JP7208464B2 - Air filter medium manufacturing method, air filter pack manufacturing method, and air filter unit manufacturing method - Google Patents

Description

The present disclosure relates to a method of manufacturing an air filter media, a method of manufacturing an air filter pack, and a method of manufacturing an air filter unit.

Air filter units with high collection efficiency, such as HEPA (High Efficiency Particulate Air) filters and ULPA (Ultra Low Penetration Air) filters, have been used in clean rooms and semiconductor manufacturing equipment to achieve a highly clean environment. is used. These air filter units are equipped with air filter media for allowing air to pass through and for collecting suspended particulates. , Some are manufactured by stretching, etc., but static electricity is generated due to contact with rolls during manufacturing, etc., and the discharge of accumulated static electricity causes damage to the filter material, resulting in the collection efficiency of the air filter. may decrease.

On the other hand, in the method for manufacturing an air filter unit described in Patent Document 1 (Patent No. 5124069), static electricity is accumulated in the air filter media by controlling the relative humidity in the clean room where the air filter media are manufactured. It is proposed to suppress the occurrence of electrostatic discharge in the air filter material and suppress the occurrence of leaks in the air filter media.

However, it has been confirmed that leaks can occur in the manufactured air filter media even under an environment where the relative humidity value is controlled to be within a specific range.

An object of the present disclosure is to provide a method for manufacturing an air filter medium, a method for manufacturing an air filter pack, and a method for manufacturing an air filter unit, all of which suppress a decrease in collection efficiency. That's what it is.

As a result of intensive studies by the inventors of the present invention, even if the air filter medium is produced in a space controlled by relative humidity, static electricity is generated, and if electrostatic discharge occurs, the air filter medium will be damaged, and the air filter medium will be damaged. Airborne particulates are not captured and may leak from the damaged part. , it was found that damage to the air filter media can be suppressed.

A method for manufacturing an air filter medium according to a first aspect includes a manufacturing process in a controlled space in which the absolute humidity is controlled to a predetermined value or higher.

In this air filter medium manufacturing method, leakage of the manufactured air filter medium is suppressed by managing the controlled space by focusing on the value of absolute humidity rather than on the value of relative humidity. , it is possible to suppress the decrease in collection efficiency due to electrostatic discharge.

A method for manufacturing an air filter medium according to the second aspect is the method for manufacturing an air filter medium according to the first aspect, wherein the manufacturing process is performed in a controlled space controlled to an absolute humidity of 7.0 g/m ³ or higher. will be

In this method for manufacturing an air filter medium, it is possible to further suppress a decrease in the collection efficiency of the obtained air filter medium.

A method for manufacturing an air filter medium according to a third aspect is the method for manufacturing an air filter medium according to the first aspect, wherein the manufacturing process is performed in a controlled space controlled to an absolute humidity of 11.0 g/m ³ or higher. will be

In this method for manufacturing an air filter medium, it is possible to more sufficiently suppress a decrease in the collection efficiency of the obtained air filter medium.

A method for manufacturing an air filter medium according to a fourth aspect is a method for manufacturing an air filter medium according to any one of the first to third aspects, wherein absolute humidity is controlled using a humidifier. The humidifying device treats the managed space as a humidifying target space and drives the humidifying device so as to satisfy the set absolute humidity condition.

In this method of manufacturing an air filter medium, the use of a humidifying device that is driven so as to satisfy a set absolute humidity condition facilitates the control of the absolute humidity in the controlled space.

A method for manufacturing an air filter medium according to a fifth aspect is a method for manufacturing an air filter medium according to any one of the first aspect to the fourth aspect, wherein the manufacturing process is performed when the ambient temperature of the controlled space is 10°C or less. Even if it is, it is performed in a space controlled so that the absolute humidity is above a predetermined value.

In this method for manufacturing an air filter medium, even if the ambient temperature in the controlled space drops below 10°C, the absolute humidity in the controlled space is maintained at a predetermined value or higher, so the ambient temperature can drop below 10°C. Also for the air filter media produced in the controlled space, it is possible to suppress the reduction in the collection efficiency.

