A kind of polyimide, polyimide film and preparation method of flexible soft board

Abstract

The present invention belongs to the technical field of organic polymer materials, and discloses a method for preparing a polyimide, a polyimide film and a flexible soft board thereof, comprising the following steps: S1, synthesizing a dihalogen monomer IF-Br containing an imine structure with a clear sequence structure; S2, synthesizing a halogenated monophenol IF-OH containing an imine structure with a clear sequence structure; S3, preparing a novel PI resin with a clear sequence structure through an aromatic nucleophilic substitution reaction, and the present invention provides a new strategy for preparing a polyimide resin through an aromatic nucleophilic substitution reaction, so that the PI resin can be prepared into a polyimide film through solution casting, casting, film blowing, melt extrusion and the like, without high-temperature thermal imidization, and the processing methods are diverse and energy-saving. The present invention solves the deficiencies of traditional polyimide resins in dielectric properties and loss properties, as well as the problem that traditional polyimide resin molding and processing means are relatively single, and is suitable for the fields of microelectronics, communications, aerospace, etc.

Description

Technical Field

[0001] The invention relates to the technical field of organic polymer materials, and in particular to a method for preparing a polyimide, a polyimide film and a flexible soft board thereof. Background Art

[0002] As an important high-performance polymer material, polyimide resin has broad application prospects in the fields of microelectronics, communications, aerospace, etc. Its low dielectric and low loss properties make it an ideal material for high-frequency electronic devices, radio frequency microwave circuits, and optical communication systems. However, traditional polyimide resins often have high dielectric constants and loss factors, which limit their application in high-frequency, high-speed, and high-density electronic devices. At the same time, traditional polyimide resins are all prepared by high-temperature imidization of polyamic acid, and the molding and processing methods are relatively simple.

[0003] In recent years, researchers have proposed a series of modification methods and new synthesis methods to address the shortcomings of traditional polyimide resins in terms of dielectric properties and loss performance. However, these modification methods and new synthesis methods are often subject to many limitations in practical applications. For example, the addition of modifiers may affect the mechanical properties and processing properties of the material. Research and analysis show that the reason why traditional polyimide (PI) resins have insufficient dielectric properties and loss performance is the presence of the intrinsic imide ring structure. The imide ring structure with a permanent dipole moment increases the dielectric constant and dielectric loss of PI while giving the PI resin excellent mechanical and thermal properties; in addition, the imide ring structure is easy to absorb moisture, which can also lead to further deterioration of dielectric properties.

[0004] In view of the above problems, the present invention proposes a method for preparing a low-dielectric, low-loss, and low-hygroscopic polyimide resin. At the same time, compared with the traditional polyimide resin molding and processing method, this method is more diverse and energy-saving. Summary of the invention

[0005] The present invention aims to provide a method for preparing a polyimide, a polyimide film and a flexible soft board thereof, so as to solve the deficiencies of conventional polyimide resins in dielectric properties and loss properties, as well as the problem that conventional polyimide resins have relatively single molding and processing methods.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a polyimide comprises the following steps:

[0008] S1. Synthesize the dihalogen monomer IF-Br containing an imine structure with a clear sequence structure through solution polycondensation reaction;

[0009] S2. Synthesize IF-OH, a halogenated monophenol containing an imine structure with a clear sequence structure, through Suzuki coupling reaction;

[0010] S3. A novel PI resin with a clear sequence structure is prepared through aromatic nucleophilic substitution reaction.

[0011] The structure of the imine-containing dihalogen monomer IF-Br with a clear sequence structure synthesized in step S1 is as follows:

[0012]

[0013] Among them, R1 is One of;

[0014] The structure of the halogenated monophenol IF-OH containing an imine structure, which is well-defined in the synthesis sequence in step S2, is as follows:

[0015]

[0016] Among them, R1 is One of: R2 is One of;

[0017] The structure of the novel PI resin with a clear sequence structure prepared in step S3 is as follows:

[0018]

[0019] Among them, R1 is One of: R2 is One of;

[0020] Furthermore, the solvent for the solution polycondensation reaction in step S1 is one of the aprotic organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide, and the dehydrating agent is acetic anhydride.

[0021] Furthermore, the solvent for the Suzuki coupling reaction in step S2 is dioxane, ethanol, toluene, xylene, and the catalyst is Pd(PPh3)4.

[0022] The solvent for the nucleophilic substitution reaction in step S3 is a mixture of one or more aprotic organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide, the catalyst is one or more alkali metal salts such as potassium carbonate, calcium carbonate, and cesium fluoride, the reaction temperature is 180-220° C., and the water-carrying agent is one of toluene and xylene or a mixture of the two.

