Large-volume side chain ester-containing diamine monomer and preparation method thereof, polyimide resin and polyimide film and preparation method and application thereof

Abstract

The invention provides a large-volume side chain ester-containing diamine monomer and a preparation method thereof, polyimide resin and a polyimide film as well as a preparation method and application thereof, and relates to the technical field of high polymer materials. According to the large-volume side chain ester-containing diamine monomer provided by the invention, the diamine monomer is designed, an ester group and a large-steric-hindrance side group are introduced at the same time, and polyimide with excellent dielectric properties, high solubility and high elongation at break can be obtained by reacting the obtained diamine monomer with a dianhydride monomer. The invention provides the polyimide resin, and the polyimide resin provided by the invention has excellent dielectric properties and mechanical properties, has good solubility in organic solvents, is convenient to process, and can be used for conveniently preparing a polyimide film with excellent properties. The obtained polyimide film is used as an interlayer dielectric insulating material in the field of 5G communication, such as the field of high-frequency flexible copper-clad plate materials, and has an important application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a bulky side-chain ester-containing diamine monomer and a preparation method thereof, a polyimide resin and a polyimide film, and a preparation method and application thereof. Background Art

[0002] Polyimide (PI) is a special engineering plastic with excellent performance. It has high thermal stability, high mechanical strength, high insulation, low moisture absorption, radiation resistance and other excellent properties. It is favored by aerospace, electronic information, national defense and military industries, and is widely used as a dielectric material in printed circuit boards and integrated circuits. However, with the development of communication technology, the miniaturization and high integration of equipment have put forward higher requirements for the loss and miniaturization of dielectric materials at high frequencies. How to reduce the delay and loss in the signal transmission process has become a key issue of concern in the industry. Therefore, the development of new polyimide materials with excellent dielectric properties at high frequencies is a major challenge. At present, existing polyimide films generally have defects of high dielectric constant and dielectric loss.

[0003] As a means of reducing the dielectric constant and dielectric loss of polyimide, it is known to introduce ester groups or fluorine atoms into diamine or dianhydride monomers. The above strategy can improve the dielectric properties of polyimide to a certain extent, but the resulting polymer has poor processing performance (poor solubility and difficulty in direct processing into film), and the mechanical properties (elongation at break) still need to be improved. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a bulky side chain ester-containing diamine monomer and a preparation method thereof, a polyimide resin and a polyimide film and a preparation method and application thereof. The bulky side chain ester-containing diamine monomer provided by the present invention reacts with a dianhydride monomer to obtain a polyimide having excellent dielectric properties, good processability (good solubility) and high elongation at break.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a bulky side chain ester-containing diamine monomer having a structure shown in Formula I:

[0007]

[0008] In Formula I, R 1 , R 2 , R 3 and R 4 are independently selected from hydrogen, fluorine, alkyl, haloalkyl, aryl or haloaryl.

[0009] The present invention provides a method for preparing a bulky side chain ester-containing diamine monomer as described in the above technical solution, comprising the following steps:

[0010] A substituted diphenol, a nitrobenzoyl chloride compound, an organic solvent and a base are mixed for esterification reaction to obtain an intermediate; the substituted diphenol, the nitrobenzoyl chloride compound and the intermediate have structures shown in Formula II, Formula III and Formula IV respectively;

[0011] The intermediate is subjected to a hydrogenation reaction under the action of a catalyst to obtain the bulky side chain ester-containing diamine monomer;

[0012]

[0013] Preferably, the base comprises one or more of triethylamine, pyridine, potassium carbonate and potassium dihydrogen phosphate; the molar ratio of the substituted diphenol, nitrobenzoyl chloride compound and the base is 1:(2-2.5):(2-3)); the temperature of the esterification reaction is 0-30°C and the time is 2-6h.

[0014] Preferably, the catalyst comprises one or more of Raney nickel, Raney cobalt and Pd / C; the hydrogenation reaction is carried out under a hydrogen atmosphere, the temperature of the hydrogenation reaction is 25 to 80° C., the pressure is 0.9 to 1.5 MPa, and the time is 8 to 12 h.

