Binder for inkjet printing inks, inkjet printing ink, and printed article

Abstract

The present invention provides a binder for inkjet printing inks, the binder comprising an aqueous urethane resin composition that comprises: a urethane resin, which is prepared using a polyol compound, a polyisocyanate compound and a neutralizing agent as essential starting materials; and an aqueous medium. In the binder, the polyol compound has an aromatic ring concentration within the range of 2,000 to 5,000 mmol / kg, the polyol compound contains a polyester polyol which is prepared using terephthalic acid and / or isophthalic acid as a starting material, the neutralizing agent contains a hydroxide of an alkali metal, and the urethane resin has an acid value within the range of 30 to 60 mgKOH / g. This binder for inkjet printing inks has excellent storage stability, ejection properties and friction resistance.

Description

Binder for inkjet printing ink, inkjet printing ink and printed matter

[0001] The present invention relates to a binder for inkjet printing ink that can form an inkjet printing ink having excellent storage stability, ejection properties, and abrasion resistance, an inkjet printing ink containing the binder for inkjet printing ink, and a printed matter printed with the inkjet printing ink.

[0002] In recent years, the inkjet printing industry has seen remarkable growth, with inkjet printers becoming more powerful and inks becoming more refined, making it possible for ordinary households to easily produce high-gloss, high-resolution images on a par with silver halide photographs. In particular, there has been rapid progress in improving inks, with the aim of improving image quality and reducing environmental impact, such as by switching from conventional dye-based inks to pigment-based inks and from solvent-based to water-based inks. Currently, active development is underway on water-based pigment-based inks.

[0003] Furthermore, with the advancement of performance in inkjet printers and the like, various performance requirements are being placed on the ink every year, including, for example, ink ejection stability that does not cause clogging of the ink ejection nozzles constituting the inkjet printer over time and does not cause ink ejection failure or abnormality in the ejection direction over a long period of time, and formulation stability that does not cause separation or aggregation over time in ink produced by mixing a pigment or dye and other additives with a binder resin.

[0004] As an ink for inkjet printing that is excellent in the ink ejection properties and formulation stability, for example, an ink composition containing at least a pigment, water, polymer particles of a water-insoluble vinyl polymer that encompasses the pigment and enables the pigment to be dispersed in the ink composition, and a urethane resin is known, and it is also known that a mixture of the ink composition with an acetylene glycol surfactant can be used (see, for example, Patent Document 1).

[0005] However, even the ink compositions described above fall short of achieving the extremely high levels of ejection properties and formulation stability required by industry, and may cause problems such as clogging of ink ejection nozzles over time when used over a long period of time.

[0006] On the other hand, as the fields of use of inkjet printed matter become more widespread, an even higher level of abrasion resistance is required, but the ink composition described in the above-mentioned document 1 still has the problem that, for example, when a strong external force is applied locally, the printed image may fade, deteriorate, or be damaged due to the pigment falling off, etc.

[0007] Therefore, there has been a demand for a material having even better storage stability, ejection properties and abrasion resistance.

[0008] Japanese Patent Application Laid-Open No. 2006-282760

[0009] The problem to be solved by the present invention is to provide an inkjet printing ink binder capable of forming an inkjet printing ink having excellent storage stability, ejection properties, and abrasion resistance, an inkjet printing ink containing the inkjet printing ink binder, and a printed matter printed with the inkjet printing ink.

[0010] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a specific urethane resin that uses a specific polyol compound and a specific neutralizing agent, and have completed the present invention.

[0011] Specifically, the present invention relates to an inkjet printing ink binder comprising an aqueous urethane resin composition containing a urethane resin (A) whose essential raw materials are a polyol compound (a1), a polyisocyanate compound (a2), a chain extender (a3), and a neutralizing agent (a4), and an aqueous medium (B), wherein the aromatic ring concentration of the polyol compound (a1) is in the range of 2,000 to 5,000 mmol / kg, the polyol compound (a1) contains a polyester polyol derived from terephthalic acid and / or isophthalic acid, the neutralizing agent (a4) contains an alkali metal hydroxide, and the acid value of the urethane resin (A) is in the range of 30 to 60 mgKOH / g; an inkjet printing ink containing the inkjet printing ink binder; and a printed matter printed with the inkjet printing ink.

