Flame-retardant bio-based epoxy resin monomer, bio-based epoxy resin and preparation method thereof

Abstract

The invention is suitable for the technical field of bio-based high polymer materials, and provides a flame-retardant bio-based epoxy resin monomer, bio-based epoxy resin and a preparation method thereof. The flame-retardant bio-based epoxy resin monomer is prepared by taking vanillin and tyramine as raw materials, introducing a DOPO flame retardant through a condensation reaction to generate a bisphenol monomer, and then performing epoxidation and ring-closure reaction. And mixing the epoxy resin with an amino-containing curing agent, and carrying out first curing and second curing to prepare the bio-based epoxy resin. The flame-retardant bio-based epoxy resin monomer provided by the invention has a rigid benzene ring and a phosphorus-containing structure, so that the thermal stability and the mechanical property of epoxy resin can be improved, the flame-retardant bio-based epoxy resin monomer and nitrogen element can be synergistically flame-retardant, a compact and continuous expanded carbon layer is formed during combustion, and the flame-retardant bio-based epoxy resin monomer shows excellent flame retardance. The monomer is prepared from renewable bio-based raw materials vanillin and tyramine, and the process steps are simple, green and environment-friendly. The prepared bio-based epoxy resin is excellent in comprehensive performance, can reduce dependence on petroleum resources, and meets the requirement of green development.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of bio-based macromolecular materials, and particularly relates to a flame-retardant bio-based epoxy resin monomer, a bio-based epoxy resin and a preparation method thereof. BACKGROUND

[0002] Epoxy resin is a kind of organic macromolecular polymer containing two or more epoxy groups in the molecular structure. Compared with most thermosetting materials, epoxy resin has excellent dimensional stability, high modulus, high strength, and good heat resistance and chemical resistance, and is widely used in the fields of coatings, adhesives, composites, electronic packaging and the like due to these excellent properties.

[0003] Although the traditional petrochemical-based epoxy resin has outstanding performance, its non-renewable and non-degradable defects are contrary to the development concept of modern green manufacturing, which seriously restricts its further application in this field. Under this background, bio-based epoxy resin gradually becomes a research hotspot in the industry due to its wide raw material sources, good degradability and other characteristics that meet the green development needs, providing a new direction for the green development of epoxy resin. However, the natural molecular structure of bio-based epoxy resin determines its insufficient flame retardant performance, which greatly limits its promotion and application in high-performance fields. Looking back at traditional epoxy resin, the industry usually uses halogen flame retardants to improve its flame retardant performance, but such flame retardants will pollute the natural environment and also have potential negative effects on human health during use, which does not meet the environmental protection and health concepts. In view of the above dual problems of insufficient flame retardant performance of bio-based epoxy resin and drawbacks of traditional flame retardant methods, the present application proposes a flame-retardant bio-based epoxy resin monomer, a bio-based epoxy resin and a preparation method thereof. SUMMARY

[0004] The purpose of the present application is to provide a flame-retardant bio-based epoxy resin monomer, a bio-based epoxy resin and a preparation method thereof, which aims to solve the problems raised in the background art.

[0005] The purpose of the present application is achieved by the following technical solutions: The flame-retardant bio-based epoxy resin monomer has a structure as shown in Formula I: Formula I: .

[0006] The preparation method of the flame-retardant bio-based epoxy resin monomer as described above comprises the following steps: The vanillin, tyramine and alcohol solvent are mixed for condensation reaction, then the DOPO is dissolved in the alcohol solvent and added dropwise into the reaction system to obtain a bisphenol monomer with a structure as shown in Formula II; Formula II: ; The bisphenol monomer, catalyst and epichlorohydrin are mixed to carry out an epoxidation reaction, and then the obtained epoxidation reaction solution is mixed with sodium hydroxide to carry out a ring closure reaction; after the reaction is completed, extraction, washing, drying, distillation and column chromatography purification are carried out to obtain the flame-retardant bio-based epoxy resin monomer of the structure shown in formula I.

[0007] Further, the molar ratio of vanillin to tyramine is 1:1-1.5; the molar ratio of vanillin to DOPO is 1:1-1.5.

