Mesocrystal epoxy monomer and preparation method thereof, mesocrystal epoxy resin and epoxy molding compound

Abstract

The invention relates to the technical field of epoxy molding compounds, and discloses a mesogenic epoxy monomer and a preparation method thereof, mesogenic epoxy resin and an epoxy molding compound. The preparation method of the mesogenic epoxy monomer comprises the following steps: performing epoxidation on an intermediate selected from any one of an aromatic ester compound as shown in a formula II, a biphenyl compound as shown in a formula III and a biphenyl compound as shown in a formula IV to prepare a mesogenic epoxy monomer product with epoxy groups at two ends, and boron tungstate quaternary ammonium salt or phosphotungstate quaternary ammonium salt is used as a catalyst. According to the preparation method, epoxidation reaction conditions are mild, reaction time is short, the product yield is high, and industrial production of the product is facilitated; the resin obtained through subsequent curing is good in corrosion resistance, the service life of a chip plastically packaged by the resin can be prolonged, and the corrosion problem caused by chlorine can be avoided possibly due to the fact that the chlorine content of the product is low.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy encapsulation materials, in particular to mesogenic epoxy monomers and their preparation methods, mesogenic epoxy resins, and epoxy encapsulants. Background Art

[0002] Epoxy monomers are a type of thermosetting resin with excellent mechanical and adhesive properties. As the main resin of epoxy encapsulant (EMC), they play an important role in the advanced packaging field of chip materials. With the rapid development of emerging technologies such as artificial intelligence, autonomous driving, 5G, and cloud computing, the demand for chips in computing speed and computing power has increased simultaneously. Optimizing heat dissipation performance and improving reliability have become new pursuits in the advanced packaging field of chips. Therefore, the thermal conductivity and corrosion resistance reliability of the EMC main resin have become key indicators.

[0003] The main resin of EMC is usually an epoxy monomer. Ordinary epoxy monomers have poor thermal conductivity and cannot meet the heat dissipation requirements of high-frequency and high-power chips. By preparing filled high-thermal-conductivity epoxy resins by adding high-thermal-conductivity fillers to epoxy monomers, the problem of insufficient thermal conductivity of epoxy monomers can be effectively solved. However, the introduction of a large amount of fillers will undoubtedly significantly affect the mechanical properties of the material. In response to this problem, the development of intrinsically thermal-conductive epoxy resins has become a hot topic. The excellent thermal conductivity of intrinsically thermal-conductive epoxy resins comes from their core component, mesogenic epoxy monomers. When mesogenic epoxy monomers and curing agents are cured in the liquid crystal temperature range, an ordered cross-linked network structure is formed. The mesogenic epoxy resin formed after monomer curing relies on the thermal vibration of neatly arranged lattices to achieve efficient heat dissipation, thereby improving the intrinsic thermal conductivity of the epoxy resin without damaging the mechanical properties of the material. The thermal conductivity of mesogenic epoxy resins can reach 1.5 times that of ordinary bisphenol A epoxy resin E-51 (the thermal conductivity of E-51 is 0.19 W / m·K). Obviously, the development of high-performance mesogenic epoxy monomers is of great significance for the development of advanced packaging materials for high-thermal-conductivity chips. Summary of the Invention

[0004] As described above, in order to solve the problems that the preparation of traditional mesogenic epoxy monomers is cumbersome and not conducive to industrialization, and the resin obtained by curing mesogenic epoxy monomers has poor corrosion resistance, the purpose of the present invention is to provide mesogenic epoxy monomers and their preparation methods, mesogenic epoxy resins, and epoxy encapsulants. The preparation method of this mesogenic epoxy monomer is simple and easy to industrialize, and the resin obtained by curing this mesogenic epoxy monomer has strong corrosion resistance.

[0005] For this purpose, in a first aspect, the present invention provides a method for preparing a mesogenic epoxy monomer, comprising the following steps: subjecting an intermediate selected from aromatic ester compounds represented by formula I, aromatic ester compounds represented by formula II, biphenyl compounds represented by formula III, or biphenyl compounds represented by formula IV to epoxidation to obtain a mesogenic epoxy monomer product with epoxy groups at both ends, wherein the conditions for the epoxidation include: using hydrogen peroxide as an oxidant and a quaternary ammonium borotungstate or a quaternary ammonium phosphotungstate as a catalyst; Formula I Formula II Formula III Formula IV In formula I, R is H or an alkyl group having 1 to 4 carbon atoms; In formula II, R 1 is H or an alkyl group having 1 to 4 carbon atoms; R 2 and R 3 are the same and are each independently an alkylene group having 1 to 4 carbon atoms; In formula III, R 1 , R 2 , R 3 and R 4 are the same and are each independently an alkyl group having 1 to 4 carbon atoms; In formula IV, R 1 , R 2 , R 3 and R 4 are the same and are each independently an alkyl group having 1 to 4 carbon atoms; R 5 and R 6 are the same and are each independently an alkylene group having 1 to 4 carbon atoms.

[0006] The preparation method of the present invention has a high product yield, mild epoxidation reaction conditions, and a short reaction time, which is beneficial to the industrial production of the product; the mesogenic epoxy prepared by this method is applied in EMC in the form of a matrix resin, which can extend the service life of the chip encapsulated by EMC. This is because the mesogenic epoxy monomer prepared by this method has an extremely low chlorine content, which can avoid the problem of poor corrosion resistance caused by chlorine impurities.

[0007] The preparation method of the present invention has a high intrinsic thermal conductivity of the resin obtained by curing the prepared mesogenic epoxy monomer. When the mesogenic epoxy is applied in EMC in the form of a matrix resin, it is not necessary to add a large amount of high thermal conductivity fillers to improve the thermal conductivity of EMC. After the filler addition amount is reduced, it is beneficial to improve the mechanical properties of EMC.

[0008] In some preferred embodiments of the present invention, the conditions for epoxidation further include: the oxidation temperature is 25°C - 80°C, preferably 30°C - 45°C. Optionally, the oxidation temperature is 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C.

[0009] In some preferred embodiments of the present invention, the conditions for epoxidation further include: the oxidation time is 1h - 8h, preferably 3h - 6h.

[0010] In some preferred embodiments of the present invention, the conditions for epoxidation further include: the stirring rate is 100rpm - 300rpm, preferably 120rpm - 200rpm.

[0011] In some preferred embodiments of the present invention, based on the weight of the intermediate, the dosage of the catalyst is 2.5 - 10.0 wt%. Optionally, the dosage of the catalyst is 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt%, 10.0wt%.

[0012] In some preferred embodiments of the present invention, based on the number of moles of carbon-carbon double bonds contained in the intermediate, the number of moles of hydrogen peroxide is 220mol% - 1100mol%. Optionally, the number of moles of hydrogen peroxide is 220mol%, 250mol%, 300mol%, 350mol%, 400mol%, 450mol%, 500mol%, 550mol%, 600mol%, 650mol%, 700mol%, 750mol%, 800mol%, 850mol%, 900mol%, 950mol%, 1000mol%, 1050mol%, 1100mol%.

