A liquid crystal polyester, its preparation method and application

Abstract

This invention discloses a liquid crystal polyester, its preparation method, and its applications. The liquid crystal polyester of this invention is polymerized from an alicyclic imide diacid, an aromatic diacid, a hydroxy aromatic carboxylic acid, and an aromatic bisphenol. The preparation method of the liquid crystal polyester of this invention includes the following steps: mixing the alicyclic imide diacid, the aromatic diacid, and the hydroxy aromatic carboxylic acid for polymerization, then adding the aromatic bisphenol for further polymerization to obtain the liquid crystal polyester. The liquid crystal polyester of this invention has advantages such as low dielectric constant at high frequencies, low dielectric loss at high frequencies, good heat resistance, and good solubility. Furthermore, its preparation method is simple, making it suitable for large-scale industrial application as an electronic circuit substrate in the 5G communication field.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a liquid crystal polyester, its preparation method, and its applications. Background Technology

[0002] With the development of 5G communication, the frequency of signal processing and transmission in electronic devices has increased significantly, which has also led to the demand for low dielectric constant (D) substrates in electronic circuits used for signal transmission. k ) and low dielectric loss (D f The performance requirements of liquid crystal polyester (LCP) are as follows. Liquid crystal polyester (LCP) refers to polyester resins that can form liquid crystals under certain conditions. It has excellent dielectric properties, low moisture absorption, and high dimensional stability. LCP films have a very broad application prospect in the field of flexible copper clad laminates (FCCL).

[0003] However, the glass transition temperature (T) of traditional liquid crystal polyesters... g The dielectric constant of traditional liquid crystal polyesters is generally low (usually below 150℃), resulting in poor heat resistance. Furthermore, traditional liquid crystal polyesters generally have poor solubility, requiring dissolution in highly corrosive solvents, making them difficult to handle. Chlorine-containing solvents also tend to leave chloride ions, which can corrode circuits. In addition, while traditional liquid crystal polyesters exhibit low dielectric loss at high frequencies (≥10GHz), their dielectric constant is relatively high. Common methods for reducing the dielectric constant (e.g., introducing fluorine atoms, large side groups) can lower the dielectric constant to some extent, but this also compromises the liquid crystallization property, increasing dielectric loss at high frequencies. Ultimately, this makes it difficult for liquid crystal polyesters to simultaneously possess both low dielectric constant and low dielectric loss at high frequencies. In summary, traditional liquid crystal polyesters have significant shortcomings and are still unable to meet the growing demands of practical applications.

[0004] Therefore, it is of great significance to develop a liquid crystal polyester that has low dielectric constant and low dielectric loss, good heat resistance and good solubility at high frequencies. Summary of the Invention

[0005] The purpose of this invention is to provide a liquid crystal polyester, its preparation method, and its application.

[0006] The technical solution adopted in this invention is:

[0007] A liquid crystal polyester is polymerized from alicyclic imide diacid, aromatic diacid, hydroxy aromatic carboxylic acid and aromatic diphenol.

[0008] Preferably, the molar ratio of carboxyl and hydroxyl groups in the alicyclic imide diacid, aromatic diacid, hydroxy aromatic carboxylic acid and aromatic diphenol is 1:0.7 to 1.3.

[0009] More preferably, the molar ratio of carboxyl and hydroxyl groups in the alicyclic imide diacid, aromatic diacid, hydroxy aromatic carboxylic acid and aromatic diphenol is 1:0.95 to 1.05.

[0010] Preferably, the content of repeating units derived from alicyclic imide diacids in the liquid crystal polyester is 1 mol% to 29 mol%, the content of repeating units derived from aromatic diacids is 1 mol% to 29 mol%, the content of repeating units derived from hydroxy aromatic carboxylic acids is 30 mol% to 70 mol%, and the content of repeating units derived from aromatic diphenols is 1 mol% to 29 mol.

