JP7399554B2 - Cleaning liquid and cleaning method - Google Patents

Description

The present invention relates to a cleaning liquid, particularly a cleaning liquid used for cleaning an inkjet printer, and a cleaning method using the cleaning liquid.

A printing method using an inkjet printer (inkjet printing method) is a method in which small droplets of ink are generated and the droplets are attached to a recording medium such as paper to perform printing. In recent years, inkjet printing methods have been increasingly applied to industrial applications. Colorants contained in inkjet inks are broadly classified into water-soluble colorants and water-insoluble colorants. Among these, water-insoluble colorants such as pigments are generally superior in various fastness properties compared to water-soluble colorants. For this reason, industrial inkjet inks often contain water-insoluble colorants.

Recording media used for industrial purposes are diversifying, including various types of paper, fibers, and films. Among recording media, there are many media that do not absorb ink, such as resin films, and media that have difficulty absorbing ink, such as coated paper. As inks used for printing such recording media, non-aqueous solvent inks, curable inks, and the like are known. However, from the viewpoint of safety to the natural environment and living organisms, there is a strong demand for water-based inks to replace these inks. Such water-based inks contain water-insoluble colorants and dispersants, and generally also contain polymers, waxes, etc. for the purpose of improving scratch resistance, solvent resistance, and the like. Therefore, such water-based inks have a high solid content and are extremely easy to dry. Drying of ink, such as during long-term storage or storage in a high-temperature, low-humidity environment, causes the formation of solid matter in the nozzle portion and ink flow path of an inkjet head, which tends to cause clogging. When clogging occurs in the inkjet head in this way, ink cannot be ejected stably. This causes problems such as deterioration of print image quality and reduction of image density. Therefore, industrial inkjet heads are generally equipped with a cap member on the nozzle portion to prevent the ink from drying out. However, when the environment in which an inkjet printer operates is harsh, it is difficult to completely avoid ink drying.

Under the above circumstances, there is a strong demand for a cleaning liquid (also referred to as a cleaning liquid, maintenance liquid, etc.) that can clean the inkjet head even if the ink dries to produce solid substances that clog the inkjet head. Patent Documents 1 to 6 disclose cleaning liquids used for cleaning inkjet recording apparatuses.

Patent No. 5027444 Patent No. 4649823 Patent No. 4397220 Patent No. 5618250 Patent No. 5819206 Patent No. 5819205

An object of the present invention is to provide a cleaning liquid that can clean solid matter even when colored ink dries to produce solid matter.

As a result of extensive research to solve the above problems, the present inventors have found that the above problems can be solved by the following 1) to 4), and have completed the present invention.

1)
A cleaning liquid containing one or more compounds selected from the compounds represented by the following formula (1) and the following formula (2), an organic solvent, and water, in which the above-mentioned compounds in the total mass of the cleaning liquid are A cleaning liquid having a total content of organic solvents of 9% by mass or more.

[In formula (1), R ¹ represents a linear or branched C1-C30 alkyl group. EO represents an ethyleneoxy group, and PO represents a propyleneoxy group, respectively. m1 and n1 each independently represent an integer of 1 to 5. m1:n1, which is the ratio of m1 and n1, is 1:2 or more and smaller than 3:2. Furthermore, the order in which EO and PO are combined is arbitrary. ]

[In formula (2), R ² represents a linear or branched C1-C30 alkyl group. OP represents an oxypropylene group, and OE represents an oxyethylene group, respectively. m2 represents an integer of 1 to 2, and n2 represents an integer of 1 to 15. Furthermore, the order in which OP and OE are combined is arbitrary. ]
2)
The cleaning liquid according to 1) above, wherein the organic solvent is one or more types selected from glycol ethers and alkanediols.
3)
Use of the cleaning liquid described in 1) or 2) above in cleaning an inkjet printer.
4)
A method for cleaning an inkjet printer, comprising cleaning inkjet ink solid matter adhering to the inkjet printer using the cleaning liquid described in 1) or 2) above.

