JPH11302119A - Production of antimicrobial silver colloid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disperse fine silver particles having an average particle diameter within a prescribed range and produce a colorless and transparent antimicrobial silver colloid useful for a coating material, a molding material, a catalyst, etc., by mixing the silver fine particles having a prescribed particle diameter with a resin and a peroxide in a dispersing medium such as water. SOLUTION: This antimicrobial silver colloid is obtained by mixing silver fine particles having 8-200 nm particle diameter with a resin such as a methacrylic resin and a peroxide such as methyl ethyl ketone peroxide in a dispersing medium such as water or a nonaqueous solution. The particle diameter of the dispersed silver fine particles in the colloid is 0.5-5 nm. The concentration of the silver fine particles contained in the colloid is preferably 10 ppm to 1 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to paints, molding materials,
The present invention relates to a colorless antibacterial silver colloid used in the field of catalysts and the like.

[0002]

2. Description of the Related Art In recent years, antibacterial inorganic fine particles in which metal ions such as silver and copper are fixed to zeolite or soluble glass have been used in many fields as low-toxic antibacterial agents. For example, an alumina silicate-type antibacterial agent represented by Japanese Patent Publication No. 6-2570 or JP-A-6-34
Phosphate-type antibacterial agents as typified by Japanese Patent No. 0514 are cited. These exhibit strong antibacterial effects due to metal ions and are said to be resistant to discoloration. However, the proportion of the antibacterial metal component contained therein is generally less than 5% by weight, and the rest is a carrier unrelated to antibacterial properties. is there. Therefore, in order to impart antibacterial properties, it is necessary to add about several percent by weight to the solid content of the resin or paint to be imparted with antibacterial properties. Further, these carriers have a particle size of about 0.1 μm, and have the disadvantage that they become opaque when added to a transparent substance.

[0003] In addition to these inorganic antibacterial agents, JP-A-4-321628 and JP-A-6-293611.
JP, JP-A-5-271718 and edited by The Chemical Society of Japan, New Experimental Chemistry, Vol. 18, Interface and Colloid, p319
340 (1977, Maruzen Co., Ltd.) to produce an aqueous solution or non-aqueous solution of silver fine particles or a dispersion in a high molecular weight organic compound by using the silver fine particles as an antibacterial agent as it is. Can be. This is an antibacterial agent different from the above-mentioned antibacterial agent, which is composed of silver fine particles having an average particle diameter of 200 nm or less, usually about 10 to 20 nm,
There is an advantage that the antibacterial effect can be exhibited with a small amount of several tens to several hundreds ppm of a solid content of a resin or a paint which is to have antibacterial properties. However, these have plasmon absorption peculiar to metal colloids, and absorption takes place in the vicinity of 410 nm of visible light in silver fine particles, so that the fine silver particles have a brown color. Examples of silver fine particles showing color are as described in The Chemical Society of Japan, New Experimental Chemistry, Vol. 18, Interface and Colloid, p335 (1977, Maruzen Co., Ltd.) and Textile and Industry, 47, 7, p392 (199).
1), 1992 Spring Meeting of the Chemical Society of Japan, p704. For this reason, the application range of these silver fine particles was very limited.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to expand the range of application by producing a colorless and transparent silver fine particle dispersion useful as an antibacterial agent.

[0005]

According to the present invention, there is provided an average particle comprising mixing silver fine particles having an average particle diameter of 8 to 200 nm, a resin and a peroxide in a water or non-aqueous dispersion medium. A method for producing a colorless antibacterial silver colloid in which silver fine particles having a diameter of 0.5 to 5 nm are dispersed, and a method for producing the above antibacterial silver colloid in which the concentration of silver fine particles contained in the silver colloid is 1 wt% or less and 10 ppm or more. Is provided.

What is important here is that the average particle size is 8 to 20.
When the colored silver fine particles of 0 nm have an average particle diameter of 0.5 to 5 nm, the brown coloring characteristic of the silver fine particles disappears. In the present invention, the average particle size is 8 to 200 nm.
It is not clear why the silver fine particles change into colorless silver fine particles of 0.5 to 5 nm in any process. However, it is considered that silver fine particles having an average particle diameter of 0.5 to 5 nm are generated because a reaction occurs between the peroxide and the silver fine particles and the silver fine particles are reduced in size. It is presumed that there is not. Also, the reason why the coloration of silver fine particles disappears is that plasmon absorption specific to metal colloid does not occur at this particle size, or even if plasmon absorption occurs, this absorption edge is out of the visible light range. Because of this, it is presumed that it looks colorless.

