Vanillin-based diepoxy monomer compound as well as preparation method and application thereof

Abstract

The invention relates to the technical field of bio-based high polymer materials, in particular to a vanillin-based diepoxy monomer compound as well as a preparation method and application thereof. The invention provides a brand new vanillin-based diepoxy monomer compound. A preparation method of the compound comprises the following steps: 1, synthesizing a bio-based bisphenol intermediate from bio-based platform compounds such as vanillin and vanillin under the catalysis of pyrrolidine acetate; 2, adding epichlorohydrin to synthesize a diepoxy monomer under the catalytic action of a phase transfer catalyst and base; and the epoxy resin can be reacted with a commercial curing agent to prepare high-performance bio-based epoxy resin. The glass transition temperature of the prepared high-performance bio-based epoxy resin is 170-220 DEG C, the initial decomposition index in nitrogen is 300-380 DEG C, the tensile strength is 85-120 MPa, and the high-performance bio-based epoxy resin has good mechanical properties and thermal stability.

Description

Technical Field

[0001] The invention relates to the technical field of bio-based polymer materials, in particular to a vanillin-based diepoxy monomer compound and a preparation method and application thereof. Background Art

[0002] Epoxy resin is widely used in aerospace, construction, transportation, electronics and other fields due to its excellent mechanical properties, thermal properties and corrosion resistance. However, commonly used epoxy resins are generally made of petroleum-based compounds such as bisphenol A, which is not green and environmentally friendly, but also threatens human health.

[0003] In addition, as oil resources are increasingly depleted, finding sustainable, high-quality, and cheap oil substitutes is the key to the existence and development of the polymer industry. Bio-based polymer materials use renewable resources as the main raw materials, which reduces the consumption of petrochemical products in the plastics industry while also reducing the pollution to the environment during the production of petroleum-based raw materials. It is an important development direction of current polymer materials and has important practical value and broad development space.

[0004] There are many types of epoxy resins based on bio-based raw materials such as vanillin, soybean oil, isosorbide, eugenol, etc. reported (Advances in sustainable thermosetting resins: From renewable feedstock to high performance and recyclability. [J]. Progress in Polymer Science, 2021.), but they all have more or less disadvantages such as low glass transition temperature and insufficient mechanical properties, which limits the promotion and use of bio-based epoxy resins.

[0005] Therefore, how to obtain a bio-based epoxy resin with excellent comprehensive performance is an important development direction for future plastics, and it is also one of the difficult problems that this field wants to solve. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention provides a vanillin-based diepoxy monomer compound and a preparation method and application thereof.

[0007] A vanillin-based diepoxy monomer compound, the specific structural formula of which is shown in the following formula (1):

[0008]

[0009] The R1, R2, R3, and R4 are hydrogen, alkyl, alkoxy, or any other substituent.

[0010] Further, the alkyl group is C 1～3 Alkyl; the alkoxy group is C 1～3 Alkoxy; the optional substituent is methyl, ethyl, hydroxyl, epoxy or carboxyl.

[0011] The structures of some of the vanillin-based diepoxy monomer compounds are shown in formulas (1a) to (11):

[0012]

[0013] The preparation method of the vanillin-based diepoxy monomer compound comprises the following steps: reacting a mixed system consisting of a phase transfer catalyst, a vanillin-based bisphenol monomer, and epichlorohydrin at 90 to 110° C. for 1 to 3 hours, then cooling the system and maintaining the temperature at -10 to 5° C., adding a main catalyst and reacting for 1 to 3 hours to obtain a reaction mixture, and obtaining the vanillin-based diepoxy monomer through post-treatment.

[0014] Furthermore, the molar ratio of the vanillin bisphenol monomer to epichlorohydrin is 1:5-20, the molar ratio of the vanillin bisphenol monomer to the phase transfer catalyst is 1:0.01-0.1; and the molar ratio of the vanillin bisphenol monomer to the main catalyst is 1:1-5.

[0015] Furthermore, the phase transfer catalyst is one or more of tetramethylammonium chloride, tetrabutylammonium bromide, benzyltrimethylammonium bromide, benzyltriethylammonium bromide, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, and hexamethylenetetramonium, mixed in any proportion.

[0016] Furthermore, the main catalyst is an aqueous solution of one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, potassium carbonate, and sodium carbonate mixed in any proportion.

[0017] Furthermore, the specific steps of the post-treatment include: washing the reaction mixture with deionized water and retaining the organic phase, removing epichlorohydrin in the organic phase by rotary evaporation, then dissolving the residue in a good solvent, and then adding a poor solvent to precipitate the vanillin-based diepoxy monomer.

[0018] Furthermore, the structure of the vanillin-based bisphenol monomer is shown in formula (2):

[0019]

[0020] Wherein R1, R2, R3, and R4 are hydrogen, alkyl or alkoxy, and the alkyl and alkoxy are optionally substituted by substituents.

