White ink for pigment printing

Abstract

The present invention provides a white ink for pigment printing, the white ink achieving a good balance between low viscosity and high concealability, while exhibiting excellent sedimentation suppression performance.　This white ink for pigment printing is characterized by containing titanium oxide and an alginic acid salt, a 10 mass% aqueous solution of which has a viscosity of 600 mPa∙s or less (at the solution temperature of 20°C).

Description

[Technical Field]

[0001] The present invention relates to a white ink used when printing on fabric. [Background technology]

[0002] Textile printing, in which dissolved dyes or pigments are printed onto fabric, has been used since ancient times as a method of coloring fabrics. In recent years, inkjet printing, which allows for simple, high-speed, continuous printing, has also become widely used.

[0003] In textile printing, when printing is performed on black or dark colored fabric, the ink color shows through and mixes with the color of the fabric, making it impossible to achieve the intended color. Therefore, a method is widely used in which the fabric is bleached before printing, but this method has the problem of insufficient whiteness of the fabric and poor clarity of the printed image.

[0004] As a means for solving this problem, a method has been proposed in which the underlying fabric is colored in advance with a white pigment ink having opacity, and then printing is performed on top of it to improve color development. For example, Patent Document 1 discloses a white ink composition for inkjet textile printing in which titanium oxide is dispersed in a polymer dispersant obtained by neutralizing a specific anionic water-soluble resin with a basic compound.

[0005] [Patent Document 1] Patent Publication No. 2008-266527 [Patent Document 2] Patent Publication No. 2018-119022 [Patent Document 3] Patent No. 6060102 [Patent Document 4] Patent application 2016-189337 [Patent Document 5] Patent Publication No. 2002-3759 Summary of the Invention [Problem to be solved by the invention]

[0006] The most important performance factor for a white ink for pigment textile printing is high hiding power (whiteness) that prevents the color of the base from showing through. In addition, it is necessary for the ink to have low viscosity, which improves handling during manufacturing and use and the quality of printed images, and sedimentation prevention performance, which prevents solidification due to pigment precipitation and ink deterioration when used in inkjet printers, preventing ejection problems due to ink deterioration.

[0007] White inks for pigment textile printing that use titanium oxide as a pigment are excellent and widely used due to their high hiding power. However, titanium oxide is difficult to disperse uniformly, and no inks capable of maintaining high hiding power while maintaining low viscosity were commercially available at the time of filing. For example, the inventors' studies revealed that the invention of Patent Document 1 had insufficient hiding power. Furthermore, it was revealed that the resin used had a low pigment-retaining capacity and insufficient sedimentation suppression, resulting in titanium oxide settling and solidification during long-term storage. Patent Document 4 also discloses a white ink for screen printing in which titanium oxide is dispersed using an acrylic resin emulsion and sodium alginate, whose viscosity in a 10% by weight aqueous solution (at 20°C) exceeds 600 mPa·s. However, due to the high viscosity and thixotropy of the ink, it is believed that inks cannot be used effectively in textile printing using inkjet printers due to poor nozzle discharge and other issues. As a method for uniformly dispersing pigments, for example, Patent Document 2 discloses a black ink for tablets in which iron oxide is dispersed in sodium alginate and microparticulated to an average particle size of 300 nm or less. However, the inventors' studies have revealed that microparticulating titanium oxide to an average particle size of 200 nm or less improves transparency and impairs hiding power, making this method unsuitable for use in white inks for pigment textile printing. It has also been found that this method tends to cause sedimentation and separation when the average particle size is greater than 200 nm, making handling difficult. Furthermore, Patent Document 3 discloses a tablet ink for inkjet printing that uses titanium oxide and the red pigment ferric oxide and disperses them in a cellulose resin such as hydroxypropyl cellulose to improve stability. However, as a result of investigations by the present inventors, it was found that the ink has poor hiding power and is unsuitable as a white ink for pigment textile printing. It was also found that it is difficult to maintain the pigment in the ink uniformly and stably for a long period of time, and that sedimentation and separation of the pigment occur over time. In addition, Patent Document 5 discloses an ink composition for inkjet color printing on paper, which uses titanium oxide and an organic white pigment dispersed in 0.5% by mass of sodium polyacrylate and 0.05% by mass of sodium alginate. However, the titanium oxide content is low at 0.5% by mass, resulting in poor hiding power, and it is thought that this composition cannot be used suitably as a white ink for pigment textile printing. Furthermore, the inventors' studies revealed that when the titanium oxide content is increased to improve hiding power, the sodium polyacrylate and sodium alginate in the above amounts cannot suppress the settling of titanium oxide, and the titanium oxide penetrates into the fabric, making it impossible to obtain the necessary hiding power and whiteness.

[0008] As described above, until now, there has been no technology available for producing a white ink for pigment textile printing that exhibits high hiding power while maintaining low viscosity. Furthermore, there has naturally been no technology available for producing a white ink for pigment textile printing that can suppress the settling of pigments such as titanium oxide in addition to these properties. An object of the present invention is to provide a white ink for pigment textile printing that combines low viscosity with high hiding power and has excellent sedimentation suppression properties.

[0009] As a result of intensive research to solve the above problems, the inventors have completed an excellent white ink for pigment textile printing, which uses an alginate salt having predetermined physical properties as a dispersant in an ink containing titanium oxide as the main pigment, and which has a low viscosity that is easy to handle in the manufacturing and coating processes and enables printing of high-quality images, yet has sufficient hiding power for textile printing and also exhibits sufficient fixation to fibers, thereby arriving at the first invention of the present application.In addition, the inventors have found that by adjusting the pH of the white ink for pigment textile printing of the first invention of the present application within a predetermined range, a white ink for pigment textile printing with excellent sedimentation-inhibiting properties that makes it suitable for use in inkjet printers can be obtained. Furthermore, by creating an ink with predetermined physical properties, the inventors have completed a white ink for pigment textile printing that can suppress the settling of pigments such as titanium oxide and maintain their dispersion for a long period of time, thereby arriving at the second invention of the present application. [Means for solving the problem]

