Synthetic reaction of rosin-modified phenolic resin for offset inks

The synthetic reaction of rosin-modified phenolic resin used as a vehicle for offset inks was studied. The two-step synthetic process to feed resol by dropping was adopted to control the formation of methylene quinone, which was derived from the dehydration of hydroxymethyl phenol. The methylene quinone could react with rosin and vegetable oil to form dibenzopyran cyclic product by Diels-Alder reaction. The dibenzopyran cyclic product was favourable for raising the molecular weight and the mineral oil tolerance of the modified resin.