JP2001162116A - Antibacterial treatment method and antibacterial filter medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter medium containing extra fine fibers, a technique to realize excellent filtration performance and antibacterial property when a filter unit in which the filter medium is assembled is coated with an antibacterial agent to be immobilized, a antibacterial filter medium having a wide antibacterial spectrum and excellent filtration performance. SOLUTION: When the filter medium containing extra fine fibers having 5 μm or finer fiber diameter is coated with the antibacterial agent to be immobilized, a water-based coating liquid containing a self-cross-linking acrylic resin and the antibacterial agent is applied to the filter medium, which is then heat- treated at 60 deg.C or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter medium composed of relatively fine fibers and a filter unit in which the filter medium is incorporated in a frame material in order to impart antibacterial properties to a filter medium used for air purification. The present invention relates to an antibacterial treatment method and a filter medium which includes relatively fine fibers and which can realize excellent antibacterial properties and filtration performance.

[0002]

2. Description of the Related Art A filter medium for purifying air is incorporated in various air conditioners as a filter unit and is used for collecting dust and the like. Depending on the required characteristics of the filter medium, fibers of different fiber diameters may be used alone or in combination.However, in order to increase the collection efficiency, melt-blown fibers and split fibers are used to reduce the distance between fibers. A fiber having a small fiber diameter of about 5 μm or less (hereinafter referred to as an ultrafine fiber) is used. In order to obtain a large amount of dust, a fiber that is thicker than the above fiber is used to increase a distance between fibers. A secure approach is used.
As an example, a filter medium in which a melt-blown non-woven fabric composed of ultrafine fibers and a short-fiber non-woven fabric having a length of about 20 μm or more are laminated,
As proposed in Japanese Patent Application Laid-Open Publication No. H10-209, a fiber web in which a melt-blown fiber having a fiber diameter of less than 1 μm and a heat-fusible fiber having a fiber diameter of 5 to 100 μm are uniformly mixed is a structure in which the heat-fusible fibers are bonded by the heat-fusible fiber. Filter media and the like are known.

[0003] As described above, various bacteria and molds in the air are liable to adhere to the filter medium having high efficiency due to the inclusion of the ultrafine fibers as dust is collected. For this reason, a technique for imparting antibacterial properties to the fiber material constituting the filter medium is required. As an example of such an antibacterial property imparting technique, there is known a technique in which various antibacterial agents are preliminarily mixed and added to a resin constituting a fiber and spinning is performed. However, this technique is suitable for relatively thick fibers, and if the fiber diameter during spinning is relatively small, nozzle clogging or yarn breakage during or after spinning is likely to occur. Further, the resin temperature during spinning is extremely high, and the antibacterial agent itself may be deactivated. Therefore, the imparting of antibacterial properties by spinning is limited to antibacterial agents having high heat resistance, and application of the technique to the above-mentioned ultrafine fibers involves considerable difficulty in consideration of thread breakage and the like. For this reason, as an antibacterial treatment technology that is not easily restricted by the heat stability of the antibacterial agent and the thickness of the fibers constituting the filter medium, a technique of attaching and drying a coating liquid containing an antibacterial agent and a binder to the filter medium is used. Conceivable.

On the other hand, in order to reduce the amount of industrial waste in recent years, attention has been paid to a filter unit washing / recycling technique which has conventionally been disposable. Such cleaning and regeneration are performed by immersing a filter unit configured by incorporating a filter medium into a frame material in a predetermined cleaning agent. Therefore, following such a washing step, it is desired to attach an antibacterial agent to impart antibacterial properties to members constituting the filter unit. In particular, the filter medium is exposed not only to dust, bacteria, and mold but also to moisture in the air, so that dew condensation may occur depending on the use environment. Many antibacterial agents have polarities and are easily eluted by dew condensation. For this reason,
In order to perform the antibacterial treatment at the time of regeneration of the filter unit, the most practical treatment technique is to adhere and fix the antibacterial agent with a binder. Various binders are known, but in addition to the physicochemical stability such as thermal stability, photochemical stability and oxidation resistance of the binder itself, advantages such as ease of handling due to emulsion formation. Therefore, an acrylic resin is used.

