Composition, polyamide imide, and polyamide imide film, preparation method therefor and use thereof

Abstract

A composition, a polyamide imide, and a polyamide imide film, a preparation method therefor and a use thereof. The composition comprises a dianhydride compound, a diamine compound, and a crosslinking agent. The crosslinking agent is selected from any one of compounds having a structure represented by the following general formula I. R1 is selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, and a substituted or unsubstituted alkoxy group; R2 is selected from a blocking group; n1 is greater than or equal to 2.

Description

Compositions, polyamide-imide, polyamide-imide films, their preparation methods and applications

[0001] This application claims priority to Chinese patent application No. 202411999051.X, filed on December 31, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of polymer technology, and in particular to a composition, a polyamide-imide, a polyamide-imide film, a method for preparing the same, and its applications. Background Technology

[0003] The increased voltage of automotive motors places higher demands on the performance of enameled wire enamel, requiring it to have a low dielectric constant and good mechanical properties to ensure that the motor does not experience electrical short circuits, current leakage, or breakdown when operating under high voltage conditions. Summary of the Invention

[0004] This disclosure provides a composition, a polyamide-imide, a polyamide-imide film, a method for preparing the same, and its applications.

[0005] In a first aspect, a composition is provided. The composition comprises: a dianhydride compound, a diamine compound, and a crosslinking agent.

[0006] The crosslinking agent is selected from any one of the structural formulas shown in General Formula I below.

[0007] R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; R2 is selected from blocking groups; n1≥2.

[0008] In some embodiments of this disclosure, the crosslinking agent, i.e., the blocking group R2 in general formula I, is deblocked at a higher temperature, resulting in the release of the blocking agent. Simultaneously, the isocyanate group in general formula I is exposed and crosslinks with the composition molecules to form polyamide-imide. The carbon dioxide molecules generated during the crosslinking reaction and the release of the blocking agent formed by the blocking group R2 leave a porous structure in the polyamide-imide. Since the dielectric constant of air is approximately 1, introducing pores into the polyamide-imide can reduce the dielectric constant of the polyamide-imide, ensuring that the polyamide-imide has a low dielectric constant. At the same time, the crosslinking reaction also forms a three-dimensional network structure between the polyamide-imides, and the main chain structure of the polyamide-imide is connected, improving the overall density of the polyamide-imide, thereby improving the mechanical properties of the polyamide-imide material.

[0009] In some embodiments, the blocking group R2 includes any of the following structural formulas.

[0010] * indicates that the key is... The C atoms are connected.

[0011] In some embodiments, the crosslinking agent is selected from at least one of the following structural formulas:

[0012] In some embodiments, the diamine compound includes at least one selected from: phenylenediamine, diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, bis(4-aminophenyl)sulfide, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)]phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-bis(4-aminophenoxy)biphenyl, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis(trifluoromethyl)benzidine.

[0013] In some embodiments, the dianhydride compound includes at least one selected from: pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-(4,4'-isopropylidenediphenoxy)bisphthalic anhydride, 4,4'-oxobisphthalic anhydride, and bis(1,3-dioxo-1,3-dihydroisobenzofuran)5-carboxylic acid)-1,4-phenylene ester.

[0014] In some embodiments, the ratio of the molar mass of the diamine compound to the molar mass of the dianhydride compound ranges from [0.9, 1.1].

[0015] In some embodiments, the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound ranges from [0.05, 0.5].

[0016] In some embodiments, the composition further includes a viscosity modifier.

[0017] In some embodiments, the tackifier includes at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol monomethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, triethylene glycol monovinyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl vinyl ether, diethylene glycol dipropyl ether, diethylene glycol divinyl ether, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, triethylene glycol monomethyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

[0018] In some embodiments, the tackifier includes at least one of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisononyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, diallyl phthalate, tri-n-butyl trimellitate, and trioctyl trimellitate.

[0019] In some embodiments, the ratio of the mass of the viscosity modifier to the total mass of the composition ranges from [0.1, 1.2].

[0020] In a second aspect, a polyamide-imide is provided. The polyamide-imide comprises any one of the following structural formulas:

[0021] R3 is selected from the remaining part of a dianhydride compound after the removal of the dianhydride group; R4 is the remaining part of a diamine compound after the removal of the diamine group; R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; n2≥2; n3≥2; n4≥2; n5≥2; n6≥1.

[0022] It is understood that the beneficial effects of the polyamide-imide provided in the above embodiments of this disclosure can be referred to the beneficial effects of the composition described above, and will not be repeated here.

[0023] In some embodiments, the structural formula of polyamide-imide includes:

[0024] m1≥1, m 2≥ 1, n8≥1, n9≥1, n 10 ≥1.

[0025] Thirdly, a polyamide-imide film is provided. The material of the polyamide-imide film is selected from any of the materials described in the above embodiments.

[0026] It is understood that the beneficial effects of the polyamide-imide film provided in the above embodiments of this disclosure can be referred to the beneficial effects of the composition described above, and will not be repeated here.

[0027] In some embodiments, the polyamide-imide film is subjected to at least one of the following conditions: the dielectric constant of the polyamide-imide film is in the range of [1.3, 3.4]. The elongation at break of the polyamide-imide film is in the range of [1%, 14%]. The elastic modulus of the polyamide-imide film is in the range of [1 MPa, 2000 MPa]. The tensile strength of the polyamide-imide film is in the range of [1 MPa, 500 MPa].

[0028] Fourthly, a method for preparing a polyamide-imide film is provided. The method for preparing the polyamide-imide film includes:

[0029] Under inert conditions, diamine compounds and dianhydride compounds react to yield a precursor solution;

[0030] A crosslinking agent is added to the precursor solution and stirred to obtain a polyamide-imide solution; the diamine compound, dianhydride compound and crosslinking agent are referred to as a composition, and the composition is any one of the compositions in the above examples;

[0031] A polyamide-imide solution is coated into a wet film, and the wet film is cured to obtain a polyamide-imide film.

[0032] It is understood that the beneficial effects of the polyamide-imide, polyamide-imide film, and polyamide-imide film preparation methods provided in the above embodiments of this disclosure can be referred to the beneficial effects of the compositions described above, and will not be repeated here.

[0033] In some embodiments, wet film curing includes: first holding the wet film at a temperature range of [80°C, 200°C] for [5 min, 20 min], and then holding it at a temperature range of [300°C, 380°C] for [5 min, 20 min].

[0034] In some embodiments, before coating the polyamide-imide solution into a wet film, the method further includes adding a viscosity modifier to the polyamide-imide solution.

[0035] In some embodiments, the viscosity range of the polyamide-imide solution is [10000 cPs, 20000 cPs].

[0036] Fifthly, this disclosure provides an application of any of the polyamide-imide films described in the above embodiments in enameled wire enamel.

[0037] It is understood that the beneficial effects that the polyamide-imide film provided in the above embodiments of this disclosure can achieve in the application of enameled wire varnish can be referred to the beneficial effects of the composition described above, and will not be repeated here. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of some embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 is a flowchart of a method for preparing a polyamide-imide film according to some embodiments;

[0040] Figure 2 is a scanning electron microscope image of a polyamide-imide film according to Example 4;

[0041] Figure 3 is a stress-strain diagram of polyamide-imide films according to some embodiments and comparative examples;

[0042] Figure 4 shows the mechanical properties of polyamide-imide films according to some embodiments and comparative examples;

[0043] Figure 5 is an infrared spectrum of a polyamide-imide film according to Example 4. Detailed Implementation

[0044] The technical solutions of some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0045] In the description of this disclosure, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or relative positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure. Unless otherwise specified, the above-mentioned orientational descriptions can be flexibly set in practical applications, provided that the relative positional relationships shown in the accompanying drawings are satisfied.

[0046] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0047] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "communication" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the meaning of the above terms in this disclosure based on the actual situation.

[0048] In some embodiments of this disclosure, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0049] In some embodiments of this disclosure, the words "exemplarily" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design described as "exemplarily" or "for example" in some embodiments of this disclosure should not be construed as being more preferred or advantageous than other embodiments or designs. Rather, the use of words such as "exemplarily" or "for example" is intended to present the relevant concepts by way of example.

[0050] In the description of this specification, features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0051] Currently, to further improve the power density, efficiency, speed range, and fast charging capabilities of automotive motors, motors are increasingly being developed towards higher voltage (≥1200V) platforms. The increased motor voltage places higher demands on the dielectric properties of the enameled wire enamel, requiring it to have a lower dielectric constant and better mechanical properties to ensure that the motor does not experience electrical short circuits, current leakage, or breakdown under high voltage conditions.

[0052] This disclosure provides some embodiments of the application of a polyamide-imide film in enameled wire coating.

[0053] Polyimide is the most widely used material for enameled wire coating. In order to reduce the dielectric constant of polyimide, air pores are introduced inside the polyimide material in some implementations. However, the introduction of pores inside the polyimide material will lead to a serious deterioration of the mechanical properties of the polyimide, mainly manifested in the simultaneous reduction of the tensile strength and elongation at break of the polyimide material. This will reduce the adhesion, wear resistance, impact resistance and flexibility of the enameled wire coating, and ultimately greatly reduce the life and reliability of the motor.

[0054] Therefore, while introducing air pore structures into the polyimide material to reduce the dielectric constant, it is necessary to simultaneously improve the mechanical properties of the polyimide enameled wire coating material.

[0055] In other implementations, fillers are introduced into polyimide to form polyimide composites. Fillers include graphene oxide, carbon nanotubes, glass fibers, etc. However, polyimide composites have the following significant drawbacks: (1) Untreated fillers have poor compatibility with polyimide, and surface treatment of fillers is often required before they can be used to introduce polyimide, which increases costs and complicates the process; (2) Introducing fillers increases the density of polyimide composites, which is not conducive to achieving lightweight design; (3) Some fillers have poor thermal stability at high temperatures, which will reduce the heat resistance of polyimide composites; (4) The introduction of fillers may increase the viscosity of polyimide melt, affecting its fluidity and molding performance; (5) The introduction of fillers will affect the dielectric properties of polyimide. For example, introducing graphene into polyimide to form polyimide composites can strengthen and toughen polyimide composites, but graphene has good conductivity, which is not conducive to reducing the dielectric constant of polyimide.

[0056] Based on this, some embodiments of the present disclosure provide a composition. The composition comprises: a dianhydride compound, a diamine compound, and a crosslinking agent.

[0057] The crosslinking agent is selected from any of the structural formulas shown in general formula (I) below.

[0058] Wherein, R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; R2 is selected from blocking groups; n1≥2.

[0059] This disclosure does not limit the order in which the dianhydride compound, diamine compound, and crosslinking agent are added. The dianhydride compound, diamine compound, and crosslinking agent can be added simultaneously to form a polyamic acid precursor resin and then crosslinked. Alternatively, the dianhydride compound and diamine compound can be added first to form a polyamic acid precursor resin, and then the crosslinking agent can be added for crosslinking.

[0060] In some embodiments, the dianhydride compound and the diamine compound can undergo a polymerization reaction to form a polyamic acid precursor resin; the crosslinking agent, i.e., the blocking group R2 in general formula (I), is unblocked at a higher temperature, forming a blocking agent that escapes. At the same time, the isocyanate group in general formula I is exposed and crosslinks with the molecular chain of the polyamic acid precursor resin to form a polyamide imide. The carbon dioxide molecules generated during the crosslinking reaction and the escape of the blocking agent formed by the blocking group R2 leave a porous structure in the polyamide imide. Since the dielectric constant of air is about 1, the introduction of pores into the polyamide imide can reduce the dielectric constant of the polyamide imide, ensuring that the polyamide imide has a low dielectric constant. At the same time, the crosslinking reaction also forms a three-dimensional network structure between the polyamide imides, and the main chain structure of the polyamide imide is connected, which improves the overall density of the polyamide imide, thereby improving the mechanical properties of the polyamide imide material.

[0061] In some embodiments, the following reaction formula is used to decompose the crosslinking agent (a) at 170°C into a product (e) and a blocking agent (f) formed by blocking groups.

[0062] In some embodiments, the following reaction is a crosslinking reaction between polyamic acid precursor resin (d) and isocyanate groups in a crosslinking agent at high temperature, which can release carbon dioxide molecules.

[0063] The process of carbon dioxide molecules being released can leave porous structures in polyamide-imide, which can give polyamide-imide a lower dielectric constant.