[0010] That is, the present invention discloses (1) A white ink for pigment textile printing, which contains titanium oxide and an anionic water-soluble polymer with a cellulose structure, the viscosity of which in a 10% by mass aqueous solution (liquid temperature: 20°C) is 600 mPa·s or less, and which contains the anionic water-soluble polymer with a cellulose structure in an amount of 0.1% by mass to 6% by mass of the total ink. (2) The white ink for pigment printing according to (1), characterized in that the anionic water-soluble polymer having a cellulose structure contains an alginate. (3) The white ink for pigment textile printing according to (1) or (2), wherein the titanium oxide has a D50 of 200 nm to 1 μm. (4) The white ink for pigment textile printing according to either (1) or (2), which has a pH of 5.0 to 12.0. (5) The white ink for pigment textile printing according to (3), which has a pH of 5.0 to 12.0. (6) A white ink for pigment textile printing, which contains at least a white pigment and has a bottom TSI value of 30.0 or less. (7) A textile printing method using at least the white ink for pigment textile printing according to claim 1. (8) A textile printing method comprising: printing and applying a composition containing at least the white ink for pigment textile printing according to claim 1 onto a resin film; and then adhering and transferring the resin film onto a fabric. is.

[0011] The present invention provides an excellent white pigment printing ink that is easy to handle, has low viscosity, and yet has sufficient hiding power and fixation to fabrics, making it suitable for use in textile printing. Furthermore, by adjusting the pH of the white pigment printing ink, it is possible to obtain a white pigment printing ink that has excellent sedimentation-inhibiting properties. DETAILED DESCRIPTION OF THE INVENTION

[0012] The white ink for pigment textile printing according to the first aspect of the present invention is characterized by containing at least titanium oxide and an anionic water-soluble polymer having a cellulose structure.

[0013] [Titanium oxide] The first invention of the present application is characterized in that titanium oxide is used as a coloring material (coloring component). Titanium oxide preferably has an average primary particle size of 0.01 to 3.00 μm, more preferably 0.03 to 2.00 μm, and even more preferably 0.05 to 1.50 μm. By making the average primary particle size of titanium oxide 0.01 μm or more, it is possible to improve the hiding power, and by making it 3.00 μm or less, the titanium oxide is crushed and pulverized, thereby improving the sedimentation suppression effect. The average primary particle diameter referred to here is the arithmetic mean diameter of the projected area equivalent circle diameter (Heywood diameter) determined based on images obtained by observing titanium oxide particles with a scanning electron microscope (SEM), but the measurement method is not limited to this as long as the same result is obtained. Examples of titanium oxide that satisfies the above range include "JR" (manufactured by Teika Corporation, average primary particle diameter 0.27 μm) and "Tipake CR-50-2" (manufactured by Ishihara Sangyo Kaisha, Ltd., average primary particle diameter 0.25 μm).

[0014] Titanium oxide is generally surface-treated with alumina, silica, or the like to improve light resistance and suppress catalytic activity, but in the present invention, it can be used regardless of whether it is surface-treated. Furthermore, while both anatase and rutile types of titanium oxide can be used as the crystalline structure, the rutile type is preferred from the viewpoint of hiding power and stability.

[0015] The titanium oxide content in the white ink for pigment printing is preferably 2.0 to 50.0% by mass, and more preferably 5.0 to 20.0% by mass. By keeping the titanium oxide content within this range, it is possible to prevent re-aggregation and suppress deterioration due to long-term storage while maintaining hiding power.

[0016] In the present invention, a mixture of different types of titanium oxides having different average primary particle sizes can be used as long as the overall average primary particle size is within the above-mentioned preferred range.

[0017] [Water-soluble polymer] The white ink for pigment printing according to the first aspect of the present invention is characterized by containing a water-soluble polymer having a cellulose structure. In this invention, the water-soluble polymer having a cellulose structure refers to a water-soluble polymer compound having a long-chain structure in which β-glucose units are polymerized via glycosidic bonds. In the water-soluble polymer having a cellulose structure used in the present invention, other substituents may be introduced into the hydroxyl groups of each β-glucose, or may be condensed with other compounds. The other substituents may be introduced into all β-glucoses in the same manner, or into only some β-glucoses, or may be introduced at different positions for each β-glucose. By including a water-soluble polymer with a cellulose structure in the blending amount described below, titanium oxide can be stably and finely dispersed, while maintaining low viscosity, thereby exhibiting high hiding power and suppressing sedimentation. The mechanism by which the cellulose-structured water-soluble polymer in the present invention exhibits excellent pigment dispersibility and sedimentation-inhibiting effects is not clear, but it is presumed that the long-chain cellulose structures overlap in the ink to form a mesh-like structure, which can hold titanium oxide within that structure, thereby achieving the effect of maintaining the titanium oxide dispersed in the liquid for a long period of time, regardless of viscosity. The white ink for pigment printing according to the first aspect of the present invention is characterized in that the water-soluble polymer having a cellulose structure is anionic. In the present invention, the water-soluble polymer having a cellulose structure being anionic means that the number of anionic substituents introduced into the hydroxyl groups of β-glucose is 0.8 or more per β-glucose. It is particularly preferable that the number of anionic substituents is 1 or more per β-glucose. The number of anionic substituents can be calculated from the structure if the chemical structure of the water-soluble polymer is specified, or it can be measured using a method appropriate for each substituent and bond. For example, for those with ether bonds such as carboxymethyl groups, the degree of etherification can be measured and calculated by ashing, adding acid, and back titrating. As an example, the method for measuring the degree of etherification of carboxymethyl cellulose neutralized salt is given below. Weigh out 0.5-0.7g of sample, wrap it in filter paper, and incinerate it in a magnetic crucible. After cooling, transfer it to a 500ml beaker, add approximately 250ml of water, and then add 35ml of 0.05mol / L sulfuric acid using a pipette, and boil for 30 minutes. After cooling, add phenolphthalein indicator, and back-titrate the excess acid with 0.1mol / L potassium hydroxide to calculate using the following formula: Degree of etherification = (162×A) / (10.000-80×A) A = [(af-bf1) / sample anhydride (g)] - alkalinity (or + acidity) a: Use ml of 0.05 mol / L sulfuric acid f: Potassium number of 0.05 mol / l sulfuric acid b: Titration of 0.1 mol / L potassium hydroxide f1: Potassium number of 0.1 mol / l potassium hydroxide Water-soluble polymers with a cellulose structure containing anionic substituents of 0.8 or more per β-glucose unit exhibit superior pigment dispersibility and sedimentation suppression compared to nonionic polymers with a cellulose structure, such as hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC). This is thought to be due to the fact that their anionic nature enhances their adsorption of cationic titanium dioxide (TiO2), which is positively charged, and allows the titanium dioxide to be firmly retained within the network structure. Furthermore, a polymer with anionic substituents of 0.8 or more per β-glucose unit also improves whiteness when used in textile printing. This is thought to be due to the adsorption of cationic compounds used in textile printing pretreatments to the fabric surface, thereby retaining the titanium dioxide near the surface and preventing it from penetrating into the interior of the fabric.

