Dispersing agent, dispersion and ink compositions, and methods for producing same

Abstract

The present invention provides: a dispersing agent characterized by including a copolymer which is (A) a copolymer based on styrene-ethyleneoxy-group-containing (meth)acrylic acid and having a weight-average molecular weight of 1,000-50,000 and has (a1) a styrene content of 1-40 mass%, and by having a surfactant content less than 0.1 mass%; dispersion and ink compositions; and methods for producing the dispersing agent, the dispersion and the ink compositions. Even when added in a small amount, the present invention can disperse dispersing dyes and pigments and can also sufficiently exhibit wetting properties and re-dispersing properties.

Description

Dispersant, dispersion and ink composition, and methods for producing the same

[0001] The present invention relates to a dispersant used to disperse disperse dyes and pigments, a dispersion and an ink composition, and methods for producing these.

[0002] Disperse dyes and pigments have traditionally been used as colorants in inks. When using disperse dyes or pigments in inks, the finely divided disperse dyes or pigments must be dispersed in water. However, because disperse dyes and pigments are insoluble in water, it is important to keep the disperse dyes and pigments in a dispersed state and keep them stable for a long period of time.

[0003] Furthermore, inks containing water-insoluble colorants such as disperse dyes and pigments have the drawback that when they lose their moisture and dry out due to some factor, the dispersion state of the pigment breaks down, causing the pigment to aggregate. Once aggregated in this way, the disperse dyes and pigments in the ink cannot be returned to a dispersed state even by adding a liquid medium such as water (poor redispersibility), and there is a strong demand for an improvement in this regard.

[0004] Nonionic surfactants, anionic surfactants, polymer surfactants, etc. have been proposed as dispersants for inks. For example, Patent Documents 1 and 2 disclose that nonionic surfactants containing an acetylene group are useful as pigment dispersants. However, although nonionic surfactants containing an acetylene group are excellent in ink penetration and foam suppression, they have inferior dispersing ability compared to other dispersants, requiring longer dispersion times, and no redispersion effect can be expected.

[0005] As a method for facilitating redispersion of pigments, for example, Patent Document 3 proposes a method in which the surface of pigment particles is coated with a silane coupling agent or a specific dispersant to suppress direct contact between pigment particles and strong aggregation and adhesion.

[0006] Furthermore, Patent Documents 4 and 5 disclose that pigment dispersions using acrylic polymers enhance the redispersibility of inks, but the processes involved are complicated, such as the need to crosslink the polymer in the pigment aqueous dispersion and the need to carry out living radical polymerization, etc. Therefore, there is a need for the development of dispersants that can be expected to more easily achieve redispersion effects.

[0007] Furthermore, Patent Document 6 discloses a dispersion resin containing a hydrophobic monomer, an acrylic monomer, and a hydrophilic vinyl monomer having a sulfonic acid group, but because the proportion of the hydrophobic monomer is high, the dispersion effect may not be achieved in aqueous inks.

[0008] Patent Document 7 discloses that an inkjet ink using a styrene-(meth)acrylic acid copolymer in combination with a specific acetylene glycol compound has high-quality and stable recording performance, and is capable of increasing the print density on the surface of a fabric while maintaining the storage stability of the ink, but does not specify redispersibility after drying.

[0009] The present inventors have also previously filed a patent application for an invention relating to a dispersant that combines a styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer with an acetylene-based surfactant (Japanese Patent Application No. 2022-155738). While this dispersant can exhibit redispersibility, this effect is only achieved by using the two components in combination, so there was room for further improvement in the styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer.

[0010] JP 2000-290578 A JP 2002-020673 A WO 2013 / 008691 A JP 2019-210389 A JP 2019-014879 A JP 2022-052994 A WO 2014 / 129323

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dispersant that can disperse disperse dyes and pigments even in a small amount and that can exhibit wettability, a dispersion that can exhibit redispersibility, an ink composition using the same, and methods for producing the same.

[0012] As a result of extensive research conducted by the present inventors to achieve the above object, they have found that when a specific styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer is used as a dispersant, the addition of a small amount thereof exhibits dispersibility and wettability, is excellent in microparticulating disperse dyes and pigments, and further exhibits redispersibility, which has led to the completion of the present invention.

[0013] Accordingly, the present invention provides the following dispersant, dispersion, and ink composition, as well as methods for producing them. 1. A dispersant characterized by containing (A) a styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer having a weight-average molecular weight of 1,000 to 50,000, wherein (a1) the copolymer contains 1 to 40% by mass of styrene, and the content of a surfactant is less than 0.1% by mass. 2. The dispersant according to above 1, wherein the component (A) is a polymer of the following (a1) to (a3): (a1) styrene: 1 to 40% by mass (a2) ethyleneoxy group-containing (meth)acrylic acid ester monomer: 1 to 59% by mass (a3) ​​monomer other than (a1) to (a2): 1 to 98% by mass. 3. The dispersant according to above 2, wherein the monomer of component (a3) ​​contains a radically polymerizable monomer containing at least one functional group. 4. The dispersant according to the above 1 or 2, wherein the component (A) is a neutralized product with a basic compound having an octanol / water partition coefficient of -5.0 or more and 0 or less. 5. The dispersant according to the above 1 or 2, which does not contain an acetylene surfactant. 6. The dispersant according to the above 1 or 2, which is for dispersing a disperse dye or pigment in an aqueous solvent. 7. A dispersion comprising a dispersant, a disperse dye and / or pigment, and an aqueous solvent, wherein the dispersant is the dispersant according to the above 1 or 2. 8. An ink composition comprising the dispersion according to the above 7. 9. A method for producing the dispersant according to the above 1 or 2, which comprises a step of neutralizing the component (A) with a basic compound having an octanol / water partition coefficient of -5.0 or more and 0 or less. 10. A method for producing a dispersion, which comprises a step of mixing and dispersing the dispersant according to the above 1 or 2, a disperse dye and / or pigment, and an aqueous solvent. 11. A method for producing an ink composition, comprising the following steps (a) and (b): (a) a step of mixing and dispersing the dispersant described in 1 or 2 above, a disperse dye and / or a pigment, and an aqueous solvent to obtain a dispersion; and (b) a step of mixing the dispersion with at least one substance selected from the group consisting of water, a water-soluble organic solvent, a resin, an ultraviolet absorber, an antioxidant, a pH adjuster, a preservative, and a viscosity adjuster.

[0014] The dispersant of the present invention can disperse disperse dyes and pigments with a small amount added, regardless of the type of disperse dye or pigment. Furthermore, dispersions and ink compositions using this dispersant exhibit wettability and dispersion stability, and can also exhibit redispersibility.

[0015] The dispersant of the present invention contains (A) a styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer having a weight average molecular weight of 1,000 to 50,000. Component (A) is preferably a neutralized product with a basic compound having an octanol / water partition coefficient of −5.0 or more and 0 or less.

[0016] The styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer of component (A) having a weight average molecular weight of 1,000 to 50,000 is preferably a polymer of: (a1) styrene: 1 to 40 mass % (a2) ethyleneoxy group-containing (meth)acrylic acid ester monomer: 1 to 59 mass % (a3) ​​monomer other than (a1) and (a2): 1 to 98 mass %. Component (A) may be a random copolymer or a block copolymer.

[0017] The content of styrene as the component (a1) is 1 to 40% by mass, preferably 10 to 30% by mass, based on 100% by mass of the monomers of the components (a1) to (a3). By setting this content within the range of 1 to 40% by mass, the effect of redispersibility can be obtained in the dispersion.

[0018] The ethyleneoxy group-containing (meth)acrylic acid ester monomer, which is the component (a2), preferably has an added mole number of ethyleneoxy groups of 1 to 100 moles, more preferably 5 to 90 moles, and even more preferably 10 to 90 moles.

[0019] The weight average molecular weight of the ethyleneoxy group-containing (meth)acrylic acid ester monomer, component (a2), is preferably 100 to 5,000.

[0020] Specific examples of the component (a2) include acrylic acid ester monomers modified with polyethylene glycol. Specific examples include polyethylene glycol mono(meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, polyethylene glycol-modified 2-isocyanatoethyl (meth)acrylate, and polyethylene glycol-propylene glycol-mono(meth)acrylate. Polyethylene glycol mono(meth)acrylate is particularly preferred.

[0021] The polyethylene glycol mono(meth)acrylate is represented by the following formula: (In the formula, R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and p represents a positive number from 1 to 100.)

[0022] Commercially available products of the component (a2) include, for example, Blenmer "PME-400", "PME-1000", "PME-4000", "PE-200", "PE-350", "AE-200", "AE-400", and "AME-400" manufactured by NOF Corporation; Light Ester "130MA" and "041MA", Light Acrylate "MTG-A" and "130A" manufactured by Kyoeisha Chemical Co., Ltd.; Fancryl "FA-400M (100)" manufactured by Showa Denko Materials Inc.; NK Ester "AM-90G", "AM-130G", "AM-230G", "M-90G", "M-130G", "M-230G", and "M-450G" manufactured by Shin-Nakamura Chemical Co., Ltd.; and VISIOMER "MPEG 750MA W", "MPEG 1005 MA W", and "MPEG 2005 MA W" and "MPEG 5005 MA W".

[0023] The content of the ethyleneoxy group-containing (meth)acrylic acid ester monomer of the component (a2) is 1 to 59% by mass, and preferably 5 to 55% by mass, relative to 100% by mass of the monomers (a1) to (a3). By keeping the content of the component (a2) within the range of 1 to 59% by mass, the effect of dispersing disperse dyes and pigments can be obtained when the component (a2) is used as a dispersant.

[0024] The monomers other than (a1) and (a2) that constitute component (a3) ​​above are not particularly limited, but examples include (meth)acrylic acid alkyl ester monomers and / or radical polymerizable monomers containing functional groups such as carboxy groups, amide groups, hydroxy groups, epoxy groups, and sulfonic acid groups. These can be used alone or in combination of two or more types, but it is preferable to contain at least one radical polymerizable monomer containing a functional group such as a carboxy group, amide group, hydroxy group, epoxy group, and sulfonic acid group. Particularly preferred are (meth)acrylic acid alkyl ester monomers and / or carboxy group-containing radical polymerizable monomers and hydroxy group-containing radical polymerizable monomers.

[0025] The (meth)acrylic acid ester monomer is not particularly limited and may be one having a linear or branched structure, one having an alicyclic group, or one having an aromatic ring group, but does not include the ethyleneoxy group-containing (meth)acrylic acid alkyl ester monomer that is the above-mentioned component (a2).

[0026] Examples of the (meth)acrylic acid alkyl ester monomer having a linear or branched structure include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate.

[0027] Examples of the (meth)acrylic acid ester monomer having an alicyclic group include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0028] Examples of the (meth)acrylic acid ester monomer having an aromatic ring group include benzyl (meth)acrylate and phenoxyethyl (meth)acrylate.

[0029] Examples of the carboxy group-containing radically polymerizable monomer include methacrylic acid, acrylic acid, carboxyethyl (meth)acrylate, fumaric acid, itaconic acid, maleic acid, crotonic acid, vinylbenzoic acid, maleic acid monobutyl ester, itaconic acid monomethyl ester, and itaconic acid butyl ester.

[0030] Examples of the amide group-containing radical polymerizable monomer include N-methoxymethylacrylamide, N-ethoxymethylacrylamide, and N-butoxymethylacrylamide.

[0031] Examples of the hydroxy group-containing radically polymerizable monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1-methyl-4-hydroxybutyl (meth)acrylate, and 1-methyl-4-hydroxypentyl (meth)acrylate.

[0032] Examples of the epoxy group-containing radical polymerizable monomer include glycidyl (meth)acrylate and methallyl glycidyl ether.

[0033] Examples of the sulfonic acid group-containing radically polymerizable monomer include sodium p-styrenesulfonate, lithium p-styrenesulfonate, N-t-butylacrylamidosulfonic acid, sodium 2-sulfoethyl methacrylate, polycyclic phenyl ether methacrylate sulfate, sodium N-sulfonate polyoxyalkylene methacrylate, and ammonium polyoxyalkylene alkenyl ether sulfonate.