[0064] In some embodiments, the polyamic acid precursor resin includes the following structural formula (i);

[0065] In some embodiments, R2 includes any of the following structural formulas;

[0066] Where * indicates that the key is associated with... The C atoms are connected.

[0067] It is understandable that any of the above structural formulas, when connected to general formula (I), can form a blocking agent upon unblocking of the crosslinking agent, wherein... It can generate ε-caprolactam (f1), It can generate 3,5-dimethylpyrazole (f5). It can produce diethylene glycol monomethyl ether (f11), and Methyl ethyl ketone oxime (f3) can be generated. When these blocking agents escape from the polyamide-imide material, they leave a porous structure, resulting in a low dielectric constant for the polyamide-imide material.

[0068] Here, the structure of the crosslinking agent can be obtained through infrared spectroscopy analysis.

[0069] In some embodiments, the crosslinking agent is selected from at least one of the following structural formulas:

[0070] The aforementioned crosslinking agents all contain at least two isocyanate groups. The excellent activity of the isocyanate groups can crosslink with the molecular chains of the polyamic acid precursor resin, resulting in better mechanical properties of the formed polyamide imide. At the same time, the carbon dioxide molecules released from the crosslinking reaction, as well as the blocking agents formed by the end-capping groups in the aforementioned crosslinking agents during the decapping process, will leave a porous structure in the formed polyamide imide, resulting in a lower dielectric constant for the polyamide imide material.

[0071] It should be noted that when the crosslinking agent is capped and decapped, it can form a substance with the structural formula (e) containing isocyanate groups and a blocking agent with the structural formula (f) containing capping groups.

[0072] In some embodiments, the substance with structural formula (e) can be isophorone diisocyanate (e1), hexamethylene diisocyanate (e2), diphenylmethane diisocyanate (e3), isophorone diisocyanate (IPDI) trimer (e4), hexamethylene diisocyanate (HDI) biuret (e5), HDI trimer (e6), toluene-2,4-diisocyanate (e7), or toluene-2,6-diisocyanate (e8). The corresponding structures of the above substances are as follows:

[0073] In some embodiments, the substance with structural formula (f) can be ε-caprolactam (f1), ethanol (f2), methyl ethyl ketone oxime (f3), phenol (f4), 3,5-dimethylpyrazole (f5), acetone oxime (f6), ethyl acetoacetate (f7), diethyl malonate (f8), imidazoles (f9), sodium bisulfite (f10), or diethylene glycol monomethyl ether (f11). Here, the structural formulas corresponding to ε-caprolactam (f1), methyl ethyl ketone oxime (f3), 3,5-dimethylpyrazole (f5), and diethylene glycol monomethyl ether (f11) are as follows:

[0074] It should be noted that the substances containing isocyanate groups (e) and (f) containing end-capping groups can also be used to synthesize crosslinking agents under certain conditions through end-capping reactions.

[0075] In other words, any one of isophorone diisocyanate (e1), hexamethylene diisocyanate (e2), diphenylmethane diisocyanate (e3), IPDI trimer (e4), HDI biuret (e5), HDI trimer (e6), toluene-2,4-diisocyanate (e7), toluene-2,6-diisocyanate (e8), and any one of ε-caprolactam (f1), ethanol (f2), methyl ethyl ketone oxime (f3), phenol (f4), 3,5-dimethylpyrazole (f5), acetone oxime (f6), ethyl acetoacetate (f7), diethyl malonate (f8), imidazoles (f9), sodium bisulfite (f10), and diethylene glycol monomethyl ether (f11) can form a crosslinking agent through a capping reaction.

[0076] The reaction combinations of a substance with structural formula (e) and a blocking agent with structural formula (f) include, but are not limited to, the following: a crosslinking agent formed by the reaction of (e1) and (f1), a crosslinking agent formed by the reaction of (e1) and (f2), a crosslinking agent formed by the reaction of (e1) and (f3), a crosslinking agent formed by the reaction of (e1) and (f4), a crosslinking agent formed by the reaction of (e1) and (f5), a crosslinking agent formed by the reaction of (e1) and (f6), a crosslinking agent formed by the reaction of (e1) and (f7), a crosslinking agent formed by the reaction of (e1) and (f8), a crosslinking agent formed by the reaction of (e1) and (f9), a crosslinking agent formed by the reaction of (e1) and (f10), a crosslinking agent formed by the reaction of (e1) and (f11), and a crosslinking agent formed by the reaction of (e2) and (f1). The crosslinking agents formed by the reaction of (e2) and (f2), the crosslinking agents formed by the reaction of (e2) and (f3), the crosslinking agents formed by the reaction of (e2) and (f4), the crosslinking agents formed by the reaction of (e2) and (f5), the crosslinking agents formed by the reaction of (e2) and (f6), the crosslinking agents formed by the reaction of (e2) and (f7), the crosslinking agents formed by the reaction of (e2) and (f8), the crosslinking agents formed by the reaction of (e2) and (f9), the crosslinking agents formed by the reaction of (e2) and (f10), the crosslinking agents formed by the reaction of (e2) and (f11), the crosslinking agents formed by the reaction of (e3) and (f1), the crosslinking agents formed by the reaction of (e3) and (f2), the crosslinking agents formed by the reaction of (e3) and (f3), and (e3) and (f4). The crosslinking agents formed by the reactions of (e3) and (f5), (e3) and (f6), (e3) and (f7), (e3) and (f8), (e3) and (f9), (e3) and (f10), (e3) and (f11), (e4) and (f1), (e4) and (f2), (e4) and (f3), (e4) and (f4), (e4) and (f5), (e4) and (f6), (e4) Crosslinking agents formed by reactions with (f7), (e4) and (f8), (e4) and (f9), (e4) and (f10), (e4) and (f11), (e5) and (f1), (e5) and (f2), (e5) and (f3), (e5) and (f4), (e5) and (f5), (e5) and (f6), (e5) and (f7), (e5) and (f8), (e5) and (f9)Crosslinking agents formed by the reaction of (e5) and (f10), (e5) and (f11), (e6) and (f1), (e6) and (f2), (e6) and (f3), (e6) and (f4), (e6) and (f5), (e6) and (f6), (e6) and (f7) The crosslinking agents formed by the reaction of (e6) and (f8), the crosslinking agents formed by the reaction of (e6) and (f9), the crosslinking agents formed by the reaction of (e6) and (f10), the crosslinking agents formed by the reaction of (e6) and (f11), the crosslinking agents formed by the reaction of (e7) and (f1), the crosslinking agents formed by the reaction of (e7) and (f2), the crosslinking agents formed by the reaction of (e7) and (f3), the crosslinking agents formed by the reaction of (e7) and (f4), and (e7) and (f5). The crosslinking agents formed by the reaction, (e7) and (f6) crosslinking agents formed by the reaction of (e7) and (f7), (e7) and (f8) crosslinking agents formed by the reaction of (e7) and (f9), (e7) and (f10) crosslinking agents formed by the reaction of (e7) and (f11), (e8) and (f1) crosslinking agents formed by the reaction of (e8) and (f2), (e8) Crosslinking agents formed by the reaction of (f3), (e8) and (f4), (e8) and (f5), (e8) and (f6), (e8) and (f7), (e8) and (f8), (e8) and (f9), (e8) and (f10), and (e8) and (f11).

