JP2002273123A - Chemical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical filter capable of being arranged even in a narrow space, filled with a large quantity of activated carbon, suppressing the increase of pressure loss and not scattering activated carbon even if vibration is generated at the time of ventilation. SOLUTION: The chemical filter is obtained by providing an adsorbing layer wherein granular activated carbon is bonded and fixed by a thermoplastic resin, between two synthetic fiber nonwoven fabric layers to integrally bond both surfaces of the adsorbing layer to the synthetic fiber nonwoven fabric layers to form a filter medium and pleating the filter medium to house the same in a filter frame. The filter medium has a structure such that the adsorbing layer, wherein granular activated carbon with a mean particle size of 100-600 μm is integrally bonded and fixed by the thermoplastic resin, is provided between two synthetic fiber nonwoven facric layers, and the adsorbing layer and the synthetic fiber nonwoven fabric layers are integrally bonded and the filling amount of activated carbon in the filter medium is 100-700 g/m<2> and the thickness of the filter medium is 2.5 mm or less and the rigidity in the longitudinal direction of the filter medium is 1-10 N.cm and the amount of gaseous organic matter generated when the constituent materials of the filter medium are heated at 100 deg.C is 1 μg/g or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical filter used for adsorbing and removing molecular chemical pollutants and harmful substances existing in air. That is, chemicals used in clean rooms in factories for manufacturing semiconductors, liquid crystals, foods, pharmaceuticals, etc., museums, museums, and other general office buildings, and used for the purpose of removing chemical pollutants and harmful substances present in the air. It is about filters.

[0002]

2. Description of the Related Art In semiconductor and liquid crystal factories, HEPA filters and UPA filters have been conventionally used due to the problem of contamination by particulate matter.
It is manufactured in a clean room equipped with an ultra-high performance air filter such as an LPA filter.
In recent years, in these fields, as various devices have been highly integrated and refined, the influence of not only particulate matter but also molecular chemical contaminants has become a problem. As one of the measures, a chemical filter has been used. In addition, chemical filters are used in food and pharmaceutical factories to prevent contamination of products, in museums and museums to prevent deterioration of exhibits and storage, and in general office buildings to purify the office environment due to increased health-consciousness. It has become. These chemical filters adsorb and remove chemical contaminants with an adsorbent represented by activated carbon.They are filled with granular activated carbon in a punched metal box and placed in a casing in a W-shape. A typical example is pleated felt and fixed using a wave separator.

[0003] Among the representative examples, a chemical filter of a type in which granular activated carbon is filled in a punched metal box and arranged in a W-shape in a casing, the filled granular activated carbon rubs against each other due to vibrations when the air is ventilated, and the like. Dust, usually HEPA filter or ULPA located downstream
There was a problem that it could cause filter clogging. Further, as a recent trend, a filter is becoming thinner with the downsizing of an air conditioner, and a fan filter unit (FFU) installed on a ceiling of a clean room or the like and a chemical filter attached to a semiconductor manufacturing apparatus are particularly remarkable. However, the filters given as the representative examples have a large filter thickness, which makes it difficult to apply them to FFU and semiconductor manufacturing equipment. In a type in which granular activated carbon is filled in a punched metal box and arranged in a W-shape in a casing, there is a method of using a flat punched metal box, but the above-described problem of dust generation similarly occurs. In the type in which the fibrous activated carbon felt is pleated and fixed using a corrugated separator, the fibrous activated carbon felt inevitably becomes bulky in the manufacturing method, and therefore the filling area becomes extremely small in a thin filter. Reducing the pleat spacing to increase the filling area causes an increase in structural pressure loss and is not practical.

On the other hand, as a thin chemical filter, there is a filter formed into a honeycomb shape using an extremely thin sheet containing activated carbon. However, there is a problem that the amount of the activated carbon to be filled is small and the life is short. If the amount of activated carbon contained in the sheet is increased, the amount of activated carbon per filter is also increased, but at the same time, the sheet becomes thicker, the opening of the honeycomb, that is, the flow path becomes narrower, and an increase in pressure loss is inevitable.
Also, in the method of filling a large amount of sheets by reducing the honeycomb pitch, similarly, the flow path becomes narrow and the pressure loss increases.

