JP7845019B2 - Aqueous polyurethane resin dispersion for inkjet inks - Google Patents

Description

This invention relates to an aqueous dispersion of polyurethane resin for inkjet inks.

In recent years, inkjet technology has begun to be used for commercial and industrial purposes, leveraging its advantages of drop-on-demand printing. Unlike conventional inks, commercial and industrial inkjet inks are used on a wide range of recording media, including not only plain paper but also coated printing paper, plastic films, and fabrics, requiring excellent initial dispersibility, storage stability, and durability (abrasion resistance).
Furthermore, in recent years, pigment printing, which eliminates the need to select colorants based on fiber type, the processing method is simpler, and it does not require steaming or washing/soaping processes, is also expected to be used with drop-on-demand inkjet inks. Using the above method reduces energy costs and eliminates wastewater, making it an environmentally safe processing method.
For commercial, industrial, and pigment printing applications like those described above, a high level of abrasion resistance is required, and therefore, polyurethane resins using polyester as a raw material (Patent Documents 1 and 2) are being considered.

Special Publication No. 2013-527267 Japanese Patent Publication No. 2015-163678

However, while the urethane resin obtained by Patent Document 1 exhibits excellent abrasion resistance when the recording medium is ordinary paper, its durability when printed on fabric is still insufficient. Similarly, while Patent Document 2 yields a pigment dispersion with excellent initial dispersibility and storage stability, its abrasion resistance to cotton fabric and coated printing paper is still insufficient, and further improvements are desired.

The object of the present invention is to provide a polyurethane resin aqueous dispersion for inkjet inks that exhibits excellent abrasion resistance to coated paper for printing, corrugated cardboard, and cotton fabrics.

The inventors of this invention arrived at this present invention as a result of diligent research to solve these problems.
In other words, the present invention is an aqueous polyurethane resin dispersion for inkjet inks, containing a polyurethane resin (U) obtained by reacting a polyol component and a polyisocyanate component, and water, wherein the polyol component is a polyol component containing a crystalline polyester polyol, and the water absorption rate of the polyurethane resin (U) is 6% by weight or less.

This invention makes it possible to provide a polyurethane resin aqueous dispersion for inkjet inks that exhibits excellent abrasion resistance to coated paper for printing, corrugated cardboard, and cotton fabrics.

The aqueous polyurethane resin dispersion for inkjet inks of the present invention contains a polyurethane resin (U) obtained by reacting a polyol component with a polyisocyanate component, and water.
The above polyol component is a polyol component containing a crystalline polyester polyol. The water absorption rate of the above polyurethane resin (U) is 6% by weight or less.

In this invention, crystallinity means that when the transition temperature of a sample is measured using a differential scanning calorimeter (DSC) in accordance with the method described in JIS K7121, an endothermic peak peak top temperature exists.
The measurement conditions for the peak top temperature of the endothermic peak are described below.
Measurements are taken using a differential scanning calorimeter (e.g., TA Instruments Q2000). The sample is first heated from 20°C to 150°C at a rate of 10°C/min, then cooled from 150°C to 0°C at a rate of 10°C/min, and then heated again from 0°C to 150°C at a rate of 10°C/min. The temperature at which the endothermic peak peaks during the second heating process are identified is defined as the endothermic peak top temperature.

By including a polyol component containing a crystalline polyester polyol in its constituent monomers (constituent units), the polyurethane resin (U) can reduce its degree of swelling in water, thereby improving its abrasion resistance.
Examples of crystalline polyester polyols include condensation-type polyester polyols obtained by dehydration condensation of a polyhydric alcohol having 2 to 20 carbon atoms and a polyhydric carboxylic acid having 2 to 20 carbon atoms or its ester-forming derivative [such as acid anhydrides, lower (1 to 4 carbon atoms) alkyl esters, and acid halides]. Crystalline polyester polyols may be used individually or in combination of two or more types.

Examples of polyhydric alcohols with 2 to 20 carbon atoms include saturated aliphatic diols with 2 to 20 carbon atoms, alicyclic diols with 6 to 20 carbon atoms, trihydric alcohols with 3 to 20 carbon atoms, and tetrahydric alcohols with 5 to 20 carbon atoms. Polyhydric alcohols with 2 to 20 carbon atoms may be used individually or in combination of two or more.

Examples of saturated aliphatic diols having 2 to 20 carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, diethylene glycol, triethylene glycol, and tetraethylene glycol, among other linear diols.

Examples of alicyclic diols having 6 to 20 carbon atoms include 1,4-cyclohexanediol, 1,3- or 1,4-cyclohexanedimethanol, 1,3-cyclopentanediol, 1,4-cycloheptanediol, 2,5-bis(hydroxymethyl)-1,4-dioxane, 2,7-norbornanediol, tetrahydrofrangimethanol, 1,4-bis(hydroxyethoxy)cyclohexane, 1,4-bis(hydroxymethyl)cyclohexane, and 2,2-bis(4-hydroxycyclohexyl)propane.

Examples of trihydric alcohols with 3 to 20 carbon atoms include aliphatic triols (such as glycerin and trimethylolpropane).

Examples of tetravalent to octavalent alcohols with 5 to 20 carbon atoms include aliphatic polyols (such as pentaerythritol, sorbitol, mannitol, sorbitan, diglycerin, and dipentaerythritol) and sugars (sucrose, glucose, mannose, fructose, methyl glucoside, and their derivatives).

Among polyhydric alcohols having 2 to 20 carbon atoms, saturated aliphatic diols having 2 to 20 carbon atoms are preferred from the viewpoint of initial dispersibility, storage stability, and abrasion resistance of polyurethane resins, more preferably aliphatic diols having 3 to 12 carbon atoms, and even more preferably aliphatic diols having 4 to 12 carbon atoms. In one embodiment, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and 1,12-dodecanediol are even more preferred as polyhydric alcohols having 2 to 20 carbon atoms, and particularly preferred are 1,4-butanediol, 1,6-hexanediol, and 1,12-dodecanediol. The weight percentage of dihydric alcohols in the polyhydric alcohols having 2 to 20 carbon atoms is preferably 80% by weight or more, more preferably 80 to 100% by weight, and even more preferably 100% by weight. In one embodiment, the weight percentage of aliphatic diols having 3 to 12 carbon atoms (preferably 4 to 12 carbon atoms) in polyhydric alcohols having 2 to 20 carbon atoms is preferably 80% by weight or more, more preferably 80 to 100% by weight, and even more preferably 100% by weight. The aliphatic diol is preferably a saturated aliphatic diol.

Examples of polycarboxylic acids having 2 to 20 carbon atoms or their ester-forming derivatives include aliphatic dicarboxylic acids (such as succinic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid (dodecane diic acid), octadecanedicarboxylic acid, decyl succinic acid, fumaric acid, and maleic acid), alicyclic dicarboxylic acids (such as dimer acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid), trivalent or higher polycarboxylic acids (such as trimellitic acid and pyromellitic acid), anhydrides thereof (such as succinic anhydride, maleic anhydride, phthalic anhydride, and trimellitic anhydride), acid halides thereof (such as adipic acid dichloride), and low molecular weight alkyl esters thereof (such as dimethyl succinate and dimethyl phthalate). A single polycarboxylic acid having 2 to 20 carbon atoms or its ester-forming derivative may be used, or two or more may be used in combination.

