Polypropylene / liquid crystal polyester alloy and preparation method and application thereof

Abstract

The invention discloses a polypropylene / liquid crystal polyester alloy which comprises the following components in parts by weight: 30-60 parts of homo-polypropylene; the weight ratio of the liquid crystal polyester to the carbon nano tube in the compound of the liquid crystal polyester and the carbon nano tube is (5-15): (0.5-1.5), and the weight ratio of the liquid crystal polyester to the carbon nano tube in the compound of the liquid crystal polyester and the carbon nano tube is (5-15): (0.5-1.5). According to the invention, homo-polypropylene is taken as a main body, a heterogeneous two-phase network is formed by utilizing the characteristic that LCP and PP are incompatible, meanwhile, LCP is distributed in PP resin in a sea island shape, responds under the action of an electric field and has the advantage of high dielectric constant, and meanwhile, the polypropylene / liquid crystal polyester alloy is insulated.

Description

Technical Field

[0001] The present invention relates to the field of polymer technology, and particularly relates to a liquid crystal polyester and a preparation method and application thereof. Background Art

[0002] LCP materials are a kind of high molecular polymer with fast crystallization speed, high temperature resistance, self-flame retardancy, excellent dielectric properties, high modulus, high strength and strong anisotropy. They are widely used in industries such as electronics and electrical appliances, home appliances, etc. Due to their unique high fluidity, high temperature resistance, dimensional stability and other characteristics, they can be applied to precision electronic devices and so on.

[0003] For existing slot antennas, wave propagation is achieved by opening slots. Through theoretical calculation, if the dielectric constant of the material can be higher than that of air, the higher the dielectric constant, the smaller the required slot, which can effectively improve the circuit board layout.

[0004] In current LCP dielectric regulation materials, usually high dielectric constant materials such as titanium dioxide are added to play a role in increasing the dielectric. There are defects such as insufficiently high dielectric constant and performance degradation after the filling amount is increased. However, by adding conductive fillers such as carbon nanotubes and metal nanowires, while increasing the dielectric constant, the resistance will be greatly reduced, becoming a non-insulating material and unable to be used in charged scenarios. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical defects and provide a liquid crystal polyester alloy with high dielectric constant and insulation, and a preparation method and application thereof.

[0006] The present invention is achieved by the following technical solutions: A polypropylene / liquid crystal polyester alloy, by weight, comprises the following components: Homopolypropylene 30 - 60 parts; Liquid crystal polyester and carbon nanotube composite 5.5 - 16.5 parts; In the composite of the liquid crystal polyester and the carbon nanotube, the weight ratio of the liquid crystal polyester to the carbon nanotube is (5 - 15):(0.5 - 1.5).

[0007] The dielectric constant of the polypropylene / liquid crystal polyester alloy of the present invention is not less than 15DK, and the surface resistance is not less than E10Ω.

[0008] In the polypropylene / liquid crystal polyester alloy of the present invention, the content of homopolypropylene can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, etc., and the content of the liquid crystal polyester and carbon nanotube composite can be 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, 15.5 parts, 16 parts, 16.5 parts, etc.

[0009] In the polypropylene / liquid crystal polyester alloy of the present invention, the percentage by weight of homopolypropylene in the total weight ranges from 43 - 92 wt%, for example, it can be optionally 65 - 84 wt%, the percentage by weight of liquid crystal polyester in the total weight ranges from 7 - 33 wt%, for example, it can be optionally 10 - 33 wt%, and the percentage by weight of carbon nanotubes in the total weight ranges from 0.5 - 4.3 wt%, for example, it can be optionally 1 - 2.2 wt%.

[0010] The described liquid crystal polyester is composed of at least 2 of terephthalic acid, biphenol, 6 - hydroxy - 2 - naphthoic acid, p - hydroxybenzoic acid, and paracetamol as repeating units. Specifically, it can be as follows: A: Terephthalic acid / biphenol / paracetamol, where the molar ratio of terephthalic acid / paracetamol ranges from (20 - 2):1.

