An all-aromatic liquid crystal polyester and its preparation method and application

Abstract

The present invention provides an all-aromatic liquid crystal polyester, which is derived from including -O-Ar1-CO- structure, -CO-Ar2-CO- structure and -O-Ar3-O- structure; and, based on the total molar percentage of Ar1+Ar2+Ar3, 1,4-phenylene accounts for 23.3-79.3 mol%, 2,6-naphthylene accounts for 20-76 mol%, 1,3-phenylene and / or 1,2-phenylene accounts for 0.02-1 mol%, and other groups account for 0-58 mol%; the molar ratio of -CO-Ar2-CO- structure to -O-Ar3-O- structure is 1.1-0.9:1. The present invention increases the phenylene structure in the molecular chain, reduces the melting enthalpy, and thereby realizes the increase of the melting point of the all-aromatic liquid crystal polyester. At the same time, a small amount of bent and asymmetric structure is introduced into the molecular chain structure, maintaining good film formability and high tensile strength of the all-aromatic liquid crystal polyester.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly to an all-aromatic liquid crystal polyester and a preparation method and application thereof. Background Art

[0002] Due to the extremely low dielectric constant / dielectric loss performance and excellent flexibility, the thermoplastic liquid crystal polyester film can meet the requirements of low signal loss of antenna materials for high-frequency signal transmission in 5G communication technology and the complex structural design requirements of multilayer three-dimensional antenna materials for personal terminal devices.

[0003] Based on the requirements of low signal loss of antenna materials for personal terminal devices in high-frequency signal transmission of 5G communication technology and the complex structural design requirements of multilayer three-dimensional antenna materials for personal intelligent communication terminal devices, the film-grade thermoplastic liquid crystal polyester resin applied to antenna materials should have extremely low dielectric constant and dielectric loss performance and excellent flexibility, and at the same time, should also have good film-forming performance.

[0004] In addition, for high-performance cutting-edge electronic devices, in order to meet the reliable connection of electronic components in antenna materials with complex three-dimensional structures, the soldering and mounting processing technology needs to be carried out at a higher temperature. Therefore, the film-grade thermoplastic liquid crystal polyester resin must also exhibit high heat resistance.

[0005] For thermoplastic liquid crystal polyester, the improvement of its heat resistance is usually achieved by increasing the melting point. Generally speaking, the increase in the melting point of thermoplastic liquid crystal polyester is achieved by reducing its melting entropy. However, excessive rigidity of the molecular chain will lead to a decrease in the melt strength of thermoplastic liquid crystal polyester, which is not conducive to film forming. In the existing patent solutions, although the introduction of a small amount of non-aromatic flexible monomers can maintain the melt strength of thermoplastic liquid crystal polyester, it is easy to cause a decrease in the mechanical properties of thermoplastic liquid crystal polyester. Summary of the Invention

[0006] The purpose of the present invention is to provide an all-aromatic liquid crystal polyester, which has the advantages of good heat resistance, good film-forming property and high tensile strength.

[0007] Another purpose of the present invention is to provide a preparation method and application of the above all-aromatic liquid crystal polyester.

[0008] The present invention is achieved by the following technical solutions:

[0009] An all-aromatic liquid crystal polyester is derived from including -O-Ar1-CO- structure, -CO-Ar2-CO- structure and -O-Ar3-O- structure; wherein,

[0010] Ar1 is at least one of 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 2,6-naphthylene, 2,7-naphthylene, 2,2'-biphenylene, 2,3'-biphenylene, 2,4'-biphenylene, 3,3'-biphenylene, 3,4'-biphenylene, 4,4'-biphenylene;

[0011] Ar2 is at least one of 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 2,6-naphthylene, 2,7-naphthylene, 2,2'-biphenylene, 2,3'-biphenylene, 2,4'-biphenylene, 3,3'-biphenylene, 3,4'-biphenylene, 4,4'-biphenylene;

