Coating composition containing polyamide-imide polymer

Abstract

An aqueous-based composition having a high solids content and a stable viscosity over time, the composition comprising a high acid number polyamideimide polymer and methylethanolamine.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 283656, filed November 29, 2021, and from European Patent Application No. 22151401.1, filed January 13, 2022, the entire disclosures of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to aqueous formulations, particularly aqueous coating formulations containing polyamide-imide polymers.

[0003] Polyamide-imide and polyamic acid polymers (hereafter referred to collectively as PAIs) are well-known thermally stable polymers that are used in many high performance coating applications due to their excellent adhesion, heat resistance, and high strength. PAIs are commonly utilized as protective coatings for metal substrates that are exposed to harsh environments such as temperature, abrasion, abrasion, and chemical exposure. PAIs also exhibit good adhesion to silicon and other substrates.

[0004] Most PAIs are only soluble in organic solvents, usually polar aprotic solvents. Commonly used solvents belong to the class of N-methylamide solvents, especially N-methylpyrrolidone (NMP). After being applied onto a substrate, the PAI composition undergoes a thermal curing process that removes the solvent and increases the molecular weight in order to achieve the optimum desired properties of the material. A significant drawback of this approach is that solvents such as NMP are known to be toxic. Furthermore, reducing the use of volatile organic compounds as solvents is highly desirable from a sustainability perspective.

[0005] Therefore, it would be highly desirable to provide water-based coating formulations containing PAI polymers that do not contain organic solvents.

[0006] Methods for producing aqueous PAI compositions are known, but they generally rely on hazardous complexing amines, involve the use of small amounts of polar organic solvents, and / or often suffer from a poor shelf life along with a constant increase in viscosity over time.

[0007] US Patent No. 4,087,394 discloses a mixture of triethylamine and diethylethanolamine to solubilize PAI polymers, however, significant amounts of the solvents, furfuryl alcohol and NMP, are used in the composition.

[0008] US 4,259,221 discloses compositions comprising PAI, water, optionally a small amount of organic solvent and a tertiary amine or mixture of amines. US 4,259,221 specifically discloses the use of PAIs with a small amount of free carboxylic acid groups, for example up to 20% free carboxylic acid groups. A list of tertiary amines suitable for preparing aqueous compositions is provided, specifically: dimethylethanolamine, triethanolamine, phenylmethylethanolamine, butyldiethanolamine, phenyldiethanolamine, phenylethylethanolamine, methyldiethanolamine and triethylamine. An exemplary composition includes Torlon® AI-10, a PAI polymer characterized by an acid value of 70-90 mg KOH / g polymer, and dimethylethanolamine.

[0009] US Patent No. 6,479,581 discloses an aqueous PAI composition comprising a PAI polymer having a high acid number, preferably greater than 120 mg KOH / g polymer, and a tertiary aliphatic amine, the most preferred amine being triethylamine.

[0010] Most tertiary amines used in practice are relatively hazardous materials, in some cases just as hazardous as the solvent system they are seeking to replace. For example, triethylamine is a flammable, corrosive, and acutely toxic liquid. Alkanol-substituted amines are generally less hazardous than alkyl-substituted amines such as triethylamine. For example, triethanolamine, in contrast to triethylamine, is classified as not hazardous. However, the exchange of the alkyl with the alkanol substituent results in a weaker base and a less effective neutralizing agent. Aqueous solutions using triethanolamine are more difficult to obtain and often result in a large amount of undissolved polymer particles that must be filtered out. Other alkanol-substituted amines, such as butyldiethanolamine, have adequate basicity, but unexpectedly result in compositions whose viscosity is not stable over time.

[0011] Unexpectedly, it has been found that by combining a PAI polymer with an optimal combination of solid content and viscosity and a high acid value with methyldiethanolamine, it is possible to obtain an aqueous composition whose viscosity is stable over time.Advantageously, methyldiethanolamine is classified as a non-hazardous substance.More advantageously, methyldiethanolamine can easily dissolve the polymer when preparing the composition. Summary of the Invention

[0012] Thus, a first object of the present invention is a composition comprising water, at least one aromatic polyamic acid / polyamideimide polymer [polymer (PAI)] having an acid number of at least 100 mg KOH / g (polymer), and methyldiethanolamine as further defined in claim 1. The composition preferably contains 1.0-35.0% by weight of polymer (PAI), relative to the total weight of polymer (PAI), methyldiethanolamine and water.

