JP3199354B2 - Antibacterial glass and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an antibacterial glass and a method for producing the same. The antibacterial glass of the present invention is:
Filler for dental restoration composite resin, cement filler for living bone repair, catheter filler, paint,
Used in places requiring antibacterial properties such as water disinfectants.

[0002]

2. Description of the Related Art Conventionally, as a method for producing an antibacterial glass, a melting method, an ion implantation method, and a sol-gel method are known as the latest technologies before the present application. The melting method is a general glass production method, for example, silicic acid as a glass raw material,
After mixing oxide powder such as boric acid with silver oxide and melting,
Quench rapidly and vitrify.

In the ion implantation method, a glass to be subjected to ion implantation is housed in a chamber of an ion implantation apparatus in advance, and ions of an antibacterial substance such as silver are injected into the glass. By heating and vaporizing, by supplying silver vapor between the electrodes in a vacuum and ionizing,
Ions are implanted (Japanese Patent Application Laid-Open No. 6-211161).

In the sol-gel method, a gel is prepared by hydrolyzing a reaction product of a metal alkoxide compound such as tetraethyl silicate and a silver coordination compound obtained by coordinating an alkoxy group-containing compound such as trimethoxysilylpropyldiethylenetriamine. Then, the gel body is subjected to a heat treatment, wherein the silver coordination compound is obtained by dissolving a silver salt in a non-aqueous organic solvent, and mixing silver ions and an alkoxy group-containing compound in a non-aqueous organic solvent such as ethanol. (JP-A-5-213621).

[0005]

According to the melting method, a flux such as boric acid or nitrite, which reduces chemical durability, must be added to the raw material in order to vitrify by rapid cooling after melting. Glass has low chemical durability. According to the ion implantation method described in Japanese Patent Application Laid-Open No. 6-211161, an expensive ion implantation apparatus is required. JP-A-5-2136
According to the sol-gel method described in No. 21, silver is present in the glass not in an ionic state but in a colloidal particle state,
(1) The obtained antibacterial glass is colored, (2) The gel body cannot be heat-treated at a temperature higher than the melting point of silver, a dense and stable glass cannot be obtained, and (3) The release rate of silver is not slow. There is such a difficulty.

Accordingly, an object of the present invention is to provide an antibacterial glass which is colorless, has excellent chemical durability, and can control a sustained release rate of an antibacterial substance without using an expensive device.

[0007]

In order to achieve the above object, the antibacterial glass of the present invention comprises SiO ₂ and M _X O _Y.
(Wherein, M represents an atomic ratio of the valence less metal atoms than the coordination number, X and Y and M, respectively O.) Tona
Wherein M is Al, La, Y, Ti, Z
at least one selected from r, Nb and Ta;
Contains antibacterial metal ions , atomic ratio M / (antibacterial gold
Genus) ≧ 1 .

[0008] A suitable method for producing the antibacterial glass of the present invention is a hydrolyzable organosilicon compound or a hydrolyzable metal M compound (provided that M is an oxide whose valence is coordinated). A material solution containing less than the number of metal atoms), a salt of an antibacterial metal and water, mixed, gelled, and fired.

When a hydrolyzable organosilicon compound and a hydrolyzable metal M compound are mixed together with water in a composition that can be vitrified in terms of oxide, each compound hydrolyzes and gels uniformly. When this gel is dried and fired, it becomes a glass substantially composed of SiO ₂ and M _X O _Y. However, drying may be omitted. A pulverizing step may be added before or after the firing step. When the salt of the antibacterial metal is contained in the raw material solution before hydrolysis, the antibacterial metal ion is simultaneously hydrolyzed, and the antibacterial metal ions are uniformly dispersed in the gel. Exist as metal ions. And the valence n of M is the coordination number Z
Less than M, the negative charge (-) is not electrically neutralized by the charge (n +) of M, and the surplus oxygen atoms having negative charge (-) exist around M, and neutralize with the antibacterial metal ion to be stable. Become Therefore, the antibacterial metal exists stably and uniformly in the ionic state. When the atomic ratio M / (antibacterial metal) ≧ 1
The antibacterial metal is easily ionized in the glass. Suitable
A good combination is M for Al and antibacterial metal for Ag
Things.

