High-frequency low-dielectric low-dielectric-loss polyimide resin as well as preparation method and application thereof

Abstract

The invention relates to the field of low-dielectric resin materials, in particular to high-frequency low-dielectric low-dielectric-loss polyimide resin and a preparation method and application thereof. The polyimide resin contains a structural unit provided by an aromatic diamine monomer as shown in a formula (1), and R1 is selected from one or more of biphenyl groups; r2 is selected from one or more of a connecting bond and alkylidene of C1-C20; each R3 is independently selected from one or more of H, C1-C6 alkyl groups and amino groups, and at least two R3 are amino groups. The polyimide resin disclosed by the invention has the characteristics of high frequency, low dielectric constant and low dielectric loss, and is good in mechanical property, and a prepared polyimide film has a wide application prospect. Formula (1) # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of low dielectric resin materials, and particularly relates to a polyimide resin with high frequency, low dielectric constant and low dielectric loss, and a preparation method and application thereof. Background Art

[0002] Due to its excellent comprehensive properties, including heat resistance, corrosion resistance, dimensional stability and mechanical properties, polyimide film has been widely used in related fields. Among them, in the field of high-frequency communication materials, especially for 6G communication materials, polyimide film has great potential due to its excellent comprehensive properties, but its high-frequency dielectric constant and dielectric loss still need to be improved.

[0003] Currently, the methods for preparing high-frequency low-dielectric polyimide films mainly include: (1) doping fillers with low dielectric properties, but the dispersion of fillers in the film is difficult to control and may have the opposite effect. (2) Preparing porous polyimide films. Due to their porous structure, such films have a lower dielectric constant, and the dielectric loss is more related to the polymer chemical structure. In addition, there is a possibility that the mechanical properties are relatively poor and unstable. (3) Designing the main chain structure to prepare polyester-based polyimide. This kind of polyimide film has a lower dielectric loss due to its higher crystallinity, but its dielectric constant is difficult to control, and usually the dielectric constant is greater than 3.

[0004] Therefore, to meet the requirements of the rapid development of modern microelectronics, high-frequency communication and other industries, developing polyimide films with low dielectric constant and low dielectric loss under high-frequency conditions has important practical significance and broad application prospects. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art, and provide a polyimide resin with high frequency, low dielectric constant and low dielectric loss, and a preparation method and application thereof. This polyimide resin has good dielectric properties and mechanical properties, and the prepared polyimide film has a wide range of application scenarios.

[0006] To achieve the above purpose, on the one hand, the present invention provides a polyimide resin, which contains a structural unit provided by an aromatic diamine monomer represented by formula (1).

[0007] Formula (1)

[0008] Wherein, R1 is selected from one or more of biphenyl groups; R2 is selected from one or more of a linking bond and C1-C20 alkylene groups; each R3 is independently selected from one or more of H, C1-C6 alkyl groups and amino groups, and at least two R3 are amino groups.

[0009] The second aspect of the present invention provides a method for preparing the above polyimide resin, which includes: polymerizing a diamine monomer and a dianhydride monomer to obtain a polyimide resin, wherein the diamine monomer includes an aromatic diamine monomer represented by formula (1).

[0010] The third aspect of the present invention provides a polyimide film prepared from the above polyimide resin.

[0011] The fourth aspect of the present invention provides an application of the above polyimide film in the field of high-frequency low-dielectric films.

[0012] In the present invention, by polymerizing an aromatic diamine monomer represented by formula (1) with a specific structure, an optional second aromatic diamine monomer, and an aromatic dianhydride monomer, a polyimide resin containing a flexible side chain is obtained. This polyimide resin has excellent dielectric properties, can simultaneously take into account the characteristics of high-frequency low dielectric constant and low dielectric loss, and has good mechanical properties, and the prepared polyimide film has broad application prospects. Description of the Drawings

[0013] Figure 1 It is the Fourier infrared spectrum of the aromatic diamine monomer represented by formula (1-1) prepared in Preparation Example 1;

[0014] Figure 2 It is the nuclear magnetic resonance spectrum of the aromatic diamine monomer represented by formula (1-1) prepared in Preparation Example 1. Detailed Description of the Invention

[0015] In the present disclosure, the endpoints and any values of the disclosed ranges are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0016] In the present invention, the alkyl group in the expressions such as "C1-C6 alkyl" and "C1-C6 alkylene" can be a straight-chain alkyl group or a branched-chain alkyl group. The same or similar expressions are the same in principle.

[0017] In the present invention, The dotted lines in structures such as represent a connecting bond.

[0018] One aspect of the present invention provides a polyimide resin, which contains a structural unit provided by an aromatic diamine monomer represented by formula (1),

[0019] Formula (1)

[0020] Among them, R1 is selected from one or more of biphenyl groups; R2 is selected from one or more of a linking bond and C1-C20 alkylene groups; each R3 is independently selected from one or more of H, C1-C6 alkyl groups, and amino groups, and at least two R3 are amino groups.

