A biphenyl-bridged thermoplastic polyester imide, a preparation method thereof, a biphenyl-bridged thermoplastic polyester imide film and applications thereof

Abstract

The application belongs to the technical field of thermoplastic polyester imides, and particularly relates to a biphenyl-bridged thermoplastic polyester imide, a preparation method thereof, a biphenyl-bridged thermoplastic polyester imide film and application. The biphenyl-bridged thermoplastic polyester imide is polymerized from biphenyl diphenylate-3,3',4,4'-tetracarboxylic dianhydride, 3,3',4,4',-biphenyl tetracarboxylic dianhydride and 2-(4-aminobenzoate)-5-aminobiphenyl. The biphenyl-bridged thermoplastic polyester imide provided by the application has a linear thermal expansion coefficient close to that of copper foil, and excellent thermoplasticity, high-temperature dimensional stability and dielectric properties.

Description

Technical Field

[0001] This invention belongs to the field of thermoplastic polyesterimide technology, specifically relating to a biphenyl-bridged thermoplastic polyesterimide and its preparation method, a biphenyl-bridged thermoplastic polyesterimide film, and its applications. Background Technology

[0002] Flexible copper clad laminate (FCCL) is a plate-shaped base material used in flexible printed circuit boards (FPCB) for connecting circuit boards and transmitting signals. Due to its excellent characteristics such as flexibility, thinness, light weight and high conductivity, it is frequently used in electronic devices such as mobile phones, tablets, and laptops.

[0003] FCCL is mainly composed of conductors (such as copper foil layers) and polymer insulating materials. The signal transmission speed is related to the dielectric constant (D) of the polymer insulating material in the FCCL. k ) and dielectric loss (D f The correlation is negative, therefore, in order to achieve faster transmission speeds, polymer insulating polymers need to move towards lower D. k Low D f It is constantly being developed in the direction of low water absorption and high thermal stability.

[0004] Polyimide (PI) not only meets these requirements but also possesses advantages such as a rigid imide ring structure, resistance to high and low temperatures and radiation, good mechanical properties, and flexible molecular designability, making it a widely used polymeric insulating polymer in FCCLs. However, due to its smooth surface and low roughness, PI results in low peel strength between the copper foil layer and the PI film formed directly by heat sealing or other methods. Therefore, adhesives are generally used during the manufacturing process, or the PI is modified to increase the adhesion between the polymeric insulating polymer and the copper foil layer. The presence of adhesives leads to problems in FCCLs such as poor thermal stability, high dielectric loss, and high porosity. Therefore, two-layer adhesive-free FCCLs are attracting more attention.

[0005] In the design of polyimide (PI) modification schemes, introducing fluorinated groups with low molar polarization is a popular method to improve dielectric properties. For example, Chinese patent CN115850699B discloses a method for preparing low-dielectric blended polyimides. This technical solution involves blending diamines containing thiaanthracene structures and ester bonds, fluorinated diamines, and polyamic acid prepared from fluorinated dianhydride monomers. The good affinity of thioether bonds with metals improves the adhesion between polyimide and copper. Simultaneously, the introduced rigid and planar structure enhances the thermal stability of polyimide, reducing its coefficient of thermal expansion. Furthermore, the ester bonds strengthen the intermolecular forces of polyimide, further reducing its coefficient of thermal expansion. The blended polyimide prepared by this technical solution through the polymerization and blending of three monomers exhibits low dielectric constant, low coefficient of thermal expansion, and high thermal stability, solving the problems of high and unstable dielectric constant and high coefficient of thermal expansion of polyimides at low frequencies.

