Cleaning fluid

Abstract

Provided is a cleaning solution capable of removing even white ink after fixation and capable of improving ejection failure of an inkjet printer. A cleaning solution comprising a first surfactant, a second surfactant, and an alkaline compound, the first surfactant being an amphoteric surfactant, the second surfactant being an anionic surfactant that is a sulfonate and / or a nonionic surfactant having a branched structure and an HLB of 7 to 14.

Description

TECHNICAL FIELD

[0001] The present application relates to a cleaning solution. BACKGROUND

[0002] An inkjet printing method is a method in which an ink droplet is ejected from a very fine nozzle toward a printing substrate by an inkjet printer to form a colored image such as a letter or a pattern.

[0003] In recent years, in order to achieve high-speed printing and quick-drying of ink, a method of reducing the viscosity of ink has been studied.

[0004] However, in the method of reducing the viscosity of ink, in an inkjet printer or the like which is left in a state where ink is not ejected for a long time, a dried film of ink is formed in a nozzle (in the vicinity of a nozzle opening) or a nozzle. Such a dried film has a technical problem of causing a flight bend of ink or a clogging of a nozzle.

[0005] Therefore, in order to remove the dried film of ink remaining in a nozzle or a nozzle, a method of using a cleaning solution for ink has been proposed.

[0006] For example, in Patent Literature 1, a cleaning solution for cleaning a portion to which an ejected aqueous inkjet ink containing a pigment and an alkali-soluble resin having an acid group in a molecule is attached in an inkjet printer for ejecting the above aqueous inkjet ink is disclosed. The cleaning solution contains an amphoteric surfactant, an alkali compound, and water, the pH is 9 to 12, the amphoteric surfactant is at least one selected from the group consisting of lauryl dimethyl amine oxide, lauryl dimethyl amino ethyl betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazoline betaine (also called "2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine"), and the content is 0.1 to 3 mass% with respect to the total amount of the cleaning solution.

[0007] Prior Art Documents

[0008] Patent Literature

[0009] Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-060156 SUMMARY

[0010] Problems to be Solved by the Invention

[0011] However, in the method described in Patent Literature 1, it is difficult to remove the ink after the ink is fixed, and it is particularly difficult to remove the fixed white ink in the case of white ink, and there is room for further improvement.

[0012] The present application has been made in view of the above technical problems, and an object thereof is to provide a cleaning solution capable of removing even white ink after the ink is fixed and capable of improving ejection failure of an inkjet printer.

[0013] Means for solving the problem

[0014] In view of the above technical problems, the present inventors etc. have conducted intensive studies, and as a result, have found that all of the above problems can be solved by using a cleaning solution containing a first surfactant, a second surfactant, and an alkaline compound, and the first surfactant is an amphoteric surfactant, the second surfactant is a specific anionic surfactant and / or a nonionic surfactant, thereby completing the present application.

[0015] That is, the present application is a cleaning solution containing a first surfactant, a second surfactant, and an alkaline compound, the first surfactant is an amphoteric surfactant, the second surfactant is an anionic surfactant as a sulfonate and / or a nonionic surfactant having a branched structure and an HLB of 7 to 14.

[0016] In the cleaning solution of the present application, it is preferable that the above-mentioned first surfactant is at least one selected from the group consisting of lauryl dimethyl amine oxide, lauryl dimethyl amino ethyl betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazoline betaine.

[0017] In addition, it is preferable to contain 0.1 to 3 mass% of the above-mentioned first surfactant with respect to the total amount of the cleaning solution.

[0018] In addition, it is preferable that the above-mentioned second surfactant is sodium alkyl sulfate sulfonate and / or polyoxyethylene isotride ether (5EO).

[0019] In addition, it is preferable to contain 0.1 to 3 mass% of the above-mentioned second surfactant with respect to the total amount of the cleaning solution.

[0020] In addition, the above-mentioned alkaline compound is preferably sodium hydroxide and / or potassium hydroxide.

[0021] In addition, the cleaning solution of the present application is preferably pH 9 to 12.

