Blending vanillin-based epoxy resin as well as preparation method and application thereof

Abstract

The invention provides bivanillin-based epoxy resin as well as a preparation method and application thereof. The structural formula of the bivanillin-based epoxy resin is shown as a formula (I). The preparation method comprises the following steps: firstly preparing a bivanillin etherate, then reducing an aldehyde group on the bivanillin etherate to prepare bio-based biphenyl dimethyl carbinol, and then preparing the bivanillin-based epoxy resin by taking the bio-based biphenyl dimethyl carbinol and epoxy halopropane as raw materials. The bivanillin-based epoxy resin disclosed by the invention has excellent intrinsic flame retardant property, high heat resistance and low viscosity, breaks through the dependence of an existing epoxy resin product on petroleum resources, is simple in preparation method, mild in reaction condition and high in yield, and has industrial application potential.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a divanillin-based epoxy resin and a preparation method and application thereof. Background Art

[0002] Commercial epoxy resins, represented by bisphenol A epoxy resin (DGEBA), are composed of three elements: carbon, hydrogen, and oxygen. They are highly flammable, which makes it difficult to meet the standards in aerospace, rail transit, and construction, which have high requirements for fire retardancy, thus greatly limiting the scope of application of epoxy resins. Intrinsic flame-retardant epoxy resins can effectively avoid the shortcomings of additive flame retardants that deteriorate the heat resistance and mechanical properties of the resin matrix, and have attracted widespread attention from researchers. In addition, the non-renewable nature of petroleum resources poses a major challenge to the sustainable development of the epoxy resin industry. Therefore, the development of intrinsic flame-retardant epoxy resins based on renewable raw materials has important scientific and practical significance.

[0003] Intrinsically flame-retardant epoxy resins usually refer to flame-retardant elements or flame-retardant structures such as phosphorus and silicon embedded in the molecular skeleton of epoxy resin in the form of chemical bonds, which can achieve flame retardant effects by their own action. Intrinsic flame retardant strategies can be roughly divided into two categories: (1) introducing flame retardant elements such as phosphorus and silicon into the structure; (2) introducing polycyclic aromatic ring structural units with high carbon-forming ability into the structure. Method (1) is considered to be one of the most effective methods due to its advantages such as simple process, abundant raw material sources and good flame retardant effect. However, nitrogen and phosphorus are both highly polar atoms, which can easily lead to the problem of strong hygroscopicity and high dielectric constant of the resin cured product, which is not conducive to the application of epoxy resin in the electronics and microelectronics industries. In addition, previous studies have shown that although the introduction of phosphorus and silicon flame retardant elements can improve the flame retardant grade of bio-based epoxy resin to UL-94V0 level, it also causes its mechanical properties or glass transition temperature to decrease to varying degrees. For example, researchers used itaconic acid as a raw material and prepared a new type of phosphorus-containing bio-based epoxy monomer EADI after reacting it with DOPO. The resin cured product EADI / MeHHPA showed good flame retardant and self-extinguishing properties and could pass the V0 level of the UL-94 test, but its glass transition temperature was only 101.9°C and its bending strength was only 125.5MPa, both lower than DGEBA / MeHHPA (109.5°C, 131.6MPa). It is worth noting that most compounds containing flame retardant elements such as phosphorus and silicon are petroleum-based products, such as DOPO and diethyl phosphite, which easily lead to low biomass content in the resulting bio-based epoxy resin.

[0004] Polyaromatic ring structures have high rigidity and good pyrolysis carbonization ability. Introducing them into epoxy resin skeletons is considered to be a valuable strategy for preparing intrinsic flame retardant bio-based epoxy resins. Currently, research focuses on the preparation of epoxy resins based on biomass raw materials containing polyaromatic ring structures, such as daidzein, resveratrol, genistein, ellagic acid, etc. Researchers prepared a bio-based epoxy resin DGED containing a deoxybenzoin structure based on biomass daidzein. Thanks to the high carbonization ability of the deoxybenzoin structure (N 2 atmosphere, the residual carbon rate at 800°C is as high as 42.9%), the resin cured product DGED / DDM can quickly self-extinguish after ignition, and reaches UL-94V0 level, showing excellent intrinsic flame retardancy. In addition, the rigid polyaromatic ring structure also makes its glass transition temperature as high as 205°C, which is 33°C higher than DGEBA / DDM. However, the above-mentioned biomass raw materials only exist in a small number of specific plants and the content is low. There are problems such as narrow sources and high prices. The resulting bio-based epoxy resin is difficult to produce on an industrial scale. Some researchers also use magnolol as a raw material to prepare bio-based epoxy resins, which also have the problems of a single source of raw materials, high prices, and difficulty in large-scale application. At the same time, there are also problems such as complex processes, a large number of by-products that are difficult to remove, and high requirements for equipment. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a divanillin-based epoxy resin having excellent intrinsic flame retardancy, high heat resistance and low viscosity, and a preparation method and application thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A divanillin-based epoxy resin, wherein the divanillin-based epoxy resin has a structural formula shown in the following formula (I):

