Pigment water dispersing agent, method for dispersing pigment in water and aqueous coating composition

Abstract

To provide a pigment water dispersing agent capable of providing an aqueous coating composition having excellent water resistance, weather resistance or the like.SOLUTION: There are provided: a pigment water dispersing agent containing a copolymer obtained by polymerizing (A) at least one reactive unsaturated compound represented by the following general formula (1) and (B) at least one reactive unsaturated compound other than component (A); a method for dispersing a pigment in water; and an aqueous coating composition. (In the formula, R1 represents a hydrocarbon group having 8 to 20 carbon atoms, A1 and A2 each independently represent an alkylene group having 2 to 4 carbon atoms, L is a reactive group in polymerization, p represents a number of 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number of 15 to 50 and n represents a number of 0 to 100.)SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pigment water dispersant, and more particularly to a pigment water dispersant containing a copolymer obtained by polymerizing a specific reactive unsaturated compound, a method for dispersing a pigment in water using the pigment water dispersant, and an aqueous paint containing the pigment water dispersant. [Background technology]

[0002] Paints are used in a wide variety of applications, including buildings, automobiles, railways and other vehicles, ships, structures, electrical machinery, metal products, gardening supplies, furniture, leather, and models. In recent years, due to the influence of environmental issues and other factors, there has been a growing trend to switch from oil-based paints to water-based paints.

[0003] Water-based paints are produced by dispersing water-insoluble pigments in water, and therefore have the disadvantages of insufficient storage stability of the paint due to poor dispersion, and reduced water resistance and weather resistance when a coating film is formed due to the generation of coarse particles.

[0004] Known examples of aqueous pigment dispersions that can reduce the generation of coarse particles and prevent the settling of pigments and the like over time include aqueous pigment dispersions that use a solid or semi-solid kneaded product obtained by kneading a mixture containing at least a resin having an anionic group, a pigment, and a basic compound in a closed kneading device (see, for example, Patent Document 1).

[0005] However, when the previously known methods of dispersing a pigment in water are used, the water resistance and weather resistance of the coating film formed from the pigment dispersion are insufficient.

[0006] Furthermore, in Patent Document 2 and the like, a specific reactive surfactant (reactive unsaturated compound) is proposed, but there is no suggestion as to a method for dispersing a pigment in water using this. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2003-226832 A [Patent Document 2] JP 2006-75808 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a pigment water dispersant for providing a pigment water dispersion capable of providing an aqueous paint having excellent water resistance and weather resistance, and further to provide a method for dispersing a pigment in water. [Means for solving the problem]

[0009] The present inventors conducted extensive research and discovered that a pigment aqueous dispersion prepared by dispersing a pigment in water using a pigment aqueous dispersant containing a copolymer obtained from a specific reactive unsaturated compound having a hydrophilic group and another reactive unsaturated compound can provide an aqueous coating material having excellent performance such as water resistance and weather resistance of the coating film, thereby completing the present invention.

[0010] That is, the present invention provides an aqueous pigment dispersant containing (A) a copolymer obtained by polymerizing at least one reactive unsaturated compound represented by the following general formula (1) and (B) at least one reactive unsaturated compound other than the component (A).

[0011] [ka]

[0012] (In the formula, R 1 represents a hydrocarbon group having 8 to 20 carbon atoms, A 1 and A 2 each independently represents an alkylene group having 2 to 4 carbon atoms, L represents a group represented by the following general formula (2), p represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 15 to 50, and n represents a number from 0 to 100.

[0013] [ka]

[0014] (In the formula, R 2 and R 3 each independently represents a hydrogen atom or a methyl group, and s represents a number from 0 to 12.

[0015] The copolymer contained in the pigment water dispersant of the present invention does not have a uniform repeating unit, but has a wide variety of structures and repeating units. Therefore, the structure of the copolymer contained in the present invention cannot be uniformly expressed by a certain general formula. Therefore, in the present invention, the invention containing such a copolymer is defined by a description that specifies the copolymer by the production method, that is, "obtained by polymerizing component (A) and component (B)."

[0016] The present invention also provides a method for dispersing a pigment in water by using a copolymer obtained by polymerizing (A) at least one reactive unsaturated compound represented by general formula (1) and (B) at least one reactive unsaturated compound other than component (A). Furthermore, the present invention relates to an aqueous paint containing the aqueous pigment dispersant of the present invention, a pigment, and water. Effect of the Invention

[0017] According to the pigment water dispersant of the present invention and the method for dispersing a pigment in water using the pigment water dispersant, it is possible to provide a pigment water dispersion capable of forming a coating film having excellent water resistance and weather resistance. This pigment water dispersion can be suitably used as a water-based paint. [Brief description of the drawings]

[0018] [Figure 1] 1 is a SEM photograph of the surface of a coating film formed by the water-based coating material of Example 3-4. [Diagram 2] 1 is a SEM photograph of the surface of a coating film formed by the water-based coating material of Example 3-5. [Diagram 3] 1 is a SEM photograph of the surface of a coating film formed by the water-based paint of Comparative Example 3-3. [Figure 4] 1 is a SEM photograph of the surface of a coating film formed by the water-based coating material of Comparative Example 3-4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] <Water dispersant for pigments> The pigment water dispersant of the present invention will be described below.

[0020] The pigment water dispersant of the present invention contains a copolymer obtained by polymerizing component (A), which is at least one reactive unsaturated compound represented by the following general formula (1), and component (B), which is at least one reactive unsaturated compound selected from the group consisting of compounds other than component (A).

[0021] [ka]

[0022] (In the formula, R 1 represents a hydrocarbon group having 8 to 20 carbon atoms, A 1 and A 2 each independently represents an alkylene group having 2 to 4 carbon atoms, L represents a group represented by the following general formula (2), p represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 15 to 50, and n represents a number from 0 to 100.

[0023] [ka]

[0024] (In the formula, R 2 and R 3 each independently represents a hydrogen atom or a methyl group, and s represents a number from 0 to 12.

[0025] In general formula (1), R 1Examples of the hydrocarbon group having 8 to 20 carbon atoms represented by the formula (I) include an alkyl group having 8 to 20 carbon atoms, an alkenyl group having 8 to 20 carbon atoms, and an aryl group having 8 to 20 carbon atoms.

[0026] Examples of the alkyl group having 8 to 20 carbon atoms include linear or branched octyl groups such as a 2-ethylhexyl group, secondary octyl groups, linear or branched nonyl groups such as a secondary nonyl group, linear or branched decyl groups such as a secondary decyl group, linear or branched undecyl groups such as a secondary undecyl group, linear or branched dodecyl groups such as a 2-butyloctyl group, secondary dodecyl groups, linear or branched dodecyl groups such as a secondary tridecyl group, etc. branched tridecyl groups such as those mentioned above, linear or 2-butyldecyl groups, 2-hexyloctyl groups, secondary tetradecyl groups and the like branched tetradecyl groups, linear or 2-hexyldecyl groups, secondary hexadecyl groups and the like branched hexadecyl groups, linear or 2-octyldecyl groups, 2-hexyldodecyl groups, monomethyl branched-isostearyl groups and the like branched stearyl groups, linear or branched eicosyl groups and the like.

[0027] Examples of the alkenyl group having 8 to 20 carbon atoms include an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tetradecenyl group, and an oleyl group.