[0034] Examples of commercially available sulfonic acid group-containing radically polymerizable monomers include Spinomer "NaSS" (sodium p-styrenesulfonate) and "LiSS" (lithium p-styrenesulfonate) manufactured by Tosoh Finechem Corporation, "ATBS" (N-t-butylacrylamidosulfonic acid) manufactured by Toagosei Co., Ltd., Antox "MS-2N-D" (sodium 2-sulfoethyl methacrylate) and "MS-60" (polycyclic phenyl ether methacrylate sulfate) manufactured by Nippon Nyukazai Co., Ltd., Eleminol "JS-20" and "RS-3000" (N-sulfonic acid sodium polyoxyalkylene methacrylate) manufactured by Sanyo Chemical Industry Co., Ltd., and Latemul "PD-104" and "PD-105" (ammonium polyoxyalkylene alkenyl ether sulfonate) manufactured by Kao Corporation.

[0035] The content of the monomers other than the components (a1) and (a2) is 1 to 98% by mass, and preferably 10 to 80% by mass, relative to 100% by mass of the monomers (a1) to (a3). If this content is less than 1% by mass, it becomes difficult to make the acrylic resin water-soluble, and if it exceeds 98% by mass, the effect of imparting redispersibility to the dispersion may be impaired.

[0036] The monomers of components (a1) to (a3) ​​can be polymerized by known polymerization methods, such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these known polymerization methods, solution polymerization is preferred because of the simplicity of the equipment and operation.

[0037] To efficiently advance the polymerization reaction, known polymerization initiators can be used. The polymerization initiator can be appropriately selected depending on the polymerization method, polymerization conditions, and solubility in the solvent. From the viewpoints of safety and polymerization efficiency, however, it is preferable for the 10-hour half-life temperature to be 70 to 110°C. If the 10-hour half-life temperature is less than 70°C, the stability at room temperature is low, which may increase the risk of fire. If the 10-hour half-life temperature is 110°C or higher, the polymerization reaction requires a high temperature and a long time, which may reduce production efficiency. Specific examples include azobis compounds such as 2,2'-azobis-isobutyronitrile, organic peroxides such as benzoyl peroxide, inorganic peroxides such as sodium persulfate, and redox catalyst systems consisting of a combination of such an oxidizing agent and a reducing agent such as bisulfite. These can be used alone or in combination of two or more.

[0038] A chain transfer agent can be added to adjust the molecular weight within a preferred range. Examples of such agents include alcohols such as catechol, mercaptans such as n-dodecyl mercaptan, and halogenated carbons such as carbon tetrachloride, and these can be used alone or in combination of two or more. In consideration of the chain transfer constant and safety, mercaptans are preferred, and high-boiling mercaptans such as n-dodecyl mercaptan are particularly preferred because they can suppress the odor of residual mercaptans.

[0039] The use of a solvent is preferred because it allows the polymer to be handled in solution and synthesized using simple equipment. An appropriate solvent can be selected depending on the polymerization method and polymerization conditions to be applied, the solubility of the raw materials, and the solvent composition of the dispersion composition using the dispersant. When producing an aqueous dispersant, it is preferable to select a solvent with a boiling point of 60 to 120°C under standard conditions. If the boiling point is less than 60°C, it may be difficult to efficiently proceed with polymerization in a short period of time. On the other hand, if the boiling point is 120°C or higher, a large amount of energy may be required for distillation under reduced pressure. Preferred solvents include water (boiling point 100°C), alcohols such as 2-propanol (boiling point 82°C), esters such as ethyl acetate (boiling point 77°C), ketones such as 2-butanone (boiling point 80°C), aromatic hydrocarbons such as toluene (boiling point 111°C), and ethers such as tetrahydrofuran (boiling point 66°C). These can be used alone or in combination of two or more. When producing an aqueous dispersion, water-miscible alcohols, ethers, and mixed solvents of these with other organic solvents and / or water are preferably used, and in consideration of safety and economy, 2-propanol and mixed solvents of 2-propanol with other organic solvents and / or water are more preferably used.

[0040] The styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer obtained by polymerization is neutralized with a basic compound characterized by an octanol / water partition coefficient of -5.0 or more and 0 or less. Neutralizing a part or all of the functional groups of the polymer with a basic compound stabilizes the dissolved or dispersed state of the polymer in the solvent. The basic compound may be added in the form of a monomer prior to polymerization, or may be added after polymerizing a monomer having an acidic functional group.

[0041] Although it depends on the water solubility and acidity of the styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer and the water solubility and basicity of the basic compound, the basic compound is preferably added so that the pH of a 20% aqueous solution of the styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer is in the range of 7 to 13, more preferably so that the pH of a 20% aqueous solution of the styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer is in the range of more than 7 to 11, and particularly preferably so that the pH of a 20% aqueous solution of the styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer is in the range of 8 to 10. If the pH of the aqueous polymer solution is less than 7, the solubility of the polymer in water may be insufficient, which is undesirable as the polymer may precipitate or deposit in water. On the other hand, if the pH of the aqueous polymer solution is higher than 13, the polymer may deteriorate over time due to hydrolysis, which is undesirable.

[0042] The octanol / water partition coefficient (log Pow) of the basic compound is in the range of -5.0 to 0, and preferably -4.0 to 0. Here, the octanol / water partition coefficient (log Pow) in the present invention is a value obtained in accordance with JIS Z7260-107 (2000) "Measurement of partition coefficient (1-octanol / water) - flask shaking method." The basic compound used in the present invention is a basic compound that is highly water-soluble and hydrophilic.

[0043] Furthermore, the basic compound can be appropriately selected in consideration of its compatibility with the dispersion system and the composition of the dispersion composition using the dispersant. By using a basic compound having a boiling point of 100° C. or higher, the basic compound remains in the dried product, and the re-solubility when water is added thereto is increased. Examples of such basic compounds include organic amine compounds such as 2-amino-2-methyl-1-propanol (partition coefficient = -0.74, boiling point 165°C), morpholine (partition coefficient = -0.84, boiling point 129°C), 1-amino-2-propanol (partition coefficient = -0.96, boiling point 159°C), 3-amino-1-propanol (partition coefficient = -1.12, boiling point 187°C), diethanolamine (partition coefficient = -1.43, boiling point 268°C), monoethanolamine (partition coefficient = -1.31, boiling point 171°C), and triethanolamine (partition coefficient = -1.59, boiling point 335°C), and alkali metal hydroxides such as sodium hydroxide (partition coefficient = -3.88, boiling point 1390°C) and potassium hydroxide (partition coefficient = -3.88, boiling point 1320°C).