[0008]

[0009] In formula (I), R is one of the following structural formulas:

[0010]

[0011] As a general technical concept, the present invention also provides a method for preparing the above-mentioned divanillin-based epoxy resin, comprising the following steps:

[0012] S1. Preparation of divanillin etherate: adding divanillin and a solvent into a reaction vessel, adding an inorganic base while stirring, reacting at a temperature of 35°C to 55°C after the addition is completed, then adding a halogenated compound, heating to 60°C to 80°C to continue the reaction, cooling to room temperature after the reaction is completed, filtering, extracting and purifying the filtrate, removing the solvent from the extract phase, and obtaining divanillin etherate;

[0013] S2. Preparation of bio-based biphenyl dimethanol: at room temperature, add the above-obtained divanillin etherate and solvent into a reaction container and mix them. After the mixture is completely dissolved, add sodium borohydride. During the addition process, control the temperature of the reaction system not to exceed 30° C. After the addition is completed, react at room temperature. After the reaction is completed, wash with acid first, then wash with water until neutral, remove the solvent, and obtain bio-based biphenyl dimethanol;

[0014] S3. Preparation of divanillin-based epoxy resin: Add the above-obtained bio-based biphenyl dimethanol, phase transfer catalyst and base catalyst into a reaction vessel and mix them. Then place the reaction system in a water bath at 0°C to 10°C, add epihalohydrin, and after the addition is completed, react at room temperature. After the reaction is completed, wash with water, and recover the excess epihalohydrin under reduced pressure to obtain the product divanillin-based epoxy resin.

[0015] In the above-mentioned method for preparing the divanillin-based epoxy resin, preferably, in step S1, the molar ratio of the inorganic base to the divanillin is 1 to 4:1, and the molar ratio of the halogenated compound to the divanillin is 2 to 5:1.

[0016] In the above-mentioned method for preparing the divanillin-based epoxy resin, preferably, in step S1, the solvent is a strong polar solvent, and the strong polar solvent includes one or more of methanol, ethanol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, 1,3-dimethylimidazolidinone and N-methylpyrrolidone; the inorganic base includes one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium bicarbonate and potassium bicarbonate; the halogenated compound is one or more of 3-bromo-1-propylene, 3-chloro-1-propylene, 3-bromopropyne and 3-chloropropyne; the extractant used for the extraction and purification includes at least one of ethyl acetate, ether, dichloromethane, chloroform and toluene.

[0017] In the above-mentioned method for preparing the divanillin-based epoxy resin, preferably, in step S2, the molar ratio of the sodium borohydride to the divanillin etherify is 0.9 to 1.5:1; and the solvent is one or more of tetrahydrofuran, methanol, ethanol, N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide and N-methylpyrrolidone.

[0018] In the above-mentioned method for preparing the divanillin-based epoxy resin, preferably, in step S3, the molar ratio of the phase transfer catalyst to the bio-based biphenyl dimethanol is 0.05 to 0.4:1, and the phase transfer catalyst is one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, hexadecyltrimethylammonium bromide and tetrabutylammonium chloride.

[0019] In the above-mentioned method for preparing the divanillin-based epoxy resin, preferably, in step S3, the alkaline catalyst includes sodium hydroxide and / or potassium hydroxide, and the molar ratio of the alkaline catalyst to the bio-based biphenyl dimethanol in step S2 is 2 to 8:1; when the alkaline catalyst is added in the form of a solution containing the alkaline catalyst, the mass fraction of the alkaline catalyst in the solution containing the alkaline catalyst is 30wt% to 50wt%.

