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 first block copolymer dispersant D1 for dispersing the pigment P, a second block copolymer dispersant D2 for dispersing the pigment P, and an aqueous carrier; wherein the first block copolymer dispersant D1 is different from the second block copolymer dispersant D2, wherein each block copolymer dispersant D1, D2 includes anchoring segments A1, A2 for anchoring to the pigment P, wherein each of the block copolymer dispersants D1, D2 further includes a matrix stabilizing segment M for aqueous stabilization of the pigment P, wherein the anchoring segment A1 of the first block copolymer dispersant D1 includes a repeating unit R1, and the anchoring segment A2 of the second block copolymer dispersant D2 includes a repeating unit R2, wherein the hydrophobicity of the repeating unit R1 is lower than that of the repeating unit R2.

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 there are also inactive groups 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. When manufacturing dispersions for inkjet inks, other undesirable side effects can occur. 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. For consistent image quality, inkjet inks require dispersion stability that can withstand conditions such as 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 concentrations of water-soluble organic solvents, or the addition of functional polymers to improve ink adhesion, drying, water resistance, or scratch resistance on substrates.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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

[0016] 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 first block copolymer dispersant D1 for dispersing the pigment P, a second block copolymer dispersant D2 for dispersing the pigment P, and an aqueous carrier; wherein the first block copolymer dispersant D1 is different from the second block copolymer dispersant D2, wherein each block copolymer dispersant D1, D2 includes anchoring segments A1, A2 for anchoring to the pigment P, wherein each of the block copolymer dispersants D1, D2 further includes a matrix stabilizing segment M for aqueous stabilization of the pigment P, wherein the anchoring segment A1 of the first block copolymer dispersant D1 includes a repeating unit R1, and the anchoring segment A2 of the second block copolymer dispersant D2 includes a repeating unit R2, wherein the hydrophobicity of the repeating unit R1 is lower than that of the repeating unit R2.

[0017] 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.

[0018] 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 ink according to the invention.

[0019] 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.

[0020] 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 first block copolymer dispersant D1 for dispersing the pigment P, a second block copolymer dispersant D2 for dispersing the pigment P, and an aqueous carrier; wherein the first block copolymer dispersant D1 is different from the second block copolymer dispersant D2, wherein each block copolymer dispersant D1, D2 includes anchoring segments A1, A2 for anchoring to the pigment P, wherein each of the block copolymer dispersants D1, D2 further includes a matrix stabilizing segment M for aqueous stabilization of the pigment P, wherein the anchoring segment A1 of the first block copolymer dispersant D1 includes a repeating unit R1, and the anchoring segment A2 of the second block copolymer dispersant D2 includes a repeating unit R2, wherein the hydrophobicity of the repeating unit R1 is lower than that of the repeating unit R2; and wherein the aqueous carrier comprises water.

[0021] Beneficial effects of the present invention

[0022] The inventors have discovered that stable colored inkjet inks can be readily manufactured using a combination of a first block copolymer dispersant D1 and a second block copolymer dispersant D2. The hydrophobicity of the repeating unit R1 of the first block copolymer dispersant D1 is lower than that of the repeating unit R2 of the second block copolymer dispersant D2. It has been found that the first block copolymer dispersant D1 improves the pigment stability required for inkjet inks and simultaneously enhances the ease of manufacturing fine pigment dispersions with fine pigment particles in a simple manner, such as using a milling process. The second block copolymer dispersant D2 further enhances the pigment stability required for inkjet inks. The combination of the first block copolymer dispersant D1 and the second block copolymer dispersant D2 in the pigment dispersion or inkjet ink surprisingly combines these advantages without any adverse effects. In addition, little or no water-soluble organic cosolvent is required to obtain the beneficial 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.

[0023] Using two block copolymer dispersants may seem to increase the complexity of pigment dispersions, but the improved milling performance and the flexibility in mixing ratios of different block copolymer dispersants enable the manufacture of versatile and stable pigment dispersions.

[0024] Pigments can have surfaces with varying degrees of hydrophobicity, meaning that one portion of a pigment surface can be less hydrophobic than other portions. It has been found that highly specialized design / selection of block copolymer dispersants is necessary to cover the entire pigment surface and thus obtain highly stable pigment dispersions.

[0025] 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 dispersants D1 and D2 used to disperse pigment P in the ink can prevent pigment P from re-agglomerating in the resulting inkjet ink.

[0026] Furthermore, the use of block copolymer dispersants D1 and D2 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.

[0027] (Pigment dispersion stability)

[0028] 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.

[0029] 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.

[0030] Embodiments of the present invention

[0031] The following exemplary embodiments are described; however, the invention is not limited to these embodiments:

[0032] (Block copolymer pigment dispersant)

[0033] It has been found that the combination of block copolymer dispersants D1 and D2 generally improves pigment stability in inks. It has also been found that selecting block copolymer dispersants D1 and D2 with different properties allows for specialized chemical fine-tuning of the dispersants to optimize 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. Modifying the pigment affinity / matrix affinity balance in block copolymers can be accomplished in several ways.

