Coumarin-based photo-thermal dual-curing benzoxazine resin and preparation method thereof

Abstract

The invention discloses a coumarin-based photo-thermal dual-curing benzoxazine resin and a preparation method thereof.The coumarin-based benzoxazine resin monomer is prepared from coumarin, an amine compound and paraformaldehyde as main raw materials through the following steps that firstly, the coumarin, the amine compound and paraformaldehyde react in an organic solvent, and the coumarin-based benzoxazine resin monomer is obtained; preparing to obtain a liquid intermediate; and then, dissolving the intermediate in another organic solvent, and reacting with methacryloyl chloride under the action of a basic catalyst to obtain a light yellow liquid benzoxazine monomer. The monomer can be thermally cured through light curing and heating to form a cross-linked polymer network. The benzoxazine resin monomer disclosed by the invention is in a liquid state, so that extrusion molding processing and 3D printing are facilitated; the adopted coumarin is a renewable biomass raw material and meets the requirements of green chemistry and sustainable development; the properties of the resin can be conveniently and quickly regulated and controlled by changing the structure of the amine compound or adjusting the light curing time.

Description

Technical Field

[0001] The present invention relates to the field of preparation of thermosetting resins, and more particularly to a coumarin-based photothermal dual-curing benzoxazine resin and a preparation method thereof. Background Art

[0002] Polybenzoxazine resin is a class of high-performance thermosetting phenolic materials that have attracted much attention due to their excellent performance and wide application. This type of material not only has high thermal stability and mechanical strength, but also exhibits advantages such as high carbon residue rate, excellent flame retardancy, low water absorption rate and near-zero volume shrinkage. In addition, one of the most outstanding features of polybenzoxazine resin is the flexibility of its molecular design, which enables it to meet the needs of different application scenarios. Thanks to these advantages, benzoxazine resin and its matrix composite materials are widely used in a variety of fields, including important fields such as molding processing technology, anti-corrosion coatings, electronic components, aerospace composites, circuit board substrates and insulation materials.

[0003] However, most benzoxazine resins on the market are still made from fossil-based materials, which poses a huge challenge to the sustainability of the environment and resources. With the intensification of environmental problems and the gradual depletion of fossil resources such as petroleum, the development of new benzoxazine resins made from bio-based materials has become an urgent need. However, both bio-based and petroleum-based benzoxazine resins have processing difficulties, which limits their widespread promotion in practical applications.

[0004] Coumarin is an important class of organic compounds, which are widely found in various plants, such as vegetables, spices, fruits and medicinal plants, including fruits, roots, stems and leaves of plants. Coumarin is not only naturally renewable, but also can be extracted from biomass derivatives, so it is of great significance in green chemistry and sustainable development. Among them, 7-hydroxy-methylcoumarin can be regarded as a substitute for phenol because its ortho-hydroxyl group on the benzene ring is not substituted, thus becoming an ideal raw material for the synthesis of benzoxazine monomers.

[0005] Nevertheless, as described in Chinese patent documents CN 114195803 B and CN 114702668 A, most of the benzoxazine monomers based on coumarin derivatives are currently in solid form, which to a certain extent limits their application in fields such as extrusion molding and 3D printing. In addition, the curing properties of such benzoxazine monomers usually need to be regulated through complex molecular design and synthesis steps, further increasing production costs and process difficulties. Therefore, it is of great technical significance and application value to develop a coumarin-based photothermal dual-curing benzoxazine resin with good processing properties and relatively simple preparation steps. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, a photothermal dual-curing benzoxazine resin based on coumarin and a preparation method thereof are provided. The raw materials are green and renewable, the synthesis method is simple and the yield is high, the obtained benzoxazine monomer is a liquid, and the crosslinking degree of the cured resin is increased by vinyl double bond polymerization and coumarin dimerization, thereby improving its thermal and mechanical properties, and the performance of the cured benzoxazine resin can be flexibly controlled by changing the ultraviolet light irradiation time. In addition, the resin synthesis process is simple, the yield is high, the equipment requirements are low, and it is suitable for large-scale production. The specific scheme is as follows:

[0007] A method for preparing a coumarin-based photothermal dual-curing benzoxazine resin, the reaction process is as follows:

[0008]

[0009] The preparation method comprises the following steps:

[0010] S1. Add coumarin, amine compounds and paraformaldehyde into a flask, add organic solvent A, react at 90-130° C. for 6-12 hours, filter the reactants after stopping the reaction, rotary evaporate and dry to obtain a liquid intermediate;

[0011] S2, the obtained intermediate is dissolved in organic solvent B and placed in an ice water bath, methacryloyl chloride is slowly added dropwise in the presence of an alkaline catalyst, and reacts at room temperature for 10-24 hours, followed by rotary evaporation and drying to obtain a light yellow liquid as a coumarin-based benzoxazine resin monomer;

[0012] S3. After being cured by ultraviolet light, thermal curing is performed to form a polymer network structure.

