JP2008143960A - Aqueous pigment dispersion, and ink composition using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous pigment dispersion providing an ink composition exhibiting good marker resistance when printed on plain paper, and good fixability when printed on glossy paper; and to provide the ink composition achieving the jetting of ink stable over a long period even in a thermal method requiring the stability of the pigment dispersion in the ink composition at a high temperature, and providing a printed product having a high optical density. <P>SOLUTION: The aqueous pigment dispersion contains at least a pigment, a polyurethane and water. The diol component of 55-95 mol% in the whole diol components constituting the polyurethane is a dihydric alcohol represented by a specific chemical formula and having a carboxy group, and the diol component of 5-45 mol% is the one constituted of a structure derived from a siloxane compound having two hydroxy groups. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aqueous pigment dispersion excellent in dispersion stability and heat resistance and an ink composition using the same. In particular, the present invention relates to an ink composition used for an ink jet printer.

  In recent years, the use of pigments having excellent fastness instead of dyes as colorants used in inks for ink jet printers and inks for writing instruments has been studied. As an ink ejection method in ink jet, a piezo method in which a piezoelectric element is deformed by applying a voltage to push out the ink and a thermal method in which the ink is blown by pressure generated during foaming by heating are generally used.

  Ink for inkjet printers for consumer use mainly uses water as a solvent, but pigments are insoluble in water unlike dyes, so pigments for inkjet printers that use pigments are stably dispersed in water in the form of fine particles. It is necessary to let In particular, in the thermal method, since the ink is instantaneously exposed to a high temperature of 400 to 500 ° C. at the time of ejection, dispersion stability of the pigment at a high temperature is required.

  As a method for dispersing pigment fine particles in water, a method using a polymer dispersant has been reported (see Patent Document 1). In this method, carbon black is stably dispersed in water using an acrylic polymer dispersant containing a sulfonic acid group and an acrylic polymer dispersant containing a carboxyl group. However, in the ink composition stabilized by the polymer dispersant, if the pigment concentration in the ink is increased to increase the optical density of the printed matter, the concentration of the polymer dispersant also increases, and the viscosity of the ink composition As a result, the discharge stability is lowered.

  On the other hand, there is a technique for stabilizing carbon black in water without a polymer dispersant or a surfactant (see Patent Documents 2 to 4). In these methods, carbon black is stably dispersed in water by introducing a hydrophilic functional group such as a carboxyl group or a sulfonic acid group directly or via a polyvalent group on the surface of carbon black. However, after printing this ink composition on plain paper and drying, rubbing the printed part with a highlighter pen, the printed part was soiled, and there was a problem in marker resistance.

  As a method for improving marker resistance when pigment ink is printed on plain paper, an acrylic polymer obtained from an ionic monomer, a hydrophobic monomer, a monomer having fluorine and / or a siloxane chain is chemically bonded to carbon black. There is a method (see Patent Document 5). This method provides an ink composition having improved marker resistance by imparting hydrophobicity to carbon black particles by fluorine and / or siloxane chains in an acrylic polymer. In this method, the acrylic polymer has a weight average molecular weight of 3000 to 20000. When the acrylic polymer has a weight average molecular weight of 50,000 or less, the entanglement between the polymers is weak, and the fixability of the pigment when printed on glossy paper is insufficient.

  In addition, in order to improve the marker resistance of carbon black, there is a method of adding a water-dispersible urethane polymer to the ink composition (see Patent Document 6). The ink-jet ink described in Patent Document 6 has improved marker resistance by containing carbon black having a hydrophilic group introduced into a water-based ink and a polyurethane dispersion having a weight average molecular weight of 30,000 or more. . Polyurethane has strong entanglement between polymers even if the weight average molecular weight is not so large due to hydrogen bonds between urethane bonds, so the weight of the pigment when printed on glossy paper by making the weight average molecular weight 10,000 or more. Fixability is improved. In this method, a polyurethane dispersion in which a carboxyl group is introduced into polyurethane is synthesized by using dimethylolpropionic acid as a diol component constituting the polyurethane. However, since dimethylolpropionic acid has a small number of carbon atoms, a polyurethane having a carboxyl group introduced into the hard segment is formed. An ink composition containing a high-molecular-weight polyurethane having a weight-average molecular weight of 10,000 or more and having a carboxyl group introduced into a hard segment and having a weight-average molecular weight of 10,000 or more tends to cause pigment aggregation at a high temperature. It is difficult to discharge stably for a period.

On the other hand, an ink jet recording sheet containing an ink receiving layer made of fine particle alumina and hydrophilic polyurethane has been proposed (see Patent Document 7). The ink jet recording sheet described in Patent Document 7 introduces a polysiloxane and a tertiary amino group into hydrophilic polyurethane so that the ink jet recording sheet after the ink jet ink containing a dye is printed and the water resistance of the ink jet recording sheet. Improves sex. That is, the fixing property of the dye and the fixing property of the printed matter are improved by the ionic bond between the tertiary amino group of the polyurethane in the ink receiving layer and the dye molecule having the anionic group in the ink-jet ink. However, when this tertiary amino group-containing polyurethane is mixed into an ink composition containing a pigment that has been dispersed and stabilized by an anionic functional group such as a carboxyl group or a sulfonic acid group, aggregation of the pigment tends to occur.
JP 2000-154343 A (2nd page) JP-A-8-3498 (2nd page) JP 10-140062 (2nd page) JP-A-10-195360 (2nd page) JP2004-115548 (2nd page, 11th to 14th page, 28th page) JP 2005-515289 A (2nd page, 9th page) JP 2005-238547 A (2nd page, 4th to 7th page)

  Provided is an aqueous pigment dispersion that can produce an ink composition that has good marker resistance when printed on plain paper and good fixability when printed on glossy paper. Furthermore, the present invention provides an ink composition capable of realizing stable ink ejection over a long period of time even in a thermal system that requires pigment dispersion stability in an ink composition at a high temperature. Moreover, the ink composition which can obtain printed matter with high optical density is provided.

  That is, the present invention is an aqueous pigment dispersion containing at least a pigment, polyurethane and water, and 55 to 95 mol% in all diol components constituting the polyurethane is derived from the compound represented by the general formula (1). It is an aqueous pigment dispersion liquid having a structure and having a structure derived from a siloxane compound having 5 to 45 mol% having two hydroxyl groups.

(R ¹ represents an organic group having 13 to 80 carbon atoms having an alkylene group and / or an ester group. R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

  The aqueous pigment dispersion of the present invention is excellent in dispersion stability at high temperatures of finely divided pigments. In addition, the ink composition produced using the aqueous pigment dispersion of the present invention can realize stable ink ejection over a long period of time even in the thermal method. Furthermore, the ink composition has a high optical density when printed on plain paper and glossy paper, has good marker resistance when printed on plain paper, and has good fixability when printed on glossy paper.

  The present invention is an aqueous pigment dispersion containing at least a pigment, polyurethane, and water, wherein 55 to 95 mol% of all diol components constituting the polyurethane are derived from the compound represented by the general formula (1). A polyurethane having a structure derived from a siloxane compound having 5 to 45 mol% having two hydroxyl groups is used.

R ¹ represents an organic group having 13 to 80 carbon atoms having an alkylene group and / or an ester group. R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

  Polyurethane is produced by an addition reaction between a compound having an isocyanate group and a compound having active hydrogen such as a hydroxyl group. Moreover, by introducing a carboxyl group or a sulfonic acid group into the molecular chain into the polyurethane and adding a neutralizing agent, it can be dispersed or dissolved in water. In order to introduce a carboxyl group into a polyurethane molecular chain, dihydroxycarboxylic acid such as dimethylolpropionic acid is generally used as a part of the diol components constituting the polyurethane. The portion where the urethane bonds of polyurethane are bonded by hydrogen bonds is a portion where the concentration of urethane bonds is high and becomes a hard segment. On the other hand, a portion where the concentration of urethane bonds is small becomes a soft segment. Control of the concentration of the urethane bond generally depends on the number of carbons attached to the hydroxyl group of a compound having an active hydrogen such as a hydroxyl group that forms a urethane bond. When a dihydroxycarboxylic acid such as dimethylolpropionic acid is used as the diol, the number of carbon atoms attached to the hydroxyl group is small, so that the carboxyl group is introduced into the hard segment. When the weight average molecular weight of the polyurethane is 10,000 or more, in the polyurethane in which the carboxyl group is introduced into the hard segment, the dispersion state of the pigment becomes unstable at a high temperature in the aqueous pigment dispersion using the polyurethane, and the ink composition In the thermal method, it is difficult to stably discharge for a long time.