[0015] The present invention provides a polyimide resin having a structure shown in Formula V:

[0016]

[0017] In Formula V, n is an integer greater than 100, R 1 , R 2 , R 3 and R 4 are independently selected from hydrogen, fluorine, alkyl, haloalkyl, aryl or haloaryl, for

[0018] The present invention provides a method for preparing the polyimide resin described in the above technical solution, comprising the following steps:

[0019] A diamine monomer, a dianhydride monomer and an organic solvent are mixed for polycondensation to obtain a polyamic acid; the diamine monomer is the bulky side chain ester-containing diamine monomer described in the above technical solution, and the dianhydride monomer is pyromellitic anhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-dibenzophenone tetracarboxylic anhydride or bisphenol A diether dianhydride;

[0020] The polyamic acid is imidized under the action of an alkali catalyst and a dehydrating agent to obtain the polyimide resin.

[0021] Preferably, the molar ratio of the diamine monomer, the dianhydride monomer, the base catalyst and the dehydrating agent is (1-1.05):1:(0.05-0.2):(0.1-0.2); the temperature of the polycondensation reaction is 20-30°C, and the time is 12-36h; the temperature of the imidization is 50-100°C, and the time is 1-5h.

[0022] The present invention provides a polyimide film, wherein the film-forming material of the polyimide film is the polyimide resin described in the above technical solution.

[0023] The present invention provides a method for preparing the polyimide film described in the above technical solution, comprising the following steps:

[0024] The polyimide film is obtained by coating the polyimide resin solution on a substrate and then removing the solvent.

[0025] The present invention provides the use of the polyimide resin described in the above technical solution or the polyimide film described in the above technical solution as an interlayer dielectric insulating material in an electronic communication device.

[0026] The present invention provides a bulky side chain ester-containing diamine monomer having a structure shown in Formula I. The present invention designs the diamine monomer, and simultaneously introduces an ester group and a bulky sterically hindered side group (a structural portion between two ester groups in the structure shown in Formula I). ​​The obtained diamine monomer reacts with a dianhydride monomer to obtain a polyimide having excellent dielectric properties (low dielectric loss and dielectric constant), high solubility, and high elongation at break.

[0027] The present invention provides a polyimide resin having a structure shown in Formula V. The polyimide resin provided by the present invention has low dielectric constant and low dielectric loss and excellent mechanical properties, and has good solubility in organic solvents, is easy to process, and can conveniently prepare a polyimide film with excellent performance to meet the needs of existing high-frequency and high-speed substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The hydrogen nuclear magnetic resonance spectrum of the diamine monomer prepared in Example 1;

[0029] Figure 2 This is the carbon NMR spectrum of the diamine monomer prepared in Example 1. DETAILED DESCRIPTION

[0030] The present invention provides a bulky side chain ester-containing diamine monomer having a structure shown in Formula I:

[0031]

[0032] In Formula I, R 1 , R2 , R 3 and R 4 independently selected from hydrogen, fluorine, alkyl, haloalkyl, aryl or haloaryl (i.e., R 1 , R 2 , R 3 and R 4 are the same or different).

[0033] In the present invention, the number of carbon atoms in the alkyl and halogenated alkyl groups is preferably 1 to 2, and the halogen in the halogenated alkyl group is preferably fluorine; the aryl group is preferably phenyl or naphthyl, and the halogen in the halogenated aryl group is preferably fluorine.

[0034] As an embodiment of the present invention, the R 1 , R 2 , R 3 and R 4 All are hydrogen.

[0035] The present invention designs a diamine monomer and simultaneously introduces an ester group and a large sterically hindered side group. The obtained diamine monomer reacts with a dianhydride monomer to obtain a polyimide having excellent dielectric properties (low dielectric loss and dielectric constant), high solubility and high elongation at break.

[0036] The present invention provides a method for preparing a bulky side chain ester-containing diamine monomer as described in the above technical solution, comprising the following steps:

[0037] A substituted diphenol, a nitrobenzoyl chloride compound, an organic solvent and a base are mixed for esterification reaction to obtain an intermediate; the substituted diphenol, the nitrobenzoyl chloride compound and the intermediate have structures shown in Formula II, Formula III and Formula IV respectively;

[0038] The intermediate is subjected to a hydrogenation reaction under the action of a catalyst to obtain the bulky side chain ester-containing diamine monomer;

[0039]

[0040]

[0041] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known in the art.

