JP2022124473A - White ink and inkjet recording method - Google Patents

Abstract

To provide an inkjet ink that exhibits high wettability to a non-absorbable medium and strikes a balance between re-solubility and water resistance, which are inconsistent properties; and a printed material that is made using the inkjet ink.SOLUTION: A white ink for inkjet contains a white pigment, water, a silicon- and/or fluorine-based surfactant, a dispersant and a fixing resin. The fixing resin is a resin obtained by polymerizing a monomer mixture containing butyl acrylate and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier. In the monomer mixture, the content of butyl acrylate is 0.1 mass% or more and less than 31.5 mass%.SELECTED DRAWING: None

Description

The present invention relates to a white ink, an inkjet recording method using the ink, and a recording medium to which the ink is attached.

A recording method using an ink jet printer, which is one of the representative methods among color recording methods, generates droplets of ink and attaches them to a recording medium such as paper to perform recording. In recent years, demand for industrial applications has increased, and support for various recording media is required.

In particular, for non-ink-absorbing media (hereinafter sometimes referred to as "non-absorbing media") typified by films, solvent inks containing organic solvents as main components and UV inks containing polymerizable monomers Development of ink and the like has progressed. However, these inks have many safety problems such as VOC and skin sensitization, and their applications are limited.

Therefore, as described in Patent Documents 1 to 5, water-based inks are currently being developed that can print highly durable images even on non-absorbent media by adding polymer fine particles and the like while using water as the main component. Development is booming. However, even if the inks obtained by these proposals are used, the water resistance of images printed on non-absorbent media such as PET (polyethylene terephthalate) and PP (polypropylene) is insufficient, and improvement is required. there is In order to improve the water resistance, it is necessary to increase the film-forming strength of the binder fixing agent containing fine polymer particles. For this reason, when the ink filled in the inkjet printer dries, solid matter is generated in the nozzles of the inkjet head and in the ink flow path, which causes clogging. When clogging occurs in the ink jet head in this manner, the ink cannot be stably discharged, resulting in a problem of deterioration in the image quality of the recorded image. In order to solve this problem, there is also a strong demand for the ability to easily wash off solid matter, even if it occurs in the ink jet head or the like. However, since the improvement in fixability and water resistance due to the formation of the above-described film is in conflict with the ability to be easily washed, an ink that satisfies both of these effects has not yet been proposed.

Japanese Patent No. 5504890 Japanese Patent No. 6295825 JP 2012-72354 A Japanese Patent No. 3257391 Japanese Patent No. 5825383

An object of the present invention is to provide an ink which has good wettability with respect to non-absorbent media and which has an excellent balance between re-solubility and water resistance, which contradict each other, and a printed material using the ink.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that an acrylic A resin obtained by polymerizing a monomer mixture containing butyl acid and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier, and acrylic acid in the monomer mixture. The inventors have found that an inkjet white ink having a butyl content of 0.1% by mass or more and less than 31.5% by mass can solve the above problems, and completed the present invention.
To achieve both resolubility and water resistance as described above, it is considered important to balance the flexibility and hardness of the dried and coated ink. This is because if the film-formed ink is too hard, the cleaning liquid will not penetrate into the ink, resulting in poor resolubility. be. In contrast, in the present invention, the fixing resin is obtained by polymerizing a monomer mixture containing butyl acrylate and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier. It is a resin that can be used, and the content of butyl acrylate in the monomer mixture is 0.1% by mass or more and less than 31.5% by mass, thereby optimizing the balance between the flexibility and hardness of the dry ink. , it is speculated that the desired performance could be exhibited.

That is, the present invention relates to the following 1) to 7).
1)
white pigment, water, silicone and/or fluorosurfactant, dispersant and fixing resin, wherein the fixing resin is at least one monomer selected from butyl acrylate and methyl methacrylate and methyl acrylate A resin obtained by polymerizing a monomer mixture containing white ink for
2)
The inkjet white ink according to 1), wherein the monomer mixture further comprises at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate.
3)
The inkjet white ink according to 1), wherein the monomer mixture further comprises at least two monomers selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate.
4)
The inkjet white ink according to any one of 1) to 3), further comprising a polyalkylene wax.
5)
An inkjet ink set comprising the inkjet white ink according to any one of 1) to 4) and another inkjet ink.
6)
A printing medium printed with the inkjet white ink according to any one of 1) to 4) or the inkjet ink set according to 5).
7)
Any one selected from the group consisting of the inkjet white ink according to any one of 1) to 4), the inkjet ink set according to 5), and the printing medium according to 6), Ink media set for inkjet.

ADVANTAGE OF THE INVENTION By this invention, the wettability with respect to non-absorbent media was favorable, and the white ink for inkjet which was excellent in ink re-solubility and the water resistance of the printed image was provided.

As used herein, "C.I." means "color index." In addition, in this specification, "%" and "parts", including those in Examples and the like, are expressed on a mass basis unless otherwise specified.
In addition, the terms "alkylene", "propylene" and "alkyl" are used herein to include both straight-chain and branched-chain structures unless otherwise specified. In addition, the white ink for inkjet may be abbreviated as ink.

