Reducing particle dispersion and aqueous ink composition for writing instruments containing the same

Abstract

To provide a reducible particle dispersion having strength and sustainability (sustained release) of the ability to reduce oxygen (oxygen absorption ability) while not adversely affecting other compounded components, etc. and also having excellent dispersion stability and a preservative property, and an aqueous ink composition for a writing tool that contains the same.SOLUTION: A reducible particle dispersion of the present disclosure includes reducible particles dispersed in water, the reducible particles containing at least a (meth)acrylic acid ester monomer represented by general formula (I) and at least one reducible component selected from the group A shown below. [In the formula (I), A is a hydrogen atom (H) or a methyl group (CH3), R is a hydrogen atom (H) or a C1-22 alkyl group, etc]. Group A: polyphenols, copper chlorophyll, flavonoids, anthocyanidins, dibutylhydroxytoluene, and butyl hydroxyanisole. Preferably, the reducible particles also include a preservative component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a reducing particle dispersion that possesses strong and sustained (sustained-release) reduction performance (oxygen absorption capacity) against oxygen, without adversely affecting other components, and also exhibits excellent dispersion stability and preservative properties, as well as an aqueous ink composition for writing instruments containing the same. [Background technology]

[0002] Traditionally, a wide variety of oxygen absorbers have been known, with different types available for various applications such as food, pharmaceuticals, cosmetics, electronic components, and inks, as well as for different types of oxygen absorbers, including iron powder-based, catechol, and ascorbic acid.

[0003] For example, the powdered oxygen absorber has a Mooney viscosity of 10 to 400 and does not have a crystal melting peak or has a melting point of less than 75°C when measured by differential scanning calorimeter (DSC). It contains a thermoplastic polymer (A) having allyl hydrogen and / or hydrogen bonded to tertiary carbon in its molecule, and an oxidation promoting component (B), with a specific surface area of ​​60 cm². 2 A powdered oxygen absorber characterized by having a concentration of 1 / g or more (see, for example, Patent Document 1), Furthermore, oxygen-absorbing particles are known to include organic oxides, transition metal compounds, inorganic particles, and organic polymers, wherein the inorganic particles are selected from inorganic porous particles and inorganic layered compound particles, and at least a portion of the organic oxide and at least a portion of the transition metal compound are present in the pores or interlayers of the inorganic particles, respectively, and at least a portion of the organic polymer covers at least a portion of the outer surface of the inorganic particles (see, for example, Patent Document 1).

[0004] However, the powdered oxygen absorbers described in Patent Documents 1 and 2 above are mainly used in packaging bags for food, pharmaceuticals, medicines, cosmetics, electronic components, etc. While they possess oxygen reduction capabilities (oxygen absorption capacity), they have drawbacks such as lack of durability and limitations on their use, as they are not intended for use with liquids such as inks.

[0005] On the other hand, as an aqueous ink composition for writing instruments that contains compounds having oxygen-absorbing properties to suppress the generation of bubbles over time and obtain stable writing performance, for example, 1) A water-based ink for ballpoint pens comprising a colorant, water, a water-soluble organic solvent, a shear viscosity reducing agent, and catechins represented by a specific formula (see, for example, Patent Document 3), 2) A water-soluble ink composition for writing instruments comprising at least a colorant, a water-soluble organic solvent, and water, wherein the water-soluble ink composition for writing instruments comprises chlorogenic acids (see, for example, Patent Document 4), 3) An ink composition for a pen-type writing instrument, wherein the barrel contains a pen nib that temporarily stores ink directly contained in an ink storage section in response to changes in internal and external pressure, a pen tip is provided at the tip of the pen nib, and an ink guide nib is arranged on the pen nib for guiding ink from the ink storage section to the pen tip, wherein a compound having oxygen-absorbing ability is added to the ink composition (see, for example, Patent Document 5). 4) A water-based ink composition for writing instruments comprising a colorant, water, and a condensation-type tannin (see, for example, Patent Document 6), 5) A water-based ink composition for writing instruments comprising a colorant, water, and a compound represented by a specific formula (juncinoside A) (see, for example, Patent Document 7). These are some of the known facts. However, the aqueous ink compositions for writing instruments described in the above-mentioned Patent Documents 3 to 7 currently have several drawbacks, such as the occurrence of aggregation over time, difficulties in maintaining oxygen absorption capacity, and adverse effects on other components. Typically, aqueous liquids containing reducing agents (such as antioxidants) still suffer from problems similar to those seen in the aqueous ink compositions for writing instruments, such as instability of the composition, instability of the dispersion system, physical gelation, or separation. Furthermore, few reducing agents (such as antioxidants) possess preservative properties themselves, making it necessary to use both reducing agents (such as antioxidants) and preservatives in aqueous liquids. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication 2006 / 095640 (Claims, Examples, etc.) [Patent Document 2] Japanese Patent Publication No. 2020-100801 (Claims, Examples, etc.) [Patent Document 3] Japanese Patent Publication No. 10-298483 (Claims, Examples, etc.) [Patent Document 4] Japanese Patent Publication No. 2005-194342 (Claims, Examples, etc.) [Patent Document 5] Japanese Patent Publication No. 2006-274017 (Claims, Examples, etc.) [Patent Document 6] Japanese Patent Publication No. 2014-91797 (Claims, Examples, etc.) [Patent Document 7] Japanese Patent Publication No. 2018-184514 (Claims, Examples, etc.) [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] In view of the problems and current status of the above-mentioned prior art, the present invention aims to resolve these issues and provides a reducing particle dispersion and an aqueous ink composition for writing instruments containing the same, which has strong and sustained (sustained-release) reduction performance (oxygen absorption capacity) for oxygen, does not adversely affect other components, has excellent dispersion stability, and has preservative properties. [Means for solving the problem]

[0008] In view of the above-mentioned conventional problems, the inventors conducted diligent research and found that a reducing particle dispersion for the above purpose and an aqueous ink composition for writing instruments containing the same can be obtained by, for example, using a reducing particle dispersion composed of at least a (meth)acrylic acid ester monomer represented by a specific formula and a specific reducing component, thereby completing the present invention.

[0009] In other words, the reducing particle dispersion of the present invention is characterized in that reducing particles, each composed of at least a (meth)acrylic acid ester monomer represented by the following general formula (I) and at least one reducing component selected from the following group A, are dispersed in water. [ka] [In formula (I) above, A is a hydrogen atom (H) or a methyl group (CH3), and R represents a substituent having a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a polyalkylene glycol chain having 2 to 18 carbon atoms. The substituent having an alkyl group or polyalkylene glycol chain may have 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 as a substituent.] Group A: Polyphenols, copper chlorophyll, flavonoids, anthocyanidins, dibutylhydroxytoluene, butylhydroxyanisole Preferably, the content of the (meth)acrylic acid ester monomer represented by the general formula (I) is 30 to 95% by mass relative to the total polymer components constituting the reducing particle dispersion. Preferably, the reducing component is contained in an amount of 1% by mass or more relative to the total polymer components constituting the reducing particles. The reducing component is preferably at least one selected from chlorogenic acid, tannin, catechin, piceatannol, dibutylhydroxytoluene, and butylhydroxyanisole. It is preferable that the reducing particles further contain a preservative component. The average particle diameter of the reducing particle dispersion is preferably 10 to 800 nm. The aqueous ink composition for writing instruments of the present invention is characterized by containing the reducing particle dispersion.

