A mixed cresol type benzoxazine and a method for preparing the same
By using excess formaldehyde and primary amine, and employing atomization technology involving heating and spraying into the reaction vessel, the problem of low yield of mixed cresol-type benzoxazine was solved, achieving a high-efficiency yield improvement.
Patent Information
- Application Number
- CN202610690114.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-19
- Publication Date
- 2026-07-24
AI Technical Summary
In the existing technology, the yield of mixed cresol-type benzoxazine is low and it is difficult to significantly improve it through conventional methods.
The method employs excess formaldehyde and excess primary amine, and heats the mixture by spraying it into the reaction vessel to ensure that the paraformaldehyde, primary amine, and mixed cresols are fully mixed before the reaction. Atomization technology is used to improve reaction efficiency and avoid the use of acidic catalysts.
Without the use of acidic catalysts, the yield of mixed cresol-type benzoxazine was significantly improved, enhancing reaction efficiency and product purity.
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Figure CN122444670A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer preparation and relates to a mixed cresol-type benzoxazine and its preparation method. Background Technology
[0002] Benzoxazine, as a relatively new polymer material, had its basic skeletal structure only elucidated in the mid-20th century. However, it was not until the late 20th century, with significant progress in the research of its polymerization mechanism, that it began to be gradually applied in practical applications. Due to its characteristics of no condensation deformation during curing, low dielectric loss, and good high-temperature resistance, it has replaced some epoxy resins in fields such as circuit boards and aerospace, and is widely used as an adhesive or matrix material.
[0003] There are three common methods for preparing benzoxazine monomers: the primary amine method, the triazine method, and the salicylaldehyde method. The primary amine method is the most widely used. This reaction belongs to the Mannich condensation process, using formaldehyde, primary amine, and phenol as raw materials in a 2:1:1 ratio. Due to its fewer steps, ease of operation, and mild conditions, the primary amine method can be considered one of the main synthetic routes for benzoxazine. Commonly used solvents include toluene, chloroform, and DMF. Benzoxazine contains an N, O six-membered ring structure, which exhibits ring strain and can spontaneously undergo ring-opening polymerization at high temperatures. Its autocatalytic properties mean that the curing reaction does not require an additional curing agent; however, a curing agent can be added to improve curing efficiency.
[0004] However, the preparation of mixed cresol-type benzoxazine has a low yield problem. In order to improve the yield, people have used acidic catalysts, excess formaldehyde, or low-polarity solvents, but the increase in yield is limited. Summary of the Invention
[0005] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing mixed cresol-type benzoxazine, which accelerates the mixing and reaction between different materials by using excess formaldehyde and excess primary amine and heating the materials and spraying them into the reaction vessel, thereby increasing the yield of mixed cresol-type benzoxazine without using an acidic catalyst.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0007] A method for preparing a mixed cresol-type benzoxazine includes the following steps:
[0008] S1) Preparation: primary amine, paraformaldehyde, mixed cresols and solvent, wherein the molar ratio of the amino group in the primary amine, the aldehyde group in the paraformaldehyde and the phenolic hydroxyl group in the mixed cresols is (1.1~1.3):(2~2.3):1, the volume ratio of solvent to paraformaldehyde is (1.2~1.5):1, and the solvent is one or more of DMF, isobutanol and 2-butanol;
[0009] S2) First, paraformaldehyde is mixed with a solvent to form a paraformaldehyde solution. Then, the primary amine, paraformaldehyde solution, and mixed cresol are heated to 95-110°C and sprayed into the reaction vessel simultaneously through a nozzle. At the same time, the solution temperature in the reaction vessel is kept not lower than 90°C. After the primary amine, paraformaldehyde solution, and mixed cresol are all added, the reaction is kept at a temperature of 90-95°C for 10-13 hours to obtain the crude product. The droplet size of the primary amine, paraformaldehyde solution, and mixed cresol sprayed into the reaction vessel is 20-80 μm.