[0008] Further, the temperature of the condensation reaction is 40-80℃, and the time is 20-26h.

[0009] Further, the molar ratio of the bisphenol monomer to the catalyst is 1:0.001-0.1; the molar ratio of the bisphenol monomer to epichlorohydrin is 1:8-30; the molar ratio of the bisphenol monomer to sodium hydroxide is 1:0.1-0.7.

[0010] Further, the catalyst is a quaternary ammonium salt selected from one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide and hexadecyltrimethylammonium bromide; the sodium hydroxide is used in the form of a sodium hydroxide aqueous solution, and the mass concentration of the sodium hydroxide aqueous solution is 5-50%.

[0011] Further, the temperature of the epoxidation reaction is 50-100℃, the time is 2-7h, the stirring speed of the epoxidation reaction is 100-500r / min; the temperature of the ring closure reaction is -5-10℃, the time is 2-7h, and the stirring speed of the ring closure reaction is 100-500r / min.

[0012] The bio-based epoxy resin is prepared from an epoxy resin monomer and a curing agent, wherein the epoxy resin monomer is the flame-retardant bio-based epoxy resin monomer described above or prepared by the preparation method described above; and the curing agent is one or more of an amino-containing curing agent, an amino-containing disulfide bond curing agent and an amino-containing silicon-oxygen-silicon bond curing agent.

[0013] Further, the amino-containing curing agent is 4,4'-diaminodiphenyl methane and / or 1,6-hexanediamine; the amino-containing disulfide bond curing agent is 4,4'-diaminodiphenyl disulfide and / or 3,3'-dithiodipropionic acid; and the amino-containing silicon-oxygen-silicon bond curing agent is 1,3-bis(3-aminopropyl)tetramethyldisiloxane and / or bis(4-aminophenoxy)dimethylsilane.

[0014] The preparation method of the bio-based epoxy resin described above comprises the following steps: The flame-retardant bio-based epoxy resin monomer and the curing agent are mixed, and then the mixture is poured into a mold to carry out curing to obtain the bio-based epoxy resin. The molar ratio of the flame-retardant bio-based epoxy resin monomer and the curing agent is 1:0.1-1. The curing comprises sequentially performing first curing and second curing, the temperature of the first curing is 60-120 DEG C, the time is 4-12h, the temperature of the second curing is 120-160 DEG C, and the time is 2-12h.

[0015] Compared with the prior art, the beneficial effects of the present application are: The flame-retardant bio-based epoxy resin monomer provided by the present application has a rigid benzene ring structure, which helps to improve the thermal stability and mechanical properties of the epoxy resin, and the monomer structure has a phosphorus-containing structure, which forms a synergistic flame-retardant effect with nitrogen elements in the epoxy network, so that a dense and continuous expanded carbon layer is formed during resin combustion, thereby imparting excellent flame-retardant properties. The monomer is prepared from tyramine (derived from tyrosine decarboxylation, green and non-toxic) and vanillin (derived from lignin depolymerization, abundant in source), both of which are renewable bio-based materials. The process steps are simple, and the consumption and dependence on petroleum chemical products can be reduced, promoting the sustainable development of the epoxy resin industry. The bio-based epoxy resin prepared has good thermal stability, mechanical properties and excellent flame-retardant properties, can reduce the consumption of petroleum resources, and meets the green development demand. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Nuclear magnetic resonance hydrogen spectrum of the bisphenol monomer synthesized in Example 1.

[0017] Figure 2 Nuclear magnetic resonance hydrogen spectrum of the flame-retardant bio-based epoxy resin monomer synthesized in Example 2.

[0018] Figure 3 Infrared spectrum of the bio-based epoxy resin obtained after curing in Example 3.

[0019] Figure 4 Bending property test diagram of the bio-based epoxy resin. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail below, but it cannot be understood as limiting the scope of the present application.

