Apparatus for extruding thermoplastic compositions

An apparatus for extruding a thermoplastic resinous composition, comprising:

• an extruder for heat plastifying the thermoplastic resinous composition and forwarding same in an extrusion direction;
• means, positioned downstream of said extruder and communicating with the outlet port of said extruder for cooling the heat plastified thermoplastic resinous composition exiting from said extruder to a uniform temperature desired for extrusion through an extrusion die, said cooling means including at least one enclosed flow path for conveying the heat plastified thermoplastic resinous composition from the inlet of said cooling means to the outlet of said cooling means, means for circulating a cooling medium about the entire circumference of each said resin flow path and means for maintaining a hydraulic balance between the inlet and the outlet of said cooling means across the entire cross-section of each said resin flow path;
• and
• an extrusion die, including a die orifice positioned downstream of said cooling means and communicating with the outlet of said cooling means for receiving cooled, heat plastified thermoplastic resinous composition therefrom for extrusion through the die orifice, said cooling means comprising a substantially cylindrical vessel having three generally concentrically arranged axial passageways, wherein said enclosed flow path comprises the middle passageway and wherein said cooling medium circulating means comprises the inner and outer passageways and wherein said hydraulic balance maintaining means comprises a plurality of first apertures evenly spaced about the circumference of the inlet end of said middle passageway and a plurality of second apertures evenly spaced about the circumference of the outlet end of said middle passageway, said second apertures being sized in relationship to said first apertures so as to maintain said hydraulic balance.