[0021] According to the present invention, in order to further improve the dielectric properties of the polyimide resin and reduce its dielectric constant and dielectric loss, the structure of the aromatic diamine monomer shown in formula (1) can be further selected. Preferably, R1 is selected from one or more of biphenylyl and terphenylyl; R2 is selected from one or more of a linking bond and C1-C12 alkylene groups; each R3 is independently selected from one or more of H, C1-C3 alkyl groups, and amino groups, and at least two R3 are amino groups.

[0022] More preferably, R1 is selected from

[0023] one or more of them; R2 is selected from one or more of a linking bond, methylene, ethylene, n-propylene, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl; each R3 is independently selected from one or more of H, methyl, ethyl, n-propyl, isopropyl, and amino groups, and at least two R3 are amino groups.

[0024] According to a preferred embodiment of the present invention, the aromatic diamine monomer shown in formula (1) is selected from

[0025] one or more of them, and more preferably one or more of them.

[0026] According to a particularly preferred embodiment of the present invention, the aromatic diamine monomer shown in formula (1) is selected from one or more of the compounds shown in the following formula:

[0027]

[0028]

[0029] According to the present invention, the polyimide resin further contains a structural unit provided by an aromatic dianhydride monomer. In order to form a better synergistic effect and improve the performance of the polyimide resin, preferably, the aromatic dianhydride monomer is selected from one or more of them; wherein, A and B are each independently selected from a benzene ring, cyclobutane, cyclohexane, and one or more of them; R 1Selected from a linking bond, an oxy group,

[0030] or one or more thereof; R 2 、R 3 、R 4 and R 5 each independently selected from C1-C6 alkylene groups, or one or more thereof.

[0031] More preferably, the aromatic dianhydride monomer is selected from one or more of the compounds represented by the following formula:

[0032]

[0033]

[0034] According to the present invention, optionally, the polyimide resin further comprises a structural unit provided by a second aromatic diamine monomer. In order to obtain a better polyimide resin, preferably, the second aromatic diamine monomer is selected from or one or more thereof; wherein each R 7 is independently selected from one or more of H, an amino group, a hydroxyl group, a carboxyl group, a trifluoromethyl group, a halogen, and a C1-C6 alkyl group, and at least one R 7 is an amino group; each R 8 is independently selected from one or more of H, an amino group, a hydroxyl group, a carboxyl group, a trifluoromethyl group, a halogen, and a C1-C6 alkyl group, and at least one R 8 is an amino group; R 6 is selected from a linking bond, an oxy group, a C1-C6 alkylene group,

[0035]

[0036] or one or more thereof; R 9 、R 10 、R 11 、R 12 and R 13 each independently selected from

[0037] or one or more thereof.

[0038] More preferably, the second aromatic diamine monomer is selected from one or more of the compounds represented by the following formula:

[0039]

[0040]

[0041] According to the present invention, as the content of the structural unit provided by the second aromatic diamine monomer increases, the properties of the polyimide resin will also decline accordingly.

[0042] According to the present invention, in order to adjust the properties of the polyimide resin to be more excellent, the content of each structural unit contained therein can be adjusted. Preferably, relative to the structural unit provided by 1 mmol of the aromatic dianhydride monomer, the total amount of the structural unit provided by the aromatic diamine monomer shown in formula (1) and optionally the structural unit provided by the second aromatic diamine monomer is 0.95 - 1.05 mmol, preferably 0.98 - 1.02 mmol, and for example, it can be values such as 0.98 mmol, 0.99 mmol, 1 mmol, and 1.02 mmol and the ranges between any of these values.

[0043] Preferably, relative to the structural unit provided by 1 mmol of the aromatic diamine monomer shown in formula (1), the amount of the structural unit provided by the second aromatic diamine monomer is 0 - 4 mmol, preferably 0 - 2 mmol, and for example, it can be values such as 0 mmol, 0.25 mmol, 1.5 mmol, and 2 mmol and the ranges between any of these values.

[0044] According to the present invention, the intrinsic viscosity of the polyimide resin can reflect its molecular weight. In order to adjust the polyimide resin to better properties and performance, preferably, the intrinsic viscosity of the polyimide resin is 0.5 - 2.5 dL / g, preferably 0.8 - 1.4 dL / g, and for example, it can be values such as 0.83 dL / g, 1.14 dL / g, 1.38 dL / g, and 1.4 dL / g and the ranges between any of these values.

[0045] According to the present invention, the structural unit provided by the aromatic diamine monomer shown in formula (1) contains a terminal biphenyl group, which, as a flexible side chain, can well improve the dielectric properties of the polyimide resin, achieving both high-frequency low dielectric constant and low dielectric loss.

[0046] The second aspect of the present invention provides a method for preparing the above polyimide resin, which includes: polymerizing a diamine monomer and a dianhydride monomer to obtain a polyimide resin, wherein the diamine monomer includes the aromatic diamine monomer shown in formula (1).

