JP5518358B2 - Cleaning liquid and cleaning method - Google Patents

Description

  The present invention relates to a cleaning liquid and a cleaning method suitable for cleaning a manufacturing facility for a water-based ink composition containing a polymer.

  Water-based inks for inkjet recording generally contain dyes or pigments as colorants, and among them, encapsulated pigments, self-dispersing pigments, resin-dispersed pigments, surfactant-dispersed pigments, etc. are used. Yes.

  In encapsulated pigments and resin-dispersed pigments, polymers are used for the purpose of maintaining dispersion stability in the ink vehicle. In addition, water-insoluble polymer particles and the like are used for the purpose of improving printing performance. Addition is generally performed.

  In the process of manufacturing ink, if ink adheres to the manufacturing equipment, or polymer components contained in the ink adhere to the ink, and the dried ink is generated by drying, and once solidified. In addition, it is very difficult to clean and remove ink in a dry state. In addition, when ink dry matter is generated, ink is further deposited on the ink, and the ink accumulated during continuous production is peeled off, resulting in poor quality of the ink itself, post-filtering, etc. It causes problems such as abnormalities in equipment.

  On the other hand, ink cleaning waste liquid not only affects the manufacturing cost due to the waste liquid processing cost, but also has problems from the viewpoint of environmental impact, so efficient cleaning and reduction of cleaning waste liquid are important technologies. It is.

  As a technique related to the above, as a method for cleaning a water-based ink containing a polymer, as a nozzle cleaning liquid for an ink jet printer, a cleaning liquid containing a surfactant, a basic compound and water and having a pH of 9 or more, or pH 8 to 11 Have disclosed a maintenance liquid comprising an aqueous medium containing an alcohol amine and a maintenance method using the same (for example, see Patent Documents 1 and 2).

JP 2000-127419 A Japanese Patent No. 2000-109733

  However, with the above-described conventional cleaning liquids, etc., mainly the head nozzles that discharge ink of the ink jet printer are to be cleaned, and for the purpose of cleaning to remove locally residual ink in the nozzle portion every time it is discharged for maintenance. Therefore, it is not suitable as a cleaning liquid for cleaning manufacturing equipment such as a tank used for ink production, such as removal of dried ink that adheres to, adheres to, and adheres to the wall surface. In other words, these cleaning liquids are mixed from the head and have a composition that does not adversely affect the ink properties, so that the cleaning effect by repeated cleaning is small, and dry ink and a wide range of cleaning suitability are obtained. I can't.

  The present invention has been made in view of the above, an ink composition containing a polymer component, a cleaning liquid excellent in detergency, such as an ink manufacturing facility to which a thickened or dried product thereof has adhered, and an ink containing a polymer component It aims at providing the washing | cleaning method which can wash | clean the composition of an ink manufacturing facility to which the composition and its thickening thing, or a dry solid matter adhered with a small amount of washing | cleaning liquids, and makes it a subject to achieve this objective.

Specific means for achieving the above object are as follows.
<1> A cleaning solution for cleaning of manufacturing equipment used in the production of the aqueous ink composition containing a pigment and a polymer, and a nonionic surfactant of 5% by mass or more with respect to the basic compound and the total mass A cleaning liquid containing water.

< 2 > The cleaning liquid according to <1> , wherein the pH (25 ° C.) is 11 or more.

< 3 > A cleaning method in which the inside of a manufacturing facility used for manufacturing a water-based ink composition containing a pigment and a polymer is repeatedly cleaned using the cleaning liquid according to <1> or <2> .

< 4 > The cleaning method according to < 3 >, wherein the water-based ink composition contains polymer particles as the polymer.

According to the present invention, an ink composition containing a polymer component (especially polymer particles) and a cleaning liquid excellent in cleaning properties (preferably for inkjet ink) such as an ink production facility to which a thickened or dried product thereof is attached, and To provide a cleaning method (preferably for inkjet ink cleaning) capable of cleaning an ink composition containing a polymer component and an ink production facility to which a thickened or dried product thereof is attached with a small amount of cleaning liquid. it can.
As a result, it is possible to prevent contamination with dry solids and defective filtration during ink filtration, to reduce the risk of quality defects and improve manufacturing stability, and to reduce waste liquid, which in turn reduces environmental impact. Can also be increased.

It is a schematic block diagram which shows the structural example of the liquid adjustment apparatus for liquid-mixing aqueous ink.

