Antimicrobial particle dispersion

Abstract

To provide an antibacterial particle dispersion, etc., having high safety and a wide antibacterial spectrum and excellent stability and antibacterial effect (including antibacterial effect).SOLUTION: Provided is an antibacterial particle dispersion, comprising at least antibacterial particles dispersed in water, the antibacterial particles being composed of a (meth)acrylate monomer represented by the following general formula (I) and at least one antibacterial component selected from the following group A. [In the above formula (I), A is a hydrogen atom (H) or a methyl group (CH3); and R represents a hydrogen atom (H), a C1-22 alkyl group, or a substituent having a polyalkylene glycol chain in which the carbon number of the alkylene chain is 2-18.] Group A: iodo-propargyl compounds, thiabendazole, p-oxybenzoic acid esters, sodium benzoate, etc.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antibacterial particle dispersion that has excellent antibacterial effects (including antifungal effects) of an antibacterial component even after long-term storage, and that is also excellent in safety and stability. [Background technology]

[0002] Conventionally, several materials have been known as antibacterial particles. For example, (1) antibiotic particles characterized in that an antibiotic compound is dispersed in a polymer containing an epoxy group, the polymer being obtained by dispersing a hydrophobic solution containing a monomer component containing an epoxy group-containing monomer and an antibiotic compound in water, and polymerizing the monomer component (see, for example, Patent Document 1); (2) An antibacterial resin for cosmetics containing an inorganic antibacterial agent, characterized in that it is composed of spherical particles with an average particle size of 0.1 μm to 1,000 μm; an antibacterial resin using, as the inorganic antibacterial agent, at least one ceramic selected from the group consisting of alumina, silica, zeolite, phosphate compounds, calcium carbonate, calcium silicate, bentonite, and titanium oxide, carrying at least one antibacterial metal selected from the group consisting of silver, copper, zinc, gold, platinum, and nickel (see, for example, Patent Document 2); (3) Made of cross-linked (meth)acrylic ester resin, with a compressive strength of 0.05 to 0.6 kgf / mm 2 and porous resin microparticles capable of releasing an active ingredient of an external preparation, characterized in that the recovery rate when the load is reduced from 1 gf to 0.2 gf is 3 to 40% (see, for example, Patent Document 3). (4) Sustained-release particles (see, for example, Patent Document 4) that are obtained by a production method comprising: an oil phase component preparation step of preparing an oil phase component containing a hydrophobic slurry by dispersing an antibiotic compound that is hydrophobic and substantially insoluble in a hydrophobic polymerizable vinyl monomer in the hydrophobic polymerizable vinyl monomer in the absence of a solvent; a water dispersion step of dispersing the oil phase component in water to prepare an aqueous dispersion; and a polymerization step of suspension-polymerizing the polymerizable vinyl monomer to produce a polymer. etc. are known.

[0003] However, the antibacterial particles described in Patent Documents 1 to 4 above have problems such as insufficient stability and safety, and the antibacterial effect (including antifungal effect) of the antibacterial component is lost over a long period of time, and further, they have problems such as having some adverse effect on other compounded components. Therefore, there is currently a strong demand for antibacterial particle dispersions that are more stable and safer, have excellent antibacterial effect (including antifungal effect) of the antibacterial component even after a long period of time, and do not affect other compounded components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-31365 A (claims, examples, etc.) [Patent Document 2] International Publication No. 2002 / 030365 (claims, examples, etc.) [Patent Document 3] JP 2002-265529 A (claims, examples, etc.) [Patent Document 4] JP 2016-6023 A (claims, examples, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned problems of the conventional art and aims to solve them, and aims to provide an antibacterial particle dispersion that is highly stable and safe, has excellent antibacterial effects (including antifungal effects) of the antibacterial component even after long-term storage, and does not affect other compounded components. [Means for solving the problem]

[0006] In view of the above-mentioned conventional problems, the present inventors have conducted extensive research and have found that the above-mentioned antibacterial particle dispersion can be obtained by dispersing antibacterial particles composed of at least a (meth)acrylic acid ester monomer represented by a specific formula and a specific antibacterial component in water, thereby completing the present invention.

[0007] That is, the antibacterial particle dispersion of the present invention is characterized in that antibacterial particles composed of at least a (meth)acrylic acid ester monomer represented by the following general formula (I) and at least one antibacterial component selected from the following Group A are dispersed in water. [ka] [In the above formula (I), A represents a hydrogen atom (H) or a methyl group (CH3), and R represents a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a substituent having a polyalkylene glycol chain in which the alkylene chain has 2 to 18 carbon atoms, and the alkyl group or the substituent having a polyalkylene glycol chain may have, as a substituent, a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, an alkoxy group having 1 to 18 carbon atoms, a perfluoroalkyl group having 1 to 18 carbon atoms, or a trialkoxysilyl group.] Group A: Iodopropargyl compounds, thiabendazole, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylsulfonyl)pyridine, parahydroxybenzoic acid esters, phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, morpholine, cresol, methylisothiazolinone, chloromethylisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine, 2-bromo-2-nitropropane-1,3-diol, sodium 2-pyridinethiol-1-oxide, sodium pyrithione, 2-(4-thiozolyl)benzimine Dazole, 4-terpinenol, 1,8-cineole, thymol, diisothiocyanate, eucalyptus oil, longifolene, isopropylmethylphenol, 2-methyl-4-isothiazolin-3-one, citral, eugenol, allyl isothiocyanate, d-limonene, tannic acid, ethylparaben, benzalkonium chloride, glyceryl caprylate, glycerin fatty acid ester, chlorphenesin, salicylic acid, ethyl parahydroxybenzoate, butyl parahydroxybenzoate, propyl parahydroxybenzoate, methyl parahydroxybenzoate, bisabolol, hinokitiol, phenylethyl alcohol, phenethyl alcohol, phenoxyethanol, butylparaben, propylparaben, benzalkonium chloride, methylparaben The content of the (meth)acrylic acid ester monomer represented by the general formula (I) is preferably 30 to 95% by mass based on the total polymer components constituting the antibacterial particle dispersion. The antibacterial component is preferably contained in an amount of 1% by mass or more based on the total polymer components constituting the antibacterial particles. The antibacterial particles in the antibacterial particle dispersion preferably have an average particle size of 10 to 800 nm. The content of the antibacterial particles is preferably 0.1 to 50% by mass based on the total amount of the antibacterial particle dispersion. body. The aqueous ink composition for a writing instrument of the present invention is characterized by containing the antibacterial particle dispersion. [Effects of the Invention]

