Aqueous composition comprising a polyamide-imide polymer and coating comprising the aqueous composition

Abstract

This document discloses an aqueous composition comprising a polyamide-imide (PAI) polymer, an alcohol, a tertiary amine, and water, which is substantially free of organic solvents having a boiling point equal to or greater than 100°C and which are not tertiary amines or alcohols. Based on the total weight of the composition, the PAI polymer is present in an amount of 20.0 wt% to 35.0 wt%, the alcohol in an amount of 0.1 wt% to 30.0 wt%, and the tertiary amine in an amount of 0.1 wt% to 25.0 wt%. When measured at 12 rpm using a Brookfield viscometer with a #64 rotor at 25°C, the composition has a viscosity of 30,000 cP or less at 25°C, making it suitable for coating applications.

Description

Citation of relevant applications

[0001] This application claims priority to U.S. Provisional Application No. 63 / 601964, filed November 22, 2023, and European Patent Application No. 24150592.4, filed January 5, 2024, the entire contents of each of these applications are incorporated herein by reference for all purposes. Technical Field

[0002] This invention relates to aqueous formulations containing polyamide-imide polymers, particularly aqueous coating formulations. Background Technology

[0003] Polyamide-imide and polyamic acid polymers (hereinafter collectively referred to as one or more PAI polymers) are well-known heat-stable polymers used in many high-performance coating applications due to their excellent adhesion, temperature resistance, and high strength. PAI polymers are commonly used as protective coatings for metallic substrates subjected to harsh environments, including temperature, abrasion, erosion, and chemical exposure. PAI also exhibits good adhesion to silicon and other substrates.

[0004] Most PAI polymers are soluble only in organic solvents, typically polar aprotic solvents. Commonly used solvents belong to the N-methylamide class, especially N-methylpyrrolidone (NMP). Once applied to a substrate, the PAI polymer composition undergoes a thermosetting process to remove the solvent and increase the molecular weight, achieving the optimal desired properties of the material. A key drawback of this method is that solvents like NMP are known to be toxic.

[0005] Methods for producing aqueous PAI polymer compositions are known, but they typically rely on hazardous complexed amines, involve the use of small amounts of hazardous polar organic solvents, and / or often exhibit poor shelf life with viscosity increasing over time. Other methods include PAI polymer compositions containing aliphatic tertiary amines such as triethylamine.

[0006] WO 2023 / 094632 discloses, for example, an aqueous composition of a PAI polymer with an acid value of at least 100 mg KOH / g polymer and methyldiethanolamine, and discloses a preferred composition containing 5.0 to 20.0 wt% of the PAI polymer.

[0007] For coating applications that cannot be handled with high-viscosity solutions, viscosity is a desirable controllable parameter. Clearly, to achieve a viscosity suitable for coating applications, aqueous PAI polymer compositions are limited by the PAI polymer concentration. Current aqueous PAI polymer compositions have had to sacrifice either PAI polymer content or viscosity, the latter rendering such solutions unusable for coating applications.

[0008] For example, US 6479581 discloses a polyamide-amic acid solution for coating applications. The solution for coating applications contains approximately 0.5 wt% to 15 wt% polyamide-amic acid because at higher concentrations, "particularly above approximately 20 wt%", the solution viscosity increases excessively, making the solution difficult to flow and thus unusable for most coating and sizing applications.

[0009] US 4087349 discloses an aqueous dispersion substantially composed 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 polyamic acid (as a salt thereof) or a polymeric quaternary hydroxide blended with a nitrogen resin, said film-forming material acting as a binder for the perfluoroolefin polymer. Specifically, US 4087349 discloses that an aqueous solution of a polyamic acid precursor of polyimide can be prepared by: (a) a salt of polyamic acid and a tertiary amine, based on 10% to 70% by weight of the solution, wherein the tertiary amine is present in an amount at least stoichiometric to the free carboxylic acid groups in the polyamic acid; (b) a water-miscible viscosity reducer, based on 5% to 25% by weight of the solution; and (c) a coalescing agent, based on 5% to 35% by weight of the solution, wherein the coalescing agent is at least one member selected from the group consisting of: N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, cresol, sulfolane, and formamide. The definition of an aqueous solution of a polyamic acid precursor of polyimide in US 4087349 references US 4014834.

[0010] US 4014834 discloses that, by using a viscosity reducer and a coalescing agent, an aqueous composition containing a salt of polyamic acid and a tertiary amine can have a solids content of up to 70% by weight based on the total solution, and a viscosity at 50°C not exceeding 10,000 centipoise. Furfuryl alcohol is provided as a preferred example of a suitable viscosity reducer. The coalescing agent is an essential component of the composition, and they are selected from highly polar organic liquids with boiling points above 100°C. Examples of suitable coalescing agents are N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, cresolic acid, sulfolane, and formamide, with N-methylpyrrolidone being preferred.

