Phenol formaldehyde resins, their manufacture and use

摘要

Low molecular weight liquid phenol formaldehyde resins and processes for producing them are described. Preferred products are used as foundry binders and are made by forming a low molecular weight liquid novolak, removing free phenol while retaining a low molecular weight, and reacting with additional formaldehyde in the presence of an alkaline catalyst under conditions that yield a low molecular weight.