Water-based ink composition

Abstract

To provide an ink having excellent resolubility while limiting the risks associated with the dried ink causing blockage in a printhead or ink supply system, and at the same time being able to produce prints with good water resistance.SOLUTION: The invention provides an aqueous printing ink composition comprising a polyurethane dispersion, where the polyurethane of the polyurethane dispersion comprises (a) properties of ketone or aldehyde groups present at one or more polymer chain ends; (b) properties of a number average molecular weight less than or equal to 50,000, preferably less than or equal to 25,000; and (c) properties of the content of ketone and / or aldehyde groups in the range from 0.02 to 4.0 mmol g-1, based on the dry polymer mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous printing ink composition comprising a polyurethane dispersion ("PUD") which is particularly suitable as an inkjet printing ink.

[0002] Advantageously, the aqueous printing ink composition according to the present invention is water-based and contains 35% (w / w) or less of an organic cosolvent, making it more environmentally friendly than comparative solvent-based ink compositions containing PUD. [Background technology]

[0003] Polyurethane dispersions (PUDs) are widely used in the preparation of printing inks. A particular challenge with conventional PUDs, especially when used in water-based inkjet inks, is that while they can impart beneficial printing properties such as moisture resistance and friction resistance, they lack particularly good resolubility. Ink resolubility refers to the ability to redissolve in itself or in a suitable flushing solution after it has partially or completely dried. This is a beneficial attribute because it reduces the risk of printhead nozzle clogging, leading to printing defects, or, in the worst case, catastrophic loss of the printhead itself.

[0004] The present invention provides an aqueous ink, particularly an aqueous inkjet printing ink, that incorporates a novel type of self-curing PUD technology capable of producing resoluble and water-resistant (wet friction) printed materials. The self-curing PUD according to the present invention has not been disclosed in the art.

[0005] Self-crosslinked PUDs and self-crosslinked styrene-acrylic dispersions (such as Daotan 7064, Joncryl FLX 5000, and Joncryl FLX 5060) have been described in the art, but they have associated problems such as poor resolubility and the potential risk of irreversible drying and clogging of printheads. The self-curing PUD technology encompassed in the present invention (referred to herein as "SC-PUD") is solely a non-crosslinked chain extension in combination with a bifunctional co-reagent such as adipic acid dihydrazide. Therefore, as will be understood by those skilled in the art and will be further described below, the SC-PUD disclosed herein is different from the self-crosslinked PUDs described in the art.

[0006] Inks produced from conventional PUDs such as Neorez R605 and Neorez R650 also have poor resolubility and redispersibility.

[0007] While hydroxy-functional PUDs (low molecular weight: typically with a number-average molecular weight of less than 15,000) have been described in the art for use in inkjet printing inks, these do not produce resistant prints unless crosslinking agents such as polycarbondiimide are used. The inventors have found that when inks are prepared using a combination of hydroxy-PUD and a polycarbondiimide crosslinking agent, the resolubility of the ink deteriorates significantly, and the prints do not exhibit the same level of water resistance (wet friction resistance) as those obtained by the present invention.

[0008] Crosslinkable PUDs are described in the art, for example, in U.S. Patent No. 7,476,705. These are polymers that contain crosslinkable groups such as ketones throughout the polymer chain (i.e., polymer backbone). The problems with these PUDs are that, like conventional PUDs, they have poor resolubility, and because crosslinkable PUD molecules may contain more than two ketone groups, crosslinking with a polyfunctional crosslinking agent such as adipic acid dihydrazide ("ADH") carries the risk of generating crosslinked, dried polymers within the printhead.

[0009] Self-crosslinking PUD Preparation of self-crosslinked PUDs containing keto-amine (or more broadly, keto-hydrazide) self-crosslinked chemical structures is described in U.S. Patents 8,568,889 and 7,476,705. However, these PUDs are prepared using diol reagents having one or more ketone groups formed, for example, by the reaction of a diepoxide and levulinic acid. Therefore, any PUD has at least two ketone groups in its polymer backbone, and if two or more of these diols are included as part of its structure in the polymer chain, the molecular structure will contain four or more ketone groups, which poses a risk of a crosslinked polymer matrix forming in the inkjet printhead when the ink dries.

[0010] Aqueous inkjet ink composition containing a self-crosslinkable styrene-acrylic dispersion The use of self-crosslinked styrene-acrylic dispersions containing keto-amine crosslinked chemical structures in inkjet applications has been described in the art.

[0011] International Publication No. 2001 / 036547 (Coates Brothers) describes a composition comprising a self-crosslinkable polymer (oligomer) emulsion containing carbonyl groups as part of the polymer structure, which can be crosslinked, for example, with adipic acid dihydrazide. The polymer dispersion has polymer molecules containing two or more carbonyl groups as part of their molecular structure, which may result in crosslinking that is undesirable in inkjet printing. The composition further comprises what is called a "re-dissolvable polymer," such as a water-soluble acrylic polymer. The inventors have found that while the composition provides excellent print resistance, its re-dissolvability is very poor. Indeed, the inherent re-dissolvability achieved by the self-curing PUD of the present invention is an extremely beneficial aspect of the present invention.

[0012] Japanese Patent Publication No. 2006-045334 (Asahi Kasei Chemicals Corporation), Japanese Patent Publication No. 2004-149600 (Sharp Corporation), Japanese Patent Publication No. 2009-140774 (Sakata Inx Corporation), and Japanese Patent Publication No. 2012-241135 (General Ltd.) also describe aqueous inkjet ink compositions containing self-crosslinked styrene-acrylic dispersions, but these are clearly significantly inferior in terms of resolubility / redispersibility compared to the ink of the present invention. Chinese Patent Application Publication No. 110982344 (Zhuhai Dongchang Pigment) describes a white aqueous inkjet ink composition containing a self-crosslinked acrylic emulsion, as well as PUD and further crosslinking agents, such as blocked isocyanates.

[0013] The use of self-crosslinked styrene-acrylic dispersions in conventional analog printing processes is well known. N. Kessel et al. (J. Coat. Technol. Res. (2008), (5), 285) adequately outline the keto-amine chemical structures of this type of polymer dispersion. The polymer contains ketone or aldehyde groups as part of its molecular structure, which, upon drying, can react with polyfunctional primary (or secondary) amines to influence the crosslinking reaction. A typical polyfunctional amine used for self-crosslinking of styrene-acrylic emulsions is adipic acid dihydrazide, but other polyfunctional amines that can react with carbonyl or aldehyde groups can also be used.

[0014] PUD and crosslinking agent Polyurethane dispersions (PUDs) are considered the primary resin chemical structures used in the preparation of colored aqueous inkjet printing inks. In particular, in textile printing, there are several examples of the use of amino resins such as maleimide-formaldehyde to crosslink aqueous inkjet printing inks containing PUDs. International Publication No. 2009 / 137753 (DuPont) describes how PUDs can be crosslinked with Cymel 303, a melamine-formaldehyde crosslinking agent, at a temperature of 160°C. Several other patents, including U.S. Patents 10513622, 10457824, and 9249324, refer to the combined use of PUDs with optional crosslinking agents to enable improved resistance, and these refer to polyurethane pigment dispersants, usefully presenting the crosslinkability of polyurethanes having any of the carboxylic acid, hydroxyl, or amine pendant functional groups. Examples of crosslinking agents include carbodiimide, epoxy, isocyanate, amino resins (e.g., melamine-formaldehyde), and aziridine.

[0015] However, the advantages of the novel SC-PUD according to the present invention, particularly in inkjet printing, are not disclosed or suggested. In fact, while many records have considered methods for crosslinking PUDs, the low molecular weight ketone (or aldehyde)-terminated functionalized self-curing PUD of the present invention has not been disclosed.

[0016] Cross-linked PUD U.S. Patent No. 8,186,822, U.S. Patent No. 9,255,207, and U.S. Patent Application Publication No. 2007 / 0060670 (all published by DuPont) refer to aqueous inkjet ink compositions containing crosslinked PUDs. These crosslinked PUDs are produced by inducing crosslinking during the preparation of the PUD with a crosslinking reagent such as triethylenetetramine. These crosslinked PUDs help improve the water and wash fastness of printed materials on a variety of substrates, including paper and textile substrates. The optional use of the types of crosslinking agents already described, such as amino resins, is a further feature of these patents. Although they help improve non-tackiness, when these crosslinked PUDs are used in ink compositions where the concentration of a cosolvent such as propylene glycol is less than 30% (w / w) of the ink composition, the resolubility / redispersibility of the ink is likely to be poor.

[0017] Re-dissolvable cross-linked PUD technology Recently, the use of acrylic polyurethane dispersions ("Ac-PUDs") in the preparation of UV and EB-curable aqueous inkjet printing compositions has been described, for example, in U.S. Patent No. 1,0076909 (Fujifilm Corporation), European Patent No. 3,390545 (Fujifilm Corporation), International Publication No. 2017 / 174981 (Fujifilm Corporation), and International Publication No. 2018 / 138525 (Fujifilm Corporation). Crosslinking of these Ac-PUDs is induced by using a suitable photoinitiator in the case of UV curing. While these Ac-PUDs can produce inks with good resolubility / redispersibility, the use of photoinitiators can lead to the undesirable migration of low molecular weight compounds from the cured ink, which is undesirable in many applications, particularly in printing food packaging. Furthermore, Ac-PUDs are prone to potential pH instability issues due to the hydrolysis of acrylate groups, which releases acrylic acid, and this is also undesirable for inkjet printing.

[0018] Hydroxy-functional polyurethane dispersion (OH-OUD) and inkjet Inks containing hydroxy-functional PUDs are described, for example, in U.S. Patent Application Publication No. 2018 / 0105710 (Sensient Imaging Technologies GmbH), and while these produce inks with enhanced re-decomposability, the printed matter has insufficient water (wet rub) resistance. This has been overcome by using crosslinking agents such as polycarbodiimides that react with the carboxylic acid pendant groups on the PUD polymer. However, when inks based on such compositions dry, they can form a crosslinked insoluble matrix that can pose a risk of clogging printhead nozzles.

[0019] Hydroxy-functional PUDs, which are relatively low molecular weight (i.e., typically have a number average molecular weight of less than 15,000), are typically produced by using a suitable end-capping reagent such as ethanolamine or diethanolamine, which attaches the required hydroxyl groups to the polymer chain ends through the formation of urea bonds between the amine of the end-capping reagent and the terminal isocyanate groups on the PUD prepolymer. As already stated, such OH-PUDs can produce inks with excellent re-solubility, but as a result of their hydroxyl functionality and low molecular weight, they produce prints with poor water (wet rub) resistance unless additional crosslinking agents such as polycarbodiimides or polyisocyanates are used. As already described, such approaches are described (e.g., in U.S. Patent Application Publication No. 2018 / 0105710), but carry the risk of forming crosslinked ink on the press, which can be significantly disadvantageous for inkjet printing.

[0020] U.S. Patent No. 8,931,889 (DuPont Electronics Inc.) describes the synthesis of OH-PUDs containing polyether diols as part of their chemical structure, and their use in aqueous inkjet ink compositions. The OH-PUDs are described as improving stability and extending nozzle life.

[0021] Chinese Patent Application Publication No. 111138626 (Trendvision Technology Co., Ltd.) describes the synthesis of PUD for aqueous inkjet printing of textile products. End-capping reagents such as N-methylethanolamine can be used in PUD synthesis to prepare hydroxy-terminated PUD. The use of such end-capping agents in the preparation of OH-PUD is well-known and widely practiced in the art. For example, U.S. Patent No. 7875355 (Sherwin-Williams Company) describes how OH-PUD for the automotive industry can be prepared by using diaminopropanol as an end-capping reagent.

[0022] U.S. Patent Application Publication No. 2018 / 0105710 describes how aqueous inkjet inks containing OH-PUD can be crosslinked by using crosslinking agents such as carbodiimides, oxazolines, amino resins (such as melamine formaldehyde), blocked isocyanates, and zirconium complexes. U.S. Patent Application Publication No. 2018 / 0105710 clearly describes OH-PUD that can reduce print head clogging because the use of OH-PUD improves the resolubility of the ink. It is clear that the use of a crosslinking agent, in the example of U.S. Patent Application Publication No. 2018 / 0105710 the use of carbodiimide, improves the tack resistance that would otherwise be inferior as a result of the use of OH-PUD, but the attendant problems already described remain. [Prior Art Documents] [Patent Documents]

[0023] [Patent Document 1] U.S. Patent No. 7476705 [Patent Document 2] U.S. Patent No. 8568889 [Patent Document 3] International Publication No. 2001 / 036547 [Patent Document 4] Japanese Patent Laid-Open No. 2006-045334 [Patent Document 5] Japanese Patent Publication No. 2004-149600 [Patent Document 6] Japanese Patent Publication No. 2009-140774 [Patent Document 7] Japanese Patent Publication No. 2012-241135 [Patent Document 8] Chinese Patent Application Publication No. 110982344 [Patent Document 9] International Publication No. 2009 / 137753 [Patent Document 10] U.S. Patent No. 10513622 [Patent Document 11] U.S. Patent No. 10457824 [Patent Document 12] U.S. Patent No. 9249324 [Patent Document 13] U.S. Patent No. 8186822 [Patent Document 14] U.S. Patent No. 9255207 [Patent Document 15] U.S. Patent Application Publication No. 2007 / 0060670 [Patent Document 16] U.S. Patent No. 10076909 [Patent Document 17] European Patent No. 3390545 [Patent Document 18] International Publication No. 2017 / 174981 [Patent Document 19] International Publication No. 2018 / 138525 [Patent Document 20] U.S. Patent Application Publication No. 2018 / 0105710 [Patent Document 21] U.S. Patent No. 8931889 [Patent Document 22] Chinese Patent Application Publication No. 111138626 [Patent Document 23] U.S. Patent No. 7875355 [Patent Document 24] U.S. Patent No. 7,947,760 [Non-patent literature]

[0024] [Non-Patent Document 1] N. Kessel et al., (J. Coat. Technol. Res. (2008), (5), 285) [Overview of the project] [Problems that the invention aims to solve]

[0025] The present invention overcomes several problems associated with commercially available materials, and in particular several problems described in the art with respect to inkjet printing. Specifically, the present invention provides an ink that has excellent resolubility while limiting the risk associated with dried inks that cause clogging of printheads or ink supply systems, and simultaneously produces printed materials with good water resistance. Furthermore, the present invention achieves this advantageous combination of properties without typically relying on the use of cosolvents such as high concentrations (i.e., more than 35% w / w / ) of glycerol or propylene glycol.

[0026] In particular, there are no records describing the use of the self-curing PUD of the invention prepared as described in printing inks for inkjet printing. The advantages of the present invention are briefly described above and will be described in more detail below, but the exceptional resolubility of inks containing this novel type of PUD makes it possible to prepare resolubility inks with reduced concentrations of solvents such as propylene glycol. The inventors have shown that resolubility inks can be produced with the content of the high-boiling solvent preferably at 25% (w / w) or less, 20% (w / w) or less, 15% (w / w) or less, and 10% (w / w) or less. This is an important aspect because inkjet ink compositions generally contain higher concentrations of solvent, such as propylene glycol, glycerol, and other high-boiling water-soluble solvents, to impart both the required viscosity and resolubility to the ink. [Means for solving the problem]

[0027] The citation or reference of any documents in this application does not constitute an admission that they are prior art to the present invention.

[0028] The present invention relates to an aqueous printing ink composition comprising a polyurethane dispersion, wherein the polyurethane in the polyurethane dispersion has the following characteristics: (a) one or more polymer chain ends have a ketone group or an aldehyde group; (b) the number average molecular weight is 50,000 or less, more preferably 25,000 or less; and (c) the content of ketone groups and aldehyde groups is 0.02 to 4.0 mmol g relative to the dry polymer mass. -1 This provides an aqueous printing ink composition that includes the characteristic of being within a certain range.

[0029] Unless otherwise specified, the ketone and aldehyde group content refers to the content of ketone and aldehyde groups at the end of the chain.

[0030] In a particularly preferred embodiment of the present invention, the group present at one or more polymer chain ends is a ketone group. Thus, the present invention relates to an aqueous printing ink composition comprising a polyurethane dispersion, wherein the polyurethane in the polyurethane dispersion has the following characteristics: (a) the presence of ketone groups at one or more polymer chain ends; (b) a number average molecular weight of 50,000 or less, more preferably 25,000 or less; and (c) a ketone group content of 0.02 to 4.0 mmol g relative to the dry polymer mass. -1 This provides an aqueous printing ink composition that includes the characteristic of being within a certain range.

[0031] To understand, groups located at the ends of a polymer chain are called "end-groups," "chain-end groups," or "terminal groups." These are different from groups located on the polymer chain or as part of the polymer molecular structure, i.e., on the polymer backbone.

[0032] Preferably, the polyurethane has a predominantly linear structure; that is, 5% or less of the polyurethane polymer chains contain branched structures (relative to the dry polymer mass). More preferably, the polyurethane has a linear structure.

[0033] As can be understood, the polyurethane is end-capped with the ketone or aldehyde group because one or more ketone or aldehyde groups are present at one or more polyurethane chain ends. The polyurethane used in the present invention preferably contains ketone or aldehyde groups at one or more polymer chain ends but not elsewhere on the polymer chain. Preferably, the polyurethane is linear and contains no more than two ketone or aldehyde groups per average polymer chain present at the polymer chain ends.

[0034] The end-capping technique for preparing self-curing PUDs and the use of such SC-PUDs in the ink compositions described herein are important features of the present invention. This not only produces low molecular weight PUDs (i.e., PUDs with a number-average molecular weight of 50,000 or less) which are beneficial for ink resolubility, but also produces PUDs that selectively contain two or fewer ketone (or aldehyde) groups per average polymer molecule. As a result, when combined with a bifunctional co-reagent such as adipic acid dihydrazide, curing in the ink results in chain extension, producing higher molecular weight linear polymers without forming an unmanageable, insoluble, crosslinked matrix. This linear extension without the formation of a crosslinked matrix distinguishes the SC-PUDs of the present invention from self-crosslinked PUDs described in the art. In particular, self-crosslinked PUDs typically contain more than two ketone groups on the polymer chain and therefore form crosslinks when combined with a bifunctional co-reagent such as adipic acid dihydrazide.

[0035] The inventors have shown that an ink containing a novel type of SC-PUD according to the present invention enables the preparation of a resoluble ink in which the total concentration of the cosolvent, such as propylene glycol, is 35% (w / w) or less, preferably 30% (w / w) or less, of the total ink composition. In particular, the inventors have shown that an ink containing a novel type of SC-PUD according to the present invention enables the preparation of a resoluble ink in which the total concentration of the cosolvent, such as propylene glycol, is less than 30% (w / w) of the total ink composition. In a more preferred embodiment of the present invention, the solvent having a boiling point above 200°C, such as glycerol, is limited to less than 5% (w / w) of the ink composition. As those skilled in the art will understand, it is a common practice to use such a cosolvent in an aqueous inkjet composition at a concentration exceeding 30% in order to ensure the required resolubility. However, such high concentrations of the cosolvent adversely affect the drying rate, particularly on impermeable substrates. [Modes for carrying out the invention]

[0036] The present invention addresses the problems of the prior art by producing an ink that has good water resistance (wet friction) and excellent resolubility. This highly desirable balance of properties is achieved by using a novel type of self-curing PUD ("SC-PUD") having a number average molecular weight of 50,000 or less, preferably 25,000 or less, more preferably 15,000 or less, and most preferably 10,000 or less, and whose polymer is end-capped with a ketone group or an aldehyde group, preferably a ketone group. By end-capping with a ketone (or aldehyde) group, the SC-PUD becomes non-bifunctional with respect to reactive ketone functional groups (preferably linear), and when it reacts with a bifunctional curing co-agent such as adipic acid dihydrazide (ADH), it can produce an exclusively linear polymer. In other words, the SC-PUD according to the present invention does not form a crosslinked matrix in the presence of a bifunctional curing co-agent such as adipic acid dihydrazide (ADH). Since the reaction between the SC-PUD of the present invention and a bifunctional curing co-reagent such as adipic acid dihydrazide (ADH) stalls under alkaline conditions, the probability of high molecular weight products being generated in the print head is reduced by using a neutralizing agent that is preferably used in the preparation of SC-PUD and ink.

[0037] [ka]

[0038] Figure 1 shows the reaction of SC-PUD having two terminal ketone or aldehyde groups with a bifunctional amine or dihydrazide. The reaction does not produce any crosslinks but results in chain extension of the two bifunctional reagents. Essentially, this can be considered an A2B2 type stepwise polymerization reaction. This figure shows that the reaction proceeds to obtain the imine reaction product.

[0039] The method for preparing SC-PUD is not particularly limited, and it may be anionically stabilized, nonionically stabilized, or either; however, anionically stabilized SC-PUD is preferred. The present invention encompasses aromatic and aliphatic SC-PUDs, and further encompasses polyether diols, polyester diols, polyacrylic diols, polycarbonate diols, and any aliphatic or aromatic diols, or any blend or hybrid thereof.

[0040] When preparing SC-PUD, an end-capping reagent containing a ketone group or aldehyde group is used to attach a reactive, curable functional group to the polymer chain ends. The end-capping reagent selectively contains a primary or secondary amine that reacts with isocyanate groups on the polyurethane precursor to form urea bonds, thereby forming the desired PC-PUD. The polyurethane precursor can be prepared from any blend of diisocyanate and diol, and examples of diols include, but are not limited to, polyester diols, polycarbonate diols, polyacrylic diols, and polyether diols. Preferably, the diols used to prepare the polyurethane precursor do not have any ketone or aldehyde groups in their molecular structure. The diisocyanates used to prepare SC-PUD include, but are not limited to, isophorone diisocyanate, hexamethylene-1,6-diisocyanate, methylenediphenyl diisocyanate, hydrogenated methylenediphenyl diisocyanate, and toluene diisocyanate, and may be aliphatic or aromatic forms. In the preparation of polyurethane precursors, diisocyanates are used in excess compared to diols to prepare the isocyanate-functionalized prepolymer for end-capping with the carbonyl-functionalized reagents already described (i.e., end-capping reagents containing aldehyde or ketone groups). Examples of such end-capping reagents include:

[0041] [ka]

[0042] It includes.

[0043] This specific end-capping reagent introduces both ketone and aldehyde groups to the ends of the SC-PUD polymer.

[0044] The present invention is preferably directed toward the preparation of linear SC-PUDs, but also encompasses the possibility of branched PC-PUDs, provided that, when the SC-PUD is branched, there are at most two ketone or aldehyde groups at the polymer chain ends. Thus, as can be understood, when PC-PUDs are branched, they are at most bifunctional with respect to reactive ketone or aldehyde functional groups and do not contain any aldehyde or ketone groups on the branches. Methods for preparing such branched polyurethanes are well known and can be achieved, for example, by using trifunctional (e.g., biuret HMDI trimer) isocyanates, trifunctional or more polyfunctional polyols, or trifunctional or more polyfunctional primary and secondary amines. It should also be understood that SC-PUDs can be synthesized using bifunctional amines to introduce urea bonds into the polyurethane backbone, thereby further enhancing non-stick properties.

[0045] When SC-PUD is anionically stabilized, it contains acid groups as part of its polymer structure (i.e., on the polymer backbone), which confer an anionic stabilization mechanism that allows for its dispersion after neutralization with a suitable inorganic or organic base. Dimethylpropionic acid (DMPA) is a typical reagent used to introduce carboxylic acid groups into the SC-PUD structure during its synthesis. It should be understood that other diol reagents containing one or more carboxylic acid groups can be used in the preparation of SC-PUD. Other acid-containing reagents can also be used in the preparation of SC-PUD. If DMPA or other acid-containing species are included in the SC-PUD backbone, they can be neutralized with any organic or inorganic base to enable the anionic stabilization mechanism. In the case of nonionically stabilized SC-PUD, the hydrophilic portion is included as part of the polyurethane dispersion (e.g., poly(ethylene oxide)) to enable its dispersion.

[0046] When SC-PUD is anionically stabilized, the acid value of SC-PUD is not limited, but it is preferable that the acid value relative to the dry polymer mass is between 0 mg KOH / g and 100 mg KOH / g. More preferably, the acid value relative to the dry polymer mass is at least 10 mg KOH / g, and more preferably at least 20 mg KOH / g. Therefore, the acid value relative to the dry polymer mass is preferably between 10 mg KOH / g and 100 mg KOH / g, and more preferably between 20 mg KOH / g and 100 mg KOH / g. To disperse the anionic SC-PUD, its dispersion in water can be enabled by neutralizing the acid group of SC-PUD using any suitable base, including organic and inorganic types. Non-limiting examples of bases used to neutralize the carboxylic acid (or other acid) of SC-PUD include, but are not limited to, triethylamine, N,N-dimethylethanolamine, any other tertiary amine, potassium hydroxide, and sodium hydroxide. If the neutralizing agent is a tertiary amine, it is preferable that its boiling point is higher than 125°C. Preferably, the neutralizing agent is N,N-dimethylethanolamine.

[0047] The dispersion of SC-PUD can also be promoted by using anionic and nonionic surfactants.

[0048] The particle size of the SC-PUD used in the preparation of the ink of the present invention is not limited. However, the average particle size is preferably 250 nm, and more preferably less than 100 nm.

[0049] The total solids content of SC-PUD in the final aqueous (inkjet) printing ink composition is not particularly limited. However, the total solids content in the final ink formulation is preferably 2.5% (w / w) to 40% (w / w) of the dry polymer mass of the final inkjet ink composition, and more preferably 5.0% (w / w) to 20.0% (w / w).

[0050] Another aspect of the present invention that helps further enhance the resolubility of inks containing new types of SC-PUD is that they can also be end-capped with hydroxyl groups, i.e., the polyurethane can be end-capped with an end-capping reagent containing both a hydroxyl functional group and a ketone or aldehyde functional group, for example, the exemplary end-capping reagents shown above. Therefore, the SC-PUD of the present invention may optionally contain chain-terminal (terminal) hydroxyl groups. In this case, the hydroxyl value of the SC-PUD is preferably 100 mg KOHg relative to the dry polymer mass. -1 Less than 50 mg KOH -1 It is less than.

[0051] To control the molecular weight of SC-PUD, an end-capping reagent is typically used that contains a ketone (or aldehyde) group and optionally additional hydroxyl groups. The SC-PUD of the invention has a number-average molecular weight of 50,000 or less, preferably 25,000 or less, more preferably 15,000 or less, and most preferably 10,000 or less. The relatively low molecular weight of this novel type of PUD also contributes to the resolubility observed in printing inks.

[0052] The SC-PUD of the present invention uses a bifunctional amine or dihydrazide, such as adipic acid dihydrazide, whose curing is influenced by its reaction with terminal carbonyl groups (i.e., ketone groups or aldehyde groups) on the polyurethane. However, the present invention also includes polyfunctional amines, i.e., polyfunctional amines having three or more primary amine groups.

[0053] The carbonyl-terminated group (i.e., ketone or aldehyde-terminated group) of the SC-PUD used in the ink of the present invention can also be cured by reaction with other co-reagents such as polyvalent metal complexes, as disclosed in U.S. Patent No. 7,947,760 (BASF). In fact, it is also possible to cure the ink containing SC-PUD by including a compound such as ammonium zirconium carbonate as a curing agent in the ink instead of the preferred diamine or dihydrazide. The ink composition according to the present invention may optionally further contain one or more acids selected from the group consisting of tartaric acid, gluconic acid, citric acid, maleic acid, succinic acid and their salts. In some embodiments, the ink composition may contain ammonium zirconium carbonate as a curing agent, and one or more acids selected from the group consisting of tartaric acid, gluconic acid, citric acid, maleic acid, succinic acid and their salts.

[0054] Preferably, SC-PUD is combined with a bifunctional amine co-reagent such as adipic acid dihydrazide to enable self-curing of the ink of the present invention.

[0055] Preferably, the molar ratio of SC-PUD to the co-agent that enables self-curing is between 0.1:10 and 10:0.1, preferably between 0.2:5 and 5:0.2, and more preferably between 0.5:2 and 2:0.5, with respect to appropriate molar concentrations of SC-PUD and the co-agent. In a more preferred embodiment, the curing co-agent is adipic acid dihydrazide (ADH), and the molar ratio of SC-PUD to ADH is between 0.1:10 and 10:0.1, preferably between 0.2:5 and 5:0.2, and more preferably between 0.5:2 and 2:0.5, with respect to appropriate molar concentrations of SC-PUD and the co-agent.

[0056] The aqueous ink of the present invention is mostly water-based. More specifically, the ink of the present invention contains water in an amount between 5% and 90% by mass, for example between 5% and 80% by mass or between 10% and 80% by mass. Preferably, the ink of the present invention contains water in an amount between 10% and 80% by mass, more preferably between 15% and 80% by mass.

[0057] The printing ink of the present invention may optionally contain any water-soluble organic cosolvent. While volatile solvents such as ethanol, propanol, and isopropanol may be used, if the ink is intended for inkjet printing, it is preferable to use solvents that are not flammable or highly volatile, typically polyols, alkylene glycols, alkylene glycol ethers, or ether acetates. Non-limiting examples include 3-methoxy-3-methyl-1-butanol, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol, diethylene glycol butyl ether, diethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monopropyl ether, dipropylene glycol, dipropylene glycol ethyl ether, and di Examples include propylene glycol methyl ether, ethylene glycol butyl ether, ethylene glycol ethyl ether, ethylene glycol isopropyl ether, ethylene glycol methyl ether, ethylene glycol propyl ether, glycerin carbonate, N-methyl-2-pyrrolidone, glycerol, propylene glycol, propylene glycol ethyl ether, propylene glycol ethyl ether acetate, propylene glycol methyl ether, propylene glycol n-propyl ether, triethylene glycol, triethylene glycol butyl ether, triethylene glycol methyl ether, tripropylene glycol, tripropylene glycol methyl ether, N-methylpyrrolidone, and urea.

[0058] Preferably, the ink of the present invention comprises propylene glycol and / or 3-methoxy-3-methyl-1-butanol (MMB). If the ink of the present invention comprises propylene glycol and / or 3-methoxy-3-methyl-1-butanol, it is preferable that their ratio (the ratio of propylene glycol to 3-methyl-1-butanol) is 3:1 to 1:3.

[0059] When organic co-solvents are used, they preferably constitute 35% (w / w) or less of the ink composition, and more preferably 30.0% (w / w) or less. For example, when organic co-solvents are used, they preferably constitute less than 35% (w / w) of the ink composition, and more preferably less than 30.0% (w / w). In practice, the total concentration of the water-soluble organic solvent is preferably 35% (w / w) or less of the ink composition, more preferably 30.0% (w / w) or less, and even more preferably 25.0% (w / w) or less.

[0060] The inventors have shown that by using SC-PUD according to the present invention, it is possible to prepare a resoluble ink by setting the concentration of the water-soluble organic cosolvent to about 10% (w / w) of the ink composition. Therefore, in a further preferred embodiment, the ink according to the present invention contains 10% (w / w) or less of the water-soluble cosolvent.

[0061] A further optional feature of the present invention is that, if any water-soluble organic cosolvent is used, it preferably has a boiling point of less than 250°C, more preferably less than 200°C. In fact, by using SC-PUD according to the present invention, a highly resolubility ink can be prepared without relying on the use of cosolvents having boiling points above 200°C, particularly above 250°C, such as glycerol and diethylene glycol in concentrations exceeding 35.0% (w / w). Using such non-volatile solvents in ink formulations at concentrations often exceeding 35% (w / w) is a common practice not only to increase the viscosity of the ink but also to give the ink acceptable resolubility. However, the use of such high-boiling point solvents has the associated disadvantage of causing a stall in the ink drying time, which is undesirable for high-throughput printing. Preferably, the ink according to the present invention does not contain solvents having a boiling point higher than 250°C, and more preferably, the ink according to the present invention does not contain solvents having a boiling point higher than 200°C. Furthermore, when used, the concentration of the solvent having a boiling point higher than 250°C is preferably less than 10.0% (w / w) of the ink composition, and more preferably less than 5.0% (w / w).

[0062] One of the advantages of the present invention is that excellent resolubility is achieved, surprisingly, when the concentration of the water-soluble cosolvent, such as propylene glycol, is 35% (w / w) or less, more specifically, 30% (w / w) or less. In fact, the inventors have shown that resolubility inks can be produced with cosolvent concentrations of 25% (w / w) or less and about 10% (w / w). Having an ink that can be easily resolubilityd without relying on the use of high concentrations of high-boiling point solvents such as propylene glycol and glycerol (also known as a humectant) is advantageous because it allows for inkjet printing inks with a faster drying response. This helps the inkjet ink of the present invention to contribute to the industrial inkjet printing market with higher throughput, such as corrugated label printing for packaging and textile products. Furthermore, the faster drying response achievable with the inkjet ink of the present invention also allows for a reduction in the energy input required to dry them. This is beneficial not only to the aforementioned printing market but also to the multi-pass inkjet graphics printing market. Currently, UV-curable inkjet compositions and solvent-based inkjet compositions are making a significant contribution to the multi-pass inkjet graphics market. Ongoing toxicological evaluations of monomers and photoinitiators used in the preparation of UV-curable inkjet compositions have increased health and safety concerns regarding these compositions. Solvent-based inkjet printing ink compositions typically contain more than 70% organic solvent blends as part of their composition. The inks of the present invention contain water as the majority of the solvent content (i.e., typically more than 70% of the solvent blend used in the present invention is water), and SC-PUD, which is inherently a polymer, poses a far lower health risk than the monomers and photoinitiators used in UV-curable inkjet printing ink compositions. Furthermore, the compositions of the invention may also use solvents derived from recyclable resources such as propylene glycol, but it is preferable that they be used at 30% (w / w) or less of the composition.

[0063] As a further optional feature of the present invention, the ink contains a solvent having a boiling point higher than 150°C at a concentration of 30% (w / w) or less, preferably 25% (w / w) or less. Said solvent, and in particular, the heat of vaporization is 500Jg -1 By minimizing the concentration of the larger solvent, faster ink drying, which is very beneficial for high-speed inkjet printing, is enabled. A further benefit of lowering the co-solvent concentration is the reduction in the amount of energy required to dry the ink. The present inventor has found that propylene glycol has a boiling point of 187°C and a heat of vaporization of 880Jg -1 while having a boiling point of 174°C and a heat of vaporization of 385Jg -1 It has been shown that a stable ink containing 3-methoxy-3-methyl-1-butanol ("MMB"), which is a water-soluble co-solvent, can be prepared. By using said solvent with a low heat of vaporization, an ink with a higher drying rate is produced. Therefore, the ink according to the present invention preferably has a heat of vaporization of 500Jg -1 It contains 30% (w / w) or less of the above solvent. For example, the ink according to the present invention preferably has a heat of vaporization of 500Jg -1 It contains less than 30% (w / w) of the larger solvent.

[0064] Accordingly, a further preferred aspect of the present invention is a water-soluble organic co-solvent, in particular, having a heat of vaporization of 500Jg -1 The concentration of the water-soluble organic co-solvent having a boiling point of more than 150°C is preferably less than 30% (w / w), more preferably 25% (w / w) or less, of the total ink composition. When such co-solvents are used, any combination of solvents having a boiling point higher than 200°C is preferably less than 10% (w / w) of the ink composition.

[0065] Furthermore, a further advantage of using the novel self-curing PUDs according to the present invention in printing ink compositions is that they can produce resoluble / redispersible inks containing pigment dispersions with anionic dispersants (e.g., anionic acrylic copolymer dispersants) and pigment dispersions with nonionic dispersants. The latter result is particularly noteworthy because the nonionic dispersants tend to be very water-sensitive, and the ability of these novel PUDs to produce inks that enable printed materials with good water resistance (wet friction) enhances the usefulness of this novel technology.

[0066] A further advantage of the present invention is that excellent water resistance (wet friction resistance) of printed materials can be achieved without using excessively high temperatures. In fact, after initial drying, the printed materials develop their resistance over time, and a high level of non-tackiness can be achieved within 24 hours of printing.

[0067] After printing and drying, the inks of the present invention can harden at room temperature or at high temperatures, for example, 50°C or higher. The inventors have found that under atmospheric conditions (i.e., 22-25°C), ink hardening can occur more than one day after printing. Heating the printed material to a temperature of 50°C or higher can accelerate ink hardening.

[0068] The advantages of an ink that combines good resolubility with the ability to produce printed materials with excellent water resistance make it possible to use the ink prepared according to the present invention in a range of applications. In particular, the ink of the present invention is suitable for a wide range of applications including printing on packaging, including flexible packaging (front and back printing) and flexible film packaging, rigid packaging (printing on coated metal substrates, i.e., metallic decoration), corrugated and paper packaging, corrugated packaging, printing on decorative laminates, printing on textile products, and graphics printing. When printing on packaging materials using the ink of the present invention, this may include food packaging. In inkjet printing, the present invention is suitable for both single-pass and multi-pass printing, terms that are well recognized in the industry.

[0069] The excellent water resistance of printed materials achievable with the technology of this application is suitable for surface printing applications without the need for overprinting varnish. Furthermore, since the resoluble / redispersible inks can be manufactured using a cosolvent such as propylene glycol at a concentration of 25% (w / w) or less, high-speed printing of these inks can be achieved in both multi-pass and single-pass inkjet printing. The excellent resolubility of the inks of the present invention is provided by the use of SC-PUD.

[0070] While this invention is primarily directed towards inkjet printing inks, it also encompasses water-based inks that can be printed by flexographic and gravure printing methods. In fact, the excellent resolubility of the SC-PUD technology according to this invention is highly beneficial in these printing markets, considering the rapid decontamination between operations and the reduced risks associated with filling anilox cylinders. A potential challenge with currently used self-crosslinking (acrylic) technologies is that the ink can dry out in the anilox cylinder, potentially causing causal print quality issues.

[0071] In inkjet printing, the ink of the present invention can be printed on any substrate that has already been pre-coated with a suitable primer composition to improve print quality. The primer typically contains a polyvalent metal salt that helps to reduce print quality issues such as droplet spreading and color clouding by "fixing" the ink. While the primer is not an integral part of the present invention, any suitable primer can be used to enhance the print quality achievable with the ink of the invention. Alternatively, the ink of the present invention can be printed on any substrate that has not already been pre-coated with a primer.

[0072] This invention discloses the finding that an aqueous printing ink having excellent resolubility / redispersibility while being able to cure after printing to produce water-resistant printed materials can be prepared using a novel type of polyurethane dispersion ("SC-PUD"). The ink of this invention is particularly suitable for inkjet printing, and the excellent resolubility imparted by this technology reduces the risk of the ink irreversibly drying in the nozzles of the print head. The PC-PUD used in the ink composition of this invention contains a ketone group or aldehyde group located at the polymer chain ends. When these SC-PUDs are cured with a bifunctional co-reagent such as a diamine or dihydrazide (e.g., adipic acid dihydrazide), they can exclusively cure to produce a higher molecular weight linear polymer with extended chains. This unique characteristic distinguishes the ink of this invention from inks that use crosslinked chemical structures. Crosslinked chemical structures currently used in the art include self-crosslinked styrene-acrylic dispersions and self-crosslinked polyurethane dispersions. When these chemical structures are dried and fully cured, a potentially insoluble cross-linked polymer matrix is ​​formed, which can pose challenges for printing inks, and especially for inkjet inks.

[0073] The use of SC-PUD according to the present invention imparts resolubility / redispersibility to the ink, a particularly useful feature for aqueous inkjet printing inks. In the present invention, and more broadly in the context of inkjet printing, resolubility / redispersibility can be expressed as the ability of the ink to be resolubilated or redispersed in itself or in a suitable "flushing" solution by drying at temperatures up to 40°C, and even up to 50°C, for up to 1 hour (or more), for example, 30 minutes. Conventional PUDs, conventional self-crosslinked PUDs, and styrene-acrylic inks typically exhibit poor resolubility.

[0074] While inks with excellent resolubility can be prepared using hydroxy-functional PUDs ("OH-PUDs"), without the addition of crosslinking agents, these inks produce printed materials with poor water resistance (wet friction resistance). In fact, the SC-PUD-containing ink of the present invention has been shown to have better resolubility compared to that achievable with OH-PUD-containing inks. Furthermore, using crosslinking agents to enhance the non-tackiness of OH-PUD-containing inks significantly impairs the ink's resolubility.

[0075] Preferably, the ink composition according to the present invention does not contain any carbodiimide (e.g., polycarbodiimide), oxazoline (e.g., polyoxazoline), azurilidine (e.g., polyazurilidine), epoxy, amino resin (e.g., melamine-formaldehyde), isocyanate (e.g., blocked isocyanate), and / or silane. More preferably, the ink composition according to the present invention does not contain any polycarbodiimide.

[0076] In inkjet printing, the present invention is particularly advantageous because its good resolubility helps prevent irreversible drying of the ink in the print head. Such irreversible drying of the ink in the print head can lead to nozzle clogging, a causal decrease in print quality performance, and, worse, damage to the print head itself. Therefore, the ideal solution for inkjet printing ink is one that has good resolubility (utilizing open time) and can harden after printing and drying to produce water-resistant printed materials. The present invention achieves this without using high-boiling point cosolvents such as glycerol and propylene glycol in excessive concentrations. In fact, the ink of the invention maintains good resolubility / redispersibility while the propylene glycol concentration is about 5.0% (w / w) of the ink composition.

[0077] A challenge associated with using conventional PUDs themselves in the preparation of aqueous inkjet ink compositions is that drying them at 40°C for 15 to 60 minutes significantly reduces their solubility in both the ink itself and in flushing solutions. This challenge is addressed by the present invention. In contrast, OH-PUDs, particularly those with a hydroxyl value greater than 50 mg KOH / g, can produce inks with excellent resolubility / redispersibility, but generally result in dried prints with poor water resistance. This challenge is also addressed by the present invention. Even if the ink dries on the faceplate rather than within the printhead body and ink supply system, the impact is limited. Printhead faceplates are often coated with what is called a non-wetting coating ("NWC"). NWCs are delicate structures containing a thin layer of ceramic, and attempting to remove insoluble residue from the NWC can damage it and affect print quality.

[0078] When intended for inkjet printing, the composition of the present invention preferably has a viscosity of less than 10.0 mPa·s, as measured at 32°C using a Brookfield DV-II+Pro viscometer equipped with a 100 rpm No. 18 spindle.

[0079] The pH of the ink is preferably in the range of 5.0 to 10.0, more preferably in the range of 6.0 to 9.5.

[0080] The SC-PUD according to the present invention contains a pendant ketone group or aldehyde group bonded to at least one end (i.e., terminal) of the polyurethane. Furthermore, the SC-PUD contains at least 0.02 to 4.0 mmol of chain-terminal ketone groups and aldehyde groups per gram of SC-PUD relative to the dry polymer mass (mmol(C=O)g -1 The amount of chain-terminal ketone groups and aldehyde groups in SC-PUD (relative to the dry polymer mass) is preferably 0.05 to 2.0 mmol g. -1 It is within the range.

[0081] Self-crosslinked PUDs (and styrene-acrylics) are well known, and keto-hydrazide crosslinked chemical structures are also well-known and used in commercially available products. Ketone groups or aldehyde groups in the polymer backbone involved in this crosslinking reaction can be introduced into the PUD backbone by using a ketone-containing diol in the production of the PUD. This can be achieved by reacting a ketone-functional acid such as levulinic acid with a diepoxide to produce the desired ketone diol. Another method involves reacting diacetone acrylamide with an alkanolamine such as diethanolamine. These self-crosslinked PUDs differ from the self-curing PUDs according to the present invention in that some of the polymer molecules contain more than two ketone groups or aldehyde groups as part of their molecular structure. When inks containing these self-crosslinked PUDs are dried in the presence of a crosslinking co-reagent such as adipic acid dihydrazide, they can react to form a crosslinked structure. The crosslinked polymer network in the ink during drying or in the dried ink adversely affects the resolubility / redispersibility of the ink and can irreversibly clog the nozzles in an inkjet printhead.

[0082] Conventional (non-crosslinked) PUDs such as Neorez R605 also exhibit poor resolubility in inkjet printing ink applications. This is likely due to the fact that the molecular weight of these polymers (i.e., number-average molecular weight exceeding 50,000) is greater than that of the SC-PUD used in the ink composition of the present invention and the hydroxy-functional PUDs ("OH-PUD") described in the art. The inventors have confirmed that inks containing OH-PUDs, such as those described in the art, do indeed exhibit excellent resolubility. However, the water resistance of prints produced by inks containing such OH-PUDs is insufficient, likely due to both their hydroxyl content and low molecular weight (typically less than 15,000 number-average molecular weight). Interestingly, the inventors have found that, with respect to the novel SC-PUDs according to the present invention, the presence of hydroxyl groups at the polymer chain ends, in addition to ketone or aldehyde groups, can enhance the ink's resolubility, although this is not essential for conferring resolubility. Perhaps the molecular weight of the PUD is more important. In some cases, SC-PUD may have a number-average molecular weight of less than 10,000, or even less than 5,000. The number-average molecular weight can be calculated (basically by chain-end analysis) by determining the ketone or aldehyde content or hydroxyl value of the PUD based on its composition. The mass-average molecular weight was also measured by gel permeation chromatography (GPC). It should be noted that the GPC measurement of the molecular weight of SC-PUD was performed in the absence of a self-curing chemical structure, typically ADH, as a co-reagent.

[0083] The SC-PUD used in the inks of the present invention is preferably combined with a diamine or dihydrazide cosolvent, preferably a primary amine and a hydrazide, which affects the curing of the SC-PUD when the ink is printed and dried. When a preferred bifunctional SC-PUD, i.e., a linear polyurethane having ketone groups at both polymer chain ends (or possibly a monofunctional SC-PUD), is combined with a bifunctional amine or hydrazide coagent, the curing process proceeds without crosslinking, producing chain-extended linear adducts of the SC-PUD and the bifunctional coagent. This distinctive feature of SC-PUD makes them particularly suitable not only for inkjet printing but also for aqueous inks applied by flexographic and gravure printing. The curing process can proceed at room temperature for 24 hours or more, or can be accelerated by heating the printed material to a high temperature, for example, 50°C or higher. Examples of water-soluble polyfunctional reagents capable of curing the ketone (or aldehyde) group of SC-PUD include, but are not limited to, adipic acid dihydrazide ("ADH"), pimelic acid dihydrazide, and any other dihydrazides derived from bifunctional acids, aliphatic two, three, or more polyfunctional amines. The latter may include polyethylene oxide containing a polyfunctional amine, commercially available from Huntsman under the trade name "Jeffamine". It is also possible to cure ketone-containing PUDs using polymer dispersions containing primary or secondary amines as part of their structure. The ketone group of SC-PUD can also be cured by using metal complexes such as ammonium zirconium carbonate. However, for the reasons already explained, both bifunctional amine and hydrazide reagents are preferred.

[0084] Self-crosslinked PUDs can be prepared using metal complexes such as ammonium zirconium carbonate ("AZC"). When present in the aqueous phase of a polymer dispersion, these metal complexes can react with carboxylic acid and carbonyl groups present in the PUD skeleton after the ink has been printed and dried. This has already been achieved for acrylic dispersions, as specified in U.S. Patent No. 7,947,760. The shelf life of compositions, which can be a challenge when using AZC, has been extended by using ammonium tartrate. This method has not yet been employed for PUD chemical structures. In this invention, the inventors have shown that adding AZC to an ink containing SC-PUD (without any ADH) produces an ink with some degree of resolubility and non-stick properties, although not to the same extent as achieved when using a similar SC-PUD ink with ADH as a curing co-agent.

[0085] While not essential features, the inks prepared according to the present invention may contain any further water-soluble, alkali-soluble, or water-dispersible resins other than SC-PUD. As is understood, alkali-soluble resins typically contain acidic functional groups as part of a monomer blend that can be neutralized with a suitable base so that the resin can be dissolved in water to form an aqueous solution. Further resins include, but are not limited to, polyurethane dispersions, self-crosslinked polyurethane dispersions, alkali-soluble acrylic resins, acrylic dispersions, self-crosslinked acrylic dispersions, polyester dispersions, copolymers of poly(vinyl acetate) and vinyl acetate dispersions, poly(vinyl alcohol), and poly(vinylpyrrolidone). Those skilled in the art will understand that the inks prepared according to the present invention can be modified by adding further resins, but such modifications are within the scope of the present invention.

[0086] In an alternative embodiment of the present invention, the ink does not contain any further water-soluble, alkali-soluble, or water-dispersible resins other than SC-PUD. The ink of the present invention does not contain further polyurethane dispersions (i.e., polyurethane dispersions other than SC-PUD), self-crosslinked polyurethane dispersions, alkali-soluble acrylic resins, acrylic dispersions, self-crosslinked acrylic dispersions, polyester dispersions, copolymers of poly(vinyl acetate) or vinyl acetate dispersions, poly(vinyl alcohol), or poly(vinylpyrrolidone), and preferably does not contain any self-crosslinked acrylic dispersions at all.

[0087] The total amount of resin that can be used in the ink prepared according to the present invention is not limited, but may be in the range of 2.5% (w / w) to 40.0% (w / w), more preferably in the range of 5.0% (w / w) to 30.0% (w / w), and most preferably in the range of 5.0% (w / w) to 20.0% (w / w), relative to the total dry mass of SC-PUD and other resins in the total ink composition.

[0088] Since the products of the present invention are primarily aqueous, it is also preferable that they contain a biocide or fungicide. Preferred examples include, but are not limited to, products based on the following biocide structural types: benzisothiazolinone, bromo-nitro-propane-diol, isothiazolinone, ethylenedioxydimethanol, or iodopropynyl butylcarbamate. Some commercially available grades include those marketed under the trade names Intercide (Akcros Chemicals) or Nipacide N (Clariant). Other possible types of biocides include sodium dehydroacetate (Lonza Geogard 111S), sodium benzoate (RT Vanderbilt Vancide 51), sodium pyridinethiol-1-oxide (Arch Chemicals Sodium Omadine), sodium salt of o-phenylphenol (Dowchemicals Dowicide A), and ethyl p-hydroxybenzoate (Aako Nipastat Sodium). These are preferably used in amounts of 0.01 to 1.00% by mass in the ink composition.

[0089] Defoaming agents may be optionally included in the formulation. These prevent foam formation during ink manufacturing and ejection. Defoaming agents are particularly important for recirculating printheads. Suitable defoaming agents include, but are not limited to, TEGO FOAMEX N, FOAMEX 1488, 1495, 3062, 7447, 800, 8030, 805, 8050, 810, 815N, 822, 825, 830, 831, 835, 840, 842, 843, 845, 855, 860, and 883, TEGO FOAMEX K3, TEGO FOAMEX K7 / K8, and TEGO TWIN 4000, all commercially available from Evonik. BYK offers the following products: BYK-066N, 088, 055, 057, 1790, 020, BYK-A530, 067A, and BYK354. Dow Corning offers the following additives: DC62, DC65, DC68, DC71, and DC74. Munzing offers the following Agitan products: 120, 150, 160, 271, 290, 298, 299, 350, 351, 731, 760, 761, and 777. Air Products offers the following Surfynol products: 104PA, AD01, DF-110, DF-58, DF-62, DF-66, DF-695, DF-70, and MD-20.

[0090] Surface conditioning additives are often used as an optional measure to adjust the moisture on the printhead faceplate and to provide the desired droplet spread across the substrate, or, in the case of multi-pass inkjet printing, to adjust the surface tension of the ink necessary to moisten the spread of dried droplets. They can also be used to adjust the levels of slip resistance and scratch resistance. Suitable surface conditioning additives include, but are not limited to, TEGO FLOW 300, 370, and 425, TEGO GLIDE 100, 110, 130, 406, 410, 411, 415, 420, 432, 435, 440, 482, A115, and B1484, all commercially available from Evonik; TEGO GLIDE ZG 400; TEGO RAD 2010, 2011, 2100, 2200N, 2250, 2300, 2500, 2600, 2650, and 2700; TEGO TWIN 4000 and 4100; TEGO WET 240, 250, 260, 265, 270, 280, 500, 505, and 510; and TEGO WET KL245. BYK offers the following commercially available products: BYK333 and 337, BYK UV 3500, BYK 378, 347 and 361, BYK UV 3530 and 3570, CERAFLOUR 998 and 996, NANOBYK 3601, 3610 and 3650, and CERMAT 258. Cytec offers EBECRYL 350 and 1360, MODAFLOW 9200 and EBECRYL 341. Sartomer's aliphatic silicone acrylate CN9800 can be used. Air Products offers Surfinol 104, 420, 440, 465, 485, 61, 82 and 2502. Croda offers Multiwet BD, EF, SU, SO and VE. DuPont offers the following Capstone models: FS-30, 31, 34, 35, 50, 51, 60, 61, 63, 64, 65, and 3100.

[0091] The ink formulation may optionally include suitable degassing agents. These prevent the formation of air pockets and pinholes in the cured ink film. They also reduce regulated diffusion, which can cause reliability issues in the printhead. Non-limiting examples include the following products commercially available from Evonik, namely TEGO AIREX 900, 910, 916, 920, 931, 936, 940, 944, 945, 950, 962, 980, and 986.

[0092] The ink composition of the present invention may optionally contain one or more colorants, including pigments and / or dyes. Examples of suitable organic or inorganic pigments include carbon black, zinc oxide, titanium dioxide, phthalocyanine, anthraquinone, perylene, carbazole, monoazo and diazobenzimidazole, rhodamine, indigoid, quinacridone, diazopyrantrone, dinitroaniline, pyrazole, diazopyrantrone, pyrazole, dianisidine, pyrantrone, tetrachloroisoindoline, dioxazine, monoazoacrylid and anthrapyrimidine. Examples of dyes include, but are not limited to, azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, and combinations thereof.

[0093] Commercially available organic pigments classified according to Color Index International may be used, without limitation, including the following trade names: blue pigments PB1, PB15, PB15:1, PB15:3, PB15:4, PB15:6, PB16, PB60; brown pigments PB5, PB23, and PB265; green pigments PG1, PG7, PG10, and PG36; and yellow pigments PY3, PY14, PY16, and PY1 7, PY24, PY65, PY73, PY74, PY83, PY95, PY97, PY108, PY109, PY110, PY113, PY128, PY129, PY138, PY139, PY150, PY151, PY154, PY156, PY175, PY180 and PY213, as orange pigments PO5, PO15, PO16, PO31, PO34, PO36, PO43, PO48, PO51, PO60, PO61 and PO71, The red pigments are PR4, PR5, PR7, PR9, PR22, PR23, PR48, PR48:2, PR49, PR112, PR122, PR123, PR149, PR166, PR168, PR170, PR177, PR179, PR190, PR202, PR206, PR207, PR224 and PR254; the purple pigments are PV19, PV23, PV32, PV37 and PV42; and the black pigments are PBk1, PBk6, PB This includes commercially available products under the names k7, PBk8, PBk9, PBk10, PBk11, PBk12, PBk13, PBk14, PBk17, PBk18, PBk19, PBk22, PBk23, PBk24, PBk25, PBk26, PBk27, PBk28, PBk29, PBk30, PBk31, PBk32, PBk33, PBk34, PBk35, NBk1, NBk2, NBk3, NBk4, and NBk6, as well as combinations thereof.

[0094] These pigments are typically ground to less than 1 micron, and after grinding, the particle size distribution is preferably 10 to 500 nm, more preferably 10 to 350 nm, to have better transparency and a wider color gamut.

[0095] To include the above-mentioned pigments in the composition of the invention, it is preferable to manufacture the pigments and store them stably as concentrates in water. This is typically achieved by dispersing the pigments in a water-soluble or water-dispersible resin using a water-soluble and / or water-dispersible surfactant that introduces hydrophilic functional groups onto the surface of the pigment particles. There are many examples of these dispersion resins, including polyvinyl alcohol, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylate copolymer, acrylic acid-acrylate copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylate copolymer, styrene-alphamethylstyrene-acrylic acid copolymer, styrene-alphamethylstyrene-acrylic acid-acrylate copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-maleate copolymer, vinyl acetate-crotonic acid copolymer, and vinyl acetate-acrylic acid copolymer, as well as their salts. These copolymers can be used in the form of random copolymers, block copolymers, alternating copolymers, and graft copolymers. Examples of such resins include Joncryl 67, 678, 8500, 586, 611, 680, 682, 683, and 69, which are commercially available from BASF. These resins are generally neutralized with ammonia to enable the preparation of polymer solutions. The resins can also be neutralized with any other organic amine or inorganic base.

[0096] The ink according to the present invention may optionally contain a pigment dispersion, for example, an aqueous dispersion containing a pigment and one or more of the water-soluble and / or water-dispersible resins listed above. The aqueous pigment dispersion may optionally further contain one or more water-soluble and / or water-dispersible surfactants.

[0097] Examples of surfactants used in pigment dispersions include, but are not limited to, anionic surfactants such as alkanesulfonates, alpha-olefin sulfonates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, acylmethyl taurinates, dialkyl sulfosuccinates, alkyl sulfates, sulfurized olefins, polyoxyethylene alkyl ether phosphates, polycarboxylic acids, and monoglycerol phosphates; amphoteric surfactants such as alkylpyridinium salts; and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamides, glycerol alkyl esters, and sorbitan alkyl esters. Examples include BASF's EFKA 1000, 4000, 5000, and 6000 series products, Dow's Tamol series products, and Lubrizol's Solspase 27,000, 40,000, 44,000, 46,000, and 47,000.

[0098] The inventors have produced an inkjet ink composition that can produce printed materials with excellent resolubility and excellent water resistance (wet friction resistance) using a pigment dispersion containing an anionic and / or nonionic dispersant. Since nonionic dispersants (surfactants) are inherently susceptible to water, inks with poor water resistance can be produced. Therefore, the finding that inks containing a pigment dispersion prepared using SC-PUD and a nonionic dispersant can produce water-resistant printed materials is significant for inkjet applications. Accordingly, an optional feature of the present invention relates to an ink containing a pigment dispersion prepared using an anionic or nonionic dispersant, or a combination thereof. When the ink contains a pigment dispersion prepared using an anionic dispersant, the anionic dispersant is preferably an anionic acrylic copolymer dispersant.

[0099] The inkjet compositions prepared according to the present invention are suitable for multi-pass or single-pass printing. Applications corresponding to the present invention include, but are not limited to, multi-pass printing of textile products, including cotton-rich fabrics; single-pass printing of textile products; multi-pass printing of packaging, including corrugated cardboard; single-pass printing of packaging, including labels, corrugated cardboard, and flexible packaging; and single-pass and multi-pass printing of metal substrates, including metal decoration and decorative printing of cans. The inkjet compositions prepared according to the present invention are also ideal for the multi-pass graphics printing market. In the graphics market, the inkjet compositions of the invention can be printed on any soft or hard substrate, including, but not limited to, paper, vinyl, acrylic, polystyrene, polycarbonate, and metal. The inventors have demonstrated that the inkjet inks of the present invention exhibit excellent performance (i.e., excellent adhesion and water (wet friction) resistance) on vinyl, acrylic, and polycarbonate substrates used in the graphics inkjet printing market, particularly on vinyl, acrylic, and polycarbonate substrates used in the multi-pass inkjet graphics market. While the present invention is directed towards inkjet compositions, it is also useful for aqueous flexograph and gravure inks.

[0100] In any case, a print-receptive primer can be applied to the substrate to be printed prior to printing the inkjet composition of the invention. Packaging substrates, particularly polyester films, polypropylene films, nylon films, cellulose acetate films, polyethylene films, aluminum foils, metal sheets and rolls, and any coatings thereof, can be further treated by corona discharge or plasma treatment before printing to improve adhesion and printability. Similarly, the printed material can be subjected to further treatments, including but not limited to overlacquering and lamination, to realize the final product. In the packaging market, the printing inks of the present invention are useful in preparing laminates that can be produced by adhesives or thermal lamination methods. Those skilled in the art will recognize various methods and the details of such methods that enable the inks of the present invention to function well in the aforementioned markets. Therefore, in a further optional embodiment of the present invention, the inkjet printing ink according to the present invention is printed on a substrate pre-coated with the primer.

[0101] definition Boiling point: Unless otherwise specified, all boiling points are measured under standard atmospheric pressure of 101 kPa.

[0102] Heat of vaporization is defined as the amount of energy (enthalpy) that must be added to a substance to convert a certain amount of liquid substance into a gas. For the purposes of this disclosure, the enthalpy of vaporization is given at the standard boiling point of the substance in question, which is the boiling point of the substance at one atmosphere.

[0103] As used herein, room temperature is 25°C.

[0104] Unless otherwise specified, solubility is measured at 25°C.

[0105] Hydroxyl value (OHV): This is defined as the number of milligrams of potassium hydroxide required to neutralize the acetic acid absorbed by the acetylation of one gram of a chemical containing free hydroxyl groups. The hydroxyl value is preferably measured according to ISO 4629-1:2016(E).

[0106] Acid value (AV): The milligram mass of potassium hydroxide (KOH) required to neutralize 1 gram of a chemical substance. Unless otherwise specified, the acid value refers to the total acid value and is preferably measured according to ISO 2114:2000(E)(Method B).

[0107] Molecular weight: Throughout this text, this refers to both the number-average molecular weight and the mass-average molecular weight. Both the number-average and mass-average molecular weights are determined by gel permeation chromatography (GPC). Preferably, the molecular weight is measured by comparison with a polystyrene standard. For example, molecular weight measurement can be performed on a Hewlett-Packard 1050 series HPLC system equipped with two GPC ultrastyragel columns, 103 and 104 Å (5 μm mixed, 300 mm × 19 mm, Waters Millipore, Milford, Massachusetts, USA) and THF as the mobile phase. Those skilled in the art will understand that this definition typically applies to polymer materials having a molecular weight distribution. In the experimental work performed here, the theoretical number-average molecular weight was calculated by end-group analysis (also called chain-end analysis) based on the carbonyl (i.e., ketone and / or aldehyde) content and the mass of the polymer, and assuming that carbonyl groups are present at each of the two chain ends of the polymer.

[0108] Carbonyl content: The carbonyl content (i.e., ketone and / or aldehyde content) is preferably quantitative. 13 It is measured using 13C NMR spectroscopy. Preferably, the carbonyl content is measured by comparison with a suitable calibration reagent, for example, an end-capping reagent used to prepare SC-PUD. For example, several end-capping reagents of known concentration 13A calibration curve can be created by performing a 1C NMR experiment and integrating a specific carbon peak, such as the carbonyl peak, on the NMR spectrum. The carbonyl content of the polymer can then be obtained by comparing the same carbon integral value as the polymer being measured with the calibration curve. In this experimental procedure, the carbonyl content is calculated from the number of moles of raw materials used to produce SC-PUD.

[0109] Particle size / average particle size: In the view of the present invention, the terms “particle size” or “average particle size” refer to the median particle size of the volume distribution (the equivalent spherical diameter corresponding to 50% of the volume of all particles read on a cumulative distribution curve relating volume % to particle diameter - often referred to as the “D(v,0.5)” value). The particle size is preferably measured by laser diffraction.

[0110] Resolubility of inkjet inks: Unless otherwise specified, resolubility is measured as follows: An ink layer of approximately 60 μm was coated onto a glass slide using a No. 6 K bar (RK Print). The ink film was then dried at 40°C for 30 minutes. The dried ink was then immersed in an aqueous mixture containing 25% (w / w) propylene glycol, 0.2% Tegowet KL245 (surfactant, e.g., Evonik), and 0.15% (w / w) triethanolamine, with the remainder being deionized water. This aqueous solution is a good simulation of an ink varnish. Highly resolubility inks typically redissolve / redisperse easily in the immersion solution within 2–5 minutes, while insoluble inks do not redisperse in the immersion solution within 60 minutes of immersion.

[0111] As those skilled in the art will understand, the terms resolubility and redispersibility are used interchangeably in the art to refer to the same ink properties.

[0112] The present invention has been described in detail, including its preferred embodiments. However, those skilled in the art will understand, by examining this disclosure, that modifications and / or alterations to the present invention can be made within the scope and spirit of the invention.

[0113] Numbered items of the present invention The present invention will be further described by the following numbered sections. 1. An aqueous printing ink composition comprising a polyurethane dispersion, wherein the polyurethane in the polyurethane dispersion has the following characteristics: (a) one or more carbonyl groups are present at the ends of the polymer chains; (b) the number average molecular weight is 50,000 or less, more preferably 25,000 or less; and (c) the carbonyl group content is 0.02 to 4.0 mmol g relative to the dry polymer mass. -1 A water-based printing ink composition that includes the characteristic of being within a certain range. 2. The composition described in item number 1, selected from the group consisting of inkjet ink, flexograph ink, and gravure ink. 3. The composition according to item number 1 or 2, wherein the polyurethane has a mostly linear structure and the average number of carbonyl groups on the polymer is 2 or less. 4. Polyurethane dispersion contains 10 mg KOH g relative to the dry polymer mass. -1 A composition having the above acid value, as described in any of item numbers 1 to 3. 5. The composition according to any one of item numbers 1 to 4, wherein the polyurethane dispersion has an average particle size of 200 nm or less, more preferably 150 nm or less. 6. The composition according to any one of item numbers 1 to 5, further comprising a reagent that can react with a carbonyl compound to cure the composition. 7. The composition according to item number 6, wherein the reagent is a bifunctional, trifunctional, or more polyfunctional primary diamine or dihydrazide, and the reagent is preferably a bifunctional reagent. 8. The composition according to item number 6, wherein the bifunctional reagent is adipic acid dihydrazide. 9. The composition according to item number 6, wherein the reagent is a polyvalent metal crosslinking agent, preferably a zirconium complex. 10. A composition according to any one of item numbers 1 to 9, further comprising one or more acids selected from the group consisting of tartaric acid, gluconic acid, citric acid, maleic acid, succinic acid, and salts thereof. 11. The polyurethane dispersion further contains hydroxyl groups, and the hydroxyl value of the polyurethane is preferably 100 mg KOHg -1 More preferably, 50 mg KOHg -1 The composition described in any of the following items, numbered 1 to 10. 12. Boiling point above 150℃ and 500Jg -1 A composition according to any one of item numbers 1 to 11, comprising 25% (w / w) or less of a blend of any solvent having the above heat of vaporization. 13. A composition according to any one of item numbers 1 to 12, comprising a pigment dispersion prepared using an anionic dispersant or a nonionic dispersant, or a blend thereof. 14. The composition according to any one of item numbers 1 to 13, further comprising any further polyurethane dispersion that does not satisfy the criteria of claim 1. 15. The composition according to any one of item numbers 1 to 14, further comprising a further styrene-acrylic dispersion. 16. A method for printing an article, comprising the steps of printing one or more compositions described in any one of items 1 to 15 onto a substrate, and curing the composition. 17. The method according to item number 16, wherein the substrate is suitable for printing on packaging, food packaging, metal substrates, textile products, decorative laminates and graphics. 18. A printed article comprising one or more compositions described in any of items 1 to 15. [Examples]

[0114] The present invention will be further illustrated by the following non-limiting embodiments, which are not intended to limit the scope of the invention and should not be interpreted as such.

[0115] material Daotan 6425: A conventional hydroxy-functional polyurethane dispersion (Allnex) with a solid content of approximately 40% and a hydroxyl value of approximately 55 mg KOH / g. Neorez R605: A conventional polyurethane dispersion (DSM Resin) with a solid content of approximately 33% and a hydroxyl value of less than approximately 5 mg KOH / g. Daotan TW7064: A conventional self-crosslinked ketone-containing polyurethane dispersion (Ornex Co.) with a solid content of approximately 40% and polymer chain ends that do not contain ketone groups. Joncryl FLX5000: A self-crosslinked acrylic dispersion with a solid content of approximately 42% (BASF). Joncryl FLX5060: A self-crosslinked acrylic dispersion (BASF) with a solids content of approximately 43% and described as having good resolubility for printing ink applications. Tegowet KL245: Surfactant (Evonik).

[0116] Triethanolamine Propylene glycol: A water-soluble cosolvent with a boiling point of approximately 188°C and a heat of vaporization of approximately 880 J / g. MMB (3-methoxy-3-methyl-1-butanol): A water-soluble cosolvent with a boiling point of approximately 174°C and a heat of vaporization of approximately 384 J / g. Cyanide pigment dispersion A: An aqueous dispersion of cyanide 15:3 pigment containing approximately 16% (w / w) of pigment and an anionic dispersant. Cyanide pigment dispersion B: An aqueous dispersion of cyanide 15:3 pigment containing approximately 20% (w / w) of cyanide, further containing a nonionic dispersion. Carbodilite SV-02: Polycarbodiimide crosslinking agent (Nisshinbo Chemical Co., Ltd.).

[0117] SC-PUD used in the example Table 1 shows details of the SC-PUDs used to prepare aqueous ink compositions suitable for inkjet compositions that satisfy the requirements of the present invention as described above. Unless otherwise specified, all SC-PUDs contain the co-reagent adipic acid dihydrazide (molar ratio of SC-PUD to ADH is 1:1) to enable curing of the printed material after drying. All SC-PUDs except SC-PUD C, which used triethylamine as the neutralizing base, used N,N-dimethylethanolamine as the neutralizing agent.

[0118] [Table 1]

[0119] test Viscosity was measured at 32°C using a Brookfield DV-II+Pro viscometer equipped with a 100 rpm #18 spindle.

[0120] Resolubility Test: An ink film approximately 60 μm thick was applied to a glass slide using a No. 6 K bar applicator (RK Print). The ink was then dried at 40°C for 30 minutes, and then immersed in an aqueous solution containing 25% propylene glycol, 0.2% Tegowet KL245, and 0.15% triethanolamine. Resolubility was evaluated according to the following criteria: "Highly resolubility" (The dried ink film dispersed in the immersion solution within 3 minutes, and no trace of undissolved ink was observed). "Resolubility" (The dried ink film dispersed in the immersion solution within 3-5 minutes, and no trace of undissolved ink was observed). "Slowly resolubility" (The dried ink film dispersed in the immersion solution within 30 minutes, and no trace of undissolved ink was observed). "Partially resolubility" (The dried ink film dispersed in the immersion solution within 30 minutes, and traces of undissolved ink were observed). "Insoluble" (There was almost no evidence that the dried ink film dispersed in the immersion solution within 30 minutes).