[0011] US 2017088746 discloses a polyimide precursor composition in which a resin and an organic amine compound are dispersed in an aqueous solvent containing 50% or more water by weight relative to the total amount of the aqueous solvent and 5% or more by weight of at least one organic solvent selected from the group consisting of urea solvents, alkoxy-containing amide solvents, and ester-containing amide solvents. The organic solvent is selected from compounds in the above categories having a boiling point of 100°C to 350°C, more preferably 120°C to 300°C, and even more preferably 150°C to 250°C.

[0012] It has now been unexpectedly discovered that by combining PAI polymers with tertiary amines (such as methyldiethanolamine) and alcohols, essentially in the absence of any other polar organic solvents with boiling points greater than 100°C, water-based compositions with an optimal combination of solids content and viscosity, and whose viscosity remains stable over time, can be obtained. Advantageously, such compositions do not contain solvents classified as hazardous substances. More advantageously, the addition of alcohols allows such compositions to achieve viscosities suitable for coating applications. Summary of the Invention

[0013] Aqueous solutions of PAI prepared using polyamide-imide (PAI) and tertiary amines are limited by high solution viscosity at relatively low solid concentrations (typically around 10 wt%). This paper describes a highly concentrated PAI solution using alcohol compounds to reduce solution viscosity. This aqueous PAI solution with alcohol compounds provides a highly concentrated solution for constructing protective coatings, thus requiring fewer passes to achieve the target thickness. The PAI solution uses alcohol compounds and tertiary amines that are considered non-toxic, providing a safe alternative to aprotic amide solvents (such as N-methylpyrrolidone, dimethylformamide, or dimethylacetamide) typically used in the plastics industry to dissolve PAI for coating applications.

[0014] This document discloses an aqueous composition comprising a polyamide-imide (PAI) polymer, an alcohol, a tertiary amine, and water. The PAI polymer is in solution. Based on the total weight of the aqueous composition, the PAI polymer is present in an amount of 20.0 wt% to 35.0 wt%, the alcohol in an amount of 0.1 wt% to 30.0 wt%, and the tertiary amine in an amount of 0.1 wt% to 25.0 wt%. The aqueous composition is substantially free of organic solvents having a boiling point greater than 100°C, other than the tertiary amine or the alcohol. The PAI polymer comprises repeating units, wherein at least 50.0 mol% of the repeating units comprises one or more of (i) an aromatic ring and (ii) an amide acid group or an imide group [repeating unit (R PAIFurthermore, the aqueous composition 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, as measured at 12 rpm using a Brookfield viscometer with a #64 rotor at 25°C. Detailed Implementation

[0015] In this application, any description of a particular embodiment is applicable to and interchangeable with other embodiments of this disclosure, and each embodiment defined theretherein may be combined with another embodiment unless otherwise specified or obviously incompatible.

[0016] When an element or component is referred to as being included in and / or selected from the list of enumerated elements or components, it should be understood that in the relevant embodiments explicitly considered herein, the element or component may also be any one of these enumerated individual elements or components, or may be a group consisting of any two or more of the explicitly enumerated elements or components; any element or component listed in the list of elements or components may be omitted from this list.

[0017] Any enumeration of numerical ranges by endpoints in this document includes all numbers contained within the enumerated range, as well as the endpoints and equivalents of that range.

[0018] The term “comprising” (or equivalent) includes “consistent with” as well as “comprises from”.

[0019] As used herein, the term "consisting essentially of / essentially consisting" indicates that the composition mentioned contains less than 5.0 wt%, typically less than 2.0 wt%, or less than 1.0 wt% of any other ingredient.

[0020] 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%, and typically less than 1.0 wt%.

[0021] The singular “a” or “one” as used herein includes the plural, unless otherwise expressly indicated.

[0022] It should be understood that the elements, properties and / or characteristics of the (co)polymer, product or article, method or use described in this specification may be explicitly or implicitly combined with other elements, properties and / or characteristics of the (co)polymer, product or article, method or use in all possible ways without departing from the scope of this specification.

[0023] If any disclosure of any patent, patent application, or publication incorporated herein by reference conflicts with the description of this application to the extent that it may lead to ambiguity in terminology, then this description shall take precedence.

[0024] This article discloses an aqueous composition comprising a PAI polymer, an alcohol, a tertiary amine, and water.

