JPH1192314A - Inorganic antimicrobial composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, capable of suppressing a reaction of an antimicrobial metallic ion with a compound in a resin and reduced in actions of discoloring a synthetic resin under the influence of heat, sunlight or the like by including an antimicrobial zeolite and specific hydrotalcites therein. SOLUTION: This composition is obtained by including (A) an antimicrobial zeolite (the one prepared by supporting an antimicrobial metallic ion on a crystalline aluminosilicate of an alkali metal or an alkaline earth metal) and (B) hyrotalcites represented by the formula Mg6 Al2 (OH)16 CO3 .4H2 O and regulated to pH 5.0-8.0. The ingredient B is preferably added during or after completing a step for preparing the ingredient A and the ingredient B is added in an amount of preferably 5-45 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an antibacterial metal ion,
In particular, an object of the present invention is to suppress the discoloration effect when zeolite supporting silver ions is added to a synthetic resin. The composition of the present invention exhibits excellent antibacterial performance when added to a synthetic resin. In addition, when mixed and molded with a synthetic resin, the synthetic resin containing the present composition is less discolored when exposed to heat, sunlight, etc., so that a plastic product which can be used widely and has excellent quality can be obtained.

[0002]

2. Description of the Related Art It is widely known that metal ions such as silver ions, copper ions, and zinc ions have antibacterial properties. In particular, the antibacterial performance of silver ions is outstanding among many metal ions, and has long been used as a disinfectant or antibacterial in the form of silver nitrate solution. However, silver ions and their compounds react sharply with light, heat, and other substances, and often exhibit discoloration. In addition, when the silver ion compound is mixed with the synthetic resin as it is, the dispersibility is poor, and even when a molded article is used, it is insufficient in terms of direct relation to antibacterial properties such as solubility and sustained release.

In recent years, antimicrobial compositions in which antimicrobial metal ions are ion-exchanged or adsorbed on zeolite, activated carbon, calcium phosphate-based compounds (hydroxyapatite), zirconium phosphate, silica, etc. have been developed in order to improve such disadvantages. (JP-A-60-181002, JP-A-49-61950, and JP-A-3-2187).
No. 65, JP-A-3-83906 and JP-A-5-339509). These antimicrobial compositions have improved dispersibility, solubility, sustained release properties and discoloration when mixed with a synthetic resin, and have been used in a wider range than conventional ones. However, the problem of discoloration due to antibacterial components has not been completely solved. The use of such antibacterial compositions for the purpose of imparting antibacterial properties to bath articles, kitchen articles, etc. is increasing, but they are discolored into white containers, utensils, etc., which are preferred by consumers from the image of cleanliness. Occurs significantly impair the commercial value.

[0004] Main causes of discoloration include oxidation of antibacterial metal ions due to heating during molding of the synthetic resin, or reaction of the metal ions with the composition in the resin. Oxidation of silver ions or the like carried on zeolite by ion exchange alone is unlikely to occur. The three-dimensional structure of zeolite is 900 ° C
This is because the antimicrobial metal ions are protected without being released by heating at the level of resin molding, since the antimicrobial metal ions are resistant to the heating up to the time of molding.
However, when a halogen, a sulfur compound or the like is present in the resin, the resin easily reacts by heating at about 200 ° C. to cause discoloration. Investigations to suppress the reaction with halogens, sulfur compounds, and the like are being actively conducted at present. Stabilization of the carrier by firing (Japanese Patent Laid-Open No. 4-134,094) and surface treatment with inorganic fine particles and organic oxides Inactivation (Japanese Unexamined Patent Publication No.
183728, Japanese Patent Publication No. 3-80814),
Addition of discoloration inhibitor and the like (JP-A-6-158551)
Have some effect. However, calcination or surface treatment extremely suppresses elution of antibacterial metal ions and easily reduces antibacterial activity. Additives such as anti-tarnish agents
Deterioration may be caused depending on the resin, and a problem remains.

[0005]

In view of the above problems, the present invention suppresses the reaction between an antibacterial metal ion and a compound in a resin, and acts to discolor the synthetic resin under the influence of heat, sunlight, and the like. An object of the present invention is to provide a reduced antibacterial composition.

[0006]

As a result of repeated studies to solve the above-mentioned problems, the antibacterial zeolite was adjusted to pH 5.
It has been found that by mixing hydrotalcites adjusted to 0 to 8.0, the discoloring action of antibacterial metal ions can be suppressed. That is, the present invention relates to an antibacterial zeolite,
It is an inorganic antibacterial composition containing hydrotalcites in which H is adjusted to 5.0 to 8.0.

