The present disclosure provides a white ink including an aqueous ink vehicle, from 5 wt % to 50 wt % of a white metal oxide pigment having an average particulate size from 100 nm to 2,000 nm, from 0.1 wt % to 4 wt % of anionic oxide particulates having an average particulate size from 1 nm to 100 nm, from 2 wt % to 30 wt % of latex particulates having a glass transition temperature from 0 C to 130 C, and a non-ionic or predominantly non-ionic dispersant having an acid number not higher than 100 mg KOH/g based on dry polymer weight. The white metal oxide pigment and anionic oxide particulates are present in the white ink at a weight ratio from 5:1 to 200:1.

The present invention relates to [1] a process for producing pigment-containing modified polymer particles, including the step of reacting pigment-containing polymer particles (A) containing a functional group and a compound (B) containing a reactive group capable of reacting with the functional group of the polymer particles (A) in a medium under such a condition that a ratio [(B)/(A)] of total moles of the reactive group of the compound (B) to total moles of the functional group of the polymer particles (A) is from 0.10 to 0.62; [2] a pigment water dispersion including an aqueous medium and the modified polymer particles produced by the aforementioned process which are dispersed in the aqueous medium; and [3] an ink including the aforementioned pigment water dispersion and an organic solvent. The modified polymer particles are free from formation of coarse particles upon production of pigment particles, so that an ink obtained by using the modified polymer particles can be prevented from suffering from increase in viscosity thereof when the ink is being concentrated by evaporation of water from the ink, and is excellent in rub fastness when printed on a low-water absorbing recording medium.

The present invention relates to [1] a process for producing pigment-containing modified polymer particles, including the step of reacting pigment-containing polymer particles (A) containing a functional group and a compound (B) containing a reactive group capable of reacting with the functional group of the polymer particles (A) in a medium under such a condition that a ratio [(B)/(A)] of total moles of the reactive group of the compound (B) to total moles of the functional group of the polymer particles (A) is from 0.10 to 0.62; [2] a pigment water dispersion including an aqueous medium and the modified polymer particles produced by the aforementioned process which are dispersed in the aqueous medium; and [3] an ink including the aforementioned pigment water dispersion and an organic solvent. The modified polymer particles are free from formation of coarse particles upon production of pigment particles, so that an ink obtained by using the modified polymer particles can be prevented from suffering from increase in viscosity thereof when the ink is being concentrated by evaporation of water from the ink, and is excellent in rub fastness when printed on a low-water absorbing recording medium.

An ink composition includes water, a co-solvent, a colorant, and a modified polymer or copolymer additive. The modified polymer or copolymer additive is selected from the group consisting of i) a hydrolyzed poly(isobutylene-alt-maleic anhydride), ii) a hydrolyzed poly(maleic anhydride-alt-1-octadecene), and iii) a modified polymer or copolymer. The modified polymer or copolymer includes a repeating unit of a backbone chain, and a long chain pendant group attached to a carbon atom of the repeating unit. In the backbone chain, the long chain pendant group of the repeating unit is separated by fewer than 8 spacer carbon atoms from another long chain pendant group of an adjacent repeating unit.

An ink composition includes water, a co-solvent, a colorant, and a modified polymer or copolymer additive. The modified polymer or copolymer additive is selected from the group consisting of i) a hydrolyzed poly(isobutylene-alt-maleic anhydride), ii) a hydrolyzed poly(maleic anhydride-alt-1-octadecene), and iii) a modified polymer or copolymer. The modified polymer or copolymer includes a repeating unit of a backbone chain, and a long chain pendant group attached to a carbon atom of the repeating unit. In the backbone chain, the long chain pendant group of the repeating unit is separated by fewer than 8 spacer carbon atoms from another long chain pendant group of an adjacent repeating unit.

Provided is a method for producing an aqueous pigment dispersion including a step of dispersing a mixture containing a pigment, an anionic group-containing organic polymer compound, a basic compound, and from 1% to 500% by mass of alkylene oxide adduct having a polyamine structure with respect to the pigment into water. The step of dispersing includes Step 1 of kneading a mixture which contains a pigment, an anionic group-containing organic polymer compound, a basic compound, and from 1% to 500% by mass of alkylene oxide adduct having a polyamine structure with respect to the pigment, and which contains no water or water equal to or less than 30% by mass with respect to a solid content thereof, and Step 2 of dispersing a kneaded material obtained in Step 1 into water.

Provided is a method for producing an aqueous pigment dispersion including a step of dispersing a mixture containing a pigment, an anionic group-containing organic polymer compound, a basic compound, and from 1% to 500% by mass of alkylene oxide adduct having a polyamine structure with respect to the pigment into water. The step of dispersing includes Step 1 of kneading a mixture which contains a pigment, an anionic group-containing organic polymer compound, a basic compound, and from 1% to 500% by mass of alkylene oxide adduct having a polyamine structure with respect to the pigment, and which contains no water or water equal to or less than 30% by mass with respect to a solid content thereof, and Step 2 of dispersing a kneaded material obtained in Step 1 into water.

The present disclosure is drawn to a fluid set for inkjet imaging which includes a white inkjet ink and a fixer fluid. The white ink can include an aqueous ink vehicle, from 5 wt % to 50 wt % of a white metal oxide pigment having an average particulate size from 100 nm to 2,000 nm, and from 0.1 wt % to 4 wt % of anionic oxide particulates having an average particulate size from 1 nm to 100 nm. The white ink can also include a non-ionic or predominantly non-ionic dispersant having an acid number not higher than 100 mg KOH/g based on dry polymer weight. The fixer fluid can include an aqueous fixer vehicle and from 0.1 wt % to 25 wt % cationic polymer.

The present disclosure is drawn to a fluid set for inkjet imaging which includes a white inkjet ink and a fixer fluid. The white ink can include an aqueous ink vehicle, from 5 wt % to 50 wt % of a white metal oxide pigment having an average particulate size from 100 nm to 2,000 nm, and from 0.1 wt % to 4 wt % of anionic oxide particulates having an average particulate size from 1 nm to 100 nm. The white ink can also include a non-ionic or predominantly non-ionic dispersant having an acid number not higher than 100 mg KOH/g based on dry polymer weight. The fixer fluid can include an aqueous fixer vehicle and from 0.1 wt % to 25 wt % cationic polymer.

A method of synthesis of two-dimensional (2D) nanoflakes comprises the cutting of prefabricated nanoparticles. The method allows high control over the shape, size and composition of the 2D nanoflakes, and can be used to produce material with uniform properties in large quantities. Van der Waals heterostructure devices are prepared by fabricating nanoparticles, chemically cutting the nanoparticles to form nanoflakes, dispersing the nanoflakes in a solvent to form an ink, and depositing the ink to form a thin film.