JPH0985026A - Manufacture of filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove dirts attached to a filter by washing the filter with water to reutilize the filter by subjecting a three-dimensional reticular porous material to a discharge plasma treatment in a mixture of treatment gas and an inert gas or in an inert gas at a pressure of about 1Atm. SOLUTION: A titanium dioxide sintered material being solid induction material 6 is placed on a lower electrode 5 in a space between an upper electrode 4 and the electrode 5, and a non-woven fabric of polyester being three- dimensionally reticular porous material 7 is disposed on the sintered material. A device is evacuated to 1Torr and helium gas is introduced from a gas introducing pipe 9 until the pressure in the device becomes 5Torr and voltage of, for example, 1.5kHz:3.1kV is applied between the electrides 4, 5 for 15 seconds to generate plasma, thereby to apply discharge plasma treatment to the non- woven fabric of the polyester. Thereby, hydrophilic property can be imparted to the fabric and dirts can easily be removed from a filter having a hydrophilic surface by washing it with water.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a filter.

[0002]

2. Description of the Related Art In recent years, the demand and interest in ventilation have increased, and the use of ventilation devices has rapidly spread. Most ventilation systems installed in kitchens, ventilation vents, etc. are equipped with filters in order to prevent equipment from getting dirty due to oily smoke, and to prevent dust from entering. The filter is generally formed by forming fibers such as polyester into a non-woven fabric. Japanese Patent Laid-Open No. 6-63328 aims to improve oil collection efficiency and lengthen filter replacement intervals.
There is disclosed a filter for a ventilation device, which is formed by laminating non-woven fabrics having different mesh roughness. However, the ventilator filter is supposed to be replaced after being attached with a certain amount of dirt, and is therefore a disposable item.

[0003]

In view of the above problems, the present invention can easily remove stains attached to a filter by washing with water by imparting hydrophilicity to the three-dimensional mesh-like porous material constituting the filter, A method of manufacturing a reusable filter is provided.

[0004]

[Means for Solving the Problems]

The method for imparting hydrophilicity to the three-dimensional mesh-like porous material in the invention according to claim 1 of the present invention (hereinafter referred to as the present invention 1) is a solid dielectric on at least one opposing surface of opposing electrodes. And a communication hole is provided between the electrode and the solid dielectric or between the facing surfaces of the solid dielectrics.
By disposing a three-dimensional mesh-like porous body and subjecting the porous body to discharge plasma treatment under a pressure near the atmospheric pressure of the mixed gas of the processing gas and the inert gas or the inert gas.

By the above plasma treatment, the discharge plasma comes into contact with the three-dimensional mesh-like porous body, and a functional group that imparts hydrophilicity to the porous body is formed.

The three-dimensional mesh-like porous body (hereinafter, simply referred to as a porous body) constituting the filter of the present invention is made of a material such as an organic polymer compound, metal or ceramic by knitting fibers into a non-woven fabric. What was formed by means, such as, can be used. Organic polymer compounds that are flexible and easy to apply are preferred. Examples of the organic polymer compound include polyolefin resins, polyester resins, polyamide resins and the like.

The plasma processing will be described below.

The inert gas is preferably a rare gas such as helium, neon, argon or xenon. These may be used alone or in combination. Since helium has a long metastable lifetime, it is advantageous for exciting the processing gas and the inert gas. When using the above-mentioned inert gas other than helium, in order to perform discharge plasma treatment stably,
It is preferable to mix 2% by volume or less of an organic compound gas.

As the processing gas, a gas containing at least one element selected from oxygen, nitrogen and sulfur can be used. As the gas containing the oxygen element, oxygen,
Examples of the gas include ozone, water, carbon monoxide, carbon dioxide, nitric oxide and nitrogen dioxide. These gases may be mixed and used. Furthermore, by mixing the fluorine element-containing gas with the gas containing the oxygen element in a range not exceeding 50% by volume, the hydrophilicity of the porous body can be promoted. As the elemental fluorine-containing gas, fluorocarbon gas such as carbon tetrafluoride, carbon hexafluoride, propylene hexafluoride, halogenated carbon gas such as monochlorinated trifluorinated carbon gas, sulfur hexafluoride, etc. And the sulfur fluoride compound. Carbon tetrafluoride, carbon hexafluoride, and propylene hexafluoride are preferable because no harmful gas such as hydrogen fluoride is generated.

