Modified Polyester Resin

Abstract

To provide a modified polyester resin that can give a water-based dispersoid and a water-based ink having high storage stability, and a water-based dispersoid and a water-based ink containing the modified polyester resin.SOLUTION: The present invention discloses [1] a modified polyester resin that has a constitutional unit derived from a compound having a specific structure, [2] a water-based dispersoid containing the modified polyester resin, and [3] a water-based ink containing the modified polyester resin and a pigment.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a modified polyester resin, and an aqueous dispersion and an aqueous ink containing the same. [Background technology]

[0002] 2. Description of the Related Art In the fields of commercial and industrial printing such as product packaging printing and advertisement printing, printing has traditionally been carried out using solvent-based inks or UV-curable inks on resin print media such as polyvinyl chloride, polyethylene terephthalate, and polypropylene. In response to this, printing using water-based inks is becoming more widespread from the standpoint of reducing the environmental impact, saving energy, safety, etc. In particular, the inkjet printing method, in which ink droplets are ejected directly from extremely fine nozzles onto a printing medium and attached to the medium to obtain characters and images, has become extremely popular due to the many advantages it offers, such as easy full-color printing, low cost, the use of ordinary paper as the printing medium, and no contact with the substrate.

[0003] In recent years, from the viewpoint of water resistance and durability of printed matter, inkjet printing using water-based pigment inks that use pigments as colorants and polymer dispersants to disperse the pigments has been attracting attention. However, water-based pigment inks have problems such as poor storage stability and ejection stability due to coarse particles derived from the pigments and polymers. Therefore, various proposals have been made to improve these problems. For example, Patent Document 1 discloses an aqueous ink for inkjet recording that contains resin particles and is capable of recording images with excellent ejection stability and abrasion resistance, the resin particles being formed of a first resin and a second resin having a carboxylic acid group, the first resin being a polyester resin that does not have a crosslinked structure, the second resin being a polyester resin or an acrylic resin that has a crosslinked structure, the crosslinked structure containing an alkylene oxide group, and the polyester resin containing BHT. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-50874 A Summary of the Invention [Problem to be solved by the invention]

[0005] The range of applications of the inkjet printing method is expanding because it is suitable for printing a wide variety of products in small quantities, but water-based inks are often stored for long periods of time, so there is a demand for water-based inks to have improved long-term storage stability. Although polyester resins have excellent durability as polymer dispersants, they have a problem of inferior storage stability compared to acrylic resins. In particular, when printing on non-liquid-absorbing media such as resin films, hydrophobic solvents are added to water-based inks to improve the wettability of the print medium surface, but the stability of the dispersion of polyester resin particles is inferior, so the storage stability of the water-based ink cannot be improved. Conventional water-based inks containing polyester resins, such as those described in Patent Document 1, have insufficient storage stability, and improvement in this regard has been desired. An object of the present invention is to provide a modified polyester resin from which an aqueous dispersion and an aqueous ink having excellent storage stability can be obtained, and an aqueous dispersion and an aqueous ink containing the same. [Means for solving the problem]

[0006] The present inventors have found that the above problems can be solved by using a modified polyester resin obtained by modifying a polyester resin with a specific reactive surfactant. That is, the present invention provides the following [1] to [3]. [1] A modified polyester resin having a structural unit derived from a compound represented by the following formula (1) or (4):

[0007] [ka] [In formula (1), R 1represents a hydrogen atom or a methyl group, R 2 represents an alkylene group having 1 to 5 carbon atoms; R 3 represents a group represented by the following formula (2) or (3).

[0008] [ka] [In the formula (2) or (3), BO represents butylene oxide, EO represents ethylene oxide, m and n each independently represent an integer of 1 or more and 200 or less, X represents a hydrogen atom, -SO3M, PO3M, or COOM (M is an alkali metal atom or an ammonium ion), and R 4 represents an alkyl group having 5 to 30 carbon atoms. * represents the bonding site with -O- in formula (1).

[0009] [ka] [In formula (4), EO represents ethylene oxide, p and q each independently represent an integer of 1 or more and 200 or less, and X represents a hydrogen atom, -SO3M, PO3M, or COOM (M is an alkali metal atom or an ammonium ion).]

[0010] [2] An aqueous dispersion containing the modified polyester resin according to [1]. [3] A water-based ink containing the modified polyester resin of [1] and a pigment. Effect of the Invention

[0011] According to the present invention, it is possible to provide a modified polyester resin from which an aqueous dispersion and an aqueous ink having excellent storage stability can be obtained, and an aqueous dispersion and an aqueous ink containing the same. [Brief description of the drawings]

[0012] [Figure 1]This is a chart obtained by 13C-NMR measurement of the modified polyester resin MP-1 obtained in Example I-1, the mixed resin P-3 of the polyester resin P-1 obtained in Production Example 1-1 and the reactive surfactant LATEMUL PD-104, and the reactive surfactant LATEMUL PD-104. [Diagram 2] 1 shows the molecular weight distribution curves of resin B-1 obtained by reacting with reactive surfactant LATEMURU PD-104, and the reactive surfactant LATEMURU PD-104, as determined by gel permeation chromatography. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Modified polyester resin] The modified polyester resin of the present invention has a structural unit derived from the compound represented by the above formula (1) or (4). The modified polyester resin of the present invention, and the aqueous dispersion and aqueous ink containing the same have excellent storage stability and can be used not only for inkjet printing, but also for flexographic printing and gravure printing, but is preferably used for inkjet printing. In this specification, the term "water-based" means that water accounts for the largest proportion of the medium contained in the ink.

[0014] The modified polyester resin of the present invention can provide an aqueous dispersion and an aqueous ink having excellent storage stability. The reason for this is not clear, but is thought to be as follows. When an aqueous dispersion or aqueous ink contains a polyester resin, the polyester resin has a highly hydrophilic hydroxyl group or carboxylic acid group at its terminal, and some of these hydrophilic groups are present on the surface of the polyester resin particles. However, the hydrophilicity of the resin particles is not sufficiently high, so the dispersion state is difficult to stabilize, and the storage stability of the ink is not improved. Therefore, the present inventors have investigated steric repulsive groups in order to improve storage stability by bonding nonionic steric repulsive groups to the surface of a polyester resin. As a result, it was discovered that polyester resins modified by bonding specific nonionic steric repulsive groups to them have stable dispersion due to steric repulsion even in hydrophobic solvents. It is believed that the storage stability has been improved by including this modified polyester resin in water-based dispersions and water-based inks.

[0015] <Modified polyester resin> The modified polyester resin of the present invention is a polyester resin modified by introducing a structural unit derived from a compound represented by the following formula (1) or (4).

