JP7459520B2 - Image forming method and water-based inkjet textile printing ink - Google Patents

Description

The present invention relates to an image forming method and an inkjet textile printing ink.

Conventional printing methods include exhaust printing, in which the fabric is immersed in a bath filled with dye, but the dyeing process takes a long time, resulting in low production efficiency. In recent years, so-called inkjet printing, in which images are formed on fabrics using an inkjet method, has been widely used because it can be dyed in a short time and has high production efficiency.

In inkjet textile printing, tiny droplets of ink are ejected from an inkjet recording head and land on fabric to form an image. The types of coloring materials contained in the ink used in inkjet textile printing include dyes and pigments.

As inkjet textile printing inks containing dyes, for example, inks containing reactive dyes are known for fabrics containing cotton, rayon fibers, linen fibers, etc. (see, for example, Patent Document 1).

An image formed with a dye-based ink as shown in Patent Document 1 dissolves in or reacts with the fibers of a fabric, so it is possible to obtain a highly durable image without losing the texture of the fibers. On the other hand, since a washing step is required to wash away undissolved dye or unreacted dye, it is desirable to be able to omit such a step from the viewpoint of further increasing production efficiency.

As an inkjet printing ink containing a pigment, for example, a pigment textile inkjet ink composition containing a pigment, a binder resin, a sulfonate-based anionic surfactant, and water is known (for example, Patent Document 2) reference). Since the pigment is difficult to adhere to the fabric by itself, it is made to adhere to the fabric by further containing a binder resin as described above. This method is an extremely simple method because the image can be fixed to the fabric using a binder resin after the image is formed, while eliminating the need for a washing step such as using a dye.

JP 2018-48414 A JP 2019-163397 A

However, in the method of Patent Document 2, since the ink containing the binder resin is applied to the fabric, the fabric becomes hard and the texture of the fibers is likely to be impaired. Furthermore, since the ink must have a low viscosity to be ejected with an inkjet, it is not possible to contain a sufficient amount of binder resin necessary for fixing, and the fixing performance and robustness are also insufficient. There wasn't.

Further, as shown in Patent Document 2, pigment-based inks used for inkjet textile printing are generally those in which pigments are dispersed with an anionic dispersant. When using ink in which pigments are dispersed with an anionic dispersant, in order to improve fixing properties and fastness, it is necessary to pre-treat the fabric with a cationic pre-treatment liquid to improve the fixing properties of the image. is commonly practiced. However, many natural products such as soy sauce, which is a typical example of stain components, exhibit anionic properties, so if these stains adhere to fabrics that have undergone cationic pretreatment, they are difficult to remove even when washed. was there.

The present invention has been made in view of the above circumstances, and aims to provide an image forming method and inkjet textile printing ink that can form an image on a fabric that is easy to remove stains and has good fixing properties. . Preferably, it is an object of the present invention to provide an image forming method and an inkjet textile printing ink that can form an image having good washing fastness and rubbing fastness on a fabric without impairing the texture of the fibers.

The present invention relates to the following image forming method and inkjet textile printing ink.

The image forming method of the present invention includes a step of applying droplets of ink containing a pigment, a cationic dispersant, and a solvent onto a fabric using an inkjet method.

The inkjet printing ink of the present invention contains a pigment, a cationic dispersant, a weak acid or an anionic surfactant having 2 to 24 carbon atoms, and a solvent.

According to the present invention, it is possible to provide an image forming method and inkjet textile printing ink that can form an image on a fabric that is easy to remove dirt and has good fixation properties. It is also possible to provide an image forming method and inkjet textile printing ink that can form an image on a fabric that has good washing fastness and friction fastness without impairing the texture of the fabric.

As mentioned above, the surface of the fabric to which the ink containing the anionic dispersant is applied is subjected to pretreatment for imparting cationic groups. However, fabrics that have been pre-treated to impart cationic groups have cationic groups (which have a high affinity with stain components) remaining in areas where no image is formed, making it easy for stains to adhere to them. Once it sticks, it is difficult to remove. Furthermore, the texture of the fibers is likely to be impaired by the resin component that imparts cationic groups.

In contrast, in the present invention, an ink containing a cationic dispersant is used as the pigment dispersant, instead of the conventional anionic dispersant. As a result, there is no need to perform pre-treatment to impart cationic groups to the fabric (which was done when using inks containing anionic dispersants), so stains do not adhere to areas of the fabric where images are not formed. You can make it more difficult to remove dirt and make it easier to remove dirt (even if it gets stuck). In particular, when using a fabric with anionic groups on its surface to improve the adsorption speed and fixing properties of pigments in ink containing cationic dispersants, anionic groups have low affinity with stain components. Dirt is more difficult to adhere to, and even if dirt does adhere, it can be removed more easily.

