Process for filtering polymer melts with dead spot reduction

摘要

A process for filtering polymer melt which minimizes the generation of dead zones in the filter and provides uniform residence time and accurate temperature control. The process is carried out in an apparatus comprising a plurality of heat exchanger pipes, each enclosing a filter cartridge surrounded by an annular space which terminates at its upper end in a plurality of narrow channels. The molten polymer is charged into the annular space and divided into primary and secondary streams. The primary stream flows through the filter cartridge and the secondary stream, which constitutes 0.03 to 3.0 weight percent of the weight of the combined streams, flows through the narrow channels, whereupon the streams are combined and discharged from the apparatus. The discharge temperature of the polymer is maintained within +/-1 DEG C. of the charging temperature and the heat exchanger fluid enters the apparatus at a temperature within 1 DEG and 5 DEG C. of the temperature of the melt.