[0013] Furthermore, the solvent A in S1 is one or a mixture of toluene, xylene, dioxane and ethanol.

[0014] Furthermore, the solvent B is one or a mixture of dichloromethane (DCM), tetrahydrofuran (THF) and N,N-dimethylformamide (DMF).

[0015] Further, the structural formula of the amine compound is:

[0016]

[0017] Furthermore, the molar ratio of the coumarin, the amine compound and the paraformaldehyde is 1:1:2 to 1:1:3, preferably 1:1:2.3.

[0018] Furthermore, the alkaline catalyst is triethylamine, sodium carbonate, sodium bicarbonate, preferably triethylamine.

[0019] Furthermore, the light curing condition is ultraviolet light with a wavelength of 300-400nm and an irradiation time of 5-10min.

[0020] The coumarin-based benzoxazine monomer prepared by the above preparation method has the following chemical structural formula:

[0021]

[0022] In formula (1), n=2,5; R=H, CH3.

[0023] Furthermore, the network structure of the polymer after the coumarin-based benzoxazine monomer is photothermally cured is as follows:

[0024]

[0025] Beneficial effects:

[0026] The present invention provides a coumarin-based photothermal dual-curing benzoxazine resin and a preparation method thereof, which has the following advantages:

[0027] (1) The present invention uses coumarin as the main raw material, which is derived from natural renewable biomass resources. The entire preparation process is environmentally friendly and meets the requirements of green chemistry and sustainable development. The coumarin-based benzoxazine monomer designed by the present invention is in a liquid state. Compared with the traditional solid benzoxazine monomer, the operability of the material in processes such as extrusion, molding and 3D printing is greatly improved, which helps to realize the manufacture of complex structures.

[0028] (2) Through the polymerization of vinyl double bonds and the dimerization of coumarin, the present invention significantly improves the crosslinking density of the cured resin. The high degree of crosslinking gives the resin excellent thermal stability, mechanical strength and flame retardancy, enabling it to perform well in scenarios requiring high performance. By adjusting the structure of the amine compounds in the raw materials, the performance of the coumarin-based benzoxazine resin can be effectively regulated. In addition, the resin performance can be further adjusted by changing the ultraviolet light irradiation time, providing a convenient and efficient performance optimization method to meet the needs of different application scenarios.

[0029] (3) The present invention adopts light-heat dual curing technology, combining ultraviolet light irradiation and heating curing to form a cross-linked polymer network structure. This not only improves the thermal stability, mechanical strength and flame retardancy of the material, but also shortens the processing cycle and further improves production efficiency.

[0030] (4) The preparation method of the present invention is simple to operate, has mild conditions, and improves reaction efficiency and reduces production costs by optimizing the selection of solvents and catalysts. At the same time, its process route is suitable for large-scale production and has good industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the infrared spectrum of the coumarin-based photothermal dual-curing benzoxazine resin precursor in Example 1.

[0032] Figure 2 This is the nuclear magnetic resonance hydrogen spectrum of the coumarin-based photothermal dual-curing benzoxazine resin precursor in Example 1.

[0033] Figure 3 This is the DSC spectrum of the coumarin-based photothermal dual-curing benzoxazine resin precursor in Example 1.

[0034] Figure 4 This is the DMA spectrum of the coumarin-based photothermal dual-curing benzoxazine cured material in Example 1.

[0035] Figure 5 This is the TGA spectrum of the coumarin-based photothermal dual-curing benzoxazine cured material in Example 1.

[0036] Figure 6 This is a contact angle diagram of water on the coumarin-based photothermal dual-cured benzoxazine resin coating in Example 1. DETAILED DESCRIPTION

[0037] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0038] Embodiment 1:

[0039] Add 0.991g of paraformaldehyde and 0.916g of ethanolamine to a 250mL round-bottom flask, dissolve 2.642g of coumarin in 60.64mL of toluene and slowly drip it into the above reaction bottle, and react in a 110℃ oil bath for 12h after dripping. After suction filtration, directly rotary evaporate to obtain a nearly golden transparent liquid as an intermediate. Add 5mL of DCM to the intermediate obtained above to obtain a mixed solution, then add 1.515g of triethylamine, place in an ice-water bath, and slowly drip a mixed solution of methacryloyl chloride (1.86mL) and DCM (5mL) into the reaction bottle, and continue to react for 12h after dripping. Suction filtration and rotary evaporation to obtain a light yellow liquid as C2-coumarinyl benzoxazine methacrylate, with a yield of 76%.