The white ink for inkjet contains a white pigment, water, a silicon-based and/or fluorine-based surfactant, a dispersant, and a fixing resin, and the fixing resin is selected from butyl acrylate, methyl methacrylate, and methyl acrylate. 31. A resin obtained by polymerizing a monomer mixture containing at least one monomer and at least one of It is less than 5% by mass.

[water]
The above ink is a water-based ink containing water. As the water contained in the ink, water containing a small amount of impurities such as metal ions, that is, ion-exchanged water, distilled water, or the like is preferable. Such water can be prepared by known methods.
The water content is usually 30 to 80% by mass, preferably 35 to 80% by mass, more preferably 40 to 80% by mass, relative to the total mass of the ink according to this embodiment.

[White pigment]
The white pigment is not particularly limited as long as it can be visually recognized as white by the human eye. Examples include white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide; white hollow resin particles. , white organic pigments such as polymer particles; As a specific example, C.I. I. Pigment White 1 (basic lead carbonate), C.I. I. Pigment White 4 (zinc oxide), C.I. I. Pigment White 5 (a mixture of zinc sulfide and barium sulfate), C.I. I. Pigment White 6 (titanium oxide), C.I. I. Pigment White 6:1 (titanium oxide containing other metal oxides), C.I. I. Pigment White 7 (zinc sulfide), C.I. I. Pigment White 18 (calcium carbonate), C.I. I. Pigment White 19 (clay), C.I. I. Pigment White 20 (titanium mica), C.I. I. Pigment White 21 (barium sulfate), C.I. I. Pigment White 22 (natural barium sulfate), C.I. I. Pigment White 23 (Gloss White), C.I. I. Pigment White 24 (alumina white), C.I. I. Pigment White 25 (gypsum), C.I. I. Pigment White 26 (magnesium oxide/silicon oxide), C.I. I. Pigment White 27 (silica), C.I. I. Pigment White 28 (anhydrous calcium silicate) and the like. The white ink for inkjet may contain one or more of the white pigments. When two or more types are included, the mixing ratio between them can be arbitrarily set according to the purpose.

As the titanium oxide, titanium oxide surface-treated with silica or alumina (hereinafter sometimes abbreviated as surface-treated titanium oxide) can also be used. The surface-treated titanium oxide is preferable from the viewpoint of excellent color developability and hiding power. Moreover, the rutile type is preferable as the crystal type of the titanium oxide. Specific examples of titanium oxide products include Tipaque (registered trademark) R-580, R-670, R-780, R-850, R-855, CR-60 (manufactured by Ishihara Sangyo Co., Ltd.). ; JR-301, JR-403, JR-405, JR-804, JR-806, JR-600A, JR-800 and the like (manufactured by Tayca Corporation).

In addition, the above-mentioned white pigment can also preferably be used as a dispersion (slurry) in a dispersed state. A specific example of the product of the dispersion (slurry) is, for example, TF-5760 WHITE (D2B) (titanium oxide slurry manufactured by Dainichiseika Kogyo Co., Ltd., titanium oxide solid content concentration: 60%, average particle size: 300 nm. ) and the like.

In addition, the above-mentioned white pigment can be dispersed in a solid state using a dispersing agent to obtain a dispersion liquid.

In addition to the white pigment, the white ink for inkjet may further contain other colorants for the purpose of adjusting the degree of whiteness and lightness, etc., as long as the effects of the present invention are not impaired.

Examples of the white hollow resin particles include, for example, US Pat. No. 4,880,465, US Pat. Well-known white hollow resin particles described in JP-A-2003-200055 and the like can be used.

The total content of the white pigment in the total mass of the ink is preferably 1 to 30%, more preferably 1 to 15%, particularly preferably 2 to 10%.
The average particle size of the white pigment in the ink is preferably 30 nm to 700 nm, more preferably 200 nm to 650 nm. The average particle size as used herein refers to the average particle size of particles measured using a laser light scattering method.

The ink contains a silicon-based and/or fluorosurfactant.

Examples of the silicone surfactant include polyether-modified siloxane and polyether-modified polydimethylsiloxane. Specific examples of commercially available products include Dynol 960 and 980 manufactured by Air Products Co., Ltd.; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 manufactured by Nisshin Chemical Co., Ltd.; BYK-345, 347, 348, 349, 3455, LP-X23288, LP-X23289, LP-X23347 manufactured by BYK Additives &Instruments; TEGO Twin 4000, TEGO Wet KL 260, 250, manufactured by Evonic Tego Chemie 265, 270, 280 and the like. The content of the silicon-based surfactant in the ink is preferably 0.05% by mass or more and 2.0% by mass or less, and 0.1% by mass, as a solid content in the silicon-based surfactant. More preferably, it is not less than 1.5% by mass and not more than 1.5% by mass.

Examples of the fluorine-based surfactant include perfluoroalkylsulfonic acid compounds, perfluoroalkylcarboxylic acid compounds, perfluoroalkylphosphoric acid ester compounds, perfluoroalkylethylene oxide adducts, and perfluoroalkyl ether groups. Examples include polyoxyalkylene ether polymer compounds having chains. Specific examples of commercially available products include Capstone FS-30 and FS-31 (manufactured by Chemours). The content of the fluorosurfactant in the ink is preferably 0.01% by mass or more and 1.0% by mass or less as a solid content in the fluorosurfactant. More preferably, it is contained in an amount of not less than 0.8% by mass and not more than 0.8% by mass.

