New non-toxic polyimide solution

Abstract

To provide a new polyimide solution having environmental and toxicological benefit in comparison with the conventional polyimide solution, and uses thereof particularly for coating.SOLUTION: A polyimide solution contains a specific solvent mixture, and one or plural polyimides, preferably an aromatic polyimide. The polyimide solution contains one or plural polyimides of 5-35 wt.% in total relative to the total weight.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to novel polyimide solutions that have environmental and toxicological advantages compared to existing polyimide solutions, and to their use, particularly for coating applications. [Background technology]

[0002] Several soluble aromatic polyimides have been developed and are commercially available for various applications. For example, WO2011 / 009919A1 discloses several soluble polyimides of type P84®, as well as methods for producing them and their use for manufacturing films. According to WO2011 / 009919A1, polyimides of type P84® can be dissolved in DMF (dimethylformamide), DMAc (dimethylacetamide), NMP (N-methyl-2-pyrrolidone), NEP (N-ethyl-2-pyrrolidone), sulfolan (tetrahydrothiophene-1,1-dioxide), and DMSO (dimethyl sulfoxide).

[0003] The most suitable commercially available solvents for polyimides are DMF, DMAc, NMP, and NEP. However, these solvents are classified as CMR (carcinogenic, mutagenic, and reproductively toxic) substances. In addition, DMF and NMP are listed on the SVHC (Substances of Very High Concern) candidate list. As a result, the processing, manufacture, transport, and use of polyimide solutions containing such solvents are subject to stringent safety requirements. In fact, these limitations are a pressing issue for many potential customers, especially small and medium-sized enterprises.

[0004] Due to environmental, toxicological, and administrative problems caused by NMP, such as those associated with solvents for polyimide or polyamide-imide resins, paint manufacturers are seeking alternatives. For example, DE102014104223A1 proposes using 3-methoxy-N,N-dimethylpropanamide instead of NMP as a solvent for paint applications.

[0005] Among the solvents listed in WO2011 / 009919A1, DMSO is a less criticized alternative. However, there are several drawbacks to processing polyimide solutions in DMSO. Firstly, its high melting temperature of 18°C ​​can cause the polyimide solution in DMSO to freeze, for example, during transport. Secondly, P84® solutions in DMSO exhibit poor storage stability in air. Upon contact with moisture, a phase reversal due to moisture absorption occurs within a short time (less than one hour). This phenomenon can be observed by the formation of a hard white film on the surface of the solution. This is particularly problematic for coating applications, as it hinders the use of polyimide solutions in DMSO.

[0006] US2004 / 0266979 discloses a method for producing solvent-soluble polyimides. The polyimides are produced by polycondensation of at least one tetracarboxylic acid component with at least one diamine component in a solvent, in the presence of a tertiary amine as a catalyst. Similar to WO2011 / 009919A1, the list of usable solvents includes DMSO (dimethyl sulfoxide) as well as CMR classification compounds such as DMF (dimethylformamide), DMAc (dimethylacetamide), NMP (N-methyl-2-pyrrolidone), hexamethylphosphoramid, and sulfolane. According to the example in US2004 / 0266979, a heterogeneous reaction mixture is obtained at the end of the polycondensation reaction. After the completion of polycondensation, a large amount of DMAc is added to the reaction mixture to obtain a homogeneous solution. In US2004 / 0266979, a homogeneous solution could not be obtained without using DMAc as the main solvent. As a result, US2004 / 0266979 has the same problems as WO2011 / 009919A1, which were previously described.

[0007] US6,916,772B2 discloses compositions for exfoliating photoresist compounds such as polyimides from a substrate, comprising: a) about 5% to about 50% by weight of alkyl-substituted pyrrolidone, alkyl-substituted piperidone, or a mixture thereof; b) about 0.2% to about 20% of one or more alkanolamines; and c) about 50% to about 94% of sulfoxides, sulfoxanes, or a mixture thereof. The majority of the compositions disclosed in US6,916,772B2 contain NMP, which is a CMR-classified solvent. Therefore, the solvents used in US'772 pose the same environmental, toxicological, and administrative problems discussed earlier. US6,916,772B2 provides no hint that the polyimide solutions disclosed therein can be used for coating applications, or that the polyimide solutions solve any of the problems solved by the present invention. US6,916,772B2 relates to an entirely different technical field.

[0008] As a result, there is a strong demand for new solvents or solvent mixtures for polyimides, particularly aromatic polyimides. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] WO2011 / 009919A1 [Patent Document 2] DE102014104223A1 [Patent Document 3] US2004 / 0266979 [Patent Document 4] US6,916,772B2 [Patent Document 5] DE2143080 [Patent Document 6] WO2015 / 091122 [Non-patent literature]

[0010] [Non-Patent Document 1] Handbook of Specialty Fluorinated Polymers, 2015 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The problem that the present invention aims to solve is to provide a new polyimide solution, or a new solvent or solvent mixture for polyimides, that does not have the disadvantages of prior art polyimide solutions, or has such disadvantages reduced to a minor degree. A further problem was to provide a method for producing such a new polyimide solution and to enable the use of the new polyimide solution in different application fields, particularly coating applications.

[0012] A first specific problem that the present invention aims to solve was to provide new solvents or solvent mixtures for polyimides. Preferably, these new solvents or solvent mixtures are less toxic and / or have beneficial environmental properties compared to solvents used in commercially available polyimide solutions at the time the invention was made, or compared to polyimide coating solutions disclosed in the prior art cited above. Preferably, the use of CMR substances should be reduced or avoided.

