Composition, polyamideimide, polyamideimide film and preparation method and application of polyamideimide film

Abstract

The invention discloses a composition, polyamideimide, a polyamideimide film and a preparation method and application thereof, relates to the technical field of high-molecular polymers, and aims to solve the problem that wire enamel is poor in mechanical property at a relatively low dielectric constant. The composition comprises a dianhydride compound, a diamine compound and a cross-linking agent. The cross-linking agent is selected from any one of the structural formulas shown in the general formula I. In the formula, R1 is selected from the group consisting of 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 > = 2.

Description

Technical Field

[0001] The present application relates to the technical field of high molecular polymers, and in particular to a composition, polyamide-imide, polyamide-imide film, and a preparation method and application thereof. Background Art

[0002] The increase in automotive motor voltage places higher demands on the performance of wire enamels, that is, wire enamels must have a lower dielectric constant and better mechanical properties to ensure that electrical short circuits, current leakage, breakdown and other faults do not occur when the motor operates under high voltage conditions.

[0003] Regarding the reduction of the dielectric constant, for example, air holes can be introduced inside the polyimide material to improve the dielectric properties of the polyimide material. However, after the holes are introduced inside the polyimide material, the mechanical properties of the polyimide are seriously deteriorated, and the tensile strength and elongation at break of the polyimide material are reduced, resulting in decreased adhesion, wear resistance, impact resistance and flexibility of the enameled wire paint film, which ultimately reduces the life and reliability of the motor.

[0004] For mechanical properties, fillers can be compounded in polyimide materials, including graphene oxide, carbon nanotubes, glass fibers, etc. However, the introduction of fillers will affect the dielectric properties of polyimide materials. For example, the introduction of graphene can make polyimide materials stronger and tougher, and have better mechanical properties, but the good conductivity of graphene and the like is not conducive to reducing the dielectric constant of polyimide materials. Summary of the invention

[0005] The purpose of the present application is to provide a composition, a polyamide-imide, a polyamide-imide film, and a preparation method and application thereof, in order to solve the problem of poor mechanical properties of wire enamel at a lower dielectric constant.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a composition comprising: a dianhydride compound, a diamine compound and a crosslinking agent.

[0008] The crosslinking agent is selected from any one of the structural formulas shown in the following general formula I.

[0009]

[0010] 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 a blocking group; and n1≥2.

[0011] The cross-linking agent in the composition provided in the embodiment of the present application, i.e., the blocking group R2 in the general formula I, is unblocked at a relatively high temperature, and the blocking agent escapes. At the same time, the isocyanate group in the general formula I is exposed and cross-linked with the composition molecules to form polyamide-imide. The carbon dioxide molecules generated during the cross-linking reaction and the blocking agent formed by the blocking group R2 escape, leaving a pore structure in the formed 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, thereby ensuring that the polyamide-imide has a lower dielectric constant. At the same time, the cross-linking reaction also forms a three-dimensional network structure between the polyamide-imides, and the main chain structure of the polyamide-imide is connected, thereby improving the overall density of the polyamide-imide, thereby improving the mechanical properties of the polyamide-imide material.

[0012] In some embodiments, R2 comprises any of the following structural formulas.

[0013]

[0014] Among them, * indicates that the key is The C atoms in are connected.

[0015] In some embodiments, the crosslinking agent is selected from at least one of the following structural formulas:

[0016]

[0017]

[0018] In some embodiments, the diamine compound includes at least one of 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.

[0019] In some embodiments, the dianhydride compound includes: at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic 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)diphthalic anhydride, 4,4'-oxydiphthalic anhydride and bis(1,3-dioxo-1,3-dihydroisobenzofuran)5-carboxylic acid)-1,4-phenylene ester.

[0020] 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 to 1.1.

[0021] In some embodiments, the ratio of the molar mass of the cross-linking agent to the molar mass of the dianhydride compound is in the range of 0.05 to 0.5.

[0022] In some embodiments, the composition further comprises: a viscosity adjusting agent.

[0023] In some embodiments, the viscosity adjusting agent includes: at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether and tetraethylene glycol monomethyl ether, diethylene glycol dimethyl 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 dimethyl ether, triethylene glycol monovinyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl propyl ether, tetraethylene glycol methyl vinyl ether, diethylene glycol dipropyl ether, diethylene glycol divinyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, triethylene glycol monomethyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0024] In some embodiments, the viscosity adjusting agent 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.

[0025] In some embodiments, the ratio of the mass of the viscosity adjusting agent to the total mass of the composition is in the range of 0.1 to 1.2.

[0026] In a second aspect, the present application provides a polyamide-imide. The polyamide-imide includes any one of the following structural formulas.

[0027]

[0028]

[0029] Among them, R3 is selected from the remaining part of the dianhydride compound after removing the dianhydride group, R4 is the remaining part of the diamine compound after removing the diamine group, and R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; among them, n2≥2; n3≥2; n4≥2; n5≥2; n6≥1.

[0030] It can be understood that the beneficial effects that can be achieved by the polyamide-imide provided in the above embodiments of the present application can refer to the beneficial effects of the composition described above, and will not be repeated here.

[0031] In some embodiments, the structural formula of the polyamideimide comprises:

[0032]

[0033] ; Among them, m1≥1, m 2≥ 1, n8≥1, n9≥1, n 10 ≥1.

[0034] In a third aspect, the present application provides a polyamide-imide film, wherein the material of the polyamide-imide film is selected from any one of the above embodiments.

[0035] It can be understood that the beneficial effects that can be achieved by the polyamide-imide film provided in the above embodiments of the present application can refer to the beneficial effects of the composition described above, which will not be repeated here.

[0036] In some embodiments, the polyamideimide film has at least one of the following conditions: the dielectric constant of the polyamideimide film is in the range of 1.3 to 3.4. The elongation at break of the polyamideimide film is in the range of 1% to 50%. The elastic modulus of the polyamideimide film is in the range of 1 MPa to 2000 MPa. The tensile strength of the polyamideimide film is in the range of 1 MPa to 500 MPa.

