NON-TOXIC POLYIMIDE SOLUTIONS

Abstract

The invention relates to new polyimide solutions having ecological and toxicological benefits compared to existing polyimide solutions as well as well as b their use, in particular for coating applications.

Claims

1-17. (canceled)

18. A polyimide solution comprising: A) one or more polyimides; B) a solvent mixture comprising: a) 55 to 90 wt. % dimethylsulfoxide; b) in sum, 0.1 to 20 wt. % of one or more primary, secondary and/or tertiary alkanolamine(s) having 3 to 15 carbon atoms; c) 0 to 40 wt. % benzyl alcohol; d) 0 to 25 wt. % cyclohexanone; e) 0 to 15 wt. % xylene; f) in sum, 0 to 20 wt. % acetophenone and/or an alkylene carbonate; g) 0 to 5 wt. % propylene glycol; h) in sum 0 to 10 wt. % DMF, NEP, NMP and/or DMAc; and i) optionally further co-solvents; wherein the weight percentages given for components a) to i) relate to the total weight of solvent mixture B, and the amounts of components a) to i) are selected such that they total, in sum, to 100 wt. % of the solvent mixture; and wherein the polyimide solution comprises, in sum, 5 to 35 wt. % of component A, relative to the overall weight of the polyimide solution.

19. The polyimide solution of claim 18, wherein the one or more polyimides are aromatic polyimides.

20. The polyimide solution of claim 18, wherein solvent mixture B) comprises one or more of the following: a) 60 to 80 wt. % dimethylsulfoxide; b) in sum, 2 to 13 wt. % of one or more primary, secondary and/or tertiary alkanolamine(s) having 4 to 9 carbon atoms; c) 5 to 15 wt. % benzyl alcohol; d) 2 to 15 wt. % cyclohexanone; e) 1 to 5 wt. % xylene; f) in sum, 5 to 15 wt. % of propylene carbonate; g) 0 wt. % propylene glycol; and h) 0 wt. % of DMF, NEP, NMP and DMAc.

21. The polyimide solution of claim 20, wherein the one or more polyimides A are aromatic polyimides.

22. The polyimide solution of claim 18, wherein the polyimide solution comprises a combination of components selected from the group consisting of: i) a, b and c; ii) a, b and d; iii) a, b, c and d; iv) a, b, c, d and e; v) a, b, e and f; and vi) a, b, d, e and f; wherein the amounts of components a and b are in the ranges given in claim 1 and wherein components c, d, e and f, if present, are in an amount selected from the following ranges: c: 0.1 to 40 wt. %; d: 1 to 25 wt. %; e: 0.1 to 15 wt. %; and f: in sum, 1 to 20 wt. %, of acetophenone and/or an alkylene carbonate.

23. The polyimide solution of claim 22, wherein one or more of components c, d, e and f, if present, are in an amount selected from the following ranges: c: 5 to 15 wt. %; d: 2 to 15 wt. %; e: 1 to 5 wt. %; and f: 5 to 15 wt. % of propylene carbonate.

24. The polyimide solution of claim 22, wherein the polyimide solution consists of a combination of components selected from the group consisting of: i) a, b and c; ii) a, b and d; iii) a, b, c and d; iv) a, b, c, d and e; v) a, b, e and f; and vi) a, b, d, e and f; wherein the amounts of components a and b are in the ranges given in claim 1 and wherein components c, d, e and f, if present, are in an amount selected from the following ranges: c: 0.1 to 40 wt. %; d: 1 to 25 wt. %; e: 0.1 to 15 wt. %; and f: in sum, 1 to 20 wt. %, of acetophenone and/or an alkylene carbonate; and wherein the amount of each component is selected such that the amounts of the components total to, in sum, 100% of solvent mixture B.

25. The polyimide solution of claim 24, wherein one or more of components c, d, e and f, if present, are in an amount selected from the following ranges: c: 5 to 15 wt. %; d: 2 to 15 wt. %; e: 1 to 5 wt. %; and f: 5 to 15 wt. % of propylene carbonate.