[0012] The binder for ink-jet printing ink of the present invention has excellent storage stability, ejection properties and abrasion resistance, and therefore can be suitably used as an ink-jet printing ink.

[0013] The binder for ink-jet printing ink of the present invention is characterized by comprising an aqueous urethane resin composition containing a urethane resin (A) and an aqueous medium (B).

[0014] The urethane resin (A) used contains, as essential raw materials, a polyol compound (a1), a polyisocyanate compound (a2), a chain extender (a3), and a neutralizer (a4).

[0015] As the polyol compound (a1), a polyester polyol is used as an essential component.

[0016] The polyester polyol is obtained by an esterification reaction between a polycarboxylic acid and a polyhydric alcohol, and the polycarboxylic acid is at least one of terephthalic acid and isophthalic acid. Furthermore, the polyester polyol preferably does not have an acid group, since this provides a binder for an inkjet printing ink that can be used to form an inkjet printing ink having excellent storage stability, ejection properties, and abrasion resistance.

[0017] In addition to terephthalic acid and isophthalic acid, other polycarboxylic acids can also be used in combination as the polycarboxylic acid. Examples of the other polycarboxylic acids include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid, and esters thereof; and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, maleic acid, pimelic acid, suberic acid, azelaic acid, itaconic acid, sebacic acid, chlorendic acid, 1,2,4-butanetricarboxylic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, dimer acid, and fumaric acid, and esters thereof. These polycarboxylic acids and esters thereof can be used alone or in combination of two or more.

[0018] Examples of the polyhydric alcohol include aromatic diols such as benzenedimethanol, toluenedimethanol, and xylene dimethanol, and aliphatic polyols such as ethylene glycol, propylene glycol, 1,3-propylene diol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, and neopentyl glycol ethylene glycol. These polyhydric alcohols can be used alone or in combination of two or more.

[0019] In the esterification reaction for producing the polyester polyol, it is preferable to use an esterification catalyst for the purpose of accelerating the esterification reaction. Examples of the esterification catalyst include metals such as titanium, tin, zinc, aluminum, zirconium, magnesium, hafnium, and germanium; and metal compounds such as titanium tetraisopropoxide, titanium tetrabutoxide, titanium oxyacetylacetonate, dibutyltin oxide, dibutyltin diacetate, dibutyltin dilaurate, tin octoate, 2-ethylhexanetin, zinc acetylacetonate, zirconium tetrachloride, zirconium tetrachloride tetrahydrofuran complex, hafnium tetrachloride, hafnium tetrachloride tetrahydrofuran complex, germanium oxide, and tetraethoxygermanium. These esterification catalysts can be used alone or in combination of two or more.

[0020] The aromatic ring concentration of the polyol compound (a1) is in the range of 2,000 to 5,000 mmol / kg, and is preferably in the range of 2,500 to 5,000, more preferably in the range of 3,000 to 4,500, because a binder for an inkjet printing ink capable of forming an inkjet printing ink having excellent storage stability, jetting property, and abrasion resistance can be obtained.

[0021] As the polyol compound (a1), polyol compounds other than the polyester polyols can also be used, if necessary.

[0022] Examples of the other polyol compounds include polyether polyols, polyester polyols other than the polyester polyols, polyester ether polyols, polycarbonate polyols, etc. These polyol compounds can be used alone or in combination of two or more.

[0023] Examples of the polyether polyol include those obtained by addition polymerization of alkylene oxide using one or more compounds having two or more active hydrogen atoms as an initiator.

[0024] Examples of the initiator include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, glycerin, trimethylolethane, and trimethylolpropane.

[0025] Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, and tetrahydrofuran.

[0026] Examples of the polyether polyol include polyoxytetramethylene glycol, polypropylene glycol, polyethylene glycol, etc. The number average molecular weight of the polyether polyol is preferably in the range of 1,000 to 3,000, since this allows for the production of a binder for inkjet printing ink that can form an inkjet printing ink having excellent storage stability, ejection properties, and abrasion resistance.

[0027] Examples of the polyester polyol include those obtained by esterifying a polycarboxylic acid other than terephthalic acid and isophthalic acid with a polyhydric alcohol.