[0028] Examples of the aryl group having 8 to 20 carbon atoms include a xylyl group, a cumenyl group, a styryl group, a trityl group, an ethylphenyl group, a propylphenyl group, a butylphenyl group, a pentylphenyl group, a hexylphenyl group, a heptylphenyl group, an octylphenyl group, a nonylphenyl group, a decylphenyl group, an undecylphenyl group, a dodecylphenyl group, a tridecylphenyl group, and a tetradecylphenyl group.

[0029] Among these hydrocarbon groups, an alkyl group having 8 to 20 carbon atoms or an aryl group having 8 to 20 carbon atoms is preferred. Of the alkyl groups having 8 to 20 carbon atoms, from the viewpoint of excellent dispersibility improving effect, an alkyl group having 8 to 15 carbon atoms is preferred, an alkyl group having 10 to 14 carbon atoms is more preferred, a branched chain alkyl group having 10 to 14 carbon atoms is even more preferred, and a branched chain alkyl group having 11 to 13 carbon atoms is most preferred. Furthermore, from the viewpoint of excellent dispersibility improving effect, among the aryl groups having 8 to 20 carbon atoms, alkylphenyl groups having 13 to 16 carbon atoms are preferred, octylphenyl groups and nonylphenyl groups are more preferred, and nonylphenyl groups are most preferred.

[0030] A in general formula (1) 1 and A 2 Examples of the alkylene group represented by the formula (I) include, independently, ethylene, propylene, isopropylene, butylene, isobutylene, secondary butylene, etc. The polymerization form of the added alkylene oxide, etc. is not limited, and may be a homopolymer of one type of alkylene oxide, a random copolymer, block copolymer, or random / block copolymer of two or more types of alkylene oxides, etc.

[0031] A 1 O and A 2 Even when O is a single group or two or more groups, the oxyethylene group (A 1 O) n Or (A 2 O) m It is preferable that the α-amino acid is present in the 1 O) n Or (A 2 O) m If the proportion of oxyethylene groups in the (A) is less than 50 mol %, the stability of the polymer emulsion formed may decrease, so the proportion is preferably 50 to 100 mol %, more preferably 60 to 100 mol %, even more preferably 80 to 100 mol %, and most preferably 100 mol %. 1 O) n n in (A) is 0 to 100, preferably 0 to 50, more preferably 0 to 20, and most preferably 0. 2 O) mThe value of m is from 15 to 50, and preferably from 20 to 40.

[0032] In the general formula (1), p represents 1 to 10, but depending on the production method, a mixture of different p's may be obtained. In the case of a mixture, p represents an average value. p is preferably a number from 1 to 8, more preferably a number from 1 to 5, even more preferably a number from 1 to 3, and most preferably 1.

[0033] In addition, in the general formula (1), L is a group represented by the general formula (2), which is a reactive group during polymerization. In the general formula (2), s is a number from 0 to 12, preferably a number from 1 to 8, more preferably a number from 1 to 5, further preferably a number from 1 to 3, and most preferably 1. In addition, R 2 and R 3 each independently represents a hydrogen atom or a methyl group. Thus, examples of the reactive group represented by general formula (2) include alkenyl groups such as vinyl, 1-propenyl, allyl, methallyl, 2-butenyl, 3-butenyl, 4-pentenyl, 3-methyl-3-butenyl, 5-hexenyl, 8-nonenyl, and 10-dodecenyl. Among these, the allyl group is most preferred from the viewpoint of reactivity with other monomers.

[0034] In the general formula (1), X is a hydrogen atom or an ionic hydrophilic group, and the ionic hydrophilic group may be an anionic hydrophilic group or a cationic hydrophilic group.

[0035] When the ionic hydrophilic group represented by X in the general formula (1) is an anionic hydrophilic group, -SO3M, -R 4 -SO3M, -R 5 -COOM, -PO3M2, -PO3MH or -CO-R 6 -COOM (wherein M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom (however, since an alkaline earth metal atom is usually divalent, 1 / 2 mole of M corresponds to the atom), or an ammonium salt; R 4 and R 5 represents an alkylene group having 1 to 6 carbon atoms; R 6represents a hydrocarbon group having 1 to 12 carbon atoms.

[0036] In the formula representing an anionic hydrophilic group, examples of the alkali metal atom represented by M include lithium, sodium, potassium, etc., and examples of the alkaline earth metal atom include magnesium, calcium, etc. Examples of the ammonium salt represented by M include -NH4, alkylamines such as monomethylamine and dipropylamine, and alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine.

[0037] R 4 , R 5 represents an alkylene group such as methylene, ethylene, propylene, butylene, pentene, pentamethylene, hexamethylene, etc. Among these, from the viewpoint of emulsifiability, alkylene groups having 1 to 4 carbon atoms such as methylene, ethylene, propylene, and butylene are preferred.

[0038] R 6 is a residue obtained by removing two carboxyl groups from a dibasic acid. Examples of dibasic acids include saturated aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, and tetradecanedioic acid, saturated alicyclic dicarboxylic acids such as cyclopentanedicarboxylic acid, hexahydrophthalic acid, and methylhexahydrophthalic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, tolylenedicarboxylic acid, and xylylenedicarboxylic acid, unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid, and unsaturated alicyclic dicarboxylic acids such as tetrahydrophthalic acid, methyltetrahydrophthalic acid, nadic acid (endomethylenetetrahydrophthalic acid), methylnadic acid, methylbutenyltetrahydrophthalic acid, and methylpentenyltetrahydrophthalic acid.

[0039] Among the anionic hydrophilic groups, groups represented by -SO3M, -PO3M2 or -PO3MH are preferred, with -SO3M being preferred. Furthermore, M is preferably an alkali metal atom or an ammonium salt, with -NH4 being more preferred because the coating film formed from the copolymer described below has excellent water resistance.

[0040] When the ionic hydrophilic group represented by X in the general formula (1) is a cationic hydrophilic group, for example, -R 7 -NR 8 R 9 R 10 -Y or -Z-NR 8 R 9 R 10 In the formula representing the cationic hydrophilic group, Y represents a halogen atom or a methylsulfate group (-CH3SO4). Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. 7 represents an alkylene group having 1 to 6 carbon atoms. Examples of the alkylene group having 1 to 6 carbon atoms include R 4 Examples of the alkylene groups include those mentioned in the above.

[0041] R 8 , R 9 and R 10 each independently represents an alkyl group having 1 to 4 carbon atoms, an alkanol group having 2 to 4 carbon atoms, or a benzyl group. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a secondary butyl group, and a tertiary butyl group. Examples of the alkanol group having 2 to 4 carbon atoms include a 2-hydroxyethyl group, a 2-hydroxypropyl group, and a 2-hydroxybutyl group. Z is a group represented by -CH2CH(OH)CH2- or -CH(CH2OH)CH2-.

[0042] The content of component (A) is preferably 0.1 to 5 mass%, more preferably 0.5 to 3 mass%, based on the total mass of component (A) and component (B) described below. If it is less than 0.1 mass%, a polymer emulsion may not be obtained when components (A) and (B) are emulsion-polymerized, whereas if it exceeds 5 mass%, the water resistance of the coating film formed using the copolymer obtained from components (A) and (B) may decrease.