Examples of the gas containing the nitrogen element include gases such as nitrogen and ammonia, and mixed gases of these and hydrogen. In order to obtain sufficient hydrophilicity, the composition when the above mixed gas is used is preferably [N] / ([N] + [H]) of 0.25 or more, more preferably 0.5 to It is 1. However, [N] and [H] are composition ratios of N or H in the mixed gas.

Examples of the gas containing the elemental sulfur include gases such as sulfur dioxide and sulfur trioxide. These gases may be mixed and used. The sulfur dioxide gas may be obtained by generating sulfuric acid vapor.

The mixing ratio of the processing gas and the inert gas is determined by the type of gas used. When the concentration of the processing gas gas exceeds 10% by volume, a uniform discharge plasma is obtained even if a voltage is applied. Is less likely to occur, so 0.01 to 1
It is preferably 0% by volume, more preferably 0.01 to 5% by volume. .

The above-mentioned pressure near the atmospheric pressure means 100 to 8
Refers to a pressure of 00 Torr. The pressure is preferably in the range of 700 to 780 Torr, which facilitates pressure adjustment and makes the apparatus simple.

The plasma treatment is performed by facing electrodes, a solid dielectric material provided on at least one facing surface of the electrodes,
It is carried out in an apparatus composed of a plasma generating part which is a space between the metal electrodes and a pipe which supplies a mixed gas of the processing gas and the inert gas to the plasma generating part.

Examples of the electrodes include those made of simple metals such as copper and aluminum, alloys such as stainless steel and brass, and intermetallic compounds. Examples of the structure of the electrode include a parallel plate type, a cylindrical opposed flat plate type, a spherical opposed flat plate type, a hyperboloid opposed flat plate type, a coaxial cylindrical type, and a structure including a plurality of thin wires and a flat plate.

The above-mentioned solid dielectric is closely attached to the pair of electrodes so as to completely cover the surface of one of the electrodes facing the other. If there is a portion that is not covered, arc discharge occurs from that portion, which is not preferable. As the solid dielectric, polytetrafluoroethylene,
Examples thereof include plastics such as polyethylene terephthalate, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, and double oxides such as barium titanate.

The solid dielectric may be in the form of a sheet or a film, but the thickness is preferably 0.05 to 4 mm. If it is too thick, a high voltage is required to generate discharge plasma, and if it is too thin, dielectric breakdown occurs when a voltage is applied and arc discharge occurs.

The porous body is arranged in a plasma generating portion which is a space between the electrode and the solid dielectric which face each other or between facing surfaces of the solid dielectrics. The treatment is performed on the portion in contact with the generated discharge plasma, but since it is a three-dimensional mesh-like porous body having continuous ventilation holes, the treatment is performed not only on the surface but also inside the pores. In the example of the attached drawing, since the porous body and the solid dielectric are in contact with each other,
No treatment is applied to this contact area. When it is desired to treat the entire porous body, it is necessary to float the porous body in the space.

The distance between the electrodes is determined by the thickness of the solid dielectric,
The thickness is appropriately determined depending on the thickness of the porous body, the magnitude of the applied voltage, the flow rate of the mixed gas, etc., but is preferably 1 to 30 mm. If it is less than 1 mm, the gas used is wasted, which is not suitable. If it exceeds 30 mm, it is difficult to generate uniform discharge plasma.

Generation of the discharge plasma is performed by applying a voltage between the electrodes. The voltage is appropriately determined, but when applied, the electric field strength is 1 to 40 kV / cm.
It is preferable that This is because if it is less than 1 kV / cm, the treatment takes too long, and if it exceeds 40 kV / cm, arc discharge occurs. The power supply unit required for applying the voltage is not particularly limited, but when the heat resistance of the porous body is low, the frequency is preferably 5 to 30 kHz.

