Aqueous compositions comprising polyamideimide polymers and coatings containing the same

Abstract

Disclosed herein are aqueous composition comprising a polyamideimide (PAI) polymer, an alcohol, a tertiary amine, and water, the composition being substantially free of organic solvents having a boiling point equal to or greater than 100°C and which is not a tertiary amine or an alcohol. The PAI polymer is present in an amount from 20.0 wt% to 35.0 wt%, the alcohol is present in an amount from 0.1 wt% to 30.0 wt%, and the tertiary amine is present in an amount from 0.1 wt% to 25.0 wt%, based on the total weight of the composition. The composition has a viscosity of 30,000 cP or less at 25°C, when measured at 25°C using a Brookfield viscometer with a #64 spindle at 12 rpm, which makes it suitable for coating applications.

Description

SSPU 2023 / 019 AQUEOUS COMPOSITIONS COMPRISING POLYAMIDEIMIDE POLYMERS AND COATINGS CONTAINING THE SAME REFERENCE TO RELATED APPLICATIONS This application claims priority from US provisional application Nr.63 / 601964, filed on November 22, 2023, and from European patent application Nr.24150592.4, filed on January 5, 2024, the whole content of each of these applications being incorporated herein by reference for all purposes. TECHNICAL FIELD

[0001] The present invention relates to aqueous formulations, in particular aqueous coating formulations containing polyamideimide polymers. BACKGROUND

[0002] Polyamideimide and polyamic acid polymers (hereinafter collectively referred to as PAI polymer or PAI polymers) are well-known, thermally stable polymers that are used for many high performance coating applications due to their excellent adhesion, temperature resistance, and high strength. PAI polymer is commonly utilized as a protective coating for metal substrates subjected to harsh environments, including temperature, wear, abrasion, and chemical exposure. PAI also exhibits good adhesion to silicon and other substrates.

[0003] Most PAI polymers are only soluble in organic solvents, typically polar aprotic solvents. Commonly used solvents belong to the class of N-methyl amide solvents, in particular N- methyl pyrrolidone (NMP). PAI polymer compositions, once applied onto a substrate, are subjected to a thermal cure process that removes the solvent and builds molecular weight in order to achieve the optimum desired properties of the material. A critical drawback to this approach is that solvents like NMP are known to be toxic.

[0004] Methods to produce aqueous PAI polymer compositions are known, but they generally rely on hazardous complexing amines, involve the use of small amounts of hazardous polar organic solvent and / or they often exhibit poor shelf-life with constantlySSPU 2023 / 019 increasing viscosity over time. Other methods include PAI polymer compositions with a tertiary aliphatic amine, such as triethylamine.

[0005] WO2023 / 094632 discloses for instance aqueous compositions of a PAI polymer having an acid number of at least 100 mg KOH / g of polymer and methyldiethanolamine, Preferred compositions are disclosed that comprise a PAI polymer in an amount of 5.0 to 20.0 wt%.

[0006] The viscosity is a desirably controllable parameter for coating applications that are inoperable with a high-viscosity solution. It is apparent that aqueous PAI polymer compositions are limited by PAI polymer concentration to achieve a usable viscosity for coating applications. Current aqueous PAI polymer compositions either have to sacrifice PAI polymer content or viscosity, the latter of which renders such solutions inoperable for coating applications.

[0007] For example, US 6479581 discloses polyamide-amic acid solutions for coating applications. The solutions for coating applications comprise about 0.5 wt% to 15 wt% polyamide-amic acid because, at higher concentrations, “particularly at concentrations above about 20 wt%,” the solution viscosity increases too much such that the solution will not flow readily, rendering the solution inoperable for most coating and sizing applications.

[0008] US4087349 discloses aqueous dispersions consisting essentially of: (A) 20 to 80% by weight of a tetrafluoroethylene / hexafluoropropylene perfluoroolefin polymer; and (B) 80 to 20% by weight of a film-forming material such as a polyamide acid (as its salt) or a polymeric quaternary hydroxide blended with a nitrogen resin, said film-forming material acting as a binder for the perfluoroolefin polymer. In particular, US4087349 discloses that aqueous solutions of polyamide acid precursors of polyimides can be prepared from: (a) 10 to 70% by weight, based on the solution, of a salt of a polyamide acid with a tertiary amine, wherein the tertiary amine is present in at least a stoichiometrically equivalent amount to the free carboxylic acid groups in said polyamide acid; (b) 5 to 25% by weight, based on the solution, of a viscosity reducing agent which is miscible with water; and (c) 5 to 35% by weight, based on the solution, of a coalescing agent, wherein said coalescing agent is at least one member selected from the group consisting of N-methylpyrrolidone, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, cresylic acid, sulfolane,SSPU 2023 / 019 formamide. US4087349 refers to US4014834 for a definition of the aqueous solutions of polyamide acid precursors of polyimides.

[0009] US4014834 discloses that aqueous compositions containing salts of polyamide acids with tertiary amines, at solids contents up to 70% by weight, based on the total solution, and at a viscosity not exceeding 10,000 centipoises at 50°C, are made possible by the use of viscosity reducing agents and coalescing agents. Furfuryl alcohol is provided as preferred example of suitable viscosity reducing agent. Coalescing agents are essential ingredients of the composition and they are selected among highly polar organic liquids with a boiling point being above 100°C. Examples of suitable coalescing agents are N-methylpyrrolidone, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, cresylic acid, sulfolane, formamide, N-methylpyrrolidone being preferred.

