Melt-processible, thermoplastic random copolyimides having recoverable crystallinity and associated processes

A process of preparing a melt processible polyimide composition by melt polymerization comprising the steps of:

• (a) blending, to substantial homogeneity, components comprising:
• (I) 93 to 98 mole parts of an aromatic dianhydride component consisting essentially of 3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA);
• (II) 100 mole parts of an aromatic diamine component consisting essentially of:
• (A) a first aromatic diamine selected from the group consisting of 1,3-bis(4-aminophenoxy)benzene (APB-134) and 3,4′-oxydianiline (3,4′-ODA);
• (B) a second aromatic diamine selected from the group consisting of 1,3-bis(4-aminophenoxy)benzene (APB-1 34), 3,4′-oxydianiline (3,4′-ODA), 1,3-bis(3-aminophenoxy)benzene (APB-133), 4,4′-oxydianiline (4,4′-ODA), 1,4-bis(4-aminophenoxy)benzene (APB-144), 1,3-diaminobenzene (MPD), 4,4′,bis(4-aminophenoxy)diphenyl sulfone (BAPS), 4,4′-bis(4-aminophenoxy)-biphenyl (BAPB), 2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP), bis(4-[4-aminophenoxy]phenyl ether (BAPE), 4,4′-oxydianiline (4,4′-ODA) and 1,3-diaminobenzene (MPD) in combination, and 4,4′-oxydianiline (4,4′-ODA) and 1,4-diaminobenzene (PPD) in combination;
• with the proviso that the second diamine is not the same as the first diamine;
• and
• (III) 4 to 14 mole parts of at least one endcapping component;
• the components (I), (II) and (III) being in substantially solventless form and the blending step producing a substantially solventless component blend;
• the blending step being carried out at a temperature below the melting point of any of components (I), (II) and (III);
• the component (I) and (II) being present in the component blend in a molar ratio of (I):(II) from 0.93 to 0.98;
• the component (III) being present in the component blend in a molar ratio (III):(II) of 0.04 to 0.14;
• (b) heating the substantially solventless component blend produced in step (a) to a predetermined melt processing temperature at which the (I) aromatic dianhydride component and the (II) aromatic diamine component are melted and will react to form a melt of a polyimide;
• the predetermined melt processing temperature being less than the temperature at which the polyimide melt chemically decomposes;
• (c) mixing the component blend and the polyimide melt produced therefrom during said heating step (b);
• (d) removing water of reaction from the component blend and the polyimide melt produced therefrom during the heating step (b);
• (e) forming the polyimide melt into an article having predetermined shape;
• and
• (f) cooling the article having predetermined shape to ambient temperature;
• wherein the polyimide exhibits a melting point in the range of 330° C. to 385° C., and the polyimide exhibits recoverable crystallinity as determined by DSC analysis.