[0005]

SUMMARY OF THE INVENTION The inventor of the present invention has made it possible to impart antibacterial properties to the above-described filter medium containing ultrafine fibers even during regeneration of the filter unit by using various acrylic resins. The antibacterial agent was applied and fixed, and its antibacterial properties and filter media performance were examined. As a result, a reactive acrylic resin requires heating at, for example, 100 ° C. or higher, usually about 130 ° C.
For example, in the case of a melt-blown fiber made of a polypropylene resin having a relatively low softening point, by performing the treatment at a curing temperature necessary for this curing, a morphological change of the filter medium due to the softening of the ultrafine fibers occurs, and the pressure loss of the filter medium is remarkable. It was found that it would increase. If this point is described in detail, even when a fiber composition containing heat-fusible fibers is used, a heat treatment for bonding between fibers is performed, but the thermosetting of the binder is performed in a state where a liquid material such as an emulsion liquid adheres to the filter medium. Heat treatment. Therefore, as compared with the dry heat treatment performed for the inter-fiber bonding, the heat curing treatment of the binder, which is the wet heat treatment, has a greater thermal effect on the fibers. For this reason, there has been a problem that it is extremely difficult to apply a technique of curing a binder at a high temperature to a filter medium containing ultrafine fibers and to impart antibacterial properties without impairing the filtration performance.

The inventor of the present application has conducted intensive studies to solve the various problems described above, and as a result, by performing an antibacterial treatment using a specific binder, it was possible to prevent a decrease in filtration performance as a filter medium, and to obtain an excellent filter. We have completed a technology that can exhibit antibacterial properties. Accordingly, an object of the present invention is to provide a filter medium containing ultrafine fibers, and a technique capable of realizing excellent filtration performance and antibacterial property when applying and fixing an antibacterial agent to a filter unit incorporating the same. Another object of the present invention is to provide an antibacterial filter medium having a broad antibacterial spectrum and excellent filtering performance.

[0007]

In order to achieve this object, according to the antibacterial treatment method of the present invention, an antibacterial agent is fixed to a filter medium containing ultrafine fibers having a fiber diameter of 5 μm or less. In this method, an aqueous coating solution containing a self-crosslinking acrylic resin and an antibacterial agent is attached to the above-mentioned filter medium, and then heat-treated at a temperature of 60 ° C. or lower.

Further, according to the antibacterial treatment method according to another method invention of the present application, a method for attaching and fixing an antibacterial agent to a filter unit in which a filter medium containing ultrafine fibers having a fiber diameter of 5 μm or less is incorporated in a frame material. After adhering an aqueous coating solution containing a self-crosslinking acrylic resin and an antibacterial agent to the filter unit, heat treatment is performed at a temperature of 60 ° C. or less.

Further, according to the constitution of the antibacterial filter medium according to the present application, the filter medium containing microfibers having a fiber diameter of 5 μm or less is provided with antibacterial properties, and the silver-organic iodine antibacterial agent is provided. Are adhered and fixed to the ultrafine fibers by crosslinking of a self-crosslinking acrylic resin.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an antibacterial treatment method according to the present invention will be described below.
According to the method of the present invention, a water-based coating liquid containing a self-crosslinking acrylic resin and an antibacterial agent is applied to a filter medium containing ultrafine fibers, or a filter unit incorporating the filter medium, and heat-treated at a predetermined temperature. Configuration. First, as the self-crosslinking acrylic resin applied to the method of the present invention, a resin that can be cured at or below the softening temperature of the constituent resin of the ultrafine fibers constituting the filter medium can be arbitrarily and suitably selected. In the case of a polypropylene resin which is likely to be generated, it is desirable to cure at a heat treatment temperature of 60 ° C. or lower, and more preferable to cure at 50 ° C. or lower. As such a self-crosslinking acrylic resin that can be cured at a low temperature, one having an average molecular weight of 15,000,000 or more is desirable.

The composition of the aqueous coating liquid is such that the weight ratio of the solid content of the self-crosslinking acrylic resin is 1 ma.
ss% to 5 mass%, preferably 1 mass% to 3 mass
% Is desirable. If a large amount of acrylic resin is added beyond this range, the specific gravity of the water-based coating liquid increases, and the thickness tends to be crushed when the liquid is attached to the filter medium and dried. Further, if the amount is less than this range, it becomes difficult to hold the antibacterial agent in the filter medium.