[Dispersant]
Examples of the dispersant include styrene and derivatives thereof; vinylnaphthalene and derivatives thereof; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; (meth)acrylic acid and derivatives thereof; derivatives; itaconic acid and its derivatives; faric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and derivatives thereof; and copolymers composed of monomers, one of which is hydrophilic. Hydrophilic monomers include monomers such as acrylic acid and methacrylic acid, in which a carboxyl group remains after polymerization.

Examples of the copolymer include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymers, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers, styrene-maleic acid copolymers, and the like. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethylene Glycol (meth)acrylate-(meth)acrylic acid copolymer is preferred; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid Acid ester-(meth)acrylic acid copolymers are more preferred; (meth)acrylic acid ester-(meth)acrylic acid copolymers are more preferred; and methacrylic acid ester-methacrylic acid copolymers are particularly preferred. Types of copolymers include, for example, block copolymers, random copolymers, and graft copolymers. These copolymers may be in the form of salts.

In this specification, the term "(meth)acryl" is used to include both "acryl" and "methacryl". The same applies to "(meth)acrylate" and the like.

The above dispersants can be synthesized or obtained commercially. Specific examples of commercially available products include styrene-acrylic copolymers such as Joncryl 62, 67, 68, 678, and 687 manufactured by BASF; polyacryl such as Aron AC-10SL manufactured by Toagosei Co., Ltd. acids and the like.

Dispersants obtained by synthesis preferably include, for example, AB block polymers disclosed in WO 2013/115071. Monomers constituting the A block of the AB block polymer disclosed in WO 2013/115071 are selected from (meth) acrylic acid and linear or branched C4 alkyl (meth) acrylates At least one type of monomer is preferably used, and at least one type of monomer selected from methacrylic acid and n-butyl methacrylate is preferred, and it is more preferred to use these two types of monomers together. Further, the monomer constituting the B block of the AB block polymer disclosed in WO 2013/115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, preferably benzyl methacrylate. Specific examples of AB block polymers include block copolymers disclosed in Synthesis Examples 3-8 of WO 2013/115071.

Although the weight average molecular weight (MW) of the dispersant is not particularly limited, it is preferably 3,000 to 50,000, more preferably 7,000 to 25,000. The mass average molecular weight of the dispersant can be measured by gel permeation chromatography (GPC method). Specifically, HLC-8320GPC (manufactured by Tosoh Corporation) is used as the GPC apparatus, and two columns of TSK gel Super Multipore HZ-H (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm) are used for elution. It can be measured using tetrahydrofuran as a liquid and TSK Standard (manufactured by Tosoh Corporation) as a standard sample.

Although the acid value is not particularly limited, it is preferably 50 to 300 KOHmg/g, more preferably 80 to 275 KOHmg/g, more preferably 80 to 250 KOHmg/g.

The above-mentioned dispersant can be used either in the state of being mixed with the above-mentioned white pigment, or in the state of covering part or all of the surface of the above-mentioned white pigment with the dispersant. It can also be used in the presence of a mixture of these states. The ratio of the total mass of the dispersant to the total mass of the white pigment (value represented by "total mass of dispersant/total mass of white pigment") is usually 0.01 to 1.0, preferably 0.01 to 0.6, more preferably 0.02 to 0.3.

[Fixing resin]
As the fixing resin, a resin obtained by polymerizing a monomer mixture containing butyl acrylate and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier is used. .

At least one monomer selected from methyl methacrylate and methyl acrylate may contain either one or both of them. From the viewpoint of improving resolubility, it preferably contains at least methyl methacrylate, and more preferably contains only methyl methacrylate.

The content of butyl acrylate is 0.1% by mass or more and less than 31.5% by mass, preferably 0.1 to 25% by mass, more preferably 1 to 25% by mass, based on the total mass of the monomer mixture. , more preferably 3 to 25% by mass, particularly preferably 4 to 22% by mass.

The total content of at least one monomer selected from methyl methacrylate and methyl acrylate is usually 0.1% by mass or more, preferably 10% by mass or more, and more, relative to the total mass of the monomer mixture. It is preferably 30 to 95% by mass, more preferably 50 to 90% by mass, particularly preferably 60 to 90% by mass, and most preferably 67 to 85% by mass.

In addition, the monomer mixture preferably further contains at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate, more preferably at least two monomers. . Among these, a combination of allyl methacrylate, butyl methacrylate and sodium styrenesulfonate, and a combination of allyl methacrylate and sodium styrenesulfonate are preferred.

When the monomer mixture contains at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate, the total content thereof is usually 0 relative to the total mass of the monomer mixture. .1 to 20% by mass, preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, still more preferably 0.5 to 7% by mass, particularly preferably 1 to 5% by mass.

