Conversion of Acid Dyes to Cationic Dyes for Printing Inks
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Cationic dyes have the desirable property of an affinity for typical mineral sizings found in many papers which renders the cationic dye-sizing interaction product rather intractable. This results in improved waterfastness and even print quality. However, these cationic dyes are, unfortunately, not readily available. A simple, 2-step procedure is now described which converts an existing sulfonated or carboxylated acid anionic dye, to a cationic dye via a sulfonyl chloride followed by treatment with an amine. This conversion is attractive since there are many acid dyes, they come in all colors, they are very well known, and the sulfonate and usually the carboxylate do not influence the chromophore to a large extent so that their conversions should not drastically alter the original color.