[0025] PAI polymer

[0026] The PAI polymer disclosed herein comprises repeating units, wherein at least 50.0 mol% of the repeating units comprise an aromatic ring and one or more of an ammonium acid group or an imide group [referred to herein as repeating units (R)]. PAI The PAI polymer advantageously contains more than 90.0 mol% repeating units (R). PAI Aqueous compositions may contain one or more PAI polymers.

[0027] The acid value (mg KOH / g polymer) of the PAI polymer can be 100 or greater, and even 120 or greater. For resins containing only amic acid units, it can be up to the theoretical acid value. In some embodiments, it can be up to 170 mg KOH / g polymer. The acid value can be determined by titration, such as potentiometric titration according to ASTM D664. In particular, it can be determined by potentiometric titration as described in ASTM D664, wherein N-methylpyrrolidone (NMP) is the solvent and the titrant is potassium hydroxide and tributylammonium chloride.

[0028] Repeating unit (R) PAI Choose from the following groups:

[0029] (R PAI -A) (R PAI -B)

[0030] (R PAI -C), (R PAI -D),

[0031] (R PAI -E),

[0032] In each formula, the symbol → indicates isomerism, such that in any repeating unit within the aromatic polyamic acid structure, the groups indicated by these arrows can be present as shown or in interchangeable positions; Ar is an aromatic tetravalent group that may contain one or more aromatic rings, and is preferably selected from the group consisting of:

[0033] , , ,and

[0034] X is selected from the following groups: -O-, -C(O)-, -S-, -SO2-, -CH2-, -C(CF3)2-, -(CF2) n - where n = 1, 2, 3, 4 or 5; R is an aromatic divalent group that may contain one or more aromatic rings, and is preferably selected from the group consisting of:

[0035] , , , ,

[0036] Y is selected from the following groups: -O-, -C(O)-, -S-, -SO2-, -CH2-, -C(CF3)2-, -(CF2) n -, where n = 1, 2, 3, 4 or 5,

[0037] ,and .

[0038] Alternatively or additionally, repeating units (R) PAI Choose the group consisting of the following units (i), (ii), and (iii):

[0039] (i) (ia),

[0040] and / or the corresponding repeating unit containing an imide group:

[0041] (ib),

[0042] The attachment of the two amide groups to the aromatic ring as shown in (ia) should be understood as representing 1,3 and 1,4 polyamide-amic acid configurations;

[0043] (ii) (ii-a),

[0044] and / or the corresponding repeating unit containing an imide group:

[0045] (ii-b),

[0046] The attachment of the two amide groups to the aromatic ring as shown in (ii-a) should be understood to represent 1,3 and 1,4 polyamide-amic acid configurations; and

[0047] (iii) (iii-a),

[0048] and / or the corresponding repeating unit containing an imide group:

[0049] (iii-b),

[0050] The attachment of the two amide groups to the aromatic ring as shown in (iii-a) should be understood as representing 1,3 and 1,4 polyamide-amic acid configurations.

[0051] Repeating unit (R) PAI ) can be a repeating unit (i), or a mixture of repeating units (ii) and (iii).

[0052] The amount of repeating units containing ammonium acid groups can be determined by any suitable technique, such as spectroscopic or titration techniques, which are known to those skilled in the art.

[0053] When repeating unit (R) PAI Selected from the formula (R) detailed above. PAI -A), (R) PAI -B), (R) PAI -C), (R) PAI -D), (R PAI When -E) are present, repeating units (R) containing at least one ammonium acid group are included. PAI The mole percentage of ) can be expressed as follows:

[0054]

[0055] Where [(R PAI -A) unit], [(R) PAI -B) unit], [(R) PAI -C) unit], [(R) PAI -D) unit] and [(R PAI -E) unit] respectively represent different repeating units (R) as described above. PAI The molar concentration of ).

[0056] When repeating unit (R) PAI Selected from the formula (R) detailed above. PAI -A) and (R) PAI When -C) are present, repeating units (R) containing at least one ammonium acid group are included. PAI The mole percentage of ) can be expressed as follows:

[0057] .

[0058] Repeating unit (R) PAI It may have at least 50.0 mol%, even at least 60.0 mol%, and at least 70.0 mol% of repeating units (R) containing at least one ammonium acid group. PAI Alternatively or additionally, 70.0 to 95.0 mol%, or even 75.0 to 90.0 mol%, of repeating units (R). PAI It contains at least one ammonium acid group.

[0059] PAI polymers can be manufactured by a method involving a polycondensation reaction between at least an aromatic polycarboxylic acid halide monomer and at least an aromatic diamine.