[0022] In addition, the cleaning solution of the present application preferably further contains a preservative and water.

[0023] The cleaning solution of the present application is a cleaning solution for cleaning an ink composition for water-based inkjet printing, and it is preferable that the above-mentioned ink composition for water-based inkjet printing contains a pigment and an alkali-soluble resin having an acid group in the molecule.

[0024] In addition, it is preferable that the above-mentioned pigment is contained at 3 to 12 mass% with respect to the total amount of the above-mentioned ink composition for water-based inkjet printing, and it is preferable that the acid value of the above-mentioned alkali-soluble resin having an acid group in the molecule is 100 mgKOH / g to 200 mgKOH / g.

[0025] Effects of Invention

[0026] The present application can provide a cleaning liquid capable of removing even a fixed white ink and capable of improving ejection failure of an inkjet printer. DETAILED DESCRIPTION

[0027] The present application is a cleaning liquid comprising a first surfactant which is an amphoteric surfactant, a second surfactant which is an anionic surfactant as a sulfonate and / or a nonionic surfactant having a branched structure and an HLB of 7 to 14, and an alkaline compound.

[0028] The present inventors and others have conducted intensive studies in order to solve the above problem, and as a result, have arrived at the following insight.

[0029] That is, the present inventors and others have surmised that, since air is hydrophobic, the drying Film The (fixed ink composition) is formed so that the hydrophobic sites of the pigments or the binder resins (including alkali-soluble resins having an acid group within the molecule) are largely exposed on the surface, and the acid group of the binder resin is oriented toward the inside of the dried film of the ink.

[0030] In a white ink composition having low coloring power, a higher pigment concentration than other colors is required in order to express high color density. In order to impart higher resistance to the dried film of the white ink, it is necessary to contain a large amount of binder resin, and therefore it is surmised that the sites (for example, acid groups) for acting to re-dissolve the white ink will inevitably be reduced on the surface of the dried film, and it will become increasingly difficult to clean.

[0031] In order to quickly dissolve and remove (clean) the dried film of the white ink, it is necessary to more quickly form a salt between the acid group of the binder resin and the alkaline compound contained in the cleaning liquid. Therefore, according to the above surmises, it can be surmised that the function of the cleaning liquid to penetrate (or adsorb) into the binder resin in a state in which the hydrophobic sites of the pigments or the binder resins are largely exposed on the surface and form a salt is important.

[0032] In the conventional cleaning liquid, among compounds having a hydrophobic site (generally, a long-chain alkyl group or an aromatic ring) and a hydrophilic site (generally, an ionic group or a polyethylene chain) within the molecule, from the viewpoint of having a higher adsorption force between the hydrophobic site and the binder resin and collecting more water molecules at the hydrophilic site, it is considered that an amphoteric surfactant is effective, but it does not have sufficient cleaning properties for the dried film of the white ink as described above.

[0033] In the cleaning solution of the present application, in addition to the amphoteric surfactant as the first surfactant, an anionic surfactant of sulfonate and / or a nonionic surfactant having a branched structure and an HLB of 7 to 14 as a second surfactant are contained.

[0034] As the anionic surfactant of sulfonate, a salt is rapidly formed between the amphoteric surfactant and the acid group of the adhesive resin on the inner side of the dried film of the white ink, and as the nonionic surfactant having a branched structure and an HLB of 7 to 14, more effective strong adsorption is exhibited with the hydrophobic site of the adhesive resin.

[0035] In the case where such a second surfactant is contained in addition to the amphoteric surfactant as the first surfactant, it is found that excellent cleaning properties are exhibited even under a strict cleaning condition such as a white ink.

[0036] Here, the present application can not be limited to the above-described mechanism.

[0037] Note that the above-described excellent cleaning properties mean that all of the re-dissolution of the ink to the dried film, the strong oscillation redispersion, and the temporal change redispersion are excellent.

[0038] (First surfactant)

[0039] The cleaning solution of the present application contains a first surfactant, and the above-described first surfactant is an amphoteric surfactant.

[0040] The first surfactant and the second surfactant described later are materials that function to reduce the surface tension of the cleaning solution and improve the wettability with the hydrophobic surface of the dried film of the ink.

