Thermotropic liquid crystal polymer as well as preparation method and application thereof

Abstract

The invention discloses a thermotropic liquid crystal polymer as well as a preparation method and application thereof. The thermotropic liquid crystal polymer comprises the following components in parts by weight: 0.01-0.4 part of anhydride modified boron nitride; the acid anhydride modified boron nitride is added into the thermotropic liquid crystal polyester, an acid anhydride functional group can form a stable chemical bond with a residue functional group at the molecular chain end of the thermotropic liquid crystal polyester, and the boron nitride has a lamellar structure, so that the crystallization temperature of the liquid crystal polymer can be improved; the transverse and longitudinal crystallization difference in the extrusion film forming process is reduced, so that the application range of the thermotropic liquid crystal polymer in the high-temperature field is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of special engineering plastics, and more specifically, to a thermotropic liquid crystal polymer, a preparation method thereof, and an application thereof. Background Art

[0002] With the popularization of the fifth-generation communication technology (5G), the signal processing and transmission frequencies of electronic devices have increased rapidly, posing requirements for the flexible circuit substrates used for signal transmission to have a low dielectric constant (D k ), and a low dielectric loss tangent (D f ). Thermotropic liquid crystal polymers (TLCPs) have excellent dielectric properties, low moisture absorption, dimensional stability, etc. After being processed into films, they have low losses under high-frequency signal transmission conditions as flexible circuit board substrates, becoming the mainstream of high-frequency communication substrates.

[0003] Processing TLCP into a film requires it to have a certain melt strength and viscosity to ensure a high draw ratio during melting. However, existing TLCPs have the properties of a liquid in the molten state, with a low viscosity, but a narrow crystallization temperature range. Once the temperature is below the crystallization temperature, strong crystallization immediately forms, resulting in easy crystallization in the extrusion film casting direction (X-axis) during the processing process, while the crystallization in the shear direction (Y-axis) is extremely weak, leading to a large difference in mechanical properties in the two directions and affecting its application. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defect or deficiency of the large difference in crystallization degree in two directions and the resulting large difference in mechanical properties after processing TLCP into a film in the prior art, and to provide a thermotropic liquid crystal polymer.

[0005] Another purpose of the present invention is to provide a preparation method of the thermotropic liquid crystal polymer.

[0006] Another purpose of the present invention is to provide an application of the thermotropic liquid crystal polymer.

[0007] To achieve the above purposes, the present invention is realized through the following technical solutions:

[0008] A thermotropic liquid crystal polymer, comprising the following components calculated by weight:

[0009] Anhydride-modified boron nitride 0.01 - 0.4 parts;

[0010] Thermotropic liquid crystal polyester 99 - 100 parts.

[0011] The present invention provides a thermotropic liquid crystal polymer. By adding acid anhydride-modified boron nitride to the thermotropic liquid crystal polyester, the acid anhydride functional group can form a stable chemical bond with the residue functional group at the end of the thermotropic liquid crystal polyester molecular chain, and the boron nitride has a lamellar structure, which can improve the crystallization temperature of the liquid crystal polymer and reduce the transverse and longitudinal crystallization differences during the film extrusion process, thereby broadening the application of the thermotropic liquid crystal polymer in the high-temperature field.

[0012] In the present invention, the amount of the acid anhydride-modified boron nitride is 0.01 to 0.4 parts, for example but not limited to 0.01 part, 0.02 part, 0.03 part, 0.04 part, 0.05 part, 0.06 part, 0.07 part, 0.08 part, 0.09 part, 0.1 part, 0.11 part, 0.12 part, 0.13 part, 0.14 part, 0.15 part, 0.16 part, 0.17 part, 0.18 part, 0.19 part, 0.2 part, 0.21 part, 0.22 part, 0.23 part, 0.24 part, 0.25 part, 0.26 part, 0.27 part, 0.28 part, 0.29 part, 0.3 part, 0.31 part, 0.32 part, 0.33 part, 0.34 part, 0.35 part, 0.36 part, 0.37 part, 0.38 part, 0.39 part or 0.4 part, etc., all of which can achieve the present invention.

[0013] Further, the thermotropic liquid crystal polymer comprises the following components calculated by weight:

[0014] Acid anhydride-modified boron nitride 0.05 to 0.25 parts;

[0015] Thermotropic liquid crystal polyester 99.75 to 99.95 parts.