From the viewpoint of initial dispersibility, storage stability, and abrasion resistance of polyurethane resins, polycarboxylic acids having 2 to 20 carbon atoms or their ester-forming derivatives are preferred, with aliphatic dicarboxylic acids having 2 to 20 carbon atoms, their ester-forming derivatives, and combinations thereof being preferred. Aliphatic dicarboxylic acids having 4 to 12 carbon atoms are more preferred, and succinic acid, adipic acid, sebacic acid, and decanedicarboxylic acid are even more preferred. The weight percentage of dicarboxylic acid in the polycarboxylic acid having 2 to 20 carbon atoms or its ester-forming derivative is preferably 80% by weight or more, more preferably 80 to 100% by weight, and even more preferably 100% by weight. In one embodiment, the weight percentage of aliphatic dicarboxylic acid having 4 to 12 carbon atoms in the polycarboxylic acid having 2 to 20 carbon atoms or its ester-forming derivative is preferably 80% by weight or more, more preferably 80 to 100% by weight, and even more preferably 100% by weight.

In this invention, from the viewpoint of initial dispersibility, storage stability, and abrasion resistance of the polyurethane resin, it is preferable that the crystalline polyester polyol is a polyester polyol obtained by dehydration condensation of an aliphatic dicarboxylic acid having 4 to 12 carbon atoms and an aliphatic diol having 3 to 12 carbon atoms (preferably 4 to 12 carbon atoms).

Crystalline polyester polyols may or may not contain monomers other than the above-mentioned polyhydric alcohols having 2 to 20 carbon atoms and polycarboxylic acids having 2 to 20 carbon atoms or their ester-forming derivatives. Preferably, the total amount of polyhydric alcohols having 2 to 20 carbon atoms and polycarboxylic acids having 2 to 20 carbon atoms or their ester-forming derivatives in the constituent monomers of the crystalline polyester polyol is 80% by weight or more, and more preferably 80% to 100% by weight.

The crystalline polyester polyol preferably has a hydroxyl value of 30 to 120 mg KOH/g, and more preferably 50 to 100 mg KOH/g. The hydroxyl value can be measured by the method described in JIS K1557.
If the hydroxyl value is less than 30 mgKOH/g, the molecular weight of the polyurethane resin may increase, and the viscosity of the polyurethane resin aqueous dispersion may increase. If the hydroxyl value is greater than 120 mgKOH/g, the abrasion resistance derived from crystalline polyester polyols may not be as pronounced.

The crystalline polyester polyol preferably has a melting point of 90°C or lower, more preferably 50 to 85°C, and even more preferably 60 to 80°C. When the melting point of the crystalline polyester polyol is within the above range, good solvent solubility is obtained, resulting in a polyurethane resin aqueous dispersion with a sharp particle size distribution and excellent abrasion resistance. The melting point is measured using a differential scanning calorimeter (DSC).
In the present invention, the melting point of a crystalline polyester polyol or resin is the temperature at the peak of the melting (endothermic) peak obtained during the second heating process in the DSC curve obtained by using a differential scanning calorimeter (DSC) to heat the crystalline polyester polyol (or resin) from 20°C to 150°C under conditions of 10°C/min for the first heating process, then holding it at 150°C for 1 minute, then cooling it from 150°C to 0°C under conditions of 10°C/min, then holding it at 0°C for 1 minute, and finally heating it from 0°C to 150°C under conditions of 10°C/min for the second heating process.

In one embodiment, aliphatic dicarboxylic acids with 4 to 12 carbon atoms and aliphatic diols with 3 to 12 carbon atoms can be produced using biomass-derived raw materials. Biomass-derived raw materials refer to plant-derived raw materials.

In one embodiment, the biomass concentration in the polyurethane resin (U) is preferably 20% by weight or more, more preferably 40% by weight, and even more preferably 60% by weight, from the viewpoint of addressing the depletion of petroleum resources and considering environmental concerns. The above biomass concentration refers to the weight ratio (percentage) of the biomass-derived constituent monomers used relative to the weight of the polyurethane resin (U).

Examples of saturated aliphatic diols derived from biomass with 2 to 20 carbon atoms (preferably 3 to 12 carbon atoms, more preferably 4 to 12 carbon atoms) include 1,3-propanediol and 1,4-butanediol.

Examples of aliphatic dicarboxylic acids with 4 to 12 carbon atoms derived from biomass include succinic acid, adipic acid, azelaic acid, and sebacic acid.

The polyol component may contain polyols other than crystalline polyester polyols. Examples of polyols other than crystalline polyester polyols include amorphous polyester polyols, polycarbonate polyols, polyether polyols, low molecular weight polyols, and polyols having hydrophilic groups. The polyols other than crystalline polyester polyols may be one type or two or more types. Among these, low molecular weight polyols and polyols having hydrophilic groups are preferred.

The weight percentage of crystalline polyester polyol in the polyol component is preferably 70% by weight or more, more preferably 75-95% by weight, and even more preferably 88-93% by weight relative to the polyol component.

As the low molecular weight polyol, a low molecular weight diol is preferred. Examples of low molecular weight diols include saturated aliphatic diols having 2 to 20 carbon atoms, preferably linear diols having 3 to 10 carbon atoms, more preferably linear diols having 4 to 10 carbon atoms, even more preferably 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol, and particularly preferably 1,4-butanediol. Using a low molecular weight polyol is preferable because it improves the cohesive force between hard segments (urethane bonding sites) in the polyurethane resin, thereby improving saturated water absorption, mechanical strength, and excellent abrasion resistance (especially wet friction fastness). When the polyol component contains a low molecular weight polyol, the amount of the low molecular weight polyol is preferably 0.1 to 3% by weight, and more preferably 0.3 to 2% by weight, relative to the total weight of the polyol component and the polyisocyanate component.

In polyols having hydrophilic groups, the hydrophilic group refers to a carboxyl group, a carboxylate anion group, a sulfo group, a sulfonate group, and a sulfamic acid group. A polyol having hydrophilic groups may have one of these hydrophilic groups, or it may have two or more. The hydrophilic group is preferably a carboxyl group and/or a carboxylate anion group. A hydrophilic diol is preferred as the polyol having hydrophilic groups.

Examples of hydrophilic polyols include diols having a carboxyl group and having 2 to 10 carbon atoms [dialkylol alkano acids (e.g., 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolheptanoic acid, and 2,2-dimethyloloctanoic acid), tartaric acid, etc.], compounds having a sulfo group and having 2 to 16 carbon atoms [e.g., 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid], compounds having a sulfamic acid group and having 2 to 10 carbon atoms [e.g., N,N-bis(2-hydroxyethyl)sulfamic acid], etc., and salts obtained by neutralizing these compounds with the neutralizing agents described later. Of these, preferred are diols having a carboxyl group and/or a carboxylate anion group and salts obtained by neutralizing them with a neutralizing agent; more preferred are 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid and salts obtained by neutralizing them with a neutralizing agent; and even more preferred are 2,2-dimethylolpropionic acid and salts obtained by neutralizing it with a neutralizing agent. The hydrophilic polyols may be used individually or in combination of two or more.

Examples of neutralizing agents used for neutralizing the hydrophilic polyols mentioned above include ammonia, amine compounds having 1 to 20 carbon atoms, and hydroxides of alkali metals (such as sodium, potassium, and lithium).
Examples of amine compounds having 1 to 20 carbon atoms include primary amines such as monomethylamine, monoethylamine, monobutylamine, monoethanolamine, and 2-amino-2-methyl-1-propanol; secondary amines such as dimethylamine, diethylamine, dibutylamine, diethanolamine, and N-methyldiethanolamine; and tertiary amines such as trimethylamine, triethylamine, dimethylethylamine, and triethanolamine.
Of these, amine compounds having 1 to 20 carbon atoms are preferred from the viewpoint of the saturation water absorption rate of polyurethane resin, and triethylamine is more preferred.

