Multiple screw extruder implemented with vacuum vent and screws configured to densify, or extract fluid from, material processed by the extruder

A method of forming, at a high rate of throughput, a compound including polymeric material and particulate filler material mixed by operation of a thermally controlled extruder without appreciable vacuum vent removal of the particulate filler material from the extruder, the extruder including multiple concatenated barrel segments defining a longitudinal axis and multiple rotatable extruder screws configured to mix material introduced into the extruder, comprising:

• introducing polymeric material in a first feed location associated with a first opening formed in a first barrel segment of the extruder, the polymeric material processed by rotation of the multiple extruder screws to form a flow of molten polymeric material, a section of each of the multiple extruder screws having lengthwise mixing elements, and the sections of the multiple extruder screws functioning as a filter zone;
• introducing particulate filler material in a second feed location associated with a second opening formed in a second barrel segment of the extruder, the second barrel segment being positioned downstream of the first barrel segment so that the multiple extruder screws mix the particulate filler material with the flow of molten polymeric material;
• and
• applying vacuum to a vacuum vent associated with a vent opening in a third barrel segment that is positioned between the first and second feed locations, the mixing elements functioning as a filter zone being located between the vacuum vent and the second opening associated with the second feed location, and the mixing elements of the filter zone cooperating to allow the flow of molten polymeric material to move along the longitudinal axis of the extruder and prevent the vacuum from drawing through the vacuum vent an appreciable amount of the particulate filler material introduced at the second feed location and to extract air present in the filter zone to thereby perform significant densification of the particulate filler as the multiple extruder screws rotate to form a compound including the densified particulate filler material mixed with the flow of molten polymeric material.

A method of extracting unwanted fluid present during operation of a thermally controlled extruder forming a compound by mixing polymeric material with added material, the extruder including multiple concatenated barrel segments defining a longitudinal axis and multiple rotatable extruder screws configured to mix material introduced into the extruder, comprising:

• introducing a first amount of polymeric material in a first feed location associated with a first opening formed in a first barrel segment of the extruder, the first amount of polymeric material processed by rotation of the multiple extruder screws to form a flow of molten polymeric material;
• introducing a second amount of polymeric material or a combination of added material and a second amount of polymeric material in a second feed location associated with a second opening formed in a second barrel segment of the extruder, the second barrel segment being positioned downstream of the first barrel segment so that the multiple extruder screws mix the second amount of polymeric material or the combination of the added material and the second amount of polymeric material with the flow of molten polymeric material;
• and
• applying vacuum to a vacuum vent associated with a vent opening in a third barrel segment that is positioned between the first and second feed locations, each of the multiple extruder screws having a first polymer flow sealing zone section located between the first barrel segment and the vent opening in the third barrel segment, a filter zone section located between the vacuum vent and the second opening associated with the second feed location, and a second polymer flow sealing zone section located downstream of the second opening associated with the second feed location, the first polymer flow sealing zone sections, the filter zone sections, and the second polymer flow sealing zone sections of the multiple extruder screws functioning as, respectively, a first polymer flow sealing zone, a filter zone, and a second polymer flow sealing zone, the filter zone including lengthwise mixing elements that allow the flow of molten polymeric material to move along the longitudinal axis of the extruder, prevent the vacuum from drawing through the vacuum vent an appreciable amount of any added material introduced at the second feed location, and allow the vacuum to extract through the vacuum vent unwanted fluid present between the first and second polymer flow sealing zones, and the first and second polymer flow sealing zones preventing loss of vacuum resulting from air entering the extruder from locations other than the second feed location.