[0010] US2017088746 discloses a polyimide precursor composition in which a resin and an organic amine compound are dispersed in an aqueous solvent which contains 50% by weight or more of water and at least one organic solvent selected from the group consisting of a urea solvent, an amide solvent containing an alkoxy group, and an amide solvent containing an ester group in an amount of 5% by weight or more with respect to the total amount of the aqueous solvent. The organic solvent is selected from the compounds in the above-mentioned classes having a boiling point from 100°C to 350°C, more preferably from 120°C to 300°C, and further preferably from 150°C to 250°C.

[0011] It has now been unexpectedly found that it is possible to obtain aqueous based compositions having an optimal combination of solid content and viscosity, and whose viscosity is stable over time, by combining a PAI polymer with a tertiary amine, such as methyldiethanolamine, and an alcohol substantially in the absence of any further polar organic solvent having a boiling point greater than 100°C. Advantageously, such compositions are free of solvents that are classified as hazardous substances. More advantageously, the addition of the alcohol allows such compositions to obtain a viscosity suitable for coating applications. BRIEF SUMMARY

[0012] Aqueous polyamide-imide (PAI) solutions made using PAI and a tertiary amine suffer from high solution viscosities at relatively low solids concentrations, typically aroundSSPU 2023 / 019 10 wt%. Herein is described a highly concentrated PAI solution using an alcohol compound to lower solution viscosity. This aqueous PAI solution with an alcohol compound offers a highly concentrated solution to build protective coatings, requiring fewer passes to reach a target thickness. The PAI solution uses an alcohol compound and a tertiary amine considered to be non-toxic, providing a safe alternative to aprotic amide solvents, such as N-methylpyrrolidone, dimethyl formamide or dimethyl acetamide, that are typically used in the plastics industry to dissolve PAI for coating applications.

[0013] Disclosed herein are aqueous compositions comprising a polyamideimide (PAI) polymer, an alcohol, a tertiary amine, and water. The PAI polymer is in solution. The PAI polymer is present in an amount from 20.0 wt% to 35.0 wt%, the alcohol is present in an amount from 0.1 wt% to 30.0 wt%, and the tertiary amine is present in an amount from 0.1 wt% to 25.0 wt%, based on the total weight of the aqueous composition. The aqueous compositions is substantially free of organic solvents having a boiling point greater than 100°C different from the tertiary amine or the alcohol. The PAI polymer comprises recurring units having at least 50.0 mol% of the recurring units comprising (i) an aromatic ring and (ii) one or more of an amic acid group or an imide group [recurring units (RPAI)]. Furthermore, the aqueous compositions is characterized by a viscosity of 30,000 cP (centipoise) or less, preferably 29,000 cP or less, more preferably 28,000 cP or less, and most preferably 27,000 cP or less, measured at 25°C using a Brookfield viscometer with a #64 spindle at 12 rpm. DETAILED DESCRIPTION

[0014] In the present application, any description, even if described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present disclosure, and each embodiment thus defined may be combined with another embodiment, unless otherwise indicated or clearly incompatible.

[0015] Where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individuals recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; anySSPU 2023 / 019 element or component recited in a list of elements or components may be omitted from such list.

[0016] Any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents.

[0017] The term “comprising” (or equivalents) includes “consisting essentially of,” and also “consisting of.”

[0018] As used herein, the term “consisting essentially of” or “essentially consisting” indicates that the referred to composition contains less than 5.0 wt%, typically less than 2.0 wt% or less than 1.0 wt%, of any other ingredient.

[0019] The expression “substantially free of X” is used herein to indicate that the amount of X is less than 5.0 wt%, preferably less than 3.0 wt%, typically less than 1.0 wt%.

[0020] The use of the singular “a” or “one” herein includes the plural unless specifically stated otherwise.

[0021] It should be understood that the elements, properties, and / or the characteristics of a (co)polymer, product or article, a process, or a use, described in the present specification, may be combined in all possible ways with the other elements, properties and / or characteristics of the (co)polymer, product or article, process or use, explicitly or implicitly, this being done without departing from the scope of the present description.

[0022] Should the disclosure of any patents, patent applications, and publications that are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0023] Disclosed herein are aqueous compositions comprising a PAI polymer, an alcohol, a tertiary amine, and water.

[0024] The PAI Polymer

[0025] The PAI polymer of the present disclosure comprises recurring units having at least 50.0 mol% of the recurring units comprising an aromatic ring and one or more of an amic acid group or an imide group [referred to as recurring units (RPAI) herein]. The PAI polymer advantageously comprises more than 90.0 mol% of recurring units (RPAI). The aqueous composition can comprise one or more than one PAI polymer.SSPU 2023 / 019

[0026] The acid number (mg of KOH / g polymer) of the PAI polymer) may be 100 or more and even 120 or more. It may be up to the theoretical acid number for a resin that comprises only amic acid units. In certain embodiments, it may be up to 170 mg KOH / g polymer. The acid number may be determined by titration, such as a potentiometric titration method according to ASTM D664. In particular it may be determined by the potentiometric titration method described by ASTM D664, where N-methylpyrrolidone (NMP) is the solvent, and titrants are potassium hydroxide and tributylammonium chloride.