The number of carbon atoms contained in R ^{1 of the} compound represented by the general formula (1) is in the range of 13 to 80, but if it is 13 or more, the flexibility of the portion into which the carboxyl group is introduced becomes sufficiently large, The site where the carboxyl group is introduced becomes the soft segment. Even if the weight average molecular weight of the polyurethane is 10,000 or more, since the carboxyl group is introduced into the soft segment, the pigment dispersion containing the polyurethane has good heat resistance and stable thermal discharge characteristics of the ink composition. Turn into. On the other hand, when the number of carbon atoms contained in R ^{1 of the} compound represented by the general formula (1) is larger than 80, the content of the carboxyl group in the molecular chain is reduced, so that the hydrophilicity of the polyurethane is lowered. In addition, the heat resistance of the pigment dispersion containing polyurethane is lowered.

  In order to obtain an ink composition having good thermal discharge characteristics and good marker resistance when printed on plain paper, the compound represented by the general formula (1) in the polyurethane used in the present invention and two hydroxyl groups are used. It is necessary to use a siloxane compound having When a polyurethane having a siloxane structure derived from a siloxane compound is used, the marker resistance of ink printed on plain paper is improved. This is because when the printed part is rubbed with an aqueous fluorescent pen, the pigment particles are protected by the polyurethane having a siloxane structure exhibiting water repellency, so that the pigment particles are difficult to elute into the water in the marker pen.

  The amount of the compound represented by the general formula (1) contained in all diol components is 55 to 95 mol%, preferably 70 to 90 mol%. When the content of the compound represented by the general formula (1) is less than 55 mol%, the aqueous pigment dispersion containing polyurethane has poor heat resistance and the thermal discharge characteristics of the ink composition become unstable, and the general formula ( If the content of the compound represented by 1) is less than 70 mol%, the optical density of the printed matter obtained from the polyurethane-containing ink composition may be lowered. Moreover, the quantity of the siloxane compound which has two hydroxyl groups contained in all the diol components is 5-45 mol%. If the content of the siloxane compound having two hydroxyl groups is less than 5 mol%, the marker resistance of the printed matter obtained from the ink composition becomes poor.

  The amount of the compound represented by the general formula (1) at the time of synthesizing the polyurethane contained in all the diol components is 55 to 95 mol% in the total diol, and the amount of the siloxane compound having two hydroxyl groups is 5 to 5 in the total diol. By setting it as 45 mol%, the content of the compound of the general formula (1) in all diols constituting the polyurethane is in the range of 55 to 95 mol%, and the content of the siloxane compound having two hydroxyl groups is 4 to 55. It can be in the range of mol%.

  The compound represented by the general formula (1) and the siloxane compound having two hydroxyl groups in the ink composition can be analyzed by the following method, for example. After adding hydrochloric acid or the like to the ink composition to precipitate the pigment and polyurethane, the pigment and polyurethane are extracted from the ink composition by centrifugation, washing with water and vacuum drying. The pigment and polyurethane are put into a solvent that dissolves only polyurethane, such as tetrahydrofuran, and then subjected to centrifugation, washing with water, and vacuum drying to extract the polyurethane. Pyridine and the like are added to the polyurethane, heated at 50 to 100 ° C. to decompose the urethane bond, and all diols constituting the polyurethane are fractionated using high performance liquid chromatography. The molecular weight and weight ratio of each diol fractionated using a mass spectrometer is estimated, and the presence or absence of carboxyl groups and siloxane groups is estimated using a nuclear magnetic resonance spectrometer and an infrared spectrometer, and the general formula (1) And a siloxane compound having two hydroxyl groups are estimated. By combining the methods as described above, it is possible to estimate the molar ratio of the compound represented by the general formula (1) and the siloxane compound having two hydroxyl groups contained in all diols.

R ¹ of the compound represented by the general formula (1) represents an organic group having 13 to 80 carbon atoms having an alkylene group and / or an ester group. The compound represented by the general formula (1) only needs to satisfy the range of 13 to 80 carbon atoms contained in R ¹ , and is not limited to any embodiment in a range generally referred to as a polymer or an oligomer. R ¹ may be either straight chain or branched, but straight chain is preferred because the flexibility of the portion where the carboxyl group is introduced in the polyurethane is increased.

  The compound represented by the general formula (1) is preferably a carboxylic acid-modified polycaprolactone diol from the viewpoints of heat resistance, light resistance, water resistance and the like of polyurethane. Carboxylic acid-modified polycaprolactone diol is a polyester diol obtained by ring-opening addition polymerization of lactones to dihydroxycarboxylic acid.

  Examples of the carboxylic acid-modified polycaprolactone diol used in the present invention include “Placcel” 205BA, 210BA, and 220BA manufactured by Daicel Chemical Industries, Ltd. Moreover, when synthesize | combining, the following methods are mentioned, for example. It is synthesized by ring-opening addition polymerization of a hydroxyl group in a dihydroxycarboxylic acid such as dimethylolpropionic acid or dimethylolbutanoic acid with a lactone such as ε-caprolactone or trimethylcaprolactone at a reaction temperature of 110 to 220 ° C.

  On the other hand, examples of the siloxane compound having two hydroxyl groups constituting the polyurethane include a compound in which two hydroxyl groups are introduced into the main chain of polysiloxane, a compound in which two hydroxyl groups are introduced into the side chain of polysiloxane, and the like. In order to increase the optical density of a printed material obtained from the ink composition, a siloxane compound in which hydroxyl groups are introduced at both ends of the polysiloxane is preferable.

  The siloxane compound having hydroxyl groups introduced at both ends of the polysiloxane is preferably a compound represented by the general formula (2).

R ^{4 to} R ⁷ may be the same or different and have at least one organic group selected from an alkyl group having 1 to 20 carbon atoms and an aryl group, and R ⁸ and R ⁹ have 1 to 20 carbon atoms. It has at least one organic group selected from an alkylene group and an arylene group. n is in the range of 4-100.

  When n in the general formula (2) is less than 4, the water repellency of the polyurethane is reduced, and the marker resistance of the ink composition containing polyurethane may be poor. Conversely, when n is greater than 100, the thermal discharge characteristics of the ink composition containing polyurethane may be poor.

  Examples of the compound represented by the general formula (2) include “both end silaplane” FM4411, FM4421, FM4425 manufactured by Chisso Corporation. Moreover, when synthesize | combining, the following methods are mentioned, for example. After mixing a siloxane compound having a Si—H group and a compound having a hydroxyl group and a carbon-carbon double bond, a carbon-carbon double bond is added to the Si—H group using a catalyst or the like.

  The polyurethane used in the present invention can be synthesized, for example, by the following method. The compound represented by the general formula (1), the siloxane compound having two hydroxyl groups, and diisocyanate are reacted in a low-boiling water-soluble organic solvent such as acetone or methyl ethyl ketone. The reaction is carried out at a temperature of 30 to 100 ° C. for 1 to 24 hours to synthesize a urethane prepolymer. During this synthesis reaction, a catalyst such as tetraethyl titanate or tetrabutyl titanate may be used. A neutralizing agent and water are added to the obtained urethane prepolymer solution. Thereafter, a chain extension reaction and, if necessary, a crosslinking reaction are performed. After removing the low-boiling water-soluble organic solvent, a polyurethane is obtained.

  Examples of the diisocyanate used when synthesizing the polyurethane include aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate. Examples of the aliphatic diisocyanate include hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 4, Examples include 4-cyclohexylmethane diisocyanate, and examples of the aromatic diisocyanate include xylylene diisocyanate and tetramethylxylene diisocyanate. In the present invention, it is preferable to use alicyclic and aliphatic diisocyanates because the light resistance of a print obtained from an ink composition containing polyurethane is improved.

  As a neutralizing agent used when synthesizing polyurethane, ammonia, ethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, monoethanolamine, dimethylethanolamine, Examples thereof include organic amines such as diethylethanolamine, morpholine, N-methylmorpholine, and 2-amino-2-ethyl-1-propanol, and inorganic alkalis such as sodium hydroxide and potassium hydroxide.

  The weight ratio of the component combining diol and diisocyanate and the low-boiling water-soluble solvent used when synthesizing the urethane prepolymer is usually the component combining diol and diisocyanate: low-boiling water-soluble solvent = 3 to 9: 7 to 1, preferably 4 to 8: 6 to 2. If the amount of the diol and diisocyanate components is too large, the viscosity of the urethane prepolymer solution becomes too high, and the production may not be easy. On the other hand, if the amount is too small, the degree of polymerization of the urethane prepolymer may be too small.