[0012] Ar3 is at least one of 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 2,6-naphthylene, 2,7-naphthylene, 2,2'-biphenylene, 2,3'-biphenylene, 2,4'-biphenylene, 3,3'-biphenylene, 3,4'-biphenylene, 4,4'-biphenylene;

[0013] Moreover, based on the total molar percentage of Ar1 + Ar2 + Ar3, 1,4-phenylene accounts for 23.3 - 79.3 mol%, 2,6-naphthylene accounts for 20 - 76 mol%, 1,3-phenylene and / or 1,2-phenylene accounts for 0.01 - 1 mol%, and other groups account for 0 - 56.68 mol%;

[0014] The molar ratio of the -CO-Ar2-CO- structure to the -O-Ar3-O- structure is 1.1 - 0.9:1.

[0015] Preferably, other groups in the Ar1 are selected from at least one of 3,4'-biphenylene and 3,3'-biphenylene, other groups in the Ar2 are selected from at least one of 3,4'-biphenylene and 4,4'-biphenylene, and other groups in the Ar3 are selected from at least one of 4,4'-biphenylene and 3,3'-biphenylene.

[0016] Preferably, based on the total molar percentage of Ar1 + Ar2 + Ar3, 1,4-phenylene accounts for 23.3 - 26.2 mol%, 2,6-naphthylene accounts for 73 - 75.9 mol%, 1,3-phenylene and 1,2-phenylene account for 0.8 - 1 mol%, and other groups account for 0 - 3 mol%.

[0017] More preferably, in terms of the total molar percentage of Ar1 + Ar2 + Ar3, 1,4-phenylene accounts for 71-77.9 mol%, 2,6-naphthylene accounts for 22-28.98 mol%, 1,3-phenylene and 1,2-phenylene account for 0.02-0.8 mol%, and other groups account for 0-6.98 mol%.

[0018] The content of each unit and structure of the liquid crystal polyester of the present invention can be tested by the following method: Dissolve the resin sample in a mixed solvent of pentafluorophenol and deuterated DMSO at 100 °C, and perform nuclear magnetic carbon spectrum characterization and calculation at 90 °C.

[0019] The melting point range of the wholly aromatic liquid crystal polyester is 260-350 °C.

[0020] The melt viscosity range of the wholly aromatic liquid crystal polyester is 30-50 Pa·s.

[0021] The tensile strength range of the wholly aromatic liquid crystal polyester is 160-230 MPa.

[0022] The preparation method of the wholly aromatic liquid crystal polyester of the present invention includes the following steps: Under the condition of inert gas pressurization, the reaction monomers are subjected to acylation reaction under the action of an acylating agent, the pressure is maintained at 0.1 MPa to 0.2 MPa, the reaction temperature is 100 °C to 180 °C, and the reaction time is 30 minutes to 10 hours; after the acylation reaction is completed, the pressure in the reaction kettle is reduced to atmospheric pressure, and the temperature is raised to 200 °C to 400 °C at a rate of 0.1 °C / min to 150 °C / min, and acetic acid and unreacted acetic anhydride are discharged from the distillation column. When the acetic acid receiving amount reaches more than 90% of the theoretical value, the pressure in the reaction kettle is reduced to 1-10 kPa, and under this reduced pressure condition, the reaction system is programmed to raise the temperature to the highest reaction temperature of 320-360 °C, and melt polycondensation is carried out to obtain a prepolymer; the prepolymer is cooled and solidified and granulated, and solid-phase polymerization is carried out in a solid-phase polymerization container to obtain wholly aromatic liquid crystal polyester particles, the vacuum degree is 0.1 Pa to 50 kPa, the solid-phase polymerization temperature is 160-340 °C, and the reaction time is 0.5 hour to 40 hours.

[0023] The acylating agent can be acetic anhydride, propionic anhydride, butyric anhydride, etc., and acetic anhydride is preferred.

