JP2007031290A - Antibacterial agent aqueous solution and its preservation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antibacterial aqueous solution that exhibits preservation stability excellent enough not to thicken during preservation by not causing the thickening phenomenon during preservation of an antibacterial agent aqueous solution comprising a silane compound bearing an antibacterial functional group that has a favorable light environmental load compared with an organic solvent solution. <P>SOLUTION: An antibacterial agent stock solution is diluted with water to give the antibacterial agent aqueous solution having a predetermined concentration. The pH of the aqueous solution is adjusted within the range of 3.5-2.0 by addition of an acid such as hydrochloric acid. The thus-obtained aqueous solution is preserved at 10°C or a lower temperature to give the stable antibacterial aqueous solution suffering from no viscosity changes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aqueous solution of an antibacterial agent containing a silane compound and excellent in storage stability. The aqueous solution of the antibacterial agent imparts antibacterial properties to the surfaces of various metals such as titanium and stainless steel, glass, ceramics, resins and fibers. Applied for.

The alkoxysilane compound is a surface modifier well known as a silane coupling agent. A technique for imparting antibacterial properties to the surface of titanium, glass, resin or the like using a silane compound in which an antibacterial functional group is bonded to this compound is disclosed (Patent Document 1).
JP 2004-209241 A

The present inventors have prepared an antibacterial solution obtained by diluting a stock solution (methanol solution) of octadecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (hereinafter abbreviated as ODQAS) excellent in antibacterial property as a silane compound disclosed in Patent Document 1 with a solvent. We have been studying antibacterial treatment of the surface of various materials using agent solutions. In that case, considering that it is preferable to use water that has less environmental impact than the organic solvent as the solvent to be diluted, the methanol stock solution was diluted with water to prepare an aqueous antimicrobial agent solution.
However, we found a phenomenon that the viscosity of the aqueous solution increased with time if it was simply diluted with water and stored. The increase in viscosity suggests that the silane compound has undergone some chemical reaction in the aqueous solution, and the diligent study has been conducted on the preparation and storage method of the aqueous solution with excellent storage stability that does not cause such changes. Was done.

上記の化学構造において、Ｒｎ（ｎは整数）は炭素数４〜２２のアルキル基、Ｒはメチル基またはエチル基である。 The said subject is solved by adjusting PH of the said aqueous solution to 3.5-2.0 in the antibacterial agent aqueous solution containing the silane compound which has the following chemical structure. Moreover, it is solved by storing an antimicrobial agent aqueous solution containing a silane compound having the following chemical structure and having a pH adjusted to 3.5 to 2.0 at a temperature of 10 ° C. or lower. As the silane compound contained in the antibacterial agent aqueous solution of the present invention, it is preferable to use ODQAS in which Rn group is an octadecyl group and R group is a methyl group in (Chemical Formula 1) because of excellent antibacterial properties.

In the above chemical structure, Rn (n is an integer) is an alkyl group having 4 to 22 carbon atoms, and R is a methyl group or an ethyl group.

  By adjusting the pH of the aqueous solution of the silane compound having antibacterial properties to a range of 3.5 to 2.0, and storing this aqueous solution at 10 ° C. or less, there is no change in viscosity of the aqueous solution over time, and storage stability. It is possible to prepare an antibacterial agent aqueous solution excellent in water resistance. This makes it possible to use an aqueous solution of antibacterial agents that does not use organic solvents and is free of environmental pollution, and can easily manufacture hygienic products with antibacterial properties by treating the surface of various antibacterial materials. .

  The antibacterial agent used in the present invention is a silane compound having a structure represented by (Chemical Formula 1). In this chemical structure, Rn (n is an integer) is an alkyl group having 4 to 22 carbon atoms, and R is a methyl group or an ethyl group. R is an alcohol residue of an alkoxysilyl group. For example, in the case of a methoxy group, the silane compound is generally obtained as a methanol solution used in the production process.