[0008] According to the present invention, there are provided an antibacterial particle dispersion that is highly stable and safe, has excellent antibacterial effects (including antifungal effects) of the antibacterial component even after long-term storage, and does not affect other blended components, and an aqueous ink composition for a writing instrument containing the same. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes in detail the embodiments of the present invention. However, it should be noted that the technical scope of the present invention is not limited to the embodiments described in detail below, but extends to the inventions set forth in the claims and their equivalents. The antibacterial particle dispersion of the present invention is characterized in that antibacterial particles composed of at least a (meth)acrylic acid ester monomer represented by the following general formula (I) and at least one antibacterial component selected from the following Group A are dispersed in water. [ka] [In the above formula (I), A represents a hydrogen atom (H) or a methyl group (CH3), and R represents a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a substituent having a polyalkylene glycol chain in which the alkylene chain has 2 to 18 carbon atoms, and the alkyl group or the substituent having a polyalkylene glycol chain may have, as a substituent, a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, an alkoxy group having 1 to 18 carbon atoms, a perfluoroalkyl group having 1 to 18 carbon atoms, or a trialkoxysilyl group.]

[0010] Group A: iodopropargyl compounds, thiabendazole, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylsulfonyl)pyridine, parahydroxybenzoic acid esters, phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, morpholine, cresol, methylisothiazolinone, chloromethylisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine, 2-bromo-2-nitropropane-1,3-diol, sodium 2-pyridinethiol-1-oxide, sodium pyrithione, 2-(4-thiozolyl)benzimidazole, 4-Terpinenol, 1,8-cineole, thymol, diisothiocyanate, eucalyptus oil, longifolene, isopropylmethylphenol, 2-methyl-4-isothiazolin-3-one, citral, eugenol, allyl isothiocyanate, d-limonene, tannic acid, sodium benzoate, ethylparaben, benzalkonium chloride, glyceryl caprylate, glycerin fatty acid ester, chlorphenesin, salicylic acid, ethyl parahydroxybenzoate, butyl parahydroxybenzoate, propyl parahydroxybenzoate, methyl parahydroxybenzoate, bisabolol, hinokitiol, phenylethyl alcohol, phenethyl alcohol, phenoxyethanol, butylparaben, propylparaben, benzalkonium chloride, methylparaben

[0011] The antibacterial component used in the present invention is an iodopropargyl compound of Group A, thiabendazole, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylsulfonyl)pyridine, parahydroxybenzoic acid esters (ethyl, methyl, propyl, isopropyl, butyl, isobutyl, etc.), phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, morpholine, cresol, methylisothiazolinone, chloromethylisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine, 2-bromo-2-nitropropane-1,3-diol, sodium 2-pyridinethiol-1-oxide, sodium pyrithione, 2-(4-thiozolyl)benzimida ethanol, 4-terpinenol, 1,8-cineole, thymol, diisothiocyanate, eucalyptus oil, longifolene, isopropylmethylphenol, 2-methyl-4-isothiazolin-3-one, citral, eugenol, allyl isothiocyanate, d-limonene, tannic acid, sodium benzoate, ethylparaben, benzalkonium chloride, glyceryl caprylate, glycerin fatty acid esters, chlorphenesin, salicylic acid, ethyl parahydroxybenzoate, butyl parahydroxybenzoate, propyl parahydroxybenzoate, methyl parahydroxybenzoate, bisabolol, hinokitiol, phenylethyl alcohol, phenethyl alcohol, phenoxyethanol, butylparaben, propylparaben, benzalkonium chloride, and at least one selected from methylparaben (each alone or as a mixture of two or more; the same applies hereinafter).

[0012] Examples of iodopropargyl compounds that can be used include 3-iodo-2-propynylpropylcarbamate, 3-iodo-2-propynylbutylcarbamate (IPBC), 3-iodo-2-propynyl m-chlorophenylcarbamate, 3-iodo-2-propynylphenylcarbamate, 3-iodo-2-propynyl 2,4,5-trichlorophenyl ether, 3-iodo-2-propynyl 4-chlorophenylformal (IPCF), di-(3-iodo-2-propynyl)hexyldicarbamate, 3-iodo-2-propynyloxyethanolethylcarbamate, 3-iodo-2-propynyloxyethanolphenylcarbamate, 3-iodo-2-propynylthioxothiazolyl, and the like. and at least one selected from the group consisting of 3-iodo-2-propynyl ethyl carbamate, 3-iodo-2-propynyl carbamate (IPC), N-iodopropargyloxycarbonylalanine, N-iodopropargyloxycarbonylalanine ethyl ester, 3-(3-iodopropargyl)benzoxazol-2-one, 3-(3-iodopropargyl)-6-chlorobenzoxazol-2-one, 3-iodo-2-propynyl alcohol, 4-chlorophenyl 3-iodopropargyl formal, 3-bromo-2,3-diiodo-2-propenyl ethyl carbamate, 3-iodo-2-propynyl-n-hexyl carbamate, and 3-iodo-2-propynyl cyclohexyl carbamate.

[0013] The antibacterial ingredients of Group A, including these iodopropargyl compounds, have been publicly known and are highly safe compounds with antibacterial and antifungal properties. The methods for producing each compound are also known, and they can be prepared by various production methods. Furthermore, if commercially available products of each compound included in Group A are available, they can be used. In the present invention, from the viewpoints of further safety and stability, among the above-mentioned iodopropargyl compounds, those containing at least 3-iodo-2-propynyl butylcarbamate (hereinafter sometimes simply referred to as "IPBC") (IPBC alone or a mixture containing IPBC) are preferred, and in addition to iodopropargyl compounds, it is desirable to use at least one of thiabendazole, 2-bromo-2-nitropropane-1,3-diol, phenoxyethanol, 4-terpinenol, 1,8-cineole, tannic acid, benzalkonium chloride, glycerin fatty acid esters, potassium sorbate, parabens (butylparaben, propylparaben, ethylparaben, methylparaben), chloromethylisothiazolinone, methylisothiazoline, and benzisothiazolinone.