In one embodiment, the polyol component preferably includes a polyol having hydrophilic groups. It is preferable that the polyurethane resin (U) contains a polyol having hydrophilic groups as a constituent monomer because it results in an aqueous dispersion of the polyurethane resin (U) with small particle size and a sharp particle size distribution.
From the viewpoint of initial dispersibility and storage stability of the polyurethane resin, the weight percentage of the polyol having hydrophilic groups is preferably 2.5 to 7.5% by weight, and more preferably 4.0 to 6.0% by weight, relative to the total weight of the polyol component and the polyisocyanate component.

Examples of polyisocyanate components used in polyurethane resin (U) include aromatic polyisocyanates having 6 to 20 carbon atoms (excluding carbon atoms in the isocyanate groups, the same applies hereinafter) having two or more isocyanate groups, aliphatic polyisocyanates having 2 to 18 carbon atoms, alicyclic polyisocyanates having 4 to 15 carbon atoms, aromatic aliphatic polyisocyanates having 8 to 15 carbon atoms, and derivatives of these polyisocyanates (e.g., isocyanurates).
The polyisocyanate component may be used alone, or two or more may be used in combination.

Examples of aromatic polyisocyanates having 6 to 20 carbon atoms include 1,3- or 1,4-phenylenediisocyanate, 2,4- or 2,6-tolylenediisocyanate (TDI), 4,4'- or 2,4'-diphenylmethanediisocyanate (MDI), 1,5-naphthylenediisocyanate, 4,4',4''-triphenylmethanetriisocyanate, m- or p-isocyanatophenylsulfonyl isocyanate, crude MDI, and the like.

Examples of aliphatic polyisocyanates having 2 to 18 carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.

Examples of alicyclic polyisocyanates having 4 to 15 carbon atoms include isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4-diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanatoethyl)-4-cyclohexene-1,2-dicarboxylate, and 2,5- or 2,6-norbornane diisocyanate.

Examples of aromatic aliphatic polyisocyanates having 8 to 15 carbon atoms include m- or p-xylylene diisocyanate (XDI) and α,α,α',α'-tetramethylxylylene diisocyanate (TMXDI).

From the viewpoint of initial dispersibility and mechanical strength of the polyurethane resin, aliphatic polyisocyanates with 2 to 18 carbon atoms and alicyclic polyisocyanates with 4 to 15 carbon atoms are preferred as the polyisocyanate component, alicyclic polyisocyanates with 4 to 15 carbon atoms are more preferred, and IPDI and hydrogenated MDI are even more preferred.

The molar ratio (NCO/OH) of isocyanate groups in the polyisocyanate component to hydroxyl groups in the polyol component is preferably 1.2 to 1.8, and more preferably 1.3 to 1.6, from the viewpoint of uniformity of the compositional distribution of the polyurethane resin and mechanical strength.

The polyurethane resin (U) has the above-mentioned polyol component and polyisocyanate component as essential constituent monomers (constituent units), but may also contain compounds other than the polyol component and polyisocyanate component as constituent monomers. Examples of constituent monomers other than the polyol component and polyisocyanate component include chain extenders and reaction inhibitors. These may be used individually or in combination of two or more. In one embodiment, the polyurethane resin (U) is preferably a reaction product of a urethane prepolymer having isocyanate groups at its terminals, obtained by reacting the above-mentioned polyol component and polyisocyanate component, and a chain extender.

It is preferable to use a chain extender in the polyurethane resin (U). Examples of chain extenders include water, C2-C10 diamines (e.g., ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, toluenediamine, and piperazine), C2-C10 polyalkylene polyamines (e.g., diethylenetriamine, triethylenetetramine, and tetraethylenepentamine), hydrazine or its derivatives (dibasic acid dihydrazides, e.g., adipic acid dihydrazide), C2-C30 polyepoxy compounds (e.g., 1,6-hexanediol diglycidyl ether, trimethylolpropane polyglycidyl ether, etc.), and C2-C10 amino alcohols (e.g., ethanolamine, diethanolamine, 2-amino-2-methylpropanol, and triethanolamine). As a chain extender, diamines having 2 to 10 carbon atoms are preferred, secondary diamines are more preferred, and isophorone diamines are even more preferred. When the polyurethane resin (U) contains the above compound as a constituent monomer, the cohesive force of the urethane group portion is improved, and the degree of swelling in water is reduced, resulting in excellent wet friction fastness. Furthermore, the use of diamines is preferable because the generation of carbon dioxide is suppressed by the amine-mediated extension reaction, reducing the amount of carbonate amine salt produced and thus improving storage stability.

The amount of chain extender used is preferably in the range of 0.1 to 2, and more preferably in the range of 0.5 to 1.5, where the molar ratio of the active hydrogen-containing group of the chain extender to the isocyanate group at the end of the urethane prepolymer is 0.1 to 2.

A reaction stopper may be used with the polyurethane resin (U) as needed. Examples of reaction stoppers include monoalcohols with 1 to 8 carbon atoms (methanol, ethanol, isopropanol, cellosolves, and carbitols, etc.) and monoamines with 1 to 10 carbon atoms (mono- or dialkylamines such as monomethylamine, monoethylamine, monobutylamine, dibutylamine, and monooctylamine; mono- or dialkanolamines such as monoethanolamine, diethanolamine, and diisopropanolamine, etc.).

Examples of methods for producing the polyurethane resin aqueous dispersion of the present invention include the following methods [1] and [2].
[1] A method for producing a polyurethane resin (U) by reacting a polyol component, a polyisocyanate component, and optionally a chain extender and a reaction stopper in one or more steps in the presence or absence of a hydrophilic solvent, and optionally dispersing the carboxyl group as a salt with a neutralizing agent in an aqueous medium, and optionally distilling off the hydrophilic solvent.
[2] A method comprising reacting a polyol component and a polyisocyanate component in one or more steps in the presence or absence of a hydrophilic solvent to produce a urethane prepolymer (P) having isocyanate groups at its termini, then, if necessary, dispersing the carboxyl groups in the urethane prepolymer (P) as a salt in an aqueous medium with a neutralizing agent, reacting a chain extender and/or reaction stopper with the isocyanate groups in the urethane prepolymer (P), and then, if necessary, distilling off the hydrophilic solvent.
Of the methods [1] and [2], method [2] is preferred from the viewpoint of dispersion stability and abrasion resistance of the polyurethane resin (U).

Hydrophilic solvents used in the production of aqueous polyurethane resin dispersions include those that are substantially inactive with NCO groups (acetone, ketones such as ethyl methyl ketone, esters, ethers, amides, and alcohols). Of these, tetrahydrofuran is preferred. The aqueous medium may be water alone, but a mixture of water and hydrophilic solvent can also be used. The weight ratio of hydrophilic solvent to water (hydrophilic solvent/water) is preferably 0/100 to 50/50, and more preferably 35/65 to 45/55.
If a hydrophilic solvent is used, it may be removed by distillation after the formation of the aqueous polyurethane resin dispersion, if necessary.

When using a polyol with hydrophilic groups, the compound can be neutralized with a neutralizing agent before, during, or after the production of the urethane prepolymer. Neutralization improves the dispersion stability of the polyurethane resin during emulsification.