Hereinafter, the cleaning liquid of the present invention and the cleaning method using the same will be described in detail.
The cleaning liquid and the cleaning method of the present invention are a cleaning liquid and a cleaning method for cleaning a water-based ink composition (including a thickened product and a dried product thereof) containing a pigment and a polymer. In particular,
The cleaning liquid of the present invention contains at least a basic compound, a surfactant of 5% by mass or more based on the total mass, and water, and is configured using other components as necessary. Further, the cleaning method of the present invention is used in the interior of a production facility used for producing a water-based ink composition containing a pigment and a polymer (for example, an inner wall of a preparation tank for preparing a water-based ink or a storage tank for storing ink). Is configured to repeatedly wash using a cleaning liquid containing a basic compound, 5% by mass or more of a surfactant and water based on the total mass. However, in the present invention, the cleaning object is a manufacturing facility used for manufacturing a water-based ink composition containing a pigment and a polymer, and a nonionic surfactant is applied as the surfactant.

  In the present invention, an aqueous ink composition containing a pigment and a polymer (hereinafter, also simply referred to as “ink”) and a cleaning liquid having a predetermined composition with respect to an object to be cleaned that is a thickened or dried product thereof. By repeatedly supplying a predetermined amount of ink, the cleaning effect of the cleaning liquid on the object to be cleaned can be further exerted, so that the ink adhering to the manufacturing facility can be cleaned and removed with a small amount of cleaning liquid. In particular, when the ink containing polymer particles as a polymer component and its thickened or dried product are washed, good cleaning properties are exhibited.

Each component constituting the cleaning liquid of the present invention will be described.
-Basic compounds-
The cleaning liquid of the present invention contains at least one basic compound. As the basic compound, either an inorganic or organic basic compound can be used.

  Preferable examples of the inorganic basic compound include hydroxides of alkali metals (for example, lithium, sodium, potassium, etc.). Of these, sodium hydroxide and potassium hydroxide are preferred because of their high versatility.

  Examples of organic basic compounds include mono-, di- or tri-lower alkylamines, mono-, di- or tri-lower alkanolamines, cyclic amines or diamines. As carbon number of the site | part of a lower alkyl or a lower alkanol, 1-6 are preferable, More preferably, it is 1-4. Further, the lower alkyl or lower alkanol moiety of the di-substituted product or tri-substituted product may be the same or different.

Examples of the mono-, di- or tri-lower alkylamine include mono-, di- or tri-methylamine, mono-, di- or tri-ethylamine, mono-, di- or tri-tert-butylamine. Can be mentioned. Examples of mono-, di- or tri-lower alkanolamines include mono-, di- or tri-methanolamine, mono-, di- or tri-ethanolamine. Examples of the cyclic amine include piperidine and pyrrolidine. Examples of the diamine include ethylene diamine and trimethylene diamine.
As the organic basic compound, tri-ethanolamine, piperidine, or ethylenediamine is preferable.

  An inorganic or organic basic compound can be used individually by 1 type or in combination of 2 or more types. Although there is no restriction | limiting in particular in content in the washing | cleaning liquid of a basic compound, As for the content, the quantity (25 degreeC; similarly below) that the pH of a washing | cleaning liquid becomes 11 or more is preferable, and the quantity that pH becomes 13 or more More preferred. By setting the content of the basic compound to an amount at which the pH is 11 or more, the cleaning property of the ink thickened product or the dried solid product becomes particularly good.

  pH is a value measured at 25 ° C. using a pH meter (HM-30G manufactured by Toa DKK Co., Ltd.).

  Specifically, the content of the inorganic basic compound is preferably 0.01 to 1 N (N), more preferably 0.1 to 1 N with respect to the total mass of the cleaning liquid. In particular, when the inorganic basic compound is an alkali metal hydroxide, the content thereof is preferably 0.01 to 1 N, more preferably 0.1 to 1 N of the cleaning liquid. In addition, the content of the organic basic compound is preferably 0.05 to 1 N, more preferably 0.1 to 1 N with respect to the cleaning liquid.

-Surfactant-
The cleaning liquid of the present invention contains at least one surfactant. The surfactant can be selected from anionic, cationic, amphoteric surfactants, and nonionic surfactants according to the purpose and composition.

  In this invention, surfactant is contained 5 mass% or more with respect to the total mass of a washing | cleaning liquid. When the content of the surfactant is less than 5% by mass, the cleaning effect of the water-based ink composition and its thickened or dried product is lowered. Especially, content of surfactant is 10 mass% or more with respect to the total mass of a washing | cleaning liquid at the point of the improvement of a repeating washing | cleaning effect. The upper limit of the surfactant content is preferably 15% by mass.