[0013] In some preferred embodiments of the present invention, the hydrogen peroxide is added in the form of a hydrogen peroxide solution, and the concentration of the hydrogen peroxide solution is 20wt% - 50wt%.

[0014] In some preferred embodiments of the present invention, the hydrogen peroxide solution is added dropwise, and based on 0.1g of the intermediate, the dropping rate is 0.001mL / min - 0.100mL / min.

[0015] In some preferred embodiments of the present invention, the hydrogen peroxide solution is added dropwise to the reaction system after adding the catalyst to activate the catalyst. Based on 0.1 g of the intermediate, the dropping amount is 1 - 3 drops, and stirring is carried out for 5 - 15 min.

[0016] In some preferred embodiments of the present invention, the hydrogen peroxide solution is added to the reaction system in two parts by dropwise addition. Based on 0.1 g of the intermediate, the first part of the hydrogen peroxide solution is added dropwise after adding the catalyst, and the addition amount is 1 - 3 drops, and stirring is carried out for 5 - 15 min; the second part of the hydrogen peroxide solution is added dropwise during the process of adjusting the reaction system to the oxidation temperature, and the dropping rate is 0.001 mL / min - 0.100 mL / min. In the present invention, adding the first part of the hydrogen peroxide solution and stirring can activate the catalyst.

[0017] In some preferred embodiments of the present invention, the epoxidation is carried out in the presence of an organic solvent, and the organic solvent is selected from at least one of benzene, toluene, ethylbenzene, and ethyl acetate.

[0018] In some preferred embodiments of the present invention, the yield of the mesogenic epoxy monomer product is above 75 wt%, preferably above 80 wt%, and more preferably 80 wt% - 99 wt%.

[0019] In some preferred embodiments of the present invention, the total chlorine content of the mesogenic epoxy monomer is below 10 ppm, and the easily hydrolyzable chlorine content is below 0.01 ppm; preferably, the total chlorine content of the mesogenic epoxy monomer is 2 ppm - 9 ppm, and no easily hydrolyzable chlorine is detected.

[0020] Therefore, in a second aspect, the present invention provides a mesogenic epoxy monomer prepared by the above preparation method.

[0021] Therefore, in a third aspect, the present invention provides a mesogenic epoxy resin, and the raw material includes the mesogenic epoxy monomer prepared by the above preparation method.

[0022] In some preferred embodiments of the present invention, the preparation method of the mesogenic epoxy resin includes curing the mesogenic epoxy monomer with a curing agent.

[0023] Therefore, in a fourth aspect, the present invention provides an epoxy molding compound (EMC), and the raw material includes the above mesogenic epoxy resin.

[0024] In some preferred embodiments of the present invention, the raw materials of the epoxy molding compound further include additives, and the additives are selected from at least one of a curing agent, a promoter, a toughening agent, and a thermal conductive filler.

[0025] The present invention has the following beneficial effects: The preparation method of the present invention has a high product yield, mild epoxidation reaction conditions, and a short reaction time, which is conducive to the industrial production of the product; the resin obtained by subsequent curing has good corrosion resistance, which can extend the service life of the chip encapsulated with this resin. This may be because the product has a low chlorine content (the total chlorine content of the mesogenic epoxy monomer prepared by the traditional method is 100 ppm - 1000 ppm), which can avoid the problem of poor corrosion resistance caused by chlorine impurities.

[0026] The preparation method of the present invention results in a resin with a high intrinsic thermal conductivity obtained by curing the mesogenic epoxy monomer. When used as the matrix resin of EMC, it is not necessary to add a large amount of high thermal conductivity fillers to improve the thermal conductivity of EMC. Therefore, the mechanical properties of the obtained EMC are excellent.

[0027] The resin obtained by curing the mesogenic epoxy monomer prepared by the preparation method of the present invention has excellent liquid crystallinity, high temperature resistance and corrosion resistance. When used as the matrix resin in EMC, the effect is significantly better than that of ordinary epoxy resins, such as o-cresol novolac epoxy (500 - 4P), dicyclopentadiene epoxy (DNE - 260), bisphenol A epoxy (128), etc. It can relieve the material warping phenomenon caused by EMC curing, improve the heat resistance stability and heat dissipation capacity of the cured sample, and improve the problems of air holes, delamination and wire flushing during the EMC molding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1a It is the infrared spectrum of the quaternary ammonium salt catalyst of boric tungstic acid obtained in Preparation Example 1.

[0029] Figure 1b It is the infrared spectrum of the quaternary ammonium salt catalyst of phosphotungstic acid obtained in Preparation Example 2.

[0030] Figure 2 It is the infrared spectrum of the mesogenic epoxy monomer MPEPB - 1 prepared in Example 1.

[0031] Figure 3 It is the 1H NMR spectrum of the mesogenic epoxy monomer MPEPB - 1 prepared in Example 1.

[0032] Figure 4 It is the DSC curve of the curing process of MPEPB - 1 prepared in Example 1.

[0033] Figure 5 It is the TGA curve of MPEPB - 1 prepared in Example 1.

[0034] Figure 6a It is the polarized light microscope (POM) image of MPEPB - 1 prepared in Example 1, (200×): heating section 170 °C.

[0035] Figure 6bPolarizing microscope (POM) image of MPEPB-1 prepared in Example 1, (200×): Cooling section at 60 °C.

[0036] Figures 7a to 7d DSC curves of the curing processes of o-cresol novolac epoxy (500-4P), dicyclopentadiene epoxy (DNE-260), bisphenol A epoxy (128), and MPEPB-3 prepared in Example 3, respectively.

[0037] Figures 8a to 8d DSC curves of the mesomorphic epoxy resins obtained by curing o-cresol novolac epoxy (500-4P), dicyclopentadiene epoxy (DNE-260), bisphenol A epoxy (128), and MPEPB-3 prepared in Example 3, respectively.

[0038] Figures 9a to 9d Back views of the molded parts obtained by encapsulating electronic components with EMC-1, EMC-2, EMC-3, and EMC-4, respectively (observing the external air holes of the EMC molded parts).

[0039] Figures 10a to 10d Photographs taken by ultrasonic scanning microscope (SAT, RCHO-LS) of the molded parts obtained by encapsulating electronic components with EMC-1, EMC-2, EMC-3, and EMC-4, respectively (testing the delamination of the EMC molded parts).

[0040] Figures 11a to 11d Internal wire-punching test result diagrams of the X-ray machines (SMX-1000) of the molded parts obtained by encapsulating electronic components with EMC-1, EMC-2, EMC-3, and EMC-4, respectively (testing the wire-punching rate of the EMC). Figure 11a In which, W1 is 10.03%; Figure 11b In which, W1 is 11.93%; Figure 11c In which, W1 is 10.72%; Figure 11d In which, W1 is 9.05%. Detailed implementation manners

[0041] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention. For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0042] In some preferred embodiments of the present invention, the preparation method of the quaternary ammonium salt catalyst of borotungstic acid includes the following steps: After tungstic acid is oxidized to peroxotungstic acid, boric acid is added for reaction to obtain borotungstic heteropolyacid; The borotungstic heteropolyacid reacts with the quaternary ammonium salt cetyltrimethylammonium bromide to obtain the quaternary ammonium salt catalyst of borotungstic acid.

