Method for producing a metal pigment composition

Abstract

To provide a method for producing a metallic pigment composition with reduced environment load.SOLUTION: A method for producing a metallic pigment composition includes the steps for (I) dispersing metal particles in a solvent including at least a hydrophobic solvent, to obtain a metal particle dispersion liquid, (II) adding an aqueous salt solution to the metal particle dispersion liquid, to obtain phases that are separated into a hydrophilic phase and a hydrophobic solvent phase, and (III) coating the surfaces of the metal particles with polysiloxane compounds, while keeping the phase-separated state.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a metal pigment composition suitable for paint compositions or ink compositions, particularly water-based paints or water-based inks. [Background technology]

[0002] Traditionally, metallic pigment compositions have been used in metallic paints, printing inks, and plastic compounding applications to achieve a metallic aesthetic effect. In recent years, the paint industry has seen a growing need to switch to water-based paints, which use less organic solvents, as a measure to conserve resources and reduce pollution. However, hydrophilic organic solvents are often used in the manufacturing methods of metallic pigment compositions that can be used in water-based paints, and further reductions in the amount of organic solvents used during manufacturing are desired.

[0003] Patent Document 1 discloses an aluminum pigment whose surface is coated with a polysiloxane compound produced under conditions using a basic catalyst, including monoethanolamine. In the method for producing the aluminum pigment described in that document, it is stated that it is preferable to use 500 parts by mass or more of a hydrophilic organic solvent per 100 parts by mass of aluminum particles, due to concerns about the viscosity of the slurry increasing.

[0004] Furthermore, Patent Document 2 discloses a metal pigment composition whose surface is coated with a polysiloxane compound produced under conditions using a basic catalyst such as ammonia or an acidic catalyst. In the method for producing the metal pigment composition described in the document, the concentration of metal particles in the slurry is preferably 5 to 20% by mass. That is, it is preferable to use 400 parts by mass or more of organic solvent per 100 parts by mass of metal particles. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 3948934 [Patent Document 2] Japanese Patent Publication No. 2019-151678 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In view of the above-mentioned prior art, the present invention aims to provide a novel method for producing polysiloxane compound-coated metal pigment compositions that reduces the amount of solvent used in the manufacturing process (particularly the amount of hydrophilic organic solvent) and reduces the amount of deposits adhering to the reaction vessel walls and stirring blades. [Means for solving the problem]

[0007] The inventors discovered that when metal particles are coated with a polysiloxane compound, adding an aqueous solution of salt to induce phase separation prevents the increase of deposits on the reaction vessel walls and stirring blades due to the resulting hydrophobic solvent phase. Furthermore, they found that this adhesion-suppressing effect of the hydrophobic solvent phase is also present when the concentration of metal particles in the slurry is high. After further investigation, we devised a water-based treatment method that utilizes phase separation to reduce the amount of solvent used (especially the amount of hydrophilic organic solvent) while providing the water resistance and dispersibility required for practical use in water-based paints. This method has now been completed as a method for producing metal pigment compositions.

[0008] In other words, the embodiments of the present invention are as follows. [1] (I) A step of dispersing metal particles in a solvent containing at least a hydrophobic solvent to obtain a metal particle dispersion, (II) A step of adding an aqueous solution of salt to the metal particle dispersion to obtain a phase separated into a hydrophilic phase and a hydrophobic solvent phase, (III) A step of coating the surface of the metal particles with a polysiloxane compound while the phase-separated phase is in a phase-separated state, A method for producing a metal pigment composition characterized by containing the following: [2] The method for producing a metal pigment composition according to [1], wherein the total amount of the solvent in the step (I) is 10 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the metal particles. [3] The method for producing a metal pigment composition according to [2], wherein the solvent in the step (I) contains a hydrophobic solvent and a hydrophilic solvent, and the mass ratio of the hydrophobic solvent to the hydrophilic solvent (mass of hydrophobic solvent / mass of hydrophilic solvent) is 1 / 1 to 1 / 24. [4] The method for producing a metal pigment composition according to any one of [1] to [3], wherein the amount of the salt added in the step (II) is 0.1 to 40 parts by mass with respect to 100 parts by mass of the metal particles. [5] The method for producing a metal pigment composition according to any one of [1] to [3], wherein the pKa of the acid constituting the salt added in the step (II) is 3.0 to 5.5. [6] In the coating treatment of the step (III), as the raw material of the polysiloxane compound, at least one silicon-containing compound selected from an alkoxysilane represented by the following general formula (1), a tetrahalosilane represented by the following general formula (2), a silane coupling agent represented by the following general formulas (3) to (5), and a partial condensate thereof is used. The method for producing a metal pigment composition according to any one of [1] to [3]. Si(OR 2 , 3 , 4-m , 2 , m , 1 , 1 , , , , )4(1) (In the formula, R 1 is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and all of them may be the same, some of them may be the same, or all of them may be different.) SiX 1 4(2) (In the formula, X 1 is any one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and all of them may be the same, some of them may be the same, or all of them may be different.) R 2 m Si(OR 3 [[ID=​​​​​R is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally include a halogen group. 3 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 2 and R 3 They may be the same or different, R 2 , or R 3 If there are two or more of these, they may be all identical, partially identical, or all different. (1 ≤ m ≤ 3.) R 4 p R 5 q Si(OR 6 ) 4-p-q (4) (In the formula, R 4 R is a group containing a reactive group that can chemically bond with other functional groups, 5 R is a hydrogen atom, or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. 6 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 4 , R 5 , or R 6 If there are two or more of these, they may all be identical, partially identical, or all different. (1 ≤ p ≤ 3, 0 ≤ q ≤ 2, and 1 ≤ p + q ≤ 3.) R 7 r SiX 2 4-r (5) (In the formula, R 7 R is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally include a halogen group. 7 They may be the same or different, R 7 If there are two or more of them, they may all be identical, partially identical, or all different. 1 ≤ r ≤ 3. X 2 X is one of the following: a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. 2 If there are two or more of these, they may all be identical, partially identical, or completely different. [7] A method for producing a metal pigment composition according to any one of [1] to [3], wherein the metal particles are aluminum. [Effects of the Invention]