[0060] The aromatic polycarboxylic acid halide monomer can be selected from the group consisting of terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, and acyl halide derivatives of trimellitic anhydride. Preferably, it is selected from trimellitic anhydride monoacyl halides. Among trimellitic anhydride monoacyl halides, trimellitic anhydride monoacyl chloride is preferred.

[0061] Alternatively or additionally, 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 using dicarboxylic anhydride monomers in this method, the excess of the acyl halide monomer relative to an equimolar concentration of the aromatic diamine monomer is calculated, taking into account the combined molar number of the acyl halide and dicarboxylic anhydride monomer.

[0062] Aromatic diamine monomers are selected from the group consisting of: 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), m-phenylenediamine (MPDA), diphenyl dimethylmethane diamine (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'-diamino-triphenylamine (DATPA), 4 4'-Diaminodiphenylmethane (MDA), diaminodiphenyl sulfone (DDS), 3,4'-diaminodiphenyl ether (3,4'-ODA), 3,3'-dimethyl-4,4'-diaminodiphenylmethane (MDI), 2,2-bis(4-(4-aminophenoxy)-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-isopropylpropane and mixtures thereof.

[0063] The aromatic diamine monomer is preferably selected from the group consisting of: 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenylmethane (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.

[0064] Polycondensation is advantageously carried out under substantially anhydrous conditions in a polar solvent and at a temperature below 150°C using a stoichiometric excess of acyl halide monomers.

[0065] Monofunctional reactants can be used as capping agents known to those skilled in the art to control the molecular weight of polymers and improve polymer stability.

[0066] PAI polymers are advantageously separated from polar reactive solvents in solid form by coagulation or precipitation under mild conditions, preferably by the addition of a miscible non-solvent (e.g., water, lower alkyl alcohols, etc.). Optionally, the solid resin can 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 to precipitate PAI polymers from solution; these non-solvents include, for example, ethers, aromatic hydrocarbons, ketones, etc.

[0067] The number average molecular weight (Mn) of the PAI polymer is at least 1000, preferably at least 1500, and more preferably at least 2000. The number average molecular weight (Mn) of the PAI polymer is 20000 or less, preferably 15000 or less. The molecular weight (Mw and Mn) of the PAI polymer can be and is usually determined using gel permeation chromatography (GPC) with polystyrene standards.

[0068] tertiary amine

[0069] The aqueous compositions disclosed herein contain tertiary amines. Tertiary amines are selected from those groups having formula (I):

[0070] NR 1 R 2 R 3 (I)

[0071] Where R 1 R 2 and R 3 Each time it appears, and independently of each other, it is selected from the group consisting of: branched or straight-chain, saturated or unsaturated alkyl groups having 1 to 6 carbon atoms, which optionally contain hydroxyl functional groups. R 1 R 2 and R 3 They can be the same, or they can be different. R 1 R 2 and R 3 Preferably selected from branched or straight-chain saturated alkyl groups having 1 to 4 carbon atoms, which optionally contain hydroxyl functional groups.

[0072] The tertiary amine is preferably a non-toxic tertiary amine.

[0073] Tertiary amines are conveniently selected from the group consisting of: methyl diethanolamine (MDEA), dimethyl ethanolamine (DMEA), butyl diethanolamine (BDEA), triethanolamine (TEA), and combinations thereof.

[0074] As will be understood by those skilled in the art, tertiary amines can help improve the water solubility of PAI polymers. Without being bound by any particular scientific theory, tertiary amines will react with acidic groups on the PAI polymer backbone to form water-soluble salts.

[0075] Therefore, a minimum amount of the desired tertiary amine can be present. The minimum amount of tertiary amine used can be approximately the stoichiometric amount required to neutralize the free carboxylic acid groups in the PAI polymer. An excess of amine, up to 3 to 5 times the stoichiometric excess, may be desirable. The molar ratio of the amine to the free carboxylic acid groups in the PAI polymer can typically be in the range of 0.8 to 5.0, preferably 0.8 to 2.5, more preferably 1.0 to 2.0. It should be understood that if the aqueous composition contains more than one PAI polymer, the amount of tertiary amine given herein takes into account all free carboxylic acid groups present in the PAI polymer.

[0076] The tertiary amine is present in the aqueous composition in amounts 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 amounts 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 aqueous composition may advantageously contain 5.0 wt% to 24.5 wt%, preferably 9.0 wt% to 24.0 wt%, or even 9.0 wt% to 19.5 wt% relative to the total weight of the aqueous composition.

