JPH10137522A - Method for judging time to replace chemical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the time to replace a chemical filter by providing a bypass packed with the same material as that in a chemical filter to the air cleaning chemical filter using an ion exchanger and measuring the physical quantity of the material in the bypass. SOLUTION: The chemical filter consists of an air cleaning part 1 having a frame for setting a filter and a reticular part 10 and a box measuring part 2 besides the cleaning part, and the rear of the air cleaning part 1 and measuring part 2 is sucked by an exhauster through a duct. The temp. and humidity are controlled in the measuring part 2 having a measuring bypass 3. The rear of the bypass 3 ia detached from the rear wall of the measuring part 2, freely projected and opened, and the front is opened in the measuring part 2 and horizontally supported. An opening 4 is formed in the front wall of the measuring part 2 at a position corresponding to the bypass 3, and a dust removing filter 5 is laid over the front of the opening 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the replacement time of a chemical filter for air cleaning using an ion exchanger which has recently been used in a clean room in the precision electronics industry such as the semiconductor industry and the pharmaceutical manufacturing industry. It is about. That is, the present invention relates to a method for determining a replacement time without destroying the chemical filter based on information such as a residual exchange capacity and a consumed exchange capacity of an ion exchanger used as a clean material of the chemical filter.

[0002]

2. Description of the Related Art As a chemical filter for removing gas components in air, there are known activated carbon particles and activated carbon fibers, or a filter obtained by impregnating them with acid or alkali. Further, a filter in which an oxide or a metal is supported on a carrier is also known. On the other hand, a chemical filter using an ion exchanger not only has a high ppb level gas component removal rate but also has no re-emission of an adsorbed substance, and has recently begun to be used particularly in the semiconductor-related industry.

[0003] As a shape of an ion exchanger used for a chemical filter, a non-woven fabric or a woven fabric which has a high removal rate, is lightweight, and is easily formed is often used. As the ion exchange group, a cation exchange group such as a sulfonic acid group and a carboxyl group, and an anion exchange group such as a quaternary ammonium group and a tertiary amino group are often used. The mechanism of removing gas components by these ion exchange groups is as follows:
It is mainly a neutralization reaction. Thus, as the filter continues to be used, the ion exchange capacity gradually decreases. If the consumption of the ion exchange capacity becomes large, the removal rate of the gas component becomes poor, and the filter must be replaced.

[0004] Regarding the time to replace the filter, see HEP
A filter for removing fine particles such as an A filter or a ULPA filter can be known by a pressure loss, but a chemical filter is intended to remove a gas component, and thus cannot be known at all by a pressure loss or the like. Only the concentration of non-target gas components at the inlet and outlet were barely measured, and it was confirmed that the removal performance had decreased, and only the replacement time was known.

However, in an environment where a chemical filter is required, the concentration of the gas to be removed is extremely low, and measurement of the concentration requires long-term suction by an impinger and careful analysis of the liquid after suction. Therefore, when the result is obtained, there is a concern that the gas component to be removed continues to flow out for a long time without being removed by the chemical filter, thereby contaminating the surface of the semiconductor product, for example. Furthermore, it is very difficult to sample a trace gas component, and even if the analysis value is correct, it is necessary to perform a number of samplings to know whether or not the sampling point is representative of the filter performance. In addition, such an analysis takes time and labor.

[0006] Also with respect to the gas adsorption mechanism, unlike physical adsorption such as activated carbon, adsorption by an ion exchanger is chemisorption. Therefore, when the ion exchange capacity is determined to a predetermined value, it is relatively simple from the inlet concentration. The life can be calculated. Therefore, there is a method of performing the above-described concentration measurement when the life is approached, but the inlet concentration is rarely stable. In that case, the gas concentration must be analyzed periodically until the removal performance deteriorates, and the above-mentioned problem is not solved. Therefore, a method is often used in which a filter used for a certain period of time is replaced despite having an ion exchange capacity, that is, an ability to remove gas components. Such a method is not suitable for the era of resource saving and energy saving, but also causes an increase in cost.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to analyze the concentration of trace gas components in the air before and after a chemical filter based on the circumstances described above, and indirectly determine when to replace the filter. Without such complication and without breaking or contacting the chemical filter, the change in the physical quantity of the clean material consisting of the ion exchanger caused by the adsorption of the gas component to be removed is directly used as an index. It is an object of the present invention to provide a method for judging the replacement time in a timely manner without delay.

