JP2006346548A - Chemical filter for removal of organic matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure removal of NO<SB>2</SB><SP>-</SP>with a chemical filter for organic matter. <P>SOLUTION: In a chemical filter using activated charcoal as a constituent member, 0.1-5 mass%, with respect to the total mass of the filter, of phosphoric acid and 0.02-1 mass% of iron or aluminum sulfate are loaded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a chemical filter for organic matter removal.

  In the semiconductor manufacturing field, product yields have been lowered due to gas contamination with inorganic gases such as ammonia, sulfur oxides, nitrogen oxides, and low-concentration gas contamination with organic gases generated from low-boiling organic solvents. It is known. As countermeasures, air purification using a chemical filter including activated carbon, activated carbon impregnated with various drugs, ion exchangers, and the like as main components is performed. In a clean room of a semiconductor manufacturing factory, various types of chemical filters are used in many places such as an outside air intake port of a clean room, an air circulation system of a clean room, and a local system attached to a manufacturing apparatus (for example, Patent Document 1). And Patent Document 2).

  In recent years, in the field of semiconductor manufacturing, yield reduction has become a serious problem due to organic gas contamination, particularly due to the influence of trace amounts of high-boiling organic substances such as phthalates released from clean room components. For this reason, the demand for the filter for organic substance removal which uses activated carbon as a main structural member increases, and the further high performance is requested | required.

However, when using a filter for removing organic substances whose main component is activated carbon, nitrite ions (NO) having a higher concentration from the downstream side of the filter, that is, the portion after passing the filter, than the upstream side of the filter, that is, the portion before passing through the filter. ₂ ^-) is a problem that is detected has occurred. Normally, inorganic gases are constantly monitored in a clean room by ion chromatograph analysis, but generally organic matter removal filters usually have little ability to remove inorganic gases, and the downstream concentration of inorganic gases is generally low. Is a slight decrease from the upstream concentration. However, depending on the installation environment of the organic matter removal filter, the NO ₂ ⁻ concentration on the downstream side exceeds the NO ₂ ⁻ concentration on the upstream side within several hours after installation, and further exceeds the NO ₂ ⁻ concentration management standard in the clean room. Sometimes.

Patent Document 3, NO ₂ filter downstream of the ^- so phenomenon that concentration becomes higher occurs when caulking material used in the clean room is de-oxime type, de-oxime type other than caulks, especially There is a description that such a problem can be solved by using a dealcoholated caulking material.

Patent Document 4 describes an air cleaning agent characterized in that a chemical containing a soluble acidic substance or basic substance as an active ingredient is supported on inorganic fiber paper. Examples of acidic substances include phosphoric acid, ferrous sulfate, ferric sulfate, and aluminum sulfate. However, these acidic substances are merely listed, and there is no suggestion or description in Patent Document 4 regarding what effect can be obtained by using which substance to what extent. Moreover, in patent document 4, an acidic substance removes basic gas, Comprising: An effect is not shown with respect to acidic gas.
Japanese Patent Laid-Open No. 06-339629 JP 2000-33217 A JP 2004-116961 A JP 62-129142 A

In the examination by the present inventor, it was confirmed that the NO ₂ ⁻ concentration on the downstream side of the filter is equal to or higher than the upstream side even in an environment where the deoxime type caulking material is not present, contrary to the description in Patent Document 3. That is, when low-concentration gaseous propylene glycol monomethyl ether acetate (hereinafter abbreviated as “PGMEA”) continues to flow through the organic substance removal filter, NO ₂ ⁻ higher than the upstream concentration was detected from downstream of the filter.

  In this regard, in the past, chlorofluorocarbon solvents were used for cleaning wafers in semiconductor manufacturing plants, but in recent years acetic acid ester organic solvents such as PGMEA have been used as an alternative solvent under the regulations of chlorofluorocarbons. It has also been reported that when these acetate organic solvents are adsorbed in the pores of activated carbon, they are hydrolyzed in the pores. When hydrolyzed, acetic acid as a decomposition product is released from the downstream side of the filter, and the surrounding metal portion and the like are corroded.