[0013] A second specific problem that the present invention aims to solve is to provide a novel solvent or solvent mixture for polyimides that enables the production of polyimide solutions having good storage stability in air, preferably improved storage stability in air compared to a solution in pure DMSO, and more preferably having a film-forming time of at least 2 hours, more preferably at least 4 hours, particularly preferably at least 6 hours, and most preferably at least 8 hours when stored in air.

[0014] A third specific problem to be solved by the present invention was to provide a new solvent or solvent mixture that enables the production, transportation, and use of a polyimide solution over a wide temperature range, particularly at low temperatures, especially below 0 °C.

[0015] A fourth specific problem to be solved by the present invention was to provide a new solvent or solvent mixture for polyimide that enables the production of a polyimide solution having a high solubility, i.e., a high solids content, and more preferably also a low viscosity.

[0016] A fifth specific problem to be solved by the present invention was to provide a new solvent or solvent mixture for polyimide that enables the production of a polyimide solution that can be used in a variety of applications, particularly coating applications. Preferably, it should be possible to obtain a high-quality coating having good performance characteristics.

[0017] A sixth specific problem to be solved by the present invention was to provide a new solvent or solvent mixture for polyimide that enables the production, transportation, and use of a polyimide solution having fewer safety and regulatory requirements.

[0018] Further problems not previously mentioned will become apparent in view of the following description, examples, and claims.

Means for Solving the Problems

[0019] The inventors have surprisingly found that a solvent mixture containing DMSO and a co-solvent as defined in claim 1 or one of the dependent claims can be used to produce a polyimide solution that solves the problems of the present invention.

[0020] The solvent mixture of the present invention can be used to dissolve polyimides, particularly aromatic polyimides, without using any CMR and SVHC classified substances such as NMP, NEP, DMAc, and DMF as a solvent or co-solvent, and is not classified as toxic in itself.

[0021] Although the solvent mixture of the present invention is based on DMSO, the formulation of the present invention, i.e., the polyimide solution, exhibits significantly better processing properties than a polyimide solution in pure DMSO. A melting point from below 0°C to -24°C has been achieved. This makes it possible to produce, transport, and use the polyimide solution of the present invention in a very low-temperature range.

[0022] Even after continuous exposure to air for 2 to over 8 hours, the polyimide formulations of the present invention do not exhibit any harmful film formation upon contact with moisture.

[0023] A solution was obtained that was good or even very good, i.e., had low viscosity and contained at least 25% by weight of polyimide.

[0024] Further benefits not previously mentioned will become apparent from the following description, examples, and claims. [Brief explanation of the drawing]

[0025] [Figure 1] This figure shows a comparative example, namely a solution of P84® type 70 in pure DMSO, as well as storage stability tests of Examples E5 and E6 of the present invention. [Modes for carrying out the invention]

[0026] The present invention relates to the polyimide solution of claim 1, a method for producing the polyimide solution of claim 13 or 14, and the use of the polyimide solution of the present invention as described in claim 16 or 17. Preferred embodiments are claimed in the dependent claims.

[0027] The terms "polyimide solution" and "polyimide formulation" are used synonymously in this invention and refer to formulations comprising a solvent mixture and at least one polyimide, wherein the term "solution" means that the polyimide is dissolved in the solvent mixture and no undissolved polyimide particles visible to the naked eye are present.

[0028] The present invention a) One or more types of polyimides, preferably aromatic polyimides, b) a. 55-90% by weight of dimethyl sulfoxide, b. One or more primary, secondary and / or tertiary alkanolamines having 3 to 15, preferably 4 to 10, more preferably 4 to 9 carbon atoms in total, in an amount of 0.1 to 20% by weight. c. 0-40% by weight of benzyl alcohol, d. 0-25% by weight of cyclohexanone, e. 0-15% by weight of xylene, f. In total, 0-20% by weight of acetophenone and / or alkylene carbonates. g 0-5% by weight propylene glycol, h. In total, 0-10% by weight of DMF, NEP, NMP and / or DMAc, i. Optionally, further cosolvents Includes, The weight percentages shown for components a-i are relative to the total weight of solvent mixture b). The amounts of components a. to i. are selected so that they total 100% by weight of the solvent mixture. Solvent mixture and A polyimide solution containing [the specified ingredient] is provided.

[0029] Preferably, the amounts of components a. to h. are selected so that they total 100% by weight of the solvent mixture, i. for example, no further co-solvent i. is included.

[0030] Aliphatic or aromatic polyimides can be used as polyimide a). Preferably, aromatic polyimides are used. Aromatic polyimides, preferably those made from dianhydrides and diisocyanates or diamines, and methods for producing them are known to those skilled in the art. Homo, random, or copolymer, or mixtures or blends of various polyimide polymers may be used. All types of solvent-soluble aromatic polyimides can be used in the present invention.

[0031] In particular, as previously described in the Prior Art section, there is a strong demand for solvents or solvent mixtures for aromatic polyimides that do not contain or contain very low amounts of solvents and SVHCs classified as CMRs. As shown in the examples below, the solvent mixture of the present invention satisfies these requirements and exhibits excellent performance when combined with an aromatic polyimide containing at least 80 mol% aromatic monomers. Therefore, the polyimide solution of the present invention preferably contains, as polyimide component a), a polyimide containing 80-100% aromatic monomers, more preferably 90-100% aromatic monomers, even more preferably 95-100% aromatic monomers, particularly preferably 97-100% aromatic monomers, and most preferably 100% aromatic monomers.