ADVANTAGE OF THE INVENTION According to the present invention, even when colored ink dries to produce solid matter, a cleaning liquid capable of cleaning the solid matter could be provided.

In this specification, unless otherwise specified, "%" and "part" are both expressed on a mass basis.

[Compound represented by formula (1)]
In the above formula (1), R ¹ is a linear or branched alkyl group, usually C1-C30, preferably C10-C18, more preferably C12-C15. Among them, straight-chain alkyl groups are preferred.
m1 and n1 each independently represent an integer of 1 to 5. The m1:n1 ratio is usually 1:2 or more and less than 3:2. The number and ratio of m1:n1 are 1:2, 2:3, 3:4, 4:5, 5:5, 4:4, 3:3, 2:2, 1:1, 5:4, 4:3 is preferred, and among these, 4:4 is more preferred.
Both m1 and n1 are average values. Therefore, in this specification, when m1 and n1 have values below the decimal point, the values of m1 and n1 are determined by rounding off the first digit after the decimal point to an integer.
The content of the compound represented by formula (1) in the total mass of the cleaning liquid is usually 0.1% to 2%, preferably 0.5% to 1%.
The compound represented by formula (1) can be synthesized by a known method. It is also available as a commercial product. Specific examples of commercial products include GENAPOL EP2424 and EP2544 manufactured by Clariant.

[Compound represented by formula (2)]
In the above formula (2), R ² is a linear or branched alkyl group, usually C1-C30, preferably C7-C13, more preferably C7-C10, still more preferably C8-C10, particularly preferably C9. Among them, straight-chain alkyl groups are preferred.
m2 represents an integer of 1 to 2, and n2 represents an integer of 1 to 15, preferably 2 to 8. The m2:n2 ratio is more preferably 1:4 or 2:4.
Both m2 and n2 are average values. Therefore, in this specification, when m2 and n2 have values below the decimal point, the values of m2 and n2 are rounded off to the first digit after the decimal point and made into an integer.
The content of the compound represented by formula (2) in the total mass of the cleaning liquid is usually 0.1% to 2%, preferably 0.5% to 1%.
The compound represented by formula (2) can be synthesized by a known method. It is also available as a commercial product. Specific examples of commercially available products include Lutensol XL40 manufactured by BASF.

m1, m2, n1 and n2 are all average values. Therefore, in this specification, when these have numerical values below the decimal point, the values of m1, m2, n1, and n2 are determined by rounding off the first digit after the decimal point to an integer.
By containing one or more compounds selected from the compounds represented by the above formulas (1) and (2), the cleaning liquid can be made into a uniform solution. Moreover, by making the cleaning liquid a uniform solution, it is possible to obtain a cleaning liquid that stably has high cleaning ability. When using two or more types of compounds represented by formula (1) and formula (2) in combination, it is preferable to select different compounds.
Further, the order in which EO and PO in the above formula (1) and OE and OP in the above formula (2) are combined is arbitrary, and is not specified in the order expressed in each formula. Preferably, the order expressed in each formula is preferred.