[0043] The method for producing the component (A) of the present invention is not particularly limited, but for example, the compound in which X corresponds to a hydrogen atom in the general formula (1) can be synthesized, and then an ionic hydrophilic group can be introduced. The compound in which X corresponds to a hydrogen atom in the general formula (1) can be produced, for example, by adding an alkylene oxide (e.g., ethylene oxide, propylene oxide, butylene oxide, 1,4-butylene oxide), tetrahydrofuran, or the like to a reaction product of a glycidyl ether having a reactive group represented by the general formula (2) and an alcohol or an alkoxylate, or a reaction product of a glycidyl ether of an alcohol and an alcohol having a reactive group represented by the general formula (2) by a known method. In addition, a catalyst can be used for the ring-opening reaction of the glycidyl ether (epoxy) as necessary. The catalyst that can be used is not particularly limited as long as it is used in the ring-opening reaction of epoxy, and examples thereof include tertiary amines, quaternary ammonium salts, boron trifluoride or its ether complex salts, aluminum chloride, barium oxide, sodium hydroxide, potassium hydroxide, and the like.

[0044] In the formula representing an ionic hydrophilic group, when sulfate esterification is performed to introduce an anionic hydrophilic group represented by -SO3M, for example, sulfamic acid, sulfuric acid, sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, and alkali metal salts and ammonium salts thereof can be used as an anionic hydrophilizing agent. The reaction conditions for sulfate esterification are not particularly limited, but the reaction temperature is usually room temperature to 150°C, the pressure is normal pressure to about 0.5 MPa, and the reaction time is about 1 to 10 hours. If necessary, a catalyst such as urea may be used. In addition, when M is a hydrogen atom, neutralization may be performed with an alkali such as sodium hydroxide or potassium hydroxide, ammonia, an alkylamine, or an alkanolamine such as monoethanolamine or diethanolamine.

[0045] In the formula representing an ionic hydrophilic group, -R 4 When an anionic hydrophilic group represented by -SO3M is introduced, for example, propane sultone, butane sultone, etc. can be used as an anionic hydrophilizing agent. The reaction conditions for sulfonation are not particularly limited, but usually the temperature is room temperature to 100°C, the pressure is normal pressure to about 0.5 MPa, and the reaction time is about 1 to 10 hours. If necessary, a solvent or an alkali such as sodium hydroxide or potassium hydroxide may be used as a catalyst.

[0046] In the formula representing an ionic hydrophilic group, -R 5 In the case of carboxylation to introduce an anionic hydrophilic group represented by -COOM, the anionic hydrophilizing agent is, for example, chloroacetic acid (R 5 corresponds to a methylene group), chloropropionic acid (R 5 (corresponding to an ethylene group) and their alkali metal salts and ammonium salts can be used. The reaction conditions for carboxylation are not particularly limited, but usually the temperature is room temperature to 150°C, the pressure is normal pressure to about 0.5 MPa, and the reaction time is about 1 to 10 hours. When M is a hydrogen atom, neutralization may be performed with an alkali such as sodium hydroxide or potassium hydroxide, ammonia, an alkylamine, or an alkanolamine such as monoethanolamine or diethanolamine.

[0047] In the case of phosphorylation to introduce an anionic hydrophilic group represented by -PO3M2 or -PO3MH in the formula representing an ionic hydrophilic group, for example, diphosphorus pentoxide, polyphosphoric acid, orthophosphoric acid, phosphorus oxychloride, etc. can be used as an anionic hydrophilizing agent. In the case of phosphorylation, a mixture of a monoester type compound and a diester type compound is obtained, but these may be separated, or if separation is difficult, the mixture may be used as it is. The reaction conditions for phosphorylation are not particularly limited, but the temperature is usually room temperature to 150°C, the pressure is normal pressure, and the reaction time is about 1 to 10 hours.

[0048] In the formula representing an ionic hydrophilic group, -CO-R 6 When dibasic oxidation is performed to introduce an anionic hydrophilic group represented by -COOM, the above-mentioned dibasic acids or their anhydrides can be used as the anionic hydrophilizing agent. For example, maleic acid (R 6 corresponds to the CH=CH group), phthalic acid (R 6 corresponds to a phenyl group), and their alkali metal salts, ammonium salts, and anhydrides. The reaction conditions for dibasic oxidation are not particularly limited, but usually the temperature is room temperature to 150°C, the pressure is normal pressure, and the reaction time is about 1 to 10 hours. If necessary, an alkali such as sodium hydroxide or potassium hydroxide may be used as a catalyst. When M is a hydrogen atom, neutralization may be performed with an alkali such as sodium hydroxide or potassium hydroxide, ammonia, an alkylamine, or an alkanolamine such as monoethanolamine or diethanolamine.

[0049] Also, X is -R 7 -NR 8 R 9 R 10When introducing a cationic hydrophilic group represented by Y, first, the hydroxyl group of the compound represented by general formula (1) in which X is a hydrogen atom is halogenated with a halogenating agent such as thionyl chloride, thionyl bromide, or phosgene, and then a tertiary amine compound is reacted to introduce the group. Alternatively, instead of a tertiary amine compound, a secondary amine compound may be reacted, followed by reaction with an alkyl halide, dimethyl sulfate, or the like. The reaction conditions for halogenating a hydroxyl group are not particularly limited, but are usually room temperature to 100°C, pressure is normal pressure to about 0.5 MPa, and reaction temperature is about 1 to 10 hours. The reaction conditions for aminating are also not particularly limited, but are usually room temperature to 150°C, pressure is normal pressure to about 0.5 MPa, and reaction temperature is about 1 to 10 hours. If necessary, an alkali such as sodium hydroxide or potassium hydroxide may be used as a catalyst.

[0050] X is -Z-NR 8 R 9 R 10 When introducing a cationic hydrophilic group represented by ·Y, it can be introduced by first reacting an epihalohydrin such as epichlorohydrin or epibromohydrin with a compound represented by general formula (1) in which X is a hydrogen atom, and then further reacting with a tertiary amine compound. Alternatively, a secondary amine compound may be reacted instead of a tertiary amine compound, and then an alkyl halide, dimethyl sulfate, or the like may be reacted. The reaction conditions when reacting with epihalohydrin are not particularly limited, but are usually room temperature to 100°C, pressure is normal pressure to about 0.3 MPa, and reaction temperature is about 1 to 10 hours. If necessary, an alkali catalyst such as sodium hydroxide or potassium hydroxide, or an acid catalyst such as sulfuric acid, phosphoric acid, iron chloride, boron fluoride, or tin chloride may be used. The reaction conditions when aminating are also not particularly limited, but are usually room temperature to 150°C, pressure is normal pressure to about 0.5 MPa, and reaction temperature is about 1 to 10 hours. If necessary, an alkali such as sodium hydroxide or potassium hydroxide may be used as a catalyst.

[0051] The component (B) used in the present invention is at least one selected from reactive unsaturated compounds other than the component (A). Examples of the reactive unsaturated compound include unsaturated carboxylic acids or esters thereof, as well as other reactive unsaturated compounds. Examples of the unsaturated carboxylic acid include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid, and citraconic acid; 2-carboxylethyl acrylate, 2-carboxylethyl methacrylate, and the like.

[0052] Examples of the unsaturated carboxylate include alkyl acrylates and alkyl methacrylates having an alkyl group with 1 to 12 carbon atoms. If the alkyl group has more than 12 carbon atoms, the coating film formed using the copolymer described below becomes hard and may crack or cause poor film formation. The alkyl group has 1 to 12 carbon atoms, and from the above-mentioned viewpoints, it preferably has 1 to 10 carbon atoms, more preferably 1 to 9 carbon atoms, and even more preferably 1 to 8 carbon atoms. That is, examples of unsaturated carboxylate esters include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, methyl methacrylate (methyl methacrylate), ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, cyclohexyl methacrylate (cyclohexyl methacrylate), and the like.