[0021] The present application provides a flame-retardant bio-based epoxy resin monomer, the structure of which is shown in formula I: Formula I: ; The present application also provides a preparation method of the flame-retardant bio-based epoxy resin monomer described above, comprising the following steps: Step 1: vanillin, tyramine and an alcohol solvent are mixed to carry out a condensation reaction, then DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) is dissolved in the alcohol solvent and added dropwise into the reaction system to obtain a bisphenol monomer with a structure as shown in formula II.

[0022] Formula II: ; The synthesis route of the bisphenol monomer is as follows: .

[0023] The molar ratio of vanillin to tyramine is preferably 1:1-1.5, and specifically 1:1.05; the molar ratio of vanillin to DOPO is preferably 1:1-1.5, and specifically 1:1.05; and the alcohol solvent is preferably methanol.

[0024] The reaction temperature is preferably 40-80℃, and specifically can be 50℃, 60℃, 70℃; the reaction is preferably carried out under reflux conditions, and the reaction time is preferably 20-26h, and specifically can be 22h, 23h, 24h, 25h. The synthesis reaction of the bisphenol monomer under the above conditions can promote the efficient progress of the reaction.

[0025] Step 2: the bisphenol monomer, a catalyst and epichlorohydrin are mixed to carry out an epoxidation reaction, then the obtained epoxidation reaction liquid and sodium hydroxide are mixed to carry out a ring closure reaction, to obtain a flame-retardant bio-based epoxy resin monomer with a structure as shown in formula I.

[0026] The reaction process of the epoxidation reaction and the ring closure reaction is comprehensively represented as follows: .

[0027] The molar ratio of the bisphenol monomer to the catalyst is preferably 1:0.001-0.1, and specifically can be 1:0.02, 1:0.03, 1:0.04, 1:0.06, 1:0.08; the catalyst is preferably one or more of quaternary ammonium salts; and the quaternary ammonium salt is preferably one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide and cetyltrimethylammonium bromide. The use of the above catalyst can promote the reaction, accelerate the reaction rate and improve the selectivity.

[0028] The molar ratio of the bisphenol monomer to epichlorohydrin is preferably 1:8-30, and can be 1:10, 1:13, 1:14 or 1:15; the molar ratio of the bisphenol monomer to sodium hydroxide is preferably 1:0.1-0.7, and can be 1:0.06, 1:0.08, 1:0.1, 1:0.2, 1:0.3, 1:0.4 or 1:0.5; the sodium hydroxide is used in the form of an aqueous sodium hydroxide solution, the mass concentration of the aqueous sodium hydroxide solution is preferably 5-50%, and can be 40%; and the aqueous sodium hydroxide solution is preferably added dropwise.

[0029] The temperature of the epoxidation reaction is preferably 50-100℃, and can be 80℃, and the time is preferably 2-7h, and can be 6h; the stirring speed is 400r / min. After the epoxidation reaction is completed, the obtained reaction liquid is preferably cooled, and an aqueous sodium hydroxide solution is added dropwise to perform a ring closure reaction.

[0030] The temperature of the ring closure reaction is preferably -5-10℃, and can be 0℃, and the time is preferably 2-7h, and can be 3h, 4h, 5h or 6h; the stirring speed is 400r / min. After the ring closure reaction is completed, the obtained reaction liquid is preferably extracted with ethyl acetate, and then washed with deionized water until neutral, and the washed liquid is distilled under reduced pressure, and then dried and purified by column chromatography to obtain the flame-retardant bio-based epoxy resin monomer shown in formula I; the eluent used in the column chromatography purification is preferably petroleum ether.

[0031] In the present application, the steps of the preparation method are preferably as follows: First, vanillin is dissolved in an alcohol solvent and then added dropwise into a three-necked round-bottom flask containing tyramine, and stirred at 50℃ for 5h, and then DOPO dissolved in an alcohol solvent is added into the system. After the reaction is completed, the obtained reaction liquid is filtered, and the obtained solid product is washed with methanol and then dried to obtain a bisphenol monomer. Then, the bisphenol monomer, a catalyst and epichlorohydrin are mixed to perform an epoxidation reaction, and the obtained epoxidation reaction liquid and sodium hydroxide are mixed to perform a ring closure reaction, to obtain the flame-retardant bio-based epoxy resin monomer shown in formula I.