[0009] According to the present invention, when surface-coating metal particles with a polysiloxane compound, sufficient stirring is possible even when the concentration of metal particles in the slurry is high, and adhesion of metal particles to the reaction vessel walls and stirring blades after the coating process is suppressed. Therefore, a metal pigment composition can be produced with high recovery efficiency while reducing the amount of solvent used (especially the amount of hydrophilic solvent). In other words, an environmentally friendly method for producing metal pigment compositions can be provided. [Modes for carrying out the invention]

[0010] The present invention will now be described in detail, with particular emphasis on its preferred embodiments.

[0011] The present invention relates to the following manufacturing method: (I) A step of dispersing metal particles in a solvent containing at least a hydrophobic solvent to obtain a metal particle dispersion, (II) A step of adding an aqueous solution of salt to the metal particle dispersion to obtain a phase separated into a hydrophilic phase and a hydrophobic solvent phase, (III) A step of coating the surface of the metal particles with a polysiloxane compound while the phase-separated phase is in a phase-separated state, A method for producing a metal pigment composition characterized by containing the following:

[0012] <Metal particles> In this embodiment, it is preferable to use base metal particles such as aluminum, titanium, zinc, iron, magnesium, copper, nickel, and chromium, as well as alloys thereof. Of these, aluminum, titanium, nickel, and chromium are more preferable, and aluminum is particularly preferred. The metal particles preferably have an average particle size (d50) of 2 to 20 μm and an average thickness (t) in the range of 0.001 to 1 μm, and more preferably in the range of 0.01 to 0.8 μm. The metal particles used as pigments are not particularly limited, but flaky particles are preferred. The average particle size (d50) of the metal particles can be measured in the same manner as described below for the average particle size (d50) of the coated particles contained in the aluminum pigment composition in the examples. The average thickness (t) of metal particles can be calculated from the water surface diffusion area and density of the particles. The water surface diffusion area refers to the area occupied by a unit mass of dry composite particles when they are uniformly diffused on the water surface using the leafing phenomenon, covering the surface without gaps. The water surface diffusion area can be measured according to the provisions of JIS K5906:1998. Particularly suitable are aluminum flakes, which are widely used as metallic pigments. Suitable aluminum flakes for use in this invention are those that have the surface properties, particle size, and shape required for metallic pigments, such as surface gloss, whiteness, and brilliance. Aluminum flakes are usually sold commercially in paste form and can be used as is, or the surface fatty acids may be removed beforehand using an organic solvent. Powdered aluminum flakes are generally obtained by grinding atomized aluminum powder and / or aluminum foil using methods commonly used in the pigment industry, such as the dry ball mill method, wet ball mill method, attritor method, and stamp mill method, in the presence of grinding aids and inert solvents to form so-called flakes. After this process, further necessary steps such as sieving (classification), filtration, washing, and mixing are taken to obtain the powder. In another embodiment, so-called aluminum vapor-deposited foil with an average particle size (d50) of 3 to 30 μm and an average thickness (t) of 5 to 50 nm can also be used.

[0013] <Silicon-containing compounds> In this embodiment, the silicon-containing compound used as a raw material for producing the polysiloxane compound is preferably at least one selected from the alkoxysilane shown in general formula (1), the tetrahalosilane shown in general formula (2), the silane coupling agents of general formulas (3) to (5), and their partial condensates.

[0014] Si(OR 1 )4(1) (In the formula, R 1 (This refers to a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, which may be entirely identical, partially identical, or entirely different.)

[0015] SiX 1 4(2) (In the formula, X 1 (These are fluorine atoms, chlorine atoms, bromine atoms, or iodine atoms, and they may all be the same, some may be the same, or all may be different.)

[0016] R 2 m Si(OR 3 ) 4-m (3) (In the formula, R 2 R is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group (any of fluorine, chlorine, bromine, or iodine atoms), 3 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 2 and R 3 They may be the same or different, R 2 , or R 3 If there are two or more of these, they may be all identical, partially identical, or all different. (1 ≤ m ≤ 3.)

