Liquid crystal polyester composite material as well as preparation method and application thereof

Abstract

The invention discloses a liquid crystal polyester composite material which comprises the following components in parts by weight: 39-71 parts of liquid crystal polyester; 5 to 15 parts of wollastonite fiber; 13 to 28 parts of a flaky filler; 5-15 parts of a spherical filler; the liquid crystal polyester is composed of the following monomers in mole percentage: 50-55 mol% of 6-hydroxy-2-naphthoic acid, 10-30 mol% of a solvent, and 10-30 mol% of a solvent. 20 to 25 mol% of terephthalic acid; 20 to 25 mol% of biphenol; 0-5 mol% of p-hydroxybenzoic acid; and 0-0.05 mol% of other monomers. According to the liquid crystal polyester composite material disclosed by the invention, the calorific value is reduced in the microwave-resistant process through the liquid crystal polyester of a specific repetitive unit, and meanwhile, excellent heat conductivity can be obtained through the cooperation of the wollastonite fibers, the flaky filler and the spherical filler, so that the generated heat can be exported, and the liquid crystal polyester composite material disclosed by the invention can resist a microwave environment. In addition, the liquid crystal polyester composite material disclosed by the invention has the advantage of low warping.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a liquid crystal polyester composite material and a preparation method and application thereof. Background Art

[0002] LCP material is a high molecular polymer with fast crystallization speed, high temperature resistance, self-flame retardant, excellent dielectric properties, high modulus, high strength, and strong anisotropy. It is widely used in the electronics, electrical, and home appliances industries. Due to its unique high fluidity, high temperature resistance, dimensional stability and other characteristics, it can be used in precision electronic devices, baking utensils, etc.

[0003] However, LCP parts will generate heat during the microwave resistance process, and the temperature rise will lead to material degradation. The existing technology improves microwave resistance materials as follows: first, improve the heat resistance level of the material, such as the melting point, but in fact, the temperature rise of the material will not decrease, and the temperature rise of the material itself will lead to a rapid decrease in mechanical properties; second, improve the rigidity of the material itself, such as increasing the content of reinforcing fibers such as carbon fiber and glass fiber, and increase the heat deformation temperature, but it is still impossible to avoid the temperature rise of the material itself. The macroscopic system has not deformed, but the local resin has undergone molecular chain movement; third, add metal or conductive shells to form a Faraday cage for microwave shielding, which cannot penetrate microwaves and is easy to discharge, limiting its use. Summary of the invention

[0004] The object of the present invention is to overcome the above technical defects and provide a microwave-resistant and low-warping liquid crystal polyester composite material.

[0005] The present invention is achieved through the following technical solutions: A liquid crystal polyester composite material, comprising the following components in parts by weight: 39-71 parts of liquid crystal polyester; Wollastonite fiber 5-15 parts; 13-28 parts of flake filler; 5-15 parts of spherical filler; In terms of molar percentage, the liquid crystal polyester is composed of the following monomers: 6-Hydroxy-2-naphthoic acid 50-55 mol%; Terephthalic acid 20-25 mol%; Biphenylene glycol 20-25 mol% p-Hydroxybenzoic acid 0-5 mol%; Other monomers 0-0.05 mol%.

[0006] Preferably, the following components are included by weight: 40-70 parts of liquid crystal polyester; Wollastonite fiber 8-12 parts; 18-22 parts of flake filler; 8-12 parts of spherical filler.

[0007] The flaky filler is selected from at least one of talc, mica and boron nitride; preferably, the flaky filler is selected from boron nitride.

[0008] The spherical filler is selected from at least one of aluminum oxide and zinc oxide.

[0009] The average particle size range of the flake filler is D50 = 15-30 microns; The average particle size range of spherical fillers is D50 = 1-20 microns; The D50 particle size refers to the standard ISO13320 (2020). The filler is dispersed with alcohol and tested with a laser particle size analyzer to obtain the D50 particle size result of the material.

[0010] The aspect ratio of wollastonite fiber is in the range of (8-20):1.

[0011] The other monomers are selected from at least one of isophthalic acid, 1,4-benzenediol and 2,6-naphthalene dicarboxylic acid.

[0012] Preferably, the melting point of the liquid crystal polyester is greater than 280°C.