That is, the image forming method of the present invention includes a step of applying droplets of an ink (inkjet textile printing ink) containing a pigment, a cationic dispersant, and a solvent onto a fabric using an inkjet method.

Furthermore, by combining the ink with a fabric having anionic groups, the fixation of the resulting image to the fabric can be further improved, and the wash fastness and abrasion fastness can be improved.

In addition, inkjet printing using ink containing such a cationic dispersant is performed by an equilibrium reaction (static reaction) in which the fabric is immersed for a long time in a bath of pigment dye at a low concentration (for example, less than 1% by mass). Unlike exhaust printing, in which a high concentration (several percent by mass) of ink penetrates into the fabric within a very short period of time, it is carried out by a dynamic reaction in which the ink is adsorbed on the adsorption sites of the fabric. In order to further improve washing fastness and abrasion fastness in such inkjet printing, it is preferable that the pigment is sufficiently adsorbed not only to the adsorption sites on the surface of the fabric but also to the adsorption sites inside; 1) It is preferable that the ink penetrates into the inside of the fabric easily, and 2) The adsorption speed of the pigment is moderately slow (slow penetration).

Regarding 1) above, for example, by further adding a certain amount or more of a high-boiling point solvent to the ink, it is possible to further reduce thickening of the ink due to drying on the surface of the fabric, and therefore further increase the ink's penetration into the fabric. Regarding 2) above, by further adding a specific weak acid or anionic surfactant to the ink, it is possible to appropriately slow down the rate at which the pigment is adsorbed to the adsorption sites. This makes it easier for the pigment to be adsorbed to the adsorption sites inside the fabric, and therefore further improves the wash fastness and friction fastness.

First, the structure of the ink used in the image forming method of the present invention will be explained.

1. Inkjet Textile Printing Ink The inkjet textile printing ink contains a pigment, a cationic dispersant, and a solvent.

1-1. Pigment The pigment is not particularly limited, but may be, for example, an organic pigment or an inorganic pigment having the following numbers as described in the Color Index.

Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53 :1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144 , 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Includes Orange 13, 16, 20, and 36.

Examples of blue or cyan pigments include Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36 , 60 are included.

Examples of green pigments include Pigment Green 7, 26, 36, 50. Examples of yellow pigments include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137 , 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193.

Examples of black pigments include Pigment Black 7, 28, and 26.

Examples of commercially available pigments include Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Fine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270 , 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Red 8040, C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B , GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichiseika Chemical Industries); KET Yellow 401, 402, 403, 404, 405, 406, 416 , 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106 , 111, 118, 124, KET Green 201 (Dainippon Ink Chemical); Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T- 13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, U GN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, ColortexBlue516, 517, 518, 519, A8 18, P-908, 510, Colortex Green402, 403, Colortex Black 702, U905 (Sanyo Color Lionol Yellow1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink), Toner Magenta E02, Permanent RubinF6B, Toner Y yellow HG, Permanent Yellow GG-02, Hostapeam BlueB2G (Hoechst Industries Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant); Carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, # 950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32 , #30, #25, #20, #10, #5, #44, and CF9 (manufactured by Mitsubishi Chemical).

The dispersed particle size of the pigment (the average particle size (Z average) of the pigment particles in the ink to which the cationic dispersant is adsorbed) may be within a range that does not impair the ejection properties using the inkjet method, and is not particularly limited, but is preferably 100 to 350 nm. The dispersed particle size of the pigment can be measured using a particle size distribution measuring device that uses dynamic scattering.

The content of the pigment is not particularly limited, but from the viewpoint of easily adjusting the viscosity of the ink within the above range and forming a high-density image, it should be 1.5 to 15% by mass based on the ink. is preferred. When the pigment content is 1.5% by mass or more, it is easy to form a high-density image, and when it is 15% by mass or less, the viscosity of the ink does not become too high, so that the injection stability is not easily impaired. From the same viewpoint, the pigment content is more preferably 5 to 15% by mass based on the ink.

1-2. Cationic Dispersant A cationic dispersant is present in the ink so as to surround the surface of the pigment particle, or is adsorbed to the surface of the pigment particle, thereby forming a pigment dispersion and dispersing the pigment well.

Examples of the cationic group possessed by the cationic dispersant include a secondary amino group (imino group), a tertiary amino group, or a quaternary ammonium group.