[0043] In some preferred embodiments of the present invention, the preparation method of the quaternary ammonium salt catalyst of phosphotungstic acid comprises the following steps: oxidizing phosphotungstic acid to peroxophosphotungstic acid, and reacting the peroxophosphotungstic acid with the quaternary ammonium salt cetyltrimethylammonium bromide to obtain the quaternary ammonium salt catalyst of phosphotungstic acid.

[0044] In some preferred embodiments of the present invention, taking the aromatic ester compound shown in Formula I (R is methyl) as an example, the preparation method of the mesomorphic epoxy monomer comprises the following steps: S1. 4-Allyloxybenzoic acid (as shown in Formula I-1) is subjected to acyl chlorination to obtain 4-allyloxybenzoyl chloride (as shown in Formula I-2); S2. The 4-allyloxybenzoyl chloride prepared in step S1 reacts with o-methylhydroquinone (as shown in Formula I-3) to obtain 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (as shown in Formula I-4); S3. The 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester prepared in step S2 is subjected to epoxidation to obtain 4,4'-bis(2,3-epoxypropoxy)benzoic acid o-methylhydroquinone ester (as shown in Formula I-5), wherein the conditions of the epoxidation include: using hydrogen peroxide as the oxidant and using the quaternary ammonium salt of borotungstic acid or the quaternary ammonium salt of phosphotungstic acid as the catalyst.

[0045] Formula I-1 Formula I-2 Formula I-3 Formula I-4 Formula I-5

[0046] Preparation Example 1 Preparation of the quaternary ammonium salt catalyst of borotungstic acid Weigh 1 g of tungstic acid solid in a beaker, and slowly add dropwise to the beaker a 30 wt% hydrogen peroxide solution until the tungstic acid solid is just completely dissolved to obtain a clear and transparent pale yellow peroxotungstic acid solution.

[0047] Next, add 0.33 g of boric acid solid to the peroxotungstic acid solution, react at 65 °C and 200 rpm for 30 min to obtain a borotungstic heteropolyacid solution. Then add 1.69 g of the quaternary ammonium salt cetyltrimethylammonium bromide to the borotungstic heteropolyacid solution, and react at 50 °C and 400 rpm for 90 min to obtain a crude sample of the quaternary ammonium salt catalyst of borotungstic heteropolyacid.

[0048] The crude sample was rinsed with deionized water multiple times to wash away the unreacted quaternary ammonium salt until there were no bromide ions in the solution (the presence of bromide ions was detected using a 5 wt% silver nitrate solution). The absence of bromide ions indicated that the solid phase had been cleaned thoroughly. The pure quaternary ammonium salt borotungstate catalyst in the solid phase was collected and could be used after being treated in a vacuum oven at 50 °C for 24 h.

[0049] Figure 1a It is the infrared spectrum of the quaternary ammonium salt borotungstate catalyst obtained in Preparation Example 1. Figure 1a In it, at wavelengths of 2922 cm -1 and 2852 cm -1 appeared the antisymmetric stretching vibration peak and symmetric stretching vibration peak of C−H in 2 ; at a wavelength of 1480 cm -1 appeared the characteristic peak of the quaternary ammonium salt; at a wavelength of 1300 cm -1 appeared the characteristic absorption peak of the B−O bond; at a wavelength of 948 cm -1 appeared the stretching vibration absorption peak of W=O; at 892 cm -1 and 801 cm -1 appeared the stretching vibration absorption peak of W−O−W. From Figure 1a it can be seen that the quaternary ammonium salt borotungstate catalyst was successfully prepared in Preparation Example 1.

[0050] Preparation Example 2 Preparation of quaternary ammonium salt phosphotungstate catalyst Weigh 3.49 g of phosphotungstic acid into a four-necked flask, add an appropriate amount of deionized water to the four-necked flask, and stir with a glass rod until the phosphotungstic acid solid is completely dissolved. Next, weigh 14.8 g of a 30 wt% hydrogen peroxide solution into a beaker, and use a peristaltic pump to drip the hydrogen peroxide solution into the flask. After the dripping is completed, treat it at room temperature and 200 rpm for 60 min. Then weigh 1.31 g of the quaternary ammonium salt cetyltrimethylammonium bromide into a beaker, add 20 mL of an appropriate amount of dichloromethane to the beaker, stir with a glass rod until the solid is completely dissolved, and use a peristaltic pump to drip the dichloromethane solution of cetyltrimethylammonium bromide into the flask. After the dripping is completed, treat it at room temperature and 200 rpm for 60 min. After the reaction is completed, centrifuge the suspension and collect the solid phase, a pale yellow solid powder. Finally, wash the solid powder with deionized water, filter it by suction, and collect the solid phase. Repeat this operation 3 - 5 times, and use a 5 wt% silver nitrate solution to detect the presence of bromide ions in the filtrate. If there are no bromide ions, it indicates that the solid phase has been cleaned thoroughly. Collect the pure quaternary ammonium salt phosphotungstate catalyst in the solid phase and it can be used after being treated in a vacuum oven at 50 °C for 24 h.

[0051] Figure 1b It is the infrared spectrum of the quaternary ammonium salt phosphotungstate catalyst obtained in Preparation Example 2. Figure 1b In it, at wavelengths of 2922 cm -1and 2852 cm -1 −CH appears at 2 the antisymmetric and symmetric stretching vibration peaks of the C−H bond in; 1052 cm -1 the antisymmetric stretching vibration peak of the P-O bond appears at; 948 cm -1 the stretching vibration peak of W=O appears at; 892 cm -1 and 801 cm -1 the stretching vibration peak of W-O-W appears at. From Figure 1b it can be seen that the quaternary ammonium salt catalyst of phosphotungstic acid [C 19 H 42 N] 3 PW 4 O 16 .

[0052] Preparation Example 3 (1) Preparation of 4-allyloxybenzoyl chloride Weigh 0.02 mol of 4-allyloxybenzoic acid, 0.2 mol of thionyl chloride and 0.005 mol of N,N-dimethylformamide into a four-necked flask in sequence, and react at room temperature (20 °C) for 2 h under mechanical stirring at 100 rpm. Then, rotate and evaporate the product at 30 °C to preliminarily remove the unreacted thionyl chloride. Then dissolve the crude acyl chloride sample with toluene to dissolve the extremely small amount of residual thionyl chloride in the crude sample in toluene to obtain a toluene solution of acyl chloride; finally, rotate and evaporate the toluene solution of acyl chloride at 45 °C to remove the solvent toluene and take away the remaining thionyl chloride reagent to obtain pure 4-allyloxybenzoyl chloride, whose structure is shown in Formula I-2.

[0053] Formula I-2 (2) Preparation of 4,4’-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester Transfer 0.1 mol of 4-allyloxybenzoyl chloride to a clean four-necked flask, and then add 20 mL of pyridine to the four-necked flask. Treat it at room temperature for 10 min under mechanical stirring at 100 rpm. Next, add an appropriate amount of a pyridine solution of o-methylhydroquinone (0.049 mol of o-methylhydroquinone / 5 mL of pyridine) to the four-necked flask, and place the four-necked flask in an ice-water bath. Treat it for 30 min under mechanical stirring at 100 rpm. Finally, transfer the four-necked flask to a room temperature (20 °C) environment and treat it for 24 h under the condition of 200 rpm. Then, rotary evaporate the product at 45 °C to remove pyridine completely, and collect the crude sample. Wash the crude sample with 5 wt% aqueous sodium carbonate solution and pure water respectively to remove the unreacted o-methylhydroquinone. Finally, recrystallize with absolute ethanol to obtain pure 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, whose structural formula is shown in Formula I-4, and is called product P1.

[0054] Formula I-4 Example 1 Preparation of mesogenic epoxy monomer Place the reaction kettle in an ice bath, add 0.6 g of product P1 prepared in Preparation Example 3, 0.018 g of buffer salt disodium hydrogen phosphate and 35 mL of solvent ethyl acetate to the reaction kettle, and stir at 100 rpm for 10 min. Next, add an ethyl acetate solution of quaternary ammonium salt of borotungstic acid catalyst (0.06 g of catalyst / 10 mL of ethyl acetate) to the reaction kettle and treat it at 100 rpm for 10 min. Then, weigh 0.32 g of 30 wt% hydrogen peroxide solution, and use a dropper to suck 3-5 drops of hydrogen peroxide solution and add it to the reaction kettle (to activate the catalyst to form tungsten oxide), and treat it at 100 rpm for 10 min. Finally, transfer the reaction kettle to a 40 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.01 mL / min. After the dropping is completed, react for 6 h under mechanical stirring at 200 rpm.

[0055] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use (the precipitate is the catalyst, and the steps for repeated use of the catalyst are the same as those in Example 1). Wash the organic phase with deionized water, dry, recrystallize and vacuum dry to obtain a pure mesogenic epoxy monomer product MPEPB-1 (whose structural formula is shown in Formula I-5).

[0056] Figure 2 It is the infrared spectrum of the mesogenic epoxy monomer MPEPB-1 prepared in Example 1. Figure 2 In, the wavelength is 2927 cm -1 and 2852 cm -1 At appears -CH2 The antisymmetric stretching and symmetric stretching vibration peaks of C−H; 1726 cm -1 The stretching vibration peak of C=O in the ester group appears at 1606 cm -1 and 1508 cm -1 The antisymmetric stretching vibration peak of C=C in the benzene ring appears at 1579 cm -1 The bending vibration peak of C=C in the benzene ring appears at 1457 cm -1 and 1371 cm -1 The antisymmetric deformation and symmetric deformation vibration peaks of C−H in −CH 3 appear at 1253 cm -1 and 1000 cm -1 The antisymmetric stretching and symmetric stretching vibration peaks of C−O−C in the aromatic ether appear at 1165 cm -1 and 1076 cm -1 The antisymmetric stretching and symmetric stretching vibration peaks of the C-O bond in the ester group appear at 1107 cm -1 and 848 cm -1 The in-plane deformation and out-of-plane deformation vibration peaks of =CH in the para-substituted benzene ring appear at 912 cm -1 at and 767 cm -1 The characteristic peaks of the terminal epoxy group appear at. The infrared spectrum is consistent with the characteristic peak appearance of 4,4’-bis(2,3-epoxypropoxy) benzoic acid o-methylhydroquinone ester. Thus, the target product is preliminarily determined to be obtained.

[0057] Figure 3 is the nuclear magnetic resonance hydrogen spectrum of the mesogenic epoxy monomer MPEPB-1 prepared in Example 1. Figure 3 In it, proton peaks are detected at chemical shift values of 2.82, 2.98, 3.43, 4.07, 4.37, 7.04, 8.17, 7.15, 7.19, 7.11, and 2.24 ppm, which correspond one by one to the proton hydrogens at positions a1, a2, b, c1, c2, d, e, f, g, h, and i in the structural formula of the target compound MPEPB. By calculating the peak areas of each proton peak, it is found that the ratio of the peak areas is consistent with the ratio of the corresponding hydrogen atom numbers in the MPEPB structure. Thus, the product is determined to be the target mesogenic epoxy monomer 4,4’-bis(2,3-epoxypropoxy) benzoic acid o-methylhydroquinone ester.

[0058] Preparation of Mesogenic Epoxy Resin Using linear phenolic (5090) as the curing agent and triphenylphosphine as the accelerator: (1) Grind MPEPB-1 and 5090 into powders respectively; (2) Then mix 11.26 g of MPEPB-1, 6.74 g of 5090 and 0.15 g of triphenylphosphine in a mortar and grind them in the mortar until they are evenly dispersed; (3) Put the mixed powder into a mold, put the mold into an oven, and cure it at 175 °C for 6 h to obtain a mesomorphic epoxy resin.

[0059] Figure 4 DSC curve of the mesomorphic epoxy monomer MPEPB-1 prepared in Example 1. Figure 5 TGA curve of the mesomorphic epoxy monomer MPEPB-1 prepared in Example 1. From Figure 4 the DSC curve of MPEPB-1, it can be seen that the melting point of MPEPB-1 is 138.84 °C. During the heating process, the liquid crystal range of MPEPB-1 is 138.84 - 207.54 °C, and the liquid crystal temperature range reaches 68.70 °C; during the cooling process, the liquid crystal range of MPEPB-1 is 150.96 - 63.59 °C, and the liquid crystal temperature range reaches 87.37 °C. From Figure 5 the TGA curve of MPEPB-1, it can be seen that the initial decomposition temperature of MPEPB-1 exceeds 200 °C; at 800 °C, the residual carbon rate is still 15 wt%, and the mesomorphic epoxy monomer MPEPB-1 has good heat resistance.

[0060] Figure 6a Polarizing microscope (POM) image of MPEPB-1 prepared in Example 1, (200×): heating section at 170 °C. Figure 6b Polarizing microscope (POM) image of MPEPB-1 prepared in Example 1, (200×): cooling section at 60 °C. From Figure 6a and Figure 6b it can be seen that MPEPB-1 shows a nematic schlieren texture during the heating process and a smectic focal conic texture during the cooling process. Therefore, it is determined that the sample MPEPB-1 is a mesomorphic material.

[0061] The yield Y of the product MPEPB-1 and the thermal conductivity of the cured resin as a function of the number of times the catalyst is used are shown in Table 1.

[0062] Table 1

[0063] As can be seen from Table 1, the yields of the quaternary ammonium salt of tungstoboric acid catalyst in the first two uses can reach over 75 wt%. The thermal conductivity of the resin obtained after curing the product MPEPB-1 is above 0.40 W / m·k, and its thermal conductivity performance is significantly better than that of the resin cured from the mesomorphic epoxy monomer prepared by the traditional method (the thermal conductivity of the traditional epoxy resin is 0.19 W / m·k). Moreover, the chlorine content in the product MPEPB-1 is extremely low, the total chlorine content is less than 10 ppm, and the hydrolyzable chlorine content is stably 0 ppm.