[0006] Chinese Patent Publication No. CN111484616B discloses a polyimide composition, polyimide, flexible copper-clad laminate, and a method for manufacturing the same. The polyimide composition comprises a diamine monomer, a dianhydride monomer, and a solvent. The weight ratio of the diamine monomer to the dianhydride monomer is 1.4–1.6:1. The diamine monomer includes 2,2'-bis(trifluoromethyl)benzidine and 2,2'-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane. This technical solution selects diamine monomers with flexible functional groups and imides them with dianhydride monomers. While maintaining the original low dielectric properties of polyimide, the resulting polyimide exhibits high flexibility, low moisture absorption, heat resistance, and strong peel strength to copper foil. Tests show that the peel strength between the polyimide and copper foil is above 7.0 N / cm.

[0007] However, fluorine-containing materials are greatly limited in use due to defects such as biotoxicity. Therefore, it is of great significance to develop a fluorine-free, two-layer adhesive-free FCCL that can be used in high-frequency applications.

[0008] Polyester imide (PEsI) is considered to have good application prospects in two-layer FCCLs due to its advantages over PI containing other chemical bonds, such as good thermal stability, low water absorption, excellent dielectric properties, and low curing temperature. However, to meet the more stringent performance requirements in the FCCL field, PEsI needs to simultaneously possess good thermoplasticity, high temperature resistance, thermal conductivity, low dielectric constant, low dielectric loss, and good adhesion to copper foil.

[0009] Therefore, how to improve PEsI through modification and obtain PEsI films with good performance in all aspects has become a hot topic for its application in the field of two-layer FCCL. Summary of the Invention

[0010] To address the aforementioned problems, this invention provides a biphenyl-bridged thermoplastic polyester imide, its preparation method, a biphenyl-bridged thermoplastic polyester imide film, and its applications. The biphenyl-bridged thermoplastic polyester imide provided by this invention is fluorine-free and possesses a linear coefficient of thermal expansion close to that of copper foil, as well as excellent thermoplasticity, high-temperature dimensional stability, and dielectric properties.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] The first aspect of this invention provides a biphenyl-bridged thermoplastic polyester imide, polymerized from biphenyl dibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and 2-(4-aminobenzoate)-5-aminobiphenyl; its structural formula is shown in formula (I):

[0013]

[0014] (I); where m represents the number of moles of biphenyl benzoate-3,3',4,4'-tetracarboxylic acid dianhydride, m is an integer from 0 to 100, and m can be 0; n represents the number of moles of 3,3',4,4',-biphenyltetracarboxylic acid dianhydride, n is an integer from 0 to 100, and n is not 0.

[0015] The structural formula of biphenyl benzoate-3,3',4,4'-tetracarboxylic dianhydride (BPTME) is as follows:

[0016]

[0017] The structural formula of 3,3',4,4',-biphenyltetracarboxylic acid dianhydride (BPDA) is as follows:

[0018]

[0019] The structural formula of 2-(4-aminobenzoate)-5-aminobiphenyl (ABABP) is as follows:

[0020]

[0021] Preferably, the ratio of m to n is 0-40:60-100.

[0022] A second aspect of the present invention provides a method for preparing the above-mentioned biphenyl-bridged thermoplastic polyester imide, comprising the following steps:

[0023] (1) Under nitrogen protection, biphenyl dibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride, 3,3',4,4',-biphenyltetracarboxylic acid dianhydride and 2-(4-aminobenzoate)-5-aminobiphenyl undergo a polymerization reaction in a solvent to obtain a polyamic acid (PAA) solution.

[0024] (2) The polyamic acid solution is subjected to thermal imidization to obtain biphenyl-bridged thermoplastic polyester imide.

[0025] Preferably, the total molar ratio of 2-(4-aminobenzoate)-5-aminobiphenyl to biphenyl dibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride and 3,3',4,4',-biphenyltetracarboxylic acid dianhydride is 1:0.9-1.1, more preferably 1:1.

[0026] Preferably, the thermal imidization is performed using a programmed temperature rise, with the following steps: 70-90℃ for 0.5-1.5h, 110-130℃ for 0.5-1.5h, 140-160℃ for 0.5-1.5h, 170-190℃ for 0.5-1.5h, 240-260℃ for 0.5-1.5h, and 290-310℃ for 0.5-1.5h.