26. The polyimide solution of claim 18, wherein the amounts of components a to h are selected such that they total to, in sum, 100 wt. % of the solvent mixture.

27. The polyimide solution of claim 18, wherein the one or more primary, secondary or tertiary alkanolamine(s) having 3 to 15 carbon atoms are selected from the group consisting of: triethanolamine; 2-(dimethylamino)ethanol; and mixtures thereof; wherein: triethanolamine is present in an amount of from 0 to 20 wt. % based on the total weight of solvent mixture B; 2-(dimethylamino)ethanol is present in an amount of from 0 to 20 wt. % based on the total weight of solvent mixture B; and wherein the amounts of triethanolamine and 2-(dimethylamino)ethanol are selected such, that both components, in sum, total to 0.1 to 20 wt. % of solvent mixture B.

28. The polyimide solution of claim 18, wherein the one or more polyimides comprise an aromatic polyimide having identical or different, recurring units of formula (1): ##STR00014## wherein: the functional group R.sup.A represents one or more, identical or different, moieties selected from the group consisting of: the moieties R.sup.A1, R.sup.A2 and R.sup.A3: ##STR00015## where ##STR00016## and functional group R.sup.B represents one or more, identical or different, moieties selected from the group consisting of the moieties R.sup.B1, R.sup.B2 and R.sup.B3: ##STR00017## wherein Y.sub.1, Y.sub.2, Y.sub.3 and Y.sub.4 are either H or CH.sub.3 or alkyl radicals with 2 to 4 carbon atoms and Y═—CH.sub.2—, —(CH.sub.3).sub.2C—, SO.sub.2, —(CF.sub.3)C—, —CO—, —COO—, —CONH—, or —O—.

29. The polyimide solution of claim 28, wherein at least 90 mol-% of building blocks R.sup.A are 3,3′,4,4′-benzophenonetetrayl and at least 90 mol-% of building blocks R.sup.B are 2,4-toluenediyl, 2,6-toluenediyl or 4,4′-methylenediphenyldiyl, with a molar ratio of 2,4-toluenediyl to 2,6-toluenediyl of from 1:9 to 9:1 and a molar ratio of the combined amount of 2,4-toluenediyl and 2,6-toluenediyl to the amount of 4,4′-methylenediphenyldiyl of from 70:30 to 100:0.

30. The polyimide solution of claim 28, wherein at least 90 mol-% of building blocks R.sup.A are 3,3′,4,4′-benzophenonetetrayl or 1,2,4,5-phenylenetetrayl, with a molar ratio of 3,3′,4,4′-benzophenonetetrayl to 1,2,4,5-phenylenetetrayl of from 50:50 to 95:5 and at least 90 mol-% of building blocks R.sup.B are 2,4-toluenediyl or 2,6-toluenediyl, with a molar ratio of 2,4-toluenediyl to 2,6-toluenediyl of from 1:9 to 9:1.

31. The polyimide solution of claim 18, wherein the polyimide is a block-copolyimide comprising, blocks (A) as per formula (3) and (B) as per formula (4): ##STR00018## wherein: the functional group R.sub.1 comprises either or both of the following functional groups: ##STR00019## and R.sub.2 comprises at least one or 2 or 3 of the following functional groups: ##STR00020## and wherein: R.sub.3 comprises one or more of the following functional groups: ##STR00021## where ##STR00022## and R4 comprises one or more of the following functional groups: ##STR00023## wherein Y.sub.1, Y.sub.2, Y.sub.3 and Y.sub.4 are either H or CH.sub.3 or alkyl radicals with 2 to 4 carbon atoms and Z═—CH.sub.2—, —(CH.sub.3).sub.2C—, SO.sub.2, —(CF.sub.3)C—, —CO—, —COO—, —CONH—, —O—, with the proviso that at least one of the radicals Y.sub.1 to Y.sub.4, is CH.sub.3 or a C.sub.2 to C.sub.4 alkyl radical.

