Block polymer for pretreatment liquid and pretreatment liquid using the same

Abstract

To provide a block polymer for a pretreatment liquid which, in printing on package packaging and label materials, enables favorable ejection stability from an inkjet head and exhibits excellent water resistance and alcohol resistance.SOLUTION: A block polymer for a pretreatment liquid used together with an aqueous inkjet ink has a hydrophilic unit (b-1) and a hydrophobic unit (b-2). A mass ratio of the hydrophilic unit (b-1) to the hydrophobic unit (b-2) is 10:90 to 70:30. A number-average molecular weight is 8,000 to 30,000. An average particle diameter is 30 to 150 nm. The hydrophilic unit (b-1) contains 5 to 45 mass% of a structural unit represented by the formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a block polymer for a pretreatment liquid, a pretreatment liquid using the same, an aqueous inkjet ink set, and a printed material. [Background technology]

[0002] Inkjet printing, a type of digital printing method, involves ejecting and landing tiny ink droplets from an inkjet head onto a substrate, which is a print medium, to form images or characters (hereinafter collectively referred to as "printed matter") on the print medium. Compared to other digital printing methods, inkjet printing is superior in terms of the size and cost of the printing device, running costs during printing, and ease of full-color printing, and has recently been increasingly used in industrial printing applications.

[0003] The inks used in inkjet printing methods vary widely, including oil-based, solvent-based, active energy ray-curable, and water-based inks. Until now, solvent-based and active energy ray-curable inks have been used for industrial printing applications. However, in recent years, there has been an increasing demand for water-based inks (also called aqueous inks) due to concerns about and responses to harmful effects on the environment and people.

[0004]

[0003] In terms of aesthetic appeal, content protection, and long-term information display, substrates used for packaging and label materials for daily necessities require printed matter with properties durable enough for practical use on impermeable substrates such as art paper and coated paper, and non-permeable substrates such as polyolefin and polyethylene terephthalate (PET) films. In particular, as the range of uses for inkjet printing has expanded in recent years, there has been a demand for inkjet printing to be compatible with such packaging applications.

[0005] When printing on poorly permeable or non-permeable substrates used for packaging and label materials, the ink droplets have difficulty penetrating and being absorbed into the substrate after landing, preventing drying through penetration, resulting in problems such as color bleeding and uneven color, which impairs the print quality.

[0006] Pretreatment liquids are known to address the problem of impaired print quality. Generally, two types of pretreatment liquids for aqueous inkjet inks are known: one that forms a layer (ink-receiving layer) that absorbs liquid components in the aqueous inkjet ink and improves drying properties (see Patent Documents 1 and 2), and one that forms a layer (ink-aggregating layer) that prevents bleeding between droplets and color unevenness and improves print quality by intentionally agglomerating solid components contained in the aqueous inkjet ink, such as colorants and resins (see Patent Documents 3 to 5).

[0007] As a printing method for these pretreatment liquids, gravure coating, flexographic roll coating, kiss coating, spray coating, curtain coating, blade coating, reverse roll coating, etc. are commonly used, and the pretreatment liquid is applied to the entire surface of the substrate, because this method is compatible with various images printed by inkjet printing and is cost-effective.

[0008] However, there is no need to apply pretreatment liquid to areas where the inkjet ink image is not printed (also known as non-image areas), which simply increases the consumption of pretreatment liquid. Furthermore, it is necessary to incorporate two different printing methods, the method for printing the pretreatment liquid and the inkjet method for printing the image, into a single device, which causes problems such as an increase in the size of the printing device and running costs.

[0009] To address this issue, pretreatment liquids for inkjet printing have been investigated. Most of these involve forming an ink aggregation layer that intentionally aggregates the solid components contained in the inkjet ink to prevent bleeding between droplets and color unevenness, and these are cationic materials that have an aggregation effect on anionic colorants and pigment dispersions (see Patent Documents 6 and 7).

[0010] On the other hand, printed materials using aqueous inks have poor resistance to liquids such as water and alcohol, resulting in problems such as the ink coating rubbing off and image bleeding. In particular, printed materials used for packaging, label materials, and the like require strong water resistance, alcohol resistance, and abrasion resistance from the pretreatment liquid coating layer, just like the ink layer that forms the image area. This is because, even if the ink layer coating is strong, if the pretreatment layer between the substrate and the ink layer is weak, the ink layer will peel off along with the pretreatment layer.

[0011] In response to this, emulsion resin particles for aqueous inkjet inks have been investigated, which have excellent water resistance and abrasion resistance and can form a tough coating film (see Patent Documents 8 and 9). However, while emulsion resin particles have excellent water resistance, they are not soluble in water, which means they tend to precipitate on the nozzle surface of the inkjet head, reducing ejection stability. Furthermore, if the ink adheres to the nozzle, the nozzle becomes clogged, making ejection impossible. In particular, in the one-pass inkjet printing method (also known as the "line printing method," but hereinafter abbreviated as the "one-pass printing method"), the blockage of just one nozzle can cause major image defects.

[0012] Similarly, emulsion resin particles have been investigated for pretreatment liquids that improve print quality (see Patent Document 10). However, when printing using a one-pass inkjet printing method, there is a problem of reduced ejection stability, similar to the case of aqueous inks used to form images. Furthermore, while Patent Document 10 improves the adhesion between the PET substrate and the pretreatment layer, problems arise, such as insufficient water friction resistance when wet and low resistance to alcohol. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-238422 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-335084 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-074655 [Patent Document 4] Japanese Patent Application Publication No. 2016-168782 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-247469 [Patent Document 6] Japanese Patent Application Laid-Open No. 2000-281947 [Patent Document 7] Japanese Patent Application Laid-Open No. 2011-127001 [Patent Document 8] Japanese Patent Application Publication No. 2019-038117 [Patent Document 9] Japanese Patent Application Laid-Open No. 2015-147919 [Patent Document 10] International Publication No. 2016-185822 Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a block polymer for a pretreatment liquid, a pretreatment liquid, and a printed matter that have excellent ejection stability from the nozzles of an inkjet head, and that also have excellent water resistance, abrasion resistance, and alcohol resistance, even when printing on poorly permeable substrates or non-permeable substrates used for packaging and label materials.

[0015] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a block polymer for a pre-treatment liquid having the following structure. [Means for solving the problem]

[0016] That is, the inventor The present invention relates to a block polymer (B) for a pretreatment liquid to be used together with an aqueous inkjet ink, the block polymer (B) having a hydrophilic unit (b-1) and a hydrophobic unit (b-2), wherein the mass ratio of the hydrophilic unit (b-1) to the hydrophobic unit (b-2) is 10:90 to 70:30, the hydrophilic unit (b-1) contains a structural unit represented by formula (1) in an amount of 5 to 45 mass % relative to the total mass % of the block polymer (B), and the block polymer (B) has a number average molecular weight of 8,000 to 30,000 and an average particle size of 30 to 150 nm. Formula (1) [ka] (In formula (1), R 1 represents a hydrogen atom or a methyl group, Y represents an oxygen atom or -NH-, Z represents a hydroxyl group or an alkylene group which may contain an oxygen atom, R 2 , R 3 , R 4 each independently represents an aliphatic hydrocarbon or an aromatic hydrocarbon which may contain a hydroxyl group or an oxygen atom.

[0017] The present invention also relates to a pre-treatment liquid containing the block polymer (B).

[0018] The present invention also provides a polymerizable composition comprising the block polymer (B) and a water-soluble cationic resin (A), The pre-treatment liquid is characterized in that the water-soluble cationic resin (A) contains the structural unit represented by formula (2) in an amount of 50 to 100% by mass relative to the total mass of the water-soluble cationic resin (A). Formula (2) [ka] (In formula (2), R 5 represents a hydrogen atom or a methyl group, L represents an oxygen atom, -NH-, or -OCHCH(OH)-, and R6 , R 7 , R 8 each independently represents a hydrocarbon group having 1 to 8 carbon atoms, X- represents a monovalent anion, and n represents an integer of 1 to 6.

[0019] The present invention also relates to a pretreatment liquid for use in printing by an inkjet recording method.

[0020] The present invention also relates to an aqueous inkjet ink set comprising a pretreatment liquid and an aqueous inkjet ink.

[0021] The present invention also relates to a printed material obtained by printing a pretreatment liquid and one or more types of aqueous inkjet inks sequentially onto a substrate. [Effects of the Invention]

[0022] The block polymer for a pretreatment liquid of the present invention makes it possible to provide a pretreatment liquid that is excellent in ejection stability from the nozzles of an inkjet head and that has water resistance, abrasion resistance, and alcohol resistance suitable for packaging materials. DETAILED DESCRIPTION OF THE INVENTION

[0023] The block polymer for a pretreatment liquid of the present invention will be described below by way of preferred embodiments. Hereinafter, the "block polymer for a pretreatment liquid" will sometimes be referred to as the "block polymer," and the "aqueous inkjet ink" will sometimes be referred to as the "aqueous ink" or "ink."

[0024] <Block polymer (B)> A block polymer is a copolymer made up of two or more types of monomers, in which two or more polymer units with different copolymerization compositions are bonded in a single polymer chain. It is also called a block copolymer or block interpolymer. Block polymers can be made by chemically bonding each polymer unit, or by polymerizing another monomer at the end of one polymer unit. Unlike disordered copolymers (also called random polymers), block polymers possess the properties of each polymer unit.

[0025] The block polymer of the present invention contains a hydrophilic unit (b-1) and a hydrophobic unit (b-2). The hydrophilic unit has a high affinity for water and dissolves in water, while the hydrophobic unit does not. Therefore, in water, it forms particulate micelles. This is because the hydrophilic and hydrophobic polymer units, which have significantly different solubilities, generate repulsion between the hydrophilic and hydrophobic units, resulting in phase separation in microscopic regions. Therefore, the presence of the hydrophobic unit allows the hydrophobic units of multiple polymers to aggregate and maintain a particulate state, thereby suppressing the viscosity of the resin dispersion, minimizing viscosity changes in the resin dispersion, and improving the ejection stability of pretreatment liquids using the block polymer. Furthermore, the water resistance and alcohol resistance of the ink coating after printing are improved. Furthermore, the presence of the hydrophilic unit allows the hydrophilic unit dissolved in water to cover the hydrophobic unit, improving dispersion stability in water. Furthermore, the water solubility of the polymer prevents nozzle clogging in inkjet heads. However, the above is based on scientific considerations, and the present invention is not limited to this effect alone.

[0026] The block polymer can be polymerized using a known living radical polymerization method. Examples of living radical polymerization methods include nitroxide-mediated polymerization, atom transfer polymerization, reversible addition-fragmentation chain transfer polymerization, organotellurium-mediated polymerization, and iodine transfer polymerization. The block polymer of the present invention is preferably produced using reversible addition-fragmentation chain transfer polymerization (also known as RAFT polymerization).