Since the antibacterial metal is dispersed in the glass in an ionic state, the glass is not colored, and a dense glass can be obtained by firing at a high temperature. Then, even if the antibacterial metal ions are released from the glass surface and consumed, the antibacterial metal inside the glass diffuses toward the glass surface in an ionic state, so that the release speed from the glass surface is continuous and slow, and Δt (T: time). The slope of the release rate-time graph can also be controlled by the ratio of metal M to antimicrobial metal and the total amount of antimicrobial metal.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrolyzable organosilicon compound and the hydrolyzable metal M compound are preferably those which can be uniformly gelled by adding water. A typical hydrolyzable organosilicon compound is an alkoxide of silicon.
The hydrolyzable metal M compound is a hydrolyzable organic metal M compound such as a metal M salt or a metal M alkoxide. M is Al, La, Y, T as described above.
One or more selected from i, Zr, Nb, and Ta. This is because these metals are inexpensive and have excellent durability.

[0012]

【Example】

[Production of antibacterial glass] An embodiment of the method for producing antibacterial glass of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a process of manufacturing an antibacterial glass.

[0013] Ethanol C ₂ H ₅ OH is added to tetraethoxysilane Si (OC ₂ H ₅ ) ₄ as a solvent. Separately, water, nitric acid HNO ₃ ,
Ethanol, silver nitrate AgNO ₃ , aluminum nitrate nonahydrate A
_{l (NO 3) 3 · 9H} 2 O are mixed and a solution. This solution was added to the tetraethoxysilane solution and hydrolyzed while stirring for 30 minutes to prepare a sol solution (FIG. 1a). The composition of the sol solution is as shown in Table 1.

[0014]

[Table 1] [molar _{ratio] ------------------------------ Si (OC 2 H 5} ) 4 H 2 O HNO ₃ C ₂ H ₅ OH AgNO ₃ Al (NO ₃ ) ₃・ 9H ₂ O 18 0.01 2 0.023 0-0.115 −−−−−−−−−−−−−−−−−−−−−−−−− −−−−−− After hydrolysis, put the sol solution into a plastic container.
Leave at 40 ° C to gel, and after gelation, continue to 40 ° C
For one week (FIG. 1b). After drying, the sample is taken out of the container, crushed with a zirconia planetary ball mill to an average particle size of about 10 microns (FIG. 1c), and the powdered sample is placed in a crucible and fired at 600 to 1000 ° C. for 2 hours. As a result, four types of glasses having different Al / Ag molar ratios were produced (FIG. 1d). Table 2 shows the theoretical composition of the obtained glass.

[0015]

[Table 2]

[Analysis of Glass] (1) Determination of Silver in Glass Next, in order to confirm whether silver remains in the glass,
The dried gel, the glass obtained at a sintering temperature of 800 ° C. and the glass obtained at a sintering temperature of 1000 ° C. are each dissolved in about 5% hydrofluoric acid, and the silver concentration in the solution is determined by high frequency inductively coupled plasma emission analysis It was measured. As a result, the concentration of silver in the solution dissolved in hydrofluoric acid almost coincided with the concentration of silver added during sol preparation, regardless of the amount of aluminum added and the firing temperature, as shown in FIG. It was confirmed that silver remained without evaporating and escaped in the glass. When the sample to which aluminum was not added was subjected to a heat treatment at 960 ° C. or more, which is the melting point of silver, the sample and the crucible were fused.

(2) State of Silver in Glass Next, the state of silver in the glass obtained by baking at 800 ° C. was analyzed by visible ultraviolet absorption spectroscopy. As a result, in the glass (Al0) to which aluminum was not added, about 410
Absorption was observed around nm, which was assigned to absorption by the silver colloid. In addition, the glass exhibited yellow because colloidal silver was present. On the other hand, in the Al1, Al2, and Al5 glasses to which aluminum was added, no absorption was recognized in any of the three types, and the glasses were colorless.

The state of silver in the dried gel and the glass obtained by firing at various temperatures was analyzed by powder X-ray diffraction. In the glass to which aluminum was not added, a peak attributed to silver was observed at a sintering temperature of 800 ° C. or higher. This seems to be due to the silver colloid. On the other hand, in the three kinds of glasses to which aluminum was added, no peak attributed to silver was observed even at a sintering temperature of 800 ° C. or higher.