[0013] In one embodiment, the composition has a viscosity of 100 to 10,000 cPoise.

[0014] In one embodiment, the polymer (PAI) is obtained via an acid halide process.

[0015] A second object of the invention is a method for preparing the composition.

[0016] A third object of the present invention is a process for the manufacture of an article, comprising the step of applying the composition onto a substrate. All these objects are defined in the claims, the details of which are provided below.

[0017] definition The use of parentheses around a symbol or number identifying a compound, chemical formula, or part of a formula has the sole purpose of better distinguishing that symbol or number from the rest of the text, and therefore, said parentheses may be omitted.

[0018] Any description, even if made in relation to a particular embodiment, is applicable to and interchangeable with other embodiments of the invention.

[0019] Any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited range, as well as the endpoints of the range and equivalents thereof.

[0020] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] According to a first aspect of the present invention, there is provided a composition comprising a polyamic acid / polyamideimide polymer containing aromatic repeat units [polymer (PAI)], wherein more than 50.0 mol % of said repeat units contain at least one aromatic ring and at least one amic acid and / or imide group [repeat units (RPAI)], and wherein said polymer (PAI) has an acid number of at least 100 mg KOH / g (polymer) as further defined in claim 1.

[0022] The composition may include one or more polymers (PAIs).

[0023] The acid number (mg KOH / g polymer) of the polymer (PAI) can be at least 110, and even at least 120. It can be up to the theoretical acid number for a resin containing only amide acid units. In certain embodiments, it can be up to 170 mg KOH / g polymer.

[0024] The acid number can be determined by titration, such as potentiometric titration according to ASTM D664, in particular the potentiometric titration method described by ASTM D664, in which N-methylpyrrolidone (NMP) is the solvent and the titrant is tributylammonium chloride.

[0025] Repeating unit (R PAI ) is advantageously [ka] wherein the compound is selected from the group consisting of: - the symbol → denotes in each formula that in any repeat unit within the aromatic polyamic acid structure, the radicals pointed to by the arrow may be present as shown or in interchanged positions; Ar is an aromatic tetravalent radical which may contain one or more aromatic rings and is preferably [ka] (X is -O-, -C(O)-, -S-, -SO 2 -, -CH 2 -, -C(CF 3 ) 2 -, -(CF 2 ) n - (n=0, 1, 2, 3, 4 or 5) selected from the group consisting of; R is an aromatic divalent radical which may contain one or more aromatic rings and is preferably [ka] (Y is -O-, -C(O)-, -S-, -SO 2 -, -CH 2 -, -C(CF 3 ) 2 -, -(CF 2 ) n - (n=0, 1, 2, 3, 4 or 5) [ka] is selected from the group consisting of:

[0026] Repeating unit (R PAI ) is preferably as defined above: [ka] is selected from the group consisting of: Repeating unit (R PAI ) is more preferably a unit (i), (ii) and (iii) as detailed below:

[0027] [ka] and / or the corresponding imide group-containing repeat unit: [ka] (wherein the attachment of the two amide groups to the aromatic ring shown in (ia) is understood to represent 1,3 and 1,4 polyamide-amic acid configurations); [ka] and / or the corresponding imide group-containing repeat unit: [ka] wherein the attachment of the two amide groups to the aromatic ring shown in (ii-a) is understood to represent a 1,3 and 1,4 polyamide-amic acid configuration; and [ka] and / or the corresponding imide group-containing repeat unit: [ka] (wherein the attachment of the two amide groups to the aromatic ring shown in (iii-a) is understood to represent a 1,3 and 1,4 polyamide-amic acid configuration.) is selected from the group consisting of:

[0028] Repeating unit (R PAI ) is preferably the repeat unit (i) or a mixture of repeat units (ii) and (iii).

[0029] Preferably, the polymer (PAI) has more than 90.0 mol % of repeat units (R PAI Even more preferably, it comprises the repeating unit (R PAI ) does not contain any repeating units other than those.

