JPWO2014017082A1 - Inkjet printing ink set - Google Patents

Abstract

In an inkjet printing ink set of dark ink and light ink containing a reactive dye having a vinyl sulfone group and a buffer having pKa in the acidic region, the pH of the dark ink is the buffer of the buffer contained in the dark ink. pKa-1.5 or more and pKa + 1.5 or less, and the pH of the light-colored ink is within the range of pKa-1.5 or more and pKa + 1.5 or less of the buffer contained in the light-colored ink. An inkjet textile printing ink set satisfying (1) and (2). Such an ink set is excellent in ink storage stability and can suppress a decrease in the color density of the image even if time elapses from the color development step. Formula (1): pH of dark ink-pH of light color ≧ 0.5 Formula (2): Reactive dye content of light color ink / Reactive dye content of dark ink ≧ 0.1

Description

  The present invention relates to an ink jet textile ink set.

  Currently, the mainstream printing methods are screen printing and roller printing. On the other hand, as a method for producing a small amount of various products, an ink-jet printing system (ink-jet printing method) is becoming widespread. The ink jet textile printing method is a method in which minute droplets of ink are ejected from an ink jet recording head and landed on a recording medium to be printed. The inkjet textile printing method has a relatively simple mechanism, is inexpensive, and can form high-definition and high-quality images.

  Ink-jet textile printing methods generally include a pretreatment step for imparting a resin component or an alkali component to a fabric, an ink application step for ejecting textile printing ink to land on the fabric, and fixing the dye in the landed ink by heat treatment or the like. -It includes a coloring step for coloring, and a washing step for removing excess printing ink and pretreatment agent components in the fabric. Unlike the conventional roller textile printing, the ink jet textile printing method does not require the production of a plate. In addition, an image rich in gradation can be formed. Furthermore, the amount of ink used in the ink jet textile printing method is only the amount necessary for image formation. Therefore, the inkjet textile printing method is an excellent image forming method with less waste liquid as compared with the conventional method.

  Examples of the color material used in the inkjet textile printing ink mainly include acid dyes, disperse dyes, reactive dyes, and pigments. A reactive dye is used for image formation on a fabric mainly composed of cellulose. The reactive dyes are roughly classified into two types, a vinyl sulfone type having high reactivity and a monochlorotriazine type having high image fastness.

  Vinyl sulfone type reactive dyes are often used in conventional screen printing and the like. However, when a highly reactive vinyl sulfone reactive dye is contained in an ink jet printing ink and stored for a long period of time, the storage stability of the ink tends to decrease. This is because the vinyl sulfone type reactive dye in the ink reacts with water or glycol.

  In order to solve this problem, it has been studied to increase the storage stability of the ink by adding a buffer to the ink jet textile ink (see Patent Documents 1 and 2).

Special table 2003-521572 gazette JP-A-6-271801

  However, Patent Documents 1 and 2 do not discuss the reduction in the color density of an image that occurs over time after the color development step. The decrease in the color density of the image after the color development step is caused by the alkali component remaining on the fabric after the image formation. As compared with the monochlorotriazine type reactive dye, the bond between the fabric and the reactive dye is not stable in the vinyl sulfone type reactive dye. For this reason, the bond between the fabric and the vinyl sulfone type reactive dye is likely to be decomposed by the alkaline component remaining in the fabric after the coloring step until the washing step. That is, the color density of the image tends to decrease with time.

  This problem is likely to occur particularly in an image formed using a light color ink of an ink jet textile printing ink set composed of a dark color ink and a light color ink containing a vinyl sulfone type reactive dye. That is, it is likely to occur in a light color image. The light color ink has a smaller content of vinyl sulfone type reactive dye than the dark color ink, so that the acid component generated by hydrolysis of the vinyl sulfone type reactive dye is also small. For this reason, the light-colored image is difficult to consume (neutralize) the alkali component applied to the fabric.

  Furthermore, when a polyfunctional vinyl sulfone reactive dye is used for the dark ink, it is necessary to pre-treat a lot of alkali components on the fabric in order to react the fabric with the vinyl sulfone reactive dye. When an image is formed on such a fabric using only light-colored ink, most of the pretreated alkali components are not consumed and remain on the fabric. Then, when an image formed using only light-colored ink is exposed to many alkali components remaining on the fabric, the color density decreases with time.

  The present invention has been made in view of the above circumstances, has excellent ink storage stability, and suppresses a decrease in color density of an image even if a long time elapses from the color development step to the washing step. An object of the present invention is to provide an ink jet textile printing ink set.

  As a result of intensive studies, the present inventor formed an image using light color ink by setting the pH of the light color ink lower than the pH of the dark color ink in the ink set including the dark color ink and the light color ink. Later, it was found that the alkaline component remaining on the fabric was consumed. As a result, the alkali component does not remain excessively on the fabric, and even when time elapses from the color development step to the washing step, it is possible to suppress a decrease in color density of the image formed with the light color ink. I found it.

The above object of the present invention is achieved by the following configurations.
[1] In an inkjet printing ink set of a dark color ink and a light color ink containing a reactive dye having a vinyl sulfone group and a buffer having a pKa in the acidic range,
The pH of the dark color ink is in the range of pKa−1.5 or more and pKa + 1.5 or less of the buffer contained in the dark color ink, and the pH of the light color ink is the buffer contained in the light color ink. Within the range of pKa-1.5 to pKa + 1.5 of the agent,
An inkjet textile printing ink set that satisfies the following formulas (1) and (2).
Formula (1): pH of dark ink-pH of light ink ≧ 0.5
Formula (2): Reactive dye content of light color ink / Reactive dye content of dark color ink ≧ 0.1
[2] The pH of the dark ink is more than pKa of the buffer contained in the dark ink, and is not more than pKa + 1.5, and
The inkjet textile ink set according to [1], wherein the pH of the light color ink is pKa-1.5 or more and less than pKa of the buffer contained in the light color ink.
[3] The molar amount of the buffer contained in the light color ink is 1 to 25 times the molar amount of the buffer contained in the dark ink. [1] or [2 ] Inkjet textile printing ink set.
[4] The inkjet printing ink set according to any one of [1] to [3], wherein the reactive dye is bifunctional.
[5] The inkjet printing ink set according to [4], wherein the reactive dye has two vinyl sulfone groups in one molecule.
[6] The reactive dye is C.I. I. The ink-jet textile ink set according to [5], wherein the ink is reactive black 5.

  According to the ink jet textile ink set of the present invention, the storage stability of the ink is excellent, and a decrease in the color density of the textile image can be suppressed even after a lapse of time from the color development process.

It is the partial schematic which shows an example of a structure of an inkjet textile printing apparatus.

1. Inkjet Textile Ink Set The inkjet textile ink set of the present invention is a set of dark color ink and light color ink. Each of the dark color ink and the light color ink contains a reactive dye having a vinyl sulfone group and a buffer having pKa in the acidic range. Each ink of the dark color ink and the light color ink may further contain a water-soluble organic solvent, other additives, and the like as necessary.

<Each component contained in inkjet textile printing ink set>
(Reactive dye)
The reactive dye used in the present invention is a reactive dye having a vinyl sulfone group (hereinafter also referred to as “vinyl sulfone-type reactive dye”). A vinyl sulfone type reactive dye has higher dyeing properties than a reactive dye having a monochlorotriazine group (hereinafter also referred to as “monochlorotriazine type reactive dye”).

The vinyl sulfone type reactive dye has an equilibrium relationship between the following general formula (1) and the structure of the following general formula (1 ′).
D—SO ₂ —CH ₂ CH ₂ —O—SO ₃ Na (1) ⇔ D—SO ₂ CH═CH ₂ + HO—SO ₃ Na (1 ′)
[Wherein D represents a pigment matrix]

  In the vinyl sulfone type reactive dye, the vinyl group of the vinyl sulfone type reactive dye undergoes a nucleophilic addition reaction to the hydroxyl group of the fabric and reacts with the fabric.

  The reactive dye used in the present invention has one or more vinyl sulfone groups. The reactive dye may have two functional groups that react with the fabric from the viewpoint of enhancing the dyeability to the fabric, but one or more of the two or more functional groups may be vinyl sulfone groups. . The bifunctional reactive dye having two reactive functional groups includes a reactive dye having two vinyl sulfone groups in one molecule (hereinafter, also referred to as “vinyl sulfone type homobifunctional reactive dye”) and one molecule. A reactive dye having one vinyl sulfone group and one monochlorotriazine group (hereinafter, also referred to as “heterobifunctional reactive dye”). The reactive dye having a vinyl sulfone group used in the present invention is preferably a vinyl sulfone type homobifunctional reactive dye from the viewpoint of further improving the dyeability on the fabric.

  When a heterobifunctional reactive dye is used as the reactive dye, the reaction between the reactive dye and the fabric can cause not only the above nucleophilic addition reaction but also a nucleophilic substitution reaction. This is caused by nucleophilic substitution reaction of the chloro group of the monochloro-substituted 1,3,5-triazin-2-yl skeleton possessed by the heterobifunctional reactive dye with the hydroxyl group of the fabric.

  Examples of reactive dyes having a vinyl sulfone group include C.I. I. Reactive Yellow 15, C.I. I. Reactive Yellow 37, C.I. I. Reactive yellow 42; I. Reactive Orange 16, C.I. I. Reactive Orange 74, C.I. I. Reactive Orange 107; C.I. I. Reactive Red 23, C.I. I. Reactive Red 35, C.I. I. Reactive Red 106, C.I. I. Reactive Red 180; C.I. I. Reactive Violet 5, C.I. I. Reactive Blue 19, C.I. I. Reactive Blue 21, C.I. I. Reactive Blue 38, C.I. I. Reactive blue 229; I. Reactive brown 18; C.I. I. Reactive Black 5, C.I. I. Reactive Black 14, C.I. I. Reactive black 31 and the like are included. Among these, C.I. is a vinyl sulfone type homobifunctional reactive dye. I. Reactive black 5 is preferred.

(Buffering agent)
A buffering agent is a compound having a property (buffering action) that does not greatly change the pH of the solution even when an acid or a base is added from the outside to the solution containing the buffering agent. The pH of the buffer can be selected depending on the type of compound.

In general, a buffering agent tends to exhibit a strong buffering action within a range of pKa ± 1.5. In addition, pKa is a logarithmic value of the acid dissociation constant (Ka) in the following acid dissociation reaction, and is a numerical value represented by pKa = −log ₁₀ Ka.
HA ⇔ [H ⁺ ] [A ⁻ ]
Ka = [H ⁺ ] [A ⁻ ] / [HA]
[Wherein H ⁺ represents a proton, A ⁻ represents a conjugate base, and HA represents an acid.]

