Coextrusion of polystyrene and polysulfones

Claim 1

A PROCESS FOR THE MANUFACTURE OF COMPOSIT SHEETING HAVING A MAJOR BASE LAYER OF POLYSTYRENE AND AT LEAST ONE RELATIVELY THIN SURFACE LAYER OF POLYSULFONE PLYMER ADHERED THERETO, COMPRISIN EXTRUDING A HEAT PLASTIFIED STREAM OF POLYSTYRENE AT A TEMPERATURE OF FROM ABOUT 440*F. TO ABOUT 480*F., EXTRUDING A HEAT PLASTIFIED STREAM OF POLYSULFONE POLYME AT A TEMPERATURE OF FROM ABOUT 540*F. TO ABOUT 565*F., CONVEYING SAID HEAT PLASTIFIED STREAM OF STYRENE POLYME IN A CONDUIT HAVING A GENERAL CIRCULAR CROSS-SECTION, JOINING TO THE EXTERIOR SURFACE TO SAID STYRENE POLYMER STREAM WITHIN SAID CONDUIT SAID HEAT PLASTIFIED STREAM OF POLYSULFONE POLYMER, THETEBY FORMING A SINGLE STRATIFIED STREAM OF HEAT PLASTIFIED MATERIALS CONFORMING TO THE CROSS-SECTION OF SAID CONDUIT AND BEING CHARACTERIZED BY DISTINCT, CONTIGUOUS LAYERS OF SAID TWO POLYMERIC MATERIALS HAVING A RELATIVELY SHAPLY DEFINED INTERFACE THEREBETWEEN, SAID INTERFACE TERMINATING AT EACH END AT A POINT ON THE INSIDE SURFACE OF SAID CONDUIT, THE RELATIVVE VOLUMETRIC PROPORTION OF THE POLYSULFONE POLYMER IN SAID STRATIFIED STREAM BEING LESS THAN ABOUT 20 PERCENT BASED UPON THE TOTAL POLYMERIC MATERIAL, AND PASSING SAID STRATIFIED STREAM OF HEAT PLASTIFIED MATERIAL THROUGH A SHEET-FORM EXTRUSION DIE, SAID DIE HAVING A DIE ORIFICE WIDTH SUBSTANTIALLY GREATER THAN THE DIAMETER OF SAID CONDUIT AND HAVING ITS DIE LIPS GENERALLY TRANSVERSELY ALIGNED WITH SAID INTERFACE BETWEEN THE TWO POLYMERIC MATERIALS.