[0018] In the present invention, any anionic water-soluble polymer having a cellulose structure can be selected. Specifically, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and ethylhydroxy cellulose, each of which has an anionic substituent group whose number falls within the above range, cellulose derivative salts obtained by modifying these derivatives with a sulfonic acid group, a phosphoric acid group, an amine group, or the like, alginic acid derivatives such as triethanolamine alginate and propylene glycol alginate, and alginates such as sodium alginate, potassium alginate, and ammonium alginate can be suitably used. Among these, it is preferable to use alginate salts, which have excellent sedimentation suppression properties, dispersibility, and safety. Furthermore, among alginate salts, sodium salts are particularly preferable, as they are easily ionized due to their high ionization tendency and tend to become anions in aqueous solvents. In the present invention, the method of adding an anionic water-soluble polymer having a cellulose structure to the ink is not particularly limited as long as it is contained in the ink. When an alginate is used, for example, it may be added as an alginate from the beginning, or a method may be appropriately selected from the following: adding alginic acid and a neutralizing agent and neutralizing them in the ink liquid to produce an alginate.

[0019] The anionic water-soluble polymer with a cellulose structure used in the present invention is characterized by having a viscosity of 600 mPa·s or less in a 10% by mass aqueous solution (liquid temperature: 20°C). The viscosity of a 10% by mass aqueous solution (liquid temperature: 20°C) is particularly preferably 100 mPa·s or less, and most preferably 50 mPa·s or less. When a water-soluble polymer with a viscosity of more than 600 mPa·s in a 10% by mass aqueous solution at 20°C is used, sufficient pigment dispersion performance cannot be obtained, making stable dispersion difficult. Furthermore, the viscosity of the resulting ink becomes high, which deviates from the object of the present invention. Commercially available anionic water-soluble polymers with a cellulose structure that satisfy the above viscosity range include "Kimica Argin ULV-L3" (viscosity of a 10% mass% aqueous solution at 20°C: 20-50 mPa·s), "Kimica Argin ULV-1" (viscosity of a 10% mass% aqueous solution at 20°C: 100-200 mPa·s), and "Kimica Argin ULV-5" (viscosity of a 10% mass% aqueous solution at 20°C: 500-600 mPa·s) (all of which are product names in parentheses, manufactured by Kimica Corporation). The viscosity referred to here is that determined by the following method, but the measurement method is not limited to this as long as the same result is obtained. Conditioning: 10% by weight aqueous solution of water-soluble polymer (20°C) Measuring equipment: Brookfield viscometer (Toki Sangyo Co., Ltd. "TVB-10" (product number)) Measurement time: 60 seconds

[0020] The anionic water-soluble polymer having a cellulose structure is contained in the white ink for pigment printing in an amount of 0.1 to 6.0% by mass, and more preferably 0.3 to 3.0% by mass. If the blending amount of the anionic water-soluble polymer with a cellulose structure is less than 0.1% by mass, the dispersion performance and sedimentation prevention performance will be insufficient, and if titanium oxide is contained in an amount sufficient to achieve the hiding power required for a white ink for pigment printing, problems such as aggregation and sedimentation may occur, and the titanium oxide may easily penetrate into the fabric, resulting in a decrease in whiteness.Furthermore, if the concentration of the anionic water-soluble polymer with a cellulose structure is more than 6.0% by mass, the viscosity and thixotropy of the ink will increase, and problems such as poor ejection may occur when used in inkjet printing.

[0021] The white ink for pigment printing according to the first aspect of the present invention can be obtained by mixing the titanium oxide and the anionic water-soluble polymer having a cellulose structure with a dispersion medium and, if necessary, with a water-soluble organic solvent, a surface tension adjuster, other additives, and the like, and then performing a dispersion treatment.

[0022] [Dispersion medium] The dispersion medium of the present invention is not particularly limited as long as it is a liquid that does not inhibit the dissolution of the water-soluble polymer, and may be selected appropriately depending on the application, but by using water as the main component, an ink with excellent safety can be obtained. Here, "mainly using water" means that 40.0% by mass or more, more preferably 50.0% by mass or more of the liquid constituting the ink is water. It is particularly preferable that the liquid components other than the specific water-soluble organic solvent described below are essentially water.

[0023] [Water-soluble organic solvent] The white ink for pigment textile printing of the present invention preferably contains a predetermined water-soluble organic solvent as a liquid component other than water. The addition of a water-soluble organic solvent makes it possible to adjust the drying speed of the ink and its penetration into fibers. Specific examples of such water-soluble organic solvents include methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, trimethylolpropane, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, diglycerin, 1,2-hexanediol, 1,6-hexanediol, 2-pyrrolidone, and N-methyl-2-pyrrolidone. Lithium ionomer, 1,5-pentanediol, monoethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, monoethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, methyl lactate, ethyl lactate, and 1,3-dimethyl-2-imidazolidinone can be suitably used, and these can be used alone or in combination of two or more. Particularly preferred are ethanol, isopropanol, polyethylene glycol, propylene glycol, and glycerin.

