Wire enamel composition containing polyamide-imide

Abstract

A composition is provided that meets all the requirements to qualify as a true alternative to wire enamel compositions containing NMP as a solvent. The present invention relates to a polyamideimide composition particularly suitable for use as primary insulation for wire, which contains 55-65 pbw Nn-butylpyrrolidone, 25-40 pbw polyamideimide resin, and 0-20 pbw other components, with the polyamideimide resin having a Mw of 10,000-40,000 g / mol (Daltons) and a Mw / Mn ratio of 1.1-2.

Description

Technical Field

[0001] The present invention relates to a wire enamel composition containing polyamide-imide.

Background Art

[0002] In transformers, generators, and electric motors, the electrical insulating material that protects copper or aluminum wires is a thin coating of a high-performance polymer. This coating, referred to as primary electrical insulation or wire enamel, is as thin as possible to obtain the maximum number of turns in each slot space. Sufficient thermal, mechanical, and electrical properties need to be maintained. One such polymer used as primary electrical insulation is poly(amide-imide) resin or polyamide-imide resin. Outstanding properties include high thermal performance, chemical resistance and wear resistance, and a low coefficient of friction.

[0003] Polyamide-imide coating compositions form flexible and resistant films and are useful, in particular, as wire enamels, varnishes, adhesives for laminates, non-adhesive coatings, polyamide-imide bodies, etc. These compositions are particularly notable for their high-temperature performance over long periods (= 220 °C (430 °F)).

[0004] Publication GB570858 discloses the preparation of aromatic polyamide-imide resins by reacting trimellitic anhydride and aromatic diamines. Usually, these reactions are carried out in an aprotic solvent, for example, in N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF).

[0005] US3541038 describes the preparation of an aromatic polyamide-imide resin using trimellitic anhydride and a polyisocyanate, preferably diisocyanate. This reaction is preferably carried out using N-methylpyrrolidone (NMP) as the solvent. Alternatively, a mixture of NMP and an aromatic hydrocarbon can be used as the solvent.

[0006] Some time ago, it was found that there may be potential health effects on people exposed to NMP. Alternative solvents, such as tetrahydrofuran (THF), methyl ethyl ketone (MEK), gamma-butyl lactone (GBL), or dimethyl sulfoxide (DMSO), are known, but they have drawbacks, such as boiling points that are too low for use as reaction solvents, poor polymer resin solubility, or poor storage stability, which can alter the properties of the polymer in the application in which they are used.

[0007] NMP can be used safely when handled in an appropriate manner and with sufficient safety and health precautions taken, but various literatures on alternative solvents have been published, for example, in US2013 / 0217812, WO2013 / 090933, WO2013 / 107822, US2015 / 0299393, and WO2015 / 144663.

[0008] US2015 / 0299393 discloses the preparation of polyamide-imides in alternative, relatively low-toxicity solvents, such as N-formylmorpholine (NFM) and N-acetylmorpholine (NAM). These relatively low-toxicity solvents (primary solvents) can be used in combination with a co-solvent (or secondary solvent), where the amount of the co-solvent is lower than that of the primary solvent. Numerous potential co-solvents are mentioned in this document. The polyamide-imide resins thus prepared are said to be usable as coating compositions for wire coating, although no commercially available wire coating systems based on this composition are known.

[0009] WO2013 / 107822 discloses various solvents that can be used as alternative solvents to NMP in wire enamel compositions containing polyamide-imide resins. WO2013 / 107822 also provides an example of a wire enamel composition suitable for use in enamelizing copper wires. The inventors of the present application repeated the experiments of WO2013 / 107822 and found that some of the properties of copper wires enamelized with these alternative solvents were equivalent to those obtained using NMP solvents. However, overall, the properties of copper wires enamelized with these alternative solvents were insufficient to justify using these compositions as a substitute for NMP-based compositions. In particular, the severance, ethanol resistance, flexibility, and tanδ did not meet the commercially available specifications for NMP-based polyamide-imide resin compositions for wire enamel applications. [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention relates to a composition that satisfies all requirements to qualify as a true substitute for wire enamel compositions containing NMP as a solvent. [Means for solving the problem]

[0011] Composition according to the present invention: a. Nn-butylpyrrolidone (NBP) at 55-65 pbw b. Polyamide-imide resin with a yield of 25-40 lbw c. Other components of 0-20pbw It contains, The polyamide-imide resin has a Mw of 10,000 to 40,000 g / mol (Daltons) and an Mw / Mn ratio of 1.1 to 2.

[0012] The present invention further relates to the use of this composition as an insulating material for copper or aluminum conductive materials.