A method for manufacturing an air filter medium according to a sixth aspect is a method for manufacturing an air filter medium according to any one of the first to fifth aspects, wherein the manufacturing process is performed so that the ambient temperature of the controlled space is 16.5° C. or less. When the low temperature condition is satisfied, it is performed in a controlled space within a predetermined relative humidity range of greater than 80% and less than or equal to 95%.

Here, for example, when the value of the managed absolute humidity is converted into relative humidity, it is preferable that the converted relative humidity falls within a predetermined relative humidity range of greater than 80% and less than or equal to 95%. .

In this method of manufacturing an air filter medium, even if the low temperature condition of the atmospheric temperature of the controlled space being 16.5° C. or less may occur, the relative humidity of the controlled space is more than 80% and less than or equal to 95%. Since the relative humidity is within the range, it is possible to suppress a decrease in collection efficiency even for an air filter medium manufactured in a controlled space where the atmospheric temperature can be 16.5° C. or less.

A method for manufacturing an air filter medium according to a seventh aspect is a method for manufacturing an air filter medium according to any one of the first to sixth aspects, wherein the manufacturing process is performed so that the atmospheric temperature of the controlled space is 25.0° C. or higher. When the high temperature condition is satisfied, it is performed in a controlled space where the relative humidity of the controlled space is within a predetermined relative humidity range of less than 60%.

Here, for example, when the managed absolute humidity value is converted into relative humidity, it is preferable that the converted relative humidity falls within a predetermined relative humidity range of less than 60%.

In this method of manufacturing an air filter medium, when the atmospheric temperature of the controlled space satisfies the high temperature condition of 25.0° C. or higher, the absolute humidity of the controlled space is maintained at a predetermined value or higher, and the relative humidity of the controlled space increases. Since it is within the predetermined relative humidity range of less than 60%, it is possible to suppress excessive humidification while ensuring necessary humidification in the managed space.

Therefore, for example, it is possible to suppress excessive output of the humidifying device.

A method for producing an air filter medium according to an eighth aspect is a method for producing an air filter medium according to any one of the first to seventh aspects, wherein the air filter medium contains PAO particles having a particle diameter of 0.3 μm. The particle collection efficiency is 99.97% or more when air is passed at a flow rate of 5.3 cm/sec. Further, the air filter medium has a pressure loss of 50 Pa or more and 500 Pa or less when air is passed at a flow rate of 5.3 cm/sec.

In this air filter medium manufacturing method, it is possible to suppress reduction in collection efficiency due to electrostatic discharge even in the air filter medium having the collection efficiency and pressure loss performance.

A method for producing an air filter medium according to a ninth aspect is a method for producing an air filter medium according to any one of the first to seventh aspects, wherein the air filter medium contains PAO particles having a particle diameter of 0.15 μm. The particle collection efficiency is 99.9999% or more when air is passed at a flow rate of 5.3 cm/sec. Further, the air filter medium has a pressure loss of 50 Pa or more and 500 Pa or less when air is passed at a flow rate of 5.3 cm/sec.

In this air filter medium manufacturing method, it is possible to suppress reduction in collection efficiency due to electrostatic discharge even in the air filter medium having the collection efficiency and pressure loss performance.

A method for producing an air filter medium according to a tenth aspect is a method for producing an air filter medium according to any one of the first to ninth aspects, wherein the air filter medium has a porous membrane containing a fluororesin. ing.

In this method for producing an air filter medium, even when producing an air filter medium having a porous membrane containing a fluorine-based resin, which tends to accumulate static electricity compared to glass fibers, etc., there is no reduction in collection efficiency due to electrostatic discharge. can be suppressed.

A method for manufacturing an air filter medium according to an eleventh aspect is the method for manufacturing an air filter medium according to the tenth aspect, wherein the porous membrane has a thickness of 1 μm or more and 100 μm or less.

