PHENOL-FORMALDEHYDE NOVOLAC RESIN HAVING LOW CONCENTRATION OF FREE PHENOL

摘要

A phenol-formaldehyde de novolac resin having a low concentration of free phenol prepared by distilling residual phenol from a molten novolac resin a nd replacing at least a portion of the phenol with a solvent having a volati lity equal to or less than phenol. Such modified novolac resins are suitable for the production of resin coated molding sands for shell molding and sand cores, as well as for the production of resin coated proppants for use in o il and gas recovery operations.