[0027] More preferably, the programmed temperature rise steps are: 80℃ for 1 hour, 120℃ for 1 hour, 150℃ for 1 hour, 180℃ for 1 hour, 250℃ for 1 hour, and 300℃ for 1 hour.

[0028] Preferably, the solvent is selected from at least one of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0029] More preferably, the solvent is N-methylpyrrolidone.

[0030] Preferably, the polymerization reaction is carried out at 5℃-35℃ for 20h-30h.

[0031] A third aspect of the present invention provides a biphenyl-bridged thermoplastic polyesterimide film, the composition of which includes the above-mentioned biphenyl-bridged thermoplastic polyesterimide.

[0032] Preferably, the linear coefficient of thermal expansion of the biphenyl-bridged thermoplastic polyesterimide film is <26×10⁻⁶. -6 / K, glass transition temperature ≥230℃, dielectric constant <3.6, dielectric loss ≤0.005.

[0033] Preferably, the thickness of the biphenyl-bridged thermoplastic polyesterimide film is 0.03-0.05 mm.

[0034] The fourth aspect of the present invention provides the application of the above-mentioned biphenyl-bridged thermoplastic polyesterimide or the above-mentioned biphenyl-bridged thermoplastic polyesterimide film in the preparation of two-layer flexible copper-clad laminates.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The biphenyl-bridged thermoplastic polyesterimide provided by this invention uses ABABP (a diamine containing ester groups and side-benzene substituents), BPTME (a dianhydride containing ester groups and biphenyl groups), and BPDA (a dianhydride containing biphenyl groups) for polymerization. The side-benzene substituents increase the molar volume of the polyesterimide molecular chain, thereby reducing the dielectric constant and dielectric loss. Simultaneously, the presence of phenyl groups can adjust the stiffness of the polyesterimide molecules, resulting in good thermoplasticity and toughness. Due to the presence of ester groups, the biphenyl-bridged thermoplastic polyesterimide exhibits low water absorption, low dielectric constant, low dielectric loss, excellent thermal stability, and good processability. The presence of rigid biphenyl groups provides good high-temperature dimensional stability, good thermal stability, and a linear coefficient of thermal expansion similar to that of copper foil. Therefore, the biphenyl-bridged thermoplastic polyesterimide film prepared by the method provided by this invention possesses characteristics such as a linear coefficient of thermal expansion similar to that of copper foil, excellent thermoplasticity, high-temperature dimensional stability, and dielectric properties, making it suitable as an insulating polymer material in two-layer flexible copper-clad laminates. Detailed Implementation

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0040] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0041] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0042] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available or prepared by conventional methods in the art.

[0043] The structural formulas of the monomers involved in the comparative examples are as follows:

[0044]

[0045]

[0046] Example 1: Biphenyl-bridged thermoplastic polyesterimide film

[0047] (1) Add ABABP (15.2170 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen gas. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; add BPDA (14.7110 g, 50.0 mmol) and NMP (49.8 g) together. The mixture was added to the reaction mixture to obtain a polymerization system with a solid content of 25 wt%. After 1 hour, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 hours, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for another 24 hours, and additional NMP (80.0 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0048] (2) The PAA solution was cast onto borosilicate glass (150mm×100mm×3mm) using a coating machine (AFA-II, Shanghai Meiyu Equipment Co., Ltd., China). The thickness of the liquid PAA film was adjusted to 0.04±0.01mm by a casting knife to obtain a coated glass substrate. The coated glass substrate was transferred to a clean oven filled with dry nitrogen. Then, thermal imidization was performed by a programmed temperature rise step of 80℃ for 1h, 120℃ for 1h, 150℃ for 1h, 180℃ for 1h, 250℃ for 1h, and 300℃ for 1h. After the oven temperature cooled to room temperature, the coated glass substrate was immersed in deionized water. The automatically peeled biphenyl bridge thermoplastic polyesterimide film was collected and dried at 120℃ for 3h to obtain the final product.

[0049] Example 2: Biphenyl-bridged thermoplastic polyesterimide film

[0050] (1) Add ABABP (15.2170 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; add BPTME (2.6722 g, 5.0 mmol) and BPDA (13.2399 g, 45.0 mmol) to... NMP (53.4 g) was added to the reaction mixture to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for another 24 h, and additional NMP (83.0 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0051] (2) Same as step (2) in Example 1.

[0052] Example 3: Biphenyl-bridged thermoplastic polyesterimide film

[0053] (1) Add ABABP (15.2170 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; add BPTME (5.3443 g, 10.0 mmol) and BPDA (11.7688 g, 40.0 mmol) to the reaction mixture. The mixture was added to the reaction mixture along with NMP (57.0 g) to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for another 24 h, and NMP (86.2 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0054] (2) Same as step (2) in Example 1.

[0055] Example 4: Biphenyl-bridged thermoplastic polyesterimide film

[0056] (1) Add ABABP (15.2170 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; add BPTME (8.0165 g, 15.0 mmol) and BPDA (10.2977 g, 35.0 mmol) The mixture was added to the reaction mixture along with NMP (60.6 g) to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for another 24 h, and NMP (89.4 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0057] (2) Same as step (2) in Example 1.

[0058] Example 5: Biphenyl-bridged thermoplastic polyesterimide film

[0059] (1) Add ABABP (15.2170 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; add BPTME (10.6886 g, 20.0 mmol) and BPDA (8.8266 g, 30.0 mmol) The mixture was added to the reaction mixture along with NMP (64.2 g) to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for another 24 h, and NMP (92.6 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0060] (2) Same as step (2) in Example 1.

[0061] Comparative Example 1: Fluorinated thermoplastic polyesterimide film

[0062] (1) Add 4-aminobenzoic acid-4-aminophenyl ester (APAB, 3.6520 g, 16.0 mmol), 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB, 7.6855 g, 24.0 mmol), and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath. Cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, APAB and TFMB are completely dissolved in the solvent, yielding the reaction mixture. Add bisphenol A diether dianhydride (TMBPA, 11.5302 g, 20.0 g) to the reaction mixture. 20.0 mmol), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA, 5.8844 g, 20.0 mmol) and NMP (46.3 g) were added to the reaction mixture to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for 24 h, and NMP (76.6 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0063] (2) Same as step (2) in Example 1.

[0064] Comparative Example 2: Fluorinated thermoplastic polyesterimide film

[0065] (1) Add 4-aminobenzoic acid-4-aminophenyl ester (APAB, 3.6520 g, 16.0 mmol), 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB, 7.6855 g, 24.0 mmol), and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath. Cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, APAB and TFMB are completely dissolved in the solvent, yielding the reaction mixture. Add bisphenol A diether dianhydride (TMBPA, 9.2242 g, 16.0 mmol) to the reaction mixture. 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA, 7.0613 g, 24.0 mmol) and NMP (42.9 g) were added to the reaction mixture to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for another 24 h, and NMP (73.6 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0066] (2) Same as step (2) in Example 1.

[0067] Comparative Example 3

[0068] The difference from Example 2 is that ABABP is replaced with an equimolar amount of bis(4-aminophenyl) terephthalate (BAPT), i.e., the preparation method is as follows:

[0069] (1) Add BAPT (17.4175 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; then react BPTME (2.6722 g, 5.0 mmol) and BPDA (13.2399 g, 45.0 mmol) with N... MP (60.0 g) was added to the reaction mixture to obtain a polymerization system with a solid content of 25 wt%. After 1 h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12 h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for 24 h, and additional NMP (88.9 g) was added to dilute the PAA solution to 15 wt%. The PAA solution was filtered through a 0.45 μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18 °C.

