A polymer based on a dicarboxylic acid and {HEAD ~ a diamine} is prepared by polycondensation in {TAIL ~ an extruder}, by 
A polymer based on a dicarboxylic acid and { HEAD ~ a diamine } is prepared by polycondensation in { TAIL ~ an extruder } , by
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH