Aqueous ink

Patent metadata

Field	Value
Publication number	US-11180671-B2
Application number	US-201816626419-A
Country	US
Kind code	B2
Filing date	Jun 29, 2018
Priority date	Jul 3, 2017
Publication date	Nov 23, 2021
Grant date	Nov 23, 2021

Abstract

The present invention relates to a water-based ink containing at least pigment-containing water-insoluble crosslinked polymer particles (A), a polymer emulsion (B) and water, in which a water-insoluble crosslinked polymer constituting the crosslinked polymer particles (A) is obtained by subjecting a polymer that contains a constitutional unit derived from a carboxylic acid monomer having an acid value of not less than 200 mgKOH/g and a constitutional unit derived from a hydrophobic monomer, to crosslinking reaction with an epoxy compound, and a polymer constituting the polymer emulsion (B) contains a constitutional unit derived from a carboxylic acid monomer and a constitutional unit derived from a hydrophobic monomer. The water-based ink of the present invention is excellent in ejection stability and fastness of the printed characters or images while maintaining good optical density.

First claim

The invention claimed is:

1. A water-based ink comprising at least pigment-containing water-insoluble crosslinked polymer particles (A), a polymer emulsion (B) and water;
wherein the pigment-containing water-insoluble crosslinked polymer particles (A) comprises a pigment and a water-insoluble crosslinked polymer, wherein the water-insoluble crosslinked polymer comprises a polymer that comprises a constitutional unit derived from a carboxylic acid monomer having an acid value of not less than 200 mg KOH/g and a constitutional unit derived from a hydrophobic monomer that is crosslinked with an epoxy compound;
wherein the polymer emulsion (B) comprises a crosslinked polymer comprising a constitutional unit derived from a carboxylic acid monomer and a constitutional unit derived from a hydrophobic monomer; and
wherein an acid value of the crosslinked polymer in the polymer emulsion (B) is not less than 50 mg KOH/g.

2. The water-based ink according to claim 1 , wherein a crosslinking degree of the water-insoluble crosslinked polymer is not less than 20 mol % and not more than 80 mol %.

3. The water-based ink according to claim 1 , wherein an acid value of the water-insoluble crosslinked polymer is not less than 80 mg KOH/g and not more than 180 mg KOH/g.

4. The water-based ink according to claim 1 , wherein the epoxy compound is a glycidyl ether compound of a polyhydric alcohol comprising a hydrocarbon group having not less than 3 and not more than 8 carbon atoms.

5. The water-based ink according to claim 1 , wherein an acid value of a crosslinking polymer constituting the polymer emulsion (B) is not less than 50 mg KOH/g and not more than 300 mg KOH/g.

6. The water-based ink according to claim 1 , wherein the crosslinked polymer constituting the polymer emulsion (B) is obtained by crosslinking reaction with a glycidyl ether compound of a polyhydric alcohol comprising a hydrocarbon group having not less than 3 and not more than 8 carbon atoms.

7. The water-based ink according to claim 1 , wherein a crosslinking degree of the polymer constituting the polymer emulsion (B) is not less than 5 mol % and not more than 80 mol %.

8. The water-based ink according to claim 1 , wherein a content of the pigment-containing water-insoluble crosslinked polymer particles (A) in the water-based ink is not less than 2% by mass and not more than 17% by mass.

9. The water-based ink according to claim 1 , wherein a content of the polymer emulsion (B) in the water-based ink is not less than 1% by mass and not more than 10% by mass.

10. The water-based ink according to claim 1 , wherein a mass ratio of the pigment-containing water-insoluble crosslinked polymer particles (A) to polymer particles in the polymer emulsion (B) [pigment-containing water-insoluble crosslinked polymer particles (A)/polymer particles)] in the water-based ink is from 10/1 to 0.3/1.

11. The water-based ink according to claim 1 , for ink-jet printing.

12. An ink-jet printing method, comprising the steps of loading the water-based ink according to claim 1 to an ink-jet printing apparatus and ejecting the water-based ink in the form of droplets of the ink from the ink-jet printing apparatus onto a printing medium to print characters or images on the printing medium.

13. An ink-jet printing method according to claim 12 , wherein the printing medium is at least one film selected from the group consisting of a polyester film, a polyvinyl chloride film, a polypropylene film and a polyethylene film.

14. The water-based ink according to claim 1 , wherein the water-insoluble crosslinked polymer in the pigment-containing water-insoluble crosslinked polymer particles (A) possesses a structure that is produced by:
polymerizing a constitutional unit derived from a carboxylic acid monomer having an acid value of not less than 200 mg KOH/g and a constitutional unit derived from a hydrophobic monomer to form a carboxy group-containing polymer;
combining the carboxy group-containing polymer, an organic solvent, a pigment and water to obtain a pigment mixture;
subjecting the pigment mixture to a dispersion treatment to obtain a first dispersion;
removing the organic solvent from the first dispersion, to obtain a pigment water dispersion; and
subjecting the pigment water dispersion to crosslinking treatment with an epoxy compound, wherein there is crosslinking between the carboxy group-containing polymer and the epoxy compound, to form the pigment-containing water-insoluble crosslinked polymer particles (A).

15. The water-based ink according to claim 14 , wherein the hydrophobic monomer for the carboxy group-containing polymer is selected from the group consisting of an alkyl (meth)acrylate monomer and an aromatic group-containing monomer.

16. The water-based ink according to claim 15 , wherein the alkyl (meth)acrylate monomer is selected from the group consisting of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate, (iso- or tertiary-)butyl (meth) acrylate, (iso)amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl (meth)acrylate, (iso)dodecyl (meth)acrylate and (iso)stearyl (meth)acrylate.

17. The water-based ink according to claim 15 , wherein the aromatic group-containing monomer is selected from the group consisting of styrene-based monomers, aromatic group-containing (meth)acrylates and styrene-based macromonomers.

Assignees

• Kao Corp

Inventors

• Inoue Masashi
• Kawata Daiki

Classifications

• C09D11/326

  characterised by the pigment dispersant · CPC title

• C09D11/106 Primary

  containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds · CPC title

• B41J2/2107

  characterised by the ink properties (supplying ink in a solid state B41J2/17593) · CPC title

• B41J2/01

  Ink jet · CPC title

• C09D11/037

  characterised by the pigment · CPC title