METHOD FOR PRODUCING POLYIMIDES

Abstract

A method is provided for producing polyimides by polycondensation of previously produced stoichiometric salts from polycarboxylic acids or their polyanhydrides and polyamines by heating the salts for dehydration. In the method, a) an aqueous solution of a water-soluble stoichiometric salt is produced from polycarboxylic acid and polyamine; b) the aqueous solution undergoes a processing step; and c) the salt contained in the solution is simultaneously or subsequently polycondensed, by heating to form a polyimide.

Claims

1.-16. (canceled)

17. 1,3-Benzenedimethaneammonium-dihydrogen-3,3,4,4-benzophenonetetracarboxylate (1): ##STR00013##

18. 1,3-Benzenedimethaneammonium-dihydrogen-1,2,3,4-butanetetracarboxylate (2): ##STR00014##

19. 1,3-Benzenedimethaneammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (3): ##STR00015##

20. Ethane-1,2-diammonium-dihydrogen-3,3,4,4-benzophenonetetracarboxylate (4): ##STR00016##

21. Ethane-1,2-diammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (5): ##STR00017##

22. Poly(N,N-(benzene-1,3-dimethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (6): ##STR00018## wherein n2.

23. Poly(N,N-(1,2-ethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (7): ##STR00019## wherein n2.

24. A method for producing polyimides from polycarboxylic acids or their polyanhydrides and polyamines by polycondensation of previously prepared stoichiometric salts by heating the salts for dehydration, wherein: a) an aqueous solution of a water-soluble stoichiometric salt of polycarboxylic acid and polyamine is prepared; b) the aqueous solution is subjected to a processing step; and c) the salt contained in the coating is simultaneously or subsequently polycondensed by heating to give a polyimide.

25. The method of claim 24, wherein heating in step c) is performed at a temperature Tp higher than the polymerization temperature of the salt.

26. The method of claim 24, wherein in processing step b), a substrate is coated with the aqueous solution in order to obtain a coating that is cured by polycondensation in the subsequent step c).

27. The method of claim 26, wherein the coating obtained in processing step b) is dried prior to polycondensation in step c).

28. The method of claim 27, wherein in processing step b), a film is drawn from the aqueous solution of the water-soluble stoichiometric salt on the substrate.

29. The method of claim 24, wherein in processing step b), the aqueous solution is foamed to obtain a foam that is cured by polycondensation in the subsequent step c) to obtain a cured polyimide foam.

30. The method of claim 24, wherein in processing step b), the aqueous solution is fed to a nozzle heated to a temperature higher than Tp, where the stoichiometric salt is simultaneously cured by polycondensation, and in step c), the resulting polyimide is forced through nozzle opening(s) to obtain a molded polyimide product.

31. The method of claim 30, wherein the obtained polyimide is wet-spun, press-molded or extruded.

32. The method of claim 24, wherein in step a), the water-soluble stoichiometric salt is prepared by mixing stoichiometric amounts of a polycarboxylic acid or its polyanhydride and polyamine in water or in an aqueous solvent mixture.

33. The method of claim 32, wherein the water-soluble stoichiometric salt is precipitated by the addition of an organic solvent for intermediate storage prior to polycondensation.

34. The method of claim 24, wherein a water-soluble stoichiometric salt is prepared from a tetracarboxylic acid and a diamine and polycondensed.

35. The method of claim 34, wherein the tetracarboxylic acid is selected from benzo-phenonetetracarboxylic acid, tetrahydrofurantetracarboxylic acid, and butanetetracarboxylic acid.

36. The method of claim 34, wherein the diamine is selected from benzenedimethaneamine and ethylenediamine.

37. The method of claim 36, wherein the stoichiometric salt is selected from 1,3-benzenedimethaneammonium-dihydrogen-3,3,4,4-benzophenonetetracarboxylate (1), 1,3-benzenedimethaneammonium-dihydrogen-1,2,3,4-butanetetracarboxylate (2), 1,3-benzenedimethaneammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (3), ethane-1,2-diammonium-dihydrogen-3,3,4,4-benzophenonetetracarboxylate (4), and ethane-1,2-diammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (5).