[0077] alcohol

[0078] The aqueous compositions disclosed herein comprise alcohols having formula (II):

[0079] R(OH) m (II)

[0080] Wherein R is a branched or straight-chain, saturated or unsaturated alkyl group having 1 to 50 carbon atoms, and m is an integer from 1 to 6. R is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 2 to 10 carbon atoms, and even more preferably an alkyl group having 2 to 6 carbon atoms. In formula (II), m is preferably an integer from 1 to 3.

[0081] Among the monohydric alcohols in formula (II) where n = 1, isopropanol (IPA) or 2-butanol has been found to be advantageous.

[0082] Among the polyols applicable to this application, 1,3-propanediol, propylene glycol and butanediol may be mentioned.

[0083] The alcohol is present in the aqueous composition in amounts 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 amounts of 30.0 wt% or less, 29.0 wt% or less, 28.0 wt% or less, 27.0 wt% or less, or 26.0 wt% or less based on the total weight of the aqueous composition. The aqueous composition may advantageously contain 8.0 wt% to 29.0 wt%, preferably 10.0 wt% to 27.0 wt% of alcohol relative to the total weight of the aqueous composition.

[0084] Aqueous Composition

[0085] The aqueous compositions disclosed herein comprise an amount of PAI polymer based on 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 of the total weight of the aqueous composition. The aqueous compositions disclosed herein may comprise an amount of PAI polymer based on 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 of the total weight of the aqueous composition. It should be understood that if the aqueous composition comprises more than one PAI polymer, the total amount of PAI polymer is as given herein. The aqueous composition may advantageously comprise 21.0 wt% to 33.0 wt%, preferably 22.0 wt% to 30.0 wt% of PAI polymer relative to the total weight of the aqueous composition.

[0086] In preparing the aqueous compositions of the present invention, any convenient method of combining the components can be employed. The solid PAI polymer can be added incrementally to a stirred mixture of the tertiary amine and water, with stirring continuing until the solid resin has dissolved. Alternatively, the tertiary amine can be slowly added to a stirred suspension of the PAI polymer in water, with stirring continuing until the solid dissolves. As with any acid-base reaction, external cooling may initially be found necessary; subsequent heating and stirring may be desirable to allow the solid resin to dissolve completely within a reasonable timeframe. For example, the suspension can be heated to a temperature of 50°C to 90°C while maintaining stirring.

[0087] Another advantage of combining tertiary amines with PAI polymers having high acid values ​​has been found to be the limited time required to dissolve the PAI polymers. The dissolution time is significantly shorter than that observed with PAI polymers having lower acid values ​​(below 100 mg KOH / g polymer).

[0088] When measured at 12 rpm using a Brinell viscometer with a #64 rotor, the aqueous compositions disclosed herein have viscosities 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. The viscosity of the compositions at 25°C is generally not less than 5,000 cP.

[0089] When measured at 12 rpm using a Brinell viscometer with a #64 rotor, the aqueous compositions disclosed herein can have viscosities of 5,000 cP or less, 4,000 cP or less, 3,500 cP or less, or 3,000 cP or less at 45°C. The viscosity of the compositions at 25°C is typically not less than 1,000 cP.

[0090] additive

[0091] The aqueous compositions according to this disclosure comprise a PAI polymer, water, a tertiary amine, and an alcohol. The compositions of this invention have low levels of any organic solvent, particularly any organic solvent having a boiling point equal to or greater than 100°C. The total amount of organic solvent having a boiling point equal to or greater than 100°C is generally less than 5.0 wt% relative to the weight of the aqueous composition. For the avoidance of doubt, the expression “organic solvent” refers to any organic compound capable of dissolving or promoting the dissolution of the PAI polymer and not a tertiary amine having formula (I) or an alcohol having formula (II). The aqueous compositions of this invention are preferably substantially free of any organic solvent. The expression “substantially free” in relation to the aqueous composition and organic solvent is intended to mean that the one or more organic solvents are present in a total amount of less than 5.0 wt%, preferably less than 3.0 wt%, and typically less than 1.0 wt% relative to the weight of the composition. The amount of organic solvent relative to the weight of the composition may be 0.1 wt% or less. Such compositions are highly desirable in applications where organic solvents are intolerable.

[0092] Depending on their end use, the compositions of the present invention may further comprise common components 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) inorganic fillers, such as carbon fibers, glass fibers, metal sulfates (such as BaSO4, CaSO4), oxides (such as Al2O3 and SiO2), zeolites, mica, talc, and kaolin; (v) organic fillers, preferably thermally stable polymers, such as PTFE; (vi) film curing agents, such as silicate compounds, such as metal silicates, for example aluminum silicate, and metal oxides, such as titanium dioxide; (vii) adhesion promoters, such as colloidal silica and phosphate compounds, such as metal phosphates, such as phosphates of Zn, Mn, or Fe.