[0011] More preferably, the content of repeating units derived from alicyclic imide diacids in the liquid crystal polyester is 5 mol% to 20 mol%, the content of repeating units derived from aromatic diacids is 5 mol% to 15 mol%, the content of repeating units derived from hydroxy aromatic carboxylic acids is 40 mol% to 60 mol%, and the content of repeating units derived from aromatic diphenols is 20 mol% to 29 mol%.

[0012] Preferably, the structural formula of the alicyclic imide diacid is:

[0013] In the formula, X is one of cyclobutyl, cyclopentyl, and cyclohexyl; R1 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl; R2 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl; R3 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl; and R4 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl.

[0014] Preferably, X is one of cyclobutyl or cyclohexyl.

[0015] Preferably, R1 is hydrogen or methyl.

[0016] Preferably, R2 is hydrogen or methyl.

[0017] Preferably, R3 is hydrogen or methyl.

[0018] Preferably, R4 is hydrogen or methyl.

[0019] Preferably, the aromatic diacid is at least one selected from terephthalic acid, isophthalic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-diphenyl ether diacid.

[0020] More preferably, the aromatic diacid is at least one of terephthalic acid, isophthalic acid, and 4,4'-diphenyl ether dicarboxylic acid.

[0021] Preferably, the hydroxy aromatic carboxylic acid is at least one selected from 4-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, 1-hydroxy-4-naphthoic acid, and 4-hydroxy-6-naphthoic acid.

[0022] More preferably, the hydroxy aromatic carboxylic acid is at least one of 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

[0023] Preferably, the aromatic diphenol is at least one selected from hydroquinone, resorcinol, methyl hydroquinone, 2-methoxyhydroquinone, 2-phenyl hydroquinone, bisphenol A, bisphenol AF, tetrafluorohydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylmethane, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene.

[0024] More preferably, the aromatic diphenol is at least one of 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, and 4,4'-dihydroxydiphenylmethane.

[0025] Preferably, the weight-average molecular weight of the liquid crystal polyester is 10,000 to 150,000.

[0026] More preferably, the weight-average molecular weight of the liquid crystal polyester is 20,000 to 100,000.

[0027] A method for preparing liquid crystal polyester as described above includes the following steps: mixing alicyclic imide diacid, aromatic diacid and hydroxy aromatic carboxylic acid for polymerization reaction, and then adding aromatic diphenol for polymerization reaction to obtain liquid crystal polyester.

[0028] Preferably, the polymerization reaction is one of melt polymerization, solution polymerization, slurry polymerization, and solid-phase polymerization.

[0029] A thin film comprising the aforementioned liquid crystal polyester.

[0030] An application of liquid crystal polyester as an electronic circuit substrate as described above in the field of 5G communication.

[0031] The beneficial effects of the present invention are: the liquid crystal polyester of the present invention has the advantages of low dielectric constant at high frequency, low dielectric loss at high frequency, good heat resistance, and good solubility, and its preparation method is simple, making it suitable as an electronic circuit substrate for large-scale industrial application in the field of 5G communication.

[0032] Specifically:

[0033] 1) The liquid crystal polyester of the present invention has both low dielectric constant and low dielectric loss at high frequencies, making it suitable for use as a high-frequency communication substrate and having a very broad application prospect.

[0034] 2) The liquid crystal polyester of the present invention has a high glass transition temperature, good heat resistance, and a wide range of applications;

[0035] 3) The liquid crystal polyester of the present invention contains alicyclic imide structural units, which can effectively improve the solubility of the liquid crystal polyester, so that the liquid crystal polyester has good solubility in conventional organic solvents, which facilitates solution processing to prepare LCP films.

[0036] 4) The preparation method of the liquid crystal polyester of the present invention is simple and suitable for large-scale industrial production and application. Attached Figure Description

[0037] Figure 1 The liquid crystal polyester in Example 1 1 H NMR spectrum.

[0038] Figure 2 The images show the FT-IR spectra of the liquid crystal polyester in Example 1 and Comparative Example 1. Detailed Implementation

[0039] The present invention will be further explained and described below with reference to specific embodiments.