In this method for manufacturing an air filter medium, even when the thickness of the porous membrane is as thin as 100 μm or less, it is possible to suppress the reduction in collection efficiency due to electrostatic discharge.

An air filter medium manufacturing method according to a twelfth aspect is the air filter medium manufacturing method according to either the tenth or eleventh aspect, wherein the air filter medium further includes a reinforcing material laminated on the porous membrane. have.

In this method for manufacturing an air filter medium, it is possible to suppress a decrease in collection efficiency due to electrostatic discharge that accompanies the step of laminating the reinforcing material on the porous membrane.

A method for manufacturing an air filter medium according to a thirteenth aspect is the method for manufacturing an air filter medium according to any one of the first to twelfth aspects, further comprising a step of neutralizing the air filter medium.

This method of manufacturing an air filter medium further includes a step of removing static electricity from the air filter medium. A decrease in collection efficiency can be suppressed more reliably.

A method for manufacturing an air filter medium according to the fourteenth aspect is the method for manufacturing an air filter medium according to the thirteenth aspect, wherein static elimination of the air filter medium is performed in at least one of the bonding process and the winding process. will be

In this method of manufacturing an air filter medium, static electricity is removed in at least one of the bonding process and the winding process, which are particularly likely to generate static electricity. be able to.

A method for manufacturing an air filter pack according to a fifteenth aspect, wherein the air filter medium according to any one of the first aspect to the fourteenth aspect is alternately mountain-folded and valley-folded in a controlled space in which the absolute humidity is controlled to a predetermined value or higher. It has a pleating process that is processed into a zigzag shape that is repeated every second time. In the pleating process, static electricity is removed from the air filter material.

In this air filter pack manufacturing method, the pleating process is also performed in a controlled space where the absolute humidity is controlled to a predetermined value or more. A decrease in collection efficiency can be suppressed.

A method for manufacturing an air filter unit according to a sixteenth aspect is characterized in that the air filter medium of any one of the first to fourteenth aspects or the air filter pack of the fifteenth aspect is placed in a controlled space where the absolute humidity is controlled to be a predetermined value or more. , and an assembling step for accommodating the frame.

In this air filter unit manufacturing method, since the assembly process is also performed in a controlled space where the absolute humidity is controlled to a predetermined value or more, it is possible to suppress a decrease in the collection efficiency of the obtained air filter unit.

FIG. 2 is an explanatory diagram of an overview of a method for manufacturing an air filter medium; FIG. 2 is an explanatory diagram of an overview of a method for manufacturing an air filter medium; FIG. 4 is an explanatory diagram of an outline of a method for manufacturing an air filter pack; FIG. 4 is an explanatory diagram of an outline of a method for manufacturing an air filter pack; 1 is a schematic external perspective view of an air filter pack; FIG. FIG. 2 is a schematic external perspective view of an air filter unit;

(1) Manufacturing method of air filter medium Figs. 1 and 2 show an outline of an example of a manufacturing method of an air filter medium.

In FIG. 1, an unwinding roll 1, a winding roll 2, rolls 3 to 5, heat rolls 6 and 7, and rolls 8 to 12 are arranged in a controlled space (for example, a clean room, etc.) where air filter media are produced. each shown. FIG. 2 also shows unwind roll 14, preheating zone 15, stretching zone 16, heat setting zone 17, laminate roll 19, and take-up roll 21, which are arranged in the controlled space where the air filter media are produced.

In the production of the air filter medium, a filter medium production process, a thermal lamination process, a winding process, and the like can be performed.