[0008]

The above objects have been achieved by the present invention as a result of the inventors' earnest studies. That is, the present invention provides (1) an air-purifying chemical filter using an ion exchanger, a bypass filled with the same material as the chemical filter, and measuring the physical quantity of the material in the bypass to obtain the chemical. A method for determining a time for replacing a chemical filter, wherein a time for replacing the filter is determined; (2) a physical quantity to be measured for the material in the bypass is selected from weight, water content, electric resistance, and high-frequency impedance (3) The method according to (1) or (2), wherein the consumption rate of the ion exchange capacity of the material filled in the bypass is the same as the consumption rate of the ion exchange capacity of the chemical filter for air cleaning. ,

(4) The method according to any one of (1) to (3), wherein the chemical filter for air cleaning is produced by a radiation graft polymerization method. (5) The chemical filter is a single fiber. , Monofilament aggregates, processed products such as woven and non-woven fabrics, and further processed products, powders and particles, processed products, membranes, hollow fiber membranes, processed products, and porous materials such as foams (1) The method according to any one of (1) to (4), wherein the material in the bypass is placed in a space where temperature and humidity are controlled. (1) to (5)
And (7) the method according to any one of (1) to (6), wherein a filter that is not an ion exchanger is installed upstream of the material in the bypass.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining the weight of an ion exchanger,
This is based on the knowledge that physical quantities such as water content, electric resistance, and high-frequency impedance change depending on the amount of chemically adsorbed gas components. Removal of gas components by a chemical filter for air cleaning using an ion exchanger is a chemical adsorption, so the weight, water content,
Various physical property changes such as electrical properties occur. The main factor of this change in physical properties is a change in the amount of adsorbed moisture. It is also conceivable to measure the change in physical properties as described above for the chemical filter actually used, and determine the replacement time based on the results.However, the actual installation location of the chemical filter is firmly attached to pipes and walls. The seal is used at the joint between the filter and the filter or between the filter and the duct, and measures are taken to prevent air leakage. Monitoring change is extremely difficult. Therefore, it is difficult to adopt such a method.

[0011] Further, regarding the measurement of physical properties other than weight,
When the measuring device is permanently installed in a controlled space such as a clean room, the shape and space of the chemical filter are limited, so that it is difficult to always measure even though the device is compact. In the present invention, in view of the above circumstances, at least in the air stream to be cleaned of the chemical filter for air cleaning using an ion exchanger, a measurement column for filling the same material into the clean material is provided. By passing the air to be cleaned through the measurement column, the gas component to be removed from the air is adsorbed on the clean material (ion exchanger), and the change in the physical quantity resulting from this adsorption is used as information to determine the timing for replacing the chemical filter. A quick and accurate determination is made. Since the installation of such a measuring column is performed in a space having a relatively small volume, temperature,
It becomes easy to control environmental conditions such as humidity and to attach a measuring device, so that continuous or discontinuous measurement can be performed stably. The main factor of the physical property change caused by the chemical adsorption of the gas to be removed by the chemical filter using the ion exchanger is a change in the amount of adsorbed moisture. In the present invention, the gas adsorbed on the chemical filter includes a basic gas such as ammonia and trimethylamine, and an acidic gas such as hydrogen chloride, hydrogen fluoride and nitric acid.

In the following, various changes in physical properties will be described, for example, in the case of using a fibrous material composed of a strongly acidic cation exchanger having a typical sulfonic acid group as an ion exchange group and adsorbing ammonia as a target gas. The reaction between the strongly acidic cation exchanger having a sulfonic acid group and ammonia is represented by the following formula. R-SO ₃ H + NH ₃ → R-SO ₃ NH ₄ As shown in this formula, when ammonia is adsorbed on the strongly acidic cation exchanger having a sulfonic acid group, the ammonia is bonded to the sulfonic acid group and corresponds to a molecular weight of ammonia of 17. It is believed that an increase in weight occurs. In fact, when a change in weight before and after ammonia adsorption is examined in a dry state, it is recognized that the change corresponds to the weight increase calculated in advance from the ion exchange capacity.

