JP2002179514A - Antifungal agent, method of producing the same and antifungal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antifungal agent that can manifest excellent antifungal properties, even when the agent is kneaded together with a resin, without discoloration of the resin, in a short time after it is applied, even in the case of a small amount of the agent applied. SOLUTION: In this antifungal agent, the diffusion layers of silver are formed on the surface of zinc oxide fine particles with an average particle size of <=1 μm in scattered dots and zinc oxide is exposed on the surface of the fine particles. The fine particles of zinc oxide are covered on their surfaces with 1-10 mass % of silver in the scattered dot form, then they are heated at 400-800 deg.C in an inert gas atmosphere whereby the silver is diffused on the zinc oxide fine particles to form the diffused silver layer thereon in the scattered dot form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as an uncolored additive or coating agent for resins, paints, fibers, cosmetics, and the like, and has an antibacterial agent exhibiting excellent antibacterial properties, a method for producing the same, and a compounded antibacterial agent. It relates to a resin composition.

[0002]

2. Description of the Related Art With an improvement in the living environment level, a desire for cleanliness has become stronger. As various kinds of daily necessities used in the daily life, those provided with antibacterial properties are preferred.
Antimicrobial agents that impart antimicrobial properties are broadly classified into organic and inorganic. Inorganic antibacterial agents have less volatilization and decomposition and have a smaller elution amount than organic antibacterial agents, so that they maintain excellent antibacterial properties over a long period of time. In addition, since it has excellent heat resistance and high safety for the human body, it is expected to be used in a wide range of fields.

As inorganic antibacterial agents, zeolite, silica gel, glass, calcium phosphate, zirconium phosphate,
It is known that inorganic powders such as calcium silicate, titanium oxide, zinc oxide, silica, and alumina carry a metal such as silver, copper, and zinc exhibiting an antibacterial action. Above all,
Silver, which has a strong antibacterial effect, is used in most inorganic antibacterial agents. For example, after blending an inorganic antimicrobial agent with a resin such as polyolefin, it is molded into various shapes such as fibrous, film, and linear, and is used in various applications as an antibacterial plastic product. I have.

However, it is difficult for an inorganic antibacterial agent to effectively exhibit antibacterial properties, and a large amount of an inorganic antibacterial agent is required to obtain a desired antibacterial property. For example, the MIC value of the antibacterial agent itself against Escherichia coli, Staphylococcus aureus, Aspergillus niger, etc. (minimum inhibitory concentration of the fungus) is 15 ppm, 8 ppm, and 3 pp for typical organic antibacterial agents, respectively.
m, 125 ppm, 250 ppm, and 1000 ppm for typical inorganic antibacterial agents, respectively.
The antibacterial property is as large as about 1/50 of that of the organic antibacterial agent. It is also a disadvantage of inorganic antibacterial agents that antibacterial properties are extremely difficult to express when kneaded into the resin. It is considered that the difficulty in exhibiting the antibacterial property is that it takes a long time until the metal such as silver, copper, zinc or the like is ionized by the moisture permeating the resin and moves to the resin surface.

[0005]

When a surfactant is added to a polyolefin resin or an ABS resin, the antibacterial property of the inorganic antibacterial agent kneaded into the resin is developed in a relatively short time (Japanese Patent Laid-Open No. 8-208945). No.). However, the mere expression of a surfactant does not provide sufficient antibacterial properties. It is also known that an inorganic antibacterial agent previously coated with a water-soluble polymer such as polyvinyl alcohol is added to the resin (Japanese Patent Application Laid-Open No. 9-48638). Sex expression is not enough.

By the way, the present inventors have proposed that the average particle diameter is 1 μm.
A sputtering method in which the surface of the following zinc oxide fine powder is covered with silver or a silver alloy in a scattered manner has been proposed (Japanese Patent Laid-Open No. 11-2).
63705). In addition, after coating in air 200 ~
It was introduced that a coagulated layer of silver or a silver alloy is formed when heated to 1000 ° C. (JP-A-11-228306).