[0032] The present application also provides a bio-based epoxy resin prepared from an epoxy resin monomer and a curing agent, wherein the epoxy resin monomer is the flame-retardant bio-based epoxy resin monomer described above or prepared by the preparation method described above; and the curing agent is one or more of an amino-containing curing agent, an amino-containing-disulfide bond curing agent and an amino-containing-silicon-oxygen-silicon bond curing agent.

[0033] The amino-containing curing agent is preferably 4,4'-diaminodiphenyl methane (DDM) and / or 1,6-hexanediamine; the amino-containing-disulfide bond curing agent is preferably 4,4'-diaminodiphenyl disulfide and / or 3,3'-dithiodipropionic acid; the amino-containing-siloxysilicon bond curing agent is preferably 1,3-bis(3-aminopropyl)tetramethyldisiloxane and / or bis(4-aminophenoxy)dimethylsilane.

[0034] The molar ratio of the flame-retardant bio-based epoxy resin monomer and the curing agent is preferably 1:1-3, and can be 1:2 in particular.

[0035] The application also provides a preparation method of the bio-based epoxy resin as described above, comprising the following steps: The flame-retardant bio-based epoxy resin monomer and the curing agent are mixed, and then the mixture is poured into a mold for curing to obtain the bio-based epoxy resin. The curing comprises sequentially performing first curing and second curing, the temperature of the first curing is 60-120℃, and the time is 4-12h, the temperature of the second curing is 120-160℃, and the time is 2-12h.

[0036] In the application, the flame-retardant bio-based epoxy resin monomer and the curing agent are preferably stirred and mixed uniformly first, and then vacuum degassed, and then poured into a mold for curing.

[0037] Taking the curing agent DDM as an example, the structure of the bio-based epoxy resin obtained after curing is shown in formula III: Formula III: .

[0038] The specific implementation of the application is described in detail below in combination with specific examples. Obviously, the described examples are only some of the examples of the application, not all the examples. Based on the examples in the application, all other examples obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0039] Example 1: Preparation of a bisphenol monomer In a three-necked round-bottom flask equipped with a thermometer and a reflux condenser, tyramine (28.80g, 0.21mol) was dissolved in methanol (100mL) under the condition of 50℃ and magnetic stirring at 400r / min, and then vanillin (37.93g, 0.2mol) dissolved in 50mL of methanol was added dropwise into the three-necked round-bottom flask, and the whole mixed system was refluxed for 5h. Then DOPO (45.36g, 0.21mol) dissolved in 100mL of methanol was added, and the whole mixed system was refluxed for 20h. After the reaction was completed, the obtained white powder was filtered, washed with methanol three times, and dried overnight to obtain the bisphenol monomer (VD).

[0040] The nuclear magnetic resonance hydrogen spectrum of the obtained bisphenol monomer is shown in Figure 1 It can be seen that the signal peak at 4.3 ppm belongs to the hydrogen signal peak on the carbon connected with DOPO, indicating the successful synthesis of the bisphenol monomer. Figure 1

[0041] Example 2: Preparation of a flame-retardant bio-based epoxy resin monomer; A three-necked flask equipped with a mechanical stirring device and a condenser was charged with 20 g (0.041 mol) of the bisphenol monomer prepared in Example 1, 65 mL (0.83 mol) of epichlorohydrin, and 1 g (0.0031 mol) of tetrabutylammonium bromide as a catalyst, and the mixture was thoroughly mixed (the stirring speed was 400 r / min). After being heated to 80°C for 6 h, the heating was stopped, the reaction system was placed in an ice water bath at 0°C, and 1.64 g of a sodium hydroxide aqueous solution (40% by mass) was added dropwise to the reaction system, which was continuously reacted for 3 h at a stirring speed of 400 r / min. After the reaction was completed, ethyl acetate was added for extraction, and then the reaction liquid was washed with deionized water for several times until it was neutral. The washed product was purified by reduced pressure distillation, and then dried and purified by column chromatography to obtain a light yellow liquid, i.e., the flame-retardant bio-based epoxy resin monomer (VDEP) of the structure shown in Formula I.