[0040] Example 1:

[0041] A liquid crystal polyester, the preparation method of which is as follows:

[0042] Under nitrogen protection, 3.8 mL (30.0 mmol) of benzenesulfonyl chloride (BsCl), 2.3 mL (30.0 mmol) of N,N-dimethylformamide (DMF), and 10 mL of pyridine (Py) were added to a three-necked flask. The mixture was allowed to stand at room temperature for 30 min to activate, then stirring was started, and 0.50 g (3.0 mmol) of isophthalic acid (IPA) and 0.98 g (2.0 mmol) of alicyclic imide diacid (M...) were added. w=490.14), stir at room temperature for 10 min, then transfer the three-necked flask to an oil bath at 120°C and stir for 10 min. Then dissolve 1.38 g (10 mmol) of 4-hydroxybenzoic acid (HBA) in 10 mL of Py, and quickly add it to the three-necked flask. Stir at 120°C for 30 min. Then add 0.47 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP) and 0.50 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP). 4'-Dihydroxydiphenylmethane (DPM) was dissolved in 10 mL of Py and then added dropwise to a three-necked flask using a constant pressure dropping funnel. The addition was completed in 30 min. After the addition was complete, the mixture was stirred at 120 °C for 3 h. After cooling to room temperature, the resulting polymer solution (viscous) was added dropwise to ethanol to precipitate the product. The solid product (grayish-white, fibrous) was washed several times with an appropriate amount of ethanol and then filtered. The product was then placed in an oven at 110 °C for 24 h to obtain liquid crystal polyester (weight average molecular weight of 35200).

[0043] Note:

[0044] The structural formula of the alicyclic imide diacid used in this embodiment is as follows:

[0045]

[0046] A thin film, prepared by the following method:

[0047] Add 0.4 g of the above-mentioned liquid crystal polyester to 20 mL of N-methyl-2-pyrrolidone (NMP), heat to 140 °C, stir to obtain a uniform and transparent solution, filter, take the filtrate and coat it on a clean glass plate, let it stand still, then place it in an oven and bake at 100 °C for 6 h, then at 210 °C for 1 h, cool to room temperature, then soak in water for 2 h, then peel off the film formed on the glass plate, and then place it in an oven at 110 °C for 12 h to obtain the film.

[0048] Example 2:

[0049] A liquid crystal polyester, the preparation method of which is as follows:

[0050] Under nitrogen protection, 3.8 mL (30.0 mmol) of benzenesulfonyl chloride (BsCl), 2.3 mL (30.0 mmol) of N,N-dimethylformamide (DMF), and 10 mL of pyridine (Py) were added to a three-necked flask. The mixture was allowed to stand at room temperature for 30 min to activate, then stirring was started. 0.50 g (3.0 mmol) of isophthalic acid (IPA) and 0.98 g (2.0 mmol) of an alicyclic imide dicarboxylic acid (same as in Example 1) were added, and the mixture was stirred at room temperature for 10 min. The three-necked flask was then transferred to an oil bath at 120°C and stirred for 10 min. Finally, 1.38 g (10 mmol) of 4-hydroxybenzoic acid (HBA) was added to 10 mL of Py... Dissolve the polymer in ethanol and quickly add it to a three-necked flask. Stir at 120°C for 30 min. Then, dissolve 0.47 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP) and 0.51 g (2.5 mmol) of 4,4'-dihydroxydiphenyl ether (ODP) in 10 mL of Py and add it dropwise to the three-necked flask using a constant pressure dropping funnel. The addition is completed over 30 min. After the addition is complete, stir at 120°C for 3 h and cool to room temperature. Then, add the resulting polymer solution (viscous) dropwise to ethanol to precipitate the polymer. Take the solid product (grayish-white, fibrous) and wash it several times with an appropriate amount of ethanol. Filter the product and then place it in an oven at 110°C for 24 h to obtain liquid crystal polyester (weight average molecular weight of 40,500).

[0051] A thin film, prepared by the following method:

[0052] Add 0.4 g of the above-mentioned liquid crystal polyester to 20 mL of N-methyl-2-pyrrolidone (NMP), heat to 140 °C, stir to obtain a uniform and transparent solution, filter, take the filtrate and coat it on a clean glass plate, let it stand still, then place it in an oven and bake at 100 °C for 6 h, then at 210 °C for 1 h, cool to room temperature, then soak in water for 2 h, then peel off the film formed on the glass plate, and then place it in an oven at 110 °C for 24 h to obtain the film.