[0016] [ka] [In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkylene group having 1 to 5 carbon atoms; R 3 represents a group represented by the following formula (2) or (3).

[0017] [ka] [In the formula (2) or (3), BO represents butylene oxide, EO represents ethylene oxide, m and n each independently represent an integer of 1 or more and 200 or less, X represents a hydrogen atom, -SO3M, PO3M, or COOM (M is an alkali metal atom or an ammonium ion), and R 4 represents an alkyl group having 5 to 30 carbon atoms. * represents the bonding site with -O- in formula (1).

[0018] [ka] [In formula (4), EO represents ethylene oxide, p and q each independently represent an integer of 1 or more and 200 or less, and X represents a hydrogen atom, -SO3M, PO3M, or COOM (M is an alkali metal atom or an ammonium ion).]

[0019] The compound represented by the formula (1) or (4) is a reactive surfactant having a radically polymerizable unsaturated double bond in the molecule, and the modified polyester resin of the present invention can be obtained by reacting this reactive surfactant with the polyester resin as a raw material. The compound represented by formula (1) or (4) has excellent monomer emulsifying properties, and can produce an aqueous dispersion with excellent stability, thereby improving the storage stability of the resulting aqueous ink.

[0020] [Raw polyester resin] There are no particular limitations on the polyester resin that is the raw material, and the polyester resin contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, and can be obtained by polycondensing the alcohol component and the carboxylic acid component.

[0021] (Alcohol content) The alcohol component, which is a raw material monomer for the polyester resin (A), preferably contains an aromatic diol, from the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink. As the aromatic diol, an alkylene oxide adduct of bisphenol A is preferred. The alkylene oxide adduct of bisphenol A is a compound having a structure in which an oxyalkylene group is added to 2,2-bis(4-hydroxyphenyl)propane, and specifically, a compound represented by the following general formula (I) is preferred. [ka]

[0022] In the general formula (I), OR 1 , R 2 Each O independently represents an oxyalkylene group having 1 to 4 carbon atoms, and is preferably an oxyethylene group or an oxypropylene group. x and y are the number of moles of alkylene oxide added, and each is independently a positive number of 0 or more. From the viewpoint of reactivity with the carboxylic acid component, the average value of the sum of x and y is preferably 2 or more, and is preferably 7 or less, more preferably 5 or less, and further preferably 3 or less. Also, x OR 1 and y R 2 Each O may be the same or different, but is preferably the same from the above viewpoint. The alkylene oxide adduct of bisphenol A is preferably a propylene oxide adduct of bisphenol A or an ethylene oxide adduct of bisphenol A, and more preferably a propylene oxide adduct of bisphenol A. From the same viewpoints as above, the content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more, and preferably 100 mol% or less.

[0023] The alcohol component, which is a raw material monomer for the polyester resin, may contain an alcohol component other than the alkylene oxide adduct of bisphenol A. Other alcohol components include ethylene glycol, propylene glycol (1,2-propanediol), glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylene oxide adducts (having a carbon number of 2 to 4) thereof (average number of moles added: 1 to 16). The alcohol components can be used alone or in combination of two or more.

[0024] (Carboxylic acid component) The carboxylic acid component, which is a raw material monomer for the polyester resin, includes carboxylic acid, its acid anhydride, and its alkyl (having 1 to 3 carbon atoms) ester. Examples of the carboxylic acid component include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and trivalent or higher polycarboxylic acids. As the aromatic dicarboxylic acid, phthalic acid, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred. The aliphatic dicarboxylic acid may be unsaturated or saturated, and the unsaturated aliphatic dicarboxylic acid may be fumaric acid or maleic acid, more preferably fumaric acid, and the saturated aliphatic dicarboxylic acid may be adipic acid or succinic acid, more preferably succinic acid. As the alicyclic dicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, and tetrahydrophthalic acid are preferred. As the trivalent or higher polyvalent carboxylic acid, trimellitic acid and pyromellitic acid are preferred, and trimellitic anhydride is also preferred. The carboxylic acid components may be used alone or in combination of two or more kinds. From the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink, the above-mentioned carboxylic acid component preferably contains one or more selected from aromatic dicarboxylic acids and aliphatic dicarboxylic acids, and more preferably uses an aliphatic dicarboxylic acid in combination with another carboxylic acid.

[0025] (Production of polyester resin) The polyester resin, which is a raw material, can be obtained by polycondensing the alcohol component and the carboxylic acid component in an appropriate combination, for example, by polycondensing the alcohol component and the carboxylic acid component in an inert gas atmosphere at a temperature of 150° C. to 250° C. using an esterification catalyst as necessary. Examples of the esterification catalyst include tin catalysts, titanium catalysts, and metal compounds such as antimony trioxide, zinc acetate, and germanium dioxide, and from the viewpoint of esterification reaction efficiency, tin catalysts are preferred. As the tin catalyst, dibutyltin oxide, tin(II) di(2-ethylhexanoate), and salts thereof are preferred, and tin(II) di(2-ethylhexanoate) is more preferred. If necessary, an esterification promoter such as gallic acid may be further used. A radical polymerization inhibitor such as 4-tert-butylcatechol may also be used in combination.

[0026] The polyester resin preferably has an acid group from the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink. The acid value of the polyester resin is preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, even more preferably 17 mgKOH / g or more, and is preferably 90 mgKOH / g or less, more preferably 70 mgKOH / g or less, even more preferably 50 mgKOH / g or less. From the same viewpoints as above, the softening point of the polyester resin is preferably 80°C or higher, more preferably 85°C or higher, and even more preferably 90°C or higher, and is preferably 180°C or lower, more preferably 160°C or lower, and even more preferably 140°C or lower.

[0027] From the same viewpoints as above, the glass transition temperature of the polyester resin is preferably 45°C or higher, more preferably 50°C or higher, even more preferably 52°C or higher, and preferably 90°C or lower, more preferably 80°C or lower, even more preferably 70°C or lower. From the same viewpoints as above, the weight average molecular weight of the polyester resin is preferably 4,000 or more, more preferably 5,000 or more, and even more preferably 6,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. The acid value, softening point, glass transition temperature, and weight average molecular weight of the polyester resin can be measured by the method described in the Examples. These physical properties can be adjusted to the desired values ​​by appropriately adjusting the type and blending ratio of the monomers used, the polycondensation temperature, and the reaction time.

[0028] [Compound represented by formula (1)] The compound represented by the following formula (1) is a polyoxyalkylene alkenyl ether or a sulfate thereof.