[0016] Further, the acid anhydride-modified boron nitride is obtained by modifying amino-functionalized nano boron nitride with a polyfunctional acid anhydride or acyl chloride.

[0017] Specifically, the polyfunctional acid anhydride or acyl chloride is trimellitic anhydride acyl chloride.

[0018] Specifically, the amino-functionalized nano boron nitride is commercially available.

[0019] Specifically, the amino content in the amino-functionalized nano boron nitride is 5 to 10 wt%.

[0020] In some preferred specific embodiments, the mass ratio of the trimellitic anhydride acyl chloride to the amino-functionalized nano boron nitride is not less than 1:1.

[0021] Specifically, the mass ratio of the trimellitic anhydride acyl chloride to the amino-functionalized nano boron nitride is (1 to 5):1.

[0022] Specifically, the anhydride-modified boron nitride is obtained by dispersing amino-functionalized nano boron nitride in a polar solvent, adding trimellitic anhydride acyl chloride, and reacting at 0-5°C for 1-5 hours, followed by filtration and drying.

[0023] Specifically, the polar solvent can be one or more of N-methylpyrrolidone, acetonitrile, and dimethylformamide.

[0024] Furthermore, the melting point of the thermotropic liquid crystal polyester is not lower than 260°C.

[0025] Even further, the melting point of the thermotropic liquid crystal polyester is 270-320°C.

[0026] Furthermore, the average particle size of the anhydride-modified boron nitride is 10-100 nm.

[0027] The present invention also protects a method for preparing the above-mentioned thermotropic liquid crystal polymer, which includes the following steps:

[0028] S1. Mix the anhydride-modified boron nitride with a part of the thermotropic liquid crystal polyester at a ratio of 0.5-10 wt%, and melt-extrude and pelletize through an extruder to obtain masterbatch;

[0029] S2. Mix the masterbatch obtained in step S1 with the remaining thermotropic liquid crystal polyester uniformly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0030] Specifically, the extruder in step S1 is a twin-screw extruder.

[0031] Specifically, the temperature of the melt-extrusion pelletization in step S1 is 345-355°C.

[0032] Specifically, in step S1, the anhydride-modified boron nitride is mixed with a part of the thermotropic liquid crystal polyester at a ratio of 1-6 wt%, and melt-extruded and pelletized through an extruder to obtain masterbatch.

[0033] Specifically, the extruder in step S2 is a twin-screw extruder.

[0034] Specifically, the temperature of the melt-extrusion pelletization in step S2 is 345-355°C.

[0035] Specifically, the mass ratio of the masterbatch to the remaining thermotropic liquid crystal polyester in step S2 is (1-10):100.

[0036] It should be noted that, on the premise of not affecting the mechanical properties and dielectric loss of the thermotropic liquid crystal polymer of the present invention, it further includes 0.1-2 parts of additives.

[0037] Specifically, the additives include one or more of antioxidants, lubricants, or weathering agents.

[0038] In the present invention, common antioxidants can be selected according to the prior art, such as but not limited to one or more of hindered phenol antioxidants, phosphite antioxidants or thioester antioxidants.

[0039] The hindered phenol antioxidants are one or several of N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamide) (Irganox 1098), pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010), triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (Iragnox 259), n-octadecyl β-(4-hydroxy-3,5-di-tert-butylphenyl)propionate (Iragno 1076) or spiroglycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (ADK AO-80).

[0040] The phosphite antioxidants are one or several of 2,4-di-tert-butylphenol (Irganox 168), bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite (PEP-36) or 627A.

[0041] The thioester antioxidants are one or several of distearyl thiodipropionate, dilauryl thiodipropionate or pentaerythritol tetrakis(3-laurylthiopropionate).

[0042] In the present invention, common lubricants can be selected according to the prior art, such as but not limited to at least one of amide lubricants, stearate lubricants, ester lubricants or silicone lubricants.

[0043] In the present invention, common weathering agents can be selected according to the prior art, such as but not limited to one or several of hindered amine types, benzotriazole types, benzophenone types or triazine benzylidene malonate types.

[0044] The present invention also protects the application of the above thermotropic liquid crystal polymer in the preparation of electronic and electrical components, such as applications in flexible printed circuit boards, chip packaging boards or display components.

[0045] The present invention also provides a film prepared from the above thermotropic liquid crystal polymer.

[0046] In some specific embodiments, the film is prepared by melt extrusion and biaxial stretching of the above thermotropic liquid crystal polymer.