By the way, the average particle diameter of the fine particles is 0.5 to
The surface energy at 5 nm is expected to be quite large, and it is considered that the particles are usually not stable and may re-agglomerate immediately. It exists stably over the above. It is considered that the reason for this is that the coexisting resin component prevents re-aggregation of these fine particles. This can be inferred from the fact that a phenomenon in which the coloration of the silver fine particles is more easily eliminated when the amount of the resin component in the solution is larger is obtained. This phenomenon becomes possible only when three kinds of 1) silver fine particles, 2) resin, and 3) peroxide are present in the dispersion medium, and any one of these components must be lacking. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the average particle size is 0.5
The silver fine particles having an average particle diameter of 8 to 200 nm or a dispersion or non-aqueous dispersion thereof used for producing a colloid in which silver fine particles having a size of 5 to 5 nm are dispersed are provided by a known method, and the production method is not particularly limited. . For example, The Chemical Society of Japan, New Experimental Chemistry, Volume 18, Interfaces and Colloids, p
319 to 340 (1977, Maruzen Co., Ltd.) can be used to prepare an aqueous dispersion of silver fine particles. Further, the preparation of an aqueous dispersion of silver fine particles in which the dispersion state is stabilized by adding a surfactant, for example, Y.Naka
o and K. Kaeriyama, Journal of Colloid and Interface
This can be performed by applying the method described in Sceince 110, No. 1, p81-87, (March 1986). Also, Japanese Patent Laid-Open No. 5-27
According to the method described in Japanese Patent No. 1718, the above aqueous dispersion is brought into contact with a non-aqueous solution which is phase-separated from water in the presence of a surfactant and a water-soluble inorganic acid salt or an organic acid salt, to form silver fine particles. Can be transferred from the aqueous dispersion into the non-aqueous liquid. In addition, JP-A-4-321628,
It can also be performed by the method described in JP-A-6-293611 or the like.

The average particle diameter of these silver fine particles is 200 n.
m or less, and preferably 50 nm or less. The amount of silver is preferably 1% by weight or less and 10 ppm or more based on the whole. If the amount of silver is higher than this range, the average particle size is finally 5
It is difficult to generate silver fine particles having a diameter of not more than nm, and if it is lower than this range, it is difficult to exhibit antibacterial properties.

The dispersion medium in the present invention may be either water or a non-aqueous solution. Examples of the non-aqueous solution include aromatic hydrocarbons such as toluene and xylene, n-hexane, n-hexane and the like.
-Aliphatic hydrocarbons such as heptane, cyclic hydrocarbons such as cyclohexane, alcohols such as methanol and ethanol,
Ethyl acetate, esters such as butyl acetate, ketones such as methyl ethyl ketone, aldehydes such as acetaldehyde, dimethyl sulfoxide, dimethylformamide, aprotic polar solvents such as N-methylpyrrolidone, and further styrene, vinyl monomers such as methyl methacrylate and These mixtures and the like can be mentioned. The amount of the dispersion medium is not particularly limited, but there is no particular problem as long as the silver fine particles and the resin component are dispersed throughout the solution.

[0011] The resin used in the present invention includes:
Either a thermoplastic resin or a thermosetting resin may be used, or a mixture thereof may be used. Examples of the thermoplastic resin include methacrylic resin, styrene resin, ABS resin, nylon, polycarbonate resin, vinyl acetate resin, vinyl chloride resin, cellulose acetate, and the like, all of which are dispersed in a silver fine particle dispersion medium. Possible ones are preferred. Examples of the thermosetting resin include an alkyd resin, an allyl resin, an amino resin, an epoxy resin, a phenol resin, an unsaturated polyester resin, a silicone resin, and a polyurethane resin, all of which are dispersed in a silver fine particle dispersion medium. Possible ones are preferred. The amount of the resin is generally proportional to the amount of silver, and is 1 or more, preferably 10 or more in terms of weight ratio to silver, and the higher the weight ratio, the more preferable. The upper limit is not particularly limited, but preferably, the ratio of the resin to the total amount is 80% by weight or less. If it is higher than this range, the fluidity of the solution becomes low, and it becomes difficult to disperse the silver fine particles uniformly. On the other hand, if it is lower than this range, it is difficult to generate silver fine particles having an average particle diameter of 5 nm or less.