  The buffer used in the present invention has pKa in the acidic range. Specifically, it is a buffer having a pKa at pH 6.5 or lower. When the buffer has a plurality of pKa, any pKa may be in the acidic range. Examples of the buffer having pKa in the acidic region include citric acid (3.1, 4.8, 6.4), oxalic acid (3.8), malonic acid (5.3), and succinic acid (4. 0, 5.2), glutaric acid (4.1, 5.0), maleic acid (5.8), lactic acid (3.9), malic acid (3.5, 5.1), tartaric acid (3. 0, 4.4), diglycolic acid (2.8, 3.9), pyridine-2-carboxylic acid (5.4), EDTA (2.7, 6.2) and the like. The values in parentheses are pKa values.

  By including a buffer in the ink, even when some acid or base is added to the ink, or even when the concentration of the ink composition changes due to evaporation or dilution of the ink, fluctuations in the pH of the ink can be suppressed. The pH value of the ink can be adjusted to some extent depending on the type of buffering agent or the content of the buffering agent.

(Water-soluble organic solvent)
Each of the dark color ink and the light color ink may contain a water-soluble organic solvent. The water-soluble organic solvent is not particularly limited as long as it can dissolve the reactive dye and the buffer.
Examples of water-soluble organic solvents that may be used in the present invention include
Alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol);
Polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol);
Amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyl Diethylenetriamine, tetramethylpropylenediamine);
Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.);
Heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.);
Sulfoxides (for example, dimethyl sulfoxide) and the like are included.

(Other additives)
The dark color ink and the light color ink may further contain other additives such as a urea compound, a surfactant, an antiseptic, an antifungal agent, and a pH adjuster.

[Urea compound]
The urea compound that may be used in the present invention may be urea, thiourea, alkyl-substituted urea, alkylthioureas and the like. More specific examples include urea, ethylene urea, dimethyl urea, monomethyl thiourea, thiourea, dimethyl thiourea, and the like, and ethylene urea is preferred from the viewpoint of ink storage stability. The urea compound enhances the dyeing property of the reactive dye to the fabric.

[Surfactant]
Examples of surfactants that may be used in the present invention include dialkyl sulfosuccinates, alkyl naphthalene sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene poly Oxypropylene block copolymers, alkylamine salts, quaternary ammonium salts, silicon surfactants, fluorine surfactants and the like are included. Among these, acetylene glycol surfactants have relatively low foaming properties and can adjust the surface tension of the ink. For this reason, the ink ejectability from the ink jet recording head is enhanced.

[Preservatives, antifungal agents]
Examples of preservatives and antifungal agents that may be used in the present invention include aromatic halogen compounds (for example, Preventol CMK), methylene dithiocyanate, halogen-containing nitrogen-sulfur compounds, 1,2-benzisothiazolin-3-one. (For example, PROXEL GXL) and the like are included. Preservatives and antifungal agents increase the storage stability of the ink.

[PH adjuster]
An example of a pH adjuster that may be used in the present invention may be sodium hydroxide. By including the pH adjusting agent, the pH of the dark ink can be adjusted to a desired value.

<About dark ink and light ink>
(Dark ink composition)
The content of the vinyl sulfone reactive dye in the dark ink in the ink jet textile ink set is preferably 5 to 30% by mass, more preferably 15 to 25% by mass with respect to the total amount of the dark ink. If the content of the vinyl sulfone reactive dye in the dark ink is excessive, the ink viscosity increases, and the ink ejectability from the ink jet recording head tends to decrease.

  The content of the buffer having pKa in the acidic region of the dark ink is preferably 0.05 to 2% by mass with respect to the total amount of the dark ink. If the content of the buffering agent is too small, the buffering action of the buffering agent contained in the dark ink is weak and it is difficult to make the pH of the dark ink constant. For this reason, during storage of the dark ink, the acid component generated from the vinylsulfone reactive dye may lower the pH of the dark ink and cause solids to precipitate in the dark ink. On the other hand, if the content of the buffering agent is excessive, the buffering agent may precipitate in the dark ink and clog the nozzles of the ink jet recording head.

  The content of the water-soluble organic solvent is preferably 5 to 50% by mass with respect to the total amount of dark ink. By setting the content of the water-soluble organic solvent within the above range, nozzle clogging caused by drying of the ink attached to the nozzle surface of the inkjet recording head can be suppressed.

  As other additives, the urea compound content is preferably 0.1 to 10% by mass based on the total amount of the dark ink; the surfactant content is 30 to 30% of the surface tension of the dark ink. It is preferable to adjust so that it may be set to 60 mN / m, and specifically, it is preferable that it is 0.0001-5 mass% with respect to the dark color ink whole quantity.

(Light ink composition)
The content of the vinyl sulfone reactive dye in the light-colored ink in the inkjet textile printing ink set satisfies the ratio: “0.1 ≦ the content of the reactive dye in the light-colored ink / the content of the reactive dye in the dark-colored ink ≦ 0.5”. .

  If the ratio is too small, that is, the reactive dye content of the light-colored ink is too small compared to the dark-colored ink, the alkali imparted to the fabric is sufficient even if the pH of the light-colored ink is lower than the pH of the dark-colored ink. Cannot be consumed (neutralized). This is because the light-colored ink has a low content of vinyl sulfone type reactive dye, and therefore, there are few acid components generated from the reactive dye. Therefore, the amount of alkali remaining on the fabric increases, and the bond between the fabric and the vinylsulfone reactive dye is easily decomposed. Then, the color density of the image formed using the light color ink is lowered with time.

