MELT-PROCESSABLE POLYIMIDES WITH HIGH GLASS TRANSITION TEMPERATURE

Abstract

The present invention relates to novel, melt-processable polyimides that shows a high glass transition temperature, a process for preparing these polyimides and also the use of the new polyimides

Claims

1-14. (canceled)

15. A polyimide comprising building units (A) and (B) having the structures (Ia) and (Ib): ##STR00065## wherein R.sub.1 comprises in total >50 mol % of: ##STR00066## with X being selected from the group consisting of: X.sub.1, X.sub.2, X.sub.3, X.sub.4 and mixtures thereof: ##STR00067## R.sub.2 is ##STR00068## R.sub.3 comprises in total >50 mol % of: ##STR00069## with Y being selected from the group consisting of Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 and mixtures thereof: ##STR00070## and wherein R.sub.4 comprises in total >50 mol % of R.sub.4a, R.sub.4b, R.sub.4c, R.sub.4d and mixtures thereof. ##STR00071## and wherein R.sub.1 and R.sub.3 may be identical or different; m=1 to 1000; n=1 to 1000; wherein the molar ratio of R.sub.2 to the sum of all R.sub.4 units is from 0.99:0.01 to 0.75:0.25; and wherein the polyimide comprises end-capping units bound to free amino group of the polymer.

16. The polyimide of claim 15, wherein m=10 to 40.

17. The polyimide of claim 16, wherein n=1 to 40.

18. The polyimide of claim 17, wherein the molar ratio of R.sub.2 to the sum of all R.sub.4 units is in a range of 0.95:0.05 to 0.80.

19. The polyimide of claim 15, wherein X=X.sub.1 or X.sub.2 or a mixture of X.sub.1 and X.sub.2, and/or Y=Y.sub.1 or Y.sub.2 or a mixture of Y.sub.1 and Y.sub.2, and/or R.sub.4 comprises R.sub.4c and/or R.sub.4d.

20. The polyimide of claim 15, wherein X=X.sub.2 and/or Y=Y.sub.2 and/or R.sub.4 comprises R.sub.4c and/or R.sub.4d.

21. The polyimide of claim 15, wherein the end-capping units are mono-functional anhydride monomers without crosslinking functionality, and the sum of all anhydride functionalities is stochiometrically balanced with the sum of all amine functionalities.

22. The polyimide of claim 15, wherein the end-capping units are mono-functional anhydride monomers selected from the group consisting of: succinic anhydride; and phthalic anhydride and its derivatives according to the following structure: ##STR00072## wherein two or three or all four of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be identical or all four of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be different and are selected from the group consisting of H, methyl, ethyl, tert-butyl and phenyl, and mixtures thereof.

23. The polyimide of claim 15, wherein said polyimide is a random copolymer, and wherein m and n are in the following ranges: m=1 to 500; n=1 to 200; or said polyimide is a block-co-polymer, wherein n and m of blocks (A) and (B) are each from 1 to 1000.

24. The polyimide of claim 23, wherein said polyimide is a random copolymer, and wherein: m=10 to 40; and n=1 to 20.

25. The polyimide of claim 15, wherein the molecular weight M.sub.n of the polyimide, as determined by gel permeation chromatography based on polystyrene standards, is from 10 000 to 200 000 g/mol, and/or the molecular weight M.sub.w of the polyimide, as determined by gel permeation chromatography based on polystyrene standards, is 15 000 to 200 000 g/mol, and/or the polydispersity index D is from 1 to 10.

26. The polyimide of claim 25, wherein the molecular weight M.sub.n of the polyimide, as determined by gel permeation chromatography based on polystyrene standards, is 20 000 to 50 000 g/mol; and/or the molecular weight M.sub.w of the polyimide, as determined by gel permeation chromatography based on polystyrene standards, is 1.4 to 2.

27. The polyimide of claims 15, wherein R.sub.1 comprises >50 mol %, of: ##STR00073## with X being selected from the group consisting of X.sub.1, X.sub.2, X.sub.3, X.sub.4 and mixtures thereof, and/or R.sub.3 consists in total of >50 mol %, of: ##STR00074## with Y being selected from the group consisting of Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 and mixtures thereof, and/or R.sub.4 consists in total to >50 mol %, of R.sub.4a, R.sub.4b, R.sub.4c, R.sub.4d and mixtures thereof.

28. The polyimide according of claim 15, wherein the polyimide comprises one or more additives selected from the group consisting of lubricants, polymer stabilizers, sterically hindered amines and phosphite esters.

29. A process for preparing the polyimide of claim 15, comprising: a) contacting one or more dianhydride(s) correlating to R.sub.1 with 4,4-diaminodiphenylsulphone and one or more diamines correlating to R.sub.4 and, if R.sub.1 is different from R.sub.3, one or more dianhydride(s) as defined by R.sub.3, to form a polyamic acid; b) performing an imidization of the polyamic acid obtained in step a); and wherein the molar ratio of 4,4-diaminodiphenylsulphone to the sum of the diamines correlating with R.sub.4 is from 0.99:0.01 to 0.75:0.25; and wherein an end-capping unit that reacts with a free amino group of the polymer before or during step a).

30. The process of claim 29, wherein, end-capping units comprise a mono-functional anhydride monomer without crosslinking functionality.

31. The process of claim 30, wherein the sum of all anhydride moieties added in step a) is stoichiometric or under stoichiometric to the sum of amine moieties added in step a).

32. The process of claim 29, wherein, in step a), the diamine components are heated to the reaction temperature and the di- and, if present, mono-anhydride components are added to the diamine components during heating or after the reaction temperature is reached, and/or in step a), the diamine components are dissolved in an aprotic dipolar solvent or a mixture of aprotic dipolar solvents or a mixture of solvents comprising an aprotic dipolar solvent, before the di- and if present mono-anhydride components are added to the diamine components, and/or step a) is carried out under water free conditions and/or inert atmosphere, and/or the reaction temperature in step a) is of from 0 to 40? C.

33. The process of claim 29, wherein the imidization in step b) is performed thermally or chemically or by precipitation imidization or by a combination of these methods.

34. The process of claim 29, comprising additional step c), isolating the polyimide and optionally: d) grinding of the polyimide obtained in step b) or c); and/or e) heating the polyimide to a temperature above its T.sub.G, under reduced pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1: Comparison of the melt viscosity of IPI 14-IP 8 containing TPEQ as diamine with PEEK and Aurum.