(1-1) Filter medium production process In the filter medium production process, a filter medium is produced through the process shown in FIG. 1 and the process shown in the left half of FIG. Although not particularly limited, a porous membrane containing a fluororesin as a filter medium can be produced here. For example, a PTFE unsintered film can be biaxially stretched to produce a PTFE porous membrane. By forming the filter medium from a porous film containing a fluororesin, it is possible to reduce the fiber diameter, but static electricity tends to accumulate in the filter medium compared to a glass filter medium made from glass fibers. However, even when such a porous membrane containing a fluororesin is used, it is possible to suppress the occurrence of electrostatic discharge by producing an air filter medium in an environment in which the absolute humidity is controlled, as described later. can be done.

The film thickness of the filter medium is preferably 1 μm or more and 100 μm or less, preferably 1 μm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less, from the viewpoint of reducing the pressure loss of the filter medium. When trying to produce such a filter medium with a relatively thin film thickness, leakage of dust due to electrostatic discharge tends to be a problem, but by controlling the absolute humidity described later, the collection It becomes possible to more stably manufacture products that meet efficiency standards.

The porous membrane containing the fluororesin contained in the filter medium has a particle collection efficiency of 99.97% or more when air containing PAO particles with a particle diameter of 0.3 μm is passed at a flow rate of 5.3 cm / sec. and a pressure loss of 50 Pa or more and 500 Pa or less when air is passed at a flow rate of 5.3 cm/sec. In addition, the porous membrane containing the fluororesin contained in the filter medium has a particle collection efficiency of 99.9999% or more when air containing PAO particles with a particle diameter of 0.15 μm is passed at a flow rate of 5.3 cm / sec. More preferably, the pressure loss is 50 Pa or more and 500 Pa or less when air is passed at a flow rate of 5.3 cm/sec. When trying to produce such a high-grade filter medium with a relatively small fiber diameter, the fibers tend to be damaged particularly by electrostatic discharge. It becomes possible to more stably manufacture products that meet the standards for collection efficiency.

(1-2) Thermal Lamination Step In the thermal lamination step (bonding step), a breathable support material 18 as a reinforcing material is attached to one or both sides of the filter medium produced in the filter medium production process by the process shown in the right half of FIG. are thermally laminated to obtain the air filter material 13. The air-permeable support material 18 is not particularly limited, but is preferably made of nonwoven fabric or the like, and its presence or absence does not substantially affect the collection efficiency and pressure loss value of the air filter material 13. is preferred.

(1-3) Winding Step In the winding step, as shown in the right part of FIG.

(2) Method for Manufacturing Air Filter Pack FIGS. 3 and 4 show an outline of an example of a method for manufacturing the air filter pack 25. FIG.

In manufacturing the air filter pack 25, an unwinding process, a pleating process, an expanding process, and, if necessary, a spacer coating process, a re-pleating process, and the like can be performed.

(2-1) Unwinding Process In the unwinding process, the air filter material 13 wound in the winding process is unwound.

(2-2) Pleating process In the pleating process, as shown in FIG. 3, the air filter material 13 is alternately folded and processed into a wavy shape (pleating), thereby forming wavy folds. do. In addition, heating at about 90° C. may be performed in order to form a crease.

(2-3) Deployment Step In the deployment step, the pleated air filter media 13 are deployed into a sheet.

(2-4) Spacer Application Process In the spacer application process, as shown in FIG. 4, spacers 24 are applied to the deployed air filter media 13 . The spacer 24 maintains the distance between the surfaces of the pleated air filter media 13 facing each other, and prevents an increase in pressure loss as the air filter pack 25 (partial surfaces of the air filter media 13 are in contact with each other). It has a function of suppressing the increase in pressure loss due to storage), and although it is not particularly limited, a hot melt resin or the like can be used.

(2-5) Re-pleating process In the re-pleating process, the air filter media 13 coated with the spacers 24 are again pleated to obtain an air filter pack 25 as shown in FIG.

(3) Manufacturing Method of Air Filter Unit FIG. 6 shows an outline of an example of the air filter unit 30 .

In manufacturing the air filter unit 30, a packing process, a taking-out process, an assembling process, and the like can be performed.

(3-1) Packing Process In the packing process, the air filter pack 25 is temporarily packed in a bag to prevent adhesion of organic substances until the subsequent assembly process is performed.

