JPH08295823A - Ink for ink jet fabric printing and printing of fabric using the same - Google Patents

Abstract

PURPOSE: To obtain an ink, having excellent color developing properties and image quality for a cellulosic fibrous structure and excellent in preservation stability and discharge stability without any problems in clogging of ink heads by selecting specific reactive dyes. CONSTITUTION: This ink comprises reactive dyes, water and, as necessary, an organic solvent. Furthermore, the ink uses an anthraquinone-based dye mixture comprising (A) 1-99wt.% anthraquinone-based dye of formula I (Q1 is a group eliminative by actions of an alkali) in the form of a free acid, (B) 0-98% anthraquinone-based dye of formula II (Q2 is a group eliminative by actions of an alkali) in the form of a free acid and (C) 1-20wt.% anthraquinone-based dye of formula III in the form of a free acid as the dyes. Furthermore, (D) a formaldehyde condensate of naphthalenesulfonic acid which may be alkylated (especially the one having one to three 1-4C alkyl groups, 50-150% degree of sulfonation and 1.1-3.0 average degree of condensation) is preferably contained in an amount of 1-100 pts.wt. based on 100 pts.wt. mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent coloring properties and image quality for fibers including natural cellulose fibers and regenerated cellulose fibers, yarns, knitted woven fabrics and non-woven fabrics (hereinafter referred to as cellulosic fiber structures). In addition, the present invention relates to an inkjet printing ink which is free from clogging of an ink head and has excellent storage stability and ejection stability, and a method of printing a cloth by an inkjet method using the ink.

[0002]

2. Description of the Related Art Generally, a screen printing method, a roller printing method, a rotary screen printing method, a transfer printing method or the like is used as a method for forming an image on fabrics. However, in recent years, there has been an increasing movement to apply and develop the inkjet recording method for fabrics, which has made remarkable progress as a paper application for these printing methods.

This is because the current printing method requires complicated and long time such as tracing for each pattern, plate making, (making a screen frame, engraving roller, transfer paper, etc.), great labor and cost, which is equivalent to that. It is impossible to keep up economically without the production of the lot size. In addition, it has been pointed out that it is unsuitable for the production of small lots and various products due to the diversification of fashion, and in response to these problems, the current process is being replaced by an inkjet recording system.

On the other hand, the ink jet recording system has a history of being developed mainly on paper as a recording material, and as a pigment component used in an ink jet print ink for paper, direct dyes, reactive dyes, food additives are still used. It is selected from pigments. The reason why reactive dyes have not been used so much in inkjet printing inks for paper is, for example, that due to problems such as chemical stability due to having a fiber reactive group, the solubility of the dye is lowered, and crystal precipitation is caused.
The ink head may be clogged.

Ink-jet printing inks used for fabrics are required to have higher dyeing density, so-called high-density dyeing, than ink-jet printing inks for paper. That is, it is not necessary for the inkjet print ink for paper to penetrate into the inside of the paper, and it suffices to form an image so that the dye covers the surface portion of the paper. Permeation occurs and the dyeing density on the surface decreases. When a reactive dye suitable for dyeing / printing on a cellulosic fiber structure is applied to an ink for inkjet printing, a part of the reactive dye is decomposed during the dyeing operation to become an unfixed dye, as with paper, so that There is a problem such as a decrease in concentration.

Up to now, an ink jet printing method using various reactive dyes has been known as an ink jet printing ink composition for dyeing a cloth. However, solution stability due to crystal precipitation in the ink, ink head clogging, Discharge performance deterioration due to viscosity increase, solving problems such as printing quality due to ink composition change, having a practically sufficient high dyeing density comparable to conventional prints, and as an inkjet printing ink having a preferable color tone, Not always enough.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a fiber structure containing a cellulosic fiber with excellent coloring properties and image quality, storage stability, ink head clogging, and other problems. It is an object of the present invention to provide an ink for inkjet printing, which has excellent ejection stability.

The inventors of the present invention have conducted intensive studies and studies to develop an ink jet printing ink suitable for the above purpose, and have found that the above problems can be solved all at once by selecting a specific reactive dye. The present invention has been completed.