Moreover, the monomer mixture may further contain other monomers than the above. Other monomers include, for example, methacrylic acid.
When the monomer mixture contains methacrylic acid, its content is usually 1 to 50% by mass, preferably 1 to 25% by mass, more preferably 1 to 15% by mass, based on the total mass of the monomer mixture. .

The fixing resin is obtained by polymerizing the above monomer mixture in the presence of a reactive emulsifier. Thus, by polymerizing the monomer mixture in the presence of a reactive emulsifier, an emulsion of the fixing resin can be obtained. When preparing the ink according to the present embodiment, it is preferable to use such an emulsion of the fixing resin.

A reactive emulsifier is an emulsifier having a radically polymerizable double bond in its molecule. The number of radically polymerizable double bonds is usually one.

Specific examples of reactive emulsifiers include polyoxyalkylene alkenyl ether ammonium sulfate, ether sulfate type ammonium, phosphoric acid ester, bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfate, 2-sodium sulfoethyl methacrylate, and alkoxypolyethylene glycol. maleic acid esters, and salts thereof. Specific examples of reactive emulsifiers include sodium alkylarylsulfosuccinate (manufactured by Sanyo Chemical Industries, Ltd., Eleminol JS-20), dipotassium alkenylsuccinate (manufactured by Kao Corporation, Latemul ASK), and polyoxyethylene alkylpropenylphenyl. Ether sulfate (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon HS-10), α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate ( ADEKA Co., Ltd., Adekaria Soap SE series such as Adekaria Soap SE-10N), polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ester ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon KH -1025 etc. Aqualon KH series), styrene sulfonate (manufactured by Tosoh Finechem Co., Ltd., Spinomer NaSS), α-[2-[(allyloxy)-1-(alkyloxymethyl)]ethyl]-ω-poly Oxyethylene sulfate ester salt (manufactured by ADEKA Co., Ltd., Adekari Soap SR series such as Adekari Soap SR-1025), polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) ether sulfate salt (Kao ( Co., Ltd., Latemul PD-104) and the like. Among these, the Adekari Soap SR series manufactured by ADEKA Corporation is preferable, and the Adekari Soap SR-1025 (that is, [({α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl ) Reaction formation of {C10-C14 branched chain alkanols with 1-(allyloxy)-2,3-epoxypropane, based on ethyl]-ω-hydroxypoly(n=1-100)(oxyethylene)} oxirane polyadduct) of the compound)) is more preferred.

The amount of the reactive emulsifier used when synthesizing the fixing resin is not particularly limited. As a standard of the amount to be used, it is usually 0.1 to 10% by mass, preferably 0.3 to 5% by mass, more preferably 0.5 to 3% by mass, more preferably 0.5 to 3% by mass, based on the total mass of the monomer mixture. It is 1 to 3% by mass. By using the reactive emulsifier within the above range, the fixing resin can be stably synthesized, and the viscosity of the fixing resin emulsion tends to be adjusted within a suitable range.

Incidentally, when synthesizing the fixing resin, an emulsifier other than the reactive emulsifier may be further used. Other emulsifiers include, for example, alkyl sulfates, alkyl allyl sulfates, alkyl sulfonates, alkyl allyl sulfonates, dialkyl sulfosuccinates, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, alkyl sulfonic acid anionic surfactants such as sodium; nonionic surfactants such as polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene carboxylic acid esters, polyoxyethylene glycol types, and polyoxyethylene propylene glycol types;4 secondary ammonium salts (alkyltrimethylammonium bromide, alkylpyridinium bromide, alkyltrimethylammonium chloride, alkylbenzylammonium chloride, imidazolinium laurate, etc.), pyridinium salts, imidazolinium salt-type cationic surfactants; . Among these, sodium dodecylbenzenesulfonate is preferred.

Moreover, a polymerization initiator can be used when synthesizing the fixing resin. Examples of polymerization initiators include persulfates such as ammonium persulfate, potassium persulfate and sodium persulfate; 2,2′-azobis[N-(2-hydroxyethyl)-2-methyl-propionamidine] dihydrochloride , 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis[2- (2-imidazolin-2-yl)propane], water-soluble azo polymerization initiators such as 4,4′-azobis(4-cyanovaleric acid); Among these, persulfates are preferred, ammonium persulfate and potassium persulfate are more preferred, and potassium persulfate is even more preferred.

Although the glass transition point of the fixing resin is not particularly limited, it is preferably 0° C. to 200° C., more preferably 80° C. to 150° C., more preferably 90° C. to 145° C., and 100° C. or higher. A temperature of less than 140° C. is particularly preferred.

The content of the fixing resin with respect to the total mass of the ink is preferably in the range of 0.1% to 30%, more preferably in the range of 1% to 20%, and more preferably in the range of 2% to 15%. more preferably, in the range of 3% to 10%, particularly preferably in the range of 5% to 7%.

