Liquid crystal polyester composite material and preparation method and application thereof

Abstract

The application discloses a liquid crystal polyester composite material, which comprises the following components in parts by weight: liquid crystal polyester 39-71 parts; wollastonite fiber 5-15 parts; flaky filler 13-28 parts; spherical filler 5-15 parts; and the liquid crystal polyester is composed of the following monomers in mole percent: 6-hydroxy-2-naphthoic acid 50-55mol%; terephthalic acid 20-25mol%; diphenylol 20-25mol%; p-hydroxybenzoic acid 0-5mol%; and other monomers 0-0.05mol%. The liquid crystal polyester with specific repeating units can reduce the heat generation in the microwave resistant process, and the synergistic effect of the wollastonite fiber, the flaky filler and the spherical filler can obtain excellent thermal conductivity to discharge the generated heat, so that the liquid crystal polyester composite material can resist the microwave environment. In addition, the liquid crystal polyester composite material has the advantages of low warping.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a liquid crystal polyester composite material, its preparation method, and its application. Background Technology

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

[0003] However, LCP materials generate heat during microwave exposure, leading to material degradation. Existing technologies for improving microwave-resistant materials include: First, increasing the material's heat resistance, such as melting point; however, this doesn't actually reduce the temperature rise, and the increased temperature leads to a rapid decrease in mechanical properties. Second, increasing the material's rigidity, such as by increasing the content of reinforcing fibers like carbon fiber and glass fiber, and raising the heat distortion temperature; however, this still cannot prevent the material's temperature from rising, resulting in no macroscopic deformation, but localized molecular chain movement within the resin. Third, adding a metal or conductive shell to form a Faraday cage for microwave shielding; however, this prevents microwave penetration, facilitates discharge, and limits its use. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical defects and provide a liquid crystal polyester composite material that is resistant to microwaves and has low warpage.

[0005] This invention is achieved through the following technical solution:

[0006] A liquid crystal polyester composite material, by weight, comprises the following components:

[0007] 39-71 parts of liquid crystal polyester;

[0008] 5-15 parts of wollastonite fiber;

[0009] 13-28 parts of sheet-like filler;

[0010] 5-15 parts of spherical filler;

[0011] The liquid crystal polyester, by molar percentage, is composed of the following monomers:

[0012] 50-55 mol% of 6-hydroxy-2-naphthoic acid

[0013] 20-25 mol% terephthalic acid

[0014] Bisphenol 20-25 mol%

[0015] p-Hydroxybenzoic acid 0-5 mol%

[0016] Other monomers: 0-0.05 mol%.

[0017] Preferably, by weight, it comprises the following components:

[0018] 40-70 parts of liquid crystal polyester;

[0019] 8-12 parts of wollastonite fiber;

[0020] 18-22 parts of sheet filler;

[0021] 8-12 parts of spherical packing material.

[0022] The sheet-like filler is selected from at least one of talc, mica, and boron nitride; preferably, the sheet-like filler is selected from boron nitride.

[0023] The spherical filler is selected from at least one of alumina and zinc oxide.

[0024] The average particle size range of the sheet-like filler is D50 = 15-30 micrometers;

[0025] The average particle size range of the spherical packing is D50 = 1-20 micrometers;

[0026] The D50 particle size is referenced 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.

[0027] The aspect ratio range of wollastonite fibers is (8-20):1.

[0028] The other monomers are selected from at least one of isophthalic acid, 1,4-dibenzene, and 2,6-naphthalenedicarboxylic acid.

[0029] Preferably, the melting point of the liquid crystal polyester is greater than 280°C.

[0030] Preferably, the LCP resin has a melting point greater than 20°C and a melting point of 1000°C. -S The melt viscosity under shear rate conditions is 10-50 Pa·s. At 20°C above the melting point, at 1000... -S Under shear rate conditions, the test method was based on the determination method of ISO 11443, and the equipment used was a Goettfert high-pressure capillary rheometer, RG20, 1mm test die.

[0031] Liquid crystal polyester can be a commercially available product or can be obtained by self-production. Self-production methods include, but are not limited to: an acylation reaction of the monomers under inert gas pressure with an acylation agent, wherein the pressure is maintained at 0.1 MPa to 0.2 MPa, the reaction temperature at 100℃ to 180℃, and the reaction time at 30 minutes to 10 hours; after the acylation reaction is completed, the pressure inside the reactor is reduced to atmospheric pressure, and the reaction is carried out at a rate of 0.1℃ / min to 150℃ / min. The temperature is increased at a rate of 200℃~400℃, and acetic acid and unreacted anhydride are discharged from the distillation column. When the amount of acetic acid received reaches more than 90% of the theoretical value, the pressure inside the reactor is reduced to 1~10 kPa. This pressure reduction condition is maintained, and the reaction system is programmed to heat to the maximum reaction temperature of 320~360℃, resulting in melt polycondensation to obtain a prepolymer. The prepolymer is cooled, solidified, and granulated. Solid-state polymerization is then carried out in a solid-state polymerization container to obtain liquid crystal polyester particles. The vacuum degree is 0.1 Pa~50 kPa, the solid-state 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.

