Process for the preparation of a biphenylenediol-type epoxy resin

Abstract

The application discloses a preparation method of a biphenyldiol type epoxy resin, which comprises the following steps: uniformly mixing and heating and stirring biphenyldiol type raw materials, epoxy halopropane and a solvent, performing reaction after adding alkali, performing reaction again after temperature rising, performing water washing, removing the solvent, obtaining a crude product, performing refining, water washing, removing the solvent and drying on the crude product, and obtaining the biphenyldiol type epoxy resin. The biphenyldiol type epoxy resin prepared by the method has low melting temperature, low dielectric constant of resin curing product, good water resistance, high heat resistance, low total chlorine content of the resin, and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of bio-based epoxy resin preparation technology, specifically relating to a method for preparing a biphenyl-type epoxy resin. Background Technology

[0002] With the development of artificial intelligence and internet technology, the requirements for dielectric polymer materials are becoming increasingly stringent, and the demand is growing significantly. In the field of communications, efficient signal transmission is crucial, and the use of low-dielectric materials can effectively prevent signal delay or loss. Ideal electronic materials must possess water resistance and dielectric properties. Epoxy resin is a representative electronic packaging material. To improve the performance of electronic materials, novel epoxy resin structures with both dielectric and thermal properties must be designed. Low-dielectric epoxy resins, with their advantages of processability, thermal stability, and electrical insulation, are widely used in electronic and electrical engineering, electronic integration, printed circuit boards, and communication materials.

[0003] Bisphenol epoxy resin is a high-performance liquid crystal epoxy resin characterized by high strength, high modulus, high temperature resistance, and low coefficient of linear expansion. Compared with ordinary resins, it exhibits better dimensional stability, heat resistance, impact resistance, and good dielectric properties, making it widely applicable in aerospace composite materials, large-scale integrated microelectronic packaging materials, and generator insulation materials. While bisphenol epoxy resin possesses low viscosity when molten (generally considered to be less than 150 mPa·s at 150°C), its high melting temperature and solid state at low to medium temperatures limit its further applications. Furthermore, the epoxy resin prepared from bisphenol is typically solid, and its poor solubility and surface tackiness cause difficulties in post-processing. Therefore, finding a preparation method to lower the melting temperature of bisphenol epoxy resin, expanding its application temperature range, while simplifying the preparation process without compromising its high heat resistance and good dielectric properties, is of significant value.

[0004] Chinese patent document CN112142953A discloses a method for preparing a dielectric and thermally enhanced bio-based high-temperature resistant epoxy resin. The method uses quaternary ammonium salt and sodium hydroxide aqueous solution as catalysts and adopts a two-step method to prepare epoxy resin. The dielectric constant of the obtained epoxy resin is 8.2-10, which has the problem of high dielectric constant.

[0005] Chinese patent document CN102633985A discloses a method for preparing high-purity bisphenol-type epoxy resin. This method uses quaternary ammonium salt and sodium hydroxide aqueous solution as catalysts, employing a two-step process to obtain crude epoxy resin. Then, high-purity crystalline epoxy resin is obtained through reverse diffusion and cooling crystallization. The tetramethylbiphenyl-type epoxy resin described in this method has a melting range of 106-111℃, which is a high melting temperature. This method uses recrystallization, which results in some product dissolving in a good solvent, making recovery difficult and causing losses, thus affecting product yield. Furthermore, the crystallization precipitation method generates large amounts of wastewater and presents challenges in recovering the mixed solvent.

[0006] Chinese patent document CN114195981A discloses a biphenyl-type epoxy resin, its synthesis method, and its application. The synthesis of this biphenyl-type epoxy resin uses biphenyl hydroquinone and epichlorohydrin as raw materials, and the reaction is carried out in the presence of an amphiphilic solvent. The biphenyl-type epoxy resin is obtained by precipitation. The total chlorine content of the obtained biphenyl-type epoxy resin is less than 400 ppm. However, this method uses a large amount of solvent (mass ratio of amphiphilic solvent to biphenyl hydroquinone raw material is 2-5:1) to ensure the smooth completion of the reaction during the product preparation process. Furthermore, a large amount of composite solvent and water are used in the post-processing of the crude product (weight ratio of crude product to solvent is 1:10-30), which increases the application and recycling costs of composite solvent and generates a large amount of wastewater. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art. In particular, it addresses the technical problems of high melting temperature, high dielectric constant of cured product and poor resin solubility in the preparation of biphenyl epoxy resin. The present invention provides a method for preparing biphenyl epoxy resin with low melting temperature, low dielectric constant of cured resin, good water resistance, high heat resistance and low total chlorine content.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0009] A method for preparing a biphenyl-type epoxy resin includes the following steps:

[0010] S1. Mix the biphenyl-type raw material, epoxy halopropane and solvent. The biphenyl-type raw material is compound (1) and compound (2). Heat the resulting mixture to 40℃~60℃, stir evenly and add alkali. React for 1h~2h, then heat to 70℃~90℃ for further reaction. After the reaction, wash with water and remove solvent to obtain crude biphenyl-type epoxy resin.

[0011]

[0012] In equation (1), R represents CH3 or H;

[0013]

[0014] S2. The crude biphenyl epoxy resin obtained above is refined, washed with water, desolventized and dried to obtain biphenyl epoxy resin.

[0015] In the above preparation method, the compound of formula (1) can simultaneously take 4,4'-biphenyl and tetramethylbiphenyl.

[0016] In the above-mentioned method for preparing biphenyl-type epoxy resin, preferably, in step S1, the amount of the compound of formula (1) accounts for 2% to 60% of the amount of the biphenyl-type raw material.

[0017] In the above-mentioned method for preparing biphenyl-type epoxy resin, preferably, in step S1, the amount of the compound of formula (1) accounts for 8% to 30% of the amount of the biphenyl-type raw material.

[0018] In the above-mentioned method for preparing biphenyl-type epoxy resin, preferably, in step S1, the mass of the epoxy halopropane is 250wt% to 500wt% of the mass of the biphenyl-type raw material.

[0019] In the above-mentioned method for preparing biphenyl-type epoxy resin, preferably, in step S1, the mass of the solvent is 10wt% to 55wt% of the mass of the biphenyl-type raw material.

[0020] In the preferred embodiment of the above-mentioned method for preparing biphenyl-type epoxy resin, in step S1, the solvent is a polar solvent, which includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, acetonitrile, diethylene glycol dimethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monoethyl ether, dipropylene glycol monobutyl ether, and dipropylene glycol monoethyl ether; the epoxy halopropane includes epichlorohydrin and / or epibromopropane.

[0021] In the preferred method for preparing the biphenyl-type epoxy resin described above, in step S1, the temperature is raised to 70°C to 90°C and the reaction is carried out for 1 to 4 hours.

[0022] In the preferred method for preparing the biphenyl-type epoxy resin described above, in step S1, the alkali is added in the form of a solid alkali or an alkali solution. When added in the form of an alkali solution, it is necessary to add it under a vacuum of 0.02 MPa to 0.07 MPa and maintain the reaction under vacuum. The alkali includes potassium hydroxide and / or sodium hydroxide, and the mass of the alkali is 30 wt% to 60 wt% of the mass of the biphenyl-type raw material.

[0023] In the preferred method for preparing the above-mentioned biphenyl-type epoxy resin, the refining process in step S2 is as follows: dissolve the crude biphenyl-type epoxy resin in a good solvent, heat to 60℃~85℃, add an alkaline solution and react for 0.5h~3h.

[0024] In the above-mentioned method for preparing biphenyl-type epoxy resin, preferably, in step S2, the mass of the alkaline solution is 30wt% to 50wt% of the crude mass of the biphenyl-type epoxy resin, the alkaline solution includes an aqueous solution of potassium hydroxide and / or an aqueous solution of sodium hydroxide, and the mass fraction of alkali in the alkaline solution is 20wt% to 50wt%.

