Careful temperature control
In the past, single screw extruder has been common to extrude hygroscopic, synthetic resins, such as ABS (acrylonitrile-butadiene-styrene resins), into finished products. However, such extrusion has in the past been preceded by a dehumidifying procedure in which the hygroscopic resins are pre-dried for several hours. When the dehumidifyed resins are extruded through a single vented extruder, a finished product substantially free of pock marks, dimples, streaks, surface roughness, and poor gloss results. A good dehumidification system is not only expensive but also requires a substantial electrical power supply. In addition, the systems occupy valuable floor area in manufacturing operations.
The invention relates generally to sheet production extruder and methods of extruding hygroscopic synthetic resinous materials. More particularly, the invention is concerned with a rotary screw extruder and a method which devolatilize and dry hygroscopic synthetic resinous materials while the materials are extruded into a finished product thereby eliminating a preliminary dehumidification of the material.
When the hygroscopic resinous material is dehumidified in a hopper dryer, the temperature must be carefully controlled to prevent overheating. Even with careful temperature control, experience has shown an occasional batch of material will become overheated and fuse together causing both loss of time and waste of material.