[0040] C2-coumarin-based benzoxazine methacrylate was irradiated under ultraviolet light for 10 minutes and then thermally cured to obtain a photo-thermal dual-cured film material and sample, and the performance of the polymer material was tested.

[0041] The hydrogen nuclear magnetic resonance spectrum, Fourier transform infrared spectrum, DSC curve, DMA curve, thermogravimetric curve and contact angle of the coating with water of the coumarin-based benzoxazine methacrylate monomer obtained in this example are shown in the attached Figure 1 , Attachment Figure 2 , Attachment Figure 3 , Attachment Figure 4 , Attachment Figure 5 and attached Figure 6 shown.

[0042] Attached Figure 1 This is the infrared spectrum of the coumarin-based photothermal dual-curing benzoxazine resin precursor. The chemical shifts around 4.95ppm and 4.24ppm are the characteristic peaks of the methylene group on the oxazine ring.

[0043] Attached Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the coumarin-based photothermal dual-curing benzoxazine resin precursor, where 928cm-1 and 1223cm-1 are the characteristic absorption peaks of the benzoxazine ring.

[0044] Attached Figure 3 This is the DSC spectrum of the coumarin-based photothermal dual-curing benzoxazine resin precursor. The peak exothermic temperature of the benzoxazine monomer curing is 217°C.

[0045] Attached Figure 4 This is the DMA spectrum of the coumarin-based photothermal dual-curing benzoxazine cured material. It can be seen that the glass transition temperature of the cured resin is 267°C.

[0046] Attached Figure 5 This is the TGA spectrum of the coumarin-based photothermal dual-curing benzoxazine cured material. It can be seen that the temperature of the polybenzoxazine resin is 316°C when the thermal weight loss is 5%, and the residual carbon rate is 35% at 800°C in an inert gas atmosphere.

[0047] Attached Figure 6 The contact angle diagram of water on the coumarin-based photothermal dual-cured benzoxazine resin coating is 130°.

[0048] Embodiment 2:

[0049] Add 0.991g of paraformaldehyde and 0.916g of ethanolamine to a 250mL round-bottom flask, stir at room temperature until slightly dissolved, dissolve 2.642g of coumarin in 60.64mL of xylene and slowly drip into the above reaction bottle, and react in a 130℃ oil bath for 10h. After suction filtration, directly rotary evaporate to obtain a nearly golden transparent liquid as an intermediate. Add 5mL of tetrahydrofuran to the intermediate obtained above to obtain a mixed solution, then add 1.590g of sodium carbonate, place in an ice-water bath, slowly drip a mixed solution of methacryloyl chloride (1.86mL) and DCM (5mL) into the reaction bottle, and continue to react for 24h after dripping. Suction filtration and rotary evaporation to obtain a light yellow liquid as C2-coumarinyl benzoxazine methacrylate, with a yield of 65%.

[0050] C2-coumarin-based benzoxazine methacrylate was irradiated under ultraviolet light for 5 minutes and then thermally cured to obtain a photo-thermal dual-cured film material and sample, and the performance of the polymer material was tested.

[0051] The latent curing benzoxazine resin monomer obtained in this example has a curing exothermic peak temperature of 217°C. After further curing and cross-linking, the carbon residue rate of the polybenzoxazine resin is 30% at 800°C in an inert gas atmosphere, and the glass transition temperature of the cured resin material is 230°C. The water contact angle on the benzoxazine resin coating is 124°

[0052] Embodiment 3:

[0053] Add 0.991g of paraformaldehyde and 0.916g of ethanolamine to a 250mL round-bottom flask, stir at room temperature until slightly dissolved, dissolve 2.642g of coumarin in 60.64mL of ethanol and slowly drip into the above reaction bottle, and react in a 130℃ oil bath for 6h after dripping. After suction filtration, directly rotary evaporate to obtain a nearly golden transparent liquid as an intermediate. Add 5mL of DMF to the intermediate obtained above to obtain a mixed solution, then add 1.260g of sodium bicarbonate and place it in an ice-water bath, slowly drip a mixed solution of acryloyl chloride (1.83mL) and DCM (5mL) into the reaction bottle, and continue to react for 12h after dripping. Suction filtration, washing, drying, and rotary evaporation to obtain a light yellow liquid as C2-coumarinyl benzoxazine acrylate with a yield of 68%.