[0029] [ka]

[0030] In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkylene group having 1 to 5 carbon atoms; R 3 represents a group represented by the following formula (2) or (3). R 1 is preferably a methyl group, R 2 is preferably an alkylene group having 1 to 3 carbon atoms.

[0031] [ka]

[0032] In the formula (2) or (3), BO represents butylene oxide, EO represents ethylene oxide, m and n each independently represent an integer of 1 or more and 200 or less, X represents a hydrogen atom, -SO3M, PO3M, or COOM (M is an alkali metal atom or an ammonium ion), R 4 represents an alkyl group having 5 to 30 carbon atoms. * represents the bonding site with -O- in formula (1). X is preferably a hydrogen atom or -SO3NH4 (ammonium sulfate). In the formula (2), m and n each independently are preferably 1 or more and 150 or less, more preferably 1 or more and 100 or less, and further preferably 1 or more and 50 or less. In the formula (3), n is preferably 1 or more and 100 or less, more preferably 3 or more and 80 or less, and further preferably 6 or more and 40 or less. R in Equation (3) 4 is an alkyl group having preferably 6 or more and 24 or less carbon atoms, more preferably 6 or more and 20 or less carbon atoms, even more preferably 8 or more and 16 or less carbon atoms, and still more preferably 8 or more and 12 or less carbon atoms.

[0033] The method for producing the compound represented by the formula (1) is not particularly limited, and the compound can be produced by a known method. For example, butylene oxide and ethylene oxide are added to an unsaturated alcohol having a terminal unsaturated group by a known method, or only ethylene oxide is added to obtain a polyoxyalkylene alkenyl ether, which is reacted with a known sulfating agent, and further neutralized with an alkali metal hydroxide or ammonia as necessary to obtain an alkali metal salt or an ammonium salt.

[0034] Examples of the compound represented by the formula (1) include polyoxyalkylene alkenyl ether, polyoxyalkylene alkenyl ether sulfate, polyoxyalkylene alkenyl ether phosphate, polyoxyalkylene alkenyl ether carboxylate, polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate, polyoxyethylene-1-(allyloxymethyl) alkyl ether phosphate, polyoxyethylene-1-(allyloxymethyl) alkyl ether carboxylate, etc. Among these, one or more selected from polyoxyalkylene alkenyl ether ammonium sulfate, polyoxyalkylene alkenyl ether, and polyoxyethylene-1-(allyloxymethyl) alkyl ether ammonium sulfate are preferred. Commercially available examples of the compound represented by formula (1) include trade names: LATEMULU PD-104, PD-105, PD-420, PD-430, and PD-450 manufactured by Kao Corporation, and trade name: AQUALON KH-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0035] [Compound represented by formula (4)] The compound represented by the following formula (4) is polyoxyethylene styrenated propenyl phenyl ether or a sulfate thereof.

[0036] [ka]

[0037] In formula (4), EO represents ethylene oxide, p and q each independently represent an integer of 1 or more and 200 or less, and X represents a hydrogen atom, -SO3M, PO3M, or COOM (M is an alkali metal atom or an ammonium ion). p is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, and further preferably 1 or more and 3 or less. q is preferably 1 or more and 100 or less, more preferably 1 or more and 50 or less, and further preferably 2 or more and 20 or less. X is preferably -SO3NH4 (ammonium sulfate).

[0038] The method for producing the compound represented by the formula (4) is not particularly limited, and the compound can be produced by a known method. For example, styrenated phenol and halogenated propenyl are reacted with a basic substance such as sodium hydroxide or potassium hydroxide to obtain styrenated propenyl phenyl ether, which is then heated to rearrange the propenyl group to obtain styrenated propenyl phenol. Next, ethylene oxide is added to the styrenated propenyl phenol in the presence of an alkali catalyst at high temperature and high pressure to obtain polyoxyethylene styrenated propenyl phenyl ether, which is reacted with a known sulfating agent, and further neutralized with an alkali metal hydroxide or ammonia as necessary to obtain an alkali metal salt or an ammonium salt.

[0039] A suitable example of the compound represented by the formula (4) is polyoxyethylene styrenated propenyl phenyl ether ammonium sulfate, in which p is 1 or more and 5 or less. Examples of commercially available products of the compound represented by the formula (4) include trade names Aqualon AR-10, AR-1025, AR-20, and AR-2020 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0040] [Production of Modified Polyester Resin] In the present invention, from the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink, the modified polyester resin is preferably produced as polymer particles dispersed as a polymer emulsion by a conventional emulsion polymerization reaction of a raw material polyester resin and a compound represented by the formula (1) or (4) in a solvent having an aqueous continuous phase. The amount of the compound represented by formula (1) or (4) used is preferably in the range of a mass ratio [(B) / (A)] of the amount (B) of the structural units derived from the compound represented by formula (1) or (4) to the total amount (A) of the structural units derived from the alcohol component and the structural units derived from the carboxylic acid component in the modified polyester resin, such that the mass ratio is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and is preferably 0.4 or less, more preferably 0.35 or less, even more preferably 0.32 or less.

[0041] In the reaction, a polymerization initiator that can be used is, for example, a persulfate such as ammonium persulfate or potassium persulfate, an organic peroxide, or an azo-based initiator. The reaction temperature varies depending on the type of polymerization initiator, etc., but is preferably 60° C. or higher, more preferably 70° C. or higher, and is preferably 90° C. or lower, more preferably 85° C. or lower. From the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink, the glass transition temperature of the obtained modified polyester resin is preferably 45° C. or higher, more preferably 50° C. or higher, even more preferably 52° C. or higher, and is preferably 90° C. or lower, more preferably 80° C. or lower, even more preferably 70° C. or lower. From the same viewpoints as above, the weight average molecular weight of the resulting modified polyester resin is preferably 100,000 or more, more preferably 200,000 or more, even more preferably 400,000 or more, and preferably 2 million or less, more preferably 1.5 million or less, even more preferably 1 million or less. The glass transition temperature and weight average molecular weight of the modified polyester resin can be measured by the method described in the Examples. These physical properties can be adjusted to the desired values ​​by appropriately adjusting the ratio of the reaction components used, the reaction temperature, and the reaction time.

[0042] D of the resulting dispersion of modified polyester resin particles 50 From the viewpoint of improving the storage stability of the aqueous dispersion and the aqueous ink, the average particle size (the cumulative 50% value calculated from the small particle side in the frequency distribution of scattering intensity) is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and is preferably 800 nm or less, more preferably 600 nm or less, even more preferably 400 nm or less. In addition, D 50 The measurement can be carried out using a laser particle analysis system ELS-8000 manufactured by Otsuka Electronics Co., Ltd. or the like.