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, in the process of studying the physical properties of a fine powder having a silver or silver alloy coating layer or an aggregation layer formed thereon, a scattered coating layer or an aggregation layer is effective for improving antibacterial properties. By further developing the knowledge and modifying the silver coating layer into a silver diffusion layer, a smaller amount of addition is required compared to conventional inorganic antibacterial agents, and discoloration of the resin is suppressed. It is another object of the present invention to provide an antibacterial agent which exhibits excellent antibacterial properties in a short time.

In the antibacterial agent of the present invention, in order to achieve the object, a silver diffusion layer is formed on the surface of zinc oxide fine powder having an average particle diameter of 1 μm or less in a scattered manner, and zinc oxide is exposed on the surface of the powder particles. It is characterized by doing. This antibacterial agent is used to powder the surface of zinc oxide
After coating in the form of spots with silver of mass%, the silver is diffused into the zinc oxide fine powder by heating to 400 to 800 ° C. in an inert gas atmosphere to form a spot-like silver diffusion layer. Manufactured. By adding this antibacterial agent to molding resins, paint resin coatings, adhesive resins, cosmetics, and the like at a ratio of 0.1 to 10% by mass, various products having a given antibacterial property can be obtained.

[0009]

As a result of various investigations and studies on the antibacterial agent kneaded into the resin, the present inventors have found that the smaller the particle size of the antibacterial agent, the more excellent antibacterial properties are exhibited in a shorter time.
The effect of the particle size on the time required for the development of antibacterial properties is attributable to the fact that the smaller the particle size, the higher the specific surface area of the powder, and accordingly the higher the silver elution rate. Investigation of the effect of the powder particle size on the time required for the antibacterial agent to exhibit the antibacterial property of the antibacterial agent having a silver diffusion layer formed on the powder surface revealed that zinc oxide fine powder having an average particle size of 1 μm or less is used. It was clarified that the amount of silver eluted significantly increased. An increase in the amount of silver eluted means that sufficient antibacterial properties are exhibited in a short time even if the mixing ratio of the antibacterial agent kneaded into the resin is reduced.

The relationship between the particle size of the zinc oxide fine powder and the silver diffusion layer and the silver elution rate is presumed as follows. For example, zinc oxide fine powder having an average particle size of 0.8 μm has a large specific surface area of about 7 m ² / g, and is extremely uniformly dispersed even when kneaded into a resin in a small mixing ratio of 0.1 to 1% by weight. In addition, since the silver diffusion layer is formed on the surface of the zinc oxide fine powder, the contact area per unit weight of silver with the resin is increased. Further, in combination with the fact that zinc oxide has an effect of promoting silver elution, silver elution is started early,
The dissolution rate also increases. On the other hand, in porous zeolites or silica gels having an average particle size of several μm to several tens μm, the particle size is large, and the supported silver is taken into the porous structure of the zeolite or silica gel, so that the weight per unit weight of the resin is The effective contact area is not so large. Therefore, it is necessary to increase the blending ratio in order to secure the amount of silver eluted necessary for exhibiting antibacterial properties.

In general, in a resin composition in which silver-coated zinc oxide fine powder or silver ion-supporting zeolite is kneaded, a chemical reaction occurs at the interface between silver and the resin due to heat during melting of the resin or ultraviolet irradiation during use of the resin molded product. Is likely to occur, and the resin molded product may turn yellow as a result of the chemical reaction. Yellowing tends to occur when an antibacterial agent having a large silver coating amount is used to enhance antibacterial properties, or when the amount of silver coating or silver-carrying antibacterial agent in a resin is increased. Coloring of the resin due to the chemical reaction between silver and the resin is suppressed by thermally diffusing the silver coating layer into the zinc oxide fine powder. Although the mechanism of this suppression is not fully understood, it is supposed that one of the causes is that the silver concentration gradient at the interface between the resin and the antibacterial agent particles is moderated by silver diffusion into zinc oxide.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Fine zinc oxide powder having an average particle diameter of 1 μm or less is prepared by a method of thermally decomposing zinc oxalate at 400 ° C. in air, a method of heating and dehydrating zinc hydroxycarbonate, a method of burning metallic zinc, and the like. . Report that the zinc oxide fine powder alone exhibits antibacterial properties (Japanese Unexamined Patent Publication No. 5-140331).
JP-A-8-59890), but has extremely weak antibacterial properties as compared with silver and copper. Further, if a large amount of zinc oxide fine powder is mixed with the resin to supplement the antibacterial property, heat resistance and mechanical properties are reduced. For this reason, it is not practical to use zinc oxide fine powder alone as an antibacterial agent.

