Inkjet inks, inkjet printing processes and ink sets for forming images on a substrate, and aqueous pigment dispersions for forming inkjet inks

Abstract

An inkjet ink for forming an image on a substrate, the inkjet ink comprising a pigment P, a block copolymer dispersant D for dispersing the pigment P and an aqueous carrier; wherein the block copolymer dispersant D comprises an anchoring segment A for anchoring to the pigment P, wherein the block copolymer dispersant additionally comprises a matrix stabilizing segment M for water phase stabilization of the pigment, wherein the anchoring segment A comprises a repeating unit R1 and a repeating unit R2 different from R1, wherein the hydrophobicity of the repeating unit R1 is lower than the hydrophobicity of the repeating unit R2, wherein the repeating unit R1 comprises a (poly)alkylene oxide coupled to a terminal group via a direct bond, a -C-O-C- ether bond or a -C-O-(C=O)-N- urethane bond, wherein the terminal group is selected from the group consisting of an alkyl group, an aryl group and combinations thereof.

Description

Invention Field

[0001] The present invention relates to inkjet inks for forming images on a substrate, inkjet printing processes, ink groups for inkjet inks, and aqueous pigment dispersions for forming inkjet inks. Inkjet printing processes for forming images on a substrate use inkjet inks according to the present invention. Ink groups for forming images on a substrate include inkjet inks according to the present invention. The present invention also relates to aqueous pigment dispersions for forming inkjet inks according to the present invention.

[0002] background

[0003] Inkjet printing, which forms an image on a substrate by applying more than one inkjet ink, is generally known. Inkjet inks used in industrial printing applications primarily use pigments as colorants, except for inkjet inks based on reactive dyes, which are still frequently used in the textile industry. Pigments are solid materials that remain solid within the inkjet ink carrier, in contrast to dyes that are actually dissolved in the carrier medium. Pigment particles are finely dispersed in the ink and have a nanoscale size. Typical inkjet printing processes use three or four colors of inkjet ink to produce multicolor images. Typical colors are cyan (C), magenta (M), yellow (Y), and black (K). CMY color inkjet inks are typically made from organic pigments, some of which contain metal atoms in a complex, while K inks use organic pigments typically made from carbon black. Pigment powders are not commercially available as nanoparticles, but rather as aggregates and clusters of pigment particles formed during the synthesis process. Pigment agglomerates and aggregates need to be reduced to a smaller size, typically achieved through grinding, milling, or other techniques that break down the agglomerates and aggregates to the nanoscale. Particle size reduction of pigment powder typically occurs in a carrier medium that will be used in subsequent stages in the ink. Such process steps to reduce pigment particle size are usually performed at higher pigment concentrations than those in the final ink, and are thus referred to as pigment dispersion.

[0004] As discussed above, pigments are mechanically broken down into sizes ranging from 30 nm to 300 nm, which necessitates stabilization by adding dispersants (or surfactants) to physically and / or electrostatically prevent pigment re-agglomeration. Typically, this is a physicochemical phenomenon because no chemical bonds exist between the pigment surface and the dispersant or surfactant, which can be a polymeric dispersant (e.g., random copolymers, block copolymers, graft copolymers).

[0005] Covalently bonded chemicals can sometimes be used to stabilize pigment particles in water-based inks, but this usually requires expensive manufacturing processes.

[0006] Known methods for preparing pigment dispersions are based on dispersants derived from random polymerization: these are used in analog inks, such as those for flexographic printing, but also in inkjet inks. Typically, random polymers consist of two monomers: one more pigment-ophilic and the other more compatible with the carrier liquid, or matrix-ophilic. These monomers are randomly dispersed within the polymer, thus there is no predefined polymer structure (i.e., monomer sequence) or number of repeating monomer units. Therefore, many polymers will have favorable structures capable of stabilizing pigment particles in the liquid, but inactive groups exist with “bad” structures for stabilization (e.g., insufficient pigment anchors, not close enough to each other, too few matrix-philic groups). These fractions are often not adsorbed or readily desorbed, resulting in unstable dispersions. Two main problems are the presence of unabsorbed high molecular weight dispersant molecules in the matrix, thus contributing to higher dispersion viscosity. Additionally, the viscoelastic properties of the final ink may be negatively affected. Both increased viscosity and the affected viscoelastic properties of the final ink can interfere with the droplet formation process, such as by increasing fog formation.

[0007] Another known method is block copolymer dispersants. Block copolymer dispersants containing hydrophobic and hydrophilic block segments have been disclosed in many inkjet ink patents. US 5859113 (DU PONT) discloses an AB block copolymer dispersant having polymer A segments and polymer B segments.

[0008] A wide variety of polymer dispersants, such as block copolymer dispersants, have been proposed, but the dispersion stability of pigments, especially in inkjet printing, still needs further improvement.

[0009] For consistent image quality, inkjet inks require dispersion stability, which can withstand, for example, high temperatures (above 60°C) during ink transport or storage to customers, as well as changes in the dispersion medium of the inkjet ink during use, such as water evaporation and increased concentration of water-soluble organic solvents, or the addition of functional polymers to improve ink adhesion, drying, water resistance, or scratch resistance on substrates.

[0010] In industrial inkjet processes, the requirements for the stability of pigment dispersions that can be used for inkjet printing are also increasing, especially in single-pass printing applications with higher jetting frequencies, smaller droplet formation, higher jetting temperatures, and / or more stringent requirements.

[0011] All ink additives (such as surfactants, latexes, polymers, oligomers, and (water-soluble) organic solvents) can compete with dispersants to interact with the pigment surface, thus negatively affecting the pigment dispersion stability. These additives are often organic in nature (and to some extent even incompatible with the ink matrix), and they will compete for the same organic surface of the pigment, particularly notably in water-based inks. If this occurs inside the printhead, it will lead to the removal of the dispersant from the surface, reducing or destroying stability, and producing irreversibly clogged nozzles, resulting in, for example, severe deterioration of white lines and image quality, or ink containing particles that are too large, negatively impacting the ink flow entering the printhead.

[0012] Due to increased demand, there is a need for further optimization of ink additives, such as optimization depending on the type of color pigment, to achieve consistent image quality and reliable inkjet processes.

[0013] Furthermore, for some colored pigments, it has been found that while enhancing the pigment stability required for inkjet inks, it is more difficult to obtain fine pigment dispersions in a simple way, such as by using milling processes.

[0014] It remains desirable to formulate block copolymer dispersants that provide high millability (i.e., can be milled very easily to the desired particle size) for different pigments without the need for additional cosolvents, and maintain a high level of stability in the pigment dispersion, so that the resulting pigment dispersion provides a wide range of versatility for the formulation of the final inkjet ink.

[0015] Therefore, there is a demand for inkjet inks capable of producing such stable coloring, where the dispersion stability of pigments in inkjet inks can be easily enhanced for a wider variety of inkjet inks. Invention Overview

[0017] According to a first aspect of the invention, an inkjet ink for forming an image on a substrate is provided, the inkjet ink comprising a pigment P, a block copolymer dispersant D for dispersing the pigment P, and an aqueous carrier; wherein the block copolymer dispersant D comprises an anchoring segment A for anchoring to the pigment P, wherein the block copolymer dispersant further comprises a matrix stabilizing segment M for aqueous stabilization of the pigment, wherein the anchoring segment A comprises a repeating unit R1 and a repeating unit R2 different from R1, wherein the hydrophobicity of the repeating unit R1 is lower than that of the repeating unit R2, wherein the repeating unit R1 comprises a (poly)epoxide coupled to a terminal group via a direct bond, a -COC-ether bond, or a -CO-(C=O)-N-carbamate bond, wherein the terminal group is selected from alkyl groups, aryl groups, and combinations thereof. In particular, the repeating unit R1 comprises a (poly)epoxide coupled to the terminal group via a direct bond or a -CO-(C=O)-N-carbamate bond.

[0018] According to another aspect of the invention, an inkjet printing process is provided for forming an image on a substrate by applying more than one inkjet ink to the substrate, wherein the more than one inkjet ink includes inkjet inks according to the invention.

[0019] According to another aspect of the invention, an inkjet ink set is provided, the inkjet ink set comprising more than one colored ink, wherein at least one of the inks is an inkjet ink according to the invention.

[0020] According to another aspect of the invention, an inkjet printer responsive to digital data signals is provided, the inkjet printer being equipped with inkjet inks or inkjet ink sets according to the invention.

[0021] According to another aspect of the invention, an aqueous pigment dispersion for forming inkjet ink is provided, the pigment dispersion comprising a pigment P, a block copolymer dispersant D for dispersing the pigment P, and an aqueous carrier; wherein the block copolymer dispersant D comprises an anchoring segment A for anchoring to the pigment P, wherein the block copolymer dispersant further comprises a matrix stabilizing segment M for aqueous stabilization of the pigment, wherein the anchoring segment A comprises a repeating unit R1 and a repeating unit R2 different from R1, wherein the hydrophobicity of the repeating unit R1 is lower than that of the repeating unit R2, wherein the repeating unit R1 comprises a (poly)epoxide coupled to a terminal group via a direct bond, a -COC-ether bond, or a -CO-(C=O)-N-carbamate bond, wherein the terminal group is selected from alkyl groups, aryl groups, and combinations thereof; and wherein the aqueous carrier comprises water.

[0022] Beneficial effects of the present invention

[0023] The inventors have discovered that stable colored inkjet inks can be readily manufactured using block copolymer dispersant D. Block copolymer dispersant D comprises a combination of repeating unit R1 and repeating unit R2, which is different from R1. Repeating unit R1 comprises a (poly)epoxide coupled to a terminal group via a direct bond, a -COC-ether bond, or a -CO-(C=O)-N-carbamate bond, wherein the terminal group is selected from alkyl groups, aryl groups, and combinations thereof.