[0041] As the above-described first surfactant, at least one selected from the group consisting of lauryl dimethyl amine oxide, lauryl dimethyl aminoethyl betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazoline betaine is preferable, and from the viewpoint of improving the cleaning properties, lauryl dimethyl amine oxide is more preferable.

[0042] The above-described first surfactant can be used alone or in combination.

[0043] From the viewpoint of improving the cleaning properties, the above-described first surfactant is preferably contained at 0.1 to 3% by mass, and more preferably at 0.5 to 1.5% by mass, with respect to the total amount of the cleaning solution.

[0044] (Second surfactant)

[0045] The cleaning solution of the present invention contains a second surfactant, which is an anionic surfactant as a sulfonate and / or a nonionic surfactant having a branched structure and an HLB of less than 14.

[0046] The cleaning solution of the present invention contains the aforementioned anionic surfactant, which improves the penetrability of the cleaning solution and allows it to rapidly form salts with the acid groups of the binder resin (the alkali-soluble resin described later) facing the inside of the dried film of the ink. Furthermore, the cleaning solution of the present invention contains the aforementioned nonionic surfactant, which allows the cleaning solution to more effectively and strongly adsorb onto the hydrophobic sites of the binder resin (the alkali-soluble resin described later) constituting the water-based inkjet printing ink composition.

[0047] Therefore, the cleaning solution of the present invention can remove even fixed white ink, thereby improving the poor ejection performance of inkjet printers.

[0048] For the anionic surfactants described above as sulfonates, sodium alkyl sulfate sulfonate and / or polyoxyethylene alkyl ether sulfonate are preferred, and sodium salts of sodium alkyl sulfate sulfonate and sodium polyoxyethylene alkyl ether sulfate are more preferred.

[0049] From the viewpoint of improving cleanability, sodium alkyl sulfate sulfonate is preferred as described above. It can have a straight chain or branched chain with 10 to 20 carbon atoms. More preferably, it can have a straight chain with 12 to 14 carbon atoms.

[0050] The aforementioned sodium polyoxyethylene alkyl ether sulfate can be an addition product of ethylene oxide (EO), for example, it can be an average 7-molar addition product (also known as 7EO).

[0051] From the viewpoint that the cleaning properties remain excellent even after changes over time (e.g., after being placed in an oven at 50°C in an open system for 3 months), sodium polyoxyethylene alkyl ether (7EO) sulfate is preferred.

[0052] As the above-mentioned nonionic surfactants with branched structures and HLB values ​​of 7 to 14, polyalkylene glycol fatty acid esters and polyoxyethylene alkyl ethers with branched structures are preferred.

[0053] More preferably, as the above-mentioned polyalkylene glycol fatty acid ester, the substance obtained by adding an average of 5 moles of ethylene oxide (EO) to isotracene tridecyl alcohol (also labeled as 5EO), the substance obtained by adding an average of 8 moles (also labeled as 8EO), etc.

[0054] The aforementioned polyoxyethylene alkyl ether is preferably an EO or PO adduct of polyalkylene glycol 2-ethylhexyl ether.

[0055] The second surfactant mentioned above can be used alone or in combination.

[0056] The HLB content of the aforementioned nonionic surfactant with a branched structure and an HLB content of 7 to 14 is 7 to 14. By keeping the HLB content within the aforementioned range, cleaning properties can be imparted for the technical objectives of this invention.

[0057] The HLB value of the nonionic surfactant with a branched structure and an HLB value of 7 to 14 is preferably 8 to 13.

[0058] In addition, in this specification, the HLB value is a value calculated for each surfactant in the form of a hypothetical compound with an infinitely long hydrophilic group added to the lipophilic group and the greatest hydrophilicity, which is set to 20, and a lipophilic compound with no hydrophilic group is set to 0. It is generally calculated using the Griffin formula.

[0059] The following is Griffin's formula for calculating HLB values.

[0060] HLB value = 20 × Mw / M

[0061] M represents the molecular weight of the nonionic surfactant, and Mw represents the molecular weight of the hydrophilic portion.

