Method for preparing polyimide and polyimide prepared thereby
View Patent ↗A method for preparing a polyimide includes introducing a mixture of an oligomer and a solvent to an extruder, removing solvent via at least one extruder vent, and melt kneading the oligomer to form a polyimide. The polyimide has a low residual solvent content. The method is faster than solution polymerization of polyimides, and it avoids the stoichiometric inaccuracies associated with reactive extrusion processes that use monomers as starting materials.
1. A method of preparing a polyimide, comprising:
introducing to an extruder an oligomer mixture comprising a solvent and an oligomer formed by the reaction of a dianhydride compound and a diamine compound;
removing solvent from the oligomer mixture via a vent in the extruder; and
melt kneading the oligomer to form a polyimide.
2. The method of claim 1 , wherein the oligomer mixture is an oligomer solution.
3. The method of claim 1 , wherein the oligomer comprises amic acid repeating units having the structure
wherein V is a tetravalent linker selected from (a) substituted or unsubstituted, saturated, unsaturated or aromatic monocyclic and polycyclic groups having about 5 to about 50 carbon atoms, (b) substituted or unsubstituted, linear or branched, saturated or unsaturated alkyl groups having 1 to about 30 carbon atoms, and (c) combinations thereof, wherein the substitutions arc ethers, epoxides, amides, esters, or combinations thereof; and
R is a substituted or unsubstituted divalent organic radical selected from (a) aromatic hydrocarbon radicals having about 6 to about 20 carbon atoms or halogenated derivatives thereof, (b) straight or branched chain alkylene radicals having about 2 to about 20 carbon atoms; (c) cycloalkylene radicals having about 3 to about 20 carbon atoms, and (d) divalent radicals of the general formula
wherein Q is a divalent moiety selected from —O—, —S—, —C(O)—, —SO 2 —, C y H 2y —, and halogenated derivatives thereof, wherein y is an integer from 1 to 5.
4. The method of claim 3 , wherein the oligomer further comprises at least one imidized repeating unit having a structure selected from
5. The method of claim 4 , wherein the oligomer comprises a number average of at least three repeating units.
6. The method or claim 1 , wherein the oligomer comprises repeating units baying the structure
7. The method of claim 1 , wherein the oligomer comprises repeating units having the structure
8. The method of claim 1 , wherein the oligomer is formed from co-oligomerization of at least three monomers selected from bisphenol A dianhydride, 4,4′-oxy-diphthalic anhydride, meta-phenylenediamine, and diaminodiphenylsulfone.
9. The method of claim 1 , wherein the oligomer has a weight average molecular weight of about 5,000 to about 40,000 atomic mass units.
10. The method of claim 1 , wherein the oligomer mixture comprises about 5 to about 90 weight percent of the oligomer.
11. The method of claim 1 , wherein the solvent is selected from halogenated aromatic solvents, halogenated aliphatic solvents, non-halogenated aromatic solvents, non-halogenated aliphatic solvents, and mixtures thereof.
12. The method of claim 1 , wherein the solvent comprises a halogenated aromatic solvent.
13. The method of claim 1 , wherein the solvent comprises ortho-dichlorobenzene.
14. The method of claim 1 , wherein the oligomer mixture comprises about 10 to about 95 weight percent of the solvent.
15. The method of claim 1 , wherein the polyimide comprises repeating units having the structure
wherein V is a tetravalent linker selected from (a) substituted or unsubstituted, saturated, unsaturated or aromatic monocyclic and polycyclic groups having about 5 to about 50 carbon atoms, (b) substituted or unsubstituted, linear or branched, saturated or unsaturated alkyl groups having 1 to about 30 carbon atoms, and (c) combinations thereof, wherein the substitutions are ethers, epoxides, amides, esters, or combinations thereof; and
R is a substituted or unsubstituted divalent organic radical selected from (a) aromatic hydrocarbon radicals having about 6 to about 20 carbon atoms or halogenated derivatives thereof, (b) straight or branched chain alkylene radicals having about 2 to about 20 carbon atoms; (c) cycloalkylene radicals having about 3 to about 20 carbon atoms, and (d) divalent radicals of the general formula
wherein Q is a divalent moiety selected from —O—, —S—, —C(O)—, —SO 2 —, C y H 2y —, and halogenated derivatives thereof, wherein y is an integer from 1 to 5.
16. The method of claim 1 , wherein the polyimide is a polyetherimide.
17. The method of claim 1 , wherein the polyimide is a polyetherimide comprising repeating units having the structure
18. The method of claim 1 , wherein the polyimide is a polyetherimide comprising repeating units having the structure
19. The method of claim 1 , wherein the polyimide comprises a number average of repeating units at least two units greater than the number average of repeating units in the oligomer.
20. The method of claim 1 , wherein the polyimide comprises a number average of repeating units at least 1.2 times greater than the number average of repeating units in the oligomer.
21. The method of claim 1 , wherein the polyimide has a weight average molecular weight greater than 30,000 to about 80,000.
22. The method of claim 1 , wherein the ratio of the polyimide weight average molecular weight to the oligomer weight average molecular weight is about 1.2 to about 10.
23. The method of claim 1 , wherein the polyimide has a polydispersity index less than 4.
24. The method of claim 1 , wherein the polyimide comprises less than 1,000 parts per million by weight of residual solvent.