[0032] Depending on actual needs, it may be optional to add 0-2 parts of an additive, which is selected from at least one of antioxidants and lubricants.

[0033] Within the scope of not impairing the effect of the present invention, known substances that can be added to synthetic resins can be appropriately added according to the required performance. These substances may include ultraviolet absorbers, antistatic agents, flame retardants, dyes, pigments and other colorants, crystallization promoters, crystal nucleating agents, etc.

[0034] The preparation method of the liquid crystal polyester composite material of the present invention includes the following steps: according to the formula, the components except fibrous inorganic filler are mixed evenly, and then extruded and granulated by a twin-screw extruder, the fibrous inorganic filler is side-fed, the screw temperature range is 260℃-355℃, the speed range is 350-900RPM, and the liquid crystal polyester composition is obtained.

[0035] The present invention relates to the application of liquid crystal polyester composite material for the preparation of parts for use in microwave environments.

[0036] The present invention has the following beneficial effects:

[0037] This invention reduces heat generation in the microwave-resistant process by using liquid crystal polyester with specific repeating units. The sheet-like filler and spherical filler together construct a more three-dimensional heat conduction network, both of which have higher thermal conductivity than the liquid crystal polyester. The fiber filler fills the gaps in the LCP composite system to reduce the amount of air in the system and prevent the thermal conductivity from decreasing. At the same time, it also plays a role in reinforcement and reducing warpage. It can achieve excellent thermal conductivity to dissipate the generated heat, enabling the liquid crystal polyester composite material of this invention to withstand the microwave environment. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0039] The sources of the raw materials used in the embodiments and comparative examples of this invention are as follows:

[0040] Liquid crystal polyester composition (mol%):

[0041] Liquid crystal polyester label 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 biphenyl hydroquinone 25 22 23 21 22.5 21 27 15 19 p-hydroxybenzoic acid 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

[0042] Preparation method of liquid crystal polyester AI: Under inert gas pressure, the reactants undergo an acylation reaction in the presence of an acylation agent (acetic anhydride). The pressure is maintained at 0.1 MPa to 0.2 MPa, the reaction temperature is 100℃ to 180℃, and the reaction time is 30 minutes to 10 hours. After the acylation reaction is completed, the pressure inside the reactor is reduced to atmospheric pressure, and the reaction is carried out at a rate of 0.1℃ / min to 150℃ / min. The temperature is increased at a rate of 200℃~400℃, and acetic acid and unreacted anhydride are discharged from the distillation column. When the amount of acetic acid received reaches more than 90% of the theoretical value, the pressure in the reactor is reduced to 1~10 kPa. This pressure reduction condition is maintained, and the reaction system is programmed to be heated to the highest reaction temperature of 320~360℃. Melt polycondensation is carried out to obtain a prepolymer. The prepolymer is cooled, solidified, and granulated. Solid-state polymerization is carried out in a solid-state polymerization container to obtain liquid crystal polyester particles. The vacuum degree is 0.1Pa~50kPa, the solid-state polymerization temperature is 160~340℃, and the reaction time is 0.5 hours~40 hours.

[0043] Fiberglass: EMG13-125C, Jushi Fiberglass;

[0044] Wollastonite fiber: The aspect ratio of wollastonite fiber is 3~8:1, purchased from Jiangxi Aote Technology Co., Ltd.;

[0045] Flaky talc: The talc 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 micrometers.

[0046] Flaky mica: The 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 micrometers;

[0047] Flaky boron nitride: The boron nitride was purchased from Tianyuan Aerospace Materials, with the grade H-BN-E and a particle size of 17-22μm;

[0048] Spherical alumina: The alumina was purchased from Qimingxing, grade W235, with a particle size of 3-7μm;

[0049] Spherical zinc oxide: The zinc oxide was purchased from Jiangsu Shenlong Zinc Industry. It is environmentally friendly zinc oxide with a particle size of 10-15μm.

[0050] Pigment: Titanium dioxide, with an average particle size of 15 micrometers, purchased from Panzhihua Iron & Steel Vanadium Titanium Resources Co., Ltd.

