Four components for description of twin screw extruder
The expression “Twin Screw Extruder” means components to be added to Single Screw Extruderand gear pump kneaded into an aromatic polycarbonate obtained by polymerization to produce a polymer suitable for obtaining a molded product of the aromatic polycarbonate. The components include (a) a compound which is chemically bonded to the main chain of the polymer, such as a terminal OH group capping agent, (b) a compound which acts on a component contained in the polymer other than a polymer to reduce, deactivate or change the function of the component, such as a catalyst deactivator, (c) a compound which is added to assist the removal of relatively volatile components such as an eliminated component (sheet production extruder)(d) resin additives which are added to improve the moldability of the aromatic polycarbonate and the physical and chemical properties of a molded product. These components will be described here inunder.
(a) Terminal OH Group Capping Agent
The produced aromatic polycarbonate has an aromatic hydroxyl group or its derivative group derived from an aromatic diol compound which uses as a monomer in the melt polycondonsation. This terminal OH as exemplified by the derivatives of aliphatic aryl carboxylates and aromatic aryl carboxylates and the derivatives of aliphatic aryl carbonates and aromatic aryl carbonates such as methoxycarbonyl phenyl phenyl carbonate and ethoxycarbonyl phenyl phenyl carbonate.
(b) Catalyst Deactivator
When a catalyst used for polymerization is contained in the aromatic polycarbonate while it retains its activity, it exerts an influence upon heat stability, color stability and hydrolysis resistance. Therefore, it is preferred to deactivate the residual polymerization catalyst.
(c) Devolatilizing Agent
Illustrative examples of the devolatilizing agent include water, nitrogen gas, the above saturated aliphatic hydrocarbon and the above aromatic hydrocarbon. Out of these, water is economically advantageous and particularly preferred.
Preferably, water used as the devolatilizing agent contains substantially no metal ions or chlorine ions. Stated more specifically, ion exchange water and distilled water are preferred.
(d) Resin Additives
The resin additives are added to the aromatic polycarbonate for specific purposes. The resin additives include, for example, a thermal stabilizer, optical stabilizer, epoxy compound, ultraviolet absorber, , inorganic filler and the like. Illustrative examples of these additives are given below.
Illustrative examples of the thermal stabilizer include phosphorus compounds, phenol-based stabilizers, organicTwin Screw Extruder abilizers, hindered amine-based stabilizers and the like.