The formation of the urethane prepolymer is preferably carried out by a reaction at 20°C to 150°C, more preferably 60°C to 110°C, with a reaction time of preferably 2 to 20 hours.
The urethane prepolymer can be formed in or out of the presence of an organic solvent that is substantially inactive with NCO groups. The urethane prepolymer typically has a free NCO group content of 0.5 to 10%. Examples of organic solvents that are substantially inactive with NCO groups include the hydrophilic solvents mentioned above, with tetrahydrofuran being preferred.

In the production of the above-mentioned urethane prepolymer, catalysts commonly used in urethane reactions may be used as needed to accelerate the reaction. Examples of catalysts include amine catalysts, such as triethylamine, N-ethylmorpholine, triethylenediamine, and cycloamidines described in U.S. Patent No. 4,524,104 [e.g., 1,8-diazabicyclo(5,4,0)undecene-7 (manufactured by Sunapro, DBU)]; tin-based catalysts, such as dibutyltin dilaurylate, dioctyltin dilaurylate, and tin octoate; and titanium-based catalysts, such as tetrabutyl titanate.

The urea group content based on the weight of the polyurethane resin (U) is preferably 0.01 to 0.2% by weight, more preferably 0.05 to 0.1% by weight. A urea group content of 0.01 to 0.2% by weight (preferably 0.05 to 0.1% by weight) in the polyurethane resin is preferable because it provides an appropriate urea group content in the polyurethane resin, allowing for a balance between mechanical strength and viscosity of the aqueous dispersion.

In polyurethane resin aqueous dispersions, particles made of polyurethane resin (U) are typically dispersed in water. From the viewpoint of storage stability and viscosity, the particle size of the particles in the polyurethane resin aqueous dispersion is preferably 20 to 100 nm, more preferably 35 to 65 nm. In this invention, particle size refers to the cumulant average diameter. The particle size can be measured and determined using a light scattering particle size distribution analyzer [for example, the "DLS-8000" manufactured by Otsuka Electronics Co., Ltd.].

The aqueous dispersion of polyurethane resin may contain additives such as emulsifiers, crosslinking agents, weather-resistant stabilizers, and smoothing agents as needed. The additives may be used individually or in combination of two or more. The amount of additive used is preferably 15% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less, based on the weight of the polyurethane resin (U).

In one embodiment, the aqueous polyurethane resin dispersion of the present invention preferably contains an emulsifier. When the aqueous polyurethane resin dispersion of the present invention contains an emulsifier, the initial dispersibility and dry friction fastness of the polyurethane resin (U) are improved. The emulsifier is preferably added during the production of the aqueous polyurethane resin dispersion.

When using an emulsifier in the production of an aqueous polyurethane resin dispersion, the emulsifier may be added at any stage of production. In one embodiment, from the viewpoint of the dispersibility of the isocyanate-terminated urethane prepolymer and the stability of the aqueous dispersion, it is preferable to add the emulsifier before or during the dispersion of the urethane prepolymer in the aqueous medium. The emulsifier may be added to either the urethane prepolymer or the aqueous medium, or to both. If the emulsifier is reactive with the urethane prepolymer, it is preferable to add it to the aqueous medium. The amount of emulsifier added is preferably 0.2 to 10% by weight, more preferably 0.3 to 6% by weight, based on the weight of the urethane prepolymer.

Examples of emulsifiers include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and other emulsifying dispersants. One type of emulsifier may be used, or two or more types may be used in combination. Among these, nonionic surfactants are preferred.

Nonionic surfactants include aliphatic alcohol (8-24 carbon atoms) alkylene oxide (AO) (2-8 carbon atoms) adducts (degree of polymerization = 1-100), (poly)oxyalkylene (2-8 carbon atoms, degree of polymerization = 1-100) higher fatty acid (8-24 carbon atoms) esters [for example, polyethylene glycol monooleate (HLB = 6-17), polyethylene glycol monostearate (HLB = 8-15), polyethylene glycol distearate (HLB = 8-14), and other mono or di-fatty acid polyethylene glycol esters], and polyvalent (2-10 or more) alcohol fatty acid (8-24 carbon atoms) esters [glyceryl monostearate, ethylene glycol monostearate, fatty acid sorbitan esters (sorbitan monooleate, sorbitan monolaurate)]. Examples include (poly)oxyalkylene (2-8 carbon atoms, degree of polymerization = 1-100) polyvalent (2-10 or more) alcohol higher fatty acid (8-24 carbon atoms) esters [polyoxyethylene sorbitan monolaurate (HLB = 10-16), polyoxyethylene dioleate methyl glucoside (HLB = 17), etc.], fatty acid alkanolamides [1:1 type coconut oil fatty acid diethanolamide, 1:1 type lauric acid diethanolamide, etc.], (poly)oxyalkylene (2-8 carbon atoms, degree of polymerization = 1-100) alkyl (1-22 carbon atoms) phenyl ethers, (poly)oxyalkylene (2-8 carbon atoms, degree of polymerization = 1-100) alkyl (8-24 carbon atoms) amino ethers and alkyl (8-24 carbon atoms) dialkyl (1-6 carbon atoms) amine oxides [lauryldimethylamine oxide, etc.].
Among these, (poly)oxyethylene higher fatty acid (8-24 carbon atoms) esters (HLB = 6-17) and polyvalent (divalent to hexavalent) alcohol fatty acid (8-24 carbon atoms) esters are preferred, and monofatty acid (preferably 12-24 carbon atoms) polyethylene glycol esters and fatty acid (preferably 12-24 carbon atoms) sorbitan esters are preferred. In one embodiment, the aqueous polyurethane resin dispersion for inkjet ink of the present invention preferably contains fatty acid sorbitan esters and/or monofatty acid polyethylene glycol esters because of excellent initial dispersibility and dry friction fastness. As fatty acid sorbitan esters, sorbitan esters of fatty acids with 12-20 carbon atoms are preferred, and sorbitan oleate is more preferred. As monofatty acid polyethylene glycol esters, polyethylene glycol esters of fatty acids with 12-20 carbon atoms (HLB = 6-17) are preferred, and monooleate polyethylene glycol esters (HLB = 8-14) are more preferred.

In this invention, HLB is a measure that indicates the balance between hydrophilicity and lipophilicity, with higher HLB values indicating higher inorganic properties. For example, it is known as a value calculated using the Oda method, as described in "Introduction to Surfactants," 2007, published by Sanyo Chemical Industries, Ltd., authored by Takehiko Fujimoto, p. 212, and is not a value calculated using the Griffin method. The HLB value can be calculated from the ratio of the organic value to the inorganic value of an organic compound.
HLB = 10 × Inorganic / Organic. The organic and inorganic values used to derive HLB can be calculated using the values in the table on page 213 of the above-mentioned "Introduction to Surfactants".