[0021] Furthermore, the vanillin-based bisphenol monomer is obtained by condensing and dehydrating one of the lignin conversion products of vanillin, syringaldehyde, and p-hydroxybenzaldehyde with vanillone and acetosyringone. The dehydration process is specifically as follows: ethanol is used as a solvent; the substrate reaction concentration is 10% to 40%; pyrrolidine acetate is used as a catalyst, and the catalyst amount is 5% to 10% of the molar number of the reactants; the temperature is 60 to 80°C, and the reaction time is 4 to 7 hours.

[0022] The vanillin-based diepoxy monomer compound is used in the synthesis of epoxy resin.

[0023] A bio-based thermosetting material is obtained by curing the vanillin-based diepoxy monomer compound with a curing agent, wherein the C=O in the original structure is converted into C=N after the curing reaction. The bio-based thermosetting material contains a characteristic structure shown in formula (3):

[0024]

[0025] Wherein R1, R2, R3, and R4 are hydrogen, alkyl, or alkoxy; and R5, R6, and R7 are ring-opened or non-ring-opened epoxypropyl.

[0026] Furthermore, the method for preparing the bio-based thermosetting material comprises the following steps: reacting a mixed system of at least one diepoxy monomer and a curing agent at 180 to 220° C. for 6 to 10 hours;

[0027] Furthermore, the curing agent includes amines, anhydrides, polyacids, phenolic resins, polyols or polythiols.

[0028] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0029] (1) The present invention uses bio-based monomer vanillin as a raw material to synthesize vanillin-based diepoxy monomers. The raw materials come from lignin in plants, so they are widely available and environmentally friendly. At the same time, they reduce dependence on fossil resources and reduce costs. In addition, the synthesis process is simple, the yield is high, the reaction conditions are mild, and it is easy to produce.

[0030] (2) The vanillin-based diepoxy monomer provided by the present invention can be used to synthesize a variety of epoxy resin materials, and can give the epoxy resin materials a higher glass transition temperature, excellent mechanical properties and excellent heat resistance.

[0031] (3) The vanillin-based diepoxy monomer provided by the present invention can be reacted with a commercial curing agent to prepare a high-performance bio-based epoxy resin. The prepared high-performance bio-based epoxy resin has a glass transition temperature of 170°C to 220°C, an initial decomposition index in nitrogen of 300°C to 380°C, a tensile strength of 85 to 120 MPa, and has excellent mechanical properties and thermal stability.

[0032] (4) This method first synthesizes a new bio-based epoxy monomer, which is then used to cure and prepare a high-performance epoxy resin. The process is simple and easy to operate and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the monomer of formula (1-1) prepared in Example 2 of the present invention.

[0034] Figure 2 This is the carbon nuclear magnetic resonance spectrum of the monomer of formula (1-1) prepared in Example 2 of the present invention.

[0035] Figure 3 This is the infrared spectrum of the monomer of formula (1-1) prepared in Example 2 of the present invention.

[0036] Figure 4 This is the infrared spectrum of the epoxy three-dimensional network prepared in Example 2.

[0037] Figure 5 This is the DSC graph of the epoxy three-dimensional network prepared in Example 2.

[0038] Figure 6 This is the TGA graph of the epoxy three-dimensional network prepared in Example 2.

[0039] Figure 7 The stress-strain curve of the epoxy three-dimensional network obtained in Example 2 DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0041] Example 1

[0042] Add 15.2 g of vanillin and 16.6 g of vanillone to a three-necked flask and dissolve them in 60 ml of ethanol. Add 1.66 ml of pyrrolidine and 1.15 ml of acetic acid. First, condense and reflux at 80 ° C for 6 hours. After the reaction, add deionized water to obtain the precipitated monomer. After filtering and drying, 28.8 g of the product is obtained with a yield of 95%. The melting point is 165-180 ° C. The product structure is shown in formula (1) as determined by H NMR and C NMR.

[0043]

[0044] Example 2

[0045] Take 29g of vanillin bisphenol, 2.9g of benzyltrimethylammonium bromide, and 182g of epichlorohydrin, and react at 100°C for 2h. Cool to room temperature, add 77g of 20wt% sodium hydroxide aqueous solution through a constant pressure dropping funnel under an ice-water bath, drip it for 30min, and react for 2h. Then wash it with deionized water 5 times, and retain the organic phase, then rotary evaporate to remove epichlorohydrin and dissolve it in dichloromethane, then add petroleum ether to the solution until solid precipitates and filter, and obtain 34g of product after vacuum drying, with a yield of 85%. The product structure is determined by nuclear magnetic hydrogen spectrum, nuclear magnetic carbon spectrum, and infrared spectrum as shown in formula (2).

