JP5599060B2 - Antibacterial ceramic surface treatment containing ultrafine silver particle dispersion - Google Patents

Description

  The present invention relates to a silver ultrafine particle dispersion mainly containing water, and particularly to a silver ultrafine particle dispersion used for a ceramic surface treatment agent imparted with antibacterial properties, and an antibacterial ceramic surface treatment agent. is there.

  Silver ultrafine particles having a primary particle diameter of 1 μm or less, particularly silver ultrafine particles of 100 nm or less, have characteristics such as a melting point decrease due to extremely high surface energy and an electric field enhancement effect due to localized surface plasmons. While applications in various fields such as surface-enhanced Raman scattering spectroscopy, solar cells, glittering paints, and coloring materials are expected, studies on the use of silver ultrafine particles as antibacterial metals are also progressing. Such silver ultrafine particle production methods are roughly classified into a dry method and a wet method, and are used in the form of a silver ultrafine particle dispersion liquid dispersed in water and / or an organic solvent.

  For example, JP-A-3-34211 discloses a method for producing a metal ultrafine particle dispersion in which various metal ultrafine particles containing silver produced by a gas evaporation method, which is a dry method, are dispersed in a high boiling point solvent. JP-A-2004-273205 discloses silver ultrafine particles obtained by dispersing silver ultrafine particles whose surfaces are coated with an amine compound in a high-boiling solvent using silver ultrafine particles synthesized by a gas evaporation method as a raw material. A method for producing a fine particle dispersion is disclosed.

  As a method for producing silver ultrafine particles by a wet method, a method published by Carey Lea in 1889 (Non-patent Document 1, Am. J. Sci., Vol. 37, pp. 491, 1889) has been known for a long time. Japanese Patent Publication No. 1-228084 (Patent Document 1), Japanese Patent Application Laid-Open No. 10-66861 (Patent Document 2), Japanese Patent Application Laid-Open No. 2003-103158 (Patent Document 3), Japanese Patent Application Laid-Open No. 2006-328472 (Patent Document 1). Document 4), Japanese Patent Application Laid-Open No. 2008-4375 (Patent Document 5), and the like contain a water-soluble polymer compound acting as a protective colloid or a dispersant and a metal ion in an aqueous medium mainly containing water. A method for producing metal ultrafine particles by reducing the metal ions with a reducing agent is disclosed. However, the silver ultrafine particle dispersion produced by such a production method has a problem that the dispersion stability of the silver ultrafine particles decreases with time.

  Regarding dispersion stability of silver ultrafine particles, International Publication No. 2005/10100 pamphlet (Patent Document 6) is a method for improving the dispersibility in a resin by modifying the surface of silver ultrafine particles using a specific polymer. In Japanese Patent Application Laid-Open No. 2008-120863 (Patent Document 7) and International Publication No. 2002/013999 (Patent Document 8), silver ultrafine particles using mercapto compounds such as mercapto acid, mercapto acid salt and mercaptoethanol are disclosed. A method for improving the dispersion stability of a dispersion is disclosed. Moreover, it is disclosed by Unexamined-Japanese-Patent No. 2007-116137 (patent document 9) to utilize a mercapto compound as a rust preventive agent of the paste which has silver as a main component.

  On the other hand, on the surface of ceramic products, by using ceramic surface treatment agent containing antibacterial metal as an antibacterial agent for imparting antibacterial properties, due to the oligodynamic effect (suppresses the growth of fungi and mold) It is known to exhibit antibacterial properties.

  For example, JP-A-5-201747 discloses composite particles in which the antibacterial metal is supported on hydroxyapatite, JP-A-6-127975 discloses composite particles contained in a calcium phosphate compound, and JP-A-7-196384. The gazette describes that silver oxide, metallic silver, or an arbitrary silver compound, and Japanese Patent Application Laid-Open No. 2008-105920 (Patent Document 10) use ultrafine metal particles. Such antibacterial metals are generally contained in ceramic surface treatment agents composed of any combination of feldspar (silicic acid), clay (kaolin), silica, soda, potash, alumina, lime, etc., which are glaze components. The In such a glaze component, even if the above-mentioned silver ultrafine particles with improved dispersion stability are used as an antibacterial metal, the ultrafine silver particles are contained at a very low concentration, Since the pH is in a high region, it was extremely difficult to obtain sufficient dispersion stability because the ultrafine silver particles in the dispersion aggregated over time and coarsened or settled.