[0025] FIG. 2: Comparison of the melt viscosity of IPI 10-IPI 13 containing BDA as diamine with PEEK and Aurum.

[0026] FIG. 3: Comparison of the melt viscosity of IPI 14-IPI 17 containing RODA as diamine with PEEK and Aurum.

[0027] FIG. 4: Comparison of the melt viscosity of IPI 18-IPI 19 containing BABI as diamine with Aurum

[0028] FIG. 5: Pictures of IPI 17 after extrusion for MFI measurement.

[0029] FIG. 6: TGA curve of CPI 10 under N.sub.2.

[0030] FIG. 7: TGA curve of IPI 6 under N.sub.2.

[0031] FIG. 8: TGA curve of IPI 9 under N.sub.2.

[0032] FIG. 9: TGA curve of IPI 12 under N.sub.2.

[0033] FIG. 10: TGA curve of IPI 17 under N.sub.2.

[0034] FIG. 11: TGA curve of IPI 18 under N.sub.2.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Before describing the invention in more details, some important terms are defined as follows:

[0036] The verb to comprise as is used in the description, examples and the claims and its conjugation is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. Comprising includes consisting of meaning that items following the word comprising, are included without any additional, not specifically mentioned items, as preferred embodiment.

[0037] Reference to an element be the indefinite article a or an does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there is one and only one of the elements. The indefinite article a or an thus usually means one or more.

[0038] Subject of the present invention are polyimides comprising building units (A) and (B) having the following structures (Ia) and (Ib)

##STR00022## [0039] wherein R.sub.1 comprises in total to an extent >50 mol % of

##STR00023## [0040] with X being selected from the group consisting of X.sub.1, X.sub.2, X.sub.3, X.sub.4 and mixtures thereof

##STR00024## [0041] and wherein R.sub.2 is

##STR00025## [0042] and wherein R.sub.3 comprises in total to an extent >50 mol % of

##STR00026## [0043] with Y being selected from the group consisting of Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 and mixtures thereof

##STR00027## [0044] and wherein R.sub.4 comprises in total to an extent >50 mol % of R.sub.4a, R.sub.4b, R.sub.4c, R.sub.4d and mixtures thereof

##STR00028## [0045] and wherein [0046] R.sub.1 and R.sub.3 may be identical or different, [0047] m=1 to 1000, preferably from 1 to 500, more preferably from 1 to 200, yet more preferably from 5 to 150, yet still more preferably from 10 to 100, yet still eve more preferably from 10 to 50 and most preferably from 10 to 40 [0048] n=1 to 1000, preferably from 1 to 500, more preferably from 1 to 200, yet more preferably from 1 to 150, yet still more preferably from 1 to 100, yet still eve more preferably from 1 to 50 and most preferably from 1 to 40, [0049] and wherein [0050] the molar ratio of R.sub.2 to the sum of all R.sub.4 units is in a range of from [0051] 0.99:0.01 to 0.75:0.25 if R.sub.4 is R.sub.4a or R.sub.4b or R.sub.4c or a mixture of two to four monomers selected from the group consisting of R.sub.4a, R.sub.4b, R.sub.4c and R.sub.4d, [0052] or [0053] 0.99:0.01 to 0.8:0.2 if R.sub.4 is R.sub.4d [0054] and wherein [0055] the polyimide comprises end-capping units bound to free amino group of the polymer .

[0056] As will be demonstrated in the examples below the molar ratio of the stiff monomer R.sub.2 to the flexible monomer R.sub.4 has strong impact on the glass transition temperature of the polyimides. If the content of the stiff polymer R.sub.2 is below 75% in combination with R.sub.4a or R.sub.4b or R.sub.4c respectively below 80 mol % in combination with R.sub.4d, the T.sub.g value of the polyimides decreases below 290? C. On the other hand, if no flexible monomer is present the resulting polyimides lack melt processability. Meaning the molar ratio of R.sub.2 to the sum of all R.sub.4 units can be varied in a range of from [0057] 0.99:0.01 to 0.75:0.25 to obtain inventive polyimides if R.sub.4 is R.sub.4a or R.sub.4b or R.sub.4c or a mixture of two to four monomers selected from the group consisting of R.sub.4a, R.sub.4b, R.sub.4c and R.sub.4d, [0058] or [0059] in a range of from 0.99:0.01 to 0.8:0.2, if R.sub.4 is R.sub.4d.

[0060] Appropriate combination will be chosen by a man skilled in the art depending on the desired glass transition temperature of the resulting polyimide. Preferred molar ratios of R.sub.2 to the sum of all R.sub.4 units are in a range of from, [0061] 0.98:0.02 to 0.78:0.22 and more preferred of from 0.95:0.05 to 0.80:0.20 if R.sub.4 is R.sub.4a or R.sub.4b or R.sub.4c or a mixture of two to four monomers selected from the group consisting of R.sub.4a, R.sub.4b, R.sub.4c and R.sub.4d, or [0062] 0.99:0.01 to 0.8:0.2, preferably of from 0.98:0.02 to 0.81:0.19 and more preferred of from 0.95:0.05 to 0.82:0.18 if R.sub.4 is R.sub.4d.

[0063] If R.sub.4 is R.sub.4c further preferred ranges for the molar ratio of R.sub.2 to R.sub.4c are 0.99:0.01 to 0.81:0.19, preferably of from 0.98:0.02 to 0.81:0.19 and more preferred of from 0.95:0.05 to 0.82:0.18 if R.sub.4 is R.sub.4c.

[0064] Within the group of flexible monomer units R.sub.4a to R.sub.4d it has been found that polyimides comprising R.sub.4c and/or R.sub.4d show best combinations of thermal resistance and melt processability. It is thus preferred, if R.sub.4 comprises R.sub.4c and/or R.sub.4d.

[0065] Selection of monomer units R.sub.1 has an impact on the glass transition temperature of the inventive polyimides, too. Analogue to the monomer units R.sub.2 and R.sub.4 the less flexible monomer unit R.sub.1 with X=X.sub.1 results in higher glass transition temperatures compared to more flexible monomer unit R.sub.1 with X=X.sub.2. It is preferred, if X=comprises X.sub.1 or X.sub.2 or a mixture of X.sub.1 and X.sub.2, preferably X comprises X.sub.2.