From the above analysis results, the relationship between the state of silver and the glass structure is considered as follows. Since silver ions have properties very similar to sodium ions, when silver ions are added to silica glass, the silver ions break the network of silica, and one non-bridging oxygen is formed for each silver ion. It seems to generate. However, since silver ions bonded to non-crosslinked oxygen are very unstable and easily reduced, the reduced silver is agglomerated and silver is present in a colloidal state in a glass to which aluminum is not added (FIG. 3). Upper). On the other hand, when a trivalent element such as aluminum is introduced into glass, the silicon in the network is partially replaced by aluminum, and aluminum forms a tetrahedron having one negative charge in excess, and this negative charge is transferred to silver. It is believed that the ions compensate. Therefore, in the glass to which aluminum is added, silver coordinates to this tetrahedron, and silver exists in an ionic state (lower part in FIG. 3).

[Effects of Examples] (1) Method of evaluating chemical durability of glass and sustained release of silver In order to evaluate the chemical durability and sustained release of silver of the obtained glass, the following method was used. Silicon from glass to water in the manner of
The elution amounts of aluminum and silver were examined. Prepare glass obtained by baking at 950 ° C without adding aluminum, and glass obtained by baking at 1000 ° C with aluminum added, weigh 0.1 g of each glass, and separately manufacture polypropylene Put 20 ml of distilled water in
The sample was placed in a thermostat at ゜ C and vibrated at a rotation radius of 3 cm and a rotation frequency of 120 rpm. After immersing the glass in water for a predetermined period while applying vibration, the container is taken out of the thermostatic bath, filtered to separate the glass from the solution, and the concentrations of silicon, aluminum and silver in the solution are determined by high-frequency inductively coupled plasma emission analysis. It was measured. The measurement results of the silicon concentration, the aluminum concentration, and the silver concentration are shown in FIGS. 4, 5, and 6, respectively.

(2) Evaluation of Chemical Durability of Glass As shown in FIG. 4, in glass (Al0) to which aluminum is not added, the amount of silicon eluted increases as the immersion period becomes longer, and two weeks after immersion. Was about 6 ppm. On the other hand, glass (Al1, Al
(2, Al5), regardless of the amount of aluminum added, the amount of silicon eluted increased with the immersion period,
The increasing tendency is considerably smaller than the case where aluminum is not added, and the elution amount in two weeks after immersion is about 1.5 ppm,
This was reduced to about 1/4 of the case where no aluminum was added.

As shown in FIG. 5, the elution amount of aluminum is almost constant even if the immersion period is prolonged regardless of the amount of aluminum added, and the elution amount of aluminum in the two weeks after immersion is extremely small. And aluminum is hardly eluted. From these results, it is recognized that the chemical durability of the glass matrix was improved by adding aluminum.

(3) Evaluation of sustained release of silver As shown in FIG. 6, the amount of silver eluted from the glass (Al0) to which aluminum was not added increased stepwise and irregularly as the immersion period became longer. The amount of elution two weeks after immersion was about 5 ppm, which corresponds to about 2.5% of silver eluted from the glass. On the other hand, in the glass to which aluminum was added (Al1, Al2, Al5), silver eluted rapidly at the beginning, regardless of the amount of aluminum added, but then eluted at a substantially constant rate, and two weeks after immersion, The amount of silver eluted was about 1 ppm, which corresponds to about 0.5% of silver eluted from the glass.

Next, the amount of silver eluted is plotted on the ordinate and the square root of dipping days Δd (d: dipping days) is plotted on the abscissa, and these values are plotted on a graph (FIG. 7), and aluminum is added. The mechanism of silver elution from three types of glasses (Al1, Al2, Al5) was studied. As a result, the amount of silver eluted in all samples was almost proportional to the square root of the number of days of immersion. In general, the amount of alkali ions eluted from glass into water is proportional to the square root of time,
Since this is known to be an ion exchange reaction between alkali ions in glass and protons in water,
It is presumed that the elution of silver into the water from the glass in this example is caused by an ion exchange reaction between silver ions in the glass and protons in the water.