[0028] Examples of the polycarboxylic acids other than terephthalic acid and isophthalic acid include aromatic dicarboxylic acids such as phthalic acid and naphthalenedicarboxylic acid, and esters thereof, and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, maleic acid, pimelic acid, suberic acid, azelaic acid, itaconic acid, sebacic acid, chlorendic acid, 1,2,4-butanetricarboxylic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, dimer acid, and fumaric acid, and esters thereof. These polycarboxylic acids and esters thereof can be used alone or in combination of two or more.

[0029] As the polyhydric alcohol, the same polyhydric alcohols as those exemplified above can be used.

[0030] Examples of the polyester ether polyol include a polyether polyol obtained by reacting a polyether polyol in which an alkylene oxide is added to an initiator with a polycarboxylic acid. The initiator may be the same as those exemplified above, and the alkylene oxide may be the same as those exemplified above. Furthermore, the polycarboxylic acid may be the same as those exemplified above, in addition to terephthalic acid and isophthalic acid.

[0031] Examples of the polycarbonate polyol include those obtained by reacting a carbonate ester with a polyol, and those obtained by reacting phosgene with bisphenol A. Examples of the carbonate ester include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, and diphenyl carbonate. Examples of the polyol that can react with the carbonate ester include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,11-undecanediol. Examples of the polyol include relatively low molecular weight dihydroxy compounds such as ethanol, 1,12-dodecanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethylpropanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydroquinone, resorcinol, bisphenol-A, bisphenol-F, and 4,4'-biphenol; polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; and polyester polyols such as polyhexamethylene adipate, polyhexamethylene succinate, and polycaprolactone.

[0032] The content of the polyol compound (a1) in the raw materials of the urethane resin (A) is preferably in the range of 0 to 80% by mass, more preferably in the range of 5 to 70% by mass, because a binder for an inkjet printing ink can be obtained that can form an inkjet printing ink having excellent storage stability, ejection property, and abrasion resistance.

[0033] Examples of the polyisocyanate compound (a2) include aromatic polyisocyanates such as phenylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimidized diphenylmethane polyisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate; and alicyclic diisocyanates such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate. These polyisocyanate compounds can be used alone or in combination of two or more kinds.

[0034] The content of the polyisocyanate compound (a2) in the raw materials of the urethane resin (A) is preferably in the range of 10 to 60% by mass, more preferably in the range of 20 to 50% by mass, because a binder for an inkjet printing ink can be obtained that can form an inkjet printing ink having excellent storage stability, ejection property, and abrasion resistance.

[0035] The neutralizing agent (a3) ​​is an alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide.

[0036] As the neutralizing agent (a3), a neutralizing agent other than the alkali metal hydroxide (hereinafter, sometimes referred to as "other neutralizing agent") can be used in combination, if necessary.

[0037] Examples of the other neutralizing agents include triethylamine, ammonia, morpholine, monoethanolamine, and diethylethanolamine.

[0038] The amount of the neutralizer (a3) ​​used is preferably in the range of 1 to 15% by mass, more preferably 2 to 10% by mass, of the raw materials for the urethane resin (A), because a binder for an inkjet printing ink can be obtained that can form an inkjet printing ink having excellent storage stability, ejection properties, and abrasion resistance.

[0039] The urethane resin (A) may also contain a chain extender (a4) as needed.

[0040] Examples of the chain extender (a4) include diamines such as ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, and 1,4-cyclohexanediamine; and amino groups having one primary amino group and one secondary amino group such as N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylaminoethylamine, and N-methylaminopropylamine. Diamines contained therein include polyamines such as diethylenetriamine, dipropylenetriamine, and triethylenetetramine, hydrazines such as hydrazine, N,N'-dimethylhydrazine, and 1,6-hexamethylenebishydrazine, dihydrazides such as succinic acid dihydrazide, adipic acid dihydrazide, glutaric acid dihydrazide, sebacic acid dihydrazide, and isophthalic acid dihydrazide, and semicarbazides such as β-semicarbazide propionic acid hydrazide, 3-semicarbazide-propyl-carbazate, and semicarbazide-3-semicarbazidemethyl-3,5,5-trimethylcyclohexane. These chain extenders can be used alone or in combination of two or more.