[0024] The amount of water-soluble organic solvent added to the ink liquid is preferably 5.0% by mass to 30.0% by mass, and more preferably 6.0% by mass to 25.0% by mass. If the amount added exceeds 30% by mass, the ink becomes highly viscous, and stability deteriorates during long-term storage, causing problems such as aggregation of titanium oxide. If the amount added is less than 5% by mass, the performance of the water-soluble organic solvent may not be fully exhibited.

[0025] [Surface tension adjuster] The white pigment printing ink of the present invention may contain a surface tension modifier, if necessary, for adjusting the penetration rate of the ink into the fibers of the fabric or, in the case of an ink for an inkjet printer, for adjusting the ejection properties from the nozzle. Specific examples of the surface tension adjuster include preferred nonionic or anionic surfactants, and specific examples include anionic surfactants such as alkylbenzenesulfonates, higher alcohol sulfates, higher fatty acid salts, higher alkyl dicarboxylates, alkylnaphthalenesulfonates, alkylsulfosuccinates, naphthalenesulfonate-formalin condensate salts, polyoxyethylene alkyl ether sulfates, and polyoxyethylene alkyl phosphate esters; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, fatty acid monoglycerides, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene fatty acid esters, glycerin fatty acid esters, and polyoxyethylene-added acetylene glycols; silicone surfactants; and fluorine-based surfactants. The amount of surface tension adjuster added may be selected appropriately depending on the required surface tension, but is preferably 0.05 to 20.0% by mass, and particularly preferably 0.1 to 5.0% by mass, based on the ink.

[0026] [Sugars and other additives] When used as an ink for an inkjet printer, sugars can be added for the purpose of improving ejection properties and adhesion. Examples of sugars include monosaccharides, disaccharides, and polysaccharides, and specific examples include glucose, galactose, mannose, gulose, talose, allose, altrose, idose, fructose, sorbose, tagatose, psicose, sucrose, maltose, lactose, maltotriose, isomaltose, maltotetraose, isomaltotriose, isomaltotetraose, panose, nigerose, kojibiose, lactellose, palatinose, kestose, nystose, fructosylnystose, inulobiose, inulotriose, inulotetraose, isomalcellose, maltosylsucrose, maltotriosylsucrose, maltopentaose, maltohexaose, and maltoheptaose. Furthermore, as derivatives of these sugars, sugars obtained by reducing or oxidizing the above sugars are preferred, and specific examples include maltitol, sorbitol, etc. The amount of sugars added to the ink liquid is preferably 1% by mass to 20% by mass, and this has the effect of improving blurring when printed and stabilizing ejection.

[0027] Furthermore, in order to impart desired physical properties to the white ink for pigment printing of the present invention, an antifungal agent and a bactericide can be used. Specifically, preferred antifungal agents include orthophenylphenol, sodium orthophenylphenol, diphenyl, thiabendazole, and imazalil, and preferred bactericides include sodium hypochlorite, hydrogen peroxide, and ethanol. In addition, additives such as antifoaming agents, anti-rust agents, and pH adjusters may be added as appropriate.

[0028] For adjusting the viscosity of the ink or for other purposes, other water-soluble polymers may be added in addition to the anionic water-soluble polymer with a cellulose structure, as long as the polymer does not impair the performance of the present invention. Examples include starch-based polymers such as guar gum, locust bean gum, agar, and methyl starch, as well as gelatin, pullulan, xanthan gum, tragacanth gum, and dextrin. Furthermore, other conventionally known dispersants such as urethane resins, acrylic resins, and styrene-acrylic copolymer resins may also be added as long as the performance of the present invention is not impaired.

[0029] The white ink for pigment textile printing according to the first aspect of the present invention is characterized by containing titanium oxide as a coloring material, but other coloring materials may also be contained within the range that does not impair the performance of the present invention. Examples of such other coloring materials that can be used include, but are not limited to, calcium carbonate.

[0030] [Ink Preparation] The white ink for pigment textile printing of the present invention can be prepared by mixing and dispersing the above-mentioned materials. The method for preparing the ink is not particularly limited, but it can be prepared by the following method. First, titanium oxide, an anionic water-soluble polymer with a cellulose structure, and predetermined additives are mixed and dissolved in water by stirring, and then dispersed using a commercially available disperser until the D50 of titanium oxide falls within the range described below to prepare a "titanium oxide dispersion." There are no particular limitations on the stirring method, and any commercially available stirrer can be used. The disperser may be any device capable of dispersing titanium dioxide in an aqueous alginate solution, and its type and type are not particularly limited. Examples include wet media dispersers such as paint shakers, bead mills, roll mills, ball mills, sand grinders, Dynomills, spike mills, DCP mills, and basket mills, as well as medialess dispersers such as nanomizers, ultimizers, and ultrasonic dispersers. When using a disperser that uses beads, the diameter of the beads is preferably 0.1 mm to 2.0 mm. Bead materials such as glass beads, alumina beads, and zirconia beads can be selected and used. To remove bead components and other foreign matter that may be mixed in during the dispersion process, processes such as filtration, centrifugation, membrane separation, water washing, purification, and magnetic separation can be included during and after the dispersion process. The amount of titanium oxide in the titanium oxide dispersion is preferably 2.0 to 50% by mass, more preferably 10 to 40% by mass. If it is less than 2.0% by mass, the amounts of solvents and additives added when making ink may be limited. If it exceeds 50% by mass, the storage stability of the dispersion may be deteriorated.

[0031] A white ink for pigment textile printing is obtained by adding a predetermined water-soluble organic solvent, a surface tension adjuster, and other additives to the titanium oxide dispersion and stirring the mixture. To improve quality, foreign matter and impurity ions can be removed by filtering or the like after preparing the ink.

[0032] [Physical properties of ink] The white ink for pigment textile printing of the present invention exhibits the following characteristics and preferable properties.