[0043] [Aqueous dispersion] The aqueous dispersion of the present invention contains the modified polyester resin of the present invention. The aqueous dispersion of the present invention can also be used as an aqueous composition containing a water-soluble organic solvent. (Water-soluble organic solvent) The water-soluble organic solvent used may be either liquid or solid at 25°C, but when the organic solvent is dissolved in 100 mL of water at 25°C, the amount of the dissolved organic solvent is 10 mL or more. From the viewpoint of improving the wetting and spreading properties of the ink, the boiling point of the water-soluble organic solvent is preferably 120° C. or higher, more preferably 150° C. or higher, and is preferably 250° C. or lower, more preferably 240° C. or lower. Examples of the water-soluble organic solvent include glycol ethers such as alkylene glycol ethers, polyhydric alcohols such as propylene glycol, amide compounds, etc. Among these, alkylene glycol ethers are preferred. The alkylene glycol ether is preferably at least one selected from diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and dipropylene glycol monomethyl ether, and more preferably diethylene glycol monobutyl ether.

[0044] [Water-based ink] The water-based ink of the present invention contains the modified polyester resin of the present invention and a pigment. The water-based ink of the present invention preferably further contains a water-soluble organic solvent, a surfactant, and, if necessary, various additives such as a humectant, a wetting agent, a penetrating agent, a viscosity adjuster, an antifoaming agent, a preservative, an antifungal agent, and an antirust agent.

[0045] (Pigments) The pigment used in the water-based ink may be either an inorganic pigment or an organic pigment. Specific examples of inorganic pigments include carbon black, metal oxides such as titanium oxide, iron oxide, red iron oxide, and chromium oxide, and pearlescent pigments. Specific examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, and chelate azo pigments; and polycyclic pigments such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, and threne pigments. There are no particular limitations on the hue, and any of achromatic pigments such as white, black, and gray; and chromatic organic pigments such as yellow, magenta, cyan, blue, red, orange, and green can be used. The above pigments can be used alone or in combination of two or more kinds.

[0046] From the viewpoint of improving the storage stability of the water-based ink, the pigment is preferably contained in the form of pigment-containing polymer particles. Polymer particles containing a pigment (hereinafter also referred to as "pigment-containing polymer particles") include particles in which the polymer encompasses the pigment, particles consisting of a polymer and a pigment with part of the pigment exposed on the surface, particles in which the polymer is adsorbed to part of the pigment, and mixtures of these forms, with the pigment-encompassing polymer particle form being more preferred.

[0047] (Polymer a) There are no particular limitations on the polymer a constituting the pigment-containing polymer particles so long as it has pigment dispersibility, but from the viewpoint of storage stability of the water-based ink, etc., vinyl resins are preferred. When polymer a is a vinyl resin, polymer a preferably contains a structural unit derived from (meth)acrylic acid and further contains a structural unit derived from a hydrophobic monomer. The term "hydrophobic" for a hydrophobic monomer means that when the monomer is dissolved in 100 g of ion-exchanged water at 25° C. until it is saturated, the amount of the monomer that dissolves is less than 10 g. Specific examples of hydrophobic monomers include those described in paragraphs

[0020] to

[0022] of JP 2018-83938 A. Among these, one or more selected from alkyl (meth)acrylates having an alkyl group having 1 to 22 carbon atoms, styrene, α-methylstyrene, and benzyl (meth)acrylate are preferred, and one or more selected from styrene and α-methylstyrene are more preferred. The polymer a may further have a structural unit derived from a nonionic monomer. Specific examples of the nonionic monomer include those described in paragraph

[0018] of JP 2018-83938 A. Among these, one or more selected from methoxypolyethylene glycol (n = 1 to 30) (meth)acrylate and polypropylene glycol (n = 2 to 30) (meth)acrylate are preferred.

[0048] (Content of each structural unit in polymer a) From the viewpoint of improving the storage stability of the water-based ink, the content of structural units derived from (meth)acrylic acid in polymer a is preferably 15% by mass or more, more preferably 20% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less. From the same viewpoints as above, the content of structural units derived from hydrophobic monomers in polymer a is preferably 85% by mass or less, more preferably 80% by mass or less, and preferably 40% by mass or more, more preferably 50% by mass or more. When polymer a contains a nonionic monomer constituent unit, the content thereof is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less. The content of the structural units derived from (meth)acrylic acid and hydrophobic monomer in the polymer a can be determined by measurement, or can be substituted by the charging ratio of the raw material monomers including (meth)acrylic acid and hydrophobic monomer during the production of the polymer a.

[0049] (Production of polymer a) The polymer a can be obtained by copolymerizing a monomer mixture of (meth)acrylic acid and a hydrophobic monomer by a known solution polymerization method or the like. There is no limitation on the solvent used in the solution polymerization method, but polar solvents such as water, lower aliphatic alcohols, ketones such as methyl ethyl ketone, ethers, and esters are preferred. In the polymerization, a polymerization initiator such as an azo compound or a persulfate, or a polymerization chain transfer agent such as a mercaptan can be used. The polymerization temperature varies depending on the type of polymerization initiator, monomer, and solvent used, but is preferably 30° C. or higher, more preferably 50° C. or higher, and is preferably 95° C. or lower, more preferably 80° C. or lower. After removing the organic solvent used in the production, the polymer a is preferably dispersed in water to prepare an aqueous dispersion, which is then used in the production of an aqueous dispersion of pigment-containing polymer particles, which will be described later.

[0050] From the viewpoint of improving the storage stability of the water-based ink, the number average molecular weight of polymer a is preferably 3,000 or more, more preferably 6,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less. From the same viewpoint as above, the acid value of polymer a is preferably 150 mgKOH / g or more, more preferably 180 mgKOH / g or more, and preferably 350 mgKOH / g or less, more preferably 300 mgKOH / g or less. The number average molecular weight and acid value of the polymer a can be measured by the method described in the Examples.

[0051] <Production of Water Dispersion of Pigment-Containing Polymer Particles> The aqueous dispersion of the pigment-containing polymer particles can be efficiently produced by a method having the following step I. If necessary, a crosslinking treatment can also be carried out. Step I: A step of dispersing a pigment mixture containing polymer a, an organic solvent, a pigment, and water to obtain a dispersion of pigment-containing polymer particles, and then removing the organic solvent from the dispersion to obtain an aqueous dispersion of pigment-containing polymer particles (hereinafter also referred to as "aqueous pigment dispersion").

