Phenol-aldehyde condensation prod. for use as foundry binder resin

摘要

The binder (I) is prepd. by condensing in aq. medium phenol and an aldehyde in molar ratio 1:0.9-2.0 in presence of divalent metal ions as catalyst. The mixt. is made alkaline as soon as content of free formaldehyde falls below 15 wt.%, then condensation is terminated when content of free formaldehyde falls below 3 wt.%, on wt. of reaction mixt. - Pref. molar ratio phenol:HCHO is 1:1-1.5. First stage is carried out at 90-100 deg.C. 0.2-1g.mol. catalyst/mol. phenol is used. Free HCHO content is reduced in second stage to 0.7-1.5 wt.%.