Next, the antimicrobial agent applied to the present invention will be described. In applying the method of the present invention, the antibacterial agent is not particularly limited, and the method can be applied and fixed at a low temperature of 60 ° C. or less by applying the self-crosslinking acrylic resin. Not only can the morphological change of the fiber be reduced, but also the range of selection of the antibacterial agent can be expanded. Further, as the filter medium incorporated in the filter unit to which the present invention is applied, a filter medium composed of only ultrafine fibers, a filter medium formed by laminating a nonwoven fabric made of ultrafine fibers and a nonwoven fabric having a relatively large diameter, or the aforementioned publication May be a filter medium in which ultrafine fibers and fibers having a diameter larger than this are uniformly mixed as one fiber web. Among these, in the case of a filter medium composed of a mixture of different diameter fibers, the proportion of the ultrafine fibers is not particularly limited, but when the ultrafine fibers contained in the filter medium are 20 mass% or more, the morphological change described above occurs. It is easy to come and the effect of applying the method of the present invention can be expected.

Next, the antibacterial filter medium according to the present invention will be described. As described in the above method invention, the configuration of the present filter medium may include a large-diameter fiber as long as it includes ultrafine fibers having a fiber diameter of 5 μm or less. Mixed with, or
A web composed of the respective fibers may be laminated. As the resin constituting the ultrafine fibers, any resin may be used as long as it is conventionally known.Polyolefin resins such as polypropylene, polyethylene, and the like widely used as filter media, polycarbonate resins, polyurethane Examples of the melt-blown fibers include polypropylene-based resins in which the fiber diameter can be easily controlled.

The self-crosslinkable acrylic resin used in the filter medium according to the present invention may be the same as that described in the above method invention. In particular, the solid content after crosslinking, that is, the adhered acrylic resin Among them, the weight ratio of the completely crosslinked resin is at least 60 mass% or more, preferably 8 mass% or more.
By setting it to 0 mass% or more, stable antibacterial properties can be maintained even when the filter medium condenses. In order to obtain such a solid content ratio, a known method is used, for example, after coating and drying a resin on a glass plate, the coated glass plate is exposed to running water at room temperature for 24 hours, and the weight immediately after the formation of the coating film is measured. In contrast, it can be calculated by calculating the percentage of the weight of the resin remaining without being eluted in running water. Further, by using a silver-organic iodine-based antibacterial agent as the antibacterial agent applied to the antibacterial filter medium of the present invention, a wide antibacterial spectrum can be realized as described later. The adhesion amount of the self-crosslinking acrylic resin and the silver-organic iodine antibacterial agent in the filter medium can be arbitrarily and suitably designed according to the design. If the amount of resin adhered is less than the above-mentioned preferred range, it becomes difficult to adhere and fix the antibacterial agent. If the amount of resin adhered beyond this range, the morphological change of the filter will be promoted. The amount of the antibacterial agent adhered was determined by the MIC (minimum inhibitory concentration: Min.
Imum Inhibitory Concentration), and it is difficult to expect antibacterial properties at a concentration lower than this.

[0015]

EXAMPLES Hereinafter, preferred examples of the present invention and a test for confirming the effect of the antibacterial filter medium obtained by the method will be described as examples. In the following embodiments, specific conditions will be exemplified. However, the present invention is not limited to only these embodiments, and any suitable design changes and modifications can be made within the above-described purpose. Can be.

First, a nonwoven fabric having a surface density of about 20 g / m ² consisting of ultrafine fibers having an average fiber diameter of about 2 μm was prepared by a melt blow method using commercially available polypropylene pellets. Also, 3.3 made of polyethylene terephthalate
5. Decitex short fiber 35 mass%, made of the same resin
35 mass% of short fibers of 7 decitex and 30 mass% of short fibers of 7.8 decitex made of modacrylic resin in which vinyl chloride is dispersed and blended as a flame retardant;
/ M ² of card web was prepared. These two types of nonwoven fabrics were laminated and fused and integrated by an ultrasonic seal (seal area 5%) to obtain a filter medium.

Next, an acryl-styrene emulsion (average molecular weight: 20,000,000, solid content ratio by running water method: 80%) was used as a self-crosslinking acrylic resin for antibacterial treatment.
%) And a commercially available silver-organic iodine antibacterial agent “MBA-C-
0520 "(trade name, manufactured by Nippon Applied Chemical Industry Co., Ltd.) to obtain an aqueous coating liquid containing 2% by mass of the self-crosslinking acrylic resin and 0.25% by mass of the antibacterial agent.
After impregnating the above-mentioned filter medium with the aqueous coating solution, the excess coating solution is allowed to flow naturally, and the solution is cooled at about 40 ° C.
The antibacterial filter material according to the example was obtained by drying for an hour.