[0066] In order to keep the complexity of the reaction and the number of monomers to be handled low, R.sub.1 and R.sub.3 are preferably identical. However, it is also possible to select R.sub.1 and R.sub.3 differently. Basically, the same principles apply to the selection of R.sub.3 as to R.sub.1. Selection of monomer units R.sub.3 has an impact on the glass transition temperature of the inventive polyimides, too. Analogue to the monomer units R.sub.2 and R.sub.4 the less flexible monomer unit R.sub.3 with Y=Y.sub.1 results in higher glass transition temperatures compared to more flexible monomer unit R.sub.3 with Y=Y.sub.2. It is preferred, if Y=comprises Y.sub.1 or Y.sub.2 or a mixture of Y.sub.1 and Y.sub.2, preferably Y comprises Y.sub.2.

[0067] R.sub.1 may comprise further monomers selected from the group consisting of 3,3,4,4-biphenyl-tetracarboxylic acid dianhydride, 2,3,3,4-biphenyl-tetracarboxylic acid dianhydride, 2,2,3,3-biphenyl-tetracarboxylic acid dianhydride, pyromellitic dianhydride, 3,4-oxxydiphthalic anhydride and mixtures thereof in sum in an amount of from 0.01 to 50 mol %, preferably of from 0.1 to 30 mol %, more preferred of from 0.01 to 30 mol %, even more preferred of from 0.5 to 20 mol %, particular preferred of from 0.5 to 10 mol % and most preferred of from 0.5 to 5 mol %. Preferably R.sub.1 comprises in total to an extent ?70 mol %, more preferred to an extent ?80 mol %, yet more preferred to an extent from 90 to 100 mol %, yet still more preferably to an extent from 95 to 100 mol % and most preferred to a 100 mol % extent of

##STR00029## [0068] with X being selected from the group consisting of X.sub.1, X.sub.2, X.sub.3, X.sub.4 and mixtures thereof, preferably X being selected from X.sub.1, X.sub.2 and mixtures thereof, more preferred X being X.sub.2.

[0069] R.sub.3 may comprise further monomers selected from the group consisting of 3,3,4,4-biphenyl-tetracarboxylic acid dianhydride, 2,3,3,4-biphenyl-tetracarboxylic acid dianhydride, 2,2,3,3-biphenyl-tetracarboxylic acid dianhydride, pyromellitic dianhydride, 3,4-oxxydiphthalic anhydride and mixtures thereof in sum in an amount of from 0.01 to 50 mol %, preferably of from 0.1 to 30 mol %, more preferred of from 0.01 to 30 mol %, even more preferred of from 0.5 to 20 mol %, particular preferred of from 0.5 to 10 mol % and most preferred of from 0.5 to 5 mol %. Preferably R.sub.3 comprises in total to an extent ?70 mol %, more preferred to an extent ?80 mol %, yet more preferred to an extent from 90 to 100 mol %, yet still more preferred to an extent from 95 to 100 mol % and most preferred to a 100 mol % extent of

##STR00030##

[0070] with Y being selected from the group consisting of Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 and mixtures thereof, preferably Y being selected from Y.sub.1, Y.sub.2 and mixtures thereof, more preferred Y being Y.sub.2.

[0071] Preferably R.sub.4 comprises in total to an extent ?65 mol %, preferably to an extent ?80 mol %, more preferably to an extent from 90 to 100 mol %, yet more preferably to an extent from 95 to 100 mol % and most preferably to a 100 mol % extent of R.sub.4a, R.sub.4b, R.sub.4c, R.sub.4d and mixtures thereof, preferably R.sub.4c, R.sub.4d and mixtures thereof, more preferred of R.sub.4c. The remaining R.sub.4 up to 100 mol % are preferably divalent spacers derived from diamines, preferably the spacers different from R.sub.4a, R.sub.4b, R.sub.4c and R.sub.4d comprise aromatic units, more preferred are selected from the group consisting of R.sub.4e, R.sub.4f, R.sub.4g and R.sub.4h, with the formula

##STR00031## [0072] and divalent spacers derived from ether-linked aromatic diamines different from R.sub.4a, R.sub.4b, R.sub.4c and R.sub.4d.

[0073] The polyimide polymers of the invention may be random copolymers, meaning all monomers are mixed before polymerization is started and polymer chains without predefined monomer order are obtained. In this case m and n are preferably in the following ranges [0074] m=1 to 500, preferably from 1 to 200, yet more preferably from 1 to 150, yet still more preferably from 1 to 100, yet still eve more preferably from 5 to 50 and most preferably from 10 to 40 [0075] n=1 to 200, preferably from 1 to 150, more preferably from 1 to 100, yet more preferably from 1 to 50, yet still more preferably 1 to 40 and most preferably from 1 to 20,

[0076] It is, however, also possible to prepare block-co-polymer, wherein the building units (A) and (B) each are building blocks (A) and (B) and wherein the block lengths n and m of blocks (A) and (B) are each from 1 to 1000, preferably from 1 to 500, more preferably from 1 to 200, yet more preferably from 5 to 150, yet still more preferably from 10 to 100, yet still even more preferably from 10 to 50 and most preferably from 10 to 40.

[0077] Best mechanical properties of the inventive polyimides have been found if [0078] the molecular weight M.sub.n of the polyimide according to the invention is in the preferred range from 10 000 to 200 000 g/mol, more preferred in the range from 15 000 to 150 000 g/mol, even more preferred in the range from 15 000 to 100 000 g/mol, particular preferred in the range of from 20 000 to 75 000 g/mol and most preferred in the range from 20 000 to 50 000 g/mol, and/or [0079] if the molecular weight M.sub.w of the polyimide is in the preferred range from 15 000 to 200 000 g/mol, more preferred in the range from 20 000 to 150 000 g/mol, even more preferred in the range from 25 000 to 100 000 g/mol, particular preferred in the range of from 30 000 to 95 000 g/mol and most preferred in the range from 35 000 to 90 000 g/mol.

[0080] It has been found that processability decreases if molecular weight is too high. If the molecular mass is too low brittleness of the inventive polyimides might be too high. Further benefits in terms of toughness, tensile strength and flexural strength have been found if the molecular mass is in the ranges defined above.

[0081] Most homogeneous properties of the inventive polymers have been found if polydispersity index D is of from 1 to 10, preferably 1.1 to 5, more preferably 1.2 to 4, yet more preferably 1.3 to 3 and most preferably 1.4 to 2.4. If the molecular mass distribution is smaller, a more homogeneous melt behavior was observed.

