Technology, processing screw extrusion

With the pressurized hydrolysis technology, water under high temperature and high pressure is applied to hydrolyze and break the crosslinks of the paint film, and then a kneading extruder is used to convert the decomposed film into particles and disperse them in the TP resin. Two types of the processing system have been developed. One is the autoclave reaction and screw extrusion processing system (batch system), and the other is the twin screw reactive extrusion processing system (continuous system). 

Integrated extrusion processes [8] provide for the production of composite materials which use the intrinsic properties of the plastics recyclate, or other waste as a compounding additive, to add value to the composite based on a matrix of virgin or recycled plastic. The method is based on modified twin-screw extrusion technology requiring assembly of well-defined process steps, which conditions the additive phase, prior to its incorporation into the polymeric matrix. Hence in the early stages of the process only the additive is present, which is then combined with the polymer further downstream. This concept is the inverse of conventional extrusion compounding procedures. 

API material characterization before manufacturing for potential impact assessment. Process understanding and evaluation of specialized technologies [twin-screw wet granulation (TSWG), extrusion, solid dispersion, etc.] for long-term resolution... 

Reactive extruders and extrusion dies of different designs can be easily included in standard technological scheme of polymer production plants, such as those for polycaproamide synthesis, as shown in Fig. 4.39. In this case, a reactive material premixed in a tank 1 is fed into a static device 2 for prepolymerization, where part of the polymerization process takes place. Then the reactive mixture enters the extruder-reactor 3. The necessary temperature distribution is maintained along the extruder. Transfer of the reactive mass proceeds by a system of two coaxial screws mounted in series in a common barrel. Controlling the relative rotation speed of both screws provides the necessary residence time for the reactive mass in the extrader, so that the material reaching the outlet section of the die is a finished polymer. 

Basic types of extruders include both screw extruders such as axial endplate, radial screen, and basket designs, as well as pelletization equipment described above, such as rotary cylinder or gear and ram or piston extruders (Fig. 21-136). See Newton [Powder Technology ana Pharm. Processes, Chulia et al. (eds.), Elsevier, 1994, p. 391]> Pietsch (Size Enlargement by Ag omeraUon, Wiley, 1992), and Benbow and Bridgwater (Paste Flow and Extrusion, Oxford University Press, 1993). 

Extruders are thermomechanical mixers that consist of one or more screws in a barrel. Extrusion technology was initially applied in the plastics processing area, and after years of development and application, it has become a well-elaborated tool with technical solutions available for other fields like the pharmaceutical industry (for the production of controlled-release formulations). 

The extrusion of PVC is a field well adapted to use of microwave technology. Use of the chemically polar basic polymer means that microwave absorption within the polymer is possible. Nonpolar polyolefins, on the other hand, cannot be heated directly by microwaves. Since, however, the counter-rotating twin-screw extruders used in PVC extrusion process practically nothing besides PVC, use of the micro-wave does not amount to a loss of flexibility as far as the range of materials an aggregate is designed to handle. 

---