[0077] In some embodiments, the end-capping reaction can be carried out for 8 hours within a temperature range of [60°C, 80°C].

[0078] In some embodiments, the capping reaction of HDI trimer (e6) and ε-caprolactam (f1) is as follows:

[0079] In some embodiments, the diamine compound includes at least one selected from: phenylenediamine, diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, bis(4-aminophenyl)sulfide, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)]phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-bis(4-aminophenoxy)biphenyl, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis(trifluoromethyl)benzidine.

[0080] In some embodiments, the dianhydride compound includes at least one selected from: pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-(4,4'-isopropylidenediphenoxy)bisphthalic anhydride, 4,4'-oxobisphthalic anhydride, and bis(1,3-dioxo-1,3-dihydroisobenzofuran)5-carboxylic acid)-1,4-phenylene ester.

[0081] It is understandable that the above-mentioned diamine compound and the above-mentioned dianhydride compound can react in a solvent to generate polyamic acid precursor resin.

[0082] It should be noted that the solvent is not particularly limited and can be an organic solvent, such as at least one selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), γ-butyrolactone (GBL), and xylene, which can produce polyamic acid precursor resins with good polymerization effect.

[0083] In some embodiments, the ratio of the molar mass of the diamine compound to the molar mass of the dianhydride compound ranges from [0.9, 1.1].

[0084] For example, the ratio of the molar mass of the diamine compound to the molar mass of the dianhydride compound can be 0.9, 0.95, 1.0, 1.05, or 1.1, etc., and this disclosure does not limit it.

[0085] It is understandable that the ratio of the molar mass of the diamine compound to the molar mass of the dianhydride compound is in the range of [0.9, 1.1]. This allows the diffusion rate and collision frequency of the diamine compound and the dianhydride compound in the reaction system to be similar, which helps to improve the efficiency and yield of the reaction. It also makes the molecular weight distribution of the polyamic acid precursor resin more uniform, which is helpful for the subsequent film formation process of polyamide imide.

[0086] In some embodiments, the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound ranges from [0.05, 0.5].

[0087] For example, the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound can be 0.05, 0.15, 0.30, 0.45 or 0.5, etc., and this disclosure does not limit it.

[0088] It is understandable that the addition of crosslinking agents helps polyamide-imide form a stable network structure. Setting the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound within the range of [0.05, 0.5] allows for more precise control of the crosslinking density of polyamide-imide. This avoids excessively high crosslinking densities that cause polyamide-imide to become brittle, as well as excessively low crosslinking densities that reduce the strength and stability of polyamide-imide, thereby improving the mechanical properties of polyamide-imide.

[0089] In some embodiments, the composition further includes a viscosity modifier.

[0090] It is understandable that adding a viscosity modifier to the composition can keep the viscosity of the composition within a suitable range, which can improve the film-forming properties of polyamide-imide and promote the uniformity of the polyamide-imide film. At the same time, keeping the viscosity of the composition within a suitable range is also conducive to the release of small molecules in the crosslinking reaction, promoting the formation of the pore structure of polyamide-imide and resulting in a lower dielectric constant of polyamide-imide.

[0091] In some embodiments, the tackifier includes at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol monomethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, triethylene glycol monovinyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl vinyl ether, diethylene glycol dipropyl ether, diethylene glycol divinyl ether, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, triethylene glycol monomethyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

[0092] In other embodiments, the viscosity modifier includes at least one of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisononyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, diallyl phthalate, tri-n-butyl trimellitate, and trioctyl trimellitate.

[0093] In some embodiments, the ratio of the mass of the viscosity modifier to the total mass of the composition ranges from [0.1, 1.2].

[0094] For example, the ratio of the mass of the viscosity modifier to the total mass of the composition can be 0.1, 0.5, 0.7, 1 or 1.2, etc., and this disclosure does not limit it.

[0095] It is understood that setting the ratio of the viscosity modifier's mass to the total mass of the composition within the range of [0.1, 1.2] can further ensure that the viscosity of the composition is within a suitable range, improve the film-forming properties of polyamide-imide, promote the formation of the polyamide-imide porous structure, and reduce the dielectric constant of the polyamide-imide material. The following is a description of the formation of polyamide-imide by the composition in any of the above embodiments.

[0096] This disclosure provides a polyamide-imide in some embodiments. The polyamide-imide comprises any of the following structural formulas.

[0097] Wherein, R3 is selected from the remaining part of a dianhydride compound after the removal of the dianhydride group, R4 is the remaining part of a diamine compound after the removal of the diamine group, and R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and substituted or unsubstituted alkoxy; here, n2≥2; n3≥2; n4≥2; n5≥2; n6≥1.

[0098] Taking the dianhydride compound selected from pyromellitic dianhydride as an example, R3 is selected from the remaining part of pyromellitic dianhydride after removing the dianhydride group. Here, the dianhydride group is the part circled in the following formula.

[0099] Taking the diamine compound selected from diaminodiphenyl ether as an example, R4 is selected from the remaining part of diaminodiphenyl ether after removing the diamine group. Here, the diamine group is the part circled in the following formula.

[0100] Here, the structure of polyamide-imide can be obtained through infrared spectroscopy analysis.