  The molar ratio of the isocyanate group in the diisocyanate and the hydroxyl group in the diol used when synthesizing the urethane prepolymer is usually isocyanate group: hydroxyl group = 51-80: 49-20, preferably 51-70: 49-30. . By setting the molar ratio of the isocyanate group to the hydroxyl group within the above range, the weight average molecular weight of the finally obtained polyurethane can be set to a preferable range, and the thermal discharge characteristics and the fixability to glossy paper are improved.

  When the polyurethane is present in the aqueous solution comprising the neutralizing agent and water, the pH is preferably 6.5 to 9.5, so that the polyurethane can be easily dissolved in the aqueous solution containing the neutralizing agent. It becomes. The pH of the aqueous solution containing the neutralizing agent in which the polyurethane is dissolved can be controlled by changing the addition amount of the neutralizing agent.

  Low-boiling organic solvents such as acetone and methyl ethyl ketone used for urethane prepolymer synthesis are usually treated at a reduced pressure and at a temperature of 40 to 100 ° C. for several hours using a rotary evaporator or aspirator after polyurethane is obtained. Removed. When part of the water is removed together with the low boiling point organic solvent, it is preferable to add water appropriately so that the polyurethane does not precipitate or gel. It is preferable that low-boiling organic solvents such as acetone and methyl ethyl ketone remain as little as possible, but they may be within the range of 0.1 to 1000 ppm, preferably 1 to 500 ppm, with respect to the polyurethane in the neutralizing agent-containing aqueous solution. If the concentration of the low-boiling organic solvent is higher than 1000 ppm, an irritating odor may remain in the aqueous pigment dispersion containing the polyurethane and the ink composition. On the other hand, when the concentration of the low boiling point organic solvent is set to 0.1 ppm, the production efficiency may be lowered.

  The polyurethane used in the present invention is usually obtained by carrying out a chain extension reaction after dispersing or dissolving a urethane prepolymer in an aqueous solution containing a neutralizing agent. The chain extension reaction is carried out by mixing a chain extender and a urethane prepolymer having a terminal isocyanate group at a temperature of 50 ° C to 100 ° C. It is preferable to use water and / or an amine as the chain extender, and examples of the amine include ethylenediamine, trimethylenediamine, hexamethylenediamine, dicyclohexylmethanediamine, and isophoronediamine.

  The acid value of the polyurethane used in the present invention is preferably 50 to 100 KOH · mg / g, more preferably 55 to 80 KOH · mg / g. If the acid value is less than 50 KOH · mg / g, the thermal discharge characteristics of the ink composition containing polyurethane may become unstable because the hydrophilicity of the polyurethane is too low. On the other hand, when the acid value of the polyurethane is greater than 100 KOH · mg / g, the hydrophilicity of the polyurethane is too high, and the marker resistance of the printed matter obtained from the ink composition contained in the polyurethane may be lowered.

  The acid value of the polyurethane can be controlled by the acid value of the compound represented by the general formula (1) and the content of the compound represented by the general formula (1) with respect to the total amount of the polyurethane. When the acid value of the polyurethane is in the above range, the acid value of the compound represented by the general formula (1) of the present invention is 50 KOH · mg / g or more, preferably 55 KOH · mg / g or more. . When the acid value of the compound represented by the general formula (1) is less than 50 KOH · mg / g, the acid value of the polyurethane is also less than 50 KOH · mg / g, so that the heat resistance of the aqueous pigment dispersion containing polyurethane is reduced. It may become defective.

  In the present invention, the acid value of polyurethane means the number of milligrams of potassium hydroxide required to neutralize 1 g of polyurethane. In the present invention, the acid value of the polyurethane is measured as follows. An aqueous hydrochloric acid solution or the like is dropped onto the polyurethane to precipitate the polyurethane, and then the supernatant is filtered and the polyurethane is sufficiently washed with ion-exchanged water. Thereafter, the neutralizing agent, hydrochloric acid, water and the like are completely removed from the polyurethane by drying at a temperature of 100 ° C. or higher for several hours, and then the polyurethane is dissolved in ethanol at a concentration of 10% by weight or less. When polyurethane does not completely dissolve in ethanol, a water-soluble organic solvent such as methyl ethyl ketone is added and dissolved. In this way, a sample for measuring the acid value of polyurethane is prepared. Based on JIS (Japanese Industrial Standard) K0070, after adding several drops of phenolphthalein solution to this polyurethane solution, titration is performed using a 0.1 mol / l potassium hydroxide solution to calculate the acid value of the polyurethane. .

  In general, the higher the weight average molecular weight of the polymer, the stronger the entanglement between the polymers, so that the fixability of the pigment on the glossy paper becomes better. However, since polyurethanes are strongly entangled with each other by hydrogen bonds between urethane bonds, polyurethane has good fixability of pigments on glossy paper even if the weight average molecular weight is not increased so much.

  The polyurethane used in the present invention has a weight average molecular weight of preferably 10,000 to 50,000, more preferably 11,000 to 40,000. If the weight average molecular weight of the polyurethane is less than 10,000, the fixability of the print obtained from the polyurethane-containing ink composition to glossy paper may be lowered. When the weight average molecular weight of the polyurethane is larger than 50000, the viscosity of the ink composition containing polyurethane may increase and the thermal discharge characteristics may be deteriorated. When the weight average molecular weight of the polyurethane is larger than 40000, the polyurethane containing ink The optical density of the print obtained from the composition tends to be small.

  In the present invention, the molecular weight of the polyurethane can be determined in terms of polystyrene using gel permeation chromatography. The molecular weight of the polyurethane can be controlled by the molecular weight of the diol, the molecular weight of the diisocyanate, the molar ratio of the hydroxyl group to the isocyanate group in the diisocyanate, the synthesis conditions of the polyurethane, and the like.

  The viscosity of the neutralizing agent-containing aqueous solution of polyurethane used in the present invention is preferably 300 mPa · s or less, more preferably 100 mPa · s or less, when the polyurethane concentration is 20% by weight. If the viscosity of the neutralizing agent-containing aqueous solution of polyurethane is greater than 300 mPa · s, the viscosity of the ink composition containing polyurethane may increase, resulting in poor thermal discharge characteristics.

  The water used in the present invention is preferably water from which impurity ions are removed. For example, ion-exchanged water or distilled water is preferably used.

  As the pigment used in the present invention, an organic pigment or an inorganic pigment can be used. Preferably, it is desirable to use an impurity ion that has been sufficiently washed with ion-exchanged water or distilled water.

  Examples of the inorganic pigment used in the present invention include various types such as iron oxide, titanium oxide, and carbon black. Carbon black is preferable as the black ink used in the ink jet printer, and examples of the carbon black include acetylene black, channel black, and furnace black. Examples of commercially available carbon blacks include Legal 400R, Legal 330R, Legal 660R (Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4 (above Degussa), MCF -88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical Corporation).

  In order to obtain an aqueous pigment dispersion having excellent dispersion stability and heat resistance, it is preferable to use oxidized carbon black. In order to obtain the oxidized carbon black, for example, a method of oxidation with a hypohalite such as sodium hypochlorite or potassium hypochlorite is mentioned, and sodium hypochlorite is particularly preferable in terms of reactivity. preferable. Carbon black and carbon black and 10-30% hypohalite (for example, sodium hypochlorite) in an effective halogen concentration are charged in an appropriate amount of water and stirred at a reaction temperature of 80-120 ° C. To do. In the synthesis of oxidized carbon black, chlorine ions and the like may be mixed into these compounds. Since chloride ions have the effect of reducing electrostatic repulsion and causing pigment aggregation, it is better to reduce this amount of contamination as much as possible. Impurity ions such as chlorine ions in the oxidized carbon black are preferably removed by dialysis or the like.

  Organic pigments used in the present invention include phthalocyanine, quinacridone, indigo, isoindolinone, isoindoline, quinophthalone, diketopyrrolopyrrole, benzimidazolone, perylene, perinone, dioxazine, anthraquinone There are various systems such as a system, an insoluble azo system, a condensed azo system, and a metal complex system.

  Examples of phthalocyanine pigments include blue pigments PB15, PB15: 2, PB15: 3, PB15: 4, B15: 5, PB15: 6, PB16, green pigments PG7 and PG36.

  Examples of the quinacridone pigment include violet pigments PV19 and PV42, red pigments PR122, PR192, PR202, PR206, PR207, PR209, orange pigments PO48 and PO49, and the like.