[0023] A method for preparing a novel PI-Ph film comprises the following steps:

[0024] A1. Dissolving the prepared novel PI resin in an organic solvent to prepare a casting solution; the organic solvent is one or more of NMP, DMF, DMAc, DMSO, and chloroform aprotic organic solvents, and the concentration of the casting solution is measured by the mass fraction of the novel PI resin, specifically 10-20%;

[0025] A2. Pour the casting solution prepared in step A1 onto a flat plate to prepare a PI film. The flat plate is a glass plate or a silicon wafer. The drying process of the film preparation process is 80° C. for 4 hours and 120° C. for 12 hours.

[0026] A method for preparing an imide flexible board comprises the following steps:

[0027] B1. Dissolving the prepared novel PI resin in an organic solvent to prepare a casting solution; the organic solvent is one or more of aprotic organic solvents such as NMP, DMF, DMAc, DMSO, and chloroform, and the concentration of the casting solution is measured by the mass fraction of the novel PI resin, specifically 10-20%;

[0028] B2. Pour the casting solution prepared in step B1 onto copper foil to prepare a flexible soft board. The drying process for preparing the soft board is drying at 80° C. for 5 hours and drying at 180° C. for 6 hours under vacuum conditions.

[0029] The beneficial effect of the technical solution is: the present invention provides a new strategy for preparing low dielectric, low loss, and low hygroscopic polyimide resin, so that PI resin can be used to prepare polyimide film through solution casting, casting, film blowing, melt extrusion, etc., without the need for high-temperature thermal imidization, and the processing methods are diverse and energy-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The synthetic preparation route map of PI in the embodiment of the present invention is shown;

[0031] Figure 2 It is the infrared spectrum of PI in the embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0033] Example 1. Preparation of polyimide

[0034] S1. Synthesis of the imine-containing dihalogen monomer IF-Br with a clear sequence structure. The specific operation is as follows: first, weigh 37.4 g of 4'-fluoro(1,1'-biphenyl)-4-amine and 45.4 g of 3-bromophthalic anhydride, add them to 200 ml of N-methylpyrrolidone (NMP), and react at room temperature for 10 hours; then slowly add a certain amount of acetic anhydride and pyridine mixed solution to the reaction system, and continue to react for 5 hours; finally, pour the reaction system into 1000 ml of ethanol, stir, filter, and dry to obtain 36 g of the target product IF-Br.

[0035] S2. Synthesis of halogenated monophenol IF-OH with an imine structure having a clear sequence structure. The specific operation is as follows: first, weigh 39.5g IF-Br, 13.7g 4-phenylboronic acid, 2.4g Pd(PPh3)4, 40g anhydrous potassium carbonate, and 250mL 1,4-dioxane, and add them in a 1L three-necked flask equipped with a magnetic stirrer in sequence. Under nitrogen protection, reflux the reaction for 12 hours; then, cool the reaction system to room temperature, dilute with 500ml tetrahydrofuran, and filter to remove the catalyst Pd(PPh3)4; finally, concentrate the filtrate under reduced pressure and pour it into 1000ml methanol. Filter, wash with water, and dry to obtain 49.5g of the target product IF-OH.

[0036] S3. Synthesis of a novel PI resin with a clear sequence structure. The specific operation is as follows: first, weigh 60g IF-OH, 10.0g anhydrous potassium carbonate, 60mL dimethyl sulfoxide, and 60mL toluene fluoride in a 500mL three-necked flask, and react at 130℃ for 3h; then, heat to 140℃ and evaporate the excess toluene solution; finally, gradually heat to 180℃ and maintain until the end of the reaction, during which solvent is added to reduce the viscosity of the system, and the reaction is stopped when the viscosity no longer increases. Add 60mL of solvent to the reaction system at one time, cool to 80℃, pour it into boiling water containing HCl, and filter to obtain a fibrous precipitate, which is the target resin.

[0037] The obtained new PI resin was subjected to infrared testing. The infrared test results are as follows: Figure 2 shown.

[0038] The obtained new PI resin was subjected to a thermal performance test. The results of the thermal performance test showed that the prepared new PI resin had a glass transition temperature of 274 degrees Celsius and a 5% thermal weight loss temperature of 526 degrees Celsius, and had excellent thermal stability.