[0054] C2-coumarin-based benzoxazine acrylate was irradiated under ultraviolet light for 10 minutes and then thermally cured to obtain a photothermal dual-cured film material and sample strip, and the performance of the polymer material was tested.

[0055] The latent curing benzoxazine resin monomer obtained in this embodiment has a curing exothermic peak temperature of 213° C. After further curing and cross-linking, the carbon residue rate of the polybenzoxazine resin is 33% at 800° C. in an inert gas atmosphere, and the glass transition temperature of the cured resin material is 264° C. The water contact angle on the benzoxazine resin coating is 132°.

[0056] Embodiment 4:

[0057] Add 0.991g of paraformaldehyde and 1.545g of 5-amino-1-pentanol to a 250mL round-bottom flask, stir at room temperature until slightly dissolved, dissolve 2.642g of coumarin in 60.64mL of dioxane and slowly drip into the above reaction bottle, and react in a 110℃ oil bath for 10h after dripping. After suction filtration, directly rotary evaporation is performed to obtain a nearly golden yellow transparent liquid as an intermediate. Add 5mL of DCM to the intermediate obtained above to obtain a mixed solution, then add 1.515g of triethylamine, place in an ice-water bath, and slowly drip a mixed solution of methacryloyl chloride (1.86mL) and THF (5mL) into the reaction bottle, and continue to react for 12h after dripping. Suction filtration and rotary evaporation give a light yellow liquid as C5-coumarinyl benzoxazine methacrylate with a yield of 77%.

[0058] C5-coumarin-based benzoxazine methacrylate was irradiated under ultraviolet light for 10 minutes and then thermally cured to obtain a photo-thermal dual-cured film material and sample strip, and the performance of the polymer material was tested.

[0059] The latent curing benzoxazine resin monomer obtained in this embodiment has a curing exothermic peak temperature of 210° C. After further curing and cross-linking, the polybenzoxazine resin has a carbon residue rate of 25% at 800° C. in an inert gas atmosphere, and a glass transition temperature of the cured resin material is 220° C. The water contact angle on the benzoxazine resin coating is 140°.

[0060] As a further improvement, the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a coumarin-based photothermal dual-curing benzoxazine resin, characterized in that: The reaction process is as follows: The preparation method comprises the following steps: S1. Add coumarin, amine compounds and paraformaldehyde into a flask, add organic solvent A, react at 90-130° C. for 6-12 hours, filter the reactants after stopping the reaction, rotary evaporate and dry to obtain a liquid intermediate; S2, the obtained intermediate is dissolved in organic solvent B and placed in an ice water bath, methacryloyl chloride is slowly added dropwise in the presence of an alkaline catalyst, and reacts at room temperature for 10-24 hours, followed by rotary evaporation and drying to obtain a light yellow liquid as a coumarin-based benzoxazine resin monomer; S3. After being cured by ultraviolet light, thermal curing is performed to form a polymer network structure.

2. The method for preparing a coumarin-based photothermal dual-curing benzoxazine resin according to claim 1, characterized in that: The solvent A in S1 is one or a mixture of toluene, xylene, dioxane and ethanol.

3. The method for preparing a coumarin-based photothermal dual-curing benzoxazine resin according to claim 1, characterized in that: The solvent B is one or a mixture of dichloromethane, tetrahydrofuran and N,N-dimethylformamide.

4. The method for preparing a coumarin-based photothermal dual-curing benzoxazine resin according to claim 1, characterized in that: The structural formula of amine compounds is:

5. The method for preparing a coumarin-based photothermal dual-curing benzoxazine resin according to claim 1, characterized in that: The molar ratio of the coumarin, the amine compound and the paraformaldehyde is 1:1:2 to 1:1:

3.

6. The method for preparing a coumarin-based photothermal dual-curing benzoxazine resin according to claim 1, characterized in that: The alkaline catalyst is triethylamine, sodium carbonate and sodium bicarbonate.

7. The method for preparing a coumarin-based photothermal dual-curing benzoxazine resin according to claim 1, characterized in that: The light curing conditions are ultraviolet light with a wavelength of 300-400nm and an irradiation time of 5-10min.

8. A coumarin-based photothermal dual-curing benzoxazine resin prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The chemical structure of coumarin-based benzoxazine monomer is as follows: In formula (1), n=2,5; R=H, CH3.

9. The coumarin-based photothermal dual-curing benzoxazine resin according to claim 8, characterized in that: The network structure of the polymer after photothermal curing of coumarin-based benzoxazine monomer is as follows:

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