[0070] (2) Same as step (2) in Example 1.

[0071] Comparative Example 4

[0072] The difference from Example 2 is that BPTME is replaced with an equimolar amount of p-phenylene-bis(phenyltrilate) dianhydride (TAHQ), i.e., the preparation method is as follows:

[0073] (1) Add ABABP (15.2170 g, 50.0 mmol) and NMP (40.0 g) to a 250 mL three-necked glass flask equipped with a mechanical stirrer, nitrogen inlet and outlet pipes, and a cold water bath; cool the reaction vessel to 10 °C using circulating cold water, and fill the three-necked glass flask with dry nitrogen. After stirring for 30 minutes, ABABP is completely dissolved in the solvent, yielding the reaction mixture; then add TAHQ (2.2916 g, 5.0 mmol) and BPDA (13.2399 g, 45.0 mmol) to NMP. MP (52.2g) was added to the reaction mixture to obtain a polymerization system with a solid content of 25wt%. After 1h, when the initial heat of polymerization was released, the cold bath was removed and the reaction temperature naturally rose to room temperature. After 12h, a uniform, transparent and viscous light brown PAA solution was obtained. The polymerization reaction was continued at room temperature for 24h, and additional NMP (82.0g) was added to dilute the PAA solution to 15wt%. The PAA solution was filtered through a 0.45μm Teflon syringe and the obtained PAA solution was stored in a refrigerator at -18℃.

[0074] (2) Same as step (2) in Example 1.

[0075] Performance testing:

[0076] 1. Thermal performance evaluation:

[0077] 1.1 Dynamic Mechanical Analysis (DMA): The films obtained in Examples 1-5 and Comparative Examples 1-4 were tested in nitrogen atmosphere using a TA Q800 thermal analysis system at a heating rate of 5 °C / min and a frequency of 1 Hz. This test yielded the glass transition temperature (Tg) data of the films, and the results are shown in Table 1.

[0078] Meanwhile, tests show that the fluorine-free thermoplastic polyesterimide film prepared by this invention has good thermoplasticity.

[0079] 1.2 Thermomechanical Analysis (TMA): The films obtained in Examples 1-5 and Comparative Examples 1-4 were tested in a nitrogen atmosphere using a Netzsch TMA402F3 thermal analysis system at a heating rate of 5 °C / min. This test yielded the linear coefficient of thermal expansion (CTE) data for the films, and the results are shown in Table 1.

[0080] 1.3 Thermogravimetric analysis (TGA) and corresponding derivative TGA (DTG): The films obtained in Examples 1-5 and Comparative Examples 1-4 were tested in a nitrogen atmosphere using a Netzsch TG 209F3 thermogravimetric analyzer at a heating rate of 20 °C / min. This test yields the 5% weight loss temperature (Tg) of the films. 5％ The temperatures at which the first and second most rapid thermal decompositions occur (T) max1 T max2 ) and the residual weight ratio at 750°C (R w750 The data and results are shown in Table 1.

[0081] 2. Dielectric Performance Evaluation: Silver electrodes were fabricated on both sides of the films obtained in Examples 1-5 and Comparative Examples 1-4, respectively. The films were pre-dried at 100°C for 1 hour using conductive silver paint, and then precisely cut into small pieces (1cm × 1cm × 3mm). The dielectric constant (Dk) was measured at 10GHz using an Agilent 4294A precision impedance analyzer at room temperature. k ) and dielectric loss (D f The data is recorded as the average of 5 parallel samples, and the results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As shown in Table 1, compared to the fluorinated thermoplastic polyesterimide films prepared with TMBPA, BPDA, APAB, and TFMB in Comparative Examples 1 and 2, the biphenyl-bridged thermoplastic polyesterimide films prepared with BPTME, BPDA, and PAPAB in Examples 1-5 exhibit better performance in terms of being fluorine-free and maintaining low D. k and D f In this case, it also has a CTE that is more compatible with copper foil, better high-temperature dimensional stability, and lower Tg; compared with Comparative Example 3, in which ABABP in Example 2 was replaced with an equimolar amount of bis(4-aminophenyl) terephthalate (BAPT), Examples 1-5 have better high-temperature dimensional stability and thermoplasticity, and lower D. k D f Compared to Comparative Example 4, in which BPTME in Example 2 was replaced with an equimolar amount of p-phenylene-bisphenyltrilate dianhydride (TAHQ), Examples 1-5 exhibit better high-temperature dimensional stability and a CTE that is more compatible with copper foil.