[0062] From the viewpoint of improving cleanliness, the second surfactant is preferably contained in 0.1 to 3% by mass relative to the total amount of the cleaning liquid, more preferably in 0.2 to 2.5% by mass, and even more preferably in 0.5 to 1.5% by mass.

[0063] From the viewpoint of operational efficiency based on foaming, the second surfactant is preferably 0.2 to 2.5 parts by mass relative to 1 part by mass of the first surfactant, more preferably 0.5 to 1.5 parts by mass.

[0064] (Alkaline compound)

[0065] The cleaning solution of the present invention contains an alkaline compound.

[0066] Examples of alkaline compounds include sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia.

[0067] From the perspective of strong alkalinity and the ability to significantly improve cleaning effect, alkali metal hydroxides are preferred, with sodium hydroxide and potassium hydroxide being preferred, and potassium hydroxide being even more preferred.

[0068] The content of the aforementioned alkaline compounds should be sufficient to adjust the pH of the cleaning solution to the range described later. This content can vary depending on the alkalinity of the alkaline compounds themselves or the presence of acidic or alkaline components in other materials.

[0069] (preservative)

[0070] The cleaning solution of the present invention preferably contains a preservative.

[0071] There are no particular limitations on the aforementioned preservatives; any known preservatives that can be used in the field of cleaning solutions can be appropriately selected and used.

[0072] Specifically, examples include PROXEL GXL (manufactured by LONZA Japan Co., Ltd.) and KORDEK MLX (manufactured by DuPont).

[0073] From the viewpoint of corrosion prevention, the above-mentioned preservative preferably contains 0.01 to 1% by mass relative to the total amount of the cleaning solution, and more preferably 0.05 to 0.5% by mass.

[0074] (water)

[0075] The cleaning solution of the present invention contains water.

[0076] Commercially available purified water, ion-exchange water, etc., can be used as the water mentioned above.

[0077] From the viewpoint of dissolving the above-mentioned materials, the water preferably contains 70-99% by mass, and more preferably 90-97% by mass.

[0078] In addition, the water content mentioned above is the total water content of all the above-mentioned components.

[0079] (other)

[0080] The cleaning solution of the present invention may, as needed, contain organic solvents, surfactants other than the first and second surfactants mentioned above, defoamers, etc.

[0081] (pH of the cleaning solution)

[0082] The cleaning solution of the present invention preferably has a pH of 9 to 12.

[0083] When the pH of the cleaning solution is less than 9, the cleaning power is easily reduced. When the pH of the cleaning solution exceeds 12, occupational health problems are likely to occur and the attached parts (such as head parts) are easily corroded.

[0084] In addition, the pH value mentioned above is the pH value measured according to JIS K 6221.

[0085] (Method for manufacturing cleaning solution)

[0086] There are no particular limitations on the manufacturing method of the cleaning agent of the present invention. As long as the above-mentioned materials are stirred and mixed using known methods, it is acceptable.

[0087] (Water-based inkjet printing ink composition)

[0088] Next, an aqueous inkjet printing ink composition that is a preferred cleaning target of the cleaning solution of the present invention will be described.

[0089] The above-mentioned water-based inkjet printing ink composition includes pigments and alkali-soluble resins with acid groups in their molecules.

[0090] The pigments mentioned above are not specifically limited to any particular type; well-known inorganic and organic pigments can be cited as examples.

[0091] Examples of inorganic pigments mentioned above include carbon black, titanium dioxide, iron oxide red, graphite, iron black, chromium oxide green, and aluminum hydroxide.

[0092] Examples of organic pigments mentioned above include dye lake pigments, azo pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perylene pigments, piperidinone pigments, diketopyrrolopyrrole pigments, isoindolinetone pigments, nitro pigments, nitroketone pigments, anthraquinone pigments, flavanolite pigments, quinolinetone pigments, pinantrone pigments, and indanone pigments.

[0093] The above pigments can also be used together.

[0094] The pigment content in the above-mentioned water-based inkjet printing ink composition is not particularly limited.

