A high thermal conductivity and low dielectric constant liquid crystal polyester composite material and its preparation method and application

Abstract

The present invention provides a high thermal conductivity low dielectric constant liquid crystal polyester composite material and its preparation method and application. The method first prepares a diol containing biphenyl monomer, and then gradually condenses the diol monomer and fluorine-containing dibasic acid in an equal molar ratio under the condition of countless zinc acetate and antimony trioxide as catalysts to prepare a fluorine-containing liquid crystal polyester as a matrix material. Highly crystalline carbon nitride is prepared using dicyandiamide as a precursor, and carbon nitride is added to the matrix material in a certain proportion, and the composite material is obtained after the solvent is volatilized after being fully mixed in a solvent. The π-π stacking effect between the matrix and the filler improves its interface compatibility, constructs a thermal conductive network, and further improves the thermal conductivity of the composite material. The prepared high thermal conductivity low dielectric constant liquid crystal polyester composite material can be prepared in a variety of thicknesses, which is suitable for application in the field of microelectronics.

Description

Technical Field

[0001] The present invention relates to the field of thermally conductive composite materials, and in particular to a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant, and a preparation method and application thereof. Background Art

[0002] With the rapid development of electronic information technology, the integration of electronic products is constantly improving, and the speed and frequency are getting higher and higher; in high-frequency circuits, the transmission speed of signals can be expressed as: V∝c / √ε, where V-signal transmission rate, C-speed of light in vacuum, ε-dielectric constant of substrate. It can be seen that when polymers are used as output end components of electronic products, the lower the dielectric constant, the more conducive to signal transmission. At the same time, with the development of mobile communication technology and the trend of high frequency, high integration and miniaturization of electronic equipment, the accumulation of local heat will seriously affect the operation safety of precision equipment and shorten its service life. Thermal management is also the most critical technical challenge facing modern electronic products. Materials with high thermal conductivity and low dielectric constant have received widespread attention. Liquid crystal polymer is a special material that combines the mechanical and rheological properties of polymer materials with the photoelectric sensitivity of liquid crystal molecules. It has good application prospects in optical data storage and nonlinear optical microelectronic devices. In recent years, the IT industry has found that liquid crystal polymers exhibit low dielectric constants and dielectric losses, which has opened up new application areas in the fields of power, electronics and communications.

[0003] Carbon nitride (C3N4) is a new type of carbon material that has emerged in recent years. It is formed by sp2 hybridization of single atoms of carbon and nitrogen. It has a unique planar structure, good electrical, optical and physicochemical properties, and a simple preparation process with low cost, which has aroused strong interest among researchers in the field of electrochemical energy storage. Among them, graphite phase carbon nitride (g-C3N4) is a new type of non-metallic photocatalytic material with certain light absorption in the visible light range, as well as good thermal stability, chemical stability and photostability. It is widely used in photocatalytic hydrogen production, water oxidation, organic matter degradation, photosynthesis and carbon dioxide reduction. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0006] Another object of the present invention is to provide an application of the above-mentioned liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A high thermal conductivity and low dielectric constant liquid crystal polyester composite material is obtained by compounding carbon nitride and fluorine-containing liquid crystal polyester.

[0009] In the liquid crystal polyester composite material with high thermal conductivity and low dielectric constant, the mass fraction of carbon nitride is 2-10%, preferably 10%.

[0010] The structural formula of the fluorine-containing liquid crystal polyester is shown in Formula I:

[0011]

[0012] The method for preparing the above-mentioned high thermal conductivity and low dielectric constant liquid crystal polyester composite material comprises the following steps:

[0013] The carbon nitride and the fluorine-containing liquid crystal polyester are dissolved in tetrahydrofuran, stirred and dried to obtain a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0014] The amount of tetrahydrofuran is based on the ability to completely dissolve the solute.

[0015] The stirring time is 5 to 8 hours, preferably 6 hours.

[0016] The drying condition is 50-60°C.

[0017] The method for preparing carbon nitride comprises the following steps:

[0018] Calcinate dicyandiamide, add acid to the product and stir, wash and dry, and continue calcining to obtain carbon nitride.