[0013] Preferably, the LCP resin is 20°C above the melting point and 1000 -S The melt viscosity under shear rate conditions is 10-50Pa·s. At 20℃ above the melting point, 1000 -S Under shear rate conditions, the test method is based on the determination method of ISO 11443, and the equipment used is Goettfert high pressure capillary rheometer, RG20, 1mm test die.

[0014] The liquid crystal polyester can be a commercially available product or can be obtained by self-production. The self-production method is, for example, but not limited to: under inert gas pressure conditions, the reaction monomer is subjected to an acylation reaction under the action of an acylating agent, the pressure is maintained at 0.1MPa~0.2MPa, the reaction temperature is 100℃~180℃, and the reaction time is 30 minutes~10 hours; after the acylation reaction is completed, the pressure in the reactor is reduced to normal pressure, and the reaction temperature is increased at 0.1℃ / min~150℃ / min The temperature is raised to 200℃~400℃ at a rate of 1.5℃, and acetic acid and unreacted anhydride are discharged from the distillation column. When the acetic acid reception reaches more than 90% of the theoretical value, the pressure in the reactor is reduced to 1~10kPa, and the reduced pressure condition is maintained and the reaction system is heated to the maximum reaction temperature of 320~360℃, and melt polycondensation is performed to obtain a prepolymer; the prepolymer is cooled, solidified and granulated, and solid-phase polymerization is performed in a solid-phase polymerization container to obtain liquid crystal polyester particles, the vacuum degree is 0.1Pa~50kPa, the solid-phase polymerization temperature is 160~340℃, and the reaction time is 0.5 hours~40 hours. The acylating agent can be acetic anhydride, propionic anhydride, butyric anhydride, etc.

[0015] It is possible to choose whether to add 0-2 parts of an auxiliary agent according to actual needs, wherein the auxiliary agent is selected from at least one of an antioxidant and a lubricant.

[0016] Known substances added to synthetic resins may also be appropriately added according to the required performance within the range that does not impair the effects of the present invention, such as ultraviolet absorbers, antistatic agents, flame retardants, colorants such as dyes and pigments, crystallization accelerators, crystal nucleating agents, etc.

[0017] The preparation method of the liquid crystal polyester composite material of the present invention comprises the following steps: according to the proportion, each component except the fibrous inorganic filler is uniformly mixed, and then extruded and granulated by a twin-screw extruder, the fibrous inorganic filler is side-fed, the screw temperature range is 260°C-355°C, and the rotation speed range is 350-900RPM, so as to obtain a liquid crystal polyester composite.

[0018] The liquid crystal polyester composite material of the present invention is used for preparing products used in microwave environments.

[0019] The present invention has the following beneficial effects: The present invention reduces the heat generation in the process of endurance to microwaves through the liquid crystal polyester of specific repeating units. The flaky fillers and the spherical fillers jointly construct a more three-dimensional heat conduction network. The thermal conductivity of both is higher than that of the liquid crystal polyester. The fiber fillers fill the gaps of the LCP composite system to reduce the tiny air in the system and avoid the reduction of the thermal conductivity. At the same time, they play the role of reinforcement and warpage reduction. Excellent thermal conductivity can be obtained to extract the generated heat, so that the liquid crystal polyester composite material of the present invention can withstand microwave environments. DETAILED DESCRIPTION

[0020] The present invention is 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 are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0021] The sources of raw materials used in the examples and comparative examples of the present invention are as follows: Liquid crystal polyester composition (mol%): Liquid crystal polyester A B C D E F G H I 6-Hydroxy-2-naphthoic acid 50 51 52 53 54 55 45 50 60 Terephthalic acid 25 22 22.99 21 22.5 21 27 15 19 Bisphenol 25 22 23 21 22.5 21 27 15 19 Parabens 0 5 2 5 1 3 1 20 2 Isophthalic acid 0 0 0.01 0 0 0 0 0 0 Melting point℃ 335 343 342 335 341 343 340 378 342 Melt viscosity Pa·s 27 26 27 28 26 27 27 28 27 Preparation method of liquid crystal polyester AI: Under inert gas pressure conditions, the reaction monomer is subjected to acylation reaction under the action of an acylating agent (acetic anhydride), the pressure is maintained at 0.1MPa~0.2MPa, the reaction temperature is 100℃~180℃, and the reaction time is 30 minutes~10 hours; after the acylation reaction is completed, the pressure in the reactor is reduced to normal pressure and the reaction temperature is increased at 0.1℃ / min~150℃ / min The temperature is raised to 200°C~400°C at a rate of 1.5°C, acetic acid and unreacted anhydride are discharged from the distillation column, and when the amount of acetic acid received reaches more than 90% of the theoretical value, the pressure in the reactor is reduced to 1~10kPa, and the reduced pressure condition is maintained and the temperature of the reaction system is raised to the maximum reaction temperature of 320~360°C, and a prepolymer is obtained by melt polycondensation; the prepolymer is cooled, solidified and granulated, and solid-phase polymerization is carried out in a solid-phase polymerization container to obtain liquid crystal polyester particles, the vacuum degree is 0.1Pa~50kPa, the solid-phase polymerization temperature is 160~340°C, and the reaction time is 0.5 hour~40 hours.