[Organic solvent]
The organic solvent contained in the above-mentioned cleaning liquid is not particularly limited. Known organic solvents can be used.
Examples of organic solvents include C1-C6 alkanols having one hydroxyl group, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, and tertiary-butanol; N,N-dimethylformamide, and N,N-dimethylformamide; Amides such as , N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidin-2-one; 1,3-dimethylimidazolidin-2-one, and 1, Cyclic ureas such as 3-dimethylhexahydropyrimid-2-one; ketones or ketoalcohols such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; cyclic ureas such as tetrahydrofuran and dioxane Ether; ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexylene glycol,
1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol, 3,3-dimethyl-1,2-butanediol, 1,2-octanediol, 5-methyl-1 , 2-hexanediol, 4-methyl-1,2-hexanediol, 4,4-dimethyl-1,2-pentanediol, and other alkanediols; diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol,
polyethylene glycol or polypropylene glycol with a molecular weight of 400 or more,
Mono-, oligo- or polyalkylene glycols or thioglycols having C2-C8 alkylene units, such as thiodiglycol or dithiodiglycol; polyols such as glycerin, diglycerin, hexane-1,2,6-triol, trimethylolpropane ( (triol); γ-butyrolactone, dimethyl sulfoxide; and glycol ether. Among these, one or more organic solvents selected from glycol ethers and alkanediols are preferred.
Examples of the alkanediol include 1,2-hexanediol, 4-methyl-1,2-pentanediol, 3,3-dimethyl-1,2-butanediol, 1,2-octanediol, 5-methyl- C6-C12 alkanediols such as 1,2-hexanediol, 4-methyl-1,2-hexanediol, and 4,4-dimethyl-1,2-pentanediol are preferred, and C6-C10 alkanediols are more preferred; -C8 alkanediols are more preferred.
As the glycol ether, monoalkyl ethers of di- or tri-C2-C4 alkylene glycols are preferred.
C2-C4 alkylene glycol moieties include ethylene glycol, propylene glycol, and butylene glycol. Among these, ethylene glycol and propylene glycol are preferred, and ethylene glycol is more preferred.
The range of the carbon number of the alkyl in the monoalkyl ether moiety is usually C1-C6, preferably C1-C5, more preferably C2-C4, still more preferably C3-C4, particularly preferably C4.
Specific examples include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether (butyl diglycol), triethylene glycol monomethyl ether, and triethylene glycol monoethyl ether. , ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, propylene glycol monopropyl ether, triethylene glycol monobutyl ether, and the like.
The total content of organic solvents in the total mass of the cleaning liquid is usually 9% or more and less than 25%, preferably 9 to 24%, more preferably 9 to 22%, and still more preferably 9 to 20%.

Among the above organic solvents, it is preferable to contain one or more selected from glycol ethers and alkanediols.
In addition, it is preferable to optionally contain one or more selected from glycol ethers, alkanediols, and mono-, oligo- or polyalkylene glycols or thioglycols having C2-C8 alkylene units.
When one or more organic solvents selected from glycol ethers and alkanediols are used together with other organic solvents, the sum of their total contents is the total content of organic solvents in the total mass of the cleaning solution. becomes. Also at this time, the total content of one or more organic solvents selected from glycol ethers and alkanediols is as described above.

In addition to the above-mentioned components, the cleaning liquid may further contain various preparation agents as necessary. Examples of such preparation agents include surfactants, preservatives, antifungal agents, pH adjusters, chelating reagents, rust preventives, water-soluble ultraviolet absorbers, and antioxidants.
The total content of the preparation agent is usually about 0% to 30%, preferably 0% to 20%, and more preferably about 0% to 10%, based on the total mass of the cleaning liquid.

The cleaning liquid does not substantially contain a colorant. As used herein, "substantially" means that no colorant is intentionally added to the cleaning solution.

[Surfactant]
Examples of the surfactant include anionic, cationic, nonionic, amphoteric, silicone, and fluorine-based surfactants. Among these, nonionic surfactants are preferred.

Examples of anionic surfactants include alkyl sulfocarboxylate, α-olefin sulfonate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether sulfate, N-acylamino acid or its salt, N-acylmethyl taurate, Alkyl sulfate polyoxyalkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol type phosphate ester, alkyl type phosphate ester, alkylaryl sulfone Examples include acid salts, diethyl sulfosuccinate, diethylhexyl sulfosuccinate, dioctyl sulfosuccinate, and the like.

Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.

Examples of nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene diphenyl ether. Styrenated phenyl ether, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate Ester systems such as; 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1- Examples include hexin-3-ol.

Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine, imidazoline derivatives, etc. Can be mentioned.

Examples of the silicone surfactant include polyether-modified siloxane, polyether-modified polydimethylsiloxane, and the like.

Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and perfluoroalkyl ether groups in side chains. Examples include polyoxyalkylene ether polymer compounds.