[0053] Examples of other reactive unsaturated compounds in component (B) include styrene, dichlorostyrene, chloromethylstyrene, methylstyrene, acrylamide, acrylonitrile, butadiene, and maleic nitrile.

[0054] In addition, as another reactive unsaturated compound in component (B), a polyfunctional monomer may be further blended as an internal crosslinking agent for the purpose of improving the physical properties of the coating film formed using the copolymer described below. Examples of the polyfunctional monomer include (poly)ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, methylenebisacrylamide, and divinylbenzene. The reactive unsaturated compounds of the component (B) may be used alone or in combination of two or more kinds.

[0055] The content of the above component (B) is preferably 95 to 99.9 mass %, and more preferably 97 to 99.5 mass %, based on the total mass of the components (A) and (B). The content of the polyfunctional monomer used as the internal crosslinking agent is preferably 0 to 2 mass %, more preferably 0 to 1.5 mass %, based on the total mass of the components (A) and (B).

[0056] The pigment water dispersant of the present invention contains a copolymer obtained by polymerizing the above-mentioned components (A) and (B). The method of producing a copolymer by polymerizing the components (A) and (B) can be carried out by adding water, a polymerization initiator, and further, if necessary, an emulsifier, etc. to a mixture of the components (A) and (B) (hereinafter also referred to as a "monomer mixture"), and polymerizing the mixture.

[0057] As an emulsifier that can be used when polymerizing the copolymer, a known surfactant can be used. For example, a general anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, a polymeric surfactant, a reactive surfactant, etc. can be used. These emulsifiers may be used alone or in combination of two or more kinds.

[0058] Examples of anionic surfactants include alkyl sulfates such as sodium dodecyl sulfate, potassium dodecyl sulfate, and ammonium dodecyl sulfate; sodium dodecyl polyglycol ether sulfate; sodium sulforicinolate; alkyl sulfonates such as alkali metal salts of sulfonated paraffin and ammonium salts of sulfonated paraffin; fatty acid salts such as sodium laurate, triethanolamine oleate, and triethanolamine abietate; alkylaryl sulfonates such as sodium benzenesulfonate and alkali metal sulfates of alkylphenol hydroxyethylene; high alkyl naphthalene sulfonates; naphthalene sulfonate-formaldehyde condensates; dialkyl sulfosuccinates; polyoxyethylene alkyl sulfate salts; polyoxyethylene alkyl aryl sulfate salts; polyoxyethylene ether phosphates; polyoxyethylene alkyl ether acetates; N-acyl amino acid salts; and N-acyl methyl taurine salts.

[0059] Examples of nonionic surfactants include fatty acid partial esters of polyhydric alcohols such as sorbitan monolaurate and sorbitan monooleate; polyoxyethylene glycol fatty acid esters; polyglycerin fatty acid esters; ethylene oxide and / or propylene oxide adducts of alcohols having 1 to 18 carbon atoms; ethylene oxide and / or propylene oxide adducts of alkylphenols; and ethylene oxide and / or propylene oxide adducts of alkylene glycols and / or alkylenediamines.

[0060] Examples of the alcohol having 1 to 18 carbon atoms constituting the nonionic surfactant include methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, tertiary butanol, amyl alcohol, isoamyl alcohol, tertiary amyl alcohol, hexanol, octanol, decane alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. Examples of the alkylphenol include phenol, methylphenol, 2,4-di-tertiary butylphenol, 3,5-di-tertiary butylphenol, 4-(1,1,3,3-tetramethylbutyl)phenol, 4-isooctylphenol, 4-nonylphenol, 4-tertiary octylphenol, and 4-dodecyl phenol. Examples of the alkylene glycol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and 1,6-hexanediol. Examples of the alkylene diamine include alkylene glycol in which the alcoholic hydroxyl group is replaced with an amino group. The ethylene oxide adduct and the propylene oxide adduct may be either a random adduct or a block adduct.

[0061] Examples of the cationic surfactant include alkylpyridinium salts such as pyridinium salts such as alkylpyridinium bromide; imidazolinium salts such as imidazolinium laurate; and quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, didecyldimethylammonium chloride, laurylbenzyldimethylammonium chloride, didecyldimethylammonium chloride, and alkyl halide quaternary ammonium salts.

[0062] Examples of amphoteric surfactants include betaine-type amphoteric surfactants such as coconut oil fatty acid amidopropyl dimethyl acetate betaine, lauryl dimethyl amino acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxymethyl imidazolinium betaine, lauryl hydroxysulfobetaine, lauroyl amidoethyl hydroxyethyl carboxymethyl betaine, and metal salts of hydroxypropyl phosphate; amino acid-type amphoteric surfactants such as metal salts of β-lauryl aminopropionic acid; sulfate ester-type amphoteric surfactants; and sulfonic acid-type amphoteric surfactants.

[0063] Among the above emulsifiers, from the viewpoint of improving the dispersion stability, such as the polymerization stability and mechanical stability, of the emulsion of the copolymer obtained by polymerization (hereinafter also referred to as the polymer emulsion) and improving the dispersion stability of the aqueous paint, anionic surfactants or nonionic surfactants are preferred, and anionic surfactants are more preferred.

[0064] The emulsifier is not essential because the reactive unsaturated compound represented by formula (1) used in the present invention also acts as an emulsifier, and is optional. When used, the amount of the emulsifier added is preferably 0.5 to 12 parts by mass, more preferably 0.8 to 8 parts by mass, and even more preferably 1 to 6 parts by mass, relative to 100 parts by mass of the monomer mixture. If the amount of the emulsifier added is 0.5 parts by mass or more, emulsion polymerization can be stably carried out. On the other hand, if the amount is 12 parts by mass or less, it is possible to prevent adverse effects such as a decrease in substrate adhesion and water resistance due to the remaining unreacted emulsifier. The emulsifier may be added directly to a liquid obtained by adding water to the monomer mixture, or may be added in advance to a polymerization vessel, or these may be used in combination.

[0065] The polymerization initiator that can be used in producing the copolymer is not particularly limited, and may be either water-soluble or oil-soluble. Specific examples of the polymerization initiator include azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile), 2.2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 2,2'-azobis(2-amidinopropane) dihydrochloride, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, and peroxides such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide. Redox initiators such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peracid and sodium ascorbate may also be used. These polymerization initiators may be used alone or in combination of two or more kinds. Among these, persulfates or redox initiators are preferred from the viewpoint of excellent polymerization stability.

[0066] The amount of the polymerization initiator added is preferably 0.01 to 6 parts by mass, more preferably 0.03 to 4 parts by mass, and even more preferably 0.1 to 2 parts by mass, relative to 100 parts by mass of the monomer mixture, from the viewpoint of accelerating the polymerization rate.

[0067] The polymerization initiator may be added in advance to a polymerization vessel, may be added immediately before the start of polymerization, or may be added in several portions after the start of polymerization. Also, the polymerization initiator may be added in advance to the monomer mixture, or may be added to the emulsion after preparing an emulsion of the monomer mixture. When adding the polymerization initiator, the polymerization initiator may be added after being dissolved in a separate solvent or monomer mixture, or the dissolved polymerization initiator may be further emulsified and then added.