[Means for Solving the Problems]

That is, the present invention provides an ink for ink-jet printing comprising a reactive dye, water and, if necessary, an organic solvent, in the form of a free acid as a reactive dye, represented by the following general formula (I):

[0010]

[Chemical-4]

[In the formula, Q ₁ represents a group capable of leaving by the action of an alkali. 1 to 99% by weight of an anthraquinone dye represented by the following general formula (II) in the form of a free acid.

[0012]

[Chemical-5]

[In the formula, Q ₂ represents a group capable of leaving by the action of an alkali. ] 0 to 98% by weight of an anthraquinone dye represented by the following general formula (III) in the form of free acid

[0014]

[Chemical-6]

An anthraquinone dye represented by
An ink for ink-jet textile printing, comprising 0% by weight of an anthraquinone dye mixture.

The ink-jet printing ink of the present invention will be described in more detail below. A feature of the present invention is that, in an ink jet printing ink comprising a reactive dye, water and, if necessary, an organic solvent, the above-mentioned general formula (I), general formula (III) and optionally general formula (II) Storage stability by selecting the anthraquinone dye mixture shown, and further mixing a formaldehyde condensate of naphthalene sulfonic acid which may be optionally alkylated, and preparing an ink using this,
Provided are ink jet printing inks having excellent discharge stability without problems such as ink head clogging, and using these inks, with a preferable color tone for a cellulosic fiber structure, excellent color developability and image quality. Give,
It is an ink-jet printing ink and a textile printing method using the same.

In the textile printing (dyeing) by ink jet in which ink droplets are sequentially deposited on a cloth, the present inventors can obtain a subtle difference in the order of driving and the dyeing conditions depending on the combination of dyes used. It has been found that the selection of the dye to be used is extremely important because it has a great influence on the finish of the printed material, and there is a problem that bleeding occurs especially when forming an image by adjoining or mixing colors.

The general formulas (I) and (I used in the present invention
In the anthraquinone dye represented by I), examples of a group represented by Q ₁ and Q ₂ that is eliminated by the action of an alkali include, for example, a sulfate ester group, a thiosulfate ester group, a phosphate ester group, an acetate ester group, a halogen atom. Are exemplified.

The anthraquinone dye used in the present invention is present in the form of a free acid or a salt thereof, and in particular,
Alkali metal salts and alkaline earth metal salts, as well as sodium salts, potassium salts and lithium salts are preferred.

The anthraquinone dye represented by the general formula (I) used in the present invention has already been described in C.I. I. Anthraquinone dyes known as Reactive Blue 19 and represented by the general formula (II) are also disclosed in JP-A-60-1084.
It is a dye known in JP-A-72.

The general formula (II) optionally used in the present invention
The anthraquinone dye represented by I) is obtained by, for example, dissolving the anthraquinone dye represented by the general formula (I) or (II) and then adding an alkali such as sodium carbonate in a dye solution kept at a temperature of 10 to 80 ° C. Agent, then 1 to 1
It is obtained after 0 minutes of neutralization and further purification by a salting out method.

Further, the optionally-alkylated formaldehyde condensate of naphthalenesulfonic acid (including its salt), which is optionally contained in the anthraquinone dye mixture of the present invention, is disclosed in JP-A Nos. 51-52435 and 56-56. -1
What is described in Japanese Patent No. 43257 is used.

The content of the formaldehyde condensate of the optionally alkylated naphthalene sulfonic acid is 100 parts by weight of the anthraquinone dye mixture represented by the general formulas (I), (III) or (II). 1-10
It is preferably used in the range of 0 parts by weight.

The formaldehyde condensate of naphthalene sulfonic acid which may be alkylated is preferably a formaldehyde condensate of naphthalene sulfonic acid having 1 to 3 C _{1 to} C ₄ alkyl groups. As the alkyl group, a formaldehyde condensate of alkylnaphthalenesulfonic acid having one or two methyl groups or ethyl groups is preferably used. These optionally alkylated naphthalenesulfonic acids may be used alone or as a mixture with those having different numbers of alkyl groups.

The formaldehyde condensate of naphthalenesulfonic acid which may be alkylated preferably has a degree of sulfonation of naphthalenesulfonic acid of 50 to 150%. Further, the optionally condensed naphthalenesulfonic acid and formaldehyde condensate preferably has an average degree of condensation of 1.1 to 3.0.

