JP5289720B2 - Air filter media and air filter - Google Patents

Description

  The present invention relates to an air filter that is suitable for use as an air filter that is used in an outside air processing facility of a clean room that manufactures semiconductors and liquid crystals, a register filter that is used for ventilation of a living room such as a condominium, and the like.

Conventionally, semiconductors and liquid crystals are manufactured in a clean room 12 of a clean room facility 1 as shown in FIG. An external air conditioner 3 and an internal air conditioner 4 are connected to such a clean room facility 1 as an outside air processing system facility 2. Usually, the external air conditioner 3 includes a pre (coarse dust) filter 5 for removing relatively large particles of about 5 μm or more from the air inflow side, and a medium performance filter 6 for removing particles of about 1 μm or more. A chemical filter 7 for removing gaseous pollutants is installed. The internal air conditioner 4 includes a chemical filter 8, a high-performance filter 9 such as a HEPA filter for removing particles of about 1 μm or less, and a blower 10 that blows air to the clean room facility 1 from the air inflow side. Is installed. The air supplied to the clean room facility 1 passes through the chemical filter 13, the fan 14, and the high performance filter 15 provided in the ceiling portion 12 a of the clean room 12 and is supplied into the clean room 12. A chemical filter 16 is also installed in the circulation path of the clean room outer chamber 11.
In recent years, for such clean rooms, in addition to contamination by particulate pollutants, gaseous pollutants such as organic gas, acid / alkaline gas, dopant gas such as boron and phosphorus, and metal gas Contamination by is a serious problem. For example, an organic substance gas gives an anomaly to an oxide film thickness formed on a semiconductor substrate, and is therefore a fatal pollutant under the present situation where the oxide film thickness tends to be reduced.
Gaseous contaminants can be removed with a chemical filter using, for example, activated carbon, activated carbon fiber, zeolite, ion exchange resin, other chemical adsorbents, and the like. However, it is desired that the filter itself installed in the clean room facility does not generate gaseous pollutants. For example, a high-performance air filter that serves as a final air processing filter has been developed from the early stage with a filter that generates less gas. In addition, as for the prefilter and the medium performance filter, a filter with a small amount of gas generation is desired.
However, so far, there has been no means for producing a medium performance filter medium in which the amount of gas generated from organic substances is sufficiently reduced without complicating the process and without reducing the performance of the filter medium. .
In order to reduce the gas generation amount of the organic substance from the filter medium, for example, a method of forcibly degassing by performing a heat treatment at a temperature below the melting point can be considered. However, when heat-treating the filter medium at a temperature lower than the melting point, the conventional low gas emission medium performance filter has the following problems although the amount of organic substance gas is reduced.
Due to the restriction of selecting a low gas generating material, the rigidity of the filter medium tends to be low and the strength of the pack itself tends to be low. For this reason, a measure for applying a hot melt ribbon can be considered, but this causes problems such as an increase in the mass of the filter unit and an increase in the amount of waste. On the other hand, in order to make a conventional high-rigidity filter medium without using a hot melt ribbon, a measure to increase the rigidity by using a reinforcing material as a chemical bond can be considered, but a conventional melamine binder can be used. When used, formaldehyde, one of the causative substances of sick house syndrome, is generated. Moreover, when using binders other than a melamine type | system | group, the subject that the rigidity of a filter medium does not fully raise occurs.
In addition to the complexity of the manufacturing process, there is a risk that the performance of the filter medium will deteriorate due to thermal deformation and shrinkage.
Japanese Patent Laid-Open No. 10-272328 JP 2001-137630 A

  The object of the present invention is to solve the above-mentioned problems of the prior art, without complicating the process, and without significantly reducing the collection efficiency of the filter medium, significantly reducing the gas generation amount of organic substances generated from the filter medium, In addition, it aims at providing the filter material for air filters which suppressed generation | occurrence | production of formaldehyde which is one of the causes of sick house syndrome, and an air filter using the same.