Examples of preservatives include organic sulfur-based, organic nitrogen-sulfur-based, organic halogen-based, haloarylsulfone-based, iodopropargyl-based, haloalkylthio-based, nitrile-based, pyridine-based, 8-oxyquinoline-based, and benzothiazole-based. , isothiazoline type, dithiol type, pyridine oxide type, nitropropane type, organotin type, phenol type, quaternary ammonium salt type, triazine type, thiazine type, anilide type, adamantane type, dithiocarbamate type, brominated indanone type, benzyl Examples include bromoacetate-based or inorganic salt-based compounds.

Specific examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and its salts. .

As the pH adjuster, any substance can be used as long as it can adjust the pH of the ink composition to 5 to 11 without adversely affecting the prepared ink composition.
Specific examples include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (aqueous ammonia); or carbonates of alkali metals such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

Specific examples of the chelating reagent include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracil diacetate.

Specific examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

Examples of the antioxidant include various organic and metal complex anti-fading agents. Examples of the above organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. It will be done.

The above-mentioned cleaning liquid can be obtained by adding the above-mentioned components and, if necessary, an ink preparation agent and mixing them thoroughly.
The above method for cleaning an inkjet printer is not particularly limited as long as it is a method for cleaning inkjet ink solid matter adhering to an inkjet printer. A typical cleaning method includes, for example, a method of absorbing a cleaning liquid into a sponge or the like and wiping off stains on the areas to which the colored ink has adhered. On the other hand, if, for example, the colored ink dries on the inkjet head and the inkjet head is heavily soiled, the inkjet head can be filled with a cleaning liquid instead of the colored ink to clean it.
When filling an inkjet head with a cleaning liquid for cleaning, it is preferable to perform precision filtration of the cleaning liquid.
When carrying out precision filtration, a membrane filter and/or glass filter paper can be used. The pore size of the filter used for precision filtration is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

The pH of the cleaning liquid is usually 5 to 11, preferably 7 to 10.5 in order to prevent corrosion of the inkjet printer components.
The surface tension of the cleaning liquid is usually 10 mN/m to 50 mN/m, preferably 20 mN/m to 40 mN/m.
The viscosity of the cleaning liquid is usually 30 mPa·s or less, preferably 20 mPa·s or less, and the lower limit is about 0.1 mPa·s.

The above-mentioned cleaning liquid can be used for cleaning water-based inks containing various colorants. Examples of colorants include water-based dye inks containing water-soluble dyes such as acid dyes, direct dyes, and reactive dyes; water-based inks containing water-insoluble colorants containing disperse dyes and pigments. It will be done.
Since the above-mentioned cleaning liquid has high cleaning power, it is preferably used for cleaning a water-based ink containing a water-insoluble colorant, especially a pigment. Moreover, the above-mentioned cleaning liquid exhibits extremely high ability as a cleaning liquid for water-based ink containing various resins as well as pigments due to its high cleaning power.

One type of all the above-mentioned components can be used alone. Moreover, two or more types can also be used together.
Further, regarding all the above-mentioned items, combinations of preferable items are more preferable, and combinations of more preferable items are still more preferable. The same applies to combinations of preferred and more preferred, combinations of more preferred and even more preferred, and the like.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples. Further, the cleaning liquid and the colored ink were prepared under stirring unless otherwise specified.
Moreover, "water" used in the examples is ion-exchanged water.

[Examples 1 to 5]: Preparation of cleaning solution.
The components listed in Table 1 below were mixed to obtain a total of 100 parts of each solution, and the resulting solution was filtered through a 3 μm membrane filter to obtain the cleaning solutions of Examples 1 to 5. "EP2424", "EP2544", and "XL40" used in Examples 1 to 5 are compounds corresponding to the above formula (1) or formula (2).

[Comparative Examples 1 to 9]: Preparation of cleaning liquid for comparison.
Comparative cleaning solutions of Comparative Examples 1 to 9 were obtained in the same manner as in Examples 1 to 5 above, except that each component listed in Table 1 below was used. "EP2564", "EP2584", "SN465", "EP7025", and "LS106" used in Comparative Examples 1 to 9 are compounds that do not correspond to the above formula (1) or formula (2).

