Anhydrous process for the preparation of expandable particulate styrene polymers

Claim 1

PROCESS FOR THE PREPARATION OF EXPANDABLE PARTICULATE STYRENE POLYMER WHICH COMPRISES COATING THE PARTICULATE STYRENE POLYMER WITH A FINELY DIVIDED, INORGANIC, ANHYDROUS SILICEOUS MATERIAL HAVING A PARTICLE SIZE LESS THAN ABOUT 150 MICRONS, REDUCING THE AMBIENT PRESSURE ON THE COATED PARTICULATE POLYMER TO SUBSTANTIALLY BELOW ATMOSPHERIC, ADMIXING A LOW BOILING LIQUID HYDROCARBON NONSOLVENT FOR THE STYRENE POLYMER HAVING A BOILING POINT BELOW THE SOFTENING TEMPERATURE OF THE STYRENE POLYMER WITH THE COATED PARTICULATE POLYMER UNDER ANHYDROUS CONDITIONS, HEATING THE RESULTING MIXTURE TO A TEMPERATURE BETWEEN ABOUT 35*C. AND 65*C., BUT BELOW THAT TEMPERATURE WHICH CAUSES PARTICLE AGGLOMERATION WHILE MAINTAINING SAID HEATED MIXTURE UNDER A PRESSURE OF FROM ABOUT 30 TO 60 POUNDS PER SQUARE INCH UNTIL AT LEAST ABOUT 1 PERCENT LIQUID HYDROCARBON HAS BEEN DIFFUSED INTO THE PARTICULATE POLYMER, AND THEREAFTER REMOVING THE EXCESS HYDROCARBON AND RECOVERING THE EXPANDABLE PARTICULATE STYRENE POLYMER.