[0005]

The present invention has been made as a result of intensive studies in view of the above problems. That is, it is an object of the present invention to provide a chemical filter which can be installed in a narrow space, is filled with a large amount of activated carbon, suppresses an increase in pressure loss, and does not scatter the activated carbon even when vibration occurs during ventilation.

[0006]

In the type in which the filter medium is pleated and arranged in the filter frame, if the thickness of the filter is reduced, the height of the pleats is inevitably reduced, and as a result, the area of the filled filter medium is reduced. Therefore, in order to fill many filter media with a low mountain height, it is necessary to increase the number of mountain pleats. However, the bulkier and thicker the filter medium, the more difficult it is to increase the number of peaks and the narrower the pleat interval, resulting in an increase in structural pressure loss during ventilation. Therefore, it is necessary to use a thin filter medium. Thin filter media tend to have a higher activated carbon filling rate and a higher pressure loss when treated air passes through the filter media, but conversely, if the area of the filled filter media increases, the wind speed when passing through the filter media increases , The increase in pressure loss is suppressed. Further, as the thickness of the filter medium becomes thinner, the pleat interval can be increased with the same area of the filter medium, and the increase in structural pressure loss can be suppressed. In the present invention, it is important that a large amount of granular activated carbon is filled and a thin filter medium is used.

In order to suppress the scattering of activated carbon due to vibration during ventilation, it is important that the activated carbon in the adsorbent layer is strongly adhered and fixed to each other, and is held in a state in which friction and falling off are difficult. Further, the nonwoven fabric is adhered as a cover material on the upstream and downstream sides of the adsorption layer, so that the activated carbon can be prevented from falling off and scattering.

In particular, in a clean room where semiconductors and liquid crystals are manufactured, there is a problem that gaseous organic substances generated from a material constituting a filter can become a pollutant, in addition to the above-mentioned falling off of activated carbon. It is important to use a material that does not easily generate such gaseous organic substances.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the chemical filter of the present invention, a filter medium having adsorptivity is pleated,
It is stored in a filter frame, the filter media,
Between two layers of synthetic fiber non-woven fabric, an average particle diameter of 100 to 600
It has an adsorption layer in which granular activated carbon of μm is adhered and fixed by a thermoplastic resin, and has a structure in which the adsorption layer and the synthetic fiber nonwoven fabric are integrally bonded.
0-700 g / m ² , thickness of filter medium is 2.5 m
It is important that the filter medium has a softness in the longitudinal direction of 1 to 10 N · cm by the slide method described in JIS L1096 “General Fabric Testing Method”. The filter medium is prepared by mixing granular activated carbon and a powdery or granular thermoplastic resin substantially uniformly, and then sprinkling the mixture into a synthetic fiber non-woven fabric so as to have a predetermined activated carbon filling amount. By laminating and pressing a mixture of granular activated carbon and a thermoplastic resin (which will become an adsorbing layer) while heating it while sandwiching it with two layers of synthetic fiber nonwoven fabric, the structure shown in the schematic cross-sectional view of FIG. 1 is obtained. Obtained as something. Also, as shown in the schematic cross-sectional view of FIG. 2, an adhesive sheet made of a thermoplastic fiber may be disposed inside each of the two layers of synthetic fiber non-woven fabric to enhance the adhesive force between the synthetic fiber non-woven fabric and the adsorption layer. It is possible.

The average particle size of the granular activated carbon constituting the adsorbing layer of the filter medium used in the chemical filter of the present invention is an average value based on a JIS standard sieve (JIS Z8801) in consideration of air permeability and workability. 100-60
0 μm, more preferably 200 to
It is 500 μm. When the average particle size is less than 100 μm, the pressure loss becomes too large to obtain a certain adsorption capacity, and when the average particle size exceeds 600 μm, the removal rate of chemical contaminants becomes extremely poor, The workability during pleating is poor. The granular activated carbon can be obtained by performing a predetermined particle size adjustment using an ordinary classifier.