32. The polyimide solution of claim 18, wherein the polyimide solution comprises, in sum, 10 to 30 wt. % of component A, relative to the overall weight of the polyimide solution.

33. The polyimide solution of claim 18, wherein the polyimide solution comprises, in sum, 95 to 65 wt. %, of component B, relative to the overall weight of the polyimide solution.

34. A process for preparation of a polyimide solution, comprising the steps: i) providing one or more polyimides; ii) providing a solvent mixture, comprising: a) 55 to 90 wt. %, dimethylsulfoxide; b) in sum, 0.1 to 20 wt. % of one or more primary, secondary and/or tertiary alkanolamine(s) having 4 to 9 carbon atoms; c) 0 to 40 wt. % benzyl alcohol; d) 0 to 25 wt. %, cyclohexanone; e) 0 to 15 wt. % xylene; f) in sum, 0 to 20 wt. % of acetophenone and/or an alkylene carbonate; g) 0 to 5 wt. % propylene glycol; h) in sum, 0 to 10 wt. % of DMF, NEP, NMP and/or DMAc; i) optionally further co-solvents; wherein the weight percentages for components a to i relate to the total weight of the solvent mixture B and are selected such that they total, in sum, 100 wt. % of solvent mixture B; iii) dissolving the polyimide provided in step i) in the solvent mixture provided in step ii).

35. The process of claim 34, wherein step iii) is carried out at a temperature of 25 to 90° C.

36. A process for preparation of a polyimide solution, comprising the steps: I) providing one or more polyimides; II) dissolving the polyimides provided in step I) partially or entirely in DMSO; III) adding the following components to the polyimide solution obtained in step II) to obtain solvent mixture B, said components comprising: a) 55 to 90 wt. %, dimethylsulfoxide; b) in sum, 0.1 to 20 wt. %, of one or more primary, secondary or tertiary alkanolamine(s) having 3 to 15 carbon atoms; c) 0 to 40 wt. % benzyl alcohol; d) 0 to 25 wt. % cyclohexanone; e) 1 to 5 wt. % xylene; f) in sum, 0 to 20 wt. % of acetophenone and/or an alkylene carbonate; g) 0 to 5 wt. % propylene glycol; h) in sum, 0 to 10 wt. % of DMF, NEP, NMP and/or DMAc; i) optionally further co-solvents; wherein the weight percentages given for components a) to i) are relative to the total weight of solvent mixture B and are selected such that they total to, in sum, 100 wt. % of solvent mixture B.

37. The process for preparation of the polyimide solution of claim 36, wherein step II) is carried out at a temperature of from 25 to 90° C.

Description

EXAMPLES

[0123] The examples below are intended to illustrate and describe the present invention in more detail but shall not be construed in any way to limit the scope of the claims.

Preparation of Polyimide Solutions

[0124] A number of polyimide solutions according to the invention and of comparative polyimide solutions were prepared and tested. For production of the polyimide solutions a dry polyimide powder is dissolved with a weight content of up to 25% in different solvent mixtures at 60° C. with stirring. The components used and their amounts are summarized in Table 1.

Chemicals Used:

[0125] P84® type 70 obtained from Evonik Fibres GmbH, Austria
P84® HT obtained from Evonik Fibres GmbH, Austria
Block-co-PI prepared according to example 13 in WO2015/091122

[0126] All of the following chemicals were used as lab grade chemicals:

DMSO obtained from abcr GmbH
2-(dimethylamino)ethanol obtained from Merck KGaA
Triethanolamine obtained from Sigma-Aldrich Chemie GmbH
Acetophenone obtained from Merck KGaA
Benzyl alcohol obtained from Sigma-Aldrich Chemie GmbH
Cyclohexanone obtained from Sigma-Aldrich Chemie GmbH
Propylene glycol obtained from Sigma-Aldrich Chemie GmbH
Xylene obtained from Sigma-Aldrich Chemie GmbH
Propylene carbonate obtained from Carl Roth GmbH+Co. KG