[0037] In a fourth aspect, the present application provides a method for preparing a polyamide-imide film. The method for preparing a polyamide-imide film comprises:

[0038] Under inert conditions, the diamine compound and the dianhydride compound react to obtain a precursor solution;

[0039] Adding a crosslinking agent to the precursor solution and stirring 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 any one of the compositions in the above embodiments;

[0040] The polyamide-imide solution is coated into a wet film, and the wet film is cured to obtain a polyamide-imide film.

[0041] It can be understood that the beneficial effects that can be achieved by the polyamideimide, polyamideimide film and method for preparing the polyamideimide film provided in the above embodiments of the present application can refer to the beneficial effects of the composition described above, which will not be repeated here.

[0042] In some embodiments, the wet film curing includes: first keeping the wet film at a temperature ranging from 80° C. to 200° C. for 5 min to 20 min, and then keeping the wet film at a temperature ranging from 300° C. to 380° C. for 5 min to 20 min.

[0043] In some embodiments, before coating the polyamideimide solution into a wet film, the method further includes: adding a viscosity adjusting agent to the polyamideimide solution.

[0044] In some embodiments, the viscosity of the polyamideimide solution ranges from 10,000 cPs to 20,000 cPs.

[0045] In a fifth aspect, the present application provides a use of the polyamide-imide film of any one of the above embodiments in wire enamel.

[0046] It can be understood that the beneficial effects that can be achieved by using the polyamide-imide film provided in the above embodiments of the present application in wire enamel can refer to the beneficial effects of the composition described above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 A flow chart of a method for preparing a polyamide-imide film is provided for an embodiment of the present application;

[0049] Figure 2 A scanning electron microscope image of a polyamide-imide film is provided for Example 4 of the present application;

[0050] Figure 3 The stress-strain diagrams of the polyamide-imide films of the embodiments and comparative examples of the present application;

[0051] Figure 4 The mechanical properties diagram of the polyamide-imide membrane of the embodiments and comparative examples of the present application;

[0052] Figure 5 An infrared spectrum of a polyamide-imide film is provided for Example 4 of the present application. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0054] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "front", "back", "inside", "outside", etc. indicate directions or positional relationships based on the directions or relative positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on this application. Unless otherwise specified, the above-mentioned directional description can be flexibly set in the process of actual application under the condition that the relative positional relationship shown in the accompanying drawings is met.

[0055] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0056] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. It can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0057] In the present application, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, article or device including the element.

[0058] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0059] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0060] At present, in order to further improve the power density and efficiency of automotive motors, increase the speed range of motors and achieve high-power fast charging, motors are gradually developing towards a high voltage (≥1200V) platform. The increase in motor voltage places higher requirements on the dielectric properties of wire enamels, that is, a lower dielectric constant, to ensure that electrical short circuits, current leakage, breakdown and other faults do not occur when the motors work under high voltage conditions.

[0061] The embodiments of the present application provide an application of a polyamide-imide film in wire enamel.

[0062] Polyimide material is the most widely used material for wire enameled paint. In order to reduce the dielectric constant of polyimide, in some implementations, air holes are introduced inside the polyimide material. However, after the holes are introduced inside the polyimide material, the mechanical properties of the polyimide will be seriously deteriorated, which is mainly manifested in the simultaneous reduction of the tensile strength and elongation at break of the polyimide material, resulting in a decrease in the adhesion, wear resistance, impact resistance and flexibility of the wire enameled paint film, which will ultimately greatly reduce the life and reliability of the motor.

[0063] Therefore, while introducing air pore structure inside the polyimide material to reduce the dielectric constant, the mechanical properties of the polyimide wire enamel material must be improved simultaneously.

[0064] In other implementations, fillers are introduced into polyimide to form polyimide composite materials, and the fillers include graphene oxide, carbon nanotubes, glass fibers, etc. However, polyimide composite materials have the following significant disadvantages: (1) The compatibility between untreated fillers and polyimide is poor, and the fillers often need to be surface treated before they can be introduced into polyimide, which increases the cost and complicates the process; (2) The introduction of fillers will increase the density of polyimide composite materials, which is not conducive to lightweight design; (3) Some fillers have poor thermal stability at high temperatures, which will reduce the heat resistance of polyimide composite materials; (4) The introduction of fillers may increase the viscosity of polyimide melt, affecting its fluidity and molding processing performance; (5) The introduction of fillers will affect the dielectric properties of polyimide. For example, the introduction of graphene into polyimide to form a polyimide composite material can make the polyimide composite material stronger and tougher, but graphene has good conductivity, which is not conducive to the reduction of the dielectric constant of polyimide.

[0065] Based on this, an embodiment of the present application provides a composition comprising: a dianhydride compound, a diamine compound and a cross-linking agent.

[0066] The crosslinking agent is selected from any one of the structural formulas shown in the following general formula I.

[0067]

[0068] 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 a blocking group; and n1≥2.

[0069] The order of adding the dianhydride compound, the diamine compound and the crosslinking agent is not limited. The dianhydride compound, the diamine compound and the crosslinking agent can be added simultaneously to form the polyamic acid precursor resin and then crosslinked. Alternatively, the dianhydride compound and the diamine compound can be added first to form the polyamic acid precursor resin, and then the crosslinking agent can be added for crosslinking.

[0070] Exemplarily, the dianhydride compound and the diamine compound can undergo a polymerization reaction to form a polyamic acid precursor resin; the cross-linking agent, i.e., the blocking group R2 in the general formula I, is unblocked at a relatively high temperature to form a blocking agent that escapes, and at the same time, the isocyanate group in the general formula I is exposed and cross-linked with the molecular chain of the polyamic acid precursor resin to form polyamide-imide. The carbon dioxide molecules generated during the cross-linking reaction and the blocking agent formed by the blocking group R2 escape, leaving a pore structure in the formed 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, thereby ensuring that the polyamide-imide has a lower dielectric constant. At the same time, the cross-linking reaction also forms a three-dimensional network structure between the polyamide-imides, and the main chain structure of the polyamide-imide is connected, thereby improving the overall density of the polyamide-imide, thereby improving the mechanical properties of the polyamide-imide material.