[0020] In the above-mentioned method for preparing the divanillin-based epoxy resin, preferably, in step S3, the epihalohydrin includes epichlorohydrin and / or epibromohydrin, and the molar ratio of the epihalohydrin to the bio-based biphenyl dimethanol is 8 to 40:1.

[0021] The preparation method of the above-mentioned divanillin-based epoxy resin is preferably that in step S1, the reaction time is 30min to 60min, and the continued reaction time is 12h to 24h; in step S2, the addition time of the sodium borohydride is controlled at 0.5h to 2h, the reaction time is 3h to 6h, the acid is dilute hydrochloric acid, the concentration of the dilute hydrochloric acid is 0.1mol / L to 1mol / L, and the acid washing is to a pH of 4 to 5; in step S3, the reaction time is 24h to 48h; the room temperature in steps S1, S2, and S3 is 10°C to 30°C.

[0022] As a general technical concept, the present invention also provides an application of the above-mentioned divanillin-based epoxy resin or the divanillin-based epoxy resin prepared by the above-mentioned preparation method in the fields of aerospace, rail transportation or construction.

[0023] In the preparation method of the present invention, the amount of solvent added in steps S1 and S2 is based on solubility and is not particularly limited.

[0024] The present invention provides a divanillin-based epoxy resin, the molecular structure of which contains a biphenyl structure that is highly rigid and easily carbonized at high temperatures, and has multiple active cross-linking sites. Unlike most bio-based epoxy resins etherified with phenolic hydroxyl glycidyl, the present invention is a benzyl alcohol-based glycidyl-etherified bio-based epoxy resin, whose benzyloxyether structure is easily decomposed under high temperature conditions to form benzyl alcohol, and benzyl alcohol can react and cross-link again, which further increases the cross-linking density of the cured product network, thereby significantly enhancing the carbonization ability and flame retardant properties of the resin. In addition to participating in curing and cross-linking, the R group is also a flexible structure that helps to improve the mobility of the molecular chain and thus reduce the viscosity of the epoxy resin. The preparation method of the present invention uses divanillin, a biomass vanillin derivative, as a raw material and is divided into three steps, namely, synthesis of divanillin etherate, reduction of divanillin etherate and preparation of divanillin-based epoxy resin, that is, firstly preparing divanillin etherate, then reducing the aldehyde group on the divanillin etherate to prepare bio-based biphenyl dimethanol, and then using bio-based biphenyl dimethanol and epihalohydrin as raw materials to prepare divanillin-based epoxy resin, and the reaction route is as follows:

[0025]

[0026] Wherein, R is one of the following structural formulas:

[0027]

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] (1) The biomass raw material used for the divanillin-based epoxy resin of the present invention is divanillin, which can be prepared from vanillin, the only lignin depolymerization monomer currently produced on an industrial scale. It has low cost, sufficient sources, and potential for industrial application. It is also helpful in promoting "carbon neutrality" in the field of epoxy resins and reducing dependence on petroleum resources. The divanillin-based epoxy resin of the present invention contains a biphenyl structure that is highly rigid and easy to form carbon at high temperatures in its molecular structure, and there are multiple active cross-linking sites. Unlike most bio-based epoxy resins etherified with phenolic hydroxyl glycidyl ethers, the present invention is a benzyl alcohol glycidyl etherified bio-based epoxy resin, and its benzyloxy ether structure is easily decomposed under high temperature conditions to form benzyl alcohol, and benzyl alcohol can react and cross-link again, which further increases the cross-linking density of the cured product network, thereby significantly enhancing the resin's carbon-forming ability and flame retardant properties. In addition, the active R side group is also a flexible structure, which helps to improve the mobility of the molecular chain and thereby reduce the viscosity of the epoxy resin. The divanillin-based epoxy resin of the present invention has excellent intrinsic flame retardant properties, high heat resistance and low viscosity at the same time, N 2The carbon residue rate at 700℃ and 800℃ in the atmosphere can reach 62.04% and 60.48% respectively, which can easily pass the highest level V0 of the vertical burning test (UL-94). g ) can reach above 290°C, and the product has low viscosity characteristics, with a viscosity as low as 260mPa·s at 25°C. Compared with the prior art, the epoxy resin of the present invention shows significant advantages and can further broaden the application scope of the epoxy resin.