In order to achieve the above object, a filter medium for an air filter according to the present invention comprises a filter medium layer made of a melt blown non-woven cloth made of polybutylene terephthalate fibers and a thermal bond non-woven cloth made of heat-bonded fibers made of polyethylene terephthalate. A filter medium for an air filter formed by laminating a reinforcing layer made of polyethylene with a hot melt powder made of polyethylene having a melting point of 100 to 120 ° C., and having a formaldehyde emission rate (μg / m ² h) based on JIS A1901 of less than 5.0 It is characterized by being.
The air filter of the present invention is characterized in that, as described in claim 2, the air filter medium according to claim 1 is housed in a filter frame.
According to a third aspect of the present invention, in the air filter of the second aspect, the total amount of organic substances adsorbed per unit area of the silicon wafer measured by the substrate surface adsorption / heat desorption method is 1.0 ng / cm ^2. It is characterized by the following.
The air filter according to claim 4 is the air filter according to claim 2, wherein the air filter is a register filter.

For an air filter media of the present invention, because it uses melt blown nonwoven fabric made of polybutylene terephthalate as filter media layer can be maintained without reducing the collection efficiency of the air filter, also from the air filter media in use The amount of gas emitted from the organic substance can be significantly reduced.
In addition, since the air filter medium of the present invention uses a thermal bond nonwoven fabric made of heat-bonded fibers made of polyethylene terephthalate as a reinforcing layer, the amount of organic substances generated from the air filter medium during use is remarkably increased. Can be reduced.
In addition, the air filter medium of the present invention, when a thermal bond nonwoven fabric that does not contain a binder as the reinforcing layer is used, there is no generation of formaldehyde, which has been a problem in conventional filter media using melamine resin, to the human body There is no problem of influence.
Moreover, since the air filter of this invention accommodated the said filter material for air filters in the filter frame, the organic substance which generate | occur | produces from an air filter can be reduced significantly.
Further, when the air filter is evaluated by the substrate surface adsorption / heat desorption method, the total amount of organic substances adsorbed per unit area of the silicon wafer can be 1.0 ng / cm ² or less.

The filter medium for an air filter of the present invention is obtained by bonding a filter medium layer made of a melt blown nonwoven fabric and a reinforcing layer made of a thermal bond nonwoven fabric of heat-bonding fibers.
As the melt-blown nonwoven fabric of the filter medium layer, fibers formed from fiber-forming polymers such as polyolefin resins such as polypropylene and polyethylene, polyester resins, polyamide resins, polycarbonate resins and polyurethane resins are used. If importance is placed on the collection efficiency, fibers formed from a polypropylene-based resin from which thin fibers can be easily obtained are particularly preferable.

Moreover, if the viewpoint of low gas generating property is considered, the melt blown nonwoven fabric of a polyester-type fiber can be used. Specifically, it can be appropriately selected from polybutylene terephthalate, polyethylene terephthalate, polycarbonate and the like. Among these polyesters, polybutylene terephthalate and polycarbonate have a smaller gas generation amount than the most general-purpose polypropylene as an air filter medium. However, Japanese Patent Application Laid-Open No. 5-279947 discloses a very fine fiber nonwoven fabric using polycarbonate fibers, in which the fibers are not substantially fused to each other. However, this polycarbonate nonwoven fabric has been subjected to electret processing in order to increase the collection efficiency, which is an important basic performance as an air filter. For this reason, for example, when exposed to a high temperature for a long time, there is a problem that the collection efficiency is lowered due to neutralization of electric charges.
Moreover, in patent 3650505 gazette, in order to solve the problem of the said collection efficiency fall, it is collected by making it into the electretized nonwoven fabric which made polybutylene terephthalate contain 1-20 mass% in the polycarbonate melt-blown nonwoven fabric. Technologies that prevent efficiency loss have been published. However, in such a method, in addition to requiring a plurality of resin raw materials, electret processing is also required, and there is a problem that the process becomes complicated.
For this reason, it is most preferable to use a melt blown nonwoven fabric made of polybutylene terephthalate as a main raw material, considering that it does not complicate the low gas generating property and the process, and does not lower the collection efficiency of the filter medium.

  For example, a core-sheath type or a side-by-side type composite fiber can be used as the thermal bonding fiber of the reinforcing layer.