[0093] Coating containing polymer solution

[0094] Another aspect of the invention is a method for manufacturing an article of articles, comprising applying a polymer solution disclosed herein onto a substrate. The disclosed aqueous composition provides a highly concentrated solution for constructing a protective coating, thereby requiring fewer passes to achieve the target thickness. Compared to current PAI solutions, the polymer solution disclosed herein provides a water-based PAI solution capable of constructing 2-3 times the dry coating thickness.

[0095] Any technique can be used in this method, and any combination of techniques can be used. Typically, the composition is applied by coating. Coating can be performed by any suitable coating process, such as spin coating, spray coating, slot spin coating, roller coating, die coating, slot die coating, dip coating, or curtain coating. The coating step is typically followed by a step in which the applied composition is cured by pre-baking the resulting film at a temperature between 120°C and 400°C, preferably between 120°C and 350°C, thereby causing the solvent to evaporate.

[0096] The thickness of the coating can vary depending on the intended purpose. The thickness is preferably in the range of 0.1 to 100 micrometers, more preferably 1 to 75 micrometers, and even more preferably 5 to 50 micrometers. The thickness can be as low as 10 micrometers.

[0097] The aqueous compositions of the present invention may be particularly useful in formulations intended for use in coated articles, providing a continuous coating with improved toughness and adhesion on the coated surface. More generally, the aqueous compositions of the present invention can be used to obtain adhesive or protective coatings in applications requiring resistance to abrasion, heat, or harsh chemical environments.

[0098] Such coatings can act as an adhesive layer for automotive topcoats to improve adhesion between existing automotive topcoat layers or with other metallic topcoat layers.

[0099] PAI polymers are known to have good adhesion to metal surfaces, and therefore the aqueous compositions of the present invention are particularly useful in providing formulations for use as enamel coatings or insulating wires (e.g., for electromagnetic wires in electric motors).

[0100] The aqueous compositions of this invention can be used to provide chemically resistant coatings for metal or other substrates; to provide adhesive layers for non-stick cookware; to provide coatings for tie rods used in cement; to provide pretreatment coatings for polymer films such as polyester, polyamide, and polyimide films (when used in metallization operations); as adhesives for various plastic or metal film materials (such as liquid crystal polymers and polyimides); and as additives for improving the performance of inks.

[0101] It can be found that the essentially "organic solvent-free" aqueous compositions of certain embodiments of the present invention are useful for film casting in which organic solvents may be undesirable or intolerable.

[0102] Formulations containing these aqueous compositions can also be used as sizing agents, and particularly for sizing fibrous materials such as glass fibers, carbon fibers and graphite fibers, alumina fibers, silicon nitride fibers, boron fibers, aramid fibers, fluorocarbon fibers, etc. The term "carbon fiber" is used herein in a general sense and includes graphite fibers as well as amorphous carbon fibers produced after thermal carbonization or graphitization.

[0103] This disclosure will now be described with reference to the following examples, which are intended to be illustrative only and not to limit this disclosure.

[0104] raw material

[0105] N-Methyldiethanolamine (MDEA) and N-butyldiethanolamine (BDEA) were purchased from Sigma Aldrich.

[0106] Torlon® polyamide-imide AI-30 LM (PAI-1) and Torlon® polyamide-imide AI-50 (PAI-2) were purchased from Solvay Specialty Polymers USA, LLC. Isopropanol (IPA) and 2-butanol (2BUT) were purchased from Thermo Fisher Scientific Inc. N-methyl-2-pyrrolidone (NMP) was purchased from VWR International, LLC.

[0107] Example 1 (E1)

[0108] Add 1.31 g of deionized (DI) water and 36.30 g of MDEA to a 500 mL four-necked round-bottom flask equipped with a water jacket and a top-mounted mechanical stirrer. Heat the solution to 85°C and then add 190.69 g of PAI-1. Vigorously stir the mixture at 85°C for 2.5 h to form a homogeneous viscous paste. Cool the paste to 60°C for 1 h, and then add 72.00 g of IPA over a 30-minute interval to prevent gelation. Vigorously stir the solution again at 60°C for one hour, and then drain it from the reactor. Immediately measure the solution viscosity and solids percentage.

[0109] Comparative Example 2 (CE2)

[0110] An aqueous solution was prepared in the same manner as in Example 1 (E1), except that 185.76 g of DI water, 17.28 g of MDEA, and 96.96 g of AI-30 LM were placed in a round-bottom flask. IPA was not added to the solution.