[0051] Lubricant: Bonnie New Materials, polyethylene wax, BN-1020;

[0052] Preparation method of liquid crystal polyester composite material in the examples and comparative examples: According to the formula, all components except fibrous inorganic filler are mixed evenly, and then extruded and granulated by twin-screw extruder. The fibrous inorganic filler is side-fed. The screw temperature range is 260℃-355℃ and the speed range is 500RPM to obtain liquid crystal polyester composition.

[0053] Test methods:

[0054] (1) Warpage: After extrusion granulation, a square sample of 60×60mm and 0.8mm thickness was injection molded using an injection molding machine. The sample was then baked in a reflow oven at a maximum temperature of 260℃ for 10 minutes. The amount of warpage before and after baking was measured. The lower the amount of warpage, the better.

[0055] (2) Thermal conductivity: After extrusion granulation, a 60×60mm square sample with a thickness of 0.8mm 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.

[0056] (3) Microwave resistance: The surface temperature of the sample is detected during microwave heating. Specifically, the microwave power is 900W, the application time is 10min, 10 plates are ultrasonically tested, and the temperature of the sample is tested. The lower the temperature, the better.

[0057] Table 1: Weight parts and test results of each component in the liquid crystal polyester composite materials of Examples 1-7

[0058] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Liquid crystal polyester label 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 Plate-shaped boron nitride 13 28 20 28 28 flake talc 28 Flake mica 28 Spherical alumina 10 5 15 5 5 5 Spherical zinc oxide 5 Pigment 0.5 lubricant 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

[0059] As can be seen from Examples 2 / 4 / 5, sheet-like fillers are preferably sheet-like boron nitride.

[0060] Table 2: Weight parts and test results of each component in the liquid crystal polyester composite materials of Examples 8-15

[0061] Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Liquid crystal polyester label 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 Plate-shaped 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

[0062] As shown in Examples 7-10, the preferred contents of wollastonite fiber, sheet filler, and spherical filler result in the lowest warpage and the lowest temperature after microwave heating. Specifically, although Example 7 has a high thermal conductivity, the higher content of spherical alumina will cause it to heat up during microwave heating.

[0063] Table 3: Weight parts and test results of each component in the comparative liquid crystal polyester composite material

[0064] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Liquid crystal polyester label 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 Plate-shaped boron nitride 13 13 13 13 13 0 23 Spherical alumina 10 10 10 10 10 23 0 Pigment 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

[0065] As can be seen from Examples 1 / Comparative Examples 1 / 2 / 3, when liquid crystal polyesters with other repeating unit structures are applied to the system of the present invention, the warpage is large.

[0066] As can be seen from Example 1 and Comparative Example 4, glass fiber replaces wollastonite fiber, resulting in a large microwave heating rate and a large warping.

[0067] As can be seen from Example 1 and Comparative Example 5, the warpage is high when wollastonite fibers are not present.

[0068] As can be seen from Example 1 and Comparative Example 6, if the content of spherical filler increases even if the content of spherical filler increases, the warpage also increases, and the temperature is very high after microwave heating due to the excessive content of spherical alumina.

[0069] Comparative Example 7 is 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; 5-15 parts of wollastonite fiber; 13-28 parts of sheet-like filler; 5-15 parts of spherical filler; The liquid crystal polyester, by molar percentage, is composed of the following monomers: 50-55 mol% of 6-hydroxy-2-naphthoic acid 20-25 mol% terephthalic acid Bisphenol 20-25 mol% p-Hydroxybenzoic acid 0-5 mol% Other monomers 0-0.05 mol% The sheet-like filler is selected from at least one of talc, mica, and boron nitride; The spherical filler is selected from at least one of alumina and zinc oxide.

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; 8-12 parts of wollastonite fiber; 18-22 parts of sheet filler; 8-12 parts of spherical packing material.

3. The liquid crystal polyester composite material according to claim 1, characterized in that, The sheet-like filler is selected from boron nitride.

4. 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-dibenzene, and 2,6-naphthalenedicarboxylic acid.

5. 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.

6. The liquid crystal polyester composite material according to claim 1, characterized in that, The product also includes 0-2 parts by weight of additives, wherein the additives are selected from at least one of antioxidants and lubricants.

7. A method for preparing the liquid crystal polyester composite material according to any one of claims 1-6, characterized in that, The process includes the following steps: mixing all components except the fibrous inorganic filler according to the specified ratio, then extruding and granulating the mixture using a twin-screw extruder, with the fibrous inorganic filler being side-fed, to obtain a liquid crystal polyester composition.

8. The application of the liquid crystal polyester composite material according to any one of claims 1-6, characterized in that, Used for manufacturing components for use in microwave environments.