As a method of directly supporting silver on the surface of the inorganic powder, an ion exchange method, a chelate method, an inclusion compound method and the like have been conventionally proposed. However, in such a wet method, zinc oxide itself is water-soluble although only slightly (solubility in water at 18 ° C .: 0.42 mg / 100 m 2).
l) Since zinc oxide is an amphoteric oxide and reacts with acid to form a zinc salt, and reacts with alkali to form a zincate and dissolves well in water, silver is supported on the surface of zinc oxide fine powder. Not applicable to letting

No need for water at all, zinc oxide fine powder particles 1
As a method of directly forming the silver coating layer 2 on the surface of FIG. 1, a dry process such as a sputtering method, vacuum deposition, or ion plating is employed. Among them, the powder sputtering method is preferable because the entire amount of silver is present on the surface of the zinc oxide fine powder particles 1 so that the elution of silver proceeds easily. In the powder sputtering method, silver vapor is sputtered toward zinc oxide fine powder particles 1 which are maintained in a fluidized state in a rotating container, and a silver coating layer 2 is formed on the surface of each zinc oxide fine powder particle 1.

The coating amount of silver on the zinc oxide fine powder is 1
The range is preferably from 10 to 10% by mass (particularly from 3 to 7% by mass).
If the coating amount is less than 1% by mass, the absolute amount of silver carried is small, and the desired antibacterial properties will not be exhibited unless a large amount of silver-coated zinc oxide fine powder is blended with the resin. The larger the silver coverage, the more
The blending amount of the silver-coated zinc oxide fine powder with respect to the resin can be reduced. However, when the silver coating amount exceeds 10% by mass, the entire surface of the zinc oxide fine powder particles 1 is covered with the silver coating layer 2, and the ionization reaction of zinc, which is effective for promoting the elution of silver, is conversely suppressed.

The silver coating layer 2 formed with a silver coating amount of 1 to 10% by mass is distributed on the surface of the zinc oxide fine powder particles 1 in a scattered manner. The zinc oxide fine powder particles 1 in which the silver coating layers 2 are distributed in a scattered manner are mixed in an atmosphere of an inert gas such as nitrogen gas or Ar gas.
When heated to 0 to 800 ° C. for about 1 hour, silver in the coating layer 2 diffuses into the zinc oxide fine powder particles 1 to form a silver diffusion layer 3. Silver diffusion actively proceeds at a heating temperature of 400 ° C. or higher, but at a heating temperature exceeding 800 ° C., silver diffusion excessively proceeds to the center of the zinc oxide fine powder particles 1 and the silver concentration on the surface of the fine particles is low. Is not preferred.

The silver diffusion layer 3 formed in a scattered manner on the surface of the zinc oxide fine powder particles 1 preferably has a crystallite diameter of 100 nm or less (preferably 50 nm or less). The size of the crystallite diameter is calculated according to the following Scherrer's formula. D = k × λ / β × cos θ where D: crystallite diameter (Å) k: constant (0.9 when the measured X-ray is CuΚα) λ: wavelength of the measured X-ray (Å) β: spread of diffraction line (Half width, radian) θ: Bragg angle of diffraction line (radian)