In order to remove NO ₂ ⁻ generated from the organic substance removal filter, it is conceivable to install an acid gas removal filter further downstream. However, the pressure loss of the filter increases when the acid gas removal filter that is originally unnecessary is stacked. In addition, because the filter installation space is limited, when it is necessary to reduce the thickness of the organic substance removing filter by an amount corresponding to the acid gas removing filter, the organic substance removing performance that is originally required is lowered.

Therefore, an object of the present invention is to make it possible to reliably remove NO ₂ ⁻ in a chemical filter for removing organic substances.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that NO ₂ ⁻ can be reliably removed if it is a chemical filter for organic matter removal having the following configuration. As a result, the present inventors have found that NO ₂ ^{− at a} higher concentration is not detected on the downstream side of the filter than on the upstream side of the filter during use. That is, the chemical filter for removing organic matter of the present invention is a chemical filter comprising activated carbon as a constituent member, and 0.1 to 5% by mass of phosphoric acid and 0.02 to 1% by mass of iron sulfate or aluminum sulfate relative to the total mass of the filter. And are attached.

The chemical filter for removing organic matter of the present invention exhibits the excellent organic matter adsorption performance of activated carbon, and in the past, it was customary to use a basic remover for removing acidic gas, but nitrous acid was used conventionally. It is a combination of activated carbon and acid to remove ions (NO ₂ ⁻ ), and NO ₂ ⁻ can be largely removed by the synergistic effect of the two types of adsorbents. It can be suitably used as a chemical filter for removing organic substances in a clean room of a semiconductor manufacturing factory that requires removal capability.

Hereinafter, the present invention will be described in detail.
The form of the activated carbon as the main constituent member of the chemical filter for removing organic matter of the present invention is not particularly limited, and various forms such as a fibrous form, a granular form, and a powder form are used. Among them, fibrous activated carbon is most preferably used because of its large surface area and high organic matter removal rate and high processability to sheets and filters. As the fibrous activated carbon, pitch-based, phenol-based, cellulose-based and the like can be used. In order to obtain high organic substance removal performance, the activated carbon preferably has a pore volume of 0.4 to 1.2 mL / g and an average pore diameter of 1.7 to 3.5 nm.

  The filter of the present invention needs to contain a binder in addition to the activated carbon as the main component for reasons such as processability into a filter shape, maintaining the strength of the filter, and preventing activated carbon from falling off. At this time, the mixing ratio of the activated carbon in the filter is preferably 30% by mass or more, and more preferably 50% by mass or more. If it is less than 30% by mass, the organic substance removal performance tends to be insufficient. Moreover, since it is necessary to contain a binder etc. as mentioned above, the upper limit of the mixture ratio of activated carbon is 90 mass% normally.

  In the filter of the present invention, 0.1 to 5% by mass of phosphoric acid and 0.02 to 1% by mass of iron sulfate or aluminum sulfate are impregnated with respect to the total mass of the filter. There are no particular restrictions on the method of attaching these two types of chemicals. The activated carbon before processing into a sheet is immersed in the aqueous chemical solution, dehydrated and dried, or the aqueous solution containing the activated carbon-containing sheet or filter is molded. Although there is a method of spraying, etc., in order to sufficiently obtain the effects of the present invention, since the uniformity of the drug distribution is important, the former method is particularly preferable. When activated carbon before processing into a sheet is immersed in two types of aqueous chemical solutions, phosphoric acid is adsorbed and concentrated in the pores of activated carbon, but iron sulfate or aluminum sulfate is not adsorbed in the pores. It is not concentrated. For example, after immersing fibrous activated carbon having a pore volume of 0.7 to 0.9 mL / g and a pore diameter of 1.8 to 2.0 nm in an aqueous solution in which two kinds of drugs are both 0.5% by mass, When dehydrated and dried until it becomes twice the mass of the original fibrous activated carbon, the amount of attachment is 4 to 6% by mass for phosphoric acid and 0.4 to 0.6% by mass for iron sulfate or aluminum sulfate. . The numerical value of the amount of attachment varies depending on the shape of the activated carbon used, the water retention of the activated carbon, the pore volume, the pore diameter, and the like. Adjust as appropriate.