The type of the granular activated carbon is not particularly limited, and for example, coconut shell, wood, coal, pitch and the like are preferably used. In terms of shape, crushed coal, granulated coal, beaded charcoal, etc. are preferably used. The amount of toluene adsorbed on the granular activated carbon as measured according to JIS K1474 is preferably 20% by weight or more. This is because high adsorption performance is required for trace amounts of chemical pollutants. Normally, activated carbon exhibits particularly good adsorption characteristics for nonpolar molecular substances, but granular activated carbon on which various chemical adsorbents are previously loaded or impregnated can be used to improve the adsorption characteristics for polar substances. For example, nitrogen compounds such as aldehyde-based gas and nitrogen dioxide, sulfur compounds such as sulfur dioxide and hydrogen sulfide, and acidic polar substances such as acetic acid, amine compounds such as ethanolamine, polyethyleneimine, aniline, and anisidine. , Sodium hydroxide, potassium hydroxide, guanidine phosphate, potassium carbonate, sodium hydrogen carbonate, etc. are preferably used. Phosphoric acid, citric acid and citric acid are used for basic polar substances such as ammonia, methylamine, trimethylamine and pyridine. Acid, malic acid, ascorbic acid and the like are preferably used.

The amount of the granular activated carbon constituting the adsorption layer of the filter medium used in the chemical filter of the present invention is from 100 to 700 per unit area of the filter medium.
g / m ² , more preferably 200 g / m ^2.
６００600 g / m ² . If the amount is less than 100 g / m ^2, a very large amount of filter material is required when the filter is filled with a predetermined activated carbon, which makes the process complicated and disadvantageous in terms of cost. If it exceeds 700 g / m ² ,
It becomes difficult to reduce the thickness of the filter medium, resulting in deterioration in workability during pleating.

The weight ratio of the thermoplastic resin, which is the other material constituting the adsorbing layer of the filter medium used in the chemical filter of the present invention, to the granular activated carbon is 15 to 50%.
It is preferably 50%, more preferably 20 to 4%.
0%. The synthetic fiber nonwoven fabric, thermoplastic resin, and granular activated carbon are integrated by disposing a mixture of the granular activated carbon and the thermoplastic resin (which becomes an adsorption layer) between the two layers of the synthetic fiber nonwoven fabric and pressing the mixture while heating. . If it is less than 15%, the adhesion between the granular activated carbons becomes insufficient, causing the activated carbon to fall off and the pleated shape of the filter medium to collapse. If it exceeds 50%, the adsorbing layer becomes unnecessarily hard, resulting in deterioration in workability during pleating. The shape of the thermoplastic resin is preferably powdery or granular, and the average particle diameter is preferably 10 to 120 μm on average according to JIS standard sieve (JISZ8801). 10 μm
If it is less than 1, when mixed with the granular activated carbon and sprayed on the synthetic fiber nonwoven fabric, the resin powder flies up, making uniform spraying difficult. If it exceeds 120 μm, the mixing with the granular activated carbon tends to be non-uniform, and the number of particles is small, so that a very large amount of resin is required to select a desired adhesion state, which is not preferable.

[0014] The thickness of the filter medium used in the chemical filter of the present invention is preferably 2.5 mm or less, more preferably 0.8 to 2.0 mm.
If it exceeds 2.5 mm, the pleat interval becomes narrow when the filter medium is filled in the thin filter, and the effect of the present invention cannot be obtained. Further, there is a problem that workability during pleating is deteriorated.

The filter medium used in the chemical filter of the present invention may have a longitudinal softness of 1 to 10 N · cm measured in accordance with the slide method described in JISL1096 “General textile test method”. preferable. If the hardness is within this range, the workability during pleating of the filter media and the handling during assembly are good.When using the manufactured filter, the pleated shape is well maintained and vibration occurs. When the pleats are used in a low wind speed region of 1 m / s or less, or when the height of the pleats is 60 mm or less, the pleat shape can be maintained without using a spacer. If it is less than 1 N · cm, the above-mentioned effects cannot be obtained. If it exceeds 10 N · cm, there occurs a problem that the rigidity is too large and pleating is difficult.