[0017] R 4 p R 5 q Si(OR 6 ) 4-p-q (4) (In the formula, R 4R is a group containing a reactive group that can chemically bond with other functional groups, 5 R is a hydrogen atom, or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. 6 R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 4 , R 5 , or R 6 If there are two or more of these, they may all be identical, partially identical, or all different. (1 ≤ p ≤ 3, 0 ≤ q ≤ 2, and 1 ≤ p + q ≤ 3.)

[0018] R 7 r SiX 2 4-r (5) (In the formula, R 7 R is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group (any of fluorine, chlorine, bromine, or iodine atoms), 7 They may be the same or different, R 7 If there are two or more of them, they may all be identical, partially identical, or all different. 1 ≤ r ≤ 3. X 2 X is one of the following: a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. 2 If there are two or more of these, they may all be identical, partially identical, or completely different.

[0019] R in equation (1) 1 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, and octyl, which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, four R 1 They may be entirely identical, partially identical, or entirely different.

[0020] Preferred examples of silicon-containing compounds (organosilicon compounds) of formula (1) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetrabutoxysilane.

[0021] R in equation (3) 2 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc. These may be branched or linear, and may contain halogen groups such as fluorine, chlorine, and bromine, or heteroatoms such as nitrogen and oxygen. Among these, hydrocarbon groups having 1 to 18 carbon atoms are particularly preferred. Also, R 2 If there are two or more of them, they may all be identical, partially identical, or all different. 2 The number of elements in equation (3) is m=1 to 3, i.e., 1 to 3, but m=1 or 2 is more preferable. 3 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, and octyl, which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Furthermore, R 2 or R 3 If there are two or more of them, they may all be identical, partially identical, or completely different.

[0022] Preferred examples of silicon-containing compounds (silane coupling agents) of formula (3) include methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, trimethylmethoxysilane, trimethylethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltributoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltributoxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, dibutyldibutoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, dihexyldimethoxysilane, dihexyldiethoxysilane, octyltrimethoxysilane, octyl Examples include riethoxysilane, dioctyldimethoxysilane, dioctyldiethoxysilane, dioctylethoxybutoxysilane, decyltrimethoxysilane, decyltriethoxysilane, didecyldimethoxysilane, didecyldiethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, dioctadecyldimethoxysilane, dioctadecyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, and 3-chloropropyltributoxysilane.

[0023] R in equation (4) 4 Examples of reactive groups that can chemically bond with other functional groups include vinyl groups, epoxy groups, styryl groups, methacryloxy groups, acryloxy groups, amino groups, ureido groups, mercapto groups, polysulfide groups, and isocyanate groups. Also, R 4 If there are two or more of them, they may all be identical, partially identical, or all different.4 In equation (4), the number of elements is from p=1 to 3, i.e., 1 to 3, but it is more preferable that p=1.

[0024] R in equation (4) 5 Examples of hydrocarbon groups include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, or bromine. Among these, hydrocarbon groups with 1 to 18 carbon atoms are particularly preferred. Also, R 5 If there are two of them, they may be the same or different.

[0025] R in equation (4) 6 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, and octyl, which may be branched or linear. Among these hydrocarbon groups, methyl, ethyl, propyl, and butyl are particularly preferred. Also, R 6 If there are two or more of them, they may all be identical, partially identical, or completely different.

[0026] Preferred examples of silicon-containing compounds (silane coupling agents) of formula (4) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-methyl-3-aminopropyl-trimethoxysilane, N-2-(aminoethyl)-3-aminoethyl Examples include nopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, and 3-isocyanatetopropyltriethoxysilane.

[0027] R in equation (5) 7 Examples of hydrocarbon groups in include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, oleyl, stearyl, cyclohexyl, phenyl, benzyl, naphthyl, etc., which may be branched or linear, and may contain halogen groups such as fluorine, chlorine, or bromine. Among these, hydrocarbon groups having 1 to 12 carbon atoms are particularly preferred. Also, R 7If there are two or more of them, they may all be identical, partially identical, or completely different.

[0028] Preferred examples of silicon-containing compounds (silane coupling agents) of formula (5) include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, octyldimethylchlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, and tetrachlorosilane.

[0029] In the metal pigment composition obtained by this embodiment, it is desirable that the metal particles are coated with a polysiloxane compound produced from the silicon-containing compound. The polysiloxane compound is preferably contained in a total amount of 0.1 to 50 parts by mass, and more preferably 1 to 40 parts by mass, per 100 parts by mass of metal particles, calculated based on the state after hydrolysis and condensation reactions are completed. From the viewpoint of easily achieving both storage stability as a paint, etc., and optical properties such as the color tone of the coating film, it is even more preferable that the polysiloxane compound is contained in an amount of 3 to 40 parts by mass per 100 parts by mass of metal particles.

[0030] The amount of polysiloxane compound produced from the alkoxysilane represented by the above general formula (1) can be estimated by multiplying the mass of the alkoxysilane represented by general formula (1) used in the production of this metal pigment composition by the mass ratio before and after the reaction, assuming that all of the alkoxysilane undergoes hydrolysis and a condensation reaction.