[0034] 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 block copolymer dispersant, which also has a second chemically different type of repeating unit and may have a different number of repeating units, can be very beneficial.

[0035] 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.

[0036] 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.

[0037] The fact that individual blocks and the complete polymer have the same size can be represented by polydispersity D, which is defined as the M of the individual blocks or the complete polymer, respectively. w / M n The polydispersity D is preferably less than 1.6, more preferably less than 1.5.

[0038] In an exemplary embodiment, the block copolymer dispersants D1 and D2 have a polydispersity D of less than 1.6, more preferably less than 1.5. In a particular embodiment, each block of the block copolymer dispersants D1 and D2 has a polydispersity D of less than 1.6, more preferably less than 1.5.

[0039] 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. Since 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.

[0040] 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.

[0041] 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.

[0042] The matrix-stabilizing and anchoring segments of a block copolymer dispersant can be arranged in any order along the block copolymer dispersant.

[0043] In an exemplary embodiment, the block copolymer dispersants D1 and D2 are water-soluble block copolymer dispersants. A block copolymer is defined as “water-soluble” when it is held in an aqueous solution at 25°C for at least one week, preferably for at least one or more months, more preferably at at least 20 wt.% of the weight of the dried polymer dissolved in water at 25°C, and most preferably at at least 25 wt.% or higher.

[0044] 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.

[0045] 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.

[0046] In an exemplary embodiment, the block copolymer dispersants D1 and D2 are composed of linear polymer chains. In another exemplary embodiment, the block copolymer dispersants D1 and D2 are at least partially crosslinked, wherein the block copolymer dispersants are attached to or at least partially encapsulate the pigment.

[0047] Block dispersants D1 and D2 each have 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 anchoring segment A and the total number of repeating units of matrix-stabilizing segments M of D1 and D2 is in the range of 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 most one pigment particle. Even without the addition of a binder, polymeric dispersants with a molecular weight above 2000 g / mol provide the benefit of adhesion to the substrate during the ink drying process. In addition, 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.

[0048] The mixture of block copolymer dispersants D1 and D2, with an acid value ranging from 50 mg KOH / g polymer to 200 mg KOH / g polymer, more preferably 60 mg KOH / g polymer to 150 mg KOH / g polymer, allows for good solubility in water. The acid value of the mixture is determined by measuring / calculating the acid value (AV) of each of the individual block copolymer dispersants D1 and D2, and then calculating the AV of the mixture based on the weight ratio of D1 and D2 in the pigment dispersion. Therefore, the acid value is a measure of the weight ratio between matrix-stabilized segments and anchoring segments. 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 excessively high AV is that the water fastness of the ink image on the substrate may be insufficient.

[0049] 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.

[0050] 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.

[0051] The combination of appropriate molecular weights and acid value ranges of block copolymer dispersants D1 and D2 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.

[0052] In an exemplary embodiment, anchoring segment A1 is formed using at least one monomer Mn1, and anchoring segment A2 is formed using at least one monomer Mn2, wherein monomers Mn1 and Mn2 are selected from the group consisting of methacrylate monomers, acrylate monomers, and vinyl monomers.

[0053] Anchoring segments are anchoring portions used to anchor to pigments, and wherein the anchoring segment A1 of block copolymer dispersant D1 is different from the anchoring segment A2 of block copolymer dispersant D2.

[0054] (Anchoring segment A1)

[0055] The first block copolymer dispersant D1 includes an anchoring segment A1 comprising a repeating unit R1. The hydrophobicity of the repeating unit R1 of the first block copolymer dispersant D1 is lower than that of the repeating unit R2 of the second block copolymer dispersant D2.

[0056] (Repeating unit R1 with low hydrophobicity and nonionic properties)

[0057] The repeating unit R1 of the anchoring segment A1 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.

[0058] Specifically, the repeating unit R1 is a nonionic repeating unit, meaning that the repeating unit R1 does not contain an ionic portion. The nonionic repeating unit R1 was chosen to enhance the anchoring interaction with pigment P.

[0059] Preferably, the hydrophobicity of R1 is lower than that of R2 based on the comparison that the Hansen solubility parameter value δ(polarity + hydrogen) of R1 is higher than that of R2. The Hansen solubility parameter according to the present invention is calculated using HSPiP software version 5.2.03 according to the Y-MB method.

[0060] The Hansen solubility parameter δ(polar + hydrogen) is the sum of the polar bond value and the hydrogen bond value of the repeating unit. According to the Hansen 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 unit: δ(polar + hydrogen) = √[δ(polar)]. 2 +δ(hydrogen) 2 ].

[0061] Preferably, the repeating unit R1 has a Hansen solubility parameter value δ(polarity + hydrogen). R1 It is the sum of the polar bond value of R1 and the hydrogen bond value of R1, where δ(polar + hydrogen) R1 >7.2cal 1 / 2 cm -3 / 2 .

[0062] The sum of the polar bond value and the hydrogen bond value of R1 is defined as the square root of the sum of the squares of the polar bond value and the hydrogen bond value of R1: δ(polarity + hydrogen) = √[δ(polarity)] 2 +δ(hydrogen) 2 ].

[0063] In an exemplary implementation, the polarity bond value of R1 is δ (polarity). R1 >4.4cal 1 / 2 cm -3 / 2 .

[0064] Preferably, the less hydrophobic anchoring monomer Mn1 of the anchoring segment A1 has heteroatoms in its substituent structure, such as dimethylaminoethyl (meth)acrylate (DMAE(M)A), N,N-dimethylacrylamide, acrylamide (ACMO), N-vinylpyrrolidone (NVP), vinylmethyloxazolidinone (VMOX), and 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA).

[0065] In a specific instance, the monomer Mn1 of the anchoring segment A1 is at least one of the following: tri(ethylene glycol) methyl ether acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, dimethylaminoethyl acrylate (DMAA), N,N-dimethylacrylamide, acrylamide (ACMO), N-vinylpyrrolidone (NVP), vinylmethyl oxazolidinone (VMOX), and 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), phenoxyethyl methacrylate, methacrylonitrile, ethylene glycol methyl ether methacrylate, 2-ethoxyethyl methacrylate, di(ethylene glycol) methyl ether methacrylate, tri(ethylene glycol) methyl ether methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, di(propylene glycol) methyl ether methacrylate, phenoxyethyl acrylate, ethylene glycol methyl ether acrylate, 2-ethoxyethyl acrylate, di(ethylene glycol) methyl ether acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, and any mixture thereof.

[0066] In a preferred embodiment, the monomer Mn1 of the anchoring segment A1 is an acrylate or a methacrylate, and contains a monoethylene glycol group or a polyethylene glycol group.

[0067] In a specific instance, the anchoring segment A1 comprises at least two different repeating units, which can be formed using at least two different anchoring monomers Mn1.

[0068] In an exemplary embodiment, the anchoring segment A1 of the first block copolymer dispersant D1 has a different repeating unit R1' from R1. Preferably, the other repeating unit R1' has a >7.2 cal 1 / 2 cm -3 / 2 The Hansen solubility parameter δ(polarity + hydrogen) R1 In the described embodiment, R1' provides an additional beneficial contribution to the grinding properties of the block copolymer dispersant D1.

[0069] (Anchoring segment A2)

[0070] The second block copolymer dispersant D2 includes an anchoring segment A2 comprising a repeating unit R2. The hydrophobicity of the repeating unit R1 of the first block copolymer dispersant D1 is lower than that of the repeating unit R2 of the second block copolymer dispersant D2.

[0071] (Hydrophobic repeating unit R2)

[0072] The repeating unit R2 of the anchoring segment A2 is formed using the hydrophobic monomer Mn2, which can be selected from the group consisting of methacrylate monomers, acrylate monomers and vinyl monomers.

[0073] In an exemplary embodiment, the repeating unit R2 has a Hansen solubility parameter value δ(polarity + hydrogen). R2 It is the sum of the polar bond value of R2 and the hydrogen bond value of R2, where δ(polar + hydrogen) R2 <7.2cal 1 / 2 cm -3 / 2 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 the hydrogen bonding value of R2.

[0074] In an exemplary implementation, the polarity bond value δ (polarity) of R2 is... R2 <4.4cal 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.

[0075] In an exemplary embodiment, the monomer Mn2 of the anchoring segment A2 comprises an alkyl group, an alkenyl group, or an aryl group.

[0076] In a specific instance, the monomer Mn2 of the anchoring segment A2 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, cyclohexyl 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, cyclohexyl acrylate, and any mixture thereof.

[0077] In a specific instance, the anchoring segment A2 comprises at least two different repeating units, which can be formed using at least two different anchoring monomers Mn2.

[0078] In an exemplary embodiment, the anchoring segment A2 of the second block copolymer dispersant D2 has a different repeating unit R2' from R2. Preferably, the other repeating unit R2' has a calorific value of <7.2 cal. 1 / 2 cm -3 / 2 The Hansen solubility parameter δ(polarity + hydrogen) R2 In the described embodiment, R2' provides an additional beneficial contribution to the pigment dispersion stability effect of the block copolymer dispersant D2.

[0079] (The relationship between repeating units R1 and R2 in anchoring chain segments A1 and A2)

[0080] In an exemplary embodiment, the repeating units R1 and R2 of the anchoring segments A1 and A2 do not have ionic groups. Therefore, the anchoring segments A1 and A2 are substantially insoluble in the aqueous support phase.

[0081] In an exemplary embodiment, the anchoring segment A1 has a number of repeating units n1, and wherein the repeating units R1 are at least 50% of the total number of repeating units n1, preferably at least 80% of the total number of repeating units n1.

[0082] In an exemplary embodiment, the anchoring segment A2 has a number of repeating units n2, and wherein the repeating units R2 are at least 50% of the total number of repeating units n2, preferably at least 80% of the total number of repeating units n2.

[0083] (Matrix stabilization segment M)

[0084] Each of the block copolymer dispersants D1 and D2 further includes a matrix-stabilizing segment M for aqueous stabilization of pigment P.

[0085] In an exemplary embodiment, the matrix-stabilized segment M is formed using at least one monomer, Mn3. Preferably, the at least one monomer, Mn3, is a monomer for obtaining an ionicly hydrophilic repeating unit for aqueous phase stabilization of the pigment. The ionicly hydrophilic repeating unit provides solubility of the matrix-stabilized segment M in the aqueous carrier phase. The ionicly hydrophilic repeating unit optionally comprises 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.

[0086] When two different monomers Mn3 are used to form a matrix-stabilized segment M, the matrix-stabilized segment M has a first repeating unit and a second repeating unit, each formed by 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 is equal to the total number n of repeating units in segment M, i.e., the matrix-stabilized portion of the first block.

[0087] In particular, at least one ionic hydrophilic repeating unit R3 of the matrix stabilization segment M includes an ionic portion.

[0088] 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.

[0089] (Ion repeating unit R3)

[0090] 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, or other ionic functional groups such as a quaternary ammonium group.

[0091] The ionic hydrophilic repeating unit R3 provides solubility of the matrix stabilizing segment M in the aqueous support phase.

[0092] In a specific example, the matrix-stabilized segment M is formed using at least one monomer Mn3, said monomer Mn3 being 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.

[0093] When the matrix stabilization segment contains hydrophilic repeating units with acidic functional groups, a significant portion of the acidic groups needs to be neutralized with a neutralizing agent to provide solubility and dispersion stability. Preferably, this is done by setting the pH level to 7.5, and most preferably to 8.5 or higher to neutralize all the acids. When the matrix stabilization segment contains hydrophilic repeating units with basic functional groups, a significant portion of the basic groups, such as protonated amino groups, is neutralized to provide solubility and dispersion stability. Preferably, this is done by setting the pH level to 6.5, and most preferably to 5.5 or lower to neutralize all the basic groups.

[0094] 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.

[0095] Possible neutralizing agents for acidic 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.

[0096] Possible neutralizing agents for basic groups such as amino 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. The invention is not limited to these exemplary embodiments.

[0097] 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 characteristics when exposed to extreme conditions. The selection of the neutralizer, pH value, and corresponding salt counterion can also affect the behavior of the final ink, such as drying rate, open time, first drop reliability, and jetting stability.

[0098] (pigment)

[0099] For water-based inks, the pigment surface is typically more hydrophobic than the bulk liquid. Therefore, hydrophobic anchoring monomers, such as alkyl acrylates and aryl acrylates, such as benzyl acrylate, can be used. However, some pigments have been found to have additional pigment surfaces with lower hydrophobicity, and it has been found that these pigments are more difficult to achieve good milling performance and dispersion stability using only a single block dispersant.

[0100] Differences 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.

[0101] Therefore, the anchoring segment A1 of block copolymer dispersant D1 and the anchoring segment A2 of block copolymer dispersant D2 comprise 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, surfaces with different chemical properties may exist, and different anchoring chemistry may be required to achieve higher pigment dispersion stability.

[0102] In an exemplary embodiment, pigment P is a colored pigment selected for adjusting the color of the ink.

[0103] In an exemplary embodiment, pigment P is an organic pigment that optionally contains metal atoms complexed with the organic components of the organic pigment.

[0104] In an exemplary embodiment, pigment P is an inorganic pigment that optionally contains a metal oxide.

[0105] 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.

[0106] (Water-based pigment dispersion)

[0107] Preferably, the amount of water in the aqueous carrier is at least 50 wt.-%, preferably at least 80 wt.-%, and more preferably at least 95 wt.-%.

[0108] 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.

[0109] 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.

[0110] 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 ink derived from the pigment dispersion, the pigment dispersion can be a concentrated dispersion of pigment P. Generally, the amount of colored pigment P in inkjet ink can be in the range of 0.5 wt% to 10 wt% based on the weight of the inkjet ink. In the case of inorganic pigments, preferably white pigments, the amount of pigment P in the pigment dispersion can be in the range of 40 wt% to 80 wt% 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 10 wt% to 50 wt%.

[0111] In an exemplary embodiment, the weight ratio between block copolymer dispersant D1 and block copolymer dispersant D2 is between 0.1 and 10, preferably between 0.2 and 5.

[0112] In an exemplary embodiment, the weight ratio between pigment P and the sum of block copolymer dispersant D1 and block copolymer dispersant D2 is between 0.2 and 10.0, preferably between 0.4 and 5.0.

[0113] In an exemplary embodiment, the weight ratio between pigment P and block copolymer dispersant D1 is between 0.05 and 10.0, preferably between 0.1 and 5.0.

[0114] In an exemplary embodiment, the weight ratio between pigment P and block copolymer dispersant D2 is between 0.05 and 10.0, preferably between 0.1 and 5.0.

[0115] (Method for preparing aqueous pigment dispersions)

[0116] Preferably, the aqueous pigment dispersion is prepared without using water-soluble organic solvents or other organic solvents.

[0117] 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. As block dispersants, a combination of block copolymer dispersant D1 and block copolymer dispersant D2 according to the invention is used.

[0118] The weight ratio between block copolymer dispersant D1 and block copolymer dispersant D2 is between 0.1 and 10, preferably between 0.2 and 5.

[0119] Other components besides pigments, dispersants, and water, such as wetting agents (usually Mw < 1000 g / mol) and similar substances, can also be added to improve the pigment dispersion process.

[0120] 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).

[0121] 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.

[0122] There are no particular limitations on the dispersion method. Examples of dispersion methods include paint vibrators, horizontal bead mills, 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 can 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 performed statically or dynamically (i.e., some kind of agitation / stirring of the dispersion during heat treatment). After milling is complete, conventional separation techniques are used to separate the milling media from the milled particles, such as by filtration, sieving via a screen, and similar separation techniques. Typically, the screen is built into the mill, for example, for a bead mill.

[0123] 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.

[0124] (Water-based inkjet inks)

[0125] 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.

[0126] 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 block copolymer dispersants D1, D2.

[0127] 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 1.0 wt%, wherein the ink preferably has a viscosity of up to 20 mPa·s at 25°C.

[0128] 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.

[0129] In an exemplary embodiment, the static surface tension of the inkjet ink is between 17 mN / m and 35 mN / m.

[0130] 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.

[0131] 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.

[0132] (Water-soluble organic solvent)

[0133] 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 or propylene glycol. In a particular exemplary embodiment, the water-soluble glycol ether compound is a glycol monobutyl ether.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] (Water-based inkjet inks)

[0140] 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.

[0141] (Inkjet printing process)

[0142] 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.

[0143] In a particular exemplary implementation, droplets are ejected using an inkjet printhead.

[0144] 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.

[0145] Detailed Explanation

[0146] 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.

[0147] 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.

[0148] 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".

[0149] As used in this article, the term "basically" means to a considerable extent, almost entirely.

[0150] 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.

[0151] The materials, methods, and examples in this article are illustrative and not intended to be limiting.

[0152] As used in this article, 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.

[0153] Water-based inks

[0154] 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.

[0155] 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 ensure 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.

[0156] 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.

[0157] pigment

[0158] 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.

[0159] Pigments may be selected from those disclosed in HERBST, W. et al., Industrial Organic Pigments, Production, Properties, Applications, 2nd ed. vch, 1997.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] In addition, inorganic pigments may include white pigments such as titanium dioxide (anatase, brookite and rutile), which may be commercially 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.

[0170] Examples of carbon black pigments that can be used in this invention include carbon black produced using a furnace method or a channel method.

[0171] Examples of commercial products are listed below, and any of these products can be used well.

[0172] 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).

[0173] 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.

[0174] Any other pigments and / or dyes that can be used to change the color of the ink can be used.

[0175] surfactants

[0176] 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.

[0177] 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); Surfynol104, Surfynol465, 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.

[0178] Water-soluble organic solvents

[0179] 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.

[0180] 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.

[0181] 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.

[0182] Examples of amides described above include formamide, N,N-dimethylformamide, N,N-dimethylacetamide, pyrrolidone, urea, and similar amides.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] Exemplary penetrants are glycol monobutyl ethers, such as diethylene glycol monobutyl ether and ethylene glycol monobutyl ether. It should be noted that some penetrants, such as diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol isopropyl ether, and 1,2-hexanediol, also possess surface tension-active properties, thereby reducing the surface tension of the ink.

[0188] Adhesive resin

[0189] 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.

[0190] 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.

[0191] biocides

[0192] 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.

[0193] 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.

[0194] Other components

[0195] 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.

[0196] Preparation of colored inkjet inks

[0197] 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.

[0198] Typically, it is desirable to prepare colored inks in the form of a concentrated aqueous pigment dispersion according to the invention, and then dilute 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 viscosity, color, hue, saturation density, and printed area coverage desired for a particular application.

[0199] 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 pL 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] experiment

[0205] Manufacturing process

[0206] Block copolymer synthesis

[0207] 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:

[0208] • Instantaneous triggering ensures that all polymer chains grow simultaneously at a specified growth rate.

[0209] • 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.

[0210] • Continuous growth is strictly controlled, thereby obtaining small polydispersity of the polymer and thus well-defined polymer compositions.

[0211] 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.

[0212] 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).

[0213] Synthesis Examples

[0214] The following procedure describes a potential synthetic method for producing a block dispersant characterized as AA. 30 -BnA 10 It has 30 monomers AA for its matrix-stabilizing block length and 10 monomers BnA for its anchoring block length. It is a block copolymer dispersant comprising two blocks, wherein the matrix-stabilizing block is formed by reacting the monomer acrylic acid (AA) and has a length of approximately 30 repeating units, and the anchoring block is formed by reacting the monomer benzyl acrylate (BnA) and has a length of approximately 10 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 dispersant can be interchanged, i.e., first preparing the BnA block and then preparing the AA block. Unless otherwise stated, "parts" in the description are based on mass.

[0215] A 250 mL three-necked flask equipped with a thermometer, reflux condenser, and nitrogen balloon was loaded with 0.43 parts Cu(I)Br, 38.5 parts tert-butyl acrylate, 41.2 parts anisole (internal standard), and 0.69 parts tris[2-(dimethylamino)ethyl]amine (Me6TREN). The mixture was degassed under vacuum, backfilled with nitrogen three times, and heated to 60 °C. Subsequently, 1.67 parts methyl 2-bromopropionate (MBP) was added to initiate the polymerization reaction, which was carried out for 0.5 hours.

[0216] In a separate flask, 16.2 parts of benzyl acrylate and 0.87 parts of N,N,N',N”,N”-pentamethyldiethylenetriamine (PMDETA) were mixed and degassed under vacuum and backfilled three times with nitrogen. This solution was added to a tert-butyl acrylate polymer solution along with 0.72 parts of CuBr and 0.19 parts of Cu(O). Polymerization was stopped after 6 h by exposing the catalyst to air (Mn = 5406 and Mw / Mn = 1.37, conversion = 96.4%). The copper catalyst was removed by column chromatography, followed by removal of excess solvent by evaporation.

[0217] 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 formed salts. Dioxane is removed by rotary evaporation to obtain an acrylate / benzyl acrylate block copolymer.

[0218] Another example of synthesis for producing a block dispersant, wherein the block dispersant is characterized as AA 15 -EOEOEA 30 It has 15 monomers AA for the block length of its matrix stabilizing segment and 30 monomers 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA) for the block length of its anchoring segment.

[0219] A 250 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.

[0220] In a separate flask, 112.9 parts of 2-(2-ethoxyethoxy)ethyl acrylate, 48.3 parts of anisole, and 1.73 parts of PMDETA were mixed, degassed under vacuum, and 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 4 hours by exposing the catalyst to air (Mn = 7165 and Mw / Mn = 1.32). The copper catalyst was removed by column chromatography, followed by removal of excess solvent by evaporation.

[0221] 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 / 2-(2-ethoxyethoxy)ethyl acrylate block copolymer.

[0222] 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 (eds.), 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.

[0223] 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.

[0224] It should be noted that the total weight of the dispersant mentioned in the following examples includes the mass of the neutralizer.

[0225] Water solubility of block copolymer dispersants

[0226] Examples of solubilization are listed in Table 1. Water solubility tests were performed according to the test procedures described further below.

[0227]

[0228] Table 1

[0229] Dissolve the polymer in a round flask using mechanical stirring. (*) Check the stability by decanting the aqueous polymer solution and examining the solid sedimentation.

[0230] It should be noted that for polymer dispersant BnA 40 -AA 25 It has a very low hydrophilic / hydrophobic balance ratio, but remains soluble in water at high concentrations for a long period of time in the absence of an organic co-solvent.

[0231] Packaging

[0232] 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, are unaffected by the addition of cosolvents and surfactants, exhibit excellent stability.

[0233] Production of pigment dispersions

[0234] 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%.

[0235] 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.

[0236] Table 2: Pigment Dispersion Composition

[0237] Components weight Pigments (according to Table 2) 4.5g Block dispersants (according to Table 2) were neutralized with sodium hydroxide. 4.5g water 21g total 30g

[0238] Analytical methods

[0239] Particle size analysis

[0240] 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.

[0241] Surface tension

[0242] 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°C and 26°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).

[0243] Viscosity

[0244] 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.

[0245] Water solubility of block copolymer dispersants

[0246] 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 for at least one week at 25°C, and most preferably for at least one week at 25°C, with a weight percentage of at least 20 wt.% of the dried polymer dissolved in water. 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.

[0247] 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.

[0248] Evaluation methods

[0249] Stability of dispersion

[0250] 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.

[0251] 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% of 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.

[0252] Grinding properties of dispersants

[0253] 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.

[0254] Hansen solubility parameters

[0255] 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.

[0256] Examples of Hansen solubility parameters for repeating units R1 and R2 are shown in Tables 3.1 and 3.2.

[0257]

[0258] Table 3.1: Examples of repeating unit R1 with low hydrophobicity

[0259] 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 terms of [cal]. 1 / 2 cm -3 / 2 ]express.

[0260]

[0261] Table 3.2: Examples of hydrophobic repeating unit R2

[0262] 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.