[0013] The present invention further relates to the preparation of polyamide-imide resins, wherein Nn-butylpyrrolidone is used as a solvent and reacted with an anhydrous polyamide with a diisocyanate at a temperature in the range of 80 to 120°C in the presence of a modifying compound.

[0014] The present invention also relates to a method for enamelizing metal wires with the composition according to the present invention. [Modes for carrying out the invention]

[0015] The polyamide-imide resin used in the present invention may be derived from a polycarboxylic acid or its anhydride having two carboxyl groups adjacent to each other and having at least one further functional group, or from a polyamine having at least one primary amino group capable of forming an imide ring, or from a compound having at least two isocyanate groups. The polyamide-imide may also be obtained by reacting a polyamide, a polyisocyanate containing at least two NCO groups, and a cyclic dicarboxylic acid anhydride having at least one further group, and these may be subjected to condensation or addition reactions.

[0016] Furthermore, polyamide-imides can also be prepared from diisocyanates or diamines and dicarboxylic acids, provided that one of these components already contains an imide group. For example, a tricarboxylic acid anhydride can be reacted with a diprimer diamine to produce a corresponding diimidocarboxylic acid, which can then be reacted with a diisocyanate to form a polyamide-imide.

[0017] For the preparation of polyamideimides, the use of tricarboxylic acids or their anhydrides having two adjacent carboxyl groups is preferred. Preferred are the corresponding aromatic tricarboxylic acid anhydrides, such as trimellitic anhydride, naphthalenetricarboxylic acid anhydride, bisphenyltricarboxylic acid anhydride, and other tricarboxylic acids having two benzene rings and two adjacent carboxyl groups in the molecule, for example, those indicated by DE-A1956512. Particularly preferred is the use of trimellitic anhydride. As the amine component, diprimer diamines already described in relation to polyamidecarboxylic acids can be used. Furthermore, aromatic diamines having a thiadiazole ring, such as 2,5-bis(4-aminophenyl)-1,3,4-thiadiazole, 2,5-bis(3-aminophenyl)-3,3,4-thiadiazole, and 2-(4-aminophenyl)-5-(3-aminophenyl)-1,3,4-thiadiazole can also be used, and even mixtures of various isomers can be used.

[0018] Diisocyanates suitable for the preparation of polyamide-imides are as follows: aliphatic diisocyanates, e.g., tetramethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate and trimethylhexamethylene diisocyanate; alicyclic diisocyanates, e.g., isophorone diisocyanate, ω,ω'-diisocyanate-1,4-dimethylcyclohexane, cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4-diisocyanate and dicyclohexylmethane 4,4'-diisocyanate; aromatic diisocyanates Anates, such as phenylenediisocyanate, tolylenediisocyanate, naphthylenediisocyanate, and xylylenediisocyanate, as well as substituted aromatics, such as diphenyletherdiisocyanate, diphenylsulfidediisocyanate, diphenylsulfonediisocyanate, and diphenylmethanediisocyanate; mixed aromatic-aliphatic diisocyanates and aromatic-hydroaromatic diisocyanates, such as 4-isocyanatemethylphenylisocyanate, tetrahydronaphthylene 1,5-diisocyanate, and hexahydrobenzidine 4,4'-diisocyanate. Preferably, 4,4'-diphenylmethanediisocyanate, 2,4- and 2,6-tolylenediisocyanate, and hexamethylenediisocyanate are used.

[0019] It has been found that polyamide-imide resins dissolved in NBP exhibiting the advantageous properties necessary to qualify as wire enamels can only be obtained when the polyamide-imide resin is prepared in NBP under clearly defined reaction conditions. The reaction temperature should not be excessively high, preferably in the range of 80°C to 130°C, more preferably in the range of 80°C to 120°C. If the reaction temperature is above 130°C, the reaction is excessively fast and uncontrollable, and it is not possible to obtain a polyamide-imide resin having at least 10,000 g / mol Mw and an Mw / Mn ratio of 1.1 to 2. If the reaction temperature is below 80°C, even if a reaction occurs, it is very slow and practically unusable for the production of polyamide-imide resins.

[0020] It has been further found that it is useful to have a small amount of modifier compound in the reaction mixture, for example, a low molecular weight monoanhydride or monocarboxylic acid. Suitable examples of low molecular weight monocarboxylic acids include (C1-C10) monocarboxylic acids or C4-C6 branched monocarboxylic acids, such as formic acid, acetic acid, propionic acid, and others, and a suitable example of an anhydride is phthalic anhydride. The amount of low molecular weight monoanhydride or monocarboxylic acid in the reaction mixture should be 4-8 mol%, based on the amount of polyamide-imide formed in the reaction.