[0030] Excellent results have been obtained with polymers (PAI) consisting of repeating units (i) or a mixture of repeating units (ii) and (iii).

[0031] The amount of repeat units containing amico groups can be determined by any suitable technique, in particular spectroscopic or titration techniques well known to those skilled in the art.

[0032] Repeating unit (R PAI ) is calculated using the formula (RPAI -A), (R PAI -B), (R PAI -C), (R PAI -D), (R PAI -E), and a repeating unit (R PAI ) can be expressed as:

number

[0033] Repeating unit (R PAI ) is represented by the formula (R PAI -A), and (R PAI -C), the repeating unit (R PAI ) mole % can be expressed as follows: [(R PAI -A)units] / {[(R PAI -A)unit]+[(R PAI -C)unit]}×100.

[0034] Usually, the repeating unit (R PAI At least 50.0 mol %, further at least 60.0 mol %, and even at least 70.0 mol % of the aryl groups comprise at least one amic acid group.

[0035] In certain embodiments, the repeating unit (R PAI ) contains at least one amic acid group in an amount of 70.0 to 95.0 mol %, and further in an amount of 75.0 to 90.0 mol %.

[0036] The polymer (PAI) can be prepared by a process comprising a polycondensation reaction of at least one aromatic polycarboxylic acid halide monomer with at least one aromatic diamine.

[0037] The aromatic polycarboxylic acid halide monomer can be selected from the group consisting of terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, and acid halide derivatives of trimellitic anhydride.Preferably, it is selected from trimellitic anhydride monoacid halides.Of the trimellitic anhydride monoacid halides, trimellitic anhydride monoacid chloride is preferred.

[0038] In some embodiments, dicarboxylic anhydride monomers can be used in combination with polycarboxylic acid halide monomers.Suitable dicarboxylic anhydride monomers include pyromellitic anhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, and trimellitic anhydride.When dicarboxylic anhydride monomers are used in the process, the excess amount of acid halide monomers relative to the equimolar concentration of aromatic diamine monomers is calculated by considering the total moles of acid halide and dicarboxylic anhydride monomers.

[0039] The aromatic diamine monomers are 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), m-phenylenediamine (MPDA), diphenyldimethylmethanediamine (DMMDA), 1,3-bis(3-aminophenoxy)benzene (BAPB), 4,4'-bisphenol A ether diamine (BAPP), 4,4'-bis(4-aminophenoxy)diphenyl sulfone (BAPS), 4,4'-bis(4-aminophenoxy)diphenyl ether (BAPE), diaminodiphenyl(methyl)ketone (DABP), 4,4'-diaminotriphenyl ether (DTA ... phenylamine (DATPA), 4,4'-diaminodiphenylmethane (MDA), diaminodiphenyl sulfone (DDS), 3,4'-diaminodiphenyl ether (3,4'-ODA), 3,3'-dimethyl-4,4'-diaminodiphenylmethane (MDI), 4,4'-diamino-diphenoxy-1",4"-benzene, 4,4'-diamino-diphenoxy-1",3"-benzene, 3,3'-diamino-diphenoxy-1",3"-benzene, 4,4'-diamino-diphenyl-4",4-phenyl-isopropylpropane and mixtures thereof.

[0040] The aromatic diamine monomer is preferably selected from the group consisting of 4,4'-diaminodiphenylether (ODA), p-phenylenediamine, (PDA), and m-phenylenediamine (MPDA) and mixtures thereof. The aromatic diamine monomer can be ODA. The aromatic diamine monomer can be PDA. The aromatic diamine monomer can be MPDA.

[0041] The polycondensation reaction is advantageously carried out under substantially anhydrous conditions, in a polar solvent, at a temperature below 150° C., using a stoichiometric excess of the acid halide monomer.

[0042] To control the molecular weight and improve the stability of the polymer, monofunctional reactants can be used as end-capping agents, as known to those skilled in the art.