[0014] The (meth)acrylic acid ester monomer represented by the above general formula (I) used in the present invention is used because it has the strength of the antibacterial component that can be encapsulated, can produce long-lasting and stable particles, does not have an adverse effect on other compounded components, and has a long-lasting effect. R in the above general formula (I) represents a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a substituent having a polyalkylene glycol chain in which the alkylene chain has 2 to 18 carbon atoms. The alkyl group or the substituent having a polyalkylene glycol chain may have, as a substituent, a phenyl group, a benzyl group, an epoxy group, a hydroxyl group, a dialkylamino group, an alkoxy group having 1 to 18 carbon atoms, a perfluoroalkyl group having 1 to 18 carbon atoms, or a trialkoxysilyl group. Examples of such a substituent include a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, and an alkyl group having 1 to 18 carbon atoms which may have, as a substituent, an epoxy group, a hydroxyl group, a dialkylamino group, or an alkoxy group having 1 to 4 carbon atoms. In particular, an alkyl group having 1 to 6 carbon atoms which may have, as a substituent, an epoxy group, a hydroxyl group, or an alkoxy group having 1 to 2 carbon atoms, and an alkyl group having 1 to 6 carbon atoms which may have, as a substituent, an epoxy group. Preferably, R in the above general formula (I) is a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a hydroxyl group, a trifluoroethyl group, a dimethylaminoethyl group, a methoxyethyl group, a hydroxyethyl group, a hydroxypropyl group, an allyl group, a tetrahydrofurfuryl group, a phenyl group, a benzyl group, a butoxydiethylene glycol group, a methoxypolyethylene glycol group, a dimethylaminoethyl group, a diethylaminoethyl group, a dimethylaminoethyl group, a glycidyl group, ethyl phosphate, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, or the like. In this specification, the expression "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0015] Specific examples of the (meth)acrylic acid ester represented by the above general formula (I) to be used include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, Isobornyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, allyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate methyl chloride salt, diethylaminoethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-Hexanediol, trimethylolpropane tri(meth)acrylate, 2-(meth)acroyloxyethyl phthalate, 2-(meth)acroyloxyethyl hexahydrophthalate, trifluoroethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, diethylene glycol (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(dimethylamino)propyl, 2-(dimethylamino)butyl (meth)acrylate, 2-isocyanoethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth)acrylate, perfluoroethyl methacrylate having perfluoroalkyl groups having 1 to 18 carbon atoms, 2-(methacryloyloxy)ethyl (meth)acrylate phosphate), trialkoxysilylpropyl (meth)acrylate, dialkoxymethylsilylpropyl (meth)acrylate, and the like (each may be used alone or in combination of two or more; the same applies hereinafter). Of these, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate are preferred, as they are easily available industrially, are easy and safe to handle during production, and further improve the effects of the present invention.

[0016] In the present invention, in addition to the (meth)acrylic acid ester monomers, hydrophobic vinyl monomers and aqueous monomers other than the (meth)acrylic acid ester monomers can be preferably used in order to obtain a sustained reduction effect. As the hydrophobic vinyl monomer, for example, at least one monomer other than the above (meth)acrylic acid ester monomers, such as styrene and methylstyrene, can be used. Examples of hydrophobic vinyl monomers that can be used include at least one of styrene, methylstyrene, chloromethylstyrene, alkylstyrenes having an alkyl group having 1 to 12 carbon atoms, methoxystyrene, chlorostyrene, bromostyrene, divinylbenzene, phenylstyrene, and vinylnaphthalene. Examples of aqueous monomers that can be used include at least one of glycerin monomethacrylate, 2-sulfoethyl sodium methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-propylene glycol monomethacrylate, polyethylene glycol-tetramethylene glycol-monomethacrylate, and propylene glycol-polybutylene glycol-monomethacrylate.

[0017] The antibacterial particle dispersion of the present invention is composed of at least the (meth)acrylic acid ester monomer represented by the above general formula (I) and at least one antibacterial component selected from the above Group A. Its production method may, for example, be a method of dissolving the antibacterial component of the above Group A in the above (meth)acrylic acid ester monomer (either alone or in combination of two or more kinds, the same applies hereinafter) or in a mixed monomer containing the above (meth)acrylic acid ester monomer and other hydrophobic vinyl monomers and / or aqueous monomers, and then subjecting the mixture to a polymerization initiator such as ammonium persulfate, potassium persulfate, or hydrogen peroxide. Further, a polymerization initiator further containing a reducing agent is used in combination, and a crosslinking agent such as triallyl isocyanurate, triallyl isocyanurate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, pentaerythritol acrylate, ditrimethylolpropane acrylate, dipentaerythritol acrylate, methoxylated bisphenol A methacrylate, pentaerythritol methacrylate, ditrimethylolpropane methacrylate, dipentaerythritol methacrylate, or ethoxylated polyglycerin methacrylate is also used. If necessary, polyoxyethylene-1-(allyloxymethyl)-alkyl ether ammonium sulfate, ether sulfate, polyoxyethylene nonylpropenylphenyl ether ammonium sulfate, polyoxyethylene nonylpropenylphenyl ether, ammonium polyacrylate, styrene-maleic acid copolymer ammonium, polyoxyethylene alkyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyalkylene decyl ether, polyoxyethylene tridecyl ether, alkylbenzene sulfonate, dioctyl sulfosuccinate, sodium lauryl sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene styrenated phenyl ether phosphate, polyoxyethylene styrenated phenyl ether sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene sorbitan monolaurate (polysorbate 20), polyoxyethylene sorbitan palmitate (polysorbate 40), polyoxyethylene sorbitan monostearate (polysorbate 60),It can be produced by emulsion polymerization using a polymerizable surfactant (emulsifier) ​​such as polyoxyethylene sorbitan oleate (polysorbate 80), and after being produced as a dispersion liquid of antibacterial particle dispersion, it can be made into an antibacterial particle dispersion by drying or the like. The use of a crosslinking agent such as triallyl isocyanurate is preferred because it improves the heat resistance, mechanical properties, hydrolysis resistance, and weather resistance of the antibacterial particle dispersion.

[0018] In the present invention, the emulsion polymerization may be carried out by further mixing an appropriate amount of dicyclopenta(thenyl)(meth)acrylate monomer, etc., with the (meth)acrylic acid ester monomer, etc. When the dicyclopenta(thenyl)(meth)acrylate monomer is further mixed and then emulsion polymerized, stability is less likely to be lost even if the water in the dispersion evaporates, and an antibacterial particle dispersion with even better stability can be obtained. Dicyclopent(en)yl (meth)acrylate monomers that can be used include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate. In the present invention, during the emulsion polymerization, in addition to the (meth)acrylic acid ester monomer, other hydrophobic vinyl monomers, and the dicyclopent(en)yl (meth)acrylate monomer, a monomer having a reactive crosslinking group such as an epoxy group, a hydroxymethylamide group, or an isocyanate group, or a polyfunctional monomer having two or more vinyl groups may be blended in an appropriate amount to cause crosslinking.