[0010] S3) The crude product obtained in step S2) is washed with alkali, then filtered and repeatedly washed with deionized water until the filtrate is neutral. The resulting solid product is then dried to constant weight to obtain mixed cresol-type benzoxazine.
[0011] In the above-mentioned method for preparing mixed cresol-type benzoxazine, the alkaline solution used in step S3) during alkaline washing is a sodium hydroxide solution or a sodium bicarbonate solution, and the concentration of the alkaline solution is 0.8–1.4 mol / L.
[0012] In the above-mentioned method for preparing mixed cresol-type benzoxazine, in step S2), the nozzle used to spray the paraformaldehyde solution into the reaction vessel is located below the nozzle used to spray the primary amine into the reaction vessel and the nozzle used to spray the mixed cresol into the reaction vessel.
[0013] In the above-mentioned method for preparing mixed cresol-type benzoxazine, in step S2), the outlet direction of the nozzle used to spray paraformaldehyde solution into the reaction vessel, the outlet direction of the nozzle used to spray primary amine into the reaction vessel, and the outlet direction of the nozzle used to spray mixed cresol into the reaction vessel are all at an angle of 20 to 40° to the horizontal direction.
[0014] In the above method for preparing mixed cresol-type benzoxazine, in step S2), the mixed cresol is heated to 100-110°C and then added to the reaction vessel.
[0015] In the above-mentioned method for preparing mixed cresol-type benzoxazine, the molar ratio of the amino group in the primary amine, the aldehyde group in paraformaldehyde, and the phenolic hydroxyl functional group in the mixed cresol is (1.15~1.25):(2.1~2.2):1.
[0016] In the above-mentioned method for preparing mixed cresol-type benzoxazine, the primary amine is one or more of aniline, furfurylamine, butanediamine, and decanediamine.
[0017] In the above-mentioned method for preparing mixed cresol-type benzoxazine, the primary amine is a mixture of a first primary amine, a second primary amine, and a third primary amine in a molar ratio of 5:2:1. The first primary amine is aniline, the second primary amine is decanediamine, and the third primary amine is either furfurylamine or butanediamine.
[0018] A mixed cresol-type benzoxazine, prepared by the above-described method for preparing mixed cresol-type benzoxazine.
[0019] The primary amine used in the preparation of the above-mentioned mixed cresol-type benzoxazine is a mixture containing aniline.
[0020] The technical solution of the present invention achieves the following beneficial technical effects:
[0021] 1. This invention utilizes atomization to atomize paraformaldehyde solution, primary amine, and mixed cresol into small droplets and add them to the reaction vessel. This allows the paraformaldehyde, primary amine, and mixed cresol to be fully mixed and undergo a preliminary reaction before converging at the bottom of the reaction vessel. It also facilitates the thorough mixing of paraformaldehyde, primary amine, and mixed cresol within the reaction vessel, thereby achieving a higher yield within the same reaction time.
[0022] 2. Spraying the paraformaldehyde solution, primary amine, and mixed cresol upwards increases the mixing and reaction time of the three in the air, thereby further improving the yield of mixed cresol-type benzoxazine. Attached Figure Description
[0023] Figure 1 The infrared spectrum of the mixed cresol-type benzoxazine prepared in Example 1;
[0024] Figure 2 The mixed cresol-type benzoxazine prepared in Example 1 1 H-NMR spectrum;
[0025] Figure 3 The infrared spectrum of the mixed cresol-type benzoxazine prepared in Example 11; Figure 4 The mixed cresol-type benzoxazine prepared in Example 11 1 H-NMR spectrum. Detailed Implementation
[0026] The present invention will be further described below with reference to specific embodiments. Obviously, the described embodiments are only some preferred embodiments of the present invention, and the present invention is not limited to these embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels.