Such a cationic dispersant is not particularly limited as long as it can form a pigment dispersion as described above, and may be, for example, a cationic polymer (polymer or prepolymer) or a cationic compound.

Examples of cationic polymers include (co)polymers of ethylenically unsaturated monomers having cationic groups (tertiary amino groups or quaternary ammonium groups).

Examples of ethylenically unsaturated monomers having tertiary amino groups include:
dialkylaminoalkyl (meth)acrylates such as dimethyl or diethylaminoethyl (meth)acrylate, dimethyl or diethylaminopropyl (meth)acrylate;
dialkylaminoalkyl (meth)acrylamides such as dimethyl or diethylaminoethyl (meth)acrylamide, dimethyl or diethylaminopropyl (meth)acrylamide;
Includes (meth)acrylamides such as acrylamide.

Examples of ethylenically unsaturated monomers having a quaternary ammonium group include:
(meth)acryloyloxyalkyltrialkylammonium salts such as 2-(meth)acryloyloxyethyltrimethylammonium chloride and 3-(meth)acryloyloxy-2-hydroxypropyltrimethylammonium chloride;
(meth)acrylamidoalkyltrialkylammonium salts such as acrylamido-2-(acryloyloxy)methyltrimethylammonium chloride, (3-(meth)acrylamidopropyltrimethylammonium chloride, and 3-(meth)acryloylamino-2-hydroxypropyltrimethylammonium chloride;
2-(meth)acryloyloxyalkylbenzyl ammonium salts such as 2-(meth)acryloyloxyethylbenzyl ammonium chloride and 2-(meth)acryloyloxyethyldimethylbenzyl ammonium chloride;
Dialkyldiallylammonium salts such as dimethyldiallylammonium chloride are also included.

There may be only one type of ethylenically unsaturated monomer having a cationic group (tertiary amino group or quaternary ammonium group), or there may be two or more types. For example, an ethylenically unsaturated monomer having a tertiary amino group and an ethylenically unsaturated monomer having a quaternary ammonium group may be copolymerized.

These ethylenically unsaturated monomers having a cationic group may also be copolymerized with other monomers. Examples of the other monomers include (meth)acrylic acid and its esters, allyl ethers, vinyl ethers, aromatic vinyl monomers, vinyl ester monomers, olefin monomers, and diene monomers.

Examples of such cationic polymers include dimethylaminoethyl methacrylate polymer, methacrylic acid-2-dimethylaminoethyl methacrylate copolymer, butyl acrylate-dimethylaminoethyl methacrylate copolymer, acrylamide-2-(acryloyloxy)methyltrimethylammonium chloride polymer, dimethyldiallylammonium chloride-acrylamide copolymer, etc.

Other examples of cationic polymers include polyethyleneimine or its modified products, and amino group-modified silicones.

The weight average molecular weight of the cationic polymer is not particularly limited, but is preferably 5,000 to 30,000. If the weight average molecular weight of the cationic dispersant is 5,000 or more, it is easy to sufficiently disperse the pigment particles, and if it is 30,000 or less, the ink does not thicken too much, so that the penetration into the fabric is not easily impaired.

The weight average molecular weight of the cationic polymer can be measured in styrene equivalent terms by gel permeation chromatography.

Examples of cationic compounds include tetraalkyl quaternary ammonium salts such as dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, dihexadecyldimethylammonium bromide; amine salts, trialkyl quaternary ammonium salts, alkylpyridinium salts, Contains Norinium salt.

The cationic group equivalent of the cationic dispersant is not particularly limited as long as it can sufficiently disperse the pigment particles, but is preferably 1 to 50 mg/eq, for example. When the amount of cationic groups per molecule is within the above range, high pigment dispersibility can be easily obtained without increasing the molecular weight of the cationic dispersant. The cationic group equivalent of the cationic dispersant can be measured by the method of measuring amine value.

The content of the cationic dispersant is not particularly limited as long as it is in a range that sufficiently disperses the pigment particles and has a viscosity that does not impair the permeability into the fabric, but it is preferably 20 to 100% by mass, and more preferably 25 to 60% by mass, relative to the pigment.

1-3. Solvent The solvent is not particularly limited, but preferably contains water, and preferably further contains a water-soluble organic solvent.

Water-soluble organic solvents are not particularly limited as long as they are compatible with water; It is preferable that the viscosity is less likely to increase. Therefore, it is preferable that the ink contains a high boiling point solvent having a boiling point of 200° C. or higher.