Effects of the Invention

[0010] According to the present invention, there are provided a reducing particle dispersion having strong reduction performance (oxygen absorption ability) and persistence (sustained release property) with respect to oxygen, without adversely affecting other compounding components, etc., and having excellent dispersion stability and antiseptic properties, and an aqueous ink composition for writing instruments containing the same. The objects and effects of the present invention are recognized and obtained by using the components and combinations particularly pointed out in the claims. Both the above general description and the following detailed description are exemplary and explanatory, and do not limit the invention described in the claims.

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, note that the technical scope of the present invention is not limited to each of the embodiments described in detail below, and extends to the invention described in the claims and its equivalents. The reducing particle dispersion of the present invention is characterized in that reducing particles composed of at least a (meth)acrylic acid ester monomer represented by the following general formula (I) and at least one reducing component selected from the following Group A are dispersed in water.

Chemical formula

[0012] The (meth)acrylic acid ester monomer represented by the above general formula (I) used in the present invention is chosen because it has a strong ability to encapsulate reducing components, can produce persistent and stable particles, does not adversely affect other ingredients, and has a long-lasting effect. In the above general formula (I), R represents a hydrogen atom (H), a C1-C22 alkyl group, or a substituent having a polyalkylene glycol chain with 2-C18 carbon atoms. The substituent having an alkyl group or polyalkylene glycol chain may have a phenyl group, benzyl group, epoxy group, hydroxyl group, dialkylamino group, C1-C18 alkoxy group, C1-C18 perfluoroalkyl group, or trialkoxysilyl group as a substituent. Examples include linear or branched alkyl groups having C1-C20 carbon atoms, cycloalkyl groups having C3-C10 carbon atoms, and alkyl groups having C1-C18 carbon atoms, which may have an epoxy group, hydroxyl group, dialkylamino group, or C1-C4 alkoxy group as a substituent. In particular, examples include alkyl groups having C1-C6 carbon atoms, which may have an epoxy group, hydroxyl group, or C1-C2 alkoxy group as a substituent, and alkyl groups having C1-C6 carbon atoms, which may have an epoxy group as a substituent. 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, etc. In this specification, the term "(meth)acrylic acid" refers to "acrylic acid and / or methacrylic acid."

[0013] Specific examples of (meth)acrylic acid esters represented by the above general formula (I) 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 methyl chloride (meth)acrylate, 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 (meth)acrylate, 2-(dimethylamino)butyl (meth)acrylate, 2-Isocyanoethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth)acrylate, Perfluoroethyl methacrylate having perfluoroalkyl groups of 1 to 18 carbon atoms, 2-(meth)acrylate (phosphate)ethyl [2-(Methacryloyloxy)ethyl Examples include at least one of the following (each individually or in combination of two or more, hereinafter the same): phosphate, trialkoxysilylpropyl (meth)acrylate, dialkoxymethylsilylpropyl (meth)acrylate, etc. 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, due to their ease of industrial availability, ease of handling and safety during manufacturing, and their ability to further enhance the effects of the present invention.

[0014] In the present invention, in addition to the (meth)acrylic acid ester monomers mentioned above, hydrophobic vinyl monomers and aqueous monomers other than the (meth)acrylic acid ester monomers can preferably be used, for the purpose of obtaining a sustained reducing effect. As the hydrophobic vinyl monomer, for example, at least one monomer other than the (meth)acrylic acid ester monomers mentioned above, 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, alkylstyrene having an alkyl group with 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, sodium 2-sulfoethyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-propylene glycol monomethacrylate, polyethylene glycol-tetramethylene glycol-monomethacrylate, and propylene glycol-polybutylene glycol-monomethacrylate.

[0015] The reducing component used in the present invention has reducing properties (oxygen absorption capacity) for oxygen, and includes at least one selected from Group A: polyphenols, copper chlorophyll, flavonoids, anthocyanidins, dibutylhydroxytoluene (BHT), and butylhydroxyanisole (BHA). The polyphenols that can be used are those that have phenolic molecules with multiple hydroxyl groups. Examples of polyphenols, flavonoids, and anthocyanidins that can be used include catechins (epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, etc.), tannic acid, tannins, chlorogenic acid, caffeic acid, neochlorogenic acid, cyanidin, proanthocyanidin, thearubidin, rutin, flavonoids (quercitrin, anthocyanin, flavanone, flavanol, flavonol, isoflavone, etc.), ferulic acid, gingerol, and anthocyanidins (pelargodinin, cyanidin, delphinidin, peonidin, malvidin, petu). Examples include pharmacophosphates (such as naringenin chalcone), flavonoids, chalcones (such as naringenin chalcone), xanthophyll, carnosic acid, eriocitrin, nobiletin, tangeretin, magnolol, honokiol, ellagic acid, lignans, curcumin, coumarin, catechol, procyanidin, theaflavin, rosmarinic acid, xanthones, quercetin, resveratrol, gallic acid, propyl gallate, phlorotannin, piceatannol [5-(dihydroxyphenylethenyl)resorcinol] (product name "Pasenol PA"), resveratrol (3,5,4'-trihydroxy-trans-stilbene), etc.

[0016] Preferred reducing agents, in terms of reducing strength and safety, include catechin, tannin, chlorogenic acid, piceatannol, copper chlorophyll, ferulic acid, curcumin, gingerol, rutin, anthocyanins, isoflavones, anthocyanidins (pelargodinin, cyanidin, delphinidin, peonidin, malvidin, petunidin), dibutylhydroxytoluene (BHT), and butylhydroxyanisole (BHA). More preferably, chlorogenic acid, tannin, catechin, ferulic acid, piceatannol, dibutylhydroxytoluene (BHT), and butylhydroxyanisole (BHA).

[0017] The reducing particle dispersion of the present invention is composed of at least a (meth)acrylic acid ester monomer represented by the above general formula (I) and at least one reducing component selected from the above group A. As for the method of production, for example, the reducing component of the above group A is dissolved in the above (meth)acrylic acid ester monomer (each individually or in pairs or more, 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 ammonium persulfate, potassium persulfate, hydrogen peroxide, etc. are used as polymerization initiators. Furthermore, a polymerization initiator is used in combination with a reducing agent, and crosslinking agents 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, and ethoxylated polyglycerin methacrylate are also used. If necessary, ammonium polyoxyethylene-1-(allyloxymethyl)-alkyl ether sulfate, ether sulfate, ammonium polyoxyethylene nonylpropenylphenyl ether sulfate, polyoxyethylene nonylpropenylphenyl ether, ammonium polyacrylate, ammonium styrene-maleate copolymer, polyoxyethylene alkyl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyalkylene decyl ether, polyoxyethylene tridecyl ether, alkylbenzene sulfonate, dioctyl sulfosuccinate, sodium lauryl sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene styrene phenyl ether phosphate, polyoxyethylene styrene 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 manufactured by emulsion polymerization using polymerizable surfactants (emulsifiers) such as polyoxyethylene sorbitan oleate (polysorbate 80), and after being manufactured as a dispersion of reducing particles, it can be converted into a reducing particle dispersion by drying or other means. Using crosslinking agents such as triallyl isocyanurate as described above is preferable because it improves the heat resistance, mechanical properties, hydrolysis resistance, and weather resistance of the reduced particle dispersion.