[0047] Specifically, it is extruded by a twin-screw extruder, the die head temperature is 280-320 °C, the roll temperature is 80-120 °C, and the drawing speed is 5 m / min.

[0048] Specifically, the biaxial stretching is achieved by synchronous or distributed stretching in the longitudinal and transverse directions, and the stretching ratio is 3 to 5 times.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] The present invention provides a thermotropic liquid crystal polymer, in which an acid anhydride-modified boron nitride is used to modify a thermotropic liquid crystal polyester. The acid anhydride-modified boron nitride can form stable chemical bonds with the residue functional groups at the molecular chain ends of the thermotropic liquid crystal polyester, and the acid anhydride-modified boron nitride can effectively improve the crystallization temperature of the liquid crystal polymer, reduce the longitudinal and transverse crystallization differences during the film extrusion process, and the mechanical property differences between the extrusion direction and the shear direction of the subsequently prepared film are not greater than 20%, and the tensile strength in both directions is generally not lower than 140 MPa. Description of the Drawings

[0051] Figure 1 is a physical diagram of the acid anhydride-modified boron nitride;

[0052] Figure 2 is a physical diagram of the extruder;

[0053] Figure 3 is a physical diagram of the masterbatch in Example 5;

[0054] Figure 4 is a two-dimensional wide-angle X-ray diffraction pattern of the thermotropic liquid crystal polyester 1;

[0055] Figure 5 is a two-dimensional wide-angle X-ray diffraction pattern of Example 5. Detailed Embodiments

[0056] The following further illustrates the present invention in conjunction with the detailed embodiments, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are raw material reagents purchased conventionally.

[0057] Raw materials used in each embodiment and comparative example:

[0058] Thermotropic liquid crystal polyester:

[0059] Thermotropic liquid crystal polyester 1: Vectra A950, with a melting point of 280 °C, manufactured by Celanese Corporation;

[0060] Thermotropic liquid crystal polyester 2: Vectra C950, with a melting point of 310 °C, manufactured by Celanese Corporation;

[0061] Acid anhydride-modified boron nitride:

[0062] Acid anhydride-modified boron nitride 1: Self-made, with a mass ratio of trimellitic anhydride chloride to amino-functionalized nano-boron nitride of 3:1;

[0063] Anhydride-modified boron nitride 2: Self-made, the mass ratio of trimellitic anhydride acyl chloride to amino-functionalized nano-boron nitride is 1:1;

[0064] Anhydride-modified boron nitride 3: Self-made, the mass ratio of trimellitic anhydride acyl chloride to amino-functionalized nano-boron nitride is 5:1;

[0065] Anhydride-modified boron nitride is as Figure 1 shown.

[0066] Anhydride-modified boron nitrides 1 to 3 are prepared by the following method:

[0067] Disperse amino-functionalized nano-boron nitride in a polar solvent (DMF), add trimellitic anhydride acyl chloride and react at 0 - 5 °C for 3 hours to obtain; the average particle size is 50 nm;

[0068] Among them, both amino-functionalized nano-boron nitride and trimellitic anhydride acyl chloride are commercially available;

[0069] Trimellitic anhydride acyl chloride (CAS: 1204 - 28 - 0), commercially available; it should be noted that the same raw materials are used in the parallel experiments of each example and comparative example in the present invention.

[0070] Example 1

[0071] The thermotropic liquid crystal polymer described in Example 1 is prepared by the following preparation method:

[0072] S1. Mix 0.05 parts by weight of anhydride-modified boron nitride 1 and 0.95 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through a twin-screw extruder (as Figure 2 shown) at 350 °C to obtain masterbatch;

[0073] S2. Mix the masterbatch described in step S1 and 99 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0074] Example 2

[0075] The thermotropic liquid crystal polymer described in Example 2 is prepared by the following preparation method:

[0076] S1. Mix 0.1 parts by weight of anhydride-modified boron nitride 1 and 1.9 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0077] S2. Mix the masterbatch described in step S1 and 98 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0078] Example 3

[0079] The thermotropic liquid crystal polymer described in Example 3 is prepared by the following preparation method:

[0080] S1. Mix 0.15 parts by weight of anhydride-modified boron nitride 1 and 2.85 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0081] S2. Mix the masterbatch obtained in step S1 and 97 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0082] Example 4

[0083] The thermotropic liquid crystal polymer described in Example 4 is prepared by the following preparation method:

[0084] S1. Mix 0.25 parts by weight of anhydride-modified boron nitride 1 and 4.75 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0085] S2. Mix the masterbatch obtained in step S1 and 95 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0086] Example 5

[0087] The thermotropic liquid crystal polymer described in Example 5 is prepared by the following preparation method:

[0088] S1. Mix 0.05 parts by weight of anhydride-modified boron nitride 1 and 4.95 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch (as Figure 3 shown);

[0089] S2. Mix the masterbatch obtained in step S1 and 95 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0090] Example 6

[0091] The thermotropic liquid crystal polymer described in Example 6 is prepared by the following preparation method:

[0092] S1. Mix 0.1 parts by weight of anhydride-modified boron nitride 1 and 9.9 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0093] S2. Mix the masterbatch obtained in step S1 and 90 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain the thermotropic liquid crystal polymer.

[0094] Example 7

[0095] The preparation method of the thermotropic liquid crystal polymer described in Example 7 is the same as that in Example 5, except that an equal amount of thermotropic liquid crystal polyester 2 is used instead of thermotropic liquid crystal polyester 1.

[0096] Example 8

[0097] The preparation method of the thermotropic liquid crystal polymer described in Example 8 is the same as that in Example 5, except that an equal amount of anhydride-modified boron nitride 2 is used instead of anhydride-modified boron nitride 1.

[0098] Example 9

[0099] The preparation method of the thermotropic liquid crystal polymer described in Example 9 is the same as that in Example 5, except that an equal amount of anhydride-modified boron nitride 3 is used instead of anhydride-modified boron nitride 1.

[0100] Comparative Example 1

[0101] The thermotropic liquid crystal polymer described in Comparative Example 1 is prepared by the following preparation method:

[0102] S1. Mix 0.005 parts by weight of anhydride-modified boron nitride 1 and 0.495 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt and extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0103] S2. Mix the masterbatch described in step S1 and 99.5 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt and extrude and pelletize through an extruder to obtain a thermotropic liquid crystal polymer.

[0104] Comparative Example 2

[0105] The thermotropic liquid crystal polymer described in Comparative Example 2 is prepared by the following preparation method:

[0106] S1. Mix 0.5 parts by weight of anhydride-modified boron nitride 1 and 49.5 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt and extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0107] S2. Mix the masterbatch described in step S1 and 50 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt and extrude and pelletize through an extruder to obtain a thermotropic liquid crystal polymer.

[0108] Comparative Example 3

[0109] The thermotropic liquid crystal polymer described in Comparative Example 3 is prepared by the following preparation method:

[0110] S1. Mix 0.05 parts by weight of amino-functionalized nano boron nitride and 4.95 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt and extrude and pelletize through a twin-screw extruder at 350 °C to obtain masterbatch;

[0111] S2. Mix the masterbatch described in step S1 and 95 parts by weight of thermotropic liquid crystal polyester 1 evenly, and melt-extrude and pelletize through an extruder to obtain a thermotropic liquid crystal polymer.

[0112] Performance Test

[0113] 1. Test Method

[0114] (1) Tensile strength and elongation at break test: Extrude the thermotropic liquid crystal polymers prepared in each example and comparative example using a twin-screw extruder, with the die head temperature at 280 - 320 °C, the roller temperature at 80 - 120 °C, the traction speed at 5 m / min, and then perform synchronous longitudinal and transverse stretching with a stretching ratio of 3 - 5 times to obtain a film (1.5 cm × 10 cm × 50 μm), and test according to standard GB / T1040.1-2018; Difference rate = (Tensile strength in the extrusion direction - Tensile strength in the shear direction)

[0115] / Tensile strength in the extrusion direction * 100%;

[0116] (2) Melting point test: For the above-mentioned film, according to GB / T3682.1-2018, electrically load the weights, with the test temperature 20 °C above the melting temperature, and measure using a standard die diameter of 2.1 mm;

[0117] (3) Dielectric loss test: Measure the dielectric loss of the above-mentioned film with a thickness of 50 μm according to the standard GB / T 31838-2019;

[0118] (4) Two-dimensional wide-angle X-ray diffraction test: Detect the thermotropic liquid crystal polymers prepared in each example and comparative example using X-ray diffraction (XRD).

[0119] 2. Test Results

[0120] The test results of the thermotropic liquid crystal polymers in the above-mentioned examples and comparative examples are shown in Table 1.