The high boiling point solvent having a boiling point of 200° C. or higher may be any water-soluble organic solvent having a boiling point of 200° C. or higher, and preferably polyols or polyalkylene oxides.

Examples of polyols with a boiling point of 200°C or higher include dihydric alcohols such as 1,3-butanediol (boiling point 208°C), 1,6-hexanediol (boiling point 223°C), and polypropylene glycol; glycerin (boiling point 290°C) and trimethylolpropane (boiling point 295°C).

Examples of polyalkylene oxides having a boiling point of 200° C. or higher include:
These include ethers of dihydric alcohols such as diethylene glycol monoethyl ether (boiling point 202° C.), triethylene glycol monomethyl ether (boiling point 245° C.), tetraethylene glycol monomethyl ether (boiling point 305° C.), tripropylene glycol monoethyl ether (boiling point 256° C.); and ethers of trihydric or higher alcohols such as polypropylene glycol, glycerin (boiling point 290° C.), and hexanetriol.

The content of the high-boiling point solvent with a boiling point of 200°C or higher is preferably 2 to 10 times that of the pigment. If the content of the high-boiling point solvent is 2 or more times that of the pigment, the ink droplets that land on the surface of the fabric are unlikely to thicken excessively due to drying, so that the ink thickens only on the surface of the fabric due to drying before it penetrates into the interior of the fabric, and it is easy to suppress the pigment from being adsorbed. If the content of the high-boiling point solvent is 10 or less times that of the pigment, the drying properties are not excessively impaired. From the same viewpoint, it is more preferable that the content of the high-boiling point solvent with a boiling point of 200°C or higher is 4 to 8 times that of the pigment.

The solvent may further contain other solvents in addition to the high boiling point solvent. Examples of other solvents include polyhydric alcohols having a boiling point of less than 200°C (e.g., ethylene glycol, propylene glycol, hexanetriol, etc.); polyhydric alcohol ethers having a boiling point of less than 200°C (e.g., ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether); monohydric alcohols (e.g., methanol, ethanol, propanol, pentanol, hexanol, cyclohexanol, butyl ether ... alcohol); amines (e.g., ethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine); amides (e.g., formamide, N,N-dimethylformamide, N,N-dimethylacetamide); heterocycles (e.g., 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidine), sulfoxides (e.g., dimethyl sulfoxide); and sulfones (e.g., sulfolane).

1-4. Other Components The inkjet printing ink may further contain other components as necessary. Examples of the other components may include anionic surfactants, preservatives, antifungal agents, pH adjusters, etc.

(Anionic Surfactant)
From the viewpoint of adjusting the aggregation speed of the pigment, specifically, from the viewpoint of making it easier for the pigment in the ink to be absorbed not only on the surface of the fabric but also inside the fabric, it is preferable that the inkjet textile printing ink further contains a weak acid or anionic surfactant having 2 to 24 carbon atoms. That is, the weak acid or anionic surfactant electrically attracts the cationic dispersant absorbed on the pigment particles, thereby appropriately weakening the electrical action between the pigment particles and the fabric, and thus slowing down the rate of absorption onto the surface of the fabric.

Examples of weak acids having 2 to 24 carbon atoms include fatty acids (salts) such as acetic acid, succinic acid, sebacic acid, and dodecanedioic acid.

Anionic surfactants are surfactants having an anionic group such as a carboxyl group, examples of which include alkyl sulfates (such as sodium lauryl sulfate), alkyl sulfates, alkylbenzenesulfonates, and alkylnaphthalenes. Sulfonate, dialkyl sulfosuccinate (e.g. Na sulfodioctylsuccinate), alkyldiphenyl ether disulfonate, alkyl phosphate ester salt, naphthalene sulfonic acid formalin condensate, alkylnaphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl Included are sulfate ester salts, polyacrylic acid and its esters, and fiber derivatives such as carboxymethylcellulose. Among these, alkyl sulfates and dialkyl sulfosuccinates are preferred from the viewpoint of low molecular weight and not increasing viscosity, as described later.

The molecular weight of the anionic surfactant is not particularly limited, but a low molecular weight is preferable from the viewpoint of preventing the viscosity of the ink from increasing too much. Specifically, the anionic surfactant preferably has a molecular weight of 100 to 500.

The anionic surfactant may be one type or two or more types.

