large, the retention of the chemical solution is deteriorated and the amount of adhesion tends to decrease.

Here, as a method of increasing the BET specific surface area of the fiber sheet 4,
(A) Including ultrafine fibers (b) Including atypical cross-section fibers (c) Including fibers with a large number of holes and slits on the surface (d) Select from supporting porous materials between the fibers Can do.

  For (a), for example, by dissolving the sea part of a multi-core sea-island type composite fiber with a solvent or destroying it by impact, taking out ultrafine fibers constituted by the island part, or from two or more types of incompatible polymers The resulting composite fiber can be divided into ultrafine fibers by physical impact. Furthermore, a method of fibrillation by beating fibers is also preferable. The ultrafine fibers constituting the fiber sheet preferably have a single yarn fineness of 1 dtex or less, more preferably 0.5 dtex or less, from the viewpoint of chemical absorption retention. The thinner the fineness of the ultrafine fibers, the better the absorption retention of the chemicals. On the other hand, if the fineness is too small, the desired air permeability cannot be obtained, so 0.01 dtex or more is even better.

  As for (b), a modified cross-section yarn can be obtained by spinning a polymer from a modified cross-section die. The atypical cross-sectional shape refers to a shape other than a circle, and the surface area of the fiber can be increased by using, for example, a flat shape, a substantially polygonal shape, or a wedge shape.

  For (c), a composite fiber obtained by alloying two or more polymers having different solubility in a solvent is obtained, and a number of slits are formed on the fiber surface by dissolving and removing the easily soluble polymer with a solvent. As a result, the fibers can be divided. This split fiber may be split until the single fiber is completely separated, but if the fiber bundle state is adjusted by appropriately adjusting the split state, it is possible to balance the breathability and the water absorption retention of chemicals. preferable.

  In addition to the method of increasing the surface area of the fiber itself described in the above (a) to (c), the same chemical adhering effect can be obtained even if a porous material having a three-dimensional structure is supported between the fibers (d) ).

  Next, as a material used for the fiber sheet 4, a thermoplastic resin capable of melt spinning is preferably used. Examples thereof include long-fiber non-woven fabric, short-fiber non-woven fabric, mat, felt, and paper made of polyester, polyamide, polyolefin, acrylic, vinylon, polystyrene, polyvinyl chloride, polyvinylidene chloride, polylactic acid, and the like. Among these materials, those suitable for chemical addition are selected from polyamide-based resins such as nylon 6 and nylon 66 as the main component from the viewpoint of balance of hydrophilicity, chemical resistance and economy. preferable.

  In addition, reinforcing fibers and heat-adhesive components may be added to the fiber sheet 4. In particular, when 20 to 80 wt% of the fiber sheet is composed of a heat-adhesive component, and the fibers in the sheet are thermally bonded in advance before attaching the chemical, swelling and dimensional changes when the chemical is applied This is preferable because it can be suppressed. In addition, the presence of this heat-adhesive component can improve processability during filter molding such as pleating as described later.

  Examples of the thermoadhesive component include fibers, particles, and powders made of thermoplastic resins such as polyester, polyamide, polyolefin, and modified resins thereof. Especially, it is a core-sheath-type composite fiber which consists of thermoplastic resins from which melting | fusing point differs, Comprising: It is preferable that it is a core-sheath-type composite fiber whose melting | fusing point of a sheath component is about 30-200 degreeC lower than that of a core component. When such a core-sheath type composite fiber is used and the temperature is such that the sheath component melts or softens when heated and pressurized, but the core component can maintain the fiber form, the strength of the filter medium can be improved, and The air permeability can be improved by holding the voids inside the fiber sheet. If the air permeability is improved, the contaminated gas and the attached chemical can be smoothly contacted to improve the adsorption performance, and the pressure loss as a filter can be reduced. When using a core-sheath type composite fiber, it is preferable to select one having a thickness in the range of 1 to several tens of dtex, particularly 2 to 20 dtex, from the balance between air permeability and adhesive strength.

  Next, the kind of chemicals attached to the fiber sheet 4 varies depending on the chemical characteristics of the ionic substance to be removed. If the substance to be removed is an alkaline substance such as ammonia or amines, attach an acidic chemical as a pair, and the substance to be removed is an acidic substance such as hydrofluoric acid, hydrochloric acid, sulfur oxide, or nitrogen oxide. In some cases, apply alkaline chemicals. Sulfuric acid, phosphoric acid, citric acid, malic acid, etc. are used as acidic chemicals, and potassium carbonate, sodium carbonate, potassium hydroxide, etc. are used as alkaline chemicals. If it is a chemical to be used, it may be selected from other than these.