[0031] For example, if tetraethoxysilane (TEOS) is used as the alkoxysilane represented by general formula (1), the amount of polysiloxane compound produced can be estimated using the mass ratios before and after the hydrolysis and condensation reactions described below. Furthermore, the theoretical amount of water required for the reaction can also be determined from this general formula, so by using an excess amount of water compared to the theoretical amount, the reaction can be carried out in a manner that essentially follows stoichiometry. (Hydrolysis) Si(OC2H5)4(molecular weight:208) + 4H2O → Si(OH)4(molecular weight:96) + (C2H5OH)4 (condensation) Si(OH)4(molecular weight:96)+ Si(OH)4(molecular weight:96) → (SiO2)2(molecular weight:60×2) + 4H2O

[0032] Based on the hydrolysis and condensation reactions described above, if all of the tetraethoxysilane undergoes hydrolysis and condensation, the mass ratio is calculated to be 60 / 208 = 0.288 times. Therefore, for example, if 40 parts by mass of TEOS are used for 100 parts by mass of untreated metal pigment particles, the amount of hydrolysates and / or their condensates produced is estimated to be 0.288 times that amount, or 11.5 parts by mass.

[0033] Similarly, the amount of polysiloxane compound produced can be estimated for the tetrahalosilane and silane coupling agents of the general formulas (2) to (5) above.

[0034] Step (I): A step of dispersing metal particles in a solvent containing at least a hydrophobic solvent to obtain a metal particle dispersion. In the method for producing metal pigments according to this embodiment, metal particles are first dispersed in a solvent containing at least a hydrophobic solvent to obtain a metal particle dispersion.

[0035] <Solvent> In this embodiment, the total amount of solvent for dispersing the metal particles is preferably 10 to 1000 parts by mass, more preferably 50 to 800 parts by mass, and even more preferably 80 to 500 parts by mass, per 100 parts by mass of metal particles. These solvents may include hydrophobic and hydrophilic solvents. The mass ratio of the hydrophobic solvent to the hydrophilic solvent (mass of hydrophobic solvent / mass of hydrophilic solvent) is preferably 1 / 1 to 1 / 24, more preferably 1 / 1 to 1 / 18, and even more preferably 1 / 1 to 1 / 15. When the ratio of hydrophobic solvent to hydrophilic solvent is within the above range, phase separation is likely to occur when an aqueous solution of salt is added, and the adhesion suppression effect of the hydrophobic solvent phase produced by phase separation is fully exhibited even when the concentration of metal particles in the slurry is high. Preferred examples of hydrophobic solvents include mineral spirits, solvent naphtha, toluene, hexane, heptane, octane, and their isomers. Hydrophilic solvents are preferably alcohol compounds. Among these, secondary alcohols are more preferred, and examples of secondary alcohols include isopropyl alcohol, 2-butanol, 2-pentanol, 3-pentanol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monobutyl ether. In this embodiment, when the metal particles to be coated are used as raw materials in the form of a paste containing a hydrophobic or hydrophilic solvent, the solvent introduced from the paste is also taken into consideration when calculating the part by mass relative to the metal particles and the ratio of hydrophobic solvent to hydrophilic solvent. For example, if the raw material is 143g of metal paste with 70% solids (non-volatile content) and 30% hydrophobic solvent, then the metal particles amount to 100g, which contains 43g of hydrophobic solvent. If the amount of solvent is set to 300 parts by mass per 100 parts by mass of metal particles, and the hydrophobic solvent / hydrophilic solvent ratio is set to 1 / 6, then the required amount of solvent will be 300g, consisting of 43g of hydrophobic solvent and 257g of hydrophilic solvent. Since the hydrophobic solvent is already contained in the metal paste, only the 257g of hydrophilic solvent needs to be added.

[0036] Step (II): A step in which an aqueous solution of salt is added to the metal particle dispersion to obtain a phase separated into a hydrophilic phase and a hydrophobic solvent phase. Next, an aqueous solution of salt is added to the metal particle dispersion obtained in step (I) to obtain phases separated into a hydrophilic phase and a hydrophobic solvent phase.

[0037] <Salt solution> In this embodiment, the amount of salt added as an aqueous solution is preferably 0.1 to 40 parts by mass, more preferably 1 to 35 parts by mass, and even more preferably 4 to 30 parts by mass, per 100 parts by mass of metal particles. When adding salt, you may use commercially available salts as an aqueous solution, or you may prepare an aqueous solution by separately preparing the acid and base. The acids that make up the salt are preferably those with a pKa of 3 to 5.5. Preferred examples include organic acids and carbonic acid, such as aromatic compounds like benzoic acid and toluic acid, as well as formic acid, acetic acid, propionic acid, acrylic acid, and carbonic acid. By using a salt composed of acids with pKas within the above range, the hydrolysis and condensation reactions of silicon-containing compounds can proceed smoothly without interfering with the effects of the catalyst described later. The bases that make up the salt are preferably hydrophilic bases, and ammonia, methylamine, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, triethanolamine, etc., which have excellent water solubility are preferred. The amount of water used to dissolve the salt is not particularly limited, but it is preferable to use an amount of water with a mass similar to that of the solvent used to disperse the metal particles.