[0024] In the Ar1 structure, the 1,4-phenylene is derived from 4-hydroxybenzoic acid, the 1,3-phenylene is derived from 3-hydroxybenzoic acid, the 1,2-phenylene is derived from 2-hydroxybenzoic acid, the 2,6-naphthylene is derived from 2-hydroxy-6-naphthoic acid, the 2,2'-biphenylene is derived from 2-hydroxy-2'-carboxybiphenyl, the 2,3'-biphenylene is derived from 2-hydroxy-3'-carboxybiphenyl, the 2,4'-biphenylene is derived from 2-hydroxy-4'-carboxybiphenyl, the 3,3'-biphenylene is derived from 3-hydroxy-3'-carboxybiphenyl, the 3,4'-biphenylene is derived from 3-hydroxy-4'-carboxybiphenyl, the 2,7-naphthylene is derived from 2-hydroxy-7-naphthoic acid, and the 4,4'-biphenylene is derived from 4-hydroxy-4'-carboxybiphenyl.

[0025] In the Ar2 structure, the 1,4-phenylene is derived from terephthalic acid, the 1,3-phenylene is derived from isophthalic acid, the 1,2-phenylene is derived from phthalic acid, the 2,6-naphthylene is derived from 2,6-naphthalenedicarboxylic acid, the 2,2'-biphenylene is derived from 2,2'-biphenyldicarboxylic acid, the 2,3'-biphenylene is derived from 2,3'-biphenyldicarboxylic acid, the 2,4'-biphenylene is derived from 2,4'-biphenyldicarboxylic acid, the 3,3'-biphenylene is derived from 3,3'-biphenyldicarboxylic acid, the 3,4'-biphenylene is derived from 3,4'-biphenyldicarboxylic acid, the 2,7-naphthylene is derived from 2,7-naphthalenedicarboxylic acid, and the 4,4'-biphenylene is derived from 4,4'-biphenyldicarboxylic acid.

[0026] In the Ar3 structure, the 1,4-phenylene is derived from hydroquinone, the 1,3-phenylene is derived from resorcinol, the 1,2-phenylene is derived from catechol, the 2,6-naphthylene is derived from 2,6-naphthalenediol, the 2,2'-biphenylene is derived from 2,2'-biphenyldiol, the 2,3'-biphenylene is derived from 2,3'-biphenyldiol, the 2,4'-biphenylene is derived from 2,4'-biphenyldiol, the 3,3'-biphenylene is derived from 3,3'-biphenyldiol, the 3,4'-biphenylene is derived from 3,4'-biphenyldiol, the 2,7-naphthylene is derived from 2,7-naphthalenediol, and the 4,4'-biphenylene is derived from 4,4'-biphenyldiol.

[0027] The application of the wholly aromatic liquid crystal polyester of the present invention is to prepare films, especially films for 5G devices.

[0028] The present invention has the following beneficial effects:

[0029] First, by increasing the phenylene structure in the molecular chain, the present invention improves the rigidity of the molecular chain to reduce the melting enthalpy, thereby achieving an increase in the melting point of the wholly aromatic liquid crystal polyester (greater than or equal to 260 °C).

[0030] Second, by introducing a certain amount of kinked asymmetric structures (1,3-phenylene and / or 1,2-phenylene) into the molecular chain structure, the present invention maintains good film formability and high tensile strength of the wholly aromatic liquid crystal polyester. Detailed Embodiments

[0031] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0032] The monomers and acylating agents used in the polymerization of the liquid crystal polyester in the examples and comparative examples are commercially available products.

[0033] Preparation methods of the liquid crystal polyester in the examples and comparative examples: Under the condition of nitrogen pressurization, the reaction monomers are subjected to an acylation reaction under the action of an acylating agent (acetic anhydride), the pressure is maintained at 0.1 MPa to 0.2 MPa, the reaction temperature is 120 °C to 160 °C, and the reaction time is 30 minutes to 2 hours; after the acylation reaction is completed, the pressure in the reaction kettle is reduced to atmospheric pressure, and the temperature is raised to 200 °C to 300 °C at a rate of 0.1 °C / min to 10 °C / min, and acetic acid and unreacted acetic anhydride are discharged from the distillation column. When the acetic acid receiving amount reaches more than 90% of the theoretical value, the pressure in the reaction kettle is reduced to 1 to 10 kPa, and under this reduced pressure condition, the reaction system is programmed to raise the temperature to the highest reaction temperature of 320 to 360 °C to obtain a prepolymer by melt polycondensation; the prepolymer is cooled and solidified and granulated, and solid-phase polymerization is carried out in a solid-phase polymerization container to obtain wholly aromatic liquid crystal polyester particles, the vacuum degree is 0.1 Pa to 50 kPa, the solid-phase polymerization temperature is 160 to 340 °C, and the reaction time is 5 hours to 20 hours.