[0053] Example 3:

[0054] A liquid crystal polyester, the preparation method of which is as follows:

[0055] Under nitrogen protection, 3.8 mL (30.0 mmol) of benzenesulfonyl chloride (BsCl), 2.3 mL (30.0 mmol) of N,N-dimethylformamide (DMF), and 10 mL of pyridine (Py) were added to a three-necked flask. The mixture was allowed to stand at room temperature for 30 min to activate, then stirring was started, and 0.50 g (3.0 mmol) of isophthalic acid (IPA) and 0.98 g (2.0 mmol) of alicyclic imide diacid (M...) were added. w=462.11), stir at room temperature for 10 min, then transfer the three-necked flask to an oil bath at 120°C and stir for 10 min. Then dissolve 1.38 g (10 mmol) of 4-hydroxybenzoic acid (HBA) in 10 mL of Py, and quickly add it to the three-necked flask. Stir at 120°C for 30 min. Then add 0.47 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP) and 0.50 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP). 4'-Dihydroxydiphenylmethane (DPM) was dissolved in 10 mL of Py and then added dropwise to a three-necked flask using a constant pressure dropping funnel. The addition was completed in 30 min. After the addition was complete, the mixture was stirred at 120 °C for 3 h. After cooling to room temperature, the resulting polymer solution (viscous) was added dropwise to ethanol to precipitate the product. The solid product (grayish-white, fibrous) was washed several times with an appropriate amount of ethanol and then filtered. The product was then placed in an oven at 110 °C for 24 h to obtain liquid crystal polyester (weight average molecular weight of 28600).

[0056] Note:

[0057] The structural formula of the alicyclic imide diacid used in this embodiment is as follows:

[0058]

[0059] A thin film, prepared by the following method:

[0060] Add 0.4 g of the above-mentioned liquid crystal polyester to 20 mL of N-methyl-2-pyrrolidone (NMP), heat to 140 °C, stir to obtain a uniform and transparent solution, filter, take the filtrate and coat it on a clean glass plate, let it stand still, then place it in an oven and bake at 100 °C for 6 h, then at 210 °C for 1 h, cool to room temperature, then soak in water for 2 h, then peel off the film formed on the glass plate, and then place it in an oven at 110 °C for 24 h to obtain the film.

[0061] Example 4:

[0062] A liquid crystal polyester, the preparation method of which is as follows:

[0063] Under nitrogen protection, 3.8 mL (30.0 mmol) of benzenesulfonyl chloride (BsCl), 2.3 mL (30.0 mmol) of N,N-dimethylformamide (DMF), and 10 mL of pyridine (Py) were added to a three-necked flask. The mixture was allowed to stand at room temperature for 30 min to activate, then stirring was started. 0.50 g (3.0 mmol) of isophthalic acid (IPA) and 0.98 g (2.0 mmol) of an alicyclic imide dicarboxylic acid (same as in Example 3) were added, and the mixture was stirred at room temperature for 10 min. The three-necked flask was then transferred to an oil bath at 120°C and stirred for 10 min. Finally, 1.38 g (10 mmol) of 4-hydroxybenzoic acid (HBA) was added to 10 mL of Py... Dissolve the polymer in ethanol and quickly add it to a three-necked flask. Stir at 120°C for 30 min. Then, dissolve 0.47 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP) and 0.51 g (2.5 mmol) of 4,4'-dihydroxydiphenyl ether (ODP) in 10 mL of Py and add it dropwise to the three-necked flask using a constant pressure dropping funnel. The addition is completed over 30 min. After the addition is complete, stir at 120°C for 3 h and cool to room temperature. Then, add the resulting polymer solution (viscous) dropwise to ethanol to precipitate the polymer. Take the solid product (grayish-white, fibrous) and wash it several times with an appropriate amount of ethanol. Filter the product and then place it in an oven at 110°C for 24 h to obtain liquid crystal polyester (weight average molecular weight of 24300).

[0064] A thin film, prepared by the following method:

[0065] Add 0.4 g of the above-mentioned liquid crystal polyester to 20 mL of N-methyl-2-pyrrolidone (NMP), heat to 140 °C, stir to obtain a uniform and transparent solution, filter, take the filtrate and coat it on a clean glass plate, let it stand still, then place it in an oven and bake at 100 °C for 6 h, then at 210 °C for 1 h, cool to room temperature, then soak in water for 2 h, then peel off the film formed on the glass plate, and then place it in an oven at 110 °C for 24 h to obtain the film.

[0066] Comparative Example 1: (without imidic acid)

[0067] A liquid crystal polyester, the preparation method of which is as follows:

[0068] Under nitrogen protection, 3.8 mL (30.0 mmol) of benzenesulfonyl chloride (BsCl), 2.3 mL (30.0 mmol) of N,N-dimethylformamide (DMF), and 10 mL of pyridine (Py) were added to a three-necked flask. The flask was allowed to stand at room temperature for 30 min to activate, then stirring was started, and 0.83 g (5.0 mmol) of isophthalic acid (IPA) was added. The mixture was stirred at room temperature for 10 min, then transferred to an oil bath at 120 °C and stirred for 10 min. Then, 1.38 g (10 mmol) of 4-hydroxybenzoic acid (HBA) was dissolved in 10 mL of Py and quickly added to the three-necked flask. In a flask, the mixture was stirred at 120°C for 30 min. Then, 0.47 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP) and 0.50 g (2.5 mmol) of 4,4'-dihydroxydiphenylmethane (DPM) were dissolved in 10 mL of Py and added dropwise to a three-necked flask using a constant pressure dropping funnel over 30 min. After the addition was complete, the mixture was stirred at 120°C for 3 h. After cooling to room temperature, the resulting polymer solution (viscous) was added dropwise to ethanol to precipitate the polymer. The solid product (grayish-white, fibrous) was washed several times with an appropriate amount of ethanol and then filtered. Finally, it was placed in an oven at 110°C for 24 h to obtain the liquid crystal polyester.

[0069] Comparative Example 2: (The imide diacid used does not have an alicyclic structure)

[0070] A liquid crystal polyester, the preparation method of which is as follows:

[0071] Under nitrogen protection, 3.8 mL (30.0 mmol) of benzenesulfonyl chloride (BsCl), 2.3 mL (30.0 mmol) of N,N-dimethylformamide (DMF), and 10 mL of pyridine (Py) were added to a three-necked flask. The mixture was allowed to stand at room temperature for 30 min to activate, then stirring was started, and 0.58 g (3.5 mmol) of isophthalic acid (IPA) and 1.02 g (1.5 mmol) of imidic acid (M...) were added. w=678.2), stir at room temperature for 10 min, then transfer the three-necked flask to an oil bath at 120°C and stir for 10 min. Then dissolve 1.38 g (10 mmol) of 4-hydroxybenzoic acid (HBA) in 10 mL of Py, and quickly add it to the three-necked flask. Stir at 120°C for 30 min. Then add 0.47 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP) and 0.51 g (2.5 mmol) of 4,4'-dihydroxybiphenyl (BP). 4'-Dihydroxydiphenyl ether (ODP) was dissolved in 10 mL of Py and then added dropwise to a three-necked flask using a constant pressure dropping funnel. The addition was completed in 15 min. After the addition was complete, the mixture was stirred at 120 °C for 4 h. After cooling to room temperature, the resulting polymer solution (viscous) was added dropwise to ethanol to precipitate the product. The solid product (grayish-white, fibrous) was washed several times with an appropriate amount of ethanol and then filtered. The product was then placed in an oven at 110 °C for 24 h to obtain liquid crystal polyester (weight average molecular weight of 25,000).