The discharge plasma treatment is performed in a mixed gas of a treatment gas and an inert gas. The mixed gas should be uniformly supplied to the plasma generating part. Since the inert gas is lighter than the processing gas, it is preferable that the device be devised so as to avoid nonuniformity during supply. In the example shown in the accompanying drawings, the processing gas is supplied from an inlet pipe through an electrode having a porous structure.
The inert gas is supplied to the plasma generation unit from an introduction pipe different from the above-mentioned processing gas. The structure is not limited to such a structure as long as the gas can be supplied uniformly, and a means such as stirring or blowing the gas at a high speed may be used.

The apparatus for performing the above discharge plasma treatment is
It is in a container equipped with an inlet pipe for processing gas and an inert gas and an outlet for excess gas. Examples of the material of the container include glass, metals such as stainless steel and aluminum which are insulated from the electrodes.

The above-mentioned discharge plasma treatment may be carried out by heating or cooling the porous body, but it is sufficiently possible at room temperature.

The time required for the discharge plasma treatment is appropriately determined depending on the magnitude of the applied voltage and the mixed gas used.

The method of imparting hydrophilicity to the three-dimensional mesh-like porous material in the invention according to claim 3 of the present invention (hereinafter referred to as the present invention 2) includes the following steps. (1) A three-dimensional mesh-like porous body in which a solid dielectric is provided on at least one of opposing surfaces of opposing electrodes, and communication holes are provided between the electrode and the solid dielectric or between opposing surfaces of the solid dielectrics. And the discharge plasma treatment is performed on the porous body under a pressure near the atmospheric pressure of the mixed gas of the processing gas and the inert gas or the inert gas. (2) The porous body subjected to the above treatment is immersed in a solution of a hydrophilic monomer, and a hydrophilic polymer chain is graft-copolymerized with the porous body.

In the step (1), the discharge plasma comes into contact with the surface of the porous body, and the surface of the porous body becomes a starting point of the grafting reaction carried out in the step (2). Radicals are formed.

The plasma treatment of the above step (1) is the same as that of the present invention 1 except for the points described below.

As the processing gas in the above plasma processing, the following gases can be used. These may be used alone or in combination. As a substance which forms a peroxide group which is a starting point of graft polymerization, oxygen,
Examples of the gas include ozone, water, carbon monoxide, carbon dioxide, nitric oxide and nitrogen dioxide. Gases such as sulfur dioxide or sulfur trioxide may be used as the thiol group forming the starting point of the graft polymerization.

The mixing ratio of the processing gas and the inert gas is determined by the type of gas used, but when the concentration of the processing gas exceeds 10% by volume, a uniform discharge plasma is obtained even if a voltage is applied. Is less likely to occur, so 0.01 to 1
It is preferably 0% by volume, more preferably 0.01 to 5% by volume.

The time required for the discharge plasma treatment is appropriately determined depending on the magnitude of the applied voltage and the mixed gas used. Radicals and peroxide groups can be formed by short-time treatment. In the helium gas atmosphere, radicals and peroxide groups are formed by the treatment for 15 seconds. In order to form many thiol groups, it is preferable to extend the treatment time.

In the step (2), the radical, the peroxide group, the thiol group and the like formed in the step (1) are used as the starting points of the graft reaction to cause the porous body to undergo graft copolymerization of the hydrophilic monomer. is there. When a hydrophilic group is directly applied to the material, the hydrophilic group layer is thin and it is difficult to secure durability. On the other hand, in the hydrophilic polymer chain formed according to the second aspect of the present invention, since the site that imparts hydrophilicity is bonded to the graft copolymer chain, the durability is excellent.

The above-mentioned discharge plasma-treated porous body is immersed in a solution of a hydrophilic monomer. The hydrophilic monomer preferably has an unsaturated bond site and a site having hydrophilicity. Examples of the hydrophilic portion include a hydroxyl group, a sulfonate group, a sulfonate group, a primary or secondary group.
Examples thereof include hydrophilic groups such as secondary or tertiary amino group, amide group, quaternary ammonium salt group, carboxylic acid group and carboxylate group, polyethylene glycol chain and the like. The monomers include acrylic acid, methacrylic acid, acrylamide,
Methacrylamide, N, N-dimethylacrylamide,
Sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, sodium styrenesulfonate, allyl alcohol, allylamine,
Examples include polyethylene glycol dimethacrylate and polyethylene glycol diacrylate. The above monomers are used alone or as a mixture.

