Antimicrobial glass and resin composition

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a glass having a property of suppressing the growth of bacteria and reducing the number of bacteria (hereinafter referred to as antibacterial property), and a polystyrene resin composition containing the glass.

【0002】

[Conventional technology]

Since silver or silver ion has an antibacterial action, antibacterial glass in which silver is contained in borosilicate glass is used.

【0003】

This antibacterial glass is usually used in the form of flakes, fibrous or powder mixed with a resin product. When water adheres to the surface of this antibacterial resin product, silver in the antibacterial glass gradually dissolves in the water, and silver or silver ions are present on the surface of the product. Shows antibacterial properties against attached bacteria.

【0004】

[Problems to be Solved by the Invention]

The conventional antibacterial polystyrene resin kneaded with silver-containing borosilicate glass is inferior in transparency because the refractive index of the antibacterial glass is smaller than that of the polystyrene resin.

【0005】

An object of the present invention is to provide an antibacterial glass capable of enhancing the transparency of a polystyrene resin product containing a borosilicate antibacterial glass, and a polystyrene resin composition containing the glass.

【0006】

[Means for solving problems]

The antibacterial glass of the present invention is an antibacterial glass made of borosilicate glass containing silver, and the refractive index of the glass is 1.57 to 1.63, and silver is added to Ag.₂It is characterized by containing 0.1 to 5.0% by weight of O and having an elution rate of silver into water of 0.005 to 5 mg / g / hr when the average particle size is 10 μm.

【0007】

The borosilicate glass preferably has the following composition.

【0008】

SiO₂ 10 ~ 50% by weight B₂O₃ 10 ~ 54% by weight R₂O (alkali metal oxide or Na₂O, L₂O and K₂1 or 2 of O Seeds and above) 0 ~ 20% by weight Al₂O₃ 0 ~ 20% by weight TiO₂ 0 ~ 10% by weight Ag₂O 0.1 ~ 5.0% by weight La₂O₃ 10 ~ 25% by weight One or more of ZnO, BaO, CaO and MgO 10 ~ 45% by weight However, La₂O₃, ZnO, BaO, CaO and MgO total 35-55% by weight.

【0009】

The antibacterial glass of the present invention is preferably in the form of powder, flakes or fibers. In particular, powder having an average particle size of 0.1 to 50 μm, flakes having an average thickness of 0.1 to 30 μm, or fibers having a fiber diameter of 0.1 to 30 μm are preferable.

【0010】

The antibacterial resin composition of the present invention is a polystyrene resin containing 0.05 to 10% by weight of the antibacterial glass of the present invention.

【0011】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail. In the following,% represents weight%.

【0012】

The antibacterial glass of the present invention is Ag.₂Contains O and, if necessary, alkali metal oxides (R₂O), Al₂O₃And TiO₂In borosilicate glass, La₂O₃It is obtained by adding one or more of ZnO, BaO, CaO and MgO together with the above to increase the refractive index thereof, and is preferably composed of the above composition. Next, the reason why this composition is preferable will be described.

【0013】

SiO₂Is a glass skeleton, and its content is preferably 10 to 50%, particularly preferably 10 to 40%. SiO₂When the content of is less than 10%, the skeleton formation of the glass becomes insufficient, and the elution of the water-soluble component in the glass into water cannot be appropriately suppressed. In this case, when the glass comes into contact with water, silver rapidly elutes into the water and the antibacterial property disappears in a short time. Further, if a large amount of silver is eluted in a short time, the resin composition may be discolored. SiO₂If it is more than 50%, the skeleton of the glass becomes excessively strong, the elution rate of silver becomes too low, and sufficient antibacterial action cannot be obtained.

【0014】

B₂O₃Is added to give boron ions that bind to silver ions. In addition, the elution of silver ions is controlled so that the water solubility of the glass of the present invention is adjusted and antibacterial properties are exhibited.

【0015】

B₂O₃The preferred content of is 10 to 54%, particularly preferably 20 to 50%. B₂O₃If the content of silver is less than 10%, the elution of silver into water becomes excessively small, and the antibacterial property is not sufficiently exhibited. B₂O₃If the content of silver is more than 54%, the elution rate of silver into water becomes excessive, the antibacterial property of the glass disappears at an early stage, and the polystyrene resin composition may be discolored due to silver.