As described above, the amount of chemicals added is 0.1 to 5% by mass of phosphoric acid and 0.02 to 1% by mass of iron sulfate or aluminum sulfate with respect to the total mass of the filter. The effect of the present invention is reduced when phosphoric acid is less than 0.1% by mass and when iron sulfate or aluminum sulfate is less than 0.02% by mass. Closed although the effect of removing some, impregnation agents pores of the activated carbon ^- and if it exceeds 5 mass% in the phosphoric acid, the the case of more than 1 wt% in the iron sulfate, or aluminum sulfate, respectively, NO ₂ in the filter Therefore, the organic substance removal performance, which is the original purpose, is lowered. The ratio of the addition amount of phosphoric acid and iron sulfate or aluminum sulfate is preferably (phosphoric acid) :( iron sulfate or aluminum sulfate) = 1: 1 to 50: 1, more preferably 5: 1 to 20: 1. When the amount of phosphoric acid is less than the amount of iron sulfate or aluminum sulfate, or when the amount of phosphoric acid is more than 50 times the amount of iron sulfate or aluminum sulfate, there is a synergistic effect of adding both. The effect of the present invention is reduced.

  The chemical filter for removing organic substances of the present invention is produced by mixing activated carbon and a binder to which a drug is attached to form a sheet, and usually further performing corrugation or pleating.

  There is no restriction | limiting in particular about the method of sheeting, A normal wet processing method and a dry-type processing method are used. However, in the case of the wet processing method, a sheet is obtained by making paper in the form of a slurry of activated carbon and a binder in water. In this case, the drug may be dissolved from the activated carbon impregnated with the drug, thereby reducing the effect of the present invention. is there. For this reason, the dry processing method is more preferable.

  When fibrous activated carbon is used as the activated carbon, the fibrous activated carbon to which the drug is attached and the heat-fusible fiber as a binder are mixed to form a web with a card machine or a random weber machine, and heat is increased to improve the strength. By passing through a drier set at a temperature higher than the melting point of the fused fiber and lower than (melting point +40) ° C., fixing between the fibers by thermal fusion, and passing a calender roll to reduce the thickness as necessary. Get a sheet. As the heat-fusible fiber, those made of a polyester-based, polyolefin-based, or polyamide-based polymer are preferable from the viewpoint of reinforcement strength, moldability, chemical resistance, and the like, and a high melting point polymer is disposed in the core portion and a sheath portion. A core-sheath composite fiber in which a low-melting-point polymer is arranged is more preferable.

  In the case of using granular or powdery activated carbon, a method in which the activated carbon and the heat-fusible material impregnated with the drug are uniformly sprayed on the nonwoven fabric, and another nonwoven fabric is laminated thereon to form a sandwich structure. Are mainly used. There are no particular restrictions on the material of the nonwoven fabric and the heat-fusible material, and those made of polyester-based, polyolefin-based, and polyamide-based polymers are preferably used in terms of strength, adhesiveness, moldability, chemical resistance, and the like.

Basis weight of the sheet is preferably ordinary 40~250g / ^{m 2,} especially if the filter is corrugated, moldability, more preferably 60 to 160 / ^{m 2} from the viewpoint of pressure loss.

  The activated carbon sheet thus obtained is processed by a known method to obtain the chemical filter for removing organic substances of the present invention. In other words, a pleated filter can be obtained by bending the sheet into a pleat shape, and a flat sheet and a corrugated sheet are laminated to form a single cardboard, and a plurality of the sheets are laminated, A corrugated filter can be obtained by cutting into a predetermined size. In either form, the required effects based on the present invention can be obtained, but a corrugated filter is more preferable from the viewpoint of pressure loss, the amount of activated carbon per volume, the efficiency of organic substance removal performance, and the like.

The chemical filter for organic matter removal of the present invention produced as described above exhibits the excellent organic matter adsorption performance of activated carbon, and by the synergistic effect of two kinds of additive agents of phosphoric acid and iron sulfate or aluminum sulfate. NO ₂ ⁻ can be reliably removed, and NO ₂ ^{− at a} higher concentration is not detected on the downstream side of the filter than on the upstream side of the filter during use, and therefore, a high performance removal capability is required. It is suitably used as a filter for removing organic substances in a clean room of a semiconductor manufacturing factory.

  Next, the present invention will be specifically described based on examples. However, the present invention is not limited to these examples. In addition, each characteristic value in the following examples and comparative examples was measured by the following tests at room temperature, and the amount of each substance was measured as follows.