Abbreviations in Table 1 below have the following meanings. Moreover, the numerical values in Table 1 are "parts".
Gly: Glycerin.
2Py: 2-pyrrolidone.
BDG: Butyl diglycol.
12HD: 1,2-hexanediol.
EP2424: GENAPOL EP2424, a nonionic surfactant manufactured by Clariant.
EP2544: GENAPOL EP2544, a nonionic surfactant manufactured by Clariant.
EP2564: GENAPOL EP2564, a nonionic surfactant manufactured by Clariant.
EP2584: GENAPOL EP2584, a nonionic surfactant manufactured by Clariant.
XL40: Lutensol XL40 manufactured by BASF.
SN465: Nonionic surfactant, Surfynol 465 manufactured by Nissin Chemical Co., Ltd.
EP7025: Softanol EP-7025, a nonionic surfactant manufactured by Nippon Shokubai Co., Ltd.
LS106: Emulgen LS-106, a nonionic surfactant manufactured by Kao Corporation.
TEA: Triethanolamine.
GXL (S): Proxel GXL (S) manufactured by Lonza.

EP2424 is a compound in the above formula (1), where R ¹ is a C12-C14 alkyl group, m1 is 1 to 3, n1 is 2 to 5, and m1:n1 is 1:2.
EP2544 is a compound in the above formula (1) in which R ¹ is a C12-C15 alkyl group, m1 is 2 to 4, n1 is 2 to 4, and m1:n1 is 1:1.
EP2564 is a compound that is not included in the above formula (1) because in the above formula (1), R ¹ is a C12-C15 alkyl group, m1 is 6, n1 is 4, and m1:n1 is 3:2. be.
EP2584 is a compound that is not included in the above formula (1) because in the above formula (1), R ¹ is a C12-C15 alkyl group, m1 is 8, n1 is 4, and m1:n1 is 2:1. be.
XL40 is a compound in the above formula (1) in which R ² is a 4-nonyl group, m2 is 1, and n2 is 4.
Since SN465 is acetylene glycol, it is a compound not included in the above formula (1).
EP7025 is a compound that is not included in the above formula (1) because R ¹ is a C12-C15 branched alkyl group, m is 2.5, and n is 7.
LS106 has an alkyl group as R ¹ and an oxyethylene group, but does not have an oxypropylene group (that is, m is 0), and is therefore a compound not included in the above formula (1).

[Preparation Example 1]: Preparation of Resin A.
25 parts of Joncryl 678 (MW: 8500) and 14.3 parts of triethanolamine were dissolved in 60.7 parts of ion-exchanged water and stirred for one hour to obtain a solution. The resulting solution is referred to as resin A.

[Preparation Example 2]: Preparation of colored dispersion.
A block copolymer described in Synthesis Example 3 of International Publication No. 2013/115071 was prepared, and 5 parts of the obtained polymer dispersant were dissolved in 20 parts of 2-butanone to form a uniform solution. A solution prepared by dissolving sodium hydroxide (0.4 parts) in water (50.6 parts) was added to this solution, and after adding resin solution A (4 parts), the mixture was stirred for 1 hour to obtain a solution. C. I. Pigment Yellow 74 (20 parts, HANSA YELLOW 5GX 01-JP manufactured by Clariant) was added, and dispersion treatment was performed in a sand grinder at 1500 rpm for 15 hours to obtain a liquid. After water (100 parts) was added dropwise to the obtained liquid, this liquid was filtered to obtain a filtrate. From the obtained filtrate, 2-butanone and a portion of water were distilled off under reduced pressure using an evaporator to obtain a colored dispersion having a pigment content of 12.4%.
The pigment content in the colored dispersion was determined by the dry weight method using MS-70, manufactured by A&D Co., Ltd., as a value converted from the total solid content in the liquid to only the pigment.

[Preparation Example 3] Preparation of resin B.
By repeating Preparation Example 4 of International Publication No. 2015/147192 Gazette, a resin emulsion with an acid value of 6 KOHmg/g, a Tg of 0° C., and a solid content of 25% was prepared. This will be referred to as "Resin B".