[0052] In step I, a method is preferred in which polymer a is first dissolved in an organic solvent, and then a pigment, water, a neutralizing agent, and optionally a surfactant, etc. are added to the obtained polymer solution and mixed to obtain an oil-in-water dispersion. There are no limitations on the organic solvent in which polymer a is dissolved, but alcohols, ketones, ethers, esters, etc. are preferred, and ketones having 4 to 8 carbon atoms are more preferred.

[0053] (Neutralization of polymer a) At least a part of the acid groups of the polymer a is preferably neutralized with a neutralizing agent. When the polymer a is neutralized, the neutralization is preferably performed so that the pH is 6 or more and 10 or less. As the neutralizing agent, from the viewpoint of improving storage stability, etc., an alkali metal compound or the like is preferable, an alkali metal hydroxide is more preferable, and sodium hydroxide is further preferable. Furthermore, prior to step I, the polymer a may be neutralized in advance. From the same viewpoint as above, the amount of the neutralizing agent used is preferably 20 mol % or more, more preferably 40 mol % or more, and preferably 150 mol % or less, more preferably 100 mol % or less. Here, the equivalent amount of the neutralizing agent used can be calculated by the following formula, where polymer a before neutralization is "polymer a'". Equivalent amount of neutralizing agent used (mol%)=[{weight of neutralizing agent added (g) / equivalent amount of neutralizing agent} / [{acid value of polymer a' (mg KOH / g) × weight of polymer a' (g)} / (56 × 1,000)]] × 100

[0054] The dispersion treatment in step I can be carried out by a known method. For example, a method is preferred in which pre-dispersion is carried out using a commonly used mixing and stirring device such as an anchor blade or a dispersing blade, and then main dispersion is carried out using a kneading machine such as a roll mill or a kneader, a high-pressure homogenizer such as a microfluidizer, or a media-type dispersing machine such as a paint shaker or a bead mill. In this dispersion, it is preferable to adjust the average particle size of the pigment particles in the pigment aqueous dispersion by controlling the treatment pressure and the number of passes using a high-pressure homogenizer.

[0055] By removing the organic solvent from the obtained dispersion by a known method, an aqueous dispersion of the pigment-containing polymer particles can be obtained. From the viewpoints of reducing coarse particles and improving the continuous ejection properties of the water-based ink, the average particle size of the pigment-containing polymer particles in the pigment water dispersion is preferably 80 nm or more, more preferably 85 nm or more, and even more preferably 90 nm or more, and is preferably 300 nm or less, and more preferably 200 nm or less. The average particle size of the pigment-containing polymer particles in the water-based ink is substantially the same as the average particle size of the pigment-containing polymer particles in the pigment water dispersion. The non-volatile component concentration (solids concentration) of the resulting pigment water dispersion is preferably 10% by mass or more, more preferably 20% by mass or more, from the viewpoint of improving dispersion stability and facilitating the preparation of a water-based ink, and is preferably 40% by mass or less, more preferably 35% by mass or less. The average particle size and solid content are measured by the methods described in the Examples.

[0056] (Water-soluble organic solvent) The water-soluble organic solvent used in the water-based ink is the same as the water-soluble organic solvent explained in the section on the water-based dispersion, and therefore the explanation thereof will be omitted here.

[0057] (Surfactant) The surfactant is not particularly limited, but a nonionic surfactant is preferred, and one or more surfactants selected from acetylene glycol surfactants and silicone surfactants are preferred. Examples of acetylene glycol surfactants include acetylene diols such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-ol, and 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, and ethylene oxide adducts thereof. Commercially available examples of acetylene glycol surfactants include the "Surfynol" series and "Olfine" series manufactured by Nissin Chemical Industry Co., Ltd., and the "Acetylenol" series manufactured by Kawaken Fine Chemicals Co., Ltd.

[0058] Examples of silicone surfactants include dimethylpolysiloxane, polyether-modified silicone, amino-modified silicone, and carboxy-modified silicone, with polyether-modified silicone being preferred. Specific examples of polyether-modified silicones include PEG-3 dimethicone, PEG-9 dimethicone, PEG-9PEG-9 dimethicone, PEG-9 methyl ether dimethicone, PEG-10 dimethicone, PEG-11 methyl ether dimethicone, PEG / PPG-20 / 22 butyl ether dimethicone, PEG-32 methyl ether dimethicone, PEG-9 polydimethylsiloxyethyl dimethicone, lauryl PEG-9 polydimethylsiloxyethyl dimethicone, and the like. Specific examples of polyether-modified silicone surfactants include KF series manufactured by Shin-Etsu Chemical Co., Ltd., Silface SAG005 manufactured by Nissin Chemical Industry Co., Ltd., and BYK-348 manufactured by BYK Japan K.K.

[0059] (Content of each component in the water-based ink of the present invention) From the viewpoint of improving the storage stability of the water-based ink of the present invention, the content of each component in the water-based ink is as follows. (Pigment content) The content of the pigment in the water-based ink is preferably 1% by mass or more, more preferably 3% by mass or more, and is preferably 15% by mass or less, more preferably 10% by mass or less. The content of the polymer in the water-based ink is preferably 1% by mass or more, more preferably 2% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less. (Modified polyester resin content) The content of the modified polyester resin of the present invention in the water-based ink is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 4% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less.

[0060] The total content of the water-soluble organic solvents in the water-based ink is preferably 15% by mass or more, more preferably 25% by mass or more, and is preferably 45% by mass or less, more preferably 40% by mass or less. The content of the surfactant in the water-based ink is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and is preferably 3% by mass or less, more preferably 2% by mass or less. The water content in the water-based ink is preferably 45% by mass or more, more preferably 50% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less. From the viewpoints of storage stability, reduced corrosiveness, etc., the pH of the water-based ink is preferably 7.0 or more, more preferably 7.5 or more, and is preferably 11 or less, more preferably 10 or less. The water-based ink of the present invention can be loaded into a known ink-jet printing device and ejected as ink droplets onto plain paper or other low water-absorbent printing medium to obtain an image or the like. EXAMPLES

[0061] In the following Production Examples, Examples and Comparative Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The methods for measuring each physical property are as follows.

[0062] (1) Acid value of polyester resin Polyester resin P-1 or P-2 was dissolved in a titration solvent of toluene and acetone (2:1) in an automatic potentiometric titrator (Kyoto Electronics Manufacturing Co., Ltd., electric burette, model number: APB-610), and titrated with 0.1N potassium hydroxide / ethanol solution by potentiometric titration, with the inflection point on the titration curve as the end point. The acid value was calculated from the titration amount of potassium hydroxide solution up to the end point.