[0027] Example 1
[0028] The preparation steps of the mixed cresol-type benzoxazine in this embodiment are as follows:
[0029] S1) Preparation: primary amine, paraformaldehyde, mixed cresols and solvent, wherein the molar ratio of amino groups in the primary amine, aldehyde groups in the paraformaldehyde and phenolic hydroxyl functional groups in the mixed cresols is 1.1:2:1, the primary amine is aniline, the molar ratio of o-cresol, m-cresol and p-cresol in the mixed cresols is 3:1:1, the volume ratio of solvent to paraformaldehyde is 1.2:1, the solvent is DMF, specifically, the amount of aniline used is 20.49g;
[0030] S2) First, paraformaldehyde is mixed with a solvent to form a paraformaldehyde solution. Then, the primary amine, paraformaldehyde solution, and mixed cresol are heated to 95°C and sprayed into the reaction vessel simultaneously through a nozzle. At the same time, the solution temperature in the reaction vessel is kept not lower than 90°C. After the primary amine, paraformaldehyde solution, and mixed cresol are all added, the reaction is kept at 90-95°C for 12 hours to obtain the crude product. The droplet size of the primary amine, paraformaldehyde solution, and mixed cresol sprayed into the reaction vessel is 20-30 μm.
[0031] S3) The crude product obtained in step S2) is washed with alkali, then filtered and repeatedly washed with deionized water until the filtrate is neutral. The obtained solid product is then dried to constant weight to obtain mixed cresol-type benzoxazine. The alkaline solution used in the alkali washing is a 1 mol / L sodium bicarbonate solution.
[0032] Example 2
[0033] In this embodiment, when preparing the mixed cresol-type benzoxazine, in step S2), the outlet direction of the nozzle used to spray the paraformaldehyde solution into the reaction vessel, the outlet direction of the nozzle used to spray the primary amine into the reaction vessel, and the outlet direction of the nozzle used to spray the mixed cresol into the reaction vessel are all 20° to the horizontal direction. The remaining operations and material ratios are the same as in Example 1.
[0034] Example 3
[0035] In this embodiment, when preparing the mixed cresol-type benzoxazine, in step S2), the outlet direction of the nozzle used to spray the paraformaldehyde solution into the reaction vessel, the outlet direction of the nozzle used to spray the primary amine into the reaction vessel, and the outlet direction of the nozzle used to spray the mixed cresol into the reaction vessel are all 30° to the horizontal direction. The remaining operations and material ratios are the same as in Example 1.
[0036] Example 4
[0037] In this embodiment, when preparing the mixed cresol-type benzoxazine, in step S2), the outlet direction of the nozzle used to spray the paraformaldehyde solution into the reaction vessel, the outlet direction of the nozzle used to spray the primary amine into the reaction vessel, and the outlet direction of the nozzle used to spray the mixed cresol into the reaction vessel are all 40° to the horizontal direction. The remaining operations and material ratios are the same as in Example 1.
[0038] Example 5
[0039] In this embodiment, the preparation of the mixed cresol-type benzoxazine differs from that in Example 3 in that the primary amine used is a mixture of aniline, decanediamine, and furfurylamine, with a molar ratio of 5:2:1.
[0040] Example 6
[0041] In this embodiment, the preparation of the mixed cresol-type benzoxazine differs from that in Example 5 in that, in step S2), the mixed cresol is heated to 100-105°C.
[0042] Example 7
[0043] In this embodiment, the preparation of the mixed cresol-type benzoxazine differs from that in Example 5 in that, in step S2), the mixed cresol is heated to 105-110°C.
[0044] Example 8
[0045] In this embodiment, the difference from Example 6 in preparing the mixed cresol-type benzoxazine is that the molar ratio of the amino group in the primary amine, the aldehyde group in the paraformaldehyde, and the phenolic hydroxyl functional group in the mixed cresol is 1.15:2.1:1.
[0046] Example 9
[0047] In this embodiment, the preparation of the mixed cresol-type benzoxazine differs from that in Example 6 in that the molar ratio of the amino group in the primary amine, the aldehyde group in the paraformaldehyde, and the phenolic hydroxyl functional group in the mixed cresol is 1.15:2.2:1.