[0042] The nuclear magnetic resonance hydrogen spectrum of the obtained flame-retardant bio-based epoxy resin monomer is shown in Figure 2 It can be seen that the signal peak at 4.3 ppm belongs to the hydrogen signal peak on the carbon connected with DOPO, indicating the successful synthesis of the bisphenol monomer. Figure 2

[0043] Example 3: Preparation of a bio-based epoxy resin; The raw materials included A material and B material, wherein the A material was the flame-retardant bio-based epoxy resin monomer prepared in Example 2, and the B material was a curing agent 4,4-diaminodiphenyl methane (DDM). The molar ratio of the A material to the B material was 1:0.5.

[0044] The specific preparation process of the bio-based epoxy resin was as follows: the A material was first added to a 25 mL beaker, and the weighed B material was added at 110°C, and the mixture was stirred for 10 min to make it uniform; then the mixture was vacuum degassed in a vacuum oven at 80°C for 10 min, and then the mixture was poured into a mold, and cured at 80°C for 8 h and then cured at 140°C for 4 h to obtain the bio-based epoxy resin (VDEP-DDM).

[0045] The infrared spectrum of the obtained bio-based epoxy resin is shown in Figure 3 It can be seen that the signal peak at 4.3 ppm belongs to the hydrogen signal peak on the carbon connected with DOPO, indicating the successful synthesis of the bisphenol monomer. Figure 3 -1 3200 cm-1 belongs to the characteristic peak of the hydroxyl group in VDEP-DDM, and 1235 cm-1 belongs to the characteristic peak of the ether bond in VDEP-DDM.​​​-1 The characteristic peak belonging to C-N in VDEP-DDM appeared, indicating the successful synthesis of bio-based epoxy resin (VDEP-DDM).

[0046] Example 4: Flexural property test of bio-based epoxy resin The cured sample bar of bio-based epoxy resin prepared in Example 3 was taken to perform flexural test on an electronic universal material machine at room temperature.

[0047] Figure 4 The flexural strength and flexural modulus results of bio-based epoxy resin were presented, and it could be seen that the flexural strength of bio-based epoxy resin prepared in Example 3 was 160 MPa, and the flexural modulus was 4.91 GPa. Due to the presence of a large number of rigid structures such as aromatic rings in the epoxy network, the bio-based epoxy resin had high mechanical strength, and the mechanical properties could be comparable to commercial epoxy resins, which could meet the use requirements as a structural material.

[0048] Example 5: Flame retardant property test of bio-based epoxy resin In order to comprehensively evaluate the performance of bio-based epoxy resin prepared in Example 3, flame retardant property test was carried out. The test method was as follows: (1) Limiting oxygen index: according to GB / T 2406.2-2009 "Plastics-Determination of the flammability of plastics-Part 2: Test method using a small-scale test apparatus", limiting oxygen index instrument was used for testing; (2) UL-94 vertical burning grade: according to GB / T 2408-2008 "Plastics-Determination of the flammability of plastics-Part 2: Test method using a small-scale test apparatus", JT-HVR5455 burning tester was used for testing.

[0049] The test results are shown in Table 1: Table 1 Test results of bio-based epoxy resin prepared in Example 3

[0050] As can be seen from Table 1, the limiting oxygen index of the flame-retardant bio-based epoxy resin prepared in Example 3 was 35.1%, and the UL-94 vertical burning grade was V-0. Combined with the mechanical properties of flexural strength of 160 MPa and flexural modulus of 4.91 GPa in Example 4, it showed that it had good mechanical properties and excellent flame retardancy. Because the flame-retardant bio-based epoxy resin monomer structure contained rigid benzene ring structure, the mechanical properties and thermal stability of the resin could be guaranteed; at the same time, the monomer structure had phosphorus-containing structure, which could form synergistic flame retardancy with nitrogen elements in the epoxy network, promote the formation of dense and continuous carbon layer during combustion, and thus achieve high-efficiency flame retardation. In addition, the raw material was renewable bio-based material, and at the same time, the resin could meet the requirements of structural material, providing a new method for the sustainable development of epoxy resin materials.