38. The method of claim 37, wherein 1,3-benzenedimethaneammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (3) is used as the stoichiometric salt and the polyimide poly(N,N-(benzene-1,3-dimethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (6) is prepared by polycondensation.

39. The method of claim 37, wherein ethane-1,2-diammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (5) is used as the stoichiometric salt and the polyimide poly(N,N-(1,2-ethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (7) is prepared by polycondensation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Below, the present invention will be further described by way of non-limiting examples with reference to the accompanying drawings, wherein FIGS. 1 to 5 are IR spectra of the water-soluble stoichiometric monomer salts obtained in Examples 1, 4, 6, 7 and 8, and FIGS. 6 and 7 are IR spectra of the polyimides obtained in Examples 12 and 13.

EXAMPLES

[0023] All reagents used in the experiments below are commercially available and were used without further purification. The IR spectra shown in the accompanying drawings were recorded by means of FT-IR ATR spectroscopy on a Bruker Tensor 27 and .sup.1H NMR spectra were recorded on an Avance 250, also from Bruker. In the following, Tp refers to the solid state polymerization temperature of the obtained stoichiometric salts.

Example 1

Preparation of 1,3-benzenedimethaneammonium-dihydrogen-3,3,4,4-benzophenonetetracarboxylate (1)

[0024] ##STR00006##

[0025] 150 mg (0.47 mmol) of 3,3,4,4-benzophenontetracarboxylic acid dianhydride were suspended in 10 ml of dist. Wasser, and 61.4 l (0.47 mmol) of 1,3-benzenedimethaneamine were added, forming a clear, yellowish solution. After stirring for 30 minutes, the water was removed on a rotary evaporator in a water bath (50 C.) under a vacuum of approximately 60 mbar and the residue was dried under high vacuum. The title compound was quantitatively obtained as a colorless amorphous solid, the IR spectrum of which is shown in FIG. 1. The solid is highly hygroscopic and gradually deliquesces in the air to a yellow liquid phase of the tetrahydrate.

[0026] Tp.: 151 C. (DSC) or 161 C. (TGA) (heating rate: 10 K/min)

[0027] .sup.1H NMR (250 MHz, DMSO-d.sub.6) : 8.51 (d, 2H, ar), 8.32 (d, 2H, ar), 7.85 (q, 2H, ar), 7.45 (m, 4H, ar), 4.01 (s, 4H, aliph).

[0028] IR (cm.sup.1): 2882, 2619, 1694, 1601, 1540, 1359.

Example 2

Precipitation of the Tetrahydrate of (1) by Addition of a Solvent

[0029] The approach of Example 1 was repeated with the addition of 30 ml of THF to the resulting aqueous solution of (1) (here: in 5 ml of dist. water), forming a precipitate in the form of a white turbidity. The mixture was allowed to stand overnight, during which time the initial precipitate forming a yellow-colored second liquid phase, which crystallized after another 24 hours of rest in the form of colorless crystals.

[0030] The data correlated with those of Example 1, except for the presence of water.

Example 3

Preparation of (1) as an Aqueous Solution and Coating of a Surface

[0031] Example 1 was repeated, wherein instead of isolating the stoichiometric salt (1) by evaporating the water, the aqueous solution was used for coating a glass plate. For this purpose, a few drops of the solution were dropped onto a glass plate and allowed to dry in air. Subsequently, polycondensation to poly(N,N-(benzene-1,3-dimethylene)-benzophenone-3,3,4,4-tetracarboxylic acid diimide) was carried out in a vacuum oven maintained at 200 C. overnight. The IR spectrum of the polyimide thus obtained corresponded to that of the product known from the literature.