[0019] The calcination conditions are 350-450° C. for 1-3 hours.

[0020] The ratio of the product to the acid is 1 g: 10-20 mL.

[0021] The acid is hydrochloric acid with a concentration of 1 mol / L.

[0022] The stirring condition for adding the acid is stirring at 150-250 rpm for 20-30 hours.

[0023] The washing is performed using water and anhydrous ethanol.

[0024] The drying condition is 70-90° C. for 10-14 hours.

[0025] The conditions for continued calcination are calcination at 500-600° C. for 3-5 hours.

[0026] The preparation method of the fluorine-containing liquid crystal polyester comprises the following steps:

[0027] (1) reflux a halogenated alcohol, biphenyl diphenol and anhydrous potassium carbonate under a protective atmosphere, add water after cooling, filter, neutralize, wash with water and dry to obtain biphenyl dihydric alcohol;

[0028] (2) After biphenyl dihydric alcohol and tetrafluorophthalic acid are mixed, a catalyst is added and heated for polycondensation reaction, and then the heating reaction is continued while filtering to obtain a liquid crystal polyester containing a hydrogen bond donor.

[0029] The halogenated alcohol is at least one of 2-bromoethanol, 3-chloro-1-propanol, 4-chlorobutanol or 6-chlorohexanol.

[0030] The molar ratio of the halogenated alcohol to biphenol is 2-4:1, preferably 3:1.

[0031] The protective atmosphere is a nitrogen atmosphere.

[0032] The reflux reaction conditions are condensation reflux for 20 to 30 hours, preferably condensation reflux for 24 hours.

[0033] The cooling is cooling to room temperature.

[0034] The neutralization is to add hydrochloric acid to adjust the pH to 1.

[0035] The drying conditions are 70-90° C. for 20-30 hours, preferably 80° C. for 24 hours.

[0036] The molar ratio of biphenyl dihydric alcohol to tetrafluorophthalic acid is 1-2:1-2, preferably 1:1.

[0037] The catalyst is anhydrous zinc acetate and antimony trioxide.

[0038] The mass of the anhydrous zinc acetate is 0.1-0.3% of the total mass of the reaction system, preferably 0.2%.

[0039] The mass of the antimony trioxide is 0.2-0.4% of the total mass of the reaction system, preferably 0.3%.

[0040] The conditions for the heating polycondensation reaction are 150-200° C. for 2-4 hours, preferably 180° C. for 3 hours.

[0041] The condition of the filtration is that the vacuum degree is lower than 30Pa.

[0042] The conditions for the continued heating reaction are to react at 150-200° C. for 2-4 hours; preferably, to react at 190° C. for 3 hours.

[0043] Application of the above-mentioned high thermal conductivity and low dielectric constant liquid crystal polyester composite material in the preparation of electronic devices.

[0044] The above-mentioned high thermal conductivity and low dielectric constant liquid crystal polyester composite material is used as a heat dissipation material for electronic devices.

[0045] Compared with the prior art, the present invention has the following advantages and effects:

[0046] (1) The fluorine-containing liquid crystal polyester synthesized in the present invention is used as a matrix material. The ordered orientation of the liquid crystal can effectively suppress phonon scattering and improve thermal conductivity. Fluorine has low polarization and high bond energy, which can effectively reduce the dielectric constant and dielectric loss.

[0047] (2) The carbon nitride prepared by the present invention is a highly crystalline carbon nitride, which is conducive to obtaining a composite material with higher crystallinity and improving the thermal conductivity of the composite material.

[0048] (3) The π-π stacking effect between the matrix and the filler improves their interfacial compatibility, builds a good thermal conductive network, and further improves the thermal conductivity of the composite material.

[0049] (4) The thermally conductive composite material prepared by the present invention has a simple preparation process. The high thermal conductivity and low dielectric constant liquid crystal polyester composite material prepared by the present invention has a dielectric constant of 2.66 and a dielectric loss of 4.57×10 -3 , thickness is 0.1 ~ 2.5mm, and materials with various thicknesses, different thermal conductivities and dielectric constants can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 1 is a curve showing the change of dielectric constant of the composite materials prepared in Examples 2 to 4 with frequency.