[0068] The water used in emulsion polymerization for producing the copolymer is preferably ion-exchanged water. The amount of water added is preferably 30 to 400 parts by mass, more preferably 35 to 200 parts by mass, and even more preferably 40 to 150 parts by mass, relative to 100 parts by weight of the monomer mixture. When the amount of water added is 30 parts by mass or more, the viscosity of the obtained polymer emulsion can be set in an appropriate range, and the polymerization stability of the obtained polymer emulsion is also good. On the other hand, when the amount of water added is 400 parts by mass or less, the solid content concentration of the obtained polymer emulsion can be set in an appropriate range.

[0069] The method for producing the copolymer contained in the pigment water dispersant of the present invention is not particularly limited, and examples thereof include emulsion polymerization including mini-emulsion polymerization, suspension polymerization, etc. Among these polymerization methods, emulsion polymerization is preferably used because it is easy to obtain a homogeneous polymer emulsion.

[0070] When emulsion polymerization is carried out, a chain transfer agent and a pH buffer may be further added. Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and decanethiol. The pH buffer is not particularly limited as long as it is a compound having a pH buffering effect, and examples thereof include sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, ammonium acetate, sodium formate, and ammonium formate.

[0071] When an emulsion of the copolymer of components (A) and (B) is produced by emulsion polymerization, the copolymer can be synthesized by adding a polymerization initiator to a monomer mixture in the presence of an emulsifier and allowing emulsion polymerization to proceed.

[0072] The procedure for carrying out the emulsion polymerization may be any of the following methods (1) to (3). From the viewpoint of ease of controlling the polymerization temperature, method (2) or (3) is preferred, and method (3) is more preferred. (1) The entire amount of the monomer mixture, emulsifier, water, etc. is placed in a reaction vessel, the temperature is raised, and the polymerization initiator dissolved in water is added dropwise or in portions to carry out polymerization. (2) Water, an emulsifier, and a portion of the monomer mixture are placed in a reaction vessel, the temperature is raised, and then a polymerization initiator dissolved in water is added dropwise or in portions to proceed with the polymerization reaction. The remaining monomer mixture is then added dropwise or in portions to continue the polymerization. (3) A polymerization initiator dissolved in water is placed in a reaction vessel and the vessel is heated. Then, an emulsion consisting of a monomer mixture, an emulsifier, and water is added dropwise or in portions to polymerize the mixture.

[0073] The polymerization conditions in the polymerization method are not particularly limited, but the following conditions are preferable. In the method (1), the temperature range is preferably 40 to 100° C., and the polymerization reaction is preferably carried out for about 1 to 8 hours after the start of heating. In the method (2), it is preferable to polymerize 1 to 50% by mass of the monomer mixture at 40 to 90°C for 0.1 to 4 hours, and then add the remaining monomer mixture dropwise or in portions over about 1 to 5 hours, and then age the mixture at the same temperature for about 1 to 3 hours. In the method (3), it is preferable to heat the polymerization initiator dissolved in water to preferably 40 to 90° C., and add the emulsion consisting of the monomer mixture, emulsifier, and water dropwise or in portions over about 2 to 5 hours, and then preferably age the mixture at the same temperature for 1 to 5 hours.

[0074] In the above polymerization method, from the viewpoint of polymerization stability, it is preferable to dissolve the emulsifier (or a part of the emulsifier) ​​in the monomer mixture, or to make the monomer mixture into an O / W type emulsion in advance.

[0075] The polymer emulsion obtained by the above polymerization method may be further adjusted to pH 5 to 9, preferably pH 6 to 8.5, by adding aqueous ammonia, various water-soluble amines, or an aqueous alkali solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution. For the polymer emulsion, it is preferable to add the above-mentioned aqueous alkaline solution to adjust the pH to within the above-mentioned range. The aqueous alkali solution can be added during or after the completion of the polymerization. From the viewpoints of polymerization stability and viscosity stability over time of the resulting polymer emulsion, it is preferred to add a part or all of the aqueous alkali solution at the maturation stage during polymerization after cooling to room temperature.

[0076] The solid content concentration in the polymer emulsion obtained by emulsion polymerization is preferably from 10 to 80% by mass, more preferably from 25 to 70% by mass. The solid content concentration here is expressed as a value obtained by dividing the amount of residue left after drying the polymer emulsion at 105°C for 2 hours by the amount of the polymer emulsion.

[0077] The viscosity of the polymer emulsion at 25° C. is preferably from 30 to 400 mPa·s, and more preferably from 50 to 300 mPa·s. The viscosity referred to here is a value measured at 25°C using a rotational viscometer.

[0078] The average particle size of the polymer emulsion is preferably from 100 to 900 nm, more preferably from 150 to 600 nm. The average particle size referred to here is measured by dynamic light scattering.

[0079] The polymer emulsion obtained by the above-mentioned production method is used as the pigment water dispersant of the present invention. The pigment water dispersant of the present invention may not be in the form of a polymer emulsion as long as it contains the copolymer of the above-mentioned (A) component and (B) component. However, the polymer emulsion form is preferable from the viewpoint of imparting coating film performance such as water resistance and weather resistance, since it has excellent function as a binder for the pigment in the water-based paint. As the pigment water dispersant, the above-mentioned polymer emulsion may be used as it is, or a polymer-type dispersant such as anionic, cationic or nonionic acrylic copolymer or block copolymer, which is generally contained in pigment water dispersants, may be added as an additive.

[0080] <How to disperse pigments in water> Next, a method for dispersing the pigment of the present invention in water (hereinafter also referred to as a pigment water dispersion method) will be described. The method for dispersing the pigment of the present invention in water is a method for dispersing the pigment in water using a copolymer obtained by polymerizing component (A) and component (B), and is a method for dispersing the pigment in water using the pigment water dispersant of the present invention. In particular, it is preferred that the copolymer obtained from components (A) and (B) is used in the form of a polymer emulsion as described above.

[0081] The amount of the copolymer added is 1 part by mass to 1000 parts by mass, and preferably 10 parts by mass to 500 parts by mass, relative to 100 parts by mass of the pigment. If the amount added is less than 1 part by mass, the pigment may not be sufficiently dispersed in water, and if more than 1000 parts by mass is used, the pigment may not be able to fully exert its effect.

[0082] The pigment to be dispersed in water by the pigment water dispersant of the present invention is not particularly limited, and known organic or inorganic pigments can be used. Examples of pigments include inorganic pigments such as iron oxide, carbon black produced by known methods such as contact method, furnace method, and thermal method, titanium oxide, and the like, azo pigments (including insoluble azo pigments such as monoazo pigments, disazo pigments, and pyrazolone pigments, benzimidazolone pigments, beta naphthol pigments, naphthol AS pigments, and condensed azo pigments), polycyclic pigments (such as quinacridone pigments, perylene pigments, perinone pigments, anthraquinone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, isoindoline pigments, quinophthalone pigments, and diketopyrrolopyrrole pigments), phthalocyanine pigments, dye chelates (such as basic dye chelates and acid dye chelates), nitro pigments, nitroso pigments, and organic pigments such as aniline black can be used. Pigments can be used alone or in combination of two or more. Pigment derivatives may also be used as the pigment, and the pigment derivatives may be pigments into which specific functional groups, which will be described later, have been introduced. Examples of the functional groups include a carboxy group, a sulfo group, an amino group, a nitro group, an acid amide group, a carbonyl group, a carbamoyl group, a phthalimide group, and a sulfonyl group.