[0051] The above are only preferred embodiments of the present application, it should be pointed out that, for those skilled in the art, without departing from the concept of the present application, can also make several variations and improvements, these should also be considered as the protection scope of the present application, these will not affect the effect and the practicality of the patent of the present application.

Claims

1. A flame-retardant bio-based epoxy resin monomer, characterized in that, The structure is shown as formula I: Formula I: .

2. The method of making a flame retardant bio-based epoxy resin monomer of claim 1, wherein, The method comprises the following steps: vanillin, tyramine and an alcoholic solvent are mixed to perform a condensation reaction, then DOPO is dissolved in the alcoholic solvent and added dropwise into the reaction system to obtain a bisphenol monomer with a structure shown as formula II; Formula II: ; The bisphenol monomer, a catalyst and epichlorohydrin are mixed to perform an epoxidation reaction, then the obtained epoxidation reaction liquid is mixed with sodium hydroxide to perform a ring closure reaction; after the reaction is completed, extraction, washing, drying, distillation and column chromatography purification are performed to obtain the flame-retardant bio-based epoxy resin monomer with the structure shown as formula I.

3. The production method according to claim 2, characterized by, The molar ratio of the vanillin to the tyramine is 1:1-1.5, and the molar ratio of the vanillin to the DOPO is 1:1-1.

5.

4. The preparation method according to claim 2, characterized in that The condensation reaction is performed at a temperature of 40-80℃ for 20-26h.

5. The preparation method according to claim 2, characterized in that The molar ratio of the bisphenol monomer to the catalyst is 1:0.001-0.1, the molar ratio of the bisphenol monomer to the epichlorohydrin is 1:8-30, and the molar ratio of the bisphenol monomer to the sodium hydroxide is 1:0.1-0.

7.

6. The preparation method according to claim 2, characterized in that The catalyst is a quaternary ammonium salt selected from one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide and hexadecyltrimethylammonium bromide; the sodium hydroxide is used in the form of a sodium hydroxide aqueous solution, and the mass concentration of the sodium hydroxide aqueous solution is 5-50%.

7. The preparation method according to claim 2, characterized in that The epoxidation reaction is performed at a temperature of 50-100℃ for 2-7h, and the stirring speed of the epoxidation reaction is 100-500r / min; the ring closure reaction is performed at a temperature of -5-10℃ for 2-7h, and the stirring speed of the ring closure reaction is 100-500r / min.

8. A bio-based epoxy resin, characterized in that, The bio-based epoxy resin is prepared from the epoxy resin monomer and the curing agent, wherein the epoxy resin monomer is the flame-retardant bio-based epoxy resin monomer of claim 1 or the flame-retardant bio-based epoxy resin monomer prepared by the method of any one of claims 2-7; and the curing agent is one or more of an amino-containing curing agent, an amino-containing disulfide bond curing agent and an amino-containing silicon-oxygen-silicon bond curing agent.

9. The bio-based epoxy resin according to claim 8, characterized in that, The amino-containing curing agent is 4,4'-diaminodiphenylmethane and / or 1,6-hexanediamine; the amino-containing disulfide bond curing agent is 4,4'-diaminodiphenyl disulfide and / or 3,3'-dithiodipropionic acid; and the amino-containing silicon-oxygen-silicon bond curing agent is 1,3-bis(3-aminopropyl)tetramethyldisiloxane and / or bis(4-aminophenoxy)dimethylsilane.

10. The method of producing a bio-based epoxy resin according to claim 8 or 9, characterized in that, The method comprises the following steps: The flame-retardant bio-based epoxy resin monomer and the curing agent are mixed, and then the mixture is poured into a mold to perform curing to obtain the bio-based epoxy resin. The molar ratio of the flame-retardant bio-based epoxy resin monomer to the curing agent is 1:0.1-1. The curing comprises sequentially performing first curing and second curing, wherein the temperature of the first curing is 60-120℃, the time of the first curing is 4-12h, the temperature of the second curing is 120-160℃, and the time of the second curing is 2-12h.

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