[0007] A feature of the present invention is that discoloration is suppressed by capturing halogens and the like in a synthetic resin by hydrotalcites having anion exchange performance. To date, p
A method of mixing hydrotalcites in which H is not controlled with a synthetic resin together with an antibacterial composition has been proposed (JP-A-4-145007, JP-A-6-1721).
No. 03), the discoloration is not completely suppressed. The present inventor has conducted various studies to find out the pH of hydrotalcites.
Was adjusted to 5.0 to 8.0 and mixed with an antibacterial zeolite, it was found that discoloration of the synthetic resin could be more effectively suppressed. The reason for adjusting the pH to 5.0 to 8.0 is that the original pH of hydrotalcites is 10.0.
This is because of the above. Under such a high pH atmosphere, there is a high possibility that the antibacterial metal ion becomes an oxide when the synthetic resin is molded or used as a product. In particular, it is well known that silver oxide is remarkably discolored and has low antibacterial performance, and the pH is adjusted to prevent this. On the other hand, it is not clear why hydrotalcites are mixed in advance with the antibacterial zeolite to increase the discoloration suppressing effect, but the present inventors speculate as follows. The compound causing discoloration in the synthetic resin is
Discoloration can be suppressed if it does not come in contact with antibacterial metal ions. That is, the hydrotalcites may be present as close as possible to the antibacterial metal ion, and the compound that induces discoloration may be removed from around the metal ion. If the hydrotalcites and the antibacterial zeolite are mixed in advance, they can be closer to each other than when individually added to the synthetic resin. Therefore, it is considered that discoloration of the synthetic resin can be more effectively prevented. Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrotalcites used in the composition of the present invention are effective for both natural and synthetic products. Synthetic products that have been synthesized industrially stably and have also been used as pharmaceuticals for capturing gastric acid components utilizing anion exchange properties are more suitable. Synthetic products are classified according to the molar ratio of magnesium oxide to aluminum oxide, specific surface area, and the like. Generally, it is represented by the following structural formula. Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O It has a layered two-dimensional structure, has a positive surface charge, and is a basic substance. The anion exchange reaction is based on the carbonate ion C in the structure.
Occurs between O ₃ ^- and an anion outside the system. The anion exchange capacity is approximately 4 meq / g. What is characteristic at this time is that the released CO ₃ ^- is completely neutral, and there is no possibility of causing a corrosive problem. Further, since the above structure does not collapse up to about 300 ° C. in synthetic hydrotalcites, most of synthetic resins endure heating during molding. These properties cause the pH to rise from around 10.0 to 5.0 to 5.0.
It is maintained even when adjusted to 8.0.

The shape of the hydrotalcites used in the present invention is preferably a powder. The particle size is not limited, but is preferably 5 μm or less depending on the application, for example, when used for a thin film or fiber. When used for general-purpose plastic products, the thickness may be several μm to 10 μm. However, considering the dispersibility of the antibacterial zeolite, it is preferable that the difference between the hydrotalcites and the particle size of the zeolite is not large.

[0010] The zeolite used in the present invention can be either a synthetic product or a natural product. Zeolites are generally known as alkali metal or alkaline earth metal crystalline aluminosilicates. Has a three-dimensional crystal structure, number ~
It has a fine pore diameter of more than 10Å inside. Natural zeolites include mordenite, chabazite, clinoptilolite, erionite, and the like, and synthetic products include A-type zeolites, X-type zeolites, and Y-type zeolites. The general formula of the synthetic product is shown below. A type zeolite xM _1/2 O.Al ₂ O ₃ .2SiO ₂ .4.5H ₂ O X type zeolite xM _1/2 O.Al ₂ O ₃ .2.5SiO ₂ .6H ₂ O Y type zeolite xM _{1 / 2 O · Al 2 O 3 ·} 4.8SiO 2 · 8.9H 2
OM represents an ion-exchangeable metal ion. Generally, it is a monovalent or divalent metal ion. The three-dimensional structure of the above zeolites does not collapse up to 900 ° C. Therefore, it can sufficiently withstand heating during molding of the synthetic resin. The ion exchange capacity of these natural and synthetic zeolites is 2.6 to 7 meq / g and can sufficiently support silver ions and the like.

The zeolite used in the present invention is preferably in the form of powder. The particle size may be selected in the same manner as for hydrotalcites.