[0083] The above pigments will be explained below by giving specific product names for each color. As black pigments, carbon black such as #2300, #980, #960, #900, #52, #45L, #45, #40, #33, MA100, MA8, and MA7 manufactured by Mitsubishi Chemical Corporation, the Regal series and Monarch series manufactured by Cabot Corporation, the Color Black series, Printex series, Special Black series, and NIPEX series manufactured by Orion Engineered Carbons Co., Ltd., and SK Water-based Color (Black) manufactured by SK Chemical Co., Ltd. can be used.

[0084] As the yellow pigment, CI Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185, and the like can be used.

[0085] As magenta pigments, CI Pigment Red 5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 146, 149, 150, 168, 176, 184, 185, 202, 209, 213, 269, 282, and the like can be used.

[0086] As the cyan pigment, CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 60, 63, 66, etc. can be used.

[0087] As the orange pigment, CI Pigment Orange 5, 13, 16, 17, 34, 36, 43, 51, 64, 71, etc. can be used.

[0088] As the violet pigment, CI Pigment Violet 1, 3, 5:1, 16, 19, 23, 38, etc. can be used.

[0089] As the green pigment, CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, 50, 58, etc. can be used.

[0090] Examples of pigments exhibiting colors other than those mentioned above include SK Water-Based Color (Oka) and SK Water-Based Color (Akasabi), both manufactured by SK Chemical Co., Ltd.

[0091] Among the pigments exemplified above, for example, inorganic pigments such as titanium oxide, silica, alumina, calcium carbonate, talc, kaolin, zinc oxide, barium sulfate, carbon black, iron oxide, aluminum dihydrogen tripolyphosphate, and mica are preferred, and titanium oxide is particularly preferred from the viewpoint of the weather resistance and hiding power of the coating film when the pigment is dispersed in water and used as an aqueous coating material.

[0092] The pigment may be in the form of a dry powder or a wet cake, and may be used alone or in the form of a mixture or solid solution containing two or more kinds.

[0093] The pigment to be used preferably has a primary particle size of 1.0 μm or less, and more preferably 0.1 μm to 0.3 μm. By using a pigment having a primary particle size within the above range, sedimentation of the pigment over time can be more effectively suppressed. The primary particle size in the pigment water dispersion can be measured, for example, using a transmission electron microscope (TEM).

[0094] The water used in the pigment aqueous dispersion method of the present invention may be pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water. In addition, it is preferable to use water that has been sterilized by ultraviolet irradiation or addition of hydrogen peroxide, for example, because this can prevent the growth of mold or bacteria when the aqueous pigment dispersion or an aqueous paint using the same is stored for a long period of time.

[0095] In addition, when dispersing the pigment in water, an aqueous solvent may be used together with water. Examples of the aqueous solvent include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; diols such as butanediol, pentanediol, and hexanediol; glycol esters such as propylene glycol laurate; diethylene glycol ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl, and carbitol; propylene glycol ether, dipropylene glycol ether, and dipropylene glycol ether. Examples of the aqueous solvent include glycol ethers such as pyrene glycol ether and cellosolve including triethylene glycol ether; alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and pentyl alcohol; lactones such as sulfolane, esters, ketones, and γ-butyrolactone; lactams such as 2-pyrrolidinone and N-(2-hydroxyethyl)pyrrolidone; glycerin and its polyalkylene oxide adducts; and various other solvents known as aqueous solvents, such as dipropylene glycol n-butyl ether (DPNB). These aqueous solvents can be used alone or in combination of two or more.

[0096] Examples of kneading machines that can be used in the pigment water dispersion method of the present invention include paint shakers, ball mills, attritors, basket mills, sand mills, sand grinders, dyno mills, dispermats, SC mills, spike mills, and agitator mills, and those that do not use media include ultrasonic homogenizers, high-pressure homogenizers, nanomizers, dissolvers, dispersers, and high-speed impeller dispersers.

[0097] When dispersing a pigment in water, it is preferable to first add a small amount of water and a polymer-type dispersant such as an anionic, cationic or nonionic acrylic copolymer or block copolymer to the pigment, stir the mixture with a disperser or the like to form a paste, and then disperse the mixture in water containing the pigment water dispersant of the present invention.

[0098] <Water-based paint> A pigment water dispersion obtained by dispersing a pigment in water using the pigment water dispersant of the present invention can be suitably used as a water-based paint. That is, the water-based paint of the present invention contains the pigment water dispersant of the present invention, a pigment, and water. The pigment in the aqueous paint of the present invention is the same as the pigment described in the method for dispersing the pigment in water, and the content of the pigment in the aqueous paint is preferably 10 to 50 mass %, more preferably 15 to 40 mass %.

[0099] The content of the pigment water dispersant in the water-based paint of the present invention is preferably 40 to 75% by mass, and more preferably 50 to 70% by mass.

[0100] The water content in the water-based coating material of the present invention is preferably 2 to 30% by mass, and more preferably 3 to 25% by mass, where the water content does not include the amount of water in the pigment water dispersant.

[0101] The water-based coating material of the present invention may contain an aqueous solvent together with water, and when it does contain an aqueous solvent, the content of the aqueous solvent is preferably 0.1 to 5 mass %, more preferably 0.5 to 3 mass %.

[0102] In the water-based paint of the present invention, any component can be blended, such as a thickener, an antifoaming agent, a preservative, a neutralizing agent, a dispersant, a film-forming aid, an antifreeze agent, an antioxidant, a hardening regulator, a metal deactivator, an ozone deterioration inhibitor, a phosphorus-based peroxide decomposer, a lubricant, an antifoaming agent, a foaming agent, an anti-termite agent, an anti-fungal agent, a catalyst, a wetting agent, a flow control agent, a smoothing agent, etc.

[0103] Examples of thickening agents include cellulose-based thickening agents such as hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), and methyl cellulose (MC), and nonionic surfactants (ADEKANOL UH-420, manufactured by ADEKA CORPORATION).

[0104] Examples of the defoaming agent include polydimethyl silicone, dimethyl silicone oil, trifluoropropylmethyl silicone, colloidal silica, polyalkyl acrylate, polyalkyl methacrylate, alcohol ethoxy / propoxylate, fatty acid ethoxy / propoxylate, sorbitan partial fatty acid ester, a blend of a nonionic surfactant and silicone (ADEKANATE B-1016, manufactured by ADEKA CORPORATION), etc. The blending amount of these defoaming agents is preferably 0.001 to 1.0% by mass, more preferably 0.001 to 0.5% by mass, based on the water-based paint.

[0105] Any type of preservative can be used as long as it is a known preservative, and examples thereof include paraoxybenzoic acid esters, sodium dehydroacetate, hinokitiol, milt protein extract, benzoic acid or its salts, sorbic acid or its salts, propionic acid or its salts, polylysine, nisin, and isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one, 1,2-benzoisothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one. These may be used alone or in combination of two or more. Among these, benzoic acid or its salts, sorbic acid or its salts, and propionic acid or its salts are preferred from the viewpoint of safety.

[0106] Examples of the neutralizing agent include aqueous ammonia, triethylamine, dimethylaminoethanol, and diethylaminoethanol.

[0107] Examples of dispersants include polymer dispersants such as sodium polycarboxylate (COL W-193 manufactured by ADEKA CORPORATION, etc.), anionic, cationic, and nonionic acrylic copolymers, and block copolymers (BYK-190 manufactured by BYK-Chemi).

