A process for the production of phenol-modified aromatic hydrocarbon-formaldehyde resins having low viscosity

there is provided a process for the preparation of a phenol-modified aromatic hydrocarbon formaldehyde resin of low viscosity (C) which includes performing a condensation reaction with an aromatic hydrocarbon-formaldehyde resin (A) and a phenol (B) in the presence of an acid catalyst , The method includes: terminating the condensation reaction, if a reaction mixture having a viscosity at 25 ° C from 200 to 1500 mPa.s, by adding an inorganic basic compound and / or a tertiary amine compound having a boiling point of 300 ° C or more ; and distilling and removing the unreacted phenol (B) and a low boiling component after completion of the condensation reaction, whereby a phenol-modified aromatic hydrocarbon formaldehyde resin of low viscosity can be produced, which remains in the liquid state and contains small amount of the unreacted phenols, and wherein the increase in viscosity even after removal of low boiling components is small.