[0034] Each test method:

[0035] (1) Melting point: The melting point is measured by DSC. Starting from room temperature, the temperature is raised to the highest temperature of the melting point + 30 °C at a heating rate of 20 °C / min. After staying at this temperature for 3 min, the temperature is then lowered to room temperature at a rate of 20 °C / min. After the test sample stays at room temperature for 3 min, the temperature is raised to the highest temperature of the melting point + 30 °C again at a heating rate of 20 °C / min to obtain the second melting curve of the liquid crystal polyester, and the melting peak of this curve is selected as the melting point.

[0036] (2) Melt viscosity: It is measured by a capillary rheometer. The test temperature is 0 to 30 °C higher than the melting point, and the shear rate is 1000 s -1 , and a die with an inner diameter of 1 mm and a length of 20 mm is used for measurement.

[0037] (3) Tensile strength: Tested in accordance with the ISO 527-2012 standard.

[0038] (4) Film-forming property: The film-forming property was verified by the blown film method in which the molten resin was extruded into a cylindrical shape by an extruder equipped with an annular die head, cooled, and wound up. The scoring is as follows:

[0039] - Unable to form a film;

[0040] + Can form a film, but the continuity is poor and there are many spots on the film surface (less than or equal to 10 spots in a 10 cm * 10 cm film);

[0041] ++ Can form a continuous film, there are relatively many spots on the film surface, but it can meet most application scenarios (less than or equal to 5 spots in a 10 cm * 10 cm film);

[0042] +++ Can form a continuous film, the film surface is smooth and there are a small number of spots (less than or equal to 2 spots in a 10 cm * 10 cm film);

[0043] ++++ Can form a continuous film, the film surface is smooth and almost spotless (less than or equal to 1 spot in a 10 cm * 10 cm film).

[0044] Liquid crystal polyester in Example 1 is derived from the following monomers:

[0045] -O-Ar1-CO- structure: 4-hydroxybenzoic acid 79.3 mol%; 2-hydroxy-6-naphthoic acid 19.3 mol%

[0046] -CO-Ar2-CO- structure: 2,6-naphthalenedicarboxylic acid 0.7 mol%;

[0047] -O-Ar3-O- structure: resorcinol 0.7 mol%.

[0048] Liquid crystal polyester in Example 2 is derived from the following monomers:

[0049] -O-Ar1-CO- structure: 4-hydroxybenzoic acid 22.6 mol%, 2-hydroxy-6-naphthoic acid 76 mol%;

[0050] -CO-Ar2-CO- structure: isophthalic acid 0.7 mol%;

[0051] -O-Ar3-O- structure: hydroquinone 0.7 mol%.

[0052] Liquid crystal polyester in Example 3 is derived from the following monomers:

[0053] -O-Ar1-CO- structure: 2-hydroxy-6-naphthoic acid 64.5 mol%, 4-hydroxybenzoic acid 34.5 mol%;

[0054] -CO-Ar2-CO- structure: 0.5 mol% of 2,6-naphthalenedicarboxylic acid;

[0055] -O-Ar3-O- structure: 0.5 mol% of resorcinol.

[0056] Example 4 The liquid crystal polyester is derived from the following monomers:

[0057] -O-Ar1-CO- structure: 73.2 mol% of 2-hydroxy-6-naphthoic acid, 25 mol% of 4-hydroxybenzoic acid;

[0058] -CO-Ar2-CO- structure: 0.9 mol% of isophthalic acid;

[0059] -O-Ar3-O- structure: 0.9 mol% of 2,6-naphthalenediol.