[0071] For example, the following reaction formula shows that the crosslinking agent (a) can be decomposed at 170° C. to form a product (e) and a blocking agent (f) formed by a blocking group.

[0072]

[0073] Illustratively, the following reaction formula is a cross-linking reaction of the polyamic acid precursor resin (d) with the isocyanate group in the cross-linking agent at high temperature, and the reaction can release carbon dioxide molecules.

[0074]

[0075] The carbon dioxide molecules can leave a hole structure in the polyamide-imide during the release process, which can make the polyamide-imide have a lower dielectric constant.

[0076] Exemplarily, the polyamic acid precursor resin comprises the following structural formula (i);

[0077]

[0078] In some embodiments, R2 comprises any of the following structural formulas;

[0079]

[0080] Among them, * indicates that the key is The C atoms in are connected.

[0081] It can be understood that any of the above structural formulas, when connected to the general formula I, can form a blocking agent when the cross-linking agent is unblocked, wherein: Can generate ε-caprolactam (f1),

[0082] 3,5-dimethylpyrazole (f5) can be generated. Diethylene glycol monomethyl ether (f11) can be produced, and Methyl ethyl ketone oxime (f3) can be generated. When these blocking agents escape from the polyamide-imide material, they leave behind a pore structure, which makes the dielectric constant of the polyamide-imide material lower.

[0083] Here, the structure obtained by the crosslinking agent can be obtained by infrared spectroscopy analysis.

[0084] In some embodiments, the crosslinking agent is selected from at least one of the following structural formulas:

[0085]

[0086]

[0087] The above cross-linking agents all contain at least two isocyanate groups. The excellent activity of the isocyanate groups can be cross-linked with the molecular chains of the polyamic acid precursor resin, so that the formed polyamide-imide has better mechanical properties; at the same time, the carbon dioxide molecules released by the cross-linking reaction, as well as the blocking groups in the above cross-linking agents that form a sealing agent when the cross-linking agent is unblocked, will form a pore structure, so that the dielectric constant of the polyamide-imide material is lower.

[0088] It should be noted that when the end-blocking of the cross-linking agent is unblocked, a substance having a structural formula (e) containing an isocyanate group and a blocking agent having a structural formula (f) containing a blocking group can be formed.

[0089] For example, the substance with the structural formula (e) can be 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). The corresponding structures are as follows:

[0090]

[0091]

[0092] Exemplarily, 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), diethylene glycol monomethyl ether (f11). Among them, 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:

[0093]

[0094] It should be noted that the substance of structural formula (e) containing an isocyanate group and the substance of structural formula (f) containing a blocking group can also be subjected to blocking reaction under certain conditions to synthesize a crosslinking agent.

[0095] That is, 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 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 blocking reaction.

[0096] The reaction combination of the substance of structural formula (e) and the blocking agent of structural formula (f) includes, but is not limited to, the following: a cross-linking agent formed by the reaction of (e1) and (f1), a cross-linking agent formed by the reaction of (e1) and (f2), a cross-linking agent formed by the reaction of (e1) and (f3), a cross-linking agent formed by the reaction of (e1) and (f4), a cross-linking agent formed by the reaction of (e1) and (f5), a cross-linking agent formed by the reaction of (e1) and (f6), a cross-linking agent formed by the reaction of (e1) and (f7), a cross-linking agent formed by the reaction of (e1) and (f8), a cross-linking agent formed by the reaction of (e1) and (f9), a cross-linking agent formed by the reaction of (e1) and (f10), a cross-linking agent formed by the reaction of (e1) and (f11), a cross-linking agent formed by the reaction of (e2) and f1 a cross-linking agent formed by the reaction of (e2) and (f2), a cross-linking agent formed by the reaction of (e2) and (f3), a cross-linking agent formed by the reaction of (e2) and (f4), a cross-linking agent formed by the reaction of (e2) and (f5), a cross-linking agent formed by the reaction of (e2) and (f6), a cross-linking agent formed by the reaction of (e2) and (f7), a cross-linking agent formed by the reaction of (e2) and (f8), a cross-linking agent formed by the reaction of (e2) and (f9), a cross-linking agent formed by the reaction of (e2) and (f10), a cross-linking agent formed by the reaction of (e2) and (f11), a cross-linking agent formed by the reaction of (e3) and f1, a cross-linking agent formed by the reaction of (e3) and (f2), a cross-linking agent formed by the reaction of (e3) and (f3), a cross-linking agent formed by the reaction of (e3) and (f4) a cross-linking agent formed by the reaction of (e3) and (f5), a cross-linking agent formed by the reaction of (e3) and (f6), a cross-linking agent formed by the reaction of (e3) and (f7), a cross-linking agent formed by the reaction of (e3) and (f8), a cross-linking agent formed by the reaction of (e3) and (f9), a cross-linking agent formed by the reaction of (e3) and (f10), a cross-linking agent formed by the reaction of (e3) and (f11), a cross-linking agent formed by the reaction of (e4) and f1, a cross-linking agent formed by the reaction of (e4) and (f2), a cross-linking agent formed by the reaction of (e4) and (f3), a cross-linking agent formed by the reaction of (e4) and (f4), a cross-linking agent formed by the reaction of (e4) and (f5, a cross-linking agent formed by the reaction of (e4) and (f6), and a cross-linking agent formed by the reaction of (e4) and (f7). a cross-linking agent formed by reacting with (f7), a cross-linking agent formed by reacting with (e4) and (f8), a cross-linking agent formed by reacting with (e4) and (f9), a cross-linking agent formed by reacting with (e4) and (f10), a cross-linking agent formed by reacting with (e4) and (f11), a cross-linking agent formed by reacting with (e5) and f1, a cross-linking agent formed by reacting with (e5) and (f2), a cross-linking agent formed by reacting with (e5) and (f3), a cross-linking agent formed by reacting with (e5) and (f4), a cross-linking agent formed by reacting with (e5) and (f5), a cross-linking agent formed by reacting with (e5) and (f6), a cross-linking agent formed by reacting with (e5) and (f7), a cross-linking agent formed by reacting with (e5) and (f8), a cross-linking agent formed by reacting with (e5) and (f9,A cross-linking agent formed by the reaction of (e5) and (f10), a cross-linking agent formed by the reaction of (e5) and (f11), a cross-linking agent formed by the reaction of (e6) and f1, a cross-linking agent formed by the reaction of (e6) and (f2), a cross-linking agent formed by the reaction of (e6) and (f3), a cross-linking agent formed by the reaction of (e6) and (f4), a cross-linking agent formed by the reaction of (e6) and (f5), a cross-linking agent formed by the reaction of (e6) and (f6), a cross-linking agent formed by the reaction of (e6) and (f7) crosslinking agent, a crosslinking agent formed by the reaction of (e6) and (f8), a crosslinking agent formed by the reaction of (e6) and (f9), a crosslinking agent formed by the reaction of (e6) and (f10), a crosslinking agent formed by the reaction of (e6) and (f11), a crosslinking agent formed by the reaction of (e7) and f1, a crosslinking agent formed by the reaction of (e7) and (f2), a crosslinking agent formed by the reaction of (e7) and (f3), a crosslinking agent formed by the reaction of (e7) and (f4), a crosslinking agent formed by the reaction of (e7) and (f5), The cross-linking agent to be formed, the cross-linking agent formed by the reaction of (e7) and (f6), the cross-linking agent formed by the reaction of (e7) and (f7), the cross-linking agent formed by the reaction of (e7) and (f8), the cross-linking agent formed by the reaction of (e7) and (f9), the cross-linking agent formed by the reaction of (e7) and (f10), the cross-linking agent formed by the reaction of (e7) and (f11), the cross-linking agent formed by the reaction of (e8) and f1, the cross-linking agent formed by the reaction of (e8) and (f2), the cross-linking agent formed by the reaction of (e8) and (f3), the cross-linking agent formed by the reaction of (e8) and (f4), the cross-linking agent formed by the reaction of (e8) and (f5), the cross-linking agent formed by the reaction of (e8) and (f6), the cross-linking agent formed by the reaction of (e8) and (f7), the cross-linking agent formed by the reaction of (e8) and (f8), the cross-linking agent formed by the reaction of (e8) and (f9), the cross-linking agent formed by the reaction of (e8) and (f10), and the cross-linking agent formed by the reaction of (e8) and (f11). ,

[0097] For example, the end-capping reaction may be carried out at 60° C. to 80° C. for 8 hours.

[0098] Exemplarily, the end-capping reaction of HDI trimer (e6) and ε-caprolactam (f1) is as follows:

[0099]

[0100] In some embodiments, the diamine compound includes at least one of 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.

[0101] In some embodiments, the dianhydride compound includes: at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic 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)diphthalic anhydride, 4,4'-oxydiphthalic anhydride and bis(1,3-dioxo-1,3-dihydroisobenzofuran)5-carboxylic acid)-1,4-phenylene ester.

[0102] It can be understood that the diamine compound and the dianhydride compound react in a solvent to generate a polyamic acid precursor resin.

[0103] It should be noted that the solvent is not particularly limited and can be an organic solvent, for example, at least one selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylformamide (DMAc), γ-butyrolactone (GBL) and xylene, which can generate a polyamic acid precursor resin with good polymerization effect.

[0104] 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 to 1.1.

[0105] 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., which is not limited here.

[0106] It can be understood 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 to 1.1, which can make the diffusion rate and collision frequency of the diamine compound and the dianhydride compound in the reaction system similar, which helps to improve the efficiency and yield of the reaction, and can also make the molecular weight distribution of the polyamic acid precursor resin more uniform, which is helpful for the subsequent film formation process of polyamideimide.

[0107] In some embodiments, the ratio of the molar mass of the cross-linking agent to the molar mass of the dianhydride compound is in the range of 0.05 to 0.5.

[0108] For example, the ratio of the molar mass of the cross-linking agent to the molar mass of the dianhydride compound can be 0.05, 0.15, 0.30, 0.45 or 0.5, etc., which is not limited here.

[0109] It can be understood that the addition of the cross-linking agent helps the polyamide-imide to form a stable network structure. By setting the ratio of the molar mass of the cross-linking agent to the molar mass of the dianhydride compound in the range of 0.05 to 0.5, the cross-linking density of the polyamide-imide can be controlled more accurately, avoiding the brittleness of the polyamide-imide caused by too high a cross-linking density and the reduction of the strength and stability of the polyamide-imide due to too low a cross-linking density, thereby improving the mechanical properties of the polyamide-imide.

[0110] In some embodiments, the composition further comprises: a viscosity adjusting agent.

[0111] It can be understood that adding a viscosity regulator to the composition can make the viscosity of the composition within an appropriate range, which can improve the film-forming performance of the polyamide-imide and promote the uniformity of the polyamide-imide film; at the same time, the viscosity of the composition is within an appropriate range, which is also conducive to the release of small molecules in the cross-linking reaction, promotes the formation of the polyamide-imide pore structure, and makes the dielectric constant of the polyamide-imide lower.

[0112] In some embodiments, the viscosity adjusting agent includes: at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether and tetraethylene glycol monomethyl ether, diethylene glycol dimethyl 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 dimethyl ether, triethylene glycol monovinyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl propyl ether, tetraethylene glycol methyl vinyl ether, diethylene glycol dipropyl ether, diethylene glycol divinyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, triethylene glycol monomethyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0113] In other embodiments, the viscosity adjusting agent 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.

[0114] In some embodiments, the ratio of the mass of the viscosity adjusting agent to the total mass of the composition is in the range of 0.1 to 1.2.

[0115] For example, the ratio of the mass of the viscosity adjusting agent to the total mass of the composition may be 0.1, 0.5, 0.7, 1 or 1.2, etc., which is not limited herein.

[0116] It can be understood that the ratio of the mass of the viscosity adjusting agent to the total mass of the composition is set in the range of 0.1 to 1.2, which can further make the viscosity of the composition within an appropriate range, improve the film-forming properties of the polyamide-imide, promote the formation of the polyamide-imide pore 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.