[0095] Here, even when the water-based inkjet printing ink composition contains a large amount of the aforementioned pigments, color concentration can be maintained even when the water-based inkjet printing ink composition is used for typing with a smaller amount of droplets. As a result, less liquid component is transferred to the printing paper, which is also beneficial for quick drying and inhibiting the penetration of coloring components into the paper.

[0096] On the other hand, in order to maintain the low viscosity of the ink, it is necessary to keep the total amount of solid components in the water-based inkjet printing ink composition at a certain level.

[0097] Therefore, if the content of pigments, which are insoluble components, increases, the content of alkali-soluble resins, which are soluble components, must be reduced. The combination of these components makes this water-based inkjet printing ink composition prone to forming a dry film with poor redissolvability, easily leading to poor ejection.

[0098] However, the cleaning solution of the present invention has sufficient cleaning power, so even dried films containing a large amount of such pigment can be removed. Specifically, even dried films containing 3 to 12% by mass of pigment relative to the total amount of the water-based inkjet printing ink composition can be sufficiently removed by the cleaning solution of the present invention.

[0099] Examples of alkali-soluble resins include: alkali-soluble resins obtained by copolymerizing monomers containing carboxyl groups such as acrylic acid, methacrylic acid, and maleic anhydride (monoalkyl ester); alkyl vinyl ethers with 8 or more carbon atoms such as 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, and 2-hydroxystearoyl acrylate; alkyl vinyl esters with 8 or more carbon atoms such as dodecyl vinyl ether; alkyl vinyl esters with 8 or more carbon atoms such as vinyl 2-ethylhexanoate, vinyl laurate, and vinyl stearate; and monomers containing alicyclic hydrocarbon groups such as cyclohexyl acrylate; and monomers containing aromatic hydrocarbon groups such as benzyl acrylate, styrene, α-styrene, and vinyltoluene.

[0100] The content of the alkali-soluble resin is, for example, 10 to 60 parts by mass relative to 100 parts by mass of the pigment.

[0101] There is no particular limitation on the acid value of the aforementioned alkali-soluble resin. However, when the acid value of the alkali-soluble resin is low, it easily causes the aqueous medium to detach from the system, exhibiting excellent drying properties. On the other hand, the area in this water-based inkjet printing ink composition that functions to redissolve the dried film is easily reduced.

[0102] However, the cleaning solution of the present invention has a high ability to effectively react the alkaline groups of the alkaline compounds contained in the cleaning solution with the acid groups contained in the molecules of the alkali-soluble resin to form salts, so even the dried film of such water-based inkjet printing ink composition can be cleaned and removed.

[0103] Specifically, the cleaning solution of the present invention can thoroughly clean and remove even dried films containing aqueous inkjet printing ink compositions with alkali-soluble resins having an acid value of 100-200 mg KOH / g.

[0104] The above-mentioned water-based inkjet printing ink composition may include water-dispersible resins, surfactants, etc., as needed.

[0105] For these, well-known materials for water-based inkjet printing ink compositions can be appropriately selected for use.

[0106] The aforementioned pigments are prepared by mixing them with an aqueous resin varnish containing alkali-soluble resin dissolved in water in the presence of an alkaline compound and then mixing them with a disperser. The resulting pigments are then coated with resin by precipitating alkali-soluble resin on the surface of the pigments using acid precipitation or ion exchange methods before being used.

[0107] On the other hand, this water-based inkjet printing ink composition is particularly prone to flight bending or nozzle clogging during drying and curing when it contains a high concentration of pigment or a small amount of low-acid-value alkali-soluble resin.

[0108] However, the cleaning solution of the present invention is unlikely to cause occupational health problems and is unlikely to cause corrosion of the attached parts (such as printhead parts). It can thoroughly clean the attached parts and dissolve the dried film of the ink, thereby improving the problem of poor spraying.

[0109] As a result, for example, in an inkjet printer where the above-mentioned water-based inkjet printing ink composition has been left unsprayed for a long time, even if the water-based inkjet printing ink composition adheres to the attachment site and causes poor spraying, the cleaning solution of the present invention can remove the dried film of the water-based inkjet printing ink composition at the attachment site.