[0043] The polymer (PAI) is advantageously isolated in solid form by coagulation or precipitation from the polar reaction solvent under mild conditions, preferably by addition of a miscible non-solvent such as, for example, water or a lower alkyl alcohol. Optionally, the solid resin may then be recovered, washed extensively with water, and centrifuged or pressed to further reduce the water content of the solid without the application of heat. Non-solvents other than water and lower alkyl alcohols are known and used in the art to precipitate polymers (PAI) from solutions including, for example, ethers, aromatic hydrocarbons, ketones, and the like.

[0044] The number average molecular weight (Mn) of the polymer (PAI) is advantageously at least 1000, preferably at least 1500, more preferably at least 2000.

[0045] The number average molecular weight (Mn) of the polymer (PAI) is advantageously at most 20,000, preferably at most 15,000.

[0046] The molecular weights (Mw and Mn) of the polymers (PAI) may be, and typically are, determined using gel permeation chromatography (GPC) with polystyrene standards.

[0047] The composition of the invention advantageously comprises at least 1.0% by weight of polymer (PAI), preferably at least 3.0% by weight, more preferably at least 5.0% by weight, relative to the total weight of polymer (PAI), methyldiethanolamine and water.

[0048] The composition of the invention advantageously comprises at most 35.0% by weight of polymer (PAI), preferably at most 30.0% by weight, more preferably at most 25.0% by weight, relative to the total weight of polymer (PAI), methyldiethanolamine and water.

[0049] For the avoidance of doubt, when the composition comprises two or more polymers (PAIs), the total amount of polymers (PAIs) is in accordance with the ratios given herein.

[0050] Polymer compositions containing 3.0-20.0 wt % and 5.0-20.0 wt % of the polymer (PAI) relative to the total weight of the polymer (PAI), methyldiethanolamine and water gave very satisfactory results.

[0051] It has been unexpectedly found that compositions comprising polymer (PAI) in an amount of 5.0 to 20.0 wt.%, and even 5.0 to 15.0 wt.%, have a viscosity suitable for use of said compositions in the manufacture of coatings.

[0052] Advantageously, a composition consisting essentially of polymer (PAI), methyldiethanolamine and water, where polymer (PAI) is present in an amount of 5.0-20.0% by weight, has a viscosity measured at 25°C of 100-10000 centipoise, typically 300-8000 centipoise.

[0053] The viscosity of the composition can be measured at 25° C. using a Brookfield viscometer.

[0054] The phrase "consisting essentially of" is used herein to indicate that the composition contains less than 5.0% by weight, typically less than 2.0% by weight or less than 1.0% by weight of other components.

[0055] The composition of the present invention comprises methyldiethanolamine. The minimum amount of methyldiethanolamine used is approximately the theoretical amount required to neutralize the free carboxylic acid groups in the polymer (PAI). An excess of amine as high as a 3-5 fold stoichiometric excess is desirable. The molar ratio of amine to free carboxylic acid groups in the polymer (PAI) is generally in the range of 0.8-5.0, preferably 0.8-2.5, more preferably 1.0-2.0. For the avoidance of doubt, when a composition comprises more than one polymer (PAI), the amount of methyldiethanolamine given herein takes into account all free carboxylic acid groups present in the polymer (PAI).

[0056] Generally, and depending on the final solids content, the composition will contain from 0.5 to about 30.0 weight percent methyldiethanolamine, even 1.0 to 20.0 weight percent, based on the total combined weight of the polymer (PAI), methyldiethanolamine, and water.

[0057] Any convenient method of combining the ingredients may be used to prepare the aqueous compositions of the present invention. The solid polymer (PAI) may be added in incremental amounts to a stirred mixture of methyldiethanolamine and water, with stirring continued until the solid resin is dissolved. Alternatively, the methyldiethanolamine may be added slowly to a stirred suspension of the polymer (PAI) in water, with continued stirring until the solid is dissolved. As with acid-based reactions, external cooling may prove necessary initially; subsequent warming and stirring may be desirable to complete dissolution of the solid resin in a reasonable period of time. For example, the suspension may be heated to a temperature of 50-90°C and held under stirring.

[0058] A further advantage of using methyldiethanolamine in conjunction with a polymer (PAI) having a high acid number has been found to be the limited time required to achieve dissolution of the polymer (PAI), which is significantly less than that observed with PAI polymers having low acid numbers of less than 100 mg KOH / g polymer.