[0039] Example 2: Preparation of a novel PI-Ph film

[0040] The novel PI prepared in the first embodiment is dissolved in NMP to prepare a PI casting solution with a mass fraction of 15%; the PI casting solution is poured onto a clean heatable glass plate, and a scraper is used to assist the casting solution in leveling; finally, the PI film is dried to remove the solvent, and the specific drying process is drying at 80°C for 4 hours and drying at 120°C for 12 hours.

[0041] The prepared new PI-Ph film was tested and found to be flexible and had good mechanical properties. The film had a tensile strength of 115MPa, a tensile modulus of 3.2GPa, and an elongation of 8%. In addition, the film had a dielectric constant of 2.8@10GHz, a dielectric loss of 0.008@10GHz, and a water absorption of 0.8%, all of which were better than commercial PI.

[0042] The performance summary of the new PI resin and the new PI-Ph film is shown in Table 1:

[0043] Table 1 Summary of the performance of PI-Ph

[0044]

[0045] Example 3: Preparation of flexible circuit board (FCCL)

[0046] The PI casting liquid prepared in Example 2 was coated on a special copper foil, and a scraping rod was used to assist the casting liquid in leveling; the system was then placed at 80 degrees Celsius for drying for 5 hours to obtain a preliminarily dried soft board; finally, it was transferred to a vacuum oven and treated at 180 degrees Celsius for 6 hours to obtain a flexible soft board. The adhesion between PI and copper foil was strong, the dimensional stability was good, and the solder resistance was good.

[0047] In summary, the new PI resin prepared by the present invention has excellent thermal stability; the new PI-Ph film prepared from the new PI resin is flexible, has good mechanical strength, and has the properties of low dielectric, low loss, and low moisture absorption, which is better than commercial PI; the flexible soft board prepared from the new PI resin has strong adhesion between PI and copper foil, good dimensional stability, and good solder resistance.

[0048] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a polyimide, characterized in that: The following steps are involved: S1. Synthesize the dihalogen monomer IF-Br containing an imine structure with a clear sequence structure through solution polycondensation reaction; S2. Synthesize IF-OH, a halogenated monophenol containing an imine structure with a clear sequence structure, through Suzuki coupling reaction; S3, preparing PI resin with clear sequence structure through aromatic nucleophilic substitution reaction; The structure of the imine-containing dihalogen monomer IF-Br with a clear sequence structure synthesized in step S1 is as follows: Among them, R1 is One of; The structure of the well-defined imine-containing halogenated monophenol IF-OH in the synthesis sequence of step S2 is as follows: Among them, R1 is One of: R2 is One of; The structure of the PI resin with a clear sequence structure prepared in step S3 is as follows: Among them, R1 is One of: R2 is One of them.

2. The method for preparing a polyimide according to claim 1, characterized in that: The solvent for the solution polycondensation reaction in step S1 is one of the aprotic organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide, and the dehydrating agent is acetic anhydride.

3. The method for preparing a polyimide according to claim 1, characterized in that: The solvent for the Suzuki coupling reaction in step S2 is dioxane, ethanol, toluene, and xylene; and the catalyst is Pd(PPh3)4.

4. The method for preparing a polyimide according to claim 1, characterized in that: The solvent for the nucleophilic substitution reaction in step S3 is a mixture of one or more aprotic organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; the catalyst is one or more alkali metal salts such as potassium carbonate, calcium carbonate, and cesium fluoride; the reaction temperature is 180-220° C.; and the water-carrying agent is one or a mixture of toluene and xylene.

5. A method for preparing a PI-Ph film, characterized in that: The following steps are involved: A1. Dissolve the PI resin prepared in claim 1 in an organic solvent to prepare a casting solution; the organic solvent is one or more of NMP, DMF, DMAc, DMSO, and chloroform aprotic organic solvents, and the concentration of the casting solution is measured by the mass fraction of the PI resin, specifically 10-20%; A2. Pour the casting solution prepared in step A1 onto a flat plate to prepare a PI film. The flat plate is a glass plate or a silicon wafer. The drying process of the film preparation process is 80° C. for 4 hours and 120° C. for 12 hours.

6. A method for preparing an imide flexible board, characterized in that: The following steps are involved: B1. Dissolving the PI resin prepared in claim 1 in an organic solvent to prepare a casting solution; the organic solvent is one or more of aprotic organic solvents such as NMP, DMF, DMAc, DMSO, and chloroform, and the concentration of the casting solution is measured by the mass fraction of the PI resin, specifically 10-20%; B2. Pour the casting solution prepared in step B1 onto copper foil to prepare a flexible soft board. The drying process for preparing the soft board is drying at 80° C. for 5 hours and drying at 180° C. for 6 hours under vacuum conditions.

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