[0082] It has been found that inventive polymer produced from the building units (A) and (B) are melt processable, in particular are injection moldable, and have a T.sub.g>290? C. It has further been found that the melt viscosity of polymers comprising building units (A) and (B) but not end-cappers increases if the polymers are repeatedly melted or if the polymers are kept in melt over a longer period of time. Without being bond to any theory this behavior might be a result of the presence of active end groups in the polymer. Active end groups may be free amine moieties that were not reacted during polymerization or imidization. A temperature increase during melt processing induces a reaction of these end groups which seems to cause an increase of the viscosity. The more often the polymers are melted, the higher the melt viscosity is until all reactive groups have reacted.

[0083] To allow repeated heating of the inventive polymers or if heating over a very long period of time is needed, inventors have found out that increase of the melt viscosity of the inventive polymers can be avoided if the active end groups are capped with end-cappers. The end cappers are preferably mono-functional anhydrides that are added during or after polymerization to react with free amino groups of the polymer, i.e. free amine moieties that were not reacted during the PAA formation and cap these groups so that they are no longer reactive if the polymer is heat treated. The inventive polyimides thus comprise end-capping units bound to free amino group of the polymer, preferred end-capping units are mono-functional anhydride monomers without crosslinking functionality, more preferred mono-functional anhydride monomers selected from the group consisting of succinic anhydride, phthalic anhydride and its derivatives according to the following structure

##STR00032## [0084] wherein two or three or all four of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be identical or all four of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be different and are preferably selected from the group consisting of H, methyl, ethyl, tert-butyl and phenyl, and mixtures thereof. The preferred mono anhydrides do not comprise crosslinking functionality to avoid increase of the melt viscosity.

[0085] As mentioned before the end-capping monomers, herein also named end-capping units or end-cappers, are preferably added during polymer synthesis. They can be added before or after addition of the dianhydride(s). More preferred the end-capping monomers are added as long as the polymer is in solution, i.e. before imidization takes place. If the end-cappers are added during polymer synthesis, it was observed that it is preferred that the amine and anhydride functionalities are stochiometrically balanced after end-capper addition. If addition of the end cappers leads to an excess of anhydride moieties, degradation of the polymer by disturbing the reaction equilibrium might be caused. This might result in a decrease of the molecular mass and the thermal stability. It is thus, preferred if the end-capper is comprised in an amount of ?0.02 mol %, preferably 0.001 to 0.015 mol % and more preferred 0.002 to 0.01 mol %. Most preferred the end-capping units is present in an amount as defined before and simultaneously the sum of all anhydride functionalities is stochiometrically balanced with the sum of all amine functionalities. Stochiometrically balanced means a mole ratio of the sum of all anhydride functionalities to the sum of all amine functionalities is of from 0.9:1 to 1 to 0.9, preferably 0.95:1 to 1 to 0.95, more preferred 0.98:1 to 1 to 0.98 and most preferred 1 to 1.

[0086] The polyimides of the invention preferably comprise one or more additives selected from the group consisting of lubricants, preferably lithium stearate, graphite, metal sulfides, and polymer stabilizers, such as sterically hindered phenols or sterically hindered amines or phosphite esters.

[0087] The polyimides of the invention may be produced by a process comprising the steps [0088] a. contacting one or more dianhydride(s) correlating to R.sub.1 with 4,4-diaminodiphenylsulphone and one or more diamines correlating to R.sub.4 and, if R.sub.1 is different from R.sub.3. one or more dianhydride(s) correlating to R.sub.3, to form a polyamic acid. [0089] b. imidization of the polyamic acid obtained in step a, [0090] wherein the molar ratio of 4,4-diaminodiphenylsulphone to the sum of the diamines correlating to R.sub.4 is in a range of from [0091] 0.99:0.01 to 0.75:0.25, preferably of from 0.98:0.02 to 0.78:0.22 and more preferred of from 0.95:0.05 to 0.80:0.20 if R.sub.4 is R.sub.4a or R.sub.4b or R.sub.4c or a mixture of two to four monomers selected from the group consisting of R.sub.4a, R.sub.4b, R.sub.4c and R.sub.4d, [0092] or [0093] 0.99:0.01 to 0.8:0.2, preferably of from 0.98:0.02 to 0.81:0.19 and more preferred of from 0.95:0.05 to 0.82:0.18 if R.sub.4 is R.sub.4d. [0094] and that an end-capping unit that reacts with free amino group of the polymer is added before or during step a.

[0095] If R.sub.4 is R.sub.4c further preferred molar ratios of R.sub.2 to R.sub.4c are 0.99:0.01 to 0.81:0.19, preferably of from 0.98:0.02 to 0.81:0.19 and more preferred of from 0.95:0.05 to 0.82:0.18 if R.sub.4 is R.sub.4c.

[0096] In step a. it is preferred [0097] that the diamine components are mixed and heated to the reaction temperature and the dianhydride components are added to the diamine components during heating or after the reaction temperature is reached,
and/or [0098] that the diamine components are dissolved in an aprotic dipolar solvent or a mixtures of aprotic dipolar solvents or a mixture of solvents comprising a aprotic dipolar solvent, preferably the aprotic dipolar solvents are selected from the group consisting of sulfolane, dimethylformamide, dimethylacetamide, N-methylpyrrolidinone, N-ethylpyrrolidinone, dimethylpropionamide, tetramethylurea, dimethylsulfoxide or mixtures thereof, and the dianhydride components are added to the solution of the diamine components during heating or after the reaction temperature is reached,
and/or [0099] step a. is carried out water free conditions and/or inert atmosphere,
and/or [0100] the reaction temperature in step a) is of from 0 to 40? C., preferably 3 to 30? C., more preferred 5 to 20? C. and most preferred 10 to 15? C. Preferably the reaction solution is cooled during polymerization to control the reaction temperature and to avoid side reactions.

[0101] It is preferred to carry out step a under water free conditions and/or inert atmosphere because water may cause an imbalance in the reaction stoichiometry, which may lead to a low molecular weight. Also the dianhydride is more likely to react with water forming orthodicarboxylic acid, which is not as reactive as the anhydride group.

[0102] To reduce potential risk of side reactions, it is preferred to conduct step a by adding the dianhydride monomers to the amine monomers as described before, even more preferred the dianhydride is added step by step during polymer growth. This leads to high molecular masses.