The anthraquinone dye mixture contained in the ink for inkjet printing of the present invention is an anthraquinone dye represented by the general formula (I), the general formula (II) or the general formula (III), and optionally alkylated. It is composed of a formaldehyde condensate of naphthalene sulfonic acid which may be added, and these can be easily obtained by mixing them by a generally known method. The mixing method is not particularly limited, and may be performed in advance before being used for inkjet printing, may be mixed at the time of inkjet printing, or may be performed at the time of producing a dye.

The anthraquinone dye mixture used in the present invention may be used in combination with other dyes, if necessary, in order to obtain a desired hue. The dye to be mixed and used is not particularly limited, and generally known dyes can be used, but as a reactive group, a sulfatoethylsulfone group, a vinylsulfone group, a monochlorotriazine group, a monofluoro group is preferable. A compound having at least one or more kinds of at least one of a monopyridiniotriazine group containing a triazine group, a hydroxycarbonyl group or an aminocarbonyl group, a dichlorotriazine group, a difluoromonochloropyrimidine group, a trichloropyrimidine group, and specifically, Sumifix , Su
mifix Supra, Remazol, Levafix, Procion, Cibacr
on, Basilen, Drimarene, Kayacion, kayacelon Reac
Dyes marketed under the generic names such as t, and further, JP-A-50-178, JP-A-56-9483 and JP-A-56.
-15481, JP-A 56-118976, JP-A 56-128380, JP-A 57-2365, JP-A 57-89679, JP-A 57-143360,
JP-A-59-15451, JP-A-58-191755
JP-A-59-96174, JP-A-59-1614
63, JP-A-60-6754, JP-A-60-123.
559, JP-A-60-229957, JP-A-60-
Dyes described in JP-A-260654, JP-A-61-155469, JP-A-63-7797, JP-A-63-225665, JP-A-1-185370, and JP-A-3-770. It is illustrated. Particularly, a dye having at least one or more of sulfatoethylsulfone group, vinylsulfone group, monochlorotriazine group and monofluorotriazine group as a reactive group, or
Dyes marketed under the generic names such as Sumifix, SumifixSupra and Remazol are preferred.

The anthraquinone dye mixture used in the present invention may further contain other dispersants, naphthalene derivatives, solubility improvers such as anthraquinone derivatives such as anthraquinone-2-sulfonic acid, pH stabilizers and polyphosphates, if necessary. A water softener, a defoaming agent, water, and other known auxiliaries can be contained.

A preferred embodiment of the present invention is a reactive dye,
In an ink jet printing ink comprising water and an organic solvent, the above formulas (I), (II) and (II
The anthraquinone dye mixture represented by I) is contained in an amount of 1 to 35% by weight, preferably 3 to 30% by weight, and more preferably 5 to 25% by weight in terms of pure product.

Here, the anthraquinone dyes represented by the above general formulas (I), (II) and (III) mean pure dyes substantially free of inorganic salts and the like and are synthesized by a usual method. The dye thus obtained is subjected to desalting treatment by ultrafiltration, reverse osmosis membrane or electrodialysis, and in the case of a commercially available dye (powder or liquid product), it is also desalted in the same manner. Used as a pure product.

The reactive dyes in the ink jet printing inks of the present invention are present in the form of free acids, salts or mixtures thereof. Here, the counter ion is present as an alkali metal, alkaline earth metal or a substituted or unsubstituted ammonium salt, and preferably a sodium salt, a potassium salt, a lithium salt, an ammonium salt or the like.

In the ink-jet printing ink of the present invention, its pH has a delicate influence on storage stability, ejection stability and the like.
It has been found that it is more preferable that the pH is in the range of 7, preferably pH 3.5 to 6. Here, the pH adjuster is not particularly limited, but sodium hydroxide, potassium hydroxide, sodium acetate, sodium carbonate, sodium bicarbonate, alkanolamine and the like are preferable for alkali, and hydrochloric acid, sulfuric acid, acetic acid and the like for acidity. Is preferred.