[0046]

[0047] Example 3

[0048] The epoxy monomer of formula (2) prepared in Example 2 and the commercial curing agent 4,4-diaminodiphenylmethane were dissolved in DMF at a stoichiometric molar ratio (1:1), mixed evenly, applied to the mold, evacuated under vacuum, and then cured at 110, 130 and 150°C for 2 hours each. The infrared spectrum is shown in FIG. Figure 3 , the epoxy group disappears, and a hydroxyl peak appears, proving that the epoxy and amine groups are completely cured. At the same time, the keto carbonyl group is significantly weakened, and a new Schiff base peak appears, proving that the keto carbonyl group and the amine group undergo a Schiff base reaction, but the reaction is not complete. The glass transition temperature of the completely obtained cured product is 180°C, the tensile strength is about 102MPa, and the 5% thermal degradation temperature is 364°C.

[0049] Example 4

[0050] The epoxy monomer of formula (2) prepared in Example 2 and the commercial curing agent diaminodiphenyl sulfone were dissolved in dimethylformamide in a stoichiometric molar ratio (1:1), mixed evenly, applied to the mold, vacuum-exhausted, and then cured at 130, 150 and 170°C for 2 hours each. The gel content and infrared characterization determined that a cured product with a Schiff base structure was obtained. The glass transition temperature of the cured product was 190°C, the tensile strength was about 108MPa, and the 5% thermal degradation temperature was 370°C.

[0051] Example 5

[0052] The epoxy monomer of formula (2) prepared in Example 2 and the commercial curing agent methyltetrahydrophthalic anhydride were dissolved in dimethylformamide in a stoichiometric molar ratio (1:2), mixed evenly, applied to the mold, and then cured at 110, 130 and 150°C for 2 hours each after vacuum exhaust. The curing was complete as shown by gel content and infrared characterization. The glass transition temperature of the cured product was 171°C, the tensile strength was about 85MPa, and the 5% thermal degradation temperature was 300°C.

[0053] Example 6

[0054] The linear bisphenol A phenolic resin curing agent was dissolved in acetone, and then mixed with the epoxy monomer represented by formula (2) prepared in Example 2 in a stoichiometric molar ratio (1:1), and cured in an environment of 170°C for 5 hours. The gel content and infrared characterization proved that the curing was complete. The glass transition temperature of the obtained cured product was 216°C, the tensile strength was about 100 MPa, and the 5% thermal degradation temperature was 376°C.

[0055] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A vanillin-based diepoxy monomer compound, characterized in that: Its specific structural formula is shown in the following formula (1): The R1, R2, R3, and R4 are hydrogen, alkyl, alkoxy, or any other substituent.

2. The compound according to claim 1, characterized in that The alkyl group is C 1～3 Alkyl; the alkoxy group is C 1～3 Alkoxy; the optional substituent is methyl, ethyl, hydroxyl, epoxy or carboxyl.

3. The method for preparing the vanillin-based diepoxy monomer compound according to claim 1, characterized in that: The method comprises the following steps: reacting a mixed system consisting of a phase transfer catalyst, a vanillin-based bisphenol monomer and epichlorohydrin at 90 to 110° C. for 1 to 3 hours, then cooling the system and maintaining the temperature at -10 to 5° C., adding a main catalyst and reacting for 1 to 3 hours to obtain a reaction mixture, and obtaining the vanillin-based diepoxy monomer through post-treatment.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the vanillin bisphenol monomer to epichlorohydrin is 1:5-20, the molar ratio of the vanillin bisphenol monomer to the phase transfer catalyst is 1:0.01-0.1; and the molar ratio of the vanillin bisphenol monomer to the main catalyst is 1:1-5.

5. The preparation method according to claim 3, characterized in that: The phase transfer catalyst is one or more of tetramethylammonium chloride, tetrabutylammonium bromide, benzyltrimethylammonium bromide, benzyltriethylammonium bromide, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide and hexamethylenetetramonium, mixed in any proportion.

6. The preparation method according to claim 3, characterized in that: The main catalyst is an aqueous solution of one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, potassium carbonate and sodium carbonate mixed in any proportion.

7. The preparation method according to claim 3, characterized in that: The specific steps of the post-treatment include: washing the reaction mixture with deionized water and retaining the organic phase, removing epichlorohydrin in the organic phase by rotary evaporation, then dissolving the residue in a good solvent, and then adding a poor solvent to precipitate the vanillin-based diepoxy monomer.

8. The preparation method according to claim 3, characterized in that: The structure of the vanillin-based bisphenol monomer is shown in formula (2): Wherein R1, R2, R3, and R4 are hydrogen, alkyl or alkoxy, and the alkyl and alkoxy are optionally substituted by substituents.

9. Use of the vanillin-based diepoxy monomer compound according to claim 1 in the synthesis of epoxy resins.

10. A bio-based thermosetting material, characterized in that: The bio-based thermosetting material contains a characteristic structure shown in formula (3): Wherein R1, R2, R3, and R4 are hydrogen, alkyl, or alkoxy; and R5, R6, and R7 are ring-opened or non-ring-opened epoxypropyl.

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