As a method for bonding the filter medium layer and the reinforcing layer, hot melt powder is used, for example, an ethylene-vinyl acetate copolymer, polyethylene, polyethylene terephthalate, etc., which are appropriately selected and used in consideration of the heating adhesion temperature .

  The thermal bond nonwoven fabric of the reinforcing layer is desirably a thermal bond nonwoven fabric that does not contain a binder. By using a thermal bond nonwoven fabric that does not contain a binder, the amount of gas generation can be reduced compared to a chemical bond nonwoven fabric that uses a melamine resin, which is a typical example of a conventional binder, and has recently become a problem. It is possible to provide a filter medium that does not generate any of the above.

The air filter medium of the present invention is preferably used, for example, as a medium performance filter medium or a register filter medium. Although not specifically illustrated, generally, in the case of a medium performance filter medium, a rectangular filter medium is formed in a rectangular filter frame, and in the case of a register filter medium, a circular filter medium is formed in a circular filter frame. And filter.
Examples of the medium performance filter medium and the register filter medium include those having an average particle collection efficiency of 50 to 99% by a test method based on JIS B 9908 and a pressure loss of 150 Pa or less at an air volume of 56 m ³ / min. preferable. Moreover, when using the filter medium for air filters of this invention as a filter medium for medium performance filters and a filter medium for register filters, the melt blown nonwoven fabric used as the filter medium layer preferably has an average fiber diameter of 0.1 to 50 micrometers. Moreover, the thermal bond nonwoven fabric used as the reinforcing layer preferably has an average fiber diameter of 1 to 100 micrometers.

The medium performance filter medium and the register filter medium preferably have a surface density of 65 to 200 g / m ² (the filter medium layer is 15 to 100 g / m ² , and the reinforcing layer is 50 to 100 g / m ² ).

  Moreover, it is preferable that the thickness (total thickness of a filter medium layer and a reinforcement layer) of the medium performance filter medium and the register filter medium is 0.3 to 2.0 mm, and is 0.5 to 1.2 mm. More preferably. When the thickness of the medium performance filter medium is less than 0.3 mm, there is a problem that the dust holding capacity is reduced and the life is shortened, and when it exceeds 2.0 mm, the pressure loss becomes too high. This is because there is a problem that the life is shortened.

The medium performance filter and the register filter are manufactured as follows, but the manufacturing method is not limited thereto.
The medium-performance filter temporarily fixes a pleated filter medium on a filter frame, and injects urethane sealants on the upper and lower surfaces, respectively, and cures them. If a hot melt ribbon is used to maintain the interval between the filter media, there is a risk of gassing of organic substances, so it is preferable not to use a hot melt ribbon. The material of the filter frame is preferably aluminum or stainless steel, which generates less organic gas and hardly corrodes. The resistor filter is formed by applying a hot-melt ribbon to a pleated filter medium to maintain a gap, and inserting a circular or square cut into a resin frame. Then, the surrounding gap is caulked with hot melt, and urethane foam is bonded to the outer periphery.

  Next, examples of the present invention will be described together with comparative examples. In addition, the filter material for air filters of this invention is limited to the following examples, and is not interpreted.

Example 1
Filter medium layer: A melt blown nonwoven fabric having an average fiber diameter of 2.0 micrometers and an area density of 40 g / m ^{2 made} of polybutylene terephthalate having a melting point of 225 ° C. was used as a filter medium layer.
Reinforcing layer: non-thermal adhesive component (core component): polyethylene terephthalate having a melting point of 255 ° C./thermal adhesive component (sheath component): a core-sheath type comprising polyethylene terephthalate having a melting point of 110 ° C. and having an average fiber diameter of 30 micrometers and a fiber length of 76 mm 100% by mass of the heat-bonding fiber was used as a non-woven fiber raw material, which was opened, and then applied to a card machine to form a non-woven fabric having a surface density of 95 g / m ² and a thickness of 0.4 mm to obtain a reinforcing layer.
Hot melt powder: Hot melt powder made of polyethylene having a melting point of 100 to 120 ° C. was used.
Next, hot melt powder with a surface density of 10 g / m ^{2 is} laminated on the reinforcing layer, heated with a dryer at 140 ° C. for 3 minutes, and then the filter medium layer and the reinforcing layer are bonded together, and then air-cooled. A medium performance filter medium having a density of 145 g / m ² and a thickness of 0.7 mm was produced.