[0027] The recurring units (RPAI) are chosen from the group consisting of: , , ,within the aromatic polyamic acid structure, the groups to which the arrows point may exist as shown or in an interchanged position; Ar is an aromatic tetravalent group, which may comprise one or more than one aromatic ring, and which are preferably selected from the group consisting of:SSPU 2023 / 019, - C(CF3)2-, -(CF2)n- with n= 1,2,3,4 or 5; R is an aromatic divalent group, which may comprise one or more than one aromatic ring, and which are preferably selected from the group consisting of: , with Y-CH2-, - C(CF3)2-, -(CF2)n- with n= 1,2,3,4 or 5, .

[0028] Alternatively, or in addition, the recurring units (RPAI) are chosen from the group consisting of units (i), (ii), and (iii) as follows: (i-a),SSPU 2023 / 019 and / or the corresponding imide-group containing recurring unit: ,wherein the attachment of the two amide groups to the aromatic ring as shown in (i-a) will be understood to represent the 1,3 and the 1,4 polyamide-amic acid configurations; (ii-a),and / or the corresponding imide-group containing recurring unit: (ii-b), whereinas shown in (ii-a) will be understood to represent the 1,3 and the 1,4 polyamide-amic acid configurations; andSSPU 2023 / 019 (iii-a), and / or theunit: (iii-b), wherein thearomatic ring as shown in (iii-a) will be understood to represent the 1,3 and the 1,4 polyamide-amic acid configurations.

[0029] The recurring units (RPAI) can be recurring units (i) or a mixture of the recurring units (ii) and (iii).

[0030] The amount of recurring units comprising an amic acid group can be determined by any suitable technique, such as spectroscopic techniques or titration techniques which are known to those of ordinary skill in the art.

[0031] When recurring units (RPAI) are selected from those of formulae (RPAI-A), (RPAI-B), (RPAI-C), (RPAI-D), (RPAI-E), as detailed above, the molar percentage of recurring units (RPAI) comprising at least one amic acid group may be expressed as follows: where [(RPAI-A) units], [(RPAI-B) units], [(RPAI-C)units], [(RPAI-D) units], and [(RPAI-E) units] denote, respectively molar concentration of the different recurring units (RPAI) as above described.SSPU 2023 / 019

[0032] When recurring units (RPAI) are selected from those of formulae (RPAI-A), and (RPAI- C), as detailed above, the molar percentage of recurring units (RPAI) comprising at least one amic acid group may be expressed as follows: [(RPAI-A) units][(RPAI-A) units]+[(RPAI-C) units]x100.

[0033] The recurring units (RPAI) can have at least 50.0 mol%, even at least 60.0 mol%, still at least 70.0 mol% of recurring units (RPAI) comprise at least one amic acid group. Alternatively, or in addition, 70.0 to 95.0 mol%, even 75.0 to 90.0 mol% of recurring units (RPAI) comprise at least one amic acid group.

[0034] The PAI polymer can be manufactured by a process which includes the polycondensation reaction between at least an aromatic polycarboxylic acid halide monomer and at least an aromatic diamine.

[0035] The aromatic polycarboxylic acid halide monomer may be chosen from the group consisting of terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, and the acid halide derivatives of trimellitic anhydride. Preferably it is selected from the trimellitic anhydride monoacid halides. Among the trimellitic anhydride monoacid halides, trimellitic anhydride monoacid chloride is preferred.

[0036] Alternatively, or in addition, a dicarboxylic anhydride monomer may be used in combination with the polycarboxylic acid halide monomer. Suitable discrboxylic anhydride monomers include pyromellitic anhydride, bis(3,4-dicarboxyphenyl)ether dianydride, and trimellitic anhydride. When a dicarboxylic anhydride monomer is used in the process, the excess of the acid halide monomer with respect to the equimolar concentration of the aromatic diamine monomer is calculated taking into consideration the combined moles of the acid halide and the dicarboxylic anhydride monomers.

[0037] The aromatic diamine monomer is selected from the group consisting of 4,4'- diaminodiphenyl ether (ODA), p-phenylenediamine, (PDA), m-phenylenediamine (MPDA), diphenyl dimethyl methane diamine (DMMDA), 1,3-bis (3-aminophenoxy) benzene (BAPB), 4,4'- bisphenol A ether diamine (BAPP), 4,4'- bis (4-aminophenoxy) diphenylsulfone (BAPS), 4,4'- bis (4-aminophenoxy) diphenyl ether (BAPE), diamino diphenyl (methyl) ketone (DABP), 4,4'- diamino-triphenylamine (DATPA), 4,4'- diaminodiphenyl methane (MDA), diaminodiphenyl sulfone (DDS), 3,4'- diaminodiphenyl ether (3,4'-ODA), 3,3 '- dimethyl-4,4'-diamino diphenyl methane (MDI), 2,2-Bis(4-(4-SSPU 2023 / 019 aminephenoxy)-phenyl)propane, 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-isopropyl propane and mixtures thereof.