The general mechanism of elution of silicon and silver with reference to FIG. 8 is as follows. First, in the glass to which aluminum is not added, silver is present as a metal colloid, but since the amount of silicon eluted is large, it is considered that the matrix near the surface is considerably melted. As a result, the silver colloid comes into contact with water, the silver is oxidized by the water, the silver elutes into the water, and the interfacial reaction between the silver colloid and water becomes the rate-determining step, and it is thought that the silver elutes irregularly. (The upper part of FIG. 8). On the other hand, in the glass to which aluminum is added, silver exists in an ionic state, and silicon and aluminum are hardly eluted. Silver elution is
As described above, since the ion exchange reaction occurs between silver ions in the glass and protons in the water, diffusion of the silver ions becomes a rate-determining step, and it is considered that silver elutes at a constant rate (the lower part in FIG. 8).

(4) Evaluation of antibacterial activity In order to evaluate the antibacterial activity of the glass of the present invention, Streptococcus mutans, a reference strain which is likely to cause dental caries, was used.
s mutans) ATCC25175 (hereinafter abbreviated as “S. mutans”) was measured for proliferation in the presence of antibacterial glass as follows.

5 ml of Tripticase Soy Broth (manufactured by BBL, USA; hereinafter abbreviated as "TSBY") containing 0.5% yeast extract was prepared, and S. mutans was added thereto.
And inoculated at 37 ° C. for 10 to 12 hours under anaerobic culturing to obtain a reduced transport fluid (reduced transport fluid).
Abbreviated as "RTF". ) To 1 × 10 ⁶ cells / ml. Separately, Al / A obtained by firing at 1000 ° C
Weigh 0.1 g or 0.01 g of three kinds of antibacterial glass whose g is 1, 2 or 5.

Each antibacterial glass was separately placed in each of the above prepared bacterial solutions under anaerobic conditions at 37 ° C. (hydrogen 10%, nitrogen 8
(0%, carbon dioxide 10%) for 2, 6 and 12 hours. In addition, a prepared bacterial solution in which glass was not immersed was used as a control. After immersion, each bacterial solution was serially diluted 10-fold with RTF, 0.1 ml of the diluted solution was dropped on a TSBY plate medium, and anaerobic culture was performed at 37 ° C for 4 days. A plate medium in which growth of about 100 colonies was observed was selected, and the number of bacteria was measured. FIG. 9 shows the measurement results.

As shown in FIG. 9, the amount of glass is 0.1
In the case of g, antibacterial properties were confirmed in glasses other than the glass of Al / Ag = 5/1. It is considered that the difference between the control when Al / Ag was 5/1 and the glass amount was 0.01 g was not desired because the absolute amount of silver was small.

[0030]

As described above, the antibacterial glass of the present invention exhibits antibacterial properties, is colorless, and is excellent in chemical durability and sustained release of antibacterial substances. Therefore, it can be used stably for a long period of time in places requiring antibacterial properties.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process of producing an antibacterial glass.

FIG. 2 is a graph showing a quantitative value of silver contained in an antibacterial glass.

FIG. 3 is a diagram illustrating a glass network structure of antibacterial glass.

FIG. 4 is a graph showing the amount of silicon dissolved in water in antibacterial glass obtained by baking at 1000 ° C.

FIG. 5 is a graph showing the amount of aluminum in antibacterial glass obtained by firing at 1000 ° C. into water.

FIG. 6 is a graph showing the amount of silver dissolved in water in antibacterial glass obtained by baking at 1000 ° C.

FIG. 7 is a graph plotting the relationship between the amount of silver eluted and the square root of immersion days.

FIG. 8 is a diagram illustrating a mechanism of elution of silver into water.

FIG. 9 is a graph showing the antibacterial degree of the antibacterial glass.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C03C 1/00-14/00 A01N 59/16

Claims (2)

(57) [Claims] 1. A SiO ₂ and M X _O Y _(provided that, M is the valence of less metal atoms than the coordination number, X and Y each represent an atomic ratio of M and O.) Was a glass consisting of hand,
M is at least one selected from Al, La, Y, Ti, Zr, Nb and Ta, contains an antibacterial metal ion, and has an atomic ratio M / (antibacterial metal) ≧ 1. Antibacterial glass characterized by the following. 2. The method according to claim 1, wherein M is Al and the antibacterial metal is Ag. The antibacterial glass according to the above.