[0101] In some embodiments, the structural formula of polyamide-imide includes:

[0102] Where m1≥1, m2≥ 1, n8≥1, n9≥1, n 10 ≥1.

[0103] The following is a description of the formation of polyamide-imide films by polyamide-imide in any of the above embodiments.

[0104] This disclosure provides a polyamide-imide film in some embodiments. The material of the polyamide-imide film includes any of the example materials described above.

[0105] In some embodiments, the thickness of the polyamide-imide film ranges from [10 μm to 50 μm].

[0106] For example, the thickness of the polyamide-imide film can be 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm, etc., and this disclosure does not limit it.

[0107] It is understandable that the thickness of polyamide-imide film is in the range of [10μm~50μm], and polyamide-imide film can be used as a coating material for enameled wire.

[0108] In some embodiments, the dielectric constant of the polyamide-imide film is in the range of [1.3, 3.4].

[0109] In some embodiments, the dielectric constant of the polyamide-imide film is in the range of [1.6, 2].

[0110] For example, the dielectric constant of the polyamide-imide film can be 1.6, 1.7, 1.8, 1.9 or 2, etc., and this disclosure does not limit it.

[0111] It is understandable that the dielectric constant of the polyamide-imide film is in the range of [1.3, 3.4], indicating that the polyamide-imide film has a small dielectric constant and good dielectric properties.

[0112] In some embodiments, the elongation at break of the polyamide-imide film ranges from 1% to 50%.

[0113] In some embodiments, the elongation at break of the polyamide-imide film ranges from [9%, 14%].

[0114] For example, the elongation at break of the polyamide-imide film can be 9%, 10%, 11%, 12%, 13%, or 14%, etc., and this disclosure does not limit it.

[0115] Understandably, the elongation at break of the polyamide-imide film is within the range of [1%, 14%], indicating that the polyamide-imide film is relatively difficult to break and has good mechanical properties.

[0116] In some embodiments, the elastic modulus of the polyamide-imide film ranges from 1 MPa to 2000 MPa.

[0117] In some embodiments, the elastic modulus of the polyamide-imide film is in the range of [1400 MPa, 1450 MPa].

[0118] For example, the elastic modulus of the polyamide-imide film can be 1400MPa, 1410MPa, 1420MPa, 1430MPa, 1440MPa or 1450MPa, etc., and this disclosure does not limit it.

[0119] It is understandable that the elastic modulus of polyamide-imide film is in the range of [1MPa~2000MPa], indicating that polyamide-imide film can maintain high shape stability when subjected to external force, is not easy to deform, and has good mechanical properties.

[0120] In some embodiments, the tensile strength of the polyamide-imide film ranges from 1 MPa to 500 MPa.

[0121] In some embodiments, the tensile strength of the polyamide-imide film ranges from 80 MPa to 110 MPa.

[0122] For example, the tensile strength of the polyamide-imide film can be 80MPa, 85MPa, 90MPa, 95MPa, 100MPa, 105MPa or 110MPa, etc., and this disclosure does not limit it.

[0123] It is understandable that the tensile strength of polyamide-imide film is within the range of [1MPa, 500MPa], indicating that polyamide-imide film can withstand a large maximum tensile force under tensile force and has good mechanical properties.

[0124] The following is a description of the preparation method of the polyamide-imide film in any of the above embodiments.

[0125] This disclosure provides a method for preparing a polyamide-imide film through several embodiments. As shown in Figure 1, the method for preparing the polyamide-imide film includes steps S1 to S3.

[0126] S1: Under inert conditions, a diamine compound and a dianhydride compound react to yield a precursor solution.

[0127] For example, the inert gas can be nitrogen (N2) or argon (Ar).

[0128] The reaction of the diamine compound and the dianhydride compound is carried out in a solvent, and the solid content in the reaction system is controlled within the range of [15%, 40%], preferably 30%.

[0129] S2: Add a crosslinking agent to the precursor solution and stir to obtain a polyamide-imide solution.

[0130] Here, the diamine compound, dianhydride compound, and crosslinking agent are referred to as a composition, which is any one of the compositions described in the above examples.

[0131] S3: Coat the polyamide-imide solution into a wet film, and obtain a polyamide-imide film after the wet film is cured.

[0132] In some embodiments, the wet film thickness can be in the range of [50 μm, 200 μm].

[0133] In some embodiments, the coating speed can be 300 mm / min.

[0134] In some embodiments, wet film curing includes: first holding the wet film at a temperature range of [80°C, 200°C] for [5 min, 20 min], and then holding it at a temperature range of [300°C, 380°C] for [5 min, 20 min].

[0135] In some embodiments, the wet film is first kept at 150°C for 10 min, and then kept at 350°C for 10 min.

[0136] In some embodiments, the wet film is first kept at 160°C for 10 min, and then at 350°C for 10 min.

[0137] In some embodiments, the wet film is first kept at 150°C for 10 min, and then kept at 380°C for 10 min.

[0138] In some embodiments, the wet film is first kept at 120°C for 10 min, then at 150°C for 10 min, and then at 380°C for 10 min.

[0139] In some embodiments, before coating the polyamide-imide solution into a wet film, the method further includes: S4.

[0140] S4: Add viscosity modifier to polyamide-imide solution.

[0141] Understandably, adding a viscosity modifier can adjust the viscosity of the polyamide-imide solution, making it easier to coat into a wet film and resulting in a more uniform polyamide-imide film.

[0142] In some embodiments, the viscosity range of the polyamide-imide solution is [10000 cPs, 20000 cPs].

[0143] For example, the viscosity of the polyamide-imide solution can be 10,000 cPs, 12,000 cPs, 14,000 cPs, 16,000 cPs, 18,000 cPs or 20,000 cPs, etc., and this disclosure does not limit it.

[0144] It is understandable that setting the viscosity of the polyamide-imide solution within the range of [10000 cPs, 20000 cPs] can improve the film-forming properties of polyamide-imide and facilitate the formation of the pore structure of polyamide-imide, resulting in a lower dielectric constant of the polyamide-imide material.

[0145] The preparation method of the polyamide-imide film in some embodiments of this disclosure is simple. It only requires adding a crosslinking agent before coating into a wet film, which can achieve pore formation and crosslinking effects at the same time as curing, so that the polyamide-imide film has both a low dielectric constant and improved mechanical properties.