[0038] The aromatic diamine monomer is preferably selected from the group consisting of 4,4'-diaminodiphenyl ether (ODA), 4,4’-diaminodiphenyl methane (MDA), p- phenylenediamine, (PDA), and m-phenylenediamine (MPDA) and mixtures thereof. The aromatic diamine monomer may be ODA. The aromatic diamine monomer may be MDA. The aromatic diamine monomer may be MPDA.

[0039] The polycondensation reaction is advantageously carried out under substantially anhydrous conditions in a polar solvent and at a temperature below 150 ℃, employing a stoichiometric excess of the acid halide monomer.

[0040] A monofunctional reactant can be employed as an end-capping agent as known to the skilled in the art to control the molecular weight and to improve stability of the polymer.

[0041] The PAI polymer is advantageously isolated in solid form under mild conditions, preferably by being coagulated or precipitated from the polar reaction solvent by adding a miscible non-solvent, for example water, a lower alkyl alcohol or the like. Optionally, the solid resin may then be collected and thoroughly washed with water, and centrifuged or pressed to further reduce the water content of the solid without applying heat. Non- solvents other than water and lower alkyl alcohols are known and have been used in the art for precipitating the PAI polymer from solution including, for example, ethers, aromatic hydrocarbons, ketones and the like.

[0042] The number average molecular weight (Mn) of PAI polymer is at least 1000, preferably at least 1500, more preferably at least 2000. The number average molecular weight (Mn) of PAI polymer is 20000 or less, preferably 15000 or less. The molecular weight of the PAI polymer (Mw and Mn) may be and is usually determined using gel permeation chromatography (GPC) using a polystyrene standard.

[0043] The Tertiary Amine

[0044] The aqueous compositions disclosed herein comprise a tertiary amine. The tertiary amine is selected from the group consisting of those of formula (I): NR1R2R3(I)SSPU 2023 / 019 wherein R1, R2and R3are at each occurrence and independently from one another selected from the group consisting of branched or linear, saturated or unsaturated alkyls having 1 to 6 carbon atoms, optionally comprising an hydroxyl functional group. R1, R2and R3may be the same or they may be different. R1, R2and R3are preferably selected from branched or linear, saturated alkyls having 1 to 4 carbon atoms, optionally comprising an hydroxyl functional group.

[0045] The tertiary amine is preferably a nontoxic tertiary amine.

[0046] The tertiary amine is conveniently selected from the group consisting of methyldiethanolamine (MDEA), dimethylethanolamine (DMEA), butyldiethanolamine (BDEA), triethanolamine (TEA), and combinations thereof.

[0047] As will be appreciated by those of ordinary skill in the art, the tertiary amine can assist in promoting water solubility in the PAI polymer. Without wishing to be bound by any particular scientific theory, the tertiary amine will react with the acid groups on the PAI polymer backbone to form a water-soluble salt.

[0048] Accordingly, there can be a minimum amount of tertiary amine that is desirable. The minimum amount of tertiary amine employed can be approximately the stoichiometric amount required to neutralize the free carboxylic acid groups in the PAI polymer. An excess of the amine, as much as a 3 to 5 factor stoichiometric excess, may be desirable. The molar ratio of amine to free carboxylic acid groups in the PAI polymer can generally lie in the range of from 0.8 to 5.0, preferably from 0.8 to 2.5, more preferably from 1.0 to 2.0. It should be understood that if the aqueous composition comprises more than one PAI polymer, the amount of the tertiary amine given herein takes into account all free carboxylic acid groups present in the PAI polymers.

[0049] The tertiary amine is present in the aqueous composition in an amount of 0.1 wt% or more, 0.5 wt% or more, 1.0 wt% or more, 2.0 wt% or more, 3.0 wt% or more, 4.0 wt% or more, 5.0 wt% or more, 6.0 wt% or more, 7.0 wt% or more, 8.0 wt% or more, 9.0 wt% or more, 10.0 wt% or more, 11.0 wt% or more, or 12.0 wt% or more based on the total weight of the aqueous composition. The tertiary amine is present in the aqueous composition in an amount of 25.0 wt% or less, 24.5 wt% or less, 24.0 wt% or less, 20.0 wt% or less, 19.0 wt% or less, 18.0 wt% or less, 17.0 wt% or less, 16.0 wt% or less, or 15.0 wt% or less based on the total weight of the aqueous composition. The aqueousSSPU 2023 / 019 composition may advantageously comprise 5.0 wt% to 24.5 wt%, preferably 9.0 wt% to 24.0 wt%, even 9.0 wt% to 19.5 wt% of the tertiary amine with respect to the total weight of the aqueous composition.

[0050] The Alcohol

[0051] The aqueous composition disclosed herein comprise an alcohol of formula (II): R(OH)m(II) wherein R is a branched or linear, saturated or unsaturated alkyl having 1 to 50 carbon atoms and m is an integer from 1 to 6. R is preferably an alkyl having 1 to 20 carbon atoms, more preferably an alkyl having 2 to 10 carbon atoms, even more preferably an alkyl having 2 to 6 carbon atoms. In formula (II) m is preferably an integer from 1 to 3.