The total amount of the weak acid having 2 to 24 carbon atoms and the anionic surfactant is preferably 25 to 85 mol% based on the amount of cationic groups derived from the cationic dispersant in the ink. When the above total amount is 25 mol% or more, the adsorption speed of the pigment particles adsorbed by the cationic dispersant to the surface of the fabric can be appropriately reduced, so that the ink can easily penetrate into the fabric, and the ink can be easily absorbed into the fabric. The pigment particles are easily adsorbed inside. Thereby, the abrasion resistance (rubbing resistance) of the fabric after image formation can be improved. When the total amount is 85 mol % or less, the pigment dispersion effect by the cationic dispersant is less likely to be impaired.

(preservative, antifungal agent)
Examples of preservatives or antifungal agents include aromatic halogen compounds (e.g., Preventol CMK), methylene dithiocyanate, halogen-containing nitrogen-sulfur compounds, 1,2-benzisothiazolin-3-one (e.g., PROXEL GXL), and the like. is included.

(pH adjuster)
Examples of pH adjusters include citric acid, sodium citrate, hydrochloric acid, sodium hydroxide, and the like.

(About binder resin)
The cationic dispersant contained in the ink of the present invention not only improves the dispersibility of the pigment, but also improves the fixability to fabrics. In addition, if there are anionic groups on the surface of the fabric, the cationic groups of the cationic dispersant contained in the ink and the anionic groups on the surface of the fabric are electrically attracted to each other, further improving the fixing properties of the ink. sell. As described above, since the ink of the present invention can form an image with good fixability on fabric, it is possible to use water-soluble resins and resin particles with a molecular weight of over 10,000, which are contained in conventional pigment-based inks. It can be substantially free of binder resin. "Substantially free" means, for example, that the content is 2% by mass or less based on the total solid content of the ink. Thereby, it is possible to obtain an image-formed product that is free from gore (due to the binder resin) and has good fixability to the fabric without impairing the feel of the fabric (of the fabric).

1-5. Physical Properties The pH of the ink at 25° C. is preferably 4 to 9. When the pH of the ink is within the above range, the cationic dispersant itself in the ink is not easily aggregated and is easily dispersed stably, but also the pH of the ink can be easily adjusted to neutrality. Thereby, the material constituting the vicinity of the ejection opening of the inkjet head can be made less susceptible to damage by the ink. The pH of the ink can be measured in accordance with JIS Z 8802:2011. The pH of the ink can be adjusted using a pH adjuster.

The viscosity of the ink at 25° C. is not particularly limited as long as the ink jetting properties are good, but it is preferably 3 to 20 mPa·s, more preferably 4 to 12 mPa·s. preferable.

The viscosity of the ink can be measured at 25°C using an E-type viscometer.

1-6. Preparation of Ink The ink of the present invention can be produced by any method, for example, by mixing the above-mentioned pigment, cationic dispersant, and solvent. Specifically, it is preferable to produce the ink by mixing the pigment, cationic dispersant, and solvent (such as water) to obtain a pigment dispersion, and then further mixing the pigment dispersion with the remaining components (such as an anionic surfactant, a high boiling point solvent, a pH adjuster, etc.). This makes it easier to obtain an ink in which the pigment is well dispersed.

Next, the image forming method of the present invention using the ink of the present invention will be explained.

2. Image Forming Method The image forming method of the present invention includes a step of applying droplets of the ink of the present invention onto a fabric by an inkjet system.

Specifically, the image forming method of the present invention includes 1) a step of ejecting ink from an inkjet recording head to apply ink droplets onto a fabric (ink application step); and 2) a step of applying ink to the fabric. (drying/fixing step).

Regarding step 1) (ink application step), ink is ejected from an inkjet recording head to apply ink droplets onto the fabric.

The type of fabric is not particularly limited as long as it can form an image with the ink of the present invention, but from the viewpoint of increasing the pigment adsorption speed and fixing properties, it is preferable that the fabric has an anionic group at least on the surface. .

The fabric having anionic groups at least on its surface may be pretreated or may not be pretreated. That is, a fabric containing an anionic group-containing fiber (for example, cotton or anionic group-containing polyester) has anionic groups even as it is, and therefore does not necessarily need to be provided with anionic groups through pretreatment. On the other hand, since a fabric that does not contain fibers having anionic groups does not have anionic groups as it is, it is preferable to impart anionic groups through pretreatment (see step 3 below).

The fiber material constituting the fabric is not limited as long as it is a fiber that can be imaged with the ink of the present invention. The fiber material constituting the fabric preferably includes natural fibers such as cotton (cellulose fibers), hemp, wool, and silk; and chemical fibers such as rayon, vinylon, nylon, acrylic, polyurethane, polyester, or acetate. The fabric may be made of these fibers in any form such as woven fabric, nonwoven fabric, or knitted fabric. Further, the fabric may be a blended woven fabric or blended nonwoven fabric of two or more types of fibers.

Regarding step 2) (drying and fixing step), in the drying step, the ink applied to the fabric is dried to remove the solvent component in the ink, thereby fixing the ink applied to the fabric.

The drying method is not particularly limited and may be a method using a heater, a hot air dryer, a heating roller, or the like. Of these, it is preferable to use a hot air dryer and a heater to heat and dry both sides of the fabric.

The drying temperature is not particularly limited, but may be, for example, 150°C or lower. The drying time depends on the drying temperature, but may be, for example, about 0.5 to 30 minutes.

The image forming method of the present invention may further include 3) a step of pretreating the fabric (pretreatment step) as necessary.

Regarding the step 3) (pretreatment step) In the pretreatment step, a pretreatment agent is applied to the fabric.

The pretreatment agent is not particularly limited as long as it can impart an anionic group to the surface of the fabric. Specifically, the pretreatment agent is an anionic pretreatment agent containing a compound having an anionic group.

The compound having an anionic group is not particularly limited, and may be the same as an anionic surfactant, or may be a polymeric compound having an anionic group. Examples of polymeric compounds having an anionic group include plant skins such as pectinic acid, cellulose derivatives such as carboxymethyl cellulose, processed starches such as carboxymethyl starch and carboxyethyl starch, and synthetic glues such as acrylic polymers having acrylic acid as a copolymerization component, such as acrylic acid-acrylic acid ester copolymers and styrene-acrylic acid copolymers.

The pretreatment agent may further contain a pH adjuster, a preservative, etc., if necessary. As the preservative, the same ones mentioned as preservatives for inkjet textile inks can be used.

The method for applying the pretreatment agent to the fabric is not particularly limited, but can be, for example, a pad method, a coating method, a spray method, or an inkjet method.

The pretreatment agent applied to the fabric can also be heated and dried using hot air, a hot plate, or a heat roller.

In order to make it easier to obtain a uniform image, natural impurities (such as fats and oils, waxes, pectins, and natural pigments) adhering to the fabric fibers, residues of chemicals used in the fabric manufacturing process (such as glues), and dirt adhering to the fabric may be washed away before applying the pretreatment agent to the fabric.

As described above, images obtained using the ink (pigment-based ink) of the present invention have excellent fixability to fabrics. Therefore, it is possible to eliminate the coloring process, washing process, etc. that are required with conventional dye-based inks. Furthermore, since at least the surface of the fabric has an anionic group, an image-formed product with excellent washing fastness and friction fastness can be obtained.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

1. Ink components (1) Pigment Pigment Red 122 (PR122)

(2) Cationic dispersant Dispersant 1: Butyl acrylate/dimethylaminoethyl methacrylate copolymer (cationic dispersant, weight average molecular weight 16000, cationic group equivalent weight 4.4 meq/g)
Dispersant 2: Dimethylaminoethyl methacrylate polymer (cationic dispersant, weight average molecular weight 12000, cationic group equivalent weight 6.4 meq/g)
Dispersant 3: Acrylamide/2-(acryloyloxy)methyltrimethylammonium chloride polymer (cationic dispersant, weight average molecular weight 11000, cationic group equivalent weight 2.3 meq/g)
Dispersant 4: Polyethyleneimine (cationic dispersant, weight average molecular weight 2400, cationic group equivalent weight 23.2 meq/g)
Dispersant 5: Dimethyldiallylammonium chloride/acrylamide copolymer (cationic dispersant, weight average molecular weight 40,000, cationic group equivalent weight 5.3 meq/g)
Dispersant 6: Styrene/acrylic copolymer (anionic dispersant, weight average molecular weight 16,000)

The weight average molecular weight of the cationic dispersant (cationic polymer) was measured using gel permeation chromatography in styrene equivalent.

(3) Weak acid or anionic surfactant Acetic acid (molecular weight 60)
Succinic acid (molecular weight 118.09)
Sodium lauryl sulfate (SDS) (molecular weight 288.38)
Sulfodioctylsuccinate Na salt (2-Sulfodioctylsuccinate Na salt, molecular weight 445)
Polyoxyethylene (n=2) sodium lauryl ether sulfate (molecular weight 376)
Naphthalene sulfonic acid formalin condensate (molecular weight 3000)

(4) Solvent: Ethylene glycol (boiling point 197.6°C)
Propylene glycol (boiling point 188.2°C)
Glycerin (boiling point 290°C)
Triethylene glycol monomethyl ether (boiling point 245°C)

2. Preparation of ink <Preparation of pigment dispersions 1 to 10>
Pigments, dispersants, and ion-exchanged water were mixed and stirred to have the compositions shown in Table 1 (unit: mass %) to obtain pigment dispersions 1 to 10.