Example 4

Preparation of 1,3-benzenedimethanammonium-dihydrogen-1,2,3,4-butanetetracarboxylate (2)

[0032] ##STR00007##

[0033] 150 mg (0.64 mmol) of 1,2,3,4-butanetetracarboxylic acid were dissolved in 10 ml of dist. water, and 84.5 l (0.64 mmol) of 1,3-benzenedimethanamine were added at once, after which the reaction mixture was shaken until a clear solution formed. Work-up and drying were carried out analogously to Example 1, and the title compound was obtained in a quantitative yield as a hygroscopic, colorless, amorphous solid, the IR spectrum of which is shown in FIG. 2.

[0034] Tp.: 151 C. (TGA)

[0035] .sup.1H NMR (250 MHz, D.sub.2O) : 7.5 (m, 4H, ar), 4.2 (s, 4H, aliph), 2.9 (m, 2H, aliph), 2.6 (m, 2H, aliph), 2.4 (m, 2H, aliph).

[0036] IR (cm.sup.1): 3386, 2918, 2626, 1701, 1620, 1542.

Example 5

Precipitation of the Tetrahydrate of (2) by Addition of a Solvent

[0037] The approach of Example 4 was repeated with the addition of 30 ml of THF to the resulting aqueous solution of (2) (here: in 5 ml of dist. water), which formed a precipitate in the form of a white turbidity. The mixture was allowed to stand overnight, during which time the initial precipitate formed a yellow-colored second liquid phase, which crystallized after another 24 hours of rest in the form of colorless crystals.

[0038] The data correlated with those of Example 4, except for the presence of water.

Example 6

Preparation of 1,3-benzenedimethanammoniumdihydrogentetrahydrofuran-2,3,4,5-tetracarboxylate (3)

[0039] ##STR00008##

[0040] 150 mg (0.60 mmol) of tetrahydrofuran-2,3,4,5-tetracarboxylic acid were dissolved in 10 ml of dist. water, and 79.8 l (0.60 mmol) of 1,3-benzenedimethanamine were added at once, after which the reaction mixture was shaken until a clear solution formed. Work-up and drying were carried out analogously to Example 1, giving a hygroscopic, colorless, amorphous solid in quantitative yield, the IR spectrum of which is shown in FIG. 3.

[0041] Mp.: 62 C. (DSC)

[0042] Tp.: 144 C. (DSC) or 151 C. (TGA) (heating rate: 10 K/min)

[0043] .sup.1H NMR (250 MHz, DMSO-d.sub.6) : 7.5 (s, 1H, ar), 7.4 (m, 3H, ar), 4.4 (m, 2H, aliph), 4.0 (s, 4H, aliph), 3.0 (m, 2H, aliph).

[0044] IR (cm.sup.1): 3393, 3052, 2929, 1714, 1600, 1568.

Example 7

Preparation of ethane-1,2-diammoniumdihydrogen-3,3,4,4-benzophenonetetracarboxylate (4)

[0045] ##STR00009##

[0046] 150 mg (0.47 mmol) of 3,3,4,4-benzophenontetracarboxylic acid dianhydride were dissolved in 10 ml of dist. water, and 31.1 l (0.47 mmol) 1,2-ethylenediamine were added at once, after which the reaction mixture was shaken until a clear solution formed. Work-up and drying were carried out analogously to Example 1, giving a hygroscopic, colorless, amorphous solid in quantitative yield, the IR spectrum of which is shown in FIG. 4.

[0047] Tp.: 128 C. (DSC) or 149 C. (TGA) (heating rate: 10 K/min)

[0048] .sup.1H NMR (250 MHz, D.sub.2O) : 8.1 (d, 2H, ar), 7.9 (q, 2H, ar), 7.7 (d, 2H, ar), 3.4 (s, 4H, aliph).

[0049] IR (cm.sup.1): 3386, 3030, 2929, 1699, 1602, 1541.

Example 8

Preparation of ethane-1,2-diammonium-dihydrogen-tetrahydrofuran-2,3,4,5-tetracarboxylate (5)

[0050] ##STR00010##

[0051] 150 mg (0.60 mmol) of tetrahydrofuran-2,3,4,5-tetracarboxylic acid were dissolved in 10 ml of dist. water, and 40.4 l (0.60 mmol) 1,2-ethylenediamine were added at once, after which the reaction mixture was shaken until a clear solution formed. Work-up and drying were carried out analogously to Example 1, giving a hygroscopic, colorless, amorphous solid in quantitative yield, the IR spectrum of which is shown in FIG. 5.