[0263] 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 ].

[0264] result

[0265] Several block copolymer dispersants were prepared according to Table 4:

[0266]

[0267]

[0268] Table 4: Composition of exemplary block copolymer dispersants

[0269] Based on the compositions mentioned in Table 2, different pigment dispersions were prepared using the block copolymer dispersants mentioned in Table 4 (Table 5). The pigment dispersions contained 15 wt% dispersant, and the pigment / total 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 did not contain any water-soluble organic solvents.

[0270]

[0271] Table 5: Evaluation of Pigment Stability in Several Pigment Dispersions

[0272] Note:

[0273] Pigment selection:

[0274] C: PB15:3, from Clariant:PV Fast Blue BG

[0275] M: PR122, from Clariant: Inkjet Magenta E02

[0276] K: PBk7, from Omsk grade N220FA

[0277] Assess stability:

[0278] V: Okay

[0279] X: Not good

[0280] 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.

[0281] From the examples in Table 3, it can be concluded that extremely stable pigment dispersions can be obtained for pigment dispersions 1-5 having type A block copolymer dispersants and type B block copolymer dispersants.

[0282] As shown in Table (5) for Examples 1-5, equivalent good grinding and stability results were obtained by using any one or more of the dispersants DA1-DA4 neutralized with triethanolamine or monoethanolamine instead of sodium salts. Therefore, it is demonstrated that the advantageous properties of these dispersants are independent of the type of counterion.

[0283] Inkjet inks were prepared according to Table 6 using the pigment dispersions from Examples 1 to 5.

[0284] Ink 1 Ink 2 Ink 3 Ink 4 Ink 5 Ink 6 Pigment dispersion Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Concentration of pigment dispersion [wt-%) 20 40 40 40 35 20 glycerin 20 18 18 18 18 18 1,2-Propanediol 10 9 9 9 9 9 Diethylene glycol monobutyl ether 3 3 3 3 3 3 surfynol 465 0.9 0.9 0.9 0.9 0.9 0.9 dynol 960 1.8 1.8 1.8 1.8 1.8 1.8 joncryl J8050E 0 0 0 0 0 7.5 nuosept 22 0.003 0.003 0.003 0.003 0.003 0.003 water margin margin margin margin margin margin

[0285] Table 6: Composition of Inkjet Inks

[0286] 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.

[0287] In the cases of these inks 1-6, using the KJ4B AQ printhead from Kyocera, excellent jetting quality and image quality were observed on both coated and uncoated paper substrates at a printing speed of 1 m / s.

[0288] Ink 6 demonstrates that the inkjet ink remains stable when using the binder resin (Joncryl J8050E). The binder 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: Pigment P, wherein pigment P is an organic pigment. A first water-soluble block copolymer dispersant D1 is used to disperse the pigment P. The second water-soluble block copolymer dispersant D2 is used to disperse the pigment P, and Aqueous carrier; The first block copolymer dispersant D1 differs from the second block copolymer dispersant D2, wherein each block copolymer dispersant D1, D2 includes anchoring segments A1, A2 for anchoring to the pigment P, wherein the anchoring segment A1 is formed using at least one monomer Mn1, and the anchoring segment A2 is formed using at least one monomer Mn2, wherein the monomers Mn1, Mn2 are selected from the group consisting of methacrylate monomers, acrylate monomers, and vinyl monomers, and each of the block copolymer dispersants D1, D2 further includes a matrix stabilizing segment M for aqueous phase stabilization of the pigment P. The anchoring segment A1 of the first block copolymer dispersant D1 includes repeating unit R1, and the anchoring segment A2 of the second block copolymer dispersant D2 includes repeating unit R2. The hydrophobicity of the repeating unit R1 is lower than that of the repeating unit R2, and The repeating unit R1 has a Hansen solubility parameter value δ (polar + hydrogen). R1 , Where δ (polar + hydrogen) R1 >7.2cal 1 / 2 cm -3 / 2 The Hansen solubility parameter value δ(polarity + hydrogen) is defined as follows: Each of the block copolymer dispersants D1 and D2 has a polydispersity of less than 1.6 and is composed of linear polymer chains. The matrix-stabilized segment M is formed using 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, 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.

2. The ink according to claim 1, wherein the dispersants D1 and D2 each have a Mw of 2000 g / mol to 20000 g / mol.

3. The ink according to claim 1, wherein the repeating unit R1 is a nonionic repeating unit.

4. 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 <7.2cal 1 / 2 cm -3 / 2 The Hansen solubility parameter value δ(polarity + hydrogen) is defined as follows:

5. The ink of claim 1, wherein the polar bonding value of R1 : δ (polar) R1 >4.4 cal 1 / 2 cm -3 / 2 .

6. The ink of claim 1, wherein R2 has a polar bonding value δ (polar) of 12.5- 14.

5. R2 <4.4 cal 1 / 2 cm -3 / 2 .

7. The ink according to claim 1, wherein the anchoring segment A1 of the first block copolymer dispersant D1 has another repeating unit R1' different from R1, and wherein the other repeating unit R1' has >7.2 cal 1 / 2 cm -3 / 2 The Hansen solubility parameter δ(polarity + hydrogen) R1 .