[0052] Among monohydric alcohols, wherein n =1 in formula (II), isopropyl alcohol (IPA) or 2-butanol have been found to be advantageous.

[0053] Among polyhydric alcohols suitable for the application mention can be made of, 1,3-propanediol, propylene glycol, and butylene glycol. The alcohol is present in the aqueous composition in an amount of 0.1 wt% or more, 0.5 wt% or more, 1.0 wt% or more, 2.0 wt% or more, 3.0 wt% or more, 4.0 wt% or more, 5.0 wt% or more, 6.0 wt% or more, 7.0 wt% or more, 8.0 wt% or more, 9.0 wt% or more, or 10.0 wt% or more based on the total weight of the aqueous composition. The alcohol is present in the aqueous composition in an amount of 30.0 wt% or less, 29.0 wt% or less, 28.0 wt% or less, 27.0 wt% or less, 26.0 wt% or less, based on the total weight of the aqueous composition. The aqueous composition may advantageously comprise 8.0 wt% to 29.0 wt%, preferably 10.0 wt% to 27.0 wt% of the alcohol with respect to the total weight of the aqueous composition.

[0054] The Aqueous Composition

[0055] The aqueous compositions disclosed herein comprise the PAI polymer in an amount of 20.0 wt% or more, 21.0 wt% or more, 22.0 wt% or more, 23.0 wt% or more, 24.0 wt% or more, 25.0 wt% or more, 25.5 wt% or more, or 25.7 wt% or more, based on the total weight of the aqueous composition. The aqueous compositions disclosed herein can comprise the PAI polymer in an amount of 35.0 wt% or less, 34.0 wt% or less, 33.0 wt% or less, 32.0 wt% or less, 31.0 wt% or less, or 30.0 wt% or less based on the total weight of the aqueous composition. It should be understood that if the aqueousSSPU 2023 / 019 composition comprises more than one PAI polymer, the total amount of PAI polymers is according to the proportions given herein. The aqueous composition may advantageously comprise 21.0 wt% to 33.0 wt%, preferably 22.0 wt% to 30.0 wt% of the PAI polymer with respect to the total weight of the aqueous composition.

[0056] Any convenient method of combining the components may be employed in preparing the aqueous compositions of the invention. The solid PAI polymer may be added in increments to a stirred mixture of the tertiary amine and water, continuing the stirring until the solid resin has been dissolved. Alternatively, tertiary amine may be added slowly to a stirred suspension of the PAI polymer in water, with continued stirring until the solid dissolves. As with any acid-base reaction, external cooling may be found necessary initially; subsequent warming and stirring may be desirable to complete dissolution of the solid resin in a reasonable time period. For instance, the suspension may be heated to a temperature of 50 to 90°C and held under stirring.

[0057] It has been found that a further advantage of using the tertiary amine in combination with a PAI polymer having a high acid number is the limited time required for achieving the dissolution of the PAI polymer. The dissolution time is significantly lower than the time observed with PAI polymers having a lower acid number, that is lower than 100 mg KOH / g polymer.

[0058]

[0059] The aqueous composition disclosed herein has a viscosity of 30,000 cP or less, 29,000 cP or less, 28,000 cP or less, or 27,000 cP or less at 25°C, when measured with a Brookfield Viscometer with a #64 spindle at 12 rpm. The viscosity of the composition is generally not lower than 5,000 cP at 25°C.

[0060] The aqueous compositionsdisclosed herein can have viscosities of 5,000 cP or less, 4,000 cP or less, 3,500 cP or less, 3,000 cP or less at 45°C, when measured with a Brookfield Viscometer with a #64 spindle at 12 rpm. The viscosity of the composition is generally not lower than 1,000 cP at 25°C.

[0061] Additives

[0062] Aqueous compositions according to the present disclosure comprise the PAI polymer, water, the tertiary amine, and the alcohol. The inventive compositions have a low level of any organic solvent, in particular any organic solvent having a boiling pointSSPU 2023 / 019 equal to or greater than 100°C. The total amount of organic solvents having a boiling point equal to or greater than 100°C is generally less than 5.0 wt% with respect to the weight of the aqueous composition. For the avoidance of doubt, the expression “organic solvent” identifies any organic compound capable of dissolving or promoting the dissolution of the PAI polymer and which is not the tertiary amine of formula (I) and the alcohol of formula (II). The aqueous composition of the invention is preferably substantially free of any organic solvent. The expression “substantially free” in connection with the aqueous composition and an organic solvent is intended to mean that said organic solvent, one or more, are present in a total amount of less than 5.0 wt%, preferably less than 3.0 wt%, typically less than 1.0 wt% with respect to the weight of the composition. The amount of organic solvent may be 0.1 wt% or less with respect to the weight of the composition. Such compositions are highly desired for use in applications where an organic solvent cannot be tolerated.