[0063] (2) Softening point of polyester resin Using a flow tester (Shimadzu Corporation, product name: CFT-500D), a part of the sample was heated at a temperature increase rate of 6°C / min while applying a load of 1.96 MPa with a plunger, and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger descent amount of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

[0064] (3) Glass transition temperature (Tg) of polyester resin Using a differential scanning calorimeter (manufactured by TA Instruments Japan, product name: Q-100), 0.01 to 0.02 parts of the sample was weighed into an aluminum pan, heated from room temperature (20°C) to 200°C at a heating rate of 10°C / min, and cooled from that temperature to 0°C at a heating rate of 10°C / min. The sample was then heated to 180°C at a heating rate of 10°C / min, and the glass transition temperature was determined as the temperature at the intersection of the extension of the baseline below the highest endothermic peak temperature and the tangent showing the maximum slope from the rising part of the peak to the apex of the peak.

[0065] (4) Weight average molecular weight (Mw) and number average molecular weight (Mn) of resin The measurement was performed by the following gel permeation chromatography method. (4-1) Preparation of sample solution Polyester resin was dissolved in chloroform to a concentration of 0.5 g / 100 mL, and the resulting solution was filtered using a fluororesin filter "FP-200" (manufactured by Sumitomo Electric Industries, Ltd.) with a pore size of 2 μm to remove insoluble components, thereby preparing a sample solution. (4-2) Molecular weight measurement A high-performance liquid chromatography measuring device (manufactured by Tosoh Corporation, product name: CO-8010) and an analytical column (manufactured by Tosoh Corporation, "GMHXL" + "G3000HXL") were used, and tetrahydrofuran was passed as a dissolving solution at a flow rate of 1 mL / min, and the column was stabilized in a thermostatic bath at 40°C. 100 μL of the sample solution was injected into the column and the measurement was performed. The average molecular weight of the sample was measured using monodisperse polystyrene (manufactured by Tosoh Corporation; 2.63 × 10 3 , 2.06×10 4 , 1.02×10 5 , GL Sciences Inc.; 2.10 x 10 3 , 7.00×10 3 , 5.04×10 4 ] was used as a standard sample and calculations were made based on a calibration curve prepared in advance.

[0066] (5) Solid content concentration 10.0 g of sodium sulfate was weighed out in a 30 mL polypropylene container (inner diameter 40 mm, height 30 mm) and 1.0 g of the sample was added thereto and mixed to obtain a mixture. The mixture was then weighed and maintained at 105°C for 2 hours to remove volatiles, and further left in the desiccator for 15 minutes, and the mass of the mixture after volatiles removal was measured. The mass of the mixture after volatiles removal minus the mass of sodium sulfate was determined as the solid content of the sample after volatiles removal, and this was divided by the mass of the sample before volatiles removal to obtain the solid content concentration (%).

[0067] (6) Average particle size of water-based dispersions and water-based inks The cumulant average particle size measured using a laser particle analysis system (Otsuka Electronics Co., Ltd., product name: ELS-8000, cumulant analysis) was taken as the average particle size of the particles in the water-based dispersion or water-based ink. The measurement conditions were a temperature of 25°C, an angle between the incident light and the detector of 90°, and 100 integrations. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measured concentration was usually 5×10 -3 It was done in %.

[0068] (7) 13 C-NMR measurement conditions The sample was dissolved in deuterated dimethyl sulfoxide, and a superconducting Fourier transform nuclear magnetic resonance spectrometer (manufactured by JEOL, product name: JNM-ECA600, 600 MHz) was used under the following conditions: pulse width: 5.9 μs (90° pulse width: 17.7 μs), observation width: 150 kHz (250 ppm), waiting time: 20 s, number of integrations: 10240, measurement temperature: room temperature. 13 C-NMR measurements were performed.

[0069] Production Examples 1-1 to 1-2 (Production of Polyester Resins P-1 to P-2) The raw material monomers (alcohol components and carboxylic acid components), esterification catalyst, and esterification promoter shown in Table 1 were mixed in the amounts shown in Table 1 and placed in a 10 L four-neck flask equipped with a thermometer, a stirrer, a downflow condenser, and a nitrogen inlet tube, and reacted in a mantle heater in a nitrogen atmosphere at 210°C for 10 hours. The pressure of the system was then reduced to -8.3 kPa (G), and the reaction was continued until the softening point reached the temperature shown in Table 1, to obtain polyester resins P-1 to P-2. The results are shown in Table 1.

[0070] [Table 1]

[0071] Production Examples 2-1 to 2-2 (Production of Water Dispersions D-1 to D-2 of Polyester Resin Particles) In a four-neck flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer, and a thermocouple, polyester resin P-1 or P-2 obtained in Production Example 1-1 or 1-2 and methyl ethyl ketone (MEK) were placed in the ratio shown in Table 2 and dissolved at 25°C. Next, a 5N aqueous solution of sodium hydroxide was added as a neutralizing agent, and ion-exchanged water was added under stirring to obtain a dispersion of polyester resin particles. The obtained dispersion was kept in the four-neck flask and stirred while being kept at 60° C., and the pressure was reduced to remove the MEK. After cooling to room temperature, ion-exchanged water was added and filtered through a 200-mesh wire screen to obtain aqueous dispersions D-1 to D-2 of polyester resin particles. The results are shown in Table 2.

[0072] [Table 2]

[0073] Example I-1 (Production of modified polyester resin having structural units derived from formula (1)) In a 1000 mL separable flask, the aqueous dispersion D-1 of polyester resin P-1 particles obtained in Production Example 2-1, polyoxyalkylene alkenyl ether ammonium sulfate (manufactured by Kao Corporation, product name: LATEMURU PD-104) as a reactive surfactant, ammonium persulfate (polymerization initiator), and ion-exchanged water were added in the ratios shown in Table 3, and nitrogen gas replacement was thoroughly performed. Under a nitrogen atmosphere, the mixture was heated to 80°C while stirring (200 rpm) with a stirring blade, and reacted for 5 hours. After cooling to room temperature, the mixture was filtered through a 200 mesh wire net to obtain an aqueous dispersion E-1 of modified polyester resin MP-1 (weight average molecular weight: 678,000) particles having a structural unit derived from the compound represented by formula (1).

[0074] Examples I-2 to I-7 (Production of modified polyester resin having structural units derived from formula (1)) In Example I-1, except for changing the conditions as shown in Table 3, the same procedure as in Example I-1 was repeated to obtain aqueous dispersions E-2 to E-7 of modified polyester resin particles MP-2 to MP-7 having structural units derived from the compound represented by formula (1).