The method for producing the inorganic antibacterial composition of the present invention will be described below. First, zeolite is made into a suspension using water from which ions have been removed. It is desirable that the pH of the aqueous zeolite suspension be adjusted to 5.0 to 8.0. In an acidic solution having a pH of less than 5.0, zeolite and hydrotalcites are easily dissolved, so that antibacterial metal ions cannot be supported. Further, the pH is 8.0.
If it exceeds, the metal oxide will precipitate and the antibacterial activity will decrease,
This is because the discoloration of the synthetic resin is easily caused. At this time, even if the pH of the zeolite is adjusted, the pH gradually approaches the original pH. This is because the buffering action of zeolite works. Immerse while replenishing acid until pH 5.0-8.0 is maintained. The acid used is nitric acid,
Any of inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid and formic acid may be used. Subsequently, an antibacterial metal ion aqueous solution is added to the zeolite. The addition method can be arbitrarily selected, such as a batch method or a column method. The antibacterial metal compound to be used may be any compound as long as it is water-soluble, for example, silver nitrate, silver acetate, zinc nitrate, zinc sulfate, zinc acetate, copper nitrate, copper sulfate, copper acetate and the like can be used. . As the antibacterial metal ion aqueous solution, a solution in which silver, zinc, a copper compound or the like is dissolved alone may be used, or two or more ions may be added continuously or as a mixed solution. Further, the zeolite may be directly immersed in the antibacterial metal ion aqueous solution. Also in this case, it is more preferable that the pH be adjusted to 5.0 to 8.0 to perform ion exchange to suppress the deposition of the metal oxide. The amount of the antibacterial metal ion carried can be adjusted by the concentration of the aqueous solution, and may be selected according to expected performance. Silver ion 3 to 60 m as the concentration in the preparation system
M, zinc ion 2-300 mM, copper ion 2-200 m
M is preferred. If the concentration is too high, the supporting reaction does not proceed efficiently, and metal oxides and hydroxides are deposited on the zeolite surface, and the antibacterial activity decreases. When prepared at the above concentration, an antibacterial composition having a silver ion content of 0.5 to 5%, a zinc ion content of 0.1 to 15%, and a copper ion content of 0.1 to 8% can be obtained. After addition of antibacterial metal ions, 3-24
Allow time to mature. At this time, it is desirable to maintain the temperature at 30 to 70 ° C. in order to efficiently perform the ion exchange reaction.
After aging, the zeolite is separated from the suspension, washed, dried and pulverized according to a conventional method to obtain an antibacterial zeolite. Drying can be arbitrarily selected, for example, at a normal pressure of 105 ° C to 120 ° C or under reduced pressure.

The addition of hydrotalcites is preferably carried out during or after the preparation of the antibacterial zeolite. Regardless of which method is used, it is desirable that the pH of the hydrotalcites be adjusted to 5.0 to 8.0. As described above, like the synthetic zeolite, synthetic hydrotalcites exhibit alkalinity.
The method of adding hydrotalcites to the system when the metal ions are supported is preferred because the process can be simplified.
The hydrotalcites may be added at any time during the preparation of the antibacterial zeolite, but after the hydrotalcites are added to the preparation system, the pH of the preparation system is adjusted to 5.
Adjust to 0-8.0. When hydrotalcites are added to the antibacterial zeolite after preparation, the pH of the hydrotalcites may be adjusted in advance. pH
After the adjustment, the hydrotalcites are dried and pulverized according to a conventional method. Mixing with the antibacterial zeolite may be performed by a generally known method, for example, dry blending. The amount of hydrotalcite added is preferably about 5 to 45% by weight of the raw material zeolite in any method. If it is less than 5% by weight, the effect of suppressing discoloration is small, and if it exceeds 45% by weight, the physical properties of the synthetic resin may be reduced. Within this range, the addition amount is arbitrarily determined by judging from the degree of suppression of discoloration, cost, physical properties of the synthetic resin and the like.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

[0015]

【Example】

(Example 1) 20 g of powder type A zeolite (Silton B, manufactured by Mizusawa Chemical Co., Ltd.) and 10 g of powdered hydrotalcite (HTD-4C, manufactured by Kyowa Chemical Industry Co., Ltd.)
It was suspended in 0 ml of ion-exchanged water. 90 ml of a 1 M aqueous nitric acid solution was added to the suspension, and the pH of the suspension was adjusted to 5.0 to 8.0.
Adjusted to zero. Keep the temperature of the suspension at 50 ° C and 0.1M
46 ml of an aqueous silver nitrate solution was added. After aging for 24 hours, the mixture was filtered, washed with 500 ml of ion-exchanged water, and filtered. The solid was left at normal pressure at 110 ° C. for 16 hours and pulverized to obtain 100 g of the inorganic antibacterial composition of the present invention.