[0146] The following describes some embodiments of this disclosure in further detail through experiments as examples and in conjunction with the accompanying drawings.

[0147] Example 1

[0148] Example 1 provides a polyamide-imide film, which is obtained through the following preparation steps:

[0149] A1: N2 was continuously introduced into the reaction flask, and 28.7081g of 4,4'-diaminodiphenyl ether and 140g of N-methylpyrrolidone were added. After stirring to fully dissolve the 4,4'-diaminodiphenyl ether, 31.2919g of pyromellitic dianhydride was added. The reaction was then stirred continuously for 8 hours within the temperature range of [20℃, 25℃] to obtain 200g of uniform polyamic acid precursor resin.

[0150] A2: 22.0178 g of crosslinking agent (a1) was added to the polyamic acid precursor resin obtained in A1 and stirred continuously for 3 h. Here, the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound is in the range of 0.2. The structural formula of the crosslinking agent (a1) is as follows:

[0151] A3: Add 60g of dibutyl phthalate to the solution obtained in A2, and stir continuously for 3 hours to obtain a polyamide-imide solution.

[0152] A4: After the polyamide-imide solution obtained in A3 was sealed and allowed to stand for [8h, 12h] to remove bubbles, a wet film was then coated using a slotted blade coating method, controlling the wet film thickness to 100μm and the coating speed to 300mm / min. The wet film was then cured at 150℃ for 10min and at 350℃ for 10min to obtain a polyamide-imide film with a thickness range of [12μm, 18μm], the structural formula of which is as follows:

[0153] Example 2

[0154] Example 2 provides a polyamide-imide film, which is obtained through the following preparation steps:

[0155] B1: N2 was continuously introduced into the reaction flask, and 25.7584 g of 2,2-bis(4-aminophenyl)hexafluoropropane and 140 g of N-methylpyrrolidone were added. After stirring to fully dissolve the 2,2-bis(4-aminophenyl)hexafluoropropane, 34.2416 g of hexafluorodianhydride (6FDA) was added. The reaction was then stirred continuously for 8 h within the temperature range of [20℃, 25℃] to obtain 200 g of uniform polyamic acid precursor resin.

[0156] B2: 11.8298 g of crosslinking agent (a1) was added to the polyamic acid precursor resin obtained in B1 and stirred continuously for 3 h. Here, the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound is in the range of 0.2. The structural formula of the crosslinking agent (a1) is as follows:

[0157] B3: Add 60g of dibutyl phthalate to the solution obtained in B2, and stir continuously for 3 hours to obtain a polyamide-imide solution.

[0158] B4: After the polyamide-imide solution obtained in B3 is sealed and allowed to stand for [8h, 12h] to remove bubbles, a wet film is then coated using a slotted blade coating method, with the wet film thickness controlled at 100μm and the coating speed at 300mm / min. The wet film is then cured at 150℃ for 10min and at 350℃ for 10min to obtain a polyamide-imide film with a thickness range of [12μm, 18μm].

[0159] Example 3

[0160] Example 3 provides a polyamide-imide film, which is obtained through the following preparation steps:

[0161] C1: N2 was continuously introduced into the reaction flask, and 28.7081 g of 4,4'-diaminodiphenyl ether and 140 g of N-methylpyrrolidone were added. After stirring to fully dissolve the 4,4'-diaminodiphenyl ether, 31.2919 g of pyromellitic dianhydride was added. The reaction was then stirred continuously for 8 h within the temperature range of [20℃, 25℃] to obtain 200 g of uniform polyamic acid precursor resin.

[0162] C2: 27.4163 g of crosslinking agent (a2) was added to the polyamic acid precursor resin obtained in C1 and stirred continuously for 3 h. Here, the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound is in the range of 0.2. The structural formula of the crosslinking agent (a2) is as follows:

[0163] C3: Add 60g of dibutyl phthalate to the solution obtained in C2, and stir continuously for 3 hours to obtain a polyamide-imide solution.

[0164] C4: After the polyamide-imide solution obtained in C3 is sealed and allowed to stand for [8h, 12h] to remove bubbles, a wet film is then coated using a slotted blade coating method, with the wet film thickness controlled at 100μm and the coating speed at 300mm / min. The wet film is then cured at 150℃ for 10min and at 350℃ for 10min to obtain a polyamide-imide film with a thickness range of [12μm, 18μm].

[0165] Example 4

[0166] Example 4 provides a polyamide-imide film, which is obtained through the following preparation steps:

[0167] D1: N2 was continuously introduced into the reaction flask, and 25.7584 g of 2,2-bis(4-aminophenyl)hexafluoropropane and 140 g of N-methylpyrrolidone were added. After stirring to fully dissolve the 2,2-bis(4-aminophenyl)hexafluoropropane, 34.2416 g of hexafluorodianhydride (6FDA) was added. The reaction was then stirred continuously for 8 h within the temperature range of [20℃, 25℃] to obtain 200 g of uniform polyamic acid precursor resin.

[0168] D2: 19.5270 g of crosslinking agent (a3) ​​was added to the polyamic acid precursor resin obtained in D1 and stirred continuously for 3 h. Here, the molar mass ratio of the crosslinking agent to the molar mass of the dianhydride compound is in the range of 0.3. The structural formula of the crosslinking agent (a3) ​​is as follows:

[0169] D3: Add 60g of dibutyl phthalate to the solution obtained in D2, and stir continuously for 3 hours to obtain a polyamide-imide solution.

[0170] D4: After the polyamide-imide solution obtained in D3 was sealed and allowed to stand for 8 hours or 12 hours to remove bubbles, a wet film was coated using a slotted blade coating method, controlling the wet film thickness to 100 μm and the coating speed to 300 mm / min. The wet film was then cured at 150°C for 10 minutes and at 350°C for 10 minutes to obtain a polyamide-imide film with a thickness range of [12 μm, 18 μm]. Figure 2 is a scanning electron microscope image of the polyamide-imide film of Example 4. As can be seen from Figure 2, the polyamide-imide film has a porous structure; its structure is shown below:

[0171] Comparative Example 1

[0172] Comparative Example 1 provides a polyamide-imide film, which is obtained through the following preparation steps:

[0173] P1: N2 was continuously introduced into the reaction flask, and 28.7081g of 4,4'-diaminodiphenyl ether and 140g of N-methylpyrrolidone were added. After stirring to fully dissolve the 4,4'-diaminodiphenyl ether, 31.2919g of pyromellitic dianhydride was added. The reaction was then stirred continuously for 8 hours within the temperature range of [20℃, 25℃] to obtain 200g of uniform polyamic acid precursor resin.