  The content of the buffer having pKa in the acidic region of the light color ink is preferably 0.1 to 5% by mass with respect to the total amount of the light color ink. In particular, the molar amount of the buffer having pKa in the acidic region contained in the light ink is preferably 1 to 25 times the molar amount of the buffer having pKa in the acidic region contained in the dark ink. More preferably, it is 1 to 10 times. Thereby, when the content of the reactive dye contained in each ink of the dark color ink and the light color ink is a desired amount, even when the image is formed using the light color ink, the alkali applied to the fabric Ingredients can be consumed. By reducing the alkali component remaining on the cloth, the bond between the cloth and the vinyl sulfone type reactive dye becomes difficult to be decomposed, and it is possible to suppress a decrease in the color density of the image that occurs over time. Note that the buffer having pKa in the acidic region contained in the light color ink may be the same as or different from that contained in the dark color ink.

  The light color ink may further contain a water-soluble organic solvent and other additives as in the case of the dark color ink.

(Physical properties of dark ink and light ink)
The pH of the dark color ink and the pH of the light color ink in the inkjet textile printing ink set of the present invention satisfy the formula “pH of dark color−pH of light color ≧ 0.5”, and “pH of dark color ink−pH of light color ink” It is preferable to satisfy “pH ≧ 1.0”, and it is more preferable to satisfy “pH of dark ink−pH of light ink ≧ 2.0”.

  The reason why the above formula is satisfied is as follows. The light-colored ink contains less vinyl sulfone reactive dye than the dark-colored ink. Therefore, when an image is formed with light-colored ink, the alkali component imparted to the fabric in the pretreatment process is hardly consumed. Therefore, the bond between the fabric and the vinyl sulfone type reactive dye is likely to be decomposed. Therefore, by making the pH of the light color ink lower than the pH of the dark color ink, it is easy to consume the alkali component applied to the fabric in the pretreatment process even when the image is formed using the light color ink. Therefore, it is possible to suppress a decrease in the color density of the image that occurs over time. Furthermore, when the polyfunctional reactive dye is included in the ink, even if a large amount of alkali component is added to the fabric in the pretreatment step, the color density of the image formed using the light color ink can be prevented from decreasing over time. . In order to satisfy the above formula, the amount of the buffering agent or the pH adjusting agent contained in each of the dark color ink and the light color ink may be appropriately adjusted.

  Further, the pH of the dark ink is pKa−1.5 or more and pKa + 1.5 or less of the buffer contained in the dark ink, and the pH of the light ink is pKa−1 of the buffer contained in the light ink. .5 or more and pKa + 1.5 or less. By adjusting the pH of each ink within a range in which the buffer has a strong buffering effect, the pH of each ink can be hardly changed. Thereby, it can suppress that the storage stability of an ink falls by the acid component produced from a vinyl sulfone type reactive dye. That is, it is effective for enhancing the storage stability of dark ink containing a large amount of vinyl sulfone type reactive dye.

  In particular, the pH of the dark ink is preferably more than pKa and not more than pKa + 1.5 with respect to the pKa of the buffer contained in the dark ink. When the pH of the dark color ink is within the above range, the buffering agent contained in the dark color ink has a higher conjugated base ratio than the acid. That is, the acid component generated from the vinyl sulfone type reactive dye is likely to be consumed.

  Furthermore, the pH of the light color ink is preferably pKa-1.5 or more and less than pKa with respect to the pKa of the buffer contained in the light color ink. Specifically, the pH of the light color ink is preferably less than 6.4, and more preferably less than 6.0. When the pH of the light-colored ink is within the above range, the buffer contained in the light-colored ink has a higher acid ratio than the conjugate base. That is, the light color ink tends to consume the alkali component remaining on the fabric.

  The dark color ink and the light color ink of the inkjet textile printing ink set of the present invention preferably have an ink viscosity at 25 ° C. of 1 to 40 mPa · s, and preferably 5 to 40 mPa · s from the viewpoint of ejection from the inkjet recording head. More preferably, it is more preferably 5 to 20 mPa · s.

  The surface tension of the ink at 25 ° C. is preferably 30 to 60 mN / m for both the dark color ink and the light color ink. When the surface tension is less than 30 mN / m, the wettability of the ink with respect to the fabric is too high, so that the image tends to bleed. On the other hand, when the surface tension is more than 60 mN / m, the wettability of the ink with respect to the fabric is lowered, and the penetrating power of the ink is likely to be lowered.

<Preparation of dark ink and light ink>
Each of the dark color ink and the light color ink of the inkjet textile printing ink set of the present invention is manufactured through a step of mixing a vinyl sulfone type reactive dye, a buffering agent, and, if necessary, other components.

2. Inkjet printing apparatus and inkjet printing method using the same <Inkjet printing method>
The inkjet printing method using the inkjet printing ink set of the present invention includes (1) a step of applying a pretreatment agent to a fabric (pretreatment step), and (2) a droplet of printing ink on the fabric provided with the pretreatment agent. And (3) a step of fixing the dye landed on the fabric to the fiber (coloring step), and (4) drying the fabric after applying the ink. A step (preliminary drying step), (5) a step of removing dyes and pretreatment agents that could not be dyed on the fabric (washing step), (6) a step of drying the washed fabric (drying step), May further be included.