[0027] Reversible addition-fragmentation chain transfer polymerization (RAC) is a reversible deactivation radical polymerization, a method that can impart living properties to radical polymerization. In living polymerization, polymerization reactions begin in all polymer chains from the initial stage of the reaction, and the polymer chains grow and polymerize at the same reaction rate. This eliminates irreversible chain transfer and termination reactions, allowing for the production of polymers with narrow molecular weight distributions (PDI = weight average molecular weight / number average molecular weight). Furthermore, polymer chains can be extended by adding additional monomers to the polymerization reaction system. This allows for the connection of multiple blocks with different properties, resulting in AB diblock polymers, ABA or ABC triblock polymers, etc.

[0028] The block polymer of the present invention has a number average molecular weight (Mn) of 8,000 to 30,000, preferably 10,000 to 25,000, and more preferably 12,000 to 20,000. By making the number average molecular weight 8,000 or more, the coating film after printing has excellent water resistance, abrasion resistance, and alcohol resistance. By making it 30,000 or less, good ejection stability is obtained.

[0029] The number-average molecular weight of the block polymer in the present invention can be measured by a conventional method. In the present invention, the measurement was performed using a TSKgel column (manufactured by Tosoh Corporation) and a GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with an RI detector, using a calcium nitrate solution as the developing solvent, and the calibration curves for both were prepared using water-soluble molecular weight standard polymers, PEG (polyethylene glycol) and PEO (polyethylene oxide).

[0030] Furthermore, block polymers obtained by living radical polymerization have a narrower molecular weight distribution than random polymers obtained by conventional radical polymerization. The more uniform the molecular weight distribution of a block polymer, the stronger the phase separation in the microscopic domain, and the stronger the characteristics of each polymer unit with different solubility can be expressed. The molecular weight distribution of the block polymer of the present invention is preferably 1.6 or less, and more preferably 1.5 or less. By making the molecular weight distribution 1.6 or less, the characteristics of each polymer unit can be easily expressed, and good discharge stability and dispersion stability can be obtained.

[0031] The block polymer of the present invention has an average particle size in the range of 30 to 150 nm, preferably 40 to 120 nm. The average particle size in the present invention was measured by dynamic light scattering particle distribution measurement using a Nanotrac UPA-EX150 manufactured by Microtrac-Bell, and the 50% volume average particle size (D50) was taken as the average particle size. Polymer samples with small average particle sizes that were impossible to measure were determined to be water-soluble resins because they did not maintain a particulate state. If the water solubility is too high and the particulate state is not expressed, not only will the water resistance and alcohol resistance of the coating film after printing be poor, but the viscosity of the dispersion will also increase, resulting in reduced ejection stability. By maintaining an average particle size of 30 nm or more, excellent ejection stability and improved ink coating film durability are achieved. By maintaining an average particle size of 150 nm or less, the storage stability of the pretreatment solution will be excellent.

[0032] Next, each component constituting the block polymer for a pre-treatment liquid of the present invention will be described in detail below.

[0033] <Hydrophilic unit (b-1)> The block polymer of the present invention contains a structural unit represented by formula (1) as a structural unit in the hydrophilic unit (b-1). Formula (1) [ka] In formula (1), R 1represents a hydrogen atom or a methyl group, Y represents an oxygen atom or -NH-, Z represents a hydroxyl group or an alkylene group which may contain an oxygen atom, R 2 , R 3 , R 4 each independently represents an aliphatic hydrocarbon or aromatic hydrocarbon which may contain a hydroxyl group or an oxygen atom.

[0034] In formula (1), R 1 , R 2 , and R 3 From the viewpoint of ejection stability of the pretreatment liquid, it is preferable that Y is a methyl group and Z is an alkylene group having 1 to 4 carbon atoms. Furthermore, it is preferable that Y is an oxygen atom from the viewpoint of water resistance and alcohol resistance of the printed matter.

[0035] Furthermore, in formula (1), R 4 is preferably an aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 20 carbon atoms, which may contain a hydroxyl group or an oxygen atom, from the viewpoints of the ejection stability of the pretreatment liquid and the water resistance and alcohol resistance of printed matter. It more preferably has 1 to 12 carbon atoms. Examples of aliphatic hydrocarbon groups having 1 to 20 carbon atoms include an ethylene group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, and a dodecyl group. Examples of aromatic hydrocarbon groups having 1 to 20 carbon atoms include a phenyl group, a tolyl group, and structures in which one methyl group in the aliphatic hydrocarbon groups is substituted with a phenyl group.

[0036] Methods for introducing the structural unit shown in formula (1) include copolymerization using a vinyl monomer containing a cationic group, and copolymerization of a vinyl monomer having a tertiary amino group as a monomer component to obtain a block polymer having a tertiary amino group, followed by reaction with an onium chloride agent to form a quaternary ammonium salt. In the present invention, the anion component that serves as a counter to the quaternary ammonium salt is a hydroxide ion, resulting in a quaternary ammonium hydroxide.

[0037] As a method for obtaining quaternary ammonium hydroxides in which the counter anion component is a hydroxide ion, Patent Document 1997-124718 discloses that a quaternary ammonium hydroxide group is generated by reacting a compound having a tertiary amino group with a compound having an epoxy group in a solvent in the presence of water. This reaction generates a quaternary ammonium hydroxide by ring-opening addition of an epoxy group to a tertiary amino group, and this reaction can be used to obtain the cationic group shown in formula (1). Examples include a method in which a vinyl monomer containing a quaternary ammonium hydroxide is synthesized and then copolymerized with another vinyl monomer to obtain a block polymer containing the structural unit shown in formula (1) in the hydrophilic unit (b-1); and a method in which a vinyl monomer having an epoxy group or a tertiary amino group is copolymerized as a monomer component to obtain a block polymer having an epoxy group or a tertiary amino group, and then the block polymer is reacted with a compound having a tertiary amino group or an epoxy group to introduce the structural unit shown in formula (1) into the hydrophilic unit (b-1) of the block polymer. Either polymerization method can be selected in the present invention.

[0038] Because the structural unit represented by formula (1) is a quaternary ammonium hydroxide, the water resistance and alcohol resistance of the coating film printed with the pretreatment liquid are improved. Although the detailed mechanism is unclear, it is presumed that hydroxide ions have a stronger nucleophilicity than halogen ions, etc., and therefore ion dissociation in water is suppressed, which is thought to result in improved water resistance and alcohol resistance after printing with the pretreatment liquid.

[0039] Furthermore, pretreatment liquids that improve print quality through aggregation use flocculants such as polyvalent metal salts and water-soluble cationic resins to impart the ability to aggregate solid components contained in the ink. These dissolve as cationic metal ions or cationic resins in aqueous solutions. This is because the solid components in the ink that form the image, primarily the pigment dispersion and binder resin, are designed to be anionic, and they aggregate upon contact, resulting in excellent print quality. Therefore, pretreatment liquids must be designed to be stable with cationic flocculants. The hydrophilic unit (b-1) of the block polymer of the present invention exhibits cationic properties due to the inclusion of the structural unit of formula (1). Therefore, it can exist stably without aggregation with the cationic flocculant, thereby improving the ejection stability and storage stability of the pretreatment liquid. In the case of anionic hydrophilic units obtained by polymerizing a block polymer from a monomer containing an acid group such as a carboxyl group and then neutralizing it, aggregation with the flocculant progresses, resulting in reduced ejection stability and storage stability.

[0040] The constituent unit represented by formula (1) is preferably contained in an amount of 5 to 45% by mass, more preferably 10 to 40% by mass, based on the total mass of the block polymer for the pretreatment liquid. By containing 5% by mass or more, the storage stability of the pretreatment liquid is improved, while by containing 45% by mass or less, the ejection stability is excellent and the water resistance and alcohol resistance of the coating film after printing are improved. Furthermore, it is preferable that the entire amount of the constituent unit represented by formula (1) is contained in the hydrophilic unit.

[0041] Examples of vinyl monomers having a tertiary amino group used when introducing a structural unit represented by formula (1) into the hydrophilic unit (b-1) from a vinyl monomer having a tertiary amino group include (meth)acrylic acid esters or (meth)acrylamides having a dialkylamino group, such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, diisopropylaminoethyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, dipropylaminopropyl (meth)acrylamide, diisopropylaminopropyl (meth)acrylamide, and dibutylaminopropyl (meth)acrylamide, but are not particularly limited to these. These can be used alone or in combination of two or more.

[0042] Examples of the vinyl monomer having an epoxy group used when introducing the structural unit represented by formula (1) into the hydrophilic unit (b-1) from a vinyl monomer having an epoxy group include, but are not limited to, unsaturated ester monomers having an epoxy group, such as acrylic acid glycidyl ester, methacrylic acid glycidyl ester, 4-hydroxybutyl acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl methacrylate. These can be used alone or in combination of two or more.

[0043] When a tertiary amino group is reacted with a composition containing an epoxy group to obtain a quaternary ammonium hydroxide, any compound containing an epoxy group can be used as the composition. However, from the viewpoint of ejection stability, compounds containing one epoxy group per molecule are preferred. Examples include aliphatic glycidyl ethers such as ethyl glycidyl ether, isopropyl glycidyl ether, butyl glycidyl ether, and 2-ethylhexyl glycidyl ether; aromatic glycidyl ethers such as phenyl glycidyl ether, 4-tert-butylphenyl glycidyl ether, and benzyl glycidyl ether; aliphatic epoxy compounds such as 1,2-epoxybutane, 1,2-epoxypentane, and 1,2-epoxyoctane; and aromatic epoxy compounds such as 1,2-epoxyethylbenzene. These compounds can be used alone or in combination.

[0044] On the other hand, when a composition containing a tertiary amino group is reacted with an epoxy group to obtain a quaternary ammonium hydroxide, any compound containing a tertiary amino group can be used as the composition, but it is preferable to have one tertiary amino group per molecule from the viewpoint of ejection stability. Examples of the tertiary amine include aliphatic tertiary amines such as dimethylaminoethanol, 1-dimethylamino-2-propanol, N,N-diethylethanolamine, 2-[ethyl(methyl)amino]-1-propanol, 3-[ethyl(methyl)amino]-1-propanol, triethanolamine, triethylamine, N,N-dimethylbutylamine, N,N-dimethylhexylamine, N,N-dimethyloctylamine, N-methyldipropylamine, N-methyldiethylamine, diethyl(methoxymethyl)amine, 2-(2-dimethylaminoethoxy)ethanol, and 2-(2-diethylaminoethoxy)ethanol, but are not limited thereto. These can be used alone or in combination of two or more.