[0064] Example 2 Place the reaction kettle in an ice bath. Add 0.6 g of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester prepared in Preparation Example 3, 0.018 g of buffer salt disodium hydrogen phosphate, and 35 mL of solvent ethyl acetate into the reaction kettle, and stir for 10 min under the condition of 100 rpm. Next, add an ethyl acetate solution of the quaternary ammonium salt of phosphotungstic acid catalyst (prepared from 0.06 g of catalyst and 10 mL of ethyl acetate) into the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Then, weigh 0.32 g of 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it into the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 40°C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.01 mL / min. After the dropping is completed, react for 6 h under the mechanical stirring at 200 rpm.

[0065] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use (the precipitate is the catalyst, and the steps for the repeated use of the catalyst are the same as those in Example 1), wash the organic phase with deionized water, dry, recrystallize, and vacuum dry it to obtain a pure mesomorphic epoxy monomer product MPEPB-2 (its structural formula is shown in Formula I-5).

[0066] The specific steps for curing the mesomorphic epoxy monomer product MPEPB-2 to prepare the resin are the same as those in Example 1. The changes in the yield Y of the product MPEPB-2 and the thermal conductivity of the cured resin with the number of times of catalyst use are shown in Table 2.

[0067] Table 2

[0068] As can be seen from Table 2, when the quaternary ammonium salt of phosphotungstic acid catalyst is reused three times, the yield of the product MPEPB-2 is still above 86 wt%; when the catalyst is reused 5 times, the yield of the product MPEPB-2 can still reach 80 wt%.

[0069] In addition, the resin obtained after the curing of product MPEPB-2 has a thermal conductivity of more than 0.50 W / m·K, and its thermal conductivity is significantly better than that of the resin cured from the mesogenic epoxy monomer prepared by the traditional method. Moreover, the chlorine content in product MPEPB-2 is extremely low, the total chlorine content is less than 10 ppm, and the easily hydrolyzable chlorine content is stably 0 ppm.

[0070] Example 3 (1)Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.03:20, add 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (0.6 g) prepared in Preparation Example 3, buffer salt disodium hydrogen phosphate and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0071] (2)Next, add an ethyl acetate solution of quaternary ammonium salt of phosphotungstic acid catalyst to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, quaternary ammonium salt of phosphotungstic acid catalyst and ethyl acetate is 1:0.100:5.

[0072] (3)Then, according to the molar ratio of carbon-carbon double bond in 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester to hydrogen peroxide of 1:5, weigh 30 wt% hydrogen peroxide solution, suck 3-5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 38°C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.02 mL / min. After the dropping is completed, react for 6 h under the mechanical stirring at 200 rpm.

[0073] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use, wash the organic phase with deionized water, dry, recrystallize and vacuum dry to obtain a pure mesogenic epoxy monomer product MPEPB-3 (its structural formula is shown in Formula I-5). The yield of product MPEPB-3 is 86.48 wt%.

[0074] The specific steps for curing the mesogenic epoxy monomer product MPEPB-3 to prepare resin are the same as those in Example 1. The thermal conductivity of the resin obtained by curing product MPEPB-3 is 0.52 W / m·K. The total chlorine content and easily hydrolyzable chlorine content of MPEPB-3 are 2 ppm and 0 ppm respectively.

[0075] Example 4 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.01:20, add 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (0.6 g) prepared in Preparation Example 3, buffer salt disodium hydrogen phosphate and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0076] (2) Next, add an ethyl acetate solution of quaternary ammonium salt of phosphotungstic acid catalyst to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, quaternary ammonium salt of phosphotungstic acid catalyst and ethyl acetate is 1:0.050:5.

[0077] (3) Then, according to the molar ratio of carbon-carbon double bond in 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester to hydrogen peroxide of 1:7.5, weigh 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 45 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.05 mL / min. After the dropping is completed, react for 7 h under the mechanical stirring at 200 rpm.

[0078] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use, wash the organic phase with deionized water, dry, recrystallize and vacuum dry to obtain a pure mesomorphic epoxy monomer product MPEPB-4 (its structural formula is shown in Formula I-5). The yield of product MPEPB-4 is 65.41 wt%, the thermal conductivity of MPEPB-4 cured resin is 0.51 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-4 are 8 ppm and 0 ppm respectively.

[0079] Example 5 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.02:20, add 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (0.6 g) prepared in Preparation Example 3, buffer salt disodium hydrogen phosphate and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0080] (2) Next, add an ethyl acetate solution of quaternary ammonium salt of phosphotungstic acid catalyst to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, quaternary ammonium salt of phosphotungstic acid catalyst and ethyl acetate is 1:0.075:5.

[0081] (3) Then, according to the molar ratio of 1:10 of the carbon-carbon double bond in 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester to hydrogen peroxide, weigh 30 wt% hydrogen peroxide solution. Use a dropper to suck 3 - 5 drops of hydrogen peroxide solution and add it to the reaction kettle, and process it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 38 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.07 mL / min. After the dropping is completed, react for 6 h under the mechanical stirring at 200 rpm.

[0082] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use, wash the organic phase with deionized water, dry, recrystallize and vacuum dry it to obtain a pure mesomorphic epoxy monomer product MPEPB-5 (its structural formula is shown in Formula I-5). The yield of product MPEPB-5 is 69.53 wt%, the thermal conductivity of MPEPB-5 cured resin is 0.53 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-5 are 6 ppm and 0 ppm respectively.

[0083] Example 6 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.04:20, add 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (0.6 g) prepared in Preparation Example 3, buffer salt disodium hydrogen phosphate and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0084] (2) Next, add an ethyl acetate solution of quaternary ammonium salt phosphotungstate catalyst to the reaction kettle and process it for 10 min under the condition of 100 rpm; in this step, the mass ratio of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, quaternary ammonium salt phosphotungstate catalyst and ethyl acetate is 1:0.025:5.

[0085] (3) Then, according to the molar ratio of 1:2.5 of the carbon-carbon double bond in 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester to hydrogen peroxide, weigh 30 wt% hydrogen peroxide solution. Use a dropper to suck 3 - 5 drops of hydrogen peroxide solution and add it to the reaction kettle, and process it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 40 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.01 mL / min. After the dropping is completed, react for 5 h under the mechanical stirring at 200 rpm.

[0086] After the reaction was completed, the reactants were centrifuged, and the precipitate was collected for future use. The organic phase was washed with deionized water, dried, recrystallized, and vacuum dried to obtain the pure mesomorphic epoxy monomer product MPEPB-6 (its structural formula is shown in Formula I-5). The yield of product MPEPB-6 was 72.59 wt%, the thermal conductivity of the MPEPB-6 cured resin was 0.51 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-6 were 6 ppm and 0 ppm, respectively.

[0087] Example 7 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.01:20, add 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (0.6 g) prepared in Preparation Example 3, buffer salt disodium hydrogen phosphate, and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0088] (2) Next, add an ethyl acetate solution of the quaternary ammonium salt catalyst of phosphotungstic acid to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, the quaternary ammonium salt catalyst of phosphotungstic acid, and ethyl acetate is 1:0.050:5.

[0089] (3) Then, according to the molar ratio of carbon-carbon double bond in 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester to hydrogen peroxide of 1:2.5, weigh 30 wt% hydrogen peroxide solution, suck 3-5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 30°C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.01 mL / min. After the dropping is completed, react for 4 h under the mechanical stirring at 200 rpm.

[0090] After the reaction was completed, the reactants were centrifuged, and the precipitate was collected for future use. The organic phase was washed with deionized water, dried, recrystallized, and vacuum dried to obtain the pure mesomorphic epoxy monomer product MPEPB-7 (its structural formula is shown in Formula I-5). The yield of product MPEPB-7 was 45.19 wt%, the thermal conductivity of the MPEPB-7 cured resin was 0.45 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-7 were 7 ppm and 0 ppm, respectively.

[0091] Example 8 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.03:20, add 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester (0.6 g) prepared in Preparation Example 3, buffer salt disodium hydrogen phosphate, and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0092] (2) Next, add an ethyl acetate solution of quaternary ammonium salt of phosphotungstic acid catalyst to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester, quaternary ammonium salt of phosphotungstic acid catalyst, and ethyl acetate is 1:0.075:5.

[0093] (3) Then, according to the molar ratio of carbon-carbon double bond in 4,4'-bis(2,3-allyloxy)benzoic acid o-methylhydroquinone ester to hydrogen peroxide of 1:2.2, weigh 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 38 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.01 mL / min. After the dropping is completed, react for 7 h under the mechanical stirring at 200 rpm.

[0094] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use, wash the organic phase with deionized water, dry, recrystallize, and vacuum dry to obtain a pure mesomorphic epoxy monomer product MPEPB-8 (its structural formula is shown in Formula I-5). The yield of product MPEPB-8 is 84.56 wt%, the thermal conductivity of MPEPB-8 cured resin is 0.53 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-8 are 3 ppm and 0 ppm respectively.

[0095] Example 9 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.03:20, add 0.6 g of the aromatic ester compound shown in Formula II (wherein, R 1 is methyl, R 2 and R 3 are methylene), buffer salt disodium hydrogen phosphate, and solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm.

[0096] (2) Next, add an ethyl acetate solution of quaternary ammonium salt of phosphotungstic acid catalyst to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of the aromatic ester compound shown in Formula II, quaternary ammonium salt of phosphotungstic acid catalyst, and ethyl acetate is 1:0.100:5.

[0097] (3) Then, according to the molar ratio of 1:5 of the carbon-carbon double bond in the aromatic ester compound shown in Formula II to hydrogen peroxide, weigh 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 38 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.02 mL / min. After the dropping is completed, react for 6 h under the mechanical stirring at 200 rpm.

[0098] After the reaction is completed, centrifuge the reactants, collect the precipitate for future use, wash the organic phase with deionized water, dry, recrystallize and vacuum dry it to obtain a pure mesomorphic epoxy monomer. The yield of product MPEPB-9 is 86.01 wt%, the thermal conductivity of the cured resin is 0.48 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-9 are 1 ppm and 0 ppm respectively.

[0099] Example 10 (1) Place the reaction kettle in an ice bath, and add 0.6 g of the biphenyl compound shown in Formula III (R 1 , R 2 , R 3 and R 4 are methyl), disodium hydrogen phosphate buffer salt and ethyl acetate solvent into the reaction kettle according to the mass ratio of 1:0.03:20, and stir for 10 min under the condition of 100 rpm.

[0100] (2) Next, add an ethyl acetate solution of the quaternary ammonium salt catalyst of phosphotungstic acid to the reaction kettle and treat it for 10 min under the condition of 100 rpm; in this step, the mass ratio of the biphenyl compound shown in Formula III, the quaternary ammonium salt catalyst of phosphotungstic acid and ethyl acetate is 1:0.100:5.

[0101] (3) Then, according to the molar ratio of 1:5 of the carbon-carbon double bond in the biphenyl compound shown in Formula III to hydrogen peroxide, weigh 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 38 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.02 mL / min. After the dropping is completed, react for 6 h under the mechanical stirring at 200 rpm.

[0102] After the reaction was completed, the reactants were centrifuged, and the precipitate was collected for future use. The organic phase was washed with deionized water, dried, recrystallized, and vacuum dried to obtain pure mesomorphic epoxy monomer. The yield of product MPEPB-10 was 85.28 wt%, the thermal conductivity of the cured resin was 0.45 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-10 were 3 ppm and 0 ppm, respectively.

[0103] Example 11 (1) Place the reaction kettle in an ice bath. According to the mass ratio of 1:0.03:20, add 0.6 g of the biphenyl compound shown in Formula IV (where R 1 , R 2 , R 3 and R 4 are methyl groups, and R 5 and R 6 are methylene groups), disodium hydrogen phosphate as a buffer salt, and ethyl acetate as a solvent, and stir at 100 rpm for 10 min.

[0104] (2) Next, add an ethyl acetate solution of a quaternary ammonium salt of phosphotungstic acid catalyst to the reaction kettle and treat it at 100 rpm for 10 min; in this step, the mass ratio of the biphenyl compound shown in Formula IV, the quaternary ammonium salt of phosphotungstic acid catalyst, and ethyl acetate is 1:0.100:5.

[0105] (3) Then, according to the molar ratio of the carbon-carbon double bond in the biphenyl compound shown in Formula IV to hydrogen peroxide of 1:5, weigh 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it to the reaction kettle, and treat it at 100 rpm for 10 min. Finally, transfer the reaction kettle to a 38°C water bath, and at the same time use a peristaltic pump to drip the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.02 mL / min. After the dripping is completed, react for 6 h under mechanical stirring at 200 rpm.

[0106] After the reaction was completed, the reactants were centrifuged, and the precipitate was collected for future use. The organic phase was washed with deionized water, dried, recrystallized, and vacuum dried to obtain pure mesomorphic epoxy monomer. The yield of product MPEPB-11 was 85.88 wt%, the thermal conductivity of the cured resin was 0.41 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-11 were 5 ppm and 0 ppm, respectively.

[0107] Comparative Example 1 The difference from Example 1 is that the quaternary ammonium salt catalyst of tungstoboric acid and 30 wt% hydrogen peroxide solution are replaced with m-chloroperbenzoic acid, and the amount of m-chloroperbenzoic acid used is the amount of hydrogen peroxide in the 30 wt% hydrogen peroxide solution, obtaining MPEPB-D1. The yield of the product MPEPB-D1 is 53.15 wt%, the thermal conductivity of the cured resin of MPEPB-D1 (the same curing steps as in Example 1) is 0.42 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-D1 are 600 ppm and 150 ppm respectively.