[0019] In the present invention, the content of the (meth)acrylic acid ester monomer among the polymer components constituting the antibacterial particle dispersion must be 30% by mass or more, preferably 30 to 95% by mass, and more preferably 30 to 70% by mass, based on the total polymer components constituting the antibacterial particle dispersion. In the present invention, the term "total polymer components" refers to the polymerizable components that constitute the antibacterial particle dispersion, and specifically refers to the total amount of the (meth)acrylic acid ester monomer used, the other monomer components used, and the crosslinking agent described below. The effects of the present invention can be achieved by making the content of the (meth)acrylic acid ester monomer 30% by mass or more relative to the total polymer components, while if this content is less than 30% by mass, the stability over time will be poor, which is not preferred.

[0020] Furthermore, among the polymer components constituting the antibacterial particle dispersion, the content of other monomer components than the (meth)acrylic acid ester monomer is the remainder of the total amount of the (meth)acrylic acid ester monomer and the crosslinking agent described below. Preferably, the content of the other monomer components is 0.5 to 70% by mass based on the total polymer components, from the viewpoints of further exerting the effects of the present invention, dispersibility, and reactivity.

[0021] In the present invention, the content (solid content) of the antibacterial component is desirably 1% by mass or more, preferably 5% by mass or more, more preferably 10 to 50% by mass, and particularly preferably 15 to 40% by mass, of the total polymer components, from the viewpoints of obtaining sufficient antibacterial performance, obtaining a sustained antibacterial effect, etc., and stability. By making the content of this antibacterial component 1% by mass or more, sufficient antibacterial performance (including antifungal effect) and sustained antibacterial effect can be exhibited, while if the content of the antibacterial component is less than 1% by mass, the antibacterial performance will be insufficient and the effects of the present invention will not be exhibited.

[0022] The polymerizable surfactant that can be used as needed is not particularly limited as long as it is a polymerizable surfactant commonly used in the emulsion polymerization, but examples of the polymerizable surfactant include anionic or nonionic polymerizable surfactants, such as Adeka Reasoap NE-10, NE-20, NE-30, NE-40, and SE-10N manufactured by Adeka Corporation, Latemul S-180, S-180A, and S-120A manufactured by Kao Corporation, Eleminol JS-20 manufactured by Sanyo Chemical Industries, Ltd., and Aqualon KH-10 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. The amount of these polymerizable surfactants used is 0 to 50% by mass, preferably 0.1 to 50% by mass, based on the total amount of the monomers. The content of the crosslinking agent such as triallyl isocyanurate is preferably 0 to 50% by mass, and more preferably 0.1 to 25% by mass, based on the total amount of the monomers.

[0023] In the present invention, an antibacterial particle dispersion (liquid dispersion) in which antibacterial particles are dispersed in water can be obtained by dissolving an antibacterial component selected from Group A in at least the (meth)acrylic acid ester monomer and emulsion-polymerizing the resulting mixture, or by polymerizing a monomer mixture containing at least the (meth)acrylic acid ester monomer and other monomer components, followed by dissolving the antibacterial component and emulsion-polymerizing the resulting mixture. The amount of antibacterial particles in the antibacterial particle dispersion obtained under these production conditions varies depending on the amounts of the (meth)acrylic acid ester monomer and antibacterial component used, the polymerization conditions, and other factors. From the standpoints of manufacturability, workability, efficiency, and the like, it is preferable to produce the dispersion so that the solid content is 1 to 50% by mass. It is even more preferable to produce the dispersion so that the solid content is 10 to 40% by mass. The antibacterial particle dispersion (liquid dispersion) of the present invention has stronger and more durable antibacterial performance (including antifungal effect) than one that uses the antibacterial component alone, without adversely affecting other blended components, and is therefore an antibacterial particle dispersion with excellent stability. In particular, an antibacterial particle dispersion can be obtained that can maintain or improve the antibacterial effect (including antifungal effect) of the antibacterial component even after long-term storage. Furthermore, in the present invention, an oil-soluble (lipophilic) preservative component or the like is preferably used as the antibacterial component, and therefore the preservative component or the like is particularly likely to adhere to plastic containers, thereby addressing the problem of the antibacterial effect, including the preservative power, being lost over time. In response to this problem, by encapsulating the antibacterial component in particles made of the (meth)acrylic acid component or the like of the present invention, adhesion to the container wall surface is suppressed, and the antibacterial effect can be maintained even after a long period of time has passed. This has the unique effect of preventing this.

[0024] In the present invention, the average particle size of the antibacterial particles in the obtained antibacterial particle dispersion will vary depending on the (meth)acrylic acid ester monomer, the type and content of other monomers used, the polymerization conditions during polymerization, etc., but is preferably 10 to 800 nm, more preferably 20 to 300 nm, and even more preferably 30 to 200 nm. By setting the average particle size within the above preferred range, the antibacterial particles can be further improved in storage stability and the like, and the antibacterial particles having an average particle size within a suitable range for each application described below can be used. When used in aqueous inks for writing instruments, the antibacterial particles do not clog the cores of writing instruments such as felt-tip pens, marking pens, and ballpoint pens, and the antibacterial particles can be further improved in storage stability and the like. The "average particle size" defined in the present invention is a histogram average particle size based on scattered light intensity distribution, and in the present invention (including the examples described below), it is the value D50 measured using a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)].

[0025] In the antibacterial particle dispersion of the present invention, the content of the antibacterial particles contained in the dispersion is preferably 0.1 to 50 mass % in terms of solid content, and more preferably 1 to 30 mass % depending on the intended use, etc., which will be described later. If the content of these antibacterial particles is less than 0.1 mass % in terms of solid content, the effects of the present invention cannot be achieved, while if it exceeds 50 mass %, the long-term storage stability is likely to decrease.