[0018] In the present invention, during the emulsion polymerization described above, an appropriate amount of dicyclopenta(thenyl(meth)acrylate monomer may be further mixed with the (meth)acrylic acid ester monomer before emulsion polymerization. When dicyclopenta(thenyl(meth)acrylate monomer is further mixed and emulsion polymerization is performed, the stability is less likely to be impaired even if the water in the dispersion evaporates, resulting in a dispersion of reducing particle dispersions and reducing particle dispersions with even greater stability. The dicyclopentanyl(meth)acrylate monomers that can be used include dicyclopentanyl acrylate monomer, dicyclopentenyl acrylate, dicyclopentanyl methacrylate monomer, and dicyclopentenyl methacrylate. Furthermore, in the present invention, when performing the emulsion polymerization described above, in addition to the dicyclopenta(thenyl)acrylate monomer, other (meth)acrylic acid ester monomers, monomers having reactive crosslinking groups such as epoxy groups, hydroxymethylamide groups, and isocyanate groups, or polyfunctional monomers having two or more vinyl groups may be appropriately blended and crosslinked.

[0019] In the present invention, the content of the (meth)acrylic acid ester monomer among the polymer components constituting the reducing particle dispersion must be 30% by mass or more, preferably 30 to 95% by mass, and more preferably 30 to 70% by mass, relative to the total polymer components constituting the reducing particle dispersion. In this invention, "total polymer components" refers to the polymerizable components that constitute the reducing 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 later. The effects of the present invention can be achieved by setting the content of the above-mentioned (meth)acrylic acid ester monomer to 30% by mass or more relative to the total polymer components. On the other hand, if the content is less than 30% by mass, the stability over time will be poor, which is undesirable.

[0020] Furthermore, among the polymer components constituting the reducing particle dispersion, the content of monomer components other than the (meth)acrylic acid ester monomer is the remainder of the total amount of the (meth)acrylic acid ester monomer used and the crosslinking agent described later. Preferably, the content of other monomer components is 0.5 to 70% by mass relative to the total polymer components, from the viewpoint of further exhibiting the effects of the present invention, dispersibility, and reactivity.

[0021] In the present invention, the (solid content) of the reducing component is preferably 1% by mass or more, more preferably 5% by mass or more, more preferably 10 to 50% by mass, and particularly preferably 15 to 40% by mass, relative to the total polymer components, in order to obtain sufficient reduction performance (oxygen absorption capacity) for oxygen, to obtain a sustained reduction effect, and to obtain stability. By ensuring that the content of this reducing component is 1% by mass or more, sufficient reduction performance (oxygen absorption capacity) and a sustained reducing effect can be achieved. On the other hand, if the content of the reducing component is less than 1% by mass, the reduction performance (oxygen absorption capacity) will not be sufficient, and the effects of the present invention cannot be achieved.

[0022] The polymerizable surfactant that can be used as needed is not particularly limited as long as it is a polymerizable surfactant that is normally used in emulsion polymerization. For example, polymerizable surfactants include anionic or nonionic polymerizable surfactants, and at least one of the following can be mentioned: Adeka Soap NE-10, NE-20, NE-30, NE-40, SE-10N manufactured by Adeka Co., Ltd., Latemul S-180, S-180A, S-120A manufactured by Kao Corporation, Eleminor JS-20 manufactured by Sanyo Chemical Industries, Ltd., and Aqualon KH-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The amount of these polymerizable surfactants used is preferably 0.1 to 50% by mass, relative to the total amount of monomer. Furthermore, the content of the crosslinking agent, such as triallyl isocyanurate, is preferably 0 to 50% by mass, more preferably 0.1 to 25% by mass, relative to the total amount of monomer.

[0023] In the present invention, a reduced particle dispersion (dispersion) in which reduced particles are dispersed in water can be obtained by, at least in the above-mentioned preferred embodiment, dissolving the above-mentioned reducing component in the above-mentioned (meth)acrylic acid ester monomer and emulsion polymerization, or by, at least in the above-mentioned mixed monomer containing the above-mentioned (meth)acrylic acid ester monomer and other monomer components, dissolving the reducing component after polymerization and emulsion polymerization. The amount of reduced particles in the reduced particle dispersion obtained under these manufacturing conditions will vary depending on the blending amounts of the above-mentioned (meth)acrylic acid ester monomer, reducing component, polymerization conditions, etc., and it is preferable to manufacture it so that the solid content is 1 to 50% by mass from the viewpoint of manufacturability, workability, efficiency, etc. More preferably, it is preferable to manufacture it so that the solid content is 10 to 40% by mass.

[0024] In the present invention, in order to further enhance the preservative effect, the reducing particles may contain a preservative component in addition to the reducing component. The reducing particles of the present invention may also contain a preservative component in addition to the reducing component, in order to further exhibit a broad antibacterial spectrum and preservative effect (including antifungal effect).

[0025] The preservative components that can be used in the present invention may be those that are conventionally known, preferably those that are highly safe, do not adversely affect the reducing components they contain, and have long-term antibacterial and antifungal properties. For example, at least one selected from group B below can be used. Group B: Iodopropagyl compounds, sodium pentachlorophenol, 1,2-benzoisothiazolin-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, 2-pyridinethiol-1-oxide sodium, 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-(4-Thiazolyl)Benzimidazole

[0026] Among the above Group B preservative components, the following are even more preferred in terms of long-term stability, ease of availability and low cost, and safety: iodopropagyl compounds, 1,2-benzoisothiazolin-3-one, 2,3,5,6-tetrachloro-4(methylsulfonyl)pyridine, sodium benzoate, sodium dehydroacetate, potassium sorbate, cresol, methylisothiazolinone, chloromethylisothiazolinone, octylisothiazolinone, dichlorooctylisothiazolinone, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine, 2-bromo-2-nitropropane-1,3-diol, 2-pyridinethiol-1-oxide sodium, sodium pyrithione, 2 -(4-thiozolyl)benzimidazole, 4-terpinenol, 1,8-cineole, diisothiocyanate, isopropylmethylphenol, 2-methyl-4-isothiazolin-3-one, citral, eugenol, allyl isothiocyanate, D-limonene, tannic acid, ethylparaben, benzalkonium chloride, glycerin fatty acid ester, salicylic acid, ethyl parahydroxybenzoate, butyl parahydroxybenzoate, propyl parahydroxybenzoate, methyl parahydroxybenzoate, hinokitiol, phenylethyl alcohol, phenethyl alcohol, phenoxyethanol, butylparaben, propylparaben, benzalkonium chloride, methylparaben, and 2-(4-thiazolyl)benzimidazole are preferred.