[0042] The reaction formula involved in preparing the bulky side chain ester-containing diamine monomer of the present invention is as follows:

[0043]

[0044] The detailed description is given below.

[0045] The present invention mixes substituted diphenol, nitrobenzoyl chloride compound, organic solvent and base for esterification reaction to obtain an intermediate; the substituted diphenol, nitrobenzoyl chloride compound and intermediate have structures shown in formula II, formula III and formula IV respectively. The present invention has no special requirements on the source of the nitrobenzoyl chloride compound, and it can be prepared by using commercial products or methods well known to those skilled in the art.

[0046] In the present invention, the base is an organic base and / or an inorganic base, preferably including one or more of triethylamine, pyridine, potassium carbonate and potassium dihydrogen phosphate. In the present invention, the molar ratio of the substituted diphenol, nitrobenzoyl chloride compound and the base is preferably 1:(2-2.5):(2-3), and can be 1:2:2. In the present invention, the organic solvent (referred to as the first organic solvent) preferably includes one or more of toluene, tetrahydrofuran, dichloromethane, N,N-dimethylformamide and acetonitrile. The present invention has no special requirements for the amount of the first organic solvent, as long as it can fully dissolve the substituted diphenol and nitrobenzoyl chloride compound.

[0047] In the present invention, the method of mixing the substituted diphenol, the nitrobenzoyl chloride compound, the first organic solvent and the base is preferably:

[0048] Mixing the nitrobenzoyl chloride compound and a first organic solvent to obtain a nitrobenzoyl chloride compound solution;

[0049] Mixing the substituted diphenol, a base and a first organic solvent to obtain a substituted diphenol / base mixed solution;

[0050] The nitrobenzoyl chloride compound solution is cooled to 0° C., and the substituted diphenol / alkali mixed solution is added dropwise thereto.

[0051] In the present invention, the temperature of the esterification reaction is preferably 0-30°C. In the embodiment of the present invention, the temperature of the esterification reaction is room temperature. The time of the esterification reaction is preferably 2-6 hours, which can be 2, 3, 4, 5 or 6 hours. The time of the esterification reaction is calculated from the completion of the dropwise addition of the substituted diphenol / alkali mixed solution. In the present invention, the esterification reaction is preferably carried out under stirring.

[0052] After the esterification reaction is completed, the present invention preferably dilutes the obtained esterification reaction liquid, adds methanol thereto, filters, and then rinses the obtained solid phase with methanol to obtain the intermediate. In the present invention, the reagent used for the dilution is preferably the same as the first organic solvent used in the esterification reaction; after the addition of methanol, preferably stir at room temperature for 30 minutes to precipitate the product.

[0053] After obtaining the intermediate, the present invention conducts a hydrogenation reaction on the intermediate under the action of a catalyst to obtain the bulky side chain ester-containing diamine monomer.

[0054] In the present invention, the catalyst preferably includes one or more of Raney nickel, Raney cobalt and Pd / C, and the mass of the catalyst is preferably 5-10% of the mass of the intermediate. In the present invention, the hydrogenation reaction is preferably carried out under a hydrogen atmosphere, the temperature of the hydrogenation reaction is preferably 25-80°C, and can be 25, 30, 40, 50, 60, 70 or 80°C, the pressure is preferably 0.9-1.5MPa, and can be 0.9, 1 or 1.5MPa, and the time is preferably 8-12h, and can be 8, 9, 10, 11 or 12h.

[0055] In the present invention, the specific operation of the hydrogenation reaction is preferably: adding the intermediate, the catalyst and the second organic solvent into a high-pressure reactor, introducing hydrogen, and performing a hydrogenation reaction. In the present invention, the second organic solvent preferably includes one or more of toluene, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide and acetonitrile. The present invention has no special requirements for the amount of the second organic solvent, as long as it can fully dissolve the intermediate.

[0056] After the hydrogenation reaction is completed, the present invention preferably filters the obtained reaction solution through diatomaceous earth to remove the catalyst, precipitates it in methanol and rinses it with methanol, redissolves the obtained product in ethyl acetate, then adds methanol again to precipitate the product, and then filters and dries it to obtain the bulky side chain ester-containing diamine monomer.