The ink for ink jet textile printing of the present invention,
Specifically as the organic solvent to be mixed as necessary,
For example, methanol, ethanol, isopropanol, n
-Propanol, n-butanol, sec-butanol,
Alcohols such as tert-butanol, isobutanol and benzyl alcohol, amides such as dimethylformamide and diethylformamide, ketones such as acetone and diacetone alcohol, ethers such as tetrahydrofuran and dioxane, lactams such as caprolactam and ethylene glycol. , Propylene glycol, butylene glycol, pentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, thiodiglycol, hexylene glycol, 2-methyl-
2,4-pentanediol, glycerin, 1,2,6-
Polyhydric alcohols such as hexanetriol, polyethylene glycol, (average molecular weight 200, 400, 600
Etc.), polypropylene glycol (average molecular weight 200,
400, 600 etc.) polyalkylene glycols,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol Lower alkyl ethers of polyhydric alcohols such as monopropyl ether, propylene glycol monobutyl ether, propylene glycol monophenyl ether, dipropylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether, acetylene glycol Derivative (trade name: Surfynol: manufactured by Nisshin Chemical Co., Ltd.), alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and nitrogen-containing heterocyclic ketones such as 1,3-dimethyl-2-imidazolidine. , 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-
Vinyl-pyrrolidone, N-octyl-2-pyrrolidone,
N- (2-hydroxyethyl) -2-pyrrolidone, N-
Cyclohexyl-2-pyrrolidone, N-dodecyl-2-
Pyrrolidone, N-isopropyl-2-pyrrolidone, N-
(N-Butyl) -2-pyrrolidone, N- (t-butyl)
-2-pyrrolidone, N-hexyl-2-pyrrolidone, N
-(3-hydroxypropyl) -2-pyrrolidone, N-
(2-Methoxyethyl) -2-pyrrolidone, N- (3-
Methoxypropyl) -2-pyrrolidone, N-benzyl-
Examples include pyrrolidones such as 2-pyrrolidone and polyvinylpyrrolidone. Among them, polyethylene glycol (average molecular weight 200, 400, 600, etc.), polypropylene glycol (average molecular weight 200, 400, 600)
Etc.) are preferably used.

The amount of the organic solvent used is 0 to 50% by weight, preferably 5 to 30% by weight in the ink for ink jet textile printing. These organic solvents improve the stability of the ink,
It has functions of preventing clogging of the inkjet head, wetting, adjusting viscosity, etc., and it is usually preferable to use an organic solvent together. In addition, these organic solvents, respectively,
Alternatively, two or more kinds may be mixed and used as long as they do not affect each other.

In addition to the above, various additives which have been conventionally used in order to have more excellent properties are used in combination in the ink for ink jet textile printing of the present invention, if necessary. Specifically, for example, penetrants, preservatives, antifungal agents (eg, sodium dehydroacetate, 4-chloro-3-methylphenol, etc.), other UV absorbers, viscosity modifiers, anionic or nonionic surfactants, etc. Surface tension adjusting agent, electric conductivity adjusting agent, pH buffering agent, specific resistance value adjusting agent, infrared absorbing agent, antioxidant, chelating agent, defoaming agent and the like.

The amount of the inorganic neutral salt such as sodium chloride and sodium sulfate contained in the ink for ink jet printing of the present invention is preferably 1% by weight or less based on the ink solution.
More preferably, it is 0.1% by weight or less.

The method of printing a cellulosic fiber structure with the ink for inkjet printing of the present invention can be realized by a conventional printing method in principle.

The cellulosic fiber structure in the method of the present invention is not particularly limited, but natural or regenerated cellulosic fibers such as cotton, linen, rayon, hemp, jute, ramie fiber, viscose silk and bemberg. Is exemplified. Fiber materials containing cellulosic fibers include cotton / polyester blended products, cotton /
Examples include nylon blended products and cotton / wool blended products.

The printing method for obtaining a printed product having an excellent image quality with respect to a cellulosic fiber structure by the ink for inkjet printing of the present invention can be realized by a conventional printing method, but the cellulosic fiber structure is In some cases, good image quality may not be obtained. Therefore, before printing, the cellulosic fiber structure is used in the conventional printing method, such as sodium alginate and carboxymethyl cellulose (CM).
C), guar gum, starch and the like are preferably treated in advance.

In the pretreatment of the cellulosic fiber structure with a sizing agent, urea, thiourea, an alkaline agent, a reduction inhibitor, a sequestering agent, a defoaming agent, etc. are optionally used in the same manner as in conventional printing pastes. It is also possible to do, and each effect can be added.