[0024] The hydrophobicity of repeating unit R1 in block copolymer dispersant D is lower than that of repeating unit R2. Block copolymer dispersant D has been found to improve the pigment stability required for inkjet inks and simultaneously enhance the ease of manufacturing fine pigment dispersions with fine pigment particles in a simple manner, such as using a milling process. The combination of repeating units R1 and R2 surprisingly combines these advantages without any adverse effects. Furthermore, little or no water-soluble organic cosolvent is required to obtain the beneficially fine pigment particles. Therefore, the pigment dispersion according to the invention can be used to provide inkjet inks with various compositions in a multifunctional manner, such as those without water-soluble organic cosolvents or containing various amounts of water-soluble organic cosolvents.

[0025] Pigments can have surfaces with varying degrees of hydrophobicity, meaning that one portion of a pigment surface may be quite hydrophobic, while another portion may be less hydrophobic. It has been found that highly specialized design / selection of block copolymer dispersants is necessary to obtain stable pigment dispersions.

[0026] Using a block copolymer dispersant D with two different repeating units R1, R2 in the anchoring segment A used to anchor to pigment P may seem to increase the complexity of the block copolymer dispersant D, but the flexibility of the mixing ratio of the different repeating units of the block copolymer dispersant leads to a significant increase in milling performance and enables the manufacture of even more functional and stable pigment dispersions.

[0027] Furthermore, even when multiple ink additives, such as water-soluble organic solvents that may compete with dispersants, are added to inkjet inks, the selected block copolymer dispersant D used to disperse pigment P in the ink can prevent pigment P from re-agglomerating in the resulting inkjet ink.

[0028] Furthermore, the use of block copolymer dispersant D for dispersing pigment P can support and enhance jetting stability in industrial inkjet printing, where there are increasing demands for ink durability and consistent image quality.

[0029] (Pigment dispersion stability)

[0030] Pigment dispersion stability as defined in this application may include the pigment particle grinding characteristics of the pigment dispersion, and may include pigment dispersion stability characteristics when exposed to extreme conditions such as high temperature conditions (relative to room temperature or the normal operating temperature of the ink) and critical aqueous carrier conditions, such as by adding a competing water-soluble organic solvent to the carrier and / or increasing the amount of the competing water-soluble organic solvent.

[0031] The pigment particle grinding characteristics of pigment dispersions demonstrate the ability to easily reduce the size of pigment agglomerates and aggregates to nanoscale dimensions such as 30 nm–300 nm, which is stabilized by adding block copolymer dispersants to physically and / or electrostatically prevent pigment reagglomeration.

[0032] Embodiments of the present invention

[0033] The following exemplary embodiments are described; however, the invention is not limited to these embodiments:

[0034] (Block copolymer pigment dispersant)

[0035] It has been found that selecting repeating units of anchoring segments of block copolymer dispersants D with different properties allows for specialized chemical fine-tuning of the dispersant, creating the possibility of optimizing the physical interaction between the polymer dispersant and the pigment surface. The balancing role in the design of copolymer dispersants lies in the balance between pigment affinity and matrix affinity. For water-based inks, the relative hydrophilicity / hydrophobicity of the polymer appears to be important. In this way, pigment particles P can be compatible with the carrier.

[0036] The inventors have discovered that, particularly when dealing with pigments that have chemically distinct regions on the surface of pigment particles, simply changing the number of repeating units in the chain segment may not be sufficient. To provide a solution to this problem, the inventors have found that using a second, chemically different type of repeating unit, possibly with a different number of repeating units, can be highly beneficial.

[0037] Unlike random copolymers, block copolymer dispersants have an engineered molecular structure in terms of chemical composition (incorporated into the polymer in a block manner), a narrow molecular weight distribution, and / or defined block chain lengths of different constituent blocks or monomers. Block copolymer dispersants can consist of two or more different monomers arranged in blocks within the polymer.

[0038] The block copolymers of the present invention have blocks with narrow molecular weight distribution and / or defined block chain lengths. Block copolymers are defined by polymers composed of different blocks, wherein each block is substantially equal in size and composition, meaning that all polymer molecules have substantially the same composition and length. Identical composition means that, in the case where a block contains one type of repeating unit, the repeating units are identical, or, in the case where a block contains two or more different repeating units, the ratio of the repeating units is the same.

[0039] The fact that individual blocks and the complete polymer have the same size can be represented by polydispersity PD, which is defined as the M of individual blocks or the complete polymer, respectively. w / M n The polydispersity PD is preferably below 1.6, more preferably below 1.5.

[0040] In an exemplary embodiment, the block copolymer dispersant D has a polydispersity PD of less than 1.6, more preferably less than 1.5. In a particular embodiment, each block of the block copolymer dispersant D has a polydispersity PD of less than 1.6, more preferably less than 1.5.

[0041] Compared to random copolymers commonly used as pigment dispersants, block copolymer dispersants can be constructed by configuring pigment-loving monomers as blocks of suitable size and chemical properties, immediately following one or more matrix-based monomer blocks of suitable size and chemical properties. This provides the option to finely tune and maximize the interaction between a specific pigment and the block copolymer-based dispersant. Maximized interaction results in a strong physicochemical bond between the dispersant and the pigment surface. Because the dispersant is positioned on the pigment surface to prevent re-agglomeration, this strong fixation of the dispersant to the pigment surface inhibits polymer desorption from the pigment surface, enabling the production of highly stable pigment dispersions, particularly when used in the final ink, and additionally providing the advantage of low levels of dispersant dissolved in the matrix.

[0042] The strong bond between the dispersant and the pigment will also withstand the competitive interaction of other ink additives, which in water-based inks tend to be (at least partially) hydrophobic in nature and therefore also want to reach the surface of the organic pigment.

[0043] In an exemplary embodiment, the block copolymer dispersant D is selected from diblock copolymers and triblock copolymers. The matrix-stabilizing segment may include one block formed from one monomer, and may also include another block formed from another monomer. The anchoring segment may include one block formed from one monomer, and may also include another block formed from another monomer. Therefore, the block copolymer dispersant may be a diblock copolymer having two blocks, a triblock copolymer having three blocks, and may have any other suitable number of blocks greater than three.

[0044] The matrix-stabilizing and anchoring segments of a block copolymer dispersant can be arranged in any order along the block copolymer dispersant.

[0045] The block copolymer dispersant D has a molecular weight (Mw) between 2000 g / mol and 20000 g / mol, more preferably between 3000 g / mol and 12000 g / mol, wherein the ratio between the total number of repeating units of the anchoring segment A and the total number of repeating units of the stabilizing segment M of D is 0.5 to 10, more preferably 1 to 5. When the molecular weight of the dispersant is below 2000 g / mol, dispersion stability is not maintained, and when the molecular weight is above 20000 g / mol, the viscosity of the dispersion is generally too high, or the dispersion stability may be affected by the dispersant polymer chains anchored to at least one pigment particle. Even without the addition of a binder, polymer dispersants with a molecular weight above 2000 g / mol provide the benefit of adhesion to the substrate during the ink drying process. Furthermore, the use of analog or digital overprinting varnishes can help further improve the properties of the printed image, such as mechanical and chemical resistance, thermal abrasion resistance, and coefficient of friction.

[0046] The block copolymer dispersant D, with an acid value ranging from 50 mg KOH / g polymer to 250 mg KOH / g polymer, and more preferably 60 mg KOH / g polymer to 200 mg KOH / g polymer, allows for good solubility in water. The acid value (AV) of the block copolymer dispersant D is determined by measuring / calculating it. Therefore, the acid value is a measure of the weight ratio between matrix-stabilized segments and anchoring segments. An excessively high AV indicates an overemphasis on the contribution of matrix-stabilized segments, and the polymer dispersant may temporarily desorb from the pigment surface, affecting, for example, the pigment dispersion stability. Another problem with an excessively high AV is that the water fastness of the ink image on the substrate may be insufficient.

[0047] On the other hand, at excessively low AV, when the contribution of anchoring segments is too high, the solubility of the polymer dispersant may be insufficient to provide an effective milling process, especially when milling with low amounts of co-solvent, or even when milling in the absence of a co-solvent. It should be noted that the benefits of substantially co-solvent-free dispersions are highly preferred, as this preserves the freedom of choice of ink components during ink formulation.

[0048] Another aspect of acid value is its importance in its interaction with primers, which are typically used to improve image quality on paper (i.e., uncoated kraft paper and recycled media, as well as offset coated media) and film substrates. Primers for analog and digital applications are used to achieve lower intercolor bleeding, higher gloss, and so on. However, primers often contain cationic components (polymeric cationic or polyvalent metal cationic) or acidic components that are intended to reduce or 'degrade' the stability of the dispersed pigments. Such primers work best when the acid value of the pigment dispersion is below 200 mg KOH / g. To create optimal bonding between the degraded pigments and the printed substrate, such primers often also contain polymeric binders.

[0049] The combination of the aforementioned molecular weight and acid value range of block copolymer dispersant D supports the preparation of pigment dispersions in a simple and cost-effective manner, for example, without the need for solvents that must be subsequently removed. This combination also supports good interaction with primers, which are typically used in ink compositions, such as for printing on uncoated corrugated boards, to enhance color intensity on the uncoated boards.

[0050] In a preferred embodiment, the block copolymer dispersant D is a water-soluble block copolymer dispersant. A block copolymer is defined as “water-soluble” when it is held in a solution of water at 25°C for at least one week, preferably for at least one or more months, more preferably for at least 20 wt% of the weight percentage of the dried polymer dissolved in water at 25°C, and most preferably for at least 25 wt% or higher of the weight percentage of the dried polymer dissolved in water at 25°C.

[0051] The blocks of the block copolymer dispersant according to the present invention may additionally include an initiator portion, a termination portion, an end group, and / or a linking portion.

[0052] The repeating unit of the block may contain substituents. After the block is polymerized or after the block copolymer is polymerized, the substituents may optionally be converted to another substituent, thereby modifying the repeating unit.

[0053] In an exemplary embodiment, the block copolymer dispersant D is composed of linear polymer chains. In another exemplary embodiment, the block copolymer dispersant D is at least partially crosslinked, wherein the block copolymer dispersant is attached to or at least partially encapsulates the pigment.

[0054] The matrix-stabilizing and anchoring segments of a block copolymer dispersant can be arranged in any order along the block copolymer dispersant.