[0022] Glass fiber: EMG13-125C, Jushi Fiberglass; Wollastonite fiber: Wollastonite fiber with an aspect ratio of 3-8:1 was purchased from Jiangxi Aote Technology Co., Ltd. Flaky talc powder: Talc powder was purchased from Guangxi Longsheng Huamei Talc Development Co., Ltd. and then screened to obtain raw materials with a specific particle size, with an average particle size of 11.5 μm; Flake mica: Mica powder was purchased from Liming Mineral Products Co., Ltd. and screened to obtain raw materials with a specific particle size, with an average particle size of 17.4 μm; Flake boron nitride: Boron nitride was purchased from Tianyuan Aviation Materials, with the brand name H-BN-E and a particle size of 17-22 μm; Spherical alumina: Alumina was purchased from Venusstar, brand W235, particle size 3-7 μm; Spherical zinc oxide: zinc oxide was purchased from Jiangsu Shenlong Zinc Industry, environmentally friendly zinc oxide, with a particle size of 10-15μm; Color powder: titanium dioxide, with an average particle size of 15 μm, purchased from Pangang Vanadium Titanium Resources Co., Ltd.; Lubricant: Bonnie new material, polyethylene wax, BN-1020; Preparation method of liquid crystal polyester composite materials of embodiments and comparative examples: According to the ratio, each component except the fibrous inorganic filler is mixed uniformly, and then extruded and granulated by a twin-screw extruder, with the fibrous inorganic filler fed on the side, the screw temperature range is 260℃-355℃, and the rotation speed range is 500RPM to obtain a liquid crystal polyester composition.

[0023] Various test methods: (1) Warpage: After extrusion granulation, a square specimen of 60×60 mm and 0.8 mm thickness was injection molded using an injection molding machine. The specimen was baked in a reflow oven at a maximum temperature of 260°C for 10 min. The warpage before and after baking was measured. The lower the warpage, the better.

[0024] (2) Thermal conductivity: After extrusion granulation, a square specimen with a size of 60×60 mm and a thickness of 0.8 mm was injection molded using an injection molding machine. The thermal conductivity was tested using the laser flash method. The higher the thermal conductivity, the better.

[0025] (3) Microwave resistance: During microwave heating, the sample surface temperature is tested. Specifically, the microwave power is 900w, the application time is 10min, 10 plates are ultrasonically heated, and the sample temperature is tested. The lower the temperature, the better.

[0026] Table 1: Weight parts of each component of the liquid crystal polyester composite material of Examples 1-7 and test results Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Liquid crystal polyester A A A A A A A Liquid crystal polyester content 40 55 70 55 55 55 55 Wollastonite fiber 15 10 5 10 10 10 5 Flake Boron Nitride 13 28 20 28 28 Talc flakes 28 Flake Mica 28 Spherical Alumina 10 5 15 5 5 5 Spherical zinc oxide 5 Toner 0.5 Lubricants 0.5 Warpage (mm) 0.68 0.63 0.71 0.70 0.68 0.70 0.78 Thermal conductivity w / (m·k) 0.55 0.75 0.72 0.54 0.56 0.75 0.75 Sample temperature ℃ 148 136 152 147 149 139 139 It can be seen from Examples 2 / 4 / 5 that the flake filler is preferably flake boron nitride.

