JPH08133919A - Solid substance having antimicrobial action, its production and antimicrobial action on liquid and its flow channel - Google Patents

Abstract

PURPOSE: To obtain a solid substance capable of minimizing the elution rate of silver and thus maintaining antimicrobial action for a long period of time. CONSTITUTION: This solid substance having antimicrobial action is obtained by forming a layer comprising silver particles on the surface of a substrate through a layer having a photocatalytic action on the substrate or forming the layer comprising the silver particles on a carrier having photocatalytic action and further making at least partially a slightly soluble silver salt (preferably silver chloride) on the surface of the layer comprising the silver particles. The antimicrobial agent comprising particles containing silver element supported through the layer having photocatalytic action on the substrate or the antimicrobial agent comprising particles containing the silver element supported on the carrier having photocatalytic action is immersed in a solution having >=30ppm and <3,000ppm chlorine concentration and the slightly soluble silver salt is formed to produce the solid substance. The antimicrobial agent is placed in a liquid or its flow channel and brought into contact with chlorine ion. Silver has high elution rate at an early stage but reduces it during the process of formation of the only slightly soluble silver salt. Silver is finally eluted in a fixed minimized elution rate to sterilize a liquid and its flow channel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid such as sewage or a solid substance having an antibacterial action which is placed and fixed in a channel thereof, and also relates to an antibacterial method for a liquid such as sewage or a channel thereof.

[0002]

2. Description of the Related Art As antibacterial methods for liquids such as sewage and the passage thereof, there are conventionally known methods using a photocatalyst, methods using an antibacterial metal, and methods combining them.
A method utilizing a photocatalyst is disclosed in Japanese Patent Publication No. 50294/1993, which discloses a sterilization reactor characterized in that it has a photosterilizable filler formed by immobilizing photosemiconductor fine particles on the surface of a base material. Successful sterilization of 99% or more in time.

On the other hand, however, Japanese Patent Publication No. 6-7905 points out a drawback of this method. Japanese Examined Patent Publication No. 6-7905 describes a photocatalyst layer made of a semiconductor, an ultraviolet lamp and a heating element provided opposite to the photocatalyst layer, and a blower. Or a photocatalyst deodorizing device in which a photocatalyst layer and a heating element move. Further, the following is stated as the purpose of making this device. That is, a mixture of polymer substances and dust adheres to the surface of the semiconductor, which is the catalyst that causes the photocatalytic reaction, and covers it, so that ultraviolet rays do not reach the catalyst, and it becomes difficult for the catalyst to receive energy, and the photocatalytic reaction deteriorates. However, it causes reaction deterioration. It is considered that such a phenomenon also occurs when it is used for antibacterial use, and particularly in a liquid such as sewage and its passages and contact portions, water is likely to occur because the mixture of these acts as a transport medium. Therefore, it is considered difficult to use the photocatalyst for a long period of time unless it is used in the above-mentioned apparatus.

A method using an antibacterial metal is disclosed in JP-A-2-
No. 19308 and the like. Japanese Unexamined Patent Publication No. 2-1930
No. 8 has an antibacterial property having a film forming ability obtained by substituting at least a part of the ion-exchangeable metal contained in the layered silicate with at least one metal selected from silver, copper and zinc. Disclosed are silicates, specifically silver montmorillonite. This silver montmorillonite is certainly excellent in initial antibacterial properties. Further, since it is sterilized by the eluted silver ions, the effect extends to the solution unlike the photocatalyst which requires contact.

However, as disclosed in Japanese Patent Laid-Open No. 6-65012, since the supporting power of silver on montmorillonite is weak, the elution rate is fast and it cannot withstand long-term use. Further, in an environment where a large amount of alkali metal ions or alkaline earth metal ions are present, such as a liquid such as sewage, its passages, and contact parts, the fixation of silver by such an ion exchange method is effective in fixing these alkali metal ions and alkaline earth ions. It is considered that the exchange of metal ions with silver occurs suddenly and the dissolution of silver is accelerated, so that the effect is lost in a shorter period of time.

Therefore, a method of combining a photocatalyst and silver is disclosed in JP-A-6-65012. Japanese Unexamined Patent Publication No. 6-65012 discloses an antibacterial and antifungal ceramics in which a substrate is coated with a titanium oxide film containing at least one metal ion selected from silver, copper, zinc and platinum. The effect is basically a photocatalytic action by the titanium oxide film and an antibacterial action by at least one metal ion selected from silver, copper, zinc and platinum. The following is disclosed as one role. That is, by changing the thickness of the titanium oxide film and the amount of contained metal, or by further coating the platinum film on the titanium oxide film and changing the thickness, the sustained release (elution) rate or life of the contained metal can be improved. It is said that it can be controlled.