[0032] Preferably, the aromatic polyimide is the same or different repeating unit of formula (1)

[0033] [ka]

[0034] (In the formula, Functional group R A is a partial R A1 , R A2 and R A3

[0035] [ka]

[0036] Represents one or more identical or different parts selected from the group consisting of, Functional group R B is a partial R B1 , R B2 and R B3

[0037] [ka]

[0038] (In the formula, Y1, Y2, Y3, and Y4 are either H, or CH3, or 2 to 4 carbon atoms, and one of the alkyl radicals having Z=-CH2-, -(CH3)2C-, SO2, -(CF3)C-, -CO-, -COO-, -CONH-, or -O-) (Represents one or more identical or different parts selected from a group consisting of these parts.) Includes.

[0039] More preferably, polyimide a) is Dianhydrides selected from the group consisting of 3,4,3',4'-benzophenonetetracarboxylic dianhydride (BTDA), 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), 3,4,3',4'-biphenyltetracarboxylic dianhydride (BPDA), 1,1,1,3,3,3-hexafluoro-2,2-propylenediphthalic acid dianhydride (6-FDA), 4,4'-oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), and mixtures thereof, Reacting with a diisocyanate selected from the group consisting of toluene-2,4-diisocyanate (2,4-TDI), toluene-2,6-diisocyanate (2,4-TDI), 4,4'-methylenediphenyl-diisocyanate (MDI), 2,4,6-trimethyl-1,3-phenylene diisocyanate (MesDI), 2,3,5,6-tetramethyl-1,4-phenylene diisocyanate, diethylmethylbenzene diisocyanate and mixtures thereof in a bipolar aprotic solvent to obtain a polyimide, or Reacting with a diamine selected from the group consisting of toluene-2,4-diamine (2,4-TDA), toluene-2,6-diamine (2,6-TDI), 4,4'-methylenediphenyl-diamine (MDA), 2,4,6-trimethyl-1,3-phenylene diamine (MesDA), 2,3,5,6-tetramethyl-1,4-phenylene diamine, diethylmethylbenzene diamine and mixtures thereof in a bipolar aprotic solvent to obtain a polyamic acid is prepared by. In this case, the polyamic acid is formed as an intermediate and later imidized.

[0040] Even more preferably, at least 90 mol% of the building block R A is 3,3',4,4'-benzophenonetetrayl, and at least 90 mol% of the building block R B is 2,4-toluenediyl, 2,6-toluenediyl or 4,4'-methylenediphenyldiyl, the molar ratio of 2,4-toluenediyl to 2,6-toluenediyl is 1:9 to 9:1, and the molar ratio of the combined amount of 2,4-toluenediyl and 2,6-toluenediyl to the amount of 4,4'-methylenediphenyldiyl is 70:30 to 100:0 or or at least 90 mol% of the building block R AThe building block is 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 50:50 to 95:5, preferably 55:45 to 65:35, and containing at least 90 mol% of building block R B These are 2,4-toluenediyl or 2,6-toluenediyl, with a molar ratio of 2,4-toluenediyl to 2,6-toluenediyl being 1:9 to 9:1.

[0041] In a first particularly preferred embodiment of the present invention, the polyimide has the following structure according to formula (2):

[0042] [ka]

[0043] (In the equation, 0 ≤ x ≤ 0.5 and 1 ≥ y ≥ 0.5, the sum of x and y = 1, and R is divided into parts L1, L2, L3 and L4)

[0044] [ka]

[0045] (Represents one or more identical or different parts selected from a group consisting of these parts.) It holds.

[0046] The polyimide is very preferably a polymer conforming to formula (2) (wherein x=0, y=1, and R consists of 64 mol% L2, 16 mol% L3, and 20 mol% L4). Such solvent-soluble polyimides are known as P84® or P84® type 70 and have CAS number: 9046-51-9.

[0047] Furthermore, very preferably, the polyimide of formula (2) is also a polymer having a composition x=0.4, y=0.6, with R consisting of 80 mol% L2 and 20 mol% L3. This solvent-soluble polyimide is known as P84(registered trademark)HT or P84(registered trademark)HT325 and has a CAS number: 134119-41-8.

[0048] Details relating to the production of these and further similar polyimides according to formula (2) can be extracted from WO2011 / 009919A1, the entire contents of which are expressly incorporated into the description of the present invention by reference. All polymers described in the examples of WO2011 / 009919A1 are particularly preferred for use in the methods of the present invention.

[0049] DE2143080 describes the preparation of solvent-soluble polyimides from BTDA and a mixture of toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, and 4,4'-methylenediphenyl-diisocyanate. DE2143080 also describes the preparation of solvent-soluble polyamic acids from BTDA and a mixture of toluene-2,4-diamine, toluene-2,6-diamine, and 4,4'-methylenediphenyl-diamine, as well as the subsequent imidation to the corresponding polyimides. Details regarding the production of these and further similar polyimides and polyamic acids can be extracted from DE2143080, and the entire contents of both documents are expressly incorporated by reference into the description of the present invention. All polymers described in the examples of DE2143080 are particularly preferred for use in the methods of the present invention.

[0050] Furthermore, preferred polyimides that can be used in the present invention are block-copolyimides, i.e., block (A) according to formula (3) and block (B) according to formula (4):

[0051] [ka]

[0052] A copolymer containing, preferably composed of, these elements.

[0053] Blocks A and B have different compositions; that is, the pair of R1 and R3 on the one hand, and the pair of R2 and R4 on the other hand, cannot be identical at the same time.

[0054] The block copolyimide contains the continuous phase of block A. Functional group R1 contains the following functional groups:

[0055] [ka]

[0056] Includes one or both of the following.

[0057] R2 is the following functional group

[0058] [ka]

[0059] It includes at least one, two, or three of the following.