[0033] The D50 (meaning the value corresponding to the particle diameter at which the volume cumulative 50% of the particle diameter is obtained when the volume cumulative particle size distribution curve of the measured values ​​by the dynamic light scattering method is plotted from the small diameter side) of the titanium oxide in the white ink for pigment textile printing of the present invention is preferably 200 nm to 1 μm, more preferably 200 to 800 nm, even more preferably 200 to 700 nm, and most preferably 200 to 500 nm. By setting the D50 of titanium dioxide within the above preferred range, the hiding power is improved, absorption into the printed material is suppressed, and visibility is improved. Furthermore, photocatalytic activity is suppressed, which prevents deterioration of the fabric components in the area where the dispersion is attached. Furthermore, separation of the colorant in the liquid is less likely, and sedimentation is further suppressed. If the D50 exceeds 1 μm, coarse particles may clog the nozzle when used in an inkjet printer, resulting in poor ejection. In addition, by adjusting the D90 (the value corresponding to the particle size at which the volume cumulative particle size distribution curve of measurements taken by dynamic light scattering is 90% when plotted from the smallest diameter side) of the titanium oxide in the ink to a dispersed particle size of 1 μm or less, more preferably 600 nm or less, a dispersion with even better sedimentation suppression performance can be obtained. While it is possible to adjust the D90 within this range by dispersion treatment alone, to prevent the generation of large amounts of particles that are too fine and cause re-aggregation, it is preferable to perform dispersion treatment until the D50 falls within the preferred range defined in claim 2, and then remove coarse particles using known methods such as centrifugation or filtration. Furthermore, it is preferable to control not only the particle size distribution but also the number of coarse particles.

[0034] The D50 and D90 of titanium oxide can be measured by the following method, but the measurement method is not limited to this as long as the same results are obtained. Conditioning: Dilute the stock solution with ion-exchanged water to fall within the specified measurement concentration range. Measuring equipment: Dynamic light scattering particle size distribution analyzer (Microtrac Bell Corporation "NanoTracWave") Measurement time: 120 seconds

[0035] The viscosity of the white ink for pigment textile printing of the present invention is preferably 1.0 to 30.0 mPa·s, more preferably 1.0 to 20.0 mPa·s, and particularly preferably 3.0 to 10.0 mPa·s. By setting the ink viscosity within the above-mentioned preferred range, it is possible to improve the handleability during production and use of the ink and the quality of printed images, as well as to suppress sedimentation and make the ink suitable for use in inkjet printers. As long as the viscosity is within the above-mentioned range, the ink viscosity can be freely set according to the printing method, printing conditions, and intended use, for example, by adding a water-soluble polymer other than the anionic water-soluble polymer having a cellulose structure, as described above. The viscosity of the ink can be measured by the following method, but the measurement method is not limited to this as long as the same results are obtained. Conditioning: Undiluted Measuring equipment: Cone-plate type rotational viscometer (Toki Sangyo Co., Ltd., "TVE-20L type") Measurement temperature: 25℃

[0036] The pH value of the white ink for pigment textile printing of the present invention is preferably in the range of 5.0 to 12.0, and more preferably in the range of 7.0 to 11.0. If the pH is lower than 5.0, the long-term stability of the ink may decrease, and if it is higher than 12.0, the titanium oxide may not be dispersed sufficiently, or when used in inkjet printing, corrosion may adversely affect the durability of the device. Furthermore, by keeping the pH within the above range, sedimentation suppression performance is improved, and the TSI value, described below, can be kept within a preferred range. The method for measuring pH is not particularly limited, and a commercially available pH measuring device can be used.

[0037] The fact that the white ink for pigment textile printing of the present invention can be made particularly excellent in terms of sedimentation suppression performance can be verified by the spatial dependence and temporal changes in transmitted light and backscattered light detected when the white ink for pigment textile printing of the present invention is irradiated with light. In other words, by comparing the rates of change in these values, it is possible to compare the uniformity and stability over time of the liquid. A typical method for this is to use the TSI value. The TSI value is a liquid stability evaluation index that can be determined using Formulaction's Turbiscan Tower, a liquid dispersion stability evaluation device. This device observes and evaluates the dispersion stability of substances in samples such as pigment dispersions by irradiating them with light and detecting the transmitted and scattered light. A stage equipped with a light source and detector moves up and down automatically, irradiating light at each position in a container filled with the sample at regular intervals and measuring (scanning) the intensity of the transmitted and scattered light to observe the degree of dispersion of the substance at each position and its changes over time. This allows evaluation without diluting liquid samples.

[0038] The TSI value is calculated using the following formula based on the light intensity measured using the method above and its change over time. As can be seen from the formula, the greater the change over time, the larger the value, so it is an index of stability.

[0039]

number

[0040] The bottom TSI value can be determined by the following method. Conditioning: White ink concentrate for pigment printing Measuring equipment: High-end liquid dispersion stability evaluation device (Formulaction, "Turbiscan Tower") Analysis software: TurbiSoft Set temperature: 60℃ Measurement period: 3 days Evaluation position: up to 10 mm from the bottom of the container Number of scans: 1 / 30 minutes (total 241 scans)

[0041] The white pigment printing ink of the present invention preferably has a bottom TSI value of 30.0 or less. The bottom TSI value is more preferably 20.0 or less, and most preferably 15.0 or less. As a result of studies by the present inventors, it has been found that there is a correlation between the bottom TSI value and the sedimentation inhibition and long-term stability of the white pigment printing ink, and that a white pigment printing ink with excellent sedimentation inhibition performance can be obtained by setting the bottom TSI value to 30.0 or less. If the bottom TSI value is 30.0 or less, the pigment is less likely to settle or solidify even when stored for a long period of time, which reduces the occurrence of problems such as the need for long, strong stirring before use and deterioration of the ink, which can cause poor ejection in inkjet printers.

[0042] The second invention disclosed in this application is a white ink for pigment textile printing, which contains at least a white pigment and has a bottom TSI value of 30.0 or less. The method for preparing the white ink for pigment textile printing, which is the second invention of the present application, is not particularly limited. However, by using the materials and method disclosed as the first invention of the present application and adjusting the pH, in particular, to fall within the range disclosed in claim 3, the bottom TSI value can be set within the above range. In the second invention of the present application, titanium oxide can be suitably used as the white pigment, but is not limited to this.

[0043] [Printing method and use]

[0033] The printing method using the white ink for pigment textile printing of the present invention is not limited, and it can be suitably used in methods conventionally used in printing, such as screen printing, but it can also maintain stable ejection properties and exhibit excellent performance when used in inkjet printing. Base prints obtained using the white ink for pigment textile printing of the present invention have excellent hiding power and fixation properties, and by printing color inks thereon, color prints with excellent color development and abrasion resistance can be obtained. The white pigment printing ink of the present invention can also be used in a direct-to-film (DTF) printing method, in which a composition comprising a mixture of ink and a paste such as a thermoplastic resin is printed or applied to a resin film, and the film is then heat-transferred to a fabric. As described above, the ink of the present invention has the sedimentation-inhibiting properties required for inkjet printing and a low viscosity, and therefore is less likely to cause ejection defects when printing the ink onto a resin film using an inkjet printer or the like in DTF printing, making it suitable for use.

[0044] [Fabric pretreatment] When using the white ink for pigment textile printing of the present invention, since the ink contains an anionic dispersant, it is preferable to impregnate the fabric of the substrate to be printed with a cationic compound in advance, so that the cationic compound present on the fabric and the colorant containing the anionic dispersant in the ink react and aggregate on the fabric, allowing the colorant to be fixed to the substrate while maintaining its hiding power. Examples of cationic compounds include polyvalent metal salts and cationic resins. Among these, polyvalent metal salts are preferred because they improve the color development of the pigment and are suitable for cotton and polyester fabrics. These cationic compounds may be used alone or in combination of two or more.

[0045] The polyvalent metal salt refers to a water-soluble compound containing a divalent or higher polyvalent metal cation and an anion that forms a salt with the polyvalent metal cation. Examples of divalent or higher polyvalent metal cations include Ca. 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Zn 2+ , Ba 2+ Divalent metal ions such as Al 3+ , Fe 3+ , Cr 3+ Examples of the anion include trivalent metal ions such as Cl. - , I - , Br - , SO4 2- , CO3 2-, ClO3 - , NO3 - , H.C.O.O. - , CH3COO - Among these polyvalent metal salts that combine polyvalent metal cations and anions, calcium salts or magnesium salts are preferably used from the viewpoints of improving the storage stability of the treatment liquid and improving color development by exhibiting an aggregating action on pigments and resin particles (emulsions). Suitable examples of calcium salts and magnesium salts include calcium nitrate, calcium chloride, and magnesium sulfate, and one or more selected from these salts are used. Of these, calcium salts are particularly preferred from the viewpoint of their strong aggregating action and further improving color development.

[0046] The polyvalent metal salt may be a hydrate. For example, calcium chloride dihydrate may be used as a calcium chloride hydrate, and for example, calcium nitrate tetrahydrate may be used as a calcium nitrate hydrate. The polyvalent metal salt may be used alone or in combination of two or more. When two or more polyvalent metal salts are used in combination, it is preferable to use a calcium salt and a magnesium salt in combination. In such a case, it becomes easier to control the aggregation action of pigments and resin particles (emulsions). Since the aggregation action can be prevented from becoming too strong, it is possible to make the image less grainy in the printed material, and as a result, it is possible to reduce uneven color development of the image. As the magnesium salt, it is preferable to use magnesium sulfate.

[0047] In addition to polyvalent metal salts, metal salts other than polyvalent metal salts may also be used as cationic compounds. - , K. - Examples of the monovalent metal cations include sodium sulfate and potassium sulfate, which are combinations of the above monovalent metal cations with the above anions. These predetermined cationic compounds can be dissolved and impregnated into the substrate, so that the substrate can be uniformly impregnated with the solution.

[0048] [Example] The present invention will be further illustrated by the following examples.

[0049] Example 1 The components shown below were mixed and stirred with a propeller stirrer at room temperature for 1 hour. Ingredient Quantity (Parts by weight (hereinafter referred to as "parts")) Titanium dioxide 20.00 Sodium alginate 2.40 (10% by mass solution viscosity: 20-50 mPa·s (20°C), number of anionic substituents: 1) Preservatives 0.50 Wednesday 77.10 Next, the resulting mixture and 370 g of zirconia beads with a diameter of 0.5 mm were placed in a paint shaker pot and shaken for 3 hours to disperse the mixture. The resulting dispersion liquid was designated "Dispersion Liquid 1" and was stirred with the following formulation using a propeller stirrer at room temperature for 30 minutes to prepare a white ink for pigment textile printing. Ingredient amount (parts) Dispersion 1 50.00 Sucrose 5.00 Propylene glycol 15.00 Glycerin fatty acid ester 0.01 Antifoaming agent 0.10 Wednesday 29.89 The appearance of the resulting ink was observed and it was confirmed that it had a uniform white color.

[0050] [Physical property measurements] The D50, viscosity, and pH of the resulting ink were measured by the following methods. Measuring D50 Conditioning: Dilute the white ink stock solution for pigment textile printing with ion-exchanged water so that it falls within the specified measurement concentration range. Measuring equipment: Dynamic light scattering particle size distribution analyzer (Microtrac Bell Corporation "NanoTracWave") Measurement time: 120 seconds Evaluation: A range of 200 to 1 μm was rated as good (◯), and anything outside the range was rated as bad (×). Viscosity measurement Conditioning: White ink concentrate for pigment printing Measuring equipment: Cone-plate type rotational viscometer (Toki Sangyo Co., Ltd., "TVE-20L type") Measurement temperature: 25℃ pH measurement Conditioning: White ink concentrate for pigment printing (20°C) Measuring equipment: pH meter (DKK-TOA Corporation, "HM-41X") The measurement results were D50 of 281 nm, viscosity of 4.4 mPa·s, and pH of 7.1. In addition, a liquid stability evaluation test and a hiding power evaluation test were carried out by the following methods.