[0041] The acid value of the urethane resin (A) is in the range of 30 to 60 mgKOH / g, and is preferably in the range of 35 to 55 mgKOH / g, and more preferably in the range of 40 to 55 mgKOH / g, because a binder for an inkjet printing ink capable of forming an inkjet printing ink having excellent storage stability, jetting property, and abrasion resistance can be obtained.

[0042] The method for producing the urethane resin (A) is not particularly limited, and any method may be used. For example, the urethane resin (A) may be produced by reacting all of the reaction raw materials including the polyol compound (a1), the polyisocyanate compound (a2), and the neutralizing agent (a3) ​​at once, or by reacting the reaction raw materials sequentially.

[0043] Examples of the aqueous medium (B) include ion-exchanged water, distilled water, etc. These aqueous media can be used alone or in combination of two or more.

[0044] The method for producing the aqueous urethane resin composition is not particularly limited, and any method may be used, for example, a method of mixing the urethane resin (A) and the aqueous medium (B).

[0045] Examples of methods for mixing the urethane resin (A) and the aqueous medium (B) include methods using a reaction vessel equipped with a stirring blade; a kneader such as a kneader, a continuous kneader, a taper roll, a single-screw extruder, a twin-screw extruder, a triple-screw extruder, a universal mixer, a Plastomill, or a Bodeta-type kneader; a rotary dispersion mixer such as a homomixer, a static mixer, FILMICS, an Ebara Milder, a Clearmix, an Ultra-Turrax, a Cavitron, or a Biomixer; an ultrasonic dispersion device; or a device such as an in-line mixer that has no moving parts and can mix by the flow of the fluid itself.

[0046] The mass ratio [(A) / (B)] of the urethane resin (A) to the aqueous medium (B) is preferably in the range of 50 / 50 to 80 / 20, and more preferably in the range of 50 / 50 to 70 / 30, because a binder for an inkjet printing ink capable of forming an inkjet printing ink having excellent storage stability, ejection property, and abrasion resistance can be obtained.

[0047] The aqueous urethane resin composition of the present invention may contain other additives as needed.

[0048] Examples of the other additives include surfactants, emulsifiers, thickeners, urethane catalysts, fillers, flame retardants, leveling agents, antiblocking agents, etc. These additives can be used alone or in combination of two or more.

[0049] Examples of the surfactant include nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyethylene-polypropylene copolymer; anionic surfactants such as fatty acid salts such as sodium oleate, alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyldiphenyl ether sulfonates; and cationic surfactants such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts.

[0050] Examples of the emulsifier include nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyethylene-polypropylene copolymer; anionic emulsifiers such as fatty acid salts such as sodium oleate, alkyl sulfate ester salts, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyldiphenyl ether sulfonates; and cationic emulsifiers such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts. These emulsifiers can be used alone or in combination of two or more.

[0051] Examples of the thickener include associative and acid thickeners.

[0052] Examples of the urethane catalyst include organotin catalysts and bismuth catalysts.

[0053] Examples of the filler include calcium carbonate and silica.

[0054] Examples of the flame retardant include phosphorus-based flame retardants.

[0055] Examples of the leveling agent include silicon-based leveling agents.

[0056] Examples of the anti-blocking agent include acrylic agents and cellulose ester agents.

[0057] The binder for inkjet printing ink of the present invention comprises the aqueous urethane resin composition.

[0058] The ink-jet printing ink of the present invention contains, in addition to the ink-jet printing ink binder, a pigment, a dye, and various other additives as required.

[0059] As the pigment, for example, known and commonly used inorganic pigments and organic pigments can be used.

[0060] Examples of the inorganic pigments include titanium oxide, antimony red, red iron oxide, cadmium red, cadmium yellow, cobalt blue, Prussian blue, ultramarine, carbon black, and graphite.

[0061] Examples of the organic pigments include quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, and azo pigments.

[0062] These pigments can be used alone or in combination of two or more. These pigments may be surface-treated and have self-dispersibility in aqueous media.

