NOVELTY - Asymmetric dianhydride and aromatic diamine (II) are introduced into an extruder (100) at its throat (140), and melt-mixed for predetermined time in at least one mixing zone to thoroughly blend them together. Endcap chosen from 4-phenylethynylphthalic anhydride and cis-5-norbornene-endo-2,3-dicarboxylic anhydride is introduced into the extruder at a zone downstream (150) from the throat and the mixing zone, and melt-mixed for predetermined time in at least one mixing zone to permit reaction to form low-melt viscosity imide oligomer. The imide oligomer is extruded from the extruder.    USE - Manufacture of low-melt viscosity imide oligomer for composite e.g. airframe component, engine component, aircraft, missile, radome, rocket, high temperature laminate, electrical transformer, engine bushing, engine bearing, oil drilling equipment, oil drilling riser, automotive chassis bearing, and films for use in electronics, fuel cells and batteries (all claimed).    ADVANTAGE - The low-melt viscosity imide oligomer is continuously manufactured.    DETAILED DESCRIPTION - Stoichiometric amount of asymmetric dianhydride of formula (I) and aromatic diamine of formula (II) are introduced into an extruder at its throat, and melt-mixed for predetermined time in at least one mixing zone in the absence of solvent to thoroughly blend them together. Endcap chosen from 4-phenylethynylphthalic anhydride and cis-5-norbornene-endo-2,3-dicarboxylic anhydride is introduced into the extruder at a zone downstream from the throat and the mixing zone, and melt-mixed for predetermined time in at least one mixing zone to permit reaction to form low-melt viscosity imide oligomer. The imide oligomer is extruded from the extruder.    X=optionally C=O, -CH2 or oxygen;and    Y'=aromatic group of formula (a)-(d).    An INDEPENDENT CLAIM is included for composite.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view illustrating reactive extrusion method.    Extruder (100)    Source of power (120)    Heated zone (130)    Throat (140)    Zone downstream (150)