[0117] The embodiment of the present application provides a polyamide-imide, which includes any one of the following structural formulas.

[0118]

[0119]

[0120] Among them, R3 is selected from the remaining part of the dianhydride compound after removing the dianhydride group, R4 is the remaining part of the diamine compound after removing the diamine group, and R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; among them, n2≥2; n3≥2; n4≥2; n5≥2; n6≥1.

[0121] Taking the dianhydride compound selected from pyromellitic dianhydride as an example, R3 is selected from the remaining part of pyromellitic dianhydride without the dianhydride group, wherein the dianhydride group is the circled part in the following formula.

[0122]

[0123] Taking the diamine compound selected from diaminodiphenyl ether as an example, R4 is selected from the remaining part of diaminodiphenyl ether without the diamine group, wherein the diamine group is the circled part in the following formula.

[0124]

[0125] Here, the structure of polyamide-imide can be obtained by infrared spectroscopy analysis.

[0126] In some embodiments, the structural formula of the polyamideimide comprises:

[0127]

[0128] Among them, m1≥1, m 2≥ 1, n8≥1, n9≥1, n 10 ≥1.

[0129] The following is a description of forming a polyamideimide film from the polyamideimide in any of the above embodiments.

[0130] The embodiment of the present application provides a polyamide-imide film, wherein the material of the polyamide-imide film includes any of the above-mentioned exemplary materials.

[0131] In some embodiments, the polyamideimide film has a thickness ranging from 10 μm to 50 μm.

[0132] For example, the thickness of the polyamide-imide film may be 10 μm, 20 μm, 30 μm, 40 μm, or 10 μm, etc., which is not limited herein.

[0133] It can be understood that the thickness of the polyamide-imide film is in the range of 10 μm to 50 μm, and the polyamide-imide film can be used as a wire enamel material.

[0134] In some embodiments, the dielectric constant of the polyamideimide film ranges from 1.3 to 3.4.

[0135] In some examples, the dielectric constant of the polyamideimide film ranges from 1.6 to 2.

[0136] For example, the dielectric constant of the polyamide-imide film may be 1.6, 1.7, 1.8, 1.9 or 2, etc., which is not limited here.

[0137] It can be understood that the dielectric constant of the polyamide-imide film is in the range of 1.3 to 3.4, which means that the dielectric constant of the polyamide-imide film is small and has good dielectric properties.

[0138] In some embodiments, the elongation at break of the polyamide-imide film ranges from 1% to 14%.

[0139] In some examples, the elongation at break of the polyamideimide film ranges from 9% to 14%.

[0140] For example, the elongation at break of the polyamide-imide film may be 9%, 10%, 11%, 12%, 13% or 9%, etc., which is not limited here.

[0141] It can be understood that the elongation at break of the polyamide-imide film is in the range of 1% to 14%, which indicates that the polyamide-imide film is difficult to break and has good mechanical properties.

[0142] In some embodiments, the elastic modulus of the polyamide-imide film ranges from 1 MPa to 2000 MPa.

[0143] In some examples, the elastic modulus of the polyamideimide film ranges from 1400 MPa to 1450 MPa.

[0144] For example, the elastic modulus of the polyamide-imide film may be 1400 MPa, 1410 MPa, 1420 MPa, 1430 MPa, 1440 MPa or 1450 MPa, etc., which is not limited herein.

[0145] It can be understood that the elastic modulus of the polyamide-imide film is in the range of 1 MPa to 2000 MPa, which means that the polyamide-imide film can maintain a high shape stability when subjected to external forces, is not easily deformed, and has good mechanical properties.

[0146] In some embodiments, the polyamideimide film has a tensile strength ranging from 1 MPa to 500 MPa.

[0147] In some examples, the tensile strength of the polyamideimide film ranges from 80 MPa to 110 MPa.

[0148] For example, the tensile strength of the polyamide-imide film may be 80 MPa, 85 MPa, 90 MPa, 95 MPa, 100 MPa, 105 MPa or 110 MPa, etc., which is not limited herein.

[0149] It can be understood that the tensile strength of the polyamide-imide film is in the range of 1 MPa to 500 MPa, which means that the polyamide-imide film can withstand a relatively large maximum tensile force when subjected to a tensile force, and has relatively good mechanical properties.

[0150] The following is a description of the method for preparing the polyamide-imide film in any of the above embodiments.

[0151] The embodiments of the present application provide a method for preparing a polyamide-imide film. Figure 1 As shown, the preparation method of the polyamide-imide film includes: S1 to S3.

[0152] S1: Under inert conditions, a diamine compound and a dianhydride compound react to obtain a precursor solution.

[0153] Exemplarily, the inert gas may be nitrogen (N2) or argon (Ar).

[0154] 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 to be 15% to 40%, preferably 30%.

[0155] S2: Add a crosslinking agent to the precursor solution and stir to obtain a polyamide-imide solution.

[0156] The diamine compound, the dianhydride compound and the crosslinking agent are referred to as a composition, and the composition is a composition as described in any one of the above embodiments.

[0157] S3: coating the polyamide-imide solution into a wet film, and curing the wet film to obtain a polyamide-imide film.

[0158] For example, the wet film thickness may be 50 μm to 200 μm.

[0159] Exemplarily, the coating speed may be 300 mm / min.

[0160] In some embodiments, the wet film curing includes: first keeping the wet film at a temperature ranging from 80° C. to 200° C. for 5 min to 20 min, and then keeping the wet film at a temperature ranging from 300° C. to 380° C. for 5 min to 20 min.

[0161] Preferably, the wet film is first kept at 150° C. for 10 min, and then kept at 350° C. for 10 min.

[0162] Preferably, the wet film is first kept at 160° C. for 10 min, and then kept at 350° C. for 10 min.

[0163] Preferably, the wet film is first kept at 150° C. for 10 min, and then kept at 380° C. for 10 min.

[0164] More preferably, the wet film is first kept at 120° C. for 10 min, then kept at 150° C. for 10 min, and then kept at 380° C. for 10 min.