  Examples of indigo pigments include blue pigments PB63 and PB66, red pigments PR88 and PR181.

  Examples of isoindolinone pigments include yellow pigments PY109, PY110, PY173, orange pigment PO61, and the like.

  Examples of isoindoline pigments include red pigment PR260, yellow pigments PY139, PY185, orange pigments PO66, PO69, and the like.

  Examples of quinophthalone pigments include yellow pigment PY138.

  Examples of diketopyrrolopyrrole pigments include red pigments PR254, PR255, PR264, PR272, orange pigments PO71, PO73, and the like.

  Examples of benzimidazolone pigments include purple pigment PV32, red pigments PR171, PR175, PR176, PR185, PR208, yellow pigments PY120, PY151, PY154, PY156, PY175, PY180, PY181, PY194, orange pigments PO36, PO60, PO62, PO72 etc. are mentioned.

  Examples of perylene pigments include purple pigment PV29, red pigments PR123, PR149, PR178, PR179, PR190, PR224, and the like.

  Examples of perinone pigments include red pigment PR194 and orange pigment PO43.

  Examples of dioxazine-based materials include violet pigments PV23 and PV37.

  Examples of anthraquinone pigments include blue pigment PB60, red pigments PR168 and PR177, yellow pigments PY24, PY108, PY147, PY193, and orange pigment PO51.

  Examples of insoluble azo pigments include red pigments PR1, PR2, PR3, PR4, PR5, PR6, PR7, PR8, PR9, PR10, PR11, PR12, PR13, PR14, PR15, PR16, PR17, PR18, PR20, PR21. PR22, PR23, PR31, PR32, PR37, PR38, PR41, PR95, PR111, PR112, PR114, PR119, PR136, PR146, PR147, PR148, PR150, PR164, PR170, PR184, PR185, PR187, PR188, PR210, PR212 PR213, PR222, PR223, PR238, PR245, PR253, PR256, PR261, PR266, PR267, PR268, PR269, yellow pigments PY1, P 2, PY3, PY5, PY6, PY10, PY12, PY13, PY14, PY17, PY49, PY55, PY60, PY63, PY65, PY73, PY74, PY75, PY81, PY83, PY87, PY90, PY97, PY98, PY106, PY111, PY113, PY114, PY116, PY121, PY124, PY126, PY127, PY130, PY136, PY152, PY154, PY165, PY167, PY170, PY171, PY172, PY174, PY176, PY188, orange pigments PO1, PO2, PO13, PO13, PO13 PO15, PO16, PO22, PO24, PO34, PO36, PO38, PO44, and the like.

  Examples of the condensed azo pigments include red pigments PR144, PR166, PR214, PR220, PR221, PR242, PR248, PR262, yellow pigments PY93, PY94, PY95, PY128, PY166, orange pigment PO31, and the like.

  Examples of the metal complex pigment include green pigment PG10, yellow pigments PY117, PY129, PY153, PY177, PY179, PY257, PY271, orange pigments PO59, PO65, and PO68.

  When an organic pigment is used as a pigment, in order to obtain an aqueous pigment dispersion having excellent dispersion stability and heat resistance, a pigment derivative having a structure in which a sulfonic acid group is introduced into the chemical structure of the organic pigment and / or the organic pigment It is preferable to contain a pigment derivative having a structure in which a sulfonic acid group is introduced into a chemical structure partially in common with the chemical structure. The pigment derivative having a sulfonic acid group introduced according to the present invention has the same chemical structure as a pigment derivative having a sulfonic acid group introduced into the same pigment as the organic pigment used or a part of the chemical structure of the organic pigment used. It refers to two types of pigment derivatives in which sulfonic acid groups are introduced into the pigment, and each may be used alone or in combination. For example, when a quinacridone red pigment PR122 is used, a pigment derivative in which a sulfonic acid group is introduced into PR122, or a pigment derivative in which a sulfonic acid group is introduced into a red pigment PR209 having a partial chemical structure identical to PR122, respectively. Used alone or in combination. These pigments and pigment derivatives are strongly bonded by intermolecular force, and negatively charge the surface of the fine particles.

  The pigment derivative introduced with a sulfonic acid group used in the present invention is synthesized, for example, by the following method. The organic pigment is added to concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or a mixture thereof to perform a sulfonation reaction. The resulting reaction solution is diluted with water and optionally neutralized with a neutralizing agent. The suspension thus obtained is filtered, washed with an aqueous washing solution, and dried.

  In the present invention, the mixing ratio of the organic pigment and the pigment derivative into which the sulfonic acid is introduced is, as a weight ratio, the organic pigment: the pigment derivative into which the sulfonic acid group is introduced = 50 to 99:50 to 1, preferably 60 to 97. : 40-3 mixed. If the amount of the pigment derivative is too small, the pigment dispersion stabilizing effect cannot be exhibited. Conversely, if the amount of the pigmented derivative is too large, the color tone may change unfavorably.

  When an aqueous pigment dispersion prepared by the above method is used to synthesize a pigment derivative into which a sulfonic acid group has been introduced, sulfate ions may be mixed into these compounds. Since sulfate ions have the effect of reducing electrostatic repulsion and causing pigment aggregation, it is better to reduce this amount of contamination as much as possible. Impurity ions such as sulfate ions in the pigment derivative introduced with a sulfonic acid group are preferably removed by dialysis or the like.

  The aqueous pigment dispersion of the present invention applies shear stress to coarse pigment particles (usually 1 to 50 μm) that are aggregates of a large number of primary particles in water, and the coarse pigment particles are converted into primary particles or a small number of primary particles. It is produced by refining and dispersing in aggregate particles.

  As a disperser for applying a shear stress to coarse particles in water, a method using a sand mill, a ball mill, a bead mill, a three roll mill, an attritor or the like is preferably employed. In order to efficiently refine coarse particles to primary particles or a collection of a small number of primary particles, it is preferable to apply a shearing stress using a dispersion medium. As the dispersion medium, zirconia beads, alumina beads, glass beads, or the like are used. be able to.

  In the present invention, the mixing ratio of the pigment and polyurethane is a weight ratio of pigment: polyurethane = 3 to 9: 7 to 1, preferably 4 to 8: 6 to 2, and more preferably 5 to 7: 5 to 3.

  If the amount of the pigment is too small, the optical density of the print obtained from the ink composition becomes small, and if the amount of the pigment is too large, the fixability to glossy paper becomes poor. The timing of mixing the pigment and the polyurethane may be any of before the coarse particles of the pigment are refined and dispersed, during the dispersion, and after the dispersion.

  The pH of the aqueous pigment dispersion containing the polyurethane and pigment of the present invention is preferably in the range of 6 to 10, more preferably 6.5 to 9.5. If the pH of the aqueous pigment dispersion is less than 6, polyurethane in the aqueous pigment dispersion may precipitate. If the pH is higher than 10, the dispersion stability and heat resistance of the aqueous pigment dispersion may be lowered. The pH of the aqueous pigment dispersion of the present invention is, for example, ammonia, ethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, monoethanolamine, dimethylethanolamine, It can be adjusted to an appropriate range by organic amines such as diethylethanolamine, morpholine, N-methylmorpholine, 2-amino-2-ethyl-1-propanol, and inorganic alkalis such as sodium hydroxide and potassium hydroxide.

  In the present invention, a water-soluble organic solvent may be used to adjust the surface tension of the aqueous pigment dispersion containing polyurethane and pigment. A water-soluble organic solvent having a relative dielectric constant of 5 to 200, preferably 10 to 100 is preferably used. If the non-dielectric constant of the water-soluble organic solvent is too small, the relative dielectric constant of the aqueous pigment dispersion is also small, so that the electrostatic repulsion between the pigment particles is weakened and the dispersion stability is lowered.

  Examples of water-soluble organic solvents that satisfy the above ranges can include various solvents such as ethers, alcohols, ether alcohols, esters, ketones, acids, amines, acid amides, For example, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, glycerin, γ-butyrolactone, N-methyl-2-pyrrolidone, dimethyl sulfoxide, ethylene carbonate, propylene carbonate Etc. can be used.

  In the present invention, the surface tension of the aqueous pigment dispersion at 25 ° C. is preferably 25 to 60 mN / m, more preferably 30 to 50 mN / m. If the surface tension is greater than 60 mN / m, coarse particles are likely to remain because the wettability of the pigment to water is poor. On the other hand, if the surface tension is larger than 50 mN / m, it is difficult to uniformly transmit the dispersion energy of the disperser to the pigment particles, and it may be difficult to obtain a pigment dispersion having a uniform pigment particle size. On the other hand, if the surface tension of the aqueous pigment dispersion is too small, the surface tension of the ink composition is also reduced, and thus the permeability of the ink into the paper is increased, which may cause bleeding.