[0060] Example 5 The liquid crystal polyester is derived from the following monomers:

[0061] -O-Ar1-CO- structure: 0.8 mol% of 3-hydroxybenzoic acid, 26.1 mol% of 4-hydroxybenzoic acid; 72.9 mol% of 2-hydroxy-6-naphthoic acid

[0062] -CO-Ar2-CO- structure: 0.1 mol% of 2,6-naphthalenedicarboxylic acid;

[0063] -O-Ar3-O- structure: 0.1 mol% of hydroquinone.

[0064] Example 6 The liquid crystal polyester is derived from the following monomers:

[0065] -O-Ar1-CO- structure: 0.8 mol% of 3-hydroxybenzoic acid, 22.3 mol% of 4-hydroxybenzoic acid, 74.9 mol% of 2-hydroxy-6-naphthoic acid;

[0066] -CO-Ar2-CO- structure: 1 mol% of 2,6-naphthalenedicarboxylic acid;

[0067] -O-Ar3-O- structure: 1 mol% of hydroquinone.

[0068] Example 7 The liquid crystal polyester is derived from the following monomers:

[0069] -O-Ar1-CO- structure: 1 mol% of 3-hydroxybenzoic acid, 23.5 mol% of 4-hydroxybenzoic acid, 74.5 mol% of 2-hydroxy-6-naphthoic acid;

[0070] -CO-Ar2-CO- structure: 0.5 mol% of terephthalic acid;

[0071] -O-Ar3-O- structure: 0.5 mol% of 2,6-naphthalenediol.

[0072] Example 8 The liquid crystal polyester is derived from the following monomers:

[0073] -O-Ar1-CO- structure: 0.01 mol% of 3-hydroxybenzoic acid, 71 mol% of 4-hydroxybenzoic acid; 28.97 mol% of 2-hydroxy-6-naphthoic acid;

[0074] -CO-Ar2-CO- structure: 0.01 mol% of isophthalic acid;

[0075] -O-Ar3-O- structure: 0.01 mol% of 2,6-naphthalenediol.

[0076] Example 9 The liquid crystal polyester is derived from the following monomers:

[0077] -O-Ar1-CO- structure: 0.1 mol% of 3-hydroxybenzoic acid, 73 mol% of 4-hydroxybenzoic acid; 26.1 mol% of 2-hydroxy-6-naphthoic acid;

[0078] -CO-Ar2-CO- structure: 0.4 mol% of isophthalic acid;

[0079] -O-Ar3-O- structure: 0.4 mol% of 2,6-naphthalenediol.

[0080] Example 10 The liquid crystal polyester is derived from the following monomers:

[0081] -O-Ar1-CO- structure: 0.1 mol% of 3-hydroxybenzoic acid, 77.9 mol% of 4-hydroxybenzoic acid; 21.8 mol% of 2-hydroxy-6-naphthoic acid;

[0082] -CO-Ar2-CO- structure: 0.1 mol% of 2,6-naphthalenedicarboxylic acid;

[0083] -O-Ar3-O- structure: 0.1 mol% of 2,6-naphthalenediol.

[0084] Example 11 The liquid crystal polyester is derived from the following monomers:

[0085] -O-Ar1-CO- structure: 22.6 mol% of 4-hydroxybenzoic acid, 64 mol% of 2-hydroxy-6-naphthoic acid, 12 mol% of 3-hydroxy-4'-carboxybiphenyl;

[0086] -CO-Ar2-CO- structure: 0.7 mol% of isophthalic acid;

[0087] -O-Ar3-O- structure: 0.7 mol% of hydroquinone.