[0045] The other vinyl monomers constituting the hydrophilic unit (b-1) may be, as hydrophilic monomers, for example, alkyl(meth)acrylate-based quaternary ammonium salt monomers such as (meth)acryloyloxyethyl trimethyl ammonium chloride, (meth)acryloyloxyethyl triethyl ammonium chloride, (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride, (meth)acryloyloxyethyl methyl morpholino ammonium chloride, and 2-hydroxy-3-(meth)acryloyloxypropyl trimethyl ammonium chloride; alkyl(meth)acryloylamide-based quaternary ammonium salt monomers such as (meth)acryloylaminopropyl trimethyl ammonium chloride, (meth)acryloylaminoethyl triethyl ammonium chloride, and (meth)acryloylaminoethyl dimethyl benzyl ammonium chloride; 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, glycerol mono ... Hydroxyl group-containing vinyl monomers such as acrylates, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, and allyl alcohol, (meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, and N,N-di(ethoxymethyl) Examples of suitable vinyl monomers include, but are not limited to, amide group-containing vinyl monomers such as N-(2-methyl-2-propoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide. These may be used alone or in combination of two or more.

[0046] Further, examples of hydrophobic monomers include linear or branched methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, and tetradecyl (meth)acrylate. Examples of the vinyl monomer include branched alkyl group-containing vinyl monomers, alicyclic alkyl group-containing vinyl monomers such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, and aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, phenoxyhexaethylene glycol (meth)acrylate, and phenyl (meth)acrylate.

[0047] The hydrophilic unit (b-1) is not particularly limited as long as it is a unit that exhibits hydrophilicity, but the content of structural units derived from hydrophilic monomers is preferably 60% by mass or more, more preferably 80% by mass or more.

[0048] <Hydrophobic unit (b-2)> Examples of vinyl monomers constituting the hydrophobic unit include, but are not limited to, the aforementioned linear or branched alkyl group-containing vinyl monomers, alicyclic alkyl group-containing vinyl monomers, aromatic vinyl monomers, hydroxyl group-containing vinyl monomers, and amide group-containing vinyl monomers. These may be used alone or in combination of two or more. The content of structural units derived from hydrophobic monomers in the hydrophobic unit (b-2) is preferably 60% by mass or more, more preferably 80% by mass or more.

[0049] More preferred vinyl monomers constituting the hydrophobic unit are monomers having a cyclic structure, and preferably include alicyclic alkyl group-containing vinyl monomers and aromatic vinyl monomers. The presence of a cyclic structure contributes to excellent water resistance, abrasion resistance, and alcohol resistance of the ink coating film after printing. Furthermore, it strengthens the repulsion with the hydrophilic unit in water, promotes phase separation in the micro region, maintains the particle state, and improves ejection stability. The vinyl monomer having a cyclic structure constituting the hydrophobic unit is preferably contained in an amount of 5 to 50% by mass relative to the total mass % of the block polymer for the pretreatment liquid.

[0050] The mass ratio of the hydrophilic unit (b-1) to the hydrophobic unit (b-2) is 10:90 to 70:30, and preferably 20:80 to 50:50. When the mass ratio of the hydrophilic units is 10 or more, storage stability is improved, and when it is 70 or less, ejection stability and the water resistance and alcohol resistance of the coating film after printing are improved.

[0051] Examples of RAFT agents (chain transfer agents) used in reversible addition-fragmentation chain transfer polymerization include dithioesters, trithiocarbonates, dithiocarbamates, and xanthates. Among these, trithiocarbonates and dithioesters are preferred because of their high activity and good reactivity with alkyl-group-containing vinyl monomers such as (meth)acrylates, aromatic vinyl monomers, amide-group-containing vinyl monomers, and aromatic vinyl monomers. Specific examples include methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, S,S-dibenzyltrithiocarbonate, bis{4-[ethyl-(2-acetyloxyethyl)carbamoyl]benzyl}trithiocarbonate, benzyl 4-methoxybenzodithioate, and 2-cyanopropan-2-yl benzodithioate. The mass of the RAFT agent used in the polymerization can be calculated from the molecular weight of the RAFT agent, the molecular weight and composition ratio of each vinyl monomer to be polymerized, and the number average molecular weight of the desired block polymer.

[0052] Although known polymerization initiators are used as the initiator for generating radicals at the initial stage of polymerization, azo compounds are preferred from the viewpoints of polymerizability and molecular weight control, and it is preferable to use 0.2 to 0.8 moles per mole of RAFT agent. Examples of azo compounds include, but are not limited to, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 2,2'-azobis(isobutyrate)dimethyl.

[0053] The total amount of the block polymer of the present invention is preferably 3% by mass or more and 30% by mass or less, based on the total amount of the pretreatment liquid. By making it 3% by mass or more, durability after printing becomes good, and by making it 30% by mass or less, excellent ejection performance is obtained. More preferably, it is 5% by mass or more and 20% by mass or less.

[0054] <Pretreatment liquid> Next, the pretreatment liquid constituting the present invention will be described. The pretreatment liquid of the present invention contains a block polymer for the pretreatment liquid, water, and a flocculant. The flocculant is used in the pretreatment liquid to flocculate and thicken the inkjet ink containing the colorant that forms the image area, thereby obtaining an excellent image. Examples of flocculants include polyvalent metal salts, organic acids, and water-soluble cationic resins. These may be used alone or in combination of two or more.

[0055] The type of polyvalent metal salt is not particularly limited as long as it is composed of a metal ion and an anion that binds to the metal ion. Among them, it is preferable that the polyvalent metal salt contains a divalent metal salt, since it can instantly interact with the pigment to suppress bleeding and color mixing and obtain a clear image. Calcium ions or magnesium ions are particularly preferable. Metal salts include inorganic metal salts and organic metal salts.

[0056] Specific examples of inorganic metal salts include, but are not limited to, aluminum chloride, polyaluminum chloride (PAC), calcium chloride, magnesium chloride, aluminum chloride, calcium bromide, magnesium bromide, aluminum nitrate, calcium nitrate, magnesium nitrate, aluminum sulfate, magnesium sulfate, calcium carbonate, and magnesium carbonate. Among these inorganic metal salts, calcium nitrate is preferably selected from the viewpoints of hygroscopicity and the coagulation and thickening effects of inkjet ink.

[0057] Specific examples of organic metal salts include, but are not limited to, aluminum salts, calcium salts, magnesium salts, nickel salts, and zinc salts of organic acids such as pantothenic acid, propionic acid, ascorbic acid, acetic acid, and lactic acid. Among these metal salts of organic acids, it is preferable to select calcium salts of lactic acid and / or acetic acid from the viewpoints of hygroscopicity and the coagulation and thickening effects of inkjet inks.

[0058] The content of the polyvalent metal salt in the pretreatment liquid of the present invention is preferably 0.25 to 8.0 mass %, more preferably 0.75 to 5 mass %, in terms of metal ions, relative to the total mass of the pretreatment liquid. By keeping the metal ion content within this range, the wettability of the pretreatment liquid for the substrate can be ensured.

[0059] When selecting a water-soluble cationic resin as the flocculant, any resin can be used as long as it reduces the dispersibility of the pigment in the ink and has suitable solubility and diffusibility. The solubility in 100 mL of water at 25°C can be used as an indicator of suitable solubility. That is, a water-soluble cationic resin having a solubility of 5 g / 100 mL or more in 100 mL of water at 25°C is preferably used in the pretreatment liquid of this embodiment.

[0060] The method for evaluating and determining the solubility of water-soluble cationic resins is described in detail below. A sample is prepared by thoroughly mixing 5 g of water-soluble cationic resin with 100 mL of water. If the water-soluble cationic resin is available only in the form of an aqueous solution, such as a commercially available product, water is added or evaporated to obtain a sample with a solid content of 5 g per 100 mL of water. If the sample is then left to stand at 25°C for 24 hours and the 50% volume average particle size cannot be measured, the solubility of the water-soluble cationic resin in 100 mL of water at 25°C is determined to be 5 g / 100 mL or more. The 50% volume average particle size can be measured, for example, using a particle size distribution analyzer (Microtrac-Bell Nanotrac UPA-EX150).

[0061] Examples of the cationic group contained in the water-soluble cationic resin include, but are not limited to, an amino group, an ammonium group, an amide group, and a -NHCONH2 group.

[0062] Examples of materials used to introduce the above-mentioned cationic group into the water-soluble cationic resin include amine compounds such as vinylamine, allylamine, methyldiallylamine, and ethyleneimine; amide compounds such as acrylamide, vinylformamide, and vinylacetamide; cyanamide compounds such as dicyandiamide; epihalohydrin compounds such as epifluorohydrin, epichlorohydrin, methylepichlorohydrin, epibromohydrin, and epiiodohydrin; cyclic vinyl compounds such as vinylpyrrolidone, vinylcaprolactam, and vinylimidazole; amidine compounds; pyridinium salt compounds; and imidazolium salt compounds.

[0063] <Water-soluble cationic resin (A)> A water-soluble cationic resin is preferably used as the flocculant. It is particularly preferred that the water-soluble cationic resin (A) contains 50 to 100% by mass of the structural unit represented by formula (2), based on the total mass of the water-soluble cationic resin. Unlike low-molecular-weight flocculants such as polyvalent metal salts and organic acids, water-soluble cationic resins form a high-molecular-weight resin film on the substrate, thereby imparting good water resistance and alcohol resistance to printed materials. Furthermore, unlike low-molecular-weight flocculants, the structural unit represented by formula (2) is less likely to interact with block polymers, resulting in excellent storage stability and ejection stability of the pretreatment liquid. Furthermore, a content of 50% by mass or more results in the ability to flocculate solid components in the inkjet ink and / or the ability to thicken components having anionic groups through interactions mediated by the water-soluble cationic resin, resulting in printed materials with good print quality. A more preferred content is 60 to 80% by mass. Formula (2) [ka] In formula (1), R 5 represents a hydrogen atom or a methyl group, L represents an oxygen atom, -NH-, or -OCHCH(OH)-, and R 6 , R 7 , R 8 each independently represents a hydrocarbon group having 1 to 8 carbon atoms; X - represents a monovalent anion, and n represents an integer of 1 to 6. Examples of hydrocarbon groups having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a benzyl group. - Examples of the anion include a halide ion, a sulfonate anion, an alkylsulfonate anion, and an alkylcarboxylate anion.

[0064] From the viewpoint of solubility in inkjet ink and ejection stability of the pretreatment liquid, L is an oxygen atom or -NH-, and R 6 , R 7 , R 8 It is preferable that at least two of these groups are methyl groups.

[0065] Methods for introducing the constituent unit represented by formula (2) into the water-soluble cationic resin (A) include copolymerization using a vinyl monomer containing a cationic group, and copolymerization using a vinyl monomer having a tertiary amino group as a monomer component to obtain a polymer having a tertiary amino group, followed by reaction with an onium chloride agent to form a quaternary ammonium salt. Either polymerization method can be selected in the present invention.