[0075] Example I-8 (Production of modified polyester resin having structural units derived from formula (4)) In Example I-1, a water dispersion E-8 of modified polyester resin MP-8 particles having a structural unit derived from the compound represented by formula (4) was obtained in the same manner as in Example I-1, except that polyoxyethylene styrenated propenyl phenyl ether ammonium sulfate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Aqualon AR-10) was used as the reactive surfactant.

[0076] Example I-9 (Preparation of modified polyester resin having structural units derived from formula (1)) In Example I-1, except that the aqueous dispersion D-2 of the polyester resin P-2 particles obtained in Production Example 2-2 was used, the same procedure as in Example I-1 was repeated to obtain an aqueous dispersion E-9 of modified polyester resin MP-9 particles having a structural unit derived from the compound represented by formula (1).

[0077] The results of Examples I-1 to I-9 are shown in Table 3. The composition (%) of the aqueous dispersion in Table 3 is the amount of effective content (solid content). Details of each reactive surfactant in Table 3 are as follows: · LATEMURU PD-104: Polyoxyalkylene alkenyl ether ammonium sulfate (RO-(BO) m -(EO) n -SO3NH4), Kao Corporation, product name, solid content: 20% · LATEMURU PD-420: Polyoxyalkylene alkenyl ether (RO-(BO) m -(EO) n -H), Kao Corporation, product name, solid content: 100% Aqualon KH-10: Polyoxyethylene-1-(allyloxymethyl) alkyl ether ammonium sulfate, product name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., average number of moles of EO added: 10, solid content: 100% Aqualon AR-10: Polyoxyethylene styrenated propenyl phenyl ether ammonium sulfate, product name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., average number of moles of EO added: 10, solid content: 100%

[0078] [Table 3]

[0079] <Confirmation of modified polyester resin structure> (1) The aqueous dispersion E-1 of modified polyester resin MP-1 particles obtained in Example I-1 (reactive surfactant LATEMURU PD-104 was used) was freeze-dried under drying conditions (freezing at -25°C for 1 hour, reducing pressure at -10°C for 9 hours, reducing pressure at 25°C for 5 hours, reducing pressure at 5 Pa) using a freeze dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain modified polyester resin MP-1 having a structure represented by formula (1). Then, 1 g of polyester resin MP-1 was dissolved in 5 g of deuterated dimethyl sulfoxide, 13 C-NMR measurements were performed. (2) 5 g of the aqueous dispersion D-1 of the polyester resin P-1 obtained in Production Example 2-1, 2.5 g of the reactive surfactant LATEMUL PD-104, and 2.5 g of ion-exchanged water were added to obtain aqueous dispersion D-3 (a mixed resin of polyester resin P-1 and reactive surfactant LATEMUL PD-104. The solids concentration of polyester resin P-1 in the aqueous dispersion: 20%, and the solids concentration of PD-104: 5%). The resulting aqueous dispersion D-3 was freeze-dried in the same manner as in (1) above to obtain mixed resin P-3 (mixed resin of polyester resin P-1 and reactive surfactant LATEMURU PD-104). Using 1 g of the resultant mixed resin P-3, the polyester resin P-3 was prepared in the same manner as in (1). 13 C-NMR measurements were performed. (3) Dissolve 1 g of reactive surfactant LATEMUL PD-104 in 5 g of deuterated dimethyl sulfoxide. 13 C-NMR measurements were performed. These 13 The C-NMR measurement chart is shown in Figure 1.

[0080] <Measurement of molecular weight distribution of reactive surfactant> (1) In a 1000 mL separable flask, 200 g of reactive surfactant LATEMURU PD-104 (40 g as solid content), 8 g of ammonium persulfate (polymerization initiator), and 592 g of ion-exchanged water were placed, and the flask was thoroughly purged with nitrogen gas. The mixture was heated to 80°C under a nitrogen atmosphere while stirring with a stirring blade (200 rpm), and reacted for 5 hours. After cooling to room temperature, the mixture was filtered through a 200 mesh wire net to obtain reaction liquid S-1. The resulting reaction solution S-1 was freeze-dried to obtain resin B-1. Thereafter, resin B-1 was dissolved in chloroform to a concentration of 0.5 g / 100 mL, and the molecular weight distribution was measured by the same method as that for measuring the weight average molecular weight of polyester resins. (2) The reactive surfactant LATEMURU PD-104 was dissolved in chloroform in the same manner as in (1) above, and the molecular weight distribution was measured. These molecular weight distribution curves are shown in FIG.

[0081] Figure 1 shows: 13 The C-NMR peaks of the reactive surfactant LATEMURU PD-104, the peaks of the mixed resin P-3 before reacting with the reactive surfactant, and the peaks of the modified polyester resin MP-1 obtained by reaction are shown in Fig. 1. It can be seen from Fig. 1 that the peaks derived from the carbon-carbon double bonds of the reactive surfactant LATEMURU PD-104 having the structure represented by formula (1) disappear in the modified polyester resin MP-1 after the reaction. On the other hand, as shown in Fig. 2, the molecular weight distribution of the reactive surfactant PD-104 hardly changes, and therefore it is understood that the reactive surfactant PD-104 hardly polymerizes by itself. This confirmed that the reactive surfactant PD-104 reacted with the polyester resin P-1 to obtain the modified polyester resin MP-1 having a constitutional unit derived from the compound represented by formula (1).

[0082] Examples II-1 to II-9 and Comparative Example II-1 (Preparation of Aqueous Composition) The aqueous dispersions E-1 to E-9 obtained in Examples I-1 to I-9, an organic solvent (BDG: diethylene glycol monobutyl ether), and ion-exchanged water were mixed according to the formulations shown in Table 4 to obtain aqueous compositions 1 to 9. The results are shown in Table 4. Comparative Example II-1 is an example in which the aqueous dispersion D-1 of the polyester resin P-1 particles obtained in Production Example 2-1 was used. The composition (%) of the aqueous composition in Table 4 is the amount of active matter (solids).

[0083] (Evaluation of storage stability) The obtained aqueous composition was stored in a constant temperature environment of 70°C, and the particle size of the aqueous composition after 14 days was measured. The rate of change in particle size (%) before and after storage was calculated using the following formula, and the storage stability was evaluated. The results are shown in Table 4. Particle size change rate (%)=[(particle size of aqueous composition after storage (nm) / particle size of aqueous composition before storage (nm))−1]×100 The smaller the rate of change in particle size, the more excellent the storage stability is, and a rate of change of 10% or less is practically acceptable.

[0084] [Table 4]

[0085] From Table 4, it can be seen that the aqueous compositions containing the modified polyester resin of the present invention obtained in Examples II-1 to II-9 have significantly superior storage stability compared to the aqueous composition not containing the modified polyester resin obtained in Comparative Example II-1.