[0047] According to the present invention, preferably, the diamine monomer is the aromatic diamine monomer shown in formula (1) and optionally a second aromatic diamine monomer, and the dianhydride monomer is an aromatic dianhydride monomer.

[0048] According to the present invention, in order to achieve better reaction effects and improve the dielectric properties of the polyimide resin, preferably, relative to 1 mmol of the aromatic dianhydride monomer, the total amount of the aromatic diamine monomer represented by formula (1) and the optional second aromatic diamine monomer is 0.95 - 1.05 mmol, preferably 0.98 - 1.02 mmol, and for example, it can be values such as 0.98 mmol, 0.99 mmol, 1 mmol, and 1.02 mmol and ranges between any of these values.

[0049] Preferably, relative to 1 mmol of the aromatic diamine monomer represented by formula (1), the amount of the second aromatic diamine monomer is 0 - 4 mmol, preferably 0 - 2 mmol, and for example, it can be values such as 0 mmol, 0.25 mmol, 1.5 mmol, and 2 mmol and ranges between any of these values.

[0050] According to the present invention, the solvent for the polymerization reaction and its amount can be selected within a relatively wide range. In order to provide a better reaction environment and enable the reaction to proceed more smoothly, preferably, the solvent for the polymerization reaction is selected from one or more of aprotic polar solvents, and preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-vinylpyrrolidone, and dimethyl sulfoxide.

[0051] Preferably, the amount of the solvent for the polymerization reaction is such that the solid content of the solution is 4 - 25 wt%, preferably 6 - 20 wt%, and for example, it can be values such as 6 wt%, 10 wt%, 15 wt%, and 20 wt% and ranges between any of these values.

[0052] According to the present invention, in order to enable the polymerization reaction to proceed better and achieve better reaction effects, preferably, the conditions for the polymerization reaction include: the temperature is -10°C to 30°C, and the time is 10 - 40 h; more preferably, the conditions for the polymerization reaction include: the temperature is -5°C to 10°C (for example, it can be values such as -5°C, 0°C, 5°C, 8°C, and 10°C and ranges between any of these values), and the time is 20 - 30 h (for example, it can be values such as 20 h, 24 h, 28 h, and 30 h and ranges between any of these values).

[0053] According to the present invention, in order to avoid the generation of impurities and by-products, preferably, the polymerization reaction is carried out in an inert gas atmosphere. Among them, the inert gas can be, for example, nitrogen and / or argon.

[0054] According to the present invention, the polyimide resin can be stored in the form of the polyimide solution obtained after the polymerization reaction, and the polyimide solution can be directly used for the preparation of polyimide films.

[0055] According to the present invention, in the preparation method of the above polyimide resin, the preparation method of the aromatic diamine monomer represented by formula (1) can be selected within a relatively wide range. Preferably, the preparation method of the aromatic diamine monomer represented by formula (1) includes: performing a reduction reaction on the compound represented by formula (B) in the presence of a reducing agent to obtain the aromatic diamine monomer represented by formula (1);

[0056] Formula (B) Wherein each R3’ independently selects one or more of H, C1-C6 alkyl, and nitro, and at least two R3’ are nitro.

[0057] According to the present invention, in order for the reaction to proceed smoothly, preferably, the reducing agent is selected from stannous chloride and / or iron powder. Among them, stannous chloride can be provided in the form of its hydrate.

[0058] Preferably, relative to 1 mmol of the compound represented by formula (B), the dosage of the reducing agent is 4-10 mmol, preferably 6-8 mmol, for example, it can be values such as 6 mmol, 6.5 mmol, 7 mmol, and 8 mmol and the ranges between any of these values.

[0059] According to the present invention, in order to provide a suitable reaction environment and enable each material to fully contact and react, preferably, the solvent for the reduction reaction is one or more of a mixed solvent of water and C1-C10 alkyl alcohol with a volume ratio of 1:6-12, preferably one or more of a mixed solvent of water and C1-C10 alkyl alcohol with a volume ratio of 1:8-10 (for example, it can be values such as 1:8, 1:8.5, 1:9, and 1:10 and the ranges between any of these values). Preferably, the C1-C10 alkyl alcohol is selected from one or more of methanol, ethanol, isopropanol, and n-butanol.

[0060] According to a preferred embodiment of the present invention, the solvent for the reduction reaction is selected from a water / ethanol mixed solvent with a volume ratio of 1:8-10.

[0061] Preferably, relative to 1 mmol of the compound represented by formula (B), the dosage of the solvent for the reduction reaction is 1-5 mL, preferably 2-4 mL, for example, it can be values such as 2 mL, 2.5 mL, 3 mL, and 4 mL and the ranges between any of these values.