[0057] The invention uses cheap phenyl-substituted bisphenol A derivatives to synthesize a bulky side-chain ester-containing diamine monomer through esterification and hydrogenation (ie, hydrogenation reaction). The synthesis steps are simple and the product purity is high (99.5%).

[0058] The present invention provides a polyimide resin having a structure shown in Formula V:

[0059]

[0060] In Formula V, n is an integer greater than 100, R 1 , R 2 , R 3 and R 4 are independently selected from hydrogen, fluorine, alkyl, haloalkyl, aryl or haloaryl, for

[0061] In the present invention, R in Formula V 1 , R 2 , R 3 and R 4With R in Formula Ⅰ 1 , R 2 , R 3 and R 4 Keep the same, no further description is given here. In the present invention, "*" represents a connection site.

[0062] The polyimide resin provided by the present invention has good dielectric properties (low dielectric constant and low dielectric loss) and excellent mechanical properties, and has good solubility in organic solvents (such as N-methylpyrrolidone), is easy to process, and can conveniently prepare a polyimide film with excellent performance.

[0063] The present invention provides a method for preparing the polyimide resin described in the above technical solution, comprising the following steps:

[0064] A diamine monomer, a dianhydride monomer and an organic solvent are mixed for polycondensation to obtain a polyamic acid; the diamine monomer is the bulky side chain ester-containing diamine monomer described in the above technical solution, and the dianhydride monomer is pyromellitic anhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-dibenzophenone tetracarboxylic anhydride or bisphenol A diether dianhydride;

[0065] The polyamic acid is imidized under the action of an alkali catalyst and a dehydrating agent to obtain the polyimide resin.

[0066] In the present invention, a diamine monomer, a dianhydride monomer and an organic solvent (referred to as the third organic solvent) are mixed to carry out a polycondensation reaction to obtain a polyamic acid.

[0067] In the present invention, the diamine monomer is the bulky side chain ester-containing diamine monomer described in the above technical solution, the dianhydride monomer is pyromellitic anhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-dibenzophenone tetracarboxylic anhydride or bisphenol A diether dianhydride; the third organic solvent is preferably N-methylpyrrolidone.

[0068] In the present invention, the method of mixing the diamine monomer, the dianhydride monomer and the third organic solvent is preferably:

[0069] After purifying the diamine monomer and the dianhydride monomer respectively, a purified diamine monomer and a purified dianhydride monomer are obtained;

[0070] The purified diamine monomer is dissolved in a third organic solvent, and the purified dianhydride monomer is added thereto.

[0071] In the present invention, the purification method is preferably: heat-treating the diamine monomer and the dianhydride monomer under vacuum conditions, respectively, and grinding them into fine powder in a dry and dust-free environment after cooling. In the present invention, the temperature of the heat treatment is preferably 120 to 160°C, and can be 120, 130, 140, 150 or 160°C, and the time of the heat treatment is preferably 6 to 12h, and can be 6, 8, 10 or 12h. The present invention removes water and partially hydrolyzed dianhydride in the monomers through the purification.

[0072] In the present invention, the temperature of the polycondensation reaction is preferably 20-30°C. In an embodiment of the present invention, the polycondensation reaction is carried out at room temperature. The time of the polycondensation reaction is preferably 12-36 hours, which can be 12, 24 or 36 hours. In the present invention, the polycondensation reaction is preferably carried out under stirring.

[0073] After obtaining the polyamic acid, the present invention performs imidization on the polyamic acid under the action of an alkali catalyst and a dehydrating agent to obtain the polyimide resin.

[0074] In the present invention, it is preferred to directly add a base catalyst and a dehydrating agent into the viscous polyamic acid solution obtained by the polycondensation reaction (ie, after the polycondensation reaction is completed, no post-treatment is required).

[0075] In the present invention, the base catalyst is preferably one or more of pyridine, triethylamine, 3-methylpyridine, isoquinoline, quinoline and imidazole; the dehydrating agent is preferably one or more of acetic anhydride, thionyl chloride, phosphorus trichloride and phosphorus oxychloride. In the present invention, the molar ratio of the diamine monomer, the dianhydride monomer, the base catalyst and the dehydrating agent is preferably (1-1.05):1:(0.05-0.2):(0.1-0.2), and can be 1:1:0.05:0.1. If the diamine monomer and the dianhydride monomer are purified as described in the above technical solution, the molar ratio is calculated based on the purified amount.