  Examples of the anionic surfactant include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acyl amino acids and salts thereof, N-acyl methyl taurates, alkyl sulfates. Polyoxyalkyl ether sulfate, alkyl sulfate polyoxyalkyl ether phosphate, rosin acid soap, castor oil sulfate ester, lauryl alcohol sulfate ester, alkylphenol type phosphate ester, alkyl type phosphate ester, alkylaryl sulfonate, diethyl Examples include sulfosuccinate, diethylhexyl sulfosuccinate, dioctyl sulfosuccinate, 2-vinylpyridine derivatives, and poly-4-vinylpyridine derivatives.

  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.

  Examples of the nonionic surfactant include polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, Ethers such as polyoxyalkylene alkyl ether, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate , Ester esters such as polyoxyethylene stearate or acetylene glycol surfactants (for example, 2,4,7,9-tetramethyl ether) Lu-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol (for example, manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol 104, 82, 465, 485, TG, etc., and Olphine E1010, etc.).

  The surfactant is preferably a surfactant that does not cause aggregation of pigment particles and polymer particles contained in the ink in consideration of the residue after washing. For example, if the charge of the ionic surfactant is different from the surface charge of the pigment-dispersed particles or polymer particles, the ionic surfactant should not be affected even if a slight amount of cleaning liquid is mixed into the ink. The charge (cationic or anionic) is preferably matched with the surface charge (cationic or anionic) of the pigment particles or polymer particles. In the present invention, a nonionic surfactant is preferred because it does not cause aggregation of pigment particles and polymer particles contained in the ink.

-Organic solvent-
It is preferable to add an organic solvent to the cleaning liquid of the present invention. By adding the organic solvent, the cleaning liquid can be given permeability to the thickened or dried product of the ink, and the cleaning effect is further improved.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, ether solvents, and the like. Examples of the alcohol solvent include methanol, ethanol, (iso) propanol, n-butanol, t-butanol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of ether solvents include dibutyl ether and dioxane.
Among these solvents, organic solvents having 5 or less carbon atoms are preferable, alcohol solvents having 5 or less carbon atoms are more preferable, and carbon solvents having 5 or less carbon atoms are more preferable. An alcohol solvent (particularly methanol) having a number of 3 or less is preferred.

  As addition amount in the washing | cleaning liquid of an organic solvent, 0.2 mass% or more is preferable with respect to the total mass of a washing | cleaning liquid, and 1-5 mass% is more preferable. When the addition of the organic solvent is 0.2% by mass or more, and further 1% by mass or more, it is possible to effectively enhance the cleaning effect of the ink thickened or dried product.

-Water-
The cleaning liquid of the present invention is an aqueous liquid, and is configured using, for example, distilled water or ion exchange water as water. The amount of water in the cleaning solution is not particularly limited.

  The cleaning liquid of the present invention can contain a viscosity modifier, a surface tension modifier, a preservative, and the like, if necessary, in addition to the above components.

~~ Water-based ink composition ~~
Here, the water-based ink composition to be cleaned in the present invention will be described.
The water-based ink composition is a colored liquid containing at least a pigment and a polymer as coloring components. When the polymer is contained, the ink tends to increase in viscosity and solidify with drying of the ink, and the cleaning effect of the cleaning liquid is more effective. Is done.

The pigment may be an organic pigment or an inorganic pigment. Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Examples of azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, and examples of polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments. Indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, and the like, and examples of dye chelates include basic dye chelates and acidic dye chelates.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black.

  The pigment may be dispersed by a resin dispersant. In this case, the pigment particles can be present in a fine particle size, and high dispersion stability can be obtained after dispersion. In the present invention, when the ink composition contains a polymer dispersant, the cleaning effect by the cleaning liquid tends to be reduced due to the increase in viscosity or solidification of the ink. Therefore, a pigment ink containing a pigment dispersed with the polymer dispersant is used. If this is the case, the effect of improving the cleaning property is further exhibited.

  The pigment does not necessarily need to be entirely coated with a resin, and the pigment may be in a state where at least a part of the particle surface is coated with a resin.