[0059] Thus, the aqueous solutions according to the invention comprise the polymer (PAI), water and methyldiethanolamine. In general, these aqueous compositions have low levels of any organic solvent, generally less than 5.0% by weight, less than 2.0% by weight, preferably less than 1.0% by weight. The compositions of the invention are preferably substantially free of organic solvents. The expression "substantially free" in relation to the composition and organic solvents is intended to mean that said organic solvent or organic solvents are present in an amount of less than 0.5% by weight, preferably less than 0.2% by weight, relative to the weight of the composition. Formulations containing organic solvents at levels as low as 0.1% by weight and even lower can also be obtained, for example, by using extended washing. Such compositions are highly desirable for use in applications where organic solvents cannot be tolerated. The term "solvent" means an organic molecule that can dissolve the polymer (PAI) or promote the dissolution of the polymer (PAI) and that is not methyldiethanolamine.

[0060] Depending on the final use, the composition may further comprise the usual ingredients of coating compositions, such as: (i) dispersants; (ii) pigments, such as carbon black, silicates, metal oxides and sulfides; (iii) additives, such as flow promoters; (iv) carbon fibres, glass fibres, BaSO. 4 or CaSO 4 Metal sulfates such as Al 2 O 3 Or SiO 2 (v) organic fillers, preferably heat stable polymers such as PTFE; (vi) film hardeners such as metal silicates, silicate compounds such as aluminum silicate, and metal oxides such as titanium dioxide; (vii) adhesion promoters such as colloidal silica and phosphate compounds such as metal phosphates, e.g. phosphates of Zn, Mn, or Fe.

[0061] A further aspect of the invention is a method of making an article comprising applying a composition of the invention onto a substrate.

[0062] Any technique may be used for the process. Usually, the composition is applied by coating. Coating can be carried out by any suitable coating process such as spin coating, slit spin coating, roll coating, die coating or curtain coating. The coating step is typically followed by a step of curing the applied composition by pre-baking the obtained film at a temperature comprised between 120 and 400°C, preferably between 120 and 350°C, in order to volatilize the solvent.

[0063] The thickness of the coating can vary depending on the intended purpose, and is preferably in the range of 0.1 to 100 microns, preferably 1 to 50 microns, more preferably 5 to 20 microns, and even more preferably the thickness is about 10 microns.

[0064] The aqueous compositions of the present invention have been found to be particularly useful in formulations intended for use in coating applications, providing an adherent, high strength, continuous coating layer with improved toughness on the coated surface.More generally, the aqueous compositions of the present invention can be used to provide adhesive or protective coatings in applications requiring resistance to abrasion, heat, or harsh chemical environments.

[0065] Such coatings may act as binders for automotive finishes and improve adhesion between existing layers of the automotive finish or with other metallic finishes.

[0066] PAI polymers are known to have good adhesion to metal surfaces and therefore the aqueous compositions of the present invention may be found particularly useful in providing formulations for use as enamels in container coating applications or in insulated wire applications, such as magnet wire for electric motors.

[0067] The aqueous compositions of the present invention may be used to provide chemically corrosion resistant coatings on metal or other substrates, to provide binders for non-stick cookware; to provide coatings for tie bars used in cement; to provide pretreatment coatings for polymeric films, such as, for example, polyester, polyamide and polyimide films, when used in metallization operations; as adhesives for various plastic or metal films, such as liquid crystal polymers and polyimides; and as additives to improve the performance of inks.

[0068] The substantially organic solvent-free aqueous compositions of certain embodiments of the present invention may be found useful in film casting where organic solvents are undesirable or unacceptable.

[0069] Formulations including these aqueous compositions may also be found to be particularly useful as sizing agents and for fibrous materials such as glass fibers, carbon and graphite fibers, alumina fibers, silicon nitride fibers, boron fibers, aramid fibers, fluorocarbon fibers, etc. The term "carbon fibers" is used herein in a generic sense and includes graphite fibers resulting after thermal carbonization or graphitization processes as well as amorphous carbon fibers.

