Abstract: A process for the manufacture of rubber process aids from blends of vulcanized rubber powders, virgin polymers and thermoplastic resins. The process is carried out in a single stage using an extruder. The extruder is fed in three sections with feed hoppers. Vulcanized rubber powder of selected origin is fed into the hopper in the first section with part of the thermoplastic resin and oxidizing agents. The balance of the thermoplastic resin is fed in the second section. Virgin polymer is fed into the hopper in the third section. The temperature of the extruder is controlled and dwell time of the material passing through each of the extruder's sections is adjusted to ensure adequate mixing of all the polymers whereby a reactive rubber process aid in free flowing particulates is produced that acts as an excellent process aid in rubber processing.