An ultralow dielectric loss liquid crystal epoxy resin composite material and a preparation method thereof

Abstract

The application relates to the field of high polymer materials, and particularly discloses a liquid crystal epoxy resin composite material with ultra-low dielectric loss and a preparation method thereof. The liquid crystal epoxy resin composite material comprises the following raw materials: liquid crystal epoxy resin, a curing agent, a monobasic single-chain aliphatic amine, carbon nanotubes and a coupling agent. The preparation method comprises the following steps: melting the liquid crystal epoxy resin, adding the monobasic single-chain aliphatic amine, the carbon nanotubes and the coupling agent into the liquid crystal epoxy resin while stirring, reacting at 150-180 DEG C. for 20-40 min. in vacuum, then adding the curing agent, uniformly stirring and obtaining a mixed melt; pouring the mixed melt into a mold, then placing the mold into an oven at 140-160 DEG C. for curing for 8 h, then increasing the temperature to 200-220 DEG C. for curing for 1-2 h, and cooling and demolding to obtain the liquid crystal epoxy resin composite material. The liquid crystal epoxy resin composite material has the advantages of high performance and low dielectric loss.

Description

Technical Field

[0001] This application relates to the field of polymer materials, and in particular to an ultra-low dielectric loss liquid crystal epoxy resin composite material and its preparation method. Background Technology

[0002] With the advancement of modern technology, electronic instruments and equipment are gradually becoming more integrated and miniaturized, leading to higher requirements for the dielectric properties of materials. Dielectric loss reduces the lifespan of equipment and causes damage, resulting in significant economic losses. Therefore, the urgent need for high-performance, low-dielectric-loss materials has become an important direction in materials research. Summary of the Invention

[0003] In order to provide high-performance, low-dielectric-loss materials, this application provides an ultra-low dielectric loss liquid crystal epoxy resin composite material and its preparation method.

[0004] In a first aspect, this application provides a liquid crystal epoxy resin composite material with ultra-low dielectric loss, employing the following technical solution:

[0005] A liquid crystal epoxy resin composite material with ultra-low dielectric loss comprises the following raw materials in parts by weight: 80-100 parts liquid crystal epoxy resin, 30-50 parts curing agent, 5-20 parts mono-chain aliphatic amine, 4-8 parts carbon nanotubes, and 2-5 parts coupling agent.

[0006] Furthermore, the liquid crystal epoxy resin comprises the following raw materials in parts by weight: 60-100 parts of liquid crystal epoxy resin monomer, 20-60 parts of E21 epoxy resin monomer, 20-60 parts of E44 epoxy resin monomer, and 20-60 parts of E51 epoxy resin monomer; wherein the liquid crystal epoxy resin monomer is [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate).

[0007] Furthermore, the [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate) is prepared from the following raw materials in the following molar amounts according to the following method:

[0008] Step 1: Weigh 1-20 parts of [2,2'-binaphthyl]-6,6'-diol and dissolve it in 30-250 parts of acetone. Add 5-10 parts of pyridine and cool in an ice-water bath to obtain the base solution. Separately, dissolve 2-40 parts of p-acetoxybenzoyl chloride in 10-50 parts of acetone to obtain a mixed solvent. Slowly add the mixed solvent dropwise to the base solution while stirring. After the addition is complete, remove the ice-water bath and react at room temperature for 8-10 hours. Filter to obtain a solid product. Wash the solid product with acetone and dry to obtain [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate), with the following molecular structure:

[0009]

[0010] Step 2: Take 1-20 parts of [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate) and add 20-100 parts of chloroform, stir until dissolved, and slowly add 20-80 parts of 25% ammonia water dropwise under an ice-water bath for 4-5 hours. After standing, take the organic phase and rotary evaporate it. Then take the solid and dry it to obtain [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate), with the following structure:

[0011]

[0012] Step 3: Take 1-20 parts of [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate) and add 40 times the amount of epichlorohydrin, then add 50-100 parts of isopropanol. Heat to 50-60℃, and slowly add 5-15 parts of sodium hydroxide solution while stirring. Reflux at 50-70℃ for 4-5 hours. Filter and wash the precipitate with water and isopropanol, then dry to obtain the liquid crystal epoxy resin monomer [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate), with the following structure:

[0013]

[0014] Furthermore, the carbon nanotubes are modified carbon nanotubes, which are obtained by acid treatment of ordinary carbon nanotubes.

