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US-12617957-B2 - Durable outdoor inkjet inks

US12617957B2US 12617957 B2US12617957 B2US 12617957B2US-12617957-B2

Abstract

An inkjet ink for printing durable outdoor images with an inkjet printer includes an basic pH aqueous ink vehicle comprising water, a soluble base, and at least one water soluble organic solvent; a pigment dispersion; and a polymer comprising base neutralized carboxylic acid groups with a glass transition temperature between 0 and 150° C. and an acid number between 50 and 1000 mg KOH/g dissolved in the vehicle, wherein the carboxylic acid groups are base neutralized; a poly-electrophilic functionalized compound capable of crosslinking the neutralized carboxylic acidic groups on the polymer wherein the ratio of the poly-electrophilic groups on the functionalized compound to carboxylic acid groups on the polymer is 1:1 or less on an equivalent basis and the ink maintains a stable viscosity and pigment particle size distribution for 6 weeks at 60° C.; the water in the ink inhibiting the crosslinking reaction until after the ink is printed and the water is substantially removed from the ink by drying.

Inventors

  • Kathryn A. Manning
  • Daniel Jude Harrison

Assignees

  • INTERNATIONAL IMAGING MATERIALS, INC.

Dates

Publication Date
20260505
Application Date
20210504

Claims (20)

  1. 1 . An inkjet ink for printing images with a thermal inkjet printer comprising: a basic pH aqueous ink vehicle including water, a non-volatile soluble base, and at least one water soluble organic solvent; a buffer; a pigment dispersion; and a polymer including base neutralized carboxylic acid groups with a glass transition temperature between 0° C. and 150° C. and an acid number between 50 and 1000 mg KOH/g dissolved in the vehicle; a poly-electrophilic functionalized compound capable of crosslinking the neutralized carboxylic acidic groups on the polymer wherein the ratio of the poly-electrophilic groups on the functionalized compound to carboxylic acid groups on the polymer is 1:1 or less on an equivalent basis and the pigment particle size distribution changes less than 200 nm in 6 weeks at 60°; said water in the ink inhibiting the crosslinking reaction until after the ink is printed and said water is substantially removed from the ink by drying; said basic pH aqueous ink vehicle not including tertiary amines and not including a volatile soluble base.
  2. 2 . The inkjet ink as claimed in claim 1 , wherein said polymer is a polystyrene-co-acrylate polymer resin binder.
  3. 3 . The inkjet ink as claimed in claim 1 , wherein said poly-electrophilic functionalized compound is a compound selected from the group consisting of a beta hydroxy amide crosslinker, an oxazoline functionalized reactive polymer crosslinker, a highly methylated, monomeric melamine crosslinker, an isocyanate crosslinker, an organic titanate crosslinker, an organosilane crosslinker, a glycidyl ether crosslinker, a multifunctional type aliphatic epoxy crosslinker, a polyfunctional aziridine liquid crosslinker, or a polymeric carbodiimide crosslinking agent.
  4. 4 . The inkjet ink as claimed in claim 1 , wherein at least one water soluble organic solvent is a humectant.
  5. 5 . The inkjet ink as claimed in claim 1 , further comprising a surfactant.
  6. 6 . The inkjet ink as claimed in claim 1 , further comprising a biocide.
  7. 7 . The inkjet ink as claimed in claim 1 , wherein the pH of said basic pH aqueous ink vehicle is between 7 and 10.
  8. 8 . The inkjet ink as claimed in claim 1 , wherein said polymer is a soluble copolymer.
  9. 9 . The inkjet ink as claimed in claim 1 , wherein said polymer is not a dispersed polymer.
  10. 10 . The inkjet ink as claimed in claim 1 , wherein said polymer is not a latex.
  11. 11 . The inkjet ink as claimed in claim 1 , wherein said poly-electrophilic functionalized compound includes at least three reactive groups.
  12. 12 . The inkjet ink as claimed in claim 1 , wherein said polymer is less than 10% of the ink by weight.
  13. 13 . The inkjet ink as claimed in claim 1 , wherein said polymer has a molecular weight less than 50,000.
  14. 14 . The inkjet ink as claimed in claim 1 , wherein said acid number is between 50 and 400.
  15. 15 . The inkjet ink as claimed in claim 1 , wherein said water soluble organic solvent is less than 50% of the ink by weight.
  16. 16 . The inkjet ink as claimed in claim 1 , wherein said water soluble organic solvent is less than 30% of the ink by weight.
  17. 17 . The inkjet ink as claimed in claim 1 , wherein an average particle size of a pigment in said pigment dispersion is less than a micron.
  18. 18 . The inkjet ink as claimed in claim 1 , wherein said pigment dispersion is less than 20% of the ink by weight.
  19. 19 . The inkjet ink as claimed in claim 1 , wherein said pigment dispersion is less than 10% of the ink by weight.
  20. 20 . The inkjet ink as claimed in claim 1 , wherein the viscosity changes less than 20% in 6 weeks at 60° C.