[0055] In an exemplary embodiment, the anchoring segment A of the block copolymer dispersant D includes: a first anchoring block A1, which includes a repeating unit R1; and a second anchoring block A2, which includes a repeating unit R2.

[0056] In an exemplary embodiment, the block copolymer dispersant D has at least three blocks, and the matrix stabilizing segment M includes a matrix stabilizing block M1 disposed between a first anchoring block A1 and a second anchoring block A2.

[0057] In an alternative or other exemplary embodiment, anchoring segment A includes an anchoring block having a distribution of repeating units R1 and R2 within the anchoring block. The distribution is not limited. It can be an alternating distribution, a statistical distribution, or any other distribution.

[0058] (Anchoring segment A)

[0059] (Repeating unit R1 with low hydrophobicity and nonionic properties)

[0060] The repeating unit R1 of anchoring segment A is formed using a nonionic monomer Mn1 with low hydrophobicity. The monomer Mn1 can be selected from the group consisting of methacrylate monomers, acrylate monomers and vinyl monomers.

[0061] In particular, the repeating unit R1 is a non-ionic repeating unit, which means that the repeating unit R1 does not include an ionic portion.

[0062] The repeating unit R1 comprises a (poly)epoxide coupled to a terminal group via a direct bond, a -COC-ether bond, or a -CO-(C=O)-N-carbamate bond, wherein the terminal group is selected from alkyl groups, aryl groups, and combinations thereof.

[0063] As provided herein, an alkyl group, whether itself or as part of another group such as an alkylaryl group or alkylene group as provided herein, refers to formula C. x H 2x+1A fully saturated hydrocarbon, where x is a number greater than or equal to 1. Typically, the alkyl group of the present invention comprises from 1 to 20 carbon atoms. In the context of the present invention, the term "alkyl" includes straight-chain or branched alkyl groups and may be substituted as indicated herein. In a particular embodiment, the terminal group comprises C1-C6 alkyl groups, wherein the C1-C6 alkyl groups include all straight-chain or branched alkyl groups having between 1 and 6 carbon atoms, and therefore include methyl, ethyl, n-propyl, isopropyl, butyl and its isomers (e.g., n-butyl, isobutyl and tert-butyl); pentyl and its isomers; and hexyl and its isomers. In another embodiment, and as part of a (poly)epoxyalkyl group, the alkyl group consists of C... 1-4 Alkyl composition, wherein the C 1-4 Alkyl groups include all straight-chain or branched alkyl groups having between one and four carbon atoms, and therefore include methyl, ethyl, n-propyl, isopropyl, butyl and their isomers (e.g., n-butyl, isobutyl and tert-butyl).

[0064] As used herein, aryl groups refer to polyunsaturated aromatic hydrocarbon groups having a single ring (i.e., phenyl), or multiple aromatic rings fused together (e.g., naphthalene or anthracene), or covalently linked, typically comprising 6 to 10 atoms; at least one of these rings is aromatic. Aryl groups are also intended to include partially hydrogenated derivatives of the carbocyclic systems listed herein. Non-limiting examples of aryl groups include phenyl, biphenyl, biphenylene, 5-tetrahydronaphthyl or 6-tetrahydronaphthyl, 1-azolyl, 2-azolyl, 3-azolyl, 4-azolyl, 5-azolyl, 6-azolyl, 7-azolyl or 8-azolyl, 1-naphthyl or 2-naphthyl, 1-indenyl, 2-indenyl or 3-indenyl, 1-anthrayl, 2-anthrayl or 9-anthrayl, 1-acenaphtylenyl, 2-acenaphtylenyl, 3-acenaphtylenyl, 4-acenaphtylenyl or 5-acenaphtylenyl, 3-dihydroacenaphtylenyl, 4- Dihydroacenaphthyl or 5-dihydroacenaphthyl, 1-phenanthyl, 2-phenanthyl, 3-phenanthyl, 4-phenanthyl or 10-phenanthyl, 1-pentalenyl or 2-pentalenyl, 1-fluorenyl, 2-fluorenyl, 3-fluorenyl or 4-fluorenyl, 4-indanyl or 5-indanyl, 5-tetrahydronaphthyl, 6-tetrahydronaphthyl, 7-tetrahydronaphthyl or 8-tetrahydronaphthyl, 1,2,3,4-tetrahydronaphthyl, 1,4-dihydronaphthyl, dibenzo[a,d]cycloheptenyl, and 1-pyrene, 2-pyrene, 3-pyrene, 4-pyrene or 5-pyrene.

[0065] In the context of this invention, the term "substituted" refers to a straight-chain, aromatic, or cyclic alkyl group that is optionally substituted at any available attachment point with one or more substituents (e.g., 1 to 4 substituents, such as 1, 2, 3, or 4 substituents or 1 to 2 substituents). Non-limiting examples of such substituents include halogens, hydroxyl groups, carbonyl groups, nitro groups, amino groups, oxime groups, imino groups, azide groups, hydrazine groups, cyano groups, aryl groups, heteroaryl groups, cycloalkyl groups, acyl groups, alkylamino groups, alkoxy groups, thiols, alkylthiols, carboxylic acids, acylamino groups, alkyl esters, carbamates, thioamides, urea, sulfonamides, and the like.

[0066] Preferably, the terminal group is an alkyl group; more preferably, it is optionally a C1-C6 alkyl group substituted with one or more substituents selected from hydroxyl and aryl groups. In a specific example, the monomer Mn1 is selected from the group consisting of alkoxy ether acrylate monomers, alkoxy ether methacrylate monomers, and urethane acrylate monomers.

[0067] In a specific example, the repeating unit R1 includes a polyepoxyalkyl group, which includes diol units independently selected from ethylene glycol and propylene glycol.

[0068] An exemplary embodiment of the repeating unit R1 is shown in Equation I:

[0069]

[0070] Where x = 0-30, y = 0-15, where x+y is at least 1, z = 0-1, A is an alkyl, aryl, or alkylaryl group; B = -H or -CH3, and wherein A is connected to the repeating unit by a direct bond or by a urethane group. Preferably, A is an alkyl group.

[0071] The repeating unit R1 according to Formula I is formed from a vinyl monomer, an acrylate monomer or a methacrylate monomer, has a terminal ether group, has A, where A is an alkyl, aryl or alkylaryl group; and includes one or more ethylene glycol groups and / or one or more propylene glycol groups.

[0072] Optional terminal ether groups can be formed by converting the hydroxyl end of the terminal diol group.

[0073] Preferably, the hydrophobicity of R1 is lower than that of R2 based on the comparison of the Hansen solubility parameter value δ(polarity + hydrogen) of R1. R1 Hansen solubility parameter δ(polarity + hydrogen) higher than R2 R2 The Hansen solubility parameter according to the present invention was calculated using the Y-MB method with HSPiP software version 5.2.03.

[0074] According to Hansen's solubility parameter theory, this sum is defined as the square root of the sum of the squares of the polar bond values ​​and the squares of the hydrogen bond values ​​of the repeating units: δ(polar + hydrogen) = √[δ(polar)] 2 +δ(hydrogen) 2 ].

[0075] In a specific instance, the repeating unit R1 has the Hansen solubility parameter δ(polarity + hydrogen). R1 , where δ (polar + hydrogen) R1 >8.0cal 1 / 2 cm -3 / 2 The Hansen solubility parameter δ(polarity + hydrogen) is defined as follows:

[0076] In an exemplary implementation, the polarity bond value of R1 is δ (polarity). R1 >5.0cal 1 / 2 cm -3 / 2 .

[0077] The repeating unit R1 is preferably formed of acrylate or methacrylate.

[0078] In specific examples, the nonionic, less hydrophobic monomer Mn1 is at least one of the following: tri(ethylene glycol) methyl ether acrylate, 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), ethylene glycol methyl ether methacrylate, 2-ethoxyethyl methacrylate, di(ethylene glycol) methyl ether methacrylate, tri(ethylene glycol) methyl ether methacrylate, phenoxyethyl methacrylate, ethylene glycol methyl ether acrylate, 2-ethoxyethyl acrylate, di(ethylene glycol) methyl ether acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, and mixtures thereof.

[0079] (Hydrophobic repeating unit R2)

[0080] The repeating unit R2 of anchoring segment A is formed using the hydrophobic monomer Mn2, which can be selected from the group consisting of methacrylate monomers, acrylate monomers and vinyl monomers.

[0081] In an exemplary embodiment, the repeating unit R2 has a Hansen solubility parameter value δ(polarity + hydrogen). R2 , where δ (polar + hydrogen) R2 <8.0cal 1 / 2 cm -3 / 2 Preferably <7.2cal 1 / 2 cm -3 / 2 The Hansen solubility parameter δ(polarity + hydrogen) is defined as follows:

[0082] The hydrophobicity of repeating unit R2 is greater than that of repeating unit R1, which corresponds to the lower sum of the polar bonding value and hydrogen bonding value of R2.

[0083] In an exemplary implementation, the polarity bond value of R2 is δ (polarity). R2 <5.0cal 1 / 2 cm -3 / 2 Preferably <4.4 cal 1 / 2 cm -3 / 2 The hydrophobicity of repeating unit R2 is greater than that of repeating unit R1, which corresponds to the lower polar bonding value of R2.

[0084] In specific examples, the hydrophobic monomer Mn2 is at least one of the following: benzyl methacrylate, butyl methacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, lauryl methacrylate, stearyl methacrylate, p-toluene methacrylate, sorbitol methacrylate, benzyl acrylate, butyl acrylate, methyl acrylate, ethyl acrylate, propyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, p-toluene acrylate, sorbitol acrylate, and mixtures thereof.

[0085] (The combination of repeating units R1 and R2 in anchoring chain segment A)

[0086] In an exemplary embodiment, the repeating unit R2 of anchoring segment A is formed using a hydrophobic monomer Mn2, wherein the monomer Mn2 is selected from the group consisting of methacrylate monomers, acrylate monomers and vinyl monomers, and the repeating unit R1 of anchoring segment A is formed using a nonionic monomer Mn1 with low hydrophobicity, wherein the monomer Mn1 is selected from the group consisting of methacrylate monomers, acrylate monomers and vinyl monomers.

