Melt polymerization method for making polyetherimides

Claim 1

In an extrusion melt polymerization method for making polyetherimides wherein a reaction mixture containing as essential ingredients (I) an organic diamine of the formula, H.sub.2 NR.sup.1 NH.sub.2 and (II) an aromatic bis(ether anhydride) of the formula, ##STR9## and (I) is present in an amount of 0.5 to 2.0 moles per mole of (II), is continuously fed through an inlet opening into a screw extruder having a barrel maintained at melt polymerization temperatures and water of reaction is continuously vented from the extruder, where R is a divalent aromatic organic radical having from 6 to 30 carbon atoms, R 1 is a divalent organic radical selected from the group consisting of said R radicals, alkylene radicals having from 2 to about 20 carbon atoms, cycloalkylene radicals, and C.sub.(2-8) alkylene terminated polydiorganosiloxane radicals, the improvement comprising: (A) using a screw extruder having a second opening through the extruder wall and having an outlet orifice, said second opening being in a second barrel zone intermediate said inlet opening and said orifice, said second barrel zone being maintained at melt polymerization temperature; (B) continuously conveying the reaction mixture through a first barrel zone maintained at a temperature below the melting point of the lowest melting essential ingredient, said first barrel zone extending from said inlet opening to said second barrel zone; and (C) continuously venting water of reaction at a temperature of up to 400° C through said second opening while continuously feeding reaction mixture through said inlet opening.