[0027] In the present invention, when a preservative component is used, the (solid content) of the preservative component is preferably 1% by mass or more, more preferably 5% by mass or more, more preferably 10 to 50% by mass, and particularly preferably 15 to 40% by mass, relative to the total polymer component, in order to obtain further effects of containing the preservative, to obtain a sustained preservative effect, and to obtain stability. By increasing the content of this preservative component to 1% by mass or more, a more sufficient preservative effect (oxygen absorption capacity) and a sustained reducing effect can be achieved. On the other hand, if the content of the preservative component is less than 1% by mass, the further effects of the present invention, which include a preservative, cannot be achieved.

[0028] The production of reducing particles containing the above-mentioned reducing component and preservative component can be carried out in accordance with the production of reducing particles containing the above-mentioned reducing component. At a minimum, a reducing particle dispersion (dispersion) in which reducing particles are dispersed in water can be obtained by dissolving the above-mentioned reducing component and preservative component in the above-mentioned (meth)acrylic acid ester monomer and emulsion polymerization, or by dissolving the reducing component and preservative component after polymerization of a mixed monomer containing the above-mentioned (meth)acrylic acid ester monomer and other monomer components and then emulsion polymerization. The amount of reducing particles produced in the reducing particle dispersion obtained under these production conditions will vary depending on the blending amounts of the above-mentioned (meth)acrylic acid ester monomer, reducing component, preservative component, etc., used, polymerization conditions, etc. From the viewpoint of manufacturability, workability, and efficiency, it is preferable to produce them so that the solid content is 1 to 50% by mass. More preferably, it is preferable to produce them so that the solid content is 10 to 40% by mass.

[0029] Furthermore, in the present invention, the average particle size of the resulting reducing particles (containing reducing components, or containing reducing components + preservative components, the same applies hereinafter) varies depending on the monomer having the structural unit of the general formula (I) above, the content, the polymerization conditions during polymerization, etc., but it is preferably 10 to 800 nm, more preferably 20 to 400 nm, and even more preferably 30 to 200 nm. By maintaining the above preferred average particle size range, the product can be suitably used for various applications and will also exhibit excellent storage stability. In this invention, the "average particle diameter" is the histogram-average particle diameter based on the scattered light intensity distribution. In this invention (including the examples described later), it is the value D50 measured using a particle size distribution analyzer [FPAR1000 (manufactured by Otsuka Electronics Co., Ltd.)].

[0030] The reducing particle dispersion of the present invention contains particles with the above-mentioned reducing component that exhibit a high degree of both reduction performance (oxygen absorption capacity) and preservative performance, while also possessing sustained release properties without adversely affecting other components, and exhibiting excellent dispersion stability. The above-mentioned preservative effect (including antifungal effect) can exert antibacterial effects (including antifungal effect) against many types of bacteria and fungi, such as Gram-negative and Gram-positive bacteria, and the sustained effects of its preservative and reducing performance are also long-lasting. Furthermore, the reducing particles containing the aforementioned reducing and preservative components achieve a high degree of balance between the antibacterial and antifungal effects of the particles, the preservative effect of the preservative component, and the reducing performance of the reducing component, without adversely affecting each other. This balances the reducing performance against oxygen (oxygen absorption capacity), the antibacterial and antifungal effects of the particles, and the preservative performance of the preservative component (hereinafter, these preservative performances are referred to as "composite preservative performance"). Moreover, it possesses sustained release properties without adversely affecting other components, and exhibits excellent dispersion stability, resulting in an unprecedented reducing particle dispersion.

[0031] As described above, the reducing particle dispersion (dispersion) of the present invention exhibits excellent effects and can therefore be used to impart reducing and preservative properties to a variety of products, such as medical devices, baby products, nursing care products, bath products, kitchenware, tableware, drinking water piping parts, hygiene products, home appliances, clothing, building materials, agricultural materials, automotive interior parts, stationery, writing instruments, and ink compositions for inkjet printers. Specific applications include, in addition to those mentioned above, detergent applications such as laundry detergents, fabric softeners, household detergents, dishwashing detergents, and hard surface cleaners; personal care applications such as shampoos, conditioners, lotions, emulsions, creams, sunscreens, foundations, eye makeup products, antiperspirants, and toothpaste; industrial water treatment applications 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 the papermaking process, cooling water and washing water for various industries); and electronic equipment applications such as medical devices, food additives, solar cell modules and organic element devices, and heat shielding films. It can also be suitably used in aquariums and medicated baths to suppress water mold growth in aquatic organisms (fish, etc.).

[0032] Furthermore, the form of the reducing particle dispersion (dispersion) of the present invention when used in an aqueous ink composition for writing instruments such as felt-tip pens, marking pens, and ballpoint pens will be described in detail below. The aqueous ink composition for writing instruments of the present invention is characterized by containing at least the above-described reducing particle dispersion, and may also contain a colorant and a water-soluble organic solvent. The amount of reducing particles in the ink composition is preferably 0.1 to 30.0% by mass, and more preferably 1.0 to 15.0% by mass, based on the solid content of the total ink composition, in order to exhibit the effects of the present invention without impairing writing performance and from the standpoint of storage stability.

[0033] Suitable colorants include water-soluble dyes and pigments, such as inorganic pigments, organic pigments, plastic pigments, hollow resin particles with voids inside can be used as white pigments, or resin particles dyed with dyes that have excellent color development and dispersibility (pseudo-pigments) can also be used. As water-soluble dyes, direct dyes, acid dyes, food dyes, and basic dyes can all be used in appropriate amounts as long as they do not impair the effects of the present invention. The content of these colorants varies depending on the type of writing instrument, but is generally between 1% and 30% by mass of the total ink composition.

[0034] Examples of water-soluble organic solvents that can be used 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. Examples include 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; and at least one of the following: N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidalidinone.

[0035] In addition, water-soluble solvents such as alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, benzyl alcohol, etc.), amides (dimethylformamide, diethylacetamide, etc.), and ketones (acetone, etc.) can also be mixed. The content of these water-soluble organic solvents varies depending on the type of writing instrument, such as felt-tip pens, marking pens, and ballpoint pens. It is particularly effective for ink compositions in which the content is 1 to 40% by mass relative to the total amount of ink composition, and 10% by mass or less is used to further improve line drying properties. More preferably, it is desirable to use 3 to 8% by mass.

[0036] The aqueous ink composition for writing instruments of the present invention contains, in addition to the particles with the above-mentioned properties, a colorant, and a water-soluble solvent, the remainder may include, as appropriate, a solvent such as water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.), a dispersant, a lubricant, a pH adjuster, a rust inhibitor, a thickener, an evaporation inhibitor, a surfactant, a binder, etc., to the extent that it does not impair the effects of the present invention.