[0087] Specifically, the repeating units R1 and R2 of anchoring segment A do not have ionic groups. Preferably, both repeating units R1 and R2 are hydrophobic compared to the aqueous matrix. Therefore, anchoring segment A is essentially insoluble in the aqueous support phase.

[0088] In an exemplary embodiment, the anchoring chain segment A has a number n of repeating units, and wherein the sum of repeating units R1 and repeating units R2 is at least 50% of the total number n of repeating units, preferably at least 80% of the total number n of repeating units.

[0089] In an exemplary embodiment, the ratio between the number of repeating units R1 (n1) and the number of repeating units R2 (n2) is between 0.05 and 20, preferably between 0.1 and 10.

[0090] (Matrix stabilization segment M)

[0091] The repeating units of the matrix-stabilized segment M can be formed using the monomer Mn3. When two different monomers Mn3 are used to form the matrix-stabilized segment M, the matrix-stabilized segment M has a first repeating unit and a second repeating unit, each formed from a different monomer Mn3. In this case, the sum of the number of the first repeating units and the number of the second repeating units in segment M equals the total number n of repeating units in segment M, i.e., the matrix-stabilized portion of the first block.

[0092] In particular, at least one ionic hydrophilic repeating unit R3 of the matrix stabilization segment M includes an ionic portion.

[0093] Additionally, the matrix stabilizing segment M may further include nonionic repeating units besides the ionic hydrophilic repeating units. In an exemplary embodiment, the matrix stabilizing segment M may include ionic hydrophilic repeating units, and the nonionic matrix stabilizing repeating units contain (poly)diol functional groups. The ionic hydrophilic repeating units and nonionic repeating units of the matrix stabilizing segment M together contribute to the water solubility of the polymer.

[0094] (Ion repeating unit R3)

[0095] In a specific example, at least one monomer Mn3 is used to form a matrix-stabilized segment M, wherein the at least one monomer Mn3 is used to obtain an ionic hydrophilic repeating unit R3. The ionic hydrophilic repeating unit R3 preferably contains a neutralized acid group, a neutralized basic group such as a protonated amino group, or other ionic functional groups such as a quaternary ammonium group.

[0096] The ionic hydrophilic repeating unit R3 provides solubility of the matrix stabilizing segment M in the aqueous support phase.

[0097] In specific examples, the monomer Mn3 is selected from the group consisting of: methacrylic acid, acrylic acid, maleic acid, maleic acid monoester, itaconic acid, itaconic acid monoester, crotonic acid, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethyl acrylate, tert-butylaminoethyl methacrylate, tert-butylaminoethyl acrylate, and mixtures thereof.

[0098] When the matrix stabilization segment contains hydrophilic repeating units with acidic functional groups, a significant portion of the acidic groups needs to be neutralized to provide solubility and dispersion stability. This is preferably achieved by setting the pH level to 7.5, and most preferably to 8.5 or higher, to neutralize all acids. Similarly, when the matrix stabilization segment contains hydrophilic repeating units with basic functional groups, a significant portion of the basic groups is neutralized to provide solubility and dispersion stability. This is preferably achieved by setting the pH level to 6.5, and most preferably to 5.5 or lower, to neutralize all basic groups.

[0099] The choice of neutralizing agent and the corresponding salt counterion used for repeating unit R3 determines the modified repeating unit R3 in such a way that it must be considered a different chemical structure.

[0100] Possible neutralizing agents for acid groups are tertiary amines, such as trimethylamine and triethylamine, triethanolamine, ammonia, 2-dimethylaminoethanol, 2-amino-2-methyl-1-propanol, 2-(2-amino-ethylamino)ethanol, 2-amino-2-methyl-1-propanol, sodium hydroxide, potassium hydroxide, and the like.

[0101] Possible neutralizing agents for basic groups include inorganic acids such as hydrochloric acid and sulfuric acid; and organic acids such as acetic acid, citric acid, maleic acid, propionic acid, lactic acid, succinic acid, and glycolic acid.

[0102] This invention is not limited to these exemplary contents.

[0103] The selection of the neutralizer and the corresponding salt counterion of repeating unit R3 can affect pigment dispersion stability, including its influence on the grinding characteristics and speed of pigment particles in the pigment dispersion and / or its influence on pigment dispersion stability properties when exposed to extreme conditions. The selection of the neutralizer, pH value, and corresponding salt counterion can affect the behavior of the final ink, such as drying rate, open time, first drop reliability, and jetting stability.

[0104] (pigment)

[0105] For water-based inks, the pigment surface is typically more hydrophobic than the bulk liquid. Therefore, anchoring monomers such as alkyl acrylates and aryl acrylates, such as benzyl acrylate, can be used. However, some pigments with less hydrophobic surfaces have been found, and these pigments have been found to be more difficult to achieve good milling performance only when they have an anchoring repeating unit in the block dispersant.

[0106] Differences or variations in pigment surfaces can be demonstrated through chemical analysis or the pigment synthesis process, or experimentally through the HSPIP / Hansen solubility method. In this method, the solubility of a substance in different solvents can be assessed, and therefore, solubility / compatibility can be expressed as hydrogen forces, dipole forces, and van der Waals forces / dispersing forces. Pigments that may have significantly different pigment surfaces include aoPR122, PBk7, PB15.3, PY74, and PY155.

[0107] Therefore, the anchoring segment A of the block copolymer dispersant D contains different repeating units, which can be selected for different anchoring points on the pigment surface. For example, in the case of a crystalline pigment structure, there may be surfaces with different chemical properties, and different anchoring chemistry may be required to achieve higher pigment dispersion stability.

[0108] In an exemplary embodiment, pigment P is a colored pigment selected for adjusting the color of the ink. In an exemplary embodiment, pigment P is an organic pigment that optionally contains metal atoms complexed with the organic components of the organic pigment.

[0109] In an exemplary embodiment, pigment P is an inorganic pigment that optionally contains a metal oxide.

[0110] In a particular exemplary embodiment, the magenta pigment is a quinacridone pigment selected from Pigment Red 122, Pigment Violet 19 and Pigment Red 202, or the magenta pigment is Pigment Red 57:1, and / or the cyan pigment is Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:6, and / or the yellow pigment is selected from Pigment Yellow 155, Pigment Yellow 74 and Pigment Yellow 180, and / or the black pigment is carbon black, preferably Pigment Black 7.

[0111] (Water-based pigment dispersion)

[0112] Preferably, the amount of water in the aqueous carrier is at least 50 wt% of the total weight of the aqueous carrier, preferably at least 80 wt%, and more preferably at least 95 wt%.

[0113] In a specific example, the total amount of water-soluble organic solvent contained in the aqueous carrier is less than 20 wt%, preferably less than 10 wt%, and particularly preferably less than 5 wt% of the total weight of the aqueous carrier. Preferably, the aqueous carrier is substantially free of water-soluble organic solvent.

[0114] The relatively high amount of water and / or relatively low amount of water-soluble or water-free organic solvents in the water-based carrier enhance the versatility and ease of use of inkjet inks derived from water-based pigment dispersions.

[0115] In an exemplary embodiment, the amount of pigment P in the pigment dispersion is in the range of 10 wt% to 60 wt% based on the weight of the pigment dispersion. Compared to inkjet inks derived from pigment dispersions, the pigment dispersion can be a concentrated dispersion of pigment P. Generally, the amount of colored pigment P in inkjet inks can be in the range of 0.5 wt% to 10 wt% based on the weight of the inkjet ink.

[0116] In the case of inorganic pigments, preferably white pigments, the amount of pigment P in the pigment dispersion can be in the range of 40wt%-80wt% based on the weight of the pigment dispersion, and in the final inkjet ink, the amount of pigment P can be in the range of 10wt%-50wt% based on the weight of the inkjet ink.

[0117] In an exemplary embodiment, the weight ratio between pigment P and block copolymer dispersant D is between 0.1 and 10.0, preferably between 0.4 and 5.

[0118] (Method for preparing aqueous pigment dispersions)

[0119] Preferably, the aqueous pigment dispersion is prepared without using water-soluble organic solvents or other organic solvents.

[0120] Pigment dispersions are prepared by mixing raw materials in appropriate ratios. Pigment concentrations are typically between 10 wt% and 60 wt%, and the weight ratio of pigment to block dispersant is typically between 0.1 and 10. Other components besides pigments, dispersants, and water, such as wetting agents (typically Mw < 1000 g / mol) and similar substances, may also be added to improve the pigment dispersion process.

[0121] Preferably, the aqueous pigment dispersion is prepared without or with only a limited amount of a water-soluble co-solvent (such as an alkyl ether or a glycol).

[0122] Advantageously, the raw materials are mixed very well by methods known in the art, such as a cowl mixer or a dissolver, to obtain a very good premix before the final dispersion step begins.

[0123] There are no particular limitations on the dispersion method. Examples of dispersion methods include paint vibrators, horizontal and vertical bead mills, and high-pressure homogenizers. To ensure very good anchoring and / or very good electrosteric stabilization of the dispersant on the pigment surface, it may be beneficial to mill at a high temperature (40°C to 80°C) or to perform heat treatment at 40°C to 80°C for a certain period of time after the milling step. This heat treatment can be carried out statically or dynamically (i.e., some kind of agitation / stirring of the dispersion during heat treatment).

[0124] After grinding, conventional separation techniques, such as filtration, sieving via screens, and similar methods, are used to separate the grinding media from the ground particles. Typically, the screen is built into the mill, for example, in a bead mill.

[0125] Preferably, the block copolymer dispersant is dissolved in an aqueous medium prior to pre-dispersion. The dissolved polymer is obtained by mixing the dried block copolymer with water at room temperature, and, if necessary, with an additional neutralizing agent, for at least 2 hours. Stirring and / or raising the temperature to 60°C can be used to accelerate the dissolution process.

[0126] (Water-based inkjet inks)

[0127] Any additional amount of water and water-soluble organic co-solvent may be added to the pigment dispersion to form the inkjet ink according to the invention. Any other suitable additives, such as surfactants, binders, dispersants, thickeners, pH adjusters, etc., may be added to the pigment dispersion to form the inkjet ink according to the invention.