[0025] In the above-mentioned method for preparing biphenyl-type epoxy resin, preferably, in step S2, the good solvent includes one or more of toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, diacetone alcohol, and methanol, and the mass of the good solvent is 50wt% to 100wt% of the crude mass of the biphenyl-type epoxy resin.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] 1. In the prior art, although low viscosity is an advantage of biphenyl-type epoxy resin, the biphenyl epoxy resin shown in formula (1) can only achieve low viscosity after being dissolved at high temperature. In order to solve the disadvantage that biphenyl epoxy resin is only suitable for high temperature conditions, this invention uses a raw material composite method to prepare biphenyl-type epoxy resin. Using the structurally similar compound of formula (2) as a modifier, the compatibility of the two epoxy structures is achieved by using a trace chain extension reaction through the principle of like dissolves like. Moreover, the allyl chain structure in the compound of formula (2) can help the resin to be soluble at room temperature. With low viscosity, the preparation method of this invention enables the modified biphenyl-type epoxy resin to have a low melting temperature. Since formula (2) has the same biphenyl structure as formula (1), it can effectively ensure the uniformity of the composite resin and the excellent properties such as the high heat resistance of the biphenyl structure resin. In addition, the uniformity of the resin is also conducive to a more complete and smoother composite biphenyl epoxidation process, resulting in a lower chlorine content in the obtained resin. However, the simple blending method cannot achieve the goal of uniform mixing of magnolol-based epoxy and biphenyl epoxy resin and low chlorine content of the resin. The biphenyl-type epoxy resin prepared by the method of this invention has a low melting temperature (≤80℃) and a total chlorine content of less than 400ppm, belonging to the low chlorine content epoxy resin series. The cured resin has good dielectric properties (5.2-7.4, 1Hz-3MHz), high water resistance (water absorption rate as low as 1.15% in 90℃ hot water, contact angle ≥105°), and high heat resistance, making it suitable for the electrical field and effectively improving the processing window of the biphenyl-type epoxy resin.

[0028] 2. As a rigid structure, the epoxy resin prepared from biphenyl is often solid due to its poor solubility, which causes difficulties in post-processing. This invention utilizes the similarity and compatibility of the raw materials and the chain extension property of the reaction between the two raw materials to effectively improve the compatibility of the two epoxy resin structures and reduce the melting temperature of the product. The preparation method uses a small amount of solvent, and the post-processing can adopt a dissolution and washing method, which can effectively reduce the amount of solvent used in the post-processing and significantly simplify the post-processing process. It has the advantages of simple operation, low wastewater volume and low product loss.

[0029] 3. The preparation method of the present invention is simple, highly reproducible, and the raw materials are derived from biomass, which is widely available. It has great potential to replace petroleum-based biphenyl-type raw materials, meets the needs of sustainable industrial development, and can better realize industrial production. Attached Figure Description

[0030] Figure 1 The infrared spectra of biphenyl-type epoxy resin, magnolol, and biphenyl in Example 2 of this invention are shown. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0032] In the following examples, the structural formula of magnolol is as follows:

[0033]

[0034] Example 1

[0035] A method for preparing a biphenyl-type epoxy resin according to the present invention includes the following steps:

[0036] S1. Add 120g of magnolol, 9g of 4,4'-biphenylhydrazine, 323g of epichlorohydrin, and 65g of methanol to a reaction flask, heat to 55℃, stir well, then add 45g of solid sodium hydroxide, react for 2 hours, then heat to 80℃ and react for another 2 hours. After washing with water and removing the solvent, 166g of crude biphenylhydrazine-type epoxy resin is obtained.

[0037] S2. Dissolve the crude biphenyl-type epoxy resin in 85g of methyl isobutyl ketone, heat to 80℃, add 50g of 40%wt NaOH aqueous solution, react for 1h, wash with water, remove solvent, and dry to obtain biphenyl-type epoxy resin. The epoxy equivalent is 224.09g / mol, the melting temperature is 63.7-65.0℃, the viscosity at 100℃ is 0.03mPa·s, the viscosity at 150℃ is 7.2mPa·s, the total chlorine content is 372.86ppm, the dielectric constant of the cured product is 5.2-6.1 (1Hz-3MHz), the water absorption rate is 1.15% (90℃ hot water), the contact angle is 109.69°, and the Tg is 150℃.