(Pretreatment process)
The pretreatment step is a step of applying a pretreatment agent to the fabric. Examples of the method for applying the pretreatment agent to the fabric include a pad method, a coating method, a spray method, or an ink jet method. By these methods, the pretreatment agent can be applied onto the fabric. Examples of the fabric provided with the pretreatment agent include fabrics having an ink receiving layer described in JP-A No. 62-53492, or an anti-reduction agent and an alkali agent described in JP-B-3-46589. Included fabrics and the like are included.

  From the viewpoint of obtaining a uniform image, before applying the pretreatment agent to the fabric, natural impurities (oils, waxes, pectic substances, natural pigments, etc.) adhering to the fabric fibers and residues of the chemicals used in the fabric manufacturing process (paste) Agent) or dirt attached to the cloth is preferably washed. The cleaning agent for cleaning the fabric includes an alkali agent such as sodium hydroxide or sodium carbonate, an anionic or nonionic surfactant, or an enzyme.

  The pretreatment agent preferably contains at least a resin component, an alkaline agent, and a hydrotropic agent, and may further contain additives such as a reduction inhibitor, an antiseptic, or a chelating agent.

  Examples of resin components include natural gums such as guar and locust bean, starches, seaweeds such as sodium alginate, funari, plant skins such as pectic acid, methyl fibrin, ethyl fibrin, hydroxyethylcellulose, carboxymethylcellulose, etc. Fibrin derivatives, roasted starch, alpha starch, carboxymethyl starch, carboxyethyl starch, hydroxyethyl starch, etc. Synthetic pastes such as acrylic esters, emulsions, and the like are included.

  Examples of alkaline agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, amines such as mono, di, and triethanolamine, and carbonates such as sodium carbonate, potassium carbonate, and sodium bicarbonate (sodium bicarbonate). Alternatively, alkali metal bicarbonate salts, organic acid metal salts such as calcium acetate and barium acetate, ammonia and ammonia compounds, and sodium trichloroacetate that becomes an alkali agent under steaming or dry heat are included. Among these, sodium carbonate and sodium hydrogen carbonate are preferable. The amount of the alkaline agent applied is preferably 0.1 to 10% by mass and more preferably 0.5 to 5% by mass with respect to the fabric. The presence of an appropriate alkaline agent in the fabric allows the printing ink containing the reactive dye to be reliably dyed. Therefore, it is preferable that the fabric contains an alkali agent in advance.

  Examples of the hydrotropic agent include urea, ethyleneurea, dimethylurea, thiourea, monomethylthiourea, alkylurea such as dimethylthiourea, and the like. This is because the image density is improved by the addition of the hydrotropic agent.

  The application amount (squeezing rate) of the pretreatment agent or the amount of the resin component contained in the pretreatment agent is appropriately set according to the type of fabric and its use.

  The pretreatment agent may further contain a reduction inhibitor, a preservative, or a chelating agent as necessary. The reduction inhibitor may be sodium m-nitrobenzenesulfonate or the like. The preservative may be the preservative exemplified as the preservative for printing ink, or may be the same. The chelating agent may be ethylenediaminetetraacetate, nitrilotriacetate, hexametaphosphate, pyrophosphate, or metaphosphate.

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

  The fiber material constituting the fabric is not particularly limited as long as it contains fibers that can be dyed with reactive dyes, but is preferably cellulose fibers such as cotton or protein fibers such as silk. The fabric may be any one of these fibers such as woven fabric, knitted fabric, and non-woven fabric. The fabric that can be used in the present invention is preferably composed only of fibers that can be dyed with reactive dyes, but may be a blended woven fabric or a blended nonwoven fabric with rayon, polyurethane, polyester, or acrylic. Good. Moreover, it is preferable that the thickness of the fiber which comprises a fabric exists in the range of 10-100d.

(Ink application process)
The ink application process is a process of forming an image before color development by ejecting ink droplets of an inkjet textile printing ink set from an inkjet recording head toward a fabric. While moving the cloth relative to a head carriage on which a plurality of ink jet recording heads are mounted, ink droplets of the ink jet textile ink set are discharged and landed on the cloth. Note that the ink droplets of dark ink and light ink may be ejected separately or simultaneously. The surface temperature of the fabric when the ink droplets are landed is not particularly limited, but is preferably heated in the range of 35 to 70 ° C. from the viewpoint of suppressing bleeding of the pre-colored image.

(Preliminary drying process)
The preliminary drying step is a step of drying the fabric after ink application. Although not particularly limited, the preliminary drying is preferably performed by drying the fabric at 150 ° C. or lower for 0.5 to 30 minutes. Examples of the drying method include an air convection method, a heating roll direct attachment method, or an irradiation method. Specifically, ink may be applied to the fabric, and the fabric may be dried under the above conditions and method before the fabric is wound.

(Coloring process)
The color development step is a step in which a reactive dye that is not sufficiently dyed in the fabric after ink application is dyed in the fabric to express the original hue of the ink. The method may be a conventionally known method, and is appropriately selected depending on textile printing ink, fabric, or the like. For example, steaming by steam; baking by dry heat; thermosol; HT steamer by superheated steam; HP steamer by pressurized steam are included. When the reactive dye in the ink is fixed by high-temperature steam (such as steaming), the cellulosic fibers are preferably treated at 95 to 105 ° C. for 5 to 15 minutes; and amide fibers such as silk and wool are It is preferable to process at 95-105 degreeC for 20-40 minutes. In addition, the fabric to which the ink has been applied may be colored immediately or after a lapse of time.