Reducing the sputtering rate or keeping the zinc oxide fine powder during sputtering at a relatively low temperature is an effective method for reducing the crystallite diameter. Specifically, as a guide for the sputtering rate, the coating rate of silver per 1 g of zinc oxide fine powder is set to about 0.01 g / hour, and by keeping the zinc oxide fine powder at a temperature of 200 ° C. or less, 100 nm or less. Can be formed. The antibacterial agent in which the silver diffusion layers 3 are formed in a scattered manner exhibits an extremely high silver elution rate as compared with the conventional antibacterial agent. The high silver elution rate is presumed to be due to the following reasons. Functional groups such as a hydroxyl group, an amino group, and a carbonyl group, and additives such as a light stabilizer, an ultraviolet absorber, and a surfactant, which constitute the resin, easily cause an ion exchange reaction with silver ions. When an ion exchange reaction occurs, silver ions are trapped in the resin and do not move to the surface of the resin molded product. This is presumed to be the reason that the antibacterial property is extremely difficult to develop.

On the other hand, in the antibacterial agent in which the silver diffusion layer 3 is dispersed on the surface of the zinc oxide fine powder particles 1 in a scattered manner, first, a large amount of zinc is ionized by moisture permeating the resin, and then various zinc ions are ionized. Functional groups and additives cause an ion exchange reaction with zinc ions. Therefore, diffusion of silver ions to the surface of the resin molded product is promoted. Such a phenomenon,
This is manifested for the first time by a form in which silver is diffused with a crystallite diameter of several に on a part of the surface of zinc oxide fine powder particles 1 having an average particle diameter of 1 μm or less. It doesn't happen just by doing it.

As the silver diffusion layer 3, not only silver alone but also copper,
Zinc, tin, nickel, chromium, cobalt, antimony,
A silver alloy containing one or more of titanium and aluminum can also be used. Among them, copper which is effective for fungicide, tin which exhibits antibacterial properties against specific bacteria such as Thiobacillus,
When the zinc oxide fine powder particles 1 are coated with a silver alloy containing nickel or the like, an antibacterial agent having these effects in addition to the antibacterial properties derived from silver can be obtained.

An antibacterial agent comprising a silver-diffused zinc oxide fine powder is
It is added or applied to various materials such as resin, paint, fiber, and cosmetics. For example, when kneaded into a thermoplastic resin such as polyethylene, polypropylene, polystyrene, ABS, polyester, polyamide, polycarbonate, silicone resin, and fluororesin, and molded by injection molding, extrusion molding, blow molding, or the like, a plastic having antibacterial properties is obtained. Product. When added to thermosetting resins such as epoxy resins, phenolic resins, and urea resins, coating resins such as alkyd resins, cellulose derivatives, and vinyl resins, and adhesives such as acrylic resins and urethane resins, various antibacterial properties can be obtained. The product is obtained.

The amount of the silver-diffused zinc oxide fine powder added to the resin is 0.1 to 1% by mass (preferably 0.3 to 0.7% by mass).
% By mass). If the amount is less than 0.1% by mass, the absolute amount of silver is insufficient, and sufficient antibacterial properties are not exhibited. Conversely, if the amount exceeds 1% by mass, the antibacterial property corresponding to the increase in the added amount is not improved, and the product is rather expensive. The silver-diffused zinc oxide fine powder is kneaded into the resin by various methods. For example, in a thermoplastic resin composition, a resin to which silver-diffused zinc oxide fine powder is added is heated and mixed by using a Banbury mixer, a tumbler, a blender, a Nauter mixer, a kneading roll, a uniaxial or biaxial vented extruder, and the like. , Molded into a predetermined shape by an injection molding machine or the like.

In mixing the silver-diffused zinc oxide fine powder,
It is preferable to add an antioxidant, an ultraviolet absorber and a light stabilizer in combination. Examples of the antioxidant include a phenolic antioxidant, a phosphorus antioxidant, a sulfur antioxidant, and the like, which prevent deterioration of the resin due to heat during molding. There are various benzotriazole compounds as UV absorbers and various hindered amine compounds as light stabilizers, all of which improve the weather resistance of molded articles. Others
Pigments, dyes, lubricants, dispersants, antistatic agents and the like can be added according to the application.

[0024]

[Example] Molded article 1 (Example of the present invention): Commercially available zinc oxide fine powder (manufactured by Sakai Chemical Industry Co., Ltd .;
0 g of the surface was covered with 1% by mass of silver in a scattered manner by a powder sputtering method. The silver-coated zinc oxide fine powder is charged into a vacuum annealing furnace, and heated at 400 ° C. for 1 hour while introducing nitrogen gas at a flow rate of 10 ccm, so that the surface of the zinc oxide fine powder particles 1 A silver diffusion layer 3 was formed. To 100 parts by mass of a polypropylene resin (J-740, manufactured by Mitsui Petrochemical Industry Co., Ltd.), 0.1 parts by mass of a silver-diffused zinc oxide fine powder, and an antioxidant (Irganox B-2)
25 Ciba-Geigy), 0.1 part by mass of an ultraviolet absorber (Tinuvin 326 Ciba-Geigy) and 0.1 parts by weight of a light stabilizer (LS-770, Sankyo).
Two parts by mass were mixed and uniformly kneaded. The obtained transparent resin compound was injection molded at 200 ° C. to prepare a plate having a thickness of 2 mm, a length of 100 mm and a width of 100 mm.

Molded product 2 (Example of the present invention): The surface of zinc oxide fine powder particles 1 was covered with 5% by mass of silver by a powder sputtering method, and then charged into a vacuum annealing furnace.
Heat treatment was performed at 600 ° C. for 1 hour while introducing nitrogen gas at ccm to obtain a silver-diffused zinc oxide fine powder in which silver diffusion layers 3 were formed in a scattered manner. ABS resin (ABS-1
2 With respect to 100 parts by mass of Nippon Synthetic Rubber Co., Ltd.), 0.5 parts by mass of the silver-diffused zinc oxide fine powder, 0.1 parts by mass of the same antioxidant as in molded article 1, and 0.2 parts by mass of the ultraviolet absorber Parts and 0.3 parts by weight of a light stabilizer. The obtained gray resin compound was injection molded at 220 ° C. to produce a plate having the same size as the molded product 1.

Molded product 3 (Example of the present invention): The surface of zinc oxide fine powder particles 1 was covered with 7% by mass of silver by a powder sputtering method in a scattered manner, and then charged into a vacuum annealing furnace at a flow rate of 5c.
Heat treatment was performed at 700 ° C. for 1 hour while introducing nitrogen gas at a density of 1 cm to obtain fine silver-diffused zinc oxide powder having silver diffusion layers 3 formed in scattered spots. For 100 parts by mass of a polystyrene resin (styrene G-20, manufactured by Nippon Steel Chemical Co., Ltd.), 0.7 parts by mass of the silver-diffused zinc oxide fine powder, 0.4 parts by mass of the same antioxidant as in the molded article 1, and ultraviolet rays 0.2 sorbent
Parts by mass, 0.4 parts by mass of light stabilizer, 0.5 parts of titanium oxide
Parts by mass were blended. The obtained white resin compound was
By injection molding at 30 ° C., a plate having the same size as the molded product 1 was produced.

Molded product 4 (Example of the present invention): The surface of zinc oxide fine powder particles 1 was covered with 10% by mass of silver by a powder sputtering method, and then charged into a vacuum annealing furnace.
Heat treatment was performed at 800 ° C. for 1 hour while introducing a nitrogen gas at ccm, to obtain a silver-diffused zinc oxide fine powder in which silver-diffused layers 3 were formed in scattered points. Polycarbonate resin (Taflon-2200 manufactured by Idemitsu Petrochemical Co., Ltd.) 10
With respect to 0 parts by mass, 1.0 part by mass of the silver-diffused zinc oxide fine powder, 0.6 parts by mass of the same antioxidant as the molded article 1, 0.3 parts by mass of the ultraviolet absorber, and 0.1 part by mass of the light stabilizer. 6 parts by mass and 0.2 parts by mass of phthalocyanine blue were blended and uniformly kneaded. The obtained blue resin compound was injection molded at 280 ° C. to produce a plate having the same size as the molded product 1.