[0044] The styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer (A) obtained by the above method has a weight-average molecular weight (Mw) of 1,000 to 50,000, preferably 3,000 to 30,000. If this weight-average molecular weight (Mw) is less than 1,000, the dispersion stabilizing ability for disperse dyes and pigments decreases, while if it is greater than 50,000, the ability to disperse disperse dyes and pigments decreases and the ink viscosity may become too high, which is undesirable. The weight-average molecular weight can be measured by GPC (gel permeation chromatography).

[0045] The acid value of the (A) styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer is preferably 50 to 300, and more preferably in the range of 100 to 250. If the acid value is less than 50, the solubility of the resin in water tends to be poor and the dispersion stabilizing ability for disperse dyes and pigments tends to be poor, while if the acid value exceeds 300, the affinity with aqueous media tends to be strong and bleeding tends to occur in printed images, which is undesirable. The acid value of the resin represents the number of milligrams of KOH required to neutralize 1 g of resin, and is measured in accordance with JIS-K 3054.

[0046] The dispersant of the present invention can be obtained by mixing component (A) with other components such as an aqueous solvent as needed, and is characterized in that the surfactant content in the dispersant is less than 0.1 mass%. In particular, it is preferable that the dispersant does not contain an acetylene-based surfactant. Even without the acetylene-based surfactant, the desired performance can be obtained.

[0047] The dispersion of the present invention contains the above-mentioned (A) styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer having a weight average molecular weight of 1,000 to 50,000, a disperse dye and / or pigment, and an aqueous solvent.

[0048] The constituent components of the dispersion are described below. In the dispersion of the present invention, the amount of dispersant blended is preferably 1 to 100 parts by mass, more preferably 3 to 80 parts by mass, and even more preferably 5 to 50 parts by mass, per 100 parts by mass of the disperse dye and pigment. If the amount of dispersant blended is too small, the disperse dye and pigment cannot be sufficiently dispersed, and if the amount of dispersant blended is too large, a large amount of dispersant will be present in the dispersion that is not adsorbed to the disperse dye or pigment, which is undesirable.

[0049] The disperse dye is not particularly limited and known disperse dyes can be used. Disperse dyes are classified into chemical structures such as benzene azo dyes (monoazo dyes, disazo dyes), heterocyclic azo dyes (thiazole azo dyes, benzothiazole azo dyes, pyridone azo dyes, pyrazolone azo dyes, thiophene azo dyes, etc.), anthraquinone dyes, and condensation dyes (quinophthalone, styryl dyes, coumarin dyes, etc.), and are characterized by being poorly soluble in water because they do not have a water-soluble group, and having a molecular weight of 2,000 or less, which is smaller than other dyes.

[0050] Examples of disperse dyes that can be preferably used in the present invention are as follows: C.I. Disperse Yellow Yellow dyes such as 3, 4, 5, 7, 9, 13, 24, 30, 33, 34, 42, 44, 49, 50, 51, 54, 56, 58, 60, 63, 64, 66, 68, 71, 74, 76, 79, 82, 83, 85, 86, 88, 90, 91, 93, 98, 99, 100, 104, 114, 116, 118, 119, 122, 124, 126, 135, 140, 141, 149, 160, 162, 163, 164, 165, 179, 180, 182, 183, 186, 192, 198, 199, 202, 204, 210, 211, 215, 216, 218, 224; Orange dyes such as C.I. Disperse Orange 1, 3, 5, 7, 11, 13, 17, 20, 21, 25, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 47, 48, 49, 50, 53, 54, 55, 56, 57, 58, 59, 61, 66, 71, 73, 76, 78, 80, 89, 90, 91, 93, 96, 97, 119, 127, 130, 139, 142; C.I. Disperse Red 1, 4, 5, 7, 11, 12, 13, 15, 17, 27, 43, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 65, 72, 73, 74, 75, 76, 78, 81, 82, 86, 88, 90, 91, 92, 93, 96, 103, 105, 106, 107, 108, 110, 111, 113, 117, 118, 121, 122, 126, 127, 128, 131, 132, 134, 135, 137, 143, 145, 146, 151, 152, Red dyes such as 153, 154, 157, 159, 164, 167, 169, 177, 179, 181, 183, 184, 185, 188, 189, 190, 191, 192, 200, 201, 202, 203, 205, 206, 207, 210, 221, 224, 225, 227, 229, 239, 240, 257, 258, 277, 278, 279, 281, 288, 289, 298, 302, 303, 310, 311, 312, 320, 324, 328;Purple dyes such as C.I. Disperse Violet 1, 4, 8, 23, 26, 27, 28, 31, 33, 35, 36, 38, 40, 43, 46, 48, 50, 51, 52, 56, 57, 59, 61, 63, 69, and 77; Green dyes such as C.I. Disperse Green 6:1 and 9; Brown dyes such as C.I. Disperse Brown 1, 2, 4, 9, 13, 19, 21, and 27; C.I. Disperse Blue 3, 7, 9, 14, 16, 19, 20, 26, 27, 35, 43, 44, 54, 55, 56, 58, 60, 62, 64, 71, 72, 73, 75, 79, 81, 82, 83, 87, 91, 93, 94, 95, 96, 102, 106, 108, 112, 113, 115, 118, 120, 122, 125, 128, 130, 139, 141, 142, 143, 146, 148, 149, 153, 1 Blue dyes such as C.I. Disperse Black 1, 3, 10, and 24 can be preferably used.