However, it has been found that under normal conditions of temperature and humidity, the opposite phenomenon that the weight is reduced instead of adsorbing ammonia appears. Based on these phenomena, the amount of ammonia adsorbed under non-uniform temperature and humidity conditions of a non-woven fabric consisting of a sulfonic acid type strongly acidic cation exchanger having a certain ion exchange capacity and the accompanying weight change were measured. It has been recognized that there is a relationship shown in FIG. That is, it can be seen from FIG. 1 that the weight of the unused nonwoven fabric made of the sulfonic acid type strongly acidic cation exchanger is 10% or more heavier than the weight after adsorption of ammonia. This phenomenon can be easily understood by considering a model as shown in FIG. This model shows the relationship between the sulfonic acid group, which is the ion exchange group of the strongly acidic cation exchanger, and the water molecule in the case of the case where ammonia is adsorbed and the case where ammonia is not adsorbed. In, there is a layer of bound water relatively strongly adsorbed around the sulfonic acid group (Zone I), and a layer of adhered water (Zone III) adsorbed more weakly outside. An intermediate layer (Zone II) can also be considered between the layer of bound water (Zone I) and the layer of attached water (Zone III). The amount of the attached water easily changes depending on the temperature and humidity in the air.

On the other hand, when a gas such as ammonia is adsorbed, the amount of bound water is reduced, and the extent varies depending on the amount of adsorption. In addition, since water has a high dielectric constant, electric properties such as electric resistance also change depending on the amount of adsorption of ammonia or the like. Therefore,
Although DC resistance can be used under certain conditions, particularly high-frequency impedance has a high correlation with water content. Here, the parameters related to impedance, that is, the absolute value of impedance, inductance, capacity, loss coefficient, Q (Qu
quality factor), reactance, phase angle θ, and the like. To use the above physical property changes, that is, weight changes, changes in water content and electrical resistance, to know the remaining exchange capacity of the ion exchange capacity, a constant temperature and constant humidity space is required. Since the measurement column is small, it is easy to control the temperature and humidity. In addition,
In a clean room in the semiconductor industry or the like, the temperature and humidity are constantly controlled at a constant level. Therefore, it is often unnecessary to control the temperature and humidity if a measuring column is placed in the room.

In order to know the consumption amount of the ion exchange capacity of the chemical filter material and determine the replacement time based on the consumption amount,
The consumption rate of the ion exchange capacity of the chemical filter material must match the consumption rate of the ion exchange capacity of the same material packed in the measurement column. A flat membrane may be installed in the measurement column so that the surface wind speed becomes the same as the surface wind speed of the chemical filter, or a spirally wound filter may be installed. In particular, when knowing the consumption of ion exchange capacity of the chemical filter material by high frequency impedance,
It is preferable to fill the measurement cell with a rolled-up material because it sufficiently surrounds the measurement terminal, and in the case of using a near-infrared moisture meter, the reflection of near-infrared light is used. Is preferably filled. If fine particles and the like mixed in the air to be cleaned adhere to the clean material packed in the measurement column, it will cause coloring and increase in weight, causing errors in the measurement results of the ion exchange capacity consumption, resulting in incorrect judgment. Therefore, it is preferable to install a filter for removing the fine particles and the like other than the chemical filter upstream of the cleaning material in the measurement column, since a more accurate measurement result can be obtained.

The material of the ion exchanger used for the chemical filter may be in the form of a single fiber, an aggregate of single fibers, a woven or non-woven fabric which is a processed product thereof, a processed product thereof, a powder or a particle, and a processing thereof. Products, membranes, hollow fiber membranes, processed products thereof, and porous materials such as foams and processed products thereof can be used, but any shape can be used. Also, regarding the structure of the base of the ion exchanger,
The product produced by the radiation graft polymerization method does not have a crosslinked structure unlike the base of the ion exchanger produced by the ordinary polymerization method, so water is absorbed due to the adsorption of gas components to the ion exchange group and changes in temperature and humidity. The absorption and desorption of molecules occur more quickly, making it ideal as a material for chemical filters.