Each plate of molded products 1-4 is exposed to direct sunlight for 3
After exposure for 0 days, the discoloration resistance was examined by visually observing the color tone of each plate. The color resistance was evaluated as ◎ when no discoloration was observed, を when little discoloration was observed, Δ when discoloration was clearly detected, and X when discoloration was significantly advanced. Further, a test piece was cut out from each plate and subjected to an antibacterial test. The antibacterial test was carried out using Staphylococcus aureus and the Society for the Study of Inorganic Antibacterial Agents such as Silver, "Self-Specific Standards and Antibacterial Test Methods for Inorganic Antibacterial Agents such as Silver: Antibacterial and Antifungal Test Methods for Antibacterial Activity (1995 Version) Film Adhesion Law ". Count the number of viable bacteria before and after the test,
The antibacterial activity was marked as ◎ when the viable cell count was significantly reduced, ○ when the viable cell count was reduced, Δ when the viable cell count was slightly reduced, and × when no viable cell count was detected. The sex was evaluated.

The results of the investigation are shown in Table 1 together with the type of silver-diffused zinc oxide fine powder and the resin compound. In addition, in Table 1, the case where the zinc oxide fine powder which did not perform the heat-diffusion process (the silver coating layer 2 was formed by the powder sputtering method) was used as the comparative example. As can be seen from Table 1, the resin molded products of the present invention using the zinc oxide fine powder particles 1 having the scattered silver diffusion layers 3 formed on the particle surfaces as antibacterial agents were all exposed to direct sunlight for 30 days. No discoloration due to silver ion elution was detected even after exposure, and very strong antibacterial properties were exhibited.

On the other hand, in the comparative example in which the zinc oxide fine powder in which the silver coating layer 2 was formed without using the diffusion treatment was used as the antibacterial agent, the discoloration did not occur when the blending ratio was as small as 0.1% by mass. Although not observed at all, the antibacterial properties were poor. On the other hand, when the compounding ratio is more than 1.0% by mass, the antibacterial property is excellent, but the discoloration progresses remarkably, and the performance is poorly balanced.

[0031]

[0032]

As described above, the antibacterial agent of the present invention covers the surface of zinc oxide fine powder having an average particle size of 1 μm or less with a scattered silver diffusion layer and exposes zinc oxide to the particle surface. As a result, the elution of silver ions is promoted by the elution of zinc ions, and the excellent antibacterial properties unique to silver are developed in a short time.
In addition, since the silver diffusion layer is diffused in the zinc oxide fine powder, the discoloration of the resin is prevented by the action of the zinc oxide even when kneaded into the resin. Therefore, even a small amount of the compound can impart excellent antibacterial properties to interior materials, exterior materials, wallpaper, carpets, unit baths, air conditioning filters,
It is an antibacterial agent used in a wide range of fields such as sanitary products, bath utensils, kitchen utensils, medical utensils, textiles for clothing, socks, stationery, water treatment parts, food containers, packaging films, antibacterial coatings, etc.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process for producing an antibacterial agent according to the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 9/02 C08K 9/02 C08L 101/00 C08L 101/00 C23C 14/00 C23C 14/00 A F term (Reference) 4H011 AA02 BA01 BB18 BC03 BC09 BC19 DA02 DA07 DC10 DH02 DH04 4J002 BB031 BB121 BC031 BD121 BN151 CF001 CG001 CL001 CP031 DE106 FB066 FB076 FD186 GB00 GH01 GK00 4K029 AA04 AA22 BA05 BB03 BC00

Claims (3)

[Claims] 1. An antibacterial agent characterized in that silver diffusion layers are formed in the form of scattered spots on the surface of zinc oxide fine powder having an average particle size of 1 μm or less, and zinc oxide is exposed on the surface of the powder particles. 2. The surface of the zinc oxide fine powder is covered with 1 to 10% by mass of silver by a powder sputtering method in a scattered manner, and then heated to 400 to 800 ° C. in an inert gas atmosphere to oxidize the silver. A method for producing an antibacterial agent, characterized by forming a scattered silver diffusion layer by diffusing zinc fine powder. 3. An antibacterial resin composition containing the antibacterial agent according to claim 1 in a ratio of 0.1 to 1% by mass.