The above hydrophilic monomer is dissolved in a solvent,
Used as a solution of a hydrophilic monomer. Examples of the solvent include organic solvents such as methanol, ethanol, and acetone, and water. The above solvents are used alone or as a mixture.

The concentration of the hydrophilic monomer solution varies depending on the type of hydrophilic monomer used, but is preferably 5 to 30% by weight from the viewpoint of efficient reaction. If the concentration is too high, unreacted monomers will remain in the solution, and if the concentration is too low, the time required for the reaction will be long.

The method for graft-copolymerizing a hydrophilic polymer chain on the above-mentioned porous body is not particularly limited, but radical polymerization of the hydrophilic monomer in which the porous body is immersed is initiated, and radicals at the end of the growing chain and the porous body. Of producing a graft copolymer by reacting the thiol group of, a redox initiator is added to the hydrophilic monomer solution in which the porous body is immersed, and the redox initiator is reacted with the thiol group of the porous body to start the thiol group. The method of graft-copolymerizing hydrophilic monomers by redox polymerization, the method of initiating graft polymerization from radicals formed in the porous body, and the thermal decomposition of peroxide groups in the monomer solution to generate radicals Examples of the points include a method of graft polymerization.

After graft copolymerization of the hydrophilic polymer, if unreacted hydrophilic monomer, homopolymer of the hydrophilic monomer or the like is attached to the porous body, water, an organic solvent or the like is used. It is preferable to wash the porous body to remove these deposits.

[0038]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 Apparatus shown in the attached drawing (made of Pyrex glass, capacity: 5
L), the upper electrode 4 (stainless steel (SUS30
4) Made, size: φ120mm, φ1mm hole is 1cm
Spaced) and lower electrode 5 (made of aluminum, size:
A titanium dioxide sintered body (size: φ120 mm, thickness: 2 mm) was installed as a solid dielectric on the lower electrode in a space of 10 mm between electrodes (φ100 mm), and a polyester non-woven fabric (as a porous body) A product manufactured by Japan Vilene Co., Ltd., product / night: PS / 150, size: φ100 mm) was placed. Evacuation was performed by an oil rotary pump until the inside of the apparatus became 1 Torr. Next, flow helium gas at a flow rate of 500 scc
At m, the gas was introduced from the gas introduction pipe 9 until the inside of the apparatus reached 757 Torr. Voltage of 15kHz: 3.1kV is applied to the electrode 1
Plasma was generated by applying for 5 seconds, and the polyester nonwoven fabric was subjected to discharge plasma treatment.

Example 2 Discharge plasma treatment was carried out in the same manner as in Example 1 except for the following points. Quartz glass (size: 120 mm x 120 mm, as a solid dielectric in a space of 10 mm between electrodes)
(Thickness: 2 mm) was installed. Helium gas flow rate 995
The flow rate of sulfur dioxide gas is 5 from the gas introduction pipe 9 at sccm.
At a sccm, the gas was introduced from the gas introduction tube 8 through the upper electrode 4 having a porous structure (the composition of the gas in the apparatus was 0.5 vol% sulfur dioxide / helium), and a voltage of 2.8 kV was applied to the electrode. It was applied for 15 seconds to generate plasma.

Example 3 The discharge plasma treatment was performed in the same manner as in Example 1 except for the following points. The distance between the electrodes was set to 9 mm, and the sprayed film of zirconium partially stabilized with 8 wt% yttrium oxide as a solid dielectric in the electrode space (size: φ120
mm, thickness: 500 μm). Helium gas was introduced from the gas introduction pipe 9 at a flow rate of 990 sccm, and oxygen gas was introduced from the gas introduction pipe 8 at a flow rate of 10 sccm through the upper electrode 4 having a porous structure (the composition of the gas in the apparatus is 1% by volume).
It is oxygen / helium. ), And a voltage of 4.1 kV was applied to the electrodes for 15 seconds to generate plasma.