[0128] In an exemplary embodiment, the ink is an aqueous ink having an aqueous carrier. The aqueous carrier is a liquid at room temperature. The aqueous carrier comprises water and optionally a water-soluble organic cosolvent or a cosolvent for carrying or suspending pigment P, said pigment P comprising a block copolymer dispersant D.

[0129] In an exemplary embodiment, the amount of pigment in the ink is at least 0.5 wt% relative to the total weight of the ink, preferably at least 1 wt%, wherein the ink preferably has a viscosity of up to 30 mPa·s at 25°C.

[0130] In an exemplary embodiment, the viscosity of the inkjet ink is between 4 mPa.s and 30 mPa.s at 25°C, preferably between 4 mPa.s and 20 mPa.s at 25°C.

[0131] In an exemplary embodiment, the static surface tension of the inkjet ink is between 17 mN / m and 35 mN / m.

[0132] Specifically, the ink may contain at least one binder resin for improving at least one of the following: adhesion to the substrate, drying, water resistance, or scratch resistance of the ink on the substrate. The binder resin may be a water-soluble resin or may be provided as resin microparticles. The resin microparticles are dispersed in the inkjet ink as an emulsion or lattice.

[0133] Inkjet inks containing binders can be used to enhance the adhesion between pigments and substrates while maintaining high pigment stability. It has been found that the pigment dispersions of the inkjet inks according to the invention maintain high stability when used in combination with the at least one binder resin.

[0134] (Water-soluble organic solvent)

[0135] In exemplary embodiments, the water-soluble organic solvent includes at least one of the following: a polyol compound, a glycol ether compound, such as a (poly)ethylene glycol ether or a (poly)propylene glycol ether compound. In the context of this application, a polyol compound is synonymous with a polyhydric alcohol, i.e., having at least two alcohol groups, such as, for example, glycerol and propylene glycol. In a particular exemplary embodiment, the water-soluble glycol ether compound is a glycol monobutyl ether.

[0136] Water-soluble organic solvents can be selected as penetrants to improve the penetration (wetting) of inks into the substrate. Penetrants help adjust the dot diameter on the substrate and / or improve the adhesion between pigments and the substrate. Certain suitable penetrants have surface tension-active properties, thereby reducing the surface tension of the ink.

[0137] Exemplary penetrants include alkanediols and glycol ethers. The inventors have found that water-soluble organic solvents with penetrant properties tend to compete with dispersants that stabilize pigments.

[0138] An exemplary penetrant is a glycol monobutyl ether, such as diethylene glycol monobutyl ether or ethylene glycol monobutyl ether. It should be noted that some penetrants, such as diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, ethylene glycol isopropyl ether, and 1,2-hexanediol, have surface tension-active properties, thereby reducing the surface tension of the ink.

[0139] In an exemplary embodiment, the weight concentration of at least one water-soluble organic solvent in the ink is in the range of 5 wt% to 40 wt% based on the total weight of the ink, preferably in the range of 5 wt% to 30 wt% based on the total weight of the ink.

[0140] In a particular embodiment, the weight concentration of at least one penetrant in the ink is in the range of 1 wt% to 15 wt% based on the total weight of the ink, preferably in the range of 2 wt% to 10 wt% based on the total weight of the ink.

[0141] (Water-based inkjet inks)

[0142] In specific examples, the inkjet inks in the ink group include cyan ink containing cyan pigment, magenta ink containing magenta pigment, yellow ink containing yellow pigment, and black ink containing black pigment. The ink group may include any other colored inks and / or colorless inks. The ink group may also include one or more non-colored inks.

[0143] (Inkjet printing process)

[0144] In an exemplary embodiment, the inkjet printing process includes jetting droplets of each inkjet ink onto a substrate to form a color image on the substrate.

[0145] In a particular exemplary implementation, droplets are ejected using an inkjet printhead.

[0146] In an exemplary embodiment, the inkjet process includes forming an image on a final corrugated board, corrugated liner, label substrate such as paper and film labels or flexible packaging substrate in a single pass at a speed of at least 30 m / min, preferably at least 50 m / min.

[0147] Detailed Explanation

[0148] As used herein, the term “dispersion” refers to a two-phase system in which one phase consists of finely divided particles (typically in the colloidal size range) distributed throughout the bulk substance, the particles being the dispersed phase or internal phase, and the bulk substance being the continuous phase or external phase.

[0149] As used herein, the term "dispersant" refers to a surfactant added to a suspension medium to promote uniform and maximum separation of extremely fine solid particles. For pigments, the dispersant may be a polymeric dispersant, and dispersions containing both the dispersant and the pigment are typically prepared using dispersion equipment.

[0150] As used herein, the term "water-based" refers to water or a mixture of water and at least one water-soluble or partially water-soluble organic solvent (co-solvent). As used herein, the term "water-based ink" has the same meaning as the term "water-based ink".

[0151] As used in this article, the term "basically" means to a considerable extent, almost entirely.

[0152] As used herein, the term "ink set" means a combination of inkjet inks used as a component kit for printing images on a substrate by applying inkjet inks to a substrate according to the present invention. In particular, an ink set is a combination of inkjet inks that can be used together in the same printing process to form a color image on a substrate.

[0153] The materials, methods, and examples in this article are illustrative and not intended to be limiting.

[0154] As used herein, the term "ethyl carbamate" must be understood to also include isomers of ethyl carbamate, such as the CO-(C=O)-N<->CO-(C-OH)=N isomer.

[0155] Water-based inks

[0156] The use of colorants in inks is the most basic form of water-based inks. However, to prevent the ink from drying at the nozzle, water-based inks used in inkjet printing methods typically also contain water-soluble organic solvents with high boiling points and good water solubility. This type of solvent can also be considered a humectant in water-based inks.

[0157] Water-based inks used in inkjet printing methods often also contain water-soluble organic solvents, which are penetrants used to improve the ink's penetration (wetting) into the substrate. Penetrants help adjust the dot diameter on the substrate and / or improve the adhesion between the pigment and the substrate. Certain suitable penetrants have surface tension-active properties, thereby reducing the surface tension of the ink. Furthermore, to achieve minimal wetting and spreading of the water-based ink in the printhead, on the substrate, etc., water-based inks used in inkjet printing methods typically also contain one or more surfactants.

[0158] Finally, water-based ink compositions can also contain various types of additives, such as antifoaming agents, thickeners, binders, and preservatives, as needed. Adding these types of additives to water-based ink compositions makes them more advantageous for use as inkjet inks.

[0159] pigment

[0160] From the viewpoint of providing excellent water resistance, light resistance, weather resistance, and gas resistance, or similar properties, pigments are preferred. Examples of pigments that can be used in this invention include conventional organic and inorganic pigments.

[0161] Pigments may be selected from those disclosed in HERBST, W. et al., Industrial Organic Pigments, Production, Properties, Applications, 2nd ed. vch, 1997.

[0162] The pigment particles in colored inkjet inks should be small enough to allow the ink to flow freely through the inkjet printing apparatus, especially at the nozzle. It is also desirable to use small particles for maximum color intensity and to reduce sedimentation.

[0163] The average particle size of the pigment in the colored inkjet ink should be between 5 nm and 1 μm, particularly preferably between 5 nm and 500 nm, and most preferably between 30 nm and 300 nm. Larger pigment particle sizes can be used as long as the objectives of this invention are achieved.

[0164] Pigments are used in the colored inkjet ink in an amount of 0.1 wt% to 30 wt%, preferably 1 wt% to 10 wt%, based on the total weight of the colored inkjet ink.

[0165] Examples of cyan pigments that can be used in this invention include CI Pigment Blue 1, 2, 3, 15:3, 15:4, 15:6, 16, and 22, and CI Vat Blue 4 and 6. These cyan pigments can be used alone or in combination of two or more pigments.

[0166] Examples of magenta pigments that can be used in this invention include CI pigments Red 5, 7, 12, 22, 23, 31, 48(Ca), 48(Mn), 49, 52, 53, 57(Ca), 57:1, 112, and 122; quinacridone solid solutions 146, 147, 150, 185, 238, 242, 254, 255, 266, and 269; and CI pigments Violet 19, 23, 29, 30, 37, 40, 43, and 50. Quinacridone mixed crystalline pigments can also be used.

[0167] Examples of yellow pigments that can be used in this invention include CI Pigment Yellow 10, 11, 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 166, 168, 180, 185, and 213.

[0168] Other organic pigments can be used to enhance the color gamut, such as CI pigments Green 36 and 7, Violet 23, and Orange 34 and 64.

[0169] Examples of black pigments that can be used in this invention include organic pigments such as aniline black, Lumogen black, and azobenzene black, as well as inorganic pigments such as carbon black and iron oxide. Furthermore, more than one colored pigment, such as the aforementioned yellow, magenta, and cyan pigments, can be mixed together and used as a black pigment.

[0170] There are no particular limitations on the inorganic pigments that can be used in this invention. Examples of inorganic pigments may also include various metal oxides.

[0171] In addition, inorganic pigments may include white pigments such as titanium dioxide (anatase, brookite and rutile), which may be available, for example, from KRONOS (e.g., 2044, 2047 grade) or as titanium dioxide coated with metal oxides (e.g., R700E.I.DuPont de Nemours) or other inorganic pigments such as zinc oxide and iron oxide.

[0172] Examples of carbon black pigments that can be used in this invention include carbon black produced using a furnace method or a channel method.

[0173] The following lists examples of commercial products, any of which can be used effectively.

[0174] Specific examples of carbon black include Nos. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8 and MCF88 (all manufactured by Mitsubishi Chemical Corporation), RAVEN 1255 (manufactured by Columbia Chemicals Co., Inc.), REGAL 330R, 400R and 660R and MOGUL L (all manufactured by Cabot Corporation), and Nipex 1601Q, Nipex 1701Q, Nipex 75, Printex 85, Printex 95, Printex 90, Printex 35 and Printex U (all manufactured by Orion Engineered Carbons LLC).