[0108] The thermal conductivity of the cured sample of MPEPB-D1 is comparable to the heat conduction effect of the cured samples of MPEPB-1 and MPEPB-2 prepared by the present invention. However, the product yield of MPEPB-D1 is much lower than that of MPEPB-1 and MPEPB-2, and the chlorine content of MPEPB-D1 is much higher than that of MPEPB-1 and MPEPB-2.

[0109] Comparative Example 2 According to the operation steps of Example 1 in Patent CN107216442A, epoxidized diallyl terephthalate was prepared. The specific operations are as follows.

[0110] (1) Preparation of terephthaloyl chloride: At room temperature, 15 g of terephthalic acid and 0.5 mL of N,N-dimethylformamide were added into a 500 ml four-necked flask equipped with a magnetic stirrer, a condensing reflux tube, a constant pressure dropping funnel and a thermometer. Under nitrogen protection, 55 g of thionyl chloride was added dropwise to the above system, and then the system was heated to 90 °C and kept warm for 1 h. The thionyl chloride was removed by a vacuum circulating water pump, and the product was recrystallized from acetone to obtain white crystalline terephthaloyl chloride; (2) Preparation of diallyl terephthalate: 20 g of eugenol and a sufficient amount of 10 wt% aqueous NaOH solution were stirred in an ice-water bath for 30 min in a four-necked flask equipped with a condensing reflux tube, a dropping funnel and a magnetic stirrer until eugenol formed a sodium salt and the system was a yellow transparent solution; 15 g of the terephthaloyl chloride prepared in step (1) was dissolved in acetone and slowly added dropwise to the above system through a constant pressure dropping funnel. After the addition was completed, the reaction was continued in the ice-water bath for 2 h; after the reaction was completed, the above system was filtered by suction, the filter cake was dissolved in dichloromethane and filtered by suction again; the filtrate was taken and the dichloromethane was evaporated to obtain a white crystalline solid; the solid was recrystallized again from absolute ethanol to obtain white crystalline diallyl terephthalate; (3) Synthesis of epoxidized diallyl terephthalate: 60 g of 75 wt% m-chloroperbenzoic acid was dissolved in dichloromethane and added into a 500 ml four-necked flask equipped with a magnetic stirrer, a thermometer and a constant pressure dropping funnel; at room temperature, it was dissolved in CH 2 Cl 222.9 g of diallyl terephthalate was added dropwise to the reaction system and reacted at room temperature for 72 h; after the reaction was completed, the white solid was removed by suction filtration, and the filtrate was washed alternately with 10% sodium sulfite solution and 10% NaHCO 3 solution three times, then washed with deionized water three times, and the organic layer was retained; the solvent was removed by rotary evaporation to obtain a white powder, which was the epoxy resin, denoted as MPEPB-D2. The yield of the product was 57.98 wt%, the thermal conductivity of the MPEPB-D2 cured resin (the same curing procedure as in Example 1) was 0.32 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-D2 were 800 ppm and 200 ppm, respectively.

[0111] Comparative Example 3 According to the experimental scheme of the present invention, the target product "diallyl terephthalate" in CN107216442A was prepared, and the specific experimental operations are described below.

[0112] (1) Preparation of terephthaloyl chloride According to the molar ratio of 1:10:0.25, terephthalic acid, thionyl chloride and N,N-dimethylformamide were weighed successively into a four-necked flask and reacted at room temperature for 2 h under mechanical stirring at 100 rpm. Then, the product was rotary evaporated at 30 °C to preliminarily remove the unreacted thionyl chloride. Then, toluene was used to dissolve the crude acyl chloride sample, and the extremely small amount of residual thionyl chloride in the crude sample was dissolved in toluene to obtain a toluene solution of acyl chloride; finally, the toluene solution of acyl chloride was rotary evaporated at 45 °C to remove the solvent toluene and take away the remaining thionyl chloride reagent to obtain pure intermediate terephthaloyl chloride.

[0113] (2) Preparation of diallyl terephthalate A four-necked flask placed in an ice bath was prepared, 1 mol of intermediate terephthaloyl chloride was transferred to a clean four-necked flask, and then 20 mL of pyridine was added to the four-necked flask and treated for 10 min under mechanical stirring at 100 rpm. Next, a pyridine solution of eugenol (1.99 mol eugenol / 50 mL pyridine) was added dropwise to the four-necked flask and treated for 30 min under mechanical stirring at 100 rpm. Finally, the four-necked flask was transferred to a normal temperature environment and treated at 200 rpm for 24 h. Then, the product was rotary evaporated at 45 °C to completely remove pyridine, and the crude sample was collected. Then, the crude sample was washed with 5 wt% aqueous sodium carbonate solution and pure water respectively to remove the unreacted eugenol. Finally, recrystallization with absolute ethanol was carried out to obtain pure intermediate diallyl terephthalate.

[0114] (3) Preparation of mesogenic epoxy monomer (epoxidized diallyl terephthalate) Place the reaction kettle in an ice bath, add 22.9 g of diallyl terephthalate, 0.687 g of buffer salt disodium hydrogen phosphate and 458 g of solvent ethyl acetate to the reaction kettle, and stir for 10 min under the condition of 100 rpm. Next, add an ethyl acetate solution of 2.29 g of quaternary ammonium salt phosphotungstate catalyst (2.29 g of quaternary ammonium salt phosphotungstate catalyst / 114.5 g of ethyl acetate) to the reaction kettle, and treat it for 10 min under the condition of 100 rpm. Then, according to the molar ratio of carbon-carbon double bond to hydrogen peroxide in diallyl terephthalate of 1:2.5, weigh 30 wt% hydrogen peroxide solution, suck 3 - 5 drops of hydrogen peroxide solution with a dropper and add it to the four-necked flask, and treat it for 10 min under the condition of 100 rpm. Finally, transfer the reaction kettle to a 40 °C water bath, and at the same time use a peristaltic pump to drop the remaining hydrogen peroxide solution into the reaction kettle at a speed of 0.01 mL / min. After the dropping is completed, react for 6 h under the mechanical stirring at 200 rpm. After the reaction is completed, centrifuge the reactants, collect the precipitate for the next use (the precipitate is the catalyst), wash the organic phase with pure water, dry, recrystallize and vacuum dry to obtain pure epoxidized diallyl terephthalate, denoted as MPEPB-D3. The yield of the product is 85.38 wt%, the thermal conductivity of the MPEPB-D3 cured resin (the same curing step as in Example 1) is 0.35 W / m·K, and the total chlorine content and easily hydrolyzable chlorine content of MPEPB-D3 are 2 ppm and 0 ppm respectively.

[0115] The yields Y of the monomer products obtained from the first use of the catalysts in Examples 1 - 11 and Comparative Examples 1 - 3, the thermal conductivities and chlorine contents of the resins cured by the monomers are shown in Table 3.