[0038] Example 2

[0039] A method for preparing a biphenyl-type epoxy resin according to the present invention includes the following steps:

[0040] S1. Add 100g of magnolol, 20g of 4,4'-biphenylhydrazine, 357g of epichlorohydrin, and 30g of dimethyl sulfoxide to a reaction flask. Heat to 55℃, stir until homogeneous, then add 43g of solid sodium hydroxide. React for 2 hours, then heat to 80℃ and react for 3 hours. After washing with water and removing the solvent, 182g of crude biphenylhydrazine-type epoxy resin is obtained.

[0041] S2. Dissolve the crude biphenyl-type epoxy resin in 100g of toluene, heat to 80℃, add 55g of 50%wt NaOH aqueous solution, react for 1h, wash with water, remove solvent, and dry to obtain the biphenyl-type epoxy resin. The epoxy equivalent is 214.93g / mol, the melting temperature is 76.5-78.3℃, the viscosity at 150℃ is 30mPa·s, the total chlorine content is 350.50ppm, the dielectric constant of the cured product is 6.3-6.6 (1Hz-3MHz), the water absorption rate is 1.18% (90℃ hot water), the contact angle is 106.59°, and the Tg is 152℃.

[0042] like Figure 1 The image shows the infrared spectrum of the biphenyl-type epoxy resin prepared in this embodiment. In the figure, MA represents the infrared spectrum of magnolol, DOD represents the infrared spectrum of biphenyl-type epoxy resin, and EMA / EDOD represents the infrared spectrum of the biphenyl-type epoxy resin. MA and DOD are in the range of 3500-3000 cm⁻¹. -1 A broad peak is observed within the range, mainly attributed to the OH stretching vibration peak. In contrast to the EMA / DOD infrared spectrum, the hydroxyl peak almost completely disappears. In the EMA / DOD infrared spectrum, the peak is visible at 2930 cm⁻¹. -1 The peak at 1652 cm⁻¹ corresponds to the methylene CH stretching vibration. MA is at 1652 cm⁻¹. -1The peak at 913 cm⁻¹ is the characteristic C=C absorption peak on the allyl group. A comparison with EMA / DOD clearly shows the presence of this characteristic C=C absorption peak on the allyl group. EMA / DOD, compared to DOD and MA, shows a peak at 913 cm⁻¹. -1 Characteristic absorption peaks of epoxy groups can be observed at the precipitate. In summary, MA and DOD were successfully epoxidized to obtain a biphenyl-type epoxy resin (EMA / EDOD epoxy resin).

[0043] Example 3

[0044] A method for preparing a biphenyl-type epoxy resin according to the present invention includes the following steps:

[0045] S1. Add 120g of magnolol, 11g of tetramethylbiphenylol, 460g of epichlorohydrin, and 65g of methanol to a reaction flask, heat to 50℃, stir well, then add 45g of solid sodium hydroxide, react for 2 hours, then heat to 80℃ and react for 3 hours. After washing with water and removing the solvent, 172g of crude biphenylol-type epoxy resin is obtained.

[0046] S2. Dissolve the crude biphenyl-type epoxy resin in 100g of methyl isobutyl ketone, heat to 80℃, add 77g of 40%wt NaOH aqueous solution, react for 1h, wash with water, remove solvent, and dry to obtain biphenyl-type epoxy resin. The epoxy equivalent is 225.77g / mol, the melting temperature is 40.1-42.6℃, the viscosity at 150℃ is 6.3mPa·s, the total chlorine content is 356.73ppm, the dielectric constant of the cured product is 6.8-7.2 (1Hz-3MHz), the water absorption rate is 1.23% (90℃ hot water), and the contact angle is 105.89°.

[0047] Example 4

[0048] A method for preparing a biphenyl-type epoxy resin according to the present invention includes the following steps:

[0049] S1. Add 100g magnolol, 9g 4,4'-biphenyl, 11g tetramethylbiphenyl, 480g epichlorohydrin, and 60g ethylene glycol monobutyl ether to a reaction flask, heat to 50℃, stir evenly, maintain a vacuum of 0.065MPa, add 90g 50%wt NaOH aqueous solution, react for 2h, then heat to 80℃ and react for 3h. After washing with water and removing the solvent, 189g of crude biphenyl-type epoxy resin is obtained.