[0060] Block A has the following composition in its most preferred embodiment: AF1: 100 mol% R1b, as well as 64 mol% R2a, 16 mol% R2b, and 20 mol% R2c. AF2: 40 mol% R1a, 60 mol% R1b, 80 mol% R2a, and 20 mol% R2b.

[0061] The molar percentages mentioned are selected with respect to functional groups R1 and R2 such that the amounts of various units for each of these groups total 100 mol%.

[0062] R3 in block B has the following functional group:

[0063] [ka]

[0064] It includes at least one or more of the following.

[0065] R4 is the following functional group

[0066] [ka]

[0067] (wherein Y1, Y2, Y3, and Y4 are either H, CH3, or an alkyl radical having 2 to 4 carbon atoms, and Z = -CH2-, -(CH3)2C-, SO2, -(CF3)C-, -CO-, -COO-, -CONH-, -O-, provided that at least one of radicals Y1 to Y4, preferably at least two of radicals Y1 to Y4, more preferably at least three of radicals Y1 to Y4, and most preferably all of radicals Y1 to Y4 are equal to CH3 or C2 to C4 alkyl radicals.) It includes at least one or more of the following.

[0068] R 4cZ is preferably -CH2-, -(CH3)2C-, -(CF3)2C-, or -O-, and more preferably Z=-CH2- or -(CH3)2C-. For R4c, it is very particularly preferable to have the following composition: Y1, Y2 and Y3=H, Y4=CH3 or C2~C4 alkyl radical, and Z=-CH2- or -(CH3)2C-, or Y1 and Y3=CH3 or C2~C4 alkyl radical, Y2 and Y4=H or CH3, and Z=-CH2- or -(CH3)2C-. For R4c, it is most preferable to have the following composition: Y1, Y2, Y3 and Y4=CH3 or C2~C4 alkyl radical, and Z=-CH2- or -(CH3)2C-, preferably -CH2-. If the radicals Y1~Y4 in the above preferred embodiments are not H, it is most preferable that they are CH3.

[0069] In one particular preferred embodiment, block (B) has the following composition: AF3: R3a in 40-60 mol%, R3b in 0-10 mol%, R3c in 60-30 mol%, and R4a in 90-100 mol%, R4b in 0-10 mol%, and R4c in 0-10 mol%. AF4: 50 mol% R3a, 50 mol% R3c, and 100 mol% R4a.

[0070] The molar percentages stated for AF3 and AF4 are given with respect to functional groups R3 and R4, respectively, and therefore the amounts of each unit are selected such that the total for each of these groups is 100 mol%.

[0071] The above-mentioned combinations of AF1 and / or AF2 with AF3 and / or AF4 are very particularly preferred. The combination of AF1 or AF2 with AF4 is most preferred.

[0072] The block lengths n and m of blocks A and B are preferably in the range of 1 to 1000, more preferably in the range of 1 to 500, even more preferably in the range of 1 to 200, even more preferably in the range of 5 to 150, even more preferably in the range of 10 to 100, even more preferably in the range of 10 to 50, and most preferably in the range of 10 to 40.

[0073] The block lengths of blocks A and B may be the same or different. The block-copolyimide may also exhibit some distribution with respect to specific block lengths of blocks A and B; that is, not all blocks A or all blocks B have to be the same length. Therefore, the ratio between blocks A and B can vary over a wide range. In this second preferred embodiment of the present invention, the proportion in the block-copolyimide may be 5-90% for block B and 10-95% for block A. Ratios of A:B = 80:20, or 70:30, or 60:40, or most preferably 50:50 are particularly preferred.

[0074] Details relating to the production of block-copolyimides can be extracted from WO2015 / 091122, the entire contents of which are expressly incorporated by reference into the description of the present invention. All polymers described in the examples of WO2015 / 091122 are particularly preferred as polymers in the methods of the present invention.

[0075] A more preferred polyimide that can be used in the present invention is: - Matrimid 5128 (CAS No. 104983-64-4, based on BTDA DAPI [diaminophenylindan]) according to formula 5

[0076] [ka]

[0077] Or its derivatives such as Br-Matrimid, - For example, polyimide-based materials disclosed in Handbook of Specialty Fluorinated Polymers, 2015 (6-FDA) one of them It is selected from the group consisting of the following.

[0078] The solvent mixture b) of the present invention contains dimethyl sulfoxide (DMSO) as the main component a) in an amount of 55-90% by weight, preferably 55-85% by weight, and more preferably 60-80% by weight, of the total weight of the solvent mixture b). When the DMSO content was too low, the solvent mixture was found to have insufficient solubility of polyimide. Depending on the solvent mixture, only partial dissolution or only swelling of polyimide was observed. When the content was too high, solubility could be very good, but the resulting polyimide solution exhibited poor applicability, particularly a high dissolution temperature, which resulted in the possibility of the solution freezing during transport.

[0079] As component b, the solvent mixture b) comprises one or more primary or secondary and / or tertiary alkanolamines having 3 to 15, preferably 4 to 10, more preferably 4 to 9 carbon atoms, or a mixture thereof.

[0080] The inventors have found that if component b is not included in the solvent mixture, either insufficient solubility or, if good solubility cannot be achieved, rapid film formation in air within 1 hour is observed. It is possible, but undesirable, to provide a solvent mixture b) comprising components a and b, wherein a and b are included in the amounts specified below. However, the inventors have found that, in terms of film formation and melting point, it is preferable that the solvent mixture b) contains at least one, preferably at least two, and more preferably at least three, components c to e as a cosolvent. In this case, component b can also be used in small amounts. If the content of component b in the solvent mixture b) is too high, the solubility of the solvent mixture decreases. Therefore, it is preferable that component b be included in the solvent mixture b) in total at an amount of 0.1 to 20% by weight, preferably 0.5 to 19% by weight, more preferably 1 to 15% by weight, and even more preferably 2 to 13% by weight, of the total weight of the solvent mixture b).