(Washing process)
The washing step is a step of removing reactive dyes and pretreatment agents that could not be dyed on the fabric after the color development step of the fabric. The removal of reactive dyes that could not be dyed on the fabric can be performed by a conventionally known cleaning method, and is appropriately selected depending on the printing ink, the fabric, or the like. For example, the cellulose fiber is generally washed with water and hot water, then treated with a soaping bath containing a nonionic detergent, and then washed with hot water and water. By removing the undyed reactive dye, the fastness to washing, the fastness to water, the fastness to sweat, and the like tend to be improved. If there is a reactive dye that could not be dyed on the fabric, it is difficult to obtain fastness to washing, fastness to water, fastness to sweat, and the like.

(Drying process)
A drying process is a process performed after the said washing | cleaning process and drying the wash | cleaned fabric. Although the drying method is not particularly limited, the washed fabric is squeezed, dried, or dried using a dryer (heat roll, iron, etc.).

<Inkjet printing device>
Hereinafter, an apparatus for performing the ink application process and the preliminary drying process will be described with reference to the drawings. However, the inkjet printing apparatus is not limited thereto.

  FIG. 1 is a partial schematic diagram illustrating an example of the configuration of an inkjet textile printing apparatus. The ink jet textile printing apparatus includes a transport means 2 for transporting the cloth P, a head carriage 5 on which a plurality of ink jet recording heads (not shown) for ejecting ink droplets of an ink jet textile ink set are mounted on the cloth P, and a temperature on the cloth P. And hot air applying means 6 for applying wind.

  The transport unit 2 includes an adhesive belt 21, a support roller 22, a transport roller 23, and a nip roller 24. The adhesive belt 21 is held by the support roller 22 and the conveyance roller 23 and circulates between the support roller 22 and the conveyance roller 23. The nip roller 24 is disposed to face the conveying roller 23 with the adhesive belt 21 interposed therebetween.

  The warm air applying means 6 and the head carriage 5 are disposed above the fabric P. The warm air applying means 6 includes a fan 6A that blows wind on the fabric and a heating element 6B that can control the temperature. On the other hand, an ink jet recording head is mounted on the head carriage 5. The type of the ink jet recording head is not particularly limited, and may be either a thermal type or a piezo type. The nozzle diameter of the ink jet recording head is preferably 10 to 100 μm, and more preferably 10 to 50 μm. This is because if the nozzle diameter is less than 10 μm, nozzle clogging due to insoluble matter is likely to occur. On the other hand, when it exceeds 100 μm, the sharpness of the formed image is lowered. The ink droplet size to be ejected is preferably 4 to 150 pl, and more preferably 5 to 80 pl. This is because when the ink droplet size is less than 4 pl, the ejected ink droplets are easily affected by the airflow in the vicinity of the head. On the other hand, when it exceeds 150 pl, the granularity of the formed image is conspicuous.

  When the transport roller 23 is driven, the fabric P disposed on the upper surface of the adhesive belt 21 is transported to the lower surface of the nip roller 24. The fabric P is pressed by the adhesive belt 21 and the nip roller 24 and fixed to the adhesive belt 21. The fabric P fixed to the adhesive belt 21 is conveyed below the head carriage 5. The plurality of ink jet recording heads mounted on the head carriage 5 eject ink droplets of the ink jet textile ink set, land on a predetermined region (landing possible region) of the fabric to which the pretreatment agent is applied, and form an image. . Next, the temperature-controlled wind or warm air is blown from the warm air applying means 6 to dry the image formed on the fabric P.

  In the following, the invention will be described in more detail with reference to examples. These examples do not limit the scope of the present invention.

<Ink composition>
(Reactive dye)
C. I. Reactive Black 5 (vinyl sulfone type homobifunctional reactive dye)
C. I. Reactive Brown 9 (a heterobifunctional reactive dye having a vinyl sulfone group and a monochlorotriazine group)
C. I. Reactive Blue 222 (a heterobifunctional dye having a vinyl sulfone group and a monochlorotriazine group)
C. I. Reactive Blue 194 (a heterobifunctional reactive dye having a vinyl sulfone group and a monochlorotriazine group)
C. I. Reactive Blue 19 (Vinylsulfone type monofunctional reactive dye)
C. I. Reactive Blue 5 (monochlorotriazine type monofunctional reactive dye)
(Buffering agent)
Citric acid (pKa: 3.1, 4.8, 6.4)
Tartaric acid (pKa: 3.0, 4.4)
Lactic acid (pKa: 3.9)
Malonic acid (pKa: 5.3)
(PH adjuster)
Sodium hydroxide

<Preparation of ink set>
(Dark color ink of Example 1)
C. as a reactive dye I. 10 parts by weight of Reactive Black 5; 0.2 parts by weight of citric acid as a buffering agent; 20 parts by weight of ethylene glycol as a water-soluble organic solvent; 5 parts by weight of glycerin; did. Ion exchanged water was added to the resulting mixture so that the total amount was 100 parts by mass to prepare a dark ink. Sodium hydroxide was added in such an amount that the pH of the dark ink becomes 6.0. The pH of the ink was measured using a HM-20S type manufactured by Toa DKK Corporation.

(Light color ink of Example 1)
C. as a reactive dye I. 2 parts by mass of Reactive Black 5; 0.2 parts by mass of citric acid as a buffering agent; 20 parts by mass of ethylene glycol as a water-soluble organic solvent, 10 parts by mass of propylene glycol, 5 parts by mass of glycerin; An appropriate amount of sodium hydroxide was mixed. Ion exchanged water was added to the resulting mixture so that the total amount was 100 parts by mass to prepare a light color ink. In addition, sodium hydroxide was added in an amount such that the pH of the light color ink was 5.5.