  The method for attaching the chemicals to the fiber sheet 4 is not particularly limited, and may be attached by a normal method. That is, it may be selected from a method of impregnating a fiber sheet with an aqueous solution containing a chemical, a method of spraying and attaching an aqueous solution containing a chemical to the fiber sheet, and the like. Further, after the fiber sheet is molded into a pleated structure or a honeycomb structure, the chemical may be attached as described above. The loading amount of these chemicals is 2 to 100% by weight, preferably 5 to 50% by weight, based on the fiber sheet, and is prepared according to the chemicals to be carried and the required removal performance.

  Next, the physical adsorption layer 20 laminated and integrated with the chemical reaction layer 10 will be described.

  The physical adsorption layer 20 may include a physical adsorbent having a pH of 5 to 9 measured according to JIS K 1474, and the physical adsorbent has an action of adsorbing and removing organic substances having a large number of pores. What is necessary is just to have. Specific examples include activated carbon, zeolite, activated alumina, aluminum silicate, porous glass, silica gel, activated clay, and porous clay, which may be granular or fibrous. is there. Among these physical adsorbents, activated carbon and zeolite are particularly preferably used because of their large specific surface area and excellent physical adsorption performance. And these may be used independently and may use 2 or more types together. When a granular physical adsorbent is selected, its particle size should be in the range of 20 to 3000 μm, preferably 100 to 1000 μm. If the particle diameter is too small, it may fall off or scatter from the non-woven sheet at the time of attachment. On the other hand, if it is too large, the surface area responsible for the adsorption action becomes small, and the adsorption speed becomes low.

  In the present invention, the physical adsorbent itself may form a fiber sheet, such as an activated carbon fiber non-woven fabric, may be used as the physical adsorption layer 20, but the physical adsorbent is sandwiched between the fiber sheets to physically The adsorption layer 20 is preferably configured. Specifically, as shown in FIG. 1, physical adsorbent 6 particles are interposed between a pair of non-woven sheets (fiber sheets) 5, and the physical adsorbent 6 particles are fixed to each non-woven sheet 5. Those are preferably used. In such a composite sheet, particles of the physical adsorbent 6 and a heat-adhesive material are laid on one surface of the non-woven sheet 5, and another non-woven sheet 5 is stacked thereon to form two non-woven sheets 5. The particles of the physical adsorbent 6 and the heat-adhesive material are interposed therebetween, the obtained multilayer sheet is heated and pressurized, and the heat-adhesive material is melted or softened so that the particles of the physical adsorbent 6 are dispersed in each nonwoven fabric sheet 5. It can be obtained by fastening to.

  The nonwoven fabric sheet 5 constituting the composite sheet gives shape retention and strength to the filter medium and prevents the physical adsorbent 6 from falling off from the nonwoven fabric sheet 5, and is a polyester that does not melt by heat and pressure during post-processing, Polyamide, polyolefin, acrylic, vinylon, polystyrene, polyvinyl chloride, polyvinylidene chloride, polylactic acid, natural fiber, a long fiber nonwoven fabric, a short fiber nonwoven fabric, mat, felt, paper, and the like can be used.

Moreover, although the nonwoven fabric sheet 5 which comprises a composite sheet needs to have air permeability, if what is melt | dissolved at the time of subsequent heating-pressing is employ | adopted, eyes will be buried or covered. Breathability decreases. And if the fabric weight of the nonwoven fabric sheet 5 is too high, the air permeability is lowered, and if it is too low, the physical adsorbent particles may fall off and it may be difficult to fix, so that the non-woven sheet 5 is 5 to 100 g / m ² , preferably 10 It is good to select what is in the range of -50 g / m < ² >.

  In the present invention, the physical adsorption layer 20 is not attached with acidic chemicals or alkaline chemicals, and the pH measured in accordance with JIS K 1474 is set to 5-9. When acidic chemicals or alkaline chemicals are attached to the physical adsorbent, the removal performance of the ionic substance gas is improved according to the amount of addition, but conversely, the chemical closes the pores of the physical adsorbent, so that the adsorption performance of organic substances is improved. descend. Furthermore, since the organic substance adsorbed and held by the physical adsorbent is in contact with the acidic chemical or alkaline chemical for a long time, the organic substance is hydrolyzed by the catalytic action of the chemical, and a large amount of decomposition products flow to the downstream side of the filter. It can also cause secondary contamination. In order to prevent these problems from occurring, in the present invention, the chemical reaction layer with chemicals and the physical adsorption layer with no chemicals are separated and stacked.