[0175] In this embodiment of the invention, the pigment is not limited to the pigments described above, and other specific colors, such as orange and green pigments, can also be used. Furthermore, more than one pigment can be combined. Additionally, in another embodiment, the aqueous ink composition of this embodiment of the invention can be combined with a pigment-free transparent ink and used as an ink group.

[0176] Any other pigments and / or dyes that can be used to change the color of the ink can be used.

[0177] surfactants

[0178] The inkjet ink according to the invention may contain at least one surfactant. The surfactant may be anionic, cationic, nonionic, or amphoteric, and is typically added in a total amount of less than 6 wt% of the total weight of the colored inkjet ink, and particularly in a total amount of less than 4 wt% of the total weight of the colored inkjet ink.

[0179] Suitable surfactants for use in inkjet inks according to the present invention include silicone surfactants, acrylic surfactants and fluorinated surfactants, fatty acid salts, ester salts of higher alcohols, alkylbenzene sulfonates, sulfosuccinate salts and phosphate salts of higher alcohols, ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkylphenols, ethylene oxide adducts of polyol fatty acid esters, and acetylene glycol and its ethylene oxide adducts. Commercial examples include Byk-348, Byk-347, Byk-3450, Dynwet 800 (Byk Chemie GmbH); Surfynol 104, Surfynol 465, Metolat 364, Dynol 800, Dynol 960 (Evonik Industries), KF-640, KF-642 (Shin-Etsu); ID-40, ID-70 (Sanyo Chemical Industries), Olfine E1004, Olfine E1010, Olfine EXP4300, Silface SAG503, all from Nisshin Chemical; and combinations thereof.

[0180] Water-soluble organic solvents

[0181] The type of water-soluble organic solvent is not particularly limited as long as the effects of the present invention can be achieved. From the viewpoint of increasing compatibility with water, it is preferred that the organic solvent is water-soluble. Examples of water-soluble organic solvents include alcohols, polyols, amines, amides, glycol ethers, 1,2-alkanediols, and similar organic solvents. Only one type of organic solvent may be used, or two or more types of organic solvents may be used.

[0182] Examples of polyols described above include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having a number of 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having a number of 4 or more propylene oxide groups, butanediol, hexanediol, pentanediol, glycerol, hexanetriol, thiodiethylene glycol, and similar polyols.

[0183] Examples of amines described above include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, and similar amines.

[0184] Examples of amides described above include formamide, N,N-dimethylformamide, N,N-dimethylacetamide, pyrrolidone, urea, and similar amides.

[0185] Examples of glycol ethers described above include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether and similar glycol ethers.

[0186] Examples of 1,2-alkanediols include 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol and similar 1,2-alkanediols.

[0187] Among these, when the water-soluble organic solvent is a polyol, blurring during high-speed printing can be preferably suppressed. Preferred examples of polyols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and similar polyols.

[0188] Water-soluble organic solvents can be selected as penetrants to improve the penetration (wetting) of inks into the substrate. Penetrants help adjust the dot diameter on the substrate and / or improve the adhesion between the pigment and the substrate. Specific suitable penetrants include alkanediols and glycol ethers.

[0189] Adhesive resin

[0190] In one embodiment, the water-based ink composition of the present invention preferably further comprises a binder resin (functional polymer). Known binder resins for use in water-based ink compositions include water-soluble resins and resin microparticles (emulsions / latexes). Examples of types of resins that can be used as resin microparticles include acrylic resins, styrene / acrylic resins, urethane resins, styrene / butadiene resins, vinyl chloride resins, vinyl acetate resins (possibly partially or completely hydrolyzed), polyester resins, and polyolefin resins.

[0191] These additional adhesive resins can help achieve a stable spraying process, ink-substrate adhesion, chemical and / or mechanical resistance of the final ink layer, or improve image quality.

[0192] biocides

[0193] Suitable biocides for the inkjet inks used for coloring in this invention include sodium dehydroacetate, 2-phenoxyethanol, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate, 2-methyl-1,2-thiazolin-3-one and 1,2-benzisothiazolin-3-one, and their salts.

[0194] The biocides are preferably added in amounts of 0.001 wt% to 3 wt%, more preferably 0.01 wt% to 1.00 wt%, each based on the total weight of the colored inkjet ink.

[0195] Other components

[0196] In inkjet printing inks, in addition to the components described above, a variety of known additives, such as polysaccharides, viscosity modifiers, film-forming agents, pH adjusters and similar additives, may be appropriately selected and used as needed to improve all performance targets.

[0197] Preparation of colored inkjet inks

[0198] The inkjet inks colored according to the present invention can be prepared by first preparing a pigment dispersion and then diluting the pigment dispersion to the desired pigment concentration and adding all other ink components such as the required water-soluble organic solvent.

[0199] The desired outcome is to prepare colored inks in the form of a concentrated aqueous pigment dispersion according to the invention, followed by dilution of the colored ink to a suitable concentration for use in an inkjet printing system. This technique allows for the preparation of larger quantities of colored ink from the equipment. Through dilution, the ink is adjusted to the desired viscosity, color, hue, saturation density, and printed area coverage for a specific application.

[0200] Inkjet inks are prepared by mixing components with a dispersion using conventional mixing equipment. The methods used for stirring and mixing are not particularly limited and can be appropriately selected as needed, such as homogenizers, paint vibrators, ultrasonic dispersers, agitators using ordinary stirring blades, magnetic stirrers, and high-speed dispersers. Finally, the ink is filtered before use. A filtration step in the range of 1 μm to 5 μm is performed using droplet sizes of less than 20 plc and printhead nozzles of less than 30 micrometers in many cases. This is crucial to ensure that no particles reach the nozzles, as a single failure can result in the replacement of the entire printhead at a considerable cost.

[0201] For colored inks, multi-stage filtration is typically used after the dispersion is formed and again after the addition and dilution of additives. The main objective here is to remove any oversized or agglomerated pigments from the dispersion, as well as any oversized particles and contaminants from other processes.

[0202] Available filter technologies have different applications, advantages, and disadvantages. Examples of filters include membrane filters, depth filters, and mixing filter types. Common suppliers of filters for inkjet inks include Pall, Porvair, and Membrane Solutions.

[0203] In a preferred embodiment, crosslinking or encapsulation is not required after milling. The stable pigment dispersion according to the invention can be obtained without crosslinking and other additional steps, such as filtration steps to remove unreacted material, which are unnecessary. This results in a simpler synthesis process and is more economically attractive because less energy and resources are required to obtain the stable pigment dispersion.

[0204] Optionally, adding crosslinking and / or encapsulation steps results in even more stable dispersions, but the process is more complex and more sensitive to unreacted crosslinking agents and / or crosslinked free dispersants. This can lead to poorer pigment dispersions and corresponding inks when no additional removal steps, such as ultrafiltration, are used.

[0205] experiment

[0206] Manufacturing process

[0207] Block copolymer synthesis

[0208] Block copolymers can be prepared using a range of different so-called living polymerization methods. The basis of this method is that the synthetic approach used remains constant:

[0209] • Instantaneous triggering ensures that all polymer chains grow simultaneously at a specified growth rate.

[0210] • Living polymerization ensures that the addition of a very small concentration of active (growing) chains to the solution at a given time avoids the termination or recombination of free radicals.

[0211] • Continuous growth is strictly controlled, thereby obtaining small polydispersity of the polymer and thus well-defined polymer compositions.

[0212] Other polymerizations can be achieved in various ways, but anionic polymerization and group transfer polymerization (e.g., atom transfer radical polymerization [ATRP], NMP, ...) are two of the most common synthetic methods. These methods have specific requirements (oxygen-free, anhydrous, ...), making them impractical and expensive for producing large quantities (industrial scale) of polymers. Two examples are the use of alkyl lithium components or naphthalimide to initiate polymerization at very low temperatures.

[0213] In an exemplary embodiment, the block copolymer is prepared by ATRP, as described in Wang and Matyjaszewski’s Controlled living radical polymerization (macromolecules 1995, 28 7901-7910).

[0214] Synthesis Examples

[0215] The following procedure describes a potential synthetic method for producing a block dispersant characterized as AA. 15 -(BnA 30 / EOEOEA 10 This dispersant comprises 15 monomers AA for its matrix-stabilizing block length and 30 monomers benzyl acrylate (BnA) + 10 monomers 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA) for its anchoring block length. It is a block copolymer dispersant containing two blocks, wherein the matrix-stabilizing segment is formed by reacting monomer AA and has a length of approximately 15 repeating units, and the anchoring segment is formed by reacting monomer BnA together with EOEOEA and has a total length of approximately 40 repeating units. Other block dispersant architectures can be generated by those skilled in the art in the same manner by adjusting the amount and type of starting materials and the reaction time, and the order of preparation of the block dispersants can be interchanged, i.e., first preparing the BnA / EOEOEA block and then preparing the AA block. Unless otherwise stated, "parts" in the description are based on mass.

[0216] A 500 mL three-necked flask equipped with a thermometer, reflux condenser, and nitrogen balloon was loaded with 1.43 parts Cu(I)Br, 38.5 parts tert-butyl acrylate, 41.2 parts anisole internal standard, and 1.73 parts N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA). The mixture was degassed under vacuum, backfilled with nitrogen three times, and heated to 80 °C. Subsequently, 3.34 parts methyl 2-bromopropionate (MBP) was added to initiate the polymerization reaction, which was carried out for 1 hour.

[0217] In a separate flask, 97.3 parts of benzyl acrylate, 37.6 parts of 2-(2-ethoxyethoxy)ethyl acrylate, 59.6 parts of anisole, and 1.73 parts of PMDETA were mixed and degassed under vacuum, then backfilled three times with nitrogen. This solution was added to a tert-butyl acrylate polymer solution along with 0.64 parts of Cu(O). Polymerization was stopped after 6 hours by exposing the catalyst to air (Mn = 8807 and Mw / Mn = 1.29). The copper catalyst was removed by column chromatography, followed by removal of excess solvent by evaporation.