Also, an antibacterial filter material according to a comparative example was obtained under the same conditions as in the above example except that the drying conditions were 140 ° C. for 10 minutes. The pressure loss of the antibacterial filter media according to each of these Examples and Comparative Examples was measured in accordance with a standard method at a surface wind speed of 10 cm / sec. Table 1 shows the results. still,
"Initial pressure loss" indicates the measurement result before the treatment with the aqueous coating liquid, and the ratio in parentheses indicates the ratio of the pressure loss after the antibacterial treatment to the initial pressure loss in percentage.

[0019]

[Table 1]

As can be understood from the results in Table 1, the present invention was applied, and even if heating was performed after the antibacterial treatment at a relatively low temperature, the pressure loss could be equal to the initial pressure loss. When the heating was performed at such a high temperature that the fiber morphology changed, the pressure loss increased by about 20%. Although a detailed description is omitted, a commercially available reactive acrylic resin is used in place of the self-crosslinking acrylic resin, and the pressure loss is measured on the filter medium under the same conditions as in the examples and comparative examples. 1
A clear increase in pressure loss was observed in the heat treatment at 40 ° C., and the same results as in Table 1 were obtained.

Subsequently, the filter medium which has not been subjected to the antibacterial treatment is
After pleating each, a filter unit was obtained which was attached to a frame material made of plywood and aluminum with a hot melt resin. Thereafter, the filter unit was mounted on an air conditioner and operated for 2150 hours. The used filter medium of the filter unit was collected, sampled by a food stamp method, and then potato dextrose agar (PDA). ) Was used as a culture medium, and the grown microorganisms were identified. Since mold was mainly identified at this time, the following 70 species were selected as the bacterial species for the inoculation test described later. (1) Acuremonium charticola (2) Alternaria alternata (3) Alternaria bassicicola (4) Alternaria candidus (5) Alternaria tenuis (6) Aspergillus flavus (7) Aspergillus fumigatus (8) Aspergillus glaucus (9) Aspergillus nidulanlus (10) Aspergillus nidulanlus (10) (11) Aspergillus ochraceus (12) Aspergillus oryzae (13) Aspergillus restrictus (14) Aspergillus terreus (15) Aspergillus versicolor (16) Aureobasidium pullulans (17) Botrytis cinera (18) Candida albicans (19) Ceresspora beticola (obo) (21) Cladosporium cladosporioides (22) Cladosporium herbarum (23) Cladosporium resinae (24) Cladosporium shaerospermum (25) Epicoccum purpurascens (26) Eurotium tonophilum (27) Fusarium moniliforme (28) Fusarium oxysporium (um) (31) Fusarium semitectum ( 2) Fusarium solani (33) Geotricham candidum (34) Geotricham lactus (35) Gliocladium virens (36) Microsporum canis (37) Monilia fructigana (38) Mucor mucedo (39) Mucor racemosus (40) Myrothecium verrucaria (41) Nigrospora 42) Penicillium citreo-viride (43) Penicillium citrinum (44) Penicillium digitatum (45) Penicillium expansum (46) Penicillium funiculosum (47) Penicillium frequentance (48) Penicillium islandicum (49) Penicillium lilaciill (50) iciumium nigricans (52) Penicillium notatum (53) Penicillium rubrum (54) Pestalotia adusta (55) Pestalotia neglecta (56) Phoma glomerata (57) Phoma terrestius (58) Pullularia pullulans (59) Rhizopus delemar (60) Rhizopus ric oryzae (62) Rhizopus storonifer (63) Trichoderma koningii (64) Trichoderma viride (65) Trichophyton ajelloi (66) Trichophyton gypseum (67) Trichophyton mentagrophytes (68) Trichophyton roseum (69) Trichophyton rubrum (70) Wallemia sebi

Next, a filter unit was prepared using the antibacterial filter medium according to the example obtained by the above-described procedure, and the above 70 molds were inoculated to the filter unit. First, according to a standard method, cells are dispersed for each bacterial species in a physiological saline solution containing a surfactant, and after germinating cells are removed by a glass bead filter, the filtered dispersion is centrifuged and redispersed. And the number of spores in this dispersion was counted by turbidimetry. Thereafter, the spores of each bacterial species were mixed so that the number of spores became equal, to prepare a spore dispersion for inoculation. Subsequently, a petri dish containing a potato dextrose agar (PDA) medium was prepared, and the filter medium of the example cut into a predetermined size was spaced apart from the dish, and the spore dispersion liquid for inoculation was sprayed on the entire surface of the petri dish. It was done by doing. After that, the inoculated petri dish was cultivated in an incubator (temperature: 30 ° C., relative humidity: 95%) for 7 days, 14 days, 21 days and 30 days from the start.
The growth of the mold was observed on each day of the day.