[0021] The present invention makes it possible to prepare a solution containing Nn-butylpyrrolidone as the main solvent and a polyamide-imide resin in an amount of more than 21% by weight, wherein the polyamide-imide resin has an Mw of 10,000 to 40,000 g / mol (Daltons) and an Mw / Mn ratio of 1.1 to 2.

[0022] This solution may contain other solvents, but the amount of these other solvents is far less than the amount of Nn-butylpyrrolidone.

[0023] The present invention also relates to the production of enameled wires by using the composition of the present invention.

[0024] Coating and curing of the composition according to the present invention do not require any specific or special procedures, and conventional application methods can be used. The wire typically has a diameter of 0.005 mm to 6 mm. Suitable wires include conventional metal wires, preferably copper, aluminum, or alloys thereof. There are no restrictions regarding the wire shape, and in particular, circular wires or rectangular wires can be used. The composition of the present invention can be applied as a single-layer coating, a double-layer coating, or a multi-layer coating.

[0025] The composition may be applied with a conventional layer thickness, and the dry layer thickness follows standard values for thin wires and thick wires. The composition of the present invention is applied onto the wire and cured in a horizontal furnace or a vertical furnace. The wire may be coated and cured one or several times continuously. As the curing temperature, an appropriate range may be various temperatures from 300 °C to 800 °C according to the conventional parameters used for enamels and the properties of the wire to be coated. The conditions of the enameling process, such as the number of passes, the enameling speed, and the furnace temperature, depend on the properties of the wire to be coated.

[0026] In order to improve the cut resistance of the wire coated with the composition of the present invention, nanoparticles may be contained in the composition according to the present invention.

[0027] The nanoparticles that can be used in the composition according to the present invention are particles whose average radius is in the range of 1 to 300 nm, preferably in the range of 2 to 100 nm, and particularly preferably in the range of 5 to 65 nm. Examples of preferred nanoparticles are nanooxides, nanometal oxides, colloidal oxides, colloidal metal oxides, metal oxides, or hydroxides of aluminum, tin, boron, germanium, gallium, lead, transition metals, and lanthanides and actinides, particularly aluminum, silicon, titanium, zinc, yttrium, vanadium, zirconium, and / or nickel, preferably aluminum, silicon, titanium, and / or zirconium, which are nano-sized in the dispersed phase and can be used individually or in combination. Among the nanometal oxides, nanoalumina is the most preferred. Examples of nanoaluminas include BYK-LP X 20693 and NanoBYK3610 from BYK Chemie, Nycol Al20OSD from Nycol nano Technologies, and Dispal X-25 SR and SRL, Disperal P2, P3, OS1 and OS2 from Sasol Germany. Among the nanoaluminas, ceramic particles of aluminum oxide pre-dispersed in a polar solvent, such as BYK-LP X 20693 and NanoBYK3610 from BYK-Chemie, are preferred. The nanoparticles can be used with a coupling agent. Any conventionally known functional alkoxysilane or allyloxysilane can be used as the coupling agent. Among the functional silanes, (isocyanate alkyl)-trialkoxysilane, (aminoalkyl)-trialkoxysilane, (trialkoxysilyl)-alkyl anhydride, and oligomeric diaminosilane systems are preferred. The alkyl radical and alkoxy group of the functional silane have 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms. The alkyl and alkoxy groups described above may further have substituents thereon. Other useful coupling agents include titanates and / or zirconates.Any conventional orthotitanic acid or zirconic acid ester may be used, for example, tetraisopropyl, tetrabutyl, acetylacetone, acetoacetic acid esters, diethanolamine, triethanolamine, cresyl titanate or zirconate.

[0028] To improve the dispersion of nanoparticles in the polymer solution matrix, a coupling agent, such as a functional silane, titanate, or zirconate, may be added directly to the nanoparticle dispersion and mixed therein before being added to the polymer resin solution, or added directly to the polymer solution before the nanoparticle dispersion is added. Alternatively, the coupling agent may be mixed into the polymer solution prior to the addition of the nanoparticle dispersion for relatively good bonding of the inorganic portion to the organic portion. The mixture of the polymer solution and the coupling agent may be stirred at room temperature or a relatively low temperature for several hours, and then the nanometal oxide solution is added.

[0029] The fabricated enameled wires were tested according to IEC60851.

[0030] <Measurement method> Mw was measured according to DIN55672-2. Mn was measured according to DIN55672-2. Viscosity was measured according to ASTM D 3288. The mandrel test was performed according to IEC 60851-Part 3. Ethanol resistance was measured according to IEC 60851-Part 4. The cutting test was performed according to IEC 60851-Part 6. Tanδ was measured according to IEC60851-Part 5. The jerk test was performed according to IEC 60851-Part 3.