  The number of stacked layers of the chemical reaction layer and the physical adsorption layer may be increased according to the purpose, and the order may be determined. For example, if three layers of a chemical reaction layer to which acidic chemicals are attached, a physical adsorption layer, and a chemical reaction layer to which alkaline chemicals are attached are laminated and integrated into a filter medium for an air filter, three of acid gas, alkaline gas, and organic gas are used. It is possible to remove types with a single filter.

  The chemical reaction layer 10 and the physical adsorption layer 20 are, for example, dispersed by fusing a thermal bonding powder or hot melt resin between the layers in consideration of passability in post-processing such as pleating processing, or adhesive. It is preferable to bond and integrate them by spraying them between the layers. Among these laminating methods, it is preferable to select a method that does not lower the sheet adsorption performance and air permeability as much as possible before and after laminating. In order not to lower the adsorption performance, it is necessary to select a heat-sealing resin or adhesive with less outgas, and in order not to reduce the air permeability, it is necessary not to spray the heat-sealing resin or adhesive excessively. As such a resin, a low melting point resin not containing an organic solvent is suitable, and specifically, a polyolefin hot melt resin such as “Hybon” manufactured by Hitachi Chemical Co., Ltd. is suitable.

  The air filter medium thus obtained may be used as it is in a planar form, but if the pleating process is further performed to increase the passage area of the processing air, the collection efficiency is improved and the low pressure loss is reduced. It becomes possible.

  The air filter medium 2 according to the present invention described above can be used as an air filter by being housed in a frame 1 as shown in FIGS. The air filter medium and the air filter are suitably used for an air purifier, an air purifying system and the like used in a healthy house, a pet-compatible apartment, an elderly entrance facility, a hospital, an office, and the like. It can also be used as a semiconductor-related clean room, a semiconductor manufacturing apparatus, or a chemical filter for a wafer transfer path. In such a case, it is possible to cope with a plurality of gases in a limited space, and it is possible to avoid secondary contamination due to decomposition products which are often a problem with the chemical impregnated activated carbon.

  In the examples and comparative examples described below, the ability to simultaneously remove ionic substances and organic substances was evaluated as follows. Specific substances to be removed are assumed to be used for chemical filters used in semiconductor clean rooms, and ammonia, which is a cause of resist resolution failure, and propylene glycol monomethyl, which is generally used as a process solvent, are used. Ether acetate (hereinafter referred to as PGMEA) was used.

An air filter having an air filter attached to a frame was attached to an experimental duct, and air having a temperature of 23 ° C. and a humidity of 45% RH was blown into the duct at a speed of 0.5 m / sec. Further adding ammonia and PGMEA from the upstream side, the ammonia gas concentration by adjusting the 200 [mu] g ^/ m 3, PGMEA gas concentration to 6000μg / ^{m 3,} by sampling the air in the upstream side and the downstream side of the filter, the concentration of both components It was measured.

  For ammonia concentration measurement, the ammonia is collected by aeration and bubbling through an impinger containing ultrapure water, and the amount of ammonia is quantified by ion chromatography, and the ammonia removal rate is obtained from the upstream and downstream concentrations. It was. PGMEA was collected by aeration through a solid adsorption tube, and then quantified with a thermal desorption gas chromatograph, and the removal rate was determined from the upstream and downstream concentrations.

  Each removal rate was measured over time and the filter life was compared.

In addition, PGMEA is converted to propylene glycol monomethyl ether (PGME) and acetic acid when hydrolyzed, and when this acetic acid is released to the downstream side, it emits an irritating odor and is known to cause health damage to workers in the clean room. It has been. In order to confirm the amount of acetic acid generated, the amount of acetic acid generated from the filter was determined by quantifying the acetic acid collected by an impinger containing ultrapure water in the same manner as ammonia. The amount of acetic acid generated from the filter was calculated by subtracting the upstream concentration from the downstream concentration.
Example 1
An ultrafine nylon 6 fiber having a fiber length of 5 mm and a fineness of 1.1 tex (fiber diameter of 3.5 μm), and a core-sheath polyester composite fiber having a fiber length of 5 mm and a fineness of 2.2 dtex (fiber diameter of 14.4 μm) (melting point of the core component: 260 ° C., melting point of sheath component: 110 ° C.) were mixed so that each fiber would be 50% by weight, and dry papermaking was performed to prepare a fiber sheet. The obtained sheet had a basis weight of 97 g / m ³ and a thickness of 0.3 mm. The fiber sheet had a BET specific surface area of 0.8 m ² / g and a bulk density of 0.32 g / cm ³ . When this fiber sheet was impregnated with an aqueous phosphoric acid solution that neutralized with ammonia and then dried, the basis weight of the sheet was 132 g / m ² , and 35 g / m ² of phosphoric acid could be easily attached. .