  The pigment resin dispersant (hereinafter also simply referred to as a dispersant) may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

The low molecular surfactant type dispersant can stably disperse the pigment in the aqueous solvent while keeping the ink at a low viscosity. The low molecular surfactant type dispersant is a low molecular weight dispersant having a molecular weight of 2,000 or less. The molecular weight of the low molecular surfactant type dispersant is preferably 100 to 2,000, and more preferably 200 to 2,000. The low molecular surfactant type dispersant has a structure including a hydrophilic group and a hydrophobic group. Moreover, the hydrophilic group and the hydrophobic group should just be independently contained 1 or more in 1 molecule, respectively, and may have multiple types of hydrophilic group and hydrophobic group. In addition, a linking group for linking a hydrophilic group and a hydrophobic group can be appropriately included.
The hydrophilic group is anionic, cationic, nonionic, or a betaine type that combines these. The anionic group may be any as long as it has a negative charge, but is preferably a phosphate group, phosphonic acid group, phosphinic acid group, sulfuric acid group, sulfonic acid group, sulfinic acid group or carboxylic acid group. More preferably a phosphoric acid group or a carboxylic acid group, and even more preferably a carboxylic acid group. The cationic group may be any as long as it has a positive charge, but is preferably an organic cationic substituent, and more preferably a nitrogen or phosphorus cationic group. Further, it is more preferably a pyridinium cation or an ammonium cation. Examples of the nonionic group include polyethylene oxide, polyglycerin, and a part of sugar unit. The hydrophilic group is preferably an anionic group.
The hydrophobic group has a hydrocarbon-based, fluorocarbon-based, silicone-based or the like structure, and is particularly preferably a hydrocarbon-based group. Further, the hydrophobic group may have a linear structure or a branched structure. Further, the hydrophobic group may have a single chain structure or a chain structure of more than this, and in the case of a structure of two or more chains, it may have a plurality of types of hydrophobic groups. The hydrophobic group is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 4 to 24 carbon atoms, and further preferably a hydrocarbon group having 6 to 20 carbon atoms.

Among the polymer dispersants, examples of the water-soluble dispersant include hydrophilic polymer compounds. For example, natural hydrophilic polymer compounds include plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, seaweeds such as alginic acid, carrageenan and agar. Examples include molecules, animal polymers such as gelatin, casein, albumin and collagen, and microorganism polymers such as xanthene gum and dextran.
In addition, in hydrophilic polymer compounds modified from natural products, fiber polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starch such as sodium starch glycolate and sodium starch phosphate And seaweed polymers such as sodium alginate, propylene glycol alginate, and the like. Further, synthetic hydrophilic polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, non-crosslinked polyacrylamide, polyacrylic acid or alkali metal salts thereof, water-soluble styrene acrylic resins, and the like. Acrylic resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium and amino And a polymer compound having a salt of a cationic functional group such as a group in the side chain, a natural polymer compound such as shellac, and the like.

  Among these, water-soluble dispersants introduced with carboxyl groups are hydrophilic polymers such as homopolymers of acrylic acid, methacrylic acid, styrene acrylic acid, and copolymers with monomers having other hydrophilic groups. Preferred as a compound.

  Among the polymer dispersants, as the water-insoluble dispersant, a polymer having both a hydrophobic portion and a hydrophilic portion can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include (meth) acrylate- (meth) acrylic acid copolymers, vinyl acetate-maleic acid copolymers, and styrene-maleic acid copolymers.

  In the present invention, it is dispersed together with the pigment in terms of the light resistance and quality of the image, the thickening of the ink, and the dissolution or redispersibility of the solidified product, while at the same time the cleaning effect by the cleaning liquid is more exhibited at the time of cleaning. It is preferable to include an agent, more preferably an organic pigment and a polymer dispersant, and still more preferably an organic pigment and a polymer dispersant containing a carboxyl group. Furthermore, the pigment contained as a colorant is coated with a polymer dispersant having a carboxyl group and is a water-insoluble water-dispersible pigment, from the viewpoint of thickening ink and dissolving or redispersing the solidified product. preferable.

Examples of the polymer include a water-insoluble resin that coats the pigment, and polymer particles that exist without coating the pigment.
As described above, the water-insoluble resin is a polymer for dispersing in a liquid by coating a pigment as a pigment dispersant. The polymer particles are dispersed particles that are dispersed and contained for fixing an ink image. In the present invention, an ink composition containing a pigment (which may contain a polymer dispersant) and polymer particles is particularly preferred in that the effect of washing with a washing liquid during washing is further exhibited.

