Process for ambient temperature grinding of soft polymers

摘要

Soft and tacky polymers can be ground at ambient temperature in the presence of a grinding aid in an atttrition mill having counter-rotating grinding elements operated above a minimum tip speed (170 m/sec) and at a throughput of more than about 90 kg/hr, the amount of grinding aid, which can be either organic or inorganic such as calcium carbonate, being about 5-20% based on the weight of polymer. The mill temperature is adjusted so that nearly all of the grinding aid is retained on the softened polymer particles, thus improving polymer flow and reducing to a minimum the amount of loose grinding aid to be disposed of. Air is drawn through the mill to serve as the material carrier medium and at the same time to cool the mill, if required. However, a portion of the exiting air can be recirculated to the mill to increase the temperature, if needed.