[0165] In some embodiments, before coating the polyamide-imide solution into a wet film, the method further includes: S4.

[0166] S4: adding a viscosity adjusting agent to the polyamide-imide solution.

[0167] It can be understood that the viscosity of the polyamide-imide solution can be adjusted by adding the viscosity adjusting agent, so as to facilitate coating into a wet film and make the polyamide-imide film more uniform.

[0168] In some embodiments, the viscosity of the polyamideimide solution is in the range of 10000 cPs to 20000 cPs.

[0169] For example, the viscosity of the polyamide-imide solution may be 10000 cPs, 12000 cPs, 14000 cPs, 16000 cPs, 10000 cPs or 20000 cPs, etc., which is not limited herein.

[0170] It can be understood that when the viscosity of the polyamideimide solution is set within the range of 10000 cPs to 20000 cPs, the film-forming performance of the polyamideimide can be better, and it is beneficial to the formation of the polyamideimide pore structure, so that the dielectric constant of the polyamideimide material is lower.

[0171] The preparation method of the polyamide-imide film of the present application is simple and convenient. It only needs to add a crosslinking agent before coating into a wet film. During curing, pore-forming and crosslinking effects can be achieved simultaneously, so that the polyamide-imide film has both a lower dielectric constant and improved mechanical properties.

[0172] The present application is further described in detail below by using specific experiments as examples and in conjunction with the accompanying drawings.

[0173] Example 1

[0174] Embodiment 1 provides a polyamide-imide film, which is obtained by the following preparation steps:

[0175] A1: N2 was continuously introduced into the reaction flask, 28.7081 g of 4,4'-diaminodiphenyl ether and 140 g of N-methylpyrrolidone were added, and after stirring to fully dissolve the 4,4'-diaminodiphenyl ether, 31.2919 g of pyromellitic dianhydride was added, and then the reaction was continued with stirring at 20°C to 25°C for 8 hours to obtain 200 g of uniform polyamic acid precursor resin.

[0176] A2: 22.0178 g of a crosslinking agent (a1) was added to the polyamic acid precursor resin obtained in A1 and stirred for 3 hours, wherein the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound was 0.2; the structural formula of the crosslinking agent (a1) is as follows:

[0177]

[0178] A3: 60 g of dibutyl phthalate was added to the solution obtained in A2, and the mixture was stirred for 3 h to obtain a polyamide-imide solution.

[0179] A4: The polyamide-imide solution obtained in A3 was sealed and allowed to stand for 8 to 12 hours to degas, and then a wet film was coated by slit coating, with the wet film thickness controlled at 100 μm and the coating speed at 300 mm / min; the wet film was cured at 150°C for 10 minutes and 350°C for 10 minutes to obtain a polyamide-imide film with a thickness of 15±3 μm, the structural formula of which is as follows:

[0180]

[0181] Example 2

[0182] Embodiment 2 provides a polyamide-imide film, which is obtained by the following preparation steps:

[0183] B1: N2 was continuously introduced into the reaction flask, 25.7584 g of 2,2-bis(4-aminophenyl)hexafluoropropane and 140 g of N-methylpyrrolidone were added, and after stirring to fully dissolve the 2,2-bis(4-aminophenyl)hexafluoropropane, 34.2416 g of hexafluorodianhydride (6FDA) was added, and then the reaction was continued with stirring at 20°C to 25°C for 8 hours to obtain 200 g of uniform polyamic acid precursor resin.

[0184] B2: 11.8298 g of a crosslinking agent (a1) was added to the polyamic acid precursor resin obtained in B1 and stirred for 3 h, wherein the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound was 0.2; the structural formula of the crosslinking agent (a1) was as follows:

[0185]

[0186] B3: 60 g of dibutyl phthalate was added to the solution obtained in B2, and the mixture was stirred for 3 h to obtain a polyamide-imide solution.

[0187] B4: The polyamide-imide solution obtained in B3 was sealed and allowed to stand for 8 to 12 hours to degas, and then a wet film was coated by slit coating, with the wet film thickness controlled at 100 μm and the coating speed at 300 mm / min; the wet film was cured at 150°C for 10 minutes and at 350°C for 10 minutes to obtain a polyamide-imide film with a thickness of 15±3 μm.

[0188] Example 3

[0189] Embodiment 3 provides a polyamide-imide film, which is obtained by the following preparation steps:

[0190] C1: N2 was continuously introduced into the reaction flask, 28.7081 g of 4,4'-diaminodiphenyl ether and 140 g of N-methylpyrrolidone were added, and after stirring to fully dissolve the 4,4'-diaminodiphenyl ether, 31.2919 g of pyromellitic dianhydride was added, and then the reaction was continued with stirring at 20°C to 25°C for 8 hours to obtain 200 g of uniform polyamic acid precursor resin.

[0191] C2: 27.4163 g of a crosslinking agent (a2) was added to the polyamic acid precursor resin obtained in C1 and stirred for 3 h, wherein the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound was 0.2; the structural formula of the crosslinking agent (a2) was as follows:

[0192]

[0193] C3: 60 g of dibutyl phthalate was added to the solution obtained in C2, and the mixture was stirred for 3 h to obtain a polyamide-imide solution.

[0194] C4: The polyamide-imide solution obtained in C3 was sealed and allowed to stand for 8 to 12 hours to degas, and then a wet film was coated by slit coating, with the wet film thickness controlled at 100 μm and the coating speed at 300 mm / min; the wet film was maintained at 150°C for 10 minutes and at 350°C for 10 minutes to cure, thereby obtaining a polyamide-imide film with a thickness of 15±3 μm.

[0195] Example 4

[0196] Embodiment 4 provides a polyamide-imide film, which is obtained by the following preparation steps:

[0197] D1: N2 was continuously introduced into the reaction flask, 25.7584 g of 2,2-bis(4-aminophenyl)hexafluoropropane and 140 g of N-methylpyrrolidone were added, and after stirring to fully dissolve 2,2-bis(4-aminophenyl)hexafluoropropane, 34.2416 g of hexafluorodianhydride (6FDA) was added, and then the reaction was continuously stirred at 20°C to 25°C for 8 hours to obtain 200 g of uniform polyamic acid precursor resin.