[0103] Preferably the sum of all anhydride moieties added in step a. is stoichiometric balanced to the sum of to the amine moieties added in step a. This allows to obtain inventive polyimides with particularly high molecular mass. Stoichiometrically balanced means a mole ratio of the sum of all anhydride functionalities to the sum of all amine functionalities is of from 0.9:1 to 1 to 0.9, preferably 0.95:1 to 1 to 0.95, more preferred 0.98:1 to 1 to 0.98 and most preferred 1 to 1.

[0104] All known imidization methods can be used in step b. Preferably imidization can be affected thermally or chemically or by precipitation imidization or by combination of these methods, more preferably by heating the polyamic acid followed by colling to causes precipitation.

[0105] If step b. is carried out by chemical imidization it is preferred to affect the imidization by adding a base and a dehydrating agent to the polyamic acid, wherein the base is more preferably admixed in just a catalytic amount. It is further preferred to control the solid content of the polyamic acid solution to be in a range of from 15 to 30% by weight, more preferred 20 to 27% by weight. Even more preferred the solid content is adjusted before the base and the dehydrating agents are added. It has been found that the polyimide powder particles obtained at higher solid contents are too hard and that larger particles are obtained that melt slower than smaller particles.

[0106] For the reasons explained before the process of the invention comprises the step adding an end-capping unit that reacts with free amino group of the polymer, preferably a mono-functional anhydride monomer, more preferred a mono-functional anhydride monomer without crosslinking functionality, even more preferred a mono-functional anhydride monomer selected from the group consisting of succinic anhydride, phthalic anhydride and its derivatives according to the following structure

##STR00033## [0107] wherein two or three or all four of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be identical or all four of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be different and are preferably selected from the group consisting of H, methyl, ethyl, tert-butyl and phenyl, and mixtures thereof, before or during step a., preferably in an amount of ? 0.02 mol %, more preferred 0.001 to 0.015 mol %, even more preferred 0.002 to 0.01 mol %, most preferred the mono-functional anhydride monomer as end-capper is present in an amount as defined before and simultaneously the sum of all anhydride functionalities is stoichiometrically balanced with the sum of all amine functionalities.

[0108] It is further preferred that the process of the invention comprises an additional step c. isolating the polyimide. To remove impurities from the polyimides, it is preferred that step c. comprises the following steps, precipitating the polyimide and separating the precipitate from the solvent, more preferred followed by washing the precipitate and drying.

[0109] It has been found that a small particle size of the polyimide powder is beneficial for melt extrusion application. Smaller particles have a larger surface. A larger surface allows better heat transfer and leads to shorter melt times. It is thus, preferred that the particles having an average particle size of from 10 to 250 microns. It is further preferred to adjust the average particle size by stirring the reaction mixture during precipitation or by applying shear forces during or after precipitation.

[0110] For the reasons mentioned before it is also preferred to conduct an additional step d. grinding of the polyimide obtained in step b. or c. Step d. can be carried out as alternative to stirring or the application of shear forces or in addition to said measures.

[0111] Inventors found out that inventive polyimides may comprise impurities even if step c. is carried out. Such impurities may cause gas formation during melt processing at higher temperatures because of thermal degradation of these impurities. This effect can be beneficial if melt extruded products with a lower density are to be produced. If, however, the gas formation needs to be avoided or reduced, meaning gas forming impurities need to be removed from the inventive polyimides, this can be done in an additional step e. heating the polyimide to a temperature above its TG. It has been found that impurities can be even better removed if step e. is carried out under reduced pressure.

[0112] The inventive polyimide can be used in any typical application for high-temperature resistant polyimides, in particular in melt-extrusion, injection molding, direct forming and hot-compression molding processes, most preferably melt-extrusion and injection molding.

Methods of Measurement

[0113] TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry) measurements were carried out with a TGA TA instruments Q5000 and a DSC TA instruments Q2000 both equipped with an autosampler. The DSC measurements were carried out under nitrogen.

Determination of Glass Transition Temperature T.SUB.g .and T.SUB.m

[0114] T.sub.G and T.sub.m were measured using DSC TA instruments Q2000 both equipped with an autosampler.

Determination of Molecular Weight M.SUB.w .and M.SUB.n

[0115] Molar mass is determined by gel permeation chromatography. Calibration is against polystyrene standards. The molar masses reported are thereto formed to be understood as relative molar masses.

TABLE-US-00004 TABLE 4 Components and settings used were as follows: HPLC WATERS 600 pump, 717 autoinjector, 2487 UV detector Precolumn PSS SDV precolumn Columns PSS SDV 10 ?m 1000, 10.sup.5 and 10.sup.6 ? Mobile phase 0.01M LiBr + 0.03M H.sub.3PO.sub.4 in DMF (sterile-filtered, 0.45 ?m) Flow 1.0 ml/min Run time 45 min Pressure ~1550 psi Wavelength 270 nm (with use of UV detector) Injection volume 50 ?l or 20 ?l (for solutions c >1 g/l) Standards PS(polystyrene) standards (narrow distribution, 300-3 .Math. 10.sup.6, PSS)

Determination of Dispersity (D)

[0116] The dispersity D of the polymer is the quotient M.sub.w/M.sub.n. The molar masses are relative molar masses based on polystyrene standards.

Determination of Degree m or n of Polymerization

[0117] The degree of polymerization is a purely arithmetic quantity and is obtained from the molar ratio of the monomers used.

EXAMPLES

[0118] The examples which follow serve to provide more particular elucidation and better understanding of the present invention, but do not limit it in any way.