Anionic surfactants include, for example, ether carboxylic acids or salts thereof having hydrocarbon groups with 8 to 24 carbon atoms [such as sodium lauryl ether acetate and (poly)oxyethylene (1 to 100 added moles) sodium lauryl ether acetate]; sulfate esters or ether sulfate esters and salts thereof having hydrocarbon groups with 8 to 24 carbon atoms [such as sodium lauryl sulfate, (poly)oxyethylene (1 to 100 added moles) sodium lauryl sulfate, (poly)oxyethylene (1 to 100 added moles) triethanolamine lauryl sulfate and (poly)oxyethylene (1 to 100 added moles) coconut oil fatty acid monoethanolamide sulfate sodium]; sulfonates having hydrocarbon groups with 8 to 24 carbon atoms [such as sodium dodecylbenzenesulfonate]; hydrocarbon groups with 8 to 24 carbon atoms Examples include sulfosuccinates having one or two hydrocarbon groups; phosphate esters or ether phosphate esters having hydrocarbon groups with 8 to 24 carbon atoms and their salts [e.g., sodium lauryl phosphate and (poly)oxyethylene (1 to 100 moles added) sodium lauryl ether phosphate]; fatty acid salts having hydrocarbon groups with 8 to 24 carbon atoms [e.g., sodium laurate and triethanolamine laurate]; and acylated amino acid salts having hydrocarbon groups with 8 to 24 carbon atoms [e.g., sodium methyl taurate, sodium sarcosinate, triethanolamine sarcosinate, triethanolamine acyl-L-glutamate, triethanolamine acyl-L-glutamate, sodium lauroyl methyl-β-alanine].

Examples of cationic surfactants include quaternary ammonium salts [such as stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, distearyldimethylammonium chloride, and lanolin fatty acid aminopropylethyldimethylammonium ethyl sulfate] and amine salts [such as diethylaminoethylamide lactate stearate, dilaurylamine hydrochloride, and oleylamine lactate].

Examples of amphoteric surfactants include betaine-type amphoteric surfactants [such as coconut oil fatty acid amidopropyl dimethylaminoacetic acid betaine, lauryl dimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, lauryl hydroxysulfobetaine, and lauroylamide ethyl hydroxyethyl carboxymethyl betaine hydroxypropyl sodium phosphate] and amino acid-type amphoteric surfactants [such as β-laurylaminopropionate sodium].

Other emulsifying dispersants include, for example, polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as carboxymethylcellulose, methylcellulose, and hydroxyethylcellulose, carboxyl group-containing (co)polymers such as sodium polyacrylate, and emulsifying dispersants having urethane groups or ester groups as described in U.S. Patent No. 5,906,704 [for example, polylactone polyols and polyether diols linked by polyisocyanate].

When the aqueous dispersion of polyurethane resin contains an emulsifier, its content is preferably 0.2 to 10% by weight, more preferably 0.3 to 6% by weight, based on the weight of the polyurethane resin (U).

In the production of aqueous polyurethane resin dispersions, the apparatus for emulsification and dispersion is not particularly limited, and examples include the emulsifier of the following type.
1) Anchor-type stirring method, 2) Rotor-stator type [e.g., "Ebara Milder" (manufactured by Ebara Corporation)], 3) Line mill type [e.g., line flow mixer], 4) Stationary tube mixing type [e.g., static mixer], 5) Vibration type [e.g., "VIBROMIXER" (manufactured by Reika Kogyo Co., Ltd.)], 6) Ultrasonic impact type [e.g., ultrasonic homogenizer], 7) High-pressure impact type [e.g., Gaurin homogenizer (Gaurin Corporation)], 8) Emulsification type [e.g., membrane emulsification module], and 9) Centrifugal thin film contact type [e.g., Filmix]. Of these, the anchor-type stirring method is preferred.

The polyurethane resin (U) in this invention has a water absorption rate of 6% by weight or less. If the water absorption rate of the polyurethane resin (U) exceeds 6% by weight, its abrasion resistance to coated printing paper, corrugated cardboard, and cotton fabrics becomes insufficient. The water absorption rate of the polyurethane resin (U) is preferably 5% by weight or less, and more preferably 3% by weight or less. The water absorption rate of the polyurethane resin (U) may be 0.5% by weight or more, and preferably 1% by weight or more. The water absorption rate of the polyurethane resin (U) can be measured by the method described in the examples. Methods for adjusting the water absorption rate of the polyurethane resin (U) include the introduction of low-polarity polymer polyols (e.g., crystalline polyester polyols), the introduction of low-molecular-weight diols, the introduction of cross-linked structures, and the use of volatile neutralizing agents.

In this invention, the polyurethane resin (U) preferably has a storage modulus G' of 0.1 to 1.0 MPa. When the storage modulus G' of the polyurethane resin (U) is within this range, the frictional fastness is improved due to increased mechanical strength and reduced saturated water absorption. A storage modulus G' of 0.2 to 0.7 MPa is more preferable. In this invention, the storage modulus G' is the storage modulus at 160°C. The storage modulus G' can be measured using a viscoelasticity measuring device.

In the present invention, the polyurethane resin (U) preferably has a melting point of 80°C or lower, or has no melting point. The melting point of the polyurethane resin (U) is measured using a differential scanning calorimeter (DSC) in the same manner as the melting point of the crystalline polyester polyol described above.
If the polyurethane resin (U) has a melting point of 80°C or less, or if the polyurethane resin (U) has no melting point, the abrasion resistance to cotton fabric will be better. If the polyurethane resin (U) has a melting point, it is preferably 65°C or less, and preferably 40 to 60°C. In one embodiment, it is more preferable that the polyurethane resin (U) has no melting point.

The solid content concentration of the polyurethane resin aqueous dispersion of the present invention is preferably 10 to 70% by weight, more preferably 20 to 50% by weight. The water content in the polyurethane resin aqueous dispersion is preferably 30 to 80% by weight, and more preferably 50 to 70% by weight.

The viscosity of the aqueous polyurethane resin dispersion is preferably 3.0 to 20.0 mPa·s at 25°C, and more preferably 5.0 to 10.0 mPa·s. The viscosity can be measured using a cone-plate viscometer under the conditions described in the examples.

The polyurethane resin aqueous dispersion of the present invention is a polyurethane resin aqueous dispersion for inkjet inks. The polyurethane resin aqueous dispersion of the present invention is used in the manufacture of inkjet inks. Inkjet inks preferably contain pigments in addition to the polyurethane resin aqueous dispersion of the present invention. Inkjet inks may also contain humectants, penetrating agents, etc.

The solid content of the polyurethane resin aqueous dispersion of the present invention in the inkjet ink is preferably 0.1 to 60% by weight, more preferably 1 to 20% by weight, based on the weight of the inkjet ink. The content of the polyurethane resin aqueous dispersion is preferably 1 to 90% by weight, more preferably 5 to 50%, based on the weight of the inkjet ink.

The pigment content is preferably 0.1 to 30% by weight, more preferably 1 to 10% by weight, based on the weight of the inkjet ink. The humectant content is preferably 0.1 to 90% by weight, more preferably 1 to 50% by weight, based on the weight of the inkjet ink.

Examples of pigments include conventionally known organic and inorganic pigments (e.g., white pigments, black pigments, gray pigments, red pigments, brown pigments, yellow pigments, green pigments, blue pigments, purple pigments, and metallic pigments; synthetic organic pigments derived from natural organic pigments; nitroso pigments; nitro pigments; pigment-type azo pigments; azo lakes made from water-soluble dyes; azo lakes made from poorly soluble dyes; lakes made from basic dyes; lakes made from acid dyes; xanthan lakes; anthraquinone lakes; pigments and phthalocyanine pigments derived from vat dyes; and organic pigments such as daylight fluorescent pigments).

Examples of specific organic and inorganic pigments are given below.
Examples of white pigments include inorganic pigments such as titanium dioxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide. In addition to inorganic pigments, hollow resin microparticles and polymer microparticles can also be used.
The average particle size of the pigment is preferably 200 to 300 nm. If the average particle size of the pigment is less than 200 nm, the opacity tends to be insufficient, and if it exceeds 300 nm, the discharge stability tends to be insufficient.

In particular, titanium dioxide is preferred from the viewpoint of opacity. Similarly, the average particle size of the titanium dioxide is preferably 200 to 300 nm.