  Examples of polymer particles include thermoplastic, thermosetting or modified acrylic, epoxy, polyurethane, polyether, polyamide, unsaturated polyester, phenol, silicone, or fluorine resins, chlorides, and the like. Amino resins such as polyvinyl resins such as vinyl, vinyl acetate, polyvinyl alcohol, or polyvinyl butyral, polyester resins such as alkyd resins and phthalic resins, melamine resins, melamine formaldehyde resins, aminoalkyd co-condensation resins, urea resins, urea resins, etc. Examples thereof include particles of a resin having an anionic group such as a system material, a copolymer or a mixture thereof. Among these, anionic acrylic resins include, for example, an acrylic monomer having an anionic group (anionic group-containing acrylic monomer) and, if necessary, other monomers copolymerizable with the anionic group-containing acrylic monomer. Obtained by polymerization in a solvent. Examples of the anionic group-containing acrylic monomer include an acrylic monomer having one or more selected from the group consisting of a carboxyl group, a sulfonic acid group, and a phosphonic group. Among them, an acrylic monomer having a carboxyl group (for example, acrylic acid) Methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid and the like), and acrylic acid or methacrylic acid is particularly preferred.

  The polymer particles are preferably self-dispersing polymer particles, more preferably self-dispersing polymer particles having a carboxyl group, from the viewpoints of ejection stability and liquid stability (particularly dispersion stability) when a pigment is used. Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (particularly acidic groups or salts thereof) of the polymer itself in the absence of other surfactants, By means of water-insoluble polymer particles containing no free emulsifier. The dispersed state is both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in a liquid state in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in a solid state in an aqueous medium. Is included. The water-insoluble polymer in the present invention is preferably a water-insoluble polymer that can be in a dispersed state in which the water-insoluble polymer is dispersed in a solid state from the viewpoint of aggregation speed and fixing property when an ink composition is used.

  The dispersion state of the self-dispersing polymer particles refers to a solution in which 30 g of a water-insoluble polymer is dissolved in 70 g of an organic solvent (for example, methyl ethyl ketone), a neutralizing agent that can neutralize 100% of the salt-forming groups of the water-insoluble polymer (for example, After the salt-forming group is anionic, sodium hydroxide, acetic acid if it is cationic) and 200 g of water are mixed and stirred (apparatus: stirring apparatus with stirring blades, rotation speed 200 rpm, 30 minutes, 25 ° C.) It means a state in which even after removing the organic solvent from the mixed solution, it can be visually confirmed that the dispersed state exists stably at 25 ° C. for at least one week.

  The water-insoluble polymer means a polymer having a dissolution amount of 10 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., and the dissolution amount is preferable. Is 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when neutralized with sodium hydroxide or acetic acid according to the kind of the salt-forming group of the water-insoluble polymer.

  The aqueous medium is configured to contain water, and may contain a hydrophilic organic solvent as necessary. In the present invention, it is preferably composed of water and 0.2% by mass or less of a hydrophilic organic solvent with respect to water, and more preferably composed of water.

  The main chain skeleton of the water-insoluble polymer is not particularly limited. For example, a vinyl polymer or a condensation polymer (epoxy resin, polyester, polyurethane, polyamide, cellulose, polyether, polyurea, polyimide, polycarbonate, etc.) is used. it can. Of these, vinyl polymers are particularly preferred. Preferable examples of the vinyl polymer and the monomer constituting the vinyl polymer include those described in JP-A Nos. 2001-181549 and 2002-88294. In addition, radical transfer of vinyl monomers using dissociable groups (or substituents that can be induced to dissociable groups), polymerization initiators, and iniferters, or dissociable groups on either initiators or terminators A vinyl polymer in which a dissociable group is introduced at the end of a polymer chain by ionic polymerization using a compound having (or a substituent that can be derived from a dissociable group) can also be used. Moreover, as a suitable example of the monomer which comprises a condensation type polymer and a condensation type polymer, what is described in Unexamined-Japanese-Patent No. 2001-247787 can be mentioned.

  The self-dispersing polymer particle is a water-insoluble polymer containing a hydrophilic constituent unit and a constituent unit derived from an aromatic group-containing monomer from the viewpoint of self-dispersibility and the improvement of the detergency of a low-detergent ink. It is preferable to include.

  The hydrophilic structural unit is not particularly limited as long as it is derived from the hydrophilic group-containing monomer, and the hydrophilic group is from the viewpoint of promoting self-dispersion, and from the viewpoint of stability of the formed emulsified or dispersed state. A dissociable group is preferable, and an anionic dissociative group is more preferable. Examples of the dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group, and a carboxyl group is preferable from the viewpoint of fixability when an ink composition is formed. Among these, from the viewpoints of self-dispersibility and aggregation, the hydrophilic group-containing monomer is preferably a dissociable group-containing monomer, and a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond is preferable. Examples of the dissociable group-containing monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

  Specific examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Specific examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. It is done. Specific examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2- Examples include acryloyloxyethyl phosphate. Of the dissociable group-containing monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

  The aromatic group-containing monomer is not particularly limited as long as it is a compound containing an aromatic group and a polymerizable group. The aromatic group may be a group derived from an aromatic hydrocarbon or a group derived from an aromatic heterocyclic ring. From the viewpoint of particle shape stability in an aqueous medium, Derived aromatic groups are preferred. The polymerizable group may be either a condensation polymerizable or addition polymerizable polymerizable group, and is preferably a group containing an ethylenically unsaturated bond.