(Preparation of ink sets of Examples 2 to 13 and Comparative Examples 1 to 7)
Examples, except that the types and addition amounts of reactive dyes and buffering agents were changed as shown in Tables 1 to 4 and the addition amount of sodium hydroxide was adjusted so that the pH of the ink was shown in Tables 1 to 4. Ink sets of Examples 2 to 13 and Comparative Examples 1 to 7 were prepared in the same manner as the ink set consisting of 1 dark color ink and light color ink.

<Inkjet printing method>
(Pretreatment process)
A 100% cotton fabric (with cotton broad sill, manufactured by Color & Color Co., Ltd.) was prepared, and the following pretreatment agent was applied at a drawing rate of 80% and then dried.
(Pretreatment agent)
Sodium alginate 5 parts by weight Urea 10 parts by weight Sodium hydrogen carbonate 5 parts by weight Ion-exchanged water 80 parts by weight

(Ink application process)
The ink sets of Examples and Comparative Examples were set on Nassenger V (manufactured by Konica Minolta IJ). Solid image 1 formed by using only dark color ink in main scanning 540 dpi × sub-scanning 540 dpi, solid image 2 in which a solid image of dark ink and a solid image of light color ink are printed in the same area, and light color ink The solid images 3 formed using only the film were formed. In addition, dpi represents the number of ink droplets (dots) per 2.54 cm.

(Coloring process)
The fabric on which the image was formed was steamed for 15 minutes under conditions of a relative humidity of 100% and a temperature of 95 ° C. to fix and develop the dye.

<Image evaluation>
(Stability evaluation after steaming)
Solid images 1 to 3 in which the fabric after the coloring process was immediately washed with a soaping agent, and solid images 1 to 3 in which the fabric after the coloring step was left to stand at 30 ° C. for 1 week and then washed with a soaping agent , Respectively. The L *, a *, and b * values of these solid images 1 to 3 were measured using a colorimeter X-Rite 938. ΔE (ΔE: difference in L *, difference in a *, difference in a *, difference in b * are added to the squares of the solid image 1 washed immediately after the coloring step and the solid image 1 washed after being left for one week, respectively. (Take the square root). Similarly to the solid image 1, ΔE was calculated for the solid image 3. The results evaluated in accordance with the following criteria are shown in Tables 1-4.
A: ΔE <2
○: 2 ≦ ΔE <3
Δ: 3 ≦ ΔE <5
×: 5 ≦ ΔE

On the other hand, in the evaluation of the solid image 2, L *, a *, and b * values were measured for the dark solid image and the light solid image included in the solid image 2, respectively. Calculate the absolute value (ΔE _diff ) of the difference between ΔE _{1 of} the dark solid image and the light solid image washed immediately after the coloring process and ΔE _{2 of} the dark solid image and the light solid image washed after standing for 1 week. did. The results evaluated in accordance with the following criteria are shown in Tables 1-4.
A: ΔE _diff <2
○: 2 ≦ ΔE _diff <3
Δ: 3 ≦ ΔE _diff <5
×: 5 ≦ ΔE _diff

(Evaluation of ink storage stability)
As an ink set used in the above-mentioned ink jet textile printing method, an ink set after one day has passed since preparation and an ink set after standing for one month from preparation were used. Using these two types of ink sets, solid images 1 and 3 were formed in the same manner as described above. The solid images 1 and 3 were all washed with a soaping agent immediately after the coloring process. Each ΔE of the solid images 1 and 3 produced using the ink set after 1 day from the preparation and the ink set after standing for 1 month from the preparation was calculated. The results evaluated in accordance with the following criteria are shown in Tables 1-4.
A: ΔE <2
○: 2 ≦ ΔE <3
Δ: 3 ≦ ΔE <5
×: 5 ≦ ΔE

  Table 1 describes an example of an ink set in which the pH of the dark ink and the pH of the light ink are adjusted. Since the ink sets of Examples 1 to 4 have ΔpH of 0.5 or more, the light color ink tends to consume the alkali component applied to the fabric. Therefore, the evaluation of “stability after steam” of the solid images 2 and 3 formed using the light color ink is good. In particular, in Examples 2 and 4 in which the ΔpH of the ink set is 1.0 or more, the evaluation of “stability after steam” of the solid images 2 and 3 is excellent.

On the other hand, since the ink sets of Comparative Examples 1 and 2 have a ΔpH of less than 0.5, the light color ink is much less likely to consume the alkali component applied to the fabric than the dark color ink. That is, ΔE ₂ between the dark solid image washed after standing for one week and the light solid image is more likely to fluctuate than ΔE ₁ between the dark solid image washed immediately after the coloring step and the light solid image. Therefore, the evaluation of “stability after steam” of the solid image 2 was low. Further, since the pH of the light-colored ink of Comparative Example 1 is high, the light-colored light-colored ink hardly consumes the alkali component applied to the fabric. For this reason, the evaluation of “stability after steam” of the solid image 3 was low.