[0007]

However, the method disclosed in Japanese Patent Laid-Open No. 6-65012 has the following problems. Changes in the thickness of the titanium oxide film and in the amount of contained metal are both controls of the absolute amount of silver contained in the film, and the life of the antibacterial and antifungal ceramics is certainly governed by it. However, in order to prolong the life of the antibacterial and antifungal ceramics, the sustained release (elution) rate should be minimized within an effective range. It is understood that the sustained release (elution) rate is rather controlled by how strongly silver is fixed to the titanium oxide film. Japanese Patent Laid-Open No. 6-65012 does not disclose that point of view. However, a method of further coating the platinum film on the titanium oxide film and changing the thickness thereof is one embodiment. However, in this method, the number of platinum coating steps is increased by one, and an expensive platinum film must be coated, which is a cost problem. In view of the above, the present invention has an object of extending the life of the antibacterial and antifungal material by minimizing the sustained release (elution) rate without applying platinum.

[0008]

In order to solve the above problems, the present invention forms a layer of silver particles on the surface of a substrate through a layer having a photocatalytic action on the substrate, and further comprises silver particles. A solid substance having an antibacterial action is characterized in that a hardly soluble silver salt is formed at least partially on the surface of the layer.

Further, an antibacterial agent in which particles containing a silver element are carried through a layer having a photocatalytic action on a substrate is disposed in the liquid and its flow path, and silver and a sparingly soluble salt are provided on the anti-surface thereof. The antibacterial method is characterized in that the liquid and its flow path are antibacterial by contacting the formed anions.

Here, the liquid such as sewage is, for example, sewage after washing of kitchen, bathroom, basin, etc., urine water, bath water, circulating water of artificial fountain, pool water, cooling water for air conditioning, etc. . The flow path of liquid such as sewage is the part where the above-mentioned water comes into contact. The air supply part, the exhaust part, and the circulation path of the artificial fountain.

The material of the carrier is ceramic, ceramic material,
Basically any material such as metal, glass, thermosetting resin, thermoplastic resin, or a composite thereof may be used. However, when a layer having a photocatalytic action is formed from an oxide semiconductor layer,
Generally, it is necessary to heat-treat at a high temperature of 300 ° C. or higher, and thus ceramic or ceramic material having excellent thermal stability is preferable. In the case of ceramics, ceramic materials and metals, it is preferable that they are porous from the viewpoint of weight reduction.

The shape of the carrier may be any of spherical, cylindrical, cylindrical, prismatic, hollow prismatic, rod-like, plate-like, powdery, and lump-like, but it is preferable that the corners and edges are not sharp. The reason is that if there are corners and edges, the degree of adhesion of silver to those portions is likely to change, and mechanically weak and preferentially peeling or elution is likely to occur. Further, the cylindrical or hollow prismatic shape has an advantage that the weight of the member can be reduced.

The layer having photocatalytic action is a layer mainly composed of particles having photocatalytic action. If the particles mainly having the photocatalytic action are included, a small amount of particles that do not cause the photocatalytic action may be included. Examples of such particles include a sintering aid added to improve the strength of the layer.

The layer having a photocatalytic action may be applied to the entire surface of the carrier or a part thereof. However, it is preferable to apply the entire surface because the absolute amount of silver firmly supported on the carrier can be increased, and since there is no terminal end, peeling or elution from the portion does not occur preferentially. The layer having the photocatalytic action may be directly supported on the carrier, or may be through an adhesive layer. However, especially when the shape is plate-like, it is preferable to interpose an adhesive layer because the bonding strength is improved. Here, as the material of the adhesive layer, an inorganic thermoplastic material such as glaze, an inorganic thermosetting material such as silicon resin, an organic thermoplastic material such as acrylic resin,
Any organic thermosetting material such as epoxy resin may be used. However, an inorganic thermoplastic material such as a glaze or an inorganic thermosetting material such as a silicone resin is more preferable because it is not decomposed by a photocatalytic action and can be heat-treated at a high temperature of 300 ° C. or higher.