The synthetic fiber nonwoven fabric, which is a constituent material of the filter medium used in the chemical filter of the present invention, is composed of long fibers having a fiber diameter of 15 to 30 μm, and has a basis weight of 20 to 50 g / m ² and a JISL1096. It is important that the tensile strength in the longitudinal direction measured according to the strip method described in "General Fabric Testing Method" is 40 N / 5 cm width or more and the elongation is 15% or more. The range of the fiber diameter and the range of the basis weight are important for preventing the activated carbon from falling off or scattering. When the fiber diameter is less than 15 μm or when the basis weight is 5
If it is 0 g / m ² or more, the pressure loss increases, which is not preferable. Further, the region of the tensile strength and the elongation in the longitudinal direction is important in order to prevent the synthetic fiber nonwoven fabric from being broken at the pleated apex, since the workability during the pleating is good.

The above-mentioned thermoplastic resin, synthetic fiber non-woven fabric, adhesive sheet made of thermoplastic fiber used for the chemical filter of the present invention, and the adhesive used for bonding and sealing the pleated filter medium and the filter frame are as follows: In all cases, it is important that the generation of gaseous organic matter is small, and it is preferable that the total amount of gaseous organic matter generated upon heating at 100 ° C. is 1 μg / g or less. As a method for analyzing the heat generated gas, a method called “P & T (purge and trap) -GC / MS (gas chromatograph / mass spectrum) method” or “dynamic headspace method” is generally used. This is done by taking a predetermined amount of sample and heating for a predetermined time while flowing helium gas,
After collecting and concentrating volatile components in a cooled adsorption tube, the components are again heated and desorbed with a carrier gas, introduced into a GC / MS, and analyzed. In this method, gaseous organic matter is usually volatilized by heating, so the amount generated in a space controlled at room temperature such as a clean room is extremely small due to the relationship between temperature and vapor pressure, and the total amount generated under heating at 100 ° C Is 1μ
The use of materials below g / g greatly reduces the risk of practical problems.

The material of the above-mentioned thermoplastic resin, synthetic fiber non-woven fabric, adhesive sheet made of thermoplastic fiber, and the adhesive for bonding and sealing the filter medium and the filter frame are not particularly limited. , For example, polyolefin, polyester, polyamide, EVA, etc. can be used, but do not contain additives such as tackifiers, antioxidants, plasticizers, mold release agents, or even trace amounts of additives. It is preferred that

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples do not limit the present invention, and all modifications and alterations that do not depart from the gist of the present invention fall within the technical scope of the present invention. Included.

Example 1 Coal-based granular activated carbon having an average particle diameter of 300 μm was
Powdered polyethylene adhesive with a diameter of 12 μm
20% by weight was added and mixed until substantially uniform.
What consists of PET long fiber of average fiber diameter 17μm,
40g / m ^Two, Strip described in JISL1096
The tensile strength in the longitudinal direction measured according to the law is 120 N
/ 5 cm width, elongation rate of 25% spunbond nonwoven fabric,
On an adhesive sheet made of polyamide fiber
And the granular activated carbon filling amount is 600 g / m^Two(Powder polye
Tile adhesive filling amount is 120g / m^Two)
After spraying, the adhesive sheet and spunbond nonwoven
With the same thing as above sandwiched and sandwiched, temperature
140 ° C, pressure 5N / cm^TwoHeat and pressure for 30 seconds under the conditions
To obtain a filter medium having a thickness of 1.7 mm.
Pleated at height 35mm, width 610mm, length 61
0mm, depth 40mm (all outer dimensions) made of aluminum
Arrange so that the distance between the pleat apexes is 7 mm in the luter frame.
Adhesive and seal with polyamide adhesive
A cal filter was obtained. This is referred to as Example 1. Book
According to the slide method described in JIS L1096,
The measured softness is 5.3 Ncm and the spacer
The pleated shape could be maintained without the use of a hole. Comparative Example 1 A basis weight of 600 g / fibrous activated carbon having a fiber diameter of 17 μm
m^Two, 10mm thick felt with 35mm height
And pleated in the same filter frame as in Example 1.
Arranged. At this time, 3mm height to keep pleat shape
Was used as a spacer. This
This is referred to as Comparative Example 1. The distance between the pleat vertices in Comparative Example 1 is
It was 30 mm.