[0051] Figure 2 3 is the curve showing the change of dielectric loss with frequency for the composite materials prepared in Examples 2 to 4. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0053] If no specific experimental conditions are specified in the following embodiments, conventional experimental conditions or experimental conditions recommended by the reagent company are generally followed. The materials and reagents used, unless otherwise specified, are all reagents and materials obtained from commercial sources.

[0054] Example 1

[0055] This embodiment provides a high thermal conductivity and low dielectric constant liquid crystal polyester composite material and a preparation method thereof, comprising the following steps:

[0056] (1) 40 ml of 6-chlorohexanol, 18.6 g of biphenyl diphenol and 124 g of anhydrous potassium carbonate were placed in a 250 ml three-necked flask, and condensed and refluxed for 24 h under nitrogen protection. After the reactants were cooled to room temperature, 250 ml of deionized water was added and stirred, and then filtered to remove the solvent. Excess hydrochloric acid was added to make the pH value 1, and the excess potassium carbonate was reacted. After washing with water for several times, the obtained product was dried in a vacuum oven at 80 degrees Celsius for 24 h to obtain biphenyl dihydroxyhexanol; 3 0.54g of biphenyl dihydric alcohol and 2.38g of tetrafluorophthalic acid were subjected to polycondensation reaction, and the reaction conditions were as follows: 0.0118g of anhydrous zinc acetate and 0.0178g of antimony trioxide were added, and the reaction was carried out at 180 degrees Celsius for 3 hours. After slowly heating to 190 degrees Celsius, the vacuum degree of the system was reduced (below 30Pa) by vacuum filtration, and water and small molecules in the system were removed at the same time, so that the polycondensation reaction was carried out in the forward direction. After continuing the reaction at 190 degrees Celsius for 3 hours, the reaction was stopped to obtain a fluorine-containing liquid crystal polyester, as shown in Formula I;

[0057]

[0058] Formula I

[0059] (2) heating dicyandiamide to 550 degrees Celsius for high temperature cracking, and taking it out after 4 hours to obtain carbon nitride;

[0060] (3) 0.02 g of the carbon nitride prepared in step (2) and 0.98 g of the fluorinated liquid crystal polyester prepared in step (1) were dissolved in 10 g of tetrahydrofuran, stirred for 6 h, and then placed in a vacuum oven at 60° C. to evaporate the solvent and obtain a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0061] The obtained composite material was characterized and tested, and its thermal conductivity was measured to be 0.169Wm -1 k -1 .

[0062] Example 2

[0063] This embodiment provides a high thermal conductivity and low dielectric constant liquid crystal polyester composite material and a preparation method thereof, comprising the following steps:

[0064] (1) Using dicyandiamide as a precursor, calcining it in a muffle furnace for 2 hours (400°C), then adding it to dilute hydrochloric acid (1 mol / L) and stirring it for 24 hours (200 rpm), adding 10 mL of dilute hydrochloric acid per gram of the calcined product, washing the solution with deionized water and anhydrous ethanol until the pH value is neutral after stirring, and vacuum drying it at 80°C for 12 hours to obtain protonated carbon nitride, and further calcining the protonated carbon nitride in a muffle furnace at 550°C for 4 hours to obtain highly crystalline carbon nitride.

[0065] (2) 0.02 g of the carbon nitride prepared in step (1) and 0.98 g of the fluorine-containing liquid crystal polyester prepared in Example 1 were dissolved in 10 g of tetrahydrofuran, stirred for 6 h, and then placed in a vacuum oven at 60° C. to evaporate the solvent and obtain a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0066] The obtained composite material was characterized and tested. The thermal conductivity of the composite material prepared by the above scheme was 0.183 Wm -1 k -1 , at a frequency of 10 MHz, the dielectric constant is 4.71 and the dielectric loss is 2.48×10 -2 The dielectric constant varies with frequency as shown in Figure 1 The dielectric loss varies with frequency as shown in Figure 2 shown.