[0174] P2: Add 60g of dibutyl phthalate to the polyamic acid precursor resin obtained in P1, and stir continuously for 3h to obtain a polyamide imide solution.

[0175] P3: After the polyamide-imide solution obtained in P2 is sealed and allowed to stand for 8h, 12h to remove bubbles, a wet film is then coated using a slotted blade coating method, with the wet film thickness controlled at 100μm and the coating speed at 300mm / min. The wet film is then cured at 150℃ for 10min and at 350℃ for 10min to obtain a polyamide-imide film with a thickness range of [12μm, 18μm].

[0176] Comparative Example 2

[0177] Comparative Example 2 provides a polyamide-imide film, which is obtained through the following preparation steps:

[0178] R1: N2 was continuously introduced into the reaction flask, and 25.7584 g of 2,2-bis(4-aminophenyl)hexafluoropropane and 140 g of N-methylpyrrolidone were added. After stirring to fully dissolve 4,4'-diaminodiphenyl ether, 34.2416 g of hexafluorodianhydride was added. The reaction was then stirred continuously for 8 h within the temperature range of [20℃, 25℃] to obtain 200 g of uniform polyamic acid precursor resin.

[0179] R2: Add 60g of dibutyl phthalate to the solution obtained in R1, and stir continuously for 3h to obtain a polyamide-imide solution;

[0180] R3: After the polyamide-imide solution obtained in R2 is sealed and allowed to stand for [8h, 12h] to remove bubbles, a wet film is then coated using a slotted blade coating method, with the wet film thickness controlled at 100μm and the coating speed at 300mm / min. The wet film is then cured at 150℃ for 10min and at 350℃ for 10min to obtain a polyamide-imide film with a thickness range of [12μm, 18μm].

[0181] Performance testing

[0182] 1. The polyamide-imide films of the above examples and comparative examples were subjected to infrared peak analysis, and the results are shown in Table 1.

[0183] Table 1. Infrared peak analysis of each polymer film in the examples and comparative examples.

[0184] As shown in Table 1 and Figure 5, the polyamide-imide film of Example 4 is in the wavenumber range

[1750] . -1 1800cm -1 At position

[1700] , there is an asymmetric stretching vibration of the imide ring C=O, which proves the presence of imide functional groups in the polymer; in the wavenumber range

[1700] ... -1 1730cm -1 At position ], there are benzene ring vibrations and imide ring C=O symmetric stretching vibrations, proving that the polymer contains both benzene and imide rings; in the wavenumber range

[1490] -1 1550cm -1 At position

[1400] , CN bending vibrations were observed at the junction of the crosslinking agent and the polyamic acid precursor resin, indicating that the crosslinking agent had been successfully incorporated into the polyamic acid precursor resin, forming a crosslinked structure; in the wavenumber range

[1400] ... -1 1460cm -1 At position

[1370] , the CN-C stretching vibration of the trimethyl isocyanurate ring, a crosslinking agent, is observed, further confirming the introduction of the crosslinking agent into the polymer; in the wavenumber range

[1370] ... -1 1390cm -1 At position ], there is an imide ring CN stretching vibration, and in the wavenumber range

[720] -1 750cm -1 At the location [a], the C=O bending vibration of the imide ring proves the existence of the imide ring structure. The above description shows that the polyamide-imide film of Example 4 has a typical imide ring and benzene ring structure, and the crosslinking agent (a3) ​​has been successfully introduced. The infrared peak analysis of the polymer films of other examples and comparative examples in Table 1 is similar to the infrared peak analysis of the polymer film of Example 4 above. Therefore, it can be determined that the structure of the polymer films in each example and comparative example is consistent with the drawn structure.

[0185] 2. The viscosity of the polyamide-imide solutions obtained in the above examples and comparative examples was tested according to GB / T 40280-2021; and the dielectric constant of the polyamide-imide films obtained in the above examples and comparative examples was tested according to ASTM D150-18. The results are shown in Table 2 below.

[0186] Table 2 shows the viscosity of the polyamide-imide solutions and the dielectric constant of the polyamide-imide films of the examples and comparative examples.

[0187] As shown in Table 2, the viscosity of Examples 1 to 4 is not much different from that of Comparative Examples 1 and 2, indicating that the addition of crosslinking agent has little effect on the viscosity of polyamide-imide solution. In other words, the crosslinking agent has little effect on the film-forming properties of polyamide-imide, which is beneficial to the formation of polyamide-imide film.

[0188] The polyamide-imide films of Examples 1, 3, and Comparative Example 1 all used the same diamine and dianhydride compounds in the preparation of the polyamide-imide solution. The only difference was that no crosslinking agent was added in the preparation of the polyamide-imide solution in Comparative Example 1. Therefore, the dielectric constant of the polyamide-imide films of Examples 1 and 3 was significantly reduced compared with that of the polyamide-imide film of Comparative Example 1. This indicates that in some embodiments of this disclosure, the addition of a crosslinking agent can reduce the dielectric constant of the polyamide-imide film compared with the absence of a crosslinking agent.

[0189] The polyamide-imide films of Examples 2, 4, and Comparative Example 2 used the same diamine and dianhydride compounds in preparing the polyamide-imide solution. The only difference was that Comparative Example 2 did not add a crosslinking agent in preparing the polyamide-imide solution. Therefore, the dielectric constant of the polyamide-imide films of Examples 2 and 4 was significantly lower than that of the polyamide-imide film of Comparative Example 2. This indicates that in some embodiments of this disclosure, adding a crosslinking agent can reduce the dielectric constant of the polyamide-imide film compared to not adding a crosslinking agent. Furthermore, the dielectric constant of the polyamide-imide film of Example 4 was even lower than that of the polyamide-imide film of Example 2. This is attributed to the addition of more crosslinking agent in Example 4, which resulted in the formation of more porous structures in the polyamide-imide film, further reducing the dielectric constant.