[0088] Example 12 The liquid crystal polyester is derived from the following monomers:

[0089] -O-Ar1-CO- structure: 22.6 mol% of 4-hydroxybenzoic acid, 64 mol% of 2-hydroxy-6-naphthoic acid, 12 mol% of 3-hydroxy-3'-carboxybiphenyl;

[0090] -CO-Ar2-CO- structure: 0.7 mol% of isophthalic acid;

[0091] -O-Ar3-O- structure: 0.7 mol% of hydroquinone.

[0092] Example 13 The liquid crystal polyester is derived from the following monomers:

[0093] -O-Ar1-CO- structure: 22.6 mol% of 4-hydroxybenzoic acid, 64 mol% of 2-hydroxy-6-naphthoic acid, 12 mol% of 2-hydroxy-2'-carboxybiphenyl;

[0094] -CO-Ar2-CO- structure: 0.7 mol% of isophthalic acid;

[0095] -O-Ar3-O- structure: 0.7 mol% of hydroquinone.

[0096] Example 14 The liquid crystal polyester is derived from the following monomers:

[0097] -O-Ar1-CO- structure: 22.6 mol% of 4-hydroxybenzoic acid, 64 mol% of 2-hydroxy-6-naphthoic acid;

[0098] -CO-Ar2-CO- structure: 0.7 mol% of isophthalic acid, 6 mol% of 3,4'-biphenyldicarboxylic acid;

[0099] -O-Ar3-O- structure: 0.7 mol% of hydroquinone, 6 mol% of 4,4'-biphenyldiol.

[0100] Example 15 The liquid crystal polyester is derived from the following monomers:

[0101] -O-Ar1-CO- structure: 22.6 mol% of 4-hydroxybenzoic acid, 64 mol% of 2-hydroxy-6-naphthoic acid;

[0102] -CO-Ar2-CO- structure: 0.7 mol% of isophthalic acid, 6 mol% of 4,4'-biphenyldicarboxylic acid;

[0103] -O-Ar3-O- structure: 0.7 mol% of hydroquinone, 6 mol% of 3,3'-biphenyldiol.

[0104] Example 16 The liquid crystal polyester is derived from the following monomers:

[0105] -O-Ar1-CO- structure: 4-hydroxybenzoic acid 22.6 mol%, 2-hydroxy-6-naphthoic acid 64 mol%;

[0106] -CO-Ar2-CO- structure: isophthalic acid 0.7 mol%, 3,4'-biphenyldicarboxylic acid 6 mol%;

[0107] -O-Ar3-O- structure: hydroquinone 0.7 mol%, 3,3'-biphenol 6 mol%.

[0108] Example 17 The liquid crystal polyester is derived from the following monomers:

[0109] -O-Ar1-CO- structure: 4-hydroxybenzoic acid 22.6 mol%, 2-hydroxy-6-naphthoic acid 64 mol%;

[0110] -CO-Ar2-CO- structure: isophthalic acid 0.7 mol%, 3,4'-biphenyldicarboxylic acid 6 mol%;

[0111] -O-Ar3-O- structure: hydroquinone 0.7 mol%, 2,3'-biphenol 6 mol%.

[0112] Example 18 The liquid crystal polyester is derived from the following monomers:

[0113] -O-Ar1-CO- structure: 4-hydroxybenzoic acid 22.6 mol%, 2-hydroxy-6-naphthoic acid 64 mol%;

[0114] -CO-Ar2-CO- structure: isophthalic acid 0.7 mol%, 2,3'-biphenyldicarboxylic acid 6 mol%;

[0115] -O-Ar3-O- structure: hydroquinone 0.7 mol%, 2,3'-biphenol 6 mol%.

[0116] Example 19 The liquid crystal polyester is derived from the following monomers:

[0117] -O-Ar1-CO- structure: 4-hydroxybenzoic acid 22.8 mol%, 2-hydroxy-6-naphthoic acid 64 mol%, 2-hydroxy-2'-carboxybiphenyl 12 mol%;

[0118] -CO-Ar2-CO- structure: phthalic acid 0.6 mol%;

[0119] -O-Ar3-O- structure: hydroquinone 0.6 mol%.