Japanese Patent Publication No. 1-228084 Japanese Patent Laid-Open No. 10-66861 JP 2003-103158 A JP 2006-328472 A JP 2008-4375 A International Publication No. 2005/10100 Pamphlet JP 2008-120863 A International Publication No. 2002/013999 Pamphlet JP 2007-116137 A JP 2008-105920 A

  An object of the present invention is a silver ultrafine particle dispersion mainly containing water, and particularly a silver ultrafine particle dispersion excellent in dispersion stability that can be used for a surface treatment agent for ceramics imparted with antibacterial properties, and The object is to provide an antibacterial ceramic surface treatment agent.

The above object of the present invention has been basically achieved by the following invention.
1. A surface treatment agent for an antibacterial ceramic industry containing a silver ultrafine particle dispersion mainly containing water and containing a compound represented by the following general formula (A).

In the general formula (A), R ₁ represents an organic residue substituted with at least one selected from the group consisting of —SO ₃ M, —COOM, —OH and —NHR ₂ , and M represents a hydrogen atom, an alkali A metal atom or a quaternary ammonium group or a quaternary phosphonium group is represented, and R ₂ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, —COR ₃ , —COOR ₃ or —SO ₂ R ₃ . R ₃ represents a hydrogen atom, an alkyl group or an aryl group .

  By using the silver ultrafine particle dispersion containing the mercaptotetrazole compound, the silver ultrafine particle dispersion and antibacterial ceramic industry can impart excellent dispersion stability and antibacterial properties even in a low concentration state in the glaze liquid. A surface treatment agent can be provided.

  Hereinafter, the present invention will be described in detail.

  As a result of intensive studies on the dispersion stability of the silver ultrafine particle dispersion mainly containing water, the present inventor has a low concentration dispersion state in the glaze liquid by containing the specific mercaptotetrazole compound described above. It was also found that a silver ultrafine particle dispersion capable of imparting excellent dispersion stability and antibacterial properties can be obtained.

  The silver ultrafine particle dispersion mainly containing water in the present invention indicates that water is at least 80% by mass or more, preferably 90% by mass or more, particularly preferably 98% by mass, as a solvent of an aqueous medium. It means that it is more than%. Examples of the solvent other than water include organic solvents having high miscibility with water, such as alcohols, glycols, and acetone.

  The silver ultrafine particles contained in the silver ultrafine particle dispersion of the present invention are preferably metal ultrafine particles in which the proportion of silver is at least 50% by mass or more, more preferably the proportion of silver is 70% by mass or more. Yes, particularly preferably 90% by mass or more. Examples of metals contained other than silver include gold, copper, platinum, palladium, rhodium, ruthenium, iridium, osmium, nickel, and bismuth. Metals other than silver may be contained in the silver ultrafine particles, or silver ultrafine particles and metal ultrafine particles other than silver may be mixed.

  The average particle diameter of the ultrafine silver particles is preferably 0.1 μm or less from the viewpoint of the obtained antibacterial properties. The average particle diameter of the ultrafine silver particles can be determined by observation under an electron microscope. Specifically, a silver ultrafine particle dispersion is coated on a polyethylene terephthalate film, dried, and observed with a scanning electron microscope. The diameter of a circle equal to the projected area of each of 100 particles existing within a certain area is obtained. The average is obtained as the particle diameter.

  Silver ultrafine particles include vapor evaporation in which the metal is evaporated in an inert gas and cooled / condensed and recovered by collision with the gas, laser ablation that is evaporated / condensed and recovered in the liquid by the energy of laser irradiation, and aqueous solution Known methods include chemical reduction methods that reduce, generate, and recover metal ions in solution, methods that involve pyrolysis of organometallic compounds, methods that involve reduction of metal chlorides in the gas phase, and methods for reducing oxides in hydrogen. Those produced by the various methods described above can be preferably used. In the present invention, silver ultrafine particles produced by a chemical reduction method are more preferable from the viewpoint of easy production of a silver ultrafine particle dispersion. The chemical reduction method is a method in which a water-soluble silver salt is reduced with a reducing agent in the presence of a basic compound and a water-soluble polymer compound.