[0050] S2. Dissolve the crude biphenyl-type epoxy resin in 95g of methyl isobutyl ketone, heat to 80℃, add 57g of 30wt% sodium hydroxide aqueous solution, react for 1h, wash with water, remove solvent, and dry to obtain biphenyl-type epoxy resin. The epoxy equivalent is 224.03g / mol, the melting temperature is 63.2-66.3℃, the viscosity at 150℃ is 33mPa·s, the total chlorine content is 351.72ppm, the dielectric constant of the cured product is 7.1-7.4 (1Hz-3MHz), the water absorption rate is 1.16% (90℃ hot water), the contact angle is 107.49°, and the Tg is 149℃.

[0051] In the above embodiments, the preparation process of the cured material used for testing is as follows:

[0052] The biphenyl-type epoxy resin prepared in the above examples was mixed with methylnadic anhydride in acetone at a stoichiometric ratio (the molar ratio of epoxy groups to anhydride was 1:1). 2-ethyl-4-methylimidazole (1 wt%, based on the total weight of the curing agent and epoxy resin) was added as a curing accelerator. The mixture was degassed under vacuum at 80°C, quickly poured into a preheated iron mold, and cured in a high-temperature oven at 120°C for 2 hours, 150°C for 2 hours, 180°C for 3 hours, and 200°C for 5 hours to obtain the cured resin.

[0053] Comparative Example 1

[0054] 100g of 4,4'-biphenylhydrazine, 400g of epichlorohydrin, and 50g of dimethyl sulfoxide were added to a reaction flask. The mixture was heated to 55°C, and 50g of solid sodium hydroxide was added. The reaction was carried out for 2 hours, then heated to 80°C and reacted for another 2 hours. The mixture was washed with water to remove the solvent and dried to obtain 4,4'-biphenylhydrazine epoxy resin. The epoxy equivalent was 182.03g / mol, the melting temperature was 169-173°C, the total chlorine content was 960.80ppm, the dielectric constant was 20.0-21.6 (1Hz-3MHz), and the Tg was 180°C.

[0055] Comparative Example 2

[0056] 100g of tetramethylbiphenylhydrazine, 300g of epichlorohydrin, and 50g of dimethyl sulfoxide were added to a reaction flask, heated to 55℃, and 40g of solid sodium hydroxide were added. The reaction was carried out for 2 hours, then heated to 80℃ and reacted for another 2 hours. The mixture was washed with water to remove the solvent and dried to obtain tetramethylbiphenylhydrazine epoxy resin. The epoxy equivalent was 210.23g / mol, the melting temperature was 101.2-111.6℃, the viscosity at 100℃ was 0.02 Pa·s, the total chlorine content was 1032.70 ppm, and the dielectric constant was 19.8-21.5 (1Hz-3MHz).

[0057] Comparative Example 3

[0058] 100g of bisphenol A, 9g of 4,4'-biphenyl, 450g of epichlorohydrin, and 65g of methanol were added to a reaction flask. The mixture was heated to 55°C, and 40g of solid sodium hydroxide was added. The reaction was carried out for 2 hours, then heated to 80°C and reacted for another 2 hours. The product was washed with water to remove the solvent, yielding crude epoxy resin. Because the crude product exhibited a solid-liquid two-phase separation during washing, dissolution and subsequent washing were difficult, making purification impossible. In this comparative example, the epoxy equivalent was 366.21 g / mol, the melting temperature was 80.6-90.2°C, the viscosity at 100°C was 1.26 Pa·s, the chlorine content was 1750.18 ppm, and the dielectric constant of the cured product was 10.6-12.3 (1Hz-3MHz).

[0059] As can be seen from the above embodiments and comparative examples:

[0060] Examples 1 and 2 are biphenyl epoxy resins obtained by mixing different amounts of biphenyl-type raw materials (approximately 10% and 20%, respectively) when formula (1) is 4,4'-biphenyl. Compared with the 4,4'-biphenyl epoxy resin prepared in Comparative Example 1, the biphenyl epoxy resin obtained by mixing formulas (1) and (2) in different proportions in this invention has a lower melting temperature, better dielectric properties, and better water resistance than the 4,4'-biphenyl epoxy resin.