[0120] Comparative Example 1 The liquid crystal polyester is derived from the following monomers:

[0121] -O-Ar1-CO- structure: 0 mol% of 3-hydroxybenzoic acid, 40 mol% of 4-hydroxybenzoic acid;

[0122] -CO-Ar2-CO- structure: 30 mol% of 2,6-naphthalenedicarboxylic acid;

[0123] -O-Ar3-O- structure: 30 mol% of 2,6-naphthalenediol.

[0124] Comparative Example 2 The liquid crystal polyester is derived from the following monomers:

[0125] -O-Ar1-CO- structure: 1.5 mol% of 3-hydroxybenzoic acid, 38.5 mol% of 4-hydroxybenzoic acid;

[0126] -CO-Ar2-CO- structure: 30 mol% of 2,6-naphthalenedicarboxylic acid;

[0127] -O-Ar3-O- structure: 30 mol% of 2,6-naphthalenediol.

[0128] Comparative Example 3 The liquid crystal polyester is derived from the following monomers:

[0129] -O-Ar1-CO- structure: 0.1 mol% of 3-hydroxybenzoic acid, 9.9 mol% of 4-hydroxybenzoic acid;

[0130] -CO-Ar2-CO- structure: 45 mol% of 2,6-naphthalenedicarboxylic acid;

[0131] -O-Ar3-O- structure: 45 mol% of 2,6-naphthalenediol.

[0132] Comparative Example 4 The liquid crystal polyester is derived from the following monomers:

[0133] -O-Ar1-CO- structure: 0.1 mol% of 3-hydroxybenzoic acid, 89.9 mol% of 4-hydroxybenzoic acid;

[0134] -CO-Ar2-CO- structure: 5 mol% of 2,6-naphthalenedicarboxylic acid;

[0135] -O-Ar3-O- structure: 5 mol% of 2,6-naphthalenediol.

[0136] Comparative Example 5 The liquid crystal polyester is derived from the following monomers:

[0137] -O-Ar1-CO- structure: 0.4 mol% of 3-hydroxybenzoic acid, 15 mol% of 4-hydroxybenzoic acid;

[0138] -CO-Ar2-CO- structure: 2,6-naphthalenedicarboxylic acid 42.3 mol%;

[0139] -O-Ar3-O- structure: 2,6-naphthalenediol 42.3 mol%.

[0140] Table 1: Test results of various liquid crystal polyesters in examples and comparative examples

[0141] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Melting point, °C 340 325 262 315 316 323 321 Melt viscosity, Pa·s 41 42 41 36 40 42 43 Tensile strength, MPa 173 174 177 191 192 190 189 Film-forming property ++ ++ ++ +++ +++ +++ +++

[0142] Continued Table 1:

[0143] Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Melting point, °C 271 281 311 317 316 314 313 Melt viscosity, Pa·s 41 40 41 39 31 39 42 Tensile strength, MPa 209 211 212 180 176 165 177 Film-forming property ++++ ++++ ++++ ++ ++ ++ ++

[0144] Continued Table 1:

[0145] Example 15 Example 16 Example 17 Example 18 Example 19 Melting point, °C 311 318 313 319 313 Melt viscosity, Pa·s 42 48 43 44 40 Tensile strength, MPa 177 178 167 160 166 Film-forming property ++ ++ ++ ++ ++

[0146] As can be seen from Examples 1-10, preferably, 1,4-phenylene accounts for 23.3-26.2 mol%, 2,6-naphthylene accounts for 73-75.9 mol%, 1,3-phenylene and 1,2-phenylene account for 0.8-1 mol%, and other groups account for 0-3 mol%. When the following ranges are preferred, the tensile strength is higher and the film-forming property is better: 1,4-phenylene accounts for 71-77.9 mol%, 2,6-naphthylene accounts for 22-28.98 mol%, 1,3-phenylene and 1,2-phenylene account for 0.02-0.8 mol%, and other groups account for 0-6.98 mol%.