[0052] Tp.: 128 C. (DSC) or 149 C. (TGA) (heating rate: 10 K/min)

[0053] .sup.1H NMR (250 MHz, D.sub.2O) : 4.8 (m, 2H, aliph), 3.5 (m, 2H, aliph), 3.4 (s, 4H, aliph).

[0054] IR (cm.sup.1): 3400, 3031, 2926, 1713, 1600, 1561.

Examples 9 to 13

Coating and Polycondensation

[0055] The approaches of Examples 1, 4, 6, 7 and 8 were repeated using the aqueous solutions for coating glass plates in a way similar to Example 3 instead of isolating the stoichiometric salts. For this purpose, 5 to 10 ml of the respective aqueous solution were applied to a glass plate, which was then heated in an oven to 250 C. at a heating rate of 5 K/min and subsequently maintained at this temperature for 30 min.

[0056] The polyimides thus obtained were three products known from the literature, namely in Example 9 (with the stoichiometric salt obtained analogously to Example 1):

poly(N,N-(benzene-1,3-dimethylene)benzophenone-3,3,4,4-tetracarboxylic acid diimide);
in Example 10 (with the stoichiometric salt obtained analogously to Example 4): poly(N,N-(benzene-1,3-dimethylene)butane-1,2,3,4-tetracarboxylic acid diimide), and
in Example 1 (with the stoichiometric salt obtained analogously to Example 7): poly(N,N-(1,2-ethylene)benzophenone-3,3,4,4-tetracarboxylic acid diimide); and two previously unknown polyimides, namely:
in Example 12 (with the stoichiometric salt obtained analogously to Example 6): poly(N,N-(benzene-1,3-dimethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (6); and
in Example 13 (with the stoichiometric salt obtained analogously to Example 8): poly(N,N-(1,2-ethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (7).

[0057] These polyimides were, inter alia, analyzed by means of IR spectroscopy. The IR spectra of the products of Examples 9 to 11 corresponded to those of the polyimides known from literature.

[0058] Regarding the novel polyimides (6) and (7), the decomposition points were determined in addition to the IR spectra shown in FIGS. 6 and 7, and furthermore a .sup.1H NMR spectrum of polyimide (6) was recorded (for polyimide (7) impossible because it was insoluble in the solvents tested), providing the following data.

Poly(N,N-(benzene-1,3-dimethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (6)

[0059] ##STR00011##

[0060] Mp.: 456 C. (dec.) (TGA, heating rate: 10 K/min)

[0061] .sup.1H NMR (250 MHz, DMSO-d.sub.6) : 7.3 (s, 1H, ar), 7.1 (d, 3H, ar), 5.2 (t, 1H, aliph), 4.7 (s, 1H, aliph), 4.6 (s, 2H, aliph), 4.5 (s, 2H, aliph), 3.9 (s, 2H, aliph).

[0062] IR (cm.sup.1): 1784, 1695, 1333.

Poly(N,N-(1,2-ethylene)tetrahydrofuran-2,3,4,5-tetracarboxylic acid diimide) (7)

[0063] ##STR00012##

[0064] Mp.: 438 C. (dec.) (TGA, heating rate: 10 K/min)

[0065] IR (cm.sup.1): 1785, 1690, 1339.

[0066] The present invention thus provides a process by which polyimide coatings can be prepared from aqueous solutions of the stoichiometric monomer salts, which is a considerable advantage over prior art because it limits or even completely avoids the use of expensive solvents that can only be removed with enormous energy input.

[0067] In addition, the invention shall not be limited to the five monomer combinations disclosed herein, since a person skilled in the artwho now has the knowledge that such water-soluble monomer salts actually existcan easily, by means of simple routine experiments, determine other combinations of polycarboxylic acid or polyanhydride and polyamines that result in a water-soluble stoichiometric salt.