[0110] Therefore, an inkjet printer cleaned with the cleaning solution of the present invention can subsequently eject water-based inkjet printing ink compositions normally.

[0111] Examples

[0112] The present invention will be further described in detail below by way of examples, but the present invention is not limited to these examples. In addition, unless otherwise stated, "%" means "percentage by mass" and "parts" means "parts by mass".

[0113] The materials used in the embodiments and comparative examples are described below.

[0114] <Preparation of Ink Compositions for Water-Based Inkjet Printing>

[0115] A water-based inkjet ink composition was manufactured using the following raw materials.

[0116] (White pigment)

[0117] Product Name: JR-809 (Trade name "JR-809" refers to titanium dioxide obtained by treating silica and alumina, with an average particle size of 0.23μm and a DBP oil supply of 24ml / 100g, manufactured by Teika Co., Ltd.)

[0118] (Alkali-soluble resin)

[0119] A copolymer of styrene / lauryl acrylate / acrylic acid with a weight-average molecular weight of 15,800 and an acid value of 144 mgKOH / g, consisting of 51 / 30 / 19.

[0120] (Water-dispersible resin)

[0121] Neo Rez R-966 (DSM) (polyether polyurethane resin, active ingredient content 33% by weight)

[0122] (surfactant)

[0123] Ethylene glycol is an ethylene oxide adduct, traded as ethynylphenol E100, manufactured by Kawaken Fine Chemicals Co., Ltd.

[0124] (High-pressure emulsification and dispersion device)

[0125] GAULIN homogenizer, manufactured by APVGAULIN INC.

[0126] 25 parts by weight of alkali-soluble resin are mixed with sodium hydroxide with a neutralization equivalent of 100% and pure water to form 100 parts by weight. The mixture is heated and stirred at 90°C to dissolve the resin and prepare an alkali-soluble resin varnish.

[0127] 40 parts by weight of the obtained water-based resin varnish, 10 parts by weight of water, and 50 parts by weight of white pigment were stirred and mixed, and then kneaded using a wet circulating mill to obtain a base ink for water-based inkjet printing.

[0128] (Water-based inkjet ink composition 1)

[0129] The obtained water-based inkjet ink mixture was stirred and mixed with 20 parts by weight of base ink, 24.2 parts by weight of water-dispersible resin, 20 parts by weight of glycerin, 10 parts by weight of propylene glycol, 1 part by weight of surfactant, and 4 parts by weight of water to obtain water-based inkjet ink composition 1 with a pigment concentration of 10% by weight and a pigment / alkali-soluble resin (mass) ratio of 10 / 2.

[0130] (Water-based inkjet ink composition 2)

[0131] The obtained water-based inkjet ink composition 2 was obtained by stirring and mixing 6 parts by mass of base ink, 24.2 parts by mass of water-dispersible resin, 25 parts by mass of glycerol, 10 parts by mass of propylene glycol, 1 part by mass of surfactant and 9 parts by mass of water to obtain water-based inkjet ink composition 2 with pigment concentration of 3% by mass and pigment / alkali-soluble resin (mass) = 10 / 2.

[0132] <Examples 1-15 and Comparative Examples 1-4>

[0133] According to the combination method shown in Table 1 below, each raw material was put into a beaker and mixed with a stirring device to prepare the cleaning solutions of Examples 1-15 and Comparative Examples 1-4 respectively.

[0134] Using the prepared cleaning liquid, according to the following evaluation methods, the re-dissolution evaluation, strong oscillation redispersion evaluation, and time-dependent redispersion evaluation were carried out on the dried films of the aqueous inkjet ink compositions 1 and 2. The results are shown in Table 1. It should be noted that in all evaluations of re-dissolution evaluation, strong oscillation redispersion evaluation, and time-dependent redispersion evaluation, an evaluation of 4 or more points was judged as qualified.

[0135] The pH of the prepared cleaning liquid was measured according to JIS K 6221.

[0136] In addition, the following various materials were used in the preparation of the cleaning liquid.