Monomers Used

Mono Functional Anhydride

[0119] Phthalic anhydride was obtained from TCI

Di Functional Anhydrides

[0120] BTDA: Benzophenone-3,3,4,4-tetracarboxylic dianhydride was obtained from Jayhawk Fine Chemicals Corporation

[0121] ODPA: 4,4-Oxydiphthalic anhydride was obtained from Jayhawk Fine Chemicals Corporation

[0122] 6FDA: 4,4-(hexafluoroisopropylidene)diphthalic anhydride was obtained from Daikin Chemicals

Diamines

[0123] 4,4DDS: 4,4-diaminodiphenylsulphone, obtained from TCI [0124] RODA: 1,3-Bis (4-aminophenoxy) benzene, obtained from TCI [0125] TPEQ: 1,4-bis(4-aminophenoxy)benzene, obtained from TCI [0126] BDA: 4,4-Bis(4-aminophenoxy)diphenyl ether, prepared as shown below [0127] BABI: 4,4-Bis(3-aminophenoxy) biphenyl, prepared as shown below

Synthesis of Bis[4-(4-nitrophenoxy)phenyl] ether

[0128] ##STR00034##

[0129] 4,4-oxydiphenol (9.30 g, 46.0 mmol) was dissolved in 160 mL DMAc. Then finely grinded, dry K.sub.2CO.sub.3 (14.11 g, 102.1 mmol) and 160 mL toluene were added. The suspension was stirred under argon at 135? C. for 1.5 h and then the temperature was increased to 175? C. Meanwhile water is collected via a Dean-Stark trap and removed with the toluene from the system. The dark suspension was afterwards cooled to room temperature, 1-fluoro-4-nitrobenzene (16.36 g, 115.9 mmol) was added, and the reaction mixture heated to 160? C. over night. After cooling to room temperature 400 mL water were added and the product was extracted with 400 mL DCM.

[0130] The organic phase was washed with water and dried with MgSO.sub.4. The solvent was removed, and the product recrystallized in acetone/EtOH (50/50). Drying in vacuum over CaCl.sub.2 yielded Bis[4-(4-nitrophenoxy)phenyl] ether (14.91 g, 33.56 mmol, 73%).

[0131] .sup.1H-NMR (300 MHz, CDCl.sub.3) ?/ppm: 8.22 (d, 4H, J=9.3 Hz), 7.10 (s, 8H), 7.04 (d, 4H, J=9.3 Hz). .sup.13C-NMR (75 MHz, CDCl.sub.3) ?/ppm: 163.3, 154.5, 150.3, 142.7, 126.1, 122.2, 120.5, 116.9. FT-IR v/cm.sup.?1: 3114, 1584, 1484, 1371, 1341, 1259, 1222, 1188, 1162, 1109, 950, 839, 770, 747, 684.

[0132] HRMS (ESI, positive): m/z calculated for C.sub.24H.sub.16N.sub.2O.sub.7 444.0958, found 445. 1012 [M+H].sup.+

Synthesis of 4,4-Bis(4-aminophenoxy)diphenyl ether (BDA)

[0133] ##STR00035##

[0134] Bis[4-(4-nitrophenoxy)phenyl] ether (9.33, 21.0 mmol) was dissolved in 100 mL dry THF in a hydrogenation bottle. 0.90 g (8.45 mmol) of 10% Pd/C were added and the bottle was placed in a Parr hydrogenator. 0.53 MPa H.sub.2 were adjusted, and the reaction was performed over night. Then the mixture was filtered over a celite patch, and the solvent removed. The product was recrystallized in EtOH to yield BDA as a beige solid (6.53 g, 16.99 mmol, 81%)

[0135] .sup.1H-NMR (300 MHz, CDCl.sub.3) ?/ppm: 6.91 (m, 8H), 6.87 (d, 4H, J=8.8 Hz), 6.68 (d, 4H, J=8.8 Hz), 3.56 (s, 4H).

[0136] .sup.13C-NMR (75 MHz, DMSO-d.sub.6) ?/ppm: 154.4, 151.7, 146.1, 145.3, 120.5, 119.6, 118.0, 114.8. FT-IR v/cm.sup.?1: 3559, 3385, 3315, 1879, 1615, 1489, 1322, 1275, 1191, 1098, 1009, 938, 825, 800, 747, 699.

[0137] HRMS (ESI, positive): m/z calculated for C.sub.24H.sub.20N.sub.2O.sub.3 384.1474, found 385. 1550 [M+H].sup.+

Synthesis of 4,4-Bis(3-aminophenoxy) biphenyl (BABI)

[0138] ##STR00036##

[0139] 4,4-diiodobiphenyl (7 g, 17.24 mmol), 3-aminphenol (9.03 g, 82.76 mmol), 2-picolinic acid (0.21 g, 1.72 mmol), copper(I) iodide (0.16 g, 0.86 mmol) and potassium phosphate (7.32 g, 34.48 mmol) were weighed under argon in a Schlenk tube. Dry DMSO (43 mL) was added, and the reaction mixture was stirred at 80? C. over night. The product was extracted with EtOAc and washed with water and a K.sub.2CO.sub.3 solution. The organic phase was washed with water until pH=7 was reached. After drying with MgSO.sub.4, the solvent was removed, and the obtained crude product was hot steam extracted with heptane. The precipitates from heptane as white solid, which was isolated by filtration, washed with heptane and dried in vacuum at 70? C. The obtained white solid was additionally purified by column chromatography (EtOAc/heptane).

[0140] .sup.1H-NMR (300 MHz, DMSO-d.sub.6) ?/ppm: 7.63 (d, 4H, J=8.9 Hz), 6.98-7.05 (m, 6H), 6.32-6.36 (m, 2H), 6.16-6.22 (m, 4H).

[0141] .sup.13C-NMR (75 MHz, DMSO-d.sub.6) ?/ppm: 157.5, 156.3, 150.5, 134.4, 130.1, 127.8, 118.9, 109.4, 106.0, 103.9.

[0142] FT-IR v/cm.sup.?1: 3404, 3311, 3210, 3040, 3011, 1587, 1465, 1327, 1286, 1235, 1166, 1133, 1073, 994, 962, 855, 830, 773, 685.

[0143] HRMS (ESI, positive): m/z calculated for C.sub.24H.sub.20N.sub.2O.sub.2 368.1525, found 369.1718 [M+H].sup.+

Example 1: Polyimides Without End Cap

[0144] In step a) a polyamic acid was prepared under nitrogen and by using a mechanical stirrer, by dissolving the diamines listed in Tables 6 to 11 were in DMF and adding the dianhydrides and optionally monoanhydrides listed in Tables 6 to 11 to the solution in portions and stirring the reaction mixture over night at room temperature. The monomer amount was adjusted for a 15% solid content.

[0145] In step b) imidization was achieved in three different ways, dependent on the diamine monomer used.

Thermal Imidization

[0146] For the thermal imidization a small amount of PAA was drop casted on a clean glass substrate and heat treated in an oven under air using the temperature program described in Table 5. The resulting film was removed by immersing the substrate into water.