(3-2) Taking Out Process In the taking out process, the packed air filter pack 25 is taken out of the bag in order to perform the next assembly process.

(3-3) Assembling Step In the assembling step, as shown in FIG. 6, the taken out air filter pack 25 is incorporated into the frame 26 to obtain the air filter unit 30 . The frame body 26 is not particularly limited, but may be, for example, a metal frame body made of aluminum or an aluminum alloy. In order to fix the air filter pack 25 to the frame 25, an adhesive such as urethane resin may be interposed.

(4) Execution of each step in an absolute humidity controlled environment All of the production of the air filter media 13, the production of the air filter pack 25, and the production of the air filter unit 30 are carried out so that the absolute humidity is equal to or higher than a predetermined value. It is preferably performed in a controlled space such as a controlled clean room.

By manufacturing such an air filter medium 13 in an environment where the absolute humidity is controlled to a predetermined value or more, static electricity is generated even if the air filter medium 13, the nonwoven fabric 18, etc. come into contact with a roll or other members. can be effectively prevented from occurring. As a result, it is possible to suppress the occurrence of electrostatic discharge due to accumulation of static electricity, suppress damage such as leaks to the air filter media 13 and the like, and suppress a decrease in collection efficiency.

In particular, in the winding process of the air filter material 13, static electricity is likely to be accumulated in the wound air filter material 13, but since it is in an environment where the absolute humidity is a predetermined value or more, moisture content in the air such as in winter It is possible to effectively suppress the occurrence of electrostatic discharge even when the amount tends to decrease.

Also, the production of the air filter pack 25 is performed in an environment where the absolute humidity is controlled to a predetermined value or more, so that the air filter medium 13 and the air filter pack 25 are not damaged due to electrostatic discharge. can be suppressed.

In addition, the production of the air filter unit 30 is also performed in an environment where the absolute humidity is controlled to a predetermined value or more, so that the air filter medium 13, the air filter pack 25, and the air filter unit 30 are free from electrostatic discharge. You can prevent damage from occurring.

The manufacturing of the air filter media 13, the air filter pack 25, and the air filter unit 30 are performed in a controlled space such as a clean room in which the absolute humidity as atmospheric humidity is controlled to a predetermined value or higher. Specifically, the absolute humidity in the controlled space is preferably controlled to 7.0 g/m ³ or higher, and more preferably 11.0 g/m ³ or higher from the viewpoint of sufficiently suppressing electrostatic discharge. .

It should be noted that the production of the air filter medium 13, the production of the air filter pack 25, and the production of the air filter unit 30 can be carried out in a controlled space whose absolute humidity is controlled to a predetermined value or higher regardless of the ambient temperature of the controlled space. preferable. For example, even if the ambient temperature of the controlled space is 10 ° C. or less, the absolute humidity of the controlled space is a predetermined value or more (preferably 7.0 g/m ³ or more, more preferably 8.0 g/m ³ or more, and further It is preferably controlled to be 11.0 g/m ³ or more). This makes it possible to prevent electrostatic discharge from occurring even though the relative humidity is relatively high.

In addition, when the low temperature condition is satisfied, that is, the ambient temperature of the controlled space is 16.5°C or less, the relative humidity (converted value) of the controlled space is within a predetermined high relative humidity range of more than 80% and less than or equal to 95%. It is preferable to manufacture the air filter media 13, the air filter pack 25, and the air filter unit 30 in the managed space. This makes it possible to prevent electrostatic discharge from occurring even when the relative humidity is higher than 80%. In addition, by setting the upper limit of the relative humidity to 95% under low temperature conditions, it becomes easier to suppress the occurrence of dew condensation in the equipment, devices, etc. used in the filter medium manufacturing process, and especially to the electric machine. It makes the problem easier to control. Under low-temperature conditions, even if the relative humidity exceeds 80%, the absolute humidity is sufficiently low, so problems are unlikely to occur in the equipment and devices used in the filter medium manufacturing process.