[0076] In the present invention, the imidization temperature is preferably 50-100°C, and can be 50, 60, 70, 80, 90 or 100°C, and the time is preferably 1-5h, and can be 1, 2, 3, 4 or 5h; the imidization is preferably carried out under stirring. The present invention adopts a chemical imidization method, and after the imidization, a solution of a polyimide resin is obtained.

[0077] In the present invention, methanol may be added to the polyimide resin solution to precipitate the polyimide resin, wash the polyimide resin repeatedly, and then vacuum dry the polyimide resin to obtain the polyimide powder.

[0078] The present invention also provides a polyimide film, the film-forming material of the polyimide film is the polyimide resin described in the above technical solution. The polyimide film provided by the present invention has low dielectric loss and dielectric constant, high solubility and high tensile performance (elongation at break).

[0079] The present invention provides a method for preparing the polyimide film described in the above technical solution, comprising the following steps:

[0080] The polyimide film is obtained by coating the polyimide resin solution on a substrate and then removing the solvent.

[0081] In the present invention, the polyimide resin solution is preferably a polyimide resin solution directly obtained after the above imidization. The present invention has no special requirements for the substrate, and a substrate well known to those skilled in the art can be used, such as a glass substrate, a polytetrafluoroethylene substrate, and a copper foil; before the coating, the present invention preferably vacuum degasses the polyimide resin solution for 30 minutes.

[0082] The present invention has no special requirements for the temperature and time of the solvent removal, as long as the solvent in the polyimide resin solution can be fully removed; in an embodiment of the present invention, the solvent removal includes a first heating stage and a second heating stage in sequence, the temperature of the first heating stage is 50°C, the insulation time is 2h, the temperature of the second heating stage is 150°C, and the time is based on reaching constant weight.

[0083] The method for preparing the polyimide film provided by the invention has simple operation and simple steps, and can quickly and efficiently prepare a polyimide film with excellent performance.

[0084] At present, the resin material for preparing high-speed and high-frequency polyimide film has poor solubility in organic solvents, and there is no clear melting temperature, which makes it difficult to directly process into a film. It is usually necessary to coat the polyamic acid precursor solution on the substrate and heat and dehydrate (300-400°C) to achieve complete imidization. However, polyamic acid is sensitive to moisture and cannot be stored for a long time. After absorbing water, it will cause a decrease in the molecular weight of the polymer. In addition, due to the problem of dimensional stability, the high-temperature thermal imidization process of the combination of polyimide film and substrate, such as copper foil, will inevitably cause the curling of the substrate, making it difficult to prepare ultra-thin copper-clad laminate materials. The polyimide resin provided by the present invention has good solubility, and the imidization process has been completed before coating. The polyimide film can be obtained by directly coating the solution of the polyimide resin on the substrate and removing the solvent, avoiding the step of high-temperature thermal imidization on the substrate, and the material has good dimensional stability and is not easy to curl during processing.

[0085] The present invention provides the use of the polyimide resin described in the above technical solution or the polyimide film described in the above technical solution as an interlayer dielectric insulating material in an electronic communication device. In the present invention, the electronic communication device is such as a device used in the field of 5G communication, specifically in the field of high-frequency flexible copper-clad laminate materials. The present invention solves the problem that existing polyimide materials are difficult to balance solubility, dielectric properties and high mechanical properties, and provides a polyimide film with good solubility and processability, excellent dielectric properties and mechanical properties, which can meet the needs of high-purity electronic chemicals for 5G communications.