[0030] (2) The preparation method of the present invention uses biomass divanillin as a raw material, obtains bio-based diphenyl dimethanol through phenolic hydroxyl etherification and aldehyde group reduction, and then epoxidizes it to obtain a new bio-based epoxy resin, breaking the dependence of existing epoxy resin products on petroleum resources. In addition, the process conditions of the present invention are mild, equipment-friendly, and by-products are easy to remove. No complicated separation and purification methods are required. It has good industrial application potential and can be widely used in aerospace, rail transportation, construction and other fields.

[0031] In summary, the divanillin-based epoxy resin of the present invention has a wide range of raw materials, a low price, mild preparation process conditions, a simple method, low requirements on equipment, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the hydrogen nuclear magnetic spectrum of the divanillin-based epoxy resin prepared in Example 1 of the present invention.

[0033] Figure 2 This is the infrared spectrum of the divanillin-based epoxy resin prepared in Example 1 of the present invention.

[0034] Figure 3 This is a graph showing the rheological test results of the divanillin-based epoxy resin prepared in Example 1 of the present invention.

[0035] Figure 4 This is the DSC spectrum of the divanillin-based epoxy resin prepared in Example 1 of the present invention.

[0036] Figure 5 These are DMA test result graphs and TGA test result graphs of the divanillin-based epoxy resin prepared in Example 1 of the present invention, wherein A is a DMA test result graph, and B is a TGA test result graph.

[0037] Figure 6 This is a screenshot of the UL-94 test video of the divanillin-based epoxy resin prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available. In the following embodiments, the room temperature is usually 10°C to 30°C (preferably 25°C).

[0039] Example 1

[0040] A divanillin-based epoxy resin of the present invention has a structural formula shown in the following formula (I):

[0041]

[0042] In formula (I), the structural formula of R is as follows:

[0043]

[0044] A method for preparing the divanillin-based epoxy resin of this embodiment comprises the following steps:

[0045] S1. Preparation of divanillin etherate: 16.35g (54.0mmol) divanillin and 45mL dimethyl sulfoxide were added to a four-necked flask equipped with a mechanical stirrer, a condensation reflux device, and a temperature sensor, and 12.60g (118.8mmol) sodium carbonate was slowly added under stirring. After the addition was completed, the temperature was controlled to react at 50°C for 30min, and then 15.42g (129.6mmol) 3-bromopropyne was added, and the temperature was raised to 80°C and the reaction was continued for 24h. After the reaction was completed, it was cooled to room temperature, filtered, and the filtrate was extracted and purified with dichloromethane, and then the dichloromethane was removed to obtain 19.83g of brown-yellow solid product, i.e., divanillin etherate, with a yield of 97.1%. After testing, 1 H NMR (400 MHz, DMSO-d 6 )δ: 9.94 (s, 2H), 7.59 (d, 2H), 7.50 (d, 2H), 4.70 (d, 4H), 3.95 (s, 6H), 3.38 (t, 2H), which indicated that propargyl-etherified divanillin was indeed obtained.

[0046] In this embodiment, divanillin can be prepared according to the following method, or can be purchased commercially.

[0047] The preparation process of divanillin is as follows: 24.00 g of vanillin and 1600 mL of deionized water are added to a 2000 mL four-necked flask equipped with a mechanical stirrer, a condensation reflux device and a temperature sensor. The temperature is raised to 50 °C. After the raw materials are completely dissolved, 0.80 g of FeSO 4 7H 2 O and 20.00g Na 2 S2 O 8 , and then the temperature was raised to 80°C to continue the reaction for 1 hour. After the reaction was completed, the mixture was filtered, washed with hot water, and vacuum dried at 80°C overnight to obtain 20.24 g of a gray solid product, namely divanillin, with a yield of 84.9%.

[0048] Divanillin purchasing channels: CAS number is 2092-49-1, purity ≥97%, provided by: Shanghai Aladdin Biochemical Technology Co., Ltd., but not limited to this.