  The aromatic group-containing monomer is preferably a monomer having an aromatic group derived from an aromatic hydrocarbon and an ethylenically unsaturated bond. Examples of the aromatic group-containing monomer include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, and a styrene monomer. Among them, an aromatic group-containing (meth) acrylate monomer is preferable, and at least one selected from phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate is more preferable, phenoxyethyl (meth) acrylate, More preferred is benzyl (meth) acrylate.

  Next, a method for cleaning using the cleaning liquid of the present invention will be described with reference to FIG. 1 as an example of cleaning the ink preparation tank. FIG. 1 is a schematic configuration diagram illustrating a configuration example of a liquid preparation device for preparing a water-based ink by mixing and stirring a pigment, a polymer, and other components as necessary.

  As shown in FIG. 1, the liquid preparation tank 1 has two propellers and includes a stirring bar 6 attached to the top so as to be rotatable at a desired speed. When, for example, water, a pigment such as a water-insoluble pigment, an organic solvent, and polymer particles such as a polymer latex (and other components as necessary) are charged, the stirring is performed by rotating the stirring rod 6, Various components can be mixed to prepare aqueous ink. For example, after mixing water or an organic solvent first, the stirring rod 6 is rotated to start stirring, and components such as pigments and polymer particles are added while stirring, or after all the desired components are added, the stirring rod For example, the stirring can be started by rotating 6.

  An injection nozzle 2 is attached to the top of the liquid preparation tank 1 to inject the cleaning liquid into a wide angle and supply the cleaning liquid into the liquid preparation tank. When the cleaning liquid is supplied to the ejection nozzle 2, the cleaning liquid is ejected by the ejection nozzle 2 so as to be uniformly supplied to the inner wall of the tank, so that the ink adhering to the inner wall of the tank can be removed. .

  The supply of the cleaning liquid from the spray nozzle can be suitably performed by spraying in a shower form or a spray form, for example. In this way, a flow of the cleaning liquid is formed in a wide area of the inner wall of the tank, and the cleaning liquid that comes into contact with the attached ink is replaced in a short time, so that the cleaning performance can be improved. The spray nozzle is preferably capable of supplying the cleaning liquid to the entire inner wall of the tank. For example, a shower nozzle or a spray nozzle having a porous spray surface can be used.

  Cleaning is preferably performed at a liquid amount per unit time supplied to the tank wall surface (object to be cleaned) of the cleaning liquid of 50 to 300 L / min. When the amount of the liquid is within the above range, it is possible to effectively remove and remove the ink thickened and dried solids by using the cleaning liquid of the present invention.

  A liquid discharge port 3 is provided at the bottom of the liquid preparation tank 1, and one end of a discharge pipe 11 for discharging the liquid in the liquid preparation tank is connected to the liquid discharge port 3.

  The buffer tank 5 is a storage tank capable of storing 100 L (liter) of cleaning liquid. The buffer tank 5 is connected to the other end of the discharge pipe 11 so that the cleaning liquid discharged from the discharge pipe 11 can be temporarily stored.

  The buffer tank 5 is connected to an injection nozzle 2 attached to the top of the liquid preparation tank 1 via a supply pipe 12, and the liquid in the buffer tank 5 is injected into the supply pipe 12 in the middle of the supply pipe 12. A liquid feed pump 4 for feeding liquid to 2 is attached.

  In this way, the discharge pipe 11, the buffer tank 5, and the supply pipe 12 are provided between the injection nozzle 2 and the liquid discharge port 3 of the liquid preparation tank 1, and the injection nozzle 2 and the liquid discharge port 3 are connected via these. By connecting, the circulation system which can repeat continuously washing | cleaning and circulation of the washing | cleaning liquid used for washing | cleaning is constructed | assembled.