8. The ink according to claim 1, wherein the anchoring segment A2 of the second block copolymer dispersant D2 has another repeating unit R2' different from R2, and wherein the other repeating unit R2' has <7.2 cal 1 / 2 cm -3 / 2 The Hansen solubility parameter δ(polarity + hydrogen) R2 .

9. The ink according to claim 1, wherein the monomer Mn2 of the anchoring segment A2 comprises an alkyl group, an alkenyl group or an aryl group.

10. The ink according to claim 1, wherein the monomer Mn2 of the anchoring segment A2 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, cyclohexyl 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, cyclohexyl acrylate, and any mixture thereof.

11. The ink according to claim 1, wherein the monomer Mn1 of the anchoring segment A1 is at least one of the following: tri(ethylene glycol) methyl ether acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, dimethylaminoethyl acrylate (DMAA), N,N-dimethylacrylamide, acrylmorpholine (ACMO), N-vinylpyrrolidone (NVP), vinylmethyl oxazolidinone (VMOX), and 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), methyl methacrylate... Phenoxyethyl acrylate, methacrylonitrile, ethylene glycol methyl ether methacrylate, 2-ethoxyethyl methacrylate, di(ethylene glycol) methyl ether methacrylate, tri(ethylene glycol) methyl ether methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, di(propylene glycol) methyl ether methacrylate, phenoxyethyl acrylate, ethylene glycol methyl ether acrylate, 2-ethoxyethyl acrylate, di(ethylene glycol) methyl ether acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, and any mixture thereof.

12. The ink according to claim 11, wherein the monomer Mn1 of the anchoring segment A1 is an acrylate or a methacrylate, and contains a monoethylene glycol group or a polyethylene glycol group.

13. 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 for aqueous stabilization of the pigment, the ionic hydrophilic repeating unit optionally comprising a neutralized acid group, a neutralized basic group or other ionic functional group.

14. The ink according to claim 1, wherein the anchoring segment A1 has a number n1 of repeating units, and wherein the repeating unit R1 is at least 50 of the total number n1 of repeating units.

15. The ink according to claim 1, wherein the matrix stabilizing segment M comprises at least one repeating unit R3, the repeating unit R3 comprising an ionic portion.

16. The ink according to claim 1, wherein the repeating units R1, R2 of the anchoring segments A1, A2 do not have ionic groups.

17. The ink of claim 1, wherein the anchoring segment A1 has a number n1 of repeating units, and wherein the repeating unit R1 is at least 80% of the total number n1 of repeating units; and The anchoring chain segment A2 has a number of repeating units n2, and the repeating unit R2 is at least 80% of the total number of repeating units n2.

18. The ink according to claim 1, wherein the weight ratio between the block copolymer dispersant D1 and the block copolymer dispersant D2 is between 0.1 and 10.

19. The ink according to claim 1, wherein the weight ratio between the pigment P and the sum of the block copolymer dispersant D1 and the block copolymer dispersant D2 is between 0.2 and 10.

0.

20. The ink according to claim 1, wherein the weight ratio between the pigment P and the block copolymer dispersant D1 is between 0.05 and 10.

0.

21. The ink according to claim 1, wherein the weight ratio between the pigment P and the block copolymer dispersant D2 is between 0.05 and 10.

0.

22. The ink according to claim 1, wherein the block copolymer dispersant D1 is a diblock copolymer and the block copolymer dispersant D2 is a diblock copolymer.

23. A pigment dispersion for forming inkjet ink, the pigment dispersion comprising an organic pigment P, a first block copolymer dispersant D1 for dispersing the pigment P, a second block copolymer dispersant D2 for dispersing the pigment P, and an aqueous carrier; wherein the first block copolymer dispersant D1 and the second block copolymer dispersant D2 are as defined in claim 1; Furthermore, the aqueous carrier comprises a total amount of water and optionally a water-soluble organic solvent, the total amount of which is less than 20 wt% of the total weight of the aqueous carrier.

24. The pigment dispersion of claim 23, wherein the repeating unit R1 has a Hansen solubility parameter value. Where δ (polar + hydrogen) R1 >7.2cal 1 / 2 cm -3 / 2 .

25. The pigment dispersion of claim 23, 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.

26. 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 claim 1.

27. The inkjet printing process of claim 26, comprising spraying droplets of each inkjet ink onto the substrate to form a color image on the substrate.

28. An inkjet ink assembly comprising more than one ink, wherein at least one of the inks is the ink according to claim 1.

29. An inkjet printer responsive to a digital data signal, the inkjet printer being equipped with inkjet ink according to claim 1 or an inkjet ink set according to claim 28.

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