[0049] S2. Preparation of bio-based biphenyl dimethanol: At room temperature, take 13.62g (36.0mmol) of the above-prepared divanillin etherate and 30mL of a mixed solvent consisting of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) (the volume ratio of DMF to THF v / v=1:3) and add them to a four-necked flask equipped with a mechanical stirrer and a temperature sensor for mixing. After complete dissolution, slowly add 1.44g (38.0mmol) of sodium borohydride to the solution within 1h (it can be added in small amounts and multiple times in batches). During the addition process, control the temperature of the reaction system not to exceed 30°C. After the addition is completed, continue to react at room temperature for 4h. After the reaction is completed, use dilute hydrochloric acid (1mol / L) to wash until the aqueous phase is weakly acidic, that is, acid wash to a pH of 4-5, then wash with deionized water to neutrality, remove the solvent, and obtain 13.56g of a reddish-brown viscous liquid product, namely bio-based biphenyl dimethanol, with a yield of 98.5%. After testing, 1 HNMR (400 MHz, DMSO-d 6 )δ: 7.05-6.99 (m, 2H), 6.71 (d, 2H), 5.18 (s, 2H), 4.46 (dd, 8H), 3.84 (s, 6H), 3.32 (d, 2H), which indicates that bio-based biphenyl dimethanol was indeed obtained.

[0050] S3. Preparation of divanillin-based epoxy resin: 8.52 g (22.3 mmol) of the above-prepared bio-based biphenyl dimethanol, 0.50 g (2.2 mmol) of benzyltriethylammonium chloride and 12.43 g of 50 wt% potassium hydroxide solution were added into a four-necked flask equipped with a mechanical stirrer for mixing. Then, the reaction system was placed in a water bath at 0°C to 10°C and 41.27 g (446.0 mmol) of epichlorohydrin was slowly added. After the addition was completed, the reaction was carried out at room temperature for 48 hours. After the reaction was completed, the excess epichlorohydrin was washed with water and recovered under reduced pressure to obtain 10.5 g of brown-black liquid, i.e., divanillin-based epoxy resin, with a yield of 95.5%.

[0051] In this embodiment, the H NMR spectrum of the target product divanillin-based epoxy resin is as follows: Figure 1 As shown, 1H NMR (400MHz, Chloroform-d) δ: 6.92 (dd, 4H), 4.62-4.46 (m, 8H), 3.91 (s, 6H), 3.78 (dd, 2H), 3.44 (dd, 2H), 3.22-3.16 (m, 2H), 2.80 (t, 2H), 2.62 (dd, 2H), 2.38-2.27 (m, 2H). The attribution of each peak in the spectrum corresponds to the structure of the target compound, and the integral is also consistent with the number of hydrogens in the structure of the target compound. The infrared spectrum is shown in the figure below. Figure 2 As shown, 3268cm -1 and 908cm -1 The peaks at 3600-3300 cm -1 No obvious hydroxyl characteristic peak appears in the range. The rheological test results of the target product are as follows Figure 3 As shown in the figure, the viscosity at 25°C is 260mPa·s, showing low viscosity characteristics. The target product is used as raw material, 4,4'-diaminodiphenylmethane (DDM) is used as a curing agent for pre-curing and curing. The DSC spectrum of the pre-cured product at a heating rate of 20°C / min is shown in the figure below. Figure 4 As shown, there are two curing exothermic peaks at different temperatures, corresponding to the epoxy functional group and the propargyl group, that is, the curing system is a double cross-linking curing. The dynamic thermomechanical analysis (DMA) and thermogravimetric analysis (TGA) test diagrams of the cured product are shown in FIG. Figure 5 As shown, T g Over 290℃, in N 2 The residual carbon rates at 700℃ and 800℃ were 62.04% and 60.48% respectively. The UL-94 test results of the cured product are as follows: Figure 6 As shown, the product was able to self-extinguish quickly after being ignited twice, and passed the highest level V0 in the vertical combustion test, showing excellent intrinsic flame retardant properties.

[0052] In the above embodiment, the reaction route is as follows, wherein the structural formula of R is as follows:

[0053]

[0054] The preparation process of divanillin ether is shown in the following formula (II):

[0055]

[0056] The preparation process of bio-based biphenyl dimethanol is shown in the following formula (III):

[0057]

[0058] The preparation process of divanillin-based epoxy resin is shown in the following formula (IV):

[0059]

[0060] The divanillin-based epoxy resin of the present invention can be applied to the fields of aerospace, rail transportation, construction, etc.