[0051] Dyes manufactured by Nippon Kayaku Co., Ltd. include Kayaset Black K-R, A-N, Kayalon Polyester Black S-200, EX-SF 300, G-SF, BR-SF, 2B-SF 200, TA-SF 200, AUL-S, Kayaset Yellow K-CL, Kayalon Polyester Yellow 4G-E, Kayalon Polyester Light Yellow 5G-S, Kayaset Red K-BL, Kayacelon Red E-BF, SMS-5, SMS-12, and Kayalon Polyester Red. TL-SF, BR-S, BL-E, HL-SF, 3BL-S200, AUL-S, Kayalon Polyester Light Red B-S200, Kayalon Polyester Rubine BL-S200, Kayaset Blue N, K-FL, MSB-13, Kayalon Polyester Blue BR-SF, T-S, Kayalon Polyester Light Blue BGL-S200, Kayalon Polyester Turq Blue GL-S200, Kayalon Polyester Blue Green FCT-S, etc. can be preferably used. Dyes manufactured by Orient Chemical Industry Co., Ltd. include Valifast Black 3806, 3810, 3820, Oil Black BS, BY, B-85, 860, Water Yellow 6C, Valifast Yellow 1101, 1105, 3110, 3120, 4120, 4126, Oplas Yellow 130, 140, Oil Yellow GG-S, 105, 107, 129, 818, Water Red 27, Valifast Red 1306, 1355, 2303, 3311, 3320, Valifast Orange 3210, Valifast Oil Brown 2402, Oil Red 5B, Oil Pink 312, Oil Brown BB, Valifast Blue 1601, 1603, 1605, 2606, 3806, 3820, Oil Blue #15, #613, 613, N14, BOS, etc. can be preferably used.Dyes manufactured by Sumitomo Chemical Co., Ltd. include Sumikaron Black S-BL, S-BF extra conc., S-RPD, S-XE 300%, and Sumikaron Yellow SE-4G, SE-5G, and SE-3GL conc. , SE-RPD, Sumikaron Brilliant Flavine S-10G, Sumikaron Red E-FBL, E-RPD (E), S-RPD (S), Sumikaron Brilliant Red S-BF, S-BLF, SE-BL, SE-BGL, SE-2BF, SE-3BL (N), Sumikaron Red E-FBL, E-RPD (E), S-RPD (S), Sumikaron Brilliant Red S-BF, S-BLF, SE-BL, SE-BGL, SE-2BF, SE-3BL (N), Sumikaron Brilliant Blue S-BL, Sumikaron Turquoise Blue S-GL, S-GLFgrain, etc. can be preferably used. Examples of dyes that can be preferably used from BASF include Basacryl Black X-BGW, Naozapon Black X-51, X-55, Neozapon Yellow 081, Lurafix Yellow 138, Zapon Blue 807, Neozapon Blue 807, Lurafix Blue 590, 660, Orasol Black RLI, RL, CN, Oracet Yellow 8GF, GHS, Orasol Red G, Oracet Pink RP, and Orasol Blue GL, GN, and 2R. Preferred examples of dyes manufactured by Taoka Chemical Co., Ltd. include Oleosol Fast Black AR, RL, Oleosol Fast Pink FB, Rhodamine A, B, B gran., Oleosol Fast Yellow 2G, and Oleosol Fast Blue ELN. Preferred examples of dyes manufactured by Hodogaya Chemical Co., Ltd. include Spilon Black BNH and MH special. Preferred examples of dyes manufactured by Mitsui Chemicals, Inc. include PS Yellow GG, MS Yellow HD-180, PS Red G, and MS Magenta VP.Preferred dyes manufactured by Bayer include Ceres Blue GN 01. Preferred dyes manufactured by Sumika Color Co., Ltd. include TS Yellow 118 cake, ESC Yellow 155, Sumiplast Yellow HLR, GC, TS Turq Blue 618, 606, ESC Blue 655, 660, Sumiplast Blue S, and OA.

[0052] The pigment is not particularly limited, and known pigments can be used. Examples of organic pigments include azo pigments such as soluble azo pigments, insoluble azo pigments, and condensed azo pigments, quinacrylonitrile pigments, perylene pigments, perinone pigments, isoindolinone pigments, isoindoline pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and polycyclic pigments such as diketopyrrolopyrrole pigments, and phthalocyanine pigments. Examples of inorganic pigments include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black.

[0053] Specific examples of pigments include red pigments such as C.I. Pigment Red 7, 9, 14, 41, 48:1, 48:2, 48:3, 48:4, 81:1, 81:2, 81:3, 122, 123, 146, 149, 168, 177, 178, 179, 187, 200, 202, 208, 210, 215, 224, 254, 255, and 264; yellow pigments such as C.I. Pigment Yellow 1, 3, 5, 6, 14, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81, 93, 97, 98, 104, 108, 110, 128, 138, 139, 147, 150, 151, 154, 155, 166, 167, 168, 170, 180, 188, 193, 194, 213; orange pigments such as C.I. Pigment Orange 36, 38, 43; blue pigments such as C.I. Pigment Blue 15, 15:2, 15:3, 15:4, 15:6, 16, 22, 60; Examples of suitable pigments include green pigments such as C.I. Pigment Green 7, 36, and 58; purple pigments such as C.I. Pigment Violet 19, 23, 32, and 50; and black pigments such as C.I. Pigment Black 7. Among these, C.I. Pigment Red 122, C.I. Pigment Yellow 74, 128, and 155, C.I. Pigment Blue 15:3, 15:4, and 15:6, C.I. Pigment Green 7 and 36, C.I. Pigment Violet 19, and C.I. Pigment Black 7 can be preferably used.

[0054] The type, particle size, processing method, etc. of the disperse dye and / or pigment contained in the dispersion can be appropriately selected depending on the purpose. The disperse dye and pigment contained in the dispersion may be used alone or in combination of two or more types.

[0055] The concentration of the disperse dye and pigment in the dispersion is preferably 1 to 50% by mass, and more preferably 5 to 50% by mass, based on 100% by mass of the dispersion. If the concentration of the disperse dye and pigment exceeds 50% by mass, the density of the disperse dye and pigment in the dispersion increases, which may hinder their free movement and cause them to aggregate.

[0056] The aqueous solvent can be water and / or a water-soluble organic solvent, and two or more types may be used in combination. It is preferable to use pure water or ion-exchanged water (deionized water) as the water. Examples of water-soluble organic solvents that can be used include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; glycols such as ethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and triethylene glycol monobutyl ether; polyhydric alcohols such as glycerin; and nitrogen-containing compounds such as N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. The proportion of water and the water-soluble organic solvent in the dispersion is preferably from 5 to 95% by mass, more preferably from 30 to 90% by mass, based on 100% by mass of the dispersion.