[0015] Furthermore, the modified carbon nanotubes are prepared by a method comprising the following steps:

[0016] Take 5-10 parts of carbon nanotubes and place them in 80-100 parts of 65% concentrated nitric acid. Sonicate at room temperature for 0.5-1 hour, then reflux at 140-160℃ for 24-26 hours. Dilute with deionized water, filter through a 0.18-0.22μm microporous membrane and wash repeatedly with water until neutral. Finally filter and dry to constant weight to obtain modified carbon nanotubes.

[0017] Furthermore, the modified carbon nanotubes have a diameter of 5-20 nm and a length of 1-10 μm.

[0018] Furthermore, the monocyclic aliphatic amine is one or more of n-hexadecylamine and n-dodecylamine.

[0019] Furthermore, the coupling agent is one or more of the following: silane coupling agent KH550, silane coupling agent KH570, and silane coupling agent KH792.

[0020] Secondly, this application provides a method for preparing an ultra-low dielectric loss liquid crystal epoxy resin composite material, employing the following technical solution:

[0021] A method for preparing an ultra-low dielectric loss liquid crystal epoxy resin composite material includes the following steps:

[0022] Preparation of mixed melt: The liquid crystal epoxy resin is melted at 150-180℃, and a mono-chain aliphatic amine, carbon nanotubes and coupling agent are added to it while stirring. The mixture is reacted under vacuum at 150-180℃ for 20-40 minutes. Then the curing agent is added and the mixture is stirred evenly to obtain the mixed melt.

[0023] Preparation of liquid crystal epoxy resin composite material: Pour the mixed melt into a mold preheated at 140-150℃, then place the mold in an oven at 140-160℃ for curing for 8 hours, then raise the temperature to 200-220℃ and cure for 1-2 hours. After natural cooling, demold to obtain the liquid crystal epoxy resin composite material.

[0024] Compared with the prior art, this application has the following advantages:

[0025] (1) The liquid crystal epoxy resin composite material is made by mixing bisphenol A epoxy resin and liquid crystal epoxy resin monomers in a certain proportion. The epoxy resin composite material prepared by the method disclosed in this application has less interfacial polarization and dipole polarization, thus giving the composite material good dielectric properties and low dielectric loss. Adjusting the content of single-chain aliphatic alkane monoamine and curing agent also endows the polymer with excellent toughness, shape memory effect and other comprehensive properties.

[0026] (2) The naphthalene epoxy resin monomer belongs to the aromatic ester liquid crystal epoxy resin, which combines the characteristics of liquid crystal order and network crosslinking. Its cured product has excellent mechanical, thermal, electrical and optical properties, especially dimensional stability, heat resistance and impact resistance. The naphthalene epoxy resin monomer itself has excellent comprehensive properties; among them, the benzene ring increases the molecular rigidity and has good orientation, which lowers the curing temperature; the ester group and ether bond increase the molecular flexibility, reduce the clearing point and improve the toughness of the polymer.

[0027] (3) The curing agent connects the bisphenol A epoxy resin and the naphthalene liquid crystal epoxy resin monomer, so that the material crosslinks into a stable solid, and also improves the performance of the composite material to a certain extent.

[0028] (4) By adding the mono-chain aliphatic amine disclosed in this application, the epoxy resin composite material has excellent shape memory effect and toughness;

[0029] (5) Carbon nanotubes are a class of high-performance epoxy resin reinforcing materials. The addition of carbon nanotubes improves the mechanical properties and thermal stability of epoxy resin composites and also improves the electromagnetic properties of the composites. The modified carbon nanotubes after acid treatment have a shorter structure and more carboxyl groups are introduced on the surface, so they can be more uniformly dispersed in the composites, thereby reducing agglomeration and further improving the comprehensive performance of epoxy resin composites.

[0030] (6) The addition of coupling agent makes epoxy resin composite material more stable, which is more conducive to practical application and service life extension. In addition, the coupling agent of this ratio also has a certain promoting effect on improving dielectric properties.

[0031] (7) The preparation method in this application has no strict requirements on curing agent and equipment, and the curing effect is good. The preparation method is simple, low in cost, and easy to industrialize.