[0051] [Evaluation of liquid stability] The test and evaluation methods for liquid stability are as follows. Conditioning: White ink concentrate for pigment printing Measuring equipment: High-end liquid dispersion stability evaluation device (Formulaction, "Turbiscan Tower") Analysis software: TurbiSoft Set temperature: 60℃ Measurement period: 3 days Number of scans: 1 / 30 minutes (total 241 scans)

[0052] [Concealment evaluation] The method for evaluating the hiding power is as follows. Calcium chloride was diluted with water to 10% and mixed, and a black membrane was soaked in it for 1 hour. After soaking, the water was removed with a roller and the fabric was dried in an oven at 125°C. Each ink was applied to the above black substrate using a No. 5 bar coater, and the whiteness was measured using the following device. Measurement equipment: Spectrophotometer (Suncolor "datacolor 850") Light source: C2 light source A Y value of 30.0 or more was judged to be good (◯) in terms of hiding power, and a Y value of 30.1 or less was judged to be poor (×) in terms of hiding power.

[0053] Example 2 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 2" was used, in which the viscosity of the sodium alginate in Example 1 was replaced with a 10 mass% solution with a viscosity of 500 to 600 mPa s (20°C), and measurements and tests were carried out on the resulting ink. The sodium alginate used had one anionic substituent group. Measurements showed that the ink had a D50 of 453 nm, a viscosity of 10.6 mPa·s, and a pH of 7.3. Observation of the ink's appearance confirmed that it was a uniform white color.

[0054] Example 3 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 3" was used, in which the amount of sodium alginate in Example 1 was replaced by 1.20 parts by weight, and the obtained ink was measured and tested. Measurements showed that the ink had a D50 of 266 nm, a viscosity of 3.3 mPa·s, and a pH of 6.9. Observation of the ink's appearance confirmed that it was a uniform white color.

[0055] Example 4 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 4" was used, in which the amount of sodium alginate in Example 1 was replaced by 6.00 parts by weight, and the obtained ink was measured and tested. Measurements showed that the ink had a D50 of 312 nm, a viscosity of 9.1 mPa·s, and a pH of 7.1. Observation of the ink's appearance confirmed that it was a uniform white color.

[0056] Example 5 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 1" in Example 1 was replaced with "Dispersion 5" having the following formulation, and the obtained ink was measured and tested. Ingredient amount (parts) Titanium dioxide 20.00 Sodium alginate 2.40 (10% by mass solution viscosity: 20-50 mPa·s (20°C), number of anionic substituents: 1) Preservatives 0.50 Sodium carbonate 0.28 Water 76.82 Measurements showed that the ink had a D50 of 258 nm, a viscosity of 4.3 mPa·s, and a pH of 10.0. Observation of the ink's appearance confirmed that it was a uniform white color.

[0057] Example 6 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 1" in Example 1 was replaced with "Dispersion 6" having the following formulation, and the obtained ink was measured and tested. Ingredient amount (parts) Titanium dioxide 20.00 Sodium alginate 2.40 (10% by mass solution viscosity: 20-50 mPa·s (20°C), number of anionic substituents: 1) Preservatives 0.50 Citric acid 0.33 Water 76.77 Measurements showed that the resulting ink had a D50 of 378 nm, a viscosity of 4.4 mPa·s, and a pH of 4.5. Observation of the appearance of the resulting ink confirmed that it was a uniform white color.

[0058] Example 7 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 1" in Example 1 was replaced with "Dispersion 7" having the following formulation, and the obtained ink was measured and tested. Ingredient amount (parts) Titanium dioxide 10.00 Calcium carbonate 10.00 Sodium alginate 2.40 (10% by mass solution viscosity: 20-50 mPa·s (20°C), number of anionic substituents: 1) Preservatives 0.50 Wednesday 77.10 Measurements showed that the ink had a D50 of 220 nm, a viscosity of 4.5 mPa·s, and a pH of 8.7. Observation of the ink's appearance confirmed that it was a uniform white color.

[0059] Example 8 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 1" in Example 1 was replaced with "Dispersion 8" having the following formulation, and the obtained ink was measured and tested. Ingredient amount (parts) Titanium dioxide 5.00 Calcium carbonate 15.00 Sodium alginate 2.40 (10% by mass solution viscosity: 20-50 mPa·s (20°C), number of anionic substituents: 1) Preservatives 0.50 Wednesday 77.10 Measurements showed that the ink had a D50 of 235 nm, a viscosity of 4.6 mPa·s, and a pH of 8.9. Observation of the ink's appearance confirmed that it was a uniform white color.

[0060] Comparative Example 1 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 9" was used, in which the viscosity of the sodium alginate in Example 1 was replaced with a 10 mass% solution with a viscosity of 1800 to 2300 mPa s (20°C), and measurements and tests were carried out on the resulting ink. The number of anionic substituents in the sodium alginate used was 1. Measurements showed that the resulting ink had a D50 of 1444 nm, a viscosity of 64.5 mPa·s, and a pH of 7.5. Furthermore, the appearance of the resulting ink was observed and it was confirmed that the ink exhibited a uniform white color.

[0061] Comparative Example 2 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 10" was used, in which the amount of sodium alginate in Example 1 was replaced by 0.10 parts by weight, and the obtained ink was measured and tested. Measurements showed that the resulting ink had a D50 of 228 nm, a viscosity of 2.2 mPa·s, and a pH of 6.6. Furthermore, the appearance of the ink obtained was observed and it was confirmed that the ink exhibited a uniform white color.

[0062] Comparative Example 3 A white ink for pigment textile printing was prepared in the same manner as in Example 1, except that "Dispersion 11" was used, in which the amount of sodium alginate in Example 1 was replaced with 16.00 parts by weight, and the obtained ink was measured and tested. Measurements showed that the resulting ink had a D50 of 384 nm, a viscosity of 55.5 mPa·s, and a pH of 6.6. Furthermore, the appearance of the ink obtained was observed and it was confirmed that the ink exhibited a uniform white color.

[0063] Comparative Example 4 An ink was prepared in the same manner as in Example 1, except that "Dispersion 12" was used, in which the sodium alginate in Example 1 was replaced with hydroxypropyl cellulose (viscosity of a 10% by mass solution: 50 to 100 mPa·s (20°C)). Measurements showed that the resulting ink had a D50 of 961 nm, a viscosity of 9.2 mPa·s, and a pH of 7.5. Observation of the appearance of the resulting ink confirmed that it was a uniform white color.