[0066] Examples of the vinyl monomer containing a cationic group that introduces the structural unit represented by formula (2) into the water-soluble cationic resin (A) include the above-mentioned alkyl(meth)acrylate-based quaternary ammonium salt-type monomers and alkyl(meth)acryloylamide-based quaternary ammonium salt-type monomers, but are not particularly limited thereto.

[0067] Examples of the vinyl monomer having a tertiary amino group used when introducing the structural unit represented by formula (2) into the water-soluble cationic resin (A) from a vinyl monomer having a tertiary amino group include the above-mentioned (meth)acrylic acid esters or (meth)acrylamides having a dialkylamino group, but are not particularly limited thereto.

[0068] Examples of onium chloride agents used when reacting a tertiary amino group with an onium chloride agent to convert it to an ammonium salt include, but are not limited to, alkyl halides such as chloromethane, chloroethane, chloropropane, chlorobutane, bromomethane, bromoethane, bromopropane, bromobutane, iodomethane, iodoethane, iodopropane, iodobutane, benzyl chloride, and benzyl bromide; alkyl sulfates such as dimethyl sulfate, diethyl sulfate, and dipropyl sulfate; and sulfonate esters such as methyl p-toluenesulfonate and methyl benzenesulfonate. These agents can be used alone or in combination. Some or all of the tertiary amino groups can be converted to ammonium salts.

[0069] Other vinyl monomers constituting the water-soluble cationic resin (A) include, but are not limited to, the above-mentioned linear or branched alkyl group-containing vinyl monomers, alicyclic alkyl group-containing vinyl monomers, aromatic vinyl monomers, hydroxyl group-containing vinyl monomers, and amide group-containing vinyl monomers. These can be used alone or in combination of two or more.

[0070] The weight-average molecular weight (Mw) of the water-soluble cationic resin (A) is preferably 10,000 to 100,000, and more preferably 20,000 to 80,000. By making the weight-average molecular weight 10,000 or more, the water resistance and alcohol resistance of the coating film after printing are excellent. By making it 100,000 or less, the ejection stability is improved.

[0071] The weight average molecular weight of the water-soluble cationic resin (A) in the present invention was measured by the same method as used to measure the number average molecular weight of the block polymer.

[0072] The water-soluble cationic resin (A) is preferably contained in an amount of 2 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the pretreatment liquid. By keeping the blending amount of the water-soluble cationic resin (A) within the above range, good ejection stability is achieved, and the water resistance and alcohol resistance of the printed matter are also improved.

[0073] Next, other constituent materials of the pretreatment liquid of the present invention will be described.

[0074] <Water-soluble organic solvent> The pretreatment liquid of the present invention may contain a water-soluble organic solvent. The water-soluble organic solvent is not particularly limited, and any known solvent may be used. However, from the viewpoints of dispersion stability of the block polymer, solubility of the coagulant, ejection stability of the pretreatment liquid, and wettability to the substrate, it is preferable for the water-soluble organic solvent to contain a glycol ether solvent and / or an alkyl polyol solvent. In particular, it is preferable for the boiling point of the water-soluble organic solvent at 1 atmosphere to be 100°C or higher but lower than 240°C. By setting the boiling point at 100°C or higher, the dispersion stability, ejection stability, and moisture retention of the pretreatment liquid are improved, while by setting the boiling point at lower than 240°C, the drying properties of the pretreatment liquid and the water resistance and abrasion resistance of the printed material are improved. The water-soluble organic solvent may be used alone or in combination of two or more types.

[0075] The boiling point at 1 atmospheric pressure can be measured using a thermal analyzer such as a DSC (differential scanning calorimetry) analyzer.

[0076] The total amount of the water-soluble organic solvents is preferably 3% by mass or more and 40% by mass or less relative to the total amount of the pretreatment liquid. Furthermore, from the viewpoint of ensuring ejection stability from the inkjet head, water resistance, and alcohol resistance, it is more preferably 5% by mass or more and 35% by mass, and particularly preferably 8% by mass or more and 30% by mass or less. By setting the total amount of the water-soluble organic solvents to 3% by mass or more, excellent moisture retention and ejection stability are achieved, and by setting it to 40% by mass or less, good drying properties are achieved, and printed matter with good water resistance and alcohol resistance is obtained.

[0077] Examples of alkyl polyol solvents that can be suitably used as the water-soluble organic solvent include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methylpentane-2,4-diol, 2-ethyl-1,3-hexanediol, diethylene glycol, and dipropylene glycol.

[0078] Examples of glycol ether-based solvents that can be suitably used as the water-soluble organic solvent include glycol monoalkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monomethyl ether; and glycol dialkyl ethers such as diethylene glycol diethyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether.

[0079] <Surfactant> The pretreatment liquid of the present invention preferably contains a surfactant to adjust its surface tension, ensure wettability on the substrate, and improve print image quality. On the other hand, if the surface tension is too low, the nozzle surface of the inkjet head will become wet with the pretreatment liquid, impairing ejection stability. Therefore, selecting the type and amount of surfactant is important. From the viewpoint of ensuring optimal wettability and achieving ejection stability, it is preferable to use surfactants such as siloxane-based, acetylene-based, acrylic-based, fluorine-based, and polyoxyalkylene alkyl ether-based surfactants, and siloxane-based and / or acetylene-based surfactants are particularly preferable. The amount of surfactant added is preferably 0.05% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 3.0% by mass or less, based on the total amount of the pretreatment liquid. A content of 0.05% by mass or more allows the surfactant to fully exert its functions, while a content of 5.0% by mass or less allows the storage stability and ejection stability of the pretreatment liquid to be maintained at an appropriate level.

[0080] <Other ingredients> In addition to the above components, additives such as a pH adjuster, an antifoaming agent, a preservative, an infrared absorber, an ultraviolet absorber, a thickener, a wax additive, a crosslinking agent, etc. may be added as needed. The amount of these additives added is preferably 0.01% by mass or more and 10% by mass or less relative to the total mass of the pretreatment liquid.

[0081] <Preparation of pretreatment solution> The pretreatment liquid of the present invention, which is composed of the above components, is prepared by, for example, adding the block polymer (B), a water-soluble cationic resin, a surfactant, water, and, if necessary, a water-soluble organic solvent, a pH adjuster, and / or any of the additive components appropriately selected as listed above, stirring and mixing the mixture, and then filtering the mixture as needed. However, the method for producing the pretreatment liquid is not limited to the above.

[0082] <Print method> When producing a printed item using the pretreatment liquid of the present invention, the pretreatment liquid is preferably printed on a substrate before printing with an aqueous inkjet ink. The printing method may be either a method of printing without contact with the substrate, such as inkjet printing, or a method of printing by bringing the pretreatment liquid into contact with the substrate. Furthermore, when a printing method of bringing the pretreatment liquid into contact with the substrate is selected as the method of printing the pretreatment liquid, a roller type coater such as a gravure coater, doctor coater, bar coater, blade coater, flexo coater, or roll coater can be preferably used.

[0083] <Inkjet ink set> The pretreatment liquid of the present invention can be used in combination with one or more aqueous inkjet inks in the form of an aqueous inkjet ink set. The components of the aqueous inks that make up the aqueous inkjet ink set will be described below.

[0084] <Pigments> Pigments used in aqueous inks can be either inorganic or organic, and are not particularly limited. Examples of organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindoline, quinophthalone, azomethine azo, and dictylopyrrolopyrrole pigments. Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, and mica. Titanium oxide preferably has a surface coated with at least silica or alumina. Pigments listed as CI pigments in the Color Index can be used as needed. These pigments can be used alone or in combination.

[0085] It is also suitable to use hollow resin particles as the white pigment. Hollow resin particles have a smaller specific gravity (apparent density) than titanium oxide and the like, and are therefore less likely to settle over time, resulting in an ink with excellent storage stability. Furthermore, to obtain a white ink that combines storage stability and opacity, hollow resin particles and titanium oxide may be used in combination as pigments.

[0086] In addition, in aqueous inks, a mixture of the above pigments can be used to achieve a suitable hue and color development for printed matter. For example, to improve color tone at low printing rates in black inks using carbon black, a small amount of one or more pigments selected from the group consisting of cyan pigments, magenta pigments, orange pigments, and brown pigments can be added.

[0087] These pigments are preferably contained in an amount ranging from 2% to 20% by mass, more preferably from 2.5% to 15% by mass, and particularly preferably from 3% to 10% by mass, of the total ink, except in the case of white ink. Furthermore, in the case of white ink, the pigment content is preferably from 5% to 40% by mass, more preferably from 8% to 30% by mass, of the total ink. By ensuring that the pigment content is 2% by mass or more (5% by mass or more for white ink), sufficient color development (hiding ability for white ink) can be achieved. Furthermore, by ensuring that the pigment content is 20% by mass or less (40% by mass or less for white ink), the ink viscosity can be kept within a range suitable for inkjet printing.

[0088] <Pigment dispersing resin> Methods for stably dispersing and maintaining pigments in aqueous inks include (1) coating at least a portion of the pigment surface with a water-soluble or water-insoluble pigment dispersing resin, (2) adsorbing a water-soluble and / or water-dispersible surfactant onto the pigment surface and dispersing it, (3) chemically or physically introducing hydrophilic functional groups onto the pigment surface and dispersing it in the ink without a dispersing resin or surfactant (self-dispersing pigment), and (4) coating the pigment with a water-insoluble resin and, if necessary, dispersing it in the ink using another pigment dispersing resin or surfactant.

[0089] The type of pigment dispersing resin is not particularly limited, and examples include (meth)acrylic, styrene (meth)acrylic, (maleic anhydride)-based, styrene (maleic anhydride)-based, α-olefin (maleic anhydride)-based, urethane-based, and ester-based resins. Among these, from the viewpoint of strengthening pigment adsorption and stabilizing the pigment dispersion, it is preferable to use one or more resins selected from the group consisting of α-olefin (maleic anhydride)-based, (meth)acrylic, and styrene (meth)acrylic. In this specification, "(maleic anhydride)" refers to maleic acid or maleic anhydride.

[0090] The weight-average molecular weight of the pigment dispersion resin is preferably 5,000 or more and 100,000 or less. It is more preferably 10,000 or more and 50,000 or less, and even more preferably 15,000 or more and 30,000 or less. Having a weight-average molecular weight within this range allows the pigment to be stably dispersed in water, and also facilitates viscosity adjustment when applied to aqueous ink. In particular, when the weight-average molecular weight is 5,000 or more, the pigment dispersion resin is less likely to dissolve in the water-soluble organic solvent added to the aqueous ink, resulting in strong adsorption of the pigment dispersion resin to the pigment and excellent dispersion stability. Furthermore, when the weight-average molecular weight is 100,000 or less, the viscosity of the aqueous ink during dispersion is kept low, and ejection stability from the inkjet head is excellent, enabling stable printing over a long period of time.