[0085] Therefore, the biphenyl-bridged thermoplastic polyesterimide film material provided by the present invention has excellent comprehensive properties without the use of fluorine-containing materials, including excellent thermoplasticity, high-temperature dimensional stability, dielectric properties, and a CTE that is more compatible with the CTE of copper foil. Moreover, the preparation process is simple to operate, the reaction is controllable, and the reaction products are adjustable. This embodiment has good industrialization prospects in two-layer FCCL at high frequencies.

[0086] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A biphenyl-bridged thermoplastic polyester imide, characterized in that, It is polymerized from biphenyl dibenzoate-3,3',4,4'-tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2-(4-aminobenzoate)-5-aminobiphenyl; the structural formula is shown in formula (I): (I); where m represents the number of moles of biphenyl benzoate-3,3',4,4',-tetracarboxylic acid dianhydride, m is an integer from 0 to 100, and m cannot be 0; n represents the number of moles of 3,3',4,4',-biphenyltetracarboxylic acid dianhydride, n is an integer from 0 to 100, and n is not 0.

2. The biphenyl-bridged thermoplastic polyester imide according to claim 1, characterized in that, The ratio of m to n is 0-40:60-100.

3. The method for preparing the biphenyl-bridged thermoplastic polyester imide according to claim 1 or 2, characterized in that, Includes the following steps: (1) Under nitrogen protection, biphenyl dibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and 2-(4-aminobenzoate)-5-aminobiphenyl undergo a polymerization reaction in a solvent to obtain a polyamic acid solution; (2) The polyamic acid solution is subjected to thermal imidization to obtain biphenyl-bridged thermoplastic polyester imide.

4. The preparation method according to claim 3, characterized in that, The total molar ratio of 2-(4-aminobenzoate)-5-aminobiphenyl to biphenyl dibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 1:0.9-1.

1.

5. The preparation method according to claim 4, characterized in that, The thermal imidization process employs a programmed temperature increase, with the following steps: 70-90℃ for 0.5-1.5h, 110-130℃ for 0.5-1.5h, 140-160℃ for 0.5-1.5h, 170-190℃ for 0.5-1.5h, 240-260℃ for 0.5-1.5h, and 290-310℃ for 0.5-1.5h.

6. The preparation method according to claim 5, characterized in that, The solvent is selected from at least one of anhydrous N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

7. The preparation method according to claim 6, characterized in that, The polymerization reaction was carried out at 5℃-35℃ for 20h-30h.

8. A biphenyl-bridged thermoplastic polyesterimide film, characterized in that, The composition includes the biphenyl-bridged thermoplastic polyester imide of claim 1 or 2.

9. The biphenyl-bridged thermoplastic polyesterimide film according to claim 8, characterized in that, The biphenyl-bridged thermoplastic polyesterimide film has a thickness of 0.03-0.05 mm and a linear coefficient of thermal expansion of <26×10⁻⁶. -6 / K, glass transition temperature ≥230℃, dielectric constant <3.6, dielectric loss ≤0.

005.

10. The use of the biphenyl-bridged thermoplastic polyesterimide film of claim 1 or 2, or the biphenyl-bridged thermoplastic polyesterimide film of any one of claims 8-9, in the preparation of a two-layer flexible copper-clad laminate.

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