  When the liquid preparation device configured as shown in FIG. 1 is started, first, for example, a water-insoluble pigment, a polymer latex, water, and an organic solvent are introduced at a predetermined timing, mixed, and stirred to prepare aqueous ink. The liquid ink thus prepared is discharged out of the tank. Thereafter, for example, after performing a liquid preparation operation a predetermined number of times, the liquid feed pump 4 is operated to inject the cleaning liquid into the liquid preparation tank 1 from the injection nozzle 2. The sprayed cleaning liquid is continuously supplied uniformly to the tank inner wall. At this time, the sprayed cleaning liquid flows down to the bottom while cleaning the surface along the inner wall of the tank, and the cleaning liquid accumulated on the bottom is discharged from the liquid discharge port 3 and once stored in the buffer tank 5 and then supplied again. It circulates through the piping 12 and is sprayed from the spray nozzle 2 and used for cleaning. In this way, by adopting a configuration in which a predetermined amount of cleaning liquid can be circulated and used to repeatedly clean the tank wall surface, the cleaning ability of the cleaning liquid is effectively exerted, and an ink (and a polymer component) with a smaller amount of cleaning liquid than in the past (and Adhesion of the thickened product and the dried product) can be effectively removed.

  In the present invention, among the above-described aqueous ink compositions containing pigments and polymer particles, and their thickened and dried products, the alkali metal hydroxide and the total mass are 10% by mass or more and 15% by mass or more. A mode in which a cleaning liquid containing a nonionic surfactant having a mass% or less, an alcohol solvent having 3 or less carbon atoms (preferably 1 to 5 mass% with respect to the total mass) and water is repeatedly used by circulation. Is particularly preferred.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1
-Preparation of cleaning solution-
A cleaning liquid was prepared by mixing and stirring components having the following composition at 25 ° C. for 1 hour. The pH measured at 25 ° C. using a pH meter (HM-30G manufactured by Toa DKK Co., Ltd.) was 12.85.
<Composition>
・ Olefin E 1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 5% by mass
・ 0.1N sodium hydroxide aqueous solution: 0.4% by mass (in terms of NaOH)
・ Methanol: 1% by mass
・ Distilled water: Remaining amount for the total amount to be 100% by mass

-Preparation of pigment ink-
Next, an evaluation ink was prepared as described below.
First, Cyanine Blue A220 (cyan pigment, manufactured by Dainichi Seika Kogyo Co., Ltd.) 15% by mass, polyvinyl pyrrolidone 8% by mass, and distilled water 77% by mass, sand grinder mill (manufactured by IMEX) with 0.1 mm diameter beads. Was dispersed at 1500 rpm for 8 hours, and the resulting dispersion was filtered through a 200 mesh filter to prepare a cyan pigment dispersion.

Subsequently, using the obtained cyan pigment dispersion, various components were mixed so as to have the following composition to prepare a cyan pigment ink (cyan ink 1).
<Composition of cyan ink 1>
・ Cyan pigment dispersion: 15% by mass
・ Glycerin: 10% by mass
・ Triethylene glycol monobutyl ether: 7% by mass
・ Olfin E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 2% by mass
・ Ion exchange water: 66% by mass

-Evaluation-
A SUS316 plate (3 cm × 4 cm) was immersed in the obtained cyan ink 1 and allowed to stand at room temperature for 2 hours in the air under a pressure of 0.1 MPa and dried to dry the ink for cleaning evaluation. It was set as thing (1).

The SUS sample provided with the dried ink for cleaning evaluation (1) was repeatedly washed with 5 ml of the above-described cleaning liquid (25 ° C.) for 3 minutes to perform a cleaning test. After finishing washing, the SUS sample was visually evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1 below.
<Evaluation criteria>
5: Repeatedly no ink dry solids could be confirmed at the initial stage of washing.
4: Ink was not confirmed at all during the repetition.
3: After repeated repeated washing, no dried ink was confirmed.
2: It was confirmed slightly that the dried ink remained.
1: No change was observed in the dried ink before and after washing.

(Example 2)
In Example 1, except that the composition of the cleaning liquid was changed to the following composition, a cleaning liquid was prepared, and a cleaning test and evaluation were performed in the same manner as in Example 1. The pH measured in the same manner as in Example 1 was 12.86. The evaluation results are shown in Table 1 below.
<Composition>
・ Olefin E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 5% by mass
・ 0.1N sodium hydroxide aqueous solution: 0.4% by mass (in terms of NaOH)
・ Distilled water: Remaining amount for the total amount to be 100% by mass

(Example 3)
In Example 1, except that the composition of the cleaning liquid was changed to the following composition, a cleaning liquid was prepared, and a cleaning test and evaluation were performed in the same manner as in Example 1. The pH measured in the same manner as in Example 1 was 10.96. The evaluation results are shown in Table 1 below.
<Composition>
・ Olefin E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 5% by mass
-0.001N sodium hydroxide aqueous solution ... 0.004 mass% (NaOH conversion)
・ Distilled water: Remaining amount for the total amount to be 100% by mass

Example 4
In Example 1, except that the amount of olefin E1010 in the composition of the cleaning liquid was changed from 5% by mass to 10% by mass, a cleaning liquid was prepared, and the cleaning test and evaluation were performed in the same manner as in Example 1. . The pH measured in the same manner as in Example 1 was 12.79. The evaluation results are shown in Table 1 below.