[0057] The method for producing the dispersion of the present invention preferably includes a step of mixing and dispersing the above-mentioned dispersant, disperse dye and / or pigment, and aqueous solvent. For example, the dispersant, disperse dye and / or pigment, and aqueous solvent can be mixed using a mixer / disperser such as a paint shaker, a bead mill, a ball mill, a dissolver, or a kneader to obtain a dispersion. When a component that is solid at room temperature is used, the components may be heated and mixed as necessary.

[0058] The static surface tension of the dispersion is preferably 60 mN / m or less, more preferably 50 mN / m or less.

[0059] The viscosity of the dispersion is preferably 50.0 mPa·s or less, more preferably 30.0 mPa·s or less. The lower limit of the viscosity of the dispersion is preferably 1.0 mPa·s or more. The viscosity in this case is measured at 25°C.

[0060] The average particle size of the disperse dye and / or pigment in the dispersion depends on the type of disperse dye and / or pigment, but is preferably 500 nm or less, more preferably 300 nm or less. The average particle size here refers to the median diameter (D50).

[0061] Furthermore, the dispersion of the present invention has excellent dispersion stability, and the interfacial migration speed is preferably 3.0 μm / s or less, more preferably 1.0 μm / s or less.

[0062] The dispersion of the present invention has excellent redispersibility. That is, when an ink containing a water-insoluble colorant such as a disperse dye or pigment dries, the dispersed state of the disperse dye or pigment breaks down and aggregation occurs. Generally, once aggregated, the disperse dye or pigment in the ink cannot be restored to a dispersed state even by adding a liquid medium such as water, and redispersibility is often poor. However, the dispersion of the present invention has excellent redispersibility. In the present invention, the elution rate of the dispersion into the dispersion medium is preferably 40% or more, more preferably 60% or more. The elution rate of the dispersion into the dispersion medium will be described in the Examples below.

[0063] The ink composition of the present invention contains the dispersion of the present invention described above, and further contains, optionally, a resin and other additives. That is, the ink composition of the present invention preferably contains the following (i) to (v): (i) a dispersant, (ii) a disperse dye and / or pigment, (iii) water and / or a water-soluble organic solvent, (iv) a resin, and (v) one or more additives selected from the group consisting of an ultraviolet absorber, an antioxidant, a pH adjuster, a preservative, and a viscosity adjuster.

[0064] The concentration of the disperse dye and / or pigment in the ink composition is preferably 0.1 to 20% by mass, and more preferably 0.1 to 10% by mass, based on 100% by mass of the ink composition.

[0065] The proportion of water and / or the water-soluble organic solvent in the ink composition is preferably 50 to 99% by mass, and more preferably 60 to 95% by mass, based on 100% by mass of the ink composition.

[0066] The resin contained in the ink composition is preferably a polymer having a hydrophobic group and a hydrophilic group. This polymer preferably has at least one functional group selected from an alkyl group, a cycloalkyl group, and an aryl group as the hydrophobic group. It also preferably has at least one functional group selected from a carboxy group, a sulfo group, a hydroxy group, an amino group, an amide group, and these functional groups as the hydrophilic group. Such a polymer can be obtained, for example, by polymerizing a monomer or oligomer having a functional group such as an acryloyl group, a methacryloyl group, a vinyl group, or an allyl group.Specific examples include styrene, tetrahydrofurfuryl acrylate, butyl methacrylate, (α, 2, 3, or 4)-alkylstyrene, (α, 2, 3, or 4)-alkoxystyrene, 3,4-dimethylstyrene, α-phenylstyrene, divinylbenzene, vinylnaphthalene, dimethylamino(meth)acrylate, dimethylaminoethyl(meth)acrylate, dimethylaminopropylacrylamide, N,N-dimethylaminoethyl acrylate, acryloylmorpholine, N,N-dimethylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, ethylhexyl(meth)acrylate, other alkyl(meth)acrylates, methoxydiethylene glycol(meth)acrylate, (meth)acrylates of diethylene glycol or polyethylene glycol having an ethoxy group, a propoxy group, or a butoxy group, cyclohexyl(meth)acrylate, benzene In addition to monofunctional (meth)acrylates such as diethyl (meth)acrylate, phenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyalkyl (meth)acrylate, other fluorine-containing, chlorine-containing, and silicon-containing (meth)acrylates, (meth)acrylamide, maleic acid amide, and (meth)acrylic acid, when a crosslinked structure is to be introduced, (mono-, di-, tri-, tetra-, or poly)ethylene glycol di(meth)acrylate, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1, Compounds having an acrylic group or a methacrylic group, such as (meth)acrylates of 8-octanediol and 1,10-decanediol, trimethylolpropane tri(meth)acrylate, glycerin (di, tri)(meth)acrylate, di(meth)acrylate of an ethylene oxide adduct of bisphenol A or F, neopentyl glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, can be used.

[0067] The proportion of the resin in the ink composition is not particularly limited, but is preferably 0 to 30% by mass, and more preferably 0 to 20% by mass, relative to 100% by mass of the ink composition. When a resin is blended into the ink composition, it is preferably 1% by mass or more.

[0068] In addition, various additives can be contained in the ink composition. Examples of additives include ultraviolet absorbers, antioxidants, pH adjusters, preservatives, viscosity adjusters, etc., and these can be appropriately selected and blended into the ink composition. These additives can be blended separately from the disperse dye and / or pigment, water and / or water-soluble organic solvent, and resin, in a proportion that makes up the remainder of 100% by mass of the dispersion and ink composition, specifically, 0 to 10% by mass of 100% by mass of the ink composition.

[0069] Furthermore, the method for producing the ink composition is not particularly limited, but it is preferable to adopt a method comprising the following steps (a) and (b): (a) a step of mixing and dispersing the above-mentioned dispersant, a disperse dye and / or pigment, and an aqueous solvent to obtain a dispersion, and (b) a step of mixing the above-mentioned dispersion with at least one substance selected from the group consisting of water, a water-soluble organic solvent, a resin, an ultraviolet absorber, an antioxidant, a pH adjuster, a preservative, and a viscosity adjuster.

[0070] The ink composition is applied to a recording medium by an ink jet recording method, a recording method using a writing instrument such as a pen, or other printing method. The ink composition of the present invention is particularly preferably used in an ink jet recording method.