[0116] Table 3

[0117] As can be seen from Table 3, the methods for preparing MPEPB monomer products in Examples 1 - 11 of the present invention have the advantages of mild reaction conditions, short reaction time, which is beneficial to the industrial production of products. Moreover, the obtained MPEPB monomer products have the advantages of high yield, low chlorine content and high thermal conductivity of the cured resin. However, Comparative Examples 1 and 2 have the defects of low yield and high chlorine content of the products, and it is difficult to industrialize; when used as the matrix resin in EMC, it will significantly reduce the corrosion resistance reliability of the electronic component materials. Comparative Example 3 is a mesomorphic epoxy monomer (epoxidized diallyl terephthalate) prepared by the method of the present invention, which has a high yield and extremely low chlorine content, reflecting the advantages of the oxidation system of the present invention. However, the thermal conductivity of the epoxidized diallyl terephthalate cured resin is relatively low.

[0118] Test Example 1 Figures 7a to 7dDSC curves during the curing of o-cresol novolac epoxy (500-4P), dicyclopentadiene epoxy (DNE-260), bisphenol A epoxy (128), and MPEPB-3 prepared in Example 3, respectively. From Figures 7a to 7d It can be seen that the inflection point of the curing reaction of MPEPB-3 is 129.03 °C, the highest value among the four groups of formulations. Therefore, its storage stability at room temperature is better; the peak temperature and reaction heat enthalpy are 150.16 °C and 167.80 J / g respectively, ranking third among the four groups of formulations. Therefore, the reaction activity of MPEPB-3 is lower. The low reaction activity helps to relieve the thermal stress generated during curing and can avoid phenomena such as warping, deformation, and cracking of the material during curing to a certain extent.

[0119] Figures 8a to 8d DSC curves during the curing of o-cresol novolac epoxy (500-4P), dicyclopentadiene epoxy (DNE-260), bisphenol A epoxy (128), and the cured resin of MPEPB-3 prepared in Example 3, respectively. From Figures 8a to 8d It can be seen that the Tg of the cured resin of MPEPB-3 is the highest, so its heat resistance stability is the best. Figures 8a to 8d The medium-cured sample is the cured resin.

[0120] Application Example 1 Using o-cresol novolac epoxy (500-4P), dicyclopentadiene epoxy (DNE-260), bisphenol A epoxy (128), and MPEPB-3 prepared in Example 3 as the matrix resins of EMC (epoxy molding compound), linear phenolic resin (5090) as the curing agent, and triphenylphosphine as the accelerator, mesomorphic epoxy resins were prepared by the same method as in Example 1. The mesomorphic epoxy resins were then combined with the additives shown in Table 4 to prepare four EMC samples, denoted as EMC-1, EMC-2, EMC-3, and EMC-4 respectively.

[0121] Table 4

[0122] In Table 4, the toughening agent is P52, the coupling agent is KH-560, the mold release agent is DIACARNA30, and the dispersant is BYK2200.

[0123] These four EMC samples were used to mold electronic components (the molding condition was curing at 175 °C for 6 h) respectively, and the influence of the matrix resin type on the molding effect of EMC was investigated. The back schematic diagrams of the molded parts obtained by encapsulating electronic components with EMC-1, EMC-2, EMC-3, and EMC-4 were obtained, denoted as Figures 9a to 9d; The influence of the matrix resin type on the delamination of EMC molded parts was investigated. Photographs of the molded parts obtained by encapsulating electronic components with EMC-1, EMC-2, EMC-3, and EMC-4 were taken with a scanning acoustic microscope (SAT, RCHO-LS), and were respectively denoted as Figures 10a to 10d . Figures 10a to 10d In Figures 10a to 10d , except for the spacer frame in the middle of the component, the parts showing red are the delamination sites.

[0124] From Figures 9a to 9d and Figures 10a to 10d it can be seen that there are local air holes on the back of the molded parts obtained by encapsulating electronic components with EMC-1, EMC-2, and EMC-3, and delamination occurs. The encapsulation effect of EMC-4 is the best, and no local air holes or delamination occur during encapsulation. This may be because MPEPB-3 has the best fluidity at the curing temperature, the second lowest curing reaction enthalpy, and the highest curing crosslinking degree, so it helps to improve the encapsulation effect of EMC-4. Electronic components were encapsulated with these four EMC samples respectively, and internal wire punching tests were carried out with an X-ray machine (SMX-1000). The results are as Figures 11a to 11d shown. The wire punching rate of EMC-4 is the lowest. The lower the wire punching rate, the less likely it is to bend the circuit during encapsulation of this EMC sample, which is beneficial to protecting the metal circuit. The excellent wire punching effect of EMC-4 benefits from its excellent fluidity under encapsulation conditions.

[0125] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as provided, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for preparing a mesogenic epoxy monomer, characterized in that: The following steps are involved: The intermediate selected from any one of the aromatic ester compounds shown in formula II, the biphenyl compounds shown in formula III and the biphenyl compounds shown in formula IV is epoxidized to obtain a mesogenic epoxy monomer product with epoxy groups at both ends, wherein the epoxidation conditions include: using hydrogen peroxide as an oxidant and using a quaternary ammonium salt of borotungstate or a quaternary ammonium salt of phosphotungstate as a catalyst; Formula II Formula III Formula IV In formula II, R1 is H or a C1-C4 alkyl group; R2 and R3 are the same and are independently a C1-C4 alkylene group; In formula III, R1, R2, R3 and R4 are the same and are independently C1-C4 alkyl; In formula IV, R1, R2, R3 and R4 are the same and are independently C1-C4 alkyl groups; R5 and R6 are the same and are independently C1-C4 alkylene groups.

2. The preparation method according to claim 1, characterized in that The epoxidation conditions also include: an oxidation temperature of 25° C.-80° C., and / or an oxidation time of 1 h-8 h, and / or a stirring rate of 100 rpm-300 rpm.

3. The preparation method according to claim 1, characterized in that Based on the weight of the intermediate, the amount of the catalyst is 2.5-10.0 wt%; and / or Based on the molar number of carbon-carbon double bonds contained in the intermediate, the molar number of the hydrogen peroxide is 220 mol%-1100 mol%.

4. The preparation method according to claim 1, characterized in that: The hydrogen peroxide is added in the form of a hydrogen peroxide solution, and the concentration of the hydrogen peroxide solution is 20wt%-50wt%.

5. The preparation method according to claim 4, characterized in that: The hydrogen peroxide solution is added dropwise, with 0.1 g of the intermediate as the reference, and the speed of addition is 0.001 mL / min-0.100 mL / min.

6. The preparation method according to claim 1, characterized in that: The epoxidation is carried out in the presence of an organic solvent, and the organic solvent is selected from at least one of benzene, toluene, ethylbenzene and ethyl acetate.

7. The preparation method according to any one of claims 1 to 6, characterized in that The yield of the mesogenic epoxy monomer product is above 75 wt %; and / or the total chlorine content of the mesogenic epoxy monomer product is below 10 ppm and the easily hydrolyzable chlorine content is below 0.01 ppm.

8. The mesogenic epoxy monomer obtained by the preparation method according to any one of claims 1 to 7.

9. Mesogenic epoxy resin, characterized in that The raw material comprises a mesogenic epoxy monomer obtained by the preparation method described in any one of claims 1 to 7.

10. Epoxy molding compound, characterized in that: The raw materials include the mesogenic epoxy resin described in claim 9.

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