[0137] <First surfactant>

[0138] AMPHITOL 20N (lauryldimethylamine oxide, active ingredient 35% by mass, manufactured by Kao Corporation)

[0139] AMPHITOL 24B (lauryldimethylaminobetaine, active ingredient 26% by mass, manufactured by Kao Corporation)

[0140] AMPHITOL 20Y-B (2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazoline betaine, active ingredient 40% by mass, manufactured by Kao Corporation)

[0141] <Second surfactant>

[0142] (Anionic surfactant)

[0143] Emulsogen EPA073 (sodium polyoxyethylene alkyl ether (7EO), active ingredient 30% by mass, manufactured by Clariant)

[0144] LATEMUL E-118B (sodium polyoxyethylene alkyl ether sulfonate, active ingredient 26% by mass, manufactured by Kao Corporation)

[0145] (Nonionic surfactant)

[0146] Genapol X050 (polyoxyethylene isotridecyl ether (5EO), active ingredient 100% by mass, HLB 10, manufactured by Clariant)

[0147] Genapol X080 (polyoxyethylene isotridecyl ether (8EO), active ingredient 100% by mass, HLB 13, manufactured by Clariant)

[0148] Tergitol EH-3 (EO / PO polyalkylene glycol 2-ethylhexyl ether, active ingredient 95% by mass, HLB 7.9, manufactured by Dow Chemical Company)

[0149] Tergitol EH-9 (EO / PO polyalkylene glycol 2-ethylhexyl ether, active ingredient 90% by mass, HLB 12.5, manufactured by Dow Company)

[0150] (Other surfactants)

[0151] Triton H-55 (anionic surfactant, phosphate ester, active ingredient 50 parts by weight, manufactured by Dow Company)

[0152] Genapol X150 (nonionic surfactant, polyoxyethylene isotridecyl ether (15EO), active ingredient 100% by mass, HLB15, manufactured by Clariant)

[0153] Tergitol SA-9 (a nonionic surfactant, a linear EO / PO polyalkylene glycol natural alcohol ether, with an active ingredient content of 95% by mass, HLB 11.1, manufactured by Dow Chemical Company)

[0154] <Alkaline compounds>

[0155] potassium hydroxide

[0156] <Preservatives>

[0157] PROXEL GXL (manufactured by LONZA Japan Co., Ltd.)

[0158] <Water>

[0159] purified water

[0160] <Evaluation of Resolubility>

[0161] 0.2 g of the aqueous inkjet ink composition was dropped onto a glass plate and placed in an oven at 40°C for 1 minute. 0.03 g of the cleaning solution used in the examples and comparative examples was added to the resulting dried film (dried film), and the solubility of the dried film was evaluated according to the following evaluation criteria.

[0162] (Evaluation Criteria)

[0163] 5: The dry membrane begins to dissolve immediately after the cleaning solution is added, and dissolves completely.

[0164] 4: The dried film begins to dissolve immediately after the cleaning solution is added, with more than 70% dissolving, but a small amount of dried film remains.

[0165] 3: The dry film begins to dissolve immediately after the cleaning solution is added, with more than 40% but less than 70% dissolving.

[0166] 2: The dry film begins to dissolve immediately after the cleaning solution is added, with more than 20% but less than 40% dissolving.

[0167] 1: The dry film dissolved less than 20% even after the cleaning solution was added.

[0168] <Evaluation of Strong Oscillation Redispersion>

[0169] Place 10g of the aqueous inkjet ink composition into a container and centrifuge (Sigma 3-30KS) at 720G for 20 minutes. Remove the supernatant and store in an open system in a 50°C oven for 3 months.

[0170] One g of the dried film of the obtained ink was immersed in 10 g of the cleaning solution used in the examples and comparative examples, and the redispersibility of the dried film after three shakes in the shaker was evaluated according to the following evaluation criteria.

[0171] (Evaluation Criteria)

[0172] 5: The dried film began to redisperse immediately after being immersed in the cleaning solution, and was completely redispersed after shaking.