The ink may further contain an organic solvent. The organic solvent is not particularly limited, but examples include C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol or tert-butanol; N,N-dimethylformamide or N,N-dimethyl carboxylic acid amides such as acetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone or N-methylpyrrolidin-2-one; 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexahydro cyclic ureas such as pyrimid-2-one; ketones, ketoalcohols or carbonates such as acetone, 2-methyl-2-hydroxypentan-4-one and ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol, Diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably molecular weight 400, 800, 1540 or higher), mono-, oligo- or polyalkylene glycols or thioglycols having C2-C6 alkylene units such as polypropylene glycol, thiodiglycol or dithiodiglycol; glycerin, diglycerin, hexane-1 , 2,6-triol, trimethylolpropane, etc.; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monopropyl ether Glycol ethers such as propylene glycol monomethyl ether (preferably C4-C10 mono-, di- or triethylene glycol ethers, and C4-C13 mono-, di- or tripropylene glycol ethers) ter); 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol , 2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, C5-C9 alkanediols; γ-butyrolactone or dimethylsulfoxide;
The organic solvent content is usually 0 to 60% by mass, preferably 1 to 60% by mass, more preferably 2 to 50% by mass, still more preferably 3 to 45% by mass, relative to the total mass of the ink according to the present embodiment. % by weight, particularly preferably 5 to 40% by weight.

The above inks require ink preparation agents such as antifungal agents, preservatives, pH adjusters, chelating reagents, rust inhibitors, antifoaming agents, water-soluble ultraviolet absorbers, antioxidants, resin emulsions, and waxes. can be included depending on As for the ink preparation agent, any one type or a plurality of types can be used, or a plurality of types can be used one by one, or a plurality of types can be used in combination. The content of the ink modifier in the ink, or, if the ink contains a plurality of the ink modifiers, the amount between each ink modifier can be arbitrarily set according to the purpose of the ink. be able to.

[Antifungal agent]
Specific examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one and salts thereof. .

[Preservative]
Examples of preservatives include organic sulfur, organic nitrogen sulfur, organic halogen, haloarylsulfone, iodopropargyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, and benzothiazole. , isothiazolines, dithiols, pyridine oxides, nitropropanes, organic tins, phenols, quaternary ammonium salts, triazines, thiazines, anilides, adamantanes, dithiocarbamates, brominated indanones, benzyl Compounds such as bromoacetate-based compounds and inorganic salt-based compounds are included.
Specific examples of organic halogen compounds include sodium pentachlorophenol.
Specific examples of pyridine oxide compounds include sodium 2-pyridinethiol-1-oxide.
Examples of isothiazolin compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5- chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, 2-methyl-4-isothiazolin-3-one calcium chloride and the like. be done.
Specific examples of other antiseptic and antifungal agents include anhydrous sodium acetate, sodium sorbate or sodium benzoate, trade names Proxel GXL (S), Proxel LV, and Proxel XL-2 (S) manufactured by Arch Chemicals. .

[pH adjuster]
Specific examples of pH adjusters include alkanolamines such as diethanolamine, triethanolamine and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide (ammonia water); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate. mentioned.

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

[anti-rust]
Specific examples of rust preventives include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate and dicyclohexylammonium nitrite.

[Antifoaming agent]
Examples of antifoaming agents include silicone-based, silica-mineral oil-based, olefin-based, acetylene-based, and the like. Examples of commercially available antifoaming agents include Surfynol DF37, DF58, DF110D, DF220, MD-20, Olefin SK-14, etc., all of which are manufactured by Shin-Etsu Chemical Co., Ltd.

[Water-soluble UV absorber]
Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone-based compounds, benzotriazole-based compounds, salicylic acid-based compounds, cinnamic acid-based compounds, and triazine-based compounds.

[Antioxidant]
Examples of antioxidants that can be used include various organic and metal complex anti-fading agents. Examples of the organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, and the like. .

[Resin emulsion]
By adding a resin emulsion to the ink in addition to the fixing resin, the image fastness such as water resistance, scratch resistance, and alcohol resistance of the image printed on the medium can be increased. In addition to the fixing resin, one or more types selected from polymers and waxes are preferable. However, a pigment dispersant is not included in the binder.
Examples of the polymer include urethane, polyester, acrylic, vinyl acetate, vinyl chloride, styrene-acrylic, acrylic-silicon, and styrene-butadiene polymers and emulsions containing them. Among these, polymers selected from urethane-based, acrylic-based, and styrene-butadiene-based polymers are preferred.
Commercially available products include, for example, Superflex 420, 470, 890 (urethane resin emulsion manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW-178, HW-163, HW-171, AP-20, AP-30, WLS-201, WLS-210 (urethane resin emulsion manufactured by DIC Corporation); 0569, 0850Z, 2108 (styrene-butadiene resin emulsion manufactured by JSR Corporation); AE980, AE981A, AE982, AE986B, AE104 (acrylic resin emulsion manufactured by ETEC Co., Ltd.) and the like.

[wax]
As the wax, a wax emulsion is preferable, and a water-based wax emulsion is more preferable. As waxes, natural waxes and synthetic waxes can be used.
Natural waxes include petroleum waxes such as paraffin wax and microcrystalline wax; lignite waxes such as montan wax; vegetable waxes such as carnauba wax and candelia wax; animal and plant waxes such as beeswax and lanolin. Examples include emulsions in which wax is dispersed in an aqueous medium.