[0011] B: Terephthalic acid / biphenol / 6 - hydroxy - 2 - naphthoic acid / paracetamol, where the molar ratio of terephthalic acid / paracetamol / 6 - hydroxy - 2 - naphthoic acid ranges from (20 - 2):1:(0.5 - 8).

[0012] C: Terephthalic acid / biphenol / p - hydroxybenzoic acid / paracetamol, where the molar ratio of terephthalic acid / paracetamol / p - hydroxybenzoic acid ranges from (20 - 2):1:(0.5 - 8).

[0013] D: Terephthalic acid / biphenol / 6 - hydroxy - 2 - naphthoic acid / p - hydroxybenzoic acid / paracetamol, where the molar ratio of terephthalic acid / paracetamol / (6 - hydroxy - 2 - naphthoic acid and p - hydroxybenzoic acid) ranges from (20 - 2):1:(0.5 - 8).

[0014] The liquid crystal polyester can be a commercially available product or can be obtained by self - preparation. Those skilled in the art can conventionally select the self - preparation method of the liquid crystal polyester. The self - preparation method of the liquid crystal polyester includes but is not limited to the following methods: Under the condition of pressurizing with inert gas, an acylation reaction is carried out on reaction monomers 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. 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. Under this reduced pressure condition, the reaction system is programmed to raise the temperature to the highest reaction temperature of 320 to 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 to 50 kPa, the solid-phase polymerization temperature is 160 to 340 °C, and the reaction time is 0.5 hours to 40 hours.

[0015] The acylating agent can be acetic anhydride, propionic anhydride, butyric anhydride, etc.

[0016] The liquid crystal polyester of the present invention has a melt viscosity of 10 - 50 Pa·s under the conditions of being 20 °C higher than the melting point and a shear rate of 1000 -s The test method for the melt viscosity of the liquid crystal polyester is: based on the determination method of ISO 11443, at a temperature 20 °C higher than the melting point and a shear rate of 1000 -s Under the shear rate condition, the equipment used is a Goettfert high-pressure capillary rheometer, RG20, with a 1 mm test die.

[0017] The carbon nanotubes selected are at least one of multi-walled carbon nanotubes and single-walled carbon nanotubes, and the average outer diameter is 1 - 100 nm. The test is carried out by TEM transmission electron microscopy with reference to GB / T26826-2011.

[0018] The melt index range of the homopolypropylene is 1 - 30 g / 10 min, preferably 3 - 12 g / 10 min, at 230 °C and 2.16 kg, and the test standard is ISO 1133-1:2022. When homopolypropylene with a preferred melt index is selected, it is easier to disperse the LCP resin evenly.

[0019] Whether to add 0 - 2 parts of additives can be selected according to actual needs. The additives selected are at least one of antioxidants, ultraviolet absorbers, colorants, and lubricants.

[0020] The preparation method of the polypropylene / liquid crystal polyester alloy of the present invention comprises the following steps: According to the ratio, first mix the liquid crystal polyester and the carbon nanotubes evenly, and extrude and pelletize them through a twin-screw extruder. The temperature range of the barrel is 330 - 380 °C, and the rotation speed is 300 - 600 revolutions per minute to obtain a liquid crystal polyester and carbon nanotube composite; then mix the liquid crystal polyester and carbon nanotube composite, the homopolypropylene and other raw materials evenly, and extrude and pelletize them through a twin-screw extruder to obtain the polypropylene / liquid crystal polyester alloy. The temperature range of the barrel is 120 - 200 °C, and the rotation speed is 300 - 600 revolutions per minute.

[0021] The application of the liquid crystal polyester alloy of the present invention is used for preparing a slot antenna.