[0086] Examples III-1 to III-9, Comparative Example III-1 (Production of Water-Based Ink) (1) Preparation of pigment dispersion polymer solution S-1 A monomer mixture was prepared by mixing 61.5 parts of acrylic acid, 129.5 parts of styrene, and 9.0 parts of α-methylstyrene. 20 parts of methyl ethyl ketone (MEK), 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the monomer mixture were mixed in a reaction vessel, and the atmosphere was thoroughly replaced with nitrogen gas. Meanwhile, a mixture of the remaining 90% of the monomer mixture, 0.27 parts of the polymerization chain transfer agent, 60 parts of MEK, and 2.2 parts of an azo-based radical polymerization initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: V-65, 2,2'-azobis(2,4-dimethylvaleronitrile)) was placed in a dropping funnel, and the monomer mixture in the reaction vessel was heated to 65°C while stirring under a nitrogen atmosphere, and the mixture in the dropping funnel was dropped over 3 hours. After 2 hours at 65°C from the end of the dropping, a solution in which 0.3 parts of the polymerization initiator was dissolved in 5 parts of MEK was added, and the mixture was further aged at 65°C for 2 hours and 70°C for 2 hours to obtain a pigment dispersion polymer (number average molecular weight of the polymer: 12000, acid value: 240mgKOH / g) solution S-1.

[0087] (2) Preparation of Pigment Water Dispersion A-1 25 parts of the polymer obtained by drying the pigment dispersion polymer solution S-1 obtained in (1) above under reduced pressure was mixed with 39.3 parts of MEK, and 7.9 parts of a 5N aqueous sodium hydroxide solution (sodium hydroxide solid content: 16.9%) was added to neutralize the ratio of the moles of sodium hydroxide to the moles of carboxyl groups of the polymer to 50% (neutralization degree: 50 mol%), and 200 parts of ion-exchanged water A were added. 58.3 parts of cyan pigment (CI Pigment Blue 15:3, manufactured by DIC Corporation, product name: TGR-SD) was added, and the mixture was stirred for 60 minutes using a disper (manufactured by Asada Iron Works Co., Ltd., product name: Ultra Disper) at 20°C with the disper blade rotating at 7000 rpm. The resulting mixture was subjected to 10-pass dispersion treatment at a pressure of 200 MPa using a Microfluidizer (trade name, manufactured by Microfluidics). 250 parts of ion-exchanged water was added to the resulting dispersion, and after stirring, MEK was completely removed at 60°C under reduced pressure, and some water was further removed. The mixture was filtered using a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a 5 μm filter (acetyl cellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to remove coarse particles, thereby obtaining a pigment water dispersion A-1 (average particle size: 108 nm) containing pigment-containing polymer particles with a solid content concentration of 30%.

[0088] (3) Manufacturing of water-based inks Using the pigment water dispersion A-1 obtained in (2) above, the water dispersion of modified polyester resin particles, an organic solvent, a surfactant, and ion-exchanged water, the components were mixed according to the formulations shown in Table 5 to obtain water-based inks 1 to 9 and 11. The results are shown in Table 5. The composition (%) of the water-based ink in Table 5 is the amount of effective content (solid content). The details of each component in Table 5 are as follows. BDG: Diethylene glycol monobutyl ether S-104PG50: Acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd., product name: Surfynol 104PG50 (2,4,7,9-tetramethyl-5-decyne-4,7-diol in propylene glycol, active content 50%) SAG005: Polyether modified silicone surfactant, manufactured by Nissin Chemical Industry Co., Ltd., product name: Silface SAG005

[0089] (Evaluation of storage stability) The obtained water-based ink was stored in a constant temperature environment of 70° C., and the particle size of the water-based ink was measured after 14 days. The rate of change (%) in particle size after storage relative to the particle size before storage was calculated, and the storage stability was evaluated. The results are shown in Table 5. Particle size change rate (%) = [(particle size of water-based ink after storage (nm) / particle size of water-based ink before storage (nm)) - 1] x 100 The smaller the rate of change in particle size, the better the storage stability is, and a rate of change of 10% or less is practically acceptable.

[0090] [Table 5]

[0091] From Table 5, it can be seen that the water-based inks containing the polyester resin of the present invention obtained in Examples III-1 to III-9 have significantly superior storage stability compared to the water-based ink obtained in Comparative Example III-1.

Claims

1. A modified polyester resin in which a structural unit derived from a compound represented by the following formula (1) or (4) is directly bonded to a polyester resin: 【Chemistry 1】 [In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents an alkylene group having 1 to 5 carbon atoms; R ３ represents a group represented by the following formula (2) or (3). 【Chemistry 2】 In the formula (2) or (3), BO represents butylene oxide, EO represents ethylene oxide, m and n each independently represent an integer of 1 or more and 200 or less, X represents a hydrogen atom, -SO ３ M., P.O. ３ M or COOM (M is an alkali metal atom or an ammonium ion), R ４ represents an alkyl group having 5 to 30 carbon atoms. * represents the bonding site with -O- in formula (1). 【Chemistry 3】 In the formula (4), EO represents ethylene oxide, p and q each independently represent an integer of 1 or more and 200 or less, and X represents a hydrogen atom or -SO ３ M., P.O. ３ M, or COOM (M is an alkali metal atom or an ammonium ion).

2. The modified polyester resin according to claim 1, wherein the compound represented by formula (1) is at least one selected from polyoxyalkylene alkenyl ether ammonium sulfate, polyoxyalkylene alkenyl ether, and polyoxyethylene-1-(allyloxymethyl) alkyl ether ammonium sulfate.

3. The modified polyester resin according to claim 1 or 2, wherein the compound represented by formula (4) is polyoxyethylene styrenated propenyl phenyl ether ammonium sulfate, in which p is an integer of 1 or more and 5 or less.

4. The modified polyester resin according to any one of claims 1 to 3, wherein the mass ratio [(B) / (A)] of the amount (B) of the structural units derived from the compound represented by formula (1) or (4) to the total amount (A) of the structural units derived from the alcohol component and the structural units derived from the carboxylic acid component in the modified polyester resin is 0.01 or more and 0.4 or less.

5. An aqueous dispersion comprising the modified polyester resin according to any one of claims 1 to 4.

6. 5. A water-based ink comprising the modified polyester resin according to claim 1 and a pigment.

7. The water-based ink of claim 6, wherein the pigment is in the form of pigment-containing polymer particles.

8. 8. The water-based ink of claim 6 or 7 for ink-jet printing.

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