(Comparative Example 1)
Example 1 except that non-thermally bonded fibers having an average fiber diameter of 20 micrometers and a fiber length of 76 mm made of polyethylene terephthalate having a melting point of 255 ° C. were used for the reinforcing layer fibers, and melamine resin was used for the reinforcing layer binder. In the same manner as above, a medium performance filter medium with an areal density of 145 g / m ² and a thickness of 1.0 mm was produced.

( Comparative Example 2)
A medium performance filter medium was prepared in the same manner as in Example 1 except that the material of the filter medium layer was polypropylene having a melting point of 160 ° C., with a surface density of 135 g / m ² and a thickness of 0.7 mm.

(Conventional example)
The material of the filter layer is polypropylene having a melting point of 160 ° C., and the reinforcing layer is made of polyethylene terephthalate having a melting point of 255 ° C. The non-thermally bonded fiber having an average fiber diameter of 20 micrometers and a fiber length of 76 mm is used as the binder of the reinforcing layer. A medium performance filter medium was prepared in the same manner as in Example 1 except that the melamine resin was used, with a surface density of 135 g / m ² and a thickness of 1.0 mm.

  Next, for the examples, comparative examples, and conventional examples of the present invention, the total amount of organic substances generated from the filter and the amount of formaldehyde generated from the filter medium were measured and evaluated as follows. The results are shown in Table 1.

Total organic substances:
Adsorbed per unit area of silicon wafer measured by the commonly used substrate surface adsorption / heat desorption method as a method of measuring contaminants generated from clean room components as the total amount of organic substances generated from the air filter The amount of total organic material released is shown. A total organic substance amount of less than 1/3 of the conventional example was evaluated as ◯, a value of 1/3 or more and less than 1/2 as Δ, and a value of 1/2 or more as x.

With reference to FIG. 2, the measuring method of the total amount of organic substances generated from the air filter by the substrate surface adsorption / heat desorption method will be described. FIG. 2A is a diagram showing a test duct 30 used for adsorbing gaseous contaminants such as organic substances generated from an air filter onto a silicon wafer. As shown in FIG. 2A, the test duct 30 made of stainless steel is cleaned by air passing through the chemical filter 33 and the high-performance filter 34 by the fan 32 and flows into the upstream sampling chamber 35. The downstream sampling chamber 36 is circulated from the upstream sampling chamber 35 through the filter unit 31 using the filter medium for the test air filter, and flows out from the outlet 37 to the outside. The test air filter unit 31 was 610 mm long × 610 mm wide × 290 mm deep. Room temperature air passed through the downstream sampling chamber 36 at a wind speed of 0.35 m / s.
The test duct 30 is preliminarily ventilated for 24 hours, and 24 hours after the start of the ventilation, the test duct 30 is opened, the sample silicon wafer 38 is installed in the upstream sampling chamber 35, and the downstream side A sample silicon wafer 39 was placed in the sampling chamber 36. For supporting the silicon wafers 38 and 39, a quartz supporting member cleaned by heating was used. Thereafter, ventilation was resumed, and the silicon wafers 38 and 39 were exposed in the sampling chambers 35 and 36 for 24 hours, and were taken out after 48 hours from the start of ventilation to obtain samples for analysis.
Next, the contaminant adsorbed on the silicon wafer for sample is used as follows, and a silicon wafer analyzer (SWA256 manufactured by GL Science Co., Ltd.) and a gas chromatograph mass spectrometer (HP manufactured by Agilent Technology Co., Ltd.). -5993).
As shown in FIG. 2B, an analysis sample 41 (sample silicon wafer) is placed in the quartz chamber 40 of the silicon wafer analyzer, and the initial temperature (40 ° C.) is supplied while supplying helium gas into the quartz chamber 40. From below) to a set temperature of 400 ° C. at a heating rate of 20 ° C. to 30 ° C. per minute and held at the set temperature of 400 ° C. for 15 minutes. Thereby, the contaminant adsorbed on the silicon wafer surface of the sample 41 for analysis was desorbed from the wafer surface by heating, sent to the collection tube, and adsorbed on the collection tube. The pollutant adsorbed on the collection tube was guided to a gas chromatograph mass spectrometer, and the total amount of organic substances adsorbed on the analysis sample 41 was measured. A calibration curve for measuring the total amount of organic substances was derived from icosane (C ₂₀ H ₄₂ ). Further, a value measured from the silicon wafer 38 as an analysis sample installed in the upstream sampling chamber 35 is set as a blank, and a blank is calculated from a value measured from the silicon wafer 39 as an analysis sample installed in the downstream sampling chamber 36. The subtracted value was defined as the total amount of organic substances.