A comparison of the filling area of the filter medium and the amount of activated carbon in Example 1 and Comparative Example 1 was carried out.
Table 1 shows the pressure loss comparison under s.

[0022]

[Table 1]

The filter medium used in Comparative Example 1 is as thick as 12 mm, and the number of pleated peaks is extremely small when pleats are filled in the filter frame. As a result, the filling area of the filter medium is reduced. It will be low, and it will not be possible to earn the amount of activated carbon. In addition, since the filling area of the filter medium is small, the wind speed passing through the filter medium is high, and the pressure loss is high. On the other hand, in Example 1, the thickness of the filter medium used was 1.7 mm, which is extremely thin as compared with Comparative Example 1, and it is possible to fill a very large amount of filter medium. Further, the wind speed passing through the filter medium can be kept low and the pleat spacing, that is, the flow path is relatively wide, so that the structural pressure loss is at a low level, and the total filter pressure loss is much lower than that of Comparative Example 1.

Further, a continuous ventilation test was conducted for 3 months at a wind speed of 1 m / s with the HEPA filter installed upstream and downstream of Example 1, and the activated carbon was scattered to the HEPA filter installed downstream of Example 1. When we checked for the presence of
No adhesion of activated carbon to the PA filter was observed, and it was confirmed that there was no scattering.

[0025]

As described above, according to the present invention, a large amount of activated carbon is filled while having a low thickness, has a low pressure loss, does not drop or scatter the filled activated carbon, and further has a low gaseous organic matter content. A chemical filter with less occurrence can be obtained. It is possible to provide a chemical filter capable of coping with a thinning tendency expected to progress in the future with sufficient performance. In addition, the present invention includes not only a thin type but also a thick type chemical filter, which can meet needs such as high filling of activated carbon and low pressure loss.

[Brief description of the drawings]

FIG. 1 shows an example of a filter medium used in the chemical filter of the present invention.

FIG. 2 shows an example of a filter medium used in the chemical filter of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adsorption layer (adhesion fixation with granular resin and thermoplastic resin) 2 Nonwoven fabric of synthetic fiber 3 Adhesive sheet made of thermoplastic fiber

Claims (6)

[Claims] Claims: 1. A filter medium having an adsorbing layer in which granular activated carbon is adhered and fixed with a thermoplastic resin between two layers of synthetic fiber nonwoven fabric, and both surfaces of the adsorbing layer are bonded and integrated with the synthetic fiber nonwoven fabric. Is a pleated and housed in a filter frame. 2. The granular activated carbon has an average particle size of 100 to 600.
μm, the activated carbon loading in the filter media is 100-7
00 g / m ² , the thickness of the filter medium is 2.5 mm or less, and the filter medium has a softness in the longitudinal direction of 1 to 10 N · cm measured according to the slide method described in JISL1096 “General Fabric Testing Method”. The chemical filter according to claim 1, wherein: 3. A synthetic fiber non-woven fabric comprising long fibers having a fiber diameter of 15 to 30 μm, and a basis weight per layer of 20 to 50 g / m
^2. Tensile strength in the longitudinal direction measured in accordance with the strip method described in JIS L1096 "General textile test method" is 4
The chemical filter according to any one of claims 1 to 2, wherein the chemical filter has a width of 0N / 5cm or more and an elongation of 15% or more. 4. The chemical filter according to claim 1, wherein the weight ratio of the thermoplastic resin constituting the adsorption layer is 15 to 50% based on the weight of the granular activated carbon. 5. The chemical filter according to claim 1, wherein the amount of gaseous organic substances generated when each of the constituent materials is heated at 100 ° C. is 1 μg / g or less. 6. The chemical filter according to claim 1, wherein a chemical adsorbent is added to or attached to the granular activated carbon.