PROCESS FOR PRODUCING INK COMPOSITION FOR OFFSET PRINTING, AND INK COMPOSITION FOR OFFSET PRINTING PRODUCED BY SAID PRODUCTION PROCESS

摘要

The present invention aims to provide a method of producing an ink composition for offset printing, which can improve the productivity of inks considerably, and in which the printing quality of printed substances obtained in using the foregoing ink composition for offset printing for sheet-fed printing is equal to or higher than that of printed substances obtained with the acid powder carbon black, while using the acid carbon black, particularly an acid bead carbon black. The present invention pertains to a method of producing an ink composition for offset printing, including the steps of wetting 100 parts by mass of an acid carbon black having a pH value of 2.0 to 6.0 with 25 to 400 parts by mass of a wetting agent containing at least water, using an oil-based varnish for a printing ink containing an alkyd resin having an acid value of 30 KOH mg/g or less to perform flushing of the wetted acid bead carbon black, and then removing the wetting agent.