Next, activated carbon particles having a BET specific surface area of 1200 m ² / g, an average particle diameter of 330 μm, and a pH of 8 measured according to JIS K 1474, a core-sheath type having a fiber length of 5 mm and a fineness of 2.2 dtex Polyester composite fiber (melting point of core component: 260 ° C., melting point of sheath component: 110 ° C.) is mixed so that the ratio of the core-sheath type polyester composite fiber is 30% by weight of the fiber sheet, and this is 20 g / m in weight. Papermaking was performed on the polyester fiber nonwoven fabric of No. ² , and the same polyester fiber nonwoven fabric was further laminated thereon. Total basis weight of the overlapping sheet is 144 g / ^{m 2,} the activated carbon particles 73 g / ^{m 2,} sheath-core polyester bicomponent fibers 31 g / ^{m 2,} polyester fiber nonwoven fabric was 40 g / ^{m 2.} The thickness was 1.0 mm.

Then, after spraying the heat-fusion powder on the above-mentioned superposed sheet not attached with phosphoric acid so as to have an amount of 5 g / m ² , it is passed through a heating furnace at 130 ° C., and the heat-fusion powder is in a molten state. Then, the phosphoric acid-impregnated fiber sheet was integrated by pressing with an overlapping roll. This composite sheet was placed on the experimental duct with the phosphoric acid-impregnated fiber sheet on the upstream side and the laminated sheet containing activated carbon particles not adhering phosphoric acid on the downstream side, and attached to the experimental duct. Ammonia removal rate, PGMEA removal rate The amount of acetic acid generated was evaluated.

As a result, each characteristic changed as follows over 30 hours immediately after the start. (Detailed data is listed in Table 1)
Ammonia removal rate: 99% → 85%
PGMEA removal rate: 91% → 32%
Acetic acid generation amount: 5 μg / m ³ → 23 μg / m ³
Ammonia and PGMEA consumed over the removal capacity over time, and the removal rate gradually decreased. However, the generation of acetic acid, a decomposition product of PGMEA, was suppressed to a slight increase.
(Example 2)
One polyester fiber nonwoven fabric of the laminated sheet is omitted, and after heat-spreading powder is sprayed on the polyester fiber nonwoven fabric to which phosphoric acid is not attached to a quantity of 5 g / m ² , a heating furnace at 130 ° C. is used. The filter material for an air filter was prepared in the same manner as in Example 1, except that the phosphoric acid-added fiber sheet was directly overlapped and integrated by pressing with a roll when the heat-sealed powder was in a molten state, evaluated.
The results were as follows.