The particles having a photocatalytic action are basically sufficient if they have a band gap to the extent that silver can be precipitated from a silver salt upon irradiation with light, but it is more preferable that the particles themselves also have an antibacterial action. There is also a theory that a semiconductor having a photocatalytic action has an antibacterial action, which causes electrocution when a voltage higher than a predetermined voltage is applied (Japanese Patent Publication No. 4-29393), but it is generally considered to be due to active oxygen generated during light irradiation. ing.
In order to generate active oxygen, the position of the semiconductor conduction band is above the hydrogen generation potential when represented by a band model,
In addition, the upper end of the valence band needs to be below the oxygen generation potential. For semiconductors that meet this condition, TiO2, S
rTiO3, ZnO, SiC, GaP, CdS, CdS
e, MoS3, etc. When atomized, the position of the conduction band shifts upward. Therefore, if the layer can be composed of fine particles of about 1 to 10 nm, SnO2, Fe2O3, WO3, Bi
2O3 and the like may also have antibacterial properties. Note that the particles having a photocatalytic action which form the layer having a photocatalytic action may be made of one kind of substance or may be made of two or more kinds of substances.

The particle size of the particles containing the elemental silver is not particularly limited, but an average particle size of 10 nm or less is preferable because the surface activity is high and therefore it is firmly supported on the lower layer and the adjacent silver.

The method of supporting the particles containing the silver element includes a method of heat treatment, a method of photoreduction, etc., but basically any method may be used. However, it is preferable that the particles containing the elemental silver are firmly bonded to the carrier or the substrate to some extent, and for that purpose, the method by photoreduction is more preferable.

An embodiment in which the particles containing the elemental silver are firmly bonded to the substrate to some extent is shown below. First, a precursor of particles having a photocatalytic action is applied to a base material and baked to obtain a composite member. This composite member is irradiated with light while rotating in a metal salt solution containing silver ions to fix ultrafine silver particles of 10 nm or less on the surface of the base material. After that, a portion weakly adsorbed in multiple layers on the substrate surface is removed by a method such as applying ultrasonic waves.

Further, silver and anions are reacted with each other to form a sparingly soluble silver salt on the layer of particles containing silver element. Examples of the anion include chlorine ion, carbonate ion, phosphate ion, iodine ion, bromine ion, oxalate ion, and oxygen ion.

The method of forming the sparingly soluble silver salt on the layer of particles containing silver element is as follows: The member containing particles of silver element fixed on the surface of the substrate is immersed in the solution containing the above anion. A sparingly soluble silver salt may be produced on the surface of the antibacterial agent, or an antibacterial agent in which particles containing a silver element are fixed to the surface of the base material is arranged in the liquid and its flow path, and the liquid contains the anion. You may make silver contact the said anion by supplying a solution.

The method of forming the sparingly soluble silver salt on the layer of particles containing silver element is as follows. The member in which the particles containing silver element are fixed on the surface of the substrate is immersed in the solution containing the above anion. The method of producing a sparingly soluble silver salt on the surface of the antibacterial agent is excellent in that the elution rate of silver can be minimized from the initial stage and stable control can be performed.

Further, the antibacterial agent in which particles containing silver element are fixed on the surface of the base material is placed in the liquid and the flow path thereof, and the solution containing the anion is supplied to the liquid to supply silver and the anion. In the method of contacting with ions, the initial elution rate is large and the bactericidal power is excellent, and then the elution rate decreases in the process of forming the sparingly soluble silver salt, and the surface of the antibacterial agent is covered with the sparingly soluble silver salt. Control will then be controlled with a minimized constant elution rate. Therefore, by reducing the number of bacteria in the initial stage, such as when the bacteria are proliferating remarkably in the flow path at the initial stage or in the case of static water such as pool water, the reproduction speed of the bacteria is significantly suppressed. This type is rather advantageous in situations where it is possible.

The antibacterial agent may be irradiated with light including ultraviolet rays. This is because the photocatalytic action existing in the lower layer can be utilized and the antibacterial activity is increased. If the anion is chlorine ion, if it is several ppm or more, it has an effect of suppressing the elution rate of silver. Therefore, since the effect is produced also by tap water, the antibacterial agent in which the particles containing the silver element are fixed to the surface of the base material is arranged in the liquid and the flow path thereof, and the solution containing the anion is supplied to the liquid. In the method of bringing silver into contact with the above-mentioned anions, it is not necessary to provide chlorine supply means other than water supply except for the mountainous region. Further, the effect of suppressing the elution rate of silver is particularly large in halide ions other than fluoride ions, and among them, chloride ions are preferable because they can be obtained at the lowest cost.

The larger the amount of anions, the more completely the surface of the antibacterial agent is covered, so that the elution rate of silver can be minimized and kept constant, which is preferable. However, if too much is added, the surface of the antibacterial agent becomes white and the translucency is lost, so that it becomes difficult to utilize the antibacterial effect of the underlying layer having a photocatalytic action, which is not preferable. For example, in the case of chlorine ions, if 30 ppm is added, the surface of the antibacterial agent will be covered with chlorine ions, and the elution rate of silver will be constant. However, if 3000 ppm or more is added, the antibacterial agent surface loses its light-transmitting property.

[0025]

The silver in the outermost layer reacts with anions to form a sparingly soluble silver salt, whereby the elution rate of silver can be minimized. Thereby, the antibacterial property is maintained for a long time.

[0026]

【Example】

Example 1 Ammonia deflocculating suspension of TiO 2 sol having an average particle diameter of 0.01 μm was applied to a porous alumina ball having a diameter of 5 mm by a spray coating method to give 700
After repeating the process of firing for 1 hour at ℃ twice, soak it in an aqueous solution of silver nitrate and rotate the ball well to make BLB
After the silver particles were fixed on the entire surface of the ball by the step of irradiating the lamp for 20 minutes, the silver excessively adhered was removed by ultrasonic dispersion and washed thoroughly with water to obtain an antibacterial agent sample. The crystal form of TiO2 at this time was anatase. The particle size of the supported silver particles was about several nm to 10 nm. The elution rate of silver and the antibacterial property of the obtained samples were evaluated by the following methods.

The elution rate of silver was evaluated by the following method. First, after preliminarily immersing in 80 vol% ethanol for 2 hours,
Five antibacterial agent samples dried at 0 ° C. for 2 hours were mixed with various solvents 10
Put it in a sterilization test tube together with ml, and use a 30 ° C incubator for 24
Left for hours. Then, it was filtered with a 0.45 μm membrane filter and analyzed by atomic absorption (Hitachi 6000 flame type).

The antibacterial property was evaluated by the following method. First, after preliminarily immersing in 80 vol% ethanol for 2 hours,
Five antibacterial agent samples dried at 0 ° C. for 2 hours were mixed with various solvents 10
It was put in a sterilized test tube together with ml and left for 3 hours in a 30 ° C. incubator. Thereafter, the antibacterial agent sample was taken out, washed in an autoclave at 121 ° C. for 20 minutes, immersed in 80 vol% ethanol for 2 hours, and then dried at 50 ° C. to wash the surface.
Next, E. coli ( Escherichia coli W
3110 strain) in various media at 105 CFU / ml
What was adjusted to 1 was sampled in a sterilized 1 ml sample bottle, one antibacterial agent sample was put therein, and the number of bacteria was examined after left for several hours in a 30 ° C. shaker. The chlorine content in the solvent used here was about 10% for artificial urine and about 10 p for broth.
It is less than 1 ppm in pm and ultrapure water.

As a result, the elution amount of silver was 16.7 with ultrapure water.
ppm, 9.13 ppm in broth medium and 1.84 ppm in artificial urine. The larger the chlorine content, the smaller the elution amount of silver. Table 1 shows the initial antibacterial properties when the antibacterial agent samples were allowed to stand in various solvents. As a result, the number of residual bacteria was less than 10 cells / ml, which was a good result even when left in artificial urine with a low dissolution rate of silver.

[0030]

[Table 1]

Table 1 shows the antibacterial properties after 2 months when the antibacterial agent samples were left in various solvents. As a result, the number of residual bacteria was 1 even when left in artificial urine with the dissolution rate of silver.
No change was observed at less than 0 cells / ml, indicating sufficient antibacterial properties. From the above results, it was found that the higher the chlorine content is, the smaller the silver elution amount is, and the sufficient antibacterial property is exhibited for a long period of time despite the small elution amount.

Comparative Example A 1% by weight silver nitrate aqueous solution was directly applied to an alumina porous ball having a diameter of 5 mm by a spray coating method and dried to prepare a solid product.
The size of the silver particles fixed on the obtained solid was slightly larger than that of the example and was about several nm to 100 nm. With respect to this sample, the elution amount of silver after 24 hours, the initial antibacterial property, and the antibacterial property after 1 month were evaluated by the same method as in Example 1 (in a broth medium). As a result, 24
The elution amount of silver after the lapse of time was as large as> 100 ppm. The initial antibacterial property is as good as 101 cells / ml, but 1
It was found that the antibacterial activity after 10 months was 103 to 104 cells / ml, and the effect was almost lost.

Example 2 The antibacterial agent sample formed in Example 1 was used to evaluate the amount of silver eluted depending on the concentration of chloride ions. The chlorine concentration was evaluated by preparing an ammonium chloride aqueous solution and changing the concentration of ammonium chloride. The results are shown in Table 2.