[0091] When a water-soluble resin is used as the pigment dispersing resin, its acid value is preferably 60 to 400 mgKOH / g. By setting the acid value within the above range, the dispersion stability of the pigment and the storage stability of the ink can be made favorable. Furthermore, the aggregation properties with the cationic groups in the pretreatment liquid become favorable, resulting in excellent print quality and good abrasion resistance of the printed matter. The acid value is more preferably 120 to 350 mgKOH / g. On the other hand, when a water-insoluble resin is used as the pigment dispersing resin, its acid value is preferably 0 to 100 mgKOH / g, and more preferably 5 to 90 mgKOH / g.

[0092] The blending amount of the pigment dispersing resin is preferably 1 to 50% by mass relative to the pigment. By blending the pigment dispersing resin in an amount of 1 to 50% by mass relative to the pigment, the viscosity of the pigment dispersion can be reduced, and the viscosity stability and dispersion stability of the pigment dispersion and water-based ink can be improved. The blending amount of the pigment dispersing resin relative to the pigment is more preferably 2 to 45% by mass, and even more preferably 4 to 35% by mass.

[0093] <Binder resin> The aqueous inkjet ink used in combination with the pretreatment liquid of the present invention preferably contains a binder resin. The binder resin may be in the form of either a water-soluble resin or resin particles, and two or more types may be used in combination depending on the properties required for the aqueous ink and printed matter. For example, resin particles can reduce the viscosity of the aqueous ink and allow a larger amount of resin to be blended, making them suitable for improving the water resistance and abrasion resistance of printed matter. Furthermore, aqueous inks using a water-soluble resin as the binder resin have excellent ejection stability and excellent print quality when combined with the pretreatment liquid of this embodiment.

[0094] Furthermore, with regard to the type of binder resin, any of (meth)acrylic resin, styrene (meth)acrylic resin, (maleic anhydride) resin, styrene (maleic anhydride) resin, olefin (maleic anhydride) resin, polyurethane resin, polyester resin, polyolefin resin, etc. Among these, (meth)acrylic resin, styrene (meth)acrylic resin, polyurethane resin, and polyolefin resin are preferably used from the viewpoints of the storage stability of the aqueous ink and the adhesion and abrasion resistance between the ink surface and the substrate of a printed matter when combined with the pretreatment liquid of this embodiment.

[0095] When resin particles are used as the binder resin, it is preferable to adjust the type and compounding ratio of the monomers constituting the resin particles to set the minimum film formation temperature (MFT) to 50°C or higher in order to achieve favorable discharge stability. The MFT can be measured, for example, using an MFT tester manufactured by Tester Sangyo Co., Ltd. Specifically, a 25% by mass aqueous solution of the binder resin is printed on a film so that the wet film thickness is 300 μm, and the film is then left to stand on the tester under a temperature gradient. After drying, the MFT is determined as the temperature at the boundary between the area where a white precipitate forms and the area where a transparent resin film is formed.

[0096] Furthermore, when a water-soluble resin is used as the binder resin, from the viewpoint of achieving both the ejection stability of the water-based ink and the abrasion resistance of the printed matter, the weight-average molecular weight is preferably in the range of 5,000 to 80,000, more preferably in the range of 8,000 to 60,000, and particularly preferably in the range of 10,000 to 50,000. For the same reason, the acid value of the water-soluble resin is preferably in the range of 5 to 80 mgKOH / g, and more preferably in the range of 10 to 50 mgKOH / g.

[0097] The content of the binder resin in the total amount of the water-based ink is preferably 1 to 20 mass %, more preferably 2 to 15 mass %, and particularly preferably 3 to 10 mass %, calculated as solid content.

[0098] <Organic solvents in water-based inks> The aqueous inkjet ink used in combination with the pretreatment liquid of the present invention preferably contains a water-soluble organic solvent. The water-soluble organic solvent is not particularly limited, and any known solvent can be used. However, from the viewpoint of compatibility and affinity with material components such as pigment dispersion resins and surfactants, it is preferable for the water-soluble organic solvent to contain a glycol ether solvent and / or an alkyl polyol solvent. In particular, the boiling point of the water-soluble organic solvent at 1 atmosphere is preferably 120°C or higher but lower than 240°C. A boiling point of 120°C or higher improves the dispersion stability, ejection stability, and moisture retention of the aqueous ink, while a boiling point of lower than 240°C improves the drying properties of the aqueous ink and the water resistance and water-rub resistance of printed matter. The water-soluble organic solvent may be used alone or in combination of two or more.

[0099] The total amount of water-soluble organic solvents is preferably 3% by mass or more and 40% by mass or less relative to the total amount of the aqueous ink. Furthermore, from the viewpoint of ensuring ejection stability from the inkjet head, water resistance, and alcohol resistance, it is more preferably 5% by mass or more and 35% by mass, and particularly preferably 8% by mass or more and 30% by mass or less. By making the total amount of water-soluble organic solvents 3% by mass or more, the aqueous ink will have excellent moisture retention and ejection stability, and by making it 40% by mass or less, the aqueous ink will dry well and printed matter will have good water resistance and alcohol resistance.

[0100] Examples of solvents that are preferably used as the water-soluble organic solvent for inkjet ink include alkyl polyol solvents and glycol ether solvents, and specifically, these are the same as the water-soluble organic solvents for the pretreatment liquid described above.

[0101] <Other components of water-based ink> As with the pretreatment liquid, the aqueous ink preferably contains a surfactant for the purposes of adjusting the surface tension, ensuring wettability on the substrate, and improving the print image quality. Furthermore, as with the pretreatment liquid, additives such as a pH adjuster, an antifoaming agent, a preservative, an infrared absorber, an ultraviolet absorber, a thickener, a wax additive, and a crosslinking agent may be added as needed.

[0102] <Inkjet ink preparation method> Methods for preparing aqueous inks include, but are not limited to, the following: First, a pigment is added to an aqueous solution containing at least a pigment dispersion resin and water, and the mixture is stirred (premixed), followed by dispersion treatment using a dispersion means described below, and optionally centrifugal separation to obtain a pigment dispersion. Next, a binder resin, a water-soluble organic solvent, water, and, if necessary, optional components such as those listed above, are added to the pigment dispersion in appropriate amounts, thoroughly stirred and mixed, and then filtered to obtain an aqueous ink.

[0103] <Inkjet printing> The aqueous inkjet ink is printed onto a substrate using an inkjet printing method. A single-pass printing method (also known as a line printing method) is preferred. The single-pass printing method requires fewer scans than a multi-pass method, which scans the inkjet head multiple times, and therefore allows for faster printing speeds, making it suitable for industrial applications requiring high printing speeds. It is also suitable because high-quality prints can be obtained at a high recording resolution of 600 dpi or higher. Note that "recording resolution" is expressed in units of dpi (dots per inch) and represents the number of inkjet ink droplets printed per inch. In this specification, "recording resolution" refers to both the recording resolution in the transport direction of the substrate and the recording resolution in the direction perpendicular to the transport direction within the substrate's surface (hereinafter referred to as the recording width direction).

[0104] When printing inkjet ink using a one-pass printing method, the ink drop volume depends largely on the performance of the inkjet head, but to obtain printed matter with excellent resistance and print quality, it is preferably in the range of 0.6 to 60 pL. It is more preferably 1 to 50 pL, and particularly preferably 1.4 to 40 pL. Furthermore, to obtain high-quality images, it is particularly preferable to use an inkjet head with gradation specifications that allows the drop volume to be changed.

[0105] Water-based inks can be used in a single color, or they can be used as an ink set combining multiple colors depending on the application. While the combination is not particularly limited, full-color images can be obtained by using three colors: cyan, yellow, and magenta. The addition of black ink can enhance the sense of black and increase the visibility of text, etc. Color reproducibility can also be improved by adding colors such as orange, green, and violet. The combined use of white ink can achieve clear print quality when printing on substrates other than white, as well as packaging materials with high concealment properties for the contents. Even on white substrates, the combined use of white ink can enhance the print quality of color inks, resulting in higher quality and clearer print quality. To achieve these goals, high cohesion between the pretreatment liquid and the water-based ink is required, which can be achieved by using the pretreatment liquid of the present invention. The ink may also contain a clear ink that does not contain pigments and therefore substantially does not contain colorant components.

[0106] <Base material> The substrate onto which the pretreatment liquid of the present invention is printed is not particularly limited, and any known substrate can be used. Among them, from the viewpoint of packaging and label materials, non-permeable substrates or poorly permeable substrates are preferred, and the pretreatment liquid of the present invention can be particularly preferred for use on non-permeable substrates.

[0107] Examples of impermeable or poorly permeable substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, and polyvinyl alcohol; coated paper substrates such as coated paper, art paper, and cast paper; metal substrates such as aluminum, iron, stainless steel, and titanium; and glass substrates.

[0108] The substrate may have a smooth or uneven surface, and may be transparent, semi-transparent, or opaque. Two or more of these recording media may be laminated together. A release adhesive layer may be provided on the side opposite the printing surface, or an adhesive layer may be provided on the printing surface after printing. The recording medium used in the inkjet recording method of the present invention may be in the form of a roll or a sheet.

[0109] It is also preferable to subject the non-permeable substrates or poorly permeable substrates exemplified above to a surface modification method such as corona treatment or plasma treatment, because these methods improve the wettability of the pretreatment liquid and the aqueous ink of the present invention, improve print image quality and drying properties, and also improve abrasion resistance and adhesion due to the uniformity of the surface of the printed matter. [Example]

[0110] The present invention will be specifically described below with reference to examples and comparative examples. In the following description, "parts" and "%" represent "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0111] <Synthesis example of block polymer BP1> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, dropping funnel, and gas inlet tube was charged with 30 parts of methacrylate DMA, 10 parts of methyl methacrylate, 2.8 parts of methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, and 55 parts of methyl ethyl ketone while introducing nitrogen gas. The mixture was heated to 80 ° C. with stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.2 parts of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. The reaction was continued for another hour at 80 ° C., and then cooled to room temperature to obtain a methyl ethyl ketone solution of hydrophilic units having tertiary amino groups.

[0112] To the resulting methyl ethyl ketone solution, 30 parts of benzyl methacrylate, 30 parts of methyl methacrylate, and 80 parts of methyl ethyl ketone were added, and the mixture was again heated to 80°C while stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.3 parts of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. The reaction was continued at 80°C for another hour, and then cooled to room temperature to obtain a methyl ethyl ketone solution containing a block polymer in which a hydrophobic unit portion was bonded to a hydrophilic unit portion.