[0067] Example 3

[0068] This embodiment provides a high thermal conductivity and low dielectric constant liquid crystal polyester composite material and a preparation method thereof, comprising the following steps:

[0069] 0.05 g of the carbon nitride prepared in Example 2 and 0.95 g of the fluorinated liquid crystal polyester prepared in Example 1 were dissolved in 10 g of tetrahydrofuran, stirred for 6 h, and then placed in a vacuum oven at 60° C. to evaporate the solvent and obtain a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0070] The obtained composite material was characterized and tested. The thermal conductivity of the composite material prepared by the above scheme was 0.223 Wm -1 k -1 , at a frequency of 10 MHz, the dielectric constant is 3.07 and the dielectric loss is 2.20×10 -2 The dielectric constant varies with frequency as shown in Figure 1 The dielectric loss varies with frequency as shown in Figure 2 shown.

[0071] Example 4

[0072] This embodiment provides a high thermal conductivity and low dielectric constant liquid crystal polyester composite material and a preparation method thereof, comprising the following steps:

[0073] 0.1 g of the carbon nitride prepared in Example 2 and 0.9 g of the fluorinated liquid crystal polyester prepared in Example 1 were dissolved in 10 g of tetrahydrofuran, stirred for 6 h, and then placed in a vacuum oven at 60° C. to evaporate the solvent and obtain a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant.

[0074] The obtained composite material was characterized and tested. The thermal conductivity of the composite material prepared by the above scheme was 0.266Wm -1k -1 , at a frequency of 10 MHz, the dielectric constant is 2.66 and the dielectric loss is 4.57×10 -3 The dielectric constant varies with frequency as shown in Figure 1 The dielectric loss varies with frequency as shown in Figure 2 According to the above case analysis, the addition of carbon nitride is beneficial to the improvement of thermal conductivity and the reduction of dielectric constant. Below a low addition amount (10%), its thermal conductivity increases with the increase of addition amount, and the dielectric constant decreases with the increase of addition amount.

[0075] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A liquid crystal polyester composite material with high thermal conductivity and low dielectric constant, characterized in that: It is obtained by compounding carbon nitride with fluorine-containing liquid crystal polyester; The mass fraction of the carbon nitride is 10%; The preparation method of the fluorine-containing liquid crystal polyester comprises the following steps: (1) 6-chlorohexanol, biphenyl and anhydrous potassium carbonate are mixed and refluxed under a protective atmosphere to obtain 4,4'-bis(6-hydroxyhexyloxy)biphenyl; (2) 4,4'-di(6-hydroxyhexyloxy)biphenyl and tetrafluorophthalic acid are mixed, a catalyst is added, and the mixture is heated for polycondensation reaction. The mixture is then filtered and heated for reaction to obtain a fluorinated liquid crystal polyester.

2. The method for preparing the high thermal conductivity and low dielectric constant liquid crystal polyester composite material according to claim 1, characterized in that The steps include: The carbon nitride and the fluorine-containing liquid crystal polyester are dissolved in tetrahydrofuran, stirred, and dried to obtain a liquid crystal polyester composite material with high thermal conductivity and low dielectric constant; The stirring time is 5 to 8 hours; The drying condition is 50-60°C; The method for preparing carbon nitride comprises the following steps: Calcinate dicyandiamide, add acid to the product, stir, wash, dry, and continue calcining to obtain carbon nitride; The calcination conditions are 350-450° C. for 1-3 hours; The ratio of the product to the acid is 1 g: 10-20 mL; The conditions for continued calcination are calcination at 500-600° C. for 3-5 hours; The conditions for adding acid and stirring are stirring at 150-250 rpm for 20-30 hours; The drying condition is 70-90° C. for 10-14 hours.

3. Use of the high thermal conductivity and low dielectric constant liquid crystal polyester composite material according to claim 1 in the preparation of electronic devices.

4. Use of the high thermal conductivity and low dielectric constant liquid crystal polyester composite material according to claim 1 as a heat dissipation material for electronic devices.

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