[0063] Depending on its final use, the inventive composition may further comprise usual ingredients of coating compositions, such as: (i) dispersion agents; (ii) pigments like carbon black, silicates, metal oxides and sulfides; (iii) additives such as flow promoters; (iv) inorganic fillers like carbon fibers, glass fibers, metal sulfates, such as BaSO4, CaSO4, oxides such as Al2O3 and SiO2, zeolites, mica, talc, kaolin; (v) organic fillers, preferably thermally stable polymers, like PTFE; (vi) film hardener, like silicate compounds, such as metal silicate, e.g. aluminum silicate and metal oxides, such as titanium dioxide; (vii) adhesion promoters, like colloidal silica and a phosphate compound, such as metal phosphate, e.g. Zn, Mn or Fe phosphate.

[0064] Coatings Comprising the Polymer Solution

[0065] A further aspect of the invention is a process for the manufacture of an article comprising applying the polymer solutions disclosed herein on a substrate. The disclosed aqueous composition offer highly concentrated solutions to build protective coatings, requiring fewer passes to reach a target thickness. The presently disclosed polymer solutions offer an aqueous-based PAI solution capable of building 2–3 times dry coating thickness relative to current PAI solutions.

[0066] Any technique may be used for the process, and any combination of techniques can be used for the process. Typically the composition is applied by coating. Coating maySSPU 2023 / 019 be performed by any suitable coating process, such as spin coating, spray coating, slit spin coating, roll coating, die coating, slot die coating, dip coating, or curtain coating. The coating step is typically followed by a step wherein the applied composition is cured by pre-baking the resulting film at a temperature comprised between 120 and 400°C, preferably between 120 and 350°C, so as to allow the solvent to be volatilized.

[0067] The thickness of the coating may vary depending on the intended purpose. The thickness is preferably in the range of from 0.1 to 100 microns, preferably from 1 to 75 microns, more preferably from 5 to 50 microns. The thickness may be as low as 10 microns.

[0068] The aqueous compositions of this invention may be particularly useful in formulations intended for use in coating an article, providing an adherent, high strength continuous coating layer having improved toughness on a coated surface. More generally, the aqueous compositions of the invention may be used to obtain adhesive or protective coatings in applications requiring resistance to friction, heat, or harsh chemical environments.

[0069] Such coatings may serve as a binder layer for automotive finishes, to improve adhesion between existing layers of automotive finishes or with other metal finishes.

[0070] PAI polymers are known for having good adhesion to metal surfaces, and aqueous compositions of this invention thus may be found particularly useful in providing formulations for use as enamels in container coating applications or in insulated wire applications, for instance magnet wires for electric motors.

[0071] The inventive aqueous compositions may be used for providing a chemically corrosion-resistant coating for metal or other substrates, for providing a binder layer for non-stick cookware; for providing a coating for tie bars for usage in cement; for providing a pre-treatment coating for polymer films such as, for example, polyester, polyamide and polyimide film, when used in a metalizing operation; as an adhesive to various plastic or metallic film materials such as liquid crystal polymers and polyimides; as an additive to improve the performance of inks.

[0072] The substantially “organic solvent-free” aqueous compositions of certain embodiments of the present invention may be found useful for film casting where organic solvents may not be desired or tolerated.SSPU 2023 / 019

[0073] Formulations comprising these aqueous compositions may also be found useful as sizing, and particularly as sizing for fiber material such as glass fiber, carbon and graphite fiber, alumina fiber, silicon nitride fiber, boron fiber, aramid fiber, fluorocarbon fiber and the like. The term “carbon fiber” is used herein in the generic sense and includes graphite fibers as well as amorphous carbon fibers that result after a thermal carbonization or graphitization treatment.

[0074] The present disclosure will be now described with reference to the following examples, whose purpose is merely illustrative and not limitative of the present disclosure.

[0075] Raw Materials

[0076] N-methyldiethanolamine (MDEA) and N-butyldiethanolamine (BDEA) were purchased through Sigma Aldrich.

[0077] Torlon® polyamide-imide AI-30 LM (PAI-1) and Torlon® polyamide-imide AI-50 (PAI-2) were sourced through Solvay Specialty Polymers USA, LLC. Isopropanol (IPA) and 2-butanol (2BUT) were purchased through Thermo Fisher Scientific Inc. N-methyl-2- pyrrolidone (NMP) was sourced through VWR International, LLC.

[0078] Example 1 (E1)

[0079] To a 500 mL 4-neck round-bottom flask equipped with a water jacket and overhead mechanical stirrer, 1.31 g of deionized (DI) water and 36.30 g of MDEA were added. The solution was heated to 85 °C and then was charged with 190.69 g of PAI-1. The mixture was stirred vigorously for 2.5 h at 85 °C to form a homogeneous, viscous paste. The paste was cooled to 60 °C for 1 h and then 72.00 g of IPA was added over a period of 30 minutes to prevent gelling from occurring. The solution was stirred vigorously for an additional hour at 60 °C before discharge from the reactor. Solution viscosity and percent solids were measured immediately.

[0080] Comparative Example 2 (CE2)

[0081] The aqueous solution was prepared in the same manner as Example 1 (E1) except 185.76 g of DI water, 17.28 g of MDEA, and 96.96 g of AI-30 LM was charged to the round-bottom flask. No IPA was added to the solution.