[0031] <Example> Example 1 (Comparison) A polyamide-imide solution in Nn-butylpyrrolidone (NBP) was prepared by repeating Example 1 from WO2013 / 107822 under exactly the same conditions. The polyamide-imide solution was obtained with an average molecular weight of 7136 g / mole (Sample 1).

[0032] Example 2 18.08 parts by weight (pbw) of trimellitic anhydride, 23.5 pbw of 4,4'-diphenylmethane diisocyanate, 0.12 pbw of formic acid, and 58.29 pbw of NBP were added to the reaction vessel and heated to 85°C. The mixture was held at 85°C for 2 hours and then slowly heated to 100°C. The temperature in the reaction vessel was maintained at this temperature for several hours.

[0033] One hour after reaching 100°C, the 10.9 pbw sample was removed from the reaction vessel, and its molecular weight was measured to be 9665 g / mole (Sample 2).

[0034] The reaction was continued, and after another hour, a further sample of 10.9 pbw was removed from the reaction vessel, and its molecular weight was measured to be 15593 g / mole (Sample 3).

[0035] The reaction was continued, and after another hour, a further sample of 10.9 pbw was removed from the reaction vessel, and its molecular weight was measured to be 16771 g / mole (Sample 4).

[0036] The reaction was continued, and after a total reaction time of 7 hours at 100°C, an additional sample of 10.9 pbw was removed from the reaction vessel, and its molecular weight was measured to be 24583 g / mole. This sample was further diluted with benzyl alcohol to a viscosity of 13000 mPas at 23°C (Sample 5).

[0037] Example 3 All samples recovered in Examples 1 and 2 were subjected to a typical wire enamel test. A commercially available NMP solution of polyamide-imide resin (Sample 6) was also used for this comparison. The results of these tests are shown in Table 1.

[0038] Table 1 This disclosure includes the following embodiments of the invention: <Aspect 1> (a) Nn-butylpyrrolidone at 55-65 pbw (b) Polyamide-imide resin with a yield of 25-40 lbw (c) Other components of 0-20pbw A composition containing, The polyamide-imide resin is characterized by having an Mw of 10,000 to 40,000 g / mol (Daltons) and an Mw / Mn ratio of 1.1 to 2. composition. <Aspect 2> The composition according to embodiment 1, further containing nanoparticles having an average diameter in the range of 1 nm to 300 nm. <Aspect 3> The composition according to embodiment 1, which can be obtained by reacting a mixture containing a tricarboxylic acid having two carboxyl groups adjacent to each other or its anhydride, a diisocyanate, a modifying compound, and Nn-butylpyrrolidone at a temperature in the range of 80°C to 120°C. <Aspect 4> A method for preparing a polyamide-imide resin, A mixture containing a tricarboxylic acid having two adjacent carboxyl groups or its anhydride, a diisocyanate, a modifier compound, and Nn-butylpyrrolidone is reacted at a temperature in the range of 80°C to 120°C until a polyamide-imide resin having an Mw of 10,000 to 40,000 g / mol (Daltons) and an Mw / Mn ratio of 1.1 to 2 is obtained. method. <Aspect 5> The method according to embodiment 4, wherein the adjusting agent is a low molecular weight monocarboxylic acid. <Aspect 6> The method according to embodiment 5, wherein the low molecular weight monocarboxylic acid is selected from the group consisting of formic acid, acetic acid, and propionic acid. <Aspect 7> The method according to any one of embodiments 4 to 6, wherein the mixture also includes nanoparticles having an average diameter in the range of 1 nm to 300 nm. <Aspect 8> A method for coating a metal wire, comprising coating the wire with a composition described in any one of embodiments 1 to 3.

Claims

1. A method for preparing a polyamide-imide resin, A mixture containing a tricarboxylic acid or its anhydride having two adjacent carboxyl groups, a diisocyanate, a low molecular weight monocarboxylic acid, and N-n-butylpyrrolidone is reacted at a temperature in the range of 80°C to 120°C until a polyamide-imide resin having Mw of 10,000 to 16,771 g / mol (Daltons) and an Mw / Mn ratio of 1.1 to 2 is obtained. method.

2. The method according to claim 1, wherein the low molecular weight monocarboxylic acid is selected from the group consisting of formic acid, acetic acid, and propionic acid.

3. The method according to claim 1 or 2, wherein the mixture also includes nanoparticles having an average diameter in the range of 1 nm to 300 nm.

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