25. The method of claim 1 , wherein the polyimide comprises less than one mole percent of unreacted anhydride end groups.
26. The method of claim 1 , wherein the polyimide comprises less than one mole percent of unreacted amine end groups.
27. The method of claim 1 , wherein the oligomer mixture is superheated when it is introduced to the extruder.
28. The method of claim 1 , wherein the oligomer mixture is introduced to the extruder via a feed inlet in fluid communication with the extruder.
29. The method of claim 28 , wherein the vent is positioned upstream from the feed inlet.
30. The method of claim 28 , wherein the feed inlet comprises a pressure control valve.
31. The method of claim 30 , wherein the pressure control valve has a cracking pressure of about 0.07 kgf/cm 2 to about 25 kgf/cm 2 .
32. The method of claim 28 , wherein the oligomer mixture is introduced to the extruder via a feed inlet positioned on a side feeder attached to the extruder.
33. The method of claim 1 , wherein the vent is positioned on a side feeder attached to the extruder.
34. The method of claim 1 , wherein melt kneading the oligomer comprises melt kneading at a barrel temperature in the range of about 280 to about 400° C.
35. The method of claim 1 , wherein the extruder is a twin-screw counter-rotating extruder, a twin-screw co-rotating extruder, a single-screw extruder, or a single-screw reciprocating extruder.
36. The method of claim 1 , characterized by a ratio of oligomer mixture introduction rate, in kilograms per hour, to extruder screw speed, in rotations per minute, of about 0.005 to about 50.
37. The method of claim 1 , further comprising removing solvent from the oligomer mixture before introducing it to the extruder.
38. The method of claim 1 , further comprising adding a dianhydride compound and/or a diamine compound to the oligomer mixture prior to introducing the oligomer mixture to the extruder.
39. The method of claim 1 , further comprising adding a stripping agent to the extruder.
40. The method of claim 1 , further comprising adding nitrogen to the extruder.
41. The method of claim 1 , further comprising melt filtering the polyimide.
42. The method of claim 1 , further comprising filtering the oligomer mixture prior to introducing it to the extruder.
43. The method of claim 1 , farther comprising adding to the extruder, downstream from oligomer mixture introduction, a polymer selected from polycarbonates, poly(arylene ether)s, polyesters, polysulfones, polyetherketone, polyolefin, polysiloxane, poly(alkenyl aromatic)s, liquid crystalline polymers, and mixtures thereof.
44. The method of claim 43 , wherein the polymer is added in the form of a polymer mixture comprising the polymer and a solvent.
45. The method of claim 1 , further comprising adding to the extruder, downstream from oligomer mixture introduction, a pigment, additive, process aid, conductive filler, non-conductive filler, fibrous filler, or mixture thereof.
46. The method of claim 1 , further comprising introducing the polyimide into a second extruder.
47. A method of preparing a polyimide, comprising:
introducing to an extruder an oligomer mixture comprising an oligomer and a solvent, wherein the oligomer mixture is superheated;
removing solvent from the oligomer mixture via a vent upstream from oligomer mixture introduction and a vent downstream from oligomer mixture introduction; and
melt kneading the oligomer to form a polyetherimide.
48. The method of claim 47 , wherein said removing solvent from the oligomer mixture comprises removing solvent via at least two vents downstream from solution introduction.
49. The method of claim 47 , wherein the vent upstream from oligomer mixture introduction is maintained at a pressure in the range of about 10 to about 760 millimeters of mercury.
50. The method of claim 47 , wherein the vent downstream from oligomer mixture introduction is maintained at a pressure of about 10 to about 500 millimeters of mercury.
51. A method of preparing a polyetherimide, comprising:
introducing to an extruder an oligomer mixture comprising an oligomer and a solvent, wherein the oligomer is formed by the reaction of bisphenol A dianhydride and meta-phenylenediamine, wherein the solvent comprises ortho-dichlorobenzene, and wherein the oligomer mixture is superheated;
removing solvent from the oligomer mixture via a vent upstream from oligomer mixture introduction, at least one vent downstream from oligomer mixture introduction, and at least one vent still further downstream from oligomer mixture introduction; wherein the vent upstream from oligomer mixture introduction is maintained at a pressure in the range of about 10 to about 760 millimeters of mercury, the vent downstream from oligomer mixture introduction is maintained at a pressure of about 250 to about 500 millimeters of mercury, and the vent still further down stream from oligomer mixture introduction is maintained at a pressure of about 10 to about 100 millimeters of mercury; and
melt kneading the oligomer to form a polyetherimide comprising less than 1000 parts per million by weight of residual solvent.
52. A method of preparing a polyimide, comprising:
reacting a dianhydride compound and a diamine compound in the presence of a solvent to form an oligomer mixture comprising an oligomer and a solvent;
introducing the oligomer mixture to an extruder;
removing solvent from the oligomer mixture via a vent in the extruder; and
melt kneading the oligomer to form a polyimide.
53. A polyimide prepared according to the method of claim 1 .
54. A polyimide prepared according to the method of claim 47 .
55. A polyimide prepared according to the method of claim 51 .
56. A polyimide prepared according to the method of claim 52 .