As the peroxide, for example, ketone peroxides such as methyl ethyl ketone peroxide and cyclopentanone peroxide as organic peroxides and 1,1
Peroxyketal such as -bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, hydroperoxide such as p-methanehydroperoxide,
Dialkyl peroxides such as dicumyl peroxide; diacyl peroxides such as isobutyl peroxide; Etc., or a mixture thereof. Among them, ketone peroxide is preferable. Alternatively, they can be used in combination with a reducing agent such as an organic amine such as dimethylaniline and a metal catalyst such as cobalt naphthenate. Examples of the inorganic peroxide include aqueous hydrogen peroxide, or persulfates such as ammonium persulfate and sodium persulfate, and sulfites such as sodium hydrogen sulfite. The amount of peroxide is generally proportional to the amount of silver, and is preferably 1 or more in weight ratio to silver, and the upper limit is not particularly limited, but is preferably 100 or less. If it is lower than this range, it is difficult to form fine particles having an average particle diameter of 5 nm or less, and if it is higher than this range, the dispersion medium is a monomer.
In the case of the above or a mixture thereof, a polymerization reaction may occur, and the resin to be added may cause an unintended polymerization reaction. However, this is not the case when the polymerization reaction is intentionally caused. Even when the polymerization reaction occurs, there is no problem in producing silver fine particles having an average particle diameter of 0.5 to 5 nm.

The order in which the silver fine particles, the resin and the peroxide are mixed is not particularly limited, but the peroxide is added while the resin and the silver fine particles are mixed, or the silver fine particles are added to the mixed solution of the resin and the peroxide. It is preferable to add. The reaction is preferably carried out at 0 to 80 ° C. under normal pressure.

[0014]

The present invention will be described below in detail with reference to examples. The brown fine silver particles used in the examples are described in
What was manufactured based on the method of -271718 was used. The composition% in each example is% by weight. For samples capable of forming a coating film, a coating film was prepared, and the antibacterial test on these samples was performed by the following method. (Antibacterial test) The test pieces were 5 cm square plates, the surfaces of which were disinfected with ethanol, and the silver fine particle colloids produced in the examples were applied. Note that a vinyl chloride plate was used as a blank. The test strain is Escherichia coli, I.
FO3301) and Staphylococcus aureus
Using EDA209P), the cells were cultured in a fixed slant medium (normal agar medium, manufactured by Nissui Co., Ltd.), and this was used as a preservation strain. At the time of the test, one platinum loop was taken from each of these, and cultured in a liquid broth medium (manufactured by Nissui Co., Ltd.) with shaking at 30 ° C. and 160 rpm for 20 hours. These were diluted 10,000 times with a sterilized 0.1 M phosphate buffer solution to obtain a test bacterial solution. The initial number of bacteria was further diluted 1000-fold and 1 m
1m and 10m of standard agar medium (manufactured by Nissui Co., Ltd.)
This was diluted with 1 to prepare a plate agar medium, and this was confirmed by measuring the number of bacteria. The antibacterial test is 1m from the test bacterial solution.
1 drop each on a test piece and a blank,
For 24 hours, then dilute the bacterium in a 10-fold series from 10 to 1000 fold,
1m each, 10m standard agar medium (Nissui Co., Ltd.)
The resulting mixture was diluted with 1 to prepare a plate agar medium, which was cultured at 28 ° C. for 48 hours, and the number of these cells was measured.

Example 1 An average particle diameter of 15 m was added to 90 g of an acrylic resin for paint (Bildick gloss varnish, trade name, manufactured by Dainippon Paint Co., Ltd.).
2,000 ppm of fine silver particles dispersed in toluene solution 1
0 g, methyl ethyl ketone peroxide (trade name:
0.5 g of MEC N (manufactured by NOF Corporation) was added and mixed well. The color at this time was reddish brown. Then, it was left at normal pressure and room temperature. After 18 hours, a clear and colorless solution was obtained. This was applied to a vinyl chloride plate, dried at room temperature, and then subjected to an antibacterial test. Table 1 shows the results. As a result of the test, sufficient antibacterial properties were observed. When the coating film was observed with a transmission electron microscope, it was confirmed that silver fine particles having an average particle size of 1.5 nm were uniformly dispersed.

Example 2 Bensoyl peroxide (trade name: Niiper-BW, Nippon Oil & Fats Co., Ltd.) was added to 100 g of a brown toluene solution in which 10 g of an acrylic resin for coating and 200 ppm of silver fine particles having an average particle diameter of 15 nm were dispersed in the same manner as in Example 1. Was added at room temperature and room temperature. After 18 hours, a clear and colorless solution was obtained. When this was observed in the same manner as in Example 1, it was confirmed that silver fine particles having an average particle diameter of 2.0 nm were dispersed.