[0027] Table 2: Weight parts of each component of the liquid crystal polyester composite material of Examples 8-15 and test results Example 8 Example 9 Example 10 Embodiment 11 Example 12 Example 13 Embodiment 14 Embodiment 15 Liquid crystal polyester A A A B C D E F Liquid crystal polyester content 55 55 55 55 55 55 55 55 Wollastonite fiber 8 12 15 10 10 10 10 10 Flake Boron Nitride 22 18 13 28 28 28 28 28 Spherical Alumina 8 12 15 5 5 5 5 5 Warpage (mm) 0.65 0.65 0.69 0.73 0.74 0.73 0.73 0.74 Thermal conductivity w / (m·k) 0.64 0.61 0.52 0.75 0.74 0.76 0.73 0.75 Sample temperature ℃ 128 132 145 136 134 134 131 137 From Examples 7-10, it can be seen that the preferred contents of wollastonite fiber, flake filler, and spherical filler result in the lowest warpage and a lower temperature after microwave heating. Specifically, although the thermal conductivity of Example 7 is high, the temperature will also rise during microwave heating due to the high content of spherical alumina.

[0028] Table 3: Weight parts of each component of the comparative liquid crystal polyester composite material and test results Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Liquid crystal polyester G H I A A A A Liquid crystal polyester content 40 40 40 40 40 40 40 Wollastonite fiber 15 15 15 0 15 15 Fiberglass 15 Flake Boron Nitride 13 13 13 13 13 0 23 Spherical Alumina 10 10 10 10 10 23 0 Toner 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Warpage (mm) 0.83 0.89 0.86 0.81 1.02 0.94 N / A Thermal conductivity w / (m·k) 0.52 0.51 0.52 0.53 0.49 0.67 N / A Sample temperature ℃ 154 153 151 156 150 158 N / A It can be seen from Example 1 / Comparative Examples 1 / 2 / 3 that if liquid crystal polyesters with other repeating unit structures are applied to the system of the present invention, the amount of warping is large.

[0029] It can be seen from Example 1 and Comparative Example 4 that after glass fiber replaces wollastonite fiber, the microwave heating temperature rise is large and the warping amount is large.

[0030] It can be seen from Example 1 and Comparative Example 5 that the warpage is high when wollastonite fiber is not contained.

[0031] It can be seen from Example 1 and Comparative Example 6 that if no flake filler is contained, the warpage will increase even if the content of spherical filler increases, and because the content of spherical alumina is too high, the temperature after microwave heating is very high.

[0032] Comparative Example 7 was difficult to process.

Claims

1. A liquid crystal polyester composite material, characterized in that: By weight, it includes the following components: 39-71 parts of liquid crystal polyester; Wollastonite fiber 5-15 parts; 13-28 parts of flake filler; 5-15 parts of spherical filler; In terms of molar percentage, the liquid crystal polyester is composed of the following monomers: 6-Hydroxy-2-naphthoic acid 50-55 mol%; Terephthalic acid 20-25 mol%; Bisphenol 20-25 mol% p-Hydroxybenzoic acid 0-5 mol%; Other monomers 0-0.05 mol%.

2. The liquid crystal polyester composite material according to claim 1, characterized in that: By weight, it includes the following components: 40-70 parts of liquid crystal polyester; Wollastonite fiber 8-12 parts; 18-22 parts of flake filler; 8-12 parts of spherical filler.

3. The liquid crystal polyester composite material according to claim 1, characterized in that: The flaky filler is selected from at least one of talc, mica and boron nitride.

4. The liquid crystal polyester composite material according to claim 3, characterized in that: The flake filler is selected from boron nitride.

5. The liquid crystal polyester composite material according to claim 1, characterized in that: The spherical filler is selected from at least one of aluminum oxide and zinc oxide.

6. The liquid crystal polyester composite material according to claim 1, characterized in that: The other monomers are selected from at least one of isophthalic acid, 1,4-benzenediol and 2,6-naphthalene dicarboxylic acid.

7. The liquid crystal polyester composite material according to claim 1, characterized in that: The melting point of the liquid crystal polyester is greater than 280°C.

8. The liquid crystal polyester composite material according to claim 1, characterized in that: By weight, the invention further comprises 0-2 parts of auxiliary agents, wherein the auxiliary agents are selected from at least one of antioxidants and lubricants.

9. The method for preparing the liquid crystal polyester composite material according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: uniformly mixing the components except the fibrous inorganic filler according to the proportion, extruding and granulating through a twin-screw extruder, and feeding the fibrous inorganic filler sideways to obtain a liquid crystal polyester composition.

10. Use of the liquid crystal polyester composite material according to any one of claims 1 to 8, characterized in that: Used to prepare parts for use in microwave environments.