[0111] Example 3 (E3)

[0112] Add 52.32 g of BDEA to a 500 mL four-necked round-bottom flask equipped with a water jacket and a top-mounted mechanical stirrer, and heat to 85°C. Slowly add 128.73 g of PAI-2 to the reactor, and then add 73.95 g of DI water to form a homogeneous solution. Stir the solution vigorously for 2 h and then cool to 60°C for 1 h. Add 45.00 g of 2BUT. Stir the solution at 60°C for another hour, and then drain it. Immediately measure the solution viscosity and solids percentage.

[0113] Example 4 (E4)

[0114] The solution was prepared in the same manner as in Example 3 (E3), except that 38.17 g of DI water was used and 72.00 g of IPA was added instead of 2 BUT.

[0115] Example 5 (E5)

[0116] The solution was prepared in the same manner as E3, except that 87.60 g of DI water was used and 38.66 g of MDEA was added instead of BDEA.

[0117] Comparison Example 6 (CE6)

[0118] The solution was prepared in the same manner as E3, except that 198.61 g of DI water, 29.30 g of BDEA, and 72.09 g of PAI-2 were placed in a round-bottom flask. No alcohol or other additives were added to the solution.

[0119] Example 7 (E7)

[0120] Add 38.66 g of MDEA to a 500 mL four-necked round-bottom flask equipped with a water jacket and a top-mounted mechanical stirrer, and heat to 85°C. Slowly add 128.73 g of PAI-2 to the reactor, and then add 78.60 g of DI water to form a homogeneous solution. Stir the solution vigorously for 2 h and then cool to 60°C for 1 h. Add 54.00 g of IPA to the solution. Stir the solution for another hour and then drain it. Measure the solution viscosity and solids percentage immediately. Heat the solution to 45°C and apply it to an aluminum substrate (alloy 3003H14) using a casting knife (gap height 0.13 mm). Cure the solution using a slow ramp from room temperature to 285°C and hold for 30 minutes. The coating appears smooth and even without cracks. The adhesion was measured using the cross-cut test according to ISO 2409 and reported in Table 2. A rating of 0 (lowest value) means that the coating has not peeled off from the substrate, while a rating of 5 (highest value) indicates that the coating has completely peeled off from the substrate.

[0121] Comparison Example 8 (CE8)

[0122] The solution was prepared in the same manner as in Example 7 (E7), except that 63.60 g of DI water was used. 15.00 g of NMP (5.0 wt% relative to the total weight of the solution) was also added to the solution. The coating was prepared in the same manner as in E7. The coating also appeared smooth and free of cracks.

[0123] Details of the compositions of Examples 1, 3 to 5 and 7, and Comparative Examples 2, 6 and 8 are summarized in Table 1.

[0124] Table 1. Solution viscosity at 25°C and 45°C

[0125]

[0126] a The measurements were performed by drying a 5.0 g aqueous solution sample at 300°C for 20 minutes.

[0127] b The measurement was performed using a Brinell viscometer with a #64 rotor.

[0128] c Samples marked as unmeasurable exhibited excessively high viscosity, making them unmeasurable at room temperature.

[0129] The data in Table 1 show that the compositions of the present invention have significantly reduced solution viscosity compared to compositions prepared in the absence of alcohol. Even when the alcohol-free compositions contain half the amount of PAI polymer contained in the compositions of the present invention, they still exhibit very high solution viscosities. The compositions of Examples 1, 3, 4, 5, and 7, containing approximately 25 wt% PAI polymer, even exhibit solution viscosities measurable at 25°C. Even though the compositions of Comparative Examples 2 and 6 contain approximately 13-17 wt% PAI polymer, these compositions exhibit solution viscosities that are too high to be measurable at 25°C.

[0130] Table 2. Properties of the coating

[0131]

[0132] a The grading and rating methods comply with ISO 2409.

[0133] The data in Table 2 show that the compositions of the present invention exhibit measurable viscosity at high solids content, which makes them suitable for preparing coatings of good quality in the absence of organic solvents (like NMP).