[0037] Suitable dispersants include nonionic and anionic surfactants and water-soluble resins. Water-soluble polymers are preferred. Examples of lubricants include nonionic compounds such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, higher polyoxyalkylene fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments; anionic compounds such as alkyl sulfonates and alkyl allyl sulfonates of higher fatty acid amides; derivatives of polyalkylene glycols; fluorinated surfactants; and polyether-modified silicones.

[0038] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of carbonic acid and phosphoric acid such as sodium tripolyphosphate and sodium carbonate, and alkali metal hydrates such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitride, and saponins. Examples of thickening agents include carboxymethylcellulose (CMC) or its salts, cellulose derivatives such as fermented cellulose and crystalline cellulose, and polysaccharides. Examples of polysaccharides that can be used include 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, nigellan, hyaluronic acid, pustulan, funoran, HM pectin, porphyran, laminaran, lichenan, carrageenan, alginic acid, tragacanth gum, alkasi gum, succinoglycan, locust bean gum, and tara gum. These may be used individually or in combination of two or more. Commercially available products of these may also be used. Examples of evaporation inhibitors include pentaerythritol, p-xylene glycol, trimethylolpropane, triethylolpropane, and dextrin. Examples of surfactants include fluorine-based, silicone-based, and acetylene glycol-based surfactants. Examples of adhesives include at least one selected from water-soluble resins having hydrophobic parts within their molecules, such as polyacrylic acid, water-soluble styrene-acrylic resin, water-soluble styrene-maleic acid resin, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble maleic acid resin, water-soluble styrene resin, polyvinylpyrrolidone, polyvinyl alcohol, water-soluble ester-acrylic resin, ethylene-maleic acid copolymer, polyethylene oxide, and water-soluble urethane resin, as well as resin emulsions such as polyolefin emulsions, acrylic emulsions, vinyl acetate emulsions, urethane emulsions, styrene-butadiene emulsions, and styrene-acrylonitrile emulsions. It is desirable to use at least one of each of these, for a total of at least two types.

[0039] The aqueous ink composition for writing instruments of the present invention can be prepared by appropriately combining the above-mentioned particles, water-soluble solvent, and other components according to the application of the ink for writing instruments (ballpoint pens, marking pens, etc.), and stirring and mixing them with a stirrer such as a homomixer, homogenizer, or disper, and further removing coarse particles from the ink composition by filtration or centrifugation as necessary.

[0040] Furthermore, the pH (at 25°C) of the aqueous ink composition for writing instruments of the present invention is preferably adjusted to 5 to 10 using a pH adjuster or the like, and more preferably to 6 to 9.5, from the viewpoint of usability, safety, stability of the ink itself, and compatibility with the ink container.

[0041] The aqueous ink composition for writing instruments of the present invention is used in ballpoint pens, marking pens, and the like, which are equipped with pen tips such as ballpoint pen tips, fiber tips, felt tips, and plastic tips. As a ballpoint pen, the water-based ink composition for writing instruments having the above composition is used with a diameter of 0.18 to 2.0 Examples include a ballpoint pen ink refill containing a ball of mm in diameter, in which an ink follower is contained, which is incompatible with the aqueous ink composition contained within the ink refill and has a lower specific gravity than the aqueous ink composition, such as polybutene, silicone oil, or mineral oil. The structure of the ballpoint pen and marking pen is not particularly limited. For example, it may be a direct-ink type ballpoint pen or marking pen equipped with a collector structure (ink holding mechanism) in which the barrel itself serves as the ink reservoir and the above-described aqueous ink composition for writing instruments is filled into the barrel.

[0042] In the aqueous ink composition for writing instruments of the present invention configured in this way, the reducing particle dispersion with the above-mentioned properties is incorporated into the aqueous ink composition for writing instruments. As a result, the ink composition exhibits strong and sustained reduction performance (oxygen absorption capacity) against oxygen, without adversely affecting other components, and possesses excellent dispersion stability and preservative properties. Therefore, it can suppress the generation of bubbles and maintain its preservative effect for a long period of time. Moreover, these particles do not impair storage stability or writing performance, further increasing the freedom of ink design and resulting in an aqueous ink composition for writing instruments suitable for ballpoint pens, marking pens, and other writing instruments. [Examples]

[0043] Next, the present invention will be described in more detail with reference to manufacturing examples, embodiments, and comparative examples, but the present invention is not limited to the following embodiments, etc. [Manufacturing Examples 1-11: Manufacturing of Reducing Particle Dispersion (Particles 1-11)] Each reducing particle dispersion was prepared according to the following manufacturing examples 1 to 11. Note that "parts" below refers to parts by mass. The reducing component is expressed as solid content.

[0044] (Manufacturing Example 1) A 2-liter flask was fitted with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input, and placed in a hot water bath. 329.5 parts distilled water, 5 parts glycerin monomethacrylate [Bremmer GLM, NOF Corporation], 5 parts sodium 2-sulfoethyl methacrylate [Acrylates SEM-Na, Mitsubishi Chemical Corporation], 20 parts polymerizable surfactant [ADEKA Corporation, Adekarya Soap SE-10N, Ether Sulfite], and 0.5 parts ammonium persulfate were charged into the flask, and the internal temperature was raised to 50°C while introducing nitrogen gas.

[0045] On the other hand, a solution was prepared by mixing a mixed monomer consisting of 55 parts of cyclohexyl methacrylate monomer and 20 parts of n-butyl methacrylate with 40 parts of a reducing component [tannin, manufactured by Fuji Chemical Industries Co., Ltd. (tannic acid S)] and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Chemical Industries Co., Ltd., TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at a temperature of approximately 50°C, under stirring for 3 hours to carry out emulsion polymerization. After further aging for 5 hours, polymerization was completed to obtain a reducing particle dispersion (dispersion) (particle 1). The content of the methacrylate ester monomer was 50.0% by mass relative to the total polymer components constituting the reducing particles, and the content of the reducing component was 36.4% by mass relative to the total polymer components. The average particle size of the reducing particles was 46 nm.

[0046] (Manufacturing example 2) In the above-mentioned Production Example 1, a reducing particle dispersion (dispersion) (particles 2) was obtained in the same manner as in Production 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 as a reducing component, 44 parts of a reducing component [chlorogenic acid, manufactured by Fuji Chemical Industry Co., Ltd. (Caphenol P100)] was used. The content of the methacrylate ester monomer was 31.6% by mass relative to the total polymer components constituting the reducing particles, and the content of the reducing component was 46.3% by mass relative to the total polymer components. The average particle size of the reducing particles was 87 nm.

[0047] (Manufacturing Example 3) A dispersion of reducing particle dispersion (particle 3) was obtained in the same manner as in Production Example 1 above, except that the amount of distilled water was 333.5 parts, the amount of cyclohexyl methacrylate monomer was 60 parts, the amount of n-butyl methacrylate was 30 parts, and the reducing component was 36 parts of a reducing component [catechin, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. ((-)-catechin, derived from green tea)]. The content of the methacrylate ester monomer was 54.5% by mass relative to the total polymer components constituting the reducing particles, and the content of the reducing component was 32.7% by mass relative to the total polymer components. The average particle size of the reducing particles was 63 nm.