The fixing treatment method of the ink-jet printing ink of the present invention is also the conventional alkali printing method, the pre-alkali thermofix method, the pre-alkali steam method, the alkali shock method, the alkali ultra rapid steam method, the alkali blotch steam method, the alkali pad. It can be applied regardless of the steam method or the alkaline cold fix method.

The ink jet printing ejection method according to the present invention includes a continuous method, an on-demand method, a bubble jet method, a thermal jet method, a piezo method, and the like. The ink jet printing ink of the present invention is the above ejection method. It can be used for both.

[0043]

According to the present invention, an ink jet having excellent coloring properties and image quality with respect to a cellulosic fiber structure, excellent storage stability, and excellent ejection stability without the problem of ink head clogging. An ink for printing is obtained, and by using the ink to print a fabric by inkjet printing,
An excellent printed material can be obtained.

[0044]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, “part” means “part by weight”.

Example 1 The following formula (I) -a in the form of free acid is used.

[0046]

[Chemical-7]

Sodium salt of anthraquinone dye represented by: 8.0 parts in the form of a free acid, represented by the following formula (II) -a

[0048]

[Chemical-8]

Sodium salt of anthraquinone dye represented by: 0.3 part by the following formula (III) in the form of free acid

[0050]

[Chemical-9]

Sodium salt of anthraquinone dye represented by: 1.0 part Formaldehyde condensation product of methylnaphthalenesulfonic acid (sodium salt) (Sulfonation degree: 75%, average condensation degree: 2.0) 5.2 parts Polyethylene glycol (average Molecular weight 200) 18.4 parts Ion-exchanged water 67.1 parts

The resulting mixture was mixed and filtered through a membrane filter made of 0.2 μm polytetrafluoroethylene (hereinafter abbreviated as PTFE) to prepare an ink composition. The physical properties of this ink are: surface tension (D / c) = 33.5, specific conductivity (m
S / c) = 20.0, viscosity (cps) = 2.52, pH = 3.
It was 6.

Example 2 Sodium salt of monoazo dye represented by formula (I) -a described in Example 1 6.3 parts Sodium salt of monoazo dye represented by formula (III) described in Example 1 0. 7 parts Formaldehyde condensate of methylnaphthalenesulfonic acid (sodium salt) (Sulfonation degree 75%, average condensation degree 2.0) 5.2 parts Polyethylene glycol (average molecular weight 200) 18.4 parts Ion-exchanged water 69.4 parts

Were mixed and filtered through a 0.2 μm PTFE membrane filter to obtain an ink composition (pH = 3.7).
I got

Example 3 Sodium salt of monoazo dye of formula (I) -a described in Example 1 5.6 parts Sodium salt of monoazo dye of formula (II) -a described in Example 1 0.7 part Sodium salt of monoazo dye represented by formula (III) described in Example 1 1.0 part Polyethylene glycol (average molecular weight 200) 18.4 parts Ion-exchanged water 74.3 parts

Were mixed and filtered through a 0.2 μm PTFE membrane filter to obtain an ink composition (pH = 3.4).
I got

Example 4 Sodium salt of monoazo dye of formula (I) -a described in Example 5.5 5.5 parts Sodium salt of monoazo dye of formula (II) -a described in Example 1 2.4 parts Sodium salt of monoazo dye represented by formula (III) described in Example 1 0.5 parts N-ethyl-2-pyrrolidone 21.5 parts Deionized water 70.1 parts

Were mixed and filtered through a 0.2 μm PTFE membrane filter to obtain an ink composition (pH = 4.0).
I got

(Printing Method 1) Using the inks of Examples 1 to 4, the following pretreatment, ink jet printing and post-treatment were carried out on the article to be printed.

(Pretreatment Method for Printed Material) Cotton broad (mercerizing treatment) is a pretreatment liquid with the following mixture,
Padded at 100% pickup rate, 120 ℃
And dried for 90 seconds to obtain a pretreated cloth.

(Pretreatment liquid composition) Snow Algin M (manufactured by Fuji Chemical Co., sodium alginate) 15 parts Sodium metanitrobenzene sulfonate (reduction inhibitor) 40 parts Water 945 parts

(Printing conditions) Using the above pre-treated cloth, the inks shown in the examples were solidly printed with Novajet II (Encad Thermal printer on-demand type). The resolution of the printer is 300 dpi.