[0022] The present invention has the following beneficial effects: In the present invention, with homopolypropylene as the main body, a heterogeneous two-phase network is formed by utilizing the incompatibility between LCP and PP. The carbon nanotubes are mainly enriched in the LCP, and at the same time, the LCP is distributed in the form of islands in the PP resin, and responds under the action of an electric field, having the advantage of a high dielectric constant. At the same time, the polypropylene / liquid crystal polyester alloy of the present invention is insulating. Specific embodiments

[0023] The present invention will be described in detail below with reference to 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 those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0024] The sources of the raw materials used in the present invention are as follows: Liquid crystal polyester A: The repeating unit is terephthalic acid / biphenol / acetaminophen, and the molar ratio is 5:4.5:0.5, with a melt viscosity of 27.2 Pa·s, and it is self-made according to the method described in the invention content.

[0025] Liquid crystal polyester B: The repeating unit is terephthalic acid / biphenol / p-hydroxybenzoic acid / acetaminophen, and the molar ratio is 8:5:3:3, with a melt viscosity of 31 Pa·s, and it is self-made according to the method described in the invention content.

[0026] Liquid crystal polyester C: The repeating unit is terephthalic acid / biphenol / 6-hydroxy-2-naphthoic acid / acetaminophen, and the molar ratio is 4:3.2:1.5:0.8, with a melt viscosity of 25.4 Pa·s, and it is self-made according to the method described in the invention content.

[0027] Liquid crystal polyester D: The repeating units are terephthalic acid / biphenol / 6-hydroxy-2-naphthoic acid / p-hydroxybenzoic acid / p-acetaminophenol, with a molar ratio of 4:5:1:2:1, a melt viscosity of 29.5 Pa·s, and it is self-made according to the method described in the invention content.

[0028] Homopolypropylene A: HP500N, manufactured by Basel, melt index 12 g / 10min, at 230°C, 2.16 kg; Homopolypropylene B: K1003, manufactured by Yanshan Petrochemical, melt index 3 g / 10min, at 230°C, 2.16 kg; Homopolypropylene C: 578P, manufactured by Sabic, melt index 25 g / 10min, at 230°C, 2.16 kg; Copolypropylene: PP EP548R, manufactured by CNOOC and Shell, melt index 28 g / 10min, at 230°C, 2.16 kg; Carbon nanotubes: Multi-walled carbon nanotubes, MWCNT (outer diameter between 20 - 30 nm, purity > 98%), from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences; Lubricant: LLDPE LL 6101RQ, manufactured by ExxonMobil.

[0029] Preparation method of polypropylene / liquid crystal polyester alloy in examples and comparative examples: According to the ratio, first mix the liquid crystal polyester and carbon nanotubes evenly, and extrude and pelletize through a twin-screw extruder. The barrel temperature range is 330 - 380°C, and the rotation speed is 300 - 600 revolutions per minute to obtain the masterbatch of the liquid crystal polyester and carbon nanotube composite; then mix the liquid crystal polyester and carbon nanotube composite with homopolypropylene (or copolypropylene) and other raw materials evenly, and extrude and pelletize through a twin-screw extruder to obtain the polypropylene / liquid crystal polyester alloy. The barrel temperature range is 120 - 200°C, and the rotation speed is 300 - 600 revolutions per minute.

[0030] Test methods for each item: (1) Dielectric constant: After extrusion and pelletization, use an injection molding machine to injection mold a square specimen with dimensions of 60×60 mm and a thickness of 0.8 mm, and test the dielectric parameters using the split resonator method under the condition of 10 GHz, with a requirement of ≥15 Dk.

[0031] (2) Surface resistance: After extrusion and pelletization, use an injection molding machine to injection mold a square specimen with dimensions of 100×100 mm and a thickness of 2 mm to test the surface resistance, with a requirement of ≥E10Ω.