The graft polymer is, for example, polyethylene,
Examples include copolymers of a backbone polymer such as polyolefin such as polypropylene and polyacrylonitrile and a halogenated polyolefin and a branch polymer such as glycidyl methacrylate, acrylic acid and styrene sulfonic acid. Specifically, such a graft copolymer is preferably produced by a radiation graft polymerization method. The radiation used in the radiation graft polymerization method is preferably an electron beam or γ-ray, and the stem polymer treated with the electron beam or γ-ray is subjected to a graft polymerization reaction with a comonomer to be a branch polymer by a known method. Preferably, the electron beam or γ-ray-treated stem polymer is immersed in a comonomer solution to cause a reaction. Conditions for the graft polymerization reaction, for example, temperature, type of solvent in a comonomer solution, comonomer concentration, reaction time, and the like are appropriately selected. Also,
The graft ratio can be appropriately selected by selecting the above reaction conditions and the like, but is usually in the range of 20 to 300%. In addition, the reaction for forming an ion exchange group in the obtained copolymer can be appropriately performed by a conventionally known method.

The types of ion exchangers used in the chemical filter include a strongly acidic cation exchanger having a sulfonic acid group as an exchange group, a weakly acidic cation exchanger having a carboxyl group, a strongly basic anion exchanger having a quaternary ammonium group, and Tertiary, secondary, or in addition to the weakly basic anion exchanger of the primary amino group, amphoteric ion exchangers, medium acidic cation exchangers, medium basic anion exchangers, and the like, other, gas Any type of ion exchanger capable of adsorbing components other than liquid can be used.

FIG. 3 shows an example of a chemical filter unit device to which the method for judging the replacement time of a chemical filter according to the present invention is applied. The apparatus shown in FIG. 3 includes an air purifying section 1 having a frame (not shown) for setting a filter and a mesh structure section 10, and a box-type measuring section 2 provided on a side of the air purifying section 1. 1 and the rear of the measuring unit 2 are sucked by a blower through a duct (not shown). The inside of the measuring section 2 can be controlled for temperature and humidity, and has a measuring bypass section 3. The measurement bypass unit 3 has a rear portion that is detachably protruded from the rear wall of the measurement unit 2 and opens, and a front portion that opens in the measurement unit 2 and is supported horizontally. On the front wall of the measuring section 2, there is an opening 4 corresponding to the position of the measuring bypass section 3, and a dust removing filter 5 is provided on the front surface of the opening 4. As shown in FIG. 4, the measurement bypass section 3 is filled with a test piece 7 or the like which is wound in a long diameter direction and a measurement terminal 9 connected to a measuring instrument 8 is passed through the opening in the rear part. 7 is set.

[0020]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Manufacture of strongly acidic cation exchange fiber non-woven fabric Weight per unit area: 50 g / m ² , thickness: 0.4 mm, fiber diameter: about 20 μm
Electron beam (1 Me)
V, 1 mA) was irradiated at 100 kGy. Next, this nonwoven fabric was immersed in a glycidyl methacrylate solution and subjected to a graft polymerization reaction to obtain a nonwoven fabric having a graft ratio of 148%. The nonwoven fabric was further treated with an aqueous sodium sulfite solution to be sulfonated, regenerated with hydrochloric acid, and then dried. As a result, a strongly acidic cation exchange nonwoven fabric having a neutral salt decomposition capacity of 2.8 meq / g (hereinafter simply referred to as nonwoven fabric) was obtained. Was.