[0147] As can be seen from Examples 11-18, among the other groups in Ar1, 3,4'-biphenylene and 3,3'-biphenylene are preferred; among the other groups in Ar2, 3,4'-biphenylene and 4,4'-biphenylene are preferred; among the other groups in Ar3, 4,4'-biphenylene and 3,3'-biphenylene are preferred.

[0148] Continued Table 1:

[0149] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Melting point, °C 314 313 * * * Melt viscosity, Pa·s 42 41 * * * Tensile strength, MPa 154 153 * * * Film-forming property - - * * *

[0150] In the above table, * indicates that curing occurred during the reaction and granulation could not be carried out.

[0151] As can be seen from Comparative Example 1, when there is no 1,3-phenylene and / or 1,2-phenylene in the chain segment structure, the film-forming property is insufficient.

[0152] As can be seen from Comparative Example 2, when the content of 1,3-phenylene and / or 1,2-phenylene in the chain segment structure is too high, good film-forming property cannot be achieved either.

[0153] As can be seen from Comparative Examples 3-5, not only the content of 1,3-phenylene and / or 1,2-phenylene needs to be within the scope of the present invention, but when the content of other groups is not within the scope of the present invention, good film-forming properties cannot be achieved either.

Claims

1. An all-aromatic liquid crystal polyester, characterized in that, Derived from the -O-Ar1-CO- structure, -CO-Ar2-CO- structure, and -O-Ar3-O- structure; wherein, Based on the total molar percentage of Ar1+Ar2+Ar3, 1,4-phenylene accounts for 71-77.9 mol%, 2,6-naphthylene accounts for 22-28.98 mol%, and 1,3-phenylene accounts for 0.02-0.5 mol%; The said Ar1 is derived from 4-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, and 3-hydroxybenzoic acid; The said Ar2 is derived from one of isophthalic acid or 2,6-naphthalenedicarboxylic acid, and when Ar2 is derived from 2,6-naphthalenedicarboxylic acid, the content of Ar2 is 0.1 mol%; The said Ar3 is derived from 2,6-naphthalenediol; The molar ratio of the -CO-Ar2-CO- structure to the -O-Ar3-O- structure is 1.1-0.9:

1.

2. The wholly aromatic liquid crystal polyester according to claim 1, characterized in that, The melting point range of the said wholly aromatic liquid crystal polyester is 260~350°C.

3. The wholly aromatic liquid crystal polyester according to claim 1, wherein The melt viscosity range of the said wholly aromatic liquid crystal polyester is 30-50 Pa·s.

4. The wholly aromatic liquid crystal polyester according to claim 1, wherein The tensile strength range of the said wholly aromatic liquid crystal polyester is 160~230 MPa.

5. A method for preparing the wholly aromatic liquid crystalline polyester according to any one of claims 1-4, characterized in that, Including the following steps: Under the condition of inert gas pressurization, the reaction monomers are subjected to acylation reaction under the action of an acylating agent, the pressure is maintained at 0.1 MPa~0.2 MPa, the reaction temperature is 100°C~180°C, and the reaction time is 30 minutes~10 hours; after the acylation reaction is completed, the pressure in the reaction kettle is reduced to atmospheric pressure, and the temperature is raised to 200°C~400°C at a rate of 0.1°C / min~150°C / min, and acetic acid and unreacted acetic anhydride are discharged from the rectifying column. When the acetic acid receiving amount reaches more than 90% of the theoretical value, the pressure in the reaction kettle is reduced to 1~10 kPa, and under this reduced pressure condition, the reaction system is programmed to raise the temperature to the highest reaction temperature of 320~360°C, and a prepolymer is obtained by melt polycondensation; the prepolymer is cooled and solidified and granulated, and solid-phase polymerization is carried out in a solid-phase polymerization container to obtain wholly aromatic liquid crystal polyester particles, the vacuum degree is 0.1 Pa~50 kPa, the solid-phase polymerization temperature is 160~340°C, and the reaction time is 0.5 hours~40 hours.

6. Use of the wholly aromatic liquid crystalline polyester according to any one of claims 1 to 4, characterized in that, For preparing films.