Formaldehyde emission from filter media:
The emission rate was measured according to JIS A1901: 2003 (small chamber method), and the result on the first day was adopted. The case where the emission rate of formaldehyde was less than 1/100 or less than the lower limit of quantification compared to the conventional example was evaluated as ◯, the case of 1/100 or more and less than 1/10 as Δ, and the case of 1/10 or more as x.

Comprehensive evaluation:
Comprehensive evaluation is ◎ if the total organic substance amount from the filter and formaldehyde emission from the filter medium are both ◎, 、 if the total organic substance amount is △ and the formaldehyde emission amount is ○, and the formaldehyde emission amount is ○ In the case where the total organic substance amount is x, Δ is marked, and in the case where the formaldehyde emission amount is x, x is marked. The results are shown in Table 1.

As shown in Table 1, it was confirmed that in Example 1, the total amount of organic substances from the filter and the emission rate of formaldehyde from the filter medium were remarkably reduced as compared with the conventional example.
On the other hand, when the material of the filter medium layer is polypropylene as in Comparative Example 2, the amount of formaldehyde generated from the filter medium is reduced to about 1/25 compared to Comparative Example 1 , but the total amount generated from the filter is reduced. The amount of organic material was not reduced.
On the other hand, when the reinforcing layer is a chemical bond nonwoven fabric containing a melamine resin as in Comparative Example 1, the amount of total organic substances from the filter is relatively reduced as compared with the conventional example, but the filter medium No formaldehyde emission rate was reduced.
Further, as in Comparative Example 2, when the material of the filter medium layer is polypropylene, the formaldehyde emission rate from the filter medium is remarkably reduced as compared with the conventional example, but the total amount of organic substances generated from the filter is sufficiently reduced. I can't say. However, it can be sufficiently used as a filter medium for a range star filter.

The present invention relates to an air filter for use in a clean room outside air treatment facility for manufacturing semiconductors and liquid crystals, and a filter medium for an air filter in which the amount of organic substances generated from the filter and the formaldehyde emission rate from the filter medium are significantly reduced. The present invention has industrial applicability in that an air filter can be provided.
Further, considering only that the formaldehyde emission rate can be remarkably reduced, the present invention has industrial applicability in that it can provide a filter material for a register filter and a register filter.

Schematic diagram of clean room facilities and outside air treatment facilities Total organic matter generated from air filter media by substrate surface adsorption / heat desorption method

Explanation of symbols

30 Duct for Testing 31 Filter Unit 32 Fan 33 Chemical Filter 34 High Performance Filter 35 Upstream Sampling Chamber 36 Downstream Sampling Chamber 37 Outlet 38 Sample Silicon Wafer 39 Sample Silicon Wafer 40 Quartz Chamber 41 Sample for Analysis

Claims (4)

An air formed by bonding a filter medium layer made of a melt blown nonwoven fabric made of polybutylene terephthalate fibers and a reinforcing layer made of a thermal bond nonwoven fabric made of thermal adhesive fibers made of polyethylene terephthalate with a hot melt powder made of polyethylene having a melting point of 100 to 120 ° C. A filter medium for a filter, wherein a formaldehyde emission rate (μg / m ² h) based on JIS A1901 is less than 5.0.   The air filter according to claim 1 is housed in a filter frame. The air filter according to claim 2, wherein the total organic substance adsorbed per unit area of the silicon wafer measured by the substrate surface adsorption / heat desorption method is 1.0 ng / cm ² or less.   The air filter according to claim 2, wherein the air filter is a register filter.

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