[0127] Storage Stability

[0128] FIG. 1 shows storage stability tests of comparison example i.e. a solution of P84® Type 70 in pure DMSO, and inventive examples E5 and E6. The Comparative Example shows a poor storage stability if in contact with air. After 30 min visible skin formation has started. Inventive examples E5 and E6 to the contrary do not show any skin formation even after 8 hours.

[0129] The prepared polyimide solutions were tested as coating solution as follows:

[0130] The polyimide solution was applied as coating to a steel or aluminum surface via a doctor blade or after dilution, via a spray coating process. The adhesion of coatings was investigated via cross-hatch tests.

[0131] After drying, the tested inventive coatings have shown a quality comparable to coatings prepared by use of P84® Type 70 solutions in NMP. The assessment and comparison of the different coatings was carried out by cross-cutting tests according to ISO 2409

[0132] Melting temperatures for different solutions 20% PI solutions were determined via DSC measurements.

TABLE-US-00001 TABLE 1 Comparative Examples CE1 CE2 CE3 CE4 CE5 CE6 CE7 CE8 CE9 Solvent DMSO wt. % 54 34.5 58.7 27.5 95 80.9 57.4 51.7 70 mixture b) Propylene glycol wt. % 7.1 6.6 2-(dimethyl-amino) ethanol wt. % 13.2 3.8 5 3.9 Acetophenone wt. % 5.7 Benzyl alcohol wt. % 20 24.9 41.3 23.8 12.5 4.5 26.2 15 Cyclohexanone wt. % 19.8 26.4 13.5 7.6 15 Triethanolamine wt. % 17 22.3 24.6 10.6 Total wt. % 100 100 100 100 100 100 100 100 100 Polyimide P84 ® type 70 wt. % 10 20 25 Solution Solvent mixture b) wt. % 90 80 75 Total wt. % 100 100 100 Application Solubility LS PS/PD PS/PD PS/SW GS PS/SW PS/PD PS/PD VS test Skin Formation at air hours N.D. N.D. N.D. N.D. 4 N.D. N.D. N.D. 1 Melting point of solution ° C. N.D. N.D. N.D. N.D. 8 N.D. N.D. N.D. −13 Cross-cutting test N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. Examples according to the invention E1 E2 E3 E4 E5 E6 E7 E8 Solvent DMSO wt. % 70 60 75 75 70 72.20 74.80 75.70 mixture b) 2-(dimethylamino) ethanol wt. % 4 4 4 4 4 4.20 Acetophenone wt. % 11.7 Benzyl alcohol wt. % 10 15 5 11 11 17.60 Cyclohexanone wt. % 10 10 10 10 15 4.40 3.40 Triethanolamine wt. % 6 11 6 8.2 11 Xylene wt. % 1.6 1.6 1.6 Propylene Carbonate wt. % 12 Total wt. % 100 100 100 100 100 100 100 100 Polyimide P84 ® type 70 wt. % 20 15 15 25 25 25 15 15 Solution P84 ® HT Block-co-PI Solvent Mixture b) wt. % 80 85 85 75 75 75 85 85 Total wt. % 100 100 100 100 100 100 100 100 Application Solubility GS MS GS VS VS VS MS GS text Viscosity (20 wt. %) Pa .Math. s 16 N.D. 19 7 6 7 N.D. 25 Skin Formation at air hours >8 N.D. >8 >8 >8 >8 4 2 Melting point of solution ° C. N.D. N.D. −1 −17 −22 −12 −5 −6 Cross-cutting test 1 N.D. 1 2 1 1 N.D. 2 Examples according to the invention E9 E10 E11 E12 E13 E14 E15 Solvent DMSO wt. % 76.30 76.80 58.10 56.00 70 70 85 mixture 2-(dimethylamino) ethanol wt. % 4.2 4.20 18.30 4 4 15 b) Acetophenone wt. % Benzyl alcohol wt. % 37.70 25.70 11 11 Cyclohexanone wt. % 12.50 9.90 15 15 Triethanolamine wt. % 11.2 9.2 Xylene wt. % Propylene Carbonate wt. % Total wt. % 100 100 100 100 100 100 100 Polyimide P84 ® type 70 wt. % 15 20 15 15 25 Solution P84 ® HT 20 Block-co-PI 20 Solvent Mixture b) wt. % 85 80 85 85 80 80 75 Total wt. % 100 100 100 100 100 100 100 Application Solubility MS GS MS MS GS GS GS text Viscosity (20 wt. %) Pa .Math. s N.D. 29 N.D. N.D. N.D. N.D. N.D. Skin Formation at air hours N.D. >8 N.D. N.D. N.D. N.D. >8 h Melting point of solution ° C. −2 −24 N.D. N.D. N.D. N.D. 2.5 Cross-cutting test N.D. 2 N.D. N.D. N.D. N.D. N.D. LS = Low Solubility <10 wt % polyimide (PI); MS = Moderate Solubility 15 wt. % PI possible; GS = Good Solubility 20 wt. % PI possible or ≥25 wt. % PI possible but viscosity ≥10 Pa .Math. s for 20 wt. % solution; VS = Very Good Solubility ≥25 wt. % PI possible and viscosity <10 Pa .Math. s for 20 wt. % solution, PS = Poor Solubility; SW = Swelling of polymer only; PD = Partial Dissolution; N.D. = Not Determined

