Novolak-Based Polyether Polyols

Novolaks are condensation products of formaldehyde with phenols, obtained by acidic catalysis (usually oxalic acid [27])  

Characteristic Unit Mannich base from phenol Mannich base from nonyl phenol 

The linkages between the aromatic nuclei are in the ortho and para positions. The novolak resins are amorphous solids which become liquid at 50-80 °C, depending on the value of n. 

By the propoxylation of novolaks in the presence of alkaline catalysts (KOH, NaOH) or better, in the presence of a low hindered tertiary amine, aromatic polyether polyols of the following structure are obtained [27, 28] (15.25)  

By the propoxylation of commercial novolaks, lower viscosities of around 3 phenolic units/mol are obtained. Novolaks with higher degrees of condensation (4-6 or more phenolic units/mol) have very high viscosities. 

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