[0081] The most preferred alkanolamines in terms of solubility, applicability, and toxicity classification are selected from the group consisting of triethanolamine and 2-(dimethylamino)ethanol, as well as mixtures thereof. - Triethanolamine is preferably included in an amount of 0 to 20% by weight, preferably 0.1 to 15% by weight, more preferably 1 to 14% by weight, even more preferably 2 to 13% by weight, and most preferably 3 to 12% by weight, relative to the total weight of the solvent mixture b). - 2-(dimethylamino)ethanol is preferably included in an amount of 0 to 20% by weight of the total weight of solvent mixture b). Considering solubility, a 2-(dimethylamino)ethanol content in the range of 0 to 20% by weight is possible and preferred, but if it is desirable to provide a mixture that is classified as low toxicity or even non-toxic in addition to good solubility, the 2-(dimethylamino)ethanol content is preferably reduced to 0.1 to 8% by weight, more preferably 1 to 7% by weight, even more preferably 2 to 6% by weight, and most preferably 3 to 5% by weight, based on the total weight of solvent mixture b). The amounts of triethanolamine and 2-(dimethylamino)ethanol are selected from the ranges shown above, such that the total amount of both components is 0.1 to 20% by weight, preferably 0.5 to 19% by weight, more preferably 1 to 15% by weight, and even more preferably 2 to 13% by weight of the solvent mixture b).

[0082] Component c, i.e., benzyl alcohol, can also be used as a co-solvent. The best results regarding the solubility and film formation of the polyimide solution were found when component c was used in combination with components a and b, or in combination with components a, b and d. Combinations of components a, b, c, d and e can also be used. Therefore, it is preferable that component c be included in the solvent mixture b) in an amount of 0 to 40% by weight, preferably 0.1 to 25% by weight, more preferably 1 to 20% by weight, and even more preferably 2 to 15% by weight of the total weight of the solvent mixture b).

[0083] Component d, i.e., cyclohexanone, can also be used as a co-solvent. The best results regarding the solubility and film formation of the polyimide solution were found when component d was used in combination with components a and b, or in combination with components a, b, and c, or in combination with components a, b, c, d, and e. However, it is also possible to use solvent mixture b) containing components a, b, d, e, and f. Therefore, it is preferable that component d be included in solvent mixture b) in an amount of 0 to 25% by weight, preferably 1 to 25% by weight, more preferably 2 to 20% by weight, and even more preferably 2 to 15% by weight of the total weight of solvent mixture b).

[0084] Component e, i.e., xylene, can also be used as a co-solvent. The best results regarding the solubility and applicability of polyimide solutions in coating applications were found when component e was used in combination with components a, b, c, and d, or when components a, b, e, and f were used in combination. However, it is also possible to use solvent mixture b) containing components a, b, d, e, and f. Therefore, it is preferable that component e be included in solvent mixture b) in an amount of 0 to 15% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, and most preferably 1 to 5% by weight of the total weight of solvent mixture b).

[0085] Component f, i.e., acetophenone and / or alkylene carbonate, can be used as a co-solvent together with components a and b. Preferably, component f is used in combination with components a, b, d, and / or e to obtain a polyimide solution with good solubility and applicability. Preferably, component f is included in the solvent mixture b) in an amount of 0 to 20% by weight, more preferably 1 to 15% by weight, and even more preferably 5 to 15% by weight, of the total weight of the solvent mixture b).

[0086] With respect to component g., i.e., propylene glycol, it has been found that this component is unsuitable for the solubility of the solvent mixture for polyimide. Therefore, component g. is included in solvent mixture b) in a maximum amount of 5% by weight, preferably 0.1 to 5% by weight, more preferably 0.01 to 3% by weight, even more preferably 0.001 to 1% by weight, and especially preferably 0 to 0.5% by weight. Most preferably, propylene glycol is not included, i.e., its content is 0% by weight of the total weight of solvent mixture b).

[0087] DMF, NEP, NMP, and / or DMAc are solvents subject to criticism because they are classified as CMRs and partially SVHC substances. While these cosolvents may be present in small amounts in the solvent mixture, their amounts are preferably minimized, and most preferably, these compounds are not present at all. In total, DMF, NEP, NMP, and / or DMAc may be included in solvent mixture b) as component h. in amounts of 0 to 10% by weight, preferably 0 to 5% by weight, more preferably 0 to 3% by weight, even more preferably 0 to 1% by weight, particularly preferably 0 to 0.1% by weight, and most preferably 0% by weight of the total weight of solvent mixture b).

[0088] Optionally, component i may include a cosolvent i., preferably a glycol ether, in particular a propylene glycol ether commercially available under the trade name Dowanol®, such as 1-methoxy-2-propanol (Dowanol® PM). Preferably, component i. is included in a solution prepared specifically for spray coating applications.

[0089] The solvent mixture b) preferably consists of the following combinations of components: 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. VI) a., b., d., e., and f. Includes or consists of The amounts of components a. and b. are selected from the previously defined range, and the amounts of components c., d., e., and f., if included, are within the following range. c. 0.1 to 40% by weight, preferably 0.1 to 25% by weight, more preferably 1 to 20% by weight, even more preferably 5 to 15% by weight, d. 1-25% by weight, preferably 1-25% by weight, more preferably 2-20% by weight, even more preferably 2-15% by weight, e. 0.1 to 15% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, most preferably 1 to 5% by weight. f. A total of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 5 to 15% by weight of acetophenone and / or alkylene carbonate, preferably propylene carbonate or ethylene carbonate, most preferably propylene carbonate. Selected from.