  The water-soluble silver salt used in the chemical reduction method is preferably a silver nitrate salt, a silver fluoride salt or a silver perchlorate salt having high solubility in water, and particularly preferably a silver nitrate salt widely used for industrial applications. The amount of the water-soluble silver salt contained in the aqueous medium mainly containing water is a mixture in which the water-soluble silver salt, basic compound, water-soluble polymer compound and reducing agent are contained in the aqueous medium. It is preferably 0.1 mol or more, more preferably 0.5 mol or more, in terms of silver ion with respect to 1 kg. In addition, since an upper limit reaches | attains the upper limit of the solution density | concentration of water-soluble silver salt and a basic compound, it is desirable to set it as about 2.8 mol or less.

  In the method for producing ultrafine silver particles of the present invention, as the basic compound, potassium hydrogen carbonate, potassium carbonate, potassium acetate, tripotassium phosphate, potassium hydroxide, sodium hydroxide, lithium hydroxide, barium hydroxide, aqueous ammonia, etc. Can also be used, and can also be used together.

  The addition amount of the basic compound is preferably added in an amount equal to or more than the silver ion derived from the water-soluble silver salt. If the amount is less than the equivalent, the amount of silver ultrafine particles formed may be reduced and the yield of silver ultrafine particles may be reduced. Although there is no particular upper limit, increasing the addition amount of the basic compound increases the total amount of the dispersion containing the ultrafine silver particles obtained after the reaction and lowers the productivity.

  A water-soluble polymer compound acts as a protective colloid or a dispersing agent for silver ultrafine particles formed by silver oxide or reduction produced temporarily during the reaction process, and is a known water-soluble high-molecular compound used for the production of silver ultrafine particles. Molecular compounds may be used. For example, polysaccharides such as gum arabic, dextran and dextrin, natural polymer compounds such as gelatin, and synthetic polymer compounds such as polyvinyl alcohol, polyvinyl pyrrolidone and polyallylamine can be widely used.

  The addition amount of the water-soluble polymer compound varies depending on the kind and the particle size of the silver ultrafine particles to be produced, but is preferably 1 to 200 g, more preferably 20 to 100 g, per 1 mol of silver ions derived from the water-soluble silver salt. It is.

  As the reducing agent, it is sufficient to select a highly soluble reducing agent that can reduce known silver ions to silver, hydroquinone known as a developing reagent for silver salt photography, hydroquinone monosulfonate potassium salt, Ascorbic acid or its salt, sodium borohydride known as a reducing agent for electroless plating, hydrazine compound, formalin, phosphinic acid or its salt, tartaric acid or its salt, as well as polysaccharides and disaccharides such as dextrin, maltose and glucose And monosaccharides.

  As for the addition amount of a reducing agent, it is desirable to add more than an equivalent with the silver ion derived from water-soluble silver salt. Although there is no upper limit, if the amount of the reducing agent added is increased, the total amount of the obtained ultrafine silver particle dispersion is increased and the productivity is lowered. However, when polysaccharides, disaccharides, and monosaccharides are used, they are hydrolyzed by basic compounds added at the same time, and aldonic acid is used to produce various acids such as glycolic acid and other oxyacids and formic acid in various proportions. Because they contribute to reduction, they cannot be stoichiometrically discussed. In practice, a reduction of at least 5 to 10 electrons per glucose or fructose unit is possible. Therefore, when using polysaccharides, disaccharides, and monosaccharides, it is preferable to make it into 0.1-0.4 equivalent with respect to the silver ion derived from water-soluble silver salt as glucose or a fructose unit.

  When polysaccharides, disaccharides, and monosaccharides are used as the reducing agent, the basic compound is consumed for hydrolysis. Therefore, the basic compound exceeds at least an equivalent amount with respect to the silver ion derived from the water-soluble silver salt. It is necessary to add, 1.15 equivalent or more is preferable, and 1.3 equivalent or more is particularly preferable. Moreover, when using a polysaccharide, the polysaccharide can also serve as an effect as a water-soluble polymer compound.