Example 2 10 g of powdered synthetic hydrotalcite was suspended in 50 ml of ion-exchanged water. 30 ml of a 1 M aqueous nitric acid solution was added to adjust the pH of the suspension to 5.0 to 5.0.
It was adjusted to 8.0. This was filtered and left at 110 ° C. for 16 hours to obtain 10 g of a solid. This was mixed with 90 g of a solid obtained by removing the powdered synthetic hydrotalcite from Example 1 to obtain 100 g of the inorganic antibacterial composition of the present invention.

Comparative Example 1 A powdery synthetic hydrotalcite was prepared from Example 1 to obtain 90 g of a solid.

COMPARATIVE EXAMPLE 2 90 g of the antibacterial zeolite obtained in Comparative Example 1 was mixed with 10 g of hydrotalcite (pH as a suspension of 10.5) which had not been subjected to pH adjustment. A solid was obtained.

The inorganic antibacterial composition obtained by the above method was evaluated for antibacterial performance and weather resistance.

(Preparation of Antibacterial Resin Sheet) In Example 1, polypropylene resin (AW-630V, manufactured by Sumitomo Chemical Co., Ltd.) was used.
2 and the antibacterial compositions of Comparative Examples 1 and 2
% And 1.0%. Then 230 ° C
The sheet was formed using an electrothermal press sheet molding machine (37 t, two-stage press type, Kansai Roll Co., Ltd.) adjusted to the above. 12
An antibacterial polypropylene resin sheet of 0 × 120 × 1 mm (thickness) was obtained.

(Evaluation of antibacterial performance) Test bacteria, Escherichia coli (Escherichia coli) and Staphylococcus cultured for 18 hours
aureus (Staphylococcus aureus) was 2.0 × 1 in sterile purified water to which 1/500 nutrient broth medium was added.
0 was prepared in ^{5 ~1.0} × 10 ⁶ (pieces / ml). The antibacterial resin sheet mixed with the above antibacterial composition is cut into a square of 5 cm, placed in a sterile petri dish, and placed on a 0.5 ml sheet.
4.5 cm square coated film (made of polyethylene, which is obtained by cutting a bag for stomacher 80)
And the dish was sealed and stored at 35 ° C. A sheet to which no inorganic antibacterial composition was added (hereinafter, abbreviated as a blank sheet) was similarly treated. Seat is 2
After 4 hours, the cells were washed with 9.5 ml of SCDLP (soybean casein digestive lecithin polysorbate) medium, and the number of viable cells in 1 ml was measured by an agar plate culture method. This test method conforms to the efficacy test method I for antibacterial processed products of the 1995 edition of the silver-based inorganic antibacterial agent research group.

The evaluation results of the antibacterial performance are shown in Table 1. The sample was 10 ² or less. No difference in efficacy between the inorganic antibacterial composition of the present invention and the antibacterial zeolite (Comparative Example 1) was observed, and it was confirmed that the composition had sufficient antibacterial activity.

[0023]

[Table 1]

(Evaluation of weather resistance performance) The polypropylene resin sheet to which the inorganic antibacterial composition was added was exposed to ultraviolet light for 24 hours.
After the exposure for 48 and 168 hours, the state of discoloration was visually confirmed and evaluated.

Table 2 shows the evaluation results of the weather resistance performance. As shown in the table, the antibacterial zeolite (Comparative Example 1) was 0.5
In the sheet with% added, discoloration began to occur after 24 hours of UV exposure, and strong discoloration was observed as the UV exposure time was increased. The sheet to which Comparative Example 2 was added had less discoloration than Comparative Example 1;
Discoloration was stronger than 2. Inorganic antibacterial composition of the present invention,
In particular, in Example 1, discoloration was slight after exposure to ultraviolet light for 168 hours even in a sheet in which the amount of addition was increased to 1%.

[0026]

[Table 2]

[0027]

The inorganic antibacterial composition of the present invention comprising a hydrotalcite having a pH adjusted to 5.0 to 8.0 and an antibacterial zeolite is molded when added to a synthetic resin. Coloring due to processing and discoloration due to ultraviolet light were suppressed. Further, a useful synthetic resin molded product having high antibacterial performance can be provided.

Claims (3)

[Claims] 1. An antibacterial zeolite having a pH of 5.0 to 5.0.
An inorganic antibacterial composition containing hydrotalcites adjusted to 8.0. 2. When preparing an antibacterial zeolite, hydrotalcites are dispersed in the reaction system to adjust the pH to 5.0 to 5.0.
The inorganic antibacterial composition according to claim 1, which is obtained by adjusting to 8.0. 3. An antibacterial zeolite and a pH of 5.0 in advance.
The inorganic antibacterial composition according to claim 1, which is obtained by mixing hydrotalcites having a pH of from 8.0 to 8.0.