[0090] In a solvent mixture comprising components a. and b., or a solvent mixture comprising components a. and b. and optionally one or more components c. to f., preferably in solvent mixtures I) to VI), each component a. to f. is included in an amount selected from the range defined above, and the amount of each component is selected such that the total amount of the components constitutes solvent mixture b) at 100%.

[0091] Combinations I), III), and IV) are more preferred, and combinations III) and IV) are most preferred.

[0092] To reduce transportation costs and for environmental reasons, it is preferable to reduce the amount of solvent mixture b) in the polyimide solution. The inventors have found that a good, i.e., a highly concentrated polyimide solution having low or acceptable viscosity can be prepared using the solvent mixture b) of the present invention. Preferably, the polyimide solution of the present invention contains, in total, 5 to 35% by weight, preferably 10 to 30% by weight, and more preferably 15 to 25% by weight of polyimide a) relative to the total weight of the polyimide solution. A strong increase in viscosity was observed as the polyimide content increased.

[0093] A preferred polyimide solution of the present invention contains component b) in an amount of 95 to 65% by weight, preferably 90 to 70% by weight, and more preferably 85 to 75% by weight, of the total weight of the polyimide solution.

[0094] In alternative embodiments, a dispersion containing inorganic particles is prepared using a polyimide solution. The dispersion preferably contains, as an additional component c), one or more fillers selected from the group consisting of graphite, metal sulfides such as molybdenum disulfide and tungsten disulfide, metal oxides such as aluminum oxide, inorganic nitrides such as aluminum nitride, silicon nitride and hexagonal boron nitride, silica, abrasive particles such as cubic boron nitride and diamond. The fillers may be present in an amount of 0 to 20% by weight of the total solid components of the dispersion. The solids of the dispersion refer to the weight of the residue obtained after evaporation of the total solvent in a vacuum oven at 230°C for 2.5 hours. If fillers are present, the given amounts of components a) and b) above are adapted accordingly.

[0095] The polyimide solution of the present invention is i. The step of preparing one or more types of polyimide a) as defined above, ii. The step of preparing the solvent mixture b) as defined above, iii. Dissolve the polyimide prepared in step i in the solvent mixture prepared in step ii. It can be prepared by a method that includes [a specific component].

[0096] In an alternative embodiment, the polyimide solution of the present invention is I. The step of preparing one or more types of polyimide a) as defined above, II. The step of partially or completely dissolving the polyimide prepared in step I in DMSO, III. Add the remaining components of solvent mixture b) to the polyimide solution obtained in step II in an amount that obtains the previously defined solvent mixture b). It can be prepared by a method that includes [a specific component].

[0097] When a dispersion containing a filler is prepared, the filler is preferably added after step iii. or III. Alternatively, the filler may be added between steps i. and ii., or between steps i. and II.

[0098] To minimize dissolution time and increase method efficiency, step iii. or step II. is preferably carried out at a temperature of 25 to 90°C, more preferably 50 to 70°C. Dissolution of polyimide can be easily carried out by techniques and apparatus known to those skilled in the art. Preferably, the preparation and / or storage of the polyimide solution is carried out under inert conditions.

[0099] The polyimide solution of the present invention can be used to coat substrates, preferably steel, aluminum, copper, and PEEK (polyether ether ketone). The inventors have found that the polyimide solution of the present invention can be applied via spray coating, dip coating, roller coating, or by squeegee. [Examples]

[0100] The following embodiments are intended to illustrate and explain the present invention in more detail, but are not intended to be construed as limiting the scope of the claims in any way.

[0101] Preparation of polyimide solutions Several polyimide solutions according to the present invention and comparative polyimide solutions were prepared and tested. To prepare the polyimide solutions, dry polyimide powder was dissolved in various solvent mixtures at 60°C with stirring, at a maximum weight content of 25%. The components used and their amounts are summarized in Table 1.

[0102] Chemicals used: P84 (registered trademark) Type 70 obtained from Evonik Fibres GmbH (Austria) P84 (registered trademark) HT obtained from Evonik Fibres GmbH (Austria) Block-co-PI prepared according to Example 13 of WO2015 / 091122

[0103] All of the following chemicals were used as laboratory-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

[0104] Storage stability Figure 1 shows the storage stability tests of a comparative example, namely a solution of P84® type 70 in pure DMSO, as well as Examples E5 and E6 of the present invention. The comparative example exhibits poor storage stability when exposed to air. Visible film formation began after 30 minutes. In contrast, Examples E5 and E6 of the present invention show no film formation even after 8 hours.

[0105] The prepared polyimide solution was tested as a coating solution as follows: Polyimide solutions were applied as coatings to steel or aluminum surfaces via a doctor blade or, after dilution, via a spray coating process. Adhesion of the coatings was studied via cross-hatch testing.

[0106] After drying, the tested coatings of the present invention showed quality comparable to those prepared using a P84(registered trademark) type 70 solution in NMP. Evaluation and comparison of various coatings were performed by cross-cut tests in accordance with ISO 2409.

[0107] The dissolution temperatures of various 20% PI solutions were determined via DSC measurements.