[0032] In summary, the liquid crystal epoxy resin in this application combines the characteristics of liquid crystal ordering and network crosslinking. Its cured product exhibits excellent mechanical, thermal, electrical, and optical properties, especially significantly improved dimensional stability, heat resistance, and impact resistance compared to ordinary epoxy resins. Liquid crystal epoxy resin overcomes the shortcomings of epoxy resin materials after curing, such as high internal stress, brittleness, poor impact resistance, crack resistance, and damp heat resistance, which limit the application of epoxy resins in high-tech fields, thus realizing the potential application value of epoxy resins. High-performance, ultra-low dielectric loss liquid crystal epoxy resin composite materials can be prepared by using liquid crystal epoxy resin as a raw material in combination with remaining raw materials. Attached Figure Description

[0033] Figure 1 The proton NMR spectrum of p-acetoxybenzoic acid prepared in Example 1 of this application;

[0034] Figure 2 The proton NMR spectrum of p-acetoxybenzoyl chloride prepared in Example 2 of this application;

[0035] Figure 3 The hydrogen spectrum of the liquid crystal epoxy resin monomer [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate) in Preparation Example 1 of this application. Detailed Implementation

[0036] The following examples will provide a more detailed explanation of the specific content of the present invention. It should be noted that: unless otherwise specified, the conditions in the following examples are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples are all from commercially available sources.

[0037] The curing agent comprises the following raw materials in parts by weight: 40 parts of 4,4'-diaminodiphenylmethane, 40 parts of m-phenylenediamine or 4,4'-diaminodiphenyl ether, and 40 parts of 4,4'-diaminodiphenyl sulfone.

[0038] Preparation example of liquid crystal epoxy resin monomer

[0039] Preparation Example 1

[0040] A method for preparing an epoxy resin monomer includes the following steps:

[0041] Step 1: Weigh 1 part of [2,2'-binaphthyl]-6,6'-diol and dissolve it in 30 parts of acetone. Add 5 parts of pyridine and cool in an ice-water bath to obtain the base solution. Separately, dissolve 2 parts of p-acetoxybenzoyl chloride in 10 parts of acetone to obtain a mixed solvent. Slowly add the mixed solvent dropwise to the base solution while stirring. After the addition is complete, remove the ice-water bath and react at room temperature for 8 hours. After filtration, obtain a solid product. Wash the solid product with acetone and dry to obtain [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate).

[0042] Step 2: Take 1 part of [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate) and add 20 parts of chloroform. Stir until dissolved. Slowly add 20 parts of 25% ammonia water in an ice-water bath and react for 4 hours. After standing, take the organic phase and rotary evaporate it. Then take the solid and dry it to obtain [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate).

[0043] Step 3: Take 1 part of [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate) and add 40 times the amount of epichlorohydrin, then add 50 parts of isopropanol. Heat to 55°C, and slowly add 5 parts of sodium hydroxide solution while stirring. Reflux at 60°C for 4 hours. Filter and wash the precipitate with water and isopropanol, and dry to obtain the liquid crystal epoxy resin monomer [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate).

[0044] The p-acetoxybenzoyl chloride in the raw material is prepared by the following method:

[0045] Add 1 part p-hydroxybenzoic acid and 50 parts acetic anhydride to a flask, then add 5 drops of concentrated sulfuric acid. Heat the mixture in an oil bath to 60°C, stir mechanically, and reflux for 2 hours using a spherical condenser. Pour the reaction solution into ice water and stir. Filter the precipitated solid. Recrystallize with ethanol to obtain the white product p-acetoxybenzoic acid (ABA), whose chemical structure is:

[0046] In a separate flask, add 1 part p-acetoxybenzoic acid, 20 parts dichlorosulfite, and 5 drops of pyridine. Slowly heat the mixture in an oil bath to 70°C, using a serpentine condenser connected to a waste gas absorption device, and mechanically stir the reaction for 3 hours. After stopping the reaction, add boiling chips, distill at atmospheric pressure, heat to 140°C, and then distill under reduced pressure to obtain a deep red oily liquid, p-acetoxybenzoyl chloride (ABC), whose chemical structure is as follows:

[0047] Preparation Example 2

[0048] A method for preparing an epoxy resin monomer includes the following steps:

[0049] Step 1: Weigh 20 parts of [2,2'-binaphthyl]-6,6'-diol and dissolve it in 250 parts of acetone. Add 10 parts of pyridine and cool in an ice-water bath to obtain the base solution. Separately, dissolve 40 parts of p-acetoxybenzoyl chloride in 50 parts of acetone to obtain a mixed solvent. Slowly add the mixed solvent dropwise to the base solution while stirring. After the addition is complete, remove the ice-water bath and react at room temperature for 8 hours. After filtration, obtain a solid product. Wash the solid product with acetone and dry to obtain [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate).

[0050] Step 2: Take 20 parts of [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate) and add 100 parts of chloroform. Stir until dissolved. Slowly add 80 parts of 25% ammonia water in an ice-water bath and react for 4 hours. After standing, take the organic phase and rotary evaporate it. Then take the solid and dry it to obtain [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate).