[0063] Examples of the dyes include azo dyes such as monoazo and disazo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoimine dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, naphthalimide dyes, perinone dyes, phthalocyanine dyes, and triarylmethane dyes.

[0064] Examples of the additives that can be used include polymer dispersants, viscosity adjusters, wetting agents, antifoaming agents, surfactants, preservatives, pH adjusters, chelating agents, plasticizers, ultraviolet absorbers, and antioxidants, as well as acrylic resins that have been used as binders in conventional inkjet printing inks.

[0065] Examples of the polymer dispersant include acrylic resins and styrene-acrylic resins, and any of random, block, and graft types can be used. When using the polymer dispersant, an acid or a base may be used in combination to neutralize the polymer dispersant.

[0066] The dispersant may be an acrylic resin or a styrene-acrylic resin having a weight average molecular weight of preferably 1,000 to 50,000, more preferably 1,000 to 20,000. The dispersant may also be one having an acid value of preferably 100 to 500, more preferably 100 to 200.

[0067] As the acrylic resin or styrene-acrylic resin, a polymer of acrylic acid or methacrylic acid, or a polymer of these with styrene, etc. can be used.

[0068] The styrene-acrylic resin is preferably one obtained by using 50% by mass to 95% by mass of styrene relative to the total amount of monomers used in the production thereof.

[0069] The ink for ink-jet printing can be prepared, for example, by the following manufacturing method.

[0070] (1) A method of preparing an ink by mixing the pigment or dye, the aqueous medium, the ink-jet printing ink binder, and, if necessary, the additives all at once using any of various dispersing devices.

[0071] (2) A method of preparing an ink precursor consisting of an aqueous dispersion of a pigment or dye by mixing the pigment or dye, the aqueous medium, and, if necessary, the additives using any of various dispersing devices, and then mixing the ink precursor consisting of the aqueous dispersion of the pigment or dye, the inkjet printing ink binder, and, if necessary, the aqueous medium and the additives using any of various dispersing devices to prepare an ink.

[0072] The ink precursor containing the pigment used in the ink production method described in (2) above can be prepared, for example, by the following method.

[0073] (i) A method of preparing an ink precursor consisting of an aqueous dispersion containing a pigment by pre-kneading a pigment and additives such as the dispersant using a twin roll, a mixer, or the like, and mixing the resulting kneaded mixture with an aqueous medium using various types of dispersing devices.

[0074] (ii) A method of preparing an ink precursor consisting of an aqueous dispersion containing a pigment by mixing a pigment and the dispersant using various types of dispersing equipment, then controlling the solubility of the dispersant to deposit the dispersant on the surface of the pigment, and further mixing them using a dispersing equipment.

[0075] (iii) A method of preparing an ink precursor consisting of an aqueous dispersion containing a pigment by mixing a pigment and the additives using various dispersing devices, and then mixing the mixture with a resin emulsion using a dispersing device.

[0076] Examples of dispersing devices that can be used in producing the inkjet printing ink include ultrasonic homogenizers, high-pressure homogenizers, paint shakers, ball mills, roll mills, sand mills, sand grinders, Dyno Mills, Dispermats, SC Mills, and Nanomizers, which can be used alone or in combination of two or more.

[0077] The inkjet printing ink obtained by the above method may contain coarse particles having a particle diameter of approximately 250 nm or more. Since the coarse particles may cause clogging of printer nozzles and deteriorate the ink ejection characteristics, it is preferable to remove the coarse particles by a method such as centrifugation or filtration after preparing the aqueous dispersion of the pigment or the ink.

[0078] The ink for ink-jet printing obtained above preferably has a volume average particle diameter of 200 nm or less, and particularly when forming an image with higher gloss such as photographic quality, it is more preferable that the volume average particle diameter is in the range of 80 to 120 nm.

[0079] The inkjet printing ink preferably contains 0.2 to 10% by mass of the polyurethane (C), 50 to 95% by mass of an aqueous medium, and 0.5 to 15% by mass of a pigment or dye, based on the total mass of the inkjet printing ink.