TABLE-US-00005 TABLE 5 Temperature program applied for thermal imidization. Duration Temperature/? C. 1 h at 80 1 h at 150 over night 250

Precipitation Imidization

[0147] The imidization reaction takes place in a three-neck round bottom flask which is equipped with mechanical stirrer, a nitrogen inlet and a column, which is packed with glass Raschig Rings. A column head is placed on the top of the column for controlling solvent reflux. 200 mL DMF with 2 g (20.4 mmol) phosphoric acid were heated to reflux until constant temperature was reached. Then the PAA was added dropwise to the solvent mixture. During PAA addition, condensate was collected via the column head in the same rate as the addition of the PAA takes place. After addition was completed, the reaction mixture was refluxed for another 2 h. The resulting precipitate was filtered, washed with water and dried at 160? C. over night.

Chemical Imidization

[0148] Acetic anhydride (2.4 equ. of the amount of dianhydride) and pyridine (4.8 eq. of the amount of dianhydride) were added dropwise as a mixture to the PAA. After addition the PAA was stirred under nitrogen over night.

[0149] If a precipitate had formed, it was collected via filtration washed with 0.5 L DMF, 3 L water and 0.5 L EtOH. The polymer was dried over night in the vacuumed desiccator over CaCl.sub.2, then finely grinded and again dried in vacuum at 150? C. for three days.

[0150] If no precipitate was formed over night, the polymer was precipitated in water and finely grinded. The polymer washing and drying was performed as described previously.

[0151] The following inventive polyimides (IPI) were prepared (T.sub.ms were detected in the first run and T.sub.gs were detected in second run of the DSC measurement):

TABLE-US-00006 TABLE 6 Polyimide made from ODPA as dianhydride and TPEQ and 4,4-DDS as diamines. Table shows molar composition of the amine mix as well as SEC and DSC results for the segmented [00037] [00038] [00039] 4,4- M.sub.n/ M.sub.w/ ? T.sub.g*/ T.sub.m*/ TPEQ DDS kDa kDa ? C. ? C. CPI9 0.05 0.95 46.6 83.6 1.8 317 360 CPI10 0.1 0.9 43.9 77.5 1.8 315 361 CPI11 0.15 0.85 41.4 72.0 1.7 313 362 CPI12 0.2 0.8 40.6 70.6 1.7 304 367

Example 2: Inventive and Non-Inventive Polyimides with End Cap

[0152] Polymers were prepared as shown in Example 1 with the modification that all polymers were end-capped with, preferably an amount of 0.01 mol, phthalic anhydride (stochiometrically balanced with the dianhydride moiety), which was added during step a) to cap free amino group at the ends of the polymer chains of the polymer back bone.

[0153] The following inventive polyimides (IPI) and comparative, non-inventive polyimides (CPI) were prepared (T.sub.ms were detected in the first run and T.sub.gs were detected in second run of the DSC measurement):

TABLE-US-00007 TABLE 7 Polyimide made from ODPA as dianhydride and TPEQ and 4,4-DDS asdiamines with phthalic anhydride as endcapper. Table shows molar composition of the amine mix, amount of endcapper. [00040] [00041] [00042] [00043] End- 4,4- M.sub.n/ M.sub.w/ T.sub.g*/ T.sub.m*/ capper TPEQ DDS kDa kDa ? ? C. ? C. IPI 5 0.01 0.05 0.95 34.2 50.9 1.5 310 358 IPI 6 0.1 0.9 36.0 55.2 1.5 310 361 IPI 7 0.15 0.85 35.9 54.9 1.5 304 360 IPI 8 0.2 0.8 32.5 50.0 1.5 297 362 CPI 1 0.3 0.7 53.0 89.0 1.7 281 380 CPI 2 0.5 0.5 32.8 51.3 1.6 264 392

TABLE-US-00008 TABLE 8 Polyimide made from BTDA as dianhydride and TPEQ and 4,4-DDS as diamines with phthalic anhydride as endcapper. Table shows molar composition of the amine mix, amount of endcapper. [00044] [00045] [00046] [00047] End- 4,4- M.sub.n/ M.sub.w/ T.sub.g*/ T.sub.m*/ capper TPEQ DDS kDa kDa ? ? C. ? C. IPI9 0.01 0.1 0.9 48.5 74.4 1.5 324 348

TABLE-US-00009 TABLE 9 Polyimide made from ODPA as dianhydride and BDA and 4,4-DDS as diamines with phthalic anhydride as endcapper. Table shows molar composition of the amine mix, amount of endcapper. [00048] [00049] [00050] [00051] End- capper BDA 4,4-DDS M.sub.n/kDa M.sub.w/kDa ? T.sub.g*/? C. T.sub.m*/? C. IPI 10 0.01 0.05 0.95 27.0 43.0 1.6 315 351 IPI 11 0.1 0.9 31.0 48.0 1.5 308 344 IPI 12 0.15 0.85 31.0 47.0 1.5 314 354 IPI 13 0.2 0.8 24.0 47.0 308 358 CPI 3 0.3 0.7 37.1 55.6 1.5 269 267

TABLE-US-00010 TABLE 10 Polyimide made from ODPA as dianhydride and RODA and 4,4-DDS as diamines with phthalic anhydride as endcapper. Table shows molar composition of the amine mix, amount of endcapper. [00052] [00053] [00054] [00055] End- 4,4- M.sub.n/ M.sub.w/ T.sub.g*/ T.sub.m*/ capper RODA DDS kDa kDa ? ? C. ? C. IPI 14 0.01 0.05 0.95 30.0 46.0 1.5 314 363 IPI 15 0.1 0.9 34.2 51.3 1.5 306 386 IPI 16 0.15 0.85 32.0 51.0 1.6 297 380 IPI 17 0.2 0.8 34.0 55.0 1.6 291 387 CPI 4 0.3 0.7 26.8 50.4 1.9 281 363 CPI 5 0.5 0.5 31.0 62.3 2.0 254 243

TABLE-US-00011 TABLE 11 Polyimide made from ODPA as dianhydride and BABI and 4,4- DDS as diamines with phthalic anhydride as endcapper. Table shows molar composition of the amine mix, amount of endcapper. [00056] [00057] [00058] [00059] End- 4,4- M.sub.n/ M.sub.w/ T.sub.g*/ T.sub.m*/ capper BABI DDS kDa kDa ? ? C. ? C. IPI 18 0.01 0.1 0.9 27.7 37.8 1.4 301 337 IPI 19 0.2 0.8 29.1 42.2 1.5 290 350 CPI 6 0.25 0.75 32.0 45.2 1.4 268 CPI 7 0.3 0.7 27.5 38.5 1.4 268 271 CPI 8 0.5 0.5 33.3 48.8 1.5 247 263