Claims

1. An aqueous composition comprising: -Based on the total weight of the aqueous composition, 20.0 wt% to 35.0 wt% of a polyamide-imide (PAI) polymer, the polyamide-imide polymer comprising repeating units, wherein at least 50.0 mol% of these repeating units comprise one or more of (i) an aromatic ring and (ii) an amide acid group or an imide group [repeating unit (R PAI )]; -Based on the total weight of the aqueous composition, 0.1 wt% to 25.0 wt% of a tertiary amine having formula (I): NR 1 R 2 R 3 (I) Where R 1 R 2 and R 3 Each time it appears and independently of each other, it is selected from the group consisting of: branched or straight-chain, saturated or unsaturated alkyl groups having 1 to 6 carbon atoms, which optionally contain hydroxyl functional groups; -Based on the total weight of the aqueous composition, 0.1 wt% to 30.0 wt% of an alcohol having formula (II): R(OH) m (II) Wherein R is a branched or straight-chain, saturated or unsaturated alkyl group having 1 to 50 carbon atoms, and m is an integer from 1 to 6, preferably from 1 to 3; R is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 2 to 10 carbon atoms, and even more preferably an alkyl group having 2 to 6 carbon atoms; and -water, The aqueous composition comprises, based on a total weight of less than 5.0 wt%, an organic solvent having a boiling point equal to or greater than 100°C and not being a tertiary amine of formula (I) or an alcohol of formula (II); and When measured at 12 rpm using a Brinell viscometer with a #64 rotor at 25°C, the aqueous composition has a viscosity of 30,000 cP or less.

2. The aqueous composition of claim 1, wherein, Repeating unit (R) PAI Choose from the following groups: (R PAI -A)、 (R PAI -B)、 (R PAI -C)、 (R PAI -D)、 (R PAI -E), in: The symbol → in each equation denotes isomerism, such that in any repeating unit R PAI In the diagram, the groups indicated by these arrows may be present as shown or in interchangeable positions; Ar is an aromatic tetravalent group that may contain one or more aromatic rings, and is preferably selected from the group consisting of: , , ,and X is selected from the following groups: -O-, -C(O)-, -S-, -SO2-, -CH2-, -C(CF3)2-, -(CF2) n - where n = 1, 2, 3, 4, or 5; and R is an aromatic divalent group that may contain one or more aromatic rings, and is preferably selected from the group consisting of: ， ， ， ， Y is selected from the following groups: -O-, -C(O)-, -S-, -SO2-, -CH2-, -C(CF3)2-, -(CF2) n -, where n = 2, 3, 4 or 5, ,and .

3. The aqueous composition according to any one of claims 1 or 2, wherein, These repeating units (R) PAI Choose from the following groups: units (i), (ii), and (iii): (i) (i-a), and / or the corresponding repeating unit containing an imide group: (i-b), The attachment of the two amide groups to the aromatic ring as shown in (ia) should be understood as representing 1,3 and 1,4 polyamide-amic acid configurations; (ii) (ii-a), and / or the corresponding repeating unit containing an imide group: (ii-b) The attachment of the two amide groups to the aromatic ring, as shown in (ii-a), represents the 1,3 and 1,4 polyamide-amic acid configurations. as well as (iii) (iii-a), and / or the corresponding repeating unit containing an imide group: (iii-b), The attachment of the two amide groups to the aromatic ring, as shown in (iii-a), represents the 1,3 and 1,4 polyamide-amic acid configurations.

4. The aqueous composition according to any one of claims 1 to 3, wherein, The PAI polymer has an acid value of 100 or greater, and preferably 120 or greater, as measured by mgKOH / g polymer.

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

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

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

8. The aqueous composition according to any one of claims 1 to 7, wherein, The tertiary amine is selected from the group consisting of: methyl diethanolamine (MDEA), dimethyl ethanolamine (DMEA), butyl diethanolamine (BDEA), triethanolamine (TEA), and combinations thereof.

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

10. The aqueous composition according to any one of claims 1 to 9, wherein, The alcohol is selected from the group consisting of isopropanol, 2-butanol, 1,3-propanediol, propylene glycol, butanediol and combinations thereof.

11. The aqueous composition according to any one of claims 1 to 10, wherein, The alcohol is selected from the group consisting of isopropanol and 2-butanol, and the tertiary amine is selected from the group consisting of methyl diethanolamine (MDEA) and butyl diethanolamine (BDEA).

12. The aqueous composition according to any one of claims 1 to 11, wherein, The alcohol is 10.0 wt% to 30.0 wt% of isopropanol, and the tertiary amine is 10.0 wt% to 15.0 wt% of methyl diethanolamine (MDEA).

13. A coating for an article of manufacture comprising an aqueous composition as described in any one of claims 1 to 12.

14. A method for coating an article, the method comprising the step of coating the article with an aqueous composition as described in any one of claims 1 to 12.

15. The method of claim 14, wherein, The coating process includes one or more of the following: spraying, roller coating, slot die coating, dip coating, spin coating, curtain coating, and combinations thereof.

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