[0218] Subsequently, the tert-butyl acrylate groups of the block copolymer were hydrolyzed. The purified block copolymer was dissolved in 2 parts by volume of dioxane under reflux, and then 0.5 equivalents of sulfuric acid relative to the amount of repeating tert-butyl acrylate units of the polymer were added to the solution. After 2 hours, an equimolar amount of base was added to stop the reaction. The reaction solution was in The mixture is filtered to remove the salts formed. Dioxane is removed by rotary evaporation to obtain an acrylic acid / benzyl acrylate / 2-(2-ethoxyethoxy)ethyl acrylate block copolymer.

[0219] The current synthetic method describes a synthesis based on a "common" reactor. Alternatively, a flow chemistry process can be used to synthesize the mentioned block dispersants. The inventors reference "FlowChemistry: Integrated Approaches for Practical Applications", Santiago V Luis, Eduardo Garcia-Verdugo (ed.), 2019, (ISBN: 978-1-78801-498-4 / 978-1-78801-609-4). The block dispersants are synthesized using a flow reactor and the same starting materials as the "common reactor", except that EBiB is used as the initiator, 365nm UV LED light is used as the photon source, the reaction is initiated by the reduction of Cu(II)Br2 to Cu(O), and the solvent used is 1:1 acetonitrile:ethanol. The flow reactor was assembled using PFA tubing (1 / 16” OD, 0.75 mm ID). Before entering the photoreactor, the flow was connected via an inline check valve, a T-piece, and a static mixer to ensure homogeneity. Sixteen LEDs (365 nm) were assembled on an octagonal reactor (built internally using PLA filaments via 3D printing). A second polymer block could be added to the first block in a subsequent reactor module. Finally, the hydrolysis and filtration steps could be performed similarly to the batch process described above or could be integrated into the flow reactor setup.

[0220] To ensure compatibility between the dispersant and the carrier, the hydrophilic monomers need to be neutralized, thereby ionizing the salifying groups of the block copolymer. As neutralizing agents, acids or bases can be used, depending on the type of salifying group; for example, basic agents such as DMAEMA, or acidic agents such as (meth)acrylic acid. Neutralizing agents for basic monomers include, for example, inorganic acids such as hydrochloric acid and sulfuric acid; and organic acids such as acetic acid, propionic acid, lactic acid, succinic acid, and glycolic acid. Additionally, neutralizing agents for acidic monomers include, for example, tertiary amines such as trimethylamine and triethylamine, triethanolamine, ammonia, 2-dimethylaminoethanol, 2-amino-2-methyl-1-propanol, 2-(2-amino-ethylamino)ethanol, 2-amino-2-methyl-1-propanol, sodium hydroxide, potassium hydroxide, and similar neutralizing agents. The invention is not limited to these exemplary contents.

[0221] It should be noted that the total weight of the dispersant mentioned in the following examples includes the mass of the neutralizer.

[0222] Water solubility of block copolymer dispersants

[0223] Examples of solubilization are listed in Table 1. Water solubility tests were performed according to the test procedures described further below.

[0224]

[0225] Table 1

[0226] Dissolve the polymer in a round flask using mechanical stirring. (*) Check the stability by decanting the aqueous polymer solution and examining the solid sedimentation.

[0227] Packaging

[0228] Optionally, crosslinking occurs immediately after the milling process by chemically coupling the dispersant together on the surface. A very popular method for achieving this appears to be adding an epoxy compound (primarily a diepoxide or triepoxide) to the dispersion to couple specific portions of the (meth)acrylic acid monomer present in the dispersant backbone (preferably on the surface of the pigment particles). If not all the dispersant is attached to the pigment surface, these free polymers will interfere with the crosslinking process, for example, by embedding themselves between the polymer particles and thus causing a portion of the dispersion to flocculate, and therefore must be removed afterwards. These encapsulated pigment particles, resulting from the formation of a "web" or "capsule" of dispersant across the particle surface, unaffected by co-solvents and surfactants, exhibit excellent stability.

[0229] Production of pigment dispersions

[0230] A pigment dispersion with the composition according to Table 2 was prepared by milling 30g of raw material in a ball jar with a pigment concentration of 15%.

[0231] The spherical grinding was carried out in a 125mL PP bottle with a diameter of 45mm. The bottle was filled with 200g of 0.3mm YTZ ceramic beads from Tosoh. Grinding was carried out at a speed of 36m / min for 7 days.

[0232] Table 2: Pigment Dispersion Composition

[0233]

[0234] Analytical methods

[0235] Particle size analysis

[0236] The particle size of the pigment was determined using a Nicomp 3.80 particle size analyzer (Particle sizing systems, Santa Barbara, California, USA). The dispersion was diluted from 10 ppm to 100 ppm to achieve optimal measurement performance (i.e., the dispersion was diluted 10 × 10⁻⁶). 6 Multiplied to 100*10 6 (times). The diluted sample was measured at 23°C using a HeNe laser, and dv50 was obtained by Gaussian analysis of the scattered light intensity profile.

[0237] Surface tension

[0238] Surface tension was measured using a SITA Pro Line T15 surface tension meter (SITA Messtechnik Co, Dresden GE.) via the bubble pressure method at temperatures between 23.0°C and 26.0°C. The bubble life used was 10 seconds, which is the time between the formation of a new air-liquid interface (at the tip of the capillary immersed in the ink liquid) and the reaching of the maximum bubble pressure. After calibrating the device in distilled water, the measured maximum pressure was automatically recalculated as the surface tension value of the liquid (in mN / m).

[0239] Viscosity

[0240] Viscosities (dispersion and supernatant) were measured using a Haake Rheostress RS6000 operating at 25°C with shear rates ranging from 0.1 lb / s to 3000 lb / s, and expressed in mPa·s. The instrument was equipped with a cone / plate geometry of type C60 / 1° and a gap set to 0.052 mm. The reported viscosity was measured at a frequency of 3000 lb / s.

[0241] Water solubility of block copolymer dispersants

[0242] A block copolymer is defined as "water-soluble" when it is kept in an aqueous solution at 25°C for at least one week, preferably for at least one month or more, more preferably at 25°C for at least one week, with a weight percentage of at least 20 wt% of the dried polymer dissolved in water, and most preferably at 25 wt% for at least one week. The polymer dispersant solution is obtained by mixing the dried block copolymer with 100 g of distilled water at a temperature of at least 25°C for at least 2 hours. Stirring and / or raising the temperature to 60°C can be used to accelerate the dissolution process. The mixing time can be selected between 2 hours and 12 hours.

[0243] When the dried block copolymer contains acidic repeating units in the matrix-stabilized segments, the "water solubility" test conditions are performed by adding a monoethanolamine (MEA) base to water to neutralize all acidic functional groups, making the polymer solution pH 8.5 or higher. When the dried block copolymer contains basic functional groups in the matrix-stabilized repeating segments, the "water solubility" test conditions are performed by adding HCl to water to neutralize all basic functional groups, making the polymer solution pH 5.5 or lower.

[0244] Evaluation methods

[0245] Stability of dispersion

[0246] The dispersion stability of the pigment dispersion was tested under very harsh conditions. After diethylene glycol monobutyl ether (DEGMBE) was added as an organic solvent to interfere with the dispersion stability of the pigment, the dispersion was stored at a high temperature of 80°C for 7 days.

[0247] A sealed glass vial containing 5 g of dispersion, 1.5 g of DEGMBE, and 8.5 g of water was used. The pigment dispersion contained 15 wt% pigment relative to the total weight of the pigment dispersion. The amount of pigment tested relative to the total weight of the composition was 15 wt% × 5 [g] / 15 [g] = 5 wt%. The amount of DEGMBE relative to the total weight of the composition was 1.5 / 15 = 10 wt%. Particle size was measured before and after heat treatment. Stability was considered good when the dv50 after heat treatment was less than 1.10 times the dv50 before heat treatment.

[0248] Grinding properties of dispersants

[0249] The grinding performance of a dispersant is determined by the particle size that can be obtained after grinding. Good grinding performance is achieved when dv50 < 175 nm. Stability testing is not performed when the grinding performance is outside the specifications.

[0250] Hansen solubility parameters

[0251] The Hansen solubility parameter according to the present invention was calculated using HSPiP software version 5.2.03 according to the Y-MB method, and expressed in cal... 1 / 2 cm -3 / 2 express.

[0252] Examples of Hansen solubility parameters for repeating units R1 and R2 are shown in Tables 3.1 and 3.2.

[0253]

[0254]

[0255] Table 3.1: Examples of repeating units R1 with low hydrophobicity containing alkoxy ether groups. Values ​​are expressed in [cal...]. 1 / 2 cm -3 / 2 ]express.

[0256] Table 3.1 shows the polar bonding value δ(polarity) and hydrogen bonding value δ(hydrogen) of R1, as well as the Hansen solubility parameter δ(polarity + hydrogen). R1 It is the sum of the polar bonding value and the hydrogen bonding value of R1. The value is expressed in [cal...]. 1 / 2 cm -3 / 2 ]express.

[0257] The sum of the polar bond value and the hydrogen bond value of the repeating unit is defined as the square root of the sum of the squares of the polar bond value and the hydrogen bond value of the repeating unit: δ(polarity + hydrogen) = √[δ(polarity)]. 2 +δ(hydrogen) 2 ].

[0258]

[0259] Table 3.2: Examples of 'hydrophobic' repeating unit R2. Values ​​are in [cal 1 / 2 cm -3 / 2 ]express.

[0260] Table 3.2 shows the polar bonding value δ(polarity) and hydrogen bonding value δ(hydrogen) of R2, as well as the Hansen solubility parameter δ(polarity + hydrogen). R2 It is the sum of the polar bonding value and the hydrogen bonding value of R2. The value is expressed in [cal...]. 1 / 2 cm-3 / 2 ]express.

[0261] result

[0262] Several block copolymer dispersants were prepared according to Table 4:

[0263]

[0264]

[0265] Table 4: Composition of exemplary block copolymer dispersants

[0266] Different pigment dispersions were prepared using the block copolymer dispersants mentioned in Table 4, based on the compositions mentioned in Table 2 (Table 5). The pigment dispersions of Examples 1-10 contained 15 wt% dispersant, and the pigment / dispersant weight ratio was 1, resulting in 30 wt% pigment plus dispersant in the pigment dispersion. During the milling experiments, the pigment dispersions contained water as an aqueous carrier and contained no water-soluble organic solvents. Examples 11 and 12 contained 7.5 wt% dispersant, and the pigment / dispersant weight ratio was 1:0.5, resulting in 15 wt% pigment plus dispersant in the pigment dispersion.