[0108] [Table 1]

[0109] LS = Low solubility <10 wt% polyimide (PI) MS=moderate solubility 15% PI soluble GS = Good solubility; 20 wt% PI soluble, or ≥25 wt% PI soluble, but viscosity of 20 wt% solution ≥10 Pa·s VS = Very good solubility; ≥25 wt% PI soluble, and viscosity of 20 wt% solution <10 Pa·s PS=poor solubility SW = only polymer expansion PD=partial lysis ND = Not detected

[0110] [Table 2]

[0111] LS = Low solubility <10 wt% polyimide (PI) MS=moderate solubility 15% PI soluble GS = Good solubility; 20 wt% PI soluble, or ≥25 wt% PI soluble, but viscosity of 20 wt% solution ≥10 Pa·s VS = Very good solubility; ≥25 wt% PI soluble, and viscosity of 20 wt% solution <10 Pa·s PS=poor solubility SW = only polymer expansion PD=partial lysis

[0112] Table 1 shows that none of the polyimide solutions in the comparative examples solve all the problems of the present invention. The most comparable solvent mixture had insufficient solubility with undissolved polyimide and / or swelling. Example E15 of the present invention shows that a solution of the present invention containing a binary solvent mixture of DMSO and a tertiary alkanolamine in the amounts according to the present invention exhibits superior storage stability, superior solubility, and a significantly improved melting point compared to comparative example CE5. CE5 is a direct comparison with E15, i.e., a direct comparison with a binary solvent mixture consisting of DMSO and 2-(dimethylamino)ethanol, but with non-inventive content of both solvents. Both E15 and CE5 show good solubility, however CE15 shows film formation after 4 hours, indicating that storage stability deteriorates when a binary solvent mixture of DMSO and a tertiary alkanolamine is used, and when the amine content in the solvent mixture is too low. CE9 shows very good solubility and a low melting point, but film formation had already begun after 1 hour. In contrast, all embodiments of the present invention have good or very good solubility, at least moderate, but mostly good. Embodiments of the present invention having good and very good solubility were further tested for their viscosity, film formation time, melting point, and in cross-cut tests after coating of substrates. All tested embodiments of the present invention were found to have a melting point below 0°C. All tested embodiments of the present invention had a film formation time of at least 2 hours, mostly more than 8 hours, which is a great advantage with respect to their application. The viscosity of the tested embodiments of the present invention was good or even very good, and the quality of the coating in the cross-cut tests was also good or very good. Examples E1 to E15 demonstrate that the present invention offers high flexibility for commercial use. It is possible to provide a solution with a very low melting point but limited storage stability (4 hours), a solution with very good storage stability but a melting point slightly above 0°C, and finally, a solution with both a very low melting point and excellent storage stability. Thus, those skilled in the art can select a suitable solvent mixture according to commercial requirements.However, in all cases, the solvents of the present invention exhibit good or even very good solubility performance and are classified as non-toxic, which is a significant advantage compared to commercially available polyimide solutions in DMF, DMAc, NMP, and NEP.

[0113] Table 1 confirms that the solvent mixture of the present invention solves all the problems of the invention and offers significant advantages over prior art solutions, commercially available polyimide solutions, and alternative polyimide solutions (CE2-CE9) that can be classified as non-toxic.

Claims

1. a) one or more polyimides; b) a. 55 to 90% by weight of dimethyl sulfoxide; b. 0.1 to 20% by weight in total of one or more primary, secondary and / or tertiary alkanolamines having 3 to 15 carbon atoms; c. 0 to 40% by weight of benzyl alcohol; d. 0 to 25% by weight of cyclohexanone; e. 0 to 15 wt. % xylene; f. 0 to 20% by weight in total of acetophenone and / or alkylene carbonate; g. 0 to 5% by weight of propylene glycol; h. 0-10 wt. % in total of DMF, NEP, NMP and / or DMAc; i. optionally, an additional co-solvent Including, The weight percentages indicated for components a. to i. are based on the total weight of the solvent mixture b), The amounts of components a. to i. are selected so that they add up to 100% by weight of the solvent mixture; Solvent mixture and A polyimide solution comprising: The polyimide solution comprises a total of 5 to 35 weight percent of component a), based on the total weight of the polyimide solution; Polyimide solution.

2. component a., b. and c. or a., b. and d. or a., b., c. and d. or a., b., c., d. and e. or a., b., e. and f. or a., b., d., e. and f. The present invention is characterized in that it comprises The amounts of components a. and b. are selected from the ranges set forth in claim 1, and the amounts of components c., d., e. and f., if included, are within the following ranges: c. 0.1 to 40% by weight, d. 1 to 25% by weight, e. 0.1 to 15% by weight, f. 1 to 20% by weight in total of acetophenone and / or alkylene carbonate Selected from: The polyimide solution according to claim 1 .

3. component a., b. and c. or a., b. and d. or a., b., c. and d. or a., b., c., d. and e. or a., b., e. and f. or a., b., d., e. and f. The present invention is characterized in that it comprises: The amounts of components a. and b. are selected from the ranges set forth in claim 1, and the amounts of components c., d., e. and f., if included, are within the following ranges: c. 0.1 to 40; d. 1 to 25% by weight, e. 0.1 to 15% by weight, f. 1 to 20% by weight in total of acetophenone and / or alkylene carbonate is selected from The amount of each component is selected such that the amounts of the components total 100% of the solvent mixture b); The polyimide solution according to claim 2.

4. 2. The polyimide solution of claim 1, wherein the amounts of components a. to h. are selected so that they total 100% by weight of the solvent mixture.

5. the one or more primary, secondary or tertiary alkanolamines having 3 to 15 carbon atoms are selected from the group consisting of triethanolamine and 2-(dimethylamino)ethanol, and mixtures thereof; The amount of triethanolamine and 2-(dimethylamino)ethanol is selected from the ranges indicated above so that both components together represent 0.1-20% by weight of the solvent mixture b). The polyimide solution according to claim 1 .