Example 4 The discharge plasma treatment was performed in the same manner as in Example 1 except for the following points. The distance between the electrodes was set to 9 mm, and polytetrafluoroethylene (size: 120 mm × 120 mm, thickness: 1 mm) was placed as a solid dielectric in this electrode space. Helium gas at a flow rate of 990 sccm and gas introduction pipe 9
Then, nitrogen gas was introduced at a flow rate of 10 sccm from the gas introduction pipe 8 through the upper electrode 4 having a porous structure (the composition of the gas in the apparatus was 1% by volume nitrogen / helium), and 3.8 kV was applied to the electrode. Was applied for 15 seconds to generate plasma.

Example 5 <Step (1)> Discharge plasma treatment was carried out by the method described in Example 1. <Step (2)> The non-woven fabric obtained in the step (1) was immersed in a degassed 10 wt% sodium styrenesulfonate aqueous solution and kept at 50 ° C. for 2 hours to carry out a reaction. Next, the non-woven fabric was taken out of the solution and subjected to ultrasonic cleaning in warm water to obtain a treated product. When the treated product was analyzed by X-ray photoelectron spectroscopy (XPS), a sulfur peak derived from a sulfonic acid group was confirmed.

Example 6 <Step (1)> Discharge plasma treatment was carried out by the method described in Example 2 except that the voltage application time was changed to 1 minute. <Step (2)> The above-mentioned discharge plasma-treated nonwoven fabric was washed with running water for 1 minute. After washing, the non-woven fabric was immersed in a degassed 10 wt% acrylamide aqueous solution, kept at 70 ° C. and left standing for 4 hours to cause a reaction. Next, the non-woven fabric was taken out of the solution and subjected to ultrasonic cleaning in warm water to obtain a treated product. When the treated product was analyzed by X-ray photoelectron spectroscopy (XPS), a peak of an amide group derived from acrylamide was confirmed in the C1s spectrum.

Example 7 <Step (1)> Discharge plasma treatment was carried out by the method described in Example 6 except that the following points were changed. Helium gas was introduced at a flow rate of 990 sccm from the gas introduction tube 9 and oxygen gas was introduced at a flow rate of 10 sccm from the gas introduction tube 8 through the upper electrode 4 having a porous structure (the composition of gas in the apparatus is 1
Volume% oxygen / helium. ), And a voltage of 4.1 kV was applied to the electrodes for 15 seconds to generate plasma. <Step (2)> The non-woven fabric that has been subjected to the discharge plasma treatment is dipped in a degassed 10 wt% acrylic acid aqueous solution to obtain 50
The reaction was carried out by keeping it at 0 ° C. for 2 hours. Next, the non-woven fabric was taken out of the solution and subjected to ultrasonic cleaning in warm water to obtain a treated product. Treated products with X-ray photoelectron spectroscopy (XPS)
As a result, the peak of the carboxyl group derived from acrylic acid was confirmed in the C1s spectrum.

Example 8 <Step (1)> Discharge plasma treatment was performed by the method described in Example 4 except that the following points were changed. Helium gas was introduced from the gas introduction pipe 9 at a flow rate of 990 sccm, and nitrogen gas was introduced from the gas introduction pipe 8 at a flow rate of 10 sccm through the upper electrode 4 having a porous structure (the composition of gas in the apparatus is 1
Volume% nitrogen / helium. ), And a voltage of 4.1 kV was applied to the electrodes for 1 minute to generate plasma. <Step (2)> The above-mentioned discharge plasma-treated nonwoven fabric was washed with running water for 1 minute. After washing, the non-woven fabric was immersed in a degassed 10 wt% N, N-dimethylacrylamide aqueous solution, cerium diammonium nitrate (IV) was added as an initiator, and the mixture was allowed to stand at 30 ° C. for 2 hours for reaction. Let it be done. Next, the non-woven fabric was taken out of the solution and subjected to ultrasonic cleaning in warm water to obtain a treated product. When the processed product was analyzed by X-ray photoelectron spectroscopy (XPS), N,
The peak of the amide group derived from N-dimethylacrylamide was confirmed in the C1s spectrum.