[0133] Table 1 shows that none of the polyimide solutions of the comparative examples solves all problems of the present invention. Most comparative solvent mixtures had poor solubility with undissolved polyimides and/or swelling. Inventive example E15 shows that inventive solutions comprising a binary solvent mixture consisting of DMSO and a tertiary alkanolamine in amounts according to the invention, show excellent storage stability, excellent solubility and significantly improved melting point compared to comparative example CE5. CE5 is a direct comparison to E15, i.e. also a binary solvent mixture consisting of DMSO and 2-(dimethylamino) ethanol but with non-inventive contents of both solvents. While both E15 and CE5 show good solubility; CE15 shows skin formation after 4 h, indicating that the storage stability is worse if a binary solvent mixture consisting of DMSO and a tertiary alkanolamine is used and if the content of the amine in the solvent mixture is too low. CE9 shows very good solubility and low melting point but skin formation started already after 1 hour. In contrast thereto, all inventive examples have at least moderate but most have good or very good solubility. The inventive examples with good and very good solubility were further tested for their viscosity, skin formation time, melting point and in a cross-cutting test after coating of a substrate. It turned out that all tested inventive examples have a melting point below 0° C. All tested inventive examples have skin formation times of at least two hours, most of more than 8 hours, which is a significant benefit for their application. The viscosities of the tested inventive examples are good or even very good and the quality of the coatings ins the cross-cutting test is also good or very good. Examples E1 to E15 show that the present invention offers high flexibility for a commercial application. While solutions can be provided having very low melting point but limited storage stability (4 h), it is also possible to provide solutions with very good storage stability but melting point slightly above 0° C. and finally it is also possible to provide solutions with both, very low melting point and excellent storage stability. Thus, a man skilled in the art can choose the right solvent mixture depending on the commercial requirements. In any case, however, the inventive solvents showed good or even very good solubility performance and are classified as non-toxic, which is a significant benefit compared commercially available polyimide solutions in DMF, DMAc, NMP and NEP.

[0134] Table 1 confirms that the solvent mixtures of the invention solve all invention and provide significant advantages over prior art solutions as well as commercially available polyimide solutions as well as to alternative polyimide solutions that could be classified non-toxic (CE2 to CE9).