[0070] To the extent that the disclosures of any patents, patent applications, and patent publications incorporated herein by reference conflict with the statements in this application to the extent that the terms may be unclear, the statements of the present invention shall control.

[0071] The present invention will now be described with reference to the following examples, the purposes of which are merely illustrative and not limiting of the invention.

[0072] raw materials Methyldiethanolamine (MDEA), and butyldiethanolamine (BDEA) - Sigma Aldrich.

[0073] Torlon® AI-30: A PAI polymer with an acid number >120 mg KOH / g polymer - commercially available from Solvay Specialty Polymers USA, LLC.

[0074] Torlon® AI-10: A PAI polymer with an acid number of approximately 80 mg KOH / g polymer - commercially available from Solvay Specialty Polymers USA, LLC.

[0075] method solution viscosity The viscosity of the polymer was measured using a Brookfield viscometer at 25° C. at a composition concentration of 8.25% by weight.

[0076] Acid number titration Acid number is determined by potentiometric titration as described in ASTM D664, where N-methylpyrrolidone (NMP) is the solvent and the titrants are potassium hydroxide and tributylammonium chloride.

[0077] Example 1 - Torlon® AI-30 Aqueous Solution with MDEA Water (2500 grams) and MDEA (162.4 grams) were charged to a 6 L jacketed flask equipped with an overhead mechanical stirrer. The mixture was preheated to 80° C. With vigorous stirring, Torlon® AI-30 powder (966.4 grams) was added in five equal portions over 30 minutes. Additional water (471 grams) was added to wash all the powder from the walls of the mixing vessel into the bulk liquid. The mixture was maintained at 80° C. for 4 hours and then pumped through a 10 micron filter bag. The initial solution viscosity was measured after 24 hours and then after 19 days. The solution was stored at 22° C. in a sealed glass jar. The results are reported in Table 1.

[0078] Comparative Example 1 - Torlon® AI-30 Aqueous Solution with BDEA Water (1500 grams) and BDEA (134.0 grams) were charged to a 6 L jacketed flask equipped with an overhead mechanical stirrer. The mixture was preheated to 80° C. With vigorous stirring, Torlon® AI-30 powder (589.3 grams) was added in five equal portions over 30 minutes. Additional water (277 grams) was added to wash all powder from the walls of the mixing vessel into the bulk liquid. The mixture was maintained at 80° C. for 4 hours and then pumped through a 10 micron filter bag. The initial solution viscosity was measured after 24 hours, then after 4, 8, and 19 days. The solution was stored at 22° C. in a sealed glass jar. The results are reported in Table 1.

[0079] [Table 1]

[0080] The data in Table 1 shows that the viscosity of the composition containing methylethanolamine surprisingly changes very little over time when compared to the composition containing butyldiethanolamine, changing by approximately four orders of magnitude over a 19 day period.

[0081] It should be noted that in both Example 1 and Comparative Example 1, the solutions were prepared with the same concentration of polymer (PAI) (approximately 33 parts by weight per 100 parts of water) and with the same molar amount of MDEA or BDEA per gram of polymer (PAI) (approximately 1.4 mmol / g of polymer (PAI)); therefore, the examples are completely equivalent in terms of their performance.

[0082] Comparative Example 2 The procedure of Example 1 was repeated using Torlon® AI-10, a PAI polymer with an acid number of 80 mg KOH / g polymer. After 8 hours, the polymer had stopped dissolving. At the end of the process, a significantly larger amount of undissolved solids was recovered on the filter than was recovered in Example 1.

Claims

1. A composition comprising, or consisting essentially of, at least one aromatic polyamic acid / polyamideimide polymer [polymer (PAI)], methyldiethanolamine, and water, wherein polymer (PAI) comprises repeating units, more than 50.0 mole percent of which contain at least one aromatic ring and at least one amic acid group and / or imide group [repeating unit (R ＰＡＩ ) )], and the polymer (PAI) has an acid number, measured as mg KOH / g polymer, of at least 100.

2. at least one aromatic polyamic acid / polyamideimide polymer [polymer (PAI)]; - methyldiethanolamine; - Water; - optionally, organic molecules other than methyldiethanolamine in a proportion of less than 1.0% by weight, preferably less than 0.5% by weight, more preferably less than 0.2% by weight; A composition consisting of The polymer (PAI) comprises repeating units, and more than 50.0 mol % of the repeating units comprise at least one aromatic ring and at least one amic acid group and / or imide group [repeating unit (R ＰＡＩ） 2. The composition of claim 1, wherein the polymer (PAI) has an acid number, measured as mg KOH / g polymer, of at least 100.

3. The repeating unit (R ＰＡＩ )but, 【Chemistry 1】 wherein the compound is selected from the group consisting of: the symbol → denotes in each formula isomerism such that in any repeat unit within the aromatic polyamic acid structure, the group pointed to by the arrow may be present as shown or in an interchanged position; Ar is an aromatic tetravalent radical which may contain one or more aromatic rings and is preferably 【Chemistry 2】 (X is -O-, -C(O)-, -S-, -SO ２ -, -CH ２ -, -C(CF ３ ) ２ -, - (CF ２ ) ｎ - (n=0, 1, 2, 3, 4 or 5) selected from the group consisting of: R is an aromatic divalent group which may contain one or more aromatic rings, and is preferably 【Transformation 3】 (Y is -O-, -C(O)-, -S-, -SO ２ -, -CH ２ -, -C(CF ３ ) ２ -, - (CF ２ ) ｎ - (n=0, 1, 2, 3, 4 or 5) 【Chemistry 4】 10. The composition of claim 1, selected from the group consisting of:

4. The repeating unit (R ＰＡＩ ) is composed of units (i), (ii), and (iii): 【Transformation 5】 and / or the corresponding imide group-containing repeat unit: 【Transformation 6】 wherein the attachment of the two amide groups to the aromatic ring shown in (ia) is understood to represent a 1,3 and 1,4 polyamide-amic acid configuration; 【Transformation 7】 and / or the corresponding imide group-containing repeat unit: 【Transformation 8】 wherein the attachment of the two amide groups to the aromatic ring shown in (ii-a) is understood to represent 1,3 and 1,4 polyamide-amic acid configurations; and 【Chemistry 9】 and / or the corresponding imide group-containing repeat unit: 【Chemistry 10】 (wherein the attachment of the two amide groups to the aromatic ring shown in (iii-a) is understood to represent a 1,3 and 1,4 polyamide-amic acid configuration.) 10. The composition of claim 1, selected from the group consisting of:

5. 2. The composition of claim 1, wherein the polymer (PAI) has an acid number, measured as mg KOH / g polymer, of at least 120.

6. 2. The composition according to claim 1, comprising 1.0 to 35.0% by weight, preferably 5.0 to 20.0% by weight, of the polymer (PAI) relative to the total weight of the polymer (PAI), methyldiethanolamine and water.

7. The composition according to claim 1, comprising 0.5 to 20.0% by weight of methyldiethanolamine, based on the total weight of the polymer (PAI), methyldiethanolamine, and water.

8. 10. The composition of claim 1, comprising less than 1.0 wt. %, preferably less than 0.5 wt. %, more preferably less than 0.2 wt. % of any organic solvent.

9. 10. A method for preparing the composition of claim 1 comprising adding the polymer (PAI) to a stirred mixture of methyldiethanolamine and water, or adding methyldiethanolamine to a stirred suspension of the polymer (PAI) in water, and stirring until the solids are dissolved.

10. 10. The method of claim 9, comprising heating to a temperature of 50 to 90°C with stirring.

11. A method for producing an article, comprising coating a composition according to any one of claims 1 to 8 onto a substrate.

12. The method of claim 11, further comprising the step of curing the coated composition by heating at a temperature comprised between 120 and 400°C.

13. 12. An article obtained from the method of claim 11.

14. 14. The article of claim 13, which is a magnet wire.

15. Use of a composition according to any one of claims 1 to 8 for providing an enamel in the manufacture of containers or insulated wire; for providing a corrosion resistant coating on metal or other substrates, for providing a binder layer on non-stick cookware; for providing a coating on tie bars used in cement; for providing a pre-treatment coating on polymeric films when used in metallization operations; as an adhesive for plastic or metal film materials; as an additive in inks.

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