Ammonia removal efficiency: 99% → 86%
PGMEA removal efficiency: 90% → 34%
Acetic acid ^{emissions: 6μg / m 3 → 41μg /} m 3
Both ammonia and PGMEA had the same removal efficiency as in Example 1, but the amount of acetic acid generated increased compared to Example 1. As the chemical reaction layer and the activated carbon were directly laminated, phosphoric acid adhered to the activated carbon, and the decomposition of PGMEA proceeded. From this result, it can be seen that the chemical reaction layer and the physical adsorbent are preferably separated.
(Comparative Example 1)
An air filter medium was obtained in the same manner as in Example 1 except that phosphoric acid was not attached to the fiber sheet of the chemical reaction layer, and the activated carbon particles were subjected to phosphoric acid addition treatment. Ammonia removal rate, PGMEA removal rate, acetic acid generation amount Evaluated. The amount of phosphoric acid attached to the activated carbon was 14 g / m ² , and the pH of the activated carbon measured according to JIS K 1474 was 4. Further, the total basis weight of the overlay sheet was 162 g / ^{m 2,} the activated carbon particles 88 g / ^{m 2,} core-sheath type polyester composite fiber 34g / ^{m 2,} polyester fiber nonwoven fabric was 40 g / ^{m 2.} Furthermore, the thickness was 1.0 mm. The results were as follows. (Detailed data is listed in Table 1)
Ammonia removal efficiency: 92% → 52%
PGMEA removal efficiency: 88% → -8% (release)
Acetic acid generation amount: 4 μg / m ³ → 165 μg / m ³
As for ammonia, since the amount of phosphoric acid added was less than that in Example 1, the removal rate decreased earlier. Even for PGMEA, although the content of activated carbon was higher than that in Example 1, the adsorption capacity decreased due to the adhering chemical covering the activated carbon surface, and it completely broke through after 30 hours. It was. Furthermore, it was confirmed that the concentration of acetic acid on the downstream side increased rapidly as the amount of PGMEA adsorbed and retained increased. This is probably because the phosphoric acid adhering chemical acts as an acid catalyst on the PGMEA adsorbed and concentrated on the activated carbon, and the hydrolysis reaction progressed.
(Comparative Example 2)
An air filter medium was obtained in the same manner as in Comparative Example 1 except that the amount of phosphoric acid attached to the activated carbon was set to 34 g / m ^{2 which} was substantially the same as in Example 1, and the ammonia removal rate, PGMEA removal rate and acetic acid generation amount were evaluated. did. Note that the pH of activated carbon measured in accordance with JIS K 1474 was 3. Further, the total basis weight of the overlay sheet was 182 g / ^{m 2,} the activated carbon particles 107 g / ^{m 2,} sheath-core polyester bicomponent fibers 35 g / ^{m 2,} polyester fiber nonwoven fabric was 40 g / ^{m 2.} Furthermore, the thickness was 1.0 mm. The results were as follows. (Detailed data is listed in Table 1)
Ammonia removal efficiency: 96% → 78%
PGMEA removal efficiency: 54% → -7% (release)
Acetic acid generation amount: 4 μg / m ³ → 246 μg / m ³
As for ammonia, the removal efficiency was improved because almost the same amount of phosphoric acid as in Example 1 was added. However, the removal efficiency of PGMEA was lower than that of Comparative Example 1 because phosphoric acid further inhibited physical adsorption of activated carbon. Also, the amount of acetic acid generated was higher than that in Comparative Example 1 due to the increase in the amount of phosphoric acid.

  The filter medium for air filter and the air filter according to the present invention include air purifiers, air purifying systems, etc. used in healthy houses, pet-friendly condominiums, elderly entrance facilities, hospitals, offices, etc., semiconductors and FPDs (flat panel displays). ) It can be suitably used as an industrial clean room in production or as a chemical filter for equipment installed in it.

It is a schematic block diagram of the filter medium for air filters which shows one Embodiment of this invention. 1 is a schematic cross-sectional view of an air filter showing an embodiment of the present invention. It is a schematic perspective view of the air filter which shows one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 2 Filter medium 3 Opening part 4 Fiber sheet 5 Nonwoven fabric sheet 6 Physical adsorbent 10 Chemical reaction layer 20 Physical adsorption layer

Claims (13)

  A chemical reaction layer including a fiber sheet to which a chemical that neutralizes and reacts with an ionic substance is adhered, and a physical adsorption layer including a physical adsorbent having a pH of 5 to 9 measured according to JIS K 1474. A filter medium for an air filter characterized by being integrated. The filter sheet for an air filter according to claim 1, wherein the fiber sheet has a BET specific surface area of 0.05 m ² / g or more and a bulk density of 0.5 g / cm ³ or less.   The filter sheet for an air filter according to claim 1 or 2, wherein the fiber sheet includes ultrafine fibers having a single yarn fineness of 1 dtex or less.   The filter sheet for an air filter according to any one of claims 1 to 3, wherein the fiber sheet includes a composite fiber composed of two or more kinds of polymers, and the composite fiber is at least partly divided.   The filter sheet for an air filter according to any one of claims 1 to 4, wherein the fiber sheet includes a polyamide fiber or a composite fiber containing polyamide as a main component.   The filter sheet for an air filter according to any one of claims 1 to 5, wherein 20 to 80 wt% of the fiber sheet is a thermal adhesive component.   The filter medium for an air filter according to any one of claims 1 to 6, wherein the filter medium is molded into a pleated structure.   The filter material for an air filter according to any one of claims 1 to 7, wherein the physical adsorbing layer is one in which the physical adsorbent is sandwiched between fiber sheets.   The air filter medium according to any one of claims 1 to 8, wherein the physical adsorbent is activated carbon and / or zeolite.   An air filter comprising the air filter medium according to claim 1.   An air cleaner comprising the air filter according to claim 10.   A clean room comprising the air filter according to claim 10.   A semiconductor manufacturing apparatus comprising the air filter according to claim 10.