[0113] Next, 100 parts of ion-exchanged water and 100 parts of ethanol were added to the reaction vessel and the temperature was raised to 30°C. After stirring for 15 minutes, 20 parts of butyl glycidyl ether, 50 parts of ion-exchanged water, and 120 parts of ethanol were mixed and added dropwise to the reaction solution over 2 hours. The reaction was continued for another 2 hours at 30°C to obtain a solution containing a block polymer in which the tertiary amino groups in the hydrophilic unit moieties were converted to quaternary ammonium hydroxides. Subsequently, the entire amount of methyl ethyl ketone and ethanol was distilled under reduced pressure at 50°C. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content was 25%, obtaining an aqueous dispersion containing block polymer BP1. The mass of butyl diglycidyl ether used was calculated from the molar amount required to convert 80% of the tertiary amino groups contained in one polymer molecule to quaternary ammonium hydroxides.

[0114] The block polymer BP1 obtained had a number average molecular weight (Mn) of 14,700, a molecular weight distribution (PDI) of 1.33, and an average particle size of 55 nm.

[0115] <Synthesis examples of block polymers BP2-14 and BP41-47> Except for using the materials listed in Table 1, 25% aqueous dispersions of block polymers BP2 to BP14 and BP41 to BP47 were obtained in the same manner as for block polymer BP1.

[0116] <Synthesis example of block polymer BP15> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, dropping funnel, and gas inlet tube was charged with 30 parts of benzyl methacrylate, 30 parts of methyl methacrylate, 2.8 parts of methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, and 50 parts of methyl ethyl ketone while introducing nitrogen gas. The mixture was heated to 80°C with stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.2 parts of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. The reaction was continued at 80°C for another 2 hours, after which the mixture was cooled to room temperature to obtain a methyl ethyl ketone solution of the hydrophobic unit moiety.

[0117] To the resulting methyl ethyl ketone solution, 30 parts of methacrylate DMA, 10 parts of methyl methacrylate, and 85 parts of methyl ethyl ketone were added, and the mixture was again heated to 80°C while stirring. After stirring for 15 minutes, 10 parts of ethanol and 0.3 parts of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. The reaction was continued for another 1 hour at 80°C to obtain a methyl ethyl ketone solution containing a block polymer in which a hydrophilic unit portion having a tertiary amino group was bonded to a hydrophobic unit portion.

[0118] Next, an aqueous dispersion containing block polymer BP15, in which the tertiary amino groups in the hydrophilic unit moieties were converted to quaternary ammonium hydroxides, was obtained in the same manner as for block polymer BP1, except that the materials listed in Table 1 were used instead.

[0119] <Synthesis example of block polymer BP16> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, dropping funnel, and gas inlet tube was charged with 25 parts of Light Ester G, 10 parts of methyl methacrylate, 2.8 parts of methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, and 47 parts of methyl ethyl ketone while introducing nitrogen gas. The mixture was heated to 80°C with stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.2 parts of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. The reaction was continued for another hour at 80°C, and then cooled to room temperature to obtain a methyl ethyl ketone solution of hydrophilic units having epoxy groups.

[0120] To the resulting methyl ethyl ketone solution, 30 parts of benzyl methacrylate, 35 parts of methyl methacrylate, and 88 parts of methyl ethyl ketone were added, and the mixture was again heated to 80°C while stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.3 parts of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. The reaction was continued at 80°C for another hour, and then cooled to room temperature to obtain a methyl ethyl ketone solution of a block polymer in which hydrophobic unit moieties were bonded to hydrophilic unit moieties.

[0121] Next, 100 parts of ion-exchanged water and 100 parts of ethanol were added to the reaction vessel and the temperature was raised to 30°C. After stirring for 15 minutes, 15.7 parts of dimethylaminoethanol, 50 parts of ion-exchanged water, and 120 parts of ethanol were mixed and added dropwise to the reaction solution over 2 hours. The reaction was continued for another 2 hours at 30°C to obtain a solution containing a block polymer in which the epoxy groups in the hydrophilic unit moieties were converted to quaternary ammonium hydroxides. Subsequently, the entire amount of methyl ethyl ketone and ethanol was distilled under reduced pressure at 50°C. After cooling to room temperature, further ion-exchanged water was added to obtain a resin solids content of 25%, yielding an aqueous dispersion containing block polymer BP16. The mass of dimethylaminoethanol used was calculated from the molar amount required to convert all of the epoxy groups contained in one polymer molecule to quaternary ammonium hydroxides.

[0122] <Synthesis example of block polymers BP17 and BP18> Except for using the materials listed in Table 1, 25% aqueous dispersions of block polymers BP17 and BP18 were obtained in the same manner as for block polymer BP16.

[0123] <Synthesis example of block polymer BP48> A methyl ethyl ketone solution of a block polymer in which a hydrophobic unit moiety is bonded to a hydrophilic unit moiety having a tertiary amino group was obtained by the same procedure as for block polymer BP1, except that the materials listed in Table 1 were used. Next, 19.3 parts of benzyl chloride was added to the resulting methyl ethyl ketone solution, and the temperature was raised again to 80°C. After stirring for 6 hours, the tertiary amino groups were converted into quaternary ammonium salts, yielding a methyl ethyl ketone solution of a block polymer in which the hydrophilic unit has a quaternary ammonium halide salt. Next, 165 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 90°C, and the entire amount of methyl ethyl ketone was distilled. After cooling to room temperature, further ion-exchanged water was added to obtain an aqueous dispersion containing block polymer BP48, with the resin solids content at 30%. The mass of benzyl chloride used was calculated from the molar amount required to convert 60% of the tertiary amino groups in one polymer molecule into quaternary ammonium salts.

[0124] <Synthesis example of block polymer BP49> An ethanol solution of a block polymer in which a hydrophobic unit moiety is bonded to a hydrophilic unit having a quaternary ammonium salt was obtained in the same manner as for block polymer BP1, except that the materials listed in Table 1 were used. Next, 165 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 90°C, and the entire amount of ethanol was distilled. After cooling to room temperature, further ion-exchanged water was added so that the resin solids content was 30%, yielding an aqueous dispersion containing block polymer BP49.

[0125] <Synthesis example of polymer P50> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, two dropping funnels, and a gas inlet tube was charged with 100 parts of methyl ethyl ketone and heated to 80°C while stirring and introducing nitrogen gas. Next, two dropping funnels were prepared. One of them was charged with 60 parts of methacrylate DMA, 20 parts of methyl methacrylate, and 20 parts of styrene dissolved in 150 parts of methyl ethyl ketone and added dropwise over 2 hours. The other was charged with 1 part of 2,2'-azobis(isobutyrate)dimethyl ester dissolved in 7.5 parts of methyl ethyl ketone and added dropwise over 2 hours. After the addition was completed, the reaction was continued at 80°C for 1 hour, after which 0.4 parts of 2,2'-azobis(isobutyrate)dimethyl ester dissolved in 2 parts of methyl ethyl ketone was added to the reaction vessel. The reaction was continued for another 1 hour, then cooled to room temperature, and terminated.

[0126] Next, 100 parts of ion-exchanged water and 100 parts of ethanol were added to the reaction vessel and the temperature was raised to 30°C. After stirring for 15 minutes, 40 parts of butyl glycidyl ether, 50 parts of ion-exchanged water, and 120 parts of ethanol were mixed and added dropwise to the reaction solution over 2 hours. The reaction was continued for another 2 hours at 30°C to obtain a solution containing a polymer in which the tertiary amino groups had been converted to quaternary ammonium hydroxides. Subsequently, the entire amount of methyl ethyl ketone and ethanol was distilled under reduced pressure at 50°C. After cooling to room temperature, further ion-exchanged water was added so that the resin solids content was 25%, obtaining an aqueous dispersion containing polymer P50. The mass of butyl glycidyl ether used was calculated from the molar amount required to convert 80% of the tertiary amino groups contained in one polymer molecule to quaternary ammonium hydroxides.

[0127] <Synthesis example of polymer P51> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, two dropping funnels, and a gas inlet tube was charged with 100 parts of methyl ethyl ketone and heated to 80°C while stirring and introducing nitrogen gas. Next, two dropping funnels were prepared. One of them was charged with 70 parts of methacrylate DMA, 15 parts of methyl methacrylate, and 15 parts of styrene dissolved in 150 parts of methyl ethyl ketone, and added dropwise over 2 hours. The other was charged with 1 part of 2,2'-azobis(isobutyrate)dimethyl ester dissolved in 7.5 parts of methyl ethyl ketone and added dropwise over 2 hours. After the addition was completed, the reaction was continued for 1 hour at 80°C. Then, 0.4 parts of 2,2'-azobis(isobutyrate)dimethyl ester dissolved in 2 parts of methyl ethyl ketone was added to the reaction vessel. The reaction was continued for another 1 hour, after which the mixture was cooled to room temperature and terminated.

[0128] Next, 100 parts of ion-exchanged water and 100 parts of ethanol were added to the reaction vessel and the temperature was raised to 30°C. After stirring for 15 minutes, 16.5 parts of butyl glycidyl ether, 50 parts of ion-exchanged water, and 120 parts of ethanol were mixed and added dropwise to the reaction solution over 2 hours. The reaction was continued for another 2 hours at 30°C to obtain a solution containing a polymer in which the tertiary amino groups had been converted to quaternary ammonium hydroxides. Subsequently, the entire amount of methyl ethyl ketone and ethanol was distilled under reduced pressure at 50°C. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content was 30%, thereby obtaining an aqueous polymer solution containing quaternary ammonium hydroxides. The mass of butyl glycidyl ether used was calculated from the molar amount required to convert 95% of the tertiary amino groups contained in one polymer molecule to quaternary ammonium hydroxides.

[0129] Next, 100 parts of the aqueous polymer solution with a solids content of 30% and 40 parts of ion-exchanged water were charged into a reaction vessel equipped with a thermometer, reflux condenser, stirrer, two dropping funnels, and a gas inlet tube. The mixture was heated to 88°C while stirring and introducing nitrogen gas. Next, two dropping funnels were prepared. One was charged with 45 parts of methyl methacrylate and 25 parts of styrene, and the mixture was added dropwise over 2 hours. The other was charged with 12 parts of a 3% aqueous solution of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) and the mixture was added dropwise over 2 hours. After the addition was completed, the reaction was continued at 88°C for 2 hours, then cooled to room temperature to terminate the reaction. Next, ion-exchanged water was added to the mixture so that the resin solids content was 30%, yielding an aqueous dispersion of polymer P51, which is a core-shell emulsion resin particle having a quaternary ammonium hydroxide in the shell.

