Extruder History

Single-screw extruders were introduced to the plastics and rubber industries in the 1870s. They were presumably used for compounding from the time of their introduction. Single-screw extrusion technology has been reviewed in the monographs of Schenkel and Herrmann.

Originally screw extruders were simply used as pumps. However, in the second decade of the 20th century, there were efforts to use single-screw extruders as continuous mixing machines. In later patents of the 1920s and 1930s, notably by Gordon and Royle, this trend became clear. Here, serrated barrels are introduced to aid the mixing process notably for rubber and its compounds. Thermoplastics became increasingly important in the post-World War II period. This led to a range of new single-screw mixers. Some of these machines involve special mixing sections at specific positions on the screw (see, for example, Figure 4a). Other machines contain pins in their barrels which approach the screw flights, which have been cut to introduce slices to allow the pins passage. Still other machines contained a threaded barrel into which the screw penetrates (transfer mix). In List's mixing machine (Buss Ko-Kneader) one has both pins inserted through the barrel and an imposed axial reciprocating motion (Figure 4b).

Figure 4. Single-screw mixers: (a) Dalmadge mixing screw;47 (b) List’s Buss Ko-Kneader