[0064] Comparative Example 5 An ink was prepared in the same manner as in Example 1, except that "Dispersion 13" was used, in which the sodium alginate in Example 1 was replaced with sodium carboxymethylcellulose ("Cellogen 5-A" (manufactured by Daiichi Kogyo Co., Ltd.), 10 mass% solution viscosity 50 to 100 mPa·s (20°C), number of anionic substituents: 0.6 to 0.7). Measurements showed that the resulting ink had a D50 of 376 nm, a viscosity of 6.7 mPa·s, and a pH of 7.1. Observation of the appearance of the resulting ink confirmed that it exhibited a uniform white color.

[0065] Comparative Example 6 An ink was prepared in the same manner as in Example 1, except that "Dispersion 14" was used, in which the sodium alginate in Example 1 was replaced with a styrene-acrylic copolymer resin. Measurements showed that the ink had a D50 of 241 nm, a viscosity of 2.5 mPa·s, and a pH of 8.2. Observation of the ink's appearance confirmed that it was a uniform white color.

[0066] Comparative Example 7 An ink was prepared in the same manner as in Example 1, except that "Dispersion 15" was used in which the sodium alginate in Example 1 was replaced with sodium polyacrylate. Measurements showed that the ink had a D50 of 326 nm, a viscosity of 3.0 mPa·s, and a pH of 6.6. Observation of the ink's appearance confirmed that it was a uniform white color.

[0067] [Table 1]

[0068] [Table 2]

[0069] The above experimental results show that the white pigment printing inks of Examples 1 to 8, which contain the specific sodium alginate characteristic of the present invention, exhibit good hiding power as measured by whiteness. In addition, they generally have low viscosity and are easy to handle. Furthermore, the inks of Examples 1, 2, 3, 4, 5, 7, and 8 have a pH within the ranges of claims 4 and 5, and evaluation of liquid stability indicates that titanium oxide is unlikely to precipitate. This shows that these inks also have improved ejection stability when used in inkjet printing.

[0070] In Comparative Example 1, which used highly viscous sodium alginate, the dispersion of titanium oxide was insufficient, resulting in a large D50 and high ink viscosity. This not only deteriorates handling, but is also highly likely to cause ejection problems and clogging of inkjet heads due to coarse particles when used in inkjet printing, etc.

[0071] In Comparative Example 2, in which the amount of sodium alginate added to the ink was less than 0.1% by mass, the measurement results for D50 of titanium oxide were good, indicating that the particle size was fine, and the viscosity was also good. However, the whiteness was low, indicating that the ink did not have the hiding power required for a white ink for pigment textile printing.

[0072] In Comparative Example 3, in which the amount of sodium alginate added in the ink was more than 6% by mass, the measurement results for D50 of titanium oxide were good, indicating that the particles were finely divided. However, the ink viscosity was high, which not only deteriorated handling during production and use, but also considered to be highly likely to cause ejection defects and clogging of inkjet heads due to coarse particles when used in inkjet printing, etc.

[0073] In Comparative Example 4, in which hydroxypropyl cellulose was used instead of sodium alginate, good results were obtained in the liquid stability evaluation and viscosity evaluation, but the whiteness was low, and the ink did not have the hiding power required for a white ink for pigment textile printing.

[0074] In Comparative Example 5, in which sodium carboxymethylcellulose having an anionic substituent group number of less than 0.8 was used instead of sodium alginate, good results were obtained in the measurement of the D50 of titanium oxide and in the evaluation of the liquid stability and viscosity, but the whiteness was low and the hiding power required for a white ink for pigment textile printing was not obtained.

[0075] In Comparative Example 6, in which a styrene-acrylic copolymer was used instead of sodium alginate, the D50 measurement results of titanium oxide were good, indicating progress in atomization, and the viscosity was also good. However, the liquid stability evaluation was poor, and sedimentation was likely to occur, so when used in inkjet printing, etc., it is thought that there is a high possibility of ejection failure and clogging due to sedimentation over time. In addition, the whiteness was low, and the hiding power required for a white ink for pigment textile printing was not achieved.

[0076] In Comparative Example 7, in which sodium polyacrylate was used instead of sodium alginate, the D50 measurement results of titanium oxide were good, indicating progress in atomization, and the viscosity was also good. However, the liquid stability evaluation was poor, and sedimentation was likely to occur, so when used in inkjet printing, etc., it is thought that there is a high possibility of causing ejection failure and clogging due to sedimentation over time. In addition, the whiteness was low, and the hiding power required for a white ink for pigment textile printing was not achieved. [Industrial Applicability]

[0077] As described above, even when a pigment such as titanium oxide, which has a high specific gravity and is difficult to uniformly and stably retain in the ink, is used, the present invention makes it possible to provide an excellent white ink for pigment printing that is easy to handle, has low viscosity, and yet has sufficient hiding power and fixation to fabrics, and is therefore suitable for use in textile printing. Furthermore, by adjusting the pH of the white ink for pigment printing, it is possible to provide a white ink for pigment printing that has excellent sedimentation-inhibiting properties.

Claims

1. A white ink for pigment textile printing, comprising titanium oxide and an alginate having a viscosity of 600 mPa·s or less in a 10% by mass aqueous solution (liquid temperature: 20°C), and containing the alginate in an amount of 0.1% by mass to 6% by mass of the total ink.

2. 2. The white ink for pigment textile printing according to claim 1, wherein the titanium oxide has a D50 of 200 nm to 1 μm.

3. 3. The white ink for pigment textile printing according to claim 1, wherein the pH is from 5.0 to 12.

0.

4. A textile printing method, comprising using at least the white ink for pigment textile printing according to claim 1.

5. A textile printing method comprising the steps of: printing and applying a composition containing at least the white ink for pigment textile printing according to claim 1 onto a resin film; and adhesively transferring the resin film onto a fabric.

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