[0130] [Table 1]

[0131] [Table 1]

[0132] The abbreviations listed in Table 1 are as follows: BM1448: BORON MOLECULAR, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid methyl ester BM1442: 2-cyano-2-butyldodecyl trithiocarbonate manufactured by BORON MOLECULAR DMC-80: Sanyo Chemical Industries, Ltd. methacrylate DMC-80; methacryloyloxyethyl trimethylammonium chloride (78% by mass aqueous solution) DMA: Sanyo Chemical Industries, Ltd. methacrylate DMA; 2-(dimethylamino)ethyl methacrylate DMAPAA: N-[3-(dimethylamino)propyl]acrylamide manufactured by KJ Chemicals GMA: Light Ester G manufactured by Kyoeisha Chemical Co., Ltd.; glycidyl methacrylate 4HBAGE: Mitsubishi Chemical Corporation 4-hydroxybutyl acrylate glycidyl ether AIBN: 2,2'-azobisisobutyronitrile Denacol EX-121: Nagase ChemteX 2-ethylhexyl glycidyl ether Denacol EX-141: Phenyl glycidyl ether manufactured by Nagase ChemteX Corporation DMAE: Dimethylaminoethanol TEA: Triethylamine

[0133] The physical properties of each resin obtained in the above synthesis examples and the detailed constitutional units represented by formula (1) are shown in Table 2.

[0134] [Table 2]

[0135] The abbreviations listed in Table 2 are as follows: *1:-CH2CH(OH)CH2(CH2)3CH3 *2:-CH2CH(OH)CH2(CH2)7CH3 *3: -CH2CH(OH)CH2OC6H5 *4: -CH2CH2OH *5: -CH2CH(OH)CH2- *6: -(CH2)4OCH2CH(OH)CH2-

[0136] Furthermore, block polymer BP43 could not be removed from the reaction vessel after synthesis, and no aqueous dispersion was obtained.Furthermore, block polymers BP44 and BP46 were determined to be water-soluble resins because particle sizes could not be obtained in particle size distribution measurements.

[0137] <Example of synthesis of water-soluble cationic resin CP1> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, two dropping funnels, and a gas inlet tube was charged with 85 parts of isopropyl alcohol and heated to 80 °C while stirring and introducing nitrogen gas. Next, two dropping funnels were prepared. One of them was charged with 96.2 parts of methacrylate DMC-80, 15 parts of methyl methacrylate, and 10 parts of benzyl methacrylate dissolved in 150 parts of isopropyl alcohol and added dropwise over 2 hours. The other was charged with 1.2 parts of 2,2'-azobis(isobutyric acid)dimethyl dissolved in 7.5 parts of isopropyl alcohol and added dropwise over 2 hours. After the addition was completed, the reaction was continued at 80 °C for 1 hour, after which 0.4 parts of 2,2'-azobis(isobutyric acid)dimethyl dissolved in 2 parts of isopropyl alcohol was added to the reaction vessel. The reaction was continued for another 1 hour and then terminated. Subsequently, 180 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 95°C, and the entire amount of isopropyl alcohol was distilled off. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content was 30%, and an aqueous solution containing the water-soluble cationic resin CP1 was obtained.

[0138] The water-soluble cationic resin CP1 thus obtained had a weight average molecular weight (Mw) of 3,8000 and a molecular weight distribution (PDI) of 1.97.

[0139] <Synthesis examples of water-soluble cationic resins CP2 to CP7> Except for using the materials listed in Table 3, 30% aqueous solutions of water-soluble cationic resins CP2 to CP7 were obtained in the same manner as for the water-soluble cationic resin CP1.

[0140] <Synthesis example of water-soluble cationic resin CP8> The polymerization reaction was carried out in the same manner as for the water-soluble cationic resin CP1, except that the materials listed in Table 3 were used. An isopropyl alcohol solution of a polymer containing tertiary amino groups was obtained. Next, 47 parts of bromobutane was added to the resulting isopropyl alcohol solution, and the temperature was raised again to 80°C. After stirring for 6 hours, 60% of the tertiary amino groups contained in the polymer were converted into quaternary ammonium salts. Next, 165 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 95°C, and the entire amount of isopropyl alcohol was distilled. After cooling to room temperature, further ion-exchanged water was added to achieve a resin solids content of 30%, yielding an aqueous solution containing the water-soluble cationic resin CP8.

[0141] The physical properties of each resin obtained in the above synthesis examples and the detailed constitutional unit represented by formula (2) are as shown in Table 3.

[0142] [Table 3]

[0143] The abbreviations listed in Table 3 are as follows: DMC-80: Sanyo Chemical Industries, Ltd. methacrylate DMC-80; methacryloyloxyethyl trimethylammonium chloride (78% by mass aqueous solution) DMAEA-BQ: 2-(dimethylamino)ethyl acrylate-benzyl chloride quaternary salt (75% by mass aqueous solution) manufactured by KJ Chemicals DMAPAA-Q: N-[3-(dimethylamino)propyl]acrylamide-methyl chloride quaternary salt (75% by mass aqueous solution) manufactured by KJ Chemicals DMA: Sanyo Chemical Industries, Ltd. methacrylate DMA; 2-(dimethylamino)ethyl methacrylate V601: 2,2'-azobis(isobutyric acid dimethyl) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0144] <Pretreatment liquid PR1 manufacturing example> 50 parts of block polymer BP1 (resin solids content 25%), 15 parts of an aqueous solution of water-soluble cationic resin CP1 (resin solids content 30%), 25 parts of 1,2-propanediol, 0.5 parts of TegoWet 280, 0.5 parts of Surfynol 440, 0.1 parts of adipic acid dihydrazide, and 0.05 parts of Proxel GXL were sequentially added to a mixing vessel, and ion-exchanged water was added to bring the total pretreatment solution to 100 parts. The mixture was then stirred in a disperser until sufficiently uniform. The mixture was then filtered through a 0.5 μm pore membrane filter to produce pretreatment solution PR1.

[0145] <Production examples of pretreatment solutions PR2-18, 20-28, 41-51> Pretreatment solutions PR2 to 18, 20 to 28, and 41 to 51 were obtained in the same manner as pretreatment solution PR1, except that the materials listed in Table 4 were used instead.

[0146] [Table 4]

[0147] The abbreviations listed in Table 4 are as follows: PAS-H-1L: Nittobo Medical Co., Ltd. Diallyldimethylammonium chloride polymer (Mw 8,500, resin concentration 28% aqueous solution) TegoWet280: Evonik siloxane surfactant Surfynol 440: Acetylene diol surfactant manufactured by Shin-Etsu Chemical Co., Ltd.

[0148] <Synthesis example of pigment dispersing resin> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, dropping funnel, and gas inlet tube was charged with 95 parts of butanol. While introducing nitrogen gas, the temperature inside the reaction vessel was raised to 110°C under stirring. After 15 minutes of stirring, 35 parts of styrene, 35 parts of acrylic acid, 30 parts of behenyl acrylate, and 6 parts of dimethyl 2,2'-azobis(isobutyrate) as polymerizable monomers were mixed and added dropwise to the reaction solution over 2 hours. The reaction was continued for another 3 hours at 110°C, after which 0.6 parts of dimethyl 2,2'-azobis(isobutyrate) were added. The reaction was continued for another 1 hour at 110°C to obtain a pigment dispersion resin solution. After cooling to room temperature, dimethylaminoethanol was added to completely neutralize the mixture, and 100 parts of ion-exchanged water was added to make it aqueous. The temperature was then raised above 100°C, and the butanol was azeotropically distilled with water to remove all of the butanol. After cooling to room temperature, ion-exchanged water was added to give a resin solids content of 30%, resulting in an aqueous solution of pigment dispersion resin. The pigment dispersion resin had a weight-average molecular weight of 28,000 and an acid value of 273 mgKOH / g.

[0149] <Production example of cyan pigment dispersion> A pigment dispersion (cyan) was obtained by mixing 20 parts of Toyocolor Lionol Blue 7358G (CI Pigment Blue 15:3), 15 parts of an aqueous pigment dispersion resin (resin solids content 30%), and 65 parts of ion-exchanged water, and pre-dispersing the mixture in a disperser. The final dispersion was then carried out in a 0.6 L Dyno-Mill filled with 1,800 g of 0.5 mm diameter zirconia beads to obtain a pigment dispersion (cyan). Pigment dispersions M (magenta), Y (yellow), and K (black) were also obtained in the same manner as pigment dispersion C, except that the CI Pigment Blue 15:3 was replaced with the pigments listed below. Magenta:CIPImment Red 122 (DIC FASTGEN SUPER MAGENTA RGT) Yellow: CI Pigment Yellow 14 (Toyocolor LIONOL YELLOW TT-1405G) Black: CI Pigment Black 7 (Printex85 manufactured by Orion Engineered Carbons)

[0150] <Production example of white pigment dispersion> 40 parts of CR-90-2 (titanium oxide) manufactured by Ishihara Sangyo Kaisha, Ltd., 30 parts of an aqueous solution of a pigment dispersion resin (resin solid content 30%), and 30 parts of water were mixed, and dispersed in the same manner as for the cyan pigment dispersion, to obtain a white pigment dispersion W.

[0151] <Example of ink binder resin synthesis> A reaction vessel equipped with a thermometer, reflux condenser, stirrer, dropping funnel, and gas inlet tube was charged with 93.4 parts of butanol. While introducing nitrogen gas, the reaction vessel was heated to 110°C under stirring. After 15 minutes of stirring, 30 parts of styrene, 5 parts of methacrylic acid, 50 parts of methyl methacrylate, 15 parts of lauryl methacrylate, and 6 parts of dimethyl 2,2'-azobis(isobutyrate) as a polymerization initiator were mixed and added dropwise to the reaction solution over 2 hours. The reaction was continued for another 3 hours at 110°C, after which 0.6 parts of dimethyl 2,2'-azobis(isobutyrate) were added, and the reaction was continued for another 1 hour at 110°C to obtain a binder resin solution. After cooling to room temperature, 5.17 parts of dimethylaminoethanol were added to neutralize the mixture, and 100 parts of ion-exchanged water was added to make it aqueous. The mixture was then heated to 100°C or higher, and the butanol was azeotropically distilled with water to distill off the entire amount of butanol. After cooling to room temperature, ion-exchanged water was added to give a resin solids content of 30%, yielding an aqueous solution of binder resin 1. The binder resin 1 had a weight-average molecular weight of 18,000 and an acid value of 32 mgKOH / g.

[0152] <Inkjet ink manufacturing example> 25 parts of cyan pigment dispersion, 30 parts of a 30% aqueous solution of ink binder resin, 20 parts of 1,2-propanediol, 1 part of TegoWet 280, 1 part of Surfynol 465 (an acetylene diol surfactant manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.05 parts of Proxel GXL (a preservative) were added sequentially to a mixing vessel, and then ion-exchanged water was added to make the total ink volume 100 parts, and the mixture was stirred in a disperser until sufficiently uniform. The mixture was then filtered through a 0.5 μm pore membrane filter to prepare Ink C.

[0153] Inkjet inks were prepared in the same manner as ink C, except that the materials listed in Table 5 were used.