[Preparation Example 4]: Preparation of colored ink.
After mixing each component listed in Table 2 below to obtain a total of 100 parts of liquid, the obtained liquid was filtered through a 3 μm membrane filter to obtain a colored ink used for evaluation of the cleaning liquid.

Abbreviations in Table 2 below have the following meanings. Further, the numerical values in Table 2 below are in "parts".
Dp1: Colored dispersion obtained in Preparation Example 2.
TEG: triethylene glycol.
1,2HD: 1,2-hexanediol.
SN465: Nonionic surfactant, Surfynol 465 manufactured by Nissin Chemical Co., Ltd.
AQ515: Polyethylene wax, AQUACER 515 (solid content 35.0%) manufactured by Bikkemie.
Further, the numbers of parts in Table 2 for Resin B and AQ515 are converted to solid content.

[Stability test]
After the cleaning liquids obtained in each example and comparative example were allowed to stand at room temperature for 12 hours, the state of the cleaning liquids was visually observed to evaluate its stability. The evaluation criteria were the following two levels. The evaluation results are shown in Table 3 below.
In addition, in the stability test, the following cleaning test was conducted using only the cleaning liquid rated "A".
[Evaluation criteria]
A: There was no change in the condition of the cleaning solution.
C: Liquid components separated from the cleaning solution were observed floating on the surface of the cleaning solution.

[Cleanability test]
20 microliters of the colored ink obtained in Preparation Example 4 above was dropped onto a glass petri dish, and the mixture was allowed to stand in a constant temperature bath at 60° C. for 1 hour to dry, thereby obtaining a solid solidified colored ink.
10 ml of each of the cleaning liquids of Examples and Comparative Examples was dropped onto the obtained solids, and whether or not the solids could be washed was visually evaluated. The evaluation criteria were the following four levels. The evaluation results are shown in Table 3 below. In Table 3, "-" indicates that the washability test was not conducted.
Note that even if a small amount of solid matter remains, it may be impossible to clean clogging of the inkjet head. For this reason, cleaning liquids with a cleaning performance rating other than "A" are not practical.
[Evaluation criteria]
A: A homogeneous liquid was obtained with no solids remaining.
B: The liquid was almost uniform, but a slight amount of solid matter remained.
C: Solid matter clearly remained, and a homogeneous liquid was not recognized.
D: The shape of the solid material did not change at all or hardly changed.

As is clear from the above results, it was confirmed that the cleaning liquid of the example was excellent in stability and cleaning performance.

The cleaning liquid of the present invention can be used as a cleaning liquid for colored ink, especially for colored inkjet ink, because even when colored ink, especially water-based ink containing a water-insoluble colorant, dries to produce solid matter, the solid matter can be washed away. It is extremely useful as a cleaning solution.

Claims (2)

An inkjet head cleaning liquid containing one or more compounds selected from the compounds represented by the following formula (1) and the following formula (2), an organic solvent, and water, the cleaning liquid containing: , the total content of the organic solvent is 9% by mass or more and 36% by mass or less, the organic solvent contains butyl diglycol or 1,2-hexanediol, and the butyl diglycol or 1,2-hexanediol in the cleaning solution A cleaning liquid for an inkjet head having a content of 1,2-hexanediol of 9% by mass or more and 20% by mass or less.

[In formula (1), R ¹ represents a linear or branched C1-C30 alkyl group. EO represents an ethyleneoxy group, and PO represents a propyleneoxy group, respectively. m1 and n1 each independently represent an integer of 1 to 5. m1:n1, which is the ratio of m1 and n1, is 1:2 or more and less than 3:2. Furthermore, the order in which EO and PO are combined is arbitrary. ]

[In formula (2), R ² represents a linear or branched C1-C30 alkyl group. OP represents an oxypropylene group, and OE represents an oxyethylene group, respectively. m2 represents an integer of 1 to 2, and n2 represents an integer of 1 to 15. Furthermore, the order in which OP and OE are combined is arbitrary. However, the case where n2 is 10 is excluded. ] A method for cleaning an inkjet printer, comprising cleaning inkjet ink solid matter adhering to the inkjet printer using the inkjet head cleaning liquid according to claim 1.