| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a pigment for a water-base ink and a water-base ink excellent in dispersion stability, suppressed in the plugging of nozzles and penpoints and having excellent delivery stability by oxidizing carbon black with ozone in the presence of water containing an organic acid in a specified concentration or higher. SOLUTION: The carbon black used may be anything that can be used as a pigment for an ink and desirably has a particle diameter of 30nm or below, a total content of alkali metals and alkaline earth metals of 0.5wt.% and contents of sulfur or sulfur compounds and chlorine compounds of 0.1wt.% or below in terms of a total sulfur analysis and a total chlorine analysis. The carbon black to be oxidized may be one treated with nitric acid or a vapor- phase ozone before it is oxidized with ozone in the presence of water. The weight ratio of the carbon black to the water is desirably 50:50 to 2:98. The amount of the ozone used can be reduced and the oxidation time can be shortened by adding an organic acid to the water to give a concentration of 0.001 N or above. The organic acids used are fatty acids, dicarboxylic acids and oxy acids.</p> |