[0154] [Table 5]

[0155] <Creating printed materials> Six inkjet heads (KJ4B-1200, manufactured by Kyocera Corporation, resolution 1200 dpi, maximum drive frequency 64 kHz) were installed above a conveyor capable of transporting the printing substrate, aligned in the direction of transport of the printing substrate. The pretreatment liquid, white ink, and color inks (K, C, M, Y) prepared above were loaded from the upstream side in the transport direction. Next, the printing substrate was fixed onto the conveyor, and the conveyor was driven at 50 m / min. As the substrate passed the inkjet head installation area, the pretreatment liquid was ejected at a drop volume of 3 pL and the inkjet ink at a drop volume of 2 pL, printing an image. The printed substrate was then immediately placed in an air oven at 70°C and dried for 3 minutes. The printing substrate used was Avery Dennison BWS854 (surface: PET clear film).

[0156] When printing to evaluate printed matter, a solid image with a coverage rate of 100% was selected for the pretreatment liquid, and a dot image with a coverage rate of 30% was selected for each inkjet ink (white and four colors). Furthermore, when printing to evaluate the ejection properties of the pretreatment liquid, only the pretreatment liquid was ejected and the image was printed. Note that because the pretreatment liquid contains virtually no colorant, it was sometimes difficult to distinguish or understand the results by observing the printed matter or ink. In this case, printing and evaluation were performed using a pretreatment liquid in which 0.05 parts of the cationic dye Rhodamine B was added and dissolved in 100 parts by mass of the pretreatment liquid.

[0157] <Evaluation 1: Initial ejection> The pretreatment liquid was printed using the inkjet printer device and printing conditions described above. The initial dischargeability of the pretreatment liquid was evaluated by visually and with a magnifying glass to check whether the initial portion of the solid print with a printing rate of 100% was printed. The evaluation criteria are as follows, with ◎ and ◯ being in the practical usable range. ◎: No chipping was found at the beginning of the stamping, even when checked visually and with a magnifying glass. 〇: No chips are visible to the naked eye, but chips less than 1 mm are found when inspected with a magnifying glass △: Chips of 1mm or more but less than 5mm were visually confirmed at the beginning of the shot ×: A chip of 5 mm or more was visually confirmed at the beginning of the shot.

[0158] <Evaluation 2: Standby discharge> A solid print with a 100% coverage of the pretreatment liquid was performed under the same printing conditions as in Evaluation 1. After printing, the inkjet ejection device was left on standby for a certain period of time in an environment of 25°C, and then a nozzle check pattern was printed and visually confirmed to determine whether any nozzles had been clogged, thereby evaluating the standby ejection performance. The evaluation criteria are as follows, with ◎ and ◯ being in the practical range. ◎: No missing nozzles even after waiting for 2 hours 〇: No missing nozzles occurred when printing after waiting for 1 hour, but missing nozzles occurred when printing after waiting for 2 hours. △: When printing after waiting for 1 hour, 1 to 9 nozzles were missing. ×: When printing after waiting for 1 hour, 10 or more nozzles were missing

[0159] <Evaluation 3: Redissolution> 0.3 g of ink was added to a 30 g small aluminum container and dried and solidified for the specified time in an air oven at 35°C. After drying for 1 hour under the above conditions, none of the pretreatment liquids adhered to the fingertips when touched. 10 g of ion-exchanged water was then added, and after leaving to stand for 1 hour, the resolubility of the dried and solidified ink was evaluated by visually observing whether the pretreatment liquid dissolved in the ion-exchanged water. The evaluation criteria are as follows, with ◎ and 〇 being in the practical range. ◎: Even ink that had been dried and solidified in an air oven at 35°C for 6 hours was dissolved in ion-exchanged water. ○: Ink dried and solidified in an air oven at 35°C for 6 hours did not dissolve in ion-exchanged water, but ink dried and solidified for 1 hour did dissolve. △: Ink dried and solidified in an air oven at 35°C for 1 hour did not dissolve in ion-exchanged water, but ink dried and solidified for 30 minutes did dissolve. ×: Even the ink that had been dried and solidified in an air oven at 35°C for 30 minutes did not dissolve in ion-exchanged water.

[0160] <Evaluation 4: Storage stability> The volume average particle diameter (D50) of the pretreatment liquid was measured using a Nanotrac UPA-EX150 manufactured by Microtrac Bell. This ink was placed in an airtight container and stored in a thermostatic chamber at 70°C for two weeks, after which the volume average particle diameter was measured again using the same device, and the change in the volume average particle diameter of the pretreatment liquid before and after aging was calculated to evaluate the storage stability of the pretreatment liquid. The criteria are as follows, with ◎ and 〇 being in the practical range. ◎: The rate of change in volume average particle size was less than ±15% ○: The rate of change in volume average particle size was ±15% or more and less than ±30% △: The rate of change in volume average particle size was ±30% or more and less than ±45% ×: The rate of change in volume average particle size after 2 weeks of storage was ±45% or more

[0161] <Rating 5: Alcohol resistance> Using the inkjet printer device and printing conditions described above, the pretreatment liquid and inkjet ink (white and four colors) were printed, and the resulting prints were rubbed with a cotton swab dipped in 99.5% ethanol and visually inspected to evaluate their alcohol resistance. The evaluation criteria are as follows, with ◎ and ◯ being in the practical range. ◎: Even after rubbing 20 times with a cotton swab soaked in ethanol, the printed material did not peel off and the pretreatment liquid did not adhere to the cotton swab. Good: After rubbing 10 times with a cotton swab soaked in ethanol, the printed material did not peel off and the pre-treatment liquid did not adhere to the cotton swab. However, after rubbing 20 times, the printed material peeled off and the pre-treatment liquid adhered to the cotton swab. △: After rubbing five times with a cotton swab soaked in ethanol, the printed material did not peel off and the pretreatment liquid did not adhere to the cotton swab. However, after rubbing 10 times, the printed material peeled off and the pretreatment liquid adhered to the cotton swab. ×: When rubbed strongly five times with a cotton swab soaked in ethanol, the printed material peeled off and the pretreatment liquid adhered to the cotton swab.

[0162] <Rating 6: Abrasion resistance (water)> The same printing as in Evaluation 5 was carried out, and the resulting print was subjected to a rubbing fastness test using a Gakushin-type rubbing fastness tester with a cotton cloth (Kanakin No. 3) soaked in ion-exchanged water at a load of 200 g / cm. 2 The printed surface was rubbed 50 times back and forth, and the water abrasion resistance (water) was evaluated based on the percentage of peeled area of ​​the printed surface. The evaluation criteria are as follows, with ◎ and ◯ being in the range of practical use. ◎: No peeling of the printed surface ○: Less than 20% of the printed surface has peeled off △: Peeling of the printed surface is 20% or more but less than 50% ×: Peeling of the printed surface is 50% or more

[0163] <Rating 7: Rub resistance (alcohol)> The same printing as in Evaluation 5 was carried out, and the resulting print was subjected to a rubbing fastness test using a Gakushin-type rubbing fastness tester with a cotton cloth (Kanakin No. 3) soaked in a 60% aqueous solution of ethanol at a load of 200 g / cm. 2 The printed surface was rubbed 20 times back and forth, and the abrasion resistance (alcohol) was evaluated based on the percentage of the area of ​​the printed surface that had peeled off. The evaluation criteria were the same as for Evaluation 6.

[0164] Table 6 shows the evaluation results of the pretreatment liquid and the resulting prints. [Table 6]

[0165] Examples 1 to 18 and 20 to 28 each contained a hydrophilic unit (b-1) and a hydrophobic unit (b-2), the mass ratio of the hydrophilic unit (b-1) to the hydrophobic unit (b-2) was 10:90 to 70:30, the number average molecular weight was 8,000 to 30,000, the average particle size was 30 to 150 nm, and a block polymer containing 5 to 45 mass% of the structural unit represented by formula (1) was used. As a result, it was possible to obtain a pretreatment liquid and a printed matter that were excellent in discharge performance, resolubility, storage stability, water resistance, and alcohol resistance.

[0166] In Comparative Example 41, the number-average molecular weight of the block polymer was less than 8,000, resulting in poor alcohol resistance, and in Comparative Example 42, the number-average molecular weight exceeded 30,000, resulting in poor ejection performance. In Comparative Examples 44 and 46, the block polymer was a water-soluble resin with no particle size, resulting in poor water resistance and alcohol resistance. In Comparative Example 45, the mass ratio of the hydrophilic unit (b-1) was 10% or less, and in Comparative Example 47, the average particle size exceeded 150, resulting in poor standby ejection performance, resolubility, and storage stability.

[0167] In Comparative Examples 48 and 49, the counter anion of the tetraammonium salt of the structural unit represented by formula (1) was not a hydroxide ion, resulting in poor alcohol resistance. Comparative Example 50, although containing the structural unit represented by formula (1), was a randomly polymerized resin, resulting in poor discharge performance and alcohol resistance. Comparative Example 51, although containing the structural unit represented by formula (1), was a core-shell emulsion resin, resulting in poor standby discharge, resolubility, and storage stability.

Claims

1. A block polymer (B) for a pretreatment liquid to be used together with an aqueous inkjet ink, the block polymer (B) having a hydrophilic unit (b-1) and a hydrophobic unit (b-2), wherein the mass ratio of the hydrophilic unit (b-1) to the hydrophobic unit (b-2) is 10:90 to 70:30, the hydrophilic unit (b-1) contains a structural unit represented by formula (1) in an amount of 5 to 45% by mass, relative to the total mass % of the block polymer (B), and the block polymer (B) has a number average molecular weight of 8,000 to 30,000 and an average particle size of 30 to 150 nm. Formula (1) 【Chemistry 1】 (In formula (1), R １ represents a hydrogen atom or a methyl group, Y represents an oxygen atom or —NH—, Z represents a hydroxyl group or an alkylene group which may contain an oxygen atom, R ２ , R ３ , R ４ each independently represents an aliphatic hydrocarbon group or an aromatic hydrocarbon group which may contain a hydroxyl group or an oxygen atom)

2. A pretreatment liquid comprising the block polymer (B) according to claim 1.

3. A water-soluble cationic resin (A) comprising the block polymer (B) according to claim 1, a pre-treatment liquid, wherein the water-soluble cationic resin (A) contains a structural unit represented by formula (2) in an amount of 50 to 100% by mass, based on the total mass of the water-soluble cationic resin (A); Formula (2) 【Chemistry 2】 (In formula (2), R ５ represents a hydrogen atom or a methyl group, and L represents an oxygen atom, —NH—, or —OCH ２ represents CH(OH)—, and R ６ , R ７ , R ８ each independently represents a hydrocarbon group having 1 to 8 carbon atoms; X － represents a monovalent anion, and n represents an integer of 1 to 6.

4. 4. The pretreatment liquid according to claim 2, wherein printing is performed by an inkjet recording method.

5. An aqueous inkjet ink set comprising the pretreatment liquid according to claim 4 and an aqueous inkjet ink.

6. A printed material obtained by sequentially printing the pretreatment liquid according to claim 4 and one or more types of aqueous inkjet inks onto a substrate.

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