[0026] The antibacterial particle aqueous dispersion of the present invention thus constructed can be used to impart antibacterial properties to a variety of products, such as medical devices, baby products, nursing care products, bath products, kitchen utensils, tableware, drinking water piping parts, hygiene products, home appliances, clothing, construction materials, agricultural materials, automobile interior parts, stationery, writing instruments, and ink compositions for inkjet printers. The antibacterial particle aqueous dispersion of the present invention having such a specific configuration can be used to impart antibacterial properties to a variety of products, such as medical devices, baby products, nursing care products, bath products, kitchen utensils, tableware, drinking water piping parts, hygiene products, home appliances, clothing, building materials, agricultural materials, automobile interior parts, stationery, writing instruments, and ink compositions for inkjet printers. Specific uses include, in addition to those mentioned above, cleaning agent uses such as laundry detergents, fabric softeners, household detergents, dishwashing agents, and hard surface cleaners; personal care uses such as shampoos, conditioners, lotions, emulsions, creams, sunscreens, foundations, eye makeup products, antiperspirants, and toothpaste; industrial water treatment uses such as paints, adhesives, building materials, resin emulsions, wood preservatives, cement admixtures, boilers, cooling equipment, wastewater treatment equipment, and industrial water (papermaking process water in papermaking processes, and various industrial cooling water and washing water); medical instruments, food additives, and electronic equipment uses such as solar cell modules, organic element devices, and heat-shielding films; and they can also be suitably used in aquariums and medicated baths to inhibit water mold in aquatic organisms (fish, etc.). The antibacterial particle aqueous dispersion of the present invention is highly stable and safe, and exhibits excellent antibacterial effects (including antifungal effects) of the antibacterial component even after long-term storage, while also being an antibacterial particle dispersion that does not affect other compounded components. Therefore, as described above, it can be used to impart antibacterial properties to a variety of products, and is particularly suitable for use in detergents, personal care products, industrial water treatment products, food additives, electronic devices, and aquariums and medicated baths to inhibit water mold in aquatic organisms (fish, etc.). For example, the use of the antibacterial particle aqueous dispersion in an aqueous ink composition for writing instruments will be described below.

[0027] The aqueous ink composition for a writing instrument of the present invention is characterized by containing at least the antibacterial particle dispersion having the above-described configuration, and may contain a colorant and a water-soluble organic solvent in addition to this antibacterial particle dispersion. The content of the antibacterial particles in the ink composition is preferably 0.1 to 30.0 mass % in terms of solid content, relative to the total amount of the ink composition, from the viewpoints of exhibiting the effects of the present invention without impairing writing performance and of storage stability, and more preferably 1.0 to 15.0 mass %.

[0028] Usable colorants include water-soluble dyes and pigments, such as inorganic pigments, organic pigments, and plastic pigments; hollow resin particles with voids inside the particles can be used as white pigments; resin particles dyed with dyes that have excellent color development and dispersibility (pseudo pigments); thermochromic pigments; and photochromic pigments. As the water-soluble dye, any of direct dyes, acid dyes, food dyes and basic dyes can be used in an appropriate amount within a range that does not impair the effects of the present invention. The content of these colorants varies depending on the type of writing implement, but is generally 1 to 30% by mass based on the total amount of the ink composition.

[0029] Examples of usable water-soluble organic solvents include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol, and 2-methylpentanediol. alkylene glycols such as 2,4-diol, 3-methylpentane-1,3,5-triol, and 1,2,3-hexanetriol; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; glycerols such as glycerol, diglycerol, and triglycerol; lower alkyl ethers of glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol mono-n-butyl ether; N-methyl-2-pyrrolidone; and 1,3-dimethyl-2-imidalidinone.

[0030] Other water-soluble solvents that can be mixed include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and benzyl alcohol; amides such as dimethylformamide and diethylacetamide; and ketones such as acetone. The content of these water-soluble organic solvents varies depending on the type of writing implement, such as a felt-tip pen, marking pen, or ballpoint pen, but is preferably 1 to 40% by mass relative to the total amount of the ink composition. In order to further improve the drying properties of drawn lines, it is particularly effective for ink compositions with a content of 10% by mass or less, and more preferably 3 to 8% by mass.

[0031] The aqueous ink composition for a writing instrument of the present invention may contain, in addition to the particles, colorant, and water-soluble solvent having the above-described properties, water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as the solvent as the remainder, as well as dispersants, lubricants, pH adjusters, rust inhibitors, thickeners, evaporation inhibitors, surfactants, and the like, as appropriate, within limits that do not impair the effects of the present invention.

[0032] Usable dispersants include nonionic and anionic surfactants and water-soluble resins, with water-soluble polymers being preferred. Examples of lubricants include nonionic lubricants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic lubricants such as alkyl sulfonates and alkyl aryl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorine-based surfactants; and polyether-modified silicones.

[0033] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonate or phosphate such as sodium tripolyphosphate and sodium carbonate, and alkali metal hydrates such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Examples of thickeners include carboxymethylcellulose (CMC) or its salts, fermented cellulose, crystalline cellulose, and polysaccharides. Usable polysaccharides include, for example, xanthan gum, guar gum, hydroxypropylated guar gum, casein, gum arabic, gelatin, amylose, agarose, agaropectin, arabinan, curdlan, callose, carboxymethyl starch, chitin, chitosan, quince seed, glucomannan, gellan gum, tamarind seed gum, dextran, nigeran, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkaloid gum, succinoglycan, locust bean gum, and tara gum. These may be used alone or in combination. Furthermore, commercially available products of these may be used. Examples of the evaporation inhibitor include pentaerythritol, p-xylene glycol, trimethylolpropane, triethylolpropane, and dextrin. Examples of surfactants include fluorine-based, silicone-based, and acetylene glycol-based surfactants.

[0034] The aqueous ink composition for a writing instrument of the present invention can be prepared by appropriately combining the antibacterial particle dispersion having the above-described properties, the water-soluble solvent, and other components depending on the intended use of the ink for the writing instrument (for a ballpoint pen, a marking pen, etc.), stirring and mixing them using a stirrer such as a homomixer, a homogenizer, or a disper, and then, if necessary, removing coarse particles from the ink composition by filtration or centrifugation.

[0035] Furthermore, the pH (25°C) of the aqueous ink composition for a writing instrument of the present invention is preferably adjusted to 5 to 10 using a pH adjuster or the like, from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container, and more preferably 6 to 9.5.