[0080] The inkjet printing ink of the present invention obtained by the above method can be used exclusively for inkjet printing using an inkjet printer, and can be used for inkjet printing on substrates such as paper, plastic films, metal films or sheets, etc. The inkjet method is not particularly limited, and known methods such as continuous jet types (charge control types, spray types, etc.) and on-demand types (piezo type, thermal type, electrostatic suction type, etc.) can be used.

[0081] Printed matters printed using the inkjet printing ink of the present invention have excellent abrasion resistance, and are therefore less susceptible to deterioration of the printed image due to loss of pigments and the like. Furthermore, they have excellent alkali resistance, and are therefore able to prevent bleeding and the like due to adhesion of alkaline detergents and the like to the surface of the printed image. Furthermore, since the inkjet printing ink of the present invention has images with high color density, the inkjet printing ink of the present invention can be used for a variety of purposes, such as photographic printing by inkjet printing and printed matters obtained by high-speed inkjet printing.

[0082] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the examples given below.

[0083] Synthesis Example 1 Synthesis of Polyester Polyol (1) In a reaction vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 5.8 parts by mass of ethylene glycol, 10.0 parts by mass of diethylene glycol, 13.8 parts by mass of terephthalic acid, 13.8 parts by mass of isophthalic acid, and 0.1 parts by mass of dibutyltin oxide were charged while introducing nitrogen gas, and a polycondensation reaction was carried out at 230°C until the acid value reached 0.1 or less, thereby obtaining polyester polyol (1).

[0084] (Synthesis Examples 2 to 7: Synthesis of polyester polyols (2) to (7)) Using the formulations shown in Table 1, polyester polyols (2) to (8) were obtained in the same manner as in Synthesis Example 1.

[0085] The compositions of the polyester polyols (1) to (8) obtained in Synthesis Examples 1 to 8 are shown in Table 1.

[0086]

[0087] Example 1: Preparation of Aqueous Urethane Resin Composition (1) A four-neck flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet tube was charged with 43.4 parts by mass of the polyester polyol obtained in Synthesis Example 1, 18.1 parts by mass of polyether polyol ("PTMG1000" manufactured by Mitsubishi Chemical Corporation), and 7.3 parts by mass of dimethylolpropionic acid according to the formulation shown in Table 1, and thoroughly stirred. Next, 26.9 parts by mass of polyisocyanate compound (1) IPDI and 0.1 parts by mass of dibutyltin dilaurate as a catalyst were added, and the mixture was allowed to react at 75°C. After the reaction, MEK was added to adjust the solids concentration to 60% with MEK, and the mixture was stirred for 30 minutes and cooled to below 40°C to obtain a urethane resin solution. A neutralizer was then added to the resulting urethane resin solution to neutralize the acid groups. Ion-exchanged water was then added under vigorous stirring to adjust the solids concentration to 20%, emulsifying the urethane, and then a chain extender was added. After the reaction was completed, MEK was removed by distillation under reduced pressure to obtain an aqueous urethane resin composition (1) having a solids concentration of 30%.

[0088] Examples 2 to 4: Preparation of aqueous urethane resin compositions (2) to (4) Using the formulations shown in Table 1, aqueous urethane resin compositions (2) to (4) were obtained in the same manner as in Example 1.

[0089] Comparative Examples 1 to 5: Preparation of aqueous urethane resin compositions (R1) to (R5) Using the formulations shown in Table 1, aqueous urethane resin compositions (R1) to (R5) were obtained in the same manner as in Example 1.

[0090]

[0091] Example 5 Preparation of Inkjet Printing Ink (1) 50 parts by mass of C.I. Pigment Red 122 (FASTOGEN Super Magenta RY manufactured by DIC Corporation) and 10 parts by mass of a styrene-acrylic acid copolymer (weight average molecular weight 11,000, acid value 180 mgKOH / g) were charged in this order into a 0.5 L jacketed tank of a mini planetary mixer (mini-PLM manufactured by Aikosha Co., Ltd.), and the mixture was stirred for 10 minutes at a rotation speed of 80 rpm and a revolution speed of 25 rpm while the temperature of the jacketed tank was heated to 80°C.