[0038] <Phase separation> In this embodiment, the surface coating treatment of metal particles with a polysiloxane compound (step (III) below) is carried out in a state where the system is in a state of phase separation between a slurry-like hydrophilic phase (hereinafter simply referred to as slurry) consisting of a hydrophilic solvent, salt, water, and metal particles, and a supernatant hydrophobic solvent phase (hereinafter simply referred to as supernatant). If phase separation is occurring, the interface between the slurry and the supernatant can be confirmed when stirring is stopped. By adding a salt that is insoluble or sparingly soluble in a hydrophobic solvent as an aqueous solution from outside the system, a slurry is formed. At the same time, the presence of a hydrophobic solvent phase separated from the slurry prevents prolonged contact between the reaction vessel wall or stirring blades and the slurry, thereby suppressing the adhesion and solidification of the metal pigment composition.

[0039] Step (III): A step in which the phase-separated phase is coated with a polysiloxane compound on the surface of the metal particles while the phase-separated phase is still in place. In this embodiment, the liquid phase obtained in step (II) (the phase-separated phase) is used to coat the surface of the metal particles with a polysiloxane compound obtained by utilizing the hydrolysis and condensation reaction of a silicon-containing compound while the liquid phase is separated. Preferably, step (III) is carried out while stirring.

[0040] <Catalyst> For this hydrolysis and condensation reaction, a basic compound may be used as a catalyst, preferably in an amount of 0.1 mol% to 120 mol%, and more preferably 5 mol% to 100 mol%, relative to the silicon-containing compound. By keeping the catalyst amount below the upper limit of this range, the hydrolysis and condensation reaction of the silicon-containing compound is maintained at an appropriate rate, preventing aggregation between metal particles and a decrease in color tone. Furthermore, by keeping the catalyst amount above the lower limit of this range, the reaction proceeds appropriately, resulting in good storage stability and sufficient dispersibility in water-based paints or inks, thereby achieving a desirable color tone. Examples of basic compounds include nitrogen compounds such as aqueous ammonia, monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, and morpholine.

[0041] <Water> Further water may be added if necessary for hydrolysis and condensation reactions. The amount of water added is not particularly limited, but it is preferably equimolar or greater relative to the silicon-containing compound.

[0042] <Temperature> The coating process can be carried out at a suitable temperature between room temperature (approximately 15-30°C) and 80°C.

[0043] <Surface modification> In the manufacturing method of this embodiment, prior to the hydrolysis and condensation reaction of the silicon-containing compound, surface modification with molybdic acid, a heteropolyanion compound, or a mixed coordination type heteropolyanion compound may be performed. This surface modification step can be carried out at an appropriate temperature between room temperature (about 15 to 30 °C) and 80 °C, for example, in an organic solvent dispersion of metal particles. As the organic solvent here, the same solvents as those exemplified below can be used. The reaction time of this step is not particularly limited, but may be, for example, 5 minutes to 5 hours.

[0044] <Surface modifier> Examples of the heteropolyanion compound used in the surface modification step include H3PMo 12 O 40 ·nH2O (phosphomolybdic acid · n hydrate), H3PW 12 O 40 ·nH2O (phosphotungstic acid · n hydrate), H4SiMo 12 O 40 ·nH2O (silicomolybdic acid · n hydrate), H4SiW 12 O 40 ·nH2O (silicotungstic acid · n hydrate) and other heteropolyacids, and it is preferable to use these (however, n ≥ 0). Examples of the mixed coordination type heteropolyanion compound include H3PW x Mo 12-x O 40 ·nH2O (phosphotungstomolybdic acid · n hydrate), H 3+x PV x Mo 12-x O 40 ·nH2O (phosphovanadomolybdic acid · n hydrate), H4SiW x Mo 12-x O 40 ·nH2O (silicotungstomolybdic acid · n hydrate), H 4+x SiV x Mo 12-x O 40Examples include mixed-coordination heteropoly acids such as nH2O (sinadomolybdic acid n-hydrate) (where 1 ≤ x ≤ 11 and n ≥ 0).

[0045] <Metallic Pigment Composition> After the step of forming metal particles coated with a polysiloxane compound is completed, it is preferable to recover the obtained coated particles by performing known treatments such as washing and solid-liquid separation. For example, it is preferable to wash the obtained slurry with water / organic solvent (preferably a hydrophilic solvent) and then filter it using a filter to remove water and unreacted substances from the slurry containing the coated particles. After that, if necessary, the filtered slurry may be heat-treated at a temperature in the range of, for example, 100 to 500°C.