[0071] (A) Styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer was synthesized by a known and commonly used method as follows. Unless otherwise specified, in this production example, "parts" means "parts by mass" and "%" means "% by mass."

[0072] <Production Example 1> [Production of aqueous polymer solution neutralized with sodium hydroxide] A three-neck flask equipped with a thermocouple, a stirrer, and a reflux condenser was charged with 33 parts of styrene (hereinafter referred to as ST), 44 parts of methyl methacrylate (hereinafter referred to as MMA), 33 parts of polyethylene glycol methacrylate (average EO addition mole number 23, "BLEMMER PME-1000" manufactured by NOF Corporation; hereinafter referred to as PEG(23)MA), 55 parts of methacrylic acid (hereinafter referred to as MAA), 3.3 parts of n-dodecyl mercaptan (hereinafter referred to as NDM) as a chain transfer agent, 1.65 parts of 2,2'-azobis-isobutyronitrile (hereinafter referred to as AIBN) as a polymerization initiator, and 169.95 parts of 2-propanol (hereinafter referred to as IPA) as a solvent, and the flask was then subjected to deoxidation and nitrogen substitution twice to create a nitrogen atmosphere. Thereafter, stirring was started and the mixture was heated until the internal temperature reached 80°C. Stirring was continued for 6 hours while maintaining the internal temperature at 80°C. After 6 hours, 145.2 parts of IPA was slowly added, and the internal temperature was cooled to 25°C or below, yielding an unneutralized polymer (IPA solution) (hereinafter referred to as "unneutralized solution A"). The polymer content of the resulting unneutralized solution A, calculated from the dry residue, was 35.2%. The weight average molecular weight of the unneutralized polymer was 18,275, and the number average molecular weight was 6,991.

[0073] The weight-average molecular weight and number-average molecular weight in the present invention are values ​​calculated in terms of standard polystyrene, obtained by drying an unneutralized polymer solution at 105°C for 3 hours, dissolving it in tetrahydrofuran so that the polymer content becomes 1%, and filtering the solution through a 0.45 µm membrane filter, and measuring the resultant solution by gel permeation chromatography (GPC) under the following conditions: Column: Shodex KF-802, Shodex KF806M (manufactured by Showa Denko KK) Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Injection volume: 10 µL Column temperature: 40°C Detector: RI detector

[0074] 140 parts of unneutralized solution A were weighed into a beaker and stirring was initiated. 6.0 parts of sodium hydroxide (distribution coefficient = -3.88, boiling point 1390 ° C) were weighed into a separate beaker, and 150 parts of ion-exchanged water was added to prepare an aqueous sodium hydroxide solution. The entire amount of the prepared aqueous sodium hydroxide solution was added to unneutralized solution A under stirring to neutralize the polymer, and the entire amount of the liquid was transferred to a recovery flask. 120 parts were distilled off using a rotary evaporator, and then 200 parts of ion-exchanged water was added, and a further 160 parts were distilled off under reduced pressure to remove IPA from the solution. 31.64 parts of ion-exchanged water were added to bring the total volume to 252.80 parts, yielding an aqueous polymer solution neutralized with sodium hydroxide, having a polymer content of 19.5% and a pH of 7.4.

[0075] <Production Example 2, Comparative Production Example 1> The type of neutralizer in unneutralized solution A was changed as shown in Table 1, and the amount of neutralizer added was changed to an amount that would result in the pH shown in the table. Except for this, production was carried out in the same manner as in Production Example 1. The types of neutralizers in Table 1 are as follows: Sodium hydroxide (partition coefficient = -3.88, boiling point 1390°C) 2-amino-2-methyl-1-propanol (partition coefficient = -0.74, boiling point 166°C) Ammonia (partition coefficient = 0.23, boiling point -33°C)

[0076] <Production Example 3, Comparative Production Example 2> Production was carried out in the same manner as in Production Example 1, except that the content (charging ratio) of each component was changed as shown in Table 1. Furthermore, Comparative Production Example 2 was produced by changing the neutralizing agent in the unneutralized solution of Production Example 3 as shown in Table 1.

[0077] Comparative Production Example 3 A three-necked flask equipped with a thermocouple thermometer, a stirrer, and a reflux condenser was charged with 135.3 parts of ST, 13.2 parts of polyethylene glycol methacrylate (average EO addition mole number 9, "Blenmer PME-400" manufactured by NOF Corporation; hereinafter referred to as PEG(9)MA), 16.5 parts of vinyl sulfonic acid (hereinafter referred to as VSA), 3.3 parts of NDM, 1.65 parts of AIBN, 305.25 parts of N,N-dimethylformamide (hereinafter referred to as DMF), and 49.5 parts of ion-exchanged water. The flask was then subjected to two cycles of deoxygenation and nitrogen substitution to create a nitrogen atmosphere. Stirring was then initiated to dissolve the VSA and AIBN, and the mixture was heated until the internal temperature reached 80°C. The internal temperature was maintained at 80°C for 6 hours, and stirring was continued to carry out the polymerization reaction. After completion of the reaction, the reaction solution was added dropwise to IPA to precipitate a polymer. After removing the supernatant, the precipitate was collected and dried to obtain unneutralized polymer B. The weight average molecular weight of the obtained unneutralized polymer B was 18,517. 15 parts of unneutralized polymer B and 70 parts of ion-exchanged water were weighed into a separable flask equipped with a thermocouple thermometer, a stirrer, a reflux condenser, and a pH electrode, and heated with stirring until the internal temperature reached 80°C. Sodium hydroxide was added thereto until the pH reached 8.0, and further ion-exchanged water was added to bring the total amount to 100 parts. Stirring was continued at 80°C for 3 hours. Unneutralized polymer B did not dissolve.

[0078] Comparative Production Examples 4 and 5: Production was carried out in the same manner as in Comparative Production Example 3, except that the type of neutralizer for unneutralized polymer B was changed as shown in the table and the amount of neutralizer added was changed to an amount that would result in a pH as shown in the table. In both cases, stirring was continued at 80°C for 3 hours, but unneutralized polymer B did not dissolve.

[0079]

[0080]

[0081] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, parts and % represent parts by mass and % by mass, respectively.