【0016】

Al₂O₃Is not an essential component, but is added as needed to provide aluminum ions that bind to silver ions. The amount added is 0 to 20%, preferably 0 to 10%.

【0017】

TiO₂Is not an essential ingredient, but can be added for glass formation. The amount added is 0 to 10%, preferably 0 to 5%.

【0018】

In addition, Al₂O₃Is over 20% or TiO₂When is more than 10%, the elution rate of silver becomes excessively low in each case, and sufficient antibacterial properties cannot be obtained. Also, Al₂O₃Has the effect of raising the melting point of glass, and if the amount added exceeds 10%, it becomes difficult to melt the glass.

【0019】

Ag₂O is added to impart antibacterial properties. The amount added is 0.1 to 5.0%, preferably 0.5 to 2.0%. In addition, Ag₂If O is less than 0.1%, the antibacterial property becomes insufficient, and if it exceeds 5%, the polystyrene resin may be discolored.

【0020】

R₂O (Na₂OK₂O and Li₂One or more of O) is not an essential ingredient, but in the range of 0-20%, particularly preferably 0-10%, as needed to increase the stability of the glass and to regulate water solubility. Is added.

【0021】

La₂O₃, ZnO, BaO, CaO and MgO are all added to increase the refractive index as described above.

【0022】

In general, the refractive index of glass can be easily increased by adding PbO, but there are problems with the handling of lead compounds during production and the safety of lead compounds in products. On the other hand, La₂O₃Etc. are chemically stable compounds, and there is no problem in terms of safety. However, it is not as effective as lead in increasing the refractive index of glass, and La₂O₃Is very expensive compared to lead, so it is necessary to reduce the amount of addition in consideration of economic efficiency. La₂O₃10 to 25%, one or more of ZnO, BaO, CaO and MgO 10 to 45% (however, La₂O₃, ZnO, BaO, CaO and MgO (35 to 55% in total), a refractive index close to that of polystyrene resin can be obtained.

【0023】

La₂O₃A particularly preferable amount of addition is 10 to 20%. The preferable amount of one or more of ZnO, BaO, CaO and MgO added is 15 to 30%.

【0024】

La₂O₃, ZnO, BaO, CaO and MgO are particularly preferably in the total amount of 35-50%.

【0025】

In general, the elution of silver ions is a very important factor for the antibacterial properties of glass. That is, when the elution of silver ions is small, antibacterial properties are not exhibited. As for the elution amount of this silver ion, the antibacterial property is not sufficiently exhibited unless the elution rate in water is 0.005 mg / g / hr or more when the average particle size is 10 μm. In addition, mg / g / hr is the amount of silver eluted from 1 g of antibacterial glass per hour. Further, when the elution rate is higher than 5 mg / g / hr, the antibacterial property is sufficiently exhibited, but the discoloration of the polystyrene resin molded product due to silver becomes large. By adjusting the elution rate of this silver ion into water to 0.005 to 5.0 mg / g / hr, a polystyrene resin molded product having a good balance between antibacterial properties and prevention of discoloration of the molded product can be obtained. The elution rate of this silver ion is the glass composition and Ag in the glass.₂This can be achieved by adjusting the amount of O.

【0026】

Since the refractive index of the polystyrene resin is about 1.6, an antibacterial glass-containing polystyrene resin molded product having good transparency can be obtained by setting the refractive index of the glass in the range of 1.60 ± 0.03.

【0027】

The antibacterial glass of the present invention provides a polystyrene resin molded product having both excellent antibacterial properties and transparency.

【0028】

The glass of the present invention is preferably composited with polystyrene resin in the form of powder, flakes or fibers. In addition, it is particularly preferable that it is in the form of powder or flakes because silver is easily eluted.

【0029】

In the case of powder, the average particle size of the glass powder is preferably 0.1 to 50 μm, particularly preferably 1 to 25 μm. If the average particle size is larger than 50 μm, it is difficult to uniformly disperse the glass powder in the resin. If the average particle size of the glass is smaller than 0.1 μm, the grinding cost will be excessive.

【0030】

When the glass is in the form of flakes, it is preferably set to have a major axis of 10 to 1000 μm and a thickness of 0.1 to 30 μm in order to facilitate uniform dispersion in the polystyrene resin.