[0036] The aqueous ink composition for writing implements of the present invention is loaded onto ballpoint pens, marking pens, etc. equipped with pen tips such as ballpoint pen tips, fiber tips, felt tips, and plastic tips. As a ballpoint pen, the aqueous ink composition for a writing instrument having the above composition is applied to a ballpoint pen having a diameter of 0.18 to 2.0 mm. The ink is contained in an ink container (refill) for a ballpoint pen equipped with a 1 mm ball, and a substance that is incompatible with the aqueous ink composition contained in the ink container and has a low specific gravity relative to the aqueous ink composition, such as polybutene, silicone oil, or mineral oil, is contained as an ink follower. The structure of the ballpoint pen or marking pen is not particularly limited, and may be, for example, a direct ink ballpoint pen or marking pen having a collector structure (ink retention mechanism) in which the barrel itself serves as an ink container and is filled with the aqueous ink composition for a writing instrument having the above-described structure.

[0037] In the aqueous ink composition for writing instruments of the present invention, which is configured in this manner, the antibacterial particle dispersion having the above-described properties is blended into the aqueous ink composition for writing instruments, and therefore the ink composition has strong and long-lasting antibacterial performance (including antifungal effect) without adversely affecting other blended components, etc., and therefore the effect can be sustained for a long period of time. Moreover, because these particles do not impair storage stability or writing performance, the degree of freedom in ink design can be further increased, and an aqueous ink composition for writing instruments suitable for ballpoint pens, marking pens, and other writing instruments can be obtained. The above describes the use of the antibacterial particle aqueous dispersion of the present invention in an aqueous ink composition for a writing instrument. However, the antibacterial particle aqueous dispersion of the present invention not only maintains excellent antibacterial effects (including antifungal effects) of the antibacterial component even after long-term storage, but is also highly safe, and by selecting the antibacterial component to be used, it is possible to use one having a wide antibacterial spectrum, and it does not adversely affect other components, etc., and is highly stable. Moreover, it can be used in a blending ratio suitable for the above-mentioned detergent applications, personal care applications, industrial water treatment applications, food additives, electronic devices, and aquarium and medicated bath applications as a water mold inhibitor for aquatic organisms (fish, etc.). [Example]

[0038] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0039] Examples 1 to 9: Production of antibacterial particle dispersions (particles 1 to 9) Antibacterial particle dispersions were produced according to the following Examples 1 to 9. In the following examples, "parts" refers to parts by mass, and the amount of the antibacterial component is the solid content.

[0040] Example 1 A 2-liter flask was equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube, and a 1000-ml separatory funnel for introducing monomers, and was placed in a warm water bath. 329.5 parts of distilled water, 5 parts of glycerin monomethacrylate (Blenmer GLM, manufactured by NOF Corporation), 5 parts of 2-sulfoethyl sodium methacrylate (acrylic ester SEM-Na, manufactured by Mitsubishi Chemical Corporation), 20 parts of a polymerizable surfactant (ADEKA Corporation, Adeka Reasoap SE-10N, ether sulfite), and 0.5 parts of ammonium persulfate were then charged, and the internal temperature was raised to 50°C while introducing nitrogen gas.

[0041] Separately, a liquid was prepared by mixing a mixed monomer consisting of 55 parts of cyclohexyl methacrylate monomer and 20 parts of n-butyl methacrylate with 20 parts of an antibacterial component [iodopropargyl compound: 3-iodo-2-propynylcarbamate, manufactured by Lonza (Omacide IPBC 100)], 14 parts of tannin [Tannic Acid S, manufactured by Fuji Chemical Industry Co., Ltd.], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Kasei Co., Ltd., TAIC]. This prepared solution was added from the separatory funnel to the flask maintained at a temperature of about 50°C over a period of 3 hours with stirring to carry out emulsion polymerization. The solution was then aged for a further 5 hours to complete the polymerization, yielding an antibacterial particle dispersion (dispersion) (particles 1). The content of the methacrylic acid ester monomer was 50 mass % of the total polymer components constituting the antibacterial particles, the content of the antibacterial component was 36.2 mass % of the total polymer components, and the average particle size of the antibacterial particles was 56 nm.

[0042] Example 2 An antibacterial particle dispersion (dispersion liquid) (particles 2) was obtained in the same manner as in Example 1 above, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 30 parts of an antibacterial component [iodopropargyl compound: 3-iodo-2-propynylcarbamate, manufactured by Lonza (omacide IPBC 100)] was used as the antibacterial component. The content of the methacrylic acid ester monomer is 37.5% by mass based on the total polymer components constituting the antibacterial particles, and the content of the antibacterial component is 100% by mass based on the total polymer components. The average particle size of the antibacterial particles was 73 nm.

[0043] Example 3 An antibacterial particle dispersion (dispersion liquid) (particles 3) was obtained in the same manner as in Example 1 above, except that the amount of distilled water was 309.5 parts, the amount of cyclohexyl methacrylate monomer was 60 parts, the amount of n-butyl methacrylate was 35 parts, and 30 parts of an antibacterial component (phenoxyethanol, manufactured by Yokkaichi Synthetic Co., Ltd.) was used as the antibacterial component. The content of the methacrylic acid ester monomer relative to the total polymer components constituting the antibacterial particles was 35.1 mass %, the content of the antibacterial component relative to the total polymer components was 37.8 mass %, and the average particle size of the antibacterial particles was 85 nm.

[0044] Example 4 An antibacterial particle dispersion (dispersion liquid) (particles 4) was obtained in the same manner as in Example 1 above, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 40 parts of an antibacterial component (paraben, manufactured by Ueno Pharmaceutical Co., Ltd.) was used as the antibacterial component. The content of the methacrylic acid ester monomer relative to the total polymer components constituting the antibacterial particles was 49.3 mass %, the content of the antibacterial component relative to the total polymer components was 35.3 mass %, and the average particle size of the antibacterial particles was 83 nm.

[0045] Example 5 An antibacterial particle dispersion (dispersion liquid) (particles 5) was obtained in the same manner as in Example 1 above, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 15 parts of an antibacterial component [chloromethylisothiazolinone / methylisothiazoline (CMIT / MIT) manufactured by Yamato Chemical Industry Co., Ltd.] was used as the antibacterial component. The content of the methacrylic acid ester monomer relative to the total polymer components constituting the antibacterial particles was 33.2 mass %, the content of the antibacterial component relative to the total polymer components was 38.9 mass %, and the average particle size of the antibacterial particles was 78 nm.