[0062] According to the present invention, in order to achieve a better reduction reaction effect, preferably, the conditions of the reduction reaction include: a temperature of 40 - 100 °C and a time of 2 - 16 h; more preferably, the conditions of the reduction reaction include: a temperature of 50 - 80 °C (for example, it can be values such as 50 °C, 60 °C, 70 °C, and 80 °C and ranges between any of these values), and a time of 4 - 10 h (for example, it can be values such as 4 h, 5 h, 8 h, and 10 h and ranges between any of these values).

[0063] According to the present invention, in order to reduce the generation of impurities and by-products, preferably, the reduction reaction is carried out in an inert gas atmosphere. Among them, the inert gas can be, for example, nitrogen and / or argon.

[0064] According to the present invention, after the reduction reaction is completed, the reaction solution can also be post-treated. The post-treatment method can be selected within a relatively wide range. Preferably, the post-treatment method of the reduction reaction includes: rotary evaporation of part of the solvent from the reaction solution and adding it to water, adjusting the pH to neutral or weakly alkaline (for example, adjusting the pH with an aqueous sodium hydroxide solution with a concentration of 2 - 10 wt%), filtering, and after rotary evaporation of the solvent from the obtained filtrate, recrystallization (for example, recrystallization with ethanol or methanol) to obtain the aromatic diamine monomer shown in formula (1).

[0065] According to the present invention, in the above method for preparing the polyimide resin, it may further include a method for preparing the compound shown in formula (B). The method for preparing the compound shown in formula (B) can be selected within a relatively wide range. Preferably, the method for preparing the compound shown in formula (B) includes: subjecting the compound shown in formula (A1) to a first contact reaction with the compound shown in formula (A2) to obtain the compound shown in formula (B);

[0066] Formula (A1) Formula (A2) Among them, the selection of each R3’ is as described above, and X1 is selected from one or more of halogens.

[0067] According to the present invention, in order to obtain a higher reaction yield, preferably, relative to 1 mmol of the compound shown in formula (A1), the amount of the compound shown in formula (A2) used is 0.6 - 1.5 mmol, preferably 0.8 - 1.2 mmol, for example, it can be values such as 0.8 mmol, 1 mmol, 1.1 mmol, and 1.2 mmol and ranges between any of these values.

[0068] According to the present invention, in order to make each material contact and react more fully, preferably, the solvent for the first contact reaction is selected from one or more of dichloromethane, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0069] Preferably, relative to 1 mmol of the compound represented by formula (A1), the amount of the solvent for the first contact reaction is 1 - 5 mL, preferably 2 - 4 mL, and can be, for example, numerical values such as 2 mL, 3 mL, 3.5 mL, and 4 mL, and ranges between any of these numerical values.

[0070] According to the present invention, in order for the first contact reaction to proceed better, preferably, the conditions for the first contact reaction include: a temperature of 10 - 100 °C and a time of 1 - 36 h; more preferably, the conditions for the first contact reaction include: a temperature of 20 - 80 °C (which can be, for example, numerical values such as 20 °C, 25 °C, 50 °C, and 80 °C, and ranges between any of these numerical values), and a time of 2 - 24 h (which can be, for example, numerical values such as 2 h, 12 h, 20 h, and 24 h, and ranges between any of these numerical values).

[0071] According to the present invention, in order to reduce the generation of impurities and by-products, preferably, the first contact reaction is carried out in an inert gas atmosphere. Among them, the inert gas can be, for example, nitrogen and / or argon.

[0072] According to the present invention, after the first contact reaction is completed, the reaction solution can also be post-treated. The post-treatment method can be selected within a relatively wide range. Preferably, the post-treatment method for the first contact reaction includes: removing the solvent from the reaction solution by rotary evaporation and then recrystallizing (for example, recrystallizing with methanol) to obtain the compound represented by formula (B).

[0073] According to the present invention, in the above method for preparing the polyimide resin, a method for preparing the compound represented by formula (A1) can also be included. Preferably, the method for preparing the compound represented by formula (A1) includes: carrying out a second contact reaction between R1OH and X2-R2-OH in the presence of a basic reagent to obtain the compound represented by formula (A1), wherein X2 is selected from one or more of halogens.

[0074] According to the present invention, in order to obtain better reaction results, preferably, relative to 1 mmol of R1OH, the amount of X2-R2-OH is 0.6 - 1.5 mmol, preferably 0.8 - 1.2 mmol, and can be, for example, numerical values such as 0.8 mmol, 1 mmol, 1.1 mmol, and 1.2 mmol, and ranges between any of these numerical values.

[0075] According to the present invention, in order to obtain better reaction effects, preferably, the basic reagent is selected from one or more of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, and preferably sodium hydroxide and / or potassium hydroxide.

[0076] Preferably, the basic reagent is provided in the form of a solution, and the concentration of the solution of the basic reagent is 0.04-1 g / mL, preferably 0.06-0.08 g / mL. For example, it can be values such as 0.06 g / mL, 0.067 g / mL, 0.073 g / mL, and 0.08 g / mL and the ranges between any of these values. The solvent for dissolving the basic reagent can be selected within a relatively wide range. For example, it can be water.