[0061] Example 2

[0062] A divanillin-based epoxy resin of the present invention has a structural formula shown in the following formula (I):

[0063]

[0064] In formula (I), the structural formula of R is as follows:

[0065]

[0066] A method for preparing the divanillin-based epoxy resin of this embodiment comprises the following steps:

[0067] S1. Preparation of divanillin etherate: 16.35g (54.0mmol) divanillin and 60mL N,N-dimethylformamide were added to a four-necked flask equipped with a mechanical stirrer, a condensation reflux device, and a temperature sensor. 16.44g (118.8mmol) potassium carbonate was slowly added under stirring. After the addition was completed, the temperature was controlled to react at 50°C for 60min, and then 26.16g (216.2mmol) 3-bromo-1-propylene was added, and the temperature was raised to 70°C and the reaction was continued for 18h. After the reaction was completed, it was cooled to room temperature, filtered, and the filtrate was extracted and purified with ethyl acetate. The ethyl acetate was then removed to obtain 19.44g of brown-black solid product, i.e., divanillin etherate, with a yield of 93.9%. After testing, 1 H NMR (400 MHz, DMSO-d 6 )δ: 9.93 (s, 2H), 7.57 (d, 2H), 7.47 (d, 2H), 5.71 (ddt, 2H), 5.09-4.99 (m, 4H), 4.47-4.42 (m, 4H), 3.94 (s, 6H), which indicated that divanillin etherate was indeed obtained.

[0068] S2. At room temperature, 15.30g (40.0mmol) of divanillin etherified product prepared in Example 2 and 40mL of a mixed solvent composed of ethanol and tetrahydrofuran (volume ratio of EtOH and THF v / v=1:4) were added to a four-necked flask equipped with a mechanical stirrer and a temperature sensor for mixing. After complete dissolution, 1.66g (44.0mmol) of sodium borohydride was slowly added to the solution within 1.5h, and the temperature of the reaction system was controlled not to exceed 30°C during the addition. After the addition was completed, the reaction was continued at room temperature for 5h. After the reaction was completed, a dilute hydrochloric acid (1mol / L) solution was used to wash until the aqueous phase was weakly acidic, i.e., pH 4-5, and then washed with deionized water until neutral, and the solvent was removed to obtain 14.06g of a reddish-brown viscous liquid product, i.e., bio-based biphenyl dimethanol, with a yield of 91.0%. 1 HNMR (400 MHz, DMSO-d 6 )δ: 6.99(d,2H),6.69(d,2H),5.73(ddt,2H),5.16(t,2H),5.09-4.97(m,4H),4.46(d,4H),4.25(d,3.82(s,6H).

[0069] S3. Preparation of divanillin-based epoxy resin: 10.25 g (26.52 mmol) of the above-prepared bio-based biphenyl dimethanol, 0.855 g (2.6 mmol) of tetrabutylammonium bromide and 5.31 g (132.75 mmol) of sodium hydroxide were added into a four-necked flask equipped with a mechanical stirrer for mixing. Then, the reaction system was placed in a water bath at 0°C to 10°C and 34.35 g (371.3 mmol) of epichlorohydrin was slowly added. After the addition was completed, the reaction was carried out at room temperature for 36 hours. After the reaction was completed, the excess epichlorohydrin was washed with water and recovered under reduced pressure to obtain 13.06 g of dark red liquid, i.e., divanillin-based epoxy resin, with a yield of 98.7%. 1 H NMR (400 MHz, DMSO-d 6 , ppm)δ:6.94(s,2H),6.85(s,2H),5.78(ddt,2H),5.12-4.96(m,4H),4.53(q,4H),4.31(d,4H),3.89(s,6H),3.76(dt,2H),3.43(dd,2H),3.21-3.15(m,2H),2.80(q,2H),2.61(dd,2H). The product was cured with DDM and heated under N 2 The residual carbon rates at 700℃ and 800℃ in atmosphere were 51.72% and 50.29% respectively, and passed the highest level V0 of the vertical combustion test.