  The surface tension of the aqueous pigment dispersion of the present invention is within the above range by setting the mixing ratio of water and water-soluble organic solvent to water: water-soluble organic solvent = 95-50: 5-50 by weight ratio. Can be controlled.

  In the aqueous pigment dispersion of the present invention, the pigment content relative to the entire aqueous pigment dispersion is 8 to 20% by weight, preferably 10 to 16% by weight. If the content is too small, the production efficiency of the dispersion is low and the cost is increased. On the other hand, if the content is too large, it becomes very difficult to stabilize the dispersion state.

The pigment dispersibility of the aqueous pigment dispersion containing the polyurethane and pigment of the present invention can be evaluated by measuring the Casson yield value of the pigment dispersion. The Casson yield value is preferably 1 × 10 ⁻² Pa or less, more preferably 1 × 10 ⁻³ Pa or less. Within this range, it can be said that the dispersibility of the pigment is stable.

  The dispersibility of the pigment can be controlled by using carbon black oxidized with the above hypohalite or a pigment derivative having a sulfonic acid group introduced.

  In the present invention, the particle size in the dispersed state of pigment particles (primary particles or an aggregate of a small number of primary particles) in an aqueous pigment dispersion containing polyurethane is 5 to 200 nm in terms of volume-based arithmetic average particle size, preferably It is preferable that it exists in the range of 10-100 nm.

When the particle diameter of the pigment in the dispersed state is too large, there is a high possibility that the inkjet nozzle will be clogged. On the other hand, if the particle diameter of the pigment in the dispersed state is too small, the specific surface area of the pigment becomes too large, and the dispersed state of the pigment may be easily destabilized. An aqueous pigment dispersion having a Casson yield value of 1 × 10 ⁻² Pa or less is stored for a long period of time even when subjected to treatments such as dilution and heating because the dispersion state of the finely dispersed pigment is stable. Even in this case, the dispersed particle diameter of the pigment is maintained without being changed due to aggregation.

  The maximum dispersed particle size of the pigment is 5 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less. When the maximum dispersed particle diameter of the pigment is large, there is a high possibility that the pigment clogs the ink ejection port, that is, the nozzle.

  The viscosity of the aqueous pigment dispersion containing polyurethane and pigment is preferably in the range of 1 to 50 mPa · s, preferably 3 to 10 mPa · s. Within this range, it becomes easy to produce an ink composition having a viscosity suitable for ink ejection. In order to keep the viscosity of the aqueous pigment dispersion containing polyurethane and pigment within the above range, the compound represented by the general formula (1) and the siloxane compound having two hydroxyl groups in all diols constituting the polyurethane It is obtained by appropriately controlling the amount, the acid value of the polyurethane, the molecular weight of the polyurethane, and the like, and further using the carbon black treated with the above-mentioned hypohalite and the pigment derivative introduced with a sulfonic acid group. .

  The pigment dispersion stability at a high temperature of the aqueous pigment dispersion of the present invention can be evaluated by treating at 65 ° C. for 30 days and measuring the rate of change in viscosity before and after the treatment. The change rate of the viscosity before and after the treatment is preferably 50% or less, more preferably 10% or less.

  Next, an ink composition using the aqueous pigment dispersion of the present invention will be described. The aqueous pigment dispersion obtained as described above is diluted with water, and various additives are added as necessary to obtain an ink composition.

  When the ink composition of the present invention is used in an ink jet printer, the viscosity of the ink composition is 10 mPa · s or less, preferably 5 mPa · s or less. If the viscosity is high, it will be difficult to generate ink droplets of an appropriate size and skip them. In order to reduce the viscosity of the ink composition to 10 mPa · s or less, various additives are added to the aqueous pigment dispersion prepared by adjusting the viscosity to the range of 1 to 50 mPa · s, in addition to an appropriate amount of water. Add and dilute as appropriate without destabilizing the state.

The yield value of the ink composition of the present invention is preferably 1 × 10 ⁻² Pa or less, more preferably 1 × 10 ⁻³ Pa or less. Within this range, it can be said that the dispersibility of the pigment is stable. In order to set the yield value of the ink composition to 1 × 10 ⁻² Pa or less, an appropriate amount is added to the aqueous pigment dispersion containing polyurethane prepared as described above with a yield value of 1 × 10 ⁻² Pa or less. In addition to the water, various additives are appropriately added and diluted as long as the dispersion state of the pigment is not destabilized.

  In the ink composition of the present invention, the concentration of the pigment relative to the entire ink composition is preferably 1 to 16% by weight, more preferably 2 to 8% by weight. If the amount of the pigment is too small, the coloring power of the print obtained from the ink composition becomes small and good drawing cannot be performed. Moreover, when there is too much pigment, possibility of causing clogging with an inkjet nozzle will become high.

  When the ink composition of the present invention is used in an ink jet printer, for the purpose of preventing the ink composition from drying at the ink jet nozzle portion or improving the wettability and permeability of the ink composition to the substrate, A water-soluble organic solvent may be contained. Examples of water-soluble organic solvents used include glycol ethers such as diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, glycerin, trimethylolpropane, etc. In addition to polyhydric alcohols such as γ-butyrolactone, N-methyl-2-pyrrolidone, 2-pyrrolidone, and dimethyl sulfoxide, acetylene glycols, acetylene alcohols, alkylene glycols, and the like can be given. The amount of these water-soluble organic solvents is preferably 50% by weight or less of the total solvent contained in the ink composition. When the water-soluble organic solvent is contained in an amount exceeding 50% by weight, the pigment dispersion state may become unstable.

  A preservative can be added to the ink composition of the present invention for the purpose of preventing the entry of mold and bacteria. Zinc pyridinethion-1-oxide, 1,2-benzisothiazolin-3-one, amine salt of 1-benzisothiazolin-3-one, and the like can be suitably used. These are contained in the ink composition in an amount of 0.05 to 1% by weight. If these addition amounts are small, the effect of preventing the mixing of mold and bacteria is not exhibited, and if the addition amount is too large, the dispersion state of the pigment may possibly be destabilized.

  The pH of the ink composition of the present invention is preferably in the range of 7.5 to 9.5. If the pH is not within this range, polyurethane may precipitate.

  By setting the pH within the above range, the thermal discharge characteristics of the ink composition containing polyurethane are improved, and the marker resistance of the printed matter obtained from the ink composition is also improved. The pH of the ink composition can be appropriately adjusted using a buffer solution such as organic amines, potassium hydroxide inorganic alkalis, and phosphoric acid as described above.

  Examples of the substrate for printing the ink composition of the present invention include plain paper, recycled paper, glossy paper, photographic paper, OHP film and the like.

  In the present invention, the optical density of the print obtained from the ink composition using carbon black as the pigment is preferably 1 or more, more preferably 1.2 or more when plain paper is used as the substrate. When glossy paper is used as the material, it is preferably 2 or more, more preferably 2.2 or more. Regardless of whether plain paper or glossy paper is used, if the optical density is too low, the coloring power of the print becomes small and it becomes difficult to obtain a good print. In order to set the optical density of the print when using plain paper to 1 or more and the optical density of the print when using glossy paper to 2 or more, the pigment concentration with respect to the total amount of the ink composition is 1 to 16% by weight, The mixing ratio of the pigment and the polyurethane in the ink is preferably 2 to 8% by weight, and the ratio of pigment: polyurethane = 3 to 9: 7 to 1, preferably 4 to 8: 6 to 2 is preferable. Furthermore, it is required to appropriately control the content of the compound represented by the general formula (1) and the siloxane compound having two hydroxyl groups, the acid value of the polyurethane, the molecular weight of the polyurethane, etc. in all the diols constituting the polyurethane. . The optical density can be measured, for example, using an optical densitometer (SPECTROEYE, manufactured by GRETAG) with a light source D50 and a viewing angle of 2 degrees.

  The marker resistance of the printed matter obtained from the ink composition of the present invention can be evaluated by, for example, the following method. Using plain paper as a base material, the printed portion obtained from the ink composition is rubbed with a fluorescent pen, and it is visually confirmed whether the printed matter is free of stains such as tailing. In addition, it is visually confirmed that there is no dirt on the tip of the highlighter pen.