[0092] Next, with the temperature of the jacketed tank maintained at 80°C, 5.3 parts by mass of a 34% by mass aqueous potassium hydroxide solution and 30 parts by mass of triethylene glycol were added to the composition, and the mixture was kneaded for 60 minutes at a rotation speed of 80 rpm and a revolution speed of 25 rpm, thereby obtaining a solid kneaded product.

[0093] To the kneaded product, 100 parts by mass of ion-exchanged water and 10 parts by mass of triethylene glycol were added, and the mixture was stirred and mixed for 10 minutes using a juicer mixer. By mixing the ion-exchanged water and Proxel-GXL (Lonza Japan Co., Ltd.), an aqueous pigment dispersion having a pigment concentration of 15.0% by mass, a triethylene glycol concentration of 12.0% by mass, a Proxel-GXL concentration of 0.1% by mass, and a non-volatile content of 18.2% by mass was obtained.

[0094] 20.0 parts by mass of the aqueous pigment dispersion, 8.0 parts by mass of 2-pyrrolidinone, 8.0 parts by mass of triethylene glycol mono-n-butyl ether, 3.0 parts by mass of glycerin, and 0.5 parts by mass of Surfynol 440 (manufactured by Air Products Co., Ltd.) were mixed, and then 1.5 parts by mass (in terms of solid content) of the binder (1) for inkjet printing ink made of the aqueous urethane resin composition (1) obtained in Example 1 was added, and the mixture was adjusted with ion exchanged water to a pigment concentration of 3.0% and a urethane solid content concentration of 1.5%, thereby obtaining an inkjet printing ink (1).

[0095] (Examples 6 to 8: Preparation of inkjet printing inks (2) to (4)) Inkjet printing inks (2) to (4) were obtained in the same manner as in Example 5, except that the inkjet printing ink binder (1) made of the aqueous urethane resin composition (1) used in Example 5 was changed to the inkjet printing ink binders (2) to (4) made of the aqueous urethane resin compositions (2) to (4) obtained in Examples 2 to 4, respectively.

[0096] (Comparative Examples 6 to 10: Preparation of Inkjet Printing Inks (R1) to (R5)) Inkjet printing inks (R1) to (R5) were obtained in the same manner as in Example 5, except that the binder (1) for inkjet printing ink made of the aqueous urethane resin composition (1) used in Example 5 was changed to the binders for inkjet printing ink (R1) to (R5) made of the aqueous urethane resin compositions (R1) to (R5) obtained in Comparative Examples 1 to 5, respectively.

[0097] The following evaluations were carried out using the inkjet printing inks (1) to (4) and (R1) to (R5) obtained in the above Examples and Comparative Examples.

[0098] [Method for evaluating storage stability] The particle diameter of each sample of the inkjet printing ink obtained in the Examples and Comparative Examples was measured after storing it in an environment of 60°C for one week, and the rate of change (%) was calculated according to the following formula and evaluated according to the following criteria. Incidentally, inks that were evaluated as having storage stability sufficient for practical use were evaluated as having a rate of change (%): (particle diameter after accelerated heating) / (particle diameter before accelerated heating)×100

[0099] A: The rate of change was 95% or more and less than 106%. B: The rate of change was 90% or more and less than 95%, or 106% or more and less than 111%. C: The rate of change was 85% or more and less than 90%, or 111% or more and less than 116%. D: The rate of change was less than 85% or 116% or more.

[0100] [Method for evaluating ink ejection properties] The inkjet printing inks obtained in the examples and comparative examples were filled into black ink cartridges of a commercially available inkjet printer ("ENVY4500" manufactured by Hewlett-Packard Company), and a solid print was performed on a transparent OHP sheet at a print density setting of 100%, to obtain a printed matter for evaluation. Then, using an unprinted OHP sheet as a reference, the absorbance (value at the maximum peak near 536 nm) of the printed surface of the OHP sheet was measured. The absorbance was compared with that of ink without binder, and the ejection property index was calculated according to the following formula and evaluated according to the following criteria. Incidentally, inks with an evaluation of A or B were evaluated as having ejection properties sufficient for practical use. Ejection property index: (absorbance of ink with binder) / (absorbance of ink without binder)

[0101] A: The ejectability index was 0.80 or more. B: The ejectability index was 0.70 or more and less than 0.80. C: The ejectability index was 0.60 or more and less than 0.70. D: The ejectability index was less than 0.60.