[0077] Preferably, relative to 1 mmol of R1OH, the amount of the solution of the basic reagent used is 0.5-2 mL, preferably 0.8-1.5 mL. For example, it can be values such as 0.8 mL, 1 mL, 1.2 mL, and 1.5 mL and the ranges between any of these values.

[0078] According to the present invention, in order to provide a suitable reaction environment, preferably, the solvent for the second contact reaction is selected from one or more of C1-C10 alkyl alcohols, preferably ethanol and / or methanol.

[0079] Preferably, relative to 1 mmol of R1OH, the amount of the solvent for the second contact reaction used is 1-8 mL, preferably 3-6 mL. For example, it can be values such as 3 mL, 4 mL, 5 mL, and 6 mL and the ranges between any of these values.

[0080] According to the present invention, in order to achieve a better reaction effect, preferably, the conditions for the second contact reaction include: the temperature is 40-100 °C, and the time is 8-40 h; more preferably, the conditions for the second contact reaction include: the temperature is 50-80 °C (for example, it can be values such as 50 °C, 60 °C, 70 °C, and 80 °C and the ranges between any of these values), and the time is 12-36 h (for example, it can be values such as 12 h, 24, 30 h, and 36 h and the ranges between any of these values).

[0081] According to the present invention, in order to reduce the generation of impurities and by-products, preferably, the second contact reaction is carried out in an inert gas atmosphere. Among them, the inert gas can be, for example, nitrogen and / or argon.

[0082] According to the present invention, after the second contact reaction is completed, the reaction solution can also be post-treated. The post-treatment method can be selected within a relatively wide range. Preferably, the post-treatment method for the second contact reaction includes: adding the reaction solution to water, stirring and filtering, and then recrystallizing the filter cake (for example, recrystallizing with methanol) to obtain the compound shown in formula (A1).

[0083] The third aspect of the present invention provides a polyimide film prepared from the above polyimide resin.

[0084] According to the present invention, the polyimide film is obtained by doctor blading and heat treatment of a polyimide solution. Among them, the polyimide solution can be the polyimide solution obtained by the above polymerization reaction, or can be the solution after further chemical imidization (for example, reacting with acetic anhydride, pyridine, triethylamine, etc.) or solution imidization (for example, reacting with quinoline, isoquinoline).

[0085] Preferably, the heat treatment can adopt continuous heating heat treatment or stepwise heating heat treatment, for example.

[0086] Preferably, the conditions of the continuous heating heat treatment include: the heating rate is 3 - 25 °C, the temperature is 250 - 350 °C, and the time is 5 - 50 min. More preferably, the conditions of the continuous heating heat treatment include: the heating rate is 5 - 20 °C / min (for example, it can be values such as 5 °C / min, 8 °C / min, 10 °C / min, and 20 °C / min and the ranges between any of these values), the temperature is 280 - 320 °C (for example, it can be values such as 280 °C, 290 °C, 300 °C, and 320 °C and the ranges between any of these values), and the time is 10 - 30 min (for example, it can be values such as 10 min, 15 min, 20 min, and 30 min and the ranges between any of these values). Among them, the starting temperature of the continuous heating heat treatment is usually 10 - 40 °C.

[0087] Preferably, the conditions of the stepwise heating heat treatment include: 70 - 90 °C, 0.8 - 1.2 h; 130 - 150 °C, 0.8 - 1.2 h; 210 - 230 °C, 0.4 - 1.2 h; 290 - 310 °C, 0.4 - 0.6 h. Among them, the starting temperature of the stepwise heating heat treatment is usually 10 - 40 °C.

[0088] According to the present invention, preferably, the heat treatment is carried out under vacuum conditions.

[0089] The fourth aspect of the present invention provides an application of the above polyimide film in the field of high - frequency low - dielectric films. For example, its application in flexible circuit boards and high - frequency microwave communications.

[0090] The present invention polymerizes an aromatic diamine monomer shown in formula (1) with a specific structure, an optional second aromatic diamine monomer, and an aromatic dianhydride monomer to obtain a polyimide resin containing flexible side chains. This polyimide resin has excellent dielectric properties, can simultaneously take into account the characteristics of high - frequency low dielectric constant and low dielectric loss, and has good mechanical properties. The polyimide film made therefrom has broad application prospects.

[0091] The present invention will be described in detail below through examples.

[0092] In the following examples, the devices used are all conventional devices in the art, the operations adopted are all conventional operations in the art, and the raw materials, reagents, etc. used can all be obtained through commercial purchase. Among them, p-phenylphenol and 6-chloro-1-hexanol were purchased from Shanghai Titan Technology Co., Ltd. 3,3’,4,4’-Biphenyltetracarboxylic dianhydride and 4,4’-diaminodiphenyl ether were purchased from Changzhou Yangguang Pharmaceutical Co., Ltd.

[0093] Preparation Example 1

[0094] This preparation example is used to illustrate the preparation of the aromatic diamine monomer shown in formula (1-1), and it is used as a representative aromatic diamine monomer shown in formula (1) in the subsequent examples.