Table 1 shows the compositions of the pigment dispersions 1 to 10 obtained.

<Preparation of inks 1 to 24>
Next, the pigment dispersion, anionic surfactant, solvent, and ion-exchanged water were mixed and stirred to obtain the compositions shown in Table 2 to obtain Inks 1 to 24.

<Evaluation>
The dispersed particle size of the pigment, the viscosity and pH of the ink in the resulting inks 1 to 24 were measured by the following methods. The amount of cationic groups and the amount of anionic groups contained in the ink were calculated from the charged amounts.

(Pigment Dispersion Particle Size)
The dispersed particle size (Z average) of the pigment in the ink was measured using a Melvern Zataizer Nano S90.

(viscosity)
The viscosity of the ink was measured at 25° C. and 20 rpm using an E-type viscometer TV-33 (manufactured by Toki Sangyo Co., Ltd.).

(pH)
The pH of the ink was measured at 25°C in accordance with JIS Z 8802:2011.

The compositions and physical properties of inks 1 to 16 are shown in Table 2, and the compositions and physical properties of inks 17 to 24 are shown in Table 3.

3. Image formation test and evaluation <Preparation of fabrics A to C>
The following fabrics were prepared as fabrics A to C.
Fabric A: Cotton fabric Fabric B: Polyester fabric Fabric C: Acrylic fabric

<Preparation of fabrics D and E>
Pretreatment agent 1 having the following composition was prepared.
(Pretreatment agent 1)
Styrene/acrylic acid copolymer (anionic pretreatment agent): 3 parts by mass Water: 97 parts by mass Then, after soaking cotton cloth and polyester cloth in the above pretreatment agent 1, squeezing and drying the cloth D and E was obtained.

<Preparation of fabric F>
Pretreatment agent 2 having the following composition was prepared.
(Pretreatment agent 2)
Poly(dimethyldiallylammonium chloride): 3 parts by mass Water: 97 parts by mass

Then, fabric F was obtained by pretreating fabric D and fabric E in the same manner and under the same conditions, except that cotton fabric was used as the fabric and pretreatment agent 2 was used as the pretreatment agent.

<Tests 1-29>
First, an inkjet head (Konica Minolta head #204) was prepared as an image forming apparatus. Then, the inks shown in Table 4 or 5 were ejected from the nozzles of the inkjet head of the image forming apparatus to form an image on a fabric. Specifically, the image was formed in the following manner.

(Ink application process)
The obtained ink was set in an image forming apparatus. A solid image was formed on the above-mentioned fabric using the obtained ink at 540 dpi in the main scanning direction and 720 dpi in the sub-scanning direction. Note that dpi refers to the number of ink droplets (dots) per 2.54 cm. The ejection frequency was 22.4 kHz.

(drying process)
The fabric to which the ink was applied was dried at 160° C. for 3 minutes in a belt conveyance dryer.

<Evaluation>
The image-formed products obtained in Tests 1 to 29 were evaluated for ease of stain removal, texture, washing fastness and friction fastness by the following methods.

(Output stability)
The resulting image-formed product was visually observed, and the output stability was evaluated based on the following criteria.
○: The image is not blurred and looks uniform. △: The image is partly faded. ×: There are many blurs in the image. If it is △ or above, it is considered to be within the acceptable range.

(Easy to remove dirt)
Approximately 1 mL of soy sauce was poured onto the obtained image formed product, and then dried to prepare a stained image formed product. The image-formed product was washed with cold water for 30 minutes using a fully automatic washing machine NA-F800P manufactured by National Corporation, and the ease with which stains were removed was evaluated. The evaluation was visually evaluated based on the following criteria.
○: Soy sauce stains are completely removed △: Some soy sauce stains remain ×: Quite a lot of soy sauce stains remain If △ or more, it was considered as an acceptable range.

(texture)
The texture of the obtained image-formed product and fabric was sensually evaluated by touching with fingers. Evaluation was performed based on the following criteria.
○: The original softness of the fabric has been maintained △: The original softness of the fabric has been lost and it has become a little stiff, but the texture of the fabric has not been impaired. The texture is impaired.If it is △ or above, it is considered as an acceptable range.