  The fixability of a print obtained from the ink composition of the present invention can be evaluated by, for example, the following method when glossy paper is used as a substrate. The print obtained from the ink composition is subjected to a cellophane tape peeling test, the peeled cellophane tape is attached to glossy paper, and the optical density of the cellophane tape is measured with an optical densitometer. The optical density of the cellophane tape after the print peeling test is preferably 0.3 or less, more preferably 0.2 or less. Since the optical density when a cellophane tape not peeled off is attached to glossy paper is usually about 0.1, the lower limit of the optical density of the cellophane tape after the peeling test is 0.1. Presumed.

  Since the ink composition of the present invention has a stable pigment dispersion state at both room temperature and high temperature and can discharge ink over a long period of time, it can also be used in a thermal ink jet printer. Furthermore, the ink composition has a high optical density when printed on plain paper and glossy paper, has good marker resistance when printed on plain paper, and has good fixability when printed on glossy paper. The ink composition of the present invention can be used in a wide range of fields for color printing such as an ink jet printer.

  Hereinafter, although this invention is demonstrated in more detail using a preferable embodiment, this invention is not limited to these Examples.

  Each evaluation of the polyurethane in the Examples, the aqueous pigment dispersion containing the polyurethane and the pigment, and the ink composition was performed by the following methods.

<Evaluation method>
Measurement of Acid Value of Polyurethane Based on JIS (Japanese Industrial Standard) K0070, the acid value of polyurethane was measured at room temperature by neutralization titration method. Ion exchange water was added to a neutralizing agent-containing aqueous solution of polyurethane to prepare a polyurethane concentration of 5% by weight. While a neutralizing agent-containing aqueous solution having a polyurethane concentration of 5% by weight was stirred in a beaker, a 0.1 mol / l hydrochloric acid aqueous solution was added until the polyurethane was completely precipitated. After the supernatant was filtered, the polyurethane was washed with ion-exchanged water. After the polyurethane was washed with water 10 times and dried at 100 ° C. for 2 hours, the neutralizing agent, hydrochloric acid and water were completely removed from the polyurethane. Polyurethane was added to a triangular flask together with ethanol to adjust the polyurethane concentration to 4% by weight, and then a few drops of phenolphthalein solution were added and shaken well until the sample was completely dissolved. If the polyurethane was not completely dissolved in ethanol, methyl ethyl ketone was added until the polyurethane was completely dissolved. Next, 0.1 mol / l ethanolic potassium hydroxide solution was added to the burette, and the polyurethane solution was titrated at room temperature. The end point was when the light red color of the indicator lasted for 30 seconds. The acid value was calculated from the following formula.
A = B × 5.661 / S
A: Acid value B: Amount of 0.1 mol / l potassium hydroxide ethanol solution used for titration (ml)
S: Weight of polyurethane (g).

Weight average molecular weight measurement of polyurethane The average molecular weight measurement of polyurethane was performed using gel permeation chromatography (water410 manufactured by Water). First, polystyrene having a weight average molecular weight / number average molecular weight of 1.1 or less and a weight average molecular weight of 1300, 9700, 21000, 66000, 370000 as a standard sample was dissolved in tetrahydrofuran so as to be 0.2% by weight. . The molecular weight of polystyrene was measured by using a packed column for organic solvent GPC (KF-804L manufactured by Showa Denko KK) at a column temperature of 40 ° C. and a flow rate of 0.8 ml / min. A calibration curve of retention time and molecular weight was prepared from the retention time and peak intensity of the obtained polystyrene. Next, it is dissolved in tetrahydrofuran so that the polyurethane concentration becomes 0.2% by weight, the retention time and the peak intensity of the polyurethane are measured under the same measurement conditions as described above, and the weight of the polyurethane is measured using a calibration curve made of polystyrene. The average molecular weight was calculated.

Viscosity Measurement of Aqueous Pigment Dispersion and Ink Composition Viscosity at 25 ° C. was measured using a conical plate viscometer (RE100L manufactured by Toki Sangyo Co., Ltd.)

Measurement of Yield Value of Aqueous Pigment Dispersion Using a cone-and-plate viscometer (RE100L manufactured by Toki Sangyo Co., Ltd.), the viscosity at three different shear rates was measured and determined by using the Casson equation. The dispersion stability of the aqueous pigment dispersion containing polyurethane and pigment was evaluated from the obtained yield value.

Evaluation of heat resistance of aqueous pigment dispersion An aqueous pigment dispersion containing polyurethane and a pigment is subjected to heat treatment at 65 ° C. for 30 days, and the viscosity before and after the heat treatment is compared. did. The viscosity was measured at 25 ° C. using a conical plate viscometer (RE100L manufactured by Toki Sangyo Co., Ltd.).

Particle size measurement in dispersion state of pigment particles in aqueous pigment dispersion liquid Aqueous pigment dispersion liquid containing polyurethane and pigment is diluted with ion-exchanged water so that the pigment concentration becomes 0.1% by weight, and dynamic light scattering type particles A volume-based arithmetic average diameter at 25 ° C. was determined using a diameter distribution measuring device (LB-500 manufactured by Horiba, Ltd.). When the Casson yield value of the aqueous pigment dispersion is 1 × 10 ⁻² Pa or less, the dispersion state of the pigment is stable, and thus the dispersibility of the pigment by dilution from 10% by weight to 0.1% by weight. Is estimated to be unchanged.

Surface tension measurement of aqueous pigment dispersion and ink composition Using a surface tension measuring instrument (A-06, manufactured by Yamamoto Metal Tester Co., Ltd.) and using A-06-P01 as a platinum ring at 25 ° C. The surface tension of the aqueous pigment dispersion containing the polyurethane and the pigment and the ink composition was measured by a ring method. The aqueous pigment dispersion whose temperature was adjusted to 25 ° C. was immersed in a petri dish, and the petri dish was set on the surface tension measuring instrument stage. Next, the surface of the aqueous pigment dispersion was brought into contact with the platinum ring by slowly lifting the stage. The surface tension was determined by slowly pulling the platinum ring vertically and measuring the force required to pull the platinum ring away from the surface of the aqueous pigment dispersion.

Measurement of pH of ink composition Using a small pH meter (B-212 manufactured by Horiba, Ltd.), the pH was measured at room temperature by the glass electrode method.

Evaluation of ejection stability during printing using ink composition Thermal ink jet printer ("Pixus" (trade name) iP3100 ink cartridge manufactured by Canon Inc. (trade name BCI- made by Canon Inc.) 3 eBK and BCI-7eC), 3 units were arranged side by side, and printed on plain paper ("White Recycled Paper" (trade name) EW-500 manufactured by Canon Inc.) for 5 hours from an inkjet nozzle, and the following evaluation was performed. When all three units did not smudge ink after 5 hours ◎ When one or more inks were smeared after 5 hours, but when fading was improved by cleaning the inkjet nozzles ○ One or more units after 5 hours The case where there was a faint ink and the fading was not improved even after cleaning was marked as x.

Optical density evaluation of a print obtained from an ink composition when applied and printed on plain paper and glossy paper The ink composition is packed in the ink cartridge of the above-described ink jet printer, printed on the above-mentioned plain paper and glossy paper, and 5 cm. A solid image of × 5 cm was obtained. The optical density of the obtained solid image portion was measured using an optical densitometer (SPECTROEYE, manufactured by GRETAG) at a light source D50 and a viewing angle of 2 degrees.

Evaluation of Marker Resistance of Prints Obtained from Ink Composition when Applied and Printed on Plain Paper The ink composition was packed in the ink cartridge of the ink jet printer described above and printed on the above plain paper to obtain a printed matter. The obtained printed matter was allowed to stand at room temperature for 24 hours, and then the printed portion of the printed matter was rubbed with an aqueous fluorescent pen (manufactured by Zebra Co., Ltd., “OPTEX” (trade name) OP-100-yellow). Thereafter, the printed portion and the fluorescent pen were visually observed, and the following evaluation was performed. ◎ If there is no stain on the tip of the highlighter and no stain on the tip of the highlighter, ◎ if there is almost no stain on the tip of the highlighter but ○ on the tip of the highlighter, ○ The case where the tip of the highlighter was dirty was marked with x.

Fixability evaluation of printed matter obtained from ink composition when coated and printed on glossy paper A solid image obtained on glossy paper was allowed to stand at room temperature for 24 hours, and then a cellophane tape having a width of 15 mm (LP-15 manufactured by Nichiban Co., Ltd.) (Product name) was pasted on the image over a length of 30 mm. After 1 minute, one corner of the cellophane tape was held with a finger, and the cellophane tape was peeled off for 1 second perpendicular to the solid image. The cellophane tape after the peel test of the printed material was attached to glossy paper, and the optical density was measured with an optical densitometer (SPECTROEYE, manufactured by GRETAG) at a light source D50 and a viewing angle of 2 degrees. In addition, when the cellophane tape with a width of 15 mm was pasted on glossy paper and measured using a light densitometer (SPECTROEYE, manufactured by GRETAG) with a light source D50 and a viewing angle of 2 degrees, the optical density was 0.1. .