[0048] (Manufacturing example 4) A reducing particle dispersion (dispersion) (particle 4) was obtained in the same manner as in Production Example 1 above, except that the amount of distilled water was 309.5 parts, the amount of cyclohexyl monomer methacrylate was 60 parts, the amount of n-butyl methacrylate was 35 parts, and the reducing component was 45 parts of the reducing component [copper chlorophyll, manufactured by Fujifilm Wako Pure Chemical Industries (copper chlorophyllin trisodium salt)]. The methacrylate ester monomer content was 52.2% by mass relative to the total polymer components constituting the reducing particles, and the reducing component content was 39.1% by mass relative to the total polymer components. The average particle size of the reducing particles was 120 nm.

[0049] (Manufacturing example 5) In the above-mentioned Production Example 1, a reducing particle dispersion (dispersion) (particle 5) was obtained in the same manner as in Production 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 as a reducing component, 44 parts of a reducing component [piceatannol, manufactured by Morinaga & Co., Ltd. (Pasenol LA)] was used. The content of the methacrylate ester monomer was 31.6% by mass relative to the total polymer components constituting the reducing particles, and the content of the reducing component was 46.3% by mass relative to the total polymer components. The average particle size of the reducing particles was 78 nm.

[0050] (Manufacturing example 6) A reducing particle dispersion (dispersion) (particles 6) was obtained in the same manner as in Production 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 as a reducing component, 44 parts of a reducing component [propyl gallate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] were used. The content of the methacrylate ester monomer was 31.6% by mass relative to the total polymer components constituting the reducing particles, and the content of the reducing component was 46.3% by mass relative to the total polymer components. The average particle size of the reducing particles was 77 nm.

[0051] (Manufacturing example 7) A reducing particle dispersion (dispersion) (particles 7) was obtained in the same manner as in Production Example 1 above, except that the amount of distilled water was 340.0 parts, the amount of cyclohexyl methacrylate monomer was 30.5 parts, the amount of n-butyl methacrylate was 45 parts, and as a reducing component, 44 parts of the reducing component [dibutylhydroxytoluene (BHT), "BHT" manufactured by JGC Universal Corporation] was used. The content of the methacrylate ester monomer was 30.5% by mass relative to the total polymer components constituting the reducing particles, and the content of the reducing component was 45.8% by mass relative to the total polymer components. The average particle size of the reducing particles was 80 nm.

[0052] (Manufacturing example 8) A reducing particle dispersion (dispersion) (particles 8) was obtained in the same manner as in Production Example 1 above, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl methacrylate monomer was 25 parts, the amount of n-butyl methacrylate was 50 parts, and as a reducing component, 45 parts of a reducing component [butylhydroxyanisole (BHA), "Susten 1-F (BHA)" manufactured by JGC Universal Corporation] was used. The methacrylate monomer content was 29.3% by mass relative to the total polymer components constituting the reducing particles, and the reducing component content was 46.8% by mass relative to the total polymer components. The average particle size of the reducing particles was 78 nm.

[0053] (Manufacturing example 9) A 2-liter flask was fitted with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and 1000 ml separatory funnel for monomer input, and placed in a hot water bath. 329.5 parts distilled water, 5 parts glycerin monomethacrylate [Bremmer GLM, NOF Corporation], 5 parts sodium 2-sulfoethyl methacrylate [Acrylates SEM-Na, Mitsubishi Chemical Corporation], 20 parts polymerizable surfactant [ADEKA Corporation, Adekarya Soap SE-10N, Ether Sulfite], and 0.5 parts ammonium persulfate were charged into the flask, and the internal temperature was raised to 50°C while introducing nitrogen gas.

[0054] On the other hand, a solution was prepared by mixing a mixed monomer consisting of 50 parts of cyclohexyl methacrylate monomer and 40 parts of n-butyl methacrylate with 30 parts of a reducing agent [tannin, manufactured by Fuji Chemical Industry Co., Ltd. (tannic acid S)], 10 parts of a preservative [phenoxyethanol, manufactured by Yokkaichi Synthetic Co., Ltd.], and 10 parts of a crosslinking agent [triallyl isocyanurate, manufactured by Nippon Chemical Corporation, TAIC]. This prepared solution was added from the separatory funnel into the flask, which was kept at a temperature of approximately 50°C, under stirring for 3 hours to carry out emulsion polymerization. After further aging for 5 hours, polymerization was completed to obtain a reducing particle dispersion (dispersion) (particle 9). The methacrylate ester monomer content was 46.3% by mass relative to the total polymer components constituting the reducing particles, the reducing component content was 25.5% by mass relative to the total polymer components, and the preservative component content was 15.5% by mass relative to the total polymer components. The average particle size of the reducing particles was 100 nm.

[0055] (Manufacturing example 10) In the above production example 9, a reducing particle dispersion (dispersion) (particle 9) was obtained in the same manner as in production example 9, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl monomer methacrylate was 45 parts, the amount of n-butyl methacrylate was 45 parts, and as a reducing component, 28 parts of a reducing component [tannin, manufactured by Fuji Chemical Industry Co., Ltd. (tannic acid S)] and 12 parts of a preservative component [benzisothiazolinone (BIT), manufactured by Yamato Chemical Industry Co., Ltd.] were used. The methacrylate ester monomer content was 53% by mass relative to the total polymer components constituting the reducing particles, the reducing component content was 21.3% by mass relative to the total polymer components, and the preservative component content was 15.1% by mass relative to the total polymer components. The average particle size of the reducing particles was 98 nm.

[0056] (Manufacturing Example 11) In the above production example 9, a dispersion of reducing particle dispersion (particles 11) was obtained in the same manner as in production example 9, except that the amount of distilled water was 340.5 parts, the amount of cyclohexyl monomer methacrylate was 30 parts, the amount of n-butyl methacrylate was 45 parts, and as a reducing component, 30.5 parts of reducing component [chlorogenic acid, manufactured by Fuji Chemical Industry Co., Ltd. (Caphenol P100)] and as a preservative component, 14.5 parts of methylisothiazoline (MIT), manufactured by Yamato Chemical Industry Co., Ltd. was used. The methacrylate ester monomer content was 38.9% by mass relative to the total polymer components constituting the reducing particles, the reducing component content was 28.1% by mass relative to the total polymer components, and the preservative component content was 17.7% by mass relative to the total polymer components. The average particle size of the reducing particles was 78 nm.

[0057] Each of the reducing particle dispersions (dispersions) obtained in the above production examples 1 to 11 was acquired. The solid content of reducing particles in each of the reducing particle dispersions obtained in production examples 1 to 8 was 35 to 40% by mass. Using the reducing particle dispersions (dispersions) obtained from Production Examples 1 to 11 above, the sustainability of the reducing performance (dissolved oxygen removal ability), dispersion stability, and preservative performance were evaluated using the evaluation method described below. As a reference example, particle A from Manufacturing Example 1 described in Japanese Patent Publication No. 2020-55971 was used. These results are shown in Table 1 below.