[0046] Example 6 An antibacterial particle dispersion (dispersion liquid) (particles 6) was obtained in the same manner as in Example 1, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 30 parts of an antibacterial component [benzisothiazolinone (BIT), manufactured by Yamato Chemical Industry Co., Ltd.] was used as the antibacterial component. The content of the methacrylic acid ester monomer relative to the total polymer components constituting the antibacterial particles was 31.6 mass %, the content of the antibacterial component relative to the total polymer components was 47.9 mass %, and the average particle size of the antibacterial particles was 100 nm.

[0047] Example 7 An antibacterial particle dispersion (dispersion liquid) (particles 7) was obtained in the same manner as in Example 1, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 25 parts of an antibacterial component [methylisothiazoline (MIT), manufactured by Yamato Chemical Industry Co., Ltd.] was used as the antibacterial component. The content of the methacrylic acid ester monomer relative to the total polymer components constituting the antibacterial particles was 31.6 mass %, the content of the antibacterial component relative to the total polymer components was 47.9 mass %, and the average particle size of the antibacterial particles was 90 nm.

[0048] Example 8 An antibacterial particle dispersion (dispersion liquid) (particles 8) was obtained in the same manner as in Example 1 above, except that the amount of distilled water was 340.0 parts, the amount of cyclohexyl methacrylate monomer was 30 parts, the amount of n-butyl methacrylate was 45 parts, and 25 parts of an antibacterial component (thiabendazole, MOLDBAN-TZ, manufactured by Mitsui Bussan Chemicals Co., Ltd.) was used as the antibacterial component. The content of the methacrylic acid ester monomer was 28.9 mass % of the total polymer components constituting the antibacterial particles, the content of the antibacterial component was 48.3 mass % of the total polymer components, and the average particle size of the antibacterial particles was 87 nm.

[0049] Example 9 An antibacterial particle dispersion (dispersion liquid) (particles 8) was obtained in the same manner as in Example 1 above, except that in Example 1, the amount of distilled water was 345.0 parts, the amount of cyclohexyl methacrylate monomer was 45 parts, the amount of n-butyl methacrylate was 30 parts, and 30 parts of an antibacterial component [2-bromo-2-nitropropane-1,3-diol, MOLDBAN-BNP, manufactured by Mitsui Bussan Chemicals Co., Ltd.] was used as the antibacterial component. The content of the methacrylic acid ester monomer was 29.3 mass % of the total polymer components constituting the antibacterial particles, the content of the antibacterial component was 45.1 mass % of the total polymer components, and the average particle size of the antibacterial particles was 98 nm.

[0050] (Comparative Examples 1 to 3) For each of the antibacterial particle aqueous dispersions B, C, and D in Examples 2, 3, and 4, an antibacterial component-containing aqueous dispersion was prepared without using any antibacterial particles, and the content of the antibacterial component before making it into particles was 15 mass %.

[0051] The antibacterial particle aqueous dispersions obtained in Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated for antibacterial effect (against bacteria, yeast, and filamentous fungi) by the following evaluation method. The antibacterial particle dispersions (dispersions) used were the antibacterial particle dispersions (dispersions) obtained in Examples 1 to 9. The solid content of the antibacterial particles in each of the antibacterial particle dispersions obtained in Examples 1 to 7 was 35 to 40% by mass. The antibacterial particle aqueous dispersions obtained in Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated for antibacterial effect (against bacteria, yeast, and mold) initially and after 3 months at 40°C by the following evaluation method. The results are shown in Table 1 below.

[0052] [Test method for antibacterial effect (antibacterial and antifungal properties)] The microbiological testing was carried out according to the following method in accordance with ISO 11930:2012 (Procedures for the interpretation of data generated by preservative effectiveness testing or microbiological risk assessment, or both). A challenge test was carried out with the following three groups of bacteria, yeast, and filamentous fungi. Bacterial group: Stapylococcus aureus NBRC13276, Escherichia coli NBRC3972 Yeast: Candida albicans NBRC1594 Filamentous fungus: Aspergillus brasiliensis

[0053] Preparation of inoculum Preparation of inoculum: The inoculum was prepared according to ISO 11930:2012. Bacterial group: Bacterial suspension was prepared for each species according to ISO 11930:2012. 1 × 10 7 ~1×10 8 Three equal amounts of bacterial solutions adjusted to cfu / ml were mixed to prepare an inoculum. Yeast: 1 x 10 according to ISO 11930:2012 6 ~1×10 7 The bacterial solution was prepared to give a concentration of cfu / ml. Filamentous fungi: 1 x 10 according to ISO 11930:2012 6 ~ 1×10 7 The bacterial solution was prepared to give a concentration of cfu / ml.

[0054] <Inoculation> The antibacterial particle aqueous dispersion was inoculated with 1% by mass of the bacterial solution. <storage> The inoculated antibacterial particle aqueous dispersion was stored at a temperature of 22.5±2.5°C and subjected to detection culture at specified intervals. <Detection culture> A total of 1g of each was smeared onto 10 plates of SCD agar medium for the bacteria, SD agar medium for the yeast, and PD agar medium for the filamentous fungi, and the bacteria and yeast were cultured at 32.5°C for 2 days, and the filamentous fungi at 22.5°C for 5 days.

[0055] <Antibacterial effect after 3 months at 40°C> The obtained antibacterial particle aqueous dispersions of Examples 1 to 9 and Comparative Examples 1 to 3 were each filled into a 60 ml polyethylene bottle with a lid, sealed, and stored at 40°C for 3 months. After that, the antibacterial effect (antibacterial and antifungal properties) of each aqueous dispersion was evaluated according to the following evaluation criteria. Evaluation Criteria A-1: No colonies appear as of the 7th day. A-2: No colonies have appeared as of the 21st day. B-1: As of the 28th day, several to several dozen colonies have appeared. B-2: As of the 28th, the number has clearly increased.

[0056] [Table 1]

[0057] Considering Table 1 above, it was found that Examples 1 to 9, which fall within the scope of the present invention, had excellent antibacterial effects (including antifungal effects) against bacteria, yeast, filamentous fungi, and bacteria (Escherichia coli and Staphylococcus aureus), which are sources of contamination, both initially and after a long period of time (40°C, 3 months), and were also highly safe and stable. Furthermore, each of the antibacterial particle aqueous dispersions of Examples 1 to 9 was placed in a sealed container and stored at 26°C for 3 months, and then subjected to a visual sensory evaluation for aggregates, etc., which showed no aggregation of particles, etc., and it was found that there were no problems with storage stability.