Comparative Example The same polyester non-woven fabric as in Examples 1 to 8 was used without treatment.

<Reuse Experiment> 300 g of carbon black
The non-woven fabric to be treated was immersed in 1 liter of pure water in which was dispersed for 5 minutes. The non-woven fabric having carbon black adhered thereto was dried at 60 ° C. for 1 hour and then immersed in pure water for 30 minutes. The water permeability after immersion was measured as an indication of the amount of carbon black removed from the nonwoven fabric by immersion in water. The same process was repeated until the transmittance became 50% or more. If the surface of the non-woven fabric is hydrophilized, the carbon black can be easily removed only by immersing it in water, and can be dispersed in the water after immersing. When the water permeability was 50% or less, it was determined that the carbon black had been sufficiently removed from the surface of the nonwoven fabric, and this was set as the number of times that cleaning could be performed easily. These results are shown in Table 1 together with the conditions of the examples.

[0049]

[Table 1]

[0050]

INDUSTRIAL APPLICABILITY In the present invention, by forming a hydrophilic group on the three-dimensional network porous body constituting the filter or by graft-polymerizing a hydrophilic monomer,
Hydrophilicity can be imparted to the porous body. Since a filter having a hydrophilic surface can easily remove dirt by washing with water, it is possible to reuse a filter that has been conventionally thrown away.

[0051]

[Brief description of drawings]

FIG. 1 is a schematic diagram of a discharge plasma processing apparatus of the present invention.

[Explanation of symbols] 1 power supply 2 Pyrex glass container 3 discharge plasma generation part 4 upper electrode 5 lower electrode 6 solid dielectric 7 three-dimensional meshed porous body 8 gas inlet pipe 9 gas inlet pipe 10 gas outlet 11 exhaust outlet

[Procedure amendment]

[Submission date] November 20, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction contents]

Example 8 <Step (1)> Discharge plasma treatment was performed by the method described in Example 4 except that the following points were changed. The helium gas from the gas introduction pipe 9 at a flow rate 990Sccm, dioxide
Sulfur gas was introduced at a flow rate of 10 sccm from the gas introduction pipe 8 through the upper electrode 4 having a porous structure (the composition of the gas in the apparatus was 1% by volume sulfur dioxide / helium), and then the electrode was formed.
A voltage of 3.6 kV was applied for 2 minutes to generate plasma. <Step (2)> The above-mentioned discharge plasma-treated nonwoven fabric was washed with running water for 1 minute. After washing, the non-woven fabric was immersed in a degassed 10 wt% N, N-dimethylacrylamide aqueous solution, cerium diammonium nitrate (IV) was added as an initiator, and the mixture was allowed to stand at 30 ° C. for 2 hours for reaction. Let it be done. Next, the non-woven fabric was taken out of the solution and subjected to ultrasonic cleaning in warm water to obtain a treated product. When the processed product was analyzed by X-ray photoelectron spectroscopy (XPS), N,
The peak of the amide group derived from N-dimethylacrylamide was confirmed in the C1s spectrum.

Claims (3)

[Claims] 1. A three-dimensional mesh structure having a solid dielectric on at least one of the facing surfaces of facing electrodes and having a communicating hole between the electrode and the solid dielectric or between facing surfaces of the solid dielectrics. A method for producing a filter, wherein a porous body is disposed, and discharge plasma treatment is performed on the porous body under a pressure of a mixed gas of a processing gas and an inert gas or an inert gas in the vicinity of an atmospheric pressure. 2. A gas containing at least one element selected from oxygen, nitrogen and sulfur is used as the processing gas, and the processing gas is 0.01 to 10% by volume of the inert gas. The method for manufacturing the filter according to claim 1. 3. After the treatment according to claim 1, the three-dimensional network porous body is immersed in a solution of a hydrophilic monomer, and a hydrophilic polymer chain is graft-copolymerized on the porous body. Of manufacturing filter.