[0070] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A divanillin-based epoxy resin, characterized in that: The divanillin-based epoxy resin has a structural formula shown in the following formula (I): In formula (I), R is one of the following structural formulas:

2. A method for preparing a divanillin-based epoxy resin as claimed in claim 1, characterized in that: The following steps are involved: S1. Preparation of divanillin etherate: adding divanillin and a solvent into a reaction vessel, adding an inorganic base while stirring, reacting at a temperature of 35°C to 55°C after the addition is completed, then adding a halogenated compound, heating to 60°C to 80°C to continue the reaction, cooling to room temperature after the reaction is completed, filtering, extracting and purifying the filtrate, removing the solvent from the extract phase, and obtaining divanillin etherate; S2. Preparation of bio-based biphenyl dimethanol: at room temperature, add the above-obtained divanillin etherate and solvent into a reaction container and mix them. After the mixture is completely dissolved, add sodium borohydride. During the addition process, control the temperature of the reaction system not to exceed 30° C. After the addition is completed, react at room temperature. After the reaction is completed, wash with acid first, then wash with water until neutral, remove the solvent, and obtain bio-based biphenyl dimethanol; S3. Preparation of divanillin-based epoxy resin: Add the above-obtained bio-based biphenyl dimethanol, phase transfer catalyst and base catalyst into a reaction vessel and mix them. Then place the reaction system in a water bath at 0°C to 10°C, add epihalohydrin, and after the addition is completed, react at room temperature. After the reaction is completed, wash with water, and recover the excess epihalohydrin under reduced pressure to obtain the product divanillin-based epoxy resin.

3. The method for preparing the divanillin-based epoxy resin according to claim 2, characterized in that: In step S1, the molar ratio of the inorganic base to the divanillin is 1 to 4:1, and the molar ratio of the halogenated compound to the divanillin is 2 to 5:

1.

4. The method for preparing the divanillin-based epoxy resin according to claim 2, characterized in that: In step S1, the solvent is a strong polar solvent, and the strong polar solvent includes one or more of methanol, ethanol, acetone, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, 1,3-dimethylimidazolidinone and N-methylpyrrolidone; the inorganic base includes one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium bicarbonate and potassium bicarbonate; the halogenated compound is one or more of 3-bromo-1-propene, 3-chloro-1-propene, 3-bromopropyne and 3-chloropropyne; the extractant used for the extraction and purification includes at least one of ethyl acetate, ether, dichloromethane, chloroform and toluene.

5. The method for preparing the divanillin-based epoxy resin according to claim 2, characterized in that: In step S2, the molar ratio of the sodium borohydride to the divanillin etherate is 0.9-1.5:1; and the solvent is one or more of tetrahydrofuran, methanol, ethanol, N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide and N-methylpyrrolidone.

6. The method for preparing a divanillin-based epoxy resin according to any one of claims 2 to 5, characterized in that: In step S3, the ratio of the amount of the phase transfer catalyst to the amount of the bio-based biphenyl dimethanol is 0.05-0.4:1, and the phase transfer catalyst is one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, hexadecyltrimethylammonium bromide and tetrabutylammonium chloride.

7. The method for preparing a divanillin-based epoxy resin according to any one of claims 2 to 5, characterized in that: In step S3, the alkaline catalyst includes sodium hydroxide and / or potassium hydroxide, and the molar ratio of the alkaline catalyst to the bio-based biphenyl dimethanol in step S2 is 2 to 8:1; when the alkaline catalyst is added in the form of a solution containing the alkaline catalyst, the mass fraction of the alkaline catalyst in the solution containing the alkaline catalyst is 30wt% to 50wt%.

8. The method for preparing a divanillin-based epoxy resin according to any one of claims 2 to 5, characterized in that: In step S3, the epihalohydrin includes epichlorohydrin and / or epibromohydrin, and the amount ratio of the epihalohydrin to the bio-based biphenyl dimethanol is 8 to 40:

1.

9. The method for preparing a divanillin-based epoxy resin according to any one of claims 2 to 5, characterized in that: In step S1, the reaction time is 30 min to 60 min, and the continued reaction time is 12 h to 24 h; in step S2, the sodium borohydride addition time is controlled at 0.5 h to 2 h, the reaction time is 3 h to 6 h, the acid is dilute hydrochloric acid, the concentration of the dilute hydrochloric acid is 0.1 mol / L to 1 mol / L, and the acid washing is performed to a pH of 4 to 5; in step S3, the reaction time is 24 h to 48 h; the room temperature in steps S1, S2, and S3 is 10° C. to 30° C.

10. Use of the divanillin-based epoxy resin according to claim 1 or the divanillin-based epoxy resin prepared by the preparation method according to any one of claims 2 to 9 in the fields of aerospace, rail transportation or construction.

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