[0102] [Method for evaluating abrasion resistance] The inkjet printing inks obtained in the examples and comparative examples were applied to photographic printing paper (HP Advanced Photo Paper, manufactured by Hewlett-Packard) using a bar coater #3 to obtain test prints. The prints were dried at room temperature for one day, and then subjected to a friction test using a Gakushin friction tester. During the test, plain paper was attached to the friction arm, and the arm was moved back and forth 20 times under a load of 200 g. The degree of abrasion on the printed surface was visually confirmed and evaluated according to the following criteria. Prints that received a rating of A or B were evaluated as having sufficient abrasion resistance for practical use.

[0103] A: No scratches on the printed surface and no peeling of coloring material was observed. B: Some scratches occurred on the printed surface, but no peeling of coloring material was observed. C: Significant scratches occurred on the printed surface, and peeling of coloring material was observed.

[0104] Table 3 shows the compositions and evaluation results of the inkjet printing inks (1) to (4) and (R1) to (R5) obtained in the above examples and comparative examples.

[0105]

[0106] Examples 5 to 8 shown in Table 3 are examples in which the binder for inkjet printing inks of the present invention was used. It was confirmed that these inkjet printing inks had excellent storage stability, jetting properties, and abrasion resistance.

[0107] On the other hand, Comparative Example 6 shown in Table 3 is an example of an inkjet printing ink containing an inkjet printing ink binder that uses a urethane resin without a polyester polyol as the polyol compound. This inkjet printing ink was found to have excellent storage stability and ejection properties, but extremely insufficient abrasion resistance.

[0108] Comparative Example 7 is an example of an inkjet printing ink containing an inkjet printing ink binder using a urethane resin with an acid value outside the range of 30 to 60 mgKOH / g. It was confirmed that this inkjet printing ink had significantly insufficient ejection properties.

[0109] Comparative Example 8 is an example of an inkjet printing ink containing an inkjet printing ink binder using a urethane resin without using an alkali metal hydroxide as a neutralizing agent. It was confirmed that this inkjet printing ink had significantly insufficient ejection properties.

[0110] Comparative Example 9 is an example of an inkjet printing ink containing a binder for an inkjet printing ink using a urethane resin that does not use an alkali metal hydroxide as a neutralizing agent and does not use terephthalic acid or isophthalic acid as a raw material for the polyester polyol. It was confirmed that this inkjet printing ink was significantly insufficient in storage stability, ejection properties, and abrasion resistance.

[0111] Comparative Example 10 is an example of an inkjet printing ink containing a binder for an inkjet printing ink using a urethane resin that does not use terephthalic acid or isophthalic acid as a raw material for the polyester polyol. It was confirmed that this inkjet printing ink had significantly insufficient storage stability and ejection properties.

Claims

1. A urethane resin (A) containing a polyol compound (a1), a polyisocyanate compound (a2), and a neutralizing agent (a3) ​​as essential raw materials; A binder for ink-jet printing inks comprising an aqueous urethane resin composition containing an aqueous medium (B), The aromatic ring concentration of the polyol compound (a1) is in the range of 2,000 to 5,000 mmol / kg; The polyol compound (a1) is The polyester polyol is made from terephthalic acid and / or isophthalic acid, The polyester polyol has no acid group, the neutralizing agent (a3) ​​contains an alkali metal hydroxide, The ink-jet printing ink binder is characterized in that the acid value of the urethane resin (A) is in the range of 30 to 60 mgKOH / g.

2. 2. The binder for ink-jet printing ink according to claim 1, wherein the number average molecular weight of the polyester polyol is in the range of 500 to 3,000.

3. 2. The binder for an ink-jet printing ink according to claim 1, wherein the urethane resin (A) further contains a chain extender (a4) as a raw material.

4. 2. The binder for ink-jet printing inks according to claim 1, wherein said alkali metal hydroxide is sodium hydroxide and / or potassium hydroxide.

5. 5. An ink-jet printing ink, comprising the ink-jet printing ink binder according to claim 1 and a pigment or a dye.

6. A printed matter, which is printed with the ink for ink-jet printing according to claim 5.