[0072] Note:

[0073] The structural formula of the imide dioic acid used in this comparative example is as follows:

[0074]

[0075] A thin film, prepared by the following method:

[0076] Add 0.4 g of the above-mentioned liquid crystal polyester to 20 mL of N-methyl-2-pyrrolidone (NMP), heat to 140 °C, stir to obtain a uniform and transparent solution, filter, take the filtrate and coat it on a clean glass plate, let it stand still, then place it in an oven and bake at 100 °C for 6 h, then at 210 °C for 1 h, cool to room temperature, then soak in water for 2 h, then peel off the film formed on the glass plate, and then place it in an oven at 110 °C for 24 h to obtain the film.

[0077] Performance testing:

[0078] 1) The proton nuclear magnetic resonance spectrum of the liquid crystal polyester in Example 1 (NMR spectrum) 1 H NMR (image) Figure 1 As shown.

[0079] Depend on Figure 1It can be seen that, from low field to high field, the spectral peaks between 9.08 ppm and 7.04 ppm belong to the aromatic hydrogen protons on the benzene rings of monomer units containing alicyclic imide diacids, isophthalic acid, 4-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl, and 4,4'-dihydroxydiphenylmethane. The peak at 4.00 ppm represents the absorption peak of hydrogen on the methylene group between the benzene rings in the 4,4'-dihydroxydiphenylmethane monomer unit. The peaks between 3.50 ppm and 2.20 ppm represent the methyl groups and hydrogen atoms in the alicyclic structure of the alicyclic imide diacid monomer units. No proton signal peak for hydroxyl groups appears around 9.45 ppm. In summary, this example successfully prepared a liquid crystal polyester with the desired structure.

[0080] 2) The Fourier Transmission Infrared (FT-IR) spectra of the liquid crystal polyester in Example 1 and Comparative Example 1 are shown below. Figure 2 As shown.

[0081] Depend on Figure 2 It can be seen that the liquid crystal polyester in Example 1 is at 3070cm. -1 ~2920cm -1 Absorption peaks at 1730 cm⁻¹ appeared, attributable to the methyl and methylene groups in the structure of the alicyclic imide diacid monomer. -1 An absorption peak at 1370 cm⁻¹ appeared, attributed to the C=O stretching vibration of the ester carbonyl group. This peak overlapped with the absorption peaks at 1370 cm⁻¹, attributed to the asymmetric and symmetric stretching vibrations of the carbonyl group on the imide. -1 and 720cm -1 The peaks at 3600 cm⁻¹ represent stretching vibrations of the CN bond in the imide ring and bending vibrations of the imide ring, respectively. These peaks indicate that the alicyclic imide diacid structure was successfully introduced into the molecular chain of the liquid crystal polyester. The liquid crystal polyester in Comparative Example 1 exhibited peaks at 3600 cm⁻¹. -1 ~3500cm -1 The intensity of the broad peak attributable to hydroxyl groups decreased significantly, indicating that the hydroxyl and carboxyl groups in the monomers had basically reacted completely. At the same time, the spectrum did not contain any structural signals related to polyimide, indicating that the liquid crystal polyester in Comparative Example 1 was just a common polyester polymer.

[0082] 3) The performance test results of the liquid crystal polyester / film in Examples 1-4 and Comparative Examples 1-2 are shown in the table below:

[0083] Table 1 Performance test results of liquid crystal polyester / film

[0084]

[0085] Note:

[0086] Glass transition temperature (T) g T0 of the liquid crystal polyester sample was determined using a differential scanning calorimeter under a nitrogen atmosphere. gThe test temperature range was 0℃~370℃, the first heating rate was 30℃ / min, the cooling rate was 10℃ / min, and the second heating rate was 30℃ / min. g Taken from the second temperature rise curve.

[0087] Solubility: Dissolve 10 mg of liquid crystal polyester sample in 1 mL of solvent, let stand at room temperature for one day, and observe the solubility of the sample. If it is difficult to dissolve, heat to the boiling point of the solvent and observe the change in solubility. "++" means soluble at room temperature, "+" means soluble after heating, and "-" means insoluble.