Synthetic waxes include polyalkylene waxes (preferably poly-C2-C4 alkylene waxes), polyalkylene oxide waxes (preferably poly-C2-C4 alkylene oxide waxes), and paraffin waxes. Among them, at least one wax selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax and paraffin wax is preferable. The average particle size of the wax is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

In addition, as the wax, emulsified wax, "wax emulsion" can also be used. Commercially available products of the wax emulsion include CERAFLOUR 925, 929, 950, 991; AQUACER 498, 515; 526, 531, 537, 539, 552, 1547; AQUAMAT 208, 263, 272; KUE-100, 11 manufactured by Sanyo Chemical Co., Ltd.; HYTEC E-6500, 9015, 6400 manufactured by Toho Chemical Co., Ltd.;

When the mixing ratio of the fixing resin and the wax in the ink is represented by the ratio relationship of "fixing resin:wax", it is preferably in the range of 95:5 to 5:95 in terms of resin solid content, and 95 :5 to 30:70, more preferably 90:10 to 60:40.

The total content of the fixing resin and the resin emulsion with respect to the total mass of the ink is preferably in the range of 1% to 20%, more preferably in the range of 3% to 10%. When the total content of the fixing resin and the resin emulsion is 1% or more, the ink shows good fixability to the printing media. Further, when the total content of the fixing resin and the resin emulsion is 20% or less, the ejection property and storage stability of the ink are improved.

When preparing the above ink, a known manufacturing method can be used. As an example, for example, an aqueous dispersion is prepared from a white pigment and a dispersant, and water, various organic solvents, and, if necessary, an ink preparation agent are added to the dispersion and mixed to obtain an ink. and a method for preparing the
A known method can be used to prepare the dispersion. One example is the phase inversion emulsification method. Specifically, a dispersant is dissolved in a solvent such as 2-butanone, and an aqueous solution of a neutralizer is added to prepare an emulsion. A white pigment is added to the obtained emulsified liquid for dispersion treatment. The desired dispersion can be obtained by distilling off the solvent and part of the water from the thus obtained liquid under reduced pressure.
Dispersion treatment can be performed using, for example, a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, or the like. As an example, when a sand mill is used, beads having a particle diameter of about 0.01 mm to 1 mm can be used, and the filling rate of the beads can be appropriately set for dispersion treatment.
Operations such as filtration and/or centrifugation can be performed on the dispersion obtained as described above. By this operation, the size of the particle diameter of the particles contained in the dispersion can be made uniform.
If foaming occurs during preparation of the dispersion, a very small amount of a known silicone-based, acetylene glycol-based, or other antifoaming agent can be added.
Dispersion preparation methods other than the above include acid precipitation method, interfacial polymerization method, in-situ polymerization method, in-liquid curing coating method, coacervation (phase separation) method, in-liquid drying method, melting dispersion cooling method, An air suspension coating method, a spray drying method, and the like can be mentioned. As the method for preparing the dispersion liquid, a phase inversion emulsification method, an acid precipitation method, and an interfacial polymerization method are preferable.

The above inks can be prepared in the same manner as conventional pigment inks using conventionally known devices such as ball mills, sand mills, attritors, basket mills, and roll mills. During preparation, coarse particles are preferably removed using a membrane filter, a mesh filter, or the like.

It is preferable that the ink contains a small amount of inorganic impurities such as metal cation chlorides (eg, sodium chloride) and sulfates (eg, sodium sulfate). Such inorganic impurities are often contained in commercially available white pigments. The standard for the content of inorganic impurities is about 1% by mass or less with respect to the total mass of the white pigment, and the lower limit is ideally below the detection limit of the analytical instrument, that is, 0%.
As a method for obtaining a white pigment with less inorganic impurities, for example, a method using a reverse osmosis membrane; the solid of the white pigment is suspended and stirred in a mixed solvent of C1-C4 alcohol such as methanol and water, and the colored body is separated by filtration. and drying; or a method of exchanging and adsorbing inorganic impurities with an ion-exchange resin.
Moreover, it is preferable that the ink is subjected to microfiltration. For precision filtration, a membrane filter and/or glass filter paper or the like can be used. The pore size of a filter or the like for microfiltration is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

An ink set containing two or more of the above inks is also included in the present invention. The present invention also includes an ink set containing the ink described above and ink other than the ink described above.
The ink other than the above is not particularly limited as long as it has a different composition from the above ink, but preferably has a different hue from the above ink.

an inkjet ink media set, comprising any one selected from the group consisting of a print medium printed using the ink or the ink set, the inkjet ink, the inkjet ink set, and the print medium; and , a method for improving water resistance using any of the above ink, the above ink set, the above print media, or the above ink media set is also included in the present invention.

The method used for the inkjet printing is a method (hereinafter sometimes referred to as a recording method) in which droplets of the ink are ejected according to a print signal and adhered to a printing medium. There are no particular restrictions on the ink nozzles and the like of the inkjet printer for ejecting ink, and they can be appropriately selected according to the purpose.
As an inkjet printing method, a method in which a large number of inks with a low white pigment content in the ink are ejected in a small volume to improve image quality; A method for improving image quality using ink; and a method for improving fixability of white pigment to printing media by using both colorless and transparent ink and ink containing white pigment. The above ink can also be used as an ink containing a white pigment in these methods.