(Washing fastness)
The washing fastness of the obtained image-formed product was evaluated using a fully automatic washing machine NA-F800P manufactured by National Corporation based on JIS L-0844 A-2 (revised in 2011).
A larger value indicates better washing fastness. A value of 3 or more is considered to be within the acceptable range.

(Rubbing fastness)
The dry abrasion fastness of the resulting imaged product was evaluated based on JIS L-0849 Type II (revised in 2013).
The larger the value, the better the friction fastness. If it is 3 or more, it is considered as an acceptable range.

The evaluation results of tests 1-16 are shown in Table 4; the evaluation results of tests 17-29 are shown in Table 5.

As shown in Tables 4 and 5, in tests 1 to 11 and 13 to 28 using inks containing cationic dispersants (other than ink 12), it is possible to obtain image-formed products that have good wash fastness and friction fastness, as well as good fixability, without impairing the texture of the fabric. It is also clear that the resulting image-formed products have good stain removal properties.

On the other hand, it can be seen that in Tests 12 and 29 using Ink 12 containing an anionic dispersant, stain removal from the resulting image formations was difficult. Further, in Test 12, it can be seen that the resulting image had insufficient fixing properties and poor washing fastness and abrasion fastness.

According to the present invention, it is possible to provide an image forming method and inkjet textile printing ink that can form an image on a fabric that is easy to remove dirt and has good fixation properties. Furthermore, it is possible to provide an image forming method and inkjet textile printing ink that can form an image on a fabric that has good washing fastness and friction fastness without damaging the texture of the fabric.

Claims (15)

A step of applying droplets of ink containing a pigment, a cationic dispersant, a fatty acid having 2 to 24 carbon atoms or a salt thereof or an anionic surfactant, and a solvent onto a fabric using an inkjet method,
The cationic dispersant includes a (co)polymer of an ethylenically unsaturated monomer having a cationic group,
At least the surface of the fabric to which droplets of the ink are applied has an anionic group;
Image forming method. The fabric is cotton or polyester having anionic groups.
The image forming method according to claim 1 . The weight average molecular weight of the (co)polymer of the ethylenically unsaturated monomer having a cationic group is 5,000 to 30,000.
The image forming method according to claim 1 or 2 . The total amount of the fatty acid having 2 to 24 carbon atoms or its salt and the anionic surfactant is 25 to 85 mol% based on the amount of the cationic group derived from the cationic dispersant in the ink.
The image forming method according to any one of claims 1 to 3 . The ink further includes a high boiling point solvent selected from the group consisting of polyols and polyalkylene oxides and having a boiling point of 200° C. or higher,
The content of the high boiling point solvent is 2 to 10 times that of the pigment,
The image forming method according to any one of claims 1 to 4 . The ink has a pH of 4 to 9 at 25° C.
The image forming method according to any one of claims 1 to 5 . the cationic dispersant is adsorbed on the surface of the pigment particles;
The average particle size of the pigment particles to which the cationic dispersant is adsorbed is 100 to 350 nm.
The image forming method according to any one of claims 1 to 6 . The viscosity of the ink at 25° C. is 3 to 20 mPa·s.
The image forming method according to any one of claims 1 to 7 . The pigment concentration is 1.5 to 15% by mass.
The image forming method according to any one of claims 1 to 8 . Contains a pigment, a cationic dispersant, a fatty acid having 2 to 24 carbon atoms or a salt thereof or an anionic surfactant, and water as a solvent,
The anionic surfactant is one or more selected from the group consisting of alkyl sulfates, alkyl sulfates, dialkyl sulfosuccinates, and polyoxyethylene alkyl sulfates.
Water-based inkjet printing ink. the total amount of the fatty acid having 2 to 24 carbon atoms or a salt thereof and the anionic surfactant is 25 to 85 mol % based on the amount of the cationic group derived from the cationic dispersant in the aqueous inkjet textile printing ink;
The water-based ink-jet printing ink according to claim 10 . The cationic dispersant is a cationic polymer.
The water-based inkjet textile printing ink according to claim 10 or 11 . The weight average molecular weight of the cationic polymer is 5,000 to 30,000.
The water-based inkjet textile ink according to claim 12 . The pH at 25°C measured according to JIS Z8802:2011 is 4 to 9.
The water-based inkjet textile printing ink according to any one of claims 10 to 13 . The ink contains a pigment, a cationic dispersant, a fatty acid having 2 to 24 carbon atoms or a salt thereof, or an anionic surfactant, and water as a solvent;
The molecular weight of the anionic surfactant is 100 to 500.
Water-based inkjet textile printing ink.