Synthesis example 1
In a four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube, 98 g of carboxylic acid-modified polycaprolactone diol (“Placcel” 205BA (trade name) manufactured by Daicel Chemical Industries, Ltd.), 22 g of hydroxyl group 2 Siloxane compound (“Both-end Silaplane” FM-4411 (trade name) manufactured by Chisso Corporation) and 120 g of methyl ethyl ketone were added.

Plaxel 205BA is a carboxylic acid-modified polycaprolactone diol in which dimethylolbutanoic acid is lactone-modified, R ¹ in the general formula (1) has an alkylene group and an ester group, and R ¹ has 25 to 25 carbon atoms. 26. R ² is CH ₂ CH ₃ . The acid value of PLACCEL 205BA is 110 KOH · mg / g, the weight average molecular weight is 500, and the hydroxyl value is 220 KOH · mg / g (nominal value according to the catalog).

Silaplane FM-4411 is a siloxane compound having hydroxyl groups at both ends, and R ⁴ , R ⁵ , R ⁶ and R ⁷ in the general formula (2) are all CH ₃ , and R ⁸ and R ⁹ are C _3. an H ₆ OC ₂ H _4, n is 9-11. The number average molecular weight of Silaplane FM-4411 is 1000 (nominal value according to the catalog).

  After stirring PLACCEL 205BA, both end silaplane FM-4411, and methyl ethyl ketone for 30 minutes, 60 g of isophorone diisocyanate was charged into a four-necked flask, stirred at room temperature for 1 hour in a nitrogen atmosphere, heated to 70 ° C., and heated to 70 ° C. The reaction was carried out at 4 ° C. for 4 hours. After the reaction, it was cooled to room temperature to obtain a urethane prepolymer solution 1 having a concentration of 60% by weight.

  17.6 g of 50 wt% KOH aqueous solution and 350 g of ion-exchanged water were put into a four-necked flask and stirred with 250 g of urethane prepolymer solution 1 at room temperature for 30 minutes. After raising the temperature to 80 ° C. in a nitrogen atmosphere, chain extension reaction was performed at 80 ° C. for 2 hours. After the reaction, methyl ethyl ketone and a part of water are removed using a rotary evaporator and an aspirator, and then ion-exchanged water is added so that the recovered amount is 429 g. ) The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 1 was 90 mol%, and the content of the siloxane compound having two hydroxyl groups was 10 mol%.

  The obtained polyurethane 1 had an acid value of 74 KOH · mg / g and a weight average molecular weight of 18,000.

Synthesis example 2
In the same manner as in Synthesis Example 1, a urethane prepolymer solution 2 having a concentration of 60% by weight was obtained using 93 g of Plaxel 205BA, 28 g of both-end silaplane FM-4411, 120 g of methyl ethyl ketone, and 59 g of isophorone diisocyanate.

  16.7 g of a 50 wt% KOH aqueous solution and 350 g of ion-exchanged water were put into a four-necked flask and stirred with 250 g of the urethane prepolymer solution 2 at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 2) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 2 was 87 mol%, and the content of the siloxane compound having two hydroxyl groups was 13 mol%. The obtained polyurethane 2 had an acid value of 63 KOH · mg / g and a weight average molecular weight of 14,000.

Synthesis example 3
In the same manner as in Synthesis Example 1, a urethane prepolymer solution 3 having a concentration of 60% by weight was obtained using 87 g of Plaxel 205BA, 36 g of both end silaplane FM-4411, 120 g of methyl ethyl ketone, and 58 g of isophorone diisocyanate.

  15.8 g of 50 wt% KOH aqueous solution and 350 g of ion-exchanged water were put into a four-necked flask and stirred with 250 g of urethane prepolymer solution 3 at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 3) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 3 was 83 mol%, and the content of the siloxane compound having two hydroxyl groups was 17 mol%. The obtained polyurethane 3 had an acid value of 59 KOH · mg / g and a weight average molecular weight of 12,000.

Synthesis example 4
In the same manner as in Synthesis Example 1, a urethane prepolymer solution 4 having a concentration of 60% by weight was obtained using 105 g of Plaxel 205BA, 13 g of both end silaplane FM-4411, 120 g of methyl ethyl ketone, and 62 g of isophorone diisocyanate.

  18.9 g of a 50 wt% KOH aqueous solution and 350 g of ion exchange water were put into a four-necked flask and stirred with 250 g of the urethane prepolymer solution 4 at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 4) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 4 was 94 mol%, and the content of the siloxane compound having two hydroxyl groups was 6 mol%. The obtained polyurethane 4 had an acid value of 77 KOH · mg / g and a weight average molecular weight of 20000.

Synthesis example 5
In the same manner as in Synthesis Example 1, a urethane prepolymer solution 5 having a concentration of 60% by weight was obtained using 64 g of Plaxel 205BA, 63 g of both end silaplane FM-4411, 120 g of methyl ethyl ketone, and 53 g of isophorone diisocyanate.

  11.5 g of a 50 wt% KOH aqueous solution and 350 g of ion-exchanged water were put into a four-necked flask and stirred with 250 g of the urethane prepolymer 5 solution at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 5) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 5 was 67 mol%, and the content of the siloxane compound having two hydroxyl groups was 33 mol%. The obtained polyurethane 5 had an acid value of 53 KOH · mg / g and a weight average molecular weight of 12,000.

Synthesis Example 6
A synthetic example except that 93 g of Plaxel 205BA, 28 g of a siloxane compound having two hydroxyl groups (manufactured by Chisso Corporation, one-end silaplane FM-DA11 (trade name)), 120 g of methyl ethyl ketone, 59 g of isophorone diisocyanate In the same manner as in Example 1, a urethane prepolymer solution 6 having a concentration of 60% by weight was obtained. One-end silaplane FM-DA11 is a siloxane compound having two hydroxyl groups, and the number average molecular weight of silaplane FM-DA11 is 1000 (nominal value according to the catalog).

  16.7 g of a 50 wt% KOH aqueous solution and 350 g of ion-exchanged water were put into a four-necked flask and stirred with 250 g of the urethane prepolymer solution 6 at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 6) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 6 was 87 mol%, and the content of the siloxane compound having two hydroxyl groups was 13 mol%. The obtained polyurethane 6 had an acid value of 64 KOH · mg / g and a weight average molecular weight of 16,000.

Synthesis example 7
In the same manner as in Synthesis Example 1, a urethane prepolymer solution 7 having a concentration of 60% by weight was obtained using 44 g of Plaxel 205BA, 88 g of both end silaplane FM-4411, 120 g of methyl ethyl ketone, and 48 g of isophorone diisocyanate.

  7.9 g of a 50 wt% KOH aqueous solution and 350 g of ion exchange water were put into a four-necked flask and stirred with 250 g of the urethane prepolymer solution 7 at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 7) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 7 was 50 mol%, and the content of the siloxane compound having two hydroxyl groups was 50 mol%. The obtained polyurethane 7 had an acid value of 34 KOH · mg / g and a weight average molecular weight of 13,000.

Synthesis example 8
A urethane prepolymer solution 8 having a concentration of 60% by weight was obtained in the same manner as in Synthesis Example 1 except that 116 g of Plaxel 205BA, 120 g of methyl ethyl ketone, and 64 g of isophorone diisocyanate were used.

  20.8 g of a 50 wt% KOH aqueous solution and 350 g of ion-exchanged water were put into a four-necked flask and stirred with 250 g of the urethane prepolymer solution 8 at room temperature for 30 minutes. In the same manner as in Synthesis Example 1, chain extension reaction, removal of methyl ethyl ketone and a part of water, and addition of ion exchange water were performed to obtain a neutralizing agent-containing aqueous solution (polyurethane 8) having a polyurethane concentration of 35% by weight. The content of the compound represented by the general formula (1) in all the diol components in the polyurethane 8 was 100 mol%, and the content of the siloxane compound having two hydroxyl groups was 0 mol%. The obtained polyurethane 7 had an acid value of 81 KOH · mg / g and a weight average molecular weight of 28,000.