[0086] To further illustrate the present invention, the bulky side-chain ester-containing diamine monomer and its preparation method, polyimide resin and polyimide film and its preparation method and application provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0087] Example 1

[0088] The synthesis of a large substituted side group containing ester diamine monomer, the reaction formula is as follows:

[0089]

[0090] The specific steps are as follows:

[0091] In a 250mL reaction bottle equipped with a magnetic, add p-nitrobenzoyl chloride (compound 3) (20mmol, 3.7g), acetonitrile (40mL), cool to 0°C, then dissolve the substituted diphenol (compound 2) (10mmol) and pyridine (20mmol, 2eq) in 20mL acetonitrile and carefully add to the reaction bottle. After the addition is complete, stir at room temperature for 2h, add 50mL acetonitrile to dilute, then add 1L methanol, stir at room temperature for 30min, filter with a Buchner funnel, and rinse with methanol to obtain a white solid powder, i.e., the intermediate (compound 4).

[0092] 10g of the intermediate (compound 4), 0.5g of Pd / C catalyst, 200g of N,N-dimethylformamide were added to a high-pressure reactor, and hydrogen gas of 1.5MPa was introduced. The reaction was carried out at 70°C for 10h. After the reaction was completed, the catalyst was removed by filtration through diatomaceous earth, and the product was precipitated in methanol and rinsed with methanol. The obtained product was redissolved in ethyl acetate, and then methanol was added again to precipitate the product. The product was filtered and vacuum dried to obtain a white solid powder, i.e., the diamine monomer (compound 5), with a purity of 99.5%. The structure of the diamine monomer prepared in Example 1 was characterized by a 400MHz nuclear magnetic resonance instrument using deuterated dimethyl sulfoxide (DMSO) as a reagent, see Figure 1 and Figure 2 , Figure 1 is the hydrogen nuclear magnetic resonance spectrum, Figure 2 It is the carbon nuclear magnetic resonance spectrum.

[0093] Example 2

[0094] A polyimide film is prepared by polymerization of diamine and dianhydride monomers, and the specific preparation steps are as follows:

[0095] (1) Purification of diamine monomer and dianhydride monomer

[0096] The diamine monomer (compound 5, prepared in Example 1) and 4,4'-oxydiphthalic anhydride (ODPA) were placed in a sublimation device, heated to 140°C under vacuum conditions, kept warm for 8 hours, and then the monomers were collected after cooling and ground into fine powder in a dry and dust-free environment to complete purification. The structural formula of ODPA is as follows:

[0097]

[0098] (2) Preparation of polyimide solution

[0099] 2 mmol of the purified diamine monomer and 2 mmol of ODPA in step (1) were dissolved in N-methylpyrrolidone (solid content 20 wt%) and stirred at room temperature for 12 h to obtain a viscous polyamic acid solution. Subsequently, 0.1 mmol of pyridine and 0.2 mmol of acetic anhydride were added, and the temperature was raised to 50° C. and stirred for 1 h for imidization to obtain a polyimide solution.

[0100] (3) Preparation of polyimide film

[0101] The polyimide solution obtained in step (2) is vacuum degassed for 30 minutes, and a film is coated on a glass or polytetrafluoroethylene substrate. The substrate is placed in a vacuum oven, and then programmed to heat up to remove the solvent at a heating rate of 2°C / min. The temperature is heated at 50°C for 2 hours, and then heated to 150°C until the weight of the substrate no longer changes, to obtain a polyimide film.

[0102] Example 3

[0103] The same as Example 2, except that the dianhydride is 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and the structural formula of BTDA is as follows:

[0104]

[0105] Example 4

[0106] The same as Example 2, except that the dianhydride is bisphenol A diether dianhydride (BPADA), and the structural formula of BPADA is as follows:

[0107]

[0108] Example 5

[0109] The same as Example 2, except that the dianhydride is pyromellitic anhydride (PMDA), and the structural formula of PMDA is as follows:

[0110]

[0111] Comparative Example 1

[0112] The same as Example 2, except that the diamine is the following structure:

[0113]

[0114] Comparative Example 2

[0115] The same as Example 2, except that the diamine is the following structure:

[0116]

[0117] The polyimide films prepared in the above embodiments and comparative examples were subjected to performance tests, including dielectric constant, dielectric loss, tensile strength, elongation at break and solubility. The tests were conducted at room temperature of 25°C. The thickness of the polyimide films was 30 μm. The test frequency of the dielectric constant and dielectric loss was 10 GHz. The solubility test method was as follows: 0.2 g of polyimide powder (the imidized polymer was precipitated in methanol and repeatedly washed, and vacuum dried to obtain polyimide powder) was added to 1 g of N-methylpyrrolidone (NMP). If the polymer powder was completely dissolved and presented a clear and transparent state, the solubility was determined to be "+", and if there were still particles of the polymer powder remaining in the solution, the solubility was determined to be "-". The test results are shown in Table 1.