When carrying out the above inkjet printing method, a known method can be used. Examples thereof include a charge control method, a drop-on-demand method (also referred to as a pressure pulse method), an acoustic inkjet method, a thermal inkjet method, and the like. It is also possible to use a multi-pass method, a single-pass method (one-pass printing method), or the like.

Further, for example, a recording medium to which the above-described ink is adhered by the above-described recording method or the like is also included in the scope of the present invention. Although there are no particular restrictions on the recording medium, non-absorbent recording media are preferred, and non-absorbent recording media are particularly preferred. Examples of non-absorbent recording media include plain paper without an ink-receiving layer, media used for gravure printing and offset printing, art paper, coated paper, matte paper, cast paper, and the like. Non-absorbent recording media include PET (polyethylene terephthalate), PP (polypropylene), vinyl chloride sheets, glass, rubber, and the like.
When using a recording medium that does not have an ink-receiving layer, surface modification treatment is also preferably carried out.
As the surface modification treatment, a known surface modification treatment selected from corona discharge treatment, plasma treatment, and flame treatment is preferred. Here, it is generally known that the effect of surface modification treatment decreases with time. For this reason, the surface modification treatment step and the inkjet recording step are preferably performed continuously, and the surface modification treatment step is preferably performed immediately before the inkjet recording step.

When recording on a recording medium by the above ink jet recording method, for example, a container containing the above ink is set at a predetermined position of an ink jet printer, and recording can be performed on the recording medium by the above recording method.
In the ink jet recording method described above, the ink of the present invention can be used in combination with inks of various colors such as green, blue (or violet) and red (or orange), if necessary.
Each color of ink is injected into a respective container, and each container can be loaded into a predetermined position of an inkjet printer in the same manner as the container containing the ink and used for inkjet recording.
For the purpose of increasing the printing speed, the industrial inkjet printer preferably has a configuration of a line head type inkjet printer and performs single-pass printing. With the ink described above, it is possible to obtain a printed image having an excellent balance between coating and abrasion resistance even under such printing conditions.

Only one type of all the above-described components can be used. Moreover, it is also possible to select a plurality and a plurality of types as necessary and use them together.
For all of the above contents, a combination of preferable items is more preferable, and a combination of more preferable items is even more preferable. The same applies to combinations of preferable and more preferable items, combinations of more preferable and more preferable items, and the like.

The ink of the present invention is excellent in storage stability, redispersibility, various abrasion resistance, color developability, and saturation. Excellent in various robustness such as gas (for example, ozone gas resistance) properties. In addition, there is little unevenness in coating during image formation, and the image formability is also excellent.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples. "Parts" and "%" in the text are based on mass unless otherwise specified. All synthetic reactions and operations such as crystallization were carried out under stirring unless otherwise specified.
In the examples, when it was necessary to quantify the pigment solid content in the dispersion liquid, it was determined by the dry weight method using MS-70 manufactured by A&D Co., Ltd. The pigment solid content is a conversion value obtained by calculating only the pigment solid content from the total amount of solid content. Each ink described in the examples is included in the ink for inkjet described above.

[Preparation Example 1] Preparation of Fixing Resin Polymer Emulsions PEM-1 to PEM-9 A glass reaction vessel (capacity: 3 liters) equipped with a stirrer was equipped with a condenser, a thermometer, and a dropping funnel. 1.4 parts by weight of sodium sulfonate and 0.3 parts by weight of potassium persulfate were charged. After replacing the internal air with nitrogen, the internal temperature was adjusted to 80° C. while stirring, and 50 parts by weight of ion-exchanged water and Adekaria Soap SR-1025 (that is, [({α-[2- (allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1-100)(oxyethylene)}, {C10-C14 branched chain alkanol and 1 - (Allyloxy)-2,3-epoxypropane reaction product} oxirane polyadduct) sulfuric acid ester] mixture) 1 part by weight and 1 part by weight of sodium dodecylbenzenesulfonate, Table 1 In the middle, a total of 100 parts of the monomer components with each monomer ratio described in each column of "PEM-1" to "PEM-9" are mixed and stirred to make an emulsion, and the obtained emulsion is It was continuously dripped into the reaction vessel over 3 hours. During the dropwise addition, the reaction was carried out at 80° C. while introducing nitrogen. After the dropwise addition was completed, the mixture was further stirred at 85°C for 2 hours, and then cooled to 40°C. After cooling, 0.8 parts by weight of triethanolamine was added to obtain a fixing resin emulsion as a bluish-white suspension. The resulting fixing resin emulsions are named "PEM-1" to "PEM-9".

Table 1 below shows the solid content (%) and the glass transition point (Tg) of the fixing resin emulsions PEM-1 to PEM-9. The glass transition point is measured with a differential scanning calorimeter DSC Q2000 (TA Instruments) at a heating rate of 10°C/min. value.