On the other hand, when the atmospheric temperature of the controlled space satisfies the high temperature condition of 25.0 ° C. or higher, the absolute humidity of the controlled space is a predetermined value or higher (preferably 7.0 g / m ³ or higher, more preferably 8.0 g / m ³ or more, more preferably 11.0 g/m ³ or more), and the relative humidity (converted value) of the controlled space is within a predetermined low relative humidity range of less than 60% It is preferable that the production of the air filter media 13, the production of the air filter pack 25, and the production of the air filter unit 30 are carried out in the managed space. As a result, even though the relative humidity is less than 60%, a sufficient absolute humidity value is ensured, making it possible to suppress the occurrence of electrostatic discharge. Also, in order to suppress the occurrence of electrostatic discharge, it is possible to suppress the output of the humidifying device, etc., as small as possible when driving the humidifying device or the like.

(5) Humidifier A specific method for controlling the absolute humidity in the controlled space above a predetermined value is not particularly limited, but it can be performed using a humidifier.

Here, the management of the absolute humidity in the managed space may be performed by a human operating the driving status of the humidifier such as ON/OFF while looking at the absolute hygrometer or the like, or the humidifier has a control function related to the absolute humidity. , the humidifier may be used to automatically maintain the absolute humidity at a predetermined value or higher.

(6) Static Elimination Process During the manufacture of the air filter media 13, the air filter pack 25, and the air filter unit 30, a static elimination process is performed to reduce the charge amount of the air filter media 13 in the controlled space. preferably done.

This static elimination process is not particularly limited, but by using a static elimination device 50 such as a known ionizer or static elimination blower for specific portions of the air filter media 13, the air filter pack 25, and the air filter unit 30, It is preferable to perform static elimination.

Since static electricity tends to occur in processes where contact and friction occur, it is preferable to remove static electricity particularly in the heat lamination process, winding process, and pleating process (the same applies to the re-pleating process). It is preferable to perform static elimination also in the film unwinding process, the PTFE porous membrane winding process, and the PTFE porous membrane unwinding process. When embossing the air filter material 13 to form irregularities, static elimination may be performed in the embossing process.

In this way, by suppressing the charge amount of the air filter media 13 and the like by the static elimination process, the generation of electrostatic discharge is suppressed, and the collection efficiency of the obtained air filter media 13, the air filter pack 25, and the air filter unit 30 is improved. A decrease can be suppressed more reliably.

<Example>
[Presence or absence of leaks in air filter media]
A measurement sample of the air filter medium was set in a filter holder with a diameter of 100 mm, the inlet side was pressurized with a compressor, and the air permeation flow rate was adjusted to 5.3 cm/sec with a flow meter. In this state, polydispersed PAO is flowed from the upstream side at a particle concentration of 10 ⁸ / 300 ml, and a particle counter (manufactured by Rion KC-22B) installed on the downstream side determines the number of permeated particles by particle size. Calculate the transmittance of PAO particles with a particle size of 0.10 to 0.2 μm and 0.2 to 0.5 μm from the ratio of the number of particles, and the transmittance of PAO particles with a particle size of 0.10 to 0.2 μm. If the transmittance was 100 times or more higher than the transmittance of PAO of 0.2 to 0.5 μm, it was determined that there was no leakage.

[Pressure loss of air filter media (Pa)]
A measurement sample of the air filter material was set in a filter holder with a diameter of 100 mm, the inlet side was pressurized with a compressor, and the flow rate of air permeation was adjusted to 5.3 cm/sec with a flow meter. Then, the pressure loss at this time was measured with a manometer.