(1) PGMEA gas aeration test of activated carbon 1 g of activated carbon was packed in a glass column having an inner diameter of 25 mm to obtain a layer height of 40 mm. PGMEA gas was generated with a permeator (manufactured by Gastec), diluted with air, adjusted to a concentration of 0.5 μg / m ³ and a relative humidity of 30%, and supplied to the sample at an air volume of 8.8 L / min. After 168 hours and 504 hours, the gas downstream from the sample was supplied to an impinger containing 40 mL of pure water at a wind speed of 2 L / min to collect the gas for 2 hours, and an ion chromatograph (Dionex) The concentration of NO ₂ ⁻ was determined by DX-100).

(2) PGMEA gas ventilation test of the filter The filter was cut into a cylindrical shape having a diameter of 25 mm and a layer height of 60 mm, and packed into a glass column having an inner diameter of 25 mm. Then, NO ₂ in the same manner as (1) ^- was determined concentration.

(3) Toluene gas ventilation test The filter was cut into a cylindrical shape having a diameter of 25 mm and a layer height of 60 mm, and packed in a glass column having an inner diameter of 25 mm. Then, toluene gas is generated with a permeator (manufactured by Gastec), diluted with air, adjusted to a concentration of 20 ppm and a relative humidity of 40%, and supplied to the sample at an air volume of 14.7 L / min. The time until the downstream toluene gas concentration reached 4 ppm was measured and used as the filter life. The measurement of the gas concentration was performed using an all-hydrocarbon automatic measuring instrument (EHF-7C) manufactured by Anatech Yanaco.

(4) Amount of phosphoric acid, iron sulfate, and aluminum sulfate attached to activated carbon 0.2 g of a sample (pre-attached activated carbon) previously dried in a vacuum dryer was subjected to pressure acid decomposition by the microwave method (1st step: H ₂ SO ₄ , 2nd step: HNO ₃ , 3rd step: HClO ₄ ), and then measured by an ICP method using IRIS / AP Advantage manufactured by Nippon Jarrel Ash.

Example 1
Ferrous sulfate heptahydrate 0.5560 g was dissolved in water, and further 85% phosphoric acid 0.5882 g was added to make a total volume of 100 mL. The concentration of ferrous sulfate in the aqueous solution was 0.3% by mass, and the concentration of phosphoric acid was 0.5% by mass. 2 g of pitch-based fibrous activated carbon (A-15 manufactured by Adol Corp., pore volume 0.8 mL / g, pore diameter 1.9 nm) was immersed in the above aqueous solution for 30 minutes, and after suction dehydration, 2 hours in a dryer at 110 ° C. The dried activated carbon was obtained.

Example 2
Instead of ferrous sulfate, 0.585 g of aluminum sulfate 13-14 hydrate was used. And otherwise, impregnated activated carbon was obtained by the same operation as in Example 1. The concentration of aluminum sulfate in the aqueous solution was 0.3% by mass.

Comparative Example 1
No phosphoric acid was added to the solution. Otherwise, impregnated activated carbon was obtained by the same operation as in Example 1.

Comparative Example 2
Do not add ferrous sulfate to the solution. Otherwise, impregnated activated carbon was obtained by the same operation as in Example 1.

Comparative Example 3
Pitch-based fibrous activated carbon (A-15 manufactured by Adol Co., Ltd., pore volume 0.8 mL / g, pore diameter 1.9 nm) not prepared was prepared.

With respect to each of the examples and comparative examples, the activated carbon that is the main component of the chemical filter for removing organic substances according to the present invention was examined for the presence or absence of two types of additive agents and the synergistic effect of the two types of agents. Table 1 shows the amount of adhesion and the results of the PGMEA gas aeration test for all five samples. As shown in Table 1, in Examples 1 and 2, almost no generation of NO ₂ ⁻ was observed on the downstream side even after 504 hours had elapsed, and the synergistic effect of the two kinds of adhering agents was clear. Further, the downstream NO ₂ ⁻ concentration did not exceed the upstream side. In Comparative Examples 1 and 2 to which only one of the two kinds of drugs was attached, the NO ₂ ⁻ concentration on the downstream side did not exceed the upstream side even after 504 hours, but from Examples 1 and 2 the NO ₂ ^- was greater in the generation. In Comparative Example 3 where no attachment was performed, it was confirmed that a large amount of NO ₂ ⁻ was generated downstream after 168 hours of ventilation.