[0154] The results shown in Tables 7 to 11 show that all inventive polyimides (IPI), having a content of 4,4DDS of minimum 80 mol % of the amine mix, show high thermal restistance and solve the problem of the invention to provide a T.sub.g of equal than or higher than 290? C. In contrast thereto the comparative polyimides (CPI) show that T.sub.g decreases below 290? C. if the 4,4DDS content of the amine mix is below 80 mol %. Comparison of inventive examples IPI 6 and IPI 9 shows that use of BTDA instead of ODPA leads to slightly higher T.sub.g and that the selection of the dianhydride component can be used to adapt the T.sub.g. Comparison of examples CPI 9 to 11 with inventive examples IPI 5 to 8 shows that use of an end-capper has minor effect on T.sub.g. Measurement of melt viscosity, however showed that the polyimides without end capper showed a higher viscosity in a second melt cycle compared to the first melt cycle while inventive polyimides with end-capper show consistent melt viscosities even if melted several times.

TABLE-US-00012 TABLE 12 Polyimide made from ODPA and 6FDA as dianhydrides and RODA and 4,4-DDS as diamines with phthalic anhydride as endcapper. Table 12 shows molar composition of the amine mix, amount of endcapper. [00060] [00061] [00062] [00063] [00064]

[0155] In a 500 ml flask, 29.796 g/0.12 mol of bis(4-aminophenyl) sulfone (4,4-DDS) and 8.77 g/0.03 mol of 1,3-bis(4-aminophenoxy)benzene (RODA) were dissolved in 257 g DMF. Then, 0.222 g/0.0015 mol of Phthalic anhydride, 23.033 g/0.0743 mol of 4,4-oxydiphthalic anhydride (ODPA) and 33.315 g/0,075 mol of 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were stepwise added to the cooled (15? C.) reaction solution.

[0156] Preparation of PAA as well as chemical imidization were carried out as described previously.

TABLE-US-00013 End-capper ODPA 6FDA RODA 4,4-DDS M.sub.n/kDa M.sub.w/kDa ? T.sub.g*/? C. T.sub.m*/? C. IPI20 0.01 0.495 0.5 0.2 0.8 36.6 53.0 1.45 312

[0157] Table 12 shows that it is possible to use mixed dianhydrides selected from the dianhydrides claimed in claim 1 as starting material.

TABLE-US-00014 TABLE 13 Polyimide made from ODPA as dianhydride and RODA and 4,4-DDS as diamines with increased amounts of phthalic anhydride as endcapper. IPI17 was repeated with increased amounts of endcappers. Table 13 shows molar composition of the amine mix, amount of endcapper. End- 4,4- T*.sub.g/ capper ODPA RODA DDS ? C. IPI21 0.02 0.990 0.2 0.8 292 IPI22 0.025 0.9875 0.2 0.8 290

[0158] Table 13 shows that even with increased amounts of endcappers Tg remains above 290? C.

Example 3: Rheological Measurements of the Polyimides

[0159] Rheological measurements of the comparative polyimides CPI 9 to 12 show that these polyimides are melt processable. After repeating the measurement in a second melt cycle the polymers show a higher viscosity compared to the viscosity measured in the first melt cycle but the polymers are still melt-processable. Thus, the polyimides can be used for injection molding applications if the number of melt cycles is low respectively if the melting time is short.

[0160] FIGS. 1 to 4 show that inventive polyimides IPI 5 to 8 and 10 to 19 are meltable, too. In contrast to CPI 9 to 12, no increase in the viscosity was found in these end capped polymers if viscosity measurements were repeated. Thus, the inventive polyimides, which comprise endcappers, can be used in injection molding applications with low and high number of melt cycles as well as in applications which require a longer time where the polymer is melted.

[0161] FIGS. 1 to 4 show a comparison to commercially available polymers PEEK and Aurum, which show lower melt viscosities at lower frequencies, but cannot be used in high temperature applications because of their T.sub.g of only 143? C. respectively 250? C.

Example 4: Melt Flowability

[0162] The melt flowability was determined via melt flow index (MFI) measurements. Inventive polymer IPI 17 was selected for the testing. The MFI measurement was performed at 400? C. and showed that the polymer is extrudable. IPI 17 showed sufficiently good flowability to be extruded from the device as shown in FIG. 5. The extrudable polymer IPI 17 did not suffer under the high temperature since the colour remained unchanged. However, bubble formation was visible in the extruded IPI 17 which is due to the evolution of gas formed by decomposition of impurities present in the polymer. For this reason, the MFI value and the melt volume index (MVI) presented in Table 14 are shown in a range.

TABLE-US-00015 TABLE 14 IPI17 MVI/cm.sup.3 MFI/g (20% RODA + 80% 4,4-DDS) 10 min.sup.?1 10 min.sup.?1 1. measurement 17.7-24.5 22.0-30.4 2. measurement 14.9-22.7 18.5-28.2 standard deviation/cm.sup.3 10 min.sup.?1 2.27 2.63 coefficient of variation/% 9.87 12.66

[0163] With the MFI results can be said that IPI 17 is processable from the melt and has a high T.sub.g of 290? C. The gas formation can be useful if less dense extruded goods are desired.

[0164] If more dense products are needed, it was found that gas evolution during extrusion could be minimized or avoided if the polyimide was heat treated before extrusion at temperatures over the To preferably under vacuum, since chain movement is increased at this temperature allowing the impurity to be removed.

Example 5: TGA Measurements

[0165] FIGS. 6 to 11 exemplarily show the results of TGA measurements for CPI 10 and inventive polyimides IPI 6, 9, 12, 17 and 18. The TGA measurements confirmed that no chain degradation of the inventive polyimides occurs even at temperatures up to 450? C.

Comparative Example

[0166] The polyimide from Example 39 of US 2008/0044684 A1 was reproduced. Table 15 shows molar composition of the amine mix as well as SEC and DSC results for the segmented polymers

TABLE-US-00016 End-capper ODPA RODA 4,4-DDS M.sub.n/kDa M.sub.w/kDa ? T.sub.g*/? C. T.sub.m*/? C. CPI13 0.00 1.0 0.2 0.8 35.1 50.7 1.44 278

[0167] CPI13 does have T.sub.g clearly below 290? C.