[0118] Table 1 Performance test results of polyimide films prepared in Examples and Comparative Examples

[0119] Serial number Dielectric constant Dielectric loss Tensile strength(MPa) Elongation at break (%) Solubility Example 2 3.07 0.003 110 10 + Example 3 3.24 0.004 83 11 + Example 4 3.21 0.002 100 7 + Example 5 3.13 0.004 104 13 + Comparative Example 1 3.81 0.005 116 2.3 - Comparative Example 2 3.25 0.003 122 5 -

[0120] By comparing the dielectric constant, dielectric loss, tensile properties and solubility of the polyimide films prepared in the above Examples 2 to 5 and Comparative Examples 1 to 2, it can be seen that the polyimide films prepared using the diamine synthesized by the present invention have lower dielectric loss, higher tensile strength, higher elongation at break and better solubility.

[0121] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A bulky side chain ester-containing diamine monomer, characterized in that: It has the structure shown in formula I: In Formula I, R 1 , R 2 , R 3 and R 4 are independently selected from hydrogen, fluorine, alkyl, haloalkyl, aryl or haloaryl.

2. The method for preparing the bulky side chain ester-containing diamine monomer according to claim 1, characterized in that: The following steps are involved: A substituted diphenol, a nitrobenzoyl chloride compound, an organic solvent and a base are mixed for esterification reaction to obtain an intermediate; the substituted diphenol, the nitrobenzoyl chloride compound and the intermediate have structures shown in Formula II, Formula III and Formula IV respectively; The intermediate is subjected to a hydrogenation reaction under the action of a catalyst to obtain the bulky side chain ester-containing diamine monomer; 3. The preparation method according to claim 2, characterized in that: The base includes one or more of triethylamine, pyridine, potassium carbonate and potassium dihydrogen phosphate; the molar ratio of the substituted diphenol, nitrobenzoyl chloride compound and the base is 1:(2-2.5):(2-3); the temperature of the esterification reaction is 0-30°C and the time is 2-6h.

4. The preparation method according to claim 2, characterized in that: The catalyst comprises one or more of Raney nickel, Raney cobalt and Pd / C; the hydrogenation reaction is carried out under a hydrogen atmosphere, the temperature of the hydrogenation reaction is 25-80° C., the pressure is 0.9-1.5 MPa, and the time is 8-12 hours.

5. A polyimide resin, characterized in that: It has the structure shown in formula V: In Formula V, n is an integer greater than 100, R 1 , R 2 , R 3 and R 4 are independently selected from hydrogen, fluorine, alkyl, haloalkyl, aryl or haloaryl, for 6. The method for preparing the polyimide resin according to claim 5, characterized in that: The following steps are involved: The diamine monomer, the dianhydride monomer and the organic solvent are mixed for polycondensation reaction to obtain polyamic acid; the diamine monomer is the bulky side chain ester-containing diamine monomer according to claim 1, and the dianhydride monomer is pyromellitic anhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-dibenzophenone tetracarboxylic anhydride or bisphenol A diether anhydride; The polyamic acid is imidized under the action of an alkali catalyst and a dehydrating agent to obtain the polyimide resin.

7. The preparation method according to claim 6, characterized in that: The molar ratio of the diamine monomer, the dianhydride monomer, the base catalyst and the dehydrating agent is (1-1.05):1:(0.05-0.2):(0.1-0.2); the temperature of the polycondensation reaction is 20-30°C, and the time is 12-36 hours; the temperature of the imidization is 50-100°C, and the time is 1-5 hours.

8. A polyimide film, characterized in that: The film-forming material of the polyimide film is the polyimide resin according to claim 5.

9. The method for preparing the polyimide film according to claim 8, characterized in that: The following steps are involved: The polyimide film is obtained by coating the polyimide resin solution on a substrate and then removing the solvent.

10. Use of the polyimide resin according to claim 5 or the polyimide film according to claim 8 as an interlayer dielectric insulating material in electronic communication devices.

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