From the above, it has been clarified that activated carbon impregnated with a chemical capable of constituting the chemical filter for removing organic substances of the present invention suppresses the generation of NO ₂ ⁻ . Then, the chemical filter for organic substance removal was created with this chemical | medical agent addition activated carbon continuously, and the effect of this invention was clarified.

Example 3
5.56 kg of ferrous sulfate heptahydrate was dissolved in water, and 5.882 kg of 85% phosphoric acid was further added to make the total amount 1000 L. The concentration of ferrous sulfate in the aqueous solution was 0.3% by mass, and the concentration of phosphoric acid was 0.5% by mass. 20 kg of pitch-based fibrous activated carbon (A-15 manufactured by Adol Co., Ltd., pore volume 0.8 mL / g, pore diameter 1.9 nm) is divided into 2.5 kg knitted bags, immersed in the above aqueous solution for 30 minutes, and after centrifugal dehydration, It was dried in a dryer at 110 ° C. for 40 hours to obtain an impregnated activated carbon. The increase in weight after attachment was 3.8%.

80% by mass of the impregnated activated carbon obtained above, and a heat-sealing fiber (manufactured by Unitika Co., Ltd.) having a polyethylene terephthalate copolymer having a melting point of 110 ° C. disposed in the sheath component and a polyethylene terephthalate polymer having a melting point of 260 ° C. disposed in the core component. Melty 4080) was mixed with 20% by mass, and the resulting mixture was put into a random weber manufacturing machine to form a web and subjected to heat treatment and calendering to obtain a sheet having a basis weight of 100 g / m ² and a thickness of 0.4 mm. Subsequently, a single corrugated board was formed by a corrugating machine, and a plurality of sheets were laminated and cut into a predetermined size, thereby obtaining a corrugated filter having 300 through holes / inch ² . The activated carbon in the corrugated filter was 77% by mass, phosphoric acid was 2.7% by mass, and ferrous sulfate was 0.3% by mass.

Comparative Example 4
The amount of 85% phosphoric acid charged was 70 kg. Otherwise, an impregnated activated carbon and a corrugated filter were obtained in the same manner as in Example 3. The increase in weight after application was 8%. Activated carbon in the corrugated filter was 74% by mass, phosphoric acid was 5.7% by mass, and ferrous sulfate was 0.3% by mass.

Comparative Example 5
No impregnation was performed on the fibrous activated carbon. Other than that, a corrugated filter was obtained in the same manner as in Example 3. The activated carbon in the corrugated filter was 80% by mass.

  Table 2 shows the results of the PGMEA aeration test and the toluene aeration test performed on the corrugated filters obtained in Example 3 and Comparative Examples 4 and 5.

In the PGMEA aeration test, in Comparative Example 5 without chemical addition, NO ₂ ⁻ began to be slightly generated after the passage of 168 hours, and after 504 hours, the concentration on the outlet side significantly exceeded the inlet side concentration. Admitted. On the other hand, in Examples 3 and Comparative Example 4 in which chemical addition was performed, NO ₂ ⁻ was not generated even after 504 hours.

In the toluene aeration test, Comparative Example 5 with no addition had the longest lifetime. In Example 3, the weight of the activated carbon was reduced by adding the chemical, and the pores of the activated carbon were blocked by the chemical, so that a performance decrease of about 10% was observed compared to Comparative Example 5. although, NO ₂ ^- because of the high removal effect of, value as a chemical filter for organic matter removal was higher here. In Comparative Example 4 On the other hand impregnated amount of phosphoric acid exceeds 5%, the significant performance degradation of about 40% as compared with Comparative Example 5 relates toluene ventilation test was observed, NO ₂ ^- and was high removal effect of No, it could not be used as a chemical filter for removing organic matter.

Claims (1)

  A chemical filter comprising activated carbon as a constituent member, wherein 0.1 to 5% by mass of phosphoric acid and 0.02 to 1% by mass of iron sulfate or aluminum sulfate are attached to the total mass of the filter. A chemical filter for organic matter removal.