A flow test of ammonia The flow test of ammonia was performed using the strongly acidic cation-exchange nonwoven fabric obtained above with the apparatus shown in FIG. In the above device, the size of the frame (30 cm × 20 cm) is placed on the frame (not shown) of the air cleaning unit 1 and the network structure 10.
The strongly acidic cation exchange non-woven fabric 6 cut in accordance with the above is stuck and fixed, the non-woven fabric is cut into 6 cm × 4 cm, and a test piece 7 wound in a longitudinal direction and wound into a roll is filled in the measurement bypass portion 3. As shown in FIG. 4, a high-frequency impedance measuring terminal 9 connected to the measuring instrument 8 is inserted into the test piece 7 through the rear opening, and the temperature in the measuring section 2 is controlled at 23 ° C. and the humidity is controlled at 55%. Then, a high frequency impedance was continuously measured by the measuring device 8 while passing the ammonia mixed air having an ammonia concentration of 0.1 ppm through the nonwoven fabric 6 and the dust removing filter 5 through the air cleaning section 1 and the measuring section 2 respectively. Although not shown, a dust filter made of the same material as that provided in the opening 4 of the measurement bypass unit 3 was naturally provided in front of the nonwoven fabric 6 of the air cleaning unit 1.

The temperature of the non-woven fabric 6 was previously set at 2
In an environment of 3 ° C. and a humidity of 55%, a calibration curve representing the relationship between the consumed ion exchange capacity due to the adsorption of ammonia and the value of the high-frequency impedance is prepared. When the value corresponding to% was indicated, the ventilation of the ammonia mixed air was stopped, the filter was immediately disassembled, and the consumed ion exchange capacity was measured by wet analysis. The value was obtained. From this, it was known that the time to replace the chemical filter can be accurately determined based on the information provided by the measurement column.

[0023]

According to the present invention, by providing a measurement column for filling the same material as a test piece into the air stream to be cleaned of a chemical filter using an ion exchanger as a cleaning material, Without being affected by the environment, consumption or residual ion exchange capacity of the material in the measurement column by aeration can be easily known by measuring physical quantities such as weight, water content, electric resistance or high-frequency impedance, This information can be used to accurately and quickly determine when to replace the chemical filter, so that the concentration of trace gas components at the inlet and outlet of the filter in use is frequently measured, or the chemical filter in use is not used. Partial sampling eliminates the complexity and non-responsiveness associated with techniques such as frequent measurement of consumption or residual ion exchange capacity. The rational use of Luther, greatly improves the workability.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the ammonia adsorption amount and the weight change of a strongly acidic cation exchange nonwoven fabric having a sulfonic acid group.

FIG. 2 is a model showing the relationship between a sulfonic acid group, which is an ion exchange group of a strongly acidic ion exchanger, and a water molecule in air, when ammonia is adsorbed and when it is not adsorbed.

FIG. 3 is a drawing showing an example of a chemical filter unit device used in an embodiment of the present invention.

FIG. 4 is a drawing for explaining one mode of measuring a change in ion exchange capacity of an ion exchange nonwoven fabric by a measurement bypass unit in a test apparatus used in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air purification part 2 Measurement part 3 Measurement bypass part 4 Opening 5 Dust removal filter 6 Strong acid cation exchange nonwoven fabric 7 Test piece 8 Measuring instrument 9 Measurement terminal 10 Network structure

Claims (7)

[Claims] 1. A chemical filter for cleaning air using an ion exchanger, a bypass filled with the same material as the chemical filter is provided, and the physical quantity of the material in the bypass is measured to determine when to replace the chemical filter. A method for determining the timing of replacing a chemical filter, comprising: 2. The method according to claim 1, wherein the physical quantity to be measured for the material in the bypass is selected from weight, moisture content, electric resistance, and high-frequency impedance. 3. The method according to claim 1, wherein the consumption rate of the ion exchange capacity of the material filled in the bypass is the same as the consumption rate of the ion exchange capacity of the chemical filter for air cleaning. 4. The method according to claim 1, wherein the chemical filter for air cleaning is produced by a radiation graft polymerization method. 5. The chemical filter is a single fiber, an aggregate of single fibers, a woven or non-woven fabric which is a processed product thereof, a molded product thereof, a powder / particle, a processed product thereof, a membrane,
The method according to any one of claims 1 to 4, wherein the hollow fiber membrane is selected from a processed product thereof, a porous material such as a foam, and a processed product thereof. 6. The method according to claim 1, wherein the material in the bypass is placed in a space where temperature and humidity are controlled. 7. The method according to claim 1, wherein a filter that is not an ion exchanger is provided upstream of the material in the bypass.