The abbreviations of the respective monomers in Table 1 below represent the following. In addition, the numerical value in the column of each monomer represents the amount (parts) of the component used, and "-" means that the monomer is not used.
MMA: Methyl methacrylate MA: Methyl acrylate MAA: Methacrylic acid BA: Butyl acrylate AMA: Allyl methacrylate BMA: Butyl methacrylate Solid content (%): Solid content content of fixing resin in polymer emulsion

[Examples 1-10] and [Comparative Examples 1-2]: Preparation of inks.
After mixing each component shown in Table 2 below, the mixture was filtered through a 3 μm membrane filter to obtain inks of Examples 1 to 10 and Comparative Examples 1 and 2 for evaluation tests.
The abbreviations and the like in Table 2 represent the following, respectively. In addition, in Table 2 below, "-" means 0 part.
White dispersion: FUJI SP WHITE 1206: white pigment dispersion, pigment concentration 54%, manufactured by Fuji Pigment Co., Ltd. PG: propylene glycol.
DPnP: dipropylene glycol monopropyl ether.
TEA: triethanolamine.
BYK349: Silicon surfactant (BYK-349 manufactured by BYK).
FS31: fluorine-based surfactant (manufactured by Chemours, Capstone FS-31, 25% concentration aqueous solution).
AQ515: polyethylene wax (manufactured by BYK, AQUACER515, concentration 35%).

[Resolubility evaluation test]
20 μL of each of the inks of the above Examples and Comparative Examples was dropped onto a glass petri dish (flat petri dish, diameter 94 mm×height 22 mm, model number FS-90B manufactured by AS ONE) using a micropipette. After that, the ink was dried in a constant temperature bath at 60° C. for 1 hour to obtain a dried ink product. There, 10 g of the cleaning liquid described in Example 2 of International Publication No. 2020/175033 was prepared, poured in, and allowed to stand for 2 hours. After that, the petri dish was horizontally shaken 10 times/5 seconds with an amplitude of 2 cm, and the dried ink was visually observed to see if it had dissolved. was evaluated in five stages. The results are shown in Table 3 below.
(Resolubility Evaluation Criteria)
A: No solid matter was observed, and no deposit was found on the petri dish.
B: No solid matter was observed, but deposits remained on the petri dish.
C: Solids with a maximum diameter of less than 5 mm remain and deposits remain on the petri dish.
D: Solids with a maximum diameter of 5 mm or more remain and deposits remain on the petri dish.
E: The dried product did not dissolve at all and remained on the petri dish.

[Water scratch resistance evaluation test]
Bar coater No. 1 was applied using an automatic coating machine (PI-1210 manufactured by Tester Sangyo Co., Ltd.). 6 was used, and the entire surface was coated on Novaclear manufactured by Mitsubishi Chemical Corporation. After that, it was dried in a constant temperature bath at 70° C. for 2 minutes to obtain a test print. The obtained test print was cut into a rectangle of 15 cm long×5.0 cm wide to obtain a test piece. The abrasion resistance of each test piece thus obtained was evaluated using No. 1 manufactured by Yasuda Seiki Seisakusho. It was evaluated using a 428 Gakushingata Dyeing Friction Fastness Tester. As the evaluation criteria, the inkjet-recorded portion was rubbed 10 times with a wiper impregnated with ion-exchanged water, and the deterioration of the image was evaluated according to the following water abrasion resistance evaluation criteria A to E. The results are shown in Table 3 below.
(Evaluation criteria for water and scratch resistance)
A: Rubbing of the image cannot be confirmed.
B: The area of the white pigment rubbed off is less than 10% of the printed portion.
C: The area of the white pigment rubbed off is 10% or more and less than 20% of the printed portion.
D: The area of the white pigment rubbed off is 20% or more and less than 30% of the printed portion.
E: The area of the white pigment rubbed off is 30% or more of the printed portion.

[Inkjet printing evaluation test]
Each of the inks of Examples 1 to 10 above was used for image formation on paper and PET film using an inkjet head KJ4B-QA (manufactured by Kyocera Corporation). Good image formation was obtained.

From the results in Table 3 above, the inks of Examples are superior to the inks of Comparative Examples 1 and 2 in at least one of resolubility and water resistance. Therefore, it can be seen that the inks of Examples are highly practical inks having both re-solubility and water abrasion resistance.

The ink of the present invention has good wettability with respect to non-absorbent media, and can provide an inkjet ink having excellent ink resolubility and water resistance of printed images. It is extremely useful as

Claims (7)

white pigment, water, silicone and/or fluorosurfactant, dispersant and fixing resin, wherein the fixing resin is at least one monomer selected from butyl acrylate and methyl methacrylate and methyl acrylate A resin obtained by polymerizing a monomer mixture containing white ink for 2. The inkjet white ink of claim 1, wherein the monomer mixture further comprises at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrene sulfonate. 2. The inkjet white ink of claim 1, wherein the monomer mixture further comprises at least two monomers selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrene sulfonate. 4. The inkjet white ink according to any one of claims 1 to 3, further comprising a polyalkylene wax. An inkjet ink set comprising the inkjet white ink according to any one of claims 1 to 4 and another inkjet ink. A printing medium printed with the inkjet white ink according to any one of claims 1 to 4 or the inkjet ink set according to claim 5. Any one selected from the group consisting of the inkjet white ink according to any one of claims 1 to 4, the inkjet ink set according to claim 5, and the printing medium according to claim 6. Inkjet ink media set, including: