JPH1160417A - Antimicrobial agent, antimicrobial resin composition and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inorganic antimicrobial agent that has high antimicrobial properties and can manifest stabilized antimicrobial action by forming a coating layer of multiple oxide containing silver on the surface of fine particles of inorganic oxide with an average particle size of a specific value. SOLUTION: Fine powdery particles of an inorganic oxide as titanium oxide, silicon oxide, aluminum oxide, calcium carbonate, zinc oxide or barium sulfate with an average particle size of <=1 μm, preferably 0.1-1 μm are coated on their surfaces with multiple oxides of one or more kinds of elements selected from aluminum, silicon, zirconium and zinc and also silver in an amount of 1-10 wt.%, particularly 5-7 wt.%, preferably in addition the resultant powders are sputtered with a silver-zinc alloy (20-80 wt.% of silver and 80-20 wt.% of zinc and the coating weight is 0.1-10 wt.%, particularly 1-4 wt%), based on the weight of the titanium oxide and they are heat-treated in the air, at 300-400 deg.C for about 1 hour.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antibacterial agent and a method for producing the antibacterial agent, and more particularly to an antibacterial agent which exhibits antibacterial properties and fungicidal properties by being added or applied to resins, paints, fibers or cosmetics and the like. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In recent years, as the level of ordinary life has improved, the desire for cleanliness of daily necessities has increased.
In such an environment, surfactants, biguanides, alcohols, phenols, anilides, iodines, isodazoles, thiazoles, isothiazolones, triazines, nitriles, fluorines, and saccharides Organic antibacterial agents such as zeolite, silica gel, glass, calcium phosphate, zirconium phosphate, calcium silicate, titanium oxide, zinc oxide whisker, silica, and alumina. Inorganic antibacterial agents carrying metals such as silver, copper, and zinc having strong antibacterial activity have been developed. It is known that such a metal component exerts an antibacterial action by being ionized and eluted like silver ions, copper ions, and zinc ions.

[0003] Compared to organic antibacterial agents, inorganic antibacterial agents do not volatilize or decompose and have a small amount of metal eluted, so they have long lasting properties, are excellent in heat resistance, and have high safety to the human body. It has been evaluated and is expected to be used in a wider range. In particular, silver has a strong antibacterial effect and is used in most inorganic antibacterial agents. Such inorganic antibacterial agents are mixed with resins such as polyolefins, then molded and processed into various shapes such as fibrous, film or pellet, and used for various types of plastic products having fungicidal and antibacterial properties. It is used for

[0004]

However, inorganic antibacterial agents do not effectively exhibit antibacterial properties, and it has been necessary to add a large amount of antibacterial metal components in order to obtain a desired antibacterial activity. . For example, judging from the MIC value (minimum inhibitory concentration of bacteria) which is an indicator of antibacterial activity, the amount of the antibacterial agent added to Escherichia coli, Staphylococcus aureus and Aspergillus niger is 15 ppm for an organic antibacterial agent, respectively. 8 ppm
And about 3 ppm, whereas the inorganic antimicrobial agents require 125 ppm and 250 pp, respectively.
m and about 1000 ppm, which is 10 times or more the amount of the organic antibacterial agent. Furthermore, since inorganic antibacterial agents are more expensive than organic antibacterial agents, the use of such inorganic antibacterial agents in large amounts is not preferable from an economic viewpoint. When an inorganic antibacterial agent is used by adding it to a resin or the like, the dispersibility is poor and a larger amount of the antibacterial agent must be used.

[0005] In addition, silver having high antibacterial properties is used as an antibacterial metal of most inorganic antibacterial agents. When this silver is eluted as colorless silver ions, it exerts an antibacterial action. Oxidation produces metal aggregates or oxides that turn brown or black. In particular, when irradiated with ultraviolet rays, the released silver ions are reduced to metallic silver, so that discoloration is more likely.
In addition, when the amount of the inorganic antibacterial agent is increased, agglomeration of the powder is likely to occur, and the content of metallic silver is also increased, so that discoloration is likely to occur. As a result, the properties of the antibacterial agent gradually change, which may hinder long-term use, and there are also appearance problems such as discoloration of the product using the antibacterial agent to an undesirable color. I was

Accordingly, an object of the present invention is to solve such a problem and to obtain an inorganic antibacterial agent having high antibacterial properties and exhibiting a stable antibacterial action.

[0007]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive studies to solve the above problems, it has been found that it is an extremely effective means to have a coating layer in which the surface of a titanium oxide powder having an average particle diameter of 1 micron or less is coated with a composite oxide containing silver. Thus, the present invention has been completed. That is, the present invention provides an antibacterial agent characterized in that the element forming the coating layer is composed of one element or two or more elements selected from aluminum, silicon, zirconium or zinc and silver, and the production thereof. Is the way. Less than,
The present invention will be described in detail.

(1) Inorganic Oxide In the present invention, titanium oxide which can be used may be either a natural product or a synthetic product, and is classified into anatase, rutile and brookite according to the crystal system. In the present invention, any crystal system may be used. The shape may be any shape, and those generally used as white pigments can be used.

Further, the inorganic oxide according to the present invention can obtain the same effect by using silicon oxide, aluminum oxide, calcium carbonate, zinc oxide, barium sulfate or the like in addition to titanium oxide. The particle size of the inorganic oxide will be described later.

(2) Refinement of Inorganic Oxide In order to enhance the antibacterial properties of the inorganic antibacterial agent, it has been attempted to increase the specific surface area of the inorganic oxide to be supported to increase the elution rate of silver. . Conventionally, in order to increase the specific surface area of the powder, porous zeolite or porous silica gel having an average particle size of several μm is used, but since the average particle size is large and the dispersibility in the resin is poor, The mixing amount is still large.

[0011] The present inventors have found that the average particle size is 0.1 to
It has been found that titanium oxide powder of 1 μm has a large specific surface area and can be uniformly dispersed in a resin, and the mixing amount has been successfully reduced. For example, in the case of titanium oxide powder having an average particle size of about 0.3 μm, the specific surface area of the powder is 5 to 40 m ^2.
/ G, and it was confirmed that when the powder was dispersed in a resin, the dispersibility was better than that of the porous zeolite and the like.

(3) Method for Carrying Silver Conventionally, a coating layer containing a metal to be supported is formed on the surface of a fine powder of an inorganic oxide, and then subjected to a heat treatment at a high temperature.
The antibacterial metal was strongly bonded to the inorganic oxide. For this reason, although there was a sufficient effect on discoloration of the antibacterial metal and maintenance of the antibacterial property for a long period of time, the amount of elution into water was reduced, and the antibacterial property was reduced.

In the present invention, a coating layer is formed by coating an oxide coating of a certain element excluding the antibacterial metal on an inorganic oxide in advance, and then forming an alloy containing the antibacterial metal again by sputtering. A method was employed in which the film was coated on top and heat-treated and diffused under appropriate conditions. According to the present method, it is possible to form a coating layer containing an antibacterial metal without binding the antibacterial metal to the inorganic oxide, and the antibacterial agent produced by such a method has a dissolution rate of the antibacterial metal. Has been found to be able to maintain fast and stable antibacterial properties for a long period of time. The method for supporting silver is described below.

(A) Formation of Coating Layer In order to obtain a coating layer having the constitution of the present invention, first, aluminum, silicon,
It is necessary to form the coating layer in advance with one or more oxides of zirconium or zinc. This coating layer serves as a medium for diffusing silver which is an antibacterial metal. Here, the fact that the coating layer does not contain silver, which is an antibacterial metal, prevents silver from being eluted when the inorganic oxide and silver are directly bonded, so that it becomes necessary to add extra expensive silver. Because.

The coating layer is formed by a commonly known method in order to improve the properties such as hydrophilicity, lipophilicity, weather resistance, light resistance and heat resistance of the titanium oxide powder as a white pigment. Can be easily obtained. That is, a titanium oxide material produced by a sulfuric acid method or a chlorine method using ilmenite ore as a raw material is dry-pulverized, then water-dispersed by adding water and a dispersant, and coarsely classified by centrifugation. The fine slurry after classification is transferred to a surface treatment tank, where the metal oxide is coated on the surface. First, a predetermined amount of an aqueous solution of a salt such as aluminum, silicon, zirconium, zinc, antimony, or tin is added, and the mixture is neutralized with an alkali or an acid. I do. By-product water-soluble salts are removed by decantation, filtration and washing, and finally the pH of the slurry is reduced.
Adjust and filter, wash with pure. The washed cake is dried with a spray dryer or a hand dryer. Finally, the dried product is pulverized by a jet mill into a product. Further, by baking after coating the surface or coating the surface a plurality of times, the weather resistance and the light resistance can be further improved.

The coating amount of one or more oxides of aluminum, silicon, zirconium or zinc is 1 to 10% by weight (hereinafter simply referred to as%), especially 5 to 5% by weight of the inorganic oxide. 7% is preferred.

When the coating amount is less than 1%, the amount of the main coating layer is relatively small with respect to the amount of silver to be diffused, and the silver concentration in the coating layer becomes high. It is not preferable because it exhibits black color.

On the other hand, when the coating amount exceeds 10%, the amount of the main coating layer, which is a silver diffusion medium, becomes relatively large and the silver concentration in the coating layer becomes low for the opposite reason. For this reason, the dissolution rate of silver ions is reduced, and the antibacterial property is reduced, which is not preferable.

(B) Coating of silver-zinc alloy As a method for supporting silver, there is a method in which an antibacterial metal is directly supported on the surface of the inorganic oxide by a method such as an ion exchange method, a chelate method, or a comprehensive compound method. Various proposals have been made. The antimicrobial agents obtained by these methods have been improved in dispersibility, mixing properties and dissolution of antimicrobial metals in organic substances, so that they can be used more widely and safely than conventional ones. Even with the obtained antibacterial agent, discoloration and elution into water could not be completely solved, and after long-term use,
Since the supported antibacterial metal discolors or its properties gradually change, it may be difficult to withstand long-term use of the antibacterial agent.

Therefore, in the present invention, a method is employed in which the surface of the titanium oxide powder on which the coating layer is formed is coated with a silver-zinc alloy by sputtering. In the sputtering method,
Since the solid atoms are repelled, silver, which is an antibacterial metal, can be placed on the surface of the inorganic oxide coating layer, and can be put in a state most suitable for completely eluting silver.
In order to coat such alloys having completely different melting points and vapor pressures, a powder spattering device, for example, a device for spattering a metal into a fluidized bed formed by rotating a container containing powder (particularly, a device). This is realized by using Japanese Unexamined Patent Publication No. 2-153068. Then, a silver-zinc alloy film can be easily formed on the surface of each of the fine particles of titanium oxide provided with the coating layer.

The silver-zinc alloy used in the present invention has a silver content of 20 to
It is a binary alloy with a composition of 80% and 80-20% zinc. This is because, in the case of a single metallic silver, the diffusion of silver into the coating layer hardly proceeds even by the heat treatment described later, and the diffusion of silver can be achieved by the coexistence of zinc. In addition, since zinc also has an action as an ultraviolet absorber, it also plays a role in preventing discoloration of the silver component.

When the composition of the silver-zinc alloy is less than 20% silver and more than 80% zinc, the absolute amount of silver diffused into the coating layer is small, and the elution life of silver ions is shortened. , And is not preferable because it cannot be used for a long time.

On the other hand, when the composition of the silver-zinc alloy is in the range of more than 80% silver and less than 20% zinc, the amount of zinc in the coating layer is small, so that silver ions are not eluted and no antibacterial action is exhibited. That is, in order to promote the dissolution effect of silver, 20
% Of zinc must be contained.

The coating amount of the silver-zinc alloy is preferably 0.1 to 10%, more preferably 1 to 4%, based on the weight of titanium oxide.

When the coating amount is less than 0.1%, the absolute amount of silver supported on the inorganic oxide is small, and the antibacterial property is not exhibited unless a large amount of the inorganic antibacterial agent is mixed in the resin. Absent.

On the other hand, when the coating amount exceeds 4%, the amount of the inorganic antibacterial agent to be added becomes extremely small. However, when the amount is too small, it becomes difficult to disperse uniformly in the resin, and as a result, the amount exceeds the required amount. Inorganic antibacterial agents must be added, which is not an efficient method.

The silver-zinc alloy contains copper, nickel,
Chromium, cobalt, antimony, manganese, titanium, aluminum, molybdenum, tantalum, zirconium, niobium, tungsten, nitrogen, boron, phosphorus
Even if it contains a kind or two or more kinds of metals, the effect of the present invention is not affected as long as the total content is 10% or less. Metals such as copper and nickel may have antibacterial activity against specific bacteria such as thiopatillus bacterium, and thus may be preferably contained.

The present invention can be used in addition to the sputtering method, as long as the antibacterial metal component can be injected into the vicinity of the surface of the inorganic oxide coating layer, such as an ion plating method.

(C) Diffusion by heat treatment In order to keep silver on the surface of the film, it is conceivable to leave silver-zinc alloy as it is. The color of the powder is also grayish black, which is not preferable.

Then, the present inventors have developed an inorganic oxide having a coating layer obtained by coating a silver zinc alloy by a sprinkling method,
It has been found that when diffusion is performed by heat treatment under appropriate conditions, the elution rate of silver ions is accelerated by about 1,000 times. In addition, when the heat treatment is performed, the inorganic oxide becomes grayish white, and can be in a preferable state as an inorganic antibacterial agent.

Specifically, after a silver-zinc alloy is coated on the surface of the inorganic oxide by the sparging method, the silver-zinc alloy is coated with 30 g of air in the air.
When the temperature is maintained at 0 to 400 ° C. and heat treatment is performed for about 1 hour, silver in the silver-zinc alloy diffuses into the coating layer without directly bonding to the inorganic oxide, and a suitable amount of silver eluted And a stable antibacterial action can be obtained.

If the heat treatment temperature is lower than 300 ° C., the diffusion of silver into the coating layer cannot be sufficiently advanced, and a part of the silver remains as a silver-zinc alloy, so that it may elute as silver ions. It is not preferable because it cannot be performed. On the other hand, when the heat treatment is performed at a temperature exceeding 500 ° C., the diffusion of silver proceeds to the titanium oxide fine powder under the coating layer, and the silver is strongly bonded to the titanium oxide. Then, since a part of the coated silver component is used for binding the titanium oxide, the silver concentration in the coating layer decreases, and the elution rate of silver ions becomes extremely slow, which is not preferable.

(D) Resin molding of inorganic antibacterial agent After the inorganic antibacterial agent of the present invention is mixed with a resin such as polyolefin, it is molded and processed into various shapes such as fibrous, film or pellet. The well-known method generally used is sufficient.

In addition, fine powders of antioxidants such as titanium oxide, zinc oxide, aluminum oxide, calcium carbonate, barium sulfate, hydrotalcite compounds or aluminum silicate, ultraviolet absorbers and light stabilizers are separately mixed. Thus, discoloration due to silver ions during resin molding can be prevented, and the powder can be made whiter, which is more preferable.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
The present invention will be described in detail.

(Preparation of Antibacterial Agent) [First Embodiment] A surface of a commercially available fine powder of titanium oxide having an average particle diameter of 0.3 μm (manufactured by Teika Co., Ltd.) is coated with 5% by weight of alumina, and further, 1% by weight of 20% silver and 80% zinc alloy was coated by using a powder sprinkling apparatus developed by the inventors (JP-A-2-153068). Next, the titanium oxide fine powder coated with the silver-zinc alloy on the coating layer was placed on an alumina boat, placed in a muffle furnace, and heat-treated at 400 ° C. for 1 hour in the air.

[Second Embodiment] The surface treatment of titanium oxide fine powder was performed by coating with 10% by weight of alumina-silica, and the coating layer was coated with 2% by weight of 40% silver and 60% zinc alloy. The same operation as in the first embodiment was performed.

[Third Embodiment] The surface treatment of titanium oxide fine powder was performed by coating with 10% by weight of alumina-zirconia, and the coating layer was coated with 3% by weight of 60% silver and 40% zinc alloy. Performed the same operation as in the first embodiment.

[Fourth Embodiment] The surface treatment of titanium oxide fine powder was performed by coating with 7% by weight of alumina-silica-zinc, and the coating layer was coated with 4% by weight of 80% silver and 20% zinc alloy. Otherwise, the same operation as in the first embodiment was performed.

Comparative Example 1 The same operation as in the third embodiment was performed except that the surface treatment of the fine titanium oxide powder was not performed.

Comparative Example 2 The same operation as in the third embodiment was performed except that the coating layer of the titanium oxide fine powder was coated with 100% by weight of silver.

Comparative Example 3 The same operation as in the third embodiment was performed except that the heat treatment was not performed after coating the titanium oxide fine powder with the silver-zinc alloy.

Comparative Example 4 The same operation as in the third embodiment was performed except that the titanium oxide fine powder was not coated with the silver-zinc alloy.

(Evaluation of antibacterial agent) For 97.4 parts of polypropylene resin (J-740 manufactured by Mitsui Petrochemical Industries, Ltd.), 1.0 part of the prepared antibacterial agent was used, and an antioxidant (Irganox manufactured by Ciba Geigy Mori) was used. B-225) is 0.2
Part, UV absorber (Tinuvin 32 manufactured by Ciba-Geigy)
6), 0.2 parts of a light stabilizer (Sanol LS-770, manufactured by Ciba Geigy), and 1.0 part of zinc oxide fine powder (manufactured by Kojundo Chemical Laboratory, average particle size: 1 μm). , And uniformly mixed at 220 ° C. using an injection molding machine (Model VS50-28V manufactured by Tanabe Plastic Machinery Co., Ltd.).
Injection molding with 2mm thickness x 100mm length x 100m
An m-wide plate was prepared.

After visually determining the color tone of the molded plate, a test piece was cut out and subjected to an antibacterial test and a fungicide test.

[Test Example 1] (Antibacterial test) In an antibacterial test, a sterilized petri dish having a diameter of 90 mm was inoculated with 500 ml of a culture solution of Escherichia coli, and 10 ml of bouillon agar medium was poured into the medium. Was fixed and cultured at 37 ± 1 ° C. for 48 hours. The number of viable bacteria before and after the culture test was investigated, and the antibacterial activity was evaluated based on the degree of decrease in the number of viable bacteria.

[Test Example 2] (Mold resistance test) In the mold resistance test, 0.5 ml of the mixed spore suspension was inoculated into a sterilized petri dish having a diameter of 90 mm, 10 ml of an inorganic salt agar medium was poured, and immediately before solidification. A disk-shaped plate having the same diameter of 30 mm was fixed to the center of the nuclear plate medium and cultured at 28 ± 1 ° C. for 7 days. Then, the number of viable bacteria before and after the test was investigated, and the antifungal property was evaluated based on the degree of decrease in the number of spores.

Table 1 shows the evaluation results. The evaluation criteria in Table 1 are as follows: ++: very antibacterial or mold-resistant, +: antibacterial or mold-resistant, ±
Is weak but has antibacterial or fungicide resistance, and-is not antibacterial or fungicide resistant.

[0049]

[Table 1]

[0050]

As described above, the product of the present invention has an average particle size of 1
It has an antimicrobial agent that has a high antibacterial property, does not discolor, and exhibits a stable antibacterial action, because it has a structure that has a coating layer coated with a composite oxide containing silver on the surface of inorganic oxide fine powder of less than micron. be able to. And the resin composition using such an inorganic antibacterial agent is used for interior materials of houses, exterior materials,
It can be used in a wide range of fields such as wallpapers, carpets, unit baths, air conditioning filters, sanitary products, bath products, kitchen products, medical products, textiles for clothing, socks, stationery, water treatment products, food containers and packaging films.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Takeshima 1 at Nisshin Steel Co., Ltd., at 7 Takayashinmachi, Ichikawa-shi, Chiba

Claims (7)

[Claims] 1. An antibacterial agent having a coating layer coated with a composite oxide containing silver on the surface of a fine powder of an inorganic oxide having an average particle size of 1 μm or less. 2. An element forming the coating layer is selected from aluminum, silicon, zirconium and zinc.
The antibacterial agent according to claim 1, comprising a composite oxide composed of the element or two or more elements and silver. 3. The coating layer is formed by coating a surface of a fine powder of an inorganic oxide with a composite oxide composed of one element or two or more elements selected from aluminum, silicon, zirconium and zinc. Thereafter, a method for producing an antibacterial agent, which comprises coating a silver-zinc alloy by a sputtering method and further performing heat treatment to diffuse silver into the coating layer. 4. The method for producing an antibacterial agent according to claim 3, wherein the silver-zinc alloy has a composition of 20 to 80% by weight of silver and 80 to 20% by weight of zinc. 5. The method for producing an antibacterial agent according to claim 3, wherein the coating weight of the silver zinc alloy is 0.1 to 10% by weight based on the inorganic oxide fine powder. 6. The temperature range of the heat treatment is 300 to 400 ° C.
The method for producing an antibacterial agent according to claim 3, wherein the method is performed in a temperature range of: 7. An antioxidant, an ultraviolet absorber, a light stabilizer,
The antimicrobial resin composition according to claim 1 or 2, further comprising one or more additives selected from zinc oxide powder.