As a result, no mold growth was observed inside and on the surface of the filter medium, and it was found that the filter medium according to the examples had extremely excellent antibacterial properties. In addition, mold growth was observed in the medium portion directly sprayed with the spore dispersion liquid for inoculation, and the suitability of the test method was confirmed. Further, using a reactive acrylic resin, a filter medium according to another comparative example subjected to a heat treatment at 40 ° C. for 15 hours was prepared, and was exposed to running water for 24 hours together with the filter medium according to the above-described example. .
Thereafter, the antibacterial test was carried out. As a result, the filter medium of the example using a self-crosslinking acrylic resin had the same antibacterial property as before the exposure to running water, whereas the reactive acrylic resin was used. In the filter media of the other comparative examples, remarkable mold growth was observed. From this, it has been clarified that when a reactive acrylic resin is applied, curing is insufficient under heat treatment conditions that do not cause morphological change of a filter medium containing ultrafine fibers, and lacks water resistance to dew condensation and the like.

In addition, a filter unit incorporating the antibacterial filter medium of the example was attached to an air conditioner and operated for 2150 hours. As a result, no mold growth was observed.
From this, it became clear that the antibacterial property of the filter medium according to the present example was maintained for a long time.

Next, after assembling the filter unit using the above-mentioned filter medium which has not been subjected to the antibacterial treatment, the filter unit was immersed in the above-mentioned aqueous emulsion liquid, except that the unit was immersed in the above-mentioned aqueous emulsion. The treatment was performed to produce an antibacterial filter unit. A filter material and a frame material constituting the filter unit were collected and subjected to an inoculation test according to the method described above. As a result, irrespective of whether the filter unit was used or not, the same antibacterial property as that obtained when only the filter material was subjected to the antibacterial treatment was also observed for the frame material. From this, it is clear that when the method invention according to the present application is applied to a used filter unit, it is possible to impart antibacterial properties not only to the filter medium but also to the members constituting the filter unit. Was. No significant increase in pressure loss was observed before and after the antibacterial treatment of the filter unit. From these facts, the method invention according to the present application is effective not only in the antibacterial treatment of the filter medium but also in the application to the used filter unit, and is applied to the environmentally friendly cleaning and regeneration of the unit. It became clear that we could do that.

[0026]

As is clear from the above description, by applying the method of the present invention, it is possible to reduce the morphological change of the ultrafine fibers due to the heat treatment required during the antibacterial treatment. It is possible to provide a filter medium which can prevent a decrease in filtration performance and exhibit excellent antibacterial properties, and a filter unit incorporating the filter medium.
Further, the configuration of the filter medium according to the present application realizes an antibacterial filter medium having a broad antibacterial spectrum and excellent filtering performance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D06M 15/263 D06M 15/263

Claims (5)

[Claims] When an antibacterial agent is adhered and fixed to a filter medium containing ultrafine fibers having a fiber diameter of 5 μm or less, a water-based coating liquid containing a self-crosslinking acrylic resin and an antibacterial agent is adhered to the filter medium. An antibacterial treatment method for a filter medium, which comprises heat-treating at a temperature of not more than ℃. 2. An aqueous coating solution containing a self-crosslinking acrylic resin and an antibacterial agent is applied when a filter medium containing ultrafine fibers having a fiber diameter of 5 μm or less is applied and fixed to a filter unit incorporated in a frame member. An antibacterial treatment method for a filter unit, comprising heat-treating the filter unit at a temperature of 60 ° C. or less after being attached to the filter unit. 3. The antibacterial treatment method according to claim 1, wherein the self-crosslinkable acrylic resin has an average molecular weight of 15,000,000 or more. 4. The method according to claim 1, wherein the antibacterial agent is a silver-organic iodine antibacterial agent. 5. An antibacterial filter medium in which an antibacterial property is imparted to a filter medium containing ultrafine fibers having a fiber diameter of 5 μm or less, wherein a silver-organic iodine antibacterial agent is crosslinked by a self-crosslinking acrylic resin to the ultrafine fibers. An antibacterial filter medium which is adhered and fixed.