[0121] Preparation of printed materials: Using a K-bar applicator (RK Print Co.), ink was applied to a white polyester-coated steel plate to a thickness of 8 μm. The printed materials were then dried for 20 seconds using a hot air blower. The printed materials were left to stand at room temperature for a further 15 minutes before being subjected to solvent resistance testing. The printed materials were then heated at 50°C and 75°C for 2 minutes and subjected to solvent resistance testing. In further testing, the printed materials were heated at 50°C for 2 minutes and then left to stand under ambient conditions (22-25°C) for 1-7 days to evaluate solvent resistance throughout this post-print curing process.

[0122] Water resistance: Water resistance was measured by rubbing the printed material with a water-soaked cotton swab. The number of double rubs required to remove or destroy the printed material was recorded. This is a well-known test in the industry.

[0123] Table 2 shows the results for several comparative inks suitable for inkjet printing, including polyurethane and acrylic dispersions that do not meet the requirements of the present invention. Table 2 also includes the results for inks containing hydroxy-functional PUDs and polycarbodiimide crosslinkers, based on the teachings of U.S. Patent Application Publication No. 2018 / 0105710.

[0124] [Table 2]

[0125] The results in Table 2 reflect the problem that the present invention solves, namely a method for producing an aqueous printing ink, particularly for inkjet printing, that combines ink properties (i.e., resolubility) and print property (i.e., the ability to produce prints with good water resistance demonstrated by double lab). Conventional polyurethane and acrylic dispersions certainly produce resistant prints, but inks containing them are extremely poorly soluble. In contrast, the ink produced by OH-PUD Daotane 6425 has high resolubility but poor non-stick properties. Adding a polycarbodiimide crosslinking agent to this ink improves non-stick properties but significantly impairs resolubility. Furthermore, Comparative Examples C5 and C6 do not exhibit sufficient water resistance even after a 24-hour post-curing period at room temperature following initial drying at 50°C.

[0126] Table 3 shows the results for inks prepared using the SC-PUDs listed in Table 1, including SC-PUD A and H, which are SC-PUDs that do not have ketone groups as part of their polymer structure, to calibrate Comparative Examples 7 and 8. These inks were tested using the methods described above. As a further test, the ink stability was evaluated by storing the inks at 50°C for 7 days and remeasuring their viscosity. An increase in viscosity of 10% or more is considered unstable. Inks containing PUDs typically show a slight decrease in viscosity.

[0127] [Table 3]

[0128] The results in Table 3 demonstrate the benefits of aqueous inks containing SC-PUD. Comparing I1 with C7 and I2 with C8, it can be seen that the removal of ketone functional groups from SC-PUD affects the water resistance of the printed material. All examples of the present invention demonstrate, in particular, that inks containing SC-PUD with the curing reagent ADH have a superior balance of ink resolubility and non-stick properties. It is interesting that Example I3, which contains ketone-functional SC-PUD but does not contain the ADH curing agent, can produce printed materials with some degree of water resistance, although it is not at the same level as I2, which is essentially the same SC-PUD except for the presence of ADH. Further noteworthy is Ink Example I4, which contains SC-PUD C, which is essentially the same as SC-PUD except that the SC-PUD is neutralized with triethylamine instead of N,N-dimethylethanolamine. This more volatile neutralizing amine has a slight adverse effect on the ink's resolubility but allows for a more rapid onset of non-stick properties. It is reasonable to assume that this is due to the slowing of the reaction between the ketone group of SC-PUD and ADH in the presence of a tertiary amine, and as a result, inks containing SC-PUD neutralized with a less volatile amine such as N,N-dimethylethanolamine (which has a boiling point of 134°C compared to 89°C for triethylamine) cure more slowly. To promote resolubility, a further aspect of the present invention is that the tertiary amine used for neutralization preferably has a boiling point above 125°C.

[0129] It is believed that inks can be prepared using blends of SC-PUD and other resins. Table 4 shows the results for several inks prepared along these lines, i.e., ink compositions following those described earlier.

[0130] [Table 4]

[0131] The results in Table 4 show that ink compositions can be prepared by combining SC-PUD with other aqueous resins. Regarding the water resistance of the final printed material, there is no clear benefit to doing so, and the excellent ink resolubility may be compromised. However, those skilled in the art will understand that other resins can be used to enhance specific properties, such as adhesion. The inventors have shown that ink examples I1 and I2 exhibit excellent adhesion to a wide range of substrates, including corona-discharged PET and OPP films, acrylic-coated PET films, and graphics substrates containing acrylic, vinyl, and polycarbonate. Both inks showed good adhesion to the coated steel plates used in these examples.

[0132] Table 5 shows aqueous compositions containing SC-PUD at various concentrations, as well as different solvent blends and concentrations. Here again, inks were prepared according to the compositions already shown. Differences in SC-PUD or solvent concentration were compensated for by adding further deionized water to the ink.

[0133] [Table 5]

[0134] The results in Table 5 show that the composition of the invention can be prepared with lower concentrations of SC-PUD, as well as with alternative solvent blends and lower total solvent concentrations. A notable feature is the improved drying response after 2 minutes at 50°C for inks containing 15% (w / w) or less of propylene glycol. All inks shown in Table 5 maintain a high level of resolubility. Table 5 also shows that the addition of MMB reduces the organic solvent concentration (%) of the composition of the invention (replaced with water). Thus, by reducing the organic solvent content while increasing the water content, the ink composition of the invention is obtained that is more environmentally friendly than the comparative ink composition while exhibiting the desired performance characteristics.

[0135] In all of the above examples, cyan pigment dispersion A, which is a dispersion prepared using a nonionic dispersant, was used. SC-PUD also enables the production of inks that have a good balance between ink resolubility and good non-stick properties by using pigment dispersions prepared with a nonionic dispersant. To demonstrate this, further ink examples were prepared using cyan pigment dispersion B. Details of these inks and the related results are shown in Table 6.

[0136] [Table 6]

[0137] Table 6 shows how much pigment dispersion B affects print water resistance compared to pigment dispersion A, i.e., how much C9 affects print water resistance compared to C4. The invention's ink example I19 was able to produce printed materials with high resolubility and excellent water resistance compared to comparative example C10, which was based on the conventional self-crosslinked acrylic dispersion Joncryl FLX5060. In contrast, the ink of comparative example C10 had very poor resolubility.

Claims

1. A water-based printing ink composition containing a polyurethane dispersion, The polyurethane in the aforementioned polyurethane dispersion is (a) The characteristic that one or more ketone groups or aldehyde groups are present at the ends of the polymer chain, but not at any other locations on the polymer chain. (b) The characteristic of having a number-average molecular weight of 50,000 or less, (c) Ketone group and aldehyde group content is 0.02 to 4.0 mmol g relative to the dry polymer mass. -1 The characteristic of being within the range Includes, (i) The polyurethane dispersion contains no more than two ketone groups or aldehyde groups per average polymer chain, which are present at the polymer chain ends but not at other locations on the polymer chain, or (ii) The polyurethane in the polyurethane dispersion is branched, and there are up to two ketone groups or aldehyde groups at the polymer chain ends, but none at other locations on the polymer chain. A water-based printing ink composition wherein the water-based printing ink composition is an inkjet ink.

2. The composition according to claim 1, wherein the polyurethane in the polyurethane dispersion has the characteristic of having a number average molecular weight of 25,000 or less.

3. The composition according to claim 1, wherein one or more groups present at the ends of polymer chains are ketone groups.

4. The polyurethane dispersion contains 10 mg KOH g relative to the dry polymer mass. -1 The composition according to claim 1, having the above acid value.

5. The composition according to claim 1, wherein the polyurethane dispersion has an average particle size of 200 nm or less.

6. The composition according to claim 5, wherein the polyurethane dispersion has an average particle size of 150 nm or less.

7. The composition according to claim 1, wherein the polyurethane dispersion further comprises a reagent that can react with a ketone group or an aldehyde group at one or more polymer chain ends to cure the composition.

8. The composition according to claim 7, wherein curing occurs via linear extension.

9. The composition according to claim 7, wherein the reagent is a bifunctional, trifunctional, or more polyfunctional primary diamine or dihydrazide.

10. The composition according to claim 9, wherein the reagent is a dihydrazide adipic acid, which is a bifunctional primary diamine.

11. The composition according to claim 7, wherein the reagent is a polyvalent metal crosslinking agent.

12. The composition according to claim 11, wherein the polyvalent metal crosslinking agent is a zirconium complex.

13. The composition according to claim 1, further comprising one or more acids selected from the group consisting of tartaric acid, gluconic acid, citric acid, maleic acid, succinic acid, and salts thereof.

14. The polyurethane in the polyurethane dispersion further contains hydroxyl groups, and the hydroxyl value of the polyurethane is 100 mg KOHg -1 The composition according to claim 1, which is as follows:

15. The composition according to claim 14, wherein the hydroxyl value of the polyurethane is 50 mg KOHg -1 or less.

16. The composition according to claim 14, wherein the hydroxyl group is present at one or more polymer chain ends.

17. Boiling point above 50°C and 500 Jg -1 The composition according to claim 1, wherein any blend containing a solvent having the above heat of vaporization is included in an amount of 25% (w / w) or less.

18. The composition according to claim 1, comprising a pigment dispersion prepared using an anionic dispersant or a nonionic dispersant, or a blend thereof.

19. The composition according to claim 1, further comprising any further polyurethane dispersions that do not meet the criteria of claim 1.

20. The composition according to claim 1, further comprising a further styrene-acrylic dispersion.

21. The composition according to claim 1, wherein the polyurethane is anionically stabilized by including a carboxylic acid in the polyurethane chain.

22. The composition according to claim 21, wherein the anionically stabilized polyurethane is neutralized with a tertiary amine, potassium hydroxide, or sodium hydroxide.

23. The anionically stabilized polyurethane is a tertiary axyl having a boiling point higher than 125°C. The composition according to claim 22, which is neutralized with mine.

24. The composition according to claim 22, wherein the anionically stabilized polyurethane is neutralized with triethylamine or N,N-dimethylethanolamine.

25. A method for printing an article, comprising the steps of printing a composition according to any one of claims 1 to 24 onto a substrate and curing the composition.

26. The method according to claim 25, wherein the substrate is suitable for printing on packaging, food packaging, metal substrates, textile products, decorative laminates and graphics.

27. A printed article comprising the composition according to any one of claims 1 to 24.

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