[0095]

[0096] (1) Under a nitrogen atmosphere, 25 mmol of p-phenylphenol and 20 mL of a 0.073 g / mL aqueous potassium hydroxide solution were added to 100 mL of ethanol, and the reaction was carried out at 50 °C for 30 min. Then, 25 mmol of 6-chloro-1-hexanol was added dropwise to the system, and the reaction was carried out at 70 °C for 24 h. After the reaction was completed, the reaction solution was added to water, stirred and filtered, and the filter cake was recrystallized with methanol to obtain the compound shown in formula (A1-1).

[0097] (2) Under a nitrogen atmosphere, 20 mmol of the compound shown in formula (A1-1) and 20 mmol of the compound shown in formula (A2-1) were added to 100 mL of dichloromethane, and the reaction was carried out at 25 °C for 24 h. After the reaction was completed, dichloromethane was removed by rotary evaporation, and the obtained yellow powder was recrystallized with methanol to obtain the compound shown in formula (B-1).

[0098] (3) Under a nitrogen atmosphere, 20 mmol of the compound shown in formula (B-1) and 130 mmol of stannous chloride were added to 110 mL of a mixed solvent of water / ethanol (the volume ratio of water to ethanol is 1:10), and the reaction was carried out at 70 °C for 6 h. After the reaction was completed, part of the solvent was removed by rotary evaporation from the reaction solution, and then it was added to 400 mL of water. The pH was adjusted to neutral with a 5 wt% aqueous sodium hydroxide solution, and then filtered. The obtained filtrate was concentrated to remove the solvent and then recrystallized with ethanol to obtain the aromatic diamine monomer shown in formula (1-1).

[0099] The Fourier transform infrared spectrum of the aromatic diamine monomer shown in formula (1-1) is as Figure 1 shown.

[0100] The nuclear magnetic resonance spectrum of the aromatic diamine monomer shown in formula (1-1) is as Figure 2 shown.

[0101] Example 1

[0102] (1) Add 20 mmol of the aromatic diamine monomer shown in formula (1-1) to 4 mL of N-methylpyrrolidone. After dissolution, add 20 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 5 mL of N-methylpyrrolidone, and react at 0 °C for 24 h to obtain a polyimide resin solution with a solid content of 15 wt% (intrinsic viscosity is 1.38 dL / g).

[0103] (2) Knife-coat the polyimide resin solution on a glass substrate, and perform stepwise temperature-raising heat treatment from room temperature under vacuum conditions. The process of stepwise temperature-raising heat treatment is as follows: 80 °C for 1 h; 140 °C for 1 h; 220 °C for 1 h; 300 °C for 0.5 h. After the heat treatment, a polyimide film is obtained.

[0104] Example 2

[0105] (1) Add 20 mmol of the aromatic diamine monomer shown in formula (1-1) to 5 mL of N,N-dimethylacetamide. After dissolution, add 20 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 6 mL of N,N-dimethylacetamide, and react at 5 °C for 20 h to obtain a polyimide resin solution with a solid content of 10 wt% (intrinsic viscosity is 0.83 dL / g).

[0106] (2) Knife-coat the polyimide resin solution on a glass substrate, and perform stepwise temperature-raising heat treatment from room temperature under vacuum conditions. The process of stepwise temperature-raising heat treatment is as follows: 70 °C for 1.2 h; 150 °C for 1 h; 210 °C for 0.8 h; 300 °C for 0.5 h. After the heat treatment, a polyimide film is obtained.

[0107] Example 3

[0108] (1) Add 20 mmol of the aromatic diamine monomer shown in formula (1-1) to 2 mL of dimethyl sulfoxide. After dissolution, add 20 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2.5 mL of dimethyl sulfoxide, and react at -5 °C for 30 h to obtain a polyimide resin solution with a solid content of 20 wt% (intrinsic viscosity is 1.14 dL / g).

[0109] (2) Knife-coat the polyimide resin solution on a glass substrate, and perform continuous temperature-raising treatment from room temperature under vacuum conditions. Raise the temperature to 300 °C at a heating rate of 10 °C / min and heat-treat for 20 min. After the heat treatment, a polyimide film is obtained.

[0110] Example 4

[0111] (1) 16 mmol of the aromatic diamine monomer represented by formula (1-1) and 4 mmol of 4,4'-diaminodiphenyl ether were added to 3 mL of N,N-dimethylformamide. After dissolution, 20 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4 mL of N,N-dimethylformamide were added, and the reaction was carried out at 5 °C for 20 h to obtain a polyimide resin solution with a solid content of 15 wt% (intrinsic viscosity: 1.57 dL / g).

[0112] (2) The polyimide resin solution was spin-coated on a glass substrate, and stepwise heat treatment was carried out from room temperature under vacuum. The process of stepwise heat treatment was as follows: 80 °C for 1 h; 150 °C for 1 h; 220 °C for 1 h; 300 °C for 0.5 h. After the heat treatment, a polyimide film was obtained.