[0051] Step 3: Take 20 parts of [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate) and add 40 times the amount of epichlorohydrin, then add 100 parts of isopropanol. Heat to 55°C, and slowly add 15 parts of sodium hydroxide solution while stirring. Reflux at 60°C for 4 hours. Filter and wash the precipitate with water and isopropanol, and dry to obtain the liquid crystal epoxy resin monomer [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate).

[0052] The p-acetoxybenzoyl chloride in the raw material is prepared by the following method:

[0053] Add 20 parts of p-hydroxybenzoic acid and 300 parts of acetic anhydride to a flask, then add 30 drops of concentrated sulfuric acid. Heat the mixture in an oil bath to 60°C, stir mechanically, and reflux for 2 hours using a spherical condenser. Pour the reaction mixture into ice water and stir. Filter the precipitated solid. Recrystallize with ethanol to obtain the white product p-acetoxybenzoic acid (ABA).

[0054] In a separate flask, add 20 parts of p-acetoxybenzoic acid, 100 parts of dichlorosulfite, and 30 drops of pyridine. Slowly heat the mixture in an oil bath to 70°C, reflux it using a serpentine condenser connected to a waste gas absorption device, and mechanically stir the reaction for 3 hours. After stopping the reaction, add zeolite, distill at atmospheric pressure, heat to 140°C, and then distill under reduced pressure to obtain a dark red oily liquid p-acetoxybenzoyl chloride (ABC).

[0055] Preparation example of modified carbon nanotubes

[0056] Preparation Example 3

[0057] A method for preparing modified carbon nanotubes includes the following steps:

[0058] Five parts of carbon nanotubes were placed in 80 parts of 65% concentrated nitric acid and sonicated at room temperature for 0.5 hours. Then, the mixture was refluxed at 140°C for 24 hours. The mixture was then diluted with an appropriate amount of deionized water, filtered through a 0.20 μm microporous membrane, and repeatedly washed with water until neutral. Finally, the filtered product was dried to constant weight to obtain modified carbon nanotubes.

[0059] Preparation Example 4

[0060] A method for preparing modified carbon nanotubes includes the following steps:

[0061] Ten parts of carbon nanotubes were placed in 100 parts of 65% concentrated nitric acid and sonicated at room temperature for 0.5 hours. Then, the mixture was refluxed at 140°C for 24 hours. After dilution with deionized water, the mixture was filtered through a 0.20 μm microporous membrane and repeatedly washed with water until neutral. Finally, it was filtered and dried to constant weight to obtain modified carbon nanotubes.

[0062] Example

[0063] Example 1

[0064] A method for preparing an ultra-low dielectric loss liquid crystal epoxy resin composite material includes the following steps:

[0065] Preparation of mixed melt: 80 parts of liquid crystal epoxy resin were melted at 160°C. While stirring, 10 parts of mono-chain aliphatic amine, 4 parts of modified carbon nanotubes prepared by the method in Preparation Example 3, and 3 parts of coupling agent were added. The mixture was reacted under vacuum at 170°C for 20 min. Then, 35 parts of curing agent were added and stirred evenly to obtain mixed melt.

[0066] The liquid crystal epoxy resin includes 80 parts of liquid crystal epoxy resin monomer, 50 parts of E21 epoxy resin monomer, 50 parts of E44 epoxy resin monomer and 50 parts of E51 epoxy resin monomer prepared by the method in Preparation Example 1.

[0067] Preparation of liquid crystal epoxy resin composite material: Pour the mixed melt into a mold preheated at 140℃, then place the mold in an oven at 160℃ for curing for 8 hours, then raise the temperature to 220℃ and cure for 2 hours. After natural cooling and demolding, the liquid crystal epoxy resin composite material is obtained.

[0068] Examples 2-4

[0069] A method for preparing an ultra-low dielectric loss liquid crystal epoxy resin composite material is carried out according to the method in Example 1, with the differences shown in Table 1.

[0070] Table 1:

[0071]

[0072] Performance testing

[0073] The performance of each of the above embodiments was tested, and the test results are shown in Table 2.

[0074] Table 2:

[0075]

[0076] Figure 1 The 1H NMR spectrum of p-acetoxybenzoic acid prepared in Example 1 of this application is shown. Figure 2 The proton NMR spectrum of p-acetoxybenzoyl chloride prepared in Example 2 of this application; Figure 1 and Figure 2 This demonstrates that the methods in Preparation Examples 1 and 2 of the present invention can prepare the expected products, proving the feasibility of the preparation methods.

[0077] Figure 3 The hydrogen spectrum of the liquid crystal epoxy resin monomer [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate) in Preparation Example 1 of this application shows that the method in Preparation Example 1 of this invention can be used to obtain the expected product, proving the feasibility of the preparation method.