[0108] The film-forming aid may be a hydrophobic solvent such as Texanol.

[0109] The water-based paint of the present invention can be suitably used, for example, in architecture (interior, exterior, roof, floor), structures (civil engineering structures, steel pipes and tubes), industry (metal products, plastics, PCM), and automobiles (middle and top coats, repairs), etc. EXAMPLES

[0110] The present invention will now be described in more detail with reference to examples.

[0111] <Preparation of pigment water dispersion (polymer emulsion)> Example 1-1 As monomers, 30 g of styrene, 35 g of methyl methacrylate, 33 g of 2-ethylhexyl acrylate, and 2 g of acrylic acid were mixed to prepare a mixed monomer liquid. A mixed monomer emulsion was prepared by mixing 85.5 g of the mixed monomer liquid, 2.18 g of a reactive unsaturated compound represented by the following formula (a), and 51.35 g of ion-exchanged water in a homomixer. Separately, 54.4 g of ion-exchanged water was placed in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet tube, and a dropping funnel, and while stirring, 4.5 g of the remaining mixed monomer liquid and 0.07 g of a reactive unsaturated compound represented by the following formula (a) were added to the reaction vessel, and the temperature was raised to 75 ° C. After that, after stabilizing at 75 ° C, 0.2 g of ammonium persulfate was dissolved in 1.8 g of ion-exchanged water as a polymerization initiator and added to start polymerization. Next, 15 minutes after the addition of the polymerization initiator, 139.03 g of the mixed monomer emulsion was dropped and polymerized over 3 hours. Furthermore, after continuing maturing for 2 hours, it was cooled and the pH was adjusted to 8 with ammonia water to obtain polymer emulsion 1-1 to be used in the evaluation experiment of the present invention.

[0112] [ka]

[0113] [Example 1-2] A polymer emulsion 1-2 was obtained in the same manner as in Example 1-1, except that the reactive unsaturated compound represented by formula (a) in Example 1-1 was changed to a compound represented by the following formula (b).

[0114] [ka]

[0115] [Examples 1-3] A polymer emulsion 1-3 was obtained in the same manner as in Example 1-1, except that the reactive unsaturated compound represented by formula (a) in Example 1-1 was changed to a compound represented by the following formula (c).

[0116] [ka]

[0117] Comparative Example 1-1 A polymer emulsion 1-4 was obtained in the same manner as in Example 1-1, except that the reactive unsaturated compound represented by formula (a) in Example 1-1 was changed to a compound represented by the following formula (x).

[0118] [ka]

[0119] Comparative Example 1-2 Polymer emulsion 1-5 was obtained in the same manner as in Example 1-1, except that the reactive unsaturated compound represented by formula (a) in Example 1-1 was changed to a compound represented by the following formula (y).

[0120] [ka]

[0121] Example 2-1 As monomers, 30 g of cyclohexyl methacrylate, 37 g of methacrylic acid, 31 g of 2-ethylhexyl acrylate, and 2 g of acrylic acid were mixed to prepare a mixed monomer liquid. 100 g of the mixed monomer liquid, 0.11 g of decanethiol as a chain transfer agent, 1.87 g of the reactive unsaturated compound represented by the above formula (a), and 30.8 g of ion-exchanged water were mixed with shaking to prepare an emulsion for dropping. Separately, 55.22 g of ion-exchanged water was placed in a reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet tube and dropping funnel, and the temperature was raised to 80°C while stirring. When the temperature was stabilized at 80°C, 0.22 g of ammonium persulfate was dissolved in 1.98 g of ion-exchanged water as a polymerization initiator and added to start polymerization. Then, 15 minutes after the addition of the polymerization initiator, 132.78 g of the mixed monomer emulsion was dropped over 3 hours to polymerize. After further aging for 1 hour, the mixture was cooled and the pH was adjusted to 7-8 with ammonia water to obtain polymer emulsion 2-1 to be used in the evaluation experiment of the present invention.

[0122] Example 2-2 Polymer emulsion 2-2 was obtained in the same manner as in Example 2-1, except that the reactive unsaturated compound represented by formula (a) in Example 2-1 was changed to the compound represented by formula (b) above.

[0123] Example 2-3 Polymer emulsion 2-3 was obtained in the same manner as in Example 2-1, except that the reactive unsaturated compound represented by formula (a) in Example 2-1 was changed to the compound represented by formula (c) above.

[0124] Comparative Example 2-1 Polymer emulsion 2-4 was obtained in the same manner as in Example 2-1, except that the reactive unsaturated compound represented by formula (a) in Example 2-1 was changed to the compound represented by formula (x) above.

[0125] Comparative Example 2-2 Polymer emulsion 2-5 was obtained in the same manner as in Example 2-1, except that the reactive unsaturated compound represented by formula (a) in Example 2-1 was changed to the compound represented by formula (y) above.

[0126] The polymer emulsions 1-1 to 1-3 of Examples 1-1 to 1-3 and the polymer emulsions 2-1 to 2-3 of Examples 2-1 to 2-3 correspond to the aqueous pigment dispersants of the present invention.

[0127] [Examples 3-1 to 3-6, Comparative Examples 3-1 to 3-4] <Preparation of water-based paint> Water-based paints containing the polymer emulsions 1-1 to 1-5 and 2-1 to 2-5 of the above Examples and Comparative Examples were produced by the following method.

[0128] In order to manufacture a water-based paint containing titanium dioxide as a pigment, a titanium dioxide paste was manufactured according to the formula shown in Table 1. In a container kept at 25°C, the ingredients were added in the order listed from the top of the table while stirring with a Disper-type disperser, and mixed to manufacture a titanium dioxide paste (TiO2 paste).

[0129] [Table 1]

[0130] HEC: Hydroxyethyl cellulose ADEKACOL W-193: ADEKA Corporation; polycarboxylic acid type anionic surfactant Ti-Pure R-706: Chemours; titanium dioxide ADEKANATE B-1016: ADEKA Corporation; Defoamer (nonionic surfactant + silicone blend) Preservatives: Isothiazolinone preservatives

[0131] The titanium dioxide paste and polymer emulsions 1-1 to 1-5 and 2-1 to 2-5 of the examples and comparative examples were mixed in the formulations shown in Table 2 using a Disper-type disperser while maintaining the temperature at 25°C to produce the water-based paints of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4.

[0132] [Table 2]

[0133] 3% HEC * 96.67 g of water, 3 g of hydroxyethyl cellulose (HEC), 0.3 g of ammonia water, and 0.03 g of isothiazolinone preservative were mixed in a disperser and kept at 25°C to produce 3% HEC. ADEKANOL UH-420: ADEKA Corporation; non-ionic surfactant Preservatives: Isothiazolinone preservatives

[0134] [Evaluation results] The following evaluation tests were carried out using the water-based coating materials of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4. The results are shown in Table 3.

[0135] [60° Gloss] Gloss The aqueous coating materials of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 were each applied to a substrate (material: stainless steel) using a 150 μm Baker-type film applicator, and the coating film formed after drying at 25° C. for 48 hours was used as an evaluation film. The 60° gloss of each coating film was measured using a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd.; VG7000). The closer the 60° gloss value is to 100%, the more excellent the gloss is, and a value of 90% or more is particularly preferable.