[0058] (Method for evaluating reduction performance) The reducing properties of the reducing particle dispersions (dispersions) obtained from manufacturing examples 1 to 11 above were evaluated by measuring the dissolved oxygen content. The evaluation was performed using a dissolved oxygen meter: WQ-320 (manufactured by Horiba, Ltd.). After preparing the reducing particle dispersions, they were left at a temperature of 25°C for 48 hours and 3 months, and the persistence of the reducing performance was evaluated according to the evaluation criteria below when measured at a measurement temperature of 25°C. Evaluation criteria: A: Dissolved oxygen level is less than 0.1-10 mg / L. B: Dissolved oxygen level is less than 10-20 mg / L. C: Dissolved oxygen level is 20 mg / L or higher.

[0059] (Method for evaluating dispersion stability) Using the reducing particle dispersions (dispersions) obtained in Production Examples 1 to 11 above, 10 ml of each obtained reducing particle aqueous dispersion was filled into 15 ml glass bottles with lids, along with a stirring ball (φ6.4 mm, stainless steel). After sealing, the bottles were stored at 40°C for one month with the caps facing upwards, and then each dispersion was shaken. The dispersion stability was evaluated according to the following criteria based on the number of shakes required before the stirring ball began to move inside the glass bottle. Evaluation criteria: A: 0 to 3 times. B: 4~10 times. C: More than 11 times. *0 times: The movement of the stirring ball can be observed when the glass jar with a lid is tilted.

[0060] (Test method for preservative effect (antibacterial and antifungal properties)) The reducing particle dispersions (dispersions) obtained from Production Examples 1 to 11 above were subjected to the following microbiological testing methods in accordance with ISO 11930:2012 (Procedures for interpreting data generated by preservation efficacy testing or microbiological risk assessment, or both). Challenge tests were conducted with the following three groups: bacteria, yeast, and filamentous fungi. Bacterial group: Stapylococcus aureus NBRC13276, Escherichia coli NBRC3972 Yeast: Candida albicans NBRC1594 Filamentous fungus: Aspergillus brasiliensis <Preparation of inoculum> Preparation of inoculum: The inoculum was prepared according to ISO 11930:2012. Bacterial group: A bacterial suspension was prepared for each bacterial species according to ISO 11930:2012. 1 × 10⁶ of bacterial species were used. 7 ~1 × 10 8 Three bacterial solutions, each adjusted to cfu / ml, were mixed in equal volumes to create an inoculum. Yeast: 1 × 10⁶ according to ISO 11930:2012 6 ~1 × 10 7 A bacterial suspension was prepared to achieve a concentration of cfu / ml. Filamentous fungi: According to ISO 11930:2012, 1 × 10 6 ~ 1 × 10 7 A bacterial suspension was prepared to achieve a concentration of cfu / ml. <Inoculation> A 1% by mass bacterial solution was inoculated into the writing instrument ink composition. <Storage> The inoculated writing instrument ink composition was stored at a temperature of 22.5±2.5℃ and detection culture was performed at specified intervals. <Detection Culture> The bacterial group was spread on 10 plates of SCD agar, the yeast on SD agar, and the filamentous fungi on PD agar, with a total of 1 g spread on each plate. The bacterial group and yeast were cultured at 32.5°C for 2 days, and the filamentous fungi were cultured at 22.5°C for 5 days. <Evaluation Criteria> A+: No colony appears by day 3. A: No colony appears by day 7. B: No colony appears by day 21. C: As of day 28, several to several dozen colonies have appeared. D: As of the 28th, the number has clearly increased.

[0061] [Table 1]

[0062] As is clear from the results in Table 1 above, the reducing particle dispersions (dispersions) of Production Examples 1 to 11 obtained above were found to have excellent sustained reducing performance (dissolved oxygen removal ability), dispersion stability, and preservative properties. Furthermore, the reducing particle dispersions (dispersions) of Production Examples 9-11 contain preservative components along with the reducing components to further enhance their preservative effect. It was confirmed that these dispersions offer even greater preservative performance than the reducing particle dispersions (dispersions) of Production Examples 1-8 that contain reducing components, while maintaining their sustained effect, not adversely affecting other components, and exhibiting superior dispersion stability.

[0063] [Examples 1-11 and Comparative Examples 1-3: Preparation of Aqueous Ink Compositions for Writing Instruments] For Examples 1 to 11, the respective reducing particle dispersions (dispersions) obtained in Production Examples 1 to 11 were prepared. The solid content of reducing particles in each of the reducing particle dispersions obtained in Production Examples 1 to 11 was 35 to 40% by mass. On the other hand, the following three known oxygen absorbers were used for Comparative Examples 1 to 3. Comparative Example 1 used an oligomer of L-sodium ascorbate, Comparative Example 2 used an oligomer of N-acetyl-cysteine, and Comparative Example 3 used an oligomer of N-vinyl-2-pyrrolidone (degree of polymerization: 2-6).

[0064] Using the reducing particle dispersions (particles 1-11) produced according to the above production examples 1-11 and the above comparative examples 1-3, aqueous ink compositions for writing instruments were prepared by conventional methods with the following formulations (total amount 100% by mass). Ink composition: (Total 100% by mass) Each reducing particle dispersion (particles 1-8) or Comparative Examples 1-3: 15.0% by mass Coloring agent (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

[0065] Each of the obtained aqueous ink compositions for writing instruments (100% by mass) was evaluated for its writing properties (difference in density between upper and lower lines), the occurrence of bubbles over time, and the occurrence of bubbles after impact, using writing instruments A and B with the following configurations and the evaluation method described below. Table 2 below shows the evaluation results for Examples 1-11 and Comparative Examples 1-3.

[0066] (Writing instrument: Ballpoint pen manufacturing) A water-based ballpoint pen was manufactured using the barrel of ballpoint pen A (manufactured by Mitsubishi Pencil Co., Ltd., product name: Signo UM-100). The refill consisted 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 ball, ball diameter 0.5 mm), and a connector connecting the reservoir tube and the tip. Each of the above-mentioned water-based ink compositions was filled into the refill, and an ink-following body mainly composed of mineral oil was loaded at the rear end of the ink to create a water-based ballpoint pen. Using the barrel of a ballpoint pen B (manufactured by Mitsubishi Pencil Co., Ltd., product name: Signo UMN152), a refill 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 ball, ball diameter 0.5 mm), and a connector connecting the reservoir tube and the tip was filled with the above-mentioned aqueous ink compositions, and an ink-following body mainly composed of mineral oil was loaded at the rear end of the ink to create a retractable aqueous ballpoint pen.