[0048] Example 10
[0049] In this embodiment, the difference from Example 6 in preparing the mixed cresol-type benzoxazine is that the molar ratio of the amino group in the primary amine, the aldehyde group in the paraformaldehyde, and the phenolic hydroxyl functional group in the mixed cresol is 1.25:2.2:1.
[0050] Example 11
[0051] In this embodiment, the difference from Example 6 in preparing the mixed cresol-type benzoxazine is that the molar ratio of the amino group in the primary amine, the aldehyde group in the paraformaldehyde, and the phenolic hydroxyl functional group in the mixed cresol is 1.25:2.1:1.
[0052] Comparative Example
[0053] In this embodiment, when preparing the mixed cresol-type benzoxazine, the paraformaldehyde solution, primary amine and mixed cresol are directly placed into the reaction vessel, mixed and heated to react. The remaining operations are the same as those in Example 1 for preparing the mixed cresol-type benzoxazine.
[0054] In this invention, the infrared spectrum of the mixed cresol-type benzoxazine prepared in Example 1 is as follows: Figure 2 As shown, 1 H-NMR spectrum as shown Figure 2 As shown; the infrared spectrum of the mixed cresol-type benzoxazine prepared in Example 11 is as follows. Figure 3 As shown, 1 H-NMR spectrum as shown Figure 4 As shown. Figure 3 Middle, 1600cm -1 These are the characteristic absorption peaks of CH2 on the benzene ring and decanediamine, at 951, 1141, and 1226 cm⁻¹. -1 A distinct Ar-OC stretching vibration absorption peak was observed at 756 cm⁻¹. -1 The absorption peak at 1256 cm⁻¹ is attributed to the bending vibration of CH on the furan ring. -1 The asymmetric stretching absorption is attributed to the COC bond on the furan ring, which confirms that furfurylamine has been introduced, thus indicating that the oxazine synthesis was successful. Figure 4 In the analysis of the molecular structure, it can be seen that the proton hydrogens with a δ value of 7.55ppm-6.75ppm are those on the benzene ring, and the methyl protons H in the cresol group of the mixed cresol are those on the benzene ring. j The chemical shift δ in the proton NMR spectrum is 2.85 ppm–3.35 ppm, and the H in the aniline-type benzoxazine oxazine ring is... d and H g The concentrations were δ=5.36ppm and δ=4.61ppm, respectively, for the H group in the benzoxazine ring of the furfurylamine type. e and H h The concentrations were δ=4.93ppm and δ=4.05ppm, respectively, for H in the oxazine ring of the decanediamine type benzoxazine. c and H f For δ=5.42ppm and δ=4.64ppm, H a and H b The chemical shift of the furan ring in furfurylamine-type benzoxazine, H k It is an aliphatic chain segment introduced by decanediamine on a decanediamine-type benzoxazine. Based on the above analysis, it can be concluded that a mixed cresol-type benzoxazine with aniline, decanediamine and furfurylamine as primary amine sources was successfully synthesized.
[0055] In this invention, the weights of materials and products used in Examples 1-11 and the comparative examples were statistically analyzed and the yields of mixed cresol-type benzoxazine were calculated. The yields of mixed cresol-type benzoxazine in Examples 1-11 and the comparative examples are shown in Table 1.