  In this antibacterial agent, the alkoxysilyl group reacts with a functional group such as a hydroxyl group present on the surface of the antibacterial material and is immobilized on the surface of the material, or polymerized by an intermolecular condensation reaction of alkoxysilyl groups. It is thought that it adheres to. It is considered that the antibacterial action is expressed by a quaternary ammonium salt present in the molecule. Among these antibacterial agents, Rn is an octadecyl group, R is a methyl group compound, and ODQAS was examined for its storage stability in order to show excellent antibacterial properties.

  The antibacterial aqueous solution referred to in the present invention is a solution obtained by diluting an antibacterial agent stock solution such as a methanol solution with water, as described above, and contains a little stock solution solvent such as methanol in water. Since the stock solution of antibacterial agent is supplied as an alcohol solution containing several tens of percent of the antibacterial agent, when diluted with water to form an aqueous solution, the concentration of alcohol is several percent or less, and most of the solution is a water solution. The dilution factor, that is, the concentration of the antibacterial agent contained in the aqueous solution is appropriately selected depending on the type, form, surface area, and the like of the antibacterial material, but is preferably used in the range of 0.1 to 5 wt%. The antibacterial treatment is simply performed by bringing these aqueous antibacterial agents into contact with the surface of the antibacterial material for a certain period of time and then washing and drying.

  However, it has been found that when an aqueous solution diluted with water is stored, the viscosity of the aqueous solution increases within a few days. On the other hand, the solution diluted with methanol was stable with no change in viscosity with time. It is considered that the ODQAS molecule has undergone some reaction between molecules or molecules in the aqueous solution, causing structural changes in the viscosity of the aqueous solution over time. investigated. Moreover, since it will become difficult for the antimicrobial agent aqueous solution to contact the surface of an antimicrobial material uniformly when a viscosity increases, it is not preferable.

  By examining the thickening phenomenon of the aqueous solution by changing the concentration of the antibacterial agent in the aqueous solution of the antibacterial agent, it was found that this phenomenon tends to occur when the concentration of the antibacterial agent in the aqueous solution is high. Examining the change in viscosity over time with an ODQAS aqueous solution at an antibacterial agent concentration of 3 wt%, it can be seen that when the aqueous solution storage temperature is low, for example, refrigerator temperature and winter room temperature increase particularly greatly. It was. The pH of the ODQAS aqueous solution varies slightly depending on the dilution ratio of the stock solution, but shows a value of 5 to 6.5 when the ODQAS concentration is in the range of 0.1 to 5 wt%. Changes in viscosity over time were examined with a solution prepared by adding a small amount of acid such as hydrochloric acid to this aqueous solution to reduce the pH.

  As a result, the change in viscosity over time does not occur by adjusting the pH of the aqueous solution, and if the pH is 3.5 or less, preferably 3.0 or less, the change in viscosity may not occur for at least one month at the refrigerator temperature. I understood. When PH is further lowered to 1.0 or less, condensation polymerization of ODQAS proceeds and a cloudy precipitate is generated. When PH is 2.0 or less, no precipitate is generated, but the acidity of the aqueous solution becomes strong, and depending on the material to be antibacterial, it may be corroded by acid during antibacterial treatment, so the lower limit is 2.0. The above is preferable. That is, by adjusting the pH of the aqueous solution to 3.5 or less, preferably 3.0 or less, 2.0 or more, an antibacterial agent aqueous solution having excellent storage stability and low corrosiveness to the antibacterial material can be obtained. found.

  On the other hand, in the antibacterial agent aqueous solution in which the ODQAS concentration in the aqueous solution was adjusted as low as 0.6 wt%, the thickening phenomenon did not occur for at least one month without adjusting the pH to a low state. However, even in an aqueous solution with a low concentration of the antibacterial agent, if the pH is high, the reaction may potentially proceed in the aqueous solution to show thickening, and the antibacterial agent concentration is low considering long-term storage exceeding 1 month. Even in an aqueous solution, it is preferable to store the solution in a pH adjusted to a range of 3.5 to 2.0.