[0061] Comparing Example 1 with Comparative Example 3, the melting temperature and dielectric constant of the biphenyl-type epoxy resin modified with magnolol were significantly lower than those of the epoxy resin modified with bisphenol A, indicating that the effect achieved by using magnolol as a modifier in this invention is significantly better than that of other materials.

[0062] Example 3 is a biphenyl-type epoxy resin prepared when formula (1) is tetramethylbiphenyl and accounts for 10% of the biphenyl-type raw material. Compared with the tetramethylbiphenyl epoxy resin prepared in Comparative Example 2, the biphenyl-type biphenyl epoxy resin of Example 3 has a lower melting temperature, better dielectric properties, water resistance and other properties than the tetramethylbiphenyl epoxy resin.

[0063] Example 4 is a biphenyl-type epoxy resin obtained by taking 4,4'-biphenyl and tetramethylbiphenyl in formula (1) at a ratio of 10% each in the biphenyl-type raw material. It is compared with Comparative Example 1 and Comparative Example 2 to show that the biphenyl-type epoxy resin obtained by this addition method also has a lower melting temperature, better dielectric properties, and water resistance than 4,4'-biphenyl epoxy resin and tetramethylbiphenyl epoxy resin.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing a biphenyl-type epoxy resin, characterized in that, Includes the following steps: S1. Mix the biphenyl-type raw material, epoxy halopropane and solvent. The biphenyl-type raw material is compound (1) and compound (2). Heat the resulting mixture to 40℃~60℃, stir evenly and add alkali. React for 1h~2h, then heat to 70℃~90℃ for 1h~4h. After the reaction, wash with water and remove solvent to obtain crude biphenyl-type epoxy resin. （1） In equation (1), R represents CH3 or H; or (2); S2. The crude biphenyl epoxy resin obtained above is refined, washed with water, desolventized and dried to obtain biphenyl epoxy resin. In step S1, the amount of the compound of formula (1) accounts for 2% to 60% of the amount of the biphenyl-type raw material; In step S1, the solvent is a polar solvent, which includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, acetonitrile, diethylene glycol dimethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monoethyl ether, dipropylene glycol monobutyl ether, and dipropylene glycol monoethyl ether; the epoxy halopropane includes epichlorohydrin and / or epibromopropane.

2. The method for preparing biphenyl-type epoxy resin according to claim 1, characterized in that, In step S1, the amount of the compound of formula (1) accounts for 8% to 30% of the amount of the biphenyl-type raw material.

3. The method for preparing biphenyl-type epoxy resin according to claim 1, characterized in that, In step S1, the mass of the epoxy halopropane is 250wt% to 500wt% of the mass of the biphenyl-type raw material, and the mass of the solvent is 10wt% to 55wt% of the mass of the biphenyl-type raw material.

4. The method for preparing the biphenyl-type epoxy resin according to any one of claims 1 to 3, characterized in that, In step S1, the alkali is added in the form of a solid alkali or an alkali solution. When added in the form of an alkali solution, it must be added under a vacuum of 0.02 MPa to 0.07 MPa and the reaction must be maintained under vacuum. The alkali includes potassium hydroxide and / or sodium hydroxide, and the mass of the alkali is 30 wt% to 60 wt% of the mass of the biphenyl-type raw material.

5. The method for preparing the biphenyl-type epoxy resin according to any one of claims 1 to 3, characterized in that, In step S2, the refining process is as follows: dissolve the crude biphenyl-type epoxy resin in a good solvent, heat it to 60℃~85℃, add an alkaline solution and react for 0.5h~3h.

6. The method for preparing biphenyl-type epoxy resin according to claim 5, characterized in that, In step S2, the mass of the alkaline solution is 30wt% to 50wt% of the crude mass of the biphenyl-type epoxy resin, the alkaline solution includes an aqueous solution of potassium hydroxide and / or an aqueous solution of sodium hydroxide, and the mass fraction of alkali in the alkaline solution is 20wt% to 50wt%.

7. The method for preparing the biphenyl-type epoxy resin according to claim 6, characterized in that, In step S2, the good solvent includes one or more of toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, diacetone alcohol, and methanol, and the mass of the good solvent is 50 wt% to 100 wt% of the crude mass of the biphenyl-type epoxy resin.

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