  Next, the mercaptotetrazole compound represented by the general formula (A) contained in the present invention will be described.

In the general formula (A), R ₁ represents an organic residue substituted with at least one selected from the group consisting of —SO ₃ M, —COOM, —OH and —NHR ₂ , and M represents a hydrogen atom. , Alkali metal atoms (eg lithium, sodium, potassium etc.), quaternary ammonium groups (eg ammonio, tetramethylammonio, benzyltrimethylammonio, tetrabutylammonio) or quaternary phosphonium groups (eg tetramethylphosphonio) R ₂ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, —COR ₃ , —COOR ₃ or —SO ₂ R ₃ . R ₃ represents a hydrogen atom, an alkyl group or an aryl group.

  Here, the organic residue specifically represents an alkyl group having 1 to 10 carbon atoms (for example, methyl, ethyl, propyl, hexyl, cyclohexyl), and an aryl group having 6 to 14 carbon atoms (for example, phenyl, naphthyl). .

The organic residue represented by R ₁ in the general formula (A) may be further substituted, and examples of the substituent include the following.

  Halogen atom (fluorine, chlorine, bromine, iodine), cyano group, nitro group, ammonio group (for example, trimethylammonio), phosphonio group, sulfo group (including salt), sulfino group (including salt), carboxy group ( Salt), phosphono group (including salt), hydroxy group, mercapto group, hydrazino group, alkyl group (eg, methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, cyclopentyl, cyclohexyl) ), An alkenyl group (eg, allyl, 2-butenyl, 3-pentenyl), an alkynyl group (eg, propargyl, 3-pentynyl), an aralkyl group (eg, benzyl, phenethyl), an aryl group (eg, phenyl, naphthyl, 4 -Methylphenyl), heterocyclic groups (eg pyridyl, furyl, imidazolyl, pipette Diyl, morpholino), alkoxy groups (eg methoxy, ethoxy, butyloxy), aryloxy groups (eg phenoxy, 2-naphthyloxy), alkylthio groups (eg methylthio, ethylthio), arylthio groups (eg phenylthio), amino Groups (eg unsubstituted amino, methylamino, dimethylamino, ethylamino, alinino), acyl groups (eg acetyl, benzoyl, formyl, pivaloyl), alkoxycarbonyl groups (eg methoxycarbonyl, ethoxycarbonyl), aryloxy A carbonyl group (for example, phenoxycarbonyl), a carbamoyl group (for example, unsubstituted carbamoyl, N, N-dimethylcarbamoyl, N-ethylcarbamoyl, N-phenylcarbamoyl), an acyloxy group (for example, , Acetoxy, benzoyloxy), acylamino groups (eg acetylamino, benzoylamino), alkoxycarbonylamino groups (eg methoxycarbonylamino), aryloxycarbonylamino groups (eg phenoxycarbonylamino), ureido groups (eg none Substituted ureido, N-methylureido, N-phenylureido), alkylsulfonylamino group (eg methylsulfonylamino), arylsulfonylamino group (eg phenylsulfonylamino), alkylsulfonyloxy group (eg methylsulfonyloxy) , Arylsulfonyloxy group (eg phenylsulfonyloxy), alkylsulfonyl group (eg mesyl), arylsulfonyl group (eg tosyl), alkoxysulfonyl Groups (eg methoxysulfonyl), aryloxysulfonyl groups (eg phenoxysulfonyl), sulfamoyl groups (eg unsubstituted sulfamoyl, N-methylsulfamoyl, N, N-dimethylsulfamoyl, N-phenylsulfa) Moyl), alkylsulfinyl groups (eg methylsulfinyl), arylsulfinyl groups (eg phenylsulfinyl), alkoxysulfinyl groups (eg methoxysulfinyl), aryloxysulfinyl groups (eg phenoxysulfinyl), phosphate amide groups (eg , N, N-diethylphosphoric acid amide) and the like. These groups may be further substituted. Moreover, when there are two or more substituents, they may be the same or different.