[0046] The metal pigment composition obtained by the method described above contains metal particles (and surface modifiers, if present) and a polysiloxane compound, and is considered to contain a solvent such as water / organic solvent (preferably a hydrophilic solvent) used in the manufacturing process as a residue of solids (non-volatile matter). In the metal pigment composition obtained by this embodiment, the polysiloxane compound is preferably contained in an amount of 0.1 to 50 parts by mass, and more preferably 1 to 40 parts by mass, per 100 parts by mass of metal particles. From the viewpoint of easily achieving both the storage stability of the metal pigment composition as a paint, etc., and the optical properties such as the color tone of the coating film, it is even more preferable that the polysiloxane compound in the metal pigment composition be contained in an amount of 3 to 40 parts by mass, per 100 parts by mass of metal particles. The metal pigment composition may preferably contain, optionally, a surface modifier such as molybdic acid, a heteropolyanionic compound, or a mixed-coordinate heteropolyanionic compound in an amount of 0.01 to 10 parts by mass per 100 parts by mass of metal particles. The metal pigment composition may contain a solvent, including water / organic solvent (preferably a hydrophilic solvent), as a residue of the above-mentioned components (non-volatile matter), which was used in the manufacturing process. The amount of the solvent containing water / organic solvent may be, for example, 0.5 to 95% by mass of the metal pigment composition. Alternatively, the amount of the solvent containing water / organic solvent may be 1 to 90% by mass, 2 to 80% by mass, or 5 to 70% by mass of the metal pigment composition.

[0047] The metal pigment composition obtained by the manufacturing method of this embodiment can be used in organic solvent-based paints, inks, etc. In this case, by adding the metal pigment composition obtained by the manufacturing method of this embodiment to an aqueous paint or aqueous ink in which resins, which are film-forming components, are dissolved or dispersed in a medium mainly composed of water, a metallic aqueous paint or metallic aqueous ink can be obtained.

[0048] The metal pigment composition obtained by the manufacturing method of this embodiment may be added directly to (water-based) paints or inks when used in paints or inks, but it is preferable to disperse it in a solvent beforehand. Examples of solvents that can be used in this case include water, texanol, diethylene glycol monobutyl ether, and propylene glycol monomethyl ether.

[0049] The content of the metal pigment composition according to this embodiment in the above-mentioned paint or ink is not limited, but is usually 0.1 to 50% by mass, and is particularly preferably 1 to 30% by mass. A content of 0.1% by mass or more allows for a high decorative (metallic) effect to be obtained. Furthermore, a content of 50% by mass or less can prevent the properties of the water-based paint or ink, such as weather resistance, corrosion resistance, and mechanical strength, from being impaired. The solvent content in this case is not particularly limited, but may be 20 to 200% by mass relative to the resin binder content. A solvent content within this range allows the viscosity of the paint or ink to be adjusted to an appropriate range, making handling and film formation easier. Furthermore, optional additives such as antioxidants, light stabilizers, polymerization inhibitors, and surfactants may be added when the metal pigment composition is incorporated into water-based paints or inks.

[0050] Furthermore, the metal pigment composition obtained by the manufacturing method of this embodiment can be kneaded with resins and the like to be used as a water-resistant binder or filler. Examples of resins include acrylic resins, polyester resins, polyether resins, epoxy resins, fluororesins, and rosin resins. Examples of acrylic resins include methacrylate esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate; methacrylate esters with active hydrogen such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; unsaturated amides such as acrylamide, N-methylolacrylamide, and diacetoneacrylamide; and acrylic resins obtained by polymerizing one or a mixture of other polymerizable monomers selected from the above. While emulsion polymerization is the most common polymerization method, it can also be produced using suspension polymerization, dispersion polymerization, or solution polymerization. Emulsion polymerization can also be carried out in a stepwise manner.

[0051] Polyester resins include, for example, a selection of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid, either individually or in mixtures, and, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2,3-butanediol, 1,6-hexanediol, 1,2-hexanediol, and 2,5-hexanediol. Polyester resins obtained by condensation reactions of polyhydric alcohols selected from the group of diols such as diols, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1,2-octanediol, 1,2-decanediol, 2,2,4-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol, triols such as glycerin and trimethylolpropane, and tetraols such as diglycerin, dimethylolpropane, and pentaerythritol, either individually or in mixtures; and polycaprolactones obtained, for example, by ring-opening polymerization of ε-caprolactone to the hydroxyl groups of low molecular weight polyols.

[0052] Polyether resins include polyether polyols obtained by adding one or a mixture of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide to one or a mixture of polyvalent hydroxy compounds using a strong basic catalyst such as hydroxides such as lithium, sodium, and potassium, alkoxides, or alkylamines; polyether polyols obtained by reacting alkylene oxides with polyfunctional compounds such as ethylenediamines; polyether polyols obtained by ring-opening polymerization of cyclic ethers such as tetrahydrofuran; and so-called polymer polyols obtained by polymerizing acrylamide, etc., using these polyethers as a medium. These resins are preferably emulsified, dispersed, or dissolved in water. To emulsify, disperse, or dissolve in water, carboxyl groups, sulfonyl groups, etc., contained in the resins can be neutralized.

[0053] As a neutralizing agent for neutralizing carboxyl groups, sulfonyl groups, etc., one or more selected from ammonia and water-soluble amino compounds such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, and morpholine can be used. Preferred neutralizing agents include tertiary amines such as triethylamine and dimethylethanolamine.