[Collection efficiency of air filter media (%)]
A measurement sample of the air filter medium was set in a filter holder with a diameter of 100 mm, the inlet side was pressurized with a compressor, and the air permeation flow rate was adjusted to 5.3 cm/sec with a flow meter. In this state, polydispersed PAO with a particle size of 0.10 to 0.2 μm is flowed from the upstream side at a particle concentration of 10 ⁸ /300 ml, and a particle counter (manufactured by Rion KC-22B) installed on the downstream side measures the particle size. The number of PAO permeable particles of 0.10 to 0.2 μm was determined, and the collection efficiency of the measurement sample was calculated by the following formula, with Ci being the upstream particle concentration and Co being the downstream particle concentration.

[Number 1]
Collection efficiency (%) = (1-Co/Ci) x 100

For the air filter media with very high collection efficiency, the suction time was lengthened and the sampling air volume was increased. For example, if the suction time is increased tenfold, the number of counted particles on the downstream side increases tenfold, ie, the measurement sensitivity increases tenfold.

[Method for measuring charge amount]
The electrostatic charge amount was measured using a vibrating electrostatic potential meter "KSD-0103" manufactured by Kasuga Denki Co., Ltd.

[Manufacture of PTFE air filter media]
First, 100 parts by weight of PTFE fine powder having a number average molecular weight of 6.2 million (“Polyflon Fine Powder F-106” manufactured by Daikin Industries, Ltd.) was added with hydrocarbon oil (“Isopar M” manufactured by Exxon Mobil Corporation) as an extrusion aid. 25 parts by weight were added and mixed.

This mixture was then molded into a round bar by paste extrusion. Then, this round bar-shaped molding was molded into a film by a calender roll heated to 70° C. to obtain a PTFE film. This film was passed through a hot-air drying oven at 250° C. to evaporate and remove the extrusion aid to obtain an unbaked film having an average thickness of 200 μm and an average width of 150 mm.

Next, this unsintered PTFE film was stretched in the longitudinal direction at a stretch ratio of 5 using the apparatus shown in FIG. The unbaked film was set on roll 1, and the stretched film was wound on take-up roll 2.

Next, the obtained longitudinally stretched film was stretched at a stretch ratio of 30 times in the width direction using a device (tenter) shown in the left half of FIG. At this time, the stretching temperature was 290° C., the heat setting temperature was 360° C., and the stretching speed was 330%/sec.

Nonwoven fabrics A and B described below were heat-sealed to both sides of the PTFE porous membrane by the device shown in the right half of FIG. 2 to obtain an air filter medium.
Nonwoven fabric A: "Elves S0403WDO" PET/PE core/sheath nonwoven fabric manufactured by Unitika Ltd., basis weight 40 g/m ²
Nonwoven fabric B: "Elves T0403WDO" PET/PE core/sheath nonwoven fabric manufactured by Unitika Ltd., basis weight 40 g/m ²

<Example 1>
An air filter medium was produced by controlling the absolute humidity and room temperature so that the relative humidity in the clean room was 80%.

Table 1 shows the pressure loss, collection efficiency, charge amount, and presence or absence of leakage measured for the air filter media produced at each absolute humidity. As for the charge amount, the charge amount on the roll surface was measured 10 minutes after winding the filter material. In addition, the presence or absence of leakage was determined by sampling 20 filter media rolls and measuring the presence or absence of leakage.

<Example 2>
An air filter medium was produced in the same manner as in Example 1 except that the absolute humidity and room temperature were controlled so that the relative humidity in the clean room was 70%.

Table 2 shows the pressure loss, collection efficiency, charge amount, and presence or absence of leakage measured for the air filter media produced at each absolute humidity.

<Example 3>
An air filter medium was produced in the same manner as in Example 1 except that the absolute humidity and room temperature were controlled so that the relative humidity in the clean room was 50%.

Table 3 shows the pressure loss, collection efficiency, charge amount, and presence or absence of leakage measured for the air filter media produced at each absolute humidity.

As is clear from Table 1, even if the relative humidity is the same at 80%, leakage occurs when the absolute humidity is low, and leakage can be suppressed when the absolute humidity is high.

