The above 2-fluoro-6-halophenols can be obtained through sulfonation reaction, halogenation reaction and deprotective reaction from 2-fluorophenol as a starting material.

When the sulfonating reaction is finished, the raw materials or wood chips are defibrated in a defibrating unit known per se and are crushed down to a preselected fineness degree.

The reactor surface is provided with sufficient length to subject the film to contact with the high velocity gaseous mixture for sufficient time to produce a sulfonation reaction product which is greater than about 85 % by weight completely reacted.