Example 1
After mixing 3 kg of carbon black (Mitsubishi Chemical Corporation MA-100 (trade name)) with 10 kg of water, it was added to 4.5 kg of sodium hypochlorite solution (effective chlorine concentration 12%), and 100-105 ° C. For 10 hours and the resulting product was filtered. The wet crystal obtained by drying was washed with water and then dried at 80 ° C. to obtain 2.5 kg of oxidized carbon black.

  Next, oxidation-treated carbon black and ion exchange water were mixed to prepare a slurry. The prepared slurry was dialyzed using a polymethylmethacrylate dialysis module (“Fill Trizer” B3-20A (trade name) manufactured by Toray Industries, Inc.) and then dried, and sodium ions and chlorine in the oxidized carbon black. Ions were removed to obtain an oxidized carbon black dialyzate.

  120 g of oxidized carbon black dialyzate, 180 g of triethylene glycol monobutyl ether and 700 g of ion exchange water were mixed and stirred with a homodisper to prepare a slurry. The beaker containing the slurry was connected with a circulation type bead mill disperser ("Dino Mill" KDL-A manufactured by Willy et Bacofen) and a tube, and dispersion treatment was performed at 1600 rpm using zirconia beads having a diameter of 0.3 mm as a medium. Aqueous black pigment dispersion A was obtained over time.

  7.1 g of 41.7 g of aqueous black pigment dispersion A, 0.7 g of 50 wt% KOH, 0.5 g of water and polyurethane 1 obtained in Synthesis Example 1 (polyurethane concentration: 35 wt%) were added, An aqueous black pigment dispersion 1 (pigment concentration: 10% by weight, polyurethane concentration: 5% by weight) was prepared, and various evaluations were performed on the aqueous black pigment dispersion 1. The results are shown in Tables 2 and 3.

  Subsequently, 25.8 g of ion-exchanged water, 3.5 g of glycerin, 1.7 g of 2-pyrrolidone, and 1.5 g of ethylene glycol were added to 17.5 g of the aqueous black pigment dispersion 1, and an ink composition (pigment concentration: 3.5 wt%, polyurethane concentration: 1.75 wt%) was prepared and evaluated. The results are shown in Tables 2 and 3.

Examples 2-6, Comparative Examples 1-2
Using the polyurethanes 2-8 (polyurethane concentration: 35% by weight) obtained in Synthesis Examples 2-8 and the aqueous black pigment dispersion A obtained in Example 1, an aqueous black pigment was produced in the same manner as in Example 1. Dispersions 2 to 8 (pigment concentration: 10% by weight, polyurethane concentration: 5% by weight) were prepared, and various evaluations were performed on the pigment dispersions 2 to 8. The results are shown in Table 2. Further, in the same manner as in Example 1, an ink composition (pigment concentration: 3.5% by weight, polyurethane concentration: 1.75% by weight) was prepared, and various evaluations were performed. The results are shown in Tables 2 and 3.

Comparative Example 3
To 41.7 g of the aqueous black pigment dispersion A obtained in Example 1, 0.7 g of 50 wt% KOH and 7.6 g of water were added, and an aqueous black pigment dispersion 9 (pigment concentration: 10 wt%) was added. It produced and various evaluation was performed about the aqueous | water-based black pigment dispersion liquid 9. FIG. The results are shown in Table 2. Further, 25.8 g of ion-exchanged water, 3.5 g of glycerin, 1.7 g of 2-pyrrolidone and 1.5 g of ethylene glycol were added to 17.5 g of the aqueous black pigment dispersion 9 to add an ink composition (pigment concentration: 3.5% by weight) and various evaluations were made. The results are shown in Tables 2 and 3.

Example 7
900 g of PB15: 3 (Clariant “Hosta Palm” Blue B2G (trade name)) was added to 12 kg of fuming sulfuric acid (28% SO3) heated to 70 ° C. with stirring. After stirring for 3 hours, it was added onto 22.5 kg of ice. After standing for 30 minutes, the resulting suspension was filtered, and the resulting product was washed with 4.5 kg of pure water. The product was put into 30 kg of pure water, neutralized with an aqueous ammonia solution (added with an aqueous ammonia solution until the pH reached 7 or more), and filtered. The obtained wet crystals were washed with pure water and then dried at 80 ° C. The wet crystals obtained by drying were washed with water and then dried at 80 ° C. to obtain 1150 g of PB15: 3 sulfonated derivative.

  Next, a slurry was prepared by mixing PB15: 3 sulfonated derivative and ion-exchanged water. The prepared slurry was dialyzed using a polymethylmethacrylate dialysis module (“Fill Trizer” B3-20A (trade name) manufactured by Toray Industries, Inc.) and then dried to obtain a PB15: 3 sulfonated derivative dialyzate. .

  96 g of PB15: 3, 24 g of PB15: 3 sulfonated derivative dialyzed material, 180 g of triethylene glycol monobutyl ether, and 700 g of ion-exchanged water were mixed and stirred with a homodisper to prepare a slurry. The beaker containing the slurry was connected with a circulation type bead mill disperser ("Dino Mill" KDL-A manufactured by Willy et Bacofen) and a tube, and dispersion treatment was performed at 1600 rpm using zirconia beads having a diameter of 0.3 mm as a medium. Aqueous cyan pigment dispersion A was obtained over time.

  41.7 g of aqueous cyan pigment dispersion A, 0.7 g of 50 wt% KOH, 0.5 g of water and 7.1 g of polyurethane 1 obtained in Synthesis Example 1 (polyurethane concentration: 35 wt%) were added, An aqueous cyan pigment dispersion 1 (pigment concentration: 10% by weight, polyurethane concentration: 5% by weight) was prepared, and various evaluations were performed on the aqueous cyan pigment dispersion 1. The results are shown in Table 4. In addition, 18.3 g of ion-exchanged water, 3.5 g of glycerin, 1.7 g of 2-pyrrolidone, and 1.5 g of ethylene glycol were added to 25 g of the aqueous cyan pigment dispersion 1, and an ink composition (pigment concentration: 5 wt. %, Polyurethane concentration: 2.5% by weight), and various evaluations were made. The results are shown in Tables 4 and 5.

Examples 8-12, Comparative Examples 4-5
An aqueous cyan pigment was produced in the same manner as in Example 7, using the polyurethanes 2 to 8 (polyurethane concentration: 35% by weight) obtained in Synthesis Examples 2 to 8 and the aqueous cyan pigment dispersion A obtained in Example 7. Dispersions 2 to 8 (pigment concentration: 10% by weight, polyurethane concentration: 5% by weight) were prepared, and various evaluations were performed on cyan pigment dispersions 2 to 8. The results are shown in Table 4. In the same manner as in Example 7, an ink composition (pigment concentration: 5% by weight, polyurethane concentration: 2.5% by weight) was prepared, and various evaluations were performed. The results are shown in Tables 4 and 5.

Comparative Example 6
To 41.7 g of the aqueous cyan pigment dispersion A obtained in Example 7, 0.7 g of 50 wt% KOH and 7.6 g of water were added, and an aqueous cyan pigment dispersion 9 (pigment concentration: 10 wt%) was added. The aqueous cyan pigment dispersion liquid 9 was prepared and various evaluations were performed. The results are shown in Table 4. Next, 18.3 g of ion-exchanged water, 3.5 g of glycerin, 1.7 g of 2-pyrrolidone and 1.5 g of ethylene glycol were added to 25 g of the aqueous cyan pigment dispersion 9 to add an ink composition (pigment concentration: 5 wt. %) And various evaluations were performed. The results are shown in Tables 4 and 5.

Claims (4)

An aqueous pigment dispersion containing at least a pigment, polyurethane and water, wherein 55 to 95 mol% of all diol components constituting the polyurethane are constituted by a structure derived from the compound represented by the general formula (1). An aqueous pigment dispersion having a structure derived from a siloxane compound having 5 to 45 mol% having two hydroxyl groups.

(R ¹ represents an organic group having 13 to 80 carbon atoms having an alkylene group and / or an ester group. R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) The aqueous pigment dispersion according to claim 1, wherein the siloxane compound having two hydroxyl groups is a compound represented by the general formula (2).

(R ^{4 to} R ⁷ may be the same or different and have at least one organic group selected from an alkyl group having 1 to 20 carbon atoms and an aryl group, and R ⁸ and R ⁹ have 1 to 20 carbon atoms. And at least one organic group selected from an alkylene group and an arylene group, and n is in the range of 4 to 100.) The aqueous pigment dispersion according to claim 1 or 2, wherein the pigment is carbon black. An ink composition comprising the aqueous pigment dispersion according to any one of claims 1 to 3.