Similarly, as is clear from Tables 2 and 3, even if the relative humidity is the same at 70% and 50%, leakage occurs when the absolute humidity is low, and leakage occurs when the absolute humidity is high. It was confirmed that it can be suppressed.

According to the results in Tables 1 to 3, it has been confirmed that the effect of suppressing the occurrence of leaks is obtained when the absolute humidity is 7.0 g/m ³ or more, regardless of the relative humidity or room temperature. was 11.0 g/m ³ or more, it was confirmed that leakage could be substantially prevented.

Although embodiments of the present disclosure have been described above, it will be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure as set forth in the appended claims. .

13 air filter material 25 air filter pack 26 frame 30 air filter unit

Patent No. 5124069

Claims (13)

A method for producing an air filter medium having a porous membrane containing a fluororesin,
Equipped with a production process in a controlled space where the absolute humidity is controlled to 7.0 g / m ³ or more ,
The manufacturing process includes at least one of a filter medium manufacturing process, a bonding process, and a winding process.
A method for manufacturing an air filter medium. The controlled space is set as a humidification target space, and the absolute humidity is controlled using a humidifying device that is driven so as to satisfy a set absolute humidity condition.
A method for manufacturing an air filter medium according to claim 1 . The manufacturing step is performed in the controlled space controlled so that the absolute humidity is 7.0 g/m ³ or more even when the atmospheric temperature of the controlled space is 10° C. or less.
The method for manufacturing the air filter medium according to claim 1 or 2 . In the manufacturing process, when the ambient temperature of the controlled space satisfies a low temperature condition of 16.5° C. or less, the relative humidity of the controlled space falls within a predetermined relative humidity range of greater than 80% and less than or equal to 95%. is performed in said controlled space,
A method for manufacturing an air filter medium according to any one of claims 1 to 3 . In the manufacturing step, when the ambient temperature of the controlled space satisfies a high temperature condition of 25.0° C. or higher, the relative humidity of the controlled space is less than 60%, which is within a predetermined relative humidity range. performed in space,
A method for manufacturing an air filter medium according to any one of claims 1 to 4 . The air filter medium has a particle collection efficiency of 99.97% or more when air containing PAO particles with a particle diameter of 0.3 μm is passed through at a flow rate of 5.3 cm/sec. The pressure loss when passing at 3 cm / sec is 50 Pa or more and 500 Pa or less.
A method for manufacturing an air filter medium according to any one of claims 1 to 5 . The air filter medium has a particle collection efficiency of 99.9999% or more when air containing PAO particles with a particle diameter of 0.15 μm is passed through at a flow rate of 5.3 cm/sec, and the air is flowed at a flow rate of 5.3 cm/sec. The pressure loss when passing at 3 cm / sec is 50 Pa or more and 500 Pa or less.
A method for manufacturing an air filter medium according to any one of claims 1 to 6 . The porous membrane has a thickness of 1 μm or more and 100 μm or less.
A method for manufacturing an air filter medium according to any one of claims 1 to 7 . The air filter material further has a reinforcing material laminated on the porous membrane,
A method for manufacturing an air filter medium according to any one of claims 1 to 8 . The manufacturing step includes a step of neutralizing the air filter medium,
A method for manufacturing an air filter medium according to any one of claims 1 to 9 . The neutralization of the air filter material is performed in at least one of the bonding step and the winding step included in the manufacturing step ,
The method for manufacturing the air filter medium according to claim 10 . The air filter medium according to any one of claims 1 to 11 is arranged in a zigzag shape in which mountain folds and valley folds are alternately repeated in a controlled space where the absolute humidity is controlled to be 7.0 g / m ³ or more. Equipped with a pleating process to process,
In the pleating step, neutralizing the air filter medium,
A method for manufacturing an air filter pack. The air filter medium according to any one of claims 1 to 11 or the air filter pack according to claim 12 is housed in a frame in a controlled space controlled to an absolute humidity of 7.0 g/m ³ or more. with an assembly process that
A method for manufacturing an air filter unit.

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