[0190] 3. The polyamide-imide films of the above examples and comparative examples were subjected to tensile tests according to GB / T 13022-2006, and the results are shown in Figure 3 and Figure 4.

[0191] In Figure 3, the downward bend in the curve indicates that the polyamide-imide film fractured under this stress. The polyamide-imide film of Comparative Example 1 fractured at a strain of 5.8% under a stress of 62 MPa; the polyamide-imide film of Comparative Example 2 fractured at a strain of 7.8% under a stress of 80 MPa; the polyamide-imide film of Example 1 fractured at a strain of 13.2% under a stress of 112 MPa; the polyamide-imide film of Example 2 fractured at a strain of 13.5% under a stress of 85 MPa; the polyamide-imide film of Example 3 fractured at a strain of 12.5% ​​under a stress of 114 MPa; and the polyamide-imide film of Example 4 fractured at a strain of 9.5% under a stress of 108 MPa. It can be seen that the mechanical properties of the polyamide-imide films of Examples 1 to 4 are significantly better than those of Comparative Example 1 and Comparative Example 2.

[0192] In Figure 4, the elongation at break of the polyamide-imide films of Examples 1 to 4 ranges from [9.6%, 13.3%], the elastic modulus ranges from [1407 MPa, 1450 MPa], and the tensile strength ranges from [84.4 MPa, 107.6 MPa]. The elongation at break of the polyamide-imide films of Comparative Examples 1 and 2 are 5.8% and 7.9%, respectively, the elastic modulus is 1225 MPa and 939 MPa, respectively, and the tensile strength is 81.7 MPa and 72.5 MPa, respectively. These values ​​are significantly lower than those of the polyamide-imide films of Examples 1 to 4. Therefore, the polyamide-imide films of Examples 1 to 4 have better mechanical properties.

[0193] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A composition comprising: Dihydride compounds, diamine compounds, and crosslinking agents; The crosslinking agent is selected from any one of the structural formulas shown in general formula (Ⅰ); Wherein, R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; R2 is selected from blocking groups; n1≥2.

2. The composition according to claim 1, wherein, The blocking group includes any one of the following structural formulas; Where * indicates that the bond is related to the bond in structural formula I. The C atoms are connected.

3. The composition according to claim 1 or 2, wherein, The crosslinking agent is selected from at least one of the following structural formulas:

4. The composition according to any one of claims 1 to 3, wherein, The diamine compound includes at least one of the following: phenylenediamine, diaminodiphenyl ether, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, bis(4-aminophenyl)sulfide, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)]phenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-bis(4-aminophenoxy)biphenyl, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis(trifluoromethyl)benzidine.

5. The composition according to any one of claims 1 to 4, wherein, The dianhydride compounds include at least one selected from: pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-(4,4'-isopropylidene diphenoxy)bisphthalic anhydride, 4,4'-oxobisphthalic anhydride, and bis(1,3-dioxo-1,3-dihydroisobenzofuran)5-carboxylic acid)-1,4-phenylene ester.

6. The composition according to any one of claims 1 to 5, wherein, The ratio of the molar mass of the diamine compound to the molar mass of the dianhydride compound ranges from [0.9 to 1.1].

7. The composition according to any one of claims 1 to 6, wherein, The ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound is in the range of [0.05, 0.5].

8. The composition according to any one of claims 1 to 7, further comprising: Thickening agent.

9. The composition according to claim 8, wherein, The viscosity modifier comprises at least one of the following: diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol monomethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, triethylene glycol monovinyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl vinyl ether, tetraethylene glycol dipropyl ether, diethylene glycol divinyl ether, diethylene glycol dibutyl ether, diethylene glycol monophenyl ether, triethylene glycol monomethyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, and propylene glycol monomethyl ether; or, The viscosity modifier includes at least one of the following: dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisononyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, diallyl phthalate, tri-n-butyl trimellitate, and trioctyl trimellitate.

10. The composition according to claim 8 or 9, wherein, The ratio of the mass of the viscosity modifier to the total mass of the composition is in the range of [0.1, 1.2].

11. A polyamide-imide comprising any one of the following structural formulas: in, R3 is selected from the remaining part of a dianhydride compound after the removal of the dianhydride group, R4 is the remaining part of a diamine compound after the removal of the diamine group, and R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and substituted or unsubstituted alkoxy; wherein, n2≥2; n3≥2; n4≥2; n5≥2; and n6≥1.

12. The polyamide-imide according to claim 11, wherein, The structural formula of the polyamide-imide includes: Where m1≥1, m 2≥ 1, n8≥1, n9≥1, n 10 ≥1.

13. A polyamide-imide film, wherein, The material of the polyamide-imide film is selected from any one of claims 11 or 12.

14. The polyamide-imide film according to claim 13, wherein, The polyamide-imide film meets at least one of the following conditions: The dielectric constant of the polyamide-imide film is in the range of [1.3, 3.4]; The elongation at break of the polyamide-imide film is in the range of [1%, 50%]; The elastic modulus of the polyamide-imide film is in the range of [1 MPa, 2000 MPa]; The tensile strength of the polyamide-imide film ranges from 1 MPa to 500 MPa.

15. A method for preparing a polyamide-imide film, comprising: Under inert conditions, diamine compounds and dianhydride compounds react to yield a precursor solution; A crosslinking agent is added to the precursor solution and stirred to obtain a polyamide-imide solution; wherein the diamine compound, the dianhydride compound, and the crosslinking agent are referred to as a composition, and the composition is the composition according to any one of claims 1 to 10; The polyamide-imide solution is coated into a wet film, and the wet film is cured to obtain the polyamide-imide film.

16. The method for preparing the polyamide-imide film according to claim 15, wherein, The curing of the wet film includes: first holding the wet film at a temperature range of [80℃, 200℃] for [5 min, 20 min], and then holding it at a temperature range of [300℃, 380℃] for [5 min, 20 min].

17. The method for preparing the polyamide-imide film according to claim 15 or 16, wherein, Before coating the polyamide-imide solution into a wet film, the method further includes adding a viscosity modifier to the polyamide-imide solution.

18. The method for preparing the polyamide-imide film according to claim 15, wherein, The viscosity range of the polyamide-imide solution is [10000 cPs, 20000 cPs].

19. The use of the polyamide-imide film according to claim 13 or 14 in enameled wire enamel.

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