[0058] Examples 10 to 18 and Comparative Examples 4 to 6: Preparation of aqueous ink compositions for writing instruments For Examples 10 to 18, aqueous ink compositions for writing instruments were prepared by a conventional method using the antibacterial particle dispersions obtained in Examples 1 to 9 and the antibacterial particle dispersions of Comparative Examples 1 to 3 (IPBC, phenoxyethanol, paraben) according to the formulation shown below (total amount 100% by mass). Ink composition: (total 100% by mass) Each antibacterial particle dispersion (Examples 1 to 7) and the antibacterial dispersions of Comparative Examples 1 to 3: 15.0 mass% Colorant (carbon black MA100, manufactured by Mitsubishi Chemical Corporation) 5.4% by mass pH adjuster (triethanolamine) 1.4% by mass Water-soluble organic solvent (propylene glycol) 15.0% by mass Ion-exchanged water 63.2% by mass

[0059] The resulting aqueous ink compositions for writing instruments (total amount 100% by mass) were evaluated for writability (difference in density between upper and lower drawn lines), stability, and antibacterial effect (antibacterial and antifungal properties) using the writing instruments having the following configurations and the evaluation methods described below. The evaluation results of Examples 10 to 18 and Comparative Examples 4 to 6 are shown in Table 2 below.

[0060] (Writing implements: ballpoint pen production) A water-based ballpoint pen was prepared by filling each of the above aqueous ink compositions into a refill using the barrel of a ballpoint pen (trade name: Signo UM-100, manufactured by Mitsubishi Pencil Co., Ltd.) consisting of a polypropylene ink reservoir tube with an inner diameter of 4.0 mm and a length of 113 mm, a stainless steel tip (carbide alloy ball, ball diameter 0.5 mm), and a joint connecting the reservoir tube and the tip, and loading an ink follower containing mineral oil as its main component into the rear end of the ink.

[0061] [Method for evaluating writing properties (difference in density between upper and lower lines)] Each of the water-based ballpoint pens having the above-described configuration was left at room temperature (25°C, the same applies below) for one month, and then writing was carried out until the end. The difference in density of the drawn line between the beginning and end of the writing was compared and evaluated according to the following evaluation criteria. Evaluation criteria: A: There is no difference in concentration. B: A slight difference in density is observed. C: The density difference is clearly observed. D: The density difference is significant, and there are some areas where the drawn lines are difficult to see.

[0062] <Stability evaluation method> Each ballpoint pen having the above structure was stored with the pen tip facing downwards at 50°C for 3 months, after which the state of the ink in each pen was visually inspected and evaluated according to the following criteria. Evaluation criteria: A: No separation or aggregation has occurred. B: Slight separation or clumping. C: Separation or clumping occurs. D: Significant separation or aggregation.

[0063] [Test method for antibacterial effect (antibacterial and antifungal properties)] The aqueous ink compositions for writing instruments of Examples 10 to 18 and Comparative Examples 4 to 6, which fall within the scope of the present invention, were also tested for antibacterial effect (antibacterial and antifungal properties) in accordance with the test method for the antibacterial particle aqueous dispersion described above (by inoculating the aqueous ink composition for writing instruments with a bacterial solution in an amount of 1% by mass).

[0064] [Table 2]

[0065] Considering Table 2 above, it was confirmed that Examples 10 to 18, which fall within the scope of the present invention, are superior in writability (difference in density between upper and lower drawn lines) and stability compared to Comparative Examples 4 to 6, which fall outside the scope of the present invention, and that they have strong and long-lasting antibacterial properties without adversely affecting other ink components. It was also confirmed that the ballpoint pen produced above had no smearing or bleeding, had sufficient line density, and drew clear lines. [Industrial Applicability]

[0066] The antibacterial particle dispersion of the present invention can be suitably used in detergent applications, personal care applications, industrial water treatment applications, food additives, electronic devices, and in aquariums and medicated baths to inhibit water mold in aquatic organisms (fish, etc.). It can also be used as a compounding component of aqueous ink compositions for writing instruments, such as felt-tip pens, marking pens, and ballpoint pens.

Claims

1. An antibacterial particle dispersion comprising antibacterial particles dispersed in water, the antibacterial particles comprising at least a cyclohexyl (meth)acrylate monomer, at least one (meth)acrylic acid ester monomer selected from the following Group X, and at least one antibacterial component selected from the following Group A: Group X: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate Group A: iodopropargyl compounds, thiabendazole, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylsulfonyl)pyridine, phenol, sodium benzoate, sodium dehydroacetate, potassium sorbate, morpholine, cresol, methylisothiazolinone, chloromethylisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine, 2-bromo-2-nitropropane-1,3-diol, sodium 2-pyridinethiol-1-oxide, sodium pyrithione, 2-(4-thiozolyl)benzimidazole, 4- Terpinenol, 1,8-cineole, thymol, diisothiocyanate, eucalyptus oil, longifolene, isopropylmethylphenol, 2-methyl-4-isothiazolin-3-one, citral, eugenol, allyl isothiocyanate, d-limonene, tannic acid, ethylparaben, benzalkonium chloride, glyceryl caprylate, glycerin fatty acid ester, chlorphenesin, salicylic acid, ethyl parahydroxybenzoate, butyl parahydroxybenzoate, propyl parahydroxybenzoate, methyl parahydroxybenzoate, bisabolol, hinokitiol, phenylethyl alcohol, phenethyl alcohol, phenoxyethanol, butylparaben, propylparaben, benzalkonium chloride, methylparaben

2. The antibacterial particle dispersion according to claim 1, wherein the total content of the cyclohexyl (meth)acrylate monomer and the at least one (meth)acrylic acid ester monomer selected from Group X is 30 to 95 mass % based on the total amount of polymer components constituting the antibacterial particle dispersion.

3. 3. The antibacterial particle dispersion according to claim 1, wherein the antibacterial component is contained in an amount of 1% by mass or more based on the total polymer components constituting the antibacterial particles.

4. 4. The antibacterial particle dispersion according to claim 1, wherein the antibacterial particles in the antibacterial particle dispersion have an average particle size of 10 to 800 nm.

5. 5. The antibacterial particle dispersion according to claim 1, wherein the content of the antibacterial particles is 0.1 to 30% by mass based on the total amount of the antibacterial particle dispersion.

6. An aqueous ink composition for a writing instrument, comprising the antibacterial particle dispersion according to any one of claims 1 to 5.

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