While not particularly limited, the following pigments are used for magenta: C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C. Examples include I. Pigment Red 178 and C. I. Pigment Red 222.

While not particularly limited, examples of pigments for yellow include C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 128, C.I. Pigment Yellow 138, and Pigment Yellow 180.

Pigments for cyan are not particularly limited, but examples include C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, and C.I. Pigment Green 7.

The humectant is used as a moisturizing component in water-based inks. The humectant is preferably a compound that has a solubility in water of 50% by weight or more, preferably 60% by weight or more, at 25°C, and a saturated vapor pressure (20°C) of less than 0.001 kPa.
The humectant is not particularly limited, but one with a boiling point of 100°C or higher is preferred. Examples of humectants include glycerin, diglycerin, propylene glycol, ethylene glycol, 1,3-propanediol, 1,4-propanediol, and triethylene glycol monobutyl ether.

In addition to the polyurethane resin (U) in the aqueous polyurethane resin dispersion of the present invention, other aqueous media dispersible resins or water-soluble resins may be used in combination with the inkjet ink, as necessary, for purposes such as assisting in film formation or improving binder function.

Other aqueous media-dispersible or water-soluble resins used in combination with inkjet inks include, for example, aqueous media-dispersible or water-soluble polyurethane resins other than the polyurethane resin used in the present invention, polyacrylic resins, and polyester resins.

Inkjet ink may further contain one or more of the following: pH adjusters, viscosity adjusters, defoamers, preservatives, degradation inhibitors, stabilizers, antifreeze agents, and water.

The inkjet ink containing the polyurethane resin aqueous dispersion for inkjet inks of the present invention can be suitably used, for example, as an inkjet ink for coated paper for printing, corrugated cardboard, and cotton fabrics. The printing method using the inkjet ink is not particularly limited, but examples include home printing, business printing, sign graphic printing, and pigment printing. Pigment printing is preferred.

This specification discloses the following:

The present disclosure (1) contains a polyurethane resin (U) obtained by reacting a polyol component and a polyisocyanate component, and water.
The polyol component is a polyol component containing a crystalline polyester polyol, and the polyurethane resin (U) has a water absorption rate of 6% by weight or less, making it an aqueous dispersion of polyurethane resin for inkjet ink.

Disclosure (2) is an aqueous dispersion of polyurethane resin for inkjet ink according to Disclosure (1), wherein the storage modulus G' of the polyurethane resin (U) is 0.1 to 1.0 MPa.

Disclosure (3) is an aqueous dispersion of polyurethane resin for inkjet ink according to Disclosure (1) or (2), wherein the crystalline polyester polyol is a polyester polyol obtained by dehydration condensation of an aliphatic dicarboxylic acid having 4 to 12 carbon atoms and an aliphatic diol having 3 to 12 carbon atoms.

Disclosure (4) is an aqueous polyurethane resin dispersion for inkjet inks, further containing a fatty acid sorbitan ester and/or a monofatty acid polyethylene glycol ester, in any combination with any of Disclosures (1) to (3).

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Hereinafter, unless otherwise specified, "parts" refers to parts by weight.

<Manufacturing Example 1>
In a reaction vessel equipped with a condenser, thermometer, stirrer, and nitrogen inlet, 451.2 parts of 1,6-hexanediol, 649.9 parts of dodecane diacitate, and 2 parts of titanium diisopropoxybistriethanolamine as a condensation catalyst were added, and the reaction was carried out at 200°C under a nitrogen stream for 3 hours while distilling off the water produced. The reaction was then carried out at 200°C for 6 hours under reduced pressure of 0.5 to 2.5 kPa. When the acid value (mg KOH/g) fell below 1, the reactants were removed from the reaction vessel, yielding a crystalline polyester polyol (B-1) with a hydroxyl value (mg KOH/g) of 100 and a melting point of 70°C.

<Manufacturing Examples 2-11>
Crystalline polyester polyols (B-2) to (B-11) were obtained in the same manner as in Production Example 1, except that the amount of raw materials used was changed to those listed in Table 1.

<Manufacturing Example 12>
In a reaction vessel equipped with a condenser, thermometer, stirrer, and nitrogen inlet tube, 39 parts sorbitol, 61 parts oleic acid, and 50 parts xylene as a solvent were added and the reaction was carried out at 180°C under a nitrogen stream for 3 hours while distilling off the water produced. When the acid value (mg KOH/g) fell below 1, the reaction system was reduced to a reduced pressure, and the xylene was removed to obtain an ester of sorbitol and oleic acid (sorbitan oleate) (O-1).

<Manufacturing Example 13>
In a reaction vessel equipped with a condenser, thermometer, stirrer, and nitrogen inlet tube, 44 parts of polyoxyethylene monomethyl ether (polyethylene glycol monomethyl ether 220, Mn=220, manufactured by Kanto Chemical Co., Ltd.), 56 parts of oleic acid, and 50 parts of xylene as a solvent were added and the reaction was carried out at 180°C under a nitrogen stream for 3 hours while distilling off the water produced. When the acid value (mgKOH/g) fell below 1, the reaction system was reduced to a reduced pressure, and the xylene was removed to obtain polyethylene glycol monooleate ester (O-2).

<Comparative Manufacturing Example 1>
Polyester polyol (B'-1) was obtained in the same manner as in Production Example 1, except that the amount of raw materials used was changed to those listed in Table 1.

The melting points and hydroxyl values of crystalline polyester polyols (B-1) to (B-11) and polyester polyol (B'-1) were measured using the method described below. The results are shown in Table 1. Polyester polyol (B'-1) had no melting point and was amorphous.

The information in Table 1 is as follows:
Biomass-derived 1,3-propanediol: 1,3-propanediol made from corn, a 100% plant-derived ingredient, "DuPont Bio-PDO".
Biomass-derived 1,4-butanediol: 1,4-butanediol made from 100% plant-derived raw materials, sugarcane and corn. ("Genomatica 1,4-butanediol")
Biomass-derived succinic acid: 100% plant-derived succinic acid made from sugarcane and corn, manufactured by GC Innovation America.
Biomass-derived sebacic acid: Sebacic acid made from castor oil, manufactured by Toyokuni Seiyu Co., Ltd.

<Example 1>
In a simple pressurized reaction apparatus equipped with a stirrer and a heating device, 57.33 parts of crystalline polyester polyol (B-1), 0.98 parts of 1,4-butanediol (1,4-BD), a low molecular weight diol, 4.96 parts of 2,2-dimethylolpropionic acid (DMPA) as a polyol component having carboxyl groups in its side chains, 36.24 parts of dicyclohexylmethane-4,4-diisocyanate (MDI-H) as a polyisocyanate component, and 100 parts of tetrahydrofuran as an organic solvent for the reaction were charged and stirred at 70°C for 12 hours to carry out a urethane formation reaction, thereby producing a tetrahydrofuran solution of urethane prepolymer (P-1) having isocyanate groups.
Next, 3.73 parts of triethylamine (TEA) as a neutralizing agent were added to the tetrahydrofuran solution of the obtained urethane prepolymer (P-1) and homogenized. Then, 250 parts of ion-exchanged water as an aqueous medium were added while stirring at 200 rpm to disperse the polyurethane prepolymer in water. 4.46 parts of isophorone diamine (IPDA) as an extension agent were added to the resulting dispersion under stirring, and the extension reaction was carried out for 30 minutes. The dispersion was then heated under reduced pressure to 60°C to remove the tetrahydrofuran by distillation. After that, water was added to adjust the solid content concentration to 30% by weight to obtain an aqueous polyurethane resin dispersion (Q-1).