[0054] Preferred resins are acrylic resins and polyester resins. If necessary, resins such as melamine-based curing agents, isocyanate-based curing agents, and urethane dispersions may be used in combination. Furthermore, these resins may be combined with inorganic pigments, organic pigments, extender pigments, silane coupling agents, titanium coupling agents, dispersants, anti-settling agents, leveling agents, thickeners, and defoaming agents commonly added to paints. Surfactants may be added to improve the dispersibility of the resins in the paint. Antioxidants, light stabilizers, and polymerization inhibitors may be added to improve the storage stability of the paint. [Examples]

[0055] The present invention will be described in more detail below with reference to examples and comparative examples of the present invention. The following examples are provided for illustrative purposes only and do not limit the present invention in any way.

[0056] [Example 1] 135g of commercially available aluminum paste (manufactured by Asahi Kasei Corporation, product name "GX-4100" (average particle size d50: 10μm of metallic aluminum particles, non-volatile content 74%)) (containing 100g of metallic aluminum particles and 35g of mineral spirits, a hydrophobic solvent) was dispersed in 245g of isopropyl alcohol (hydrophilic solvent) (step (I)), and then phosphotungstomolybdic acid (H3PW6Mo6O 40 0.5 g of the hydrate of ) was added, and the slurry was stirred for 1 hour while maintaining the slurry temperature at 50°C. Then, 2 g of ammonium benzoate was dissolved in 250 g of water and added (aqueous solution of salt) (step (II)). Furthermore, 42 g of tetraethoxysilane (a raw material for polysiloxane compounds) and 12.1 g of 28% aqueous ammonia (catalyst) were added. At this point, stirring was temporarily stopped 1 minute after adding the aqueous ammonia to confirm that phase separation had occurred. Stirring was immediately resumed and continued for 6 hours (step (III)). After the reaction was complete, the slurry was filtered after cooling to room temperature to obtain an aluminum pigment composition with a non-volatile content of 50%. Here, the mass ratio of the hydrophobic solvent (derived from the raw material aluminum paste) to the hydrophilic solvent (isopropyl alcohol) was 35 / 245, or 1 / 7. The total amount of solvent in step (I) was 280 (=35+245) parts by mass per 100 parts by mass of metal particles. The processing conditions for the examples and comparative examples are shown in Table 1.

[0057] [Example 2] The procedure was carried out in the same manner as in Example 1, except that 0.1 g of 3-aminopropyltrimethoxysilane (a raw material for polysiloxane compounds) was added 6 hours after the addition of ammonia water (i.e., at the end of the reaction), and the mixture was stirred for 2 hours, to obtain an aluminum pigment composition with a non-volatile content of 50%. Here, the ratio of hydrophobic solvent (derived from the raw material aluminum paste) to hydrophilic solvent (isopropyl alcohol) was 35 / 245, or 1 / 7. The total amount of solvent in step (I) was 280 (=35+245) parts by mass per 100 parts by mass of metal particles.

[0058] [Example 3] The procedure was carried out in the same manner as in Example 1, except that 140 g of propylene glycol monomethyl ether was used instead of 245 g of isopropyl alcohol as the hydrophilic solvent, to obtain an aluminum pigment composition with a non-volatile content of 50%. Here, the ratio of hydrophobic solvent (derived from the raw material aluminum paste) to hydrophilic solvent (propylene glycol monomethyl ether) was 35 / 140, or 1 / 4. The total amount of solvent in step (I) was 175 (=35+140) parts by mass per 100 parts by mass of metal particles.

[0059] [Example 4] An aluminum pigment composition with 50% non-volatile content was obtained by following the same procedure as in Example 1, except that the hydrophilic solvent was replaced with 350 g of propylene glycol monomethyl ether instead of 245 g of isopropyl alcohol, and 5 g of ammonium benzoate was added. Here, the ratio of hydrophobic solvent (derived from the raw material aluminum paste) to hydrophilic solvent (propylene glycol monomethyl ether) was 35 / 350, or 1 / 10. The total amount of solvent in step (I) was 385 (=35+350) parts by mass per 100 parts by mass of metal particles.

[0060] [Comparative Example 1] The procedure was carried out in the same manner as in Example 1, except that the hydrophilic solvent was replaced with 1000 g of propylene glycol monomethyl ether instead of 245 g of isopropyl alcohol, and ammonium benzoate was added to 40 g, to obtain an aluminum pigment composition with a non-volatile content of 50%. Here, the ratio of hydrophobic solvent (derived from the raw material aluminum paste) to hydrophilic solvent (propylene glycol monomethyl ether) was 35 / 1000, or 1 / 29, and no phase separation was observed. The total amount of solvent in step (I) was 1035 (=35+1000) parts by mass per 100 parts by mass of metal particles. In other words, Comparative Example 1 had a larger total amount of solvent in step (I) and a larger amount of hydrophilic solvent compared to Example 1 (the mass ratio of hydrophobic solvent to hydrophilic solvent (mass of hydrophobic solvent / mass of hydrophilic solvent) was lower).

[0061] [Comparative Example 2] The procedure was carried out in the same manner as in Example 1, except that an aqueous solution of ammonium benzoate (an aqueous solution of salt) was not added, and an aluminum pigment composition with a non-volatile content of 50% was obtained. In other words, step (II) was not performed. Here, the ratio of hydrophobic solvent (derived from the raw material aluminum paste) to hydrophilic solvent (isopropyl alcohol) was 35 / 245, or 1 / 7, and no phase separation was observed. The total amount of solvent in step (I) was 280 (=35+245) parts by mass per 100 parts by mass of metal particles.

[0062] [Evaluation 1 (Amount of deposits on the reaction vessel walls and stirring blades)] The amount of deposits adhering to the reaction tank walls and stirring blades used in the aqueous treatment was confirmed and evaluated as follows. The evaluation results are shown in Table 2. ◎: Almost no attached substances ○: There is a slight amount of residue. ×: Many attached substances

[0063] [Evaluation 2 (Water Resistance Evaluation)] 20 g (10 g of non-volatile content) of the obtained aluminum pigment composition was placed in a flask, and the cumulative amount of hydrogen gas generated was observed for up to 24 hours in a 60°C constant temperature water bath. The amount of gas generated was evaluated as follows and used as an indicator for the aqueous treatment of the aluminum pigment composition. The evaluation results obtained are shown in Table 2. ○: Less than 5.0 mL... Sufficiently treated with water. ×: 5.0 mL or more... Insufficient aqueous treatment.

[0064] [Table 1]

[0065] [Table 2] [Industrial applicability]

[0066] According to the present invention, a metal pigment composition usable in paint compositions or ink compositions, particularly in aqueous paints or water-based inks, can be provided by an environmentally friendly method that reduces the amount of solvent used (especially the amount of organic solvent) compared to the conventional technology. Therefore, the metal pigment composition of the present invention has high practical value and can be suitably used in a wide range of fields, including the manufacture of paints and inks, as well as in industries such as automobiles, home appliances, and printing.

Claims

1. (I) A step of dispersing metal particles in a solvent containing at least a hydrophobic solvent to obtain a metal particle dispersion, (II) A step of adding an aqueous solution of salt to the metal particle dispersion to obtain a phase separated into a hydrophilic phase and a hydrophobic solvent phase, (III) A step of adding a raw material and catalyst for the polysiloxane compound, and while the phase-separated phase is in a phase-separated state, coating the surface of the metal particles with the polysiloxane compound, A method for producing a metal pigment composition characterized by containing the following:

2. A method for producing a metal pigment composition according to claim 1, wherein the total amount of solvent in step (I) is 10 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of metal particles.

3. A method for producing a metal pigment composition according to claim 2, wherein the solvent in step (I) comprises a hydrophobic solvent and a hydrophilic solvent, and the mass ratio of the hydrophobic solvent to the hydrophilic solvent (mass of hydrophobic solvent / mass of hydrophilic solvent) is 1 / 1 to 1 / 24.

4. A method for producing a metal pigment composition according to any one of claims 1 to 3, wherein the amount of salt added in step (II) is 0.1 to 40 parts by mass per 100 parts by mass of metal particles.

5. A method for producing a metal pigment composition according to any one of claims 1 to 3, wherein the pKa of the acid constituting the salt added in step (II) is 3.0 to 5.

5.

6. A method for producing a metal pigment composition according to any one of claims 1 to 3, wherein in the coating process of step (III) above, a silicon-containing compound which is at least one of the following general formula (1), tetrahalosilane, silane coupling agents of general formulas (3) to (5), and partial condensates thereof is used as a raw material for the polysiloxane compound. Si(OR １ ) ４ (1) (In the formula, R １ (These are hydrogen atoms or hydrocarbon groups having 1 to 8 carbon atoms, and may be entirely identical, partially identical, or entirely different.) SiX １ ４ (2) (In the formula, X １ (These are fluorine atoms, chlorine atoms, bromine atoms, or iodine atoms, and they may all be the same, some may be the same, or all may be different.) R ２ ｍ Si(OR ３ ) ４－ｍ (3) (In the formula, R ２ R is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and may optionally contain a halogen group. ３ R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. ２ and R ３ They may be the same or different, R ２ , or R ３ If there are two or more of these, they may all be identical, partially identical, or completely different. (1 ≤ m ≤ 3.) R ４ ｐ R ５ ｑ Si(OR ６ ) ４－ｐ－ｑ (4) (In the formula, R ４ R is a group containing a reactive group that can chemically bond with other functional groups, ５ R is a hydrogen atom, or a hydrocarbon group having 1 to 30 carbon atoms, which may optionally contain a halogen group. ６ R is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. ４ , R ５ , or R ６ If there are two or more of these, they may all be identical, partially identical, or all different. (1 ≤ p ≤ 3, 0 ≤ q ≤ 2, and 1 ≤ p + q ≤ 3.) R ７ ｒ SiX ２ ４－ｒ (5) (In the formula, R ７ R is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and may optionally contain a halogen group. ７ They may be the same or different, R ７ If there are two or more of them, they may all be identical, partially identical, or all different. 1 ≤ r ≤ 3. X ２ X is one of the following: a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. ２ If there are two or more of these, they may all be identical, partially identical, or completely different.

7. A method for producing a metal pigment composition according to any one of claims 1 to 3, wherein the metal particles are aluminum.

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