6. The polyimides a) are each composed of identical or different repeating units of formula (1) 【Chemistry 1】 (In the formula, Functional group R A is the part R A1 , R A2 and R A3 【Chemistry 2】 represents one or more identical or different moieties selected from the group consisting of: Functional group R B is the part R B1 , R B2 and R B3 【Chemistry 3】 (In the formula, Y 1 , Y 2 , Y 3 and Y 4 is H or CH 3 or an alkyl radical having 2 to 4 carbon atoms, where Y=-CH 2 -, -(CH 3 ) 2 C-, SO 2 , -(CF 3 ) C-, -CO-, -COO-, -CONH-, -O- (representing one or more identical or different moieties selected from the group consisting of:

2. The polyimide solution according to claim 1, which is an aromatic polyimide comprising:

7. At least 90 mol % of the building block R A is 3,3',4,4'-benzophenonetetrayl, and at least 90 mol % of the building blocks R B is 2,4-toluenediyl, 2,6-toluenediyl or 4,4'-methylenediphenyldiyl, the molar ratio of 2,4-toluenediyl to 2,6-toluenediyl is 1:9 to 9:1, and the molar ratio of the combined amount of 2,4-toluenediyl and 2,6-toluenediyl to the amount of 4,4'-methylenediphenyldiyl is 70:30 to 100:

0.

8. At least 90 mol % of the building block R A is 3,3',4,4'-benzophenonetetrayl or 1,2,4,5-phenylenetetrayl, the molar ratio of 3,3',4,4'-benzophenonetetrayl to 1,2,4,5-phenylenetetrayl being 50:50 to 95:5, and at least 90 mol % of the building block R B 7. The polyimide solution according to claim 6, wherein is 2,4-toluenediyl or 2,6-toluenediyl, and the molar ratio of 2,4-toluenediyl to 2,6-toluenediyl is 1:9 to 9:

1.

9. The solvent-soluble aromatic polyimide comprises a block (A) according to the following formula (3) and a block (B) according to the following formula (4): 【Chemistry 4】 (In the formula, Functional group R 1 contains the following functional groups: 【Chemistry 5】 including either or both of R 2 is the following functional group 【Chemistry 6】 At least one, two or three of R 3 is the following functional group: 【Chemistry 7】 and R4 is the following functional group 【Chemistry 8】 (In the formula, Y 1 , Y 2 , Y 3 and Y 4 is H or CH 3 or an alkyl radical having 2 to 4 carbon atoms, Z=-CH 2 -, -(CH 3 ) 2 C-, SO 2 , -(CF 3 ) C—, —CO—, —COO—, —CONH—, —O—, provided that the radical Y 1 ~Y 4 At least one of 3 Or C 2 ~C 4 (provided that it is equal to an alkyl radical) (including one or more of the following) The polyimide solution of claim 1 , comprising:

10. 2. The polyimide solution according to claim 1, comprising a total of 10 to 30% by weight of component a), based on the total weight of the polyimide solution.

11. 2. The polyimide solution according to claim 1, comprising a total of 95 to 65% by weight of component b), based on the total weight of the polyimide solution.

12. 10. A dispersion comprising the polyimide solution of claim 1, further comprising, as component c), one or more fillers selected from the group consisting of graphite, metal sulfides, metal oxides, inorganic nitrides, silica, and abrasive particles.

13. 1. A method for preparing a polyimide solution, comprising: i. providing one or more polyimides a); ii. a. 55 to 90% by weight of dimethyl sulfoxide; b. 0.1 to 20% by weight in total of one or more primary, secondary, or tertiary alkanolamines having 3 to 15 carbon atoms; c. 0 to 40% by weight of benzyl alcohol; d. 0 to 25% by weight of cyclohexanone; f. 0 to 20% by weight in total of acetophenone and / or alkylene carbonate; g. 0 to 5% by weight of propylene glycol; h. 0-10 wt. % in total of DMF, NEP, NMP and / or DMAc; i. optionally, an additional co-solvent Including, The weight percentages indicated for components a. to i. are based on the total weight of the solvent mixture b), The amounts of components a. to i. are selected so that they add up to 100% by weight of the solvent mixture b); Steps and iii. dissolving the polyimide prepared in step i. in the solvent mixture prepared in step ii.; A method comprising:

14. 1. A method for preparing a polyimide solution, comprising: I. Providing one or more polyimides a); II. Partially or completely dissolving the polyimide prepared in step I. in DMSO; III. Adding the remaining components of the solvent mixture b) to the polyimide solution obtained in step II. in amounts to obtain the solvent mixture b); Including, Solvent mixture b) is a. 55 to 90% by weight of dimethyl sulfoxide; b. 0.1 to 20% by weight in total of one or more primary, secondary, or tertiary alkanolamines having 3 to 15 carbon atoms; c. 0 to 40% by weight of benzyl alcohol; d. 0 to 25% by weight of cyclohexanone; f. 0 to 20% by weight in total of acetophenone and / or alkylene carbonate; g. 0 to 5% by weight of propylene glycol; h. 0-10 wt. % in total of DMF, NEP, NMP and / or DMAc; i. optionally, an additional co-solvent Including, The weight percentages indicated for components a. to i. are based on the total weight of the solvent mixture b), The amounts of components a. to i. are selected so that they add up to 100% by weight of the solvent mixture b); method.

15. The method for preparing a polyimide solution according to claim 13 or 14, characterized in that step iii. or step II. is carried out at a temperature of 25-90°C.

16. 10. Use of the polyimide solution according to claim 1 for coating a substrate.

17. 10. The use of the polyimide solution of claim 1 in processing, wherein the polyimide solution is applied via spray coating, dip coating, roller coating, or with a squeegee.

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