An improved extruder apparatus is disclosed and which includes a cylindrical barrel having a feed end and a discharge end, the feed end having an inlet in fluid communication with a hopper. The extruder screw is mounted in the cylindrical barrel, and the screw has an outer surface having one or more helical flights mounted thereon. wherein the inlet end of the cylindrical barrel has a support frame mounted thereto, wherein an upper surface of the support frame is connected to a throat of a hopper, wherein an insert is mounted to the support frame and has a lower end which extends down into the cylindrical barrel, wherein the insert has an internal passageway having a first opening on the lower end and a second opening upstream of the screw for relieving the pressure.

Plasiticized polyvinylacetal films with greater film-to-film uniformity are produced by a process of extruding a melt stream containing a polyvinyl acetal and a plasticizer at 150-250 C., the film having a predefined melt viscosity at 60-170 C., by providing a first melt stream of at least a first plasticizer and a first polyvinyl acetal resin and measuring its melt viscosity at 60-170 C. online; and adjusting the 60-170 C. melt viscosity by adding a second plasticizer and/or a second polyvinyl acetal resin to the first melt stream in an amount to provide a second melt stream with a melt viscosity at 60-170 C. having a difference of at most 20% to the predefined melt viscosity at 60-170 C.

Plasiticized polyvinylacetal films with greater film-to-film uniformity are produced by a process of extruding a melt stream containing a polyvinyl acetal and a plasticizer at 150-250 C., the film having a predefined melt viscosity at 60-170 C., by providing a first melt stream of at least a first plasticizer and a first polyvinyl acetal resin and measuring its melt viscosity at 60-170 C. online; and adjusting the 60-170 C. melt viscosity by adding a second plasticizer and/or a second polyvinyl acetal resin to the first melt stream in an amount to provide a second melt stream with a melt viscosity at 60-170 C. having a difference of at most 20% to the predefined melt viscosity at 60-170 C.

Plasiticized polyvinylacetal films with grater film-to-film uniformity are produced by a process of extruding a melt stream containing a polyvinyl acetal and a plasticizer at 150-250 C., the film having a predefined melt viscosity at 60-170 C., by providing a first melt stream of at least a first plasticizer and a first polyvinyl acetal resin and measuring its melt viscosity at 60-170 C. online; and adjusting the 60-170 C. melt viscosity by adding a second plasticizer and/or a second polyvinyl acetal resin to the first melt stream in an amount to provide a second melt stream with a melt viscosity at 60-170 C. having a difference of at most 20% to the predefined melt viscosity at 60-170 C.

A device for influencing the volume flow of extruded plastically deformable material conveyed to an outlet nozzle. A flange arranged between an extrusion unit and an outlet nozzle and is connected to the extrusion unit and the outlet nozzle. A duct from the extrusion unit and the outlet nozzle is incorporated in the flange. A piston is mounted in the flange to be rotatable perpendicular to the longitudinal axis of the duct and is located through the duct. In the piston there is a hole which opens into a bypass duct routed to a bypass nozzle. On the outer lateral surface of the piston there is at least one groove in the region of the duct so that, depending on the angular positions of the piston, material can be conveyed through the at least one groove to the outlet nozzle or through the hole to the bypass nozzle.

An extrusion foaming device uses pressurized working fluid as a self-sealing medium between a foaming extruder and an extrusion screw transport section in a feed tube. Shaft diameter of the extrusion screw increases in a compression section such that material therein is compressed. Material from a foaming extruder is split between the compression and transport sections and a bypass valve connected to both sections allows adjustment of pressure in the compression section and the valve. Keeping pressure above saturation pressure of a dissolved supercritical fluid in the working fluid inhibits precipitation thereof and intrusion of precipitate into the extrusion section.

An extrusion foaming device uses pressurized working fluid as a self-sealing medium between a foaming extruder and an extrusion screw transport section in a feed tube. Shaft diameter of the extrusion screw increases in a compression section such that material therein is compressed. Material from a foaming extruder is split between the compression and transport sections and a bypass valve connected to both sections allows adjustment of pressure in the compression section and the valve. Keeping pressure above saturation pressure of a dissolved supercritical fluid in the working fluid inhibits precipitation thereof and intrusion of precipitate into the extrusion section.