[0113] Example 5

[0114] According to the method of Example 4, except that in step (1), the amount of the aromatic diamine monomer represented by formula (1-1) was 12 mmol, and the amount of 4,4'-diaminodiphenyl ether was 8 mmol, and finally a polyimide resin solution with a solid content of 15 wt% (intrinsic viscosity: 1.74 dL / g) was prepared.

[0115] Example 6

[0116] According to the method of Example 4, except that in step (1), the amount of the aromatic diamine monomer represented by formula (1-1) was 8 mmol, and the amount of 4,4'-diaminodiphenyl ether was 12 mmol, and finally a polyimide resin solution with a solid content of 15 wt% (intrinsic viscosity: 2.02 dL / g) was prepared.

[0117] Example 7

[0118] According to the method of Example 4, except that in step (1), the amount of the aromatic diamine monomer represented by formula (1-1) was 4 mmol, and the amount of 4,4'-diaminodiphenyl ether was 16 mmol, and finally a polyimide resin solution with a solid content of 15 wt% (intrinsic viscosity: 2.38 dL / g) was prepared.

[0119] Comparative Example 1

[0120] According to the method of Example 1, except that in step (1), the aromatic diamine monomer represented by formula (1-1) was replaced with 4,4'-diaminodiphenyl ether, and finally a polyimide resin solution with a solid content of 15 wt% (intrinsic viscosity: 4.56 dL / g) was prepared.

[0121] Test Example

[0122] The polyimide films prepared in Examples 1-7 and Comparative Example 1 were tested, and the specific test methods are as follows.

[0123] Dielectric constant and dielectric loss: The relative dielectric constant and loss tangent of the thin film were tested at 17 - 40 GHz using a split cylinder resonator. The test conditions were a temperature of (25 ± 2) °C and a relative humidity of (50 ± 5)%. The test results are shown in Tables 1 and 2.

[0124] Mechanical property test: The tensile strength, elongation at break, and Young's modulus of the samples were tested according to the method in "GB / T 1040.1 - 2018 Plastics - Determination of tensile properties - Part 1: General principles". The test results are shown in Table 3.

[0125] Table 1

[0126]

[0127] As can be seen from Table 1, in Examples 1 - 7 adopting the technical solution of the present invention, the dielectric constants at various frequencies are mostly better than those of Comparative Example 1. Among them, the dielectric constant of Example 2 at 40 GHz is as low as 2.77. From Examples 4 - 7, it can be seen that as the amount of the aromatic diamine monomer shown in formula (1 - 1) decreases, the dielectric constant begins to increase.

[0128] Table 2

[0129]

[0130] As can be seen from Table 2, in Examples 1 - 7 adopting the technical solution of the present invention, the dielectric losses at various frequencies are mostly better than those of Comparative Example 1. Among them, the dielectric constant of Example 3 at 40 GHz is as low as 0.47×10 -2 . From Examples 4 - 7, it can be seen that as the amount of the aromatic diamine monomer shown in formula (1 - 1) decreases, the dielectric loss begins to increase.

[0131] Table 3

[0132]

[0133]

[0134] As can be seen from Table 3, Examples 1 - 7 adopting the technical solution of the present invention have good mechanical properties.

[0135] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A polyimide resin, characterized in that, The polyimide resin contains a structural unit provided by an aromatic diamine monomer represented by formula (1). Wherein, R1 is selected from one or more of biphenyl-based groups; R2 is selected from one or more of a linking bond and C1-C20 alkylene groups; each R3 is independently selected from one or more of H, C1-C6 alkyl groups, and amino groups, and at least two R3 are amino groups.

2. The polyimide resin according to claim 1, wherein R1 is selected from one or more of biphenylyl and terphenylyl; R2 is selected from one or more of a linking bond and C1-C12 alkylene groups; each R3 is independently selected from one or more of H, C1-C3 alkyl groups, and amino groups, and at least two R3 are amino groups; Preferably, R1 is selected from one or more of; R2 is selected from one or more of a linking bond, methylene, ethylene, n-propylene, isopropyl, n-butylene, isobutylene, n-pentylene, isopentylene, n-hexylene, n-heptylene, n-octylene, n-nonylene, n-decylene, n-undecylene and n-dodecylene; each R3 is independently selected from one or more of H, methyl, ethyl, n-propyl, isopropyl and amino, and at least two R3s are amino; Preferably, the aromatic diamine monomer represented by formula (1) is selected from one or more of; More preferably, the aromatic diamine monomer represented by the formula (1) is selected from one or more of the compounds represented by the following formula:

3. The polyimide resin according to claim 1 or 2, wherein, The polyimide resin further contains a structural unit provided by an aromatic dianhydride monomer and optionally a structural unit provided by a second aromatic diamine monomer; Preferably, the aromatic dianhydride monomer is selected from or one or more thereof; wherein, A and B are each independently selected from a benzene ring, cyclobutane, cyclohexane, and or one or more thereof; R 1 is selected from a linking bond, an oxy group, or one or more thereof; R 2 , R 3 , R 4 and R 5 are each independently selected from C1-C6 alkylene groups, or one or more thereof; More preferably, the aromatic dianhydride monomer is selected from one or more of the compounds represented by the following formula: Preferably, the second aromatic diamine monomer is selected from one or more of; wherein each R 7 is independently selected from one or more of H, amino, hydroxyl, carboxyl, trifluoromethyl, halogen, and C1-C6 alkyl, and at least one R 7 is amino; each R 8 is independently selected from one or more of H, amino, hydroxyl, carboxyl, trifluoromethyl, halogen, and C1-C6 alkyl, and at least one R 8 is amino; R 6 is selected from a linking bond, an oxy group, C1-C6 alkylene, one or more of; R 9 , R 10 , R 11 , R 12 and R 13 are each independently selected from one or more of; More preferably, the second aromatic diamine monomer is selected from one or more of the compounds represented by the following formula:

4. The polyimide resin according to claim 3, wherein, Relative to 1 mmol of the structural unit provided by the aromatic dianhydride monomer, the total amount of the structural unit provided by the aromatic diamine monomer represented by formula (1) and optionally the structural unit provided by the second aromatic diamine monomer is 0.95 - 1.05 mmol, preferably 0.98 - 1.02 mmol; And / or, relative to 1 mmol of the structural unit provided by the aromatic diamine monomer represented by formula (1), the amount of the structural unit provided by the second aromatic diamine monomer is 0 - 4 mmol, preferably 0 - 2 mmol; And / or, the intrinsic viscosity of the polyimide resin is 0.5 - 2.5 dL / g, preferably 0.8 - 1.4 dL / g.

5. The preparation method of the polyimide resin according to any one of claims 1-4, characterized in that, The method includes: polymerizing a diamine monomer and a dianhydride monomer to obtain a polyimide resin, wherein the diamine monomer includes the aromatic diamine monomer represented by formula (1).

6. The method according to claim 5, wherein, The diamine monomer is the aromatic diamine monomer represented by formula (1) and optionally a second aromatic diamine monomer, and the dianhydride monomer is an aromatic dianhydride monomer; Preferably, relative to 1 mmol of the aromatic dianhydride monomer, the total amount of the aromatic diamine monomer represented by formula (1) and optionally the second aromatic diamine monomer is 0.95 - 1.05 mmol, preferably 0.98 - 1.02 mmol; Preferably, relative to 1 mmol of the aromatic diamine monomer represented by formula (1), the amount of the second aromatic diamine monomer is 0 - 4 mmol, preferably 0 - 2 mmol; Preferably, the solvent for the polymerization reaction is selected from one or more of aprotic polar solvents, preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-vinylpyrrolidone, and dimethyl sulfoxide; Preferably, the amount of the solvent for the polymerization reaction is such that the solid content of the solution is 4 - 25 wt%, preferably 6 - 20 wt%; Preferably, the conditions for the polymerization reaction include: a temperature of -10°C to 30°C and a time of 10 - 40 h; more preferably, the conditions for the polymerization reaction include: a temperature of -5°C to 10°C and a time of 20 - 30 h.

7. The method according to claim 5 or 6, wherein The preparation method of the aromatic diamine monomer shown in formula (1) includes: carrying out a reduction reaction on the compound shown in formula (B) in the presence of a reducing agent to obtain the aromatic diamine monomer shown in formula (1); Formula (B) wherein each R3' is independently selected from one or more of H, C1-C6 alkyl, and nitro, and at least two R3' are nitro.

8. The method according to claim 7, wherein, The reducing agent is selected from stannous chloride and / or iron powder; And / or, relative to 1 mmol of the compound shown in formula (B), the dosage of the reducing agent is 4 - 10 mmol, preferably 6 - 8 mmol; And / or, the solvent for the reduction reaction is a mixed solvent of water and C1 - C10 alkyl alcohol with a volume ratio of 1:6 - 12, preferably one or more of the mixed solvents of water and C1 - C10 alkyl alcohol with a volume ratio of 1:8 - 10; preferably, the C1 - C10 alkyl alcohol is selected from one or more of methanol, ethanol, isopropanol and n - butanol; And / or, relative to 1 mmol of the compound shown in formula (B), the dosage of the solvent for the reduction reaction is 1 - 5 mL, preferably 2 - 4 mL; And / or, the conditions for the reduction reaction include: the temperature is 40 - 100 °C and the time is 2 - 16 h; more preferably, the conditions for the reduction reaction include: the temperature is 50 - 80 °C and the time is 4 - 10 h.

9. A polyimide film prepared from the polyimide resin according to any one of claims 1 - 4.

10. The application of the polyimide film according to claim 9 in the field of high - frequency low - dielectric films.

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