[0032] Table 1: Component weight parts and test results of polypropylene / liquid crystal polyester alloy in Examples 1 - 8 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Liquid crystal polyester A 10 5 15 5 5 Liquid crystal polyester B 5 Liquid crystal polyester C 5 Liquid crystal polyester D 5 Homopolypropylene A 60 40 30 40 40 40 Homopolypropylene B 40 Homopolypropylene C 40 Carbon nanotubes 1.5 1 0.5 1 1 1 1 1 Lubricant 0.4 0.3 0.3 0.3 0.3 0.3 0.3 Dielectric constant, Dk 26 20 15 21 19 21 20 17 Surface resistivity, Ω E10 E10 E10 E11 E10 E10 E10 E10 As can be seen from Examples 2 / 7 / 8, when the melt index of homopolypropylene is optimized, the dielectric constant is higher.

[0033] Table 2: Parts by weight of each component of the polypropylene / liquid crystal polyester alloy in the comparative example and test results Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Liquid crystal polyester A 0 25 5 70 Homopolypropylene A 70 45 Random copolymer polypropylene 40 Carbon nanotubes 1.5 1.5 1.5 1.5 Lubricant 0.4 0.4 0.4 0.4 Dielectric constant, Dk 27 17 23 25 Surface resistivity, Ω E5 E9 E9 E4 As can be seen from Comparative Example 1, when the liquid crystal polyester is not contained, the carbon nanotubes are uniformly dispersed in the PP, resulting in too low surface resistivity.

[0034] As can be seen from Comparative Example 2, when the content of the liquid crystal polyester is too high, the dielectric constant and the surface resistivity decrease.

[0035] As can be seen from Comparative Example 3, the rubber phase in the copolymerized polypropylene will affect the dispersion of the liquid crystal polyester, and thus affect the surface resistivity.

[0036] As can be seen from Comparative Example 4, when the homopolypropylene is not contained, the surface resistivity is low, which affects the insulation performance.

Claims

1. A polypropylene / liquid crystal polyester alloy, characterized in that: By weight, it includes the following components: Homopolymer polypropylene 30-60 parts; 5.5-16.5 parts of a composite of liquid crystal polyester and carbon nanotubes; In the composite of liquid crystal polyester and carbon nanotubes, the weight ratio of liquid crystal polyester to carbon nanotubes is (5-15): (0.5-1.5).

2. The liquid crystal polyester alloy according to claim 1, characterized in that: The dielectric constant of the polypropylene / liquid crystal polyester alloy is not less than 15DK, and the surface resistance is not less than E10Ω.

3. The liquid crystal polyester alloy according to claim 1, characterized in that: The carbon nanotubes are selected from at least one of multi-walled carbon nanotubes and single-walled carbon nanotubes, and have an average outer diameter of 1-100 nm.

4. The liquid crystal polyester alloy according to claim 1, characterized in that: The liquid crystal polyester comprises at least two of terephthalic acid, biphenol, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid and acetaminophen as repeating units.

5. The liquid crystal polyester alloy according to claim 1, characterized in that: The liquid crystal polyester is 20°C above the melting point, 1000 -s Under shear rate conditions, the melt viscosity is 10-50 Pa·s.

6. The liquid crystal polyester alloy according to claim 1, characterized in that: The melt index range of the homopolymer polypropylene is 1-30 g / 10 min, preferably 3-12 g / 10 min, 230° C., 2.16 kg.

7. The liquid crystal polyester alloy 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, ultraviolet absorbers, colorants and lubricants.

8. The method for preparing the liquid crystal polyester alloy according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: firstly, liquid crystal polyester and carbon nanotubes are uniformly mixed according to a ratio, and extruded and granulated by a twin-screw extruder to obtain a liquid crystal polyester and carbon nanotube composite; then, the liquid crystal polyester and carbon nanotube composite are uniformly mixed with homopolymer polypropylene and other raw materials, and extruded and granulated by a twin-screw extruder to obtain a polypropylene / liquid crystal polyester alloy.

9. A slot antenna comprising the liquid crystal polyester alloy according to any one of claims 1 to 7.