Example 3 10 g of urethane resin (transparent varnish for wood and floor, manufactured by Rock Paint Co., Ltd.), silver fine particles 20 having an average particle diameter of 15 nm
To 100 g of a 0 ppm dispersed thinner solution for brown paint (manufactured by Rock Paint Co., Ltd.) was added methyl ethyl ketone powder.
Oxide (trade name: Permec N, manufactured by NOF Corporation)
0.1 g, and allowed to stand at normal pressure and room temperature. After 10 minutes,
It became a colorless and transparent solution. When this was observed in the same manner as in Example 1, it was confirmed that silver fine particles having an average particle diameter of 0.8 nm were dispersed.

Example 4 Polyester resin (trade name: Rigolac, Daiso Co., Ltd.)
Manufactured) 100 g, silver fine particles 2000 having an average particle diameter of 15 nm
1.5 g of the above methyl ethyl ketone peroxide was added to 100 g of a brown toluene solution in which
It was left at room temperature. After 18 hours, a clear and colorless solution was obtained. When this was observed in the same manner as in Example 1, it was confirmed that silver fine particles having an average particle diameter of 1.0 nm were dispersed.

Example 5 Acrylic silicone resin (trade name: SKA-500, manufactured by Daiso Corporation) 20 g, silver fine particles 2 having an average particle diameter of 15 nm
0.1 g of the above methyl ethyl ketone peroxide was added to 100 g of a 00 ppm dispersed brown toluene solution, and the mixture was allowed to stand at normal pressure and room temperature. After 10 minutes, a clear and colorless solution was obtained. This was applied to a vinyl chloride plate and subjected to an antibacterial test. Table 1 shows the results. As a result of the test, sufficient antibacterial properties were confirmed. Further, when observed in the same manner as in Example 1, it was confirmed that silver fine particles having an average particle diameter of 1.0 nm were dispersed.

Example 6 Copolymer dispersant (trade name: disperbyk-1)
61, manufactured by Big Chem Co., Ltd.) 0.5 g, average particle size 1
0.05 g of the above methyl ethyl ketone peroxide was added to 100 g of a brown toluene solution in which 200 ppm of 5 nm silver fine particles were dispersed, and the mixture was allowed to stand at normal pressure and room temperature. After 10 minutes, a clear and colorless solution was obtained. When observed in the same manner as in Example 1, it was confirmed that silver fine particles having an average particle diameter of 1.5 nm were dispersed.

Example 7 Copolymer dispersant (trade name: disperbik-1)
82, manufactured by Big Chem Co., Ltd.) 0.5 g, average particle size 1
0.05 g of 25% hydrogen peroxide solution was added to 100 g of a brown aqueous solution in which 200 ppm of 5 nm silver fine particles were dispersed.
It was left at room temperature. After 10 minutes, a clear and colorless solution was obtained. Observation in the same manner as in Example 1 revealed that silver fine particles having an average particle diameter of 0.9 nm were dispersed.

Example 8 50 g of diallyl phthalate prepolymer (trade name: Daiso-Dap A, manufactured by Daiso Co., Ltd.), average particle diameter: 15 nm
Then, 50 g of a 2000 ppm brown toluene solution in which silver fine particles were dispersed and 2.5 g of the above methyl ethyl ketone peroxide were added, and the mixture was allowed to stand at normal pressure and room temperature. One hour later,
It became a colorless and transparent solution. Observation in the same manner as in Example 1 revealed that silver fine particles having an average particle diameter of 2.0 nm were dispersed.

[0023]

[Table 1]

[0024]

According to the present invention, the average particle size is 0.5 to 5
It is possible to easily produce an antibacterial silver colloid in which fine silver fine particles are dispersed. Since this colloid is colorless and transparent and does not exhibit a brown color peculiar to silver fine particles, it can be widely used in various fields such as paints and molding materials. Particularly when used for paints, it does not impair the ground color of the object to be coated, so it can maintain its beautifulness even when applied to a white or light-colored surface, and is useful for interiors such as hospitals and food factories. It is.

Claims (2)

[Claims] Claims: 1. A silver fine particle having an average particle diameter of 0.5 to 5 nm, which is obtained by mixing silver fine particles having an average particle diameter of 8 to 200 nm, a resin and a peroxide in a dispersion medium of water or a non-aqueous solution. Production of dispersed colorless antibacterial silver colloid. 2. The method according to claim 1, wherein the concentration of the silver fine particles contained in the silver colloid is:
The method for producing an antibacterial silver colloid according to claim 1, wherein the content is 10 ppm or more at 1% by weight or less.