Kao Corporation

Toshiya Iwasaki

Tsuyoshi Oda

Shuichi Abe

Koji Kamei

Yusuke Shimizu

Ryuma Mizushima

Takehiro Tsutsumi

Koji Azuma

Hirotaka Takeno

Takahiro Sato

Hiroyuki Yoshida

Masayuki Narita

Toshiyuki Matsumoto

Yoshio Koga

The present invention relates to [1] a process for producing a pigment composition, including the step of subjecting a raw material pigment composition containing PY74 and a specific by-product to a treatment with an oxidizing agent, in which a content of the specific by-product in the pigment composition after the treatment on the basis of a content of PY74 in the pigment composition after the treatment is not more than 1,200 mg/kg; [2] a process for producing a pigment composition, including the step of subjecting a raw material pigment composition containing PY74, a specific by-product and water to a treatment with hydrogen peroxide; [3] a method of reducing a content of a specific by-product in a raw material pigment composition containing PY74 and the specific by-product, said method including the step of subjecting the raw material pigment composition to a treatment with an oxidizing agent; and [4] a method of preventing an ink for ink-jet printing from suffering from ejection defects, including the step of compounding the pigment composition produced by any of the aforementioned processes in the ink for ink-jet printing.

Pigment composition production method

The present invention relates to [1] a process for producing a pigment composition, including the step of subjecting a raw material pigment composition containing C.I. Pigment Yellow 74, a specific by-product and water to heat treatment at a temperature of from 160 to 210&#xb0; C.; and [2] a method of reducing a content of a by-product in a raw material pigment composition containing C.I. Pigment Yellow 74, the specific by-product and water, said method including the step of subjecting the raw material pigment composition to heat treatment at a temperature of from 160 to 210&#xb0; C.

The first invention relates to a water-based ink for ink-jet printing which includes colorant-containing polymer particles (A) obtained by dispersing a colorant with a water-soluble polymer (x) and a water-insoluble polymer (y), a water-soluble organic solvent (B) and water, wherein a weight ratio of the water-insoluble polymer (y) to the water-soluble polymer (x) [(y)/(x)] is from 2.0 to 5.0, and a content of the water-soluble organic solvent (B) in the ink is from 10 to 70% by weight. The water-based ink for ink-jet printing according to the first invention is excellent in ejection property and optical density and exhibits a low viscosity. The second invention relates to a process for producing a water dispersion for ink-jet printing, which includes a step (I) of mixing a dispersion of a colorant with an emulsion of a water-insoluble polymer containing an organic solvent; a step (II) of subjecting the resulting mixture to dispersing treatment to obtain a dispersion of the colorant onto which the water-insoluble polymer is deposited; and a step (III) of removing the organic solvent from the resulting dispersion. The water dispersion produced by the process of the second invention is capable of exhibiting a high optical density suitable for high-speed printing.

Water-based ink for inkjet printing

The present invention relates to a process for producing a water-based pigment dispersion which includes a first step of mixing (A) an emulsion composition including a water-insoluble polymer having a specific weight-average molecular weight and containing a salt-forming group, an organic solvent having a specific solubility in water, a neutralizing agent and water, with (B) a pigment to obtain a preliminary dispersion having a content of non-volatile components of from 5 to 50% by weight and a weight ratio of the organic solvent to water [organic solvent/water] of from 0.1 to 0.9; a second step of continuously dispersing the preliminary dispersion by using a media-type dispersing device and continuously separating the resultant dispersion from media particles; and a third step of further dispersing the resultant dispersion by using a homogenizer, as well as a water-based ink for ink-jet printing containing the water-based pigment dispersion which not only satisfies a high optical density but also exhibits excellent gloss and rubbing resistance.

Process for producing aqueous pigment dispersion

The invention provides a process for producing a water dispersion for ink jet recording,which comprises the following steps 1 and 2:

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Wakayama, Japan

Toshiya Iwasaki