[0067] [Method for evaluating writability (difference in line density between upper and lower lines)] Each water-based ballpoint pen A with the above configuration was left at room temperature (25°C, the same applies below) for one month, then used for writing until the end of writing. The difference in line density between the beginning and end of writing was compared, and the pens were evaluated according to the following evaluation criteria. Evaluation criteria: A: There is no difference in concentration. B: A slight difference in concentration is observed. C: A clear difference in concentration is observed. D: Significant differences in density are observed, making it difficult to see the drawn lines in some areas.

[0068] <Method for evaluating bubble formation over time> Each ballpoint pen A with the above configuration was stored with the pen tip facing downwards in an atmosphere of 50°C and 30% RH for one month. After the above period had elapsed, the pen was left at room temperature for 6 hours with the pen tip still facing downwards, and the bubbles appearing at the interface between the ink and the ink-following body were visually inspected and evaluated according to the following evaluation criteria.

[0069] <Method for evaluating bubble formation after impact> The above-described retractable ballpoint pen B was pressed five times with the pen tip facing downwards, then stored for one week in the above-described atmosphere of 50°C and 30% RH with the pen tip still facing downwards. After the above period had elapsed, the pen was left at room temperature for 6 hours with the pen tip still facing downwards, and the bubbles appearing at the interface between the ink and the ink-following body were visually inspected and evaluated according to the following evaluation criteria. Evaluation criteria: A: There are absolutely no air bubbles at the interface between the ink and the ink-following material. B: One air bubble less than 1 mm in diameter is present at the interface between the ink and the ink-following material. C: One or more bubbles with a diameter of 1 mm or more, or two or more bubbles with a diameter of less than 1 mm, are present at the interface between the ink and the ink-following material. D: The ink-following material is pushed up by air bubbles, creating a gap between it and the ink interface.

[0070] Each of the obtained aqueous ink compositions for writing instruments (100% by mass) was subjected to the following microbiological testing methods in accordance with ISO 11930:2012 (procedures for interpreting data generated by preservation efficacy tests or microbiological risk assessments, or both). Challenge tests were conducted with the following three groups: bacteria, yeast, and filamentous fungi. Bacterial group: Stapylococcus aureus NBRC13276, Escherichia coli NBRC3972 Yeast: Candida albicans NBRC1594 Filamentous fungus: Aspergillus brasiliensis <Preparation of inoculum> Preparation of inoculum: The inoculum was prepared according to ISO 11930:2012. Bacterial flora: For each bacterial species, the inoculum was prepared according to ISO 11930:2012. For each bacterial species, the inoculum adjusted to 1×10 7 ~1×10 8 cfu / ml was mixed in equal amounts of three kinds and used as the inoculum. Yeast: According to ISO 11930:2012, the inoculum was prepared to be 1×10 6 ~1×10 7 cfu / ml. Filamentous fungi: According to ISO 11930:2012, the inoculum was prepared to be 1×10 6 ~1×10 7 cfu / ml. 〈Inoculation〉 The ink composition for writing instruments was inoculated with the inoculum in an amount of 1% by mass. 〈Storage〉 The inoculated ink composition for writing instruments was stored at a temperature of 22.5±2.5°C, and detection culture was performed at specified intervals. 〈Detection culture〉 For the bacterial flora, on SCD agar medium, for yeast, on SD agar medium, and for filamentous fungi, on PD agar medium, a total of 1 g was smeared on 10 plates each, and the bacterial flora and yeast were cultured at 32.5°C for 2 days, and the filamentous fungi were cultured at 22.5°C for 5 days. 〈Evaluation criteria〉 A+: No colonies appear on the 3rd day. A: No colonies appear on the 7th day. B: No colonies appear on the 21st day. C: A few to several tens of colonies appear on the 28th day. D: It is clearly increasing on the 28th day.

[0071]

Table 2

[0072] Considering Table 2 above, it was confirmed that Examples 1 to 11, which fall within the scope of the present invention, exhibited superior writing performance (difference in density between upper and lower lines), no bubble formation even after time had passed, and no bubble formation even after impact. They also demonstrated strong and persistent oxygen reduction performance (oxygen absorption capacity) without adversely affecting other ink components. Furthermore, the aqueous ink compositions for writing instruments using the reducing particle dispersions (dispersions) of Examples 9 to 11 further contain preservative components along with the reducing components to enhance the preservative effect. It was confirmed that these compositions offer even greater preservative performance than the reducing particle dispersions (dispersions) containing reducing components of Examples 1 to 8, without negatively affecting their duration of effect or other components, and also exhibit superior dispersion stability. Furthermore, it was confirmed that both ballpoint pens A and B, created as described above, produced clear lines without smudging or bleeding, and had sufficient line density. [Industrial applicability]

[0073] The reducing particle dispersion of the present invention possesses strong and sustained (sustained-release) reduction performance (oxygen absorption capacity) against oxygen, without adversely affecting other components, and also exhibits excellent dispersion stability and preservative properties. Therefore, it can be used to impart reducing and preservative properties to a wide range of products, such as medical devices, baby products, nursing care products, bath products, kitchenware, tableware, drinking water piping parts, hygiene products, home appliances, clothing, building materials, agricultural materials, automotive interior parts, stationery, writing instruments, and ink compositions for inkjet printers.

Claims

1. A reducing particle dispersion characterized in that reducing particles containing a reducing component, which is composed of emulsion polymerization of at least a (meth)acrylic acid ester monomer represented by the following general formula (I) and at least one reducing component selected from the following group A, are dispersed in water. 【Chemistry 1】 [In the above formula (I), A is a hydrogen atom (H) or a methyl group (CH ３ ) where R represents a substituent having a hydrogen atom (H), an alkyl group having 1 to 22 carbon atoms, or a polyalkylene glycol chain having 2 to 18 carbon atoms in the alkylene chain, and the substituent having an alkyl group or polyalkylene glycol chain may have 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 as a substituent. Group A: Catechin, tannin, chlorogenic acid, piceatannol, copper chlorophyll, ferulic acid, curcumin, gingerol, rutin, anthocyanin, isoflavone, pelargodinin, cyanidin, delphinidin, peonidin, malvidin, petunidin

2. The reducing particle dispersion according to claim 1, characterized in that the content of the (meth)acrylic acid ester monomer represented by the general formula (I) is 30 to 95% by mass with respect to the total polymer components constituting the reducing particle dispersion.

3. The reducing particle dispersion according to claim 1 or 2, characterized in that the reducing component is contained in an amount of 1% by mass or more relative to the total polymer components constituting the reducing particles.

4. The reducing particle dispersion according to any one of claims 1 to 3, characterized in that the reducing component is at least one selected from chlorogenic acid, tannin, catechin, and piceatannol.

5. The reducing particle dispersion according to any one of claims 1 to 4, characterized in that the reducing particles further contain a preservative component.

6. The reducing particle dispersion according to any one of claims 1 to 5, characterized in that the average particle size of the reducing particle dispersion is 10 to 800 nm.

7. An aqueous ink composition for writing instruments according to any one of claims 1 to 6, characterized by comprising the aforementioned reducing particle dispersion.

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