[0088] Dielectric constant (D) k ) and dielectric loss factor (D f The test was conducted using a high-frequency network analyzer (PNA-L NetworkAnalyzer N5234B). The thin film sample was 6cm × 6cm in size and the test was performed at 10GHz.

[0089] Tensile strength and tensile modulus: Tested according to tensile mode 5967 of the ASTM D882-12 material testing system. The film sample was cut into dumbbell-shaped standard tensile specimens with a size of 120mm × 15mm. The test was conducted at room temperature with a tensile load of 1000N and a tensile rate of 5mm / min. Each specimen was tested in parallel for 5 times and the average value was taken.

[0090] As shown in Table 1:

[0091] a) The liquid crystal polyesters in Examples 1-4 have low dielectric constants and dielectric losses at high frequencies, and also have high T0. g And excellent mechanical properties;

[0092] b) The solubility of the liquid crystal polyester in Comparative Example 1 is very poor, significantly worse than that of the liquid crystal polyester in Examples 1 to 4, indicating that the introduction of alicyclic imide structural units can effectively improve the solubility of liquid crystal polyester.

[0093] c) The liquid crystal polyester in Comparative Example 2 is a polyester-type liquid crystal with phenyl groups introduced as large side groups. It and the liquid crystal polyesters in Examples 1-4 all have good solubility and high thermodynamic properties. However, the liquid crystal polyesters in Examples 1-4 have significantly lower dielectric constant and dielectric loss at high frequencies (for example, compared with the liquid crystal polyester in Comparative Example 2, the dielectric constant of the liquid crystal polyester in Example 3 decreased by 7.8% and the dielectric loss decreased by 36.4%), indicating that the liquid crystal polyesters in Examples 1-4 have greater potential as a substrate in the field of high-frequency communication.

[0094] In summary, the liquid crystal polyester in this invention has excellent solubility and heat resistance, and also has low dielectric constant and dielectric loss at high frequencies, making it applicable in fields such as insulation and high-frequency flexible copper-clad laminates.

[0095] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A liquid crystal polyester, characterized in that, It is polymerized from alicyclic imide diacid, aromatic diacid, hydroxy aromatic carboxylic acid, and aromatic diphenol; the liquid crystal polyester contains repeating units derived from alicyclic imide diacid at a content of 1 mol% to 29 mol%, repeating units derived from aromatic diacid at a content of 1 mol% to 29 mol%, repeating units derived from hydroxy aromatic carboxylic acid at a content of 30 mol% to 70 mol%, and repeating units derived from aromatic diphenol at a content of 1 mol% to 29 mol%; the structural formula of the alicyclic imide diacid is: In the formula, X is one of cyclobutyl, cyclopentyl, and cyclohexyl; R1 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl; R2 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl; R3 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl; and R4 is one of hydrogen, C1-C4 alkyl, methoxy, and trifluoromethyl. The aromatic diacid is at least one of terephthalic acid, isophthalic acid, 2,3,5,6-tetrafluoroterephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-diphenyl ether dicarboxylic acid. The hydroxy aromatic carboxylic acid is 4- The aromatic diphenol is at least one of hydroquinone, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, 1-hydroxy-4-naphthoic acid, and 4-hydroxy-6-naphthoic acid; the aromatic diphenol is at least one of hydroquinone, resorcinol, methylhydroquinone, 2-methoxyhydroquinone, 2-phenylhydroquinone, bisphenol A, bisphenol AF, tetrafluorohydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylmethane, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene.

2. The liquid crystal polyester according to claim 1, characterized in that: The weight-average molecular weight of the liquid crystal polyester is 10,000 to 150,000.

3. A method for preparing liquid crystal polyester as described in claim 1 or 2, characterized in that, The process includes the following steps: mixing alicyclic imide diacid, aromatic diacid and hydroxy aromatic carboxylic acid for polymerization, and then adding aromatic diphenol for polymerization to obtain liquid crystal polyester.

4. A thin film, characterized in that, It comprises the liquid crystal polyester as described in claim 1 or 2.

5. An application of the liquid crystal polyester as described in claim 1 or 2 as an electronic circuit substrate in the field of 5G communication.

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