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US-12617956-B2 - Aqueous inkjet compositions comprising hydroxy-functional polyurethane dispersions

US12617956B2US 12617956 B2US12617956 B2US 12617956B2US-12617956-B2

Abstract

Ink and coating compositions, including inkjet inks, comprising a blend of OH-PUDs having hydroxyl values preferably greater than 25, and more preferably greater than 50 mgKOH/g, with PUDs having hydroxyl values of less than 25, and more preferably less than 5 mgKOH/g.

Inventors

  • Derek Illsley

Assignees

  • SUN CHEMICAL CORPORATION

Dates

Publication Date
20260505
Application Date
20220331

Claims (20)

  1. 1 . An aqueous ink or coating composition comprising a first hydroxyl-functionalised polyurethane dispersion having a hydroxyl value of 25 mgKOH/g or greater, and a second polyurethane dispersion having a hydroxyl value of less than 25 mgKOH/g, wherein the ratio of the first hydroxyl-functionalised polyurethane dispersion to the second polyurethane dispersion, based on the dry polymer weight, is in the range 20:1 to 1:10.
  2. 2 . The ink or coating composition of claim 1 , wherein the first hydroxyl-functionalised polyurethane dispersion has a hydroxyl value of 50 mgKOH/g or greater, and/or the second polyurethane dispersion has a hydroxyl value of less than 10 mgKOH/g.
  3. 3 . The ink or coating composition of claim 1 , wherein the second polyurethane dispersion component is a self-crosslinking type and comprises a ketone, aldehyde, or silane group as part of its structure.
  4. 4 . The ink or coating composition of claim 1 , wherein the total solids content of the first hydroxyl-functionalised polyurethane dispersion in the ink or coating composition is in the range 1% (w/w) to 20% (w/w) based on the total weight of the composition, and wherein the total solids content of the second polyurethane dispersion in the ink or coating composition is in the range 0.5% (w/w) to 15% (w/w) based on the total weight of the composition.
  5. 5 . The ink or coating composition of claim 1 , which is suitable for printing via an inkjet printing process and has a viscosity of 10 mPa·s or less at 32° C. and a pH in the range of 5.0 to 10.0.
  6. 6 . The ink or coating composition of claim 1 , comprising one or more water-soluble co-solvents.
  7. 7 . The ink or coating composition of claim 1 , comprising less than 40% (w/w) of any blend of organic water-soluble co-solvents having boiling points of greater than 150° C. and comprising less than 10% (w/w) of any blend of water-soluble organic co-solvents with boiling points in excess of 200° C.
  8. 8 . The ink or coating composition of claim 1 , further comprising an amine with a boiling point of greater than 130° C. and less than 200° C.
  9. 9 . The ink or coating composition of claim 8 , wherein the amine is selected from the group consisting of N,N-dimethylethanolamine, N-methylethanol amine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol, ethanolamine, and combinations thereof.
  10. 10 . The ink or coating composition of claim 1 , further comprising a crosslinker selected from the group consisting of carbodiimide, oxazoline, aziridine, amino resin, a blocked isocyanate, and combinations thereof.
  11. 11 . The ink or coating composition of claim 1 , further comprising a colorant, wherein the colorant includes an organic or inorganic pigment selected from the group consisting of carbon black, zinc oxide, titanium dioxide, phthalocyanine, anthraquinones, perylenes, carbazoles, monoazo and disazobenzimidazoles, rhodamines, indigoids, quinacridones, diazopyranthrones, dinitroanilines, pyrazoles, diazopyranthrones, pyrazoles, dianisidines, pyranthrones, tetracholoroisoindolines, dioxazines, monoazoacrylides and anthrapyrimidines and/or wherein the colorant includes a dye selected from the list consisting of azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, and combinations thereof.
  12. 12 . A substrate comprising a cured layer of the ink or coating of claim 1 , wherein the substrate is selected from the group consisting of metal, packaging material; paper; carton board; a textile material, or a flexible plastic selected from the group consisting of vinyl, acrylic, polystyrene, polycarbonate, polyester, polypropylene, nylon, cellulose acetate, and polyethylene.
  13. 13 . A printed article comprising the substrate of claim 12 .
  14. 14 . The printed article of claim 13 , further comprising a primer layer between the substrate and the cured layer of the ink or coating, wherein the primer comprises a multivalent salt.
  15. 15 . A method of making the ink or coating composition of claim 1 comprising the steps of combining a first hydroxyl-functionalised polyurethane dispersion having a hydroxyl value of 25 mgKOH/g or greater, with a second polyurethane dispersion having a hydroxyl value of less than 25 mgKOH/g to provide the composition.
  16. 16 . The method of claim 15 , further comprising the step of adding an amine with a boiling point of greater than 130° C. to the composition wherein the first hydroxyl-functionalised polyurethane dispersion and/or the second polyurethane dispersion is/are anionically stabilized and the amine is added to neutralize the first hydroxyl-functionalised polyurethane dispersion and/or the second polyurethane dispersion prior to combining the first hydroxyl-functionalised polyurethane dispersion with the second polyurethane dispersion.
  17. 17 . A method of printing, comprising the steps of: a) providing the composition according to claim 1 ; and b) printing said composition onto a substrate; wherein the method of printing is selected from the group consisting of flexographic printing, gravure printing, inkjet printing, and screen printing.
  18. 18 . The method of claim 17 , further comprising: step c) curing the printed composition; wherein step c) is performed after steps a) and b), and wherein step c) is performed at a temperature of 50° C. or greater.
  19. 19 . The method of claim 17 , wherein before step a), the substrate is coated with a primer layer, wherein the primer comprises a multivalent salt.
  20. 20 . The method of claim 19 , wherein the multivalent salt comprises, calcium chloride, calcium acetate, magnesium chloride, magnesium acetate, or aluminum sulphate.

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present application is a § 371 National Phase application based on PCT/GB2022/050814 filed Mar. 31, 2022, which claims the benefit of U.S. Provisional Application No. 63/169,362, filed Apr. 1, 2021, the subject matter of each of which is incorporated by reference in their entirety. FIELD OF THE INVENTION The present invention relates to ink and coating compositions, and specifically inkjet ink compositions, comprising polyurethane dispersions, which have a desirable combination of both good resolubility and good print resistance. BACKGROUND OF THE INVENTION Polyurethane Dispersions (PUDs) are a widely used resin used in the preparation of pigmented aqueous inkjet printing inks. One problem with using PUDs in aqueous inkjet ink compositions is that upon drying, such as at temperatures of up to 40° C. for between 15 and 60 minutes, they become insoluble and cannot then be resolubilized in either the ink itself or a flushing solution. Hydroxyl-Functional PUDs (OH-PUDs) and their use in inkjet inks are known in the art and, due to the presence of the hydroxyl functionalization, provide compositions with improved resolubility/redispersibility when OH-PUDs are incorporated. This is especially useful for aqueous inkjet printing inks; wherein insoluble inks cause clogging of the printhead. However, incorporating OH-PUDs can be detrimental to properties of ink and coating compositions such as water resistance, as the improved resolubility means that the dried films can be quickly eroded with water. U.S. Pat. No. 8,931,889B2 discloses OH-PUDs comprising polyether diols as part of their chemical structure and their use in aqueous inkjet ink compositions. U.S. Pat. No. 8,931,889B2 discloses OH-PUDs with improved stability and long nozzle life. CN111138626 discloses PUDs for aqueous inkjet printing of textiles, wherein end-capping reagents such as N-methylethanolamine are used to prepare OH-PUDs (hydroxy-terminated). Indeed, the use of end-capping agents in the preparation of OH-PUDs is well known in the art. For example, U.S. Pat. No. 7,875,355B2 discloses OH-PUDs for use in the automotive coating industry, prepared using a diaminopropanol end-capping reagent. US2010105710 discloses that OH-PUDs can reduce printhead clogging; improvements that likely result from the improved resolubility of the inks due to incorporation of OH-PUDs. To mitigate the reduction in water resistance that results from the inclusion of OH-PUDs, the PUDs can be crosslinked. Aqueous inkjet printing inks comprising PUDs can be crosslinked using a variety of crosslinking agents and, including amino resins such as melamine-formaldehydes. A number of crosslinking methodologies are disclosed in the art for polyurethanes comprising carboxylic acid, hydroxyl, or amine pendant functional groups, using crosslinkers such as carbodiimides, epoxies, isocyanates, amino resins (e.g. melamine-formaldehyde), and aziridines. Crosslinking PUDs is especially important in the printing of textiles. WO2009/137753 discloses crosslinking of PUDs with Cymel 303, a melamine-formaldehyde crosslinker, at a temperature of 160° C. U.S. Pat. Nos. 10,513,622, 10,457,824, and 9,249,324 disclose the use of optional crosslinkers in combination with polyurethane pigment dispersants to improve resistance properties. U.S. Pat. Nos. 8,186,822, 9,255,207 and US20070060670 disclose aqueous inkjet ink compositions comprising crosslinked PUDs. The crosslinked PUDs are produced by crosslinking during the preparation of the PUD, using a crosslinking reagent such as triethylene tetraamine. U.S. Pat. Nos. 8,568,889B2 and 7,476,705 disclose the preparation of self-crosslinking PUDs comprising the keto-hydrazide crosslinking chemistry, from diol prepolymers formed through a reaction of diepoxides with levulinic acid. US20180105710 discloses the use of a crosslinker (a carbodiimide is used in the examples) to improve print resistance of a OH-PUD-containing composition, which would otherwise be poor due to the inclusion of OH-PUD. Print resistance has been achieved for OH-PUDs using crosslinkers such as carbodiimides, oxazolines, amino resins (such as melamine formaldehydes), blocked isocyanates and zirconium complexes (see, e.g. US20180105710). However, while the use of crosslinking agents improves the water resistance of OH-PUD containing inks and coatings, it can negatively impact ink resolubility. Furthermore, crosslinking agents such as amino resins, blocked isocyanates, carbodiimides, oxazolines and the like, can cause health issues, particularly for inks and coatings used in the printing of food packaging, pharmaceutical packaging, personal care packaging, personal care products (such as baby nappies) and other sensitive applications. The literature has not adequately shown how it is possible to produce aqueous inks, especially inkjet inks, with excellent resolubility/redispersibility, which at the same time can produce prints with excellent wat