    It was found that the aqueous antibacterial agent solution having a pH adjusted to a range of 3.5 to 2.0 does not show thickening when stored at a low temperature, but slightly thickens at room temperature such as summer. As a result of examining the storage temperature, it was found that if it is 10 ° C. or less, even in a high concentration antibacterial agent aqueous solution, it does not show thickening for at least one month. Accordingly, the antibacterial agent aqueous solution is adjusted to a pH of 3.5 to 2.0 and stored at a temperature of 10 ° C. or less, preferably 8 ° C. or less. Antibacterial agents that do not work can be stored in an aqueous solution.

  The increase in the viscosity of the aqueous antibacterial agent effected by the storage temperature is larger in the aqueous solution (PH: 5 to 6.5) where the pH is not adjusted than in the case where the storage temperature is low, and the above PH is 3.5 to The temperature dependence opposite to that of the antimicrobial agent aqueous solution of the present invention adjusted to the range of 2 was shown. Therefore, it is considered that the denaturation reaction related to thickening is different in each aqueous solution.

  Next, the adjustment method of the antimicrobial agent aqueous solution of this invention is demonstrated. In the case of ODQAS, for example, it is supplied in a state of a 60 wt% methanol solution. This methanol solution is diluted with purified water so that the concentration of ODQAS is 0.1 to 5 wt%. The pH of the diluted aqueous solution varies depending on the concentration of ODQAS, but the pH is in the range of 5 to 6.5. An acid is added to this aqueous solution to adjust the pH to 3.5 or less, preferably 3.0 or less, and 2.0 or more. As the acid, any of inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid and organic acids such as formic acid and acetic acid can be used, but hydrochloric acid is preferred.

  The present invention will be described in more detail with reference to the following examples, but the technical scope of the present invention is not limited to these examples. In addition,% shows weight% unless there is particular notice.

  A commercially available ODQAS 60% methanol solution was diluted with purified water to an ODQAS concentration of 3%. The pH of this diluted solution was 5.35 (referred to as solution A). This A liquid was divided into B liquid and C liquid, and a small amount of 1N hydrochloric acid was added to each to make PH = 4.10 (liquid B) and PH = 3.11 (C) liquid. The A, B, and C liquids were placed in a glass container, sealed, and allowed to stand at room temperature, and the change with time in viscosity was measured. The viscosity was measured at 20 ° C. using a rotary viscometer. The results are shown in Table 1. From this result, it can be seen that the liquid C is stable with no change over time in viscosity even after one month as compared with the liquids A and B.

  This experiment was conducted in Hiroshima City for about a month from January 25, 2005. The temperature of Hiroshima City during this period was the highest, lowest, and average in February as measured on the Hiroshima Regional Meteorological Observatory website. The air temperatures were 16.2 ° C, -4.0 ° C, and 4.9 ° C, respectively.

  A liquid A was prepared in the same manner as in Example 1. A small amount of acetic acid was added to this liquid A to adjust the pH to 2.99 (referred to as liquid D). The liquid D was allowed to stand at room temperature for the same period as in Example 1, and the change with time in viscosity was examined. The viscosity was almost the same as that of the liquid C in Example 1, and hardly changed even after one month.

  A liquid A was prepared in the same manner as in Example 1. The solution A was divided and a small amount of 1N hydrochloric acid was added to prepare solution E (PH = 2.85). The A and E liquids were put in a glass container, sealed and allowed to stand at room temperature, and the change with time in viscosity was measured for about 1 month. The results are shown in Table 2. This experiment was conducted in Hiroshima City for about a month from June 2, 2005. The temperature of Hiroshima City during this period is the highest, lowest, and average in June as measured on the Hiroshima Regional Meteorological Observatory website. The temperatures were 32.4 ° C, 15.6 ° C and 24.5 ° C, respectively.