[0267]

[0268] Table 5: Evaluation of Pigment Stability in Several Pigment Dispersions

[0269] Remark:

[0270] Pigment selection:

[0271] C: PB15:3, from Clariant:PV Fast Blue BG

[0272] M: PR122, from Clariant: Inkjet Magenta E02

[0273] M1: PR122, from BASF: Cinquasia magenta D 4450J

[0274] K: PBk7, from Omsk: N220FA

[0275] Assess stability:

[0276] V: Okay

[0277] X: Not good

[0278] When dv50 < 175 nm, the grinding performance is considered good (V). When the dv50 after heat treatment is less than 1.10 times the dv50 before heat treatment, the heat treatment stability is considered good.

[0279] As shown in Table (5) for Examples 1-4, equivalent good grinding and stability results were obtained by using dispersants DA2 and DA4 neutralized with triethanolamine or monoethanolamine instead of sodium salts. Therefore, it is demonstrated that the advantageous properties of these dispersants do not depend on the type of counterion.

[0280] The examples in Table 5 demonstrate that pigment dispersions 1-4 and 11-12, which contain block copolymer dispersants comprising a hydrophobic repeating unit R2 and a repeating unit R1 with an ethoxydiol group in their anchoring segments, are extremely stable in an aqueous carrier free of water-soluble organic solvents. Comparative Examples 5-10 show that block copolymer dispersants containing only a benzyl-containing hydrophobic repeating unit R2 in their anchoring segments, or only a repeating unit R1 with an ethoxydiol group in their anchoring segments, do not provide a combination of good milling behavior and good thermal stability in the dispersion.

[0281] Inkjet inks were prepared according to Table 6 using the pigment dispersions from Examples 1 to 4.

[0282]

[0283] Table 6: Composition of Inkjet Inks

[0284] All inks have a viscosity between 4 mPa·s and 7 mPa·s, and a surface tension between 20 mN / m and 27 mN / m as measured by a Sita bubble tensiometer after 10 seconds.

[0285] With these inks, excellent jetting and image quality were observed at a printing speed of 1 m / s on both coated and uncoated paper substrates using the KJ4B AQ printhead from Kyocera.

[0286] Example 5 demonstrates that inkjet inks remain stable when using an adhesive resin (Joncryl J8050E). The adhesive resin Joncryl J8050E improves the adhesion of pigments to a variety of paper and film substrates.

Claims

1. An inkjet ink for forming an image on a substrate, the inkjet ink comprising a pigment P, a block copolymer dispersant D for dispersing the pigment P, and an aqueous carrier; wherein The block copolymer dispersant D is a diblock copolymer having an anchoring segment A and a matrix-stabilizing segment M. The anchoring segment A is used to anchor to the pigment P, and the matrix stabilizing segment M is used for the aqueous phase stabilization of the pigment. The anchoring segment A represents an anchoring block having an alternating or statistically distributed distribution of repeating units R1 and repeating units R2 different from R1, wherein repeating units R1 and R2 are arranged within the anchoring block, wherein the hydrophobicity of repeating unit R1 is lower than that of repeating unit R2. The repeating unit R1 comprises a polyepoxide coupled to a terminal group via a direct bond, a -COC-ether bond, or a -CO-(C=O)-N-carbamate bond, wherein the terminal group is selected from alkyl groups, aryl groups, and combinations thereof. The repeating unit R2 is formed using a hydrophobic monomer Mn2, which is selected from the group consisting of methacrylate monomers, acrylate monomers, and vinyl monomers. The repeating unit R1 is formed using a nonionic monomer Mn1, which is at least one of the following: tri(ethylene glycol) methyl ether acrylate, 2-(2-ethoxyethoxy) ethyl acrylate (EOEOEA), ethylene glycol methyl ether acrylate, 2-ethoxyethyl acrylate, di(ethylene glycol) methyl ether acrylate, ethylene glycol methyl ether methacrylate, 2-ethoxyethyl methacrylate, di(ethylene glycol) methyl ether methacrylate, tri(ethylene glycol) methyl ether methacrylate, 2-[[(butylamino)carbonyl]oxy] ethyl acrylate, and mixtures thereof; in, The repeating units R1 and R2 arranged within the anchoring block do not have ionic groups; The anchoring block is formed by reacting the monomer Mn2 with the monomer Mn1, such that the repeating unit R1 and the repeating unit R2 are located within the same anchoring block.

2. The ink according to claim 1, wherein the terminal group is an alkyl group, wherein... The repeating unit R2 is formed using a hydrophobic monomer Mn2, which is selected from the group consisting of acrylate monomers and vinyl monomers. The polyepoxide included in the repeating unit R1 is coupled to the terminal group via a -CO-(C=O)-N-carbamate bond.

3. The ink according to claim 1, wherein the repeating unit R1 comprises a polyepoxyalkyl group.

4. The ink according to claim 1, wherein the repeating unit R1 has a Hansen solubility parameter value δ (polarity + hydrogen). R1 , where δ (polar + hydrogen) R1 > 8.0 cal 1 / 2 cm -3 / 2 The Hansen solubility parameter value δ(polarity + hydrogen) is defined as follows: .

5. The ink according to claim 1, wherein the ratio between the number of repeating units R1 (n1) and the number of repeating units R2 (n2) within the anchoring segment A is between 0.05 and 20.

6. The ink of claim 1, wherein the polar bonding value of R1 : δ (polar) R1 > 5.0 cal 1 / 2 cm -3 / 2 .

7. The ink according to claim 1, wherein the repeating unit R2 of the anchoring segment A is formed using a hydrophobic monomer Mn2, wherein the hydrophobic monomer Mn2 is an acrylate monomer.

8. The ink according to claim 7, wherein the hydrophobic monomer Mn2 is benzyl acrylate.

9. The ink according to claim 1, wherein the nonionic monomer Mn1 is 2-[[(butylamino)carbonyl]oxy]ethyl acrylate.

10. The ink according to claim 1, wherein the repeating unit R2 has a Hansen solubility parameter value δ (polarity + hydrogen). R2 , where δ (polar + hydrogen) R2 < 8.0 cal 1 / 2 cm -3 / 2 The Hansen solubility parameter value δ(polarity + hydrogen) is defined as follows: .

11. The ink according to claim 1, wherein the polar bonding value of R2 is: δ (polarity) R2 < 5.0 cal 1 / 2 cm -3 / 2 .

12. The ink according to claim 1, wherein the matrix stabilizing segment M is formed using at least one monomer Mn3, the at least one monomer Mn3 being used to obtain an ionic hydrophilic repeating unit R3, the ionic hydrophilic repeating unit R3 comprising a neutralized acid group, a neutralized basic group or other ionic functional group.

13. The ink according to claim 12, wherein the at least one monomer Mn3 is selected from the group consisting of: methacrylic acid, acrylic acid, maleic acid, maleic acid monoester, itaconic acid, itaconic acid monoester, crotonic acid, crotonic acid monoester, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethyl acrylate, tert-butylaminoethyl methacrylate, tert-butylaminoethyl acrylate, and mixtures thereof.

14. The ink according to claim 12 or 13, wherein the repeating unit R3 comprises an ionic portion.

15. The ink of claim 1, wherein the anchoring block is formed by copolymerizing the monomer Mn1 with the monomer Mn2; and The copolymer dispersant D is obtained by further polymerization of the formed anchoring block with at least one monomer Mn3, wherein the monomer Mn3 is selected from the group consisting of: methacrylic acid, acrylic acid, maleic acid, maleic acid monoester, itaconic acid, itaconic acid monoester, crotonic acid, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethyl acrylate, tert-butylaminoethyl methacrylate, tert-butylaminoethyl acrylate, and mixtures thereof.

16. The ink according to claim 15, wherein monomer Mn2 is benzyl acrylate, and wherein monomer Mn1 is 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA).

17. An aqueous pigment dispersion for forming inkjet ink, the pigment dispersion comprising pigment P, a block copolymer dispersant D for dispersing said pigment P, and an aqueous carrier; wherein said block copolymer dispersant D is the block copolymer dispersant D as defined in any one of claims 1-16, and wherein said aqueous carrier comprises a total amount of water and optionally a water-soluble organic solvent, the total amount of said water-soluble organic solvent being less than 5 wt% of the total weight of said aqueous carrier.

18. The aqueous pigment dispersion according to claim 17, wherein the terminal group is an alkyl group.

19. The aqueous pigment dispersion according to claim 17 or 18, wherein the repeating unit R1 comprises a polyepoxyalkyl group.

20. The aqueous pigment dispersion according to claim 17 or 18, wherein the repeating unit R1 has a Hansen solubility parameter value δ (polarity + hydrogen). R1 , where δ (polar + hydrogen) R1 > 8.0 cal 1 / 2 cm -3 / 2 The Hansen solubility parameter value δ(polarity + hydrogen) is defined as follows: .

21. The aqueous pigment dispersion according to claim 17 or 18, wherein the amount of pigment P in the pigment dispersion is in the range of 10 wt% to 80 wt% based on the weight of the pigment dispersion.

22. The aqueous pigment dispersion according to claim 17 or 18, wherein the amount of water in the aqueous carrier is at least 50 wt% based on the total weight of the aqueous carrier.

23. An inkjet printing process for forming an image on a substrate by applying more than one inkjet ink, wherein the more than one inkjet ink comprises the ink according to any one of claims 1-16.

24. The inkjet printing process of claim 23, comprising spraying droplets of each inkjet ink onto the substrate to form a color image on the substrate.

25. An inkjet ink kit comprising more than one ink, wherein at least one of the inks is an ink according to any one of claims 1-16.

26. An inkjet printer responsive to a digital data signal, the inkjet printer being equipped with inkjet ink according to any one of claims 1-16 or an inkjet ink set according to claim 25.

Images