[0136] [Concealment rate] The aqueous paints of the Examples and Comparative Examples were applied to a hiding rate test paper using a 150 μm Baker film applicator, and dried at 25° C. for 48 hours, after which the coating film formed was used as the evaluation film. B ) and the white part (Y W ) was measured using a color difference meter, and the hiding ratio (Y) was calculated using the following formula. The closer the hiding ratio value is to 100%, the more excellent the water resistance of the coating film can be evaluated.

[0137]

number

[0138] 〔viscosity〕 The viscosity of each of the water-based coating materials of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 was measured using a Brookfield viscometer (B8H type, 10 rpm). The viscosity values ​​shown in Table 3 are 10 rpm viscosity values ​​(unit: mPa s).

[0139] [Water resistance] Color difference To the water-based paints of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4, 3 g of color pigment paste (SK water-based color (black) / SK water-based color (Oka) / SK water-based color (Akasabi) mixed at a weight ratio of 1 / 1 / 1) was added per 100 g of water-based paint, and the water-based paint was colored by stirring with a disperser. The colored paint was applied to a SUS plate with a film thickness of 150 μm using a 150 μm Baker-type film applicator, and dried at 25 ° C. for 48 hours. Thereafter, the SUS plate on which the coating film was formed was immersed in water at 50 ° C. for 24 hours. The color difference (ΔE) was measured for the coating surface of the SUS plate before and after immersion in water using a spectrophotometer (CM-3700d; manufactured by Konica Minolta). ΔE is a value calculated by the following formula, and it can be evaluated that the smaller the ΔE value, the better the water resistance of the coating film.

[0140]

number

[0141] [Water resistance] Gloss To 100 g of the water-based paint of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4, 3 g of color pigment paste (SK water-based color (black) / SK water-based color (Oak) / SK water-based color (Red rust) mixed at a weight ratio of 1 / 1 / 1) was added, and the water-based paint was colored by stirring with a disperser. The colored paint was applied to a SUS plate in a film thickness of 150 μm and dried at 25° C. for 48 hours. Thereafter, the SUS plate on which the coating film was formed was immersed in water at 50° C. for 24 hours. The 60° gloss of the coated surface of the SUS plate before and after immersion in water was measured using a VG7000 manufactured by Nippon Denshoku Industries Co., Ltd., and the 60° gloss retention was calculated using the following formula. The closer the 60° gloss retention value is to 100%, the more excellent the water resistance of the coating film can be evaluated.

[0142]

number

[0143] [Weather resistance] Gloss The aqueous coating materials of Examples 3-1 to 3-4 and Comparative Example were applied to a SUS plate in a film thickness of 150 μm and dried for 48 hours at 25° C. Using a tester QUV / spray (manufactured by Q-Lab), a weather resistance test was performed in an 8-hour cycle (4 hours of UV irradiation at 60° C. + 4 hours of condensation at 50° C. (no UV irradiation)) and the 60° gloss of the coated surface of the SUS plate after 400 hours was measured using a VG7000 manufactured by Hondenshoku Kogyo Co., Ltd., and the 60° gloss retention was evaluated using the following formula. The closer the 60° gloss retention value is to 100%, the more excellent the weather resistance of the coating film can be evaluated.

[0144]

number

[0145] [Table 3]

[0146] [SEM coating surface analysis] The water-based paints of Examples 3-4 and 5 and Comparative Examples 3-4 and 5 were applied to the surface of a SUS plate in a film thickness of 150 μm using a 150 μm Baker-type film applicator, and dried for 48 hours at 25° C. The surface of the resulting coating film was observed using a Schottky scanning electron microscope (SEM) (SU5000, manufactured by Hitachi High-Tech Corporation) (accelerating voltage: 3 kV, vacuum degree: 100 Pa, magnification: ×5000). The results are shown in Figures 1 to 4. In Figures 1 to 4, the areas shown in red in the photographs are 1.28 μm 2 The yellow area is 0.96 to 1.28 μm. 2 The yellow-green region is 0.64 to 0.96 μm 2 The light blue area is 0.32 to 0.64 μm 2 , the area shown in blue is 0.32 μm 2 In the photograph, the areas shown in red or yellow are considered to be areas where titanium oxide is aggregated.

[0147] Compared with the SEM photographs of the coating film surface formed by the water-based paint of Example 3-4 (FIG. 1) and the SEM photographs of the coating film surface formed by the water-based paint of Example 3-5 (FIG. 2), the SEM photographs of the coating film surface formed by the water-based paint of Comparative Example 3-3 (FIG. 3) and the SEM photographs of the coating film surface formed by the water-based paint of Comparative Example 3-4 (FIG. 4) show many yellow areas indicating the aggregation of titanium oxide, and it was confirmed that the aggregation of titanium oxide was particularly abundant in FIG. 3. Therefore, it was confirmed that the water-based paints of Examples 3-4 and 3-5 of the present application have better dispersibility of titanium oxide when coating films are formed.

[0148] Furthermore, as shown in Table 3, it was confirmed that the water-based paints of Examples 3-1 to 3-6, in which the pigment was dispersed using the aqueous pigment dispersant of the present invention, were capable of forming coating films having excellent water resistance and weather resistance, as compared with the water-based paints of Comparative Examples 3-1 to 3-4. [Industrial Applicability]

[0149] The pigment water dispersion of the present invention and the method for dispersing a pigment in water using the pigment water dispersant are suitable for use in applications such as water-based paints because of their characteristics.

Claims

1. A pigment water dispersant containing a copolymer obtained by polymerizing (A) at least one reactive unsaturated compound represented by the following general formula (1) and (B) at least one reactive unsaturated compound other than the component (A). 【Chemistry 1】 (In the formula, R １ represents a hydrocarbon group having 8 to 20 carbon atoms; A １ and A ２ each independently represents an alkylene group having 2 to 4 carbon atoms, L represents a group represented by the following general formula (2), p represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 15 to 50, and n represents a number from 0 to 100. 【Chemistry 2】 (In the formula, R ２ and R ３ each independently represents a hydrogen atom or a methyl group, and s represents a number from 0 to 12.

2. 2. The pigment water dispersant according to claim 1, wherein the reactive unsaturated compound (B) is at least one member selected from the group consisting of acrylic acid, methacrylic acid, an acrylic acid ester, a methacrylic acid ester, and styrene.

3. 3. The pigment water dispersant according to claim 1, wherein the content of the component (A) is 0.1 to 5 mass % based on the total mass of the components (A) and (B).

4. The pigment water dispersant according to any one of claims 1 to 3, wherein the copolymer is in the form of a polymer emulsion.

5. The pigment water dispersant according to any one of claims 1 to 4, which is used for dispersing an inorganic pigment in water.

6. A method for dispersing a pigment in water using a copolymer obtained by polymerizing (A) at least one reactive unsaturated compound represented by the following general formula (1) and (B) at least one reactive unsaturated compound other than the component (A). 【Chemistry 3】 (In the formula, R １ represents a hydrocarbon group having 8 to 20 carbon atoms; A １ and A ２ each independently represents an alkylene group having 2 to 4 carbon atoms, L represents a group represented by the following general formula (2), p represents a number from 1 to 10, X represents a hydrogen atom or an ionic hydrophilic group, m represents a number from 15 to 50, and n represents a number from 0 to 100. 【Chemistry 4】 (In the formula, R ２ and R ３ each independently represents a hydrogen atom or a methyl group, and s represents a number from 0 to 12.

7. 5. An aqueous paint comprising the pigment water dispersant according to claim 1, a pigment, and water.

8. 8. The water-based paint according to claim 7, wherein the pigment is an inorganic pigment.

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