[0121] Table 1 Test Results of Each Example and Comparative Example

[0122]

[0123]

[0124] As can be seen from Table 1, the film prepared from the thermotropic liquid crystal polymer prepared in the present invention can effectively reduce the mechanical property difference between the extrusion direction and the shear direction. The difference in tensile strength between the two directions is not more than 20%, and the tensile strength in both directions is generally not less than 140 MPa (commercial films usually require not less than 140 MPa), and the dielectric loss does not increase significantly.

[0125] It can be seen from Examples 5, 8 to 9 that as the mass ratio of the polyfunctional anhydride or acyl chloride in the anhydride-modified boron nitride to the amino-functionalized nano boron nitride increases, the difference in the tensile strength of the prepared film in two directions first decreases and then increases, and the dielectric loss increases. Generally speaking, the comprehensive performance is the best when the mass ratio is 3:1.

[0126] It can be seen from Comparative Example 1 that when the amount of anhydride-modified boron nitride in the thermotropic liquid crystal polymer is too small, no stable chemical bond is formed with the thermotropic liquid crystal polyester, and the improvement of the material performance is not obvious.

[0127] It can be seen from Comparative Example 2 that when the amount of anhydride-modified boron nitride in the thermotropic liquid crystal polymer is too large, pores will be formed in the system, resulting in obvious deterioration of the mechanical properties and dielectric loss properties.

[0128] It can be seen from Comparative Example 3 that if other boron nitrides are used to replace the anhydride-modified boron nitride in the present invention, the comprehensive performance of the prepared film is significantly worse than that of the examples.

[0129] The test results of two-dimensional wide-angle X-ray diffraction of Example 5 and thermotropic liquid crystal polyester 1 are as Figures 4 - 5 shown. It can be seen from Figure 4 that for the film prepared from pure thermotropic liquid crystal polyester 1, the crystallization difference along the extrusion direction and the shear direction is relatively large, showing a semi-circular bright spot; it can be seen from Figure 5 that for the film prepared from the thermotropic liquid crystal polymer in the present invention, the difference in crystallinity in different directions is significantly improved, and the two directions are almost the same, showing a circular bright spot.

[0130] Obviously, the above-mentioned examples of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A thermotropic liquid crystal polymer, characterized in that: The composition comprises the following components calculated by weight: 0.01 to 0.4 parts of anhydride-modified boron nitride; Thermotropic liquid crystal polyester 99-100 parts.

2. The thermotropic liquid crystal polymer according to claim 1, characterized in that: The anhydride-modified boron nitride is obtained by modifying amino-functionalized nano boron nitride with multifunctional anhydride or acyl chloride.

3. The thermotropic liquid crystal polymer according to claim 1, characterized in that: The melting point of the thermotropic liquid crystal polyester is not less than 260°C.

4. The thermotropic liquid crystal polymer according to claim 1 or 2, characterized in that: The average particle size of the anhydride-modified boron nitride is 10 to 100 nm.

5. The thermotropic liquid crystal polymer according to claim 2, characterized in that: The amino content in the amino-functionalized nano-boron nitride is 5-10 wt %.

6. The thermotropic liquid crystal polymer according to claim 2, characterized in that: The mass ratio of the multifunctional acid anhydride or acid chloride to the amino-functionalized nano boron nitride is not less than 1:

1.

7. A method for preparing the thermotropic liquid crystal polymer according to any one of claims 1 to 6, characterized in that: The steps include: S1. The anhydride-modified boron nitride is uniformly mixed with a portion of the thermotropic liquid crystal polyester in a ratio of 0.5 to 10 wt %, and the masterbatch is obtained by melt extrusion and granulation by an extruder; S2. The masterbatch described in step S1 and the remaining thermotropic liquid crystal polyester are uniformly mixed, and melt-extruded and granulated by an extruder to obtain a thermotropic liquid crystal polymer.

8. The preparation method according to claim 7, characterized in that: In step S1, the anhydride-modified boron nitride is uniformly mixed with a part of the thermotropic liquid crystal polyester in a ratio of 1 to 6 wt %, and the mixture is melt-extruded and granulated by an extruder to obtain a master batch.

9. Use of the thermotropic liquid crystal polymer according to any one of claims 1 to 8 in the preparation of electronic and electrical components.

10. A film, characterized in that: It is prepared by using the thermotropic liquid crystal polymer described in any one of claims 1 to 6.

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