[0082] Example 3 (E3)SSPU 2023 / 019

[0083] To a 500 mL 4-neck round bottom flask equipped with a water jacket and overhead mechanical stirrer, 52.32 g of BDEA was added and heated to 85 °C.128.73 g of PAI-2 was added slowly to the reactor, and then 73.95 g of DI water was charged, forming a homogeneous solution. The solution was stirred vigorously for 2 h and then cooled to 60 °C for 1 h. To this was added 45.00 g of 2BUT. The solution was stirred for an additional hour at 60 °C before discharge. Solution viscosity and percent solids were measured immediately.

[0084] Example 4 (E4)

[0085] The solution was prepared in the same manner as Example 3 (E3) except 38.17 g of DI water was used and 72.00 g of IPA was added in place of 2BUT.

[0086] Example 5 (E5)

[0087] The solution was prepared in the same manner as E3 except 87.60 g of DI water was used and 38.66 g of MDEA was added in place of BDEA.

[0088] Comparative Example 6 (CE6)

[0089] The solution was prepared in the same manner as E3 except 198.61 g of DI water, 29.30 g of BDEA, and 72.09 g of PAI-2 was charged to the round-bottom flask. No alcohol or other additives was added to the solution.

[0090] Example 7 (E7)

[0091] To a 500 mL 4-neck round bottom flask equipped with a water jacket and overhead mechanical stirrer, 38.66 g of MDEA was added and heated to 85 °C.128.73 g of PAI-2 was added slowly to the reactor, and then 78.60 g of DI water was charged, forming a homogeneous solution. The solution was stirred vigorously for 2 h and then cooled to 60 °C for 1 h. To this was added 54.00 g of IPA. The solution was stirred for an additional hour before discharge. Solution viscosity and percent solids were measured immediately. The solution was heated to 45 °C and coated onto an aluminum substrate (Alloy 3003 H14) using a casting knife with a gap height of 0.13 mm. The solution was cured using a slow ramp from room temperature to 285 °C and held for 30 minutes. The coating appeared smooth and even with no cracks. The adhesion was measured using the cross hatch method according to ISO 2409 and reported in Table 2. A rating of 0 (the lowest value) means that the coating did not delaminate from the substrate whereas a rating ofSSPU 2023 / 019 5 (the highest value) indicates that the coating completely delaminated from the substrate.

[0092] Comparative Example 8 (CE8)

[0093] The solution was prepared in the same manner as Example 7 (E7) except 63.60 g of DI water was used. 15.00 g of NMP (5.0 wt% with respect to the total weight of solution) was also added to the solution. Coatings were prepared in the same manner as E7. The coating likewise appeared smooth and without cracks.

[0094] Details of the compositions of Examples 1, 3 to 5 and 7 and of Comparative Examples 2, 6 and 8 are summarized in Table 1. Table 1. Solution viscosity at 25°C and 45°C ExamplePAI TertiaryAlcohol Other Percent Solution Solution amine additives solids viscosity at viscosity at (wt%) (wt%) (wt%) (wt%) 45°C (cP) 25°C (cP) E1 PAI-1 MDEA IPA --- 25.7 1350 26390CE2 PAI-1 MDEA --- --- 13.7 39090 Not 6.8 measurable E3 PAI-2 BDEA 2BUT --- 30.3 1950 14050 17.4 15.0 E4 PAI-2 BDEA IPA --- 31.7 1800 13100 18.0 24.7 E5 PAI-2 MDEA 2BUT --- 28.0 2400 18900 12.9 15.0 CE6 PAI-2 BDEA --- --- 16.5 7250 Not 10.0 measurable E7 PAI-2 MDEA IPA --- 28.6 3000 26240 12.9 18.0 CE8 PAI-2 MDEA IPA NMP 29.0 1400 8900 12.9 18.0 5.0 Measured by drying a 5.0 g sample of aqueous solution at 300 °C for 20 minutes. Measured using a Brookfield viscometer with a #64 spindle. Samples noted as not measurable demonstrated too high of viscosity to be measured at room temperature.

[0095] The data in Table 1 show that the inventive compositions had a greatly reduced solution viscosity compared to compositions prepared in the absence of an alcohol. TheSSPU 2023 / 019 alcohol-free compositions had a very high solution viscosity even when they contained half of the amount of polymer PAI contained in the inventive compositions. The compositions of Examples 1, 3, 4, 5 and 7, which contain about 25 wt% of PAI polymer, exhibit measurable solution viscosities even at 25°C.. The compositions of Comparative Examples 2 and 6 exhibit solution viscosities at 25°C that are too high to be measured even if the content of the PAI polymer in the composition is about 13-17 wt%. Table 2. Properties of the coating Example PAITertiaryOther Dry coating Cross hatch amine Alcoholadditives thickness

[0096] The data in Table 2 show that the inventive compositions exhibit measurable viscosities at high solids content which make them suitable for the preparation of good quality coatings in the absence of organic solvents, like NMP.