Description

PRIORITY INFORMATION The present application is a continuation application of PCT Patent Application Number PCT/US2019/061898, filed on Nov. 17, 2019, and claims priority, under 35 U.S.C. § 120, from PCT Patent Application Number PCT/US2019/061898, filed on Nov. 17, 2019. The entire content of PCT Patent Application Number PCT/US2019/061898, filed on Nov. 17, 2019, is hereby incorporated by reference. PCT Patent Application Number PCT/US2019/061898, filed on Nov. 17, 2019, claims priority, under 35 U.S.C. § 119(e), from U.S. Provisional Patent Application No. 62/768,883, filed on Nov. 17, 2018. The present application claims priority, under 35 U.S.C. § 119(e), from U.S. Provisional Patent Application No. 62/768,883, filed on Nov. 17, 2018. The entire content of U.S. Provisional Patent Application No. 62/768,883, filed on Nov. 17, 2018, is hereby incorporated by reference. BACKGROUND Digital inkjet printing has been rapidly replacing analog printing of graphic images, information signage, and photographs. The transition from analog to digital started with indoor print applications but is now growing into many outdoor print applications. Aqueous inkjet inks have been widely used for such indoor print applications while solvent and UV curable inkjet inks have been used for both indoor and outdoor graphical printing due to their higher durability. In addition to the greater outdoor durability of solvent and UV curable inkjet inks, they may be printed directly on to a wide variety of outdoor durable substrates without the need for an ink receptive layer. Pigmented aqueous inkjet inks prepared with soluble resin binders are used for printing onto a wide variety of substrates. The pigment-based colorants used in these inks are much more resistant to fade than dye-based colorants and are thus suitable for applications requiring exposure to direct sunlight. However, because the water soluble resin binder in these inks may re-dissolve when exposed to moisture, these inks are not suitable for many outdoor display applications, especially on uncoated substrates. When Pigmented aqueous inkjet inks are printed onto outdoor durable substrates which do not have an ink receptive layer, the image substrate will exit the printer in a wet state and be easily damaged. Aqueous, pigmented, latex inkjet ink technology began to be utilized in an effort to improve the durability of inkjet prints, see for example U.S. Pat. Nos. 6,019,828 and 6,177,498. The use of latex polymer particles in printing inks is well known. European Patent Number EP0068903B1 discloses the use of dye containing latex particles in inkjet ink; polymeric latex particles in inkjet inks are also disclosed in published Japanese Patent Application Number 2,867,491 and U.S. Pat. No. 5,284,894. U.S. Pat. No. 5,112,399 discloses the use of styrene-acrylate emulsions and styrene-butadiene latex in inkjet inks. U.S. Pat. No. 5,284,894 discloses that “a volatile base, or alkaline material is required in a fortified latex to maintain the polyelectrolyte resin in solution. Preferably, this base is ammonia, because it is volatile and relatively inexpensive. The ready evaporation of ammonia favors faster drying and guarantees quick development of water resistance that most of the inks must acquire after printing. Other volatile bases include any of the lower boiling amines such as methyl amine, dimethyl amine, trimethyl amine, ethyl amine, diethyl amine, and triethyl amine. Monoethanol amine, diethanol amine, and morpholine can also be used to achieve special effects such as better redispersibility on the press or slower drying. Sodium hydroxide, potassium hydroxide, sodium carbonate and other inorganic bases may be useful for special applications. The amount of a volatile base used must be sufficient to maintain solubility and uniformity of the ink, without settling out of the resin polyelectrolyte. We have found a pH of 8.0 to 8.5 to be a preferred range. World Patent Application Number WO1999023182A discloses latex binders as “particles” and not as solution polymers. U.S. Pat. No. 8,114,923 discloses that the term “latex” or “latex dispersion” includes both latex particulates as well as the aqueous medium in which the latex particulates are dispersed. The term latex is widely used to refer to a dispersion or suspensions of polymer particles in a liquid medium. The use of the term latex differentiates the state of the polymer in the liquid ink. Whereas a polymer which is soluble in a liquid is considered to be in the liquid state once dissolved in the liquid, the latex polymer is clearly in the solid state as in insoluble particle suspended in a liquid. The terms emulsion and latex are frequently interchanged. U.S. Pat. Nos. 5,990,202; 6,019,828; 6,498,202; 6,417,249; 6,858,301; 7,030,175; 7,371,273; 8,267,505; 8,268,910; 8,314,163; 8,487,036; 8,573,761; and 8,939,568 disclose the use of polymers dispersed in a liquid inkjet ink. The entire contents of U.S. Pat. Nos. 5,99