  From the results shown in Table 2, it was found that even with the E solution having a lowered PH, thickening slightly occurs when the storage temperature is high. Further, the degree of thickening of the liquid A was lower than that of Example 1, and it was found that an aqueous solution having a high pH was difficult to thicken when the storage temperature was high.

  A liquid A was prepared in the same manner as in Example 1. The solution A was divided and a small amount of 1N hydrochloric acid was added to prepare solution F (PH = 2.85). The A and F liquids were put in a glass container, sealed, stored in a refrigerator adjusted to 8 ° C., and the change with time in viscosity was measured for about 1 month. The results are shown in FIG. 1. The liquid A showed a large increase in viscosity as in Example 1, but the viscosity of the liquid F did not change.

  A commercially available ODQAS 60% methanol solution was diluted with purified water so that the ODQAS concentration was 0.6% to prepare solution G (PH = 5.67). This G liquid was divided | segmented and 1N hydrochloric acid was added a little and H liquid (PH = 2.83) was adjusted. G liquid and H liquid were each put in a glass container, sealed, stored in a refrigerator adjusted to 8 ° C. and a constant temperature room at 45 ° C., and the change with time in viscosity was measured for about 1 month. In both G and H liquids, no change in viscosity occurred at storage temperatures of 8 ° C. and 45 ° C. for one month.

Antibacterial aqueous solutions A and C immediately after adjustment were prepared under the same conditions as those prepared in Example 1. Using a titanium plate (a titanium washer having a diameter of 10 mm and an inner diameter of 4.5 mm) as an antibacterial material, an antibacterial treatment was conducted by the following method.
Antibacterial treatment: Titanium plates were immersed in each of liquid A and liquid C for 30 minutes at room temperature for antibacterial treatment, and the titanium plate was taken out, washed with purified water and dried. Separately, the titanium plate was immersed in purified water for 30 minutes and subjected to the same treatment to obtain an untreated titanium plate.
Antibacterial test: The test was performed by the method of Nikawa et al. (Nikawa H, Nishimura H, Yamamoto T, Hamada T, Samarayanake LP, Microbial Ecol Health and Dis 9: 35-48 1996). 50 μl of Candida albicans bacterial solution adjusted to 1.0 × (10 7) cfu / ml was inoculated on the titanium plate, and left at 37 ° C. for 2 hours to allow the bacteria to adhere to the titanium plate. Thereafter, 2 ml of Sabouraud medium was added and cultured at 37 ° C. for 48 hours. After culturing, excess bacteria on the surface of the titanium plate were removed by washing with water, and the amount of ATP (adenosine triphosphate) was extracted from the biofilm formed on the titanium plate and quantified.
-Results: The titanium plate treated with the A solution and the C solution had a significantly reduced ATP amount compared to the untreated plate, and the bacterial adhesion was clearly less. Moreover, the difference between A liquid and C liquid was hardly seen.

  This antibacterial aqueous solution is capable of imparting antibacterial properties to the surface of various materials such as metals, glass, ceramics, resins, and fibers with a simple treatment that does not cause environmental pollution. It can be used effectively in certain fields.

FIG. 3 is a view showing a change with time in viscosity of an antibacterial aqueous solution. (Example 4)

Claims (4)

An antibacterial aqueous solution containing a silane compound having the following chemical structure, wherein the aqueous solution is adjusted to a pH of 3.5 to 2.0.

In the above chemical structure, Rn (n is an integer) is an alkyl group having 4 to 22 carbon atoms, and R is a methyl group or an ethyl group.   The antibacterial aqueous solution according to claim 1, wherein the silane compound is octadecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride. An antibacterial aqueous solution storage method comprising storing an antibacterial aqueous solution containing a silane compound having the following chemical structure and having a pH adjusted to 3.5 to 2.0 at a temperature of 10 ° C. or lower.

In the above chemical structure, Rn (n is an integer) is an alkyl group having 4 to 22 carbon atoms, and R is a methyl group or an ethyl group.   The method for preserving an aqueous solution of an antimicrobial agent according to claim 3, wherein the silane compound is octadecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride.

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