【0031】

Similarly, when the glass is in the form of fibers, the fiber diameter is preferably 0.1 to 30 μm in order to facilitate uniform dispersion in the polystyrene resin. The fiber length is preferably 1 to 50 mm in the case of chopped strands and 10 to 500 μm in the case of milled fibers.

【0032】

The method of mixing the powdery, flake or fibrous glass with the polystyrene resin is not particularly limited, and the glass may be mixed in a state where the polystyrene resin is heated and / or pressurized as necessary.

【0033】

This glass is contained in the polystyrene resin in an amount of 0.05 to 10%, preferably 0.1 to 5%, particularly preferably 0.2 to 2%. If the blending ratio of glass is less than 0.05%, the antibacterial property of the resin becomes insufficient, and if it exceeds 10%, more effect than the antibacterial property cannot be expected, resulting in high cost.

【0034】

[Example]

Examples and comparative examples will be described below. The performance of the glass powder produced in the following Examples and Comparative Examples and the polystyrene resin composition containing the same was judged by the following measurement, judgment method and judgment criteria.

【0035】

(1) Judgment of antibacterial performance of polystyrene resin composition (a) Type of strain used E. coli: IFO3972 Staphylococcus aureus: IFO12732 (b) Judgment of antibacterial property Established a study group on inorganic antibacterial properties such as silver "Antibacterial activity test method 1 for antibacterial processed products (Supplementary version in 1996)" (c) Judgment criteria The criteria for determining antibacterial properties are shown in Table 1 below.

【0036】

Here, logD in Table 1 is a value showing the viable cell count D after culturing as a common logarithm in the results of "Antibacterial activity test method 1 for antibacterial processed products (Supplementary version in 1996)".

【0037】

(2) Judgment of transparency (a) Judgment method The refractive index of the antibacterial glass was measured. The measurement method is the immersion method.

【0038】

(b) Judgment criteria The judgment criteria are shown in Table 1.

【0039】

[table 1]

<img file="JP2000264674A_D0001.tif" />【0040】

(3) Amount of silver water eluted Approximately 1 g of the water-soluble glass of the present invention is precisely weighed in 100 ml of distilled water, then added and stirred for 1 hour. Then, it was filtered through a filter having a pore size of 080 μm, and silver was quantified by atomic absorption spectroscopy on the filtrate.

【0041】

(Examples 1 to 13, Comparative Examples 1 to 3) The raw materials for glass having the compositions shown in Tables 2 and 3 are melted in an electric furnace at 1400 to 1500 ° C for 2 hours, cooled to obtain glass, and then milled. The mixture was pulverized to obtain a glass powder having an average particle size of 10 μm.

【0042】

The refractive index was determined by the immersion method using each glass powder. The amount of Ag elution was also determined.

【0043】

The above glass powder was kneaded into a commercially available polystyrene resin by extrusion molding at a cylinder temperature of 210 ° C (as shown in Tables 2 and 3, 0.5 parts by weight of glass was mixed with 99.5 parts by weight of polystyrene resin). Next, a 60 mm × 60 mm × 3 mm molded plate was produced by injection molding at a cylinder temperature of 210 ° C. The antibacterial property was evaluated using this molded plate.

【0044】

As shown in Tables 2 and 3, the antibacterial glasses of Examples 1 to 13 all have a refractive index in the range of 1.57 to 1.63, and the polystyrene resin kneaded with them has sufficient antibacterial properties. On the other hand, all of the glasses of Comparative Examples 1 to 3 have a refractive index outside the range of 1.57 to 1.63. Comparative example 1 is La₂O₃And BaO total 30%, and the refractive index is excessively low. Comparative example 2 is La₂O₃And BaO total 60%, and the refractive index is excessively high. Comparative example 3 is La₂O₃Is 30%, and the refractive index is excessively high. Further, in Comparative Example 2, the antibacterial property of the glass-blended polystyrene resin is also insufficient.

【0045】

[Table 2]

<img file="JP2000264674A_D0002.tif" />【0046】

[Table 3]

<img file="JP2000264674A_D0003.tif" />【0047】

[Effect of the invention]

As described above, according to the present invention, an antibacterial glass having sufficient antibacterial properties is provided, and a highly transparent polystyrene resin containing the antibacterial glass is provided.