(Example 5)
In Example 4, the washing test and the evaluation were performed in the same manner as in Example 4 except that the dried ink (1) was replaced with the dried ink (2) described below. The evaluation results are shown in Table 1 below.

-Preparation of dried ink-
Using the cyan pigment dispersion prepared in Example 1, various components were mixed so as to have the following composition to prepare a cyan pigment ink (cyan ink 2). A SUS316 plate (3 cm × 4 cm) was immersed in the obtained cyan ink 2 and allowed to stand for 2 hours at room temperature under a pressure of 0.1 MPa in the air and dried to dry the ink for cleaning evaluation. It was set as thing (2).
<Composition of cyan ink 2>
・ Cyan pigment dispersion: 15% by mass
・ Glycerin: 10% by mass
・ Triethylene glycol monobutyl ether: 7% by mass
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 2% by mass
・ Jonkrill 538J (manufactured by BASF Japan) ... 15% by mass
・ Ion exchange water: 41% by mass

(Comparative Example 1)
In Example 1, except that the composition of the cleaning liquid was changed to the following composition, a cleaning liquid was prepared, and a cleaning test and evaluation were performed in the same manner as in Example 1. The pH measured in the same manner as in Example 1 was 6.98. The evaluation results are shown in Table 1 below.
<Composition>
・ Olefin E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 5% by mass
・ Distilled water: 95% by mass

(Comparative Example 2)
In Example 1, except that the composition of the cleaning liquid was changed to the following composition, a cleaning liquid was prepared, and a cleaning test and evaluation were performed in the same manner as in Example 1. The pH measured in the same manner as in Example 1 was 6.69. The evaluation results are shown in Table 1 below.
<Composition>
・ Sodium oleate (surfactant): 5% by mass
・ Distilled water: 95% by mass

(Comparative Example 3)
A cleaning liquid was prepared in the same manner as in Example 1 except that the cleaning liquid was changed to a 0.1N sodium hydroxide aqueous solution (composition: NaOH 100%) in Example 1, and a cleaning test and evaluation were performed. Moreover, pH measured like Example 1 is 12.98. The evaluation results are shown in Table 1 below.

(Comparative Example 4)
In Example 1, except that the composition of the cleaning liquid was changed to the following composition, a cleaning liquid was prepared, and a cleaning test and evaluation were performed in the same manner as in Example 1. The pH measured in the same manner as in Example 1 was 12.89. The evaluation results are shown in Table 1 below.
<Composition>
・ Olefin E1010 (manufactured by Nissin Chemical Industry Co., Ltd .; surfactant): 1% by mass
・ 0.1N sodium hydroxide aqueous solution: 0.4% by mass (in terms of NaOH)
・ Distilled water: Remaining amount for the total amount to be 100% by mass

(Comparative Example 5)
In Example 1, except that the amount of olefin E1010 in the composition of the cleaning liquid was changed from 5% by mass to 3% by mass, a cleaning liquid was prepared, and a cleaning test and evaluation were performed. The pH measured in the same manner as in Example 1 was 12.95. The evaluation results are shown in Table 1 below.

  As shown in Table 1, in the examples, the dryness of the solid matter fixed to the SUS plate was excellent. Thereby, when manufacturing ink with the equipment which performed washing, the number of coarse particles can be reduced before the filtration process which filters coarse particles. In contrast, the comparative example was inferior in the cleaning effect.

Claims (4)

A cleaning solution for cleaning of manufacturing equipment used in the production of the aqueous ink composition containing a pigment and a polymer, and water non-ionic surfactant than 5 wt% with respect to the basic compound and the total mass Contains cleaning solution. cleaning solution of claim 1 pH (25 ° C.) is characterized in that 11 or more. A cleaning method for repeatedly cleaning the inside of a manufacturing facility used for manufacturing a water-based ink composition containing a pigment and a polymer, using the cleaning liquid according to claim 1 or 2 in a circulating manner. The cleaning method according to claim 3 , wherein the water-based ink composition contains polymer particles as the polymer.

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