<Example 2>
To the tetrahydrofuran solution of the urethane prepolymer (P-1) obtained in Example 1, 3.73 parts of triethylamine as a neutralizing agent and 5.00 parts of the sorbitol and oleic acid ester (O-1) prepared in Production Example 12 were added and homogenized. Then, 250 parts of ion-exchanged water as an aqueous medium were added while stirring at 200 rpm to disperse the polyurethane prepolymer in water. 4.46 parts of isophorone diamine as an extension agent were added to the resulting dispersion under stirring, and the extension reaction was carried out for 30 minutes. The mixture was then heated under reduced pressure to 60°C to remove the tetrahydrofuran. Subsequently, water was added to adjust the solid content concentration to 30% by weight to obtain an aqueous polyurethane resin dispersion (Q-2).

<Example 3>
A polyurethane resin aqueous dispersion (Q-3) was obtained in the same manner as in Example 2, except that the amount of raw materials used was changed to those listed in Table 2.

<Examples 4-14>
Aqueous polyurethane resin dispersions (Q-4) to (Q-14) were obtained in the same manner as in Example 1, except that the amount of raw materials used was changed to those listed in Table 2.

<Examples 15 and 16>
Aqueous polyurethane resin dispersions (Q-15) and (Q-16) were obtained in the same manner as in Example 2, except that the amount of raw materials used was changed to those listed in Table 3.

<Examples 17-19>
Aqueous polyurethane resin dispersions (Q-17) to (Q-19) were obtained in the same manner as in Example 1, except that the amount of raw materials used was changed to those listed in Table 3.

<Comparative Examples 1-4>
Aqueous polyurethane resin dispersions (Q'-1) to (Q'-4) were obtained in the same manner as in Example 1, except that the amount of raw materials used was changed to those listed in Table 3.

The particle size and viscosity of the aqueous polyurethane resin dispersions (solid content concentration 30% by weight) obtained in Examples 1-19 and Comparative Examples 1-4 were measured by the following method (initial dispersibility). The results are shown in Tables 2 and 3.

<Method for measuring particle size>
The particle sizes of the polyurethane resin aqueous dispersions (Q-1) to (Q-19) and (Q'-1) to (Q'-4) were measured using a light scattering particle size distribution analyzer [DLS-8000 manufactured by Otsuka Electronics Co., Ltd.], and the resulting cumulant average diameter was defined as the particle size.

<Method for measuring viscosity>
The viscosity of the polyurethane resin aqueous dispersions (Q-1) to (Q-19) and (Q'-1) to (Q'-4) was measured using the following measuring device and conditions.
Equipment: MCR92 (manufactured by Anton Paar)
Fixture: 50mm cone plate; Shearing speed: 200 1/s
Measurement temperature: 25℃

<Method for evaluating storage stability>
Aqueous polyurethane resin dispersions (Q-1) to (Q-19) and (Q'-1) to (Q'-4) were left to stand for one week at 70°C in a circulating air dryer [SPH-201 from ESPEC Corporation], and the particle size and viscosity after removal were measured using the method described above.
The percentage change (100 × measured value after accelerated testing / measured value before accelerated testing) was calculated from the particle size and viscosity measurements before and after the accelerated testing (1 week at 70°C). The percentage changes in particle size and viscosity (%) are shown in Tables 2 and 3 (storage stability). A percentage change of 10% or less in particle size and viscosity is considered to be at a practical level.

<Method for preparing a dried resin coating>
8.5 g each of the polyurethane resin aqueous dispersions (Q-1) to (Q-19) and (Q'-1) to (Q'-4) obtained in Examples 1 to 19 or Comparative Examples 1 to 4 was poured into a disposable tray DT-2 (manufactured by AS ONE Corporation), the liquid surface was leveled uniformly, and after standing at room temperature for 5 hours, it was dried at 105°C for 3 hours to obtain polyurethane resins (U-1) to (U-19) and (U'-1) to (U'-4).

The melting points, storage modulus G', and water absorption rates of polyurethane resins (U-1) to (U-19) and (U'-1) to (U'-4) were measured using the method described below. The results are shown in Tables 2 and 3.

<Method for measuring hydroxyl value>
The hydroxyl values of polyester polyols (B-1) to (B-11) and (B'-1) were measured by the method described in JIS K1557.

<Method for measuring the melting point>
The melting points of polyester polyols (B-1) to (B-11), (B'-1), polyurethane resins (U-1) to (U-19), (U'-1) to (U'-4) were measured using a differential scanning calorimeter (DSC) (TA Instruments Q2000) under the following conditions. A graph of endothermic and heat generation and temperature was created from the obtained measurement results, and the temperature at the peak of the melting (endothermic) peak obtained in the second heating process was defined as the melting point.
• Sample container: Aluminum sample pan • Sample quantity: 2.5 mg
• Reference aluminum sample pan (empty container)
• Atmosphere: Nitrogen (flow rate 50 mL/min)
(First heating process)
・Starting temperature: 20℃
• Heating rate: 10°C/min
・End temperature: 150℃
・Holding time: 1min
・Cooling rate: 10℃/min
・Ending temperature: 0℃
・Holding time: 1min
(Second heating process)
• Heating rate: 10°C/min
・End temperature: 150℃

<Method for measuring the storage modulus G'>
The storage modulus G' of polyurethane resins (U-1) to (U-19) and (U'-1) to (U'-4) was measured using the viscoelasticity measuring device described below. The storage modulus G' (160°C) (MPa) at 160°C is shown in Tables 2 and 3.
Equipment: MCR92 (manufactured by Anton Paar)
Fixture: 8mm parallel plate; Frequency: 11Hz
Distortion rate: 0.5%
Heating rate: 5°C/min Heating start: 20°C
Heating complete: 160°C
The sample used for measurement was cut into 1 cm x 1 cm pieces.

<Method for measuring water absorption rate>
Polyurethane resin samples (U-1) to (U-19) and (U'-1) to (U'-4) were cut into 2cm x 2cm pieces. The original weights of these samples were weighed using an electronic balance, and then immersed in 100g of deionized water at 25°C. After one hour, the samples were collected with tweezers, any moisture adhering to the surface was removed, and the weight (weight after immersion) was measured again. The water absorption rate of the resin was calculated from the measured weight using the following formula.
Water absorption rate (%) = 100 × (Weight after immersion - Original weight) / Original weight The water absorption rates (%) of polyurethane resin are shown in Tables 2 and 3.

<Manufacturing of printing inks (L-1) to (L-19), (L'-1) to (L'-4)>
20 parts each of the polyurethane resin aqueous dispersions (Q-1) to (Q-19) and (Q'-1) to (Q'-4) obtained in Examples 1 to 19 or Comparative Examples 1 to 4, 20 parts of pigment [carbon black aqueous dispersion {Aqua-Black 162 manufactured by Tokai Carbon Co., Ltd., solid content concentration 20% by weight}], 15 parts of glycerin as a humectant, 1.5 parts of propylene glycol, 1.5 parts of triethylene glycol as a penetrating agent, and 42 parts of water were placed in a container and mixed for 10 minutes to produce printing inks (L-1) to (L-19) and comparative printing inks (L'-1) to (L'-4).