(Post-Processing Method for Printed Material) The printed material was left for about 1 hour and then printed with 45 ° Baume sodium silicate,
After 24 hours of batch up, washing with water, soaping, and drying were sequentially performed.

(Evaluation) The obtained printed matter was evaluated for the following items. Storage stability: The ink filled in the cartridge was left for one week with the nozzle portion left open, and then a printing operation was performed to determine the ejection stability. Immediately stable discharge was obtained.

Print Quality: The inks of Examples 1 to 4 had almost no bleeding and were excellent in sharpness.

(Printing Method 2) Using the inks of Examples 1 to 4, the following pretreatment, ink jet printing and post-treatment were performed on the article to be printed. The inks of the present invention all showed excellent performance.

(Pretreatment Method for Printed Material) Cotton broad (mercerizing treatment) is a pretreatment liquid with the following mixture,
Padded at a pick-up rate of about 70%, 120 ° C
And dried for 90 seconds to obtain a pretreated cloth.

(Pretreatment liquid composition) Snow Algin M (manufactured by Fuji Chemical Co., sodium alginate) 15 parts Urea 1.5 parts Sodium metanitrobenzene sulfonate (reduction inhibitor) 40 parts Baking soda 20 parts Ripol CR (water repellent) 1.5 parts water 922 parts

(Printing conditions) Using the above pre-treated cloth, the inks shown in the respective examples were solidly printed with Novajet II (Encad thermal printer on-demand type). The resolution of the printer is 300 dpi.

(Post-Processing Method for Printed Material)
Steaming was performed at 60 ° C. for 60 seconds, and washing with water, soaping, and drying were sequentially performed.

Even when the above-mentioned printing method is applied to a cloth mainly composed of rayon and hemp instead of cotton broad (mercury processing), the same excellent ink-jet printing can be performed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Yabushita 3-98 Kasugadeka, Konohana-ku, Osaka Sumitomo Chemical Co., Ltd.

Claims (9)

[Claims] 1. An inkjet printing ink comprising a reactive dye, water and, if necessary, an organic solvent, in the form of a free acid represented by the following general formula (I) as a reactive dye: [In the formula, Q ₁ represents a group capable of leaving by the action of an alkali. 1 to 99% by weight of an anthraquinone dye represented by the following general formula (II) in the form of a free acid: [In the formula, Q ₂ represents a group capable of leaving by the action of an alkali. ] 0 to 98% by weight of an anthraquinone dye represented by the following general formula (III) An ink for ink-jet printing, comprising an anthraquinone dye mixture containing 1 to 20% by weight of the anthraquinone dye represented by 2. The ink for inkjet printing according to claim 1, wherein an anthraquinone dye mixture containing 0.5 to 50% by weight of the anthraquinone dye represented by the general formula (II) is used. 3. The ink for inkjet printing according to claim 1, wherein an anthraquinone dye mixture containing 0.2 to 15% by weight of the anthraquinone dye represented by the general formula (III) is used. 4. 1 to 100 parts by weight of a formaldehyde condensate of an optionally alkylated naphthalene sulfonic acid is contained with respect to 100 parts by weight of the anthraquinone dye mixture. Ink for inkjet printing according to any one of 1. 5. The formaldehyde condensate of an optionally alkylated naphthalene sulfonic acid is a formaldehyde condensate of a naphthalene sulfonic acid having 1 to 3 C _{1 to} C ₄ alkyl groups. Inkjet printing ink. 6. The ink for ink jet printing according to claim 4, wherein the formaldehyde condensate of naphthalene sulfonic acid which may be alkylated has a degree of sulfonation of naphthalene sulfonic acid of 50 to 150%. 7. The ink for inkjet printing according to claim 4, wherein the formaldehyde condensate of optionally alkylated naphthalene sulfonic acid has an average degree of condensation of 1.1 to 3.0. . 8. An ink-jet printing method, which comprises printing a cloth made of a cellulosic fiber structure with the ink-jet printing ink according to any one of claims 1 to 7. 9. A cloth made of a cellulosic fiber structure obtained by the inkjet printing method according to claim 8.