Here, there may be two or more substituents —SO ₃ M, —COOM, —OH and —NHR ₂ of R ₁ , and the substituents may be the same or different.

In General Formula (A), R ₂ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, —COR ₃ , —CO ₂ R ₃ , or —SO ₂ R ₃ , and R ₃ represents a hydrogen atom or a carbon number 1 to 20 alkyl groups (for example, methyl, ethyl, propyl, hexyl, cyclohexyl, dodecyl, octadecyl) and aryl groups (for example, phenyl, naphthyl) are represented. These groups may be substituted by the substituents exemplified as the substituent for R ₁ .

  The amount of the mercaptotetrazole compound used in the present invention is preferably 10 g to 0.01 g, more preferably 5 g, with respect to 1 mol of silver converted from the water-soluble silver salt used in the production of silver ultrafine particles. ~ 0.5g.

  Specific examples of the compound represented by formula (A) are shown below, but the present invention is not limited thereto.

  The silver ultrafine particle dispersion obtained in the present invention can be used for purposes other than antibacterial surface treatment agents. Ultrafiltration of salts and excessive water-soluble polymer compounds contained together with silver ultrafine particles can be performed. The concentration of ultrafine silver particles is adjusted according to the purpose, and a viscosity modifier or binder is added as necessary to obtain a composition containing ultrafine silver particles. It can also be used for known applications such as a conductive material, surface-enhanced Raman scattering spectroscopy, a solar cell, a glittering paint, and a coloring material. Further, the ultrafine silver particles can be taken out from the dispersion containing the ultrafine silver particles by a method such as drying and used as a powder, or can be redispersed in an organic solvent or the like.

  Next, the surface treatment agent for antibacterial ceramics of the present invention will be described. A surface treatment agent for ceramics is generally composed of any combination of feldspar (silicic acid), clay (kaolin), silica, soda, potash, alumina, lime, etc., and such glaze components are alkaline. The surface treatment agent for ceramic industry is used in a region where the pH is as high as 10 or more. The antibacterial surface treatment agent for ceramics according to the present invention is obtained by adding a silver ultrafine particle dispersant to the above-mentioned surface treatment agent for ceramics, and the effect of dispersion stability is particularly noticeable when the pH is contained at 12 or more. Become.

  The preferable amount of the ultrafine silver particles of the present invention contained in the antibacterial ceramic surface treatment agent of the present invention is 0.0001 to 1% by mass with respect to the total amount of the antibacterial ceramic surface treatment agent in consideration of antibacterial properties, More preferably, it is 0.001-0.1 mass%.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the content of this invention is not restricted to an Example.

Example 1
<Preparation of silver ultrafine particle dispersion 1>
16 g of low molecular weight gelatin (molecular weight of about 10,000) and 181 g of pure water were added to a beaker and swollen, dissolved at 50 ° C., cooled to 15 ° C., and then added with 6.3 g of glucose to dissolve. Further, 1 g of mercaptotetrazole compound A-1 was added to the solution and dissolved, and then a solution of 71.5 g of silver nitrate dissolved in 78.5 g of pure water was added and stirred to dissolve. This solution is cooled to about 10 ° C. in an ice bath, and a solution at 10 ° C. in which 32.8 g of potassium hydroxide is dissolved in 67.2 g of pure water is added with stirring, and a reduction reaction is performed for 30 minutes. Thus, a 10% by mass silver ultrafine particle dispersion 1 was obtained.

Example 2
<Preparation of silver ultrafine particle dispersion 2>
A 10% by mass silver ultrafine particle dispersion 2 was prepared in the same manner as in Example 1 except that A-2 was added instead of the mercaptotetrazole compound A-1 in Example 1.

Example 3
<Preparation of silver ultrafine particle dispersion 3>
A 10% by mass silver ultrafine particle dispersion 3 was prepared in the same manner as in Example 1 except that A-6 was added instead of the mercaptotetrazole compound A-1 in Example 1.

Example 4
<Preparation of silver ultrafine particle dispersion 4>
A 10% by mass silver ultrafine particle dispersion 4 was prepared in the same manner as in Example 1 except that A-9 was added instead of the mercaptotetrazole compound A-1 in Example 1.