[0198] D2: 19.5270 g of a crosslinking agent (a3) ​​was added to the polyamic acid precursor resin obtained in D1 and stirred for 3 h, wherein the ratio of the molar mass of the crosslinking agent to the molar mass of the dianhydride compound was 0.3; the structural formula of the crosslinking agent (a3) ​​was as follows:

[0199]

[0200] D3: 60 g of dibutyl phthalate was added to the solution obtained in D2, and the mixture was stirred for 3 h to obtain a polyamide-imide solution.

[0201] D4: The polyamide-imide solution obtained in D3 was sealed and allowed to stand for 8h to 12h to degas, and then a wet film was coated by slit coating method, with the wet film thickness controlled at 100μm and the coating speed at 300mm / min; the wet film was kept at 150℃ for 10min and 350℃ for 10min to cure, and a polyamide-imide film with a thickness of 15±3μm was obtained, such as Figure 2 The scanning electron microscope image of the polyamide-imide film of Example 4 is shown in FIG. Figure 2 It can be seen that the polyamide-imide film has a porous structure; its structure is as follows:

[0202]

[0203] Comparative Example 1

[0204] Comparative Example 1 provides a polyamide-imide film, which is obtained by the following preparation steps:

[0205] P1: N2 was continuously introduced into the reaction flask, 28.7081 g of 4,4'-diaminodiphenyl ether and 140 g of N-methylpyrrolidone were added, and after stirring to fully dissolve the 4,4'-diaminodiphenyl ether, 31.2919 g of pyromellitic dianhydride was added, and then the reaction was continued with stirring at 20°C to 25°C for 8 hours to obtain 200 g of uniform polyamic acid precursor resin.

[0206] P2: Add 60 g of dibutyl phthalate to the polyamic acid precursor resin obtained in P1, and continue stirring for 3 hours to obtain a polyamide-imide solution;

[0207] P3: The polyamide-imide solution obtained in P2 was sealed and allowed to stand for 8 to 12 hours to degas, and then a wet film was coated by slit coating, with the wet film thickness controlled at 100 μm and the coating speed at 300 mm / min; the wet film was cured at 150°C for 10 minutes and at 350°C for 10 minutes to obtain a polyamide-imide film with a thickness of 15±3 μm.

[0208] Comparative Example 2

[0209] Comparative Example 2 provides a polyamide-imide film, which is obtained by the following preparation steps:

[0210] R1: N2 was continuously introduced into the reaction flask, 25.7584 g of 2,2-bis(4-aminophenyl)hexafluoropropane and 140 g of N-methylpyrrolidone were added, and after stirring to fully dissolve 4,4'-diaminodiphenyl ether, 34.2416 g of hexafluorodianhydride was added, and then the reaction was continued with stirring at 20°C to 25°C for 8 hours to obtain 200 g of uniform polyamic acid precursor resin.

[0211] R2: Add 60 g of dibutyl phthalate to the solution obtained in R1 and continue stirring for 3 h to obtain a polyamide-imide solution;

[0212] R3: The polyamide-imide solution obtained in R2 was sealed and allowed to stand for 8 to 12 hours to degas, and then a wet film was coated by slit coating, with the wet film thickness controlled at 100 μm and the coating speed at 300 mm / min; the wet film was cured at 150°C for 10 minutes and at 350°C for 10 minutes to obtain a polyamide-imide film with a thickness of 15±3 μm.

[0213] Performance Testing

[0214] 1. The polyamide-imide films of the above-mentioned embodiment and comparative example were subjected to infrared peak analysis respectively. The results are shown in Table 1.

[0215] Table 1 Infrared peak analysis of each polymer film in the examples and comparative examples

[0216]

[0217]

[0218] As shown in Table 1 and Figure 5 As shown, the polyamide-imide film of Example 4 has a wave number of 1750 -1 ~1800cm -1 There is an asymmetric stretching vibration of the imide ring C=O, which can prove the existence of imide functional groups in the polymer; at wave number 1700 -1 ~1730cm -1 At wave number 1490, there are benzene ring vibrations and imide ring C=O symmetric stretching vibrations, proving that the polymer contains both benzene rings and imide rings; -1 ~1550cm -1 At the wave number 1400, there is CN bending vibration at the connection between the cross-linking agent and the polyamic acid precursor resin, indicating that the cross-linking agent has been successfully connected to the polyamic acid precursor resin to form a cross-linked structure; -1 ~1460cm -1 At wave number 1370, there is CN stretching vibration of trimethyl isocyanurate ring, which further proves that the crosslinker is introduced into the polymer. -1 ~1390cm -1 There is stretching vibration of the imide ring CN at wave number 720 -1 ~750cm -1 The C=O bending vibration of the imide ring proves the existence of the imide ring structure. The structure of the polyamide-imide film of Example 4 described above has typical imide ring and benzene ring structures, and the cross-linking agent (a3) ​​has been successfully introduced. The infrared peak analysis of the polymer films of other embodiments 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 film in each embodiment and comparative example is consistent with the drawn structure.

[0219] 2. The polyamide-imide solutions of the above embodiments and comparative examples were subjected to viscosity tests according to GB / T 40280-2021; and the polyamide-imide films obtained in the above embodiments and comparative examples were subjected to dielectric constant tests according to ASTM D150-18. The results are shown in Table 2 below.

[0220] Table 2 Viscosity of polyamideimide solutions of examples and comparative examples and dielectric constants of polyamideimide films of examples and comparative examples

[0221]

[0222] As can be seen from 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 the crosslinking agent has little effect on the viscosity of the polyamideimide solution, that is, the crosslinking agent has little effect on the film-forming properties of the polyamideimide, which is beneficial to the formation of the polyamideimide film.

[0223] The diamine compounds and dianhydride compounds used in the preparation of the polyamideimide solution of the polyamideimide films of Example 1, Example 3 and Comparative Example 1 are all the same, and the only difference is that no cross-linking agent is added in the preparation of the polyamideimide solution of Comparative Example 1. Therefore, the dielectric constants of the polyamideimide films of Example 1 and Example 3 are significantly reduced compared with the dielectric constant of the polyamideimide film of Comparative Example 1, indicating that after adding a cross-linking agent, the dielectric constant of the polyamideimide film can be reduced compared with that without adding a cross-linking agent.

[0224] The diamine compounds and dianhydride compounds used in the polyamideimide films of Example 2, Example 4 and Comparative Example 2 in the preparation of the polyamideimide solution are the same, and the only difference is that no cross-linking agent is added in the preparation of the polyamideimide solution in Comparative Example 2. Therefore, the dielectric constants of the polyamideimide films of Example 2 and Example 4 are significantly reduced compared with the dielectric constant of the polyamideimide film of Comparative Example 2, indicating that after adding a cross-linking agent, the dielectric constant of the polyamideimide film can be reduced compared with that without adding a cross-linking agent. At the same time, the dielectric constant of the polyamideimide film of Example 4 is smaller than the dielectric constant of the polyamideimide film of Example 2, which is attributed to the addition of more cross-linking agents in Example 4, so that more hole structures are formed in the polyamideimide film, further reducing the dielectric constant.

[0225] 3. The polyamide-imide films of the above examples and comparative examples were subjected to tensile tests according to GB / T 13022-2006. The results are as follows: Figure 3 and Figure 4 shown.

[0226] Figure 3The inflection point of the middle curve indicates that the polyamide-imide film breaks under this stress. The polyamide-imide film of comparative example 1 breaks at a strain of 5.8% under a stress of 62 MPa; the polyamide-imide film of comparative example 2 breaks at a strain of 7.8% under a stress of 80 MPa; the polyamide-imide film of example 1 breaks at a strain of 13.2% under a stress of 112 MPa; the polyamide-imide film of example 2 breaks at a strain of 13.5% under a stress of 85 MPa; the polyamide-imide film of example 3 breaks at a strain of 12.5% ​​under a stress of 114 MPa; the polyamide-imide film of example 4 breaks 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 the polyamide-imide films of comparative examples 1 and 2.

[0227] Figure 4 Among them, the elongation at break of the polyamide-imide films of Examples 1 to 4 ranges from 9.6% to 13.3%, the elastic modulus ranges from 1407 MPa to 1450 MPa, and the tensile strength ranges from 84.4 MPa to 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, which are significantly lower than the various data indicators of the polyamide-imide films of Examples 1 to 4. It can be seen that the polyamide-imide films of Examples 1 to 4 have better mechanical properties.

[0228] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A composition, characterized in that include: A dianhydride compound, a diamine compound, and a cross-linking agent; The cross-linking agent is selected from any one of the structural formulas shown in the following 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 a blocking group; and n1≥2.

2. The composition according to claim 1, characterized in that The blocking group includes any one of the following structural formulas; Wherein, * indicates the bond with the The C atoms in are connected.

3. The composition according to claim 1 or 2, characterized in that The cross-linking agent is selected from at least one of the following structural formulas:

4. The composition according to any one of claims 1 to 3, characterized in that The diamine compound includes at least one of 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, characterized in that The dianhydride compound includes at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic 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)diphthalic anhydride, 4,4'-oxydiphthalic 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, characterized in 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 to 1.

1.

7. The composition according to any one of claims 1 to 6, characterized in that The ratio of the molar mass of the cross-linking agent to the molar mass of the dianhydride compound is in the range of 0.05 to 0.

5.

8. The composition according to any one of claims 1 to 7, characterized in that Also includes: Viscosity adjuster.

9. The composition according to claim 8, characterized in that The viscosity adjusting agent comprises: at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether and tetraethylene glycol monomethyl ether, diethylene glycol dimethyl 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 dimethyl ether, triethylene glycol monovinyl ether, triethylene glycol dipropyl ether, tetraethylene glycol methyl propyl ether, tetraethylene glycol methyl vinyl ether, diethylene glycol dipropyl ether, diethylene glycol divinyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, triethylene glycol monomethyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, polyethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol monomethyl ether and propylene glycol monomethyl ether; or, The viscosity adjusting agent comprises 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.

10. The composition according to claim 8 or 9, characterized in that The ratio of the mass of the viscosity adjusting agent to the total mass of the composition is in the range of 0.1 to 1.

2.

11. A polyamideimide, characterized in that: Including any of the following structural formulas; Among them, R3 is selected from the remaining part of the dianhydride compound after removing the dianhydride group, R4 is the remaining part of the diamine compound after removing the diamine group, and R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkoxy; among them, n2≥2; n3≥2; n4≥2; n5≥2; n6≥1.

12. The polyamideimide according to claim 11, characterized in that The structural formula of the polyamide-imide includes: Among them, m1≥1, m 2≥ 1, n8≥1, n9≥1, n 10 ≥1.

13. A polyamide-imide film, characterized in that: 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, characterized in that: 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 to 3.4; The elongation at break of the polyamide-imide film ranges from 1% to 50%; The elastic modulus of the polyamide-imide film ranges from 1 MPa to 2000 MPa; The tensile strength of the polyamide-imide film is in the range of 1 MPa to 500 MPa.

15. A method for preparing a polyamide-imide film, characterized in that: include: Under inert conditions, the diamine compound and the dianhydride compound react to obtain a precursor solution; Adding a crosslinking agent to the precursor solution and stirring 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 as claimed in 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 a polyamide-imide film according to claim 15, characterized in that: The wet film curing comprises: firstly keeping the wet film at a temperature range of 80° C. to 200° C. for 5 minutes to 20 minutes, and then keeping the wet film at a temperature range of 300° C. to 380° C. for 5 minutes to 20 minutes.

17. The method for preparing a polyamide-imide film according to claim 15 or 16, characterized in that: Before coating the polyamide-imide solution into a wet film, the method further includes: adding a viscosity adjusting agent into the polyamide-imide solution.

18. The method for preparing a polyamide-imide film according to claim 15, characterized in that: The viscosity of the polyamide-imide solution ranges from 10000 cPs to 20000 cPs.

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

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