PREPARATION METHOD OF HIGH VISCOELASTIC GEL VARNISH FOR PRINTING INK

摘要

PROBLEM TO BE SOLVED: To provide a method for preparing efficiently a high viscoelastic gel varnish excellent in suitability for a high-speed printing.

SOLUTION: The preparation method of the high viscoelastic gel varnish for a printing ink comprises the step (A) wherein a phenol formaldehyde precondensation product (resol condensate) and a rosin ester are reacted at 100-250°C in a system containing an ink solvent or a system further containing a drying oil and the like to prepare a resin varnish; the step (B) wherein the above resin varnish is mixed with a gelatinizing agent and the like to make a gel varnish; and the step (C) wherein the above gel varnish is allowed to again react with the resol condensate and the amount used of the resol condensate in this step is 5-30 wt.% against that of the step (A). By adding the resol condensate in portions in the two stages of the initial step (A) and the re-addition step (C), it is possible to promote making the gel varnish highly viscoelastic and to prepare the printing ink superior in suitability for high-speed printing.

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