Claims

1. A liquid crystal epoxy resin composite material with ultra-low dielectric loss, characterized in that: The raw materials include the following components in parts by weight: 80-100 parts liquid crystal epoxy resin, 30-50 parts curing agent, 5-20 parts monocyclic aliphatic amine, 4-8 parts carbon nanotubes, and 2-5 parts coupling agent. The liquid crystal epoxy resin comprises the following raw materials in parts by weight: 60-100 parts of liquid crystal epoxy resin monomer, 20-60 parts of E21 epoxy resin monomer, 20-60 parts of E44 epoxy resin monomer, and 20-60 parts of E51 epoxy resin monomer; wherein the liquid crystal epoxy resin monomer is [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate). The carbon nanotubes are modified carbon nanotubes, which are obtained by acid treatment of ordinary carbon nanotubes. The [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate) was prepared from the following raw materials in the following molar amounts according to the following method: Step 1: Weigh 1-20 parts of [2,2'-binaphthyl]-6,6'-diol and dissolve it in 30-250 parts of acetone. Add 5-10 parts of pyridine and cool in an ice-water bath to obtain the base solution. Separately, dissolve 2-40 parts of p-acetoxybenzoyl chloride in 10-50 parts of acetone to obtain a mixed solvent. Slowly add the mixed solvent dropwise to the base solution while stirring. After the addition is complete, remove the ice-water bath and react at room temperature for 8-10 hours. Filter to obtain a solid product. Wash the solid product with acetone and dry to obtain [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate), the molecular structure of which is shown in the figure below. Step 2: Take 1-20 parts of [2,2'-binaphthyl]-6,6'-bis(4-methoxybenzoate) and add 20-100 parts of chloroform. Stir until dissolved. Slowly add 20-80 parts of 25% ammonia solution in an ice-water bath and react for 4-5 hours. After standing, take the organic phase and rotary evaporate it. Then take the solid and dry it to obtain [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate), the structure of which is shown in the figure below: Step 3: Take 1-20 parts of [2,2'-binaphthyl]-6,6'-bis(4-hydroxybenzoate) and add 40 times the amount of epichlorohydrin, then add 50-100 parts of isopropanol. Heat to 50-60℃, and slowly add 5-15 parts of sodium hydroxide solution while stirring. Reflux at 50-70℃ for 4-5 hours. Filter and wash the precipitate with water and isopropanol, then dry to obtain the liquid crystal epoxy resin monomer [2,2'-binaphthyl]-6,6'-bis(4-(ethylene oxide-2-ylmethoxy)benzoate), the structure of which is shown in the figure. ； The monocyclic aliphatic amine is one or more of hexadecylamine and dodecylamine.

2. The ultra-low dielectric loss liquid crystal epoxy resin composite material according to claim 1, characterized in that: The modified carbon nanotubes are prepared by a method comprising the following steps: Take 5-10 parts of carbon nanotubes and place them in 80-100 parts of 65% concentrated nitric acid. Sonicate at room temperature for 0.5-1 hour, then reflux at 140-160℃ for 24-26 hours. Dilute with deionized water, filter through a 0.18-0.22μm microporous membrane and wash repeatedly with water until neutral. Finally filter and dry to constant weight to obtain modified carbon nanotubes.

3. The ultra-low dielectric loss liquid crystal epoxy resin composite material according to claim 1, characterized in that: The modified carbon nanotubes have a diameter of 5-20 nm and a length of 1-10 μm.

4. The ultra-low dielectric loss liquid crystal epoxy resin composite material according to claim 1, characterized in that: The coupling agent is one or more of the following: silane coupling agent KH550, silane coupling agent KH570, and silane coupling agent KH792.

5. A method for preparing an ultra-low dielectric loss liquid crystal epoxy resin composite material as described in any one of claims 1-4, characterized in that, Includes the following steps: Preparation of mixed melt: The liquid crystal epoxy resin is melted at 150-180℃, and a mono-chain aliphatic amine, carbon nanotubes and coupling agent are added to it while stirring. The mixture is reacted under vacuum at 150-180℃ for 20-40 minutes. Then the curing agent is added and the mixture is stirred evenly to obtain the mixed melt. Preparation of liquid crystal epoxy resin composite material: Pour the mixed melt into a mold preheated at 140-150℃, then place the mold in an oven at 140-160℃ for curing for 8 hours, then raise the temperature to 200-220℃ and cure for 1-2 hours. After natural cooling, demold to obtain the liquid crystal epoxy resin composite material.

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