[0082] Example 1 15 parts of Hostaperm Blue BT-617-D (manufactured by CLARIANT, Pigment Blue 15:4) as a blue pigment, 61.9 parts of ion-exchanged water as an aqueous solvent, 23.1 parts of the dispersant, and 300 parts of zirconia beads (diameter 0.3 mm) were placed in a plastic container (made of polypropylene, capacity 0.5 L) and dispersed for 1 hour using a PAINT SHAKER (manufactured by Asada Iron Works Co., Ltd.). After dispersion, the zirconia beads were filtered off to obtain a dispersion.

[0083] [Examples 2 and 3, Comparative Examples 1 to 5] Dispersions of each example having the compositions shown in Table 3 below were prepared in the same manner as in Example 1.

[0084] The surface tension, viscosity, average particle size, dispersion stability, redispersibility (visual observation), and redispersibility / elution rate of each dispersion were measured by the following methods. The results are shown in Table 3.

[0085] <Surface Tension> The static surface tension of the dispersion immediately after dispersion was measured at 25°C using a DY-500 high-performance surface tensiometer (manufactured by Kyowa Interface Science Co., Ltd.).

[0086] <Viscosity> The viscosity (25°C) of the dispersion immediately after dispersion was measured using a TVE-20 E-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0087] <Average Particle Diameter> The average particle diameter (D50) of the dispersion immediately after dispersion was measured using an ELSZ-2000 Zeta Potential / Particle Diameter / Molecular Weight Measurement System (manufactured by Otsuka Electronics Co., Ltd.).

[0088] <Dispersion Stability> Dispersion stability was evaluated using a dispersion stability analyzer LUMiSizer (manufactured by LUM Corporation). This analysis was performed under the conditions of a temperature of 25°C immediately after dispersion, a rotation speed of 4,000 rpm, and an analysis time of 50 minutes, and the interfacial migration velocity (particle settling velocity) was measured. A smaller interfacial migration velocity indicates better dispersion stability.

[0089] <Redispersibility (visual observation)> Immediately after dispersion, 100 μL of the dispersion was measured out using a micropipette and placed in a petri dish, and allowed to dry at room temperature (approximately 25° C.) for approximately 15 hours. After drying, 3 mL of ion-exchanged water was added, and the state of redispersion of the dried dispersion in the ion-exchanged water was visually observed. The evaluation criteria for redispersibility are as follows: (Evaluation criteria) ◎: The dried material disappeared and was redispersed. ○: Some dried material remained, but was mostly redispersed. △: Most of the dried material remained, and some was redispersed. ×: Redispersion of the dried material could not be confirmed.

[0090] <Redispersibility Dissolution Rate> Immediately after dispersion, 100 μL of the dispersion was measured using a micropipette into a petri dish and allowed to dry at room temperature (approximately 25° C.) for approximately 15 hours. After drying, the mass of the dried dispersion (mass before redispersion) was measured using an electronic balance, and then 3 mL of ion-exchanged water was added and allowed to stand for 3 minutes at room temperature (approximately 25° C.). After standing, undissolved matter was removed using an 80-mesh filter cloth, and the resulting filtrate was dried in a dryer at 60° C. for 3 hours. After drying, the dried product (redispersed mass) was returned to room temperature and measured using an electronic balance, and the dispersion dissolution rate in ion-exchanged water was calculated using the following formula [1]. Redispersibility Dissolution Rate [%] = (redispersed mass) / (mass before redispersion) × 100 ... [1]

[0091]

[0092] From Table 3 above, it can be seen that the elution rate can be improved by about 40% by changing from "ammonia neutralization of Comparative Production Example 1" to "sodium hydroxide neutralization of Production Example 1" and "2-amino-2-methyl-1-propanol neutralization of Production Example 2," and further, the elution rate can be improved by about 20% by changing from "ammonia neutralization of Comparative Production Example 2" to "sodium hydroxide neutralization of Production Example 3." Therefore, by using as a dispersant a styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer neutralized with a basic compound having an octanol / water partition coefficient of -5.0 or more and 0 or less, a dispersion with excellent resolubility can be obtained.

Claims

1. A dispersant comprising (A) a styrene-ethyleneoxy group-containing (meth)acrylic acid copolymer having a weight average molecular weight of 1,000 to 50,000, (a1) a copolymer having a styrene content of 1 to 40 mass%, and containing less than 0.1 mass% of a surfactant.

2. The dispersant according to claim 1, wherein the component (A) is a polymer of the following (a1) to (a3): (a1) styrene: 1 to 40% by mass; (a2) ethyleneoxy group-containing (meth)acrylic acid ester monomer: 1 to 59% by mass; and (a3) ​​monomers other than (a1) and (a2): 1 to 98% by mass.

3. The dispersant according to claim 2, wherein the monomer of component (a3) ​​comprises a radical polymerizable monomer containing at least one functional group.

4. The dispersant according to claim 1 or 2, wherein the component (A) is a neutralized product with a basic compound having an octanol / water partition coefficient of -5.0 or more and 0 or less.

5. The dispersant according to claim 1 or 2, which does not contain an acetylene-based surfactant.

6. The dispersant according to claim 1 or 2, which is used for dispersing disperse dyes or pigments in an aqueous solvent.

7. A dispersion comprising a dispersant, a disperse dye and / or a pigment, and an aqueous solvent, wherein the dispersant is the dispersant defined in claim 1 or 2.

8. An ink composition comprising the dispersion according to claim 7.

9. The method for producing a dispersant according to claim 1 or 2, characterized in that the component (A) is neutralized with a basic compound having an octanol / water partition coefficient of -5.0 or more and 0 or less.

10. A method for producing a dispersion, comprising the step of mixing and dispersing the dispersant according to claim 1 or 2, a disperse dye and / or a pigment, and an aqueous solvent.

11. A method for producing an ink composition, comprising the following steps (a) and (b): (a) a step of mixing and dispersing the dispersant according to claim 1 or 2, a disperse dye and / or a pigment, and an aqueous solvent to obtain a dispersion, and (b) a step of mixing the dispersion with at least one substance selected from the group consisting of water, a water-soluble organic solvent, a resin, an ultraviolet absorber, an antioxidant, a pH adjuster, a preservative, and a viscosity adjuster.

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