[0173] 4: The dried film begins to redisperse immediately after being immersed in the cleaning solution, and after shaking, all but a portion have been redispersed.

[0174] 3: After the dried film is immersed in the cleaning solution, it begins to redisperse by shaking. Except for a portion, it has already been redispersed.

[0175] 2: After the dried film is immersed in the cleaning solution, it begins to redisperse through shaking, and a portion of it is redispersed.

[0176] 1: The dried film did not redisperse even after being immersed in the cleaning solution and shaken.

[0177] <Evaluation of the Redispersibility of Time-Related Changes>

[0178] Place 10g of the aqueous inkjet ink composition into a container and centrifuge (Sigma 3-30KS) at 720G for 20 minutes. Remove the supernatant and store in an open system in a 50°C oven for 3 months.

[0179] 1g of the cleaning solution used in the examples and comparative examples was added dropwise to 1g of the dried film of the obtained ink, and the redispersibility of the dried film over time was evaluated according to the following evaluation criteria.

[0180] (Evaluation Criteria)

[0181] 5: The dried film began to redisperse immediately after the washing solution was added, and more than 80% of the dried film was redispersed after 2 hours.

[0182] 4: The dried film began to redisperse immediately after the washing solution was added. Two hours later, more than 50% but less than 80% of the dried film had been redispersed.

[0183] 3: The dried film began to redisperse immediately after the washing solution was added. Two hours later, more than 30% but less than 50% of the dried film was redispersed.

[0184] 2: The dried film was not redispersed immediately after the addition of the cleaning solution, but more than 10% but less than 30% of the dried film was redispersed 2 hours later.

[0185] 1: The dry film did not redisperse even when cleaning solution was added.

[0186] surface 1

[0187]

[0188] Cleaning solutions containing, in addition to the first surfactant, specific anionic and / or nonionic surfactants as second surfactants are excellent in all evaluations, including redispersibility evaluation, strong oscillation redispersibility evaluation, and time-dependent redispersibility evaluation.

[0189] On the other hand, in Comparative Example 1, which does not contain a second surfactant, Comparative Example 2, which contains an anionic surfactant as a phosphate ester, Comparative Example 3, which contains a nonionic surfactant with an HLB content of more than 14, and Comparative Example 4, which contains a nonionic surfactant with a linear structure, sufficient cleaning power is not achieved.

[0190] Industrial applicability

[0191] Based on the present invention, a cleaning fluid can be provided that can remove even white ink that has been fixed and bonded, and can improve the problem of poor ink ejection in inkjet printers.

Claims

1. A cleaning solution for cleaning water-based inkjet printing ink compositions, comprising a first surfactant, a second surfactant, and an alkaline compound. The first surfactant is an amphoteric surfactant. The second surfactant is sodium alkyl sulfate sulfonate and / or polyoxyethylene isotridecyl ether (5EO).

2. The cleaning solution as described in claim 1, wherein, The first surfactant is selected from at least one of the group consisting of lauryl dimethylamine oxide, lauryl dimethylaminoacetic acid betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazoline betaine.

3. The cleaning solution as described in claim 1 or 2, wherein, The content of the first surfactant relative to the total amount of the cleaning solution is 0.1 to 3% by mass.

4. The cleaning solution as described in claim 1 or 2, wherein, The content of the second surfactant relative to the total amount of the cleaning solution is 0.1 to 3% by mass.

5. The cleaning solution as described in claim 1 or 2, wherein, The alkaline compound is sodium hydroxide and / or potassium hydroxide.

6. The cleaning solution as described in claim 1 or 2, wherein, The pH value is 9–12.

7. The cleaning solution as described in claim 1 or 2, further comprising a preservative and water.

8. The cleaning solution as described in claim 1 or 2, wherein, The water-based inkjet printing ink composition comprises pigments and alkali-soluble resins with acid groups within their molecules.

9. The cleaning solution as described in claim 8, wherein, The pigment content relative to the total amount of the water-based inkjet printing ink composition is 3-12% by mass. The acid value of the alkali-soluble resin containing acid groups within the molecule is 100 mgKOH / g to 200 mgKOH / g.

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