Claims

SSPU 2023 / 019 CLAIMS 1. An aqueous composition comprising: - 20.0 wt% to 35.0 wt%, based on the total weight of the aqueous composition, of a polyamideimide (PAI) polymer which comprises recurring units having at least 50.0 mol% of the recurring units comprising (i) an aromatic ring and (ii) one or more of an amic acid group or an imide group [recurring units (RPAI)]; - 0.1 wt% to 25.0 wt%, based on the total weight of the aqueous composition, of a tertiary amine of formula (I): NR1R2R3(I) wherein R1, R2and R3are at each occurrence and independently from one another selected from the group consisting of branched or linear, saturated or unsaturated alkyl having 1 to 6 carbon atoms, optionally comprising an hydroxyl functional group; - 0.1 wt% to 30.0 wt%, based on the total weight of the aqueous composition, of an alcohol of formula (II): R(OH)m(II) wherein R is a branched or linear, saturated or unsaturated alkyl having 1 to 50 carbon atoms and m is an integer from 1 to 6, preferably 1 to 3; R is preferably an alkyl having 1 to 20 carbon atoms, more preferably an alkyl having 2 to 10 carbon atoms, even more preferably an alkyl having 2 to 6 carbon atoms; and - water, wherein the aqueous composition comprises an amount which is less than 5.0 wt%, based on the total weight of the aqueous composition, of an organic solvent having a boiling point equal to or greater than 100°C and which is not a tertiary amine of formula (I) or an alcohol of formula (II); and wherein the aqueous composition has a viscosity of 30,000 cP or less, when measured at 25°C using a Brookfield viscometer with a #64 spindle at 12 rpm.

2. The aqueous composition of Claim 1, wherein recurring units (RPAI) are chosen from the group consisting of:SSPU 2023 / 019 ,the symbol → in each formula denotes isomerism so that, in any recurring unit RPAI, the groups to which the arrows point may exist as shown or in an interchanged position; Ar is an aromatic tetravalent group, which may comprise one or more than one aromatic ring, and which is preferably selected from the group consisting of:-, -S-, -SO2-, -CH2-, - C(CF3)2-, -(CF2)n- with n= 1,2,3,4 or 5; and R is an aromatic divalent group, which may comprise one or more than one aromatic ring, and which is preferably selected from the group consisting of:SSPU 2023 / 019 ,-SO2-, -CH2-, - C(CF3)2-, -(CF2)n- with n=,2,3,4 or 5, .

3. The aqueous composition of any of Claims 1 or 2, wherein the recurring units (RPAI) are chosen from the group consisting of units (i), (ii) and (iii): ,,ring as shown in (i-a) will be understood to represent the 1,3 and the 1,4 polyamide-amic acidSSPU 2023 / 019 configurations; ,(ii-b),ring as shown in (ii- a) represent the 1,3 and the 1,4 polyamide-amic acid configurations; and ,recurring unit: (iii-b),amide groups to the aromatic ring as shown in (iii- a) represent the 1,3 and the 1,4 polyamide-amic acid configurations.SSPU 2023 / 019 4. The aqueous composition of any of Claims 1 to 3, wherein the PAI polymer has an acid number of 100 or more, and preferably of 120 or more, as measured by mg KOH / g polymer.

5. The aqueous composition of any of Claims 1 to 4, wherein the PAI polymer is present in the polymer solution in an amount from 22.0 wt% to 30.0 wt%, based on the total weight of the composition.

6. The aqueous composition of any of Claims 1 to 5, wherein the aqueous composition has a viscosity of 5,000 cP or less, measured at 45°C using a Brookfield viscometer with a #64 spindle at 12 rpm.

7. The aqueous composition of any of Claims 1 to 6, wherein the tertiary amine is present in an amount from 9.0 wt% to 24.5 wt%, based on the total weight of the aqueous composition.

8. The aqueous composition of any of Claims 1 to 7, wherein the tertiary amine is selected from the group consisting of methyldiethanolamine (MDEA), dimethylethanolamine (DMEA), butyldiethanolamine (BDEA), triethanolamine (TEA), and combinations thereof.

9. The aqueous composition of any of Claims 1 to 8, wherein the alcohol is present in an amount from 8.0 wt% to 29.0 wt%, preferably from 10.0 wt% to 27.0 wt%, based on the total weight of the aqueous composition.

10. The aqueous composition of any of Claims 1 to 9 wherein the alcohol is selected from the group consisting of isopropyl alcohol, 2-butanol, 1,3-propanediol, propylene glycol, butylene glycol, and combinations thereof.

11. The aqueous composition of any of Claims 1 to 10 wherein the alcohol is selected from the group consisting of isopropyl alcohol, 2-butanol and the tertiary amine isSSPU 2023 / 019 selected from the group consisting of methyldiethanolamine (MDEA) and butyldiethanolamine (BDEA).

12. The aqueous composition of any of Claims 1 to 11 wherein the alcohol is isopropyl alcohol in an amount of 10.0 wt% to 30.0 wt% and the tertiary amine is methyldiethanolamine (MDEA) in an amount of 10.0 wt% to 15.0 wt%.

13. A coating for an article, the coating comprising the aqueous composition of any of Claims 1 to 12.

14. A process for coating an article, the process comprising the step of coating the article with the aqueous composition of any of Claims 1 to 12.

15. The process of Claim 14, wherein the step of coating comprises one or more of spray coating, roll coating, slot die coating, dip coating, spin coating, curtain coating and combinations thereof.

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