  Table 2 shows an example in which the amount and type of reactive dye contained in the dark color ink and light color ink and the amount of buffering agent are changed. The light color ink of Example 5 contains 1.0% by mass of reactive dye. Therefore, the evaluation of “stability after steam” of the solid images 2 and 3 formed using the light color ink is good. In particular, the light-colored ink of Example 5 containing a vinylsulfone type homobifunctional reactive dye having two vinylsulfone groups in one molecule has a large amount of acid components generated from the reactive dye, and consumes an alkali component applied to the fabric. Cheap. Therefore, the evaluation of “stability after steam” of the solid image 3 formed using only light color ink is excellent.

  On the other hand, since the light color inks of the ink sets of Comparative Examples 3 and 4 have too little reactive dye content, it is difficult for the alkali component applied to the fabric to be consumed. For this reason, if the time from the color development step to the washing step is long, the bond between the fabric and the reactive dye is decomposed, and the evaluation of “stability after steam” of the solid images 2 and 3 is low. Further, the light color ink of Comparative Example 5 does not contain a buffer. It is considered that since the light color ink does not contain a buffer, the pH of the light color ink is lowered by the acid component generated from the reactive dye, and the reactive dye reacts with the component contained in the light color ink. Therefore, the amount of reactive dye that can be bonded to the fabric was small, and the evaluation of “ink storage stability” of the solid image 3 was low. Furthermore, in the ink set of Comparative Example 6, since the concentration of the reactive dye in the light-colored ink was too low relative to the concentration of the reactive dye in the dark-colored ink, the “post-steam stability” evaluation of the solid images 2 and 3 was evaluated. It was low.

  Table 3 describes an example in which the type of reactive dye contained in the dark color ink and the light color ink is changed. The reactive dye contained in the ink sets of Examples 6 to 10 is a reactive dye having a vinyl sulfone group. In particular, since the reactive dye contained in the ink set of Example 6 is a vinyl sulfone type homobifunctional reactive dye, there are many acid components generated from the reactive dye during the color development process to the washing process; Alkaline components are easily consumed. Therefore, the evaluation of “stability after steam” of the solid image 3 is superior to Examples 7 to 10 containing other reactive dyes.

  On the other hand, the reactive dye contained in the ink set of Comparative Example 7 is a monochlorotriazine type monofunctional reactive dye in which the reactive functional group is only a monochlorotriazine group. Monochlorotriazine type monofunctional reactive dyes generate less acid component than vinyl sulfone type reactive dyes. The light-colored ink containing a small amount of the reactive dye does not easily consume the alkali component applied to the fabric; the bond between the fabric and the reactive dye is likely to be decomposed. Therefore, in Comparative Example 7, the evaluation of “stability after steam” of the solid image 3 was lower than in Examples 8 to 12.

Table 4 shows an example in which the type of the buffer contained in the dark color ink and the light color ink is changed. In Examples 11 to 13, even if the types of buffering agents included in each ink set are different, the difference between the pH of the dark ink and the pH of the light ink is 0.5 or more, and the pH of the dark ink is The buffer contained in the dark ink has a pKa of -1.5 or more and pKa + 1.5 or less, and the pH of the light-colored ink contained in the light-colored ink is pKa-1.5 or more and pKa + 1.5 or less. Therefore, good results are obtained. In particular, in the ink sets of Examples 11 and 13, the pH of the dark ink is higher than the pKa of the buffer contained in the dark ink, and is less than or equal to pKa + 1.5, and the pH of the light ink is included in the light ink. PKa-1.5 or more and less than pKa. Therefore, excellent results are obtained for all evaluation items.
This application is accompanied by a priority claim based on a Japanese patent application previously filed by the same applicant, ie, Japanese Patent Application No. 2012-162532 (filing date: July 23, 2012). The contents of which are incorporated herein as part of the present invention.

  According to the present invention, it is possible to provide an ink-jet printing ink set that is excellent in ink storage stability and that can suppress a decrease in the color density of a printed image even after a lapse of time from the color forming step.

P Fabric 2 Conveying means 21 Adhesive belt 22 Support roller 23 Conveying roller 24 Nip roller 5 Head carriage 6 Warm air applying means 6A Fan 6B Heating element

Claims (6)

In an inkjet printing ink set of a dark color ink and a light color ink containing a reactive dye having a vinyl sulfone group and a buffer having a pKa in the acidic range,
The pH of the dark color ink is in the range of pKa−1.5 or more and pKa + 1.5 or less of the buffer contained in the dark color ink, and the pH of the light color ink is the buffer contained in the light color ink. Within the range of pKa-1.5 to pKa + 1.5 of the agent,
An inkjet textile printing ink set that satisfies the following formulas (1) and (2).
Formula (1): pH of dark ink-pH of light ink ≧ 0.5
Formula (2): Reactive dye content of light color ink / Reactive dye content of dark color ink ≧ 0.1 The pH of the dark color ink is greater than the pKa of the buffer contained in the dark color ink and not greater than pKa + 1.5, and
2. The inkjet textile printing ink set according to claim 1, wherein the pH of the light-colored ink is not less than pKa-1.5 and less than pKa of a buffer contained in the light-colored ink.   The inkjet according to claim 1 or 2, wherein a molar amount of the buffer contained in the light-colored ink is 1 to 25 times a molar amount of the buffer contained in the dark-colored ink. Textile ink set.   The inkjet printing ink set according to any one of claims 1 to 3, wherein the reactive dye is bifunctional.   The inkjet printing ink set according to claim 4, wherein the reactive dye has two vinyl sulfone groups in one molecule. The reactive dye is C.I. I. The inkjet textile ink set according to claim 5, wherein the ink is a reactive black 5.

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