| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain the subject carbon black capable of retaining a good dispersion stability to an aqueous medium and providing a water-based ink with no nozzle cloggings and a coating material without a generation of stripes or spittings, by oxidation treatment of carbon black containing a specific quantity of carbonaceous minute foreign matter. SOLUTION: The subject carbon black is obtained by oxidation treatment of carbon black (A) containing not more than 50 pieces/visual field of spherical carbonaceous minute foreign matter, preferably not more than 30 pieces/visual field. The oxidation treatment is performed, for example, by mixing A with water (B) in the weight ratio of A:B so as to be (95:5) to (0.5:99.5), preferably (50:50) to (2:98), and passing ozone or an ozone-containing gas through the mixture until the quantity of the total acid group comes to 3μequ./m<2> or more, preferably 6μequ./m<2> or more.</p> |
