Method for producing rosin modified phenolic resin for offset printing ink, gel varnish for offset printing ink, and offset printing ink

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a rosin-modified phenolic resin for an offset printing ink, in which the rosin-modified phenolic resin has a high molecular weight and excellent solubility in an aliphatic hydrocarbon solvent, and can improve glossiness and emulsifiability while maintaining misting resistance and low tackiness of the offset printing ink.SOLUTION: Rosins (A) obtained by heat-treating raw material rosin in the presence of a sulfonic acid catalyst (B) is reacted with an alkylphenol formaldehyde condensate (C), in which a ratio of the total amount of the palustric acid, abietic acid, and neoabietic acid contained in the rosins (A) to the total amount of the palustric acid, abietic acid, and neoabietic acid contained in the raw material rosin is 88% or more, and the rosins (A) contain 5 to 12% of a component having a molecular weight of 199 or less, and 4 to 6% of a component having a molecular weight of 401 to 2000, subsequently the resulting reactant is used to carry out esterification reaction with polyols (D) to obtain a rosin modified phenolic resin for offset printing ink.SELECTED DRAWING: None