<< Comparative Example 1 >>
<Preparation of silver ultrafine particle dispersion 5>
A 10% by mass silver ultrafine particle dispersion 5 was prepared in the same manner as in Example 1 except that the mercaptotetrazole compound of Example 1 was not added.

<< Comparative Example 2 >>
<Preparation of silver ultrafine particle dispersion 6>
A 10% by mass silver ultrafine particle dispersion 6 was prepared in the same manner as in Example 1 except that mercaptoacetic acid was added instead of the mercaptotetrazole compound A-1 in Example 1.

<< Comparative Example 3 >>
<Preparation of silver ultrafine particle dispersion 7>
A 10% by mass silver ultrafine particle dispersion 7 was prepared in the same manner as in Example 1 except that 2-methylbenzothiazole was added instead of the mercaptotetrazole compound A-1 in Example 1.

<< Comparative Example 4 >>
<Preparation of silver ultrafine particle dispersion 8>
A 10% by mass silver ultrafine particle dispersion 8 was prepared in the same manner as in Example 1 except that 2-mercaptoimidazole was added instead of the mercaptotetrazole compound A-1 in Example 1.

<Preparation of antibacterial ceramic surface treatment agent>
As a glaze component, it mixed with 70 mass parts feldspar, 25 mass parts lime, 5 mass parts clay, and 100 mass parts water, and prepared the surface treatment agent for ceramics so that pH might be set to 12.

<Antimicrobial evaluation 1>
After applying and drying the antibacterial ceramic surface treatment agent, in which 0.02 g of each of the silver ultrafine particle dispersions 1 to 8 is added to 100 g of the prepared ceramic surface treatment agent, the electric furnace The antibacterial glaze layers 1 to 8 were formed by heating and baking for 30 minutes. After 1 ml of a strain of Staphylococcus aureus was dropped on the surface of each glaze layer, a sterilized polyethylene film was placed and allowed to stand at 25 ° C. for 24 hours, and {(control viable count−sample viable count) / control The number of viable bacteria} × 100 = sterilization rate (%) was obtained. The antibacterial rate exceeded 1% to 8%, and the antibacterial property was good by adding the silver ultrafine particle dispersion.

<Evaluation 1 of dispersion stability>
As a glaze component, 35 parts by mass of sodium silicate 2 and 65 parts by mass of water were mixed to prepare a surface treatment agent for ceramics having a pH of 12. Antibacterial ceramic surface treatment agents 1 to 8 were prepared by adding 0.02 g of silver ultrafine particle dispersions 1 to 8 to 100 g of ceramic surface treatment agent, and the dispersion stability over time was evaluated. As an evaluation method, yellow plasmons of silver ultrafine particles were visually confirmed every 12 hours, and the time until aggregation and sedimentation and the color disappeared was observed and confirmed for up to one week. The results are shown in Table 1.

<Evaluation 2 of dispersion stability>
This was carried out in the same manner as in Evaluation 1 of dispersion stability, except that the amount of the silver ultrafine particle dispersions 1 to 8 was changed to 0.2 g. The results are shown in Table 1.

<Evaluation 3 of dispersion stability>
It carried out like the evaluation 1 of dispersion stability except having made the addition amount of the silver ultrafine particle dispersions 1-8 into 1.0g. The results are shown in Table 1.

  From the above results, it can be seen that the silver ultrafine particle dispersion of the present invention provides a silver ultrafine particle dispersion that can impart excellent dispersion stability and antibacterial properties even in a low concentration state in the glaze.

Claims (1)

A surface treatment agent for an antibacterial ceramic industry containing a silver ultrafine particle dispersion mainly containing water and containing a compound represented by the following general formula (A).

In the general formula (A), R ₁ represents an organic residue substituted with at least one selected from the group consisting of —SO ₃ M, —COOM, —OH and —NHR ₂ , and M represents a hydrogen atom, an alkali A metal atom or a quaternary ammonium group or a quaternary phosphonium group is represented, and R ₂ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, —COR ₃ , —COOR ₃ or —SO ₂ R ₃ . R ₃ represents a hydrogen atom, an alkyl group or an aryl group.