[0034]

[Table 2]

As a result, as shown in the conceptual diagram 1, the elution rate rapidly decreased until the chloride ion concentration reached 30 ppm.
It was observed that above 0 ppm, it became almost constant. This phenomenon can be explained as follows. First, up to 30 ppm (region of FIG. 1), as shown in FIG. 2, fast elution from the Ag layer and slow elution from the part where AgCl is formed simultaneously occur. And as the chloride ion concentration increases, AgC
The forming part of 1 increases, and the rate of rapid elution from the Ag layer decreases. Therefore, as the chloride ion concentration increases, the elution rate decreases. On the other hand, as shown in FIG. 3, the Ag layer is AgC at 30 ppm or more (region of FIG. 1).
l will be completely covered. Therefore, only the slow elution from AgCl occurs, and the elution rate of silver becomes constant.

The amount of elution of silver decreases at 30 ppm or more because silver chloride is formed on the film containing silver element particles formed on the photocatalyst layer, and the silver chloride on the film is reduced. It seems that this is due to the elution of. Also, some fluctuations
It is considered that desorption of silver chloride in the outermost layer causes some elution from the layer containing silver element particles.

[0037]

[Effects of the Invention] An antibacterial agent in which particles containing a silver element are supported on a substrate through a layer having a photocatalytic action, and an anion forming a sparingly soluble salt with silver are brought into contact with each other to make the sparingly soluble silver. By forming a salt on the surface of the antibacterial agent, the elution rate of silver on the antibacterial agent can be suppressed, whereby the life of the antibacterial agent can be extended.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between chlorine concentration and silver elution rate.

FIG. 2 is a diagram showing the elution state of silver up to a chlorine concentration of 30 ppm.

FIG. 3 is a diagram showing a silver elution state at a chlorine concentration of 30 ppm or more.

Claims (11)

[Claims] 1. A substrate is provided with a layer having a photocatalytic action,
A solid substance having an antibacterial action, characterized in that a layer made of silver particles is formed on the surface of a base material, and a hardly soluble silver salt is formed at least partially on the surface of the layer made of silver particles. 2. A carrier having a photocatalytic action, wherein a layer composed of silver particles is formed on the surface of the carrier, and further, a sparingly soluble silver salt is formed at least partially on the surface of the layer composed of silver particles. A solid substance having an antibacterial action characterized by: 3. The solid substance having an antibacterial action according to claim 1, wherein the hardly soluble silver salt is silver chloride. 4. An antibacterial agent in which particles containing a silver element are supported on a substrate through a layer having a photocatalytic action, and a chlorine concentration of 30 is used.
A method for producing a solid substance having antibacterial properties, which comprises immersing in a solution having a concentration of not less than 3000 ppm and less than 3000 ppm. 5. A method for producing a solid substance having antibacterial properties, which comprises immersing an antibacterial agent in which particles containing a silver element are supported on a carrier having a photocatalytic action in a solution having a chlorine concentration of 30 ppm or more and less than 3000 ppm. 6. An antibacterial agent in which particles containing a silver element are carried on a liquid and a channel thereof through a layer having a photocatalytic action on a substrate, and the surface of the antibacterial agent is hardly soluble with silver ions. An antibacterial method for a liquid and its flow path, which comprises contacting salt-forming anions. 7. An anion which forms an antibacterial agent in which a particle having a silver element is carried on a carrier having a photocatalytic action in a liquid and a channel thereof, and forms a sparingly soluble salt with silver ions on the surface of the antibacterial agent. An antibacterial method for a liquid and its flow path, which comprises contacting ions. 8. An antibacterial agent, in which a particle containing a silver element is carried on a liquid and its flow path on a substrate through a layer having a photocatalytic action, and the surface of the antibacterial agent is sparingly soluble in silver ions. An antibacterial method comprising contacting with anions that form a silver salt and irradiating with light including ultraviolet rays. 9. A liquid and an antibacterial agent in which particles containing a silver element are carried on a carrier having a photocatalytic action are disposed in a flow path of the liquid, and a silver ion hardly soluble with silver ions is formed on the surface of the antibacterial agent. Antibacterial method characterized by contacting with anions and irradiating with light including ultraviolet rays 10. The antibacterial method for a liquid and its flow path according to claim 6, wherein the anion is chloride ion. 11. The concentration of the chloride ion in the liquid is 30.
The antibacterial method for the liquid and the flow path thereof according to claim 10, wherein the content is at least ppm and less than 3000 ppm.