[0056] Table 1. Yields of mixed cresol-type benzoxazines in Examples 1-11 and Comparative Examples
[0057]
[0058] According to the data recorded in Table 1, the yield of mixed cresol-type benzoxazine increases when both primary amine and paraformaldehyde are used in excess, and the primary amine exceeds the paraformaldehyde by a greater margin. Furthermore, the yield of mixed cresol-type benzoxazine is further increased when the primary amine, paraformaldehyde solution, and mixed cresol are heated, atomized, and sprayed into the reaction vessel, followed by continued heating. This is because the formation of mixed cresol-type benzoxazine increases the viscosity of the reaction system, and even with increased stirring, unreacted primary amine will be released. Amines, paraformaldehyde, and mixed cresols are unevenly distributed in the reaction system. However, by using atomization technology to heat and spray the primary amine, paraformaldehyde solution, and mixed cresols into the reaction vessel, the primary amine, paraformaldehyde solution, and mixed cresols can be fully mixed before they gather at the bottom of the reaction vessel. This avoids the uneven mixing that occurs during mechanical stirring. As a result, even if the amount of mixed cresol-type benzoxazine increases, the reaction between the primary amine, paraformaldehyde, and mixed cresols in the reaction system will not be affected, thereby improving the yield of mixed cresol-type benzoxazine.
[0059] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.
Claims
1. A method for preparing a mixed cresol-type benzoxazine, characterized in that, Includes the following steps: S1) Preparation: primary amine, paraformaldehyde, mixed cresols and solvent, wherein the molar ratio of the amino group in the primary amine, the aldehyde group in the paraformaldehyde and the phenolic hydroxyl group in the mixed cresols is (1.1~1.3):(2~2.3):1, the volume ratio of solvent to paraformaldehyde is (1.2~1.5):1, and the solvent is one or more of DMF, isobutanol and 2-butanol; S2) First, paraformaldehyde is mixed with a solvent to form a paraformaldehyde solution. Then, the primary amine, paraformaldehyde solution, and mixed cresol are heated to 95-110°C and sprayed into the reaction vessel simultaneously through a nozzle. At the same time, the solution temperature in the reaction vessel is kept not lower than 90°C. After the primary amine, paraformaldehyde solution, and mixed cresol are all added, the reaction is kept at a temperature of 90-95°C for 10-13 hours to obtain the crude product. The droplet size of the primary amine, paraformaldehyde solution, and mixed cresol sprayed into the reaction vessel is 20-80 μm. S3) The crude product obtained in step S2) is washed with alkali, then filtered and repeatedly washed with deionized water until the filtrate is neutral. The resulting solid product is then dried to constant weight to obtain mixed cresol-type benzoxazine.
2. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, In step S3), the alkaline solution used for alkaline washing is sodium hydroxide solution or sodium bicarbonate solution, and the concentration of the alkaline solution is 0.8 to 1.4 mol / L.
3. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, In step S2), the nozzle for spraying the paraformaldehyde solution into the reaction vessel is located below the nozzle for spraying the primary amine into the reaction vessel and the nozzle for spraying the mixed cresol into the reaction vessel.
4. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, In step S2), the outlet direction of the nozzle used to spray the paraformaldehyde solution into the reaction vessel, the outlet direction of the nozzle used to spray the primary amine into the reaction vessel, and the outlet direction of the nozzle used to spray the mixed cresol into the reaction vessel are all at an angle of 20 to 40° to the horizontal direction.
5. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, In step S2), the mixed cresols are heated to 100-110°C and then added to the reaction vessel.
6. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, The molar ratio of the amino group in the primary amine, the aldehyde group in paraformaldehyde, and the phenolic hydroxyl functional group in the mixed cresol is (1.15–1.25):(2.1–2.2):
1.
7. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, Primary amines are one or more of aniline, furfurylamine, butanediamine, and decanediamine.
8. The method for preparing mixed cresol-type benzoxazine according to claim 1, characterized in that, The primary amine is a mixture of a first primary amine, a second primary amine, and a third primary amine in a molar ratio of 5:2:
1. The first primary amine is aniline, the second primary amine is decanediamine, and the third primary amine is either furfurylamine or butanediamine.
9. A mixed cresol-type benzoxazine, characterized in that, The mixed cresol-type benzoxazine prepared by the method for preparing the mixed cresol-type benzoxazine according to claim 1.
10. The mixed cresol-type benzoxazine according to claim 9, characterized in that, The primary amine used in the preparation of mixed cresol-type benzoxazine is a mixture containing aniline.