Para-toluolsulfonic acid

Organic sulfonic acid which is used as a hardener for furan resin and phenol cold-hardening resin binders.

This hardener contains sulfur which gets into the mold material if used sand regeneration is insufficient and can accumulate there when it used repeatedly.

Due to this, mainly in cast iron materials with nodular graphite and vermicular graphite in the rim zone of the casting, graphite degeneration (rim zone graphite degeneration) may develop which then has a disruptive effect on the dynamic properties.

Additional references:
No-bake process