<Method for evaluating the abrasion fastness (abrasion resistance) of coated paper for printing>
Printing inks (L-1) to (L-19) and comparative printing inks (L'-1) to (L'-4) were applied to coated printing paper [high-grade art paper manufactured by Mitsubishi Paper Mills Ltd.] using a bar coater so that the thickness after drying was 1 μm. The paper was dried at 70°C for 2 minutes to prepare test pieces (2 cm x 6 cm) coated with polyurethane resin on the coated printing paper. The prepared test pieces were attached to the measurement area of a speed-variable friction measuring machine [Tribomaster μv1000 manufactured by Trinity Labs Co., Ltd.], and a 1 cm x 1 cm piece of cotton cloth (Kanahaba No. 3) was attached to the indenter with double-sided tape. A load of 200 g was applied, and 100 back-and-forth cycles were performed with a friction stroke of 2 cm and a friction speed of 2400 mm/min. The color transfer density on the cotton fabric (No. 3) side of the indenter was measured at 9 points using a spectrophotometer [X-rite 938, manufactured by X-Rite Corporation], and the average of the measurement results was taken as the color transfer density. The color transfer density was evaluated according to the following criteria, and the results are shown in Tables 2 and 3. The lower the color transfer density, the better the abrasion fastness.
◎: Transfer concentration 0.10 or less ○: Transfer concentration greater than 0.10 and 0.15 or less △: Transfer concentration greater than 0.15 and 0.20 or less ×: Transfer concentration greater than 0.20 and 0.30 or less A transfer concentration of 0.15 or less is at a practical level.

<Method for evaluating the friction fastness (abrasion resistance) of corrugated cardboard>
A test piece (2 cm x 6 cm) was prepared by coating corrugated cardboard [Prefine, manufactured by Oji Container Co., Ltd.] with printing inks (L-1) to (L-19) and comparative printing inks (L'-1) to (L'-4) using a bar coater so that the thickness after drying was 1 μm, and drying at 70°C for 2 minutes to create a polyurethane resin coating on the corrugated cardboard. The prepared test piece was attached to the measurement area of a speed-variable friction measuring machine [Tribomaster μv1000, manufactured by Trinity Lab Co., Ltd.], and a 1 cm x 1 cm cotton cloth (Kanahaba No. 3) was attached to the indenter with double-sided tape. A load of 200 g was applied, and 100 back-and-forth cycles were performed with a friction stroke of 2 cm and a friction speed of 2400 mm/min. The color transfer density on the cotton cloth (Kanahaba No. 3) side of the indenter was measured at 9 points using a spectrophotometer [X-rite 938, manufactured by X-Rite Corporation], and the average value of the measurement results was taken as the color transfer density. The color transfer concentration was evaluated according to the following criteria, and the results are shown in Tables 2 and 3. Lower color transfer concentrations indicate better abrasion fastness.
◎: Transfer concentration 0.10 or less ○: Transfer concentration greater than 0.10 and 0.15 or less △: Transfer concentration greater than 0.15 and 0.20 or less ×: Transfer concentration greater than 0.20 and 0.30 or less A transfer concentration of 0.15 or less is at a practical level.

<Method for evaluating the dry abrasion fastness (abrasion resistance) of cotton fabrics>
Plain cotton broadcloth was coated with printing inks (L-1) to (L-19) and comparative printing inks (L'-1) to (L'-4) using a bar coater to a dry thickness of 1 μm. The coated cotton broadcloth was dried at 160°C for 10 minutes to create test pieces (4 cm x 12 cm) coated with polyurethane resin. Dry rubbing fastness was evaluated according to JIS L0849-2. A load of 200 g was applied, and the pieces were rubbed back and forth 100 times. The color transfer density on the No. 3 cloth side was measured at 9 points using a spectrophotometer [X-rite 938], and the average of the measurement results was taken as the color transfer density. The color transfer density was evaluated according to the following criteria, and the results are shown in Tables 2 and 3. A lower color transfer density indicates better rubbing fastness.
◎: Transfer concentration 0.10 or less ○: Transfer concentration greater than 0.10 and 0.15 or less △: Transfer concentration greater than 0.15 and 0.20 or less ×: Transfer concentration greater than 0.20 and 0.30 or less A transfer concentration of 0.15 or less is at a practical level.

<Method for evaluating the wet abrasion fastness (abrasion resistance) of cotton fabrics>
Plain cotton broadcloth was coated with printing inks (L-1) to (L-19) and comparative printing inks (L'-1) to (L'-4) using a bar coater to a dry thickness of 1 μm. The coated cotton broadcloth was dried at 160°C for 10 minutes to create test pieces (4 cm x 12 cm) coated with polyurethane resin. Wet friction fastness was evaluated according to JIS L0849-2. A load of 200 g was applied, and the pieces were rubbed back and forth 100 times. The color transfer density on the No. 3 cloth side was measured at 9 points using a spectrophotometer [X-rite 938], and the average of the measurement results was taken as the color transfer density. The color transfer density was evaluated according to the following criteria, and the results are shown in Tables 2 and 3. A lower color transfer density indicates better friction fastness.
◎: Transfer concentration 0.20 or less ○: Transfer concentration greater than 0.20 and 0.25 or less △: Transfer concentration greater than 0.25 and 0.30 or less ×: Transfer concentration greater than 0.30 and 0.40 or less A transfer concentration of 0.25 or less is at a practical level.

The information in Tables 2 and 3 is as follows:
1,4-BD: 1,4-butanediol DMPA: 2,2-dimethylolpropionic acid polycarbonate diol: Duranol® G4672 manufactured by Asahi Kasei Corporation
MDI-H: Dicyclohexylmethane-4,4-diisocyanate IPDI: Isophorone diisocyanate TEA: Triethylamine IPDA: Isophorone diamine Production Example 12 (O-1): Ester of sorbitol and oleic acid produced in Production Example 12 (O-1)
Manufacturing Example 13 (O-2): Polyethylene glycol monooleate ester (O-2) manufactured in Manufacturing Example 13

The printing inks (L-1) to (L-19) of Examples 1 to 19 exhibited excellent initial dispersibility and storage stability, as well as excellent abrasion resistance to coated paper for printing, corrugated cardboard, and cotton fabrics. Comparative printing inks (L'-1) and (L'-2), which used aqueous dispersions of polyurethane resin that did not use crystalline polyester polyol as a raw material, had insufficient abrasion fastness (Comparative Examples 1 and 2). Comparative printing inks (L'-3) and (L'-4), which used aqueous dispersions of polyurethane resin with a water absorption rate greater than 6% by weight, also had insufficient abrasion fastness (Comparative Examples 3 and 4).

Claims (3)

It contains a polyurethane resin (U) obtained by reacting a polyol component, a polyisocyanate component, and a chain extender, and water.
The polyol component is a polyol component containing a crystalline polyester polyol and a saturated aliphatic diol having 2 to 20 carbon atoms .
The crystalline polyester polyol is a polyester polyol obtained by dehydration condensation of an aliphatic dicarboxylic acid having 4 to 12 carbon atoms and an aliphatic diol having 3 to 12 carbon atoms.
An aqueous dispersion of polyurethane resin for inkjet ink, wherein the water absorption rate of the polyurethane resin (U) is 6% by weight or less, and the storage modulus G' of the polyurethane resin (U) is 0.1 to 1.0 MPa. The aqueous dispersion of polyurethane resin for inkjet ink according to claim 1, wherein the chain extender is a diamine having 2 to 10 carbon atoms. The aqueous polyurethane resin dispersion for inkjet ink according to claim 1 or 2, further containing a fatty acid sorbitan ester and/or a monofatty acid polyethylene glycol ester.