Catalysis of novolacs by p‐phenolsulfonic acid

The reaction rate of phenol and aqueous formaldehyde in the presence of p‐phenolsulfonic acid has been studied. The increase in pH during the reaction, which decreases the reaction rate, can be correlated with the disappearance of polyoxymethylene (formaldehyde), but not as previously supposed solely with the dilution effect of the water formed from the reaction. Gel‐permeation chromatography was used to monitor the consumption of phenol and the growth of polymeric species. It has been demonstrated that the formation of a second liquid phase during the novolac process is independent of the amount of catalyst. The liquid two‐phase system and its relation to the reaction rate have been examined. The final molecular weight distribution of novolacs is dependent not only on the initial pH of the system, but also on the pH at the onset of devolatilization.